A CO.sub.2 separation system configured to separate CO.sub.2 from mixed gas containing CO.sub.2 includes a CO.sub.2 separator, a CO.sub.2 collector, and a pressure difference generator. The CO.sub.2 separator includes a separation membrane configured to separate the CO.sub.2 from the mixed gas, and a separation-membrane upstream chamber and a separation-membrane downstream chamber demarcated by the separation membrane. The CO.sub.2 separator is disposed to cause the mixed gas to flow into the separation-membrane upstream chamber. The pressure difference generator includes at least a negative pressure generator. The negative pressure generator is disposed on a gas path of the permeating gas that connects the separation-membrane downstream chamber and the CO.sub.2 collector.

A membrane modification method for improving liquid membrane separation of carbon dioxide (CO.sub.2) includes grafting an organic substance containing an amine group on a porous membrane material, and loading water into pore channels of the porous membrane material to prepare a supported liquid membrane for a gas mixture separation experiment of CO.sub.2. In the method, the amine group is introduced through chemical grafting to make the water being alkaline when used as membrane liquid. Compared with an alkaline solution as the membrane liquid, the method can avoid the loss of active alkaline substances and increase the permeation flux of CO.sub.2.

A system and method for producing hydrogen from hydrocarbon and steam, including a membrane reformer with multiple membrane reactors each having a tubular membrane. The bore of the tubular membrane is the permeate side for the hydrogen. The region external to the tubular membrane is the retentate side for carbon dioxide. A sweep gas flows through the bore to displace hydrogen in a direction countercurrent to flow of hydrocarbon and steam in the region external to the tubular membrane. The method includes discharging hydrogen as permeate with the sweep gas from the bore, and discharging carbon dioxide in the region external to the tubular membrane as retentate from the membrane reactor.

An H.sub.2-rich fuel gas stream can be advantageously produced by reforming a hydrocarbon/steam mixture in to produce a reformed stream, followed by cooling the reformed stream in a waste-heat recovery unit to produce a high-pressure steam stream, shifting the cooled reformed stream a first shifted stream, cooling the first shifted stream, shifting the cooled first shifted stream to produce a second shifted stream, cooling the second shifted stream, abating water from the cooled second shifted stream to obtain a crude gas mixture stream comprising H.sub.2 and CO.sub.2, and recovering a CO.sub.2 stream from the crude gas mixture stream. The H.sub.2-rich stream can be advantageously combusted to provide thermal energy needed for residential, office, and/or industrial applications including in the H.sub.2-rich fuel gas production process. The H.sub.2-rich fuel gas production process can be advantageously integrated with an olefins production plant comprising a steam cracker.

An air composition adjusting device includes: a carbon dioxide separator that separates carbon dioxide from air-to-be-treated to be supplied to a target space; a gas supply path including a high concentration gas supply path through which the carbon dioxide separator communicates with the target space; and a controller that performs a carbon dioxide concentration raising operation of supplying a high carbon dioxide concentration gas, which has a higher carbon dioxide concentration than air-to-be-treated before being treated, to the target space through the high concentration gas supply path.

An air separation module includes a cylindrical canister and a separator. The cylindrical canister has a longitudinal axis, an inlet, an oxygen-depleted air outlet, and a drain portion with an oxygen-enriched air outlet. The separator is arranged within the cylindrical canister to separate a compressed air flow into an oxygen-depleted air flow fraction and an oxygen-enriched air flow fraction, the oxygen-depleted air flow fraction provided to the oxygen-depleted air outlet and the oxygen-enriched air flow fraction to the drain portion of the canister. The drain portion extends tangentially from the cylindrical canister to issue the oxygen-enriched air flow fraction with entrained condensate from the oxygen-enriched air outlet with a tangential flow component. Nitrogen generation systems and methods of removing condensate from air separation modules are also described.

Methods of sequestering carbon dioxide (CO.sub.2) are provided. Aspects of the methods include contacting an aqueous capture ammonia with a gaseous source of CO.sub.2 under conditions sufficient to produce an aqueous ammonium carbonate. The aqueous ammonium carbonate is then combined with a cation source under conditions sufficient to produce a solid CO.sub.2 sequestering carbonate and an aqueous ammonium salt. The aqueous capture ammonia is then regenerated from the from the aqueous ammonium salt. Also provided are systems configured for carrying out the methods.

A carbon dioxide separator includes an absorption tower for producing a carbon dioxide-rich absorbent and a carbon dioxide-depleted flue gas by reaction of a carbon dioxide-containing flue gas and an absorbent contained therein; a regeneration tower for removing the carbon dioxide-rich absorbent transferred from the absorption tower in the presence of the flowing gas to separate the same into a carbon dioxide-rich treatment gas and a carbon dioxide-lean absorbent; and a separation membrane module for selectively membrane-separating and concentrating the carbon dioxide, wherein the carbon dioxide-containing flue gas is transferred to the absorption tower as a carbon dioxide-lean flue gas obtained via the separation membrane module, and the flowing gas is transferred to the regeneration tower as the carbon dioxide-rich flue gas obtained via the separation membrane module from the carbon dioxide-containing flue gas.

In an aspect, a hydrogen separation unit includes an electrochemical cell stack that includes a separator stack located in between an anode side and a cathode side; a mixed gas conduit for receiving a mixed gas stream to the anode side; an anode removal conduit for removing a helium rich stream from the anode side; and a cathode removal conduit for removing a hydrogen rich stream from the cathode side. The separation stack includes a plurality of electrochemical cells, each of which includes a proton exchange membrane located in between an anode and a cathode. The proton exchange membrane can include a cation. The separation stack can be a cascading separation stack.

The invention relates to a method (200-400) for extracting pure helium using a first membrane separation stage (1), a second membrane separation stage (2), and a third membrane separation stage (3), in which a first helium-containing feed mixture is supplied to the first membrane separation stage (1), a second helium-containing feed mixture is supplied to the second membrane separation stage (2), and a third helium-containing feed mixture is supplied to the third membrane separation stage (3), and in which a first permeate and a first retentate are formed in the first membrane separation stage (1), a second permeate and a second retentate are formed in the second membrane separation stage (2), and a third permeate and a third retentate are formed in the third membrane separation stage (3). According to the invention, the first feed mixture is formed using at least one portion of a helium-containing starting mixture, the second feed mixture is formed using at least one portion of the first permeate, the third feed mixture is formed using at least one portion of the second retentate, the second permeate is at least partially processed by pressure-swing adsorption in order to obtain the pure helium and a remaining mixture, and at least one portion of the third permeate and/or at least one portion of the third retentate is guided back into the method (200). The invention also relates to a corresponding system.