SU1296612A1 - Method for automatic control of continuous furnace temperature conditions - Google Patents

Abstract

This invention relates to the field of controlling the heating of a metal in a furnace. The purpose of the invention is to increase the productivity of the furnace and save fuel. The essence of the invention consists in the fact that pyrometer 1 continuously controls the temperature of the metal surface in the first or second heating zones of the furnace. The signal from the pyrometer 1 through the converter 2 and the secondary device 3 is fed to the control device 4, which also determines the current furnace output. The signal from the device 4 is fed to the controllers 5-9, which maintain the set temperature values in the furnace zones. When the furnace productivity decreases or rolling stops, the temperature in the furnace zones is made only if the measured metal surface temperature exceeds the permissible value determined from the condition that the specified metal temperature is reached at the furnace exit at the maximum possible metal advance rate in the furnace. 3 il. s with e yD Y: 35 th of FIG. /

Description

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The invention relates to ferrous metallurgy, in particular, to controlling the heating of a metal in a methodical process.

The purpose of the invention is to increase the productivity and fuel economy by eliminating the downtime of the complex methodically the furnace - rolling mill.

Fig. 1 shows a block diagram of an automatic control system implementing the method in Fig. 2 — graphs of the temperature of the surface and the metal (0) at the end of the initial part of the furnace and temperature in one zone of the furnace (s) before it stops. stops and after stopping the rock at a fast and med rate, respectively.

The automated control system that implements the method (FIG. 1) contains sequentially included radiation pyrometer 1, secondary measuring transducer 2, secondary device 3s control device 4, the output of which is connected to the inputs of regulators 5–9. The temperature of the metal surface at the end of the initial section of the furnace (for example, at the end of the first zone) is monitored by a radiation pyrometer 1 (figl), for example, a type of PPT, and its secondary measuring transducer 2 of type PVV, IdoMeHT, reaching the metal surface temperature of minimum 35 an allowable value of 9 at the end of the initial section of the furnace is determined using a signal device of the secondary device 3, for example, type A 542. Temperature change in the zones in accordance with the change in the furnace output is carried out by means of and Changing 5 to temperature regulators 5–9 in zones, for example, of the PH 2 type. The determination of furnace production and change of reference to regulators 5–9 is performed using a control device 4. A control device determines the furnace output continuously, and the formation of a control signal that reduces the setting of temperature controllers 5–9 begins only after receiving a permit signal from the secondary 55-bop 3 signaling device.

As permissible values of the temperature of the metal surface at the end

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the initial part of the furnace is understood to be such values at which even at the maximum subsequent rate of rolling, i.e. the maximum rate of advancement of the metal along the furnace, it still has time to heat the rest of the furnace to the desired final temperature with which it should be taken out of the furnace during rolling, using maximum permissible temperatures or maximum thermal loads in the zones.

From the definition itself, it is permissible, 1x values that not reaching these values can not begin to reduce temperatures in the zones, because if, after idleness or decline in productivity, there is a maximum rolling rate (and in practice it often happens), the metal will not have time. heat to the final temperature and it will be necessary to stop the furnaces and the heating mill, and this loss of productivity will be caused only by a control error.

On the other hand, if one chooses a lower temperature out of two permissible temperatures, then the temperature reduction in the zones will start earlier and the 3 time-averaged temperatures of the 3 zones will be lower, which will increase fuel saving, reduce metal loss in scale and the danger of metal overheating.

Thus, with a decrease in the productivity of the furnace, a corresponding decrease in temperature in the zones is most advisable to begin after heating the metal surface at the end of the initial section of the furnace to the minimum permissible value. In this case, the shutdown of the heating of the metal due to the premature decrease in temperature in the zones is excluded, and the maximum possible economic effect from control is achieved due to the decrease in temperature in the zones.

Usually, the first zone along the metal is taken as the initial section of the furnace. When measuring the temperature of the metal surface in this zone is difficult, for example, in a step furnace with step beams and an upper position of the heat exchanger, and when the aei-ibie is heated (blanks) lie with gaps, and the first zone is heated312

The temperature of the slab surface in the first zone is very uneven across the width (the edges of the slabs are heated to a much greater degree), and it is advisable to measure the temperature of the metal surface in the next zone, increasing the initial part of the furnace.

However, the initial part of the furnace can cover both the first and second (partially or fully) zones of the furnace.

An automatic control system implementing the method works as follows.

The pyrometer 1, the secondary measuring transducer 2 and the secondary device 3 continuously monitor the surface temperature of the metal 0 IB end of the initial section of the furnace. The control device 4 continuously determines the capacity of the furnace. Regulators 5-9 maintain the set temperatures in the zones. When performance decreases or rolling stops, two cases are possible.

If the stop at time t occurs during rolling at a relatively fast pace (FIG. 2) and is actual. The surface temperature of the metal 8 at the end of the initial section of the furnace is less than the minimum permissible value of 8 c, then the signal device is in an inoperative state and does not issue an enable signal to the control device 4 to generate a control signal. Therefore, regulators 5–9 still maintain the temperatures in the U zones at maximum values, although the furnace output has dropped to zero.

This situation continues until the metal is heated in such a way that its surface temperature 0 at the end of the initial section of the furnace at time t, the minimum allowable value &

At this moment, the signal device of the secondary device 3 is activated and the permitting 1st signal is issued to the control device 4, which begins to generate a correction signal. This signal, entering regulators 5–9, begins to reduce their task, and the actual temperatures U in the zones begin to decrease. After rolling resumes at time tj yn

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the equalization signal gradually decreases to zero, and the reference to the controllers 5–9 and the actual temperature in the zones respectively increase to the initial values.

If the stop occurs after rolling at a relatively slow pace (Fig. 3) and at the time t stops the temperature of the metal surface at the end of the initial section exceeds the minimum allowable value of br, then by the time the enabling signal is already raised to the control device -4 and it is immediately the control signal begins to form, and the temperatures and in the zones immediately begin to decrease. When rolling is resumed, the system works in the same way as in the first case.

Thus, the proposed method can be used both at slow and fast rolling rates without loss of productivity due to control errors, the method allows to obtain the maximum economic effect (fuel economy, reduction of metal loss in scale) from lower temperatures in zones with decrease in productivity, since this reduction is carried out immediately, as soon as the danger of loss of productivity disappears, the method is convenient to use, since it is fully automated and doesn’t Fucks systematic manual switching on and off of the control device.

Compared with the known method, the proposed method allows to increase productivity by 1-3%, which is due to the exception of the downtime of the complex methodical furnaces - rolling mill due to erroneous control.

The method is most expedient to use on large methodical furnaces of modern rolling mills when rolling row steels, for which ensuring maximum performance is of paramount importance, especially in the initial period after the start of the mill, since it is in this period that rolling is often interrupted due to equipment malfunction and control. The temperature regime of the furnaces in accordance with the change in their performance is particularly relevant and effective.

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Claims (1)

Invention Formula The method of automatic control of the temperature mode of a method furnace, including measuring the temperature of the metal surface in the first or second heating zones of the furnace, determining the productivity of the method furnace and changing the temperature in its zones depending on production-OUT, differing in that. 12 6 that, in order to improve performance and save fuel by eliminating the complex's simple setups, the furnaces are a rolling mill, while reducing the furnace productivity, the measured temperature is compared with the minimum Admissible technology value and reduces the temperature in the furnace zones when the measured temperature exceeds the minimum acceptable value. Time FIG. 2 FIG. 3 Editor K. Voloshchuk Compiled by A.Abrosimov Tehred A. Kravchuk- Proofreader S. Cherni Order 720/30 Circulation 550 Subscription VNISHI of the USSR State Committee for Inventions and Discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5 Production and printing company, Uzhgorod, Projecto st., 4 Time