A process and an apparatus are disclosed for the recovery of components from a hydrocarbon gas stream which is divided into first and second streams. The first stream is cooled, expanded to lower pressure, and supplied to a fractionation tower. The second stream is cooled and separated into vapor and liquid streams. The vapor stream is divided into two portions. A first portion is cooled, expanded to tower pressure, and supplied to the tower at an upper mid-column feed position. The second portion and the liquid stream are expanded to tower pressure and supplied to the tower. After heating, compressing, and cooling, a portion of the tower overhead vapor is cooled, expanded, and supplied to the tower at the top feed position. The quantities and temperatures of the feeds to the tower maintain the overhead temperature of the tower whereby the major portion of the desired components is recovered.

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.

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 process and an apparatus are disclosed for a compact processing assembly to improve the recovery of C.sub.2 (or C.sub.3) and heavier hydrocarbon components from a hydrocarbon gas stream. The preferred method of separating a hydrocarbon gas stream generally includes producing at least a substantially condensed first stream and a cooled second stream, expanding both streams to lower pressure, and supplying the streams to a fractionation tower. In the process and apparatus disclosed, the tower overhead vapor is directed to an absorbing means and a heat and mass transfer means inside a processing assembly. A portion of the outlet vapor from the processing assembly is compressed to higher pressure, cooled and substantially condensed in a heat exchange means inside the processing assembly, then expanded to lower pressure and supplied to the heat and mass transfer means to provide cooling. Condensed liquid from the absorbing means is fed to the tower.

A thermally integrated separation method, including exchanging heat indirectly between an inlet stream and a liquid carbon dioxide/NGL containing stream in a heat exchanger, thereby producing a cold inlet stream and a vaporized carbon dioxide/NGL containing stream, introducing the cold inlet stream into a cryogenic separation unit, thereby producing the liquid carbon dioxide/NGL containing stream and a methane-rich stream, introducing the methane-rich stream into a membrane separation unit, thereby producing a methane rich product stream, and a permeate stream, and introducing the vaporized carbon dioxide/NGL containing stream into a carbon dioxide/NGL separation unit, thereby producing a carbon dioxide rich product stream and a NGL rich product stream. Wherein, at least a portion of the liquid carbon dioxide/NGL containing stream bypasses the heat exchanger and is introduced into the carbon dioxide/NGL separation unit in liquid phase.

A process for liquefying a natural gas feed stream including cooling a feed gas stream to obtain a liquefied natural gas stream; introducing the liquefied natural gas stream into a deazotization column to produce a liquefied natural gas stream and a nitrogen-enriched vapor stream; at least partially condensing at least part of the nitrogen-enriched vapor stream to produce a two-phase stream; introducing the two-phase stream into a phase-separating vessel to produce a first liquid stream and a first nitrogen-enriched gas stream; introducing at least part of the nitrogen-enriched gas stream into a distillation column thereby producing a second nitrogen-enriched stream containing less than 1 mol % of methane and a second liquid stream containing less than 10 mol % of nitrogen; wherein at least part of the liquefied natural gas stream is used to cool the at least part of the nitrogen-enriched vapor stream in said heat exchanger.

A method and system for controlling the nitrogen concentration in an LNG product and fuel from flash gas within preferred ranges. A cooled LNG stream is separated into a nitrogen-enriched vapor stream, a fuel stream, and an LNG product stream using a plurality of phase separating devices, such as flash drum or rectifying column. A portion of the vapor stream is recycled to the rectifying column as reflux. A portion of a stream having a higher concentration of nitrogen is combined with the fuel stream to maintain the fuel stream within a desired nitrogen concentration range.

A design is provided to convert a gas subcooled process plant to a recycle split vapor process for recovering ethane and propane from natural gas. When in operation, the recovery of ethane and propane can exceed 97 to 99 wt. % of the stream being processed. A second smaller demethanizer column is added to the gas subcooled process plant as well as the addition of several cryogenic pumps.

Implementations described and claimed herein provide systems and methods for processing liquefied natural gas (LNG). In one implementation, a dry feed gas is received. The dry feed gas is chilled with clean vapor from a heavies removal column to form a chilled feed gas. The chilled feed gas is partially condensed into a vapor phase and a liquid phase. The liquid phase retains freezing components. The freezing components are extracted using a reflux stream in the heavies removal column. The freezing components are removed as a condensate. The vapor phase is compressed into a clean feed gas. The clean feed gas is free of the freezing components for downstream liquefaction.

A system and method for liquefaction of natural gas using two distinct refrigeration circuits having compositionally different working fluids and operating at different temperature levels is provided. The turbomachinery associated with the liquefaction system are driven by a single three-pinion or four-pinion integral gear machine with customized pairing arrangements. The system and method of natural gas liquefaction further includes the conditioning of a lower pressure natural gas containing feed stream to produce a purified, compressed natural gas containing stream at a pressure equal to or above the critical pressure of natural gas and substantially free of heavy hydrocarbons to be liquefied.