JPH0633743A - Denitration control device - Google Patents

Abstract

PURPOSE:To provide a control device so that FF control can be backed up by an FB control system, and performance deterioration can be prevented regardless of changing a condition of a gas turbine, to further well control a reference O2 correction value of exhaust gas NOx concentrate always to a reference value even in the case of fluctuating residual oxygen concentration in exhaust gas. CONSTITUTION:A speed type fuzzy controller 139 is provided with a fuzzy inference mechanism 137, FB rule 135 and an FF rule 136, and in the case of such as no load change of a gas turbine, feedback control is performed by the FB rule, to control exhaust gas nitrogen oxide concentration to a target set value. When received disturbance of load fluctuation or the like of a gas turbine, a disturbance detection signal is fluctuated to ignite the FF rule, and feedforward control is performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a denitration control device for controlling the concentration of nitrogen oxides in exhaust gas by adjusting the amount of ammonia injected into the exhaust gas of a gas turbine of a power plant.

[0002]

2. Description of the Related Art In recent years, the increase in energy demand has tended to rely on fossil fuels, the amount of energy supplied by fossil fuels has increased, and the amount of CO ₂ emission has also increased accordingly. For this reason, the crisis of global warming has been exclaimed, and movements are underway to regulate CO ₂ emissions on a global scale. From such a background, a combined cycle power plant that combines a gas turbine cycle and a steam turbine cycle can be expected to have high efficiency, which is expected to lead to reduction of CO ₂ .

Hereinafter, description will be made with reference to the schematic system diagram of the combined cycle power generation plant shown in FIG. The combined power generation plant shown in FIG. 11 includes a gas turbine device 1, an exhaust heat recovery boiler device 3 that generates steam by using the exhaust gas 2 as a heat source, a steam turbine device 4 that uses the generated steam as drive steam, and heat recovery. And a chimney 16 for exhausting exhaust gas. Further, the gas turbine device 1 is operated by an air compressor 6 that pressurizes the introduced air 5, a combustor 8 that combusts the compressed air together with the fuel supplied from the fuel system 7, and a combustion gas generated by the combustion. A gas turbine 9 and a generator 10 that takes a load are provided. In addition, the exhaust heat recovery boiler device 3
Is provided with a superheater 12, an evaporator 13, a denitration device 14 and a economizer 15 along the upstream side to the downstream side of the exhaust gas duct 11 through which the exhaust gas 2 flows, and the steam generated in the superheater 12 is supplied by a steam pipe 17. It is supplied to the steam turbine device 4. The steam turbine device 4 includes a steam turbine 18 that is operated by the steam generated in the exhaust heat recovery boiler device 3, a generator 19 that takes a load, and a condenser that condenses the steam after working in the steam turbine 18. 20 and 20 are provided. Condenser 2
Condensed water from 0 is led to the economizer 15 by the water supply pipe 21, where it is first heated and then evaporated in the evaporator 13,
The steam is further heated by the superheater 12. In the evaporator 13, the feed water is heated and evaporated while being forcedly circulated or naturally circulated by a temperature difference.

In a combined cycle power plant having such a structure, it has been researched to raise the combustion temperature in order to increase the efficiency of the plant and reduce CO ₂ relatively. Nitrogen oxide (NO _x ) discharged from the turbine device 1 exponentially increases with respect to temperature.

As a measure for reducing the concentration of nitrogen oxides (NO _x ), a method of injecting water or steam into the combustor 8 to lower the fuel temperature, and fuel and air for preventing a local high temperature portion are used. There are methods such as premixing in which they are mixed and led to a combustor, and two-stage combustion for averaging combustion temperatures.

However, with these means alone, N
It is difficult to achieve the regulation value of O _x . For this purpose, a denitration device 14 is installed in the exhaust gas passage. Ammonia injection / dry selective catalytic reduction cracking method, which is one of the denitration methods,
Ammonia is injected into the exhaust gas, and on the downstream side, the catalyst 2
This is a method of reducing nitrogen oxides into harmless nitrogen and steam by causing a reaction such as shown by the following formula 2NO + 4NH ₃ + 2O ₂ → 6H ₂ O + 3N ₂ by passing 2 through. This method is generally installed between the evaporator 13 and the economizer 15 because the reaction efficiency at 300 to 400 ° C. is good due to the temperature characteristics of the catalyst.

Such control of the denitration device 14 is performed by the amount of ammonia injected from the ammonia injection system 23. The conventional technique will be described below with reference to the control block diagram shown in FIG. The NO _x concentration set value 100 determined from the ordinance and the NO _x concentration detection value 101 of the exhaust gas discharged from the plant are subtracted by the adder 102 and input to the FB controller 104 as a deviation signal 103.

The FB controller 104 is a proportional controller 105,
It is composed of an integration controller 106 and an adder 107, which proportionally integrates the deviation signal 103 and outputs an FB control signal 108. The proportional gain at this time is Kp, and the integration time constant is T
_Although it is _I sec, in the denitration control, since it is necessary to increase NH ₃ when the NO _x concentration increases, the proportional gain Kp is a negative value.

The disturbance detection signal 109 consisting of a plurality of NO _x fluctuation factors is subjected to feedforward control processing by the FF controller 110, and becomes an FF signal 111. This F
The F signal 111 becomes the FF control signal 113 when the contact 112a is closed. The above-mentioned FB control signal 108 is added to the FF control signal 113 in the adder 114 to become the control signal 115. The control signal 115 is an output signal of the denitration control device 116, and opens and closes the ammonia flow rate adjusting valve 118 via the actuator 117. In the absence of disturbance, the contact 112a is open and the control signal 11
5, the FB control signal 108 controls the NO _x concentration detection value 101 to be equal to the NO _x concentration set value 100.

However, there is a time delay of about 4 minutes from the opening / closing operation of the ammonia flow rate adjusting valve 118 until the NO _x concentration detection value 101 is affected. On the other hand, the exhaust gas of the gas turbine is out of the gas turbine and reaches the chimney in a few seconds or less. In this case, the load fluctuation of the gas turbine is detected,
Since a relay (not shown) operates and the contact 112a is closed, the FF control signal 11 from the disturbance detection signal 109 is generated.
3 is added to the control signal 115 to follow the disturbance with little delay. At this time, since the FB controller 104 has almost no effect, the deviation signal 103 moves freely.
Therefore, by using the load change detection relay described above, the proportional controller 1
The contact 112b between 05 and the integration controller 106 is opened to cut off the input of the integration controller 106 to prevent unnecessary history from remaining in the integration controller 106. As described above, N
The _Ox concentration detection value 101 is controlled within a predetermined range.

[0011]

However, such a conventional technique has the following problems.

(1) It is difficult to accurately detect the load fluctuation of the gas turbine, and the load change detection relay that switches between opening and closing of the contacts 112a and 112b does not always operate properly. Further, even if the load change detection relay accurately captures the load change of the gas turbine, the feedback control system is proportional control at that time, and therefore, even if the deviation signal 103 becomes excessive, control with an offset is performed. . This means that in feed-forward control that cannot follow aging well, the feedback control system cannot back up when the target system is affected by aging or the like.

(2) NO exhausted from the gas turbine 9
When _x concentration increases, will increase the denitrification rate in order to maintain the outlet concentration of NO _x denitration unit 14 constant. As the denitrification rate increases, the denitrification effect due to the ammonia injection decreases. In the above-mentioned conventional technology, since the reduction of the denitration effect accompanying the increase of the denitration rate is not taken into consideration, the control performance is deteriorated when the state change such as the load change that increases the NO _x discharged from the gas turbine is received.

By the way, a concentration regulation system is adopted for the exhaust gas standard value, but there is a system for converting the NO _x concentration by the residual oxygen concentration of the exhaust gas so that the exhaust gas cannot be diluted with air to conform to the standard value. To be taken. It is required that the converted value, that is, the reference O ₂ correction value of the NO _x concentration be suppressed to the reference value or less.

Therefore, in the prior art, as shown in FIG. 13, NO actually measured from the exhaust gas discharged from the plant
From _x density measured values 101a and the residual oxygen concentration measured value 121, to calculate the concentration of NO _x correction value 101b by the reference oxygen concentration correction arithmetic unit 122, the concentration of NO _x correction value 101b
Is used as the above-mentioned NO _x concentration detection value 101. That is, the NO _x concentration set value 10 which is the NO _x concentration reference value
0 and the NO _x concentration correction value 101b are subtracted by the adder 102 and input to the FB controller 104 as the deviation signal 103, so that the NO _x concentration correction value 101b becomes NO _x.
The density is controlled to be equal to the reference value.

However, such a conventional technique has the following problems.

(3) The residual oxygen concentration is large when the load on the turbine is small, and takes a small value when the load is large. Therefore, the actual value 121 of the residual oxygen concentration varies greatly depending on the operating condition. Along with the variation of the residual oxygen concentration measured value 121, the NO _x concentration correction value 101b and the deviation signal 10
3 also fluctuates, and as a result, the closed loop gain of the feedback control system also fluctuates. That is, since the denitrification device to be controlled is hardly affected by the residual oxygen concentration, the fluctuation of the control system closed loop gain is caused by the fluctuation of the residual oxygen concentration measured value 121 when viewed as the entire control system. In the conventional configuration, there is a problem in that the characteristics of the control system change due to this gain variation, the control performance deteriorates, the control deviation increases, and the NO _x concentration exceeds the reference value. Further, due to this gain variation, the control system may become unstable in the worst case.

The present invention has been made to solve the above problem (1), and it is not necessary to accurately determine the load change of the gas turbine, and feedback is provided even with respect to the secular change of the controlled object. An object of the present invention is to provide a flexible and safe denitration control device in which a control system can back up feedforward control.

Further, the present invention has been made to solve the above-mentioned problem (2) and considers the change in the state of the gas turbine by taking into consideration the decrease in the denitration effect accompanying the increase in the denitration rate. It is an object of the present invention to provide a flexible and safe denitration control device that can prevent deterioration of the performance.

Further, the present invention has been made to solve the above problem (3). Even when the residual oxygen concentration in the exhaust gas fluctuates, the reference O ₂ correction value of the exhaust gas NO _x concentration is always used as a reference. It is an object of the present invention to provide a denitration control device that can control the value satisfactorily.

[0021]

That is, in order to solve the above-mentioned problem (1), the present invention relates to a denitration device for injecting ammonia into exhaust gas of a gas turbine and removing nitrogen oxides by a chemical reaction. In the denitration control device that controls the nitrogen oxide concentration in the exhaust gas by increasing or decreasing the injection amount of ammonia, the deviation between the detected value of the nitrogen oxide concentration in the exhaust gas after denitration processing released to the atmosphere and its target setting value Signal, its deviation change rate signal, and the change rate signal of the disturbance factor detection value that affects the nitrogen oxide concentration detection value are input, and the feedback control output is based on the deviation signal and the deviation change rate signal. Fuzzy controller that calculates the feedforward control output by fuzzy inference based on the change rate signal of Characterized by comprising an integrator for calculating the A injection amount. (Hereinafter, the present invention for solving the problem of (1) is referred to as a first invention.) The above (2)
In order to solve the above-mentioned problem, the present invention is to inject ammonia into the exhaust gas of a gas turbine and increase or decrease the injection amount of this ammonia in a denitration device that removes nitrogen oxide by a chemical reaction. In the denitration control device that controls the concentration, of the denitration device inlet nitrogen oxide concentration detection value, the denitration device inlet nitrogen oxide concentration predicted value based on the gas turbine state quantity, and the denitration rate calculation value based on the gas turbine state quantity It is characterized by comprising a gain compensator for compensating the control gain so that the control gain also increases based on at least one value. (Hereinafter, the present invention for solving the problem of (2) is referred to as a second invention.) In the second invention, the denitration device inlet nitrogen oxide concentration detection value, the gas are input as the input signal of the gain corrector. Instead of the predicted NOx concentration at the denitration unit inlet based on the state quantity of the turbine and the calculated denitration rate based on the state quantity of the gas turbine, the detected gas flow rate of the gas turbine and the ratio of the fuel flow rate to the air flow rate of the gas turbine It is also possible to correct by using at least one value of the F / A ratio that is, so that the control gain increases when this value increases.

Further, the gain compensator for adjusting the control gain by using at least one of the fuel flow rate detection value and the F / A ratio of the gas turbine is used when the gas turbine has a two-stage combustor. It is preferable to additionally correct the control gain based on the ratio of the fuel flow rate passing through the main burner so that the control gain decreases as the ratio of the fuel flow rate increases.

In order to solve the above-mentioned problem (3), the present invention is to increase or decrease the injection amount of ammonia in a denitration device for injecting ammonia into exhaust gas of a gas turbine and removing nitrogen oxides by a chemical reaction. In the denitration control device that controls the nitrogen oxide concentration at the standard oxygen concentration of the exhaust gas to a predetermined value, the detected value of the nitrogen oxide concentration in the exhaust gas after the denitration process released to the atmosphere is corrected by the correction function of the exhaust gas residual oxygen concentration. Reference oxygen concentration correction calculator that converts the nitrogen oxide concentration value at the reference oxygen concentration, and feedback control that calculates the control signal based on the deviation signal between the nitrogen oxide concentration value at the reference oxygen concentration and its target set value System and a reference oxygen concentration inverse correction calculator for performing an inverse correction on a processing signal of the feedback control system by an inverse correction function inversely proportional to the correction function of the residual oxygen concentration Characterized by including the. (Hereinafter, the present invention for solving the problem (3) will be referred to as a third invention.) In the third invention, the processing signal of the feedback control system is a deviation signal or a speed type control system. The integrator input signal is preferred.

Further, instead of the reference oxygen concentration inverse correction calculator, a gain adjuster for adjusting the proportional gain of the feedback control system by an inverse correction function inversely proportional to the residual oxygen concentration correction function may be installed.

[0025]

In the first aspect of the invention, the speed type fuzzy controller is provided with the fuzzy inference mechanism and the FB rule and the FF rule. When there is no change in the load of the gas turbine, feedback control is performed by the FB rule. The exhaust gas nitrogen oxide concentration is controlled to the target set value. When a disturbance such as load fluctuation of the gas turbine is received, the disturbance detection signal fluctuates and fires the FF rule to perform feedforward control. In this fuzzy controller, the feedback control and the feedforward control are not switched at the contact. Therefore, the feedback control coexists even during the feedforward control, and if the deviation signal fluctuates greatly, it is suppressed by the feedback control.

According to the second aspect of the present invention, the denitration device inlet nitrogen oxide concentration detected value, the denitration device inlet nitrogen oxide concentration predicted value, the denitration ratio calculated value, the fuel flow rate detected value, or the gain with the F / A ratio input Since the control gain is corrected by the compensator, even if the exhaust gas NOx concentration of the gas turbine changes due to load changes, etc., and the denitrification rate to be achieved by the denitrification equipment fluctuates, the effect of ammonia injection due to the fluctuation of the denitrification rate The fluctuation can be canceled by the gain corrector, and the closed loop gain including the target system can be maintained constant. This makes it possible to construct a control system that always maintains good control performance.

In the third aspect of the invention, feedback control is performed based on the deviation signal of the nitrogen oxide concentration value at the reference oxygen concentration corrected by the correction function of the residual oxygen concentration from the target set value. In the denitration control device that controls the nitrogen oxide concentration value to its target setting value, the processing signal of the feedback control system is inversely corrected by the inverse oxygen correction function that is inversely proportional to the residual oxygen concentration correction function by the reference oxygen concentration inverse correction calculator. By performing this, even if the residual oxygen concentration in the exhaust gas fluctuates, the fluctuation can be canceled by the reference oxygen concentration inverse correction calculator, and the closed loop gain of the control system can be maintained constant. This makes it possible to construct a control system that always maintains good control performance. Further, instead of the reference oxygen concentration inverse correction calculator, a gain adjuster is used to adjust the proportional gain of the control system by an inverse correction function that is inversely proportional to the residual oxygen concentration correction function, and the same effect can be obtained.

[0028]

Embodiments of the present invention will be described below with reference to the drawings. The same parts as those of the conventional example are designated by the same reference numerals,
A duplicate description will be omitted.

Embodiment 1 FIG. 1 shows an embodiment of the denitration control device of the first invention. This denitration control device 116a detects the difference between the NO _x concentration set value 100 and the NO _x concentration detection value 101. The adder 102 that outputs the deviation signal 103 and the differentiator 13 that differentiates the deviation signal 103 with respect to time and outputs the deviation change rate signal 131
2, a differentiator 134 that time-differentiates the disturbance detection signal 109 and outputs a disturbance change rate signal 133, a deviation signal 103,
A fuzzy reasoning mechanism that receives the deviation change rate signal 131 and the disturbance change rate signal 133 as inputs, and fires a corresponding rule according to the FB rule 135 having a feedback function, the FF rule 136 having a feedforward function, and the input to perform fuzzy inference. The fuzzy controller 139, which includes the valve opening operation signal 138 of the ammonia flow rate adjusting valve 118, and the integrator 140 that integrates the valve opening operation signal 138 and outputs the control signal 115.

Next, the operation of the denitration control device 116a having the above structure will be described.

NO _x concentration set value 100 determined by regulations
The deviation signal 103 is obtained by the adder 102 from the detected NO _x concentration value 101 discharged from the plant and is input to the fuzzy controller 139. Also, the deviation signal 10
3 is time-differentiated in the differentiator 132, and is input to the fuzzy controller 139 as the deviation change rate signal 131.

The deviation signal 103 and the deviation change rate signal 131 are input to the conditional section of the FB rule 135, and the fuzzy controller 139 performs feedback control. In this feedback control, for example, when the value of the deviation signal 103 is E and the value of the deviation change rate signal 131 is DE, each of which is clustered and expressed by seven membership functions as shown in FIG. However, as shown in FIG. 3A, it is realized by firing the FB rule, performing fuzzy inference, and calculating the value of the DU, that is, the valve opening operation signal 138. In addition, the FB rule of FIG.
This is a known feedback control rule as Sugano's improved control rule.

Next, when a disturbance such as a load change of the gas turbine occurs, the disturbance detection signal 109 changes and the disturbance change rate signal 133 changes. The disturbance change rate signal 133 is input to the fuzzy controller 139 and is input to the conditional section of the FF rule 136, and feedforward control is performed. In this feedforward control, for example, when the value of the disturbance change rate signal 133 is FA and this is clustered and represented by seven membership functions as shown in FIG. F shown in
This is realized by firing the F rule, performing fuzzy inference, and calculating the value of DU, that is, the valve opening operation signal 138. At this time, the FB rule is also fired at the same time, but it is usually absorbed by the inference result of the FF rule.
However, when the deviation becomes large, conversely, the inference of the FB rule becomes dominant and the feedback control is automatically and automatically changed to the bumpless.

In this way, the valve opening operation signal 138 output from the fuzzy controller 139 is integrated by the integrator 140 to become the control signal 115, and the actuator 1
The ammonia flow rate adjusting valve 118 is opened and closed via 17.

As described above, in this embodiment, since the feedback control and the feedforward control are fused by fuzzy logic, there is no conventional concept of complete switching, and the feedback control system is always backed up even during the feedforward control. It has a flexible system that enables safe and stable control. Therefore, it is possible to perform flexible and safe denitration control in which the feedback control system does not need to accurately determine the load change of the gas turbine and the aging change of the controlled object in the feedforward control can be backed up.

Embodiment 2 FIG. 4 shows an embodiment of the denitration control device of the second invention, in which the denitration device inlet NO _x concentration detection value 141 is input to the denitration control device 116 shown in FIG. A gain corrector 142 is added to correct the proportional gain K _P of the FB controller 104 so that the gain of the FB controller 104 also increases when the NO _x concentration detection value 141 increases. FB controller 1
The proportional gain K _{P of} 04 is adjusted by the gain correction signal 143 output from the gain corrector 142.

[0037] In denitration control device 116b having the above configuration, the gain compensator 142 outputs a gain correction signal 143 in accordance with the denitrator inlet concentration of NO _x detection value 141, FB
The proportional gain KP of the proportional controller 105 of the controller 104 is corrected. The FB controller 104 determines NO _x determined by regulations and the like.
The deviation signal 103 between the concentration set value 100 and the NO _x concentration detection value 101 discharged from the plant is input, and the FB control signal 108 according to the gain correction signal 142 is output.

On the other hand, the FF controller 110 outputs the FF signal 111 based on the disturbance detection signal 109 such as load change. During the load change, the contact 11 by the load change detection relay
2a is closed, and the FF signal 111 becomes the FF control signal 113.
In the adder 114, the above-mentioned FB control signal 108
Is added to form a control signal 115. This control signal 115
Is an output signal of the denitration control device 116b, and opens and closes the ammonia flow rate adjusting valve 118 via the actuator 117.

[0039] Thus, in the present embodiment, the gas turbine exhaust gas concentration of NO _x That denitrator inlet concentration of NO _x increases, the gain corrector 142 proportional controller 10
It acts to increase the absolute value of the proportional gain K _P of 5 and can compensate for the decrease in system gain that accompanies an increase in the denitration rate. Therefore, the NO _x concentration detection value 101 is satisfactorily controlled so that the NO _x concentration set value 100 becomes equal to the NO _x concentration setting value 100 regardless of the fluctuation of the denitration rate.

Third Embodiment Although the second embodiment has been described as the position type, the same effect can be obtained by the speed type control system shown in FIG. In FIG. 5, the denitration control device 116b uses the NO _x concentration detection value 101 and NO _x.
The deviation signal 103 with respect to the concentration set value 100 is input, and the velocity type FB controller 152 performs feedback control calculation by the proportional controllers 105 and 150 and the derivative controller 151, and the disturbance detection signal including a plurality of NO _x fluctuation factors. Speed type FF controller 15 for performing feedforward control processing on 109
3, an adder 114 for adding the output of the speed type FB controller 152 and the output of the speed type FF controller 153, and the contact 112a is closed and the contact 112b is opened during the load change to output the output of the proportional controller 105. gain corrector 142 to output a load change detection relay (not shown) to cut, the gain correction signal 143, such as the concentration of nO _x detected value 141 enter a denitrator inlet concentration of nO _x detection value 141 increases the control gain to increase A multiplier 155 that multiplies the output of the adder 114 and the gain correction signal 142 to generate a valve opening operation signal 154; and an integrator 140 that integrates the valve opening operation signal 154 to generate a control signal 115. Composed of.

In the above construction, the NOx inlet NO _x
Depending on the concentration, the gain corrector 142 changes the denitration device inlet N
By O _x concentration detection value 141 applies a gain correction to increase also the control gain to increase, it is possible to compensate for the reduction of system gain associated with similar increases in the denitrification rate in the embodiment of FIG. According to the present embodiment, the gain of the feedforward control system is also corrected, so that the effect can be further enhanced.

[0042] In Examples 2 and Example 3, were subjected to a control system of the gain correction by using the denitration unit inlet concentration of NO _x detection value 141, denitrator inlet NO _x prediction based on the state of the gas turbine The same effect can be obtained by performing gain correction such that the control gain increases as these values increase, using the values or calculated values of the denitration rate based on the state quantity of the gas turbine. Further, in this case, since the predicted value is used, quick response and stable control can be performed.

Further, if the F / A ratio, which is the ratio of the fuel flow rate of the gas turbine or the fuel flow rate of the gas turbine to the air flow rate, increases, the turbine exhaust NO _x concentration also increases. Therefore, the fuel flow rate or the F / A ratio is detected. Then, a gain correction can be applied so that the control gain also increases when the detected value increases. In such an embodiment, when the combustor of the gas turbine is of a two-stage type, the turbine exhaust gas NO _x concentration tends to decrease as the ratio of the fuel flow rate passing through the main burner increases. As shown, the fuel flow rate detection value or the F / A ratio 161 is input, and the main burner fuel flow rate ratio 162 is also input. As the main burner fuel flow rate ratio 162 increases, the increase rate of the control gain due to the detection value 161 decreases. Gain correction signal 16
A gain corrector 164 for calculating 3 is provided. As a result, the gain of the control system can be adjusted to a value that corresponds well to the denitration rate, and deterioration of control performance due to an increase in the denitration rate can be prevented.

Embodiment 4 FIG. 7 shows one embodiment of the denitration control device of the third invention, in which the NO _x concentration actual measurement value 101a is based on the residual oxygen concentration actual measurement value 121 and NO _x at the time of the reference oxygen concentration. The reference oxygen concentration correction calculator 122 for converting the concentration, and the NO _x concentration at this reference oxygen concentration, that is, the NO _x concentration correction value 101b and N
A deviation signal 103 from the NO _x concentration set value 100, which is the O _x concentration reference value, is input, and based on the residual oxygen concentration actually measured value 121, the reference O ₂ reverse correction, that is, the reference oxygen concentration correction calculator 122 is input. NO _x concentration measured value 101
The reference oxygen concentration reverse correction calculator 171 that multiplies the reciprocal of the correction multiplied by a and the signal 172 that has passed through the reference oxygen concentration reverse correction calculator 171 are subjected to proportional integral calculation and the FB control signal 108
And an FB controller 104 that outputs

Next, the operation of the denitration control device having the above structure will be described. Concentration of NO _x measured value 101a of the exhaust gas discharged from the plant, correcting the concentration of NO _x correction value 101b is a concentration of NO _x at the reference oxygen concentration by a reference oxygen concentration correction arithmetic unit 122 from the remaining oxygen concentration measured value 121 of the exhaust gas To be done. The adder 102 obtains the difference between the NO _x concentration set value 100 and the NO _x concentration correction value 101 b to obtain the deviation signal 10
3 is output. The deviation signal 103 is subjected to the reference O ₂ reverse correction by the next reference oxygen concentration reverse correction calculator 171.

Here, the reference oxygen concentration inverse correction calculator 171
Is the calculation of the inverse function of the reference oxygen concentration correction calculator 122 when obtaining the NO _x concentration correction value 101b.
The signal 172 thus obtained is input to the FB controller 104, proportionally calculated by the proportional calculator 105, and then integrated by the integral calculator 106.
The control signal 108 is sought.

In such a denitration control device, the reference oxygen concentration inverse correction calculator 171 applies the reference O ₂ inverse correction to the deviation signal 103, so that the residual oxygen concentration detected value 1
The fluctuation of the deviation signal 103 due to the fluctuation of 21 can be canceled by the reference oxygen concentration inverse correction calculator 171 and the closed loop gain of the control system can be maintained constant regardless of the value of the residual oxygen concentration. Therefore, since the loop gain of the control system does not change even when the residual oxygen concentration value changes like noise, stable and good control performance can always be maintained.

Embodiment 5 FIG. 8 shows another embodiment of the denitration control device of the third invention. In contrast to the position type of Embodiment 4, a velocity type control system is provided with the above-mentioned reference oxygen concentration reverse. A correction calculator 171 is installed.

In this embodiment, the proportional controllers 105, 15
0 and differential controller 151 speed type FB controller 152
A reference oxygen concentration reverse correction calculator 171 is provided for applying the reference O ₂ reverse correction to the output of the above.

Also in this case, the control system closed loop gain is kept constant regardless of the value of the residual oxygen concentration, so that the fourth embodiment
The same effect as can be obtained.

Embodiment 6 FIG. 9 shows still another embodiment of the denitration control device of the third invention. The reference oxygen concentration inverse correction calculator 1 of the embodiment 4 is shown.
Instead of 71, a gain corrector 181 for adjusting the proportional gain K _P of the proportional controller 105 with an O ₂ inverse correction function based on the detected residual oxygen concentration 121 is installed.

In this embodiment, the gain corrector 18
1 adjusts the proportional gain K _P of the proportional controller 105 so as to cancel the fluctuation of the deviation signal 103 due to the fluctuation of the residual oxygen concentration detection value 121, and therefore, like the fourth embodiment, the residual oxygen concentration value has noise-like characteristics. It is possible to always maintain stable and good control performance against various fluctuations.

Embodiment 7 FIG. 10 shows still another embodiment of the denitration control device of the third invention. Instead of the reference oxygen concentration inverse correction calculator 171 of Embodiment 5, the residual oxygen concentration detection value is shown. A gain corrector 181 for adjusting the proportional gain K _P of the speed type FB controller 152 based on 121 with an O ₂ inverse correction function is installed.

Also in this embodiment, similarly to Embodiments 4 to 6, it is possible to maintain stable and good control performance against noise-like fluctuations in the residual oxygen concentration value.

[0055]

As is apparent from the above description, according to the present invention, the feedback control system and the feedforward control system are caused to coexist by fuzzy control.
It is not necessary to accurately judge the load change of the gas turbine,
Moreover, since the feedback control system can back up the performance deterioration of the feedforward control due to aging, flexible and safe denitration control can be realized.

Further, according to the present invention, by adjusting the control gain according to the NO _x concentration of the gas turbine exhaust gas,
It is possible to prevent deterioration of control performance due to fluctuations in the denitration rate due to changes in the load of the gas turbine, etc., and it is possible to realize flexible and safe denitration control.

Further, according to the present invention, in the denitration control device for controlling the exhaust gas NO _x concentration correction value converted at the time of the reference oxygen concentration to the reference value, the feedback control system performs the inverse correction for canceling the fluctuation of the residual oxygen concentration value. By
The closed-loop gain of the control system becomes constant regardless of the fluctuation of the residual oxygen concentration value, and stable and good control performance can always be maintained.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a denitration control device according to the first invention.

FIG. 2 is a diagram showing a membership function.

FIG. 3 is a diagram showing a fuzzy rule.

FIG. 4 is a block diagram showing an embodiment of a denitration control device according to the second invention.

FIG. 5 is a block diagram showing another embodiment of the denitration control device according to the second invention.

FIG. 6 is a block diagram showing still another embodiment of the denitration control device according to the second invention.

FIG. 7 is a block diagram showing an embodiment of a denitration control device according to the third invention.

FIG. 8 is a block diagram showing another embodiment of the denitration control device according to the third invention.

FIG. 9 is a block diagram showing still another embodiment of the denitration control device according to the third invention.

FIG. 10 is a block diagram showing still another embodiment of the denitration control device according to the third invention.

FIG. 11 is a block diagram showing a schematic system diagram of a combined cycle power plant.

FIG. 12 is a block diagram showing a conventional example of a denitration control device including a feedback control system and a feedforward control system.

FIG. 13 is a block diagram showing a conventional example of a denitration control device that controls an exhaust gas NO _x concentration correction value converted at a reference oxygen concentration to a reference value.

[Explanation of symbols]

100 ......... NO _x concentration setting 101 ......... NO _x concentration detected value 102 ......... adder 103 ......... deviation signal 104 ......... FB controller 105 ......... proportional controller 106 ......... integral control Unit 107 ... Adder 108 ... FB control signal 109 ... Disturbance detection signal 110 ... FF controller 112a. Load change detection relay contact 112b. Load change detection relay contact 113 .... FF control signal 114 ... Adder 115 ... Control signal 116 ... Denitration control device 117 ... Actuator 118 ... Ammonia flow rate adjusting valve 121 ... ...... Measured residual oxygen concentration 122 ... Concentration correction calculator 131 ………… Deviation change rate signal 132 ………… Differentiator 133 ………… Disturbance change rate signal 134 ……… Differentiator 135 ……… FB rule 136 ……… F Rule 137 ......... fuzzy inference mechanism 138 ......... valve opening operation signal 139 ......... fuzzy controller 140 ......... integrator 141 ......... denitrator inlet concentration of NO _x detected value 142 ......... gain corrector 143 ... Gain correction signal 150 ... Proportional controller 151 ... Derivative controller 152 ... Speed FB controller 153 ... Speed FF controller 155 ... Multiplier 161 ... Fuel Flow rate detection value or F / A ratio 162 ………… Main burner fuel flow rate ratio 163 ………… Gain correction signal 164 ………… Gain corrector 171 ………… Reference oxygen concentration reverse correction calculator 181 ………… Gain corrector

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Claims (8)

[Claims] 1. A denitration control device for controlling the concentration of nitrogen oxides in the exhaust gas by increasing or decreasing the injection amount of this denitration device for injecting ammonia into the exhaust gas of a gas turbine and removing nitrogen oxides by a chemical reaction. , The deviation signal between the detected value of the nitrogen oxide concentration in the exhaust gas after denitration processing released to the atmosphere and its target set value, the deviation change rate signal, and the disturbance factor affecting the detected value of the nitrogen oxide concentration. A fuzzy control which inputs a rate-of-change signal of a detection value, calculates a feedback control output based on the deviation signal and the rate-of-deviation change signal, and calculates a feedforward control output based on the rate-of-change signal of the disturbance factor detection value by fuzzy inference. And an integrator that calculates the ammonia injection amount by integrating the output signal of the fuzzy controller. Denitration control device for. 2. A denitration control device for controlling the concentration of nitrogen oxides in the exhaust gas by increasing or decreasing the injection amount of this denitration device for injecting ammonia into the exhaust gas of a gas turbine and removing nitrogen oxides by a chemical reaction. Based on at least one of the denitration device inlet nitrogen oxide concentration detection value, the denitration device inlet nitrogen oxide concentration predicted value based on the gas turbine state quantity, and the denitration rate calculated value based on the gas turbine state quantity. A denitration control device comprising a gain corrector that corrects the control gain so that the control gain also increases when this value increases. 3. A denitration control device for controlling the concentration of nitrogen oxides in the exhaust gas by increasing or decreasing the injection amount of this denitration device for injecting ammonia into the exhaust gas of a gas turbine and removing nitrogen oxides by a chemical reaction. In accordance with at least one of the detected value of the fuel flow rate of the gas turbine and the F / A ratio which is the ratio of the fuel flow rate of the gas turbine to the air flow rate, the control gain is increased so that the control gain also increases. A denitration control device comprising a gain corrector for correcting the above. 4. The denitration control device according to claim 3,
The gain corrector additionally corrects the control gain based on the ratio of the fuel flow rate passing through the main burner of the two-stage combustor of the gas turbine so that the control gain decreases as the ratio of the fuel flow rate increases. Denitration control device. 5. A nitrogen oxide concentration at a reference oxygen concentration of the exhaust gas is set to a predetermined value by increasing or decreasing an injection amount of this ammonia in a denitration device that injects ammonia into the exhaust gas of a gas turbine and removes nitrogen oxide by a chemical reaction. In the denitrification control device that controls the value, the standard for converting the detected value of nitrogen oxide concentration in the exhaust gas discharged into the atmosphere after the denitrification process to the nitrogen oxide concentration value at the time of the reference oxygen concentration by the correction function of the exhaust gas residual oxygen concentration An oxygen concentration correction calculator, a feedback control system that calculates a control signal based on a deviation signal between the nitrogen oxide concentration value at the reference oxygen concentration and its target set value, and a processing signal of this feedback control system Denitration, comprising a reference oxygen concentration inverse correction calculator that performs inverse correction by an inverse correction function that is inversely proportional to the residual oxygen concentration correction function. Control device. 6. The denitration control device according to claim 5,
A denitration control device, wherein the processing signal of the feedback control system is a deviation signal. 7. The denitration control device according to claim 5,
A denitration control device, wherein the feedback control system is a velocity type equipped with a differentiator and an integrator, and a processing signal of the feedback control system is an input signal of the integrator. 8. A nitrogen oxide concentration at a reference oxygen concentration of the exhaust gas is set to a predetermined value by increasing or decreasing the injection amount of this ammonia in a denitration device for injecting ammonia into the exhaust gas of a gas turbine and removing nitrogen oxide by a chemical reaction. In the denitrification control device that controls the value, the standard for converting the detected value of nitrogen oxide concentration in the exhaust gas discharged into the atmosphere after the denitrification process to the nitrogen oxide concentration value at the time of the reference oxygen concentration by the correction function of the exhaust gas residual oxygen concentration An oxygen concentration correction calculator, a feedback control system that calculates a control signal based on the deviation signal between the nitrogen oxide concentration value at the reference oxygen concentration and its target set value, and the proportional gain of this feedback control system A denitration control device comprising: a gain adjuster that adjusts by an inverse correction function that is in inverse proportion to a correction function of oxygen concentration.