JP4145469B2 - Side fired furnace equipped with a regenerative alternating combustion device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a side-fired furnace equipped with a regenerative alternating combustion apparatus.
[0002]
[Prior art]
Conventionally, in a side-fired heating furnace in which a direct-fired burner is provided on both side walls, a combustion flame is ejected toward the center of the furnace, so the furnace temperature at the center of the furnace is higher than the furnace temperature at the side wall of the furnace. It becomes high and it has the problem that to-be-heated materials, such as a steel piece, are heated unevenly in the furnace width direction.
[0003]
Therefore, in Japanese Utility Model Publication No. 61-38905, a refractory wall extending in the furnace length direction is disposed in the furnace front of the direct fire burner, and a part of the combustion flame from the direct fire burner is disposed in the refractory wall. It has been proposed to improve the temperature distribution in the width direction of the furnace by changing the flow direction of the combustion gas. In addition, 400-500 degreeC preheated air is used as the combustion air of the said direct fire burner.
[0004]
[Problems to be solved by the invention]
In the above method, the temperature distribution in the width direction of the furnace can be made uniform, but a new problem that NOx significantly increases (in some cases about three times) as compared with the case where no refractory wall is installed. Have.
[0005]
When the cause of this significant increase in NOx was examined, when the flame collides with the refractory wall, the fuel and combustion air were stirred and mixed at that part and rapidly burned, so the flame temperature increased locally and NOx increased. In particular, it has been found that when a refractory wall is present in the visualization flame, the surface of the refractory wall acts as a catalyst, and further NOx increases.
[0006]
Accordingly, an object of the present invention is to provide a side-fired heating furnace provided with a regenerative alternating combustion apparatus in which the refractory wall is provided to prevent the occurrence of partial heating in the furnace width direction but NOx is not increased. And
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a plurality of regenerative alternating combustion devices that alternately perform combustion and exhaust with a pair of regenerative direct fire burners on opposing furnace walls, and the regenerative direct fire A refractory wall is provided which is substantially parallel to the furnace wall surface beyond the combustion flame formation position in front of the burner in the furnace and whose front end face is located at the approximate center of the regenerative direct fire burner.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings.
In FIG. 1, T is a side-fired walking beam type heating furnace, and a fixed beam 4a and a moving beam 4b are installed in the furnace as the in-furnace conveying means 4, and the workpiece is conveyed in the furnace by the rectangular motion of the moving beam 4b. To do.
[0009]
Further, at least one heat storage type alternating combustion device Bra composed of a pair of heat storage type direct combustion burners Bra ₁ and Bra ₂ is provided at the upper zone of the opposing furnace side walls 2 and 2, and a pair of heat storage type direct fires are also provided at the lower zone. At least one heat storage type alternating combustion device Brb composed of burners Brb ₁ and Brb _{2 is} disposed at a predetermined interval, and in the furnace front of each of the heat storage type direct combustion burners Bra ₁ , Bra ₂ , Brb ₁ , Brb _2. A refractory wall 5 is provided. More specifically, an upper refractory wall 5a is provided in parallel with the furnace side wall 2 from the ceiling 1 in the upper belt, while a lower refractory wall is provided in parallel with the furnace side wall 2 from the hearth 3 in the lower belt. 5b is provided.
[0010]
Note that the lower end of the upper refractory wall 5a and the upper end of the lower refractory wall 5b are positioned at the approximate center BC of the regenerative direct flame burner, and the distance L from the furnace side wall inner surface of both the refractory walls 5a and 5b. Is beyond the combustion flame formation position (for example, 0.5 to ₂ m) of the heat storage type burners Bra ₁ , Bra ₂ , Brb ₁ , and Brb ₂ .
[0011]
Incidentally, as is well known, the heat storage direct fire burner Bra ₁ , Bra ₂ , Brb ₁ , Brb ₂ is composed of a burner portion 6 and a heat storage chamber 7, and one of the heat storage direct fire burners, for example, Bra ₁ , Brb ₂ , etc. During combustion, the other regenerative direct-burn burners Bra ₂ and Brb ₁ suck the combustion exhaust gas from Bra ₁ and Brb ₂ , and the high-temperature combustion exhaust gas is exhausted through the heat storage chamber 7 of Bra ₂ and Brb _1. In the meantime, the sensible heat of the combustion exhaust gas is stored in the heat storage body in the heat storage chamber 7. When a predetermined time has elapsed, the regenerative direct burner in the exhaust is switched to the combustion state, and the regenerative direct burner in the combustion state is alternately switched to the exhaust state.
[0012]
Therefore, in the regenerative burner in the combustion state, the combustion air is preheated to about 1000 ° C. by the heat accumulator and used for combustion.
[0013]
Note that the heat storage body includes a plurality of stacked heat storage materials having a ceramic honeycomb structure, a stack of ceramic or metal spherical heat storage materials having a predetermined height, and a plurality of ceramic storage materials. Alternatively, it is configured by cutting a metal pipe into a predetermined length.
[0014]
In the side-fired walking beam furnace T having the regenerative alternating combustion apparatus having the above-described configuration, as shown in FIG. 1, the regenerative direct flame burners Bra ₁ and Brb ₂ are in a combustion state, and the regenerative direct flame burner Bra. ₂ and Brb ₁ are set in an exhaust state, and when a predetermined time elapses, the combustion and exhaust states are switched, and thereafter, this is repeated, and a heat treatment is performed while a material to be processed (not shown) is transported by the in-furnace transport means 4.
[0015]
By the way, a part of the combustion flame of the regenerative burner during combustion collides with the refractory wall 5 like the conventional one, and high-temperature combustion gas flows toward the furnace side wall 2 and also in the furnace length direction. Therefore, as shown in FIG. 2, the temperature difference in the furnace width direction is within 20 ° C., that is, the material to be treated is uniformly heated.
[0016]
On the other hand, regarding the generation of NOx, in general, when a fuel and a high-temperature combustion air of about 1000 ° C. exist in the vicinity in a certain space, a combustion reaction occurs instantaneously, and at that time, the NOx generation occurs. A peak is determined.
[0017]
However, as described above, when the combustion air is at a high temperature of about 1000 ° C., the flow velocity in the furnace is 100 to 130 m / sec (in the case of using the conventional combustion air at 400 to 500 ° C. 50-60 m / sec), which is very fast. Therefore, the exhaust gas in the furnace having a low oxygen concentration in the vicinity of the burner is sucked and recirculated in a large amount by the momentum of the combustion air, and the exhaust gas in the furnace having the low oxygen concentration is recirculated. The circulating flow diffuses the fuel, and the combustion of this low oxygen field is high in temperature, but the volume of the combustion flame is large, and the temperature gradient and concentration gradient (oxygen, exhaust gas and unreacted substances present in the flame) The fuel is a small and uniform combustion.
[0018]
Therefore, the combustion of the regenerative direct burner is a uniform combustion that suppresses the generation of a local high temperature region, and therefore, even if the refractory wall 5 is installed, it does not cause an increase in NOx.
[0019]
【The invention's effect】
As is apparent from the above description, according to the present invention, as the burner to be installed on the furnace side wall, a regenerative direct flame burner is used, and more than the combustion flame formation position in the front of the regenerative direct flame burner in the furnace. Since a refractory wall that is substantially parallel to the furnace wall and is located at the center of the regenerative direct flame burner is disposed far away, the high-temperature combustion gas that has collided with the refractory wall is on the furnace wall side. And the temperature difference in the furnace width direction is greatly improved.
[0020]
Moreover, as described above, in the case of a regenerative burner, the exhaust gas in the furnace with a low oxygen concentration in the vicinity of the burner is involved in the combustion flame, that is, the fuel diffuses uniformly by performing a powerful exhaust gas circulation action. Thus, the generation of a local high temperature region is suppressed and the NOx generation amount is reduced. In addition, although the refractory wall is provided, combustion exhaust gas with a small amount of NOx is generated up to the refractory wall, so that the generation of NOx is affected by the stirring action caused by the collision with the refractory wall. Without being done, the NOx value remains low.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a side-fired furnace according to the present invention.
2 is a furnace temperature distribution diagram in FIG. 1. FIG.
[Explanation of symbols]
1 to ceiling, 2 to furnace side wall, 3 to furnace hearth, 4 to in-furnace transport means, 5 (5a, 5b) to refractory wall, 6 to burner section, 7 to heat storage chamber, Bra, Brb to regenerative alternating combustion Apparatus, Bra ₁ , Bra ₂ , Brb ₁ , Brb ₂ ~ Regenerative burner.

Claims (1)

A plurality of regenerative type alternating combustion devices that alternately perform combustion and exhaust with a pair of regenerative direct flame burners are arranged on the facing furnace wall, and beyond the position where the combustion flame is formed in front of the regenerative direct flame burner in the furnace. A side-fired heating furnace provided with a regenerative alternating combustion apparatus, characterized in that a refractory wall, which is substantially parallel to the furnace wall surface and whose front end surface is located at substantially the center of the regenerative direct burner, is disposed.

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