Coal Gas
Learn how gas is manufactured from coal. There are several methods like carbonization, cracking, Lurgi process.
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Coal measures are produced where coastal swamps once existed. As the sea moved in over the land and receded, various layers of rock formed between the coal measures.
Some coal measures occur at the surface and can be dug from quarries instead of mines. In Australia, coal measures are stripped from the surface at Moura mine in Queensland.
Coal
Coal is valuable not only as a fuel but also as a raw material for industry. Many people still burn it for heat. Power stations burn it to produce electricity. Gasworks convert it to coke and gas. Manufacturers also produce a wide variety of chemicals from coal, including drugs, plastics and dyes. But petroleum is rapidly replacing coal as a raw material for the chemical industry.
Coal is often called a fossil fuel because it was formed about 250 million years ago during a period of prehistory called the Carboniferous Period. At this time, the Earth was covered with swamps and gigantic plants. Ferns grew as high as trees do today. When the plants died, they fell to the bottom of the swamps and decayed. Deposits of mud formed over them. More plants grew and decayed and were buried under mud. Heat and pressure in the Earth's crust gradually changed the layers of mud into rock and the plant remains into coal seams.
Soft brown coal, or lignite, was formed first. Then this changed into dull, black bituminous coal, and finally into shining anthracite. Coal mining, digging the coal from the ground is a very big industry. The countries which produce the most coal are Russia, the United States, China, East and West Germany, and Britain, in that order.
Some coal is mined on the surface, but most is mined deep underground. Both forms of mining are now highly mechanized. On or near the surface, coal is mined by the strip mining method. Huge power shovels first strip off the earth overburden above the coal seam. Then the coal is broken up by explosives and shoveled into trucks.
Underground mining is more complicated, more expensive, and more dangerous. Shafts are sunk down in the ground, and tunnels are struck outwards from the shafts to the coal seams. In most mines coal winning, hewing it from the coal face is done by machinery.
One machine, called a continuous miner, rips coal from the face and loads it onto a conveyor belt. In another method, miners cut a slice near the base of the face and bring down the coal with explosives.
A great many precautions have to be taken to prevent accidents in the mines. They are well ventilated to keep suffocating and explosive gases from collecting. They are constantly drained to prevent flooding. The tunnels are shored up, or supported, with steel and concrete to prevent collapse. Much of the coal mined goes to be burned in power stations or in the home. But an enormous amount is made into coke and gas by carbonization heating without air. This process also yields coal-tar, benzole, ammonia, and other gases. From these raw materials perfumes, insecticides, drugs, dyes, plastics, saccharin, fertilizers, resins, creosote and tar can be made.
