INTEGRATED MULTICOMPONENT REFRIGERANT AND AIR SEPARATION PROCESS FOR PRODUCING LIQUID OXYGEN

Abstract

A process for the production of a liquid oxygen stream and a liquid hydrocarbon-rich 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.

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 and a gaseous hydrocarbon rich stream against a cooled multicomponent refrigerant circuit in at least one heat exchanger, thereby producing a cooled air stream and a liquefied hydrocarbon rich 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, further comprising cooling the inlet aft stream and the gaseous hydrocarbon rich stream against the cooled multicomponent refrigerant circuit and a cold waste nitrogen stream.

3. The process of claim 1, wherein the hydrocarbon rich stream is dried natural gas or primarily methane.

4. The process of claim 1, wherein the hydrocarbon rich stream has a pressure greater than 20 bara.

5. The process of claim 1, wherein at least one of the following streams is reduced in pressure by a dense fluid expander or a Joule Thompson valve: the condensed first portion, the expanded second portion, and the liquefied hydrocarbon rich stream.

6. The process of claim 1, further comprising withdrawing an oxygen-argon containing stream from the distillation column, thereby producing at least an argon-lean stream and an argon-rich stream, wherein the argon-lean stream is reintroduced into the distillation column, and the argon-rich stream is withdrawn.

7. 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.

8. 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.

9. The process of claim 1, wherein the expanded multicomponent refrigerant stream has a first temperature, and the liquefied hydrocarbon-rich stream has a second temperature, wherein the first temperature is greater than the second temperature.

10. The process of claim 9, wherein the first temperature is at least 3 C greater than the second temperature,

11. The process of claim 9, wherein the hot collective flowrate is less than the cold collective flowrate in a section of the at least one heat exchanger which is at least 3 C colder than liquefied hydrocarbon-rich stream when withdrawn from the at least one heat exchanger.

12. The process of claim 1, wherein the inlet air stream, gaseous hydrocarbon rich stream, multicomponent refrigerant streams exchange heat in a common heat exchanger.

13. The process of claim 12, wherein no oxygen-rich stream having an oxygen composition greater than air enters the common heat exchanger.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0031] 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

[0032] FIG. 1 is a schematic representation of a combined multicomponent refrigerant cycle used with an air separation unit, as known in the art.

[0033] FIG. 2 is another schematic representation of a combined multicomponent refrigerant cycle used with an air separation unit, as known in the art.

[0034] FIG. 3 is a schematic representation of the heat flow within the main heat exchanger in a system configured as described in FIG. 2.

[0035] FIG. 4 is a schematic representation of a combined multicomponent refrigerant cycle used with an air separation unit.

[0036] FIG. 5 is a schematic representation of the heat flow within the main heat exchanger in a system configured as described in FIG. 4.

[0037] FIG. 6 is a schematic representation of a combined multicomponent refrigerant cycle used with an air separation unit.

[0038] FIG. 7 is a schematic representation of a combined multicomponent refrigerant cycle used with an air separation unit to produce both a liquid oxygen stream and liquid hydrocarbon stream, in accordance with one embodiment of the present invention.

[0039] FIG. 8 is a schematic representation of an argon column that may be used in combination with the cycle as indicated in FIG. 7, in accordance with one embodiment of the present invention.

[0040] FIG. 9 is a schematic representation of a typical heat flow through an independent air separation unit, as is known in the art.

[0041] FIG. 10 is a schematic representation of a typical heat flow through an independent liquefaction unit, as is known in the art.

[0042] FIG. 11 is a schematic representation of the heat flow through an integrated air separation unit and liquefaction unit, in accordance with one embodiment of the present invention.

ELEMENT NUMBERS

[0043] 101=purified feed air stream

[0044] 102=main heat exchanger

[0045] 103=higher pressure column

[0046] 184=nitrogen enriched vapor stream

[0047] 105=main condenser

[0048] 106=nitrogen-enriched liquid stream

[0049] 107=sub-cooler

[0050] 108=lower pressure column

[0051] 109=product liquid nitrogen stream

[0052] 110=oxygen enriched liquid stream

[0053] 111=sub-cooler

[0054] 112=first portion (of oxygen-enriched liquid)

[0055] 113=second portion (of oxygen-enriched liquid)

[0056] 114=argon column condenser

[0057] 115=nitrogen rich vapor stream

[0058] 116=waste stream

[0059] 117=nitrogen enriched liquid (to sub-cooler)

[0060] 118=oxygen rich vapor stream

[0061] 119=product gaseous oxygen stream

[0062] 120=liquid oxygen

[0063] 121=oxygen and argon containing stream

[0064] 122=argon column

[0065] 123=oxygen-richer fluid (from argon column)

[0066] 124=product liquid argon

[0067] 125=low pressure multicomponent refrigerant stream

[0068] 126=multicomponent refrigerant recycle compressor

[0069] 127=multicomponent refrigerant aftercooler

[0070] 128=compressed multicomponent refrigerant stream

[0071] 129=cooled, compressed multicomponent refrigerant stream

[0072] 130=multicomponent refrigerant stream throttle valve

[0073] 131=refrigeration bearing multicomponent refrigerant stream

[0074] 201=warm multicomponent refrigerant return steam

[0075] 202=multicomponent refrigerant compressor

[0076] 203=pressurized multicomponent refrigerant stream

[0077] 204=multicomponent refrigerant cooler

[0078] 205=cooled pressurized multicomponent refrigerant stream

[0079] 206=first phase separator vessel

[0080] 207=first vapor portion (from first phase separator)

[0081] 208=first liquid portion (from first phase separator)

[0082] 209=liquefaction heat exchanger

[0083] 210=first nitrogen recycle stream

[0084] 211=LP nitrogen compressor

[0085] 212=warm medium-pressure nitrogen stream

[0086] 213=first nitrogen cooler

[0087] 214=cooled medium-pressure nitrogen stream

[0088] 215=air separation unit

[0089] 216=second nitrogen recycle stream

[0090] 217 =combined medium-pressure nitrogen stream

[0091] 218=MP nitrogen compressor

[0092] 219=warm intermediate-pressure nitrogen stream

[0093] 220=second nitrogen cooler

[0094] 221=cooled intermediate-pressure nitrogen stream

[0095] 222=HP nitrogen booster

[0096] 223=high-pressure nitrogen stream

[0097] 224=first nitrogen refrigeration stream

[0098] 225=second nitrogen refrigeration stream

[0099] 226=nitrogen expander

[0100] 227=expanded nitrogen stream

[0101] 228=third phase separator vessel

[0102] 229=nitrogen vapor portion

[0103] 230=nitrogen liquid portion

[0104] 231=combined nitrogen stream

[0105] 232=internal liquid nitrogen stream

[0106] 233=return portion (of internal liquid nitrogen stream)

[0107] 234=storage portion (of internal liquid nitrogen stream)

[0108] 235=cold nitrogen recycle stream

[0109] 236=inlet natural gas stream

[0110] 237=liquid natural gas stream

[0111] 238=compressed and purified inlet air stream

[0112] 239=first heat exchanger

[0113] 240=medium-pressure nitrogen stream

[0114] 241=liquid oxygen stream

[0115] 242=warmed first vapor stream

[0116] 243=second phase separator vessel

[0117] 244=second vapor portion

[0118] 245=second liquid portion

[0119] 246=at least partially condensed portion

[0120] 247=warm second liquid portion

[0121] 248=warmed first liquid stream

[0122] 249=third phase separator vessel

[0123] 250=third vapor portion

[0124] 251=third liquid portion

[0125] 252=third combined multicomponent refrigerant stream

[0126] 253=warm combined nitrogen steam

[0127] 254=fourth phase separator vessel

[0128] 255=fourth vapor portion

[0129] 256=fourth liquid portion

[0130] 257=fourth combined multicomponent refrigerant stream

[0131] 301=warm multicomponent refrigerant return steam

[0132] 302=multicomponent refrigerant compressor

[0133] 303=pressurized multicomponent refrigerant stream

[0134] 304=multicomponent refrigerant cooler

[0135] 305=cooled multicomponent refrigerant stream

[0136] 306=multicomponent refrigerant stream throttle valve

[0137] 307=expanded multicomponent refrigerant stream

[0138] 308=first phase separator vessel

[0139] 309=first vapor portion (from first phase separator)

[0140] 310=first liquid portion (from first phase separator)

[0141] 311=warmed first vapor stream

[0142] 312=second phase separator vessel

[0143] 313=second vapor portion

[0144] 314=second liquid portion

[0145] 315=second combined multicomponent refrigerant stream

[0146] 316=warm combined nitrogen steam

[0147] 317=warmed first liquid stream

[0148] 318=third phase separator vessel

[0149] 319=third vapor portion

[0150] 320=third liquid portion

[0151] 321=third combined multicomponent refrigerant stream

[0152] 322=inlet air stream

[0153] 323=main air compressor

[0154] 324=inlet air cooler

[0155] 325a/b=air purification vessel

[0156] 326=purified inlet air stream

[0157] 327=Claude compressor

[0158] 328=boosted air cooler

[0159] 329=cooled, boosted air stream

[0160] 330=cold air stream

[0161] 331=condensed first portion (of cooled inlet air)

[0162] 332=second portion (of cooled inlet air)

[0163] 333=Claude expander

[0164] 334=expanded second portion

[0165] 335=distillation column

[0166] 336=liquid nitrogen product

[0167] 337=liquid oxygen product stream

[0168] 338=liquid oxygen stream

[0169] 339=liquid oxygen pump

[0170] 340=high pressure liquid oxygen stream

[0171] 341=high-pressure gaseous oxygen product stream

[0172] 342=waste nitrogen stream

[0173] 343=warmed waste nitrogen stream

[0174] 344=waste nitrogen heater

[0175] 345=hot waste nitrogen stream

[0176] 346ab=regeneration waste stream

[0177] 347=liquefaction heat exchanger

[0178] 348=multicomponent refrigerant cycle

[0179] 601=first portion (of purified air stream)

[0180] 602=cooled feed air stream

[0181] 603=second portion (of purified air stream)

[0182] 604=booster air compressor

[0183] 605=pressurized first portion

[0184] 701=warm multicomponent refrigerant return steam

[0185] 702=first multicomponent refrigerant compressor

[0186] 703=first pressurized multicomponent refrigerant stream

[0187] 704=first multicomponent refrigerant cooler

[0188] 705=first cooled multicomponent refrigerant stream

[0189] 706=first phase separator vessel

[0190] 707=first vapor portion (from first phase separator)

[0191] 708=first liquid portion (from first phase separator

[0192] 709=second multicomponent refrigerant compressor

[0193] 710=second pressurized multicomponent refrigerant stream

[0194] 711=second multicomponent refrigerant cooler

[0195] 712=second cooled multicomponent refrigerant stream

[0196] 713=second phase separator vessel

[0197] 714=second vapor portion (from second phase separator)

[0198] 715=second liquid portion (from second phase separator)

[0199] 716=warmed first liquid stream

[0200] 717=warmed second liquid stream

[0201] 718=warmed combined nitrogen stream

[0202] 719=fourth phase separator vessel

[0203] 720=fourth vapor portion (from fourth phase separator)

[0204] 721=fourth liquid portion (from fourth phase separator)

[0205] 722=fourth combined multicomponent refrigerant stream

[0206] 723=warmed first vapor stream

[0207] 724=third phase separator vessel

[0208] 725=third vapor portion (from third phase separator)

[0209] 726=third liquid portion (from third phase separator)

[0210] 727=third combined multicomponent refrigerant stream

[0211] 728=supplemental compressor

[0212] 729=cold inlet stream

[0213] 730=inlet natural gas stream

[0214] 731=liquid natural gas stream

[0215] 732=dense fluid expander

[0216] 733=Joule Thompson valve

[0217] 734=dense fluid expander

[0218] 735=Joule Thompson valve

[0219] 736=dense fluid expander

[0220] 737=Joule Thompson valve

[0221] 801=argon column

[0222] 802=oxygen-Argon containing stream

[0223] 803=argon-lean stream

[0224] 804=argon-rich stream

[0225] 805=crude argon stream

[0226] 901=feed air stream

[0227] 902=cold waste nitrogen stream

[0228] 903=main heat exchanger

[0229] 904=liquid air stream

[0230] 905=warm waste nitrogen stream

[0231] 1001=natural gas feed stream

[0232] 1002=cold multicomponent refrigerant stream

[0233] 1003=main heat exchanger

[0234] 1004=liquid natural gas stream

[0235] 1005=warm multicomponent refrigerant stream

[0236] 1101=main heat exchanger

Description of Preferred Embodiments

[0237] 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.

[0238] 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.

[0239] 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.

[0240] 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.

[0241] 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.

[0242] 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.

[0243] 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.

[0244] 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.

[0245] 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 distillation column 335.

[0246] The compressed air expanding across Claude expander 333 removes heat from expanded second air stream 334, thereby effectively increasing the amount of refrigeration as it then enters distillation column 335. This allows distillation column 335 to produce additional distillation products such as liquid nitrogen product stream 336, liquid oxygen product stream 337, liquid oxygen stream 338, and/or waste nitrogen stream 342. The cold vapor streams (i.e. waste nitrogen stream 342) then provide (in addition with multicomponent refrigerant cycle 348) additional cooling and liquefaction for the air and hydrocarbon streams.

[0247] 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.

[0248] 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.

[0249] 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.

[0250] In this case the ASU main exchanger heat transfer is balanced, as indicated in the parallel heat exchange lines as indicated in FIG. 5.

[0251] 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%.

[0252] 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.

[0253] 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,

[0254] 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.

[0255] 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.

[0256] 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.

[0257] 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 distillation column 335. 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.

[0258] 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.

[0259] 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

[0260] Turning now to FIG. 7, a system wherein a gaseous hydrocarbon stream is integrated into the air separation process. By integrating the natural gas liquefaction cooling into the air separation process, it is possible for the excess refrigeration at a cold range in the air separation unit to be utilized. This excess refrigeration is typically created by the air separation unit flow imbalance between the liquid air (low flow warm stream) and the waste nitrogen stream (high flow cold stream). This imbalance tends to arise between about −150 C and about −170 C. It is desirable to pinch the exchange diagram within this region by increasing the flowrate of warm stream into this region. Specifically the liquefied natural gas (warm stream) can be cooled by the waste nitrogen stream without the need for multicomponent refrigerant cooling. This enables the multicomponent refrigerant to be warmed significantly (i.e. from about −167 C to about −150 C). This is described below, and may result in a net efficiency improvement of about 5%.

[0261] The process scheme illustrated in FIG. 7 is approximately 7% to 8% more efficient (i.e. uses less power) than a traditional air separation unit integrated with a nitrogen cycle. This is because the nitrogen cycle must be warmed and re-cooled through the entire temperature range to the warm end (typically from −190 C to +40 C) just to provide refrigeration at the cold end.

[0262] Turning again to FIG. 7, the multicomponent refrigerant cycle 348 includes warm multicomponent refrigerant return steam 701, which is at reduced pressure. Warm multicomponent refrigerant return stream 701 has the pressure increased in first multicomponent refrigerant compressor 702, thereby producing first pressurized multicomponent refrigerant stream 703. First pressurized multicomponent refrigerant stream 703 enters first multicomponent refrigerant cooler 704, thereby producing first cooled multicomponent refrigerant stream 705. First cooled multicomponent refrigerant stream 705 is introduced into first phase separator vessel 706, which produces first vapor portion 707 and first liquid portion 708.

[0263] First vapor portion 707 has the pressure increased in second multicomponent refrigerant compressor 709, thereby producing second pressurized multicomponent refrigerant stream 710. Second pressurized multicomponent refrigerant stream 710 enters second multicomponent refrigerant cooler 711, thereby producing second cooled multicomponent refrigerant stream 712. Second cooled multicomponent refrigerant stream 712 is introduced into second phase separator vessel 713 which produces second vapor portion 714 and second liquid portion 715,

[0264] After passing through liquefaction heat exchanger 347, second vapor portion 714 exits as warmed first vapor stream 723. Warmed first vapor stream 723 is introduced to third phase separator vessel 724, which produces third vapor portion 725 and third liquid portion 726. Third vapor portion 725 and third liquid portion 726 are combined to form third combined multicomponent refrigerant stream 727 which is introduced into liquefaction heat exchanger 347. After passing through liquefaction heat exchanger 347 third combined multicomponent refrigerant stream 727 exits as warmed combined nitrogen stream 718

[0265] After passing through liquefaction heat exchanger 347, first liquid portion 708 exits as warmed first liquid stream 716. After passing through liquefaction heat exchanger 347, second liquid portion 715 exits as warmed second liquid stream 717. Warmed first liquid stream 716, warmed second liquid stream 717, and warmed combined nitrogen stream 718 are introduced into fourth phase separator vessel 719. Fourth phase separator vessel 719 produces fourth vapor portion 720 and fourth liquid portion 721. Fourth vapor portion 720 and fourth liquid portion 721 are combined to form fourth combined multicomponent refrigerant stream 722, which is introduced into liquefaction heat exchanger 347. After passing through liquefaction heat exchanger 347, fourth combined multicomponent refrigerant stream 722 exits as warm multicomponent refrigerant return steam 701.

[0266] Multicomponent refrigerant cycle and nitrogen refrigeration cycle work together to provide sufficient refrigeration duty to liquefy inlet natural gas stream 730 into liquid natural gas stream 731. Liquid natural gas stream 731 may optionally have the pressure reduced in either dense fluid expander 736 or Joule Thompson valve 737. In addition, these combined refrigeration streams also provide sufficient additional refrigeration duty via internal nitrogen stream 342, to satisfy the duty requirements of air separation unit 215.

[0267] 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 air stream 326 is then compressed in Claude compressor 327 and cooled in boosted air cooler 328, after which it enters liquefaction heat exchanger 347 as cooled, boosted air stream 329. First portion 331 of cold air stream 330 exits liquefaction heat exchanger 347, is optionally further compressed in supplemental compressor 728, and then enters distillation column 335 as cold inlet stream 729. Cold inlet stream 729 may optionally have the pressure reduced in either dense fluid expander 732 or Joule Thompson valve 733. Second portion 332 of cold air stream 330 exits liquefaction heat exchanger 347 and then enters Claude expander 333. Expanded second air stream 334 then enters distillation column 335. Expanded second air stream 334 may optionally have the pressure reduced in either dense fluid expander 732 or Joule Thompson valve 733

[0268] Distillation column 335 produces at least liquid nitrogen product stream 336, waste nitrogen stream 342, optional liquid oxygen stream 338, and liquid oxygen product stream 337. In order to produce the desired flowrate in optional 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.

[0269] One potential application for this system is the space industry. In the space industry the demand is for liquid natural gas and liquid oxygen for rocket fuels. In such an application, there will be no gaseous oxygen in the main heat exchanger. This is an important feature because this would make it safe to have an integrated exchanger (MR and NG integrated in ASU exchanger) without O2 in the shared exchanger.

[0270] 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.

[0271] Turning now to FIG. 8, an option argon column 801 may be integrated into distillation column 335 as illustrated in FIG. 7. Oxygen-Argon containing stream 802 is introduced into argon column 801, thereby producing argon-lean stream 803, and argon-rich stream 804. Argon-lean stream 803 is returned to distillation column 335. Argon-rich stream 804 is either combined with internal nitrogen stream 342 or exits the system as crude argon stream 805 for export or further purification.

[0272] One skilled in the art would recognize that even if crude argon stream 805 is not desired as a product, argon column 801 is useful due to the low reflux flow (argon-lean stream 803) to distillation column 335, which serves to improve oxygen recovery. This oxygen recovery may be improved by as much as 5%.

[0273] As used herein, the term “cold stream” is defined as the streams which are having their temperature increased by the described heat exchange. Such streams may include a waste nitrogen stream exiting the distillation column and, after being warmed, being used to regenerate front end purification units. A “cold stream” may also be a stream exiting a multicomponent refrigerant system after being expanded and cooled.

[0274] As used herein, the term “hot stream” is defined as the streams which are having their temperature decreased by the described heat exchange. Such streams may include an inlet air stream that is cooled and at least partially liquefied prior to entering the distillation column. A “hot stream” may also be a natural gas stream that is liquefied into liquefied natural gas.

[0275] As used here, the term “hot composite” or “hot stream” is defined as collectively including cooled, boosted air stream 329 and natural gas feed stream 730. As used herein, the term “hot collective flow rate” is defined as the total mass flowrate of cooled, boosted air stream 329 and natural gas feed stream 730.

[0276] As used here, the term “cold composite” or “cold stream” is defined as collectively including high-pressure liquid oxygen stream 340, waste nitrogen stream 342, cold multicomponent refrigerant stream 708, cold multicomponent refrigerant stream 714, cold multicomponent refrigerant stream 715, fourth combined multicomponent refrigerant stream 722, and third combined multicomponent refrigerant stream 727. As used herein, the term “cold collective flow rate” is defined as the total mass flow rate of high-pressure liquid oxygen stream 340, waste nitrogen stream 342, cold multicomponent refrigerant stream 708, cold multicomponent refrigerant stream 714, cold multicomponent refrigerant stream 715, fourth combined multicomponent refrigerant stream 722, and third combined multicomponent refrigerant stream 727

[0277] Turning now to FIG. 9, the heat flow within the main heat exchanger 903 of a generic system comprising an independent air separation unit is shown. Such a system is not integrated into a multicomponent refrigerant system or any other cryogenic system. Feed air stream 901 enters main heat exchanger 903 and exchanges heat with cold waste nitrogen stream 902, which may be arriving from the distillation column (not shown). As a result of this heat transfer, liquid air stream 904 and warm waste nitrogen stream 905 are produced. As is indicated in the heat flow diagram, in this particular simulation, there is a significant temperature difference between the “hot stream” and the “cold stream” above −155 C. This is because of the low liquid air flow relative to the waste nitrogen flow yielding small temperature differential at the cold end and a large temperature differential at the warm end. One skilled in the art would recognize these diverging lines as an indication of less efficient heat transfer having taking place as compared to ideal efficient process of parallel lines.

[0278] Turning now to FIG. 10, the heat flow within the main heat exchanger 1003 of a generic system comprising an independent natural gas liquefaction unit is shown. Such a system utilizes a multicomponent refrigerant system but no other cryogenic system. Natural gas feed stream 1001 enters main heat exchanger 1003 and exchanges heat with cold multicomponent refrigerant stream 1002, Cold multicomponent refrigerant stream 1002 is coming directly from the cold end of the multicomponent refrigerant system (not shown). As a result of this heat transfer, liquid natural gas stream 1004 and warm multicomponent refrigerant stream 1005 are produced. As is indicated in the heat flow diagram, in this particular simulation, there is a significant temperature difference between the “hot stream” and the “cold stream” during the entire process. This is because of the small temperature differential at the warm end and the large temperature differential at the cold end. One skilled in the art would recognize these diverging lines as an indication of less efficient heat transfer having taking place. as compared to ideal efficient process of parallel lines,

[0279] Turning now to FIG. 11, the heat flow within the main heat exchanger 1101 of an integrated system comprising an air separation unit and a natural gas liquefaction unit is shown. As this is a slightly simplified representation of the system described above in FIG. 7, element numbers from FIG. 7 are being used for clarity.

[0280] Feed air stream 329 enters main heat exchanger 1101 and exchanges heat with waste nitrogen stream 342, natural gas feed stream 730, and cold multicomponent refrigerant stream 708/714/715, As a result of this heat transfer, liquid air stream 331, liquid natural gas stream 731, warm waste nitrogen stream 343, and warm multicomponent refrigerant stream 701 are produced. As is indicated in the heat flow diagram, in this particular simulation, the temperature difference between the “hot stream” and the “cold stream” at all points between −150 C and −170 C are closer to one another. One skilled in the art would recognize this as an indication of more efficient heat transfer having taking place.

[0281] One of ordinary skill in the art will recognize that when the flow of composite “hot streams” is less than the flow of composite “cold streams” and in the heat exchange zone the cold inlet temperature is colder than the liquefied hydrocarbon withdraw temperature, the resulting exchange diagram will tend to pinch at the cold end and tend to open up (i.e. exhibit a larger temperature differential) at the warm end of this zone. Because of this design inefficiency, the larger temperature differential at the point of liquid hydrocarbon withdrawal means that there is excess refrigeration available at the hydrocarbon withdrawal temperature. Thus, the mixed refrigerant stream can be warmed up. For example, the multicomponent refrigerant inlet temperature is warmer than hydrocarbon outlet. This is in stark contrast to the prior art where the refrigerant must be colder than the stream to be cooled.

[0282] The object of the current invention is the optimization of the heat transfer at the cold end of liquefaction heat exchanger 347 when the natural gas liquefaction process is integrated with the air separation process. This is preferentially accomplished with no oxygen-rich stream also in liquefaction heat exchanger 347. The “hot stream” (i.e. the liquid air composite streams) has a lower mass flowrate than the “cold stream” (i.e. the waste nitrogen flow), and excess refrigeration capacity exists in the region of liquefaction heat exchanger 347 where liquid natural gas stream 731 is withdrawn. This allow multicomponent refrigeration cycle 348 to be warmed significantly, saving a considerable amount of energy. The inlet multicomponent refrigerant stream is warmer than the natural gas stream that it is cooling. It should be noted that in the prior art, the mixed refrigerant stream is colder than the natural gas stream that it is intended to cool.

[0283] 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.