A system for cooling a gas includes a pre-cool heat exchanger and a liquefaction heat exchanger. The pre-cool heat exchanger uses a pre-cool refrigerant to pre-cool a feed gas stream prior to the stream being directed to a liquefaction heat exchanger. The liquefaction heat exchanger uses a mixed refrigerant to further cool the pre-cooled gas. The pre-cool heat exchanger also pre-cools the liquefaction mixed refrigerant used by the liquefaction heat exchanger.

A system and method for producing liquefied natural gas from a natural gas source is provided. The method may include feeding natural gas provided by the natural gas source to a liquefaction module. The method may also include flowing the natural gas through a product stream of the liquefaction module. The method may further include flowing a process fluid through a liquefaction stream of the liquefaction module to cool at least a portion of the natural gas flowing through the product stream to produce the liquefied natural gas.

A refrigeration system for use in petrochemical plants, such as an ethylene production plant includes a refrigerant vent rectifier. The rectifier purifies the refrigerant by removing low molecular weight inerts. The refrigeration system is more efficient, consumes less energy and increases plant capacity.

Processes for purifying and liquefying natural gas in conjunction and integration with cryogenic processing natural gas to recover natural gas liquids (NGL) is disclosed. In the process, the natural gas stream to be purified and liquefied is taken from top outlet stream of demethanizer in the cryogenic NGL recovery plant, first purified and then cooled under moderate pressure to condense it as a liquefied natural gas (LNG) product stream. Some of the cooling required for the demethanizer reflux stream is provided by natural gas liquefaction section before supplied to top of the column to serve as reflux. The top outlet stream from the demethanizer preferentially contains up to 3 mole percent of CO.sub.2 and the majority of methane and small portion of any hydrocarbon heavier than methane, a split portion of this stream is taken and routed to cryogenic CO.sub.2 removal section, in which a molecular sieve that forms a physical adsorption column is used to extract pure CO.sub.2 as a product stream, then purified stream is routed to the liquefaction section where only two stages of coil-wound exchangers with a Semi-C3-MR cycle are used to liquefy natural gas. This present invention process is suited for LNG production in small-scale. This zeolite-based small-scale LNG process can be integrated with the design of any new natural gas facility and the technology can also be retrofitted to existing natural gas liquid (NGL) recovery plants, allowing for co-production of LNG and CO.sub.2 with high purity.

A system and method for liquefaction of a natural gas stream utilizing a plurality of asymmetric parallel pre-cooling circuits. The use of asymmetric parallel cooling circuits allows for greater control over each refrigerant stream during the cooling process and simplifies process control by dedicating heat exchangers to performing similar duties.

A gas recovery system separates a mixed gas including a process gas and an inert gas. The gas recovery system includes a cooling section for cooling and liquefying the process gas contained in the mixed gas by cooling the mixed gas at a temperature higher than a condensation temperature of the inert gas and lower than a condensation temperature of the process gas, a separating section for separating the cooled mixed gas into the process gas in a liquid state and the inert gas in a gas state, and a process gas recovery line that is connected to the separating section which circulates and gasifies the liquid-state process gas and then supplies the process gas into the a compressor. The mixed gas is formed by mixing the process gas, which is compressed by the compressor, and the inert gas, which is supplied to a seal portion of the compressor.

A system and method for increasing the efficiency of natural gas liquefaction processes by using a hybrid cooling system and method. More specifically, a system and method for converting a transcritical precooling refrigeration process to a subcritical process. In one embodiment, the refrigerant is cooled to sub-critical temperature using an economizer. In another embodiment, the refrigerant is cooled to a sub-critical temperature using an auxiliary heat exchanger. Optionally, the economizer or auxiliary heat exchanger can be bypassed when ambient temperatures are sufficiently low to cool the refrigerant to a sub-critical temperature. In another embodiment, the refrigerant is isentropically expanded.

A system and method for increasing the efficiency of natural gas liquefaction processes by using a hybrid cooling system and method. More specifically, a system and method for converting a transcritical precooling refrigeration process to a subcritical process. In one embodiment, the refrigerant is cooled to sub-critical temperature using an economizer. In another embodiment, the refrigerant is cooled to a sub-critical temperature using an auxiliary heat exchanger. Optionally, the economizer or auxiliary heat exchanger can be bypassed when ambient temperatures are sufficiently low to cool the refrigerant to a sub-critical temperature. In another embodiment, the refrigerant is isentropically expanded.

A method and system for liquefying a methane-rich high-pressure feed gas stream using a system having first and second heat exchanger zones and a compressed refrigerant stream. The compressed refrigerant stream is cooled and directed to the second heat exchanger zone to additionally cool it below ambient temperature. It is then expanded and passed through the first heat exchanger zone such that it has a temperature that is cooler, by at least 5 F., than the highest fluid temperature within the first heat exchanger zone. The feed gas stream is passed through the first heat exchanger zone to cool at least part of it by indirect heat exchange with the refrigerant stream, thereby forming a liquefied gas stream. At least a portion of the first warm refrigerant stream is directed to the second heat exchanger zone to cool the refrigerant stream, which is compressed.

A method and system for liquefying a methane-rich high-pressure feed gas stream using a first heat exchanger zone and a second heat exchanger zone. The feed gas stream is mixed with a refrigerant stream to form a second gas stream, which is compressed, cooled, and directed to a second heat exchanger zone to be additionally cooled below ambient temperature. It is then expanded to a pressure less than 2,000 psia and no greater than the pressure to which the second gas stream was compressed, and then separated into a first expanded refrigerant stream and a chilled gas stream. The first expanded refrigerant stream is expanded and then passed through the first heat exchanger zone such that it has a temperature that is cooler, by at least 5 F., than the highest fluid temperature within the first heat exchanger zone.