JPS5977041A - Denitrification control device - Google Patents

Abstract

PURPOSE:To enhance economy as well as effectiveness in operations with a device, which is to remove NOx from the exhaust gas of an exhaust heat collecting boiler for a gas tunbine, by providing possibility to perform two controls simultaneously as in a single body, i.e. the control for suppression of NOx amount using water etc. and the control for removal of NOx by means of a denitrating device. CONSTITUTION:In an arrangement in which a fuel is combusted in a combustor 2 under intervention of the compressed air fed from a compressor 1 and the gas generated shall drive a gas turbine, and in which the exhaust gas is introduced to an exhaust heat collecting boiler 8, water is injected in the combustor 2 through an injection rate adjusting valve 5 so as to suppress the NOx production in the combustor 2. The boiler 8 is equipped with a denitrating device 13, into which ammonium is injected through a rate-of-flow adjusting valve 6 so as to remove NOx from the exhaust gas. Here the change in the rate of NOx removal at this denitrating device 13 is sensed, and the setting value for the amount of ammonium injection is corrected on the basis of the amount of change thus sensed. When this amount of change has exceeded a certain level, the setting value for the rate of water injection is corrected on the basis of this deviation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a control device for a denitrification device that removes nitrogen oxides from exhaust gas of a gas turbine exhaust heat recovery boiler.

[Prior art]

Generally, in order to effectively utilize the energy of combustion exhaust gas discharged from a gas turbine, heat recovery is performed using an exhaust heat recovery boiler (hereinafter referred to as a WH boiler) K. In such a combined facility of a gas turbine and a WH boiler, nitrogen oxides (hereinafter referred to as NO) are produced by the combustion of the gas turbine.
In order to maintain the NOx value of the exhaust gas released into the atmosphere below the specified value, water or steam is injected into the combustor to suppress the generation of NOx, and denitrification is also performed. Devices are used to remove NOX from exhaust gas.

The amount of NOx generated in the combustor is controlled by controlling the injection amount of water or steam to a predetermined rate relative to the fuel or gas turbine output. In addition, denitrification equipment is known that removes NOx by applying ammonia to exhaust gas in the presence of a denitration catalyst.
: The molar ratio and injection amount of ammonia are controlled according to the following.

In this way, in a system that comprehensively controls the NOx value in exhaust gas by controlling the amount of NOx generated and the removal rate, it is important to consider factors such as the NOx reduction effect and economic efficiency of both. Based on this, it is desirable to share the load in a well-balanced manner.

However, in the past, both of them were completely independent and controlled separately, so the control conditions for both could be changed each time according to changes in the amount of exhaust gas or deterioration of the denitrification catalyst over time.
This has the disadvantage that it requires manual correction and is complicated to operate. Moreover, the results of such human operations are not always optimal, and in some cases, more water or steam may be injected than necessary, leading to a decrease in turbine efficiency and an increase in industrial water consumption. This could lead to a decline in economic efficiency.

[Object of the Invention] An object of the present invention is to integrate control of NOx amount suppression by water or steam injection and NOx removal by a denitrification device, automatically optimize the load sharing between the two, and improve operation. An object of the present invention is to provide a denitrification control device that can improve efficiency and economy.

[Summary of the invention]

The present invention detects aging deterioration of the denitrification catalyst and corrects the ammonia injection amount based on this to maintain the NOx concentration at the WH boiler 2 outlet at a specified value. By correcting the injection amount, the objective is to perform comprehensively optimal denitrification control and improve operability and economic efficiency.

In other words, depending on the deterioration of the denitrification catalyst, when the efficiency is high, the injection amount of water or steam is minimized by mainly controlling the ammonia injection, and when the efficiency decreases, the ammonia injection amount is increased. The amount of water or steam injected is increased to the minimum necessary amount.

[Embodiments of the invention]

Hereinafter, the present invention will be explained based on examples.

FIG. 1 shows a schematic system of a combined power generation facility combining a gas turbine and an exhaust heat recovery boiler to which an embodiment of the present invention can be applied. In the figure, air compressed by an air compressor 1 is led to a combustor 2, where it reacts with fuel supplied via a fuel flow rate regulating valve 7 to become combustion gas, which is then sent to a gas turbine 3. It is designed to be guided by. The gas turbine 3 is driven by this combustion gas, and the generator 4
Electrical output can be obtained from. On the other hand, the combustion gas that has done work in gas turbine 3 is WI as exhaust gas.
(The exhaust gas is led to the boiler 8. After exchanging heat in the superheater 12 and evaporator 1, NOx is removed in the denitrification device 13, and heat exchanged in the economizer 9, and then released into the atmosphere. The boiler feed water is supplied by a condensate pump 15, the flow rate is controlled by a feed water flow rate adjustment valve 14, and a water saver 9,
It passes through a drum 0, an evaporator 11, and a superheater 12 before being sent out as steam. .

On the other hand, ammonia is injected into the denitrification device 13 via the ammonia flow rate adjustment valve 6, and the ammonia and NOx in the exhaust gas react under the catalyst to perform denitrification. ing.

Further, water is injected into the gas turbine combustor 2 via a water injection flow rate regulating valve 5 to suppress the generation of NOx in the combustor 2.

FIG. 2 shows a control block diagram of an embodiment of the present invention.

As shown in FIG. 2, the output signal P output from the power generation output transmitter 21 of the gas star pin generator is
is man-powered. This function generator 22 is formed to output a molar ratio signal M⇠◎ set corresponding to the power generation output P.

Here, the molar ratio is the ratio of ammonia injection amount/NOx amount hb
, p and MRo are set in advance based on initial values obtained in a denitrification test. This molar ratio signal 'Ml(O) is input to the multiplier 39 via the multiplier 23 and the high selector 24t.
N detected by the boiler inlet NOX concentration detector 34
The OX concentration signal CI and the total inlet NOx amount signal N0Xt obtained by multiplying the exhaust gas flow rate signal G detected by the exhaust gas flow rate detector 33 and the t1 multiplier 38 are input. The multiplier 39 outputs the molar ratio signals M0 and N.
The preceding value signal AO of the ammonia injection amount is calculated by multiplying the OX total amount signal NOx summer. This advance value signal AO is input to the flow rate control valve 6 for the ammonia injection amount via a proportional-integral controller (PID) 43. In this way, the advance value signal AO of the required ammonia injection amount is set according to the power generation output P and the total NOx amount N0xx, and the ammonia injection amount is controlled based on this.

On the other hand, the specified value of the NOx concentration discharged from the WH boiler 8 is set by the outlet NOx concentration setting device 37, and the concentration setting value signal C++ and the exhaust gas flow rate signal G are multiplied by the multiplier 3.
6 is multiplied by
40 is input. In addition, this PID40 has a WH
A total output NOX amount signal N0XD obtained by multiplying the NOX concentration signal CD detected by the outlet NOX concentration detector 32 of the boiler 8 and the exhaust gas flow rate signal G by the multiplier 35 is input. There is. Then, in PID40, NOxs and NOXD are compared, and the deviation ΔNOX is used as a foot check signal for controlling the ammonia injection amount.
It is outputted to the multiplier 41 to correct the preceding value signal A. As a result, in PID4a, the corrected ammonia injection amount setting value signal A and the detected injection amount signal A detected by the ammonia injection amount detector 42
! The opening degree of the flow rate regulating valve 6 is controlled based on the deviation ΔQm.

The control system for the amount of water supplied to the combustor 2 of the gas turbine is configured to control the water injection amount set in advance from the function generator 49 in response to the fuel flow signal F detected by the gas turbine fuel flow rate detector 48. A value signal WI+ is output, and this set value signal Ws and a water injection amount signal W! detected by the water injection amount detector 51 are output. are compared in the PID 52, and the opening degree of the water injection amount adjusting valve 5 is controlled based on the deviation ΔW.

Next, parts related to the characteristic structure of the present invention will be explained.

First, the subtracter 44 subtracts the total outlet NOx amount NOXo from the total inlet NOx amount NOxx of the WH boiler output from the multipliers 35 and 38 to obtain the total amount of NOx removed by the denitrification device 13 NOXn. . In the function generator 45, the input total amount of removed NOx N0XR
% Inlet NOx u amount N0xX and initial molar ratio signal M
From RO, a corrected molar ratio signal ΔM expressed by the following equation (1) is calculated.

Since the molar ratio correction signal ΔMR is a function of the denitrification efficiency, it is a signal corresponding to the decrease in the efficiency of the denitrification catalyst. This ΔMR is input to the multiplier 23, and the multiplier 23 outputs a molar ratio set value signal MR obtained by correcting the molar ratio signal M⇠◎ by ΔMB.

Further, when the ΔM value input to the multiplier 23 exceeds a certain value, the switch 26 is turned on by the monitor relay 28, and the molar ratio upper limit value is output from the signal generator 30 to the high selector 2.
4, thereby setting the upper limit of the molar ratio set value signal MR.

The molar ratio correction signal ΔMR is also applied as a correction signal for the water quantity control system for water injection, and when this ΔM exceeds a certain value, the switch 46 is turned on by the monitor relay 29, and the ΔMR is turned on. It is designed to be input to a function generator 47.

The function generator 47 is configured to output a water injection correction signal ΔW expressed by the following equation (2) based on the input ΔMR and the fuel flow rate signal F.

ΔW=f (ΔMR-F) ・・・・・・・・・
・ΔW with (2) is output from the function generator 49 mentioned above.
The water injection amount setting value signal W11 is added and corrected in an adder 50.

Since it is configured in this way, initially, the amount of ammonia to be injected is set according to the initial efficiency (maximum efficiency) of the denitrification catalyst based on the preset correlation, and the amount of water to be injected is similarly set. Set to minimum. When the efficiency of the denitrification catalyst deteriorates as the operating time passes, the amount of ammonia injected is increased based on the denitrification efficiency calculated from the NOx concentration detection values at the inlet and outlet of the WH boiler 8, and this increased amount is the first When the amount of ammonia injection reaches a certain value or more, the amount of water injection is increased according to the amount of increase to reduce the amount of NOx generated, and when the amount of increase in the amount of ammonia injection exceeds a second certain value, the amount of ammonia injection is It is now controlled to be fixed at the upper limit value.

Therefore, according to this embodiment, in order to maintain the NOx value in the exhaust gas within the specified value, the NOx value in the denitration equipment is
Since the ammonia injection amount is controlled so that the x removal rate is maximized, the suppression of NOx generation in the combustor is alleviated, so that the injection amount of water or steam can be minimized.

In addition, as the efficiency of the denitrification catalyst deteriorates, the amount of ammonia injected is increased to maintain the NOx removal rate in the denitrification equipment at its maximum, and only when denitration progresses further, the amount of water injection is increased to generate NOx. Since this is suppressed, the water injection amount can be significantly reduced, and comprehensively optimal denitrification control can be performed.

[Effects of the Invention] As explained above, according to the present invention, NOx amount suppression control using water or steam and NOx removal control using a denitrification device can be integrally controlled, and both can be automatically controlled. The economical efficiency and operability can be improved by optimizing the load sharing.

[Brief explanation of the drawing]

FIG. 1 is a system configuration diagram of a gas turbine/exhaust heat recovery boiler as an example to which the present invention can be applied, and FIG. 2 is a control block diagram of an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Air compressor, 2... Combustor, 3... Gas turbine, 4... Generator, 5... Water injection flow rate adjustment valve,
6... Ammonia flow regulating valve, 7... Fuel flow regulating valve, 8... Exhaust heat recovery boiler, 13... Denitrification device, 2
1... Power generation output transmitter, 22... Function generator, 23
...Multiplier, 24...High selector, 26...Switcher, 28...Monitor relay, 29...Monitor relay, 30...Signal generator, 32...Outlet NOX
Concentration detector, 33... Exhaust gas flow rate detector, 34...
Inlet NOx concentration detector, 35... Multiplier, 36...
Multiplier, 37... Outlet NOX concentration setting device, 38...
Multiplier, 39... Multiplier, 40... Proportional-integral controller, 41... Multiplier, 42... Ammonia injection amount detector, 43... Proportional-integral controller, 44...
・Subtractor, 45...Function generator, 46...Switcher,
47...Function generator, 48...Gas turbine fuel flow rate detector, 49...Function generator, 50...Adder,
51...Water injection amount detector, 52...Proportional-integral controller. Agent Patent Attorney Akiharu Takahashi Kaya I

Claims (1)

[Claims] 1. Nitrogen oxides (hereinafter referred to as N) discharged from gas turbines
In a denitrification control device that maintains NOx (referred to as OX) at a specified value, NOx is injected into the gas turbine combustor.
A means for controlling the injection amount of a generation inhibitor, and a means for reacting exhaust gas of a gas turbine with a denitrification agent in the presence of a denitrification catalyst to generate NO.
means for controlling the amount of denitrification agent injected into a denitrification device that removes x, and detecting a change in the NOx removal rate of the denitrification device;
The set value of the denitrification agent injection amount is corrected based on the amount of change in the removal rate, and when the amount of change in the removal rate reaches a certain value or more, the set value of the injection amount of the inhibitor is corrected based on the deviation. A denitrification control device characterized by being adapted to perform correction.