A Membrane Approach to CO2 Capture

For the past eight years, Membrane Technology and Research, Inc. (MTR) sponsored by the U.S. Department of Energy, has been developing membrane technology to capture CO2 from power plant flue gas. A 20 ton/day test system has been built and operated at two field sites. The technology is moving to the 200 ton/day (10 MWe) demonstration scale. A block diagram of the MTR process is shown in Figure 1. One innovation of this process is the use of a two-step membrane design where the second step uses a membrane operating with air sweep to selectively recycle CO2 to the boiler. The use of combustion air to provide driving force for CO2 separation significantly reduces the energy cost. Because the air to the boiler already contains CO2, the CO2 concentration in the flue gas leaving the boiler increases from 13% CO2 to as much as 20% CO2. The removal rate required by the first step membrane is then reduced and the concentration of CO2 in the membrane permeate is increase to the 60 to 75% range. Please click Additional Files below to see the full abstract