CN114807590A

CN114807590A - Heating furnace-based billet heating two-stage control method and system

Info

Publication number: CN114807590A
Application number: CN202210356169.5A
Authority: CN
Inventors: 黄远凤; 张燕焕; 冯小勇; 张馨予; 刘其坤; 张永兴
Original assignee: Yunnan Tianlang Energy Technology Co ltd
Current assignee: Yunnan Tianlang Energy Technology Co ltd
Priority date: 2022-04-06
Filing date: 2022-04-06
Publication date: 2022-07-29
Anticipated expiration: 2042-04-06
Also published as: CN114807590B

Abstract

The invention discloses a heating furnace-based billet heating two-stage control method and system. The method comprises the steps of acquiring data information of a steel billet entering a furnace and state data information in the heating furnace in real time; creating an online thermal simulation mathematical model in real time according to the acquired data information; the heat supply temperature in the heating furnace is adjusted and controlled in real time by combining the online thermal simulation mathematical model; according to the heat supply quality, generating and sending a temperature steel-tapping permission signal in real time, and a system corresponding to the method; the method can realize that the heating furnace determines the optimal temperature set value of each section of the furnace according to the process change, provides the billet with qualified heating quality for the rolling mill according to the requirements of the rolling mill, namely, the furnace is operated by the most effective method to minimize the fuel consumption, thereby effectively improving the working efficiency, improving the safety, and simultaneously reducing the fuel waste and the burning loss.

Description

Heating furnace-based billet heating two-stage control method and system

Technical Field

The invention belongs to the technical field of heating furnaces, and particularly relates to a two-stage control method and a system based on heating furnace billet heating.

Background

At present, a heating furnace is a device for heating materials or workpieces to a rolling forging temperature, a mathematical model of the temperature of a steel billet in the heating furnace is generally adopted to calculate the temperature of the steel billet in a hot-rolled strip mill heating furnace, the calculation accuracy of the temperature model of the steel billet is verified through a buried couple experiment, then the calculation deviation of the model is corrected according to the experimental result, the deviation of the model calculated steel temperature is corrected, and the accuracy of the calculated temperature is enhanced.

However, in the prior art, in the process of heating the steel billet by the steel rolling heating furnace, how to control the heating temperature of the steel billet to reach the optimal temperature and discharge the steel billet out of the furnace can not be realized, and the problem of overheating in the heating process can not be generated, thereby achieving the purpose of reducing fuel waste and burning loss.

That is, at present, the heating furnace has low operating efficiency, the billet is not uniformly heated in the heating furnace, the thermal efficiency is low, and the problems of fuel waste and billet burnout are easily caused.

Therefore, the problem that how to control the heating temperature of the billet to reach the optimal temperature and discharge the billet from the furnace cannot be realized, and excessive heating in the heating process is not generated, so that the waste and burning loss of fuel are reduced. And the technical problems of low working efficiency of the heating furnace, uneven heating of the billet in the heating furnace, low thermal efficiency, easy generation of fuel waste and billet burning loss are overcome, and a billet heating two-stage control method and a billet heating two-stage control system based on the heating furnace are urgently needed to be designed and developed.

Disclosure of Invention

The first purpose of the invention is to provide a heating furnace-based billet heating two-stage control method;

the second purpose of the invention is to provide a heating furnace-based billet heating secondary control system;

the first object of the present invention is achieved by: the method specifically comprises the following steps:

acquiring data information of a steel billet entering a furnace and state data information in the heating furnace in real time;

creating an online thermal simulation mathematical model in real time according to the acquired data information;

the heat supply temperature in the heating furnace is adjusted and controlled in real time by combining the online thermal simulation mathematical model;

and generating and sending a temperature allowable tapping signal in real time according to the heat supply quality.

The second object of the present invention is achieved by: the system specifically comprises:

the acquisition unit is used for acquiring data information of the steel billets entering the furnace and state data information in the heating furnace in real time;

the model creating unit is used for creating an online thermal simulation mathematical model in real time according to the acquired data information;

the temperature regulating and controlling unit is used for regulating and controlling the heat supply temperature in the heating furnace in real time by combining the online thermal simulation mathematical model;

and the generating unit is used for generating and sending a temperature steel tapping permission signal in real time according to the heat supply quality.

The method comprises the steps of acquiring data information of a steel billet entering a furnace and state data information in the heating furnace in real time; creating an online thermal simulation mathematical model in real time according to the acquired data information; the heat supply temperature in the heating furnace is adjusted and controlled in real time by combining the online thermal simulation mathematical model; according to the heat supply quality, generating and sending a temperature steel-tapping permission signal in real time, and a system corresponding to the method; the method can realize that the heating furnace determines the optimal temperature set value of each section of the furnace according to the process change, provides the billet with qualified heating quality for the rolling mill according to the requirements of the rolling mill, namely, the furnace is operated by the most effective method to minimize the fuel consumption, thereby effectively improving the working efficiency, improving the safety, and simultaneously reducing the fuel waste and the burning loss.

Drawings

FIG. 1 is a schematic flow chart of a heating furnace-based billet heating two-stage control method of the invention;

FIG. 2 is a schematic diagram of a two-stage control system based on heating furnace billet heating according to the present invention.

Detailed Description

The invention is further illustrated in the following figures and examples in order to provide the person skilled in the art with a detailed understanding of the invention, without restricting it in any way. Any variations or modifications made in accordance with the teachings of the present invention are intended to be within the scope of the present invention.

The invention is further elucidated with reference to the drawing.

As shown in fig. 1, the invention provides a heating furnace-based billet heating two-stage control method, which specifically comprises the following steps:

s1, acquiring data information of the steel billet entering the furnace and state data information in the heating furnace in real time;

s2, creating an online thermal simulation mathematical model in real time according to the acquired data information;

s3, combining the online thermal simulation mathematical model, adjusting and controlling the heat supply temperature in the heating furnace in real time;

and S4, generating and sending a temperature steel-tapping permission signal in real time according to the heat supply quality.

The step of acquiring the data information of the steel billet entering the furnace and the state data information in the heating furnace in real time further comprises the following steps:

and S11, presetting critical billet data information and time data information.

The step of creating the online thermal simulation mathematical model in real time according to the acquired data information further comprises the following steps:

s21, generating a mathematical model operation cycle;

and S22, calculating the section temperature of the billet steel when running along the length direction of the heating furnace in real time.

and S23, calculating the flue gas flow and components on the control section of each section with heat input into the furnace.

The step of adjusting and controlling the heating temperature in the heating furnace in real time by combining the online thermal simulation mathematical model further comprises the following steps:

s31, comparing the actual temperature of the steel billet with the required optimal temperature;

s32, calculating the set values of each section of the furnace, and eliminating the deviation between the steel temperature curves in real time;

the step is combined with the online thermal simulation mathematical model to adjust and control the heat supply temperature in the heating furnace in real time, and the method also comprises the following steps:

s33, determining whether the actual billet heating profile matches the calculated optimal billet heating profile for the temperature change of each segment at the set point.

The formula of the temperature change of each section temperature on the set point and the optimal billet heating curve calculated by the calculation formula is as follows:

△T=K1*E+ K2*△E+ K3*△V+ K4*TAVE+ K5*Ez （1）

wherein, DeltaT is the temperature change of each section of temperature on a set point, and E is the weighted average temperature error of the product; delta E is the change value of the parameter E from the last to the calculation period of the process; Δ V is the variation of the actual furnace production rate from the last to the process calculation cycle; TAVE is the variation value of the actual average temperature of all steel billets in each control section from the last to the process calculation period; ez is the maximum actual error found along the length of the furnace; k1, K2, K3, K4, and K5 are constants, respectively.

In order to achieve the purpose of the scheme of the invention, the invention also provides a heating furnace-based billet heating secondary control system, which specifically comprises:

The acquisition unit is further provided with:

the presetting module is used for presetting critical billet data information and time data information;

the model creating unit is further provided with:

the first generation module is used for generating a mathematical model operation cycle;

the first calculation module is used for calculating the section temperature of the billet steel in real time when the billet steel runs along the length direction of the heating furnace;

the second calculation module is used for calculating the flue gas flow and components on the control section of each section with heat input into the furnace;

in the temperature regulation and control unit, still be provided with:

the first judgment module is used for comparing the actual temperature of the steel billet with the required optimal temperature;

and the calculation elimination module is used for calculating the set values of all the sections of the furnace and eliminating the deviation between the steel temperature curves in real time.

In the temperature regulation and control unit, still be provided with:

and the second judging module is used for judging whether the actual billet heating curve of the temperature change of each section of temperature on the set point is consistent with the calculated optimal billet heating curve.

Specifically, in the embodiment of the invention, the primary function of the 2-level super control system is related to the heating furnace 2-level super control system (RHFL 2), and the primary function of the heating furnace 2-level super control system is to determine the optimal temperature set values of each section of the furnace according to process changes and provide steel billets with qualified heating quality to the rolling mill according to the requirements of the rolling mill. I.e. the most efficient way to operate the furnace, minimizing fuel consumption.

Other functions of the furnace level 2 super control system include: providing a real-time change chart of the state in the furnace; providing real-time information of the thermal state in the furnace; recording and reporting thermotechnical historical data; historical alerts and events are exchanged with other computer systems.

The system functions are as follows: inputting rolling data; product tracking; online thermal simulation of a mathematical model; controlling heat supply of each section in the furnace; automatic delay control; a discharge request and step size function; system event and reporting records; storage and reporting of historical data; data exchange with other computers; a system management function; and operating an interface.

Inputting rolling mill data: the PDI information for each incoming billet is transmitted from the mill 2 stage system to the furnace 2 stage system where it is manually entered by the operator. The mill operator enters this information on a separate billet view. The transmission data contained is listed in the interface design description.

This data is given by the tracking function when the billet is charged into the furnace and is maintained throughout the entire process of the billet in the furnace.

Product tracking: the tracking program is responsible for displaying the state in the furnace in real time, and presetting critical billet information and time data during charging. These data are used to display the target and provide it to other level 2 systems.

The tracking function maintains information received by the level 1 materials handling system (L1 MHS).

Acquiring data information of the steel billet: PDI information of each furnace entering billet is processed through a rolling mill data input function. These data are given by the tracking system as the billet is charged and stored until the billet is discharged.

Automatic tracking operation: the trace events are formed in the L1MHS and are tabulated to accommodate the RHFL 2. Each trace event is defined by a uniform code, and when a fault occurs, the L1MHS stores the event code in a table, replacing the oldest with the newest fault. Events with relevant values are stored in corresponding data tables. An indicator is provided for indicating the storage location of most recent events in the table. The indicator is read periodically by RHFL 2-a change in the indicator value indicates that a tracking event has occurred.

The data corresponding to each tracking failure is described below. Several different trace events can be classified as follows: pre-loading operation; loading operation; operating a walking beam; discharging operation; abnormal operation; the RHFL1MCS keeps track of the billets with a unique sequence number for each billet.

Pre-charging operation: the billet is placed on a charging roller way outside a charging furnace door through a rolling mill control system. The events related to these pre-charging are communicated from the mill system to the RHFL1MCS and ultimately to the RHFL2 system.

The pre-load is used for: pre-charging positioning; modifying the pre-loading; and deleting the preloaded material.

Pre-charging positioning: the rolling mill system had a room to position two short billets (4210-. Only one long billet (6000-. Depending on the billet length, it may be positioned centrally or north or south. The value associated with this is the billet's ordinal number.

The short billet is positioned on the south side; the short billet is positioned at the north side; the long billet is positioned on the south side; the long billet is positioned in the center; the long billet is positioned on the north side.

Modifying pre-loading: once the billet has been positioned on the charging roller table, its data can be modified by the rolling mill system. Modifying the south short billet; modifying the short billet on the north side; modifying the south long billet; modifying the central long blank; modifying the north side long billet.

And (3) deleting pre-loaded materials: if a billet has been removed from the charging table, the corresponding event number data will also be removed from the furnace system.

Deleting the south short billet; deleting the short billets on the north side; deleting the south long billet; deleting the central long blank; and deleting the long billet on the north side.

And (3) charging operation: and opening a charging furnace door, pushing the steel billets on the charging roller way into the furnace by a pusher, and then closing the furnace door.

Feeding a steel billet into a furnace: the data associated with this event is the distance the pusher has advanced into the furnace. It indicates the position of the leading edge of the billet or billet just entered into the furnace. Upon receipt of a loading event signal, the tracking function initiates tracking of the position of the billet within the furnace. At this time, the thermal model will also start to calculate the temperature of the steel billet and the thermal data of the steel billet in the whole process in the furnace will be updated regularly.

The operation of the walking beam: walking beam operations include events related to the running of a steel billet within a furnace. The method comprises the following steps: the walking beam is positively circulated;

the walking beam positive circulation: when the walking beam machine completes a positive cycle, the L1MHS sends a signal to the RHFL2 tracking function to increment the position of each furnace billet based on the advance distance.

Reverse circulation of the walking beam: when the walking beam machine completes a reverse cycle, the L1MHS sends a signal to RHFL 2. The tracking function reduces the position of the billet in each furnace based on the retreat distance.

Discharging operation: the tapping operation includes events associated with tapping from the discharge area of the furnace. A tapping event signal is generated for each of the following 3 cases:

discharging a short steel billet from the north side of the furnace-discharging the short steel billet from the north side; discharging a short steel billet from the south side of the furnace-discharging from the south side; one long billet is discharged from the furnace in double rows-the north side and the south side.

Discharging at the north side: when a north-listed material signal is received, the tracking function will check whether the serial number of the discharged billet in the level 1 system is consistent with the serial number in the corresponding side tracking diagram in the furnace. If the serial numbers are consistent, the billet is discharged from the furnace. Otherwise, an alarm is generated and steel tapping cannot be performed.

Numerical value PLC sequence number

The south lists the following materials: when a south side discharge signal is received, the tracking function checks whether the serial number of the discharged steel billet in the level 1 system is consistent with the serial number of the steel billet in the south side tracking graph in the furnace. If the serial numbers are consistent, the steel billets are discharged from the furnace. Otherwise, an alarm is generated and steel tapping cannot be performed.

Discharging from the north side and the south side: when a north/south discharge signal is received, the tracking function checks whether the serial number of the discharged steel billet in the level 1 system is consistent with the serial number in the north/south tracking diagram of the discharged steel billet in the furnace. If the serial numbers are consistent, the billet is discharged from the furnace. Otherwise, an alarm is generated and steel tapping cannot be performed.

The operation behaviors are as follows: the operator can make manual corrections through the level 1 HMI data entry screen. Such operations are summarized as follows:

deleting the steel billets in the furnace; wiping off the distribution diagram in the furnace; modifying a steel billet in the furnace; and inserting a billet in the furnace.

And (3) deleting steel billets in the furnace: this operation selects a billet on the level 1 screen and eliminates it from the figure. The level 2 system also eliminates data from the level 2 graph.

Wiping off the distribution diagram in the furnace: this operation eliminates all billets from the level 1 diagram. When the level 2 system receives this event code, it also clears its profile.

Modifying steel billets in the furnace: this operation allows a level 1 operator to modify the data for a selected billet. The level 2 system will also make corresponding changes to the stored data of the billet, but will mark the billet data with unreliable markings so that the billet can only be tapped manually.

Inserting a steel billet in the furnace: this operation allows a level 1 operator to insert an entirely new billet into the level 1 map. The RHFL2 system will insert in its profile accordingly, but will mark the billet data with an unreliable mark so that the billet can only be tapped manually.

Level 2/level 1 control system trace graphs are consistent: the RHFL2 tracking function will periodically check the contents of the level 2 control system map against the profiles stored in the L1 MHS. The L1MHS diagram is regarded as a control object where a deviation exists. The RHFL2 map will be automatically corrected and any changes made will be recorded.

Online thermal simulation of a mathematical model: the primary purpose of the mathematical model is to provide the calculated temperature of the in-furnace product to the control logic function. This model can be utilized when the furnace control system is performing various control regimes as appropriate.

By comparing the actual temperature of the steel billet with the desired optimum temperature, the control logic calculates the set point for each segment of the furnace to eliminate the deviation between the two steel temperature curves.

Another purpose of the mathematical modeling function is to make a heating record appropriate for each billet, including temperature distribution and average temperature. These data are used to report the thermal state of the product.

To summarize: the heating process of the steel billet is vividly simulated by an online rectangular coordinate system mathematical model, and the mathematical model calculates the section temperature of the steel billet when the steel billet runs along the length direction of the heating furnace. The temperature distribution is obtained by solving the heat conduction through a differential method by a series of Fourier inequalities.

For each slab, the heat exchange between the furnace and the slab is calculated and is considered a function of the furnace temperature and the steel temperature.

The model theoretically considers the heat and mass transfer phenomena between the different parts of the furnace (billet, wall, roof, hearth, burners, flue gas).

The running period of the model is as follows: in addition to the initial value coefficient setting work, the entire mathematical model is run by the control system periodically every 150 seconds, which period coincides with the period selected by the entire control system.

At each calculation, the model determines how much heat has been transferred to the billet since the last calculation cycle.

A simulation time period of 150 seconds was chosen in order to ensure the following conditions: when the average value is substituted for the continuous trend value for the calculation period, the maximum variation of the analog variable involved in the calculation cycle is not too large to cause a serious error.

The calculation cycle time interval exceeds the process time that the computer requires to complete the model run and perform other tasks within the safety limits of the same cycle.

Determining the performance of the steel billet: the furnace was modeled in two rows along the length of the furnace. The temperature of each billet will depend on its position within the furnace and the furnace temperature.

The performance parameters required for each billet heating calculation are as follows: the size of the product; the position in the furnace; determining the internal temperature distribution of the steel billet before the calculation period; at the end of the last cycle, the furnace temperature at the middle position of the billet steel; chemical composition of the steel billet; charging temperature; the mathematical model uses the chemical composition of the steel billet to determine the following properties of the steel billet: density; emissivity coefficient; percent by weight of carbon; a temperature profile of dependent heat transfer; a temperature profile associated with enthalpy.

Determination of furnace temperature distribution: the model uses thermocouple readings along the length of the furnace to construct a thermal profile of the furnace from which the heat exchange between the furnace and the steel blank can be calculated. Thus, for each billet an associated furnace temperature can be found.

The temperatures of the top and bottom of each furnace were calculated along the length of the furnace. The temperature at any given point is a function of the two thermocouple readings closest to it. The system is designed for a thermocouple no-signal failure to cause a transition in the instrumentation control level. Any loss of thermocouple signal will generate an alarm and the temperature read from the nearest thermocouple in the longitudinal and vertical position at that point will be considered representative of the temperature on both sides of the furnace. Loss of both thermocouple signals at the same longitudinal and vertical position in the furnace will cause a control transition at the instrument level.

Calculation by mathematical model: calculation of gas stoichiometric ratio

And calculating the flow rate and the components of the flue gas on the control section of each section with heat input into the furnace. The actual air flow, fuel type and stoichiometric data from the fuel chemical composition table are input to the calculation formula.

Waste gas resource balance: the balancing of the individual control sections takes into account the flue gas flow through the furnace. This balance must be combined with the flue gas flow measured at each stage as the flue gas moves from the soaking section to the flue near the charging furnace doors.

Oxidation and decarburization metallurgy kinetics: the oxidation and decarburization phenomena of the slab are generally quantitatively expressed by the thickness of the iron oxide scale and the depth of decarburization on the upper and lower surfaces of the slab. The decarburization depth is defined as the thickness of the billet at which the carbon content reaches 95% of the original carbon content.

Both phenomena are controlled by diffusion movements: the oxidation means diffusion of metal particles in the oxide layer, and the decarburization means diffusion of metal particles in the decarburized layer. The oxidation and decarburization depths can be approximated by a set of differential equations describing the kinetics of the oxidation and decarburization diffusion metallurgy. The calculation formula for oxidation and decarburization is a function of the furnace atmosphere and the composition of the steel slab. It is assumed that the oxidation and decarburization depth of the slab at the charging end of the furnace is equal to zero.

Furnace-billet heat exchange: the model study simulates the heat exchange between the billet surface and the furnace temperature interpolated at the longitudinal position of the billet. In practice, there are different temperature factors inside the furnace, which are subject to heat exchange both with each other and with the billet. However, the furnace temperature readings from each thermocouple segment represent the combined results of the heat exchange between the flame, crown, hearth, flue gases and the slab there, which is a true reaction to the thermal state of the furnace. The radiative heat exchange S-B law is used in the model to represent the heat exchange from the furnace to the billet, and a constant coefficient is used in order to make the model more accurate.

More importantly, it is necessary to remember that the radiation is not merely heat exchanged by mechanical means. In fact, transmission and conduction phenomena also exist, albeit rarely, between the furnace and the steel slab. These secondary phenomena can be corrected for the effective heat input into the billet by appropriate coefficients. These values are determined when the system initiates calibration of the mathematical model.

Calculation of internal temperature: according to the fourier equation, the heat diffusion inside the steel slab can be classified into several types, where the thermal conductivity and specific heat of the steel slab are functions of temperature and steel type. These equations must account for boundary conditions such as the physical dimensions, the billet entry temperature, and the initial position of the billet in the mold, i.e., the billet loading position outside the furnace. The above mentioned boundary conditions are used as precondition, and are decomposed into finite inequalities, which can be solved digitally.

And (3) digital solving: and (3) approaching the continuous temperature distribution in the steel billet through a rectangular coordinate system difference model.

Because thermal conductivity and specific heat are not constants, the system of equations consisting of the finite difference model is not linear, but they are a function of temperature itself. Thus, the heat flow into the center point of the surface is a function of the surface temperature at these points.

Among the validated possible solution methods, a feasible method was chosen because of its good computational stability and fast characteristics and simplicity.

The method consists of the following basic calculation steps:

a. the initial instantaneous temperature of the calculation cycle is assumed to be an estimate of the steel temperature at a given time.

b. And performing combustion calculation and smoke material balance.

c. Performing calculations including the core temperature, in particular:

i. and (4) calculating the total heat exchange rate between the furnace and the steel billet.

And ii, calculating heat flow between surface elements of the furnace and each billet.

d. The heat conductivity and specific heat of the steel billet at the average temperature between different points of the central model are calculated.

e. Solving the equation system by using Gauss-Seidel iterative mode. Typically 4 iterations are sufficient.

f. The result thus calculated is taken as a new temperature value for the entire slab and subjected to a fencing test by comparing it with the previous temperature value.

g. If the receiving sword is not obtained yet, recalculation back to the origin is necessary, and the receiving sword can be obtained by repeating the recalculation for 6 or 7 times.

Initial value: when the furnace control system is first started, the mathematical model does not have a detailed position/time/temperature history for any steel billet in the furnace. From this point on, the mathematical model calculates the corrected temperatures of all the billets as they run in the furnace and are tracked for physical and thermal performance during each calculation cycle. The mathematical model has an accurate calculation of all the temperatures of the billet inside the furnace when the furnace is heat-exchanged from the beginning through a complete billet.

Hot restart of the mathematical model: if the task between restarting the model and stopping and resuming the model is not too great, then a "hot resume run" mathematical model must be provided. The billet position and temperature obtained from the last model calculation are saved until the model is restarted. This feature is very useful during system commissioning, which advantageously avoids waiting for "furnace charging" before control resumes.

Charging temperature: the charging temperature of the billet is measured when the billet is charged and is measured by an optical temperature measuring instrument positioned near the charging roller way. The measurement of the loading temperature assumes a uniform temperature distribution on the blooms and is equal to the measurement of the optical pyrometer.

Controlling heat supply of each section in the furnace: the "control logic" function determines the set point for each control section for optimal thermal control of the furnace. This is done by first determining the optimal steel temperature profile distribution in the furnace and comparing it with the actual steel temperature profile distribution obtained from the mathematical model and adjusting the set point to eliminate any deviation between the actual and optimal heating curves for the purpose of heat supply control.

The tasks of the heating furnace heat control system are as follows: the method provides the rolling mill with the steel billet with the thermal and mechanical properties meeting the requirements, reduces the fuel consumption and the oxidation/decarburization loss, and prevents the abnormal starting of equipment or the defects (such as excessive scale, burning out of refractory materials, overheating and overburning of the steel billet) related to the thermal state of the furnace.

The first difficulty in implementing such a control scheme is that the temperature inside the steel billet inside the furnace varies considerably and cannot be measured directly. Therefore, conventional control systems are based on control of alternative parameters, usually replaced by the temperatures of the sections and in some cases the surface temperature of the steel blank measured by an optical thermometer.

However, when the heating conditions are changed (such as the type of the charged billet, the yield, etc.), the internal temperatures of the charged billets vary with respect to the furnace temperature of each stage, and therefore, it is necessary to frequently adjust the set values for proper plant control. Moreover, it is difficult to determine how much and how often the set point is adjusted without long-term operational data collection and statistical analysis.

A very reliable "on-line" mathematical model that simulates the changing heating process would overcome these first difficulties and provide closed loop control by providing feedback to the actual billet internal temperature.

A second type of difficulty with continuous furnace control is achieving a reasonable balance between different control strategies to maximize throughput, minimize fuel consumption, provide for heating acceptable products, protect preheaters, reduce decarburization and oxidation losses, etc. The control principle employed by the super-control system consists in heating the billet according to a specific fuel consumption with an optimal heating profile, which is off-line and limited by these constraints.

To summarize: under the super heating control, the control logic function determines the set value of the furnace, and heats the billet in the furnace to the required tapping temperature on the premise of minimum fuel consumption and iron scale generation. This is accomplished by taking into account the mixing of the particular product, the steel grade and the desired tapping temperature.

These optimal heating profiles are stored in a computer in the form of a table which determines the desired billet temperature along the length of the furnace as a function of steel grade, charging temperature, product size and throughput.

When the supercomputer is operated, it estimates the mix of the billets in the furnace, the tapping speed and the desired final tapping temperature and selects the most appropriate heating curve for each billet in the furnace.

An on-line mathematical model determines the actual thermal state of the steel billet in the furnace along the length of the furnace. The model is calculated from the actual temperature of the billet read from the thermocouple and the position/time history of each billet as it travels in the furnace. The "follow-up" function is used both to check the steel grade and the billet mix in a given zone in order to select an appropriate optimal heating profile.

Once the actual and optimal steel temperatures are determined, the control logic function adjusts the segment set points to eliminate any deviation between the actual temperature of the billet and the desired thermal state of the incoming billet. Adjustment of the set point takes into account: planning the yield; planned and unplanned delays; actual yield; actual steel temperature; the required steel temperature; maximum safe furnace temperature gradient; this ensures that the furnace is free of either superheated or cryogenic billets at maximum thermal efficiency. Because this is an all-on-line, timely control system that can react quickly to any change in operation and adjust in the most accurate and efficient manner.

Determination of the optimal heating profile: by appropriate control of the settings of the control sections, it is possible to use a number of heating methods to accomplish the heating of the steel slab. The problem is how to select an optimal billet heating profile from a number of possibilities.

For simplicity we assume that the only important factor for optimal thermal control of the furnace is to reduce fuel consumption, without regard to other constraints. Accordingly, the temperature of the steel billet in the furnace is kept as low as possible while the temperature of the discharged steel billet is ensured to meet the heating requirement.

According to the operation of the method, the geometric center of heat supply along the length direction of the furnace is moved to the discharging end of the furnace, and a more reasonable coal gas heat supply scheme is adopted, so that the fuel consumption is fundamentally reduced.

Furthermore, this operating method minimizes various undesirable metallurgical phenomena, the dynamic properties of which are strongly affected by long-term high temperatures (e.g. decarburization and oxidation). In addition, the minimum temperature gradient between the surface temperature and the central temperature of the billet can be ensured. This reduces thermal stresses due to internal temperature gradients. Therefore, in many cases, unnecessary metallurgical phenomena and the amount of burning due to oxidation can be reduced in the same manner as the reduction of fuel consumption.

For each steel type, calculation is performed by an off-line computer according to factors such as production and the like to determine an optimal billet heating profile.

The optimal billet heating profile is stored in a database in tabular form. The optimum end-segment average temperature for the desktop display for each control segment is a function of: the size of the billet; the final product size; the charging temperature of the steel billet; yield; these optimum temperatures are entered into the database as part of the heating operation with the different steel grades, the charging temperature and the final product. They are a detailed falling temperature given in the reference heating operation table. The drop temperature value may be adjusted as described below. Any adjustments made are added to the end target billet temperature.

Location of computer controlled area: an upper preheating section; a lower preheating section; an upper heating section; a lower heating section; the north side of the upper soaking section; the south side of the upper soaking section; a fire seal section; the north side of the lower soaking section; the middle part of the lower soaking section; the south side of the lower soaking section; the control logic function divides the furnace into 3 computer control sections along the length direction; a preheating section; a heating section; a soaking section; for control purposes, the unfired section of the furnace is considered to be part of the preheat section.

At various points along the computerized control section of the furnace, the control logic functions determine the optimal billet target temperature profile.

Planned yield principle: to ensure that the system reaches a new thermal state before a change in production, the "ideal" furnace thermal control should estimate the change in production in advance. Therefore, the required optimum steel temperature must be determined by taking into account the speed at which the billet is run in the furnace to ensure that the billet is properly heated under different operating conditions. In this method, sudden changes in the steel slab in the furnace due to furnace heating of different steel grades or changes in rolling grades can be predicted by the control logic function, and the corresponding furnace thermal control can be changed prior to the actual change in the steel slab.

The standard delay time between two steel blanks is also entered into the loading information received from the original steel blank database.

The projected production is determined based on the time each billet is run in the furnace. The planning step will be set to meet the minimum mill yield or furnace yield limit (which is determined by the furnace control system from the internal tables).

And determining the target steel temperature by using the actual yield if the actual yield exceeds the planned yield for a certain number of cycles. If the actual production is lower than the planned production, the planned production is used to determine a target steel temperature. The method ensures the final heating quality of the steel billet under various production quantities.

Clearly, furnace thermal control will be optimal when the actual production equals the planned production. However, when the delay information is matched to the mill operating conditions, the method minimizes fuel consumption while meeting the required final heating quality.

It should be noted that the projected throughput is only used to determine the target temperature of the steel slab. The control equation that determines the furnace set point based on this information will correspond to the actual production.

And (3) heat supply control: as mentioned previously, heating control involves comparing the actual billet temperature profile with the optimum temperature and by controlling the segment setpoints to reduce the differences between them.

The operations performed by the control logic are based on: information directly collected by the field instrument device; the position of the billet in the furnace provided by the tracking function; the hot working and metallurgical conditions of the steel billet are provided by the mathematical model; the current characteristic parameters (physical properties and specific rolling properties) of the steel billet in the furnace; the tasks performed by this function are described in detail in the following sections.

Determination of product specifications on each section: this is done by examining the profile of the furnace constituents provided by the tracking function. The diagram includes the steel type, size, temperature charge, final product specifications, etc. corresponding to each billet in the furnace. Each steel type is composed of a group of steel billets having the same thermo-physical characteristics during heating. The optimal heating profile and the desired final heating quality for each billet are determined by retrieving the corresponding charging temperature, finished product specifications and production volume for that steel grade. Each hybrid data defined by the mathematical model and the control logic is stored on disk.

Calculation of actual and planned speeds: the furnace plan speed is determined based on information provided from the billet database. The actual speed is determined by an average calculation which is the average of the tapping speeds over several operating cycles.

Determination of the rated production rate: the "rated" production rate is determined by calculating the approximate tapping time of each billet in the furnace, depending on the actual and planned production rates, and preferably on the number and specifications of the target products. This productivity must be taken into account when determining the target heating profile for the required billet temperature.

Favorable product average temperature error calculation: the optimum product average temperature is calculated based on the following factors: the rated production rate of the billet in the furnace, the steel number of each section of billet at present, the charging temperature, the finished product specification and the rated billet tapping temperature required during tapping are adopted so as to minimize the fuel consumed when the tapping temperature is reached.

The weighted average temperature error (E) of each section of products is determined by an average error of the temperature errors of all the steel billets of each section at present. In this relationship, the load factor of each billet is determined by its previous heating pattern.

E = Σ heating operation load factor (optimum steel temperature-actual steel temperature)/∑ heating operation load factor

The temperature change Δ T of the temperature of each section at the set point is required to match the actual billet heating curve with the optimal billet heating curve calculated by the following formula:

△T=K1*E+ K2*△E+ K3*△V+ K4*TAVE+ K5*Ez （1）

here: e = product weighted average temperature error (estimated for each control segment); Δ E = change value of the parameter E from last to process calculation cycle; Δ V = the value of the change in the actual production rate of the furnace from the last to the process calculation cycle; TAVE = the variation value of the actual average temperature of all steel billets in each control section from the last to the process calculation cycle; ez = maximum actual error found along the length of the furnace (desired average temperature-actual average temperature); k1, K2, K3, K4, K5= constant.

For each control segment, a change in the set value has to be determined for each adjustment segment contained in the control segment. Each segment contains two control segments (top and bottom). The set point for each conditioning segment within a particular control segment is determined taking into account the desired temperature difference between the control segments. (temperature difference between bottom and top)

The change in the set value for each control segment in the furnace was calculated every 150 seconds. For each control segment, the adjustment is limited between the maximum and minimum allowable set points, and within the maximum variation allowed for the set values in each calculation cycle.

Heating control operation constraint conditions: such conditions that may occur are as follows: the external characteristic limit of the set value of the control section; the maximum gradient of temperature of each section.

And (3) external characteristic constraint of each set value: this constraint will ensure that the desired settings for each segment are within the specified range. If the set point required by the control logic is greater than the maximum allowable value, the set point needs to be limited in order to achieve the thermal characteristics of the furnace and the steel billet.

Similarly, the minimum temperature of each stage is limited to ensure that the furnace temperature is maintained at a minimum safe temperature and consistent with the target temperature of the steel slab.

Temperature gradient of each section: an additional control effect performed by the control logic is to control the maximum temperature gradient allowed for the temperature of the various sections. The control function is used for preventing the furnace temperature from sharply rising and falling to damage the refractory materials of the furnace body.

And (3) automatic delay control: "time delay countermeasure" is defined as a special control of the slab temperature that is taken when the slab in the furnace stops operating for any reason. The control function is accomplished by controlling the furnace settings at each stage to reduce fuel consumption and reduce the amount of iron oxide scale in the time delay process.

There are two ways to start the delay strategy: planned delays or unplanned delays. The planned delay refers to a delay that occurs after a planned or specified billet has been delivered. They usually consist of scheduled maintenance work (e.g. roll changes). Unplanned delays are those caused by unexpected faults that have caused the furnace shutdown operation.

Planned/unplanned delays: as defined in the summary, there are two basic types of latency: planned/unplanned delays.

In the scheduled delay, when to start the delay is predetermined (e.g., scheduled roll change before the discharge of a specific billet). The schedule delay information (ID code and time of production) may be entered into the billet database or received in the loading information repository. The final delay information received by the furnace control system for a particular steel slab will be considered the most important plan. For unplanned delays, unforeseeable factors will cause sudden delays (furnace shutdowns). The control logic detects that no steel billet is discharged within the specified time, and according to the information, the control logic informs an operator of the impending unplanned delay and requests the required delay time.

The required delay time cannot be precisely specified for planned and unplanned delays. To accommodate this, the system will notify the operator that the delay time is ending soon when the delay time is ending soon.

The operation is as follows: the furnace control logic operates on the same basic principles as the normal operating settings. However, the required steel temperature is lower than that calculated during normal operation.

The adjustment of the set point is known in advance for the planned delay situation. Before the time delay occurs, the control logic reduces the target steel temperature of the heating section so as to gradually reduce the heat supply of each section from the preheating section.

For the case of unplanned delays, the delay information is known only when the delay occurs. For this reason, the target steel temperature is lowered only after the delay information is manually input. However, even if the delay information is not entered, the logic control system will lower the furnace temperature set point because the temperature of the billet will be too high if the furnace heat supply is not reduced and the billet is operated according to the normal heating profile. The furnace will enter a "keep warm" model and exit the model as soon as normal production resumes.

The reduction of the steel temperature set point for planned and unplanned delays depends on the length of the delay and the maximum temperature gradient that the steel slab and refractory can withstand when the furnace is brought back to operating temperature. The temperature drop is adjusted on site and can be set to have the maximum or minimum influence on the temperature of the target billet, and the temperature set value of each section is continuously adjusted.

The furnace automatically returns to "normal operation" conditions before a prescribed recovery time. At the end of the delay, the steel temperature has risen to the desired tapping temperature.

Discharge request/speed function: when the product has reached the desired heating quality at the tapping position and is ready for tapping, the tapping request function signals a temperature at which tapping is permitted. This function also determines the maximum productivity of the furnace at which the furnace can operate normally while ensuring the required heating quality of the billets inside the furnace. The maximum production rate is displayed on the HMI for the furnace operator to view.

When the furnace is operated in automatic tapping mode, the tapping enable signal can be linked to the level 1 tapping logic.

System event/alarm logging: the furnace control system will maintain a history of alarm conditions that have been detected by the software system. These states will include problems and states of the associated process such as "level 2 system available for segment 3". The date and time of the failure occurrence is printed before the information job name is issued. A predicted maximum number of fault/alarm limits will be stored by RHF 2.

The part of the RHF2 level HMI providing the alarm display function will be described below: c-1091-a02 human-machine interface function description.

Storage and reporting of historical data:

the task of the TOT totalizer is to take care of the archiving of data for production reporting.

The following reports are provided by the level 2 control system RHF: reporting the billet data; a subject graphical report; monthly fuel usage and production summary; a production report on the same day; monthly production reports; annual production reports; and reporting the heating quality of each shift.

Data exchange with other computer systems: the level 2 super control system exchanges data with other computer systems. These systems include: a heating furnace level 1 material control system (RHFL 1 MCS); a heating furnace level 1 combustion control system (RHFL 1 CCS); a 2-stage mill computer system (other party supply); details of the level 2 hypervisor system and other computer systems may be found below.

Design function description of C-1091-A03 interface

The system management function is as follows: a system management apparatus for software development and control is provided by the ITAM together with the system. Devices and programs for starting and stopping system tasks and viewing system status are provided with the RHFL 2. All RHFL2 programs for normal operation will start automatically based on the conditions of purge and logging into the computer. The monitoring function will also automatically resume the stopped system tasks.

Operator intervention is not required to maintain system task execution under normal system operating conditions. Providing a system maintenance facility and other functions that allow for adjustments to the parameters.

Maintenance and alignment facilities: the following facilities are used by the system author only personally.

Exe or by moving an icon from desktop "MTC". The maintenance display menu screen includes a set of selection controls for each of the following displays. The operator may select one control with the mouse.

And (3) system management: heating operation data; adjusting control logic; adjusting thermal distribution; each of these displays is described below.

And (3) system management: the system management display enables the system itself to change the level 2 RHF system user information. This display is used to modify the HMI username and password.

Heating operation data: the heating operation display enables the system itself to view and program one of 200 possible heating operation methods. A heating operation includes the following data: the target temperature of the product at the discharge end at different production rates. A heating operation number for easy indexing. Priority numbers (1 to 100) for determining the importance of the billet when the slab defines a temperature. The initial rolling target temperature is achieved through the self-adaptive feedback function. Heating the billet to the minimum dwell time required for the required tapping temperature; one description describes the heating operation.

Control logic adjusts: the control logic display enables the system to view itself and to program the adjustable variables through the control logic functions. These values will affect the heating of the various sections of the furnace.

Proportionality constant-used to calculate the change of temperature setting value of each section according to the favorable billet average deviation.

Derivative constant-used to calculate the change in temperature set-point values for each segment based on the difference between the current proportional value and the previous proportional value.

Rate constant-is used to calculate the change in temperature settings for each segment based on the difference between the current furnace rate and the previous rate.

And the cold fluctuation constant is used for calculating the change of the temperature set value of each section according to the temperature deviation value of the steel billet with the lowest temperature in each section.

Maximum SP increment-the maximum rate of rise allowed for each segment temperature set point.

Maximum SP decrement-the maximum rate of descent allowed by the temperature set point for each segment.

Maximum delay slope-the rate at which the temperature set point for each segment changes as the projected delay affects each segment.

Adjusting heat distribution: the model adjustment display allows the operator to view and edit the variables used to determine the temperature distribution along the length of the furnace based on the thermocouple readings.

An operation interface: the level 2 RHFL2 operational interface is implemented on a PC keyboard and includes all of the display and required data entry functions for operating and maintaining the level 2 control system.

Hardware: the following is a list of major hardware components contained in the level 2 superordinate control system computer: 500-Mhz Pentium III CPU with 512Kb memory; 128Mb RAM; 20-Gbyte hard drive; 19 "SVGA color monitor; a 250Mb zip drive for backing up files; 1.44Mb floppy drive; keyboard, mouse 48 XCD-ROM; 10/100 Ethernet card.

Software: the following is a software listing contained in the level 2 super control system computer: microsoft Visual Studio 6.0, Professional Edition; level 1 interface software — OPC client software written by a technician; mill interface software-TCP/IP client software written by a technician; the level 2 super control system runs under the Microsoft NT Workstation version 4.0 operating system. The primary software development was written in Microsoft Visual C/C + +; HMI software development is written using Microsoft Visual Basic Professional Edition.

Claims

1. A heating furnace-based billet heating two-stage control method is characterized by comprising the following steps:

2. The method of claim 1, wherein the step of obtaining the data information of the incoming steel ingot and the data information of the status of the heating furnace in real time further comprises the steps of:

and presetting critical billet data information and time data information.

3. The heating furnace-based two-stage control method for billet heating according to claim 1, wherein the step of creating an online thermal simulation mathematical model in real time according to the acquired data information further comprises the steps of:

generating a mathematical model operation cycle;

and calculating the section temperature of the billet steel when the billet steel runs along the length direction of the heating furnace in real time.

4. The heating furnace-based billet heating secondary control method according to claim 1 or 3, wherein the step of creating an online thermal simulation mathematical model in real time according to the acquired data information further comprises the steps of: and calculating the flow rate and components of the flue gas on the control section of each section with heat input into the furnace.

5. The method of claim 1, wherein the step of adjusting and controlling the temperature of the heat supplied to the heating furnace in real time in combination with the online thermal simulation mathematical model, further comprises the steps of:

comparing the actual temperature of the steel billet with the required optimal temperature;

and calculating the set values of all the sections of the furnace, and eliminating the deviation between the steel temperature curves in real time.

6. The method of claim 1 or 5, wherein the step of adjusting and controlling the temperature of the heating furnace in real time in combination with the online thermal simulation mathematical model, further comprises the steps of:

and judging whether the temperature change of each section of temperature on the set point is consistent with the calculated optimal billet heating curve or not.

7. The method of claim 6, wherein the temperature variation of each segment at the set point is related to the optimal slab heating profile calculated by the calculation formula as follows:

△T=K1*E+ K2*△E+ K3*△V+ K4*TAVE+ K5*Ez （1）

8. A heating furnace-based billet heating secondary control system is characterized by specifically comprising:

9. The heating furnace-based billet heating secondary control system according to claim 8, wherein the acquiring unit further comprises:

the model creating unit is further provided with:

in the temperature regulation and control unit, still be provided with:

10. The heating furnace-based billet heating secondary control system according to claim 8 or 9, wherein the temperature regulation unit further comprises: