HEAT EXCHANGER

Abstract

An object of the present invention is to provide a heat exchanger that can be used in an air separation unit including a low-pressure column, a high-pressure column, and a mixing column, and that can suppress increases in equipment costs. The present invention provides a heat exchanger used in an air separation unit (1100) including a low-pressure column (600), a high-pressure column (500), and a mixing column (400), wherein the heat exchanger is composed of plates and fins, and wherein a warm gas which is at least a part (at least one of W1, W2, W3) of a feed air and at least one warm liquid (at least one of W4 and W5) which is led out from the mixing column (400) are cooled by at least one cold gas (at least one of C2 and C3) which is led out from the low-pressure column (600) and a cold gas (C1) which is led out from the mixing column (400), and a cold liquid (C6) which is led out from the low-pressure column (600) through a pressure boosting pump (800) and supplied to the mixing column (400) is heated.

Claims

1. A heat exchanger used in an air separation unit including a low-pressure column, a high-pressure column, and a mixing column, wherein the heat exchanger is composed of plates and fins, and wherein a warm gas which is at least a part of a feed air and at least one warm liquid which is led out from the mixing column are cooled by at least one cold gas which is led out from the low-pressure column and a cold gas which is led out from the mixing column, and a cold liquid which is led out from the low-pressure column through a pressure boosting pump and supplied to the mixing column is heated.

2. The heat exchanger according to claim 1, wherein at least one warm liquid which is led out from the high-pressure column is cooled.

3. The heat exchanger according to claim 1, wherein the heat exchanger further includes a cold liquid passage through which the cold liquid flows, a cold gas passage through which the cold gas flows, a warm liquid passage through which the warm liquid flows, and a warm gas passage through which the warm gas flows, and wherein the warm gas passage is arranged so that the warm gas flows in a counter-flow to the cold liquid and the cold gas, and the warm liquid passage is arranged so that the warm liquid flows in a cross-flow to the cold liquid and the cold gas.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] FIG. 1 is an explanatory diagram of an air separation unit equipped with a heat exchanger according to the first embodiment.

[0018] FIG. 2 is an explanatory diagram of the internal structure of the heat exchanger according to the first embodiment.

[0019] FIG. 3 is an explanatory diagram of an air separation unit equipped with a heat exchanger according to the second embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Embodiment

[0020] FIG. 1 shows an example of an air separation unit using the heat exchanger according to the present embodiment.

[0021] The heat exchanger 110 according to the present embodiment is a heat exchanger used in an air separation unit 1100 including a low-pressure column 600, a high-pressure column 500, and a mixing column 400, as shown in FIG. 1.

[0022] The heat exchanger 110 of the present embodiment is a heat exchanger that is composed of plates and fins, and that a warm gas (at least one of W1, W2, and W3) which is at least a part of the feed air and at least one warm liquid (at least one of W4 and W5) which is led out from the mixing column 400 are cooled by at least one cold gas (at least one of C2 and C3) which is led out from the low-pressure column 600 and cold gas (C1) which is led out from the mixing column 400, and a cold liquid (C6) which is led out from the low-pressure column 600 through a pressure boosting pump 800 and supplied to the mixing column 400 is heated.

[0023] First, the overall configuration of the air separation unit 1100 including the heat exchanger 110 will be described with reference to FIG. 1, and then the internal structure of the heat exchanger 110 will be described.

[0024] In the present description, a fluid marked with C (the initial of cold) is a cold fluid, and a fluid marked with W (the initial of warm) is a warm fluid.

<Explanation of the Configuration of the Air Separation Unit>

[0025] The air separation unit 1100 includes a high-pressure column 500, a low-pressure column 600, a mixing column 400, a subcooler 190, and a heat exchanger 110.

[0026] A part (W2) of a feed air (W1, W2, W3) which has compressed by the compressor 90 and purified by the purifier 91 is supplied to the heat exchanger 110 through a pipe 21. In the heat exchanger 110, a part (W2) of the feed air is cooled by heat exchange with a product oxygen gas (C1) which is supplied from the top of the mixing column 400 through a line 1, a nitrogen gas (C2) which is supplied from the top of the low-pressure column 600 through the subcooler 190 and a line 2, a medium-pressure nitrogen gas (C3) which is supplied from the top of the high-pressure column 500 through a line 3, and a liquid oxygen (C6) which is supplied from the bottom of the low-pressure column 600 and pressurized by a pressure boosting pump 800, and then is supplied to the bottom of the high-pressure column 500 through a line 22.

[0027] Another part (W1) of the feed air is pressurized in a recompressor 92 and then supplied to the heat exchanger 110 through a line 11. In the heat exchanger 110, the other part (W1) of the feed air is cooled by heat exchange with cold fluids, namely the product oxygen gas (C1), the nitrogen gas (C2), the medium-pressure nitrogen gas (C3), and the liquid oxygen (C6), and then supplied to the bottom of the mixing column 400 through a line 13.

[0028] Furthermore, still another part (W3) of the feed air is pressurized by the recompressor 93 and then supplied to the heat exchanger 110 through a line 31. In the heat exchanger 110, the another part (W3) of the feed air is cooled by heat exchange between the product oxygen gas (C1), the nitrogen gas (C2), and the medium-pressure nitrogen gas (C3), which are cold fluids, and is further expanded by the expansion turbine 94, after which it is supplied to the low-pressure column 600 through a line 32.

[0029] A part (W2) of the feed air which has supplied to the high-pressure column 500 through a pipe 22 ascends while coming into gas-liquid contact with a reflux liquid descending inside the high-pressure column 500, and nitrogen, which is a low boiling point component, is concentrated, producing nitrogen gas at the top of the high-pressure column 500.

[0030] In addition, an oxygen-enriched liquid air, which is enriched in oxygen, which is a high boiling point component, is produced at the bottom of the high-pressure column 500 and is led out through a line 53.

[0031] The nitrogen gas which has produced in the high-pressure column is liquefied in the main condenser 300, and a part of it is supplied to the subcooler 190 where it is cooled through a line 51, reduced in pressure through a line 52, and then supplied as reflux to the top of the low-pressure column 600.

[0032] In addition, an oxygen-enriched liquid air which is led out from the bottom of the high-pressure column 500 through a line 53, and supplied to the subcooler 190 through a line 43 together with a liquid air which has led out from the mixing column 400 through a line 41, the heat exchanger 110, and a line 42, cooled, decompressed through a line 44, and then supplied as reflux to the low-pressure column 600.

[0033] The cooling source for these liquids in the subcooler 190 is a nitrogen gas supplied through a line 60 from the top of the low-pressure column 600.

[0034] The reflux liquid which has supplied to the low-pressure column 600 descends due to gas-liquid contact with the ascending gas in the low-pressure column 600, and oxygen, which is a high boiling point component, is concentrated as it flows down, producing liquid oxygen at the bottom of the low-pressure column 600. Meanwhile, nitrogen, which is a low boiling point component, is concentrated in the ascending gas as it rises, producing nitrogen gas at the top of the low-pressure column 600.

[0035] The liquid oxygen (C6) which has produced at the bottom of the low-pressure column 600 is led out through a line 61, pressurized by a pressure boosting pump 800, and then introduced to the heat exchanger 110 through a line 62. In the heat exchanger 110, the pressurized liquid oxygen (C6) exchanges heat with the liquid which is side-cut from the mixing column 400 (hereinafter referred to as side-cut liquid) through a line 45, the bottom liquid (W4) from a line 41, and a part of the feed air (W1, W2), and is heated. After that, it is led out through a line 64 and supplied to the top of the mixing column 400.

[0036] In the mixing column 400, the liquid oxygen supplied and the gaseous air introduced through a line 13 come into direct contact with each other, and a product oxygen (C1) with low-purity is produced and led out from the top of the mixing column 400 through a line 1.

<Explanation of Heat Exchanger>

[0037] The heat exchanger 110 can be a plate-fin heat exchanger in which layers composed of plates and fins are stacked. FIG. 2 shows each layer of the heat exchanger 110 separated into flow paths.

[0038] As shown in FIG. 2, the heat exchanger 110 has three warm fluid passages A1 to A3 and three cold fluid passages B1 to B3.

[0039] The warm fluid passage A1 has a warm gas passage a1 through which a warm gas W1 flows between the warm end and the cold end.

[0040] The warm fluid passage A2 is divided into two flow areas between the warm end and the cold end, with the warm end section having a warm gas passage a2 through which a warm gas W2 flows, and the cold end section having a warm liquid passage a4 through which a warm liquid W4 flows.

[0041] The warm fluid passage A3 is divided into two flow areas between the warm end and the cold end, with the warm end section having a warm gas passage a3 through which a warm gas W3 flows, and the cold end section having a warm liquid passage a5 through which a warm liquid W5 flows.

[0042] Furthermore, the cold fluid passage B1 is divided into two flow areas between the warm end and the cold end, with the warm end section having a cold gas passage b1 through which a cold gas C1 flows, and the cold end section having a cold liquid passage b6 through which a cold liquid C6 flows.

[0043] The cold fluid passage B2 has a cold gas passage b2 through which a cold gas C2 flows between the warm end and the cold end.

[0044] The cold fluid passage B3 has a cold gas passage b3 through which a cold gas C3 flows between the warm end and the cold end.

[0045] The warm gas passages a1, a2, a3 (see FIGS. 2(a), (b), and (c)), through which the feed air (W1, W2, W3), which is a warm gas, flows, are arranged so that the warm gases flow in a counter-flow to the cold gases in the cold gas passages b1, b2, b3 (see FIGS. 2(d), (e), and (f)), through which the product oxygen gas (C1), the nitrogen gas (C2), and the medium-pressure nitrogen gas (C3), which are the cold gases, flow, and to the cold liquid passage b6 (see FIG. 2(d)), through which the liquid oxygen (C6), which is a cold liquid, flows.

[0046] In addition, the warm liquid passages a4, a5 (see FIGS. 2(b) and (c)), through which the bottom liquid (W4) and side-cut liquid (W5), which are warm liquids led out from the mixing column 400 through the lines 41 and 45, flow, are arranged so that the warm liquids flow in a cross-flow to the cold gases in the cold gas passages b2, b3 (see FIGS. 2(e) and 2(f)), through which the nitrogen gas (C2) and the medium-pressure nitrogen gas (C3), which are the cold gases, flow, and to the cold liquid passage b6 (see FIG. 2(d)), through which the liquid oxygen (C6), which is a cold liquid, flows.

[0047] The passage for the bottom liquid (W4) (see FIG. 2(b)) consists of five paths, and the passage for the side-cut liquid (W5) (see FIG. 2(c)) consists of seven paths.

[0048] As shown in FIG. 2(b), the bottom liquid (W4) of the mixing column 400 which is led out through the line 41 flows into the inlet (in) of the passage and flows in a cross-flow to the nitrogen gas (C2), the medium-pressure nitrogen gas (C3), and the liquid oxygen (C6), then flows in the opposite direction through the path located in a direction of the cold end, passing through a total of five paths before being led out from the outlet (out).

[0049] As shown in FIG. 2(c), the side-cut liquid (W5) of the mixing column 400 led out through line 45 flows in from the inlet (in) of the passage and flows crosswise against the nitrogen gas (C2), the medium-pressure nitrogen gas (C3) and the liquid oxygen (C6), then flows in the opposite direction through the path located in a direction of the cold end, passing through a total of seven paths before being led out from the outlet (out). The inlets (in) of the bottom liquid (W4) and the side-cut liquid (W5) are provided closer to the warm end than the respective outlets (out), and are connected to the mixing column 400 by the lines 41 and 45.

[0050] In the present embodiment, as shown in FIGS. 2(b) and (c), the passages for the bottom liquid (W4) and the side-cut liquid (W5) are separated and arranged below the passages for the feed air (W2, W3), but they may also be arranged below the passages for the feed air (W1) and the product oxygen gas (C1).

[0051] In addition, the outlet (out) for the liquid oxygen (C6) connected to the top of the mixing column 400 and the inlet (in) for the side-cut liquid (W5) connected to the side-cut of the mixing column 400 are provided closer to the warm end than the outlet (out) for the feed air (W1, W2). The outlet (out) and inlet (in) are arranged so that the efficiency of heat exchange is high, taking into account the temperature of each fluid. This arrangement is possible because of the integrated heat exchanger 110. The heat exchanger 110 of the present embodiment is not a simple combination of an auxiliary heat exchanger, a heater that was provided separately in the conventional example, and a main heat exchanger. However, depending on the pressure of the mixing column 400, the outlet (out) for the liquid oxygen (C6) and the inlet (in) for the side-cut liquid (W5) may be placed toward the cold end.

[0052] As described above, since the heat exchanger 110 has the above functions, it is not necessary to install a heater or an auxiliary heat exchanger, which were separately provided in the conventional example. Furthermore, the cold box space for storing these devices can be reduced, and the equipment costs can be reduced.

Second Embodiment

[0053] FIG. 3 shows an air separation unit 1200 using a heat exchanger 120 according to a second embodiment, which includes a high-pressure column 500, a low-pressure column 600, a mixing column 400, and a heat exchanger 120. In FIG. 3, the same parts as in FIG. 1 are denoted by the same reference numerals.

[0054] The heat exchanger 120 is the heat exchanger 110 shown in FIGS. 1 and 2, to which a passage for cooling liquid including an oxygen-enriched liquid air (hereinafter simply referred to as oxygen-enriched liquid air) (W6) from the bottom of the high-pressure column 500 through the line 43, and a passage for cooling liquid nitrogen (W7) from the main condenser 300 through the line 51 are added.

[0055] The cooling sources for the oxygen-enriched liquid air (W6) and the liquid nitrogen (W7) are nitrogen gas (C2) which is introduced into the heat exchanger 120 from the top of the low-pressure column 600 through the line 60, and the medium-pressure nitrogen gas (C3) which is introduced into the heat exchanger 120 from the top of high-pressure column 500 through the line 3.

[0056] The oxygen-enriched liquid air (W6) and the liquid nitrogen (W7) cooled in the heat exchanger 120 are led out from the lines 44 and 52, and supplied to the low-pressure column 600 after being depressurized.

[0057] As described above, according to the heat exchanger 120, it is possible to eliminates the conventional heater, the auxiliary heat exchanger, and the subcooler 190 that were installed in the first embodiment, and further reduces the cold box space for storing these devices, thereby reducing equipment costs.

EXPLANATION OF SYMBOLS

[0058] 1100, 1200 air separation unit [0059] 800 pressure boosting pump [0060] 500 high-pressure column [0061] 600 low-pressure column [0062] 400 mixing column [0063] 300 main condenser [0064] 190 subcooler [0065] 110, 120 heat exchanger [0066] 90 compressor [0067] 91 purifier [0068] 92, 93 recompressor [0069] 94 expansion turbine [0070] 1, 2, 3, 11, 13, 21, 22, 31, 32, 41, 42, 43, 44, 45, 51, 52, 53, 60, 61, 62, 64 line [0071] A1-A3 warm fluid passage [0072] B1-B3 cold fluid passage [0073] a1, a2, a3 warm gas passage [0074] a4, a5 warm liquid passage [0075] b1-b3 cold gas passage [0076] b6 cold liquid passage [0077] C1 product oxygen gas [0078] C2 nitrogen gas [0079] C3 medium-pressure nitrogen gas [0080] C6 liquid oxygen [0081] W1, W2, W3 feed air [0082] W4 bottom liquid [0083] W5 side-cut liquid [0084] W6 oxygen-enriched liquid air [0085] W7 liquid nitrogen