A low cost and efficient design is used to convert a propane recovery process based on low nitrogen content feed gas to an ethane recovery process based on a high nitrogen feed gas while achieving over 95 mole % ethane recovery while maintaining a 99% propane recovery, and achieved without additional equipment.

Provided are an apparatus and a method for separation and recovery of propane and heavier hydrocarbons from LNG. The apparatus has, from the upstream side toward the downstream side of LNG supply, first column (3) equipped with first column overhead condenser (2), first column bottom reboiler (4) and side reboiler (5), and second column (14) equipped with second column overhead condenser (11) and second column bottom reboiler (15). The first column (3) separates methane and a part of ethane as an overhead vapor and separates remaining ethane and C3 or higher hydrocarbons as a bottom liquid. The second column (14) separates ethane as an overhead vapor and separates C3 or higher hydrocarbons as a bottom liquid.

An improved method for separating hydrocarbons for separating feed LNG into product LNG and a liquid fraction enriched in C3+ components is provided. Feed LNG is heated and partially vaporized by a heat exchanger to obtain a vapor-liquid two-phase stream; the whole or a liquid phase of the vapor-liquid two-phase stream is separated into first overhead vapor enriched in methane and first bottom liquid enriched in ethane and C3+ components at a first distillation column; the first bottom liquid is separated into second overhead vapor enriched in ethane and second bottom liquid enriched in C3+ components by the second distillation column; the second overhead vapor is cooled and wholly or partially condensed to obtain condensed liquid; one of two or more streams obtained by dividing the condensed liquid is mixed with the first overhead vapor; the mixed stream is totally condensed to obtain a liquid stream by heat exchange with feed LNG by the heat exchanger; the whole or a part of the liquid stream is discharged as product LNG; another of the divided streams is refluxed to the second distillation column; and the second bottom liquid is discharged as the liquid fraction enriched in C3+ components.

Embodiments relate generally to systems and methods for operating a natural gas liquids plant in ethane rejection and in ethane recovery. A natural gas liquid plant may comprise an absorber configured to produce an ethane rich bottom stream and an ethane depleted vapor stream; a stripper fluidly coupled to the absorber configured to, during ethane rejection, fractionate the ethane rich bottom stream from the absorber into an ethane overhead product and a propane plus hydrocarbons product, and configured to, during ethane recovery, fractionate the ethane rich bottom stream into an ethane plus NGL stream and an overhead vapor stream; and an exchanger configured to, during ethane recovery, counter-currently contact the ethane rich bottom stream from the absorber with the ethane depleted vapor stream from the absorber, thereby heating the vapor stream and chilling the ethane rich bottom stream before the ethane rich bottom stream is fed to the stripper.

A system for liquefying a gas includes a liquefaction heat exchanger having a feed gas inlet adapted to receive a feed gas and a liquefied gas outlet through which the liquefied gas exits after the gas is liquefied in the liquefying passage of the heat exchanger by heat exchange with a primary refrigeration passage. A mixed refrigerant compressor system is configured to provide refrigerant to the primary refrigeration passage. An expander separator is in communication with the liquefied gas outlet of the liquefaction heat exchanger, and a cold gas line is in fluid communication with the expander separator. A cold recovery heat exchanger receives cold vapor from the cold gas line and liquid refrigerant from the mixed refrigerant compressor system so that the refrigerant is cooled using the cold vapor.

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.

A method for separating nitrogen from an inlet gas having less than 25 mole % nitrogen includes supplying the inlet gas having less than 25 mole % nitrogen to a nitrogen separation system configured with cryogenic refrigeration.

The invention relates to a process and device for the cryogenic separation of a methane-containing feed gas predominantly consisting of hydrogen and carbon monoxide, that is partially condensed in this case by cooling, in order to obtain a hydrogen-containing first liquid phase predominantly consisting of carbon monoxide and methane, from which first liquid phase, in an H.sub.2 separation column that is heated via a circulation heater, a second liquid phase is generated by separating off hydrogen, from which second liquid phase, in a CO/CH.sub.4 separation column, a carbon monoxide-rich gas phase is obtained having a purity that permits release thereof as carbon monoxide product. It is characteristic in this case that a low-methane material stream is withdrawn from the H.sub.2 separation column and is then applied to the CO/CH.sub.4 separation column as reflux.

A method to pre-treat an inlet natural gas stream at gas pressure reduction stations to produce LNG removes water and carbon dioxide from a natural gas stream. The energy required for the process is provided by recovering pressure energy in the inlet gas stream. The process eliminates the conventional gas pre-heating process at pressure reductions stations employing gas combustion heaters. The process provides a method to produce LNG at natural gas pressure reduction that meets product specifications.

A system and method for argon and nitrogen extraction and liquefaction from a low-pressure tail gas of an ammonia production plant is provided. The preferred tail gas of the ammonia production plant comprises methane, nitrogen, argon, and hydrogen. The disclosed system and method provides for the methane rejection via rectification and hydrogen rejection by way of a side stripper column or phase separator. The resulting nitrogen and argon containing stream is separated and liquefied in a double column distillation system.