Improvement of the Uniformity of Radial Solids Concentration Profiles in Circulating Fluidized-Bed Risers

In order to enhance the uniformity of the radial solids distribution and thereby the performance of industrial circulating fluidized-bed (CFB) risers, an approach by using the air jet from the riser circumference is proposed. The Eulerian-Eulerian computational fluid dynamics (CFD) model with the kinetic theory of granular flow is adopted to simulate the gas-solids two-phase flow in a CFB riser with fluid catalytic cracking (FCC) particles. The numerical results indicate that by employing the circumferential air jet approach under appropriate jet velocities, the maximum solids concentration in the near-wall region can be greatly reduced, the entrance region can be shortened, and the uniformity of the flow structure can be significantly improved. A circumferential air jets approach is proposed to improve the uniformity of lateral or radial solids concentration distributions mainly in the fully developed region. A comprehensive numerical study on the effects of this approach on the flow structure of gas-solids two-phase flows in a circulating fluidized-bed (CFB) riser is conducted. The results could permit optimal designs and operations of CFBs.