Subbituminous
Subbituminous coal is a low-rank, dark brown to black coal, less lustrous than bituminous but harder than lignite, sitting between them in the coalification process, characterized by 35-45% carbon, higher moisture, lower sulfur, and moderate heating value (8,300-11,500 Btu/lb), primarily used for electricity due to cleaner burning and large U.S. reserves in places like Wyoming, making it a key energy source despite lower energy density than bituminous coal.
Key Characteristics:
Appearance: Dark brown to black, generally dull but can have some luster, with distinct bright and dull bands.
Rank: Intermediate between lignite (brown coal) and bituminous coal.
Composition: 35-45% carbon (dry basis), higher moisture (10-25%), lower sulfur than bituminous coal.
Energy: Lower heating value (8,300-11,500 Btu/lb) compared to bituminous, but higher than lignite.
Properties: Less friable (crumbly) than lignite, making it easier to transport, but can be prone to spontaneous combustion if stored improperly.
Uses & Significance:
Electricity Generation: Its primary use in power plants, often preferred for its lower sulfur content, which helps meet environmental regulations.
U.S. Production: A major component of U.S. coal, with vast reserves in the Powder River Basin (Wyoming, Montana).
Formation: Formed from partially coalified peat, undergoing more heat and pressure than lignite but less than bituminous coal, resulting in its transitional properties.
Key Characteristics:
Appearance: Dark brown to black, generally dull but can have some luster, with distinct bright and dull bands.
Rank: Intermediate between lignite (brown coal) and bituminous coal.
Composition: 35-45% carbon (dry basis), higher moisture (10-25%), lower sulfur than bituminous coal.
Energy: Lower heating value (8,300-11,500 Btu/lb) compared to bituminous, but higher than lignite.
Properties: Less friable (crumbly) than lignite, making it easier to transport, but can be prone to spontaneous combustion if stored improperly.
Uses & Significance:
Electricity Generation: Its primary use in power plants, often preferred for its lower sulfur content, which helps meet environmental regulations.
U.S. Production: A major component of U.S. coal, with vast reserves in the Powder River Basin (Wyoming, Montana).
Formation: Formed from partially coalified peat, undergoing more heat and pressure than lignite but less than bituminous coal, resulting in its transitional properties.
