Effect of back pressure on gas-solid distribution characteristics of cyclone distributor applied in powdered coal-fired circulating fluidized bed combustion system

Abstract

The cyclone distributor is an essential part of the powdered-coal-fired circulating fluidized bed (PC-CFB) combustion system, and its gas-solid distribution characteristics are significantly affected by the back pressure of the lower outlet. A four-way coupling method using a dense discrete phase model (DDPM) was adopted to simulate the cyclone distributor. The results indicate that the effect of the back pressure on the axial gas velocity is more pronounced compared to that on the tangential gas velocity. With the increase in the back pressure, the particle separation efficiency decreases monotonically, while the rate of change gradually increases. Meanwhile, the gas separation efficiency increases as the back pressure becomes higher. Furthermore, increasing back pressure improves the particle concentration at the outlets of the cyclone distributor. To maintain high particle separation efficiency and ensure the safe operation of the boiler, it is recommended to set the back pressure between 1000 Pa and 2000 Pa.