SU1149107A1 - System for controlling fuel combustion in continuous heating furnace - Google Patents

Abstract

1. SYSTEM OF CONTROL OF COMBUSTION OF FUEL IN THE PASSING HEATING FURNACE, Including furnace temperature and fuel and air flow sensors, furnace temperature setter, temperature and ratio controls, fuel and air actuators, the first adder, the first input of which is connected to the furnace temperature setpoint, and the output is with a temperature regulator, and the second adder, the first input of which is connected to the code of the fuel consumption sensor, the second input is via a corrector with the output of the fuel regulator, the third input is from the output m of the air flow sensor, and the output of the second adder is connected to a ratio controller, which is different in order to increase the regulation accuracy, it additionally contains soda, holds a furnace effective temperature detection unit, a furnace temperature period fluctuation unit, a furnace advance sensor, a generator clock pulses, an analog-to-digital converter and a digital-analog converter, with the first input of the unit for determining the effective temperature of the furnace connected. through an analog-to-digital converter with an output of a furnace temperature sensor, a second input with an output of a furnace for determining the period of temperature oscillations of the furnace, a third input for an output of a clock generator, and an output of a furnace for determining the effective temperature of a furnace is connected via a digital-analog converter to a second input of the first adder, (L above the input of the block for determining the period of oscillations of the furnace temperature is connected to the output of the sensor moving the workpieces in the furnace, and the second input is connected to the output of the clock pulse generator. 2. System ma pop.1, characterized in that the furnace's effective temperature determination unit contains re; the displacement shear, the decoder, the OR elements, the controlled valves, the adder and the pressure element, the output of which is connected to the code of the effective furnace temperature determining unit, the first input This block is connected to the information input of the first shift register, the second input is connected to the input of the decoder and the first input of the division element, and the third input of the block for determining the average temperature of the furnace is connected to the control inputs of the registers, the shift connected x interconnected in series on the Information ka Nala, the outputs of the decoder (except for

Description

last) are connected to the first inputs of the OR elements, the output of each of which is connected to the second input of the previous OR element and to the control input of the corresponding controlled valve; the last output of the decoder is connected directly to the second input of the last OR element and to the control input of the last controlled valve , the information input of each of the controlled gates is connected to the output of the corresponding shift register, and its output is connected to one of the inputs of the adder, the output of which is connected to the second input. .

3. System pop.1, I differ from the fact that the block is defined 49107

The lingering period of the furnace temperature fluctuations contains a pulse counter, a shift register, a limiter and a setpoint for the maximum permissible oscillation period, the output of which is connected to the second limiter input, the first input of the furnace temperature period oscillation unit is connected to the input of the pulse counter reset input, and the second block input - with the information input of the pulse counter, the information input of the shift register is connected to the output of the pulse counter, and its output - with the first input of the limiter , The output of which is connected to the output of the unit for determining the period of oscillation of the temperature of the furnace.

one

The invention relates to the automatic regulation of the combustion process of fuel and can be used in ferrous and non-ferrous metallurgy in automating the control of passage heating furnaces.

A system for regulating the combustion of fuel is known, which maintains the furnace temperature at a given level and the ratio between the consumption of fuel and air supplied to the working space. The system contains temperature and flow rate sensors for fuel and air, temperature and ratio controls, and actuators for fuel and air supply lj.

A distinctive feature of the combustion control systems is the sequential nature of the operation of temperature controllers and the ratio in transient conditions, which is caused by compaction made by fuel and air flow sensors into the system. The resulting large dynamic errors in the regulation of the ratio lead either to underburning of the fuel in case of its excess, or to an increased increase in scale - on the surface of the heated metal in

If there is an excess of supplied air, i.e. the quality of heating and quality of fuel combustion decreases.

A combustion control system is known that includes furnace temperature and fuel and air flow meters, fuel and air flow correction devices, temperature and ratio controls, and actuators for the fuel and air supply.

In this system, the redistribution of the sequence of operation of the temperature regulators and the ratio depending on the sign of deviation from the furnace temperature is organized. In this case, in the case of a decrease in temperature, the ratio controller is the master, and the slave controller is the temperature controller, and, conversely, as the temperature rises, the controller is the temperature controller, and the slave controller is the ratio controller. As a result, only excess air takes place in the combustion zone in transient conditions. Thus, the disadvantage of this system is insufficient regulation quality, since the system does not provide the required ratio between fuel consumption.

and air in transient conditions, which is uneconomical.

Closest to the invention, in technical terms, is a combustion control system in which the reduction of dynamic adjustment errors is achieved by simultaneously moving the fuel and air actuators when the furnace temperature deviates from the reference.

The system contains furnace temperature and fuel and air flow sensors, furnace temperature setting unit, temperature and ratio controllers, fuel and air supply mechanisms, the first adder, the first input of which is connected to the furnace temperature setting unit, and the output is connected to the temperature controller, and the second an adder, the first input of which is connected to the output of the fuel consumption sensor, the second input - via a corrector with the output of the fuel regulator, the third input - with the output of the airflow sensor, and the output of the second adder is connected to the regulator by the ratio ratio.

When the oven temperature i: a deviates the output of the first adder, a mismatch signal appears, which simultaneously through the second adder enters the input of the temperature regulator and through this regulator, the equalizer, the logic unit and the third adder to the input of the ratio regulator. As a result, the controllers simultaneously trigger signals to the actuators for fuel and air.

The controllers move the actuators until the output signal of the second and third adders misalignment signal is less than the dead zone of the controller. At the same time, the logic block breaks the circuit connecting the corrector with the third adder and switches the circuit between the second differentiator and the second input of the second C5gmmator.

When the fuel pressure changes, a signal proportional to the rate of this change appears at the output of the second differentiator, which through the logic unit and the second adder enters the temperature controller, which moves the fuel supply mechanism, thereby compensating for the change in fuel pressure. In a similar way, the system compensates for the change in air pressure 3J.

However, the known system has insufficient accuracy in controlling the combustion process due to the substantial non-linearity of the flow characteristics of the regulating bodies, as well as the presence of significant backlashes in the articulation of the actuators with the regulating organs.

In the case of using the system through continuous heating furnaces

error increases. This is due to the fact that the pass-through heating furnaces, in comparison with many other thermal units, are characterized by a higher degree of influence from external disturbances and above all the discrete movement of the heated load of metal in the furnace. The effect of such a disturbance takes place in this case since the metal is propelled in the furnace only immediately before the next billet is issued, and IB is in motion for the rest of the time. Under these conditions, the change in the temperature of the metal surface takes a sawtooth shape, in which periods of uninterrupted increase in the parameter alternate with its abrupt drops during the next advancement of the blanks. As a result, changes in oven temperature caused by tempo changes. The heat of the billet (furnace capacity) is superimposed on the high-frequency component.

The aim of the invention is to improve the accuracy of regulation.

This goal is achieved by the fact that the system for regulating the combustion of fuel in a continuous heating furnace, contains furnace temperature and fuel and air flow sensors, furnace temperature setter, temperature and ratio controls, fuel and air actuators, the first adder, the first input of which is connected to the furnace temperature setting device, and the output - with a temperature controller, and the second adder, the first input of which is connected to the output of the fuel consumption sensor, the second input - through a corrector with the controller output the third input is connected to the output of the air flow sensor, and the output of the second adder is connected to the ratio controller, additionally contains a block for determining the effective temperature of the furnace, a block for determining the period of the furnace temperature oscillations, a sensor for moving the workpieces in the furnace, a clock generator, an analog-digital converter and -Analog converter, with the first input of the block for determining the effective temperature of the furnace connected via an analog-digital converter with the output of the furnace temperature sensor, W The input is with the output of the oven temperature detection unit, the third input is with the clock pulse output, and the output of the furnace effective temperature detection unit is connected via a digital-to-analog converter to the second input of the first adder, the first input of the furnace temperature oscillation period detection unit billets. in the furnace, and the second input - with the output of the generator of clock pulses.

In addition, the effective furnace temperature determination unit contains shift registers, a decoder, OR elements, controlled valves, an adder and a division element, the output of which is connected to the output of the effective temperature determination unit, the first input of this unit is connected to the information input of the first shift register, the second input with the input of the decoder and the first input of the division element, and the third input of the block for determining the average temperature of the furnace is connected to the control inputs of the shift registers interconnected in series information channel, the decoder outputs (except the last one) are connected to the first inputs of the OR elements, the output of each of which is connected to the second input of the previous OR element and to the control input of the corresponding controlled valve, the last output of the decoder is connected directly to the second input of the last OR element and with the control input of the last controllable valve, the information input of each of the controllable valves is connected to the output of the corresponding shift register, and its output is connected to one of the su inputs Matora whose output is connected to the second input of the dividing member.

The unit for determining the oven temperature fluctuations and contains a pulse counter, a shift register, a limiter and a setpoint for the maximum permissible oscillation period, the output of which is connected to the second input of the limiter, the first input of the furnace for determining the period of temperature oscillations of the furnace is connected to the Pulse counter reset and control the input of the shift register, and the second input of the block - with the information input of the pulse counter, the information input of the shift register is connected to the output of the pulse counter, and its output - with th input

0 limiter, the output of which is connected with the output of the unit for determining the period of oscillations of the furnace temperature.

Introduction to the fuel control system of the unit for determining the effective temperature of the furnace, the unit for determining the period of oscillation of the furnace temperature, the sensor for the advancement of the blanks in the furnace, the pulse clock generator,

0 A / D converters and 1Shch1 allows smoothing the furnace temperature fluctuations caused by the discrete movement of the heated billets, which ensures a decrease in the share of transients in the total

5 times and as a result, improves the quality of combustion, fuel. At the same time, the smoothing of the gnaw; (it is determined by averaging the readings of the furnace temperature sensor over the interval

0 where 2 is the current time, and SC is the period of oscillation of the furnace temperature, determined by the time interval between the movements of the heated billets.

5 Since the system achieves a high degree of suppression of the oscillatory components of the signal in terms of the furnace temperature, the result obtained with smoothing can be considered as the effective temperature of the furnace, i.e. as a temperature that does not take into account the effect on it of random perturbations (including the discrete movement of the blanks in the furnace) and,

5 therefore, it is more reliably characterizing at each time point / heat flux falling on the heated billet.

7

However, the introduction of these elements does not significantly delay the temperature control loop of the furnace, and therefore does not degrade the quality of the metal

Fig. 1 shows a diagram of the proposed combustion control system in heating furnaces through passage; Fig. 2 is a block diagram of the determination of the effective temperature of the furnace; FIG. 3 is a block diagram of determining the period of oscillation of the furnace temperature; Fig. A shows curves of the change in the temperature of the furnace as a function of the time interval between the movements of the heated blanks, where A is the curve of the change in the time interval between the movements of the blanks in the working space of the furnace B and the curve of the temperature change of the surface of the heated billets; B - curve of the furnace temperature; G - curve of the change in the effective temperature of the furnace; D is the curve of change in the furnace temperature smoothed with the help of a damping filter; Fig. 5 shows the transient curves occurring in the proposed and known systems with a stepwise increase in the furnace productivity, where E is the curve of the furnace temperature change when the control system is turned off; W - the initial consumption of fuel supplied to the heating zone; 3 - curve of the furnace temperature in the proposed system; And - the curve of the change in the effective temperatures in the proposed system; K - curve of change in fuel consumption in the proposed system; L is the curve of change in the temperature of the furnace in a known system; M is the curve of the change in fuel consumption in a known system; .H is the task for the furnace temperature; O is the dead zone of the temperature controller in the proposed system, and P the dead zone of the temperature controller in the known system.

The combustion control system contains a furnace temperature sensor 1, a furnace 2, analog-to-c4) a rotary converter (ADC) 3, a block 4 for determining the effective temperature of the furnace, a block 5 for determining the period of oscillations of the furnace temperature, a generator 6 clock pulses, a sensor 7 for moving the workpieces in the furnace, digital-to-analog converter (D / A converter) 8, first 8

mater 9, furnace temperature setting device 10, temperature controller 11, fuel supply actuator 12, corrector 13, second adder 14, fuel consumption sensor 15, air consumption sensor 16, ratio regulator 17, air supply actuator 18.

The furnace temperature sensor 1 is installed in the working space of furnace 2 and is connected via an ADC 3 to a block 4 for determining the effective temperature of the furnace, the second and third inputs of which are connected to the block 5 for determining the period of temperature oscillations of the furnace and the generator 6 clock pulses. The first input of the block 5 is connected to the sensor 7 for moving the workpieces in the furnace, and the second input is connected to the output of the generator 6. The output of the block 4 is connected via a DAC 8 to the first input of the first adder 9, the second input of which is connected to the furnace temperature setpoint 10 and the output - with temperature controller 11. The output of the controller 11 is connected to the actuator 4 of the fuel supply mechanism 12 and through the corrector 13 to the second input of the second adder 14, the first input of which is connected to the output of the fuel consumption sensor 15, the third input to the output of the air consumption sensor 16, and the output of the adder 14 is connected to the regulator 17 by control air supply actuator 18. The actuators 12 and 18 are installed on the furnace 2 and connected to the sensors 15 and 16, respectively.

Unit 4 for determining the effective temperature of the furnace (Fig. 2) contains the shift register 19, the decoder 20, the division element 21, the OR element 22 controls the valve 23, the adder 24.

The first input of block 4 is connected to the information input of the first shift register 19, the second input is connected to the input of the decoder 20 and the first input of division element 21, and the third input of block 4 is connected to the control inputs of the shift registers 19 connected in series through the information channel. The outputs of the decoder 20 (except the last one) are connected to the first inputs of the OR 22 elements, the output of each of which is connected to the second input of the previous SHSh 22 element and to the control input of the corresponding control valve 23. The last output of the decoder 20 Is connected directly to the second input of the last element OR 22 and with the control input of the last control valve 23, the information input of each of the valves 23 is connected to the output of the corresponding shift register 19, and its output is connected to one of the inputs of the adder 24, the output is the same The aperture 24 is connected to the second input of the division element 21, the output of which is connected to the output of the block 4.

The unit 5 for determining the period of oscillations of the furnace temperature (FIG. 3) contains a pulse counter 25, a shift register 26, a limiter 27, a unit 28 of the maximum permissible period of oscillation of the furnace temperature.

The first input of block 5 is connected to the Reset input of counter 25 and to the control input of register 26, and the second input of block 5 is connected to information input of counter 25, the information input of register 26 is connected to the output of counter 25, and its output to the first input of limiter 27, the second input of which is connected to task 28, and the output to the output of block 5.

  .

The corrector 13 is a block of nonlinear transformations of the BNP type from the nomenclature of the complex of electrical analogue means of regulation in the microelectronic version AKESR,

The advancement sensor 7 of the blanks in the furnace is standard and is an indicator of the position of a metal of the IRM type, which is mounted above the furnace unloading table of the heated billets.

A 5 clock pulse generator is standard.

To determine the effective (reduced) furnace temperature in the proposed system, the following expression is used;

f Fi

HS -1 - TC J

-) 0

where i

- effective temperature

HS

ovens, KJ tfp - measured temperature

 ovens, ki

 - discrete moments of meni;

u1 - time step size, s;

about. number of steps in time.

stacked during the period of oscillation of the furnace temperature.

The period Sc is determined by the interval between the moments of the last 0 and the penultimate advance of the blanks in the furnace, i.e.

.LpI, 2 „..). In order to prevent the appearance of volatile deviations between the measured furnace temperature and its effective value, which can occur immediately after the end of the mill mill shutdowns, characterized by large intervals between the advances of the heated billets, the oscillation period found by expression (2) is limited by the maximum acceptable value, so what

. G81, lr

, at 8th about Lg.

The system works as follows.

The generator 6 at equal intervals of time equal to bD absorbs the clock pulses, which, entering through the second input of block 5, are summed in the counter 25, In the moment of advancement of the blanks in the working space of the furnace, the sensor 7 is activated and the first input of block 5 receives a single impulse, by which the contents of counter 25 are rewritten into register 26 and then zeroed. As a result, in register 26, a number O of time steps is formed, which lies in the interval between the moments of advancement of the heated blanks, With the help of limiter 27 numbers about time steps are limited by the maximum allowable value St / ut); we set the setpoint ohm 28; the result is fed to the second input of block 4,

Together with this, the input of block 4 also receives signals from the outputs of the generator 6 and the sensor 1 of the furnace temperature. The last signal previously converted by digital converter 3 is fed to the first input of block 4, and further to the information input of the first register 19, the total number of which in block 4 is equal to the maximum allowable number of time steps j When entering through the third input of block 4 the next clock pulse from generator 6, the contents of registers 19 are cyclically shifted up by one element. In this case, the current value of the furnace temperature coming from sensor 1 is recorded in the register being cleared, and the last register is overwritten with information from the previous register. The decoder 20, whose input receives the number of steps in time J, feeds the unit to the first input of that element OR 22, the sequence number of which is J, and at the output of all IPI elements 2, the sequence number of which is less than or equal to 3, unit. As a result, the control valves 23 with the sequence numbers from 1 to 3 are open, and the input of the adder 24 receives the contents of only those registers 19 that have the same sequence numbers. The result of the addition in the adder 24 after dividing in element 21 by the number of J steps in time is the output signal of block 4, the effective furnace temperature, which, unlike the measured signal, does not contain high-frequency vibrations caused by discrete movement of the workpieces in the furnace working space. Subsequently, the found effective furnace temperature in the adder 9 is compared with the task coming from the setting unit 10, and according to the error signal at the output of the adder 9, the temperature controller 11 controls the fuel supply mechanism 12. The ratio controller 17 controls the air supply actuator 18, by the error signal from the adder 14, in which the signals from the output of the fuel consumption sensor 15 and through the equalizer 13 from the output of the regulator 11 are compared to the signal from the output sensor 16 air flow. In this case: when: the error signal is exceeded at the output of the adder 9 of the dead zone of the regulator 11, the actuators 12 and 18 begin to move simultaneously. The regulators 712 and 11 and 17 move the actuators 12 and 18 until the signal at the output of the adders 9 and 14 becomes less than the dead zone of the regulators. To illustrate the operation of the unit for determining the effective temperature of the furnace, the curves of the dependence of the furnace temperature on the time interval between the advances of the heated billets are presented (Fig. 4). At the same time, the time is recorded when the billets are being moved in the furnace L; (, ..., 8) and determine the time intervals between these advances 8 о о п - о ,, ,, (П 1,..., 8). As can be seen from the dependence in FIG. 4, the discrete movement of the metal charge in the furnace imparts a sawtooth character to the temperature change of the surface blanks, which is reflected in the temperature change of the furnace in the form of high-frequency vibrations. The frequency of such oscillations coincides with the frequency of the pro-. movement of the blanks in the furnace, and their amplitude during the transitional process, caused by a change in the productivity of the furnace, takes values in the range from 5 to 10 K. As an example, FIG. A shows (curve G) the view of the smoothed (effective) temperature of the furnace . In all cases, including the one shown in Fig. 4, the amplitude of the residual oscillations in the smoothed signal does not exceed 0.5 K. In connection with the fact that during the advancement of the heated billets, the effective temperature of the furnace is entered into the unit for determining the effective temperature. the new period of the oscillation temperature of the furnace, the smoothed signal at these times can contain jumps of up to 1 K. It can be assumed that the amplitude of oscillations of the effective Тe: paratyr of the furnace does not exceed 0.5 K, which is much higher than the insensitivity zone established by the controller by that perature. At the same time, the introduction of elements into the combustion control system, which ensured the smoothing of the signal according to the furnace temperature, introduces a certain delay in it, which can be compensated by reducing the sensitivity of the temperature regulator. Determined that

in order to achieve accuracy in controlling the furnace temperature of 1 10 K, the dead zone must be reduced to a value of ± 2 K. Such a decrease in the value of the dead zone is justified, since it is also in this case at least four times greater than the maximum possible amplitude of oscillations: ,

To illustrate the operation of the entire combustion control system as a whole, as well as to compare it with the operation of a known system, the transient curves (Fig. 5) obtained under conditions of a change in furnace productivity are presented. These curves are based on the results of simulating the processes of regulating the combustion of fuel in continuous heating furnaces, which, according to the proposed system, is carried out at the stage of preliminary design and is intended to preliminarily verify the correctness of the adopted technical solution. The modeling of regulatory processes is carried out using digital computers. In this case, its mathematical model is used as the control object, which studies the effect on the furnace temperature of all fundamental disturbances, including the discrete movement of the blanks in the furnace.

The transient curves (Fig. 5) are obtained by simulating a stepwise increase in the furnace productivity in a manner similar to that in real conditions (Fig. 4). Since the duration of such transient processes is much (ten times) longer than the adjustment time, they are not fully depicted (Fig. 5) but as separate fragments, and the presented fragments are referred to the part of the transient process where the maximum rate of fall of the furnace is reached Curve E (Fig. 5) shows the change in the temperature of the furnace without controlling the combustion of the fuel, i.e. at a constant flow rate (right). When using the proposed system for regulating the combustion of fuel (regulation in this case starts from the moment about 0, Fig. 5), this change in the temperature of the furnace takes the form shown by curve 3. Having

the place where the effective temperature of the furnace and the fuel consumption change is shown by the curves I and K, respectively. When using a known system for controlling the combustion of fuel, the temperature change of the furnace at the time interval in question takes the form, as shown by the curve L, and the change in fuel consumption - the curve M. In both cases, the temperature regulators are set to 20% overshoot, and the setting for the furnace temperature is 1290 ° C (rms H) The dead zone of the temperature controller in the proposed systems e is set to ± 2K (direct o), and in the known system, -i 4 K (direct P).

The delay in determining the effective temperature of the furnace at the beginning of the transition process in the proposed system (interval 3 0-300 .5) is associated with the absence of regulation until 2 0. This delay is generally proportional to the rate of change of the effective temperature of the furnace: If, for example, at the beginning of the regulation (T 0), it is 6 K. Since the regulation of the combustion of the fuel causes the effective temperature of the furnace to stabilize around a predetermined value, its rate of change becomes much less than without regulation. As a result, the marked lag is almost negated. For the transition process shown in FIG. 5, for example, this takes place starting from -300 s.

Under conditions of change in performance, furnaces transient processes in the system proceed in aperiodic type, while in the known system they are oscillatory. At the same time, the frequency of application of control actions (the number of actuations of the temperature regulator per unit time) in the first case is two times less than in the second.

In the established modes (and they occupy more than half of the total operating time of the furnaces), the effective temperature of the furnace practically does not change and, therefore, the response of the temperature controller in the system may be absent altogether. Average

however, (taking into account the share of transitional and established furnace operating modes), the simulation results for the proposed system more than tenfold decrease in the number of times obtained.

You are putting control yyrps effects. At the same time, the standard deviation of the furnace temperature from the setting in the proposed system is 9 in the known system - 7 K.

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Claims (3)

1. CONTROL SYSTEM FOR FUEL BURNING IN THE PASS OF THE HEATING FURNACE, Containing sensors of the temperature of the furnace and fuel and air consumption, the temperature of the furnace, temperature and ratio controllers, actuators of fuel and air supply, the first adder, the first input of which is connected to the temperature of the furnace, and the output is with a temperature controller, and the second adder, the first input of which is connected to the output of the fuel consumption sensor, the second input through the corrector with the output of the fuel regulator, the third input with the output of the sensor Single air flow, and the output of the second adder is coupled to the ratio controller, wherein ¹ that in order to improve the accuracy of regulation, it additionally comprises a determination of the effective furnace temperature determination unit period of oscillations furnace temperature sensor advancing workpieces in a furnace, clock pulses, an analog-to-digital converter and a digital-to-analog converter, while the first input of the unit for determining the effective temperature of the furnace is connected through an analog-to-digital converter to the output furnace temperature sensor, the second input - with the output of the oven temperature fluctuation period determination unit, the third input - with the output of a clock pulse generator, and the output of the furnace effective temperature determination unit is connected via a digital-analog converter to the second input of the first adder, the first input of the furnace temperature oscillation period determination unit connected to the output of the progression sensor of the workpieces in the furnace, and the second input to the output of the clock pulse generator. 2. The system according to claim 1, characterized in that the unit for determining the effective temperature of the furnace contains shift registers, a decoder, OR elements, controlled valves, an adder and a pressure element, the output of which is connected to the output of the unit for determining the effective temperature of the furnace, the first input of this the unit is connected to the information> input of the first shift register, the second input to the decoder input and the first input of the division element, and the third input of the unit for determining the average temperature of the furnace is connected to the control inputs of the registers. the shift, interconnected in series through the information channel, the outputs of the decoder (except for SLL> 1149107 of the last) are connected to the first inputs of the OR elements, the output of each of which is connected to the second input of the previous OR element and to the control input of the corresponding controlled valve, the last output of the decoder is connected directly with the second input of the last OR element and with the control input of the last controlled valve, the information input of each of the controlled valves is connected to the output accordingly of translations of the register n, and its output - to one of inputs of the adder, whose output is connected to the second input of the dividing member. 3. The system according to claim 1, characterized in that the unit for determining the period of fluctuations in the temperature of the furnace contains a pulse counter, a shift register, a limiter and a dial for the maximum allowable period of oscillation, the output of which is connected to the second input of the limiter, the first input of the unit for determining the period of oscillation the furnace temperature is connected to the reset pulse counter input and to the control input of the shift register, and the second block input is connected to the pulse counter information input, the shift register information input is connected to the output of the impulse counter of ice, and its output - with the first input of the limiter, the output of which is connected to the output of the unit for determining the period of temperature fluctuations of the furnace.