Modelling of gas-liquid-solid distribution in the cocurrent three-phase moving bed

Abstract

The three-phase moving bed reactors (TMBRs) can supply a potential solution for the multi-phase reactions with deactivating catalysts to realize Online Catalyst Replacement (OCR). In this work, computational fluid dynamics (CFD) simulations were employed to investigate the flow behavior of each phase in a cocurrent TMBR. The Euler-Euler multi-phase flow model and two different liquid-solid force models were employed to describe the dense-phase particle flow and liquid-solid interaction, respectively. The results revealed that the solid flow rate increased due to the gas-liquid flow, but radial solids distribution had not changed significantly. The effect of gas-liquid flow on the solid volume distribution was mainly reflected in the wall and inlet region, which led to lower solid volume fraction and higher granular temperature in the local area. Meanwhile, compared with trickle beds, with the increasing gas flow rate or decreasing liquid flow rate, both the liquid holdup and flow dead zone decreased in TMBRs. With the increase in liquid flow rate, the effect of liquid migration (from the wall to the center) on the liquid distribution was weakened. Besides, due to the competition between the pressure gradient force and gas-liquid drag force, the variations of volume and velocity of each phase depended on operating conditions, which were divided into three typical ranges. The gas-liquid-solid distribution could significantly advance the understanding of flow behaviors in TMBRs, based on which the reactor development could be further promoted.