A feed containing methane and nitrogen gas is processed in a three-stage membrane system, each stage of which is selective for methane over nitrogen. The methane enriched permeate from the first stage is removed as product gas. The methane-depleted residue from the second stage is purified in second and third cascaded stages to provide second and third permeates and second and third residues. The third stage permeate is recycled to the feed.

A process for purifying a gaseous feed stream of natural gas including methane, CO.sub.2 and heavy hydrocarbons including step a): cooling the gaseous feed stream in a heat exchanger; step b): introducing the cooled stream into a phase-separating chamber to produce a liquid stream depleted in methane and enriched in heavy hydrocarbons and a gaseous stream; step c): separating the gaseous stream obtained from step b) in a first membrane producing at least one CO.sub.2-enriched permeate stream and a residual stream enriched in methane; step d): introducing the residual stream obtained from step c) into a phase-separator to produce a liquid stream and a gaseous stream; step e): heating the gaseous stream obtained from step d) by introducing it into the heat exchanger used in step a) counter-currentwise with the feed stream thereby producing a gaseous stream depleted in CO.sub.2 and enriched in methane.

A system used to recycle exhaust gas during olefin polymer production, comprising: a compression cooling mechanism (101); a hydrocarbon membrane separation mechanism (102) and a hydrogen membrane separation mechanism (103), both connected to a first outlet (202) of the compression cooling mechanism; and a deep cooling mechanism (104) connected to a first outlet (208) of the hydrogen membrane separation mechanism. A method used to recycle exhaust gas during olefin polymer production, comprising a compression cooling step, a hydrocarbon membrane separation step, a hydrogen membrane separation step and a deep cooling step.

A method and device for purifying heptafluoroisobutyronitrile and a dilution gas from a used gas mixture comprising heptafluoroisobutyronitrile, a dilution gas and arcing by-products. The method comprising the steps of (a) contacting the used gas mixture with at least one adsorbent material to generate a gas stream depleted in arcing by-products; (b) contacting the gas stream depleted in by-products with a first membrane to obtain a first permeate stream rich in the dilution gas, and a first retentate stream rich in heptafluoroisobutyronitrile; (c) contacting the first permeate stream rich in the dilution gas with a second membrane to obtain a second permeate stream rich in the dilution gas and a second retentate stream rich in heptafluoroisobutyronitrile; and (d) combining the first and second retentate streams rich in heptafluoroisobutyronitrile.

A feed fluid mixture including at least one condensable component and at least one non-condensable component is separated into a gaseous permeate and an at least partially liquid retentate with a gas separation membrane through simultaneous condensation of at least one of said at least one condensable component on a retentate side of the membrane and permeation of at least one of said at least one non-condensable component through the membrane.

Disclosed is an aircraft environmental control and fuel tank inerting coupling system based on a membrane separation method. The dehumidification of gas in an aircraft environmental control system and the separation of oxygen and nitrogen in a fuel tank inerting system are realized respectively, based on the selective permeability of a membrane to water vapour/air and oxygen/nitrogen. In the coupling system, part of drying gas passing through a membrane dehumidification heat exchanger (5) enters a membrane air separator (9), and the other part thereof is cooled through a large expansion turbine (8) and then directed into a cockpit for refrigeration; and nitrogen-rich gas generated by the membrane air separator (9) is directed into a fuel tank for inerting. Oxygen-rich gas is mixed with gas supplied by the environmental control system, thus increasing the oxygen content of gas supplied by the aircraft cockpit.

An acidic gas separation device includes: a first separation device which has an inorganic separation membrane and is configured to separate a gaseous hydrocarbon fluid containing an acidic gas into a first gaseous fluid having a large acidic gas content and a second gaseous fluid having a smaller acidic gas content than the first gaseous fluid by the inorganic separation membrane; and a second separation device which has an organic polymer separation membrane and is configured to separate the second gaseous fluid into a third gaseous fluid having a large acidic gas content and a fourth gaseous fluid having a smaller acidic gas content than the third gaseous fluid by the organic polymer separation membrane.

An apparatus utilizes a membrane unit to capture components from atmospheric air, including carbon dioxide, enriches the carbon dioxide concentration, and delivers the enriched concentration of carbon dioxide to a sequestering facility. The membrane is configured such that as a first gas containing oxygen, nitrogen and carbon dioxide is drawn through the membrane, a permeate stream is formed where the permeate stream has an oxygen concentration and a carbon dioxide concentration higher than in the first gas and a nitrogen concentration lower than in the first gas. A permeate conduit, having a vacuum applied to it by a vacuum generating device receives the permeate stream and a delivery conduit delivers at least a portion of the enriched carbon dioxide to a sequestering facility. The apparatus may comprise a component of a system where the system may have a flue gas generator and/or a secondary enrichment system disposed between the vacuum generating device and the sequestering facility.

An apparatus for capturing carbon dioxide has a membrane separator with a gas inlet, a gas outlet, a channel that extends between the gas inlet and the gas outlet, and pores configured to permit carbon dioxide to pass therethrough, the gas inlet being connected to receive a mixed gas that contains carbon dioxide, wherein carbon dioxide in the mixed gas exits the membrane via the pores, and a remainder of the mixed gas exits the membrane separator via the gas outlet. The pores may be functionalized with nano-particles. A container is filled with an aqueous solution includes a carbon capturing agent and the membrane separator is submerged within the aqueous solution. The carbon capturing agent may be produced by a membrane reactor upstream of the membrane separator. Carbon dioxide exiting the membrane separator via the functional pores reacts with the carbon capturing agent to produce a carbon negative compound.

A source gas introduction line for introducing source gas containing CO.sub.2, a first membrane separator for membrane-separating CO.sub.2 from source gas, a first permeable gas discharge line for discharging first permeable gas permeated by membrane separation of the first membrane separator, a first non-permeable gas discharge line for discharging first non-permeable gas not permeated by membrane separation of the first membrane separator, a second membrane separator provided at a downstream side of the first membrane separator and for further membrane-separating CO.sub.2 from the first non-permeable gas, a second permeable gas discharge line for discharging second permeable gas permeated by membrane separation of the second membrane separator, a second permeable gas return line branched from a part of the second permeable gas discharge line and for returning the second permeable gas to a source gas side, and a CO.sub.2 concentration meter are included.