CN102000482B - System and method for controlling oxynitride removal - Google Patents
System and method for controlling oxynitride removal Download PDFInfo
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- CN102000482B CN102000482B CN 201010545351 CN201010545351A CN102000482B CN 102000482 B CN102000482 B CN 102000482B CN 201010545351 CN201010545351 CN 201010545351 CN 201010545351 A CN201010545351 A CN 201010545351A CN 102000482 B CN102000482 B CN 102000482B
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Abstract
The invention provides a system and a method for optimally controlling ammonia denitration, which are characterized in that according to the content of oxynitride which is detected by an oxynitride sensor at the inlet of a reactor and fed into the reactor, the content of oxynitride which is detected by the oxynitride sensor at the outlet of the reactor and discharged from the reactor, and the continuous online measuring value of the oxynitride at the outlet of the reactor and the escaped ammonia amount detected by an ammonia sensor at the outlet of the reactor, the ammonia-injected amount is calculated according a transfer function; the control system has positive and negative feedback correction effects on feedforward loops, and monitors the continuous online measuring value of the oxynitride, thereby ensuring the implementation of meeting the qualified oxynitride discharge index; the control system is provided with two lag time functions so as to overcome the effect of time lag, eliminate the fluctuations of the oxynitride content and ammonia-injected amount at the outlet of the reactor; and meanwhile, the control system is also provided with an ammonia escape detection sensor for preventing the escape of ammonia.
Description
[technical field]
The present invention relates to control system and method that a kind of nitrogen oxide is removed, particularly relate to and adopt selective catalytic reduction (SCR), SNCR method (SNCR) or SNCR and SCR combination method (SNCR-SCR) to carry out control system and method that nitrogen oxide is removed.
[background technology]
China is the developing country take coal as main energy sources, the electric power energy of country is mainly provided by the thermal power plant of burning coal, and the coal that is directly used in burning every year reaches more than 1,200,000,000 tons, gives off a large amount of pollutants behind the coal burning, such as SO2, SO3 (common name SOX, sulfide); NO, NO2 (common name NOX, nitrogen oxide, industrial being commonly called as " nitre "); Nitrogen oxide, brings outside the irreversible consequence soil and aquatic ecosystem except causing acid rain with other compounds the pollution of atmospheric environment, also since the generation of their participation photochemical fogs be subject to people's attention.Along with new environmental regulation comes into force successively in the whole world, the increasing that increasingly strictly reaches law enforcement dynamics of China environmental protection rules, more and more stricter to the standard limit of the highest permission concentration of emission of nitrogen oxide.
The method (being also referred to as the denitration control technology) of the removal row discharging nitrogen oxide of thermal power plant generally has burning control denitration and denitrating flue gas etc.Burning control denitration be the amount of nitrogen oxides itself that produces behind the coal burning just seldom, so discharge capacity is seldom, this method is the one preferred technique of coal-burning power plant's nitrogen oxide reduction of discharging.And denitration method for flue gas be the flue gas of discharging after coal burning can be with a large amount of nitrogen oxide, by the nitrogen oxide in the flue gas is processed, make the content of nitrogen oxide of the flue gas that finally gives off controlled.
The mode of burning control denitration is to use the electricity generation boiler of low nitrogen burning technology, so that the amount of nitrogen oxides that produces behind the coal burning itself just seldom.But existing low nitrogen burning technology discharged nitrous oxides concentration when using bituminous coal and brown coal is lower.But limited for the unit nitrogen oxide control effect that uses anthracite or meager coal, can not control the discharging of nitrogen oxide fully, nitrous oxides concentration or total amount can not reach discharge standard or total emission volumn requirement, still need to build the denitrating flue gas facility.
Gas denitrifying technology mainly comprises: selective catalytic reduction (SCR), SNCR method (SNCR), SNCR and SCR combination method (SNCR-SCR), liquid absorption method, microbial method, active carbon adsorption, electronic beam method etc.Wherein, first three methods is the industrial method of generally using in the world at present, and other method seldom has the example of industrial applications.
Selective catalytic reduction (SCR), SNCR method (SNCR), SNCR are similar to the denitration principles of chemistry of these three kinds of methods of SCR combination method (SNCR-SCR).Mainly be by allowing the flue gas that contains nitrogen oxide by reacting with ammonia, finally producing the nitrogen G﹠W that does not have to pollute and reach the effect of discharging nonnitrogenous oxide in the flue gas.
For the technology that adopts the SCR method to carry out denitration, its chemical reaction is:
4NO+4NH3+O2→4N2+6H2O (1)
6NO+4NH3→5N2+6H2O (2)
2NO2+8NH3+O2→3N2+6H2O (3)
For the technology that adopts the SNCR method to carry out denitration, its chemical reaction is:
4NO+4NH3→4N2+6H2O (4)
6NO2+8NH3→7N2+12H2O (5)
Because temperature is larger on adopting the SNCR method to carry out the impact of reduction reaction of denitration.When temperature was higher than 1100 ℃, the removal efficiency of NOx was owing to the thermal decomposition of ammonia reduces; When temperature was lower than below 800 ℃, the reaction rate of NH3 descended, and reduction reaction is carried out insufficiently, and the NOx removal efficiency descends, and the escaped quantity of ammonia may also increase simultaneously.Selective catalytic reduction (SCR) be use in the world at most at present, the most ripe and the most fruitful a kind of gas denitrifying technology.Since the states such as Europe in 1986, Japan use the SCR technology, at present by the extensive use of institute of the developed countries such as Europe, the United States, day.This technology denitration efficiency generally can reach 80%～90%, and discharged nitrous oxides concentration can be down to about 100mg/m3; In the Flue Gas Denitrification Engineering that China builds or plans to build, mostly adopt the SCR method.
Formula (1)-(5) according to the front can find out, carry out denitration by SCR method and SNCR method or both methods of associating, all need reducing agent ammonia (NH3), and the consumption of ammonia is the key of above-mentioned reaction.In denitrating system, the practicality amount of ammonia is the key factor that guarantees system optimized operation, denitration efficiency and avoid secondary pollution (ammonia is overflowed or the escape amount).The consumption of ammonia is crossed the major general and is caused denitration to reduce; Thereby the consumption of ammonia is too high will to be caused amount of ammonia slip to increase causing secondary pollution.
At present extensive at the research and comparison that carries out aspect the mobile source vehicle exhaust denitration control.For example United States Patent (USP) 4963332 is used the measured value of the NOx of SCR reactor upstream and downstream, and ammonia nitrogen was adjusted by the concentration of downstream NOx than (being equivalent to ammonia spraying amount).United States Patent (USP) 4751054 adopts ammoniacal sensor applications similar method to regulate ammonia spraying amount.United States Patent (USP) 5522218 utilizes the FEEDFORWARD CONTROL logic to control ammonia spraying amount, but its method is the ammonia spraying amount that utilizes table lookup default.United States Patent (USP) 5628186 then is to use feedback, and the consumption of ammonia is adjusted the adsorption and desorption rate of reducing agent by the catalyst wall.These researchs all are the control that denitration is carried out for the mobile source vehicle exhaust, and relatively difficulty is used in the large-scale stationary source denitration technologies such as thermal power plant.
The system block diagram of existing typical stationary source SCR denitration control system as shown in Figure 1, existing denitration control system mainly is the denitration efficiency η according to the content NOx_out computing system of the nitrogen oxide of the amount of nitrogen oxides NOx_in of the import of SCR reactor and outlet
SCR., computing formula is:
η
SCR＝(NOx_out-NOx_in)/NOx_in*100％
Then according to the denitration efficiency η of the system that calculates
SCR. compare with predefined denitration efficiency, when reaching predefined denitration efficiency, then adjust end, if the efficient of denitration does not reach predefined efficient, then adjust ammonia spraying amount.Existing this control system, to control according to the efficient of denitration, spray ammonia (NH3) amount is jointly to determine by the feedback control loop of the nitrogen oxide emission NOx_out of outlet with by the front feedback controller at the amount of nitrogen oxides NOx_in place of SCR import department, although this control logic can guarantee the denitration efficiency of SCR system, but because only control the efficient of denitration, and the efficient of denitration is not only relevant with the nitrogen oxide NOx _ out that discharges, also relevant with the amount of nitrogen oxides NOx_in of SCR import, the nitrogen oxide NOx that may export _ out content is also defective, but whole efficiency also can reach predefined efficient, therefore this control logic can not guarantee to discharge the NOx value NOx_out of qualified SCR outlet, nor can guarantee that amount of ammonia slip is in a certain scope.And the employing that system time lags behind will produce a very large impact control validity.Therefore be necessary to improve existing SCR control system.
[summary of the invention]
The object of the present invention is to provide a kind of control system of removing nitrogen oxide, it can overcome impact time lag, eliminate reactor outlet nitrogen oxide and ammonia spraying amount in the operating fluctuation of reaction, and can avoid ammonia to overflow, guarantee to reach qualified discharged nitrous oxides index.
Another object of the present invention is to provide a kind of control method of removing nitrogen oxide, it can overcome impact time lag, eliminate reactor outlet nitrogen oxide and ammonia spraying amount in the operating fluctuation of reaction, and can avoid ammonia to overflow, guarantee to reach qualified discharged nitrous oxides index.
For reaching aforementioned purpose, a kind of control system of removing nitrogen oxide of the present invention, it comprises:
Reactor; Be used for providing reacting environment;
The NOx sensor at Reactor inlet place is for detection of the amount of nitrogen oxides that enters reactor;
The NOx sensor of reactor exit is for detection of the amount of nitrogen oxides of the emission of discharging from reactor;
The ammoniacal sensor of reactor exit is for detection of the discharge capacity of discharging ammonia from reactor;
Computation processor, the data message that gathers according to the ammoniacal sensor of reactor exit calculates the continuous on-line measurement value of the nitrogen oxide of reactor exit, and the emission intensity amount that the ammoniacal sensor of the continuous on-line measurement value of the nitrogen oxide in the amount of nitrogen oxides of the emission that detects of the NOx sensor of the amount of nitrogen oxides that enters reactor that detects according to the NOx sensor at Reactor inlet place, reactor exit, previous reaction device exit and reactor exit detects is calculated ammonia spraying amount according to transfer function;
Spray ammonia controller is controlled spurting of ammonia according to the ammonia spraying amount that computation processor calculates.
Further, aforementioned transfer function comprises: the front present that the amount of nitrogen oxides that enters reactor that detects according to the NOx sensor at Reactor inlet place calculates is with function and FEEDFORWARD CONTROL function; The interior ring controller function that the nitrogen oxide measured value in the exit that is recorded by the NOx sensor of reactor exit calculates by interior ring controller C_in; The outer ring controller C_out function that forms according to the continuous on-line measurement value preset value of the nitrogen oxide of the continuous on-line measurement value of the nitrogen oxide of reactor exit and reactor exit; And the ammonia feedback function of the content of the ammonia that detects according to the ammoniacal sensor of reactor exit.
Further, aforementioned interior ring controller C_in is ratio (propotional)-differential (derivative) controller, can be expressed as: C_in (s)=KP_in+KD_in*s, KP_in, KD_in is interior chain rate example, the yield value of micro component, s is Laplce's variable, is obtained by simulated test.
Further, aforementioned outer ring controller C_out is a ratio (propotional)-integration (integral)-differential (derivative) controller, can be expressed as: C_out (s)=KP_out+KI_out/s+KD_out*s, KP_out, KI_out, KD_out are the outer shroud ratio, integration, the yield value of micro component, s is Laplce's variable, is obtained by simulated test.
Further, aforementioned transfer function also comprise two time lag function, one before aforementioned interior ring controller C_in function, one before aforementioned outer ring controller C_out function, its functional form is e-sT, time factor T is decided by system model simulation, can use Simulink and calculate.
Further, at least part of use of described transfer function obtains through overtesting according to the probability statistics model of setting up under the particular reactor system.
Further, described system also comprises a warning device, if system can not reach control range, warning device will send early warning signal.
For reaching aforementioned purpose, a kind of method of removing the control system of nitrogen oxide of the present invention, it comprises:
Detect in real time the content of the nitrogen oxide that enters reactor by the import NOx sensor that is arranged on the reactor inlet place;
Calculated the quantity of needs spray ammonia according to transfer function default in the computation processor by computation processor;
Computation processor is controlled the quantity of spraying ammonia by spray ammonia controller after calculating ammonia spraying amount;
The flue gas that boiler is discharged carries out catalytic reduction reaction with the ammonia of spray ammonia controller ejection in reactor;
Set one period lag time, the content of nitrogen oxide of the outlet of actual measurement reactor feeds back to computation processor with the content of the nitrogen oxide of the outlet of the reactor that measures as feedback information;
The reaction efficiency of the cubage reactor of the nitrogen oxide of the content of the nitrogen oxide that enters reactor that detects according to the import NOx sensor of previous reaction device import department and the outlet of reactor;
Set one period system lag time, calculate the continuous on-line measurement value of the amount of nitrogen oxides of outlet after a period of time at system stable operation;
The continuous on-line measurement predetermined value of nitrogen oxide of wanting to reach emission request of reading pre-set, the continuous on-line measurement value of the nitrous oxides concentration content of reactor outlet and the predefined continuous on-line measurement predetermined value of nitrogen oxide of wanting to reach emission request are compared, when continuous on-line measurement value when wanting to reach the measurement predetermined value of emission request, represent that then current ammonia spraying amount meets the requirements, adjust and finish; When continuous on-line measurement value when wanting to reach the measurement predetermined value of emission request, recomputate a new value of feedback and feed back to computation processor;
Ammoniacal sensor by reactor outlet detects the escape amount of ammonia, and the escape amount of ammonia is fed back to computation processor;
The emission intensity amount that the new value of feedback of the continuous on-line measurement value of the amount of nitrogen oxides of the emission that the amount of nitrogen oxides that enters reactor that computation processor detects according to the NOx sensor at Reactor inlet place, the NOx sensor of reactor exit detect, the nitrogen oxide in previous reaction device exit and the ammoniacal sensor of reactor exit detect recomputates ammonia spraying amount according to aforementioned transfer function, and the ammonia spraying amount control ammonia that is calculated according to computation processor by spray ammonia controller spurt quantity.
Further, default transfer function comprises in the aforementioned computation processor: the front present that the amount of nitrogen oxides that enters reactor that detects according to the NOx sensor at Reactor inlet place calculates is with function and FEEDFORWARD CONTROL function; The interior ring controller function that the nitrogen oxide measured value in the exit that is recorded by the NOx sensor of reactor exit calculates by interior ring controller C_in; The ammonia feedback function of the content of the outer ring controller C_out function that forms according to the continuous on-line measurement value preset value of the nitrogen oxide of the continuous on-line measurement value of the nitrogen oxide of reactor exit and reactor exit and the ammonia that detects according to the ammoniacal sensor of reactor exit.
Further, aforementioned interior ring controller C_in is ratio (propotional)-differential (derivative) controller, can be expressed as: C_in (s)=KP_in+KD_in*s, KP_in, KD_in is interior chain rate example, the yield value of micro component, s is Laplce's variable, is obtained by simulated test.
Further, aforementioned outer ring controller C_out is a ratio (propotional)-integration (integral)-differential (derivative) controller, can be expressed as: C_out (s)=KP_out+KI_out/s+KD_out*s, KP_out, KI_out, KD_out are the outer shroud ratio, integration, the yield value of micro component, s is Laplce's variable, is obtained by simulated test.
Further, in the computation processor default function also comprise two time lag function, one before aforementioned interior ring controller C_in function, one before aforementioned outer ring controller C_out function, its functional form is e-sT, time factor T decides by system model simulation, can use Simulink and calculate.
Further, the default at least part of use of function obtains through overtesting according to the probability statistics model of setting up under the particular reactor system in the described computation processor.
Further, described method also comprises if system can not reach control range, will send early warning signal by warning device.
Removal nitrogen oxide control system of the present invention and method thereof, than traditional, conventional control system, control system of the present invention is according to the amount of nitrogen oxides that enters reactor of the NOx sensor detection at Reactor inlet place, the amount of ammonia slip that the amount of nitrogen oxides that the reactor that the NOx sensor of reactor exit detects is discharged and the continuous on-line measurement value of nitrogen oxide of reactor outlet and reactor exit ammoniacal sensor detect is calculated ammonia spraying amount according to transfer function, this control system just has feedforward loop circuit, the negative-feedback debugging functions, and the continuous on-line measurement value of monitoring nitrogen oxide, can guarantee the discharged nitrous oxides index that reaches qualified, this set-up of control system have two lag time function, impact time lag be can overcome, outlet nitrogen oxide and ammonia spraying amount eliminated in the operating fluctuation of reactor; Be provided with simultaneously ammonia effusion detecting sensor, can avoid ammonia to overflow.
[description of drawings]
Fig. 1 is the simulation block diagram of existing SCR control system.
Fig. 2 is that the present invention adopts SCR to carry out the structural representation of the Optimal Control System of ammonia-denitration.
Fig. 3 is the control flow chart of system shown in Figure 2.
Fig. 4 is the transfer function schematic diagram of SCR control system of the present invention.
[specific embodiment]
Alleged " embodiment " or " embodiment " refer to be contained in special characteristic, structure or the characteristic at least one implementation of the present invention herein.Different local in this manual " in one embodiment " that occur not are all to refer to same embodiment, neither be independent or the embodiment mutually exclusive with other embodiment optionally.In addition, represent the sequence of unit in method, flow chart or the functional block diagram of one or more embodiment and revocablely refer to any particular order, also be not construed as limiting the invention.
In one embodiment of the invention, denitration control system of the present invention is to be applied in the coal-burning power plant, and the flue gas that contains nitrogen oxide that the burning boiler of this coal-burning power plant gives off gives off the flue gas that reaches qualified discharged nitrous oxides standard after processing through denitration control system of the present invention.
See also shown in Figure 2ly, denitration control system of the present invention comprises the SCR reactor 202 that is connected with the burning boiler 201 of power plant, the pressure that arranges at the gas approach place of SCR reactor 202, temperature sensor 203, import NOx sensor 204 (import NOx sensor), the pressure that arranges at the smoke outlet of SCR reactor 202, temperature sensor 205, outlet NOx sensor 206 (outlet NOx sensor) and ammoniacal sensor 207 (NH3 sensor), computation processor 208, and by the spray ammonia controller 209 of computation processor 208 control.The below will tell about the effect of each unit one by one.
SCR reactor 202 provides flue gas and ammonia carries out the place that SCR reacts, the boiler 201 of coal-burning power plant produces emission gases, this emission gases is the flue gas that contains nitrogen oxide, the flue gas of this discharging is delivered to SCR reactor 202, in SCR reactor 202, react with ammonia, concrete reaction formula can be with reference to aforementioned formula (1)-(5), may be several formula wherein, also may be all formulas.Through producing the nitrogen G﹠W after the reaction, then reach the flue gas of discharging is removed the purpose of nitrogen oxide (being industrial " denitration " that is commonly called as).Will consider two factors when design SCR reactor 202, one is the air speed of reactor, allows the higher expression catalyst activity of air speed higher, and the device disposal ability is larger.But air speed can not infinitely improve.For given device, inlet amount increases hourly space velocity and increases, and air speed means that greatly the raw material by catalyst is many in the unit interval, and the time of staying of raw material on catalyst is short, and reaction depth is shallow.On the contrary, air speed is little to mean that the reaction time is long, and reducing air speed is favourable for the conversion ratio that improves reaction.But lower air speed means in the situation that the catalyst amounts that the same treatment amount needs is more, and reactor volume is larger, is irrational economically.So the selection of industrial air speed will comprehensively be determined according to each side such as the activity of investment, the catalyst of device, feedstock property, product requirements.Another one should make the interior gas flowfield of reactor be evenly distributed as far as possible.
The pressure that SCR reactor 202 porch arrange, temperature sensor 203 are used for gathering the pressure and temperature of the flue gas that gives off from burning boiler 201, be provided with equally pressure, temperature sensor 205 in the exit of SCR reactor 202, be used for gathering the pressure and temperature from SCR reactor 202 outlets emission gases out.Because the pressure and temperature of gas can affect the reaction of carrying out in the SCR reactor 202, therefore when control, need to monitor this pressure and temperature in order to regulate.
The import NOx sensor 204 that SCR reactor 202 porch arrange is for detection of the content NOx_in of the nitrogen oxide that enters the SCR reactor.
The outlet NOx sensor 206 that SCR reactor 202 exits arrange is for detection of the content NOx_out through nitrogen oxide in the Exhaust Gas after 202 reactions of SCR reactor.
Because the reaction of in SCR reactor 202, carrying out, may there be the incomplete situation of reaction, the situation of the escape of ammonia can occurs, therefore, be provided with an ammoniacal sensor 207 in the exit of SCR reactor 202, be used for detecting the escape amount NH3_slip of ammonia in the SCR reactor 202.
The content NOx_out of contained nitrogen oxide calculates the continuous on-line measurement value NOx_CEM of Exhaust Gas in the Exhaust Gas that the outlet NOx sensor 206 that described computation processor 208 arranges according to aforementioned SCR reactor 202 exits detects, and the pressure that arranges according to SCR reactor 202 porch, gas pressure and the temperature of temperature sensor 203 monitorings, the pressure that the SCR reactor exit arranges, gas pressure and temperature that temperature sensor detects, the content NOx_in of the nitrogen oxide that contains in the air inlet that the import NOx sensor 204 that SCR reactor 202 porch arrange detects, the content NOx_out of contained nitrogen oxide in the Exhaust Gas that the outlet NOx sensor 206 that SCR reactor 202 exits arrange detects, these parameters of amount of ammonia slip NH3_slip that the ammoniacal sensor 207 that the continuous on-line measurement value NOx_CEM of Exhaust Gas and SCR reactor exit arrange detects, calculate by a transfer function (hereinafter say in detail and tell about), determine the amount of the ammonia that needs in the SCR reactor 202.
If system still can not reach control range through repeatedly adjusting, computation processor 208 will be exported an early warning signal, report to the police by warning device (not shown).
See also shown in Figure 3ly, it shows the control method flow chart of system of the present invention.The control method of control system of the present invention comprises the steps: as shown in the figure
S1: the content NOx_in that detects in real time the nitrogen oxide that enters the SCR reactor by the import NOx sensor that is arranged on SCR reactor inlet place.
S2: the quantity of being calculated needs spray ammonia by computation processor according to transfer function default in the computation processor, because when the initial work of whole system, reaction in the SCR reactor does not also begin, the feedback information of various SCR reactor exits all is 0, for example the content NOx_out of nitrogen oxide is 0 in the ammoniacal sensor amount of ammonia slip that detects and the Exhaust Gas that exports the detection of NOx sensor, computation processor is according to the pressure sensor of SCR porch, temperature sensor and import NOx sensor detect the content NOx_in of the nitrogen oxide that enters the SCR reactor in real time, calculate an ammonia spraying amount according to the transfer function that computation processor inside prestores.
S3: computation processor is controlled the quantity of spraying ammonia by spray ammonia controller after calculating ammonia spraying amount.
S4: the flue gas that boiler is discharged carries out catalytic reduction reaction with the ammonia of spray ammonia controller ejection in the SCR reactor.
S5: set one period lag time, be set one period lag time be because below need to measure the SCR reactor the parameter of each data of outlet as feedback information, and the SCR reactor need to react a period of time.
S6: the content NOx_out of the nitrogen oxide of the outlet of actual measurement SCR reactor.The content NOx_out of the nitrogen oxide of the outlet of the SCR reactor that measures is fed back to computation processor as feedback information.
S7: the content NOx_out of the nitrogen oxide of the content NOx_in of the nitrogen oxide that enters reactor that detects according to the import NOx sensor at aforementioned SCR Reactor inlet place and the outlet of SCR reactor, calculate the reaction efficiency of SCR reactor.
S8: set one period system lag time, it is because will calculate at system stable operation the continuous on-line measurement value NOx_CEM of the amount of nitrogen oxides of outlet after a period of time that this system time hysteresis function is set.
S9: the outlet NOx sensor by the SCR outlet is surveyed NOx concentration online, obtains the continuous on-line measurement value NOx_CEM of the nitrous oxides concentration content of SCR outlet through integral and calculating mean value according to the online actual measurement NOx concentration of a period of time.
S10: the continuous on-line measurement predetermined value of the nitrogen oxide NOx_sp that wants to reach emission request of reading pre-set.
S11: the continuous on-line measurement value NOx_CEM of the nitrous oxides concentration content of SCR outlet and the predefined continuous on-line measurement predetermined value of the nitrogen oxide NOx_sp that wants to reach emission request are compared, when continuous on-line measurement value NOx_CEM when wanting to reach the measurement predetermined value NOx_sp of emission request, represent that then current ammonia spraying amount meets the requirements, do not need to regulate.
S12: when continuous on-line measurement value NOx_CEM when wanting to reach the measurement predetermined value NOx_sp of emission request, the gas of expression discharging does not reach requirement, recomputate a new value of feedback and feed back to computation processor this moment.
S13: the ammoniacal sensor by the SCR reactor outlet detects the escape amount of ammonia, and the escape amount of ammonia is fed back to computation processor.
Aforementioned feedback parameter all feeds back to computation processor, then re-executes step S2: the emission intensity amount that the new value of feedback of the continuous on-line measurement value of the amount of nitrogen oxides of the emission that the amount of nitrogen oxides that enters reactor that computation processor detects according to the NOx sensor of previous reaction device import department, the NOx sensor of reactor exit detect, the nitrogen oxide in previous reaction device exit and the ammoniacal sensor of reactor exit detect recomputates ammonia spraying amount according to aforementioned transfer function.
Computation processor calculates the ammonia spraying amount that makes new advances is controlled ammonia afterwards by spray ammonia controller the quantity of spurting.(not shown) then circulates execution in step S3 to step S13, finishes until the continuous on-line measurement value of nitrogen oxide NOx_CEM adjusts during less than the measurement predetermined value NOx_sp that wants to reach emission request.
If system still can not reach control range through repeatedly adjusting, computation processor can be by a warning device output early warning signal (not shown).
As shown in Figure 4, the transfer function that prestores in the computation processor in aforementioned control system and the control method comprises:
Import NOx feedforward function: the feedforward amount is made of with function f (x) and FEEDFORWARD CONTROL function a front present; The FEEDFORWARD CONTROL function is simple differentiation element control C_feed;
SCR function time lag, its functional form are e-sT, time factor T is decided by system model simulation, for example can use Simulink and calculate;
The content NOx_out feedback function of the nitrogen oxide of the outlet of reactor, the content NOx_out of nitrogen oxide feeds back to computation processor by interior ring controller C_in, C_in is ratio (propotional)-differential (derivative) (brief note is PD) controller, can be expressed as: C_in (s)=KP_in+KD_in*s, KP_in, KD_in are interior chain rate example, the yield value of micro component, s is Laplce's variable, is obtained by simulated test;
System time hysteresis function, its functional form are e-sT, time factor T is decided by system model simulation, for example can use Simulink and calculate;
Continuous on-line measurement value NOx_CEM feedback function, the preset value NOx_sp of NOx_CEM feedback and NOx_CEM forms outer ring controller C_out and feeds back to computation processor, C_out is a ratio (propotional)-integration (integral)-differential (derivative) (brief note is PID) controller, can be expressed as: C_out (s)=KP_out+KI_out/s+KD_out*s, KP_out, KI_out, KD_out is the outer shroud ratio, integration, the yield value of micro component, s is Laplce's variable, is obtained by simulated test;
The escaping of ammonia feedback function detects the escape amount of ammonia and sets an ammonia feedback function according to the ammoniacal sensor of SCR reactor outlet.
Wherein " the interior ring " in the aforementioned transfer function and " outer shroud " refer to this function relative position in the present embodiment, the content NOx_out feedback function that does not limit nitrogen oxide must be interior ring control, and on-line measurement value NOx_CEM feedback function must be outer shroud control continuously.
Functional relation at least a portion of aforementioned whole control system is to use the probability statistics model of setting up under specific SCR system to draw through overtesting.
Control system of the present invention and method thereof are according to the amount of nitrogen oxides that enters reactor of the NOx sensor detection at Reactor inlet place, the amount of ammonia slip that the amount of nitrogen oxides that the reactor that the NOx sensor of reactor exit detects is discharged and the continuous on-line measurement value of nitrogen oxide of reactor outlet and reactor exit ammoniacal sensor detect is calculated ammonia spraying amount according to aforementioned transfer function, this control system just has feedforward loop circuit, the negative-feedback debugging functions, and the continuous on-line measurement value of monitoring nitrogen oxide, can guarantee the discharged nitrous oxides index that reaches qualified, this set-up of control system have two lag time function, impact time lag be can overcome, outlet nitrogen oxide and ammonia spraying amount eliminated in the operating fluctuation of reactor; Be provided with simultaneously ammonia effusion detecting sensor, can avoid ammonia to overflow.
The Optimal Control System of the ammonia-denitration that the present invention relates to and method because the denitration principles of chemistry of these three kinds of methods of SCR, SNCR and SNCR-SCR are similar, have only been enumerated the system and method that adopts SCR to carry out the optimal control of ammonia-denitration among the embodiment.Control system of the present invention and method all are applicable to adopt these three kinds of methods of selective catalytic reduction (SCR), SNCR method (SNCR), SNCR and SCR combination method (SNCR-SCR) to carry out the optimal control of ammonia-denitration.
Above-mentioned explanation has fully disclosed the specific embodiment of the present invention.It is pointed out that and be familiar with the scope that any change that the person skilled in art does the specific embodiment of the present invention does not all break away from claims of the present invention.Correspondingly, the scope of claim of the present invention also is not limited only to previous embodiment.
Claims (6)
1. control system of removing nitrogen oxide, it comprises:
Reactor; Be used for providing reacting environment;
The NOx sensor at Reactor inlet place is for detection of the amount of nitrogen oxides that enters reactor;
The NOx sensor of reactor exit is for detection of the amount of nitrogen oxides of the emission of discharging from reactor;
The ammoniacal sensor of reactor exit is for detection of the discharge capacity of discharging ammonia from reactor;
Computation processor, the data message that gathers according to the ammoniacal sensor of reactor exit calculates the continuous on-line measurement value of the nitrogen oxide of reactor exit, and the emission intensity amount that the ammoniacal sensor of the continuous on-line measurement value of the nitrogen oxide in the amount of nitrogen oxides of the emission that detects of the NOx sensor of the amount of nitrogen oxides that enters reactor that detects according to the NOx sensor at Reactor inlet place, reactor exit, previous reaction device exit and reactor exit detects is calculated ammonia spraying amount according to transfer function;
Spray ammonia controller is controlled spurting of ammonia according to the ammonia spraying amount that computation processor calculates;
Wherein aforementioned transfer function comprises: the front present that the amount of nitrogen oxides that enters reactor that detects according to the NOx sensor at Reactor inlet place calculates is with function and FEEDFORWARD CONTROL function; The interior ring controller function C_in (s) that the nitrogen oxide measured value in the exit that is recorded by the NOx sensor of reactor exit calculates by interior ring controller C_in; The outer ring controller C_out function C_out (s) that forms according to the continuous on-line measurement value preset value of the nitrogen oxide of the continuous on-line measurement value of the nitrogen oxide of reactor exit and reactor exit; And the ammonia feedback function of the content of the ammonia that detects according to the ammoniacal sensor of reactor exit;
Wherein aforementioned interior ring controller C_in is proportional-plusderivative controller, can be expressed as: C_in (s)=KP_in+KD_in*s, KP_in, KD_in are interior chain rate example, the yield value of micro component, and s is Laplce's variable, is obtained by simulated test; Aforementioned outer ring controller C_out is a proportional-integral derivative controller, can be expressed as: C_out (s)=KP_out+KI_out/s+KD_out*s, KP_out, KI_out, KD_out are the outer shroud ratio, integration, the yield value of micro component, s is Laplce's variable, is obtained by simulated test; Aforementioned transfer function also comprise two time lag function, one before aforementioned interior ring controller C_in function, one before aforementioned outer ring controller C_out function, its functional form is e-sT, time factor T decides by system model simulation, can use Simulink and calculate.
2. removal nitrogen oxide control system as claimed in claim 1, it is characterized in that: at least part of probability statistics model according to setting up under the particular reactor system of described transfer function obtains through overtesting.
3. removal nitrogen oxide control system as claimed in claim 1, it is characterized in that: described system also comprises a warning device, if system can not reach control range, warning device will send early warning signal.
4. control method of removing nitrogen oxide, it comprises:
Detect in real time the content of the nitrogen oxide that enters reactor by the import NOx sensor that is arranged on the reactor inlet place;
Calculated the quantity of needs spray ammonia according to transfer function default in the computation processor by computation processor;
Computation processor is controlled the quantity of spraying ammonia by spray ammonia controller after calculating ammonia spraying amount;
The flue gas that boiler is discharged carries out catalytic reduction reaction with the ammonia of spray ammonia controller ejection in reactor;
Set one period lag time, the content of nitrogen oxide of the outlet of actual measurement reactor feeds back to computation processor with the content of the nitrogen oxide of the outlet of the reactor that measures as feedback information;
The reaction efficiency of the cubage reactor of the nitrogen oxide of the content of the nitrogen oxide that enters reactor that detects according to the import NOx sensor of previous reaction device import department and the outlet of reactor;
Set one period system lag time, calculate the continuous on-line measurement value of the amount of nitrogen oxides of outlet after a period of time at system stable operation;
The continuous on-line measurement predetermined value of nitrogen oxide of wanting to reach emission request of reading pre-set, the continuous on-line measurement value of the nitrous oxides concentration content of reactor outlet and the predefined continuous on-line measurement predetermined value of nitrogen oxide of wanting to reach emission request are compared, when continuous on-line measurement value when wanting to reach the measurement predetermined value of emission request, represent that then current ammonia spraying amount meets the requirements, adjust and finish; When continuous on-line measurement value when wanting to reach the measurement predetermined value of emission request, recomputate a new value of feedback and feed back to computation processor;
Ammoniacal sensor by reactor outlet detects the escape amount of ammonia, and the escape amount of ammonia is fed back to computation processor;
The emission intensity amount that the new value of feedback of the continuous on-line measurement value of the amount of nitrogen oxides of the emission that the amount of nitrogen oxides that enters reactor that computation processor detects according to the NOx sensor at Reactor inlet place, the NOx sensor of reactor exit detect, the nitrogen oxide in previous reaction device exit and the ammoniacal sensor of reactor exit detect recomputates ammonia spraying amount according to aforementioned transfer function, and the ammonia spraying amount control ammonia that is calculated according to computation processor by spray ammonia controller spurt quantity;
Wherein default transfer function comprises in the aforementioned computation processor: the front present that the amount of nitrogen oxides that enters reactor that detects according to the NOx sensor at Reactor inlet place calculates is with function and FEEDFORWARD CONTROL function; The interior ring controller function C_in (s) that the nitrogen oxide measured value in the exit that is recorded by the NOx sensor of reactor exit calculates by interior ring controller C_in; The ammonia feedback function of the content of the outer ring controller C_out function C_out (s) that forms according to the continuous on-line measurement value preset value of the nitrogen oxide of the continuous on-line measurement value of the nitrogen oxide of reactor exit and reactor exit and the ammonia that detects according to the ammoniacal sensor of reactor exit;
Wherein aforementioned interior ring controller C_in is proportional-plusderivative controller, can be expressed as: C_in (s)=KP_in+KD_in*s, KP_in, KD_in are interior chain rate example, the yield value of micro component, and s is Laplce's variable, is obtained by simulated test; Aforementioned outer ring controller C_out is a proportional-integral derivative controller, can be expressed as: C_out (s)=KP_out+KI_out/s+KD_out*s, KP_out, KI_out, KD_out are the outer shroud ratio, integration, the yield value of micro component, s is Laplce's variable, is obtained by simulated test; In the computation processor default function also comprise two time lag function, one before aforementioned interior ring controller C_in function, one before aforementioned outer ring controller C_out function, its functional form is e-sT, time factor T decides by system model simulation, can use Simulink and calculate.
5. the control method of removal nitrogen oxide as claimed in claim 4 is characterized in that: at least part of probability statistics model according to setting up under the particular reactor system of function default in the described computation processor obtains through overtesting.
6. the control method of removal nitrogen oxide as claimed in claim 4, it is characterized in that: described method also comprises if system can not reach control range, will send early warning signal by warning device.
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