JPH09101006A - Two-stage fuel supply type low NOx burner - Google Patents

Abstract

(57) [Abstract] [Problem] The secondary burner of a low NOx burner is originally
It burns fuel in a diluted state and burns it at a low temperature to reduce NOx.However, when the furnace temperature is high, such as in boilers and heating furnaces where the furnace load is extremely high, the fuel is diluted. Since the combustion is started before the start, the generation of prompt NOx cannot be suppressed. That is, since the amount of NOx generated from the secondary burner rapidly increases as the temperature rises, the NOx suppressing effect decreases as the furnace temperature increases. SOLUTION: The secondary fuel supplied to the secondary burner 2 is mixed with a water spray or a steam spray 11 and immediately cooled to delay the ignition timing of the secondary fuel so that the secondary fuel is slow at a relatively low temperature. Combustion was caused and NOx generation was suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-stage fuel supply type low NOx applied to, for example, various heating furnaces and boilers.
It's about burners.

[0002]

2. Description of the Related Art FIG. 7 shows a conventional combustion furnace 20 of a two-stage fuel combustion system. That is, a burner 24 including a primary burner 22 and a secondary burner 23 is arranged on one end side of the furnace wall 21 in the horizontal direction. In the wind box 25 of this burner 24,
The primary nozzle 26 and the secondary nozzle 27 supply almost the same amount of air as the amount of air required to burn all the fuel supplied, and a part of the total fuel is also supplied from the primary nozzle 26 to the burner. It is burned by 24.

According to this method, the combustion temperature in the primary burner 22 is remarkably lowered because of the high air ratio combustion with an air ratio of 1.7 or more, and the generation of heat NOx and prompt NOx is suppressed. Next, in the secondary burner 23, the jet energy of the secondary nozzle 27 sucks in the combustion gas having a low oxygen concentration existing around the jet flow, and the fuel is diluted and then burned. Due to this effect, when the temperature in the furnace is low, the combustion of the secondary burner 23 is performed slowly, the combustion temperature is lowered, the generation of thermal NOx is suppressed, and the fuel is diluted, so that prompt NOx is generated. Is suppressed.

[0004]

However, in the conventional two-stage fuel combustion type combustion furnace 20 described above, even in a boiler furnace having a water cooling wall, the water cooling wall is up to the tip of each nozzle 26, 27. , There is no cooling effect near the tip of the secondary burner 23. That is, the secondary burner 23 with a low NOx burner
Originally, the fuel is burned in a diluted state and burned at a low temperature to reduce NOx. However, when the furnace temperature is high, such as in a boiler or a heating furnace with a very high furnace load, the fuel is Since the combustion was started before the dilution, generation of prompt NOx could not be suppressed. That is, since the amount of NOx generated from the secondary burner rapidly increases as the temperature rises, the NOx suppressing effect decreases as the furnace temperature increases.

Therefore, the invention according to claim 1 of the present invention is a two-stage fuel supply type low NOx burner capable of suppressing generation of NOx generated from the secondary burner by positively cooling or diluting the secondary fuel. The purpose is to provide.

[0006]

In order to achieve the above-mentioned object, a two-stage fuel supply type low NOx burner according to claim 1 of the present invention has a primary burner and a secondary burner. It is characterized by having a structure in which water spraying or steam spraying is performed from around the secondary burner.

Therefore, according to the first aspect of the invention, the secondary fuel supplied to the secondary burner is immediately cooled by being mixed with the water spray or steam spray, and as a result, the ignition timing of the secondary fuel is delayed, Slow combustion occurs at a relatively low temperature, and NOx generation can be suppressed.

A two-stage fuel supply type low NOx burner according to a second aspect of the present invention is the same as the above-mentioned first aspect, in which a spray nozzle for spraying water or steam is used.
It is characterized in that a plurality of them are arranged around the secondary nozzle.

Therefore, according to the second aspect of the present invention, the secondary fuel supplied from the secondary nozzle is sufficiently and uniformly mixed from the entire area around the secondary fuel by the water spray or the steam spray from the spray nozzle group. It will be cooled immediately, and further reduction of NOx can be expected.

According to a third aspect of the present invention, a two-stage fuel supply type low NOx burner is characterized in that, in the above-mentioned constitution of the first aspect, a venturi is provided in the outlet of the secondary burner. .

Therefore, according to the third aspect of the present invention, since the energy injected into the venturi is increased more than when only the secondary fuel is used, the suction amount of the combustion exhaust gas is increased and the generation of heat NOx can be suppressed. .

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.
The state adopted in the combustion furnace of the two-stage fuel combustion system will be described with reference to FIG.

That is, on one end side of the combustion furnace 10 in a horizontal direction,
A burner 3 consisting of a primary burner 1 and a secondary burner 2 is arranged, and these primary burner 1 and secondary burner 2 are
The tips of the primary nozzles 4 and the secondary nozzles 5 are configured to face the heating ports 6 and 7. In the wind box 8 of the burner 3,
The primary nozzle 4 and the secondary nozzle 5 supply almost the same amount of air as the amount of fuel required to burn all the fuel supplied, and a part of the total fuel is also supplied from the primary nozzle 4 to the burner. 3 is burned.

The burner 3 has a structure for spraying water or steam from around the secondary burner 2.
That is, immediately below each of the secondary nozzles 5, spray nozzles 9 for spraying water or steam are arranged in parallel in pairs.

The operation of the above-described embodiment will be described below. The secondary fuel supplied from the secondary nozzle 5 by spraying water or steam from around the secondary burner 2 by the spray nozzle 9. Is mixed with a water spray or steam spray 11 and immediately cooled. As a result,
Since the ignition timing of the secondary fuel is delayed, the secondary fuel burns slowly at a relatively low temperature, and NOx generation is suppressed.

Next, an experimental example will be described with reference to FIGS. FIG. 2 shows a two-stage fuel combustion type combustion furnace 10 used in this experiment. That is, the heat insulating material 16 is spread around the inner surface of the side wall 15 of the furnace facing sideways.
By supplying cooling water 17 to the outer surface of 15, the outside is cooled via the heat insulating material 16 and the inner wall 15 of the furnace.

In the present experiment using such a combustion furnace 10, the relationship between the area of the heat insulating material 16 and the NOx generation amount was investigated, and the effect of water cooling, that is, the influence of the furnace temperature on NOx generation was investigated in advance. It was As a result, as shown in FIG. 3, the lower the area ratio of the water cooling wall, the higher the furnace temperature, and the NOx concentration increases accordingly.

When water spraying or steam spraying is performed from around the secondary burner 2 in such a state, for example, when the area ratio of the water cooling wall is 0%, the N around the secondary nozzle 5 is reduced.
Ox concentration is reduced from around 100 ppm to around 40 to 50 ppm. That is, when the furnace temperature is around 1400 ° C, the generated N
The amount of Ox will be reduced to a temperature corresponding to 900 ° C to 1000 ° C.

Next, another embodiment of the present invention will be described with reference to FIG.
A description will be given based on FIG. That is, a plurality of spray nozzles 9 for spraying water or steam are arranged around the secondary nozzle 5, for example, a total of four spray nozzles are arranged in the vertical and horizontal directions.

According to this another embodiment, the secondary fuel supplied from the secondary nozzle 5 is the upper, lower, left and right spray nozzles 9.
By spraying water or steam from the above, the mixture will be sufficiently and uniformly mixed from the entire area around it and immediately cooled, and further reduction of NOx can be expected.

FIG. 6 shows another embodiment of the present invention. That is, the secondary nozzle 5 and the spray nozzle 9 are arranged in parallel and integrated, and the venturi 13 is provided at the fire port 7 of the secondary burner 2 where the tip portions of these nozzles 5 and 9 face.

According to this further embodiment, since the energy injected into the venturi 13 is increased more than when only the secondary fuel is used, the suction amount of the combustion exhaust gas is increased and the generation of heat NOx is suppressed. obtain.

[0023]

According to claim 1 of the present invention described above, the secondary fuel supplied to the secondary burner can be immediately cooled by mixing it with water spray or steam spray, and as a result, the ignition timing of the secondary fuel is achieved. It is possible to delay the above, to perform slow combustion at a relatively low temperature, to suppress the generation of NOx, and to reduce NOx even in a high temperature furnace.

According to the second aspect of the present invention,
The secondary fuel supplied from the secondary nozzles can be mixed immediately and sufficiently from the entire area around it by water spray or water vapor spray from the spray nozzle group, and it is expected to further reduce NOx. it can.

According to claim 3 of the present invention described above, since the energy injected into the venturi can be increased more than when only the secondary fuel is used, the suction amount of the combustion exhaust gas can be increased, and heat NOx is generated. Can be suppressed.

[Brief description of the drawings]

FIG. 1 shows an example of an embodiment of the present invention and is a vertical cross-sectional view of a main part of a combustion furnace equipped with a two-stage fuel supply type low NOx burner.

FIG. 2 is a schematic vertical sectional view of a combustion furnace used in the same experiment.

FIG. 3 is a result of the same experiment, showing a water cooling wall area ratio and NOx.
It is a graph which shows the relationship between concentration and furnace temperature.

FIG. 4 is a side view showing another embodiment of the present invention and showing the periphery of a secondary nozzle in a two-stage fuel supply type low NOx burner.

FIG. 5 is a front view showing the periphery of a secondary nozzle in the same fuel two-stage supply low NOx burner.

FIG. 6 is a side view showing still another embodiment of the present invention and showing the periphery of a secondary nozzle in a two-stage fuel supply low NOx burner.

FIG. 7 is a longitudinal sectional view of a combustion furnace equipped with a two-stage fuel supply type low NOx burner showing a conventional example.

[Explanation of symbols]

 1 Primary Burner 2 Secondary Burner 3 Burner 4 Primary Nozzle 5 Secondary Nozzle 6 Firing Port 7 Firing Port 9 Spray Nozzle 11 Water Spray or Steam Spray 13 Venturi

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Kazunori Nakamura 5-3-8 Nishikujo, Konohana-ku, Osaka City, Osaka Prefecture Hitachi Shipbuilding Co., Ltd. (72) Inventor Katsuhiko Yamazaki 5-chome, Nishikujo, Osaka, Osaka City No. 28 in Hitachi Shipbuilding Co., Ltd.

Claims (3)

[Claims] 1. A primary burner and a secondary burner are provided,
A two-stage fuel supply type low NO fuel having a structure in which water spraying or steam spraying is performed from around the secondary burner.
x burner. 2. A two-stage fuel supply type low NOx burner according to claim 1, wherein a plurality of spray nozzles for spraying water or steam are arranged around the secondary nozzle. 3. A two-stage fuel supply type low NOx burner according to claim 1, wherein a venturi is provided at the outlet of the secondary burner.