All over the world most of the ethyl alcohol is prepared from molasses. Molasses is the mother liquor left after the crystallization of cane sugar from concentrated juice. It is dark colored thick syrupy mass. Molasses contains about 60% fermentable sugars, mostly sucrose, glucose, and fructose. It forms an excellent cheap source of industrial ethyl alcohol. Molasses is converted into ethyl alcohol by the following steps:
Molasses is first diluted with water. One volume of molasses is mixed with five volumes of water.
- Addition of Ammonium Sulphate
Molasses usually contains enough nitrogenous matter to act as food for yeast during fermentation. If the nitrogen content of the molasses is poor, it may be fortified with ammonium sulphate or ammonium phosphate.
- Addition of Sulphuric Acid
The solution is then made acidic with a small amount of sulphuric acid. Acidity is favorable to the growth of yeast but unfavorable to most other bacteria. Care should be taken to avoid an excess of acid as the yeast may be killed.
- Addition of Yeast ( Fermentation )
The resulting solution is received in a large fermentation tank and yeast is added to it. The mixture is maintained at about 30-degree celsius for 2 or 3 days. During this period the enzymes invertase and zymase present in yeast bring about the conversion of sugars into ethyl alcohol. During the process, the liquor froths owing to the evolution of carbon dioxide. The fermented liquor is known as WASH.
- Fractional Distillation of Wash
The wash contains 15-18% ethyl alcohol. It is subjected to fractional distillation in a special column. The column is divided into a number of compartments by means of plates. These plates are provided with valves and dropping tubes. Wash is admitted near the top. As it travels down the column, it meets the up-coming current of steam, The steam converts ethyl alcohol into vapors. These vapors rise up and are fed into the condenser. The high boiling impurities travel down the column. The fractional distillation of the wash yields three fractions:
Fraction 1. Low boiling fraction is drawn from the head of the column. It consists of acetaldehyde.
Fraction 2. The main fraction is drawn near the top of the column. It consists of 95% ethyl alcohol. It is sold under the name Rectified Spirit or Commercial Alcohol.
Fraction 3. High boiling fraction ( 125-140 ) degree celsius drawn near the base of the column. It is called Fusel Oil. It consists mainly of amyl alcohol.
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