Bituminous coal, sometimes nicknamed "bit coal," is the most common type of coal. This dense, dark rock can have striations of bright and dull matter. It has more volatile matter and less fixed carbon than anthracite.
Bituminous and sub-bituminous coal together represent more than 90 percent of all the coal used in the U.S. Bituminous coal includes two subtypes: thermal and metallurgical.
Thermal coal is sometimes called steaming coal because it is used to fire power plants that produce steam for electricity and industrial uses. Steam locomotives may use "bit coal" as fuel.
Metallurgical coal is also referred to as coking coal, because it is used in the process of creating coke necessary for iron and steel-making. Coke is a porous, hard black rock of concentrated carbon that is created by heating bituminous coal without air to extremely high temperatures. This process of melting the coal in the absence of oxygen to remove impurities is called pyrolysis.
Heating value: Bituminous coal provides approximately 10,500 to 15,000 Btu per pound as mined.
Characteristics: Bituminous coal contains moisture up to about 17 percent. Its fixed carbon content can range up to about 85 percent, with ash content up to 12 percent by weight. Bituminous coal can be categorized further by the level of volatile matter it contains: high-volatile A, B, and C, medium-volatile, and low-volatile. About 0.5 to 2 percent of the weight of bituminous coal is nitrogen.
Bituminous coal lights on fire easily and can produce excessive smoke and soot (particulate matter) if improperly burned.
Bituminous coal commonly contains the mineral pyrite, which can serve as a host for impurities such as arsenic and mercury. Burning of bituminous coal releases trace mineral impurities into the air as pollution. During combustion, about 95 percent of the sulfur content of bituminous coal gets oxidized and released as gaseous sulfur oxides.
Hazardous emissions from bituminous coal combustion include particulate matter (PM), sulfur oxides (SOx), nitrogen oxides (NOx), trace metals such as lead (Pb) and mercury (Hg), vapor-phase hydrocarbons (such as methane, alkanes, alkenes, benzenes, etc.) and polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (known popularly as dioxins and furans). When burned, bituminous coal can also release hazardous gases such as hydrogen chloride (HCl) and hydrogen fluoride (HF).
Burning bituminous coal at higher temperatures reduces its carbon monoxide emissions. Therefore, large combustion units and well-maintained ones generally have lower pollution output. Bituminous coal has slagging and agglomerating characteristics.
Availability: Abundant. More than half of all available coal resources are bituminous.
Location: Illinois, Kentucky, West Virginia, Arkansas (Johnson, Sebastian, Logan, Franklin, Pope, and Scott counties), and locations east of the Mississippi river.
Additional notes: Bituminous coal combustion releases more pollution into the air than sub-bituminous coal combustion, but due to its greater heat content, less of the fuel is required to produce a given output of electricity. Therefore, bituminous and sub-bituminous coals produce approximately the same amount of pollution per kilowatt of electricity generated.
Tiny particles of waste bituminous coal that are left over after preparation of commercial grade coal are called "coal fines." Fines are light, dusty, and difficult to handle, and traditionally were stored with water in slurry impoundments to keep them from blowing away. New technologies have been developed to reclaim fines that were formerly considered waste. One approach is to use a centrifuge to separate the coal particles from slurry water. Other approaches have been developed to bind the fines together into briquettes that have low moisture content, making them suitable for fuel use.