Anthracite will be the highest rank of coal, used primarily for residential and commercial space heating. It is a hard, brittle, and black lustrous coal, known as hard coal, containing a top percentage of fixed carbon as well as a low percentage of volatile matter. The moisture content of fresh-mined anthracite usually less than 15%. The heat content of anthracite ranges from 20 to 25 Mn Btu per t on a moist, mineral-matter-free basis. Since the 1980's, anthracite refuse or mine waste has been used for steam electrical energy generation. This fuel typically carries a heat content of 13.5 Mn Btu per t or fewer.
A dense coal, usually black, sometimes darkish, often with well-defined bands of bright and dull material, it's used primarily as fuel in steam-electric power generation, with substantial quantities also utilized for heat and power applications in manufacturing also to make coke. Its moisture content articles are usually less than 20%. The warmth content of this coal varies from 19 to 27 Mn Btu per t on a moist, mineral-matter-free basis.
A coal whose properties vary from those of lignite to those with this coal type, it is used primarily as fuel for steam-electric power generation. It may be dull, dark brown to black, soft and crumbly, in the lower end of the range, to bright, jet black, hard, and comparatively strong, at the upper end. Sub-bituminous coal contains 20-30% inherent moisture by weight. The heat content of sub-bituminous coal ranges from 15 to 22 Mn Btu per t on a moist, mineral-matter-free basis.
Lignite could be the lowest rank of coal, sometimes called brown coal and it's also used almost exclusively as fuel for steam- electrical energy generation. It is brownish-black and possesses a high inherent moisture content, sometimes of up to 45% The heat content of lignite ranges from 8 to 15.5 Mn Btu per t with a moist, mineral-matter-free basis.Steam coal
Steam coal will be the total of anthracite and bituminous coal.