Origins of Coal Egee

Coal Power for progress

THE ORIGINS OF COAL

C

oal is the altered remains of prehistoric vegetation that originally accumulated as

was converted into lignite or brown coal – coal-types with low organic ‘maturity’. Over many more millions of years, the continuing effects of temperature and pressure produced additional changes in the lignite, progressively increasing its maturity and transforming it into the range known as sub-bituminous coals. As this process continued, further chemical and physical changes occurred until these coals became harder and more mature, at which point they are classified as bituminous or hard coals. Under the right conditions, the progressive increase in the organic maturity continued, ultimately to form anthracite. The degree of ‘metamorphism’ or coalification undergone by a coal, as it matures from peat to anthracite, has an important

plant material in swamps and peat bogs.The accumulation of silt and other sediments, together with movements in the earth’s crust (tectonic movements) buried these swamps and peat bogs, often to great depth.

Current coal reserve/production ratios confirm over 200 years of resource availability.

With burial, the plant material was subjected to elevated temperatures and pressures, which caused physical and chemical changes in the vegetation, transforming it into coal. Initially the peat, the precursor of coal,

COAL

CARBON/ENERGY CONTENT HIGH

bearing on its physical and chemical properties, and is referred to as the ‘rank’ of the coal. 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 a low carbon content, and hence a low energy content. Higher rank coals are typically harder and stronger and often have a black vitreous lustre. Increasing rank is accompanied by a rise in the carbon and

HIGH

MOISTURE CONTENT

% of World Reserves

LOW RANK COALS...