Flow and mass transfer performance in the ejector and reaction kettle of a loop reactor: A CFD-PBM Analysis

Abstract

Loop reactors, recognized for their exceptional gas-liquid mixing and mass transfer capabilities, have been less explored in the context of methanol carbonylation, particularly regarding mass transfer performance within the ejector mixing tube and reaction kettle. This study, aimed at an annual acetic acid production of 250,000 tons, evaluates key performance metrics of the loop reactor—such as gas holdup and Sauter mean bubble diameter—using the CFD-PBM method and calculates the mass transfer coefficient. By keeping other structural parameters of the ejector optimized and constant, the findings reveal that the mass transfer coefficient at the end of the mixing tube initially increases with tube length, peaks at H_T/D_T = 1, and then declines. Meanwhile, gas holdup decreases as the mixing tube length increases. For the reaction kettle, modeled using the ejector outlet conditions as the inlet, an increase in the height-to-diameter ratio and the number of ejectors results in a larger Sauter mean bubble diameter, thereby reducing mass transfer efficiency. Notably, positioning the ejector at r/R = 0.6 produces the smallest bubble size, maximizing mass transfer effectiveness.