SU987863A1 - Method and apparatus for control of electric arc steel melting furnace electric mode - Google Patents

Description

The invention relates to electrical (thermal, namely electric arc furnaces, and may be applied in ferrous metallurgy to ₅ control the electric mode in ^E high power arc steel furnaces.

There is a known method of controlling the electric mode in arc steel-smelting furnaces (DSP), by which the voltage steps of the furnace Transformer are sequentially switched according to the consumption of electric energy or time and they support the given power at each voltage stage (11.

A device for automatic control of the melting process in chipboard is also known, which contains a sensor of consumed active power connected with a current and voltage transformer on the high side of the furnace transformer, a power regulator; connected with the actuator for moving the electrodes, the device for monitoring the temperature of the liquid bath 25, the voltage stage selector for the furnace transformer and the software device connected to the temperature control device, 30-volt power regulator, the voltage stage selector and the active power sensor [2].

This method and device cannot provide the maintenance of the set maximum useful power, and controlling the process of charge melting based on a tough program in time or power consumption even for the same steel grade and constant mass of the loaded charge can be very irrational due to the untimely switching of the furnace voltage levels transformer for increased power at various technological intervals of the melting period, since control according to a strict program is not always. t real process.

The closest in technical essence to the proposed one is a method of controlling the electric mode of a blast furnace, in which at each technological stage of melting at a given voltage level of the furnace transformer, active power is maintained by moving the electrodes, and the moment of switching the voltage stages to go to the next stage is determined by according to a given and controlled electrical parameter.

A device is also known for controlling the electric mode of an arc steel furnace, comprising reactive and active power sensors connected to a three-phase current and voltage sensors connected to a three-phase current and voltage sensors installed on the high voltage side of the furnace transformer, the output of the latter being connected to the input of the power regulator control unit equipped with an executive the mechanism of movement of the electrodes, the block of program control of the electric mode, connected by inputs to a thermal probe for monitoring the temperature of the lining oven and switch stage of the furnace transformer voltage, and the control exits the regulator Perea - with block steps klyuchatelom power PP}.

A known method of maintaining a given foot power or of each voltage step of the fifth τι ::

transformer, which leads to an increase in 25 electrodes to increase the duration of the melting period, i.e. to reduce furnace productivity due to inaccurate determination of the beginning of technological intervals.

The device does not provide high accuracy in determining the onset of formation of a liquid bath due to insufficient reliability of a sensor for forming a liquid bath mounted on an electric displacement electric motor of the furnace 35 _β , the two inputs of which are subgeners in an aeon of high temperatures and high dust content, and difficulties in counting pulses reciprocating (up, down) movements of the electrodes during melting of the charge.

In addition, this device does not have a sensor to determine the beginning of the technological interval — burning closed arcs and re-melting the charge — and for this reason it cannot cure the timely repayment of power at these melting intervals, which will lead to a decrease in furnace productivity.

The purpose of the invention - an increase proiz- "vodatelnosti furnace and reducing the length ⁵⁰ telnosti melting period due · / more accurately determine the beginning of melting Technological periods minutes timely switching voltage levels..

To achieve this goal, in the method of controlling the electric mode of an arc steel-smelting furnace, at each technological stage of melting at a given voltage stage ^ О the furnace transformer maintains active power by moving the electrodes, and the moment of switching the voltage stages to go to the next stage is determined by the equality 65 does not allow the maximum poblieku to it on a given and controlled electrical parameter, measure the flow of active and reactive electricity for 2-3 mi n, and as a controlled parameter for switching the steps, the power utilization coefficient is taken, which is determined by the formula and the active power voltages from which the co-regulation of supplied with is - cos4, where W _a is the consumption of active energy; ' ^w d3 <»A“ specified consumption of active electricity;

cos4 is the power factor.

A device for controlling the electric mode of an electric arc furnace containing three-phase current sensors connected to a three-phase current transducer installed on the high-voltage side of the furnace transformer, output of the last tribute with the input of the power regulator unit, additional movement mechanism ... I, electric program control unit * the mode associated with the inputs to the temperature probe of the temperature control of the furnace lining and the voltage stage selector of the furnace transformer, and the outputs are controlled by the unit I step switch and power regulator is provided with a sensor and the time utilization rate measurement unit cardinality keys to the outputs of sensors of active and reactive power, third input to the output of the time detector, connected to the current sensor input, and output - with a control input of the program control unit.

In addition, the power utilization factor measuring unit contains a memory unit connected to the input and output of a microprocessor connected via an output matching unit to a program control unit, and inputs to outputs of active and reactive power sensors and a timer, the input of which is connected to the output of a time sensor .

Figure 1 shows the structural diagram of the device; figure 2 is a structural diagram of a unit for measuring the power utilization factor; in Fig.Z - technological stages and electrical modes. These stages.

The device contains current sensors 1 and voltage 2, mounted on the high voltage side of the furnace transformer 3, 4 and other L ^and NII sensors of active reactive 5 power, connected to secondary circuits of voltage current sensors 2, power supply unit .6, the input of which is connected to sensor 4 active power

the output is to the input of the power regulator 7 with the actuator 8 for moving the electrodes 9 of the furnace, the control unit 10 of the voltage stage switch connected to the switch 11 of the voltage levels of the furnace transformer, thermoelectric 12 to control the temperature of the lining 13 of the furnace, the electric control program unit 14, connected with power control unit b, thermal probe 12 of the lining control, power controller 7, switch 11 voltage steps and control unit 10 switch voltage steps, sensor 15 time, the input of which is connected to the current sensor 1, and the output to the power utilization unit 16 for each voltage stage of the furnace transformer, the other inputs of which are connected to the active 4 and reactive 5 power sensors, and the output is connected to the electric power program control unit 14.

The power utilization factor block for each voltage stage of the furnace transformer contains a memory unit 17, a timer 18, connections to a time sensor 15, a microprocessor 19, the input and output of which is connected to a memory unit 17, and a matching unit 20, the inputs of which are connected to a timer 18, to sensors active 4 and reactive 5 power, and the output is to block 14 of the program control electric mode.

Shown in figure 3, the technological intervals of melting of the metal ishkhta and the electrical regimes for these intervals have the following notation: 'I, 6, c, d, and E are respectively the intervals of penetration of wells, the formation of a liquid bath, closed arcs, the addition of a charge, and the heating of liquid metal, where 9 is the 'electrode; 21 - charge; 22 - liquid metal; Зр - the set rational current of the furnace;

Uf-Uj - voltage levels of the furnace. >

transformer (and _u <y ₂ <^ s)

The blocks of the device are made on standardized equipment, microprocess-ed sor type K-580, matching block type A (common bus).

The control of the electric mode, the melting of the metal charge in a high-power chipboard is that at each technological stage it is necessary to maintain a given voltage level of the furnace transformer and a given useful power.

The device operates as follows.

Before calculating the smelting, the steelmaker sets the desired useful “-------” with the help of adjusters in the block 14 of the program for electric mode control.

power and voltage level of the furnace “to burn continuously transformer 3 days of each technological interval - the melting period. Block 14 of the program control of the electrical mode using block 10 sets the switch 11 voltage steps a predetermined voltage level. The power control unit 6 sets the power controller 7 to a predetermined amount of current corresponding to a predetermined value ι of useful power. The steelmaker turns on the stove. Automatic power controller 7 with an actuator 8 moves the electrodes 9 down. Arcs light up. The process of melting the mixture begins (penetration of the wells of Fig. 3, a). During this melting period, due to cold metal and a cooled furnace, arcs have a very short arc length (several millimeters), burn uneasily, and are transferred from one piece of metal to another. Wells are formed in the charge in which the electrode is lowered. The collapse of the walls of these wells causes frequent current surges and a short circuit, resulting in sharp fluctuations in power. Each short circuit leads to a sharp decrease or termination of the useful output power and a significant decrease in the power factor ¹ (cos H) of the furnace.

From the sensors of current 1 and voltage, signals proportional to the magnitude of the current and phase voltage are supplied to the active power unit 4. These signals are supplied to the power control unit 6, which compares the actual RF. and given Pj powers according to the equation, ^P L-b = ⁰

If the actual power * deviates from the data, block b corrects the furnace current for elimination through the power regulator 7 and the actuator 8. Correction is introduced into the * melting period of the charge and only if there is a load on all three phases. The power control unit 6 more accurately maintains the values of the phase currents corresponding to the maximum of the useful power or close to it, thereby contributing to the increase in the input power and, consequently, the productivity of the furnace. A command to turn on the time sensor 15 is provided from the current sensor 1 at the time of arcing. The countdown of time intervals begins.

By the time · when the electrode cuts through the thickness of the charge, a pool of liquid metal is formed at the bottom of the well (Fig. 3,6) and Dgga starts to burn on. its surface. Long arc breaks cease, and it begins ι. Curve. Current strengths of varying degrees of sinusoid. Power factor (K *) composition 0.68-0.75.

from the active 4 sensors, the set Til value of phases corresponding to close to the maximum of the useful power is lived, and if Kf>, K ₃ 7, 0, the voltage stage is switched. The next technological interval of the melting process begins - re-melting of the charge (Fig.Z ,?). The end of this period and the transition to the next voltage stage is carried out using a temperature probe 12 to control the temperature of the furnace lining 13, which, when the specified allowable temperature of the internal surface of the furnace is reached, sends a signal to the electric mode program control unit 14. This block 14 acts on the block 10 switching voltage steps, which is carried out using the switch 11 STU. voltage stays switching to the next (lower) voltage stage of the furnace transformer. The last technological melting interval begins - the heating of liquid metal.

The proposed device for controlling the electric mode of the melting period of a metal charge in a high-power chipboard provides timely switching of voltage levels depending on the melting state of the charge and maintains a given maximum net power.

I.

Claims (3)

1.Pirozhnikov V.E., Kablukovsky A.F. Automation of control and management of electric steel plants. M., Metallurgists, p. 142 2. Automation of metallurgical production. Thematic industry collection, W 5. M., Metallurgists, 1977, p. 95 3. Automation of metallurgical production. Thematic industry collection, 8, M., Metallurgists, 1979, p. 51. CD dJ ff : i ffm f / ro / eef 0ar ff / Kf / (ff "f & rrSfWCf / J fyO / fy /