SU1647927A1 - Device for automatic monitoring of pit depth in burden of electric arc-furnace - Google Patents

Abstract

The invention relates to electrical engineering. The purpose of the invention is to improve the accuracy of determining the depth of the well. In the comparator 9, the signals from the output of the converter 8, proportional to the displacement of the electrode, are summed from the output of block 15. proportional to the length of the arc, and from the output of block 13, proportional to the length of the burnt part. This sum is compared with the output signal of the well depth setting unit 12, and when exceeded, indicator 10 is triggered, signaling that the well is going to collapse or the bath is turned. 1 il. about CHO

Description

The invention relates to electrothermal.

The purpose of the invention is to increase the precision control of the depth of the well in the charge.

The drawing shows the train is a functional diagram of the device.

The device for automatically controlling the depth of the well in the charge contains a sensor 1 for moving the electrode 2, associated with the last one through the detection unit 3 for the direction of movement of the electrode 2, the output of which through the first adder A is connected to the first indicator 5. The input of the unit 3 is also connected via the first key 6, the second an adder 7 and a digital-to-analog converter 8 with a first input of the comparator 9. The output of which is connected to the second indicator 10 of the first input of the memory unit 11, the output of which is connected to the control input of the second adder. The output of the well depth unit 12 is connected to the second input of the comparator 9, the output of the power converter 14 to the third input through the block 13 for determining the length of the burned part of the electrode, the output of the power converter 14 to the fourth input through the automatic correction unit 15 to the output of the dividing unit 16. The output of the arc sensor 17 is connected to the first inputs of the power converter 14, the division unit 16, the automatic correction unit 15, the first key 6 and the second key 18, the output of which is connected to the second input of the memory unit.

The arc voltage sensor is connected to the second input of the power converter 14 and the dividing unit 16. The unit 20 of the electrode combustion coefficient is connected to the input of the unit 13 for measuring the length of the burned-out part of the electrode.

The device automatically controls the depth of the well in the mixture works as follows.

When the electrode 2 of phase 1 is moved from the extreme upper position downward from the sensor 1 of movement, signals are received that are recognized in the directional recognition unit 3, summed in the adder 4, and recorded by the first indicator 5.

At the initial moment of ignition of the arc, a signal appears on the output of current sensor 17, which turns on key 18, with this memory block 11, information on the first arc ignition is recorded and the contents of adder 7 are erased, key 6 is turned on, connecting the second adder 7 to main measuring circuit. When the charge is melted, the electrode 2 moves downwards; in the second adder 7, the signals about the movement of electrode 2 are accumulated. The depth IK of the well in the charge is equal to

0

1k 1p-D1e + d, (1)

where In is the displacement of the electrode;

D) e is the length of the burned part of the electrode during the melting time tn;

d - arc length.

From the output of the digital-to-analog converter 8, the proportional signal Vi is fed to the first input of the comparator 9

1p e +.

The second input of the comparator 9 receives the signal Vo from the output of the setter of the depth of the well, the third input receives the signal Uz proportional to the length of the burned part of the electrode and formed in the block 13 for determining the burned part of the electrode

20

V3 Kc-P-tn,

(2)

where Kc is the electrode combustion coefficient, specified in block 20 and dependent on the type of electrode;

P is the power released in the arc;

tn is the net melting time since the first ignition of the arc.

The fourth input of the comparator 9 is supplied with a CHI for Va, proportional to the arc lg, formed in pressure block 16 and corrected in block 15;

lg k (lg) rg

(3)

where Gd - arc resistance;

Od, g - voltage and arc current;

) - a correction factor, depending on the current strength of the arc, transverse arc blowing at high currents is taken into account.

The K (Ig) value is generated in the automatic correction block 15. The arc resistance rg is calculated in division block 16.

If the length of the well Ik is less than the specified io, then Vi + V2- / 3 -dVo, and if it is greater, then

Vi + V2-V3 V0l, and at the output of comparator 9, a signal appears that turns on the second indicator 10. This signal, after lifting the electrode and breaking the arc, erases from the memory block the information about the first ignition of the shower. Further, if the electrode is lowered after the collapse of the well or bath turn, the signal from the current sensor 17 arrives at the input of the memory unit 11, this information is recorded again and the contents of the adder 7 are erased at the same time. The device is ready for subsequent measurement of the depth of the well . As a displacement sensor 1, it is better to use a digital sensor, for example PDF-3 with a roller converter, as block 3 - a known electronic circuit, made on logic elements K155TA2, K155LAZ. The adders 4 and 7 are made of reversible counters of the type K155IE7., The digital-to-analog converter 8 is made from the KP572P1 microcircuit and the K140UD6 operational amplifier. The keys 6 and 18 use optoelectronic switches, for example, K249KP1, as the memory unit - the trigger K155TM2. As the power converter 14, an E829 type converter is used, and the dividing unit 16 is an integrated microcircuit K525GGS2.

The automatic correction unit 15 is made on the basis of an operational amplifier K140UD8 with a transmission coefficient that depends nonlinearly on the arc current. Zadachi 20 and block 12 are resistive, the comparator 9 is based on the operational amplifier K140UD6. LED indicator 10 1B8702.

The device eliminates electrode failures during electrodynamic shocks during moments of short circuits and when oversized heavy (up to 5 tons) pieces of the charge fall, while simultaneously increasing the productivity of the electric steel-arc furnace. Electrodynamic shocks occur during the operational short circuits of the electrodes with the charge. When an oversized steel scrap is melted, electrodynamic forces F arise between the electrode and the piece of charge (Fig. 1), which can act as a tire. Electrodynamic force F, acting on the electrode in the direction of scrapping, depends on the depth of the well 1k. current strength and gap and the gap between the electrode 2 and a piece of charge (Fig. 1. phase 1):

tf-2 lk

For the limiting values of the current li-2 and the gap, the force at which the electrode is destroyed is determined by the final value of the depth of the well IK. For each chipboard, type of electrode, there is an acceptable depth of 1D according to the electrodynamic stability conditions of the electrode. Approximately at the same depth Oogt si 500 mm), the pieces of the charge collapse with the breakage of the electrode (Fig. 1, phase 2). Two cases are possible. In the first case, if the electrodes are more often raised to turn the bath, but at the same time the furnace turns off more often and stays idle longer, its performance decreases. In the second case, if IK dop, the probability of electrode breakage sharply increases with eectrodynamic shocks and falling large pieces of the charge. With precise control of the well depth (), the furnace performance will be optimal with simultaneous shutdown of electrode breakages. The accuracy of monitoring the depth of the well in the charge with the proposed device is increased by no less than 60%.

For example, for the true depth of the well IK Ig + e 500 mm, at which the probability of dangerous electrodynamic shocks and large pieces of the charge on the electrode with its breakdown sharply arises, the error of the known control devices is

20

d.) (1e + 1d)

100

 (D1E - 1D) 100 500

 66%

where D e 350 mm - the length of the burned part of the electrode for 1 hour of melting pieces of the charge of 5 tons;

1d 20 mm - the maximum length of the arc when the charge is melted.

The proposed device makes it possible to eliminate this error and by increasing the accuracy of control to avoid electrode breakages during electrodynamic impacts and the fall of large pieces of the charge during the smelting of special steels and at the same time increase the furnace productivity.

40

Claims (1)

Invention Formula A device for automatically controlling the depth of a well in an electric arc furnace charge, comprising an electrode displacement sensor connected 5 With the input of the directional direction recognition unit, the output of which is connected to the input of the first indicator through the first adder and through the first key to the input of the second adder. 0 whose output is connected via a digital-to-analog converter to the first input of the comparator, the second input of which is connected to the output of the well depth depth block, and the output to the input of the second indicator and the first input of the memory block, the second input of which is connected via the second switch to the output of the current sensor, and the output is with the second input of the second adder, and the power converter, the inputs of which are connected to the outputs of the current sensors and voltage, the output of the current sensor is also connected to the control input of the first key, characterized in that, in order to increase accuracy, it is equipped with a unit for determining the length of the burnt part of the electrode, a unit for the combustion coefficient of the electrode, a dividing unit, an automatic correction unit, the output of the setpoint of the combustion coefficient is connected to the first input of the length determination unit the burned-out part of the electrode, the second input of which is connected to the output of the power converter, and the output to the input of the third comparator input, the input of the fourth input is connected to the output of the automatic correction unit, the first input of which is connected to the output of the current sensor, and the second input to the output of the division unit The inputs of which are connected to the inputs of current and voltage sensors.