Washington, D.C. — In a project funded by the U.S. Department of Energy’s Office of Fossil Energy (FE), researchers at The Ohio State University have developed a groundbreaking new hybrid membrane that combines the separation performance of inorganic membranes with the cost-effectiveness of polymer membranes. The breakthrough technology has vast commercial potential for use at coal-fired power plants with carbon capture, utilization, and storage (CCUS), a key element in national efforts to mitigate climate change.
Before the carbon dioxide (CO2) generated at a power plant can be securely stored or put to beneficial use, it must first be separated from the flue gas stream. Unfortunately, the energy cost of current separation technologies is too high to make rapid commercial deployment of CCUS technologies feasible. To overcome this barrier, high-performance membrane separation is a focus of FE’s Carbon Capture Program, under which the Ohio State project is managed. The program supports the DOE goal of cost-effective deployment of CCUS technologies within 10 years to position the United State as a leader in the global clean energy race.
Membranes consist of thin layers of either polymer (organic, plastic) or inorganic (metal, ceramic) materials that are permeable to the molecules they are meant to capture, such as water, CO2, or oxygen. The layers are generally deposited on a membrane support structure. Polymer membranes are mass produced and very cost effective, while inorganic membranes are expensive to produce but exhibit much better performance.
To illustrate how membranes are more energy efficient than other separation methods, scientists sometimes use a familiar substance: seawater. Pure water can be obtained by boiling the seawater and condensing the salt-free vapor, but boiling requires heat, which means using energy. Alternatively, membrane processes for separating salt from water don’t require heat, making them more cost effective and environmentally friendly. Separating CO2 from flue gas is similar. Energy is still required for pre- and post-separation processes, such as compressing the gas, but for the key process of separating the CO2, new membrane technologies pioneered by FE’s National Energy Technology Laboratory (NETL) and its research partners are designed to eliminate most of the energy costs.
Ohio State’s new hybrid membrane consists of a thin, inorganic “zeolite Y” layer sandwiched between an inorganic intermediate and a polymer cover. These three layers sit atop a polymer support, which in turn rests on a woven backing. According to NETL project manager José Figueroa, “Combining inorganic and organic membrane materials in a hybrid configuration is a breakthrough that could potentially lower costs associated with clean coal technologies.”
Ohio State researchers realized a first prototype by combining new nanotechnology characterization and fabrication methods with state-of-the-art manufacturing techniques. In the laboratory, they were able to slash the zeolite Y growth rate from 8 hours to less than 15 minutes and reduce ceramic processing time from 43 hours to 20 minutes, resulting in inorganic/organic membrane development within one hour. They have also achieved adhesion of the inorganic intermediate layer onto a polymer support.
The Ohio State team, which has emphasized the membrane’s broader separation applications in their reports, received funding for the project beginning October 1, 2011, and presented their first results at the NETL Carbon Capture and Storage meeting July 9–12, 2012. The promising results follow previous success the team has had in making continuous, intact inorganic layers on polymer supports and developing new membrane-production techniques.