A process for recovering valuables from vent gas in polyolefin production is disclosed. The process includes a compression cooling separation step, a heavy hydrocarbon separation step, a light hydrocarbon separation step, a N.sub.2 purification step, and a turbo expansion step in sequence. The N.sub.2 purification step comprises a membrane separation procedure. The light hydrocarbon separation step comprises at least one gas-liquid separation procedure. A first gas, which is obtained by the gas-liquid separation procedure and is heated through heat exchange with multiple streams in the light hydrocarbon separation step, enters the heavy hydrocarbon separation step and is further heated; the heated first gas then enters the N.sub.2 purification step; a first generated gas, which is obtained by the membrane separation procedure of the N.sub.2 purification step, enters the heavy hydrocarbon separation step and the light hydrocarbon separation step in sequence, and is cooled through heat exchange with multiple streams in the heavy hydrocarbon separation step and the light hydrocarbon separation step; and then the cooled first generated gas enters the turbo expansion step. The energy consumption of a compressor can be greatly reduced. An external cooling medium with a temperature lower than an ambient temperature is not needed. The purity and recovery of N.sub.2 and hydrocarbons can be improved, which can facilitate reduction of energy consumption of a whole system, an investment, and a material consumption.

A system used to recycle exhaust gas during olefin polymer production, comprising: a compression cooling mechanism (101); a hydrocarbon membrane separation mechanism (102) and a hydrogen membrane separation mechanism (103), both connected to a first outlet (202) of the compression cooling mechanism; and a deep cooling mechanism (104) connected to a first outlet (208) of the hydrogen membrane separation mechanism. A method used to recycle exhaust gas during olefin polymer production, comprising a compression cooling step, a hydrocarbon membrane separation step, a hydrogen membrane separation step and a deep cooling step.

An integrated method for the production of liquefied natural gas (LNG) and syngas is provided. The method can include the steps of: utilizing letdown energy of a high pressure natural gas stream that is withdrawn from a natural gas pipeline to provide a warm temperature cooling; utilizing a refrigeration cycle to provide a cold temperature cooling, wherein the refrigeration cycle comprises a refrigerant recycle compressor that is powered utilizing a steam turbine; and cooling a second high pressure natural gas stream using the warm temperature cooling and the cold temperature cooling to produce an LNG product stream. The second high pressure natural gas stream is withdrawn from the natural gas pipeline, and the steam turbine is powered by high pressure steam that is produced from a syngas production facility.

In an aspect, the present disclosure provides a method for the oxidative coupling of methane to generate hydrocarbon compounds containing at least two carbon atoms (C.sub.2+ compounds). The method can include mixing a first gas stream comprising methane with a second gas stream comprising oxygen to form a third gas stream comprising methane and oxygen and performing an oxidative coupling of methane (OCM) reaction using the third gas stream to produce a product stream comprising one or more C.sub.2+ compounds.

A system (102; 302) for recovering natural gas liquid from a low pressure gas source (110; 310), comprising a gas/gas heat exchanger (104; 304), fluid from the gas source flowing therethrough; at least one separator (108; 308) for receiving the fluid from the gas/gas heat exchanger (104; 304) and separating liquid from the gas, the gas being directed via a connecting pipe (116; 316) to the gas/gas heat exchanger (104; 304) where it cools the fluid from the gas source; characterised in that the connecting pipe (116; 316) includes expansion means (106; 322) for cooling the gas therein and liquid injection means (120; 320) for saturating the gas with liquid.

A device for separating a gas mixture containing at least 35 mol % carbon dioxide and also at least one gas lighter than carbon dioxide, comprising a first phase separator configured to receive a first partially condensed flow from an exchange line; a first phase separator configured to separate the gas phase from the liquid phase; a cooling means configured to receive the gas phase from the first phase separator and cool said gas phase to form a second partially condensed flow. The resulting liquid phase is then sent to a first valve and is expanded to a lower pressure that is at most 300 mbar lower in order to form a first expanded liquid, which is then mixed with a second liquid originating from the second phase separator in a mixing means that is located upstream of a third valve.

A system and method for argon and nitrogen extraction from a feed stream comprising hydrogen, methane, nitrogen and argon, such as a low-pressure tail gas of an ammonia production plant is provided. The disclosed system and method provides for a rectification system wherein an argon depleted gaseous stream and a methane rich liquid stream are produced and subsequently combined in whole or in part prior to vaporization. Nitrogen and argon containing streams may also be produced from the rectification system. An argon stripping column arrangement is also disclosed where residual argon is removed from the methane-rich fuel gas and recycled back to the feed stream.

A system and method for argon and nitrogen extraction from a feed stream comprising hydrogen, methane, nitrogen and argon, such as tail gas of an ammonia production plant is provided. The disclosed system and method provides for nitrogen-argon rectification and the methane rejection within a column system comprised of at least one distillation column. Nitrogen and argon are further separated and to produce liquid products. An argon stripping column arrangement is disclosed where residual argon is further removed from the methane-rich fuel gas and recycled back to the feed stream.

Integrated systems are provided for the production of higher hydrocarbon compositions, for example liquid hydrocarbon compositions, from methane using an oxidative coupling of methane system to convert methane to ethylene, followed by conversion of ethylene to selectable higher hydrocarbon products. Integrated systems and processes are provided that process methane through to these higher hydrocarbon products.

A method is described for removing carbon dioxide during Liquid Natural Gas production from natural gas at gas pressure letdown stations. The above method removes carbon dioxide from a Liquid Natural Gas production stream by using hydrocarbon fractions taken from a gas for consumption stream as a carbon dioxide stripping adsorption agent for a stripping column used to remove carbon dioxide.