US3624261A - Self-baking electrode structure and method of operating same - Google Patents

Self-baking electrode structure and method of operating same Download PDF

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Publication number
US3624261A
US3624261A US63251A US3624261DA US3624261A US 3624261 A US3624261 A US 3624261A US 63251 A US63251 A US 63251A US 3624261D A US3624261D A US 3624261DA US 3624261 A US3624261 A US 3624261A
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Prior art keywords
electrode
bar
baking
carbon mass
measuring
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Expired - Lifetime
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US63251A
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English (en)
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Mario Cavigli
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Montedison SpA
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Montedison SpA
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    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
    • C25C3/00—Electrolytic production, recovery or refining of metals by electrolysis of melts
    • C25C3/06—Electrolytic production, recovery or refining of metals by electrolysis of melts of aluminium
    • C25C3/20—Automatic control or regulation of cells
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
    • C25C3/00—Electrolytic production, recovery or refining of metals by electrolysis of melts
    • C25C3/06—Electrolytic production, recovery or refining of metals by electrolysis of melts of aluminium
    • C25C3/08—Cell construction, e.g. bottoms, walls, cathodes
    • C25C3/12—Anodes
    • C25C3/125—Anodes based on carbon
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
    • G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
    • G01N27/041—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of a solid body
    • 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
    • H05B7/06—Electrodes
    • H05B7/08—Electrodes non-consumable
    • H05B7/085—Electrodes non-consumable mainly consisting of carbon
    • H05B7/09—Self-baking electrodes, e.g. Söderberg type 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

  • AuomeyHubbell, Cohen & Stiefel ABSTRACT improved results in operating self-baking electrodes are achieved by constantly maintaining a bar made of an electrically conductive material well immersed in a carbon mass contained within a metal shell, measuring the voltage drop between the bar and the metal shell and measuring a ratio between this voltage drop and the electrode current.
  • the present invention relates to a method for operating selfbaking electrodes. More particularly this invention relates to a method for continuously measuring the baking degree of selfbaking electrodes especially suitable for submerged arc furnaces. This invention also relates to an apparatus for carrying out said method.
  • a self-baking electrode substantially comprises a metallic, peripherally extending, vertical shell and a carbon mass contained therein.
  • This metallic shell is generally provided with a metallic internal reinforcing structure.
  • One of the purposes of the reinforcing structure is to support the weight of the carbon mass.
  • the electrode is fed at its top end with a raw electrode-forming paste, made up of pieces of calcined coal of various particle size mixed with a binder, usually pitch.
  • the electrode-forming paste undergoes a process of gradual transformation.
  • the carbon mass may be schematically subdivided, from the top downward, into four zones.
  • the paste in the first or top zone, where the temperature is lower than about 100 C., the paste is in the solid state.
  • the second zone wherein the temperature is generally between about l and 300 C. (depending on the characteristics of the raw paste), the paste takes on the characteristics of a liquid phase, the viscosity thereof gradually increasing downwardly. In this zone the paste may be termed molten.”
  • the third zone wherein the temperature is generally between about 300 and 700 C., the paste is in its baking stage. The tarry and pitchy substances decompose and distill; the electrode-forming paste then gradually changes into a tough, compact carbon mass highly suitable for carrying the electrode current.
  • the electrode is baked.
  • the transformation process extends to new portions of the electrode; a new portion of molten paste enters the baking stage and a new portion of solid paste goes over into the molten state.
  • metal conductors carrying the electric current to the electrode must be fitted to the baked part of the carbon mass, that is, to the conducting portion of the self-baking electrode.
  • the electrical conductors When, during the furnace operation, the electrode is periodically lowered into the furnace, the electrical conductors must be shifted to a new electrode zone.
  • This shifting of the electrode with respect to the electric conductors (which is usually referred to as the slipping of the electrode) is in general carried out periodically.
  • the slipping, for instance the daily slipping, of an electrode must of course compensate for the wear out of the electrode during the same period of time.
  • the slipping frequency and the thereto related length of each slipping depends on the baking degree of the electrode-forming paste, since one must avoid having the unbaked or partially baked paste carry the current as it is a poor electrical conductor.
  • index C is a measure of the baking degree of the electrode.
  • index C is inversely proportional to the baking degree of the electrode inasmuch as high values of C correspond to low values of the baking degree and, thus, in practice to situations in which the electrode should not be slipped and in which the current density is or should be reduced.
  • my invention provides a method which overcomes the drawbacks and uncertainties of the above-mentioned empirical evaluation methods of the prior art.
  • my invention makes possible continuous and reliable information on the baking degree of the electrode forming paste in a self-baking electrode, and thereby enables an operator to know how much the electrode may be slipped with respect to the electrical contacts without having to decrease the electrode current and therefore the output capacity of the furnace without running the risk of breakages.
  • my invention allows a furnace operator to continuously monitor the baking process of the raw electrode-forming paste (for instance, at the startup of a new furnace or after a long shutdown of a furnace) through the constant indication of the progress of the baking, up to the attainment of a normal baking degree.
  • FIG. 1 is a diagrammatic illustration of a self-baking electrode and of an apparatus for carrying out the method of the present invention.
  • FIG. 1 DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. 1 in detail, there is shown a self-baking electrode device suitable for carrying out the method in accordance with my invention.
  • a cylindrical metal shell I contains a carbon mass M consisting of an upper layer 2 of solid raw paste, a second layer 3 of molten paste, a paste baking zone 4 and section 5 of baked electrode.
  • the current-carrying plates 6 and conductors 7 connect the electrode to the external electrical circuit not shown in FIG. 1.
  • the carbon mass is of the type that is well known in the prior art. Specifically, it is commonly prepared in the form of a paste made up of finely divided particles of calcined coal mixed with a binder, preferably pitch. In this state the carbon mass is what has been termed above alayer 2 of solid raw paste.
  • the paste is subjected to the heat from the joule effect of electric current passing through the electrode structure it is progressively converted from solid raw paste to molten paste and ultimately to a baked electrode.
  • a metal bar 8 is disposed within the carbon mass M, preferably along the longitudinal axis of the electrode throughout the length thereof.
  • tension rods (not shown in FIG. 1) made of an insulating material such as wood or Bakelite may be employed to fix conductive bar 8 to the previously mentioned conventional reinforcing structure of the electrode.
  • the lower portion'of the conductive bar 8 is well immersed in the baked zone 5 of the carbon mass so as to ensure a good electrical contact with this zone.
  • the bar material for instance a metal
  • the conductive bar is preferably shaped to offer a widesurface of contact with the baked carbon mass, for instance in the shape of a strap or ribbon or any other equivalent shape easily determined by the skilled art worker.
  • the conductive bar is intended to be consumed together with the carbon electrode and must be therefore periodically restored by adding a new length of bar. This addition may be carried out simply by welding a new length of bar to the upper end of the conductive bar, although other connecting procedures may be employed.
  • a device 9 for measuring the voltage drop between bar 8 and shell I is connected by means of conductors 10 and 11 to the upper ends of bar 8 and shell 1.
  • the measuring of the voltage drop is preferably carried out between shell 1 and bar 8, inasmuch as when measuring between bar 8 and the current carrying plates 6, the contact resistance between shell 1 and current-carrying plates 6 would decrease the sensitivity of the method.
  • the measuring of the electrode current is conveyed, as by conductors I2 and 13.
  • the electrodes In a threephase electrical furnace producing calcium carbide, the electrodes have a diameter of 950 mm. and were delta connected and supplied with alternating current through a delta-delta transformer.
  • the electrodes have an outside shell made of a steel sheet and an inside reinforcing structure consisting of six fins welded radially to the inner wall of the outside shell. On the axis of each electrode there was arranged a steel strap 30 mm. wide and 2mm. thick.
  • Device 9 was a double moving element recording ohmmeter.
  • Conductors l0 and 11 are connected to the upper ends of the central bar 8 and of the metal shell 1 and to the input terminals of the recording ohmmeter.
  • the same meter 9 was used to measure the electrode current, suitably derived from a current transformer on the primary side of the current supply to the transformer of the furnace. This is not necessary to the invention and is not shown in FIG. 1 for simplicitys sake.
  • Ohmmeter 9 recorded the ratio between the two quantities introduced, that is, the potential between shell 1 and bar 9, and the electrode current.
  • the electrode current of the nor mal operation of the furnace was 45,000 A.
  • Voltage drops detected between shell 1 and bar 8 varied from about 0.2 to about 0.8 v., depending on the degree of baking of the carbon mass layer 5, and on the electrode current.
  • the index C figures corresponding respectively to excellent and poor baking conditions will also change.
  • the scale of the recording device While operating at a fixed and constant electrode current, after having determined the voltage drop figure corresponding to the best baking conditions, the scale of the recording device will be recalibrated and the value 1 of index C will be made to correspond to this new ratio Voltage drop corresponding to the best baking conditions Elec uqis 91 3595 9- In FIG. 2 the typical graph of C is shown. The electrode was slipped down 2 cm. every hour without varying the electrode current.
  • FIG. 3 shows the graph of C during the period of time immediately subsequent to the time period graphed in FIG. 2.
  • the electrode after the repeated slippages shown in FIG. 2, was very long; slippage was therefore discontinued for ll hours. During this period the value of C dropped below unity, stabilizing itself around 0.8 and thus indicating a baking degree higher than the normal one.
  • FIG. 4 illustrates a dangerous situation in which the electrode was slipped 8 cm. at the 10th hour and again at the llth hour, before the value of C was restored to normal, and then the electrode was caused to be slipped 4 cm.
  • Index C after the usual fast peak, returned towards the figure 2.2, while the electrode, loaded at the normal current of 45,000 A, demonstrated a serious risk of breakage which compelled the immediate reduction of electrode current to 20,000 A., with a consequential reduction in the output capacity of the furnace.
  • means for measuring a voltage drop between said bar and said shell comprising means for connecting said voltage drop measuring means to said bar and said shell;
  • d. means for measuring an electrode current.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Plasma & Fusion (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
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  • Discharge Heating (AREA)
  • Pharmaceuticals Containing Other Organic And Inorganic Compounds (AREA)
US63251A 1969-08-22 1970-08-12 Self-baking electrode structure and method of operating same Expired - Lifetime US3624261A (en)

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Application Number Priority Date Filing Date Title
IT2115069 1969-08-22

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US (1) US3624261A (xx)
JP (1) JPS4815975B1 (xx)
BE (1) BE755140A (xx)
CH (1) CH510241A (xx)
DE (1) DE2040854C3 (xx)
FR (1) FR2058897A5 (xx)
GB (1) GB1268619A (xx)
NL (1) NL7012133A (xx)
NO (1) NO127374B (xx)
SE (1) SE371734B (xx)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4122294A (en) * 1976-12-28 1978-10-24 Jury Fedorovich Frolov Method of and device for forming self-baking electrode
CN1908239B (zh) * 2005-08-02 2011-03-09 高德金 利用铝电解槽大电流对导电材料部件进行电压降测试的方法

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
IT1243899B (it) * 1989-11-14 1994-06-28 Elkem Technology Procedimento e mezzi per la produzione continua di corpi di carbone.
DE102015223692A1 (de) 2015-11-30 2017-06-01 Sms Group Gmbh Backstatusüberwachung einer selbstbackenden Elektrode

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1751177A (en) * 1928-09-26 1930-03-18 Norske Elektrokemisk Ind As Process in the manufacture of self-baking electrodes
US3513245A (en) * 1968-11-22 1970-05-19 Air Reduction Method and apparatus for joining shell sections of soderberg electrodes

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1751177A (en) * 1928-09-26 1930-03-18 Norske Elektrokemisk Ind As Process in the manufacture of self-baking electrodes
US3513245A (en) * 1968-11-22 1970-05-19 Air Reduction Method and apparatus for joining shell sections of soderberg electrodes

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4122294A (en) * 1976-12-28 1978-10-24 Jury Fedorovich Frolov Method of and device for forming self-baking electrode
CN1908239B (zh) * 2005-08-02 2011-03-09 高德金 利用铝电解槽大电流对导电材料部件进行电压降测试的方法

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Publication number Publication date
DE2040854A1 (de) 1971-03-04
FR2058897A5 (xx) 1971-05-28
NO127374B (xx) 1973-06-12
DE2040854B2 (de) 1979-07-05
CH510241A (de) 1971-07-15
SE371734B (xx) 1974-11-25
DE2040854C3 (de) 1980-03-20
JPS4815975B1 (xx) 1973-05-18
GB1268619A (en) 1972-03-29
BE755140A (fr) 1971-02-22
NL7012133A (xx) 1971-02-24

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