Effects of cyclone structures on the pressure drop across different sections in cyclone under gas–solid flow

Abstract

The pressure drop is a key performance of the cyclone in the circulating fluidized beds, and it shows a nonlinear change with the increase in inlet solids loading at certain gas flow rate. The nonlinear characteristic is related to the effect of solid behaviors on the pressure drop in different sections of the cyclone. The adjustment of cyclone structures would influence the pressure drop of different sections, changing the nonlinear characteristic. To improve the understanding of the nonlinear characteristic, the pressure drops across the inlet, the swirling part, and the vortex finder are measured, respectively, under different inlet solid loadings, and effects of the inlet dimensions, the barrel dimensions, and the vortex finder dimensions are investigated. Compared with the pure gas flow, the solid behaviors influence the gas flow in different section of the cyclone, leading to the changes in pressure drop across each section. The pressure drop across the inlet is positive related to the solid loading because of the solid acceleration; however, the pressure drop across the swirling section is negative related to the solids loading due to the weak effect on the swirling energy. The effect of solid loading on the pressure drop across the vortex finder is obscure due to the low solid loading in the upward gas flow accompanying the rotation movement. In addition, the narrowing of the inlet enhances the solid acceleration in the inlet and improves the swirling energy in the barrel by increasing the input tangential velocity, which greatly increases the pressure drop across the inlet and the swirling section. The extending of barrel enhances the weak effect caused by the solid loading on the swirling energy and reduces the pressure drop across the swirling section. The enlarging of vortex finder greatly reduces the axial velocity, reducing the pressure drop across the vortex finder.