JPH08261468A - Gas turbine combustor - Google Patents

Abstract

PURPOSE: To make NOx low in the emission characteristics of a gas turbine in the entire load range by providing a fuel feed system advantageous.for ease of combustion in effecting diffuse combustion. CONSTITUTION: Fuel ejected from fuel nozzles 16 is made to spread together with combustion air by a swirler 11, sent spiraling into an inner tube 3, and by being ignited forms a pilot flame in a manner of diffuse combustion. A premix fuel is ejected from the fuel nozzles 16 in a showerlike flow and premixed with combustion air 19 evenly in a premix duct 15. This premixed fuel gains speed as it flows downstream, reaches a flow velocity of more than twice that of a turbulent combustion, and flows into the inner tube 3 through ejection holes 17a-17c. Upon entering the inner tube 3, the premixed fuel is ignited by the pilot flame upstream and burned, and thus forms a premixed flame. As regards the temperature of this premixed flame the rates of the respective flows of fuel are so controlled by a computing element as to hold the combustion temperature in the range (<1,600 deg.C) free from producing NOx .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas turbine combustor used in a gas turbine power plant or a combined cycle power plant, and particularly to a gas turbine capable of reducing the NOx concentration contained in the exhaust gas of the gas turbine. Regarding combustor.

[0002]

2. Description of the Related Art A gas turbine used in a gas turbine power generation plant or a combined cycle power generation plant has operating conditions of high temperature and high pressure in order to improve efficiency, which increases NOx (nitrogen oxide). There is a tendency.

Although there are various causes of NOx generation, the flame temperature is mainly dominant, and therefore, in order to reduce NOx, it depends on how low the flame temperature is kept. Therefore, various measures have been taken from the past,
As the simplest NOx reduction method, steam injection or water injection is often performed in a high temperature combustion region in a combustor to reduce the temperature of the flame during combustion.

However, although this method is easy to apply and has an excellent aspect, a large amount of steam or water is used, and the use of steam or water results in a decrease in plant efficiency and an increase in efficiency. There are various drawbacks such as contrary to the intended purpose, the injection of a large amount of steam or water in the combustor increases combustion oscillation, etc., and shortens the life of the combustor.

From the above, as means for lowering the flame temperature without using the method of steam injection or water injection,
A so-called premixed multi-stage lean combustion method, in which fuel and combustion air are premixed and burned under lean fuel conditions, is adopted, and it is possible to achieve the NOx reduction level achieved by conventional steam injection or water injection. Has become.

[0006] In the premixed multi-stage lean combustion method, in order to cover the narrow combustion range, which is a drawback of the premixed combustion, a flame structure is employed in which diffusion combustion flames capable of stable combustion in a wide air-fuel ratio range are used together. ing.

[0007]

Although a dry type gas turbine combustor using the premixed multi-stage lean combustion method can achieve certain results, it has the following problems.

That is, FIG. 5 shows the gas turbine load and NOx.
As shown in the characteristic diagram of the relationship with the generated amount, the NOx emission characteristic curve a of the steam or water injection type gas turbine combustor is compared with the NOx of the dry type low NOx gas turbine combustor that does not use steam or water. The emission characteristic curve b is considerably reduced for the gas turbine load regions d to e, but has a problem in the low load side regions cd to d. In the dry type gas turbine combustor, in order to reduce NOx in the low load region, the fuel system is conventionally multistaged, and a part of the NOx characteristic curve b is changed to the low NOx characteristic indicated by the one-dot chain line f to reduce NOx. Has been improved. However, the NOx target value characteristic h that can be set with a margin to the theoretically possible minimum NOx characteristic g from the load c to the rated load e, which is the full load range of the gas turbine, is set to the NOx characteristic (for example, the characteristic curve b). Is quite high.

That is, the NOx characteristic j of the conventional dry type low NOx gas turbine combustor that maintains stable combustion by the premixed combustion flame supported by the diffusion combustion flame is as shown in FIG. It is almost inversely proportional to the ratio. Therefore, in order to further reduce NOx, it is desirable to make the diffusion fuel flow rate ratio as small as possible.

However, in the configuration and shape of the conventional dry type low NOx gas turbine combustor, as shown in FIG. 7, the smallest diffusion fuel flow rate ratio is CO at each gas turbine load.
It is determined by the diffusion fuel flow rate ratio l that can clear the limit value k. If the diffusion fuel flow rate ratio is smaller than this flow rate ratio l, CO (or THC, etc.) increases, and the combustion efficiency decreases and combustion oscillation increases, resulting in stability. However, there is a problem in that if the diffusion fuel flow rate ratio m is smaller than m, a misfire will occur. Therefore, in order to prevent stable combustion and misfire, the diffusion fuel flow rate ratio cannot be reduced to zero and NOx cannot be reduced to the minimum value.

The present invention realizes a low NOx emission characteristic in the entire load range of a gas turbine, which cannot be achieved by a conventional dry type NOx gas turbine combustor due to an increase in temperature and a reduction in NOx of the gas turbine combustor. An object is to provide a gas turbine combustor capable of

[0012]

In order to achieve the above object, a gas turbine combustor according to the present invention is a gas turbine combustor having a multi-stage combustion system by diffusion combustion and premixed combustion with air. The fuel supply system with good combustibility is provided for the diffusion combustion.

It is a second aspect of the present invention that the fuel supply system of good combustibility supplies the fuel of good combustibility to the diffusion combustion fuel only when a part of the combustor is operated under load.

Further, a reformer for converting a fuel having a good combustibility into a fuel having a good combustibility by a reforming reaction of the fuel is provided in a supply system of the fuel having a good combustibility. Further, the combustion gas at the combustor outlet is used as a heat source required for the reforming reaction of the reformer.

[0015]

[Operation] By using a fuel with good combustibility as the diffusion fuel, even if the load of the gas turbine is low, even if the ratio of the diffusion fuel (diffusion fuel flow rate) is reduced, there is no misfire and stable diffusion. It is possible to obtain combustion, and therefore, it is possible to suppress the generation of NOx even under a low load, and it is possible to suppress the generation of NOx from the gas turbine combustor over the entire load of the gas turbine. Also the conventional dry type low NO
Even in the case of the x gas turbine combustor, the same effect can be obtained by switching the diffusion fuel to the fuel having good combustibility only when the load is low.

[0016]

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

FIG. 1 shows a cross section of an embodiment of a gas turbine combustor according to the present invention. The gas turbine combustor is provided between a compressor A and a gas turbine B. The gas turbine combustor has an outer wall 1, a flow sleeve 2 as a sleeve outer cylinder of a combustor liner provided inside thereof, and an inner cylinder 3 as a sleeve inner cylinder provided further inside thereof, and one end of these An end wall 4 is provided at the other end, and a transition piece 5 which is a transition piece is connected to the other end of the inner cylinder 3 via a spring seal 6.

A combustion chamber is defined in the inner cylinder 3, and the combustion chamber has a diffusion combustion zone 7 and a premixed combustion zone 8. In the diffusion combustion region 7, a diffusion fuel nozzle 9 inserted through the end wall 4 is made to face the end wall 10 of the inner cylinder 3 with the swirler 11 inside the inner cylinder 3.

Two kinds of fuel supply lines 12 and 13 are connected to the diffusion fuel nozzle 9 through a switching valve 14, and one of the fuel supply lines 12 and 13 is selected by switching the switching valve 14. Predetermined fuel can be supplied. One of the fuel supply lines 12 constitutes a fuel supply system with good combustibility, and the fuel supply line 12 supplies the combustible fuel processed by reforming or the like.

In the premix combustion zone 7, between the flow sleeve 2 and the inner cylinder 3, four to eight premix ducts 15 as a premix device are arranged in the circumferential direction of the inner cylinder 3. An air intake port 15a is formed on the upstream side of the premixing duct 15, and a fuel nozzle 16 faces the air intake port 15a. The fuel nozzle 16 is provided on the end wall 4 of the outer wall 1, and the premixed fuel is ejected from the fuel nozzle 16 in a shower shape so as to be uniformly mixed with the combustion air in the premixing duct 15. . The premixed fuel is accelerated as it flows downstream (to the right in the drawing) through the premixing duct 15, and has a flow velocity that is twice or more the turbulent fuel velocity and is formed in the inner cylinder 3 of the premixed fuel injection port 17a. , 17b, 17c are injected into the premixed combustion zone 8 in the inner cylinder 3 and flow in.

Fuel is supplied to the fuel nozzle 16 by a shutoff valve,
Although it is performed via a fuel flow rate adjusting valve and a distribution valve (both not shown), these are controlled in response to a load signal according to a schedule such as a gas turbine load input to a computing unit. Reference numeral 18 indicates an ignition igniter.

Next, the operation of the gas turbine combustor shown in FIG. 1 will be described.

First, the flow of air in FIG. 1 will be described. A part of the high-temperature, high-pressure air discharged from the compressor A goes to the cooling of the gas turbine, and a part thereof becomes the combustor air 19 in FIG. . A part of the combustor air 19 is used for cooling the inner cylinder 3 and the transition cylinder 5. The remaining combustion air flows into the diffusion combustion zone 7 and the premixing duct 15 of the premixing device as combustion air, respectively.

On the other hand, as for the flow of fuel, the fuel ejected from the fuel nozzle 16 in FIG.
1 diffuses, is given each momentum, and flows into the inner cylinder 3 while turning. Simultaneously with the inflow of fuel and combustion air, it is ignited by the igniter 18 to form a pilot flame by diffusion combustion. Further, the premixed fuel is ejected in a shower shape from the fuel nozzle 16 and premixed with the combustion air 19 uniformly in the premixing duct 15. This premixed fuel is accelerated as it flows downstream, has a flow velocity that is more than twice the turbulent combustion velocity, and flows from the injection ports 17a, 17b, 17c to the inner cylinder 3
Flows into. At this time, the backflow into the premixing duct 15 due to the pilot flame is prevented because the flow velocity is twice or more the turbulent combustion velocity.

The inflowing premixed fuel is ignited and burned by the pilot flame on the upstream side to form a premixed flame.
At this time, the fuel flow rate is controlled by the computing unit so that the flame temperature of the premixed flame becomes the combustion temperature (<1600 ° C.) at which NOx is not generated.

Next, the combustion method will be described.

In FIG. 2, reference character a indicates a conventional fuel distribution relationship between diffusion and premixing with respect to a load. In this fuel distribution, a large amount of fuel for diffusion combustion is used in order to stabilize diffusion combustion in a low load region. are doing. Therefore, the NOx at the combustor outlet in the low load region operation is high as shown in FIG. Therefore, in the present invention, reference numeral b in FIG. 2 shows the fuel distribution in the case where the fuel is switched to a fuel that is easily combustible as the fuel used for diffusion combustion in the low load region, for example, hydrogen. The NOx at the combustor outlet in this case can be suppressed over the entire load of the gas turbine, as shown in FIG. The NOx characteristics of the gas turbine combustor according to the present invention are indicated by the symbol i in FIG. Further, it is needless to say that the fuel that is easily combustible as the diffusion fuel may be supplied at full load, and the same effect can be obtained in this case as well.

FIG. 3 shows an embodiment of the structure of the fuel supply system for the combustible fuel. The fuel supply line 12 in FIG.
The reformer 20 is connected to. The reformer 20 uses a reforming reaction of the fuel to produce a fuel having a good combustibility, and is reformed by using a reforming catalyst and adding steam 21 to the fuel. Since this reforming catalyst is an endothermic reaction, it requires a heat source, but in this embodiment, it is heated by the burner 22.

FIG. 4 shows an embodiment in which a part of the combustion gas 23 at the combustor outlet is used as the heat source for heating the reformer 20 in FIG. According to this embodiment, the heat can be effectively used, and it is highly effective in improving the total efficiency of the plant.

Although the case where the reforming catalyst is used in the reformer 20 for reforming the fuel is shown, the present invention is not limited to the example in which the reformer is used. Needless to say, the gas turbine combustor can also be applied to various types of gas turbines that use gas fuel or liquid fuel. Since the gas turbine combustor in FIGS. 3 and 4 is the same as that in FIG. 1, corresponding reference numerals are given and description thereof is omitted.

In this gas turbine combustor,
As the fuel for diffusion combustion, a fuel having good combustibility may be used over the entire load of the gas turbine.

[0032]

As described above, according to the present invention, it is possible to simultaneously eliminate the instability of diffusion combustion in a low load region and the increase in NOx, which are problems of the conventional gas turbine combustor. As a result, it is possible to suppress the generation of NOx in the entire operating range. By reducing the generation of NOx, the NOx removal equipment can be reduced or omitted, and the consumption of ammonia can be greatly reduced, including the reduction of ammonia consumption, which can contribute to a cleaner global environment. You can contribute.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a gas turbine combustor according to the present invention.

FIG. 2 is a characteristic diagram showing NOx characteristics with respect to a diffusion fuel ratio.

FIG. 3 is a sectional view showing another embodiment of the gas turbine combustor according to the present invention.

FIG. 4 is a sectional view showing still another embodiment of the gas turbine combustor according to the present invention.

FIG. 5 is a graph showing the relationship between NOx at the gas turbine combustor outlet and load.

FIG. 6 is a NOx characteristic diagram based on a diffusion fuel ratio.

FIG. 7 is a characteristic diagram of NOx and CO with respect to the diffusion fuel ratio.

[Explanation of symbols]

 1 outer wall 2 slow sleeve 3 inner cylinder 4 end wall 5 tail cylinder 6 spring seal 7 diffusion combustion area 8 premix combustion area 9 diffusion fuel nozzle 10 end wall 11 swirler 12, 13 fuel supply line 14 switching valve 15 premix duct 16 Fuel nozzles 17a, 17b, 17c Premixed fuel jet 18 Igniter 20 Reformer 22 Burner

Claims (4)

[Claims] 1. A gas turbine combustor having a multi-stage combustion system comprising diffusion combustion and premixing combustion by premixing with air, wherein a fuel supply system having good combustibility is provided for the diffusion combustion. Characteristic gas turbine combustor. 2. The gas turbine combustion according to claim 1, wherein the fuel supply system with good combustibility is adapted to supply the fuel with good combustibility to the diffusion combustion fuel only when a part of the combustor is operated under load. vessel. 3. The gas turbine combustor according to claim 1, wherein the fuel supply system having good combustibility has a reformer for converting the fuel into a fuel having good combustibility by a reforming reaction of the fuel. 4. The gas turbine combustor according to claim 3, wherein the combustion gas at the combustor outlet is used as a heat source required for the reforming reaction of the reformer.