JPH0480285B2 - - Google Patents

Description

[Detailed Description of the Invention] (Field of Application of the Invention) The present invention relates to a denitrification burner, which is particularly suitable for reducing nitrogen oxides (hereinafter referred to as NOx) in exhaust gas when applied to an in-furnace denitrification combustion method. This relates to the structure of a denitrification burner.

Since NOx is considered to be one of the causative agents of photochemical oxidants and acid rain, there has been a demand in recent years for the development of combustion methods that effectively suppress the generation of NOx.

Combustion methods that meet these objectives include (1) exhaust gas recirculation method, (2) two-stage combustion method, and (3) in-furnace denitrification combustion method, among which the NOx reduction effect is The in-furnace denitrification combustion method is attracting particular attention because of its excellent properties. Conventionally, the equipment applied to this method is
As shown in the figure, a lower stage (main) burner 2, a middle stage (main) burner 3, and an upper stage (denitration) burner 4 are installed in order from below to above on the front and rear walls of the furnace 1, and the upper stage burner 4 is located above the upper stage burner 4. It is mainly composed of an after-air port 5 provided in the. In addition, in the figure, 6
1 is a wind box, which is partitioned by a partition plate 7 corresponding to each stage burner and after air port, and 10 and 11 are gas flow control valves provided upstream of the waste combustion main pipe 12, respectively. and a gas cutoff valve, the downstream flow of the main pipe 12 is branched corresponding to each burner stage, and each of the branch pipes is provided with a burner inlet valve 13.

In such a configuration, the air-fuel ratio is set to 1 or more in the burner section, and combustion of gas fuel is performed (for example, lower stage burner 2: 0.8 to 1.0, middle stage burner 3: 0.6 to 1.0, upper stage burner 4: 0.3 to 0.6 ).

In this case, the combustion flame occurred in the combustion flame area 8 of the lower burner 2 and middle burner 3, where there is a relatively large amount of air.
NOx comes into contact with reducing radicals such as ・CN, ・NH ₂ and ・NH generated in the combustion flame zone 9 of the upper stage burner 4 where there is excess fuel, and is reduced to N ₂ , thereby achieving low NOx. The Rukoto.

Incidentally, each stage of the burner described above is generally as shown in FIG. 4, and from the center to the outer periphery, the flame stabilizing plate 14 for flame stabilization, the speed adjustment vane 15 of the secondary air 19, and the burner inlet valve are installed in order from the center to the outer periphery. Gas fuel injection nozzle 1 opening into a gas fuel branch pipe equipped with 13
6. The structure includes a throttle valve 17 for the tertiary air 20 and a throat 18 that widens toward the inside of the furnace.

The air ratio setting described above is performed by each stage burner having such a configuration, but at this time, the gas fuel supply is kept almost constant by operating the burner inlet valve 13, so that the air supply amount is set to the upper stage burner. adjusted to be as small as possible. This adjustment is performed by throttling the speed adjusting vane 15 and throttle valve 17 to reduce the air passage cross-sectional area of the throat portion.

In this way, in the conventional in-furnace denitrification combustion method, the upper burner, which is the denitrification burner, has the same structure as the lower and middle burners, which are the main burners, and its function as a denitrification burner is affected by the relative reduction in the amount of air supplied. It was given.

However, when such a burner is used as a denitrification burner, the following drawbacks cannot be avoided. The first drawback is that a sufficient flame penetration force cannot be obtained due to the occurrence of vortices downstream of the speed regulating vane 15 and the decrease in air flow rate as the throttling ratio of the vane increases. The problem is that mixing with the combustion gas generated in the process is insufficient, and there is a limit to the denitrification effect. The second drawback is that the recent
This is difficult to deal with regarding NOx regulations. In other words, conventional NOx regulations were based on the total amount or the boiler's rated output, but in recent years, NOx has been
There is a growing demand to reduce the concentration. When responding to such requests with conventional denitrification burners, it takes time as it is necessary to throttle the speed adjustment vane until an air-fuel ratio suitable for the denitrification reaction is obtained. The problem is that it can't be done.

The purpose of the present invention is to overcome the drawbacks of the prior art,
It is easy to transition to denitrification combustion and reduces exhaust gas, etc.
An object of the present invention is to provide a denitrification burner for denitrification combustion in a furnace that can reduce NOx.

In order to achieve the above object, the present invention provides a burner equipped with a fuel injection nozzle and a throat downstream of the nozzle, which is configured such that the operating area of the gas fuel nozzle can be increased or decreased depending on the load situation. In addition, the throat has a bench lily structure, and its air passage cross-sectional area is that of the main burner.
It is characterized by being 0.3 to 0.6 times larger.

In the present invention, the means for increasing or decreasing the operating area of the fuel (typically gas fuel) jetting nozzle depending on the load situation may be any known means, but preferably there are two systems of gas fuel branch pipes, and each Preferably, burner inlet valves are provided, and the same number of burner sections are provided via a double ring-shaped body that opens into either of the above-mentioned systems, so that one or both of the burner systems can be used selectively. In this case, the fuel amount can be adjusted from doubling to half by switching, but the present invention is not limited to this range.

With this configuration of the present invention, the air passage cross-sectional area of the throat is suppressed to 0.3 to 0.6 times that of the main burner, and the operating area of the gas fuel injection nozzle is reduced during low load such as startup. Normal combustion is possible by reducing the amount of fuel by half (the amount of fuel supplied is also halved, so the air ratio increases to 0.8 to 1.0). On the other hand, if denitrification combustion becomes necessary as the load increases, the gas fuel injection nozzle By simply doubling the operating area, the amount of fuel supplied can be doubled, and the air ratio can be reduced accordingly to 0.3 to 0.6, making it possible to shift to denitrification combustion in a short time. . Moreover, by making the throat part a bench lily structure with low air resistance,
It is possible to control vortex generation in the wake and improve flame penetration, thereby further promoting the denitrification reaction.

Hereinafter, the present invention will be explained in more detail with reference to embodiments shown in the drawings.

FIG. 1 shows a side cross section of a denitrification burner according to an embodiment of the present invention, and shows parts having the same reference numerals and explanations as shown in FIG. 4, and an inner ring 25A.
and an outer ring 25B, four inner burners 16A extending from the inner ring 25A, four outer burners 16B extending from the outer ring 25B, and a throat 23 having a bench lily structure. configured. In the figure, 21 indicates a sleeve for adjusting the amount of secondary air, and 22 indicates a sleeve for adjusting the amount of tertiary air.

In addition, the above-mentioned inner ring 25A and outer ring 2
5B, as shown in FIG. 2, each opens into one of two branch pipes branched from the gas fuel main pipe 12, and each of the branch pipes has burner inlet valves 13A and 13B (see FIG. 2). ) is provided. The air passage cross-sectional area S of the bench lily structure throat 23 is set to be 0.3 to 0.6 times that of the main burner.

In a denitrification burner with such a configuration, NOx
When the load is low, such as during startup, when there is little occurrence of
If either one of 13B and 13B is closed and the amount of gas fuel supplied is halved, normal combustion with excellent combustion efficiency can be performed at an air ratio of about 0.8 to 1.0.
On the other hand, if denitrification combustion is desired as the load increases, the burner inlet valve, which was previously closed, can be opened to double the amount of fuel supplied, resulting in an air ratio of 0.3 to 0.6.
Denitrification combustion suitable for forming a reducing atmosphere can be performed at a certain level. Moreover, in this case, the throat 23
Because it has a bench lily structure with low air resistance,
It is possible to suppress the generation of vortices in the wake and improve the penetration power of the flame 24.

If such a denitrification burner is applied in place of the upper stage burner 4 in FIG. This can be achieved by simply opening the burner inlet valve of the burner, thereby reducing the transition time. This is particularly effective in the operation of DSS boilers, which have such strong requirements.

Furthermore, during denitrification combustion, it is possible to form a good reducing atmosphere, suppress the generation of vortices in the wake of the throat, and improve flame penetration, so that NOx generated in the upstream main burners (lower burner 2 and middle burner 3) is This improves the miscibility of the denitrification reaction, which further promotes the denitrification reaction.

The above describes typical embodiments of the present invention. The present invention is not limited to this, and various other modifications can be considered. For example, the penetrating force of the denitrification burner flame described above can be achieved by increasing the amount of air passing through the throat by manipulating the secondary air amount adjustment sleeve 21 and the tertiary air amount adjustment sleeve 22 in addition to using a bench lily structure for the throat. It can be further increased.

(Effects of the Invention) As described above, according to the present invention, regarding the denitrification burner applied to the in-furnace denitrification combustion method, the operating area of the fuel jet nozzle can be increased or decreased depending on the load situation, and the throat has a bench lily structure. In addition, by making the air passage cross-sectional area 0.3 to 0.6 times that of the main burner, the nozzle operating area is halved during low loads such as during startup, allowing normal combustion to be carried out, and even when the load increases. If denitrification combustion is desired, this can be achieved by doubling the nozzle operating area. Moreover, the transition from normal combustion to denitrification combustion is possible in a short time, and after the transition to denitrification combustion, the penetration power of the reducing flame is improved due to the effect of the throat having a bench lily structure with low air resistance. , the miscibility with NOx generated in the upstream main burner is improved. This further accelerates the denitrification reaction, making it possible to reduce NOx.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view of a denitrification burner according to an embodiment of the present invention, FIG. 2 is a partial front view showing the burner section of the denitrification burner shown in FIG. 1 together with a gas fuel supply system, and FIG. FIG. 4 is a side sectional view of a denitrification burner applied to the device shown in FIG. 3. FIG. 1...Furnace, 2...Lower stage (main) burner, 3...
Middle stage (main) burner, 4... upper stage (denitrification) burner,
9... Upper burner combustion flame area, 12... Gas fuel main pipe, 13, 13A, 13B... Burner inlet valve,
15... Secondary air speed adjustment vane, 16... Gas fuel injection nozzle, 16A... Inner burner, 16
B... Outer burner, 17... Throttle valve, 18... Throat, 19... Secondary air, 20... Tertiary air,
21... Secondary air amount adjustment sleeve, 22... Tertiary air amount adjustment sleeve, 23... Bench lily structure throat, 24... Flame, 25A... Inner ring,
25B...Outer ring.

Claims (1)

[Claims] 1. In the case where a fuel injection nozzle and a throat are provided downstream of the nozzle, the operating area of the fuel injection nozzle can be increased or decreased depending on the load situation, and the throat has a bench lily structure, Its air passage cross section is that of the main burner.
A denitrification burner characterized by a ratio of 0.3 to 0.6.