Flue gas dehydration using polymer membranes

Coal-fired power plants produce electricity and in addition to that large volume flows of flue gas. To prevent condensation of the water vapor present in this flue gas stream, water has to be removed before emission to the atmosphere. The application of membrane technology for this separation is attractive due to the additional energy savings and the possible re-use of water. In the present work, we present such a membrane system with extremely high separation factors and fluxes for the removal of water vapor from flue gasses. Process simulations indicate the importance of a membrane material with very high water vapor permeabilities combined with very low inert gas fluxes. Two potential membrane materials for flue gas dehydration (PEBAX (R) 1074, a block copolymer, and sulfonated poly(ether ether ketone) (SPEEK)) are compared and the results clearly show the superior performance of SPEEK. Composite hollow fiber membranes with a top layer of SPEEK were developed and built into fiber bundles. Twenty of such fiber bundles were placed in large gas flows of artificial and real flue gas. Short- and long-term testing of the membrane bundles revealed good mass transport properties and resistance against the flue gas conditions. This study not only demonstrates the technical viability of flue gas dehydration, but also suggests that polymer membranes may be a viable option in direct removal of CO2 from flue gas. (C) 2008 Elsevier B.V. All rights reserved.