INTEGRATED MULTICOMPONENT REFRIGERANT AND AIR SEPARATION PROCESS FOR PRODUCING LIQUID OXYGEN

Abstract

A process for the production of a liquid oxygen stream by the cryogenic rectification of an inlet air stream, including dividing the inlet air stream into a first portion, and a second portion. Cooling the first portion, and the second portion against a cooled multicomponent refrigerant circuit, thereby producing a first cooled portion, and a second cooled portion. Condensing the first cooled portion, thereby producing a condensed first portion, then introducing the condensed first portion into one or more distillation columns. Expanding the second cooled portion in a turbo-expander, thereby producing an expanded second portion, then introducing the expanded second portion within the one or more distillation columns. Producing within the one or more distillation columns at least a waste nitrogen stream, a nitrogen enriched stream, and an oxygen enriched stream. Withdrawing the oxygen enriched stream from the one or more distillation columns as a liquid oxygen stream.

Claims

1. A process for the production of a liquid oxygen stream by the cryogenic rectification of an inlet air stream, comprising: cooling an inlet air stream against a cooled multicomponent refrigerant circuit, thereby producing a cooled air stream, and splitting the cooled air stream into at least a first cooled portion, and a second cooled portion, the multicomponent refrigerant circuit comprising: compressing a multicomponent refrigerant stream, thereby producing a pressurized multicomponent refrigerant stream, cooling the pressurized multicomponent refrigerant stream, thereby producing a cooled multicomponent refrigerant stream, expanding the cooled multicomponent refrigerant stream, thereby producing an expanded multicomponent refrigerant stream, and warming the expanded multicomponent refrigerant stream by indirect heat exchange with the compressed multicomponent refrigerant stream and with the first portion, and the second portion, condensing the first cooled portion, thereby producing a condensed first portion, then introducing at least a portion of the condensed first portion into one or more distillation columns, expanding at least a portion of the second cooled portion in a turbo-expander, thereby producing an expanded second portion, then introducing at least a portion of the expanded second portion within the one or more distillation columns, producing within the one or more distillation columns at a nitrogen enriched stream, and an oxygen enriched stream, and withdrawing the oxygen enriched stream from the one or more distillation columns as a liquid oxygen stream.

2. The process of claim 1, wherein at least a portion of a nitrogen enriched stream is withdrawn from the one or more distillation columns as product liquid nitrogen.

3. The process of claim 1, wherein the multicomponent refrigerant stream comprises one or more of the following components: nitrogen, argon, methane, ethane ethylene, propane, butane, pentane, a fluorocarbon.

4. A process for the production of a liquid oxygen stream by the cryogenic rectification of an inlet air stream, comprising: dividing the inlet air stream into a first portion, a second portion, and a third portion, cooling at least a portion of the first portion, at least a portion of the second portion, and at least a portion of the third portion against a cooled multicomponent refrigerant circuit, thereby producing a first cooled portion, a second cooled portion, and a third cooled portion, the multicomponent refrigerant circuit comprising: compressing a multicomponent refrigerant stream, thereby producing a compressed multicomponent refrigerant stream, cooling the compressed multicomponent refrigerant stream, thereby producing a cooled multicomponent refrigerant stream, expanding the cooled multicomponent refrigerant stream, thereby producing an expanded multicomponent refrigerant stream, and warming the expanded multicomponent refrigerant stream by indirect heat exchange with the compressed multicomponent refrigerant stream and with the first portion, the second portion, and the third portion, condensing the first cooled portion, thereby producing a condensed first portion, then introducing at least a portion of the expanded first portion into one or more distillation columns, expanding at least a portion of the second cooled portion in a turbo-expander, thereby producing an expanded second portion, then introducing at least a portion of the expanded second portion into the one or more distillation columns, introducing at least a portion of the third cooled portion into one or ore distillation columns producing within the one or ore distillation columns at least a nitrogen enriched stream and an oxygen enriched stream, and withdrawing the oxygen enriched stream from the one or more distillation columns as a liquid oxygen stream.

5. The process of claim 4, wherein at least a portion of a nitrogen enriched stream is withdrawn from the one or more distillation columns as product liquid nitrogen.

6. The process of claim 4, wherein the multicomponent refrigerant stream comprises one or more of the following components: nitrogen, argon, methane, ethane ethylene, propane, butane, pentane, a fluorocarbon.

7. The process of claim 4, further comprising a booster air compressor, wherein the booster air compressor increases the pressure of at least a portion of the first portion and the second portion.

8. A process for the production of liquid oxygen by the cryogenic rectification of an inlet air stream, comprising: compressing at least a portion of the inlet air stream in a main air compressor to a pressure greater than 10 bara, thereby producing a compressed inlet air stream, removing water and carbon dioxide from the compressed inlet air stream, thereby forming a purified inlet air stream, boosting at least a portion of the purified inlet air stream in a booster driven by a turbo-expander, thereby producing a boosted inlet air stream, cooling at least a portion of the boosted inlet air stream, thereby producing a cooled boosted inlet air stream, splitting at least a portion of the cooled boosted inlet air stream into a first boosted inlet air stream and a second boosted air stream, liquefying at least a portion of the first boosted inlet air stream, thereby producing a liquefied inlet air stream, which is then introduced into the distillation column, expanding at least a portion of the second boosted air stream in one or more turbo-expanders, thereby producing an expanded air stream, which is then introduced into a distillation column, compressing a multicomponent refrigerant stream, thereby producing a compressed multicomponent refrigerant stream, cooling the compressed multicomponent refrigerant fluid, thereby producing a cooled multicomponent refrigerant stream, expanding the cooled multicomponent refrigerant stream, thereby producing an expanded multicomponent refrigerant stream, warming the expanded multicomponent refrigerant stream by indirect heat exchange with the compressed multicomponent refrigerant stream and with the boosted inlet air stream to produce the cooled boosted inlet air stream, producing in the one or more distillation columns a nitrogen enriched stream and an oxygen enriched stream, and withdrawing the oxygen enriched stream from the one or more distillation columns as a liquid oxygen stream.

9. The process of claim 8, wherein at least a portion of the inlet air stream is compressed in the main air compressor to a pressure of greater than 15 bara.

10. The process of claim 8, wherein at least a portion of the inlet air stream is compressed in the main air compressor to a pressure of greater than 20 bara.

11. The process of claim 8, wherein nitrogen enriched stream is withdrawn from the one or more distillation columns as product liquid nitrogen.

12. The process of claim 8, wherein the multicomponent refrigerant stream comprises one or more of the following components: nitrogen, argon, methane, ethane ethylene, propane, butane, pentane, a fluorocarbon.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0034] For a further understanding of the nature and objects for the present invention, reference should be made to the following detailed description, taken in conjunction with the accompanying drawings, in which like elements are given the same or analogous reference numbers and wherein:

[0035] FIG. 1 is a schematic representation of a combined multicomponent refrigerant cycle used with an air separation unit, as known in the art.

[0036] FIG. 2 is another schematic representation of a combined multicomponent refrigerant cycle used with an air separation unit, as known in the art.

[0037] FIG. 3 is a schematic representation of the heat flow within the main heat exchanger in a system configured as described in FIG. 2.

[0038] FIG. 4 is a schematic representation of a combined multicomponent refrigerant cycle used with an air separation unit, in accordance with one embodiment of the present invention.

[0039] FIG. 5 is a schematic representation of the heat flow within the main heat exchanger in a system configured as described in FIG. 4.

[0040] FIG. 6 is a schematic representation of a combined multicomponent refrigerant cycle used with an air separation unit, in accordance with one embodiment of the present invention.

ELEMENT NUMBERS

[0041] 101=purified feed air stream

[0042] 102=main heat exchanger

[0043] 103=higher pressure column

[0044] 104=nitrogen enriched vapor stream

[0045] 105=main condenser

[0046] 106=nitrogen-enriched liquid stream

[0047] 107=sub-cooler

[0048] 108=lower pressure column

[0049] 109=product liquid nitrogen stream

[0050] 110=oxygen enriched liquid stream

[0051] 111=sub-cooler

[0052] 112=first portion (of oxygen-enriched liquid)

[0053] 113=second portion (of oxygen-enriched liquid)

[0054] 114=argon column condenser

[0055] 115=nitrogen rich vapor stream

[0056] 116=waste stream

[0057] 117=nitrogen enriched liquid (to sub-cooler)

[0058] 118=oxygen rich vapor stream

[0059] 119=product gaseous oxygen stream

[0060] 120=liquid oxygen

[0061] 121=oxygen and argon containing stream

[0062] 122=argon column

[0063] 123=oxygen-richer fluid (from argon column)

[0064] 124=product liquid argon

[0065] 125=low pressure multicomponent refrigerant stream

[0066] 126=multicomponent refrigerant recycle compressor

[0067] 127=multicomponent refrigerant aftercooler

[0068] 128=compressed multicomponent refrigerant stream

[0069] 129=cooled, compressed multicomponent refrigerant stream

[0070] 130=multicomponent refrigerant stream throttle valve

[0071] 131=refrigeration bearing multicomponent refrigerant stream

[0072] 201=warm multicomponent refrigerant return steam

[0073] 202=multicomponent refrigerant compressor

[0074] 203=pressurized multicomponent refrigerant stream

[0075] 204=multicomponent refrigerant cooler

[0076] 205=cooled pressurized multicomponent refrigerant stream

[0077] 206=first phase separator vessel

[0078] 207=first vapor portion (from first phase separator)

[0079] 208=first liquid portion (from first phase separator)

[0080] 209=liquefaction heat exchanger

[0081] 210=first nitrogen recycle stream

[0082] 211=LP nitrogen compressor

[0083] 212=warm medium-pressure nitrogen stream

[0084] 213=first nitrogen cooler

[0085] 214=cooled medium-pressure nitrogen stream

[0086] 215=air separation unit

[0087] 216=second nitrogen recycle stream

[0088] 217=combined medium-pressure nitrogen stream

[0089] 218=MP nitrogen compressor

[0090] 219=warm intermediate-pressure nitrogen stream

[0091] 220=second nitrogen cooler

[0092] 221=cooled intermediate-pressure nitrogen stream

[0093] 222=HP nitrogen booster

[0094] 223=high-pressure nitrogen stream

[0095] 224=first nitrogen refrigeration stream

[0096] 225=second nitrogen refrigeration stream

[0097] 226=nitrogen expander

[0098] 227=expanded nitrogen stream

[0099] 228=third phase separator vessel

[0100] 229=nitrogen vapor portion

[0101] 230=nitrogen liquid portion

[0102] 231=combined nitrogen stream

[0103] 232=internal liquid nitrogen stream

[0104] 233=return portion (of internal liquid nitrogen stream)

[0105] 234=storage portion (of internal liquid nitrogen stream)

[0106] 235=cold nitrogen recycle stream

[0107] 236=inlet natural gas stream

[0108] 237=liquid natural gas stream

[0109] 238=compressed and purified inlet air stream

[0110] 239=first heat exchanger

[0111] 240=medium-pressure nitrogen stream

[0112] 241=liquid oxygen stream

[0113] 242=warmed first vapor stream

[0114] 243=second phase separator vessel

[0115] 244=second vapor portion

[0116] 245=second liquid portion

[0117] 246=at least partially condensed portion

[0118] 247=warm second liquid portion

[0119] 248=warmed first liquid stream

[0120] 249=third phase separator vessel

[0121] 250=third vapor portion

[0122] 251=third liquid portion

[0123] 252=third combined multicomponent refrigerant stream

[0124] 253=warm combined nitrogen steam

[0125] 254=fourth phase separator vessel

[0126] 255=fourth vapor portion

[0127] 256=fourth liquid portion

[0128] 257=fourth combined multicomponent refrigerant stream

[0129] 301=warm multicomponent refrigerant return steam

[0130] 302=multicomponent refrigerant compressor

[0131] 303=pressurized multicomponent refrigerant stream

[0132] 304=multicomponent refrigerant cooler

[0133] 305=cooled multicomponent refrigerant stream

[0134] 306=multicomponent refrigerant stream throttle valve

[0135] 307=expanded multicomponent refrigerant stream

[0136] 308=first phase separator vessel

[0137] 309=first vapor portion (from first phase separator)

[0138] 310=first liquid portion (from first phase separator)

[0139] 311=warmed first vapor stream

[0140] 312=second phase separator vessel

[0141] 313=second vapor portion

[0142] 314=second liquid portion

[0143] 315=second combined multicomponent refrigerant stream

[0144] 316=warm combined nitrogen steam

[0145] 317=warmed first liquid stream

[0146] 318=third phase separator vessel

[0147] 319=third vapor portion

[0148] 320=third liquid portion

[0149] 321=third combined multicomponent refrigerant stream

[0150] 322=inlet air stream

[0151] 323=main air compressor

[0152] 324=inlet air cooler

[0153] 325a/b=air purification vessel

[0154] 326=purified inlet air stream

[0155] 327=Claude compressor

[0156] 328=boosted air cooler

[0157] 329=cooled, boosted air stream

[0158] 330=cold air stream

[0159] 331=condensed first portion (of cooled inlet air)

[0160] 332=second portion (of cooled inlet air)

[0161] 333=Claude expander

[0162] 334=expanded second portion

[0163] 335=distillation column

[0164] 336=liquid nitrogen product

[0165] 337=liquid oxygen product stream

[0166] 338=liquid oxygen stream

[0167] 339=liquid oxygen pump

[0168] 340=high pressure liquid oxygen stream

[0169] 341=high-pressure gaseous oxygen product stream

[0170] 342=waste nitrogen stream

[0171] 343=warmed waste nitrogen stream

[0172] 344=waste nitrogen heater

[0173] 345=hot waste nitrogen stream

[0174] 346ab=regeneration waste stream

[0175] 347=liquefaction heat exchanger

[0176] 348=multicomponent refrigerant cycle

[0177] 601=first portion (of purified air stream)

[0178] 602=cooled feed air stream

[0179] 603=second portion (of purified air stream)

[0180] 604=booster air compressor

[0181] 605=pressurized first portion

DESCRIPTION OF PREFERRED EMBODIMENTS

[0182] Illustrative embodiments of the invention are described below. While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.

[0183] It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developer's specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.

[0184] Using Claude Turbine Booster (Claude compressor 327 and Claude expander 333) with a condensing air stream at the cold section of main exchanger combined with a multicomponent refrigerant cycle for the warm section of the main exchanger. The MAC outlet is ˜30 to 35 bara and the outlet of the booster is 35 to 45 bara such that the condensing air stream is 34 to 45 bara resulting in low latent heat of condensation.

[0185] Prior art integration of MR cycle with an ASU produces at least some oxygen which enters the main heat exchanger for indirect heat exchange with the multicomponent refrigerant fluid. The current application does not have any oxygen enriched stream in main heat exchanger. Nothing greater than air, 21% O2. This provides safer management of flammable multicomponent refrigerants than prior art.

[0186] Turning now to FIG. 4, the multicomponent refrigerant cycle 348 includes warm multicomponent refrigerant return steam 301, which is at reduced pressure. Warm multicomponent refrigerant return stream 301 has the pressure increased in multicomponent refrigerant compressor 302, thereby producing pressurized multicomponent refrigerant stream 303. Pressurized multicomponent refrigerant stream 303 enters multicomponent refrigerant cooler 304, thereby producing cooled multicomponent refrigerant stream 305. Cooled multicomponent refrigerant stream 305 is introduced into multicomponent refrigerant stream throttle valve 306, thereby forming expanded multicomponent refrigerant stream 307. Expanded multicomponent refrigerant stream 307 is introduced into first phase separator vessel 308, which produces first vapor portion 309 and first liquid portion 310.

[0187] After passing through liquefaction heat exchanger 347, first vapor portion 309 exits as warmed first vapor stream 311. Warmed first vapor stream 311 is introduced to second phase separator vessel 312, which produces second vapor portion 313 and second liquid portion 314. Second vapor portion 313 and second liquid portion 314 are combined to form second combined multicomponent refrigerant stream 315, which is introduced into liquefaction heat exchanger 347. After passing through liquefaction heat exchanger 347 second combined multicomponent refrigerant stream 315 exits as warmed combined nitrogen stream 316.

[0188] After passing through liquefaction heat exchanger 347, first liquid portion 310 exits as warmed first liquid stream 317. Warmed first liquid stream 317 and warmed combined nitrogen stream 316 are introduced into third phase separator vessel 318. Third phase separator vessel 318 produces third vapor portion 319 and third liquid portion 320. Third vapor portion 319 and third liquid portion 320 are combined to form third combined multicomponent refrigerant stream 321, which is introduced into liquefaction heat exchanger 347. After passing through liquefaction heat exchanger 347, third combined multicomponent refrigerant stream 321 exits as warm multicomponent refrigerant return steam 301.

[0189] Multicomponent refrigerant cycle and nitrogen refrigeration cycle work together to provide sufficient refrigeration duty to liquefy inlet natural gas stream 236 into liquid natural gas stream 237. In addition, these combined refrigeration streams also provide sufficient additional refrigeration duty via internal liquid nitrogen stream 233, to satisfy the duty requirements of air separation unit 215.

[0190] Inlet air stream 322 enters main air compressor 323 wherein the pressure is increased, and the pressurized air is cooled in inlet air cooler 324. The cooled, compressed air stream is then directed to one of air purification vessel 325a/b, wherein the inlet air stream is purified, thereby producing purified inlet air stream 326. Purified inlet air stream 325 is then compressed in Claude compressor 327 and cooled in boosted air cooler 328. Cooled, boosted air stream 329 then enters liquefaction heat exchanger 347, thereby forming cold air stream 330. After having the temperature reduced, first portion 331 of cold air stream 330 exits liquefaction heat exchanger 347 and then enters distillation column 335. Second portion 332 of the cold air stream 330 continues through liquefaction heat exchanger 347 and exits liquefaction heat exchanger 347 and then enters Claude expander 333. Expanded second air stream 334 then enters Claude expander 333. Distillation column 335 produces at least liquid nitrogen product stream 336, waste nitrogen stream 342, liquid oxygen stream 338, and liquid oxygen product stream 337. In order to produce the desired flowrate in both liquid oxygen stream 338 and liquid oxygen product stream 337, it is necessary to introduce additional refrigeration duty, in the form of expanded second air stream 334. At least a portion of the liquid oxygen from distillation column 335 may be exported as a liquid oxygen product stream 337.

[0191] Optionally, liquid oxygen stream 338 may be removed from distillation column 335. Liquid oxygen stream 338 is increased in pressure in liquid oxygen pump 339, thereby producing high-pressure liquid oxygen stream 340. High-pressure liquid oxygen stream 340 is then introduced into liquefaction heat exchanger 347, wherein it is heated and vaporized, thereby producing optional high-pressure gaseous oxygen product stream 341, which then exits the system. One skilled in the art will recognize that liquid oxygen pump 339 may just as easily product low-pressure or medium-pressure liquid oxygen, and therefore the system may produce low-pressure or medium-pressure gaseous oxygen (not shown) in addition to the high-pressure gaseous oxygen system as illustrated. All oxygen product streams may be only liquid. Or a portion may be liquid and additional (optional) portions maybe low-pressure gaseous oxygen and/or high-pressure gaseous oxygen.

[0192] After passing through liquefaction heat exchanger 347, warmed waste nitrogen stream 353 is heated in waste nitrogen heater 354, thereby producing hot waste nitrogen stream 355. Hot waste nitrogen stream 355 is then used to regenerate air purification vessels 325a/b as needed, with the resulting regeneration waste exiting in regeneration waste streams 356a/b.

[0193] In this case the ASU main exchanger heat transfer is balanced, as indicated in the parallel heat exchange lines as indicated in FIG. 5.

[0194] In an alternative embodiment, as illustrated in FIG. 6, the process cycle may utilize a booster air compressor and a LP main air compressor, rather than the above cycle that utilized a HP main air compressor and no booster air compressor. This cycle results in a slightly less overall efficiency of approximately 2%.

[0195] Turning now to FIG. 6, the multicomponent refrigerant cycle 348 includes warm multicomponent refrigerant return steam 301, which is at reduced pressure. Warm multicomponent refrigerant return stream 301 has the pressure increased in multicomponent refrigerant compressor 302, thereby producing pressurized multicomponent refrigerant stream 303. Pressurized multicomponent refrigerant stream 303 enters multicomponent refrigerant cooler 304, thereby producing cooled multicomponent refrigerant stream 305. Cooled multicomponent refrigerant stream 305 is introduced into multicomponent refrigerant stream throttle valve 306, thereby forming expanded multicomponent refrigerant stream 307. Expanded multicomponent refrigerant stream 307 is introduced into first phase separator vessel 308, which produces first vapor portion 309 and first liquid portion 310.

[0196] After passing through liquefaction heat exchanger 347, first vapor portion 309 exits as warmed first vapor stream 311. Warmed first vapor stream 311 is introduced to second phase separator vessel 312, which produces second vapor portion 313 and second liquid portion 314. Second vapor portion 313 and second liquid portion 314 are combined to form second combined multicomponent refrigerant stream 315, which is introduced into liquefaction heat exchanger 347. After passing through liquefaction heat exchanger 347 second combined multicomponent refrigerant stream 315 exits as warmed combined nitrogen stream 316.

[0197] After passing through liquefaction heat exchanger 347, first liquid portion 310 exits as warmed first liquid stream 317. Warmed first liquid stream 317 and warmed combined nitrogen stream 316 are introduced into third phase separator vessel 318. Third phase separator vessel 318 produces third vapor portion 319 and third liquid portion 320. Third vapor portion 319 and third liquid portion 320 are combined to form third combined multicomponent refrigerant stream 321, which is introduced into liquefaction heat exchanger 347. After passing through liquefaction heat exchanger 347, third combined multicomponent refrigerant stream 321 exits as warm multicomponent refrigerant return steam 301.

[0198] Multicomponent refrigerant cycle and nitrogen refrigeration cycle work together to provide sufficient refrigeration duty to liquefy inlet natural gas stream 236 into liquid natural gas stream 237. In addition, these combined refrigeration streams also provide sufficient additional refrigeration duty via internal liquid nitrogen stream 233, to satisfy the duty requirements of air separation unit 215.

[0199] Inlet air stream 322 enters main air compressor 323 wherein the pressure is increased, and the pressurized air is cooled in inlet air cooler 324. The cooled, compressed air stream is then directed to one of air purification vessel 325a/b, wherein the inlet air stream is purified, thereby producing purified inlet air stream 325. Purified air stream 325 is split into two portions.

[0200] First portion 601 enters liquefaction heat exchanger 347 and exits as cooled feed stream 602, which then enters distillation column 335. Second portion 603 enters booster air compressor 604, thereby producing pressurized first portion 605. Pressurized first portion 605 is then compressed in Claude compressor 327 and cooled in boosted air cooler 328, after which it enters liquefaction heat exchanger 347. First portion 331 of the cooled inlet air exits liquefaction heat exchanger 347 and then enters distillation column 335. Second portion 332 of the cooled inlet air exits liquefaction heat exchanger 347 and then enters Claude expander 333. Expanded second air stream 334 then enters Claude expander 333. Distillation column 335 produces at least liquid nitrogen product stream 336, waste nitrogen stream 342, and liquid oxygen product stream 337. In order to produce the desired flowrate in liquid oxygen product stream 337, it is necessary to introduce additional refrigeration duty, in the form of expanded second air stream 334, At least a portion of the liquid oxygen from distillation column 335 may be exported as a liquid oxygen product stream 337.

[0201] Optionally, liquid oxygen stream 338 may be removed from distillation column 335. Liquid oxygen stream 338 is increased in pressure in liquid oxygen pump 339, thereby producing high-pressure liquid oxygen stream 340. High-pressure liquid oxygen stream 340 is then introduced into liquefaction heat exchanger 347, wherein it is heated and vaporized, thereby producing optional high-pressure gaseous oxygen product stream 341, which then exits the system. One skilled in the art will recognize that liquid oxygen pump 339 may just as easily product low-pressure or medium-pressure liquid oxygen, and therefore the system may produce low-pressure or medium-pressure gaseous oxygen (not shown) in addition to the high-pressure gaseous oxygen system as illustrated. All oxygen product streams may be only liquid. Or a portion may be liquid and additional (optional) portions maybe low-pressure gaseous oxygen and/or high-pressure gaseous oxygen.

[0202] After waste nitrogen stream 342 passes through liquefaction heat exchanger 347, warmed waste nitrogen stream 343 is heated in waste nitrogen heater 344, thereby producing hot waste nitrogen stream 345. Hot waste nitrogen stream 345 is then used to regenerate air purification vessels 346a/b as needed, with the resulting regeneration.

[0203] It will be understood that many additional changes in the details, materials, steps and arrangement of parts, which have been herein described in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims. Thus, the present invention is not intended to be limited to the specific embodiments in the examples given above.