3D models guide the design of hollow fiber membrane contactors with complex internal structures for CO₂ capture

Membrane contactors have good prospects in the field of CO2 capture. In this study, the effects of operation conditions (gas velocity, liquid flow, CO2 pressure, amine concentration, and CO2 loading) on CO2 absorption flux (J(CO2)) for CO2 absorption into N-methyl-4-piperidinol (MPDL) solution in membrane contactors were investigated through experiments and simulations. A three-dimensional (3D) model was developed using COMSOL Multiphysics software to study the comprehensive CO2 mass transfer process in the multifiber membrane contactor and the effect of the number of fibers on the flow and CO2 concentration distribution without simplifying the geometry compared with those of traditional one-dimensional (1D) and two-dimensional (2D) models. Non-ideal effects occurring in hollow fiber membrane contactors can be explained using a 3D modeling. By comparing the simulated J(CO2) with the experimental J(CO2), the effectiveness of the model was determined. The simulation results emphasize that the spatial concentration distribution has a great correlation with the corresponding velocity distribution. Additionally, reducing the uneven velocity distribution of gas and liquid is a very important factor to improve the mass transfer performance of CO2. Increasing the number of fibers with a constant total volumetric flux can reduce the thickness of the boundary layer and promote the mass transfer.