JPH08134534A - Heating furnace - Google Patents

Abstract

PURPOSE: To reduce the producing quantities of NOX and scale on a material to be heated by arranging plural reducing combustion burners close to the material to be heated in the furnace lengthwise direction of the side walls of the furnace body and distributedly arranging plural combustion-assist as supplying devices. CONSTITUTION: Plural reducing combustion burners 5 are arranged close to the material 4 to be heated. The reducing combustion is executed in the condition of oxygen shortage. Since the reducing combustion burners 5 are arranged close to the material 4 to be heated, the reducing gas layer is formed on the surface of the material 4 to be heated and the high temp. oxidation of the material 4 to be heated is restrained and the production of the scale is reduced. The combustion-assist gas such as fuel, high temp. air, high concn. oxygen, is distributedly supplied from plural combustion-assist gas supplying devices 7 arranged at the upper and the lower walls 3a, 3b of the furnace body. Distributed secondary combustion of the reducing combustion flame 6 is executed. Since the fuel is distributedly burnt in the burners 5 and the zone 1 of the heating furnace, the max. temp. of the flame is restrained and the producing quantity of NOX is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating furnace, a heat treatment furnace, etc. (hereinafter collectively referred to as a heating furnace) for heating a material to be heated such as a slab, billet or strip to a predetermined target temperature with a high temperature combustion burner. is there.

[0002]

2. Description of the Related Art Conventionally, in order to save energy in this type of heating furnace, an indirect heat exchanger is installed in the flue to recover the sensible heat of combustion exhaust gas as preheated air and use it for combustion of fuel. However, in this indirect heat exchange system, the upper limit temperature of the preheated air is 600 because of the material and structure of the heat exchanger.
Since the temperature is limited to about ℃, it is not possible to significantly increase the combustion flame temperature, that is, the amount of radiant heat transfer to the material to be heated, and therefore the material to be heated cannot be rapidly heated, so the heating furnace cannot be made compact. There was a problem.

On the other hand, recently, a method has been put into practical use, in which a fuel is burned with high temperature air or a combustion gas of high concentration oxygen to generate a high temperature flame and the material to be heated is rapidly heated with this high temperature flame. For example, in the former method using high-temperature air combustion, a pair of regenerative burners in which a burner and a heat accumulator are alternately switched and burned to generate 1000
It generates high temperature air above ℃, burns fuel with this high temperature air to generate high temperature flame, and rapidly heats the material to be heated.In the latter method by high concentration oxygen combustion,
By burning fuel and high-concentration oxygen with an oxygen burner, the amount of combustion gas is reduced and a high-temperature flame is generated to rapidly heat the material to be heated.

As described above, in the method of burning high-temperature air or high-concentration oxygen-supporting gas to generate high-temperature flame, the amount of radiative heat transfer from the high-temperature flame to the material to be heated is increased. Since the material to be heated is rapidly heated and the heating time is shortened, it has the advantage that the heating furnace can be made compact, but on the other hand, the fuel is burned with high-temperature air with a fast reaction rate or combustion gas with a high concentration of oxygen. Therefore, the combustion flame becomes a high temperature short flame, and as a result, NOx in the combustion gas is
In addition to a large increase in the scale of (nitrogen oxide) and the material to be heated, there is a problem that the material to be heated cannot be heated uniformly because the furnace temperature distribution in the burner axis length direction becomes uneven.

On the other hand, for example, Japanese Unexamined Patent Application Publication No. Sho 5-5 shown in FIG.
There is a low NOx burner for a high temperature firing furnace such as that shown in 6-82306. The feature of this technique is to suppress NOx of high temperature combustion, and in order to achieve this, as shown in FIG. The fuel supplied from the combustion nozzle 8 is subjected to two-stage combustion with the combustion air supplied from the primary air nozzle 9 and the secondary air nozzle 10. That is, in the primary combustion chamber 11, the primary combustion gas containing unburned components is generated, and in the secondary combustion chamber 12, the primary combustion gas and
Secondary combustion is performed with secondary air, and NOx in high temperature combustion is suppressed by two-stage combustion in the burner.

[0006]

However, the burner having the above-mentioned structure is effective for reducing NOx having a preheated air temperature of 600 ° C. or lower as compared with the conventional burner, but the preheated air temperature which has recently been put to practical use or studied has been used as a fuel. In high-temperature air burners and high-concentration oxygen burners that have an ignition temperature (for example, about 700 ° C for coke oven gas) or higher, the combustion reaction rate of fuel and combustion-supporting gas is extremely fast. Since combustion is completed and the flame becomes a high temperature short flame,
There is a problem that it cannot be applied to a heating furnace that requires low NOx property, low scale property, and uniform heating property.

The present invention was devised to solve the above problems, and its purpose is to provide a heating furnace for rapidly heating a material to be heated by burning fuel with high temperature air or a combustion supporting gas of high concentration oxygen. , NOx and scale are suppressed, and at the same time, a heating furnace that secures a flat furnace temperature distribution required for uniform heating of a material to be heated is provided.

[0008]

The present invention has the following features in order to solve the above problems. That is, in a heating furnace that heats a material to be heated by burning fuel with high temperature air or a combustion gas of high concentration oxygen, in the furnace length direction of the furnace body side wall of the heating furnace, close to the material to be heated. , A plurality of reducing combustion burners are arranged, and a plurality of combustion gas supplying devices are provided on the upper and lower walls of the furnace body on the extension line of the reducing combustion burner or on the side wall of the furnace body on the side of the material to be heated of the reducing combustion burner. Are dispersedly arranged.

[0009]

[Function] The fuel is reduced and combusted with hot air or a combustion gas of high concentration oxygen to form a reducing combustion flame containing the unburned gas in layers on the surface of the material to be heated, and the high temperature oxidation of the material to be heated is performed. That is, scale generation is suppressed. Since the combustion reaction rate of the high temperature air or the combustion supporting gas of high concentration oxygen is high, soot which is a problem in the reduction combustion of the air burner is not generated.

Further, the unburned gas in the reducing combustion flame is secondarily burned in the heating furnace by the hot air supplied from the upper and lower walls of the furnace body or the side wall of the furnace body, or the combustion gas of high concentration oxygen, to be secondarily burned. Uniform the internal temperature distribution. Further, since the fuel is dispersed and burned in the reducing combustion burner and the heating furnace, the maximum flame temperature is lowered and the generation of NOx is suppressed.

[0011]

1 is a plan view of one zone of a side burner type heating furnace showing an embodiment of a heating furnace of the present invention, and FIG. 2 is a vertical sectional view taken along the line AA of the heating furnace of FIG. . As shown in FIGS. 1 and 2, the outer shell of the zone 1 of the heating furnace is composed of the furnace body side wall 2, the furnace body upper wall 3a and the furnace body lower wall 3b, and the furnace length of the furnace body side wall 2 of the furnace. Direction, a plurality of reduction combustion burners 5 are arranged close to the material to be heated.
The fuel and high-temperature air above the ignition temperature of the fuel or combustion-supporting gas of high-concentration oxygen are supplied through the pipe, and the fuel is reduced and burned in the state of lack of oxygen, and this unburned gas (H ₂ , CO, etc.) The material to be heated 4 is heated by the contained high-temperature reducing combustion flame 6, but since the reducing combustion burner 5 is arranged close to the material to be heated 4, a reducing gas layer is formed on the surface of the material to be heated 4. ,
As a result, the high temperature oxidation of the material to be heated 4 is suppressed, and the amount of scale formation is reduced.

Further, a plurality of combustion-supporting gas supply devices 7 are arranged on the upper and lower walls 3a, 3b of the furnace body on the extension line of the burner shaft of the reduction combustion burner 5, and combustion from this combustion-supporting gas supply device 7 with fuel is performed. High-temperature air or a high-concentration oxygen-supporting gas, which has a fast reaction rate, is dispersed and supplied in multiple stages into zone 1 of the heating furnace,
Dispersion secondary combustion of the reduction combustion flame 6 containing unburned gas from the reduction combustion burner 5 is performed to form a uniform furnace temperature distribution in the zone 1 of the heating furnace and to uniformly heat the material 4 to be heated. .

Usually, the heating furnace is a zone 1 as shown in FIG.
Are connected in the furnace length direction of the heating furnace,
The material to be heated 4 is charged into the heating furnace through a charging door on one end side in the furnace length direction of the heating furnace, and is heated to a predetermined temperature while moving in the zone 1 of the heating furnace by a conveying device such as a walking beam. , Is extracted from the extraction door on the other end side. Further, the fuel is burned at a high temperature with the hot air or the combustion supporting gas of high concentration oxygen, but the fuel is dispersed and burned in the reducing combustion burner 5 and the zone 1 of the heating furnace, so that the maximum flame temperature is suppressed and NOx is generated. The amount decreases.

FIG. 3 shows another embodiment of the heating furnace of the present invention, in which the combustion-supporting gas supply device 7 is arranged on the side wall 2 of the reducing combustion burner 5 opposite to the heated material 4, It is suitable for a heating furnace having a relatively narrow furnace width in relation to the reach distance of the combustion supporting gas in the furnace width direction, and when the combustion supporting gas supply device 7 is provided on the upper and lower walls 3a and 3b of the furnace body in FIG. The same effect as can be obtained.

The present invention is not limited to the above embodiment, and for example, (1) the combustion-supporting gas supply device 7 is attached to an existing in-furnace partition wall, skid pipe, skid support pipe, or the like. (2) Dispersing and supplying the combustion-supporting gas into the heating furnace is performed by gas nozzles charged in the heating furnace. (3) The reducing combustion burner 5 is used as a regenerative burner, and a part of the preheated air of the regenerative burner is distributed and supplied to the combustion supporting gas supply device 7. It goes without saying that various changes can be made without departing from the scope of the present invention.

[0016]

EFFECTS OF THE INVENTION According to the heating furnace of the present invention, (1) since the reducing combustion burner is arranged on the side wall of the furnace body in the vicinity of the material to be heated, a reducing gas layer is formed on the surface of the material to be heated. , The amount of scale generation of the heated material is reduced. (2) The unburned gas from the reduction combustion burner is dispersed and secondarily burned by the combustion-supporting gas from the upper and lower walls of the furnace body or the side wall of the furnace body, so that the furnace temperature distribution is made uniform and the material to be heated is uniformly heated. it can. (3) Since the fuel is dispersed and burned in the reducing combustion burner and the heating furnace, the maximum flame temperature is suppressed and the amount of NOx produced is reduced.
And so on.

[Brief description of drawings]

FIG. 1 is a plan view of one zone of a side burner type heating furnace showing an embodiment of a heating furnace of the present invention.

FIG. 2 is a vertical sectional view in a furnace width direction showing an embodiment of a heating furnace of the present invention.

FIG. 3 is a vertical sectional view in a furnace width direction showing another embodiment of the heating furnace of the present invention.

FIG. 4 is a longitudinal sectional view of a low NOx burner for a high temperature firing furnace showing a conventional technique.

[Explanation of symbols]

 1 zone 2 furnace side wall 3a, 3b furnace upper wall, furnace lower wall 4 heated material 5 reducing combustion burner 6 reducing combustion flame 7 combustion-supporting gas supply device 8 fuel nozzle 9 primary combustion air nozzle 10 secondary combustion air Nozzle 11 Primary combustion chamber 12 Secondary combustion chamber 13 Burner tile

Claims (1)

[Claims] 1. A heating furnace for heating a material to be heated by burning fuel with high temperature air or a combustion-enhancing gas of high-concentration oxygen, the material being heated in a furnace longitudinal direction on a side wall of the heating furnace. A plurality of reduction combustion burners are arranged in close proximity to each other, and a plurality of combustion supporters are provided on the upper and lower walls of the furnace body on the extension line of the reduction combustion burner or on the side wall of the furnace body on the side of the material to be heated of the reduction combustion burner. A heating furnace in which gas supply devices are dispersedly arranged.