Regenerative burner device

Abstract

The object of the present invention is to provide a regenerative burner device that can easily reduce NOx contained in combustion exhaust gas by simply adding an extremely simple means. [Solution] The regenerative burner comprises a cylindrical body having an inlet and outlet for fuel gas, a heat storage body surrounding the cylindrical body, a fuel supply unit that supplies fuel gas to the inlet of the cylindrical body, and a housing that houses the cylindrical body and the heat storage body and is connected to the fuel supply unit and radiant tubes. The housing has an inlet / outlet for introducing combustion air into the housing during combustion, a flow path that flows the combustion air introduced from the inlet / outlet toward the outlet of the cylindrical body via the heat storage body, and a space formed on the flow path between the inlet / outlet and the heat storage body. The fuel supply unit has a first supply path that supplies fuel gas to the inlet of the cylindrical body and a second supply path that supplies fuel gas to the space in the housing.

Description

[Technical Field]

[0001] The present invention relates to a regenerative burner device that alternately burns a pair of regenerative burners, each connected to a radiant tube. [Background technology]

[0002] A regenerative burner device is known that consists of a pair of regenerative burners, each equipped with a regenerative heat storage. During combustion in one regenerative burner, all or part of the combustion exhaust gas is directed to the regenerative heat storage of the other regenerative burner to recover heat. After a predetermined time has elapsed, combustion is switched to the other regenerative burner for continued operation. This type of regenerative burner device can preheat the combustion air in the combustion-side regenerative burner to 800°C or higher by passing it through the high-temperature regenerative heat storage, enabling highly efficient and energy-saving operation. Regenerative burner devices include those in which the combustion exhaust gas from both regenerative burners is discharged openly into a heat treatment furnace, and those in which both regenerative burners are connected by a radiant tube to form a closed combustion exhaust gas circuit.

[0003] Regardless of the type of regenerative burner device, operation under low NOx combustion conditions is required. Several proposals have been made regarding methods for achieving low NOx operation of regenerative burner devices. Patent Document 1 describes a method for reducing NOx using an external exhaust gas recirculation system in which a portion of the combustion exhaust gas, whose temperature has been reduced after passing through a regenerative body and being discharged to the outside, is mixed with combustion air using a blower. Patent Document 2 describes a method for lowering the maximum temperature of the combustion flame and reducing NOx by constantly mixing a gas other than fuel, such as steam or an inert gas, with the fuel gas and injecting it from a fuel injection port. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 6-288519 [Patent Document 2] Japanese Patent Application Publication No. 5-157212 Summary of the Invention [Problem to be solved by the invention]

[0005] The aforementioned regenerative burner devices, particularly regenerative radiant tube burner devices, are used in various heat treatment furnaces. Depending on the size of the heat treatment furnace, dozens to hundreds of regenerative burners may be installed in a single heat treatment furnace. Therefore, a regenerative burner device with as simple a configuration as possible and reduced operating costs is desired. However, the external exhaust gas recirculation system described in Patent Document 1 requires an exhaust gas recirculation path and a blower, making the entire system large and complex, and increasing operating costs. The system described in Patent Document 2, which constantly mixes non-fuel gases into the fuel gas, requires equipment for mixing the non-fuel gases, and the constant mixing increases the consumption of the non-fuel gases, resulting in high operating costs. For these reasons, there is a need for a regenerative burner device that can reduce NOx emissions more economically and easily.

[0006] The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a regenerative burner device that can easily reduce NOx contained in combustion exhaust gas by simply adding extremely simple means. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems, the regenerative burner device of the present invention is a regenerative burner device that alternately burns a pair of regenerative burners, each connected to a radiant tube, and the regenerative burner comprises a cylindrical body having an inlet for introducing fuel gas into the inside and an outlet for discharging the fuel gas that has flowed in from the inlet toward the radiant tube, a regenerative heat storage body that surrounds the cylindrical body between the inlet and the outlet of the cylindrical body, a fuel supply unit that supplies the fuel gas to the inlet of the cylindrical body, and a housing that houses the cylindrical body and the regenerative heat storage body, one end of which is connected to the fuel supply unit and the other end of which is connected to the radiant tube, and the housing has a front The fuel supply unit has an inlet / outlet that is located closer to the heat storage body than the heat storage body and that introduces combustion air into the housing during combustion and discharges combustion exhaust gas from the housing during heat storage, a flow path that directs the combustion air introduced from the inlet / outlet during combustion toward the outlet of the cylindrical body via the heat storage body and directs the combustion exhaust gas discharged from the radiant tube during heat storage to the inlet / outlet via the heat storage body, and a space formed on the flow path between the inlet / outlet and the heat storage body, and the fuel supply unit has a first supply path that supplies the fuel gas to the inlet of the cylindrical body and a second supply path that supplies the fuel gas to the space in the housing. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a regenerative burner device that can easily reduce NOx contained in combustion exhaust gas by simply adding an extremely simple means. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a diagram illustrating a regenerative burner device according to an embodiment of the present invention; [Figure 2] FIG. 2 is a diagram illustrating details of a fuel supply unit shown in FIG. 1. [Figure 3] 6 is a graph showing the results of an experiment that determined the relationship between the ratio of the second flow rate to the total flow rate and the NOx concentration. [Figure 4]10 is a graph showing the results of an experiment to determine the relationship between the ratio of the second flow rate to the total flow rate and efficiency. [Figure 5] FIG. 2 is a diagram illustrating a modified example of the regenerative burner device shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Components with the same reference numerals in each embodiment have similar components in each embodiment unless otherwise specified, and description thereof will be omitted.

[0011] First, the configuration of the regenerative burner device 1 of this embodiment will be described with reference to Figures 1 and 2. Figure 1 is a diagram illustrating the regenerative burner device 1 of this embodiment. Figure 2 is a diagram illustrating the details of the fuel supply unit 10 shown in Figure 1.

[0012] The regenerative burner device 1 is a radiant tube burner device that alternately burns a pair of regenerative burners 2a, 2b, each connected to a radiant tube 3. The regenerative burner device 1 includes at least a pair of regenerative burners 2a, 2b. Each of the pair of regenerative burners 2a, 2b is connected to a radiant tube 3. The pair of regenerative burners 2a, 2b are attached substantially parallel to the furnace wall F1 of the heat treatment furnace F, with the radiant tube 3 penetrating the furnace wall F1. The radiant tube 3 penetrates the furnace wall F1 and extends into the furnace interior F2. Combustion heat heats the heated object in the furnace interior F2 through the radiant tube 3. Note that although the radiant tube 3 shown in FIG. 1 is U-shaped, the radiant tube 3 may also be W-shaped, I-shaped, or the like.

[0013] The combustion region 30 of the pair of regenerative burners 2a, 2b is formed inside the radiant tube 3. A primary combustion liner 31 is attached to the inside of the radiant tube 3 via a support base 32 in order to reduce NOx. The primary combustion liner 31 is arranged to extend along the axis of the radiant tube 3. In the combustion region 30, primary combustion takes place in the primary combustion liner 31, and secondary combustion takes place in the radiant tube 3 on the furnace interior F2 side of the primary combustion liner 31. A pilot burner 33 is provided near the opening of the primary combustion liner 31 on the opposite side from the furnace interior F2.

[0014] In this embodiment, the regenerative burner 2a or the regenerative burner 2b is also collectively referred to as the "regenerative burner 2." The regenerative burner 2 comprises a fuel supply unit 10 that supplies fuel gas, and a heat exchange unit 20 that exchanges heat between the combustion air or combustion exhaust gas and the regenerator 24.

[0015] The heat exchange section 20 of the regenerative burner 2 includes a mixing tube 21, a regenerator 24, and a housing 25. The mixing tube 21 has an inlet 22 through which fuel gas flows into the interior during combustion, and an outlet 23 through which the fuel gas that has flowed in from the inlet 22 flows out toward the radiant tube 3. The mixing tube 21 is formed by a cylindrical body extending along the axial direction of the primary combustion tube 31. The mixing tube 21 is arranged so that its axis coincides with the axis of the primary combustion tube 31. The regenerator 24 is arranged between the inlet 22 and the outlet 23 of the mixing tube 21 so as to cover the periphery of the mixing tube 21.

[0016] The housing 25 houses the mixing cylinder 21 and the heat storage body 24. The housing 25 is formed of a box body arranged to extend along the axial direction of the mixing cylinder 21. One end of the housing 25 is connected to the fuel supply unit 10. The other end of the housing 25 is connected to the radiant tube 3.

[0017] The housing 25 has a combustion air / combustion exhaust gas inlet / outlet 26, a flow path 27, a space 28, and a recirculation gas inlet / outlet 29. The combustion air / combustion exhaust gas inlet / outlet 26 (hereinafter also referred to as "inlet / outlet 26") is an inlet / outlet that introduces combustion air into the housing 25 during combustion and discharges combustion exhaust gas from the housing 25 during heat storage. The inlet / outlet 26 is provided in a wall of the housing 25 that is located closer to the fuel supply unit 10 than the heat storage body 24 in the axial direction of the housing 25.

[0018] The inlet / outlet port 26 provided in each regenerative burner 2 is connected to a first port 42 of an air intake / exhaust switching valve 41 directly or via a pipe 45. A second port 43 of the air intake / exhaust switching valve 41 is connected to an exhaust fan 47 via a combustion exhaust gas pipe 46. A third port 44 of the air intake / exhaust switching valve 41 is connected to a combustion air source (not shown). The combustion air source may be the atmosphere, in which case the third port 44 is open to the atmosphere.

[0019] Flow path 27 is a flow path that allows combustion air introduced from inlet / outlet 26 during combustion to flow toward outlet 23 of mixing cylinder 21 via heat storage body 24, and also allows combustion exhaust gas discharged from radiant tube 3 during heat storage to flow toward inlet / outlet 26 via heat storage body 24. Flow path 27 is formed by the space formed between the wall of housing 25 and mixing cylinder 21. Flow path 27 connects inlet / outlet 26 and outlet 23 of mixing cylinder 21 via heat storage body 24.

[0020] The space 28 is a space formed on the flow path 27 between the inlet / outlet 26 and the regenerator 24. Combustion air introduced from the inlet / outlet 26 during combustion and fuel gas supplied from a second supply path 15 of the fuel supply unit 10, which will be described later, are introduced into the space 28. The combustion air and the fuel gas are mixed in the space 28. The space 28 functions as a mixing chamber that mixes the combustion air and the fuel gas.

[0021] The recirculation gas inlet / outlet 29 is an inlet that introduces a portion of the combustion exhaust gas from the other regenerative burner 2 into the casing 25 during combustion, and discharges a portion of the combustion exhaust gas from the casing 25 toward the other regenerative burner 2 during heat storage. The recirculation gas inlet / outlet 29 is provided in the wall of the casing 25 near the inlet 22 of the mixing tube 21. The recirculation gas inlet / outlet 29 communicates with the inlet 22. The recirculation gas inlet / outlet 29 is connected to a connecting pipe 40. The connecting pipe 40 connects the recirculation gas inlet / outlet 29 provided in the casing 25 of one regenerative burner 2 with the recirculation gas inlet / outlet 29 provided in the casing 25 of the other regenerative burner 2. The connecting pipe 40 self-recirculates a portion of the combustion exhaust gas from the regenerative burner 2 on the heat storage side to the regenerative burner 2 on the combustion side. In other words, the housing 25 of one regenerative burner 2 and the housing 25 of the other regenerative burner 2 are connected by a connecting pipe 40 that self-recirculates a portion of the combustion exhaust gas from the regenerative burner 2 on the storage side to the regenerative burner 2 on the combustion side.

[0022] As shown in FIG. 2, the fuel supply section 10 of the regenerative burner 2 includes a fuel inlet 11, a fuel chamber 12, a first supply passage 13, and a second supply passage 15. The fuel inlet 11 is an inlet for introducing fuel gas into the fuel supply section 10. The fuel inlet 11 provided in each regenerative burner 2 is connected to a fuel gas inlet pipe 51. The fuel gas inlet pipe 51 is connected to a fuel gas supply source (not shown). A fuel gas on-off valve 52 is provided on the fuel gas inlet pipe 51 between the fuel gas supply source and the fuel inlet 11.

[0023] The fuel chamber 12 is a space formed inside the fuel supply unit 10 and stores the fuel gas introduced from the fuel inlet 11. The first supply path 13 and the second supply path 15 are pipes that supply the fuel gas to the housing 25.

[0024] The first supply passage 13 is a pipe that supplies fuel gas to the inlet 22 of the mixing cylinder 21. The first supply passage 13 is formed to extend from the fuel chamber 12 toward the inlet 22 of the mixing cylinder 21. A first gas nozzle 14 that injects fuel gas toward the inlet 22 of the mixing cylinder 21 is provided at the tip of the first supply passage 13. The fuel gas injected from the first gas nozzle 14 is mixed with combustion exhaust gas introduced from a recirculation gas port 29 near the inlet 22 of the mixing cylinder 21, and flows into the mixing cylinder 21 from the inlet 22. The periphery of the first supply passage 13 may be covered from the outside by a cooling air pipe (not shown) through which cooling air flows.

[0025] The second supply passage 15 is a pipe that supplies fuel gas to the space 28 in the housing 25. The second supply passage 15 is formed to extend from the fuel chamber 12 toward the space 28 in the housing 25. A second gas nozzle 16 that injects fuel gas toward the space 28 in the housing 25 is provided at the tip of the second supply passage 15. The fuel gas injected from the second gas nozzle 16 mixes with the combustion air introduced from the inlet / outlet 26 in the space 28 and flows through the flow path 27 toward the regenerator 24.

[0026] Next, the operation of the regenerative burner device 1 of this embodiment during operation will be described. The explanation will be given assuming that one regenerative burner 2a is in a combustion state and the other regenerative burner 2b is in a regenerative state. During operation, the exhaust fan 47 is operating, and the regenerative burners 2a, 2b are all in a negative pressure state. The intake and exhaust switching valve 41 connected to the combustion-side regenerative burner 2a has the first port 42 and third port 44 set to a communicating state. The intake and exhaust switching valve 41 connected to the regenerative burner 2b on the regenerative side has the first port 42 and second port 43 set to a communicating state.

[0027] Fuel gas is introduced into the fuel chamber 12 of the fuel supply unit 10 from the fuel inlet 11 of the regenerative burner 2a. Most of the fuel gas in the fuel chamber 12 flows through the first supply passage 13 and is sprayed from the first gas nozzle 14 near the inlet 22 of the mixing cylinder 21. Some of the fuel gas in the fuel chamber 12 flows through the second supply passage 15 and is sprayed from the second gas nozzle 16 into the space 28 of the housing 25.

[0028] Because the entire regenerative burners 2a, 2b are maintained at negative pressure, and due to the ejector effect caused by the injection of fuel gas, cooling air is introduced into a cooling air pipe (not shown). The cooling air flows through the cooling air pipe and exits near the inlet 22 of the mixing tube 21. The cooling air cools the first supply passage 13, the first gas nozzle 14, and the cooling air pipe. This prevents a reduction in the lifespan of these components due to thermal damage. The fuel gas and cooling air that reach the vicinity of the inlet 22 of the mixing tube 21 flow into the mixing tube 21 from the inlet 22 while mixing with the combustion exhaust gas introduced from the recirculation gas inlet / outlet 29. The fuel gas mixed with the combustion exhaust gas flows through the mixing tube 21, exits from the outlet 23, and reaches the primary combustion tube 31 in the combustion region 30.

[0029] Combustion air is introduced into a pipe 45 from a third port 44 of the air supply / exhaust switching valve 41 connected to one of the regenerative burners 2a. The combustion air introduced into the pipe 45 is then introduced into the space 28 of the housing 25 through the inlet / outlet 26. The combustion air introduced into the space 28 of the housing 25 mixes with fuel gas injected into the space 28 from the second gas nozzle 16 of the second supply passage 15, flows through the flow path 27 toward the regenerator 24, and passes through the regenerator 24. The regenerator 24 has been heated to a high temperature by the combustion exhaust gas in the previous combustion cycle. The combustion air mixed with the fuel gas is a lean mixture, and burns as it passes through the regenerator 24. This combustion reduces the oxygen concentration of the combustion air. After passing through the regenerator 24, the combustion air flows through the flow path 27 with a reduced oxygen concentration and reaches the vicinity of the outlet 23 of the mixing tube 21. A portion of the combustion air that reaches the vicinity of the outlet 23 of the mixing tube 21 mixes with the fuel gas that has been mixed with the combustion exhaust gas that has flowed out from the outlet 23 of the mixing tube 21 to form an air-fuel mixture, which passes through the primary combustion tube 31 in the combustion region 30. The remaining portion of the combustion air passes outside the primary combustion tube 31. The air-fuel mixture undergoes primary combustion as it passes through the primary combustion tube 31, and after flowing out of the primary combustion tube 31, it mixes with the remaining combustion air and undergoes secondary combustion in the radiant tube 3.

[0030] In this way, the regenerative burner device 1 reduces the oxygen concentration of the combustion air by mixing the fuel gas supplied from the second supply passage 15 with the combustion air and burning it in the high-temperature regenerator 24. The regenerative burner device 1 then mixes the combustion air with the reduced oxygen concentration with the fuel gas supplied from the first supply passage 13 to perform primary and secondary combustion. This allows the regenerative burner device 1 to slow combustion and suppress peak flame temperatures, thereby reducing the NOx contained in the combustion exhaust gas.

[0031] The combustion exhaust gas generated by the primary combustion or the secondary combustion flows through the radiant tube 3 and flows into the other regenerative burner 2b. A portion of the combustion exhaust gas that flows into the other regenerative burner 2b passes through the regenerator 24, exchanges heat with the regenerator 24, and is then discharged to the outside of the housing 25 through the inlet / outlet 26. The combustion exhaust gas discharged from the housing 25 flows through the pipe 45, passes through the first port 42 and the second port 43 of the intake / exhaust switching valve 41, and reaches the combustion exhaust gas pipe 46. The combustion exhaust gas that reaches the combustion exhaust gas pipe 46 is released into the atmosphere by the exhaust fan 47.

[0032] Furthermore, a portion of the combustion exhaust gas that flows into the other regenerative burner 2b flows into the mixing tube 21. The combustion exhaust gas that flows into the mixing tube 21 is sucked in by the ejector effect caused by the injection of fuel gas from one of the regenerative burners 2a (combustion side) and is introduced into the connecting pipe 40 from the recirculation gas port 29. The combustion exhaust gas introduced into the connecting pipe 40 flows through the connecting pipe 40 toward one of the regenerative burners 2a and is introduced into the housing 25 of the one of the regenerative burners 2a. The combustion exhaust gas introduced into the housing 25 of the one of the regenerative burners 2a flows into the mixing tube 21 while being mixed with fuel gas injected from the first gas nozzle 14, and reaches the primary combustion tube 31 in the combustion region 30. By adding this self-recirculating combustion exhaust gas to the combustion flame, the regenerative burner device 1 can slow combustion and suppress the occurrence of peak flame temperatures, thereby reducing the NOx contained in the combustion exhaust gas.

[0033] After a certain time has passed, the intake and exhaust switching valve 41 is switched, and one regenerative burner 2a becomes the regenerative side, and the other regenerative burner 2b becomes the combustion side. That is, the intake and exhaust switching valve 41 connected to the regenerative burner 2b on the combustion side is set so that the first port 42 and the third port 44 are in communication. The intake and exhaust switching valve 41 connected to the regenerative burner 2a on the regenerative side is set so that the first port 42 and the second port 43 are in communication. This puts the regenerative burner 2b in a combustion state, and its combustion exhaust gas is introduced into the regenerative burner 2a. The combustion exhaust gas introduced into the regenerative burner 2a heats (stores heat) the regenerator 24 of the regenerative burner 2a, whose temperature has dropped due to heat exchange with the combustion air in the previous combustion cycle. As a result, the regenerative burner 2a enters a heat storage state. Thereafter, this switching is performed every certain time period, so that the combustion cycle progresses and the operation of the regenerative burner device 1 continues.

[0034] Next, the flow rates of the fuel gas supplied from the first supply path 13 and the second supply path 15 of the fuel supply unit 10 will be described with reference to FIGS.

[0035] As described above, the fuel supply unit 10 supplies most of the fuel gas introduced from the fuel inlet 11 to the inlet 22 of the mixing cylinder 21 of the housing 25 via the first supply path 13. In addition, the fuel supply unit 10 supplies a portion of the fuel gas introduced from the fuel inlet 11 to the space 28 of the housing 25 via the second supply path 15 in order to reduce the oxygen concentration of the combustion air before it is mixed with the fuel gas supplied from the first supply path 13.

[0036] That is, the flow rate of fuel gas supplied from the second supply path 15 to the housing 25 is smaller than the flow rate of fuel gas supplied from the first supply path 13 to the housing 25. In this embodiment, the flow rate of fuel gas supplied from the first supply path 13 to the inlet 22 of the mixing cylinder 21 of the housing 25 is also referred to as the "first flow rate." The flow rate of fuel gas supplied from the second supply path 15 to the space 28 of the housing 25 is also referred to as the "second flow rate."

[0037] The first flow rate and the second flow rate may be set, for example, by providing a flow rate adjustment valve in second supply line 15. Alternatively, the first flow rate and the second flow rate may be set in advance based on the hole diameter of first gas nozzle 14 provided in first supply line 13 and the hole diameter of second gas nozzle 16 provided in second supply line 15, respectively. In this case, the hole diameter of second gas nozzle 16 is set to be smaller than the hole diameter of first gas nozzle 14.

[0038] The first flow rate and the second flow rate can be managed as a ratio of the second flow rate to the total flow rate of the first flow rate and the second flow rate. When the hole diameter of the first gas nozzle 14 is d1 and the hole diameter of the second gas nozzle 16 is d2, the ratio R (%) of the second flow rate to the total flow rate can be calculated by the following formula (1):

[0039] R={d2 2 / (d1 2 +d2 2 )}×100 …(1)

[0040] Fig. 3 is a graph showing the experimental results of determining the relationship between the ratio R of the second flow rate to the total flow rate and the NOx concentration. The horizontal axis of Fig. 3 represents the ratio R (%) of the second flow rate to the total flow rate. The vertical axis of Fig. 3 represents the relative value (%) of the NOx concentration, where the concentration of NOx contained in the combustion exhaust gas when no fuel gas is supplied from the second supply passage 15 (i.e., ratio R is 0%) is set to 100%.

[0041] As shown in Figure 3, as the ratio R of the second flow rate to the total flow rate increases, the NOx concentration decreases. For example, when the ratio R of the second flow rate to the total flow rate is 16%, the relative value of the NOx concentration is 55%, which is 45% lower than when the ratio R is 0%. It can be seen that the NOx concentration can be reduced when the ratio R of the second flow rate to the total flow rate is greater than 0% and at least 16% or less. Therefore, it can be seen that supplying a portion of the fuel gas to the space 28 of the housing 25 via the second supply path 15 to mix it with the combustion air, and then burning the combustion air in the regenerator 24 before the combustion air mixes with the fuel gas supplied from the first supply path 13 to reduce the oxygen concentration of the combustion air is effective in reducing the NOx concentration of the combustion exhaust gas.

[0042] Fig. 4 is a graph showing the experimental results of determining the relationship between the ratio R of the second flow rate to the total flow rate and the efficiency E. The horizontal axis of Fig. 4 represents the ratio R (%) of the second flow rate to the total flow rate. The vertical axis of Fig. 4 represents the relative value (%) of the efficiency E when the efficiency E is 100% when no fuel gas is supplied from the second supply path 15 (i.e., the ratio R is 0%).

[0043] When the combustion heat amount of the fuel gas is H1 and the heat loss amount of the combustion exhaust gas is H2, the efficiency E (%) can be calculated by the following formula (2). That is, the efficiency E may be the combustion efficiency of the regenerative burner device 1.

[0044] E = {(H1 - H2) / H1} × 100 … (2)

[0045] As shown in Fig. 4, when the ratio R of the second flow rate to the total flow rate is less than 5%, the efficiency E is almost unchanged compared to when the ratio R is 0%. When the ratio R of the second flow rate to the total flow rate is in the range of 5% to 10%, the efficiency E gradually decreases as the ratio R increases. When the ratio R of the second flow rate to the total flow rate exceeds 10%, the degree to which the efficiency E decreases as the ratio R increases becomes greater.

[0046] However, when the ratio R of the second flow rate to the total flow rate is in the range of 5% to 15%, it is clear that the relative value of the efficiency E can be maintained at approximately 80% (79% to be precise) or more, while the NOx concentration can be significantly reduced, as shown in Figure 3. Therefore, when the ratio R of the second flow rate to the total flow rate is in the range of 5% to 15%, it is clear that the regenerative burner device 1 can significantly reduce the NOx concentration while maintaining a certain level of efficiency E.

[0047] Furthermore, when the ratio R of the second flow rate to the total flow rate is in the range of 5% to 10%, it is clear that the relative value of the efficiency E can be maintained at 95% or more, while the NOx concentration can be reduced as shown in Figure 3. Therefore, when the ratio R of the second flow rate to the total flow rate is in the range of 5% to 10%, it is clear that the regenerative burner device 1 can reliably reduce the NOx concentration without causing a significant reduction in the efficiency E.

[0048] Furthermore, when the ratio R of the second flow rate to the total flow rate is in the range of greater than 0% and less than 5%, it is possible to ensure a relative value of the efficiency E of 99% or more while reducing the NOx concentration as shown in Fig. 3. Therefore, when the ratio R of the second flow rate to the total flow rate is in the range of greater than 0% and less than 5%, it is clear that the regenerative burner device 1 can reliably suppress a reduction in the efficiency E while reducing the NOx concentration.

[0049] Next, a modified example of the regenerative burner device 1 will be described with reference to Fig. 5. Fig. 5 is a diagram illustrating a modified example of the regenerative burner device shown in Fig. 1.

[0050] The regenerative burner device 1 shown in Fig. 5 differs from the regenerative burner device 1 shown in Fig. 1 in that it does not have a connecting pipe 40 for self-recirculation of combustion exhaust gas. Since the regenerative burner device 1 shown in Fig. 5 does not have a connecting pipe 40, the configuration of the first supply passage 13 of the fuel supply unit 10 and the configuration of the heat exchange unit 20 are partially different from those of the regenerative burner device 1 shown in Fig. 1.

[0051] That is, as shown in FIG. 5 , the first supply passage 13 of the fuel supply unit 10 is connected to a fuel pipe 61 provided in the housing 25 of the heat exchange unit 20. The fuel pipe 61 is provided in place of the mixing tube 21. The fuel pipe 61 has an inlet 62 through which fuel gas flows into the interior during combustion, and an outlet 63 through which the fuel gas flowing in from the inlet 62 flows toward the radiant tube 3. The fuel pipe 61 is formed by a cylindrical body extending along the axial direction of the primary combustion tube 31. The fuel pipe 61 is arranged so that its axis coincides with the axis of the primary combustion tube 31. The fuel pipe 61 is covered from the outside by a cooling air pipe 64 through which cooling air flows. The regenerator 24 is arranged between the inlet 62 and outlet 63 of the fuel pipe 61 so as to surround the periphery of the cooling air pipe 64. A first gas nozzle 14 may be provided at the tip of the first supply path 13, but as shown in Figure 5, the first gas nozzle 14 may not be provided and the first supply path 13 may be connected to the fuel pipe 61 so as to form a pipe wall continuous with the fuel pipe 61.

[0052] Furthermore, the fuel pipe 61 may be formed integrally with the first supply passage 13. That is, the first supply passage 13 may extend to a position beyond the heat storage body 24. In this case, the first gas nozzle 14 may be provided at the tip of the first supply passage 13, but as shown in FIG. 5 , the first gas nozzle 14 may not be provided and the first supply passage 13 may have an open shape.

[0053] The operation of the regenerative burner device 1 shown in Fig. 5 during operation is substantially the same as that of the regenerative burner device 1 shown in Fig. 1 during operation. A portion of the fuel gas is supplied to the space 28 of the casing 25 via the second supply passage 15 and mixed with the combustion air, and before the combustion air is mixed with the fuel gas supplied from the first supply passage 13 and the fuel pipe 61, the combustion air is burned in the regenerator 24 to reduce the oxygen concentration of the combustion air. In this way, the regenerative burner device 1 shown in Fig. 5, like the regenerative burner device 1 shown in Fig. 1, can slow combustion to suppress the occurrence of peak flame temperatures and reduce NOx contained in the combustion exhaust gas.

[0054] Although Figures 1 and 5 show a regenerative burner device 1 equipped with a pair of regenerative burners 2a, 2b, the regenerative burner device 1 may be equipped with multiple pairs of regenerative burners 2a, 2b depending on the size of the heat treatment furnace F.

[0055] As described above, the regenerative burner device 1 of this embodiment is a regenerative burner device that alternately burns a pair of regenerative burners 2, each connected to a radiant tube 3. The regenerative burner 2 comprises a cylindrical body (mixing cylinder 21, fuel pipe 61) having inlets 22, 62 for introducing fuel gas therein and outlets 23, 63 for discharging the fuel gas that has flowed in from inlets 22, 62 toward radiant tube 3, a regenerative body 24 that surrounds the cylindrical body between inlets 22, 62 and outlets 23, 63, a fuel supply unit 10 that supplies fuel gas to inlets 22, 62 of the cylindrical body, and a housing 25 that houses the cylindrical body and regenerative body 24 and has one end connected to fuel supply unit 10 and the other end connected to radiant tube 3. Housing 25 is provided closer to fuel supply unit 10 than heat storage body 24, and has an inlet / outlet 26 that introduces combustion air into housing 25 during combustion and discharges combustion exhaust gas from housing 25 during heat storage, a flow path 27 that directs the combustion air introduced from inlet / outlet 26 toward outlets 23, 63 of the cylindrical body via heat storage body 24 during combustion and directs the combustion exhaust gas discharged from radiant tube 3 toward inlet / outlet 26 via heat storage body 24 during heat storage, and a space 28 formed above flow path 27 between inlet / outlet 26 and heat storage body 24. Fuel supply unit 10 has a first supply path 13 that supplies fuel gas to inlets 22, 62 of the cylindrical body, and a second supply path 15 that supplies fuel gas to space 28 in housing 25.

[0056] As a result, the regenerative burner device 1 supplies a portion of the fuel gas through the second supply passage 15 to the space 28 of the housing 25 to mix it with the combustion air, and burns the combustion air in the regenerator 24 before mixing it with the fuel gas supplied from the first supply passage 13, thereby reducing the oxygen concentration of the combustion air. Therefore, the regenerative burner device 1 can slow combustion to suppress peak flame temperatures and reduce NOx contained in the combustion exhaust gas. Furthermore, by simply adding the very simple means of providing the second supply passage 15 for supplying fuel gas to the space 28 of the housing 25, the regenerative burner device 1 can reduce the oxygen concentration of the combustion air and reduce NOx contained in the combustion exhaust gas. Therefore, according to this embodiment, a regenerative burner device can be provided that can easily reduce NOx contained in the combustion exhaust gas by simply adding the very simple means.

[0057] Furthermore, in the regenerative burner device 1 of this embodiment, the second flow rate, which is the flow rate of fuel gas supplied from the second supply passage 15 to the space 28 of the housing 25, is smaller than the first flow rate, which is the flow rate of fuel gas supplied from the first supply passage 13 to the inlets 22, 62 of the cylindrical body.

[0058] As a result, the regenerative burner device 1 can easily and reliably reduce NOx contained in the combustion exhaust gas while preventing an extreme drop in efficiency E or the generation of soot and the like due to insufficient combustion caused by an excess supply of fuel gas from the second supply passage 15 to the space 28 of the housing 25. Therefore, according to this embodiment, by simply adding an extremely simple means, it is possible to provide a regenerative burner device that can easily and reliably reduce NOx contained in the combustion exhaust gas while achieving stable and efficient combustion.

[0059] Furthermore, in the regenerative burner device 1 of this embodiment, the housing 25 of one regenerative burner 2 and the housing 25 of the other regenerative burner 2 are connected by a connecting pipe 40 that self-recirculates a portion of the combustion exhaust gas from the regenerative burner 2 on the regenerative side to the regenerative burner 2 on the combustion side.

[0060] As a result, the regenerative burner device 1 can slow combustion and suppress peak flame temperature occurrence, further reducing the NOx contained in the combustion exhaust gas. Therefore, according to this embodiment, by simply adding an extremely simple means, it is possible to provide a regenerative burner device that can further easily reduce the NOx contained in the combustion exhaust gas.

[0061] Furthermore, in the regenerative burner device 1 of this embodiment, the fuel supply unit 10 further has a fuel inlet 11 that introduces fuel gas into the fuel supply unit 10, and a fuel chamber 12 that is formed inside the fuel supply unit 10 and that retains the fuel gas introduced from the fuel inlet 11. The first supply path 13 extends from the fuel chamber 12 toward the inlets 22, 62 of the cylindrical body. The second supply path 15 extends from the fuel chamber 12 toward the space 28 of the housing 25.

[0062] As a result, in the regenerative burner device 1, the fuel supply unit 10 can divide the fuel gas introduced from the single fuel inlet 11 and cause the fuel gas to flow into the first supply path 13 and the second supply path 15. Therefore, the regenerative burner device 1 can supply a portion of the fuel gas to the space 28 in the casing 25 via the second supply path 15 while preventing the fuel gas piping system from becoming complicated. Therefore, according to this embodiment, it is possible to provide a regenerative burner device that can further easily reduce NOx contained in combustion exhaust gas by simply adding an extremely simple means.

[0063] Furthermore, in the regenerative burner device 1 of this embodiment, a first gas nozzle 14 that injects fuel gas toward the inlets 22, 62 of the cylindrical body is provided at the tip of the first supply passage 13. A second gas nozzle 16 that injects fuel gas toward the space 28 in the housing 25 is provided at the tip of the second supply passage 15.

[0064] This allows the regenerative burner device 1 to easily mix the fuel gas with the combustion air or the combustion exhaust gas, thereby suppressing the generation of soot and the like due to insufficient combustion. Therefore, according to this embodiment, by simply adding a very simple means, it is possible to provide a regenerative burner device that can easily reduce NOx contained in the combustion exhaust gas while achieving stable and efficient combustion.

[0065] Furthermore, in the regenerative burner device 1 of this embodiment, the first flow rate and the second flow rate are set in advance based on the hole diameter of the first gas nozzle 14 and the hole diameter of the second gas nozzle 16, respectively. The hole diameter of the second gas nozzle 16 is smaller than the hole diameter of the first gas nozzle 14.

[0066] As a result, the regenerative burner device 1 can make the second flow rate of the fuel gas supplied by the second supply path 15 smaller than the first flow rate of the fuel gas supplied by the first supply path 13, without the need to install a flow rate adjustment valve in the second supply path 15. Therefore, according to this embodiment, by simply adding an extremely simple means, it is possible to provide a regenerative burner device that can easily achieve stable and efficient combustion while easily and reliably reducing NOx contained in the combustion exhaust gas.

[0067] Furthermore, in the regenerative burner device 1 of this embodiment, the ratio R of the second flow rate to the total flow rate of the first flow rate and the second flow rate is greater than 0% and equal to or less than 16%.

[0068] This allows the regenerative burner device 1 to reduce the concentration of NOx contained in the combustion exhaust gas. Therefore, according to this embodiment, it is possible to provide a regenerative burner device that can easily reduce the NOx contained in the combustion exhaust gas by simply adding an extremely simple means.

[0069] Furthermore, in the regenerative burner device 1 of this embodiment, the ratio R of the second flow rate to the total flow rate is 5% or more and 15% or less.

[0070] As a result, the regenerative burner device 1 can reliably reduce the concentration of NOx contained in the combustion exhaust gas without substantially reducing the efficiency E. Therefore, according to this embodiment, by simply adding an extremely simple means, it is possible to provide a regenerative burner device that can easily and reliably reduce the NOx contained in the combustion exhaust gas while achieving efficient combustion.

[0071] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to these embodiments and various modifications can be made without departing from the spirit of the present invention. In the present invention, elements of one embodiment can be added to elements of another embodiment, elements of one embodiment can be replaced with elements of another embodiment, or some of the elements of one embodiment can be deleted. [Explanation of symbols]

[0072] 1...Regenerative burner device, 2, 2a, 2b...Regenerative burner, 3...Radiant tube, 10...Fuel supply section, 11...Fuel inlet, 12...Fuel chamber, 13...First supply passage, 14...First gas nozzle, 15...Second supply passage, 16...Second gas nozzle, 20...Heat exchange section, 21...Mixing tube (cylinder), 22...Inlet, 23...Outlet, 24...Heat storage body, 25...Housing, 26...Combustion air / combustion exhaust gas inlet / outlet (inlet / outlet), 27...Flow path, 28...Space, 29...Recirculation Gas inlet / outlet, 30... combustion area, 31... primary combustion cylinder, 32... support base, 33... pilot burner, 40... connecting pipe, 41... intake / exhaust switching valve, 42... first port, 43... second port, 44... third port, 45... pipe, 46... combustion exhaust gas pipe, 47... exhaust fan, 51... fuel gas introduction pipe, 52... fuel gas on / off valve, 61... fuel pipe (cylinder), 62... inlet, 63... outlet, 64... cooling air pipe, F... heat treatment furnace, F1... furnace wall, F2... furnace interior

Claims

1. A regenerative burner device that alternately burns a pair of regenerative burners, each connected to a radiant tube, The regenerative burner is a cylindrical body having an inlet for introducing fuel gas thereinto and an outlet for discharging the fuel gas having flowed in from the inlet toward the radiant tube; a heat storage body that surrounds the cylindrical body between the inlet and the outlet of the cylindrical body; a fuel supply unit that supplies the fuel gas to the inlet of the cylindrical body; a housing that houses the cylindrical body and the heat storage body, one end of which is connected to the fuel supply unit and the other end of which is connected to the radiant tube; The housing includes: an inlet / outlet that is provided closer to the fuel supply unit than the heat storage body and that introduces combustion air into the housing during combustion and discharges combustion exhaust gas from the housing during heat storage; a flow path that allows the combustion air introduced from the inlet and outlet during combustion to flow toward the outlet of the cylindrical body via the heat storage body, and allows the combustion exhaust gas discharged from the radiant tube during heat storage to flow toward the inlet and outlet via the heat storage body; a space formed on the flow path between the inlet / outlet and the heat storage body, The fuel supply unit a first supply passage for supplying the fuel gas to the inlet of the cylindrical body; a second supply passage for supplying the fuel gas to the space in the housing; A regenerative burner device characterized by:

2. A second flow rate, which is a flow rate of the fuel gas supplied from the second supply passage to the space in the housing, is smaller than a first flow rate, which is a flow rate of the fuel gas supplied from the first supply passage to the inlet of the cylindrical body.

2. The regenerative burner device according to claim 1.

3. The housing of one of the regenerative burners and the housing of the other regenerative burner are connected by a connecting pipe that self-recirculates a portion of the combustion exhaust gas from the regenerative burner on the regenerative side to the regenerative burner on the combustion side.

3. The regenerative burner device according to claim 2.

4. The fuel supply unit a fuel inlet for introducing the fuel gas into the fuel supply unit; a fuel chamber formed inside the fuel supply unit and configured to retain the fuel gas introduced through the fuel inlet, the first supply passage extends from the fuel chamber toward the inlet of the cylindrical body, The second supply passage extends from the fuel chamber toward the space in the housing.

4. The regenerative burner device according to claim 3.

5. a first gas nozzle that injects the fuel gas toward the inlet of the cylindrical body is provided at a tip end of the first supply passage; A second gas nozzle that injects the fuel gas toward the space in the housing is provided at the tip of the second supply path.

5. The regenerative burner device according to claim 4.

6. the first flow rate and the second flow rate are set in advance based on a hole diameter of the first gas nozzle and a hole diameter of the second gas nozzle, respectively; The hole diameter of the second gas nozzle is smaller than the hole diameter of the first gas nozzle.

6. The regenerative burner device according to claim 5.

7. A ratio of the second flow rate to a total flow rate of the first flow rate and the second flow rate is greater than 0% and not more than 16%.

3. The regenerative burner device according to claim 2.

8. The ratio of the second flow rate to the total flow rate is equal to or greater than 5% and equal to or less than 15%.

8. The regenerative burner device according to claim 7.

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