JP2001021117A - Radiant tube burner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate such problems as deformation of an igniter and deterioration of insulation by forming a tubular axial channel of a refractory member along the inner wall at a corresponding part in the furnace wall of a radiant tube. SOLUTION: A combustion air supply pipe 3 and a fuel gas supply pipe 4 are provided at an end of a radiant tube 1 positioned on the outside of a furnace and a cup-like flame holder 5 is provided on the forward end side of the fuel gas supply pipe 4. Igniting part of an igniter 6, e.g. a pilot burner or a spark rod, is positioned on the inside of the cup-like flame holder 5 and an interconnecting opening 7 is made through the rear wall of the cup-like flame holder 5. Further, a tubular axial channel 9 is formed of a refractory member, e.g. ceramic or porous ceramic, along the inner wall at a corresponding part 8 in the furnace wall of the radiant tube 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiant tube burner.

[0002]

2. Description of the Related Art A radiant tube burner burns in a thin tube installed in a heating chamber through a furnace wall made of a heat insulating material or the like, and indirectly heats an object to be heated in the furnace by radiation from the tube. FIG. 8 shows an example of a conventional ordinary radiant tube burner. As shown in FIG. 8, in the radiant tube, it is not necessary to heat the part located in the furnace wall, that is, the corresponding part in the furnace wall, and when this part is heated with a burner flame, the tube is overheated,
Problems such as deterioration of combustion efficiency and tube deformation occur. Therefore, in order to prevent such a problem from occurring, conventionally, the following contrivance has been made.

A. As shown in FIG. 8, the flame holding part of the burner is installed near the heating chamber of the furnace, that is, at the back side when viewed from the outside of the furnace to prevent the flame from heating the corresponding part in the furnace wall. . b. As shown in FIG. 9, when the flame holding part of the burner is installed on the outside of the furnace instead of on the back side, unlike in a, the fireproof heat insulating material is installed on the inner surface of the radiant tube corresponding to the inside of the furnace wall. c. When regenerative burners are installed at both ends of the tube, as shown in FIG. 10, the flame holding part of the burner is installed near the heating chamber of the furnace as in FIG. Place your body.
It should be noted that the configuration and operation of the radiant tube burner shown in FIGS.

[0004]

The above-mentioned prior art has the following problems. (1) In a and c where the flame holding part is installed on the back side, as shown in FIGS. 8 and 10, it is necessary to insert an ignition device such as a pilot burner or a spark rod to the back side according to the flame holding part. Therefore, problems such as deformation due to the influence of heat radiation in the radiant tube and deterioration of insulation properties are likely to occur.
When such a problem occurs, maintenance work such as taking out the ignition device and mounting it again becomes difficult, and at the same time, a large space behind the burner is required to pull out the ignition device. (2) Install a burner outside the furnace and apply fireproof insulation to the radiant tube corresponding to the inside of the furnace wall. With b, the problems caused by maintenance of the ignition device and overheating can be avoided, but the fireproof fire installed on the inner surface of the radiant tube The heat insulating material is burnt in a flame, and when the temperature rises, nitrogen oxides (NO
As the discharge concentration of x) increases, the diameter of the radiant tube, that is, the flow path is narrowed, the pressure loss increases, and the supply pressure of the combustion air and the fuel gas increases. An object of the present invention is to solve such a problem.

[0005]

According to the present invention, there is provided a radiant tube having a cylindrical axial flow path formed of a refractory member along an inner wall of a corresponding portion of a radiant tube in a furnace wall. Suggest a tube burner.

According to the present invention, in the above configuration, the cylindrical axial flow path is formed by installing a tube of a refractory member slightly smaller in diameter than the inner diameter of the radiant tube, coaxially with the radiant tube. Alternatively, it is proposed that a large number of small-diameter tubes of refractory members be annularly installed along the inner wall.

According to the present invention, in a configuration in which a large number of small-diameter tubes of refractory members are installed along the inner wall, an appropriate number of the small-diameter tubes is configured to be longer than a corresponding portion in the furnace wall. Then, it is proposed that their tip sides be located deeper than the corresponding parts in the furnace wall. In this case, it is proposed that the appropriate number be configured in a plurality of stages to be longer than the corresponding portion in the furnace wall.

According to the present invention, in the above structure, an inner axial flow path is formed inside the cylindrical axial flow path, and the inner axial flow path has an outer axial flow path at the front end. It is proposed to configure it inside the road.

According to the present invention, in the above configuration, the inner axial flow path is formed by coaxially installing a tube of a refractory member having a diameter slightly smaller than the inner diameter of the outer cylindrical axial flow path. Suggest to do.

According to the present invention, in the above structure, the inner axial flow path is formed in a cylindrical shape by installing a large number of small diameter tubes of refractory members inside the outer cylindrical axial flow path. It is proposed that the inner axial flow path be configured by installing an appropriate number of small-diameter tubes of a refractory member inside the outer cylindrical axial flow path.

According to the present invention, a portion of the combustion air flowing into the radiant tube from the end flows through the cylindrical axial flow path, so that the flame holding portion of the burner is installed outside the furnace. As a result, even if a flame is formed at the position of the radiant tube corresponding to the inside of the furnace wall, the combustion air flowing through the cylindrical axial flow path takes heat and cuts off heat transfer, so that the radiant tube corresponds to the inside of the furnace wall. The parts are not overheated. In addition, the combustion air flowing in the axial flow path also suppresses overheating of the refractory member itself forming the flow path. And even if a member for blocking the heat transfer to the corresponding portion in the furnace wall of the radiant tube is installed in the radiant tube, since this member constitutes the axial flow path,
Pressure loss is unlikely to increase as in conventional refractory insulation.

When an axial flow path is formed by arranging a large number of small-diameter tubes of refractory members along the inner wall, an appropriate number of them are formed to be longer than a portion corresponding to the furnace wall. By locating the tip end of the small diameter tube on the far side beyond the portion corresponding to the furnace wall, the outflow position of air from these small-diameter tubes can be made different, and thus multistage combustion of three or more stages can be easily performed.

An axial flow path can also be formed inside a cylindrical axial flow path formed along the inner wall of a corresponding portion of the radiant tube in the furnace wall. Because it can be configured shorter than the corresponding part inside,
By configuring the end on the tip side inside the outer axial flow path, multistage combustion can be performed with different air outflow positions.

[0014]

Next, an embodiment of the present invention will be described with reference to the drawings. FIGS. 1A and 1B show a radiant tube burner according to a first embodiment of the present invention, wherein FIG. 1A is a longitudinal sectional view, and FIG. 1B is a sectional view taken along line A-AA of FIG. In FIG. 1, reference numeral 1 denotes a radiant tube, 2 denotes a furnace wall made of a heat insulating material or the like, and the right side of the furnace wall 2 in the figure is a heating chamber in the furnace, and the left side is the outside of the furnace. At the end of the radiant tube 1 located outside the furnace, a combustion air supply pipe 3 and a fuel gas supply pipe 4 are provided, and at the tip side of the fuel gas supply pipe 4, a cup-shaped flame stabilizer 5 is provided. ing. An ignition portion of an ignition device 6 such as a pilot burner or a spark rod is located inside the cup-shaped flame stabilizer 5, and a communication port 7 is formed in a rear wall of the cup-shaped flame stabilizer 5. Reference numeral 8 indicates a portion of the radiant tube 1 corresponding to the inside of the furnace wall.
Along the inner wall of the corresponding portion 8 inside the furnace wall, a cylindrical axial flow path 9 formed of a refractory member such as ceramic or a porous ceramic body is formed. In this embodiment, the axial flow path 9 is configured by installing a large number of small-diameter tubes 11 of refractory members along the inner wall of the corresponding portion 8 in the furnace wall.

In the above configuration, the fuel gas supply pipe 4
And the fuel gas supplied to the axial center of the radiant tube 1 through the cup-shaped flame stabilizer 5 and the combustion air supplied to the end of the radiant tube 1 from the combustion air supply pipe 3 and reaching the center. Are mixed and burned on the downstream side of the cup-shaped flame stabilizer 5. At this time, a part of the combustion air flows into the cup-shaped flame stabilizer 5 through the communication port 7 to perform flame holding. On the other hand, part of the combustion air supplied to the end of the radiant tube 1 flows in from the upstream end of the small-diameter tube 11 constituting the axial flow path 9 and flows, and flows out of the downstream end. Provided for combustion. Therefore, in the above configuration, the combustion air mixed with the fuel gas on the downstream side of the cup-shaped flame stabilizer 5 flows out of the primary air and the downstream end of the axial flow path 9 for combustion. Two-stage combustion is performed using combustion air as secondary air.

In the combustion state described above, the flame 10 moves from the cup-shaped flame stabilizer 5 located outside the furnace to the center of the corresponding portion 8 in the furnace wall of the radiant tube 1 as shown by a two-dot chain line in FIG. As a result, the small-diameter tube 11 that forms the cylindrical axial flow path 9 is heated, but the combustion air flowing in the axial flow path 9 takes away heat, so that heat transfer is performed. Of the radiant tube 1 is not overheated. Therefore, problems such as deterioration of combustion efficiency and tube deformation due to overheating of the corresponding portion 8 in the furnace wall are prevented. Since the axial flow path 9 prevents such a problem caused by overheating of the corresponding portion 8 in the furnace wall, its length is appropriately shorter than the length of the corresponding portion 8 in the furnace wall ( (For example, about several centimeters), or may be appropriately long as described later. Since a large number of small-diameter tubes 11 acting as a fire-resistant heat insulating material for preventing overheating of the corresponding portion 8 in the furnace wall constitute the axial flow path 9, the pressure is reduced as in the conventional fire-resistant heat insulating material. Losses rarely increase.
On the other hand, the combustion air flowing through the axial flow passage 9 is simultaneously supplied to the small-diameter tube 11 which is a refractory member constituting the axial flow passage 9.
Since overheating of itself is also suppressed, an increase in nitrogen oxides (NOx) due to this overheating can be suppressed. In addition, since the two-stage combustion is performed by providing the axial flow path 9 as described above, NOx is reduced by the effect.

FIG. 2 shows a second embodiment of the radiant tube burner according to the present invention, in which (a) is a longitudinal sectional view, and (b) is a portion corresponding to the line A-AA in FIG. (A) is a longitudinal sectional view taken along line B-BB of (b). In the second embodiment, similarly to the first embodiment, the axial flow path 9 is formed by arranging a large number of small-diameter tubes 11 of refractory members along the inner wall of the corresponding portion 8 in the furnace wall. Make up. However, in the second embodiment, a large number of small-diameter tubes 11 are configured such that an appropriate number thereof is longer than the corresponding portion 8 in the furnace wall, and the distal ends thereof extend beyond the corresponding portion 8 in the furnace wall to the inner side. Is located. In the example shown in (b), a long number of small-diameter tubes 11 are configured to be long every other one. However, they are appropriately designed such that they are long every two or small lengths and are not regular. can do. In FIG. 2, a small-diameter tube having a length corresponding to the corresponding portion 8 inside the furnace wall is denoted by 11a, and a small-diameter tube longer than that is denoted by 11b.
The other components and operations of the second embodiment are the same as those of the first embodiment, and the corresponding components are denoted by the same reference numerals and overlapping description will be omitted. In the second embodiment, the combustion air mixed with the fuel gas on the downstream side of the cup-shaped flame stabilizer 5 is converted into the primary air and the axial flow path 9.
The secondary air flows through the small-diameter tube 11b, flows through the small-diameter tube 11b, and flows out from the downstream end thereof for combustion. Three-stage combustion is performed using the combustion air as tertiary air. In the above example, many small diameter tubes 11 are 2
Although the length is made different at each stage, the length can be made different at further stages, and it is easy to perform multistage combustion of four or more stages accordingly. By changing the stage of combustion in this way, it is possible to achieve different NOx reduction effects and adjustment of the surface temperature distribution of the radiant tube 1.

FIGS. 3 and 4 show another embodiment of the configuration of the cylindrical axial flow passage 9. FIG. First, in FIG.
As described above, the cylindrical axial flow path 9 is provided with a tube 12 made of a refractory member having a diameter slightly smaller than the inner diameter of the radiant tube 1 coaxially with the radiant tube 1. The space is configured as a flow path. In FIG. 4, the flow path configured in FIG. 3 is divided into a plurality of flow paths by a partition 13.

FIGS. 5 to 7 show a third embodiment of a radiant tube burner according to the present invention.
6 is a longitudinal sectional view, and FIGS. 6 and 7 are sectional views of a portion corresponding to line A-AA in FIG. In the third embodiment, the first
Similarly to the embodiment, the axial flow path 9 is configured by arranging a number of small-diameter tubes 11 of refractory members along the inner wall of the corresponding portion 8 in the furnace wall. In the third embodiment, an inner axial flow path 14 is further formed inside the axial flow path 9, and the inner axial flow path 14 is configured such that a distal end portion is formed in an outer axial direction. It is configured inside the flow path 9. In the embodiment shown in FIG. 6, this inner axial channel 14
As in the case of the axial flow path 9, a large number of small-diameter tubes 15 of refractory members are annularly installed inside the axial flow path 9 to form a cylindrical shape. In this embodiment, the combustion air mixed with the fuel gas on the downstream side of the cup-shaped flame stabilizer 5 flows through the primary air and the axial flow path 12 composed of the small-diameter tube 15, and from the downstream end thereof. The combustion air that flows out and is used for combustion flows through the secondary air and the axial flow path 9 formed by the small-diameter tube 11, and the combustion air that flows out from the downstream end and is used for tertiary combustion. Three-stage combustion with air is performed. In the embodiment shown in FIG. 6, the inner axial flow path 14 is formed in a cylindrical shape by arranging a number of small-diameter tubes 15 in a ring shape. However, in the embodiment shown in FIG. Is a suitable number inside the axial channel 9, in this case 4
The small-diameter tubes 15 of the refractory members are installed and configured. In addition to the above embodiment, the inner axial flow path 14
As described with reference to FIGS. 3 and 4 for the axial flow path 9, a tube made of a refractory member having a diameter slightly smaller than the inner diameter of the axial flow path 9 is installed coaxially with the axial flow path 9. Can be configured.

[0020]

As described above, the present invention has a configuration in which overheating of a portion of the radiant tube corresponding to the inside of the furnace wall is prevented by the cylindrical axial flow path, and has the following effects. a. Since the burner flame holding part can be installed outside the furnace instead of inside the furnace wall, problems such as deformation of the ignition device and deterioration of insulation properties do not occur. Maintenance work such as mounting becomes easy, and a large space behind the burner is not required. b. Since overheating of the refractory member itself constituting the axial flow path is also prevented, an increase in NOx due to overheating can be suppressed. c. The pressure loss does not deteriorate. d. It is easy to carry out two-stage combustion or more stages of combustion, which makes it possible to achieve various effects of reducing NOx and adjust the surface temperature of the radiant tube.

[Brief description of the drawings]

FIG. 1 shows a radiant tube burner according to a first embodiment of the present invention, in which (a) is a longitudinal sectional view,
(B) is a sectional view taken along line A-AA of (a).

FIG. 2 shows a second embodiment of the radiant tube burner according to the present invention, wherein (a) is a longitudinal sectional view,
FIG. 2B is a cross-sectional view taken along line A-AA in FIG. 1A, and FIG. 2A is a vertical cross-sectional view taken along line B-BB in FIG.

FIG. 3 is a sectional view showing another embodiment of a cylindrical axial flow path.

FIG. 4 is a sectional view showing still another embodiment of a cylindrical axial flow path.

FIG. 5 is a longitudinal sectional view showing a third embodiment of the radiant tube burner according to the present invention.

FIG. 6 shows an embodiment of the inner axial flow path,
FIG. 6 is a cross-sectional view of a portion in FIG. 5 corresponding to the line A-AA in FIG. 1.

7 shows another embodiment of the inner axial flow path, and is a cross-sectional view taken along the line A-AA in FIG. 1 and taken along the line in FIG.

FIG. 8 is a longitudinal sectional view showing a conventional example of a radiant tube burner.

FIG. 9 is a longitudinal sectional view showing another conventional example of a radiant tube burner.

FIG. 10 is a longitudinal sectional view showing still another conventional example of a radiant tube burner.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Radiant tube 2 Furnace wall 3 Air supply pipe for combustion 4 Fuel gas supply pipe 5 Cup-shaped flame stabilizer 6 Ignition device 7 Communication port 8 Corresponding part in furnace wall 9 Axial flow path 10 Flame 11 Small diameter tube 12 Tube 13 Partition 14 Inner axial flow path 15 Small diameter tube

Claims (9)

[Claims] 1. A radiant tube burner, wherein a cylindrical axial flow path made of a refractory member is formed along an inner wall of a corresponding portion of a radiant tube in a furnace wall. 2. The tubular axial flow path includes a tube made of a refractory member having a diameter slightly smaller than the inner diameter of the radiant tube.
2. The radiant tube burner according to claim 1, wherein the radiant tube burner is arranged coaxially with the radiant tube. 3. The radiant tube burner according to claim 1, wherein the cylindrical axial flow path is formed by arranging a number of small-diameter tubes of refractory members in an annular shape along the inner wall. 4. An appropriate number of the small-diameter tubes of a large number of refractory members is configured to be longer than a corresponding portion in the furnace wall, and their distal ends are located deeper than the corresponding portions in the furnace wall. The radiant tube burner according to claim 3, characterized in that: 5. The radiant tube burner according to claim 4, wherein an appropriate number of the small-diameter tubes of the large number of refractory members is configured to be longer than a corresponding portion in the furnace wall in a plurality of stages. 6. An inner axial flow path is formed inside the cylindrical axial flow path, and the inner axial flow path has a front end portion located inside the outer axial flow path. The radiant tube burner according to any one of claims 1 to 5, characterized in that: 7. The inner axial flow path is formed by coaxially installing a tube of a refractory member having a diameter slightly smaller than the inner diameter of the outer cylindrical axial flow path. Radiant tube burner described in 8. The inner axial flow path is formed by cylindrically installing a large number of small diameter tubes of refractory members inside the outer cylindrical axial flow path. Radiant tube burner according to 6. 9. The inner axial flow path according to claim 6, wherein an appropriate number of small-diameter tubes of a refractory member are provided inside the outer cylindrical axial flow path. Radiant tube burner