The disclosure describes processes which include cooling a natural gas product stream to a cryogenic liquid storage temperature by way of refrigeration streams which include a primary refrigeration stream, a secondary refrigeration stream, and a tertiary refrigeration stream in a refrigeration system. After leaving the refrigeration system, the pressure of each refrigeration stream is increased, and upon reaching a sufficient pressure, the refrigeration streams are recycled to flow back into the refrigeration system as a recycle stream. The disclosure further describes systems capable of performing the processes. The processes and systems can include one or more sensors and one or more controls capable of adjusting a flow rate, flow volume, and/or flow ratio among one or more gas streams to maximize cooling efficiency based on monitoring from the one or more sensors. Mobile natural gas liquefaction systems are also described.

A process and apparatus integrate a deethanizer column with a cryogenic heat exchanger by reboiling the deethanizer column with a refrigerant stream and/or cooling a deethanizer overhead line in the cryogenic heat exchanger. A single stage separator and a single deethanizer column may be used to obtain high purity hydrogen in the net gas stream and an ethane rich off-gas stream, whereas conventionally a dual stage separator and two deethanizer columns were necessary for equivalent purity, respectively.

A process and apparatus reboil a propylene splitter bottoms by heat exchange and/or a deethanizer bottoms stream with a compressed propylene splitter overhead stream. Use of single splitter compressor and operation of the propane-propylene splitter column at lower pressure are enabled, whereas conventionally two splitter compressors and higher splitter pressure were necessary to provide a propylene product stream and a propane recycle stream of equivalent quality.

A process and an apparatus are disclosed for separation of a hydrocarbon gas stream containing methane and heavier hydrocarbons and significant quantities of nitrogen and carbon dioxide. The gas stream is cooled and expanded, then fractionated in a first distillation column into a first overhead vapor and a hydrocarbon liquid stream containing the majority of the carbon dioxide. The hydrocarbon liquid stream is fractionated into a hydrocarbon vapor stream and a less volatile fraction comprised of heavier hydrocarbons. The first overhead vapor is cooled, expanded, and separated into vapor and liquid streams. Both streams are cooled and expanded before feeding a second distillation column that produces a second overhead vapor that is predominantly nitrogen and a bottom liquid that is predominantly methane. The bottom liquid is vaporized and combined with the hydrocarbon vapor stream to form a volatile residue gas fraction containing the majority of the methane.

A process for producing biomethane by scrubbing a biogas feed stream includes introducing the feed gas stream into a pretreatment unit wherein a CO.sub.2-depleted gas stream is partially separated from a CO.sub.2 stream and an oxygen stream and is compressed to a pressure P1 above 25 bar abs. Subjecting the CO.sub.2-depleted gas stream to cryogenic separation in a distillation column to separate a nitrogen stream and produce a CH.sub.4-enriched stream, the distillation column comprising n plates, n being an integer between 8 and 100. Recovering a pressurized CH.sub.4-enriched stream by pumping the CO.sub.2-depleted gas stream to a pressure P2 above 25 bar absolute.

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.

In a propane dehydrogenation (PDH) process, the purpose of the deethanizer and chilling train systems is to separate the cracked gas into a methane-rich tail gas product, a C2, and a C3 process stream. By the use of staged cooling, process-to-process inter-change against propane feed to the reactor and use of high efficiency heat exchangers and distributed distillation techniques, refrigeration power requirements are reduced and a simple and reliable design is provided by the process described herein.

Plant and process for the production of liquid methane from a feed gas stream comprising at least methane and carbon dioxide. A feed gas stream is injected into a CO.sub.2 crystallizer in countercurrent fashion against a stream of predominantly liquid methane, thereby crystallizing amounts of carbon dioxide from the feed gas stream. Gaseous methane recovered from the CO.sub.2 crystallizer is liquefied at a liquefaction exchanger.

A system for natural gas cooling using nitrogen. The system can include a nitrogen liquefier and a natural gas cooler. The nitrogen liquefier can provide liquid nitrogen to the natural gas cooler. One or more heat exchangers of the natural gas cooler can include a gaseous nitrogen output that is in fluid communication with the nitrogen liquefier. In response to receiving gaseous nitrogen at the nitrogen liquefier, from the one or more heat exchangers, a production rate of the the nitrogen liquefier is adjusted.

A process for producing biomethane by scrubbing a biogas feed stream including introducing a feed gas stream into a pretreatment unit wherein the gas stream is partially separated from a CO.sub.2 stream and an oxygen stream, thereby producing a CO.sub.2-depleted gas stream, which is compressed, thereby producing a pressurized CO.sub.2-depleted gas stream; separating the pressurized CO.sub.2-depleted gas stream by cryogenic separation by introducing the pressurized CO.sub.2-depleted gas stream into a distillation column thereby producing a nitrogen stream and a CH.sub.4-enriched stream, recovering a pressurized CH.sub.4-enriched stream by pumping the CH.sub.4-enriched stream; wherein the separation of the CO.sub.2 stream and the oxygen stream from the feed gas stream is performed by a unit comprising at least two separating membrane stages in order that the CO.sub.2-depleted gas stream comprises between 0.3 mol % and 2 mol % of CO.sub.2.