Coal is a complex mixture of compounds of carbon, hydrogen, oxygen along with small amounts of nitrogen and sulphur compounds and some free carbon. Most of our coal was formed about 300 million years ago when much of the earth was covered by steamy swamps. Eventually bacterial and chemical action at high temperature and pressure inside the earth gradually changed the materials to coal. The slow chemical process of the conversion of wood into coal by a biochemical process extending over millions of years is called carbonization. Ø TYPES OF COAL
Coal formation is a continuing process. Depending on carbon content, moisture and volatile compounds, coal is classified into four categories: Peat, Lignite, Bituminous and Anthracite. Type of coal
Bituminous(the common variety
of coal)-grey black
Anthracite(best variety of coal)hard coal
% of carbon content
In thermal power plants
As a reducing agent for the
extraction of metals.
The different varieties of coal formed depend on how long and at what temperature and pressure the coal is buried under the surface of the earth. Peat is the most inferior quality coal and anthracite the most superior quality coal. Bituminous and anthracite are generally used fuels in industries and in our households.
Peat (dead plant material)
Lignite (brown coal)
Bituminous (household soft coal)
Anthracite (hard coal)
Uses of coal:
Coal is used as a fuel because it burns easily and has high calorific value.
It is used to make other fuels like coal gas, synthetic petrol, methane and coke
Coal is used in the manufacture of industrially useful compounds like benzene, phenol, naphthalene, etc.
Destructive Distillation of Coal:
On strong heating coal in a closed tube it breaks down into
different components such as coal gas, coal tar, ammoniacal liquor and coke. This process is called the destructive distillation of coal.
Products of Destructive Distillation of Coal:
Coal gas – It is a mixture of hydrogen, methane and carbon monoxide •
gases. It is a good fuel with a high calorific value. Coal gas finds its use as cooking gas and for lights. Because of the presence of hydrogen it is used for many chemical and metallurgical processes to create reducing atmosphere. Coal tar – The residue left behind after destructive distillation of coal •
is called coal tar. Coal tar is the black liquid that settled under water in the test tube. It is the mixture of as many as two hundred carbon compounds which can be separated by fractional distillation. Compounds obtained from coal tar like benzene, phenol, naphthalene, etc are used to make medicines , dyes , paints , explosives , plastics , synthetic , pesticides, etc. Coal tar is used in making surface roads, water proof roofs.
Coke: Coke mainly contains carbon. It is a very good fuel with high •
calorific value than coal itself. It is an excellent reducing agent in industries. Coal is a good starting material for the preparation of acetylene, acetic acid and plastic polyvinyl chloride.
Ammoniacal Liquor: A solution of ammonia in water is called •
ammoniacal liquor. It reacts with sulphuric acid giving ammoniacal fertilizers.
Petroleum is a fossil fuel (Petra =rock, Oleum=oil). Thus
petroleum means rock oil. It is a complex mixture of several solid, liquid and gaseous hydrocarbons mixed with water, salts and earthy particles. It is a dark coloured, foul smelling viscous liquid.
How is petroleum formed?
It is believed that petroleum oil was formed from the remains of tiny sea plants and animals that died millions of years ago. When the plants and animals die they sink into the bottom of the oceans and were soon covered by sand and silt.
The chemical effects of enormous pressure, heat and bacteria converted the remains of microscopic...