Question

Sub-bituminous is:

• A. a dull black coal with a higher heating value.
• B. a dark black coal with a lower heating value.
• C. a soft, intermediate grade of coal
• D. none of these

Answer 1

The correct option is A a dull black coal with a higher heating value.

Sub-bituminous coals may be dull, dark brown to black, soft and crumbly at the lower end of the range, to bright jet-black, hard, and relatively strong at the upper end. They contain 15-30% inherent moisture by weight and are non-coking (undergo little swelling upon heating). The heat content of sub-bituminous coals ranges from 8300 to 11,500 Btu/lb or 19.3 to 26.7 MJ/kg.

Their relatively low density and high water content render some types of sub-bituminous coals susceptible to spontaneous combustion if not packed densely during storage to exclude free airflow.

Hence, the correct option is $\text{A}$