JPS60226610A - Denitration burner - Google Patents

Abstract

PURPOSE:To facilitate migration of a burner to denitration combustion and to reduce production of nitrogen oxide in exhaust gas, by a method wherein the working area of an injection nozzle for fuel is adjustable according to a load condition, and a throat is of a Venturi structure. CONSTITUTION:An inner ring 25A and an outer ring 25B of a denitration burner are respectively open to either of 2 branch pipe systems branched from a gas fuel main pipe 12. During low load operation during the starting in which production of nitrigen oxide is decreased, if an mount of gas fuel supplied is reduced to half by closing either burner inlet valves 13A or 13B respectively mounted in the fuel branch pipes, and in which case, ordinary combustion having an air ratio of about 0.8-1.0, which is excellent in combustion efficiency, is practicable. Meanwhile, in case denitration combustion is needed with the increase in a load, an amount of the fuel supplied is doubled through opening control of the two burner inlet valves, and this enables to perform denitration combustion, having an air ratio of about 0.3-0.6, which is well suitable for formation of a reduction atmosphere. Besides, in which case, a throat 23 is designed to be of a Venturi structure, in which air flow resistance is decreased, and this enables prevention of generation of vortex at a following wake and improvement of the penetration force of a flame 24.

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 a combustion method that effectively suppresses the generation of NOx.

As combustion methods for this purpose, (1) exhaust gas recirculation method, (2) two-stage combustion method, and (3) in-furnace denitrification combustion method are known, but among these, NOx reduction effect is The in-furnace denitrification combustion method is attracting particular attention because of its excellent properties. Conventionally, the apparatus applied to this method has a furnace 1 as shown in FIG.
A lower stage (main) burner 2, a middle stage (main) burner 3, and an upper stage (denitrification) burner 4 are provided in order from the bottom to the top on the front and rear walls of the It mainly consists of 5. In addition, in the figure, 6
1 is a wind box, which is partitioned by a partition plate 7 to correspond to each stage burner and after aero, and 10 and 11 are gas flow control valves and gas flow control valves provided upstream of the gas fuel main pipe 12, respectively. A gas cutoff valve branches the downstream stream of the main pipe 12 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: O, S ~ 1.0, middle stage burner 3: 0.6 ~ 1.0.
0, upper burner 4: o, 3-0.6).

In this case, NOx generated in the combustion fire area 8 of the lower stage burner 2 and middle stage burner 3, where there is a relatively large amount of air, is generated in the combustion fire area 9 of the upper stage burner 4, where there is excess fuel.
, ・NH2 and ・NH in contact with reducing radicals such as
2, thereby achieving a reduction in NOx.

By the way, each stage of the burner described above is generally as shown in FIG. It has a configuration including a gas fuel injection nozzle 16 that opens into a gas fuel branch pipe equipped with a gas fuel branch pipe, a throttle valve 17 for 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, and at that time, the gas fuel is supplied through the burner inlet valve 1.
By the operation 3, the air supply amount is adjusted to be almost constant, so that the air supply amount is adjusted to be smaller as the burner becomes a two-stage burner. 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 sufficient fire penetration force cannot be obtained due to the occurrence of eddies 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 NO.
It is difficult to deal with the x regulations. In other words, conventional NOx regulations were based on the total amount or the boiler's rated output, but recently there has been a strong demand to reduce the NOxfi degree from an extremely low load stage, such as 10% of the turbine rated output. It has become. 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.

An object of the present invention is to provide a denitrification burner for in-furnace denitrification combustion that eliminates the drawbacks of the prior art, allows easy transition to denitrification combustion, and reduces NOx in exhaust gas.

In order to achieve the above object, the present invention provides a burner equipped with a fuel jet nozzle and a throat downstream of the nozzle, in which the operating area of the gas fuel jet nozzle can be increased or decreased according to load conditions. The present invention is characterized in that the throat has a Hentschuri structure, and its air passage cross-sectional area is 0.3 to 0.6 times that of the main burner.

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, in combination with suppressing the air passage cross-sectional area of the throat to 0.3 to 0.6 times that of the main burner, the gas fuel injection nozzle Normal combustion is possible by reducing the operating area 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, By simply doubling the operating area of the gas fuel injection nozzle, the amount of fuel supplied can be doubled, and the air ratio can be reduced to 0.3 to 0.6, leading to a transition to denitrification combustion. can be done in a short time. Furthermore, by making the throat part a venturi structure with low air resistance, it is possible to suppress the generation of vortices in the wake and improve the flame penetration power, 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, showing portions to which reference numerals and explanations similar to those shown in FIG.
It is mainly composed of a double ring-shaped body consisting of B, four inner burners 16A extending from an inner ring 25A, four outer burners 16B extending from an outer ring 25B, and a throat 23 having a venturi structure. . 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.

Moreover, the above-mentioned inner ring 25A and outer ring 25B are
As shown in FIG. 2, each opens into one of the branch pipes branched into two systems from the gas fuel main pipe 12, and the burner inlet valves 13A and 13B (second
(see figure) is provided. The air passage cross-sectional area S of the venturi structure throat 23 is 0.3 of that of the main burner.
It is set to ~0.6 times.

In a denitrification burner with such a configuration, during low load such as during startup when little NOx is generated, either one of the burner inlet valves 13A and 13B provided in the fuel (gas) branch pipe is closed to supply gas fuel. If the amount 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, by opening the burner inlet valve that was closed as described above and doubling the amount of fuel supplied, a reducing atmosphere can be created with an air ratio of about 0.3 to 0°6. Denitrification combustion suitable for formation can be performed. Moreover, in this case, since the throat 23 has a venturi structure with low air resistance, it is possible to suppress the generation of vortices in the wake and to increase the penetration direction of the fire 24.

If such a denitrification burner is applied in place of the upper burner 4 in FIG. 3, combustion efficiency at low loads can be improved, and
If you do not wish to shift to denitrification combustion due to an increase in load,
This can be achieved by simply opening a closed burner inlet valve, thereby reducing transition times. 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 fire penetration, so that NOx generated in the upstream main burners (lower stage burner 2 and middle stage burner 3) can be reduced. This improves the miscibility of the denitrification reaction, which further promotes the denitrification reaction.

Although typical embodiments of the present invention have been described above, the present invention is not limited thereto, and various other modifications can be considered. For example, the penetrating force of the denitrification burner fire 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 venturi 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 venturi 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 load times such as during start-up, allowing normal combustion to be carried out, and even when the load increases. If unique denitrification combustion is desired, this can be achieved by doubling the nozzle operating area. Moreover, the transition from the above-mentioned normal combustion to denitrification combustion is possible in a short time, and after the transition to denitrification combustion, the penetration power of the reduction fire is improved due to the effect of the throat having a venturi structure with low air resistance. , the miscibility with NOx generated in the upstream main burner is improved. This further promotes the denitrification reaction, making it possible to reduce NOx.

[Brief explanation of drawings]

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 part 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 apparatus shown in FIG. 3. FIG. 1...Furnace, 2...Lower stage (main) burner, 3...Middle stage (main) burner, 4...Upper stage (denitrification) burner, 9...
・Upper stage burner combustion flame area, 12... Gas fuel main pipe, 1
3.13A, 13B... Burner inlet valve, 15... Secondary air speed adjustment vane, 16... Gas fuel injection nozzle, 16A... Inner burner, 16B... 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, 2
3... Venturi structure throat, 24... Flame, 2
5A...inner ring, 25B...outer ring. Agent Patent Attorney Takeshi Kawakita 1

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 venturi structure. Also, a denitrification burner characterized in that its air passage cross-sectional area is 0.3 to 0.6 times that of the main burner.