Experimental investigation of hydrodynamics and mass transfer in a slurry multistage internal airlift loop reactor

Abstract

Hydrodynamics and mass transfer of gas-liquid-solid slurry flow in a simple pilot multistage internal airlift loop reactor with a classic stage clearance are investigated experimentally. The presence of a critical superficial gas velocity to keep the multistage internal airlift loop reactor operating normally without particle deposit was first observed at a certain solid concentration and a fixed height of stage clearance, and an empirical model related to solid concentrations for a constant stage gap is also put forward here to predict the minimum critical superficial gas velocity in the slurry multistage internal airlift loop reactor. The results showed that compared to hydrodynamics and mass transfer in the gas-liquid two-phase flow at the same conditions, the solid concentration and the superficial gas velocity have some distinct effects. The increment of superficial gas velocity can increase the gas holdup, circulating liquid velocity, and volumetric mass transfer coefficient and at the same time decrease the mixing time, while the addition of solid particles would get the opposite effects. Additionally, compared to the two-phase flow, reverse tendencies of the gas holdup and circulating liquid velocity in different stages in the three-phase slurry multistage internal airlift loop reactor are first observed due to axial non-uniform distribution of solid particles. Therefore, solid particles can change the nature of multiphase flow in the multistage internal airlift loop reactor, and some critical information for designing this type of reactor was provided in this work.