Mega Factories: Ethanol Project
Informative Note: Grain Alcohol Production
1. The selection of grain for alcohol production depends upon higher starch %, the % of starch commonly present in cereals is given under: –
| Serial | Starch | Yield | |
|---|---|---|---|
| A. | Sorghum (millet) | 70 – 72% | 440 BL/T |
| B. | Rice (polished) | 70 – 72% | 460 BL/T |
| C. | Corn | 61 – 65% | 400 BL/T |
| D. | Wheat | 60 – 65% | 395 BL/T |
| E. | Barley | 58 – 63% | 375 BL/T |
| F. | Potato | 15 – 22% | 120 BL/T |
| G. | Cassava | 25 – 30% | 165 BL/T |
2. The alcohol production from the above cereals is based on the conversion of starch into fermentable sugars and then onwards the fermentation and distillations are almost the same as molasses. The conversion efficiency of starch will be around 96 % if proper meshing and cooking have been done.
3. The pH and Ca++ concentrations are also important. The enzyme, which is been used in the first step for the conversion of starch into dextrin, is temperature-resistant α amylase this enzyme acts on 1 – 4 α linkage of glucosidic bonds. The favorable temperature is 92 ~ 95° C and the pH is 6.2 with a minimum 70 ppm of Ca++ concentration.
4. The particle size of grain flour is also important, and it should be between 0.7 mm to 0.4 mm or between 25 ~ 40 mesh alternatively between 28 ~ 38 GG. A grain flour slurry of about 30 % solids at pH 6.2 and temp 55 ~ 60° C will be made in a slurry tank.
5. The grain slurry should be cooked through a jet cooker at 110° C with some enzyme for its liquefaction. This sudden rise of temperature up to 110° C will enable the enzyme to act on starch faster and facilitate the gelatinization process.
6. The jet cooker should have at least 4 to 7 Kg/cm2 steam pressure, whereas we can do it with a venturi heater which works at 2 ~ 3 Kg/ cm2 steam pressure.
7. After the jet cooker the slurry will be followed in cooking coil a retention time of 7 ~ 8 minutes and then it will be taken in a flash vessel, where the temperature of the slurry comes down to 95° C, the part of the liquefaction enzyme is added into the slurry and a holding time of ranges from 1 ½ hrs to 3 hrs is to be given for total conversion of starch into dextrin.
8. After the liquefaction the slurry is cooled to 32° C and taken directly into fermenters, where Saccharification enzyme will be added and the yeast is inoculated with desired nutrients, the fermentation time required is 48 ~ 52 hrs minimum.
9. The whole fermented brought is then fed to the distillation column for separation of alcohol and the spent liquor is either decanted in a decanter for removal of sludge which has high value of fodder or it may be settled in settling ponds and the supernatant liquid will be fed to BMR and followed by aeration system.
10. The settled sludge can be removed from settling tanks and should be kept for drying on sludge beds and after drying it should be disposed off.