A PBM-CFD Model with Optimized PBM-Customized Drag Equations for Chemisorption of CO2 in a Bubble Column

In this work, a computational fluid dynamics (CFD) approach based on two-fluid model (TFM) is introduced to describe the reversible two-step reactions found in the chemisorption process of CO2 by an aqueous NaOH solution in a lab-scale bubble column reactor. The population balance model (PBM) is applied to track the bubble size distribution with considering the coalescence and breakage terms, which then leads to a CFD-PBM model for describing the chemisorption of CO2 in an aqueous NaOH solution. Drag force is considered for the interfacial momentum transfer and a modified PBM-customized drag model with the correction factor is subsequently adopted, in which the contribution of different bubble size groups in each computational cell is computed. The tested boundary conditions include superficial gas velocities, gas-inlet sparger and the reactor dimension. Detailed and comprehensive investigations are done in the evolution of gas holdup, pH value, concentration distribution and bubble diameter distribution which are essential in optimizing the reactor performance in terms of yield and selectivity. Importantly, the current CFD-PBM model is able to predict the entire reaction process.