Coal was discovered in the fire pits of cave dwellings, supplying evidence it has been used as a source of energy throughout man’s history. The Chinese considered coal a ‘stone that could burn’ and were mining it over 3000 years ago. The Greek scientist, Theophrastus, recorded the use of coal for smelting metal around 300 BC and the Romans used coal to heat their public baths. The increased use of coal for power generation in Britain in the 18th century fuelled the global Industrial Revolution.
Coal is now one of the world’s largest sources of energy. Global coal consumption grew by 7.6% in 2010, with Asia Pacific countries accounting for 79.7% of the increase.
What is black coal made from?
Coal is a combustible sedimentary rock found in layers under the earth known as coal seams or coal beds. Considered a fossil fuel, coal is formed when the build-up of organic material and fossil remains is pressurised over millions of years by layers of sediment, causing a breakdown of this material into hydrocarbons (referred to as ‘coalification’).
During its formation over millions of years, coal matures from a soft peat, through to its hardest form, graphite. Depending on both its colour and composition, the product is classified as brown coal
or black coal. Black coal is the highest grade of coal and includes sub-bituminous and bituminous coal, through to shiny black anthracite. Graphite is technically the hardest form of coal, however, it does not easily ignite and is used in pencils and lubricants, rather than energy production.
Coal is primarily composed of carbon (from 50 to 98 per cent) and hydrogen (3 to 13 percent) with the remainder comprised of varying amounts of oxygen, sulphur and nitrogen. Black coal has a relatively high carbon content (71 to 91 percent) and low moisture content (under 10 percent).
In some cultures, children are told that if they don’t behave, they will receive a lump of coal for Christmas
. In Italy, this legend has resulted in a Christmas joke, where children are given a hard black rock-like candy (Carbone dulce) that resembles coal.
How is black coal used?
Varieties of black coal are used for different purposes, depending on the composition and heating properties:
- Thermal (steaming) coal is used mainly for generating electricity in power stations where it is burned to heat water, producing steam to run the power turbines.
- Metallurgical (coking) coal is suited to making coke used in the production of pig iron. These coals must have low sulphur and phosphorus contents, and are relatively scarce; attracting a higher price than thermal coals.
Not only is black coal used to generate electricity, it is extensively used in primary industries, such as cement manufacturing and steel production.
Black coal is mostly used in its raw form, however, some coal by-products are further used in the chemical industry. Refined coal tar is used to manufacture chemicals such as pitch, creosote oil, naphthalene, phenol, pyridine, benzene and toluene. Ammonia gas recovered from coke ovens is used to manufacture ammonia salts, nitric acid and agricultural fertilisers (such as sulphate of ammonia and ammonium nitrate).
Thousands of other products have coal or coal by-products as components, including soap, aspirin, solvents, dyes, plastics and fibres like rayon and nylon.
Where is black coal found?
Coal is found in coal beds under the earth at various depths and is often exposed above the ground, which aided its discovery by early humans. Mined from the surface (open pit) or underground, surface mining is more economical and hence most common.
Most countries have coal deposits, however not all of them are commercially viable for extraction. The “BP Statistical Review of World Energy
” estimated the world’s black coal reserves at approximately 456 billion tonnes in 2010. The countries containing the largest amount of black coal reserves include:
- Russian Federation
- South Africa
In 2009, economically recoverable black coal resources in Australia were reported to be 43.8 billion tonnes with over 96% of these resources in New South Wales and Queensland. Australia has about 7% of the world's economically recoverable black coal and ranks fifth behind USA (31%), Russia (22%), China (14%) and India (8%). Coal accounts for around three quarters of Australia’s electricity generation, with coal-fired power stations located in every mainland state.
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