JPH08257371A - Exhaust gas denitration apparatus - Google Patents

Abstract

PURPOSE: To safely and certainly suppress the concn. of NOx, in constitution controlling an ammonia injection amt. on the basis of a feedback signal and a feedforward signal, by correcting the feedforward signal based on the feedback signal so as to correspond to an increase in an ammonia injection amt. CONSTITUTION: In an exhaust gas denitration apparatus wherein the exhaust gas of a gas turbine is introduced into a catalytic reaction device and NOx in the exhaust gas is reacted with ammonia to denitrate the exhaust gas, the concn. of NOx in the exhaust gas after denitration is measured by a measuring device 26 and a measuring flow rate PV is calculated on the basis of the measured value by a multiplier 31. A set flow rate SV is calculated on the basis of the set value SV of an NOx concn. setting device 28 to operate feedback signal Q=PV-SV by an operator 33. A feedforward signal P is calculated on the basis of an estimated NOx flow rate and the signal P is added (34) to a correction factor C to output a feedforward signal Y after correction. An ammonia injection amt. setting signal S is outputted by adding (36) the signal Q to the signal Y.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flue gas denitration device such as a boiler or turbine.

[0002]

2. Description of the Related Art Conventionally, as an apparatus of this kind, a catalytic reaction apparatus for reacting NO _{x in} the exhaust gas with ammonia, an ammonia injection apparatus for injecting ammonia into the catalytic reaction apparatus, and an exhaust gas at the outlet of the catalytic reaction apparatus a setter for setting the concentration or flow rate of the NO _X, a measuring device for measuring the concentration of the NO _X in the exhaust gas of the catalytic reactor outlet, the feedback obtained from the deviation of the measured values of the measuring instrument with the set value of the setting device A signal and a control means for controlling the ammonia injection amount so as to increase the ammonia injection amount as the catalyst deteriorates with time, based on the feedforward signal obtained from the predicted NOx flow rate in the exhaust gas at the catalyst reactor inlet. What is known is.

[0003]

In the conventional apparatus THE INVENTION An object you try solving], with the deterioration of the catalyst, when the concentration of the NO _X in the exhaust gas of the catalytic reactor outlet tends to increase, the feed-forward signal, remains at a fixed value Therefore, the amount of ammonia injection is increased by increasing the control ratio by the feedback signal.

The feedback signal may not be able to follow the fluctuation of the NO _x concentration in the exhaust gas at the inlet of the catalytic reaction device due to the dead time of sampling by the measuring instrument, the response delay and the like. . Therefore, if the ratio of control by the feedback signal becomes high, the concentration of NO _{X in} the exhaust gas at the outlet of the catalytic reaction device may be increased to a set value or more.

An object of the present invention is to solve the above problems,
An object of the present invention is to provide a flue gas denitration device capable of increasing the amount of ammonia injection without increasing the control ratio by the feedback signal.

[0006]

A flue gas denitration apparatus according to the present invention comprises a catalytic reaction apparatus for reacting NO _{x in} the exhaust gas with ammonia, an ammonia injection apparatus for injecting ammonia into the catalytic reaction apparatus, and a catalytic reaction apparatus outlet. In the exhaust gas of
A setter for setting the concentration or the flow rate of O _X, a measuring device for measuring the concentration of the NO _X in the exhaust gas of the catalytic reactor outlet,
Based on the feedback signal obtained from the deviation between the set value of the setter and the measured value of the measuring instrument, and the feedforward signal obtained from the predicted NOx flow rate in the exhaust gas at the catalyst reactor inlet, ammonia In a flue gas denitration device that includes a control unit that controls the ammonia injection amount so as to increase the injection amount, a correction unit that corrects the feedforward signal based on the feedback signal so as to correspond to the increase in the ammonia injection amount is provided. It is characterized by having.

Further, it is preferable that the correction by the correction means is performed so that the feedback signal is within ± 2% to 5% of the signal obtained by adding the feedback signal and the feedforward signal.

[0008]

The flue gas denitration apparatus according to the present invention is provided with the correction means for correcting the feedforward signal based on the feedback signal so as to correspond to the increase of the ammonia injection amount. By correcting the signal, the ammonia injection amount is increased.

Further, if the correction by the correction means is performed so that the feedback signal is within ± 2% to 5% of the signal obtained by adding the feedback signal and the feedforward signal, the control accuracy becomes good.

[0010]

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

FIG. 1 shows an outline of a power plant.

The generator 11 is driven by a steam turbine 12 and a gas turbine 13. The gas turbine 13 is driven by the compressor 14 and the combustor 15 and controlled by the controller 16. The exhaust gas of the gas turbine 13 is
A conduit 17 leads to a chimney 18. The conduit 17 is provided with an ammonia injection chamber 19 and a catalytic reactor 21. A supply pipe 22 is connected to the ammonia injection chamber 19. The supply pipe 22 is provided with a flow rate measuring device 23 and a flow rate control valve 24. The measurement value M of the flow rate measuring device 23 is input to the ammonia injection control device 25. The flow rate control valve 24 is controlled by the control signal R of the ammonia injection control device 25. The exhaust gas flow rate, the predicted NOx flow rate, and the operating time are input to the ammonia injection control device 25 from the gas turbine control device 16. The exhaust gas flow rate is expressed as a function of f (air amount, fuel amount). The predicted NOx flow rate is expressed as a function of f (exhaust gas flow rate, fuel amount, vapor amount, atmospheric temperature). The catalytic reaction device 21 reacts NOx in the exhaust gas with ammonia to generate nitrogen and water. Catalytic reactor 21
A NO _x concentration measuring device 26 is provided at the outlet of the. NO
The measured value PV of the _X concentration measuring device 26 is input to the ammonia injection control device 25. The gas turbine control device 16 and the ammonia injection control device 25 are controlled by the load command of the power feeding control panel 27. The power supply control panel 27 has a NO _X concentration setter 28
Is provided. The set value SV of the setter 28 is input to the ammonia injection control device 25.

FIG. 2 shows the configuration of the ammonia injection control device.

The measured value PV of the NOx concentration measuring device 26 is sent to the measured concentration / flow rate converting multiplier 31. The exhaust gas flow rate is input to the measured concentration conversion multiplier 31, the measured concentration value PV and the exhaust gas flow rate are multiplied, and the measured concentration PV (PPM) is converted to the measured flow rate PV (Nm3 / h). The set value SV of the NOx concentration setter 28 is sent to the set concentration / flow rate conversion multiplier 32. The exhaust gas flow rate is input to the set-concentration conversion multiplier 32, the concentration set value SV is multiplied by the exhaust gas flow rate, and the set concentration SV (PPM) is converted to the set flow rate SV (Nm3 / h). The measured flow rate PV (Nm3 / h) and the set flow rate SV (Nm3 / h) are input to the subtractor 33, and the feedback signal Q =
It is output as PV-SV.

The feedforward signal P is determined based on the predicted NOX flow rate. Feed forward signal P
Is sent to the adder 34. A correction coefficient C described later is input to the adder 34, the feedforward signal P and the correction coefficient C are added, and this is output as a corrected feedforward signal Y = P + C.

The feedback signal Q and the feedforward signal Y obtained as described above are input to the adder 36. In the adder 36, the feedback signal Q and the feedforward signal Y are added, and S = Y + Q
The ammonia injection amount setting signal of is output. In the control valve control adjuster 37, the deviation of the measured value M from the flow rate measuring device 23 with respect to the ammonia injection amount setting signal S is corrected by the PI operation, and this is finally output as the control valve control signal R.

The feedback signal Q and the ammonia injection amount setting signal S are input to the divider 38 to obtain the process value Z = Q / S. The set value SV is subtracted from the process value Z by the subtractor 39, and the process value V = Z-SV
Is obtained, and this is input to the gain setter 40. The set value SV is set within a range of ± 0.02 to 0.05. The gain setter 40 is provided with a dead zone in which it does not operate within a range of ± 2 to 5% so as to enhance control stability.
The output signal ΔV of the gain setting device 40 is input to the proportional integrator 41, and the output signal ΔV of the gain setting device 40 is proportionally integrated to obtain the correction coefficient C.

When the feedforward signal P is corrected by the correction coefficient C, the process value Z,
That is, the ratio between the feedback signal Q and the ammonia injection amount setting signal S is within ± 2 to 5%.

[0019]

According to the present invention, not only the feedback signal but also the feedforward signal is corrected, so that the amount of injected ammonia is increased, so that the concentration of NO _{X in} the exhaust gas at the inlet of the catalytic reactor is changed. Even if the value is large, NO _{x at the} outlet of the catalytic
It is possible to control the density of the so as to be a set value.

Further, since the control accuracy becomes good, the concentration of NO _{x in} the exhaust gas at the outlet of the catalytic reaction device can be controlled safely and reliably.

[Brief description of drawings]

FIG. 1 is a system diagram showing a configuration of a flue gas denitration device according to the present invention.

FIG. 2 is a block diagram showing an electrical configuration of an ammonia injection control device of the same flue gas denitration device.

[Explanation of symbols]

 21 Catalytic reaction device 22 Ammonia supply device 25 Ammonia injection control device 26 NOX measuring device 28 NOX setting device 38 Divider 40 Gain setting device Q Feedback signal Y Feedforward signal

Claims (2)

[Claims] 1. A catalytic reactor 21 for reacting NO _x in the exhaust gas with ammonia, an ammonia injector 22 for injecting ammonia into the catalytic reactor 21, an NO _x concentration in the exhaust gas at the outlet of the catalytic reactor 21, or Setting device for setting the flow rate
28, a measuring device 26 for measuring the concentration of NO _{x in} the exhaust gas at the outlet of the catalytic reaction device 21, a set value SV of the setting device 28, and a measuring device 26.
Based on the feedback signal Q obtained from the deviation of the measured value PV and the feedforward signal Y obtained from the predicted NOX flow rate P in the exhaust gas at the inlet of the catalytic reaction device 21, the amount of ammonia injection is determined as the catalyst deteriorates with time. Control means 25 for controlling the ammonia injection amount so as to increase 25
In the flue gas denitration device, the flue gas denitration device is provided with a correction means for correcting the feedforward signal Y based on the feedback signal Q so as to correspond to an increase in the ammonia injection amount. 2. The correction according to claim 1, wherein the correction is performed such that the feedback signal Q is within ± 2 to 5% of the signal (Y + Q) obtained by adding the feedback signal Q and the feedforward signal Y. Smoke denitration equipment.