RU2493519C2 - Device for ore-thermal furnace control - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: device for ore-thermal furnace control contains transformer with tap changing device, which each phase of secondary winding is connected to electrode moved inside furnace bath using its drive connected by inlet to outlet of comparison element, which outlet is connected to outlet of electrode current sensor, block of current determination, at least two additional temperature sensors, heat current evaluation unit, furnace watt transducer, divider, furnace voltage sensor, nonlinear element, connected by its inlet to outlet of voltage sensor, and multiplier.

EFFECT: increasing productivity of furnace and lining lifetime by improving accuracy of maintaining of chemical reactions conditions in bath of ore-thermal furnace: molten metal temperature, reaction zone geometry, availability and thickness of skull layer.

3 dwg

Description

The proposed technical solution relates to means for controlling ore-thermal furnaces and can be used in the metallurgical and chemical industries to control technological processes in ore-thermal furnaces intended, for example, for producing ferroalloys.

A device is known (Automatic control of electrothermal installations. / Ed. By AD Svenchansky. - M .: Energoatomizdat, 1990. - P.310-312), containing a transformer with switching voltage levels, each phase of the secondary winding of which is connected to the electrode, moved inside the furnace bath with its drive connected to the output of the comparison element connected by one input to the current setting unit and the second to the output of the electrode current sensor.

The main disadvantage of this device is that only current control, without taking into account heat generation in the reaction zone of the furnace, which depends on a number of technological factors, leads to a decrease in furnace productivity and product yield due to violation of the conditions for chemical reactions in the furnace bath, as well as to reduce the life of the lining due to its overheating.

Closest to the solution proposed by the authors is a device (Electrical equipment and automation of electrothermal installations: a Handbook. / Ed. By A.P. Altgauzen. - M .: Energy, 1978. - S.265-267), containing a transformer with switching voltage levels , electrode movement drive, comparison unit, current setting unit and additional sensors of technological parameters, such as exhaust gas temperature, pressure under the furnace lid, gas purification electrostatic precipitator, by the signals of which the steps are switched her stress.

The disadvantages of this device are the difficulty of establishing a connection between the measured technological parameters and the reaction conditions in the furnace bath, as well as the sufficient complexity of the sensors used and their limited service life in an aggressive environment of exhaust gases.

The technical problem solved by the proposed device is to increase the productivity of the furnace and the service life of the lining by improving the accuracy of maintaining the conditions of chemical reactions in the bath of the ore-thermal furnace: melt temperature, geometry of the reaction zone, presence and thickness of the skull layer.

The stated technical problem is solved in that in a known device containing a transformer with a voltage stage switch, each phase of the secondary winding of which is connected to an electrode that is moved inside the furnace bath with its drive connected to the output of the comparison element, the input of which is connected to the output of the current sensor an electrode, a current setting unit, at least two temperature sensors located inside the furnace lining at different distances from the lining surface are additionally introduced, a calculation unit heat flow, the inputs of which are connected to the outputs of the corresponding temperature sensors, the furnace active power sensor, the division unit, connected by the first input to the output of the heat flow calculation unit, and the second - to the output of the power sensor, a three-position relay element connected by the input to the output of the division unit, and the output is to the input of the voltage stage switch, the furnace voltage sensor, a nonlinear element connected by the input to the output of the voltage sensor, and a multiplication unit connected by the output to the other input of the element Ia, the first input - to the output current setting unit, and the second input - to the output of the nonlinear element.

The proposed device is illustrated by drawings, where Fig. 1 is a functional diagram of the proposed device, Fig. 2 is a characteristic of a three-position relay element, and Fig. 3 is a characteristic of a non-linear element.

The device comprises a transformer 1 with a voltage stage switch 2. Electrodes 3 are connected to the secondary windings of various phases of the transformer (Fig. 1 shows one electrode). Each electrode is equipped with an electrode current sensor 4. The electrode moves vertically in the furnace bath with its drive 5, which can be used as an electromechanical or electro-hydraulic drive.

The input of the drive 5 is connected to the output of the comparison element 6, connected by the first input to the output of the current sensor 4, and the second input to the output of the multiplication unit 7, connected by the first input to the output of the current setting unit 8, and the second input to the output of the nonlinear element 9 connected to the output of the voltage sensor of the furnace 10, which measures the voltage of the secondary winding of the transformer.

The input of the voltage step switch 2 is connected to the output of the relay element 11, the input of which is connected to the output of the division unit 12, connected by the first input to the output of the heat flux calculation unit 13, and the second input to the output of the power sensor 14.

The heat flow calculation unit 13 is connected by its inputs to the outputs of the temperature sensors 15, 16, moreover, at least two temperature sensors are installed in the furnace lining at different distances from the surface of the lining. As temperature sensors 15, 16, for example, thermoelectric converters (thermocouples) can be used.

The device operates as follows.

The ore-thermal furnace is powered by a transformer 1 with a voltage stage switch 2. Electrodes 3 are connected to the secondary windings of the various phases of transformer 1. Each electrode can be connected to a separate single-phase transformer. The electrode current is measured by current sensor 4.

The electrode moves in the furnace bath in the vertical direction with its drive 5, the input signal of which is generated by the comparison element 6 based on the current value of the electrode current measured by the current sensor 4, and the current set by the multiplier 7 by multiplying the signal at the output of the current setting unit 8 by the signal, generated by the nonlinear element 9 based on the voltage stage used. The number of the used voltage stage is determined by the voltage of the secondary winding of the transformer, measured by the voltage sensor 10.

The current value of the heat flux is calculated by the heat flux calculation unit 13 according to the signals of the temperature sensors 15, 16 installed in the lining. At a minimum, two temperature sensors are required that are installed at different distances from the lining surface in the same radial direction from the geometric center of the furnace bath at the same height relative to the hearth of the furnace. The heat flux from the signals of two temperature sensors is defined as

$$q=\lambda \cdot \frac{\Delta t}{S},\begin{array}{ccc}& & \end{array}\left(\mathrm{one}\right)$$

where Δt is the temperature difference measured by the first and second sensors; λ is the thermal conductivity of the lining material; S is the distance between the sensors.

It is possible to install more than two temperature sensors in the same radial direction from the center of the furnace bath at the same height relative to the furnace bottom, while the heat flux is calculated according to (1) for each pair of adjacent temperature sensors, and its average value is calculated from the results of these calculations. It is also possible to organize several rows of temperature sensors (at least two sensors in each row) in different radial directions from the center of the bath and at different heights relative to the hearth of the furnace. In this case, the heat flux values calculated as described above for each row of sensors are averaged. Averaging the heat flux over the radial directions and the height of the furnace improves the accuracy of determining the state of the reaction zone.

The division unit 12 determines the ratio of the heat flux through the furnace lining, calculated by the calculation unit 13, to the active power consumed by the furnace, measured by the power sensor 14. The options for the performance of the power sensor 14 can be different, so the active power can be determined by measuring the actual voltage values and current and phase angle. In this case, measurements are carried out for each electrode separately, the power values determined for each electrode are summed. Given some distortions in the shape of the curve of the current consumed by the furnace, relatively sinusoidal, the most accurate active power is determined by integrating over time the product of the instantaneous values of voltage and current in analog or digital form.

The rational mode of using the power introduced into the furnace in the reduction reactions in the furnace bath can in practice be determined by the ratio of the heat loss power (heat flux through the lining) to the consumed active power, which must lie within certain limits specified experimentally for a specific furnace. Exceeding the upper limit of this ratio indicates that the input power is excessive, underused in the reactions in the furnace bath and leads only to increased values of heat loss and accelerated wear of the lining. In this case, it is necessary to reduce power by switching to a lower voltage level of the supply transformer.

If the ratio of the heat flux through the lining to the power consumption is below the lower limit, then to increase the productivity of the furnace, it is necessary to increase the power by switching to a higher voltage level of the supply transformer.

The command to switch the voltage stage with switch 2 is supplied by a three-position relay element with a dead zone 11 connected to the output of the division unit 12. The characteristic of the relay element is shown in FIG. 2. The value of the output signal of the relay element U _o , equal to -E, leads to a transition to a lower voltage stage, equal to + E to a transition to a higher stage.

The nonlinear element 9 generates, depending on the voltage stage used (the stage number is determined by the voltage of the transformer secondary winding, measured by the voltage sensor 10), the value of the output signal, which, at the maximum value of the signal at the output of the current setting unit 8, ensures that the furnace operates at the maximum useful power at this stage voltage taking into account the permissible current values of the furnace transformer. The characteristic of the nonlinear element 9 is presented in figure 3. The type of characteristic should be specified for a specific furnace transformer.

Thus, the ore-thermal furnace is controlled by moving the electrode as a function of current with the correction of the set current value by the number of the used voltage step and switching the voltage steps depending on the ratio of the heat flux through the lining and the active power consumed by the furnace.

The heat flow calculation unit, the comparison element, the division unit, the multiplication unit, the relay element and the non-linear element can be implemented, for example, on digital computing means.

The technical solutions used can increase the furnace productivity and product yield by improving the accuracy of maintaining the conditions of chemical reactions in the bath of the ore-thermal furnace (melt temperature, reaction zone geometry, presence and thickness of the skull layer) and increase the service life of the furnace lining.

Claims (1)

A device for controlling an ore-thermal furnace, containing a transformer with a voltage stage switch, each phase of the secondary winding of which is connected to an electrode that is moved inside the furnace bath using its drive connected to the output of the comparison element, the input of which is connected to the output of the electrode current sensor, current setting unit , characterized in that it further comprises at least two temperature sensors located inside the lining of the furnace at different distances from the surface of the lining, the calculation unit heat flow, the inputs of which are connected to the outputs of the corresponding temperature sensors, the furnace active power sensor, the division unit connected to the output of the heat flow calculation unit by the first input and the second to the output of the active power sensor, a three-position relay element connected to the output of the division unit and the output is to the input of the voltage step switch, the furnace voltage sensor, a nonlinear element connected by the input to the output of the voltage sensor, and the multiplication unit connected by the output to another electronic input ment comparison, a first input - to the output current setting unit, and the second input - to the output of the nonlinear element.

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