A two-phase model to describe the combustion of coal in a fluidized bed of dolomite would be critically influenced by the properties, at minimum fluidization, of bed materials of a range of particle sizes and shapes. To aid in developing the model, experiments were performed with dolomite particles of a size distribution in the range of about 1410-88 mu m in a 6-in.-diameter fluidized-bed reactor. The bed voidage at fluidization and the minimum fluidizing air velocities were determined as a function of temperature (70-800 exp 0 F) and pressure (26-121 psia). The experimental data suggest that, at a given temperature, the minimum fluidization velocity decreases with increasing pressure and that, at a given pressure, probably, it is independent of temperature. These data were correlated using the Ergun relation. The mean sphericity of the particles required in the Ergun correlation was determined from experimental pressure drop data at low Reynolds number. Other methods often employed for predicting the minimum fluidization velocity of a bed of single-size spherical particles were examined with appropriate modifications for their applicability to a bed consisting of a wide range of particle sizes and shapes. Specific recommendations have been made as to the applicability of the different methods for calculating minimum fluidization velocities.
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