JPH075980B2 - Heating furnace temperature control method - Google Patents

Description

Description: [Industrial field of application] The present invention properly adjusts the temperature of a material to be heated during unsteady operation such that extraction of the material to be heated is stopped in a heating furnace of a hot rolling line. The present invention relates to a heating furnace temperature control method for controlling.

[Conventional technology]

In the heating furnace of a normal hot rolling line, the material to be heated is rolled at least once while passing through the heating furnace by changing the rolling rolls due to restrictions such as the number of rollings per rolling roll, or stopping the rolling depending on the result of rolling pitch control. A pause was encountered and as a result extraction from the furnace was also stopped.

When operating such a heating furnace, there is an extraction stop time, but if heating is performed in a normal (steady-state) heating pattern that does not consider this stop (pause) time, the material to be heated during the extraction stop period As the temperature of the heated material increases, the temperature of the heated material extracted from the heating furnace becomes higher than the target heating temperature after the extraction is restarted, resulting in overheating, and quality deterioration due to poor accuracy of temperature control for the heated material. Not only that, but also in terms of fuel, it will be a great loss.

The simplest of such countermeasures is, as shown in FIG. 5, a control for maintaining the temperature of the material to be heated as a stop heating pattern 2 for heating with a steady heating pattern 1 and lowering the output of the burner when the extraction is stopped. Then, there is a method of controlling the temperature of the heating furnace in which the steady heating pattern 1 is restored when the extraction is restarted.

However, with this method of controlling the temperature of the heating furnace, although the material to be heated during the extraction stop can be maintained at a constant temperature, high-temperature exhaust gas is continuously discharged, and the heat loss is extremely large. Become.

As a temperature control method for a heating furnace, which is a method for further improving the problems of the temperature control method for a heating furnace shown in FIG. 5, there is, for example, the temperature control method for a heating furnace disclosed in Japanese Patent Publication No. 60-143.

The temperature control method of the heating furnace shown in this Japanese Patent Publication No. 60-143 corresponds to a steady heating pattern when the extraction is not stopped and each down time when the extraction is stopped, and
At the end of the stop time, the steady heating temperature corresponding to the stop position of the material to be heated in the furnace is reached, and a heating pattern for pause with an average heating rate slower than the steady heating pattern is set in advance, and heating with pause is performed. The material is heated along the rest heating pattern until the end of the rest time, and is heated in the steady heating pattern after the end of the rest time.

[Problems to be solved by the invention]

Since the conventional heating furnace temperature control method is performed as described above, a large number of pause heating patterns are prepared by combining the scheduled stop position of the heated material, the scheduled stop time, the steel type of the heated material, etc. There is a need to.

Even if the heat loss can be reduced, having a large number of pause heating patterns for one material to be heated in the online control is in terms of the storage capacity of the computer and the calculation speed. There were some problems such as lack of practicality.

The present invention has been made to solve the above problems, and during a non-steady operation in which the extraction of the heated material is stopped, the steady heating pattern is changed to appropriately adjust the temperature of the heated material. It is an object of the present invention to obtain a temperature control method for a heating furnace, which can reduce fuel consumption while controlling the temperature, and can speed up calculation with an electronic computer having a small storage capacity.

[Means for solving problems]

The temperature control method of the heating furnace according to the present invention, in the unsteady operation in which the extraction stop is predicted, according to the predicted stop time on the existing furnace time axis the steady heating pattern at the timing when the predicted extraction stop time is input. Of the steady heating shift pattern shifted to the extraction side and the minimum heating pattern that heats the material to be heated at the minimum heating temperature that is the constraint condition of the heating furnace, the maximum value is synthesized and the resting heating pattern is obtained. To heat.

[Action]

The heating pattern for pause determined by the temperature control method of the heating furnace in the present invention, the average heating rate is slower than the steady heating pattern in each zone on the insertion side from the extraction stop prediction zone, and on the extraction side of the extraction stop prediction zone. The material to be heated is heated to the same temperature as the steady heating pattern.

〔Example〕

 An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a flow chart for explaining a temperature control method for a heating furnace according to the present invention. In the figure, ST1 to ST7 indicate respective steps.

FIG. 2 is a block diagram showing a temperature control device for a heating furnace for carrying out the present invention. In FIG. 2, 11 is a heating pattern determination circuit for determining a heating pattern of a material to be heated based on slab information and mill line information. , 12 is a current temperature calculation circuit that calculates the current temperature of all materials to be heated in the heating furnace at each timing based on the slab information and the temperature information in the heating furnace to be described later. The heating pattern of the material to be heated output from the pattern determination circuit 11 is compared with the current temperature output from the current temperature calculation circuit 12, and the fuel for the burner described below provided in each zone (control zone) of the heating furnace is compared. Is to determine the flow rate of.

Reference numeral 14 is a heating furnace, and 15A, 15B, 15C are thermometers for detecting the temperature of each zone in the heating furnace 14, and the detected temperature is supplied to the current temperature calculation circuit 12 as temperature information.

16A, 16B and 16C indicate fuel adjusting valves, and the fuel flow rate setting circuit 13
The fuel supplied to the burners 17A, 17B and 17C provided in each zone of the heating furnace 14 is adjusted based on the output signal of the above.

3 and 4 are characteristic diagrams showing the heating pattern in the present invention. In the drawings, 21 and 24 are steady heating patterns, 22 and 25 are steady heating patterns when the extraction is stopped,
The actual heating pattern heated at 24, and the heating patterns 23 and 26 for pause when the extraction stop is scheduled.

Next, the operation will be described.

In the temperature control of the heating furnace shown in FIG. 2, normally, the heating pattern of the material to be heated without the extraction stop is
As shown in FIG. 3, the steady heating pattern 21 is determined by the heating pattern determining circuit 11 according to the furnace position, depending on the steel type of the material to be heated, the extraction target temperature and the existing furnace time at the time of entering 14. .

If the material to be heated is stopped in the j zone at the position in the furnace and heated by the steady heating pattern 21, the temperature of the material to be heated changes like the actual heating pattern 22, and the temperature at the extraction position is the target extraction. Higher than temperature. for that reason,
The temperature of the material to be heated is controlled to be lower than the temperature of the steady heating pattern 21 up to the j zone where the extraction is stopped like the resting heating pattern 23.

In each heating pattern 24-26 shown in FIG. 4, the position in the furnace on the horizontal axis of each heating pattern 21-23 shown in FIG. 3 is the furnace time.

Next, a method for obtaining the resting heating pattern 26 (23) will be described with reference to FIG.

First, assuming that the extraction stop time is Δt _x , the steady heating pattern 24 that does not consider the extraction stop during normal operation is shifted to the extraction side by the time Δt _x on the existing reactor time axis that considers the extraction stop. A heating shift pattern 26A is created.

Next, the steady heating shift pattern 26A has an extraction stop time (Δt
_Since only _x ) is shifted to the extraction side, the heating temperature of the material to be heated at the extraction end becomes the same as the heating in the steady heating pattern 24, and the accuracy of the extraction temperature is maintained.

However, since shifting the constant heating pattern 24 to the time Delta] t _x by extraction side, the heating pattern is no longer present only insertion end time Delta] t _x.

Therefore, the minimum heating pattern 26B for heating the material to be heated is determined by using the minimum heating temperature which is one of the constraints of each zone (control zone) of the heating furnace. At this time, since the existing furnace time of each zone of the heating furnace 14 is calculated, the minimum heating pattern 26B can be calculated by temperature calculation. In order to obtain this minimum heating temperature, there is a temperature in the furnace that must not be lowered below this value in each zone of the heating furnace.Therefore, this temperature in the furnace is used in the zone according to the known heat conduction equation. It is possible to solve the temperature of the material to be heated. Usually, the temperature is periodically calculated by numerical calculation by differentially expanding the heat conduction equation with the amount of heat entering the material to be heated at a constant cycle as a boundary condition. Since the in-reactor time in each zone is known, the temperature obtained by repeating this time by the cycle time for the number of times divided by the cycle time is the minimum heating temperature at the exit side of each zone. The pattern connecting the side temperatures means the minimum heating pattern 26B.

Next, both heating patterns 26A and 26B are compared on the existing furnace time axis in consideration of the extraction stop, and the heating pattern (26A or 26B) with the higher temperature at the exit side of each zone is selected and synthesized, followed by a pause. Heating pattern 26 can be determined. That is, pattern 26B
Is adopted pattern 26B in the section higher than pattern 26A,
In the section where the pattern 26A is higher than the pattern 26B, the pattern 26A is adopted, and these two patterns are the final resting heating pattern 26. In this way, the output side target temperature of each zone exists in each pattern 26A, 26B, and only a high temperature is adopted.

Further, the procedure for obtaining the resting heating pattern 26 (23) will be described with reference to FIG.

First, it is determined whether there is a new material to be heated in the heating furnace 14 (step ST1), and if there is a new material to be heated, the heating pattern is calculated based on the existing furnace time according to the conventional procedure ( Step ST2).

Next, when there is no new heated material in step ST1, and subsequent to step ST2, the extraction pitch is changed until all the heated materials existing in the heating furnace 14 are extracted based on the information from the mill line side. Determine presence / absence (STEP ST
3).

If the extraction stop is predicted, the determination is made based on the fact that the extraction pitch is extended before and after the heated material where the extraction stop occurs.

Next, if there is no change in the extraction pitch in step ST3,
Hold the heating pattern up to the last time (step ST4).

Also, if there is a change in the extraction pitch in step ST3,
As described in FIG. 4 for all the materials to be heated in the heating furnace 14, the steady heating pattern 24 is shifted to the extraction side by the time Δt _x on the existing furnace time axis considering the extraction stop prediction time, and the steady heating is performed. After the pattern 26A is determined (step ST5) and the minimum heating pattern 26B according to the minimum heating temperature of each zone is determined (step ST6), both heating patterns 26A, 26B on the exit side of each zone on the existing furnace time axis The heating pattern (26A or 26B) having the higher temperature is selected and synthesized, and the resting heating pattern 26 is determined (step ST7).

Therefore, the heating patterns for rest 23, 26 are the steady heating pattern 2 in each zone on the insertion side from the extraction stop prediction zone.
The average rate of temperature rise is slower than that of 1, 24, and the material to be heated is heated so that the extraction side of the extraction stop prediction zone has the same temperature as the steady heating patterns 21, 24.

〔The invention's effect〕

As described above, according to the present invention, the steady heating shift pattern in which the steady heating pattern is shifted to the extraction side according to the predicted stop time on the existing furnace time axis at the timing when the predicted extraction stop time is input, and the heating furnace Since the rest heating pattern is obtained by synthesizing the maximum value with the minimum heating pattern that heats the material to be heated at the minimum heating temperature that is the constraint condition of, the extraction temperature of the material to be heated during unsteady operation can be controlled accurately. At the same time, fuel consumption can be reduced and heating can be performed efficiently.

Further, the calculation of the heating pattern for pause becomes simple, so that there is an effect that the calculation of the heating pattern for pause can be speeded up even in an electronic computer having a small storage capacity.

[Brief description of drawings]

FIG. 1 is a flow chart for explaining the temperature control method of the heating furnace of the present invention, and FIG. 2 is a configuration diagram showing a temperature control device of the heating furnace for carrying out the present invention, FIGS. 3, 4 Is a characteristic diagram showing a heating pattern in the present invention, and FIG. 5 is a characteristic diagram illustrating a conventional temperature control method for a heating furnace. In the figure, 11 is a heating pattern determination circuit, 12 is a current temperature calculation circuit, 13 is a fuel flow rate setting circuit, 14 is a heating furnace, and 15A to 1A.
5C is a thermometer, 16A to 16C are fuel adjustment valves, 17A to 17C are burners, 21 and 24 are steady heating patterns, 22 and 25 are actual heating patterns, 23 and 26 are rest heating patterns, and 26A is a steady heating shift pattern. , 26B shows the lowest heating pattern. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A method for controlling a temperature of a heating furnace in which an extraction pitch is changed due to a stop of extraction of a material to be heated or the like, and in an existing furnace time that does not consider the stop of extraction, etc. at a timing when an estimated time of extraction stop is input. The corresponding steady heating pattern is a steady heating shift pattern shifted to the extraction side according to the predicted stop time on the existing furnace time axis in consideration of the extraction stop and the like, and the furnace constraint conditions in each zone of the heating furnace. A temperature control method for a heating furnace, comprising: combining a maximum value with a minimum heating pattern for heating the material to be heated at the lowest heating temperature to obtain a resting heating pattern to heat the material to be heated.