JPS6114884B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling a rolling equipment, and particularly to power saving control in a rolling equipment having a plurality of rolling lines.

Recently, large-scale steel mills have been constructed in various places, and the power load fluctuations that occur when the various rolling mills installed in these steel mills, especially hot rolling mills, etc., are in operation are as follows:
It is very large and rapid, sometimes reaching 200MW. These power load fluctuations are so sudden that they cannot be fully controlled by feedback control systems such as AFC (automatic frequency control) installed at power companies, and even if they are controlled, they may have the opposite effect. In some cases, some kind of countermeasure was required. One of them is a predictive control method, which takes into consideration the response characteristics of the generator before the rolled material reaches the rolling mill, and uses an HMD, for example, to
In some cases, a control system such as Hot Metal Detecton (Hot Metal Detecton) that detects the movement of the material using a detector and commands the generator to increase or decrease the output is adopted, but the magnitude of the load on the rolling equipment is determined by the finished quality of the slab. Depending on the situation, the power plant must know the steelworks' production plan in advance, but this is impossible. Therefore, there is a limit to absorbing power load fluctuations caused by the rolling mill by controlling the generator, even if it is predictive control. On the other hand, the steelworks themselves usually have in-house power generation equipment installed, and the same applies to these in-house generators as to the electric power company's generators. Recently, there has been a trend toward predictive control aimed at preventing power peak cuts, etc., but compared to power company generators, it is impossible to absorb the sudden mill load fluctuations mentioned above due to capacity etc. It is.

An object of the present invention is to minimize sudden load fluctuations through operational control within a rolling facility.

In order to achieve the above object, the present invention is characterized in that the operation of the rolling equipment is controlled by the following method.

The first step is to determine the rolling schedules of multiple rolling lines in consideration of mutual power load fluctuations so as to reduce power load fluctuations for the rolling equipment as a whole.

The second purpose is to actively control the rolling bits in each rolling line so as to reduce the power load fluctuations of the entire rolling equipment.

These so-called mill pacing techniques have conventionally tended to be aimed only at rolling efficiency, but with the aim of smoothing out the power load on the entire rolling equipment, they reduce fluctuations in the total power load on the rolling equipment, and also reduce the power load itself. This is what we are trying to do.

First, an overview of a steelworks having multiple rolling lines, which is the basis of the present invention, will be described.

Generally, large steel mills have multiple hot strip mills or cold strip mills, each of which is an independent rolling line. Conventionally, scheduling has been carried out to best utilize the capacity of each mill based on supply of rolling materials to each mill and rolling pitch production plan. That is, T/H (Tonper Hour) Max rolling has been considered ideal. However, in recent years this T/
Energy costs for the entire factory based on the concept of Hmax
At present, the idea of Min is becoming more important than T/Hmax, and control such as extraction pitch control of the furnace for the purpose of energy saving is becoming more important. The present invention focuses on the power used in the entire steelworks, and in particular, the power used by rolling mills accounts for a large proportion, and the main reason for large power load fluctuations in steelworks is related to rolling mills. This invention was developed based on the study that a very large advantage could be obtained by controlling the operating schedule of the rolling mill so as to minimize this power load fluctuation.

Figure 1b shows the power load when material is rolled in a hot strip mill.
In the rough rolling mill, a load of 8 to 13 MW is applied intermittently, but in the finishing mill, the load increases rapidly in stages, and then suddenly decreases when the tip of the slab is applied to the winder. It shows. The load at this time is large, approximately 35 to 70 MW. The time required for this load to rise is approximately 10 to 20 seconds, the time required for fall to be approximately 8 to 15 seconds, and the rolling time is approximately 40 to 80 seconds, although it varies depending on the specifications of the rolling material. Also, the time it takes for the next rolled material to reach the finishing mill after the material passes through the finishing mill (hereinafter referred to as the pitch between bars) varies depending on the capacity of the roughing mill, etc., but the earliest is 6 to 7 days.
Some are about seconds. By the way, c, d in Figure 1,
As shown in e, let us consider a case where there is a separate hot strip mill line within the same steel mill and rolling is performed independently. It has been shown that in extreme cases, the finish rolling pitch becomes heavy and has the potential to further increase power load fluctuations.

For example, Figure 1c shows the power load fluctuation P ₁ when a hot tandem mill is operated as the first line.
(t) is shown. Further, FIG. 1d shows the power load fluctuation P ₂ (t) when a hot tandem mill is operated as the second line. Solid line is _P2
(t), and the dotted line indicates P ₂ (t−τ). The dotted line shows the case where the operation is shifted by τ in consideration of the load overlap with P ₁ (t). Solid line is _P2
This shows that the first and second lines are operated in exactly the same manner as in (t), that is, the first and second lines are operated on the same time schedule.

Figure 1c shows the total power load fluctuation of the above-mentioned first and second lines.The solid line shows the case where both the first and second lines are operated in the same phase, and the maximum value of the power load is the individual You can see that it has doubled. The dotted line represents the superposition of the dotted lines in FIGS. 1c and 1d. That is, the solid line indicates P ₁ (t)+P ₂ (t), and the dotted line indicates P ₁ (t)+P ₂ (t−τ).

Even in the case of the dotted line, the peak value of the power load is
Corresponds to 2P ₁ (t). Therefore, it is necessary to consider the amount of power to be supplied in advance, assuming such a worst case scenario, and it is necessary to make a contract for the amount of power to be used with sufficient margin.

Furthermore, even if a portion of the electricity is supplied through private power generation, such sudden power fluctuations inevitably lead to poor energy efficiency.

Therefore, the present invention aims to actively control the operation of the rolling mill so as to avoid such large power load fluctuations.

FIG. 1a shows an outline of the rolling line, where 1 shows a heating furnace, 2 a rough rolling mill, and 3 a finishing mill.

Next, an example in which the present invention is applied to a hot strip mill will be explained. FIG. 2 shows an embodiment in which there are two hot tandem mill lines No. 1 and No. 2, each of which can be operated independently. Now, when the material is extracted one after another from the heating furnace 21 of the No. 1 line, rolled several passes each in the rough rolling mill 22, and rolled in the finishing mill 23, similarly, the material is extracted from the heating furnace 24 of the No. 2 line, If the rolling mill 25 and the finishing mill 26 are also rolling, the power load fluctuations in the finishing mills 23 and 26 are specifically represented by time charts such as c and d in FIG.

In this case, the following can be easily inferred. That is, No.
When the time chart of the 2 lines is shifted from the current state on the time axis (τ time in the figure), the total power load fluctuation of the No. 1 and No. 2 lines (shown in e of Fig. 1).
The variation will be much smaller than before the shift. This operation of shifting on the time axis actually corresponds to shifting the extraction timing, and if the rolling time charts for No. 1 and No. 2 are predicted in advance, the temporal change in power load fluctuation can be minimized. can do. This can be done, for example, by controlling the extraction pitch of the material to be rolled from the heating furnace.

FIG. 2 shows an example where attention is paid to a finishing rolling mill, which is a cause of particularly large power load fluctuations. Material movement detectors _27-1 to 27-6 are installed on the entry side of the finishing rolling mills 23 and ₂₆ to detect the position of the material. They are provided, for example, on the exit sides of the first line heating furnace 21 and the second line heating furnace 24, on the exit sides of the first and second line rough rolling mills 22 and 25, and on the entry side of the finishing rolling mill. In this way, a bar-to-bar pitch controller on the entry side of the finishing mill is installed to detect the position of the material and control the so-called pitch between bars at a constant level from the passing of the finish-rolling material to the arrival of the next rolling material. An extraction pitch controller is provided to control the extraction timing of the rolling mill for extraction from each heating furnace. The extraction pitch controller controls the time difference τ with respect to other rolling lines, as shown in FIG. 1d, for example.

Next, the control method of the present invention will be explained. First, it is assumed that the specifications of the materials to be rolled on the No. 1 and No. 2 lines are given. Therefore, it is possible to predict and calculate the rough rolling time, finish rolling time, required electric power, etc. for each rolled material in advance.

For example, in the No. 1 rolling line, at the timing of completion of bar extraction, the power load fluctuation in the finishing mill, including the material on the line up to that point, is predicted, and P ₁ (t) in the time chart of Fig. 1c is calculated. It is possible to understand load fluctuations.

At this time, it is assumed that the power load fluctuation prediction for the No. 2 rolling line has already been made and the time chart of P ₂ (t) has been grasped. Therefore, we will consider how much the time difference τ between the material extraction timings of the No. 1 and No. 2 rolling lines should be set to reduce the time change in the total power load fluctuation.

As one of the methods, we introduce the following evaluation function.

J(τ)=1/T∫ ^T ₀ (φ(t, τ)−φ(t))
² dt Here, φ (t, τ) = W ₁ P ₁ (t) + W ₂ P ₂ (t - τ) W ₁ , W ₂ : Weighting coefficient T: Average time required from completion of extraction of rolled material to finish removal Value τ: τ _L < τ < τ _U τ _L , τ _U is a constant depending on heating furnace capacity, etc. φ(t): Target power load fluctuation function Here, find τ that minimizes J(τ). The procedure is shown, for example, in the flow diagram of FIG.

In step~1, first, the rolling material extraction pitch of the No. 1 rolling line is determined. In step~2, P ₁ (t) (first
Create a time chart (corresponding to figure c) and step~
In step 3, a composite function φ(t, τ)=W _{1 P 1 (} t)+W ₂ P ₂ (t-τ) with P 2 (t-τ) of the No. 2 rolling line is calculated.

In step~4, an evaluation function J(τ) is calculated from ψ(t, τ), the target power load fluctuation function, and φ(t). Then, in steps to 5, τ that satisfies J(τ)min is calculated for τ within the range of τ _L < τ < τ _U. step~6
Now, calculate the expected next extraction time for the No. 1 rolling line. That is, (previous bar extraction completion time + τ) becomes the next extraction time.

Then, from τ determined above, the next No.1
The extraction time of the rolling line is determined and set in the extraction pitch controller. On the other hand, at the timing when the front bar extraction of the No. 2 line is completed, the next material heating furnace extraction time of the 2nd line is determined in the same process flow and similarly set in the extraction pitch controller. (The flow in this case is from No. 1 to No. 2 in the flow in Figure 3.
The change will be from P ₁ (t) to P ₂ (t). ) Naturally, it is conceivable that the rolling may not be performed according to the originally expected time chart, so in the present invention, for example, each (No. 1 or No.
Both lines) are equipped with material movement detectors, making it possible to make corrections based on actual passing times. Specifically, it has a bar-to-bar pitch controller that controls the bar-to-bar pitch on the finishing entry side according to the flow shown in FIG. 4 so as to be constant at a preset value. That is, after step 1 (the process of creating the above-mentioned time chart prediction function (P ₁ (t) or P ₂ (t)), extraction begins as a timing for correcting the expected passage time in order to keep the pitch between bars on the finishing side constant, and the rough There are three points for passing the material on the entry side of finishing, and at each timing, each step process shown in Figure 4 is performed so that the difference between the actual passing time and the expected passing time does not disturb the constant pitch between the bars on the finishing entry side. Each step is controlling the pitch between bars on the finishing side by modifying the time chart function.
To explain in detail, in Step~1, at the timing of completion of extraction of the previous bar, the expected time of passage of each material movement detector of the next bar is calculated, and P ₁ (t) and P ₂
(t) Create a time chart.

In step~2, at the timing of the start of extraction, predictions are made based on the actual passing time and P ₁ (t) or P ₂ (t) created in step ~1 for the bar between the furnace and the finishing rolling mill entry side. Compare the predicted passing times of each detector to check whether there is a delay. If there is no delay, an extraction start is output, and if there is a delay, the extraction start time is delayed by the amount of delay.

Further, in step ~3, it is checked whether the timing of the rolled material omission signal of the rough rolling mill is delayed with respect to the bar on the rolling line. If the material in front of the rough rolling mill is delayed, the table between the rough rolling mill and the heating furnace is stopped, the bar waits for the delay time, and then the front is checked again.
If OK, start the table and advance the bar. Then, in step~4, if the material passing time at the finishing entrance side detector is delayed compared to the expected time when the material passes through the finishing rolling machine entrance side detector,
Delays the estimated passing time of all bars behind you.

If the expected time chart function is corrected by this control, the aforementioned optimal extraction pitch will be recalculated. That is, this finishing input side bar pitch controller monitors the material movement status of the line by using the material movement detectors _27-1-27- installed on the line.
If the difference between the expected passing _time obtained from the expected time chart function at each passing point and the actual passing time is within the allowable range, it is considered OK, and if it exceeds the allowable range, it is judged as OK. To do this, the process flow shown in Figure 4 is carried out to correct the expected time chart function, and at the same time, the corrected time chart function is given to the optimum extraction pitch determination device, and the predetermined evaluation function is Min.
The extraction pitch controller is made to recalculate the extraction pitch such that .

In the embodiment of the present invention, the present invention is applied to a hot strip mill whose power load fluctuations are most pronounced, but it may naturally be applied to a cold strip mill. Alternatively, although the present invention is applied to two hot strip mills, it is also applicable to a complex of two or more rolling mills.

Furthermore, although the evaluation function used in the embodiment of the present invention uses the sum of squares of the difference from the target power load, if the purpose is to avoid only the peak, it is also possible to create an extraction pitch determination logic that does not exceed the allowable peak value. It is possible.

In the present invention, the rolling schedule of the phase rolls of multiple rolling lines is determined so as to minimize the power load fluctuation of the entire rolling equipment, so that the maximum load power can be suppressed and power-saving operation can be realized.

[Brief explanation of the drawing]

Figure 1a is a schematic layout of a hot strip mill line, Figure 1b is a graph showing power load fluctuations in a hot strip mill, and Figure 1c is a graph showing the power load in a finishing mill like a hot strip mill. Show variation. Figure d shows the power load fluctuations of the hot strip mill line showing the power load fluctuation of c and another hot strip mill line. Figure e shows the TOTAL power load fluctuations of c and d, Figure 2 is a diagram explaining an embodiment of the present invention, Figure 3 is a flow diagram explaining the optimal extraction pitch determination logic of the present invention,
FIG. 4 is a flowchart illustrating the finishing bar pitch constant control process of the present invention. 21, 24...first rolling line and second rolling line heating furnace, 22,25...rough rolling mill, 23,
26... Finishing rolling mill.

Claims (1)

[Claims] 1. In a rolling facility that has a plurality of rolling lines and performs rolling, the power consumption as a function of time accompanying the rolling schedule of one rolling line is predicted and calculated, and the power consumption of the other lines with respect to the rolling schedule is calculated. For the rolling schedule, the power consumption as a function of time is sequentially predicted and calculated, and the deviation between the power consumption of the entire rolling equipment calculated for the plurality of rolling lines and the predetermined target power consumption as a function of time is calculated. is calculated as an evaluation value, the rolling schedule of the other rolling line is corrected by a rolling schedule adjustment shift time (τ) so that the evaluation value is as small as possible, and rolling is performed according to the corrected rolling schedule. A rolling equipment control method. 2. Rolling equipment control characterized in that the evaluation value as set forth in claim 1 is the root mean square value of the deviation between the power consumption of the entire rolling equipment and a predetermined target power consumption. Method. 3. A rolling equipment control method according to claim 1, characterized in that the rolling schedule shift time (τ) is determined by an adjustable extraction pitch from the heating furnace to the plurality of rolling lines.