A crude helium stream is recovered from a natural gas feed by distillation. Refrigeration from expanding a portion of the bottoms liquid is used to partially condense the helium-enriched overhead vapor and generate a crude helium vapor and a helium-containing liquid stream that is recycled to the distillation column to maximize helium recovery. The helium-depleted natural gas stream can be returned at pressure for utilization or transportation.

A natural gas liquefaction method and system having integrated nitrogen removal. Recycled LNG gas is cooled in a separate and parallel circuit from the natural gas stream in the main heat exchanger. Cooled recycled gas and natural gas streams are directed to a nitrogen rectifier column after the warm bundle. The recycle stream is introduced to the rectifier column above the natural gas stream and at least one separation stage is located in the rectifier column between the recycle stream inlet and the natural gas inlet. The bottom stream from the rectifier column is directed to a cold bundle of the main heat exchanger where it is subcooled.

A system and method for removing nitrogen and producing a high pressure methane product stream from natural gas feed streams having wide variations in nitrogen and methane content are disclosed. Optional add-on systems may be incorporated into the nitrogen and methane separation to produce an NGL sales stream to reduce excess hydrocarbons in the nitrogen vent stream, or to recover helium. The system and method of the invention are particularly suitable for use with feed streams in excess of 50 MMSCFD and up to 300 MMSCFD and containing up to 100 ppm carbon dioxide. Typical power requirements for compressing the methane product stream to produce a suitably high pressure stream for sale are reduced according to the systems and methods of the invention.

In a process for separating at least one heavy impurity such as hydrogen sulfide from crude carbon dioxide comprising significant quantities of at least one light impurity such as non-condensable gases, involving at least one heat pump cycle using carbon dioxide-containing fluid from the process as the working fluid, the light impurity is removed from the crude carbon dioxide and carbon dioxide is subsequently recovered from the removed light impurity, thereby improving overall carbon dioxide recovery and efficiency in terms of energy consumption.

Helium can be recovered from nitrogen-rich natural gas at high pressure with low helium loss by cryogenic distillation of the natural gas after pre-treatment of the gas to remove incompatible impurities and then recovery of natural gas liquid (NGL) from the pre-treated gas by distillation. Overall power consumption may be reduced, particularly if the feed to the helium recovery column system is at least substantially condensed by indirect heat exchange against a first portion of nitrogen-enriched bottoms liquid at first pressure, and a second portion of nitrogen-enriched bottoms liquid at a second pressure that is different from the first pressure.

Overall power consumption in a cryogenic distillation process for recovering helium from nitrogen-rich gases comprising helium may be reduced if the feed to the distillation column system is at least substantially condensed by indirect heat exchange against a first bottoms liquid at first pressure, and a second bottoms liquid at a second pressure that is different from the first pressure.

A process for separating the components of a gas mixture comprising methane, nitrogen, and at least one hydrocarbon having at least two carbon atoms, or a mixture of these hydrocarbons, including the following steps: a) demonization of the gas mixture with at least one demethenization column; b) extraction of a liquid comprising at least 85 mol % of the hydrocarbons having at least two carbon atoms, partial condensation of a gas mixture in order to obtain a liquid, at least a portion of which is treated in order to be extracted as denitrogenated natural gas product and a second gas; d) introduction of the second gas and/or the gas mixture into a nitrogen removal column, obtained from which are a gas and a liquid, e) treatment of the gas in a nitrogen removal system in order to produce a gas stream comprising 5 mol % at most of nitrogen.

Recovering helium from a gaseous stream includes contacting an acid gas removal membrane with a gaseous stream to yield a permeate stream and a residual stream, removing a majority of the acid gas from the residual stream to yield a first acid gas stream and a helium depleted clean gas stream, removing a majority of the acid gas from the permeate stream to yield a second acid gas stream and a helium rich stream, and removing helium from the helium rich stream to yield a helium product stream and a helium depleted stream. A helium removal system for removing helium from a gaseous stream including hydrocarbon gas, acid gas, and helium includes a first processing zone including a first acid gas removal unit, a second processing zone including a second acid gas removal unit, a third processing zone, and a helium purification unit.

Device and method for purifying a gas mixture to produce a concentrated gas, notably neon, starting from a mixture comprising neon, said device including, in a cold box housing a cryogenic purification circuit comprising, in series, at least one unit for purifying the mixture by cryogenic adsorption at a temperature between 65K and 100K and notably 65K, then a unit for cooling the mixture to a temperature between 25 and 65 K and then a unit for cryogenic distillation of the mixture to produce the concentrated liquid at the outlet of the cryogenic distillation unit, characterized in that the unit for cooling the mixture to a temperature between 25 and 65 K comprises at least one cryocooler that extracts thermal power from the mixture via a heat exchanger.

A process for the separation of the components of a gas mixture to be treated comprising methane, nitrogen and at least one hydrocarbon having at least two carbon atoms, or a mixture of these hydrocarbons, including introducing the gas mixture to be treated into a first distillation column thereby producing, at the column top, a first gas stream enriched in methane and, at a level lower than that of the top of the column, another gas stream; and introducing the other gas stream resulting from step a) into a second distillation column, at a level lower than that of that of the top of the second column, thereby producing, at the top of this column, a second gas stream rich in methane.