Brown Coal

brown coal: see lignite.

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brown coal

a low-quality coal intermediate in grade between peat and lignite

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brown coal [¦brau̇n ¦kōl]

(geology)

lignite

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Brown Coal 

a flammable mineral of vegetable origin; a transitional form between peat and hard coal. It is distinguished from peat by its greater density and lesser content of discernible vegetable remains and from hard coal mostly by its brownish coloring (from coffee- and straw-colored to black). Brown coal breaks easily into small pieces in air.

High hygroscopicity, moistness, and the presence of humic acids are characteristic of brown coal. In a combustible mass of brown coal the carbon content is 55-78 percent, the hydrogen content 4.0-6.5 percent and higher, and the oxygen content 15-30 percent. The heat of combustion of a combustible mass is 22.6-31.0 megajoules per kg (5,400-7,400 kilocalories per kg). The yield of primary resin is 5-20 percent and higher, and the content of volatile substances, depending on the petrographic composition of the coals, varies from 65 to 40 percent. Brown coal is divided according to genetic characteristics into dense and earthy varieties; occasionally the latter includes lignites, which are a particular type of transformation and preservation of fragments, with a woody structure. Apart from the structural differences, the unequal content of moisture, oxygen, volatile substances, and primary resin is also taken into account. According to the industrial classification used in the USSR, brown coal is divided into three technological groups: B1, with a moisture content higher than 40 percent; B2, with 30-40 percent; and B3, with less than 30 percent.

The largest deposits and basins of brown coal are characteristic of the Mesozoic and Cenozoic eras. Brown coal is laid down both as small layers and as huge strata up to 100-120 m thick. The geological reserves of brown coal in the USSR are almost 3.5 trillion tons. A significant quantity of the reserves are concentrated in basins with sheets of brown coal 60-90 m thick. The majority of them are suitable for strip mining (the Kansk-Achinsk basin, the Babaevo deposit of the Southern Ural basin, the Svobodnyi deposit of Amur Oblast, and others). Abroad, the overwhelming majority of brown coal is mined in the German Democratic Republic and the Federal Republic of Germany. There is also considerable mining in Czechoslovakia. Brown coal is used as an energy-producing fuel and as chemical raw material for the manufacture of liquid fuel and various synthetic substances, gas, and fertilizers.

REFERENCES

Zhemchuzhnikov, Iu. A., and A. I. Ginzburg. Osnovy petrologii uglei. Moscow, 1960.
Zikeev, T. A. Spravochnik po kachestvu iskopaemykh uglei i goriuchikh slantsev Sovetskogo Soiuza. Moscow, 1957.
Gapeev, A. A. Tverdye goriuchie iskopaemye (Kaustobiolity). Moscow, 1949.

A. K. MATVEEV