CFD study on partial oxidation of methane in fixed-bed reactor

Partial oxidation of methane (POM) is a preferred method for synthesis gas, which usually occurs in fixed bed reactors. In this paper, the discrete element method (DEM) is used to reconstruct the structure of a reactor bed via simulating the process of filling the reactor with catalyst. The particle resolved CFD physical model with the detailed micro-kinetcis of the POM reaction was established to study the interaction among reactant flow, heat and mass transfer, and reaction in the fixed bed. The gas composition and temperature distribution in the reactor were obtained based on the simulation results. The effects of the space velocity and the reaction temperature on the CH₄ conversion, catalyst selectivity, and catalyst surface coke formation were analyzed. The simulation results show that the temperature hot spots of the catalyst in the bed occur at the inlet and the temperature increases further near the wall. With the increase in space velocity, the conversion rate of CH₄ decreases gradually, and the selectivity does not change significantly. As the temperature increases, the conversion rate of CH₄ gradually increases and the selectivity decreases. The risk of coke formation on the catalyst surface rises axially and the C species concentration is relatively higher near the outlet. Appropriately increasing the gas velocity and increasing the temperature helps to reduce the surface coke accumulation of the catalyst.