■» o "+ (0- «* '3'. w <• O, * O N r ^' •; ?§' :«fe "°* -life"' ^ 0< ^^ "Wilier* ?V 0v ^ *S£zm&> £°-*> -W^^o iO^ ^^^^W , ' 4 0, ^ .- ^,^^V ./^^>o /,^A /.^> 4 ^ % : *r * ^-k. \ *' A o o « o <* ^^n o^%|^» a V< ^ : " \5, 'o . » * a i0 A^ "i'i* > V .»J »*•,,• Vf" o * OK o' ,0-' ** v \ IC 8959 Bureau of Mines Information Circular/1983 Economic and Technical Evaluation of the Sulfurous Acid-Caustic Purification Process for Producing Alumina From Kaolinitic Clay By Deborah A. Kramer UNITED STATES DEPARTMENT OF THE INTERIOR Information Circular 8959 Economic and Technical Evaluation of the Sulfurous Acid-Caustic Purification Process for Producing Alumina From Kaolinitic Clay By Deborah A. Kramer UNITED STATES DEPARTMENT OF THE INTERIOR James G. Watt, Secretary BUREAU OF MINES Robert C. Horton, Director # op ^\<^. # Library of Congress Cataloging in Publication Data: Kramer, Deborah A Economic and technical evaluation of the sulfurous acid-caustic purification process for producing alumina from kaolinitic clay. (Information circular / United States Department of the Interior, Bu- reau of Mines ; 8959) Bibliography: p. 11-12. Supt. of Docs, no.: I 28.27:8959. 1. Aluminum oxide. 2. Sulphurous acid. 3. Clay. 4. Leaching. I. Title. II. Series: Information circular (United States. Bureau of Mines) ; 8959. TN295.U4 [TP245.A4] 622s [669'. 722] 83-600303 CONTENTS Page Abstract 1 Introduction 2 Process description 2 Clay preparation section 4 Sulf urous acid leaching section 4 Sulfite precipitation and decomposition section 4 Sulfur dioxide handling section. 5 Caustic digestion section 5 Trihydrate precipitation and calcination section 6 Digestion liquor regeneration section 6 Cost estimate 7 Capital costs 7 Operating costs. 9 Economic and technical discussion 9 References 11 Appendix. — Utility requirements, direct labor requirements, daily thermal re- quirements, equipment cost summaries, and material balances 13 ILLUSTRATIONS 1 . Sulf urous acid digestion and crude alumina production 3 2 . Caustic purification 3 A-l. Material balance, clay preparation section 24 A-2. Material balance, sulfurous acid leaching section..... 24 A-3. Material balance, sulfite precipitation and decomposition section 24 A-4. Material balance, sulfur dioxide handling section 25 A-5. Material balance, caustic digestion section 25 A-6. Material balance, trihydrate precipitation and calcination section 26 A-7. Material balance, digestion liquor regeneration section 26 TABLES 1 . Composition of the calcined kaolinitic clay (dry basis) 4 2. Estimated capital cost 7 3. Estimated annual operating cost 10 A-l. Raw material and utility requirements 13 A-2. Direct labor requirements, operators per shift 13 A-3. Daily thermal requirements 14 A-4. Major items of equipment 15 A-5. Equipment cost summary , clay preparation section 16 A-6. Equipment cost summary, sulfurous acid leaching section 17 A-7. Equipment cost summary, sulfite precipitation and decomposition section. 18 A-8. Equipment cost summary, sulfur dioxide handling section 19 A-9. Equipment cost summary, caustic digestion section 20 A-10. Equipment cost summary, trihydrate precipitation and calcination section 21 A-ll. Equipment cost summary, digestion liquor regeneration section 22 UNIT OF MEASURE ABBREVIATIONS USED IN THIS REPORT Btu British thermal unit gal/ft 2 «h gallon per square foot per hour Btu/d British thermal unit per day h hour Btu/gal British thermal per gallon unit h/d kW»h hour per day kilowatt-hour Btu/lb British thermal unit per pound lb pound °c degree Celsius Mgal thousand gallon d/wk day per week min minute d/yr day per year MMBtu million British thermal unit °F degree Fahrenheit pet percent i ft foot psig pound per square inch, ft 2 square foot gauge gal gallon ton/d short ton per day gal/d gallon per day yr year ECONOMIC AND TECHNICAL EVALUATION OF THE SULFUROUS ACID-CAUSTIC PURIFICATION PROCESS FOR PRODUCING ALUMINA FROM KAOLINITIC CLAY By Deborah A, Kramer ABSTRACT An economic and technical evaluation of a proposed process to recover alumina by leaching calcined kaolinitic clay with sulfurous acid is pre- sented in this Bureau of Mines report. After the insoluble portion of the clay has been removed by leaching, monobasic aluminum sulfite is precipitated from the pregnant leach solution by partial hydrothermal decomposition. Further heating completes the decomposition to an impure alumina hydrate. This intermediate is purified in a modified Bayer pro- cess, which includes dissolving the alumina hydrate in a caustic solu- tion at high temperature and pressure, then decreasing the temperature and pressure to precipitate alumina trihydrate. Calcining the trihy- drate produces the alumina product. A cost estimate was prepared for a plant producing 1,000 tons of alu- mina per day, 350 d/yr. The estimated operating cost is approximately $475 per ton of alumina. This is substantially higher than a comparable estimated operating cost for the Bayer process of $250 per ton of alu- mina. The proposed process does not appear economically attractive, even as a method to modify a current Bayer processing plant to use a kao- linitic clay feed. High capital costs and high energy requirements make the process prohibitively expensive. 1 Chemist, Avondale Research Center, Bureau of Mines, Avondale, MD. INTRODUCTION The Bureau of Mines is investigating technologies for the recovery of alumina from domestic nonbauxitic resources. Most of the alumina consumed in the United States is produced from imported bauxite. The United States has very lim- ited supplies of bauxite, but has large reserves of alumina-containing clay and other resources. Development of an eco- nomic process to recover the alumina from kaolinitic clay or other domestic re- sources would insure a continuing alumina supply to meet national needs. The Bureau of Mines has previously evaluated a number of processes for re- covering alumina from clay and anortho- site. None of these processes appeared economically competitive with the Bayer process; however, a few warranted further investigation because their costs were not appreciably higher than those of the Bayer process. The technology developed by these investigations could prove sig- nificant if the cost of imported bauxite increases. One of these processes involves sulfur- ous acid leaching of kaolinitic clay, then purification of the crude alumina product by a modified Bayer process. Two previous evaluations of the sulfurous acid process, based on limited data, indicated that the proposed process appeared economically attractive (1-2). 2 The sulfurous acid process dates back to the late 1800' s. Development was attributed to Th. Goldschmidt A.G. This process occasioned numerous patents (3- 10). In 1938, VAWAG at Lippewerk, Ge7- many, tried the Goldschmidt process on a commercial scale but found that the alu- mina product contained an excessive amount of impurities. It was then that Bayer purification was added to produce a cell-grade alumina ( 11 ) . In the early 1980' s researchers at the Bureau of Mines investigated the sulfur- ous acid leaching process on a laboratory scale. The objective of this research was to expand the experimental data base on the process, to confirm assumptions used in previous evaluations, and to determine if additional investigations in the Bureau's miniplant project were war- ranted (12). The present study includes data (poor alumina recoveries, longer leaching time, etc.) from the recent Bureau research (12) and has been prepared to reassess the potential economics and compare the results with the previous evaluations. PROCESS DESCRIPTION In the proposed process, raw kaolinitic clay is calcined to convert the contained alumina to an acid-soluble form. The calcined clay is leached with a sulfurous acid solution. Alumina is extracted in the form of aluminum sulfite, which is separated from the insoluble residue by filtration. The temperature and pressure of the pregnant leach solution are in- creased to precipitate monobasic aluminum sulfite. Decomposition of the monobasic aluminum sulfite produces an impure alu- mina hydrate. The impure alumina hydrate is purified in a modified Bayer process. First, it is dissolved in a caustic solution at high temperature and pressure. Undis- solved impurities are removed, and alumi- na trihydrate is precipitated by cooling the solution to the point of supersatura- tion, then seeding with fine trihydrate crystals. The trihydrate is calcined to obtain the final alumina product. A ba- sic process flowsheet is shown in figures 1 and 2 for a plant designed to pro- duce 1,000 tons of alumina per day based on 3 shifts per day operation, 350 d/yr. For purposes of discussion, the plant is divided into seven major ^Underlined numbers in parentheses re- fer to items in the list of references preceding the appendix. Recycle sulfurous acid COMPRESSION ' 1 1 I MISTING « Water 1 1 V m Oust CALCINATION Calcined _ LEACHING ~~ loss clay t Aluminum sulfite , slurry Leach ^ residue Recycle leach solution ' FILTRATION S0 2 from leaching * P regnant liquor 4 1 Wash water PRECIPITATION S0 2 from precipitation ' 1 THICKENING DECOMPOSITION Decomposition fc CONDENSATION * * vapor l 1 Waste FILTRATION 1 solution Alu monohj 1 lina drate Concentrated S0 2 gas ■ Stripping ABSORPTION 1 Stripped SULFUR BURNING r Air Elemental sulfur FIGURE 1. - Sulfurous acid digestion and crude alumina production. Al umi na monohydrate Steam 1 i 1 Wash water gestion residue A1 2 3 -3H 2 _ DIGESTION tf ' ' \ ' FLASH COOLING FILTRATION Causti i k 1 ' < Pregnant solution Filtrate and washings i f PRECIPITATION THICKENING FILTRATION AND WASHING CALCINATION St'rdTl filter cake" * See d crysta Is Recyc so 1 e caustic i I 1 Watery. ' 1 EVAPORATION Alumina vapor Wash water Makeu reagen P . ts c leach so lution 1 1 FIGURE 2. - Caustic purification. sections. The material balances for these sections are shown in the appendix. CLAY PREPARATION SECTION Kaolinitic clay is delivered to the plant by truck from a nearby clay pit and dumped into a hopper. The clay is then conveyed to a covered storage pile con- taining a 30-day supply. Clay is withdrawn from this pile as needed and fed to hammer mills for crush- ing to minus 16 mesh. Discharge from the hammer mills is conveyed to a pelletizing disk, where the clay is misted before being fed to surge bins. Minus 16-mesh clay is calcined in a fluidized bed at 750° C (1,382° F) to remove the 18 pet free moisture and the combined water. The calcination reac- tion, which converts the contained alu- mina to an acid-soluble form, is assumed to be Al 2 3 '2Si0 2 '2H 2 -»- Al 2 3 *2Si0 2 + 2H 2 0. Calcined clay is cooled to 65° C (150° F) and conveyed to the leaching section. The analysis of the calcined clay, shown in table 1, was taken from the material balance prepared by the researchers the calcined (12). The Si0 2 content of clay reported by the re- searchers was assumed to include TiOo clay. The shown sepa- known to be present in the estimated Ti0 2 content is rately in the analysis given in table 1. TABLE 1. - Composition of the calcined kaolinitic clay, dry basis Constituent wt pet A1 2 3 41.2 Si0 2 54.4 Ti0 2 3.1 Fe 2 3 1.3 Total 100.0 SULFUROUS ACID LEACHING SECTION Calcined clay is mixed with sulfurous acid leach solution and pumped to 12 trains of 10 pressure-leach tanks. The pressure is maintained at 160 psig and the temperature at 60° C (140° F) during the 17-h leach. Sulfurous acid is in- jected into the tanks to maintain a 30- pct sulfurous acid solution. Calcined clay reacts with sulfurous acid to pro- duce aluminum sulfite by the following reaction: 3H 2 S0 3 + Al 2 3 »2Si0 2 + A1 2 (S0 3 ) 3 + 2Si0 2 + 3H 2 0. Sixty-seven percent of the alumina in the clay is assumed to react. The leach slurry is pumped to pressure- leaf filters where the solids are sepa- rated from the pregnant liquor at a rate of 3.8 gal/ft 2 »h and washed. The filter cake is dumped from the filters into sumps, where the solids are reslurried, neutralized with slaked lime, and then pumped to a tailings pond. Filtrate and washings are combined in a surge tank and pumped to the sulfite precipitation and decomposition section. Due to the pressure drop during filtration, a por- tion of the sulfurous acid decomposes to form sulfur dioxide. This vapor is col- lected as it is blown off from the fil- trate receiving vessels and sent to the sulfur dioxide handling section. SULFITE PRECIPITATION AND DECOMPOSITION SECTION Pregnant liquor from leaching is pumped to autoclaves that operate at 110° C (230° F) and 60 psig. Under these condi- tions, aluminum sulfite precipitates as monobasic aluminum sulfite by the follow- ing reaction: A1 2 (S0 3 ) 3 + 5H 2 ->- A1 2 3 «2S0 2 '5H 2 + S0 2 . Ninety-four percent of the aluminum sul- fite decomposes in 2 h. Sulfur dioxide formed during the reaction is vented and sent to the sulfur dioxide handling sec- tion. The exiting hot slurry is depres- surized, partially cooled by preheating the incoming solution in heat exchangers, and then pumped to a thickener. Overflow from the thickener is recycled to the sulfurous acid leach tanks. Underflow, consisting of a 19-pct monobasic aluminum sulfite slurry, is pumped to a second set of autoclaves operating at 150° C (302° F) and 50 psig. At this tempera- ture and pressure, the monobasic aluminum sulfite will further decompose to form alumina monohydrate by the following reaction: A1 2 3 »2S0 2 »5H 2 + A1 2 3 'H 2 + 2S0 2 + 4H 2 0. Decomposition requires a 1-h residence time in the reactors. Sulfur dioxide and water vapor that are produced and vented during decomposition are collected and sent to the sulfur dioxide handling section. All sulfur dioxide process losses are included with the decomposition vapor in the material balance. Exiting hot slurry is used to preheat the autoclave feed and then pumped to rotary-vacuum drum filters. The alumina monohydrate filter cake is conveyed to the caustic digestion sec- tion. Filtrate from the drum filters is reslurried with the leach residue and pumped to the tailings pond for neutralization. SULFUR DIOXIDE HANDLING SECTION Makeup sulfur dioxide is produced by burning liquid sulfur. This process forms a hot gas containing approximately 19 pet sulfur dioxide. The gas is par- tially cooled in a waste-heat boiler and then passed through an absorption tower, where the sulfur dioxide is absorbed by water. This weak sulfurous acid solution is then passed through a stripping tower, where most of the water is removed to produce a concentrated sulfur dioxide gas stream. Stripping wastes are used to reslurry the process residues for dis- posal in the tailings pond. Mixed sulfur dioxide and water vapors produced in the sulfite precipitation and decomposition section are concentrated by removing some of the water through con- densation. This vapor is combined with the concentrated makeup sulfur dioxide gas stream and the two sulfur dioxide- rich gas streams recovered from leaching and sulfite precipitation. The combined streams are compressed to form a strong sulfurous acid and recycled to the leach tanks. CAUSTIC DIGESTION SECTION To remove excessive quantities of im- purities from the crude decomposition product, the filter cake is processed by a modified Bayer process. Caustic solu- tion is mixed with the alumina monohy- drate filter cake and pumped into pressure-digestion vessels. Steam is injected directly into these tanks to maintain the operating condition of 230° C (446° F) and 400 psig (L3). Alu- mina monohydrate reacts in the following manner: A1 2 3 «H 2 + 2NaOH ■> 2NaAl0 2 + 2H 2 0. Ninety-eight percent of the alumina mono- hydrate is dissolved during the 30-min retention time. The slurry is exposed to air containing carbon dioxide in open tanks and thicken- ers, and by the air-lift agitators used in the precipitation tanks. This causes some of the caustic to react to form sodium carbonate. Since sodium carbonate does not dissolve alumina, lime is added in the digestion liquor regeneration sec- tion to react with the sodium carbonate and regenerate the caustic solution by forming insoluble calcium carbonate by the following reaction: Ca(0H) 2 + Na 2 C0 3 ->- CaC0 3 + 2NaOH. Slurry exiting the digestion tanks is depressurized and cooled in a series of nine flash tanks. Steam is recovered from the flash tanks at the pressures shown in the material balance, and used to preheat the caustic leach solution. Cooled slurry is filtered, and the solids are washed, reslurried, and pumped to the tailings pond for neutralization. Fil- trate and washings are combined and pumped to the trihydrate precipitation and calcination section. TRIHYDRATE PRECIPITATION AND CALCINATION SECTION Pregnant solution from the caustic digestion section is pumped to 30 pre- cipitation tanks, 30 ft in diameter by 64 ft in height, which are equipped with air lifts for agitation. Seed alumina trihy- drate crystals are fed to the precipita- tion tanks in an amount equivalent to 100 pet of the alumina trihydrate pre- cipitated. Seeding the supersaturated solution precipitates alumina trihydrate by the following reaction: 2NaA10 2 + 4H 2 -*- A1 2 3 »3H 2 + 2NaOH. Forty hours are allowed for precipitation. The slurry from precipitation is pumped to a series of three thickeners. Coarse alumina trihydrate crystals are recovered in the underflow from the primary thick- ener. They are filtered, washed, and fed to a fluidized-bed calciner. In the cal- ciner, alumina trihydrate is converted to alumina by the following reaction: A1 2 3 3H 2 ->- A1 2 3 + 3H 2 0, This reaction occurs at 950° to 1,050° C (1,740° to 1,920° F). The cooled alumina product is conveyed to silos with a 60-day capacity for storage and shipment. Filtrate and washings from the calciner filters are combined with overflow from the primary thickener and pumped to a secondary thickener. Overflow from this thickener is sent to a tertiary thick- ener. The clarified overflow from the tertiary thickener is pumped to the digestion liquor regeneration section. Underflows from both the secondary and tertiary thickeners are combined and recycled to the precipitation tanks to provide the alumina trihydrate seed crystals. DIGESTION LIQUOR REGENERATION SECTION Clarified solution from the tertiary thickener in the trihydrate precipitation and calcination section is concentrated in a five-effect evaporator and pumped to storage tanks. A bleed stream is pumped from the storage tank to a single-effect evaporator. Further concentration of the bleed stream allows for removal and con- trol of minor impurities and organic com- pounds, which build up in the process stream. Water vapor is condensed and returned to the storage tanks along with the purified bleed stream. Concentrated solution is pumped to a mixing tank where makeup caustic and lime are added. This solution is preheated using steam recovered from flash-cooling the digestion liquor and recycled to the digestion tanks. Equipment has been provided for clean- ing and descaling the heat exchangers used throughout the process. This equip- ment consists of tanks to store the solu- tion removed from the heat exchangers, tanks containing a sulfuric acid cleaning solution, and tanks for the spent clean- ing solution, as well as the necessary pumps and feed tanks. COST ESTIMATE The cost estimate presented in this cost for the plant described. Although report is based on laboratory data from the degree of confidence in any specific the Bureau of Mines (12) and Bayer pro- study estimate is not great with respect cess data from published and nonpublished to the actual cost, greater confidence is sources. justified when comparing a group of simi- lar processes evaluated by identical CAPITAL COSTS methods. The capital cost estimate is of the The estimated fixed capital cost on a general type called a study estimate by fourth quarter 1982 basis (Marshall and Weaver and Bauman (14). This type of Swift (M and S) index of 749.3) of a estimate, prepared from a flowsheet and a plant producing 1,000 tons of alumina per minimum of equipment data, can be ex- day is about $752 million, as shown in pected to be within 30 pet of the actual table 2. This is equivalent to a cost of TABLE 2. - Estimated capital cost 1 Fixed capital: Clay preparation section $46,084,000 Sulfurous acid leaching section 255,061,600 Sulfite precipitation and decomposition section 40,371,600 Sulfur dioxide handling section 11 , 008 ,500 Caustic digestion section 18,205,100 Trihydrate precipitation and calcination section 36,828,900 Digestion liquor regeneration section 24 ,685 ,600 Tailings pond 5 ,879,400 Steamplant 30,895,600 Subtotal 469 ,020, 300 Plant facilities, 10 pet of above subtotal 46,902,000 Plant utilities, 12 pet of above subtotal 56,282,400 Total plant cost 572,204,700 Land cost Subtotal 572,204,700 Interest during construction period 135,366,800 Fixed capital cost 707,571,500 Working capital: Raw material and supplies 1,283,800 Product and in-process inventory 13,686, 000 Accounts receivable 13,686,000 Available cash 8,738,200 Working capital cost 37,394,000 Capitalized startup costs 7,075,700 Subtotal 44,469,700 Total capital cost 752,041,200 1 Basis: M and S equipment cost index of 749.3. about $2,000 per annual ton of product. The plant is designed to operate 3 shifts per day, 7 d/wk, 350 d/yr, except for some of the clay receiving facilities, which operate 2 shifts per day, 5 d/wk, and the clay crushing facilities, which operate 2 shifts per day, 7 d/wk. Equipment costs for the proposed pro- cess are based on cost-capacity data and manufacturers' cost quotations. Cost data are brought up to date by the use of inflation indexes. Capital costs for the f luidized-bed flash calciner are based on a paper by Lussky (15). The tailings pond is designed as a lined pond with a 2-yr life. It is assumed that after 2 yr, the mine site will be developed to dispose of the remainder of the process residue as backfill. In developing the plant capital costs, corrosion-resistant materials of construction were used where appropriate. For example, the leach tanks are constructed of stainless steel to withstand the acid environment. Factors for piping, etc. , except for the foundation and electrical factors, are assigned to each section, using as a basis the effect fluids, solids, or a combination of fluids and solids may have on the process equipment. The foundation factor is estimated for each piece of equipment individually, and a factor for the entire section is calculated from the totals. The electrical factor is based on the motor horsepower requirements for each section. A factor of 10 pet, re- ferred to as miscellaneous, is added to each section to cover minor equipment and construction costs that are not shown with the equipment listed. For each section, the field indirect cost, which covers field supervision, inspection, temporary construction, equipment rental, and payroll overhead, is estimated at 10 pet of the direct cost. Engineering cost is estimated at 10 pet, and administration and overhead cost is estimated at 5 pet of the con- struction cost. A contingency allowance of 15 pet and a contractor's fee of 5 pet are included in the section costs. The costs of plant facilities and plant utilities are estimated as 10 and 12 pet, respectively, of the total process sec- tion costs and include the same field indirect costs, engineering, administra- tion and overhead, contingency allowance, and contractor's fee as are included in the section costs. Included under plant facilities are the costs of material and labor for auxiliary buildings such as offices, shops, laboratories, and cafe- terias, and the cost of nonprocess equip- ment such as office furniture, and safety, shop, and laboratory equipment. Also included are labor and material costs for site preparation such as clear- ing, grading, drainage, roads, and fences. The costs of water, power, and steam distribution systems are included under plant utilities. The cost for interest on the capital borrowed for construction is included as interest during construction, assuming an interest rate of 11 pet. To determine the interest cost during construction, the total plant cost is factored by an adjusted interest rate, which de- pends upon the length of the construction period and the interest rate at which the money is borrowed. Cost for the plant owner's supervision is not included in the capital cost of the proposed plant. Working capital is defined as the funds in addition to fixed capital, land in- vestment, and startup costs that must be provided to operate the plant. Working capital, also shown in table 2, is esti- mated from the following items: (1) Raw material and supplies inventory (cost of raw material and operating supplies for 30 days), (2) product and in-process inventory (total operating cost for 30 days), (3) accounts receivable (total operating cost for 30 days), and (4) available cash (direct expenses for 30 days). Capitalized startup costs are estimated as 1 pet of the fixed capital, which is shown in table 2. OPERATING COSTS The estimated operating costs are based on the average of 350 d/yr of operation over the life of the plant. This allows 15 days' downtime per year for inspec- tion, maintenance, and unscheduled inter- ruptions. The operating costs are divided into direct, indirect, and fixed costs. Direct costs include raw materials, utilities, direct labor, plant mainten- ance, payroll overhead, and operating supplies. The raw material costs do not include transportation costs because the plant is assumed to be located adjacent to the clay pit. Electricity, water, fuel oil, and coal are purchased utili- ties. The temperature of the water from the cooling tower is assumed to be 32° C (90° F). Raw material and utility re- quirements per ton of alumina are shown in table A-l (appendix). The direct labor assignments are shown by sections in table A-2. The direct labor cost is estimated on the basis of assigning 4.2 employees to each position that operates 24 h/d, 7 d/wk and 2.8 employees to each position that operates 16 h/d, 7 d/wk. The cost of labor super- vision is estimated as 15 pet of the labor cost. Plant maintenance is separately esti- mated for each piece of equipment and for the buildings, electrical system, piping, plant utility distribution systems, and plant facilities. Payroll overhead, estimated as 35 pet of direct labor and maintenance labor, includes vacation, sick leave, social security, and fringe benefits. The cost of operating supplies is esti- mated as 20 pet of the cost of plant maintenance. Indirect costs are estimated as 40 pet of the direct labor and maintenance costs. The indirect costs include the expenses of control laboratories, ac- counting, plant protection and safety, plant administration, marketing, and com- pany overhead. Research and overall company administrative costs outside the plant are not included. Fixed costs include the cost of taxes (excluding income taxes), insurance, and depreciation. The annual costs of both taxes and insurance are each estimated as 1 pet of the plant construction cost. Depreciation is based on a straight-line, 20-yr period. The estimated annual operating cost, shown in table 3, for a plant producing 1,000 tons of alumina per day is about $166 million, or $475 per ton of alumina product. ECONOMIC AND TECHNICAL DISCUSSION From the cost estimate presented in this report, the proposed process does not appear to be an economically competi- tive method for producing alumina. The operating cost of $475 per ton of alumina vastly exceeds the estimated operating cost of about $250 per ton of alumina for the Bayer process (16). Costs for utilities, mainly electric power and coal for producing steam, account for over 30 pet of the total operating cost. Total steam requirements for this process are over 19 billion Btu/d, which is equivalent to almost 24,000 lb of steam per ton of alumina. Sulfite precipitation and decomposition are responsible for 72 pet of this steam requirement. Most of the electric power required is utilized in the leach tanks and the sulfur dioxide compressors. The slurry in the leach tanks must be contin- ually agitated during the 17-h retention time, and with the large number of leach tanks necessary, this operation consumes an inordinate amount of electric power. Compressors require a large amount of electricity to compress over 12,000 ton/d of sulfur dioxide gas. 10 TABLE 3. - Estimated annual operating cost Annual cost Cost per ton alumina Direct cost: Raw materials: Kaolinitic clay at $3 per ton Lime at $31.25 per ton Sodium hydroxide, 50-pct at $175 per ton. Sulfur at $114.75 per ton , Limestone at $4 per ton , Chemicals for steamplant water treatment, Total , Utilities: Electric power at $0,032 per kW'h, Process water at $0.25 per Mgal... Coal at $45 per ton , Heavy oil at $1 per gallon , Total , Direct labor: Labor at $9 per hour , Supervision, 15 pet of labor, Total Plant maintenance: Labor , Supervision, 20 pet of maintenance labor. Materials Total , Payroll overhead, 35 pet of above payroll , Operating supplies, 20 pet of plant maintenance, Total direct cost, Indirect cost, 40 pet of direct labor and maintenance, Fixed cost: Taxes, 1 pet of total plant cost , Insurance, 1 pet of total plant cost , Depreciation, 20-yr life Total operating cost, $5,616,500 273,400 1,041,300 2,128,600 112,000 547,400 9,719,200 12,108,100 668,600 30,835,300 6,634,000 50,246,000 3,425,800 513,900 3,939,700 13,408,900 2,681,800 13,408,900 29,499,600 7,010,600 5,899,900 106,315,000 13,375,700 5,722,000 5,722,000 35,378,600 166,513,300 $16.05 .78 2.98 6.08 .32 1.56 27.77 34.59 1.91 88.10 18.95 143.55 9.79 1.47 11.26 38.31 7.66 38.31 84.28 20.03 16.86 303.75 38.22 16.35 16.35 101.08 475.75 The estimated capital cost for the pro- posed plant is very high, resulting in high depreciation costs. In this esti- mate, depreciation accounts for about 20 pet of the operating costs. Basically, all the tanks and filters necessary for the process are high-capital-cost items. However, the largest equipment cost items are the leach tanks, the pressure-leaf filters, and the sulfite precipitation tanks in decreasing order. Because of the long retention time, a large number of leach tanks is necessary. Each tank must be designed to withstand the leach pressure and be constructed of stainless steel to withstand the acid environment. 11 A large number of pressure-leaf filters is necessary because of the poor filtra- tion rate of the leach residue. Originally it had been assumed that the sulfurous acid technology could be used to produce an alternate feed for an existing Bayer plant. The use of an existing Bayer plant could reduce the capital investment required for recover- ing alumina from domestic clay by about 20 pet, compared with that required for a totally new plant. (This does not in- clude the extra capital required to mod- ify the existing Bayer plant to enable it to accept the crude alumina from the sul- furous acid plant.) Direct operating costs for a totally new plant or a modi- fied plant will be similar. Therefore, the only operating cost advantage will be in reduced depreciation charges. Reduc- ing depreciation costs by 20 pet is not sufficient to allow the crude alumina produced by the sulfurous acid process to compete with bauxite as feed to a Bayer plant. The sulfurous acid leaching process was originally investigated because of the previously estimated low cost and rela- tive ease of recovery of sulfur dioxide as a reagent, and because it would pro- vide a feed suitable for use in a Bayer process. A suitable feed for the Bayer process has not been obtained in the laboratory with respect to impurity lev- els. In previous evaluations, it was assumed that the crude alumina would be soluble at atmospheric pressure, but since it must be pressure-leached, the cost of the process has escalated. One of the assumptions made necessary in preparing this evaluation is that an alumina product of cell-grade purity can be obtained. This has not been demon- strated in the laboratory. The small- scale studies have concentrated on the sulfurous acid leaching and sulfite pre- cipitation and decomposition steps with only minimal investigation of the caustic digestion step in the Bayer process. Research on sulfurous acid leaching in the laboratory did not produce a product with a low enough sulfur content to meet cell-grade specifications. In previous evaluations, the process was judged to be economically competitive with current practices. Recent Bureau of Mines research on the sulfurous acid pro- cess determined that a longer leaching time was required, and that alumina extraction was poorer than anticipated (67 pet as compared to 80 pet, which was previously assumed based on work with German clay ( 11 ) ) . In light of the new data, this process has become more costly and therefore does not appear econom- ically competitive. REFERENCES 1. Bengtson, K. B., P. Chuberka, L. E. Malm, A. E. McLaughlin, R. F. Nunn, and D. L. Stein. Alumina Process Feasibility Study and Preliminary Pilot Plant Design. Task I Final Report. Comparison of Six Processes. BuMines OFR 18-78, 1977, 253 pp.; NTIS PB 286 638/AS. 2. Peters, F. A. , P. W. Johnson, and R. C. Kirby. Methods for Producing Alu- mina From Clay — An Evaluation of the Sul- furous Acid-Caustic Purification Process. BuMines RI 5997, 1962, 21 pp. 3. Buche, K. , and H. Ginsberg (as- signed to Th. Goldschmidt Corp. , New York). Solubilizing Claylike Minerals. U.S. Pat. 2,267,490, Dec. 23, 1941. 4. Fulda, W. , E. Wiedbrauck, and K. Buche (assigned to Th. Goldschmidt A. G. , Essen, Germany). Process for the Recovery of Aluminum Compounds From Aluminiferous Minerals. U.S. Pat 2,123,650, July 12, 1938. 12 5. Fulda, W. , E. Wiedbrauck, and K. Buche (assigned to Th. Goldschmidt Corp. , New York). Manufacture of Monobasic Aluminum Sulphite. U.S. Pat. 2,243,060, May 20, 1941. 6. Fulda, W. , E. Wiedbrauck, and R. Wittig (assigned to Vereinigte Aluminium- Werke Aktiengesellschaf t and Th. Gold- schmidt A.-G. , Essen, Germany). Method of Producing Pure Alumina. U.S. Pat. 2,021,546, Nov. 19, 1935. 7. Fulda, W. , W. Wrigge, and H. Loge- mann (assigned to Th. Goldschmidt Corp. , New York). Separating Sulphurous Acid From Aluminum Sulphites. U.S. Pat. 2,261,113, Nov. 4, 1941. 8. Staufer, R. , and K. Konopicky (assigned to Alterra A. G. , Luxemburg). Process for Treating Argillaceous Mate- rial. U.S. Pat. 1,956,139, Apr. 24, 1934. Process for the Decomposition of Sili- ceous Aluminous Minerals. U.S. Pat. 2,006,851, July 2, 1935. 11. Anderson, R. J. The German Alu- minum Industry. Min. Mag., v. 62, 1940, pp. 274-284. 12. Raddatz, A. E., J. M. Gomes, and M. M. Wong. Laboratory Investigation of a Sulfurous Acid Process for Preparing Alumina From Kaolin. BuMines RI 8533, 1981, 15 pp. 13. Gerard, G. V., and P. T. Stroup. Extractive Metallurgy of Aluminum. In- terscience, New York, v. 1, 1963, 355 pp. 14. Weaver, J. B., and H. C. Bauman. Cost and Profitability Estimation. Sec. 25 in Perry's Chemical Engineers' Hand- book, ed. by R. H. Perry and C. H. Chilton. McGraw-Hill, 5th ed. , 1973, p. 46. 9 . Wiedbrauck , E . , and K. Buche (assigned to Th. Goldschmidt A.-G. , Essen-Ruhr, Germany). Process for the Production of Monobasic Aluminum Sul- phite. U.S. Pat. 1,971,668, Aug. 28, 1934. 10. . (assigned to Th. Gold- schmidt A.-G., Essen-Ruhr, Germany). 15. Lussky, E. W. Experience With Operation of the Alcoa Fluid Flash Cal- ciner. Light Metals, 1980, pp. 69-79. 16. Kramer, D. A., and F. A. Peters. A Cost Estimate of the Bayer Process for Producing Alumina — Based on 1982 Equip- ment Prices. BuMines IC 8958, 1983. 13 APPENDIX. —UTILITY REQUIREMENTS, DIRECT LABOR REQUIREMENTS, DAILY THERMAL REQUIREMENTS, EQUIPMENT COST SUMMARIES, AND MATERIAL BALANCES Raw material and utility requirements per ton of alumina are shown in table A- 1 , and direct labor requirements and daily thermal requirements for each sec- tion are shown in tables A-2 and A-3, respectively. Major items of equipment for each section are shown in table A-4. The equipment cost summaries for each section in the process are contained in TABLE A-l. - Raw material and utility requirements Quantity per ton alumina Raw materials, tons: Kaolinitic clay Lime Sodium hydroxide, 50-pct. , Sulfur Limestone Utilities: Electric power kW*h, Process water Mgal. Coal tons . Heavy oil gal. 5.349 .025 .017 .053 .080 1,081.085 7.641 1.958 18.954 tables A-5 to A-ll. Material balances are shown for each section in figures A-l to A-7. TABLE A-2. - Direct labor requirements, operators per shift Section Clay preparation section Sulfurous acid leaching section Sulfite precipitation and decomposition section Sulfur dioxide handling section Caustic digestion section Trihydrate precipitation and calcination section Digestion liquor regen- eration section Steamplant General plant Total Shifts per week TIT 4 14 4 1 3 2 2 11 41 x 3 shifts per day, 7 d/wk. 2 2 shifts per day, 7 d/wk. 3 1 shift per day, 5 d/wk. ^1T ^5 14 TABLE A-3. - Daily thermal requirements Section and item Steam, MMBtu Heavy oil, MMBtu* Coal, MMBtu 2 Cooling water, Mgal Clay preparation section: 128 9,870 o 128 9,870 o 65,971 Sulfite precipitation and decomposition section: 8,295 5,644 o o 13,939 Sulfur dioxide handling section: -295 41 o o 14,135 -254 14,135 Caustic digestion section: 751 845 2,207 -495 -437 -510 -961 -999 -560 -525 -513 -349 o o o o Flash tank 2 o o o o o o o Flash tank. 9 o -1,546 2,900 o Trihydrate precipitation and calcination o Digestion liquor regeneration section: 1,549 182 437 495 349 513 525 560 999 961 510 3,379 408 o 89 7,080 40 3,876 19,347 -19,347 2,900 9,910 39,035 83,982 2,900 48,945 3,982 Canity of heavy oil (153,000 Btu/gal) = 18,954 gal/d. ^Quantity of coal (12,500 Btu/lb) = 1,958 ton/d. TABLE A-4. - Major items of equipment 15 Section and item Clay preparation section: Hammer mills , Felletizing disks Fluidized-bed calciners Sulfurous acid leaching section: Leach tanks , Pressure-leaf filters. , Sulfite precipitation and decomposition section: Precipitation tanks , Thickener Decomposition tanks Sulfur dioxide handling section: Absorption tower. Stripping tower , Caustic digestion section: Digestion tanks Pressure-leaf filters Trihydrate precipitation and calcination section: Precipitation tanks , Primary thickeners , Secondary thickeners , Tertiary thickeners , Fluid-flash calciner , Digestion liquor regeneration section: Multief f ect evaporator , Evaporator , Unit size 60 by 48 in. 12-ft diam. 1,500 ton/d. 15-ft diam by 45 ft. 1,645 ft 2 . 15-ft diam by 45 ft. 76-ft diam. 15-ft diam by 45 ft. 5.9-ft diam by 22.7 ft, 4.6-ft diam by 19.8 ft, 12-ft diam by 36 ft, 1,644 ft 2 . 30-ft diam by 64 ft, 27-ft diam. 59-ft diam. 1 15-ft diam. 2.9 billion Btu/d. 15,699 ft 2 /effect. 1,519 ft 2 /effect. 16 TAbLE A-5 .-Equi pment cost summary* clay preparation section Item Equipment CostU) Labor Total Apron feeder Belt conveyor •••• • Belt conveyor,.. ,. Keclaimer feeders. belt conveyor, Hoppers Apron feeders., Hammer mills Belt conveyor.,.,.. Belt conveyor... Storage bin Apron feeder... Belt conveyor Pelletizing disks Screw feeders. Coal preparation equipment Bag dust collectors,.,,,.. Screw f eede rs ............ • Total , Unloading hopper.......... F 1 ui di zed-bed calciners... Lime scrubber............. Front-eno loaders 208 671 1746 313 1964 97 23b 5126 133 634 2261 174 467 6012 121 3623 316 67 00. 00, 00. 00. 00, 00. 00. 00. 00. 00. 00. 00. 00. 00. <| 00. 00. 00. 00. 2440600, Total equipment cost x factor indicated: Foundations* x .157 Buildings* x .563,. Structures* x ,100..., , Instrumentation* x ,060.,,.,,,,.,,,,,, Electrical* x .164 , , Piping* x .200 Painting* x ,020 Miscellaneous* x ,100 Total Total di rect cost Field indirect* 10,0 pet of total direct cost Total construction cost, 3100. 13300. 33400. 4700. 35600. 600. 3500. 71800. 2500. 12700. 44500, 2600. 6600. 3600. 1800. 34900. 500, 1300. 23900. 80400, 208000. 36000. 234200. 10500. 27000. 584400. 15800. 76100. 270600. 20000. 53300, 604800, 13900. 417200, 32100. 10000. 277400. 2718200. (2) 17900. (2)20931300. (2) 2938600. 136200, 382000, 1375000. 244100. 195300. 450100. 488200, 48800. 244100. 3427600. 30169800. 3017000. Engineering* 10.0 pet of total construction cost Aami ni st rat i on and overhead* 5,0 pet of total construction cost. Suototal.. • 33166800. 3318700. 1659300. Contingency* 15.0 pet of above subtotal Subtotal 38164800. 5724700. Contractor's fee* 5.0 pet of above subtotal Section cost 43889500. 2194500. 46084000. (1) Equipment costs are based on the M end S index of 749.3. (2) Instal 1 ed cost . 17 TABLE A-6 .-Equi pment cost summary, sulfurous acid leachinc section Item Equ i pment costcn Labo'p Total Belt conveyor........ Belt conveyor Storage bins Screw feeders Mixing tanks.... Pumps. • Leach tanks Pressure- 1 eaf filters Pumps. Sumps........... Pumps. Hoppers.. •••• Belt conveyors....... Total * 12300. 12200 0. 575600. 37200. 17 2 0. 261500. 73939700. 5207500. 67800. 210700, 155000: 19600. 281100. 81062200. Total equipment cost x factor inoicated: Foundations, x .049 buildings, x .010 ,. Structures, x .100,. Insulation, x .011............ Instrumentation, x .180... Electrical, x .020 Piping, x .500 Painting, x .080... Miscellaneous, x .100 Total Total di rect cost Field inoirect, 10.0 pet of total direct cost Total construction cost.. • 2200. 22300. 117000. 5600. 34900. 34100. 184300. 312900. 23600. 44900. 35900. 6800. 65400. 889900. Engineering, 10.0 pet of total construction cost Administration and overheaa, 5.0 pet of total construction cost.,...,.,. Subtotal Contingency, 15.0 pet of above subtotal Subtotal,., Contractor's fee, 5.0 pet of above subtotal Section cost 1450 0. 144300. 692600. 4280 0. 206900. 295600. 7^124000. 5520400. 914 0. 255600. 190900. 26600. 346500. 81952100. 3944100. 774600. 8106200. 895000. 14591200. 1595600. 40531100. 6465000. 8106200. 85029000. 166981100. 16698100. 183679200. 18367900. 9184000. 211231100. 31684700. 242915800. 12145800. 255061600. (1) Equipment costs are Dased on the N' and S index of 749.3. 18 TABLE A-7 . -Equi pment cost summary* sulfite precipitation ana decomposition section I tern Equi pment costm Labor Total Precipitation tanks Blowdown tanks..... Heat exchangers. • Thickener., ...... .......... Overflow pumps Underflow pumps Decomposition tanks........ Blowdown tanks... Heat exchangers... Pumps. Rotary- vacuum arum filters. Pumps ••...•••••••.•••• Reslurry tanks Pumps ..................... . Sulfur oioxiae storage tank Total Cooling tower $ 3153600 46300 1003200 459500 24100 39100 912300 21200 262900 62400 4443200 98700 121300 102900 319400 22300. 23700. 31400. 30000. 4700. 500Q. 7000. 9500. 8700. 11900. 222200. 26300. 23500. 21000. 1100. 3175900. 70000. 1034600. 489500. 28800, 44100. 919300, 30700. 271600. 74300. 4665400. 125000. 144800, 123900. 320500. 11070100 448300. 11518400. (2) 1886400. Total equipment cost x factor inaicateo; Foundations, x .093 buildings/ x .029 Structures, x ,100 , Insulation/ x .062., Instrumentation, x ,180.,,,. Electrical/ x .034 Piping, x .500 Painting/ x .060 Miscellaneous/ x .100 ,. Total 1024300 318200 1107000 684400 1992600 371000 5535100 885600, 1107000 13025200 Total di rect cost Field indirect/ 10.0 pet of total direct cost Total construction cost • 26430000. 2643000. Engineering/ 10.0 pet of total construction cost Administration and overhead/ 5.0 pet of total construction cost. Subtotal ••••. 29073000. 2907300. 1453700. Contingency/ 15.0 pet of above subtotal Subtotal , 33434000. 5015100. Contractor's fee/ 5,0 pet of above subtotal Section cost 38449100. 1922500. 40371600. (1) Equipment costs are based on the M and S index of 749.3, (2) Instal 1 ed cost . 19 TABLE A-8.-Equi pment cost summary* sulfur dioxide handing section Cost (1) Item Equi pment Labor Total Liquid sulfur storage tank Pumps.... • • Sulfur furnace............ haste-heat boiler .. Blowers... Absorption tower , Pumps. Pumps • Stripping tower , Keboi 1 er •• , Pumps , Condenser. •• , Pumps.. , Compressors.. , Total ■ water chiller • , 65900. 1^800. 9100. 47400. 117100. 41900. 12600. 12800. 27900. 4600. 7900. 66300. 16300. 2578000, 32000. 1400. 14300. 1500. 700. 800. 3200. 3200. 500. 300. 2200. 1700. 3900. 226-00. 97900. 16200. 23400. 48900. 117800. 42700. 16000, 16000. 28400. 4900. 10100. 68000, 20200. 2600800. 3022800. 88500. (2) 3111300. 50900. Total equipment cost x factor indicated: Foundations/ x .078 Buildings? x .011 Structures* x .200.. Insulation/ x .031...,..,...,.., Instrumentation/ x ,080 Electrical/ x .228.,, Piping/ x .600 Painting/ x .010 Miscellaneous/ x .100 Total 234800 34100 604600 93300 241800 689900 1813700 30200 302300 4044700 Total direct cost Field indirect/ 10,0 pet of total airect cost Total construction cost 7206900. 720700. Engineering/ 10.0 pet of total construction cost Administration and overhead/ 5.0 pet of total construction cost.......... , Subtotal , 7927600. 792800. 396400. Contingency/ 15.0 pet of above subtotal Subtotal 9116800. 1367500. Contractor's fee/ 5,0 pet of above subtotal Section cost. 10484300. 524200. 11008500. (1) Equipment costs are based on the M and S index of 749.3. (2) Instal 1 ed cost • 20 TABLE A-9. -Equipment cost summary* caustic digestion section Item CostCl) fcauipment Labor Total Bel t conveyors • Hopper. ........ Sc rew f eeoer ... i^i x i ng tank. ... Pumps Pu^ps heat exchanger. Heat exchanger. Pumps.......... Digestion tanks PI ash tank 1 . . . tank tank tank tank tank tank tank tank Fl ash Fl ash Flash Flasn Flash Fl ash F I ash Flash Pumps. Pressure-leaf filters Neslurry tanks Pumps...... Total , Slurry storage tank.., 566700 5400 li600 29400 22900 21400 21000 27500 146100 2747200 73000 55800 U4200 35000 33*00 33^00 33*00 33400 33400 27900 356700 80600 1014 . $ 4545000 Total equipment cost x factor indicated Foundations, x .211 Buildings, x .041.... Structures, x .100 Insulation, x .017 Instrumentation, x .180 Electrical, x .056 , Piping, x .700 Painting, x .080 Miscellaneous, x .100 Total..... Tota 1 oi rect cost Field indirect, 10.0 pet of total direct cost Total construction cost 142600. 900. 700. 5500. 4300. 4300. 1100. 1300. 9200. 4600. 600. 800. 600. eoo. 800. eoo. 800. eoo. 800. 4200. 35700. 24800. 18800, 711300. 6300. 14300. 34900. 27200. 25700. 22100, 26600. 155300. 2751800. 73800. 56600. 45000. 35800. 34200. 34200. 34200. 34200. 34200. 32100. 392400. 105600. 120200. 265200. (2D 4810200. 355200. 958600 186600 454500 79300 818100 256300, 3181500, 363600, 454500, 6753000 Engineering, 10.0 pet of total construction cost Administration and overhead, 5.0 pet of total construction cost Subtotal Contingency, 15,0 pet of above subtotal Subtotal Contractor's fee, 5,0 pet of above subtotal Section cost 11918400. 1191800. 13110200, 1311000. 655500. 15076700. 2261500. 17338200. 866900. 16205100. (1) Equipment costs are based on the H ano S index of 7*9,3. (2) Inst al 1 eo cost . 21 TABLE. A-lO.-Equi pment cost summary* trihydrate precipitation and calcination section Item Equi pment CostCl) Labor Total Pumps..,. Precipitation tanks. Pumps .............. . Primary thickeners.. Sumps..... Underflow pumps..... Secondary thickeners Sumps........ Underflow pumps Tertiary thickeners. Sumps...... ,, Underflow pumps Surge tanks Pumps Overflow pumps...... Surge tanks Pumps Belt conveyor.. Screw feeaers ...... , Total Air compressors...... Fluid-flash calciner, Silos....... ..., 62200. 1740100. 226000. 338300. 4100. 29500. 644400. 20600. 52900. 1578200. 5700. 24700. 29600. 61600. 41800. 25400. 41800. 146700. 32500. 5106100. 24U0Q. 660800. 62800. 49900. 5300. 5700. 96800. 14500. 9600. 170500. 6500. 5400. 11800. 10000. 9200. 16400. 9200. 28700. 4900. 86600. 2420900. 288800. 388200. 9400. 35200. 741200. 35100. 62500. 1748700. 12200. 30100. 41400. 71600. 51000. 41800. 51000. 175400. 37400. 1222400. 6328500. (2) 223400. (2) 6148600. (2) 4817300. Total equipment cost x factor inaicateo: Foundations, x .429. buildings* x .025... Structures* x .050 Instrumentation* x ,150 Electrical* x .087 Piping* x .400 Painting* x .050 Miscellaneous* x .100 Total 2191200. 130100. 255300. 765900. 442100. 2042400. 255300. 510600. 6592900. Total direct cost Field indirect* 10.0 pet of total direct cost Total construction cost • 24110700. 2411100. Engineering* 10.0 pet of total construction cost Administration ana overhead* 5.0 pet of total construction cost Subtotal 26521800. 2652200. 1326100. Contingency* 15.0 pet of above subtotal Subtotal 30500100. 4575000. Contractor's fee* 5.0 pet of above subtotal Sect ion cost 35075100. 1753800. 36828900. (1) Equipment costs are based on the M and S index of 749.3. (2) Inst al 1 ed cost . 22 TABLE A-l 1 .-Equi pment cost summary/ Digestion liauor regeneration section Cost(l) Item Equi pment Labor Total $ 3067000, 1220C. 23300. 10 0. 17600. 490 0. 1500. 490 0. 234500, 20 0. 4900. 4900. 65000. 31000. 3270 0. 3940C. 5360 0. 56000. 6 7 0. 109000. 1219 0. 9 79 00. 101500. 139300. 54100. 415200. 12100. 14800. 1700. 15300. 1210 0. 15300. 9900. 23700. 4900. 14800. 4900. 247800. 10900. 36300. 410 0. 2200. 4900. $ 300800. 3100. 8000. 2700. 4100. 1200. 1600. 1200. 47500. 400. 800. 900. 23300. 8700. 8700. 1100. 1400. 1400. 1500. 2300. 2600. 1900. 2C00. 2400. 17 0. 152900. 8800. 3900. 2600. 3900. 8800. 3900. 50 0. 8800. 400. 1300. 500. 129200. 1600. 5700. 1900. 300. 900. 4 3367600. 15300 . 31300 , 12700 . 217 0. 6100. 3100, 6100 . 262000 . 600 . 5700. 58 0. 86300. 397Cv. 41 400 . 40500. 55200. 57400, 62200, 1 1 1300, 124500. 9960 0. 103500. 141700, 71100, 568100 . 20900. 18700. 4300, 19200, 20900. 19200, 10400, 32500. 53 0. 1610 0. 5400. 377000. 12500. 4200C. 6000, 2500. 5600. 5199100. 782500. 5981600 . (2) 1643800. (2) 55700. TAdLE A-l 1 ,-£qui pment cost summary/ oigestion liquor regeneration section (cont i nued) 23 Total equipment cost x factor indicated: Foundations/ x .345.. •••....•. Buildings, x .015.. Structures/ x .050 Insulation/ x .289... Instrumentation/ x .150 Electrical/ x .032 Piping/ x .600 •••.. • Painting/ x .050 Miscellaneous/ x .100 Total Total oirect cost.. Field indirect/ 10.0 pet of total direct cost... Total construction cost... Engineering/ 10.0 pet of total construction cost Administration and overhead/ 5.0 pet of total construction cost..... • Subtotal Contingency/ 15.0 pet of above subtotal Subtotal.... Contractor's fee/ 5.0 pet of above subtotal.,.. Section cost... • 1794200 77500 260000 1501300 779900 167500 3119500 260000 519900 8479800 16160900. 1616100. 17777000. 177770 0. 888900. 20443600. 3066500. 23510100. 1175500. 24685600. (1) Equipment costs are based on the M and S index of 749.3. (2) Jnstal 1 eo cost . 24 Dust loss A1 2 3 Si0 2 Ti0 2 h 2 o ; Total 16 21 1 ,652 ,690 Water H 2 113 w t Raw c ay Calcined clay A1 2 3 Si0 2 Fe 2 3 Ti0 2 H 2 Total 1,571 2,073 49 117 1,539 5,349 A1 2 3 Si0 2 Fe 2 3 Ti0 2 Total 1,555 2,052 49 116 3,772 SIZE REDUCTION MISTING CALCINATION FIGURE A-l. - Material balance, clay preparation section (tons per day). Recycle sulfurojs acid H 2 SO 2 Total 8,477 12,054 20,531 1 Ca cined clay A1 2 3 Si0 2 Fe 2 3 Ti0 2 Total 1,555 2,052 49 116 3,772 1 LEACHING ^1 1 Recycle leach solution AI2O3 Si0 2 Fe 2 3 H 2 S0 2 Total 27 14 18 17,343 572 17,974 S0 2 from leaching Wash water S0 2 6,187 H 2 13,014 a Pregnant iquor I f AI2O3 Si0 2 Fe 2 3 H 2 S0 2 Tota 1 1,068 20 45 36,260 6,402 43,795 FILTRATION 1 ' Leach residue A1 2 3 514 Si0 2 2,046 Fe 2 3 22 Ti0 2 116 H 2 2,574 S0 2 37 Total 5,309 FIGURE A-2. - Material balance, sulfurous acid leaching section (tons per day). S0 2 from precipitation S0 2 3,850 J i PRECIPITATION THICKENING i 1 J Pregnant liquor Recycle leach solution A1 2 3 1,068 Si0 2 20 Fe 2 3 45 H 2 36,260 S0 2 6,402 Total 43,795 A1 2 3 27 Si0 2 14 Fe 2 3 18 H 2 17,343 S0 2 572 Total 17,974 Oxygen 28 DECOMPOSITION Decomposi tion vap or H 2 S0 2 Total 9 1 11 ,916 912 ,828 -Oxygen shown entering is assumed to have dissolved in the system and oxidized some sulfites to sulfates. FILTRATION Waste so ution Si0 2 1 Fe 2 3 10 H 2 5,970 so 2 14 Total 5,995 FIGURE A-3. - Material balance, sulfite precipitation and decomposition section (tons per day). 25 Absorption water H,0 5,300 Air 2 N 2 106 352 "555 S0 2 from precipitation S0 2 from leaching S0 2 3,850 S0 2 6,187 Decomposition vapor 1 u n Q QIC ■ SO 2 1,912 CONDENSATION * » COMPRESSION Total 11,828 li w v Condensate Recycle sulfurous acid H 2 1,440 H 2 8,477 S0 2 12,054 Total 20,531 Stripped air 2 53 N 2 352 H 2 5 Total 410 i 1 ABSORPTION STRIPPING i i " Stripping wastes SULFUR BURNING Elemental sulfur H 2 5,294 S0 2 Total 1 5,295 FIGURE A-4. - Material balance, sulfur dioxide handling section (tons per day). Alumina monohydrate A1 2 3 Si0 2 Fe 2 3 SOi, H 2 Total 1,041 5 17 82 3,031 4,176 H,0 Steam 1,444 DIGESTION 1 Caustic leach solution A1 2 3 Na 2 H 2 C0 2 CaO Total 1,006 2,601 7,922 572 12,126 Recovered stean 275 psig 305 225 psig 264 175 ps ig 301 100 psig 545 50 psig 549 30 psig 302 15 psig 278 5 psig 267 ps ig 180 Total 2 ,991 FLASH COOLING H,0 Wash water 1,200 FILTRATION Digestion residue A1 2 3 Si0 2 , Fe 2 3 Na 2 C0 2 CaO H 2 Total 31 5 17 3 21 25 97 199 Pregnant solution A1 2 3 Na 2 H 2 C0 2 SO,, Total 2,016 2,598 10,509 551 82 15,756 FIGURE A-5. - Material balance, caustic digestion section (tons per day). 26 Carbon dioxide Wash water C0 2 * 22 H 2 1 ,010 H Pregnant solution A1 2 3 Na 2 H 2 C0 2 SO,, Total 2,016 2,598 10,509 551 82 15,756 V PRECIPITATION PRIMARY THICKENING FILTRATION AND WASHING l 1 i [_ ' SECONDARY THICKENING 1 TERTIARY THICKENING ' Dust loss A1 2 3 10 C0 2 1 H 2 731 Total 742 l\ CALCINATION 1 1 Alumina A1 2 3 1 ,000 Na 2 5 H 2 5 SO,, 82 Total 1 ,092 V Recycle caustic solution A1 2 3 1,006 Na 2 2,593 H 2 10,783 C0 2 572 Total 14,954 -Carbon d i ox i de shown entering here is assumed to have dissolved in the system and converted some sodium hydroxide to sodium carbonate . FIGURE A-6. - Material balance, trihydrate precipitation and calcination section (tons per day). Water vapor H 2 2 870 Recycle caustic solution I I Caustic leach solution A1 2 3 1,006 Na 2 2,593 H 2 10,783 C0 2 572 Total 14,954 A1 2 3 1,006 Na 2 2,601 H 2 7,922 C0 2 572 CaO 25 Total 12,126 EVAPORATION ♦ ] I ! J Makeup r eagents CaO Na 2 H 2 Total 25 8 9 42 FIGURE A-7. - Material balance, digestion liquor regeneration section (tons per day). 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