布风方式对流化床混合特性的影响

通过将离散单元法同计算流体力学相结合,对流化床内物料混合过程进行了研究。给出了水平布风板均匀布风、倾斜布风板非均匀布风2种情况下的示踪颗粒场历变过程。模拟结果表明:瞬时颗粒场组图能够较为直观表征床内混合现象;其中,在均匀布风情况下,床内气泡横向运动受到限制,颗粒整体横向运动能力较弱,混合方式以扩散混合为主;而对于非均匀布风流化床,床内存在较大的横向颗粒浓度梯度,对流混和起主要作用,且混合速度较为迅速。

Impact of gas supply patterns on mixing characteristics in fiuidized beds

Discrete element method(DEM) combined with computer fluid dynamics(CFD) was used to research the micro-mixing process in fluidized beds of uniform particles.With the aid of snapshots,mixing evolvement for two cases was discussed:(1) fluidized bed using horizontal distributor incorporated with even gas supply;(2) fluidized bed using inclined distributor together with uneven gas supply.The results indicate that in the case of horizontal distributor incorporated with even gas supply,diffusive mixing pattern is predominant,since bubbles lateral motion is reduced in such a bed;whereas,there is a fast convective mixing process in fluidized bed using inclined distributor together with uneven gas feed.Localized air supply induces the density gradient of particle distribution in such a bed,which is the basic agent of convective particle stream.