There are three basic types of coal. These are:
Lignite or Brown Coal
This is the lowest category of coal with a high moisture content
It is smoke because it still retains some of its original vegetative matter
It has a low heat value and carbon
It has a carbon content of less than 4% and gives out only moderate amounts of heat.
It is used mainly for the production of thermal electricity.
It has a carbon content of between 45 and 80%. Because of this it gives off more heat than lignite.
This is the most common type of coal
Some bituminous coal has high gas content. This is called gas coal or steam and it is used for making gas.
Steam coal is the superior grade of bituminous coal
Another type of bituminous coal is used for making coke which is used in blast furnaces. This type is called coking coal.
it is very hard coal that has at least 90% carbon content
It is the best type of coal. This enables it to burn with great heat and little smoke.
Due to its scarcity and its high prices, it is only used when other types of coal are less