Intensification of high-density CFB by standpipe aeration under elevated pressure

Abstract

The computational particle fluid dynamics approach is applied to investigate the effect of aeration scheme on gas-solid flow characteristics in a pressurized high-density circulating fluidized bed. The simulated pressure profiles in both riser and standpipe agree well with experimental data under pressurized conditions. Two types of aeration schemes are proposed, and their effects on the solids circulation behavior under different pressures are compared. It is found that a small increase of the standpipe aeration and the turning aeration can obviously increase the solids circulation rate. With the increase of solids circulation rate, there is no distinct interface between the packed bed and the free moving region under high pressure, while alternatively a dense transition region emerges. The standpipe aeration makes the pressure gradient distribution in the packed bed more uniform. The falling particles in the bottom region of the standpipe are fluidized and the frictional resistance is reduced, which is beneficial for particles being transported through the valve by the turning aeration.