Posted by Andrew Craig-Bennett on October 26, 2005 at 16:33:08 from 213.38.124.194 user ACB.
In Reply to: Re: Tower Colliery posted by Owen Roberts on October 25, 2005 at 23:43:31:
If we are going to talk about coal,;let us first define our terms
Coals are sorted by rank, ash content, volatiles content, sulphur content and hardness.
The terms "thermal coal" and "steam coal" are interchangeable and are used in contradistinction to "coking coal", also called "metallurgical coal" which is used in steel making.
Anthracite is high rank, and tends to evolve methane in storage; brown coal is low rank, is unlikely to evolve methane but is prone to spontaneous combustion. All other coals are somewhere in between.
"Best Welsh dry steam coal" was a high rank, low ash, low volatiles, high hardness coal, that burned without significant clinkering, and was favoured for Scotch boilers aboard ship.