Ferrule for heat transfer tube of heat exchanger and method for assembling the same

Abstract

To propose a ferrule for a heat transfer pipe of a heat exchanger capable of effectively suppressing adhesion of solid particles to a heat transfer pipe and blockage of the heat transfer pipe caused by the adhesion, to extend a stop interval of a facility, and a method for assembling the ferrule.SOLUTION: For a heat exchanger comprising a heat transfer pipe through which fluid flows, a ferrule is assembled to a fluid inlet part of the heat transfer pipe of the heat exchanger. The ferrule is configured to have a short pipe part inserted into the heat transfer pipe, and a flange part provided at an end part of the short pipe part, and a vitrified glaze layer is provided on an inner surface of at least an inlet side part of the short pipe part.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a ferrule for a heat transfer tube that is to be assembled to a fluid inlet portion of a heat transfer tube of a heat exchanger, and a method for assembling the ferrule. [Background technology]

[0002] Shell-and-tube heat exchangers are widely known as heat exchangers used in boilers and other equipment. They have multiple heat transfer tubes fixed and supported by tube plates near the fluid inlet and outlet, and heat is exchanged between the inside and outside of these heat transfer tubes.

[0003] The inlet of the heat transfer tube is susceptible to damage due to turbulence that occurs when fluid flows into the tube, so a ferrule (short tube) is often installed at this location to protect the heat transfer tube.

[0004] As a prior art relating to this point, for example, Patent Document 1 discloses a protective tube having a flange protruding from the outer periphery of the end portion and an inner diameter substantially equal to the inner diameter of the main body of the heat transfer tube.

[0005] Furthermore, Patent Document 2 discloses a structure in which the ceramic layer covering the tube plate on the gas inlet side is made up of a plurality of rectangular columnar sockets arranged adjacent to each other and abutting each other along their outer edges, each socket having a conical opening tapering toward the tube portion, and the tube portion being inserted into each tube of the tube bundle of the heat exchanger.

[0006] In addition to damage caused by turbulence that occurs when a fluid flows into the heat transfer tubes of a heat exchanger, solid matter in the fluid flowing through the heat transfer tube or solid matter produced by chemical reactions of components in the fluid can adhere to the inner surface of the heat transfer tube and block the flow path of the heat transfer tube, causing an increase in the differential pressure in the heat exchanger and making stable operation difficult.

[0007] In this case, the techniques disclosed in Patent Documents 1 and 2 above cannot be used to deal with the problem, so the operation of the equipment is stopped when an increase in differential pressure is observed and the blockage is removed, or the blockage is removed periodically before the increase in differential pressure in order to avoid the increase in differential pressure.

[0008] In addition, Patent Document 2 lists the problem of protecting the gas inlet side from high-temperature corrosion and erosion, and claims that the shape of the inside of the socket narrows toward the entrance of the heat transfer tube, which accelerates the fluid (gas) and prevents solid particles from accumulating in the fluid inlet part of the socket. However, because the flow velocity of the fluid inside the heat transfer tube is the same whether or not there is a socket, under conditions where blockage occurs inside the heat transfer tube, the blockage cannot be suppressed by simply increasing the flow velocity by installing a socket. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Publication No. 9-292195 [Patent Document 2] Japanese Patent Application Publication No. 5-306893 Summary of the Invention [Problem to be solved by the invention]

[0010] An object of the present invention is to provide a ferrule for a heat transfer tube of a heat exchanger, and an assembly method thereof, which can effectively suppress adhesion of solid particles to the heat transfer tube and the resulting blockage of the heat transfer tube, thereby extending the interval between equipment shutdowns. [Means for solving the problem]

[0011] The inventors conducted a detailed investigation into the cause of heat transfer tube clogging and discovered that the main cause is that the heat-resistant porcelain generally used for ferrules has a porous structure and an uneven surface, making it easy for fine particulate solid matter contained in gas to penetrate into the interior or onto the uneven surface and adhere to it, leading to adhesion and growth on the inner surface of the heat transfer tube.

[0012] Therefore, the inventors investigated the possibility of suppressing the adhesion of solid substances by applying a glaze to a ferrule and firing it to form a dense glassy coating on its surface.As a result, they found that for a ferrule having a flange portion that is not inserted into a heat transfer tube and a short tube portion that is inserted into the heat transfer tube, applying a glaze to the inner surface of the entry side of the short tube portion to form a glass layer can effectively suppress the adhesion of solid substances and the clogging of the heat transfer tube, which led to the completion of the present invention.

[0013] That is, the present invention relates to a ferrule for a heat exchanger heat transfer tube that is provided with a heat transfer tube through which a fluid flows, and is to be assembled to a fluid inlet portion of the heat transfer tube of the heat exchanger, the ferrule having a short tube portion that is inserted into the heat transfer tube and a flange portion provided at the end of the short tube portion, and the short tube portion having a vitrified glaze layer on at least the inner surface of the inlet side.

[0014] The present invention also relates to a ferrule for a heat exchanger heat transfer tube that is fitted to a fluid inlet of the heat transfer tube of a heat exchanger, the ferrule having a short tube portion that is inserted into the heat transfer tube and a flange portion provided at the end of the short tube portion, and the short tube portion has a coating layer of a glaze that can be vitrified by heating on at least the inner surface of the inlet side.

[0015] The heat exchanger is preferably a heat exchanger in which a combustion exhaust gas produced by burning a substance containing sulfur flows as a fluid through the heat transfer tube.

[0016] The present invention also provides a method for assembling a ferrule for a heat transfer tube of a heat exchanger, comprising the steps of: forming a glaze coating layer on the inner surface of at least the inlet side of the short tube section when assembling the ferrule to the fluid inlet section of the heat transfer tube; assembling the ferrule to the fluid inlet section of the heat transfer tube; and then heating the ferrule to convert the coating layer into a vitrified glaze layer; and assembling the short tube section of the ferrule to the fluid inlet section of the heat transfer tube; forming a glaze coating layer on the inner surface of at least the inlet side of the short tube section; and then heating the ferrule to convert the coating layer into a vitrified glaze layer. [Effects of the Invention]

[0017] According to the present invention, at least the inner surface of the inlet side of the short tube section inserted into the heat transfer tube is covered with a vitrified glaze layer, which makes it possible to suppress adhesion of solid substances, enabling the equipment to operate for a long period of time and also achieving a long life for the ferrule itself. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a schematic diagram of a heat exchanger combined with a combustion furnace. [Figure 2] FIG. 2 is a diagram showing the AA end face of FIG. [Figure 3] 3 is a view showing a part of the cross section taken along the line BB in FIG. 2. FIG. [Figure 4] 1 is a graph showing the relationship between the number of operating days of a heat exchanger and the differential pressure. DETAILED DESCRIPTION OF THE INVENTION

[0019] The present invention will be described in more detail below with reference to the drawings. Fig. 1 is a schematic diagram of a heat exchanger combined with a combustion furnace, Fig. 2 is a diagram showing the AA end face of Fig. 1 (the dashed line in the figure shows the heat transfer tubes omitted), and Fig. 3 is a diagram showing the BB cross section of Fig. 2.

[0020] The ferrule according to the present invention is to be attached to the fluid inlet of a heat transfer tube of a heat exchanger such as that shown in FIG.

[0021] 1 to 3, reference numeral 1 denotes a combustion furnace, 2 denotes a heat exchanger connected to the combustion furnace 1, 3 denotes a tube plate attached to the heat exchanger 2, 4 denotes refractory material attached to the surface of the tube plate 3, and 5 denotes a heat transfer tube. The heat transfer tube 5 has a fluid inlet and a fluid outlet fixedly supported by the tube plate 3. Reference numeral 6 in FIGS. 1 to 3 denotes a ferrule attached to the fluid inlet of the heat transfer tube 5. The heat exchanger 2 may be a heat exchanger in which a combustion exhaust gas produced by burning a substance containing sulfur flows as a fluid through the heat transfer tube 5, but the fluid is not limited to the combustion exhaust gas produced by burning a substance containing sulfur.

[0022] The ferrule 6 can be made of ceramics containing alumina as its main component, and is composed of a short tube portion 6a that is inserted into the heat transfer tube 5 and a flange portion 6b that is provided at the end of the short tube portion 6a and is used to fix the short tube portion 6a to the tube sheet 3 or the like. Reference numeral 7 denotes a vitrified glaze layer that is provided on at least the entry side of the inner surface of the short tube portion 6a.

[0023] The heat exchanger 2 having the above-described configuration is provided with a passage 8 for circulating a secondary fluid such as water, and when a high-temperature fluid (gas) supplied from the combustion furnace 1 passes through the heat transfer tubes 5, the heat of the fluid is transferred to the secondary fluid via the heat transfer tubes 5, thereby performing heat exchange.

[0024] The vitrified glaze layer 7 can be made of a material containing sodium borosilicate, for example, which can be converted into a glassy substance by firing the applied glaze layer. It is preferable to use a glaze that can be applied to ceramics or metals directly or in the form of a liquid in which the solid is suspended in water.

[0025] The ferrule 6 according to the present invention is made by applying a glaze to the surface of a bisque-fired ceramic substrate to form a coating layer, and then firing the coating layer to form a vitrified glaze layer 7, which is then assembled to the fluid inlet of the heat transfer tube 5 of the heat exchanger 2.

[0026] Furthermore, in the heat exchanger 2 in which a high-temperature fluid sufficient for firing the glaze is circulated through the heat transfer tubes 5, a glaze coating layer can be formed in advance on at least the inlet side of the inner surface of the short tube section 6a, and after the ferrule 6 is installed at the fluid inlet section of the heat transfer tube 5, or after the ferrule 6 is installed at the fluid inlet section of the heat transfer tube 4, a glaze coating layer can be formed at least on the inlet side of the short tube section 6a, and a high-temperature fluid can be circulated through the heat transfer tubes 5 of the heat exchanger 2, whereby the heat from the fluid causes the glaze coating layer to be fired, thereby forming a vitrified glaze layer 7.

[0027] By forming the vitrified glaze layer 7 using the procedure described above, the firing of the glaze and the assembly of the ferrule 6 can be performed simultaneously, making it possible to efficiently assemble the ferrule 6 to the heat exchanger 2.

[0028] The effective range for applying the glaze is at least 10 mm from the entry side of the short tube portion 6a, and it is more effective to apply it within a range of 20 mm to 50 mm from the entry side.

[0029] The reason for this is that precipitates such as particulate solid matter contained in the fluid flowing through the heat transfer tube 5 are most likely to precipitate at the inlet side of the short tube portion 6a of the ferrule 6, and tend to precipitate most in the range of 50 mm from the inlet side.

[0030] It is possible to further extend the application range of the glaze, but even if the application range extends more than 50 mm from the entry side of the ferrule 6, the effect of preventing blockage at the entry side of the heat transfer tube 5 will saturate, so application more than 50 mm from the entry side is optional.

[0031] The glaze can also be applied to the surface of the flange portion 6b, which is preferable because it can suppress the formation of deposits on the surface of the flange portion 6b. However, in order to prevent the heat transfer tube 5 from clogging, it is more important to cover the inlet side of the short tube portion 6a with glass than the surface of the flange portion 6b, so the formation of a vitrified glaze layer 7 on the flange portion 6b is not essential.

[0032] The glaze is preferably applied so that the thickness of the vitrified glaze layer 7 is 0.1 mm or more and 3 mm or less. If the thickness of the vitrified glaze layer 7 is less than 0.1 mm, unevenness is likely to occur when the glaze is applied, and if it exceeds 3 mm, the flow of the fluid (gas) will be disturbed at the tip of the glaze layer 7. Note that disturbance of the fluid flow can also be suppressed by making the thickness of the vitrified glaze layer 7 thicker at the entrance side of the short tube portion 6a of the ferrule 6, for example, and thinner at the back.

[0033] The vitrified glaze layer 7 seals the small pores and irregularities on the surface of the ferrule 6 to form a smooth surface, which makes it difficult for particulate matter contained in the fluid to adhere, thereby suppressing clogging of the heat transfer tubes 5 and enabling long-term operation of the heat exchanger 2. [Example]

[0034] A heat exchanger such as that shown in Fig. 1 was installed in a facility that produces sulfuric acid by burning a sulfur-containing slurry recovered from carbonization gas generated in a coke manufacturing plant. Ferrules according to the present invention were attached to the heat transfer tubes of the heat exchanger, and combustion exhaust gas at a temperature of approximately 1050°C discharged from a combustion furnace was passed through the heat transfer tubes to bake the glaze coating on the ferrules. The differential pressure between the inlet and outlet of the heat exchanger was measured, and the relationship between the number of days after the start of operation and the differential pressure was investigated. The results are shown in Fig. 4, along with the results for heat exchangers using ferrules without a glaze coating attached to the heat transfer tubes (Comparative Examples 1 and 2).

[0035] The combustion furnace used in this example is a furnace in which a sulfur-containing slurry, coke oven gas, combustion air, steam, etc. are injected, and the coke oven gas and sulfur are combusted to generate a high-temperature gas (primary fluid).

[0036] The heat exchanger (boiler) used in this example has a main body (shell) inner diameter of 2700 mm, 313 heat transfer tubes, a heat transfer tube length of approximately 6000 mm, and a processing air volume of 23000 Nm 3 / h, gas temperature at the inlet of the heat transfer tube: 1050°C, gas temperature at the outlet: 440°C or less, operating pressure: gauge pressure of approximately 1 kPa, combustion exhaust gas: containing CO2, H2O, N2, O2, etc. in addition to SO2 generated by the combustion of sulfur, secondary fluid: water.

[0037] The ferrule was made of a bisque-fired ceramic whose main component was alumina, with the short tube section measuring approximately 160 mm in length, the inner diameter of the short tube section being approximately 50 mm, the thickness of the short tube section being approximately 4 mm, the diameter of the flange section being approximately 70-80 mm, and the thickness of the flange section being approximately 10 mm. A glaze whose main component was sodium borosilicate was applied to a thickness of approximately 1 mm over a length of 50 mm from the entry side, including the surface of the flange section (the surface that comes into contact with the gas), to form a glaze coating layer.

[0038] As shown in Figure 4, in Comparative Examples 1 and 2, the differential pressure reached 1 kPa within approximately 60 to 100 days, and clogging of the heat transfer tubes became noticeable. In contrast, in the heat exchanger equipped with the ferrule according to the present invention, the differential pressure reached 1 kPa 165 days after the start of operation, confirming that providing a vitrified glaze layer on the ferrule can significantly extend the period until clogging of the heat transfer tubes becomes noticeable. We also conducted an investigation in which the glaze application range was extended from the inlet end of the short tube portion of the ferrule to 10 mm, and even in this case, it took approximately 140 days for the differential pressure between the inlet and outlet ends of the heat exchanger to reach 1 kPa, demonstrating that a sufficient effect can be expected. [Industrial Applicability]

[0039] According to the present invention, it is possible to provide a ferrule for a heat transfer tube of a heat exchanger, which can effectively suppress adhesion of solid particles to the heat transfer tube and the resulting blockage of the heat transfer tube, thereby extending the interval between equipment shutdowns, and a method for assembling the same. [Explanation of symbols]

[0040] 1. Combustion furnace 2 Heat exchanger 3 tube plate 4 Refractories 5 Heat transfer tubes 6 ferrules 6a Short pipe section 6b Flange part 7. Vitrified Glaze Layer 8 Routes

Claims

1. A ferrule to be assembled to a fluid inlet portion of a heat transfer tube of a heat exchanger having a heat transfer tube through which a fluid flows, comprising: the ferrule has a short pipe portion inserted into the heat transfer tube and a flange portion provided at an end of the short pipe portion, the short tube portion has a vitrified glaze layer on at least the inner surface of the inlet side portion, 10. A ferrule for a heat transfer tube of a heat exchanger, wherein the glaze layer is provided within a range of 10 mm to 50 mm from the inlet side of the short tube portion.

2. A ferrule to be assembled to a fluid inlet portion of a heat transfer tube of a heat exchanger having a heat transfer tube through which a fluid flows, comprising: the ferrule has a short pipe portion inserted into the heat transfer tube and a flange portion provided at an end of the short pipe portion, the short tube portion has a coating layer of a glaze that can be vitrified by heating on at least the inner surface of the inlet side portion, 10. A ferrule for a heat transfer tube of a heat exchanger, wherein the glaze coating layer is provided within a range of 10 mm to 50 mm from the inlet side of the short tube portion.

3. 3. The ferrule for a heat transfer tube of a heat exchanger according to claim 1, wherein the heat exchanger is a heat exchanger in which a combustion exhaust gas produced by burning a substance containing sulfur flows as a fluid through the heat transfer tube.

4. When the ferrule according to claim 2 is assembled to a fluid inlet of a heat transfer tube of a heat exchanger, A method for assembling a ferrule for a heat transfer tube of a heat exchanger, comprising: forming a glaze coating layer on the inner surface of at least the inlet side of a short tube section; assembling the ferrule to the fluid inlet section of the heat transfer tube; and then heating the ferrule to convert the coating layer into a vitrified glaze layer.

5. When the ferrule according to claim 2 is assembled to a fluid inlet of a heat transfer tube of a heat exchanger, a method for assembling a ferrule for a heat transfer tube of a heat exchanger, comprising: assembling the short tube portion of the ferrule to the fluid inlet portion of the heat transfer tube; forming a coating layer of glaze on at least the inner surface of the inlet portion of the short tube; and then heating the ferrule to convert the coating layer into a vitrified glaze layer.

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