LIQUEFIED GAS SUPPLY SYSTEM AND AIR SEPARATION UNIT COMPRISING SAME

Abstract

An air separation unit comprises a first rectification column, having a top condenser and a second rectification column placed side by side, a heat exchanger, a first pump and a second pump connected in parallel, the first pump being capable of producing liquid at a first liquid pressure and the second pump being capable of producing liquid at a second liquid pressure, higher than the first pressure, each pump having an inlet connected to the second column, a first outlet of the first pump being connected to a first outlet conduit, a second outlet of the second pump being connected to a second outlet conduit, the first and second outlet conduits being connected to the condenser section

Claims

1. An air separation unit comprising: a first rectification column having an operating pressure, which is a first pressure; a second rectification column having an operating pressure, which is a second pressure, less than the first pressure, wherein the first rectification column comprises a top condenser enclosed within a condenser section having an operating pressure which is the second pressure; a supply source, which is a lower region of the second rectification column, wherein the first rectification column and the second rectification column are disposed side by side; a heat exchanger; means for sending feed air to the heat exchanger to be cooled and from the heat exchanger to the first rectification column; means for sending a gas from the condenser section to the bottom of the second rectification columns; a conduit configured to send the gas removed from the top of the second rectification column to the heat exchanger to be warmed; a first pump and a second pump connected in parallel, the first pump being configured to produce liquid at a first liquid pressure and the second pump being configured to produce liquid at a second liquid pressure, higher than the first pressure, each pump having an inlet connected to the supply source; a first outlet of the first pump being connected to a first outlet conduit; and a second outlet of the second pump being connected to a second outlet conduit, the first outlet conduit being connected at a first removal point via a first valve to the condenser section and the second outlet conduit being connected at a second removal point via a second valve to the condenser section.

2. The air separation unit according to claim 1, further comprising means for mixing liquid removed via the first valve with liquid removed via the second valve and sending the mixed liquid in a common conduit to the condenser.

3. The air separation unit according to claim 1, wherein the first valve and the second valve are connected to the condenser section via separate conduit means.

4. The air separation unit according to claim 1, wherein the first removal point is upstream of the third removal point and/or the second removal point is upstream of the fourth removal point.

5. An air separation process comprising the steps of: providing a first rectification column operating at a first pressure, a second rectification column operating at a second pressure, less than the first pressure, the first rectification column having a top condenser enclosed within a condenser section operating at the second pressure, wherein the second rectification comprises a supply source that is disposed in a lower region of the second rectification column, the first rectification column and the second rectification column being placed side by side; sending feed air to a heat exchanger to be cooled and then from the heat exchanger to the first rectification column; sending a gas from the condenser section to a bottom section of the second rectification column; removing a top gas is removed from a top section of the second rectification column, and then sending the top gas from the top section to the heat exchanger to be warmed, wherein in normal operation, the process further comprises the steps of: using a first pump and a second pump that are connected in parallel to pressurise liquid from the bottom of the second rectification column, the first pump producing liquid at a first liquid pressure and the second pump producing liquid at a second liquid pressure, higher than the first liquid pressure, and using the first pump to send liquid at the first liquid pressure to the condenser section and using the second pump to send liquid at the second liquid pressure to the heat exchanger, wherein liquid at the second liquid pressure is at least sometimes sent from the second pump to the condenser section.

6. The process according to claim 5, wherein no liquid is sent in normal operation from the first pump to the heat exchanger.

7. The process according to claim 5, wherein the liquid at the second liquid pressure sent from the second pump to the condenser section has a flowrate corresponding to between 3 and 100%, or to between 3 and 50% or even between 3 and 15%, preferably between 5 and 10% of the flowrate of the liquid at the first liquid pressure sent from the first pump to the condenser section in normal operation.

8. The process according to claim 5, wherein the liquid at the second pressure is not expanded between the second removal point and the condenser section.

9. The process according to claim 5, wherein the liquid at the first liquid pressure and the liquid at the second liquid pressure are mixed upstream of the condenser section.

10. The process according to claim 5, wherein the first and second liquid pressures differ by no more than 10 bars, preferably by no more than 7 bars.

11. The process according to claim 5, wherein part of the refrigeration for the process is provided by liquid nitrogen from an external source.

12. The process according to claim 5, wherein liquid at the second liquid pressure is sent from the second pump to the condenser section if the first pump is not operating.

13. The process according to claim 12, wherein during normal operation liquid at the second liquid pressure is not sent from the second pump to the condenser section.

14. The process according to claim 5, wherein liquid at the second liquid pressure is sent from the second pump to the condenser section if the first pump is operating at a reduced rate as compared to the rate during normal operation.

15. The process according to claim 14, wherein the liquid at the second liquid pressure is reduced in pressure upstream of the condenser section.

16. The process according to claim 5, wherein the first outlet conduit is connected at a third removal point via a third valve to the heat exchanger and the second outlet conduit is connected at a fourth removal point via a fourth valve to the heat exchanger.

17. An air separation unit comprising a liquefied gas supply system, the liquefied gas supply system comprising: a first liquid feed pump which is used to feed a first liquefied gas from a supply source to a low-pressure supply destination for low-pressure purposes; a second liquid feed pump which is used to feed a second liquefied gas from the supply source to a high-pressure supply destination for high-pressure purposes; and a control unit for controlling the first liquid feed pump and the second liquid feed pump, wherein the control unit: implements first circulation liquid in-feed processing for feeding in the first liquefied gas from the supply source to the low-pressure supply destination by means of the first liquid feed pump which is in a low-pressure operating mode; and first product liquid in-feed processing for feeding in the second liquefied gas from the supply source to the high-pressure supply destination by means of the second liquid feed pump which is in a high-pressure operating mode; and/or implements second circulation liquid in-feed processing for feeding in the first liquefied gas from the supply source to the low-pressure supply destination by means of the first liquid feed pump which is in the low-pressure operating mode, and also for feeding in a portion of the second liquefied gas from the supply source to the low-pressure supply destination by means of the second liquid feed pump which is in the high-pressure operating mode; and second product liquid in-feed processing for feeding in the remainder of the second liquefied gas from the supply source to the high-pressure supply destination by means of the second liquid feed pump which is in the high-pressure operating mode.

18. The air separation unit according to claim 17, wherein the control unit is configured to: control an amount of the first liquefied gas fed from the supply source to the low-pressure supply destination by means of the first liquid feed pump, and controls an amount of the second liquefied gas fed from the supply source to the high-pressure supply destination by means of the second liquid feed pump, correspondingly with liquid amount data from a liquid amount measurement unit for measuring an amount of liquid at the supply source; and/or control an amount of the first liquefied gas fed from the supply source to the low-pressure supply destination by means of the first liquid feed pump, and controls an amount of the second liquefied gas fed from the supply source to the high-pressure supply destination by means of the second liquid feed pump, correspondingly with liquid amount data from a flow rate measurement unit for measuring an amount of liquid fed to the low-pressure supply destination.

19. The air separation unit according to claim 17, wherein the control unit is configured to: when the first liquid feed pump is in a stopped state, implements first liquid feed pump stoppage processing for feeding in a portion of the second liquefied gas from the supply source to the high-pressure supply destination and for feeding in the remainder of the second liquefied gas to the low-pressure supply destination by means of the second liquid feed pump; and when the second liquid feed pump is in a stopped state, implements second liquid feed pump stoppage processing for feeding in a portion of the first liquefied gas from the supply source to the low-pressure supply destination and for feeding in the remainder of the first liquefied gas to the high-pressure supply destination by means of the first liquid feed pump.

20. The air separation unit according to claim 17, further comprising: a pipe configuration in which a first low-pressure liquid feed line running from the first liquid feed pump to the low-pressure supply destination, and a second low-pressure liquid feed line running from the second liquid feed pump to the low-pressure supply destination do not merge, or merge; and a pipe configuration in which a first high-pressure liquid feed line running from the first liquid feed pump to the high-pressure supply destination, and a second high-pressure liquid feed line running from the second liquid feed pump to the high-pressure supply destination do not merge, or merge.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0098] Further developments, advantages and possible applications of the invention can also be taken from the following description of the drawing and the exemplary embodiments. All features described and/or illustrated form the subject-matter of the invention per se or in any combination, independent of their inclusion in the claims or their back-references.

[0099] FIG. 1A is a configuration example of an air separation unit according to embodiment 1.

[0100] FIG. 1B is a configuration example of an air separation unit according to embodiment 2.

[0101] FIG. 1C is a configuration example of an air separation unit according to embodiment 3.

[0102] FIG. 1D is a configuration example of an air separation unit according to embodiment 4.

[0103] FIG. 2 is a configuration example of an air separation unit capable of operating at higher pressures than the unit of FIG. 1A-FIG. 1D.

[0104] FIG. 3 is a configuration example of a high-pressure air separation unit comprising an argon rectification column.

DETAILED DESCRIPTION OF THE INVENTION

[0105] Several embodiments of the present invention will be described below. The embodiments described below illustrate examples of the present invention. The present invention is in no way limited by the following embodiments, and also includes a number of variant modes which are implemented within a scope that does not alter the gist of the present invention. It should be noted that not all of the components described below are essential components of the present invention.

[0106] In this specification, upstream and downstream are based on flows of gas (e.g., feed air, oxygen gas, nitrogen gas, argon gas) or various liquefied gases.

Embodiment 1

[0107] An air separation unit 100 according to embodiment 1 illustrated in FIG. 1A constitutes a low-pressure air separation unit.

[0108] The air separation unit 100 comprises: a main heat exchanger 101, a first rectification column 2, a nitrogen condenser 3, a second rectification column 4, an expansion turbine 7 for feed air, a first heat exchanger 102, and a liquefied gas supply system 1.

[0109] The first rectification column 2 comprises a column bottom portion 21, a rectification portion 22, and a column top portion 23. The second rectification column 4 comprises a column bottom portion 41, a rectification portion (lower rectification portion, first intermediate rectification portion 42, second intermediate rectification portion 43 in a stage above, and upper rectification portion), and a column top portion 44.

[0110] The main heat exchanger 101 exchanges heat between feed air and another gas. A portion of the feed air drawn from the main heat exchanger 1 is introduced into the column bottom portion 21, which is a lower portion of the first rectification column 2, via a first feed air pipe L21.

[0111] The remainder of the feed air is drawn from partway through the main heat exchanger 1 by means of a second feed air pipe L21a which branches from the first feed air pipe L21, and fed to the expansion turbine 7. The feed air used in the expansion turbine 7 is introduced into the second intermediate rectification portion 43 of the second rectification column 4 by means of the second feed air pipe L21a.

[0112] A portion of the nitrogen gas drawn from the column top portion 23 of the first rectification column 2 by means of a nitrogen-rich substance drawing pipe L23 is fed to the nitrogen condenser 3, and after being cooled by means of cold heat of a refrigerant (oxygen-enriched liquid) therein, the condensed nitrogen liquid is returned to the column top portion 23 of the first rectification column 2 by pipe L23.

[0113] The remainder of the nitrogen liquid condensed in the condenser 3 is introduced into the column top portion 44 of the second rectification column 4 via a first branch pipe L23a branching from the nitrogen-rich substance drawing pipe L23.

[0114] An oxygen-enriched liquid drawn from the column bottom portion 21 of the first rectification column 2 by means of an oxygen-enriched liquid drawing pipe L211 undergoes heat exchange with another gas in the first heat exchanger 102, and is then fed to the intermediate rectification portion 42 of the second rectification column 4.

[0115] An oxygen-enriched gas drawn from the column top portion 32 of the nitrogen condenser 3 by means of a low-pressure oxygen pipe L321 (or a waste gas pipe) is passed through the main heat exchanger 101 and then extracted (supplied externally) as low-pressure oxygen gas (or waste gas).

[0116] An oxygen-enriched gas drawn from the column top portion 32 of the nitrogen condenser 3 by means of a low-pressure oxygen pipe L32 is sent to the bottom of the second rectification column.

[0117] Nitrogen gas drawn from the column top portion 44 of the second rectification column 4 by means of a product nitrogen gas pipe L44 is passed through the first heat exchanger 102 and passed through the main heat exchanger 101, and is then extracted as product nitrogen gas.

[0118] The liquefied gas supply system 1 comprises: a first liquid feed pump 11 operable in a low-pressure operating mode or a high-pressure operating mode; a second liquid feed pump operable in a low-pressure operating mode or a high-pressure operating mode; and a control unit 15 for controlling the first liquid feed pump 11 and the second liquid feed pump 12 in the low-pressure operating mode and/or the high-pressure operating mode.

[0119] Liquefied oxygen is drawn from the column bottom portion 41 of the second rectification column 4 by means of a first drawing pipe L1, and fed downstream to suit a predetermined purpose by means of the first liquid feed pump 11 and the second liquid feed pump 12.

[0120] The low-pressure operating mode is determined, for example, by totaling a pressure on the refrigerant side (liquid oxygen side) of the nitrogen condenser 3 or in the second rectification column 4, a pressure corresponding to a lift height required to supply a liquid from the first liquid feed pump 11 or the second liquid feed pump 12 to the refrigerant side of the nitrogen condenser 3, and pipe pressure loss.

[0121] The high-pressure operating mode is determined, for example, when a liquid is to be supplied to a supply destination, by totaling an operating pressure at the supply destination, a pressure corresponding to a lift height from the pump to the supply destination, and pipe pressure loss.

[0122] The high-pressure operating mode is determined, when the liquid is vaporized for supply to the supply destination as a gas, by totaling a pressure corresponding to the lift height from the pump to a liquid vaporization point and pipe pressure loss with the pressure at the supply destination. The low pressure is 1.5-5 barA and the high-pressure is 5-20 barA, in terms of rectification column pressure, for example.

(First Circulation Liquid In-Feed Processing and First Product Liquid In-Feed Processing)

[0123] The first drawing pipe L1 branches into a first branch pipe L11 and a second branch pipe L12 to feed liquefied oxygen. The first branch pipe L11 communicates with the nitrogen condenser 3, via a first removal point of pipe L13. The control unit 15 controls the first liquid feed pump 11 in the low-pressure operating mode so that a portion of branched first liquefied oxygen (corresponding to a first liquefied gas) is fed to the nitrogen condenser 3 as a circulation liquid (for the purpose of a refrigerant) (first circulation liquid in-feed processing). In this processing, a first gate valve V1 and a third gate valve V3 provided in the first branch pipe L11 are controlled to an open state by means of the control unit 15. Furthermore, a circulation branch pipe L14 branching from the second branch pipe L12 merges with the first branch pipe L11. A second gate valve V2 provided upstream from a merging position thereof and downstream of a second removal point of pipe L12 is controlled to a closed state by means of the control unit 15.

[0124] The second branch pipe L12 extends as far as the main heat exchanger 101. The control unit 15 controls the second liquid feed pump 12 in the high-pressure operating mode so that second liquefied oxygen (corresponding to a second liquefied gas) fed by the second branch pipe L12 undergoes heat exchange with another gas and is then extracted as product oxygen gas (first product liquid in-feed processing). In this processing, a fifth gate valve V5 provided in the second branch pipe L12 is controlled to an open state by means of the control unit 15. Furthermore, a product liquid branch pipe L13 branching from the first branch pipe L11 merges with the second branch pipe L12 via a third removal point. A fourth gate valve V4 provided upstream from a merging position and downstream of a fourth removal point thereof is controlled to a closed state by means of the control unit 15.

[0125] In certain embodiments, the third and fourth removal points may be the same points, since pipes L12, L13 merge. However, pipe L13 does not necessarily exist downstream of the first removal point. Furthermore, pipes L12 and L13 do not necessarily merge upstream of the heat exchanger, so that the liquid from pumps 11, 12 could be vaporized independently.

(Second Circulation Liquid In-Feed Processing and Second Product Liquid In-Feed Processing)

[0126] The control unit 15 feeds the first liquefied oxygen to the nitrogen condenser 3 using the first liquid feed pump 11 which is in the low-pressure operating mode, and at the same time feeds a portion (W1) of the second liquefied oxygen to the nitrogen condenser 3 also using the second liquid feed pump 12 which is in the high-pressure operating mode (second circulation liquid in-feed processing). The control unit 15 opens the second gate valve V2 to cause the portion (W1) of the second liquefied oxygen to merge into the first branch pipe L11 through the circulation branch pipe L14. Furthermore, the control unit 15 feeds the remainder (W2) of the second liquefied oxygen to the main heat exchanger 101, after which it is extracted as product oxygen gas (second product liquid in-feed processing).

[0127] In certain embodiments, the portion W1 may correspond to between 3 and 50% or even between 3 and 15%, preferably between 5 and 10% of the flowrate of the liquid at the first liquid pressure sent from the first pump 11 to the condenser section 3 in normal operation.

[0128] The control unit 15 controls the amount of circulation liquid and the amount of product oxygen gas by adjusting opening/closing or flow rate of the second gate valve V2.

[0129] In certain embodiments, during normal operation, the molar flowrate of liquid sent from the first pump to the condenser is at least five times, preferably at least eight times higher than the molar flowrate of liquid sent from the first pump to the heat exchanger; for example 95% of the liquid from the first pump 11 is sent to condenser 31 and 5% of the liquid from the first pump 11 is sent to the heat exchanger 101.

Embodiment 2

[0130] An air separation unit 100 according to embodiment 2 illustrated in FIG. 1B comprises first and second return pipes L16, L17, in addition to the components of embodiment 1. The same component reference numbers denote the same functions, and components having additional functions or different functions will be described in particular.

[0131] The first return pipe L16 branches from the first branch pipe L11 downstream from the first liquid feed pump 11 and communicates with the column bottom portion 41 of the second rectification column 4. A sixth gate valve V6 is provided in the first return pipe L16. Opening/closing and flow rate of the sixth gate valve V6 are controlled and a return amount of the first liquefied oxygen is adjusted by means of the control unit 15.

[0132] The first return pipe L17 branches from the second branch pipe L12 downstream from the second liquid feed pump 12 and communicates with the column bottom portion 41 of the second rectification column 4. A seventh gate valve V7 is provided in the second return pipe L17. Opening/closing or flow rate of the seventh gate valve V7 is controlled and a return amount of the second liquefied oxygen is adjusted by means of the control unit 15.

Embodiment 3

[0133] An air separation unit 100 according to embodiment 3 illustrated in FIG. 1C comprises a liquid level measurement unit F1 for the column bottom portion 41 of the second rectification column 4 and/or a flow rate measurement unit F2 for the product oxygen gas, in addition to the components of embodiment 1 or 2. The same component reference numbers denote the same functions, and components having additional functions or different functions will be described in particular.

[0134] The liquid level measuring unit F1 measures an amount of liquefied oxygen in the column bottom portion 41 of the second rectification column 4. The control unit 15 controls a feed amount of the first liquefied oxygen by means of the first liquid feed pump 11, correspondingly with the measurement data. Furthermore, the control unit 15 controls a feed amount of the second liquefied oxygen by means of the second liquid feed pump 12 correspondingly with the measurement data.

[0135] The flow rate measurement unit F2 is provided in the second branch pipe L12 downstream from the main heat exchanger 101, and measures the flow rate of product oxygen gas for a demand destination. The control unit 15 controls the feed amount of the first liquefied oxygen (the amount of circulation liquid which is fed) by means of the first liquid feed pump 11, and the feed amount of the second liquefied oxygen (feed amount of the circulation liquid and amount of product oxygen gas) by means of the second liquid feed pump 12, correspondingly with the measurement data.

[0136] The air separation unit 100 may comprise both the liquid level measurement unit F1 and the flow rate measurement unit F2, or may comprise either one thereof.

[0137] The control unit 15 may operate the second liquid feed pump 12, which is in the high-pressure operating mode, at the minimum flow rate, and may operate the first liquid feed pump 11, which is in the low-pressure operating mode, so as to respond to process fluctuations.

Embodiment 4

[0138] An air separation unit 100 according to embodiment 4 illustrated in FIG. 1D is in accordance with the configurations of embodiments 1, 2 and 3, but has a different pipe configuration in the liquefied gas supply system 1. The same component reference numbers denote the same functions, and components having additional functions or different functions will be described in particular.

[0139] The first branch pipe L11 communicates with the nitrogen condenser 3 and feeds the liquefied oxygen to the nitrogen condenser 3 as a circulation liquid. A gate valve V11 is provided in the first branch pipe L11. The fourth gate valve V4 is provided in the product liquid branch pipe L13 which branches from the first branch pipe L11 at a position upstream from the gate valve V11. The gate valve V11 is opened and the fourth gate valve V4 is closed, whereby the first liquefied oxygen is fed to the nitrogen condenser 3 by means of the first liquid feed pump 11.

[0140] The second branch pipe L12 extends to the main heat exchanger 101 and feeds liquefied oxygen. The fifth gate valve V5 is provided in the second branch pipe L12. The circulation branch pipe L14 branching from the second branch pipe L12 at a position upstream from the fifth gate valve V5 communicates with the nitrogen condenser 3. A gate valve V12 is provided in the circulation branch pipe L14. The gate valve V12 is closed and the fifth gate valve V5 is opened, whereby the second liquefied oxygen is fed only to the main heat exchanger 101 by means of the second liquid feed pump 12. Meanwhile, the gate valve V12 is opened and the fifth gate valve V5 is also opened, whereby a portion of the second liquefied oxygen (W1) is fed to the nitrogen condenser 3, and the remainder (W2) thereof is fed to the main heat exchanger 101.

[0141] According to the configuration above, by virtue of the fact that the first branch pipe L11 and the circulation branch pipe L14 do not merge, it is possible to suppress turbulence which would be at risk of occurring inside the pipes due to a liquid flow from high-pressure lines to low-pressure lines.

Embodiment 5

[0142] Embodiment 5 illustrated in FIG. 1D, which is in accordance with embodiments 1, 2, 3 and 4, comprises first and second liquefied oxygen tanks T1, T2.

[0143] The first liquefied oxygen tank T1 is a tank for extracting the first liquefied oxygen from the first branch pipe L11 as it runs to the nitrogen condenser 3, and for storing the first liquefied oxygen.

[0144] The second liquefied oxygen tank T2 is a tank for extracting the second liquefied oxygen from the second branch pipe L12 as it runs to the main heat exchanger 101, and for storing the second liquefied oxygen.

[0145] The first and second liquefied oxygen storage tanks T1, T2 may supply the liquefied oxygen as a product, and may be utilized as primary storage buffers.

Embodiment 6

[0146] In embodiments 1-5, either one of the first liquid feed pump 11 and the second liquid feed pump 12 is stopped, and only the other is operated in the high-pressure operating mode, and opening/closing of the gate valves in the pipes is controlled. When only the first liquid feed pump 11 is operated in the high-pressure operating mode, a portion of the first liquefied oxygen is fed to the nitrogen condenser 3 as a circulation liquid, and the remainder thereof is fed to the main heat exchanger 101. When only the second liquid feed pump 12 is operated in the high-pressure operating mode, a portion of the second liquefied oxygen is fed to the nitrogen condenser 3 as a circulation liquid, and the remainder thereof is fed to the main heat exchanger 101.

[0147] This portion may correspond to between 3 and 100% of the liquid sent from the first pump 11 to the condenser 3 in normal operation i.e. when the first and second pumps both operate, one sending liquid to the condenser and the other to heat exchanger.

[0148] When the first liquid feed pump 11 has been stopped, the control unit 15 closes the first gate valve V1 (or gate valve V11) and the fourth gate valve V4, and opens the second gate valve V2 and third gate valve V3 (or gate valve V12), and the fifth gate valve V5. The second liquid feed pump 12 is operated in the high-pressure operating mode.

[0149] Meanwhile, when the second liquid feed pump 12 has been stopped, the control unit 15 closes the second gate valve V2 (gate valve V12) and the fifth gate valve V5, and opens the first gate valve V1 and third gate valve V3 (or gate valve V11), and the fourth gate valve V4. The first liquid feed pump 11 is operated in the high-pressure operating mode.

Embodiment 7

[0150] An air separation unit 200 according to embodiment 7 illustrated in FIG. 2 constitutes a high-pressure air separation unit. The same component reference numbers denote the same functions, and components having additional functions or different functions will be described in particular.

[0151] The air separation unit 200 comprises: a main heat exchanger 101, a first rectification column 2, a nitrogen condenser 3, a second rectification column 4, an expansion turbine 71, a first heat exchanger 102, and a liquefied gas supply system 1.

[0152] An oxygen-enriched gas drawn from the column top portion 32 of the nitrogen condenser 3 is fed to the expansion turbine 71 after this gas has passed through a portion of the main heat exchanger 101 via a low-pressure oxygen line L3211. The oxygen-enriched gas which has been used in the expansion turbine 71 is once again fed to the main heat exchanger 101 from where it is extracted as low-pressure oxygen gas (or waste gas).

[0153] An expansion turbine 7 such as in embodiment 1 is not provided.

[0154] The configurations of embodiments 1-6 are applied to the liquefied gas supply system 1.

Embodiment 8

[0155] An air separation unit 300 according to embodiment 8 illustrated in FIG. 3 constitutes a high-pressure air separation unit (embodiment 7) comprising an argon rectification column. The same component reference numbers denote the same functions, and components having additional functions or different functions will be described in particular.

[0156] The argon rectification column 5 comprises a column bottom portion 51, a rectification portion 52, and a column top portion 53. A first rectified substance (e.g., an oxygen-enriched gas) drawn from the first intermediate rectification portion 42, or the rectification portion below, of the second rectification column 4 by means of an intermediate drawing pipe L42 is fed to the column bottom portion 51 of the argon rectification column 5 via the intermediate drawing pipe L42. A second rectified substance drawn from the column bottom portion 51 by means of a bottom portion drawing pipe L51 is fed to the first intermediate rectification portion 42 via the bottom portion drawing pipe L51.

[0157] An oxygen-enriched liquid drawn from the column bottom portion 21 of the first rectification column 2 passes through the first heat exchanger 102 via an oxygen-enriched liquid drawing pipe L211, and is fed to the first intermediate rectification portion 42 of the second rectification column 4. The oxygen-enriched liquid is fed to a refrigerant portion of a first condensing portion 6 by means of an oxygen-enriched liquid drawing branch pipe L211a branching from the oxygen-enriched liquid drawing pipe L211 at a position downstream from the first heat exchanger 102.

[0158] An argon-rich substance drawn from the column top portion 53 of the argon rectification column 5 by means of an argon extraction pipe L53 is extracted as product argon via the argon extraction pipe L53.

[0159] A separation pipe L53a separating from the argon extraction pipe L53 communicates with the first condensing portion 6 and feeds the argon-rich substance to the first condensing portion 6, where the argon-rich substance is condensed (liquefied) and returned to the column top portion 53 of the argon rectification column 5.

[0160] A gas (oxygen-enriched gas) drawn from the column top portion 62 of the first condensing portion 6 is fed to the first intermediate rectification portion 42 of the second rectification column 4 via a gas drawing pipe L62. In FIG. 3, the gas drawing pipe L62 merges with the oxygen-enriched liquid drawing pipe L211, but this is not limiting.

[0161] The configurations of embodiments 1-6 are applied to the liquefied gas supply system 1.

Other Embodiments

[0162] (1) In embodiments 1-8, the liquefied gas supply system 1 comprises the two liquid feed pumps, i.e., the first and second liquid feed pumps, but this is not limiting, and three or more liquid feed pumps may be provided.

[0163] (2) Application of the liquefied gas supply system 1 is not limited to the air separation units of embodiments 1-8, and it may also be applied to other air separation units.

Key to Symbols

[0164] 1 Liquefied gas supply system [0165] 2 First rectification column [0166] 3 Nitrogen condenser [0167] 4 Second rectification column [0168] 5 Argon rectification column [0169] 7 Expansion turbine [0170] 11 First liquid feedpump [0171] 12 Second liquid feed pump [0172] 15 Control unit [0173] 100 Air separation unit [0174] 101 Main heat exchanger

[0175] Additional refrigeration may be supplied for all the figures by the addition of liquid nitrogen to a column 2, 4 from an external source (liquid assist).

[0176] In certain embodiments, the present invention solves above technical problems by the configuration characterized as follows.

TABLE-US-00001 Dedicated pump arrange- ment with one pump feeding the condenser Shared only and another feeding pumps Case Invention the heat exchanger only (JP6257656B2) Heat leak 20 19 22 (Mcal/h) Compensation 6 Base 15 by N2 liquid assist (kW) Investment ?1 ?7 ?1 (mJPY) NPV (mJPY) ?4.9 ?9.2 ?10.7

[0177] While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and broad scope of the appended claims. The present invention may suitably comprise, consist or consist essentially of the elements disclosed and may be practiced in the absence of an element not disclosed. Furthermore, if there is language referring to order, such as first and second, it should be understood in an exemplary sense and not in a limiting sense. For example, it can be recognized by those skilled in the art that certain steps can be combined into a single step.

[0178] The singular forms a, an and the include plural referents, unless the context clearly dictates otherwise.

[0179] Comprising in a claim is an open transitional term which means the subsequently identified claim elements are a nonexclusive listing (i.e., anything else may be additionally included and remain within the scope of comprising). Comprising as used herein may be replaced by the more limited transitional terms consisting essentially of and consisting of unless otherwise indicated herein.

[0180] Providing in a claim is defined to mean furnishing, supplying, making available, or preparing something. The step may be performed by any actor in the absence of express language in the claim to the contrary.

[0181] Optional or optionally means that the subsequently described event or circumstances may or may not occur. The description includes instances where the event or circumstance occurs and instances where it does not occur.

[0182] Ranges may be expressed herein as from about one particular value, and/or to about another particular value. When such a range is expressed, it is to be understood that another embodiment is from the one particular value and/or to the other particular value, along with all combinations within said range.

[0183] All references identified herein are each hereby incorporated by reference into this application in their entireties, as well as for the specific information for which each is cited.