Coal is a kind of solid combustible organic rock, mainly by the plant remains with biochemical action, buried after the geological change and become. Coal is ancient plant buried in underground through biochemical and complex physical and chemical changes gradually formed solid combustible mineral, is a non renewable resources.
The type of coal
Increased pressures and heat from overlying strata causes buried peat to dry and harden into lignite. Lignite is a brownish-black coal with generally high moisture and ash content and lower heating value. However, it is an important form of energy for generating electricity. Significant lignite mining operations are located in Texas, North Dakota, Louisiana, and Montana.
Under still more pressure, some lignite was changed into the next rank of coal subbituminous. This is a dull black coal with a higher heating value than lignite that is used primarily for generating electricity and for space heating. Most subbituminous reserves are located in Montana, Wyoming, Colorado, New Mexico, Washington and Alaska.
Even greater pressure results in the creation of bituminous, or “soft” coal. This is the type most commonly used for electric power generation in the U.S. It has a higher heating value than either lignite or subbituminous, but less than that of anthracite. Bituminous coal is mined chiefly in Appalachia and the Midwest. Also used to make coke.
Sometimes also called “hard coal,” anthracite forms from bituminous coal when great pressures developed in folded rock strata during the creation of mountain ranges. This occurs only in limited geographic areas – primarily the Appalachian region of Pennsylvania. Anthracite has the highest energy content of all coals and is used for space heating and generating electricity.
The application of coal
Coal is an important energy, important raw materials and metallurgy, chemical industry. At present, our direction is comprehensive, reasonable, effective development and utilization of coal resources, and focused on the coal into clean fuel. Mainly used for burning coal, coking, gasification, pyrolysis, hydrogenation liquefaction etc..
- The combustion. Any kind of coal can be used as industrial and civilian fuel.
- The coking. The coal in the retort furnace, organic matter with the increase of the temperature is gradually decomposed, become the coke oven gas and coal tar and coke. Coke oven gas as a fuel, but also an important raw material for chemical industry. Coal tar can be used in the production of chemical fertilizer, pesticide, synthetic fiber, synthetic rubber, paints, dyes, pharmaceuticals, explosives etc.. Coke is mainly used in blast furnace and casting, also can be used to make fertilizer, calcium carbide. Calcium carbide is plastic, synthetic fiber, synthetic rubber, synthetic chemical products.
- The gasification. Gasification refers to the transformation to a gas industry or civilian fuel and chemical raw materials.
- The low temperature carbonization. The coal under low temperature (550 ℃) can be prepared under low temperature carbonization of low-temperature tar and coke oven gas, coal tar can be used for production of liquid fuel and as a chemical raw material.
- The hydrogenation liquefaction. The coal, catalyst and heavy oil mixed together, so that the destruction of organic material in the coal in the high temperature and high pressure, conversion and hydrogen effect of low molecular liquid and gaseous products, further processing can be gasoline, diesel oil and other liquid fuels. The raw material of coal liquefaction by hydrogenation of lignite, long flame coal, gas coal.