THE UNIVERSITY OF MICHIGAN CUPOLA PERFORMANCE: THE POTENTIAL FOR OIL INJECTION R. D. Pehlke June, 1965 IP-708

ACKNOWLEDGEMENT The contribution of IBM 7090 time by the University of Michigan Computing Center is gratefully acknowledged. ii

TABLE OF CONTENTS Page ACKNOWLEDGEMENT o o. o.. o o.. o o o.. o o.............................. o ii LIST OF FIGURESo. o o.. o o o oo........o............ o iv INTRODUCTION o o o o..................................................... o 1 THE THERMOCHEMICAL MODEL..... o.. o...................... o o o.........o o o.. 1 PREDICTED CUPOLA PERFORMANCE o.......o..... o e oo.. o o...... o 2 TUYERE ZONE TEMPERATURE.................................,........ 3 USE OF BURNERS.................................. 4 CONCLUSION o........................... o........................ 4 sY..o............................................. 4 REFERENCES.......................................... 5

LIST OF FIGURES Figure Page 1 Calculated Effect of Fuel Oil Injection on Coke Requirement...o............................... 7 2 Calculated Effect of Simultaneous Oxygen Enrichment and Fuel Oil Injection on Coke Requirement,...o.... 8 3 Calculated Effect of Fuel Oil Injection on Melting Rate.................................................. 9 4 Calculated Effect of Simultaneous Oxygen Enrichment and Fuel Oil Injection on Melting Rate................ 10 5 Calculated Adiabatic Flame Temperature in Tuyere Zone of Cupola for Various Levels of Blast Enrichment. 11 iv

INTRODUCTION Fifty years ago Bradley Stoughton presented a sumnmary of his operating experience with the oil-fired cupola. This early exploration provided a clear cut description of some of the limitations imposed on cupola operation with fuel oil injection; the limitations were seen to manifest themselves in a decreasing temperature in the tuyere zone unless the oil was presented to the tuyere zone at high temperatures as a partially or fully combusted fuel-air mixture. Stoughton's study indicated that combustion chambers in or directly behind the tuyere could provide a means for utilization of fuel oil in the cupola. A number of investigations have been carried out in an attempt to replace all or part of the cupola coke charge with fuel oil. It has been observed that the use of oil injection in normal cupola iron melting, because of the endothermic nature of the initial combustion reactions, requires either a hot blast or oxygen enrichment. The utilization of oil alone will decrease the tuyere zone temperature''7 and results in operating difficulties. However, adoption of hot blast operation and the availability of low cost oxygen can facilitate a satisfactory cupola operation, taking advantage of oil injection. The challenge of cupola operation with fuel oil injection has been placed before the foundry industry for some time. The purpose of the present study is to describe the operating conditions which can be realized through the use of fuel oil as a cupola injectant, and thereby provide a basis for defining the potential economies associated with fuel oil injection. THE THERMOCHEMICAL MODEL Performance of the cupola using oil injection and simultaneous oxygen enrichment with hot blast has been evaluated in a computer study using a previously discussed thermochemical model.'9 This model is based on a mass and energy balance 10 for the furnace and employs a kinetic relationship which is based on wind rate. The model utilizes prior furnace performance data to establish a standard reference for the operation of a given furnace and charge. A mass and energy balance is then applied to predict the coke consumption and melting rate under slightly varying operating conditions. The validity of predictions based on this thermochemical model is dependent -1

-2upon a fairly constant operating condition for the cupola furnace. In exploring fuel oil injection in the cupola, it must be recognized that these predictions are valid only under conditions which are relatively close to the present operating conditions. Iron melting in the cupola requires that certain physical and chemical limitations be met; the temperature distribution in the tuyere zone and upward into the stack must be within a certain range, and the oxygen potential which the molten metal moves into as it melts and flows downward through the interstices of the coke must be within a certain range. That these conditions are met is assumed in the present computer predictions. PREDICTED CUPOLA PERFORMANCE In recognizing the need for a higher tuyere zone temperature with oil injection, a standard cupola practice has been used as a reference operation, and higher blast temperature and oxygen enrichment have been incorporated simultaneously with oil* injection in the calculations. Coke rate. The predicted coke requirement with fuel oil injection is described in Figure 1. The curves slope downwardly to the right showing that the coke requirement decreases with increasing blast temperature. As the level of oil,injection increases, the coke requirement further decreases. Superimposed upon this curve is a furnace operating requirement regarding tuyere zone temperature distribution, and it is expected that the zone of potential cupola operation lies to the lower right of this diagram; i.e., with increasing levels of oil injection, a corresponding increase in blast temperature would be required. Figure 2 represents predicted coke requirements for various blast temperatures with simultaneous oxygen enrichment. The coke saving with oxygen enrichment alone has been shown to be relatively small, 19 and hence the curves are of the same general shape shown in Figure 1. It would be expected, however, that the operating zone for this figure would be in the lower right hand area of the diagram, but not to as great an extent as for Figure 1, since the increase in oxygen level in the blast should provide suitable combustion conditions to handle higher levels of oil injection. Melting rate. The predicted melting rates at various levels of oil injection are presented in Figure 3. The melting rate increases with increasing blast temperature. Furthermore, the melting rate increases with increased levels of oil injec*Bunker C

-3tion. The acceptable operating conditions would be expected to lie to the upper right of the diagram. It should be noted that these potential increases in melting rate represent a significant increase in production capacity. In Figure 4 the predicted melting rate is shown as a function of blast temperature for various levels of simultaneous oil injection and oxygen enrichment. These curves reflect the marked increases in melting rate associated with oxygen 12-19 injection. The operating zone would again lie to the upper right of this diagram, but not so far as for Figure 3 since higher blast temperatures and increased oxygen enrichment would produce correspondingly higher tuyere zone temperatures. The curves of Figure 4 lie well above the curves of Figure 3, and predict the possibility for a marked increase in melting rate for hot blast operation with simultaneous oxygen enrichment and fuel oil injection. TUYERE ZONE TEMPERATURE The distribution of temperature in the tuyere zone is an important operating condition in cupola melting. It is a major factor in determining metal temperature, and also influences the oxygen potential of the gas in the melting zone, thereby influencing the extent of oxidation of the metal. Tuyere zone temperature can be controlled by balancing the blast temperature and fuel or oxygen injection level. The control of tuyere zone temperature based on adiabatic flame temperature for combustion of the blast with the hot coke has met with success in iron blast furnace operation and offers a useful means for effecting cupola blast control9'22 A previously described computer calculation of adiabatic flame temperature has been carried out for fuel oil injection with simultaneous oxygen enrichment over a range of blast temperatures. The results of these calculations are shovn in Figure 5. The injection of fuel oil at the tuyeres decreases the melting zone temperature because of the endothermic decomposition of the oil, and maintenance of the desired temperature distribution therefore requires either oxygen injection or an increased blast temperature. The results presented in Figure 5 are based on an assumed coke temperature and combustion to CO and H2. The flame temperatures are calculated based on adiabatic conditions. Although these calculated values are not the actual values reached during operation, they should prove useful for comparing changes in blast conditions.

-4Operating experience has shown that the combustion of oil does not take place as rapidly as in the case of gaseous fuel injection. Consequently, the use of a special burner to insure combustion of the injected oil may be required. Recent development work has led to improved burner designs of the oxy-fuel type, which operate efficiently with oil injection. USE OF BURNERS The early experience of Stoughton1 demonstrated the necessity for precombus23,24 tion of injected oil. Recent development of oxy-fuel furners offers a means for accomplishing simultaneous oxygen enrichment and oil injection. These burners offer a very efficient means for mixing fuel and oxidizer in a combustion chamber of simple construction. The detonation and turbulent conditions in the combustion chamber provide for effective mixing and the discharge of the combustion products at high velocity. The jet exiting from the combustion chamber could be directed into the cupola bed or into the blast, and then into the furnace in an indirect manner. A reasonably wide range of air/fuel ratios can be reached using these burners. CONCLUSION Oil injection in the cupola can be achieved in a variety of ways, most of which permit precombustion to occur to various degrees, and allow the injected combustion products to enter the furnace at any desired temperature and over a range of compositions. The injection of oil precombusted to a desired composition and raised to a suitable temperature should permit efficient cupola operation, putting the furnace performance outlined in the foregoing sections within reach by using straightforward modifications of present equipment. The determining factor in the use of oil injection will be set by fuel costs, including the price of oil relative to coke, natural gas, and other supplementary fuels. SUMMARY 1. Fuel oil represents a potential blast injectant for the cupola which could reduce coke requirements and increase melting rates. 2. The use of oil injection requires either oxygen enrichment or hot blast for successful cupola operation, as well as equipment for insuring proper combustion of the injected oil.

REFERENCE S m 1. Bradley Stoughton, "The Oil-Fired Cupola," Transactions AFS, Vol. 24, 1915, p. 525. 2. H. J. Leyshon and R. B. Coates, "Effect of Injecting Fuel Oil Through the Tuyeres of a Cold Blast Cupola," BCIRA Journal, Vol. 10, 1962, pp. 181-83. It IT 3. H. K1hne, "Uber die Olzusatzfeuerung bei Kupol3fen," Giessereitechnik, December, 1955, p. 240. 4. E. E. Geiger, "Oil-Fired Cupola Furnaces," Techn. Industr., Vol. 32, 1954, p. 185. 5. H. DeRycker, "Flaven Furnace," presented at TvB3C Association Congress, Lisbon, 1961. 6. C. R. Loper, Jr., "Supplementary Cupola Fuels," Foundry, January, 1963, p. 48. 7. F. Henke, "Improvement of Cupola Operations Through Fuel Addition and Oxygen Injection," Giesserei Praxis, No. 10, 1964, p. 181. 8. R. D. Pehlke, "Thermochemical Model for Computer Prediction of Cupola Performance," Modern Castings, Vol. 44, 1963, p. 580. 9. R. D. Pehlke, "Computer Prediction of Cupola Performance Utilizing Oxygen and Natural Gas in Blast," Modern Castings, Vol. 47, 1965, p. 806. 10. H. Jungbluth and P. A. Heller, "Blast Volume, Coke Charge, and Melting Rate with Cupolas," Technische Mitteilungen Krupp, Vol. 1, 1933, p. 99, Brutcher Translation No. 917. 11. "Report of Sub-committee TS 52: Developments in the Melting of Metals for Foundries,tt British Foundryman, Vol. 54, 1961, p. 103. 12. H. J. Leyshon and R. B. Coates, "Acid-Lined Cupola Operation with Cold Blast, Cold Blast with Oxygen,and Hot-Blast," BCIRA Journal, Vol. 10, 1962, p. 28. 13. Francois Danis, "Oxygen in the Cupola," Fonderie, Vol. 145, 1958, p. 79. 14. F. Moraw, "Enriching the Blast of the Cupola Furnace with Oxygen," Giesserei, Vol. 17, 1930, pp. 132 and 155. 15. W. C. Wick, "Cupola Operations Improved with Oxygen-Enriched Blast," American Foundryman, Vol. 13, 1948, p. 64. 16. W. C. Wick, "Oxygen-Enriched Cupola Blasts," Transactions AFS, Vol. 56, 1948, p. 246. 17. F. J. Webbere, "Auxiliary Oxygen Applied in 72 Inch Production Cupolas," American Foundryman, Vol. 17, June, 1950, p. 40.

-618. A. K. Higgins, Discussion 1 to Ref. 25, Transactions AFS, Vol. 56, 1948, p. 256. 19. A. K. Higgins, "Oxygen Enrichment of the Cupola Blast," Iron Age, Vol. 161, 1948, p. 72. 20. J. A. Cordier, "Injection of Different Materials in the Blast," Blast-Furnace, Coke Oven and Raw Materials roceding A AIME, Vol. 19, 1960, p. 238. 21. H. N. Lander, H. W. Meyer, and F. D. Delve, "Prediction of Blast Furnace Performance from Operating and Thermal Data, " Blast Furnace, Coke Oven and Raw Materials Proceedings, AIME, Vol. 19, 1960, p. 219.. 22. R. D. Pehlke, "Computer Calculation of Adiabatic Flame Temperatures at the Tuyeres of a Coke-Fueled Shaft Furnace," presented at ASM Metal Congress, October, 1964. 23. T. F. Pearson and C. Armstrong, "Development and Usage of an Oxy-Fuel Burner," Steel Times, October 16, 1964. 24. J. G. C. Pope, "The Toroidal Oxy-Fuel Burner," Journal of Metals, Vol. 16, 1964, p. 520.

0 BASED ON BUNKER C INJECTED INTO 42 INCH DIAMETER CUPOLA 5 BLOWN AT 3290 CFM BLAST z w X. 10 I.w a w 15 w o 20 0 <& z w25 U) < 0 w 30 40 435 w 4304 50 200 400 600 800 1000 1200 1400 1600 1800 2000 BLAST TEMPERATUREOF Figure 1. Calculated Effect of Fuel Oil Injection on Coke Requirement.

0 BASED ON BUNKER C INJECTED INTO 42 INCH DIAMETER CUPOLA 5 BLOWN AT 3290 CFM BLAST I — z w w 10 a: CY w 0 L.I n-150 20 - w C') ~ o Pol w 0 25-, 0 00 w 040 W 35 450 200 400 600 800 1000 1200 1400 1600 1800 2000 BLAST TEMPERATURE, OF Figure 2. Calculated Effect of Simultaneous Oxygen Enrichment and Fuel Oil Injection on Coke Requirement.

140 BASED ON BUNKER C INJECTED INTO 42 INCH DIAMETER CUPOLA BLOWN AT 3290 CFM BLAST 120 w I-.I n100 z, — w; 80 z w n 60-? 0UJ40 ~ )P _z IwZ a. 20 0 200 400 600 800 1000 1200 1400 1600 1800 200 BLAST TEMPERATURE, OF Figure 3. Calculated Effect of Fuel Oil Injection on Melting Rate.

140 BASED ON BUNKER C INJECTED INTO 42 INCH DIAMETER CUPOLA BLOWN AT 120 3290 CFM BLAST 1200 ~,I0O 0"' <[ 60 \5 ~L BLAST TEMPERATURE, Fuel Oil Injection on Melting Rate. w 4 0 200 400 600 800 1000 1200 1400 1600 1800 2 000 BLAST TEMPERATURE, OF Figure 4. Calculated Effect of Simultaneous Oxygen Enrichment and Fuel Oil Injection on Melting Rate.

-114250 COKE 2800 oF MOISTURE FREE BLAST AT 3290 SCFM 4000 - E 3750 - 0 Li:350.1 6 LB. OIL/ MIN - 5 % 02 3 LB. OIL/MIN -2.5 % 02 3500 LUe~ ~NO OIL LUI LLI 3LB OIL/MIN 3250 I. // / 6 LB.OIL/MIN c) IT 3000 2750 2500 I... I I I I I 0 500 1000 1500 2000 BLAST TEMPERATURE, ~F Figure 5. Calculated Adiabatic Flame Temperature in Tuyere Zone of Cupola for Various Levels of Blast Enrichment.