Study On Influence Of Inlet Duct Layouts On Cyclone Performance In CFB Boiler

A cyclone separator is the most part in a circulating fluidized bed(CFB) boiler, its performance affects the operation of the CFB boiler directly.The pressure drop and the separation efficiency are the two most important criterions for evaluating the performance of a cyclone.It is common in a large capacity circulating fluidized bed boiler to adopt several cyclones in parallel to the furnace.The lengths of the inlet ducts of the cyclones are very short due to CFB boilers design.Different inlet ducts layouts affect the cyclones performance.This thesis includes cold experiments and numerical simulation.The effects of inlet duct layouts on the pressure drop and the separation efficiency are investigated in the same inlet velocities and inlet solid loadings.The body diameter of the cyclone is 1000 mm,and the diameter of the riser is 400 mm.Two kinds of inlet duct layouts are inner-side and outer-side.Cold experiment results show that there is significant difference between the two kinds of layouts.In the same inlet velocities and inlet solid loadings,the separation efficiency of the cyclone with an outer-side inlet duct is lower than the one with an inner-side inlet duct,and the pressure drop is also lower.The effect of inlet duct layouts on cyclone performance was evaluated with FLUENT 6.3 in the same conditions as the experiments,using the Reynolds stress model and the discrete phase model.Simulation results show that inlet duct layouts affect the distribution of particles directly.For outer-side layout,some particles from the riser rush to the vortex finder of the cyclone directly resulting in the reduction of separation efficiency.The numerical simulation results correspond with the experiment results.