A post-combustion polymeric membrane system that promises to separate and capture 90% of the carbon dioxide emitted from a pulverized coal plant has been successfully demonstrated and last week received approval from  the Department of Energy (DOE) to advance to a larger-scale field test.

The Polaris membrane system, tested by developer Membrane Technology and Research (MTR) and its partners in an $18.75 million project that was funded by the American Recovery and Reinvestment Act of 2009, uses CO2-selective polymeric membrane material (which consists of micro-porous films that act as semi-permanent barriers to separate two different mediums) and module to capture CO2 from a plant’s flue gas. According to the DOE’s National Energy Technology Laboratory (NETL), post-combustion separation and capture of CO2 is challenging due to the low pressure and diluted concentration of CO2 in the waste stream. Trace impurities in the flue gas also affect removal processes. Researchers have also been looking to tamp down the amount of energy required for CO2 capture and compression.

“Because the Polaris membranes are 10 times more permeable to CO2 than conventional materials (reducing the membrane area required), and use a slipstream of combustion air as a sweep gas, the system has great potential for reduced energy requirements, reasonable capture costs and greater efficiencies for post-combustion capture, all important factors for retrofitting existing coal-based plants,” the DOE said in a statement last week.

MTR and partners will now build a membrane skid capable of 90% CO2-capture from a 20-ton-per-day slipstream of coal-fired flue gas (equivalent to the CO2 generated by 1 MWe of power generation). The skid will be operated during a six-month field test at the DOE’s National Carbon Capture Center in Wilsonville, Ala., starting in 2013, and will utilize MTR’s Polaris membranes. Test data from the skid will be used to clarify the process design and economics of membrane-based CO2 capture from power plant flue gas and will be used by MTR to develop a preliminary 20-MW full-scale commercial design in cooperation with partners Vectren and WorleyParson. Other collaborators on the three-year project include the Electric Power Research Institute, Southern Company and Babcock & Wilcox.

“Demonstrating and further validating this innovative, cost-effective membrane CO2 separation process at the 1 megawatt equivalent (MWe) pilot scale is expected to be a major step toward meeting DOE’s program goals of capturing more than 90 percent of CO2 from flue gas with less than a 35 percent increase in the cost of electricity,” the DOE said. Other objectives of the project, part of DOE’s Clean Coal Research Program portfolio, include reducing the capital cost, footprint, and energy penalty for CO2 capture in conventional coal-fired power plants, compared to existing commercial systems.

The announcement by the DOE follows news from Ohio State University researchers who last week said they had developed what they call a groundbreaking new hybrid membrane that combines the separation performance of inorganic membranes with the cost-effectiveness of polymer membranes.

Source: POWERnews, DOE