JPH06341610A - Combustor - Google Patents

Abstract

PURPOSE:To reduce the amount of NOx emitted from a combustor without reducing the amount of gas fuel for use in a pilot nozzle. CONSTITUTION:In a combustor such as gas turbine combustor, at least one reducing gas nozzle 31 is provided on the outer peripheral part of the end (or on the inner wall surface) of a burner throat 6 for a pilot nozzle and a reducing gas fuel 34 is blown from this nozzle 31 to the interior and forward end part of the diffusion flame 20 formed by the burning of pilot nozzle gas fuel 18 to form a reducing region 36.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustor applied to a gas turbine, a gas fired boiler, a chemical industrial furnace and the like.

[0002]

2. Description of the Related Art FIG. 5 is a cross-sectional view showing a conventional combustor applied to a gas turbine as an example of the prior art, and FIG. 6 is an enlarged detailed view of a pilot nozzle portion in FIG. FIG. 7 is an enlarged detailed view of one main nozzle portion in FIG.

In these figures, a combustor inner cylinder 2 is provided inside the combustor body 1. A plurality of premixing type main nozzles 3 are circumferentially arranged on one end side of the combustor inner cylinder 2, and a pilot nozzle 4 is provided in the central portion thereof. Further, burner throats 5 and 6 are provided on the outer peripheral portions of the tips of the main nozzle 3 and the pilot nozzle 4, respectively. Pilot nozzle 4
A swirl vane 7 is provided between the burner throat 6 and the burner throat 6, and an ignition electrode 8 is provided near the tip of the pilot burner 4 as shown in FIG. Furthermore, the inside of the combustor inner cylinder 2 forms a combustion chamber 9, and the space outside thereof, that is, the space between the inner surface of the combustor main body 1 and the combustor inner cylinder 2 is an air flow passage 10. In FIG. 5, 11 is a gas turbine chamber.

In the configuration described above, the combustion air 12 sent into the combustor body 1 from the air compressor (not shown) is the primary air 13 for the pilot nozzle and the primary air 1 for the premixing main nozzle. The secondary air 14 and the secondary air 15 are divided into three systems. Then, the primary air 13 for the pilot nozzle is sent into the throat 6 of the pilot nozzle 4 through the swirl vanes 7, and the primary air for the premix type main nozzle 1
The secondary air 14 is sent into the throat 5 of each premixing type main nozzle 3, and the secondary air 15 further flows through the air flow path 10 and passes through a large number of secondary air holes 16 to burn in the combustor inner cylinder 2. It is sent to the chamber 9.

On the other hand, the gas fuel 17 sent from a gas fuel supply facility (not shown) is a pilot nozzle gas fuel 18 and a premix type main nozzle gas fuel 19
It is divided into two systems. Then, the pilot nozzle gas fuel 18 is fed into the pilot nozzle 4, and the pilot nozzle burner throat 6 is supplied from the plurality of pilot nozzle gas fuel injection holes 4a formed at the tip thereof.
Is injected into the burner throat 6 for ignition by the ignition electrode 8 (see FIG. 6) and swirled into the burner throat 6 for the pilot nozzle.
A flame is formed and combustion is continued while diffusing and mixing with the primary air 13 for the pilot nozzle sent through the flame. The flame formed is a diffusion flame 20.

In addition, the premixed main nozzle gas fuel 1
9 is sent to each premixing type main nozzle 3, and is injected into the premixing type main nozzle burner throat 5 from a plurality of premixing type main nozzle gas fuel injection holes 3a formed at the tip thereof. . In this case, as shown in detail in FIG. 7, the injection direction of the premixed main nozzle gas fuel 19 is separately sent into the burner throat 5 from the outer peripheral portion of the premixed main nozzle 3. In order to perform the mixing with the primary air 14 for the premixing main nozzle quickly and effectively, it is blown at about 90 ° with respect to the flow of the primary air 14 for the premixing main nozzle. .

The premixed main nozzle burner throat 5 and the primary air 14 blown into the premixed main nozzle burner throat 5 in this manner are fed into the premixed main nozzle burner throat 5. After being sufficiently mixed, they are blown into the combustion chamber 9 and ignited by the diffusion flame 20 formed by the pilot nozzle 4 to form a premixing flame 21.

The diffusion flame 20 formed by the pilot nozzle 4 is a premixing flame 2 formed by the premixing type main nozzle 3.
I stabilize the ignition of 1. That is, since the premixed flame 21 formed by the premixed main nozzle 3 has a high speed of blowing out the premixed gas and does not have a flame stabilizer, it is difficult to hold the flame by itself. Further, if a flame stabilizer is provided in the premixing type main nozzle 3 and the ignition point is approached, flashback occurs when the premixed gas flows back to another place, and the premixing type main nozzle 3, the burner throat 5, and the flame holding There is concern about burning of vessels. Therefore, the stable ignition of the premixed flame 21 formed by the premixed main nozzle 3 is maintained by the diffusion flame 20 formed by the pilot nozzle 4.

Further, in a gas turbine combustor, normally, the fuel distribution ratio of the premixed main nozzle gas fuel 19 is 90% or more of the total gas fuel 17, and the pilot nozzle gas fuel 18 accounts for several% of the whole. Not too much. And
In the conventional gas turbine combustor, the air ratio of the premixing flame 21 formed by the premixing main nozzle 3 [= the amount of primary air 14 for the premixing main nozzle / (the amount of gas fuel 19 for the premixing main nozzle 19 X theoretical air amount)] to about 2.0, and the air ratio of the diffusion flame 20 formed by the pilot nozzle 4 [= amount of primary air 13 for pilot nozzle / (amount of gas fuel 18 for pilot nozzle x theoretical air Amount)] about 0.8-1.0
And the combustion is almost completed in the first half of the combustion chamber 9.

In the latter half of the combustion chamber 9, the combustion gas thus generated is mixed with the secondary air 15 separately sent into the combustion chamber 9 and adjusted to a predetermined temperature to drive the gas turbine. The exhaust gas 22 (containing O ₂ ≈10.5%) is sent to the gas turbine chamber 11.

[0011]

By the way, the NOx content in the exhaust gas 22 for driving the gas turbine generated by the conventional gas turbine combustor described above is about 60 ppm.
(O ₂ = 15% basis). And
Recently, from the viewpoint of environmental protection, NOx in gas turbine exhaust gas
The momentum for restraint is increasing, and improvements in gas turbine combustors are needed.

That is, in the conventional gas turbine combustor, the fuel distribution ratio of the premixing type main nozzle 3 is planned to be about 90 to 95% as described above, but the premixing type main nozzle 3 is formed. Since it is difficult to hold the premixed flame 21 by itself, it is necessary to stabilize the ignition by the flame formed by the pilot nozzle 4. Therefore, the flame formed by the pilot nozzle 4 is required to be always stable and have a length and size capable of stably holding all the flames of the plurality of premixing type main nozzles 3. It is well known that the diffusion flame 20 becomes longer than the flame 21. Therefore, many conventional pilot nozzles 4 have been considered to form the diffusion flame 20.

The NOx contained in the combustion exhaust gas 22 produced by such a gas turbine combustor is
N generated from the premixed flame 21 having a fuel distribution ratio of 90% or more and the diffusion flame 20 having a fuel distribution ratio of several%.
It is the sum of Ox.

FIG. 8 shows an example of a combustion test result using a gas fuel and shows the relationship between the NOx generation amount and the air ratio. From FIG. 8, if the fuel distribution ratio is premixed flame 21 / diffusion flame 20 = 95% / 5%, (1) air ratio = 2.0
The NOx generation amount of the premixed flame 21 is 8 ppm, and (2) the NOx generation amount of the diffusion flame 20 having an air ratio of 0.8 to 1.0 is 170 ppm at an air ratio of 0.9. N
Ox is (premixed flame side: 8 x 0.95 = 7.6 ppm) +
(Diffusion flame side: 170 × 0.05 = 8.5 ppm) = 16.
Since it is 1 ppm, (4) NOx is (7.6 / 16.1) × 100 = 47.2% from the side of the premixed flame, and (8.5 / 16.1) × 100 = 52. It means that it occurs at a rate of 8%.

As described above, in the diffusion flame 20 formed by the pilot nozzle 4, the NOx generation amount occupies as much as 1/2 or more of the whole, even though the fuel distribution ratio is several% of the whole. Furthermore, in order to reduce NOx, it is necessary to reduce the fuel distribution ratio of the pilot nozzle 4, but this may impair the combustion stability of the entire gas turbine combustor, so this is also a limit.

The present invention has been made to solve the problems of the prior art, and in a combustor such as a gas turbine combustor, the gas fuel for the pilot nozzle is discharged from the combustor without reducing the amount thereof. The purpose is to reduce the amount of NOx generated.

[0017]

In order to solve the above-mentioned problems, the present invention is directed to a combustor such as a gas turbine combustor at the tip outer peripheral portion of the burner throat for a pilot nozzle or on the inner wall surface of the burner throat. The reducing gas fuel is blown into the inside of the diffusion flame formed by the combustion of the pilot nozzle gas fuel and the tip of the diffusion flame.
At least one reducing gas nozzle is provided.

[0018]

According to the above means, the reducing gas fuel is supplied from the reducing gas nozzle provided on the outer peripheral portion of the tip of the burner throat for the pilot nozzle or on the inner wall surface of the burner throat,
Blown in the diffusion flame formed by combustion of the pilot nozzle gas fuel and the tip of the diffusion flame,
Form a reducing region. Therefore, NOx generated from the diffusion flame is decomposed in this reduction region, and most of it is N ₂
Therefore, the residual NOx in the combustion gas generated by the gas fuel for the pilot nozzle is drastically reduced. As a result, the amount of NOx discharged from the combustor can be reduced without reducing the amount of gas fuel for the pilot nozzle.

[0019]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a sectional view showing an embodiment in which the present invention is applied to a gas turbine combustor.
The same parts as those shown in FIGS.

As shown in FIG. 1, according to the present embodiment, a plurality of reducing gas nozzles 31 are provided on the outer peripheral portion of the tip of the burner throat 6 for pilot nozzle. When there is no space to install the reducing gas nozzle 31 on the outer periphery of the tip of the burner throat 6 for pilot nozzles, as shown in FIG. The gas nozzle 31 is provided. Each reducing gas nozzle 31 is connected to a reducing gas nozzle header 32, and the reducing gas nozzle header 32 is connected to a reducing gas fuel pipe 33.

A portion 34 of the pilot nozzle gas fuel 18 is supplied to the reducing gas fuel pipe 33 as the reducing gas fuel. Therefore, the reducing gas fuel 34 is used as the reducing gas fuel pipe 33 and the reducing gas nozzle header 32.
Is supplied to and injected through the reducing gas nozzle 31. In this case, for example, in the embodiment shown in FIG. 2, since the reducing gas nozzle injection hole 35 is bored straight and inward (toward the diffusion flame 20) at the tip of the reducing gas nozzle 31, the reducing gas is reduced. The fuel 34 is blown from these injection holes 35 into the inside of the diffusion flame 20 formed by the combustion of the gas fuel 18 for the pilot nozzle and the tip portion of the diffusion flame 20, and forms the reduction region 36 (see FIG. 1).

Therefore, the NO generated by the diffusion flame 20
x (mostly NO) is in the reduction region 36, It is decomposed by chemical reaction such as. Here, in the above formula, * represents a radical at the initial stage of the chemical reaction, and NHi represents the N compound as a representative.

It is generally known that the NO decomposition reaction is more active as the reaction zone temperature is higher and the air ratio in the reduction zone is lower. That is, the experimental results conducted by the present inventors will be described with reference to FIGS. 3 and 4. FIG.
FIG. 4 shows the relationship between the O decomposition rate [= {(1-reduction area outlet NO) / reduction area inlet NO} × 100] and the air ratio in the reduction area, and FIG. 4 shows the relationship between the NO decomposition rate and the gas temperature in the reduction area. Show the relationship. As is clear from these figures, the NO decomposition rate tends to be higher as the air ratio in the reduction region is lower than that in FIG. 3, and the gas temperature in the reduction region is 1000 ° C. or higher as shown in FIG. To 12
It can be seen that the temperature is higher than 00 ° C.

Therefore, in consideration of these matters, in the present invention,
Since the diffusion flame 20 shown in FIG. 1 is used as a strong stabilizer, an air ratio (≈) that can maintain stable ignition and combustion.
1), and then the reducing gas fuel 34 is injected into the high temperature region inside the diffusion flame 20 and at the tip of the diffusion flame 20 to form a high temperature / low air ratio reduction region 36. This is intended to reduce the NOx generated.

In the above-described embodiment, the pilot nozzle gas fuel 18 is used as the reducing gas fuel 34.
Although a part of the gas fuel 17 is used, it is not limited to this, and a part of the gas fuel 17 can be diverted from an appropriate location for use. Further, the reducing gas nozzle 31 may be single. Furthermore, the present invention can be widely applied not only to gas turbine combustors, but also to combustors such as gas-fired boilers and chemical industrial furnaces.

[0026]

As described above, according to the present invention, in a combustor such as a gas turbine combustor, at least one reduction is provided on the outer periphery of the tip of the burner throat for the pilot nozzle or on the inner wall surface of the burner throat. Since the reducing gas fuel is provided from the nozzle to blow the reducing gas fuel into the diffusion flame formed by the combustion of the pilot nozzle gas fuel and into the tip of the diffusion flame, the reducing region is formed. Most of the NOx generated from the diffusion flame is reduced in this reduction region without reducing the amount of the gas fuel for use, and the NO discharged from the combustor is reduced.
It is possible to reduce x.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment in which the present invention is applied to a gas turbine combustor.

FIG. 2 is a sectional view of a pilot nozzle portion showing another embodiment of the present invention.

FIG. 3 is a diagram showing a relationship between a NOx decomposition rate and a reduction region air ratio.

FIG. 4 is a diagram showing a relationship between a NOx decomposition rate and a reduction region gas temperature.

FIG. 5 is a sectional view showing a conventional gas turbine combustor.

FIG. 6 is an enlarged detailed view of a pilot nozzle portion in FIG.

FIG. 7 is an enlarged view showing in detail one main nozzle portion in FIG.

FIG. 8 is a diagram showing a relationship between NOx and an air ratio.

[Explanation of symbols]

 3 Main Nozzle 4 Pilot Nozzle 6 Burner Throat for Pilot Nozzle 12 Combustion Air 17 Gas Fuel 18 Gas Fuel for Pilot Nozzle 20 Diffusion Flame 31 Reduction Gas Nozzle 34 Reduction Gas Fuel 36 Reduction Area

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masaharu Oguri 5-717-1, Fukahori-cho, Nagasaki-shi, Nagasaki Nagahishi Engineering Co., Ltd.

Claims (2)

[Claims] 1. A reduction gas fuel is blown into the inside of a diffusion flame formed by combustion of gas fuel for a pilot nozzle, and at least one reduction gas fuel is blown into the tip portion of the diffusion flame at the outer periphery of the tip of a burner throat for a pilot nozzle. A combustor having a gas nozzle for use. 2. At least one reduction in which a reducing gas fuel is blown into the inside of a diffusion flame formed by combustion of the gas fuel for the pilot nozzle and the tip portion of the diffusion flame on the inner wall surface of the burner throat for the pilot nozzle. A combustor having a gas nozzle for use.