Novel Membrane Process to Utilize Dilute Methane Streams

Methane is the second largest contributor to global warming after carbon dioxide. As public awareness has increased in the last 2 decades, various technologies and process improvements have been developed to curb methane emissions in the United States. There is still a lack of economically viable technology, however, to utilize dilute methane streams containing 10 to 14 percent methane in which the other component is primarily carbon dioxide. These streams, often available at older landfill sites or produced at natural gas processing plants, cannot be directly burned or flared due to their low Btu values. As a result, the streams are vented, contributing to the climate change effects associated with greenhouse gas. Membrane Technology and Research, Inc. (MTR) estimates that the methane emissions from these streams could be up to 4.3 Tg (million metric tons) per year. Conventional carbon dioxide separation technologies (e.g., amine absorption, pressure swing adsorption, and membrane technology) cannot economically recover methane from these dilute streams due to the high carbon dioxide content and low stream pressure usually encountered. MTR proposes a new type of economical membrane process that will increase the effective methane concentration of the gas and make the stream useful as a fuel. Utilization of this methane on or near the recovery site can help meet demands for heat and electricity, and will provide product credits to offset the costs associated with the more environmentally responsible management of dilute methane vent streams proposed here. In the Phase I project, the feasibility of using a membrane-based process to upgrade dilute methane into useful fuel gas will be determined. The new process does not require compression of the feed stream and will use MTR’s newly developed membrane with exceptionally high carbon dioxide permeability, and sufficient carbon dioxide/methane selectivity to separate the two gases. Bench-scale spiral-wound modules will be fabricated and tested to provide enough data for preliminary technical and economic analysis. If the Phase I project demonstrates feasibility at the bench scale, a small demonstration system will be constructed in the Phase II project. This unit will be operated in the laboratory and at a field site. Also, a commercialization plan will be developed to bring the new membrane technology to market.