LIGNITE


Meaning of LIGNITE in English

brown to black coal that has been formed from peat under moderate pressure; it is one of the first products of coalification and is intermediate between peat and subbituminous coal. Dry lignite contains about 60 to 75 percent carbon. It has been estimated that about 45 percent of the world's total coal reserves are lignitic, but these reserves have not been exploited to any great extent because lignite is inferior to higher-rank coals (e.g., bituminous coal) in heating value, storage stability, and other properties. In some areas, however, the scarcity of fuel has led to extensive developments, especially in eastern Germany, where the production of lignite far exceeds that of bituminous coal. Schemes for its use, particularly by briquetting, have received attention in Australia, New Zealand, Canada, the United States, and elsewhere. The fuel is used by local utility, industrial, and domestic consumers close to the mine site. There are two types of raw lignite: one is brown and amorphous; the other, black and pitchlike. Raw lignite has a high water content, amounting to as much as 60 percent in the brown varieties; upon weathering, a proportion of this water is given up, and disintegration, or crumbling, of the material occurs, which reduces the value of lignite as a fuel. Lignite also tends to disintegrate during combustion, and hence the losses through a grate may be relatively high. It requires special care in storing, is uneconomical to transport long distances, and is liable to spontaneous combustion. Against these drawbacks, many lignite beds lie close to the surface and are of great thickness, sometimes more than 30 m (100 feet); they are thus easily worked and the cost of production is low. See also brown coal.

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