流化催化裂化提升管反应器的CFD-PBM耦合模型:矩方法适用性比较

Comparison of suitability of MOMs in solving CFD-PBM coupling model for FCC riser reactors

建立了描述FCC提升管中气-固流动行为的CFD-PBM耦合模型,模型同时考虑了颗粒动力学和颗粒聚并破碎内核。讨论了求解耦合模型中众体平衡方程(PBE)的3种典型矩方法[即:正交矩方法(quadrature method of moments,QMOM),直接正交矩方法(direct quadrature method of moments,DQMOM)和固定轴点正交矩方法(fixed pivot quadrature method of moments,FPQMOM)]对模拟结果的影响。研究结果表明3种矩方法均能合理预测提升管内径向和轴向颗粒体积分数和颗粒速度分布。通过将模拟结果与实验结果进行比较,表明QMOM在反应器结构简单情况下,计算结果更接近于实际情况。

A CFD-PBM coupling model was developed to simulate turbulent gas-solid flow in FCC riser reactors with consideration of kinetics of granular flow as well as agglomeration and core breakage of particles. Three representative methods of numerical moments, namely, the quadrature method of moments（QMOM）, the direct quadrature method of moments（DQMOM）, and the fixed pivot quadrature method of moments（FPQMOM）, were used to solve PBEs in the model and the simulation results were evaluated to compare the effect of each numerical method. All three MOMs could predict reasonably both radial and axial distributions of time-averaged volume fraction and velocity of particles in FCC riser reactors. Compared to DQMOM and FPQMOM, QMOM yielded calculations most agreeable to the experimental data with regards to time-averaged solid density distribution, solid mass flux distribution, and axial pressure drop. The study suggested that QMOM could be applied to solve PBEs in CFD-PBM coupling model for such simple structured reactors.