TWI671493B - Radiant tube type heating device - Google Patents

Abstract

The invention provides a radiant tube heating device capable of achieving one or both of suppression of nitrogen oxide (NO _x ) generated by a burner and significant improvement in thermal efficiency. The radiant tube heating device (1) includes a radiant tube (2), two end portions (2a, 2b) of the radiant tube (2) pass through a furnace wall (furnace body) (W), and the radiant tube (2) A turning portion (2c) on the front end side protrudes to the inside of a furnace; and a burner (B), a hollow portion (3) on the side (2a) of one end of the radiant tube (2) The central part is coaxially arranged in the hollow part (3), wherein the radiant tube heating device (1) further includes a temperature rise suppressing member (10), which has a cylindrical shape and is arranged on the radiant tube (2) In the hollow portion (3) and at a position surrounding the opening portion on the front end side of the burner (B), and wherein the temperature rise suppressing member (10) is in the inner wall surface of the radiant tube (2) and the A pair of internal and external flow paths (12a, 13) are formed between the outer peripheral surface of the burner (B) through which the burned gas can flow.

Description

Radiant tube heating device

The present invention relates to a radiant tube heating device for heating air in a heat treatment furnace while keeping the air clean.

Generally, a radiant tube heating device is required to effectively increase the temperature of the combustion air, thereby improving the overall thermal efficiency. For example, a radiant tube type heating device has been proposed in which a burner is disposed on one end portion of a radiant tube, and an exhaust gas discharged from the other end of the radiant tube is installed on an outer peripheral side of the burner The heat exchanger circulates in a spiral heat exchanger, and the combustion air supplied to the burner is heated in advance to be in a required temperature region (for example, refer to Patent Document 1).

However, in the case where the combustion air is heated in advance by using the heat of the exhaust gas in the radiant tube heating device as described above, there is a problem in that as the combustion temperature in the burner increases, the Nitrogen oxidizes, so it produces nitrogen oxides (NO _x ) that are harmful to the environment like nitric oxide or nitrogen dioxide. Furthermore, the ratio of nitrogen oxides contained in the combustion exhaust gas tends to increase exponentially as the temperature of the preheated combustion air increases. Therefore, the Japanese Air Pollution Control Act or the like stipulates the ratio of nitrogen oxides. As a result, since the predetermined value limits the preheating temperature, improvement in thermal efficiency is limited.

Patent Document 1: JP-A-2013-194977

In order to solve the above problems, an object of the present invention is to provide a radiant tube heating device capable of achieving one or both of suppression of nitrogen oxide (NO _x ) generated by a burner and significant improvement in thermal efficiency.

In order to achieve the above object, the present invention has been completed according to the following idea: a temperature rise suppressing member is disposed in a hollow portion of a radiant tube and at a position surrounding an opening on the front end side of a burner, and the temperature rise suppress The member forms a pair of internal and external flow paths between the inner wall surface of the radiant tube and the outer wall surface of the burner to allow the burned gas to flow through.

In other words, the present invention provides a first radiant tube-type heating device including a radiant tube, two end portions of the radiant tube passing through a furnace body, and a turning portion of the radiant tube protruding on the front end side. To the inside of a furnace; and a burner arranged coaxially in the hollow portion of the hollow portion on one end side of the radiant tube, wherein the radiant tube heating device further includes a temperature rise suppressing member , Which has a substantially cylindrical shape and is disposed in a hollow portion of the radiant tube and at a position surrounding an opening portion on the front end side of the burner, and wherein the temperature rise suppressing member is on an inner wall surface of the radiant tube and A pair of internal and external flow paths are formed between the outer peripheral surface of the burner to allow the burned gas to flow.

According to such a radiant tube heating device, the following effects (1) to (3) can be achieved.

(1) The cylindrical temperature rise suppressing member is disposed in a hollow portion of the radiant tube and at a position surrounding an opening portion on the front end side of the burner. The temperature rise suppressing member provides a pair of internal and external flow paths through which the burned gas can flow, and is formed between the inner wall surface of the radiant tube and the outer peripheral surface of the burner so as to surround the flame on the center side. Therefore, due to the thermal expansion of the burned gas, the pressure of the burned gas on the outlet (downstream) side in the through hole of the temperature rise suppressing member increases higher than the pressure on the inlet (upstream) side. As a result, a portion of the burned gas on the outlet side circulates (backflows) in an outer flow path between the inner wall surface of the radiant tube and the outer peripheral surface of the temperature rise suppressing member, and when the burned gas When the portion reaches the vicinity of the opening of the through hole on the inlet side of the temperature rise suppressing member, it is due to the Venturi effect caused by the burned gas recently discharged at a high speed from the front end of the burner. ) And inhaled. Then, a part of the burned gas is mixed into the new burned gas containing air, while passing through an inner wall surface of the through hole on the inlet side of the temperature rise suppressing member and an outer peripheral surface of the burner. The inner flow path flows toward the exit side. According to this mixing, since the oxygen concentration in the burned gas is reduced and the combustion temperature is reduced, a local increase in the temperature of the flame on the center side can be suppressed. Therefore, generation of harmful nitrogen oxides (NO _x ) can be suppressed.

(2) By disposing the temperature rise suppressing member at a position surrounding the opening on the front end side of the burner, the radiant tube is relatively uniformly heated in the vicinity of the flame from the burner. Therefore, unlike the conventional case, the radiant tube is not locally overheated, and no cracks are generated in the tube. As a result, the life (durability) of the radiant tube can be extended.

(3) According to the effect (1), since the generation of nitrogen oxides contained in the burned gas can be suppressed, a preheating limit (that is, thermal efficiency) can be extended based on a prescribed value conforming to the Japanese Air Pollution Control Act or the like. The upper limit). Therefore, the overall thermal efficiency of the radiant tube heating device can be further improved, for example, by increasing the preheating temperature of the combustion air.

The radiant tube is usually a metal tube made of cast iron or the like, and Its front end usually has a side U-shape or a side W-shape.

The furnace body also includes a furnace top and a furnace wall, for example, a heat treatment furnace or a sintering furnace.

The burner burns a mixture of preheated air and fuel, and discharges (emits) an elongated flame from an open portion at its front end along the axial direction of the hollow portion to the hollow portion of the radiant tube.

As will be described later, a plurality of spiral or linear protrusions are provided on a cylindrical outer peripheral surface of the temperature rise suppressing member, which protrude outward and define a plurality of spiral grooves or a plurality of linear grooves. The top surface of the protruding portion is in contact with or near the inner peripheral surface of the hollow portion of the radiation tube.

In addition, a cross section orthogonal to the axial direction of the through hole of the temperature rise suppressing member is generally substantially circular, which is similar to the outer shape of the burner.

In addition, the present invention provides a second radiant tube type heating device, comprising: a radiant tube, two end portions of the radiant tube passing through a furnace body, and a turning portion of the radiant tube on the front end side protruding to a The interior of the furnace; and a burner disposed coaxially in the hollow portion in a central portion of the hollow portion on one end side of the radiant tube, wherein the radiant tube heating device further includes a device for passing exhaust gas through A heat exchanger for pre-heating combustion air is disposed in the hollow portion on the other end side of the radiant tube, and wherein the heat exchanger is made of ceramic, and includes: a cylindrical body; a front end Part, which is arranged on the turning part side of the radiant tube, A concave portion is opened to the front end portion, a spiral outer groove is communicated with the concave portion and is formed along the axial direction of the main body on the outer peripheral surface of the main body, and a spiral inner groove is formed in the An inner side of the main body is formed between adjacent grooves of the spiral outer groove along an axial direction of the main body, and an air supply pipe is provided for allowing the combustion air to flow through and arranged along a main body axial direction to be a The front end side of the cylindrical space surrounded by the bottom surface of the inner wall surface of the spiral inner groove is open.

According to such a radiant tube heating device, the following effect (4) can be achieved.

(4) The burned gas that has passed through the turning part of the radiant tube flows from the recess along the spiral outer groove, wherein the spiral outer groove is formed on the outer periphery of the main body of the heat exchanger along the axial direction. On the surface, and the recess is opened from the front end of the heat exchanger. Therefore, the new combustion air flowing in the spiral inner groove located on the inner side of the main body can be effectively heated in advance. Therefore, the preheated combustion air can be caused to flow in the air supply pipe provided in the columnar space surrounded by the bottom surface of the inner wall surface of the spiral inner groove. Therefore, since the upper limit of the temperature at which the combustion air is heated in advance can be increased, the thermal efficiency can be significantly improved.

The front end of the heat exchanger has, for example, a hemispherical, conical or semi-ellipsoidal shape.

Furthermore, the present invention provides a third radiant tube heating device including the temperature rise suppressing member and the heat exchanger for heating the combustion air in advance by the heat of the exhaust gas.

According to such a radiant tube heating device, the following effect (5) can be achieved.

(5) The effects of these first and second radiant tube heating devices can be presented synergistically Fruits (1) to (4). In other words, together with the effect (1) of suppressing the generation of nitrogen oxides in the burned gas discharged from the burner, the upper limit of the temperature at which the combustion air is heated in advance can be increased. Therefore, the thermal efficiency can be significantly improved, and measures for environmental impact and high thermal efficiency can be promoted.

Examples of ceramics constituting the heat exchanger include SiC, WC, B ₄ C, alumina (Al ₂ O ₃ ), aluminum nitride, TiN, and mullite. Among them, from the viewpoint of a high heat transfer coefficient and a high thermal shock resistance, it is recommended to use SiC.

Heat exchangers with complex internal and external shapes can be easily manufactured with three-dimensional (3D) printers.

The outer peripheral surface of the main body of the heat exchanger is in contact with or near the inner wall surface of the hollow portion of the radiant tube.

There are no particular restrictions on the number of the recesses, the spiral outer grooves, and the spiral inner grooves that are formed at the front end of the heat exchanger. For example, it may be a specific example of providing a recess, a spiral outer groove, and a spiral inner groove; providing a plurality of recesses, a spiral outer groove communicating with it, and a spiral on the inner side of the spiral outer groove Specific examples of the inner grooves; and any one of specific examples of providing a plurality of recesses and the same number of the spiral outer grooves and the spiral outer grooves as parallel to each other.

It is desirable that the gas supply pipe is made of a heat-resistant metal.

In addition, the present invention also includes a radiant tube heating device, wherein the temperature rise suppressing member is made of ceramic and includes: a through hole formed in the central portion along the axial direction and surrounding the front end side of the burner, and Having a gap that becomes a flow path on the inside; and a plurality of spiral grooves or a plurality of linear grooves, which are formed parallel to each other in the axial direction It is formed on the outer peripheral surface of this temperature rise suppression member.

According to such a radiant tube heating device, the following effect (6) can be achieved.

(6) According to a state in which the plurality of spiral grooves are formed on the outer peripheral surface of the temperature rise suppressing member in parallel with each other along the axial direction, the circulation speed of the burned gas can be suppressed to a certain degree. Therefore, the effect (1) can be achieved more reliably. Furthermore, since the plurality of spiral or linear protrusions are located between the plurality of spiral grooves or the plurality of linear grooves and are formed on the outer peripheral surface of the temperature rise suppressing member, the temperature rise suppressing member can be easily and It is correctly arranged at a desired position in the hollow portion of the radiant tube.

Examples of ceramics constituting the temperature rise suppressing member include SiC, WC, B ₄ C, aluminum oxide (Al ₂ O ₃ ), aluminum nitride, TiN, and mullite.

In addition, the present invention also includes a radiant tube heating device, which further includes a heat radiating member disposed in a hollow portion of the radiant tube between the front end portion of the heat exchanger and the turning portion, wherein the heat radiating member It is made of ceramic and includes a plurality of spiral flow paths.

According to such a radiant tube heating device, the following effect (7) can be achieved.

(7) Because the burned gas that has been discharged from the burner and passed through the turning portion flows along a plurality of spiral flow paths of each heat radiation member, after receiving the latent heat contained in the burned gas, the heat The radiating member may radiate the heat into the furnace via the radiating tube. Furthermore, since the burned gas that is continuously conveyed can be heated in advance, the thermal efficiency can be significantly increased in conjunction with the effect (1).

Examples of ceramics constituting the heat radiation member include SiC, WC, B ₄ C, aluminum oxide (Al ₂ O ₃ ), aluminum nitride, TiN, and mullite. The heat radiation member may be made of the same ceramic material as the temperature rise suppressing member or the heat exchanger.

In addition, it is used to define a plurality of spiral flows in the heat radiation member. The outermost sides of the plurality of spiral protrusions in the portion between the paths contact or are close to the inner wall surface of the hollow portion of the radiation tube.

In a specific example, a plurality of heat radiation members may be arranged along the axial direction of the hollow portion of the radiation tube.

1‧‧‧ radiant tube heating device

2‧‧‧ radiant tube

2a‧‧‧ One end of the radiation tube

2b‧‧‧ the other end of the radiation tube

2c‧‧‧ Radiation tube turning part

2d‧‧‧ Radial tube turning part

Hollow part of 3‧‧‧ radiant tube

4‧‧‧ end plate

5‧‧‧Air supply pipe

5a‧‧‧Air supply pipe

6‧‧‧ exhaust pipe

6a‧‧‧Connecting section

7‧‧‧ air supply pipe

7a‧‧‧Front

7b‧‧‧ vertical

8‧‧‧ Heat-resistant bellows

9‧‧‧ Gripper

10‧‧‧ Temperature rise suppression member

10a‧‧‧Temperature rise suppression member

12‧‧‧through hole

12a‧‧‧ Internal Flow Path

13‧‧‧ Outer flow path

13a‧‧‧ Outer flow path

14‧‧‧ protrusion

15‧‧‧ heat radiation component

16‧‧‧ spiral plate

17‧‧‧ spiral flow path

18‧‧‧ center axis

20a‧‧‧Heat exchanger

20b‧‧‧Heat exchanger

21‧‧‧ cylindrical body

22‧‧‧ front end

23‧‧‧ front end

24‧‧‧ Spiral outer groove

25‧‧‧Screw inner groove

26‧‧‧Concave (entrance)

28‧‧‧ space

29‧‧‧ Vent

B‧‧‧ burner

F‧‧‧ Flame

W‧‧‧furnace wall (furnace body)

FIG. 1 is a vertical sectional view illustrating a radiant tube heating device according to a specific example of the present invention.

FIG. 2 is a side view illustrating a temperature rise suppressing member of the specific example, which is used in the heating device.

Fig. 3 is a vertical sectional view of the temperature rise suppressing member.

FIG. 4 (A) is a front view of the temperature rise suppression member; FIG. 4 (B) is a front view of the temperature rise suppression member describing another specific example; and FIG. 4 (C) is a temperature rise description of another specific example. Front view of the restraint member.

FIG. 5 (A) is a side view illustrating a specific example of a heat radiation member used in the heating device; and FIG. 5 (B) is a front view of the heat radiation member.

Fig. 6 is a side view illustrating a specific example of a heat exchanger used in the heating device.

Fig. 7 is a vertical sectional view of the heat exchanger.

FIG. 8 (A) is a front view of the heat exchanger, and FIG. 8 (B) is a front view of a heat exchanger describing another specific example.

Fig. 9 is a side view illustrating a heat exchanger according to still another specific example.

Fig. 10 is a side view illustrating a heat exchanger according to still another specific example.

FIG. 11 is a schematic diagram of a radiant tube of another specific example, and the radiant tube is used in the Heating device.

The manner to implement the present invention will be described below.

Fig. 1 is a vertical sectional view illustrating a radiant tube heating device 1 according to a specific example of the present invention. This radiant tube heating device 1 corresponds to the third radiant tube heating device described above.

As shown in FIG. 1, the radiant tube heating device 1 includes a tubular radiant tube 2 that passes through a furnace wall (furnace body) W in parallel in an inward and outward direction; a burner B, which is coaxially Arranged in the central portion of the hollow portion 3 of the radiant tube 2 on one end side of the radiant tube 2; a temperature rise suppressing member 10 disposed in the hollow portion 3 and surrounding the front end side of the burner B And a heat radiating member 15 and a heat exchanger 20 a that are continuously arranged in the hollow portion 3 on the other end side of the radiating tube 2. The furnace wall W is exemplified by the furnace wall (W) of a heat treatment furnace.

The radiant tube 2 may be, for example, an integrated member made of cast steel, has a generally substantial side U-shape according to a side view, and includes: parallel to each other along the furnace inward and outward directions Passing through one end 2a and the other end 2b of the furnace wall W; a turning portion 2c protruding to the inside of the furnace in a hemispherical shape on the front end side; and the hollow portion 3 continuously passing through the end portions 2a, Inside the other end portion 2b and the turning portion 2c.

Further, as shown in FIG. 1, the temperature rise suppressing member 10 is formed between the outer peripheral surface of the temperature rise suppressing member 10 and the inner wall surface of the radiant tube 2 in a state where the temperature rising suppressing member 10 is disposed at a position of the hollow portion 3. The temperature rise suppressing member 10 has a plurality of spiral-shaped outer flow paths 13 in the axial direction. This temperature rise suppressing member 10 is also A cylindrical inner flow path 12a is formed between an inner wall surface of the through hole 12 passing through the center side of the temperature rise suppressing member 10 along the axial direction and an outer peripheral surface on the front end side of the burner B.

The temperature rise suppressing member 10 is made of, for example, a SiC-like ceramic having a high heat transfer coefficient and a high thermal shock resistance. As shown in FIGS. 2, 3, and 4 (A), the temperature rise suppressing member 10 of this specific example has a substantially cylindrical shape and includes the through hole 12 that passes through the center side along the axial direction; 5 ( A plurality of) spiral grooves constituting the outer flow paths 13 and parallel to each other along the axial direction of the outer peripheral surface; and 5 protrusions 14 protruding in a spiral shape along a boundary between the outer flow paths 13 . The plurality of protruding portions 14 contact or approach the inner wall surface of the radiation tube 2. In addition, the cross section of the groove of this specific example is arc-shaped along the width direction, but may be substantially fan-shaped as described later.

As shown in FIGS. 1 to 3, the inner wall surface side of the through hole 12 constitutes the inner flow path 12 a, and a space surrounded by the groove and the inner wall surface of the radiation tube 2 constitutes the outer flow path 13.

As shown in FIG. 4 (B), the temperature rise suppressing member 10 may be configured by six spiral grooves (outer flow path 13) and the same number of protrusions 14 between the grooves. As long as the number of the grooves (outer flow paths 13) and the protrusions 14 are plural and the same as each other, the numbers are arbitrary.

Meanwhile, as shown in FIG. 4 (C), a specific example of the temperature rise suppressing member 10a may be used in the same manner as described above, in which six (plural) protruding portions 14 are linearly mounted on the outer peripheral surface of the columnar body, Protruding symmetrically with each other in the axial direction, and the same number of grooves are formed in a straight line between the protrusions 14 in the axial direction, the grooves constituting the outer flow path 13a. The cross section of the groove (outer flow path 13a) of this specific example is along the wide The degree direction is roughly fan-shaped, but like the above specific example, it may be arc-shaped.

As shown in FIG. 1, at a position in the hollow portion 3 of the radiant tube 2 between the front end portion 22 and the turning portion 2 c of the heat exchanger 20 a, the plurality of heat is arranged along the axial direction of the hollow portion 3. Radiation member 15. Each heat radiating member 15 is made of ceramic and has three (plural) spiral flow paths 17 symmetrically.

As shown in the front view of FIG. 5 (A) and the right view of FIG. 5 (B), the heat radiation member 15 is configured by a central axis 18 and three spiral plates 16 parallel to the axial direction of the hollow portion 3. Therefore, the three spiral plates 16 extend symmetrically from the central axis 18 to each other, so that three spiral flow paths 17 are disposed adjacent to each other on the front and back surfaces of the three spiral plates 16 and the intervals are set at equal intervals. The arc-shaped cross section of the equal spiral plate 16.

In the specific example shown in FIG. 1, four (plural) heat radiating members 15 are arranged so that their central axes 18 are continuous with each other at a predetermined position in the hollow portion 3, but the heat to be arranged The total number of the radiating members 15 is arbitrary and may be a specific example in which only one heat radiating member 15 is provided.

In addition, the heat radiation member 15 may be appropriately modified so as to change the number of the spiral plates 16 to have two or more (plural) spiral flow paths 17.

As shown in FIG. 1, at the other end portion 2 b in the hollow portion 3 of the radiant tube 2, the heat exchanger 20 a is configured to pre-heat the combustion air supplied to the burner B by the heat of the exhaust gas. .

The heat exchanger 20a of this specific example is made of ceramic and manufactured by a 3D printer. As shown in FIGS. 6, 7 and 8 (A), the heat exchanger 20 a includes a substantially cylindrical body 21 and the hemispherical front end on the side of the turning portion 2 c of the radiant tube 2. Part 22, and the three (plural) recesses (entrances) 26 opened to the front end part 22 communicate with three (plural) spiral outer grooves 24, which are along the main body The axial directions of 21 are formed on the outer peripheral surface of the main body 21 in parallel.

In addition, three (plural) spiral inner grooves 25 are formed on the inner side of the main body 21 at each portion between the adjacent spiral outer grooves 24. The three (plural) spiral inner grooves 25 are formed in parallel with each other along the axial direction of the main body 21, and are columns surrounded by the bottom surface on the inner wall surface of each of the spiral inner grooves 25 An air supply pipe 7 is provided along the axial direction of the main body 21 to allow combustion air to flow therethrough, and is open in a space 28 on the front end 22 side.

As shown in FIG. 7, the front end side of each of the three spiral inner grooves 25 communicates with the space 28 on the farther front end portion 22 side, instead of the air supply pipe 7 shown by the dotted line in the figure. The front ends communicate. Therefore, as shown by the empty arrows in FIG. 1, the plurality of spiral inner grooves 25 are spirally supplied to the front end portion 22 through a vent hole 29 installed to open the end wall 27 behind the main body 21. Combustion air is transmitted from the front end 7a side of the pipe 7 to the vertical portion 7b in the air supply pipe 7 through the space 28. During this transfer, the heat of the exhaust gas flowing into each of the spiral outer grooves 24 adjacent to each spiral inner groove 25 adjacent to each other from the heat radiating member 15 side is continuously preheated by the heat Burning air.

As shown in FIG. 8 (B), the heat exchanger 20a may have the following structure: six symmetrical recesses 26 are formed in the front end portion 22, and the same number of spiral outer grooves 24 are formed. The grooves 24 communicate with the bottom edge of the corresponding recessed portion 26, and the same number of spiral inner grooves 25 are formed on the inner side of the spiral outer grooves 24 as in the above specific example. In other words, as long as the spiral outer grooves 24, spiral inner grooves 25, and recesses 26 have the same number as each other, their number may be one Or two or more. However, in the case where a spiral outer groove 24 and a spiral inner groove 25 are provided, the concave portion 26 may be formed at a plurality of positions.

As shown by the empty arrows in FIG. 1, the combustion air preheated by the heat exchanger 20a passes through the vertical portion 7b of the air supply pipe 7 and a heat-resistant bellows pipe 8 and passes through A holder 9 supported by an end plate 4 that closes the end portion 2a of the radiant tube 2 is supplied into the burner B mounted to the end portion of the base of the holder 9.

As shown in FIG. 1, new combustion air is supplied to the air supply pipe 7 through the original air supply pipes 5 a and 5 communicating with the air vent 29. At the same time, as shown by the gray arrows in FIG. 1, the exhaust gas flowing into the spiral outer grooves 24 is communicated from a connection portion 6 a between the other end portion 2 b of the radiation tube 2 and the end plate 4. The exhaust pipe 6 is discharged to the outside.

Hereinafter, the operation of the radiant tube heating device 1 will be described mainly with reference to FIG. 1.

As shown in FIG. 1, in the hollow portion 3 between the end portion 2a side of the radiant tube 2 and the turning portion 2c, the temperature rise suppressing member 10 disposed at the position on the inner wall surface of the radiant tube 2 and A pair of inner and outer flow paths 12a and 13 are formed between the outer peripheral surface of the burner B so that the burned gas surrounding the flame F on the center side can flow.

Therefore, due to the thermal expansion of the burned gas, the pressure of the burned gas on the outlet side in the through hole 12 of the temperature rise suppressing member 10 becomes higher than the pressure on the inlet side. As a result, as shown by a solid line arrow in FIG. 1, each of the outer flow paths 13 between the inner wall surface of the radiant tube 2 and the outer peripheral surface of the temperature rise suppressing member 10 of the burned gas on the outlet side Intermediate circulation (backward flow), and when the portion of the burned gas reaches the inlet side of the temperature rise suppressing member 10 Near the opening of the through-hole 12, it was sucked in due to the local effect caused by the burned gas recently discharged at a high speed from the front end of the burner B.

Due to the cultural effect, the part of the burned gas flows into the outlet side into the inner flow path between the inner wall surface of the through hole 12 on the inlet side of the temperature rise suppression member 10 and the outer peripheral surface of the burner B 12a, and at the same time, as shown by the dashed line in FIG. 1, it is mixed into the new burned gas surrounding the flame F. According to the mixing, since the oxygen concentration in the burned gas is reduced and the combustion temperature of the burned gas is reduced, a local increase in the temperature of the flame F on the center side can be suppressed. Therefore, it is possible to suppress or reduce generation of harmful nitrogen oxides (NO _x ).

Next, as shown by an empty arrow in FIG. 1, the burned gas is supplied to the plurality of heat radiating member 15 sides through the turning portion 2 c of the radiant tube 2, and during this transfer period, because the burned gas continues The heat is radiated into the furnace through the tube wall of the radiant tube 2, so the temperature in the furnace can be increased to a desired temperature range and the temperature can be maintained within the temperature range.

Furthermore, as shown by the empty arrows in FIG. 1, the burned gas that has passed through the turning portion 2 c passes through the spiral flow paths 17 along the axial direction of the heat radiating members 15. At this time, since the burned gas discharged from the burner B flows along the plurality of spiral flow paths 17 in each of the plurality of heat radiating members 15, it is included in receiving the burned gas After the latent heat, the heat radiating members 15 radiate the heat into the furnace through the wall of the radiating tube 2.

In addition, as shown by the gray arrows in FIG. 1, because the burned gas that has passed through the plurality of heat radiating members 15 passes from the recessed portion 26 of the front end 22 of the heat exchanger 20 a along the main body 21 of the heat exchanger 20 a Each spiral outer groove 24 formed in the flow flows, so it can be effectively preheated on the inside of the spiral outer groove 24 The new combustion air flows into the spiral inner groove 25. Furthermore, since the generation of nitrogen oxides in the burned gas emitted from the burner B is suppressed by the temperature rise suppressing member 10, the upper limit of the temperature for heating the combustion air in advance can be increased. Therefore, the thermal efficiency can be significantly improved.

As described above, the radiant tube heating device 1 can be understood through the first to third radiant tube heating devices, so the above effects (1) to (7) can be achieved. In addition, according to the effect (1) of suppressing the generation of nitrogen oxide, a significant improvement in thermal efficiency can be achieved due to the synergistic effect of the effect (1) and the effects (3) to (5).

The present invention is not limited to each aspect described above.

For example, as shown in FIG. 9, the heat exchanger 20 a may have a structure in which a tapered front end portion 23 is integrally included on the front end side in the similar body 21. In this specific example, the plurality of concave portions 26 are also formed in a substantially linear manner on the tapered tapered surface of the front end portion 23, and each concave portion 26 communicates with the corresponding spiral outer groove 24.

Further, as shown in FIG. 10, a heat exchanger 20b may be used, which includes the similar cylindrical body 21, the hemispherical front end portion 22 on the front end side thereof, and a spiral outer portion on the outer peripheral surface of the main body 21. The groove 24 and a spiral inner groove (not shown). The spiral inner groove is located inside and opposite to the outer groove 24. In the heat exchanger 20b, as shown in FIG. 10, there is only one recessed portion 26 as an inlet of the burned gas. However, a plurality of recessed portions 26 may be formed, and the plurality of recessed portions 26 open in parallel from the front end portion 22 to the spiral outer groove 24 adjacent to the front end portion 22.

Furthermore, as shown in FIG. 11, the radiant tube 2 may also have a structure in which a side W-shaped turning portion 2d is provided between the two parallel end portions 2a and 2b when viewed from a side view. Water in the side U-shape located at the center of the turning part 2d The flat portion can be extended horizontally to the left of the figure.

In addition, the radiant tube heating device of the present invention is not limited to the heat treatment furnace, and can be used in a sintering furnace, a preheating furnace, a soaking furnace, or a heating furnace.

The present invention is based on Japanese Patent Application No. 2015-084026 filed on April 16, 2015, and the contents are incorporated herein by reference.

Industrial applicability

According to the present invention, it is possible to reliably provide a radiant tube heating device capable of achieving one or both of suppression of nitrogen oxide (NO _x ) generated in a burner and significant improvement in thermal efficiency.

Claims (5)

A radiant tube type heating device includes: a radiant tube whose two ends pass through a furnace body, and a turning portion of the radiant tube on the front end side protrudes to the inside of a furnace; and a combustion A radiator arranged coaxially in the hollow portion in a central portion of the hollow portion on one end side of the radiant tube, wherein the radiant tube heating device further includes a temperature rise suppressing member having a cylindrical shape and disposed in A position of the hollow portion of the radiant tube surrounding an opening on the front end side of the burner, wherein the temperature rise suppressing member forms a pair of allowable portions between an inner wall surface of the radiant tube and an outer peripheral surface of the burner. The internal and external flow paths through which the combustion gas flows, wherein the radiant tube heating device further includes a heat exchanger for pre-heating the combustion air by the heat of the exhaust gas, the hollow portion being disposed on the other end side of the radiant tube And wherein the radiant tube heating device further includes a heat radiating member disposed in a hollow portion of the radiant tube between the front end portion of the heat exchanger and the turning portion. Wherein the heat radiating member made of ceramic and includes a plurality of helical flow paths. A radiant tube type heating device includes: a radiant tube whose two ends pass through a furnace body, and a turning portion of the radiant tube on the front end side protrudes to the inside of a furnace; and a combustion A radiator arranged coaxially in the hollow portion of the hollow portion on one end side of the radiant tube, wherein the radiant tube heating device further includes a heat for preheating the combustion air by the heat of the exhaust gas An exchanger arranged in the hollow portion on the other end side of the radiant tube, and wherein the heat exchanger is made of ceramic and includes: a cylindrical body; a front end portion arranged on the radiation On the side of the turning part of the tube, a recessed part is opened to the front end part, a spiral outer groove is communicated with the recessed part and is formed on the outer peripheral surface of the main body along the axial direction of the main body, a spiral inside A groove formed on the inner side of the main body between adjacent grooves of the spiral outer groove along the axial direction of the main body, and an air supply pipe for allowing the combustion air to flow through and along the main body's axis Set to the groove inside the spiral An end portion of the cylindrical space surrounded by the bottom surface of the inner wall surface is open on the side, wherein the radiant tube heating device further includes a heat radiating member disposed between the front end portion of the heat exchanger and the rotating portion. In the hollow portion of the radiant tube, the heat radiating member is made of ceramic and includes a plurality of spiral flow paths. The radiant tube heating device of claim 1, wherein the heat exchanger is made of ceramic and includes: a cylindrical body; a front end portion, which is arranged on the side of the turning portion of the radiant tube, and a concave portion A spiral outer groove communicating with the recess and formed on the outer peripheral surface of the main body along the axial direction of the main body, and a spiral inner groove on the inner side of the main body. An upper groove is formed between adjacent grooves of the spiral outer groove along the axial direction of the main body, and an air supply pipe is provided to allow the combustion air to flow through and is arranged to be concaved by the spiral along the axial direction of the main body. A front end side of a cylindrical space surrounded by the bottom surface of the inner wall surface of the groove is open on the side. The radiant tube heating device of claim 1, wherein the temperature rise suppressing member is made of ceramic and includes a through hole formed in the central portion along the axial direction and surrounding the front end side of the burner, and There is a gap that becomes a flow path on the inside; and a plurality of spiral grooves or a plurality of linear grooves are formed on the outer peripheral surface of the temperature rise suppressing member in parallel with each other along the axial direction. The radiant tube heating device of claim 3, wherein the temperature rise suppressing member is made of ceramic and includes a through hole formed in the central portion along the axial direction and surrounding the front end side of the burner, and There is a gap that becomes a flow path on the inside; and a plurality of spiral grooves or a plurality of linear grooves are formed on the outer peripheral surface of the temperature rise suppressing member in parallel with each other along the axial direction.