JPH07224689A - Gas turbine combustion controller and its control method - Google Patents

Abstract

PURPOSE:To suppress NOx below the limit value in any combustion condition by classifying combustion according to respective states of the combustion conditions, storing maps of NOx concentration limit values according to zones set in the same conditions, and controlling combustion based on the maps. CONSTITUTION:Air temperature, air pressure, air humidity, and fuel calorific value of combustion conditions are measured by sensors 282, 278, 286, 254 respectively and the measurement results are stored in respective can maps 708. An air flow control signal 716 and a fuel flow control signal 718 are stored as substitute values of air quantity and fuel quantity. Combustion conditions of a burner are measured by an exhaust gas sensor 280 or a combustion chamber ratio sensor 281 so as to store them by comparing with the respective can maps 708. In the combustion controller 708, maps corresponding to the combustion conditions are detected from the respective can maps 708 based on measurement values of air temperature, air humidity, and combustion calorific value, and the air flow control signal 716 and the fuel flow control signal 718 are made based on the searched maps and load instruction values so as to control a burner 200.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion control device for a gas turbine combustor and a control method thereof, and more particularly to a combustion control device and method for always realizing low NOx combustion regardless of the state of the atmosphere and the fuel.

[0002]

2. Description of the Related Art In order to protect the global environment, low NOx combustion is required as part of exhaust gas regulation. For this reason,
Instead of diffusion combustion in which fuel and air are supplied from different ejection ports and burned while being mixed in a combustion chamber, premixed combustion in which fuel and air are premixed and then burned is being used.

In this premixed combustion, the reaction region of combustion can be reduced, so that high load combustion can be performed. Also,
When the ratio of the fuel amount to the air amount is called the fuel-air ratio, by using the lean premixed combustion method in which the fuel is burned in a state where the fuel is less than the theoretical fuel-air ratio required for complete combustion,
The NOx emission amount can be reduced. This lean premixed combustion method is being adopted in gas turbine combustors and the like.

By the way, it has been found that the stability of the premixed flame and the NOx emission amount are influenced by the humidity in the atmosphere, the temperature, the temperature of the combustion air, the property of the fuel, the calorific value and the like. For example, when the humidity in the atmosphere is high, the NOx emission amount is small, but the flame stability is low and the misfire tends to occur.

As a means for dealing with such a decrease in flame stability due to changes in the atmospheric temperature and humidity, the properties of the fuel, the amount of heat generated, etc., for example, Japanese Patent Laid-Open No. 5187271 discloses the atmospheric humidity and humidity and the fuel. A method of detecting a change in the amount of heat generation and controlling the amount of air and the amount of fuel supplied to the premix combustion burner by a detection signal of this change is disclosed.

Further, in Japanese Unexamined Patent Publication No. 4-318233, a limit line of exhausted NOx according to the state of the humidity of the atmosphere is stored in advance, and if the measured value of NOx exceeds the limit value, NOx is determined. It is disclosed that the amount of air and the amount of fuel supplied to the combustor are controlled so that the ratio is below the limit value.

Further, Japanese Patent Application Laid-Open No. 62-111135 discloses controlling the fuel-air ratio in response to changes in atmospheric conditions (atmospheric temperature) and fuel conditions (calorific value).

[0008]

However, the above-mentioned Japanese Patent Laid-Open No. 5-187271 discloses that the air amount and the fuel are changed by using the changes in the atmospheric temperature and the humidity and the calorific value of the fuel in order to maintain the stability of the flame. The amount of air was controlled, and the amount of air and the amount of fuel were not controlled so that the NOx value maintained the desired limit value.

Further, in the prior art described in the above-mentioned Japanese Patent Laid-Open No. 4-318233, since the NOx emission amount changes with changes in atmospheric humidity, the ratio of fuel to air in the premixed flame depending on changes in atmospheric humidity, ( It has been known as described above that it is necessary to change the fuel-air ratio). However, it is necessary to change gas turbine combustion control elements such as atmospheric temperature and humidity and combustion conditions such as heating value of fuel. For that reason, no specific control method is proposed, and therefore,
Satisfactory NOx limits could not be achieved throughout operation.

It is an object of the present invention to provide this specific control method, and thus to a given NOx throughout operation.
It is an object of the present invention to provide a gas turbine combustion apparatus and method that are kept within a limit value.

When the combustor is composed of a plurality of combustors (cans), it is another object of the present invention to suppress an increase in NOx emission amount due to variations in the characteristics of the combustors (cans). Has an aim.

[0012]

[0013]

In order to achieve the above-mentioned object, a gas turbine combustion control system according to the present invention comprises:
(A) Fuel amount control means for controlling the fuel amount supplied to the combustor of the gas turbine; (b) Air flow rate control means for controlling the air flow rate supplied to the combustor; (c) The fuel. In the relationship of the mixture ratio with air, at least the heat generation amount of the fuel and the temperature and humidity of the air are classified, and the limit value of the NOx concentration in the exhaust gas that is predetermined corresponding to the set zone is set. And (d) searching the map corresponding to the measured values of the calorific value of the fuel and the temperature and humidity of the air, and mixing ratio in the searched map based on the load command value. And a combustion control means for applying a control signal to the fuel amount control means and / or the air flow rate control means.

A second feature of the present invention is that when the combustor is composed of a plurality of combustors (cans), the storage means is provided for each combustor (can), and the storage means is provided in the storage means. Based on this, the fuel amount and / or the air amount is controlled for each combustor (can).

Furthermore, a third feature of the present invention that achieves another object of the present invention is that the stored contents of the storage means in the case of the above second feature of the present invention can be updated, and the measured value of the NOx concentration can be obtained. When the NOx concentration exceeds the limit value, a predetermined correction amount is applied to the fuel supply means and / or the air supply means until the NOx concentration becomes equal to or less than the limit value, and the NO
When the x concentration is equal to or less than the limit value, the mixing ratio is
It is to add learning means for storing instead of the stored contents of the storage means corresponding to the calorific value of the fuel at that time and the measured values of the temperature and humidity of the air.

Furthermore, in the gas turbine combustion control method according to the fourth feature of the present invention, the amount of fuel and / or the amount of air is divided for each state of the calorific value of the fuel and the temperature and humidity of the air, and the same. The limit value of the NOx concentration corresponding to the zone set as the condition is obtained, the predetermined mixing ratio of fuel and air is controlled based on the load demand, and the NOx concentration of the exhaust gas of the combustor is measured. When it becomes larger than the limit value, the fuel amount and / or the air amount is corrected by a predetermined amount so as to become smaller than the limit value, and when the mixture ratio becomes smaller than the limit value, the heat generation amount of fuel and air Instead of the mixing ratio corresponding to the temperature and the humidity, it is stored, and in the next control stage of the fuel amount and / or the air amount, the control is performed based on the stored contents.

The limit value may be approximately 10 ppm.

[0018]

[0019]

According to the first feature of the present invention, the combustion condition is determined by at least the atmospheric temperature and humidity and the calorific value of the fuel, and the map of the NOx concentration limit value is stored corresponding to each state of the combustion condition. However, since the combustion control is performed based on the stored contents, the NOx concentration can be suppressed to the limit value or less under any combustion condition.

Further, in this case, in order to correspond to the variety of combustion conditions such as the above-mentioned gas turbine combustion control element, for example, the atmospheric temperature and humidity and the calorific value of the fuel, the respective states of these combustion conditions are classified and set. A map of the NOx concentration limit value was stored corresponding to each zone.

That is, the above-mentioned combustion conditions exist in a wide variety depending on the climate and the operating state of the gas turbine, and if all of them are to be stored, not only a huge storage capacity is required, but also the search time becomes long. Since the controllability is also deteriorated, the combustion conditions are divided into respective states, and when the NOx concentration in the set zone, for example, the atmospheric temperature 10 ° C to 30 ° C is substantially the same, the range is regarded as the same condition. This is for setting and storing a map of the NOx concentration limit value corresponding to the range, which not only keeps the NOx concentration below the limit value in the zones set as the same condition, but also contributes to the reduction of the storage capacity. .

Therefore, even if the number of control elements for performing combustion control increases, low NOx combustion control can be performed correspondingly.

According to the second feature of the present invention, the storage means is provided for each combustor (can), and the combustion control of each combustor (can) is performed based on this storage means. First
In addition to the effect of the characteristics of NOx in each combustor (can)
It is also possible to keep the amount of emissions below the limit value.

Further, according to the third feature of the present invention, NO
When the measured value of x concentration exceeds the limit value, a predetermined correction amount is applied to the fuel supply unit and / or the air supply unit until the NOx concentration becomes equal to or less than the limit value, and the NOx concentration is Combustion control with a learning means for storing the mixing ratio when it becomes less than or equal to the limit value instead of the stored contents of the storage means corresponding to the measured values of the heat value of the fuel and the temperature and humidity of the air at that time By adding to the device,
Under all combustion conditions, the mixing ratio corresponding to NOx below the limit value can be grasped in real time and quantitatively, and the combustion control is performed by the newly grasped mixing ratio. It is possible to suppress an increase in the NOx emission amount due to the deterioration of NOx and variations in the characteristics of each combustor (can).

That is, each time combustion control is performed, a combustor (can)
The optimum fuel-air ratio for each can be grasped.

Furthermore, according to the fourth aspect of the present invention,
When the measured NOx concentration exceeds the limit value,
The fuel amount and / or the air amount is corrected by a predetermined amount so as to be smaller than the limit value, and when the mixture ratio becomes smaller than the limit value, the mixing ratio corresponds to the calorific value of the fuel and the temperature and humidity of the air at that time. Instead of the ratio, it is stored, and in the next fuel amount and / or air amount control stage, control is performed based on this stored content, so combustion control is performed based on the mixed ratio of the stored content, and the actual control at that time is performed. Even if the NOx value exceeds the limit value, the mixture ratio corresponding to NOx below the limit value under the combustion conditions at that time can be quickly obtained and reflected in the next combustion control.

By using the above-mentioned map, the limit value can be set to about 10 ppm, and it is possible to realize a low NOx combustor which has not been available in the past.

[0028]

EXAMPLES Before explaining the examples of the present invention, the matters clarified by the present inventors will be described.

The present inventors have found that the burner is used in the premixed combustion with excess air, particularly preferably in the premixed combustion with the fuel-air ratio of 1.0 or less and 0.5 or more (the value normalized by setting the theoretical fuel-air ratio to 1). Depending on the combustion conditions such as the composition of the inflowing fuel, the moisture concentration of the air, the temperature of the air, and the fuel-air ratio, the NOx concentration and CO concentration discharged from the combustor, the flame blowout limit, the vibration combustion generation limit, the flame Calculate the correlation such as flashback limit,
The present invention has been completed in which these are stored, the conditions of smaller NOx and CO concentrations are learned, and the conditions are adapted to each fuel-air ratio control. The stable combustion range of premixed combustion shows a good correlation between the fuel-air ratio and the load ratio.

The matters investigated by the present inventors are shown below.

[I] The NOx emission amount is substantially the same as long as the fuel composition (fuel heat generation amount), the fuel-air ratio, the mixture temperature before combustion, and the water concentration in the mixture are the same.

[Ii] Since the NOx emission amount shows a relatively good correlation with the fuel component at the same fuel-air ratio, a physical amount of fuel, for example, a specific gravity sensor is provided to increase or decrease the fuel-air ratio with respect to the fuel that changes for a while. .

[Iii] The jet speed of the mixed gas when the flame is blown out is substantially the same even if the fuel composition, the water content in the mixed gas, and the mixed gas temperature before combustion change.

[Iv] The jetting speed of the mixed gas when oscillating combustion occurs is substantially the same even if the fuel composition, the water content in the mixed gas, and the mixed gas temperature before combustion change.

Based on the above, atmospheric humidity, temperature,
The combustion condition and air amount of the fuel composition, the fuel amount and the change of the combustion state by the exhaust gas sensor or the flame image are measured and stored. When the ratio of the fuel amount to the air amount is called the fuel-air ratio, the fuel-air ratio and the combustion state are measured in contrast and stored. Then, the optimization of the fuel-air ratio of stable combustion and low NOx is learned with an actual combustor (can) and mapped. Depending on the combustion condition being measured and the load request from the host computer, the pointer moves on the referenced map to recognize the optimum fuel amount and air amount. Of the combustion conditions, the atmospheric humidity and the temperature change slowly as described above, and therefore, if only the change in the fuel composition can be predicted, the fuel-air ratio required to keep the combustion state optimum can be known in advance. Here, the change of the fuel composition is a slow change and a fast change when the safety valve of the fuel tank operates. Slow changes can be accommodated by some means of observing combustion conditions. In the case of a rapid change, the air amount in the combustor may be adjusted with a time delay from the safety valve operation detection signal.

Therefore, as a concrete method of controlling the combustion state, for example, NO for the fuel-air ratio is set according to the load.
x Emission concentration and flame stability are measured and stored. The NOx emission concentration and flame stability with respect to the fuel-air ratio when the humidity, temperature, and fuel composition of the combustion air are changed are measured and stored as a map. Based on this map, the amount of fuel and / or the amount of air supplied to the burner is controlled so that a flame with low NOx emission concentration and good stability is formed.

Further, in the present invention, it is preferable that the operation command has a pattern suitable for low NOx operation, high efficiency operation, load fluctuation operation, and the like. Further, learning is an indirect value of NOx and fuel amount / air amount such as a command value, a command voltage, a command current, a control target, a control voltage, a control current, a displacement of a control mechanism, a measured value by a flow meter, and the like. You can also do it in.

By the way, premixed combustion in which fuel and air are mixed and ejected from a nozzle in advance is a combustion system capable of reducing NOx as compared with diffusion combustion, but our research results show that it is unstable at low load. It became clear that it would be in a burning state. Further, in the premixed combustion, the NOx value changes depending on the fuel-air ratio, and the fuel-air ratio is low, that is, the lean combustion is N
Ox value becomes low. By the way, this fuel-air ratio is slightly different not only in the can of the combustor but also in the combustor as a whole.
It was also revealed that the value was higher overall.

In the present invention, the fuel amount and / or the air amount can be controlled for each of a plurality of combustor cans, and the combustion conditions and the combustion conditions (results) are stored in comparison with each other. The feature is that the optimum values of the fuel amount and the air amount are learned so as to satisfy the condition of low NOx combustion.

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

FIG. 1 is a schematic diagram showing an embodiment of the system configuration of a thermal power generation system for carrying out the fuel-air ratio control of the present invention.

The memory area 707 stores the NOx value indicating the combustion result for the combustion condition, the load command value, the fuel amount and the air amount. As will be described later, these conditions have a complicated causal relationship, and the fuel amount and the air amount have been appropriately adjusted so far based on experiments. In the present invention, these conditions are zoned within a range where there is no significant difference, and the fuel amount, air amount, and NOx value with respect to the load are actually measured for each condition and stored in comparison.

As described above, the exhausted NOx value is the atmospheric temperature,
Since it is affected by changes in humidity and fuel calorific value, it is necessary to perform combustion control in consideration of all of these conditions, but there are numerous combinations of these, and if all of them are to be stored, a large-capacity storage device is required. Therefore, the combustion conditions are zoned in a range where there is no significant difference, that is, in the range where they can be regarded as the same condition, and the fuel amount, the air amount and the NOx value for the load are stored and corresponded for each condition. did.

These values are close to the amounts of fuel and air that have been experimentally obtained in the past, but especially the configuration of the present invention continues the operation when the conditions determined during the trial run deviate from the optimum values. The optimum value is learned over time, and the accuracy error and design error of the combustor can be corrected for a while. Furthermore, as described below, a plurality of combustors of the thermal power generation device,
Specifically, it is composed of a dozen or more cans of combustor, and each can has an imbalance in the amount of fuel and / or air. The present invention is configured so that the flow rate of fuel and / or air can be controlled for each can, and each can be controlled to a fuel-air ratio with a small NOx.

The air temperature of the combustion condition is measured by the air temperature sensor 28.
2. The air pressure is measured by the air pressure sensor 278, the air humidity is measured by the air humidity sensor 286, and the fuel heat generation amount is measured by the fuel heat generation sensor 254, and is taken into each can map 708 as the combustion condition. Also, the air flow rate and the fuel flow rate are replaced by the air flow rate control signal 71
6. The fuel flow rate control signal 718 is taken in. The combustion conditions, the air amount, and the combustion state of the combustor with respect to the fuel amount are measured by the exhaust gas sensor 280 or the fuel-air ratio sensor 281,
It is captured in comparison with each can map 708. When controlling the flow rate of each conventional can as a whole, there are variations in the flow rate due to the difference in the flow path resistance to each can and the shape accuracy inside each can. It could not be burned at the fuel-air ratio. On the other hand, in the present invention, not only can the flow rate be controlled for each can, but it can also be controlled to an optimum fuel-air ratio given or learned in advance.

Combustion control unit MPU-2 (control of each can) 703
Is an output signal representing each state of the air temperature sensor 282, the air humidity sensor 286, and the fuel heat generation sensor 254, and a map corresponding to the state, that is, the combustion condition at that time is searched from each can map 708 serving as a storage unit. To do. Each can map 708 stores a map that represents a NOx value equal to or less than the limit value corresponding to the combustion condition in the fuel-air ratio relationship as shown in FIG. 4, FIG. 5, or FIG. 7 to FIG. . Then, the air flow rate control signal 716 and the fuel flow rate control signal 718 are created based on the retrieved map and the load command value,
The combustion control of the combustor 200 is performed. Furthermore, MPU-
2 (control of each can) 703 includes a learning unit that learns the optimum fuel-air ratio described above. Specific learning by this learning means will be described later with reference to FIG.

In this manner, the optimum fuel amount and air amount command values peculiar to the combustor with respect to the combustion conditions and load demands are stored in each can map. As described above, since the combustion conditions are innumerable depending on the combination of the respective conditions, the ranges having no significant difference in the combustion conditions are regarded as the same conditions and handled.

The MPU-1 (overall control) 701 outputs an operation command and a load command for each can based on a load request to the host computer 700 and a basic control plan input in advance. The MPU-2 (can control for each can) 703 receives the operation command and load command for each can, determines the fuel flow rate and the air flow rate for each can, and outputs the flow command value. Here, the air temperature, the humidity, etc. of the combustion conditions are appropriately measured by each sensor and serve as a pointer for map reference. When there is a change in the combustion condition, the pointer immediately refers to the map corresponding to the combustion condition and changes to a flow rate control signal to appropriately change the fuel amount and the air amount. In the present embodiment, the sampling times of the combustion conditions are made different in consideration of the changing speed of the combustion conditions. That is, the change in temperature and humidity is gradual, so the sampling is slowed down and the sampling is speeded up in response to the load demand. By the way, although the fuel calorific value usually changes slowly, the fuel calorific value becomes high when the safety valve 250 of the fuel tank is activated. The NOx value occurs when nitrogen in the air is exposed to a high temperature. Therefore, in the case of a fuel gas having a high calorific value, it is generally preferable to set the fuel-air ratio low. This change in the amount of heat generation reaches the combustor with a time constant that depends on the length of the pipe from the safety valve to the combustor. Since this time constant is unique to each device, the operation of the safety valve can be detected and interrupt control can be performed. When the operation of the safety valve 250 is restored, it returns to the normal command value of the fuel-air ratio with a constant time constant. Here, although not shown, an interrupt can be generated based on the operation signal of the safety valve, and the fuel flow rate control signal 718 with a matched time constant can be output.

As means for not using the operation signal of the safety valve,
It is also possible to deal with this by increasing the heating value sampling time.

Although the control for increasing / decreasing the fuel amount has been described above with respect to the operation of the safety valve, the air amount may be controlled. It is also an effective means to let the gas from the safety valve escape to another pipe. Actually, it is sufficient to prepare a table or map of about 2 to 5 as a representative property of the change in the calorific value of the fuel when the safety valve operates or including the difference in the composition of liquefied natural gas (LNG). As a result, the fuel-air ratio corresponding to the heat value of the fuel can be output.

By the way, the control of the flow rate at the rated rotation has been described so far, but since the rotation speed of the compressor 100 sent to the combustor changes at the time of starting the generator, the air pressure of the compressor changes. For this reason, the flow rate control at the time of startup needs to have a pattern different from that at the time of rating. Therefore, a startup pattern 710 is separately provided at the time of startup to control the flow rate at startup. This activation pattern is also air volume temperature, humidity, pressure,
It holds the differences in combustion conditions such as fuel heating value and starting conditions.

Next, each can default value 712 in the memory area is an area for inputting a design value for each can map 708 to be learned at the time of test operation. This is an area for inputting the optimum values of the same type combustor from the past combustor database before the test run. This area is a ROM for backup
It is better to use a protector or a RAM so that it cannot be easily rewritten. At the beginning of the operation of the new combustor, this command value is used to control the flow rate according to the combustion conditions and load demand.

Here, for example, it is conceivable that the value of NOx is fed back in real time to control to the optimum fuel-air ratio, but in the present invention, it is installed at the outlet of the turbine because of the heat resistance of the NOx sensor. , Because it is practical,
There is a time lag between the measured values of the fuel-air ratio and NOx, and feedback control is difficult, so past data is used offline.

By adopting the gas turbine power generator and control method of the present invention, changes in NOx emissions due to seasonal changes, fuel composition changes, installation areas, etc. are minimized, and low N
It is Ox and can maintain good flame stability. Generally, in order to eliminate the need for a denitration device, the NOx concentration discharged from the gas turbine combustor is 1% in terms of 16% O ₂ conversion.
It is said that it should be 0 ppm or less.

Next, a concrete learning means by the above-mentioned learning means will be described with reference to FIG.

In step 21, the fuel-air ratio control is performed based on the retrieved map and the load request command value. Step two
It is determined whether or not the NOx value measured in 2 exceeds the limit value. If the measured NOx value does not exceed the limit value in step 22, the fuel-air ratio control is performed in step 23 using the map used in step 21 as it is. If the NOx value measured in step 22 exceeds the limit value, a predetermined amount of air and / or fuel is corrected. This predetermined amount may be arbitrarily set within a range in which the fuel-air ratio does not significantly change. Then, in step 25, the measured NOx value and the limit value are compared again. The fuel-air ratio is corrected stepwise in step 24 until this measured value falls below the limit value. If the measured value is below the limit value, in step 26, the corrected fuel-air ratio at that time is stored and updated in the map corresponding to the combustion condition measured at that time.

If such learning is sequentially repeated,
Since it is possible to quantitatively grasp the optimum fuel-air ratio corresponding to all combustion conditions and perform combustion control with this optimum fuel-air ratio, it is possible to always suppress NOx to below the limit value regardless of the combustion conditions. It is also possible to suppress an increase in exhausted NOx due to deterioration of combustor characteristics due to secular change of the combustor.

Further, the learning in steps 24 to 26 described above can be carried out at the time of steady operation in consideration of the time until the air and fuel enter the combustor and the time delay from the combustor to the exhaust gas sensor. desirable.

This learning may be carried out for the entire combustor or for each combustor (can). In the latter case, there is an effect that variation in characteristics of each combustor (can) can be suppressed.

FIG. 2 shows a gas turbine combustor (can) of the present invention.
An example of a configuration for controlling the flow rate and measuring the NOx value will be described. Reference numerals not described indicate the same or the same functions as those described above. The combustor (can) is composed of a plurality of cans as described above, and in this figure, the combustor (can) 202, the combustor (can) 204, the combustor (can) 206, the combustor (can) 208. , Only five of the combustors (cans) 210 are shown.

An air flow rate control valve and a fuel flow rate control valve are provided in each of the cans, and the flow rate can be controlled individually.
Although not shown here, a measuring instrument such as an air temperature / humidity sensor for combustion conditions is provided. The fuel calorific value sensor and the exhaust gas sensor provide the calorific value and NOx value. The combustion condition and the NOx value when the fuel amount and the air amount are increased / decreased for each of these cans are measured and stored. With this configuration, even if there is a flow loss to each can or a variation in flow control characteristics, equalization can be achieved by appropriately giving a flow control command to each can.

FIG. 3 is an explanatory view of the entire thermal power generation device, with one of the combustors (cans) as a representative. Fuel is the fuel tank 244
Is supplied to the fuel supply pipe 256 by the vaporizer 248. The fuel is measured by the calorific value measuring device 254, the flow rate is controlled by the fuel flow rate control valve 252, and the fuel is sent to the gas turbine combustor 200 . Here, when the fuel used is a fuel having a low boiling point such as LNG, a part of the fuel is vaporized in the fuel tank 244 and the pressure in the fuel tank 244 rises. At this time, in order to prevent the destruction of the fuel tank 244, the pressure in the tank is measured by the fuel tank pressure gauge value 246, and when the pressure in the tank exceeds the limit value, the fuel tank pressure adjustment valve 250 is opened to A part of the gas is discharged to the fuel supply pipe 256. Many of the vaporized gases in the tank have low boiling points,
Since the composition of the fuel that is normally supplied is different, when the pressure adjustment valve 250 in the fuel tank is opened, the fuel composition and the calorific value change. For this reason, the calorific value measuring device 254 has a pressure adjusting valve 250.
It is installed after.

After the air flow rate measuring device 284 measures the air flow rate and the atmospheric humidity measuring device 286 measures the humidity, the air 270 is sucked into the air compressor 100 and becomes high pressure air. The high-pressure air is sent to the gas turbine combustor 200 after the pressure is measured by the air pressure measuring device 290 and the temperature is measured by the gas turbine combustor inlet temperature measuring device 288. Here, if the amount of air taken into the air compressor 100 can be calculated from the atmospheric temperature and humidity and the characteristics of the air compressor 100, the control is performed so that the amount of air taken into the air compressor 100 is constant. The air flow measurement device 284 is not necessary if the device is provided.

The gas turbine combustor is composed of an outer cylinder 261 and an inner cylinder 267. High pressure air 271 flows between the outer cylinder 261 and the inner cylinder 267 and is supplied to the F2 premix combustor 260 as combustion air. A part of the high pressure air 271 is supplied to the combustion chamber as inner cylinder cooling air. A dilution air amount control device is provided on the downstream side of the combustion chamber. When the load on the gas turbine is small, a part of the combustion air is discharged to the downstream side of the combustor as diluted air. Fuel is supplied from a fuel nozzle, mixed with combustion air and then combusted in a premix combustor 260. By the action of the flame stabilizer 273 provided in the premix combustion combustor 260, a circulating flow of high temperature gas is formed downstream of the flame stabilizer, and the heat from this circulating flow stabilizes the premix flame. The gas generated from the premixed flame is mixed with the air for cooling the inner cylinder and the diluted air to become the high temperature combustion gas 274, which is guided to the gas turbine 300 through the transition piece. The high-temperature combustion gas 274 that drives the gas turbine, the air compressor 100 connected to the gas turbine, and the generator 400 becomes low-temperature combustion exhaust gas 274 and is guided to the flue gas denitration device. Nitrogen oxide in the low-temperature combustion exhaust gas reacts with ammonia in the flue gas denitration device, is converted into nitrogen, and is guided to the waste heat recovery boiler 502. The steam turbine 500 is driven by the steam 504 generated in the waste heat recovery boiler 502. This steam turbine is also connected to the generator 400. The steam that has driven the steam turbine 500 becomes water in the condenser 508, and is supplied to the waste heat recovery boiler 502 again. Here, the positions of the waste heat recovery boiler and the flue gas denitration device may be reversed. A denitration device may be incorporated in the waste heat recovery boiler. Combustion exhaust gases are mixed with exhaust gases from other gas turbines at the chimney and released into the atmosphere.

FIG. 4 shows combustion in the case where the air temperature is 250 to 275 degrees, the air humidity is 80 to 85%, and the calorific value of the fuel is 35,800 calories. It is an example of actual measurement showing a state. Combustion conditions were classified into the same conditions as the temperature and humidity conditions and there was no significant difference from the experimental results, and they were regarded as the same condition.
For example, the air temperature Ai = 1 and the air humidity Aj =
1, the heat generation amount of fuel is summarized as Fk = 1.

FIG. 4 shows a range in which the fuel amount and the air amount are stably burned, and the NOx amount is 70 ppm or less and 10 ppm.
The following combustion ranges are shown. When the amount of air is the same, the NOx value is lower when the fuel amount is smaller, and when the fuel amount is smaller, the NOx value is out of the stable combustion range. When both the fuel amount and the air amount increase, the output of the generator increases.
FIG. 5 is an example of actual measurement showing the combustion state when the ratio of the fuel amount and the air amount in the case where the fuel calorific value is 42700 calories is changed and the air temperature and humidity under the combustion conditions are the same as those in FIG. Combustion conditions are temperature Ai = 1,
The air humidity is the same as Aj = 1, and the fuel calorific value is Fk = 10. Compared to Fig. 4, the lower the air-fuel ratio, the lower the NO.
x burning is shown.

FIG. 6 shows the relationship between the fuel-air ratio and NOx. Fig. 6 (a) shows the amount of fuel in each can of the conventional combustor,
This is the case when the flow rate of air varies. The combustion temperature becomes maximum and the NOx value becomes high near the theoretical fuel-air ratio.
When the fuel amount is smaller than the theoretical fuel air ratio, that is, when the fuel air ratio is made smaller, the NOx value decreases. If the amount of fuel is reduced too much, combustion becomes unstable and there is a risk of misfiring, so the amount of fuel is set to a higher range. Since there were variations among the cans, the NOx exhausted in the entire combustor was an average value thereof, and the exhausted NOx could not be kept below a certain value.

FIG. 6 (b) is one of the present invention, and since the fuel amount and / or the air amount can be controlled for each can, the variation in the fuel-air ratio is reduced and the exhausted NOx is reduced. I was able to do it. Due to the structure of the combustor, it may be advantageous in terms of cost not to individually control the flow rate of the air amount, and a difference in the air amount may occur between the cans due to variations in flow path resistance. At this time, since it is difficult to grasp the absolute value of the air amount of each can, the present invention makes it possible to obtain an appropriate fuel amount for each can by measuring the exhausted NOx while controlling the fuel amount for each can. I can. Therefore, NOx is reduced by controlling the air amount as a whole and by controlling only the fuel amount for each can to equalize the fuel-air ratio.

In FIGS. 7 and 8, the horizontal axis represents the air flow rate control signal,
The vertical axis indicates the stable combustion range and NOx indicated by the fuel flow rate control signal.
It is a value. It is difficult to grasp the absolute values of the air flow rate and the fuel flow rate in FIGS. 5 and 6, and here, the stable combustion range and the NOx value were measured using the control signal as a function of the flow rate. Thus, even if the absolute value cannot be grasped, stable combustion and low NOx combustion can be realized by learning the combustion condition and the control signal based on the flow rate control signal.

9 and 10 show the relationship between the air flow rate control signal and the fuel flow rate control signal with the NOx value of 10 ppm or less. As described above, even if the absolute value of the flow rate cannot be grasped, stable combustion and low NOx combustion can be realized by learning the combustion condition and the control signal based on the flow rate control signal.

The range of the NOx value is not always 10p.
If it is difficult to set this value, it may be set to 20 to 30 ppm, for example.

[0072]

The present invention classifies each state of combustion conditions, stores a map of NOx concentration limit values corresponding to zones set as the same condition, and performs combustion control based on this map. Even if there are various combustion conditions, NOx can always be kept below the limit value.

Further, the optimum values of the fuel amount and the air amount which differ depending on the combustion conditions such as atmospheric temperature, humidity and fuel composition and the load factor are learned, so that the change of the combustion condition and the load demand due to the difference of the climate and the fuel heat generation amount. Correspondingly, since the optimum fuel amount and air amount can be controlled in real time for each can, it is possible to realize low NOx emission gas that is not affected by climate change, fuel heat generation amount change, and secular change of the combustor.

[0074]

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a thermal power generation system that implements fuel-air ratio control of the present invention

FIG. 2 is a system diagram for learning each can flow rate control and combustion result of the present invention.

FIG. 3 is a diagram showing an entire gas turbine for thermal power generation and a combustor.

FIG. 4 is a diagram showing a combustion state depending on the amount of fuel and the amount of air (fuel calorific value is low)

FIG. 5 is a diagram showing a combustion state depending on the amount of fuel and the amount of air (high fuel calorific value)

FIG. 6A is a diagram showing the relationship between the fuel-air ratio and NOx. FIG. 6B is a diagram showing the relationship between the fuel-air ratio and NOx.

FIG. 7 is a diagram showing a fuel amount, an air amount control signal, and a combustion state (high calorific value).

FIG. 8 is a diagram showing a fuel amount, an air amount control signal, and a combustion state (high calorific value).

FIG. 9 is a diagram showing a fuel-air ratio control signal and an actual measurement value of NOx (high fuel calorific value).

FIG. 10 is a diagram showing a fuel-air ratio control signal and an actual measurement value of NOx (fuel heat generation amount is low).

FIG. 11 is a flowchart showing a fuel-air ratio learning method of the present invention.

[Explanation of symbols]

200 ... Combustor (can), 244 ... LNG tank, 252 ... Fuel flow rate control valve, 254 ... Fuel calorific value sensor, 259 ... Air flow rate control valve, 280 ... Exhaust gas sensor, 282 ... Air temperature sensor, 286 ...
Air humidity sensor, 702 ... Load command, 703 ... Combustion control device,
708 ... Each can map

Claims (6)

[Claims] 1. A fuel amount control means for controlling an amount of fuel supplied to a combustor of a gas turbine; and an air flow rate control means for controlling a flow rate of air supplied to the combustor.
(C) In the exhaust gas, in the relationship of the mixing ratio of the fuel and air, at least the heat generation amount of the fuel and the temperature and humidity of the air are classified and predetermined in correspondence with the set zone. Storage means for storing a map representing the limit value of the NOx concentration, and (d) searching the map corresponding to the measured values of the heat value of the fuel and the temperature and humidity of the air, and searching the map based on the load command value. And a combustion control means for applying a control signal to the fuel amount control means and / or the air flow rate control means according to the mixing ratio in the map. 2. Fuel supply means for individually supplying fuel to each of a plurality of combustors (cans) of a gas turbine, and / or air supply means for individually supplying air to each of the combustors (cans), In a gas turbine combustion control device having a combustion control means for applying a control signal of a fuel amount and / or an air amount according to a load command value of the gas turbine to the fuel supply means and / or the air supply means, (A) In the relationship of the mixing ratio of the fuel and air, at least the heat generation amount of the fuel, the temperature and the humidity of the air, and the like are classified, and are determined in advance corresponding to the set zone. N in exhaust gas
Storage means for storing a map representing a limit value of the Ox concentration corresponding to each of the combustors (cans); and (b) searching the map corresponding to the calorific value of fuel and the measured values of air temperature and humidity. Then, the mixing ratio in the searched map is obtained for each combustor (can) based on the load command value, and a control signal based on this mixing ratio is applied to the fuel supply means and / or the air supply means. A gas turbine combustion control device comprising: a control unit. 3. Fuel supply means for individually supplying fuel to each of a plurality of combustors (cans) of a gas turbine, and / or air supply means for individually supplying air to each of the combustors (cans), In a gas turbine combustion control device having a combustion control means for applying a control signal of a fuel amount and / or an air amount according to a load command value of the gas turbine to the fuel supply means and / or the air supply means, (A) In the relationship of the mixing ratio of the fuel and air, at least the heat generation amount of the fuel, the temperature and the humidity of the air, and the like are classified, and are determined in advance corresponding to the set zone. N in exhaust gas
Storage means for storing a map representing a limit value of the Ox concentration corresponding to each of the combustors (cans); and (b) searching the map corresponding to the calorific value of fuel and the measured values of air temperature and humidity. Then, the mixing ratio in the searched map is obtained for each combustor (can) based on the load command value, and a control signal based on this mixing ratio is applied to the fuel supply means and / or the air supply means. Control means, (c) when the measured value of the NOx concentration exceeds the limit value, a predetermined correction amount is given to the fuel supply means and / or the air supply means until the NOx concentration becomes equal to or less than the limit value. When the NOx concentration is applied and the NOx concentration becomes equal to or less than the limit value, the mixing ratio is stored in place of the stored content of the storage unit corresponding to the calorific value of the fuel at that time and the measured values of the temperature and humidity of the air. Characterized by having learning means Gas turbine combustion control device for. 4. The gas turbine power generator according to any one of claims 1 to 3, wherein the limit value is approximately 10 ppm.
A gas turbine combustion control device characterized in that 5. A gas turbine combustion control method for controlling the amount of fuel and / or the amount of air supplied to a combustor of a gas turbine according to the load demand of the gas turbine, wherein the amount of fuel and / or the amount of air is The NOx concentration limit value corresponding to the zones set as the same condition is obtained by classifying the heat generation amount of the fuel and the temperature and humidity of the air, and the predetermined mixing ratio of the fuel and air is determined based on the load request. The NOx concentration of the exhaust gas of the combustor is measured, and when the measured value exceeds the limit value, the fuel amount and / or the air amount is corrected by a predetermined amount so as to be smaller than the limit value. The mixture ratio when it becomes smaller than the limit value is stored instead of the mixture ratio corresponding to the heat value of the fuel and the temperature and humidity of the air at that time, and the next fuel amount and / or air is stored. In the control stage,
A gas turbine combustion control method, characterized in that control is performed based on the stored contents. 6. The gas turbine combustion control method according to claim 5, wherein the limit value is approximately 10 ppm.