When ethyl alcohol is used as a fuel in internal combustion engine, it is called as power alcohol.
Generally ethyl alcohol is used as it 5-25% mixture with petrol.
Use of ethyl alcohol in petrol reduces our dependence for petrol on foreign countries & even 5% ethyl alcohol blending in petrol saves our foreign reserves by about Rs. 5000 crores/ annum.
Further it gives boost to indigenous manufacturers of ethyl alcohol & farmers get better price of their grain produce.
Ethyl alcohol is mainly manufactured by fermentation of molasses, starch, carbohydrates on a large scale & cheaply. It can also be obtained from synthesis gas (CO, $H_2$)
The ethyl alcohol obtained contains 95.5% alcohol & 4.5% water.
This water is separated either by use of suitable dehydrating agent or by distilling it along with benzene.
ADVANTAGES OF POWER ALCOHOL:
- Ethyl alcohol has good Ant knocking property and its octane number is 90.
- It has property of absorbing any traces of water if present in petrol.
- If a specially designed engine with higher compression ratio is used then the disadvantage and lower CV can be overcome.
- It contains O atoms which help for complete combustion of power alcohol & the polluting emission of CO, hydrocarbon, particulates are reduced largely.
- Use of ethyl alcohol in petrol reduces our dependence on foreign countries for petrol and saves foreign currency considerably.
- Power alcohol is cheaper than petrol.