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Show INTRODUCTION In recent years, this country has experienced a renewed emphasis on the use of solid fuels as energy alternatives to imported oil. Considerable research is being directed at various conversion schemes in which coal may be converted to liquid or gaseous fuels. While it is imperative that these processes be developed, it is also a virtual certainty that, for the next one or two decades, the primary mode of solid fuel utilization will be direct combustion. Considerable research has been focused on combustion of pulverized coal and its associated environmental problems. However, many current industrial and commercial boilers are stoker-fired systems; these systems have been largely overlooked in energy and environmental research programs. Stoker-fired boilers are significant in terms of both fuel consumption and pollutant emissions. Almost 20% of the coal consumed in the U.S. is burned in stokers. They represent the single largest source of particulate emissions and a major source of NO emissions. (1) The pollutants from stoker combustion processes often represent an enhanced environmental problem because of their proximity to congested metropolitan areas. Furthermore, as the utilization of coal and wood wastes increases, it seems likely that stoker firing will be implemented in more industrial and commercial boilers. The spreader stoker is the most common large mechanical stoker because it can burn a wide variety of fuels and follow rapid swings in load. In this system, a multi-bladed rotor projects the coal particles (80%>8 mesh, max. size lV) onto a moving grate. The smaller particles burn in suspension while the heavier pieces fall to the grate and burn in a thin fuel bed. In typical full scale furnace operation, approximately 85 percent of the air is injected as underfire air, i.e. through small (0.25 inch) holes in the grate. The remaining air is injected as overfire air through rows of ports on the front and back walls of the furnace at elevations of approximately 1.5 feet and 6 feet above the grate. Heat release rates are typically less than 750,000 Btu/hr/ft . This paper describes the results of investigation funded by the U.S. Environmental Protection Agency and the Weyerhaeuser Company into the 25-2 |