JPH11257611A - Radiant heater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify the control of fuel gas by a method wherein a heat radiating tube is attached to the front surface of a burner provided with air supplying and discharging ports so as to cover a burner nozzle as well as left-and-right air supplying and discharging ports while the supplying of air and discharging of exhaust gas into and out of the heat radiating tube are effected alternately to burn the fuel, injected out of the burner nozzle, in the heat radiating tube. SOLUTION: A central burner nozzle 1 is provided with heat storage chambers 2a, 2b at the left and right sides of the same respectively while a heat radiating tube 4, constituted of a metal or a ceramic and the section of the same is formed so as to be long in the lateral direction thereof while the tip end of the same is closed, is attached to the front surface of the heat storage chambers 2a, 2b so as to cover the left and right air supplying and exhaust gas discharging ports 3a, 3b of the burner nozzle 1. In this case, an air duct and an exhaust gas duct are connected to respective heat storage chambers 2a, 2b through an air supply and exhaust gas discharge switching valve to supply air into the heat radiating tube 4 and suck exhaust gas out of the heat radiating tube 4 through both of heat storage chambers 2a, 2b alternately and burn the fuel, injected out of the burner nozzle 1, in the heat radiating tube 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiant tube type heater heated by a gas burner.

[0002]

2. Description of the Related Art A radiant heater is usually installed in a heat treatment furnace or the like to perform indirect heating by radiation. Conventionally, a radiant heater has a double tube type with a heat exchange type heat exchanger as shown in FIG. As shown in FIG. 3, a U-shaped or W-shaped tube with a heat storage type heat exchanger is mainly used. As shown in FIG. 2, the double-tube radiant heater has a single-end tube 12 composed of an outer tube 12 having a closed end and an inner tube 13 having an open end attached to a gas burner 5 with a heat exchanger. The combustion air flow burned in the inner pipe portion 13 is reversed at the tip, and the outer pipe 12
Comes back while heating. According to this method, the installation is easy because the furnace wall 8 can be installed by making only one round hole, and the tubes 12 and 1 can be easily installed.
3 has an advantage that it is hardly subjected to thermal stress during thermal expansion because it has only one end fixed, and thus it is difficult to break even when a high melting point ceramic material suitable for a high temperature furnace is used. As compared with a U-shaped or W-shaped radiant heater as shown in FIG. 1, the total length of the tube 12 is short and the diameter of the inner tube 13 is small, so that the burner burning amount is small. In order to obtain the same amount of heat as the above, the number of units is required to be twice or more.

[0003] Of course, the above-mentioned problem can be solved by using a large-diameter tube. However, since the processing object usually enters the central portion of the furnace and the tube is installed near the furnace wall, When the diameter of the tube becomes large, it becomes necessary to make the processed material small or the furnace body large,
Further, in order to perform exhaust heat recovery equivalent to that of the heat storage type in the double tube system, a very large heat transfer area is required, and the heat exchanger becomes large. In addition, since the inner tube is hotter than the outer tube in a double tube, the upper limit is suppressed by the temperature of the inner tube even if a ceramic material is used, and the outer tube temperature is kept several hundred degrees lower than the heat-resistant temperature of the ceramic. There is a problem that is.

On the other hand, in the heat storage type radiant heater, as shown in FIG. 3, burners 5 having heat storage chambers 2a and 2b are attached to both ends of a U-shaped or W-shaped radiant tube 12, and each burner 5 is kept for several tens of seconds. The tube 12 is heated by alternately burning at intervals and heating the tube 12 while recovering exhaust heat and preheating the combustion air by the heat storage body. Switching between the combustion air and the exhaust gas supplied to both burners 5 is performed by: This is performed using a four-way valve or four on-off valves. According to this method, the surface area of the radiant tube 12 can be made sufficiently large, so that the combustion amount of the burner 5 can be increased, but there are the following problems.

[0005]

That is, the regenerative radiant heater as shown in FIG. 3 requires two burners 5 due to its structure, complicates piping and control, and also causes two burners 5 to be generated on the furnace wall 8. In order to fill the space between the burners 5, it is also necessary to perform a troublesome operation such as attaching two burners 5 to a frame 14 previously covered with a heat insulating material 15 and attaching the frame 14 to the opening of the furnace wall 8. Met. Furthermore, since the tube 12 is fixed at both ends, thermal stress is applied when elongation occurs due to heating, and when a ceramic material having a high heat-resistant temperature is used, it may be damaged by thermal stress due to low elasticity. . Therefore, the upper limit of the usable temperature is lower than the heat-resistant temperature of the material metal, and the radiant tube 12
In a high-temperature furnace having a surface temperature of more than 1000 ° C., it has been difficult to use it for a long time. Therefore, an object of the present invention is to eliminate the above-mentioned disadvantages of the heat storage type radiant heater.

[0006]

As shown in FIG. 1, the radiant heater according to the present invention comprises heat storage chambers 2a and 2b on the left and right sides of a central burner nozzle 1, respectively.
The burner nozzle 1 and the left and right supply / exhaust ports 3 are provided on the front side of a burner having supply / exhaust ports 3a, 3b provided on the front sides of the burner nozzles 3a, 3b.
A radiant tube 4 that is made of metal or ceramic and has a horizontally long cross section and a closed end, that is, a radiant tube, is attached so as to cover a and 3b, and an air duct and an exhaust duct are connected to each of the heat storage chambers 2a and 2b via a supply / exhaust switching valve. By connecting, the supply of air into the radiator tube 4 and the suction of exhaust gas are alternately performed through the heat storage chambers 2a and 2b, and the fuel ejected from the burner nozzle 1 is burned in the radiator tube 4. is there. When the burner nozzle 1 is used with a reduced amount of combustion, the burner nozzle 1 is constituted by a double pipe composed of the inner pipe 6 and the outer pipe 1,
Along with supplying fuel to the inner tube 6, auxiliary air having a pressure equal to or higher than the fuel gas pressure during rated combustion is supplied to the outer tube 1 so that high-pressure auxiliary air is ejected from around the fuel gas. This can prevent the unburned gas from flowing into the heat storage chamber on the suction side.

[0007]

FIG. 1 shows an embodiment of a radiant heater according to the present invention.
Is composed of a double pipe consisting of an inner pipe 6 to which fuel gas is supplied and an outer pipe 1 to which auxiliary air having a pressure equal to or higher than the fuel supply pressure during rated combustion is always supplied.
The heat storage chambers 2a and 2b are provided on the left and right sides, respectively.
At the front of the burner nozzle 1 and the heat storage chambers 2a and 2b, the interior of the furnace is partitioned by a burner tile 7, and the burner tile 7 is formed with nozzle holes and supply / exhaust ports 3a and 3b. In the figure, reference numeral 8 denotes a lattice for accommodating a heat storage body (ceramic ball), which is formed of metal or ceramic tile. On the front face of the burner, an elliptical or rectangular parallelepiped radiant tube 4 made of metal or ceramic and having an oblong cross section and a closed end, that is, a radiant tube, is provided so as to cover the burner nozzle 1 and the left and right supply / exhaust ports 3a and 3b. It is attached by fixing the flange part of the opening end to the flange part of the burner main body 5, and the left and right heat storage chambers 2a,
An air duct and an exhaust duct are connected to a rear portion of 2b via a supply / exhaust switching valve (not shown). Thus, both heat storage chambers 2
The supply of air into the radiator tube 4 and the suction of exhaust gas are alternately performed through a and 2b, and the fuel ejected from the burner nozzle 1 is burned in the radiator tube 4.

The auxiliary air is for preventing unburned gas from flowing into the heat storage chamber on the suction side when the burner combustion amount is reduced. By blowing auxiliary air around the fuel gas at a pressure equal to or higher than the fuel gas pressure during rated combustion, the fuel gas with a low injection speed is prevented from being sucked to the side. Things. Therefore, in the case of a furnace which always uses a constant amount of combustion, it is not always necessary to make the burner nozzle 1 a double pipe structure as in this embodiment.

[0009]

According to the above-described structure, the shape of the heat radiating tube 4 is laterally long and the outer contour is similar to the conventional U-shaped radiant tube 15, and the air flow inside the heat radiating tube 4 is the same as that of the U-shaped radiant tube. As a result, almost the same performance as that of the conventional heat storage type shown in FIG. 3 can be obtained. Further, since only one burner is required, the fuel gas piping and control can be simplified, and two burners can be used. There is no need for a picture frame 16 to fill the space between the burners, and since the radiator tube 4 is fixed only at one end, there is no risk of breakage due to thermal stress as in the conventional case. Can withstand the use of. In addition, since there is no inner tube as in the double tube type, the surface temperature of the heat radiating tube 4 can be raised to about the heat resistant temperature of the ceramic material.
Can be used for a long time without causing deformation or breakage.

On the other hand, when the heater of the present invention is compared with the single-end type double tube type shown in FIG. 2, the heat storage type has a higher heat exchange efficiency as described above, and furthermore, when the protruding lengths of the radiating tubes are equal. Since the volume of the combustion chamber and the heat transfer area of the radiator tube 4 in the present invention are several times or more, the number of burners can be reduced accordingly. For example, when the surface temperature of the heat radiating cylinder is 1000 ° C. and the air ratio is 1.2, the final exhaust temperature is about 900 ° C. in the double tube type shown in FIG. , A fuel saving of about 40% is possible.

[Brief description of the drawings]

FIGS. 1A and 1B show an embodiment of the present invention, in which FIG. 1A is a longitudinal sectional view, and FIG. 1B is a view taken along the line XX in a state where the heater of FIG.

FIG. 2 is a longitudinal sectional view of a conventional example.

FIG. 3 is a longitudinal sectional view of another conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Burner nozzle (outer tube) 2a, 2b Heat storage chamber 3a, 3b Supply / exhaust port 4 Radiation tube or radiant tube 5 Supply / exhaust switching valve 6 Inner tube 7 Burner tile 8 Furnace wall 12 Radiant tube 13 Inner tube 14 Frame 15 Insulation material

Claims (2)

[Claims] 1. A heat dissipating unit comprising: a heat storage chamber provided on the left and right sides of a central burner nozzle; and a burner comprising a supply / exhaust port provided on a front surface of each heat storage chamber; A radiant heater in which a tube is mounted, and air is alternately supplied and exhausted into the radiator through each heat storage chamber, so that fuel ejected from the burner nozzle is burned in the radiator. 2. The burner nozzle is constituted by a double pipe composed of an inner pipe and an outer pipe, and supplies fuel to the inner pipe and supplies auxiliary air having a pressure equal to or higher than the fuel gas pressure during rated combustion to the outer pipe. The radiant heater according to claim 1, wherein the radiant heater is supplied.