Coal combustion studies in a fluidized-bed test facility

A fluidized-bed combustor has been designed, constructed, installed, and tested for the combustion of coal. A cylindrical (0.152 m i.d.) fluidized-bed, equipped with a specially designed propane burner to preheat the inert bed of sand and ignite an Illinois Basin coal sample (IBC-103), was employed in the test runs. The flue-gas composition is established by using a Cole-Parmer KM 9004 electronic combustion analyzer. A methodology is developed to compute the percentage utilization efficiency of carbon and the fuel-combustion efficiency, based on knowledge of fuel and flue-gas compositions and operating conditions of the combustor. Thirteen combustion-test results are reported, emphasizing the quality and efficiency of combustion for different coal-feed rates (0.66–1.58 g/s), bed temperatures (1003–1216 K), fractional excess air values (0.48–1.52), and gas-fluidization numbers (1.25–3.26). In addition, the hydrodynamic fluidization quality of the bed has been investigated on the basis of a series of measurements relating the calming-section pressure drops through the gas-distributor plates, pressure drops across the total bed and across its two sections, and the pressure-drop fluctuation history for various temperatures as functions of the fluidizing air velocity. These data provide bed-property parameters such as the minimum fluidization velocity, bed voidage, variance in bed pressure-drop fluctuation, and variations of these properties with operating conditions. The results are compared with limited related experimental data in the literature.