Numerical Simulation of a Fixed-Bed Reactor for Ethane Catalytic Combustion Based on the Discrete Element Method Coupled with Computational Fluid Dynamics

Catalytic combustion technology is currently one of the most commonly used methods for treating industrial volatile organic compounds (VOCs) due to its high efficiency and low energy consumption. In this work, a model of a three-dimensional particle-resolved fixed-bed reactor for ethane catalytic combustion is established by means of the discrete element method (DEM) coupled with computational fluid dynamics (CFD). The characteristics of internal gas flow, as well as heat and mass transfer, have been computationally analyzed. Comparisons were made with the traditional porous media model, and the effects of particle size changes and working condition fluctuations on the reactor performance were investigated. The results indicate that the actual stacking structure of catalyst particles more accurately reflects the real physicochemical characteristics within the fixed-bed reactor. The catalytic reaction is mainly concentrated in the precatalyst section, where the ethane concentration decreases rapidly and the temperature increases rapidly. Meanwhile, the flow rate, pressure drop, ethane concentration, and temperature within the bed show an inhomogeneous distribution in both radial and axial directions. Reducing the catalyst particle size could optimize the flow field and enhance the heat and mass transfer, but the overall pressure drop would increase. Appropriately decreasing the flow rate could increase the ethane conversion rate and reduce the pressure drop together with the temperature difference in the catalyst bed. There is a positive correlation between the ethane concentration and catalytic reaction rate, but the macroscopic performance of the reactor is less sensitive to it. The study can provide theoretical guidance for the optimization of the catalytic combustion process of VOC exhaust gases.