A plant for producing at least partially desulfurized biogas, comprising a biomass digester and/or post-digester, the digester and/or post-digester comprising: a chamber (1) comprising the biomass (2) and the gas space (3), and a system (6) for injecting an oxidizing gas into the gas space,
wherein the injection system comprises a tubular means (4) comprising a T-shaped portion the vertical bar of which is placed in the axis of symmetry of the chamber and the horizontal bar of which has micro-injectors (5).

An alkaline aqueous ferric iron salt solution is disclosed. Generally, the alkaline aqueous ferric iron salt solution comprises ferric ions (Fe.sup.3+), potassium ions (K.sup.+), carbonate ions (CO.sub.3.sup.2−), bicarbonate ions (HCO.sub.3.sup.−), hydroxide ions (OH.sup.−), optionally nitrate ions (NO.sub.3.sup.−). Further, a molar ratio of the potassium ions to the ferric ions is generally at least 5.0. The ferric iron is complexed with carbonate, bicarbonate or both to form a water-soluble complex that is anionic in nature and highly soluble in the alkaline aqueous ferric iron salt solution at pH above 8.5, and a pH of the alkaline aqueous ferric iron salt solution is at least 8.5.

A biogas treatment process is integrated with a water treatment process to adjust the pH level of the water and to provide more effective disinfection of the water. A water wash process is utilized to separate methane and carbon dioxide present in the biogas. During the water wash process, the biogas is mixed with water and the carbon dioxide is absorbed into the water. Because the process typically occurs at an elevated pressure and reduced temperature to enhance the solubility of carbon dioxide in water, the water stream becomes supersaturated with carbon dioxide. This water stream, which is supersaturated with carbon dioxide, is provided to the water treatment process to adjust the pH level of the water treatment process. The pH level is regulated to a desired level such that an increased relative concentration of hypochlorous acid is produced when sodium hypochlorite is added to the treatment process.

A method for separating a raw feed gas stream using a plurality of membrane separation stages includes separating a pressurized feed gas stream into a first nonpermeate stream and a first permeate stream, compressing the first permeate stream to form a compressed first permeate stream, separating the compressed first permeate stream into a second nonpermeate stream and a second permeate stream, separating the second permeate stream into a third nonpermeate stream and a third permeate stream, combining the third nonpermeate stream with a raw feed gas stream to form a combined feed stream, compressing the combined feed stream to form a compressed combined feed stream, and combining the second nonpermeate stream with the compressed combined feed stream to form the pressurized feed gas stream.

A multi-stage system comprising a digester, a bioreactor, a scrubber, a biofilter, and a membrane filter extracts and purifies biogas from a wastewater feed. The digester separates raw biogas from wastewater, the wastewater is then purified with a three-stage bacterial process in a bioreactor. The scrubber receives raw biogas from the digester under pressure, dissolving waste gases and purifying the methane, which can be further condensed and purified in the membrane filter. The bioreactor receives waste gases from the scrubber and membrane filter, with the ammonia portion of the waste gases rising through water from the bioreactor and being converted by annamox bacteria into nitrogen gas. The multiply recycled gas and water feeds produce a biogas having high purity and reduced atmospheric emissions of waste gases.

A carbon dioxide adsorbent including a hierarchical zeolite. The hierarchical zeolite defines micropores having a pore width between about 0.4 nm and about 2 nm, and at least one of: mesopores having a pore width between about 2 nm and about 50 nm; and macropores having a pore width greater than about 50 nm.

A process for producing biomethane by scrubbing a biogas feed stream including introducing a feed gas stream into a pretreatment unit wherein the gas stream is partially separated from a CO.sub.2 stream and an oxygen stream, thereby producing a CO.sub.2-depleted gas stream, which is compressed, thereby producing a pressurized CO.sub.2-depleted gas stream; separating the pressurized CO.sub.2-depleted gas stream by cryogenic separation by introducing the pressurized CO.sub.2-depleted gas stream into a distillation column thereby producing a nitrogen stream and a CH.sub.4-enriched stream, recovering a pressurized CH.sub.4-enriched stream by pumping the CH.sub.4-enriched stream; wherein the separation of the CO.sub.2 stream and the oxygen stream from the feed gas stream is performed by a unit comprising at least two separating membrane stages in order that the CO.sub.2-depleted gas stream comprises between 0.3 mol % and 2 mol % of CO.sub.2.

A method for separating carbon dioxide and water from a gas mixture by cyclic adsorption/desorption, using a unit containing an adsorber structure, comprising the following repeating steps: (a) contacting said mixture with sorbent material; (b) at least one of evacuating said unit and heating said sorbent material and extracting the gaseous carbon dioxide and water vapour and separating gaseous carbon dioxide from water vapour; (c) cooling the adsorber structure and re-pressurisation; wherein (i) in step (c) the heat released is stored in a first heat storage device; (ii) during step (b) the sensible and latent heat of gaseous carbon dioxide and water vapour as product gases is stored in second heat storage device; and (iii) during step (b) the heat required for heating said sorbent material is supplied from heat recovered in at least one of step actions (i) and (ii) of previous sequence(s).

A facility and method for membrane permeation treatment of a feed gas flow containing at least methane and carbon dioxide that includes a compressor, a pressure measurement device, at least one valve, and first, second, third, and fourth membrane separation units for separation of CO.sub.2 from CH.sub.4 to permeates enriched in CO.sub.2 and retentates enriched in CH.sub.4, respectively. A temperature of the first retentate is adjusted at an inlet of the second membrane separation unit with at least one heat exchanger as a function of the measured CH.sub.4 concentration in such a way so as to reduce the determined difference.

Plant and method for the separation of a gas mixture containing a plurality of gaseous components, comprising first and second membrane-based separation stages and a third gas separation stage with adsorption with oscillating pressure, the first, second and third gas separation stages acting in combination to obtain a first final flow of gas enriched in a first component of the initial gas mixture, for example methane, and a second final flow of gas, enriched in a second component of the initial gas mixture, for example carbon dioxide.