Coal, comprising mainly carbon of vegetative origin, is one of the oldest forms of power. It provided the basis for the Industrial Revolution. Its importance as both fuel and raw material was greatly enhanced with the invention of the steam engine by James Watt in 1769.
Coal became the greatest single factor of industrial location. The pull of coalfields on industrial locations was so great that the majority of the world’s manufacturing areas are located on or near coalfields. The discovery of oil and the invention of electricity have greatly altered the prominence of coal in almost every field. Its low heat output, its untidy appearance and its great bulk, which raises transport costs, have all contributed to the decline of coal as a modern fuel.
However, in most parts of Europe, America and some Asiatic countries, coal is still extensively used as a domestic fuel, a source of industrial power and a vital raw material for the chemical industries. Coal yields gas, tar, benzole and sulphate of ammonia which have many industrial uses.
Coal mining methods
Coal, which occurs in sedimentary rocks in layers or seams of varying thickness, may be exposed or concealed. That which outcrops on the surface (exposed) is easily and economically mined by opencast or strip-mining methods.
The coal-bearing rocks are simply stripped off by giant shovels and the coal scooped up into the trucks to be carried away.
When the coal occurs underneath the earth’s surface in concealed beds, underground mining is necessary. This involves the excavation of the coal by driving vertical shafts down to the seams and removing the coal through tunnels.
This method is more expensive and also more dangerous. It has to take into consideration problems of ventilation, water supply and underground transport, not to mention the possibilities of gas poisoning; explosion and the collapse of the tunnel roofs. There are many instances of coalminers being buried alive in the underground mines.
When the coal seam lies beneath the sea, offshore marine mining methods have to be employed.
Types of coal
There are different types of coal which vary greatly in their properties and industrial uses. The following categories of coal are arranged in descending order of hydrocarbon content and calorific value.
A) Anthracite: This is the best coal, and constitutes not more than 5 percent of the world’s total coal output. It is the hardest, with the highest hydrocarbon content. It has very little volatile matter, is practically smokeless, burns quietly with great heat and leaves very little ash behind. It is used mainly for steam-raising in industrial plants and for domestic heating. Due to its scarcity and its higher price, anthracite is only used when other types of coal are less suitable.
B) Bituminous coal: This is the most abundant type of coal and may be subdivided into three classes:
- Steam coal: Its hydrocarbon content is a little less than that of anthracite. It is a superior grade of the bituminous coal, occurring in seams that have been highly compressed. It is black, very hard and burns readily with great heat. As it is relatively smokeless, like anthracite, it is extensively used as ‘bunker coal’ in steamships, and in locomotives and engines where soot accumulation is undesirable.
- Coking coal: This is a very useful type of coal which is burnt in closed ovens to drive off the volatile matter and increase its carbon content. This particular class of coal softens and fuses while burning and produces coke, a hard, grey porous material, which is used in blast furnaces to extract iron from its ores.
- Gas coal: The low-rank bituminous coal has a high percentage of moisture and volatile matter. When heated, it gives out much of its gases and vapour which are collected for use as coal gas and other chemical by-products.
C) Lignite or brown coal: This is the lowest category of coal with a high moisture and ash content. It is smoky, for it still retains some of its original vegetative matter. It has comparatively little carbon and has low heat value. Half the world’s lignite resources are in West and East Germany and a quarter in the Tula brown-coal deposits of Russia It is extensively used for domestic heating, generating thermal electricity and in the chemical industry. Nigeria has vast deposits of lignite yet to be tapped.
D) Peat: This is exclusively of vegetative matter and represents the initial stage of coal formation. Its carbon content is in the form of wood or decayed plants and it is highly charged with moisture. A large amount of peat is found in the bogs of Ireland and Scotland where it is cut in pieces like turf, dried and burnt as domestic fuel. It has only local importance and is not traded.
World coal distribution
Coal is mainly found in three continents, Europe, North America and Asia. The greatest producer of both anthracite and bituminous coal is U.S.A. (27 percent), from thePennsylvanian, Central and Rockies Coalfields. This is followed by China (23 per cent); and Russia (20 percent), from the Donbas, Kuzbas, Karaganda Ural and Tula coalfields.
Amongst the European producing countries, Poland (6.4 percent) has displaced United Kingdom as the greatest producer. United Kingdom now produces only 2 percent of world coal. It has eighteen coalfields flanking the Pennines and the Welsh Mountains, in the Midlands of England and the Central Valley of Scotland. Germany is the second greatest European coal producer (3 percent), mainly from the Ruhr and Saar. The other coalfields of Europe include the Franco-Belgian coalfield, the Limburg (Netherlands), the Kempen or Campine (Belgium) and scattered fields in France and Spain.
In Asia, China has the greatest coal reserves, though much is still untouched. The coal reserves in North China, in the provinces of Shanxi and Shensi, are so great that it is referred to as the second Pennsylvania’. Large deposits are located in Szechwan, Hunan, Yunnan, Shantung and Manchuria. India’s only sizeable coal deposit is in the Damodar Basin centred at Raniganj. Japan has limited coal deposits in Hokkaido, northern Kyushu and central Honshu. She is a net importer, particularly of cooking coal. Coal is unimportant in Malaysia. The only commercial deposit at Batu Arang, which was developed by the Malayan Colleries Limited in 1915, was forced to close down when the Malayan Railways and the Central Electricity Board switched to imported diesel oil.
In the southern hemisphere, coal deposits are relatively insignificant. The greatest deposits are in Australia, around Newcastle, New South Wales and much is exported. Greymouth and Westport are the coal-mining towns of New Zealand. In Africa, coal is mined in Transvaal and Natal, South Africa, and in Zimbabwe and Nigeria. Coal is least important in South America where scattered deposits occur in Concepcion, Chile and Southern Brazil.