LOW-RANK COAL: ITS PRESENT AND FUTURE ROLE IN THE UNITED STATES.

Abstract

Resources of low-rank coals in the United States are comparable in quantity to available resources of bituminous coals. In most cases, the relatively thick seams of low-rank coal found close to the surface can be strip-mined at a fraction of the cost required to produce US bituminous coals. The importance of low-rank coal in the US energy system increased dramatically in the 1970s. This increase resulted from a combination of factors, including the escalating prices of oil and natural gas, the possibility of using low-rank coal to comply with clean-air regulations in some regions, and the development of improved combustion technology. Low-rank coals are noted for causing ash-related problems during combustion. However, the high alkali and low sulfur contents of many low-rank coals make them attractive for reducing sulfur emissions without much addition of limestone or lime. Some low-rank coals are especially attractive for gasification and liquefaction and are likely to dominate the early development of synthetic fuel plants and coal gasification/combined-cycle utility power plants. With all these factors considered, the role of low-rank coals in the United States is likely to continue growing as process improvements are made.