Abstract:When the ultra-low calorific value coal sludge is used as the main fuel in CFB boiler, a large amount of fly ash will be produced undoubtedly.and the unreasonable U-shaped inertial separator structure and aerodynamic parameters will cause the coarse ash to be concentrated at the bottom of the U-shaped inertial separator, which will cause the ash blocking and coking problems in the return channel to occur frequently. The separation efficiency of the separator is low, and the burden of the latter stage cyclone is increased, resulting in the reduction of the dust removal efficiency of the boiler.In order to investigate the paths to improve the separation effect of U-shaped separator, the computational fluid dynamics of FLUENT software is used with corresponding air-solid two phase flow model being set up as the Lagrange method being used particle phase, the κ-ε turbulent model being chosen for air phase, The effects of different baffle depth and mass flow rate on the separation efficiency of U separator were simulated. The separation efficiency of U separator is calculated when different baffle depth and mass flow rate are calculated. The results show that the method can simulate the movement of solid particles in U-shaped separator well. The separation efficiency of particles does not increase with the increase of baffle depth or mass flow rate, but changes within a certain range. The research results provide a basis for optimizing the structure of U separator to a certain extent.