CO2 capture by modified hollow fiber membrane contactor: Numerical study on membrane structure and membrane wettability

This work aims at capturing CO2 from natural gas using a verified finite element mathematical model by improving the membrane wettability, membrane structure, the type of absorbents used in the system, and the physical parameters like membrane porosity and the number of fibers used in hollow fiber membrane contactor (HFMC). The model is developed to simulate the CO2 removal using membranes by considering mass transfer equations in the presence of chemical reactions. Simulations were performed using a membrane system including 10 fibers with 175 mm length, 830 μm outer fiber radius and 450 μm inner fiber radius. The effect of adding montmorillonite nanoparticles (MMT) in weight percentages of 1%, 3%, and 5% to the PVDF membrane was perused to demonstrate the influence of membrane structure modification on system performance. The results show that the modification of membrane structure with montmorillonite nanoparticles could increase the efficiency of the system in the removal of CO2 particles by 8%. Four absorbents including MEA (monoethanol amine), PZ (piperazine), TEA (triethanolamine), and EDA (ethylenediamine) are used to identify the most effective absorbent where PZ absorbent shows the highest and EDA absorbent has the lowest carbon capture efficiency. Wettability is found to have a considerably negative impact on membrane carbon capture capacity. For instance, the modeling results show that even a 10% wetting of the membrane reduces the efficiency of the CO2 removal process by more than 47%. In addition, the results illustrate that the increase in membrane tortuosity and gas velocity have negative impacts on the separation process, while increase in the absorbent concentration, packing density and porosity enhance the separation of CO2.