Mathematical Modeling of Carbon Dioxide Removal from the CO2/CH4 Gas Mixture Using Amines and Blend of Amines in Polypropylene: A Comparison between Hollow Fiber Membrane Contactor and Other Membranes

In this work, a mathematical model is established to describe the removal of CO2 from gaseous mixtures including CH4 and CO2 in a polypropylene hollow fiber membrane contactor in the presence of conventional absorbents such as monoethanolamine (MEA), methyldiethanolamine (MDEA), and a blend of them. Modeling was performed in axial and radial directions under the fully-wet condition for countercurrent gas-liquid flow arrangement. Both of axial and radial diffusions have been considered in three segments, including shell, membrane, and tube. To evaluate the model, the results of this model were compared with the experimental data and the results of COMSOL software and the results were in agreement with the experimental data and COMSOL outputs. In addition, the effect of various parameters on the removal percentage of carbon dioxide from gas mixtures was studied. It was found out that the CO2 removal percentage is the best by using MEA solution as the absorbent. This modeling shows that the removal of CO2 increases by adding MEA into MDEA solution. In this study, the factors that influence the removal percentage of CO2 from gaseous mixture were investigated. The CO2 removal efficiency increased with an increase in the liquid flow rate, number of fibers, membrane length, porosity-to-tortuosity ratio, and solvent concentration. The results show that increasing gas flow rate reduces CO2 removal due to decreasing the contact time. Finally, the performance of this membrane was compared with other membranes such as polyvinyl difluoride (PVDF) and polytetrafluoroethylene (PTFE). The results show that the percentage of CO2 removal by the polypropylene HFM is higher than that of the PVDF and PTFE hollow fiber membranes in the presence of MEA as the absorbent.