Effect of elevated pressure on gas-solid flow characteristics in a circulating fluidized bed

Abstract

Pressurized circulating fluidized beds are applied in a range of applications because of intensified heat and mass transfer and chemical reaction. The gas density increases linearly with the pressure, which influences the gas-solid flow characteristics. In this work, the effects of operating pressure (0.1 MPa–0.6 MPa) on the distribution of particle volume fraction and gas-solid slip velocity in the riser are studied under different conditions. The particle belongs to Geldart B group, the solids circulation rate ranges from 20 to 50 kg/(m2.s), and the fluidizing gas velocity ranges from around 2 to 8 m/s. With an increase in pressure from 0.1 to 0.6 MPa, in order to achieve the same solids circulation rate, the fluidizing gas velocity decreases approximately to a half. Under pressurized conditions, the profile of particle volume fraction along the axial direction shows a similar trend, while the particle volume fraction in the bed central zone at the upper riser increases slightly. Under different pressures, the plot of the nondimensional gas-solid slip velocity against the particle volume fraction converges on a power correlation. The present study is a first step towards the aim of correlating the solids circulation rate and gas-solid slip velocity with operating parameters under pressurized conditions.