A control system and method for silicon steel normalizing heat treatment and safety interlocking

Abstract

The application discloses a control system and method for silicon steel normalizing heat treatment and safety interlocking based on a CFC function block and a PLC online mathematical model. The system comprises an oxidation-free furnace combustion execution unit, a PLC control unit, an online mathematical model module, and temperature control, burner timing control, air-fuel ratio double-cross limiting amplitude, and safety interlocking function blocks. The online mathematical model calculates the heat demand of each heating area and / or the target strip steel temperature based on the heating area parameters, the strip steel specifications, and the process data in real time, as a disturbance value and a set value participating in PID control, and supports area temperature control, strip steel temperature control, and direct actuator mode. By reasonably distributing the burner load and dynamically adjusting the gas and combustion air flow, fine combustion within the range is realized; combined with pre-blowing, gas pipeline airtightness testing, and exhaust gas and furnace pressure, safety chain monitoring, the strip steel temperature control precision and furnace temperature uniformity are improved, the energy consumption is reduced, and the production line safety and stability are improved.

Description

Technical Field

[0001] This invention belongs to the field of automated control technology for heat treatment in iron and steel metallurgy, and in particular relates to a control system and method for normalizing heat treatment and safety interlocking of silicon steel. Background Technology

[0002] In the continuous normalizing heat treatment process, non-oriented silicon steel needs to undergo multiple stages, including heating, holding, and cooling, in a non-oxidizing atmosphere to obtain stable magnetic properties and dimensional accuracy. In the normalizing heat treatment production line, the non-oxidizing furnace is a key heating equipment, typically employing a multi-heating zone arrangement and multiple sets of open flame burners to directly heat the strip steel. With the diversification of steel grades and the increase in production line cycle time, process conditions such as strip width, thickness, running speed, and coil sequence change frequently, placing higher demands on furnace temperature uniformity, strip temperature control accuracy, and combustion system safety.

[0003] In existing silicon steel normalizing heat treatment production lines, heating control mostly adopts conventional PID control or inertial pure time delay model control based on ladder diagram programs. Typically, the heating zone temperature is the primary control object, employing simple zone temperature setpoint and process value closed-loop control. Although some production lines have established certain process models in upper-level computers or offline systems, the model calculation results are often manually adjusted to adjust the setpoints, making it difficult to participate in timely and continuous field control. Existing control methods usually lack online mathematical models closely coupled with process data such as strip specifications, operating speed, weld location, and ambient temperature. This makes it impossible to calculate the heat demand of each heating zone in real time and perform feedforward compensation under conditions such as strip specification switching and speed fluctuations. This leads to strip outlet temperature overshoot and fluctuations, insufficient temperature uniformity between zones, affecting the magnetic properties and sheet quality of silicon steel, and also results in a large workload for debugging and parameter maintenance.

[0004] In terms of combustion control, traditional non-oxidizing furnace combustion systems mostly employ simple air-fuel ratio distribution or ratio control, adjusting the gas and combustion air flow rates proportionally according to the furnace load. Some systems only implement closed-loop control for gas or air flow rates, lacking closed-loop constraints on the λ value or carbon monoxide content. With changes in gas calorific value, combustion air preheating temperature, and valve characteristics, existing controls struggle to maintain a suitable air factor across different loads and temperature ranges. At lower furnace temperatures, a low air-fuel ratio can lead to combustible gas accumulation, posing safety risks; at higher furnace temperatures, a persistently high air-fuel ratio exacerbates strip surface oxidation and increases energy consumption. Furthermore, existing dual-cross-limit control systems are often simplified, lacking sufficient consideration of the theoretical flow rate corresponding to λ=1, the conversion of maximum / minimum limits, and fault diagnosis of the main and slave flow loops. The linkage protection mechanism between gas flow control and combustion air flow control is also inadequate.

[0005] In terms of system safety, traditional silicon steel normalizing heat treatment production lines rely heavily on hardware interlocks in the gas system and some decentralized software logic for safety protection. Safety conditions such as pre-purging, gas pipeline airtightness testing, exhaust system operating status, combustion air supply, carbon monoxide / λ value, zone temperature, and emergency shutdown buttons are often scattered across different logic or control units, resulting in complex interlocking relationships and unintuitive status monitoring. In some cases, only a one-time check is performed before ignition, and continuous monitoring and interlocking actions during operation are not detailed enough. Once a flow measurement failure, abnormal air-fuel ratio, exhaust system malfunction, or failure of certain hardware safety chains occurs, the existing system struggles to switch the faulty area to a safe state in a timely and accurate manner, posing certain safety hazards.

[0006] Furthermore, some existing production lines lack process optimization functions that match the characteristics of the furnaces. They cannot predict the furnace transition state based on the future production list of steel coils, making it difficult to optimize strip speed, furnace temperature settings, and production sequence while meeting process requirements such as soaking time and soaking temperature. In actual operation, they rely heavily on operator experience for adjustments, resulting in high energy consumption, frequent changes in furnace settings, and difficulty in further improving production line cycle time and equipment utilization.

[0007] Therefore, there is an urgent need for a control system and method for normalizing heat treatment and safety interlocking of silicon steel that can deeply integrate the PLC online mathematical model with the CFC functional block control, so as to improve the temperature control accuracy and temperature uniformity of strip steel while taking into account combustion efficiency, system safety and production line operation economy. Summary of the Invention

[0008] In view of this, the present invention aims to provide a control system and method for normalizing heat treatment and safety interlocking of silicon steel, so as to at least solve one of the problems in the background art.

[0009] To achieve the above objectives, the technical solution of the present invention is implemented as follows: Firstly, this solution discloses a control system for the normalizing heat treatment and safety interlocking of silicon steel, comprising: The oxidation-free furnace combustion execution unit is used to supply fuel gas and combustion air to each heating zone and exhaust exhaust gas. The PLC control unit uses CFC function blocks for graphical programming. The online mathematical model module integrated with the PLC control unit is used to calculate the target strip temperature and / or required heating heat of each heating zone in real time based on process parameters, and output the calculation results as disturbance values ​​and / or set values. The set of CFC functional blocks for temperature control and combustion control includes at least: The heating zone temperature control function block is used to perform PID calculations based on the disturbance value output by the online mathematical model module and the measured values ​​of zone temperature and / or strip temperature to obtain the zone power demand. The burner timing control function block is used to calculate the opening degree of the burner gas and combustion air pipeline regulating valves and set the corresponding air-fuel ratio λ based on the power demand of the area, the working range of the burners in the heating area and the number of burners. The dual cross-limiting function block for air-fuel ratio is used to calculate the set values ​​of gas flow rate and combustion air flow rate based on the regional power demand, excess air coefficient set value and gas calorific value, and to perform upper and lower limit control based on the actual process values ​​of combustion air flow rate and / or gas flow rate to maintain the target air factor. The set of safety interlocking (CFC) function blocks is used to monitor both hardware and software safety chains before the heating system starts up and during operation. When any safety chain condition is not met, the corresponding heating zone is switched to safety mode and combustion is shut off.

[0010] Furthermore, the online mathematical model module includes an empirical mathematical model for calculating the power of the heating zone and the strip temperature, the empirical mathematical model being based on: Heating zone parameters, including the zone's maximum heating power, actual heating power, physical dimensions, and insulation performance; Strip parameters, including strip width, thickness, running speed, and emissivity; Temperature control parameters include temperature setpoint, process value, control output, integral term and deviation. Based on the above parameters, the heat demand required for each heating zone is calculated in real time, and the heat demand is used as a disturbance value and connected to the PID temperature control loop.

[0011] Furthermore, the PLC control unit is equipped with a temperature control mode selection function, used to switch between zone temperature control mode, strip temperature control mode, and direct actuator mode, wherein: In zone temperature control mode, only the zone temperature controller is in working condition. The set value of the zone temperature controller is input by the human-machine interface or the secondary system, and the process value is collected by the zone temperature measuring device. In strip temperature control mode, both the strip temperature controller and the zone temperature controller are in operation. The output of the strip temperature controller is used to determine the set value of the zone temperature controller, and the zone temperature controller performs control based on the set value output by the strip temperature controller. In direct actuator mode, all temperature controllers stop working, and the setpoint is directly transmitted to the regional power output terminal, retaining only the temperature monitoring function.

[0012] Furthermore, the temperature control function block is configured with a disturbance value selection function DISV_SEL, which allows selection among at least three disturbance value input methods: DISV_OFF: Turns off disturbance value input, preventing the supply of disturbance values ​​to the temperature controller; DISV_MF: The disturbance value is obtained based on simplified mass flow rate calculation; DISV_EXP: The disturbance value is calculated based on the empirical mathematical model and is preferentially used for feedforward control under normal production conditions.

[0013] Furthermore, the air-fuel ratio dual-cross limiting function block controls the air factor in the following way: Based on the set excess air coefficient and the minimum air demand determined by the flue gas analysis system, the actual air factor is calculated in real time from the process values ​​of gas flow and air flow, and compared with the set air ratio. When an air factor deviation is detected, it is determined whether there is a fault in the corresponding gas flow control circuit or air flow control circuit. If a fault is detected in one flow control circuit, the air factor is kept within the allowable range by limiting the set value of the other flow control circuit. The air-fuel ratio dual cross-limiting function block further calculates the maximum and minimum limits of gas flow and air flow based on the theoretical flow corresponding to λ=1, where the maximum limit is based on a coefficient with λ greater than 1 and the minimum limit is based on a coefficient with λ less than 1.

[0014] Furthermore, the PLC control unit also includes a pre-purge control (CFC) function block, which is used to pre-purge the furnace and exhaust gas pipeline in the heating zone according to the combustion air flow and pre-purge time before the heating system is started. When the temperature of all heating zones is lower than the preset temperature and no ignition occurs within the preset time, the pre-purge program is automatically re-executed.

[0015] Furthermore, the set of security interlocking CFC functional blocks includes: The hardware security chain monitoring unit is used to monitor hardware quantities such as main gas pressure high monitoring, main gas pressure low monitoring, main gas overpressure monitoring, main gas vent valve status, ignition gas pressure high and low monitoring, ignition gas vent valve status, and hardware area temperature monitoring. The software security chain monitoring unit is used to monitor software quantities such as exhaust gas system heating interlock, combustion air supply heating interlock, carbon monoxide / λ value monitoring, and fuel gas / air ratio monitoring. When any monitoring unit of the hardware security chain or the software security chain detects an anomaly, the safety interlock CFC function block issues a shutdown command to the corresponding heating area and shuts off the gas supply to that area.

[0016] Furthermore, the PLC control unit also includes a CFC function block for controlling the exhaust gas and internal pressure of the oxidation-free furnace, used for: In normal operation mode, the furnace pressure is stabilized within the preset slightly positive pressure range by adjusting the opening of the exhaust gas valve plate and the speed of the exhaust gas fan; When the strip speed suddenly drops or a strip breakage occurs, the combustion power of the corresponding furnace section is reduced, and the exhaust gas valve plate and fan speed are automatically adjusted according to the pressure changes in the furnace to maintain a slight positive pressure in the furnace and prevent oxygen from entering the furnace chamber.

[0017] Furthermore, the PLC control unit also includes a combustion system over-temperature protection (CFC) function block, used for: When the temperature of the combustion air exceeds the first set value, the opening of the combustion air exhaust valve is controlled so that part of the combustion air bypasses the heat exchanger and enters the chimney directly, thereby cooling the heat exchanger and the combustion air. When the exhaust gas temperature exceeds the second set value, the dilution air valve plate is opened to allow ambient air to mix into the exhaust gas to reduce the exhaust gas temperature, thereby protecting the exhaust gas fan.

[0018] Furthermore, the online mathematical model module also includes an optional mathematical model for process optimization, used to achieve at least one or more of the following functions: The optimal strip speed is continuously calculated based on the set heating time and heating temperature, and this value is sent to the production line control system as the strip speed offset value. Based on the production lists of multiple steel coils to be produced, predict furnace characteristics and transition states, and calculate the optimal furnace settings to meet the production cycle time. When the strip thickness changes, the change in heat demand is compensated by adjusting the strip speed; Under the strip conversion condition, the corresponding thermal cycle curve is generated based on the homogenization time and target temperature of the strip before and after the conversion, and the furnace temperature and strip speed are dynamically adjusted. While meeting process requirements, the furnace should be operated at maximum capacity and the production sequence optimized to reduce energy consumption and minimize furnace setup changes.

[0019] Secondly, this solution discloses a control method for the normalizing heat treatment and safety interlock of silicon steel, applied to a non-oxidizing furnace normalizing heat treatment production line, including: S1. Collect process data such as strip specifications, running speed, weld position, furnace temperature, process gas flow rate, and ambient temperature, and input the process data into the PLC online mathematical model module; S2. The online mathematical model module calculates the required heating heat and / or target strip temperature for each heating zone in real time based on an empirical mathematical model, and generates corresponding disturbance values ​​and / or set values. S3. Input the disturbance value and / or set value into the heating zone temperature control function block, perform PID calculation to obtain the zone power demand, and transmit the zone power demand to the burner timing control function block. S4, the burner timing control function block calculates the opening degree of the burner gas and combustion air pipeline regulating valves according to the regional power demand, and sets the corresponding air-fuel ratio λ. S5. Input the regional power demand and excess air coefficient setting value into the air-fuel ratio dual cross-limiting function block. The air-fuel ratio dual cross-limiting function block calculates the gas flow setting value and the combustion air flow setting value based on the gas calorific value, and performs limiting processing in combination with the actual flow process value, and outputs it to the flow controller to adjust the gas valve and the combustion air valve. S6. The CFC function block of the safety interlock performs dual hardware and software monitoring of the status of the exhaust gas system, the status of the combustion air supply, the gas pressure, the carbon monoxide / λ value, the zone temperature and the status of the emergency shutdown button. The safety chain detection is performed before the heating system is started, the safety chain status is continuously monitored during operation, and the corresponding zone combustion is shut down and the zone enters the safety mode when any safety chain condition is not met.

[0020] Furthermore, prior to step S2, the following steps are also included: Before the heating system is started, the pre-purge control function block pre-purges the furnace in the heating zone and the exhaust gas pipeline from the furnace to the chimney according to the combustion air flow and pre-purge time. When it is detected that the temperature of all heating areas is lower than the preset temperature and more than the preset time has passed since the last ignition, the pre-purge step will be automatically re-executed.

[0021] Furthermore, prior to step S3, the temperature control mode is selected based on input from the operator or secondary system: When the zone temperature control mode is selected, the zone temperature controller setting value is set to the zone temperature setting value input by the human-machine interface or the secondary system. When the strip temperature control mode is selected, the strip temperature controller setpoint is set to the strip temperature setpoint input by the human-machine interface or secondary system, and the strip temperature controller output is used as the setpoint of the zone temperature controller. When the direct actuator mode is selected, the temperature controller calculation is skipped, and the set value is directly transmitted to the zone power output terminal.

[0022] Furthermore, in step S2, the online mathematical model module adopts a combination of feedforward control and feedback control: Feedforward control predicts the heat demand of strip steel based on real-time process data and generates disturbance values. Feedback control fine-tunes the temperature controller output based on actual measurements of zone temperature and / or strip temperature to reduce temperature deviation and improve temperature control stability.

[0023] Furthermore, in step S6, the safety interlock CFC functional block performs an airtightness test on the gas pipeline before the heating system is put into operation. Only when the airtightness test of the main gas pipeline and the ignition gas pipeline is passed and the exhaust gas system, combustion air supply system, main gas pressure and over-temperature protection system are all in normal condition, is it allowed to ignite the burner and put it into heating operation. During operation, when a continuous abnormal air-fuel ratio or a continuous flow measurement failure is detected, the heating zone shutdown procedure is triggered.

[0024] Compared with existing technologies, the control system and method for normalizing heat treatment and safety interlocking of silicon steel described in this invention have the following advantages: (1) This invention integrates an online mathematical model module within the PLC. Through an empirical mathematical model, it comprehensively calculates heating zone parameters (maximum heating power, actual heating power, zone size, insulation performance), strip parameters (width, thickness, running speed, emissivity), and temperature control parameters (setpoint, process value, control output, integral term, deviation), obtaining the heat demand and / or target strip temperature of each heating zone in real time. This heat demand is then used as a disturbance value and connected to the PID temperature control loop. In the temperature control function block, a disturbance value selection switch flexibly selects whether to use mass flow disturbance or empirical model disturbance, achieving an organic combination of feedforward control and feedback control. Compared to traditional control methods that rely solely on zone temperature feedback, this invention can predict heat demand in advance when strip specifications change, speed is adjusted, and ambient temperature fluctuates, reducing temperature overshoot and fluctuations, improving the stability of the strip outlet temperature and the temperature uniformity of each heating zone, thereby improving the magnetic properties and surface quality of silicon steel.

[0025] (2) The PLC control unit of the present invention has three temperature control modes in the CFC function block: zone temperature control mode, strip temperature control mode, and direct actuator mode. It can control either zone temperature or strip temperature, and can also bypass the temperature controller in the direct actuator mode during debugging or special working conditions. Each mode supports input of set values ​​through the human-machine interface and the secondary system, which facilitates coordination with the upper production line control system.

[0026] The control logic employs CFC graphical programming and a modular design based on function block sets. Functional modules such as temperature control, burner timing control, air-fuel ratio dual cross-limiting, and safety interlocks are clearly defined, and the relationships between parameters and signals are readily apparent. Compared to traditional ladder diagram implementations, this invention is more intuitive in terms of function expansion, fault diagnosis, and subsequent maintenance, reducing system maintenance costs.

[0027] (3) The burner timing control function block of the present invention calculates the opening degree of the regulating valve of the burner gas and combustion air pipeline according to the regional power demand output by the temperature controller and the working range of the number of burners, and sets the corresponding air-fuel ratio λ. By setting the burner start-up threshold and the paired start-up strategy, each burner is made to work within its effective output range as much as possible, avoiding the burner being in a state of extremely low load or frequent start-stop for a long time.

[0028] When some burners malfunction, the burner timing control function block recalculates the maximum allowable power of the area based on the number of available burners and limits the area's power to ensure safe operation even in the event of equipment failure. Compared to simply starting and stopping burners by a percentage, this invention achieves more precise heat distribution and power limitation, which is beneficial for improving combustion stability, reducing energy consumption, and minimizing mechanical and thermal stress on burners and related equipment.

[0029] (4) The air-fuel ratio dual-cross-limiting function block of the present invention takes online heat demand as input, combines the set excess air coefficient, gas calorific value and minimum air demand provided by the flue gas analysis system to calculate the gas flow setpoint and combustion air flow setpoint, and converts the maximum / minimum limits of gas and air through the theoretical flow corresponding to λ=1. This function block determines the air limit based on the actual gas flow process value and the gas limit based on the actual air flow process value, realizing bidirectional limiting in the main and slave flow control loops.

[0030] By controlling the λ value within the range of 0.9 to 1.15, a λ≈1.15 is used at lower furnace temperatures to ensure complete combustion and prevent the accumulation of combustible gas. At higher furnace temperatures and with stringent process requirements, a substoichiometric combustion with λ≈0.9 is employed to reduce strip surface oxidation. Simultaneously, supplemental air ensures complete combustion of the fuel gas. Compared to control methods that adjust the fuel gas and combustion air at a fixed ratio, this invention can dynamically adjust the air-fuel ratio under different loads and operating conditions, achieving comprehensive optimization between safe combustion, strip surface protection, and energy utilization efficiency.

[0031] (5) The present invention stabilizes the furnace pressure in a slightly positive pressure range through the exhaust gas and furnace pressure control function block, which not only prevents oxidation caused by backflow of external air, but also avoids overpressure of the furnace body. The pre-purge control function block fully purges the furnace and exhaust gas pipeline according to the combustion air flow rate and pre-purge time, and automatically re-executes the pre-purge step after a long period of shutdown, thereby improving ignition safety.

[0032] Over-temperature protection control blocks are installed for both the combustion air and exhaust gas passages. When the temperature of the combustion air at the heat exchanger outlet or the temperature at the exhaust fan outlet exceeds the protection setpoint, the temperature of the relevant parts is reduced by opening the exhaust valve or dilution air valve plate, preventing overheating damage to the heat exchanger, pipes, and fan. Compared with relying solely on simple temperature alarms and manual intervention, this invention achieves proactive protection of critical equipment through automated control, extending the service life of the equipment.

[0033] (6) The safety interlock CFC function block set of the present invention uniformly monitors multiple safety conditions such as the operating status of the exhaust gas system, combustion air supply, instrument air, main gas and ignition gas pressure, carbon monoxide / λ value, zone temperature, and emergency shutdown button. Before the heating system is started, a complete safety chain test and gas pipeline air tightness test are performed. Ignition and operation are only allowed after all hardware safety chain and software safety chain conditions are met and the air tightness test is passed.

[0034] During operation, the safety interlock function block continuously monitors the aforementioned safety conditions. When any condition is not met, or when a persistent abnormal air-fuel ratio or a persistent flow measurement failure occurs, the corresponding combustion zone is automatically shut down, and the zone is switched to safety mode. Compared with traditional solutions that distribute safety logic across multiple control modules or rely solely on hardware interlocks, this invention, through its CFC modular safety interlock design, achieves more comprehensive and visualized safety monitoring and faster, more reliable interlock actions, significantly improving the inherent safety level of the system.

[0035] (7) The online mathematical model module of this invention is not only used to calculate heat demand and strip temperature, but can also be equipped with strip speed optimization model, production prediction model, thickness change compensation model, strip conversion thermal cycle model, and output maximization and optimal production sequence model. The system can automatically calculate the optimal strip speed according to the set homogenization time and homogenization temperature, predict furnace characteristics and transition state according to the production list of multiple steel coils to be produced, generate thermal cycle curves adapted to different steel coil specifications, and operate the furnace in a manner close to the upper limit of production capacity while meeting process requirements.

[0036] Compared to relying entirely on operators' experience to adjust process parameters, this invention can reduce frequent furnace setting changes, lower energy consumption and debugging time, improve production line cycle time and equipment utilization, and facilitate the upgrading of silicon steel normalizing heat treatment production lines towards high efficiency, low consumption and intelligence. Attached Figure Description

[0037] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1This is a schematic diagram of the dual-cross control described in an embodiment of the present invention; Figure 2 This is a schematic diagram illustrating the overall control principle of the heating zone according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the temperature control principle according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the air-fuel ratio control principle according to an embodiment of the present invention; Figure 5 This is a schematic diagram of the combustion control safety interlock principle according to an embodiment of the present invention; Figure 6 This is a schematic diagram illustrating an example of NOF zone combustion control according to an embodiment of the present invention; Figure 7 This is a schematic diagram of the control logic for normalizing heat treatment and safety interlocking of silicon steel according to an embodiment of the present invention. Detailed Implementation

[0038] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0039] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention 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 the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0040] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; 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; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0041] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0042] Example 1: Overall Structure of a Control System for Normalizing Heat Treatment and Safety Interlocking of Silicon Steel This embodiment provides a control system for the normalizing heat treatment and safety interlocking of silicon steel, applied to the non-oxidizing furnace section of a continuous normalizing heat treatment production line for oriented and non-oriented silicon steel, comprising: 1. Combustion execution unit of non-oxidizing furnace The combustion execution unit of the oxidation-free furnace (NOF) includes: a combustion air supply system, including a combustion air fan, heat exchanger, combustion air valve plate, and corresponding flow measurement device; a gas supply system, including a main gas pipeline, an ignition gas pipeline, gas valves, and flow measurement device; multiple open flame burners in the furnace, each burner consisting of an ignition burner and a main burner, used to directly inject flames into the furnace; and an NOF exhaust gas system, including an exhaust gas fan, an exhaust gas valve plate, and an exhaust gas pipeline leading to the chimney. The main differences between the heating zones are the number of burners and the rated heating power. Each heating zone can be independently equipped with gas and air flow measurement and adjustment devices.

[0043] 2. PLC control unit and CFC function block program The preferred PLC control unit is the SIMATIC S7-1500 series PLC, which is used in conjunction with Siemens WinCC for monitoring and human-machine interaction. The PLC program is implemented using the CFC (Continuous Function Chart) graphical programming method.

[0044] Configure the following set of function blocks in the CFC program: heating zone temperature control function block; burner timing control (BSC) function block; air-fuel ratio double cross-limiting function block (DoubleCrossModule); exhaust gas and furnace pressure control function block; pre-purge control function block; over-temperature protection control function block; and safety interlock CFC function block set (including hardware safety chain HWSC and software safety chain SWSC).

[0045] 3. Online Mathematical Model Module The online mathematical model module is fully integrated into the PLC program and runs on the same control platform as the CFC function block. Based on an empirical mathematical model, this module receives process parameters including strip specifications, running speed, weld location, furnace temperature, process gas flow rate, and ambient temperature, and performs real-time calculations. The strip outlet temperature of each heating zone; soaking time; required heating / cooling power for each heating zone; thermal cycle curve under strip temperature control mode; strip speed offset value; and process optimization parameters such as production forecast, output maximization, and optimal production sequence.

[0046] The heat demand and / or target strip temperature output by the online mathematical model are transmitted as disturbance values ​​and / or setpoints to the corresponding CFC temperature control function block to achieve temperature control that combines feedforward and feedback.

[0047] 4. Temperature control and combustion control CFC functional block set In this embodiment, the temperature control and combustion control CFC functional block set includes at least: The heating zone temperature control function block is used to perform PID calculations based on the disturbance value output by the online mathematical model and the measured values ​​of the zone temperature and / or the strip temperature in either zone temperature control mode or strip temperature control mode, to obtain the zone power demand. The burner timing control function block is used to calculate the opening degree of the burner gas and combustion air pipeline regulating valves and set the corresponding air-fuel ratio λ according to the regional power demand, the working range and number of burners in the heating area; The air-fuel ratio dual cross-limiting function block is used to calculate the gas flow rate setting value and the combustion air flow rate setting value based on the regional power demand, the excess air coefficient setting value and the gas calorific value, and to perform upper and lower limit processing based on the actual flow process value. The set of safety interlocking (CFC) function blocks is used to dual monitor the hardware safety chain and software safety chain before the heating system starts up and during operation. If the condition of either safety chain is not met, the corresponding heating area will switch to safety mode and shut down combustion.

[0048] Example 2: Temperature control of heating zone and burner timing control The overall control principle of the heating zone is as follows: Figure 2 As shown, in this embodiment, the NOF heating system is equipped with open flame burners, and each burner is uniformly managed by the BSC burner timing control system. The core objective of the heating zone is to provide the strip with the precise heat required under the current operating conditions. The control principle of the heating zone adopts a structure of "feedforward calculation + PID control": 1. Feedforward heat calculation The heat demand is calculated in real time by the empirical mathematical model in the online mathematical model module based on the following parameters: Heating zone parameters: maximum heating power of the zone, actual heating power of the zone, physical dimensions of the heating zone, heat preservation performance, etc. Strip data: strip width, thickness, running speed, and emissivity; Temperature control parameters: setpoint SV, process value PV, control output Y, integral term I, and deviation ER.

[0049] The heat demand result given by the empirical model is used as the disturbance value DISV and connected to the PID control loop of the temperature controller of the heating area.

[0050] 2. PID Temperature Control and Disturbance Selection like Figure 3 As shown, the disturbance value selection switch DISV_SEL in the temperature control function block has the following selectable states: DISV_OFF: Disable perturbation values; DISV_MF: The disturbance value is obtained using a simplified calculation based on mass flow rate; DISV_EXP: The perturbation value is calculated using an empirical mathematical model.

[0051] Under normal production conditions, DISV_SEL is set to DISV_EXP, meaning that the disturbance value is given by the empirical model based on real-time process data. In this case, PID control only needs to compensate for small deviations, which significantly improves the system response speed and stability.

[0052] 3. Temperature control mode selection The PLC control unit has a temperature control mode selection function set in the temperature control function block, which can be used to switch between the following three modes: Mode A: Zone Temperature Control Mode A1: The set value is input by the operator through the human-machine interface; A2: The set value is input from the secondary system; In this mode, only the zone temperature controller is operational, and process values ​​are collected by thermocouples arranged within the zone.

[0053] Mode B: Strip temperature control mode B1: Strip temperature setting value is entered by the operator / HMI; B2: The strip temperature setpoint is input from the secondary system; In this mode, the strip temperature controller and the zone temperature controller work simultaneously. The strip temperature controller calculates the strip temperature based on an empirical model as the process value, and its output is used as the set value of the zone temperature controller, thereby achieving indirect control of the furnace temperature.

[0054] Mode C: Direct Executor Mode C1: The setting value is entered by the operator / HMI; C2: The set value is input from the secondary system; In this mode, all temperature controllers stop PID calculations, and the setpoints are directly transmitted to the zone power output terminal. Only the temperature monitoring function is retained for manual / semi-automatic control during debugging or under special operating conditions.

[0055] 4. Burner timing control function block The zone power demand ZONE_Y output by the temperature controller is transmitted to the burner timing control function block. In this function block, the maximum allowable power of the zone is calculated by combining the burner operating range and the total number of burners.

[0056] The formula for calculating the burner start-up threshold ON_THR is: Where: ON_THR = burner start-up threshold (unit: %, representing the percentage of area power required to start a single burner); N_BR = total number of burners installed in this heating zone; WR = burner operating range (e.g., 1:10 means the burner can operate within 10% to 100% of its rated power, and the ratio is taken as 1 / 10 in the calculation).

[0057] Based on the above calculations, the burner timing control function block ignites the burners sequentially according to the "paired start" principle, while simultaneously monitoring the operating status of each burner. If some burners malfunction, the number of available burners, BR_AVL, is calculated, and the maximum allowable power of the region, MAX_Y, is calculated using the following formula: The burner timing control function block outputs the corresponding heat demand, which is then passed as input to the air-fuel ratio dual cross-limiting function block.

[0058] Example 3: Dual Cross-Limiting Function Block for Air-Fuel Ratio and λ Control 1. λ range and control objectives The combustion control of the non-oxidizing furnace adopts an enhanced dual-cross control principle, achieving fuel gas / combustion air ratio control through a dual-cross limiting function block for the air-fuel ratio. According to process requirements, the combustion λ value of the non-oxidizing furnace in this embodiment is adjusted within the range of 0.9 to 1.15. When the furnace or exhaust gas temperature is below 750℃, λ is fixed at 1.15 to ensure complete combustion and prevent the presence of combustible gas in the furnace. When under normal process conditions or when the furnace temperature is above 750℃, the system switches to a substoichiometric combustion condition with λ≈0.9 to avoid oxidation of the strip surface. Unburned fuel gas is then re-burned with supplemental air in the afterburning zone.

[0059] 2. Working process of the dual-cross limiting function block like Figure 4 As shown, the main functions of the dual cross-limiting air-fuel ratio function block include: Based on the heat demand, the function block calculates the gas and air setpoints. It receives the regional power demand from the temperature control and burner timing control function block. Combining the set excess air coefficient, gas calorific value, and minimum air demand value provided by the flue gas analysis system, it calculates the required gas flow rate setpoint and combustion air flow rate setpoint.

[0060] The calculation of gas and air flow limits uses the theoretical flow rate corresponding to λ=1 as a benchmark to calculate the maximum and minimum limits for gas and air. When air demand is the primary factor: the actual required airflow (based on λ=1) is converted to the airflow at λ=1.1 as the maximum airflow limit; similarly, it is converted to the airflow at λ=0.9 as the minimum airflow limit.

[0061] When gas demand is the primary factor: the actual required gas flow rate (based on λ=1) is converted to the gas flow rate at λ=1.1 and used as the maximum gas limit; the gas flow rate at λ=0.9 is converted to the minimum gas limit.

[0062] In addition, the gas flow limit is calculated based on the current actual combustion air flow process value, while the combustion air flow limit is calculated based on the current actual gas flow process value, to ensure that a reasonable air factor is maintained even if there is a deviation on either side.

[0063] 3. Master-slave flow control loop and fault detection The setpoints and corresponding limits for gas and air flow rates output by the dual-cross limiting function block are transmitted to the gas flow control loop and the combustion air flow control loop. Depending on the operating conditions, one of the two flow control loops will act as the master control loop, and the other as the slave control loop. During the process of increasing heating power, the gas flow control loop takes the lead, while the air flow control loop follows. During the process of reducing heating power, the air flow control circuit takes the lead, while the gas flow control circuit follows.

[0064] The system continuously monitors the gas flow, air flow, and actual air factor. When the air factor deviates from the set range or a continuous flow measurement failure occurs, the dual cross-limiting function block of the air-fuel ratio determines whether there is a fault in the corresponding main control circuit. If a fault is confirmed in a flow control circuit, the air factor is maintained within the allowable range by limiting the set value of another flow control circuit. If necessary, the heating zone shutdown procedure is triggered.

[0065] Valve characteristic curve linearization and disturbance value calculation To improve flow control performance and response speed, the dual cross-limiting function block also linearizes the relationship between the opening degree and flow rate of the gas valve and the combustion air valve based on the valve characteristic curves measured during the commissioning phase, and uses the linearization result as the disturbance value input of the flow controller.

[0066] Because NOF uses preheated combustion air, the density of the combustion air changes with temperature, which causes changes in the valve characteristic curve. The enhanced double cross-limiting function block can also perform online verification and recalibration of the damper characteristics during operation to maintain control accuracy.

[0067] Example 4: Exhaust gas and furnace pressure control, pre-purge and over-temperature protection 1. Control of Exhaust Gas and In-Furnace Pressure in Non-Oxidizing Furnace: To ensure stable combustion and furnace safety, this embodiment includes a CFC function block for controlling exhaust gas and furnace pressure, achieving the following functions: The exhaust gas system stabilizes the furnace pressure within a slightly positive pressure range of 30–60 Pa by jointly adjusting the opening of the exhaust gas valve plate and the speed of the exhaust gas fan. This prevents oxidation caused by backflow of external air and also prevents the furnace body from being overpressurized. When the strip speed drops suddenly or abnormal conditions such as strip breakage occur, the system first reduces the combustion power in that area. If the furnace pressure changes significantly, the pressure control function block will readjust the position of the exhaust valve plate and the fan speed to ensure that the furnace is always maintained in a safe micro-positive pressure state.

[0068] 2. Pre-purge control function block Before the heating system is started, the pre-purge control function block pre-purges the furnace in the heating area and the exhaust gas pipeline from the furnace to the chimney according to the set pre-purge time and combustion air flow rate, so as to remove residual combustible gases.

[0069] The pre-purge control module in the PLC calculates the required air volume for pre-purge by monitoring the combustion air flow rate in the area and controls the opening of the combustion air valve plate to complete the purging process. At the same time, the hardware loop monitors the flow rate signal and the pre-purge time. The pre-purge step is only considered complete when the pre-purge time meets the requirements and the flow rate is within the normal range.

[0070] During furnace operation, if the temperature of all heating zones is detected to be below 750°C and more than 3600 seconds have passed since the last ignition, the pre-purge procedure will be automatically re-executed to ensure a safe furnace environment before re-ignition.

[0071] 3. Over-temperature protection control function block To prevent damage to the heat exchanger and exhaust fan due to overheating, this embodiment includes an over-temperature protection control block to ensure safe protection of the combustion air temperature and exhaust gas temperature. Combustion air over-temperature protection: The temperature of the combustion air is measured by thermocouples placed at the inlet and outlet of the heat exchanger, and the measured value is sent to the heat exchanger protection temperature controller; the set value of the heat exchanger protection temperature controller is usually in the range of 420 to 460°C; when the temperature of the combustion air exceeds the set value, the controller drives the combustion air exhaust valve plate to open, so that some high-temperature air is directly discharged into the chimney to reduce the temperature of the heat exchanger and pipeline.

[0072] Exhaust gas fan over-temperature protection: A thermocouple is installed downstream of the exhaust gas fan to measure the exhaust gas temperature and the measured value is sent to the exhaust gas fan protection temperature controller; the protection temperature setting value is generally in the range of 250 to 350℃; when the exhaust gas temperature is too high, the controller opens the dilution air valve plate to introduce cold air into the exhaust gas, reduce the exhaust gas temperature, and protect the fan and subsequent pipeline equipment.

[0073] Example 5: Safety Interlock CFC Functional Block Assembly and Airtightness Test like Figure 5 , Figure 6 As shown, the safety interlocking system in this embodiment consists of a hardware safety chain (HWSC) and a software safety chain (SWSC), which performs dual monitoring of critical safety conditions before the heating system starts up and during operation.

[0074] 1. Safety chain check before startup Before the NOF zone combustion control system is put into operation, the safety interlock function blocks shall be tested in the following order: Check whether the exhaust gas system is running and in good condition; check whether the exhaust gas system heating interlock is normal; check whether the combustion air supply system is running and in good condition; check whether the combustion air supply heating interlock is normal; check whether the instrument air supply is normal; check the status of the emergency flameout buttons on the inlet and outlet control panels; check the status of the main gas supply and whether the main gas pressure high, low, and overpressure monitoring is normal; check the status of the main gas vent valve; check the ignition gas pressure high and low monitoring and the status of the ignition gas vent valve; check whether the PLC zone temperature monitoring and hardware zone temperature monitoring are normal; check the carbon monoxide / λ value monitoring, gas / air ratio monitoring, and the overall status of the hardware safety chain.

[0075] When all the above testing conditions are met, the system allows the next step of gas pipeline airtightness testing to be performed.

[0076] 2. Gas pipeline air tightness test After the combustion heating zone is activated, the airtightness test of the main gas supply and ignition gas supply controlled by the safety interlock CFC functional block is performed: First, check whether the gas release conditions are met, including: gas timing control is ready, hardware safety chain test passed, etc.; conduct air tightness tests on the main gas pipeline and ignition gas pipeline in sequence, monitor pressure changes or leakage during the test, and release gas supply only when the test results are qualified; after the gas air tightness test is passed, burner ignition and subsequent heating operation can be started, and relevant over-temperature protection and air-fuel ratio monitoring functions are activated at the same time.

[0077] 3. Safety monitoring and interlocking actions during operation During system operation, the safety interlock CFC functional block continuously monitors safety interlock conditions such as the exhaust gas system, combustion air supply system, main combustion gas pressure, carbon monoxide / λ value, zone temperature, and emergency flameout button status. When any hardware or software safety chain condition is not met, the corresponding heating area immediately switches to safety mode, shuts off all combustion in that area, and maintains a safe purging or heat preservation state. When a persistent abnormal air-fuel ratio or a persistent flow measurement failure is detected, the heating zone shutdown procedure is triggered, and an alarm message is displayed on the human-machine interface to alert the operator and help them quickly locate the fault.

[0078] Example 6: Online Mathematical Model Module and Process Optimization Function In this embodiment, in addition to calculating the heat demand of each heating zone, strip temperature, and soaking time in real time, the PLC online mathematical model module can also enable the following optional process optimization models as needed to optimize the silicon steel normalizing heat treatment process as a whole: 1. Strip speed control model: Based on the set homogenization time and homogenization temperature, the optimal strip speed is continuously calculated and sent as the strip speed offset value to the secondary control system of the production line to maximize the production cycle while ensuring the microstructure performance.

[0079] 2. Production Forecasting Model: Based on the production list of 8-10 steel coils to be produced in the future, combined with the furnace's thermal inertia, heat preservation capacity and transition state, the model predicts the furnace temperature change trend and calculates the optimal furnace setting to meet the production cycle, thereby reducing frequent and large-scale furnace temperature adjustments.

[0080] 3. Strip thickness variation compensation model: When the strip thickness changes, the strip speed is adjusted to compensate for the change in heat demand and avoid strip temperature deviation caused by thickness change.

[0081] 4. Thermal Cycling and Strip Conversion Model: Under the strip conversion condition, the corresponding thermal cycling curve is generated based on the homogenization time and target temperature of the two strip coils. Taking into account the material specifications and emissivity changes, the furnace temperature and strip speed are dynamically adjusted to ensure the microstructure and surface quality of the two strip coils.

[0082] 5. Production Maximization Model and Optimal Production Sequence Model: Under the premise of meeting process constraints, the furnace is operated at maximum capacity, and the furnace load is brought close to the capacity limit by increasing the strip speed; at the same time, the production of steel coils with smaller furnace settings is prioritized, thereby reducing the number of furnace setting changes and reducing energy consumption.

[0083] The online mathematical model module works in conjunction with the CFC function block to enable the control system to have rapid response and process optimization capabilities, achieving high-precision, low-energy-consumption, high-scalability, and easy-to-maintain control of the normalizing heat treatment process of silicon steel.

[0084] Example 7: Operation Flow of the Control Method Based on the above system structure, the steps of the control method for normalizing heat treatment and safety interlocking of silicon steel in this embodiment during typical operation can be summarized as follows: 1. Process data acquisition and model input: Collect process data such as strip specifications (width, thickness, material), running speed, weld position, furnace temperature, process gas flow rate, and ambient temperature, and input them into the PLC online mathematical model module.

[0085] 2. Online mathematical model calculation and disturbance value generation: The online mathematical model module calculates the required heating heat and / or target strip temperature for each heating zone in real time based on the empirical mathematical model. It outputs disturbance values ​​and / or set values ​​in a feedforward manner and forms a feedforward + feedback combined control with the actual zone temperature and / or strip temperature.

[0086] 3. Temperature control and zone power demand calculation: Input the disturbance value and / or set value into the heating zone temperature control function block, perform PID calculation to obtain the zone power demand ZONE_Y, and switch between zone temperature control mode, strip temperature control mode and direct actuator mode according to the control mode input by the operator or secondary system.

[0087] 4. Burner timing control and maximum allowable power calculation for each area: The burner timing control function block controls the start and stop of the ignition burner and the main burner according to the power requirements of the area, the number of burners in the heating area and the working range of the burners, so as to ensure that the burners operate within their working range and start in pairs, thereby achieving efficient and uniform heating.

[0088] 5. Dual cross-limiting control of air-fuel ratio and λ limitation: Input the regional power demand and excess air coefficient setting value into the dual cross-limiting function block of air-fuel ratio. The block calculates the gas flow rate setting value and the combustion air flow rate setting value based on the calorific value of the gas, and performs limiting processing in combination with the actual flow process value to ensure that λ changes within the set range, thereby achieving a balance between complete combustion and strip surface protection.

[0089] 6. Safety Interlock Monitoring and Protection Actions: Before the heating system is started, the furnace and exhaust gas pipeline are pre-purged through the pre-purge control function block, and the safety interlock CFC function block completes the safety chain detection and gas pipeline air tightness test. During system operation, the exhaust gas system, combustion air supply, gas pressure, carbon monoxide / λ value, zone temperature and emergency flameout button status are monitored by both hardware and software. If any safety chain condition is not met or a continuous abnormal air-fuel ratio is detected, the corresponding zone combustion is automatically shut down and put into safety mode.

[0090] Through the above embodiments, the present invention deeply integrates the CFC-based graphical control logic with the PLC online mathematical model to form a high-precision, low-energy-consumption combustion control system and method with complete safety interlocks suitable for the normalizing heat treatment stage of oriented and non-oriented silicon steel. This can significantly improve the temperature control accuracy of strip steel and the stability and safety of production line operation.

[0091] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A control system for normalizing heat treatment and safety interlocking of silicon steel, characterized in that, include: The oxidation-free furnace combustion execution unit is used to supply fuel gas and combustion air to each heating zone and exhaust exhaust gas. The PLC control unit uses CFC function blocks for graphical programming. The online mathematical model module integrated with the PLC control unit is used to calculate the target strip temperature and / or required heating heat of each heating zone in real time based on process parameters, and output the calculation results as disturbance values ​​and / or set values. The set of CFC functional blocks for temperature control and combustion control includes at least: The heating zone temperature control function block is used to perform PID calculations based on the disturbance value output by the online mathematical model module and the measured values ​​of zone temperature and / or strip temperature to obtain the zone power demand. The burner timing control function block is used to calculate the opening degree of the burner gas and combustion air pipeline regulating valves and set the corresponding air-fuel ratio λ based on the power demand of the area, the working range of the burners in the heating area and the number of burners. The dual cross-limiting function block for air-fuel ratio is used to calculate the set values ​​of gas flow rate and combustion air flow rate based on the regional power demand, excess air coefficient set value and gas calorific value, and to perform upper and lower limit control based on the actual process values ​​of combustion air flow rate and / or gas flow rate to maintain the target air factor. The set of safety interlocking (CFC) function blocks is used to monitor both hardware and software safety chains before the heating system starts up and during operation. When any safety chain condition is not met, the corresponding heating zone is switched to safety mode and combustion is shut off.

2. The control system according to claim 1, characterized in that: The online mathematical model module includes an empirical mathematical model for calculating the power of the heating zone and the temperature of the strip steel. This empirical mathematical model is based on: Heating zone parameters, including the zone's maximum heating power, actual heating power, physical dimensions, and insulation performance; Strip parameters, including strip width, thickness, running speed, and emissivity; Temperature control parameters include temperature setpoint, process value, control output, integral term and deviation. Based on the above parameters, the heat demand required for each heating zone is calculated in real time, and the heat demand is used as a disturbance value and connected to the PID temperature control loop.

3. The control system according to claim 1, characterized in that: The PLC control unit is equipped with a temperature control mode selection function, used to switch between zone temperature control mode, strip temperature control mode, and direct actuator mode, wherein: In zone temperature control mode, only the zone temperature controller is in working condition. The set value of the zone temperature controller is input by the human-machine interface or the secondary system, and the process value is collected by the zone temperature measuring device. In strip temperature control mode, both the strip temperature controller and the zone temperature controller are in operation. The output of the strip temperature controller is used to determine the set value of the zone temperature controller, and the zone temperature controller performs control based on the set value output by the strip temperature controller. In direct actuator mode, all temperature controllers stop working, and the setpoint is directly transmitted to the regional power output terminal, retaining only the temperature monitoring function.

4. The control system according to claim 1, characterized in that: The air-fuel ratio dual-cross limiting function block controls the air factor in the following way: Based on the set excess air coefficient and the minimum air demand determined by the flue gas analysis system, the actual air factor is calculated in real time from the process values ​​of gas flow and air flow, and compared with the set air ratio. When an air factor deviation is detected, it is determined whether there is a fault in the corresponding gas flow control circuit or air flow control circuit. If a fault is detected in one flow control circuit, the air factor is kept within the allowable range by limiting the set value of the other flow control circuit. The air-fuel ratio dual cross-limiting function block further calculates the maximum and minimum limits of gas flow and air flow based on the theoretical flow corresponding to λ=1, where the maximum limit is based on a coefficient with λ greater than 1 and the minimum limit is based on a coefficient with λ less than 1.

5. The control system according to claim 1, characterized in that: The online mathematical model module also includes an optional mathematical model for process optimization, which is used to achieve at least one or more of the following functions: The optimal strip speed is continuously calculated based on the set heating time and heating temperature, and this value is sent to the production line control system as the strip speed offset value. Based on the production lists of multiple steel coils to be produced, predict furnace characteristics and transition states, and calculate the optimal furnace settings to meet the production cycle time. When the strip thickness changes, the change in heat demand is compensated by adjusting the strip speed; Under the strip conversion condition, the corresponding thermal cycle curve is generated based on the homogenization time and target temperature of the strip before and after the conversion, and the furnace temperature and strip speed are dynamically adjusted. While meeting process requirements, the furnace should be operated at maximum capacity and the production sequence optimized to reduce energy consumption and minimize furnace setup changes.

6. A control method for the normalizing heat treatment and safety interlock of silicon steel, applied to a non-oxidizing furnace normalizing heat treatment production line, characterized in that, include: S1. Collect process data such as strip specifications, running speed, weld position, furnace temperature, process gas flow rate, and ambient temperature, and input the process data into the PLC online mathematical model module; S2. The online mathematical model module calculates the required heating heat and / or target strip temperature for each heating zone in real time based on an empirical mathematical model, and generates corresponding disturbance values ​​and / or set values. S3. Input the disturbance value and / or set value into the heating zone temperature control function block, perform PID calculation to obtain the zone power demand, and transmit the zone power demand to the burner timing control function block. S4, the burner timing control function block calculates the opening degree of the burner gas and combustion air pipeline regulating valves according to the regional power demand, and sets the corresponding air-fuel ratio λ. S5. Input the regional power demand and excess air coefficient setting value into the air-fuel ratio dual cross-limiting function block. The air-fuel ratio dual cross-limiting function block calculates the gas flow setting value and the combustion air flow setting value based on the gas calorific value, and performs limiting processing in combination with the actual flow process value, and outputs it to the flow controller to adjust the gas valve and the combustion air valve. S6. The CFC function block of the safety interlock performs dual hardware and software monitoring of the status of the exhaust gas system, the status of the combustion air supply, the gas pressure, the carbon monoxide / λ value, the zone temperature and the status of the emergency shutdown button. The safety chain detection is performed before the heating system is started, the safety chain status is continuously monitored during operation, and the corresponding zone combustion is shut down and the zone enters the safety mode when any safety chain condition is not met.

7. The control method according to claim 6, characterized in that: Before step S2, the following is also included: Before the heating system is started, the pre-purge control function block pre-purges the furnace in the heating zone and the exhaust gas pipeline from the furnace to the chimney according to the combustion air flow and pre-purge time. When it is detected that the temperature of all heating areas is lower than the preset temperature and more than the preset time has passed since the last ignition, the pre-purge step will be automatically re-executed.

8. The control method according to claim 6, characterized in that: Before step S3, the temperature control mode is selected based on input from the operator or secondary system: When the zone temperature control mode is selected, the zone temperature controller setting value is set to the zone temperature setting value input by the human-machine interface or the secondary system. When the strip temperature control mode is selected, the strip temperature controller setpoint is set to the strip temperature setpoint input by the human-machine interface or secondary system, and the strip temperature controller output is used as the setpoint of the zone temperature controller. When the direct actuator mode is selected, the temperature controller calculation is skipped, and the set value is directly transmitted to the zone power output terminal.

9. The control method according to claim 6, characterized in that: In step S2, the online mathematical model module adopts a combination of feedforward control and feedback control: Feedforward control predicts the heat demand of strip steel based on real-time process data and generates disturbance values. Feedback control fine-tunes the temperature controller output based on actual measurements of zone temperature and / or strip temperature to reduce temperature deviation and improve temperature control stability.

10. The control method according to claim 6, characterized in that: In step S6, the safety interlock CFC functional block performs an airtightness test on the gas pipeline before the heating system is put into operation. Only when the airtightness test of the main gas pipeline and the ignition gas pipeline is passed and the exhaust gas system, combustion air supply system, main gas pressure and over-temperature protection system are all in normal condition, can the burner be ignited and put into heating operation. During operation, when a continuous abnormal air-fuel ratio or a continuous flow measurement failure is detected, the heating zone shutdown procedure is triggered.

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