4 -u -—- ”IiiIlnlunzilyllguiwillingly]uuglm Illlllll ‘ 252 LIBRARY Michigan State Unfvtrrrity (N This is to certify that the thesis entitled DESIGN, ENERGY, AND ECONOMIC ANALYSIS OF SMALL SCALE ETHANOL FERMENTATION FACILITIES presented by Joseph William Geiger has been accepted towards fulfillment of the requirements for M. S. degree inChemical Engineering MM Major professor Date June I], 1981 0-7639 OVERDUE FINES: 25¢ per any per item RETURNING LISjflBY raimggsu; Place in book return to rerun. charge from circulation re w DESIGN, ENERGY, AND ECONOMIC ANALYSIS OF SMALL SCALE ETHANOL FERMENTATION FACILITIES BY Joseph William Geiger A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Chemical Engineering 1981 a 99 .) GM ABSTRACT DESIGN, ENERGY, AND ECONOMIC ANALYSIS OF SMALL SCALE ETHANOL FERMENTATION FACILITIES BY Joseph William Geiger Industrial scale fermentation ethanol production from corn has been prOposed as a way to produce liquid fuel, but can only achieve a positive liquid energy balance and positive economics by careful plant design. In comparison, small scale production of alcohol on corn- producing farms and farms which use the by-product might reduce costly corn drying and transportation energy charges involved in industrial scale production. If corn stillage could be stored in a wet state, it would be fed to livestock without being dried and the ethanol product would be used by farm equipment as fuel. The purpose of this study was to determine the requirements for a small scale ethanol production scheme with relatively low energy requirements and evaluate the overall energetic and economic feasibility of the pro- cesses compared to large scale industrial production. This project also involved the construction of a pilot small scale ethanol production facility by the combined Joseph William Geiger efforts of the Chemical Engineering, Agricultural Engineering, and Animal Science Departments of Michigan State University with a grant from the Michigan Depart- ment of Agriculture. The Chemical Engineering Department was responsible for the design, construction, and Opera- tion of the distillation apparatus and the energy and material balances around the system. This pilot facility was used in this study as a source of data to support the designs of farm scale processes. Three small scale ethanol production schemes or scenarios were evaluated in this study. Scenario I, Farm Production of Anhydrous Ethanol, was used as a base case of 15 farms, each producing 100,000 gallons of anhydrous ethanol per year, in which all processing to produce anhydrous ethanol was done entirely on each farm. Scenarios II and III use large scale process centraliza- tion variations on the base case in an attempt to reduce the overall energy requirements of the process. Scenario II, Centralized Azeotropic Distillation, is the same as Scenario I except for a centralized large scale azeotropic distillation facility for water extraction from the ethanol-water azeotrOpe to produce the anhydrous ethanol product. Scenario III, Centralized Ethanol Rectifica- tion and AzeotrOpic Distillation, incorporates central- ized large scale ethanol rectification for low grade Joseph William Geiger ethanol refining together with azeotropic distillation for anhydrous ethanol production. The best overall production scheme was Scenario III which had an overall energy efficiency of 0.694 BTU out/BTU in, compared to 1.00 for industrial scale pro; duction (5 million gallons of anhydrous ethanol per year). This lower energy efficiency for small scale production is significant since the corn stillage by-product was not dried in the small scale case and was dried in the indus- trial scale case. The energy losses in the small scale process can be attributed to the inefficiencies of the small scale steam boiler and low pressure steam and heat losses due to large surface to volume ratios of small scale equipment. The energy savings from feeding wet corn stillage and lower transportation requirements did not offset these small scale energy inefficiencies and resulted in a significant decrease in the overall energy efficiency compared to industrial scale production. Scenario III produced anhydrous ethanol for $3.77 per gallon, which could be produced for $1.98 per gallon by an industrial scale facility. This increased cost of ethanol is primarily due to greater fuel, labor, and equipment costs of small scale production. Small scale fermentation ethanol production from corn is not economi- cally or energetically favorable, compared to indus- trial scale production, as shown by these results. TABLE OF CONTENTS Page LIST OF TABLES. . . . . . . . . . . . . . . . . iii LIST OF FIGURES . . . . . . . . . . . . . . . . v I. INTRODUCTION. . . . . . . . . . . . . . . 1 II. PRODUCTION SCHEMES. . . . . . . . . . . . 4 A. Scenario I Process: Farm Production of Anhydrous Ethanol. . . . . . . . 10 B. Scenario II Process: Centralized AzeotrOpic Distillation . . . . . . 13 C. Scenario III Process: Centralized Ethanol Rectification and AzeotrOpic Distillation . . . . . . 15 III. SCENARIO ENERGY BALANCES. . . . . . . . . 18 A. Scenario I Energy Balance . . . . . . 22 B. Scenario II Energy Balance. . . . . . 24 C. Scenario III Energy Balance . . . . . 26 IV. ECONOMIC ANALYSIS . . . . . . . . . . . . 30 A. Scenario I Economics. . . . . . . . . 33 B. Scenario II Economics . . . . . . . . 37 C. Scenario III Economics. . . . . . . . 38 V. CONCLUSIONS AND RECOMMENDATIONS . . . . . 40 APPENDIX A: Design, Operation and Experimental Results of Small Scale Ethanol Production Facility. . . . . . . . 48 APPENDIX B: Scenario Equipment Lists . . . . . 89 APPENDIX C: Scenario Equipment and Operating Costs. . . . . . . . . . 95 BIBLIOGRAPHY. . . . . . . . . . . . . . . . . . 105 ii Table A1. A2. A3. A4. A5. A6. A7. A8. A9. A10. A11. LIST OF TABLES Basis of Scenarios. . . . . . . . . . . . Scenario Energy Efficiencies. . . . . . . Economic Assumptions. . . . . . . . . . . Total Capital Investment. . . . . . . . . Summary of Overall Economics. . . . . . . Summary of Results, Process Requirements and Costs: Farm-Scale vs. Industrial Scale Ethanol Production. . . . . . . . Comparison of Energy Efficiencies (Outputs/Inputs) and Production Costs for Farm—Scale to Industrial Scale Ethanol Production. . . . . . . . Pilot-Scale Distillation Column Design Specifications . . . . . . . . . Hardware for Distillation Column. . . . . Control Operations and Equipment. . . . . Control Equipment for Distillation COlumn O O O O C O O O O O O O 0 O O O 0 Raw Data for Material Balance . . . . . . Overall Material Balance. . . . . . . . . Overall Material Balance. . . . . . . . . Overall Material Balance. . . . . . . . . Overall Material Balance. . . . . . . . . Material Balance Summary. . . . . . . . . Summary of Ethanol Losses . . . . . . . . iii Page 21 31 34 36 41 43 51 53 56 57 66 67 69 71 73 77 78 Table A12. A13. B1. B2. B3. C1. C2. C3. C4. C5. C6. Raw Data for Energy Balance. . Energy Balance Results . . . . Scenario Scenario Scenario Scenario Scenario Scenario Scenario Scenario Scenario I: Equipment List. . II: Equipment List . III: Equipment List. I: Equipment Costs . II: Equipment Costs. III: Equipment Costs I: Operating Costs . II: Operating Costs. III: Operating Costs iv Page 83 84 89 91 93 95 96 98 100 101 103 LIST OF FIGURES Figure Page 1. Scenario I Process. . . . . . . . . . . . ll 2. Scenario II Process . . . . . . . . . . . l4 3. Scenario III Process. . . . . . . . . . . 16 4. Energy Balance of Scenario I. . . . . . . 23 5. Energy Balance of Scenario II . . . . . . 25 6. Energy Balance of Scenario III. . . . . . 27 Al. Schematic Diagram of Combination Stripping-Rectification Column Design. . . . . . . . . . . . . . . . . 52 A2. Schematic Diagram of Stripping- Rectification Column Controls . . . . . 55 A3. Modes of Operation for Small-Scale Distillation Column . . . . . . . . . . 60 A4. Small-Scale Ethanol Fermentation Process Diagram . . . . . . . . . . . . 65 A5. Flow Diagram for Distillation Column Energy Balance Calculations. . . . . . . . . . . . . . 85 A6. Photograph of Distillation Apparatus of Experimental Small-Scale Facility. . . . . . . . . . . . . . . . 87 A7. Photoqraph of Sieve Trays in Rectification Mode of Operation . . . . 88 I . INTRODUCTION Ethanol production from biomass has been considered as an alternative liquid fuel since gasoline was first used as a fuel, and is revived whenever oil prices in- crease or availability is questionable. Foreign control of oil reserves and dramatic price increases have again forced many countries to consider using ethanol as a fuel. The United States, with its abundant grain reserves, is a prime candidate for fermentation ethanol production. Many Midwestern states, together with the United States government, are promoting and giving economic incentives for ethanol production and use. Large scale production of ethanol by fermentation of biomass is currently in practice in many parts of the United States. The energetic and economic feasibility of large scale production is therefore well known and is usually favorable.(6'7’12) One of the problems encountered with large scale fermentation ethanol production from corn, which is popular in the Midwest, is the large energy re— quirements of the overall process. Energy is not only re- quired for corn grinding, cooking, fermentation, and dis- tillation, but is also needed for the drying of the corn stillage byproduct and the transportation of all feedstocks and products. Small scale fermentation ethanol production (less than one million gallons of anhydrous ethanol per year) on a corn-producing farm is one proposed method for reducing some of these energy requirements. On-farm pro- duction might reduce some of these energy requirements by the close proximity of the corn to the plant, a local market for ethanol as a fuel for farm equipment, and the use of the corn stillage by-product as a livestock feed on the farm. A substantial energy savings might also be realized by feeding the grain by-product wet instead of drying it. The storage life of wet grain by-product is still being researched. Large scale plants dry the by- product because of the storage, transportation, and mar- keting problems involved with a wet-corn stillage by-pro- duct. The small scale facility could feed the wet by- product on the farm immediately after processing and alleviate these storage, transportation, and marketing problems. If it is determined that wet by-products can be stored and fed to livestock, the feeding of wet grain by- product on the farm could also save energy and costs normally incurred in drying the by-product. This method of processing ethanol has obvious energy-saving advan- tages, but it also has disadvantages with energy losses through small scale process inefficiencies. The ener- getic and economic feasibility of such a system has not been researched in the literature. The purpose of this study is to evaluate three small scale ethanol production schemes, or scenarios (chosen for their low energy and economic requirements) to find the Optimal production schemes, and determine the overall energetic and economic feasibility of such a process. All material and energy balance data used in this study were obtained from a pilot facility constructed on the Michigan State University campus by joint effort of the Chemical Engineering, Agricultural Engineering, and Animal Science Departments with a grant from the Michigan Department of Agriculture. The pilot small scale facility was used to evaluate all facets of on-farm small scale ethanol production. The distillation column design, construction, and Optimization and the overall material and energy balances were carried out by the Chemical Engineering Department. Livestock nutrition from by-product feeding and ‘the utilization of the ethanol product by farm equipment were studied by the Animal Science and Agricultural Engineering Departments. I I . PRODUCTION SCHEMES The objective of evaluating different small scale ethanol production schemes or scenarios was to choose an overall process of relatively low energy and economic requirements. Typical farming conditions in Michigan were used to provide a realistic basis for the comparison. An overall knowledge of the problems and limita- tions of small scale fermentation ethanol production is required in devising a base case for the scenarios and is not available in the current literature. The experiences gained from constructing and Operating the small-scale fermentation ethanol facility at Michigan State were used as a source of reliable data for this study. The experi- mental design, Operation procedure and problems, and overall results of the pilot facility are documented in Appendix A. These results were then used to support the design of an efficient, but realistic, base case on farm small scale ethanol production facility (Scenario I) and two variations in the base design (Scenarios II and III). The basis for the scenarios is outlined in Table l. A biomass feedstock of corn was used because of the avail- ability of corn in the Midwestern states, its high (11) ethanol yield in comparison to other feedstocks and TABLE 1. Basis for Scenarios BiOmass Feedstock: Corn Location: Saginaw Valley Area, Michigan Ethanol Production: 100,000 gallons Anhydrous Ethanol per Farm.per Yeara Facility Utilization: 8000 Hours (48 Weeks) per Year Ethanol Yield: 2.34 Gallons Anhydrous Ethanol per Bushelb ( 56 lbs @ 15.5% moisture) Farm Size: 535 acres of Corn per FarmC Corn USage: 42,735 Bushels per Year Nunber of Farms: 15 Farms (in 30-Mile Radius)d Byproduct Use: "Wet" corn stillage byproduct with filler fed to livestock on farme (1917 lbs dry/day) Required Livestock: 780-960 Beef Cattle per Farm, or 2550-2760 Hogs per Farmf Process Energy Efficiencies: 62% Boiler Efficiency 35% Electric Efficiency Fuel Source: Coal ($40/Ton) Electricity: Purchase (Coal or Nuclear: $0.032/kwh) aLargest production size for one Operator per shift bAverage yield of experimental facility (Appendix A) CSize required for given yield and 80 bushels per acre (average for Saginaw Valley Area)10 dAverage distribution of farms with 535 acres or more of corn in Saginaw Valley Area10 e"Wet" means that no moisture is removed from stillage. sting 7-15% corn byproduct ration.11 6 the substantial amount Of information available on large scale ethanol production for comparison. The Saginaw Valley area in Michigan was chosen for the study because it is in the heart of Michigan's corn belt. The ethanol production of 100,000 gallons of anhydrous ethanol per farm per year was used because it is the maximum possible size for one Operator per shift and is a minimum in labor cost per gallon produced. This estimate is based on the experience gained at the M.S.U. facility. This produc- tion size requires a minimum of 535 acres of corn per farm using an average ethanol yield of 2.34 gallons of anhydrous ethanol per bushel of corn and a corn yield of 80 bushels per acre, which is consistent with yields in the Saginaw Valley area. The ethanol yield of 2.34 gallons of anhydrous ethanol per bushel is an average experimental yield from the batch fermentation studies documented in Appendix A. The fifteen farms in the study were assumed to be within a 30-mile radius, which is the average distribution of farms growing 535 or more acres (10) The corn still— of corn in the Saginaw Valley area. age by-product of each farm would be fed wet to livestock without any moisture being removed to save energy used in drying. Dry fillers would also be used to lower the overall moisture content and to add required nutrients to the feed. The livestock requirements for each farm are 780-960 beef cattle or 2,550-2,760 hogs using a 7-15% ration of by-product.(ll) 7 A boiler efficiency of 62% was used to account for losses of energy in the production of steam from a coal fired boiler. Coal was used for the process since the purpose of the project is to produce liquid fuel, which is in short supply, from non-liquid fuel materials which are not in short supply, such as coal. An electrical efficiency of 35% was used to represent the energy losses in production and usage of electricity. Coal or nuclear power was assumed to be the source of the electricity used in the process. Large scale fermentation ethanol production from corn is a well documented process in the literature(6’7'12) and involves the same basic steps as small scale production except for soluble protein concentration and drying of by- product. The basic steps of production are grinding, cooking, saccharafication, fermentation, distillation, and dehydration. The first step in the process is grinding of the corn to expose starch for the cooking step. Water and enzymes (i.e. alpha amylase) are added to the milled corn for the cooking or liquification step. In this step, the starch in the corn slurry is converted into soluble high molecular weight sugars called dextrins by heat and enzymatic action. This process can be carried out in either batch or continuous flow cookers at high or low pressures. High pressure cooking has the advantages of increased conversion and considerably shorter cooking times, but much more elaborate equipment is required and 8 is generally used only for large scale processing. The temperatures and steam pressures used range from 250°F at 15 pounds pressure for 15 minutes to 360°F at 160 pounds (15) Low pressure batch cooking pressure for 30 seconds. was used for this study for reasons of cost and practi- cality. The next step in the process is the saccharifi- cation step which converts the non-fermentable dextrin sugars into fermentable sugars. This is done while the slurry is still hot from the cooking step with a gluco- amylase enzyme. The slurry is held at 135 - l40°F only long enough to permit a portion of the dextrins to be converted, then the mixture is cooled to fermentation temperature of 85 - 90°F. This fermentation process may be initiated as soon as sufficient sugars are available to support a yeast population. In the fermentation step, yeasts convert the sugar into ethanol and carbon dioxide. The time required for the completion of fermentation is dependent upon the strain of yeast used, but the average time required is 48 hours. All equipment currently being marketed utilizes a batch fermentation process, as was used for this study. Continuous fermentation units could allow for the use of smaller fermentation equipment and substantial reductions in production time, but compli- cated problems of contamination with such systems have not been solved. After completion of the batch fermentation, the ethanol is separated from the fermented slurry or beer in the distillation step. In this step, the beer is heated to vaporize the alcohol in a stripping column and the vapors are further refined in a rectifying column and cooled, and condensed to produce an azeotropic ethanol-water solution. The residue or corn stillage by-product contains the resi- dual grain, protein, spent yeast, and water. The final step in the process is the dehydration of water extraction from the ethanol-water azeotrOpe to produce the anhydrous ethanol product. This process can be performed with either a hydrocarbon solvent distillation or a water absorbing molecular sieve. This overall ethanol production process uses corn, water, heat, enzymes, and yeast to produce anhydrous ethanol to be used as a fuel, and corn stillage to be used as a livestock feed. 10 A. Scenario I Process: Farm ProductiOn of Anhydrous Ethanol In Scenario I, the process of producing anhydrous ethanol is carried out entirely on the farm, as illus- trated in Figure 1. All required processing equipment is itemized in Table B1 of Appendix B. The corn is grown, dried, stored, and milled on the farm. The milled corn, together with water, is added to a 6,000 gallon batch cooker. The starch is converted to glucose with enzymes. This process takes four to eight hours, depending on the corn and enzymes used. The resultant slurry is then transferred to one of four 6,000 gallon fermentation tanks, with yeast, to be fermented for 48 hours. Four fermenters are used so that one tank will always be empty for prOper cleaning. The cooker is also cleaned and pre- pared for another cycle, which is run every 24 hours. These maintenance schedules are essential in combatting contamination which is a major problem with batch fermen- tations. After 48 hours of fermentation, the beer is dis- tilled in a sieve tray stripping column and a packed rectifying column to produce a 95 volume % ethanol-water azeotrOpe. A sieve tray stripping column is used so that the solids in the fermented beer can be run through the column. The solids are run through the stripping column to reduce ethanol losses which occur if the solids are separated before distillation. A packed rectifying 11 mmoooum H OHHmcoom .H onomwm Asmara. zov A ZOHfioghxm mm 9&3 BUDoomm AOZflmBm mDOmQNEZ¢ MDMH m MSDUWAOZ IIHIIL AOdeBm w MSDHO> mm mowmmmmsv 25$ 29 A 32»sz \ Eng 28 Emma 29 / T oneaoEHmmmooamfiA moaquam 2035333 oneasszmmm mmedz zmou oza 9,558 A zmoo 12 column is used for easier Operation and control and lower capital cost. The 5% water in the azeotrOpe is then extracted with a regenerative molecular sieve column to obtain the anhydrous ethanol product. Azeotropic distil— lation with benzene solvent is the most common method for water removal from an ethanol—water azeotrOpe, but is not practical for this small scale facility. Benzene is a hazardous chemical which requires strict controls for safety. The benzene process requires much more equip- ment, labor, and capital investment and is a higher technology process than the molecular sieve process. One disadvantage of the molecular sieve process is that it requires more energy to operate than benzene-azeotropic distillation, but electricity can be used as the heat source which is also more practical than steam on a small scale farm process. The wet corn stillage by-product from the beer distillation is mixed with nutrients and fillers and fed to livestock on the farm. The overall process requires only one operator per shift, primarily for batch start-ups and tank cleaning. Fermentation, distillation, and water extraction processes are fully automated and run 24 hours per day. All yield and economic calculations use 8,000 hours or 48 weeks of operation per year, leaving a reasonable amount of time for maintenance shutdowns. Quality control of the process is performed with laboratory tests of product streams on every eight hour 13 shift change. The laboratory work is assumed to be done by a local laboratory but no allowance is made for re- processing Of contaminated ethanol. The anhydrous ethanol product (100,000 gallons per year) is assumed to be used by farm equipment which had been converted for ethanol fuel or sold to a local retailer. It is assumed that a local gasoline distributor is willing to buy and blend the anhydrous ethanol with gasoline. B. Scenario II Process: Centralized Azeotropic Distillation The overall process scheme for Scenario II (Figure 2) is the same as that for Scenario I with the exception of the water extraction from the 95 volume % ethanol-water azeotrOpe. All required processing equipment for Sce- nario II is listed in Tables B2 of Appendix B. The water extraction process for the 15 farms of Scenario II is centralized into one cooperative water extraction plant. The plant, which uses the benzene-azeotrOpic distillation method of water removal, is equally owned and Operated by the 15 farms that use the facility. This change in pro- cessing not only uses less energy than Scenario I by using the more efficient large scale plant, but also simplifies the small scale processing for the farmer. The large scale cooperative facility can also produce a more consistent and pure product with extensive equip- ment and process controls and thorough product analysis 14 mmwoonm HH Owumcoom .m musmflm Aezaqm m>He mm Emma A 2mg 20 c a .m o A mooemmad A E a 20 c x 2% 2 V oneaonHmamooam mocqu am onefifiemHo oneaezmeamm A o a zmoo z oszOOO \ mmSMNZm mme¢3 A zmou 15 which is not practical or even possible with small scale production. This is an important factor in fermentation ethanol production because of possible acetic acid con- tamination of the anhydrous ethanol product which can occur with improper process Operation. The 95 volume % ethanol-water azeotrOpe is hauled by tanker truck from the producing farms, each of which produces 100,000 gallons of ethanol per year on an an- hydrous basis, to the centrally-located plant. The water is removed from the ethanol—water azeotrOpe with azeo- tropic distillation using benzene as a solvent. The pro- cess requires the use of three atmospheric pressure dis- tillation columns and a two-phase liquid separator or decanter, as listed in Table B2 of Appendix B. The anhydrous ethanol product is then trucked back to the farms after the process is completed to be used or sold to local farmers for fuel. An average distance of 30 miles between each farm and the plant is used for energy consumption calculations, which is the average distribu- tion of farms of this size in the Saginaw Valley area. (10) C. Scenario III Process: Centralized Ethanol Rectification and Azeotropic Distillation The process scheme for Scenario III (Figure 3) is identical to Scenario II except for the centralization of the rectification distillation process, which is performed 16 Aommm sooemm>qu mmoooum HHH OHHmcoom .m musmflm Aszfim m>Heammmooov ZOHBUdMme mmad3_ ZOHBfiddHBmHQ BUDnomm AOZ mm Ami WOdAAHBm zmou A 2mg zoc ZOHBdAAHBmHD A 2mg 20 v A 2mg 20 V m mmzwmzm \ onagzmzamm T onafiHmHgooam AA mama: ozc 3588 LA zmoo 17 on the farm site in Scenarios I and II. All required equipment for this process is listed in Table B3 of Appen- dix B. The distillation process on the farm is changed to a simple stripping column which produces a low-grade product (65 volume % ethanol). This low-grade product is then trucked to the cooperative plant and distilled in a rectifying column which produces a 95 volume % ethanol azeotrOpe. The water is extracted from the azeotrOpe with the same benzene-azeotropic distillation process used in Scenario II. The anhydrous ethanol produced by this distillation is then trucked back to the producing farms. This process change simplifies the small scale processing by moving the rectification portion of the distillation process from the small scale farm units to the centralized large scale plant. By making this change, the stripping of the fermented beer is the only distil- lation process carried out on the farm. This stripping process is far less complicated and easier to control than both a stripping and rectifying column as used in Scenario I and II. Simplification of farm processing is considered favorable by most farmers even if energy and economic savings are not realized, as illustrated by dairy farmers with the centralization of milk processing. This process change is also suggested for its possible energy and economic savings resulting from increased efficiencies of large scale processing. III. SCENARIO ENERGY BALANCES The energy balances around each scenario process are performed in several different ways, as illustrated in Figures 4 - 6. The energy contained in the corn feed is listed both as (a.) the energy required to grow the corn, and (b.) the energy obtainable if the corn is burned. The energy contained in the corn stillage by-product is also given two values of energy content, both of which repre- sent the energy required to replace the protein in the by-product as an animal feed. One value (c.) includes the soluble protein when all the by-product is used and the other value (d.) neglects soluble proteins to be used if the by-product is dewatered by screening before use. These two sets of energy content values are used so that the reader may choose the parameters or values which fit specific cases of interest. The author favors the (a.) and (c.) assumptions because the values fit the condi- tions Of the corn and stillage used in this study. The actual measuring of energy efficiency of a pro- cess is done with an energy efficiency ratio. The energy efficiency of a process is equal to the energy output of that process divided by the energy put into that process. 18 19 All efficiency values of the scenarios are listed in Table 2. The energy data from the energy balances are used directly for the efficiency calculations which give several different ways of measuring efficiency. The efficiency values used are the process fuel energy effic- iency, from the fuel energy balance of the conversion process, and the overall energy efficiency. The process fuel energy efficiency is equal to the total fuel energy produced in ethanol divided by the total fuel energy in- put in coal and electricity to produce the ethanol. This figure does not include energy used to grow corn. Total Energy In Process Fuel Energy== Ethanol Produced Efficiency Total Energy in Coal and Electricity to Produce Ethanol The overall energy efficiency is equal to the ratio of the total output energy of corn stillage and ethanol divided by the total input energy of coal, electricity, and corn. Total Energy In Corn Stillage Overall Energy _ And Ethanol Produced Efficiency - Total Energy Input of Coal, Electricity, And Corn The overall energy efficiency, like the overall energy balance, is calculated in four different ways for reader convenience in Table 2. 20 Total Energy In Corn Stillage And Ethanol Produced Overall Energy Efficiency = Total Energy Input of Coal, Electricity, And Corn The overall energy efficiency, like the overall energy balance, is calculated in four different ways for reader convenience in Table 2. ANHV ANHV .poom HmEHcm mm cfiououm oomamou ou OOHHDOOH woumcm I moanoaom DOOQUHS U .poow Hmeflcm mm aflwuonm OOOHOOH Op ponwsomu mouocm I ommaaflum waoczo fl ohm.o mmm.o hmv.o 5H¢.o mam.o Nmm.o vmm.o 5mm.o mwm.o omm.o .HOSM mm poms ma cuoo Scum manmcwouno hmnmcm b .cHOU 3oum O muasoou ammo: mom.o A p .Q.v mav.o A O .3 V mmm.o A O .m v «mm.o A O .m v moc00flmmm mmnocm Hamuw>o mvm.o wocmflowmmm mmumcm Hoom mmmooum HHH OHHMCGOW HH OHHMCOUW mocwHOHmmm H Ofluocoom came mmcowOfimmm moaocmflOflmmm mmwmcm uoflmcoom .m canoe 22 A. Scenario I: Energy Balance The overall energy balance for Scenario I is given in Figure 4. The fuel requirement for azeotrOpe production of 90,252 BTU/gallon anhydrous ethanol is the amount of coal energy required to produce steam for the cooking of the corn, fermentation, and distillation to azeotrOpe. The fuel consumption for water removal of 3,500 BTU/gallon anhydrous ethanol is to assist in heating the molecular sieves for regeneration. The electric requirement to pro- duce the ethanol-water azeotrOpe of 20,600 BTU/gallon anhydrous ethanol is used for pumps, fermentation agita- tion, fan condenser, and fermentation coolers, corn and by-product conveyers, controls, and other miscellaneous equipment. The electric requirements for the water removal section of 17,130 BTU/gallon anhydrous is pri- marily for heating and molecular sieves and the gaseous nitrogen which is passed through the sieves to remove the water. All efficiency values are given on Table 2. The process fuel energy efficiency, which is the energy of the anhydrous ethanol divided by the total fuel and electric energy required to produce that ethanol is 0.645 for this case. This value shows that more fuel energy is put into the process than is produced in ethanol. The overall energy efficiency which takes the energy content of the corn fed into the process and the corn stillage by-product 23 esnca Amm\sem oms.qm Hocmnum w HO> m.mm Buoaomm A H Oflumcoom mo oocmHmm houocm .ooow mm cwououm momamou Ou ooufioowu >muocm I mOHQDHOm poocuflz .v mnamfim ANHV O Amav.oomm mm cfiououm OOOHQOH Ou omuwsvmu >ouocm I mmmaaaum OHO£30 AHHV.Hoom mm poms «A choc Eouw manmcflmuno monocmn .cuoo 3Com Ou muasoou >mumcm Am: a m wanna Hm6\oem oom.m amDm Aessca Amo\n3x No.mc osnca Hmm\oem oma.ha UHMBUMAM A zmaa 20 V Asunca Amm\nsx «0.65 esnca Amm\aem omv.om qa>ozmm mmeaz usage Amm\oem ooo.om Hocmnum w HO> mm m>mHm mddDUmAOE A zmam 20 c onsomqm seHoHoam s os\amm Acofiumaaflumflo mom com com Ame usage Ammxaam ~m~.om amps ooo.ooH A eAessca Amo\oem omv.AAv oesnca Hma\pam on~.a~ MU m.mm economa HH OHumcoom mo oucmHom >ooocm .pmom mo cflwuoum oooamou ou OOMHOOOH >muocm Immansaom poonuflz ANHV .m ousmflm U .omom mm cwououm womamou Op oouflsoou >muocm Immmaaflum OHOSBO ANHV .Hoom mm com: ma cuoo Eoum wanmcflmuno >ouocm AHHV ANHV Q .cuoo 3Com Ou OOMMDUOM >muwcmm AmeHm gamezmov osnca Hmm\oem omo.ma Amos essca Hmm\:zx an. ossaa Amm\pem mam oneomom osnem azaqm Hmm\oem omv.om m oneoamex Hocmcom w Ao> mm mmsaz ounce Amm\s3x v0.6 osnca Hmm\oem ooo.om A swam 20 V oneomqm squHoaa A .omAAHumHo new cam oom.smc.|: > c mm . u>\Hmm e a a A \aem mmm om Amos ooo.ooH AMi, e Deanna Hmm\oem os~.v~ Ae>nca Amm\oem ONA.AAV mU¢AAHBm ZmOU BDQBDO mmmuomm Aesnca Amm\aem osa.amav mesgca Hmm\osm oom.~m Asoo naxaem oomov o i omsuo oa\oem omoa zmoo BDQZH 26 I Of 0.645, as shown in Table 2. The overall energy efficiency range of 0.667 to 0.368 is also slightly better than that of Scenario I of 0.662 to 0.366. This increase in efficiency ratios of Scenario II over Scenario I is less than 1%, but is significant in the fact that it re- veals a trend that further increases in process centraliza— tion might also further increase efficiency. Scenario III increases process centralization to test the efficiency trend by moving the ethanol rectification process to a COOperative plant together with the water extraction process. C. Scenario III: Energy Balance The overall energy balance for Scenario III is given in Figure 4. The corn, electric and corn stillage energy values are unchanged in this case. The fuel energy requirement for the farm facility of 72,675 BTU/gallon anhydrous ethanol is substantially lower than the 90,252 BTU/gallon anhydrous for the other cases. This reduction can be attributed to producing 65 volume % ethanol with a stripping column and transporting it to the central refinery, instead of the process used in the other scenarios, which produces a 95 volume % ethanol distilled in a stripping and rectifying column. This low grade product is distilled to 95 volume % ethanol with benzene extraction at the central distillation and extraction facility. The fuel requirement for the central facility 27 HHH Ofluocoom mom oocmaom >muocm .0 musmflh .cofiomHAHomHe =mamom HmfluumseeH= scum emomsflommm Amav.omom mm cwououm OOMHQOM ou oouflooou amnocm I OOHQOHOm uponufizo Amav.oomm mm cflououm oomamon Op ponwsomu wmuocm I ommaawum oaon3o AHHV.HOOM o no poms ma cuoo Eoum manmcaouno honocmn .cuoo 3oum Ou OOHHOOOM >ouocmo ANAL mousse Hmm\oem omn+mm some esece Hmm\e3x me. cause HmU\oeoneeA weHoneomqm vague Amo\ezx eo.m AmaHm oemezmoe usage Hmmxoem oom.o~ AM . seHoneomqm o>£c< HomVDBm omh om onBU¢maxm ocmnum w HO> no A zmdm 20 v Hocmnum w Ho> 0.0m mmeez 02¢ uosooum oomuo 30A econome oneequemHo wquHoem eoflumAAHuon you Dem omoqmme. usage emm.aam mso.ms H> \ Hmm amam An ooo.ooa s o . eAe see .3 \PE owe A: nAesece 335.3 211:: pounce Hmm\D.H.m CAINJVN mpemncd Hmm\DBm oom.~m oAsuo oH\oem oomov moeqfiew zmoo msuo n Amuoco ouoo now cuoo scum Ou ocuflsomu mmuoco mcflms .o:ao> amuoco auspOumI>b Cuoo uOu comm Hmefico o .Hocmcuo on» OOOOOOO Ou Hozu mm000um c“ >muoco HmDOO on» >o oocw>fio cocoo0uo Hocmcuo ca >muocm Hmuoeo mm.Hm oma.HINHm.o 0mm.0Imom.o ANAemamom HmAuumsocH Aaococum moOupwcc¢ mo coHHmo umm my ss.mm ma.mw «H.4m umoo coauosooue eam.o soo.o mom.o asoconAuum Hamum>o mmo.o omm.o mee.o socoaoauum Macaw mmOOOum coaumHAAumao caucuuomue coaumAHAumAa Hocmaom msouowece cc< COAOOOAMMuoom OAmOquowd mo coauoo©Oum Eumm Hocmcum omNfiHmucou oonwaouucoo ”HHH ofiumcoom "HH Oflumcmom "H Owumcoom oamom Eumm .cofiuoscoum Hococum mamom HowuumsocH O» uOm muwov cofluoscOum ocm AmusmcH\musmuoov wwwocofiofiumm wmuocm mo cOmAummEOU .5 manna 44 efficiency of 0.650 and an overall energy efficiency of 0.667. Both the efficiency and the ethanol selling price are better than those of Scenario I because of the addi- tion of a more efficient centralized large scale process. The best of the three scenarios for small scale fermentation ethanol production from corn, both economi- cally and energetically, is Scenario III. This scheme produces low grade ethanol entirely on the farm (65 vol %) by stripping the fermented corn beer. The stripped stillage is then fed to livestock on the farm. The low grade product is then trucked to a centrally-located cooperative plant for anhydrous ethanol production. .The , energy and economic savings in this scenario results from the greater use of efficient large scale facilities over the other two scenarios, where more processing is done with less efficient small scale facilities on the farm. The resultant ethanol selling price for Scenario III is $3.77 per gallon anhydrous ethanol. Scenario III also has an overall energy efficiency of 0.694 and an overall process fuel efficiency of 0.683. Both the ethanol price and the efficiency values are the best of the three scenarios, but they are not competitive with commercial scale costs and energy usage. The current market value (14) of anhydrous ethanol is $1.98 per gallon and most large scale commercial processes have efficiencies close (12) to unity. These results show that small scale 45 production of ethanol to be economically and energeti- cally unfavorable compared to large scale production. The operating costs ($2.41 per gallon of anhy- drous ethanol) are one of the major causes of the high price of ethanol in Scenario III. The price of corn $1.15 per gallon of anhydrous ethanol at $2.70 per bushel) is one reason for these high operating costs and can only be lowered with increased yields of ethanol per bushel. Yields would be difficult to improve over the value used in this study (2.34 gallons anhydrous ethanol per bushel of corn) with small scale batch fermentation since the value used was obtained under carefully controlled experimental conditions. Overall operating and equipment cost could be reduced if continuous fermentation processes were per— fected. Continuous fermentation would allow for smaller fermentation equipment and substantial reductions in pro- duction time, but complicated problems of contamination with such systems have not been solved. A breakthrough in this area could vastly improve the overall economics of small and large scale fermentation ethanol production. Operating costs might be further reduced by using wood, corn stalks, or some other farm residue for fuel to produce steam. Labor and energy costs are also responsible for the high ethanol price in small scale production. Labor 46 costs ($.53 per gallon of anhydrous ethanol) are very high with respect to large scale production labor costs ($.21 per gallon anhydrous ethanol for a 5 million gallon (12) This value could possible be re- per year plant). duced with further process centralization or increased process automation. Energy costs of Scenario III ($.42 per gallon of anhydrous ethanol) are close to large scale energy costs ($.37 per gallon of anhydrous ethanol),(12) but could be further reduced by using high moisture corn instead of drying the corn and the extruder for corn cooking and saccharification over batch processing. High moisture corn can save up to 3,000 BTU per gallon of anhy- drous ethanol and an extruder up to 11,000 BTU per gallon of anhydrous ethanol. Even with these proposed savings, which decrease the price of ethanol by 1.4¢ per gallon of anhydrous, the small scale production of ethanol from corn is still not currently feasible, compared to large scale production. The results of the overall scenario studies indicate the importance of minimizing small scale pro- cesses. Even with the centralized processes of these scenarios, small scale fermentation ethanol production from corn cannot currently compete with large scale industrial production. APPENDICES 47 APPENDIX A: DESIGN, OPERATION AND EXPERIMENTAL RESULTS OF SMALL SCALE ETHANOL PRODUCTION FACILITY APPENDIX A DESIGN, OPERATION AND EXPERIMENTAL RESULTS OF SMALL SCALE ETHANOL PRODUCTION FACILITY Distillation Column Design Basis The distillation column has been designed using current chemical engineering techniques to meet the requirements of maximum efficiency and minimal height. The column was designed to handle a continuous feed of 8-10% ethanol solution with slurried solid byproducts. A column height of 10 feet was used to avoid the require- ments of a tall containment building. This small size was Obtained by using the column only as a stripping column (no reflux) for the initial beer feed. If a product over 65 vol % ethanol was required, the product could be further purified by using the same column in a separate distillation step as a rectifying column. This procedure can also save energy since the energy costs of producing ethanol increase with increasing reflux. Stainless steel sieve tray plates with downcomers were used for their ability to handle slurries and resis- tance to ethanol corrosion. Steam coils were used for the heat source instead of steam injection because of the energy savings and no byproduct dilution. The vapor condenser was cooled with well water which was recycled to the cooking stage of the process. 48 49 Since the distillation column was also to be used as a demonstration tool, glass externals were used. The glass column does not corrode like soft steel and was easy to disassemble for maintenance. A11 pipes leading to the column were either PVC plastic or stainless steel, in order to resist ethanol corrosion. 50 1. Design Methods Table A1 lists the design specifications of the column. Figure A1 has a schematic diagram of the equip- ment. Table A2 shows the costs of the hardware purchased for the column. The calculation of the diameter of the distillation column was done using a feed flow rate of 25 gallons per hour and 9% ethanol composition. The design capacity of the column was 8,000 gallons of anhydrous ethanol (1'4) used the per year. The method for calculation maximum allowable vapor velocity in the column as a basis which was calculated from the surface tension and the densities of the liquid and vapor. The downcomer and weir height sizings for the sieve trays were done by assuming the dimensions and then calculating the resulting flowrates and plate hydraulics (height of liquid in downcomer, height of liquid and froth on plate, (1) The calculated liquid etc.) to prove the design. and froth heights were also used to decide on the spacing between the plates. The vapor hole sizes and downcomer collector dimensions were based upon the average size of the ground corn particles (% inch) being used in the process. Both the collectors and vapor holes were made large enough so the corn particles could pass through them freely. The total number of vapor holes or open area of the plates 51 Table A1. Pilot-Scale Distillation Column Design Specifications. 1. Column 9 inch diameter column 9 feet 5 inch overall height Corning glass 2. Sieve Trays 11/32 inch vapor holes 38 vapor holes per plate (7.28% Open area) 1% inch diameter downcomer 3 inch diameter collectors 1% inch weir height 9 inch spacing between plates 10 plates in column Stainless steel construction 3. Reboiler 30 feet of a-inch COpper tubing 4 square feet heat exchange area 4. Condenser 16 square feet heat exchange area Vapor on shell side Cooling water through tubes (4 pass) 3/8 inch co-per tubes 5 inch diameter brass shell 5. Piping 3/4 inch feed and bottoms lines Figure Al. Schematic Diagram of Combination Stripping - Rectification Column Design . ’7‘) i (5;? Cooling FEEDI :DEIZU [._> n . ‘1 U I is. U L. n _ CONDENSER SIEVE / (16 SC] I‘I) TR Y ‘ ” U H REFLUX «twat:— ‘ SURGE FEEDIJ‘k’EU n L TANK t i . !.—H | REBOILER (0:92?“ D (4sq ft) (:3 ondenso e BOT TOM S 53 Table A2. Hardware for Distillation Column # Units Description Cost/Unit* Glass Straight Pipe 9" x 59" Unequal Galss Tee 9" x 1.5" Glass Reducing E11 9” x 3" Glass Straight Pipe 9" x 12" Glass Straight Pipe 9" x 9" Connecting Flange Kit 9" Gaskets 9" Misc. Fittings, Flanges, Gaskets HHO‘ml—‘i-‘l—‘NH Condenser (Copper 8 Brass, 16 sq. ft.) |-‘ O Sieve Trays (Stainless) fabricated Column Support Valves, Piping, Misc. Plumbing Progressive Cavity Pumps 3/4" (ANT-“H Plastic Storage Tanks, 250 gal. 1 Misc. (paint, lumber, etc.) Total Distillation Cost (without assembly) = $10,375.48 5 soo.oo(1) 270.00 247.00 278.00 220.00 98.00 58.25 284.10 550.00(2) 181.30(3) 634.80 980.00(4) 1,500.00 270.00 391.08 *SOURCE: 1. Corning Glassware (1980 Prices) 2. American Standard 3. University Engineering ShOp 4. Local Industrial Suppliers 54 was known from the literature(l' 5' 6' 7) to be within a range Of 6-10% of the active area. An open area of 8% was chosen initially and was experimented with by plugging holes to find the Optimal value for the column. The condenser was sized to condense the vapor from 100 gallons per hour of feed to be sure it was large enough for a wide range of vapor flowrates. The reboiler was designed with a large fouling factor (100 Btu/°F- sq. ft.-hr.) because of the fouling tendency of corn mash and the low energy of available steam ((100 psig). 2. Column Controls The Operational control of the distillation column can be done by numerous methods depending on what parameters are important to the process. In this case, the complete stripping of the ethanol from the bottoms was the most important. The column controls were designed to ensure this condition. Table A3 and Figure A2 contain the control equipment and the control schematic diagram. Table A6 lists the costs of control and process monitoring equipment for the column. Throughout most of this study, the distillation column was Operated without instrument controls because of the long lead time required for their specification and delivery. Process monitors and controllers have now been installed. The column can be controlled by adjusting two parameters, which are the maximum number that can Figure A2. Schematic Diagram of Stripping - Rectification Column Controls 55 Temperature Recorl‘der‘ Vapor (.1923 I N l 9980* I aOd‘IO‘ I I L v A v A . W. __ Temp ] Control Level _ “I A Control 7 a u >‘ Flow Meter_ 56 Table A3. Control Operations and Equipment Operations Equipment Reboiler Bottoms Control Valve Transducer Level Controller Steam Control Thermocouple and Transmitter Steam Control Valve Constant Feed Controller Flow Meter Faed Control Valve Temperature Monitor Thermocouples Recorder Steam and Process Flow Monitors Steam Flow Meter Bottoms Flow Meter Distillate Flow Meter Recorder 57 Table A4. Control Equipment for Distillation Columns. Description Price Reboiler level Controller $1,001.00 (1) control Transducer (Remote Seals) 1,410.00 Control Valve 3/4" 458.00 Feed Control Mass Flow Meter 3,225.00 (2) Control Valve 3/4" 458.00 (1) Steam Control Control Valve (air) 8" 386.00 Thermoc00p1e8 Transmitter 850.00 Temperature 12 Point Recorder 2,095.00 Monitor Thermocouples (12) 840.00 Flow Meters Steam Meter & Transmitter 987.00 (3) Steam Flow Indicator 747.00 Mass Flow Meter (Bottoms) 3,225.00 (2) Total Automated Control (without installation) = $18,977.00 *Source: 1. Taylor Instruments (1980 Prices) 2. Micro Motion Inc. 3. Foxboro 58 be controlled for this type of column. The steam flow and the bottoms flow are the controlled variables because of the large effect both have on the bottoms composition. The steam flow is controlled by temperature of the bottoms liquid and the bottoms flow controlled by the level of the liquid in the reboiler. The feed to the column fluctuated in our system because of the decreasing level in the tank from which the feed was being pumped. The column feed should be constant since the entire column is disrupted by feed fluctuations. A flow meter and a control valve are specified for keeping the feed constant. This is not a controlled parameter (i.e., adjusted by column conditions) but only a means of reducing fluctuations in the feed. Temperature and flowrate monitors are not crucial to column operation but are recommended for an automated system. A temperature log of the top vapor and the bottoms liquid is important for observing how well the column has been operating and serves as a check on distillate and bottoms purity. Steam and process flowmeters are less important than temperature recorders but were purchased for this project because of the importance of knowing exact flowrates for the experiments. 59 Columnggperation 1. Modes of Operation The distillation column was used in three different modes of operation (Figure A3). In Mode I, the ethanol was stripped from the fermented corn mash. This Mode used nine trays with no reflux, resulting in a product of 65 vol % ethanol and an ethanol-free bottoms product. Mode I operation had a feed or mash flowrate of 43.1 gallons per hour, and a distillate flowrate of 6.9 gallons per hour. The bottoms product was screened and used for feed and the distillate was either used for fuel in tractor experiments or was further purified in Mode II. Mode II was operated with reflux and 10 trays and used the Mode I distillate (65 % ethanol) as feed. It produced a distillate of 85 vol % ethanol and a bottoms of 15 vol % ethanol. The bottoms were mixed with the corn mash feed for Mode I and the distillate was either used as fuel or further purified in Mode III. Mode III was never required in our work since all of the Mode II distillate was used for fuel. Theoretically, Mode III (using reflux and 10 trays) should produce a 95 Vol % ethanol distillate and an 80 vol % ethanol bottoms from the 85 vol % ethanol feed. It should be noted that distillation in the higher ethanol concentration ranges was far less efficient than in the lower ranges. MODE I. Beer Stripping 65 vol % Ethanol + Water 4: (Mode II Feed) Fermentation Beer 10 wt % Solids 9 vol % Ethanol ' ' Bottoms Product < 0.2 vol % Ethanol 12 wt % Solids MODE II. Ethanol Rectifying 85 vol % Ethanol + Water 65 vol % Ethanol + Water 15 vol % Ethanol + Water (Recycle to Mashing Operation) MODE III. Ethanol Rectifying _-———5" 95 vol % Ethanol + Water ,______T 85 vol % Ethanol"""'"5'l + Water L—J '*—-—-> 80 vol % Ethanol + Water (Recycle to Mode II feed) Figure A3. Modes of Operation for Small-Scale Distillation Column 61 2. Manual Column Operation Fermentation mash was stripped of ethanol in a con- ventional stripping column to less than 0.2 vol % ethanol in the bottoms product. The subcooled feed entered the top tray and moved down the column. Vapor was generated using a steam coil immersed in a column bottoms. Overhead vapors were condensed and recovered. Bottoms were dewatered using a vibrating sceen system. Information for energy and material balances was obtained manually. Operation of the distillation column revealed some unique features of corn mash distillation. The most important feature is the sensitivity of the overheads composition to vapor velocity through the tray holes. The column was initially configured with 42 holes of 11/32" diameter on each plate, resulting in overheads product of 22-26% ethanol. Since some weeping was observed under normal column Operation conditions, 10% of the holes were plugged on each plate. The overheads product jumped to 66-70% ethanol with no change in the other operating conditions. Plugging another 10% of the holes caused a reduction in the overheads ethanol composition. The distillation of fermented mash seemed sensitive to the Open area on the plates, which controlled the vapor flow rate across the trays. Liquid flow rates of feed and bottoms also required careful adjustment to obtain maximum separation in the stripping Operation. Apparently there was a narrow Operating range of vapor 62 and liquid flow rates for optimal separation when fermen- tation beer was the feed. The feed and boilup rates should be controlled as suggested in the control discussion to ensure Operation within this narrow range. Operation of the column was completely manual, re- quiring an operator to watch over the process at all times. The distillation of a normal-sized 500 gallon batch required 10 hours of Operation which usually produces 35 to 40 gallons of ethanol on an anhydrous basis. The column was cleaned after every batch by flushing with water immediately after distillation. Plugging was a problem when the mash was allowed to dry, so washing the column after each batch was necessary. Plugging could be detected in a steel column by observing an increase in pressure drop through the column. This might be done by installing pressure taps on the column. Material Balance One of the goals of this project was to make material and energy balances on the small scale ethanol process. The material balances were vital for identifying causes of material and energy losses. Low yields of ethanol from the corn feed were caused by poor starch conversion or ethanol losses in the process. The material balance pin- pointed these problems. Specific material balance data of four typical runs are tabulated in Tables A6 to A9. The starch conversion and overall yield values are listed in Table A10. 63 was 7% of the total ethanol produced. The amount of ethanol lost by evaporation during fermentation was found to be higher than the amount lost with the column bottoms (2%). In support of this high fermentation loss is the fact that most designs in the literature for larger ethanol plants recommend ethanol scrubbers for fermentation vapors. (6’7) This 7% loss of ethanol is significant and scrubbers should be considered for all size facilities even though many small-scale designs overlook the importance of scrubbers for fermenters.(5) The difference between the gas chromatograph and the hydrometer measurements ranged from 1.7 to 4.6% in the four trials. This error is low enough to permit using hydrometers for small scale plants. The only problem is the measurement of low ethanol concentrations in the column bottoms if losses are expected. Hydrometers are not accurate at very low concentrations and other methods should be used. A bottoms temperature monitor or a bottoms temperature control are two alternatives which can be used to assure bottoms purity. The hydrometer used in the trials had a built-in thermometer for temperature correction and had an overall precision of 0.25 volume %. This range of error can be expected for all material and yild calculations when using a hydrometer of similar quality for ethanol concentration measurements. 64 Fenmentation ethanol was produced from ground corn (see Figure A4 ) via the following steps: (1) cooking and saccharification; (2) fermentation; (3) distillation; (4) ethanol upgrading; (5) bottoms dewatering. All per- tinent weights and compositions were measured and recorded for each batch (Table A5). Corn with 12 vol % moisture and 60 vol % starch was the process feed. The slurry in the fermenter was 17 vol % solids at the beginning of fermentation. About 5 vol % of the fermentor contents was lost during the fermentation to a starch endpoint. Most of this loss was carbon dioxide gas. Only 6 to 7 vol % starch was left in the stripped product. Sixty- five vol % ethanol was produced by stripping the beer under Mode I operation. Ethanol compositions were measured by both a gas chromatograph and a hydrometer as a check on the accuracy of the hydrometer readings. Separate material balances were also done using the data from each method (Tables A6 to A9) to find any propagation of error caused by using hydrometer measurements. Starch compositions of the initial corn and bottoms product were measured using the Macrae and Armstrong method . (9 ) This method used a specific hydrolysis of starch to glucose and measured the resultant glucose to determine the starch content. All component weights were measured in the cooker- fermenter tank. The apparatus was constructed on a scale 65 H20 00 B Enzymes 2 L I D Cooking C i . Ground —-? Saccharification § Fermentation Corn E Mode I ' F 9 Storage, Mode II Distillation Distillation G Bottoms Dewatering, to Storage and Feed Figure A4 . Small-Scale Ethanol Fermentation Process Diagram. Table A5. Raw Data for Material Balance 10/24 10/28 11/3 11/19 Batch Batch Batch Batch Lbs. Wet Corn 992.0 881.0 951.0 940.0 Fraction Dry Material .882 .882 .879 .9032 Lbs. Water Plus Corn 4815.0 4145.0 4475.0 4428.0 Fraction (8) Starch .596 .596 .598 .587 Lbs. Lost in Fermentation 254.0 332.0 300.0 300.0 Fraction Starch (8) in Bottoms Mash .0653 .0700 .0628 .0628 Gallons Ethanol- Water Product 60.0 68.0 60.0 63.0 a vo1 % Ethanol in Product 62.3 60.2 69.0 60.0 b VOl % Ethanol in Product 64.17 62.29 70.25 72.80 b VOl % Ethanol in Feed 8.63 10.40 10.27 7.52 b Vol % Ethanol in Bottoms .30 .33 .60 .08 aHydrometer Measurement bGas Chromatograph Measurement 7 6 newscasmmoz nmmumoumEOOcU moon ooumasoamo SHHOOAOOuoocam mmm. u .>coo cOumum cuoo =m\HOcmcum .mbm .Hmm HH.~ u Ceca» o.moaq v.mme o.amme o.vmm o.m~mm o.~mm Hmuoa III III III om.Am~ III Noo Akwus v~.v bAwuz 5H.wmv o.a H.vmm H.mwm mm.~ III Hocmcum v.aebm m.mma h.mmmm mq.o o.m~mm H.hHH nouns Am.emmv III Am.emmv III AH.mmmv cwouOum A¢.mmv III Ae.mmv III Am.ammv cOumum «.mmm III ~.mmm III m.eem Asuov euoo 0 .m m o d Emmuum muCOEousmmoz cofiuMuucoocoo qu cumumOumEOunu new means .e Aeooeo\moH. ooemamm Heeuoooz HAouo>o .ee oases 68 ucoeousmmmz nouoEOupmmo ooumasoamo MHHMOMuOHOwsBm mam. 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I .>cou scumum cuoo OO\Hocmnuo .mom\Hmm H¢.~ u mama» m.m~sm H.mee o.msee o.oom o.msee o.e~mm o.emm Hobos III III III em.mm~ III III III Noo oAmuz we.c kooz om.~ev s.oe «.msw m.em~ om.m III III III Hoeoeom m.osem m.eee ~.smom om.A A.mmmm o.e~mm H.mHH nouns Ao.smmv III Ae.e~mv III As.mmmc III As.mmmv :Aoooum Am.mec III Am.mee III A~.emmc III A~.oomv toumom m.~e~ III m.~e~ III m.mmm III o.mmm Soot euoo o a m o o m e soouum mucmeousmmoz cofiumuucoocoo uOm ammuOOumEOuco moo momma .¢ Aeouoo\moec ooemaom Heauouoz Heouo>o .m< manna ucweousmmoz noquOuommo nonmaaoamo Adamofiuouoocam pom. u .>cou scumum :uOO so\HOcmnuo .mom Ham hm.m I came» 72 m.mmsm s.oee e.msae e.oom o.mhee o.e~mm o.Hmm Hobos Io" '5' '5' 0 II" '5' In" N am omm oo ko03 ~.Hec III «.msm e.mem 8H.SH III III III Hosanna H.moem m.msa e.omem as.~ H.mmom o.e~mm H.mHH cones Am.me~c III Am.ee~c III As.mmms III As.mmm. eaoooum As.eAe III As.eec III A~.oomc III A~.oomc noomum ~.mo~ III «.mem III m.mmm III m.mmm Aweoe eooo 0 m m a U m c ammuum mmusmooz cOMumuucoocOU qu uOuOEOuo>m magma .m Aooseaoeoos .ee oases 3 O nAwu mo v 73 .>coo sputum o.mNHv bAmus bh.emv H.mwN ¢.mhmm Am.Hh~V A~.mav m.mm~ ucoEouommoz smmum0umEOuco now a nonmaouamo adamofiuouoonam cuoo sb\Hocmcuo .mbm .Hmm mm.~ came» Hence NOU Hocmcum nouns cwouOum buyoum Anny CHOU o.m~ee o.emem o.oem o.msmm o.mmem o.em Ao.emmc III Ao.emmc Ao.eoe. III Ao.mmec o.mem III o.mem O m e ammuum mucoEOuswmoz coflumuucoocou uOu Aeooeo\IoH. ooeeeem Heauoooz Hemom>o cONHOOuoEOuso moo mean: .a .m< wanna 74 ucoEousmmoz wou050uo>mb coumasoamo >HHo0quuoocBm Hom. u .>cou scumum ouoo ab\aocmcuo .mom Hum ma.m n oaofiw o.meem o.oee o.m~ee e.oom o.m~ee o.mmem o.oem Hobos III III III ~.ee~ III III III Noo kouz mm.Amc III e.me~ e.me~ o~.sm III III III Hoemoum m.mmmm e.om~ e.oemm me.m o.msmm o.mmem o.em ”one; Am.mm~s III Am.mm~e III Ao.Hmmv III Ao.emmc enououe Ae.mAs III Ae.mec III Ao.maec III Ao.mmev souoom «.mom III ~.mom III o.aem III o.mem Azuos euoo U h m a U m e ammuum mucoEouzwooz coAumuucmocoo uOm nouOEOupmm magma .m Aoooceocoov .me wanna 75 so all measurements can be easily taken. The only draw- back to this scale is its low precision of i% lb. The material balance summary for four typical runs is shown in Table A10.0verall yield values, though quite variable, were all below the maximum possible yield of 2.7 gallons absolute ethanol per bushel and can be improved upon.with further work.(9) The large yield fluctuations in the trials (2.11-2.62 gal. anhydrous ethanol/Btu) were due primarily to cooking and fermen- tation problems. Cooking times, temperatures, and pH variations along with enzyme and yeast amounts were the major causes. This problem was also revealed by the variations in starch conversion. Further experimen- tation with these parameters and a more automated system could solve most of these problems. Ethanol losses in the process occurred in fermen- tation and distillation. The fermentation losses were from evaporation during the 48 hours of fermentation. The distillation losses occured from low concentrations of ethanol in the bottoms liquid. . AS shown by Table A11, fermentation ethanol losses appeared to be substantial, but these losses were calculated from the theoretical yield of CO2 and the relative vola- tility of ethanol to water. The wide variation in the values can be attributed to the method of calculation. The best estimate for ethanol losses during fermentation 76 was 7% of the total ethanol produced. The amount of ethanol lost by evaporation during fermentation was found to be higher than the amount lost with the column bottoms (2%). This high fermentation loss seemed reasonable since most designs in the literature for larger ethanol plants recommend ethanol scrubbers for (6' 7) This 7% loss of ethanol is fermentation vapors. significant and scrubbers should be considered for all size facilities even though many small-scale designs overlook the importance of scrubbers for fermenters.(5) The difference between the gas chromatograph and the hydrometer measurements ranged from 1.7 to 4.6% in the four trials. This error was low enough to permit using hydrometers for small scale plants. The only problem was the measurement of low ethanol concentration in the column bottoms if losses are expected. Hydrometers were not accurate at very low concentrations and other methods should be used. A bottoms temperature monitor or a bottoms temperature control are two alternatives which can be used to assure bottoms purity. The hydrometer used in the trials had a built-in thermometer for temperature correction and had an overall precision of 0.25 volume %. This range of error can be expected for all material and yield calculations when using a hydrometer of similar quality for ethanol concentration measurements. 77 Table A10. Material Balance Summary 10/24 10/28 11/3 11/19 Batch Batch Batch Batch Average Yielda (Gal. Abs. Ethanol/ bu Corn) 2.11 2.62 2.41 2.23 2.34 Yieldb (Gal. Abs. Ethanol/ bu Corn) 2.05 2.52 2.37 2.13 2.27 % Error in Hydro- meter Measurements 2.9 3.5 1.7 4.6 3.2 Starch Conversion .955 .980 .969 .964 .967 aGas Chromatograph Measurement bHydrometer Measurement Table All. 78 Summary of Ethanol Losses 10/24 10/28 11/3 11/19 Batch Batch Batch Batch Average Total lbs. absolute Ethanol Produced 265.4 317.3 303.1 286.2 293.0 Lbs. Ethanol Losta in Fermentation 2.3 25.1 8.2 23.1 14.7 Wt% Ethanol in Bottoms .24 .26 .48 .06 .26 Total lbs. Ethanol Lost in Bottoms 9.0 8.2 16.7 2.0 9.0 % of Total Lost in Fermentation .87 7.9 2.7 8.1 5.0 % of Total Lost in Distillation 3.4 2.6 5.5 .70 3.1 % Of Total Lost in Overall Process 4.3 10.5 8.2 8.8 8.1 aValues include weight loss from secondary fermentations, aldehyde evaporation and all other weight losses except water. 79 Energy Balance One of the unanswered questions about small-scale ethanol production is whether the energy balance around the process is positive. Distillation is one of the most energy-intensive steps in fermentation ethanol production. In this project an energy balance was made around the distillation column for the purpose of iden- tifying energy losses and their magnitude. The energy balance was performed by measuring the temperatures, flowrates and compositions of all streams to the column. The 100 psig steam used in the reboiler was assumed saturated and the condensate was weighed for the flowrate. The compositions of the streams were measured by a gas chromatograph and all stream flows (distillate (D), feed (F), steam (S), and bottoms (B), [see Figure A5 ]) were also collected and measured. This raw data, which is listed in Table All, was the basis for the energy balance calculation around the distillation column. Energy losses in the distillation process and total energy input values were the most important results of the energy balance. The energy loss data located energy leaks in the system to be corrected (i.e., insu- lation) to improve the efficiency of the column. The total energy input per gallon of anhydrous ethanol produced gave an energy cost for distillation and suggested that further energy saving steps should be taken. 80 The results in Table A13 show an average energy loss from the column of 23% which is the amount of the total energy input lost to the surroundings. The dis- tillation column was k-inch thick glass. Glass is a farily good insulator; therefore, it was assumed that no insulation was required. An energy loss of 23% proves that further insulation is definitely required. The measured total energy input per gallon of an- hydrous ethanol is 32,076 Btu/gal anhydrous ethanol for Mode 1 operation producing a 65 vol % ethanol product. Mode II and Mode III operation to purify the ethanol would require a calculated total input energy of 56,578.4 Btu/gal. Anhydrous ethanol.* Producing a 95 vol % ethanol overheads product from one large column would require 42,971.0 Btu/gal anhydrous ethanol.** This value includes 23% loss of heat to the atmosphere and no energy recovery systems (heat exchangers) in the process. SRI (7) estimated that 39,560 Btu/gal. anhydrous ethanol was required to distill a 95 vol % overhead product in a 25 million gallon per year plant using no energy recovery. Based on the energy balance of this study, the SRI estimate seems to be realistic. The difference between the SRI estimate (39,560 Btu/gal.) and the estimate of this study (42,971 Btu/gal.) can be attributed to small- scale inefficiencies and lack of proper insulation. *Measured Value **Ca1culated Values 81 An absolute minimum value of 21,220 Btu/gal anhydrous ethanol was calculated assuming an infinite number of trays, perfect heat transfer, and no energy recovery. This is an ideal or perfect value and is not physically possible to attain but serves as a basis to compare with other values to judge their validity. The large difference between this minimum value (21,220 Btu/gal) and the estimated values of SRI (39,560 Btu/gal) and of this study (42,971 Btu/gal) can be attributed to normal inefficiencies in equipment and error in techniques. One gallon of anhydrous ethanol contains 84,800 Btu of usable energy as fuel. The distillation of 95 vol % ethanol from corn mash uses about 50% of this obtainable energy. These high values of energy consumption for distillation illustrates the need for energy recovery systems or heat exchangers to recover the heat from hot exiting streams. As an example of the possible energy (6) estimated for a 50 million gallon savings, Katzen per yearpdant with extensive energy recovery that 18,140 Btu/gal anhydrous ethanol would be required to distill at 100 vol % ethanol product. This is a 54% savings over the SRI value (39,560) in distillation energy usage which illustrates the importance of energy recovery systems. This distillation energy balance also underscores the importance of using nonpetroleum energy sources for producing ethanol on the small scale. 82 Experimental Conclusions and Recommendations The feasibility of small scale fermentation ethanol production is highly dependent on the efficiency of the distillation process. The distillation column design basis for this project was directed at the goal of max- imum efficiency as well as column Operation. The resultant column provided much useful information to help meet these ends. Having glass as the column wall proved to be extrememly useful in troubleshooting problems, such as tray plugging and other flow problems during Operation. The glass column is also corrosion resistant, easy to disassemble for maintenance, and a better insulator than metal. The reboiler to the process used steam heated coils. A heat exchanger system, such as steam coils, is highly recommended over injected steam because of the higher solids content of the bottoms product. By using a heat exchanger, the condensate latent heat can be recovered by recycling condensate back to the boiler to make more steam. This procedure conserves energy in the overall steam production process. Injected steam increases the liquid flow rates below the feed tray and thereby increases the vapor flow rate and reduces column efficiency. The energy efficiency of the distillation process is measured by the energy loss to the surroundings and the total energy required per gallon of anhydrous ethanol produced. The measured values of 23% loss of input heat 83 mNA.o wNm mma. memo. oMN Ame. wwo.n wAHN ooA.N ON wm~.o NoN ONq. oomo. maN Aoo. mmN.N OANA Now.A AN mmm.o owe moc. mAmm. CNN Ame. mwN.n «NNN mON.N NN mmm.o mmm BNO. mon.o RON Ace. wAA.m owmA non.~ ON mA.m mum Nmm. Nww.o mmN moo. ooo.w mNAN moH.N 0A oo.m mmm qu. ooc.o moA coo. n.m NmnA NAN.A mA omo.m mNm New. qnn.o owA mmo. ¢N¢.o Amwd mum.A 0A oom.o Nmm mam. oom.o mON Aoo. A.~ oAmA om.A oA mNo.o oem omm. oow.o «AN mmo. mN<.n AawA mmw.A oA mAm.m «Nm on. oom.o ch wmo. m~q.w Aqu wNm.H m CHE\nH m afifixpum a ax OHB\bN a cfia\=um m mx awe\pa cfla\:um .m cHE\oH .m ON: meOuuom .umfin .omum .umfin boom umnm comm ammum ammum Hm>uoucH .u3 us mafia mocmamm mwuocm How mumn 3mm . N 2 canon. 84 Table A13. Energy Balance Results Time Interval Heat Input Heat Output Heat Loss Min. F&S Btu/min. D+B Btu/min. HLoss Btu/min. 9 1784 1763 21 10 2105 1744 361 10 2121 1677 444 10 2077 1541 536 15 1897 1357 540 16 2358 1816 542 20 1987 1652 335 22 2454 1581 873 21 1959 1453 506 20 2354 1584 770 Figure A5. Flow Diagram for Distillation Column Energy Balance Calculations 85 DlSTlLLATE QQ> C9 STEAM g > é. BOTTOMS 86 and 32,076 Btu/gal anhydrous ethanol to produce 65 vol % ethanol product should be typical of uninsulated small- scale distillation columns. These values also indicate that the distillation column is inefficient by comparison to literature sources and should be improved. Insulation around all hot surfaces and heat exchangers for recovery of heat from hot exiting streams should be used to maximize efficiency and save energy. A distillation column has no effect on ethanol yields since an efficient column loses very little ethanol as shown in Table All. Yields are primarily dependent on starch conversion and fermentation processes. If gallons of ethanol per bushel yields are low, these are the steps that should be reviewed. Column controls are important in Obtaining consistent and optimal operation while reducing labor requirements of the distillation process. Temperature-controlled steam flow and reboiler level control are recommended to maximize ethanol stripping from the bottoms product. Feed control is also recommended to ensure consistent fuel flowrates which stabilize column operation. The cost of control components as shown in Table high but can be justified by the savings in labor costs and the efficient column Operation. Figure A6. Photograph of Distillation Apparatus of Experimental Small Scale Facility Figure A7. Photograph of Sieve Trays in Rectification Mode of Operation APPENDIX B: SCENARIO EQUIPMENT LISTS Quantity F‘ F‘ F1 F‘ F‘ F4 I» Is I-l IA 1500 ft. 1 NJ #9 F' H TABLE B1. 89 Scenario I: EQUIPMENT LIST Description 6000 Gal. Batch Cooker (Mild Steel) Cooker Transfer Cavity Pump (.75 Hp) 6000 Gal. Farmentation Tank (Mild Steel) Circulation and Transfer Cavity Pump (.75 Hp) 55 Gallon Enzyme Prep. Tank (Stainless) Enzyme Agitator (.5 Hp) Enzyme Centrifugal Pump (.25 Hp) Ferment Fan Cooler (525 ft.2, 2 Hp) Grain Conveyor (100 ft., 5 Hp) Distillation Assembly Stripping Column - Sieve (9" x 20', Glass) Rectifying Column - Packed (9" x 30', Glass) Column Supports Vapor Cbndenser (40 ft.2, Stainless) Feed Preheater (50 ft.2, Stainless) Control Valves Manual Valves Centrifugal Reflux Punp (.5 Hp) Cavity Stillage - Feed Pumps (.75 Hp) Stillage Surge Tank - 5000 Gal. (Mild Steel) 20,000 Gallon Alcohol Storage Tank (Fiberglass) Dehydration Unit (Molecular Sieve) 2 Absorption Columns 1000 16 Sieves 2.7 Hp. Blower, 23 Hp. Heater Cavity Byproduct Pump (.75 Hp.) Piping (1000 ft. PVC, 500 ft. Stainless) Boiler Facility (14 psi) Coal Fired Boiler J75 lb/hr) Boiler Feed Pump (.5 Hp) Water Filter and Softener Well Water Pump (1 Hp) Vibrating Screen and Press (1 Hp) Stillage - Filler Mixer (5 Hp) Filtrate Centrifugal Pumps (.75 Hp) 90 TABLE Bl. (continued) Quantity Description 1 55 Gallon Water Surge Tank (Mild Steel) 1 Roller Mill (5 Hp) l 5000 Bu Grain Storage Bin (Mild Steel) 1 Grain Dryer 1 Storage Building (30' x 60') 91 TABLE B2. Scenario II: EQUIPMENT LIST A) Farm Facility Quantity 1 so F‘ F' F' u: a» F‘ 1400 ft. 1 I: k' F‘ F‘ P‘ k: F‘ F‘ F‘ Description 6000 Ga. Batch Cooker (Mild Steel) Cooker Transfer Cavity Pump (.75 Hp) 6000 Gal. Fermentation Tank (Mild Steel) Circulation and Transfer Cavity Pumps (.75 Hp) 55 Gal. Enzyme Prep. Tank (Stainless) Enzyme Agitator (.5 Hp) Ferment Fan Cooler (525 ft.2, 2 Hp) Distillation Assembly Stripping Column - Sieve (9" x 20', Glass) Rectifying Column - Packed (9" x 30', Glass) Vapor Condenser (40 ft.2, Stainless) Feed Preheater (50 ft.2, Stainless) Centrifugal Reflux Pump (.5 Hp) Cavity Stillage - Feed Pumps (.75 Hp) Control Valves Manual Valves 5000 Gal. Stillage Surge Tank (Mild Steel) 20,000 Gal. Alcohol Storage Tank (Fiberglass) Cavity Byproduct Pumps (.75 Hp) Piping (1000 ft. PVC, 400 ft. Stainless) Boiler Facility (14 psi) Coal Fired Boiler (75 lb/hr) Boiler Feed Pump (.5 Hp) Water Filter and Softener well Water Pump (1 Hp) Vibrating Screen and Press (1 Hp) Stillage - Filler Mixer (5 Hp) Filtrate Centrifugal Pumps (.75 Hp) 55 Gallon Water Surge Tank (Mild Steel) Roller Mill (5 Hp) 5000 Bu Grain Storage Bin (Mild Steel) Grain Dryer Storage Building (30' x 60') 92 TABLE BZ . (continued) B) Water Extraction Plant Quantity HHI—‘HHHNNQJNNN 600 ft. 600 ft. 15 50 1 Des cription Tanker Trucks (20,000 Gallon, 4 mi/gallon) 50,000 Gallon Storage Tanks (Mild Steel) Centrifugal Transfer Pumps (2.0 Hp) Centrifugal Reflux Pumps (.75 Hp) Centrifugal Feed Pumps (.75 Hp) Centrifugal Bottoms Pumps (.75 Hp) Alcohol Removal Column (15" x 40', Stainless) Benzene Removal Colunn (10" x 30' , Stainless) Water Removal Column (8" x 30', Stainless) Settler (200 gal., Mild Steel) Condenser (500 ft.2, Stainless) 5,000 Gal. Benzene Storage Tank (Mild Steel) PVC Piping (Sched. 80) Stainless Piping (Sched. 40) Control Valves Manual'Valves Steam Boiler Unit Coal Fired Boiler (20 lb/hr) Office and Storage Building (60' x 80') 93 TABLE B3. Scenario III: EQUIPMENT LIST A) Farm Faci lity Quantity p. s: s» F: u: o. F‘ F‘ (DNHH 1200 ft. 1 H H I4 r4 N: P» F: H Description 6000 Gal. Batch Cooker (Mild Steel) Cooker Transfer Cavity Pump (.75 Hp) 6000 Gal. Fermentation Tank (Mild Steel) Circulation and Transfer Cavity Pumps (.75 Hp) 55 Gal. Enzyme Prep. Tank (Stainless) Enzyme Agitator (.5 Hp) Ferment Fan Cooler (525 ft.2, 2 Hp) Distillation Assembly Stripping Column - Sieve (9" x 20', Glass) Column Supports Vapor Condenser (40 ft.2, Stainless) Feed Preheater (50 ft.2, Stainless) Cavity Stillage - Feed Punps (.75 Hp) Control valves Manual Valves 5000 Cal. Stillage Surge Tank (Mild Steel) 20,000 Gal. Alcohol Storage Tank (Fiberglass) Cavity Byproduct Pumps (.75 Hp) Piping (800 ft. PVC, 400 ft. Stainless) Boiler Facility (14 psi) Coal Fired Boiler (18.7 Hp, 75 lb/hr) Boiler Feed Pump (.5 Hp) Water Filter and Softener Well Water Pump (1 Hp) Vibrating Screen and Press (1 Hp) Stillage - Filler Mixer (5 Hp) Filtrate Centrifugal Pumps (.75 Hp) 55 Gal. Water Surge Tank (Mild Steel) Roller Mill (5 Hp) Grain Dryer 5000 Bu. Grain Storage Bin (Mild Steel) Storage Building (30' x 60') 94 TABLE B3 : (continued) B) Refinery and Water Extraction Plant Quantity F‘ F‘ #9 F’ h» P‘ u: u) a. k) k) k: 700 ft. 800 ft. 20 50 Description Tanker Trucks (20,000 Gallon, 4 mi/gal.) 50,000 Gallon Storage Tanks Centrifugal Tansfer Pumps (2.0 Hp) Centrifugal Reflux Pumps (.75 Hp) Centrifugal Feed Pumps (.75 Hp) Centrifugal Bottoms Pumps (.75 Hp) Alcohol Rectification Column (15" x 30' , Stainless) Alcohol Removal Colunn (15" x 40' , Stainless) Benzene Removal Column (10" x 30', Stainless) Water Removal Column (8" x 30', Stainless) Settler (2000 gal., Mild Steel) 5000 Gal. Benzene Storage Tank (Mild Steel) PVC Piping (Sched. 80) Stainless Piping (Sched. 40) Cbntrol Valves Manual Valves Steam Boiler Unit (500 psi) Coal Fired Boiler (25 lb/hr) Office and Storage BuiLding (60' x 80') APPENDIX C: SCENARIO EQUIPMENT AND OPERATING COSTS 95 TABLE CH” Scenario I: EQUIPMENT COSTS Capital Annual Payment Description Costs 10-Yr. @ 15% Batch Cooker $30,000.00 $5977.55 Fermenter Tanks (4) 40,000.00 7970.08 Prog. Cavity Pumps (8) 20,000.00 3985.03 Enzyme Tank & Agitator 1,000.00 199.25 Fermentation Cooler 4,000.00 797.00 Distillation Aparatus 75,000.00 14,943.88 Vapor Condenser 5,000.00 996.26 Feed Preheater 3,000.00 597.76 Reflux Pump 1,500.00 298.88 Stillage Surge Tank and Agitator 8,000.00 1,594.01 Alcohol Storage Tank 10,000.00 1,992.52 Dehydration Unit 32,500.00 6,475.69 Piping - 1000 ft. PVC 1,000.00 199.25 Piping - 500 ft. Stainless 3,000.00 597.76 Boiler Unit 25,000.00 4,981.29 Stillage — Filler Mixera 18,800.00 3,745.93 Control Valves 6,500.00 1,295.14 Manual Valves 3,500.00 697.38 Building 30,000.00 5,977.55 Surge Tank 100.00 19.93 Roller Mill 1,550.00 308.84 Grain Storage Bin 3,000.00 597.76 Grain Dryer 8,300.00 1,653.79 TOTAL $330,750.00 $65,902.49 aTo centrifuge, add $39,200 and water treatment. To screen, subtract $8,000 and add water treatment. 96 TABLE (:2. Scenario II: EQUIPMENT COSTS A) Farm Facility Capital Annual Payment Description Costs 10-Yr. @ 15% Batch Cooker $30,000.00 $ 5977.55 Fermenter Tanks (4) 40,000.00 7970.08 Cavity Pumps (8) 20,000.00 3985.03 Enzyme Tank and Agitator 1,000.00 199.25 Fermentation Cooler 4,000.00 797.00 Distillation Apparatus 75,000.00 14,943.88 Vapor Condenser 5,000.00 996.26 Feed Preheater 3,000.00 597.76 Reflux 1,500.00 298.88 Stillage Surge Tank and Agitator 8,000.00 1,594.01 Alcohol Storage Tank 10,000.00 1,992.52 800 ft. PVC Piping 800.00 159.40 400 ft. Stainless Piping 2,400.00 478.20 Boiler Unit 25,000.00 ’ 4,981.28 Stillage-Filler Mixer 3 18,800.00 3,745.93 Control Valves 5,400.00 1,058.00 Manual Valves 3,500.00 697.38 Building 30,000.00 5,977.55 Surge Tank 100.00 19.93 Roller Mill 1,550.00 308.84 Grain Storage Bin 3,000.00 597.76 Grain Dryer 8,300.00 1,653.79 TOTAL $296,350.00 $59,048.23 aTo centrifuge, add $39,200 and water treatment. To screen, subtract $8,000 and add water treatment. 97 TABLE C2. (continued) B) Water Extraction Plant Capital Annual Payment Description Costs 10-Yr. @ 15% Tanker Trucks (2) $150,000.00 $29,887.75 Storage Tanks (2) 37,000.00 7,372.31 2-Hp Centrifugal Pumps (2) 4,000.00 797.01 .75-Hp Centrifugal Pumps (7) 10,500.00 2,092.14 Alcohol Removal Column 45,000.00 8,966.33 Benzene Removal Column 40,000.00 7,970.07 Water Removal Column 38,000.00 7,571.56 Settler 3,000.00 597.76 Condenser 23,000.00 4,587.79 Benzene Storage Tank 2,000.00 398.50 Piping 4,200.00 836.86 Control Valves 7,500.00 1,494.39 Manual Valves 3,500.00 697.38 Steam Boiler 20,000.00 3,985.03 Building 100,000.00 19,925.17 TOTAL $487,700.00 $97,175.04 98 TABLE (13. Scenario III: EQUIPMENT COSTS A) Farm Faci lity Capital Annual Payment Description Cbsts 10-Yr @ 15% Batch Cooker $30,000.00 $5,977.55 Fermenter Tanks (4) 40,000.00 7,970.08 Cavity Pumps (8) 20,000.00 3,985.03 Enzyme Tank and Agitater 1,000.00 199.25 Fermentation Cooler 4,000.00 797.00 Distillation Apparatus 45,000.00 8,966.33 Vapor Condensor 5,000.00 966.26 Feed Preheater 3,000.00 597.76 Stillage Surge Tank and Agitater 8,000.00 1,594.01 Alcohol Storage Tank 10,000.00 1,992.52 800 ft. PVC Pipe 800.00 159.40 400 ft. Stainless Pipe 2,400.00 478.20 Boiler Unit 25,000.00 4,981.28 Stillage-Filler Mixer a 18,800.00 3,745.93 Control Valves 4,300.00 856.78 Manual Valves 3,500.00 697.38 Building 30,000.00 5,977.55 Surge Tank 100.00 19.93 Roller Mill 1,550.00 308.84 Grain Storage Bin 3,000.00 597.76 Grain Dryer 8,300.00 1,653.79 TOTAL $263,750.00 $52,552.63 aTo centrifuge, add $39,200 and water treatment. To screen, subtract $8,000 and add water treatment. TABLE C3. 99 (continued) B) Refinery and Water Extraction Plant Capital Annual Payment Description Costs 10-Yr. @ 15% Tanker Trucks (2) $150,000.00 $ 29,887.75 Storage Tanks (2) 37,000.00 7,372.31 2-Hp Centrifugal Pumps (2) 4,000.00 797.01 .75-Hp Centrifugal Pumps (10) 15,000.00 2,988.78 Alcohol Rectification Column 20,000.00 7,970.07 Alcohol Removal Column 45,000.00 8,966.33 Benzene Removal Column 40,000.00 7,970.07 Water Removal Column 38,000.00 7,571.56 Settler 3,000.00 597.76 Ethanol Condenser 5,000.00 996.26 Benzene Condenser 23,000.00 4,587.79 Piping 5,500.00 1,095.88 Control Valves 10,200.00 2,032.37 Manual Valves 3,500.00 697.38 Steam Boiler 52,000.00 10,361.09 Building 100,000.00 19,925.17 TOTAL $571,200.00 $113,812.55 100 TABLE C4. Scenario I: Cost .lEEE Per Unit Corn $ 2.70/Bu Alpha Amylase 2.62/Liter Glucoamylase 1.30/lb. Sulfuric Acid 1.17/ga1. Yeast .90/lb. Electricity .032/kwh Coal 40.00/ton Watera 1.25/1000 gal. Water Treatment b ----- Labor $15,000.00/operator Molec. Sieve 1.00/lb. Nitrogen C 16.00/100 lbs. Lab Tests 10.00/Test Insurance ----- Maintenance ------ Taxes ------ OPERATING COSTS Units Annual Per Year Cost 42,735 Bu $115,385 1,700 Liters 4,458 1,355 lbs. 1,761 810 gal. 945 1,140 lb. 1,026 1,105,500 kwh 35,400 673 tons 26,900 1,103,000 Gal. 1,380 ------ 2,900 3 operators 45,000 3,000 lbs. 3,000 17,750 lbs. 2,800 875 tests 8,750 ---- 6,000 ----- 5,000 ----- 2,500 $263,205 Annual Operating Cost: aWell water. bCharge for upgrading well water for boiler feed. C100 1b. cylinders. 101. OPERATING COSTS TABLE C5. Scenario II: A) Farm Facility Cost Item Per Unit Corn $ 2.70/Bu Alpha Amylase 2.62/Liter Glucoamylase 1.30/lb. Sulfuric Acid 1.17/Gal. Yeast .90/lb. Electricity .032/kwh Coal 40.00/ton Water a 1.25/1000 gal. b Water Treatment Labor Insurance Maintenance Taxes a Well water. 15,000.00/operator Units Annual Per Year Cost 42,735 Bu $115,385 1,700 Liters 4,458 1,355 lb. 1,761 810 gal. 945 1,140 lbs. 1,026 603,580 kwh 19,315 648 tons 25,920 1,081,600 gal. 1,352 ----- 2,900 3 operators 45,000 ---- 6,000 ----- 5,000 ---- 2,500 Annual Operating Cost: $231,562 bCharge for upgrading well water for boiler feed. TABLE C5. (continued) B) Water Extraction Plant Cost Units Annual Item Per Unit Per Year Cost Diesel Fue1a$ 1.30/gal. 3,000 gal. $ 3,900 Benzene 1.85/gal. 750 gal. 1,390 Electric .032/kwh 359,511 kwh 11,504 Coal 40.00/ton 135 tons 5,400 water 1.25/1000 gal. 3,299,714 gal. 4,125 Water TreatmentC ----- ---- 8,668 Lab Tests 10.00/test 1,900 tests 19,000 Labor 15,000.00/operator 8 operators 120,000 Insurance ---- --—-- 15,000 Maintenance ---------- 10,000 Taxes ----- ----- 4,500 Annual Operating Cost: $203,487 aTransport. bWell Water. CCharge for upgrading well water for boiler feed. 103 TABLE C6. Scenario III: OPERATING COSTS A) Farm Facility Cost Units Annual Item Per Unit Per Year Cost Corn $ 2.70/Bu 42,735 Bu. $115,385 Alfa Amylase 2.62/Liter 1,700 Liters 4,458 Glucoamylase 1.30/1b. 1,355 lb. 1,761 Sulfuric Acid 1.17/gal. 810 gal. 945 Yeast .90/lb. 1,140 lb. 1,026 Electricity .032/kwh 603,580 kwh 19,315 Coal 40.00/ton 522 tons 20,872 Water a 1.25/1000 gal. 870,953 gal. 1,090 Water Treatment b ---- ---- 2,338 Labor 15,000.00/operator 3 operators 45,000 Insurance ----- ----- 6,000 Maintenance ----- ---- 5,000 Taxes ---- ---- 2,500 Annual Operating Cost: $225,690 aWell water. bCharge for upgrading well water for boiler feed. 104 TABLE C6. (continued) B) Distillation and Water Extraction Plant bWell Water. CCharge for upgrading well water for boiler feed. Cost Unit Annual Item Per Unit Per Year Cost Diesel Fuela $ 1.30/Gal. 4,210 Gal. $ 5,473 Benzene 1.85/Gal. 750 Gal. 1,390 ‘ Electric .032/kwh 632,880 kwh 20,252 Coal 40.00/ton 310 tons 12,400 Water b 1.25/1000 Gal. 5,283,139 gal. 6,604 Water TreatmentC: ----- ---- 13,877 Lab Tests 10.00/test 2,000 tests 20,000 Labor 15,000.00/operator 8 operators 120,000 Insurance ---—- --—-- 17,000 Maintenance ----- ----- 12,000 Taxes ----- ----- 4,500 Annual Operating Cost: $233,496 aTransport. BIBLIOGRAPHY 10. 11. BIBLIOGRAPHY Chemical Engineer's Handbook, Fifth Edition, McGraw- Hill Book Co., pp. 18.5-18, 3.85, 3.171. Chase, David J., Sieve Tray Design, Part I, Chem. Eng., July 31, 1967, pp. 116, Part II. Chem. Eng., August 28, 1967, pp. 139. Handbook of Chemistry and Physics, 55th Ed., CRC Press, McCabe, W., and J. Smith, Unit Operations of Chemical Engineering, 3rd Ed., McGraw-Hill Book Co., 1976, pp. 591—593. Farm Scale Ethanol Plants, Office of Alcohol Fuels, Department of Energy, 1980. Raphael Katzen Associates, Grain Motor Fuel Technical and Economic Assessment Study, U.S. Department of Energy. June 1979. S.R.I. International, Biochemical Conversion 9f Biomass to Fuels and Chemicals, U.S. Department of Energy, December 1978. Macrae, J.C., and Armstrong, D.G., Enzyme Method for Determination of Alpha-linked Glucose Polymers in Biological Materials, g. S31, Ed. Agric., Vol. 19, October 1968. Miller, Dwight L., Ethanol Fermentation and Potential, Biotechnol. and Bioeng. gymp. No. 5, 345-352, John Wiley & Sons, Inc. (1975). Kelsey, M. P. and Johnson, A., Business Analysis Summary For Saginaw Valley Cash Crop Farms, Agricultural Economics Report Number 358, Department of Agricultural Economics, Michigan State University, July 1979. Raphael Katzen Associates, Farm And Cooperative Alcohol Plant Study, U.S. National Alcohol Fuels Commission, October 1980. 105 12. l3. 14. 15. 106 Hawley, M.C., Black, J.R., and Grulke, E.A., Ethanol For Gasohol - Production And Economics, Prepared for Symposium on Gasohol Production And Nutritional Utilization Of By-Product by Non-Ruminants and Ruminants. Coulson, J.M. and Richardson, J.F., Chemical Engineerin , Vol. 2: Unit Operations, 3rd Ed., Pergamon Press, 1978. Chemical Marketing Reporter, Schneil Publishing Company, Inc., April 27, 1981. Crombie, Lance, Making Alcohol Fuel, Recipe and Procedure, Rutan Publishing, Minneapolis, 1979. "I7'1111111.1111171111111115