Types of Coal
The degree of change undergone by a coal as it matures from peat to anthracite – known as coalification – has an important bearing on its physical and chemical properties and is referred to as the ‘rank’ of the coal.
Low rank coals
Low rank coals, such as lignite and sub- bituminous coals are typically softer, friable materials with a dull, earthy appearance. They are characterised by high moisture levels and low carbon content, and therefore a low energy content.
Higher rank coals
Are generally harder and stronger and often have a black, vitreous lustre. They contain more carbon, have lower moisture content, and produce more energy. Anthracite is at the top of the rank scale and has a correspondingly higher carbon and energy content and a lower level of moisture.
The degree of change undergone by a coal as it matures from peat to anthracite – known as coalification – has an important bearing on its physical and chemical properties and is referred to as the ‘rank’ of the coal.
Low rank coals
Low rank coals, such as lignite and sub- bituminous coals are typically softer, friable materials with a dull, earthy appearance. They are characterised by high moisture levels and low carbon content, and therefore a low energy content.
Higher rank coals
Are generally harder and stronger and often have a black, vitreous lustre. They contain more carbon, have lower moisture content, and produce more energy. Anthracite is at the top of the rank scale and has a correspondingly higher carbon and energy content and a lower level of moisture.