JP2003279043A - Low NOx combustor for gas turbine - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To control essentially the problems of spontaneous ignition, flashback, oscillating combustion, etc. of a premixed lean burn type air-fuel mixture, have small pressure loss, and control air flow and fuel flow. Is easy,
Simple structure, low N comparable to premixed lean burn
Provided is a low NOx combustor for a gas turbine that can be converted to Ox. SOLUTION: A central fuel injection pipe 12 having a central fuel injection port 11 at a front end and disposed at a center portion, and an annular duct which surrounds the central fuel injection pipe at intervals and forms a combustion air flow path 13 therebetween. 14 and a combustion chamber chamber 16 for expanding gas exiting the air passage. Combustion air passage 1
3 indicates that the flow path area gradually increases after gradually decreasing and during this time the throat portion 1
3a and a throat injection port 15 for injecting fuel into the throat portion.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low NOx combustor for a gas turbine, which can stably burn low-calorie gas and reduce NOx.

[0002]

2. Description of the Related Art In recent years, in order to protect the environment, it is obligatory to reduce NOx (nitrogen oxide) in exhaust gas from combustion by a gas turbine. Therefore, in a conventional low NOx combustor for a gas turbine, a combination of a plurality of main burners for performing lean combustion by a premixed lean combustion method and a pilot burner for performing flame holding by a diffusion combustion method is mainly used. Was there.

In such a premixed lean burn type combustor,
In the main burner, the fuel is premixed with a sufficient amount of air and the fuel is lean-burned. Therefore, there is no hot spot, high temperature flame is eliminated, and low NOx can be realized.

[0004]

However, in the premixed lean burn type combustor, it is necessary that the fuel and the air are sufficiently mixed, and the NOx generation amount increases in the portion where the fuel concentration is excessively high. On the contrary, there is a problem that the combustion temperature is low and unburned gas is generated in an excessively thin portion. Further, since the fuel and air are premixed, there is a risk of spontaneous ignition or flashback of the air-fuel mixture. If these occur, not only the NOx sudden increase, oscillating combustion, etc. will occur, but not only the performance will deteriorate, but also the equipment There was also a risk of damage to the.

In order to solve the above-mentioned problems of the premixed lean burn type combustor and to achieve low NOx, FIG.
"Low NOx burner for gas turbine" shown in JP-A-9-152105 has been proposed.

This low NOx burner includes a first air swirler 1, a first air passage 2 which is connected to the first air swirler, and whose cross section is reduced or enlarged toward the outlet, and air flowing in the first air passage. A first fuel nozzle 3 for injecting fuel into the flow, an annular second air swirler 4 mounted coaxially with the outlet of the first air passage on the outer peripheral portion thereof, and a partition of the second air swirler. The second air passage 5 including a plurality of passages in the annular passage and the second fuel nozzle 6 for injecting fuel into the air flow flowing through the second air passage are provided.

However, this low NOx burner has the following problems. (1) The pressure loss is large because the first air swirler 1 and the second air swirler 4 accelerate the mixing of air and fuel by violent turbulence. (2) Since there are two combustion air passages (the first air passage 2 and the second air swirler 4), it is difficult to distribute the air flow rate. (3) It is necessary to control the fuel flow rate in accordance with the amount of air flowing through the two air passages, which complicates the operation control for optimizing both combustions to achieve low NOx. (4) The structure becomes complicated as a whole.

In order to solve the above problems, the present invention provides
It was invented. That is, the main object of the present invention is to
The problems such as spontaneous ignition, flashback, and oscillating combustion of the air-fuel mixture of the premixed lean burn method can be essentially solved, the pressure loss is small, the air flow rate and the fuel flow rate can be easily controlled, and the structure is simple. Therefore, it is an object of the present invention to provide a low NOx combustor for a gas turbine capable of reducing NOx comparable to a premixed lean combustion system. Another object of the present invention is also applicable to a flame-retardant low-calorie gas fuel such as biomass gas, and provides a low-NOx combustor for a gas turbine that can achieve low NOx reduction and stable combustion. Especially.

[0009]

According to the present invention, there is provided a central fuel injection pipe (12) having a central fuel injection port (11) arranged at the center and having a fuel injection port (11) at the tip, and the central fuel injection pipe is spaced from the central fuel injection pipe (12). An annular duct (14) that surrounds and separates from each other to form a combustion air flow path (13) and a combustion chamber chamber (16) that expands the gas that has exited the air passage are provided, and the combustion air flow path ( 13) is a low-pressure turbine for a gas turbine, characterized in that the flow passage area gradually decreases and then gradually increases, has a throat portion (13a) therebetween, and further has a throat injection port (15) for injecting fuel into the throat portion. A NOx combustor is provided.

According to the above configuration of the present invention, the fuel is injected from the central injection port (11) and the throat injection port (15) to the combustion air passing through the combustion air flow path (13). To achieve uniform fuel concentration, NO
It is possible to suppress the x emission amount and improve the combustion efficiency.

That is, a single combustion air flow path (13)
However, since it is formed between the central fuel injection pipe (12) and the annular duct (14), it is easy to control the air flow rate. Further, the combustion air flow path (13) has a flow path area that gradually decreases and then gradually increases, and has a throat section (13a) between them, and fuel is injected into this throat section, so flashback can be effectively prevented, Moreover, since the air flow and the fuel can be efficiently mixed, the NOx can be reduced. In addition, the pressure loss is small as compared with the case where a violent turbulence is formed only by the air swirler. further,
Since the fuel from the central injection port (11) and the fuel from the throat injection port (15) form a flame at substantially the same position, it is easy to control the fuel flow rate.

Further, since the combustion chamber (16) expands the gas leaving the air passage, the throat injection port (15)
The burning velocity and the flow velocity are the same at a position away from, and a floating flame can be stably formed. Furthermore, its mixing efficiency is high,
It was confirmed in the examples that the structure is simple and that the NOx can be reduced to be comparable to the premixed lean combustion system. Further, flame-retardant low-calorie gas fuel such as biomass gas may be flame-retarded from the central injection port (11) using general fuel, and the low-calorie gas fuel may be injected from the throat injection port (15). Thus, even low-calorie gas fuel can be burned stably.

According to a preferred embodiment of the present invention, the combustion chamber chamber (16) includes an annular taper portion (16a) for gradually expanding the gas leaving the air passage into an annular shape, and the annular duct (14). And an annular recess (16b) forming an annular recess therebetween.

With this configuration, the throat injection port (15)
The flame burned at a position away from the annular taper part (16
Position where the combustion speed and the flow velocity are the same after decelerating gradually in a)
In addition, a floating flame can be stably formed. Also, the annular recess
Combustion products (H ₂O, CO₂, Etc) Lisa
Since it can be curated, low NOx can be realized.

Further, it is preferable that a swirler (13b) for imparting a swirl flow to the combustion air flow is provided in the combustion air flow path (13).

With this configuration, the combustion air flow path (13)
It is possible to impart a swirl flow to the combustion air flow, and to more effectively perform dispersion of fuel injection, uniform fuel concentration, suppression of NOx emission amount, and improvement of combustion efficiency.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will be described below with reference to the drawings. In each drawing, common portions are denoted by the same reference numerals, and redundant description will be omitted.

FIG. 1 is an overall configuration diagram of a low NOx combustor for a gas turbine of the present invention. As shown in the figure, the low NOx combustor 10 for a gas turbine of the present invention includes a central fuel injection pipe 12, an annular duct 14, and a combustion chamber chamber 16.

The central fuel injection pipe 12 has a tip (right end in the figure).
Is a closed hollow cylindrical tube and is arranged in the center of the low NOx combustor 10. Further, the central injection port 1 for injecting fuel into the combustion chamber 16 at the tip of the central fuel injection pipe 12
Has 1.

The fuel injected at the central injection port 11 is preferably the same gas fuel (for example, LNG) as the fuel injected at the throat injection port 15 described later. Further, particularly when the fuel injected from the throat injection port 15 is a flame-retardant low-calorie gas fuel such as biomass gas, in order to ensure flame holding, the fuel injected from the central injection port 11 has a combustible property. It is better to use a good gas fuel (eg LNG). The fuel injection direction of the central injection port 11 may be obliquely outward toward the floating flame formed in the combustion chamber 16 as shown in this figure.

The annular duct 14 surrounds the central fuel injection pipe 12 with a space therebetween, and forms a combustion air flow path 13 therebetween. The combustion air flow passage 13 is smoothly formed so that the flow passage area gradually decreases and then gradually increases, and has a throat portion 13a having the smallest flow passage area therebetween. Further, a swirler 13b is provided for imparting a swirling flow to the combustion air flow passing through the combustion air flow path 13 upstream of the throat portion 13a.

Further, the throat portion 13a of the annular duct 14
A throat injection port 15 for injecting fuel toward the throat portion 13a is provided in a portion surrounding the. The fuel injection direction of the throat injection port 15 is preferably obliquely inward toward the throat portion 13a as shown in this figure.

The central jet 11 and the throat jet 1
The relative position of 5 is preferably such that the throat injection port 15 is located slightly upstream of the central injection port 11, but it may be the opposite relationship position. The ejection position of the throat injection port 15 is preferably the throat portion 13a, but may be slightly downstream.

The combustion chamber chamber 16 has an annular taper portion 16 for gradually expanding the gas (air mixture) leaving the air passage into an annular shape.
a, the air-fuel mixture exiting the air passage is uniformly expanded and decelerated. In addition, the annular duct 14 and the annular tapered portion 16a
And an annular recess 16b forming an annular recess between
Combustion products (H ₂ O, CO ₂ , etc.) are to be recirculated.

According to the above-described configuration of the present invention, the combustion air flow passage 13 has a throat portion 13a between which the flow passage area gradually increases and then gradually increases, and fuel is injected into this throat portion. Can be effectively prevented, and the air flow and the fuel can be efficiently mixed, so that NOx can be reduced. Also,
The pressure loss can be reduced as compared with the case where a severe turbulence is formed only by the air swirler. Furthermore, since the fuel from the central injection port 11 and the fuel from the throat injection port 15 form the floating flame 7 at substantially the same position, it is easy to control the combustion air and the fuel flow rate.

Further, since the combustion chamber chamber 16 uniformly expands the gas (mixture) that has exited the air passage, the combustion velocity and flow velocity match at a position away from the throat injection port 15 and the floating flame 7 is stabilized. Can be formed. Further, the mixing efficiency is high, the structure is simple, and the NOx reduction comparable to the premixed lean combustion system can be achieved.

Furthermore, flame-retardant low-calorie gas fuel such as biomass gas is flame-retarded from the central injection port 11 using general fuel, and low-calorie gas fuel is injected from the throat injection port 15. It is possible to stably burn even low-calorie gas fuel.

[0028]

FIG. 2 is a configuration diagram showing an embodiment of a low NOx combustor for a gas turbine of the present invention, and FIG. 3 is a performance comparison diagram in the embodiment of the present invention. Using the combustor 10 of the present invention shown in FIG. 1, the following four combustion tests were carried out using the same fuel (LNG).

A: upstream (premixing) ... lean combustion in which air and fuel are premixed upstream of the combustion air flow path B: central ... diffusion diffusion C in which fuel is injected only from the central injection port 11: Outer periphery 1 ... Diffusion combustion in which fuel is injected only from the throat injection port D: Outer periphery 2 ... Diffusion combustion in which fuel is injected only from the downstream side of the throat injection port 15

In FIG. 3, the horizontal axis is the combustor outlet temperature, and the vertical axis is the generated NOx amount. The four curves in the figure are the test results corresponding to A to D above. From this figure, it can be seen that at the combustor outlet temperature almost equal to that of the conventional premixed lean combustion method (A), only the throat injection port 15 of C (outer circumference 1) has substantially the same NOx generation amount. Also,
It can be seen that in B (center) and D (outer periphery 2), the generated NOx amounts are of the same level at lower combustor outlet temperatures. Therefore, B (center) and C (outer circumference 1) or D
The low NOx combustor of the present invention corresponding to the combination of (periphery 2) not only essentially solves the problems of spontaneous ignition, backfire, oscillatory combustion of the air-fuel mixture, but also has a low level of combustion comparable to the lean mixed combustion system. It can be seen that NOx can be obtained.

The present invention is not limited to the above-described embodiments and examples, and it goes without saying that various modifications can be made without departing from the gist of the present invention.

[0032]

As described above, according to the present invention, fuel is injected from the central and outer peripheral burner throats or downstream thereof to the air flowing into the burner, the fuel injection is dispersed, and the fuel concentration is made uniform. Control emissions and improve combustion efficiency. In addition, even for flame-retardant low-calorie gas fuel such as biomass gas, a common fuel is used to hold the flame from the center and low-calorie gas fuel is injected from the outer periphery to ensure stable combustion. You can

Therefore, the low NOx for the gas turbine of the present invention
The combustor can essentially solve problems such as spontaneous ignition of a premixed lean combustion type air-fuel mixture, flashback, and oscillating combustion, and has a small pressure loss and easy control of air flow rate and fuel flow rate.
The structure is simple and low N which is comparable to the premixed lean burn method.
It can be converted to Ox and can be applied to flame-retardant low-calorie gas fuels such as biomass gas, and low N
It has excellent effects such as achieving Ox and stable combustion.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a low NOx combustor for a gas turbine of the present invention.

FIG. 2 is a configuration diagram showing an embodiment of a low NOx combustor for a gas turbine of the present invention.

FIG. 3 is a performance comparison diagram in an example of the present invention.

FIG. 4 is a configuration diagram of a conventional low NOx combustor.

[Explanation of symbols]

1 1st air swirler, 2 1st air passage, 3 1st fuel nozzle, 4 2nd air swirler, 5 2nd air passage, 6
Second fuel nozzle, 7 floating flame, 10 low NOx combustor for gas turbine, 11 central injection port, 12 central fuel injection pipe, 13 combustion air flow path, 13a throat part, 1
3b swirler, 14 annular duct, 15 throat injection port, 16 combustion chamber chamber, 16a annular taper part,
16b annular recess

Claims (3)

[Claims] 1. A central fuel injection pipe (12) having a central fuel injection port (11) at a tip end and a central fuel injection pipe (12), and the central fuel injection pipe surrounded by a space, and a combustion air flow path therebetween. An annular duct (14) forming (13) and a combustion chamber chamber (16) for expanding the gas leaving the air passage are provided, and the combustion air flow passage (13) has a flow passage area after gradually decreasing. A low NOx combustor for a gas turbine, characterized in that it has a throat portion (13a) which is gradually increased and further has a throat injection port (15) for injecting fuel into the throat portion. 2. The combustion chamber (16) has an annular taper portion (1) for gradually expanding the gas leaving the air passage into an annular shape.
The low NOx combustor for a gas turbine according to claim 1, further comprising an annular recess (16b) that forms an annular recess between the annular recess (6a) and the annular duct (14). 3. A swirler (13b) for imparting a swirling flow to the combustion air flow is provided in the combustion air flow path (13).
A low NOx combustor for a gas turbine according to claim 1 or 2.