A method for producing liquid nitrogen using a residual gas stream derived from a flue gas of a power plant is provided. The residual gas stream is purified in a front-end purification unit to remove freezable components and then the purified stream is compressed. Following compression, the stream can be divided into a first portion and a second portion, wherein the first portion is cooled and sent to a distillation column, wherein oxygen and argon are separated, thereby leaving an essentially pure gaseous nitrogen stream. The gaseous nitrogen stream can then be liquefied using refrigeration provided by expanding the second portion of the purified stream. In a preferred embodiment, the second portion is expanded in two turbines, and the gaseous nitrogen is compressed in a cold nitrogen booster, which is powered by one of the two turbines. In an additional embodiment, after warming, the expanded second portion of the purified stream can be used to regenerate the front-end purification unit.

Disclosed techniques include controlled liquefaction and energy management. A gas within a first pressure containment vessel is pressurized using a column of liquid. The gas that is being pressurized is cooled using a liquid spray, wherein the liquid spray is introduced into the first pressure containment vessel in a region occupied by the gas. The liquid spray keeps the pressurizing to be isothermal. The gas that was pressurized is metered into a second pressure containment vessel, wherein the metering enables liquefaction of the gas. The gas that was pressurized is stored in a gas capacitor prior to the metering. The gas that was liquefied in the second pressure containment vessel is pushed into a holding tank, wherein the holding tank stores a liquefied state of the gas, and wherein the pushing is accomplished by the pressure of the gas that was metered into the second pressure containment vessel.

A solvent is dispersed into a natural gas feed at a solvent injection point to produce a mixed feed. The mixed feed contains heavy components with a potentially fouling portion that can cause obstructions in a heat exchanger. A fluid injection system can inject the solvent intermittently, for instance, based on an amount of accumulation or expected accumulation of heavy component solids in the heat exchanger. The solvent prevents the potentially fouling portion of the heavy components from freezing, melts or dissolves the accumulation, and reduces the obstructions in the heat exchanger. The fluid injection system includes a solvent supply, an optional atomizer, an injection controller, optionally one or more sensors, and/or optionally a heater. The solvent injection system can disperse the solvent onto a flow surface for the natural gas feed and/or mixed feed to form a solvent film which further reduces heavy component solids.

The invention relates to a cooling system (1) comprising at least: a Stirling heat pump (2) designed to cool an inlet gas (G.sub.e) down to a cryogenic temperature so as to form a cryogenic liquid (L), a primary electric motor (3), intended to put said Stirling heat pump (2) into operation, a primary pump (4) intended to cause said cryogenic liquid (L) to circulate under pressure, and a cooling means (5) intended to cool said primary electric motor (3) with the aid of the cryogenic liquid (L) output by said primary pump (4). The invention is particularly suitable for the production of a cryogenic liquid and the applications thereof.

A photoelectric hydrogen production energy storage and cold energy recovery coupled dry ice production device and a use method are disclosed. The device comprises a photoelectric conversion liquid hydrogen energy storage unit, photoelectricity participates in electrolysis of water in the storage unit to prepare hydrogen, and surplus hydrogen meeting downstream process requirements is liquefied in the unit; liquid hydrogen is output, so that intermittent photoelectric energy is converted into hydrogen energy to be stored. When hydrogen production through electrolysis of water is insufficient but industrial hydrogen is continuously used, high-grade and low-grade cold energy of low-temperature liquid hydrogen serving as cold sources in the unit is recovered from industrial tail gas purified CO.sub.2 and air separation nitrogen, liquid nitrogen and liquid CO.sub.2 are output and used for the storage unit and dry ice production respectively, and the liquid hydrogen is reheated and supplied to a downstream process.

The present invention is a modification of a typical single mixed refrigerant (SMR) cycle for LNG re-liquefaction in particular, that allows the use of a cost-efficient oil-injected screw compressor in the mixed refrigerant system. In comparison with the typical arrangement, the present innovation allows for reduced complexity, fewer pieces of equipment, and reduced capital cost. There is shown a method of cooling a boil-off gas (BOG) stream from a liquefied gas tank using a single mixed refrigerant (SMR) comprising at least the step of heat exchanging the BOG stream with the SMR in a liquefaction heat exchanger system to provide a cooled BOG stream, wherein the SMR is provided in an SMR recirculating system comprising at least the steps of: (a) compressing the SMR using at least one oil-injected screw compressor to provide a post-compression SMR stream; (b) separating the post-compression SMR stream to provide an oil-based stream and a first SMR vapour stream; (c) passing the first SMR vapour stream into the liquefaction heat exchanger system to cool the first SMR vapour stream and provide a cooled first SMR vapour stream; (d) withdrawing the cooled first SMR vapour stream from the liquefaction heat exchanger system; (e) separating the cooled first SMR vapour stream to provide a liquid-phase SMR stream and an oil-free SMR vapour stream; (f) passing the oil-free SMR vapour stream through the liquefaction heat exchanger system to provide a condensed SMR stream; and (g) expanding the condensed SMR stream to provide an expanded lowest-temperature SMR stream to pass through the liquefaction heat exchanger system for heat exchange against the BOG stream.

A system and method for producing liquefied natural gas (LNG) from a natural gas stream. Each of a plurality of LNG trains liquefies a portion of the natural gas stream to generate a warm LNG stream in a first operating mode, and a cold LNG stream in a second operating mode. A sub-cooling unit is configured to, in the first operating mode, sub-cool the warm LNG streams to thereby generate a combined cold LNG stream. The warm LNG streams have a higher temperature than a temperature of the cold LNG streams in the second operating mode and the combined cold LNG stream. The combined cold LNG stream has, in the first operating mode, a higher flow rate than the flow rate of the cold LNG streams in the second operating mode.

Methods and apparatus are disclosed for efficient cooling within air liquefaction processes with integrated use of cold recycle from a thermal energy store.

Methods and apparatus are disclosed for efficient cooling within air liquefaction processes with integrated use of cold recycle from a thermal energy store.

Disclosed is a BOG reliquefaction system. The BOG reliquefaction system includes: a compressor compressing BOG; a heat exchanger cooling the BOG compressed by the compressor through heat exchange using BOG not compressed by the compressor as a refrigerant; a pressure reducer disposed downstream of the heat exchanger and reducing a pressure of fluid cooled by the heat exchanger; and a second oil filter disposed downstream of the pressure reducer, wherein the compressor includes at least one oil-lubrication type cylinder and the second oil filter is a cryogenic oil filter.