Direct concurrent multi-scale CFD modeling: The effect of intraparticle transfer on the flow field in a MTO FBR

Abstract

In this study, a coupled model based on a direct concurrent multi-scale approach incorporating a single particle model and a two-phase CFD model was developed to predict the effects of intraparticle transfer on the flow field and main composition distributions of a catalytic reaction to convert methanol to olefins (MTO) in a fluidized bed reactor (FBR). A single particle model was first constructed to describe the individual intraparticle molecular diffusion and reaction kinetics, while a CFD model characterized the gas–solid flow field in the FBR. Because the grid cells generated in the CFD model were too small compared with the size of the FBR, no distributions were considered in a single grid. In this case, all catalyst particles inside each small computational cell for the CFD model experienced the same external conditions, thus ensuring the effective coupling of the two models. This was validated by comparing the above assumption with simulation results and with experiment results. On the basis of the coupled model, the intraparticle transfer limitation and the flow field in the FBR were predicted numerically. The simulated results indicated that the intraparticle transfer limitation did exist and had significant effects on the reactor flow field. This model is expected to be useful in predicting the intraparticle transfer limitation in FBRs.