Described herein are methods and systems for producing liquefied natural gas (LNG) from a methane-containing synthetic gas (MCSG). An MCSG feed stream may be cooled and partially liquefied using one or more heat exchanger units. A first phase separator and a second phase separator in downstream fluid flow communication with the first phase separator may be used to separate the partially liquefied MCSG stream into a first residue gas stream and first and second feed streams, the first and second feed streams then being fed into a distillation column to produce an LNG stream and a second residue gas stream.

A heavies removal heat exchanger cools at least a portion of a feed gas stream. A scrubbing section receives the cooled main feed gas stream. A stripping section receives a fluid stream from the scrubbing section. A stripping gas feed expansion device receives a portion of the feed gas stream and is in fluid communication with the stripping section. A side draw vapor line receives a vapor stream from the vapor outlet of the stripping section and is in fluid communication with a reflux stream cooling passage of the heavies removal heat exchanger. A reflux separation device receives fluid from the heavies removal heat exchanger and has a liquid outlet and a vapor outlet. The liquid outlet is in fluid communication with the scrubbing section. A return vapor expansion device receives a vapor stream from the scrubbing section and directs a cooled vapor stream to a return vapor stream warming passage of the heavies removal heat exchanger. The reflux separation device vapor outlet is configured so that fluid passing therethrough joins with fluid that has exited the return vapor expansion device either before or after the fluid that has exited the return vapor expansion device flows through the return vapor stream warming passage of the heavies removal heat exchanger.

In a process for the separation of a mixture containing hydrogen and carbon monoxide to produce gaseous hydrogen, the mixture is cooled down to a temperature below −180° C. and then separated at a temperature below −100° C. to produce a gas enriched in hydrogen and a fluid enriched in carbon monoxide, at least a part of the gas enriched in hydrogen is sent to a pressure swing adsorption separation apparatus operating at a temperature above 0° C. to produce a gas rich in hydrogen at a pressure of at least 20 bars, and at least a part of the gas rich in hydrogen is cooled in the heat exchanger down to a temperature below −100° C., reduced in pressure in a turbine down to a pressure of at least 8 bars and reheated in the heat exchanger to constitute a product rich in hydrogen at a pressure of at least 8 bars.

A system and method for capturing and separating carbon dioxide from mixed gas streams. The gas stream is processed in a structure including a compression module comprising a plurality of compressors, intercoolers and inter-stage condensate separators. The flow path from the compression module includes a plurality of flow separators, gas stream splitters, heat exchangers and at least a first mixer and a first expander. The gas stream is sequentially compressed and cooled to form process condensate and separate it from the compressed gas stream. The gas stream is further dried and cooled to liquefy carbon dioxide and separate it from the non-condensable portion. Selective expansion of liquid carbon dioxide streams provides cooling for the system, and further energy efficiency is achieved by selective recycling of portions of gas streams, allowing for compact equipment and economical operation, while providing for high purity product streams of carbon dioxide.

A pressurized CO.sub.2 rich gas is cooled down to condense at least part of the stream in a heat exchanger. A bulk of the CO.sub.2 is separated by partial condensation and distillation in order to obtain at least one non-condensable gas from a separation vessel. The non-condensable gas is optionally heated up to a temperature lower than −20° C. (membranes performances is greatly enhanced by low temperature operation). The non-condensable gas is introduced into a membrane permeation unit, producing a residue stream and a permeate stream (the permeate stream is enriched in CO.sub.2). The permeate stream is recycled to the process, optionally after compression. The method is auto-refrigerated, i. e. no external refrigerant is used to provide cooling below 0° C.

In a process for the combined production of a) a hydrogen-enriched gas and a carbon monoxide-enriched gas and/or b) a mixture of hydrogen and carbon monoxide by cryogenic distillation and scrubbing, a still liquor is extracted from a scrubbing column and sent to a stripping column, a still liquor is extracted from the stripping column and sent to a separating column for carbon monoxide and methane and a cooling fluid is used at a pressure greater than that of the head of the separating column for cooling at least one fluid extracted at an intermediate level from the scrubbing column.

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.

This method envisions cooling the supply flow in a first heat exchanger, separation in a first separation flask in order to produce a light upper flow and a heavy lower flow and dividing the light upper flow into a supply fraction of a dynamic pressure reduction turbine and a supply fraction of a first distillation column. A cooled reflux flow is formed from an effluent from a dynamic pressure reduction turbine, the portion of the effluent being cooled and at least partially liquefied in a heat exchanger. The cooled reflux flow is introduced from the heat exchanger into the first distillation column.

A system and methods for processing a feed gas in a column are provided herein. A method includes feeding a feed gas into a port of a sleeve disposed around at least a portion of a periphery of the column. The sleeve includes a space between an outer wall of the column and an inner wall of the column. The sleeve releases the feed gas into the column through an opening disposed at an opposite end of the sleeve from the port.

A method and a plant for producing liquid CO.sub.2 from flue gas as described with reduced energy consumption and a stable behavior.