Hybrid membrane-absorption CO2 capture process

The development of CO2 capture systems has largely focused on single separation technologies (absorption, adsorption, membranes, cryogenics, etc.). Few studies have examined the merits of combining multiple separation technologies into a hybrid capture system. Membrane Technology & Research, Inc. (MTR) and the University of Texas at Austin (UT Austin) are collaborating to investigate two variations of a hybrid membrane-absorption capture system which combine MTR's air-swept Polaris (TM) membrane contactor with UT Austin's 5 m piperazine advanced flash stripper (AFS; 5 m PZ-AFS) capture technology with cold and warm-rich bypass. In one embodiment, the systems are arranged in series and in another, in parallel. In the series configuration, the absorber removes approximately half of the CO2 in the flue gas, followed by additional separation by the membrane contactor to achieve 90% total removal of CO2 by the hybrid capture system. In this arrangement, the absorber operates at a higher lean-loading state and also benefits from the ability of the downstream membrane to mitigate fugitive amine emissions. In the parallel configuration, the flue gas leaving the power plant is split and treated by each system in a parallel arrangement. The principal advantage is that the absorber can be roughly half the size it would normally be. In both configurations, the 5 m PZ-AFS system will treat a more concentrated CO2 stream which is a preferred condition. The project team found that the minimum O-2 content in the combustion air stream (18% for retrofit, 17% for Greenfield) acted to limit the potential of the hybrid-series configuration. In the best case design of the hybrid-parallel arrangement, the 5 m PZ-AFS system treats 53% of the total flue gas volume with a CO2 concentration in the flue gas greater than 23%. (C) 2014 Published by Elsevier Ltd.