Experiment And Model Study On Pressurized Circulating Fluidized Bed

Circulating fluidized beds(CFB),being a high efficiency reactors,have been widly used in many industry fields.Pressurized circulating fluidized bed(PCFB)has several advantages over a CFB,such as higher gas density,more homogeneous mixture of gas-solid two-phase fluid,better fluidization quality and so on.Till now, many researches of PCFB are for FCC.However,researches of coal gasification and combustion in PCFB are at initial stage.The researches of PCFB in this thesis were conducted under the background of coal gasification and combustion.A PCFB gasifier test rig was built and some preliminary experiments on Datong coal gasification were made.The effect of pressure on minimum fluidization velocity(U_mf)was investigated on a cold state pressurized fluidized bed test rig.Experiment results show that the U_mf of small particles is influenced less by pressure while that of large particles is influenced more strongly by pressure.The effects of pressure,air leakage rate and inlet solid loading on pressure drop of a cyclone were investigated on a cold state pressurized test rig.The pressure drop of the cyclone increases with the increasing of pressure and decreases with the increasing of the air leakage rate from the standpipe and with the increasing of the inlet solid loading.When the air leakage rateχ＜4%,the change of the separation efficiency is little,however,when the air leakage rateχ＞4%,the separation efficiency decreases with the increasing of the air leakage rate.A semi-empirical model was developed for the prediction of the pressure drop of the cyclone separator at different operate pressures with the effect of air leakage rate and inlet solid loading considered.Experiments on solid recycle rate in a pressurized loop seal were made on a cold state test rig.The results show that when the fluidization number of flexible air and fluidized air are fixed,effects of pressure on solid recycle rate are little.Based on theoretical analysis and experimental results,a pressure balance model of circulating loop in PCFB was built,and discussion of design of PCFB was made.