Effects of membrane properties on CO_2 recovery performance in a gas absorption membrane contactor

摘要

Global warming is a serious global environmental problem. CCS (Carbon dioxide Capture and Storage) is considered to be an emergency measure to mitigate the increase in atmospheric CO_2. Chemical absorption is the major separation technique employed in CCS. Recently, the focus has been on chemical absorption using a membrane contactor with microporous hollow fibres because of the large contact area between the gas and liquid as well as the absence of problems such as flooding and channelling. In this study, we changed the properties of the polyethylene microporous hollow fibre membranes by two treatments: i) drawing in the axial direction and ii) soaking in concentrated nitric acid solution. The effects of these treatments on CO_2 recovery performance were investigated by a CO_2 recovery experiment using the untreated and treated membranes and a MEA aqueous solution. The CO_2 recovery rate for the membrane treated by drawing was higher than that for the untreated membrane. Additionally, the CO_2 recovery rate increased with an increase in the drawing ratio. The nitric acid treatment also increased the CO_2 recovery rate compared with the untreated membrane. Changes in membrane dimensions, porosity and pore size distribution were expected to be major reasons for the increase in CO_2 recovery rate for the membrane treated by drawing. On the other hand, nitric acid treatment did not induce any changes in membrane dimensions or pore size distribution but only reduced the surface roughness. As a result, the decrease in surface roughness was a major reason for the increase in CO_2 recovery rate for the membrane treated with nitric acid.