CN110501901B - SCR ammonia injection regulation optimization method based on full-load accurate denitration requirement - Google Patents
SCR ammonia injection regulation optimization method based on full-load accurate denitration requirement Download PDFInfo
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- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 title claims abstract description 168
- 229910021529 ammonia Inorganic materials 0.000 title claims abstract description 79
- 238000002347 injection Methods 0.000 title claims abstract description 67
- 239000007924 injection Substances 0.000 title claims abstract description 67
- 238000000034 method Methods 0.000 title claims abstract description 33
- 230000033228 biological regulation Effects 0.000 title abstract description 10
- 238000005457 optimization Methods 0.000 title abstract description 6
- 239000003546 flue gas Substances 0.000 claims abstract description 76
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 claims abstract description 70
- 238000005259 measurement Methods 0.000 claims abstract description 28
- 230000008859 change Effects 0.000 claims abstract description 18
- 238000012937 correction Methods 0.000 claims abstract description 18
- 230000008569 process Effects 0.000 claims abstract description 12
- 239000003054 catalyst Substances 0.000 claims abstract description 11
- 230000009467 reduction Effects 0.000 claims abstract description 8
- 230000000694 effects Effects 0.000 claims abstract description 6
- 239000000779 smoke Substances 0.000 claims abstract description 6
- 230000001105 regulatory effect Effects 0.000 claims abstract description 5
- 238000005507 spraying Methods 0.000 claims abstract description 5
- 239000000446 fuel Substances 0.000 claims description 12
- 229910000069 nitrogen hydride Inorganic materials 0.000 claims description 10
- 238000006243 chemical reaction Methods 0.000 claims description 7
- 230000002159 abnormal effect Effects 0.000 claims description 5
- 150000001875 compounds Chemical class 0.000 claims description 3
- 238000010586 diagram Methods 0.000 description 6
- 238000006722 reduction reaction Methods 0.000 description 5
- 230000008901 benefit Effects 0.000 description 3
- 230000006872 improvement Effects 0.000 description 3
- BIGPRXCJEDHCLP-UHFFFAOYSA-N ammonium bisulfate Chemical compound [NH4+].OS([O-])(=O)=O BIGPRXCJEDHCLP-UHFFFAOYSA-N 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 238000010531 catalytic reduction reaction Methods 0.000 description 2
- 230000001934 delay Effects 0.000 description 2
- 230000008021 deposition Effects 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 230000007613 environmental effect Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 230000035484 reaction time Effects 0.000 description 2
- 239000002912 waste gas Substances 0.000 description 2
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000004202 carbamide Substances 0.000 description 1
- 239000003638 chemical reducing agent Substances 0.000 description 1
- 239000003245 coal Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000003111 delayed effect Effects 0.000 description 1
- 230000004069 differentiation Effects 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 230000010354 integration Effects 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 238000010248 power generation Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
- G05B13/00—Adaptive control systems, i.e. systems automatically adjusting themselves to have a performance which is optimum according to some preassigned criterion
- G05B13/02—Adaptive control systems, i.e. systems automatically adjusting themselves to have a performance which is optimum according to some preassigned criterion electric
- G05B13/0205—Adaptive control systems, i.e. systems automatically adjusting themselves to have a performance which is optimum according to some preassigned criterion electric not using a model or a simulator of the controlled system
- G05B13/024—Adaptive control systems, i.e. systems automatically adjusting themselves to have a performance which is optimum according to some preassigned criterion electric not using a model or a simulator of the controlled system in which a parameter or coefficient is automatically adjusted to optimise the performance
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Abstract
The invention discloses an SCR ammonia injection regulation optimization method based on full-load accurate denitration requirements, which comprises the following steps of: taking the boiler flue gas volume, NOx at the inlet of the denitration SCR and the change rate of NOx at the outlet of the denitration SCR as feed-forward signals to obtain a basic value of the ammonia spraying flow; the flow of ammonia injection is taken as an adjustment quantity, and the anti-interference brought by taking the opening of the ammonia injection adjustment valve as the adjustment quantity is eliminated; establishing an adjusting and correcting loop by taking the real-time value of the NOx at the outlet of the SCR as an object, and adjusting the ammonia injection amount; eliminating deviation between SCR outlet NOx and net smoke NOx; providing judgment basis for measuring faults of ammonia injection flow or activity reduction of the SCR catalyst; and the parameter shielding and loop cutting functions during the calibration of the SCR system and the calibration of the clean smoke are added to keep the normal work of the regulating loop in the calibration process. The method utilizes the original measuring point of the SCR system of the power station boiler, introduces key functions of misalignment correction of ammonia injection flow, measurement deviation correction of NOx at the SCR outlet and clean flue gas NOx and the like, and adds an automatic judgment and undisturbed switching strategy in the calibration process of a NOx meter.
Description
Technical Field
The invention belongs to the technical field of coal-fired power generation, and particularly relates to an SCR ammonia injection regulation optimization method based on a full-load accurate denitration requirement.
Background
Selective Catalytic Reduction (SCR) is a treatment process for NOx, i.e. NOx in exhaust gas is reduced to N2 and H2O by injecting ammonia or urea as a reducing agent under the action of a catalyst. The Selective Catalytic Reduction (SCR) technology is also widely applied to the treatment of the waste gas of the chemical boiler, and the effective denitration of the waste gas is realized.
The SCR technology in the prior art has the following problems: the method has the advantages of solving the problems of large numerical deviation of NOx and clean smoke NOx after SCR, adjustment lag of an ammonia injection adjusting system, overlarge NOx fluctuation in a variable working condition or coal quality process and the like, and simultaneously not meeting the requirements of ultralow emission, full-load denitration, deep peak regulation and the like of a unit.
Disclosure of Invention
In order to solve the problems, the invention discloses an SCR ammonia injection regulation and optimization method based on full-load accurate denitration requirements, which utilizes original measuring points of an SCR system of a power station boiler, forms a cascade regulation loop by taking NOx at an SCR outlet and NOx in clean flue gas as regulated quantities, introduces key functions of misalignment correction of ammonia injection flow, measurement deviation correction of NOx at the SCR outlet and NOx in clean flue gas and the like by taking the change rate of parameters such as boiler flue gas quantity (boiler fuel quantity + total air quantity), NOx at an SCR inlet, NOx at an SCR outlet and the like as feed-forward quantities on the basis of chemical reaction balance, and adds an automatic judgment and undisturbed switching strategy in the calibration process of a NOx meter.
In order to achieve the above purpose, the invention provides the following technical scheme:
an SCR ammonia injection regulation optimization method based on full-load accurate denitration requirements comprises the following process steps:
firstly, taking the boiler flue gas volume, NOx at a denitration SCR inlet and the change rate of NOx at a denitration SCR outlet as feed-forward signals, obtaining a basic value of the ammonia injection flow, and adapting to the adjustment requirement of variable working conditions; wherein, the boiler flue gas amount is the boiler fuel amount and the total air volume;
secondly, the ammonia injection flow is used as an adjustment quantity, and the anti-interference problem caused by using the opening of the ammonia injection adjustment valve as the adjustment quantity is eliminated;
thirdly, establishing a main adjusting loop by taking the hour average value of the clean flue gas NOx of the chimney as an object so as to adapt to the assessment requirement of environmental protection indexes;
fourthly, establishing an adjusting and correcting loop by taking the real-time value of the NOx at the outlet of the SCR as an object, quickly adjusting the ammonia injection amount, and solving the problem of long delay time in the adjusting process;
fifthly, calculating an hour average value of measurement deviation between the SCR outlet NOx and the net flue gas NOx according to the measurement time difference between the SCR outlet NOx and the net flue gas NOx under different loads, correcting a given value of the SCR outlet NOx, and solving the problem of large deviation between the SCR outlet NOx and the net flue gas NOx;
sixthly, establishing a performance correction loop by taking the deviation between the set value and the actual value of the clean flue gas NOx as an object, solving the problem of regulation deviation after the misalignment of the ammonia injection flow, and providing a judgment basis for the ammonia injection flow measurement fault or the activity reduction of the SCR catalyst; and the parameter shielding and loop cutting functions during the calibration of the SCR system and the calibration of the clean smoke are added to keep the normal work of the regulating loop in the calibration process. Because deviation exists between the SCR outlet NOx and the net flue gas NOx at the same moment all the time, the time from an SCR outlet NOx measuring point to a net flue gas NOx measuring point of the same flue gas is measured, different times are measured according to different loads, the measuring time difference between the SCR outlet NOx and the net flue gas NOx under different loads is obtained, and the small average value is calculated by dividing the time delay by the sum of different time delays.
Preferably, based on the principle that the molar ratio of NH3/NOx is approximately equal to 1 during the denitration reaction, a basic value of the ammonia injection flow rate is obtained according to the boiler fuel quantity, the air quantity and the NOx parameter at the SCR inlet, and the basic value of the ammonia injection flow rate is calculated by the following formula:
GNH3＝Gfluegas×(NOxinlet-NOxsp)/22.4 x 17+Bias
in the formula (I), the compound is shown in the specification,
GNH3: basic value of ammonia spraying flow, kg/h.
Gfluegas: dry flue gas volume (dry basis) of the boiler, Nm 3/h.
NOxinlet: actual value of SCR inlet NOx, ppm.
NOxsp: SCR outlet NOx setpoint, ppm.
And (3) Bias: correcting the deviation of the actual value of the NOx at the SCR outlet from a set value, kg/h; and calculating the difference value of the actual value and the set value by adopting the auxiliary PD regulator, and limiting the output range of the auxiliary PD regulator.
Preferably, the change rate of the boiler flue gas volume (the boiler fuel volume plus the total air volume) is used as a feedforward volume, chemical reaction delay factors under different loads and different inlet temperatures are introduced, the ammonia injection accuracy is improved, the delay factors are different in the reaction time of the denitration catalyst under the conditions of different loads and different inlet temperatures, and different delay times are set according to different working conditions.
Preferably, the change rate of NOx before denitration SCR and the change rate of NOx after denitration SCR are used as feed-forward quantities, a relevant automatic judgment loop is introduced, the ammonia injection quantity is adjusted in advance, the ammonia injection accuracy is improved, and the automatic judgment loop opens or closes an ammonia supply valve in advance according to the change conditions of NOx before denitration SCR and NOx after denitration SCR.
Preferably, the difference between the small average value of the NOx in the clean flue gas and a given value is considered to perform PI operation, a relevant misalignment correction loop is introduced, and the accuracy of key index control is improved.
Preferably, considering that under different loads, the time difference and the measurement deviation exist between the NOx after SCR and the clean flue gas NOx, a correlation misalignment correction loop is introduced to correct the ammonia injection amount, and the shortages caused by the time difference and the measurement deviation are made up by using the hour mean value because a time difference always exists between the time when the same flue gas passes through an SCR outlet NOx measuring point and the time when the same flue gas passes through a clean flue gas NOx measuring point and the time when the same flue gas passes through the SCR outlet NOx measuring point and the clean flue gas NOx measuring point, and the measurement deviation exists due to the change of parameters such as humidity, oxygen and the like existing in the system.
Preferably, the ammonia injection amount is corrected by introducing a correlation misalignment correction circuit in consideration of problems such as a decrease in the measurement accuracy of the ammonia injection amount and a lack of representativeness of the post-SCR NOx measurement point under different loads. Because the flow measurement may be inaccurate after the equipment runs for a long time, only one NOx measuring point is arranged at the back of SCR at the same side under different loads, the average value of the whole space cannot be truly reflected, the problem of inaccurate adjustment caused by the inaccurate adjustment is not prevented, the deviation between the set value and the actual value of the clean flue gas NOx is introduced as an object, the hour average values of the set value and the actual value are respectively selected for comparison, and therefore the problem of the adjustment deviation after the ammonia injection flow is inaccurate is solved, and meanwhile, a judgment basis can be provided for the ammonia injection flow measurement fault or the activity reduction of the SCR catalyst.
Furthermore, the abnormal fluctuation of parameters during the regular calibration of the NOx meter is considered, a relevant automatic judgment and undisturbed switching loop is introduced, and the ammonia injection accuracy is improved. During calibration of different gauges, the control loop can be switched to the original control loop, for example: when the measuring point of the NOx in the clean flue gas is calibrated, the control loop can be switched to control the NOx at the outlet of the SCR, so that the control disorder caused by abnormal fluctuation of parameters during calibration is avoided.
The invention has the following advantages:
the method is accessed to the original logic system of the unit through the SLC switching device without changing the original logic;
by utilizing chemical reaction balance, the NOx emission is not overproof in the normal operation process, and the ammonia injection automatic input and the NOx emission are not overproof in the unit starting and stopping process.
The variation rate of parameters such as boiler flue gas amount (boiler fuel amount + total air volume), NOx at an inlet of a denitration SCR, NOx at an outlet of the denitration SCR and the like is used as a feed-forward amount, ammonia injection flow misalignment correction and measurement deviation correction of NOx at the outlet of the SCR and net flue gas NOx are introduced, ammonia gas consumption is reduced, and ammonium bisulfate deposition is avoided;
compared with the prior art, the invention has the following beneficial effects:
the control function is strong, and the large fluctuation of ammonia injection amount and the instantaneous standard exceeding of clean flue gas NOx caused by working condition disturbance such as rapid load increase and decrease, start-stop powder making system and the like are eliminated;
the adjusting range is wide. The method can be normally operated in the full-load period of the unit, and can be normally adjusted in the range of 100mg/m 3-500 mg/m3 of NOx concentration at the SCR inlet;
the control precision is high. Accurate control of the clean flue gas NOx is realized, the deviation between the hour mean value of the clean flue gas and a set value is not more than 1mg/m3, and the hour mean value zero standard exceeding of the unit clean flue gas NOx is realized;
the economic benefit is good, the function is independently researched and developed by an operation innovation studio, no cost is spent, and compared with an INFIT control system, the technical improvement cost is saved by about 10 ten thousand yuan; excessive ammonia injection is eliminated through precise control, the control of clean flue gas NOx is more reliable, the cost can be saved by about 12 ten thousand yuan only by reducing the consumption of liquid ammonia (about 3%), the ammonia escape is reduced, the deposition of ammonium bisulfate on an SCR catalyst, an air preheater, a flue cooler and the like is reduced, the prior denitration SCR catalyst operates for more than 8 years, but the resistance of the WGGH flue cooler is only 50% of the design value, the resistance of the air preheater is only 80% of the design value, and the waste can be gained by about 60 ten thousand yuan only by reducing the power consumption (about 0.03%).
Drawings
FIG. 1 is a control logic diagram of an ammonia injection valve;
FIG. 2, denitration SCR NH3SPOUT logic diagram;
FIG. 3 is a difference compensation logic diagram of a denitration SCR pipeline;
FIG. 4 is a logic diagram of an average small difference between a set value and an actual value of a clean flue gas NOx;
FIG. 5 is a logic diagram of SCR inlet dry flue gas mass flow calculation.
Wherein: 1. denitration SCR NH3 SPA; 2. theoretically consuming ammonia; 3. denitration SCR COR FACT; 4. denitration SCR NH3 SPOUT; denitration SCR mixed ammonia flow; 6. denitration SCR inlet dry flue gas mass flow; 7. NOx concentration at an inlet of the denitration SCR reactor; 8. NOx concentration at an outlet of the denitration SCR reactor; 9. a chimney inlet NOX concentration set value; 10. compensating a difference value of the denitration SCR pipeline; 11. the NOx concentration at the inlet of the denitration chimney comes from FGD; 12. the denitration SCR NOX AVR theoretical actual difference is an hour average value; 13. the total air volume of the boiler; 14. the amount of boiler fuel.
Detailed Description
The present invention will be further illustrated with reference to the accompanying drawings and specific embodiments, which are to be understood as merely illustrative of the invention and not as limiting the scope of the invention.
firstly, taking the boiler flue gas volume, NOx at a denitration SCR inlet and the change rate of NOx at a denitration SCR outlet as feed-forward signals, obtaining a basic value of the ammonia injection flow, and adapting to the adjustment requirement of variable working conditions; wherein, the boiler flue gas amount is the boiler fuel amount and the total air volume;
secondly, the ammonia injection flow is used as an adjustment quantity, and the anti-interference problem caused by using the opening of the ammonia injection adjustment valve as the adjustment quantity is eliminated;
thirdly, establishing a main adjusting loop by taking the hour average value of the clean flue gas NOx of the chimney as an object so as to adapt to the assessment requirement of environmental protection indexes;
fourthly, establishing an adjusting and correcting loop by taking the real-time value of the NOx at the outlet of the SCR as an object, quickly adjusting the ammonia injection amount, and solving the problem of long delay time in the adjusting process;
fifthly, calculating an hour average value of measurement deviation between the SCR outlet NOx and the net flue gas NOx according to the measurement time difference between the SCR outlet NOx and the net flue gas NOx under different loads, correcting a given value of the SCR outlet NOx, and solving the problem of large deviation between the SCR outlet NOx and the net flue gas NOx;
sixthly, establishing a performance correction loop by taking the deviation between the set value and the actual value of the clean flue gas NOx as an object, solving the problem of regulation deviation after the misalignment of the ammonia injection flow, and providing a judgment basis for the ammonia injection flow measurement fault or the activity reduction of the SCR catalyst; and the parameter shielding and loop cutting functions during the calibration of the SCR system and the calibration of the clean smoke are added to keep the normal work of the regulating loop in the calibration process. Because deviation exists between the SCR outlet NOx and the net flue gas NOx at the same moment all the time, the time from an SCR outlet NOx measuring point to a net flue gas NOx measuring point of the same flue gas is measured, different times are measured according to different loads, the measuring time difference between the SCR outlet NOx and the net flue gas NOx under different loads is obtained, and the small average value is calculated by dividing the time delay by the sum of different time delays.
Based on the principle that the NH3/NOx molar ratio is approximately equal to 1 during the denitration reaction, a basic value of the ammonia injection flow is obtained according to the boiler fuel quantity, the air quantity and the SCR inlet NOx parameter, and the basic value of the ammonia injection flow is calculated by the following formula:
GNH3＝Gfluegas×(NOxinlet-NOxsp)/22.4 x 17+Bias
in the formula (I), the compound is shown in the specification,
GNH3: basic value of ammonia spraying flow, kg/h.
Gfluegas: dry flue gas volume (dry basis) of the boiler, Nm 3/h.
NOxinlet: actual value of SCR inlet NOx, ppm.
NOxsp: SCR outlet NOx setpoint, ppm.
And (3) Bias: correcting the deviation of the actual value of the NOx at the SCR outlet from a set value, kg/h; and calculating the difference value of the actual value and the set value by adopting the auxiliary PD regulator, and limiting the output range of the auxiliary PD regulator.
The method is characterized in that the change rate of boiler flue gas volume (boiler fuel volume + total air volume) is used as a feedforward volume, chemical reaction delay factors under different loads and different inlet temperatures are introduced, the ammonia injection accuracy is improved, the delay factors are that the reaction time of a denitration catalyst is different under the conditions of different loads and different inlet temperatures, and different delay times are set according to different working conditions.
The change rates of NOx before and after the denitration SCR are used as feed-forward quantities, a relevant automatic judgment loop is introduced, the ammonia injection quantity is adjusted in advance, the ammonia injection accuracy is improved, and the automatic judgment loop opens or closes an ammonia supply throttle in advance according to the change conditions of NOx before and after the denitration SCR.
And (4) performing PI operation by considering the difference between the small mean value and the given value of the NOx in the clean flue gas, introducing a related misalignment correction loop, and improving the accuracy of key index control.
Considering that under different loads, the time difference and the measurement deviation of NOx and clean flue gas NOx after SCR exist, a relevant misalignment correction loop is introduced to correct the ammonia injection amount, and the time difference exists between the time when the same flue gas passes through an SCR outlet NOx measuring point and the time when the same flue gas passes through a clean flue gas NOx measuring point, and meanwhile, the measurement deviation exists due to the change of parameters such as humidity, oxygen amount and the like existing in the system, so that the defects caused by the time difference and the measurement deviation are made up by using the hour mean value.
And (4) taking the problems of reduction of the measurement accuracy of the ammonia injection amount, insufficient representativeness of NOx measuring points after SCR under different loads and the like into consideration, introducing a relevant misalignment correction loop, and correcting the ammonia injection amount. Because the flow measurement may be inaccurate after the equipment runs for a long time, only one NOx measuring point is arranged at the back of SCR at the same side under different loads, the average value of the whole space cannot be truly reflected, the problem of inaccurate adjustment caused by the inaccurate adjustment is not prevented, the deviation between the set value and the actual value of the clean flue gas NOx is introduced as an object, the hour average values of the set value and the actual value are respectively selected for comparison, and therefore the problem of the adjustment deviation after the ammonia injection flow is inaccurate is solved, and meanwhile, a judgment basis can be provided for the ammonia injection flow measurement fault or the activity reduction of the SCR catalyst.
And (3) taking the abnormal fluctuation of the parameters during the regular calibration of the NOx meter into consideration, introducing a relevant automatic judgment and undisturbed switching loop, and improving the ammonia injection accuracy. During calibration of different gauges, the control loop can be switched to the original control loop, for example: when the measuring point of the NOx in the clean flue gas is calibrated, the control loop can be switched to control the NOx at the outlet of the SCR, so that the control disorder caused by abnormal fluctuation of parameters during calibration is avoided.
Fig. 1, fig. 2, fig. 3, fig. 4, and fig. 5 show the calculation logic diagrams of the present invention. Adding the total air volume (13) of the boiler and the fuel volume (14) of the boiler, and calculating to obtain the mass flow (6) of the dry flue gas at the inlet of the denitration SCR; a chimney inlet NOX concentration set value (9) and a denitration chimney inlet NOX concentration (11) are subtracted from FGD, are subjected to different delay times respectively, are summed and averaged to calculate an average value (12) of a denitration SCR NOX AVR theoretical actual difference value hour and then are output to a denitration SCR COR FACT (3) through a controller; because deviation exists between the concentration (8) of NOx at the outlet of the denitration SCR reactor and the concentration (11) of NOx at the inlet of the denitration chimney from FGD, a time function calculated by introducing total air volume (13) of a boiler is delayed, and then a difference value (10) of the denitration SCR pipeline is calculated for compensation; and obtaining a denitration SCR NH3SPA (1), namely a throttle opening instruction, by taking the change rate of the denitration SCR inlet dry flue gas mass flow (6), the denitration SCR reactor inlet NOX concentration (7) and the denitration SCR reactor outlet NOX concentration (8) as feed-forward quantities and performing PID (proportion integration differentiation) operation.
The technical means disclosed in the scheme of the invention are not limited to the technical means disclosed in the above embodiments, but also include the technical means formed by any combination of the above technical features. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of the present invention, and such improvements and modifications are also considered to be within the scope of the present invention.
Claims (5)
1. A method for adjusting and optimizing SCR ammonia injection based on full-load denitration requirements is characterized by comprising the following steps: the method comprises the following process steps:
the method comprises the steps that firstly, the boiler flue gas volume, NOx at an inlet of a denitration SCR and the change rate of NOx at an outlet of the denitration SCR are used as feed-forward signals, and a basic value of the ammonia spraying flow is obtained; wherein, the boiler flue gas amount is the boiler fuel amount and the total air volume;
secondly, the flow of ammonia injection is taken as an adjustment quantity, and the interference resistance brought by taking the opening of the ammonia injection adjustment valve as the adjustment quantity is eliminated;
thirdly, establishing a main adjusting loop by taking the hour average value of the clean flue gas NOx of the chimney as an object;
fourthly, establishing an adjusting and correcting loop by taking the real-time value of the NOx at the outlet of the SCR as an object, and adjusting the ammonia injection amount;
fifthly, calculating an hour average value of measurement deviation between the SCR outlet NOx and the net flue gas NOx according to the measurement time difference between the SCR outlet NOx and the net flue gas NOx under different loads, correcting a given value of the SCR outlet NOx, and eliminating the deviation between the SCR outlet NOx and the net flue gas NOx;
sixthly, establishing a performance correction loop by taking the deviation between the set value and the actual value of the clean flue gas NOx as an object, and providing a judgment basis for ammonia injection flow measurement faults or SCR catalyst activity reduction; the parameter shielding and loop cutting functions during the calibration of the SCR system and the calibration of the clean smoke are added to keep the normal work of the regulating loop in the calibration process;
obtaining a basic value of the ammonia injection flow according to the boiler fuel quantity, the total air volume and the NOx parameter at the SCR inlet, wherein the basic value of the ammonia injection flow is calculated by the following formula:
GNH3＝Gfluegas×(NOxinlet-NOxsp)/22.4×17+Bias
in the formula (I), the compound is shown in the specification,
GNH3: basic value of ammonia spraying flow, kg/h;
Gfluegas: the dry flue gas volume of the boiler, dry basis, Nm 3/h;
NOxinlet: actual value of SCR inlet NOx, ppm;
NOxsp: SCR outlet NOx set point, ppm;
and (3) Bias: correcting the deviation of the actual value of the NOx at the SCR outlet from a set value, kg/h; adopting an auxiliary PD regulator to calculate the difference value between the actual value and the set value, and limiting the output range of the auxiliary PD regulator;
the change rate of the boiler flue gas amount is used as a feedforward amount, and chemical reaction delay factors under different loads and different inlet temperatures are introduced, so that the ammonia injection accuracy is improved; the change rates of NOx at the inlet and the outlet of the denitration SCR are used as feed-forward quantities, an automatic judgment loop is introduced to adjust the ammonia injection quantity in advance, the ammonia injection accuracy is improved, and the automatic judgment loop opens or closes an ammonia supply throttle in advance according to the change conditions of the NOx at the inlet and the outlet of the denitration SCR.
2. The method of claim 1, wherein: and performing PI operation on the difference between the small mean value of the NOx in the clean flue gas and a given value, and introducing a misalignment correction loop.
3. The method of claim 1, wherein: according to the measurement time difference and measurement deviation between the NOx at the SCR outlet and the NOx in the clean flue gas under different loads, a misalignment correction loop is introduced to correct the ammonia injection amount.
4. The method of claim 1, wherein: and introducing a misalignment correction loop according to the reduction of the measurement accuracy of the ammonia injection amount and the representative shortage of NOx measuring points at the outlet of the SCR under different loads, and correcting the ammonia injection amount.
5. The method of claim 1, wherein: according to the abnormal fluctuation of the parameters during the regular calibration of the NOx meter, an automatic judgment and undisturbed switching loop is introduced, and the ammonia injection accuracy is improved.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201910607878.4A CN110501901B (en) | 2019-07-08 | 2019-07-08 | SCR ammonia injection regulation optimization method based on full-load accurate denitration requirement |
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| CN201910607878.4A CN110501901B (en) | 2019-07-08 | 2019-07-08 | SCR ammonia injection regulation optimization method based on full-load accurate denitration requirement |
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| CN110501901B true CN110501901B (en) | 2022-05-10 |
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| CN113457396B (en) * | 2021-06-29 | 2023-12-22 | 华能伊敏煤电有限责任公司 | Automatic ammonia spraying control method based on SCR denitration control system of thermal power plant |
| CN114632417B (en) * | 2022-03-17 | 2023-04-25 | 国能龙源环保有限公司 | Denitration ammonia supply automatic regulating system with accurate feedforward signal |
| CN114904379A (en) * | 2022-04-06 | 2022-08-16 | 华光环保能源(西安)设计研究院有限公司 | Optimization method for automatic ammonia injection of denitration system of power station boiler |
| CN115155310B (en) * | 2022-07-13 | 2024-04-26 | 浙江大学 | SCR denitration system ammonia spraying accurate optimization method |
| CN116047894B (en) * | 2022-12-30 | 2025-09-26 | 内蒙古京达发电有限责任公司 | An optimization control method and system for an SCR denitrification ammonia injection automatic control system |
| CN116603389B (en) * | 2023-07-07 | 2025-02-07 | 华能国际电力股份有限公司上安电厂 | A method for automatically controlling a denitrification process in a urea-ammonia production method |
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