Pressure swing adsorption process for reducing fluctuations in the flow rate of tail gas from the adsorption unit. The flow rate of the stream of blowdown gas is regulated responsive signals from a sensor measuring the pressure and/or flow rate of the tail gas comprising the blowdown gas and purge gas effluent before the tail gas is introduced into a surge vessel.

A process and apparatus for producing a hydrogen-enriched product and recovering CO.sub.2 from an effluent stream from a hydrogen production process unit are described. The process utilizes a CO.sub.2 recovery system integrated with a PSA system that produces at least two product streams to recover additional hydrogen and CO.sub.2 from the tail gas stream of a hydrogen PSA unit in the hydrogen production process.

A process and apparatus for producing a hydrogen-enriched product and recovering CO.sub.2 from an effluent stream from a hydrogen production unit are described. The effluent from the hydrogen production unit, which comprises a mixture of gases comprising hydrogen, carbon dioxide, water, and at least one of methane, carbon monoxide, nitrogen, and argon, is sent to a PSA system that produces at least two product streams for separation. The PSA system that produces at least two product streams separates the gas mixture into a high-pressure hydrogen stream enriched in hydrogen, optionally a second gas stream containing the majority of the impurities, and a low-pressure tail gas stream enriched in CO.sub.2 and some impurities. The CO.sub.2-rich tail gas stream is compressed and sent to a CO.sub.2 recovery unit, where a CO.sub.2-enriched stream is recovered. The CO.sub.2-depleted overhead gas stream is recycled to the PSA system that produces at least two product streams.

Provided are apparatus and systems for performing a swing adsorption process. This swing adsorption process may involve performing dampening for fluctuations in the streams conducted away from the adsorbent bed unit. The process may be utilized for swing adsorption processes, such as rapid cycle TSA and/or rapid cycle PSA, which are utilized to remove one or more contaminants from a gaseous feed stream.

Methods and systems for capture of CO.sub.2 from a hydrated gaseous stream are described. Systems can be utilized for direct air capture of CO.sub.2 and incorporate a low energy temperature-vacuum swing adsorption (TVSA) process. A TVSA process can include a multi-step CO.sub.2 capture bed regeneration process that includes depressurization of the bed, heating of the bed, venting and purging of the bed, and cooling of the bed. Multiple beds can be cycled between CO.sub.2 capture and regeneration, during which captured CO.sub.2 is recovered. Off-gas from a CO.sub.2 capture bed can be used in regenerating a parallel bed for increased efficiency.

A control circuit of an oxygen concentrator maintains pressure within a compressor of the oxygen concentrator. The control circuit includes a microprocessor that controls functioning of a controller based on two or more of: a user-adjustable flow rate of oxygen delivered by the oxygen concentrator to a user, an ambient temperature, and an ambient pressure. The functioning of the controller further controls the adsorption of various gases by sieve beds of the oxygen concentrator to produce oxygen enriched gas.

Provided are apparatus and systems for performing a swing adsorption process. This swing adsorption process may involve passing an input feed stream through two swing adsorption systems as a purge stream to remove contaminants, such as water, from the respective adsorbent bed units. The wet purge product stream is passed to a solvent based gas treating system, which forms a wet hydrocarbon rich stream and a wet acid gas stream. Then, the wet hydrocarbon rich stream and the wet acid gas stream are passed through one of the respective swing adsorption systems to remove some of the moisture from the respective wet streams.

A multi-stage process to remove contaminant gases from raw methane streams is provided. The present technology is an innovative solution to recover and purify biogas by use of a process having at least two pressure swing adsorption stages. Taking advantage of the presence of carbon dioxide in the raw biogas streams, nitrogen and oxygen are bulky removed in the first stage, using selective adsorbents, and a nitrogen and oxygen-depleted intermediate stream is yielded to the second stage. The second stage employs an adsorbent or adsorbents to selectively remove carbon dioxide and trace amounts of remaining nitrogen and oxygen, thus producing a purer methane stream that meets pipeline and natural gas specifications

Provided are apparatus and systems for performing a swing adsorption process. This swing adsorption process may involve performing a startup mode process prior to beginning a normal operation mode process to remove contaminants from a gaseous feed stream. The startup mode process may be utilized for swing adsorption processes, such as TSA and/or PSA, which are utilized to remove one or more contaminants from a gaseous feed stream.

A method of recovering paraxylene in a pressure swing adsorption unit with varying hydrogen purge pressures. The pressure swing adsorption zone is adapted to adsorb and desorb paraxylene based on the cycling of partial pressure in the zone. A first hydrogen purge is fed concurrent to the feed. A second hydrogen purge is countercurrent to the feed.