coal

We used the term coal to describe a variety of fossilized plantv materials but no two coals are exactly alike.heating value ash melting temperature sulfur and other chemical and physical properties must be considered when matching specific coals to a particular application.
Coal is classified into four general categories or rks.
Antharcite is coal with the highest carbon content between 86 and 98 percent and a heat value of nearly 15000 BTUs per pound.most frequently associated.
Bituminous coal is used primarily to generates electricity and make coke for the steel industry.bituminous coal has a carbon content ranging from 45 to 86 percent carbon content and a heat value of 10,500 to 15,5000 BTUs per pound.
Ranking value below bituminous is sub bituminous coal with 35 45 percent carbon  content and a heat value between 8,3000 and 13000 BTUs per pound