JPH07332610A - Gas turbine combustor and combustion method therefor - Google Patents

Abstract

PURPOSE:To provide a method wherein an amount of NOx generated resultant from combustion of a gas turbine combustion is eminently reduced at a low cost. CONSTITUTION:After a flow rate is measured by a fuel flow rate meter 5, first stage fuel la of a gas turbine combustion effects diffusion combustion together with compressed air 11b by a diffusion pilot burner 3 after the flow of it through a fuel nozzle 2. The measurements of the fuel flow rate meter 5 are fed to an additive injection valve control device 16 through a control line 18 and an additive injection valve 17 is controlled by using a control line 19 therefrom. This constitution eminently reduces NOx density through a simple method and effectively prevents the occurrence of pollution of the atmosphere at a low cost.

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 and a combustion method thereof, and more particularly to N generated by combustion.
The present invention relates to a gas turbine combustor that reduces the amount of Ox and a combustion method thereof.

[0002]

2. Description of the Related Art At present, it is necessary to reduce the NOx value emitted into the atmosphere in order to prevent air pollution due to combustion exhaust gas. The method that has been conventionally implemented to meet such a need is described in “Mechanisms for Generation and Suppression of Environmental Pollutants Associated with Combustion”, edited by Japan Society of Mechanical Engineers, published in 1980.

Further, as conventional techniques for removing NOx, there are JP-A-55-112824 and JP-A-5-92124.

[0004]

However, with the recent close-up of environmental problems, especially for large industrial combustors, the regulation of NOx emissions is being strengthened, and the NOx production amount is being strengthened. It has become clear that the above-mentioned suppression method alone cannot comply with the regulatory standards, and that it is obliged to rely on the denitration method of decomposing the generated NOx by the ammonia reduction method or the like.

An object of the present invention is to provide a gas turbine combustor and a combustion method for the same which solve the problems of the conventional NOx reduction method at low cost.

[0006]

The present invention relates to a gas turbine combustor in which a fuel having hydrocarbons and air are mixed and combusted, and CH generated in the combustion process.
A substance that reacts with radicals is added to the C
It is characterized in that an amount capable of reducing the CH radicals is added only to a portion where a large amount of H radicals are generated to reduce the generation amount of NOx at low cost.

The gas turbine combustor used in the present invention combusts using a premix burner and a diffusion pilot burner. The premix burner performs lean premix combustion to reduce the amount of NOx produced. However, in the premix burner, since the fuel concentration is lowered and the flame temperature is lowered in order to perform lean premix combustion, misfire is likely to occur. Therefore, the combustion of the premix burner is assisted by the flame of the diffusion pilot burner so that the premix burner does not misfire.

The gas turbine combustor of the present invention comprises a means for supplying fuel that occupies hydrocarbons, a means for supplying air that occupies oxygen, a diffusion pilot burner for assisting the combustion of the premix burner, and a premix passage. A premixing nozzle and a combustion chamber for combusting the fuel and air, the device comprising means for adding a substance that reacts with the CH radical in order to reduce CH radicals generated in the combustion chamber, The addition amount of the substance that reacts with CH radicals is controlled to an amount capable of reducing CH radicals based on the mixing ratio of the fuel and air.

CH radicals generated in the present invention are
It is an active chemical species and is dominant in the generation of prompt NO. Although NOx includes prompt NO and thermal NO, the latter can be reduced by lowering the combustion temperature, such as lean premixed combustion. It is necessary to reduce it. Therefore, by reducing both prompt NO and thermal NO, the total NOx
The amount can be reduced.

The gas turbine combustor used in the present invention is
The premixed burner reduces NOx by lean premixed combustion, and the diffusion pilot burner adds a substance that reacts with CH radicals to reduce NOx. The substance that reacts with CH radicals is preferably injected into the fuel or air while monitoring the combustion state, or is preferably injected into the combustor. This makes it possible to minimize the amount of additive used.

The present invention is intended to reduce the amount of NOx produced at a low cost, by removing CH radicals with an additive,
It suppresses the NOx production reaction.

The substance that reacts with the CH radical in the present invention is, for example, hydrogen, alkane, CCl ₄ , or CH ₃
F, and it is necessary to add an amount capable of reducing CH radicals. It is preferable to consider the addition amount in relation to the nitrogen concentration, and the nitrogen concentration is several ppm to
It is desirable to add several thousand ppm. Hydrogen is the most preferable additive, and when an alkane is used, it is necessary to control the addition amount to several hundreds ppm or less in consideration of the generation of CH radicals. Also, CCl ₄ and CH ₃
When F 2 is used, it is necessary to control the content of the additive to several tens of ppm or less so as not to disturb the original combustion reaction.

Further, the combustion method of the present invention is for burning a mixture of a fuel occupying a hydrocarbon and oxygen, wherein an additive substance that reacts with a CH radical generated during the combustion is a CH radical and nitrogen. Constant of reaction of CH and CH
It is characterized in that the addition is carried out at a concentration equal to or higher than the ratio of the rate constant of the reaction between the radical and the additive substance multiplied by the nitrogen concentration in the mixture.

Here, when the rate constant of the reaction between the CH radical and nitrogen is k ₁ and the rate constant of the reaction between the CH radical and the added substance is k ₂ , the addition amount of the substance that reacts with the CH radical is The concentration is equal to or higher than the concentration of nitrogen in the mixture multiplied by the ratio of k ₁ and k ₂ . When hydrogen is used as a substance that reacts with CH radicals, in order to effectively reduce the generation of prompt NO, the addition amount is preferably 4 ppm to 1% or more, and may be 1% or less. . When hydrogen is used, the combustion temperature may increase, so it is necessary to add hydrogen in an amount that does not increase thermal NO.

When an alkane is used as a substance that reacts with CH radicals, the amount added is preferably 3 ppm to 200 ppm, and may be several hundred ppm or less, in order to effectively reduce the prompt NO. If the amount of alkane is increased to more than several thousand ppm, for example, CH
It is not preferable because it may accelerate the generation of radicals. The effect of alkane addition depends on the combustion temperature,
It is preferably 2000 ° C.

CCl as a substance that reacts with CH radicals
_{When 4} is used, the addition amount is preferably ₃ ppm to 100 ppm (several hundreds of ppm or less) in order to effectively reduce the prompt NO, and when CH ₃ F is used as a substance that reacts with CH radicals , Its addition amount is 30ppm
It is preferable that the amount is from ~ 1200 ppm (several thousands ppm or less).
The present invention, in order to reduce the NOx amount itself generated during combustion, a method such as a lean combustion method, a water / steam injection method, an exhaust gas recirculation method, or the like, which lowers the flame temperature and suppresses the amount of NOx produced, and its principle. Be different. For example, in a gas turbine combustor, a two-stage combustion method in which combustion is divided into two stages to shorten the time in the high temperature combustion region of the flame to suppress the amount of NOx produced corresponds to this. It is even more effective to use the NOx reduction method. Also,
It is more effective when used together with a conventional denitration method using a catalyst or ammonia. Further, it is more effective when used together with a conventional denitration method using a catalyst or ammonia.

[0017]

[Function] To generate NOx by combustion of hydrocarbon fuel,
Two chemical reaction mechanisms are possible. One is the next chain reaction mechanism called the extended Zeldovich mechanism.

[0018]

[Formula 1] N ₂ + O → NO + N (Formula 1)

[0019]

[Formula 2] N + O ₂ → NO + O (Formula 2)

[0020]

[Chemical Formula 3] N + OH → NO + H (Chemical Formula 3) As shown in “Chemical Formula 1”, in this reaction mechanism, decomposition of nitrogen necessary to generate NO is performed by the oxygen atom O, and “Chemical Formula 1” is strong. There is temperature dependence. Although NO generated by such a reaction mechanism is called thermal NO, a method of lowering the flame temperature to suppress the generation of NOx is to reduce the thermal NO by paying attention to the temperature dependence of "Chemical formula 1". To do. In addition to the above reaction mechanism, the following NOx generation mechanism, which is the basic principle of the present invention, can be considered.

[0021]

[Formula 4] N ₂ + CH → HCN + N (Formula 4)

[0022]

[Chemical formula 5] HCN + OH → CN + H ₂ O (Chemical formula 5)

[0023]

[Chemical Formula 6] CN + O ₂ → NO + CO (Chemical Formula 6) That is, in this reaction mechanism, as shown in “Chemical Formula 4”, the decomposition of nitrogen is performed by the CH radicals generated in the combustion reaction, and the generated N is “Chemical Formula 2” NO by "Chemical 3"
In addition to the change to, the HCN generated at the same time also generates NO by "Chemical formula 5" and "Chemical formula 6". The NO generated by this reaction mechanism is called a prompt (Prompt) NO. Prompt NO is particularly likely to be generated in a state where the fuel concentration is high, and most of NOx generated in diffusion combustion is prompt NO.

In the present invention, the substance X, which reacts rapidly with CH radicals, is added to the combustible mixture and reacted with the CH radicals as shown in "Chemical formula 7" to suppress the CH radical concentration. It suppresses the decomposition of nitrogen and reduces the generation of prompt NO.

[0025]

CH + X → Y (Chem. 7) Currently, the premix burner uses a lean premix combustion method to suppress the amount of thermal NO generated. on the other hand,
A large amount of prompt NO is generated in the diffusion pilot burner, but no countermeasure is taken. Prompt NO
Can be suppressed by adding a substance that reacts with CH radicals in the combustion process. However, it is costly to add it to the combustion process of all fuels, so it is necessary to reduce the addition amount as much as possible.

In general, the reactivity between substances is represented by a reaction rate constant. As substances having a particularly large rate constant for reaction with a CH radical, in addition to hydrogen, C ₃ H ₈ , C ₄ H ₁₀ , C ₅ H
Alkanes such as _{12 and the} like, CCl ₄ , CH ₃ F can be mentioned.

Hydrogen has the effect of raising the flame temperature if the amount of hydrogen added is too large, and the amount of thermal NO produced increases. Therefore, it is necessary to suppress the amount of hydrogen added within a concentration range effective for suppressing NOx. _{Also, C 3 H 8, C 4} H 10, C 5 H
_The influence of alkanes such as ₁₂ and CCl ₄ , CH ₃ F on combustion is considered to be misfiring due to increase in heat capacity as the addition amount is increased and combustion reaction being controlled. Therefore, these substances must be added in the minimum necessary amount. This amount is determined as follows. Rate constant k ₁ of the reaction of "Formula 4", when the rate constant of the reaction of "Formula 7" is k _2,
If the reaction rates of both reactions are the same, both reactions can occur to the same degree, so that the prompt NO production amount can be reduced by 50%.
Therefore, the concentration [X] of the additive is determined so as to satisfy the conditional expression "Equation 1" at this time.

[0028]

[Equation 1]

As the reaction rate constant k ₁ , 1.6 × 10
^-11 exp (-53.1 / RT) cm ³ / s has been reported (K.
H. Becker, et al., Chemical Physics Letter, 195, p.
332, 1992).

When hydrogen is used as X, the reaction rate constant k ₂ is about 10 ^-14 cc / mol · s, X at 800K.
When an alkane is used as the above, it is about 10 ^-10 c at 298K.
m ^{3 / s (} S. Zabarnick, et al., Chemical Physics, 11
2, p409, 1987), and when CCl ₄ , CH ₃ F is used as X, it is about 10 ^-10 cm ^{3 / s at} 296K (S. Zabarni
ck, et al., Chemical Physics, 120, p311,1
988). These reaction rate constants can be used to determine the required addition at flame temperature. Flame temperature 800,1 when a large amount of nitrogen is present
Table 1 shows the calculated values of the required addition amounts for 500 and 2000 ° C.
Shown in.

[0031]

[Table 1]

From this, the required amount of addition is 4 to 8 for hydrogen.
400 ppm, _{3 to} 200 ppm for alkanes, _{3 to} 100 ppm for CCl ₄ , 30 to 1000 ppm for CH ₃ F
It can be seen that it is. By adding these substances within this concentration range and reacting with CH radicals, it is possible to suppress the concentration of CH radicals, suppress the decomposition of nitrogen due to "Chemical formula 4", and reduce the generation of prompt NO.

[0033]

EXAMPLES The present invention will be described in detail below with reference to examples.

FIG. 1 is a block diagram showing an embodiment in which the present invention is applied to a gas turbine combustor, in which a substance that suppresses NOx production is added to the combustion chamber of a diffusion pilot burner when the gas turbine is started. is there.

The first stage fuel 1a of the gas turbine combustor is
After the flow rate is measured by the fuel flow meter 5, it is supplied to the diffusion pilot burner 3 through the fuel nozzle 2. On the other hand, the air 11a is compressed by the compressor 12 and then compressed air 11b.
Next, it enters the combustor casing 9 and is supplied to the diffusion pilot burner 3, where it is diffused and burned. The measured value of the fuel flow meter 5 at the time of starting the gas turbine is sent to the additive injection valve control device 16 via the control line 18, and the additive injection valve control device 16 determines the additive amount based on this signal, The control line 19 is used to control the additive injection valve 17. As a result, the additive 15a becomes the additive 15b whose flow rate is adjusted, and is injected from the additive injection port 20 to the diffusion pilot burner 3 only when the gas turbine is started. The second stage fuel 4 is
After premixing with the compressed air 11b by the second stage premixing swirler 7 through the fuel nozzle 6, premixing burner 8 performs premixing combustion. After leaving the transition piece 10, the combustion gas 14b rotates the turbine 13 to generate electricity, and becomes exhaust gas 14a which is discharged into the atmosphere.

With the above structure, hydrogen, alkane, CC
Addition of a substance that reacts with CH radicals such as l ₄ or CH ₃ F to the vicinity of the diffusion pilot burner in an amount that can reduce the CH radicals according to the change in the fuel supply amount of the diffusion pilot burner only when the gas turbine is started. Is possible. Therefore, the additive substance and the CH radical react quickly without adversely affecting the combustion reaction, and the CH radical concentration is effectively reduced. As a result, the decomposition of nitrogen by the CH radicals is suppressed, and the amount of prompt NO generated can be reduced.

FIG. 2 is a diagram showing an example of the fuel flow rate characteristic with respect to the load change of the gas turbine combustor. The vertical axis is
The ratio of the fuel flow rate of each burner to the total fuel flow rate when the gas turbine load is 100% is shown. The fuel flow rate of the diffusion pilot burner changes with changes in the gas turbine load.When the load is small, such as when starting the gas turbine, only the diffusion burner is used, and the proportion of the premix burner increases as the load increases. . Therefore, by adding the additive to the fuel of the diffusion pilot burner only at the time of starting the gas turbine, the generation amount of the prompt NO can be reduced with the minimum necessary amount of the additive.

FIG. 3 is a block diagram showing an embodiment in which the present invention is applied to a gas turbine combustor, in which a substance that suppresses the generation of NOx is added to the fuel of the diffusion pilot burner at the time of starting the gas turbine. is there.

The first stage fuel 1a of the gas turbine combustor is supplied to the diffusion pilot burner 3 through the fuel nozzle 2 after the flow rate is measured by the fuel flow meter 5. On the other hand, the air 11a is compressed by the compressor 12 and then compressed air 11b.
Next, it enters the combustor casing 9 and is supplied to the diffusion pilot burner 3, where it is diffused and burned. The measured value of the fuel flow meter 5 at the time of starting the gas turbine is sent to the additive injection valve control device 16 via the control line 18, and the additive injection valve control device 16 determines the additive amount based on this signal, The control line 19 is used to control the additive injection valve 17. As a result, the additive 15a becomes the additive 15b whose flow rate is adjusted, and is injected from the additive injection port 20 into the first stage fuel only when the gas turbine is started. The second-stage fuel 4 passes through the fuel nozzle 6, is premixed with the compressed air 11b by the second-stage premixing swirler 7, and is then premixed and burned in the second-stage combustion chamber. After leaving the transition piece 10, the combustion gas 14b rotates the turbine 13 to generate electricity, and becomes exhaust gas 14a which is discharged into the atmosphere.

With the above structure, hydrogen, alkane, CC
A substance that reacts with CH radicals such as l ₄ or CH ₃ F is added to the fuel of the diffusion pilot burner only in an amount that can reduce the CH radicals according to the change in the fuel supply amount of the diffusion pilot burner only when the gas turbine is started. It becomes possible to do. Therefore, the additive radical and the CH radical react rapidly without adversely affecting the combustion reaction, and CH
Effectively reduce radical concentration. As a result, the CH
The decomposition of nitrogen by radicals is suppressed, and the prompt NO
Can be reduced.

If this method is carried out, the additive is added to the diffusion combustion portion at the time of starting the gas turbine, which accounts for most of the generation rate of prompt NO, so that the generation of prompt NO can be effectively suppressed at low cost. .

From the above, when the present invention is carried out, the amount of the additive used can be suppressed to a necessary minimum, and therefore air pollution can be prevented effectively and at low cost. Further, it is possible to cope with future tightening of NOx emission regulations without the need for a denitration device.

FIG. 4 is a block diagram showing an embodiment in which the present invention is applied to a gas turbine combustor, in which a substance that suppresses the generation of NOx is added to the combustion air of the diffusion pilot burner when the gas turbine is started. It is a thing.

The first stage fuel 1a of the gas turbine combustor is
After the flow rate is measured by the fuel flow meter 5, it is supplied to the diffusion pilot burner 3 through the fuel nozzle 2. On the other hand, the air 11a is compressed by the compressor 12 and then compressed air 11b.
Next, it enters the combustor casing 9 and is supplied to the combustion air 11c of the diffusion pilot burner 3, where it is diffused and burned. The measured value of the fuel flow meter 5 at the time of starting the gas turbine is sent to the additive injection valve control device 16 via the control line 18, and the additive injection valve control device 16 determines the additive amount based on this signal, Additive injection valve 1 using control line 19
Control 7 As a result, the additive 15a becomes the additive 15b whose flow rate is adjusted, and is injected from the additive injection port 20 into the combustion air 11c of the diffusion pilot burner 3 only when the gas turbine is started. The second-stage fuel 4 passes through the fuel nozzle 6 and is premixed with the compressed air 11b by the second-stage premixing swirler 7, and then premixed and burned by the premixing burner 8. After leaving the transition piece 10, the combustion gas 14b rotates the turbine 13 to generate electricity, and becomes exhaust gas 14a which is discharged into the atmosphere.

With the above structure, hydrogen, alkane, CC
In the combustion air of the diffusion pilot burner, an amount of a substance that reacts with CH radicals such as l ₄ or CH ₃ F can be reduced only when the gas turbine is started according to the change in the fuel supply amount of the diffusion pilot burner. Can be added to. Therefore, the additive substance and the CH radical react quickly without adversely affecting the combustion reaction, and the CH radical concentration is effectively reduced. As a result,
The decomposition of nitrogen by the CH radicals is suppressed, and the amount of prompt NO generated can be reduced.

By carrying out this method, since the additive is added to the diffusion combustion portion at the time of starting the gas turbine, which accounts for most of the proportion of generation of prompt NO, it is possible to effectively suppress the generation of prompt NO at low cost. .

[0047]

According to the present invention, the NOx amount generated by the combustion of the gas turbine combustor can be greatly reduced by a simple device, so that the air pollution can be effectively prevented at a low cost. be able to.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing an example of a fuel flow rate characteristic with respect to a load change of a gas turbine combustor.

FIG. 3 is a configuration diagram showing an embodiment of the present invention.

FIG. 4 is a configuration diagram showing an embodiment of the present invention.

[Explanation of symbols]

1a, 1b ... First stage fuel, 2, 6 ... Fuel nozzle, 3 ... Diffusion pilot burner, 4 ... Second stage fuel, 5 ... Fuel flow meter, 7 ... Second stage premixing swirler, 8 ... Premixing burner,
9 ... Combustor casing, 10 ... Transition piece,
11a ... Air, 11b ... Compressed air, 11c ... Combustion air, 12 ... Compressor, 13 ... Turbine, 14a ... Exhaust, 1
4b ... Combustion gas, 15a, 15b ... Additive, 16 ... Additive injection valve control device, 17 ... Additive injection valve, 18, 19 ...
Control line, 20 ... Additive injection port.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Osamu Yokomizo 7-2-1, Omika-cho, Hitachi-shi, Ibaraki Hitachi Ltd. Energy Research Laboratory

Claims (6)

[Claims] 1. A means for supplying a fuel containing a hydrocarbon,
In a gas turbine combustor having a means for supplying air containing oxygen and a combustion chamber of a diffusion burner for combusting the fuel and air, a reaction with the CH radicals is performed in order to reduce the CH radicals generated in the combustion chamber. A gas turbine combustor, comprising means for adding a substance to the combustion chamber. 2. A means for supplying a fuel containing a hydrocarbon,
In a gas turbine combustor having a means for supplying air containing oxygen and a combustion chamber of a diffusion burner for combusting the fuel and air, a reaction with the CH radicals is performed in order to reduce the CH radicals generated in the combustion chamber. A gas turbine combustor, characterized in that it is provided with means for adding the substance to be added to the fuel of the diffusion burner. 3. A means for supplying a fuel containing a hydrocarbon,
In a gas turbine combustor having a means for supplying air containing oxygen and a combustion chamber of a diffusion burner for combusting the fuel and air, a reaction with the CH radicals is performed in order to reduce the CH radicals generated in the combustion chamber. A gas turbine combustor, comprising means for adding a substance to be added to combustion air of a diffusion burner. 4. The gas turbine combustor according to claim 1, wherein
Combustion method for gas turbine combustor, characterized in that the amount of a substance that reacts with CH radicals, which is determined based on the fuel flow rate of the diffusion burner, is added to the combustion chamber of the diffusion burner to reduce the generation amount of NOx. . 5. The gas turbine combustor according to claim 2, wherein
Combustion method for gas turbine combustor, characterized in that an addition amount of a substance that reacts with CH radicals, which is determined based on the fuel flow rate of the diffusion burner, is added to the fuel of the diffusion burner to reduce the generation amount of NOx. . 6. The gas turbine combustor according to claim 3,
A gas turbine combustor characterized in that the amount of a substance that reacts with CH radicals determined based on the fuel flow rate of a diffusion burner is added to the combustion air of the diffusion burner to reduce the amount of NOx produced. Combustion method.