CN120888758A - Material tracking-based furnace temperature control method for roller hearth heat treatment furnace - Google Patents
Material tracking-based furnace temperature control method for roller hearth heat treatment furnaceInfo
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- CN120888758A CN120888758A CN202511063816.3A CN202511063816A CN120888758A CN 120888758 A CN120888758 A CN 120888758A CN 202511063816 A CN202511063816 A CN 202511063816A CN 120888758 A CN120888758 A CN 120888758A
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Abstract
The invention provides a material tracking-based furnace temperature control method for a roller hearth heat treatment furnace, which comprises the steps of adding a furnace temperature feedforward section in an original temperature control area, arranging heating power controllers in a plurality of temperature control areas of a furnace inlet section, adopting a heating power control mode when the load change is greater than or equal to a set threshold value, otherwise adopting a conventional PID controller, and combining steel plate tracking data in an electrical control system with a combustion control system.
Description
Technical Field
The invention relates to the technical field of roller hearth heat treatment furnaces, in particular to a roller hearth heat treatment furnace temperature control method based on material tracking.
Background
With the rapid development of the economy in China, the demand of steel for engineering machinery is increasing. At present, the requirement of the steel plate for the high-strength engineering machinery is not matched with the existing productivity, and the steel plate for the thin-specification engineering machinery with the yield strength of over 900MPa is mainly imported. This severely restricts the development of high-end engineering machinery in China. The roller hearth heat treatment furnace is used as key equipment of a high-strength steel plate production line, and the furnace temperature control of the roller hearth heat treatment furnace has an important influence on the product quality.
The furnace temperature of the roller hearth heat treatment furnace is a control object with large hysteresis and large inertia, is difficult to control, and is interfered by a plurality of factors such as heat load change, possible fuel heat value change and the like, so that the control difficulty of the furnace temperature is higher. But the accurate control of the furnace temperature plays a vital role in the quality of the product, so that the furnace temperature control method needs to be researched to meet the furnace temperature control requirement.
The heat treatment furnace with roller bottom adopts refractory fiber, its furnace wall heat accumulating capacity is very small, and once cold steel enters a certain heat supply section in the furnace, the sudden increase of heat load will cause the abrupt decrease of the furnace temperature of the section. In particular, when using radiant tube combustion, there is a certain lag in the heat radiated into the furnace through the radiant tube wall after the fuel is burned in the tube. If the temperature PID regulator is in an automatic state, the output value of the temperature PID regulator automatically rises, and the heat supply quantity of the section is increased. As the steel sheet leaves, the heat load suddenly decreases and the furnace temperature of the section increases sharply, so that in a roller hearth heat treatment furnace for heating the steel sheet, the furnace temperature of the first few sections of the furnace greatly fluctuates. In the latter sections of the furnace, the temperature of the steel plate is raised to be relatively close to the furnace temperature, so that the disturbance to the furnace temperature is not too large, and the temperature control is relatively easy. How to control the furnace temperature of the first sections of the roller hearth heat treatment furnace as stably as possible is an urgent problem to be solved.
Disclosure of Invention
The invention aims to solve the technical problems by providing a roller hearth heat treatment furnace temperature control method based on material tracking, combining steel plate tracking data in an electric control system with a combustion control system and providing a furnace temperature feedforward control scheme.
Embodiments of the present application are implemented as follows:
The embodiment of the application provides a roller hearth heat treatment furnace temperature control method based on material tracking, which is characterized by comprising the following steps:
S 1, dividing each temperature control area according to the distance of a position designed in the earlier stage, sequentially dividing the temperature control area into each temperature control area along the length direction of the furnace from the furnace door of the furnace inlet section, numbering the temperature control areas by numbers, dividing each temperature control area into an upper furnace temperature control section and a lower furnace temperature control section, adding a heating power controller into a plurality of temperature control areas with the numbers in front, and adopting a PID controller in the subsequent temperature control areas;
Step S 2, dividing each temperature control area into a furnace temperature feedforward section and a furnace temperature control section from front to back, determining the length of the furnace temperature feedforward section according to actual conditions, adjusting the length of the furnace temperature feedforward section as a control parameter, and numbering the length of the feedforward section of the temperature control area in front longer than the length of the furnace temperature feedforward section of the subsequent temperature control area;
Step S 3, judging whether to enable the heating power controller according to the feedforward algorithm, and setting a thermal load change threshold When the thermal load changesAnd when the heat load change is higher than the threshold value, starting the heating power controller to perform feedforward compensation.
In some alternative embodiments, the furnace temperature feed forward section length in step S 2 is determined experimentally, including the following:
When the furnace temperature in the empty furnace state reaches a target set value and the furnace temperature is stabilized, the furnace temperature can be changed, and when the furnace temperature change deviates from the target temperature by more than a temperature change threshold value, the length of the steel plate entering the furnace is recorded, namely the length of a furnace temperature feedforward area in a1 st temperature control area, and the length of a furnace temperature feedforward area in a subsequent temperature control area is treated similarly.
In some alternative embodiments, the length of the steel sheet into the furnace is calculated as follows:
The position of the furnace door of the furnace entering section is defined as a position of a coordinate 0 point, the head of the steel plate is taken as a tracking point, the position of the steel plate in the furnace is marked as x 1,x1, when the position is negative, the distance from the furnace door is the distance of |x 1 | and the steel plate is not entered, when the position is not entered into the furnace, x 1 is positive, the distance from the head of the steel plate to the furnace door x 1 after the steel plate enters the furnace is the length of the steel plate, and meanwhile, the number of a temperature control area where the steel plate is judged according to the numerical value of x 1 and the length of the steel plate.
In some alternative embodiments, the thermal load of the temperature control zone described in step S3 variesThe calculation process is as follows:
In the formula, Is thatThe thermal load of the temperature control zone at the moment in time,For the temperature control zone
Summarizing coefficients, which are determined by theory, then tested by a black box and recalculated for correction,For the steven boltzmann constant,For the number of steel plates in the temperature control zone,Is thatTime of day (time)The area of the block steel plate in the temperature control area,Indicating the furnace temperature set point for that zone,Representation ofTime of day (time)The block steel plate is positioned at the average temperature of the steel plate in the area, namely the temperature of the steel plate positioned at the middle position of the temperature control area is taken,The load correction coefficient is represented and adjusted according to actual conditions.
In some alternative embodiments, the temperature of the steel plateThe calculation was performed using a one-dimensional heat conduction equation in the thickness direction as follows:
wherein, the Is the density of the steel plate,The specific heat is fixed for the steel plate under constant pressure,In order to be able to take time,Is the thermal conductivity of the steel plate,The distance from the center point of the steel plate in the thickness direction;
boundary conditions consider heat radiation and heat convection, and consider the upper and lower surfaces of the steel sheet, and the upper furnace temperature control section heat flow is calculated as follows:
wherein, the As the actual value of the furnace temperature,The surface temperature of the steel plate is the surface temperature of the steel plate,Is the convective heat transfer coefficient;
In the length direction of the steel plate, the temperatures of the plate head, the plate middle and the plate tail are calculated according to the above method and are respectively named as 、、The temperature of other positions of the steel plate is calculated according to the linear difference.
In some alternative embodiments, the temperature at other positions of the steel plate is calculated as a linear difference as follows:
the tail part of the steel plate is defined as a position 0, the head part is defined as L, the length of the steel plate is defined as L/2, and the temperature calculation of the rest points is divided into two cases:
when the point position y is more than or equal to 0 and less than or equal to y < L/2, the temperature of the point is as follows:
When the point position y meets L/2<y <≤L, the temperature of the point is:
。
in some alternative embodiments, the feed forward algorithm determination process is as follows:
When the thermal load changes Greater than or equal toThe heating power controller is started for feedforward, and the heat load output of the section is fed forwardFor the output value of PID controllerAdding to,The definition of (2) is as follows:
the thermal load at 100% output of the PID controller is defined as The value is determined at the beginning of the design of the temperature control zone, and is the maximum heating power of the burners in the temperature control zone multiplied by the number of the burners;
In order to avoid excessive load variation, a limit of load variation is set, i.e When the value is at the limit value;
Adding toIf the number is greater than 100, taking 100; Adding to If the value is smaller than 0, 0 is taken.
In some alternative embodiments, the lower furnace temperature control section takes a proportionality coefficient based on the upper furnace temperature control sectionIt is calculated that the current value, i.e.,。
The roller hearth heat treatment furnace temperature control method based on material tracking has the advantages that a furnace temperature feedforward section is added in an original temperature control area, a plurality of temperature control areas of a furnace inlet front section are provided with heating efficiency controllers, steel plate temperature calculation is conducted through tracking calculation by adopting a heat conduction equation, parameters in boundary conditions are determined through combination with black box tests, temperatures of three parts of a plate head, a plate middle and a plate tail are calculated respectively in the length direction of the steel plate, temperatures of other positions of the steel plate are calculated according to linear differences, when load change is larger than or equal to a set threshold value, a heating power control mode is adopted, otherwise conventional PID control is adopted, and the furnace temperatures of the front sections of the roller hearth heat treatment furnace are controlled stably.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the embodiments will be briefly described below, it being understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered as limiting the scope, and other related drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram illustrating the division of temperature control zones according to an embodiment of the present application;
FIG. 2 is a logic diagram of a feedforward judgment algorithm according to an embodiment of the present application.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present application more apparent, the technical solutions of the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application, and it is apparent that the described embodiments are some embodiments of the present application, but not all embodiments of the present application. The components of the embodiments of the present application generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.
Thus, the following detailed description of the embodiments of the application, as presented in the figures, is not intended to limit the scope of the application, as claimed, but is merely representative of selected embodiments of the application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
It should be noted that like reference numerals and letters refer to like items in the following figures, and thus once an item is defined in one figure, no further definition or explanation thereof is necessary in the following figures.
The features and capabilities of the present application are described in further detail below in connection with the examples.
The invention combines the steel plate tracking data in the electric control system with the combustion control system to provide a furnace temperature feedforward control scheme.
And defining the position of the furnace door of the furnace inlet section as a coordinate 0 point position, and dividing the distance of each temperature control area according to the position designed in the earlier stage. From the start of furnace entry, divide into control district 1,2,3,4 in proper order along the stove length direction. Each zone is divided into an upper furnace temperature control section and a lower furnace temperature control section.
Taking the steel plate head as a tracking point, when the position of the furnace is marked as x 1.x1 to be negative, the distance from the furnace door is represented by the residual value of |x 1 |. x 1 is positive and indicates that the steel plate head is spaced from the oven door x 1. And according to the numerical value of x 1 and the length of the steel plate, judging the temperature control area where the steel plate is positioned.
In the original furnace temperature control section 1 of the furnace inlet section, a furnace temperature feedforward section 2 (see figure 1) is added in front of each section. The heating power controller is added in the temperature control area of the furnace inlet section, and is determined according to the furnace length and the production condition, and is set to be started or not in the program, so that the operation is convenient. The first three zones are generally recommended to be started, and the subsequent temperature control zone is controlled by adopting a conventional PID.
The length of the furnace temperature feedforward section of each temperature control zone is determined according to actual conditions and is used as a parameter for adjustment in a program. The length of the furnace temperature feedforward area of the 1 st temperature control area is longer than that of the subsequent area generally, because when the steel plate enters the furnace, the steel plate can enter the furnace rapidly to reduce the overflow of the furnace gas, namely the steel plate enters the furnace at a higher running speed, and the feedforward area needs to be enlarged to ensure the time required by the load change. The length of the furnace temperature feedforward region can be determined according to experiments, firstly, the furnace temperature in an empty furnace state reaches a target set value, a typical steel plate is selected to enter the furnace after the furnace temperature is stabilized, the furnace temperature can be changed at the moment, when the furnace temperature is deviated from the target temperature by a certain temperature threshold value, the temperature is preferably 15 ℃, and the length of the steel plate entering the furnace is recorded, namely the length of the furnace temperature feedforward region in the 1 st temperature control region. Subsequent regions are treated similarly.
Every 5s (this time can also be set reasonably according to the equipment configuration), the thermal load change caused by the steel plate in the temperature control area is calculated according to the plate temperature calculated by the model temperature tracking, and the definition is as follows:
wherein, the Is thatThe thermal load of the temperature control zone at the moment in time,For the temperature control zone
Summarizing coefficients, which are determined by theory, then tested by a black box and recalculated for correction,For the steven boltzmann constant,For the number of steel plates in the temperature control zone,Is thatTime of day (time)The area of the block steel plate in the temperature control area,Indicating the furnace temperature set point for that zone,Representation ofTime of day (time)The block steel plate is positioned at the average temperature of the steel plate in the area, namely the temperature of the steel plate positioned at the middle position of the temperature control area is taken,The load correction coefficient is represented and adjusted according to actual conditions.
Steel plate temperatureThe calculation was performed using a one-dimensional heat conduction equation in the thickness direction as follows:
wherein, the Is the density of the steel plate,The specific heat is fixed for the steel plate under constant pressure,In order to be able to take time,Is the thermal conductivity of the steel plate,Is the distance of the steel plate from the center point in the thickness direction.
Boundary conditions consider heat radiation and heat convection, and consider the upper and lower surfaces of the steel sheet, and the upper furnace temperature control section heat flow is calculated as follows:
wherein, the As the actual value of the furnace temperature,The surface temperature of the steel plate is the surface temperature of the steel plate,Is the convective heat transfer coefficient;
In the length direction of the steel plate, the temperatures of the plate head, the plate middle and the plate tail are calculated according to the above method and are respectively named as 、、The temperature of other positions of the steel plate is calculated according to the linear difference.
The tail part of the steel plate is defined as a position 0, the head part is defined as L, the length of the steel plate is defined as L/2, and the temperature calculation of the rest points is divided into two cases:
when the point position y is more than or equal to 0 and less than or equal to y < L/2, the temperature of the point is as follows:
When the point position y meets L/2<y <≤L, the temperature of the point is:
。
the thermal load at 100% output of the PID controller is defined as The value is determined at the beginning of the design of the temperature control zone, and is the maximum heating power of the burners in the temperature control zone multiplied by the number of the burners.
Whether the heating power controller is enabled for the feed forward determination algorithm is shown in fig. 2.The temperature of the original furnace can be controlled accurately by the PID controller when the load changes less with time, and the heating power controller can only show the effect when the load changes more. When the thermal load changesGreater than or equal toThe heating power controller is started for feedforward, and the heat load output of the section is fed forwardOutput value HD of PID controller when heat load changesLess thanThe heating power controller is not enabled for feed forward, the thermal load output of the segmentFor the output value of PID controller,The definition of (2) is as follows:
In order to avoid excessive load variation, a limit of load variation is set, i.e When the value is at the limit value. Note that when there is no steel plate at the previous time, i.e=0。
Adding toIf the number is greater than 100, taking 100; Adding to If the value is smaller than 0, 0 is taken.
The roller hearth heat treatment furnace is divided into an upper temperature control section and a lower temperature control section, and the influence of the steel plate on the furnace temperature of the upper temperature control section and the lower temperature control section is different. The influence of the steel plate on the lower temperature PID control section is much smaller than that of the upper temperature control section due to the shielding of the furnace roller, and in the calculation, only the influence on the upper temperature control section can be calculated, and the lower temperature control section can take a proportional coefficient on the basis of the upper temperature control sectionIt is calculated that the current value, i.e.,。
Example 1
In this example, the steel sheet had a width of 1.5m, a length of 8m, a charging speed of 0.6m/s, an initial temperature of 25℃and a furnace temperature set point of 900 ℃. Wherein the sum-up coefficient of the 1 st temperature control zoneLoad correction factor of 0.50.6. The total heating power of the upper temperature control section of the 1 st temperature control zone is=900 KW. The load change threshold was 3%. The distance between the head of the steel plate and the furnace door is-2.5 m, and after 5s, the distance between the head of the steel plate and the furnace door is 0.6x5-2.5=0.5 m, so that the area of the steel plate control area is 2.5x1.5=3.75 m 2.
The temperature of the plate head at this time was 35 ℃, and the intermediate temperature of the steel plate was 25 ℃ (not charged). At this time, the liquid crystal display device,
=25+2*(6.75-4)/8*(35-25)=31.875°C
ThenThe calculation is as follows:
((900+273)^4-(31.875+273)^4)*5.67*10^(-8)*0.5/0.6/1000/900*100%=37%
37% is more than 3%, the heating power controller is started, and 37% is added on the basis of the output of the original PID controller.
The coefficient of the lower temperature control section in the 1 st temperature control area is 0.8, and then the lower temperature control section is added with 0.8 x 37% = 30% on the basis of PID output.
The final furnace temperature fluctuation is less than 30 ℃, and is obviously improved compared with the fluctuation of 90 ℃ before the scheme is implemented.
Claims (8)
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