Flooding is an unstable operating phenomenon in countercurrent gas-solids fluidized beds,which is very detrimental to the performance of catalyst strippers and the smooth operation of FCC units.In this study,the flooding phenomenon in two different types of catalyst strippers was studied in a large cold-flow fluidized model using measurements of pressure drop and pressure fluctuation.The experiment results show that the flooding is more prone to happen in the disc-donut stripper which is a traditional design in commercial FCC units.When flooding occurs,the bed pressure drops suddenly and the pressure fluctuation increases sharply,which are accompanied by high fluctuations of solids circulation rate and particle bridging.In the operating range of this study,the critical flooding flux of the disc-donut stripper is in 40 ～ 60 kg/(m2 · s) and it decreases with increasing superficial gas velocity.However,flooding didn't appear in the packed stripper with Crosser grid in the same operating range.Based on the correlation of critical solids flux of Bi,the different flooding phenomena in different operating conditions and different strippers are analyzed as well as the possibility of the occurrence of flooding in commercial disc-donut strippers.%固泛现象是发生逆流接触的气固流化床装置中一种不稳定操作现象,对汽提器的性能和装置的平稳操作均具有很大的危害.利用压力降和压力脉动的测量,在一套大型冷模实验装置上研究了两种不同催化剂汽提器中的固泛现象.结果发现,目前工业上常用的盘环型汽提器很容易发生固泛.固泛发生时,床层压力降出现陡降,压力脉动陡增,同时伴随着颗粒架桥及循环量的大幅度波动.在本实验操作范围内,盘环型挡板汽提器临界固泛流率在40 ～60 kg/(m2·s),且随着表观气速增大而减小,但在整个操作范围内Crosser格栅型填料汽提器均未出现固泛现象.利用Bi提出的临界固泛流率公式,分析了不同操作条件下和不同汽提器结构中发生固泛的原因,同时分析了工业汽提器中发生固泛的可能性.
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