JP3107352B2 - Hot air burner - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-temperature air burner for a heating furnace for heating a material to be heated such as a slab, a billet or a bloom to a predetermined target temperature.

[0002]

2. Description of the Related Art Conventionally, in a burner for a heating furnace of this type, when the amount of combustion decreases, the outflow speed of fuel gas and combustion air from the burner decreases, causing a flame lifting phenomenon. There has been a problem that the material to be heated cannot be uniformly heated due to an increase in the furnace temperature.

On the other hand, for example, Japanese Patent Publication No. 63-23
There is a burner for low load combustion countermeasures as disclosed in Japanese Patent No. 447.

[0004] The feature of this burner is to uniformly heat the material to be heated by making the temperature distribution in the furnace width direction uniform at the time of low load combustion of the heating furnace. A motive air supply means for supplying an appropriate amount of motive air at an appropriate pressure so that the motive air is supplied to the internal air baffle, the external air baffle, or the motive air provided in the gas fuel ejection hole area. The technical means is to make the vehicle go straight from the ejection hole.

[0005]

However, in this method, the preheating temperature of the combustion air is relatively lower than the ignition temperature of the fuel (for example, about 700 ° C. in the case of coke oven gas). Is very effective, but the combustion speed is extremely fast in a high-temperature air burner where the preheating air temperature is higher than the ignition temperature of the fuel, such as a regenerative burner that has recently been put into practical use, and the preheating air temperature is 1000 ° C. Therefore, when motivated air is used to extend the flame, the combustion reaction of the fuel is accelerated by the motivated air, and the flame becomes a high-temperature short flame. As a result, the temperature distribution in the furnace becomes uneven. And nitrogen oxides (hereinafter,
There is a problem that the generation amount of "NOx" is increased.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to prevent the flame lifting phenomenon at the time of low load combustion of a burner and to produce steam which does not perform a combustion reaction on the motive fluid. High-temperature air burner for heating furnaces that uses a high-temperature air combustion to prevent the flame from shortening to a high temperature and to make the temperature distribution in the furnace uniform, that is, to uniformly heat the material to be heated and to suppress the generation of NOx. Is to provide.

[0007]

SUMMARY OF THE INVENTION The present invention comprises a fuel nozzle for supplying fuel gas, an air nozzle for supplying hot combustion air, and a motive fluid nozzle for extending a flame. In the high-temperature air burner, the motive fluid is steam, and the steam is supplied from a steam nozzle provided in the fuel nozzle.

Further, the present invention is characterized in that the motive steam is generated by sensible heat of the combustion exhaust gas.

[0009]

[Function] Since motivated steam is blown into fuel having a smaller volume ratio than combustion air (for example, about 5 Nm ³ of combustion air is required for 1 Nm ³ of fuel in coke oven gas),
The flame can be extended efficiently with a small amount of motivated steam.

Further, since steam does not cause a combustion reaction with the fuel, direct injection of motive steam into the fuel delays the combustion reaction and makes the temperature distribution in the furnace uniform. And generation of NOx is suppressed.

Further, since steam has a greater gas radiating power than carbon dioxide, the amount of heat transferred to the material to be heated increases.

In addition, since motive steam is generated using sensible heat of the combustion exhaust gas, a special energy source for generating steam is not required.

[0013]

1 is a longitudinal sectional view schematically showing a high-temperature air burner according to the present invention.

In FIG. 1, a burner main body 3 is integrally connected to a baffle 2 which is inserted through a furnace wall 1 of a heating furnace.

The burner body 3 has a fuel nozzle 4 having an annular cross section.
And the primary air nozzle 5 are coaxially arranged, the steam nozzle 7 is further arranged in the fuel nozzle 4, and the secondary air nozzle 6 is formed with a plurality of holes on a virtual circle coaxial with the fuel nozzle 4. It has a structure arranged as a thing. These nozzles 4 to 7 can communicate with the supply holes 2a, 2b, 2c, 2d, respectively, and the supply holes 2a, 2b have an annular cross section.
The supply hole 2c has a hole shape and opens inside the furnace, and the nozzle 2d opens at the center of the burner.

A fuel supply source such as a coke oven gas is connected to the fuel nozzle 4, and a high temperature (700 ° C. or higher) preheated air used for recovering and using heat during the furnace operation is connected to the secondary air nozzle 6. The steam nozzle 7 is similarly connected to a steam generator (not shown) that generates steam using sensible heat of exhaust gas during furnace operation.

In such a system, the fuel gas,
It is a matter of course that the high-temperature air and the steam can be optimally burned according to the load by controlling the valve operation in the same manner as in the publications described in the section of the prior art.

FIG. 2 shows an example of a furnace temperature distribution between the conventional burner and the high-temperature air burner according to the present invention.

That is, (a) the temperature distribution in the furnace for normal preheating air (700 ° C. or less) combustion using motivated air in the prior art burner, and (b) high temperature air (700 ° C. or more) using motivated air in the conventional burner (C) In-furnace temperature distribution of combustion, and (c) In-furnace temperature distribution of high-temperature air combustion using motivated steam in the burner of the present invention.

FIG. 2A shows, as shown by a one-dot chain line in FIG.
The temperature is highest at a part slightly away from the burner, and the temperature decreases toward the furnace center.

In FIG. 2B, as indicated by a dotted line in FIG. 2, the temperature near the burner is considerably high, and the temperature decreases toward the center of the furnace. This is because the combustion is promoted by the hot air, and the motivated air also acts to accelerate the combustion. In this pattern of combustion, the flame becomes a high-temperature short flame, so that NOx is likely to be generated, and the uniformity of the furnace temperature is also inferior to that of (a).

In (c), the temperature distribution is as shown by the solid line in FIG. That is, even in the vicinity of the burner, there is no excessive temperature rise as in the case of the pattern (b), and the degree of the temperature drop toward the furnace center is smaller than that in the case of (b). Is improved. The characteristics of the phenomenon of combustion due to (c) can be explained as follows.

In general, in high-temperature air combustion, the combustion reaction is accelerated and the flame becomes a high-temperature short flame. In the high-temperature air burner of the present invention, motivated steam having no combustion reaction with fuel is blown into the fuel nozzle 4. Therefore, the temperature distribution in the furnace becomes uniform by delaying the combustion reaction and preventing the flame lifting phenomenon during low load combustion.

Further, since steam is ejected from the supply hole 2d toward the center of the cross section in the combustion flame and is added to the flame,
The maximum flame temperature can be reduced by the dilution effect of steam. This is clear from the comparison with (b) shown in FIG. Accordingly, it is possible to avoid an excessive increase in the flame temperature, and it is also possible to suppress the generation of NOx.

Further, since steam has a greater gas radiating power than carbon dioxide gas, the amount of heat transferred to the material to be heated can be increased by blowing steam into the flame.

[0026]

The hot air burner of the present invention blows motivated steam into the fuel nozzle, so that the following effects can be obtained.

(1) Since the motivated steam is blown into the fuel having a smaller volume ratio than the combustion air, the flame can be efficiently extended with a small amount of the motivated steam.

(2) Since steam does not cause a combustion reaction with the fuel, direct injection of motive steam into the fuel delays the combustion reaction and makes the temperature distribution in the furnace uniform, and the maximum flame due to the dilution effect of the steam. The temperature decreases, and the generation of NOx is suppressed.

(3) Since the gas radiating power of carbon dioxide gas is larger than that of water vapor, the amount of heat transferred to the material to be heated increases.

(4) Since the motive steam is generated by the sensible heat of the combustion exhaust gas, no special energy source is required.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view of a burner of the present invention.

FIG. 2 is a diagram showing furnace temperature distributions of a prior art burner and a burner of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Furnace wall 2 Baffle 3 Burner main body 4 Fuel nozzle 5 Primary air nozzle 6 Secondary air nozzle 7 Steam nozzle

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Claims (2)

(57) [Claims] A fuel nozzle for supplying fuel gas; an air nozzle for supplying high-temperature combustion air;
A hot air burner equipped with a motive fluid nozzle for extending a flame, wherein the motive fluid is steam,
A high-temperature air burner characterized in that the steam is supplied from a steam nozzle provided in the fuel nozzle. 2. The high-temperature air burner according to claim 1, wherein the motive steam is generated by sensible heat of flue gas.