Effect of Capillary Pressure on the Co2 Flux in Membrane Absorption

A simulation model was developed to evaluate the effect of capillary pressure on CO2 capture by membrane absorption. More specifically, the model calculates changes in the interfacial pressure and CO2 flux as the gas-liquid interphase moved along the pore opening to its exit. Two cases were considered, where the membrane materials used were either hydrophilic with a contact angle below 90o or hydrophobic with a contact angle above 90o. It was discovered that CO2 flux is higher when the membrane is hydrophilic due to escalating gas pressure in the pores by the capillary pressure. The effect of capillary pressure increases as the membrane pores become smaller, which in turn augments CO2 flux provided porosity and pore length are kept constant. It was also revealed that the CO2 flux could be significantly increased when water as the absorbent is replaced by 1 M monoethanolamine solution due to increased CO2 solubility. Topological analysis using the AIM/NCI technique for the MEA/CO2 reaction found that two bond paths connecting MEA and CO2 were formed, i.e., N—C and H—O bonds and steric repulsion between the two molecules was also absent.