Separation of a gas mixture comprising first and second gases may be improved using four stages of gas separation membrane modules that includes the additional techniques of cooling the feed gas stream that is fed to the first (feed) stage and using a portion of the fourth (second permeate) stage retentate as a sweep gas on the permeate stage.

Separation of a gas mixture comprising first and second gases may be improved using two cascaded stages of gas separation membrane modules that includes the additional techniques of cooling the feed gas stream that is fed to the feed stage and using a portion of the feed stage retentate as a sweep gas on the feed stage.

A gas separation system includes: a first gas separation membrane unit; a second gas separation membrane unit; a material gas feed line connected to a gas inlet port of the unit; a first compressor interposed to the line; a first connection line connecting a permeated gas discharge port of the unit and a gas inlet port of the unit; and a second connection line connecting a non-permeated gas discharge port of the unit and the line. The unit and unit each have a gas separation selectivity of 30 or greater. The CH.sub.4 recovery rate is 98% or higher. The CO.sub.2 content in non-permeated gas of the unit is 5 mol % or less. The flow rate of gas fed to the unit is 60% or less of the flow rate of material gas fed to the unit.

Disclosed herein are 2-stage membrane separation methods for capturing CO.sub.2 from a feed gas. The methods can employ two selectively permeable membranes, which may be the same or different. The selectively permeable membrane can have a carbon dioxide permeance of from 500 to 3000 GPU at 57° C. and 1 atm feed pressure and a carbon dioxide:nitrogen selectivity of from 10 to 1000 at 57° C. and 1 atm feed pressure. High pressure ratios across the membranes can be achieved by compressing the feed gas to a high pressure, by using vacuum pumps to create a lowered pressure on the permeate side of the membrane, by using a sweep stream, or a combination thereof. When a sweep stream is used, the sweep stream may include a portion of the retentate gas stream obtained from the retentate side of one or more of the membranes used.

At least some VOCs are removed from a feed gas in an adsorption unit comprising at least three adsorbers following a pressure cycle with a phase shift, wherein the feed gas comprises at least methane, carbon dioxide and volatile organic compounds (VOCs). The VOC depleted gas is fed to at least one membrane separation to produce a carbon dioxide-enriched permeate and a methane-enriched retentate. The flow of the feed gas stream is adjusted based upon one or both of a pressure or methane concentration of the gas stream entering the membrane separation unit and/or a pressure in the adsorption unit.

The present invention is directed to a method of capturing CO2 from a FCC regenerator using select membranes.

The present invention relates to a separation and recovery system and method of hydrogen from a coke oven gas (COG) in a steel industry, and more particularly, to a separation and recovery system and method of hydrogen from a coke oven gas (COG) in a steel industry, the system including a pre-processing unit removing impurities including tar, moisture, oil, hydrogen sulfide, and dusts from the coke oven gas (COG), a membrane separation unit including a polymer separation membrane module to generate a hydrogen concentrated gas stream by membrane-separating the coke oven gas (COG) processed in the pre-processing unit, and an adsorption unit separate and recover the hydrogen by allowing the hydrogen concentrated gas stream to contact an absorbent.

A facility and a process with four membrane separation units, where the second separation unit separates the retentate of the first unit, the third separation unit separates the permeate of the first unit, the fourth separation unit separates the retentate of the third unit, the permeate of the second unit and the retentate of the fourth unit are recycled to the feed to the first unit, the permeate of the fourth unit is passed to a methane oxidation unit and the permeate of the third unit is discharged to the atmosphere allows separating methane and carbon dioxide from a gas stream, providing a methane rich stream with the retentate of the second unit at a high methane yield and adhering to low limits for methane discharge to the atmosphere with a small size methane oxidation unit.

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.

The invention relates to a method for membrane permeation of a gas flow including methane and carbon dioxide, wherein said gas flow is cooled to a temperature of 0° C. to −60° C. before being fed into a membrane separation unit.