A Review of the Trends of Development and Performance Improvement of Polymeric Membranes for Helium Separation and Extraction

Due to its unique characteristics, helium gas has found widespread applications, particularly in medical, nuclear and space industries. At the present, natural gas is considered as the main industrial source of helium and should contain at least 0.05 mole% helium in order to make the extraction process which is primarily based on cryogenic economically available. Because of multiple advantages of membrane technology, helium extraction using membranes has been the subject of numerous studies for more than half a century. Some inorganic membranes such as silica have shown good performance for helium separation, but the fabrication of such membranes is costly and complicated. On the contrary, polymeric membranes are low-priced and require performance improvement through modifications. Besides blending and employment of inorganic fillers, one of the most effective ways to improve the performance of these membranes is the development of copolymeric membranes. In addition, a hybrid system comprising a combination of cryogenic distillation, membrane technology, and pressure swing adsorption can lead to lower energy consumption and costs.