There are five parts to the ethanol process. Conversion, fermentation, distillation, filtration and dehydration.
Conversion takes place in the boiler. It uses two enzymes.
The first enzyme is alpha amylase. Alpha amylase is used for the liquefaction of the starting grain.
The second enzyme used is glucoamylase. Glucoamylase converts the liquefied starch into glucose.
Fermentation can take place in the boiler or in a separate fermentation vessel. Fermentation converts the enzyme-produced glucose into ethanol and carbon dioxide. Depending on yeast strain, fermentation can take one to five days.
Distillation exploits the difference in the boiling point of two liquids. In this case, the two liquids are ethanol and water. Using a fractional still, we can separate ethanol and water.
Filtration utilizes activated carbon to remove dangerous aldehydes and fusel oils from the ethanol.
Dehydration is the removal of the residual water left by distillation. A high quality still should produce 90ethanol with repeatability. Ethanol can be dehydrated chemically or mechanically. In mechanical dehydration, a non-consumed molecular sieve called zeolite adsorbs the water, leaving ethanol in its highest purity. The zeolite is regenerated by heating and pass air through the material. Normally this is achieved industrially by the use of hot captured carbon dioxide.