JPH0763334A - Control method of gas turbine having two-stage type burner - Google Patents

Abstract

PURPOSE:To permit the continuous operation of a gas turbine even when abnormal combustion is generated in a second stage combustion unit by a method wherein combustion is shifted to the independent combustion of a first stage combustion unit only when the conditional amount with respect to burning condition has exceeded an allowable amount. CONSTITUTION:When a difference between the maximum value 3 and the minimum value 4 of respective exhaust gas temperatures 1, detected by (n) pieces of thermocouples, has exceeded an allowable value, it is deemed that abnormal combustion has occured and a signal 7 is transmitted. When one of (n) pieces of thermocouples is disconnected and a difference between a second value 8 from the minimum value of exhaust gas temperatures and the maximum value 3 has exceeded an allowable value, it is deemed that abnormal combustion has occured and a signal 11 is transmitted. Further, when either one of respective widths of fluctuations in the exhaust gas temperature 1 has exceeded an allowable width of fluctuation, it is deemed that abnormal combustion has occured and a signal 14 is transmitted. In this case, the command of shifting to the independent operation of a first stage combustion unit is transmitted by the transmission of either one of the signal 7, the signal 11 and the signal 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for controlling a gas turbine having a two-stage combustor.

[0002]

2. Description of the Related Art A conventional example of a method for controlling a gas turbine having a two-stage combustor will be described with reference to the drawings. Figure 4
FIG. 4 is an explanatory diagram of a gas turbine having a conventional two-stage combustor.

One of the characteristics of the combustor of the gas turbine is that the change range of the fuel-air ratio, that is, the ratio of the fuel amount to the air amount, from the start to the rated load is very wide. A gas turbine having a two-stage combustor is a system capable of achieving low NOx in such an extremely wide range of change of the fuel-air ratio. The first-stage combustor 34 and the second-stage combustor 18 and.

Since the first-stage combustion section 34 is used from start-up to the rated load, a diffusion combustion system having a wide operating range is adopted, and the second-stage combustion section 18 is the first-stage combustion section. It is used after switching from single combustion of 34 to simultaneous combustion with the first stage combustion section 34.

The second-stage combustion section 18 uses the combustion air 35 and the combustion nozzle 3 in order to reduce NOx in the high load region.
The fuel 37 from 6 is mixed in the swirler 19 in advance, and a premixing method is used in which it is burned.

Further, the outlet air 3 flowing out from the compressor 30
1 is guided to the combustor 17, and becomes a combustion gas 32 which flows into the turbine section 33.
The flow rate control of No. 5 is performed by the air flow rate adjuster 38 according to the fuel amount.

In the diffusion combustion, when the fuel 37 is injected, the amount of air required for stable combustion can be used,
Since the remaining air can also be used for dilution, the NOx concentration is insensitive to the fuel-air ratio and the combustion range is wide. But,
Even if there is a large amount of air in the surroundings, there is a limit in reducing NOx only by diffusion combustion, and the second stage combustion unit 18
Will be required.

FIG. 5 is a relationship diagram of the fuel-air ratio and the NOx concentration or the CO concentration in the premixing section of the second stage combustion section 18. As shown in FIG. 5, NOx concentration 39 and CO concentration 4
There is a range 41 where the fuel air ratio is low when both 0 are present. That is,
When the fuel-air ratio is adjusted to be within this range 41,
A stable combustion can be obtained with a low NOx concentration.

That is, when the premixed combustion system shown by the swirler 19 in FIG. 4 is adopted in the second stage combustion section 18,
It is possible to reduce the NOx concentration by lowering the flame temperature by lowering the fuel-air ratio because the degree of mixing of fuel and air becomes good.

However, the combustion is subtly changed due to individual differences in the combustor, changes in the temperature and humidity of the combustion air, changes in the calorific value and components of the fuel, and the like. In particular, when the gas turbine is provided with a plurality of combustors, stable combustion may not be obtained because the combustors have different combustion conditions.

Since the change in NOx concentration is sensitive to the fuel-air ratio and the stable combustion range is narrow, it is necessary to finely control the fuel-air ratio. In addition, the combustion air 35 at the time of premixed combustion
The flow rate control is performed by the air flow rate adjuster 38 according to the fuel amount, as described above.

Next, the state of attachment of the combustor in the conventional gas turbine will be described with reference to the drawings.

FIGS. 6A and 6B are explanatory views of a mounting condition of a combustor in a conventional gas turbine. FIG. 6A is a schematic side view of a gas turbine main body, and FIG. 6B is FIG. 6A. 6A is a view taken along the line AA of FIG. 6, and FIG. 6C is a view taken along the line BB of FIG.

As shown in FIG. 6 (a), the combustor 17 is attached to the left end and the exhaust end 42 is provided at the right end. Further, as can be seen from FIG. 6B, the combustor 1
A plurality of 7 are provided in the peripheral portion of the gas turbine body in the same direction at substantially equal intervals. In addition, all the combustors 17 are provided with an air flow rate regulator (not shown).

The air flow controller controls the total number of combustors simultaneously or individually, but the combustion state tends to become very unstable due to the influence of individual differences in the combustors.

For the above reason, even if the secondary fuel, which is the fuel of the second stage combustion section, is introduced into the second stage combustion section, the fire transfer from the first stage combustion section to the second stage combustion section is possible. Instead, the secondary fuel may not ignite, or the second-stage combustion section of the combustor may misfire. In such a case, the secondary fuel is discharged as it is without burning, resulting in a significant decrease in efficiency.

Regarding such a large decrease in efficiency, as shown in FIG. 6C, the temperature distribution of a plurality of exhaust gas temperature measuring thermocouples 43 arranged in the circumferential direction of the exhaust portion 42 is shown. It can be captured from the measurement results.

FIG. 7 is a measurement diagram of the temperature distribution of exhaust gas. In contrast to the normal temperature distribution 44 when each combustor is operating normally, the abnormal temperature distribution 45 in which some of the combustors are in an unstable combustion state shows the exhaust gas temperature Since a partial decrease appears, it is possible to catch a defective condition of the combustor.

Further, in Japanese Patent Laid-Open No. 2-86927,
Disclosed is a method of controlling a gas turbine that continuously operates a gas turbine even when a failure occurs in a thermocouple that is a monitoring device.

[0020]

In the second-stage combustion section of a gas turbine having a two-stage combustor of premixing type, it is necessary to control the fuel-air ratio within a very narrow range of the fuel-air ratio. Therefore, the control tends to be unstable, and incomplete combustion is likely to occur. An example of this incomplete combustion will be described with reference to the drawings.

FIG. 8 is a diagram showing the time variation of the exhaust gas temperature of each combustor. That is, in FIG.
Plural (n) provided corresponding to each combustor
The figure shows a case where the exhaust gas temperature is measured by the thermocouple of the book and the occurrence of unstable combustion in one combustor is detected. That is, the temperature fluctuation 46 of the exhaust gas is caused by the unstable combustion in the combustor.

As described above, abnormal combustion occurs due to ignition failure or misfire. In such a state,
A method for continuously operating the gas turbine has not been disclosed in the past.

An object of the present invention is to provide a gas turbine control method capable of continuously operating a gas turbine even when a problem such as abnormal combustion occurs in the second stage combustion section of the gas turbine. It is in.

[0024]

The above object can be achieved as follows.

(1) In a method of controlling a gas turbine having a two-stage combustor having a diffusion combustion type first stage combustion section and a premixing type second stage combustion section, a first stage combustion section and a second stage combustion section are provided. The combustion state with the combustion unit is monitored, the state quantity related to the combustion state is taken in as a control factor, and when the state quantity exceeds the allowable amount, the combustion in the second stage combustion section is regarded as abnormal combustion, Promptly shift to single combustion only in the staged combustion section.

(2) In (1), the state value which is a constituent factor of the state quantity is at least one of combustion gas temperature, exhaust gas temperature and combustor metal temperature.

(3) In (1) or (2), the state quantity is the difference between the maximum value and the minimum value in the state value, or the difference between the maximum value and the second minimum value in the state value. To be.

(4) In (1) or (2), the state quantity is the fluctuation range of the state value.

[0029]

In the present invention, at least one of the combustion gas temperature, the exhaust gas temperature and the combustor metal temperature, or a combination of these temperatures is measured by a plurality of thermocouples, and the temperature in the second stage combustion section is measured. Since the state quantity of unstable combustion is captured and it is possible to quickly shift to the single combustion of the first-stage combustion section, without suddenly changing the combustion state,
It is possible to continue the operation of the gas turbine.

Further, the state quantity of unstable combustion in the second stage combustion section is set when the difference between the maximum value and the minimum value of the measured temperature exceeds the allowable value. Can be caught.

Further, since the difference between the maximum value and the second value of the measured temperature, which is the second value from the minimum value, of the state quantity of unstable combustion in the second-stage combustion section exceeds the allowable value, the minimum temperature Even if it is impossible to measure the value, the state quantity of unstable combustion can be captured, and the reliability of capturing the state quantity of unstable combustion is improved.

Further, since the unstable combustion state quantity in the second stage combustion section is set when the fluctuation range of the measured temperature exceeds the allowable fluctuation range, this also allows the unstable combustion state quantity to be accurately captured. be able to.

[0033]

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

FIG. 1 is an explanatory view of an embodiment of the present invention.
FIG. 1A is a block diagram showing the progress of the first-stage combustion section to the independent combustion, and FIG. 1B is a state diagram of the temperature change of exhaust gas and the like with the passage of time. The measured temperatures include the exhaust gas temperature, the combustion gas temperature, and the combustor metal temperature. The exhaust gas temperature will be described as an example.

In FIG. 1, each exhaust gas temperature 1 detected by n thermocouples is taken into a distribution calculator 2,
The maximum value 3 and the minimum value 4 in the exhaust gas temperature taken in to find instability of combustion are taken out, the difference is obtained by the adder 5, and the difference is preset by the monitor relay 6. If it is determined that the value exceeds the limit, it is considered that the combustion is abnormal, and the signal 7 is transmitted.

In consideration of the case where one of the n thermocouples is broken, the second value 8 from the minimum value side in the taken-in exhaust gas temperature is taken out, and the adder is added. 9, the difference from the maximum value 3 in the exhaust gas temperature is taken, and when the monitor relay 10 determines that the difference exceeds a preset allowable value, it is considered as combustion abnormality,
Send signal 11.

At the same time, the respective exhaust gas temperatures 1 detected by the n thermocouples are taken in, and any one of the individual fluctuation widths in the exhaust gas temperatures 1 is set in advance. When it is determined that the allowable fluctuation range is exceeded, it is considered that the combustion is abnormal, and the signal 14 is transmitted.

That is, signal 7, signal 11 and signal 14
A command to shift the first stage combustion unit to the islanding operation is transmitted by transmission from any of the above.

In addition, signal 7, signal 11 and signal 14
When the restriction conditions provided by combining
A method of issuing a command to shift the first stage combustion unit to the independent operation is also incorporated.

Although the above description has been made by taking the exhaust gas temperature as an example of the measured temperature, the combustion gas temperature 15 or the combustor metal temperature 1 is used as another item for monitoring the combustion state.
However, since the temperature change when combustion is unstable shows the same tendency as the exhaust gas temperature 1, abnormal combustion can be caught by the same method as in the case of the exhaust gas temperature. The measurement position of the combustion gas temperature or the combustor metal temperature will be described next.

FIG. 2 is an explanatory view of the measurement position of the combustion gas temperature or the combustor metal temperature. As shown in FIG. 2, regarding the combustion gas temperature, the combustor 17 close to the second stage combustor 18
Insert the combustion gas temperature measuring thermocouple 20 into the
The combustor metal temperature is measured by mounting a combustor metal temperature measuring thermocouple 21 in the swirler 19.

When abnormal combustion in which combustion is unstable is caught by the above method, the secondary fuel gas cutoff valve is fully closed and the primary fuel gas flow rate control valve is fully opened by the fuel command signal, and the second combustion is performed. Combustion in the stage combustion section is stopped.

A basic system of fuel gas flow rate distribution related to the stop of combustion in the second stage combustion section will be described with reference to the drawings.

FIG. 3 is a block diagram showing a basic system of fuel gas flow rate distribution. That is, a fuel command signal is issued from the control device in response to a load request, and based on this signal, a first-stage combustion section that employs diffusion combustion and a second-stage combustion section that employs premixed combustion are used. Has decided to allocate fuel gas to.

That is, during transmission of the fuel command signal 22 for the entire gas turbine requested by the load, the high value limiter 23 for limiting the fuel command signal 22 for the entire gas turbine from exceeding the set value, the first stage combustion And a high-value limiter 25 for limiting the fuel command signal to the first-stage combustion section from exceeding a set value, respectively. Yes, high price limiter 2
The primary fuel command signal 26 is transmitted from 5 to determine the opening degree of the primary fuel gas flow rate control valve.

On the other hand, the opening degree of the secondary fuel flow rate control valve is determined as follows. That is, for the fuel command signal 22 of the entire gas turbine after passing through the high price limiter 23,
An adder 27 is provided on a line different from the line for transmitting the primary fuel command signal 26, and the adder 27 allows the high price limiter 2 to operate.
The fuel command signal 22 for the entire gas turbine after passing through the multiplier 24 is subtracted from the fuel command signal 22 for the entire gas turbine after passing through the multiplier 24.

The signal after such subtraction passes through the high limiter 28 for limiting the fuel command signal to the second stage combustion section from exceeding the set value, and then the secondary fuel command signal 29. Is transmitted to determine the opening degree of the secondary fuel flow rate control valve.

In such a basic system of fuel gas flow rate distribution, the fuel supply ratios to the first-stage combustion section and the second-stage combustion section set by the multiplier 24 are 100% and 0%, respectively.
Thus, the combustion in the second stage combustion section is stopped.

In the present embodiment, the control method as described above is adopted, and when abnormal combustion in which combustion is unstable occurs in the gas turbine, the combustion of the second stage combustion section is stopped and the first stage combustion section is independently operated. The gas turbine is continuously operated while maintaining a stable combustion state of only combustion, and the first-stage combustion section is smoothly shifted to independent combustion.

That is, when only the first-stage combustion section is switched to the single combustion only, the NOx concentration temporarily rises as compared with the case where the second-stage combustion section adopting the premixed combustion system is used together. However, the CO concentration decreases and the operation can be continued while maintaining a stable combustion state of only the single combustion in the first stage combustion section.

[0051]

According to the present invention, in a gas turbine having a two-stage combustor, when abnormal combustion occurs in the second-stage combustor, the first-stage combustor alone is swiftly transferred to independent combustion. It is possible to continue operation while maintaining a stable combustion state without stopping the gas turbine.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a temperature measurement position according to an embodiment of the present invention.

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

FIG. 4 is an explanatory diagram of a gas turbine having a conventional two-stage combustor.

FIG. 5 is a relationship diagram of a fuel-air ratio and a NOx concentration or a CO concentration.

FIG. 6 is an explanatory diagram of a mounting state of a conventional combustor.

FIG. 7 is a measurement diagram of a temperature distribution of exhaust gas.

FIG. 8 is a diagram showing the change over time in the exhaust gas temperature of each combustor.

[Explanation of symbols]

1 ... Exhaust gas temperature, 2 ... Distribution calculator, 3 ... Maximum value, 4 ...
Minimum value, 5, 9, 27 ... Adder, 6, 10, 13 ... Monitor relay, 7, 11, 14 ... Signal, 8 ... Second value from the minimum value side, 12 ... Fluctuation range, 15 ... Combustion gas temperature , 16
... combustor metal temperature, 17 ... combustor, 18 ... second stage combustion section, 19 ... swirler, 20 ... combustion gas temperature measuring thermocouple,
21 ... Thermocouple for measuring combustor metal temperature, 22 ... Fuel command signal for the entire gas turbine, 23, 25, 28 ... High limiter, 24 ... Multiplier, 26 ... Primary fuel signal, 29 ... Secondary fuel signal, 30 ... Compressor, 31 ... Outlet air, 32 ... Combustion gas, 33 ... Turbine section, 34 ... First stage combustion section, 35 ... Combustion air, 36 ... Fuel nozzle, 37 ... Fuel, 38 ... Air flow controller, 39 ... NOx concentration, 40 ... CO concentration, 41
... Fuel-air ratio range where both NOx and CO concentrations are low, 42 ... Exhaust section, 43 ... Thermocouple for measuring exhaust gas temperature, 44 ... Normal temperature distribution, 45 ... Abnormal temperature distribution, 46 ... Exhaust gas Temperature fluctuations.

Front page continuation (72) Inventor Koji Takahashi 3-1-1, Saiwaicho, Hitachi, Ibaraki Hitachi Ltd. Hitachi factory (72) Inventor Isao Sato 3-1-1, Saiwaicho, Hitachi, Ibaraki Hitachi Ltd., Hitachi Works (72) Inventor Akira Shimura 3-1-1, Sachimachi, Hitachi, Ibaraki Prefecture Hitachi Ltd., Hitachi Works, Hitachi (72) Inventor Minoru Takaba, 3-chome, Sachimachi, Hitachi City, Ibaraki Prefecture 1-1 Hitachi Ltd., Hitachi Works, Hitachi Plant (72) Inventor, Masae Takahashi 5-2-1 Omika-cho, Hitachi City, Ibaraki Prefecture Hitachi Ltd., Omika Plant, (72) Inventor, Shiromaru Isao Hiroshima City, Hiroshima Prefecture Chugoku Electric Power Co., Inc. 4-33 Komachi, Naka-ku

Claims (4)

[Claims] 1. A method of controlling a gas turbine having a two-stage combustor comprising a diffusion combustion type first stage combustion section and a premixing type second stage combustion section, wherein the first stage combustion section and the second stage combustor are used. The combustion state with the stage combustion section is monitored, the state quantity relating to the combustion state is taken in as a control factor, and when the state quantity exceeds an allowable amount, the combustion of the second stage combustion section is regarded as abnormal combustion, A method for controlling a gas turbine having a two-stage combustor, characterized in that a single combustion of only the first-stage combustion section is rapidly changed. 2. A state value, which is a constituent factor of the state quantity,
The method for controlling a gas turbine having a two-stage combustor according to claim 1, wherein the method is at least one of a combustion gas temperature, an exhaust gas temperature, and a combustor metal temperature. 3. The state quantity is a difference between a maximum value and a minimum value in the state value or a difference between a maximum value and a second value from the minimum value side in the state value. Of a gas turbine having a two-stage combustor according to claim 1. 4. The method for controlling a gas turbine having a two-stage combustor according to claim 1, wherein the state quantity is a fluctuation range of the state value.