CN110865623A - NO in SCR denitration controlxMeasurement signal substitution system and control method thereof - Google Patents

NO in SCR denitration controlxMeasurement signal substitution system and control method thereof Download PDF

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CN110865623A
CN110865623A CN201911286057.1A CN201911286057A CN110865623A CN 110865623 A CN110865623 A CN 110865623A CN 201911286057 A CN201911286057 A CN 201911286057A CN 110865623 A CN110865623 A CN 110865623A
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signal
flue gas
measuring device
substitution
denitration
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金国强
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Xian Xire Control Technology Co Ltd
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    • G05B19/418—Total factory control, i.e. centrally controlling a plurality of machines, e.g. direct or distributed numerical control [DNC], flexible manufacturing systems [FMS], integrated manufacturing systems [IMS], computer integrated manufacturing [CIM]
    • G05B19/41875—Total factory control, i.e. centrally controlling a plurality of machines, e.g. direct or distributed numerical control [DNC], flexible manufacturing systems [FMS], integrated manufacturing systems [IMS], computer integrated manufacturing [CIM] characterised by quality surveillance of production
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    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
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    • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
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    • B01D53/8625—Nitrogen oxides
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    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
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    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P90/00—Enabling technologies with a potential contribution to greenhouse gas [GHG] emissions mitigation
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Abstract

The invention discloses NO in SCR denitration controlxMeasurement signal substitution system and control method thereof, wherein NO is passed when CEMS device purging signal is triggeredxThe measurement signal substitution system controls an ammonia injection control valve of the denitration system, substitutes the measurement signal for a substitution signal by using a substitution switching module, inputs the substitution signal into the denitration control system to participate in forming the opening adjustment of the ammonia injection control valve, and adjusts the opening of the ammonia injection control valve by NOxThe measurement signal substitution system generates a substitution signal a ', a substitution signal B ', a substitution signal C ', a substitution signal D ', and a substitution signal Z ', respectively. The present invention is directed to NOxThe measured raw signal is processed during purging of the device to form NOxA surrogate signal is measured. The system comprises two links: denitration flue gas continuous monitoring system NOxThe dynamic measurement module and the dynamic correction module. The system generates a reasonable substitution signal to substitute NO in a purge statexThe measured original signal enters a control link of a denitration system, so that reasonable denitration control quality is guaranteed, and NO is preventedxThe denitration control system fluctuates widely.

Description

NO in SCR denitration controlxMeasurement signal substitution system and control method thereof
[ technical field ] A method for producing a semiconductor device
The invention belongs to the technical field of SCR denitration automatic control of a coal-fired power plant, and relates to NO in SCR denitration controlxA measurement signal substitution system and a control method thereof.
[ background of the invention ]
Nitrogen Oxides (NO)x) Mainly from coal, oil, natural gasThe combustion process is one of the main atmospheric pollutants. In the secondary energy structure of China, the coal-fired power generation proportion is up to more than 70%. Thus controlling NO in coal-fired power plantsxThe emissions being reduction of NO in the atmospherexOne of the main measures of content.
Reduction of NOxThere are various methods of discharge. The Selective Catalytic Reduction (SCR) denitration technology has the advantages of small influence on the operation of a boiler, simple device structure, easy control of reaction conditions, mature technology, reliable operation, small occupied area, no by-product, no secondary pollution, convenient maintenance, high denitration efficiency (which can reach more than 90 percent) and the like, and is a denitration technology commonly adopted by coal-fired power stations.
The existing denitration control system is a flue gas outlet NO of a coal-fired generator setxThe concentration is taken as a control target, and the flue gas flow represented by the unit load is multiplied by the NO of the inlet and outlet of the flue gasxCalculating the deviation of concentration to remove NOxIn an amount of NH3/NOxCalculating the required ammonia injection amount according to the molar ratio, and controlling the opening of an ammonia injection valve to ensure that the ammonia injection amount is equal to the calculated ammonia required amount, thereby indirectly realizing NO of the flue gas outletxControlling the content; or on the basis of the control mode, the NO is taken as the smoke outletxThe concentration is used as the regulated quantity, the deviation of the concentration from the set value forms a correction signal after PID operation, and the correction signal is supplemented with inlet NOxThe concentration is corrected for the calculated ammonia injection amount.
Analysis from the aspects of the operation status and the control logic: the SCR denitration control system depends on a denitration reactor inlet denitration flue gas continuous monitoring system (CEMS), a denitration reactor outlet denitration flue gas continuous monitoring system (CEMS), and a total outlet denitration flue gas continuous monitoring system (CEMS) aiming at NOxAnd measuring the content in real time and designing a denitration control system by using the measurement signal. Due to these 3 NOxMeasurement signals were purged periodically (once per hour), with NO collected during purgingxLoss of authenticity, large variations in measured values, affecting NOxThe measurement accuracy and the corresponding time cause that the automatic ammonia injection control cannot adapt to the change of the working condition.
[ summary of the invention ]
The invention aims to overcome the defect that the measured NO is caused by periodic purging of a CEMS device in SCR denitration control in the prior artxThe problem of signal interruption and distortion in the process is solved, and NO in SCR denitration control is providedxA measurement signal substitution system and a control method thereof.
In order to achieve the purpose, the invention adopts the following technical scheme to realize the purpose:
NO in SCR denitration controlxA measurement signal substitution system comprising:
a purging keeping module which keeps the measuring signal at the current moment as the purging initial value E at the purging moment when the purging keeping module receives the purging signal0And purging the initial value E0Outputting the signal to a substitute signal output module;
the purging switching module generates the predicted value basic quantity R in the purging process together with the predicted value basic quantity output module when the CEMS purges0；
The input end of the predicted value basic quantity correction coefficient module receives a pressure signal P collected by a pressure measuring device, a temperature signal T collected by a temperature measuring device and a flue gas oxygen quantity signal Q collected by a flue gas oxygen quantity measuring device, carries out weighting processing with gain coefficients on the pressure signal P, the temperature signal T and the flue gas oxygen quantity signal Q, and outputs a predicted value basic quantity R0η to a predicted delta value output module;
a prediction increment value output module which is a multiplication module and is used for predicting a basic quantity R of a predicted value0The predicted increment value output module corrects the predicted value basic quantity output module according to the dynamic correction coefficient η and outputs a predicted increment value delta R of the measurement signal;
the substitute signal output module is an addition module and is used for realizing the purge initial value E0And the addition of the predicted increment value delta R, and outputting a substitution signal to the substitution switching module;
and the substitution switching module substitutes the measurement signal A with a substitution signal A 'when receiving the purging signal, so that the substitution signal A' enters the denitration control system to participate in forming the opening adjustment of the ammonia injection control valve, and the opening and closing of the ammonia injection control valve in the denitration system are controlled.
A denitration system using the above alternative system, the denitration system comprising:
the smoke side outlet of the boiler descending section heat exchanger is sequentially connected with an air preheater, an electric dust remover, an absorption tower and a chimney; an ammonia injection grid and an SCR reactor are sequentially arranged in a flue between the boiler descending section heat exchanger and the air preheater along the flow direction of flue gas;
the ammonia injection grid is connected with the ammonia-air mixture;
ammonia-air mixing, wherein an air inlet of the ammonia-air mixing is connected with a dilution fan, and an ammonia inlet is connected with a liquid ammonia storage tank through an ammonia evaporator;
the device comprises a pressure measuring device and a temperature measuring device, wherein the pressure measuring device and the temperature measuring device are respectively provided with two groups and are respectively arranged at a steam inlet and a steam outlet on the flue gas side of a heat exchanger at the descending section of the boiler;
the device comprises a flue gas oxygen content measuring device, a gas-liquid separator and a gas-liquid separator, wherein the flue gas oxygen content measuring device is arranged at a steam inlet at the flue gas side of a heat exchanger at a descending section of a boiler;
first inlet flue gas NOxMeasuring device and second inlet flue gas NOxMeasuring device, said first inlet flue gas NOxMeasuring device and second inlet flue gas NOxThe measuring devices are arranged on one side of the steam inlet end of the ammonia injection grid and are arranged oppositely;
first outlet flue gas NOxMeasuring device and second outlet flue gas NOxMeasuring device, said first outlet flue gas NOxMeasuring device and second outlet flue gas NOxThe measuring devices are arranged on one side of the steam outlet end of the SCR reactor and are arranged oppositely;
and total exhaust outlet flue gas NOxMeasuring device 21, said total exhaust outlet flue gas NOxThe measuring device is arranged in the chimney.
Adopt NO in SCR denitration controlxMethod for controlling a measurement signal substitution system by means of NO when a CEMS device purge signal is triggeredxThe measurement signal substitution system is used for controlling an ammonia injection control valve of the denitration system, substituting the measurement signal into a substitution signal by using a substitution switching module, inputting the substitution signal into the denitration control system to participate in forming the opening adjustment of the ammonia injection control valve, and the measurement signal comprises first inlet flue gas NOxMeasuring signal A of measuring device and first outlet flue gas NOxMeasurement signal B of measuring device and total exhaust outlet flue gas NOxMeasuring signal Z and second inlet flue gas NO of measuring devicexMeasuring signal C of measuring device and second outlet flue gas NOxA measurement signal D of the measurement device; by NOxThe measurement signal substitution system generates a substitution signal a ', a substitution signal B ', a substitution signal C ', a substitution signal D ', and a substitution signal Z ', and the generation methods of the substitution signal a ', the substitution signal B ', the substitution signal C ', the substitution signal D ', and the substitution signal Z ' are the same, and the generation of the substitution signal a ' is used to describe the control method, and the specific control method includes the following steps:
step 1: when a purging signal of the CEMS device is triggered, the purging keeping module keeps the first inlet flue gas NO at the purging momentxTaking the current value of the measuring device as an initial purging value E0；
Step 2: using first inlet flue gas NOxSecond inlet flue gas NO on opposite side of the measuring devicexMeasuring signal C of measuring device in first inlet flue gas NOxMeasuring the variation of the device in the purging process to obtain the first inlet flue gas NOxPredicted value basic quantity R in purging process of measuring device0；
And step 3: inputting a pressure signal P acquired by a pressure measuring device, a temperature signal T acquired by a temperature measuring device and a flue gas oxygen content signal Q acquired by a flue gas oxygen content measuring device into a predicted value basic quantity correction coefficient module for weighting processing to obtain a predicted value basic quantity R0η;
and 4, step 4: prediction valueBasic quantity R0Correcting according to the dynamic correction coefficient η through a prediction increment value output module to obtain the first inlet flue gas NOxPredicting an increment value delta R in the purging process of the measuring device:
ΔR＝R0×η
and 5: according to the initial value E of purging0And predicting the increment value delta R to obtain the first inlet flue gas NOxAlternative signal a' of the measuring device:
A′＝E0+ΔR
step 6: and when the substitution switching module receives the purging signal, the substitution signal A 'is substituted for the measurement signal A, so that the substitution signal A' enters the denitration control system to participate in forming the opening adjustment of the ammonia injection control valve, and the opening and closing of the ammonia injection control valve in the denitration system are controlled.
Compared with the prior art, the invention has the following beneficial effects:
the present invention is directed to NOxThe measured raw signal is processed during purging of the device to form NOxA surrogate signal is measured. The system comprises two links: denitration flue gas continuous monitoring system NOxThe dynamic measurement module and the dynamic correction module. The system generates a reasonable substitution signal to substitute NO in a purge statexThe measured original signal enters a control link of a denitration system, so that reasonable denitration control quality is guaranteed, and NO is preventedxThe denitration control system fluctuates widely.
[ description of the drawings ]
FIG. 1 shows NO according to the inventionxMeasuring a schematic of the alternate system;
FIG. 2 is a schematic structural diagram of a denitration system according to the present invention;
FIG. 3 shows NO according to the inventionxMeasurement replacement system logic block diagram.
Wherein: 1-boiler descending section heat exchanger; 2-ammonia injection grid; 3-an SCR reactor; 4-an air preheater; 5, an electric dust remover; 6-a recovery column; 7-a chimney; 8-a liquid ammonia storage tank; 9-an ammonia evaporator; 10-a safety control valve; 11-ammonia injection flow meter; 12-ammonia injection control valve; 13-dilution fan; 14-an air baffle; 15-ammonia-air mixer; 16-a pressure measuring device; 17-a temperature measuring device; 18-flue gasAn oxygen amount measuring device; 19-first inlet flue gas NOxA measuring device; 20-first outlet flue gas NOxA measuring device; 21-denitration total exhaust port flue gas NOxA measuring device; 22-second inlet flue gas NOxA measuring device; 23-second outlet flue gas NOxA measuring device; 24-a predicted value base quantity correction coefficient module; t1-purge maintenance module; t2-purge maintenance module; t3-alternative switching module; a SUM-substitute signal output module; a DEV-predicted value basis quantity module; MUL-predict increment value output module.
[ detailed description ] embodiments
In order to make the technical solutions of the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, not all of the embodiments, and are not intended to limit the scope of the present disclosure. Moreover, in the following description, descriptions of well-known structures and techniques are omitted so as to not unnecessarily obscure the concepts of the present disclosure. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Various structural schematics according to the disclosed embodiments of the invention are shown in the drawings. The figures are not drawn to scale, wherein certain details are exaggerated and possibly omitted for clarity of presentation. The shapes of various regions, layers and their relative sizes and positional relationships shown in the drawings are merely exemplary, and deviations may occur in practice due to manufacturing tolerances or technical limitations, and a person skilled in the art may additionally design regions/layers having different shapes, sizes, relative positions, according to actual needs.
In the context of the present disclosure, when a layer/element is referred to as being "on" another layer/element, it can be directly on the other layer/element or intervening layers/elements may be present. In addition, if a layer/element is "on" another layer/element in one orientation, then that layer/element may be "under" the other layer/element when the orientation is reversed.
It should be noted that the terms "first," "second," and the like in the description and claims of the present invention and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the invention described herein are capable of operation in sequences other than those illustrated or described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
The invention is described in further detail below with reference to the accompanying drawings:
referring to FIG. 1, NO in SCR denitration control according to the present inventionxMeasurement signal substitution system in DCS between NOxBetween the measurement system and the denitration control system. NO when CEMS measurement device is purgedxThe measurement signal remains unchanged and cannot be used for denitration control. The replacement system of the present invention functions at the purging time of the CEMS measurement device to produce NOxA surrogate signal for the measurement signal that transitions to the true measurement signal when the purge device ends the purge.
As shown in fig. 2, fig. 2 is a denitration system applied in the present invention, flue gas combusted by a boiler flows through a boiler drop section heat exchanger 1 to reach an ammonia injection grid 2, then is mixed with an injected ammonia-air mixture, enters an SCR reactor 3 to perform a denitration chemical reaction, enters an air preheater 4 to further recover heat, and finally is discharged into the atmosphere through a chimney 7 after passing through an electric precipitator 5 and an absorption tower 6.
The liquid ammonia working medium is stored in a liquid ammonia storage tank 8, is changed into ammonia vapor through an ammonia evaporator 9, sequentially flows through a safety control valve 10, an ammonia injection flow meter 11 and an ammonia injection adjusting valve 12, controls proper ammonia injection flow through the ammonia injection adjusting valve 12, enters an ammonia-air mixer 15, is mixed with dilution air flowing through an air baffle 14 from a dilution fan 13 to form an ammonia-air mixture, and is injected into a flue gas channel from an ammonia injection grid 2 to implement denitration.
In the flue gas flow, a pressure measuring device 16, a temperature measuring device 17, a flue gas oxygen measuring device 18 and a first inlet flue gas NO are arranged in front of and behind the descending section of a boiler fluexMeasuring device 19, first outlet flue gas NOxMeasuring device 20, second inlet flue gas NOxMeasuring device 22, second outlet flue gas NOxMeasuring device 23 and total exhaust outlet flue gas NOxA measuring device 21.
NO of the inventionxMeasurement signal substitution system for designing first inlet flue gas NOxAlternative signals for the measurement signal a of the measurement device 19 are example a': design substitution signal replaces first entry flue gas NO in denitration control systemxThe measurement device 19 measures the signal a, which alternative signal a' is only active during purging.
As shown in fig. 2 and 3, in this embodiment, taking the measurement signal a as an example, when the measurement signal a is in the purging state, after the substitute signal a 'of the measurement signal a is determined by the purging determination logic, the substitute switching module T3 switches the measurement signal, so that the substitute signal a' substitutes for the measurement signal a and enters the denitration control system to participate in the denitration control.
First inlet flue gas NOxThe substitute signal A' of the measuring device 19 is derived from the initial value E of the purge0And a predicted increase value Δ R.
A′＝E0+ΔR (1)
In formula (1): e0Representing an initial purge value, Δ R representing a predicted delta value; the initial purging value of the substitute signal A' tracks the actual measurement signal A in real time when the CEMS is not purged; preservation of NO when purging is completed by purging initial value logicxThe measured value at the purging moment is saved as a purging initial value; the initial purge value is derived from the purge time measurement signal holding the current time value through the purge holding module T1, forming the initial purge value of the alternative signal a'. SubstitutionThe signal output module SUM is an addition module, whose function is to implement the addition of the purge initial value and the prediction increment value. The predicted increment value output module MUL is a multiplication module, and has the function of multiplying the predicted value basic quantity and the dynamic correction coefficient to output the predicted value part of the substitute signal a'.
ΔR＝R0×η (2)
In formula (2): r0Representing basic quantity of a predicted value, η representing a dynamic correction coefficient, and tracking the NO of the second inlet flue gas in real time when the CEMS is not purged by the predicted increment valuexThe amount of change in the actual measurement signal of the measurement device 22 is determined by the purge logic, and the predicted increase value Δ R output always outputs 0. When CEMS purging is performed, the purging switching module T2 works, and the purging switching module T2 and the predicted value basic quantity output module DEV jointly generate the predicted value basic quantity R in the purging process0. And the prediction increment value logic is used for performing real-time prediction increment value processing on the current smoke in a purging stage to generate a prediction increment value part of the substitute signal. And the substitution signal output module SUM completes the addition of the purging initial value part and the prediction increment value part and outputs a substitution signal. This completes NO purging for CEMSxThe solution to this problem cannot be measured.
Wherein, the pressure signal P collected by the pressure measuring device 16, the temperature signal T collected by the temperature measuring device 17 and the flue gas oxygen content signal Q collected by the flue gas oxygen content measuring device 18 are all input into a predicted value basic quantity correction coefficient module 24, the predicted value basic quantity correction coefficient module 24 is used for weighting the pressure signal P, the temperature signal T and the flue gas oxygen content signal Q with gain coefficients, and the output of the predicted value basic quantity correction coefficient module 24 is a predicted value basic quantity R0Dynamic correction coefficient η dynamic correction coefficient η enters predicted increase value output module MUL to correct predicted basic quantity output module DEV, and the corrected result is predicted increase value Δ R of measurement signal a during CEMS purging.
The predicted increment value output module MUL outputs a predicted increment value delta R, the predicted increment value delta R and a purging initial value E0The weighted sum results in a substitution signal a'. The same process is used to obtain the first outlet flue gas NOxA substitute signal B' for the measurement signal B of the measurement device 20.
The substitution signal A 'and the substitution signal B' enter the denitration control system to participate in forming the opening adjustment of the ammonia spraying control valve and controlling the opening and closing of the ammonia spraying control valve 12, so that the problems of large change and lag adjustment of the denitration system caused by the blowing of the measurement signal A and the measurement signal B are solved.
The present invention controls NO based on the above denitrationxThe control method of the measurement signal substitution system comprises the following steps:
denitration inlet flue gas NOxThe core of the design for measuring the predicted substitute signal is to maintain the first inlet flue gas NO at the purging moment when the purging signal of the CEMS device is triggeredxInitial value of the measuring device 19, using the flue gas NO of the second inlet on the opposite sidexMeasurement signal C of measuring device 22 in first inlet flue gas NOxMeasuring the variation of the device 19 in the purging process to obtain the first inlet flue gas NOxThe measurement device 19 predicts the basic quantity during purging. The basic quantity of the predicted value is corrected by the pressure signal P collected by the pressure measuring device 16, the temperature signal T collected by the temperature measuring device 17 and the flue gas oxygen quantity signal Q collected by the flue gas oxygen quantity measuring device 18 to obtain the first inlet flue gas NOxThe measurement device 19 predicts the incremental value during purging.
ΔR＝(k1×P+k2×T+k3×Q)×k4×C (3)
In the formula (3), k1A gain factor representing the pressure signal P; k is a radical of2A gain factor representing the temperature signal T; k is a radical of3A gain coefficient representing a smoke oxygen content signal Q; k is a radical of4And the comprehensive gain coefficients of the pressure signal P, the temperature signal T and the flue gas oxygen content signal Q are represented, and the gain coefficients are fitted through the historical data of the unit.
The generation of the substitute signal A' solves the problem of NO brought by CEMS purgingxThe measured value is not a measurable problem.
The method is utilized to realize the NO of the first outlet flue gasxMeasurement signal B of the measurement device 20, second inlet flue gas NOxMeasurement signal C of measuring device 22, second outlet flue gas NOxMeasuring deviceMeasurement signal D at 23 and total exhaust outlet flue gas NOxThe measuring device 21 measures the substitution signal B ', the substitution signal C', the substitution signal D 'and the substitution signal Z' of the signal Z.
The principle and advantages of the invention are as follows:
the invention uses a prediction signal to replace NOxThe difficulty of maintaining the measured value caused by the purging process of the measuring device. Because denitration reactor entry denitration flue gas continuous monitoring system sweeps regularly, denitration reactor export denitration flue gas continuous monitoring system sweeps regularly, and total discharge port denitration flue gas continuous monitoring system sweeps regularly, and above 3 signals sweep once every hour, the flue gas NO who gathers when sweepingxThe measured value loses the authenticity, and the measured value changes by a wide margin, has influenced measuring accuracy and corresponding time, and then influences the input of denitration control system, influences the environmental protection index that denitration system controlled.
The invention adopts the signal of the denitration reactor inlet denitration flue gas continuous monitoring system with basically different cross sections to generate the prediction increment value of the substitute signal, namely the prediction increment value part of the substitute signal, thereby having smaller calculation error, good stability and higher real-time property and being capable of ensuring the normal work of the denitration control system PID.
The invention adopts three signals of a pressure signal P, a temperature signal T and a flue gas oxygen content signal Q to generate a large dynamic correction coefficient with a large predicted value basic quantity for carrying out purging correction, and a prediction mathematical model has a moderate advance in time and can advance in NOxTimely change of ammonia injection amount during change to avoid NOxMeasuring the hysteresis of the predicted change of the temperature signal a'; on the other hand, the excessive advance is avoided, the control balance of the ammonia injection main PID controller is disturbed, and the instability of the system is caused;
by means of NO in the inventionxMeasuring the surrogate signal for SCR denitration control is limited to the CEMS device measuring the signal only during the blow-through process, and after the end of the blow-through process, the predictive signal is switched back to the actual NO measured by the CEMS devicexThe signal is measured. The middle switching process is switched at a certain speed, so that the stability of the denitration control system is ensuredTherefore, the accuracy of the calculation basis of the ammonia injection control is guaranteed.
Finally, the first inlet flue gas NO in the denitration control system of the inventionxMeasurement signal A of measurement device 19, first outlet flue gas NOxMeasurement signal B of measurement device 20, total exhaust outlet flue gas NOxMeasuring device 21 measures signal Z and second inlet flue gas NOxMeasurement signal C of measuring device 22 and second outlet flue gas NOxAfter the alternative scheme that the measurement signal D of the measurement device 23 is respectively implemented by the alternative signal a ', the alternative signal B ', the alternative signal C ', the alternative signal D ' and the alternative signal Z ', the denitration system can greatly reduce the adverse effect of the purging of the measurement device on the denitration control, and improve the control effect and the accuracy.
The above-mentioned contents are only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited thereby, and any modification made on the basis of the technical idea of the present invention falls within the protection scope of the claims of the present invention.

Claims (3)

1. NO in SCR denitration controlxA measurement signal substitution system, comprising:
a purge maintenance module (T1) which maintains the current measurement signal as the purge initial value E at the purge time when the purge signal is received0And purging the initial value E0Output to a substitute signal output module (SUM);
a purge switching module (T2) which, when CEMS purging, generates a predicted value basic quantity R during purging in cooperation with a predicted value basic quantity output module (DEV)0；
A predicted value basic quantity correction coefficient module (24), wherein the input end of the predicted value basic quantity correction coefficient module (24) receives a pressure signal P acquired by a pressure measuring device (16), a temperature signal T acquired by a temperature measuring device (17) and a flue gas oxygen quantity signal Q acquired by a flue gas oxygen quantity measuring device (18), and the pressure signal P, the temperature signal T and the flue gas oxygen quantity signal Q are weighted by gain coefficientsProcessing and outputting the predicted value basic quantity R0η to a predicted delta value output Module (MUL);
a prediction increment value output Module (MUL) which is a multiplication module and is used for predicting the basic quantity R of the value0The predicted increment value output Module (MUL) corrects the predicted value basic quantity output module (DEV) according to the dynamic correction coefficient η and outputs the predicted increment value delta R of the measuring signal;
a substitute signal output module (SUM) which is an addition module and is used for realizing the purging initial value E0And the addition of the predicted delta value Δ R, outputting a substitution signal to the substitution switching module (T3);
and the replacing switching module (T3) replaces the measurement signal A with a replacing signal A 'when receiving the purging signal, so that the replacing signal A' enters the denitration control system to participate in the adjustment of the opening degree of the ammonia injection control valve, and the opening and closing of the ammonia injection control valve (12) in the denitration system are controlled.
2. A denitration system using the alternative system of claim 1, the denitration system comprising:
the device comprises a boiler descending section heat exchanger (1), wherein a smoke side outlet of the boiler descending section heat exchanger (1) is sequentially connected with an air preheater (4), an electric dust remover (5), an absorption tower (6) and a chimney (7); an ammonia injection grid (2) and an SCR reactor (3) are sequentially arranged in a flue between the boiler descending section heat exchanger (1) and the air preheater (4) along the flow direction of flue gas;
the ammonia injection grid (2), the ammonia injection grid (2) is connected with an ammonia-air mixture (15);
an air inlet of the ammonia-air mixer (15) is connected with a dilution fan (13), and an ammonia inlet is connected with a liquid ammonia storage tank (8) through an ammonia evaporator (9);
the device comprises a pressure measuring device (16) and a temperature measuring device (17), wherein the pressure measuring device (16) and the temperature measuring device (17) are respectively provided with two groups and are respectively arranged at a steam inlet and a steam outlet of the smoke side of the boiler descending section heat exchanger (1);
the device comprises a flue gas oxygen content measuring device (18), wherein the flue gas oxygen content measuring device (18) is arranged at a steam inlet on the flue gas side of a boiler descending section heat exchanger (1);
first inlet flue gas NOxMeasuring device (19) and second inlet flue gas NOxA measuring device (22), the first inlet flue gas NOxMeasuring device (19) and second inlet flue gas NOxThe measuring devices (22) are arranged on one side of the steam inlet end of the ammonia injection grid (2) and are arranged oppositely;
first outlet flue gas NOxMeasuring device (20) and second outlet flue gas NOxA measuring device (23), the first outlet flue gas NOxMeasuring device (20) and second outlet flue gas NOxThe measuring devices (23) are arranged on one side of the steam outlet end of the SCR reactor (3) and are arranged oppositely;
and total exhaust outlet flue gas NOxMeasuring device 21, said total exhaust outlet flue gas NOxThe measuring device (21) is arranged in the chimney (7).
3. The method for controlling NO in SCR denitration according to claim 1xMethod for controlling a measurement signal substitution system, characterized in that NO is passed when a purge signal of a CEMS device is triggeredxThe measurement signal substitution system is used for controlling an ammonia injection control valve of the denitration system, substituting the measurement signal into a substitution signal by using a substitution switching module (T3), inputting the substitution signal into the denitration control system to participate in forming the opening adjustment of the ammonia injection control valve, wherein the measurement signal comprises first inlet flue gas NOxMeasurement signal A of the measurement device (19), first outlet flue gas NOxMeasurement signal B of measurement device (20), total exhaust outlet flue gas NOxThe measuring device (21) measures a signal Z and a second inlet flue gas NOxMeasurement signal C of the measuring device (22) and second outlet flue gas NOxA measurement signal D of the measurement device (23); by NOxThe measurement signal substitution system generates a substitution signal A ', a substitution signal B ', a substitution signal C ', a substitution signal D ', and a substitution signal Z ', respectivelyD ' is the same as the generation method of the substitute signal Z ', and the control method will be described with reference to generation of the substitute signal a ', and the specific control method includes the following steps:
step 1: when the CEMS device purging signal is triggered, the purging maintenance module (T1) maintains the first inlet flue gas NO at the purging timexThe current value of the measuring device (19) is used as the initial purging value E0；
Step 2: using first inlet flue gas NOxA second inlet flue gas NO on the opposite side of the measuring device (19)xMeasuring signal C of the measuring device (22) in the first inlet flue gas NOxMeasuring the variation of the device (19) in the purging process to obtain the first inlet flue gas NOxPredicting a basic quantity R during purging of a measuring device (19)0；
And step 3: pressure signals P collected by a pressure measuring device (16), temperature signals T collected by a temperature measuring device (17) and flue gas oxygen quantity signals Q collected by a flue gas oxygen quantity measuring device (18) are input into a predicted value basic quantity correction coefficient module (24) for weighting processing to obtain predicted value basic quantity R0η;
and 4, step 4: predicted value of the basic quantity R0Correcting according to the dynamic correction coefficient η by a prediction increment value output Module (MUL) to obtain the first inlet flue gas NOxPredicted increment value DeltaR during purging of the measuring device (19):
ΔR＝R0×η
and 5: according to the initial value E of purging0And predicting the increment value delta R to obtain the first inlet flue gas NOxAlternative signal a' of the measuring device (19):
A′＝E0+ΔR
step 6: and when receiving the purging signal, the replacing switching module (T3) replaces the measurement signal A with a replacing signal A ', so that the replacing signal A' enters the denitration control system to participate in forming the opening adjustment of the ammonia injection control valve, and the opening and closing of the ammonia injection control valve (12) in the denitration system are controlled.
CN201911286057.1A 2019-12-13 2019-12-13 NO in SCR denitration controlxMeasurement signal substitution system and control method thereof Pending CN110865623A (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112185475A (en) * 2020-09-28 2021-01-05 齐鲁工业大学 Aiming at SCR denitration system distortion NOxHigh-precision intelligent concentration prediction method
CN113433980A (en) * 2021-04-27 2021-09-24 国能南京电力试验研究有限公司 Calculating denitration inlet NO under blowing working condition by system error methodxMethod for measuring values

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112185475A (en) * 2020-09-28 2021-01-05 齐鲁工业大学 Aiming at SCR denitration system distortion NOxHigh-precision intelligent concentration prediction method
CN112185475B (en) * 2020-09-28 2023-07-14 齐鲁工业大学 Distortion state NO for SCR denitration system x High-precision intelligent prediction method for concentration
CN113433980A (en) * 2021-04-27 2021-09-24 国能南京电力试验研究有限公司 Calculating denitration inlet NO under blowing working condition by system error methodxMethod for measuring values

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