Energy content, coal anthracite

Anthracite. Anthracite is a hard, black, shiny form of coal that contains virtually no moisture and very low volatile content. Because of this, it bums with little or no smoke and is sold as a "smokeless fuel. In general, coals only approach anthracite composition where bituminous coal seams have been compressed further by local crustal movements. Anthracites can have energy contents up to about 32 MJ/kg, depending on the ash content. 

With an increasing coaliflcation (i.e., progressing from lignite to subbituminous coal to bituminous coal to anthracite), the moisture content decreases while the carbon content and the energy content both increase. 

Among the types of coal listed in Table 22.3, anthracite has the highest carbon content and consequently yields the most energy per mass when burned. Bituminous coal also contains a relatively high amount of carbon but has in addition high levels of sulfur, which results in increased formation of sulfur oxides when this type of coal is burned. Sulfur oxides are the pollutants that create acid rain (see Sections 3.6 and 15.12). 

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