JP2635643B2 - Denitration control device for gas turbine plant - Google Patents

Description

The present invention relates to a denitration control device for a gas turbine plant, and more particularly to a control device for reducing noise with respect to a control signal and for controlling a change in a process state quantity. The present invention relates to a denitration control device for a gas turbine plant that can respond quickly and quickly and has no environmental pollution.

(Prior Art) A gas turbine plant burns liquid fuel in a combustor, expands the generated high-temperature and high-pressure combustion gas to rotate a turbine, and uses the rotational force as rotational power of a generator or the like. .

Since harmful nitrogen oxides (hereinafter abbreviated as NO _x ) are generated by high-temperature combustion in the combustor, a denitration device for removing NO _x in exhaust gas is provided. In this denitration apparatus, NO _x in exhaust gas and ammonia (NH ₃ ) added as a reducing agent are subjected to an oxidation-reduction reaction on a catalyst to convert NO _x into harmless nitrogen (N ₂ ) and steam (H ₂ O). And decompose into This is the operation of the denitration apparatus always properly control the amount of ammonia attach to correspond to _the amount of NO _x in the exhaust gas, the denitration control device provided for the purpose of adjusting to not generate ammonia unreacted contaminating the environment Have been.

A conventional denitration control device of a gas turbine plant is generally configured as shown in FIG. 2, and the flow rate of the exhaust gas is calculated based on the process state quantities such as the intake air amount to the combustor of the gas turbine, the fuel flow rate, and the exhaust gas temperature from the combustor. And expected
It has a calculator 1 for calculating the NO _x amount.

Among the expected NO _x amount signal 2 and the exhaust gas flow rate signal 3 output from the arithmetic unit 1, the expected NO _x amount signal 2 is obtained by the NO _x amount setting signal 5 previously set by the NO _x amount setting device 4 and the comparator 6. The difference signal 7 is compared and input to the adder 8.

The deviation signal 7 is determined by the NO at the catalyst layer outlet of the denitration device.
corresponding to ammonia injection amount signal 9 which gives ammonia injection amount required for equalizing _x amount to the set value of the NO _x amount setter 4.

Reason for the deviation signal 7 is _the amount of NO _x becomes equal to the ammonia injection amount signal 9 as it is, nitrogen monoxide and ammonia (NH in is denitration reaction nitric oxide Most (NO) of the NO _x contained in the exhaust gas ₃ ) performs the oxidation-reduction reaction at the same molar ratio as in the following reaction formula.

4NO + 4NH ₃ + O ₂ → 4N ₂ + 6H ₂ O As described above, the predicted NO _x amount signal 2 is calculated from the input / output process amount of the gas turbine, so that there is no time delay. Therefore, ammonia injection amount signal 9 to be adjusted by the estimated amount of NO _x signal 2 to the reference is used as a feedforward signal in denitration control.

On the other hand, the exhaust gas flow rate signal 3 calculated at the same time as the expected NO _x amount signal 2 in the calculator 1 is multiplied by the actual NO _x concentration signal 11 from the deNOx catalyst outlet NO _x meter 10 in the multiplier 12 and The actual NO _x amount signal 13 is obtained. This actual NO _x amount signal 13
Is compared in the comparator 14 with the NO _x amount setting signal 5 from the NO _x amount setting device 4, the deviation thereof is calculated, and the difference is input to the adder 8 as the ammonia injection amount correction signal 15. The ammonia injection amount correction signal 15, the is intended to correct the excess and deficiency of the expected amount of NO _x signal 2 with reference to the injected amount of ammonia, ammonia injection amount from the actual concentration of NO _x in the catalyst layer outlet of denitrator Is used as a feedback signal for controlling

The ammonia injection amount signal 9 as the feedforward signal and the ammonia injection amount correction signal 15 as the feedback signal are added by the adder 8, and the adder 8 adds the ammonia injection amount as a target value of the ammonia injection amount necessary for the denitration control. The quantity target signal 16 is output to the PID calculator 17. PID
The arithmetic unit 17 performs PID control using the ammonia injection amount target signal 16 as a set amount and the ammonia flow signal 19 from the ammonia flow meter 18 as a process amount, and performs a control signal 2
0 is output to the ammonia flow control valve 21. Ammonia flow control valve 21 to open and close operation by a control signal 20 to control the ammonia injection amount, and controls the amount of NO _x of the exhaust gas to a value set by the amount of NO _x setter 4.

In (0007), however denitration conventional control system of a gas turbine plant, the influence of noise is large relative to the expected amount of NO _x signal as the first problem, a low accuracy and reliability of the control operation There are drawbacks.

That is, the expected NO _x amount is determined by the intake air flow rate, the fuel flow rate,
Since the instantaneous measured value of the process state variable that fluctuates, such as the exhaust gas temperature, is obtained by arithmetic processing, the instantaneous change in the process state variable used for the calculation has a large effect as it is. Therefore, as a feed forward signal in the denitration control, expected NO _x affected by Using disturbance only calculated value from the amount is increased, there is a problem that controllability is decreased.

The second problem is that the control system has a large time delay and low response.

Denitration reaction occurring in the denitration apparatus is one in which ammonia adhered to the denitration catalyst undergoes a first oxidation-reduction reaction in contact with the NO _x passing through the denitration catalyst layer, to decompose the NO _x.
However, since the ammonia flow control valve and the denitration catalyst layer are separated via an ammonia pipe or the like, even if the opening of the ammonia flow control valve is control-changed, the ammonia amount corresponding to the valve opening is actually changed to the denitration catalyst layer. Before it adheres to
A considerable time delay will result.

On the other hand, for the actual concentration of NO _x signal from the NO x removal catalyst outlet NO _x meter, NO _x meter sampling pipe length and NO _x meter there is caused to time the delay time or the like required for the analysis results.

Further load change of the gas turbine, if the amount of NO _x in the gas turbine outlet is suddenly changed by other reasons,
The influence of the time delay of the control system is further increased, and the controllability is reduced.

As a third problem, unreacted ammonia may be generated depending on the temperature of the catalyst layer of the denitration reactor, and may contaminate the environment inside and outside the apparatus.

That, NO _x amount which is decomposed by an oxidation-reduction reaction with ammonia on the denitration catalyst surface is a function of the temperature of the denitration catalyst. Therefore as in the conventional denitration controller, there is a possibility that ammonia is excessively injected in a controlled manner performed based only on the deviation between the actual amount of NO _x in the amount of NO _x set value and the denitration catalyst outlet. That is, beyond the processable amount of NO _x in the temperature with the denitration catalyst, the excess of ammonia injection amount in proportion in the case where _the amount of NO _x is increased. Therefore, some unreacted ammonia is discharged from the outlet of the denitration catalyst, which has a bad influence on the inside of the system or the environment.

The present invention has come to in order to solve the above problems, reduces noise to ammonia injection rate signal as a feedforward signal, and the control to changes in _the amount of NO _x due to the sudden change of the process state quantity It is an object of the present invention to provide a denitration control device for a gas turbine plant, which can improve exhaust gas and prevent unreacted ammonia from being discharged.

[Configuration of the invention]

(Means for Solving the Problems) denitration control device for a gas turbine plant according to the present invention is the quantity of combustion air, from the process amount of the fuel flow rate, etc., it calculates the estimated amount of NO _x generated, corresponding to the amount of expected NO _x outputs the ammonia amount as a feed-forward signal, and calculates the actual amount of NO _x in the NO x removal catalyst outlet, the actual amount of NO _x and predicted NO _x
A computing device that outputs the ammonia injection amount corresponding to the deviation from the amount as a feedback signal, an adder that adds the feedforward signal and the feedback signal to output an ammonia injection amount target signal, and outputs the ammonia injection amount target signal as a PID. calculated, and inputs the denitration control device for a gas turbine plant and a PID operator for adjusting and controlling the ammonia flow control valve, the adder ammonia injection amount calculated from the denitration catalyst inlet _the amount of NO _x concentration as a feedforward signal denitration and catalyst inlet concentration of NO _x management device,
A load correction device that inputs the ammonia injection amount corresponding to the load command signal to the adder as a feedforward signal with respect to a load change at the time of turbine startup, and measures the temperature of the denitration catalyst and corresponds to the maximum reaction amount under the temperature condition. An ammonia injection amount limiting device that calculates an ammonia injection amount and outputs it as an ammonia injection amount limit signal, the adder and the PI
A low-value priority circuit that is disposed between the D arithmetic unit and selects one of the low-value signals of the ammonia injection amount limit signal and the ammonia injection amount target signal from the adder, and is input to the PID arithmetic unit. It is characterized by having.

(Operation) According to the denitration control device for a gas turbine plant having the above configuration, the expected NO _x actual in ammonia injection amount signal and the denitration catalyst outlet give ammonia injection amount corresponding to the amount of NO
In addition to the structure of the conventional apparatus that the ammonia injection amount signal corresponding to a deviation between the _x amount and the estimated amount of NO _x is input to the adder, ammonia injection amount calculated from the denitration catalyst inlet concentration of NO _x as a feed-forward signal Input to the adder,
Further, the ammonia injection amount corresponding to the load command with respect to the load change at the time of starting the gas turbine is input to the adder as a feedforward signal.

That is, the number of signal elements input to the adder increases, and the influence of the fluctuation of each signal element is dispersed. Therefore, the noise of the ammonia injection amount target signal output from the adder is also reduced, and the ammonia flow control valve is controlled. The reliability of the control signal to be performed is increased, and stable denitration control is enabled.

The output from the denitration catalyst inlet concentration of NO _x management apparatus, ammonia injection amount correction signal inputted to the adder, because it is calculated directly from the measured values by the denitration catalyst inlet NO _x meter, a large conventional variation Its reliability is higher than that calculated from the expected NO _x amount. However, it takes a time to the sampling and analysis steps in the denitration catalyst inlet NO _x meter, a little longer delay occurs.

Further, ammonia injection amount signal corresponding to the load command of the load correction device, because it corresponds to the command signal of the load change of the gas turbine, which is an element that can most quickly quickly predict changes in the amount of NO _x. Therefore, by adding this ammonia injection amount signal as a feed forward signal, even if the operating conditions are suddenly changed, the ammonia injection amount can be increased or decreased in advance, and quick response control can be performed.

Further provided the ammonia injection amount limiting device, ammonia injection amount limit signal corresponding to the maximum reaction amount of the NO _x in the temperature of the denitration catalyst is emitted by the device, ammonia injection amount from the ammonia injection amount limit signal adder The signal having the lower value of the target signal is selected by the lower value priority circuit. Therefore, an excessive amount of ammonia exceeding the maximum reaction amount at a certain denitration catalyst temperature is not injected. For this reason, ammonia is not discharged without reacting, and contamination of the apparatus system or the plant environment is prevented.

Embodiment An embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a block diagram showing an embodiment of a denitration control device for a gas turbine plant according to the present invention.
The same elements as those in the conventional example shown in the figures are denoted by the same reference numerals, and detailed description thereof will be omitted.

Denitration control device for a gas turbine plant according to the present embodiment, the amount of combustion air, and calculates the estimated amount of NO _x generated from the process of the fuel flow rate, etc., the ammonia injection amount corresponding to the amount of expected NO _x as a feed-forward signal Output, calculate the actual NO _x amount at the denitration catalyst outlet, and calculate the actual NO _x amount and the expected NO
an arithmetic unit A that outputs the ammonia injection amount corresponding to the deviation from the _x amount as a feedback signal; an adder 8 that adds the feedforward signal and the feedback signal to output an ammonia injection amount target signal 16; the target signal 16 to PID operation, and a PID calculator 17 for adjusting and controlling the ammonia flow control valve 21, further inputs the ammonia injection amount calculated from the denitration catalyst inlet _the amount of NO _x concentration in the adder 8 as a feed-forward signal a denitration catalyst inlet concentration of NO _x management device B, a load compensation device C to enter the ammonia injection amount corresponding to the load command signal to the load change at the time of startup of the gas turbine to the adder 8 as a feedforward signal, the denitration catalyst Measure the temperature, calculate the ammonia injection amount corresponding to the maximum reaction amount under that temperature condition, and calculate the ammonia injection amount. And ammonia injection amount limiting device D for outputting a field signal 22, is disposed between the adder 8 and the PID calculator 17, the ammonia injection limit signal
A low-value priority circuit 24 for selecting one of the low-value signals 22 and the ammonia injection amount target signal 16 from the adder 8 and inputting it to the PID calculator 17 is provided.

Computing device estimated amount of NO _x signal 2 which is calculated from the various process variables in the calculator 1 of A, NO _x from _the amount of NO _x setter 4
The amount setting signal 5 is compared with the comparator 6, and the ammonia injection amount signal 9 corresponding to the difference between the two is input to the adder 8 as a feedforward signal.

On the other hand, the actual NO _x from the denitration catalyst outlet NO _x total 10 of the arithmetic unit A
The concentration signal 11 is multiplied by the multiplier 12 with the exhaust gas flow rate signal 3 calculated by the calculator 1 to obtain the actual NO.
_{The x} amount signal 13 is obtained. This actual NO _x amount signal 13 is compared with the NO _x amount setting signal 5 from the NO _x amount setting device 4 in the comparator 14, the amount of ammonia necessary for eliminating the deviation is calculated, and the ammonia injection amount correction signal 15 is input to the adder 8. This ammonia injection amount correction signal 15 is based on the expected NO.
_This is for correcting an excess or deficiency of the injected ammonia amount based on the _x amount signal 2. That is, the ammonia injection amount correction signal 15 is used as a feedback signal for controlling the ammonia injection amount.

Further, the denitration catalyst inlet concentration of NO _x management device B, is measured by the denitration catalyst inlet NO _x meter 25, the actual concentration of NO _x signal 26 at the inlet of the output denitration catalyst, the exhaust gas flow rate signal calculated by the arithmetic unit 1 3 and input to the multiplier 27. Compare multiplier 27 denitration catalyst inlet actual amount of NO _x signal 28 29
To enter. The comparator 29 compares the NO _x amount setting signal 5 with the actual NO _x amount signal 28 at the denitration catalyst inlet, and inputs an ammonia injection amount correction signal 30 corresponding to the deviation to the adder 8. Then, the ammonia injection amount is increased or decreased in a direction to eliminate the above-described deviation.

The load command signal 32 from the load command device 31 of the load correction device C is input to the converter 33, and the converter 33 inputs to the adder 8 an ammonia injection amount signal 34 corresponding to a load change at the time of starting the gas turbine. I do. The ammonia injection amount signal 34 is output to the adder 8 as a bias amount only when a large load change occurs at the time of startup or the like, and is not output for a normal load change.

On the other hand, in the ammonia injection amount limiting device D, the temperature signal 36 from the denitration catalyst temperature detector 35 is input to the function generator 37. The function generator 37 calculates the ammonia injection amount determined by the maximum reaction amount under the temperature condition, and inputs the calculated ammonia injection amount to the low value priority circuit 24 as the ammonia injection amount limit signal 22.

The low value priority circuit 24 selects one of the low value signals 23 of the ammonia injection amount limit signal 22 and the ammonia injection amount target signal 16 from the adder 8, and inputs the low value signal 23 to the PID calculator 17.

The PID calculator 17 performs PID control with the low value signal 23 serving as a control signal as a set amount, and the ammonia flow signal 19 from the ammonia flow meter 18 as a process amount, and sends a control signal 20 to the ammonia flow control valve 21. Output. Ammonia flow control valve 21 to open and close operation by a control signal 20 to control the ammonia injection rate, to control the amount of NO _x of the exhaust gas to a value set by the amount of NO _x setter 4.

Since the signal components to be input to the adder 8 in the conventional device was only ammonia injection quantity correction signal 15 which is calculated from the concentration of NO _x in the ammonia injection amount signal 9 and a denitration catalyst outlet was calculated from the amount expected NO _x, It has a drawback that the noise is large and the time delay is remarkable.

However in this embodiment, in addition to the signal components in the conventional apparatus, the ammonia injection amount correction signal 30 is calculated from the concentration of NO _x in the NO x removal catalyst inlet, load correction apparatus ammonia injection amount correction signal 34 is summed output from the C Input to the container 8.

That is, according to this embodiment, the number of signal elements input to the adder 8 increases, and the influence of the fluctuation of each signal element is dispersed. Therefore, the noise of the ammonia injection amount target signal 16 output from the adder 8 is also reduced. As a result, the reliability of the control signal 20 for controlling the ammonia flow control valve 21 is improved, and stable denitration control is possible.

The output from the denitration catalyst inlet concentration of NO _x management device B,
The ammonia injection amount correction signal 30 input to the adder 8 is
Because it is calculated directly from the measured values by the denitration catalyst inlet NO _x meter 25, the high reliability as compared with the case of calculating from the larger estimated amount of NO _x conventional variations. However, some time delay occurs because it takes time to sampling and analysis steps in the denitration catalyst inlet NO _x meter 25.

Further, ammonia injection amount signal 34 which is proportional to the load command signal 32 of the load corrector C is because it corresponds to the command signal of the load change of the gas turbine, an element that can most quickly quickly predict changes in the amount of NO _x is there.

Therefore, by loading the above-mentioned ammonia injection amount signal 34 as a feedforward signal onto the adder 8, it is possible to increase or decrease the ammonia injection amount in advance when the operating conditions are suddenly changed, thereby enabling quick response control. Becomes

Further provided the ammonia injection amount limiting device D, the maximum reaction amount of the NO _x in the temperature of the denitration catalyst during operation by the device is calculated, ammonia injection amount limit signal 22 that corresponds to the maximum reaction amount is output. One of the lower values of the ammonia injection amount limit signal 22 and the ammonia injection amount target signal 16 from the adder 8 is selected by the low value priority circuit 24. Therefore, excess ammonia exceeding the maximum reaction amount at a certain denitration catalyst temperature is not supplied. That is, since unreacted ammonia is not discharged, contamination of the inside of the apparatus system or the plant environment is prevented.

 Next, another configuration example of the present invention will be described.

As shown in FIG. 1, the prediction calculated by the arithmetic unit 1
Detecting the amount of NO _x change rate, providing the estimated amount of NO _x change rate detector 39 for inputting the ammonia injection amount signal 38 corresponding to the detected change rate to the adder 8 to the arithmetic unit A.

The detecting an actual amount of NO _x of the rate of change in the denitration catalyst inlet, ammonia injection amount signal 40 corresponding to the detected change rate
The actual amount of NO _x change rate detector 41 to be input to the adder provided in the denitration catalyst inlet concentration of NO _x management device B.

Similarly, a load command signal change rate detector that detects a change rate of the load command signal 32 from the load command signal 31 and inputs an ammonia injection amount signal 42 corresponding to the detected change rate to the adder 8.
43 is provided in the load correction device C.

The estimated amount of NO _x, the rate of change of the denitration catalyst inlet definitive actual amount of NO _x and the load command signal is measured by each detector 39, 41, 43, respectively, if the rate of change has reached a predetermined value or more,
The ammonia injection amount signals 38, 40, 42 are input to the adder 8,
Further, the set amount of the PID calculator 17 is biased, and the required amount of ammonia is rapidly injected in advance.

Therefore, the expected NO _x amount, the actual NO at the denitration catalyst inlet
_It is possible to quickly respond to a change in the NO _x amount due to a sudden change in the _x amount or the load command, and the control response characteristics of the denitration control device are improved.

〔The invention's effect〕

As described above, according to the denitration control device for a gas turbine plant according to the present invention, in addition to the expected amount of NO _x signal noise that was used is greater in the conventional apparatus, and the actual amount of NO _x signal in the denitration catalyst inlet, Since the signal to which the load command signal is added is used as a feedforward signal and is finally used as a control signal for the ammonia flow control valve, the influence of noise of each signal element is dispersed and reduced. Therefore, a highly reliable denitration control operation can be performed.

In addition, an ammonia injection amount limiting device is provided, and the device monitors the temperature of the denitration catalyst and limits the maximum amount of ammonia that can react at the temperature. Therefore, it is possible to prevent unreacted ammonia from being discharged and contaminating the inside and outside of the apparatus.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of a denitration control device for a gas turbine plant according to the present invention, and FIG. 2 is a block diagram showing a configuration example of a conventional device. 1 ... Calculator, 2 ... Expected NO _x amount signal, 3 ... Exhaust gas flow rate signal, 4 ... NO _x amount setting device, 5 ... NO _x amount setting signal, 6
...... comparator, 7 ...... deviation signal, 8 ...... adder 9 ...... ammonia injection amount signal, 10 ...... denitration catalyst outlet NO _x meter, 11 ...
... actual concentration of NO _x signal, 12 ...... multiplier, 13 ...... denitration catalyst Minoru Ideguchi amount of NO _x signal, 14 ...... comparator, 15 ...... ammonia injection amount correction signal, 16 ...... ammonia injection amount target signal, 17 ...... PI
D calculator, 18… Ammonia flow meter, 19… Ammonia flow signal, 20… Control signal, 21… Ammonia flow control valve, 22… Ammonia injection amount limit signal, 23 …… Low value signal, 24… ... lower-value preference circuit, 25 ...... denitration catalyst inlet NO _x meter, 2
6 ...... actual concentration of NO _x signal, 27 ...... multiplier, 28 ...... denitration catalyst inlet actual amount of NO _x signal, 29 ...... comparator, 30 ...... ammonia injection amount correction signal, 31 ...... load command device 32 …… Load command signal, 33 …… Converter, 34 …… Ammonia injection amount signal, 35…
... DeNOx catalyst temperature detector, 36 ... Temperature signal, 37 ... Function generator, 38 ... Ammonia injection amount signal, 39 ... Expected NO _x amount change rate detector, 40 ... Ammonia injection amount signal, 41 ... ... real
NO _x amount change rate detector, 42 ... ammonia injection amount signal, 43
...... Load command signal change rate detector, A ... Calculator, B ...
... denitration catalyst inlet concentration of NO _x management device, C ...... load correction device, D ...... ammonia injection amount limiting device.

Claims (4)

(57) [Claims] 1. A quantity of combustion air, from the process amount of the fuel flow rate, etc., calculates the estimated amount of NO _x generated, and outputs an ammonia amount corresponding to the amount of expected NO _x as a feed-forward signal, the actual in denitration catalyst outlet Calculate the NO _x amount and calculate the actual N
An arithmetic unit for outputting the ammonia injection amount corresponding to the deviation between the O _x amount and the estimated amount of NO _x as a feedback signal, an adder for outputting the ammonia injection amount target signal by adding said feedforward signal and the feedback signal,
A PID calculator for PID calculation of the ammonia injection amount target signal and a PID calculator for adjusting and controlling the ammonia flow control valve.
denitration catalyst inlet concentration of NO _x management apparatus and the ammonia injection rate feedforward signal corresponding to the load command signal to the load variation during turbine starting to be input to the adder ammonia injection amount calculated from _x amount density as a feedforward signal A load correction device to be input to the adder, and an ammonia injection amount limiting device that measures the temperature of the denitration catalyst, calculates an ammonia injection amount corresponding to the maximum reaction amount under the temperature condition, and outputs it as an ammonia injection amount limit signal. ,
A low value signal, which is provided between the adder and the PID calculator and selects one of the ammonia injection amount limit signal and the ammonia injection amount target signal from the adder, is input to the PID calculator. A denitration control device for a gas turbine plant, comprising a value priority circuit. 2. An arithmetic device includes an expected NO _x amount change rate detector for detecting a change amount of the calculated expected NO _x amount and inputting an ammonia injection amount signal corresponding to the detected change rate to an adder. The denitration control device for a gas turbine plant according to claim 1. 3. A denitration catalyst inlet _the amount of NO _x concentration control device, the actual NO inputting detecting an actual amount of NO _x of the rate of change in the denitration catalyst inlet, an ammonia injection amount signal corresponding to the detected change rate to the adder _2. The denitration control apparatus for a gas turbine plant according to claim 1, further comprising an _x- rate change rate detector. 4. A load command signal change rate detector for detecting a change rate of a load command signal from a load command device and inputting an ammonia injection amount signal corresponding to the detected change rate to an adder. The denitration control device for a gas turbine plant according to claim 1, further comprising: