JP2002022119A - Radiation heating apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radiation heating apparatus capable of preventing any crack from being produced in a metal wall by making uniform temperature distribution on the metal wall of a radiant box. SOLUTION: A radiation heating apparatus is provided in which a fuel is combusted in the box shaped radiant box 2 to heat an article to be heated in a furnace by radiation heat from the radiant box heated mainly by a flame. In the apparatus, a rectification plate 20 is provided on the inner surface of a radiant box metal wall 2a for controlling the flow of combustion produced gas.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiant heating apparatus in which a radiant box metal wall has a more uniform temperature distribution.

[0002]

2. Description of the Related Art Radiant tube type heating devices have been used in heating furnaces, such as an atmosphere heat treatment furnace, which indirectly heats a combustion product gas without directly entering the furnace. However, in the radiant tube type heating device, the combustion is performed in a narrow combustion chamber called a radiant tube, so that the temperature of the combustion portion tends to be high.

[0003] Thus, cracking or deformation radiant tube near the burner is on the prone, has a problem that NO _x generation amount is large. In addition, since a flat steel plate is radiatively heated from a small-diameter tube, there is a problem that the view factor is small and thermal efficiency is poor. A radiant heating device that solves this problem is disclosed in Japanese Patent Application Laid-Open No. 7-218142. In this method, a plurality of burners provided on a furnace wall, a metal box surrounding a flame from the burner, and a part of retained heat of combustion exhaust gas generated by a combustion reaction of fuel injected from the burner are recovered. It is a radiant heating device having an exhaust heat recovery device.

FIG. 9 shows this device. In the figure, reference numeral 1 denotes a furnace wall, and 2 denotes a metal box radiant box provided between the furnace walls 1 and 1 provided opposite to each other. On one side of the radiant box 2, two main burners (primary combustion burners) 3a and 3b are arranged vertically, and around the main burner 3, two secondary combustion nozzles 5a and 5b are arranged. A heat storage element 7 is provided upstream of the main burner 3.
Downstream of the primary combustion nozzle 4, and a pilot burner 6 downstream of the primary combustion nozzle 4.

[0005] Then, the air fed from an air blower (not shown) is regulated in its flow direction by a four-way switching valve 8 and enters the regenerator 7 through one supply pipe, where it receives heat and becomes preheated air. To the main burner 3a. Fuel (gas or heavy oil) is injected from the primary combustion nozzle 4 into the preheated air, and the preheated air and the fuel are uniformly mixed while moving downstream, and the mixed fluid reaches the pilot burner 6 and is ignited by the combustion flame. And a combustion product gas is generated. The combustion flame and the combustion product gas are ejected from the four-way switching valve 8 into the radiant box 3, and a part of the heat is applied to the metal wall of the radiant box 2 to heat it. At this time, the fuel is also injected from the secondary combustion nozzle 5a to the outer edge of the combustion flame of the main burner 3a to form a combustion flame. Then, the combustion exhaust gas holding the remaining heat is sucked into the other main burner 3b and exchanges heat with the heat storage body 7 located downstream of the main burner 3b.
After being sucked into the exhaust gas blower 9 through the exhaust gas, it is released to the atmosphere via a chimney or the like.

In the above, the main burner 3a is on the combustion side, and the other main burner 3b is on the intake side of the combustion product gas. However, after a certain time (for example, 30 seconds), the main burner 3b is switched to the combustion side and the main burner is turned on. 3a The combustion product gas is on the intake side. That is,
The two main burners 3a, 3b alternately become the combustion side at regular intervals. As described above, the radiant heating apparatus heats the metal wall of the radiant box 2 by heating the metal wall of the radiant box 2 by alternately burning the two main burners and the secondary combustion nozzles attached thereto, thereby applying radiant heat to the material to be heated in the furnace. Is what you do.

[0007]

The above-described radiant heating apparatus has been developed for the purpose of uniformly heating the metal wall of the radiant box by alternately burning the main burners. Has not been reached. FIG. 10 shows the temperature distribution of the radiant box metal wall when the above-described radiant heating device is used.
The main burners 3a, the majority and space close to these surfaces of the opposing surfaces 2a and the upper surface and the lower surface 2b that follows the space and the surface 2a close to the surface becomes high temperature portion T _h to 3b, the main burners 3a, 3b between the And a space close to this surface is a low-temperature portion _Tl . And the temperature in the radiant box is 900
For ° C., the temperature difference of the hot part T _h and the low temperature portion T _l: ΔT = T _h
−T _l = 200 ° C., and since this value is large, thermal stress occurs on the metal walls 2 a, 2 b, etc. of the radiant box 2,
There is a problem that cracks occur and the temperature of the metal wall becomes uneven.

[0008] It is an object of the present invention to solve the above-mentioned problems and to provide a radiant heating device capable of making the temperature distribution of the metal wall of the radiant box more uniform and thereby preventing the occurrence of cracks in the metal wall.

[0009]

SUMMARY OF THE INVENTION The object of the present invention is to achieve the above object by burning fuel in a box-shaped radiant box and heating an object to be heated in a furnace by radiation from the radiant box mainly heated by a flame. A radiant heating apparatus characterized in that a rectifying plate for controlling a flow of combustion product gas is provided on an inner surface of a radiant box metal wall facing a main burner.

[0010] The combustion product gas from the main burner on the combustion side hits the opposing metal wall, descends and is guided by the rectifying plate, proceeds obliquely downward, and reaches the vicinity of the main burner on the suction side and is quickly sucked. Due to this and alternate combustion of the radiant heating device, the temperature distribution in the radiant box and the metal wall has a small deviation.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of a radiant heating device according to the present invention, and FIG. 2 is an explanatory diagram showing a flow of a combustion product gas of the device of the present invention. In FIG. 1, the flow direction of the air sucked by the air blower 10 is regulated by a four-way switching valve 8, and when passing through the heat storage element 7, heat is obtained from the heat storage element 7 to obtain high-temperature (about 900 ° C.) preheated air. To reach the primary combustion nozzle 7. From the primary combustion nozzle 4,
Primary fuel (fuel gas or liquid fuel) is injected and ignited by the pilot burner 6 while mixing with high-temperature preheated air,
Burn. The combustion flame and the combustion product gas are ejected from the main burner 3b into the radiant box 2. At this time, 2
Fuel is injected from the next combustion nozzle 5a to the outer edge of the combustion flame of the main burner 3b.

The combustion gas is first supplied to the metal wall 2 shown in FIG.
It proceeds in the direction of the solid arrow perpendicular to the a-plane, changes its direction upon contacting the metal wall 2a, and descends along the metal wall 2a.
Since a straightening plate 20 having a predetermined width and extending horizontally is attached to the center of the surface of the metal wall 2a, the falling combustion product gas changes its flow direction obliquely downward after collision with the straightening plate 20, and becomes the intake side. Reaches the main burner 3a.

More specifically, as shown in FIG. 5 and FIG. 6, after the downward flow hits the flow straightening plate 20, it turns obliquely downward. At this time, the flow is diverted right and left by the sizing plate 20. , Left and right metal side walls 2 of radiant box
b, 2b. Thereby, the metal side wall 2b
Are kept hot. In particular, as shown in FIG. 6, the flow velocity of the mainstream gas along the left and right metal side walls 2b, 2b of the radiant box is higher than the gas velocity flowing through the central part. Thereby, the heat possessed by the gas is efficiently transmitted to the left and right metal side walls 2b, 2b of the radiant box.

During this time, radiant heat radiated from the combustion flame and the high-temperature combustion product gas is generated by the metal wall 2 of the radiant box.
a, etc. are heated and maintained at a high temperature.

The high-temperature combustion product gas that has reached the main burner 3a passes through the inside of the main burner 3a and gives heat to the heat storage element 7,
The temperature of the gas itself becomes low, passes through the four-way switching valve 8, and is discharged from the exhaust gas blower 9 to the atmosphere via a chimney (not shown).
This state continues for a fixed time (for example, 30 seconds). After a certain period of time, the valve plate of the four-way switching valve 8 rotates 90 ° as shown by the broken line in FIG. This causes the main burner 3a to be on the combustion side and the main burner 3b to be on the suction side. In this case, the combustion product gas passes through the flow path indicated by the two-dot chain line in FIG. 2 and heats the metal wall 2a and the like of the radiant box and maintains the high temperature state. In this manner, the four-way switching valve 8 is switched at regular intervals, and alternate combustion is repeated between the main burner 3a and the main burner 3b, thereby heating the metal wall 2a and the like of the radiant box and maintaining a high temperature state.

The width of the current plate 20 needs to be set to an appropriate value according to the size of the radiant box 2. That is, the width dimension should be such that the combustion product gas whose direction has been changed by the rectifying plate 20 reaches the main burner on the suction side. In the above-described example, the rectifying plate 20 is mounted at the center of the metal wall 2a and orthogonal to the metal wall 2a, but the mounting position of the rectifying plate 20 is not necessarily limited to this example. The two straightening plates 20, 20 may be mounted above and below the metal wall 2a so as to be inclined so that the combustion product gas reaches the main burner on the suction side. Further, the cross-sectional shape of the current plate 20 may be a tapered triangle or a semi-elliptical shape shown in FIGS. 4A and 4B in addition to the rectangular shape.

FIG. 7 shows a case where the current plate 20 having a rectangular cross section is connected to the metal wall 2.
3 shows the result of examining the temperature distribution in the radiant box 2 by performing a combustion test attached to the center of a. In the test, the temperature in the radiant box 2 was set to 9
The temperature was adjusted to 00 ° C. As a result, the high-temperature portion T _h is generated in the metal wall 2a side of the on the center line extended line of the main burner, the low temperature portion T _l is generated in the upper and lower corners of the metal wall 2a, the temperature difference [Delta] T =
(T _h −T _l ) was 30 ° C., which was about 15% as compared with the case of the conventional radiant box without the rectifying plate 20, and it was found that there was a great effect on temperature uniformity.
Thereafter, a long-term combustion operation was performed using the radiant box to which the current plate 20 was attached. However, no crack was generated on the metal wall due to thermal stress as in the related art. Note that _Th
Denotes the temperature of the high temperature part or the high temperature part, and _Tl denotes the temperature of the low temperature part or the low temperature part.

FIG. 8 is a longitudinal sectional view of a heating furnace to which the apparatus of the present invention is attached and radiantly heats the material to be heated. In the drawing, reference numeral 30 denotes a heating furnace, and 31 denotes an in-furnace transfer means such as a walking beam for transferring the material 32 to be heated. In this example, the radiant box 2 according to the present invention is placed in the heating furnace 30.
The figure shows a state in which a plurality is provided above and below the material to be heated 32 and radiantly heated. The material to be heated 32 is transported from the right side to the left side.

[0019]

As described above, according to the present invention, the deviation of the temperature in the radiant box including the metal wall can be greatly reduced as compared with the conventional box. Can be prevented.
Further, since the temperature deviation of the radiant box metal wall can be reduced, the material to be heated can be more uniformly heated.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a radiant heating device according to the present invention.

FIG. 2 is an explanatory diagram showing a flow of a combustion product gas of the apparatus of the present invention.

FIG. 3 is a view as viewed in the direction of arrows AA in FIG. 2;

FIG. 4 is a view showing an example of a cross-sectional shape of the current plate according to the present invention.

FIG. 5 is a perspective view illustrating a gas flow by a sizing plate according to the present invention.

6 is a view as viewed in the direction of the arrow A in FIG. 5;

FIG. 7 is a diagram showing a temperature distribution in a radiant box according to the present invention.

FIG. 8 is a longitudinal sectional view of a heating furnace to which the apparatus of the present invention is attached and radiantly heats a material to be heated.

FIG. 9 is a configuration diagram of a conventional radiation heating device.

FIG. 10 is a diagram showing a temperature distribution in a conventional radiant box of a radiant heating device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Furnace wall 2 Radiant box 2a, 2b Metal wall 3a, 3b Main burner 4 Primary combustion nozzle 5a, 5b Secondary combustion nozzle 6 Pilot burner 7 Heat storage unit 8 Four-way switching valve 9 Exhaust gas blower 10 Air blower 20 Straightening plate

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroshi Kuze 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. (72) Inventor Shuzo Uchino 1-2-2 Marunouchi, Chiyoda-ku, Tokyo Sun Inside the Kokan Co., Ltd. (72) Inventor Kazuki Tachibana 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Japan Inside the Kokan Co., Ltd. (72) Inventor Norihide Iwasa 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Sun F-term (reference) within Honko Co., Ltd. 3K017 BB06 BC01 BG01 3K023 QA03 QA18 QB02 QC05 SA01 3K091 AA18 AA20 BB07 BB21 CC02 CC06 CC22 CC11

Claims (1)

[Claims] 1. A radiant heating device for burning fuel in a box-shaped radiant box and heating an object to be heated in a furnace mainly by radiant heat from the radiant box heated by a flame, comprising: a main burner; A radiant heating device characterized in that a rectifying plate for controlling the flow of combustion generated gas is provided on an inner surface of a radiant box metal wall facing the radiant box.