Recuperator

Abstract

To provide a recuperator capable of increasing an amount of combustion exhaust gas to be mixed with combustion air and reducing generation of NOx.SOLUTION: A recuperator 3 exchanges heat between combustion exhaust gas flowing in a radiant tube 1 and combustion air used for heating the radiant tube 1. A tip part 32 of the recuperator 3 includes a hemispherical part 33 located at a tip and a cylindrical part 34 connected to the hemispherical part 33. An opening part 35 that receives the combustion exhaust gas in the recuperator 3 is formed in the cylindrical part 34. The opening part 35 extends toward an inner side of the recuperator 3 so as to form an angle θ to a direction Y vertical to an axial direction X of the recuperator 3.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a recuperator that performs heat exchange between combustion exhaust gas flowing through radiant tubes and combustion air used to heat the radiant tubes. [Background technology]

[0002] As a technology for reducing NOx in exhaust gas in a radiant tube heating device, for example, Patent Documents 1 to 3 disclose a configuration in which combustion air is preheated in a recuperator, and further, a portion of the combustion exhaust gas is received into the recuperator and mixed with the combustion air. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-199610 [Patent Document 2] Japanese Patent Application Laid-Open No. 2000-146118 [Patent Document 3] Japanese Patent Application Publication No. 2019-196855 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in all of the above configurations, the flue gas is mixed with the combustion air from a direction perpendicular to the flue gas flow, making it difficult to smoothly introduce the flue gas into the recuperator, and as a result, it was not possible to mix a sufficient amount of flue gas with the combustion air to reduce NOx.

[0005] Therefore, an object of the present invention is to provide a recuperator that can increase the amount of combustion exhaust gas mixed with combustion air and reduce the generation of NOx. [Means for solving the problem]

[0006] The present invention is a recuperator that performs heat exchange between combustion exhaust gas flowing through radiant tubes and combustion air used to heat the radiant tubes, The tip of the recuperator is provided with a hemispherical portion located at the tip and a cylindrical portion connected to the hemispherical portion, an opening is formed in the cylindrical portion to receive the combustion exhaust gas into the recuperator; The opening extends inward of the recuperator at an angle relative to a direction perpendicular to the axial direction of the recuperator.

[0007] According to the above configuration, the cylindrical portion of the recuperator has an opening for receiving the combustion exhaust gas, which extends obliquely inward of the recuperator at an angle relative to the direction perpendicular to the axial direction of the recuperator. This allows the combustion exhaust gas to be smoothly introduced into the combustion air flow path, increasing the amount of combustion exhaust gas mixed with the combustion air. As a result, the combustion temperature during combustion is prevented from becoming too high, and the amount of NOx generated during combustion is reduced. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a recuperator that can increase the amount of combustion exhaust gas mixed with combustion air and reduce the generation of NOx. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic diagram of a radiant tube heating device including a recuperator according to an embodiment of the present invention. FIG. [Figure 2] FIG. 2 is a cross-sectional view taken along the arrows AA in FIG. [Figure 3] FIG. 3 is a cross-sectional view taken along the arrows BB in FIG. 2. [Figure 4] FIG. 4 is a view taken along the arrow CC in FIG. 3. [Figure 5] FIG. 2 is a schematic diagram of a recuperator according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] Figure 1 is a schematic diagram of a radiant tube heating apparatus 10 equipped with a recuperator according to an embodiment of the present invention. As shown in Figure 1, the radiant tube heating apparatus 10 includes a cylindrical radiant tube 1, which is heated from the inside, and the material to be treated placed in the furnace is heated by radiant heat from the outer surface of the radiant tube 1.

[0011] In the radiant tube heating device 10 of this embodiment, a U-shaped radiant tube 1 is used, and the main body 11 of the U-shaped radiant tube is placed inside the furnace. Both ends of the radiant tube 1 extend outside the furnace through the furnace wall. Note that the radiant tube 1 is not limited to a U-shape, and may have a W-shape, I-shape, or other shape.

[0012] A burner 2 that burns fuel gas such as hydrocarbon gas with combustion air is inserted into one end of the radiant tube 1. The burner 2 generates combustion exhaust gas by burning the fuel gas using the combustion air, and heats the radiant tube 1 from the inside using the combustion exhaust gas that flows through the radiant tube 1.

[0013] A recuperator 3 is inserted into the other end of the radiant tube 1. The recuperator 3 heats the combustion air supplied from outside by exchanging heat between the combustion exhaust gas that heated the radiant tube 1 and the combustion air introduced into the recuperator 3 through the combustion air inlet pipe 4. The tip of the recuperator 3 has a structure as shown in Figures 2 and 3, which will be described later. A portion of the combustion exhaust gas is introduced into the recuperator 3 through an opening 35, which will be described later, and mixed with the combustion air that has exchanged heat with the combustion exhaust gas. The combustion air heated by the recuperator 3 and a portion of the combustion exhaust gas introduced into the recuperator 3 are supplied through the combustion air supply pipe 5 to one end of the radiant tube 1, where the burner 2 is installed. A portion of the combustion exhaust gas supplied to one end of the radiant tube 1 is used for combustion in the burner 2, becoming high-temperature combustion exhaust gas that flows through the main body 11 of the radiant tube 1 and toward the recuperator 3.

[0014] The combustion exhaust gas that has exchanged heat with the combustion air in the recuperator 3 is discharged from an exhaust port 6.

[0015] Fig. 2 is a cross-sectional view taken along line AA in Fig. 1, Fig. 3 is a cross-sectional view taken along line BB in Fig. 2, and Fig. 4 is a cross-sectional view taken along line CC in Fig. 3. As shown in Figs. 2 to 4, recuperator 3 includes a main body 31 and a tip end 32 connected to main body 31. Main body 31 has a double-pipe structure including an outer pipe 311 and an inner pipe 312.

[0016] The tip portion 32 includes a hemispherical portion 33 located at the tip and a cylindrical portion 34 connected to the hemispherical portion 33. The cylindrical portion 34 has a double-pipe structure including an outer pipe 341 and an inner pipe 342.

[0017] The outer tube 311 of the main body 31 and the outer tube 341 of the cylindrical portion 34 are connected by welding, and the inner tube 312 of the main body 31 is attached to the outer surface of the inner tube 342 of the cylindrical portion 34 so as to be slidable relative to the outer surface of the inner tube 342, for example, by a plug-in method. Specifically, the inner tube 342 is held to the outer tube 341 by a plurality of ribs 36, and spaces 37 are formed between the ribs 36 to allow the flow of combustion air. In addition, openings 35, which will be described later, are formed in the ribs 36 as flow paths for mixing the combustion exhaust gas with the combustion air.

[0018] The cylindrical portion 34 is formed with openings 35 that form a flow path that receives a portion of the combustion exhaust gas into the recuperator 3. A plurality of openings 35 are provided at equal intervals around the circumference of the cylindrical portion 34; in this embodiment, four openings 35 are provided at 90-degree intervals around the circumference. The shape of each opening 35 on the outer surface of the cylindrical portion is an ellipse that is elongated in the axial direction X of the cylindrical portion 34. Furthermore, the openings 35 extend toward the inside of the recuperator 3 (toward the main body portion 31) so as to form an angle θ with a direction Y perpendicular to the axial direction X of the cylindrical portion 34 (the axial direction P1 of the openings 35 forms an angle θ with the direction Y), preferably at an angle of 45 to 60 degrees with respect to the perpendicular direction Y. That is, the openings 35 preferably extend so as to form an angle of 30 to 45 degrees with respect to the axial direction X of the cylindrical portion 34.

[0019] The region where the opening 35 is formed is manufactured by casting so that the outer pipe 341 and inner pipe 342 of the cylindrical portion 34 are connected, and the opening 35 forms a flow path that penetrates the casting from the outer surface of the outer pipe 341 of the cylindrical portion 34 to the inner surface of the inner pipe 342 of the cylindrical portion 34. The combustion exhaust gas that enters the opening 35 enters the inner pipe 342 of the cylindrical portion 34 from the inner surface of the inner pipe 342 of the cylindrical portion 34 and is mixed with the combustion air.

[0020] Heat exchange members 313 such as fins or protrusions are provided on the outer surface of the outer tube 311 of the main body 31 to increase the contact area with the high-temperature combustion exhaust gas, and on the outer surface of the outer tube 311 of the main body 31, on the cylindrical portion 34 side from the part where the heat exchange members 313 are provided, a reduced diameter portion 314 is formed whose diameter reduces radially inward of the main body 31.

[0021] (Flow of combustion air and combustion exhaust gas in radiant tube heating equipment) Combustion air introduced through the combustion air introduction pipe 4 is led into the recuperator 3 from between the inner pipe 312 and outer pipe 311 of the main body 31 of the recuperator 3. The combustion air flowing between the inner pipe 312 and outer pipe 311 of the main body 31 of the recuperator 3 is heated by heat exchange with the combustion exhaust gas generated by combustion in the burner 2 and flowing between the outer pipe 311 of the recuperator 3 and the radiant tube 1.

[0022] The flow direction of the combustion air flowing between the inner pipe 312 and outer pipe 311 of the main body 31 of the recuperator 3 and the flow direction of the combustion exhaust gas flowing between the outer pipe 311 of the recuperator 3 and the radiant tube 1 are opposite to each other (counterflows), thereby promoting heat exchange.

[0023] The combustion exhaust gas obtained by heating the combustion air in the recuperator 3 is discharged from an exhaust port 6 .

[0024] At the tip 32 of the recuperator 3, the combustion air heated by the combustion exhaust gas passes between the outer pipe 341 and the inner pipe 342 of the cylindrical portion 34, passes through the space 37, turns around inside the hemispherical portion 33, and enters the central flow path 38 inside the inner pipe 342 of the cylindrical portion 34. The combustion air that has entered the inner pipe 342 of the cylindrical portion 34 mixes with a portion of the combustion exhaust gas received from the opening 35 of the cylindrical portion 34, and enters the inner pipe 312 of the main body 31.

[0025] The flow direction of the combustion air flowing between the outer pipe 311 and the inner pipe 312 of the main body 31 of the recuperator 3 and the flow direction of the combustion air and part of the combustion exhaust gas flowing inside the inner pipe 312 of the main body 31 of the recuperator 3 are opposite to each other (counterflows), thereby promoting heat exchange.

[0026] The combustion air and a portion of the combustion exhaust gas flowing inside the inner pipe 312 of the main body 31 are supplied to one end of the radiant tube 1, on which the burner 2 is installed, through the combustion air supply pipe 5. The burner 2 burns the fuel gas with the combustion air supplied from the combustion air supply pipe 5 and a portion of the combustion exhaust gas, generating new combustion exhaust gas.

[0027] Here, in the recuperator 3, if the combustion air is heated (preheated) to a high temperature by the heat of the combustion exhaust gas and then introduced from the combustion air supply pipe 5 to the burner 2 to burn the fuel gas, the energy saving effect will be improved, but the combustion temperature will become too high during combustion, increasing the amount of NOx generated during combustion, and combustion exhaust gas containing a large amount of NOx will be exhausted from the exhaust port 6 at the other end of the radiant tube 1.

[0028] In contrast, when the combustion exhaust gas is introduced into the burner 2 through the combustion air supply pipe 5 together with heated combustion air to combust the fuel gas, the oxygen concentration of the combustion air decreases, slowing the combustion rate in the burner 2. As a result, the combustion temperature during combustion is prevented from becoming too high, and the amount of NOx generated during combustion can be reduced. Note that the higher the temperature of the combustion air heated by the combustion exhaust gas, the more preferably the amount of combustion exhaust gas mixed into the heated combustion air.

[0029] The combustion exhaust gas heats the radiant tube 1 from the inside, and the material to be treated placed in a furnace equipped with a radiant tube type heating device 10 is heated by the heat radiated from the outer surface of the radiant tube 1.

[0030] The radiant tube type heating device 10 having the above-described configuration can achieve the following effects.

[0031] (1) The cylindrical portion 34 of the recuperator 3 is provided with an opening 35 for receiving combustion exhaust gas, which extends obliquely toward the inside of the recuperator 3 at an angle relative to the direction perpendicular to the axial direction of the recuperator 3. This allows the combustion exhaust gas to be smoothly introduced into the combustion air flow path, increasing the amount of combustion exhaust gas mixed with the combustion air. As a result, the combustion temperature is prevented from becoming too high during combustion, and the amount of NOx generated during combustion is reduced.

[0032] (2) The inner tube 312 of the main body 31 is attached to the cylindrical portion 34 in a plug-in manner so that it can slide against the outer surface of the inner tube 342. Therefore, even if the inner tube 312 of the main body 31 expands due to heat, deformation between the main body 31 and the cylindrical portion 34 can be prevented.

[0033] (3) By forming a reduced diameter section 314 on the outer surface of the outer tube 311 of the main body 31, closer to the cylindrical section 34 than the section where the heat exchange member 313 is provided, the cross-sectional area of ​​the flow path outside the outer tube 311 of the main body 31 can be reduced, thereby increasing the flow rate of the combustion exhaust gas passing through. This improves the efficiency of heat exchange between the combustion exhaust gas flowing outside the outer tube 311 of the main body 311 and the fuel air flowing inside the outer tube 311 of the main body 31, in the section where the heat exchange member 313 is provided.

[0034] (Another embodiment) In addition to the above embodiment, an eductor 39 may be provided in the inner pipe of the recuperator 3 to improve the suction performance of the combustion exhaust gas.

[0035] 5 is a schematic diagram of a recuperator 3 according to another embodiment of the present invention. This embodiment differs from the above embodiment in that an eductor 39 is provided inside the inner pipe 342 of the cylindrical portion 34 and the inner pipe 312 of the main body portion 31, which are the inner pipes of the recuperator 3. The other configuration is the same as that of the above embodiment. Therefore, in the description of this embodiment, the same parts as those in the above embodiment are denoted by the same reference numerals, and detailed description of their contents will be omitted.

[0036] 5, an injector 343 is formed in the inner pipe 342 of the cylindrical portion 34 to improve the suction of combustion air from the hemispherical portion 33 into the inner pipe 342 of the cylindrical portion 34. The injector 343 protrudes inward from the inner surface of the inner pipe 342 so that the diameter of the central flow passage 38 in the internal space of the inner pipe 342 narrows toward the main body portion 31.

[0037] A side surface 344a of the protrusion 344 of the injector 343 on the main body 31 side is located at a position facing an opening surface 35a of the opening 35 that opens into the inner surface of the inner tube 342 of the cylindrical portion 34, in a direction Y perpendicular to the axial direction X of the cylindrical portion 34. Furthermore, an end portion 344b of the protrusion 344 of the injector 343 on the main body 31 side is preferably located on an extension of the axial center line P2 of the opening 35.

[0038] Furthermore, a tubular portion 315 having a reduced diameter portion 315a that curves inward over the entire circumferential direction is provided in the vicinity of the cylindrical portion 34 within the inner pipe 312 of the main body 31. The eductor 39 includes an injector 343 formed in the inner pipe 342 of the cylindrical portion 34 and a tubular portion 315 having a reduced diameter portion 315a that is provided within the inner pipe 312 of the main body 31.

[0039] According to the above configuration, by providing the injector 343 on the inner surface of the inner pipe 342, the flow rate of the combustion air entering the inner pipe 342 is increased, generating negative pressure. As a result, the suction of the combustion exhaust gas into the inner pipe 342 can be promoted. Furthermore, by providing the cylindrical portion 315 having the reduced diameter portion 315a inside the inner pipe 312 of the main body 31, the suction of the combustion air and the combustion exhaust gas into the inner pipe 312 can be promoted, the flow rate from the inner pipe 312 toward the combustion air supply pipe can be increased, and the efficiency of heat exchange can be improved. That is, by providing the eductor 39 inside the inner pipe 342 of the cylindrical portion 34 and the inner pipe 312 of the main body 31, the suction of the combustion exhaust gas into the inner pipe 342 can be promoted, and the efficiency of heat exchange can be improved.

[0040] Furthermore, since the side surface 344a of the protrusion 344 on the main body 31 side of the injector 343 is positioned opposite the opening surface 35a of the opening 35, the combustion air whose flow rate has been increased by the injector 343 can promote the suction of the combustion exhaust gas into the inner pipe 312.

[0041] In the above embodiment and other embodiments, a heat exchange member 313 is provided on the outer surface of the outer tube 311 of the main body 31 as a heat-receiving surface, but a heat exchange member may also be provided on the inner surface of the outer tube 311 as a heat-dissipating surface in a position opposite the heat exchange member provided on the outer surface.

[0042] Furthermore, in the above embodiment and other embodiments, the inner tube 312 of the main body portion 31 is attached so as to be slidable against the outer surface of the inner tube 342 of the cylindrical portion 34, but it may also be attached so as to be slidable against the inner surface of the inner tube 342 of the cylindrical portion 34.

[0043] The present invention and embodiments can be summarized as follows.

[0044] (1) One embodiment of the present invention is a recuperator that performs heat exchange between combustion exhaust gas flowing through radiant tubes and combustion air used to heat the radiant tubes, The tip of the recuperator is provided with a hemispherical portion located at the tip and a cylindrical portion connected to the hemispherical portion, an opening is formed in the cylindrical portion to receive the combustion exhaust gas into the recuperator; The opening extends inward of the recuperator at an angle relative to a direction perpendicular to the axial direction of the recuperator.

[0045] According to the above configuration (1), the cylindrical portion of the recuperator has an opening for receiving the combustion exhaust gas, which extends obliquely toward the inside of the recuperator at an angle with respect to the direction perpendicular to the axial direction of the recuperator. This allows the combustion exhaust gas to be smoothly introduced into the combustion air flow path, thereby increasing the amount of combustion exhaust gas mixed with the combustion air. As a result, the combustion temperature during combustion is prevented from becoming too high, and the amount of NOx generated during combustion is reduced.

[0046] (2) In the configuration (1), the recuperator has a double-pipe structure consisting of an outer pipe and an inner pipe, the cylindrical portion is connected to the recuperator body; The inner tube of the body portion is slidably mounted relative to the inner tube of the cylindrical portion.

[0047] According to the above configuration (2), the inner tube of the main body portion is slidably attached to the inner tube of the cylindrical portion, so that even if the inner tube of the main body portion expands due to heat, deformation between the main body portion and the cylindrical portion can be suppressed.

[0048] (3) In the configuration (2), a heat exchange member is provided on the outer surface of the outer tube of the main body, A tapered portion is formed on the outer surface of the outer tube of the main body, closer to the cylindrical portion than the portion where the heat exchange member is provided, and the diameter of the tapered portion is tapered radially inward of the main body.

[0049] According to the above configuration (3), by forming a reduced diameter portion on the outer surface of the outer tube of the main body portion closer to the cylindrical portion than the portion where the heat exchange member is provided, the flow rate of the combustion exhaust gas passing outside the outer tube of the main body portion can be increased in the portion where the heat exchange member is provided, and the efficiency of heat exchange between the combustion exhaust gas flowing outside the outer tube of the main body portion and the fuel air flowing inside the outer tube of the main body portion can be improved.

[0050] (4) In the configuration (2) or (3), the inner tube of the cylindrical portion is formed with an injector having a protrusion that protrudes inward from the inner surface of the inner tube to improve the suction of fluid into the inner tube.

[0051] According to the configuration (4), by forming an injector in the inner tube of the cylindrical portion, the flow rate of the combustion air entering the inner tube can be increased, and as a result, the suction of the combustion exhaust gas into the inner tube can be promoted.

[0052] (5) In the configuration (4), the side surface of the protrusion on the main body side of the injector is positioned opposite to the opening surface of the opening that opens to the inner surface of the inner tube of the cylindrical portion.

[0053] According to the configuration (5), the side surface of the protruding portion of the main body of the injector is positioned opposite the opening surface of the opening, so that the combustion air whose flow rate has been increased by the injector can promote the suction of the combustion exhaust gas into the inner pipe.

[0054] (6) In any one of the configurations (2) to (5), an eductor is provided in the inner pipe of the recuperator to increase the suction force of the fluid into the inner pipe.

[0055] According to the above configuration (6), by providing an eductor in the inner tube of the main body, it is possible to promote the suction of the combustion exhaust gas into the inner tube with the combustion air, thereby reducing the generation of NOx in the combustion exhaust gas after combustion by the burner.

[0056] Various modifications and variations may be made without departing from the spirit and scope of the present invention as set forth in the following claims. [Industrial Applicability]

[0057] The present invention can provide a recuperator that can increase the amount of combustion exhaust gas mixed with combustion air and reduce the generation of NOx, and is therefore of great industrial utility. [Explanation of symbols]

[0058] 1 Radiant tube 11 Main body 2 Burner 3 Recuperator 31 Main body 311 Outer tube 312 Inner tube 313 Heat exchange member 314 Reduced diameter portion 315 Cylindrical part 315a Reduced diameter part 32 Tip 33 Hemisphere 34 Cylindrical part 341 Outer tube 342 Inner tube 343 Injector 344 Protrusion 344a Side 344b End 35 Opening 36 Rib 37 Space 38 Central flow path 39 Eductor 4 Combustion air intake pipe 5 Combustion air supply pipe 6 exhaust port 10 Radiant tube heating device

Claims

1. A recuperator that performs heat exchange between combustion exhaust gas flowing through a radiant tube and combustion air used to heat the radiant tube, The tip of the recuperator is provided with a hemispherical portion located at the tip and a cylindrical portion connected to the hemispherical portion, an opening is formed in the cylindrical portion to receive the combustion exhaust gas into the recuperator; the opening extends inward of the recuperator at an angle with respect to a direction perpendicular to the axial direction of the recuperator; The recuperator has a double-pipe structure consisting of an outer pipe and an inner pipe, the cylindrical portion is connected to the recuperator body; The recuperator wherein the inner tube of the body portion is slidably mounted relative to the inner tube of the cylindrical portion.

2. a heat exchange member is provided on the outer surface of the outer tube of the main body, 2. The recuperator according to claim 1, wherein a tapered portion is formed on the outer surface of the outer tube of the main body, closer to the cylindrical portion than the portion where the heat exchange member is provided, the tapered portion tapering radially inward of the main body.

3. 2. The recuperator according to claim 1, wherein the inner tube of the cylindrical portion is formed with an injector having a protrusion protruding inward from the inner surface of the inner tube to improve the suction force of the fluid into the inner tube.

4. 4. The recuperator according to claim 3, wherein a side surface of the protrusion on the main body side of the injector is positioned opposite an opening surface of the opening that opens into the inner surface of the inner tube of the cylindrical portion.

5. 5. The recuperator according to claim 1, wherein an eductor is provided in the inner pipe of the recuperator to increase the suction force of the fluid into the inner pipe.

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