exchanger Uses Membranes are employed in: The separation of nitrogen or oxygen from air (generally only up to 99.5%) Separation of hydrogen from gases like nitrogen and methane Recovery of hydrogen from product streams of ammonia plants Recovery of hydrogen in oil refinery processes Separation of methane from the other components of biogas Enrichment of air by oxygen for medical or metallurgical purposes. One of the methods used for commercial production of nitrox breathing gas for underwater diving. Enrichment of ullage by nitrogen in inerting systems designed to prevent fuel tank explosions Removal of water vapor from natural gas and other gases Removal of SO2, CO2 and H2S from natural gas (polyamide membranes) Removal of volatile organic liquids (VOL) from air of exhaust streams Air separation Oxygen-enriched air is in high demanded for a range of medical and industrial applications including chemical and combustion processes. Cryogenic distillation is the mature technology for commercial air separation for the production of large quantities of high purity oxygen and nitrogen. However, it is a complex process, is energy-intensive, and is generally not suitable for small-scale production. Pressure swing adsorption is also commonly used for air separation and can also produce high purity oxygen at medium production rates, but it still requires considerable space, high investment and high energy consumption. The membrane gas separation method is a relatively low environmental impact and sustainable process providing continuous production, simple operation, lower pressure/temperature requirements, and compact space requirements. Current status of CO2 capture with membranes A great deal of research has been undertaken to utilize membranes instead of absorption or adsorption for carbon capture from flue gas streams, however, no current projects exist that utilize membranes. Process engineering along with new developments in materials have shown that membranes have the greatest potential for low energy penalty and cost compared to competing technologies. Background Today, membranes are used for commercial separations involving: N2 from air, H2 from ammonia in the Haber-Bosch process, natural gas purification, and tertiary-level enhanced oil recovery supply. Single-stage membrane operations involve a single membrane with one selectivity value. Single-stage membranes were first used in natural gas purification, separating CO2 from methane. A disadvantage of single-stage membranes is the loss of product in the permeate due to the constraints imposed by the single selectivity value. Increasing the selectivity reduces the amount of product lost in the permeate, but comes at the cost of requiring