Abstract: The rheological properties of the material during the gelation process of fluid catalytic cracking (FCC) catalyst are complex, exhibiting pseudoplastic fluid characteristics with shear-thinning behavior. In order to enhance the mixing efficiency in the FCC catalyst gelation agitated tank, the computational fluid dynamics (CFD) numerical simulation method was used in conjunction with rheological characterization obtained by a rotational rheometer. This method was employed to investigate the influence of different impeller configurations on the mixing effect of high-viscosity, variable-viscosity systems. Due to the difference of rheological properties in different steps of gel process, it needed to be discussed separately and strengthened. By comparing and contrasting the flow field distribution, shear rate distribution and viscosity distribution inside the kettle for different gelation processes, the most appropriate stirring device for each stage can be determined. Based on the design of a new type of folded blade propeller, the multi-layer combination propeller was used in order to achieve the uniform distribution of the flow field and shear rate within the gelation agitated tank. This reduced the high viscosity weak mixing zone in the tank and improved mixing efficiency. The marked grid method was employed to compare the mixing time under different combination structures. The results showed that the optimized multi-layer impeller combination can realize the mixing strengthening of the gelation process. In the mixing process of kaolin, the combined impeller of lower SBT+upper FBT was adopted. In the mixing process of FCC catalyst colloid, the combined impeller of lower SBT+middle FBT+upper PBT was used. Considering the requirements of industrial design, the combined impeller of lower SBT+middle PBT+upper PBT was adopted in industry. This ultimately resulted in a significant reduction in the mixing time required for gelation, which strongly supported energy saving and consumption reduction in factories.

Key words: FCC catalyst, non-Newtonian fluid, shear thinning, mixing, reactors, computational fluid dynamics

摘要： 流化催化裂化(FCC)催化剂成胶过程中的物料具有复杂的流变特性，是具有剪切变稀行为的假塑性流体。为强化FCC催化剂成胶搅拌釜内的混合效果，采用计算流体力学(CFD)数值模拟方法，结合旋转流变仪获取的流变性质表征，探究不同搅拌桨构型对高黏、变黏体系的混合效果。基于新型折叶桨设计多层组合桨，实现成胶搅拌釜内流场和剪切速率分布均匀，减少了釜内高黏弱混合区，提高了混合效率。基于标记网格法，比较不同组合结构下的混合时间。结果表明，多层搅拌桨组合(下层直叶+中层折叶+上层斜叶)可以显著缩短混合时间。

关键词: FCC催化剂, 非牛顿流体, 剪切变稀, 混合, 反应器, 计算流体力学