Thermally enhanced membrane gas separation

Abstract

An enhancement of membrane gas separation, which makes use of the temperature difference in addition to the pressure difference across the porous membrane, is proposed. The thermal transpiration flow through the membrane induced by the temperature difference enables control of two physical quantities of the permeate flow, since the temperature difference is controllable separately from the pressure difference. It is possible to establish the molecular exchange state of the permeate flow, where a component gas of binary mixture flows in the opposite direction from the flows of the other component. A model gas separation device, which makes use of the counter flow arrangement to accumulate the molecular exchange of the micro-channels in the membrane, is devised using a single mixed cellulose ester membrane of 110 μm thickness and 3 × 3 cm size. The device induces 15% variation of mole percentage of a helium–argon mixture by a temperature difference of 45 K when the speed of the counter flow is around 50 cm/s. The performance of the device is well represented by numerical simulations that use the results of molecular gas dynamics for mixture flow in micro-channels.