JP3495188B2 - Radiant tube - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiant tube used for indirect heating in a heat treatment furnace or the like, and more specifically, to a combustion side tube portion containing a combustion burner and the combustion burner. While circulating the combustion exhaust gas, the exhaust side pipe portion having a heat exchange portion with the combustion air to be supplied to the combustion burner, in a state of being arranged side by side,
The present invention relates to a radiant tube in which one end side portions of the combustion side pipe portion and the exhaust side pipe portion are fixedly connected to a furnace wall by connecting the respective one end side portions to each other through a communication portion.

[0002]

2. Description of the Related Art Conventionally, a radiant tube used for indirect heating in a heat treatment furnace or the like is the radiant tube as described above, and the combustion side pipe portion and the exhaust side pipe portion are connected by a U-shaped pipe. A pipe having a tubular heat exchange portion on the outside of the exhaust side pipe portion is usually used (see FIG. 6). Such a radiant tube is usually used by inserting a tube portion inside a heat treatment furnace or the like and fixing it to a furnace wall by a fixing portion.

On the other hand, from the viewpoint of energy saving, in recent years, there has been a growing demand for using a radiant tube by gas combustion as an alternative to a heater for an electric furnace. Generally, the mounting portion of the electric heater has a narrow width and the opening diameter of the mounting portion is small. Therefore,
In order to replace with the radiant tube, it is necessary to expand the opening until the combustion side pipe part and the exhaust side pipe part can be inserted, so the separation distance between the combustion side pipe part and the exhaust side pipe part is made as small as possible. It is desirable to make the diameter of the pipe including the heat exchange portion as small as possible.

[0004]

However, in the radiant tube in which the combustion side pipe portion and the exhaust side pipe portion are connected by the U-shaped pipe as described above, the separation distance between the combustion side pipe portion and the exhaust side pipe portion is increased. If the radius of curvature of the U-shaped tube is made smaller in order to make it smaller, the deviation of the flame in the U-shaped section becomes larger and U
There is a problem that the outer peripheral side of the character tube portion is locally heated and easily becomes high in temperature, and the life of the device is shortened due to heat damage or high temperature corrosion. Moreover, if the separation distance between the combustion side pipe part and the exhaust side pipe part is simply reduced via the U-shaped pipe part, the stress caused by the difference in thermal expansion between the combustion side pipe part and the exhaust side pipe part is U-shaped. The pipe part cannot be relaxed well, and damage due to stress concentration is likely to occur in the U-shaped pipe part or its vicinity.

Further, in the conventional radiant tube in which the heat exchange section is provided outside the exhaust side tube section, the tube diameter is increased due to the existence of the heat exchange section, and the width of the mounting portion of the electric heater is narrow. There has been a problem that an opening having a sufficient size for mounting cannot be opened.

Therefore, in view of the above problems, it is an object of the present invention to reduce the distance between the combustion side pipe portion and the exhaust side pipe portion while preventing local heating, and to reduce the mounting opening.
It is to provide a radiant tube that can replace the heater of an electric furnace.

[0007]

To achieve this object, a characteristic structure of the present invention is that a combustion side pipe portion having a combustion burner installed therein and a combustion exhaust gas from the combustion burner are circulated, and the combustion burner is provided with the combustion side exhaust gas. In the state where the exhaust side pipe part having a heat exchange part with the supplied combustion air is arranged side by side,
A radiant tube provided with a fixing portion that is fixed to the furnace wall is connected to each one end side portion through a communication portion, and the other end side portion of the combustion side pipe portion and the exhaust side pipe portion,
The gas retention part is provided on the tip side of the connection part of the combustion side pipe part with the communication part. Here, the "gas retention part" refers to a space provided separately from the gas flow path in which gas retention can occur.

In the present invention, it is preferable that the second gas retention portion is provided in the vicinity of the connection portion of the exhaust side pipe portion with the communication portion, in order to obtain the operation and effect described later. Specifically, for example, the tip portion may be formed by an H-shaped tube, or a recess may be formed on the extension line on the downstream side of the straight tubular communication portion. Further, it is more preferable that at least one of the combustion side pipe portion and the exhaust side pipe portion is provided with a bellows pipe portion that is expandable and contractable in the longitudinal direction, in view of the function and effect described later. Further, in the heat exchange part, it is particularly preferable that a double pipe for forming a forward path and a return path of the combustion air to be concentrically provided inside the exhaust side tube part is more advantageous than a function and effect described later. . The effects of the above configuration are as follows.

[Operation and Effect] That is, by providing the gas retention portion on the tip side of the connection portion of the combustion side pipe portion with the communication portion, the gas flowing through the combustion side pipe portion mainly passes through the communication portion. Then, the gas flows to the exhaust side pipe portion, so that gas accumulates in the gas accumulation portion provided on the tip side of the connection portion. At this time, almost no new combustible component is newly supplied to the gas retention portion, the concentration becomes equal to or lower than the combustion limit, and the low temperature gas without combustion is continuously retained in the portion. Such stagnant gas buffers the flame from heating the inner wall of the tip portion of the combustion side tube portion, and can prevent local heating of the tube. Further, in the communication part, the gas flowing therethrough is partially cooled by taking in the retained gas, and therefore is not locally heated. As a result, U with a small radius of curvature
It is possible to reduce the distance between the combustion side pipe and the exhaust side pipe without shortening the life of the device due to heat damage, local overheating, etc. as in the case of using the letter pipe part, and to reduce the mounting opening. Thus, it becomes possible to replace the heater of the electric furnace.

In the present invention, when the second gas retention portion is provided in the vicinity of the connection portion with the communication portion in the exhaust side pipe portion, when the recess is formed on the extension line on the downstream side of the straight tubular communication portion, Similar to the above, the gas retention portion can prevent local heating of the inner wall due to the flame. In the case where the second gas retention part does not exist on the downstream side extension line of the communication part like the H-shaped pipe, the gas flowing to the exhaust side pipe part is cooled by taking in a part of the retained gas, so that the exhaust gas It is possible to prevent local heating in the vicinity of the connection portion of the side pipe portion with the communication portion.

Further, when at least one of the combustion side pipe portion and the exhaust side pipe portion is provided with a bellows pipe portion which is expandable and contractible in the longitudinal direction, the distance between the combustion side pipe portion and the exhaust side pipe portion is reduced. Even in this case, the bellows tube portion can efficiently expand and contract to alleviate the stress caused by the difference in thermal expansion, and prevent damage to the communication portion between the combustion side pipe portion and the exhaust side pipe portion or in the vicinity thereof.

Further, in the heat exchange section, a double pipe for forming the forward and return paths of the combustion air concentrically is provided.
When the exhaust side pipe portion is internally provided, the pipe diameter can be reduced as compared with the case where the heat exchange portion is provided outside the exhaust side pipe portion because the heat exchange portion does not exist outside. Even when the heat exchange part is provided outside the exhaust side pipe part, it is possible to reduce the pipe diameter of the exhaust side pipe part only for the part where heat is exchanged, and to reduce the pipe diameter of the tubular heat exchange part. However, the heat transfer area in the case where the exhaust gas flow paths have the same cross-sectional area is smaller than that in the case where the double pipe is installed as in the present invention, so that there is a drawback that the efficiency of heat exchange is reduced.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings. As shown in Figure 1,
The radiant tube according to the present embodiment includes heat generated between a cylindrical combustion side tube portion 4a in which the combustion burner 1 is installed and the combustion air supplied to the combustion burner 1 while flowing the combustion exhaust gas from the combustion burner 1. The exhaust side pipe part 4c provided with the exchange part 2 is connected in parallel with each other through one end side part thereof through a communication part 4b having a rectangular cross section, and the combustion side pipe part 4a and the exhaust side pipe are connected. A radiant tube having a fixing portion 3 for fixing to a furnace wall at the other end of the portion 4c, wherein a cylindrical gas is provided on the tip side of a connecting portion of the combustion side pipe portion 4a with the communicating portion 4b. Retention part 4
d is provided. Here, the cylindrical recess is provided as the gas retention portion, but the shape is not particularly limited as long as there is a space where gas retention can occur, and various shapes can be adopted.

By forming the combustion-side pipe portion 4a, the communication portion 4b, and the exhaust-side pipe portion 4c with an H-shaped pipe, the vicinity of the connection portion of the exhaust-side pipe portion 4c with the communication portion 4b. Is provided with a second gas retention section 4e. H
The cross-sectional shape of the communicating portion 4b of the mold tube is shown as a rectangular shape,
The shape is not particularly limited as long as it does not hinder the smooth flow of gas, and various shapes such as a circular tube shape can be adopted.

Further, the bellows tube portion 5 which is expandable and contractible in the longitudinal direction is provided on the fixed portion 3 side of the combustion side tube portion 4a. The bellows tube portion is composed of the combustion side tube portion 4a and the exhaust side tube portion 4c.
It may be provided on at least one of the above, and its position is not particularly limited. Specifically, for example, an elastic metal or the like may be used so that it can be expanded and contracted in the longitudinal direction.

Further, the double pipe 2a forming the forward and return paths of the combustion air in a concentric manner is internally provided in the exhaust side pipe portion 4c to form the heat exchange portion 2, and the double pipe 2a The gap is used as the outward path for combustion air, the inside of the double tube 2a is used as the return path for combustion air, and the forward combustion air and exhaust gas are heat-exchanged in countercurrent to supply to the combustion burner 1. Preheating the combustion air.

Further, as shown in FIG.
A combustible gas supply unit 3a for supplying combustible gas such as LPG, a combustion air supply unit 3b for supplying combustion air such as air, a gas exhaust unit 3c for exhausting exhaust gas, and a site hole 3d for confirming combustion. It may be provided, and further, a spark plug 6 for performing ignition and a flame sensor 7 for detecting flame.
May be provided.

The operation of the above radiant tube will be described. As shown in FIG. 2, the combustion burner 1 has a combustible gas supplied from the combustible gas supply section 3a and a heat exchange section supplied from the combustion air supply section 3b. The combustion air preheated in 2 is supplied, and the mixed gas is ignited by the spark plug 6 to perform combustion. The gas flows in the combustion side pipe portion 4a, flows in the exhaust side pipe portion 4c through the communication portion 4b, and the gas exhaust portion 3c.
The concentration of combustible components decreases toward the downstream side as it burns, and the flame becomes continuous until it reaches a concentration below the combustion limit.High temperature gas flows without flame at the downstream side. To do. In the heat exchange section 2, the combustion air is preheated mainly by heat exchange between the combustion air flowing in the gap between the double tubes 2a and the high-temperature exhaust gas.

According to the above-mentioned structure, the low temperature gas continuously accumulates in the gas accumulating portion, whereby the flame heats the inner wall of the tip portion of the combustion side tube portion to locally raise the temperature. Can be prevented. As a result, the distance between the combustion side pipe portion and the exhaust side pipe portion can be reduced without shortening the life of the device. Further, since the gas flowing to the exhaust side pipe part is cooled by taking in a part of the staying gas, local heating near the connection part with the communication part can also be prevented. Furthermore, the bellows tube portion can efficiently expand and contract to alleviate the stress caused by the difference in thermal expansion, and prevent breakage in the communication section between the combustion side tube section and the exhaust side tube section or in the vicinity thereof. Since the exhaust side pipe portion is internally provided, the pipe diameter can be reduced.

Another embodiment will be described below. (1) In the above embodiment, the combustion side pipe portion, the communication portion, and the exhaust side pipe portion are formed by H-shaped pipes. However, as shown in FIG. 3, the communication portion 4b is formed by a U-shaped pipe. The gas retention portion 4d may be formed only at the tip of the combustion side tube portion. In this way, simply by adding a gas retention section to the conventional U-shaped tube, the low temperature gas continues to accumulate in the gas retention section, which causes the flame to heat the inner wall of the tip of the combustion side tube section and locally It is possible to prevent the temperature from becoming high. As a result, the distance between the combustion side pipe portion and the exhaust side pipe portion can be reduced without shortening the life of the device. (2) In the above embodiment, the combustion-side pipe portion, the communication portion, and the exhaust-side pipe portion are formed by H-shaped pipes. However, as shown in FIG. 4, the combustion-side pipe portion has a conical shape. Gas retention part 4d
In addition to forming the above, a recess serving as the second gas retention portion 4e may be formed on the extension line on the downstream side of the straight tubular communication portion. In this case, the low-temperature gas continuously accumulates in both gas retention parts, which causes the flame to locally heat the inner wall of the tip of the combustion-side tube and the inner wall on the downstream extension line of the communication part. It is possible to prevent the temperature from becoming high. Further, by forming the conical gas retention portion 4d, it is possible to reduce the gas flow in that portion and prevent local overheating more efficiently. As a result, the distance between the combustion side pipe portion and the exhaust side pipe portion can be reduced without shortening the life of the device. (3) In the above embodiment, an example in which the combustion-side pipe portion and the exhaust-side pipe portion each consist of one straight pipe is shown. However, as shown in FIG. The pipe portion 4a and the three exhaust side pipe portions 4c may be connected to each other by a U-shaped pipe, and the gas retention portion 4d may be formed at the tip of the combustion side pipe portion. In this case as well, similarly to the above, it is possible to prevent the flame from locally heating to high temperature on the inner wall of the tip portion of the combustion side pipe portion, and without shortening the life of the device, the combustion side pipe portion It is possible to reduce the distance between the exhaust side pipe part and the exhaust side pipe part. Further, when the temperature becomes high in the downstream side due to the long flame length, consider the two upstream pipes as the combustion side pipe portion, and further provide a similar gas retention portion at the position P in FIG. You may form.
Also in this case, the width of the entire tube can be reduced for the same reason as above.

In the claims of the utility model registration, reference numerals are given for convenience of comparison with the drawings, but the present invention is not limited to the configuration of the accompanying drawings by the entry.

[Brief description of drawings]

FIG. 1 is a view showing a radiant tube which is an embodiment of the present invention, in which (a) is a front view showing a part in section,
(B) is a cross-sectional view of the line, and (c) is a cross-sectional view thereof.

FIG. 2 is a perspective view showing a gas flow in the radiant tube shown in FIG.

FIG. 3 is a diagram showing a main part of a radiant tube according to an embodiment of the present invention, in which (a) is a left side view and (b) is a longitudinal sectional view.

FIG. 4 is a diagram showing a main part of a radiant tube according to an embodiment of the present invention, in which (a) is a left side view and (b) is a longitudinal sectional view.

5A and 5B are diagrams showing a main part of the radiant tube according to the embodiment of the present invention, in which FIG. 5A is a left side view and FIG.

FIG. 6 is a vertical sectional view showing the structure of a conventional radiant tube.

[Explanation of symbols]

1 combustion burner 2 heat exchange section 2a double tube 3 Fixed part 4a Combustion side tube 4b Communication part 4c Exhaust side pipe part 4d gas retention part 4e Second gas retention part 5 Bellows tube part 6 Combustion section

Front page continuation (58) Fields surveyed (Int.Cl. ⁷ , DB name) F23D 14/12 F23C 3/00 301 F23C 11/00 F23L 15/00-15/04

Claims (4)

(57) [Claims] 1. A combustion side pipe portion (4a) having a combustion burner (1) built therein, and combustion air supplied to the combustion burner (1) while allowing combustion exhaust gas from the combustion burner (1) to flow therethrough. The exhaust side pipe portion (4c) provided with the heat exchange portion (2) of each of the combustion side pipes is connected to each other through their communicating portions (4b) in a state where they are arranged side by side. A radiant tube comprising a portion (4a) and a fixing portion (3) fixed to a furnace wall at the other end side portion of the exhaust side pipe portion (4c), wherein the combustion side pipe portion (4a) is provided. A radiant tube provided with a gas retention part (4d) on the tip side from the connection part with the communication part (4b). 2. A second gas retention part (4) in the vicinity of a connection part of the exhaust side pipe part (4c) with the communication part (4b).
The radiant tube according to claim 1, wherein e) is provided. 3. The bellows pipe portion (5) which is expandable and contractable in the longitudinal direction is provided on at least one of the combustion side pipe portion (4a) and the exhaust side pipe portion (4c). Radiant tube. 4. In the heat exchange section (2), a double pipe (2a) that concentrically forms the forward and return paths of the combustion air is provided inside the exhaust side pipe section (4c). The radiant tube according to any one of claims 1 to 3.