US3375318A - Method and an arrangement for measuring and controlling electrode positions in electric furnaces and the like - Google Patents

Method and an arrangement for measuring and controlling electrode positions in electric furnaces and the like Download PDF

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Publication number
US3375318A
US3375318A US405726A US40572664A US3375318A US 3375318 A US3375318 A US 3375318A US 405726 A US405726 A US 405726A US 40572664 A US40572664 A US 40572664A US 3375318 A US3375318 A US 3375318A
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Prior art keywords
electrode
measuring
resistance
furnace
electric
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Expired - Lifetime
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US405726A
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English (en)
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Kjolseth Ove
Willners Sven Harry
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Elektrokemisk AS
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Elektrokemisk AS
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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B7/00—Heating by electric discharge
    • H05B7/02—Details
    • H05B7/10—Mountings, supports, terminals or arrangements for feeding or guiding electrodes
    • H05B7/109—Feeding arrangements
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B7/00—Heating by electric discharge
    • H05B7/02—Details
    • H05B7/144—Power supplies specially adapted for heating by electric discharge; Automatic control of power, e.g. by positioning of electrodes
    • H05B7/148—Automatic control of power
    • H05B7/152—Automatic control of power by electromechanical means for positioning of electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/25—Process efficiency

Definitions

  • KJQLSETH 8 SVEN HARRY WILLNERS ATTORNEYS March 26, 1968 o. KJQLSETH ET AL 3,375,318
  • a furnace electrode is displaced by an arbitrary differential in height and the effect of such displacement upon a dependent electrical parameter, such as the resistance, is measured.
  • the derivative of the change in resistance with respect to the displacement in height is formed and such derivative alone, or multiplied by the resistance value comprising one or the other of the limits of the change in resistance or preferably the average of the limits, is correlated to the actual height of the submerged tip of the electrode above a pool of molten material in the furnace. In this way, the position of the electrode tip can be accurately determined even though it is not directly observable during operation of the furnace.
  • the present invention relates to the control of electrothermic processes and, more particularly, to the control of such processes in apparatus of the type where the heat is generated by an electric current passing through a re sistant medium, in which a number of electrodes are submerged.
  • the invention is primarily concerned with electric reduction furnaces in which the resistive medium is formed by the charge introduced in the furnace.
  • the invention is generally applicable in connection with all electrothermic processes based on the generation of heat in a resistive fluid.
  • it could be utilized also in e.g. electric boilers.
  • the invention will be described hereinbelow in connection with such a furnace.
  • reference will be made to a furnace in which the electric current passes through one or more electrodes, thence through the charge and finally back to the current source through the melt located below the charge.
  • a reaction zone is formed in the charge, i.e. between the electrode point and the surface of the melt. While the exact shape of that zone is not entirely known. it has been assumed here that it has an annular crosssection and is located between the sides of two imaginary concentric, frustrated cones, the bases of which coincide with the surface of the melt and apexes of which are located inside the electrode a distance above the submerged point thereof. On the other hand, it is well-known that the operational economy of the electrothermic process and the composition and properties of the resulting melt are optimized if the electric heat power, generated within each volume unit of the reaction zone, exceeds a certain minimum value and preferably is held substantially constant.
  • the measuring of the location of the electrode point is instead based on the measurement of some electric variable, e.g. resistance, current intensity, power or phase lag.
  • the measured values are then transformed into pulses triggering a displacement of the electrode upwards or downwards so that the desired optimum furnace operating condition is maintained as much as possible.
  • some electric variable e.g. resistance, current intensity, power or phase lag.
  • the measured values are then transformed into pulses triggering a displacement of the electrode upwards or downwards so that the desired optimum furnace operating condition is maintained as much as possible.
  • some electric variable e.g. resistance, current intensity, power or phase lag.
  • the measured values are then transformed into pulses triggering a displacement of the electrode upwards or downwards so that the desired optimum furnace operating condition is maintained as much as possible.
  • these prior art measuring and controlling methods can only give results which are at best very rough approximations.
  • a further limitation is that the change of the level of an electrode point made on the basis of eg current or power control causes a
  • the main object of this invention is to provide a method and an arrangement which eliminates the disadvantages and limitations described above and permits exact determination of the position of the point of an electrode submerged in a resistive medium, e.g. the charge of a furnace.
  • the invention is based on the concept that even if the level of the electrode point is not available for direct observation or measuring, this is not true concerning changes in the position of that level. It is therefore possible to determine such changes in the vertical position of the electrode and the resulting variations in one or more electric variables andto create therefrom a number of comparison which with great accuracy can be utilized for measuring or controlling the position of the electrode point.
  • this number of comparison at the minimum comprises the derivative of the variation in the measured electrical parameter with respect to the displacement in height of the electrode point level (relative to an arbitrary reference level).
  • others may be used, e.g. the capacitance between the electrode and the melt or between the electrode and some other portion of the furnace.
  • the sole essential requirement is that use is made of the variations of the electrode point level and of the variations to which one or more electric parameters are subjected in consequence of the electrode displacement. Calculations and experiments have shown that the simplest and most suitable expedient is to utilize the resistance variation, i.e. the derivative of change in resistance in respect of the electrode position is determined.
  • the last-mentioned valve should be the average value of the two resistance values which are measured in succession in order to determine the limits of resistance variation caused by the arbitrary displacement of the electrode. But it is also possible instead to use one of those two limit values although the accuracy is then lesser.
  • FIGURE 1 is a diagram illustrating how variations in the composition of the charge inside a reduction furnace may affect the resistance of the charge
  • FIGURE 2 is a diagram illustrating the absolute value of the resistance and also its derivative in respect of ,the electrode level. Both curves have been drawn as a function of the electrode level;
  • FIGURE 3 is a block diagram showing the principal design of an arrangement for carrying out the method according to this invention.
  • Curves I and II in FIGURE 1 show resistance R as a function of H, i.e. the distance between the electrode point and the top surface of the melt, curve I corresponding to a higher resistivity than curve II.
  • the area marked with inclined lines corresponds to a range of furnace operating conditions in which the variations experienced in reaction zone volume and temperature variations are tolerable from a practical point of view.
  • the figure also shows that if the power control of the furnace is regulated in such a manner that the resistance is maintained constant within the limits of the resistivity variations defined by curves I and II, it will be possible to keep the resistance at a selected constant for very different H values, ie, for very different sizes of the reaction zone volume.
  • H values ie, for very different sizes of the reaction zone volume.
  • regulation of the furnace to a constant resistance in conventional manner cannot be relied upon to maintain the submerged end of the electrode at proper height to produce an optimum reaction zone volume in the furnace.
  • FIGURE 2 shows that curve dR/dH has a steeper slope than curve R or, stated in other words, that a certain change of H causes a greater change of dR/tiH than of R. It follows therefore that for this added reason a control based on the derivative in accordance with the invention is more sensitive, and moreover feasible as a practical matter, than a simple resistance control.
  • FIGURE 3 reference numeral 1 therein relates to a furnace having a cover 2 traversed by three electrodes 3 partially submerged in a charge 4. Below the charge is a melt 5. H indicates the distance between the lower electrode point and the top surface of the melt.
  • dB change
  • the corresponding feeding device has been shown for one of the electrodes only but it is to be understood that in practice all electrodes are equipped with similar control units.
  • Each such control unit consists of an electric motor 6 which over a shaft 7 drives a pulley or a winch 8 from which there is suspended a rod or wire 9 supporting the electrode 3.
  • the measured value dH is fed into block 10 which is also supplied with information concerning the voltage V and the current intensity I at the controlled electrode. Since suitable electric equipment for such transmission of information can be designed in many difierent ways and as several suitable designs are known, it is not necessary in this context to describe their nature. To understand the invention it is only necessary to realize that on the basis of the values supplied to block 10 it is possible to determine the impedance, or the resistance R, and its derivative with respect to height H. An electric signal representing that derivative dR/dH is then fed to block 11. If desired and preferably, block 11 is also supplied with information concerning the absolute resistance value R. That supply takes place if an electric switch 14 is in its closed position.
  • Block 12 accordingly contains means, e.g. a switch .or a phase shift apparatus, which in response to the character of the control pulse delivered from block 11 causes motor 6 to rotate in the one or in the opposite direction whereby electrode 3 is raised or lowered.
  • the arrangement may be calibrated by means .of curves or tables compiled empirically. It is also clear that the arrangement may operate fully automatically or semi-automatically and continuously or discontinuously. Of course, it is also possible to arrange instiuments indicating and/ or registrating the electrode positions. For the formation of the product of the absolute resistance value and the derivative it is feasible qiute simply to use an instrument, the indication of which is proportional to the product of two input voltages e.g. a
  • each electrode may utilize two motors 6 one of which provides the displacement on which the measuring is based while the other carries out the control based on the result of that measuring.
  • one motor only may be used which is operable at difierent speeds or has means for variation of its gear ratio so that the measuring movement can take place at a slower rate than the control movement.
  • the time interval between two successive measurements may correspond to a constant magnitude i5 dH This gives a control which is optimized as far as distance H is concerned.
  • a method for determining the location of an electrode end in an electrical apparatus comprising a resistive medium in which at least one such axially displaceable electrode is partially submerged and which is electrothermically heated by the passage of electric current there through, the steps of axially displacing said electrode to vary the position of its submerged end, measuring the magnitude of said displacement and the magnitude of the corresponding variation caused thereby in one of the electrical parameters which are dependent upon the electrode position, forming a number of comparison which includes the derivative of said parameter variation with respect to said electrode displacement, and correlating said number of comparison to the actual position of said submerged electrode end.
  • a method as in claim 1 which includes the step of converting said number of comparison into an electrical signal.
  • a control device for determining the position of the submerged end of an axially displaceable electrode in a furnace comprising means for axially displacing said electrode to vary the position thereof, means for measuring the magnitude of said displacement, means for measuring the magnitude of the corresponding variations thereby caused in an electrical parameter which is dependent upon the electrode position, means for forming the derivative of said parameter variation with respect to said electrode displacement, and means for converting said derivative into a signal representing the actual position of the submerged electrode end.
  • a device as in claim 5 which further includes means for controlling the position of said electrode in response to said signal.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Plasma & Fusion (AREA)
  • Power Engineering (AREA)
  • Vertical, Hearth, Or Arc Furnaces (AREA)
  • Crystals, And After-Treatments Of Crystals (AREA)
  • Manufacture And Refinement Of Metals (AREA)
  • Control Of Resistance Heating (AREA)
  • Waste-Gas Treatment And Other Accessory Devices For Furnaces (AREA)
  • Measurement Of Resistance Or Impedance (AREA)
  • Furnace Details (AREA)
US405726A 1963-10-24 1964-10-22 Method and an arrangement for measuring and controlling electrode positions in electric furnaces and the like Expired - Lifetime US3375318A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
SE11683/63A SE315057B (cs) 1963-10-24 1963-10-24

Publications (1)

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US3375318A true US3375318A (en) 1968-03-26

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Country Status (8)

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US (1) US3375318A (cs)
CH (1) CH442559A (cs)
DE (1) DE1540879B1 (cs)
ES (1) ES305226A1 (cs)
FR (1) FR1440631A (cs)
GB (1) GB1071799A (cs)
NO (1) NO120241B (cs)
SE (1) SE315057B (cs)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3890457A (en) * 1974-02-21 1975-06-17 Pavel Ioelievich Fain Device for program controlling metal remelting processes
DE2456512A1 (de) * 1974-11-29 1976-08-12 Leybold Heraeus Gmbh & Co Kg Anordnung zur regelung der eintauchtiefe von abschmelzelektroden in elektroschlacke-umschmelzoefen
US4303797A (en) * 1980-06-20 1981-12-01 Consarc Corporation Method and apparatus for controlling electrode drive speed in a consumable electrode furnace
US5930284A (en) * 1997-01-15 1999-07-27 Sandia Corporation Multiple input electrode gap controller
CN107504819A (zh) * 2017-10-13 2017-12-22 中国恩菲工程技术有限公司 矿热电炉电极插深的智能检测装置及检测方法

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2581498B1 (fr) * 1985-05-06 1987-05-29 Pechiney Electrometallurgie Procede de regulation a resistance constante de fours a arc electriques

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2766313A (en) * 1955-11-08 1956-10-09 Demag Elektrometallurgie Gmbh Furnace improvement

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2422362A (en) * 1944-06-13 1947-06-17 Delaware Engineering Corp Furnace electrode regulator
US2721948A (en) * 1953-02-10 1955-10-25 Ohio Ferro Alloys Corp Automatic voltage and electrode control for electric-arc furnaces
DE1049000B (de) * 1957-03-05 1959-01-22 Asea Ab Vorrichtung zur Messung der Resistanz in Elektrodenschmelzoefen waehrend des Betriebes
DE1188227B (de) * 1961-12-30 1965-03-04 Asea Ab Verfahren zur Regelung der Elektroden in einem Elektrodenwiderstandsofen und Anordnung zur Durchfuehrung des Verfahrens

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2766313A (en) * 1955-11-08 1956-10-09 Demag Elektrometallurgie Gmbh Furnace improvement

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3890457A (en) * 1974-02-21 1975-06-17 Pavel Ioelievich Fain Device for program controlling metal remelting processes
DE2456512A1 (de) * 1974-11-29 1976-08-12 Leybold Heraeus Gmbh & Co Kg Anordnung zur regelung der eintauchtiefe von abschmelzelektroden in elektroschlacke-umschmelzoefen
US4075414A (en) * 1974-11-29 1978-02-21 Leybold-Heraeus Gmbh & Co. Kg Apparatus for regulating the immersion depth of electrodes in electrode-melting furnaces
US4303797A (en) * 1980-06-20 1981-12-01 Consarc Corporation Method and apparatus for controlling electrode drive speed in a consumable electrode furnace
US5930284A (en) * 1997-01-15 1999-07-27 Sandia Corporation Multiple input electrode gap controller
CN107504819A (zh) * 2017-10-13 2017-12-22 中国恩菲工程技术有限公司 矿热电炉电极插深的智能检测装置及检测方法
CN107504819B (zh) * 2017-10-13 2023-11-03 中国恩菲工程技术有限公司 矿热电炉电极插深的智能检测装置及检测方法

Also Published As

Publication number Publication date
ES305226A1 (es) 1965-03-16
DE1540879B1 (de) 1971-08-12
NO120241B (cs) 1970-09-21
GB1071799A (en) 1967-06-14
FR1440631A (fr) 1966-06-03
CH442559A (de) 1967-08-31
SE315057B (cs) 1969-09-22

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