Coal:
- It is an important source of energy since earlier time. In India and other country also coal is used to generate electricity.
- Coal formed beneath the earth surface by the slow decomposition of plant for a longer period.
- It is type of fossils fuel.
There are four types of coal:
On heating coal at a temperature in the range of 1270-1675 in the absence of air, it decomposed to give the following products.
- Coke: It is the solid residue left after the distillation of coal; it is used as a fuel and as a reducing agent in different metallurgical process.
- Coal Tar: It is a thick black colour viscous liquid. It is used in various industries such as dying and drugs and mainly used in the metalling of road. Now a day’s bitumen a petroleum product is used in the metalling of road.
- Fractional distillation of Coal Tar produces the following products: light oil, middle oil or carbolic oil, heavy oil or creosote oil, green oil or anthracene oil and pith.
Petroleum:
Petroleum (Petra means rock and oleum means oil) is a fossil fuel.
It is formed under beneath the earth surface by the decomposition of dead remains of organism living in the sea.
Over the year these dead remains converts into the petroleum and natural gas due to the absence of air, high temperature and high pressure.
World first oil well was drilled in Pennsylvania (USA) in 1859 and second in India in 1867 at Makum in Assam.
Refining of petroleum is carried out in refinery.
Knocking
Knocking is a metallic sound produced in engine due to low quality of petrol. Knocking can be reduce by adding antiknock compound.
TetraethylLead (TEL) and Benzene-Toluene-Xylene(BTX) are common antiknock compounds. TEL creates pollution, so its use has been stopped in India.
Octane number
The antiknocking property of petrol is measured in terms of octane number. Higher the octane number, better is the quality of fuel. Gasoline used in automobiles has an octane number 80 or higher while in aeroplane, it has an octane number 100 or over higher.
Rocket Fuel
The fuel used in rockets is called rocket propellant. It is a combination of an oxidiser and a fuel which on combination releases large quantities of hot gas. Propellants are of following types:
Liquid propellants: They are alcohol, liquid hydrogen, liquid ammonia, kerosene oil, nitromethane and hydrogen peroxide.
Solid propellants: Example of solid propellants are polybutadiene and acrylic acid used along with oxidiser such as aluminium per chlorate, nitrate or chlorate.
Hybrid propellant: They consists of a solid fuel and liquid oxidisers.