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Show 1.0. Introduction Alternate fuels, for electric utilities, are typically those materials that do not enter ordinary, organized co~erce. These fuels are typically residuals from other material processes, or from usage by socIety: sawdust from sawmills; urban wood waste including broken pallets, tree trimmings, and construction or demolition debris; tire-derived fuel (TDF); and waste paper and plastics from manufacturing or printing processes. Refuse-derived fuel (RDF) produced from municipal solid waste (MSW) is also fired as an alternate fuel. Utilities are increasingly interested in alternate fuels as a means for accomplishing the following objectives: reducing fuel costs at coal-fired generating stations; increasing fuel diversity at coal-fired stations; satisfying customer needs for waste management, with the consequence of improving the health of industries served and with the consequence of maintaining or increasing load; and addressing environmental impacts of generation including reducing emissions of sulfur dioxide (S02) and oxides of nitrogen (NOx), as well as reducing emissions of greenhouse gases such as fossil-based carbon dioxide (C02). Reducing fossil-based CO2 emissions is of consequence for utilities making voluntary commitments to the global climate challenge program, when cofiring alternate fuels provides a cost-effective means for accomplishing this objective. Numerous utilities have cofired alternate fuels with coal in both cyclone and pulverized coal (PC) boilers as well as fluidized bed and stoker boilers, either as a commercial practice or in test programs, in the past few years. These utilities include The Tennessee Valley Authority (TVA) with programs at the Allen Fossil Plant, the Kingston Fossil Plant, and the Colbert Fossil Plant; Northern States Power with commercial programs including the 600 MW cyclone boiler at the King Station, the spreader-stokers installed at the Bayfront Station and the Red Wing generating station, and the French Island fluidized bed installation; GPUlPenelec with testing at the Shawville Generating Station and a companion program at the Seward Generating Station; Tacoma Public Utilities with Steam Plant #2 repowered with fluidized bed boilers designed to fire a combination of wood waste, coal, and RDF; Otter Tail Power with co firing activities at the Big Stone cyclone boiler; Southern Company with co firing testing and commercial activities at Plants Hammond and Yates of Georgia Power Co., and testing at Plant Kraft of Savannah Electric Co.; and numerous other utility installations as well. The Electric Power Research Institute (EPRI) has supported much of this development with test programs and support studies as documented extensively in the literature (see, for example, Ebasco Environmental, 1994, Foster Wheeler Environmental, 1994, Tillman et. aI., 1996a, Tillman et. aI., 1996b, Prinzing and Hunt, 1996, Boylan, 1993, Battista et. aI., 1996, Hughes and Tillman, 1996). Utilities such as TV A have provided direct support for cofiring evaluation and assessment as well. TVA, with the support of EPRI, has performed the most extensive parametric testing of cofiring sawdust, and trifiring sawdust and TDF with both interior province bituminous coal and western bituminous coal at the Allen Fossil Plant in Memphis, TN. Alternate fuels supplied up to 10 percent of the fuel on a Btu basis, or 20 percent of the fuel on a mass basis, at this cyclone boiler installation. These parametric tests have provided key insights into the potential influences of cofiring alternate fuels on the performance of cyclone boilers. They are particularly significant given the inherent flexibility associated with cyclone boilers, and their inherent design and operational characteristics. 2 |