Gas separation by liquid membrane accompanied by permeation of membrane liquid through membrane physical transport

A novel liquid membrane for gas separation is proposed in which a membrane liquid is continuously supplied to the feed side (high pressure side) of a Supported liquid membrane (SLM) and is forced to permeate through the membrane from the feed to the permeate side (low pressure side). The membrane liquid is circulated between the feed and the strip side of the membrane. In this mode of operation, gas permeation rate is enhanced by the convective or bulk flow of the membrane liquid dissolving gas. In addition, the fouling of membrane caused by the loss of the membrane liquid from the membrane due to drying-up and transmembrane pressure difference can be prevented. Experiments on the separation or CO2 from CH4 Were performed using water as a membrane liquid. It was demonstrated that the convective flow of water through the membrane enhanced the gas permeabilities remarkably. For example, CO2 permeability when the water permeation rate was 1.2 l/(m(2) min) was about 20 times that without water permeation. The effect of convective flow on the gas permeability was discussed on the basis of a simple permeation model. It was found that if the parameter (Peclet number) m = uL/D-e (u is the linear velocity of water through membrane or volumetric water flux, L the membrane thickness and D-e is the effective diffusivity in membrane) is large, convective water transport considerably enhances gas permeability. Experimentally observed gas permeance was approximately simulated by the proposed model. (C) 2000 Elsevier Science B.V. All rights reserved.