Numerical Investigation of the Effect of Inhomogeneous Flow Behaviors inside a Particle Cluster in the OCM Reaction

Abstract

Fluidized bed reactors are commonly considered as more effective devices for the oxidative coupling of methane (OCM) reaction in comparison to traditional fixed bed reactors. In a fluidized bed, particles are prone to agglomerate to generate clusters, changing the original fluidization state and weakening the catalytic ability of catalyst particles. In this study, the inhomogeneous flow behaviors of gaseous species inside a particle cluster were investigated via the computational fluid dynamics (CFD) method compared to isolated particles. The effect of flow characteristics on the heat transfer and the spatial distribution of products of the OCM reaction were subsequently studied. The results indicated that obstruction caused by outer particles of the cluster resulted in the inhomogeneous flow behaviors inside the cluster, leading to the formation of hot spots, the excessive oxidation of C 2 H 4 , and the generation of CO 2 . C 2 H 4 was found to be unevenly concentrated inside the particle cluster, with a higher level on the upwind side and a lower level on the downwind side, while it was more uniformly distributed in the isolated particle model. The C 2 H 4 yield was significantly lower in the particle cluster model than that in the isolated particle model, with reductions of 47.66% from the peak value and 37.12% from the average value under different working conditions in a model of three-layer 13 particle structure. These results emphasized the uneven flow behaviors of fluids, which impeded the heat transfer between gas and solid and ultimately resulted in the formation of CO 2 and the reduction of C 2 H 4 yield. A prediction model was developed to describe the inhibition effect of uneven flow behaviors on the C 2 H 4 yield. Furthermore, improving uneven flow behaviors to alleviate the cluster effect on reaction efficiency could be a key focus for future research.