JPS58138907A - Whirl type combustion device - Google Patents

Abstract

PURPOSE:To perform the denitration in a boiler more effectively, by making the mixing of reducing flames with main burner flames containing NOX sufficient, and prolonging the staying time of the reducing flames in the boiler. CONSTITUTION:Combustion air 10 flowed in a blast box 7 is provided with a whirling force at an air register 6, and is jetted from a throat 4 as combustion air for the main burner 1 to produce the main burner flames. In this case, the air-fuel ratio in the main burners 1 is to be about 1 or slightly over 1. On the other hand, only feul 12 is jetted from the reducing burners 2, that is, the fuel 12 is jetted with the air-fuel ratio being 0, so that the fuel is burned with oxygen remaining in the fire furnace 15 to perform low oxygen burning to form reducing flames. Then other combustion air 10 is supplied from air inlets 13, and whirling streams are generated in the furnace by this supply of the combustion air so that the main burner flames and the reducing burner flames are favorably mixed, and therefore NOX, in the main burner flames is reduced with the reducing intermediate products such as CN, NH, etc. in the reducing burner flames to N2.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a combustion apparatus that can efficiently perform denitration in a furnace.

Nitrogen oxides (hereinafter abbreviated as "NOx") are one of the air pollutants, and various combustion methods and combustion devices have been proposed and put into practical use to reduce their emissions. First, (1) those generated when the N content in the fuel is oxidized at relatively low temperatures (fuel NOX), and (2) OH radicals generated by thermal decomposition of the fuel after the combustion reaction has progressed to some extent. etc. acts on Np in the air to produce HON, which is further acted on by 02 to produce HON (prong) NO
x), (3) Stable N in the combustion air is oxidized in a locally generated high-temperature region as combustion progresses further (it is thought that there is thermal NO).

Conventional NOx reduction combustion methods include: (a) Exhaust gas recirculation method in which a portion of exhaust gas is mixed with combustion air to lower oxygen partial pressure and combustion temperature.

(b) A two-stage combustion method in which combustion air is divided into two or more stages, the air supply amount in the first stage is less than the theoretical air amount, and the insufficient amount of air is supplied in the second and subsequent stages.

(c) Various methods have been proposed, such as methods of lowering the combustion temperature by lowering the temperature of the combustion air, but all of them have problems such as a significant decrease in thermal efficiency and unstable combustion. It is difficult to further increase the NOx reduction rate using only these methods.

Recently, as part of the bias combustion method, reducing intermediate products generated in burners with extremely low air-fuel ratios have been
A method for reducing and removing Ox during the combustion stage, that is, an in-furnace denitrification method, has been developed and is attracting attention.

This combustion method mainly reduces NOx generated in the main burner, which receives the heat load, using reducing intermediate products generated from the burner, which performs combustion at an extremely low I/) air-fuel ratio. If this is done incorrectly, there are problems such as unstable combustion and the discharge of a large amount of unburned matter, so a combustion device that can effectively perform denitration in the furnace is desired.

In view of the above-mentioned needs, the purpose of this invention is to
It is an object of the present invention to provide a combustion device that can perform denitrification in the furnace more effectively by improving the mixing with the main burner flame containing x and increasing the residence time of the reducing flame in the furnace.

In short, this invention forms an air port in the side wall of a combustion device in which a main burner and a reducing burner are arranged on the front wall, and depending on the case, another reducing burner is arranged for this air port, thereby increasing the temperature inside the furnace. This combustion device forms a swirling flow and improves the mixing of the main burner flame and the reducing burner flame.

Embodiments of the present invention will be described below with reference to the drawings.

1 and 2, a flame holding plate 3 is arranged at the center of the burner throat 4 of the front wall 5 of the furnace, and a plurality of main burners 1 (not shown) are arranged around this flame holding plate 3. In the case of , 4 pieces) are arranged. 8 is a manifold for fuel 11 (for example, natural gas). 2 is a reduction burner arranged around the main burner 1, and 9 is a manifold for supplying fuel 12'' to the reduction burner 2.

Next, 14 is a side wall forming the furnace 15 of the combustion device,
An air port 13 is formed in this side wall 14 . FIG. 3 shows a state in which the air port 13 is installed obliquely to the side wall, that is, in the tangential direction of the swirling flow, in order to improve the swirling of the flame within the furnace.

In this combustion device, combustion air 1 flowing into the wind box 7
0 is given a swirling force in the air register 6 and is injected from the throat 4 as combustion air for the main burner 1 to form a main burner flame. In this case, the air-fuel ratio in the main burner 1 is approximately 1 or slightly higher. On the other hand, only the fuel 12 is injected from the reducing parner 2, that is, it is injected with an air-fuel ratio of 0, and the oxygen remaining in the furnace 15 performs low-oxygen combustion to form a reducing flame.

Next, another combustion air 1o is supplied from the air port 13,
By supplying this air, a swirling flow as shown in Figs. 2 and 3 is generated in the furnace, and the main flame and the reducing burner flame mix well, and the (1!N, NH NOx in the main burner flame is reduced to N2 by reducing intermediate products such as.

In this case, NOx can be reduced by supplying the total amount of combustion air supplied from the main burner 1 and combustion air supplied from the air port 13 so that the air-fuel ratio with respect to the total amount of fuel supplied to the device is approximately 1.1. It was confirmed that the combustion rate was high and the amount of unburned matter generated was small.

FIG. 4 shows a second embodiment. In this embodiment, instead of the air port 13 shown in the previous embodiment, an air nozzle 20 is arranged at approximately the same location as the air port 13. As shown in FIG. 4, the air nozzle 2o is bent so that its opening end faces downstream of the burner flame. Reference numeral 21 denotes a reduction burner placed near the installation part of this air nozzle 20, and is installed in addition to or in place of the reduction burner 2 installed on the front wall of the furnace wall as shown in FIG.

However, the one shown in FIG. 5 shows one installed on the side wall instead of the reduction burner installed on the front wall.

Next, the combustion state of this device will be explained with reference to FIGS. 4 and 5. The flame from the main burner 1 attached to the front wall 5 is transmitted sequentially from the flame upstream side to the main combustion zone 22. Reduction burner 21
Denitrification zone 23, where denitrification is carried out in the furnace by mixing with the flame of Complete combustion zones 24 are each formed in which unburned matter is combusted by combustion air supplied from the air nozzles. In this case, since the flame of the reduction burner 21 rotates in the furnace 15, the residence time in the furnace becomes long, and sufficient time can be taken for the reduction reaction of NOx.

By implementing this invention, part of the combustion air is allowed to flow in from the side wall of the furnace, making it possible to swirl the flame.
Ox and reducing intermediate products are mixed well, and the denitrification effect can be enhanced.

In addition, since combustion air is supplied again downstream of the flame, the unburned matter generated mainly in the reducing burner flame can be burned, reducing the amount of unburned matter discharged outside the furnace. I can do it.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of a combustion device showing a first embodiment of the present invention, Fig. 2 is a cross-sectional view taken along line A-A in Fig. 1, and Fig. 3 is a schematic cross-sectional view with the air port installed differently. 4 is a sectional view of a furnace showing another embodiment, and FIG. 5 is a longitudinal sectional view of the combustion apparatus shown in FIG. 4. 1... Main burner 2, 21... Reduction burner 5... Furnace front wall 1o... Combustion air 13... Air port 14 ...! ...
Furnace side wall 15... Furnace □ ゛・2o...
・Air nozzle M3 diagram

Claims (1)

[Scope of Claims] 1. In a device that reduces nitrogen oxides produced by combustion in a main burner with reducing intermediate products produced by combustion in a reduction burner, the main burner is installed on the front wall of the furnace, and the main burner is installed on the side wall of the furnace. forms an air port that supplies part of the combustion air, and the combustion air supplied from this air port forms a swirling flow in the furnace to improve the mixing of nitrogen oxides and reducing intermediate products. A swirl-type combustion device characterized by the following: 2. The swirl-type combustion apparatus according to claim 1, characterized in that, in place of the air port, an air nozzle whose end opens downstream of the flame is attached to the furnace side wall. 3. The swirl-type combustion device according to claim 2, characterized in that a reduction burner is installed on the side wall of the furnace near the air nozzle installation part in place of or in addition to the reduction burner installed on the front wall of the furnace. .