Heat exchangers and air separation units

Abstract

To provide a heat exchanger capable of improving a recovery rate of argon by improving separation efficiency of a low-pressure tower.SOLUTION: A heat exchanger 200 includes: one or more cold fluid passage which has a first passage in which any one of cold flow gases is circulated from a cold end side toward a hot end side; and one or more hot fluid passage which has a second passage in which any one of hot flow gases is circulated from a hot end side toward a cold end side and a third passage in which any one of hot flow liquids is circulated from the hot end side toward the cold end side, and in which the second passage is disposed at the hot end side and the third passage is disposed at the cold end side. The third passage has an introduction port and a lead-out port positioned at the cold end side with respect to the introduction port. The introduction port is connected to a high-pressure tower 500 by a conduit, and any one of the lead-out ports is connected to an argon condenser 400 for producing reflux of the argon tower 700 by a conduit.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a heat exchanger and an air separation unit. [Background technology]

[0002] In an air separation unit consisting of a high-pressure column, a low-pressure column, and an argon column, the feed air is cooled to near its dew point in the main heat exchanger because it is based on a distillation operation. The liquid produced in the high-pressure column is supplied to the low-pressure column through a pressure reducing valve, but is cooled in a subcooler to reduce the amount of vapor generated during pressure reduction, improve the separation efficiency of the low-pressure column, and increase the product recovery rate.

[0003] However, in an air separation unit, each component, including the distillation column, is large, which makes the entire unit large. Therefore, Patent Document 1 discloses a heat exchanger in which a main heat exchanger and a subcooler are integrated, with the aim of reducing the size of the entire unit, and an air separation unit equipped with the heat exchanger.

[0004] The heat exchanger disclosed in Patent Document 1 is a plate-fin type heat exchanger that uses one or more gases extracted from a low-pressure column as cold stream gases, one or more liquids extracted from a high-pressure column as warm stream liquids, and at least a portion of feed air as warm stream gases, and cools the one or more warm stream liquids and the one or more warm stream gases using the one or more cold stream gases. This heat exchanger includes one or more cold fluid passages having a first passage through which one of the cold stream gases flows from the cold end side to the warm end side, a second passage through which one of the warm stream gases flows from the warm end side to the cold end side, and a third passage through which one of the warm stream liquids flows from the cold end side to the warm end side, the second passage being located on the warm end side and the third passage being located on the cold end side. The third passage has an inlet and an outlet located closer to the warm end than the inlet, and the inlet is connected to the high-pressure column by a conduit.

[0005] According to the heat exchanger disclosed in Patent Document 1, the cold gas flow and the warm liquid flow flow in the same direction, and the temperature difference between the cold gas flow and the warm liquid flow decreases toward the outlet, so the amount of heat exchanged can be limited and the area for cooling the warm liquid can be made compact. As a result, although the amount of heat exchanged in the area for cooling the warm gas flow increases, the impact is small, and the entire heat exchanger can be made smaller. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] U.S. Patent No. 6,044,902 Summary of the Invention [Problem to be solved by the invention]

[0007] However, in the heat exchanger disclosed in Patent Document 1, the temperature of the warm liquid discharged from the heat exchanger is relatively high, and the amount of steam generated by the pressure reducing valve for supplying the liquid to the low-pressure column increases, reducing the separation efficiency in the low-pressure column. Therefore, when the heat exchanger disclosed in Patent Document 1 is applied to an air separation unit equipped with an argon column, there is a problem in that the argon recovery rate decreases.

[0008] The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a heat exchanger and an air separation unit that can improve the separation efficiency of a low-pressure column and thereby improve the argon recovery rate. [Means for solving the problem]

[0009] In order to achieve the above object, the present invention employs the following configuration. [1] A plate-fin type heat exchanger used in an air separation plant having a high-pressure column, a low-pressure column, and an argon column, in which one or more gases extracted from the low-pressure column are used as cold stream gases, one or more liquids extracted from the high-pressure column are used as warm stream liquids, and at least a portion of the feed air is used as warm stream gases, and one or more of the warm stream liquids and one or more of the warm stream gases are cooled by one or more of the cold stream gases, One or more cold fluid passages, each having a first passage through which any one of the cold flow gases flows from the cold end side to the hot end side; One or more hot fluid passages include a second passage through which any one of the hot gas flows from the hot end side to the cold end side, and a third passage through which any one of the hot liquid flows from the hot end side to the cold end side, the second passage being disposed on the hot end side, and the third passage being disposed on the cold end side; the third passage has an inlet and an outlet located closer to the cold end than the inlet, the inlet is connected to the high-pressure column by a conduit; any one of the outlets is connected by a conduit to an argon condenser for producing reflux liquid for the argon column. [2] The heat exchanger according to [1], wherein the first passage and the second passage are arranged so as to flow in countercurrent. [3] At least one of the third passages is composed of two or more paths; The heat exchanger according to [1] or [2], wherein the first passage and the third passage are arranged to form a cross flow. [4] At least one of the hot fluid passages has one of the second passages and two of the third passages; The heat exchanger according to any one of [1] to [3], wherein the outlet of one of the third passages is located closer to the warm end than the outlet of the other of the third passages. [5] A heat exchanger according to any one of [1] to [4], wherein the outlet of the second passage of at least one of the hot fluid passages is located closer to the hot end than the outlets of the second passages of the other hot fluid passages. [6] The liquid taken out from the low-pressure column is a cold stream liquid; The heat exchanger according to any one of [1] to [5], wherein at least one of the cold fluid passages has a fourth passage through which the cold fluid flows from the cold end side to the warm end side. [7] An air separation unit comprising a high-pressure column, a low-pressure column, an argon column, and the heat exchanger according to any one of [1] to [6]. [Effects of the Invention]

[0010] The heat exchanger and air separation unit of the present invention can improve the separation efficiency of the low-pressure column and increase the recovery rate of argon. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a system diagram showing the configuration of an air separation unit according to an embodiment of the present invention. [Figure 2] 1 is a schematic diagram showing a part of the configuration of a heat exchanger in an air separation unit according to an embodiment of the present invention. [Figure 3] 1 is a schematic diagram showing a part of the configuration of a heat exchanger in an air separation unit according to an embodiment of the present invention. [Figure 4] FIG. 2 is a system diagram showing the configuration of an air separation unit as a comparative example of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] A heat exchanger according to an embodiment of the present invention and an air separation unit including the same will be described in detail below with reference to the drawings. Note that the drawings used in the following description may show characteristic portions enlarged for ease of understanding, and the dimensional proportions of the components may not necessarily be the same as those in reality.

[0013] First, the configuration of a heat exchanger according to one embodiment of the present invention will be described together with an air separation unit equipped with the heat exchanger, with reference to Figure 1. Figure 1 is a schematic diagram showing an air separation unit equipped with a heat exchanger according to one embodiment of the present invention.

[0014] <Heat exchanger> As shown in FIG. 1 , the heat exchanger 200 of this embodiment is a plate-fin type heat exchanger used in an air separation unit 100 including a high-pressure column 500, a low-pressure column 600, and an argon column 700, and which converts one or more gases extracted from the low-pressure column 600 into cold stream gases, one or more liquids extracted from the low-pressure column 600 into cold stream liquids, one or more liquids extracted from the high-pressure column 500 into warm stream liquids, at least a portion of the feed air into warm stream gases, and cools the one or more warm stream liquids and the one or more warm stream gases using the one or more cold stream gases and the cold stream liquids. Hereinafter, an example will be described in which one cold liquid flow C1, two cold gas flows C2 and C3, three warm gas flows W1 to W3, and three warm liquid flows W4 to W6 are used.

[0015] As shown in FIG. 1, a part of the compressed and purified raw air is supplied to a heat exchanger 200 through a pipe 21 as a warm gas stream W2. Nitrogen gas supplied from the top of low-pressure column 600 via line 2 is supplied to heat exchanger 200 as cold gas stream C2. The exhaust gas supplied from a position near the top of the low-pressure column 600 via a pipe 3 is supplied to the heat exchanger 200 as a cold gas stream C3. The warm gas stream W2 supplied to the heat exchanger 200 is cooled by heat exchange with the cold gas streams C2 and C3, and is supplied to the bottom of the high-pressure column 500 through the pipe 22.

[0016] Furthermore, a portion of the raw air is pressurized and then supplied to the heat exchanger 200 through a pipe 11 as a warm gas stream W1. Liquid oxygen supplied from main condenser 300 via line 1 is supplied to heat exchanger 200 as cold liquid stream C1. The warm gas stream W1 supplied to the heat exchanger 200 is cooled and liquefied by heat exchange with the cold liquid stream C1, and is supplied to the lower part of the high-pressure column 500 via the pipe 12.

[0017] Furthermore, a portion of the feed air is pressurized and then supplied as warm gas stream W3 to heat exchanger 200 via pipe 31. The warm gas stream W3 supplied to heat exchanger 200 is cooled by heat exchange with cold gas streams C2 and C3, expanded in a turbine, and then supplied via pipe 32 to a position from the middle to the upper part of low-pressure column 600.

[0018] A portion of the liquid nitrogen produced in the main condenser 300 located at the top of the high-pressure column 500 is supplied as warm liquid stream W6 to the heat exchanger 200 via a pipe 61. The warm liquid stream W6 supplied to the heat exchanger 200 is cooled by heat exchange with the cold gas streams C2 and C3, and is then reduced in pressure via a pipe 62 before being supplied to the top of the upper column 600 as a reflux liquid.

[0019] The oxygen-enriched liquid air produced at the bottom of the high-pressure column is supplied as warm liquid stream W4 to heat exchanger 200 via line 41. The warm liquid stream W4 supplied to heat exchanger 200 is cooled by heat exchange with cold gas streams C2 and C3, and is reduced in pressure via line 42 before being introduced into argon condenser 400 located at the top of the argon column. The warm liquid stream (oxygen-enriched liquid air) W4 introduced into the argon condenser 400 is evaporated and supplied to the low-pressure column 600 via a line 43.

[0020] Meanwhile, liquid air withdrawn from the bottom of the high-pressure column is supplied as warm liquid stream W5 to heat exchanger 200 through pipe 51. Warm liquid stream W5 supplied to heat exchanger 200 is cooled by heat exchange with cold gas streams C2 and C3, and is then reduced in pressure through pipe 52 before being supplied to low-pressure column 600.

[0021] Fig. 2 is a cross-sectional view showing an example of the configuration of a hot fluid passage constituting the heat exchanger 200 of this embodiment. Fig. 3 is a cross-sectional view showing an example of the configuration of a cold fluid passage constituting the heat exchanger 200 of this embodiment. As shown in FIGS. 2(1) to 2(4) and 3(1) to 3(3), the heat exchanger 200 of this embodiment includes four hot fluid passages A1 to A4 and three cold fluid passages B1 to B3.

[0022] 2(1), the hot fluid passage A1 is divided into two regions between the hot end and the cold end, closer to the cold end, and the hot end region of the divided regions has a passage (second passage) a1 through which the hot gas W1 flows from the hot end to the cold end. The passage a1 for the hot gas W1 has an inlet (W1in) located on the hot end side of the hot fluid passage A1 and an outlet (W1out) located on the cold end side of the hot fluid passage A1.

[0023] 2(2), the hot fluid passage A2 is divided into two regions between the hot end side and the cold end side, closer to the cold end side, and the hot end side of the divided regions has a passage (second passage) a2 through which the hot gas W2 flows from the hot end side to the cold end side. The passage a2 for the hot gas W2 has an inlet (W2in) located on the hot end side of the hot fluid passage A2 and an outlet (W2out) located on the cold end side of the hot fluid passage A2.

[0024] Furthermore, the cold end region of the hot fluid passage A2 is further divided into two regions, and the warm end region has a passage (third passage) a4 through which hot fluid W4 flows from the hot end to the cold end. The passage a4 for hot fluid W4 has an inlet (W4in) and an outlet (W4out) located closer to the cold end than the inlet (W4in). Furthermore, the passage a4 has five flow paths (paths) extending in a direction perpendicular to the direction from the hot end to the cold end, and these flow paths are connected in a staggered manner. As a result, the oxygen-enriched liquid air extracted through pipe 41 connected to high-pressure column 500 flows into the inlet (W4in) of passage a4 as warm liquid W4, flows crosswise relative to the cold fluid, flows in the opposite direction through the subsequent path arranged on the cold end side, and is discharged from the outlet (W4out) after passing through a total of five paths.

[0025] Furthermore, the cold end region of the hot fluid passage A2, which is further divided into two regions, has a passage (third passage) a6 through which hot fluid W6 flows from the hot end to the cold end. The passage a6 for hot fluid W6 has an inlet (W6in) and an outlet (W6out) located closer to the cold end than the inlet (W6in). The passage a6 also has two flow paths (paths) extending in a direction perpendicular to the direction from the hot end to the cold end, and these flow paths are connected alternately. As a result, the liquid nitrogen extracted through the pipe 61 connected to the main condenser 300 flows into the inlet (W6in) of the passage a6 as the warm liquid W6, flows in a cross direction relative to the cold fluid, passes through two paths, and is discharged from the outlet (W6out).

[0026] That is, the hot fluid passage A2 has one passage (second passage) a2 located on the hot end side and two passages (third passages) a4 and a6 located on the cold end side. Furthermore, in the hot fluid passage A2, the two passages (third passages) a4 and a6 are each composed of two or more flow paths. Furthermore, in the hot fluid passage A2, the outlet (W4out) of the passage (third passage) a4 for the hot fluid W4 is located closer to the hot end than the outlet (W6out) of the passage (third passage) a6 for the hot fluid W6.

[0027] 2(3), the hot fluid passage A3 is divided into two regions between the hot end and the cold end, closer to the cold end, and the hot end region of the divided regions has a passage (second passage) a2 through which the hot gas W2 flows from the hot end to the cold end. The passage a2 for the hot gas W2 has an inlet (W2in) located on the hot end side of the hot fluid passage A3 and an outlet (W2out) located on the cold end side of the hot fluid passage A3.

[0028] Furthermore, the cold end region of the hot fluid passage A3 is further divided into two regions, and the hot end region has a passage (third passage) a5 through which hot fluid W5 flows from the hot end to the cold end. The passage a5 for hot fluid W5 has an inlet (W5in) and an outlet (W5out) located closer to the cold end than the inlet (W5in). The passage a5 also has three flow paths extending in a direction perpendicular to the direction from the hot end to the cold end, and these flow paths are connected in a staggered manner. As a result, the liquid air drawn from the bottom of the high-pressure column 500 through the pipe 51 flows as warm liquid W5 from the outlet (W5in) of the passage a5, flows crosswise relative to the cold fluid, flows in the opposite direction through the subsequent path disposed on the cold end side, and passes through a total of three paths before being discharged from the outlet (W5out).

[0029] Furthermore, the cold end region of the hot fluid passage A3, which is further divided into two regions, has a passage (third passage) a6 through which hot fluid W6 flows from the hot end to the cold end. The passage a6 for hot fluid W6 has an inlet (W6in) and an outlet (W6out) located closer to the cold end than the inlet (W6in). The passage a6 also has two flow paths extending in a direction perpendicular to the direction from the hot end to the cold end, and these flow paths are connected alternately.

[0030] That is, the hot fluid passage A3 has one passage (second passage) a2 located on the hot end side and two passages (third passages) a5 and a6 located on the cold end side. Furthermore, in the hot fluid passage A3, the two passages (third passages) a5 and a6 are each composed of two or more flow paths. Furthermore, in the hot fluid passage A3, the outlet (W5out) of the passage (third passage) a5 for the hot fluid W5 is located closer to the hot end than the outlet (W6out) of the passage (third passage) a6 for the hot fluid W6.

[0031] 2(4), the hot fluid passage A4 is divided into two regions between the hot end and the cold end, closer to the cold end, and the hot end region of the divided regions has a passage (second passage) a3 through which the hot gas W3 flows from the hot end to the cold end. The passage a3 for the hot gas W3 has an inlet (W3in) located on the hot end side of the hot fluid passage A4 and an outlet (W3out) located on the cold end side of the hot fluid passage A4. The outlet (W3out) of the passage (second passage) a3 of the hot fluid passage A4 is located closer to the hot end than the outlets (W1out, W2out) of the passages (second passages) a1, a2 of the hot fluid passages A1 to A3.

[0032] As shown in Figure 3(1), the cold fluid passage B1 is divided into two regions between the hot end and the cold end, closer to the cold end, and the hot end region of the divided regions has a passage (fourth passage) b1 through which the cold flow liquid C1 flows from the cold end to the hot end. The passage b1 for the cold flow liquid C1 has an inlet (C1in) located on the cold end side of the cold fluid passage B1 and an outlet (C1out) located on the hot end side of the cold fluid passage B1.

[0033] As shown in Figure 3(2), the cold fluid passage B2 has a passage (first passage) b2 through which the cold flow gas C2 flows from the cold end side to the hot end side. The passage b2 for the cold flow gas C2 has an inlet (C2in) located on the cold end side of the cold fluid passage B2 and an outlet (C2out) located on the hot end side of the cold fluid passage B2.

[0034] As shown in Figure 3 (3), the cold fluid passage B3 has a passage (first passage) b3 through which the cold flow gas C3 flows from the cold end side to the hot end side. The passage b3 for the cold flow gas C3 has an inlet (C3in) located on the cold end side of the cold fluid passage B3 and an outlet (C3out) located on the hot end side of the cold fluid passage B3.

[0035] As shown in FIGS. 1 to 3, the heat exchanger 200 of this embodiment is a plate-fin type heat exchanger configured by alternately stacking four hot fluid passages A1 to A4 and three cold fluid passages B1 to B3. In the heat exchanger 200, passages (second passages) a1 to a3 through which raw air (warm gas streams W1 to W3) flows, a passage (fourth passage) b1 for liquid oxygen (cold liquid gas stream C1), a passage (first passage) b2 for nitrogen gas (cold gas stream C2), and a passage (first passage) b3 for exhaust gas (cold gas stream C3) are arranged so as to flow in countercurrent.

[0036] In addition, in the heat exchanger 200 of this embodiment, the passages (third passages) a4 to a6 for the liquids (warm flow liquids W4 to W6) extracted from the high-pressure column 500 through pipelines, the passage (first passage) b2 for the nitrogen gas (cold flow gas C2), and the passage (first passage) b3 for the exhaust gas (cold flow gas C3) are arranged to form a cross flow.

[0037] In the heat exchanger 200 of this embodiment, the inlets (in) of the passages (third passages) a4 to a6 for the warm liquid W4 to W6 are all located on the warm end side of the heat exchanger 200 relative to the outlets (out), and are connected to the high-pressure column 500 by pipelines (conduits).

[0038] As described above, according to the heat exchanger 200 of this embodiment, by arranging the inlets (in) of the passages (third passages) a4-a6 for the warm liquids W4-W6 connected to the high-pressure column 500 closer to the warm end of the heat exchanger 200 than the outlets (out), the outlet temperatures of the warm liquids W4-W6 can be further lowered. Furthermore, since the outlet (W4out) of the passage (third passage) a4 for the warm liquid W4 is connected to the argon condenser 400 for producing reflux liquid for the argon column 700 via the pipe (conduit) 42, a warm liquid W4 with a sufficiently low temperature can be supplied to the argon condenser 400. Therefore, the amount of steam generated at the pressure reducing valves when supplying the warm liquid W4 to the low-pressure column 600 and the argon condenser 400 is reduced, the separation efficiency of the low-pressure column 600 and the argon column 700 can be increased, and the argon recovery rate in the air separation unit 100 can be improved.

[0039] 1 to 3, the heat exchanger 200 includes two hot fluid passages A1 to A4, each of which is located between the hot end and the cold end and is divided into two regions closer to the cold end. The hot end region includes passages (second passages) a1 to a3 for hot gas flows W1 to W3, and the cold end region includes passages (third passages) a4 to a6 for hot liquid flows W4 to W6. That is, the heat exchanger 200 is divided into two regions closer to the cold end, with the hot end corresponding to a conventional main heat exchanger and the cold end corresponding to a subcooler. Thus, the heat exchanger 200 of this embodiment integrates the main heat exchanger and the subcooler, allowing for a more compact air separation unit 100 compared to a configuration in which the main heat exchanger and the subcooler are separately installed.

[0040] <Air separation unit> Next, the configuration of the air separation unit 100 equipped with the heat exchanger 200 of this embodiment will be described. As shown in FIG. 1, the air separation unit 100 of this embodiment includes a high-pressure column 500, a low-pressure column 600, an argon column 700, and the heat exchanger 200 described above.

[0041] According to the air separation unit 100 of this embodiment, the outlet temperatures of the warm liquid flows W4 to W6 can be further lowered by the above-mentioned heat exchanger 200. Furthermore, since the outlet of any one of the warm liquid flows is connected to the argon condenser 400 by a conduit, and warm liquid flow W4 with a sufficiently low temperature can be supplied to the argon condenser 400, the amount of steam generated at the pressure reducing valves when supplying the warm liquid to the low-pressure column 600 and the argon condenser 400 is reduced, the separation efficiency of the low-pressure column 600 and the argon column 700 can be increased, and the argon recovery rate can be improved.

[0042] Furthermore, according to the air separation unit 100 of this embodiment, the main heat exchanger and the subcooler are integrated in the heat exchanger 200 described above, so the air separation unit 100 can be made smaller than in a configuration in which the main heat exchanger and the subcooler are installed separately.

[0043] The technical scope of the present invention is not limited to the above-described embodiments, and includes designs within the scope of the present invention. The heat exchanger 200 of the above-described embodiment has been described as including warm fluid passages A2 and A3 in which warm liquids W4 to W6 are disposed on the cold end side of the warm gas W2, but is not limited to this. For example, the heat exchanger 200 may be configured to include warm fluid passages in which warm liquids W4 to W6 are disposed on the cold end side of the warm gas W1 or the warm gas W3. [Example]

[0044] The effects of the present invention will be specifically described below, but the present invention is not limited to the following description.

[0045] <Example> Using air separation unit 100 equipped with heat exchanger 200 shown in FIG. 1, liquid argon was collected as a product under the following conditions.

[0046] (Operating conditions) Liquid nitrogen (warm liquid W6) temperature drop: 10.9K - Temperature drop of oxygen-enriched liquid air (warm liquid W4): 6.4K Argon gas extraction volume: 760Nm 3 / h

[0047] <Comparative Example> Using air separation unit 101 equipped with heat exchanger 201 shown in FIG. 4, liquid argon to be used as a product was collected under the following conditions. The heat exchanger 200 shown in Figure 1 differs in that the inlets of the passages (third passages) for the warm liquids W4 to W6 are all located closer to the warm end than the outlets, whereas the heat exchanger 201 shown in Figure 4 differs in that the inlets of the passages (third passages) for the warm liquids W4 to W6 are all located closer to the cold end than the outlets.

[0048] (Operating conditions) Liquid nitrogen (warm liquid W6) temperature drop: 7.7K - Temperature drop of oxygen-enriched liquid air (warm liquid W4): 4.6K Product liquid argon collection amount: 690Nm3 / h

[0049] <Verification results> As a result of comparing the above-mentioned Example and Comparative Example, it was confirmed that the amount of recovered product liquid argon increased by about 10% in the Example compared to the Comparative Example. [Explanation of symbols]

[0050] 100 Air Separation Unit 200 heat exchanger 400 Argon Condenser 500 High Pressure Tower 600 Low Pressure Tower 700 Argon Tower a1~a6 aisle A1~A4 Hot fluid passage b1~b3 aisle B1~B3 Cold fluid passage C1 cold flow liquid C2 Cold Gas C3 Cold Gas W1~W3 Warm gas W4~W6 Hot flow liquid

Claims

1. 1. A plate-fin type heat exchanger for use in an air separation unit comprising a high-pressure column, a low-pressure column, and an argon column, wherein one or more gases extracted from the low-pressure column are cold stream gases, one or more liquids extracted from the high-pressure column are warm stream liquids, and at least a portion of feed air is warm stream gases, and the one or more warm stream liquids and the one or more warm stream gases are cooled by the one or more cold stream gases, one or more cold fluid passages, each having a first passage through which any one of the cold flow gases flows from the cold end side to the hot end side; one or more hot fluid passages, each of which includes a second passage through which one of the hot gas flows from the hot end side to the cold end side, and a third passage through which one of the hot liquid flows from the hot end side to the cold end side, the second passage being disposed on the hot end side, and the third passage being disposed on the cold end side; the third passage has an inlet and an outlet located closer to the cold end than the inlet, the inlet is connected to the high-pressure column by a conduit; any one of the outlets is connected by a conduit to an argon condenser for producing a reflux liquid for the argon column; At least one of the third passages is composed of two or more paths; The first passage and the third passage are arranged to form a cross flow; and a heat exchanger in which the inside of the hot fluid passage is divided into two regions, a warm end region located on the warm end side and a cold end region located on the cold end side, the second passage being arranged to fit within the warm end region, and the third passage being arranged to fit within the cold end region.

2. The heat exchanger according to claim 1 , wherein the first passage and the second passage are arranged in counterflow.

3. At least one of the hot fluid passages includes one of the second passages and two of the third passages; 3. The heat exchanger according to claim 1, wherein an outlet of one of the third passages is located closer to the warm end than an outlet of the other of the third passages.

4. 4. The heat exchanger according to claim 1, wherein the outlet of the second passage of at least one of the hot fluid passages is located closer to the hot end than the outlets of the second passages of the other hot fluid passages.

5. The liquid withdrawn from the low-pressure column is a cold stream liquid; 5. The heat exchanger according to claim 1, wherein at least one of the cold fluid passages includes a fourth passage through which the cold fluid flows from the cold end side to the warm end side.

6. An air separation unit comprising a high-pressure column, a low-pressure column, an argon column, and the heat exchanger according to any one of claims 1 to 5.

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