JP6323366B2 - Radiant tube - Google Patents

Description

  The present invention relates to a radiant tube used in an industrial heating furnace.

  Conventionally, a burner using a radiant tube (radiant tube burner) is often installed as a heating device for a metal strip or the like in an industrial heating furnace (for example, Patent Document 1).

  The radiant tube includes a U type, a W type, a Z type, and the like depending on the shape thereof. Here, a W type radiant tube will be described as an example.

  An example of such a conventional radiant tube is shown in FIG. 5 (a) is a side view, FIG. 5 (b) is a P sectional view in FIG. 5 (a), and FIG. 5 (c) is a Q sectional view in FIG. 5 (a).

  As shown in FIG. 5, the radiant tube 80 includes four straight pipes (a first straight pipe 81, a second straight pipe 82, a third straight pipe 83, and a fourth straight pipe 84) having a circular cross section. It has a structure including a curved pipe (a first curved pipe 85, a second curved pipe 86, and a third curved pipe 87) having a circular cross section.

  And the radiant tube 80 is installed in a heating furnace, and the side surface of the straight pipes 81-84 is opposed to the surface of a heated material (not shown) such as a metal strip that travels in the vertical direction in the heating furnace. Has been placed. The combustion gas 7 injected from the burner body (not shown) passes through the radiant tube 80 and is discharged out of the system as the exhaust gas 8.

  At that time, the combustion gas 7 may be operated at an extremely high temperature of 1000 ° C. or higher. For this reason, the tubes 81 to 87 (particularly, the straight tubes 81 to 84) of the radiant tube 80 are respectively in the tube axis direction. It grows hot. Therefore, the radiant tube 80 is supported by the furnace side support 2 installed on the furnace wall 1 and the tube side support 3 provided on the radiant tube 80 side, and the sliding between the furnace side support 2 and the tube side support 3 is performed. The moving part 4 is slid by the amount corresponding to the thermal elongation, so that the heat restraining force is not generated in the radiant tube 80.

  Conventionally, such a radiant tube 80 has been generally manufactured integrally by casting. However, since a casting defect called a puddle peculiar to casting occurs, a certain amount of the molten metal spreads uniformly. It was necessary to cast with a wall thickness (for example, about 8 mm). As a result, there is a problem that the weight increases and the creep deformation due to its own weight increases in the heating furnace.

  Therefore, in recent years, welded pipes formed by heat-resistant metal plates and welded are used for the straight pipes 81 to 84 and the curved pipes 85 to 87 of the radiant tube 80, and these pipes 81 to 87 are connected by welding ( Welding structure) has become the mainstream. As a result, each of the tubes 81 to 87 of the radiant tube 80 can be made thinner (for example, about 3 mm) and lighter, and creep deformation due to its own weight can be prevented.

  However, as each of the tubes 81 to 87 of the radiant tube 80 is thinned, the cross-sectional performance of each of the tubes 81 to 87 of the radiant tube 80 is remarkably deteriorated. In particular, the straight tubes 81 to 84 are damaged by the bending load. There was a problem. That is, since the temperature of the gas in the radiant tube 80 becomes lower as it goes downstream in the gas flow direction, the straight pipe portions 81, 82, 83, 84 do not heat equally. For this reason, the heat elongation absorbing action at the sliding portion 4 described above does not function properly, the entire radiant tube 80 is distorted and a bending load is applied, and the straight pipes 81 to 84 are damaged.

  For this problem, a radiant tube as shown in FIG. 6 has been proposed (for example, Patent Document 2). 6A is a side view, FIG. 6B is an R sectional view in FIG. 6A, and FIG. 6C is an S sectional view in FIG. 6A.

  As shown in FIG. 6, this radiant tube 90 includes four straight pipes (first straight pipe 91, second straight pipe 92, third straight pipe 93, and fourth straight pipe 94) having an elliptical cross section. The curved pipes of the circular cross section (the first curved pipe 95, the second curved pipe 96, and the third curved pipe 97) are connected. In addition, the elliptical shape of the cross section of the straight pipes 91 to 94 has the major axis in the vertical direction (traveling direction of the material to be heated).

  Thus, since the cross-sectional performance is improved by using the straight pipes 91 to 94 having an elliptical cross section as compared with the straight pipes 81 to 84 having the circular cross section, it is possible to reduce breakage due to a bending load.

JP-A-9-303711 JP-A-5-285533

  However, recently, the demand for high performance and high quality for industrial products has become stronger, and the heating conditions in industrial heating furnaces have become stricter, so that the heat load of radiant tubes has also increased.

  Accordingly, even in the radiant tube 90 having the straight pipes 91 to 94 having an elliptical cross section as shown in FIG. 6, the breakage due to the bending load has increased.

  In addition, as shown in FIG. 6, the radiant tube 90 has an abrupt cross-sectional change portion 99 at the connection portion between the straight pipes 91 to 94 having an elliptical cross section and the curved pipes 95 to 97 having a circular cross section. There is also a breakage starting from 99.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a radiant tube having a high strength and a long life as a radiant tube having a welded structure used in an industrial heating furnace. is there.

  In order to solve the above problems, the present invention has the following features.

  [1] In a radiant tube having a welded structure in which a straight pipe made of a welded pipe and a curved pipe are connected by welding, the straight pipe and the curved pipe have the same elliptical cross-sectional shape and are used for preventing the straight pipe from being bent. A radiant tube having a reinforcing material.

  [2] The radiant tube according to [1], wherein the reinforcing material is a reinforcing material arranged on the major axis or / and the minor axis of the ellipse inside the straight pipe.

  [3] The radiant tube according to [1] or [2], wherein the straight pipe includes a heat transfer fin.

  In the present invention, the sectional shape of a straight pipe or a curved pipe means a shape of a cross section perpendicular to the tube axis of the straight pipe or the curved pipe.

  ADVANTAGE OF THE INVENTION According to this invention, a high intensity | strength and long life radiant tube can be provided as a radiant tube of the welding structure used for an industrial heating furnace.

It is a figure which shows the radiant tube which concerns on Embodiment 1 of this invention. It is a figure which shows the radiant tube which concerns on Embodiment 2 of this invention. It is a comparison figure of the section performance in Example 1 of the present invention. It is a comparison figure of the temperature change (thermal efficiency) in Example 2 of this invention. It is a figure which shows the conventional radiant tube (a straight pipe is circular cross section). It is a figure which shows the conventional radiant tube (a straight pipe is an elliptical cross section).

  Embodiments of the present invention will be described with reference to the drawings.

[Embodiment 1]
FIG. 1 is a view showing a radiant tube 10 according to Embodiment 1 of the present invention. 1 (a) is a side view, FIG. 1 (b) is a cross-sectional view A in FIG. 1 (a), and FIG. 1 (c) is a cross-sectional view B in FIG. 1 (a).

  As shown in FIG. 1, the radiant tube 10 includes four straight pipes (first straight pipe 11, second straight pipe 12, third straight pipe 13, and fourth straight pipe 14) having an elliptical cross section. The bent pipes having the elliptical cross section (the first bent pipe 15, the second bent pipe 16, and the third bent pipe 17) are connected by welding.

  Here, the straight pipes 11 to 14 and the curved pipes 15 to 17 are welded pipes having the same cross-sectional shape. ) Is the long axis, and the curved pipes 15 to 17 are connected to the straight pipes 11 to 14 so as not to cause a sudden change in section. In addition, about the ellipse of said cross section, it is preferable to make ratio of a major axis and a minor axis about 1.2-1.4 in consideration of interference etc. of adjacent straight pipes.

  In addition, the radiant tube 10 includes a reinforcing material for preventing bending of the straight pipes 11 to 14 inside the straight pipes 11 to 14, as shown in FIG. 31 and 32 are arranged. Here, the reinforcing material 31 is arranged on the long axis of the elliptical cross section of the straight pipes 11 to 14, and the reinforcing material 32 is arranged on the short axis of the elliptical cross section of the straight pipes 11 to 14. The reinforcing members 31 and 32 may be disposed over the entire pipe axis direction of the straight pipes 11 to 14, or depending on the case, may be arranged at a predetermined interval in the pipe axis direction of the straight pipes 11 to 14. It may be.

  Thus, in the radiant tube 10 according to the first embodiment, since the straight pipes 11 to 14 are provided with the reinforcing members 31 and 32 for preventing the bending, the cross-sectional performance is improved and the straight pipe due to the bending load is provided. While the breakage of 11 to 14 is suppressed and there is no sudden section change between the straight pipes 11 to 14 and the curved pipes 15 to 17, breakage due to sudden section change does not occur.

  Therefore, the radiant tube 10 according to the first embodiment is a radiant tube having a high strength and a long life.

  In addition, what is necessary is just to make the material of the reinforcing materials 31 and 32 the same as the material (for example, heat resistant steel) of the straight pipes 11-14 and the curved pipes 15-17. Further, the thickness of the reinforcing members 31 and 32 may be about 5 to 10 mm.

  And as mentioned above, when arrange | positioning the reinforcing materials 31 and 32 in the inside of the straight pipes 11-14, the straight pipes 11-14 are divided | segmented into 2 along a pipe axis beforehand, and there is a reinforcing material there. What is necessary is just to weld-join the part divided into 2 after arrange | positioning 31 and 32. FIG.

  At that time, the reinforcing members 31 and 32 can exhibit the function of preventing the bending of the straight pipes 11 to 14 even if they are not joined to the straight pipes 11 to 14. What is necessary is just to be welded and joined to such an extent that positioning is performed.

  Moreover, when arrange | positioning the reinforcing materials 31 and 32 over the whole pipe-axis direction of the straight pipes 11-14, you may make it insert the reinforcing materials 31 and 32 from the pipe end of the straight pipes 11-14.

  In the first embodiment, the elliptical long-axis side reinforcing material 31 and the elliptical short-axis side reinforcing material 32 are arranged, but only one of the reinforcing materials 31 and 30 is arranged. But you can. Moreover, you may arrange | position a reinforcing material in the other elliptical part of the straight pipes 11-14. Furthermore, you may arrange | position a reinforcing material outside the straight pipes 11-14.

[Embodiment 2]
FIG. 2 is a view showing a radiant tube 20 according to Embodiment 2 of the present invention. 2A is a side view, FIG. 2B is a C cross-sectional view in FIG. 2A, and FIG. 2C is a D cross-sectional view in FIG. 2A.

  As shown in FIG. 2, the basic configuration of the radiant tube 20 is the same as that of the radiant tube 10 described above.

  That is, the radiant tube 20 has four oval cross-section straight pipes (first straight pipe 21, second straight pipe 22, third straight pipe 23, fourth straight pipe 24) and three oval cross-sections. The curved pipes (first curved pipe 25, second curved pipe 26, and third curved pipe 27) are connected by welding.

  Here, the straight pipes 21 to 24 and the curved pipes 25 to 27 are welded pipes having the same cross-sectional shape. ) Is the long axis, and the bent pipes 25 to 27 are connected to the straight pipes 21 to 24 so as not to cause a sudden change in section.

  Then, as shown by the straight pipe 21 as a representative in FIG. 2B, reinforcing members 31 and 32 for preventing the bending of the straight pipes 21 to 24 are arranged inside the straight pipes 21 to 24. Here, the reinforcing material 31 is arranged on the long axis of the elliptical cross section of the straight pipes 21 to 24, and the reinforcing material 32 is arranged on the short axis of the elliptical cross section of the straight pipes 21 to 24. The reinforcing members 31 and 32 may be arranged over the entire pipe axis direction of the straight pipes 21 to 24, or depending on the case, arranged at a predetermined interval in the pipe axis direction of the straight pipes 21 to 24. It may be.

  In addition, unlike the radiant tube 10, the radiant tube 20 has heat transfer fins 33 in the straight pipes 21 to 24 as shown in FIG. Is arranged.

  The reason is as follows. That is, by making the cross section of the straight pipes 21 to 24 elliptical, the surface area facing the surface of the material to be heated (metal strip) increases, so that the radiation efficiency increases, but on the other hand, the flow of combustion gas Since the road area increases, the flow rate of the combustion gas decreases, the amount of heat transfer from the combustion gas to the inner surface of the pipe decreases, and the overall thermal efficiency may decrease. Therefore, by disposing the heat transfer fins 33 inside the straight pipes 21 to 24, the contact area between the combustion gas and the pipe inner surface is increased, and the amount of heat transfer from the combustion gas to the pipe inner surface is increased. , Improve the thermal efficiency.

  In addition, although it is preferable that the fin 33 is arrange | positioned over the whole pipe-axis direction of the straight pipes 21-24, depending on the case, it is arrange | positioned at predetermined intervals in the pipe-axis direction of the straight pipes 21-24. Also good.

  Thus, in the radiant tube 20 according to the second embodiment, since the straight pipes 21 to 24 are provided with the reinforcing materials 31 and 32 for preventing the bending, the cross-sectional performance is improved and the straight pipe due to the bending load is provided. Breakage of 21 to 24 is suppressed, and since there is no sudden change section between the straight pipes 21 to 24 and the bent pipes 25 to 27, breakage due to sudden change in cross section does not occur. Furthermore, since the straight pipes 21 to 24 are provided with the heat transfer fins 33, the thermal efficiency can be improved.

  Therefore, the radiant tube 20 according to the second embodiment is a radiant tube with high strength, long life, and high efficiency.

  The material of the fin 31 may be the same as the material of the straight pipes 21 to 24 and the curved pipes 25 to 27 (for example, heat resistant steel), similarly to the reinforcing members 31 and 32. In addition, the dimensions of the fin 31 may be about 2 to 4 mm in thickness and about 10 to 20 mm in width (length in the tube diameter direction).

  Further, as described above, when the reinforcing members 31 and 32 and the fins 33 are arranged inside the straight pipes 21 to 24, the straight pipes 21 to 24 are divided into two along the pipe axis in advance. After the reinforcing members 31 and 32 and the fins 33 are arranged, the two parts may be welded and joined.

  At that time, even if the reinforcing members 31 and 32 are not joined to the straight pipes 21 to 24, the function of preventing the bending of the straight pipes 21 to 24 can be exhibited. What is necessary is just to perform welding joining of the grade which positions.

  Moreover, when arrange | positioning the reinforcing materials 31 and 32 over the whole pipe-axis direction of the straight pipes 21-24, you may make it insert the reinforcing materials 31 and 32 from the pipe end of the straight pipes 21-24.

  On the other hand, the fin 33 is integrated with the straight pipes 21 to 24 by welding so that the heat transfer improving function can be sufficiently exhibited.

  In the second embodiment, the elliptical long-axis-side reinforcing material 31 and the elliptical short-axis-side reinforcing material 32 are arranged, but only one of the reinforcing materials 31 and 30 is arranged. But you can. Moreover, you may arrange | position a reinforcing material in the elliptical part of the straight pipes 21-24. Further, a reinforcing material may be disposed outside the straight pipes 21 to 24.

  In the first and second embodiments, the W-type radiant tube has been described. However, the present invention can be similarly applied to other radiant tubes such as a U-type and a Z-type.

  As Example 1 of the present invention, the cross-sectional performance of the radiant tube was examined.

  At that time, as Example 1 of the present invention, the radiant tube 10 according to Embodiment 1 of the present invention shown in FIG. 1 was used. In the straight pipes 11 to 14 and the curved pipes 15 to 17, the ratio of the major axis to the minor axis of the elliptical cross section was 1.3, and the wall thickness was 3 mm. And the reinforcing materials 31 and 32 were 6 mm in thickness, and were arrange | positioned over the full length of the straight pipes 11-14.

  On the other hand, for comparison, a conventional radiant tube 80 shown in FIG. The straight pipes 81 to 84 and the curved pipes 85 to 87 had the same circular cross-sectional diameter as the short diameter of Example 1 of the present invention, and the wall thickness was 3 mm.

  Further, as the conventional example 2, a conventional radiant tube 90 shown in FIG. 6 was used. In the straight pipes 91 to 94, the ratio of the major axis to the minor axis of the elliptical cross section was 1.3, and the wall thickness was 3 mm. The curved pipes 95 to 97 had the same circular cross-sectional diameter as that of the first example of the present invention, and a thickness of 3 mm.

  FIG. 3 shows a comparison of the cross-sectional performance (section modulus) between Example 1 of the present invention and Conventional Examples 1 and 2. In FIG. 3, the section modulus of Conventional Example 1 is 1.0.

  As shown in FIG. 3, in the first example of the present invention, the cross-sectional performance (section modulus) is greatly improved as compared with the first and second examples.

  As Example 2 of the present invention, the thermal efficiency of the radiant tube was examined.

  At that time, the radiant tube 20 according to the second embodiment of the present invention shown in FIG. In the straight pipes 21 to 24 and the curved pipes 25 to 27, the ratio of the major axis to the minor axis of the elliptical cross section was 1.3, and the wall thickness was 3 mm. And the reinforcing materials 31 and 32 were 6 mm in thickness, and were arrange | positioned over the full length of the straight pipes 21-24. Further, the fin 33 has a thickness of 3 mm, a width (length in the tube diameter direction) of 15 mm, and is disposed over the entire length of the straight tubes 21 to 24.

  On the other hand, for comparison, a conventional radiant tube 80 shown in FIG. The straight pipes 81 to 84 and the curved pipes 85 to 87 had the same circular cross-sectional diameter as that of the short axis of Example 2 of the present invention, and the wall thickness was 3 mm.

  Similarly, the conventional radiant tube 90 shown in FIG. In the straight pipes 91 to 94, the ratio of the major axis to the minor axis of the elliptical cross section was 1.3, and the wall thickness was 3 mm. The curved pipes 95 to 97 had the same circular cross-sectional diameter as that of the short axis of Example 2 of the present invention and a thickness of 3 mm.

  FIG. 4 shows the surface temperature and exhaust gas temperature of the first straight pipe to the fourth straight pipe in Invention Example 2 and Conventional Examples 3 and 4.

  As shown in FIG. 4, in Example 2 of the present invention, the amount of decrease in the surface temperature as the first straight pipe, the second straight pipe, the third straight pipe, and the fourth straight pipe are reduced as compared with the conventional examples 3 and 4. Finally, the exhaust gas temperature is significantly lower than that of the conventional examples 3 and 4.

  This means that in Example 2 of the present invention, the amount of heat transfer from the combustion gas to the straight pipe is increased as compared with the conventional examples 3 and 4, and the thermal efficiency is good.

DESCRIPTION OF SYMBOLS 1 Furnace wall 2 Furnace side support 3 Pipe side support 4 Sliding part 7 Combustion gas 8 Exhaust gas 10 Radiant tube 11 1st straight pipe 12 2nd straight pipe 13 3rd straight pipe 14 4th straight pipe 15 1st curved pipe 16 1st 2nd curved pipe 17 3rd curved pipe 20 Radiant tube 21 1st straight pipe 22 2nd straight pipe 23 3rd straight pipe 24 4th straight pipe 25 1st curved pipe 26 2nd curved pipe 27 3rd curved pipe 31 Long axis side Reinforcing material 32 Short shaft side reinforcing material 33 Fin 80 Radiant tube 81 First straight pipe 82 Second straight pipe 83 Third straight pipe 84 Fourth straight pipe 85 First curved pipe 86 Second curved pipe 87 Third curved pipe 90 Radiant tube 91 1st straight pipe 92 2nd straight pipe 93 3rd straight pipe 94 4th straight pipe 95 1st curved pipe 96 2nd curved pipe 97 3rd curved pipe 99 Section sudden change part

Claims (2)

In a radiant tube having a welded structure in which a straight pipe made of a welded pipe and a curved pipe are connected by welding, the straight pipe and the curved pipe have the same elliptical cross-sectional shape, and the elliptical shape is formed inside the straight pipe. arranged in the longitudinal and / or minor axis, across the tube axis direction of the straight tube, or have a reinforcing member for preventing bending of the straight pipe that is disposed at a predetermined interval in the axial direction of the tube, previously A radiant characterized in that the pipe shaft is divided into two along the pipe axis, a reinforcing material for preventing the bending of the straight pipe is disposed therein, and the two divided portions are welded to form a straight pipe. tube. The radiant tube according to claim 1, further comprising a heat transfer fin inside the straight pipe.

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