Described herein are systems and processes for precooling hydrogen or helium gas streams for liquefaction using liquid nitrogen having reduced energy consumption and amount of liquid nitrogen usage. The systems include a stream of pressurized liquid nitrogen, at least one turboexpander, and at least one heat exchanger.

A method for converting excess liquid oxygen into liquid nitrogen, including introducing a gaseous nitrogen stream into a main heat exchanger, therein exchanging heat with a vaporized oxygen stream, a vapor phase nitrogen steam, and a waste liquid nitrogen stream; thereby producing a cold gaseous nitrogen stream, an oxygen vent stream, a nitrogen vent steam, and a gaseous nitrogen waste stream, introducing the cold gaseous nitrogen stream into a secondary heat exchanger, therein exchanging heat with a liquid oxygen stream; thereby producing the vaporized oxygen stream and a cold liquid nitrogen stream, introducing the cold liquid nitrogen stream into a nitrogen pressure reduction valve thereby producing a two-phase nitrogen stream, introducing the two-phase nitrogen stream into a nitrogen flash vessel thereby producing a liquid phase nitrogen stream and the vapor phase nitrogen stream, wherein the method is performed in the absence of refrigerant turbo-expanders, refrigerant expansion turbines, or refrigerant compressors.

An apparatus for converting excess liquid oxygen into liquid nitrogen, including a main heat exchanger to exchange heat between a gaseous nitrogen stream, a vaporized oxygen stream, a vapor phase nitrogen steam, and a waste liquid nitrogen stream; thereby producing a cold gaseous nitrogen stream, an oxygen vent stream, a nitrogen vent steam, and a gaseous nitrogen waste stream, a secondary heat exchanger to exchange heat between a liquid oxygen stream and the cold gaseous nitrogen stream; thereby producing the vaporized oxygen stream and a cold liquid nitrogen stream, a nitrogen pressure reduction valve to reduce the pressure of the cold liquid nitrogen stream; thereby producing a two-phase nitrogen stream, a nitrogen flash vessel to receive the two-phase nitrogen stream, and to generate a liquid phase nitrogen stream and a vapor phase nitrogen stream, wherein the apparatus does not include any refrigerant turbo-expanders, refrigerant expansion turbines, or refrigerant compressors.

A moderate pressure nitrogen and argon producing cryogenic air separation unit is provided that includes a three distillation column system and turbine air stream bypass arrangement or circuit. The turbine air stream bypass arrangement or circuit is configured to improve argon and nitrogen recoveries in select operating modes by optionally diverting a portion of the turbine air stream to a nitrogen waste stream circuit drawn from the lower pressure column of the cryogenic air separation unit such that the diverted portion of the turbine air stream bypasses the distillation column system.

A liquefaction apparatus that automatically adjusts the load on the liquefaction apparatus correspondingly with an upper limit value of contracted power in different time slots, and which is capable of maximizing the amount of liquefied product produced and of achieving optimum operating efficiency is provided. In certain embodiments, the liquefaction apparatus can include: a production amount calculation unit 91 for obtaining an actual production amount of a liquefied product; a predicted power calculation unit 92 for obtaining a predicted power amount after a predetermined time has elapsed, on the basis of an integrated power value obtained by integrating a usage power; and a power demand control unit 93 for comparing the predicted power amount and a moving average of instantaneous power, and controlling a discharge flow rate of a compressor 3 in such a way as to come infinitely close to a target value, without exceeding the target value, and while using the larger value of the predicted power amount and the moving average of instantaneous power as a value being controlled.

A method and system for liquefying a natural gas feed stream and removing nitrogen therefrom.

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.

A moderate pressure air separation unit and air separation cycle is disclosed that provides for up to about 96% recovery of argon, an overall nitrogen recovery of 98 percent or greater and limited gaseous oxygen production. The air separation is configured to produce a first high purity oxygen enriched stream and a second lower purity oxygen enriched stream from the lower pressure column, one of which is used as the refrigerant to condense the argon in the argon condenser, with the resulting vaporized oxygen stream used to regenerate the temperature swing adsorption pre-purifier unit. All or a portion of the first high purity oxygen enriched stream is vaporized in the main heat exchanger to produce the gaseous oxygen products.

A moderate pressure, argon and nitrogen producing cryogenic air separation unit and air separation cycle having a higher pressure column, a lower pressure column and an argon column arrangement is disclosed. The moderate pressure, argon and nitrogen producing cryogenic air separation unit is configured to take a first portion of an oxygen enriched stream from the lower pressure column, which together with an external source of liquid nitrogen is used as the boiling side refrigerant to condense the argon in the argon condenser. Use of the external source of liquid nitrogen in the argon condenser allows a second portion of the oxygen enriched stream from the lower pressure column to be taken as a liquid oxygen product stream.

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.