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.

Systems, devices, and methods for recovering mixed refrigerant and/or nitrogen within liquefaction systems are provided. The systems, devices, and methods facilitate recovering mixed refrigerant (MR) and/or nitrogen vapor that can leak from a compressor, separating the MR from the nitrogen, and reusing the MR and/or the nitrogen within the liquefaction system. Recovering and reusing MR and/or nitrogen can minimize loss of MR and nitrogen which can lower the total operating cost of a liquefaction system. Additionally, recovering the MR, rather than burning it, can reduce environmental emissions by reducing the amount of MR that is burned.

Methods and systems for removing moisture from a refrigerant can utilize a desiccant-based system. The methods and systems can be employed in conjunction with a liquid natural gas (LNG) refrigeration circuit in either an online mode or an offline mode. For example, a system for removing moisture from a refrigerant can include: a refrigerant source; a moisture removal unit containing desiccant; and a refrigeration circuit comprising a refrigerant compressor, a refrigerant condenser, and a heat exchanger that are fluidly connected in a loop, wherein the refrigerant source is fluidly coupled to the moisture removal unit to supply a refrigerant from the refrigerant source to the moisture removal unit, and the moisture removal unit is fluidly coupled to the refrigeration circuit to supply the refrigerant from the moisture removal unit to the refrigeration circuit.

Described herein is a method of removing refrigerant from a natural gas liquefaction system in which vaporized mixed refrigerant is withdrawn from the closed-loop refrigeration circuit and introduced into a distillation column so as to be separated into an overhead vapor enriched in methane and a bottoms liquid enriched in heavier components. Overhead vapor is withdrawn from the distillation column to form a methane enriched stream that is removed from the liquefaction system, and bottoms liquid is reintroduced from the distillation column into the closed-loop refrigeration circuit. Also described are methods of altering the rate of production in a natural gas liquefaction system in which refrigerant is removed as described above, and a natural gas liquefaction systems in which such methods can be carried out.

The present invention pertains to a cooling method for liquefying a feed gas, comprising the steps of providing a cooling cycle with a refrigerant stream; dividing the refrigerant stream into a first partial stream and a second partial stream; expanding the first partial stream in a first expansion device; and transferring cooling energy from the expanded first partial stream to a feed gas stream to be cooled, particularly comprising hydrogen and/or helium. Further the method comprises the steps of guiding the expanded first partial stream to a suction inlet of an ejector; and guiding the second partial stream to a propellant inlet of the ejector such that, upon expanding the second partial stream in the ejector, the expanded first partial stream is compressed and merged with the expanded second partial stream.

The present invention relates to a refrigerant composition. According to the invention it is envisioned that the composition comprises comprising an inert gas selected from nitrogen, argon, neon and a mixture thereof, and a mixture of at least two C.sub.1-C.sub.5 hydrocarbons. The present invention further relates to the use of the refrigerant composition in a method for liquefying a gaseous substance, particularly hydrogen or helium.

Provided are an apparatus and method for liquefying natural gas. The apparatus for liquefying natural gas includes a gas compressor configured to receive and compress the natural gas from a natural gas feed stream, a heat exchanging unit configured to cool a high-pressure natural gas passing through the gas compressor through heat exchange, an expansion valve configured to expand the cooled natural gas passing through the heat exchanging unit, a hold-up drum configured to phase-separate a gas-liquid mixture produced by passing through the expansion valve and divide the gas-liquid mixture into a liquefied natural gas and a cryogenic recycle gas having nitrogen content greater than that of the liquefied natural gas so as to discharge the liquefied natural gas and the cryogenic recycle gas, and a bypass line configured to provide the recycle gas discharged from the hold-up drum to the heat exchanging unit.

A method of operating, during an at least partial shutdown of a refrigerant distribution subsystem in a natural gas liquefaction facility, can include: draining down at least a portion of a mixed refrigerant in one or more components of the refrigerant distribution subsystem into a high-pressure holding tank of a drain down subsystem, wherein draining down to the high-pressure holding tank is achieved by pumping the mixed refrigerant from the refrigerant distribution subsystem to the high-pressure holding tank or backfilling the refrigerant distribution subsystem with a backfill gas; and optionally, transferring at least a portion of the mixed refrigerant into a low-pressure drum from the high-pressure holding tank.

Described herein are systems and processes of removing contaminants in a liquid nitrogen (LIN) stream used to produce liquefied natural gas (LNG). Greenhouse gas contaminants are removed from the LIN using a greenhouse gas removal unit. The LNG is compressed prior to being cooled by the LIN.

A technology liquefies natural gas. The natural gas liquefaction method pre-cools treated natural gas by ethane evaporation, sub-cools liquefied gas using cooled nitrogen as a refrigerant, reduces liquefied gas pressure, separates non-liquefied gas and diverts liquefied natural gas. Before pre-cooling the natural gas is compressed, ethane is evaporated during the multi-stage pre-cooling of liquefied gas with simultaneous evaporation of ethane using cooled ethane as a refrigerant. Ethane generated by evaporation is compressed, condensed and used as a refrigerant during the cooling of liquefied gas and nitrogen, with nitrogen being compressed, cooled, expanded and fed to the natural gas sub-cooling stage. The natural gas liquefaction unit contains a natural gas liquefaction circuit, an ethane circuit and a nitrogen circuit. The natural gas liquefaction circuit includes a natural gas compressor, a cooler unit, ethane vaporizers, a closed-end subcooling heat exchanger, and a separator, connected in series.