99/00209 Coal-water slurry fuel production: its evolution and current status in the United States

Abstract

Interest in the US in utilizing bituminous coal in a slurry form has evolved substantially over the last two decades. In the mid-1970`s, technologies to utilize coal-oil mixtures (COMs) as potential fuel oil replacements for utility and industrial boilers were developed as a consequence of escalating world oil prices. To further reduce dependency on imported oil, interest shifted away from COMs to coal-water slurry fuels (CWSFs) because higher solids loadings were obtainable while eliminating the use of oil. Research which focused on the use of CWSF as a potential fuel oil replacement peaked in the mid to late-1980`s as a result of a decline in world oil prices. During the late 1980`s and early 1990`s, coal suppliers and coal-fired utilities began to evaluate the production of CWSF using bituminous coal fines from fine coal cleaning circuits in an effort to reduce dewatering/drying costs. This marked a philosophical change in the driving force behind the utilization of CWSF in the US. In an effort to broaden the supply of coal fines, The Pennsylvania State University (Penn State) and the Pennsylvania Electric Company (Penelec) surveyed a series of fine coal impoundments in western Pennsylvania to determine the quality, cleanability, and slurryability ofmore » the coal fines contained therein. The development and commercialization of recovery technologies, cleaning techniques, and CWSF reentrainment circuits, coupled with an interest by utilities to utilize low-cost fuels, has fostered the recovery of impounded coal fines. In addition to the fine coal impoundments, fine coal cleaning circuits which actively dispose of process water having suspended coal fines (e.g. centrifuge effluent) are being examined to determine if the fines can be recovered and thickened into a low solids CWSF. The paper describes required physical and chemical properties of a CWSF for boiler applications. There is a growing awareness that CWSF is a fuel form that can be cofired with coal. The current political, environmental, and economic climates mandate greater efficiency in the production and use of coal. Coal suppliers and coal-fired utilities must establish the actual cost of the CWSF production for the technology to move forward. Coal-fired utilities that own fine coal impoundments and/or operate fine coal cleaning circuits need to determine how these coal fines can be used to reduce operating cost.« less