CN116928893A - Method for optimizing fire grate control strategy of biomass boiler - Google Patents

Method for optimizing fire grate control strategy of biomass boiler Download PDF

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Publication number
CN116928893A
CN116928893A CN202211251020.7A CN202211251020A CN116928893A CN 116928893 A CN116928893 A CN 116928893A CN 202211251020 A CN202211251020 A CN 202211251020A CN 116928893 A CN116928893 A CN 116928893A
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China
Prior art keywords
temperature
hearth
loop
water
auxiliary
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CN202211251020.7A
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Chinese (zh)
Inventor
姜永成
安鑫
宋欣
吴海云
华秀萍
杨磊
刘建波
姜佩军
栾积毅
吴玉青
王昀昊
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HARBIN HADONG XINCHUN BOILER CO Ltd
Tianjin Yunchun Technology Co ltd
Tianjin Agricultural University
Original Assignee
HARBIN HADONG XINCHUN BOILER CO Ltd
Tianjin Yunchun Technology Co ltd
Tianjin Agricultural University
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Application filed by HARBIN HADONG XINCHUN BOILER CO Ltd, Tianjin Yunchun Technology Co ltd, Tianjin Agricultural University filed Critical HARBIN HADONG XINCHUN BOILER CO Ltd
Priority to CN202211251020.7A priority Critical patent/CN116928893A/en
Publication of CN116928893A publication Critical patent/CN116928893A/en
Pending legal-status Critical Current

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
    • F24H15/00—Control of fluid heaters
    • F24H15/20—Control of fluid heaters characterised by control inputs
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N3/00—Regulating air supply or draught
    • F23N3/08—Regulating air supply or draught by power-assisted systems
    • F23N3/085—Regulating air supply or draught by power-assisted systems using electrical or electromechanical means
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N5/00—Systems for controlling combustion
    • F23N5/02—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
    • F24H15/00—Control of fluid heaters
    • F24H15/30—Control of fluid heaters characterised by control outputs; characterised by the components to be controlled
    • F24H15/305—Control of valves
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
    • F24H15/00—Control of fluid heaters
    • F24H15/30—Control of fluid heaters characterised by control outputs; characterised by the components to be controlled
    • F24H15/335—Control of pumps, e.g. on-off control
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
    • F24H15/00—Control of fluid heaters
    • F24H15/40—Control of fluid heaters characterised by the type of controllers
    • F24H15/414—Control of fluid heaters characterised by the type of controllers using electronic processing, e.g. computer-based
    • F24H15/421—Control of fluid heaters characterised by the type of controllers using electronic processing, e.g. computer-based using pre-stored data
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
    • F24H15/00—Control of fluid heaters
    • F24H15/40—Control of fluid heaters characterised by the type of controllers
    • F24H15/486—Control of fluid heaters characterised by the type of controllers using timers

Abstract

The application provides a method for optimizing a control strategy of a fire grate of a biomass boiler, which comprises the following steps: a main loop of the control system is provided with a water outlet temperature controller, a hearth temperature controller and a feeder frequency converter; the auxiliary control loop is provided with a hearth temperature controller and a feeder frequency converter; the auxiliary control loop is provided with a wind material proportioning controller and a blower frequency converter; and a multi-closed-loop cascade control loop is formed among the main loop, the auxiliary control loop and the auxiliary control loop of the control system. The application has the beneficial effects that: a method for optimizing the fire grate control strategy of biomass boiler features that a new control theory is put forward for the automatic control scheme of biomass boiler, and an oxygen content auxiliary control loop is added to the original single-layer cascade control loop, so effectively increasing the steady-state characteristics of system.

Description

Method for optimizing fire grate control strategy of biomass boiler
Technical Field
The application belongs to the technical field of intelligent control of biomass boilers, and particularly relates to a method for optimizing a control strategy of a grate of a biomass boiler.
Background
Under the call of environmental protection, energy conservation and emission reduction, the biomass boiler market is of a first scale. But biomass boiler combustion condition is poor, combustion efficiency is low and causes a large amount of fuel waste and environmental pollution, and at present, the scholars propose various control schemes and models for biomass boiler control systems. However, due to the fact that the related technology is imperfect, the product investment period is short, most references of the control technology are that the control system also has a plurality of blank areas by considering the gas and coal-fired boilers, and the advantages of the biomass boiler cannot be fully exerted, so that the actual running efficiency of the biomass boiler is not optimal, and a large amount of waste is caused.
The biomass fuel boiler is a typical multi-input and multi-output, strong-coupling and large-time-lag system. The control strategy of the fire grate determines the steady-state operation of the water outlet temperature of the boiler, in a water supply system of the boiler, the water supply system of the system inevitably leads to the sudden drop of the water outlet temperature, the feeding amount is increased, the combustion efficiency is reduced, and the oxygen content of the flue gas is increased, so that the emission does not reach the standard. If the combustion heat value is changed due to the fuel quality change or the blockage of a feeder, the outlet water temperature is not changed in a short time due to the hysteresis of the system. The fluctuation range of the outlet water temperature is overlarge, and the overall control quality is reduced.
The fire grate control strategy is used as the core of the system to greatly influence the combustion efficiency of the boiler, and is very necessary for scientifically and reasonably designing the configuration and the combustion process of the boiler, optimizing key operation parameters, improving the combustion efficiency, reducing the manufacturing and operation cost and reducing the atmospheric pollution.
Disclosure of Invention
In view of the above, the present application aims to propose a method for optimizing a control strategy of a grate of a biomass boiler, so as to solve at least one of the problems in the background art.
In order to achieve the above purpose, the technical scheme of the application is realized as follows:
a system for optimizing a biomass boiler grate control strategy, comprising:
a main loop of the control system is provided with a water outlet temperature controller, a hearth temperature controller and a feeder frequency converter;
the auxiliary control loop is provided with a hearth temperature controller and a feeder frequency converter;
the auxiliary control loop is provided with a wind material proportioning controller and a blower frequency converter;
and a multi-closed-loop cascade control loop is formed among the main loop, the auxiliary control loop and the auxiliary control loop of the control system.
Further, in a main loop of the control system, the difference between the actual value of the water outlet temperature and the set value of the water outlet temperature is used as a main instruction signal for controlling a frequency converter of the feeder, and the rotating speed of a fire grate motor in the feeder is regulated;
in the auxiliary control loop, the hearth temperature deviation value is used as an auxiliary controlled variable, when the hearth temperature deviation value is generated, the main command signal is used as a supplementary feedback signal to be input into a hearth temperature controller, and the hearth temperature controller directly outputs an output signal to a feeder frequency converter after the input signal is operated and processed, so that the rotating speed of a fire grate motor is regulated and controlled;
in the auxiliary control loop, the flue gas oxygen content acquired by the flue gas oxygen content tester is used as a feedforward signal to be fed back to the input end of the air-material proportioning controller in the auxiliary control loop and the input end of the hearth temperature controller in the auxiliary control loop respectively, and the air-material proportioning controller in the auxiliary control loop is used for calculating an oxygen change difference value, so that the air-feeding quantity of the blower is regulated in real time according to the oxygen change difference value until the optimal air-material ratio is reached.
Further, a first disturbance regulation strategy for the occurrence of the main loop of the control system is included:
when the boiler is supplemented with water, or the water supply flow is increased due to the increase of the boiler load, the measured value of the water outlet temperature is changed, and the water outlet temperature information is fed back to the main control loop to serve as primary disturbance of the system;
because the measured value of the water outlet temperature deviates from the preset value greatly, the water outlet temperature controller outputs a control signal to the feeder frequency converter by adjusting the hearth temperature controller, so that the feeding amount is adjusted, and the measured value of the water outlet temperature is kept to be stable near the preset value.
Further, a second disturbance regulation strategy for the occurrence of the secondary control loop is included:
when the biomass boiler is broken, a feeder is blocked or the heat value of the fuel is changed due to poor fuel quality, and the temperature of the hearth is changed, the information of the temperature of the hearth is fed back to the auxiliary control loop to serve as secondary disturbance of the system;
because the change of the temperature of the hearth in a short time can not cause the change of the temperature of the discharged water, when the temperature controller of the discharged water does not output signals and the auxiliary controller can sensitively receive the change information of the temperature of the hearth, signals are timely output to the frequency converter of the feeder at the moment, and the feeding quantity is adjusted to enable the combustion in the hearth to be recovered to a normal state.
Further, a third disturbance regulation strategy for the occurrence of the auxiliary control loop is included:
when the biomass boiler is in a normal combustion state, when the air supply quantity is overlarge or the fire grate frequency is higher, the steady-state output of the water outlet temperature and the hearth temperature can still be maintained, but the combustion state at the moment is in an insufficient combustion state, the biomass fuel is not completely burned and is sent to a slag remover of the hearth, at the moment, the oxygen content of a smoke outlet is used as an effective evaluation standard of the combustion state of the boiler, the combustion state of the boiler can be accurately reacted, the oxygen content change information is timely fed back to an auxiliary loop to serve as three disturbance of the system, an auxiliary loop controller outputs a signal to a blower frequency converter, and the air supply quantity is adjusted to enable the fuel to be restored to the full combustion state.
A method of optimizing a biomass boiler grate control strategy comprising the steps of:
s1, collecting outlet water temperature: collecting outlet water temperature information T in real time P Preset value T with outlet water temperature S Compares and calculates the difference T d ＝T P -T S ，
S2, collecting the temperature of a hearth: the temperature information of the hearth is acquired in real time, the time interval is set to be 3 seconds, and the difference E between two adjacent times is calculated d ＝E n -E (n-1) ；
S3, collecting oxygen content of flue gas: collecting the oxygen content information of the flue gas, setting the time interval to be 5 seconds, collecting 3 times to form a period, calculating the average value in the period, and storing the average value in a register D1; the loop is executed, the average value in the second period is calculated and stored in a register D2, and the average value in the third period is stored in a register D3 and … …; simultaneously calculate the N-th period and N-1Period difference Δn=d n -D (n-1) ；
S4, inputting variable factors and interference factors to form a main loop taking the outlet water temperature as a main controlled variable, an auxiliary control loop taking the furnace temperature as an auxiliary controlled variable and taking the flue gas oxygen content as an auxiliary controlled variable, wherein the main loop, the auxiliary control loop and the auxiliary control loop form a multi-closed-loop cascade control loop;
s5, inputting a preset value of the outlet water temperature and a preset value of the oxygen content of the flue gas, and controlling the outlet water temperature according to the first disturbance regulation strategy, the second disturbance regulation strategy and the third disturbance regulation strategy.
Further, in step S1, when the biomass boiler heats the water in the water tank to a set temperature, the circulating pump pressurizes the water to the water separator, and then the valve of the water separator is opened and closed to control the hot water to go to the user;
an integrated temperature transmitter is arranged on the water separator, the temperature of the water separator is acquired in real time, temperature information is fed back to a water outlet temperature controller, a set temperature value is compared with a field temperature feedback value, and a temperature change difference value T is calculated d And transmitting the calculation result to a hearth temperature controller at the next stage.
Further, in step S2, an integrated temperature transmitter is installed above the inside of the biomass boiler furnace, the furnace temperature information is collected in real time, the furnace temperature information is fed back to the furnace temperature controller, and the furnace temperature difference E is compared and converted in real time d According to the temperature difference E of the hearth d And (5) judging the change of the material layer according to the change of the material layer.
As can be seen, as the layer thickness decreases, the furnace temperature also decreases, and the change in furnace temperature has hysteresis relative to the change in layer thickness, which does not result in an immediate change in furnace temperature. Meanwhile, the material layer is broken, the fuel is mixed with coal, and the temperature change of a hearth can be caused by uneven fuel quality. Meanwhile, the hearth temperature controller transmits hearth temperature information to the frequency converter of the actuating mechanism feeder, the core mechanism of the feeding device is a fire grate motor, the change of feeding quantity is realized by adjusting the frequency of the fire grate motor, the steady-state output of hearth temperature is further maintained, and the frequency converter of the feeder transmits feeding information to the air-material proportioning controller, so that the air quantity is adjusted in real time according to the feeding quantity.
Further, in step S3, a flue gas oxygen content tester is installed at the position of the straight main flue, the flue gas oxygen content information is collected in real time and fed back to the air-material proportioning controller, the oxygen change difference is calculated, and the air quantity of the blower is adjusted in real time according to the oxygen change difference until the air-material ratio is optimal, so that the combustion efficiency of the boiler is improved.
Further, in step S4, when a plurality of disturbances occur simultaneously, if the effects of the two on the controlled variables of the main and the auxiliary are in the same direction, that is, the output frequency of the frequency converter of the feeder is greatly increased or decreased, and the control effect is enhanced to make the water outlet temperature of the water tank be stabilized at a preset value as soon as possible; if the two actions on the controlled variables of the main and the auxiliary are reversed, the control actions of the water outlet temperature controller and the hearth temperature controller on the frequency converter of the feeder are reversed at the moment, and under the counteracting action of the two actions, the control requirement can be met by only changing the output frequency of the frequency converter of the feeder by a small extent.
Compared with the prior art, the method for optimizing the control strategy of the biomass boiler grate has the following beneficial effects:
the application provides a method for optimizing a fire grate control strategy of a biomass boiler, which provides a new control theory for an automatic control scheme of the biomass boiler, adds an oxygen content auxiliary control loop for an original single-layer cascade control loop, and effectively improves the steady-state characteristic of the system. The water outlet temperature, the hearth temperature and the oxygen content are used as boiler load control signals, so that stable output of the water outlet temperature is ensured, the condition of overlarge fluctuation of controlled variables is avoided, the problem of mismatching between fuel combustion and air supply of the biomass boiler is solved by using a flue gas oxygen content change rate control strategy, the combustion efficiency of the boiler is improved, the phenomenon that emission does not reach standards in order to respond to the control strategy is avoided, and the load adjustment control strategy for the biomass hot water boiler is scientific and effective.
Drawings
The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain the application. In the drawings:
FIG. 1 is a schematic diagram of control logic according to an embodiment of the present application;
FIG. 2 is a schematic diagram of a control page according to an embodiment of the present application;
FIG. 3 is a schematic diagram of a structure according to an embodiment of the present application;
FIG. 4 is a schematic diagram illustrating a variation of a material layer according to an embodiment of the present application;
fig. 5 is a schematic view of a biomass boiler arrangement according to an embodiment of the present application.
Detailed Description
It should be noted that, without conflict, the embodiments of the present application and features of the embodiments may be combined with each other.
The application will be described in detail below with reference to the drawings in connection with embodiments.
A method of optimizing a biomass boiler grate control strategy comprising the steps of:
s1, collecting outlet water temperature information T in real time P Preset value T with outlet water temperature S Compares and calculates the difference T d ＝T P -T S ；
S2, acquiring hearth temperature information in real time, wherein the time interval is 10 seconds, and calculating the difference E between two adjacent times d ＝E n -E (n-1) 。
S3, collecting the oxygen content information of the flue gas, collecting once every 5 seconds, and calculating an average value in one period and storing the average value into a register D1 three times as one period;
the loop is executed, the average value in the second period is calculated and stored in a register D2, the average value in the third period is stored in a register D3,
……；
simultaneously calculating the difference deltan=d between the nth period and the N-1 th period n -D (n-1)
S4, inputting a variable factor water outlet temperature set value and an interference factor, wherein the interference factor comprises a hearth temperature, a flue gas oxygen content and a water tank temperature, so as to form a main loop taking the water outlet temperature as a main controlled variable, a secondary loop taking the hearth temperature as a secondary controlled variable and an auxiliary control loop taking the flue gas oxygen content as an auxiliary controlled variable.
The main loop, the auxiliary loop and the auxiliary loop form a multi-closed-loop cascade control loop.
S5, inputting a preset value of the outlet water temperature and a preset value of the oxygen content of the flue gas, and controlling the outlet water temperature according to the combined action of the main controlled loop, the auxiliary controlled loop and the auxiliary controlled loop.
The step S1 includes the following steps:
when the biomass boiler heats water in the water tank to a set temperature, the circulating pump pressurizes the water to the water separator, and then the valve of the water separator is opened and closed to control the hot water to reach the user. An integrated temperature transmitter is arranged on the water separator, the temperature of the water separator is acquired in real time, temperature information is fed back to a water outlet temperature controller, a set temperature value is compared with a field temperature feedback value, and a temperature change difference value T is calculated d . And transmitting the calculation result to a hearth temperature controller at the next stage.
The step S2 comprises the following steps:
an integrated temperature transmitter is arranged above the inside of a biomass boiler hearth, hearth temperature information is acquired in real time, and the hearth temperature information is fed back to a hearth temperature controller. Real-time comparison of the transformed furnace temperature difference E d . According to the temperature difference E of the hearth d And (5) judging the change of the material layer according to the change of the material layer. E in the case of unchanged fuel quality d The larger the layer, the more pronounced the thinning of the layer. If the furnace temperature suddenly drops, the reasons such as material layer breakage, fuel blending, fuel quality reduction and the like can be caused. And meanwhile, the hearth temperature controller transmits hearth information to the frequency converter of the actuator feeder, and the core mechanism of the feeding device is a fire grate motor. The frequency of the fire grate motor is adjusted to change the feeding quantity. Thereby maintaining steady-state output of the furnace temperature. The feeder frequency converter transmits feeding information to the air-material proportioning controller, and the air-feeding quantity is regulated in real time according to the feeding quantity, so that the fuel combustion efficiency is improved, and the nitrogen is reducedOxide emissions;
e, in particular, without changing the fuel quality d The larger the layer, the more pronounced the thinning of the layer. According to experimental data, in the operation process of the 10-ton biomass boiler, the height of a slag plate is manually adjusted, so that the thickness of a material layer is gradually decreased from 20cm to 8cm, each time is decreased by 2cm, the time interval is 3 minutes, and the result is shown in fig. 4;
the step S3 comprises the following steps:
and installing a flue gas oxygen content tester at the position of the straight main flue, collecting flue gas oxygen content information in real time, feeding back to the air-material proportioning controller, calculating an oxygen content difference value, and adjusting the air supply quantity of the air blower in real time according to the oxygen content difference value until the air-material ratio is optimal, thereby improving the combustion efficiency of the boiler. The oxygen content in the air is generally 20.6%, and the oxygen content gradually decreases to less than 6% along with the combustion, and the sudden increase of the oxygen content is mostly caused by layer faults, blockage of a feeder and the like when the boiler operates. Meanwhile, the oxygen content of the flue gas is also used as a basis for increasing the load of the system, the oxygen content information is used as feedback information and is transmitted to a hearth temperature controller, the feedback information and the feedback information are combined to a feeding system after being calculated by the system, the operating frequency of a fire grate motor is adjusted, and the load of the boiler is adjusted through the change of the feeding quantity.
The step S4 comprises the following steps:
when a plurality of disturbance occurs simultaneously, if the two actions on the controlled variables of the main and the auxiliary are in the same direction, the output frequency of the frequency converter of the feeder is greatly increased or reduced, so that the outlet water temperature of the water tank is stabilized at a preset value as soon as possible; if the two actions on the controlled variables of the main and the auxiliary are reversed, the control actions of the water outlet temperature controller and the hearth temperature controller on the frequency converter of the feeder are reversed at the moment, and under the counteracting action of the two actions, the control requirement can be met by only changing the output frequency of the frequency converter of the feeder by a small extent.
The step S5 comprises the following steps:
and setting a manual input window on the man-machine interaction interface. The parameters of the outlet water temperature set value, the flue gas oxygen content set value, the hearth temperature change value, the outlet water temperature change value, the oxygen content change value and the like are set.
In a specific implementation process, the application provides a method for optimizing a biomass boiler grate control strategy, which comprises a multi-closed loop feedforward-cascade control loop consisting of a main loop and a plurality of auxiliary loops.
S1, collecting outlet water temperature information T in real time P Preset value T with outlet water temperature S Compares and calculates the difference T d ＝T P -T S ；
The water outlet temperature controller, the hearth temperature controller, the feeder frequency converter, the hearth and the water tank form a main loop of the control system. And taking the difference value between the actual outlet water temperature value and the set outlet water temperature value as a main instruction signal for controlling the frequency converter of the feeder to regulate the rotating speed of the fire grate motor.
S2, acquiring hearth temperature information in real time, wherein the time interval is 3 seconds, and calculating the difference E between two adjacent times d ＝E n -E (n-1) 。
And the hearth forms a secondary control loop. When the difference value is generated, the auxiliary controlled variable is used as a supplementary feedback signal of the main controlled variable (water outlet temperature) to be input to a hearth temperature controller, and the hearth temperature controller carries out operation treatment on the input signal (water outlet temperature) and then outputs a control signal to a feeder frequency converter directly so as to regulate and control the rotating speed of the fire grate motor. Thereby regulating and controlling the feeding amount.
S3, collecting information of oxygen content of the flue gas, collecting the information once every 5 seconds, and calculating an average value D1 in one period, wherein three times are one period; the loop is executed, the average value D2 in the second cycle is calculated, and the average value D3, … … in the third cycle is calculated.
Simultaneously calculating the difference delta between the N-th period and the N-1 th period n ＝D n -D (n-1) . The oxygen content of the flue gas is respectively fed back to the input end of the air-material proportioning controller and the input end of the hearth temperature controller as feedforward signals.
The air-material ratio controller, the blower frequency converter, the hearth and the flue form an auxiliary control loop, and the oxygen content is not only a key parameter for adjusting the air-material ratio, but also an important judgment standard for judging whether the boiler burns efficiently. The hearth temperature controller is mainly used for calculating the difference value between the actual value and the set value of the oxygen content of the flue gas, and when the difference value is generated, the boiler is not in an optimal combustion state, and the fuel is insufficiently burned. The hearth temperature controller processes the input signals and outputs the output value of the grate motor frequency converter, and the feeding amount is increased to the optimal running state of the boiler. According to the principle of 'wind material proportion', the change of the feeding quantity is coordinated with the air supply quantity. The 'wind material proportion' is also a real-time change value in the furnace starting process and has correlation with oxygen content change.
Different from the coal-fired boiler, "wind-coal ratio" is the definite value, and biomass boiler's wind-material ratio changes along with the combustion condition of boiler, in order to guarantee that fuel can be quick safe to the combustion state in the stage of starting, both guarantee that the air supply volume is sufficient, avoid taking away unnecessary heat yet. With the spreading of the flame, the air supply quantity is gradually increased, so that enough oxygen is provided for the fuel, and the combustion efficiency is improved. When the boiler operates to the optimal combustion state, the feed amount and the air supply amount ratio are maintained unchanged. Therefore, in the process from starting the boiler to normal combustion of the boiler, the difference value of the oxygen content variation of the flue gas is the indirect expression of the combustion working condition of the boiler. In the experiment, the oxygen content change value and the wind material ratio are recorded for a plurality of times by using a repeated experiment method. And fitting by using data processing software to form a relation curve of oxygen content and wind material proportion.
Inputting a variable factor water outlet temperature set value and interference factors, wherein the interference factors comprise a hearth temperature, a flue gas oxygen content and a water tank temperature, so as to form a main control loop consisting of a water outlet temperature controller, a hearth temperature controller, a feeder frequency converter, a hearth and a water tank,
a hearth temperature controller, a feeder frequency converter and a hearth form a secondary control loop,
the main loop and the auxiliary loop form a multi-closed-loop cascade control loop.
The air-material proportioning controller, the blower frequency converter, the hearth and the flue form an auxiliary control loop.
The outlet water temperature control system is as follows:
the system is a double closed-loop cascade control loop formed by connecting a main control loop and an auxiliary control loop in series, and an auxiliary control loop taking oxygen content as a feedback signal is used as an auxiliary control loop to form a multistage linkage multi-closed-loop control system. The oxygen content of the flue gas is fed back to the auxiliary circuit as three-time disturbance, and is fed back to the auxiliary circuit in a closed loop. Effectively eliminates the defects of unstable output of the temperature of the water outlet, weak anti-interference capability of the system and the like. The regulation process of the water outlet temperature control system mainly comprises the following aspects:
1. when the boiler is supplemented with water, or the water supply flow caused by increasing the load of the boiler is increased, the measured value of the water outlet temperature is changed, and the water outlet temperature information is fed back to the main loop to serve as one disturbance of the system at the moment. Maintaining the measured value of the outlet water temperature to be stable near a preset value.
2. When the biomass boiler is broken, a feeder is blocked or the heat value of the fuel is changed due to poor fuel quality, and the temperature of the hearth is changed, the information of the temperature of the hearth is fed back to the secondary loop to serve as secondary disturbance of the system. The change of the hearth temperature in a short time does not cause the change of the outlet water temperature, so the main loop controller (outlet water temperature controller) has no signal output. The auxiliary controller can sensitively receive the temperature change information of the hearth and timely output signals to the frequency converter of the feeder, and the feeding quantity is adjusted to enable the combustion in the hearth to be recovered to a normal state.
3. When the biomass boiler is in a normal combustion state, when the air supply quantity is too large or the fire grate frequency is higher, the steady-state output of the water outlet temperature and the hearth temperature can still be maintained, but the combustion state is in an insufficient combustion state under the condition, the biomass fuel is not burnt out and is sent to the slag remover, the waste of the air supply quantity is caused, and even a large amount of harmful gas is generated. The oxygen content is used as an effective evaluation standard of the combustion state of the boiler, the combustion state of the boiler can be accurately reflected, the oxygen content change information is timely fed back to an auxiliary circuit to serve as three disturbance of the system, the auxiliary circuit controller outputs signals to a blower frequency converter, and the air supply quantity is adjusted to enable the fuel to be recovered to the full combustion state.
4. When the biomass boiler is in a furnace starting state, the oxygen content of the flue gas is fed back to a hearth temperature controller as an important basis for judging the furnace starting state of the boiler, and the feeding amount is regulated to enable the boiler to quickly and stably reach a normal running state.
5. When primary disturbance, secondary disturbance and tertiary disturbance are simultaneously generated, if the three are in the same direction under the action of the primary controlled variable and the secondary controlled variable, the regulation and control modes of the water outlet temperature controller and the hearth temperature controller on the frequency converter of the feeder are the same, namely, the output frequency of the fire grate motor is greatly increased and regulated, so that the water outlet temperature of the water tank is stabilized at a preset value as soon as possible. When the three functions are reversed, the regulation and control modes of the water outlet temperature controller and the hearth temperature controller on the frequency converter of the feeder are reversed, and the presented result is that the output frequency of the fire grate motor is slightly increased and regulated, so that the water outlet temperature of the water tank is stabilized at a preset value.
Those of ordinary skill in the art will appreciate that the elements and method steps of each example described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both, and that the elements and steps of each example have been described generally in terms of functionality in the foregoing description to clearly illustrate this interchangeability of hardware and software. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the solution. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present application.
In the several embodiments provided in the present application, it should be understood that the disclosed methods and systems may be implemented in other ways. For example, the above-described division of units is merely a logical function division, and there may be another division manner when actually implemented, for example, a plurality of units or components may be combined or may be integrated into another system, or some features may be omitted or not performed. The units may or may not be physically separate, and components shown as units may or may not be physical units, may be located in one place, or may be distributed over a plurality of network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the embodiment of the present application.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present application, and not for limiting the same; although the application has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the application, and are intended to be included within the scope of the appended claims and description.
The foregoing description of the preferred embodiments of the application is not intended to be limiting, but rather is intended to cover all modifications, equivalents, alternatives, and improvements that fall within the spirit and scope of the application.

Claims (10)

1. A system for optimizing a biomass boiler grate control strategy, comprising:
a main loop of the control system is provided with a water outlet temperature controller, a hearth temperature controller and a feeder frequency converter;
the auxiliary control loop is provided with a hearth temperature controller and a feeder frequency converter;
the auxiliary control loop is provided with a wind material proportioning controller and a blower frequency converter;
and a multi-closed-loop cascade control loop is formed among the main loop, the auxiliary control loop and the auxiliary control loop of the control system.
2. The method of optimizing a biomass boiler grate control strategy of claim 1, wherein:
in a main loop of the control system, taking the difference value between the actual value of the outlet water temperature and the set value of the outlet water temperature as a main instruction signal for controlling a frequency converter of the feeder, and adjusting the rotating speed of a fire grate motor in the feeder;
in the auxiliary control loop, the hearth temperature deviation value is used as an auxiliary controlled variable, when the hearth temperature deviation value is generated, the main command signal is used as a supplementary feedback signal to be input into a hearth temperature controller, and the hearth temperature controller directly outputs an output signal to a feeder frequency converter after the input signal is operated and processed, so that the rotating speed of a fire grate motor is regulated and controlled;
in the auxiliary control loop, the flue gas oxygen content acquired by the flue gas oxygen content tester is used as a feedforward signal to be fed back to the input end of the air-material proportioning controller in the auxiliary control loop and the input end of the hearth temperature controller in the auxiliary control loop respectively, and the air-material proportioning controller in the auxiliary control loop is used for calculating an oxygen change difference value, so that the air-feeding quantity of the blower is regulated in real time according to the oxygen change difference value until the optimal air-material ratio is reached.
3. The method of optimizing a biomass boiler grate control strategy of claim 1, comprising a first disturbance adjustment strategy for the occurrence of a control system main loop:
when the boiler is supplemented with water, or the water supply flow is increased due to the increase of the boiler load, the measured value of the water outlet temperature is changed, and the water outlet temperature information is fed back to the main control loop to serve as primary disturbance of the system;
because the measured value of the water outlet temperature deviates from the preset value greatly, the water outlet temperature controller outputs a control signal to the feeder frequency converter by adjusting the hearth temperature controller, so that the feeding amount is adjusted, and the measured value of the water outlet temperature is kept to be stable near the preset value.
4. The method of optimizing a biomass boiler grate control strategy of claim 1, comprising a second disturbance adjustment strategy for the occurrence of a secondary control loop:
when the biomass boiler is broken, a feeder is blocked or the heat value of the fuel is changed due to poor fuel quality, and the temperature of the hearth is changed, the information of the temperature of the hearth is fed back to the auxiliary control loop to serve as secondary disturbance of the system;
because the change of the temperature of the hearth in a short time can not cause the change of the temperature of the discharged water, when the temperature controller of the discharged water does not output signals and the auxiliary controller can sensitively receive the change information of the temperature of the hearth, signals are timely output to the frequency converter of the feeder at the moment, and the feeding quantity is adjusted to enable the combustion in the hearth to be recovered to a normal state.
5. The method of optimizing a biomass boiler grate control strategy of claim 1, comprising a third disturbance adjustment strategy for the occurrence of an auxiliary control loop:
when the biomass boiler is in a normal combustion state, when the air supply quantity is overlarge or the fire grate frequency is higher, the steady-state output of the water outlet temperature and the hearth temperature can still be maintained, but the combustion state at the moment is in an insufficient combustion state, the biomass fuel is not completely burned and is sent to a slag remover of the hearth, at the moment, the oxygen content of a smoke outlet is used as an effective evaluation standard of the combustion state of the boiler, the combustion state of the boiler can be accurately reacted, the oxygen content change information is timely fed back to an auxiliary loop to serve as three disturbance of the system, an auxiliary loop controller outputs a signal to a blower frequency converter, and the air supply quantity is adjusted to enable the fuel to be restored to the full combustion state.
6. A method of optimizing a biomass boiler grate control strategy, comprising the steps of:
s1, collecting outlet water temperature: collecting outlet water temperature information T in real time P And the outlet water temperature is preset to be T S Compares and calculates the difference T d ＝T P -T S ，
S2, collecting the temperature of a hearth: the temperature information of the hearth is acquired in real time, the time interval is set to be 3 seconds, and the difference E between two adjacent times is calculated d ＝E n -E (n-1) ；
S3, collecting oxygen content of flue gas: collecting the oxygen content information of the flue gas, setting the time interval to be 5 seconds, collecting 3 times to form a period, calculating the average value in the period, and storing the average value in a register D1; the loop is executed, the average value in the second period is calculated and stored in a register D2, and the average value in the third period is stored in a register D3 and … …; simultaneously calculating the difference deltan=d between the nth period and the N-1 th period n -D (n-1) ；
S4, inputting a variable factor water outlet temperature set value and an interference factor, wherein the interference factor comprises a hearth temperature, a flue gas oxygen content and a water tank temperature, a main loop taking the water outlet temperature as a main controlled variable, an auxiliary control loop taking the hearth temperature as an auxiliary controlled variable and an auxiliary control loop taking the flue gas oxygen content as an auxiliary controlled variable are formed, and the main loop, the auxiliary control loop and the auxiliary control loop form a multi-closed-loop cascade control loop;
s5, inputting a preset value of the outlet water temperature and a preset value of the oxygen content of the flue gas, and controlling the outlet water temperature according to the first disturbance regulation strategy, the second disturbance regulation strategy and the third disturbance regulation strategy.
7. The method for optimizing a fire grate control strategy of a biomass boiler according to claim 1, wherein in the step S1, when the biomass boiler heats water in the water tank to a set temperature, the circulating pump pressurizes the water to the water separator, and then the valve of the water separator is opened and closed to control the hot water to the user;
an integrated temperature transmitter is arranged on the water separator, the temperature of the water separator is acquired in real time, temperature information is fed back to a water outlet temperature controller, a set temperature value is compared with a field temperature feedback value, and a temperature change difference value T is calculated d And transmitting the calculation result to a hearth temperature controller at the next stage.
8. The method for optimizing fire grate control strategy of biomass boiler according to claim 1, wherein in step S2, an integrated temperature transmitter is installed above the inside of the biomass boiler furnace, furnace temperature information is collected in real time, and furnace temperature information is fed back to furnace temperature controlDevice for real-time comparison and conversion of hearth temperature difference E d According to the temperature difference E of the hearth d And (5) judging the change of the material layer according to the change of the material layer.
9. The method for optimizing a fire grate control strategy of a biomass boiler according to claim 1, wherein in the step S3, a flue gas oxygen content tester is installed at the position of a straight main flue, flue gas oxygen content information is collected in real time and fed back to a wind material proportion controller, an oxygen content change difference value is calculated, and the wind quantity of a blower is adjusted in real time according to the oxygen content change difference value until the wind material ratio is optimal, so that the combustion efficiency of the boiler is improved.
10. The method for optimizing a fire grate control strategy of a biomass boiler according to claim 1, wherein in the step S4, when a plurality of disturbances occur simultaneously, if the effects of the two on the primary and secondary controlled variables are in the same direction, the output frequency of the frequency converter of the feeder is greatly increased or decreased, and the control effect is enhanced to make the water outlet temperature of the water tank be stabilized at a preset value as soon as possible; if the two actions on the controlled variables of the main and the auxiliary are reversed, the control actions of the water outlet temperature controller and the hearth temperature controller on the frequency converter of the feeder are reversed at the moment, and under the counteracting action of the two actions, the control requirement can be met by only changing the output frequency of the frequency converter of the feeder by a small extent.
CN202211251020.7A 2022-10-12 2022-10-12 Method for optimizing fire grate control strategy of biomass boiler Pending CN116928893A (en)

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CN202211251020.7A CN116928893A (en) 2022-10-12 2022-10-12 Method for optimizing fire grate control strategy of biomass boiler

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Application Number Priority Date Filing Date Title
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