Power Alcohol

POWER ALCOHOL

When ethyl alcohol is blended with petrol at concentration of 5-10%, it is called power alcohol. In other words absolute alcohol (100% ethyl alcohol) is also called power alcohol. Ethyl alcohol is used in an internal combustion (IC) engine. The addition of ethyl alcohol to petrol increases its octane number. When ethyl alcohol is blended with diesel it is called E diesel.

Manufacture

Manufacture of power alcohol involves the following two steps

Step I : Manufacture of Ethyl alcohol

Ethyl alcohol can be synthesised by fermentation of carbohydrates (sugar material). Fermentation of molasses, which is the residue left after the crystallization of sugar, with yeast generates alcohol. This fermentation yields only about 20% alcohol.

Concentration of alcohol can be increased up to 97.6% by fractional distillation yields rectified spirit. The concentration of alcohol cannot be increased by distillation above 97.6%, because it forms a constant boiling mixture with water. The constant boiling mixture has a lower boiling point than alcohol.

Step II : Conversion of ethyl alcohol into power alcohol

But, for the use in IC engines, 100% alcohol (absolute alcohol) is prepared by removing last traces of water from rectified spirit. It can be done by the following two methods.

(i) Alcohol, containing traces of water, is distilled with benzene. When benzene passes over with a portion of alcohol and water, it leaves behind absolute (power) alcohol.

(ii) Alcohol is distilled in the presence of dehydrating agent, which holds the water.

Finally absolute alcohol is mixed with petrol at concentration of 5-10% to get power alcohols.

Properties

1. Power alcohol has a lower calorific values (7000 k.cal/kg).

2. It has high octane number (90).

3. Its anti-knocking properties are good.

4. It generates 10% more power than the gasoline of same quantity.

5. Its compression ratio is also higher.

Uses

It is used, as a very good fuel, in motors.

1. Advantages and Disadvantages of power alcohol

Advantages

1. It is cheaper than petrol.

2. If any moisture is present, power alcohol absorbs it.

3. As ethyl alcohol contains oxygen atoms, complete combustion occurs, so emission of CO, hydrocarbon, particulates are reduced.

Disadvantages

1. As the calorific value of power alcohol (7000 cal/gm) is lower than petrol (11,500 cal/gm), specially designed engine is required.

2. Output power is reduced upto 35%.

3. Due to its high surface tension, atomization of power alcohol is difficult, so it causes starting trouble.

4. It may under go oxidation to give acetic acid, which corrodes engine part.

5. As it contains oxygen atoms, the amount of air required for combustion is less therefore, the engine and carburetor need to be modified.