JP2017062085A - Burner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new and improved burner that can prevent damage due to thermal stress from occurring caused by a temperature difference between an outer pipe and the burner while suppressing a decline in furnace interior heating efficiency and an increase in generation amount of NOx caused by emission of cooling gas into a furnace.SOLUTION: A tubular burner for injecting fuel gas from the tip side toward inside of a furnace includes: an outer pipe provided on the outer periphery of the burner and forming a double pipe structure together with the burner; a cooling gas passage provided between the outer pipe and the burner; an inner pipe provided on the inner periphery of the outer pipe and the outer periphery of the burner to partition the cooling gas passage into an outer peripheral side passage and an inner peripheral side passage that are communicated with each other on the tip side; a lid portion for closing an opening on the tip side between the outer pipe and the burner; and an annular slit communicating the cooling gas passage and inside of the furnace with each other and provided in the lid portion in the peripheral direction of the burner.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a burner.

  Conventionally, burners have been widely used as means for heating the inside of a furnace. The tip end side where the fuel gas of such a burner is injected is provided toward the inside of the furnace and is exposed to a high temperature environment, so that it is easy to burn out. Therefore, a technique relating to the cooling of the burner for preventing burner burnout has been proposed.

  For example, in Patent Document 1, in order to provide a safe burner that retains the advantages of a water-cooled burner and that does not risk the furnace from causing a steam explosion, in the burner that is directed to the combustion chamber in the furnace body, A technique is disclosed in which a metal is used for the material of the burner body, and water cooling type cooling means is provided on the outer periphery of the portion of the entire length of the burner body that protrudes outside the furnace body.

  Patent Document 2 discloses a technique in which a thermal expansion / contraction absorbing device is provided at the rear portion of the combustion nozzle pipe in order to absorb expansion / contraction of the air cooling pipe due to thermal expansion.

JP-A-11-257613 JP 2001-182915 A

  By the way, as an air-cooled burner cooling device, a cooling gas is provided on the outer periphery of a tubular burner for injecting fuel gas, and forms an outer tube forming a double tube structure with the burner, and between the outer tube and the burner. And a cooling device including the passage. FIG. 1 is a schematic diagram illustrating an example of a schematic configuration of a conventional cooling device 90. As shown in FIG. 1, the cooling device 90 is provided so as to cover the outer periphery of the tubular burner 10 and is provided so as to penetrate through an opening 302 provided in the furnace wall 30 surrounding the combustion chamber 20 in the furnace. . The burner 10 has a fuel gas passage 102 through which fuel gas passes on the inner peripheral side, and injects the fuel gas that has passed through the fuel gas passage 102 into the furnace from the front end side. The cooling device 90 includes an outer pipe 902, a cooling gas passage 904, and a cooling gas inflow pipe 910.

  The outer tube 902 is provided on the outer periphery of the tubular burner 10 and forms a double tube structure with the burner 10. The outer tube 902 penetrates the opening 302 of the furnace wall 30 and is joined to the furnace wall 30 by welding, for example. The rear end portion of the outer tube 902 is joined to the burner 10 on the outside of the furnace from the furnace wall 30 by, for example, welding.

  The cooling gas passage 904 is provided between the outer tube 902 and the burner 10, and a cooling gas such as air passes through the cooling gas passage 904. The cooling gas is supplied to the cooling gas passage 904 from the cooling gas inflow pipe 910 connected to the outer pipe 902 on the outside of the furnace from the furnace wall 30. By supplying the cooling gas to the cooling gas passage 904 covering the outer periphery of the burner 10, the portion inside the furnace of the burner 10 can be cooled, so that the burner 10 can be prevented from being burned out. The cooling gas that has passed through the cooling gas passage 904 is discharged into the furnace from the opening 920 on the distal end side between the outer tube 902 and the burner 10.

  Here, in the heating furnace using the burner 10, two burners 10 form a pair, and each of the burners 10 constituting the pair may be configured to inject combustion gas alternately. While one burner 10 is injecting fuel gas, in order to reuse the waste heat of the heating furnace, the exhaust gas having the waste heat of the heating furnace 1 is supplied to the heat storage body corresponding to the other burner 10. The fuel gas injection by the other burner 10 is stopped. As described above, even when the fuel gas injection by the burner 10 is stopped, it is necessary to supply the cooling gas to the cooling gas passage 904 in order to prevent the burner 10 from being burned out. An excessive amount of cooling gas can be released into the furnace. Therefore, a decrease in heating efficiency in the furnace due to a decrease in the temperature in the furnace and an increase in the amount of NOx generated due to an excessive amount of supplied air can occur.

  For example, in the burner described in Patent Document 1, the entire circumference of the main pipe is surrounded by the sub pipe with an interval, and the fuel is sent to the first flow path in the main pipe, and the main pipe and the sub pipe are also surrounded. Air or the like is sent to the second flow path between the pipes, and fuel, air, and the like are discharged from the leading end of the main pipe and the leading end of the sub pipe, respectively. Therefore, since the air etc. are discharged | emitted in a furnace, the problem mentioned above may arise.

  Here, in order to avoid the discharge of the cooling gas into the furnace, it is conceivable to close the opening on the tip side between the outer tube and the burner. For example, in the conventional cooling device 90 shown in FIG. 1, it is conceivable to close the opening 920 on the distal end side between the outer tube 902 and the burner 10. In that case, a cooling gas discharge pipe for discharging the cooling gas supplied to the cooling gas passage 904 can be provided outside the furnace wall 30 of the outer pipe 902. Since the outer tube 902 is exposed to the atmosphere of the combustion chamber 20 in the furnace, it can be at a higher temperature than the burner 10. As shown in FIG. 1, when the opening 920 on the distal end side between the outer tube 902 and the burner 10 is opened, the outer tube 902 and the burner 10 have different thermal expansion amounts. Since the deformation of the outer tube 902 and the burner 10 is not restricted in the radial direction of the burner 10 on the distal end side, the generation of thermal stress in the axial direction and the radial direction of the burner 10 can be suppressed. .

  On the other hand, when the opening 920 on the distal end side between the outer tube 902 and the burner 10 is closed, the deformation of the outer tube 902 and the burner 10 is restricted in the axial direction of the burner 10. Further, the deformation of the outer tube 902 and the burner 10 is restricted in the radial direction of the burner 10 on the distal end side. Therefore, the axial and radial thermal stresses of the burner 10 are generated due to the temperature difference between the outer tube 902 and the burner 10. Thereby, the cooling device 90 or the burner 10 may be damaged. Specifically, a crack may occur in a portion where stress is easily concentrated, such as a connection portion between the front end portion and the rear end portion of the outer tube 902 and the burner 10.

  For example, in the technique described in Patent Document 2, the opening on the distal end side between the outer tube and the burner is closed, but the outer tube and the burner are different in thermal expansion amount from each other by the thermal expansion / contraction absorber. Since it is expandable in the axial direction, generation of thermal stress in the axial direction of the burner can be suppressed. However, since the deformation of the outer tube and the burner is restricted in the radial direction of the burner on the tip side, thermal stress is generated in the radial direction of the burner due to the temperature difference between the outer tube and the burner. Therefore, there is a possibility that cracks may occur at the connection portion between the outer tube and the burner due to the thermal stress in the radial direction.

  Accordingly, the present invention has been made in view of the above problems, and an object of the present invention is to reduce the heating efficiency in the furnace and increase the amount of NOx generated by releasing the cooling gas into the furnace. It is an object of the present invention to provide a new and improved burner capable of preventing the occurrence of breakage due to thermal stress caused by a temperature difference between an outer tube and a burner while suppressing the occurrence of damage.

  In order to solve the above problems, according to an aspect of the present invention, in a tubular burner for injecting fuel gas from the front end side into the furnace, the burner is provided on the outer periphery of the burner, and the burner and double tube structure A cooling gas passage provided between the outer pipe and the burner, an inner circumference of the outer pipe and an outer circumference of the burner, and the passage of the cooling gas is communicated on the tip side. An inner pipe that is divided into an outer circumferential path and an inner circumferential path, a lid that closes an opening on the distal end side between the outer pipe and the burner, the cooling gas path, and the interior of the furnace And an annular slit provided in the lid portion along the circumferential direction of the burner.

  The slit may have a tapered shape that increases in diameter toward the distal end side.

  As described above, according to the present invention, the temperature difference between the outer tube and the burner is suppressed while suppressing the decrease in the heating efficiency in the furnace and the increase in the generation amount of NOx due to the discharge of the cooling gas into the furnace. It is possible to prevent the occurrence of breakage due to thermal stress caused by this.

It is a schematic diagram which shows an example of schematic structure of the conventional cooling device. It is a schematic diagram which shows an example of the heating furnace using a burner. It is a schematic diagram which shows an example of schematic structure of the cooling device which concerns on this embodiment. It is an enlarged view of the tip part of the cooling device and burner concerning the embodiment. It is an enlarged view of the tip of a cooling device and a burner concerning a modification. It is a schematic diagram which shows the result of the stress analysis which concerns on a comparative example. It is a schematic diagram which shows the result of the stress analysis which concerns on an Example.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

<0. Introduction>
Conventionally, as a means for heating the inside of the furnace, a heating furnace using a burner has been widely used in production processes. For example, a heating furnace using a burner is used in a process of heating the steel material as a pre-process of the rolling process of the steel material. FIG. 2 is a schematic diagram illustrating an example of the heating furnace 1 using the burner 10. The heating furnace 1 shown in FIG. 2 is used, for example, in a process of heating a thick steel material having a thickness of 600 mm to 1200 ° C.

  The heating furnace 1 includes an upper furnace wall 30a and a lower furnace wall 30b that surround the combustion chamber 20 inside the heating furnace 1, and a transport device 40 that transports the steel material M1. The burner 10 injects fuel gas from the tip side toward the combustion chamber 20 in the heating furnace 1 and has a tube shape. In the following description, a tube shape, a tubular shape or an annular shape is not limited to a shape having a circular cross section, and includes a shape having a cross section such as an ellipse or a polygon.

  As shown in FIG. 2, the burner 10 is provided so as to penetrate the upper furnace wall 30 a or the lower furnace wall 30 b and have the tip side directed toward the combustion chamber 20. The rear end side of the burner 10 is located on the outside of the furnace from the upper furnace wall 30a or the lower furnace wall 30b, and the fuel gas is supplied to the burner 10 from the rear end side of the burner 10. The supplied fuel gas passes through a passage provided on the inner peripheral side of the burner 10 and is injected from the front end side of the burner 10 toward the combustion chamber 20. Thereby, the inside of the heating furnace 1 is heated. For example, in the process of heating the steel material M1, the steel material M1 charged into the combustion chamber 20 is transported from the combustion chamber 20 after being transported in the combustion chamber 20 by the transport device 40 while being heated by the burner 10. Discharged.

  In the heating furnace 1 using the burner 10, the tip end side of the burner 10 is located on the combustion chamber 20 side of the heating furnace 1 and is exposed to a high temperature environment, so that it is easily burned out. Therefore, in order to prevent burning of the burner 10, a cooling device for cooling the burner 10 is used. Hereinafter, in this specification, due to the temperature difference between the outer tube and the burner while suppressing the decrease in the heating efficiency in the furnace due to the discharge of the cooling gas into the furnace and the increase in the generation amount of NOx, A cooling device 50 according to an embodiment of the present invention capable of preventing the occurrence of breakage due to the generated thermal stress will be described.

<1. Configuration of cooling device>
First, the configuration of the cooling device 50 according to the present embodiment will be described with reference to FIG. FIG. 3 is a schematic diagram illustrating an example of a schematic configuration of the cooling device 50 according to the present embodiment. FIG. 3 shows an example in which the cooling device 50 according to the present embodiment is applied to the heating furnace 1 described with reference to FIG. The cooling device 50 according to the present embodiment can be applied to any heating furnace using a burner, and can be applied to the heating furnace 1 described with reference to FIG. 2 as an example.

  As shown in FIG. 3, the burner cooling device 50 is provided so as to cover the outer periphery of the tubular burner 10, and is provided so as to penetrate the opening 302 provided in the furnace wall 30 surrounding the combustion chamber 20 in the furnace. It is done. The burner 10 has a fuel gas passage 102 through which fuel gas passes on the inner peripheral side, and injects the fuel gas that has passed through the fuel gas passage 102 into the furnace from the front end side. The cooling device 50 includes an outer pipe 502, a cooling gas passage 504, a lid 506, an inner pipe 508, a cooling gas inflow pipe 510, and a cooling gas discharge pipe 512.

  The outer tube 502 is provided on the outer periphery of the tubular burner 10 and forms a double tube structure with the burner 10. The outer tube 502 passes through the opening 302 of the furnace wall 30 and is joined to the furnace wall 30 by welding, for example. The distal end side of the outer wall 502 of the outer tube 502 is located in the combustion chamber 20 in the furnace, and is exposed to the atmosphere in the furnace. Further, the distal end portion of the outer tube 502 is joined to the rear end portion on the outer peripheral side of the lid portion 506 by, for example, welding, and the rear end portion of the outer tube 502 is connected to, for example, the inner tube 508 on the outside of the furnace from the furnace wall 30. They are joined by welding. Note that the rear end portion of the outer tube 502 and the inner tube 508 may be directly joined or may be joined via another member.

  The cooling gas passage 504 is provided between the outer tube 502 and the burner 10, and the cooling gas passes through the cooling gas passage 504. As the cooling gas supplied to the cooling gas passage 504, for example, air or nitrogen can be applied. The cooling gas passage 504 is divided into an outer passage 504 a and an inner passage 504 b by an inner tube 508 provided on the inner periphery of the outer tube 502 and on the outer periphery of the burner 10. The outer peripheral side passage 504a and the inner peripheral side passage 504b communicate with each other via a space between the distal end portion of the inner tube 508 and the lid portion 506 on the distal end side. The rear end portion of the inner tube 508 is joined to the burner 10, for example, by welding, outside the furnace wall 30 from the furnace wall 30. Note that the rear end portion of the inner tube 508 and the burner 10 may be directly joined or may be joined via another member.

  The lid 506 closes the opening on the distal end side between the outer tube 502 and the burner 10. The rear end portion of the outer peripheral side of the lid portion 506 is joined to the front end portion of the outer tube 502 by, for example, welding, and the rear end portion of the inner peripheral side of the lid portion 506 is joined to the front end portion of the burner 10, for example, by welding. Yes. The lid 506 is provided with an annular slit 506 a that communicates the cooling gas passage 504 with the inside of the furnace and extends along the circumferential direction of the burner 10.

  In the present embodiment, the opening on the distal end side between the outer tube 502 and the burner 10 is closed by the lid 506 so that the opening on the distal end side between the outer tube 502 and the burner 10 is opened. Compared to the case, the amount of cooling gas released into the furnace can be reduced. Thereby, it is possible to suppress a decrease in heating efficiency in the furnace and an increase in the generation amount of NOx due to the discharge of the cooling gas into the furnace.

  The cooling gas inflow pipe 510 is connected to the outer pipe 502 on the outer side of the furnace from the furnace wall 30, and the cooling gas discharge pipe 512 is connected to the inner pipe 508 on the outer side of the furnace from the furnace wall 30. The cooling gas is supplied from the cooling gas inflow pipe 510 to the outer peripheral side passage 504a of the cooling gas passage 504, and after passing through the outer peripheral side passage 504a, is sent to the inner peripheral side passage 504b. Then, the cooling gas that has passed through the inner peripheral side passage 504 b is discharged to the cooling gas discharge pipe 512.

  The cooling device 50 includes an inner pipe 508 that is provided on the inner circumference of the outer pipe 502 and on the outer circumference of the burner 10 and divides the cooling gas passage 504 into an outer passage 504a and an inner passage 504b. The passage 504b on the inner peripheral side and the passage 504a communicate with each other on the tip side. Accordingly, the cooling gas can pass through the outer peripheral side passage 504a adjacent to the outer tube 502 before the inner peripheral side passage 504b. Therefore, the outer tube 502 that is exposed to heat input from the atmosphere in the furnace or from the high-temperature refractory in the furnace can be effectively cooled as compared with the burner 10.

<2. Deformation due to thermal expansion of cooling device and burner>
Then, with reference to FIG. 4, the deformation | transformation by the thermal expansion of the cooling device 50 and the burner 10 which concern on this embodiment is demonstrated.

  FIG. 4 is an enlarged view of the cooling device 50 and the tip of the burner 10 according to the present embodiment shown in FIG. 4 shows the cooling device 50 and the tip of the burner 10 before the inside of the furnace is heated. 4 shows the cooling device 50 and the tip of the burner 10 after the inside of the furnace is heated to a high temperature.

  Since the outer tube 502 and a part of the lid portion 506 located on the outer periphery of the burner 10 are exposed to the atmosphere in the furnace and heat input from the high-temperature furnace refractory, the inside of the furnace was heated to a high temperature. Later, it may be hotter than the burner 10. In the present embodiment, the outer cover 506b on the outer periphery side of the slit 506a in the cover 506 is joined to the tip of the outer tube 502, and the inner periphery of the cover 506 on the inner periphery of the slit 506a. The lid 506c and the tip of the burner 10 are joined. On the other hand, the outer peripheral side cover part 506b and the inner peripheral side cover part 506c are separated by a slit 506a.

  Therefore, the outer tube 502 and the outer peripheral side cover part 506b and the burner 10 and the inner peripheral side cover part 506c can expand in the axial direction of the burner 10 with different thermal expansion amounts. Moreover, the front end side and outer peripheral side cover part 506b of the outer tube 502 and the front end side and inner peripheral side cover part 506c of the burner 10 can expand in the radial direction of the burner 10 with different thermal expansion coefficients. Therefore, as shown in FIG. 4, the distal end side and the outer peripheral side cover portion 506 b of the outer tube 502 are restrained from being deformed by the front end side and the inner peripheral side cover portion 506 c of the burner 10 in the axial direction and the radial direction of the burner 10. Without being done, it can be deformed with heating in the furnace. Thereby, generation | occurrence | production of the thermal stress of the axial direction of the burner 10 and radial direction resulting from the temperature difference between the outer tube | pipe 502 and the burner 10 can be suppressed. Therefore, it is possible to prevent the occurrence of breakage due to the thermal stress caused by the temperature difference between the outer tube 502 and the burner 10.

<3. Modification>
Then, with reference to FIG. 5, the deformation | transformation by the thermal expansion of the cooling device which concerns on a modification, and the burner 10 is demonstrated.

  FIG. 5 is an enlarged view of the tip of the cooling device and the burner 10 according to the modification. 5 shows the cooling device and the tip of the burner 10 before the inside of the furnace is heated. The diagram on the right side in FIG. 5 shows the cooling device and the tip of the burner 10 after the inside of the furnace is heated to a high temperature.

  In the cooling device according to the modification, the shape of the slit provided in the lid is different from that of the cooling device 50 described with reference to FIG. As shown in FIG. 5, the slit 606 a provided in the lid 606 according to the modification has a tapered shape that increases in diameter toward the distal end side. In the modification, similarly to the cooling device 50 and the front end portion of the burner 10 according to the present embodiment described with reference to FIG. 4, the outer peripheral side cover portion 606 b and the outer tube 502 on the outer peripheral side of the slit 606 a in the cover portion 606. It is joined to the tip of the. Moreover, the inner peripheral side cover part 606c and the front-end | tip part of the burner 10 of the inner peripheral side rather than the slit 606a among the cover parts 606 are joined. Moreover, the outer peripheral side cover part 606b and the inner peripheral side cover part 606c are separated via the slit 606a. Therefore, by providing the slit 606a in the lid portion 606, it is possible to suppress the deformation of the outer tube 502 and the burner 10 from being restrained.

  Here, after the inside of the furnace is heated, a part of the outer tube 502 and the lid portion 606 can be at a higher temperature than the burner 10, so the shaft of the burner 10 of the outer tube 502 and the outer side lid portion 606b. The amount of thermal expansion in the direction is larger than that of the burner 10 and the inner peripheral side cover 606c. Further, the thermal expansion coefficient in the radial direction of the burner 10 at the distal end side and the outer peripheral side lid portion 606b of the outer tube 502 is larger than that at the distal end side and the inner circumferential side lid portion 606c of the burner 10. Therefore, as shown in FIG. 5, in the axial direction of the burner 10, the outer lid portion 606 b moves relative to the inner circumferential lid portion 606 c in the distal direction with heating in the furnace. Moreover, as shown in FIG. 5, the outer peripheral side cover part 606b moves in the radial direction of the burner 10 in a direction relatively away from the inner peripheral side cover part 606c with heating in the furnace.

  Here, the slit 606a according to the modified example has a tapered shape whose diameter is increased toward the distal end side. The said taper shape is formed along the relative moving direction of the outer peripheral side cover part 606b with respect to the inner peripheral side cover part 606c in the expansion process of the cooling device and the burner 10 accompanying the heating in the furnace. Thereby, the outer periphery side cover part 606b moves along the taper direction of the slit 606a relatively with respect to the inner periphery side cover part 606c with the heating in a furnace. Therefore, the space between the surface adjacent to the slit 606a of the outer cover 606b and the surface adjacent to the slit 606a of the inner cover 606c is approximately before and after the expansion of the cooling device and the burner 10 accompanying heating in the furnace. Maintained constant. Thereby, it can suppress that the clearance gap between the slits 606a increases by the expansion of the cooling device and the burner 10 accompanying the heating in the furnace. Therefore, in the modified example, the amount of the cooling gas released into the furnace can be further reduced. Therefore, it is possible to more effectively suppress a decrease in heating efficiency in the furnace and an increase in the amount of NOx generated due to the discharge of the cooling gas into the furnace.

  In order to confirm the effect of the present invention, a stress analysis was performed on the thermal stress generated in the cooling device and the burner after the inside of the furnace was heated to a high temperature. In the stress analysis, Mises stress generated in the cooling device and the burner is calculated based on the temperature distribution of the cooling device and the burner after the inside of the furnace is heated to a high temperature. The temperature distribution of the cooling device and the burner used in the stress analysis is obtained, for example, by measuring the temperature of each part of the cooling device and the burner after actually heating the inside of the furnace. Note that the temperature distribution of the cooling device and the burner used in the stress analysis may be obtained by temperature distribution analysis based on various conditions such as the material and shape of the cooling device and the burner.

  As a comparative example, unlike the above-described embodiment, an example in which the opening on the distal end side between the outer tube and the burner is closed by a lid portion that does not have a slit. Stress analysis was performed on the thermal stress generated in the burner.

  Further, as an example, like the above-described embodiment, the cooling gas passage and the inside of the furnace are communicated, and the tip between the outer tube and the burner is formed by a lid portion having an annular slit along the circumferential direction of the burner. For an example in which the opening on the side was closed, a stress analysis was performed on the thermal stress generated in the cooling device and the burner after the inside of the furnace was heated.

  In both the comparative example and the example, in the stress analysis, the set value of the temperature of the atmosphere in the furnace is set to 1350 ° C., the set value of the temperature of the cooling gas supplied to the cooling gas passage is set to 30 ° C., and the material of the cooling device and the burner Was set to austenitic stainless steel.

  The results are shown in FIGS. FIG. 6 is a schematic diagram illustrating a result of stress analysis according to the comparative example. FIG. 7 is a schematic diagram illustrating a result of stress analysis according to the example. In FIG.6 and FIG.7, the distribution of Mises stress obtained by the stress analysis about the tip side of a cooling device and a burner is shown by the contour line. 6 and FIG. 7, the difference in the pattern given to each region partitioned by the contour lines indicates the difference in stress in each region. In FIG. 6, as a comparative example, a portion 702 corresponding to the outer tube, a portion 710 corresponding to the burner, a portion 704 corresponding to the cooling gas passage, and a portion 706 corresponding to the lid portion are shown. FIG. 7 shows a portion 802 corresponding to the outer tube, a portion 810 corresponding to the burner, a portion 804 corresponding to the cooling gas passage, a portion 806 corresponding to the lid portion, and a portion 806a corresponding to the slit. Has been.

  In the comparative example, the value of the Mises stress that can occur in the region A10 where the stress shown in FIG. 6 tends to concentrate is approximately 500 MPa. Therefore, in the comparative example, it is predicted that a thermal stress higher than the 0.2% proof stress of austenitic stainless steel can be generated in the region A10. On the other hand, in the example, the value of Mises stress that can occur in the burner 10 and the cooling device 50 in the entire region to be analyzed was approximately 50 MPa or less. Therefore, in an Example, it is estimated that the thermal stress which can be generated in the whole analysis object region can be lower than the 0.2% proof stress of austenitic stainless steel. In the embodiment, it is predicted that stress concentration in the region A20 shown in FIG. 7 corresponding to the region A10 shown in FIG. 6 can be prevented. From the results, it was confirmed that the present invention can prevent the occurrence of breakage due to the thermal stress caused by the temperature difference between the outer tube and the burner.

<4. Summary>
As described above, according to the present embodiment, the lid 506 closes the opening on the distal end side between the outer tube 502 and the burner 10. Therefore, the amount of the cooling gas released into the furnace can be reduced as compared with the case where the opening on the distal end side between the outer tube 502 and the burner 10 is opened. Thereby, it is possible to suppress a decrease in heating efficiency in the furnace and an increase in the generation amount of NOx due to the discharge of the cooling gas into the furnace.

  In the present embodiment, the lid portion 506 is provided with an annular slit 506 a that communicates the cooling gas passage 504 with the inside of the furnace and extends along the circumferential direction of the burner 10. Thereby, it is possible to suppress the deformation of the outer tube 502 and the burner 10 from being restrained. Therefore, generation of thermal stress in the axial direction and radial direction of the burner 10 due to the temperature difference between the outer tube 502 and the burner 10 can be suppressed. Therefore, it is possible to prevent the occurrence of breakage due to the thermal stress caused by the temperature difference between the outer tube 502 and the burner 10.

  The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can make various modifications or application examples within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

1 Heating furnace 10 Burner 20 Combustion chamber 30 Furnace wall 30a Upper furnace wall 30b Lower furnace wall 40 Transfer device 50, 90 Cooling device 102 Fuel gas passage 502, 802, 902 Outer pipe 504, 804, 904 Cooling gas passage 504a passage 504b passage 506, 606, 806 Lid 506a, 606a Slit 506b, 606b Outer peripheral side lid 506c, 606c Inner peripheral side lid 508 Inner pipe 510, 910 Cooling gas inflow pipe 512 Cooling gas discharge pipe

Claims (2)

In a tubular burner that injects fuel gas from the tip side toward the furnace,
An outer tube provided on the outer periphery of the burner to form a double tube structure with the burner;
A cooling gas passage provided between the outer tube and the burner;
An inner pipe that is provided on the inner circumference of the outer pipe and the outer circumference of the burner, and divides the cooling gas path into an outer circumferential path and an inner circumferential path that communicate with each other on the tip side;
A lid that closes the opening on the tip side between the outer tube and the burner;
An annular slit provided in the lid portion along the circumferential direction of the burner, and communicating the cooling gas passage and the furnace;
With a burner.   The burner according to claim 1, wherein the slit has a tapered shape that increases in diameter toward the distal end side.

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