THE UNIVERSITY OF MICHIGAN INDUSTRY PROGRAM OF THE COLLEGE OF ENGINEERING PLATE EFFICIENCIES AND MASS TRANSFER FOR, VALVE TRAYS AND TRAYS WITH LARGE PERFORATIONS Robert H. Miller A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the University of Michigan 1958 March, 1959 IP-360

Doctoral Committee: Professor Brymer Williams, Chairman Professor Julius To Banchero Assistant Professor Kenneth Fo Gordon Professor Victor L, Streeter Professor Robert R. White ii

ACKNOWLEDGEMENTS The author wishes to express his appreciation to the following people who materially aided him during the course of the investigation: To Professor Brymer Williams, whose advice and counsel served as a constant guide. To the members of the Doctoral Committee, for their many suggestions and help in planning the work. To Messrs. Cleatis Bolen, Frank Drogosz, and William Hines, who helped with the construction and modification of the experimental equipment. To Mr. Robert Norman and Mr. Keith Coats, for aid in programming and operation of the IBM 650 computer. To Mr. John Begley, who was always willing to take time from his own work to discuss problems as they arose. To the Phillips Petroleum Company, Allied Chemical Corporation, and the Research Committee of the American Institute of Chemical Engineers, for their fellowship grants. To the Industry Program of the College of Engineering for preparation and printing of the dissertation. 111

TABLE OF CONTENTS Page ACKNOWLEDGEMENTS............................................. iii LIST OF TABLES * O.............. O...... O.........O..n vi LIST OF FIGURES.......viii SJUMMARY oeoeoneBr~eed*0o*T@.......... xi INTRODUCTION.... O.......................................... 1 VAPOR-LIQUID CONTACTING APPARATUS.......................eo.....e. 2 PLATE DESIGNS..................O..........................o 7 METHODS FOR EXPRESSING PERFORMANCE............................... 12 Overall Column Efficiency,................... 12 Murphree Plate Efficiency....... O e.... o.oOO P 13 Point Efficiencies..........Oe eo..o............ooo. 16 LIQUID MIXING............. O...Oo........ o..........o 18 INTERPHASE MASS TRANSFER...........o........... o.o........... 25 The Relationship Between Mass Transfer Coefficients and Efficiencies.........................27 The Effects of Concentration on Mass Transfer...........,... 34 APPLICATION OF MASS TRANSFER DATA TO PREDICT EFFICIENCIES.o..Eoo.. 38 CORRELATIONS OF MASS TRANSFER DATA......................... 40 Gas Phase Resistance.................................... O.. 40 Liquid Phase Resistance.............o.......o....oo......... 44 APPARATUS............................ e............O...... 46 The Test Column....................................... 50 Vapor Handling System..........* *.. 6..................... 63 Liquid Handling System..................................... 65 Solute Gas Supply.................e................. 67 Sampling and Analytical Equipment - Humidification...... 68 Sampling and Analytical Equipment - Absorption............ 69 Auxiliary Equipment.......O................O...........0.. 73 MATERIALS. O*O.........oeoe............v............... 75 iv

TABLE OF CONTENTS (CONT' D) Page EXPERIMENTAL PROCEDURE.......................................... 77 Procedure - Humidification Runs............................ 77 Procedure - Absorption Runs.... o........................... 79 EXPERIMENTAL RESULTS............................... 84 General Observations....................................... 84 Hydraulic Data.......... o................................. 86 Mass Transfer Results - Humidification..................... 106 Mass Transfer Results - Absorption...........06.......... 106 Gas Phase Transfer Units.................................... 119 Correlation of the Data.......................... 124 Comparison with Results of Previous Investigators......... 136 CONCLUSIONS..................................................... 144 APPENDIX A - ORIGINAL AND CALCULATED DATA.................... 146 APPENDIX B - SOURCES OF EXPERIMENTAL ERROR............. 162 APPENDIX C - SOLUBILITY AND CALIBRATION DATA.................... 168 APPENDIX D - SAMPLE CALCULATIONS........................ 173 NOMENCLATURER............................................. 181 BIBLIOGRAPHY.................................................... 186

LIST OF TABLES Table Page I Summary of the Number of Transfer Units............... 30 II Interfacial Areas and Corresponding Integration Limits., ~ 31 III Characteristics of the Bubble Cap Tray Layout........... 56 IV Dimensions of the Valve Tray......................... 59 V Dimensions of the Perforated Tray........................ 60 VI Average Analysis of Ann Arbor Water..................... 76 VII Weeping Limit of Valve and Perforated Trays............. 105 VIII Comparison of EOG with EMV for Ammonia Absorption........ 122 IX Typical Values of Calculated Data for Gas Phase Transfer Units................................. o 124 X Summary of Correlations for NG..................... 128 XI Factors to Relate Performance of Various Trays......... 140 XII Humidification of Air with Water Using Valve Tray with 1-1/2-inch Weir................................ 147 XIII Humidification of Air with Water Using Valve Tray with 3-1/2-inch Weir...os.................................... 149 XIV Ammonia Absorption from Air by Water Using Valve Tray with 2-inch Weir........................................ 15.0 XV Ammonia Absorption from Air by Water Using Valve Tray with 3-1/2-inch Weir...o................................ 152 XVI Ammonia Absorption from Air by Water Using Perforated Tray with 2-inch Weir.................................... 154 XVII Ammonia Absorption from Air by Water Using Perforated Tray with 3-1/2-inch Weir............................. 155 XVIII Hydraulic Studies with Valve Tray Using 2-inch Weir...... 156 XIX Hydraulic Studies with Valve Tray Using 3-1/2-inch Weir.. 157 XX Hydraulic Studies with Perforated Tray Using 2-inch Weir. 158 vi

LIST OF TABLES (CONT'D) Table Page XXI Hydraulic Studies with Perforated Tray Using 3-1/2-inch Weir,................................. 159 XXII Dry Tray Pressure Drop for Valve Tray................... 160 XXIII Dry Tray Pressure Drop for Perforated Tray............. 161 XXIV Error in NG Caused by a One-Half Per Cent Error in EOG. 163 XXV Error in NG Resulting from Errors in yo, Y1l or y... 6.. XXVI Error in NG Resulting from Errors in NL................. 165 XXVII Ammonia Solubility in Water at Low Partial Pressures.... 169 XXVIII Calibration of Rotameter W70402A/1................ 170 XXIX Calibration of Rotameter 5601 D 1038B1................... 171 XXX Calibration of Rotameter V5-1200/1...................... 171 XXXI Calibration of Wet Test Meter H9SS....................... 172 XXXII Calibration of Wet Test Meter J5SS..................... 172 vii

LIST OF FIGURES Figure Page 1. Various Types of Plates.............................. 8 2. Fluid Streams in an Absorber or Distillation Column..... 27 3. General View of Column............................ 47 4. Simplified Flow Diagram for Humidification.............. 48 5. Simplified Flow Diagram for Ammonia Absorption....... 49 6. Test Column During Construction....................... 51 7. Column Construction Details............................ 52 8. Bubble Cap Plate Layout........................3...... 53 9. Removable Trays and Tray Installation.................. 54 10. Valve Tray Details........................................57 11. Top and Bottom Views of Assembled Valve Tray............ 58 12. Perforated Tray Installed in Column..................... 61 13. Position of Probe for Outlet Vapor Sample............. 70 14. Liquid Sampling Positions.............................. 72 15. Dry Tray Pressure Drop for Valve and Perforated Trays... 87 16. Pressure Drop for Valve Tray, Ammonia-Air-Water System., 88 17. Pressure Drop for Perforated Tray, Ammonia-Air-Water System....... O.......... 89 18. Froth Height for Valve Tray, Ammonia-Air-Water System.. 91 19. Froth Height for Perforated Tray, Ammonia-Air-Water System.o........................................... o..92 20. Average Clear Liquid Height for Positions C and D on Valve Tray, Ammonia-Air-Water System.................... 94 21. Average Clear Liquid Height for Positions C and D on Perforated Tray, Ammonia-Air-Water System.................o 95 22. Gas Holdup on Valve Tray, Ammonia-Air-Water System 96 viii

LIST OF FIGURES (CONT'D) Figure Page 23. Gas Holdup on Perforated Tray, Ammonia-Air-Water System.. 97 24. Relative Froth Density for Valve Tray, Ammonia-Air-Water System........................... 99 25. Relative Froth Density for Perforated Tray, Ammonia-Air-Water System........................... 100 26. Relative Froth Density with Ammonia-Air-Water System..... 101 27. Entrainment with Valve Tray, Ammonia-Air-Water System..., 102 28. Entrainment with Perforated Tray, Ammonia-Air-Water System.e................................................ 103 29. Murphree Vapor Efficiency for Humidification with Valve Tray, Ammonia-Air-Water System.................. 107 30, Murphree Efficiencies for Ammonia Absorption with Valve Tray, Weir Height 2-inches.............. o o..o... 109 31. Murphree Efficiencies for Ammonia Absorption with Valve Tray, Weir Height 3-1/2-inches.................... 110 32. Murphree Efficiencies for Ammonia Absorption with Perforated Tray, Weir Height 2-inches................... 111 33. Murphree Efficiencies for Ammonia Absorption with Perforated Tray, Weir Height 3-1/2-inches................ 112 34. Concentration Profiles for Ammonia Absorption with Valve Tray.................................. 114 35. Concentration Profiles for Ammonia Absorption with Perforated Tray..................o................. 115 36. Mixing Parameter C for Valve Tray...................... 117 37. Mixing Parameter C for Perforated Tray.................. 118 38. Values of NG for Humidification with Valve Tray, Air-Water System...................... 120 39. Values of NG for Ammonia Absorption with Valve Tray...... 125 40. Values of NG for Ammonia Absorption with Perforated Tray. 126 ix

LIST OF FIGURES (CONT'D) Figure Page 41. Comparison of Experimental and Predicted Values of NG for Humidification of Air with Valve Tray............. 130 42. Comparison of Experimental and Predicted Values of NG for Ammonia Absorption with Valve Tray............... 131 43. Comparison of Experimental and Predicted Values of NG for Ammonia Absorption with Perforated Tray........... 132 44. Effect of Gas Velocity on Correlation of NG for Humidification with Valve Tray.......................... 133 45. Effect of Gas Velocity on Correlation of NG for Ammonia Absorption with Valve Tray....,.......... 134 46. Effect of Gas Velocity on Correlation of NG for Ammonia Absorption with Perforated Tray................. 135 47. Comparison of Ammonia Absorption Data with Valve Tray with Correlation for Bubble Cap Tray.............. 137 48. Comparison of Ammonia Absorption Data with Perforated Tray with Correlation for Bubble Cap Tray................ 138 49. Comparison of Humidification Data with Valve Tray with Correlation for Bubble Cap Tray.................... 139 50. Comparison yf {umidification Data of West, Gilbert and Shimizu 67) with Correlations for Valve Trays and Bubble Cap Trays................................. 141 51. Comparison of Ammonia Absorption Data of Gerster et al.(1) with Correlation for Valve Tray.......................... 143

SUMMARY The purpose of the study was to obtain plate efficiency, mass transfer, and hydraulic data for the valve and perforated trays, and ascertain if their performance could be predicted from presently available data on bubble cap trays. Two types of tray design were investigated using two systems in which the resistance to mass transfer is controlled by the vapor phase. The valve tray contained nine 7/8-inch holes fitted with 1-1/2inch valves stamped from 18 gauge sheet and located on a 2-1/2-inch square pitch. The perforated tray was identical to the valve tray except that the valves were not used. The trays were installed in a rectangular column previously used by the Tray Efficiency Program of the American Institute of Chemical Engineers. The tray was 7-1/2 inches wide and 13 inches long from inlet downcomer to overflow weir. A splash baffle was installed upstream from the weir to smooth the liquid flow and to confine the bubbling action. The splash baffle limited the length of the active tray to 11-13/16 inches. The front of the column was fitted with a glass window so that the bubbling action on the tray could be observed. Data for the humidification of air with water, using the valve tray, covered an operating range in which the weir height was 1-1/2 and 3-1/2 inches, liquid rate was from 8 to 24 gallons per minute, and gas velocity varied from 1 to 5 feet per second, based on the active area of the tray. For the absorption of ammonia from air by water, using both the valve tray and the perforated tray, the weir height was 2 and xi

3-1/2 inches, Liquid rate was from 8 to 32 gallons per minute, and gas velocity varied from 1 to 5 feet per second. It was found that the Murphree vapor efficiency for both systems investigated increases with either an increase of weir height or an increase of liquid rate. At a weir height of 3-1/2 inches, the efficiency was almost independent of vapor rate if the tray was in the stable operating range. At weir heights of 1-1/2 and 2 inches, the efficiency decreased as the vapor rate was first increased. As the vapor rate was further increased, the efficiency remained constant or increased slightly, The weeping limit of the perforated tray was found to be primarinly a function of the vapor velocity through the holes, with values falling in the range of from 30 to 40 feet per second. Liquid mixing was greater for the perforated tray than for the valve tray, but in each case was not as large as that previously found for bubble cap trays. The entrainment was greater for the perforated tray than for the valve tray. The mass transfer data for the two systems were correlated by the following equations Humidification, Valve Tray N = 5.84(Zf- Zc)o0475 U-o.382 z 0.183 G w Ammonia Absorption, Valve Tray NG = 40 97.(ZfZc ) 0621 -0.458 O0.287 = 97(ZfZc) u Z Ammonia Absorption, Perforated Tray NG =3.72(ZfZc)0'650 u-0.459 Zw0.407 where N is the number of individual gas phase transfer units; Zf is xii

the froth height, feet; Zc is the clear liquid height, feet; u is the gas velocity based on the active bubbling area, feet per second; and Zw is the height of the overflow weir, inches. It was found that the inclusion of weir height as an independent variable improved the correlation over that obtained using the same form but omitting weir height. Performance of the valve and perforated trays can be estimated from existing correlations for bubble cap trays. The estimates can be improved by use of correction factors that were determined and found to be a function of tray design and weir height. xiii

INTRODUCTI ON The use of bubble cap plate towers in the petroleum and chemical industries has been standard for thirty to thirty-five years. In recent years, as costs have risen, manufacturers have begun to investigate other types of vapor-liquid contacting devices in the hope of reducing their equipment and operating expenses. Many new plate designs have appeared, and their designers claim that the new plates have operating characteristics which make them superior to bubble cap plates. In addition, perforated plates, whose use dates back to the 1830's, have been reinvestigated and their use is beginning to increase. The present research was designed to investigate two types of plate design and compare their performance with bubble cap plates. The designs selected were the valve plate and a perforated plate in which the size of the perforations was three to four times as large as those normally used. (29) The research was carried out in a rectangular column which had previously been used to investigate bubble cap plates. Two experimental systems were used: humidification of air and the absorption of ammonia from air by water. The first system is one in which all of the resistance to mass transfer is in the vapor phase. In the second, the majority of resistance is in the vapor phasebut some liquid phase resistance is present. The amount of liquid phase resistance varies with the operating conditions and ranged from a negligible amount to about fifteen per cent of the total resistance. As both the column and the systems have been previously investigated with bubble cap plates, a direct comparison can be made between the performance of bubble cap plates and the valve and perforated plate.

VAPOR-LIQUID CONTACTING APPARATUS The use of vapor-liquid contacting apparatus in the chemical engineering field is of great importance. It is the basis of many types of separations. These separations can be broken down into three major categories (17) Distillation, where heat is used to drive off vapors from the liquid, the vapors being later condensed; Absorption, where the material being transferred passes from the vapor phase to the liquid phase; and Stripping or Desorption, where the material being transferred passes from the liquid phase to the vapor phase. The types of apparatus that can be used to effect the separations are multitudinous, although the packed tower and plate tower are the ones that have been used most frequently. The packed tower consists of a column shell which is filled with material so constructed as to break up the liquid flow and provide a large liquid surface area to contact the rising vapors, Many types of packing material have been used such as coke, stone, ceramic rings and saddles, glass helices and other proprietary types. The use of packed towers is normally limited to towers having a diameter of less than two or three feet as the larger towers can be more economically constructed by using plates. In the plate tower, the column shell contains horizontal plates spaced at fixed intervals. Liquid flows across the plate where it is contacted by the rising vapors and passes to the tray below via downcomers. The method of contacting the vapor and liquid varies with the -2

-3plate design, the most simple being the perforated plate. The perforated plate contains a large number of small holes, usually from 1/8 to 1/4inch in diameter, through which the vapor passes. The vapor is thus broken up into small bubbles which provide good contacting with the liquid. The passage of the vapors through the perforations prevents the liquid from leaking through the holes as long as the vapor velocity through the holes is above a minimum value. This minimum value fixes the lower operating condition if effective separation is to be maintained. Although the perforated plates have been used for many years, it was believed that their operating range was small;and their use was restricted to specialized separations such as those in which the liquid contained a large amount of suspended solid material, More recently it has been found(41) that when properly designed they have a wide range of stable, efficient operation, and they are being used more and more in the chemical and petroleum industry. (29). Until the time when the perforated plates started to return to favor, the standard type of design was the bubble cap plate. The bubble cap plate contains a large number of holes into which are fitted risers to conduct the vapors from the space beneath the plate. Over the risers are mounted caps. Caps are available in a large number of shapes and sizes with the hemispherical and cylindrical-shaped caps normally used, although bell-shaped and rectangular caps are sometimes used. In commercial equipment, the caps normally range from 2-1/2 to 6 inches in diameter, The lower edge or skirt of the cap usually contains a large number of slots or serrationso Vapor from the riser is diverted downward by the cap and issues from the slots or serrations. An overflow weir is

-4installed at the outlet of the plate to insure that the skirts of the caps are below the liquid level on the plate~ Although the plate columns described provide intimate contacting between the liquid and vapor and have the advantage of essentially counter current flow, their operation sometimes presents problems. Each tray has an associated pressure drop of the vapor stream, Approximately, this is the sum of the pressure drop of a dry tray, i.e., with no liquid flow, and the pressure drop due to the liquid present on the tray when operating, This pressure drop may be on the order of several inches of water per plate. In most cases, this does not present much of a problem with towers operating at atmospheric or high pressure, but with vacuum towers with large numbers of plates a high pressure drop through the column can cause the bottom temperature to be high enough to cause damage to a heat sensitive product. The high pressure at the base of the column canin some cases, decrease the relative volatility of the materials being separated and increase the difficulty of the separation, (26) Another factor of concern is the stability of the operating plates. A plate is called stable if all bubble caps or perforations are functioning. The liquid flowing across the plate has a hydraulic gradient. If the length of liquid path is long or if the liquid rates are high, the hydraulic gradient may be large enough to prevent the upstream caps or perforations from bubbling. In extreme cases, it may cause liquid to "dump" or "back trap" through the upstream caps or perforations to the plate below. Unstable operation can be eliminated by proper design(12'26'33), and in large columns multipass plates are often used

-5to reduce the length of the liquid path and,consequently, the hydraulic gradient. Unfortunately, the vapor is never completely separated from the liquid on the plate and will carry some liquid to the plate above in the form of a fine mist or spray. Liquid may also be carried over due to the splashing and agitation of liquid on the plate. The liquid reaching the tray above is called entrainment. If the entrainment becomes large, the effectiveness of the separation is decreased. Entrainment can be decreased by increasing the plate spacing, but this results in a taller and more expensive tower. It can also be decreased by lowering the allowable vapor velocity in the column, but this results in either limiting the vapor handling capacity or a column of larger diameter. Thus the economic aspect is also important and may well determine the column design. If the column does not provide sufficient vapor and liquid handling capacity, it will not operate properly. If vapor handling capacity is limiting, the column will flood, If liquid handling capacity is limiting, the column will prime. The result in either case is that the column fills with liquid and separation ceases. In the many years that plate towers have been in use, a large number of individual designs have evolved. Until recently, few of them have been used in commercial equipmento As the cost of manufacturing, operating and maintaining columns continues to rise, manufacturers are looking for less expensive ways to obtain the desired separations. In general, the new trays have been designed along one or more of the following categories:

-6I. Increase the degree of contacting between the liquid and vapor phases, or maintain the degree of contacting over a wider range of liquid and vapor flow rates, and thus increase the capacity of a given piece of equipment. 2. Decrease the vapor pressure drop through the plate. 3d Decrease the liquid hydraulic gradient across the plate. 4. Decrease the entrainment produced by the plate. Unfortunately, the four categories are interrelated and the improvement of one category may result in unsatisfactory performance in one or more of the other categories. Thus, a satisfactory design is usually a compromise to obtain the best results for a given set of operating conditions. In the following section, a description will be given of some of the newer plate designs presently available.

PLATE DESIGNS Most of the new plate designs are proprietary developments and have seen relatively limited service. Whether or not they will replace bubble cap or perforated plates remains to be seen. Some of the designs that will be described are not new, but are being investigated in the attempt to improve performance or increase capacity. Sketches of the plates are presented in Figure 1. Baffles(27) - This is a type of construction that has been used for some time for easy separationso Baffles are used instead of trays. They are of the disc and doughnut type or segmental cross baffles which extend over half of the tower area set at 1800 to each other. This equipment has a low pressure drop and high capacity, but performance is not as good as bubble cap plates, Benturi(27,38,63) - In this design, a series of bent venturis (hence the name) are used to convey the vapor. They have roughly a 90~ bend and discharge the vapor in a horizontal plane in the same direction as the liquid flowo Vertical perforated baffles are located above the plate to reduce entrainment. Dual Flow(27) - This is a variation of the perforated plate. However, the holes are much larger and downcomers are not used, the holes passing both vapor upwards and liquid downwards. Flexitray(27'63) - This is one of the valve trays and is also a modification of the perforated plate. The plate contains a number of large holes about two inches in diameter. The holes are covered by a disc that rises off the plate as vapor flows through the column. A retaining spider prevents horizontal motion of the disc and -7

-8(a) BAFFLES (b) BENTURI (C) DUAL FLOW (d) FLEXITRAY (e) JET TRAY (f) KASKADE (g) KITTEL,,h) NUTTER (l) RIPPLE TRAY (j)SHOWER DECK (k) TURBOGRID (() UNIFLUX Figure' 1. Va'ioue ATpes of Plytea

-9limits the amount of vertical travel. A wider range of operating conditions is enhanced by using discs of different weights in adjacent rows. Jet Tray(27) - This may also be thought of as a modified perforated plate. Incomplete circular cuts are made in the plate and the metal bent upward. The cuts are made so that the vapor issuing from them is directed across the tray in the direction of liquid flow. Overflow weirs are not used. Kaskade(27,30) - This is somewhat similar to the Benturi design. Instead of venturis they consist of a series of S-shaped baffles which are set on their sides and arranged stepwise across the path of liquid flow. A nearly vertical perforated baffle is attached to the lower part of the S-shaped unit. Vapor rising through the S portion of the baffles impinges against the perforations and carries along the liquid which flows down the steps. Kittel(27) - A unit is made from several sheets of expanded metal plates. The cuts in the metal are made at various angles so that the desired flow pattern can be obtained, Downcomers are not used, and the unit passes both liquid and vapor. Nutter(27,48) - This type is similar to the Flexitray; however, the holes in the plate are rectangular and are located at right angles to the path of liquid flow. The holes are covered with an angle-shaped valve with the vertical leg on the downstream side. As vapor flow increases in the column, the valve starts to lift, pivoting on the apex of the angle. Liquid flowing over the plate will also help to pivot the valve. If the vapor flow is further increased, the valve will lift completely off the plate. Brackets limit the rise of the valve unit and prevent horizontal motion.

-10Ripple(7,27,35) - In this design, weirs and downcomers are not used. The tray is perforated in the flat much like a perforated tray and then bent into a series of sinusoidal waves. The plates are installed with the wave axis rotated 90~ on adjacent plates. Increased capacity is claimed as the holes in the bottom of the waves will preferentially pass liquid while those in the top will preferentially pass vapor. Shower Deck(27) - This is an older design and a modification of the baffle type. The column contains a number of horizontal baffles that occupy most of the tower cross section. At the edge of the baffle is a dam which prevents liquid from overflowing. Adjacent to the dam is a series of perforations which allow the liquid to flow through the plate and be broken up into drops which contact the rising vapors. Each succeeding tray is turned 1800 from the adjacent one. The operating characteristics are similar to the baffle columns,and they are used for the same types of service. Turbogrid(23'27'38'56) - This design is simple in construction and consists of a grid of parallel slots that cover the entire crosssectional area of the column, Weirs and downcomers are not used. The slots can be stamped from metal plate or can be the spaces between parallel bars. Adjacent trays are installed with the slots at right angles to each othero Uniflux(!3-15,27,38) - The basic elements of the Uniflux tray are a series of S-shaped members with slots along one face. These are installed on their sidaes in an overlapping manner at right angles to the path of iquid fl owO The spaces between the members act as bubble cap

-11risers and the slots as bubble caps. They have been operated both with and without downcomers.

METHODS FOR EXPRESSING PERFORMANCE Of the several ways available to express the performance of vapor-liquid contacting devices, the one most frequently used is the efficiency concept~ If the degree of contacting of the liquid and vapor on a plate were perfect, the liquid and vapor leaving the plate would be in equilibrium; and such a plate is called an equilibrium plate or ideal plate. Unfortunately the plates in use do not produce equilibrium streams, and the term efficiency has been introduced to describe the actual performance. Three separate efficiencies have been defined: overall column efficiency, Murphree plate efficiency, and point efficiency. The choice of which efficiency to use depends on the individual situation, although under certain conditions the three are related as will be shown later. Overall Column Efficiency If all of the plates in a given column operate as ideal plates, the number of such plates required to effect a given separation can be readily calculated by methods based on a set of material and energy balances.(10,17,52,54) As the actual plates are not ideal plates, the number of actual plates required for the separation will be different. The ratio of these two numbers is termed the overall column efficiency. Thus Number of Ideal Plates, E = (1) 0 Number of Actual Plates where Eo = overall column efficiency. -12

-13Drickamer and Bradford(28) investigated the performance of columns operating with petroleum and similar hydrocarbon materials and found their performance could be expressed by the following empirical relationship. E= 18- 60 log g (2) where. = molal average viscosity of feed at the average column temperature, centipoises. O'Connell(49) added the relative volatility of the key components as a correlating factor and improved the correlation and extended its range of applicability. His correlation is normally presented in graphical form as a plot of overall column efficiency versus the product of relative volatility times molal average viscosity.(17,54,60 ) Later investigators(3771l) have added data in the same type of plot while Chu(2122) has added the liquid to vapor mass ratio and submergence to improve the correlation. Unfortunately the overall column efficiency does not appear to be a simple function of the variables listed above, and in order to obtain a better prediction of column performance other methods have been used and will be described later. Murphree Plate Efficiency Murphree(46) defined the approach to equilibrium on a plate. Although first developed for a single bubble, it is now applied to the entire plate, The Murphree plate efficiency can be defined in terms of either the vapor or liquid compositionso Using vapor compositions, the

-14efficiency of plate n (numbered from the bottom of the column) is Yn-l Yn where EMV = Murphree vapor efficiency for plate n n-1 = average concentration of solute in vapor leaving the plate below plate n, mole fraction Yn - average concentration of solute in vapor leaving plate n, mole fraction y* = concentration of solute in vapor that would be in n equilibrium with the average concentration of solute in liquid leaving plate n, mole fraction. In terms of liquid compositions, the efficiency is Xn - Xn+l () E X* x(4) where EML = Murphree liquid efficiency for plate n xn = average concentration of solute in liquid leaving plate n, mole fraction Xn+l - average concentration of solute in liquid leaving the plate above plate n, mole fraction x* = concentration of solute in liquid that would be in equilibrium with the average concentration of solute in the vapor leaving plate no Thus, it can be seen for either definition the Murphree plate efficiency is the ratio of the actual concentration gain to that theoretically possible if the liquid and vapor streams leaving the plate were at equilibrium. By setting up a material balance around plate n, a relationship between the Murphree vapor efficiency and Murphree liquid

-15efficiency can be obtained(59) EML E (5) MV mGM. + - I(1 - EML) or EML EMV HGM (6) EM (1 EML) P LM where GM - superficial molar mass velocity of vapor, lb mole/hr-sq ft, based on column cross section LM = superficial molar mass velocity of liquid, lb mole/hr-sq ft, based on column cross section m 5 slope of the equilibrium curve, dy*/dx H = Henry's Law constant, atm/mole fraction P - pressure on tray, atm. If the operating and equilibrium lines are straight and EMV is constant throughout the column, a relationship between EMV and Eo, the overall column efficiency5 can be obtained (44) E n _ L(7) ~ In mGM LM If liquid from the plate is being entrained by the vapor stream, the change in composition of the latter will not be as great as if there were no entrained liquid. The apparent efficiency of the plate will be lower than the plate operating under the same conditions but with no entrainment. Colburn(24) has derived an expression relating the apparent efficiency and the plate efficiency when no entrainment is present) An

approximate form of this expression is Ea G (8) OM 1 + e — EMV where Ea = apparent vapor plate efficiency in the presence of entrainment, and. E _ moles liquid entrained per mole dry vapor. This expression is rigorous only for the case where the operating and equilibrium lines are parallel and the liquid is completely mixed. However,, it can be used for cases where the operating and equilibrium lines are not widely divergent. In cases where there is great divergence between operating and equilibrium lines, the exact expression given by Colburn should be used. Point Efficiencies Whereas the Murphree vapor efficiency was defined over the entire tray, the vapor point efficiency is defined over a vertical line above a given point on the tray. E n n Y~-2 - Yhf (9) where EOG the vapor point efficiency, and the primes indicate vapor concentrations at points lying on a vertical line through the tray. This is equivalent to taking the liquid as well mixed in the vertical direction but not necessarily in the horizontal direction. It can readily be seen that if the liquid on the tray is completely mixed, then the

-17Murphree vapor efficiency and the vapor point efficiency will be equal, or EMV = EOGo Analogously a liqvuid point efficiency is defined over a horizontal line in the direction of liquid flow. n Xn+l where EOL = the liquid point efficiency, and the primes indicate liquid samples lying on a horizontal line. This is equivalent to taking the vapor to be well mixed in the horizontal direction but not necessarily in the vertical direction. This might be true in a case where the gas composition changes so little that value of x'* is essentially constant, but in the majority of cases this is a questionable assumption. It should be noted that the physical models used in the expression for point efficiencies are not compatible, It is not surprising, therefore, that difficulty arises when the two models are assumed to exist simultaneously,

LIQUID MIXING The relationship between plate and point efficiency depends greatly on the degree of liquid mixing on the plate. As has been stated previously, if the liquid on the plate is completely mixed, EMV = EOG. If the liiuid is unmixed or partiall y mixed, a different relationship will result, Likewise, if the vapor is completely mixed and of uniform composition at all vertical levels, the Murphree liquid plate efficiency will be equal to the liquid point efficiency, or EML = EOL. Lewis(43) investigated three types of liquid and vapor flow patterns and obtained relationships between the Murphree plate efficiency and the point efficiency, which was assumed to remain constant across the plate. One type was the case of vapor of uniform composition entering the plate and contacting liquid that flows across the plate without mixing. This is often referred to as the "plug flow model". The relationship he obtained is LM mGM EM m- [exp (EoG M) -1] (11) MV mGM J. - OG LK where exp (x) = ex. The other types involved non-mixing of the vapor between plates and nonmixing of the liquid flowing in various directions on successive plates. These appear to be muach more artificial models, and the relationships will not be presented here. Of the three models, only the plug flow type has found much acceptance and appears to be reasonably valid in large columns under conditions of low vapor and high liquid loadings. -18

-19In actual operation, most plates operate somewhere in the range between plug flow and completely mixed flow. Several models have been developed to describe the degree of mixing and the relationship between point and plate efficiencies, Kirschbaum(39'40) and Gautreaux and O'Connell(31) have proposed a model in which the plate is considered to be composed of a number of completely mixed pools or stages. By assuming that the liquid and vapor loads are equal for each pool, the equilibrium relationship is linear, and EOG is constant across the plate, they have derived relationships between point and plate efficiency, The equation presented by Gautreaux and O'Connell is in much simpler form than that of Kirschbaum and is LM mGM EOGn 1] (12) EMV [(1+ ) -1] (12) mGM LM n where n = number of pools or stages on the plate, If the tray is completely mixed, the number of pools is one and Equation (12) reduces to EMV = EOGn However, if plug flow exists, an infinite number of pools would be required, Under such conditions Equation (12) is indeterminate, but in the limit reduces to Equation (11). Attempts to correlate the number of pools on a plate have not met with much success. In the absence of other data Gautreaux and O'Connell recommend the use of one pool per foot of liquid travel on the plate. Warzel(66) and Oliver and Watson(50) have postulated a mixing model based on a fictitious liquid stream of quantity (C-l)L which is

-20recycled from the overflow weir back to the liquid inlet without contacting the vapor stream. Thus, the net flow of liquid across the tray is CL, and the relation between point and plate efficiency is C XEOG EMV = [exp( 0) - 1] (13) where mGM X = --- the ratio of slopes of the equilibrium and "M operating lines, and Xn Xn+l1 C = (14) Xn xe where Xe - concentration of solute in the liquid at a point on plate n between the inlet and the first row of caps, mole fraction. If the liquid on the tray is completely mixed, then x and x are n e identical and C becomes infinite. If plug flow exists, Xn+l and Xe are identical as the liquid has not yet been contacted by the vapor, and C is unity. Crozier(25) derived a mixing model in which the turbulence of the vapor bodily carries liquid from a point on the plate to another point upstream. Using a differential difference equation he obtained the relationship E [exp( G(15) Mv X 1+7) 13 (15) where Y = mixing parameter, defined as Xn+l - xn Xn+l (16) xe -xn Xe

-21It can be seen that the result is similar to that obtained by Warzel. (66) The net liquid flow across the tray is (l+y)Lo For a completely mixed liquid 7 becomes infinite, and for the plug flow case y is zero. Although Crozier also measured his mixing parameter by a dye decay technique, both his and Warzel's model suffer from the fact that their mixing parameters are defined in terms of exit liquid concentration, As the exit liquid concentration is a function of the efficiency, the mixing parameter must also be dependent on the efficiency. Anderson(6) and Robinson(55) have derived equations relating plate and point efficiency based on the eddy diffusion concept. They postulate that material is transported from point to point in the froth by eddies as well as by bulk flowo Anderson obtained the relationship 1 - A1M 1 - A2/M +EMV (l-A/A2)exp A1 + (l-A2/A1)exp A2 (17) where M A! = 2+ + X EOGM A2 =- +X E OGM s2 M= DEtL and S plate length, ft. DE -eddy diffusivity, ft2/sec. tL - liquid residence time, sec.

-22He used a boundary condition that related the liquid concentration at the tray entrance to the entering liquid concentration and to material transferred by eddy diffusion to the tray boundary. Robinson used as boundary conditions the relationships that at the exit of the tray the liquid concentration gradient was zero and the liquid concentration was that overflowing the weir. The expression he obtained is EOG[! - exp(-Al)] EOG[l - exp(-A2)] EMV A(-A1/A2) + A2(1 (-A2/A) (18) where the nomenclature is the same as for Equation (17). Wharton(69), Stone(6l), Brown(18), and Byfield(l9) have obtained some data on the eddy diffusivity on sieve and bubble cap plates with values falling in the range of 70 to 150 ft2/hr. Unfortunately the amount of data presently available does not allow Equations (17) and (18) to be readily used. Johnson and Marangozis(36) postulate a model in which the liquid that passes a given point on the plate consists of a layer on the plate floor and that carried by splashing from points both upstream and downstream. This is similar to the model of Crozier(25) who used unidirectional splashing. They define a parameter in terms of the fraction splashed in each direction and the distance from which the liquid was splashed QFWF - QBWB (19) where = mixing parameter, and QF = fraction of liquid rate splashing downstream

-23QB = fraction of liquid rate splashing upstream. WF = normalized distance of downstream liquid splashing. WB = normalized distance of upstream liquid splashing. The general solution for their differential equation contains two constants which they evaluate using vapor concentrations obtained above the entrance and exit of the plate. It was found that one of the constants was several orders of magnitude smaller than the other and could be considered to be zero for the operating range studied, They thus obtained the result EOG(l - eA2) EMfV A (20) where 11 XEOG A2 =2- 2 ~ A2 arises from the auxiliary quadratic equation, and it can be seen that mathematically the splashing model is identical to the eddy diffusivity model with P = 1/M. It should be mentioned that Equation (20) can also be obtained from the differential equation by using the boundary conditions x = xn dx at the exit of the tray and dw = 0 at w = oo. The latter boundary condition is artificial as w is the normalized distance along the tray and has the value w = 1 at the tray exit. If one uses the same boundary conditions as Robinson, the solution is identical to Equation (18)o Thus, measurement of the splashing on a tray is another way of obtaining eddy diffusivity data. In presenting the work of Johnson and Marangozis, their equations have been normalized. If their correlation for f is used, it should be normalized before being used with the equations presented herein.

-24Although the models and equations listed previously were derived for use on bubble cap or perforated plates, they are equally applicable for all types of plate columns, The variation of the mixing parameters with plate design has not been investigated to much extent. The author has obtained some data with a valve tray and a perforated tray with large holes which will be presented later.

INTERPHASE MASS TRANSFER As correlations of efficiencies per se have not given the desired accuracy, investigators have turned to the basic concepts of mass transfer in order to describe the performance of vapor-liquid contacting devices. The two film, or two resistance theory proposed by Whitman(70) and the additivity of resistances presented by Lewis and Whitman(42) have served as the model. This model is based on the assumption that on each side of the gas-liquid interface there is a film, and the mass transfer between the two phases is controlled by the resistances in these films. Gordon and Sherwood(32) have shown that the two film theory is in fact dependent on the validity of three assumptions: (1) the rate of mass transfer within each phase is proportional to the difference in concentrations in the main body of the fluid and at the interface; (2) the phases are at equilibrium at the interface, i.e,, no interfacial resistance; and (3) the holdup of diffusing solute in the film or region near the interface is negligible with respect to the total amount of material being transferred. If the above assumptions are valid, then the steady state rate equations can be written NA = KOG(PG - P*) = KoL(cX - cL) = kG(PG - Pi) = kL(Ci - CL) (21) where NA = rate of mass transfer, lb moles/hr-sq ft KOG = overall gas phase mass transfer coefficient, lb moles/hr-sq ft-atm -25

-26KOL = overall liquid phase mass transfer coefficient, lb moles/hr-sq ft - lb moles/cu ft kG = individual gas phase mass transfer coefficient, lb moles/hr-sq ft - atm kL = individual liquid phase mass transfer coefficient, lb moles/hr-sq ft - lb moles/cu ft PG = partial pressure of solute in gas phase, atm Pi = partial pressure of solute in gas at the interface, atm p* = partial pressure of solute in gas in equilibrium with liquid, atm CL = concentration of solute in liquid, lb moles/cu ft Ci = concentration of solute in liquid at the interface, lb moles/cu ft c* = concentration of solute in liquid in equilibrium with gas, lb moles/cu ft Now, if Henry's Law is applicable so that Pi = Hci and p* = HcL, then the interfacial values in Equation (21) can be eliminated to yield 1 - 1 H (22) KOG kG kL and ~~~~~1 1 +~~~1 ~(23) KOL kL + k Analogously if the vapor-liquid equilibrium is presented in the standard y-x form, then Equations (22) and (23) become 1 1 + Pm (24) KOG kG PMLkL and 1 1 PML (25)

-27where m = slope of the equilibrium curve, dy*/dx P = total pressure, atm PML - liquid molal density, lb moles/cu ft Since the mass transfer coefficients are analogous to conductances, the left hand side of Equations (22) through (25) represents the overall resistance to mass transfer, and the individual terms on the right hand side represent the resistance of the individual films. The Relationship Between Mass Transfer Coefficients and Efficiencies Consider the fluid streams in an element of an absorber or distillation column as shown in Figure 2. x y+dy LM GM+dGM dZ LM+dLM GM x+dx y Figure 23 Fluid Streams in an Absorber or Distillation Column

-28A material balance around the element gives the rate of mass transfer as dNA = d(GMy) = - d(LMx) (26) But the rate of mass transfer can also be expressed in terms of mass transfer coefficients dNA = KOGav(y*-y)PdZ = kGa (Yi-y)PdZ (27) dNA = KOLa (x-x*)MLdZ = kLa' (X-xi)pMLdZ (28) where a' = interfacial area, sq ft/cu ft of gas and liquid holdup. Now if the gas rate is constant as is essentially so in distillation and for absorption from a dilute gas, then d(GMy) = GMdy. By combining Equations (26) and (27) one obtains KOGa' P dy GM dZ - (29) GM y*-y Considering KOGalP/GM constant, the integration is carried out over the mass transfer zone to obtain KOGa PZ Y1 dy GM Y-Y — NOG (30) Yo where NOG = the number of overall gas phase transfer units. Also Z GM OG NOG KOGaP (31) where HOG = the height of an overall gas phase transfer unit, ft.

-29These equations defining the transfer unit and height of a transfer unit were originally proposed by Chilton and Colburn(20) for use in a packed column, but their usage is now applied to plate columns as well. When y* is constant, the integration can be carried out analytically with the limits y = yo at Z = 0 and y = yl at Z - Z to yield KOGa'PZ Y-Y NOG GM - n ( ) =- n (1- EOG) (32) Under conditions when an inert carrier gas is present and the gas rate varies as in the absorption from an ammonia-air stream, then d(GMY) is given by (GM)avg 1-Y and NOG is then defined as KOGa' PZ Y1 dy NOG = (GM)avg Y (l-y)(y*-y) (33) Likewise if y* is constant, integration of the right hand side yields KOGa'PZ 1 F(lyo)(y*yl) -yO NOG =(GM)avg y*-l,n (l-yy.*yo) -y* )J l en1ny (1EoG) (34) The expressions for the number of overall liquid phase and individual gas and liquid phase transfer units are similarly obtained and are presented in Table I. It should be mentioned that several other definitions of interfacial area have been used. These are a, the square feet of interfacial area per cubic foot of gas holdup, and a, the square feet of interfacial area per cubic foot of liquid holdup. Accordingly, the vertical distance over which the integration is performed will vary depending on which volume the interfacial area is based. This is shown in Table II.

TABLE I SUMMARY OF THE NUMBER OF TRANSFER UNITS BASIS SYMBOL ABSORPTION(1) DISTILLATION (i) KOGa'PZ Y1 1 1-y0 Y*-Y1l KOGa'PZ Y1dy JYY1 OVERALL GAS PHASE N l - y - An Mavg Yo *1 Yj y*-y KOLa' PMLZ X2 _________x = 1u- ___ -x x*-x2l K0JLa'PMIZ - 2 ____C-2` OVERALL LIQUID PHASE NOL Klx) (x*Z x dx 1 * -n -r M)\ L X (i \ X *- / X -L ll-x2 X*-xi L X, X*tX 1jtX7 LMavg 1 2 O k~a'PZ yl dy1 1 oYiy kaPZ Y dy Y INDIVIDUAL GAS PHASE NG f - =__ _ fn pYo - kGa' PZ f In - i (GM)avg YO -(1y)(y1-y) Yi-l 11-y1 YiYoJ GM y0 Yi-Y li7YoJ kLa'pMLZ X2 dx 1 rl-x1 xi-x2) kLa'pMLZ x2 __ INDIVIDUAL LIQUID PHASE NL = f in AnJ 21 vg xi 1 kX)k(iX.j x'-x1xxli LM x1Xi 7 i- - l %.. (j(-) i nl xx I I) (1) Integrated forms obtained by assuming that y*, yi, x* and xi remained constant.

-31TABLE II INTERFACIAL AREAS AND CORRESPONDING INTEGRATION LIMITS Area Lower Limit Upper Limit at = sq ft/cu ft gas and liquid holdup Z = O Z = Zf a = sq ft/cu ft gas holdup Z = Zc Z = Zf a = sq ft/cu ft liquid holdup Z = 0 Z = Zc where Zf = froth height Z = clear liquid height If the interfacial area a is used in the definition of NOL given in Table I, the factor MLc has units of time. This represents LM the liquid residence time of a plate having an area of one square foot. Accordingly, NOL can be defined NOL = KOLatL (35) where tL = liquid residence time, sec KOL = overall liquid phase mass transfer coefficient, (lb moles/sec-sq ft-lb moles/cu ft)(sq ft/cu ft), or sec-1 and similarly NL = kL atL (36) where kLa = individual liquid phase mass transfer coefficient, sec

-32The gas phase coefficients can also be defined on a concentration basis leading to NOG KcGatG (37) and NG = klat, (38) where (ZfZc)PMG tG = gas residence time G -, sec PMG = molar gas density, lb moles/cu ft K' a = overall gas phase mass transfer coefficient, sec 1 OG k-a = individual gas phase mass transfer coefficient, sec 1 G It can be readily seen that the two definitions for KOG are related by KOG KOG (39) where atm-cu ft R = ideal gas law constant, lb.m. tR lb mole- R T = absolute temperature, 0R A similar relationship holds for kG and k In practice the bubbling action on a plate is so complex that it is impossible to determine accurately the interfacial area for mass transfer. For this reason the area is combined with the mass transfer coefficient, for example K8Ga, and the resulting expression is also termed a mass transfer coefficient. The relationship between overall and individual transfer units can be obtained by substituting the definitions listed in Table I into Equations (24) and (25) to obtain 1 1 X NOG "~G + NL (4o)

-33and 1 1 1 + -(41) NOL - NL XNG In a similar manner using Equations (22) and (23), one obtains 1 1 HPMLGM NOG NG PLMNL and 1+1 1 PLM NOL NL HpMLGMNG As with the expressions for mass transfer coefficients, the left hand side of Equations (40) to (43) is proportional to the total resistance to mass transfer while the terms on the right hand side are proportional to the individual phase resistances. Thus, a system in which the gas phase resistance is larger than the liquid phase resistance is termed a gas phase controlling system and vice versa. If liquid phase resistance is zero as in the case of vaporization of pure liquids, the system is said to be a pure gas phase resistance system. In systems where the solubility of the gas is very small as in the carbon dioxide-water or oxygen-water systems, the Henry's Law constant is so large that the gas phase resistance is often negligible. However, this assumes that the values of NL and NG are of the same order of magnitude. Much work has been done on this premise, and it appears to be a valid assumption. These systems are not, however, pure liquid phase resistance systems. Such a system might be a gas which is sparingly soluble in a liquid that has no vapor pressure —a rather artificial system, to say the least.

The Effects of Concentration on Mass Transfer In the previous presentation of the equations concerning mass transfer, it was assumed that there was no variation of diffusion rate with concentration. The theory of molecular diffusion in gases indicates that this assumption may not be valid in some cases. In the case of equimolar counter current diffusion, the theory based on Fick's Law states(65) that the amount of material transferred per unit time per unit area is DG(Pl-P2) NA RT z' so DG kG =-Z (45) where DG = molecular gas diffusivity R = ideal gas law constant z = length of element through which diffusion takes place Pl,P2 = partial pressure of the diffusing gas at the extremities of the element. However, in the case of a material diffusing through a layer of non-diffusing gas, the relationship is N DGP(P-P2) A RTpBMZ so kG RP (47) k = w~ _ ~ (47)

-35where P = total pressure PBM = logarithmic mean partial pressure of the non-diffusing gas = (pB2-PB1)/en(PB2/PBl) Thus, it appears that the expressions listed in Table I are valid for cases where equalmolar counterdiffusion is present but may not be so in absorption or desorption. Analogously, in liquid diffusion through a stagnant layer, a PML/CBM term is included in which the denominator represents the logarithmic mean concentration of the non-diffusing liquid. This term cannot be justified on the basis of the kinetic theory of liquids, but is included on the assumption that liquid diffusion is similar to gaseous diffusion. By substituting (l-y)f for PBM and (l-x)f for CBM, the equation for the number of transfer units can be written(52) KOGa'Z(l-y)f (l-y)f NoG= -I (ly)y (48) OG GM (l-y)(-Y) y( KOLatZ(l-x)f (1-x)f N0L = LM (49) k " (1-XY)x*-Xx kGaaZ(l-y) f (1-Y)f NG GM T(1-y)(yK-y (50) kLa'Z(1-x)f (l-x)f NL LM f (l-x)(x*-x) dX (51) where (l-y)f - logarithmic mean of l-y and l-y*, and (l-x)f = logarithmic mean of l-x and l-x*.

-36Thus, the relationships between the transfer units are 1 1 X(1-x)f NOG N G ---- I(52) NOG NG NL(L-y f 1! (iy)f ( NOL NL (53) If y* is constant, then the integral in Equation (48) can be evaluated analytically. By replacing (l-y)f by the definition for the logarithmic mean, one obtains 1Yo (in 1-y )(l-y)(Y*-Y) and by combining terms and factoring NOG = Yl dy (55) Yo (l-y) Rn 1By*! —y Use a change of variables, q = l-y*' to obtain N - =/ y* d (56) OG yl % _n q l-y* the solution of kwhich is N = n -yl (57) OG jn( In many cases, the solute concentration is not large, and the logarithmic mean can be replaced by the arithmetic mean without

appreciable error, Thus, the expression for NOG becomes N0 fYl [(l y)+(l-y*) dy (58) NOG=f 2 (l_,y)(y*-y) Yo If y* is constant, this may be integrated to obtain(59) NOG = 2 On y - _ n OG) (59) For cases where the solute concentration is low or for equimolar counter diffusion, the relationships given in Table I and Equations (40) through (43) can be used. In practice the expressions involving pBM/P or cBMPML are not often used. Usually these ratios are relatively close to unity and the precision of diffusivity data and correlation of mass transfer coefficients have not been sufficiently exact to justify their usage. In addition, Westkaemper(68) conducted studies on the evaporation of carbon tetrachloride into air-carbon tetrachloride mixtures in which the concentration of carbon tetrachloride varied up to 65 mole per cent. He found that the data could be correlated equally well either with or without the PBM/P variable and concluded that this term had not been established as being fundamental. His work was performed by passing the gas stream over a relatively quiescent liquid in a rectangular channel and may not be directly applicable to the studies in a plate column where a more complex type of vapor-liquid contacting takes place~ Studies of this nature in plate columns are needed to determine whether or not the theory is valid in this type of equipment.

APPLICATION OF MASS TRANSFER DATA TO PREDICT EFFICIENCIES The previous sections have described the relationship between the quantities in the mass transfer concept and efficiencies. In this section it will be shown how one might use these quantities to predict the performance of actual equipment. The basic values that will be needed are data on mass transfer in the individual phases. This might come from a correlation of NG and NL, or alternatively kGa and kLao Use of the former would be easier as hydraulic data are required to convert the latter by the equations kGaP (Zf-Zc) NG GM (60) kL~aPMLZc NL = LM (61) The correlating equations should be functions of the physical properties of the system and ideally would be applicable to all types of plate design. This is the approach that was used by the American Institute of Chemical Engineers research program on bubble cap plates, and it is hoped that their results can be applied to other plates without major modifications. Once the individual phase properties have been determined, the performance on the overall basis can be computed by Equation (40) 1 1 X NOG N+G NL From the number of overall gas phase transfer units, the point efficiency can be obtained by Equation (32) for distillation -38

-39systems or systems where the gas flow rate does not change appreciably NOG -; -4n ( -EOG) (32) To obtain the Murphree plate efficiency, one must have some knowledge of the degree of mixing expected. This will vary, of course, with the particuar system, size of equipment, liquid and vapor flow rates, etco At the present time the mixing problem has not been solved completely, and the engineer must rely a good deal on his own judgment. Let it be said, however, that the Murphree plate efficiency can be obtained by EMV = p(EOG) (62) where cp is some function of the degree of mixing. If the equilibrium and operating lines are straight, then the overall column efficiency is computed by Equation (7) in[lsEM (x-z)] E = - (7) 0o nX Thus, although the path to be followed in obtaining efficiencies is straightforward, it is not without its pitfalls. The above method is illustrated in the Fourth Annual Report of the Ao I Ch. Eo Research Committee(5) where the performance of a 4-ft diameter distillation column, operated by Fractionation Research Inc, separating cyclohexane and n-heptane is predicted from data obtained in a 2-ft diameter column with the systems acetone-benzene and oxygen-water. Mixing was described by using the method of Gautreaux and O'Connell(31) with n taken as l.2o A Murphree vapor efficiency of 8659 per cent was predicted, which compares to an experimental value of 85.4 per cent.

CORRELATIONS OF MASS TRANSFER DATA Until recently, the majority of mass transfer investigations were carried out in equipment other than plate columns. Packed columns were often used as were wetted wall columns. In addition, mass transfer from various geometrical shaped objects such as spheres, cylinders and plates, was also studied. The results can be found in the standard texts such as Sherwood and Pigford(58), Treybal(64), and Perry(51). The most comprehensive work on plate columns has been done under the auspices of the American Institute of Chemical Engineers. Although this work has been performed exclusively with bubble cap plates, it is hoped that the results will be able to be applied to other plates as wello Unfortunately, the program is still in progress and the final results are not yet available.3 However, the work performed by Warzel (66), Ashby(9), and Begley(ll) in this program has been correlated. These investigators used the same column as the author. They used bubble cap plates while the present investigation was carried out with a valve plate and a perforated plate with large holes. Since only the plate design was varied, a direct comparison can be made between bubble cap plates and those used in the present investigation. Gas Phase Resistance Ashby conducted experiments on the adiabatic vaporization of pure liquids. The liquids used were water, isobutyl alcohol, and methyl isobutyl ketone, while the gases werte air, helium, nitrogen, and Freon 12 (d ichlorodaifluoromethane ), A constant liquid rate of 8 gallons per

-41minute and a weir height of 1-1/2 inches were used. The gas velocity based on the active tray area varied from 0.6 to 7.5 feet per second. He found that the data could be correlated by 4G -0.23 (DuPG) -0-33 DsPG 0.16 hL 0.62 G = 0.297 (G G (PL)-O01 4L -0O005 F(p) (p(63) If the second and third dimensionless groups are combined and the last two groups with very small exponents are eliminated, a much simpler form is obtained 02553 (G -0.23 0,16 hL 0.62 where Ds = bubble cap slot width DG = gas diffusivity a= surface tension u = vapor velocity based on active tray area hL = vertical distance between bottom of slot opening and top of liquid flowing over weir PG' PL = density of gas and liquid 4G' 4L = viscosity of gas and liquid As the groups in the above equations are dimensionless, any set of consistent units can be used. Ashby found that his correlation would not predict the ammonia absorption and desorption data of Warzel, the average deviation being

-42-40 per cent. Warzel operated at liquid rates of from 4 to 32 gallons per minute and with weir heights of 2 and 5-1/2 inches, while the gas velocity varied from 1 to 4j7 feet per second. Although Ashby reasoned that the correction for liquid phase resistance in the ammonia-air-water system had not been properly applied, Begley found that this reasoning was not supported and that the failure was due to the choice of hL/Ds as a correlating variable. Begley adiabatically vaporized cyclohexanol and ethylene dibromide into nitrogen to find the effect of liquid properties on mass transfer. Operating conditions were in the same range as mentioned previously. He found that his data and the data of Ashby and Warzel could be correlated by Zf-Zc 0 532 kG o)-892 DsuPG)o-0408 L G-0.070 NG =4528 Ds - GDG 4G )-O. 694 Ds PL -0.370 (65) The average absolute deviation was 11.6 per cent with the maximum being 31.8 per cent. Begley performed an intercorrelation analysis on Equation (65) to find how much a change in one dimensionless group would affect each of the others. He found that about 86 per cent of the change in the Ds OPL surface tension group 2 could be accounted for by the change in the 4L viscosity ratio A L/G'. No significant intercorrelation was found among the remaining groupso He then recorrelated the data omitting the surface

-43tension group as a variable. The resulting equation had approximately twice the deviation as Equation (65) although if only Ashby's and WarzelVs data were used, the deviation was about the same as when the surface tension group was used. Begley thus concluded that the dimensionless group form of a correlating equation might not be able to be extrapolated beyond the range of variables studied, and a second type of correlation was performed. This latter correlation was based on graphical analysis and the previously presented relationship Zf-ZC NG = k'atG - kga f (38) Using this definition for k~a Gerster(4) was able to correlate AshbyVs data by the expression kVa = C u0'23 (66) where C = 18.19 DG 33 and DG = gas diffusivity sq ft/hr u = linear gas velocity based on bubbling area, ft/sec. Begley used Ashby's and Warzel's data as well as his own to obtain the correlation DG 0.526 Fn kpa 523.9 0.834 (zfc)0.28 (67) G PL fZ where n = 0.852 ( L/PL)0X238 F = F-factor = u -GG

-44PGt PL = gas and liquid density, lb/cu ft AL = liquid viscosity ib/ft-hr Zf-Zc = gas holdup, cu ft/sq ft Equation (67) can also be expressed in terms of NG by using Equation (38) to obtain DG0. 526 pG0.5 Fn-1l (Zf-Zc) 0. 72 NG= 5239 pLO 834 (68) Liquid Phase Resistance Begley was unable to completely correlate his liquid phase resistance systems because of the uncertainty of the diffusivity data of high viscosity systems. However, he did obtain the form of the correlation which is kLa =' DL/ (IL/PL/) C F0 575 (69) where PI and a are functions of the liquid kinematic viscosity, 1L/PL, sq ft/hr, and DL = liquid diffusivity, sq ft/hr. The value of Cx appears to have the value 0,5 at high viscosities, and decreases as the kinematic viscosity is decreased. The value of P' is also a function of kinematic viscosity but cannot be specified in general because of the uncertainty in the diffusivity data mentioned above. However, Begley also analyzed Warzel's data on the absorption and desorption of carbon dioxide in water where the diffusivity is better known. From these results a correlation is obtained that appears to be valid for aqueous solutions whose kinematic viscosity is close to

-45that of pure water at temperatures near 25~C. The correlation obtained is 1/2 0.'575 kLa = 55.4 DL F (70) or alternatively in terms of NL NL = 4 D1/2 F0O575 tL (71) where tL = liquid contact time, sec.

APPARATUS The apparatus used in the present study was designed and constructed by personnel of the Department of Chemical and Metallurgical Engineering for use inr the Tray Efficiency Research Program sponsored by the American Institute of Chemical Engineers.(2'3'5) It has been used for tray efficiency studies by Warzel(66), Ashby(9), and Begley(ll) Although their work was done exclusively with bubble cap trays, modification of the equipment to use valve trays and perforated trays was relatively simple and will be described later, A description of the bubble cap trays will also be included, as a comparison between these trays and trays used by the author will be made. The basic equipment was a rectangular column containing five trays. Only one active tray was used in the present study. Vapor and liquid handling systems were arranged so that both streams could be either recirculated or run on a once-through basis. A general view of the column and some of the auxiliary equipment is shown in Figure 3. Blowers for vapor circulation were located on the floor above, while pumps for liquid circulation can be seen in the area behind the test column. Figures 4 and 5 show simplified flow diagrams for use in humidification and ammonia absorption, respectively. The size and shape of the test tray was designed with specific requirements in mind~ A short liquid path was used in the hope that the liquid on the tray would be completely mixed. It was found, however, that mixing was not complete and concentration gradients did exist. The author also found this to be true with the trays investigated. A rectangular shape was used as it was desired to have uniform liquid -46

S-/lj: -$: n:::i::ii~i...iii. %;~,i....'.....':'.... - - - r e Figure 3. General View of Column Burli lilt:n irii.Lbeia Cn inat:::;i

VENT LEGEND T -TEMPERATURE MEASURED. P- PRESSURE MEASURED. S- VAPOR SAMPLE T,P Figure 4. Simplified Flow Diagram for Humidification

LEGEND VENT T - TEMPERATURE MEASURED P- PRESSURE MEASURED )- HUMIDITY MEASURED S- VAPOR SAMPLED TP VAPORIZED "TP,'rP crrY I - CITY WAITER AI R STEAM TO. DRAIN Figure 5- Simplified Flow Diagram for Ammonia Absorption

-50distribution even though this shape prevented operation at greater than atmospheric pressure,, This shape also made visual observation easier as the front of the column could be fitted with glass or Plexiglas windows. Nine bubble caps were located in three rows on a square pitch with a center-to-center spacing of 2-1/2 inches. This gave one cap which was completely surrounded by active caps. The Test Column The test column was constructed previous to this work and had been used by Warzel(66), Ashby(9), and Begley(ll), Warzel gives complete details on the column's design and construction which will be summarized here. A single piece of 3/16-inch Incoloy sheet approximately 10 feet long and 37 inches wide was bent by the Central Boiler and Manufacturing Company of Detroit, to form a channel 17-1/2 inches wide and 7-1/2 inches deep The channel had a 2-inch. flanged lip on each side against which the windows could be seated. The trays, inlet and outlet weirs, and splash baffles were made removable. The remaining Incoloy members, top, bottom, downcomers, plate support, and front braces, were welded in permanently. The column was tack-welded inside a frame of 4 x 4 x 1/2-inch mild steel angle which added rigidity to the column as well as providing support for the steel window frames. Figure 6 shows the column during construction and Figure 7 gives the details of the construction. Bubble Cap Trays - The bubble cap trays used previously contained nine 1-1/2-inch bubble caps on a 2-1/2-inch square pitch. The complete tray layout is given in Figure 8. Figure 9 shows the removable trays and installation details. The bubble caps were manufactured by

0 ~r1 ~ C) ~:::::::ili:i'ii:.i~:.::'i lii':iliii~i:'iii'[i i:..~I':'~ ~.: IIIii~iiiiiiii p~~~~s I ~ a~~I i:.!!!ii~!iiiiiiiii'iii~'i:li:li ii:ii:li~iig':::::":'ii ~ -~~iii i i i~~88~~8BB L~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~i:iiii!!?'~i~'~,:~?''i,: orl,i,~:~:i:i;~,;~iiiiiiii~!:!i!i —::i: - LC:o H r~~~~~~~~~~~~~~~~~~e~ P~~~~~d o:~~~~~~~~~~~s~~~~~i ~:::i~~~~~~~~~~~~~~~~~~~~~~i i6:~~~~~~~~~~~~~~~C c iiiil~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~0 rl ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~~~~~~ riii~~~~~~~~~~~~~~~~~~~~~~~~~b U\~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~.

Ia SHELL AND CROSS 4"x 4x 2- MILD STEEL PIECES T!O INCOLOY ANGLE FRAME 6"- -— o -" 3o-' 3"83 lo" 8 4 " 4 8,,, -: - -- -Cf 3.-.- -_.- -_ TO_ _''. i... _ J S ANGLE 7 3 ALL DOWN O ERS 258 1 0.093"1INCO OY 20"I l l __.. _ F re_ 7.. Cu C u t SI!~f I Il I Is 25 I,' o.o93".co!o1 _ 20" -I 14 4-~L:' 46.2" x 2 x MILD STEEL ABGLE TOP. VIEW BOTTOM SIDE VIEW Figure 7. Column Construction Details

17 L._' - T' -A ".2 -- - 4j 21 2 ___ ___ - Vl N I __ 1 r Figu\re.HOES B ROD.., l i, RISERS TRAYS. I DRLL 4 OL'ES @13 DO'WN L J 1 t FRONT V -I e l1 Figure 8. Bubble Cap PlAte layout

-54Ii:i:'::i:i:iiiiiiiii ii riiii:,j:'i':::,':iI....iil.. i.iiiiii iiiiiii:::i,~-?.........-..',E':,::,::::::::.:Efi:;.:.!:i:::E'S::.'..S,"'.,,%.'.:,'L:':: E:.......'.,,:...::::::.-.: i: i-i:E;;-Si0: E i:;:tit::::i:: -.;E:.?::?............................. 0E#0:::........:.:- E.:.: i::i;; -:?~~~~~.................;i; -E i' E i'-'#''''''""_l.'''-.i'..';;:EED -SiE E:::'; E i-' -"' ":.. ~ ~ ~ ~ ~ ~ ~ ~ ~ ~........... i i:i;! iii,iiiiii i-,,!Ef!!:i:ji:::,::: gcii? -?; "........ si i...............?!! i;i;;;Eiiii:. S..g. i:iiiii.....::2;?:?8.??...........? i {; a a 88: i ii:iEiiii::'.?:;.:'i;.'..;i~i!i;..:.'.'.8';!ii?.i:iiiii $iiiiiiiii.iiiii iii.:i:::;i.::;!.!;::,:iI i~~~~~~~~I"~~~~~~~~~~~~::~~~~'-::::,:.,?,.:???,,'i,?,?.~:i?&,,?,?,:,ii'~"~',;.?.i i8/ ~~~~~~~~~~~~~~~~~~~~~~~~fi i -',O;>.R..........i..........?,.' Figure 9. Removable Trays and Tray Installation

-55Fritz Glitsch & Sons, Dallas, Texas, from type 304 stainless steel. Their dimensions are listed in Table III. Valve Tray - The valve tray was designed to be as geometrically similar to the bubble cap tray as possible. Nine 1-1/2=inch valves were used on a 2-1/2-inch square pitch~ The vertical rise of the valve was such that in the fully open position the peripheral area under the edge of the valve was essentially the same as the slot area for the bubble cap trays. The perforations in the tray floor were the same diameter as the inside diameter of the risers on the bubble cap tray. The tray was fabricated of type 302 stainless steel by personnel of the Chemical and Metallurgical Engineering Departmento The valve discs were stamped from 18 gauge type 302 stainless steel by Ann Arbor Machinery Company. Stainless steel machine screws were used to hold the yokes and spacers in place. Taps in the tray floor were provided so that the height of the liquid on the tray could be measured, By a suitable valve and tee arrangement these taps were also used to withdraw liquid samples from the tray floor during the ammonia absorption runs, The taps were constructed by cutting a stainless steel Swagelock 1/4-inch tubing connector in half and welding it to the underside of the tray. A 3/16-inch hole was drilled through the tray from the underside using the bore of the connector as a centering device. After the tray had been mounted in the column, 1/4inch stainless tubing was connected to the taps and led to the liquid manometers and the sampling lines. Figure 10 shows the construction details of the tray, and Figure 11 shows the assembled tray. Table IV summarizes the dimensions of the valve tray.

-56TABLE III CHARACTERISTICS OF THE BUBBLE CAP TRAY LAYOUT Cap Diameter (O.D.) 1-1/2 inch Height 1-1/2 inch Me tal Thickness 1/16 inch Height 3/4 inch Width 1/8 inch Number, per cap 18 Area, per cap 0.0117 sq ft Area, per plate 0o105 sq ft Area, fraction of bubbling area 0.171 Risers Diameter (O.D.) 1 inch Diameter (ID.) 7/8 inch Area, per cap 0.00417 sq ft Area, per plate 0,0375 sq ft Area, fraction of bubbling area o.o061 Weir (variable) Length 7-3/8 inches Height 3-1/2 and 2 inches Splash Baffle (variable) Length 7-3/8 inches Clearance above tray floor 4 and 2-1/2 inches Downcomer Size 7-3/8 x 2-1/8 inches Area, cross sectional 0.137 sq ft Bubbling Area (taken as space between downcomer and splash baffle) Width 7-1/2 inches Length 11-13/16 inches Area 0.615 sq ft Tray Spacing 18 inches

-57"lif \t jL5IA. NO. II DRILL b 8 DIA. 0I SAMPLE TAP o0g i0() (~I I0 00 4'" 4'''"''+2 w' 5" I" TRAY FLOOR- 7 1,x 1 -x II GA. TYPE 302. STAINLESS STEEL 16~" ~~~~1 /- / 1 DRILL VatV5S 9 _ NO. I DRILL VALVES- 9 REQ. 18 GA. 302S.S, 0.435" YOKES- 9 REQ. -- O'437 I8GA. 302S.S. NO. II DRILL SPACERS- 27 REQ. *' 304 S.S.TUBING Figure 10. Valve Tray Detail.

ri ~~~~~~~~~~~~~~.~~~~~~ BII 1~~~~~~~~~~~~~~~~~~ iiiil~ tC i'i'i~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ cH O CO 3~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~C;i ~i" ti O~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~i=~~i,~1':::ii c I~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~.!1::':i'.:I~:'i':'i?~11~~'..k:;::::: " 0 -:.:::::,~;i:~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~i:~:i:~~~ >':':i:..!'':'./' ~!il i. I:!'::::::':: iiiiii:~!iii1~ 1ii ~i~/.... AD AD.r-I

-59TABLE IV DIMENSIONS OF THE VALVE TRAY Perforations Diameter 7/8 inch Spacing 2-1/2 inches square pitch Number, per tray 9 Area, per tray 0.0375 sq ft Area, fraction of bubbling area 0.06i Tray thickness 11 gauge (0.125 inch) Valve s Diameter 1-1/2 inches Metal thickness 18 gauge (0.0475 inch) Height of vertical travel 0.390 inch Peripheral area, per valve 0.0128 sq ft Peripheral area, per tray 0o115 sq ft Peripheral area, fraction of bubbling area 0.187

-60Perforated Tray - The perforated tray was essentially a valve tray without the valves and yokes. Nine 7/8-inch holes were drilled on a 2-1/2-inch square pitch. Sampling taps were installed as on the valve tray, Figure 12 shows the perforated tray installed in the column. Table V summarizes the dimensions of the perforated tray. The trays were installed in the column using Teflon sheet and epoxy resin as a gasket. TABLE V DIMENSIONS OF THE PERFORATED TRAY Hole Diameter 7/8 inch Spacing 2-1/2 inches square pitch Number, per tray 9 Area, per tray 0.0375 sq ft Area, fraction of bubbling area 0.061 Tray thickness 11 gauge (0.125 inch) Weirs - Adjustable overflow weirs were used to control the liquid level on the tray. These weirs were constructed of 1/16-inch stainless steel in the shape of a channel which fitted inside the downcomer. In preparing the column for operation., a weir of the appropriate height was fitted inside the downcomer, adjusted for proper height, leveled, and bolted to the wall of the downcomr beneath the tray. Liquid leakage was prevented by sealing all joints with epoxy resin. The downcomers were completely enclosed to avoid an extra seal between the downcomer and the glass face of the window~ Accordingly, the length of the outlet weirs was 7-1/8 inches as compared to the full column width of

-61 11''" W...I,:..,~'' I.. - "'...:::::::.........:.::,: I........l~i~:il:::::::l: -... I.::-I!:i'::.-.....I........:..........:I::jlji:::ili~~~~~~~~~~~~~~~~~~~~~~~~~~~~i~~~ilj~~~~~jljijiiijijiiiiiiii iii~~~~~~~~~~~..11....... I. - I I....:::-.-,: I::siI....iiii.iii:iiiii:::::::i:l:::.::::::iiiiii:iiiliiiliiri iiiii': -li;ii l::.l:::iill:llllii iiii:::::.:::::.:::: Ii: 11..... -,"ii~i~~ll:i~iij~~i:::::~lj::l~~ll::liiij~:ili~~j,:i::........ 11 II.... I,., - -l.1..1-1-~~li~~l~ iiii~~r:iiiiiiii::~~iiiiii:i; ~l~i il~i' i'ii'i:~il:l~': 6ii i~~~:~;~~'~i:'~'~::. I I -:::::::::'i'il i-11- -~~iiiiiii l:::::~ ~~i:~::I:~:: I~iii:ii::: li~i i:ii.ijiiiiiii.1 I....:: ii:ii:::::~-:::::::......I~ii~~l'::ii~ii~ iiii:::::il.'iii....ii.......... li:~:l~i::i:. ~I.- I.,.......'::,::::.,.-, —:......,. - - -l'.....l-I..... i:':''"";':;i- --...........i:: i......_...... i:I:I:::~:::ii::::::::: iil::: I~~li~ii iliii-i —...::::: i:: ll''l:: l';,::i:llli:::::i:i:,:::I::I:......:i... I..."......,.......::::::::::::::::::::::::::::::::i I.".:::::::::..::::.ii:i::::iiiii:~li~ii~ -.........-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~i:.:..:::~~~::~i::....,. ~ ~......:,.:...::,...... I:,:: I..~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~:: 1;........-:i~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~i!.I~ ~ ~ ~~~~~~~~::::...........-,:. ~::::- -:::;:....:....,-. Figur. 1. -,::.......Ins..:.. Cown~

-627-1/2 inches. This did not appear to have any effect on the flow patterns observed on the tray. Although the column was designed to use an inlet weir, it was found that its use caused the upstream slots on the first row of caps to remain inactive. To prevent this, the weir was not used on the bubble cap tray, with the valve tray, or perforated tray. Splash Baffle - During all runs using this column, a splash baffle was installed one inch upstream of the overflow weir with the top of the baffle 1/2 inch above the top of the weir. The baffle was made of 1/16-inch Incoloy and was 12-1/2 inches long by 7-3/8 inches wide. It was supported by bolting to a piece of angle welded to the back of the column. A piece of Tygon tubing was used as a gasket between the edge of the baffle and the glass window to prevent leakage. Warzel(66) found that without the baffle, liquid would splash unevenly over the weir. In addition, at high vapor rates the froth would not maintain a reasonably steady level but would flow over the weir into the downcomer with a steep gradient. Windows - Previously, difficulty had been encountered in maintaining a good seal between the windows and the face of the column. As only one active tray was used for most studies with the column, Begley(ll) replaced the Plexiglas windows with 3/8-inch stainless steel sheets which fitted between the window frames and the column face, and were welded to the frames for ease in installation. Since observations were to be made on trays 1 and 2, rectangular holes slightly smaller than the original window were cut in the stainless steel sheet and safety glass windows installed, This increased the width of the tray so a plate of safety glass was fitted to the inside of the window assembly on the

-63test tray to preserve the column dimensions. This was not done on tray 2 as this 7as not an active tray, and was only used to collect the entrained liquid in the vapor stream. The window assembly was bolted to the face of the column using Teflon tape and epoxy resin as a gasket. An access plate was cut in the assembly which covered the space beneath the first tray so that the trays could be changed and weirs could be adjusted without removing the assembly from the column. Vapor Handling System The vapor handling system consisted of two blowers operat:ing in series, metering devices, a heat exchanger for regulating the temperature and an entrainment separator. Standard 3-inch galvanized pipe was used with both screwed and flanged fittings. Although the piping could be arranged for recirculation of the vapor stream, for the present investigation it was handled on a single pass basis. Air from the laboratory was compressed in the first blower, metered, heated if desired, and fed to the test column. From the test column the air went to an entrainment separator, was compressed in the second blower, and fed to a vent line which exhausted outside the laboratory. Blowers - TWO identical blowers were used. They were brass two-lobe rotary blowers, type RCB, manufactured by the Sutorbuilt Corporation, Los Angeles, The blowers displaced 0.18 cubic foot per revolution with a maximum operating speed of 1800 revolutions per minute. The first blower was driven by a 10 h.p. electric motor, type K, serial P93912, manufactured by Robbins and Myers Co., Springfield, Ohio. The

-64second blower was driven by a 10 hap~ electric motor, type CSP, serial 5201, manufactured by Westinghouse Electric Company. An Allis Chalmers variable speed drive was belted between the motor and the first blower. This gave approximately a three-fold change in blower speed. Fine control in air rate was accomplished by a gate valve in a 2-inch bypass line connected between the blower inlet and outlet. The second blower was belted directly to the motor and was primarily used to regulate the pressure in the column. A valved bypass line was installed as with the first blower. Although the air flow rate and column pressure were dependent upon settings of the individual blowers, no difficulty was encountered in obtaining the desired conditions. Metering - Total vapor flow rate to the column was measured by a size 12 Fischer and Porter Flowrator, tube no. 12LL-25, serial noo D8-1609, figure no. 26P-E, Chemical and Metallurgical Department No. C17-200. The precision bore tube was calibrated for 0-200 cubic feet per minute of 0.877 gravity gas at 14,7 psia and 600F. Warzel(66) checked the calibration of the meter and found it to be sufficiently accurate for measuring gas flow rates providing corrections for gas density were made, Heat Exchanger - For the humidification runs the gas was heated in a Ross type SSCF, No. 804, 8-inch heat exchanger. The tube bundle was 4 feet long, and the header design gave four tube side passes while the shell side was baffled at one foot intervals. Construction was entirely of type 316 stainless steel. The gas flowed through the shell side while the heating medium passed inside the tubes. The exchanger was connected so that either steam or hot water could be used as the heating medium.

-65Entrainment Separator - A steel 55-gallon drum fitted with 3-inch pipe connections was used as an entrainment separator to collect any droplets not removed on the dry tray in the column. Liquid Handling System Two different flow patterns were used for the liquid handling system, For the humidification runs, distilled water was used and recirculated to the column. For the ammonia absorption runs, city water was normally used in a single pass system, although part of the liquid flow was recirculated for runs at the higher liquid rates. Flow diagrams for the two systems are shown in Figures 4 and 5. Both systems consisted of circulating pumps, meters, and control valves. For the humidification runs, a heat exchanger was used to maintain the liquid temperature at the desired level. For the absorption runs, city water was passed through a heat exchanger to raise the temperature of the water to test conditions. Pumps - Two identical centrifugal pumps were installed, They were Durcopumps Model 40, series WS7RD-74 with 7-1/2-inch open impellers fabricated of Durimet 20, a stainless steel alloy, manufactured by the Duriron Company, Inc The pumps were direct coupled to 3 h.p. induction motors, model 5K213B6228, manufactured by General Electrico The original rope-type packing glands in both pumps were replaced by Begley(ll) with mechanical seals type DU3151152, manufactured by the Durametallic Corporation, Kalamazoo, Michigan. This was done to eliminate packing gland grease as a possible source of contamination in the liquids. One pump was used to recirculate water to the column for the humidification runs or to both recirculate and discharge the water to the drain for the

-66absorption runs. The second pump was used to circulate city water to the column for the absorption runs. Control Valves - The control valves were globe valves, Figure 2475 Flanged End, F and D, 150-1lb,, 0 S and Y, Bolted Bonnet fabricated of Durimet 20 by the Wm. Powell Company. For the absorption runs, a one-inch globe valve, drawing B16573 REV6, body and stem F8, catalog 9815, manufactured by Henry Vogt Machinery Co., Louisville, Kentucky, was used to control the water flowing to the drain, and thus maintain the desired liquid level in the base of the column. Metering - Two identical size 8, series 700 Fischer and Porter Flowrators, tube no. B9-27-10/70G and float no. BSVT-93 were used to measure the liquid flow rates. They were calibrated from 10 to 100 per cent of maximum capacity (32 gallons of water per minute) in increments of one per cent. The first meter, serial W70-4024/1iwas used to measure the flow rate of the recirculated stream, The second meter, serial 5601D1038B1, was used to measure the flow rate of city water fed to the column. Piping - Standard 2-inch, Schedule 5, welding type, type 304 stainless steel pipe was used for all liquid piping, except for a 2-inch galvanized pipe which fed city water from the mains to the inlet of the circulating pump. Both flanged and welded joints were used. Heat Exchangers - Two heat exchangers were used. The first was constructed from a 4-1/2-foot length of 2-inch stainless steel pipe, and contained 3 coils of 1/4-inch stainless steel tubing. Liquid flowed in the shell side and cooling water in the tubes. This was used only in the humidification runs to cool the liquid which had been heated by the

-67pump and maintain the desired operating temperature in the column, A brass heat exchanger was used to heat city water to the desired temperature before feeding the water to the test column. Steam was condensed at atmospheric pressure in the four-pass tube side while water flowed through the shell side. This exchanger was used only for the absorption runs. Solute Gas Supply For the ammonia absorption studiesjliquid anhydrous ammonia was vaporized, metered, reduced in pressure, and introduced into the vapor line between the discharge of the first blower and the rotameter which measured the total vapor flow rate. Liquid ammonia was fed from a 150-lb cylinder through a check valve to a vaporizer. The vaporizer was constructed of a 3-foot length of 4-inch steel pipe, and contained a heating coil of 3/8-inch copper tubing in the bottom, The coil was heated by condensing steam at atmospheric pressure. An excess amount of steam was used to insure a steady flow rate of ammonia. If insufficient steam were used, the condensate would freeze and the ammonia flow from the cylinder would have to be shut off until all the liquid in the vaporizer had evaporated and the condensate had melted. The vaporizer was operated at a pressure of from 110-130 psig, corresponding to a saturation temperature of 550-65Fo. As the piping from the vaporizer was warm to the touch, it indicated that the ammonia was slightly superheated, and that the liquid was vaporized immediately. Apparently, there was little or no liquid hold-up in the vaporizer. The vaporizer was fitted with a pressure gauge and a spring loaded relief valve, 3/4-inch inlet, all iron,

-68No. 1118, manufactured by the Crane Co. The relief valve was set to open at 150 psi. Before use, the vaporizer was hydrostatically tested to 300 psi~ The vaporized ammonia was reduced to a pressure of about 20 psig before being metered and fed to the air stream. This was done by a Matheson No. 12A ammonia regulator. The regulator had an aluminum body and stainless steel internal fittings, Flow rate of the ammonia was controlled by a Metrol 1/4-inch steel needle valve. For a given flow rate, the valve setting in the ammonia cylinder had to correspond to the needle valve setting in order to maintain a steady pressure in the vaporizer. The ammonia was metered into the air stream by a Fischer and Porter Flowrator, serial V5-1200/1, tube B5-27-10/70G, float BSVT53. The beaded, precision bore tube was graduated in from 10 to 100 per cent of maximum capacity in increments of one per cent. The meter was calibrated using a Critical Flow Orifice Prover. Due to the temperature drop of the expanding gas and the rapid heat transfer through the aluminum body of the pressure regulator, the temperature of the ammonia metered to the air stream was within several degrees of room temperature, and remained very stable. Sampling and Analytical Equipment - Humidification The methods used for sampling and analysis varied with the system investigated. For the humidification runs, only vapor samples were required. The inlet vapor sample was taken by a 1/4-inch stainless steel probe located about three inches below the test plate. The outlet vapor sample was taken by a stainless steel probe located on the dry tray above the test tray. The location of the probe with respect to a

-69a modified bubble cap is shown in Figure 13. The tray above the test tray is referred to as a dry tray, as the liquid enters the column in the downcomer feeding the test tray, and is not contacted on the second tray. The only liquid which reaches the dry tray is that which is entrained with the vapor stream. Any liquid reaching the dry tray was withdrawn to prevent accumulation although the surface of the tray was often wet. Inlet and outlet vapor samples were withdrawn simultaneously through lines heated with electrical resistance wire, passed through drying tubes to absorb the water vapor, resaturated in bubblers, and the volume measured by wet test meters. Drying Tubes - The drying tubes were 4-1/2-inch glass U-tubes fitted with ground glass stoppers and sidearms. They were filled with anhydrous calcium sulfate (Drierite) and quantitatively removed water vapor from the sample. Wet Test Meters - Two wet test meters, serial nos. J5SS and H9SS, manufactured by Precision Scientific Coo, and rated at 0.1 cubic foot per revolution, were used to measure the volume of the sample. Balance - The drying tubes were weighed before and after sampling on a Christian Becker Projectomatic Balance model AB-1, using class S stainless steel weights. The balance and weights were checked against a second set of weights which had been calibrated by the National Bureau of Standards. It was found that no correction need be made to remain within a tolerance of + 0.2 mg. Sampling and Analytical Equipment - Absorption The same sampling probes were also used for obtaining vapor samples in the absorption runs. From the column, the sampling lines

-70Figure 13. Position of Probe for Outlet Vapor Sample

-71ran to a train of bubblers where the ammonia reacted with an excess of hydrochloric acid solution~ After passing through a water bubbler, the volume of the samples was measured in the wet test meters. The ammonia concentration in the samples was determined by back-titrating the unreacted hydrochloric acid, Hydrochloric Acid Bubblers - The bubblers were 4-ounce glass bottles fitted with rubber stoppers and connected with rubber tubing. A total of eight liquid samples were taken for each run. They were taken with a hypodermic syringe from sample lines fitted with rubber serum stoppers. The liquid sampling points are shown in Figure 14, After withdrawal, the samples were transferred to bottles containing an excess of hydrochloric acid. The samples were analyzed by back-titration of the excess acid. Hypodermic Syringe - A Becton, Dickinson and Co., Yale B-D 50Y, 50 cc hypodermic syringe with a 3-1/2-inch no. 13 stainless steel needle was used. The plunger head was enclosed in an aluminum housing which was fitted with a push rod. At the desired sample volume, the push rod could be made to engage the shoulder of the sleeve by rotating the plunger slightly. No liquid could then be expelled from the syringe without further rotating the plungerm This insured a constant volume for all samples. The push rod length was adjusted so that the sample volume was approximately 50 cc, and the delivery was calibrated using a Kimble Normax burette noo 8275. Liquid Sample Bottles - The liquid sample bottles were 8-ounce Boston round glass bottles, fitted with rubber serum stoppers,

-72PROBE its H 24'+ 2" 2 2 3 2 2B C D E F SPLASH BAFFLE WEIR B C D E F H Point H at base of downcomer, Point I in line to drain. Figure 14, Liquid Sampling Locations

-73Bu-rette - All titrations were performed with a 50 ml Kimble Normax burette no. 8275. pH Meter - The end point of the titrations was determined using a Beckman pH meter model H-2, serial 82945, with a type 4990-80 glass electrode and type 8970-13 calomel reference electrode. Stirrer - Agitation of the sample during titration was accomplished with a Labline magnetic stirrer, catalog no. 1250o The impeller was a polyethylene covered stirring bar placed in the 250-mi Griffin beaker holding the sample. Auxiliary Equipment Temperatures of the liquid entering and leaving the test tray were measured with 0-500C mercury filled glass thermometers graduated to 0ol~C, and calibrated for 76 mm immersion. Similar 0-1000C thermometers were used to measure the temperature of the gas beneath the test tray and in the gas rotameter. The thermometers were checked against a National Bureau of Standards calibrated thermometer. Temperatures of the liquid leaving the rotameters and of the gas above the test tray were measured with copper-constantan thermocouples. The thermocouples were connected through a 11-point Mallory selector switch, and readings were taken with a Leeds and Northrup portable precision potentiometer, model 8662, serial no 773919. Pressures in the test column and in the gas rotameters were measured with mercury filled 30-inch Meriam manometers. The pressure drop across the test tray was measured with a water-filled 50-inch Meriam manometer.

-74The clear liquid heights at four positions on the tray floor were measured by manometers connected to the taps previously described. The lines above the manometer board were manifolded and vented to the vapor space above the test tray. The scale was zeroed by vertical adjustment of the manometer board so that corrections for capillary effect need not be applied. The froth height on the tray was measured by a scale fastened to the face of the glass window.

MATERIALS Ammonia - The anhydrous ammonia was manufactured by Barada and Page, Inco, and was obtained in 150-lb cylinders from the Davis Supply CoO, DetroitO Nitrogen - The water-pumped nitrogen used was obtained in 200 cubic feet cylinders from The Liquid Carbonic Corporation via the General Stores Department of the University of Michigan. Air - Air from the laboratory was drawn into the blower suction, and after passing through the column, was exhausted via a vent line leading to the roof of the laboratory. This prevented the accumulation of ammonia in the laboratory. The laboratory compressed air lines were used to purge lines and dry equipment. Water - Distilled water for the humidification runs was obtained from the Department of Chemical and Metallurgical Engineering, City water for the absorption runs was obtained from the mains in the laboratory. The city obtains its water from the Huron River and wells, and it is softened by the lime-soda process. A small amount of ammonia is added to remove the chlorine tastebefore the water is pumped to the mains. The analysis of a composite sample taken over a one-month period was obtained from the Ann Arbor Water Department, and is presented in Table VI. Steam - Steam from the 60 psi main was throttled for use in the heat exchangers and normally condensed at atmospheric pressure. Analytical Reagents- Stock solutions were made from reagent grade chemicals and distilled water. The normality of the solutions was determined by using standardization grade potassium acid phthalate as described by Willard and Furman(72) except that the pH of the end point was determined with a pH meter instead of with phenolphthalein. -75

-76TABLE VI AVERAGE ANALYSIS OF ANN ARBOR WATER Ions Concentration, Parts per Million Carbonate 15.0 Hydroxide 2.0 Calcium 18.8 Magnesium 9.2 Sodium and Potassium 10.6 Chloride 17.2 Sulfate 56.5 Iron 0 Residual Fluoride 1.1 Dissolved Solids 18.8 Total Hardness 83.0 Non-carbonate Hardness 50.0 Total Alkalinity, as calcium carbonate 33.0 pH 10.2

EXPERIMENTAL PROCEDURE Basically, the experimental procedure consisted of selecting the operating conditions, starting the equipment, taking samples and operating data after steady state conditions had been reached, and analyzing the samples, The actual procedure differed in the humidification and absorption runs, and will be described in detail. Procedure - Humidification Runs Before operation, the column and all the lines were thoroughly cleaned to remove any organic material that might have been left from previous investigations. The valve tray was installed and the appropriate overflow weir was bolted in place. The variable speed drive on the first blower was adjusted to give a gas rate slightly higher than desired. The proper orifice was inserted in the inlet line to the second blower. The column was filled with distilled water to the proper level; the liquid recirculating pump was started and flow adjusted to the desired rate. The blowers were started and the two bypass valves adjusted to give the desired flow rate at a normal operating pressure. This operating pressure was from one to four inches of mercury on the test tray. The lower limit was fixed by the pressure drop through the sampling apparatus, and the upper limit was fixed by safety requirements. The cooling water to the liquid heat exchanger was turned on and the water temperature adjusted to the desired level. The steam to the vapor heat exchanger was turned on to heat the air so that the water in the column would be at the adiabatic saturation temperature of the entering air stream. Because of the high heat capacity of the gas and -77

the vapor lines, it normally took several hours to obtain this temperature. While the gas stream was being heated, the wet and dry bulb temperatures of the air in the laboratory were taken with a sling psychrometer. From these temperatures and a psychrometric chart(53), the correct gas temperature to be used was determined. While waiting for the gas stream to come up to temperature, the drying tubes were prepared. The U-tubes were filled with indicating Drierite and fitted with a glass wool plug to prevent any loss of material. A total of twelve tubes was prepared —three tribes for each inlet and outlet vapor sample of the duplicate runs. The tubes were weighed on the analytical balance and placed in a sample holder for transportation to the laboratory. The sample line heaters were turned on. As the gas temperature approached the desired value, the steam flow was regulated until the temperature of the entering gas stream agreed with the correct value previously determined. Although it took a considerable time to reach the correct temperature, once it had been obtained, the temperature was very steady. The liquid temperature was rechecked and adiabatic operation confirmed by noting the constancy of temperature of the liquid entering and leaving the test tray. After making any final adjustments in temperature, the drying tubes were connected in series to the sampling lines. The outlets of the drying trains were connected to water bubblers before being connected to a wet test meter. Before the actual sampling, the drying trains were briefly disconnected and the sampling lines purged with nitrogen to remove any waterr vapor that might have collected in them. The drying trains were reconnected and sampling was started, taking samples of both the

-79inlet and outlet vapor. The vapor samples taken had a volume of 0.5 cubic foot for most runs although for the series at a 3-1/2-inch weir height it was found that the reproducibility could be improved by taking a 1.0 cubic foot sample. While the vapor samples were being withdrawn the fluid-dynamic and other operating data were recorded. These consisted of the pressure on the test tray and in the gas rotameter, temperatures of the liquid and gas entering and leaving the test tray and in the gas and liquid rotameters, the pressure drop across the tray, froth height above the tray floor, clear liquid heights at four positions on the tray, gas and liquid rotameter readings, and the atmospheric pressure. After the runs had been completed, the U-tubes were removed to the balance room and re-weighed to determine the amount of water absorbed. It was found that usually the first drying tube removed over 95 per cent of the water vapor and the third tube showed no change in weight. Procedure - Absorption Runs As in the humidification runs, before operation the appropriate tray and weir were placed in the column. The city water circulating pump was turned on, and the flow rate adjusted to the operating value. As the column filled with water, the drain pump was started and the outlet valve adjusted to maintain the desired liquid level in the column beneath the test tray. The liquid level could be observed in a gauge glass, and the level was kept high enough to insure a liquid seal at the base of the downrcomer leading from the test tray. As the capacity of the drain line was limited, at high ISiuid rates part of the liquid from the

-80column was recirculated to the column, mixing with the city water before entering the downcomer feeding the test tray. The steam line to the city water heat exchanger was opened and adjusted so that the temperature of the water entering the column was 770F. The blowers were adjusted as for the humidification runs and started. Steam to the ammonia vaporizer was turned on. The ammonia control valve was opened. The valve on the liquid ammonia cylinder was gradually opened and the pressure gauge on the vaporizer observed. As the pressure reached the operating range (110-135 psig), the cylinder valve was closed slightly and the control valve adjusted to give the desired flow rate. Usually several adjustments of the valves were required to obtain the desired flow rate, but, once obtained, delivery was very stable, The pressure regulator was adjusted to reduce the pressure of the vaporized ammonia to about 20 psig, and this setting was used for all runs. The steam flow to the vaporizer was adjusted to insure that a slight excess of steam was used. Too little steam would cause the condensed steam to freeze and plug the line; while, if too great an excess were used, difficulty would be encountered in maintaining the ammonia fed to the vapor line at a constant temperature. Once the ammonia rate was fixed, the total gas flow to the column was set at the desired level by regulating the bypass valves on the air blower. The residence time of the gas on the plate was less than 0.5 second, and the residence time of the liquid less than 20 seconds. The column was operated for 20 minutes before sampling to insure steady state conditions had been reached. This time interval was sufficient as shown by the reproducibility of the check runs. While waiting for the column to reach steady state conditions, the sample line heaters were turned on and the lines purged with nitrogen.

The entrained liquid carried to the dry plate was removed by a probe connected to a water aspirator. A tared container was placed in this line to measure the amount of entrainment. Once steady state conditions had been reached, sampling was begun. Inlet and outlet vapor samples were withdrawn simultaneously. The samples were passed through a train of bubblers containing hydrochloric acid, a water bubbler, and a wet test meter. The first acid bubbler contained sufficient acid to neutralize the ammonia in the sample. The remaining two served to insure all ammonia was removed. At the same time the vapor samples were being withdrawn, liquid samples were taken and operating data recorded. Eight liquid samples were taken for each run. Seven of the sampling positions are shown in Figure 14. In addition, a sample was taken from the drain line leaving the column. A blank sample was taken to correct for the alkalinity of the city water. This was also sample A for the runs where water was not recirculated. If water were recirculated, a separate city water sample was taken. The liquid samples were taken with a 50 cc hypodermic syringe from sample lines fitted with a serum stopper. Sampling was done at a slow rate to avoid trapping gas bubbles. If any bubbles were taken with the sample, they were expelled from the syringe before the sample was transferred to the liquid sample bottles. The liquid sample bottles contained an excess of hydrochloric acid. The same operating and hydraulic data were taken as for the humidification runs. In addition, the wet and dry bulb temperatures at the blower inlet were taken so that a correction could be made for the

-82humidity of the laboratory air. The ammonia rotameter reading, temperature and pressure in the ammonia rotameter, and pressure in the ammonia vaporizer were also recorded. The nominal size of the vapor sample taken was 0.4 cubic foot, while the liquid samples were 50 ml. It was found that these sample sizes gave good reproducibility and were convenient to analyze. The analysis was performed by transferring the sample to a 250-ml beaker and back-titrating the hydrochloric acid with sodium hydroxide. The samples were titrated to an end-point pH of 5.4 using a Beckman model H-2 pH meter. As the last two bottles in the gas train contained little or no ammonium ion, these samples were titrated to an end point of 7.0. The procedure followed was to record the volume of solution used and the pH as the end point was approached and passed. The correct volume of solution used was then determined from a graph of pH versus quantity of solution. The end point was very sharp; the addition of 0.02 ml of base caused a change of pH of 1l0 units. The sodium hydroxide solution used had a nominal strength of 0.35 N and was prepared from reagent grade sodium hydroxide pellets by the procedure given by Willard and Furman. (72) The acid solution had a nominal strength of 1.0 N and was prepared from reagent grade hydrochloric acid by dilution with distilled water. The sodium hydroxide was standardized with potassium acid phthalate. The hydrochloric acid was standardized using the sodium hydroxide. The standardizations were carried out one after the other to avoid any possible inaccuracies caused by change in concentration of the sodium hydroxide. In addition, the relative strengths of the

-83solutions were checked frequently and restandardized if the amount of base required to neutralize the acid varied by more than 0.02 ml out of a total of 30 ml.

EXPERIMENTAL RESULTS General Observations The action on the tray could be observed through the window that covered the front of the column. In addition, the access plate to the vapor space beneath the test tray was replaced by a Plexiglas window for some runs. This permitted the observer to see if liquid were weeping through the perforations in the tray floor. When operating with the air water system, the appearance of the liquid and froth on the tray seemed to be similar to that observed when operating with bubble caps. At high liquid and gas rates there were two pronounced eddies. The liquid was bodily lifted in the center of the tray by the rising gas stream and returned to the tray floor at either extremity of the tray. Begley(ll) had noticed this previously, especially with the high liquid viscosity of the cyclohexanol-nitrogen system, and took high speed motion pictures of the action. Stable operation was observed at linear gas velocities of 2 feet per second or greater, where the gas velocity is based on the active tray area between the inlet downcomer and the splash baffle. At lower gas velocities the trays were not stable. When the valve tray was in use, it was found that at a gas velocity of one foot per second only five or six of the valves would be open; the remainder would be closed. The valves would be either fully open or completely closed. In no case was a valve observed operating in a partially opened position. The location of the closed valves varied randomly, and over a period of time one could observe various valves opening and closing with the total number

-85of operating valves remaining constant. Visual observation of the space beneath the tray showed the weepage to be negligible even when the tray was not stable. With the perforated tray the instability at low vapor rates appeared in a different form. The holes would alternately pass liquid and vapor. This could also be confirmed by observing the underside of the tray even though the liquid and froth on the tray appeared to be relatively uniform. This latter uniformity was also an unstable condition. After a short period of time the liquid on the tray was distributed so that weeping occurred simultaneously through the three holes along one side of the tray. This caused liquid to flow crosswise to the net liquid flow and lowered the liquid level on the other side of the tray. This in turn decreased the hydrostatic head on one side while increasing it on the other. The weeping holes could not handle all of the liquid, and part of it struck the side of the column and was reflected in the opposite direction. This set up a liquid cycling pattern on the tray with the perforations in the rows along the side of the column alternately passing vapor and dumping liquids Once this cycling process started, it could not be stopped unless the vapor velocity was increased above the point where the weepage stopped, The weeping limit occurred at a gas velocity of about 2 feet per second which corresponds to a velocity through the holes of about 32 feet per second. This latter value is in the range reported by Arnold et alo (8) for perforated plates with hole diameters ranging from 0oo6 to 0o37 inch.

-86Hydraulic Data The data obtained in the study divided into two categories: hydraulic data, and mass transfer data. The hydraulic data were taken while samples were being withdrawn. In addition, some hydraulic studies alone were made with the air-water system. Pressure Drop - Although the pressure drop through the tray was not used as a correlating variable, it was observed so that a comparison with the bubble cap tray could be made. The dry tray pressure drop through the two trays investigated is shown in Figure 15. The pressure drop for the perforated tray was almost identical to that of the bubble cap tray of Warzel.(66) The valve tray pressure drop was slightly higher. Also there was a definite Bernoulli effect with the valves. As the valve started to rise, the gas flowing between the valve and the tray floor had a high velocity which lowered the pressure. This pressure differential between the gas above and beneath the valve would keep the valve from rising. This would continue until the impact force on the valve from the gas passing through the holes in the tray was sufficient to overcome the pressure differential due to the Bernoulli effect. This effect could have been eliminated by making the diameter of the valve closer to that of the hole, but it was desired to keep the geometry of the tray as close as possible to that of the bubble cap tray. It was found that as soon as liquid was fed to the tray, the Bernoulli effect stopped, and the valves were either fully open or fully closed. Pressure drops through the operating trays are presented in Figures 16 and 17. These were taken during mass transfer studies of the ammonia-air-water system. Additional data on the air-water system at

-87NUMBER OF VALVES 5 FULLY OPEN cw 0VALVE TRAY 9- 0 4 IZ 4 x 5 ~4 + 6 0 V 7 cn w ab 8 x. 0 9 C.)~~~7 z + 25~~1 x >- x cE: 0 m x LE: X 90. 0 0 W. w M. PERFORATED TRAY C) cn 1.0 2.0 3.0 4.0 5.0 6.0 GAS VELOCITY, FT/SEC.. I..t I I I I 0.3 0.4. 0.6 0.8 LO 1.2 1.4 1.6 F FACTOR Figure 15. Dry Tray Pressure Drop for Valve and Perforated Trays

_888 2" WEIR 4,, ILd U): 9 3-! WEIR 4 J 7L7 6 (2) 4, L,'P. 3_ 2 -J QI 0.2 03 0.4 Q5, Q6 0.7 0,8 Q9 1.0 1.1 L2 1.3 1.4 F FACTOR 1.0 2,0 3.0 4.0 5.0 GAS.VELOCITY, FT./SEC. Figure 16, Presoure' Drop for Valve Tray, Ammonia-Air-Water 8yatem

-892 WEIR 4- (2) hi-2 0: a WEIR CC.7 (2)l)~~(2) W r(2) (2) 0.1 0.2 0.3 0.4 0.5 06 0.7 08 0.9 1.0 1.1 1.2 1,3 1.4 F FACTOR 1,0 2.0 3.0 4.0 5.0 GAS VELOCITY, FT./SEC. Figure 17, Pressure Drop for Perforated Tray, Arnxnonina-Air-Water System

-90slightly different parameters of liquid flow rate are presented in the Appendix. All data were taken with a splash baffle installed one inch upstream from the weir, with the lower edge one-half inch above the top of the weir. As only one tray was active, the flooding point could not be exactly determined. However, it appeared that flooding would occur when the pressure drop across the tray was about 8.5 inches of water, and would be caused by froth build up rather than by limited downcomer capacity. Froth Height - The froth heights observed when operating with the ammonia-air-water system are presented in Figures 18 and 19. Additional data for the air-water system are presented in the Appendix. The measurements were obtained by comparing the height of the froth on the tray with a scale fixed to the window covering the front of the column. This measurement is the least precise of all the data observed, as the froth-gas interface was not at a constant level but fluctuated greatly due to the turbulence on the tray. The action was observed for a period of time, and the average value was recorded. Observations made by the author and Begley(ll) checked within 1/4-inch in most cases; thus, even though the actual froth height may be slightly different from the recorded values, the readings are consistent. It was found that the addition of ammonia to the gas stream caused the froth height to be lower than for the air-water system alone. This is similar to what was found by Warzel(66), but he reported the difference between the two systems to be slight. With ammonia in the system, the author found that the turbulence of the gas-liquid mixture on the tray did not appear to be as violent as for the air-water system.

'O3S/i..4' A11DO13A SV9 0~9 O'f O' ~ 01 NO. OV:I:1 t'l ~1'1 I' 0'1 6'0 8'0 Lo 9'0 9'0'o ~'o I'O 9 X, — I m 0 -II -4 m 0I 01 813M,13 ElEI~1

teuACgS *t:R wv-JTV-vTuCuu'XXvu poaj~.xo3e JOj 40?0H t4oW0'6T Klnita'33S/'.L.' AIIOOT13A SV9 o'g 0'b 0'9 O' 0'1 Ho ov 4. - I -013tlV VI 1'1 Z'l I 0'1 60 80 LO 9D0 9'0 ~'0 0 0 10 9 -Z. 06 i rr II,13M IC -. 9. z L"n 01 Nj 113M #,, i1,,,,,,,,! i6

-93As ammonia lowers the surface tension, it is possible that the local surface tension was lowered sufficiently to promote a more stable froth. This would also account for the lowered entrainment found for the ammonia -air-water system. Clear Liquid Height - The clear liquid heights as indicated by the liquid manometers for the ammonia-air-water system are presented in Figures 20 and 21. The data plotted are the average heights for the two points in the active region of the tray, points C and D of Figure 14. It was found that these two points normally showed a clear liquid height lower than those at points B and D. The difference was usually few tenths of an inch and increased with increasing liquid rate and weir height. This difference in liquid height can be explained by the large eddies previously mentioned. The eddies tended to accumulate liquid at the inlet and exit of the tray and, thus, the clear liquid heights would be higher at these points. It was found that the addition of ammonia to the gas stream had no effect on clear liquid height. Additional data for the air-water system is presented in the Appendix. Gas Holdup - The gas holdup on the tray was computed by subtracting the clear liquid height from the froth height. Values obtained for the ammonia-air-water system are presented in Figures 22 and 23. Values for the air-water system may be computed from froth height and clear liquid height data presented in the Appendix. As the clear liquid height does not vary a great deal for a given liquid rate, the curves of gas holdup will have the same general shape as those for froth heightQ Relative Froth Density - The relative froth density is the ratio of the clear liquid height to the froth height. The computed values for

-947.i 2" WEIR 5 Ls32 GI_ (2 4, Lz24GPM _... - = L 4 GPM L 2GPM l La16 GPM = LSGPM 2.0 4.0?i2-gr 20, Averag8 0ear Liqd Height 1or P 0iti 1 P o4 I<~Vlve T.ay.ArWater Sytem 0.0 2.0

-956 2" WEIR 4 I L: 24 GPM (2) ~ [ X1 L=16 GPM h 2, 8 GPM. _,- o S A. _L: --— [M,l $~' WEIR'hiS 57 5 - ttA L=24 GPM.. 4 e~ L:16 GPM Lc 8 GP8M Q.I 0.2 03 04.5 0. 0.7 0.8 0.9 1.0 1.1 L2 I.: L4 F FACTOR 1.0 2.0 3.0 4.0 5.0 GAS VELOCITY, FT./SEC. Figure 21. Average Clear'LiLuld Height for Positiena C and D on Perforated Tray, Ammenia-Air-Water System

WenetXg zoji-r-vjuomV'Awtq sAJ\TA uo dnpTog ety'eZa MB'39/'id' A11.3013A SY9 _0~, ___.......... OJ0 VI i.... fl ~1 Z'I I' 1 0 10 60 90 L 9) Go ~ to0 OX I I/ 0 IN in~~~~~~1~~~~~~P &13M2,,= -96 -96-~~~~

-972" WEIR 7 6 V w 2 z s- 0 0 2 3.0 4,0 5.0 GAS VELOCITY, FT./SEC. Figure 23. Gas Holdup on Perforated Tray, AmmonLa-Air.Wator 8yatem

-98the ammonia-air-water system are presented in Figures 24 and 25. It can be seen that for a given gas rate and weir height, the relative froth density is quite insensitive to liquid rate. The lines drawn through the data in Figures 24 and 25 have been replotted on Figure 26 to show the effect of weir height and tray design. From the latter figure, it is apparent that over most of the operating range the relative froth density is greater for the valve tray than for the perforated tray. This difference is very slight and a single curve could be drawn to represent both trays within the precision of the data. The higher weir also causes an increased relative froth density, but the curves through the data have the same shape and are almost parallel. Entrainment - The entrained liquid from the test tray carried to the dry tray was withdrawn by a probe located on the tray floor. This prevented the accumulation of liquid on the dry tray~ The entrained liquid was collected in a tared container, and the results for the ammoniaair-water system are presented in Figures 27 and 28 where the entrainment, e, is expressed as moles of liquid per mole of vapor. Entrainment was not measured for the air-water system, as operating conditions were limited to those with negligible entrainment to avoid gas sampling difficulties. When operating with ammonia, a small amount of entrainment in the vapor sample would not appreciably affect the composition~ Water would have no effect, and the quantity of dissolved ammonia would be negligible unless the sampling probe were immersed in liquid, a condition that did not occur. With the air-water system, a small amount of entrained liquid in the vapor sample would

-991.0 2"WEIR 0.8- LIOUID RATE O 8 GPM 13 16 GPM \ 24 GPM 0.6 v 32 GPM 0.4 - 0 U- 0.6 N I0.6 0 0.4 0.2 I I I I I 0 0.1 0.2 0.3 0.4 0.5 0,6 0.7 0.8 0.9 1L0 1.1 1.2 1.3 L4 F FACTOR O LO 2.0 3.0 4.0 5.0 GAS VELOCITY, FT/SEC. Figure 24, Relative Froth Density for Valve Tray, Ammonia-Air-Water Byetem

-1001.0 2" WEIR 0.8p LIQUID RATE - _8 GPM El _ 16 GPM A - 24 GPM N- B 0.6- ((I\I z -J. 0.8 - 0.6 0.4 0.2 0 02 0. 4 G6 o0.8.0 1.2 1.4 F FACTOR.0 1.0......2. 3......$....i0 A.0 GAS VELOCITY, FT/SEC Figure 25. Relative Froth Density for Perforated Tray, Ammonia-Air.Water System

-1010.9 0.8 - _ VALVE TRAY, 2" WEIR VALVE TRAY, 31/2" WEIR 0,7 PERFORATED TRAY, 2"WEIR N PERFORATED TRAY, 31/2"'WEIR I0.0 z 0.5: I 0.1 0.1 0.2 0.3 0.4 0.5 0.6 Q7 0.8 0.9 1.0 11, 1.2 F FACTOR 1.0 2.O 3.0 4.0 GAS VELOCITY, FT./SEC. Figure 26. Relative Froth Density with Ammonia-Air-Water System

-1020.1.......... 0.08 2"WEIR 3 WEIR 0.06 0.04 0 a CD - 0.02V Q ~~~~~~~~~~~u p~~~~~~(,9 4~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~..J LIJ~~~~~~~~~~~~~ Di0. < CY~~~~~~~~~~~~~~~~DC > m~~~~~~~~~~~~I w 0 w 0.01 z - 0.008 z~~~~~~~~~~~~~~ w 0.006-R o( 04 0.004 C, %/, 0.002 - Q3 co 0.0~~~~~0013~~ 0LO O20 3.0 4.0 5.0 6.0 1.0. 2,0 3.0 4.0 5.0 6.0 GAS VELOCITY, FT/SEC...I. I I II. I.I I 0.3 0.4 0.6 0.8 1:2 1.6 0.3 0.4 0.6 0.8 1.2 1.6 F FACTOR Figure 27. E1ntrainmedt with Valve Tray, Ammonia-AAr-Warte System

-1030.06 2" WEIR 3 WEIR 0.040.02 - ix 4.;le 0 X 4J rL~~~~~~~~~~~~~~4 0 0.01 iZ o.ooe~- - 0.00600Q ~.1,. -1 3 -4. CO I.Z z 0.004 - w r z 0 0.002 - 0'004 I. 0 1.0 2.0 3~~~:.0 4.0,50 6.0 1020 30 4. GAS VELOCITY, FT/SEC...I -A.I I I. I.I I I. 0$- G4 6 U 0.8 12 1.6 03 0,A.0.6 8 1,2 1,6 F FACTOR Figuae 28, Entrainment with Perforated Tray, AmmoniA-Air.Water System

-104greatly affect the calculated efficiency as the vapor leaving the test tray was usually close to the saturation point. The data shown in Figures 27 and 28 must be regarded as qualitative rather than quantitative because the efficiency of the dry tray as an entrainment collector is not knowno It is estimated that most of the droplets with a diameter greater than 75 microns are collected. Since the drop size distribution is not known, it is not possible to determine the collection efficiency. In addition, since the gas leaving the test tray is not completely saturated, there will be some mass transfer from the entrained liquid to the gas stream. Liquid Weepage Through the Tray - The amount of liquid that weeps through an operating tray was measured by Talvalkar. (62) He used the one tray unit of Crozier(25) which has the same dimensions as the column used by the author. Talvalkar measured the leakage for two tray designso One was the valve tray used by the author, and the other was a perforated tray similar to the one used by the author except the perforations had a diameter of one inch instead of 7/8-inch. He found that the weepage was a function of vapor velocity, weir height, and liquid rate. For the air-water system he found the weeping limit to be as shown in Table VII, where the weeping limit is defined as the point where the liquid leakage is one per cent of the liquid fed to the tray. Thus, at vapor velocities above this limit any effect of weepage is negligible. The weeping limits given in Table VII are in the range reported by Arnold et a1,(8) and Hunt et al.(34), for perforated plates with hole diameters up to one-half inch~ The primary factor that affects weeping is the gas velocity through the holes and the weeping limit ranges from

-105TABLE VII WEEPING Lt MT** OF VALVE AND PERFORATED TRAYS* Superficial Hole Vapor Tray Weir Height Iiquid Rate Vapor Velocity Velocity Inches gal/min ft/sec ft/sec Valve 3-1/2 8 1.64 16 1.46 24 1.35 28.8 1.30 Perforated 1-1/2 8 2.98 37.4 16 2.71 34.0 24 2.55 32.0 28.8 2.49 531. Perforated 3-1/2 8 3.28 41.1 16 3.01 37.7 24 2.85 35.7 28.8 2.77 34~7 + Data of Talvalkar(62) ** Defined as the point where liquid weepage is one per cent of the liquid fed to tray.

30 to 40 ft/sec, Minor variations in the above range are caused by differences in hole spacing, plate thickness, liquid seal, and liquid flow rate. Mass Transfer Results - Humidification The humidification runs were carried out with the air-water system using the valve tray. The range of operating variables was as follows. 1. 1-1/2-inch weir height; Liquid rate 8.0, 16.0, and 24.0 gpm 2. 3-1/2-inch weir height; Liquid rate 8.0 gpm The vapor velocity was varied from 1.0 to 5.3 ft/seco The Murphree vapor efficiencies for the humidification runs are plotted in Figure 29. Several items can be noticed. First, the efficiency increases as the liquid rate is increased; second, the efficiency is increased by an increase in the height of the overflow weir; third, for the 1-1/2-inch weir as the vapor velocity increases the efficiency decreases until a minimum point is reached, after which a further increase in vapor velocity scuses an increase in the efficiency; and, fourth, for the 3-1/2-inch weir the efficiency is essentially constant over the range of variables studied. Mass Transfer Results - Absorption Absorption was studied by absorbing ammonia in water from an ammonia-air stream. Both the valve tray and perforated tray were used. The range of operating variables was as follows. 1. Valve Tray: Weir height 2 and 3-1/2 inches; Liquid Rate 8.0, 16.0, 24o0, and 32.0 gpmO

I- WEIR'Ii 96 92 \2/ z 0 13 aJ z 9.I 9 11 I IWEIR 1O 2.0 3.0 4.0 5.0 6.0 GAS VELOCITY * FT/SEC. Figure 29. Mrphree Vapor Efficiency for Humidification with Valve Tray, Air-Water System e4 ~ ~ ~ rdI0

2. Perforated Tray: Weir Height 2 and 3-1/2 inches; Liquid Rate 8,0, 16o0, and 24.0 gpm. The vapor velocity was varied from 1.0 to 5.0 ft/sec. The amount of ammonia in the entering gas stream was constant for most runs so the concentration depended on the vapor flow rate and varied from 2.2 to 119 mole per cent. This resulted in an exit vapor concentration from the tray that was usually less than one mole per cent. At this level the partial pressure of the ammonia in the exit vapor stream was low enough that the Henry's Law constant was a function of temperature only and not of the composition of the liquid on the tray. The experimentally determined Murphree liquid and vapor efficiencies for ammonia absorption are presented in Figures 30 through 33. For a given vapor rate, the efficiencies were higher for the runs with a 5-1/2-inch weir than with those with a 2-inch weir for both the valve and perforated trays. The perforated tray showed lower efficiencies at the lowest gas rate (about one ft/sec). In this region the liquid is cycling back and forth on the test tray. Consequently, part of the vapor passes through the tray without contacting the liquid to any degree. This ace counts for the lower efficiencies obtained. The broken lines in Figures 32 and 33 indicate what the efficiencies might be if there were no liquid cycling and are based in general on the curves drawn through the data for the valve tray. The cycling is probably due to the large hole diameter and may not occur with smaller holes even though the tray may be weeping. As in the humidification studies, the Murphree vapor efficiency increased with liquid rate. Also for both trays the data taken

MURPHREE LQOUID EFFICIENCY, E PERCENT MURPHREE VAPOR EFFICIENCY, EM, PERCENT 0 0 0 0 0 CD 0r.~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~C G a r D 0~~~~~~~~~~~~~~~~~~~ o.o -4 0) 4.Pb C+~ ~ ~ ~~~~~~~~~~~~~~~~~~~~~~~6 O,a Gb ~~ ~ ~ ~ ~ G! -.-' a4'fl ~~~~~~ 0" 0o 0 c.+ +.~0 G ~o. to ~~~~~~~~~.5 0~~~~~~~~.ci (P 3~~~~~~~~~~ or

sa9ouJ/z/TC OreTQH JTOA'Ac9XJ 0AtA Mt4A txo'q.xogqy owuo"nm aojt sToupaTje j aoqdm'TF amsRd'03S/'1'A110013A StV9 O'g OlO 0': 0'l _tOIO1l.-i'ol'1 Z'1I rI 01 6'0 9o0 V'0 9'0 90'p0 ~ 0 2'0 1' 1% C m r z 09 C 09 O'rn C) -0TOTII-~~O T= lu z~~~~ W &D V Z 0~~~~~s 96.

MURPHREE LIQUID EFFICIENCY3 EML, PERCENT MURPHREE VAPOR EFFICIENCY, EM, PERCENT N CA 04 04., co CD o30 0 0 0 N 0 0 0C 0 1 0 )C )!-'m~~ 1 - / ~CD b " Tn 110CC)0 ro c~~~.,'-,0 CD I'1 0 0 0 I~ 0 _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

MURPHREE VAPOR EFFICIENCY MURPHREE LIQUID EFFICIENCY, EML PERCENT E,,,PERCENT, co i7 D (D (0 o o 0 0 0 0 CD N C WEEIN LIMI S o 0 o o:31~~~~o ~~>// prp ~~~~~~~~~/ / "' I'0 CD WAEEPING LtMI~T _____'d C)D'i' U) 0 CD pY r'' P, n- r 0 0 4 I ~.CD -~ N H 0 0(. do.l bV!o CD 1 O C) -) -u 0 c b. Im 0 3W~~~~~~~~~~~~~~~~~ r r bY b a )d~~~C U' 0O.i1

-113with the 3-1/2-inch weir showed the Murphree vapor efficiency to be almost independent of vapor rate if the tray operation is stable. With the valve tray, the 2-inch weir height data showed a gradual decrease of Murphree vapor efficiency as the vapor rate was increased with the exception of the set taken at a liquid rate of 32 gpmo The latter set showed the efficiency to be essentially constanto The 2-inch weir height data for the perforated tray showed an increase of Murphree vapor efficiency with vapor rate for the set with a liquid rate of 8 gpm. With the higher liquid rates the efficiency was essentially constant. Concentration Profiles - For all ammonia absorption runs, samples were taken of the liquid entering and leaving the tray and at four points on the tray floor. Typical concentration profiles are shown in Figures 34 and 35, and the complete data are tabulated in the Appendix. In plotting the data, the experimental values were normalized to give an entrance concentration of zero and an outlet concentration of unity so that runs of different concentration levels could be compared. The data show that the liquid on the tray is neither completely mixed nor conforms to the plug flow model. For plug flow the theoretical concentration profile can be calculated by the following equation(44) [(yn) -y,1 ]exp (EQoXW) Yn-1 n - m EO m (72) where w = fractional distance across tray. By expanding the exponential term in series it can be seen that in the case where (EoGX)2/2' is small when compared with (1 + EOGX) the concentration profile is essentially linear. As the maximum value of X in the

(.2 O.8 - 0 z 4 < 0.4 — RUN 125 / RUN 116 / m...G = 0. 0 0674 / mG = 0.0390 w L / L 0 N I I. I 0 p 0 M.24 4 4 0.- 0.4 - / RUN -106 / RUN 110 mG = 0.0860 _G = 0.128 o kLL L 0 0.2 0.4 0.6 0.8 0 0.2 0.4 0.6 0.8 1.0 FRACTIONAL DISTANCE ACROSS TRAY Figure 34. Concentration Profiles for Ammonia Absorption with Valve Tray

1 2 ir | / m = 0.00953 = / mG" 0.0335l z o 1 /0' l l 0.4- RUN 23517 / RUN 20712 aM G 01A 0 0mL= 0.0:50 | m335 fL._. II0I L1 0 0.2 0.4 0.6 0.8 0 0.2 0.4 0.6 0.8 1.0 FRACTIONAL DISTANCE ACROSS TRAY Figure 35. Concentration Profiles for Amonia Absorption with Perforated Tray -Z~ Figure 35- Concentration Profiles for Amrmonia Absorption with Perforated Tray

present study is 0.133jand EOG has an average value of about 0.90, the concentration profile should be linear if plug flow exists. The dotted lines in Figures 34 and 35 show the plug flow concentration profile if the active tray is considered to end at the last sampling point on the tray floor. It can be seen that plug flow is approximated when the ratio of gas to liquid is low, but at higher ratios the plug flow model is not valid. In fact, there appear to be two pools of completely mixed liquid. Liquid Mixing - Warzel's mixing parameter was calculated using the liquid sample obtained from position B of Figure 14 as xe with Equation (14)o Xn-Xn+l C = (14) Xn-xe The results are presented in Figures 36 and 37. Warzel's ammonia absorption data(66) for a bubble cap tray with a liquid rate of 9.16 gpm is shown for comparison. The values obtained for C are smaller for the valve and perforated tray than for the bubble cap tray, indicating that there is less mixing on the former trays than on the bubble cap tray. This is to be expected as the bubble caps on the tray present an obstruction to the liquid flow. The mixing was slightly greater on the perforated tray than on the valve tray. At first glance, this might seem to be contradictory, as the valves do present some obstruction to liquid flow. However, the vapor emerging from under the disk of the valve has an appreciable velocity component in the horizontal direction whereas the vapor issuing from the perforations has only a vertical component. This vertical component of velocity tends to carry the liquid with the vapor. This is confirmed by the fact that the perforated tray has a greater froth

-1174 - 3. WEIR 3 - G m 2" WEIR 4- I. 3 - 2 _ 0.1 02 0.3 0.4 0.5 0.6.7 0.8 0.9 1.0 1.1 1.2 1,3 1.4 F FACTOR * 1.0 2.0 3.0 4.0 - - 5.0 GAS VELOCITY, FT./SEC. Figure 36. Mixing Parameter C for Valve Tray

-1183 3~WEIR 3 - 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 F FACTOR......... I..I.. GAS VELOCITY, FT/SEC. Figure 37. Mixing Parameter C for Perforated Tray

-119height than the valve tray at comparable operating conditions. The liquid carried up by the vapor returns to the tray and promotes mixing. Gas Phase Transfer Units In order to base the correlation of the data on the individual gas film resistance, it was necessary to calculate NG, the number of individual gas phase transfer units. In general, this can be done most easily by obtaining NOG, the number of overall gas phase transfer units, and correcting for liquid phase resistance to obtain NG. The procedure used in this investigation depended on the particular system and the methods used were as follows. Humidification - In the air-water system there is no resistance to mass transfer in the liquid phase. Also, since the liquid is of uniform composition and the vapor is assumed to be completely mixed, the point vapor efficiency EOG will be the same as the Murphree vapor efficiency EKTf. Thus, the number of individual gas phase transfer units is the same as the number of overall gas phase transfer units, and can be calculated by Equation (59) if liquid phase resistance is absent. NG = NOG = n( - n (l-EOG) (59) 2 1-Y0 This equation takes into account the change in gas raze on the plate and the effect of unidirectional mass transfer. It was found that for the humidification runs, the value of the first term was negligible compared to the second term and was omitted in the calculations. Values of NG for each run are tabulated in the Appendix, and are also presented in Figure 38.

-1204 Is WEIR 300 z 3-E WEIR 0 ~2- _~G 0 Ls 8 GPM Q2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 F FACTOR _ I.. I, 1.0 2.0 3.0 4.0 5.0 GAS VELOCITY FT./SEC. Figure 38. Values of NG for Humidlfication with Valve Tray, Air-Water System

-121Absorption - In the ammonia-air-water system, unless the liquid on the tray is completely mixed, EOG and EMV will not be identical. The relation between the two depends on the degree of mixing and the value of mG/L. If plug flow exists, then EOG can be calculated by Equation (11) EOG - n(XEMV+l) (11) If the liquid is partially mixed, a different relationship will hold. Using Warzelts(66) parameter, C, to describe the mixing, EOG can be calculated by Equation (13) E = An('EMV+l) (13) G x C A comparison of EOG with EMV has been made for eight runs covering the range of operating conditions for both trays, and is presented in Table VIII, It can be seen that the difference between EOG and EMV is greater when the value of mG/L is large, especially for the case of plug flow. As the concentration profile data showed that plug flow did not exist except at the lowest values of mG/L, the partial mixing model represents a more accurate relationship between EOG and EMV. By comparing the values of EOG and EMV for the mixing model, it is apparent that the difference between the values is very small, even at the higher values of mG/L,and that the value of EOG is intermediate between EMV and EOG calculated for plug flow. Accordingly, the experimentally values of EMV can be used as EOG without incurring appreciable error, and this procedure was followed in the calculations. An error analysis is presented in the Appendix and shows that a one percent error in EOG will result in less than a five per cent error in NG in most cases.

-122TABLE VIII COMPARISON OF EOG WITH EMV FOR AMMONIA ABSORPTION Observed Mixing Plug(2) Run (3) mG C Model 1) Flow L EOG E OG 125 0.o00674 1.22 o.960 0.959 0.953 116 005390 2.26 0.928 o.916 0.912 o106 o.o0860 3.23 0.901 o.890 0.868 110 0.128 3.71 0.898 0.884 0.850 217 0o00953 1.37 o.831 o.830 0.826 212 0o0335 1.64 0.822 0.815 0.810 2355 o0501 2.40 0.913 0.o904 0.892 207 0.133 3.37 0o812 0.798 0.771 (1) Calculated from EMV by Equation (13) (2) Calculated from EMV by Equation (11) (3) 100 Series-Valve Tray, 200 Series-Perforated Tray

-123Once EOG has been determined, NOG can be evaluated by Equation (59) 1 l-yl NOG = nn(l-y) - n(lEOG) (59) Since liquid phase resistance exists, NOG is not equal to NG as was true for the humidification system. In order to relate NOG to NG, the liquid phase resistance must be known. NL, the number of individual liquid phase transfer units, was calculated by using Equation (71). HL = 55.4 DL /2O L (71) Although this equation was developed from experiments with bubble cap trays, it was used for the valve and perforated tray for two reasons. The Murphree vapor efficiencies obtained with bubble cap trays were very close to those obtained with the valve and perforated trays so it might be expected that a correlation for bubble cap trays would be a good approximation to what occurs in the trays used in this investigation. In addition, since the liquid phase resistance is relatively small in the ammonia-air-water system, an error in the calculated NL will cause only a slight error in the value of NG. Using the values of NOG and NL as determined by the above procedure, NG was calculated by Equation (52). 1 1 X(1-x)f _ _.C (52) G OG 77YL f A few typical values obtained are listed in Table IX, while the values for the individual runs are presented in the Appendix, and in Figures 39 and 40O

-124TABLE IX TYPICAL VALUES OF CALCULATED DATA FOR GAS PHASE TRANSFER UNITS mG Run L EMV NOG NL NG 125 ooo674 o0960 3.28 0.976 3.36 116 0.0390 0.928 2.67 2.51 2.79 106. o860 0o901 2.34 3.94 2.48 110 0.128 0.898 2.30 4.78 2.45 217 0.00953 0.831 1.81 0.739 1.86 212 0 0335 0.822 1.76 1.53 1.83 235 0.0501 0.913 2.45 2.93 2.56 207 0.133 0.812 1 69 3.05 1.82 Correlation of the Data As the physical properties of the air-water and ammonia-airwater systems were almost identical, it was not practical to develop a new correlation based on these properties; and this was not the intent of the present work. Rather, the purpose was to compare the results of the valve and perforated trays with the previous correlations for bubble cap trays and determine if the bubble cap correlations were valid for other tray designs and, if not, what changes need be made. Based on the expression for NG given in Equation (38) Zf-ZC NG = k'atG = k'a u (38) it seemed probable that a correlation for NG, or alternatively kra, should

4 2 WEIR 3 L=32 GPM i. L.24GPM e a -La 16 GPM..A. II 3j WEIR 3 16 GP L 24GPh + 2 - ~ O 2I _ 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 F FACTOR.... I..I... I.... 1.0 2.0 3.0 4.0 5.0 GAS VELOCITY, FT./SEC. Figure 39, Values of NG for Ammonia Absorption with Valve Tray

-1262" WEIR 3 _L24GPM 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 13 1.4 1.5 F FACTOR I I I _I 2 Figure 0.4 0.5 0.6 0.7 0for8 0.9 1.0.Aborption 1.2 1.3 1.4 1.5with 1.0rfora 2.0 3.0 4.0 5.0 GAS VELOCITY, FT./SEC. Petrforated Tray

-127contain the variables gas holdup and gas velocity. This same reasoning was used by Gerster(4) and Begley(Il). In working with the data, the author found that the weir height also had a significant effect on NG and might be included as a correlating variable. Accordingly, the form of the correlation chosen was NG A(ZfZc)b UC Zwd (73) This equation is identical in form to that used by Begley except for the addition of the weir height. The actual correlation was done on the IBM 650 digital computer using the multiple regression program developed by Norman. (47) The program was so written so that the correlation coefficients could be obtained for order n, the number of independent variables, or for lesser orders 1, 2,. o., (n-l) This permitted the correlation of the data either with or without using weir height as a variable. The first part of the program computed the regression coefficients for a least square fit to a linear equation, and accordingly the data input was in logarithmic form. The standard deviation of the dependent variable, Rn NG in this case, was also obtained. The second part of the program read the correlation coefficients and the data, predicted values of the dependent variable, and computed the deviation of the experimental value from the predicted value. The results obtained are summarized in Table X. It can be seen from the table that the use of weir height as an independent variable improves the correlation. With the absorption data, the average deviation is only about one-half as large as when weir height is not used. With the humidification data, the improvement is not as noticeable, but

-128TABLE X SUMMARY OF CORRELATIONS FOR NG NG = A(Zf-Zc)b u Zwd Average Maximum Absolute Absolute Tray Type A b c d Deviation Deviation Humidification: Air-Water System Valve 5 84 o.475 -0 381 o.183 6.1% 20.4% Valve 8.73 0.656 -0.478 -- 8.1% 24.1% Absorption: Ammonia-Air-Water System Valve 4.97 0.621 -0o458 0.287 4.0% 10.9% Perforated 3.72 0.650 -0.459 0.407 3.9% 22.0% Valve 7.76 01729 -0 545 -- 7.5% 19.3% Perforated 8 48 0.916 -02689 -10 0% 38.6% where NG = Gas phase transfer units, dimensionless ZfCZc = Gas holdup, feet u = Gas velocity, feet/second Zw = Weir height, inches

-129this may be partially due to the fact that only about one-third of the data were taken at the 3-1/2-inch weir height and, then, only at a single liquid rate. The absorption runs were divided about evenly between the 2-inch and 3-1/2-inch weir heights. Figures 41, 42, and 43 show the comparison between the experimental values of NG and the values calculated using the correlations. It can be seen that the agreement between the values is quite good with only a few data points having a deviation greater than 10 per cent. In Figures 44, 45, and 46, the data is plotted to show the effect of gas velocity on the correlation. Table X shows that the coefficients in the correlation for NG using the valve tray for humidification, differ slightly from those for ammonia absorption. It might be expected that the coefficients would be the same for both systems as the transport properties are similar. However, the gas diffusivity for air-water is about 10 per cent higher than for air-ammonia at 25~C. (51) In addition, the gas stream in the humidification runs was heated to maintain adiabatic conditions, and therefore the average gas temperature was higher than for the absorption runs. The gas diffusivity would also be higher. The exponents on gas holdup and gas velocity in the correlations are partly self-compensating, i.e., the exponents for ammonia absorption are both larger than for humidification, but the exponent on gas velocity is negative. Thus, the fact that the constant A is larger for humidification than for absorption can be explained by the difference in gas diffusivity. This has been shown also by Begley() who used gas diffusivity to correlate the values of A obtained from a large number of systems.

-1306 5 II" WEIR XO\ QE 3' WEIR / I/ / / 4,* / / / 3 // _, / 0 "w. /I Z / / AVERAGE ABSOLUTE DEVIATION = 6.1% 0.f475 -0,382 0.183 NG= 5.84 (Zf -ZC) U Zw 2 3 4 5 6 N. FROM CORRELATION Figure 41. Comparison of Experimental and Predicted Values of NG for Humidification of Air with Value Tray

-1315 0 2" WEIR x ~4 t 3jWEIR / / Ng 49 0.2/1 /6 / I Zip I // J/ AVERAGE ABSOLUTE DEVIATIO/N ~ 4.0 % _ 0.9(f-Zos21 -0. 4sa o.aa7 /wNg4,97(Z-Z,) U Zw 122 3 4 No FROM CORRELATION Figure 42. Comparison of Experimental and Predicted Values of NG for Ammonia Absorption with Valve1 Tray

-1320 2'" WEIR o\o 4 DR 32 WEIR o\o 3(-~0/ / 7.0/ a. 2 4 2- I AVERAGE ABSOLUTE DEVIATION x$.9% N= 3.72 (Zf-Z)650 U 459 Z NF FROM CORRELATION Figure 43. Comparison of Experimental and Predicted Values of NG for Ammonia Absorption with Perforated Tray

1.0 0.9 SLOPE= -02382 0.8 _-, G 0.7 2co LIQUID RATE N 2 0 8 GPM Ol 16 GPM 0.4- 24 PM 0.3 2 3 4 5 6 7 GAS VELOCITY, FT./SEC. Figure 44. Effect of Gas Velocity on Correlation of NG for Humidification with Valve Tray

1.2 li 1.01 SLOPE =-0.458 0.8 0.7 C; z o LIQUID RATE N i | l 2 "WEIR 3(WEIR fJ' I 1 8 GPM | lE 16 GPM a 0.4- A 24 GPM A V 32 GPM 0.3 1.0 2.0 3.0 4.0 5.0 6.0 7.0 GAS VELOCITY, FT./ SEC. Figure 45. Effect of Gas Velocity on Correlation of NG for Ammonia Absorption with Valve Tray

I.1 1.0.9 SLOPE= -0.459 LIQUID, RATE 0 H 2" WEIR 3 WEIR 0 8 GPM ~ 0.5 El 16 GPM l A -24 GPM A 0.4 0.3 I 1.0 2.0 3.0 4.0 5.0 6.0 GAS VELOCITY, FT./SEC. Figure 46. Effect of Gas Velocity on Correlation of NG for Ammonia Absorption with Perforated Tray

-136Comparison with Results of Previous Investigators The data that can be most readily compared with that obtained in the present investigation is that of Warzel(66) and Ashby(9) who, using bubble cap trays, studied ammonia absorption and humidification in the same column used by the author. Begley(ll) used the above data in addition to his own to obtain the correlation previously given. He correlated NG in terms of gas holdup and gas velocity for each system, and then related the value of the coefficients to the physical properties of the systems. Figures 47 and 48 show the comparison between the author's data and Begley's correlation of Warzelis ammonia absorption and desorption data. The correlation was obtained by a least square fit of the data in a manner similar to that used by the author. The correlation fits the valve tray data fairly well for the data taken at a weir height of 5-1/2 inches, but gives values of NG about 10 per cent high for the 2-inch weir data. The perforated tray data do not agree too well with the bubble cap correlation. The latter predicts values of NG about 10 per cent too high for the 3-1/2-inch weir data and about 30 per cent too high for the 2-inch weir data. Figure 49 shows the comparison between the author's humidification data and Begley's correlation of Ashby's data. As with the ammonia data, the comparison of the 3-1/2-inch weir data is not bad, but the 1-1/2-inch weir data fall about 15 per cent below the values predicted by the bubble cap correlation. As the deviation is almost constant for a given weir height, there arises the possibility of using a correction factor to relate

-1374 ~ O 2" WEIR E1 3 WEIR 3 - - z z 80.1 NG 7.67 (zZf-Z' U 0.496 AVERAGE ABSOLUTE DEVIATION = 8.8%/o 2 3 4 5 NG FROM CORRELATION Figure 47, Comparison of Ammonia Absorption Data with Valve Tray with Correlation for Bubble Cap Tray

-1384 0 2" WEIR El 3 WEIR -_j Ef w 2 0 0 0.72 -0.496 NG -7.67( Zf-Z) U AVERAGE DEVIATION =-28.8% I 2 3 4 5 NG FROM CORRELATION Figure 48. Comparison of Ammonia Absorption Data with Perforated Tray with Correlation for Bubble Cap Tray

-1395 0 I"WEIR El 3 WEIR E! J/~~ Now 1.(-.70.620 AVERAGE ABSOLUTE DEVIATION 11.9 x 0 I 2 3 4 5 NG FROM CORRELATION Figure 49. Comparison of Humidification Data with Valve Tray with Correlation for Bubble Cap Tray

-140the performance of other trays to that of bubble caps. The correction factor would be a function of the design and possibly other variables such as weir height, although the latter might be accounted for in the correlation of bubble cap data, Based on the author's data and Begley s correlations, typical correction factors are listed in Table XI. TABLE XI FACTORS TO RELATE PERFORMANCE OF VARIOUS TRAYS Multiplication Factor Tray Design Weir Height to be Applied to NG's for Bubble Cap Trays Valve 3-1/2 1.0 2 0.9 1-1/2 0.85 Perforated (7/8" holes) 3-1/2 0.9 2 0,7 The correction factor admittedly is a simplification of the situation and does not preclude the correlation of performance data from the various types of trays. However, it does give a method of estimating the performance of a particular tray design if some data is available. Figure 50 shows the comparison of the data obtained by West et al. (67) with the correlations for humidification with valve and bubble cap trays. The data were obtained with a 3-1/4 x 3-9/16-inch tray containing eighty-three 1/8-inch perforations spaced on 3/8-inch equilateral triangular centers. The active tray area was 0.077 square foot

-141 INITIAL LIQUID LEVEL 5L O 0.5 in. A I.0 in. VALVE TRAY CORRELATION * 0.5 in. BUBBLE CAP TRAY * I.0Oin. CORRELATION A.oin l3 0 0 I AVERAGE ABSOLUTE_5"2% -VALVE TRAY DEVIATION 16%- BUBBLE CAP TRAY 2 3 4 5 NG FROM CORRELATIONS Figure 50. Comparison.Sf Humidificatlon Data of West, Gilbert, and Shimizu(67) with Correlations for Valve Trays and Bubble Cap Trays

-142and the free area was 9.2 per cent. Their data show better agreement with the valve tray correlation than with the bubble cap correlation. It is suspected that the use of weir height as a correlating variable may be a prime reason for the closer agreement. Figure 51 shows the comparison of the data of Gerster et al.(1), with the valve tray correlation for ammonia absorption. The data were taken in a 24-inch diameter column containing forty-one 1-1/2-inch bubble caps on 2-1/2-inch square spacing. The bubble cap design is the same as that used by Warzel(66), Ashby(9), and Begley(ll). The data agree fairly well with the correlation at the lower weir heights, but at the higher weir heights the correlation predicts values of NG 10 to 20 per cent higher than those obtained experimentally. The deviations at the higher weir heights might be expected as a 3-1/2-inch weir was the highest used by the author.

-1430 I IN WEIR V 43,, V, 74 _ If 2 )b 3 V X 3C X 5 /.X z,v x w O 0 AVERAGE ABSOLUTE DEVIATION 13.9% 0.621 -0.458 0.287 I,I I P~2 3 4 5 NG FROM CORRELATION Figure 51. Comparison of Amnonia Absorption Data of Gerster et al. 1) with Correlation for Valve Tray

-144CONCLUSIONS The following conclusions can be drawn with regard to the performance of valve and perforated trays in humidification and ammonia absorption. 1. The Murphree vapor efficiency increases with an increase of weir height and an increase of liquid rate. 2. At a weir height of 3-1/2 inches, the Murphree vapor efficiency for a given liquid rate is almost independent of vapor rate if the tray is in the stable operating range. 3. At weir heights of 1-1/2 and 2 inches, the Murphree vapor efficiency decreases as vapor rate is first increased. As the vapor rate is further increased, the efficiency remains constant or increases slightly. 4. The number of individual gas phase transfer units can be correlated by the following equations Humidification, Valve Tray NG = 5%84(Zf-Zc)0'475 u-0.382 Zw0.183 (74) Ammonia Absorption, Valve Tray NG = 4.97(f- Zc)0.621 u-o0458 Zw0.287 Ammonia Absorption, Perforated Tray NG = 3672(zf-zc)0~650 u-0459 Z o.407 (76) 5. The inclusion of weir height as an independent variable improves the correlation over that obtained using the same form but omitting weir height.

-1456. Operation of a perforated tray in the region when the amount of liquid weepage is considerable results in lower efficiencies than obtained when operating in the stable region. 7, Performance of the valve and perforated trays can be estimated from present correlations for bubble cap trays. The estimation can be improved by application of a correction factor that is a function of the tray design and the weir height. 8. The weeping limit of the perforated tray is dependent primarily on the vapor velocity through the holes and the latter values are in the range of 30 - 40 ft/sec. These values have been reported previously for smaller holes, so the weeping limit appears to be essentially independent of hole diameter. 9, Liquid mixing with the perforated tray is greater than with the valve tray, but for either tray is not as large as produced by bubble cap trays, 10 The entrainment produced by the perforated tray is greater than that from the valve tray. This occurs because the vapor rising from the perforated tray has a much larger vertical velocity component than is present on the valve tray.

APPENDIX A ORIGINAL AND CALCULATED DATA -146

TABLE XII HUMIDIFICATION OF AIR WITH WATER USING VALVE TRAY WITH 1-1/2-INCH WEIR RUN NUMBER 1 2 3 4 5 6 7 8 9 10 11 12 13 14 WATER RATE Gallons per minute 8.0 6.0 8.0 8.0 8.0 6.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 Lb moles per minute 3.70 5.70 3.70 3.70 3.70 3.70 3.70 3.70 3.70 3.70 3.70 3.70 3.70 3.70 Temperature ~F, Tray Inlet 90.50 90.23 91.58 90.03 89.80 89.96 88.99 89.28 90.14 89.98 88.99 88. $6 90.01 $9.98 Temperature ~F, Tray Outlet 90.50 90.07 91.38 90.16 89.80 89.92 89.58 89.73 90.64 90.50 89.44 89.33 90.50 90.52 VAPOR FLOW THROUGH TRAY (Avg. Conditions) Lb moles per minute x 102 19.49 19.63 19.67 29.43 29.7~ 29.78 40.31 40.31 40.01 40.00 46.32 46.32 46.14 46.16 Velocity, ft o~r sec. 2.25 2.26 2.26 3.34 3.43 3.42 4.58 4.58 4.53 4.53 5.28 5.29 5.35 5.35 F Factor, up17 0.58 0.59 0.59 0.87 0.89 0.89 1.20 1.20 1.18 1.18 1.38 1.38 1.3~ 1.38 EQUILIBRIUM CONDITIONS ON TRAY! Liquid Temperature, ~F 90.50 90.15 91.48 90.11 89.80 ~9.94 89.29 89.50 90.39 90.24 89.22 89.10 90.26 90.25 ~-J Pressure, in Hg 30.22 30.45 30.50 30.63 30.90 30.90 31.51 31.51 31.61 31.61 31.26 31.16 30.90 50.91 Vapor Pressure, in Hg 1.4441 1.4215 1.4853 1.4260 1.4127 1.4189 1.3903 1.399~ 1.4391 1.4333 1.3881 1.3819 1.4342 1.4333! VAPOR COMPOSITION~ MOLE PER CENT Yo 1.995 1.34'3 1.325 2.499 1.198 1.112 1.024 1.016 1.230 1.195 1.052 1.015 1.196 1.184 y 4.476 4.324 4.449 4.376 4.168 4.202 4.073 4.137 4.210 4.203 4.097 4.147 4.332 4.339 ~1 4.779 4.639 4.870 4.656 4.572 4.592 4.412 4.440 4.553 4.534 4.440 4.435 4.641 4.637 MURPHREE VAPOR EFFICIENCY, PER CENT 89.1 90.4 88.1 87.0 88.0 88.8 90.0 91.1 89.7 90.1 89.9 91.6 91.0 91.4 NG 2.22 2.35 2.13 2.04 2.12 2.19 2.30 2.42 2.27 2.31 2.29 2.48 2.41 2.45! kGa, sec-1 20.19 23.36 20.66 21.38 21.57 22.08 27.17 27.43 22.87 23.12 25.66 28.32 28.38 27.71 HYDRAULIC DATA Pressure drop, in water 2.50 2.40 2.40 3.25 3.50 3.30 5.07 5.00 4.90 4.75 6.00 6.00 6.06 5.80 Froth height, in 4.6 4.4 4.5 5.5 5.5 5.5 6.1 6.3 6.7 6.8 7.1 7.0 6.8 7.1 Clear liquid height, in Position B 1.90 1.95 1.95 2.00 2.00 2.00 2.00 2.05 2.00 2.05 2.00 2.00 1.95 1.90 C 1.60 1.65 1.65 1.70 1.35 1.25 1.35 1.30 1. lO 1.10 1.40 1.40 1.20 i 45 D 1.65 1.70 1.75 1.65 1.55 1.60 1.55 1.60 1.50 1.65 1.50 1.50 1.50 1.40 E 1.80 1.90 1.90 1.90 1.90 1.95 1.95 l o 95 1.90 1.95 1.90 1.90 1.85 1.75 Gas contact time, sec. O.110 O~lO1 0.103 0.096 0.0984 0.0992 0.0847 0.0883 0.0993 0.0999 0.0892 0.0874 0.0849 0.0884

TABLE XII (CONTID) RUN NUMBER 15 16 17 18 19 20 21 22 25 24 25 26 27 28 29 30 512 WATER BATE Gallons per minute 8.0 8 0 16.0 16.o 16.0 16.o 16.0 16.0 16.0 16.0 16.o 16.0 24.0 24.0 24.0 24.0 24. 24 Lb moles per minute 3.70 5.70 7.40 7.40 7.40 7.40 7.40 7.40 7.40 7.40 7.40 7.40 11.10 11.10 11.10 11.10 11.1 11 Temperature'F, Tray Inlet 86.oo 86.oo 77.00 77.14 76.98 76.91 76.91 76.87 77.14 7.1 7.2 7.2 7.0 7.0 7.8 7.5 7.4 769 Teprtr F, Tray Orutlet 86.18 86.25 77.13 77.25 77.02 77.00 76.98 76.95 77.18 77.12 77.56 77.59 77.14 77.09 77.51 77.54 77.1 71 VAPOR FLOW THROUGH TRAY (Avg. Conditions) Lb moles per minute x 102 9.80 9.78 9.81 9.81 19.70 19.68 29.69 29.68 59.95',9.89 47.52 47.53 19.56 19.56 29.75 29.75 996 96 Velocity., ft pr sec. 1.09 1.09 1.05 1.05 2.09 2.08 5.17 5.17 4.19 4.19 4.97 4.97 2.6 20 3.11 5 11 1.8 10 F Gatr u/202 0.9 08 028 0.56 0.56 o.85 0.85 1.14 1.14 1.55 1.55 0.56 0.56 o 85 o 85 0.9 02 EQUILIBRIUM CONDITIONS ON TRAY Liquid Temperature,'F 86.09 86.12 77.07 77.20 77.00 76.96 76.95 76.90 77.16 77.15 77.29 77.56 77 07 77.05 77 24 77.45 77.0 70 Pressure, in Hg 51.07 51.07 51.41 51.41 51.65 51.62 51.59 51.59 51.81 51.77 52.24 -)2.24 51 96 51.96 52.15 52.15 50.4 04 Vapor Pressure, to Hg 1.2565 1.2571 0.9574 0.9409 0.9552 0.9340 0.9557 0 9318 0.9402 0.9587 0.9445 0.9528 0.9574 0.9568 0.9421 0.9495 0.55 097 VAPOR COMPOSITIOR, MOLE PER CENT Yo ~~~~~~~~2.050 2.056 1.156 1.161 1.258 1.508 0.958 0.951 0.868 0.867 0.756 0.758 1.014 1.012 o.963 0.958 1.5 168 yl 3.955 5.920 2.908 2.927 2.851 2.818 2.785 2.778 2.815 2.799 2.775 2.858 2.824 2.826 2.860 2.892 5.03.1 yi* ~~~~~~~4.o43 4.046 2.984 2.996 2.957 2.954 2.975 2.968 2.956 2.955 2.929 2.955 2.953 2.931 2.952 2.955 5.73.6 MURPHREE VAPOR EFFICIENCY, PER CENT 95.5 95.7 95.8 96.5 92.6 91.7 90.5 90.6 95.5 92.6 92.9 94.6 94.5 94.5 96.5 96.8 95.0 9. NG 5.10 2.76 5.17 5.29 2.60 2.49 2.56 2.56 2.70 2.60 2.65 2.95 2.87 2.90 5.51 5.46 5.0 55 k's, sec-1 21.68 18.55 14.81 14.85 19.05 17.70 20.95 20.74 25.51 22.75 22.62 26.26 15.96 15.58 16.05 17.28 15.9 145 HYDRAULIC DATA Pressure drop, in water 2.25 2.25 2.66 2.66 2.84 2.85 5.75 5.95 5.55 5.52 6.95 7.05 5.84 5.-70 6.35 6.60 5.0 51 Froth height, in 3.8 5.9 5.0 5.1 5.5 5.6 6.4 6.5 8.2 8.1 9.5 8.9 7.9 8.1 11.0 lo.8 5.. Clear liquid height, in Position B 1.95 1.95 2.40 2.40 2.50 2.50 2.70 2.70 5.10 5.00 2.95 2.90 3 50 5.50 4.00 4.00 2.0 29 C 1.90 1.90 2.25 2.25 1.95 1.95 2.00 2.05 2.55 2.50 2.55 2.50 2.75 2.75 5.20 5.25 2.5 25 D 1.95 1.95 2.55 2.55 2.20 2.20 2.25 2.50 2.50 2.40 2.50 2.20 2.90 2.90 3.40 3.4o 2.5 27 E 2 10 2.05 2.45 2.45 2.55 2.55 2.50 2.55 2.60 2.70 2.60 2.55 5.10 5.10 5.70 5.70 2.0 26 Gas contact time, sec. 0.145 0.150 0.214 0.222 0.158 0.141 0.112 0.114 0.115 0.114 0.117 0.112 0.206 0.214 0.206 0.200 0.1 029

TABLE XIII HUMIDIFICATION OF AIR WITH WATER USING VALVE TRAY WITH 3 1/2 INCH WEIR RUN NUMBER 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 WATER RATE Gallons per minute 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 Lb moles per minute 3.70 3.70 3.70 3.70 3.70 3.70 3.70 3.70 3.70 3.70 3.70 3.70 3.70 3.70 3.70 3.70 3.70 Temperature ~F, Tray Inlet 75.96 75.81 77.11 77.02 75.29 75.34 77.14 76.82 75.20 76.84 76.78 76.98 77.09 75.38 75.25 74.98 75.06 Temperature ~F, Tray Outlet 76.14 76.05 77.34 77.14 75.56 75.56 77.38 77.04 75.38 77.00 76.98 77.03 77.18 75.60 73.49 75.22 75.34 VAPOR FLOW THROUGH TRAY (Avg. conditions) Lb moles per minute x 102 10.34 10.34 19.86 19.86 19.96 19.94 29.10 29.08 29.35 29.67 29.56 39.46 39.43 39.79 39.78 49.43 49.42 Velocity, ft Der sec. 1.12 1.12 2.12 2.12 2.16 2.15 3.18 3.17 3.20 3.16 3.15 4.24 4.24 4.18 4.18 5.01 5.02 F Factor, UPG172 0.30 0.30 0.57 0.57 0.58 0.58 0.85 0.85 0.85 0.85 0.85 1.14 1.14 1.14 1.14 1.39 1.39 EQUILIBRIUM CONDITIONS ON TRAY Liquid Temperature, ~F 76.05 75.93 77.22 77-08 75.42 75.45 77- 26 76.93 74. 29 76.92 76.88 77.02 77-13 75.49 75.38 75.10 75.20! Pressure, in Hg 31.18 31.20 31.72 31.72 31.21 31.21 30.65 50.65 30.94 31.61 31.61 31.37 31.36 32.00 32.00 33.09 33.07 Vapor pressure, in Hg 0.9061 0.9028 0.9421 0.9374 0.8874 0.8883 0.9424 0.9331 0.8836 0.9340 0.9312 0.9358 0.9393 0.8895 0.8862 0.8788 0.8809 kO! VAPOR COMPOSITION, MOLE PER CENT 0.826 0.811 0.665 0.656 0.798 0.772 1.405 1.262 0.565 0.750 0.744 0.609 0.573 0.553 0.541 0.543 0.533 Yo Yl 2.862 2.851 2.861 2.822 2.768 2.746 3.028 2.990 2.793 2.903 2.861 2.878 2.880 2.690 2.687 2.587 2.594 2.906 2.894 2.970 2.955 2.843 2.846 3.075 3.044 2.856 2.955 2.946 2.983 2.995 2.779 2.769 2.656 2.664 Y~i MURPHREE VAPOR EFFICIENCY, PER CENT 97.9 97-9 95.2 94.2 96.3 95.2 97.2 97.0 97.3 97-7 96.2 95.6 95.3 96.0 96.3 96.7 96.7 NG 3.85 3.89 3.05 2.85 3.30 3.03 3.58 3.50 3.60 3.76 3.26 3.12 3.05 3.21 3.30 3.42 3.42 kGa, sec-1 15.65 15.81 17.71 16.37 20.45 18.73 23.93 23.15 24.85 25.92 21.71 23.66 22.48 24.58 24.54 26.29 25.72 HYDRAULIC DATA Pressure drop, in water 3.90 3.90 3.80 3.80 3.60 3.57 4.34 4.30 4.81 4.45 4.55 5.48 5.66 6.38 6.30 7.39 8.00 Froth height, in 6.5 6.5 7.1 7.1 6.8 6.8 8.2 8.3 8.1 8.1 8.3 9.3 9.5 9.5 9-7 10.6 10.7 Clear liquid height, in Position B 3.40 3.40 3.10 3.10 3.10 3.05 3.00 3.00 3.10 3.15 3.15 3.15 3.15 3.55 3.55 3.25 3.15 C 3.20 3.20 2.75 2.70 2.65 2.60 2.60 2.65 2.65 2.65 2.70 2.70 2.70 3.15 3.10 2.95 2.85 D 3.20 3.20 2.70 2.65 2.60 2.65 2.40 2.45 2.45 2.55 2.55 2.50 2.30 2.75 2.80 2.60 2.55 E 3.35 3.35 3.10 3.05 3.05 3.00 3.00 3.00 3.00 3.05 3.05 3.10 3.10 3.35 3.35 3.10 3.10 Gas contact time, sec. 0.246 0.246 0.172 0.174 O.161 0.162 0.150 0.151 0.145 0.145 0.150 O.131 0.136 0.131 0.135 0.130 0.133

— 150TABLE XIV A~e~O~mA ABSOR~'rION FaOM Ara BY WATER USINO VALVE TRAY wrrH 2-INCH WEIR RUN NUMBER 129 130 131 132 133 134 135 136 137 158 139 140 141 142 143 144 145 Gallons per minute 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 16.0 16.0 16.0 16.0 16.0 16.0 16.0 Lb moles per minute 3.70 3.70 3.70 3.70 3.70 3.70 3.70 3.70 3.70 3.70 7~40 7.40 7.40 7.40 7.40 7-40 7.40 Temperature ~F, Tray Inlet 76.5 76.5 77.2 76.8 76.8 77.2 76.8 76.8 77.2 76.6 77.2 76.8 77.0 77.2 76.8 77.0 77.0 Temperature ~F, Tray Outlet 78.2 77.9 79.9 79.5 79.5 79.9 79.0 79.2 78.4 77.9 78.6 78.4 78.3 78.6 78.1 78.4 78.6 AMMONIA FLOW Lb moles per minute x 102 1.17 1.17 1.93 1.93 2.07 2.07 1.91 1.91 2.02 2.02 2.07 2.06 2.02 2.00 1.91 1.89 1.90 Temperature ~F at blower suction Dry bulb 81.0 81.0 90.0 90.0 87.5 87.5 85.2 85.2 8~.0 82.0 87.5 87.5 84.0 84.0 80.1 80.1 83.1 Wet bulb 59.0 59.0 66.0 66.0 70.0 70.0 69.8 69.8 59.0 59.0 64.5 64.5 61.0 61.0 58.7 58.7 65.5 AIR-AMMONIA FLOW THROUGH TRAY (Avg. conditions) Lb moles per minute x lO2 9.65 9.64 19.54 19.52 28.97 28.69 38.94 38.82 49.77 49.40 49.02 49.09 39.15 39.07 29.41 29.53 19.39 Velocity, ft_.Der sec 0.99 0.99 1.95 1.93 3.07 3.04 4.08 4.07 5.04 5.00 5.05 5.05 4.12 4.11 3.05 5.06 2.00 F Factor, uo~/2 0.27 0.27 0.54 0.55 0.82 0.81 1.10 1.10 1.39 1.38 1.38 1.38 1.11 1.11 0.83 0.83 0.54 EQUILIBRIUM CONDITIONS ON TRAY Temperature, ~F 78.2 77.9 79.9 79.5 79.5 79.9 79.0 79.2 78.4 77.9 78.6 78.4 78.3 78.6 78.1 78.4 78.6 Pressure, in Hg 30.92 30.92 32.03 32.20 30.17 30.15 30.45 50.43 31.43 31.43 30.96 50.96 50.26 50.26 50.73 50.75 30.97 Henry's Law Constant, In Hg/mole fraction 31.20 50.77 32.60 32.27 32.27 32.60 31.77 31.93 31.27 50.77 31.44 31.27 31.12 31.43 50.93 31.27 31.43 LIQUID COMPOSITION, MOLE FRACTION x lO4 x2 0 0 0 0 0 0 0 0 ~ 0 0 0 0 0 0 0 xI 24.78 25.83 41.65 41.48 43.66 43.85 39.61.90 39.70.49 22.42 23.04 22.06 21.82 21.45 21.08 21.13 ~ -~ 193.3 198.8 190.8 193.3 149.1 147.5 116.5 115.2 107.3 110.2 83.13 82.96 95.02 93.98 109.5 107.5 144.7 VAPOR COMPOSITION, MOLE FRACTION x l04 Yo 1200 1203 972.1 973.3 701.8 697.9 480.2 482.3 402.6 405.0 410.0 409.9 506.9 505.7 639.4 636.5 965.8 Yl 195.0 197.8 194.2 193.7 159.5 159.4 121.5 120.9 106.8 107.9 84.42 83.79 97.72 97.61 110.2 109.4 146.9 25.00 25.71 42.39 41.57 46.70 47.41 41.32 40.82 39.49 59.64 22.77 23.27 22.69 22.66 21.59 21.45 21.44 Y~l MURPHREE EFFICIENCY, PER CENT Vapor, EMV 85.5 85.4 83.7 83.7 82.8 82.8 81.7 81.9 81.5 81.2 84.1 84.3 84.5 84.5 85.7 85.7 86.7 Liquid, EML 12.8 13.0 21.8 21.5 29.5 29.7 54.0 33.8 37.0 36.7 27.0 27.8 25.2 23.2 19.6 19.6 14.6 NUMBER OF TRANSFER UNITS NOG 1.99 1.98 1.85 1.85 1.79 1.79 1.72 1.73 1.70 1.69 1.85 1.87 1.89 1.88 1.97 1.97 2.06 NL 1.53 1.58 2.10 2.09 2.49 2.60 2.91 3.32 3.15 3.18 2.06 2.08 ].88 1.86 1.68 1.69 1.38 Nc. 2.06 2.05 1.95 1.95 1.91 1.90 1.84 1.83 1.84 1.82 1.98 1.99 2.00 2.00 2.07 2.07 2.15 GAS PHASE MASS TRANSFER COEFFICIENT k~a, sec-1 ll.06 9.96 15.21 14.61 16.91 17.56 17.42 18.66 18.62 18.64 15.55 16.17 15.62 15.79 15.53 15.63 13.39 LIQUID CONCENTRATION PROFILE, MOLE FRACTION x l04 xA 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 ~ 7.551 9.141 16.66 15.44 20.97 20.23 19.52 19.02 21.80 22.52 11.06 11.28 9.582.979 7.068 7.389.119 ~B xC 13.50 14.44 19.84 19.85 22.67 22.59 20.13 19.51 24.83 24.18 ll.81 12.03 10.58 10.65 9.005 8.800 8.081 xD 21.64 22.89 40.74 40.58 44.78 44.71 59.25 39.50 42.80 42.88 25.62 24.04 22.50 22.58 20.86 19.97 19.93 xE 27.54 29.20 41.45 41.39 42.22 42.47 38.86 37.80 40.18 40.39 22.5 4 22.42 22.23 22.20 21.37 21.15 21.79 xF 24.79 25.83 41.65 41.48 43.66 45.85 39.61 38.90 39.70 40.49 22.42 23.04 22.06 21.82 21.45 21.08 21.13 28.36 27.11 43.67 44.14 44.43 44.07 39.22 57.54 41.11 41.01 22.83 22.97 22.71 22.55 22.15 22.05 22.33 XG xH 29.53 27.51 43.33 43.96 45.71 44.80 39.77 58.71 41.17 41.29 22.97 23.27 25.04 22.79 22.50 22.20 22.96 HYDRAULIC DATA Pressure drop, in water 2.75 2.75 2.85 2.94 3.57 5.55 4.50 4.58 5.80 6.15 6.80 6.95 5.40 5.50 4.40 4.40 3.70 Froth height, in 4.5 4.8 5.1 5.2 6.1 6.0 7.1 7.0 7.8 7.7 lO.1 9.9 8.8 8.7 7.5 7.5 6.6 Clear liquid height, in Position B 2.45 2.50 2.40 2.35 2.55 2.50 2.35 2.40 2.50 2.50 3.25 3.50 3.50 3.25 3.15 3.20 3.20 C 2.50 2.35 2.10 2.10 1.95 2.05 1.95 2.20 1.95 1.95 2.45 2.50 2.40 2.40 2.45 2.50 2.60 D 2.25 2.35 2.10 2.10 1.95 2.05 1.90 2.20 1.70 1.75 2.35 2.35 2.55 2.50 2.80 2.75 2.90 E 2.40 2.40 2.35 2.50 2.25 2.50 2.20 2.35 2.25 2.20 3.00 3.05 3.00 3.00 3.10 3.00 3.10 Gas contact time, sec. 0.187 0.206 0.128 0.134 0.113 0.108 0.106 0.0985 0.0987 0.0975 0.127 0.123 0.128 0.126 0.133 0.133 0.161 Liquid contact time, sec. 6.54 6.77 6.04 6.04 5.61 5.89 5.53 6.52 5.25 5.32 3.45 3.49 3.56 3.52 3.77 5.77 3.95 Mixing Parameter C 1.44 1.55 1.67 1.59 1.92 1.86 1.97 1.96 2.22 2.25 1.97 1.96 1.77 1.70 1.49 1.54 1.41 mG/L = X 0.0263 0.0259 0.0537 0.0529 0.0857 0.0859 0.1098 0.1101 0.1338 0.1507 0.0675 0.0670 0.0544 0.0548 0.0400 0.0406 0.0266 ENTRAINMENT, MOLES LIQUID/MOLE VAPOR x 103........ 1.05 -- 5.88 -- 5.45 -- 6.98 -- 5.22 -- 4.12....

TABLE XIV (TONT'D) RUN NUMMER 146 147 148 149' 150 151 152 153 154 155 156 157 150 159 16o 161 162 WATER RATE Gallons per minute 16.o 16.o 16.o 24.8 24.0 24.0 24.0 24.0 24.0 24.0 24.0 32.0 32.0 32.0 32.0 32.0 32.0 Lb moles per minute 7.40 7.40 7.40 10.10 11.10 11.10 11.10 bib.1 11.10 11.10 11.10 14.00 14.80 14.00 14.00 14.80 14.8o Temperature'F, Tray Inlet 77.0 77.4 77.0 77.0 76.0 77.0 77.2 77.5 77.2 76.5 76.5 77.0 77.0 77.0 77.2 76.8 77.0 Temperature'F, Tray Outlet 70.6 78.3 77.9 77.9 77.7 78.1 70.4 78.6 70.3 77.5 77.5 77.7 77.7 77.9 70.1 77.5 77.7 AMMONIA FLOW Lb moles per minute x 102 1.00 1.16 1.16 1.17 1.17 1.91 1.87 2.03 2.07 1.77 1.77 1.16 1.15 1.92 1.89 1.72 1.69 AIR FLOW Temperature'F at blower suction Dry bulb 03.1 79.5 79.5 81.0 81.0 75.0 75.0 01.0 01.0 83.0 83.0 82.5 02.5 73.5 73.5 70.0 78.0 Wet bulb 65.5 58.5 58.5 70.5 70.5 63.0 63.0 66.5 66.5 62.0 62.0 72.5 72.5 54.5 54.5 50.0 58.0 100-AMMONIA FLOW THROUGH TRAY (Avg. conditions) Lb moles per minute x 102 19.29 12.59 12.58 11.85 11.81 24.59 24.57 36.81 36.92 47.83 47.29 8.99 9.96 23.54 23.50 33.71 33.52 Velocity, TO per see 1.98 1.33 1.33 1.22 1.22 2.54 2.54 3.87 3.88 4.71 4.66 i.o6 1.05 2.43 2.43 3.44 3.42 F Factor, up1/2 0.54 0.36 0.36 0.33 0.33 0.69 C.69 1.04 1.05 1.32 1.30 0.28 0.28 o.66 o.66 0.94 0.94 EQUILIRRIUM CONDITIONS ON TRAY Temperature,'F 78.6 78.3 77.9 77.9 77.7 78.1 78.4 78.6 78.3 77.5 77.5 77.7 77.7 77.9 78.1 77.5 77.7 Pressure, in Hg 30.97 30.13 30.14 30.78 30.78 30.79 30.79 30.30 30.30 32.30 32.25 30.03 30.03 30.78 30.78 31.19 31.17 Henry's Law Constant, In Hg/mole fraction 31.43 31.12 30.77 30.77 30.6o 30.94 31.19 31.43 31.11 30.43 30.43 30.60 30.60 30.77 30.93 30.43 30.60 LIQUID COMPOSITION, MOLE FRACTION x 104 02 0 0 0 4.932 4.855 6.861 7.322 7.909 7.832 6.734 6.849 11.09 11.05 17.49 17.47 15.64 15.31 X1 21.17 12.74 13.02 13.74 13.66 23.02 22.31 23.75 24.35 20.57 20.23 17.71 17.00 29.32 29.26 25.00 25.57 Xl* 1414.2 117.7 121.4 91.17 00.55 94.64 92033 75.25 78.01 59.98 59.92 84.98 81.96 77.87 76.67 52.52 53.71 VAFOR COMPOSITION, MOLE TRACTION x 104 Yo 964.4 859.7 859.8 877.8 878.6 817.0 739.4 531.5 544.o 359.4 358.2 1003 1024 774.3 770.3 487.4 482.2 1 l 46.4 121.6 123.9 91.14 90.02 95.10 93.53 78.05 80.09 56.51 56.53 86.59 83.52 77.04 77.04 51.24 52.73 Yl* 21.48 13.16 13.29 13.73 13.58 23.14 22.60 24.64 25.00 19.38 19.08 18.05 18.24 29.31 29.40 25.21 25.10 1 ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~~~~~~~~~V MURPFREE EFFICIENTY, FER CENT Vapor, EMV 86.8 87.2 86.9 91.0 91.2 90.9 90.1 89.5 89.4 89.1 09.0 93.0 93.5 93.5 93.6 94.4 94.0 Liquid, 100 14.7 10.8 10.7 10.2 10.3 1B.4 17.6 23.5 23.5 26.0 25.2 9.0 9.7 19.6 19.9 27.6 26.7 1700ER OF TRANSFER UNITS N(G 2.07 2.09 2.07 2.45 2.47 2.44 2.35 2.27 2.27 2.23 2.22 2.71 2.78 2.77 2.78 2.90 2.83 NL 1.36 1.15 i.o6 0.88 0.88 1.34 1.34 1.66 1.67 1.85 1.00 0.72 0.72 1.23 1.24 1.55 1.55 NG 2.16 2.17 2.15 2.53 2.55 2.55 2.45 2.39 2.38 2.35 2.33 2.79 2.86 2.88 2.89 3.03 2.95 GAS PHASE MASS TRANSFER COEFFICIENT WEa, sec-1 13.61 11.18 11.34 11.29 10.59 15.78 14.86 15.42 15.94 14.95 15.76 10.28 10.99 13.07 13.01 15.42 14.43 LIQUID CONCENTRATION PROFILE, MOLE FRACTION W 1O xA 0 0 0 4.932 4.855 6.861 7.321 7.909 7.832 6.734 6.849 1i.og 11.05 17.49 17.47 15.64 15.31 xB 6.799 2.771 2.009 6.465 6.414 11A54 11.67 13.48 13.66 11.31 11.73 11.84 12.10 19.49 20.02 17.00 17.62 RC 7.812 4.118 3.964 7.538 7.372 13.24 13.40 14.73 13.63 12.29 13.34 12.82 12.00 21.75 21.55 18.99 18.90 xD 19.54 11.53 11.97 11.52 11.46 21.55 21.04 22.87 23.57 18.32 19.71 16.52 16.30 28.88 28.76 25.4o 25.09 XE 21.88 12.78 13.26 13.76 13.74 23.64 22.33 23.74 24.39 20.29 20.51 17.59 17.91 29.39 29.29 26.13 25.63 xF 21.17 12.74 13.02 13.74 13.66 23.02 22.31 23.75 24.35 20.57 20.23 17.71 17.00 29.32 29.26 25.84 25.57 00 22.51 13.37 13.20 14.11 13.00 23.02 22.85 23.73 24.48 20.88 20.67 17.77 17.99 29.55 29.35 26.15 25.75 xH 22.78 14.34 14.34 15.06 15.09 23.59 23.09 24.17 24.00 21.07 21.01 18.78 18.85 29.72 29.71 26.46 26.10 HYDRAULIC DATA Pressure drop, in water 3.75 3.44 3.25 4.10 4.10 4.85 4.85 6.1R 5.00 7.10 7.20 4.00 4.70 5.60 5.75 6.70 6.80 Froth height, in 6.5 6.0 5.7 6.8 7.0 8.4 8.5 10.6 10.4 12.2 11.7 7.6 7.5 10.8 10.9 12.6 12.9 Clear liquid height, in Position B 3.15 3.10 2.90 3.80 3.70 4.00 4.10 4.15 4.20 4.30 4.30 4.50 4.50 5.10 5.10 5.40 5.60 C 2.60 2.00 2.55 3.4o 3.35 3.35 3.35 3.30 3.30 3.25 3.35 4.10 4.10 4.35 4.35 4.6o 4.50 D 2.85 3.00 2.80 3.60 3.60 3.60 3.60 3.50 3.60 3.40 3.40 4.20 4.30 4.40 4.5o 4.40 4.50 E 3.10 3.05 3.00 3.75 3.70 3.90 3.75 4.00 4.00 3.75 3.00 4.40 4.5o 4.70 4.70 4.70 4.80 Gas contact time, sec. 0.159 0.194 o.10 0.225 0.241 0.161 0.165 0.155 0.149 0.157 o.148 0.272 0.261 0.220 0.222 0.196 0.205 Liquid contact time, sec. 3.92 4.17 3.85 3.35 3.33 3.33 3.33 3.26 3.31 3.19 3.28 2.98 3.02 3.14 3.10 3.23 3.23 Mixing Parameter C 1.47 1.28 1.28 1.21 1.22 1.41 1.41 1.54 1.54 1.49 1.57 1.13 1.18 1.20 1.28 1.27 1.29 G/L = 1 0.0265 0.0176 0.0074 -0.0108 0.16 0.0223 0.0224 0.0344 0.0341 0.0406 0.0402 m.oo688 0.00686 0.0159 o.oi6o 0.0222 0.0222 ENTRAINMENT, MOLES LIQUID/MOLE VAPOR x 03 -- - -- -- - - 3.11 -- 13.8 -- 28.7 -- -- 7.41 -- -- 102.5

-152TABLE XV AMMONIA ABSORPTION FROM AIR BY WATER USING VALVE TRAY WITH 3-1/2-INCH WEIR RUN NUMBER 101 102 103 o104 105 106 107 108 109 110 111 112 113 114 WATER RATE Gallons per minute 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 16.0 16.0 16.0 16.0 Lb moles per minute 3.70 3.70 3.70 3.70 3.70 3.70 3.70 3.70 3.70 3.70 7.40 7.40 7.40 7.40 Temperature'F, Tray Inlet 76.5 75.9 76.1 78.2 75.4 78.4 77.2 77.0 77.4 77.2 75.7 76.8 77.0 76.6 Temperature ~F, Tray Outlet 79.0 77.4 77.9 79.7 77.4 79.9 78.6 78.3 78.4 78.3 76.6 77.9 78.4 78.1 AMMONIA FLOW Lb moles per minute x 102 0.503 0.501 1.76 1.75 2.11 2.09 2.11 2.11 2.13 2.13 1.16 1.17 2.08 2.08 AIR FLOW Temperature'F at blower suction Dry bulb 80.0 83.0 83.0 83.0 82.0 80.0 88.0 87.0 82.0 82.0 83.0 81.5 82.0 82.0 Wet bulb 61.5 58.0 55.0 56.0 57.0 57.0 60.0 61.0 57.0 57.0 58.0 56.5 63.0 63.0 AIR-AMMONIA FLOW THROUGH TRAY (Avg. conditions) Lb moles per minute x 102 11.17 11.16 20.01 20.77 28.97 29.51 39.23 39.58 47.07 46.98 9.52 9.62 19.31 19.24 Velocity, ft per sec 1.17 1.18 2.10 2.21 2.97 3.12 4.06 4.10 4.86 4.85 1.00 1.00 2.01 2.00 F Factor, upl/2 0.32 0.32 0.56 0.59 0.81 0.84 1.11 1.12 1.33 1.32 0.27 0.27 0.54 0.54 EQUILIBRIUM CONDITIONS ON TRAY Temperature,'F 79.0 77.4 77.9 79.7 77.4 79.9 78.6 78.3 78.4 78.3 76.6 77.9 78.4 78.1 Pressure, in Hg 30.35 30.13 30.38 30.05 31.02 30.23 30.77 30.75 30.81 30.83 30.33 30.74 30.63 30.61 Henry's Law Constant, In Hg/mole fraction 31.77 30.27 30.77 32.43 30.27 32.60 31.44 31.10 31.27 31.10 29.64 30.77 31.27 30.94 LIQUID COMPOSITION, MOLE FRACTION x 104 x2 0 0 0 0 0 0 0 0 0 0 15.01 15.16 0 0 x1 10.80 13.27 40.05 42.49 47.95 47.81 47.06 46.34 46.96 46.21 27.61 29.34 26.90 25.63 X* 47.07 50.28 128.4 109.0 113.5 107.3 92.32 93.87 84.12 85.91 95.96 91.43 94.29 94.34 1 VAPOR COMPOSITION, MOLE FRACTION x 104 Yo 465.0 483.9 881.9 818.3 711.1 699.6 519.7 516.9 446.8 437.9 1100 1156 1035 1035 y1 49.27 50.52 130.0 117.7 110.8 115.7 94.33 94.94 85.38 86.66 93.77 91.52 96.26 95.36 y* 11.31 13.33 40.57 45.86 46.79 51 56 48.08 46.86 47.66 46.62 26.98 29.37 27.47 25.91 MURPHREE EFFICIENCY, PER CENT Vapor, EMV 91.6 92.1 89.4 90.7 90.4 90.1 90.2 89.8 90.5 89.8 93.8 94.5 93.2 93.1 Liquid, EML 23.0 26.4 31.2 39.0 42.2 44.5 51.0 49.4 55.8 53.8 15.6 18.6 28.5 27.2 NUMBER OF TRANSFER UNITS NOG 2.50 2.56 2.28 2.41 2.37 2.34 2.34 2.30 2.38 2.30 2.83 2.95 2.73 2.73 NL 2.40 2.55 3.32 3.40 3.92 3.94 4.46 4.49 4.83 4.78 1.36 1.42 2.05 2.04 NG 2.59 2.64 2.38 2.53 2.49 2.48 2.49 2.44 2.54 2.45 2.91 3.04 2.84 2.83 GAS PHASE MASS TRANSFER COEFFICIENT isa, sec1 14.90 15.25 16.26 19.25 19.30 19.50 19.43 19.22 20.28 18.92 11.05 11.10 16.60 15.36 LIQUID CONCENTRATION PROFILE, MOLE FRACTION x 104 "A 0 0 0 0 0 0 0 0 0 0 15.01 15.15 0 0 "B 8.744 6.943 24.77 23.73 29.96 33.03 33.63 27.44 34.10 33.75 17.62 18.29 10.75 11.53 "C 11.32 8.819 27.07 25.58 32.98 34.76 36.35 35.27 35.65 34.48 20.78 20.36 14.20 14.10 ~~~~~xD ~~11.67 12.10 39.62 42.78 48.58 47.27 48.26 48.28 48.52 47.94 26.54 26.77 26.16 25.78 xE 12.45 12.36 38.93 38.61 48.45 48.12 46.82 46.05 46.53 45.64 28.12 29.08 27.06 25.32 F m10.81 13.27 40.05 42.49 47.95 47.81 47.06 46.34 46.96 46.21 27.61 29.34 26.91 25.63 fG 8.719 13.15 40.87 41.42 48.77 48.43 47.13 46.21 46.76 45.84 28.06 29.34 24.38 23.79 XH 13.30 12.50 43.18 41.32 47.78 47.91 47.45 46.67 46.87 45.99 29.73 29.83 25.11 25.71 HYDRAULIC DATA Pressure drop, in water 3.80 3.96 4.16 3.90 4.80 4.90 5.90 5.95 7.00 7.00 4.75 4.85 5.10 5.20 Froth height, in 5.7 5.9 6.9 6.7 7.7 7.8 9.2 9.2 10.2 10.4 7.2 7.5 8.2 8.5 Clear liquid height, in Position B 3.50 3.70 3.55 3.55 3.65 3.60 3.70 3.70 3.60 3.70 4.30 4.55 4.50 4.60 C 3.30 3.45 3.20 3.20 3.05 3.00 3.00 3.00 3.00 3.00 4.00 4.25 4.00 4.00 D 3.20 3.45 3.25 3.25 3.15 3.10 2.90 2.90 2.75 2.70 4.10 4.20 4.15 4.15 E 3.35 3.50 3.40 3.40 3.50 3.40 3.50 3.50 3.45 3.50 4.25 4.30 4.35 4.40 Gas contact time, sec. 0.174 0.173 0.146 0.131 0.129 0.127 0.128 0.128 0.125 0.130 0.264 0.274 0.171 0.184 Liquid contact time, sec. 9.34 9.92 9.27 9.27 8.91 8.77 8.48 8.48 8.27 8.19 5.82 6.07 5.86 5.86 Mixing Parameter C 5.24 2.10 2.62 2.26 2.67 3.23 3.50 2.45 3.65 3.71 1.26 1.28 1.66 1.82 mG/L = k 0.0316 0.0303 0.0548 0.0606 0.0764 0.0860 0.1083 0.1082 0.1291 0.1281 0.0126 0.0130 0.0266 0.0263 ENTRAINMENT, MOLES LIQUID/MOLE VAPOR x 103 -- -- -- 1.98 3.73 -- 5.50 5.32 9.64 9.57 -- -- 1.78

TABLE XV (CONT'D) RUN NUMBER 115 116 117 118 119 120 121 122 123 124 125 126 127 128 WATER RATE Gallons per minute 16.0 16.0 16.0 16.0 24.0 24.0 24.0 24.0 24.0 24.0 32.0 32.0 32.0 32.0 Lb moles per minute 7.40 7.40 7.40 7.40 11.1 11.1 11.1 11.1 11.1 11.1 1.8 11.8 14.8 14.8 Temperature'F, Tray Inlet 76.5 76.4 77.0 76.6 77.0 76.7 77.9 77.4 77.0 77.2 77.0 77.7 76.6 76.5 Temperature'F, Tray Outlet 77.9 77.7 78.3 78.1 77.7 77.5 79.2 78.6 77.9 78.1 77.7 78.3 77.5 77.4 AMMONIA FLOW Lb moles per minute x 102 2.13 2.13 2.07 2.07 1.15 1.14 2.04 2.04 1.85 1.84 1.15 1.15 1.90 1.89 AIR FLOW Temperature'F at blower suction Dry bulb 87.0 87.0 87.0 85.0 80.0 80.0 82.5 82.5 80.0 80.0 85.0 85.0 79.0 79.0 Wet bulb 62.0 62.0 62.0 60.0 64.5 64.5 65.0 65.0 60.0 60.0 63.0 63.0 58.0 58.0 AIR-AMMONIA FLOW THROUGH TRAY (Avg. conditions) Lb moles per minute x 102 29.15 29.09 34.29 34.92 9.47 9.44 19.40 19.05 30.12 30.04 9.727 9.913 19.44 19.08 Velocity, ft per sec 3.01 3.00 3.53 3.68 1.02 1.01 2.04 2.00 2.98 2.98 1.04 1.06 2.01 1.97 F Factor, upl/2 0.82 0.82 0.96 0.99 0.27 0.27 0.55 0.54 0.83 0.83 0.28 0.28 0.55 0.54 0 EQUILIBRIUM CONDITIONS ON TRAY Temperature,'F 77.9 77.7 78.3 78.1 77.7 77.5 79.2 78.6 77.9 78.1 77.7 78.3 77.5 77.4 Pressure, in Hg 30.86 30.85 30.94 30.32 29.64 29.64 30.38 30.38 32.15 32.10 29.86 29.85 30.75 30.75 Henry's Law Constant, In Hg/mole fraction 30.77 30.60 31.11 30.93 30.60 30.44 31.94 31.44 30.77 30.94 30.60 31.10 30.43 30.26 LIQUID COMPOSITION, MOLE FRACTION x 104 x2~~ ~ ~~0 0 0 0 4.816 4.854 8.607 8.381 7.607 7.568 9.120 8.980 12.12 12.53 x2 01 25.39 25.37 25.29 24.91 13.65 13.46 25.74 25.52 22.86 22.63 15.82 16.24 23.58 24.37 x1 73.92 74.26 65.63 61.46 71.20 66.11 70.29 71.96 48.79 49.62 55.76 56.21 50.62 54.38 VAPOR COMPOSITION, MOLE FRACTION x 104 697.8 700.9 602.2 572.5 1114 1086 1015 1036 599.0 604.0 1046 1070 916.9 952.4 Yj51~~~ ~73.70 73.66 65.99 62.69 73.51 67.90 73.90 74.47 46.70 47.83 57.14 58.56 50.09 53.52 Yl 25.32 25.16 25.43 25.42 14.09 13.82 27.07 26.41 21.88 21.81 16.21 16.92 23.33 23.98 MURPHREE EFFICIENCY, PER CENT Vapor, EMV 92.8 92.8 93.0 93.2 94.6 95.0 95.3 95.2 95.7 95.5 96.0 96.0 9.0 96.8 Liquid, EML 34.4 31.2 38.5 40.5 13.3 14.0 27.8 27.0 37.0 35.8 14.4 15.4 29.8 28.3 NUMBER OF TRANSFER UNITS ~~~~~~~~NOG ~2.66 2.67 2.68 2.71 2.97 3.04 3.10 3.10 3.18 3.14 3.28 3.29 3.55 3.50 NL 2.51 2.51 2.76 2.79 1.08 1.11 1.67 1.67 2.05 2.06 0.98 0.97 1.45 1.43 NL NG 2.79 2.79 2.81 2.85 3.05 3.12 3.22 3.21 3.31 3.27 3.36 3.37 3.68 3.61 GAS PHASE MASS TRANSFER COEFFICIENT k's secl 16.34 16.06 16.01 17.99 10.34 11.07 13.43 12.82 15.59 15.86 11.36 10.76 14.67 13.64 k~a, seeLIQUID CONCENTRATION PROFILE, MOLE FRACTION x 104 A0 0 0 0 4.816 4.854 8.607 8.381 7.607 7.568 9.121 8.979 12.12 12.53 xB 13.41 14.12 14.12 13.27 8.081 6.893 14.39 13.99 13.83 13.39 10.31 9.967 15.35 16.03 15.51 15.51 16.41 15.35 9.470 7.981 17.11 16.48 16.46 16.27 11.07 11.19 17.32 17.73 xD 25.62 25.93 25.78 25.33 10.51 10.73 25.82 25.52 22.82 22.40 14.70 14.61 21.83 22.78 01 25.28 25.32 25.21 24.84 13.97 13.52 25.64 25.63 22.67 22.65 15.82 15.82 24.18 24.50 XE xF 25.39 25.37 25.29 24.92 13.65 13.46 25.74 25.52 22.86 22.63 15.82 16.24 23.58 24.37 xG 25.63 25.63 25.24 24.91 14.07 13.77 25.69 25.71 22.94 22.79 16.15 16.01 23.91 24.64 25.82 25.82 25.79 25.29 14.87 14.94 26.13 26.20 23.36 23.26 16.69 16.82 24.77 25.13 XH HYDRAULIC DATA Pressure drop, in water 5.86 5.88 6.45 6.30 5.42 5.30 5.90 6.05 6.95 7.75 6.18 6.15 6.65 6,83 Froth height, in 10.1 10.2 11.1 10.9 8.1 8.1 10.8 11.0 12.4 12.2 9.4 9.6 11.8 12.0 Clear liquid height, in Position B 4.60 4.60 4.65 4.65 4.97 5.10 5.50 5.45 5.50 5.50 6.00 5.90 6.30 6.20 C 3.90 3.90 3.90 3.90 4.60 4.95 4.90 4.90 4.70 4.75 5.75 5.60 5.70 5.65 D 4.00 4.00 4.00 3.95 5.00 5.00 5.00 5.10 4.90 4.90 5.70 5.65 5.80 5.80 E 4.40 4.40 4.50 4.40 4.90 5.05 5.30 5.35 5.20 5.20 5.90 5.80 6.00 5.90 Gas coatact time, sec. 0.170 0.174 0.176 0.159 0.295 0.282 0.239 0.250 0.212 0.206 0.296 0.313 0.251 0.265 Liquid contact time, sec. 5.68 5.68 5.68 5.64 4.60 4.77 4.74 4.79 4.60.62 4.11 4.04.13.11 Mixing Parameter C 2.12 2.26 2.26 2.14 1.59 1.31 1.51 1.49 1.69 1.63 1.22 1.16 1.39 1.42 mG/L= X 0.0393 0.0390 0.0466 0.0481 0.00881 0.00873 0.0184 0.0178 0.0260 0.0261 0.00674 0.00698 0.0130 0.0127 ENTRAINMENT, MOLES LIQUID/MOLE VAPOR x 1o3 11.93 -- 15.16 -- -- --.03 70.2 -- -- -- 20.

TABLE. XVI AMMONIA ABSORPTION FROM AIR BY WATER USING PERFORATED TRAY WITH 2-SNUB WHIR BEN NURNEB 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 220 22 WATE RATE Ga los per inute 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 16.0 16.o 16.0 16.0 16.o 16.0 06.0 16.0 24.0 24.0 24.0 24.0 2A.o 24. 1.0 mols~ per minute 3.70 3.70 3.70 3.70 3.70 3.70 3.70 3.70 7.40 7.40 7.Ao 7.40 7.Ao 7. 40 7.40 7.Ao 11.10 11. 10 11.10 41.10 11.10 11.1 TepratuFreF'F, Tray In-let 76.9 76.8 76.6 76.9 77.1. 76.6 T6AT 77.2 76.9 77.0 77.4 77.0 77.0 77.0 77.0 77.3 77.0 77.5 76.8 77.0 77.1 77. TRBperatu0re'F, Tr-ay Ou~tlet 70.4 70.0 79.9 00.1 70.9 79.0 00.2 81.0 78.1 70.3 79.2 79.0 79.0 79.3 79.2 79.7 78.1 70.6 70.4 70.6 7R.6 70. AMMONIA FLOW Lb moesE per mnuteA. 102 1.16 1.16 1.95 1.95 1.95 1.92 2.00 1.99 1oil 1.13 1.78 1.77 1.99 1.90 2.12 2.11 1.10 1.15 1.75 1oAR 1.66 15 AIR FLOW Temperature'P Nt bowerE BsuctHon Sry bul0 00.0 80.0 93.1 93.1 92.5 92.0 85.5 05.5 00.5 00.5 00.0 08.0 94.5 94.5 90.7 90.7 80.5 00.5 86.0 86.0 95.0 95. Wet bulb8 69.0 69.0 73.0 73.0 70.5 70.5 73.5 73.5 72.0 72.0 67.5 67.5 76.5 76.5 75.5 75.5 71.5 71.5 73.0 73.0 78.5 78. AIR-AMMONIA FLOW THROUGH TEAT (Avg. cEondtioEB) Lb molsB per mnuBte x 12 9.96 9.94 23.20 23.17 36.10 35.80 49.56 48.55 10.27 10.24 24.33 24.23 36.77 36.47 49.04 49.73 10.31 10.28 22.97 22.96 35.86 35.8 Velocity, ft peB sc1.03 1.-03 2.38 2.38 3.04 3.Oo 4.79 4.64 1.08 1.12 2.50 2.49 3.68 3.65 4.96 4.95 1.09 1.09 2.44 2.44 3.72 37 P FactoB-, upl/2 0.28 0.20 0.65 0.65 1.03 1.02 1.35 1.31 0.29 0.30 0.60 0.60 1.02 1.01 1.38 1.37 0.29 0.29 0.65 0.65 1.01 10 EQUILIBRIUM CONDITIONS ON TEAT TemeraTtuIe,'F 70.4 70.3 79.9 86.1 79.9 79.3 80.2 81.0 78.1 78.3 79.2 79.0 79.0 79.3 79.2 79.7 70.1 70.6 78.4 7. 78.6 78.6 PreBseB, in Hg 30.75 30.77 31.1.6 31.1.6 30.1.2 30.12 33.05 33.47 30.16 30.16 31.03 31.03 31.08 31.8B6 32.05 32. 05 30.14 30.14 29.93 29.90 30.73 30.7 BHenry's Law Constant, In Hg/mole fracionB 31.27 31.11 32.60 32.76 32.60 32.10 32.93 33.60 30.93 31.12 31.93 31.77 31.77 32.10 32.10 32.43 30.93 31.43 31.27 31.43 31.43 314 1.IQ001 COMNPOSITION, MOLE FRACTION x10 4 x2 ~ ~ ~ ~~~~0 0 5 0 0 0 0 0 0 0 0 0 0 0 o 0 4.587 4.523 6.580 6.478 6.069 559 xi ~~~~~~~15.93 14.86 37.11 38.73 39.63 37.54 39.56 39.27 7.564 8.075 18.83 18.74 20.90 20.90 22.41 22.26 10.63 10.27 19.60 19.17 18.55 173 ER 209.6 209.7 203.0 201.9 134.4 134.1 186.6 105.7 163.1 157.6 142.0 14o.o 115.1 112.7 87.96 86.31 138.2 135.4 106.6 103.0 75.66 685 VAPOR COMPOSITION, MOLE FRACTION B 10S4 Yo ~~~~~~~815.4 793.3 813.7 815.3 532.6 526.7 395.2 397.3 738.7 806.8 717.4 715.2 521.3 518.7 400.0 394.8 786.4 033.0 717.1 697.3 437.4 405. 51 213.1 212.0 212.4 212.2 145.5 142.9 106.2 106.1 167.2 160.2 146.1 142.9 114.7 113.6 80.10 87.33 141.8 141.2 111.4 100.0 77.30 701 yi* ~~~~~~16.20 15.02 38.83 40.72 42.89 40.01 39.42 39.42 7.757 8.618 19.30 19.19 20.09 21.07 22.45 22.52 10.91 10.71 20.56 20.10 18.90 17.7 MERPHREE EFFICIENCY, PER CENT Vapor, 0MV 75.4 74.7 77.6 77.9 79.1 78.9 01.2 81.4 78.2 80.0 81.8 80.2 01.2 01.4 82.6 82.6 83.1 04.1 87.0 87.0 86.0 86. Liquid, ENS, 7.6 7.1 18.3 19.2 29.5 20.0 37.1 37.2 4.6 5.1 13.3 13.4 18.2 18.6 25.5 25.0 4.5 4.4 13.1 13.1 17.9 10. NOUMBER OP TRANSFER TRITE N80 1.43 1.41 1.53 1.54 1.58 1.57 1.69 1.70 1.55 1.64 1.74 1.76 1.70 1.70 1.76 1.76 1.81 1.88 2.07 2.07 1.99 20 N1. 144 1.40 2.33 2.25 2.76 2.67 3.05 3.09 0.80 0.91 1.46 1.53 1.66 1.72 2.10 2.06 0.74 0.77 1.23 1.23 1.48 15 N0 1.48 1.45 1.60 1.62 1.69 1.68 1.02 1.83 1.59 1.69 1.81 1.83 1.79 1.79 1.087 1.88 1.8B6 1. 92 2.15 2.15 2. 08 21 OHS PHASE 8000 TRANSFER COEFFICIENT HE, sec-l 7.00 8.31 11.42 10.78 12.96 12.46 14.37 13.80 8.65 9.36 11.45 11.35 12.53 12.49 13.85 13.96 8.83 0.96 11.47 12.14 11.20 117 LEQUID CONCENTRATION PROFILE, MOLE FRACTION B 1E 4 xA 0 0 0 0 0 0 0 0 0 E E 0 5 0 0 0 4.587 4.523 6.580 6.478 6.o69.9 xB 6.1.20 5.737 21.72 21.29 25.24 24.86 27.83 26.94 2.262 2.67E 6.849 7.283 11.26 12.13 1.3.01 1.4.32 6.222 5.903 1.0.83 1.1.03 11.02E 1.05 01 7.960 7.781 23.37 23.46 25.07 25.85 27.99 27.34 3.948 4.293 9.212 9.468 12.04 13.51 14.44 14.76 7.36E 7.142 12.80 12.83 13.20 12.3 XD 11.58 13.34 35.25 34.26 35.80 35.44 37.71 37.34 6.478 6.465 15.52 15.52 16.48 17.80 17.72 16.87 9.046 9.263 17.20 15.90 14.90 14.3 XE 16.61 16.76 37.54 36.36 37.90 36.70 39.83 38.81 8.113 7.973 18.64 18.83 20.71 21.04 22.10 22.86 l0.46 10.50 19.77 19.03 18.59 17.3 FR 15.93 14.86 37.12 38.73 39.63 37.54 39.56 39.27 7.564 8.075 18.03 18.74 20.90 20.92 22.41 22.26 10.63 10.27 19.68 19.17 18.55 17.3 xG ~~~~~~~18.08 15.81 40.55 38.79 39.04 38.04 4E.28 39.55 0.042 8.944 19.56 19.68 21.53 21.43 22.79 22.50 11.24 11.38 20.32 19.49 18.34 17.4 XH ~~~~~~~26.67 26.32 41.12 40.34 39.65 38.43 40.52 4~o.1 14.E9 14.12 20.09 2E.15 21.89 21.8E 22.86 22.73 14.37 14.08 2E.78 20.09 18.81 17.8 HYBRAULIC SATE PressueB dopR, in water 2.35 2.40 3.20 3.20 4.50 4.40 6.10 6.00 3.00 3.00 3.90 3.90 4.90 4.90o 6.60 6.70 3.60 3.60 4.85 4.80 5.7E0.7 PFrBtB height, in 4.7 4.2 6.1 6.3 7.9 8.0 9.1 9.7 4.9 5.0 7.3 7.5 8.6 8.7 10.5 10.4 5.9 6.1 8.8 8.5 11.4 11. Clear liquid height, in Position, B 2.10 2.1.0 2.25 2.30 2.20 2.10 2.10 2.05 2.70 2.75 3.80 3.00 2.80 2.86 2.90 2.90 3.30 3.35 3.70 3.75 3.90 4.0 C 2.10 2.00 2.00 1.95 1.80 1.70 1.60 1.70 2.40 2.60 2.30 2.55 2.10 2.10 2.10 2.00 3.00 3.20 3.10 3.30 2.90 31 0 2.10 2.00 2.20 2.10 2.00 2.00 2.80 2.00 2.60 2.55 2.80 2.80 2.50 2.70 2.80 2.80 3.30 3.40 3.50 3.30 3.30 32 2.15 2.15 2.35 2.30 ~~2.20 2.35 2.35 2.3 2.70 2.70 2.90 2.90 2.80 2.90 3.0 3.05 3.40o.5 37.8.0 37 GsE cBntact timet, sec. 0.210 0.174 0.140 0.150 0.130 0.135 0.127 Solo4 0.104 0.181 0.158 0.161 0.143 0. 144 0.135 0.135 0.210 0.215 0.187 0.177 0.186 018 Liquid contBct time,, Bec. 6.04 5.09 6.04 5.82 5.46 5.32 5.18 5.32 3.59 3.70 3.67 3.85 3.31 3.45 3.52 3.45 3.02 3.16 3.16 3.16 2.907.0 MBixig Parame~ter C 1.62 1.63 2.41 2.22 2.75 2.90 3.37 3.10 1.43 1.49 1.57 1.64 2.16 2.38 2.61 2.81 1.37 1.32 1.48 1.56 1.66.17 mG/L = 1. 0.0274 0.0272 0.8656 o.8658 0.1058 0.1034 0.1336 0.1317 0.0142 0.148 0.0338 0.0335 o.0495 O.0o496 0.0675 0.0680 0.00953 omo965 0.0216 0.0217 0.0330 003 ENTRAINMENT, MOLES 1.00100/MOLE VAPOR B 103 -- 5.13 5.65 - - 20.8 -- 29.5 -- 5.07 -- 3.47 11.35 -- 24.0 -- 2.964 - 3.56 -- -- 171

-'55AMMONIA ABSOOPTION FROAM AIR BY WATER USING PERFORATED TRAY WITH 3-1/2-INCH WEIR RON NUMBER 223 221 225 226 227 228 229 230 231 232 233 231 235 236 237 238 239 210 Ga~llons per minue 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 16.0 16.0 16.0 16.o 16.0 16.0 21.0 21.0 24.0 21.0 Lb moles1 per minute 3.70 3.70 3.70 3.70 3.70 3.70 3.70 3.70 7.40 7.40 7.40 7.40 7.10 7.10 11.10 11.10 11.10 11.10 TemperEatre'0, Tray Inlet 77.0 77.2 77.0 77.2 77.0 76.9 77.1 77.2 76.9 76.8 76.7 76.8 77.2 77.2 76.8 77.0 76.8 76.8 Tempeature'F, Tray Outlet 78.8 78.8 79.2 79.3 70.8 78.6 78.1 78.1 78.1 78.1 77.9 77.9 78.1 77.9 77.7 77.9 77.9 78.1 AMMONIA FLAW Lb moles per minute x 102 1.16 1.15 1i44 1.37 1.27 1.18 1.29 1.17 1.16 1.15 0.26 1.17 1.31 1.18 1.18 1.17 1.29 1.22 TMIR PMROW WMTWI1WARWE DrF bulR 9R.W 98.0 90.0 90.0 77.5 77.5 73.5 73.5 86.0 86.0 77.5 77.5 76.0 76.0 76.5 76.5 86.1 86.4 AMY bulb 77.8 77.8 73.5 73.5 69.5 69.5 62.0 62.0 72.0 72.0 67.5 67.5 61.5 61.5 65.0 65.0 71. 5 71.5 AIR-AMMONIA FLOW THROUGH TRAY (Av.g. condiionsM) Lb molMs per miWWteM x 102 9.84 9.80 24.19 24.45 36.94 36.89 19.12 19.09 1~I.06 10.02 21.23 21.18 37.16 37.12 10.49 9.93 21.51 21.18 Velocity, FE per sIR 1.03 1.02 2.55 2.54 3.83 3.82 5.06 5Nob 1.06 1.05 2.52 2.52 3.82 3.82 1.08 0.02 2.55 2.55 F FacWoW., 021/2 0.28 0.28 0.69 0.69 1.01 1.01 1.39 1.38 0.28 0.28 0.60 0.68 1.05 1.o4 0.29 0.28 0.69 0.69 08011100002 COMMOTIONS ON TRAY TemperIatre,'F 78.8 78.8 79.2 79.3 78.8 78.6 78.1 78.1 78.1 78.1 77.9 77.9 78.1 77.9 77.7 77.9 77.9 78.1 PAMAsWre, in Hg 30.60 30.60 30.67 30. 67 30.76 3E.76 31.00 31.01 30.33 30.33 30.56 30.57 30.98 30.97 30.92 30.99 30.53 30.51 HenAF's Law1 ConsantW, 0n Hg/moll fraWtion 31.62 31.62 31.93 32.10 31.62 31.43 30.93 30.93 30.93, 30.93 30.77 30.77 30.93 30.77 30.60 30.77 30.77 30.93 108001 COMMOSITION, MOLE TRACTION W 104 W2 0 0 E 0 C 0 C 0 0 0 0 0 0 0 5.025 5.097 5.240 5.054 Wi 17.88 10.06 32.02 30.74 27.32 25.11 27.58 24.98 00.51 10.19 14.96 13.71 15.20 13.87 11.99 12.12 15.72 11.73 xi ~~~~~~~132.6 133.7 96.55 90.14 61.82 6o.51 52.51 4ly.70 101.0 loo.4 58.15 53.86 4).23 10.68 86.92 87.28 17.68 11.65 VAPOR COMMOSITION, MOLE FRATION W 104 FE 747.4 825.6 569.1 512.1 335.1 3~2_.0 252.6 229.1 867.0 836.5 502.3 468.9 336.1 307.8 922.8 1863 502.1 172.7 Fl 137.0 038.1 1OE.5 91.36 66.63 61.86 52.39 17.53 103.0 003.1 58.55 54.21 13.16 10.12 86.o2 86.66 48.05 15.22 1 18.18 18.66 33.31 32.1E 28.08 25.96 27.52 21.09 10.72 10.39 15.06 13.86 15.18 13.78 11.86 12.33 15.84 11.92 MURPHREE 0FFICIENCT, FER CENT VapEr, 090 83.7 85.3 87.5 87.8 87.1 07.9 89.0 80.9 89.0 88.7 91.1 91.1 91.3 90.9 91.9 92.5 93.1 93.1 LiquiA, 890L 13.5 13.5 33.2 31.1 12.2 12.0, 52.5 52.1 10.1 10.1 25.7 21.5 35.2 341. 8.5 8.9 21.7 21.1 N02 1.85 1.95 2.10 2.13 2.09 2.13 2.20 2.20 2.21 2.22 2.11 2.11 2.15 2.12 2.55 2.61 2.71 2.71 NL 2.25 2.25 3.63 3.66 1.31l 1.11 1.5i 1.64 1.37 1.10 2.33 2.38 2.93 2.78 1.08 1.12 1.85 1.83 NG 1.89 2.00 2.19 2.22 2.20 2.2W 2.717 2.36 2.30 2.28 2.53 2.53 2.56 2.53 2.61 2.70 2.83 2.83 k'a, secI1 11.61 12.26 14.41 11.98 15.20 15.69 15.77 15.50 11.43 12.22 12.16 12.13 1.6 13.61 9.6 10.32 12.97 130 LIQUID CONCENTRATION PROFILE, MOLE TRACTION A 1041 WA 0 0 0 0 0 0 0 0 0 0 0 0 0 0 5.025 5.097 5.210 5S054 XB lo~~~~~~1.19 10.19 22.24 21.10 19.87 19.35 20.86 18.71 3.546 3.701 6.116 6.417 8.872 7.753 6.762 6.475 9.217 8.861 AC 12.55 12.59 23.67 23.09 21.13 20.01 21.75 19.17 5.226 5.210 8.211 7.983 10.16 9.088 7.666 7.710 10.71 10.31 xD 16.70 15.52 31.06 29.17 25.71 21.61 25.57 23.21 8.772 8.557 12.68 12.53 13'2 11.63 10.71 9.834 13.21 13.19 xE ~~~~~~~17.69 17.97 32.70 30.69 27.31 25.25 27.51 21.85 10.32 10.31 11.97 13.71 15.39 13.93 12.02 11.96 15.76 11.86 xF ~~~~~~~17.86 18.86 32.02 30.71 27.32 25.11 27.58 21.98 10.51 10.19 11.90 13.71 15.20 13.87.11.99 12.12 15.72 11.73 xG 17.86 17.89 31.10 31.13 27.13 25.87 27.55 21.95 10.77 10.86 11.89 13.86 15.05 13.87 12.00 11.87 15.82 11.64 EH 28.22 28.28 32.864 31.19 27.41 26.oo 27.71 25.18 11.59 11.36 15.12 14.1.o 15.16 14lol 15.52 14.64 16.11 14.92 HYDRAULIC 06TA Pressure drop, 0n water 3.55 3.60 4I50 1.10 5.45 5.b 7.70 7.30 4.4o 4.15 5.25 5.30 7.85 7.90 5.20 5.20 6.20 6.10 TRoth height, in 5.3 ~5.3 7.8 7.7 9.6 9.5 11.8 11.9 6.5 6.1 10.2 10.3 12.3 12.3 8.0 8.1 12.5 11.4 Clear liquid height, 10 Fosition B 3.4o 3.4o 3.50 3.60 3.30 3.30 3.30 3.20 1.20 4.20 4I50 4.50 4I50 1.50 4.9 1.90 5.30 5. 30 C 3.30 3.30 3.00 3.15 2.70 3.00 2.50 2.60 3.86 1.10 3.86 1.02 3.70 3.50 1.10 1.90 1.60 1.80 D 3.30 3.30 3.30 3.20 3.20 2.90 2.86 2.86 1.10 1.0o 4.0 4.30 1.30 I 4o1lo 1.86 4.o 5.02 1.70 E 3.10 3.30 3.50 3.50 3.10 3.10 3.20 3.20 1.20 1.20 4I50 1.10 1.50 1.30 1.90 1.90 5.10 5.10 Gas conEacE tNim, sec. 0.163 0.163 0.152 o.148 oils5 0.143 0.150 0.152 0.201 0.186 0.203 0.286 0.181 0.186 0.262 0;262 0.219 0.217 Liquid conEacE till, sec. 9.19 9.49 9.86 9.13 8.48 8.48 7.62 7.76 5.68 5.02 5.02 5.97 5.75 5.16 1.11 1.70 1.60 4.55 MWixig FIrIameter C 2.10 2.39 3.28 3.29 3.67 1.19 1.07 3.98 1.51 1.57 1.69 1.02 2.10 2.27 1.33 1.23 1.61 1.63 mG/L = 1 0.0275 0.0274 0.0689 0.8692 0.1026 0.1019 0.1333 0.1322 0.0139 0.0138 0.0330 0.0329 0.0501 0.8690 0.00935 0.8888 0.0223 0.0223 ENTRAINMENT, MOLES 108000/MOLE VAFOR A 103 -- 2.56 3.ol4 - 12.82 -- 4.614. 1.62 -- 6.68 -- 56.8 -- 1.05 -- 30.8 -

-156TABLE XVIII HYDRAULIC STUDIES WITH VALVE TRAY USING 2 INCH WEIR Liquid Rate Vapor Rate Pressure Drop Froth Height Clear Liquid Heightin gal/min u,ft/sec F Factor in H20 in B C D E 8.0 1.05 0.28 2.80 5.0 2.20 2.10 2.10 2.20 12.8 1.03 0.28 5.10 5.6 2.50 2.35 2.40 2.55 19.2 1.05 0.28 3.26 6.o 2.80 2.55 2__.70 2.80 22.4 1.00 0.27 5.60 6.6 3.10 2.75 5.00 5.10 30.4 1.00 0.27 4.40 7.8 4.0o 3.80 5.90 4.00 8.0 2.01 0.56 2.80 5.5 2.50 1.90 1.95 2.10 12.8 2.01 0.56 5.01 6.4 2.60 2.10 2.50 2.50 19.2 2.01 0.56 5.80 7.4 5.50 2.75 2.95 5.15 22.4 2.01l 0.56 4.45 9.0 4.05 5.50 5.60 5.80 30.4 1.98 0.55 5.65 11.5 5.20 4.5o 4.50 4.8o 8.0 5.08 0.84 3.40 6.1 2.15 1.75 1.65 2.05 12.8 3.05 o.83 3.80 7.5 2.70 2.10 2.2-0 2.50 19.2 3.05 0.83 4.70 9.6 3.60 2.90 5.10 5.50 22.4 5.02 0.82 5.40 11.2 4.30 3.50 3.70 4.00 50.4 5.05 0.85 6.60o- 5.70 4.90 4.80 5.10 8.0 4.06 1.12 4.65 7.5 2.20 1.75 1.60 2.00 12.8 4.o6 1.12 5.00 8.4 2.70 2.10 2.15 2.50 19.2 4.06 1.12 5.80 11.5 5.75 2.90 5.00 5.50 22.4 4.05 1.11 6.355- 4.40 5.50 3.60 4.00 30.4 4.00 1.10 7.55 — 6.10 5.00 4.80 4.8o 8.0 4.95 1.57 6.1o 8.0 2.15 1.75 1.60 2.00 12.8 4.97 1.57 6.55 9.7 2.70 2.15 2.00 2.50 19.2 4.95 1.57 7.20 12.5 5.50 2.70 2.75 5.00 22.4 4.95 1.56 7.75 — 4.70 5.80 5.80 4.3o 30.4 4.9o 1.55 9.10 — 5.70 4.50 4.5o 4.50

-157TABLE XIX HYDRAULIC STUDIES WITH VALVE TRAY USING 3 1/2 INCH WEIR Liquid Rate Vapor Rate Pressure Drop Froth Height Clear Liquid Heightin gal/min u,ft/sec F Factor in H20 in B C D E 8.o 0.79 0.21 5.78 6.4 3.6o 5.55 5.50 3)40 12.8 0.79 0.21 4.46 7.6 4.oo 5.95 3.8o 5.95 19.2 ~0.76 0.21 5.02 8.4 4.50 4.15 4o4.35 22.4 0.76 0.21 5.20 9.1 4.85 4.70 4.55 4.9o 50.4 0.74 0.20 5.50 10.1 5.50 5.55 5.50 5.50 8.o 1.05 0.28 3.8o 6.9 5.50 5.50 5.55 3.40 12.8 1.00 0.27 4.50 8.0 4.oo 3.90 5.85 5.90 19.2 1.00 0.27 4.95 9.4 4.70 4.60 4.4o 4.50 22.4 0.98 0.26 5.42 9.9 5.15 5.05 4.8o 4.90 3o.4 0.95 0.26 6.io 10.9 5.85 5.60 5.60 5.65 8.o 2.05 0.56 5.60 7.4 5.05 2.60 2.55 5.00 12.8 2.05 0.56 4.15 9.1 3.8o 5.30 3.55 3.65 19.2 2.05 0.56 5.20 11.2 4.8o 4.20 4.55 4.5o 22.4 2.05 0.56 5.80 12.5 5.45 4.75 4.90 5.10 30.4 2.02 0.55 6.90 15.5 6.50 5.90 6.00 6.10 8.o 5.05 0.85 4.20 8.5 5.05 2.60 2.50 5.10 12.8 5.00 0.85 4.95 10.5 5.75 5.20 5.20 5.70 19.2 2.98 0.82 6.15 12.8 5.00 4.50 4.50 4.60 22.4 5.00 0.85 6.60 -- 5.60 4.90 4.90 5'.20 30.4 5.00 0.85 8.10 -- 6.70 6.00 6.00 6.10 8.o 3.56 0.97 4.85 9.1 5.10 2.55 2.50 5.10 12.8 3.54 0.97 5.65 11.5 4.oo 3.55 5.50 5.80 19.2 5.51 0.96 6.60 15.5 5.10 4.4o 4.50 4.85 22.4 5.51 0.96 7.00 — 5.55 4.75 4.80 5-.i5 50.4 5.46 0.95 8.50 — 6.40 5.70 5.70 5.90 8.0 4.43 1.26 6.50 10.7 5.15 2.70 2.4-0 5.00 12.8 4.43 1.26 6.80 12.6 4.00 5.40 3.50 5.60 19.2 4.38 1.24 8.60 -- 5.50 4.8o 4.70 5.00

-158TABLE XX HYDRAULIC STUDIES WITH PERFORATED TRAY USING 2 INCH WEIR Liquid Rate Vapor Rate Pressure Drop Froth Height Clear Liquid Height,in gal/min u,ft/sec F.Factor in H20 in B C D E 8.o 1.00 0.28 2.45 4.4 2.20 2.10 2.10 2.50 12.8 1.00 0.28 2.75 4.7 2.40 2.20 2.50 2.40 19.2 1.00 0.28 5.16 5.6 2.80 2.50 2.80 2.90 22.4 1.00 0.28 5.60 6.5 5.50 2.90 5.20 5.50 30.4 1.00 0.28 4.30 7.6 4.00 3.5o 5.80 4.oo 8.o 2.05 0.56 2.75 5.8 2.10 1.90 2.00 2.10 12.8 2.05 0.56 3.10 6.7 2.50 2.10 2.50 2.50 19.2 2.05 o.56 3.90 8.2 3.50 2.70 3.00 5.20 22.4 2.05 0.56 4.55 9.8 5.90 3.3o 3.60 5.80 3o.4 2.05 o.56 5.60 12.2 5.00 4-.so 4.60 5.00 8.o 5.02 o.83 4.oo 6.3 2.10 1.70 1.80 2.00 12.8 5.02 o.83 4.40 7.8 2.50 2.00 2.20 2.40 19.2 5.02 o.83 5.15 9.5 5.40 2.60 5.00 3.1o 22.4 5.02 o.83 5.90 12.2 4.90 4.oo 4.30 4.60 50.4 5.02 o.83 6.30 -- 5.10 4.20 4.30 4.60 8.0 4.15 1.12 4.75 8.0 1.70 1.55 1.75 1.80 12.8 4.13 1.12 5.05 9.0 2.00 1.80 2.10 2.20 19.2 4.13 1.12 5.70 11.1 2.80 2.20 2.50 2.70 22.4 4.15 1.12 6.70 -- 5.70 4.60 4.80 5.so 50.4 4.15 1.12 7.20 -- 5.40 4.20 4.50 4.80 8.o 5.12 1.40 6.20 9.5 1.80 1.50 1.60 1.70 12.8 5.12 1.40 6.50 10.7 2.60 2.00 2.50 2.70 19.2 5.12 1.40 7.00 -- 5.10 2.20 2.50 2.90 22.4 5.12 1.40 8.3 - 4.20 5.00 3.40 4.oo 3o.4 5.12 1.40 8.1 — 4.20 5.00 3.40 4.00

-159TABLE XXI HYDRAULIC STUDIES WITH PERFORATED TRAY USING 3 1/2 INCH WEIR Liquid Rate Vapor Rate Pressure Drop Froth Height Clear Liquid Heightin gal/min u,ft/sec F Factor in H20 in B C D E 8.o 1.01 0.28 5.70 6.7 5.40 5.10 3.20 5.40 12.8 1.01 0.28 4.35 7.0 3.8o 3.40 5.60 5.70 19.2 1.01 0.28 4.70 7.7 4.50 4.00 4.20 4.3o 22.4 1.01 0.28 5.10 8.8 4.8o 4.4o 4.7o 4.8o 3o.4 1.01 0.28 16'.oo 10.7 5.50 5.00 5.50 5.60 8.o 1.99 0.55 3.60 7.6 5.20 5.00 2.90 5.20 12.8 1.99 0.55 4.45 9.1 3.8o 5.20 5.50 5.70 19.2 1.99 0.55 5.50 11.5 5.00 4.4o 4.60 4.8o 22.4 1.99 0.55 5.8o 12.5 5.40 4.70 4.90 5.20 30o.4 1.99 0.55 7.00 — 6.1o 5.40 5.8o 5.90 8.0 5.07 0.84 5.25 8.9 5.20 2.70 2.70 5.00 12.8 5.07 0.84 6.10 11.5 5.50 2.90 5.10 5.50 19.2 5.07 0.84 7.50 -- 5.20 4.40 4.70 5.00 22.4 5.07 0.84 7.90 — 5.60 4.60 5.00 5.20 30.4 5.07 0.84 8.80 - 6.20 5.40 5.50 5.80 8.o 4.09 1.10 5.60 10.6 2.90 2.40 2.60 2.80 12.8 4.09 1.10 6.50 15.0 5.40 2.60 5.00 5.20 19.2 4.09 1.10 8.50 -- 5.20 4.40 4.4.0 5.20 8.o 5.02 1.40 7.90 12.0 2.80 2.20 2.60 2.80 12.8 5.02 1.40 8.70 -- 5.80 5.00 5.50 5.90

-16oTABLE XXII DRY TRAY PRESSURE DROP FOR VALVE TRAY Gas Velocity F Factor Pressure Drop Number of Valves ft/sec inH20 Fully Open 1.20 0.52 1,40 5 1.40 0.38 1.65 3 1.69 0.45 1.55 4 1.96 0.55 1.96 4 2.21 0.59 1.84 5 2.79 0.75 2.68 5 2.22 0.60 2.06 5 2.45 o.66 2.31 5 2.66 0.71 2.56 5 5.14 o.84 2.92 6 2.91 0.78 2.47 6 2.08 0.56 1.40 6 2.50 0.62 1.50 7 3.34 ~~0.90 2.28 8 3.72 1.00 2.82 8 ~.96 1.06 5.22 8 5.82 1.06 2.76 8 4.11 1.10 2.85 9 4.72 1.27 5.75 9 5.05 1.55 4.20 9 5.55 1.44 4.78 9 2.72 0.75 1,28 9 4.68 1.26 5.70 9 4.60 1.25 3.4o 9 4.33 ~~1.17 5.05 9 5,,98 1.06 2.65 9

TABLE XXIII DRY TRAY PRESSURE DROP FOR PERFORATED TRAY Gas V.1ocity F Factor Pressure Drop ft/sec in H20 0.77 0.21 0.17 L.0l 0,28 0.25 1.25 0.354 0.355 1.52 0.42 0.45 1177 o.48 0O,52 1.98 0.55 0.62 2.51 0.69 0.90 2.99 o.83 1L27 5.55 0.97 i.65 4.00 1.11 2.25 4.43 1.25 2.75 s.oo 1.40 3.44

APPENDIX B

SOURCES OF EXPERIME~NTAL ERROR It'is almost impossible to determine the absolute error in the experiments conducted. However, the sources of possible error will Ibe discussed, and their effect on the results will be shown. The effect of an error on N0 will vary with the efficiency of the tray. For example, an experimental error causing a one-half per cent error in EGG will cause an error in NG that depends on the value of EGG. This can be seen in Table XXIV. In computing the values in Table XXIV, liquid phase resistance was assumed to be absent. TABLE XXIV ERROR IN NG CAUSED BY A ONE-HALF PER CENT ERROR IN EOGG EGG Error in NG, per cent 0.95 3.7 0.90 2.2 0.85 1.9 0.80 1.6 0.75 1.1 The possible errors that will influence the values of NG may be grouped into four classes: (1) errors in determination of the correct inlet and outlet gas compositions, (2) errors in the determination of the correct equilibrium composition of the gas above the test

-164Table XXV shows the error that would be caused by a one per cent error in yo Y1, and y*. The values are based on runs No. 10 and 152 where the plate vapor efficiency was 90,l%. TABLE XXV ERROR IN NG RESULTING FROM ERRORS IN yo, Y1, OR y* % Error in NG Resulting System from a 1% Error: Yo Y l Y* Air-Water 0.2 5.6 5o6 Ammonia-Air-Water 0.4 o. 4 0.2 It can be seen from Table XXV that the air-water system is more sensitive to gas composition errors than the ammonia-air-water system. This is to be expected since the difference between inlet and outlet concentration is considerably greater for the system containing ammonia. An error in y is almost self-compensating as it appears in both the numerator and the denominator in the expression for plate efficiency. However,, since yo is so much larger than either y1 or y*., an error in the latter terms is overshadowed by the size of yo. In the air-water system, this is not the case. The values of y1 and y* are much closer to yo so an error in the former terms will cause a larger error in plate efficiency and NG' Table XXVI shows the error that would be caused in N G by a ten per cent error in NL. In making this table, it was assumed that the

-165TABLE XXVI ERROR IN NG RESULTING FROM ERRORS IN NL mG % Error in NG L for 10% Error in NL o-oo8 0.1 0.,02 0.2 0.08 l.o 0.12 1.5 Thus, a large error in N L has a relatively small effect on N G, especially where the liquid phase resistance is smallest. In the determination of gas compositions, errors can arise from several sources. These depend on the particular sample, and for the equilibrium composition are: 1. Measurement of the average bulk liquid temperature. 2. Assumption that the liquid surface temperature was equal to the bulk temperature. 5. Vapor pressure or solubility data. 4. Influence of impurities. 5. Measurement of the pressure above the test plate. Ashby~g) discussed these sources for the air —water system and estimated the maximum error in 4* to be less than one per cent. For the ammoniaair-water system, items 1 and 2 above can be combined. The liquid flowing across the tray showed a temperature rise of from 1 - 20F in most

-166temperature. To compensate for this heating effect the equilibrium temp-. erature was taken to be the temperature of the liquid leaving the tray. It is estimated that the maximum error in 4* is less than two per cent f or the ammonia-air-water system. The errors in inlet and outlet gas compositions could be caused by: L. Weighing the drying tubes or analyzing the bubblers. 2. Failure of the drying tubes or bubblers to remove all of the solute. 3, Inaccuracy of the wet test meters. Ashby estimated the maximum errors in yo and y1 to be less than two per cent for the air-water system. For the ammonia-air-water system the errors should be about the same value. The error in NL would be caused by the application of the bubble cap correlation to other types of trays, or possibly by an error in the correlation itself. This is a minor correction as was shown in Table XXVI. Miscellaneous errors might arise from: 1. Measurement of liquid and gas flow rates. 2. Variation of gas composition with time. 15. Failure to obtain a uniform sample. 4. Entrained liquid in the outlet vapor sample. The fluid flow rates enter into the expression for N G only'in the ammoniaair-water, and they have only a slight effect. It is believed that the flow I- _ —_ _ —_ L - _- - - L -_ 1 rat mesurmens ae acurte nouh s tha an erro cause is -1 -

-167It was found that even for the duplicate runs the composition of the gas samples varied somewhat,, This variance was quite small and had a relatively minor effect as can be seen by comparing the experimental results. The problem of obtaining a unif orm vapor sample is one that arises in experiments on gas-liquid contacting apparatus. It is assumed that the turbulence on the tray is sufficient to completely mix the vapor. As the material balance over the tray closed within five per cent for all runs, it appears that the error caused by a non-uniform sample would be very small. Entrained liquid in the exit vapor sample would cause a very large error in the air-water system as the vapor is very close to saturation. It would be expected the entrainment would increase with increasing vapor rate. It was found that the reproducibility of the data was as good for high vapor velocities as for the low velocities so it appears that the entrainment was negligible. In the ammonia-air-water system entrainment would not have much effect as the ammonia in the entrained liquid is insignificant compared to the ammonia in the vapor sample. If all of the errors did exist and were additive, a large error in NG would result. This could be as high as 25 per cent f or the airwater system, and 5 per cent for the ammonia-air-water system. As the exit gas is close to equilibrium conditions in gas phase controlling systems, there is a possibility of a large error as NG is very sensitive to changes in the exit gas or equilibrium vapor compositions. This is

APPENDIX C

SOLUBILITY AND CALIBRATION DATA The ammonia solubility data used in this work were obtained from the survey made for the A.I.Ch.E. Tray Efficiency Program. (2) values listed in the following table are taken from the above survey and are based primarily on the data of Sherwood(57), Breitenbach(16) and Morgan and Maass (45). TABLE XXVII AMMONIA SOLUBILITY IN WATER AT LOW PARTIAL PRESSURES* Temperature Henry's Law Constant, H, UC- -'T'~ ~in Hg/Mole Fraction 20 68.o 23.07 22 71.6 25.62 24 75.2 28.46 25 77.0 29,95 26 78.8 51.,62 27 8o.6 55.25 28 82.4 34.96 29 84. 36 77 50 86.o 38.66 *For partial pressures of ammonia less than 10 mm Hg and liquid concentrations less than 1.5 mole per cent, Rotameter Calibrations Liquid rotameters were calibrated by weighing the water col-.

-170readings were converted to ammonia rates by Q = Qc P/P7 where Q = volumetric flow rate at given reading = calibrated volumetric flow rate at same reading = density at calibration conditions p = density at flowing conditions Wet Test Meter Calibrations The wet test meters were calibrated by passing a known volume of saturated air through one of them and comparing the known volume with the indicated volume. The air was obtained by forcing air from a five-gallon jug with water. The volume of air used was found by weighing the jug before and after testing. The two meters were then placed in series and the readings compared after passing a 4uantity of saturated air through them. Knowing the calibration of one meter and the ratio of the two, the calibration of the second was readily computed. TABLE XXVIII CALIBRATION OF ROTAMETER W70-402A/1(9) Water at 54 OF Scale Reading Water, gpm 20 6.38 40 12.77 60 19.14

-171TABLE XXIX CALIBRATION OF ROTAMETER 5601 D 1o038B1 (25) Water at 60 OF Scale Reading Water, gpm 19o0 6.20 34 5 11i 03 48,o 15.50 60.0 18.95 75.0 23.45 90.0 28.40 96.5 30.00 TABLE XXX CALIBRATION OF ROTAMETER V5-1200/1 cfm NH3 at 70~F Scale Reading and 30.00 in Hg 25.5 5.25 38.8 8.75 49.3 11.02 58.5 13.65 69.,5 15.8 79,1183 88,,8 20.49 89.0 22.69

-172TABLE XXXI CALIBRATION OF WET TEST METER H9SS Actual Indi cated Corre ction Volume, ft3 Volume, ft3 Factor 0o5740 0.5872 0.9775 0.5771 0.5886 O. 9805 O.6080 0.6237 0.9748 avg. 0.9776 TABLE XXXII CALIBRATION OF WET TEST METER J5SS Reading, ft3 Reading, ft3 Correction Factor Meter, H9SS Meter, J5SS Ratio for Meter J5SS 0~4949 0.4907 1o0085 0.9859 0.5037 0.4993 1o0085 0.9859 avg. 0.9859

APPENDIX D

SAMPLE~ CALCULATIONS The data from ammonia absorption run 115 will be used to show the methods used to calculate the results. l,, Vapor Sample Concentrations a, Inlet Sample HCl in bubblers = (35oo0 miL)(l.0486N) = 36.7010 meqi, NaOH to neutralize = (12.78 ml)(0.5461N) = 4.4232 me cp NH in sample = 32.2778 Humidity of air = 0.01009 mole water/mole dry air Wet Test Meter conditions T = 84.O0F P = 29.28 in Hg Vapor pressure of water = 1.1750 in Hg Mole fraction dry air = (29.28-1Ll750)/29.28 = 0.9599 Molar density = (29.28)/(2l.85) (544)=246.3xl0-5 lb moles/ft5 Measured volume = 0.4025 ft53 Meter factor =0.9859 Moles dry air in sample = (0.4025)(0.9599)(0.9859)(246,3xl05 95.82 x l0-5 Moles =water in sample 5=o946x1=(0-0l009)(93.82 x 105)=096 0 Moles ammonia in sample =(32.2778)/(454)(1) = 7.110 x l0Total moles in sample x l05 = 95. 82 + O0 9466 + 7.-110 = 101. 8766 7.110 =0.06979 mole fraction - 101.8766

-175b. Outlet Sample In the same manner as for the inlet sample are found: Moles dry air in sample = 95.35 x lO-5 Moles ammonia in sample = 0.7156 x lO-5 The outlet gas is assumed to be saturated with water at the temperature on the test tray. T = 77.90F P = 50.86 in Hg Vapor pressure of water = 0.9635 in Hg Yhl = (o,,9635)/30o,86 = 0.05122 mole fraction Total moles in sample x lO5 = (93-33 + 0.7156)/(1-0.03122) = 97.076 Yl= (0.7156)/(97y-o06) = 0,,007371 mole fraction 2. Liquid Sample Concentrations a. Blank Correction (Sample A) HCl in bottle = (5-oo ml) (1.0486 N) = 5.2430 meqi. NaOH to neutralize = (15.05 ml) (0.5461 N) = 5.2088 Correction for alkalinity of tap water = 0.0342 meq. b. Sample B HCl in bottle = (50o0)(l~o486) = 5.2450 meql. NaGH to neutralize = (4.33)(0.3461) = 1.4986 3.7444 meql. Less correction 0.0542 me c. NH in sample 3.7102

-176c. Other Liquid Sample Concentrations Other liquid sample concentrations are calculated'in the same manner. XF = 25-39 x 10- mole fraction Thus x2 = 0 x = 135,41 x lOe X,= 25.59 x lO5. Mixing Parameter C a =xl-x2 (P4) =(25-39 - 01soC (25.59 - 13.41)lo~ =2.12 4. Equilibrium Concentrations Henry's Law constant = 30J77 in Hg/mole fraction y*= Hx1l/P = (30.77)(25.39 x lO" 4)/ (30.86) = 25.21 x 10O4 mole fraction 1 X*= Py1/Hj = (50.86) (75.71 x 10O4)/ (30i77) = 75.95 x 10O4 mole fraction 5. Plate Efficiencies Yoy 697.9 - 25.21 -v lX2-* 257.59 - 252 ML xlx2 75.95 - 0 6. Liquid Flow Bate Rotameter reading = 50

-'777. Vapor Flow Rate Rotameter is calibrated in cfm for gas with a gravity of 0.877 at 600F and 14,,7 Psi (p = 0.06678 lb/ft3). Molecular weight of gas flowing in rotarneter (17) (0,o6979) + (18)(0,00929) + (2Z8.9)(o.92092) = 27,97 Pressure in rotameter = 51.71 in Hg Temperature in rotarneter = 102aJKF Density of gas = (31.71) (27.97)/(21.85) (562.7)= 0.07214 lb/ft3 Rotamneter reading = 120 Volumetric flow rate Q = 120 4J (o~o6678)/(0.07214)'- 115.5 cfrn Go = (ll5.5) (0-072l4)/(27.97) = 0.2977 lb moles/mmn This is also the flow rate beneath the test tray. G= G0 (l - yo - Yh.)/ (l - yl - Yh1) =1 (0.2977)(0c92092)/(0,96141) = 0~,2852 lb moles/ruin =Go+G1 0,2977 + 0.2852 = 0.2915 lb moles/min avg 2 2 8. Vapor Velocity The vapor velocity is based on the active tray area between the inlet downcomer and the splash baffle, 0.615 sq ft. U=(0.2915) (359)(29,92) (537.9)=301fse (60) (o,,615) (30o86) (49-27.1f/e 9. F Factor Molecular weight of gas above test tray (17)(0ooo7371) + (l8)l(o.O —l22) + (2.)(.64)= 28.47

-178(30.86) (28.22) 004ol/t ~avg =(21.85) (537.9) = 0040l/t F =ufNJp = (35,1) (0-041o)1/ -.8i8 10. Ammonia Balance on Ta NH5 Out _(Glyl+Lxl) =[(0.2852)(73.71lxi04)~(7.40)(25.59xli04)] NH in - __ __ __x2_ __ _ __ __4_ _ __ __ _ 3 ~(0y0 2 [(0.2977) (697.9x10O-)(7.40)(0)] = L005 11. Residence Times a. Gas Residence Time zf=10,,1 inches Zc = 5.95 inches (Zf-Zc) (10.1 - 5.95) 010sc G 12 u- = (12) (5. 01) =0.7se b. Liquid Residence Time t =Zc 12 LQ t (o. 95) (o.61 5) (7.48) (60) 5%68 sec L (1L2)(1L6.07 12,, Transfer Units a. Overall Gas Phase (i-Yj) NOG = 1/2 in -Y in (1-E OG) (59) Using EIAiV as EOG,9 NOG = 1/2 in (1-0o,06979) in (1 - 0. 928)= 2.665 b. Liquid Phase

-179DL = 8,,o4 x io-5 ft2/hr NL = (~554)(8.o4 x 1o-5)1/2(o,818)0_575 (5s68) = 2.513 c., Individual Gas Phase 1 1 +X (i-x)f (52) NOG NG NL (l-y)f HG (30-77) (0,2 91s) =_ 09 PX (30.86) (7.40) 009 = ~~(0.0393) [0 -25,39xl0-4] in 1- 0.06979 NG 2 -6 (.1)i(1 - 25.5-9Xl0-4 (2-513) in1 -0 )[73-717- 697.9110NG =2.785 15. Gas Phase Mass Transfer Coefficient kta = NG _ 2j785 - 16.34 sec1i G tG 0.170 Calculations for the humidification runs were in the most part identical to those for the absorption runs and only the methods that differed are shown,, 14. Vapor Sample Concentrations -Run 17 a. Inlet Sample Moles dry air in sample =121.05 x l0- Water absorbed = 0.1157 grams = 1.4158 x l0-5 lb moles Total moles in sample = 121.05 + 1.4158 = 122.4658 x l0-5 - 1.4158 -0.01156 mole fraction 0 122.4658 b. Outlet Sample

15. Equilibrium Concentration Liquid temperature = 77.10F Vapor pressure of water = 0.9574 in Hg Pressure on tray = 3i.41 in Hg 4j = (0-9374)/31.41 0.02984 mole fraction 16, Plate Efficiency E =E =O (o029o07 -0101156) 956 MV O (0.02984 -0.01156)=956 17. Individual Gas Phase Transfer Units NOG =NG = -in (1-E OG) (52) NG = -ln (1-0.956) = 5.171

NOMENCLATURE a interfacial area, sq ft/cu ft gas holdup. at interfacial area., sq ft/cu ft gas and. liquid holdup. a interfacial area., sq ft/cu ft liquid holdup. A constant in Equation (73). A1 function defined for Equation (17). A2 function defined for Equations (17) and (20). b constant in Equation (73). c constant in Equation (73). c concentration of solute'in liquid, lb moles/cu ft. c* concentration of solute in liquid in equilibrium with gas, lb moles/cu ft. cBM logarithmic mean concentration of non-diffusing component. C mixing parameter defined by Equation (14). C function in Equation (66). d constant in Equation (73). d differential operator. IDE eddy diffusivity, ft2/sec. DG gas phase diffusivity, ft2/sec. DL liquid phase diffusivity, ft2/sec. Bs bubble cap slot width. Ea apparent vapor plate efficiency in presence of entrainment. EML ~Murphree liquid efficiency. EMV ~Murphree vIapor efficiency.

-182EO liquid point efficiency exp (x) ex F F factor, u 4fGj, based on active bubbling area between inlet downcomer and splash baffle (0.615 sq ft). G molar gas rate, lb moles/hr. GM molar gas velocity, lb moles/hr-sci ft. hL vertical distance between bottom of bubble cap slot opening L ~and top of liquid flowing over weir. H Henry's Law constant,, atm/mole fraction, or in Hg/mole fraction. HO height of an overall gas phase transfer unit, ft. kG individual gas phase mass transfer coefficient, lb moles/hrsq ft - atm. kL individual liquid phase mass transfer coefficient, lb moles/ L ~hr - sq ft - lb moles/cu ft. k'a individual gas phase mass transfer coefficient based on gas G ~holdup, sec. k La individual liquid phase mass transfer coefficient based on liquid holdup, sec-1. KO overall gas phase mass transfer coefficient, lb moles/ hr - sq ft - atm. K' a overall gas phase mass transfer coefficient based on OG ~gas holdup, sec-1. KOL overall liquid phase mass transfer coefficient, lb moles/ hr - sq ft - lb moles/cu ft. ~~n natural logarithm. L molar liquid rate, lb moles/hr. LM molar liquid velocity, lb moles/hr - sq ft. m slope of the equilibrium curve, dy*/dx. M function defined for Equation (17).

-183A rate of mass transfer of component A, lb moles/hr - sqi ft. AGnme fidvda a hs rnfruis NL number of individual liqui phase transfer units. N number of overall gas phase transfer units. OG NOL number of overall liquid phase transfer units. p partial pressure of solute in gas phase, atm. P* ~partial pressure of solute'in gas in equilibrium with liquid, atm. PBM ~logarithmic mean partial pressure of non-diffusing component ~~BM in the gas phase. P total pressure, atm. Q ~~volumetric flow rate, cu. ft/min. QB ~fraction of liquid rate splashing upstream. QF ~fraction of liquid rate splashing downstream. R ideal gas law constant, atm - cu. ft/lb mole - OR. S length of plate, ft, tG gas residence time, sec. tL liquid residence time, sec. T absolute temperature,, OR. u linear gas velocity through column, based on active bubbling area between inlet downcomer and splash baffle (0.615 sq ft). w dimensionless distance along plate. wB omlzddsac fusra iudslsig BF normalized distance of upwstream liquid splashing. x mole fraction solute in liquid. X* ~mole fraction solute in liquid in equilibrium with vapor.

y mole fraction solute in vapor., Y* ~mole fraction solute in vapor in equilibrium with liquid. Y1 ~ mole fraction solute in vapor, taken in a given vertical plane. y ~mole fraction solute in vapor in equilibrium with liquid, taken in a given vertical plane. z length of element through which diffusion occurs, ft. Z vertical distance through liquid or froth, ft. Z clear liquid height, in. or ft. Zf froth height, in. or ft. function in Equation (69). mixing parameter defined by Equation (19). function in Equation (69). Y ~mixing parameter defined by Equation (16). C entrainment, moles liquid/mole vapor. X ~~mGM/ILM, slope of equilibrium line/ slope of operating line. viscosity, centipoises or lb/ft - hr. CP ~functional notation. p density,, lb/cu ft. PML molar liquid density, lb moles/cu ft. CY surface tension Sub scripts avg average value c refers to calibrated value

-185G gas phase i at the interface. L liquid phase. n stream leaving plate n. 0 entering plate 1 from below (gas). 1 on or leaving plate 1. 2 entering plate 1 from above (liquid),,

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