Self-adaptive control system and control method for denitration of header system boiler

Abstract

The invention discloses a header system boiler denitration self-adaptive control system and a control method, relates to a boiler denitration self-adaptive control system and a control method, and aims to solve the problem that emission of nitrogen oxides in boiler flue gas exceeds the standard easily due to an existing denitration automatic control method. According to the method, the NOx real-time value or the NOx hourly mean value serves as the main controlled quantity, and the NOx at a denitration outlet is stably controlled by adjusting the opening degree of the ammonia adjusting valve; in the control process, the denitration operation condition analyzer calculates the denitration operation condition state; the average hour value is controlled to be output in a stable state, the real-time value is controlled to be output in an unstable state, and the ammonia flow controller outputs an ammonia injection adjusting door opening degree control increment calculation value according to an ammonia flow given value output by the fuzzy controller; the ammonia adjusting door is quickly adjusted in the transient control process, and the ammonia adjusting door is slowly adjusted in the steady state stage to achieve fine adjustment of NOx at a denitration outlet; the method has the beneficial effects that the problem that emission of nitric oxide in flue gas exceeds the standard is effectively solved, and long-term automatic operation of denitration control is achieved.

Description

Technical Field

[0001] The invention relates to a boiler denitration adaptive control system and method. Background Art

[0002] A master-pipe boiler system involves multiple boilers operating in parallel, with all steam produced entering a single main steam header. The turbine steam supply and other external heating loads all originate from this main steam header. If a boiler malfunctions, it can be shut down without affecting the operation of other boilers, improving unit safety and stability. Master-pipe boiler operation is widely used in captive thermal power plants and centralized heating systems in my country's petroleum, chemical, metallurgical, and pharmaceutical industries.

[0003] Boiler denitrification systems are a key technology for controlling nitrogen oxide (NOx) emissions from boiler flue gas. Their core objective is to reduce NOx concentrations in the flue gas to meet increasingly stringent environmental protection requirements. NOx is a major atmospheric pollutant, and its emissions not only pose a serious threat to the environment and human health but can also contribute to environmental problems such as acid rain and photochemical smog. Therefore, the operational efficiency of boiler denitrification systems and the level of NOx concentration control are directly linked to achieving environmental protection goals.

[0004] During boiler denitration, controlling the NOx concentration at the denitration outlet is a complex dynamic process involving multiple factors, including combustion conditions, flue gas temperature, reducing agent injection rate, and catalyst activity. The denitration automatic control system is time-varying, nonlinear, and has a hysteresis mechanism. During boiler operation, the main factors affecting the NOx concentration at the denitration outlet include: timed backflush of the NOx measurement device, boiler load disturbances, pulverizing system startup and shutdown, and coal shortages in the pulverizing system's coal feeder.

[0005] Existing automatic control methods for NOx concentration at the denitrification outlet of boilers mainly use single-loop PID control and simple dual-loop cascade PID control. Single-loop control uses the NOx concentration at the denitrification outlet as the controlled object and the ammonia control valve as the actuator. Due to the large hysteresis and time-varying characteristics of the controlled object, the single-loop PID control method often results in large fluctuations in NOx concentration, easy exceeding of standards, and high ammonia slip, making it difficult for the control quality to meet environmental protection requirements. In the simple dual-loop automatic control method, the inner loop controls the ammonia flow rate, the outer loop controls the NOx concentration at the denitrification outlet, and the ammonia control valve serves as the actuator. When interference occurs, the controller needs to use large proportional parameters for rapid adjustment, while in steady state, it uses small proportional parameters for slow adjustment. The simple dual-loop control scheme cannot simultaneously meet steady-state and transient regulation requirements, and NOx concentration often exceeds standards or fluctuates.

[0006] The existing denitrification automatic control method has the following problems:

[0007] 1. When the NOx measuring device is backflushed regularly, the NOx measurement signal remains unchanged, and the measured value deviates greatly from the actual NOx value, resulting in excessive NOx emissions.

[0008] 2. When the boiler load is disturbed, the flue gas volume of the combustion system will fluctuate greatly. Due to the lag characteristics of the control object, the amount of ammonia injection does not match the actual demand, causing the NOx at the reactor outlet to fluctuate greatly, resulting in NOx emissions exceeding the standard.

[0009] 3. When the pulverizing system is started, stopped, or the coal feeder is cut off, the amount of pulverized coal entering the furnace changes suddenly, the flue gas volume fluctuates greatly, and the amount of ammonia sprayed does not match the actual demand, causing the NOx at the denitrification outlet to fluctuate greatly, resulting in NOx emissions exceeding the standard.

[0010] 4. Unreasonable automatic control parameters lead to excessive ammonia spraying, equipment corrosion, increased ammonia escape, and increased operating costs. Summary of the Invention

[0011] The purpose of the present invention is to solve the problem that the existing automatic denitration control method easily leads to excessive nitrogen oxide emissions in boiler flue gas, and proposes a main-tube boiler denitration adaptive control system and control method.

[0012] The present invention provides a main tube boiler denitration adaptive control system comprising a denitration operating condition analyzer, a main feedforward compensator, a fuzzy controller, an ammonia flow controller, an ammonia flow meter, a NOx measuring device, a differentiator, and a denitration controlled quantity selector.

[0013] NOx measuring device, used to obtain the NOx concentration value in the denitrification outlet;

[0014] The denitrification operation condition analyzer is used to collect the NOx control error at the denitrification outlet, the change in the NOx control error at the denitrification outlet, the backflush disturbance of the NOx measuring device, the boiler load disturbance, and the pulverizing system disturbance, and derive the backflush state H1 based on the backflush disturbance of the NOx measuring device; derive the main loop disturbance feedforward D1 based on the boiler load disturbance and the pulverizing system disturbance; and derive the denitrification control state S1 based on the NOx control error at the denitrification outlet, the change in the NOx control error at the denitrification outlet, the boiler load disturbance, and the pulverizing system disturbance; wherein the NOx control error at the denitrification outlet is the difference between the NOx concentration value at the denitrification outlet obtained by the NOx measuring device and the set value of the NOx concentration at the denitrification outlet; and the change in the NOx control error at the denitrification outlet is the output value after the NOx control error at the denitrification outlet is input into the differentiator;

[0015] A main feedforward compensator is used to receive the main loop disturbance feedforward D1 and output the main loop feedforward compensation amount according to the main loop disturbance feedforward D1;

[0016] The fuzzy controller is used to receive the backflush state H1 and, when the NOx measuring device is not in the backflush state, output a given value of the denitration ammonia injection amount by inputting the denitration outlet NOx control error and the denitration outlet NOx control error variation;

[0017] an ammonia flow controller, configured to take a denitration ammonia injection amount control error as input, output a calculated value of an ammonia injection regulating valve opening control increment, and adjust the opening of the ammonia regulating valve according to the calculated value of the ammonia injection regulating valve opening control increment; wherein, when the NOx measuring device is in a backflush state, the denitration ammonia injection amount control error is equal to the hourly average of the denitration outlet NOx concentration set value superimposed on the main loop feedforward compensation amount output by the main feedforward compensator, and the difference between the denitration ammonia injection amount obtained by the ammonia flow meter; and when the NOx measuring device is not in a backflush state, the denitration ammonia injection amount control error is equal to the difference between the denitration ammonia injection amount set value output by the fuzzy controller and the denitration ammonia injection amount obtained by the ammonia flow meter;

[0018] The denitrification controlled quantity selector is used to receive the denitrification control state S1, and when the denitrification control state S1 is a stable state, select the NOx hourly average value as the denitrification outlet NOx controlled quantity; when the denitrification control state S1 is a transient control state, select the NOx real-time value as the denitrification outlet NOx controlled quantity.

[0019] Furthermore, it also includes a sub-feedforward compensator;

[0020] The auxiliary feedforward compensator is used to receive the denitration ammonia injection amount output by the ammonia regulating gate, and output the auxiliary loop feedforward compensation amount according to the denitration ammonia injection amount; the auxiliary loop feedforward compensation amount is used to compensate the calculated value of the ammonia injection regulating gate opening control increment to generate the actual value of the ammonia injection regulating gate opening control increment.

[0021] A method for adaptively controlling denitration of a main-tube boiler comprises the following steps:

[0022] The back-blowing state H1 is determined based on the back-blowing disturbance of the NOx measuring device (7); the main loop disturbance feedforward D1 is comprehensively calculated based on the boiler load disturbance and the pulverizing system disturbance; and the denitrification control state S1 is determined based on the denitrification control process state;

[0023] Perform main loop feedforward calculation on the main loop disturbance feedforward D1 to obtain the main loop feedforward compensation amount;

[0024] According to the backflush state H1, it is judged whether the NOx measuring device (7) is in the backflush state; if it is, the hourly average of the ammonia flow set value is added to the main circuit feedforward compensation amount as the secondary circuit denitrification ammonia injection amount set value; otherwise, according to the denitrification control state S1, it is judged whether it is in the steady state process.

[0025] If the denitrification control state S1 is a stable state, the hourly average value of NOx is used as the controlled amount of NOx at the denitrification outlet, and the hourly average value of NOx is used as the input of the fuzzy controller (3);

[0026] If the denitration control state S1 is a transient control state, the real-time value of NOx is used as the controlled amount of NOx at the denitration outlet, and the real-time value of NOx is used as the input of the fuzzy controller (3);

[0027] The fuzzy controller (3) is used to calculate the given value of the denitrification ammonia injection amount of the secondary circuit, and the given value of the denitrification ammonia injection amount of the secondary circuit is obtained;

[0028] The ammonia injection amount is calculated based on the given value of the denitrification ammonia injection amount of the auxiliary circuit, and the calculated value of the ammonia injection regulating door opening control increment is obtained;

[0029] The opening of the ammonia regulating door (5) is adjusted according to the calculated value of the ammonia injection regulating door opening control increment, thereby completing the adaptive control of the denitration of the mother tube boiler.

[0030] Furthermore, the expression of the main loop disturbance feedforward D1 is:

[0031] D1=[D Q1 D F1 ] T

[0032] Among them, D Q1 is the boiler load disturbance; D F1 is the disturbance of the pulverizing system.

[0033] Furthermore, the specific calculation formula for the main loop feedforward compensation is:

[0034] C fb1 =R1·D1=[R Q1 R F1 ]·[D Q1 D F1 ] T =R Q1 D Q1 +R F1 D F1

[0035] Among them, C fb1 is the feedforward compensation of the main loop; R Q1 is the boiler load disturbance feedforward compensation coefficient; R F1 is the disturbance feedforward compensation coefficient of the pulverizing system; R1 is the compensation coefficient of the main feedforward compensator.

[0036] Furthermore, the expression of the denitrification control state S1 is:

[0037]

[0038] Among them, S1=0 represents the steady-state control process; S1=1 represents the transient control process; δ1 is the steady-state judgment limit of the control error; σ1 is the steady-state judgment limit of the control error variation; e1 is the control error of NOx at the denitration outlet; e1' is the control error variation of NOx at the denitration outlet.

[0039] Furthermore, the expression of backflush state H1 is:

[0040]

[0041] Among them, D M1 H1 is the backflush disturbance of the NOx measuring device; H1=0 indicates that the NOx measuring device is not in the backflush state; H1=1 indicates that the NOx measuring device is in the backflush state.

[0042] Furthermore, it also includes the step of using a sub-feedforward compensator to compensate the calculated value of the ammonia injection regulating door opening control increment, wherein the sub-feedforward compensator receives the denitrification ammonia injection amount output by the ammonia regulating door, and outputs a sub-loop feedforward compensation amount according to the denitrification ammonia injection amount; the sub-loop feedforward compensation amount is used to compensate the calculated value of the ammonia injection regulating door opening control increment to generate the actual value of the ammonia injection regulating door opening control increment; and at the same time, the actual value of the ammonia injection regulating door opening control increment is used to adjust the opening of the ammonia regulating door.

[0043] Furthermore, the method further includes a control initialization step;

[0044] The initialized data includes the initial value of the hourly average value of NOx at the denitration outlet, the initial value of the main loop feedforward compensation amount, the initial value of the control error of NOx at the denitration outlet, the initial value of the average value of the denitration ammonia injection amount output by the ammonia regulating gate and the initial value of the secondary loop feedforward compensation amount.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] The present invention proposes an adaptive control method for denitrification of a main-tube boiler, which effectively solves the problem of excessive nitrogen oxide emissions in flue gas when complex operating conditions such as load fluctuations, start-up and shutdown of the pulverizing system, coal outages, and backflushing of the NOx measuring device occur during boiler operation, thereby realizing long-term automatic operation of denitrification control. The method of the present invention can effectively reduce the amount of ammonia injection, lower denitrification costs, alleviate equipment corrosion, improve operational safety, further prevent ammonia escape, and protect the atmospheric environment while meeting environmental protection requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 This is a schematic diagram of the working principle of a mother-tube boiler denitrification adaptive control system according to the first embodiment;

[0048] Figure 2This is a flow chart of a control method of a main tube boiler denitration adaptive control system according to the third embodiment;

[0049] Among them, 1 is the denitrification operating condition analyzer; 2 is the main feedforward compensator; 3 is the fuzzy controller; 4 is the ammonia flow controller; 5 is the ammonia regulating gate; 6 is the ammonia flow meter; 7 is the NOx measuring device; 8 is the differentiator; 9 is the denitrification controlled quantity selector; and 10 is the auxiliary feedforward compensator. DETAILED DESCRIPTION

[0050] Specific implementation method 1. Combination Figure 1 This embodiment describes a denitration adaptive control system for a main-tube boiler, which includes a denitration operating condition analyzer 1, a main feedforward compensator 2, a fuzzy controller 3, an ammonia flow controller 4, an ammonia flow meter 6, a NOx measuring device 7, a differentiator 8, and a denitration controlled quantity selector 9.

[0051] NOx measuring device 7, used to obtain the NOx concentration value in the denitrification outlet;

[0052] The denitrification operation condition analyzer 1 is used to collect the denitrification outlet NOx control error, the denitrification outlet NOx control error change, the backflush disturbance of the NOx measuring device 7, the boiler load disturbance, and the pulverizing system disturbance, and derive the backflush state H1 based on the backflush disturbance of the NOx measuring device 7; derive the main loop disturbance feedforward D1 based on the boiler load disturbance and the pulverizing system disturbance; and derive the denitrification control state S1 based on the denitrification outlet NOx control error, the denitrification outlet NOx control error change, the boiler load disturbance, and the pulverizing system disturbance; wherein the denitrification outlet NOx control error is the difference between the NOx concentration value at the denitrification outlet obtained by the NOx measuring device 7 and the set value of the denitrification outlet NOx concentration; and the denitrification outlet NOx control error change is the output value after the denitrification outlet NOx control error is input into the differentiator 8;

[0053] A main feedforward compensator 2 is configured to receive a main loop disturbance feedforward D1 and output a main loop feedforward compensation value according to the main loop disturbance feedforward D1;

[0054] The fuzzy controller 3 is used to receive the backflush state H1 and output a given value of the denitration ammonia injection amount by inputting the denitration outlet NOx control error and the denitration outlet NOx control error variation when the NOx measuring device 7 is not in the backflush state;

[0055] an ammonia flow controller 4 for taking a denitration ammonia injection amount control error as input, outputting a calculated value for the ammonia injection regulating valve opening control increment, and adjusting the opening of the ammonia regulating valve 5 based on the calculated value for the ammonia injection regulating valve opening control increment; wherein, when the NOx measuring device 7 is in a backflush state, the denitration ammonia injection amount control error is equal to the difference between the hourly average of the denitration outlet NOx concentration set value superimposed on the main loop feedforward compensation amount output by the main feedforward compensator 2 and the denitration ammonia injection amount obtained by the ammonia flow meter 6; and when the NOx measuring device 7 is not in a backflush state, the denitration ammonia injection amount control error is equal to the difference between the denitration ammonia injection amount set value output by the fuzzy controller 3 and the denitration ammonia injection amount obtained by the ammonia flow meter 6;

[0056] The denitrification controlled quantity selector 9 is used to receive the denitrification control state S1 and select the NOx hourly average as the denitrification outlet NOx controlled quantity when the denitrification control state S1 is a stable state; when the denitrification control state S1 is a transient control state, select the NOx real-time value as the denitrification outlet NOx controlled quantity.

[0057] In this embodiment, the denitration controlled variable selector 9 uses the real-time NOx value or hourly average NOx value as the primary controlled variable Y1, and the ammonia flow rate Y0 as the secondary controlled variable. Stable control of NOx at the denitration outlet is achieved by adjusting the opening of the ammonia control gate 5. During the control process, the denitration operating condition analyzer 1 calculates the denitration operating state (stable or unstable). During the stable state, the hourly average NOx value is used as the output. During the unstable state, S1 selects the hourly average NOx value as the denitration outlet. The ammonia flow controller 4 calculates the ammonia flow setpoint based on the outlet fuzzy controller 3, achieving rapid adjustment of the ammonia control gate during transient control and slow adjustment of the ammonia control gate 5 during the steady state phase to achieve fine-tuning of NOx at the denitration outlet.

[0058] According to the attached Figure 1 , explain the definitions of related variables:

[0059] Y1: NOx at the denitrification outlet, the main controlled quantity, select the NOx real-time value or NOx hourly average value according to the working condition;

[0060] Y0: Denitrification ammonia injection amount, secondary controlled amount;

[0061] SP1: Denitrification outlet NOx set value, set manually;

[0062] SP0: Denitrification ammonia injection amount given value, calculated by fuzzy controller 3;

[0063] D Q1 : Boiler load disturbance, main circuit disturbance; obtained by subtracting the boiler's current load from the last boiler calculation cycle load;

[0064] D F1: The disturbance of the pulverizing system and the main circuit; it is the disturbance generated during the startup or shutdown of the pulverizing system;

[0065] D M1 :7-point back-blowing disturbance of NOx measuring device, main circuit disturbance; back-blowing disturbance of NOx measuring device at denitrification outlet

[0066] du0: calculated value of the control increment of the ammonia injection regulating door opening;

[0067] du: Actual value of the control increment of the ammonia injection regulating door opening;

[0068] e1: NOx control error at the denitrification outlet;

[0069] e'1: variation of NOx control error at the denitrification outlet;

[0070] e0: Denitrification ammonia injection control error;

[0071] H1: Backflush hold command, 0 means the measurement signal is available, 1 means the backflush measurement signal is held;

[0072] S1: Denitrification control stage, 0 represents a slow adjustment process, and 1 represents a fast adjustment process.

[0073] C fb1 It is the feedforward compensation of the main loop;

[0074] C fb0 is the feedforward compensation of the secondary loop;

[0075] In this embodiment, the ammonia flow controller 4 includes a sub-controller selector and multiple PID controllers; the sub-controller selector selects different PID controllers according to the control error, which can realize rapid adjustment of the ammonia injection gate when the deviation is large, slow adjustment of the ammonia injection gate when the deviation is small, and adaptively meet the requirements of the ammonia injection gate adjustment speed under different working conditions; the denitrification controlled quantity selector 9 includes a main controlled quantity selector, a NOx real-time value output pipeline and a NOx hourly average value output pipeline; when the denitrification control state S1 output by the denitrification operating condition analyzer 1 is a stable state, the main controlled quantity selector controls the NOx hourly average value output pipeline to be connected to the denitrification outlet; when the denitrification control state S1 output by the denitrification operating condition analyzer 1 is an unstable state, the main controlled quantity selector controls the NOx real-time value output pipeline to be connected to the denitrification outlet.

[0076] Specific embodiment 2: This embodiment further defines the adaptive control system for denitration of a main-pipe boiler described in specific embodiment 1. In this embodiment, a secondary feedforward compensator 10 is further included.

[0077] The secondary feedforward compensator 10 is used to receive the denitration ammonia injection amount output by the ammonia regulating gate 5, and output a secondary loop feedforward compensation amount based on the denitration ammonia injection amount; the secondary loop feedforward compensation amount is used to compensate the calculated value of the ammonia injection regulating gate opening control increment to generate the actual value of the ammonia injection regulating gate opening control increment.

[0078] In this embodiment, the auxiliary feedforward compensator 10 is added to eliminate the uncertainty affecting the ammonia flow measurement, such as the inaccuracy of the flow meter or the time-varying variable; and further improve the control accuracy, so that the NOx concentration at the denitrification outlet is closer to the NOx set value at the denitrification outlet.

[0079] Specific implementation method three, combined Figure 2 This embodiment is described based on the control method of a main-tube boiler denitration adaptive control system described in the first embodiment. In this embodiment, the following steps are included:

[0080] The backflush state H1 is determined based on the backflush disturbance of the NOx measuring device 7; the main loop disturbance feedforward D1 is comprehensively calculated based on the boiler load disturbance and the pulverizing system disturbance; the denitrification control state S1 is determined based on the denitrification control process state;

[0081] Perform main loop feedforward calculation on the main loop disturbance feedforward D1 to obtain the main loop feedforward compensation amount;

[0082] According to the backflush state H1, it is judged whether the NOx measuring device 7 is in the backflush state; if so, the hourly average of the ammonia flow set value is added to the main circuit feedforward compensation amount as the secondary circuit denitration ammonia injection amount set value; otherwise, according to the denitration control state S1, it is judged whether it is in the steady state process.

[0083] If the denitration control state S1 is a stable state, the hourly average value of NOx is used as the controlled amount of NOx at the denitration outlet, and the hourly average value of NOx is used as the input of the fuzzy controller 3;

[0084] If the denitration control state S1 is a transient control state, the real-time value of NOx is used as the controlled amount of NOx at the denitration outlet, and the real-time value of NOx is used as the input of the fuzzy controller 3;

[0085] The fuzzy controller 3 is used to calculate the given value of the denitration ammonia injection amount of the secondary circuit, and the given value of the denitration ammonia injection amount of the secondary circuit is obtained;

[0086] The ammonia injection amount is calculated based on the given value of the denitrification ammonia injection amount of the auxiliary circuit, and the calculated value of the ammonia injection regulating door opening control increment is obtained;

[0087] The opening of the ammonia regulating door 5 is adjusted according to the calculated value of the ammonia injection regulating door opening control increment to complete the adaptive control of the denitrification of the mother tube boiler.

[0088] In this embodiment, the denitration operation condition analyzer 1 has the following inputs: the control error e1 of the denitration outlet NOx, the control error variation e1' of the denitration outlet NOx, the boiler load disturbance D Q1 , pulverizing system disturbance D F1 , NOx measuring device 7 backflush disturbance amount D M1 ;

[0089] The output quantities are: control process status S1, backflush status H1, and main loop disturbance feedforward D1.

[0090] The working status is determined based on the disturbance situation, controlled quantity, and rate of change of the controlled quantity.

[0091] NOx real-time value control error:

[0092] e R1 (k) = SP1(k) - Y R1 (k)

[0093] NOx real-time value control error change:

[0094] e' R1 (k) = e R1 (k)-e R1 (k-1)

[0095] Among them, k is the control calculation sampling time; e R1 (k) is the NOx control error at sampling time k; e' R1 (k) is the change in NOx control error between sampling time k and sampling time (k-1); SP1(k) is the NOx set value at the denitrification outlet at sampling time k; Y R1 (k) is the sampling time k at which the NOx measuring device 7 obtains the NOx concentration value at the denitration outlet; e R1 (k-1) is the NOx control error at sampling time (k-1);

[0096] Calculation of given value of denitrification ammonia flow rate:

[0097]

[0098] in: is the hourly average value of ammonia flow rate, C F (e,e') is the output value calculated by the fuzzy controller.

[0099] The formula means that when the NOx measuring device is backflushing, the measurement signal cannot represent the real-time value and closed-loop control cannot be performed. The hourly average of the previous ammonia flow set value plus the feedforward compensation amount is used as the secondary loop ammonia flow set value to control the NOx at the denitrification outlet. This ensures that the NOx at the denitrification outlet can still be automatically controlled during the backflushing process.

[0100] NOx hourly mean control error:

[0101] e M1 (k) = SP1(k) - Y M1 (k)

[0102] NOx hourly mean control error change:

[0103] e' M1 (k) = e M1 (k)-e M1 (k-1)

[0104] Fuzzy controller control error:

[0105]

[0106] The fuzzy controller controls the error variation:

[0107]

[0108] The control increment of the fuzzy controller is calculated based on the designed fuzzy control table FT.

[0109] Table 1. NOx fuzzy controller ammonia flow given increment fuzzy table FT

[0110]

[0111]

[0112] In Table 1, the row number is determined by the NOx control error e1, and the column number is determined by the NOx control error change e1';

[0113] Δ: represents the quantitative value of ammonia flow rate increment adjustment, the value is determined according to actual commissioning;

[0114] ZO: indicates moderate amplitude;

[0115] PS: indicates a small positive amplitude;

[0116] PM: indicates positive medium amplitude;

[0117] PL: indicates positive amplitude;

[0118] NS: indicates a small negative amplitude;

[0119] NM: indicates negative medium amplitude;

[0120] NL: Indicates a large negative amplitude.

[0121] The given increment of ammonia flow is determined based on the control error and the change in control error, such as:

[0122] FT(ZO, ZO) = 0: Indicates that the NOx control error is small, NOx is close to the given value, NOx changes slowly, and the ammonia injection amount should be maintained.

[0123] FT(PS,PL)=0: indicates that the NOx control error is positive, NOx is low, NOx decreases rapidly, and the amount of ammonia injection should be reduced by 3Δ.

[0124] Fuzzification process: Calculate the values of control error and control error variation to correspond to the corresponding fuzzy row number I e (k), column number I e' (k).

[0125]

[0126] The classification interval [a i ,a i+1 ), [b j ,b j+1 ) Coordinate values are obtained based on actual debugging.

[0127] Defuzzification process:

[0128] The incremental output of the fuzzy controller is obtained based on the row number and column number in the fuzzy table calculated according to the control error and the control error change.

[0129] du1(k)=FT[I e (k),I e' (k)]

[0130] SP0(k)=SP0(k-1)+du1(k)=SP0(k-1)+FT[I e (k),I e '(k)]

[0131] Ammonia flow controller calculation process:

[0132] Ammonia flow control error:

[0133] e0(k)=SP0(k)+fb1(k)-Y0(k)

[0134] Determine the controller number l based on the ammonia flow control error:

[0135] l=i,c i ≤e0(k)<c i+1 ,i=0,1,2

[0136] Among them, the ammonia flow controller serial number calculation interval [c i ,c i+1) coordinate values are obtained through actual commissioning. By selecting different PID controllers based on the control error, the ammonia injection valve can be adjusted quickly when the deviation is large, and slowly when the deviation is small, adapting to the ammonia injection valve adjustment speed requirements under different operating conditions.

[0137] Calculation of control increment of denitrification ammonia flow PID controller:

[0138]

[0139] in:

[0140] is the proportional control coefficient, and its specific value is obtained by adjustment based on engineering experience;

[0141] is the integral control coefficient, and its specific value is obtained by tuning based on engineering experience;

[0142] is the differential control coefficient, and its specific value is obtained by tuning based on engineering experience;

[0143] Feedforward compensator compensation calculation:

[0144] fb0(k)=(D0(k)-D0(k-1)) T R0(k)

[0145] Denitrification ammonia injection regulating door opening control instructions:

[0146] U(k)=U(k-1)+du0(k)+fb0(k)

[0147] Output the denitrification ammonia injection regulating gate control instruction to the denitrification ammonia injection regulating gate to adjust the ammonia injection flow rate, thereby controlling the denitrification outlet NOx, and finally controlling the denitrification outlet NOx to be close to the actual set value; T s Calculate the sampling period for control.

[0148] Specific embodiment 4: This embodiment further limits the adaptive control method for denitration of a main-pipe boiler described in specific embodiment 3. In this embodiment, the expression of the main loop disturbance feedforward D1 is:

[0149] D1=[D Q1 D F1 ] T

[0150] Among them, D Q1 is the boiler load disturbance; D F1 is the disturbance of the pulverizing system.

[0151] In this embodiment, the main loop disturbance feedforward D1 is obtained by comprehensively analyzing the boiler load disturbance and the pulverizing system disturbance.

[0152] Specific embodiment 5: This embodiment further limits the adaptive control method for denitration of a main-pipe boiler described in specific embodiment 4. In this embodiment, the specific calculation formula of the main loop feedforward compensation amount is:

[0153] C fb1 =R1·D1=[R Q1 R F1 ]·[D Q1 D F1 ] T =R Q1 D Q1 +R F1 D F1

[0154] Among them, C fb1 is the feedforward compensation of the main loop; R Q1 is the boiler load disturbance feedforward compensation coefficient; R F1 is the disturbance feedforward compensation coefficient of the pulverizing system; R1 is the compensation coefficient of the main feedforward compensator 2.

[0155] In this embodiment, R Q1 is the boiler load disturbance feedforward compensation coefficient; R F1 It is the disturbance feedforward compensation coefficient of the pulverizing system, which is obtained through debugging during the actual operation process.

[0156] Specific embodiment 6: This embodiment further limits the adaptive control method for denitration of a main-tube boiler described in specific embodiment 4. In this embodiment, the expression of the denitration control state S1 is:

[0157]

[0158] Among them, S1=0 represents the steady-state control process; S1=1 represents the transient control process; δ1 is the steady-state judgment limit of the control error; σ1 is the steady-state judgment limit of the control error variation; e1 is the control error of NOx at the denitration outlet; e1' is the control error variation of NOx at the denitration outlet.

[0159] In this embodiment, when the NOx control error is small, the NOx change is small, the boiler load is stable, there is no pulverizing system disturbance, and there is no backblowing, the denitrification control enters steady-state control and slowly adjusts the ammonia injection amount; otherwise, the denitrification control enters transient control and quickly adjusts the ammonia injection amount.

[0160] Specific embodiment 7: This embodiment further limits the adaptive control method for denitration of a main-tube boiler described in specific embodiment 3. In this embodiment, the expression of the backflush state H1 is:

[0161]

[0162] Among them, D M1 H1 is the backflush disturbance of the NOx measuring device 7; H1=0 indicates that the NOx measuring device 7 is not in the backflush state; H1=1 indicates that the NOx measuring device 7 is in the backflush state.

[0163] In this embodiment, when the NOx measuring device is backflushing, the measurement signal cannot represent the real-time value and closed-loop control cannot be performed. The hourly average of the previous ammonia flow set value superimposed on the feedforward compensation amount is used as the secondary loop ammonia flow set value to control the NOx at the denitrification outlet, so that the NOx at the denitrification outlet can still be automatically controlled during the backflushing process.

[0164] Specific embodiment eight. This embodiment further limits the adaptive control method for denitrification of a mother tube boiler described in specific embodiment three. In this embodiment, it also includes a step of compensating the calculated value of the ammonia injection regulating door opening control increment by using a sub-feedforward compensator 10, wherein the sub-feedforward compensator 10 receives the denitrification ammonia injection amount output by the ammonia regulating door 5, and outputs a sub-loop feedforward compensation amount according to the denitrification ammonia injection amount; the sub-loop feedforward compensation amount is used to compensate the calculated value of the ammonia injection regulating door opening control increment to generate the actual value of the ammonia injection regulating door opening control increment; and at the same time, the actual value of the ammonia injection regulating door opening control increment is used to adjust the opening of the ammonia regulating door 5.

[0165] In this embodiment, by adding the secondary feedforward compensator 10, the uncertainty affecting the ammonia flow measurement, such as the inaccurate flow meter or time-varying variables, is eliminated; the control accuracy is further improved, so that the NOx concentration at the denitrification outlet is closer to the NOx set value at the denitrification outlet.

[0166] Specific embodiment 9. This embodiment further defines the adaptive control method for denitration of a mother-tube boiler described in specific embodiment 3. In this embodiment, it further includes a control initialization step;

[0167] The initialized data includes the initial value of the hourly average value of NOx at the denitration outlet, the initial value of the main loop feedforward compensation amount, the initial value of the control error of NOx at the denitration outlet, the initial value of the average value of the denitration ammonia injection amount output by the ammonia regulating gate 5 and the initial value of the secondary loop feedforward compensation amount.

[0168] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A main tube boiler denitrification adaptive control system, characterized in that: It includes a denitrification operating condition analyzer (1), a main feedforward compensator (2), a fuzzy controller (3), an ammonia flow controller (4), an ammonia flow meter (6), a NOx measuring device (7), a differentiator (8) and a denitrification controlled quantity selector (9); A NOx measuring device (7) for obtaining the NOx concentration value at the denitration outlet; The denitrification operation condition analyzer (1) is used to collect the denitrification outlet NOx control error, the denitrification outlet NOx control error variation, the backflush disturbance of the NOx measuring device (7), the boiler load disturbance and the pulverizing system disturbance, and obtain the backflush state H1 according to the backflush disturbance of the NOx measuring device (7); obtain the main loop disturbance feedforward D1 according to the boiler load disturbance and the pulverizing system disturbance; and obtain the denitrification control state S1 according to the denitrification outlet NOx control error, the denitrification outlet NOx control error variation, the boiler load disturbance and the pulverizing system disturbance; wherein the denitrification outlet NOx control error is the difference between the denitrification outlet NOx concentration given value and the denitrification outlet NOx concentration value obtained by the NOx measuring device (7); the denitrification outlet NOx control error variation is the output value obtained after the denitrification outlet NOx control error is input into the differentiator (8); A main feedforward compensator (2) is used to receive a main loop disturbance feedforward D1 and output a main loop feedforward compensation amount according to the main loop disturbance feedforward D1; The fuzzy controller (3) is used to receive the backflush state H1 and output a given value of the denitration ammonia injection amount by inputting the denitration outlet NOx control error and the denitration outlet NOx control error variation when the NOx measuring device (7) is not in the backflush state; An ammonia flow controller (4) is used to take a denitration ammonia injection amount control error as input, output an ammonia injection regulating door opening control increment calculation value, and adjust the opening of the ammonia regulating door (5) according to the ammonia injection regulating door opening control increment calculation value; wherein, when the NOx measuring device (7) is in a backflush state, the denitration ammonia injection amount control error is equal to the hourly average of the denitration outlet NOx concentration given value superimposed on the main loop feedforward compensation amount output by the main feedforward compensator (2), and the difference between the denitration ammonia injection amount obtained by the ammonia flow meter (6); when the NOx measuring device (7) is not in a backflush state, the denitration ammonia injection amount control error is equal to the difference between the denitration ammonia injection amount given value output by the fuzzy controller (3) and the denitration ammonia injection amount obtained by the ammonia flow meter (6); The denitration controlled quantity selector (9) is used to receive the denitration control state S1 and select the NOx hourly average value as the denitration outlet NOx controlled quantity when the denitration control state S1 is a stable state; and select the NOx real-time value as the denitration outlet NOx controlled quantity when the denitration control state S1 is a transient control state.

2. The adaptive denitration control system for a main-tube boiler according to claim 1, characterized in that: Also included is a secondary feed-forward compensator (10); A secondary feedforward compensator (10) is used to receive the denitration ammonia injection amount output by the ammonia regulating gate (5), and output a secondary loop feedforward compensation amount according to the denitration ammonia injection amount; the secondary loop feedforward compensation amount is used to compensate the calculated value of the ammonia injection regulating gate opening control increment to generate an actual value of the ammonia injection regulating gate opening control increment.

3. The control method of the adaptive control system for denitrification of a main-tube boiler according to claim 1 is characterized in that: The following steps are involved: The back-blowing state H1 is determined based on the back-blowing disturbance of the NOx measuring device (7); the main loop disturbance feedforward D1 is comprehensively calculated based on the boiler load disturbance and the pulverizing system disturbance; and the denitrification control state S1 is determined based on the denitrification control process state; Perform main loop feedforward calculation on the main loop disturbance feedforward D1 to obtain the main loop feedforward compensation amount; According to the backflush state H1, it is judged whether the NOx measuring device (7) is in the backflush state; if it is, the hourly average of the ammonia flow set value is added to the main circuit feedforward compensation amount as the secondary circuit denitrification ammonia injection amount set value; otherwise, according to the denitrification control state S1, it is judged whether it is in the steady state process. If the denitrification control state S1 is a stable state, the hourly average value of NOx is used as the controlled amount of NOx at the denitrification outlet, and the hourly average value of NOx is used as the input of the fuzzy controller (3); If the denitration control state S1 is a transient control state, the real-time value of NOx is used as the controlled amount of NOx at the denitration outlet, and the real-time value of NOx is used as the input of the fuzzy controller (3); The fuzzy controller (3) is used to calculate the given value of the denitrification ammonia injection amount of the secondary circuit, and the given value of the denitrification ammonia injection amount of the secondary circuit is obtained; The ammonia injection amount is calculated based on the given value of the denitrification ammonia injection amount of the auxiliary circuit, and the calculated value of the ammonia injection regulating door opening control increment is obtained; The opening of the ammonia regulating door (5) is adjusted according to the calculated value of the ammonia injection regulating door opening control increment, thereby completing the adaptive control of the denitration of the mother tube boiler.

4. The method for adaptive denitration control of a main-tube boiler according to claim 3, characterized in that: The expression of the main loop disturbance feedforward D1 is: D1=[D Q1 D F1 ] T Among them, D Q1 is the boiler load disturbance; D F1 is the disturbance of the pulverizing system.

5. The method for adaptive denitration control of a main-tube boiler according to claim 4, characterized in that: The specific calculation formula for the main loop feedforward compensation is: C fb1 =R1·D1=[R Q1 R F1 ]·[D Q1 D F1 ] T =R Q1 D Q1 +R F1 D F1 Among them, C fb1 is the feedforward compensation of the main loop; R Q1 is the boiler load disturbance feedforward compensation coefficient; R F1 is the disturbance feedforward compensation coefficient of the pulverizing system; R1 is the compensation coefficient of the main feedforward compensator (2).

6. The method for adaptive denitration control of a main-tube boiler according to claim 4, characterized in that: The expression of denitrification control state S1 is: Among them, S1=0 represents the steady-state control process; S1=1 represents the transient control process; δ1 is the control error steady-state judgment limit; σ1 is the control error change steady-state judgment limit; e1 is the control error of NOx at the denitration outlet; e1' is the control error change of NOx at the denitration outlet; D M1 is the back-blowing disturbance of the NOx measuring device (7).

7. The method for adaptive denitration control of a main tube boiler according to claim 3, characterized in that: The expression of backflush state H1 is: Among them, D M1 is the back-blowing disturbance amount of the NOx measuring device (7); H1=0 indicates that the NOx measuring device (7) is not in the back-blowing state; H1=1 indicates that the NOx measuring device (7) is in the back-blowing state.

8. The method for adaptive denitration control of a main-tube boiler according to claim 3, characterized in that: The method further includes the step of compensating the calculated value of the ammonia injection regulating door opening control increment by using a secondary feedforward compensator (10), wherein the secondary feedforward compensator (10) receives the denitration ammonia injection amount output by the ammonia regulating door (5), and outputs a secondary loop feedforward compensation amount according to the denitration ammonia injection amount; the secondary loop feedforward compensation amount is used to compensate the calculated value of the ammonia injection regulating door opening control increment to generate an actual value of the ammonia injection regulating door opening control increment; and simultaneously, the actual value of the ammonia injection regulating door opening control increment is used to adjust the opening of the ammonia regulating door (5).

9. The method for adaptive denitration control of a main-tube boiler according to claim 8, characterized in that: It also includes a control initialization step; The initialized data includes the initial value of the hourly average value of NOx at the denitration outlet, the initial value of the main loop feedforward compensation amount, the initial value of the control error of NOx at the denitration outlet, the initial value of the average value of the denitration ammonia injection amount output by the ammonia regulating gate (5) and the initial value of the secondary loop feedforward compensation amount.

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