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Show addition, they give off an offensive odor and form dense smoke. Hence, scrap tire combustion in conventional incinerators leaves much to be desired. The fluidized-bed combustion process, due to its inherent ability to control these pollutant emissions, would be the best means to solve che unretreadable scrap tire disposal problem and, at the same time, recover energy from the tires Feasibility studies of fluidized-bed combustion of scrap tires have recently been conducted at the Morgantown Energy Technology Center of the U.S. Department of Energy. The objectives of the preliminary study were to: o Investigate the feasibility of the direct combustion of scrap tires in an atmospheric pressure fluidized-bed combustor. o Determine the combustion, emission, and operational characteristics which may be unique to scrap tire combustion in fluidized beds. o Perform the conceptual design of a fluidized-bed combustor for the direct combustion of scrap tires based on the experimental data. The preliminary study, which included six tests, was carried out using one of the 6-inch diameter laboratory-scale fluidized-bed combustors. 5.1 Experimental Facilities Six-inch Diameter Laboratory-Scale Fluidized-Bed Combustor The experimental apparatus of the 6-inch diameter laboratory-scale fluidized-bed combustor is shown schematically in Figure 4. This laboratory-scale fluidized-bed combustor consists of a 6-inch diameter, refractory-lined, cylindrical vessel. The bed region is 16 inches high. The expanded freeboard section, of an 8-inch diameter, is 64 inches high. The 6-inch unit has a conical distributor plate with an open area totalling 2.77 percent of the distributor area. Fluidizing air from the plenum passes through 64 1/8-inch nozzles arranged in three concentric circles. Fuel from the feedhopper is fed directly into the bed by a 1-inch variable-speed metering screw which is protected by a water jacket. Limestone, when it is needed, is fed directly into the top of the expanded bed using a 3/4-inch feed screw. Spent bed material can be extracted from the combustor through a 3/4-inch drain pipe at the bottom of the conical distributor, or removed through an overflow tube which penetrates the side wall at an upward angle of about 30 degrees to the vertical. The in-bed opening of the overflow tube is typically set at a level of 4 1/2-inches above the top of the distributor plate; however, this level is adjustable. During tests, the overflow tube also serves to control the expanded bed height. The overflow tube discharges into a lockhopper which is periodically emptied. Flue gases are continuously sampled 11-19 |