Air separation device

Abstract

To provide an air separation device capable of recovering high-purity oxygen at a high yield without reducing a production amount of argon.SOLUTION: An air separation device comprises a main heat exchanger 1, a first rectification tower 2, a nitrogen condenser 3, a second rectification tower 4, a third rectification tower 5, a crude argon condenser 6, a high-purity oxygen rectification tower 8, and a high-purity oxygen reboiler 9. The air separation unit uses a portion of raw material air having passed through the main heat exchanger 1 as a heat source for the high-purity oxygen reboiler 9.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an air separation unit for producing high purity oxygen and argon and a method for producing the same. [Background technology]

[0002] High-purity oxygen and argon, free of high-boiling components such as hydrocarbons, are in high demand in the semiconductor industry and elsewhere. To produce this high-purity oxygen and argon, a cryogenic air separation unit is used, as disclosed in, for example, Patent Document 1, which includes three fractionation columns: a medium-pressure column, a low-pressure column, and a crude argon column. Patent Document 1 describes a method for concentrating an oxygen-enriched liquid, from which high-boiling components have been removed and which is obtained from the middle of the crude argon column, using medium-pressure nitrogen gas as a reboil source. However, in the process of Patent Document 1, when medium-pressure nitrogen gas is used to reboil the high-purity oxygen, the amount of medium-pressure nitrogen gas supplied to the bottom of the low-pressure column is correspondingly reduced. This reduces the vapor flow in the low-pressure column, significantly reducing the recovery of argon, which is particularly difficult to separate. This raises concerns about a possible reduction in argon recovery (20-30%), for example.

[0003] Patent Document 2 discloses a cryogenic air separation unit comprising a first rectification column, a second rectification column, a third rectification column for rectifying argon, and a high-purity oxygen rectification column for rectifying ultra-high-purity oxygen. Recycled nitrogen is used as a reboiler source for the high-purity oxygen. The use of recycled nitrogen complicates the design of the main heat exchanger and also requires a nitrogen compressor. The use of recycled nitrogen requires extra energy input into the high-purity oxygen rectification column, but does not increase argon recovery.

[0004] Patent Document 3 discloses introducing recycled nitrogen into the main condenser (top of the high-pressure column) and the high-purity oxygen reboiler. The high-purity oxygen reboiler can also receive recycled nitrogen or high-pressure nitrogen gas derived from the high-pressure rectification column. After condensation, the liquefied recycled gas in the outlet of the high-purity oxygen reboiler is sent to either the high-pressure or low-pressure rectification column as reflux liquid. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] U.S. Patent Publication No. 5,049,173 [Patent Document 2] Patent No. 7355978 [Patent Document 3] International Patent Publication No. WO2022 / 058043 Summary of the Invention [Problem to be solved by the invention]

[0006] In view of the above circumstances, an object of the present disclosure is to provide an air separation unit capable of recovering high-purity oxygen at a high yield without reducing the amount of argon produced compared to conventional techniques, and a method for producing the same. Another object of the present invention is to provide an air separation unit and a method for producing the same that can maintain high recovery of argon and high-purity oxygen more effectively than conventional techniques without making the unit configuration more complex or increasing the number of units. [Means for solving the problem]

[0007] The method for producing argon and ultra-high purity oxygen disclosed herein comprises producing argon and high-purity oxygen using an air separation unit (A1, A2) equipped with a main heat exchanger (1), a first rectification column (medium-pressure rectification column) (2), a nitrogen condenser (3), a second rectification column (low-pressure rectification column) (4), a third rectification column (crude argon column) (5), a crude argon condenser (6), an upper rectification section (7), a high-purity oxygen rectification column (8), and a high-purity oxygen reboiler (9), A part of the feed air is used as a heat source for a high purity oxygen reboiler (9). The feed air used as the heat source may be introduced into the rectifying sections (43, 44) of the second rectifying column (4) or into the upper rectifying section (7).

[0008] The air separation units (A1, A2) a heat exchanger (1) for exchanging heat with feed air; a first rectification column (medium-pressure column) (2) into which the feed air that has passed through the heat exchanger (1) is introduced, the first rectification column (medium-pressure column) (2) having a first bottom (21) in which an oxygen-enriched liquid accumulates, a first rectification section (22) that rectifies the feed air, and a first column top (23) that is disposed above the first rectification section (22) and in which a first evaporated gas accumulates; a nitrogen condenser (3) disposed above the first column top (23) and configured to condense the first evaporated gas from the first column top (23); a second rectification column (4) having second rectification sections (41, 42, 43) and a second column top (44) from which low-pressure nitrogen gas is discharged; a third rectification column (crude argon column) (5) for rectifying argon, the third rectification column (5) having a third bottom (51) into which a crude argon feed gas discharged from an intermediate section (41) of a second rectification section (40) of the second rectification column (4) is introduced, a third rectification section (52) for rectifying the crude argon feed gas, and a third column top (53) in which argon accumulates; a crude argon condenser (6) disposed above the third column top (53) and configured to condense argon from the third column top (53); an upper rectification section (7) disposed above the crude argon condenser (6); a high-purity oxygen rectification column (8) for rectifying high-purity oxygen, the high-purity oxygen rectification column (8) having an oxygen column bottom (81) below which a high-purity oxygen reboiler (9) is disposed; an upper portion (823) of the oxygen rectification section (82) into which an oxygen-enriched liquid (intermediate section outlet liquid) discharged from an intermediate section of the third rectification section (52) of the third rectification column (5) is introduced; and an oxygen column top (83) from which oxygen evaporated gas is discharged to be returned to the intermediate section of the third rectification section (52) of the third rectification column (5); a feed air inlet line (L1) for passing feed air through the main heat exchanger (1) and introducing the feed air below the first bottom (21) or the first rectification section (22) of the first rectification column (2); A part of the feed air is used as a heat source for a high purity oxygen reboiler (9). The air separation units (A1, A2) A first heat source introduction line (L11) branching from the feed air introduction line (L1) and used as a heat source for the high-purity oxygen reboiler (9) and introduced into the rectifying section (43, 44) of the second rectification column (4) or a second heat source introduction line (L12) branching from the feed air introduction line (L1) and used as a heat source for the high-purity oxygen reboiler (9) and introduced into the upper rectifying section (7) may be provided.

[0009] The air separation units (A1, A2) an oxygen outlet line (L3) for extracting oxygen from the refrigerant phase (31) of the nitrogen condenser (3) and passing through the heat exchanger (1) to be extracted as product oxygen; a liquid pump (11) disposed in the oxygen outlet line (L3) for transferring liquid oxygen; an argon gas outlet line (L53) for extracting argon (gaseous and / or liquid) (which may be used as a product) from the third column top (53); an argon-containing liquid discharge line (L51) for introducing the argon-containing liquid discharged from the third bottom (51) into the first intermediate stage (41) of the second rectification section (40) of the second rectification column (4); an evaporation gas introduction line (L71) for introducing the evaporation gas discharged from above the crude argon condenser (6) into the second intermediate stage (42) of the second rectification section (40); a high-purity liquid oxygen outlet line (L81) for extracting high-purity liquid oxygen (as a product) from the bottom (81) of the oxygen tower; It may also be equipped with:

[0010] The air separation unit a product nitrogen gas line (L44) for introducing low-pressure nitrogen gas discharged from a second column top (44) of the second rectification column (4) into the heat exchanger (1); an expansion turbine (10) for expanding the gas discharged from the rectification section (41) below the second rectification column (4) and introduced into the main heat exchanger (1) and discharged from the main heat exchanger; and a waste gas line (L41) through which the gas discharged from the rectification section (41) at the lower part of the second rectification column (4) is introduced into the heat exchanger (1), discharged from an intermediate stage, subjected to work in the expansion turbine (10), and then passed through the main heat exchanger (1) again to be discharged as waste gas.

[0011] According to the above-described configuration, the oxygen-enriched liquid, from which components with a boiling point higher than that of oxygen, such as hydrocarbons, have been removed, is supplied from the lower part of the rectification section of the third rectification column (crude argon column) (5) to the high-purity oxygen rectification column (8), where it is rectified and re-boiled. The vapor is returned to the third rectification column, and ultra-high purity oxygen (UPOX) is recovered from the bottom (81). A part of the feed air cooled in the main heat exchanger (1) is used as a heat source for the ultra-high purity oxygen reboiler (9) for rectifying the ultra-high purity oxygen. The feed air flow rate is controlled to produce constant purity argon and high purity oxygen according to demand points. This eliminates the need for a nitrogen compressor or an additional condenser, reducing the number of pieces of equipment, and enabling high-purity oxygen to be produced without reducing the amount of argon produced. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a diagram showing an air separation unit of a first embodiment. [Figure 2] FIG. 1 is a diagram showing an air separation unit according to a second embodiment. [Figure 3] 1 is a diagram showing air separation units of an embodiment and a reference example. [Figure 4] FIG. 1 is a graph showing the relationship between high-purity oxygen production and argon recovery rate in an example. DETAILED DESCRIPTION OF THE INVENTION

[0013] Several embodiments of the present invention will be described below. The embodiments described below are merely examples of the present invention. The present invention is not limited to the following embodiments, and includes various modified forms that are implemented within the scope of the present invention. Note that not all of the configurations described below are necessarily essential configurations of the present invention.

[0014] (Embodiment 1) A cryogenic air separation unit A1 of the first embodiment will be described with reference to FIG. The air separation unit A1 basically comprises a heat exchanger 1, a first rectification column (medium pressure column) 2, a nitrogen condenser 3, a second rectification column (low pressure column) 4, a third rectification column (crude argon column) 5, a crude argon condenser 6, an upper rectification section 7, a high-purity oxygen rectification column 8, and a high-purity oxygen reboiler 9.

[0015] Feed air passes through the heat exchanger 1 via a feed air inlet line L1 and is supplied to the first bottom 21 or the first rectifying section 22 of the first rectifying column 2. The first rectification column 2 has a first bottom 21 in which oxygen-enriched liquid accumulates, a first rectification section 22 in which the feed air is rectified, and a first column top 23 located above the first rectification section 22 in which the first evaporated gas accumulates. The nitrogen condenser 3 is disposed above the first column top 23. The nitrogen condenser 3 condenses the first evaporated gas at the first column top 23.

[0016] The second rectification column 4 is disposed above the nitrogen condenser 3. The second rectification column 4 has a second rectification section 40 (41, 42, 43) and a second column top 44 from which low-pressure nitrogen gas is discharged. The third rectification column 5 rectifies argon. The third rectification column 5 has a third column bottom 51 into which crude argon feed gas is introduced, the crude argon feed gas being discharged from the intermediate section 41 of the second rectification section 40 of the second rectification column 4, preferably from a stage lower than the central position of the second rectification section 40, a third rectification section 52 that rectifies the crude argon feed gas, and a third column top 53 in which argon (gaseous and / or liquid) accumulates. The crude argon condenser 6 is disposed above the third column top 53. The crude argon condenser 6 condenses the argon (gaseous and / or liquid) in the third column top 53.

[0017] The high-purity oxygen rectification column 8 rectifies the ultra-high purity oxygen. The high-purity oxygen rectification column 8 has an oxygen column bottom section 81 below which the high-purity oxygen reboiler 9 is disposed, an oxygen rectification section 82 into which the oxygen-enriched liquid (intermediate section outlet liquid) discharged from the intermediate section of the third rectification section 52 of the third rectification column 5 is introduced, and an oxygen column top section 83 from which the oxygen evaporated gas is discharged to be returned to the intermediate section of the third rectification section 52 of the third rectification column 5.

[0018] The first oxygen-enriched liquid introduction line L21 is a line for introducing the oxygen-enriched liquid discharged from the first bottom 21 of the first fractionator 2 into the intermediate section 42 of the second fractionating section 40 (preferably, a stage above the central position of the second fractionating section 40). A first branch line L212 branching off from the first oxygen-enriched liquid introduction line L21 is a line for introducing the oxygen-enriched liquid into the upper rectification section 7. The first evaporation gas introduction line L23 is a line for introducing the first evaporation gas discharged from the first column top 23 of the first fractionator 2 into the second column top 44 of the second fractionator 4. A portion of the first evaporation gas is introduced as a heat source for the nitrogen condenser 3 through a branch line L231 branched from the first evaporation gas introduction line L23, where it dissipates heat and is cooled before returning to the first column top 23.

[0019] The oxygen outlet line L3 is a line for passing oxygen (gaseous and / or liquid) extracted from the refrigerant phase 31 of the nitrogen condenser 3 through the heat exchanger 1 to extract the oxygen as product oxygen. The liquid feed pump 11 is disposed in the oxygen outlet line L3 and feeds liquid oxygen. The intermediate section discharge line L42 is a line for introducing crude argon feed gas discharged from the intermediate section 42 of the second rectification section 40, preferably from a stage below the central position of the second rectification section 40, into the third column bottom 51 of the third rectification column 5.

[0020] The product nitrogen gas line L44 is a line for introducing the low-pressure nitrogen gas discharged from the second column top 44 of the second rectification column 4 into the heat exchanger 1 and extracting it as a product. The expansion turbine 10 expands the gas that is discharged from the rectification section 41 below the second rectification column 4, introduced into the main heat exchanger 1, and discharged from the middle of the expansion turbine. By expanding the gas in the expansion turbine 10 and generating refrigeration, it is possible to maintain the refrigeration balance of the device while using the process gas. The waste gas line L41 is a line through which the gas discharged from the rectification section 41 below the second rectification column 4 is introduced into the heat exchanger 1, discharged from an intermediate stage, subjected to work in the expansion turbine 10, and then passed through the main heat exchanger 1 again to be extracted as waste gas.

[0021] The argon-containing liquid discharge line L51 is a line for introducing the argon-containing liquid discharged from the third column bottom 51 into the intermediate section 41 of the second rectification section 40 of the second rectification column 4, preferably into a stage below the central position of the second rectification section 40. The intermediate section discharge line L52 is a line for introducing oxygen-enriched liquid (intermediate section discharge liquid) discharged from the intermediate section of the third rectification section 52, preferably from a section below the central position of the third rectification section 52, into the upper part of the oxygen rectification section 82, preferably from a section above the central position of the oxygen rectification section 82. The argon gas outlet line L53 is a line for taking out argon (gaseous and / or liquid) from the third column top 53. Argon (gaseous and / or liquid) is introduced as a heat source into the crude argon condenser 6 through a branch circulation line L531 branching off from the argon gas outlet line L53, where it dissipates heat, is cooled, and is liquefied before returning to the third column top 53.

[0022] The second condenser evaporated gas introduction line L71 is a line for introducing the second condenser evaporated gas derived from above the crude argon condenser 6 or from the upper rectification section 7 into the intermediate section 42 of the second rectification section 40, or a line for merging with the first oxygen-enriched liquid introduction line L21 and then introducing it into the intermediate section 42.

[0023] The high-purity liquid oxygen discharge line L81 is a line for taking out high-purity liquid oxygen from the bottom 81 of the oxygen tower. The oxygen evaporation gas discharge line L83 is a line for sending the oxygen evaporation gas discharged from the oxygen column top 83 to a stage above the discharge position of the intermediate section discharge line L52 of the rectification section 52 of the third rectification column 5.

[0024] The high-purity oxygen reboiler 9 is disposed in the oxygen tower bottom 81 below the high-purity oxygen rectification tower 8. A portion of the feed air that has passed through the main heat exchanger 1 is used as the heat source for the high-purity oxygen reboiler 9. The first heat source introduction line L11 branches off from the feed air introduction line L1 and is used as a heat source for the high-purity oxygen reboiler 9, and is a line for introducing the heat source into the middle stage or upper part (43 or 44) of the rectification section of the second rectification column 4.

[0025] (Embodiment 2) An air separation unit A2 of the second embodiment will be described with reference to Fig. 2. Configurations different from those of the first embodiment shown in Fig. 1 will be described, and descriptions of the same configurations will be omitted or simplified. The second heat source introduction line L12 branches off from the feed air introduction line L1, and is a line used as a heat source for the high-purity oxygen reboiler 9 and introduced into the upper rectification section .

[0026] (Example) 3 shows an example (Embodiment 1) and Reference Examples 1 and 2. In Reference Example 1, instead of Embodiment 1, a portion of the first evaporation gas is introduced as a heat source for the high-purity oxygen reboiler 9 through a branch line L232 branching off from the first evaporation gas introduction line L23. In Reference Example 2, a portion of the oxygen-enriched liquid is introduced as a heat source for the high-purity oxygen reboiler 9 through a second branch line L213 branching off from the first oxygen-enriched liquid introduction line L21. To produce the same amount (1 mol) of high-purity oxygen, the amount of heat supplied to the high-purity oxygen reboiler (9) was as follows: In other words, using the feed air as a heat source is more efficient than the others. Example (part of feed air) 1:10 Reference Example 1 (part of nitrogen gas) 1:140 Reference Example 2 (part of oxygen-enriched liquid) 1:375

[0027] The nitrogen generator of embodiment 1 is 65 kNm 3 The plant was designed with a capacity of 1000 Nm / h. When the production amount of high-purity oxygen is increased, the production amount of argon decreases. In this embodiment, the production amount of high-purity oxygen can be maintained while suppressing the decrease in the argon production amount. Table 1 and Figure 4 show the relationship between the production amount of high-purity oxygen and the argon recovery rate. For example, when the production amount of high-purity oxygen is 300 to 400 Nm 3 When a certain amount of high-purity oxygen (product oxygen content purity of 99.0% or more) was produced in the range of / h, the argon recovery rate decreased from about 88.58% to about 82-85%. In this example, the argon recovery loss can be suppressed to about 5% compared to Reference Examples 1 and 2.

[0028] [Table 1]

[0029] (Another embodiment) Although not specifically shown, a pressure regulator, a flow rate controller, or the like may be installed in each line to regulate the pressure or flow rate.

[0030] 1 Main heat exchanger 2 First rectification tower 3 Nitrogen condenser 4 Second rectification tower 5 Third rectification tower 6. Crude Argon Condenser 7 Upper rectification section 8. High-purity oxygen condenser 9. Ultra-high purity oxygen reboiler 10 Expansion turbine 11 Liquid transfer pump

Claims

1. a heat exchanger for exchanging heat with the raw air; a first rectification column into which the feed air that has passed through the heat exchanger is introduced, the first rectification column having a first bottom portion in which an oxygen-enriched liquid accumulates, a first rectification section that rectifies the feed air, and a first column top portion that is disposed above the first rectification section and in which a first evaporated gas accumulates; a nitrogen condenser disposed above the top of the first column and configured to condense the first evaporated gas at the top of the first column; a second rectification column having a second rectification section and a second column top from which low-pressure nitrogen gas is discharged; a third rectification column for rectifying argon, the third rectification column having a third bottom portion into which a crude argon feed gas derived from an intermediate portion of the second rectification section of the second rectification column is introduced, a third rectification section for rectifying the crude argon feed gas, and a third column top portion in which argon accumulates; a crude argon condenser disposed above the top of the third column and configured to condense argon from the top of the third column; a high-purity oxygen rectification column for rectifying high-purity oxygen, the high-purity oxygen rectification column having an oxygen column bottom section below which a high-purity oxygen reboiler is disposed, an upper section of the oxygen rectification section into which oxygen-enriched liquid withdrawn from an intermediate section of the third rectification column is introduced, and an oxygen column top section from which oxygen evaporated gas is withdrawn to be returned to the intermediate section of the third rectification column; a feed air inlet line for introducing the feed air into the first bottom or below the first rectifying section of the first rectifying column after passing through the main heat exchanger, A part of the feed air is used as a heat source for the high-purity oxygen reboiler. Air separation unit.

2. an upper rectifying section disposed above the crude argon condenser; A portion of the oxygen-enriched liquid introduced from the first bottom of the first rectification column is introduced into the upper part of the upper rectification section, and oxygen in the oxygen-enriched liquid is rectified.

10. The air separation unit of claim 1.

3. a first heat source introduction line branching from the feed air introduction line, used as a heat source for the high-purity oxygen reboiler, and introduced into a rectifying section of the second rectifying column; the feed air used as a heat source for the high-purity oxygen reboiler is introduced into an intermediate portion of the second rectification section of the second rectification column; 3. An air separation unit according to claim 1 or 2.

4. a second heat source introduction line branching from the feed air introduction line, used as a heat source for the high-purity oxygen reboiler, and introduced above the upper rectifying section; Feed air used as a heat source for the high-purity oxygen reboiler is introduced into the upper rectifying section.

3. The air separation unit of claim 2.

5. A method for producing argon and ultra-high purity oxygen, comprising: producing argon and high purity oxygen using an air separation unit comprising a main heat exchanger, a first rectification column, a nitrogen condenser, a second rectification column, a third rectification column, a crude argon condenser, an upper rectification section, a high purity oxygen rectification column, and a high purity oxygen reboiler; a part of the feed air that has passed through the main heat exchanger is used as a heat source for the high-purity oxygen reboiler; method.

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