Influence of the Density of Microspherical Catalysts on the Operating Modes of Fluidized Beds

Abstract

Two types of fine particles of the Geldart class A with different bulk density, ρ n = 1200 kg/m3 and ρ n = 1300 kg/m3, were used for experimental studies of the circulating fluidized bed. A bench (0.7 m in diameter and 5.75 m in height) was used for the studies at room temperature with air as the fluidizing gas. The fluidization speed ranged from 0.1 to 0.75 m/s. The bed was sectioned in height using a set of horizontal diffuser grids. Fluctuations in average pressure drops and pressure distribution among the height of the fluidized bed were measured to determine the influence of the particle density on the operating modes of the fluidized bed. The transition rate, U c , was determined from mean square deviations of pressure drop fluctuations to equal U c = 0.40 m/s for lighter particles and Uc = 0.35 m/s for heavier particles. The transition rate, Uc, determined from the power energy spectrum of pressure fluctuations was 0.45 and 0.40 m/s for the lighter and heavier particles, respectively. The results of pressure measurements along the bed height showed that the pressure decreased linearly upward the bed, the decrease being faster for the heavier particles than for the lighter particles.