Fixed fluidized bed reactor is widely used to evaluate the crackability of heavy oils and the activity of catalysts. To understand the hydrodynamics, reaction kinetics and thermodynamics in conventional and modified fixed fluidized bed reactors, the computational fluid dynamics method, energy-minimization multi-scale-based two-fluid model coupled with a six-lump kinetic model was used to investigate the gas–solid flow and cracking reactions. The gas mixing and particle volume fraction distributions, as well as product yields in the conventional and modified fixed fluidized bed reactors were analyzed. The residence time distribution model was utilized to obtain the parameters indicating the back-mixing degree, such as mean residence time and dimensionless variance of the gas. The results showed that the simulated product distribution is in reasonable agreement with the experimental data; the modified fixed fluidized bed reactor is closer to the ideal plug flow reactor, which can efficiently enhance the gas–solid mixing, reduce the gas back-mixing degree, and hence improve the reaction performance.

中文翻译：

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固定流化床反应器中流体动力学和裂化反应的多尺度CFD模拟。

固定流化床反应器被广泛用于评估重油的裂解性和催化剂的活性。为了了解常规和改进的固定流化床反应器中的流体动力学，反应动力学和热力学，我们使用了计算流体力学方法，基于能量最小化的多尺度两流体模型和六集总动力学模型来研究气体。 –固流和裂化反应。分析了常规和改进的固定流化床反应器中的气体混合和颗粒体积分数分布以及产物收率。利用停留时间分布模型获得指示回混程度的参数，例如平均停留时间和气体的无量纲方差。结果表明，模拟产品的分布与实验数据基本吻合。改进的固定流化床反应器更接近理想的活塞流反应器，可以有效地增强气固混合，降低气体反混度，从而提高反应性能。