Enhancements to a dual column, nitrogen producing cryogenic air separation unit are provided. Such enhancements include an improved air separation cycle that uses multiple condenser-reboilers and recycles a portion of the vapor from one or more of the condenser-reboilers to the incoming feed stream and or the compressed purified air streams to yield improvements in such dual column, nitrogen producing cryogenic air separation units. The multiple condenser-reboilers preferably include an integrated condenser-reboiler arrangement comprising a heat exchanger having a set of nitrogen condensing passages, a first set and second set of boiling passages, and a phase separator.

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.

A method for flexible production of argon from a cryogenic air separation unit is provided. The disclosed cryogenic air separation unit is capable of operating in a ‘no-argon’ or ‘low-argon’ mode when argon demand is low or non-existent and then switching to operating in a ‘high-argon’ mode when argon is needed. The recovery of the argon products from the air separation unit is adjusted by varying the percentages of dirty shelf nitrogen and clean shelf nitrogen in the reflux stream directed to the lower pressure column. The cryogenic air separation unit and associated method also provides an efficient argon production/rejection process that minimizes the power consumption when the cryogenic air separation unit is operating in a ‘no-argon’ or ‘low-argon’ mode yet maintains the capability to produce higher volumes of argon products at full design capacity to meet argon product demands.

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 system and method for argon production in an air separation plant facility or enclave having multiple cryogenic air separation units is provided. The present system and method include a centralized argon refining system disposed within one of the cryogenic air separation units and which is configured to include an argon superstaged or ultra-superstaged column arrangement having one or more argon columns and an argon condenser. Crude argon streams from one or more of the other cryogenic air separation units are directed to the argon superstaged or ultra-superstaged column arrangement of the centralized argon refining process.

An annular divided wall column for the cryogenic rectification of air or constituents of air is provided. The annular divided wall column includes a first annular column wall and a second annular column wall disposed within the first annular column wall to define an annulus column region and an interior core column region. The present annular divided wall column further includes structured packing elements disposed within at least the annulus column region as well as a ring-shaped cantilevered collector; and a ring-shaped distributor disposed in the annulus column region above or below the plurality of structured packing elements. The thermal expansion and contraction of the second annular column wall in a radial direction and in an axial direction is independent of the thermal expansion and contraction of the first annular column wall in the radial and axial directions.

An annular divided wall column is provided. The annular divided wall column includes a first annular column wall and a second annular column wall disposed within the first annular column wall and radially spaced therefrom to define an annulus column region as the space between the first annular column wall and the second annular column wall. An interior core column region is also defined by the interior space of the second annular column wall. The present annular divided wall column further includes a plurality of packing elements, disposed within the interior core column region within the annulus column region having different surface area densities and optionally, also have different geometries.

An annular divided wall column for the cryogenic rectification of air or constituents of air is provided. The annular divided wall column includes a first annular column wall and a second annular column wall disposed within the first annular column wall to define an annulus column region and an interior core column region. The present annular divided wall column further includes structured packing elements disposed within at least the annulus column region as well as a ring-shaped cantilevered collector; and a ring-shaped distributor disposed in the annulus column region above or below the plurality of structured packing elements. The thermal expansion and contraction of the second annular column wall in a radial direction and in an axial direction is independent of the thermal expansion and contraction of the first annular column wall in the radial and axial directions.

An annular divided wall column is provided. The annular divided wall column includes a first annular column wall and a second annular column wall disposed within the first annular column wall and radially spaced therefrom to define an annulus column region as the space between the first annular column wall and the second annular column wall. An interior core column region is also defined by the interior space of the second annular column wall. The present annular divided wall column further includes a plurality of packing elements, disposed within the interior core column region within the annulus column region having different surface area densities and optionally, also have different geometries.

An annular divided wall column for the cryogenic rectification of air or constituents of air is provided. The annular divided wall column includes a first annular column wall and a second annular column wall disposed within the first annular column wall and radially spaced therefrom to define an annulus column region as the space between the first annular column wall and the second annular column wall. An interior core column region is also defined by the interior space of the second annular column wall. The present annular divided wall column further includes a plurality of packing elements, plurality of trays or a heat exchange device disposed within the interior core column region; and a plurality of packing elements disposed within the annulus column region.