CO₂ removal from natural gas at high pressure using membrane contactors: Model validation and membrane parametric studies

Nowadays, many industrial gas absorption processes are carried out in harsh environment conditions such as high temperatures and pressures. Therefore, in order to replace these conventional methods with new membrane technologies, several studies and investigations must be established to gain valuable knowledge on the transport mechanism under real operating conditions. In this work, a comprehensive 2-D mathematical model was developed for the physical and chemical absorption of CO₂ from natural gas at high pressure up to 50bar using membrane contactors. Although, pseudo-wetting conditions could be ignored at low pressure operations, it was found to be an important factor at high pressures even for hydrophobic membranes such as PTFE. Using chemical solvents such as MEA solutions enhanced the removal of CO₂, however, the surface tension of the solvent decreased with increasing concentrations which resulted in higher percent wetting of the membrane. The effect of membrane properties such as porosity and tortuosity was negligible on the physical absorption of CO₂ using water as the absorbent solvent. However, this effect was more dominant on the chemical absorption using MEA. The model predictions agreed very well with the experimental data as the percent removal of CO₂ increased with increasing pressure for both physical and chemical absorption.