下行式循环流化床用于催化裂化过程的数学模拟

采用十一集总动力学，结合气固流体力学行为和轴、径向扩散行为，建立了适合于提升管及下行式循环流化床催化裂化的数学模型，采用此模型对催化裂化过程计算的结果表明，下行床内目的产品选择性显著高于提升管，但在与工业提升管相同的操作条件下，下行床内原料转化率较低，优势不能发挥。适当增加下行床长度、增大床径、使物料循环反应、增加剂油比、提高反应温度或反应压力等可以改善下行床的反应效果。下行床用于催化裂化过程，与之较匹配的应该是具有更高活性的催化剂，研制新型高活性催化剂也是下行床推向工业的重要措施之一。

Simulation of Fluid Catalytic Cracking in Downer

By combining the following sub-models, the fluid catalytic cracking 11-lumped kinetic model, the hydrodynamic model and the axial and lateral dispersion model, models for the fluid catalytic cracking (FCC) in riser and in downer were built up to obtain appropriate operating conditions. Using the built up models the FCC process in riser and in downer were simulated respectively. The results show that the selectivity of the desired product is significantly higher in the downer than that in the riser. However, the advantages of the downer are not obvious because the conversion of the feedstock in downer is lower than that in the commercial riser under the same operating conditions. By simulating under various operating conditions, it is found that the following arrangments, such as elongating the downer, enlarging the downer diameter, recycling the reactants, increasing the catalyst/oil ratio and the temperature or the pressure, can be used to improve the performance of the downer. And catalysts of higher activity should be developed to fit the new kind of circulating fluidized bed reactor, downer, for the FCC process.