Use of permeation and absorption methods for CO2 removal in hollow fibre membrane modules

Abstract

Hollow fibre membrane modules have been investigated experimentally for removing CO2 from a gas stream using both permeation and absorption methods. These membrane modules consist of a bundle of hollow fibres made from either silicone rubber or polyethersulphone. The silicone rubber membrane is the homogenous type, while the polyethersulphone membrane is asymmetric type with a dense skin layer at the outer edge of the fibre. The gas mixture containing 4% CO2 was introduced into the hollow fibre lumen and in cocurrent or countercurrent flow with fluids in the module shell. Both experimental and simulation results have been obtained and the beneficial effect of the permeate gas absorption have been demonstrated. It has been shown that the use of water as an absorbing liquid in the permeate side of the modules can greatly improve the extent of CO2 removal. This improved carbon dioxide selectivity is attributed to the presence of the liquid film which, on the other hand, creates the liquid film resistance, resulting in much reduced CO2 permeation flux and hence the loading capacities of the modules. The loading capacities of the modules can be improved using an alkaline solution instead of neutral water.