In a process for separating a mixture containing hydrogen and carbon dioxide, the mixture is compressed to form a compressed mixture, the compressed mixture is separated by partial condensation and/or distillation generating a first CO2-depleted stream, the first CO2-depleted stream is separated by permeation through a membrane system to form a residue of the membrane system which is depleted in hydrogen and carbon dioxide and a portion of the residue is recycled, after expansion, to the compressor to be compressed therein.

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 nitrogen separation system includes a pressurizing apparatus, a temperature regulation apparatus, a nitrogen separation apparatus. The pressurizing apparatus is configured to pressurize a raw material gas to configure a pressurized raw material gas which is in a vapor-liquid equilibrium state with a liquefied gas and contains methane as a principal component and greater than or equal to 1 mol % nitrogen. The nitrogen separation apparatus is configured to separate nitrogen contained in the pressurized raw material gas by use of a nitrogen selective permeation membrane configured from an inorganic material. The pressurization apparatus pressurizes the raw material gas so that a partial pressure of nitrogen in the pressurized raw material gas is greater than or equal to 2 times and less than or equal to 5 times a pressure of the nitrogen-enriched gas.

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.

The invention relates to a method for treating a mixture in order to separate carbon dioxide and hydrogen from said mixture, in which: i) the mixture is cooled and partially condensed and a first liquid is separated from the rest of the mixture in a first phase separator; ii) a gas from or derived from a gas from the first phase separator is treated in a hydrogen pressure swing adsorption module in order to produce a hydrogen-rich gas and a hydrogen-depleted residual gas; and iii) said hydrogen-depleted residual gas or a gas derived from said depleted gas is cooled and partially condensed and a second liquid is separated from the remaining gas in a second phase separator, separate from the first phase separator, wherein the first and/or second liquid being rich in carbon dioxide. The invention also relates to an installation for implementing such a method.

A system and method for recovering high-quality biomethane (RNG) from biogas sources is provided. The gas stream is compressed and liquids are separated from the gas stream at elevated pressure and reduced temperature. The compressing is performed using a plurality of compressors operating in parallel with common control set points. The system and method improve upon conventional practices and yield a biomethane product which meets strict gas pipeline quality specifications. Additionally, the system and method are an improvement to the overall methane recovery efficiency for biogas processing facilities.

A process to produce at least carbon dioxide and carbon monoxide from a feed gas containing carbon dioxide, hydrogen and carbon monoxide; comprises separating at least part of the carbon dioxide from the compressed feed gas by partial condensation and/or distillation producing a carbon dioxide product and a carbon dioxide depleted stream, treating the carbon dioxide depleted stream in a treatment unit to produce a feed stream containing carbon monoxide and hydrogen, less rich in carbon dioxide than the carbon dioxide depleted stream and feeding at least part of the feed stream containing carbon monoxide and hydrogen to a separation unit operating at cryogenic temperatures to produce a carbon monoxide product.

In a purification method, a carbon dioxide-rich gas is cooled in a first brazed aluminum plate-fin heat exchanger, the cooled gas or at least one fluid derived from the cooled gas is sent to a purification step comprising a distillation step, the purification step produces a carbon dioxide-rich liquid which is cooled, then expanded, then sent to a second heat exchanger where it is heated by means of a fluid of the method, the exchanger carrying out an indirect heat exchange only between the carbon dioxide-rich liquid and the fluid of the method, the carbon dioxide-rich liquid at least partially vaporizes in the second exchanger and the vaporized gas formed heats up again in the first exchanger to form a carbon dioxide-rich gas.

Systems and methods for liquefying a gaseous fluid that comprises at least 50% by volume methane into a liquefied fluid that comprises at least 85% by volume methane. Processing can include increasing a pressure of the incoming gaseous fluid to between 10 and 50 bar; pre-treating the gaseous fluid using membrane filtering to a retentate stream having a methane content of at least 85% by volume; liquefying the retentate stream by cryogenic cooling to a temperature between 100 C. and 140 C.; flashing the liquefied fluid into a container; retrieving processed liquid fluid at a first container level at a pressure of between 1 and 10 bar, a temperature of between 120 C. and 160 C., and a methane concentration of at least 85% by volume into a storage device; and retrieving a slurry flow comprising solid CO.sub.2 and water ice at a second container level below the first container level.

In a method for separating a mixture containing carbon dioxide, the mixture is cooled in a heat exchanger and partially condensed and a first liquid is separated from the mixture in a first system operating at low temperature comprising at least one first phase separator and a gas from the first system is treated in a membrane system to produce a permeate and a non-permeate, the gas from the first system being divided into two portions, a first portion being sent to the membrane system without being heated and a second portion being heated to at least an intermediate temperature of the heat exchanger and then sent to the membrane system without being cooled.