coal

[NW Modeling List]

Coal isn't coal!!!! There are a number of types, the most well-known of 
which are lignite, sub-bituminous, bituminous, and anthracite. I recall 
that there are assigned to their classification according to the ratio of 
burnable carbon to other contents, to BTU content per measure, to moisture 
content, and possibly some other reasons. The heat content of each type is 
vastly different, and within types, the heat content can differ widely 
according to the exact ingredients of the coal.

Coal for market was frequently blended at the mine or at a processing 
facility so that a hopper car load would, overall, be of a certain heat 
content. Blending is still done for power plant coal, to reach appropriate 
heat content as well as satisfy emissions requirements.

The subject of coal is, actually, pretty complex.

Ivan Abrams