The invention relates to a method and device for obtaining compressed oxygen and compressed nitrogen by the low-temperature separation of air in a distillation column system for nitrogen-oxygen separation, said distillation column system having at least one high-pressure column (8) and one low-pressure column (460), wherein the low-pressure column (460) is in a heat-exchanging connection with the high-pressure column (8) by means of a main condenser (461) designed as a condenser-evaporator. Feed air is compressed in an air compressor (2). The compressed feed air (6, 734, 802, 840) is cooled down in a main heat exchanger (20) and at least partially introduced into the high-pressure column (8). An oxygen-enriched liquid (462, 465) is removed from the high-pressure column (8) and fed to the low-pressure column (460) at a first intermediate position (464, 467, 906). A nitrogen-enriched liquid (468, 470) is removed from the high-pressure column (8) and/or the main condenser (461) and fed to the head of the low-pressure column (460). A liquid oxygen flow (11, 12) is removed from the distillation column system for nitrogen-oxygen separation, brought to an elevated pressure in the liquid state (13), introduced into the main heat exchanger (20) at said elevated pressure, evaporated or pseudo-evaporated and heated to approximately ambient temperature in the main heat exchanger (20), and finally obtained as a gaseous compressed oxygen product (14). A high-pressure process flow (34, 734) is brought into indirect heat exchange with the oxygen flow in the main heat exchanger (20) and then depressurized (36, 38; 736, 738), wherein the depressurized high-pressure flow (37, 737) is introduced at least partially in the liquid state into the distillation column system for nitrogen-oxygen separation. A gaseous circuit nitrogen flow (18, 19) is drawn from the high-pressure column and at least partially (21) compressed in a circuit compressor (22). A first sub-flow (45, 46; 244, 242, 230; 845, 846) of the circuit nitrogen flow is removed from the circuit compressor (22, 322), cooled down in the main heat exchanger (20), at least partially condensed in the bottom evaporator (9, 209) of the high-pressure column (8) in indirect heat exchange with the bottom liquid of the high-pressure column (8), and conducted back into the distillation column system for nitrogen-oxygen separation. A second sub-flow of the circuit nitrogen flow is branched

The invention relates to a method for a low-temperature air separation in which an air separation unit is used comprising a first rectification column and a second rectification column. The first rectification column is operated at a first pressure level, and the second rectification column is operated at a second pressure level below the first pressure level. Fluid which is oxygen-enriched compared to atmospheric air is drawn from the first rectification column in the form of one or more first material flows. At least one fraction of the fluid which has been drawn from the first rectification column in the form of the one or more first material flows is heated in a heat exchanger; a fraction of the fluid which has been heated in the heat exchanger is compressed using a compressor and is returned to the first rectification column.

An air separation device according to the present invention is an air separation device in which air is distilled at a low temperature, and includes a high-pressure column which separates high-pressure raw material air into high-pressure nitrogen gas and high-pressure oxygen-enriched liquefied air; a low-pressure column which separates the high-pressure oxygen-enriched liquefied air into low-pressure nitrogen gas, low-pressure liquefied oxygen, and argon-enriched liquefied oxygen; an argon column which separates the argon-enriched liquefied oxygen having a pressure higher than the pressure into argon gas and medium-pressure liquefied oxygen; a first indirect heat-exchanger which heat-exchanges between the argon gas and the low-pressure liquefied oxygen; a second indirect heat-exchanger which heat-exchanges between the high-pressure nitrogen gas and the medium-pressure liquefied oxygen; a first gas-liquid separation chamber which separates the low-pressure oxygen gas which has been vaporized by the first indirect heat-exchanger and the low-pressure liquefied oxygen which has not been vaporized; a second gas-liquid separation chamber which separates the medium-pressure oxygen gas which has been vaporized by the second indirect heat-exchanger and the medium-pressure liquefied oxygen which has not been vaporized; a first passage which communicates the gas phase of the low-pressure column and the gas phase of the second gas-liquid separation chamber; a second passage which communicates the liquid phase of the low-pressure column and the second gas-liquid separation chamber; a first opening/closing mechanism located on the first passage; and a second opening/closing mechanism located on the second passage.

An apparatus for the separation of air by cryogenic distillation comprises three columns, including two concentric columns, the external diameter of the third column being at most equal to that of the second distillation column, a pipe for feeding the third column with air, a reflux pipe connected to an intermediate level of the upper section of the first distillation column in order to withdraw a liquid enriched in nitrogen, the pipe being connected to the head of the second distillation column and passing through a region of the third column devoid of heat exchange means and of mass exchange means, and an intermediate pipe for withdrawing a liquid at an intermediate level of the first distillation column.

A method and apparatus for producing high-purity nitrogen and low-purity oxygen using three-column rectification are provided, in which: nitrogen and oxygen undergo rectification in different columns, with high-purity nitrogen and low-purity oxygen being separated out of air simultaneously, thereby overcoming the shortcomings of conventional low-purity oxygen production equipment, and also reducing equipment investment, lowering energy consumption, increasing product added value, and realizing a circular economy effect.

In a method for separating air by cryogenic distillation, cooled air purified to remove water is sent to a first column operating at a first pressure, where it is separated into a nitrogen-enriched gas as an oxygen-enriched liquid; a gas enriched in argon relative to the air is withdrawn from the second column; at least a portion of the oxygen-enriched liquid is vaporized by heat exchange with the argon-enriched gas; and the vaporized, oxygen-enriched liquid is sent to an intermediate level of the second column.

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 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 process comprises a first set of distillation columns and a second set of distillation columns, a low-pressure column of the first set being connected to a column operating at higher pressure of the second set by means of a gas arriving from the top of the column operating at a higher pressure and/or by means of a fluid arriving from the low-pressure column.

An air separation unit and associated method for separating air by cryogenic distillation using a distillation column system including a higher pressure column, a lower pressure column, an intermediate pressure kettle column, and an argon column arrangement is provided. The disclosed air separation unit and method is particularly suited for production of an argon product as well as several nitrogen products wherein a portion of the nitrogen overhead intermediate pressure kettle column is taken as an intermediate or elevated pressure nitrogen product. The present air separation unit and associated method employs a once-through kettle column reboiler, a once-through kettle column condenser while the argon condenser condenses an argon-rich vapor stream against a pumped oxygen stream from the bottom of the lower pressure column.