Low temperature membrane gas separation for nitrogen removal and helium recovery from natural gas

• Applicant: Professor Dr.-Ing. Matthias Wessling
• Subject Area: Chemical and Thermal Process Engineering ; Technical Chemistry
• Term: from 2014 to 2017
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 258012131

Gas permeation membranes operate successfully since the 1980s to separate hydrogen and carbon monoxide as well as recover hydrogen from purge gases of the Haber-Bosch process. Since that time gas permeation membranes have been applied in various other gas separation applications, where natural gas sweetening is by far the largest application today. In general most research today focusses on membrane gas separation at room temperature and at elevated temperatures. Almost nothing is known about membrane gas separation at sub-ambient temperatures. A potential application however is in natural gas treatment, i.e. the removal of nitrogen and the recovery of helium from methane. It is most challenging and is currently done by cryogenic separation demanding enormous amounts of energy and large process equipment. The combination of gas permeation membranes and conventional cryogenic separation technology in so-called membrane hybrid processes has the potential to drastically improve the process performance. We hypothesize that performing an integrated separation with a membrane gas permeation system in various combination with cryogenic separation will significantly reduce the total energy demand and the process equipment size. State of the art gas permeation materials inherent only low CH4/N2 selectivities which are not efficient for CH4/N2 separation at room temperature. Even though the permeation rates will be lower, this problem can be overcome by operating the gas permeation modules at sub-ambient temperature which results in increased CH4/N2 selectivities. The cooling of the raw gas upstream of the gas permeation stage can be done by heat integration which enhances the energy efficiency of the separation process. Furthermore, gas permeation is accompanied by the Joule-Thomson effect resulting in significant cooling of the gas permeating through the membrane. Taking advantage of this low temperature gas stream would further increase the energy efficiency of the separation process. The objective of the proposed project is to identify and optimize new membrane-cryogenic processes to remove nitrogen and to recover helium from methane in natural gas treatment. Viable process scenarios will give access to new natural gas resources that would otherwise remain unexplored.

• DFG Programme: Research Grants