THE UNIVERSITY OF MICHIGAN INDUSTRY PROGRAM OF THE COLLEGE OF ENGINEERING A STUDY OF A METHOD OF MANUFACTURING DISSOLVER PULP FROM INDIAN BAMBOO Lalit H. Udani Gunvant C. Sutaria Professor H. A. Ohlgren Advisor This report was submitted in partial fulfillment of requirements for CM 210, a graduate course in Chemical and Metallurgical Engineering. April, 1956 IP-159

ACKNOWLEDGEMENT We wish to express our appreciation to the authors for permission to distribute this report under the Industry Program of the College of Engineering. ii

TABLE OF CONTENTS Page ACKNOWLEDGEMENT ii ABSTRACT v I. INTRODUCTION 1 A. Availability and Pulp Quality of Bamboo Species in India 1 B. Cultivation of Bamboo 1 1. Propagation 1 2. Soil 2 3. Harvesting methods 2 4. Yield 2 C. Properties of Bamboo 4 II. MANUFACTURING PROCESS 4 A. Considerations for a Manufacturing Process 4 B. Process for Manufacturing 50 Tons/day of Dissolver Pulp from Bamboo 6 1. Cultivation, Harvesting, Seasoning, and Storing of Bamboo 6 2. Preparation of Bamboo Chips 7 3. Prehydrolysis of Bamboo Chips 7 4. Fractional Digestion of Bamboo Chips 8 5. Screening, Refining, and Lapping 9 6. Recovery Processes 11 C. Flowsheets Figure 1 - Chipping and Hydrolyzing 13 Figure 2 - Digestion System 14 Figure 3 - Bleaching Section 15 Figure 4 - Recovery System 16 III. MATERIAL AND HEAT BALANCES 17 A. Material Balance 17 B. Heat Balance 21 C. Summary of Raw Materials and Utility Requirements 23 iii

TABLE OF CONTENTS (cont.) Page IV. PRELIMINARY ECONOMIC STUDY 24 A. Item-list and Cost of Equipment 24 B. Summary of Preliminary Estimates on Capital Cost 26 C. Summary of Annual Cost of Operation 27 D. Break-even Chart 28 E. Study of the Economics of the Process 29 V. RECOMMENDATIONS AND CONCLUSIONS 29 A. Suggestions for Further Development 29 B. Conclusions 30 VI. BIBLIOGRAPHY 31 iv

Abstract This report presents the results of a study to determine the design of a rayon-grade pulp plant using bamboo as a raw material. The study consisted of preliminary investigations based on available information. Various process variables are defined, and a process to manufacture 50 tons of pulp per day is evolved. Preliminary estimates show that such a plant would cost about $4,200,000. The high break-even point of 11,200 tons of pulp per year necessitates consideration of a plant with higher capacity or modifications in the processo v

A STUDY OF A METHOD OF MANUFACTURING DISSOLVER PULP FROM INDIAN BAMBOO Io INTRODUCTION The factor that mostly controls the development of the rayon industry in India is that vital raw materials such as rayon-grade pulp, caustic soda, and sulfur must be imported. Vast forest areas of India are, however, a great source of cellulose for the paper and pulp industries; and, furthermore, vigorous studies are being made to find means of harnessing this natural potential at the pilot plant level, and, to some extent, at a full-scale industrial level. One of the great sources of cellulose that India can offer to the paper and pulp industries is bamboo. The suitable climate and soil in India engenders a prolific growth of bamboo there, and, because bamboos grow rapidly and plentifully and yield good pulp, they are a potential source of dissolver pulpo With these factors in mind, the study presented in this paper is an attempt to define the process variables that must be considered in making rayon-grade pulp out of bamboo, to evolve such a process, and to investigate the economic feasibility of such a processo A. Availability and Pulp Quality of Bamboo Species in India The high potential of pulp production in India may easily be seen from Table I which shows the availability and pulp quality of some important bamboo species in Indiao Bo Cultivation of Bamboo There are essentially two classes of bamboo: the clump-forming and the running. Since the clump-forming class is most common in India, the study applies to this variety0 1. Propagation Clump-forming bamboos are propagated by cutting clumps into divisions containing one or thTO nodes each. Some clump-forming species respond well to propagation by culm cuttings in which single node sections are planted, - 1

2. Soil For the cultivation of bamboo, a tropical or warm temperate climate is preferable. The most desirable soil for most species is fertile friable soil with good drainage. 3. Harvesting methods The following are the three common methods of harvesting bamboo. a. Selective cutting. Every culm is marked with its year of emergenceo Culms of proper age are selected and cut with axe or saw, annually or biennially. b. Strip cutting. A portion of the grove is cut away be machine. This method is cheaper. c. Clear or total harvesting. Each grove is completely cut off. It is inefficient as it takes long for the grove to recover. Selective cutting is cumbersome and expensive while clear harvesting is obviously inefficient. Therefore, the strip cutting method is preferred as the best method. 4. Yield Harvest varies from four to eight tons per acre per year in India.9 - 2 -

TABLE I BAMBOO SPECIES IN INDIA Species (with references) Availability Pulp Quality Bambusa Polymorph (Bhargava, Chemical Abstracts 42, 4746 Pearson, C. A. 8, 246 Raitt, C. A. 6, 2527) Bambusa Tulda Cephlostachyum Pergracile (Bhargava, Pearson & Raitt. loc. cit.) Deudrocalamus longispathie s (Bhargava loco cit.) Dendrocalamus Strictus (Ahmed & Karnik C. A. 39, 184) Bhargava, Singh Biol. Abs. 18, 2405 Karnik & Sen C. A. 43, 2768) Melocanna Baonbusoide s (Bhargava, Pearson, Raitt. loc. cit.) Ochlandra Brandisi Ochlandra nigrociliata Ochlandra Travencorica Most suitable species both in terms of location and quantity Plentiful Plentiful, promising source of pulp manufacture Plentiful Enormous reserves Plentiful, promising for location and pulping Plentiful. (One of the principal sources used in Rayon manufacture) Good bleachable pulp Difficult to bleach Good. a-cellulose content Yield of a-cellulose as high as 62% Difficult to bleach Good, a-cellulose content Good, a-cellulose content -3

C. Properties of Bamboo 1,2 Table II gives average properties of bamboo. TABLE II Chemical Properties Total cellulose Pentosans Lignins Ash Total N2 Soluble matter Alcohol extract Benzene-alcohol extract Cold water extract Hot water extract 1% NaOH extract Normal moisture 42-55% 20-27% 20-30% 3-4.75% 1.93=5.73% 10% 2.39-6.31% 4.49% 2.12% 6.32% 20.0% 9-10% Physical Properties Density between nodes Density at nodes fiber length width (length/width) ratio 35=45 lbs./ft.3 47 lbs./ft.3 1.6 to 3.8 mm. 0.009 to 0.036 mm. 100 to 193 IIo MANUFACTURING PROCESS A. Considerations for a Manufacturing Process The chemical characteristics of a suitable viscose pulp are: c -cellulose Pentosans Lignins Ash Alcohol-Benzene Solubility Viscosity - Tappi Brightness - Higgins 88% 5% 9 0,15% 0,.15 o.5s 1 to 25 C.P. 85% - 4 -

There are two common processes of manufacturing pulp from wood, the Kraft process and the Soda process.5 Low lignin and ash content and good bleachability characterize a good pulpo In these terms, the pulp produced from bamboo by the Kraft process has been found superior to that produced by the soda process. This can be seen from the following table of average compositions given by Jogleker6. TABLE III Average Composition Soda Pulp Active Na20 Total yield Screened yield Ash Alcohol-Benzene Solubility 1% NaOH Solubility Pentosans Lignins — cellulose Viscosity ru(En)- C.P, Ash in C-cellulose Brightness (Higgins) 10% consumption of C12 16-20% 37-41% 36-39% 1.4-1.6% O. 0% 4.6-5% 16% 3~5-4.5% 85% 392-640 0.6-0,8% o6- 63.i Kraft Pulp 16-20% 38-6% 32.7-37.8% 1.3-1.4% o.0o-o.4 4.9-5.4% 17.6-16.5% 2.84-2.24% 80-78% 967-575 o,46-0.48 78-82 Jogleker6 notes that the high pentosan content of bamboo was a prohibitive factor in converting bamboo into dissolver pulp. The pentosan content in the Kraft pulp could not be reduced below 7% even with drastic purification treatments. However, better results were obtained by prehydrolysing the bamboo chips using 2% sulfuric acid at 110~ C for 22 hours. Pulp produced by this method required no more purification than that normally required. According to Raitt7 the plant substance of bamboo falls into four different chemical groups. Each group has one substantially basic substance which manifests individual color reactions and reacts in a distinct special manner to the action of the solvents and temperature. The four groups are: lo Starch, sugars, tarmins, gums, earth salts, coloring matter, and secondary starches and sugars soluble in water. This group includes all neuatral substances which are soluble in water at 1000 Co -5

2o All acid bodies soluble in 1% NaHO at 1000 Co 3o Lignins and acid bodies soluble in 4% NaOH at 130~ Co 4o a- ^ -, and- -cellulose as insoluble residue from the action of the solvents above. Raitt8 suggested that during digestion, groups 1 and 2 produce a dye that is not entirely discharged. To obviate this difficulty, Raitt developed a fractional digestion method in which the components of groups 1 and 2 are removed by treating the bamboo with the spent liquor from a previous cook, and the bamboo residue is then treated with a stronger caustic solutiono When these starches and pectins are removed prior to delignification, the pulping action takes place in a non-staining medium, producing an easy-to-bleach pulpo Jogleker6, Bhargava and Singh3 concluded that adequate purification of the prehydrolysed bamboo pulp could be secured through a 3-stage bleach consisting of chlorination, alkaline extraction and a NaOC1 bleacho Hence, a conventional 3-stage bleach was found to be satisfactory for purification of Kraft pulp from prehydrolysed bambooo For all multi-stage treatments, the total consumption of chlorine in bleaching was found to remain constantO B. Process for ~Manufacturing 50 Tons/day of Dissolver Pulp from Bamboo Because of the rapid market growth for rayon i P I.ndia whTich has a low per capita rayon consumption, it is anticipated that the production of rayon will be increased from about 35 tons/day at present to about 100 tons/day in the next ten yearso Pulp requirements on the basis of the rayon production will increase from about 40 tons/day to about 110 tons/dayo Two pulp plants of about 50 tons per day capacity would satisfy the needs of the rayon industry in Indiao In the present study, therefore, a 50 tons/day pulp plant is consideredo Likewise, in view of the peculiar chemical characteristics of bamboo, the process considered here is a modified Kraft process The process, beginning with the cultivation of bamboo in the forest to the final stage of lapping the pulp in a wet machine would consist of six main stages of operations0 In the following pages a complete description of each of these processes is given, and Figures 1, 2, 3, and 4 on pages 13, 14, 15, arnd 16 represent the process flowsheetso 10 Cultivating, Harvesting, Seasoning, and Storing of Bambooo The average yield of bamboo is 6 tons per acre, On an average, therefore, on a six-year harvesting cycle, about 700 acres of land would be required

per 1000 tons of pulp per year, For a 50 tons/day plant the land required would be 10,900 acres. The partial harvesting method, ieo, the partial cutting of the grove, is advisable for better control of the cultivation cycle. Raitt7 has suggested that a seasoning period of not less than three months should elapse before the culms are used. Likewise, to avoid any contingency arising out of transportation difficulties, six months' requirements of bamboo should always be stocked. This stock should be piled in heaps 50' square by 60' high. These piles should be set 100 ft apart as a precaution against fire. For the 50 tons/day pulp plant, about 27,000 tons of dry bamboo would be stored, requiring about half an acre of land for storage near the plant. 2. Preparation of Bamboo Chips Seasoned bamboo is conveyed to crushing rolls by a sluice conveyer, soaking the bamboo before crushing and thus reducing fines. A closed cycle watersystem is used in the sluice conveyero The soaked bamboo is fed to the roll crusher through the feed chute, The fibrous structure of the wood is loosened by crushingo The crushed bamboo on the way out of the rolls is fed to a multi-knife chipper giving chips 1-3 mmo thick and about ~ in. long. Average composition of chips is as follows:2,6 Moisture 8,5 to 9,5% Lignin 26025% Pentosans 19o75% Total cellulose 52,884% (c-cellulose 76065% of total) Ash 3o0% N2 0o26% Chips leaving the chipper are conveyed to a screen. The undersize chips are fed by a conveyer to the boiler, and the oversize chips are returned by a conveyer to the crusher. The screened chips are conveyed to a storage silo by a redler conveyer, where three days' requirements of chips are stored. The chips are fed from the silo discharge to chip bins situated above the hydrolyser feed system by bucket elevatorso 3. Prehydrolysis of Bamboo Chips The prehydrolysis of chips consists of treating the chips with 2% H2S04 at a pressure of 70 psi and at 1200 C for two hours with liquor-tochips ratio of 4:1, thus ensuring better penetration of the liquor, in a hy-rolyzer kwich is a large pressure vessel with a recirculating system for process liqu<oro

D.ilute acid solution is fed to the chip feed system, thus flushing the feeder and ensuring uniform distribution of chips in the hydrolyzer. The liquor i s recirculated by a pump through a two-tube-pass heat exchanger- to maintain the reaction temperature At the end of the reaction period, the liquor is drained off to a storage tank for recycle. While draining, the liquor is passed through the heat exchanger to heat up cold water which is then passed on the shell side instead of steamo Hot water is stored in a presurge tank. Th*e chips in the hydrolyser are washed for one hour with hot water at 1000 Co The wash water is drained to the liquorr-storage tank. A relief valve on the hydrolyser maintains a constant pressure, letting off air and steam during the operation. The excess dilute acid solution which is not recycled is pumped over to a yeast-recovery plant for the recovery of the yeast, Terula Utilis. The prehydrolysed chips are then screw-conveyed to a digester feed system in the digester room. 4. Fractional Digestion of Bamboo Chips The fractional digestion is a batch process consisting of treating the chips with a dilute caustic soda solution and then with an alkaline solution of 33% sulfidityo Five digesters are estimated to be required for the planto Each digester consists of a stainless steel-lined pressure vessel with a recirculating system. In the first stage of digestion the chips are treated with an alkaline solution of 8.63% NaO2 content at a temperature of 1200 C and with a liquor ratio of 5 1 for 3 hours, to e-nsure uni.form digestion of chipso Caustic soda is dissolved and stored as a 30% solution and mixed with white liquor obtained from the recovery section to give required alkali concentrationO The liquor is pumped to the digester feed system consisting of screw conveyers and flushing boxes. The liquor carries chips with it so that a uniform distribution of chips is achieved. A strainer at the bottom of the digester ensures thrat only the liquor passes to the recirculating system, comprised of a circulating pump and a heat exchanger. The recirculated liquor is sprayed in the digester through a sprayer so as to form a 600 solid a e e eat exangler maintains e eat exchangerction temperature during the reaction period, using steam on the shell-side, and heats water which is passed on the shell-side, instead of steam, when the liquor is drained. The drained liquor is stored in an alkaline-liquor- storage tank. The chips

are now ready for the second digestion. A constant pressure and relief valve is employed to let out air and steam during reaction and the blow-off steam at the end of reaction period. The steam is condensed in a jet type of condenser Part of the alkaline liquor in the storage tank is recycled, and part of it is pumped over to the recovery system from which the white liquor, used as working liquor in the process, is obtained. In the second stage of digestion, an alkaline liquor of 15.6% Na2O and 33% sulfidity6'7 is fed to the digester. The liquor is made up of white liquor from the recovery system and recycled black liquor from the previous batch. The temperature of digestion is maintained at 170~ C. The liquor-to-chip ratio is 3:1 and the reaction period is four hours. The liquor is recycled as in the first digestion. At the end of the digestion the liquor is blown into the blow-off tank, and the steam released on blow-off is condensed in a jet condenser. The slurry is stirred by a bottom-driven agitator. The slurry is then pumped to a multistage washer by the pumpo The multi-stage washer,for filtering and washing, consists of three countercurrent type two-stage vacuum filters in serieso The slurry from the blow tank is pumped to the first filter, and the filtrate, called black liquor, is sent to the black-liquor-storage tank. Fresh wash water at 180~ F is sprayed on the cake leaving the washer. Dilute wash liquor is pumped to the previous stage washing system. The wash liquor from the first stage is sent to the black-liquor-storage tank, Cake is passed from one stage to the other by a screw conveyerstype of repulper. The washing operation takes one hour. Part of the black liquor is recycled in the digestion process, and the rest is sent over to the recovery system. The washed cake is dumped through a chute to the consistency regulator. 5. Screening, Refining, and Lapping The consistency of the pulp from the digester is adjusted to 2% in a consistency regulator and the slurry stored in a stock chest for continuous supply to the screenso The screening process separates the coarser fibres from the finer and removes dirt and foreign mattero Horizontal centrifugal Cowan-type screens separate the tailings through a fine screen and discharge them into a sewer via a knotter, while the fine slurry is passed over a vacuum filter to thicken the slurry to a consistency of 16%. The pulp is now passed on to bleaching towers by a screw conveyero - 9

Pulp is refined in a three-stage processo The screened pulp is fed to the first-stage retention tower by flushing with dilute chlorine water so that the consistency in the tower is 2%. The temperature is maintained at 25~ C for one houro The slurry is recirculated by centrifugal pumps through a cooler. At the end of the reaction period the slurry is filtered, and the pulp is washed in a rotary vacuum filter. The liquor and wash water are stored in a weak-liquor-storage tanko The filter cake is pulped and conveyed to the next stage by a pulper-conveyoro Part of the weak liquor is then recycled and the remaining liqiuor is pumped over to the third stage to be used in the third-stage process, Makeup chlorine solution is prepared in achlorine make-up tank and fed to the liquor makeup tanko In the second stage, the alkaline extraction stage, a consistency of 10% is maintained. The alkali content of the liquor is 2%, and the retention period in the tower is one hour. The slurry is recycled through a heat exchanger to maintain the temperature at 40~ Co The extracted slurry is filtered and the pulp washed with hot water at 50~ C in a rotary vacuum filter. The weak liquor and wash water are stored in the weak-liquorstorage tanko The filter-cake is pulped and passed over to the final stage by a pulp-conveyoro Part of the weak liquor is recycled in the process and the rest is pumped over for use in the third-stage processo Makeup NaOCI solution is fed as 30% NaOH solution from caustic storage tanks to the liquor makeup tank. The third stage of refining involves the treatment of pulp with dilute NaOCl solution of pH = 10 for one hour. The pulp is flushed into the retention tower with Adilute NaOCl liquor so that consistency is maintained at 5%. The temperature is maintained at 35~ C. The liquor is recirculated through a cooler to bring down the temperature of pulp and liquor to 35~ C and to maintain the temperature. The liquor is made up of weak liquors from the first and second stages and wash water from the third stage. Makeup NaOC1 solution is fed as 10% NaOC1 solution from the LaOC1 makeup tank to the liquor makeup tanko The slurry is filtered and washed in a rotary filter. The pulp is conveyed by a conveyor to the wet machine. The filtrate is stored in a tank; part of it is recycled and the rest discharged to the sewer. Lapping: In order to convert the chemical pulps to a form suitable for transportation or temporary storage, it is necessary to dewater the stock and collect the pulp into sheets dry enough to hold together. The sheets are stacked into bundles. The lap (bundle) contains 50-55% by weight of air dry pulp. A wet press or a wet machine is employed for this purpose. A wet machine has a production capacity of 5500 lbs/24 hrs of chemical pulp - 10 -

per foot width. A Rogers Wet Machine is installed to perform the lapping operation, and lapped pulp is either stored or transported to a rayon mill. The filtrate is thrown away as effluent. 6. Recovery Processes The economics of the Kraft process is greatly dependent on the recovery of chemicals used in digestion. The waste liquors from digesters at 18% concentration are stored in black liquor storage tanks and are pumped to a seven-body sextuple-effect falling film evaporator. Feed is pumped countercurrent to steam to the fifth and sixth effects, and the concentrated liquor from both of these is fed to the fourth effect by feed pumps. This process is repeated for each subsequent effect until the first effect is reached. From the first effect the liquor is flushed into a liquor storage tank at 55% concentration. Steam is fed to the first two effects, and the vapor from these two effects is passed on to the next effect, and the process is repeated until the sixth effect is reached. Condensate from all the effects is collected and pumped to a hot well. The steam pressure varies from 38.5 psi in the first effect to 22" Hg vacuum in the sixth effecto The liquor temperature rises from 130~ F in the sixth effect to 285~ F in the first effect. Soap formed due to the presence of fats and waxes in wood are removed in a screen tank between the third and fourth effects. The thick liquor is stored in a thick-liquor-storage tank from which it is pumped into'a direct contact evaporator where the liquor comes into direct contact with hot gases from the furnace. The liquor is then sprayed in the furnace through a system of nozzles where once ignited, the liquor at a concentration of more than 60% solids burns by itself due to the presence of organic combustibles from woodo The unrbnrnt solids collect on the opposite wall of the furnace and form a crust. As the crust becomes larger, it cannot hold its weight and falls to the smelting floor. The smelt then drains out to the smelt-dissolver tanko A preheater and a tubular boiler are built irn the furnace to recover heat from hot gases which pass through a direct contact evaporator before passing on to the stack. The average analysis of the smelt is: Na2CO3 65% Na2S 20.5% Na2SO3 0.7% Na2S04 6.0% insolubles 2,5% " 11 -

The smelt is dissolved in weak liquor from a clarifier, and solution, called green liquor, is stored in a green-liquor storage tank. The green liquor is clarified and pumped to the causticisers. The underflow of the green liquor clarifier is washed in a dreg washer. The dregs are thrown to the sewer and the overflow is stored in the weak-liquor-storage tank. The green liquor is mixed with slaked lime coming from the lime slaker and agitated for one hour in causticisers. The causticised liquor is pumped to a white. liquor-thickener. The overflow is then stored as white liquor which is pumped to the digestion room and the mud is washed and thickened in a mud thickener. The weak liquor from the thickener is stored in the weak-liquorstorage tank. Part of it is used in dissolving smelt, and the remainder is sent to the sewer. The mud is filtered in a rotary vacuum filter and washed. The filtrate and wash water are pumped to the mud thickener, and the cake is conveyed to a rotary lime kiln. Make-up limestone is fed to the kiln. Lime produced is conveyed to lime bins situated over the lime slaker. - 12 -

I-J FIG. I CHIPPING S HYDROLYSING

H-1 FIG.2 DIGESTION SYSTEM

^-"""^^^413 COOLING I r - - —'.Er= WATER It STAGE COOLER 2nd BLEACH 430-1 BLE TOWER TO0 206-1' TTO 204 UN.IT 425-1 WASTE LIOUOR TANK 126 - FIG. 3 BLEACHING SECTION

C0 I BOILER RECOVERY FURNACE 204 116 r SEXTUPLE EFFECT EVAPORATOR FIG. 4 RECOVERY SYSTEM

III. MATERIAL AND HEAT BALANCES Ao Material Balance Chipping Bamboos Cellulose Lignin Pentoses Ash Water 46,2.23.4 17.6 2.8 10.0 Total 100.0 75.3 38.0 2806 4.6 16.2 162.8 Fines Cellulose Lignin Pentoses Ash Water 46.2 23.4 17.6 2.8 10.0 Total 100.0 3.8 1.9 1.4 0,2 0,8 8.1 Chips Cellulose Lignin Pentoses Ash Water 46.2 23.4 17.6 2.8 10.0 Total 100.0 71.5 36.1 27.2 4.4 15.5 154.7 Hydrolysis Dil. H2o04 solution H2so4(100o ) 7.08 Water 92.92 Total 100.00 Process Water 100.00 8.9 128.2 137.1 417.6 - 17 -

Hydrolysiss Hydrolyzing liquor Water H2S04 (dil.) Cellulose Lignin Pentoses Ash 95064 1.56 0.00 0.00 2044 0.36 Total 100.00 545.8 8.9 0.0 0.0 13.9 2.1 570.7 Hydrolyzed Chips Cellulose Lignin Pentoses Ash Moisture 51o5 26.0 9~7 1.7 11.1 Total 100.0 71.5 36.1 13.3 2.3 15.5 138.7 Digestion and Chemical Recovery Makeup 30.7% NaOH solution NaO. Water 30.7 69.3 Total 100.0 4.73 10.70 15.43 Makeup salt cake (Na2SO4, 10 H120) Makeup limestone to kiln Water to the system Steam to evaporator Air to furnace 100 100 100 100 100 7.65 11.8 2372.0 188 300 Weak liquor from recovery Water 98.95 Na2S + Na2SO4, o.65 10 H20 NaOH O.4 Total 100.0 1153~5 7.6 4.73 1165.83 - 18 -

Digestion Material lost as hot and gases Chemical Vapors Recovery,;r 1-1-LI T< 27 73 otal 100 110 300 410 Steam condensate From relief vapors 13 From evaporators 87 Total 100 146.5 942.0 1088.5 Causticising mud Water Insolubles CaCO3 78 4 18 Total 100 4o.o00 2.2 1108 53.0 Pulp Cellulose Lignin Pentoses Ash Water 15.15 0.07 0.78 0.002 84.000 100.000 48.45 0o21 2.55 0.07 270.00 321.28 Screening Knots Cellulose Lignin Pentoses Ash Water 15.15 0 07 0.78 0.002 84.000 Total 100.000 1 00 o. oo4 0.040 0o 000 5.56 6.6o 69060 Screened pulp Cellulose Lignin Pentoses Ash Water 15.15 0.07 0.78 0.002 84.000 Total 100.000 47.45 0.21 2.51 0.07 264.44 314.68 - 19 -

Screening Chlorine gas NaOH NaOC1 Bleaching Wash water and Wet-machine Waste water Water C12 NaOH NaOC1 Lignin, etc. Pulp Cellulose Lignin Pentoses Ash Water 100.00 100.00 100.00 100.00 99.71 0.29 Total 100.00 56.95 0.13 2.84 0.08 40.00 Total 100.00 1.45 2.03 0.95 1317 00 1548.11 1.45 2.03 0095 0.24 1552.78 47.45 0.11 2.37 0.07 33.33 83.33 - 20 -

B. Heat Balance Btu of Heat Btu of Heat Btu of Net Btu of Net Lbs of Steam Nature of Heat Load Consumed Recovered Heat Load Heat Load Consumed per per Day per Day per Day per Ton of Ton of Pulp Pulp Hydrolysis Hydrolyser: starting load continuous load 20 95x107 1.44x107 heat recovered from exit liquors 13.3x107 9.09x107 18.18x107 1818 Digestion and Recovery 1st digester: starting load continuous load 16.561x107 2,19x107 I! blow heat heat recovered from discharge liquor sensible heat of pulp by lowering temp. -co 180~ F. water heating load 2nd digester: starting load continuous load blow heat heat recovered from discharge liquor sensible heat of cooling pulp to 180~ F water heating load 6.08x107 3050x107 0 291x107 8.78x107 17.460x107 34.92x105 3492 19.951x107 2.358x107 12.41ox1o7 2,68x107 16.808x107 33.616x105 3361.6 0 191x107 8.78x107 Recovery Evaporator continuous 37 6x107 37.6x107 75 2x105 7520 Bleaching 2nd Stage Heat required to heat liquor to 104~ C 2 36x10 2.36x10 4o 72x10 472 Total 16663o6

Cooling Nature of Load Btu of Heat to be Tons of Refrigeration RemovNatured per Day Removed per Day Required per Day I I Bleaching 1st Stage Retention tower: Heat removed in cooling liquor 3.54xlO7 123 tons

C. Summary of Raw Materials and Utility Requirements No, Material " ---- 1o Bamboo 2. Sulfuric Acid (100%) 3o Caustic Soda 4. Salt cake (Na2S4O~10 H20) 5. Limestone 6. Chlorine gas 7. NaOC1 8. Water 9, Steam 10o Power Consumption per ton of dry dissolved pulp 3 256 tons 0O1416 ton 00135 ton 00153 ton 0.235 ton 0.029 ton 0 0189 ton 20,400 U.SoG. 16,663 lbs 400 KWH Consumption for 50 per day production dry pulp 162.8 tons 7.08 tons 6.76 tons 70 65 tons 11 80 tons o 45 tons 0 95 ton 4240,30 tons 416.5 tons 20,000 KWH tons of - 23 -

IV. PRELIMINARY ECONOMIC STUDY A. Item List and Cost of Equipment Item No. Equipment Unit Capacity Number Approximate Material of Required Cost in Dollars Construction 101 102 103 104 105 106 107 107A 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 H2S04 (98%) storage tank Presurge tank H2S04 makeup tank Chips storage silos Liquor storage tank Blow tank with agitators (41) Dissolving tank Storage tank for NaOH Alk. liquor storage tank Black liquor storage Consistency regulator Smelt dissolver Green liquor storage tank Causticizers White liquor storage tank Weak liquor storage tank Lime bin Strong liquor clarifier Weak liquor thickener Dreg washer Green liquor clarifier Dilute chlorine tanks Chlorine makeup tank Dilute caustic liquor tank NaOCl preparation tank Dilute NaOC1 makeup tank Waste liquor storage tank 8,000 U.S.G. 10,000 U.S.G. 4,000 U.S.G. 32,000 cu ft 8,000 U.S.G. 3,000 cu ft 5,000 U.S.G. 6,000 U.S.G. 2,500 U.S.G. 25,000 U.S.G. 1,000 U.S.G. 16,000 U.S.G. 16,000 U.S.G. 1,000 U.S.G. 15,000 U.S.G. 15,000 U.S.G. 1,000 U.S.G. 25' diam. 30o diam. 1,000 U.S.G. 16,000 U.S.G. 12,500 U.S.G. 1,000 U.S.G. 12,500 U.S.G. 1,000 U.S.G. 20,000 U.S.G. 4,000 U.S.G. 1 1 1 1 1 5 1 5 10 5 2 1 1 3 1 1 1 1 1 1 1 2 1 2 1 1 6 2,500 3,000 3,200 17,000 2,500 65,000 2,000 26,000 48,000 24,000 1,700 3,500 3,500 2,400 3,300 3,300 850 9,600 11,500 2,500 8,000 26,000 3,000 9,600 3,000 12,000 28,800 steel 308 steel lead-lined steel steel steel stainless-clad steel steel steel steel steel steel steel steel steel steel steel steel ro!p steel steel stainless-clad steel type 304 stainless steel type 304 stainless stainless-clad steel steel cost of agitated vessels 201 202 203 204 205 206-1 206-2 206-3 207 Hydrolyzers Digesters Evaporators, falling film and vertical tube type Recovery furnace (tubular) Lime kiln (rotary) Bleaching tower Bleaching tower Bleaching tower Wet-machine 3,000 cu ft 5,200 cu ft 3,000 sq ft heating surface each 20 x 106 Btu/hr 300 sq ft peripheral area 50,000 U.S.G. 15,000 U.S.G. 30,000 U.S.G. 16,000 lbs of H20 2 34,000 5 125,000 7 25,000 1 40,000 1 20,000 1 20,000 1 9,500 1 16,000 1 50,000 Total $ 604,250 stainless-clad steel stainless-clad steel steel steel tubes steel stainless-clad steel stainless-clad steel stainless-clad steel cost is assumed

Number Approximate Material of Item No. Equipment Capacity Remarks Required Cost in Dollars Construction Total of previous sheet 604,250 301-316 except 303, 305, and 317 303 305 317 Conveyors of different types Equivalent of 700 ft of 39,200 screw conveyor of 9" diam.} steel Crusher and chipper Chips-screen Pulp screen 50 H.P. 200 so ft ~ 200 sq ft surface area } 445 H.P. 400 sq ft surface area } 27 H.P. 1 2 1 8,000 2,000 5,000 ro n 401-428 Pumps, centrifugal except (1) steel 408, 410, (2) stainless steel 411, 412, 413, 414, 419, 420, and 424 408 Hydrolyzer heaters 411 Digester heaters 412 Blow-off condenser 413 Vacuum filter ] 414 Rotary vacuum washer ] 419 Lime slaker 420 Mud-filter ] 424 Cyclone-vapor separator 429 Bleach pulp washer ] 430 Bleach heaters 431 Screened pulp rotary thickener 501 Boiler (tubular) 502 Water processing station 503 Bamboo storage yard including handling equipment Avg. 10 H.P. Avg. 10 H.P. 480 sq ft 3000 sq ft 40 22 2 5 48,000 steel 110,000 stainless steel 14,600 steel-shell and stainless steel tubes 110,000 Steel-shell and stainless steel tubes 10,000 steel 3,000 screen of monel 9,000 screen of monel 5,000 steel 3,000 screen of monel 1,500 steel 12,000 screen of monel 15,000 steel-shell and stainless steel tubes 4,000 screen of monel 500 sq ft L2'diam. x 8' width L2'diam. x 8' width 6 tons/hr of lime L2'diam. x 5' width 15' diam. 12'diam. x 12' width 500 sq ft L2'diam. x 8' width L7,000 lb/hr steam 353,000 lb/hr 5 1 3 1 1 1 3 2 1 2 102,000 86,000 5,000 $ 1,196,550 three dollars per lb/hr of steam Total The total equipment cost on the basis of 400 E.N.R. index = 1,196,550 dollars.. Cost of process equipment including foundation supports and installation= 1.715 x 106 dollars

Bo Summary of Preliminary Estimates on Capital Cost Items of Expenditure Estimated Cost1 in $ A Yard maintenance and improvements B Buildings including services 83,660 334, 64 C Process equipment 1,715,030 D Piping 418,300 E Electrical installations F Service facilities G Contingency H Insurance premium and taxes I Field office expenses including temporary construction and central office expenses including overhead Total cost 167,320 418,300 472,000 245,200 328,550 $ 4,183,000 Cost figures are based on a construction cost index of 400 as compiled by Engineering News Recordo - 26 -

C. Summary of Annual Cost of Operation Annual capacity: 17,250 tons of dissolving pulp Items of Expenditure Estimated cost in $ Interest on fixed capital investment Interest on working capital State taxes and local taxes Insurance, fire;, explosion Depreciation Royalties Research and development costs 125,490 25,098 83,660 41,830 245,000 11,380 68,880 601,338 To-cal Fixed Expenses 601,338 Raw materials Operating, or direct, labor Supervisory labor & clerical help Repairs and maintenance Operating supplies Payroll overhead Utilities and power Distribution costs, contingency etco Total Variable Expenses Manufacturing cost for the annual production of 50 x 365 - 17,250 tons of dry dissolving pulp 690,000 120,800 12,080 125,490 31,500 19,500 195,500 125,490 1,310, 36o 1,310,360 $ 1,911,698 - 27 -

3.0 28 2.E 24 22 2.C 1.8 1.6 1.4 1.2 1.0 0.8 0.6 - 28 -

E. Study of the Economics of the Process: -,...,.,~.,,,, The adjoining tables and break-even chart indicate the following: 1. The cost of raw materials is 36% of the cost of production. 2. The break-even point is at 11,200 tons/year, indicating that unless the operational cost is reduced considerably, the economies of the 50 tons/day pulp plant are very delicate. 3. The estimates on which this chart is based should be made on more precise data, 4. A rigorous study for a better control of raw material consumption, especially of expensive chemicals, should be made. 5. The loss of alkali from black liquor should be reduced to a bare minimum. 6. A study should be made of whether the recovery of lignins from alkaline liquor would more than offset the cost of alkali lost in neutralization and thus contribute towards reduction in operational cost. 7. Maintenance and utility requirements form the next largest bulk of operational cost. A study of liquor ratios and dilution factors should be made to bring them to optimum, This would in all probability reduce the materials handled and hence the capacities of equipment. This, in turn, would reduce the maintenance cost and utility requirements. Vo RECOMMENDATIONS AND CONCLUSIONS A. Suggestions for Further Development For a rigorous economic consideration of the feasibility of manufacturing dissolving pulp from bamboos, it is necessary to know the process variables more precisely. The following recommendations briefly outline the areas of the unknowns and desired development. 1. Study of the dependence of chip size on (a) cellulose, degree of polymerization, (b) reactivity, and (c) pulp. - 29 -

2o Determination of the rate of change of pentosans, ash and degree of polymerization, for pressures varying from 14.7 psia to 50 psia, in the temperature range of 80~ C to 120~ C, using dil. H2SO4 and dilo HC1 of different concentrations up to 30 gpl as hydrolyzing agents. 3. A study should be made of the kinetics of lignin removal during digestion of prehydrolyzed bamboo chips using sulphate liquors with varying concentrations of NaOH and Na2S at temperatures varying from 1000 C to 170~ C under pressures from 14.7 to 115 psia, and using different liquor-to-chip ratios. 4. An investigation of the feasibility of a continuous bleaching system. 5. Lignin could be recovered as sodium lignates by mild acid treatment or by carbonating the liquor with flue-gases. This possibility should be explored and on the basis of experimental study, its industrial application should be evaluated. 6. Quantitative study of recovering yeast from the spent hydrolysis liquor should be madeo 7. The effect of the degree of polymerization distribution in pulp on rayon yarn should also be studied. B. Conclusions 1. It is economically feasible to manufacture dissolving pulp from bamboos. 2. A 50 tons/day capacity plant would cost $4,200,000. One can expect about 10% profit if the selling price is $130 per ton of air dry pulpo 3. More experimental rate data are needed in order to pin down the process variables and estimate the cost accurately. 4. A high break-even point suggests a need for increasing the pulp plant capacity or economically recovering the by-products, lignins and yeast or modification of the process itself. - 30 -

VI. BIBLIOGRAPHY 1. Engineering Experiment Station of Georgia Institute of Technology. Bulletin No. 18, Vol. XV of 1955. 2. Bhargava M., "Bamboo for Pulp Manufacture" Indian Forest Bulletin No. 129, Degradun, India (1947) 3. Bhargava and Singh, Paper Trade Journal, 128, No. 8: 65-69 (Feb. 26, 1949). 4. Casey, Pulp and Paper Vol. 1, InterScience Publishers, Inc., New York (1952). 5. Stephenson, Pulp and Paper Manufacture, Vol. I, McGraw-Hill Publishing Co., New York. 6. Jagleker and Donofrio, Tappi 54, No. 6, 254-261 (June 1951). 7. Raitt, W., Indian Forest Records, 5:181 (1912). 8. Raitt, W., Digestion of Bamboo and Grasses for Paper Making, London, Lockwood and Sons, 1931. 9. Pearson, "Paper Pulp from Bamboo", Chemical Abstracts 8, 246 (1914). 10. Pearson and Raitt, "Paper Industry in India", Chemical Abstracts 18, 3716 (1924). 11. Parekh, K. M., "Fractional Digestion of Pulp", Chem. and Met. Eng., 46, No. 8, 474 (1939). 12. Perry, J. H., Chemical Engineers' Handbook, (3rd edition). 13. Ohlgren, Udani and Landrum, Manual of Heat Exchanger Design. IP-139. University of Michigan, Industry Program of the College of Engineering publication. - 31 -