Comprehensive experimental study of acid gases removal process by membrane-assisted gas absorption using imidazolium ionic liquids solutions absorbent

摘要

For the first time the comprehensive study of a unique hybrid technique - membrane-assisted gas absorption (MAGA) for the acid gases removal was performed. As a case study, the influences of the presence of imidazolium ionic liquids in the methyldiethanolamine (MDEA) absorbent solutions on process separation efficiency were evaluated on the example of separation of two binary methane-based gases mixtures containing impurities of carbon dioxide or hydrogen sulfide. It was shown, that the addition of small amount (5 vol%) of ionic liquids provides the significant increase on the process separation efficiency in a comparison with pure MDEA performance, which was taken as a reference. Also, the proposed technique was compared with a conventional single-stage membrane gas separation method and it was shown, that membrane-assisted gas absorption provides much higher separation efficiency in a whole observed range of processes productivity. The achieved purity of target component (methane) using absorbent solutions containing imidazolium ionic liquids exceeds the pure MDEA results more when 6 vol% and equals to 90.2 vol% in case of CH4/CO2 separation. In case of hydrogen sulfide removal (the initial content in the mixture is 5 vol%) using a sorbent containing an ionic liquid, the methane purity is 99.87 vol%, which exceeds the purity of methane achieved by using pure MDEA by 1.8 vol%. Moreover, as an important part of process study the dynamics of establishing the steady state under a closed-mode operation was studied and the most efficient operational time regions and ultimate separation performance of a process was observed.