Heat exchanger and separation apparatus comprising heat exchanger

Abstract

To boost cooling of rich liquid without creating a dead passage in the heat exchanger, with saving in terms of compactness.SOLUTION: This invention discloses a heat exchanger for indirect heat exchange between a first and a second fluids B, C to be cooled and at least a third fluid to be heated, made up of a plurality of passages, namely a first series of passages 1 for the flow at least of the first and of the second fluids, a second series of passages for the flow of the third fluid to be placed in a heat exchange relation with the first and second fluids, the exchanger comprising three sections, the second section being between the first and third sections and means R1 for introducing the first fluid into only a portion of the first series of passages in the second section.SELECTED DRAWING: Figure 5A

Description

[Technical Field]

[0001] The present invention relates to a heat exchanger and a separation apparatus equipped with a heat exchanger. The heat exchanger may be of the direct-flow or alternating-flow type, but the invention can also be applied to counter-flow heat exchangers, such as those described for supercoolers in “Cryogenic Engineering” edited by BA Hands, Academic Press, 1986, pages 213-216, EP1338856, and DE102018009780. [Brief explanation of the drawing]

[0002] [Figure 1] The present invention relates to a separation apparatus comprising a first column K1 operating at a first pressure and a second column K2 adapted to operate at a second pressure below the first pressure, wherein the head of the first column is thermally connected to the tank of the second column, and means for supplying purified and cooled air 10 to at least the first column. [Figure 2A] The following describes one of the n passages in a series of passages: - Liquid B enters the first section SB of the prior art heat exchanger S via box B1 and exits via box B2. - Liquid C enters the second section SC of the prior art heat exchanger S via box C1 and exits via box C2. - The two sections SB and SC are in series. [Figure 2B] To heat the passages in Figure 2A, which are located above both sides of the passage in Figure 2B, one of a series of n+1 or 2n passages, particularly for gas A, extending along the entire length of the prior art exchanger S is shown. [Figure 3A] Entering the first section SB of the exchanger S via box B1 and leaving via box B2, we show one of passage 1 of a series of n passages, specifically for liquid B. [Figure 3B] Entering the second section SC of the exchanger S via box C1 and leaving via box C2, we show one of a series of p passages 2, specifically for liquid C. [Figure 3C] To heat the passages in Figures 3A and 3B, which are located above the passage in Figure 3C, one of a series of n+P+1 or 2n+2p passages extending along the entire length of the exchanger S is shown, particularly for gas A. [Figure 4A] Figure 3A shows a modified form in which liquid B leaves the exchanger at a temperature lower than the temperature at which liquid C enters the exchanger. [Figure 4B] Figure 3B shows a modified form in which liquid B leaves the exchanger at a temperature lower than the temperature at which liquid C enters the exchanger. [Figure 4C] Figure 3C shows a modified form in which liquid B leaves the exchanger at a temperature lower than the temperature at which liquid C enters the exchanger. [Figure 5A] In particular, one of passages 1 of a first series of passages for cooling the liquid inside the exchanger is shown. [Figure 5B] In particular, another passage 2 of the first series of passages for cooling the liquid inside the exchanger is shown. [Figure 5C] In particular, one of the passages 3 of a second series of passages for heating the gas inside the exchanger is shown. [Modes for carrying out the invention]

[0003] Figure 1 shows a separation apparatus comprising a first column K1 operating at a first pressure and a second column K2 adapted to operate at a second pressure below the first pressure, wherein the head of the first column is thermally connected to the tank of the second column, and means for supplying purified and cooled air 10 to at least the first column.

[0004] To create reflux in the second column, liquid B from the oxygen-rich tank of the first column is supercooled and expanded before being sent to the intermediate stage of the second column. Similarly, liquid C from the nitrogen-rich head of the first column is often supercooled in the same supercooler S as the oxygen-rich liquid, then expanded before being sent to the head of the second column. These two liquids are called the rich liquid and the poor liquid, respectively.

[0005] The liquid is cooled by heat exchange with a gaseous nitrogen stream A in a second column that is heated in the supercooler.

[0006] In the subcooler of an apparatus for separating air by low-temperature distillation, particularly in a direct-to-alternating configuration, the cooling of the depleted and rich liquids is carried out in two series-connected exchangers, as shown in US2840994. These exchangers can be integrated into a single exchanger having separate sections. This means that the rich liquid is cooled to a temperature above the entry temperature of the depleted liquid. The present invention aims to enable the cooling of the rich liquid without creating non-functional passages within the exchanger, with savings from the viewpoint of miniaturization.

[0007] The rich liquid B coming from the tank of the first column K1 leaves the supercooler S at a temperature lower than the entry temperature of the poor liquid C coming from the head of column K1.

[0008] Liquid or gaseous oxygen 90 is removed as a product at the bottom of column K2.

[0009] Figures 2A and 2B show passages constituting a prior art heat exchanger having separate sections for cooling liquids B and C.

[0010] Figure 2A shows one of the n pathways in a series of pathways as follows: -Liquid B passes through box B1 to the first section S of the heat exchanger S according to the prior art. B Enter and exit via box B2. - Liquid C enters the second section S of the heat exchanger S according to the prior art through box C1 C and exits through box C2. - The two sections S B and S C are in series. <​​​​​​​​​​​​​​​​​​​​​​​​​Figure 3C shows one of a series of n+P+1 or 2n+2p passages, specifically for gas A, extending along the entire length of the exchanger S to heat the passages of Figures 3A and 3B, which are located above the passage in Figure 3C. The gas starts at inlet A1 and descends, being heated in a dedicated series of passages before reaching outlet A2. Thus, in the first section, gas A exchanges heat only with liquid B, and in the second section, gas A exchanges heat only with liquid C.

[0017] The switcher S consists of a stack of paths combining the three sets of paths shown in Figures 3A, 3B, and 3C, and the pattern, when n=p, is typically as follows: (3132)*n'3 or (313323)*n, where n' is the number of repetitions of the pattern and is 1 or greater.

[0018] Figures 4A, 4B, and 4C show modified forms of Figures 3A, 3B, and 3C in which liquid B leaves the exchanger at a temperature lower than the temperature at which liquid C enters the exchanger. From this, the central section S of the exchanger in which gas A exchanges heat with two liquids B and C simultaneously is shown. BC It exists.

[0019] According to the subject matter of the present invention, a heat exchanger for indirect heat exchange between first and second fluids to be cooled and at least a third fluid to be heated, wherein the heat exchanger is composed of a stack of spaced rectangular plates, the stack having a length, width, and height, and the rectangular plates having a length and width which are the length and width of the stack, and the rectangular plates having a plurality of passages, i.e., a first series of passages for the flow of at least the first and second fluids and a second series of passages for the flow of the third fluid which is in a heat exchange relationship with the first and second fluids The passages are parallel to each other so as to be defined between them, and the range is defined by the periphery, and the heat exchanger is three sections defined by the height and width of the stack and the length of the stack, the three sections comprising a first section having one end of the stack, a second section, and a third section having the other end of the stack, the second section being between the first section and the third section, and at least two of the first, second, and third sections being juxtaposed, the three sections and the first and second sections Means for closing a first set of passages in which sections are juxtaposed and / or second and third sections are juxtaposed; means for introducing a first fluid into the first set of passages at the free end of the first section; means for drawing out the first fluid from the first set of passages in the first section; means for introducing the first fluid only into a portion of the first set of passages in the second section; means for drawing out the first fluid from a portion of the first set of passages; and means for introducing a second fluid into another portion or actually the remaining portion of the first set of passages in the second section. A heat exchanger is provided, comprising means for introducing a fluid; means for drawing a second fluid from another portion or actually the remaining portion of the first series of passages in the second section; means for introducing a second fluid into the first series of passages in the third section; means for drawing a second fluid from the first series of passages at the free end of the third section; means for introducing a third fluid into the third section; means for passing the third fluid through the third, second, and first sections in succession; and means for withdrawing a third fluid from the first section.

[0020] According to another optional aspect: - The n first series of passages are for the first fluid, particularly in the first section, and the n - m first series of passages are for the first fluid, particularly in the second section. - None of the passages are connected for the flow of the first fluid in the third section. - The n first series of passages are for the second fluid, particularly in the third section, and the q first series of passages with q <= m are for the second fluid, particularly in the second section. - q ≠ m - The n first series of passages are for the second fluid, particularly in the third section, and the m first series of passages with m < n are for the second fluid, particularly in the second section. - None of the passages are connected for the flow of the second fluid in the first section. - The number of the first series of passages for the first fluid, particularly in the first section, is n, and the number of the first series of passages for the first fluid, particularly in the second section, is n / 2. - The number of passages for the second fluid, particularly in the second section, is n / 2, and the number of passages for the second fluid, particularly in the third section, is n. - The exchanger is adapted to cool only two fluids. - The rectangular plates are made of aluminum and are separated from each other by fins forming channels in the plurality of passages, and the rectangular plates and the fins are both brazed. - The exchanger comprises only the first and second series of passages. - The exchanger comprises a third series of passages for heating a fourth fluid. - The first series of passages comprises at least a first passage formed between two consecutive plates and at least a second passage formed between two consecutive plates, each of which is adjacent to the second series of passages.

[0021] According to further subject matter of the present invention, a first column adapted to operate at a first pressure and a second column adapted to operate at a second pressure below the first pressure, wherein the head of the first column is thermally connected to the tank of the second column, the first column and the second column, means for supplying purified and cooled air to at least the first column, means for supplying a first fluid which is liquid from the tank of the first column to the second column, means for supplying a second fluid which is liquid from the head of the first column to the second column, and the second column An air separation apparatus is provided, comprising means for extracting a third fluid, which is a nitrogen-rich gas, from a first column; means for extracting an oxygen-rich fluid from a second column; and a heat exchanger as described above, connected to means for supplying a first fluid from a tank of the first column to the second column, means for supplying a second fluid from a head of the first column to the second column, and means for extracting a third fluid from the second column, enabling heating of at least a third fluid by indirect heat exchange with at least the cooled first and second fluids.

[0022] The present invention involves superimposing two fluids within an exchanger in a central area where a rich liquid and a poor liquid coexist, and by, for example, dividing the number of passages for each fluid by 2, so that a portion of the passages is assigned to one fluid and at least a portion of the other passages is assigned to the other fluid, and an external redistribution box starting with n passages allows to become n / 2 within this central area.

[0023] This avoids dead zones within the exchange, increasing efficiency and miniaturization.

[0024] Although this invention is applicable to DC-AC exchanges, it can also be applied to counterflow heat exchangers.

[0025] It should be noted that the exchanger may also be used to heat a third liquid.

[0026] The present invention will be described in more detail with the help of the drawings: Figure 5A shows one of passages 1 of a first series of passages specifically for cooling the liquid inside the exchanger. Figure 5B shows another of passages 2 of the first series of passages, specifically for cooling the liquid inside the exchanger. Figure 5C shows one of the passages 3 of a second series of passages specifically for heating the gas inside the exchanger.

[0027] The heat exchanger according to the present invention is composed of a stack of spaced-apart rectangular plates, the stack having a length, width, and height, and the rectangular plates having a length and width that are the length and width of the stack, and the rectangular plates are arranged parallel to each other so as to define a plurality of passages between the rectangular plates.

[0028] The passage comprises a first series of passages for the flow of first and second fluids, and a second series of passages for the flow of a third fluid that is in a heat exchange relationship with the first and second fluids.

[0029] In the case described, the heat exchanger comprises only a first and a second series of passages. However, in other cases, more than two liquids may be cooled.

[0030] The first series of passages comprises at least a first passage 1 formed between two consecutive plates and at least another second passage 2 formed between two consecutive plates, each of which is adjacent to the second series of passages.

[0031] The boundaries of a passageway are defined by its periphery.

[0032] In this example, the heat exchanger comprises three sections defined by the height and width of the stack and a fraction of the length of the stack, the three sections comprising a first section comprising one end of the stack, a second section comprising one end of the stack, and a third section comprising the other end of the stack, the second section being located between the first and third sections, and the first, second, and third sections being juxtaposed.

[0033] In the section at the end of the exchanger, all of the first series of passages preferably receive a single liquid to be cooled. In at least the central section, only a portion of the first series of passages is supplied with liquid B, while the other or actually the remaining portion is supplied with liquid C.

[0034] FIG. 5A shows one of the passages 1 of the first series of passages of the heat exchanger in which liquids B and C are cooled, while FIG. 5B shows another one of the passages 2 of the first series of passages of the heat exchanger in which liquids B and C are cooled. Each of these passages is in contact with passage 3 for heating gas A according to FIG. 5C. <J

[0035] Each series of passages includes a first section S B , a second section S BC , and a third section S C . The subscripts indicate the liquid cooled in the section, from which it follows that only liquid B is cooled in the first section S B , two liquids B, C are cooled in the second section S BC , and only liquid C is cooled in the third section S C .

[0036] Looking at FIGS. 5A and 5B, liquid B enters the exchanger at the lower end that constitutes the high-temperature end in each of the passages in the first section S B ]>. The inlet box B1 communicates with the set of passages and the other passages 1 and 2, enabling circulation essentially in a direction perpendicular to the axis of the exchanger. The partially subcooled liquid B leaves the first section S via the box R1 B , which does not allow liquid B to circulate through passage 1 of FIG. 5A but sends liquid B to the other passage 2 of FIG. 5B, where liquid B circulates in a portion, in this case half, of the set of passages of the second section S BC . Next, liquid B leaves the exchanger via the box B2 of the other passage 2 of FIG. 5B and does not pass through the passages of the third section S C .

[0037] Similarly, liquid C is in the first section S B Without passing through the second section S BC It enters directly into the second section S. Liquid C is cooled only in the other passage 2 in Figure 5A. BC The liquid in passage 1 in Figure 5B is not cooled. Next, box R2 distributes the partially cooled liquid C through the set of passages as well as the other passages 1 and 2 in Figures 5A and 5B, so that it is fully cooled and leaves box C2.

[0038] Gas A passes through the third, second, and first sections in succession, then through the exchanger, and is heated and withdrawn from the first section.

[0039] The three sections thus comprise a first section comprising one end of the stack, a second section comprising the other end of the stack, with the second section located between the first and third sections. Each of the three sections is defined by the height and width of the stack and a fraction of the stack's length.

[0040] The present invention has been described here in terms of an air separator with an equal number of passages in a second section for liquids B and C, e.g., a rich liquid and a poor liquid. It can be described with a different number of passages and different or additional fluids.

[0041] The exchange includes a first series of passages consisting of passage 1 and other passages 2 shown in Figures 5A and 5B, and a second series of passages consisting of passage 3 shown in Figure 5C.

[0042] The switcher S consists of a stack of paths that combine two sets of paths, and the pattern is typically as follows: (3132)*n'3 or (313323)*n, where n' is the number of repetitions of the pattern, and is 1 or greater.

[0043] In the configuration of the exchanger, there are no dead zones where heat exchange does not occur.

[0044] The switch is "divided" into three sections: Section S is where only the rich liquid B circulates. B , A shared section S in which rich liquid B and poor liquid C coexist. BC , Section S where only a small amount of liquid C is circulating. C .

[0045] In a specific example of air separation, the liquid B rich in air is located at the bottom, in section S B Enter the n passages inside, then exit via the outer box, and then enter the shared section S. BC At the bottom, a portion re-enters, for example, n / 2 passages, and then departs at the top of the shared area.

[0046] The scarce liquid C is absorbed into a portion of the passage, or actually the rest of it, for example, the shared section S. BC Enter the n / 2 passages at the bottom, then exit through the outer box at the top of the shared section, and section S C Entering the n passages again at the bottom, then section S C It departs at the top of it.

[0047] External boxes R1 and R2 allow for changing the number of passages through which the fluid circulates in the exchanger.

[0048] Entrances / exits B1, B2, C1, and C2 may be on the same or opposite sides, depending on the number of passages.

[0049] The principle can be extended to a different number of passages between the rich and poor liquids, and the distribution in the shared area may be other than 50 / 50.

[0050] Fluids other than rich and poor liquids, typically liquid air, liquid nitrogen, and liquid oxygen, may also be present. Similarly, pure nitrogen may be present in addition to residual nitrogen.

[0051] The exchange comprises a wall P that closes a first series of passages, where the first and second sections are juxtaposed, and / or where the second and third sections are juxtaposed.

[0052] Preferably, the plates of the exchanger are made of aluminum and separated from each other by fins that form channels in multiple passages, and the rectangular plates and fins are brazed together.

[0053] The heat exchanger according to the present invention may be of the DC-AC type, but it can also be applied to counterflow heat exchangers.

[0054] The exchanger may be integrated into an air separation unit comprising: a first column adapted to operate at a first pressure; a second column adapted to operate at a second pressure below the first pressure, the head of the first column being thermally connected to a tank of the second column; a first column and a second column; means for supplying purified and cooled air to at least the first column; means for supplying a first fluid B, which is liquid, from the tank of the first column to the second column; means for supplying a second fluid C, which is liquid, from the head of the first column to the second column; means for extracting a third fluid A, which is nitrogen-rich gas, from the second column; and means for extracting an oxygen-rich fluid from the second column. The heat exchanger is connected to allow heating of the third fluid by indirect heat exchange with the first and second fluids, preferably with its main vertical axis.

[0055] A heat exchanger can be used to heat at least two fluids, for example, two gaseous nitrogen streams, by adding at least one additional series of heating passages or by separating a second series of passages.

[0056] A heat exchanger can be used to cool at least three fluids by separating the passages of a second section into at least three.

Claims

1. 1. A heat exchanger for indirect heat exchange between first and second fluids (B, C) to be cooled and at least a third fluid (A) to be heated, said heat exchanger consisting of a stack of spaced apart rectangular plates, said stack having a length, a width and a height, said rectangular plates having a length and a width which are said length and said width of said stack, respectively, said rectangular plates being parallel to one another so as to define between them a plurality of passages, namely a first series of passages (1, 2) for the flow of at least said first and second fluids and a second series of passages (3) for the flow of said third fluid in heat exchange relationship with said first and second fluids, said plurality of passages being delimited by a periphery; The heat exchanger comprises: three sections each defined by the height and width of the stack and a fraction of the length of the stack, wherein the three sections include a first section (S B ), the second section (S BC ), and a third section comprising the other end of the stack, the second section being between the first section and the third section, and at least two of the first, second, and third sections being juxtaposed; means (P) for closing the first series of passages in which the first and second sections are juxtaposed and / or the second and third sections are juxtaposed; means (B1) for introducing said first fluid into said first series of passages at the free end of said first section; means (R1) for withdrawing said first fluid from said first series of passages of said first section; means (R1) for introducing said first fluid into only a portion of said first series of passages in said second section; means (B2) for withdrawing said first fluid from said portion of said first series of passages; means (C1) for introducing said second fluid into another part or indeed the remainder of said first series of passages in said second section; means (R2) for withdrawing said second fluid from said other part or indeed said remaining part of said first series of passages of said second section; means (R2) for introducing said second fluid into said first series of passages in said third section; means (C2) for withdrawing said second fluid from said first series of passages at the free end of said third section; means for introducing the third fluid into the third section; means for passing the third fluid through the third, second, and first sections in succession; and means for withdrawing the third fluid from the first section.

2. The first series of n passages is particularly B ) for the first fluid in the second section (S BC 2. The heat exchanger of claim 1, wherein the first fluid is in a gas phase.

3. Any passageway is connected to the third section (S C 3. A heat exchanger according to claim 1, wherein the first fluid is not connected for flow in the first direction.

4. The first series of n passages is particularly C ) for the second fluid in the second section (S BC 3. The heat exchanger according to claim 1, wherein the second fluid is in a gas phase.

5. Any passageway is connected to the first section (S B 3. A heat exchanger according to claim 1, wherein the second fluid is not connected for flow in the first fluid.

6. In particular, the first section (S B The number of the first series of passages for the first fluid in the second section (S BC 3. A heat exchanger according to claim 1, wherein the number of said first series of passages for said first fluid in said first series is n / 2.

7. In particular, the second section (S BC The number of passages for the second fluid in the third section (S C 3. A heat exchanger according to claim 1, wherein the number of passages for the second fluid in

8. 3. The heat exchanger of claim 1, wherein the rectangular plates are made of aluminum and are separated from one another by fins that form channels in the plurality of passages, and the rectangular plates and the fins are brazed together.

9. 3. A heat exchanger according to claim 1 or 2, comprising only the first and second series of passages (1, 2, 3).

10. a first column (K1) adapted to operate at a first pressure; a second column (K2) adapted to operate at a second pressure lower than the first pressure, wherein the head of the first column is thermally connected to the tank of the second column; means for delivering purified and cooled air (10) to at least the first column; and means for delivering a first fluid (B) in liquid form from a tank of the first column to the second column. means for delivering a second fluid (C), which is a liquid, from the head of the first column to the second column; means for withdrawing a third fluid (A) from said second column, said third fluid being a nitrogen-rich gas; means for withdrawing an oxygen-rich fluid (90) from said second column; a heat exchanger (S) according to claim 1 or 2, connected to the means for sending the first fluid from the tank of the first column to the second column, the means for sending the second fluid from the head of the first column to the second column, and the means for withdrawing the third fluid from the second column, making it possible to heat at least the third fluid by indirect heat exchange with cooled at least the first and second fluids; An air separation unit comprising:

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