深层鼓泡床内偏涌现象的实验研究与数值模拟

针对催化裂化空筒汽提器中存在的气体偏涌现象,在一套大型空筒催化剂汽提器冷模实验装置中利用光纤探针法系统研究了偏涌的特性及其随床层高度的发展变化情况,并进一步利用一种新的离散颗粒计算流体力学模型(CPFD模型)对该现象进行了数值模拟研究.结果表明,在催化裂化汽提器操作条件下,偏涌主要发生在临近床层边壁的位置,造成周向上颗粒浓度分布呈现严重的不均匀性,偏涌的强度会随着床层高度的增大而减弱.CPFD模型不仅能够成功预测深层鼓泡床中存在的偏涌现象,而且可以定性预测偏涌强度沿床层高度的发展趋势,但定量预测结果较实验结果偏大.上述结果对工业汽提器的设计和故障诊断具有指导意义.

Experimental study and numerical simulation on jet streaming in deep bubbling fluidized-bed

By means of optical fiber probe, the jet streaming phenomenon in FCC baffle-free strippers was studied in a large cold-model experimental unit. Its properties as well as its development with bed height were studied. A newly developed computational particle fluid dynamics (CPFD) model was further used to explore this phenomenon. Jet streaming mainly happened near the stripper wall, resulting in serious non-uniformity in circumferential solids distribution. The strength of jet streaming decreased with increasing bed height. CPFD model could successfully predict the existence of jet streaming in this system. Although the predicted jet streaming strengths at higher bed heights were slightly overestimated, its trend with increasing bed height qualitatively agreed with the experimental fact. The deeper understanding acquired in this study can be used as a good reference for design and troubleshooting of the industrial FCC strippers.