CN114719251A - Primary and secondary air quantity control method for circulating fluidized bed boiler directly doped with wet sludge - Google Patents
Primary and secondary air quantity control method for circulating fluidized bed boiler directly doped with wet sludge Download PDFInfo
- Publication number
- CN114719251A CN114719251A CN202210359976.2A CN202210359976A CN114719251A CN 114719251 A CN114719251 A CN 114719251A CN 202210359976 A CN202210359976 A CN 202210359976A CN 114719251 A CN114719251 A CN 114719251A
- Authority
- CN
- China
- Prior art keywords
- air volume
- primary air
- inertia
- instruction signal
- signal
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Images
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN A CARRIER GAS OR AIR
- F23C10/00—Fluidised bed combustion apparatus
- F23C10/18—Details; Accessories
- F23C10/28—Control devices specially adapted for fluidised bed, combustion apparatus
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23N—REGULATING OR CONTROLLING COMBUSTION
- F23N3/00—Regulating air supply or draught
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN A CARRIER GAS OR AIR
- F23C2206/00—Fluidised bed combustion
- F23C2206/10—Circulating fluidised bed
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23N—REGULATING OR CONTROLLING COMBUSTION
- F23N2237/00—Controlling
- F23N2237/16—Controlling secondary air
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E20/00—Combustion technologies with mitigation potential
- Y02E20/12—Heat utilisation in combustion or incineration of waste
Abstract
The invention discloses a primary air quantity and secondary air quantity control method of a circulating fluidized bed boiler for directly co-burning wet sludge, which is characterized in that a parameter adjustable non-minimum phase dynamic compensation link is added in the calculation logic of a primary air quantity feedforward instruction, the inertia time of the non-minimum phase link is adjusted by utilizing the ratio signal of the wet sludge input quantity and the coal supply quantity, and the reverse differential time of the non-minimum phase link is adjusted by utilizing a bed temperature signal, so that the matching of the time and the amplitude of primary air quantity change and the coal supply quantity change is realized; meanwhile, a coal feeding quantity command signal is adopted to calculate a total air quantity feedforward command signal through a multipoint broken line function, a primary air quantity feedforward command signal is subtracted after filtering is carried out in a first-order inertia link with adjustable inertia time to obtain a secondary air quantity feedforward command signal, and the inertia time of the first-order inertia link is adjusted by using a bed temperature signal, so that the opportunity and amplitude of total air supply in the combustion process can be guaranteed to be matched with the coal feeding quantity change when the coal feeding quantity and the primary air quantity change.
Description
Technical Field
The invention belongs to the technical field of automatic control of thermal engineering, and particularly relates to a primary air quantity control method and a secondary air quantity control method of a circulating fluidized bed boiler for directly blending and burning wet sludge.
Background
The sludge has complex components, including water, inorganic matters, organic matters, water-soluble matters and the like, and simultaneously contains a large amount of harmful and toxic matters such as pathogenic bacteria, viruses, polychlorinated biphenyl, heavy metals and the like. The conventional treatment methods such as dumping, landfill and the like have the serious disadvantages of environmental pollution, waste of land resources and the like. The circulating fluidized bed boiler burns sludge in a blending manner, so that the environmental pollution can be reduced, the heat in the sludge can be utilized for power generation, the normal operation of the boiler can not be obviously influenced under the condition of proper operation, and the method is a promising sludge treatment method capable of realizing harmlessness, reclamation and reduction.
The water content of the sludge after simple filter pressing treatment reaches 60 to 80 percent, and the sludge is called wet sludge.
The method for blending and burning wet sludge in the circulating fluidized bed boiler comprises two modes of blending and burning after drying and direct blending and burning. The mixed combustion after drying has little influence on the combustion state, can carry out a large amount of mixed combustion, but needs to add equipment for drying, storing, treating odor and the like of wet sludge, and has large investment and engineering construction amount; the direct blending combustion is that wet sludge is pressed into a conveying pipeline from a buffer bin through a screw conveyor and a plunger pump and then distributed to a plurality of sludge guns to be directly sent into a bed for blending combustion, the equipment structure is simple, the investment is low, and adverse effects on combustion can be caused. Direct co-firing is the mainstream mode of the current equipment modification.
The adverse effect of directly blending and burning wet sludge on combustion is mainly embodied in that the dense-phase combustion temperature in a circulating fluidized bed boiler bed is generally between 850 ℃ and 950 ℃, and when the direct input amount of the wet sludge accounts for 20 percent of the fuel amount, the average bed temperature is reduced by 10-20 ℃. The reason is that: (1) the wet sludge contains a large amount of moisture, and the moisture is heated to 850-950 ℃ in the bed, so that a large amount of latent heat of vaporization and heating heat are required to be absorbed; (2) moisture and ash in the wet sludge can cause the increase of circulation rate, so that the diffusion speed of heat in the hearth is accelerated. The reduction of the bed temperature and the increase of the circulation rate bring adverse effects to the ignition and combustion process of the raw coal entering the furnace in the bed.
Unlike pulverized coal boilers, the raw coal fed into a circulating fluidized bed boiler is directly fed into the bed without being ground, dried and heated. Due to the low temperature and large particles, the preheating time and the burning duration time required for reaching the ignition burning state are obviously longer than those of a pulverized coal boiler. When a large amount of raw coal is fed in, a certain degree of 'fire-fighting' phenomenon can be generated, namely, the raw coal enters a bed to absorb heat so as to reduce the bed temperature, so that the combustion intensity and the heat release are reduced instantaneously, and the combustion intensity and the heat release can not be increased gradually until coal particles start to combust. From the analysis of control, the phenomenon of 'fire suppression' is represented by non-minimum phase characteristics of a controlled object, namely when the control input is increased, the output of the controlled object is firstly reduced and then gradually increased after a period of time, and the controlled object is a characteristic which is very difficult to control. When wet sludge is directly blended and burned, the bed temperature and the combustion intensity are lower than those of the non-blended and burned working condition, and the preheating time and the combustion duration time required for coal particles to reach the combustion temperature in the bed are further increased. Overall, it appears that the inertia and delay time of the coal quantity signal affecting the oxygen quantity, the main steam pressure, the generated power, etc. are further increased, and even the non-minimum phase characteristics appear. The control operation mode of the unit needs to be adjusted to overcome the defect.
Fig. 1 is a schematic diagram showing a step response curve of a controlled object with inertia, delay and non-minimum phase characteristics, and as shown in the figure, the control difficulty of the controlled object is increased in sequence. When the wet sludge is not doped and burnt, the controlled object presents a large inertia characteristic, and gradually presents a large delay characteristic or even a non-minimum phase characteristic along with the increase of the doped burning amount. Control systems designed according to the characteristics of large-inertia objects and well-set controller parameters become unsuitable, which can cause oscillation of the control system. If the controller parameters are set according to the most conservative mode, although oscillation can be avoided, the disturbance rejection capability and the load response capability of the system are greatly reduced.
Under the state of blending and burning wet sludge, the control target of a combustion related control system of the circulating fluidized bed boiler emphasizes the guarantee of the stability, the rapidity, the high efficiency and the cleanness of combustion, wherein the stability is the most core target, and the key of the control lies in the guarantee of the accuracy of the dynamic air-coal ratio, including the accuracy of the total amount ratio and the accuracy of the time ratio, namely, the primary air volume and the secondary air volume are changed by correct amount at the correct time when the coal feeding amount is changed. When the boiler operates under variable working conditions or is disturbed, the accuracy of time proportioning is more important.
Under normal conditions, the primary air quantity and the secondary air quantity of the circulating fluidized bed boiler change along with the change of the coal feeding quantity, namely 'air feeding during coal feeding'. The feedforward control logics are as follows: an equivalent coal feeding amount instruction signal which is output by the main control of the boiler and is corrected by a heat value is subjected to a multi-point broken line function and then is set to calculate an air volume value corresponding to the current coal feeding amount, so that the matching of the total amount is realized; and then an inertial filtering link is carried out to realize the time matching and obtain the feedforward instruction signals of the primary air quantity and the secondary air quantity. The feedforward instruction control logic of the primary air volume and the secondary air volume of a traditional circulating fluidized bed boiler is shown in fig. 2, wherein the inertia time of the primary air volume inertia filtering link is set to just take away the heat generated after raw coal is combusted in time, and the stability of bed temperature and circulation multiplying power is mainly ensured; the inertia time of the secondary air volume inertia filtering link is set to provide proper air volume when coal is combusted, and the sufficiency of the combustion of raw coal particles is mainly ensured. The inertia time of the primary air volume is larger than that of the secondary air volume so as to adapt to respective control targets.
The instantaneous increase of the primary air quantity can bring more heat away from the bed, so that the bed temperature is reduced. When raw coal is fed into the bed, there is an endothermic heating process that also causes the bed temperature to decrease. If the primary air volume is increased at the wrong time after coal feeding, the interaction of the primary air volume and the secondary air volume is superposed, the bed temperature is further reduced, and the controlled object has obvious non-minimum phase characteristics. Similarly, the timing of the secondary air flow addition is important, and both early and late addition can result in fluctuations in oxygen and combustion conditions. After the circulating fluidized bed boiler is mixed with wet sludge, the optimal matching time of the primary air quantity, the secondary air quantity and the coal supply quantity changes. The control is needed to adjust the wet sludge blending combustion amount and the bed temperature in real time, so that the combustion state deterioration is avoided from influencing the stable, efficient and clean operation of the boiler.
In addition, in order to eliminate power grid frequency fluctuation caused by large-scale grid connection of renewable energy sources represented by wind power and photovoltaic, the circulating fluidized bed unit needs to be put into AGC (automatic gain control) and primary frequency modulation functions, and boiler combustion disturbance is aggravated due to frequent changes of power generation loads. The primary and secondary air volume control systems also need to be optimized to ensure the stability of boiler operation and the rapidity of response under the variable load working condition after blending combustion.
Object of the Invention
The invention aims to provide a primary air quantity and secondary air quantity control method suitable for a circulating fluidized bed boiler directly co-fired with wet sludge, aiming at the problems that the traditional primary air quantity and secondary air quantity control method cannot adapt to the operating condition requirement of the circulating fluidized bed boiler directly co-fired with wet sludge, and combustion fluctuation is easily caused by improper dynamic proportion of air and coal during variable load, so that the oxygen quantity, bed temperature and main steam pressure stability are influenced. The invention adds a parameter adjustable non-minimum phase dynamic compensation link in the calculation logic of a primary air volume feedforward instruction, adjusts the inertia time of the non-minimum phase link by using the ratio signal of the wet sludge input amount and the coal feeding amount, and adjusts the reverse differential time of the non-minimum phase link by using a bed temperature signal to realize the matching of the opportunity and the amplitude of primary air volume change and the coal feeding amount change; meanwhile, a coal feeding quantity command signal is adopted to calculate a total air quantity feedforward command signal through a multipoint broken line function, a primary air quantity feedforward command signal is subtracted after filtering is carried out in a first-order inertia link with adjustable inertia time to obtain a secondary air quantity feedforward command signal, and the inertia time of the first-order inertia link is adjusted by using a bed temperature signal, so that the opportunity and amplitude of total air supply in the combustion process can be guaranteed to be matched with the coal feeding quantity change when the coal feeding quantity and the primary air quantity change.
Disclosure of Invention
The invention provides a primary air quantity and secondary air quantity control method of a circulating fluidized bed boiler for directly blending and burning wet sludge, which adjusts the time difference of the primary air quantity and the secondary air quantity which change along with the change of fuel quantity according to the difference of the flow quantity and bed temperature of the directly blended and burned wet sludge, and ensures that the time and amplitude of the total air supply in the burning process are matched with the change of the coal supply quantity when the coal supply quantity and the primary air quantity change, and is characterized by comprising the following steps:
Preferably, aiming at the circulating fluidized bed boiler directly mixed with wet sludge, in a boiler distributed control system DCS or a programmable logic controller PLC, a primary air volume and secondary air volume feedforward control logic is realized in a configuration or programming mode, and the specific signal control flow comprises the following steps:
step S1Bed temperature signal passes through a third multi-point broken line function digital-analog modelA block F (x)3, obtaining a correction coefficient of the bed temperature to primary air volume inverse differential gain, and obtaining a correction coefficient of the filtered bed temperature to primary air volume inverse differential gain through a third-order inertia module LAG 3;
step S2The wet sludge feeding amount instruction signal is divided by the equivalent coal feeding amount instruction signal through a calculation module DIV to obtain a ratio signal of wet sludge and coal feeding amount, the ratio signal of wet sludge and coal feeding amount passes through a fourth multi-point broken line function module F (x)4 to obtain a correction coefficient of the ratio of wet sludge and coal feeding amount to primary air volume inertia time, and the correction coefficient of the ratio of filtered wet sludge and coal feeding amount to primary air volume inertia time is obtained through a fourth first-order inertia module LAG 4;
step S3The equivalent coal feeding quantity instruction signal passes through a fifth multipoint broken line function module F (x)5 to obtain a primary air quantity instruction signal corresponding to the equivalent coal feeding quantity, and passes through a fifth first-order inertia module LAG5 to obtain a primary air quantity instruction signal after first-order inertia filtering;
step S4The primary air volume instruction signal after the first-order inertial filtration is subtracted from the primary air volume instruction signal after the second-order inertial filtration through a first subtraction calculation module SUB1, the difference value of the primary air volume instruction signal is multiplied by a correction coefficient of the ratio of filtered wet sludge to coal feeding amount to the primary air volume inertia time through a first multiplication calculation module MUL1, the output value is subjected to integration processing through a first integration calculation module INTE1, and the primary air volume instruction signal after the second-order inertial filtration is output;
step S5The first-order filtered primary air volume instruction signal is subtracted from the second-order filtered primary air volume instruction signal through a second subtraction calculation module SUB2, the second-order filtered primary air volume instruction signal is multiplied by a correction coefficient of the ratio of the filtered wet sludge to the coal feeding amount to the primary air volume inertia time through a second multiplication calculation module MUL2, and after the output value is subjected to amplitude limiting through a high-low amplitude limiting module H/L, the output value is continuously multiplied by a correction coefficient of the filtered bed temperature to the primary air volume inverse differential gain through a third multiplication calculation module MUL3 to obtain a primary air volume instruction inverse differential signal;
step S6The first air volume command signal passes through the adderAdding a primary air quantity instruction reverse differential signal to the computing module ADD to obtain a primary air quantity feedforward instruction signal;
step S7The bed temperature signal passes through a seventh multi-point broken line function module F (x)7 to obtain a correction coefficient of the bed temperature to the total air volume inertia time, and then passes through a seventh-order inertia module LAG7 to obtain a correction coefficient of the filtered bed temperature to the total air volume inertia time;
step S8The equivalent coal feeding quantity instruction signal is processed by a sixth multipoint broken line function module F (x)6 to obtain a total air quantity instruction signal corresponding to the equivalent coal feeding quantity, and is processed by a sixth first-order inertia module LAG6 to obtain a first-order filtered total air quantity instruction signal;
step S9The first-order filtered total air volume command signal subtracts the second-order inertia filtered total air volume command signal through a third subtraction calculation module SUB3, the difference value of the first-order filtered total air volume command signal is multiplied by a correction coefficient of the filtered bed temperature to the total air volume inertia time through a fourth multiplication calculation module MUL4, the output value is subjected to integration processing through a second integration calculation module INTE2, and the second-order inertia filtered total air volume command signal is output;
step S10And subtracting the primary air volume feedforward instruction signal from the total air volume instruction signal subjected to the second-order inertia filtering through a fourth subtraction calculation module SUB4 to obtain a secondary air volume feedforward instruction signal.
Drawings
FIG. 1 is a schematic diagram of a step response curve of a controlled object with inertia, delay and non-minimum phase characteristics.
FIG. 2 is a feedforward instruction control logic of primary and secondary air volume of a conventional circulating fluidized bed boiler.
Fig. 3 is a structural block diagram of a first-order inertia filtering element with adjustable inertia time.
FIG. 4 is a SAMA diagram of feedforward control configuration logic of primary air quantity and secondary air quantity of a co-combustion wet sludge circulating fluidized bed boiler.
Detailed description of the preferred embodiments
The present invention is described in detail below with reference to the attached drawings, and it should be noted that the embodiments and examples herein are only illustrative of the present invention and should not be construed as limiting the present invention.
The invention provides a method for controlling primary air quantity and secondary air quantity of a circulating fluidized bed boiler for directly blending and burning wet sludge, and the key points for ensuring the combustion stability, rapidness, high efficiency and cleanness when the circulating fluidized bed directly blends and burns the wet sludge are that the time for matching the primary air quantity and the secondary air quantity to change along with the coal supply quantity is good.
In the circulating fluidized bed boiler, raw coal enters a fluidized bed from a feeding port at the lower part of a hearth through a coal feeder and a coal dropping pipe, the temperature rises after heat is absorbed in the bed, powdery particles start to catch fire at first, and large particles can catch fire only after being continuously heated for a period of time, so that the whole catching fire process presents an inertia characteristic. The inertia time of the ignition process is related to the bed temperature, and the ignition time is long when the bed temperature is low. In order to adapt to the situation and ensure the air supply in each stage of ignition and combustion, two first-order inertia links are adopted to match the change of the total air quantity and the coal supply quantity, one inertia link with fixed inertia time compensates the time difference from the change of a coal supply quantity instruction to the change of the raw coal entering a fluidized bed and from the change of a secondary air quantity instruction to the change of the secondary air entering the fluidized bed, and the other inertia link with variable inertia time compensates the inertia time of the raw coal on ignition in the bed.
The method comprises the following steps that the best time for adding primary air is provided when raw coal starts to release heat after being ignited and combusted in a fluidized bed, and firstly, an inertia link with fixed inertia time is adopted to compensate the time difference between the change of a coal supply instruction to the raw coal entering the fluidized bed and the change of a primary air quantity instruction to the change of the primary air entering the fluidized bed; and then a non-minimum phase link is adopted to compensate the dynamic process from heat absorption and ignition to heat release of the raw coal, and the non-minimum phase link has reverse variation characteristics, namely, a process of reducing the primary air volume and then increasing the primary air volume exists when the coal volume is increased, and the primary air volume is instantaneously reduced, so that the bed temperature is favorably improved, and the heat absorption and ignition process of the raw coal is accelerated.
In summary, the key dynamic links required for implementing the present invention include: (1) when the primary air volume feedforward instruction is calculated, a non-minimum phase link is added, the inertia time of the non-minimum phase link is adjustable, and the inertia time is adjusted by a ratio signal of the wet sludge input amount and the coal feeding amount; the reverse differential time of the non-minimum phase link is adjustable and is adjusted by a bed temperature signal, so that the non-minimum phase link with adjustable inertia time and reverse differential time is required to be constructed. (2) When the total air volume signal is processed in the secondary air volume feedforward instruction calculation process, a first-order inertia filtering link is needed, the inertia time is adjustable, and the adjustment is carried out by bed temperature signals, so that a first-order inertia link with adjustable inertia time is needed to be constructed.
The control method comprises the following steps:
a parameter-adjustable non-minimum phase dynamic compensation link is added in the primary air volume feedforward instruction calculation logic, the inertia time of the non-minimum phase link is adjusted by using a ratio signal of wet sludge input amount and coal supply amount, and the reverse differential time of the non-minimum phase link is adjusted by using a bed temperature signal, so that the matching of the primary air volume change opportunity and amplitude with the coal supply amount change is realized;
and 3, calculating a total air volume feedforward instruction signal by adopting the coal feeding amount instruction signal through a multi-point broken line function, filtering the total air volume feedforward instruction signal through a first-order inertia link with adjustable inertia time, subtracting the primary air volume feedforward instruction signal to obtain a secondary air volume feedforward instruction signal, and adjusting the inertia time of the first-order inertia link by using the bed temperature signal so as to ensure that the time and the amplitude of total air supply are matched with the change of the coal feeding amount in the combustion process when the coal feeding amount and the primary air volume change.
The first-order inertia link construction process with adjustable inertia time comprises the following steps:
the transfer function of the first-order inertia link with adjustable inertia time is expressed as shown in formula (1):
in the formula, TfIs inertia time in seconds; s is a complex variable of Laplace transformation and has no unit; transforming the formula (1) to obtain a compound shown as a formula (2):
fig. 3 is a structural block diagram of a first-order inertial filtering link with adjustable inertial time, and according to a closed loop transfer function solving method of a classical control theory, it can be found that the block diagram shown in fig. 3 can exactly realize the transfer function described in formula 2. According to the block diagram shown in fig. 3, a first-order inertial filtering link with adjustable inertial time can be constructed by a subtraction calculation module, a multiplication calculation module and an integral calculation module. When inputting a signal
When the time of inertia of the input signal to the output signal changes, the inertia time of the input signal to the output signal changes accordingly. As shown in fig. 3, the transfer function shown in formula (2) is constructed by a subtraction calculation module, a multiplication calculation module and an integral calculation module, specifically, the laplace transform r(s) of the input signal is operated by the subtracter module and the laplace transform y(s) of the output signal, and the operation result is input into the multiplication calculation module and the multiplication calculation module
Multiplication operation is carried out, and then the operation enters an integral operation module
After the operation, the Laplace transform y(s) of the output signal is obtained.
And (3) carrying out an actual differential element, wherein the transfer function of the differential element is expressed as shown in formula (3):
transforming the formula (3) to obtain a compound shown as a formula (4):
namely, the transfer function of the actual differential element is obtained by subtracting the first-order inertia element from the unit gain and dividing the result by the inertia time.
Wherein, the transfer function of the non-minimum phase link is expressed as shown in formula (5):
wherein, TdThe unit of the reverse differential time is second, and the reverse differential time is a non-minimum phase link;
and (3) deforming the formula (5) to obtain a product shown in a formula (6):
that is, the transfer function of the non-minimum phase element is determined by subtracting the differential element from the first order inertia element and multiplying the inverse differential time TdAnd then obtaining the compound.
Aiming at the mixed combustion type sludge circulating fluidized bed boiler, in a boiler DCS (distributed control system) or a PLC (programmable logic controller), a feedforward control logic of primary air volume and secondary air volume is realized by a configuration or programming mode. FIG. 4 is a SAMA diagram of feedforward control configuration logic for primary air volume and secondary air volume of a wet sludge mixed combustion circulating fluidized bed boiler, as shown in FIG. 4, F (x) 3-F (x)7 are respectively a third to seventh multi-point polygonal line function modules; LAG 3-7 are respectively third to seventh first order inertia modules; DIV is a division calculation module, and the input end marked with'd' is a dividend input end; SUB 1-SUB 4 are respectively the first to fourth subtraction calculation modules, the input end marked with "+" is the input end of the subtracted number, and the input end marked with "-" is the input end of the subtracted number; MUL 1-MUL 4 are respectively a first multiplication module, a second multiplication module, a third multiplication module, a fourth multiplication module and a fourth multiplication module; INTE1 and INTE2 are respectively a first integral calculation module and a second integral calculation module; H/L is a high/low amplitude limiting module which carries out high/low amplitude limiting processing on the input signal; and the ADD is a method calculation module.
The signal flow is as follows: the bed temperature signal passes through a third multi-point broken line function module F (x)3 to obtain a correction coefficient of the bed temperature to primary air volume inverse differential gain, and then passes through a third first-order inertia module LAG3 to obtain a correction coefficient of the filtered bed temperature to primary air volume inverse differential gain. The wet sludge feeding amount instruction signal is divided by the equivalent coal feeding amount instruction signal through a calculation module DIV to obtain a ratio signal of wet sludge and coal feeding amount, the ratio signal of wet sludge and coal feeding amount passes through a fourth multi-point broken line function module F (x)4 to obtain a correction coefficient of the ratio of wet sludge and coal feeding amount to primary air volume inertia time, and the correction coefficient of the ratio of filtered wet sludge and coal feeding amount to primary air volume inertia time is obtained through a fourth first-order inertia module LAG 4. The equivalent coal feeding quantity instruction signal passes through a fifth multi-point broken line function module F (x)5 to obtain a primary air quantity instruction signal corresponding to the equivalent coal feeding quantity, and passes through a fifth first-order inertia module LAG5 to obtain a primary air quantity instruction signal after first-order inertia filtering. The primary air volume instruction signal after the first-order inertia filtering is subtracted from the primary air volume instruction signal after the second-order inertia filtering through a first subtraction calculation module SUB1, the difference value of the primary air volume instruction signal is multiplied by a correction coefficient of the ratio of the filtered wet sludge to the coal feeding amount to the primary air volume inertia time through a first multiplication calculation module MUL1, the output value is subjected to integration processing through a first integration calculation module INTE1, and the primary air volume instruction signal after the second-order inertia filtering is output. The first-order filtered primary air volume instruction signal is subtracted from the second-order filtered primary air volume instruction signal through a second subtraction calculation module SUB2, the second-order filtered primary air volume instruction signal is multiplied by a correction coefficient of the ratio of the filtered wet sludge to the coal feeding amount to the primary air volume inertia time through a second multiplication calculation module MUL2, and the output value is further multiplied by a correction coefficient of the filtered bed temperature to the primary air volume inverse differential gain through a third multiplication calculation module MUL3 after being subjected to H/L amplitude limiting through a high-low amplitude limiting module, so that a primary air volume instruction inverse differential signal is obtained. The primary air volume instruction signal is added with the primary air volume instruction reverse differential signal through the addition calculation module ADD to obtain a primary air volume feedforward instruction signal. The bed temperature signal passes through a seventh multi-point broken line function module F (x)7 to obtain a correction coefficient of the bed temperature to the total air volume inertia time, and then passes through a seventh-order inertia module LAG7 to obtain a correction coefficient of the filtered bed temperature to the total air volume inertia time. The equivalent coal feeding quantity instruction signal passes through a sixth multipoint broken line function module F (x)6 to obtain a total air quantity instruction signal corresponding to the equivalent coal feeding quantity, and passes through a sixth first-order inertia module LAG6 to obtain a first-order filtered total air quantity instruction signal. The first-order filtered total air volume instruction signal subtracts the second-order inertia filtered total air volume instruction signal through a third subtraction calculation module SUB3, the difference value is multiplied by a correction coefficient of the filtered bed temperature to the total air volume inertia time through a fourth multiplication calculation module MUL4, the output value is subjected to integration processing through a second integration calculation module INTE2, and the second-order inertia filtered total air volume instruction signal is output. And subtracting the primary air volume feedforward command signal from the total air volume command signal subjected to the second-order inertia filtering through a fourth subtraction calculation module SUB4 to obtain a secondary air volume feedforward command signal.
This is further illustrated below by a specific example.
Examples
The embodiment takes a typical 300MW circulating fluidized bed unit directly mixed with wet sludge as an example to illustrate the implementation steps of the invention, and specifically comprises the following steps:
(1) the input signal is verified.
Implementing the method of the invention requires verification of the following input signals: (1) a bed temperature signal. And a plurality of temperature measuring points are arranged in the dense-phase region of the hearth of the circulating fluidized bed boiler, and the average value of the measured temperatures of all the normal measuring points is taken as a bed temperature signal. (2) A wet sludge feed rate command signal. And (4) taking a wet sludge feeding amount instruction signal for controlling the rotating speed of the screw conveyor, wherein the unit is t/h. (3) Equivalent coal feeding quantity command signal. And taking a coal feeding quantity instruction signal which is output by the boiler master control in the coordinated control system and is subjected to coal heat value correction, wherein the unit is t/h.
(2) Soft measurement logic configuration.
According to fig. 4, in a field control device such as a plant DCS (distributed control system) or PLC (programmable logic controller), logic of feedforward commands of primary air volume and secondary air volume is implemented in a configuration manner. Replace the original feedforward instruction control logic of primary air quantity and secondary air quantity
(3) And setting and adjusting parameters.
The following parameters need to be set or tuned according to the design and actual operating conditions of the circulating fluidized bed boiler:
1. initial values of inertia time of the first-order inertia links LAG3, LAG4 and LAG7 are all set to be 90s, initial values of inertia time of the first-order inertia links LAG5 are set to be 60s, and initial values of inertia time of the first-order inertia links LAG6 are set to be 15 s. During field debugging, if the equivalent coal supply instruction signal has large fluctuation and the characteristic of an actuating mechanism for controlling the primary air quantity and the secondary air quantity is poor, the inertia time can be increased and is maximally 125 percent of the initial value; otherwise, the inertia time can be reduced to a minimum of 75% of the initial value.
2. The initial parameter values of the polyline function F (x)3 are set in the manner shown in Table 1. No debugging is required.
TABLE 1 initial value settings for the polyline function F (x)3
| |
1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |
| X | 600 | 800 | 840 | 880 | 920 | 960 | 1000 | 1200 |
| Y | 32 | 32 | 16 | 8 | 4 | 2 | 0 | 0 |
3. The initial values of the parameters of the polyline function F (x)4 are set in the manner shown in Table 2. When the coal is debugged on site, the Y line number can be adjusted according to the equal proportion of the coal granularity and the volatile matter content of the coal as fired, and when the granularity is small, the volatile matter content is high and the coal is easy to catch fire, the Y line number can be reduced by the equal proportion, and the minimum value is 75 percent of the initial value; conversely, the number of rows Y can be increased in equal proportion to a maximum of 125% of the initial value.
TABLE 2 initial value settings for the polyline function F (x)4
| |
1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |
| X | -10 | 0 | 4 | 8 | 12 | 16 | 20 | 50 |
| Y | 0.1 | 0.1 | 0.066 | 0.041 | 0.026 | 0.016 | 0.01 | 0.01 |
4. The physical meaning of the multi-point broken line function F (x)5 parameter is the static ratio of the coal feeding quantity to the primary air quantity, and the set numerical value is consistent with the original control, namely the static ratio numerical value of the coal feeding quantity to the primary air quantity is ensured to be unchanged. No debugging is required.
5. The physical meaning of the multi-point broken line function F (x)6 is the static distribution ratio of the coal supply quantity and the total air quantity, and the total air quantity is the sum of the primary air quantity and the secondary air quantity. And F (x)6, the initial value setting mode is that the output point value of the static proportioning multi-point broken line function of the coal supply instruction and the primary air quantity instruction and the output point value of the static proportioning point broken line function of the coal supply instruction and the secondary air quantity instruction in the original control logic are summed to form a new multi-point broken line function. No debugging is required.
6. The initial parameter values of the polyline function F (x)7 are set in the manner shown in Table 3. When the coal is debugged on site, the Y line number can be adjusted according to the equal proportion of the coal granularity and the volatile matter content of the coal as fired, and when the granularity is small, the volatile matter content is high and the coal is easy to catch fire, the Y line number can be reduced by the equal proportion, and the minimum value is 75 percent of the initial value; conversely, the number of rows Y can be increased in equal proportion to a maximum of 125% of the initial value.
TABLE 3 initial value settings for the polyline function F (x)3
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | |
| X | 700 | 830 | 860 | 890 | 920 | 950 | 980 | 1200 |
| Y | 0.03 | 0.03 | 0.06 | 0.09 | 0.12 | 0.016 | 0.1 | 0.1 |
After parameter setting and debugging are completed, the control logic can be put into use.
In conclusion, the invention solves the problems of large combustion disturbance, variable load response speed, large oxygen amount, bed temperature and steam pressure fluctuation when the circulating fluidized bed boiler is mixed with wet sludge, and has the advantages of good control effect, clear configuration logic and physical significance, simple and convenient debugging and the like, and the method specifically comprises the following steps:
(1) the control effect is good. The method for controlling the primary air quantity and the secondary air quantity is suitable for the circulating fluidized bed boiler directly burning wet sludge accounting for 0-20% of the coal supply quantity. The adding time and the adding amount of primary air and secondary air can be automatically adjusted when the coal feeding amount changes according to the wet sludge blending combustion amount and the bed temperature, the combustion stability under variable load working conditions and disturbance working conditions is maintained, and the high efficiency, the cleanness and the load response rapidity of the operation of the circulating fluidized bed boiler are further ensured.
(2) The physical significance is clear, and the parameter setting is convenient. The control logic of each sub-loop in the control system is designed according to a certain characteristic of a controlled object, and has definite physical significance. The parameter setting of the control loop is regular and can be circulated, and the debugging and setting are convenient.
Claims (4)
1. A primary air quantity and secondary air quantity control method of a circulating fluidized bed boiler directly blending and burning wet sludge adjusts time difference of primary air quantity and secondary air quantity changing along with fuel quantity according to difference of flow and bed temperature of the directly blended and burned wet sludge, and guarantees that opportunity and amplitude of total air supply in a combustion process are matched with coal supply quantity change when coal supply quantity and primary air quantity change, and the control method is characterized by comprising the following steps:
step 1, adding a parameter adjustable non-minimum phase dynamic compensation link in primary air volume feedforward instruction calculation logic, and adjusting inertia time of the non-minimum phase link by using a ratio signal of wet sludge input amount and coal feeding amount; the bed temperature signal is used for adjusting the reverse differential time of the non-minimum phase link, so that the opportunity and amplitude of primary air volume change are matched with the coal supply volume change;
step 2, calculating a total air volume feedforward instruction signal by adopting a coal feeding instruction signal through a multi-point broken line function; after filtering by a first-order inertia link with adjustable inertia time, subtracting the primary air volume feedforward instruction signal to obtain a secondary air volume feedforward instruction signal; the inertia time of the first-order inertia link is adjusted by bed temperature signals, and the matching of the time and amplitude of the secondary air volume change and the coal supply volume change is realized.
2. The method for controlling the primary air quantity and the secondary air quantity of the circulating fluidized bed boiler directly co-fired with wet sludge according to claim 1, wherein for the circulating fluidized bed boiler directly co-fired with wet sludge, feedforward control logics of the primary air quantity and the secondary air quantity are realized in a boiler Distributed Control System (DCS) or a Programmable Logic Controller (PLC) in a configuration or programming mode, and a specific signal control flow comprises:
step S1The bed temperature signal passes through a third multi-point broken line function module F (x)3 to obtain a correction coefficient of the bed temperature to primary air volume inverse differential gain, and then passes through a third-order inertia module LAG3 to obtain a correction coefficient of the filtered bed temperature to primary air volume inverse differential gain;
step S2The wet sludge feeding amount instruction signal is divided by the equivalent coal feeding amount instruction signal through a calculation module DIV to obtain a ratio signal of wet sludge and coal feeding amount, the ratio signal of wet sludge and coal feeding amount passes through a fourth multi-point broken line function module F (x)4 to obtain a correction coefficient of the ratio of wet sludge and coal feeding amount to primary air volume inertia time, and the correction coefficient of the ratio of filtered wet sludge and coal feeding amount to primary air volume inertia time is obtained through a fourth first-order inertia module LAG 4;
step S3The equivalent coal feeding quantity instruction signal is processed by a fifth multi-point broken line function module F (x)5 to obtain a primary air quantity instruction signal corresponding to the equivalent coal feeding quantity, and then is processed by a fifth first-order inertia module LAG5 to obtain a primary air quantity instruction signal after first-order inertia filtering;
step S4Subtracting the primary air volume instruction signal subjected to the second-order inertia filtering from the primary air volume instruction signal subjected to the first-order inertia filtering by a first subtraction calculation module SUB1, multiplying the difference value by a correction coefficient of the ratio of the filtered wet sludge to the coal feeding amount to the primary air volume inertia time by a first multiplication calculation module MUL1, performing integration processing on the output value by a first integration calculation module INTE1, and outputting the primary air volume instruction signal subjected to the second-order inertia filtering;
step S5The primary air volume instruction signal after the first-order filtering subtracts a primary air volume instruction signal after the second-order filtering through a second subtraction calculation module SUB2, then is multiplied by a correction coefficient of the ratio of filtered wet sludge to coal feeding quantity to primary air volume inertia time through a second multiplication calculation module MUL2, and after an output value is subjected to H/L amplitude limiting through a high-low amplitude limiting module, the output value is continuously multiplied by a correction coefficient of the filtered bed temperature to primary air volume inverse differential gain through a third multiplication calculation module MUL3 to obtain a primary air volume inverse differential gainThe air volume instruction reverse differential signal;
step S6The primary air volume instruction signal is added with a primary air volume instruction reverse differential signal through an addition calculation module ADD to obtain a primary air volume feedforward instruction signal;
step S7The bed temperature signal passes through a seventh multi-point broken line function module F (x)7 to obtain a correction coefficient of the bed temperature to the total air volume inertia time, and then passes through a seventh-order inertia module LAG7 to obtain a correction coefficient of the filtered bed temperature to the total air volume inertia time;
step S8The equivalent coal feeding quantity instruction signal is processed by a sixth multipoint broken line function module F (x)6 to obtain a total air quantity instruction signal corresponding to the equivalent coal feeding quantity, and is processed by a sixth first-order inertia module LAG6 to obtain a first-order filtered total air quantity instruction signal;
step S9The first-order filtered total air volume command signal subtracts the second-order inertia filtered total air volume command signal through a third subtraction calculation module SUB3, the difference value of the first-order filtered total air volume command signal is multiplied by a correction coefficient of the filtered bed temperature to the total air volume inertia time through a fourth multiplication calculation module MUL4, the output value is subjected to integration processing through a second integration calculation module INTE2, and the second-order inertia filtered total air volume command signal is output;
step S10And subtracting the primary air volume feedforward instruction signal from the total air volume instruction signal subjected to the second-order inertia filtering through a fourth subtraction calculation module SUB4 to obtain a secondary air volume feedforward instruction signal.
3. The method for controlling the primary and secondary air volume of the circulating fluidized bed boiler for directly co-firing wet sludge according to claim 2, wherein the circulating fluidized bed boiler is a 300MW circulating fluidized bed unit, and the method further comprises the following steps:
step one, input signal verification, comprising the following substeps:
a substep S11 of verifying bed temperature signals, specifically, measuring the average value of the measured temperatures of all normal measuring points as the bed temperature signals through a plurality of temperature measuring points arranged in the dense-phase region of the hearth of the circulating fluidized bed boiler;
a substep S12 of verifying a wet sludge feeding amount instruction signal, specifically, taking the wet sludge feeding amount instruction signal for controlling the rotating speed of the screw conveyer, wherein the unit is t/h;
a substep S13 of verifying an equivalent coal feeding quantity command signal, specifically, taking a coal feeding quantity command signal which is output by a boiler master control in a coordinated control system and is corrected by a coal heat value, wherein the unit is t/h;
step two, soft measurement logic configuration, specifically, in a boiler distributed control system DCS or a programmable logic controller PLC, the logic of the primary air quantity feedforward instruction and the secondary air quantity feedforward instruction is realized in a configuration mode;
and step three, setting and adjusting parameters.
4. The method for controlling the primary air quantity and the secondary air quantity of the circulating fluidized bed boiler for directly co-combusting wet sludge according to claim 3, wherein the parameter setting and the whole step in the third step comprise:
substep S31, setting initial values of inertia time of first-order inertia links LAG3, LAG4 and LAG7 to 90S; setting an initial value of inertia time of a first-order inertia link LAG5 to be 60 s; setting an initial value of inertia time of a first-order inertia link LAG6 to be 15 s; during field debugging, the inertia time of each inertia link can be increased or reduced, wherein the maximum inertia time is 125% of the corresponding initial value; the minimum inertia time is 75% of the corresponding initial value;
substep S32, setting initial parameter values of the multi-point polyline functions F (x)3, F (x)4, F (x)5, F (x)6 and F (x) 7; after the initial value of the parameter is set and the debugging is finished, the control logic is ready to be used.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210359976.2A CN114719251B (en) | 2022-04-07 | 2022-04-07 | Primary and secondary air flow control method for circulating fluidized bed boiler directly blending and burning wet sludge |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210359976.2A CN114719251B (en) | 2022-04-07 | 2022-04-07 | Primary and secondary air flow control method for circulating fluidized bed boiler directly blending and burning wet sludge |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN114719251A true CN114719251A (en) | 2022-07-08 |
| CN114719251B CN114719251B (en) | 2023-05-23 |
Family
ID=82242722
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202210359976.2A Active CN114719251B (en) | 2022-04-07 | 2022-04-07 | Primary and secondary air flow control method for circulating fluidized bed boiler directly blending and burning wet sludge |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN114719251B (en) |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2001304525A (en) * | 2000-02-15 | 2001-10-31 | Mitsubishi Heavy Ind Ltd | Waste incinerator and its operation method |
| CN101713536A (en) * | 2009-12-03 | 2010-05-26 | 太原理工大学 | Control method of combustion system of circulating fluidized bed boiler |
| CN105258134A (en) * | 2015-10-20 | 2016-01-20 | 上海理工大学 | Coal-sludge composite firing system based on dual-medium flue gas drying and circulating fluidized bed boiler |
| CN107143864A (en) * | 2017-06-23 | 2017-09-08 | 济南市琦泉热电有限责任公司 | A kind of technique of full combustion slime circulating fluidized bed boiler burning sludge |
-
2022
- 2022-04-07 CN CN202210359976.2A patent/CN114719251B/en active Active
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2001304525A (en) * | 2000-02-15 | 2001-10-31 | Mitsubishi Heavy Ind Ltd | Waste incinerator and its operation method |
| CN101713536A (en) * | 2009-12-03 | 2010-05-26 | 太原理工大学 | Control method of combustion system of circulating fluidized bed boiler |
| CN105258134A (en) * | 2015-10-20 | 2016-01-20 | 上海理工大学 | Coal-sludge composite firing system based on dual-medium flue gas drying and circulating fluidized bed boiler |
| CN107143864A (en) * | 2017-06-23 | 2017-09-08 | 济南市琦泉热电有限责任公司 | A kind of technique of full combustion slime circulating fluidized bed boiler burning sludge |
Also Published As
| Publication number | Publication date |
|---|---|
| CN114719251B (en) | 2023-05-23 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| WO2020015694A1 (en) | Combustion air volume control system and method for biomass boiler | |
| CN105888744B (en) | The thermal power plant unit control method of main steam pressure deviation is compensated using heat supply network accumulation of energy | |
| CN102425807B (en) | Combustion feedforward and feedback composite optimization controlling method for pulverized coal fired boiler | |
| US5626085A (en) | Control of staged combustion, low NOx firing systems with single or multiple levels of overfire air | |
| CN104390234A (en) | Coordinated control method for ultra-supercritical generator set with dual-inlet and dual-outlet coal mill | |
| CN108679592B (en) | A kind of the boiler load control system and control method of biomass boiler | |
| CN111142377B (en) | Fuel quantity feedforward control method of coordinated control system considering operation state of coal mill | |
| CN104141958A (en) | Tail flue gas afterheat recycling system of mechanical waste incineration grate boiler and automatic control method thereof | |
| CN2711539Y (en) | Automatic combustion adjusting system for circulating fluidized bed boiler | |
| CN112097250A (en) | W flame boiler deep peak regulation system and method based on flue gas recirculation | |
| CN111239360B (en) | Based on pulverized coal combustion overall process gas composition monitoring air distribution system | |
| CN111678113A (en) | Environment-friendly and energy-saving supercritical CFB unit slip-stopping method | |
| CN113390099B (en) | Coordination control method under coal-fired cogeneration unit self-adaptive BTU | |
| CN114719251B (en) | Primary and secondary air flow control method for circulating fluidized bed boiler directly blending and burning wet sludge | |
| CN106705034B (en) | A kind of supercritical circulating fluidized bed boiler unit quick load change control method | |
| CN109058968A (en) | A kind of depth peaking boiler control method, device and thermal power generation system | |
| CN106524141B (en) | A kind of subcritical circulating fluidized bed boiler unit quick load change control method | |
| Zhu et al. | Revealing steam temperature characteristics for a double-reheat unit under coal calorific value variation | |
| CN105114960B (en) | A kind of method of garbage incinerator thorax Stress control | |
| CN202868676U (en) | Boiler hearth negative pressure control device of large-size biomass direct-combustion circulating fluidized bed | |
| CN114719242B (en) | Main steam pressure control method for circulating fluidized bed boiler directly blending and burning wet sludge | |
| CN105972609B (en) | A kind of refuse furnace of on-load correction burns autocontrol method and system | |
| CN213453608U (en) | W flame boiler degree of depth peak shaving system based on flue gas recirculation | |
| CN110500595B (en) | Method suitable for waste incineration air distribution of Martin furnace | |
| CN204063028U (en) | Supercritical cfb boiler bed temperature control system |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |