Processes and systems for recovering hydrogen may include feeding a gas stream, comprising hydrogen and additional gases, to a pressure swing adsorption (PSA) system and feeding a membrane permeate stream comprising hydrogen to the PSA system. In the PSA system, a portion of the hydrogen may be separated from the additional gases to recover a hydrogen product stream and a PSA tail gas stream comprising unseparated hydrogen and the additional gases. The PSA tail gas stream may be fed to a membrane separation unit for separating hydrogen from the additional gases and to recover (i) the membrane permeate stream comprising hydrogen fed to the PSA system and (ii) a membrane tail gas stream comprising the additional gases. Embodiments herein may additionally include a refrigeration system for partially condensing one or both of the feed gas stream and the PSA tail gas stream, enhancing the efficiency of the membrane separation unit.

A module for a natural gas liquefaction apparatus is provided to include air-cooled heat exchanger groups and another equipment group. The air-cooled heat exchanger groups another equipment group. The air-cooled heat exchanger groups are arranged side by side on an upper surface of a structure, and are each configured to cool a fluid handled in the natural gas liquefaction apparatus. The another equipment group is arranged on a lower side from an arrangement height of each air-cooled heat exchanger groups, and forms a part of the natural gas liquefaction apparatus. When equipment groups are classified into a pretreatment unit equipment group provided in a pretreatment unit configured to perform pretreatment of natural gas before being liquefied, and a liquefaction processing unit equipment group provided in a liquefaction processing unit associated with processing of liquefying the natural gas after being treated in the pretreatment unit, the another equipment group is formed of the pretreatment unit equipment group.

A process for purifying a feed gas including methane and heavy hydrocarbons, including: step a): cooling the feed gas in a heat exchanger; step b): introducing the resulting into a first phase separator to produce a liquid stream depleted in methane and enriched in heavy hydrocarbons and a gas stream; step c): separating the gas stream in a membrane from which a methane-enriched permeate stream and a partially condensed residue stream exit; step d): introducing the residue stream from step c) into a second phase separator vessel in order to produce a liquid stream and a gas stream; step e): introducing at least one portion of the gas stream resulting from step d) into a JT expansion means; and step f): heating at least one portion of the expanded stream in the heat exchanger used in step a) counter-current to the feed stream in order to cool the latter.

A process for producing biomethane by scrubbing a biogas feed stream includes introducing the feed gas stream into a pretreatment unit wherein a CO.sub.2-depleted gas stream is partially separated from a CO.sub.2 stream and an oxygen stream and is compressed to a pressure P1 above 25 bar abs. Subjecting the CO.sub.2-depleted gas stream to cryogenic separation in a distillation column to separate a nitrogen stream and produce a CH.sub.4-enriched stream, the distillation column comprising n plates, n being an integer between 8 and 100. Recovering a pressurized CH.sub.4-enriched stream by pumping the CO.sub.2-depleted gas stream to a pressure P2 above 25 bar absolute.

A pretreatment system and method for a floating liquid natural gas (“FLNG”) facility are presented. The inlet natural gas stream flows through a membrane system to remove carbon dioxide and a heat exchanger, producing first and second cooled CO.sub.2-depleted non-permeate streams. The first cooled CO.sub.2-depleted non-permeate stream is routed to additional pretreatment equipment, while the second cooled CO.sub.2-depleted non-permeate stream is routed directly to a LNG train. Alternatively, the inlet natural gas stream may flow through a membrane system to produce a single cooled CO.sub.2-depleted non-permeate stream that is routed to the LNG train after sweetening and dehydration. Because the pretreatment system delivers the incoming gas stream to the LNG train at a lower temperature than conventional systems, less energy is needed to convert the gas stream to LNG. In addition, the pretreatment system has a smaller footprint than conventional pretreatment systems.

A process for purifying a natural gas feed gas stream including methane and hydrocarbons, including step a): cooling the feed gas stream; step b): introducing the cooled stream into a first phase separator vessel in order to produce a liquid stream and a gas stream; step c): separating the gas stream resulting from step b) in a membrane unit from which a methane-enriched permeate stream and one partially condensed residue stream enriched in hydrocarbons exit; step d): introducing the residue stream resulting from step c) into a second phase separator vessel to produce a liquid stream and a gas stream; step e): introducing at least one portion of the liquid stream resulting from step d) into a JT expansion means; step f): heating at least one portion of the expanded by introduction into the heat exchanger used in step a) counter-current to the feed stream.

The present invention relates to a cold box cycle which allows for independent control of the heat supplied for reboilers associated with the separation columns. More specifically, the invention relates to the tight control of the hydrogen removal separation, thus avoiding the possibility of excess reboiling in this separation. Optimal reboiling also results in a lower temperature of the hydrogen depleted liquid from this separation. As this stream is used to provide a portion of the cooling at the cold end of the primary heat exchanger, lower temperatures facilitate cooling of the incoming syngas feed, reducing carbon monoxide (CO) losses into the crude hydrogen stream from the high pressure separator. Lower CO in the crude hydrogen allows for smaller hydrogen purification equipment.

Systems and processes are provided to prevent light ends such as methane, ethylene and ethane from building up in an olefin/paraffin separation system that uses a combination of a membrane and distillation column for this separation. In one embodiment a small stripper column is provided downstream from a selective hydrogenation reactor. In the other embodiment, a surge vessel with a receiver is added to the retentate stream of the membrane unit.

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 system for recovering valuables from vent gas in polyolefin production is disclosed. The system includes a compression device, a drying device, a condensation and separation device, and a membrane separation device that are connected to each other in sequence. The drying device includes a first adsorption bed and a second adsorption bed which are in parallel connection with each other and in which a desiccant is provided, and a third adsorption bed which is in communication with the first adsorption bed and the second adsorption bed respectively and in which a desiccant is provided. The first adsorption bed and the second adsorption bed are in an adsorption process and a regeneration process alternately, and the third adsorption bed is in an auxiliary regeneration process. A process for recovering valuables from vent gas in polyolefin production is further disclosed. When the system and the process are used, one part of the normal temperature compressed gas stream output by the compression device directly serves as a regeneration gas for regeneration of saturated desiccant in adsorption bed, and it is unnecessary for external supply of regeneration gas, whereby the actual recovery of nitrogen can be effectively improved. Membrane separation technology is combined, and hydrocarbon recovery can be effectively improved as well.