Tobacco production coal-fired boiler control method
By constructing a regulation model and a DCS distributed control system, the problem of optimizing the steam-water ratio and steam-coal ratio in tobacco production boilers using traditional control strategies was solved, achieving stable boiler operation and rapid supply, and improving combustion efficiency and energy utilization.
Patent Information
- Application Number
- CN202511239513.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-01
- Publication Date
- 2025-11-18
AI Technical Summary
Traditional control strategies are difficult to quickly optimize the steam-water ratio and the steam-coal ratio, resulting in boilers being unable to meet the gas load and rapid supply requirements in tobacco production processes, and making it difficult to guarantee the dynamic balance of steam flow and energy structure.
An adjustment model for the feedwater header, boiler drum water, air-coal ratio, furnace negative pressure, and deaerator is constructed. Stable control is achieved through a DCS distributed control system, including constant pressure single-parameter setpoint adjustment of the feedwater header, three-parameter feedforward adjustment of the boiler drum water level, air-coal ratio adjustment, two-parameter feedforward adjustment of the furnace negative pressure, and single-parameter setpoint adjustment of the deaerator, to realize fully automatic combustion of the boiler.
Stable boiler operation was achieved, meeting the gas load and rapid supply requirements of tobacco production processes, improving combustion efficiency and energy utilization, and avoiding instability during boiler start-up and shutdown.
Smart Images
Figure CN120969808A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of boiler control technology, specifically relating to a control method for a coal-fired boiler used in tobacco production. Background Technology
[0002] Because a boiler is a complex control object with multiple inputs and outputs, multiple parameters that are logically related, strongly coupled, and with uncertain time delays, coupled with the large fluctuations in load and special switching characteristics of tobacco processing, conventional control strategies and traditional control algorithms are unlikely to achieve ideal control results.
[0003] Due to the special operating conditions of tobacco production, traditional control strategies cannot quickly optimize and adjust the steam-water ratio and steam-coal ratio, and cannot guarantee the dynamic balance of steam, water and coal in the boiler. Moreover, the boiler controlled by traditional control algorithms cannot meet the process requirements of gas load and rapid supply in tobacco production, as well as the dynamic balance of real-time steam flow and energy structure. Summary of the Invention
[0004] The purpose of this invention is to provide a control method for coal-fired boilers used in tobacco production, so as to solve or partially solve the problems existing in the above-mentioned background art.
[0005] To achieve the above objectives, this application employs the following technical solution:
[0006] A method for controlling a coal-fired boiler used in tobacco production is disclosed. This method can construct adjustment models for the feedwater header, boiler drum water, air-coal ratio, furnace negative pressure, and deaerator, and then stably control the feedwater header pressure, boiler drum water level, air-coal ratio, furnace induced draft fan, and deaerator, respectively, to achieve stable boiler operation and meet the gas load and rapid supply requirements of the tobacco production process.
[0007] The first aspect of this application provides a method for controlling a coal-fired boiler used in tobacco production, comprising:
[0008] Retrofit coal-fired boilers and build a boiler DCS distributed control system;
[0009] A control model for a coal-fired boiler is constructed, which includes a constant pressure single-parameter setpoint regulation model for the feedwater header, a three-parameter feedforward regulation model for the boiler drum water level, a coal-air ratio regulation model, a two-parameter feedforward regulation model for the furnace negative pressure, a single-parameter setpoint regulation model for the deaerator, and a boiler safety interlock control model.
[0010] Based on the above models, the pulse width modulation parameters of the water pump variable frequency speed controller, the opening degree of the boiler feedwater regulating valve, the pulse width modulation parameters of the grate motor and blower variable frequency speed controller, the pulse width modulation parameters of the furnace induced draft fan variable frequency speed controller, and the valve opening degrees of the deaerator steam regulating valve and the inlet water regulating valve are calculated to achieve fully automatic combustion of the boiler.
[0011] Furthermore, the constant pressure single-parameter setpoint regulation model for the water supply main pipe includes:
[0012] A constant pressure single-parameter setpoint regulation loop for the feedwater header is constructed. The feedwater header pressure regulation loop consists of a boiler feedwater pump, a feedwater pump frequency converter, and a main pipe pressure transmitter. The configuration selects pump mode and power frequency conversion mode. The pump speed is adjusted through the feedwater pump PID control module.
[0013] The controlled variable of the feedwater pump PID control module is the feedwater main pipe pressure, which is detected by the field pressure transmitter. AI_OUT is used as the PV input value of the feedwater pump PID control module. The set value of the feedwater main pipe pressure of the feedwater pump PID control module comes from the human-machine interface input. The PID_OUT value is output to the feedwater pump frequency converter to adjust the output frequency.
[0014] The constant pressure single-parameter setpoint adjustment model for the jellyfish pipe is as follows:
[0015] ,
[0016] In the formula, The values represent the deviation, ± represent positive and negative action, negative action +, positive action -, KNL represents the nonlinear gain applied to P+I but not to D, P(s) represents the variable to which the proportional action is applied, and L(s) represents the external integral input from BKCAL_IN or OUT. The integral time (parameter integral) is expressed in seconds. GAINa represents the nominal gain after scaling the parameter GAIN from PV to OUT. F(s) represents the feedforward effect.
[0017] Furthermore, the three-parameter feedforward regulation model for boiler drum water level includes:
[0018] A three-parameter feedforward regulation loop for boiler drum water level is constructed based on the boiler drum water level, steam flow rate, and feedwater flow rate. The steam flow rate and feedwater flow rate are calculated and used as feedforward for the main loop of boiler drum water feedwater regulation to overcome the interference caused by changes in feedwater flow rate. The boiler drum liquid is controlled by adjusting the opening of the boiler feedwater regulating valve.
[0019] By optimizing and tuning the proportional, integral, and derivative parameters, the control valve can respond promptly and quickly control the feedwater flow rate to achieve a high degree of stability in the steam drum water level.
[0020] The feedforward regulation model for the three parameters of the boiler drum water level is as follows:
[0021] ,
[0022] ,
[0023] In the formula, D(s) represents the variable to which the differential action is applied, and α represents the coefficient. F(s) represents the differential time (parameter ratio) in seconds, F(s) represents the feedforward action, and K represents an empirical constant with a value range of 0.8-1.5.
[0024] Furthermore, the wind-coal ratio adjustment model includes:
[0025] A dual-parameter feedforward regulation loop for the air-coal ratio is constructed based on steam pressure. The dual-parameter feedforward regulation loop for the air-coal ratio consists of a steam drum pressure transmitter, a grate frequency converter, a grate motor, a blower frequency converter, and a blower.
[0026] The steam pressure setting is input to the PV value of the blower PID control module, and the output value of the blower PID control module is used as the pulse width modulation parameter of the blower frequency converter.
[0027] The temperature of the front arch of the furnace, T1 - the temperature of the rear arch of the furnace, T2 * k1 * P * K2, is used as the input value of the grate speed PID control module. The output value of the grate speed PID control module is used as the pulse width modulation parameter of the grate speed frequency converter. K1 is the supplementary coefficient for the temperature difference between the front and rear arches of the furnace, with a value of 0.8-1.5. K2 is the air-coal ratio coefficient under the condition of ensuring full combustion of coal, with a value of 0.5-0.8.
[0028] Furthermore, the dual-parameter feedforward regulation model for furnace negative pressure includes:
[0029] The furnace negative pressure regulation circuit is composed of an induced draft variable frequency speed controller, an induced draft fan, and a furnace negative pressure transmitter.
[0030] A dual-parameter feedforward control loop is adopted, with the furnace negative pressure regulation as the main control and the air volume as the feedforward proportional-integral controller. The furnace pressure setpoint is used as the PV input value of the induced draft fan PID control module, and the blower derivative value is used as the feedforward input value of the induced draft fan.
[0031] Furthermore, the deaerator single-parameter setpoint regulation model includes:
[0032] The automatic water level regulation loop of the deaerator consists of a deaerator feedwater regulating valve and a deaerator water level transmitter.
[0033] The deaerator water level automatic control loop is a single-parameter setpoint control loop, configured as a proportional-integral controller;
[0034] The deaerator pressure setpoint is used as the PV input value of the steam regulating valve PID control module. The output value of the steam regulating valve PID control module is used to control the valve position switch of the regulating valve positioner. The valve opening degree is calculated through an effective formula.
[0035] The deaerator level setpoint is used as the PV input value of the inlet regulating valve PID control module. The output value of the inlet regulating valve PID control module is used to control the valve position switch of the regulating valve positioner, and the valve opening degree is calculated through an effective formula.
[0036] Furthermore, the boiler safety interlock control model includes:
[0037] When critical parameters exceed limits during boiler operation, alarm signals are triggered. Interlock activation, cut-off functions, and filter delay settings are configured through permissions. The signal is transmitted through two levels to the interlock trigger to stop the boiler. During the boiler shutdown process, the equipment is stopped step by step according to process safety requirements.
[0038] When a high liquid level alarm, a low steam drum liquid level alarm, a high main steam pressure alarm, a high main steam temperature alarm, an induced draft fan malfunction, a blower malfunction, or a feedwater pump malfunction occurs, the host computer is triggered to sequentially delay and stop the coal feeder, grate fan, blower, and induced draft fan.
[0039] Furthermore, a boiler DCS distributed control system is constructed, including:
[0040] The boiler feedwater regulating valve, main pipe pressure transmitter, feedwater flow meter, steam flow meter, steam drum level differential pressure transmitter, frequency converter, furnace negative pressure transmitter, pressure transmitter, furnace temperature sensor and level transmitter are connected to the DCS controller through corresponding I / O cards. Through network communication technology, DCS system integration technology and configuration development technology, the detection device and human-machine interface are seamlessly connected.
[0041] The beneficial effects of this invention are:
[0042] By constructing adjustment models for the feedwater header, boiler drum water, air-coal ratio, furnace negative pressure, and deaerator, the pressure of the feedwater header, the water level in the boiler drum, the air-coal ratio, the furnace induced draft fan, and the deaerator are stabilized to achieve stable boiler operation and meet the gas load and rapid supply requirements of tobacco production processes. Attached Figure Description
[0043] The above and other objects, features and advantages of this application will become more apparent from the more detailed description of exemplary embodiments thereof in conjunction with the accompanying drawings, wherein the same reference numerals generally represent the same components in the exemplary embodiments thereof.
[0044] Figure 1This is a schematic flowchart illustrating the control method for a coal-fired boiler in tobacco production, as shown in an embodiment of this application.
[0045] Figure 2 This is a schematic diagram of the automatic control logic algorithm for constant pressure in the boiler feedwater header, as shown in an embodiment of this application.
[0046] Figure 3 This is a schematic diagram of the automatic control logic algorithm for boiler drum water level shown in an embodiment of this application;
[0047] Figure 4 This is a schematic diagram of the automatic control logic algorithm for optimizing the air-coal ratio, as shown in an embodiment of this application.
[0048] Figure 5 This is a schematic diagram of the automatic control logic algorithm for furnace negative pressure shown in an embodiment of this application;
[0049] Figure 6 This is a schematic diagram of the automatic control logic algorithm for a deaerator shown in an embodiment of this application;
[0050] Figure 7 This is a schematic diagram of the automatic control logic algorithm for boiler safety interlocking shown in the embodiments of this application;
[0051] Figure 8 This is a schematic diagram illustrating the calculation of the nonlinear tuning parameter KNL in an embodiment of this application, wherein:
[0052] NL_MINMOD is the gain applied when the absolute value of the error is less than NL_GAP. To obtain dead-zone action, set NL_MINMOD to 0.
[0053] NL_GAP is the control blind zone. When the absolute value of the error is less than NL_GAP, KNL = NL_MINMOD.
[0054] NL_TBAND is the transformation bandwidth of KNL as a linear correction of the error function.
[0055] NL_HYST is a hysteresis value. KNL = NL_MINMOD until the absolute value of the error exceeds NL_GAP + NL_HYST. Once the absolute value of the error exceeds NL_GAP + NL_HYST, the absolute value of the error must return to a value less than NL_GAP before KNL returns the value of NL_MINMOD. If NL_GAP is 0, then the value of NL_HYST is meaningless (it is usually assumed to be 0). Detailed Implementation
[0056] Embodiments of this application will now be described in more detail with reference to the accompanying drawings. While embodiments of this application are shown in the drawings, it should be understood that this application may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to make this application more thorough and complete, and to fully convey the scope of this application to those skilled in the art.
[0057] It should be understood that although the terms "first," "second," "third," etc., may be used in this application to describe various information, this information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, without departing from the scope of this application, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.
[0058] In the description of this application, it should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.
[0059] Unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.
[0060] Due to the special operating conditions of tobacco production, traditional control strategies cannot quickly optimize and adjust the steam-water ratio and steam-coal ratio, and cannot guarantee the dynamic balance of steam, water and coal in the boiler. Moreover, the boiler controlled by traditional control algorithms cannot meet the process requirements of gas load and rapid supply in tobacco production, as well as the dynamic balance of real-time steam flow and energy structure.
[0061] To address the aforementioned issues, this application provides a method for controlling a coal-fired boiler used in tobacco production. This method can establish adjustment models for the feedwater header, boiler drum water, air-coal ratio, furnace negative pressure, and deaerator. These models allow for stable control of the feedwater header pressure, drum water level, air-coal ratio, furnace induced draft fan, and deaerator, thereby achieving stable boiler operation and meeting the gas load and rapid supply requirements of the tobacco production process.
[0062] The technical solutions of the embodiments of this application are described in detail below with reference to the accompanying drawings.
[0063] Figure 1 This is a schematic flowchart illustrating the control method for a coal-fired boiler used in tobacco production, as shown in an embodiment of this application.
[0064] See Figure 1 A method for controlling a coal-fired boiler used in tobacco production, comprising:
[0065] S101. Modify the coal-fired boiler and build a boiler DCS distributed control system;
[0066] Optionally, a boiler DCS distributed control system may be constructed, including:
[0067] The boiler feedwater regulating valve, main pipe pressure transmitter, feedwater flow meter, steam flow meter, steam drum level differential pressure transmitter, frequency converter, furnace negative pressure transmitter, pressure transmitter, furnace temperature sensor and level transmitter are connected to the DCS controller via corresponding I / O cards.
[0068] Specifically, field control equipment and instruments are connected to the corresponding IO card channels of the DCS system via communication cables. Through computer software technology, network communication technology, DCS system integration technology, graphics and animation technology, and programming configuration development technology, the field equipment and human-machine interface are seamlessly connected according to the control strategy and logic algorithm principle, ultimately realizing a fully automatic combustion system for the boiler.
[0069] Boiler feedwater regulating valves, main pipe pressure transmitters, feedwater flow meters, steam flow meters, steam drum level differential pressure transmitters, frequency converters, furnace negative pressure transmitters, pressure transmitters, furnace temperature sensors, and level transmitters provide the measurement basis for the overall automatic control function of the boiler.
[0070] S102. Construct a control model for a coal-fired boiler. The control model includes a constant pressure single-parameter setpoint regulation model for the feedwater header, a three-parameter feedforward regulation model for the boiler drum water level, a coal-air ratio regulation model, a two-parameter feedforward regulation model for the furnace negative pressure, a single-parameter setpoint regulation model for the deaerator, and a boiler safety interlock control model.
[0071] Optionally, the constant pressure single-parameter setpoint regulation model for the water supply header includes: constructing a constant pressure single-parameter setpoint regulation loop for the water supply header, wherein the water supply header pressure regulation loop consists of a boiler feedwater pump, a feedwater pump frequency converter, and a main pipe pressure transmitter; configuring the pump mode and the power frequency conversion mode; and regulating the pump speed through the feedwater pump PID control module.
[0072] The controlled variable of the feedwater pump PID control module is the feedwater main pipe pressure, which is detected by the field pressure transmitter. AI_OUT is used as the PV input value of the feedwater pump PID control module. The set value of the feedwater main pipe pressure of the feedwater pump PID control module comes from the human-machine interface input. The PID_OUT value is output to the feedwater pump frequency converter to adjust the output frequency.
[0073] The constant pressure single-parameter setpoint adjustment model for the jellyfish pipe is as follows:
[0074] ,
[0075] In the formula, The values represent the deviation, ± represent positive and negative action, negative action +, positive action -, KNL represents the nonlinear gain applied to P+I but not to D, P(s) represents the variable to which the proportional action is applied, and L(s) represents the external integral input from BKCAL_IN or OUT. This represents the integration time in seconds (parameter integration), and GAINa represents the nominal gain after scaling the parameter GAIN from PV to OUT. It indicates a feedforward function.
[0076] The calculation of KNL, such as Figure 8 As shown, NL_MINMOD is the gain applied when the absolute value of the error is below NL_GAP. To obtain dead-zone action, set NL_MINMOD to 0. NL_GAP is the control blind zone. When the absolute value of the error is below NL_GAP, KNL = NL_MINMOD. NL_TBAND is the conversion bandwidth of KNL as a linear correction of the error function. NL_HYST is a hysteresis value. KNL = NL_MINMOD until the absolute value of the error exceeds NL_GAP + NL_HYST. Once the absolute value of the error exceeds NL_GAP + NL_HYST, the absolute value of the error must return to a value less than NL_GAP before KNL returns to the value of NL_MINMOD. If NL_GAP is 0, then the value of NL_HYST is meaningless (it is usually assumed to be 0).
[0077] The selection and limits of setpoints are determined by the mode. Setpoints are limited by the SP_HI_LIM and SP_LO_LIM parameters. In cascade mode, setpoints are derived from the CAS_IN input. In automatic mode, setpoints are adjusted by the operator. The percentage change of setpoints is limited by configuring the SP_RATE_UP and SP_RATE_DN parameters.
[0078] This system employs a parallel constant-pressure water supply method using multiple variable frequency pumps. The control strategy utilizes a single closed-loop control circuit with multiple outputs. The number of operating pumps and frequency converters is determined by load demand, with the rest on standby or in reserve. Automatic switching between power frequency and variable frequency is implemented based on pump power to achieve optimal energy-saving operation. Automatic pump increase / decrease based on pressure gradient differences ensures real-time constant pressure tracking of the mains pressure setting. This effectively prevents large fluctuations in boiler steam flow from affecting the mains pressure and causing untimely responses, as well as low steam drum levels leading to interlocking shutdowns. Through power frequency / variable frequency switching and pump increase / decrease, economical and stable operation is effectively achieved.
[0079] Optionally, a three-parameter feedforward regulation model for boiler drum water level includes: constructing a three-parameter feedforward regulation loop for boiler drum water level based on the drum water level, steam flow rate, and feedwater flow rate; calculating the steam flow rate and feedwater flow rate as feedforward for the main loop of boiler drum water feedwater regulation; overcoming interference caused by changes in feedwater flow rate; and controlling the boiler drum liquid by adjusting the opening of the boiler feedwater regulating valve.
[0080] A three-impulse combination consisting of drum water level, steam flow rate, and feedwater flow rate is integrated into a boiler drum water PID control module with predictive control functionality. This enables algorithmic modeling for the control of multivariable dynamic processes where interactions occur. The feedforward value of the steam flow rate directly affects the output of the boiler drum water PID module, suppressing false water level readings. The introduction of feedwater flow rate effectively eliminates the adverse effects of feedwater pressure disturbances on water level self-control. The PID control module, with its self-tuning function, optimizes and tunes the proportional, integral, and derivative parameters, and controls the regulating valve to respond promptly, rapidly controlling the feedwater flow rate to stabilize the drum water level.
[0081] The feedforward regulation model for the three parameters of the boiler drum water level is as follows:
[0082] ,
[0083] ,
[0084] In the formula, D(s) represents the variable to which the differential action is applied. Represents the coefficient. F(s) represents the differential time (parameter ratio) in seconds, F(s) represents the feedforward action, and K represents an empirical constant with a value range of 0.8-1.5.
[0085] The boiler drum water level is controlled by a multi-parameter variable combination consisting of the drum water level, steam flow rate, and feedwater flow rate, integrated into a control module with predictive control functionality. This allows for rapid control of the dynamic interactions of multiple variables. The feedforward value of the steam flow rate directly affects the output of the boiler drum water PID module, suppressing false water level readings. The introduction of feedwater flow rate effectively eliminates the adverse effects of feedwater pressure disturbances on water level self-control. A self-tuning module optimizes and tunes the proportional, integral, and derivative parameters and controls the regulating valve, responding promptly and quickly to control the feedwater flow rate, achieving stable drum water level. Dynamic regulation ensures that the drum water level is maintained at the set value with high precision during boiler startup, shutdown, and when steam flow changes drastically, effectively preventing "false water levels" and interlocking reactions caused by drastic fluctuations in drum water level during boiler startup, shutdown, and rapid steam flow changes.
[0086] Optionally, the air-coal ratio adjustment model includes: constructing a dual-parameter feedforward adjustment loop for the air-coal ratio based on steam pressure. The dual-parameter feedforward adjustment loop for the air-coal ratio consists of a steam drum pressure transmitter, a grate frequency converter, a grate motor, a blower frequency converter, and a blower.
[0087] The steam pressure setting is input to the PV value of the blower PID control module, and the output value of the blower PID control module is used as the pulse width modulation parameter of the blower frequency converter.
[0088] The difference between the front arch temperature T1 and the rear arch temperature T2*k1*P*K2 is used as the input value of the grate speed PID control module, and the output value of the grate speed PID control module is used as the pulse width modulation parameter of the grate speed frequency converter. K1 is the supplementary coefficient for the temperature difference between the front and rear arches of the furnace, with a value of 0.8-1.5, and K2 is the air-coal ratio coefficient under the condition of ensuring complete coal combustion, with a value of 0.5-0.8.
[0089] The automatic control system for optimizing the air-coal ratio involves several steps. First, a PID control module with self-tuning function optimizes the proportional, integral, and derivative parameters to achieve proactive automatic adjustment of the air supply. Then, compensation variables from the furnace front and rear arch temperatures are calculated by a predictive control module. The results are sent to a fuzzy control module for nonlinear process adjustment, and finally, output is limited based on the air-coal ratio, achieving high stability and efficiency in combustion control. By incorporating the correction of furnace front and rear arch temperatures to the grate speed, and ensuring stable steam drum pressure, the combustion in the firebed becomes more even and stable, reducing "fire escape" phenomena, improving combustion thermal efficiency, saving coal feed, and extending the life of the rear arch.
[0090] Optional, a dual-parameter feedforward regulation model for furnace negative pressure includes:
[0091] The furnace negative pressure regulation circuit consists of an induced draft variable frequency speed controller, an induced draft fan, and a furnace negative pressure transmitter.
[0092] A dual-parameter feedforward control loop is adopted, with the furnace negative pressure regulation as the main control and the air volume as the feedforward proportional-integral controller. The furnace pressure setpoint is used as the PV input value of the induced draft fan PID control module, and the blower derivative value is used as the feedforward input value of the induced draft fan.
[0093] Under the condition of slight negative pressure in the furnace, the differential signals of the furnace negative pressure and the air supply speed are optimized by the predictive control (Predict) function calculation module. The results are sent to the self-tuning (Tune) PID control module to optimize and tune the proportional, integral and derivative parameters, and adjust the induced draft volume. At the same time, a feedforward quantity is output directly to the self-tuning (Tune) PID module to suppress the interference of the air supply volume, stabilize the furnace negative pressure, and achieve the purpose of balancing the amount of air entering and leaving the furnace, effectively ensuring the safe and stable operation of the boiler.
[0094] Optionally, the deaerator single-parameter setpoint regulation model includes: the deaerator water level automatic regulation loop consists of a deaerator water supply regulating valve and a deaerator water level transmitter;
[0095] The deaerator water level automatic control loop is a single-parameter setpoint control loop, configured as a proportional-integral controller;
[0096] The deaerator pressure setpoint is used as the PV input value of the steam regulating valve PID control module. The output value of the steam regulating valve PID control module is used to control the valve position switch of the regulating valve positioner, and the valve opening degree is calculated through an effective formula.
[0097] The deaerator level setpoint is used as the PV input value of the inlet regulating valve PID control module. The output value of the inlet regulating valve PID control module is used to control the valve position switch of the regulating valve positioner, and the valve opening degree is calculated through an effective formula.
[0098] The deaerator is automatically controlled. The dissolved oxygen content of the boiler water must be less than 0.1 mg / L. To achieve this standard, the deaerator pressure must be controlled at 0.02 MPa and the deaerator temperature at 104℃. The deaerator pressure control is primarily to ensure sufficient steam pressure for deoxygenating the softened water. The input parameter is the deaerator pressure, and the output parameter controls the deaerator steam inlet valve to stabilize the deaerator pressure. This achieves constant temperature control of the deaerator, effectively ensuring the safe and stable operation of the micro-pressure vessel and guaranteeing that the boiler water quality meets the required standards.
[0099] Optionally, the boiler safety interlock control model includes: triggering alarm signals when important parameters exceed limits during boiler operation; setting interlock activation, deactivation, and filtering delay settings through permission settings; transmitting signals through two levels to trigger the boiler shutdown; and stopping the equipment step by step according to process safety requirements during the boiler shutdown process.
[0100] When a high liquid level alarm, a low steam drum liquid level alarm, a high main steam pressure alarm, a high main steam temperature alarm, an induced draft fan malfunction, a blower malfunction, or a feedwater pump malfunction occurs, the DCS controller is triggered, and the coal feeder, grate fan, blower, and induced draft fan are stopped sequentially every 5 seconds.
[0101] When critical parameters exceed limits during boiler operation and trigger alarm signals, the signal is transmitted through two levels to the interlock trigger to stop the boiler by setting interlock activation, deactivation function, and filter delay settings through permission settings. During the boiler shutdown process, the equipment is stopped step by step according to process safety requirements, thereby ensuring equipment safety and process safety.
[0102] S103. Based on the control model, calculate the pulse width modulation parameters of the water pump frequency converter, the opening degree of the boiler feedwater regulating valve, the pulse width modulation parameters of the grate motor and blower frequency converter, the pulse width modulation parameters of the furnace induced draft fan frequency converter, and the valve opening degrees of the deaerator steam regulating valve and the inlet water regulating valve to achieve fully automatic boiler combustion.
[0103] The various embodiments of this application have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.
Claims
1. A method for controlling a coal-fired boiler in tobacco production, characterized in that, include: Retrofit coal-fired boilers and build a boiler DCS distributed control system; A control model for a coal-fired boiler is constructed, which includes a constant pressure single-parameter setpoint regulation model for the feedwater header, a three-parameter feedforward regulation model for the boiler drum water level, a coal-air ratio regulation model, a two-parameter feedforward regulation model for the furnace negative pressure, a single-parameter setpoint regulation model for the deaerator, and a boiler safety interlock control model. Based on the above models, the pulse width modulation parameters of the water pump variable frequency speed controller, the opening degree of the boiler feedwater regulating valve, the pulse width modulation parameters of the grate motor and blower variable frequency speed controller, the pulse width modulation parameters of the furnace induced draft fan variable frequency speed controller, and the valve opening degrees of the deaerator steam regulating valve and the inlet water regulating valve are calculated to achieve fully automatic combustion of the boiler.
2. The method for controlling a coal-fired boiler in tobacco production according to claim 1, characterized in that, The constant pressure single-parameter setpoint adjustment model for the water supply main pipe includes: A constant pressure single-parameter setpoint regulation loop for the feedwater header is constructed. The feedwater header pressure regulation loop consists of a boiler feedwater pump, a feedwater pump frequency converter, and a main pipe pressure transmitter. The configuration selects pump mode and power frequency conversion mode. The pump speed is adjusted through the feedwater pump PID control module. The controlled variable of the feedwater pump PID control module is the feedwater main pipe pressure, which is detected by the field pressure transmitter. The feedwater main pipe pressure is used as the input value of the feedwater pump PID control module. The set value of the feedwater main pipe pressure of the feedwater pump PID control module comes from the human-machine interface input. The output value of the PID is output to the feedwater pump frequency converter to adjust the output frequency. The constant pressure single-parameter setpoint adjustment model for the jellyfish pipe is as follows: ， In the formula, The values represent the deviation, ± represent positive and negative action, negative action +, positive action -, KNL represents the nonlinear gain applied to P+I but not to D, P(s) represents the variable to which the proportional action is applied, and L(s) represents the external integral input from BKCAL_IN or OUT. This represents the integration time in seconds (parameter integration), and GAINa represents the nominal gain after scaling the parameter GAIN from PV to OUT. It indicates a feedforward function.
3. The method for controlling a coal-fired boiler in tobacco production according to claim 1, characterized in that, The boiler drum water level three-parameter feedforward regulation model includes: A three-parameter feedforward regulation loop for boiler drum water level is constructed based on the boiler drum water level, steam flow rate, and feedwater flow rate. The steam flow rate and feedwater flow rate are calculated and used as feedforward for the main loop of boiler drum water feedwater regulation to overcome the interference caused by changes in feedwater flow rate. The boiler drum liquid is controlled by adjusting the opening of the boiler feedwater regulating valve. By optimizing and tuning the proportional, integral, and derivative parameters, the control valve can respond promptly and quickly control the feedwater flow rate to achieve a high degree of stability in the steam drum water level. The feedforward regulation model for the three parameters of the boiler drum water level is as follows: ， ， In the formula, D(s) represents the variable to which the differential action is applied, and α represents the parameter ratio. The function represents differential time quantization, F(s) represents the feedforward action, K represents an empirical constant with a value range of 0.8-1.5, E(s) represents the bias, P(s) represents the variable with applied proportional action, and L(s) represents the external integral input from BKCAL_IN or OUT.
4. The method for controlling a coal-fired boiler in tobacco production according to claim 1, characterized in that, The air-coal ratio adjustment model includes: A dual-parameter feedforward regulation loop for the air-coal ratio is constructed based on steam pressure. The dual-parameter feedforward regulation loop for the air-coal ratio consists of a steam drum pressure transmitter, a grate frequency converter, a grate motor, a blower frequency converter, and a blower. The steam pressure setting is input to the variable input value of the blower PID control module, and the output value of the blower PID control module is used as the pulse width modulation parameter of the blower frequency converter. The difference between the furnace front arch temperature T1 and the furnace rear arch temperature T2*k1*P*K2 is used as the input value of the grate speed PID control module, and the output value of the grate speed PID control module is used as the pulse width modulation parameter of the grate speed frequency converter. K1 is the furnace front arch temperature difference compensation coefficient with a value of 0.8-1.5, and K2 is the air-coal ratio coefficient with a value of 0.5-0.8 under the condition of ensuring full combustion of coal.
5. The method for controlling a coal-fired boiler in tobacco production according to claim 1, characterized in that, The dual-parameter feedforward regulation model for furnace negative pressure includes: The furnace negative pressure regulation circuit is composed of an induced draft variable frequency speed controller, an induced draft fan, and a furnace negative pressure transmitter. A dual-parameter feedforward control loop is adopted, with the furnace negative pressure regulation as the main control and the air volume as the feedforward proportional-integral controller. The furnace pressure setpoint is used as the PV input value of the induced draft fan PID control module, and the blower derivative value is used as the feedforward input value of the induced draft fan.
6. The method for controlling a coal-fired boiler in tobacco production according to claim 1, characterized in that, The deaerator single-parameter setpoint adjustment model includes: The automatic water level regulation loop of the deaerator consists of a deaerator feedwater regulating valve and a deaerator water level transmitter. The deaerator water level automatic control loop is a single-parameter setpoint control loop, configured as a proportional-integral controller; The deaerator pressure setpoint is used as the PV input value of the steam regulating valve PID control module. The output value of the steam regulating valve PID control module is used to control the valve position switch of the regulating valve positioner. The valve opening degree is calculated through an effective formula. The deaerator level setpoint is used as the PV input value of the inlet regulating valve PID control module. The output value of the inlet regulating valve PID control module is used to control the valve position switch of the regulating valve positioner, and the valve opening degree is calculated through an effective formula.
7. The method for controlling a coal-fired boiler in tobacco production according to claim 1, characterized in that, The boiler safety interlock control model includes: When critical parameters exceed limits during boiler operation, alarm signals are triggered. Interlock activation, cut-off functions, and filter delay settings are configured through permissions. The signal is transmitted through two levels to the interlock trigger to stop the boiler. During the boiler shutdown process, the equipment is stopped step by step according to process safety requirements. When a high liquid level alarm, a low steam drum liquid level alarm, a high main steam pressure alarm, a high main steam temperature alarm, an induced draft fan malfunction, a blower malfunction, or a feedwater pump malfunction occurs, the host computer is triggered to sequentially delay and stop the coal feeder, grate fan, blower, and induced draft fan.
8. The method for controlling a coal-fired boiler in tobacco production according to claim 1, characterized in that, The construction of the boiler DCS distributed control system includes: The boiler feedwater regulating valve, main pipe pressure transmitter, feedwater flow meter, steam flow meter, steam drum level differential pressure transmitter, frequency converter, furnace negative pressure transmitter, pressure transmitter, furnace temperature sensor and level transmitter are connected to the DCS controller through corresponding I / O cards. Through network communication technology, DCS system integration technology and configuration development technology, the detection device and human-machine interface are seamlessly connected.