低密度循环流化床反应器床层截面平均颗粒速度的变化规律

THE AXIAL DISTRIBUTION OF CROSS-SECTIONAL AVERAGED PARTICLE VELOCITY IN A DILUTE-PHASE CIRCULATING FLUIDIZED BED REACTOR

本文在高8m,内径186mm 的循环流化床中采用 FCC 颗粒,利用 TSI 光纤激光多普勒测速仪测定了局部颗粒速度的径向分布,并获得了床层截面平均颗粒速度。实验结果表明:截面平均颗粒速度随操作气速的增大而增大,随固体循环速率的增大而略有减小。由实验数据回归得到了计算本实验条件下低密度速度的经验关联式。论文还从基本流体力学理论出发,在考虑颗粒加速运动的条件下,建立了一维气、固两相流模型,可以用于预测床层截面平均颗粒速度和空隙率的变化规律,模型计算结果和实验数据吻合较好。

In this paper,the result of investigation on the cross-sectional averaged particle velocity in a dilute-phase circulating fluidized bed(186 mm ID and 8 m hight)with FCC catalysts is presented. A fiber-optic probe laser Doppler Velocimetry was employed to measure the radial profile of local particle velocities,so as to obtain the cross-sectional averaged particle velocity.The rsults showed that the cross-sectional averaged particle velocity increases with increasing superfcial gas velocity and decreases with increasing solid circulating rate.An empirical correlation was recommended to predict cross-sectional averaged particle velocities in the bed. Besides,a one-dimensional two-phase hydrodynamic model which take the particle acceleration into account was proposed to predict the cross-sectional averaged particle velocity and voidage in the bed.The predictions agree with the experimental data well.