Application of CPFD method in the simulation of a circulating fluidized bed with a loop seal Part II—Investigation of solids circulation

摘要

The Computational Particle Fluid Dynamics (CPFD) numerical method was used to study the gas solid flow characteristics in a circulating fluidized bed (CFB) with a loop seal in this work. The influences of operating parameters, including loop seal aeration rate (Q_l), fluidized air velocity in the riser (U_r) and total bed inventory (M_p) on the solid circulation characteristics were mainly investigated in this part. The solid circulating rate (G_s), total pressure drop in the riser (ΔP_r), particle packed height (H_s), pressure gradient (ΔP_s/H_s) and gas flow rate (G_g) in the stand-pipe, as well as the particle concentration and pressure distributions in the loop were carefully analyzed under different operating conditions. The simulation results were compared with the experimental results also reported in this work and good agreements were obtained. The results showed that the increase of Q_l resulted in a decrease of H_s and increases of G_s, AP_r and ΔP_s/H_s. By increasing U_r, the increase of G_s was limited and the maximum value was approaching. An increase of M_p also had a positive effect on G_s while an elevated H_s was obtained as a result of mass and pressure balance. No gas bypass flow phenomenon occurred in the operating cases of this work from the simulation results. The pressure drop in the riser could be properly predicted while the gas-solid interactions in the standpipe and loop seal were slightly underestimated by the CPFD method, where a relatively lower ΔP_s/H_s was obtained for CFB modeling. KCFB;; Solids circulation;; Pressure distribution;; CPFD;; Modeling