Heat exchanger and method of use thereof

Abstract

The objective is to provide a heat exchanger having a configuration for improving corrosion resistance and a method for using the same. [Solution] A heat exchanger with a configuration designed to improve corrosion resistance is equipped with a liquid spray device in the space through which the high-temperature fluid flows. By spraying liquid onto the heat exchange portion, a liquid film is formed on the surface of the heat exchange portion, thereby improving corrosion resistance.

Description

Technical Field

[0001] The present invention relates to a heat exchanger and a method of using the same.

Background Art

[0002] In the concentration process of acids such as sulfuric acid and hydrochloric acid, when the liquid is heated, evaporation components such as water vapor and mist accompanying boiling are generated. These gas-phase components are condensed by a heat exchanger, recovered, or neutralized and discarded. In this case, corrosion of the heat exchanger by the acid becomes a problem. Even in corrosion-resistant metals, corrosion becomes a problem in the gas phase where acid vapor and acid mist are present. Therefore, in the acid concentration process, as materials for equipment constituted in the gas phase, resin-based acid-resistant materials or materials such as carbon and silicon carbide are used. However, among these materials, inexpensive ones cannot be used in equipment that requires heat resistance, thermal conductivity, and flexibility, and there is a situation where expensive materials have to be used.

[0003] In the case of a heat exchanger, the carbon material has no problem with corrosion resistance, but has a lower thermal conductivity than metal, and in order to ensure sufficient strength, it is necessary to increase the thickness. When carbon is used, the installation area of the equipment and the weight of the equipment tend to be larger compared to the case of using metal. As a result, there is a problem that the plant construction cost also increases.

[0004] Conventionally, when using a metal material, in order to prevent a situation where the heat exchanger is corroded by the condensed acidic water that has condensed and the internal fluid leaks out, measures such as coating the surface of the heat exchanger with an acid-resistant paint have been taken. However, only coating with paint etc. could not obtain sufficient corrosion protection because pinholes or other missing parts occurred in the coating film, or the coating film deteriorated and missing parts occurred.

[0005] Patent Document 1 discloses a technique for performing cathodic protection by placing electrodes near the part to be protected from corrosion and spraying water onto the electrodes. The purpose of spraying water is to maintain a wet state that allows for cathodic protection. However, this method requires placing electrodes and continuously spraying water and applying voltage, which is not only cumbersome to operate but also presents problems such as increased maintenance costs and the need for wastewater treatment. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 11-201690 [Overview of the project] [Problems that the invention aims to solve]

[0007] Conventional heat exchangers, when using materials such as carbon, suffer from problems such as increased installation area and higher plant construction costs due to their low thermal conductivity and low strength. Furthermore, even when using low-corrosion metals, metal corrosion is unavoidable, especially in acid concentration processes. Cathodic protection techniques require continuous water spraying and voltage application, resulting in complicated operation, increased maintenance costs, and the need for wastewater treatment.

[0008] The object of this invention is to provide a heat exchanger having a configuration for improving corrosion resistance and a method for using the same. [Means for solving the problem]

[0009] The means to solve the above problems are as follows:

[0010] (First aspect) A heat exchanger having a primary fluid supply port and an outlet port, and a secondary fluid supply port and an outlet port, A liquid spraying means is provided to form a liquid film in the heat exchange portion where the primary and secondary fluids exchange heat. heat exchanger.

[0011] (Effects and Benefits) Under acidic conditions, metals face challenges in terms of corrosion resistance in gases. These gases include, for example, hydrochloric acid gas or gases containing sulfuric acid mist. Furthermore, corrosion tends to accelerate at higher temperatures.

[0012] In a heat exchanger where a high-temperature acid-containing fluid is supplied as the primary fluid and a low-temperature fluid is supplied as the secondary fluid, if the supplied primary fluid is a gas, the primary fluid, being a gas, will condense and produce droplets when it comes into contact with the heat exchange area. An acid-containing fluid is, for example, a gas containing acid-containing water vapor or other evaporated components, or mist produced when a liquid is heated during the concentration process of an acid such as sulfuric acid or hydrochloric acid. In this case, the parts not immersed in the condensed liquid are particularly susceptible to corrosion.

[0013] Furthermore, even if the primary fluid is a liquid, the heat exchange parts that do not directly come into contact with the fluid are not immersed in the liquid but are in a gaseous atmosphere, and are therefore more susceptible to corrosion compared to parts that are immersed in the liquid.

[0014] In such cases, the corrosion resistance of the heat exchange portion can be improved by spraying the liquid onto the portion of the heat exchange portion that is not directly immersed in the liquid, thereby creating a liquid film on the surface of the heat exchange portion. This is because the corrosion rate increases in a gaseous environment compared to a liquid environment.

[0015] (Second aspect) The heat exchanger is a plate type heat exchanger, The invention is characterized by having a liquid spraying means that forms a liquid film on the plate portion of the plate-type heat exchanger that comes into contact with the primary fluid. A heat exchanger according to the first embodiment.

[0016] (Effects and Benefits) A plate-type heat exchanger is a heat exchanger that stacks a plurality of heat transfer plates and alternately flows a high-temperature fluid and a low-temperature fluid between them for heat exchange. The heat transfer plates are usually thin metal plates. The heat transfer plates are stacked at a certain interval and joined with gaskets. The fluid flows through the holes in the plates over the surface of each plate, and the high-temperature fluid and the low-temperature fluid alternately flow to the overlapping portions of the plates, forming a countercurrent flow. The heat of the high-temperature fluid is transferred to the plates, and then the heat moves to the low-temperature fluid.

[0017] In this case, the plates in the part where the primary fluid is supplied may not be immersed in the liquid and may be in contact with the gas. Such parts are prone to corrosion. For example, when the primary fluid is an acidic gas containing vapor generated in an acid concentration process or the like, condensation of the gas does not proceed in the high-temperature part of the plate and it may be dry, and in such a case, corrosion is likely to progress. In this aspect, in particular, a liquid film is generated by spraying a liquid on the part in contact with the gas, thereby enhancing the corrosion resistance of the heat exchanger, especially the plate part.

[0018] (The third aspect) The heat exchanger is a plate-type heat exchanger, The liquid spraying means for forming a liquid film on the plate part is provided at the supply port of the primary fluid, which is a feature of the heat exchanger according to the first aspect. The heat exchanger according to the first aspect.

[0019] (Function and effect) Normally, in a plate-type heat exchanger, there is a supply port for the high-temperature primary fluid at the upper part and a discharge port for the primary fluid at the lower part. The vicinity of the supply port of the primary fluid is most likely to be the hottest and is likely to be in a dry state, so the plates near the supply port of the primary fluid are most likely to be corroded. This aspect is a mode in which liquid spraying means is provided inside the supply port of the primary fluid, and the liquid is sprayed from here to the plates near the supply port of the primary fluid.

[0020] By intensively spraying liquid onto the plate near the end of the supply port of the primary fluid that is susceptible to corrosion to generate a liquid film, it is possible to efficiently prevent the corrosion of the plate.

[0021] (The fourth aspect) The heat exchanger is a plate heat exchanger, The liquid spraying means is a tubular liquid spraying pipe inserted into the supply port of the primary fluid, and a plurality of liquid spraying ports are provided along the longitudinal direction of the pipe for the liquid spraying pipe, characterized in that. The heat exchanger according to the first aspect.

[0022] (Function and effect) In a plate heat exchanger, the fluid flows through the surfaces of each plate in a form passing through the holes in the plate. For the flow path on the supply side of the primary fluid, the holes in the plate are connected to the supply port of the primary fluid. In this aspect, a tubular liquid spraying pipe is inserted and provided through the holes in the plate from the supply port. By spraying liquid from a plurality of liquid spraying ports provided at intervals in the longitudinal direction of the liquid spraying pipe, a liquid film can be evenly generated on the plate contacted by the primary fluid.

[0023] Normally, the plate near the supply port of the primary fluid is most susceptible to corrosion, but when the flow rate of the primary fluid is large, the plates inside may also be corroded. According to this aspect, since a liquid film can be evenly generated on the plate contacted by the primary fluid, it is possible to suppress the corrosion of the internal plates even in such cases.

[0024] (The fifth aspect) The heat exchanger is a plate heat exchanger, One supply port of the primary fluid is provided on each of the front and rear surfaces of the plate heat exchanger, and the two supply ports are in communication, Characterized by having liquid spraying means for forming a liquid film on the plate portion in contact with the primary fluid. The heat exchanger according to the first aspect.

[0025] (Effects and Benefits) In this embodiment, two primary fluid supply ports are located on both the front and rear surfaces of the plate heat exchanger. If the primary fluid flow rate is high, the temperature near the primary fluid supply ports 11 rises, promoting drying and accelerating corrosion. In such cases, it is preferable to provide the primary fluid supply ports 11 separately, communicating with the front and rear surfaces of the plate heat exchanger 10, in order to distribute the flow rate of the primary fluid. In this embodiment, by providing one primary fluid supply port each on the front and rear surfaces of the plate-type heat exchanger, it is possible to avoid insufficient condensation of the primary fluid, which is a gas.

[0026] Typically, plate heat exchangers have a supply port for high-temperature primary fluid at the top and a discharge port for primary fluid at the bottom. In this embodiment, one supply port is provided at the top of both the front and rear of the plate heat exchanger. Since the plates tend to become hottest near the supply ports for primary fluid, the plates near the supply ports are most susceptible to corrosion. In this embodiment, a liquid spraying means is provided to form a liquid film on the plate portion in contact with the primary fluid, making it possible to suppress plate corrosion with the formed liquid film.

[0027] Alternatively, two liquid spraying means may be provided near the two supply ports of the primary fluid, and the liquid may be sprayed from these means onto the plate near the supply ports of the primary fluid. Another method is to spray the liquid along a tubular liquid spraying pipe, which is provided across two communicating supply ports located at the front and rear of the plate heat exchanger, from liquid spraying ports provided at intervals along the longitudinal direction of the pipe.

[0028] (Sixth aspect) The heat exchanger according to any one of the second to fifth embodiments, wherein the amount of liquid sprayed is 10% to 65% when the volume of liquid supplied to the space between the two plates per minute is divided by the volume of the space between the two plates and expressed as a percentage.

[0029] (Effects and Benefits) If the amount of liquid sprayed is too much, the efficiency of heat exchange will decrease. Conversely, if it is too little, the formation of a liquid film on the plates will be insufficient. The spray amount is preferably 10% to 65% of the distance between the plates. Here, the spray amount as a percentage of the distance between the plates is the volume of liquid supplied to the space between the two plates per minute divided by the volume of the space between the two plates. If the spray volume exceeds 65%, the heat exchange efficiency decreases. If the spray volume falls below 10%, the liquid film formation becomes insufficient, making the plates more susceptible to corrosion.

[0030] (Seventh aspect) A method for using a heat exchanger having a primary fluid supply port and an outlet port, and a secondary fluid supply port and an outlet port, This method is characterized by forming a liquid film on the heat exchange portion by spraying a liquid using a liquid spraying means. How to use a heat exchanger.

[0031] (Effects and Benefits) According to this embodiment, corrosion resistance can be improved by forming a liquid film in the heat exchange portion of the heat exchanger. This is because metals corrode more rapidly in air than in liquid in an acidic atmosphere. [Effects of the Invention]

[0032] According to the present invention, it is possible to improve the corrosion resistance of a heat exchanger. [Brief explanation of the drawing]

[0033] [Figure 1] This is a schematic diagram representing the first embodiment. [Figure 2] This is a front view and cross-sectional view of a plate heat exchanger. [Figure 3] This is a perspective view of a plate heat exchanger. [Figure 4] This is a schematic cross-sectional view corresponding to the XX cross-sectional view in Figure 2 of a plate heat exchanger equipped with a liquid spraying means according to the second embodiment. [Figure 5]This is a schematic diagram of a tectonic plate. [Figure 6] This is a schematic cross-sectional view corresponding to the XX cross-sectional view in Figure 2 of a plate heat exchanger equipped with a liquid spraying means according to the third embodiment. [Figure 7] This is a schematic cross-sectional view corresponding to the XX cross-sectional view in Figure 2 of a plate heat exchanger equipped with a liquid spraying means according to the fourth embodiment. [Figure 8] This is a schematic diagram of a plate representing the fifth embodiment. [Modes for carrying out the invention]

[0034] The following describes a method and apparatus for improving the acid resistance of a heat exchanger with reference to the drawings. However, the following description and drawings are merely examples of the present invention, and the content of the present invention should not be interpreted as being limited to these embodiments.

[0035] (First Embodiment) A first embodiment of the present invention will be described with reference to Figure 1. Figure 1 shows a schematic diagram of a shell-and-tube type heat exchanger. Heat exchange takes place between the primary fluid on the shell side and the secondary fluid on the tube side. The primary fluid is often a gas, but it may also be a liquid, or a gas containing liquid. The following description will focus on the case where the primary fluid is a gas when supplied and condenses into a liquid due to heat exchange.

[0036] In Figure 1, the primary fluid, a gas, is supplied into the shell 7 from the primary fluid supply port 1. The secondary fluid, which cools the primary fluid, is supplied into the tube 8 from the secondary fluid supply port 3. The primary fluid introduced into the shell 7 from the primary fluid supply port 1 is cooled by contact with the tube 8, condenses, becomes a liquid, and is discharged from the primary fluid outlet port 2. On the other hand, the secondary fluid supplied from the secondary fluid supply port 3 exchanges heat with the primary fluid inside the shell 7 via the tube 8, is heated, and is discharged from the secondary fluid outlet port 4.

[0037] Figure 1 shows a state in which the condensed primary fluid, now liquid, is stored in the lower part of the shell 7 and discharged from the primary fluid outlet 2, with the tube 8 not immersed in the liquid. Therefore, the outer surface of the tube 8 is either dry or has condensed droplets adhering to it. Corrosion is accelerated in such cases. In particular, if the primary fluid is vapor generated when an acid such as hydrochloric acid or sulfuric acid is heated and concentrated, the vapor contains acidic gaseous and misty components, making the inner surface of the shell 7 and the outer surface of the tube 8 susceptible to corrosion.

[0038] Here, the following is considered to be the reason why the inner surface of the shell 7 and the outer surface of the tube 8, which are not immersed in the liquid, are susceptible to corrosion. Specifically, the inner surface of the shell 7 and the outer surface of the tube 8 are in contact with high-temperature steam and are therefore at high temperatures. As acid-containing condensed droplets adhering to these surfaces evaporate, the acid concentration increases. For this reason, they are considered to be more susceptible to corrosion than when immersed in the liquid.

[0039] In such cases, corrosion can be suppressed by spraying liquid into the shell 7 and forming a liquid film on the inner surface of the shell 7 and the outer surface of the tube 8. In Figure 1, a liquid spray pipe 5 is provided at the top of the inside of the shell 7. The liquid spray pipe 5 is provided with one or more liquid spray nozzles 9 from which the liquid is sprayed. The direction of spraying may be downward as shown in Figure 1, upward, or radially. In particular, in the case of a primary fluid containing acidic gas components, the metal surface inside the shell may be corroded, so it is preferable to spray the liquid so that a liquid film is evenly formed on the surface that may be corroded. The sprayed liquid forms a liquid film on the inner surface of the shell 7 and the outer surface of the tube 8, suppressing corrosion.

[0040] The liquid spray tube 5 is hollow, and its vertical cross-sectional shape may be circular or polygonal, such as a square. It is preferable that multiple liquid spray nozzles 9 are provided at intervals along the axial direction of the liquid spray tube 5. The material of the liquid spray tube 5 should be corrosion-resistant, and for example, stainless steel, aluminum, titanium, nickel, or alloys thereof are preferred. Alternatively, it may be made of resin such as polyvinyl chloride, fiber-reinforced plastic (FRP), or polytetrafluoroethylene.

[0041] The sprayed liquid may be ordinary water, or it may be a condensate obtained by condensing the primary fluid. If the condensate contains acidic components and the condensate is concentrated and the acid is utilized, using ordinary water as the sprayed liquid is undesirable because it reduces the concentration of acidic components in the condensate, requiring more energy during concentration. Furthermore, if the condensate needs to be discarded, it leads to an increase in liquid volume, which is also undesirable from an economic standpoint. Therefore, a condensate obtained by condensing the primary fluid is preferred.

[0042] When the condensate of the primary fluid is to be reused, it is preferable to store it in a tank or the like. This is because the condensate of the primary fluid discharged from the primary fluid outlet 2 is at a high temperature, and it is preferable to use condensate that has been cooled by heat dissipation or the like, in terms of heat exchange efficiency and corrosion suppression.

[0043] (Plate heat exchanger) Plate heat exchangers have a large heat transfer surface area and excellent thermal efficiency, and can be made smaller and lighter. Furthermore, their capacity can be easily increased by adding more plates. They are also widely used because the plates are replaceable, maintenance is easy, and initial costs are low. They consist of multiple thin plates made of materials such as stainless steel or titanium, stacked with gaps between them to create spaces. Primary and secondary fluids are supplied alternately to these spaces between plates, and heat exchange occurs through the plates.

[0044] Figure 2(A) shows a front view of the plate heat exchanger 10, and Figure 2(B) shows a cross-sectional view of the XX. Figure 3 shows a perspective view of the plate heat exchanger 10. The plate heat exchanger 10 is provided with a front cover plate 15 on the front and a rear cover plate 16 on the rear, as well as a primary fluid supply port 11, a primary fluid outlet 12, a secondary fluid supply port 14, and a secondary fluid outlet 13. The primary fluid is introduced through the primary fluid supply port 11 and discharged through the primary fluid outlet 12. If the primary fluid is a gas such as steam, the gaseous primary fluid is introduced through the primary fluid supply port 11, becomes a condensate as a result of heat exchange, and is discharged through the primary fluid outlet 12. The secondary fluid for cooling the primary fluid is introduced through the secondary fluid supply port 14, is heated by heat exchange, and is discharged through the secondary fluid outlet 13.

[0045] Referring to Figure 2(B), multiple plates 19 are stacked while maintaining a constant gap between them. Primary fluid supplied from the primary fluid supply port 11 flows through the primary fluid supply channel 17, passing through every other plate 19 and through the space between the plates 19, and is discharged from the primary fluid outlet 12 through the primary fluid discharge channel 18. In the space between adjacent plates 19 through which the primary fluid flows, secondary fluid introduced from the secondary fluid supply port 14 flows upward through the secondary fluid supply channel 27 and is discharged from the secondary fluid outlet 13 through the secondary fluid discharge channel 28. As the primary fluid flows downward, it exchanges heat with the secondary fluid flowing in the space between the adjacent plates 19. The thickness of plate 19 and the distance between plates 19 vary, but typically, the thickness of plate 19 is about 0.3 to 0.7 mm, and the distance between plates 19 is about 3 to 6 mm.

[0046] (Second Embodiment) A second embodiment is illustrated with reference to Figure 4. In one embodiment of the plate heat exchanger 10, a primary fluid, which is a high-temperature gas, is supplied from the primary fluid supply pipe 20 to the primary fluid supply port 11. In this case, the primary fluid supply port 11 becomes the hottest area. As a result, condensation of the high-temperature gas does not proceed, and the plates 19 near the primary fluid supply port 11 tend to dry out, making them susceptible to corrosion. Therefore, it is particularly effective to spray a liquid from the primary fluid supply port 11 onto the nearby plates 19 to form a liquid film.

[0047] The second embodiment is for improving the corrosion resistance of the plate heat exchanger 10. A liquid spray pipe 21 is arranged from the primary fluid supply pipe 20 to the inlet of the primary fluid supply channel 17. The liquid spray pipe 21 may be located in the center of the primary fluid supply pipe 20, in the lower center, or directed towards the upper center. When located in the upper center, it is advantageous because it allows the liquid to be sprayed over a wider area of ​​the plate 19. A liquid spray nozzle 22 for spraying liquid is provided at the tip of the liquid spray pipe 21. However, the liquid spray nozzle 22 does not necessarily have to be at the tip of the liquid spray pipe 21; it may be located within the primary fluid supply port 11 and provided on the pipe wall of the liquid spray pipe 21. In this case, there may be one or more liquid spray nozzles 22. The second embodiment involves forming a liquid film on the plate 19 near the primary fluid supply port 11, which is susceptible to corrosion. Therefore, it is preferable that the liquid spray nozzle 22 be located above the plate 19 near the primary fluid supply port 11.

[0048] The liquid spray tube 21 is hollow, and the outer shape of its vertical cross-section may be circular, or it may be a polygon such as a square. The material of the liquid spray tube 21 should be corrosion-resistant, and for example, stainless steel, aluminum, titanium, nickel, or alloys thereof are preferred. Alternatively, it may be made of resin such as polyvinyl chloride, fiber-reinforced plastic (FRP), or polytetrafluoroethylene.

[0049] The liquid to be sprayed may be water, or it may be a condensate obtained by condensing the primary fluid. If the primary fluid is vapor produced when an acidic liquid is heated and concentrated, this vapor contains acidic gas, acidic mist, etc. When water is used as the liquid to be sprayed, the amount of condensate increases because it contains the spray liquid. This is because further concentration of the condensate requires energy and time, and disposal leads to an increase in the volume of liquid, resulting in an undesirable outcome in either case from an economic standpoint. The plates 19 of the plate heat exchanger 10 are made of corrosion-resistant materials such as stainless steel, aluminum, titanium, nickel, and their alloys, and these materials do not corrode in the condensate. Therefore, even if the condensate is used as the spraying liquid and a liquid film is formed on the surface of the plates 19, the corrosion of the plates 19 will not be accelerated. For this reason, the condensate obtained by condensing the primary fluid is preferred as the spraying liquid.

[0050] Figure 5 shows a schematic diagram of the surface of plate 19 through which the primary fluid flows. The heat exchange region 31, where the primary fluid flows and heat exchange occurs, is surrounded by a gasket 30, preventing leakage into the outer region. In addition, the secondary fluid supply channel 27 and the secondary fluid discharge channel 28 are surrounded by gaskets 30, preventing the secondary fluid from flowing out onto this surface of plate 19. Gasket 30 can be a non-metallic gasket, semi-metallic gasket, metal gasket, etc.

[0051] The spray liquid is dispensed from a liquid spray nozzle 22 located in a liquid spray pipe 21 positioned within the primary fluid supply channel 17. The liquid spray may be directed downwards, upwards, or radially. In the plate 19 configuration shown in Figure 5, the primary fluid supply channel 17 is located on the left center, and therefore the liquid spray pipe 21 is also located on the left center. In such cases, it is effective to design the liquid spray nozzle 22 to spray more liquid on the right side so that a sufficient liquid film is formed in the heat exchange region 31 on the right side in Figure 7.

[0052] Typically, the thickness of the plate 19 is about 0.3 to 0.7 mm, and the distance between the plates 19 is about 3 to 6 mm. The spray droplets are sprayed between the plates 19 and need to form a uniform liquid film on the surface of the plates 19. For this reason, the liquid spray nozzle 22 preferably has a structure with multiple holes, and the size of the holes is preferably 0.3 to 2.5 mm, more preferably 0.5 to 1.5 mm. The spray droplets are preferably 0.15 to 0.5 mm, more preferably 0.25 to 0.4 mm. In addition, the number of holes in one liquid spray nozzle 22 is preferably 10 to 40, more preferably 15 to 30.

[0053] The amount of liquid to be sprayed is preferably 10% to 65% of the distance between the plates 19. Here, the spray amount relative to the distance between the plates 19 is expressed as a percentage of the volume of liquid supplied per minute to the space between the two plates 19 divided by the volume of the space between the two plates 19. If the spray volume exceeds 65%, contact between the primary fluid and the plate 19 is restricted, and heat exchange occurs between the sprayed liquid and the secondary fluid, reducing the efficiency of the heat exchange between the primary and secondary fluids. If the spray volume falls below 10%, the formation of a liquid film becomes insufficient, making the plate 19 more susceptible to corrosion.

[0054] (Third embodiment) A third embodiment will be described with reference to Figure 6. In the plate heat exchanger 10, the primary fluid supply port 11 is the area that tends to become the hottest, but when the flow rate of the primary fluid is large, the internal plates 19 also become hot and tend to dry out, which is expected to lead to corrosion. In such cases, it is desirable to spray liquid not only on the plates 19 near the primary fluid supply port 11 but also on the internal plates 19 to form a liquid film.

[0055] The following are possible reasons why corrosion progresses in dry conditions: Acid-containing condensed droplets adhering to a dry surface become concentrated as the water evaporates, increasing the acid concentration. Therefore, corrosion is more likely to occur than when the material is immersed in liquid.

[0056] Figure 6 shows a plate heat exchanger 10 with a liquid spray pipe 21 positioned within the primary fluid supply channel 17, extending from the front to the rear of the plate heat exchanger 10. The liquid spray pipe 21 may be located in the center of the primary fluid supply channel 17, in the lower center, or directed towards the upper center. When located in the upper center, it is advantageous because it allows for spraying the liquid over a wider area of ​​the plate 19. The liquid spray tube 21 is equipped with multiple liquid spray nozzles 22, from which liquid is sprayed. There is no limit to the number of liquid spray nozzles 22, but it is preferable that liquid is sprayed onto all plates 19. Typically, the thickness of the plates 19 is about 0.3 to 0.7 mm, and the distance between the plates 19 is about 3 to 6 mm. It is preferable to have 10 to 40 liquid spray nozzles 22 per liquid spray tube, and more preferably 15 to 30 liquid spray nozzles 22 per liquid spray tube. Here, nozzles / liquid spray tube refers to the number of liquid spray nozzles 22 provided on one liquid spray tube.

[0057] Similar to the second embodiment, the liquid spray may be directed downwards or upwards. It may also be sprayed radially. In the plate 19 of the embodiment shown in Figure 5, the primary fluid supply channel 17 is located on the left center, and therefore the liquid spray pipe 21 is also located on the left center. In such cases, it is effective to design the liquid spray nozzle 22 to spray more liquid on the right side so that a sufficient liquid film is formed in the heat exchange region 31 on the right side in Figure 7.

[0058] The sprayed liquid flows downward, forming a liquid film on the surface of plate 19. This film formation suppresses corrosion on the surface of plate 19. The amount of liquid sprayed is preferably 10% to 65% of the distance between the plates 19. Here, the spray amount relative to the distance between the plates 19 is expressed as a percentage of the volume of liquid sprayed per minute into the space between the two plates 19 divided by the volume of the space between the two plates 19. Specifically, this can be obtained by expressing as a percentage the total amount of liquid sprayed per minute divided by the sum of the volumes between the plates 19 on which the liquid is sprayed. If the spray volume exceeds 65%, contact between the primary fluid and the plate 19 is restricted, and heat exchange occurs between the sprayed liquid and the secondary fluid, reducing the efficiency of the heat exchange between the primary and secondary fluids. If the spray volume falls below 10%, the formation of a liquid film becomes insufficient, making the plate 19 more susceptible to corrosion.

[0059] (Fourth Embodiment) A fourth embodiment will be described with reference to Figure 7. The primary fluid supply port 11 may be provided in a state that communicates with the front and rear surfaces of the plate heat exchanger 10. If the flow rate of the primary fluid is large, the temperature near the primary fluid supply port 11 will rise, accelerating the drying of the plate 19 and making it more susceptible to corrosion. In such cases, it is preferable to provide the primary fluid supply port 11 separately in a state that communicates with the front and rear surfaces of the plate heat exchanger 10, thereby distributing the flow rate of the primary fluid. Here, the front surface may refer to the front cover plate of the plate heat exchanger 10, and the rear surface may refer to the rear cover plate of the plate heat exchanger 10. This mitigates the rise in temperature near the primary fluid supply port 11 and suppresses the progression of corrosion. Furthermore, it is possible to avoid insufficient heat exchange on the plate 19 near the primary fluid supply port 11, which would result in insufficient condensation of the gas, which is the primary fluid.

[0060] In the fourth embodiment, it is preferable to arrange the liquid spray pipe 21 within the primary fluid supply channel 17, extending from the front to the rear of the plate heat exchanger 10. This is because the primary fluid may come into contact with a wide area of ​​the front, rear, and intermediate plates 19 of the plate heat exchanger 10 in a dry state, potentially leading to corrosion. Typically, considering that the thickness of the plate 19 is about 0.3 to 0.7 mm and the distance between the plates 19 is about 3 to 6 mm, it is preferable that the liquid spray nozzles 22 be provided at a rate of 10 to 40 per liquid spray tube, and more preferably at a rate of 15 to 30 per liquid spray tube. Here, "nozzles / liquid spray tube" refers to the number of liquid spray nozzles 22 provided on one liquid spray tube. This ensures that a liquid film is evenly formed on the surface of the plate 19, preventing corrosion.

[0061] The amount of liquid to be sprayed is preferably 10% to 65% of the distance between the plates 19. Here, the spray amount relative to the distance between the plates 19 is expressed as a percentage of the volume of liquid supplied per minute to the space between the two plates 19 divided by the volume of the space between the two plates 19. If the spray volume exceeds 65%, contact between the primary fluid and the plate 19 is restricted, and heat exchange occurs between the sprayed liquid and the secondary fluid, reducing the efficiency of the heat exchange between the primary and secondary fluids. If the spray volume falls below 10%, the formation of a liquid film becomes insufficient, making the plate 19 more susceptible to corrosion.

[0062] (Fifth embodiment) Figure 8 shows a fifth embodiment. Figure 8(A) is a front view of the plate heat exchanger 10. Figure 8(B) shows the surface of the plate 19 through which the primary fluid flows inside the plate heat exchanger 10. A primary fluid supply port 11 and a primary fluid supply channel 17 are located at the upper center of the plate 19. A liquid spray pipe 21 is located in the primary fluid supply channel 17, and the liquid spray pipe 21 is provided with a plurality of liquid spray ports 22.

[0063] A primary fluid outlet 12 is located below the primary fluid supply port 11, and a secondary fluid outlet 28 is located below the primary fluid supply channel 17. Below that, a secondary fluid supply port 14 and a secondary fluid supply channel 27 are located. Further down, two primary fluid outlets 12 and two primary fluid outlets 18 are located spaced apart to the left and right.

[0064] The primary fluid is supplied to the plate heat exchanger 10 from the primary fluid supply port 11, flows downward through the space between the plates 19 via the primary fluid supply channel 17, and exchanges heat with the secondary fluid flowing in the space on the opposite side of the plates 19 in the heat exchange region 31. In Figure 8, the primary fluid flows in the region enclosed by the gasket 30.

[0065] The liquid spray pipe 21, located within the primary fluid supply channel 17, is provided with multiple liquid spray nozzles 22. The configuration of the liquid spray pipe 21 and liquid spray nozzles 22 may be that of the second or third embodiment, but the configuration of the third embodiment is more preferred. The liquid spray pipe 21 may be located in the center of the primary fluid supply channel 17, in the lower center, or directed towards the upper center. When located in the upper center, it is advantageous because it allows for spraying liquid over a wider area of ​​the plate 19. Liquid is sprayed from the liquid spray nozzle 22, forming a liquid film on the area of ​​the plate 19 surrounded by the gasket 30. As a result, the dry areas of the plate 19 and the droplets formed from condensed primary fluid are covered by the liquid film, thus suppressing corrosion. In the fifth embodiment, since the primary fluid supply channel 17 is located at the upper center of the plate 19, the liquid is sprayed symmetrically, the liquid is sprayed more uniformly, and a more uniform liquid film is formed on the surface of the plate 19. The liquid to be sprayed is preferably a condensed liquid obtained by condensing the primary fluid.

[0066] The amount of liquid to be sprayed is preferably 10% to 65% of the distance between the plates 19. Here, the spray amount relative to the distance between the plates 19 is expressed as a percentage of the volume of liquid supplied per minute to the space between the two plates 19 divided by the volume of the space between the two plates 19. If the spray volume exceeds 65%, contact between the primary fluid and the plate 19 is restricted, and heat exchange occurs between the sprayed liquid and the secondary fluid, reducing the efficiency of the heat exchange between the primary and secondary fluids. If the spray volume falls below 10%, the formation of a liquid film becomes insufficient, making the plate 19 more susceptible to corrosion. [Industrial applicability]

[0067] The method and apparatus for improving the corrosion resistance of heat exchangers of the present invention can be used to improve the corrosion resistance of heat exchangers. In particular, when condensing gases such as vapors generated in the concentration process of acids such as sulfuric acid and hydrochloric acid, the heat exchanger is susceptible to corrosion because the gases contain acidic gases and acidic mist. The present invention is particularly useful in such applications.

[0068] It should be noted that the technical scope of the present invention is not limited to the embodiments described above, and various modifications can be made without departing from the spirit of the invention. [Explanation of symbols]

[0069] 1...Primary fluid inlet, 2...Primary fluid outlet, 3...Secondary fluid inlet, 4...Secondary fluid outlet, 5...Liquid spray tube, 6...Condensed water, 7...Shell, 8...Tube, 9...Liquid spray nozzle, 10...Plate heat exchanger, 11...Primary fluid inlet, 12...Primary fluid outlet, 13...Secondary fluid outlet, 14...Secondary fluid inlet, 15...Front cover plate, 16...Rear cover plate, 17...Primary fluid supply channel, 18...Primary fluid outlet channel, 19...Plate, 20...Primary fluid supply tube, 21...Liquid spray tube, 22...Liquid spray nozzle, 27...Secondary fluid supply channel, 28...Secondary fluid outlet channel, 30...Gasket, 31...Heat exchange area

Claims

1. A heat exchanger having a primary fluid supply port and an outlet port, and a secondary fluid supply port and an outlet port, A liquid spraying means is provided to form a liquid film in the heat exchange portion where the primary and secondary fluids exchange heat. heat exchanger.

2. The heat exchanger is a plate type heat exchanger, The invention is characterized by having a liquid spraying means that forms a liquid film on the plate portion of the plate-type heat exchanger that comes into contact with the primary fluid. The heat exchanger according to claim 1.

3. The heat exchanger is a plate type heat exchanger, The liquid spraying means that forms a liquid film on the plate portion is provided at the supply port of the primary fluid, characterized in that The heat exchanger according to claim 1.

4. The heat exchanger is a plate type heat exchanger, The liquid spraying means is a tubular liquid spraying tube inserted into the supply port of the primary fluid, and the liquid spraying tube is characterized in that a plurality of liquid spraying ports are provided along the longitudinal direction of the tube. The heat exchanger according to claim 1.

5. The heat exchanger is a plate type heat exchanger, The supply ports for the primary fluid are provided one each on the front and rear surfaces of the plate-type heat exchanger, and the two supply ports are in communication with each other. The invention is characterized by having a liquid spraying means that forms a liquid film on the plate portion that comes into contact with the primary fluid. The heat exchanger according to claim 1.

6. The heat exchanger according to any one of claims 2 to 5, wherein the amount of liquid sprayed is 10% to 65% when the volume of liquid supplied to the space between the two plates per minute is divided by the volume of the space between the two plates and expressed as a percentage.

7. A method for using a heat exchanger having a primary fluid supply port and an outlet port, and a secondary fluid supply port and an outlet port, This method is characterized by forming a liquid film on the heat exchange portion by spraying a liquid using a liquid spraying means. How to use a heat exchanger.

8. The method of using a heat exchanger according to claim 7, wherein the liquid to be sprayed is the liquid discharged from the outlet of the primary fluid.

9. The heat exchanger is a plate type heat exchanger, A liquid film is formed on the plate portion that comes into contact with the primary fluid by spraying the liquid onto the plate portion. The method for using a heat exchanger according to claim 7 or 8, wherein the amount of liquid sprayed is 10% to 65% when the volume of the space between the two plates is obtained by dividing the accumulated amount of liquid supplied to the space between the two plates per minute by the volume of the space between the two plates, expressed as a percentage.

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