The Gildred/Butterfield Fuel Alcohol Plant
1. Ethanol storage tank, one day production; 300 gallon horizontal tank of crosslinked polyethylene (XLPE) on stand
2. Beer well; 2300 gallon vertical tank of XLPE on stand
3. Water storage tank; 2300 gallon vertical tank of XLPE on stand
4. Water pump and motor; Price P-100 centrifugal pump, belt driven at 2700 RPM by a 1 HP, TEFC motor
5. Pneumatic water storage tank; 85 gallons
6. Water softener
7. Stillage storage tank; 500 gallon vertical tank of XLPE on stand
8. Fermenter, four total; 1700 gallon vertical tanks of XLPE on stand
9. Distillation section; see Plate 6
10. Beer pump and motor; Teel No 1P898 positive displacement rotary screw pump, belt-driven by a 1/3 HP TEFC motor
12. Screw press; see Plate 4
13. Sweco separator; Model No LS30S66 - D with #64 TBC screen and self-clean kit
14. Mash storage bin; box steel frame with 3/4" plywood walls and roof
15. Portable utility pump and motor; Teel No 1P746 centrifugal pump direct driven by a 2HP, 3450 RPM, TEFC motor
16. Portable utility pump; Sandpiper SA2-A air-operated diaphragm pump
17. Boiler; packaged, 10HP, low-pressure boiler
18. Water storage tank; 500 gallon vertical tank of XLPE on stand
19. External heat exchanger; 2-inch copper tube inside a 2-1/2" copper tube
20. Cooker; see Plate 3
22. Auger motor; 3/4 HP, 1750 RPM, TEFC
23. Auger; 4-inch diameter
24. Auger hopper
26. Auger motor; 1/2 HP, 1750 RPM, TEFC
27. Auger; 4-inch diameter
28. Ground feedstock storage tank; steel, cone-bottomed tank on stand, approximately 6 ton capacity
29. Air compressor; approximately 25 CFM free air capacity
1. All tanks numbered 2, 3, 7, 8, 18 and 20 have outlets consisting of a 2-inch ball valve and female kamlock connector. Connections to pumps are made via 2-inch hoses and kamlocks.
2. Connection to heat exchanger 19 is via hoses and kamlocks.
3. All fermenters have a second 2-inch outlet placed 2 feet above the drain outlet for connection to heat exchanger 19.
1. Mixer motor; 2HP, 1750 RPM, TEFC
2. Mixer drive; right-angle gear reducer, 43 RPM output
3. Cook tank; 3000 gallon horizontal steel tank insulated with minimum 2-inch thick, spray-on polyurethane foam
4. Mixer chain and sprockets; #80 chain with 24 T driver, 21 T idler and 32 T driven sprockets (chain guard not shown but necessary)
5. Steam inlet check valve; 1-1/4 inch diameter
6. Steam inlet piping; 1-1/4 inch diameter
7. 2-inch full-opening ball valve
8. 2-inch female kamlock connector
9. 2-inch medium duty flange block
10. 2-inch solid steel drive shaft
11. 2-inch steel pipe agitator shaft
12. 1-1/4 inch steel steam distribution pipe
1. Drive motor; 2HP, 1750 RPM, TEFC
2. Gear reducer; 60 RPM output
3. Chain and sprockets; #60 chain with 27 T driver and 34 T driven sprockets (chain guard not shown but necessary)
4. Press screw; 8-inch diameter with double flights on 9-inch pitch; heavy duty
5. 2-inch diameter medium duty flange block
6. 2-inch diameter medium duty pillow block
7. Press screw tube; 16 gauge perforated sheet metal with 1/16-inch diameter holes on 1/8-inch centers
8. Door springs; 1-1/4 inch diameter with 7 coils per inch
9. Catch basin; 16 gauge galvanized sheet metal
10 Centrifugal pump & motor; Price P100 centrifugal pump, direct driven at 1750 RPM by 1/3 HP, TEFC motor
1. Heat exchanger; stillage/beer feed preheater, American Standard No BCF 05014, 4-pass
2. Pressure relief valve; 15 pound Bell and Gossett No 480-15
3. Pneumatic valve; 1/2 inch diameter operated by liquid level controller, Applied Technologies Inc.
4. Pneumatic liquid level controller; proportional output, Applied Technologies Inc.
5. Liquid level gauge
6. Centrifugal pump and motor; Price P100 centrifugal pump, direct driven at 1750 RPM by 1/3 HP explosion proof motor
7. Heat exchanger; condenser/feed preheater, American Standard No. BCF 06048, 4-pass
8. Air-cooled condenser; 24 inch by 32 inch radiator
9. Air-cooled condenser fan; 3500 CFM, 1/12 HP
10. Heat exchanger; subcooler, water-cooled, American Standard No. 03024, single-pass
11. Heat exchanger; vent and product cooler, water cooled, American Standard No. 03024, single-pass
12. Pneumatic temperature controller; with flow meter, Applied Technologies Inc.
13. Air-pressure regulator; Speedaire Model No 4ZO29
14. Pneumatic valve; 1/2 inch diameter operated by temperature controller, Applied Technologies Inc.
Plant Equipment Costs
Plant Equipment Costs1 Item Description Equipment Cost Associated Labor Cost2 Total Cost 1. Front-end handling equipment Very dependent on feedstock type and need for storage $ 3,000-$20,000 2. Cooker, including stand, agitator and drive, steam line and insulation $5,000 $1,300 $ 6,300 3. External Heat Exchanger $1,000 $200 $ 1,200 4. Solid Liquid Separators - Sweco $5,000 $1,500 $6,500 - Screw Press $2,500 $2,500 $ 5,000 5. Mash Storage $1,000 $200 $1,200 6. Fermenters (4) including stands and fittings $8,200 $2,000 $10,200 7. Distillation Section, including two columns with internals, pumps, heat exchangers and controls $8,500 $3,000 $11,500 8. Boiler, including feedwater system and water softener $6,000 $1,500 $ 7,500 9. Stillage Recovery, including tank and fittings $600 $200 $800 10. Warm Water Storage, tank, pneumatic tank and pump $3,500 $1,000 $ 4,500 11. Utility Pump, includes two portable pumps (one air-opened), air compressor and controls $4,500 $1,500 $ 6,000 12. General Plumbing $4,000 $1,500 $ 5,500 13. General Electrical Service $4,000 $2,000 $6,000 14. Lab Equipment $1,000 - $1,000 15. Miscellaneous, includes catwalks, special tools and maintenance equipment $3,000 $1,000 $ 4,000 Total (Less Front-End Equipment) $57,800 $19,400 $77,200 1. Costs shown are approximate and for new equipment in 1982 dollars. These costs may be reduced substantially by purchasing used equipment.
2. Approximate labor cost to construct and install based on labor rate of $7.00 per hour.
Plant Operating Costs
Following is a discussion of each of the major factors affecting plant operating costs:
1. Feedstock -- The feedstock price and practical alcohol yield are usually primary factors affecting operating costs. The practical alcohol yield is the yield actually obtained under operating conditions which may be considerably less than the potential yield obtained from lab tests (the practical yield will be less when there are losses from filling and emptying tanks, at the solid-liquid separation stage, and upon distillation start-up or shut down). The following table illustrates the possible feedstock operating costs that can arise from a grain type source.
Feedstock Operating Cost ($/gal. a1c.) Feedstock Cost ($/ton) 50 60 70 80 90 100 110 120 130 140 150 1.00 1.20 1.40 1.60 1.80 2.00 2.20 2.40 2.60 2.80 3.00 0.83 1.00 1.17 1.33 1.50 1.67 1.83 2.00 2.17 2.33 2.50 0.71 0.86 1.00 1.14 1.29 1.43 1.57 1.71 1.86 2.00 2.14 0.63 0.75 0.88 1.00 1.13 1.25 1.38 1.50 1.63 1.75 1.88 0.56 0.67 0.78 0.89 1.00 1.11 1.22 1.33 1.44 1.56 1.67 0.50 0.60 0.70 0.80 0.90 1.00 1.10 1.20 1.30 1.40 1.50
2. Labor -- At low production rates labor can be a significant operating cost. Usually, a successful small operation cannot afford to have a person in attendance full-time (for example, assuming a labor cost of $7.00 per hour and a 10 gal/hr production rate, the operating cost of labor would be $0.70 per gallon of alcohol). For the plant described herein, the labor requirements outside of monitoring the distillation process are about 25-30% of the total operating period (i.e. plant operation throughout a 24 hour period requires about 6-8 hours of labor to cook and separate). If the distillation process is fully automated, the need for operating labor can be reduced to about 30% of the total operating period resulting in a labor cost of about $0. 23 per gallon alcohol (assuming a $7.00 per hour labor cost).
3. Energy -- The cost for steam energy in the plant can vary substantially. Cooker steam consumption depends on the temperature at which steam addition begins, the amount of liquid used initially, heat loss and boiler system efficiency.
The initial cook temperature is determined by the temperature of liquids available for recycle (are stillage and hot water available for recycle?) and, in some cases, by the feedstock and/or enzyme type. The example shown in Plant Performance Data, Table 1 shows a cooker steam energy requirement of 2441 BTU's per gallon alcohol. If the propane cost is $0.80 per gallon and the propane contains 90,000 BTU's per gallon then the cooker's steam energy cost is: (2441 / 90,000) x $0.80 = $0.02 per gallon alcohol. However, if the initial cook temperature is reduced to 130 degrees F from 170 degrees F then this cost more than doubles. If the initial cook temperature is reduced to 90 degrees F from 170 degrees F then the cost more than triples.
The amount of liquid used initially is dependent on mixer power and efficiency and on feedstock type (for example, barley, with a low bushel weight, requires a relatively greater percentage of initial water than wheat to maintain the same mixer load).
Raising the liquid-to-feedstock ratio over that shown in Plant Performance Data, Table 1 (i.e. 600 gallons to 3000 lbs.) will increase the cooker energy requirement by an almost equal amount. For example, a cook begun with 900 gallons of liquid would raise the energy requirement about 45%.
The heat loss from the cooker is about 5% of the total heat load for a fully insulated system. Depending on cooker size and shape and local climate, this loss could increase to as much as 20% or more without insulation and the energy requirement would increase an equal amount.
Boiler system efficiency has a direct effect on both the cooker and the distillation section steam energy requirement. A 70% boiler system efficiency will increase the energy use figures cited in Plant Performance Data (which assume 80% efficiency) by 14%, a 60% efficiency will increase the figures by 33%.
The energy requirement for distillation is affected by the percentage of alcohol in the beer, the inlet beer feed temperature, the reflux flow rate, the reflux liquid temperature, the heat loss and the boiler system efficiency.
Distillation system steam useage will be greater than that shown on page 32 for beers that contain less than 10% ethanol (because there is less ethanol and also because the reflux will have to be increased to achieve a 190 proof product). Using the $0.80 per gallon propane cost and 90,000 BTU per gallon energy content figures, distillation steam energy cost as shown in Plant Performance Data, Table 2 is:
(18,436 / 90,000) x $0.80 = $0.16 per gallon alcohol.
Distillation of an 8% ethanol beer would raise the necessary reflux ratio to approximately 4 to 1, the BTU requirement to 27,380 per gallon and the associated cost to $0.24 per gallon alcohol. This is an approximately 50% increase in cost.
Failure to preheat the beer feed to the 180 degree F design temperature will increase distillation steam energy consumption. This can happen if the alcohol vapors are not used as a preheat source or if small preheat heat exchangers are used in place of those specified. For example, a 130 degree F beer feed temperature will increase the energy requirement shown in Plant Performance Data, Table 2 by about 4,200 BTU's per gallon or 23%.
A major factor affecting distillation steam energy consumption is the reflux ratio. The amount of reflux that is used should always be maintained at the minimum that is necessary to achieve the desired product quality. This minimum is related to sieve plate design and percent alcohol in the beer. An increase in reflux ratio alone, from 3 to 1 to 4 to 1 raises the energy use figures shown in Plant Performance Data, Table 2 by 19%. The temperature to which the reflux liquid is subcooled has only a minor effect on steam consumption because more subcooling allows a smaller reflux flow and vice-versa. Excessive subcooling can raise operating costs however, by allowing the use of too much cooling water.
Heat loss from the distillation system can be maintained at a low value by the use of complete insulation. Without insulation the heat loss may amount to 15-20% or more of the total load, depending on the local climate. A lack of insulation also makes system control more difficult as the process is affected by ambient conditions.
The cost for electrical energy in the alcohol production process is usually only a minor cost item. Table 3 of the text does not include the electricity use of the front-end equipment, which may vary substantially for different feedstocks. In general, plant electricity use for grain-type feedstocks will be in the 0.6-1.0 kwh per gallon range., resulting in a cost of $0.04-$0.08 per gallon alcohol.
4. Enzymes -- The cost of enzymes will depend on the feedstock type and alcohol yield obtained from each processed batch. Operating experience should allow substantial reduction in the quantities of enzyme needed to obtain desired results. Generally, the enzyme cost should amount to no more than $0.10 per gallon alcohol.
5. Yeast -- The cost of yeast should be less than $0.02 per gallon alcohol with the use of some yeast recycle (from one fermenter to another) and a yeast starter tank (for new cultures).
6. Chemicals -- The cost of lime, acid and softener salt should generally be less than $0.01 per gallon alcohol unless boiler water requires extensive treatment.
7. Fixed Charges -- The charge for depreciation, licenses, maintenance, taxes and insurance will depend on construction costs and on plant capacity. If the plant is going to be operated only infrequently, these costs can become very significant.
As evidenced by the material presented above, the costs of producing alcohol on a small scale can be extremely variable. A profitable operation requires a thorough understanding of each of the variables affecting operating costs and the ability to keep these costs to a minimum. Also required is the ability to profitably sell or use the alcohol, processed feedstock, and stillage.
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