US3365533A - Continuous electrodes - Google Patents

Continuous electrodes Download PDF

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Publication number
US3365533A
US3365533A US618175A US61817567A US3365533A US 3365533 A US3365533 A US 3365533A US 618175 A US618175 A US 618175A US 61817567 A US61817567 A US 61817567A US 3365533 A US3365533 A US 3365533A
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US
United States
Prior art keywords
electrode
casing
furnace
carbon
shell
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US618175A
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English (en)
Inventor
John R Alexander
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Monsanto Co
Original Assignee
Monsanto Co
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Monsanto Co filed Critical Monsanto Co
Priority to US618175A priority Critical patent/US3365533A/en
Application granted granted Critical
Publication of US3365533A publication Critical patent/US3365533A/en
Priority to NL6802049A priority patent/NL6802049A/xx
Priority to FR1556531D priority patent/FR1556531A/fr
Priority to BE710976D priority patent/BE710976A/xx
Priority to DE19681608031 priority patent/DE1608031A1/de
Priority to GB8677/68A priority patent/GB1172941A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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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
    • H05B7/107—Mountings, supports, terminals or arrangements for feeding or guiding electrodes specially adapted for self-baking electrodes
    • 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

Definitions

  • This electrode consists of an electrically conductive casing and fins extending inwardly for supporting a paste which is electrically and thermally conductive but which is thermally sensitive and partially decomposes to form carbon.
  • the paste consists of relatively small carbon granules and hydrocarbons. This mixture is relatively plastic at the temperatures at which it is placed into the electrode which generally are in the range of from about 0 to about 200 C. The higher temperatures which exist inside the furnace cause the hydrocarbons to vaporize and to decompose to carbon.
  • the present invention overcomes many of the difficulties heretofore encountered by the previous electrodes by insuring that the carbon which is formed upon the decomposition of the hydrocarbons is deposited in the voids between the carbon granules in the paste.
  • the improved self-baking electrode of this invention has an outer electrically and thermally conductive casing, and an electrically and thermally conductive tubular shell positioned inside the casing to form an annular space between the shell and the casing.
  • These elements will generally be round in shape, however, other geometric figures, such as ovals, hexagons, octagons and the like can be used with satisfactory results.
  • the casing and the shell are connected and held in their relative positions to each other by electrically and thermally conductive support means, which can be, in general, any shape such as fins, studs, ribs and the like.
  • the annular space between the casing and the shell is filled with a heat insulating material.
  • Typical heat insulating materials include the cements used in furnace mortar and brick work which will be described more in detail hereinafter.
  • the space inside the shell is fiiled with an electrically and thermally conductive, thermally sensitive, carbon-forming composition or paste.
  • Typical examples include the electrode past-es normally employed in self baking types of electrodes. which also will be described in more detail hereinafter.
  • the casing when the temperatures inside the furnaces are relatively high, such as in the production of elemental phosphorus, it is preferred to construct the casing primarily from carbon steel and use a relatively thin layer of a highly electrically conductive material such as copper, aluminum and various highly electrically conductive alloys.
  • a highly electrically conductive material such as copper, aluminum and various highly electrically conductive alloys.
  • This preferred embodiment enables a reduction in the operating temperature of the casing by reducing the electrical resistance and retains a relatively low cost casing.
  • copper will be the preferred material for plating the carbon steel.
  • the thickness of the layer of the highly conductive material will be dependent upon the particular electrode and the thickness of the casing. In most in stances the layer will be from about 1.0% to about 25% of the total thickness of the casing.
  • the shell and support means can generally be constructed of carbon steel, however, any of the materials which are suitable for the casing can be used for either the shell or the support means.
  • the heat insulating material can be, in general, any material which is thermally and electrically stable up to about 700 C. and has a thermal conductivity coeflicient of below about 12 B.t.u./hr./sq. ft./ F./ in. at about 500 F. In most instances it is preferred to use an insulating material which will undergo a hydraulic set at temperatures as low as about 25 C. and will undergo a thermal set at temperatures of about 600 C. Suitable materials include those which have thermal and electrical stability equivalent to the various refractory materials such as a high alumina content cement, cements prepared from bauxite clay, chrome brick, fireclay brick and the like. Especially preferred are the high alumina content cements that have a thermal conductivity coefficient of about 2 to B.t.u./hr./sq. ft./ F./in. at about 500 F.
  • the paste which is thermally and electrically conductive and which is partially decomposed to form solid carbon is typically a blend of carbon granules and a high temperature pitch such as that obtained from petroleum and coal tar distillation.
  • the carbon granules are generally smaller than about of an inch and generally constitute from about 75% to about 83% by weight of the mixture, with the pitch constituting the remainder of the material.
  • Suitable materials include those known in the art used in the traditional self-baking electrodes.
  • Electrode breakage is significantly reduced in the electrode of this invention because weakspots are not developed in the carbon and mechanical linkages are not employed in the carbon portion of the electrode.
  • the invention therefore enables the use of larger electrodes with appreciable less electrode consumption.
  • the electrodes of this invention can also be continuous electrodes, that is, columns can be built containing the casing, support means and shell upon the partially consumed electrode and then the cement and paste pours into place.
  • Electrodes for electric furnaces can be either solid or hollow.
  • the solid electrode is utilized on furnaces where the furnace burden is fed to the furnace externally to the electrode.
  • Hollow electrodes have one or more passages running the length of the electrode and thereby enable the burden to be fed through the electrode to the furnace hearth.
  • Hollow electrodes are also used to provide a passage for removal of the gases which are produced in the furnace.
  • the electrode of this invention can be either the solid type or the hollow type as desired for the particular use.
  • In the hollow electrode of this invention at least one tubular member runs inside the paste the length of the electrode.
  • This member can be constructed from any of the materials used for the casing, however, in most instances it will be made of carbon steel since the temperatures inside the passage will normally not be as high as those outside the electrode, since the tubular member will not generally carry the electric current. In most instances the tubular member will be round in shape, however, other shapes can be used if desired. In most instances only one tubular member is necessary, however, if desired a plurality of members can be used.
  • FIGURES l, 2 and 3 refer to a solid electrode
  • FIGURES 4, 5 and 6 refer to a hollow electrode.
  • FIGURE 1 is a longitudinal sectional view of a phosphorous furnace equipped with a solid electrode of this invention.
  • FIGURE 2 is an enlarged view of a horizontal segment taken along line 2-2. in the electrode of FIGURE 1.
  • FIGURE 3 is an enlarged longitudinal sectional view of a segment of the lower portion of the electrode of FIGURE 1.
  • FIGURE 4 is a longitudinal sectional view of an electric furnace equipped with a hollow electrode of this invention.
  • FIGURE 5 is an enlarged view of horizontal segment taken along line 4-4 in the electrode of FIGURE 4.
  • FIGURE 6 is an enlarged longitudinal sectional view of a segment of the lower portion of the electrode of FIGURE 4.
  • a phosphorous furnace 10 is provided with a solid electrode 11.
  • a burden is supplied to the furnace through a conventional means 12 and an electric current is supplied to the electrode 11 through a conduit 13.
  • the carbon steel casing 14, receives the current and transmits it through the carbon steel support means 15 (shown in FIGURE 2 which are fins extending the length of the electrode) and the carbon steel tubular shell 16 to an electrically and thermally conductive, thermally decomposable paste 17.
  • the temperature of the lower portion of the electrode 11 is about 2000 C. This results in the electrode being gradually consumed.
  • the temperature outside the furnace housing above the sealing means 18 will generally approach the temperature of the air, however, due to the conduction of heat from inside the furnace, the paste 17 will be at about 200 C.
  • the electrode paste 17 is a typical paste used in a self-baking electrode and contains carbon granules of a relatively small size, that is, smaller than about /3 diameter and contains about 17% by weight of a high temperature pitch derived from the distillation of coal tar.
  • the hydrocarbons in the paste 17 decomposes to form hydrogen and carbon at temperatures of from about 400 C. to 600 C.
  • the hydrogen escapes downwardly through the electrode tip since the tubular member 16 is protected from the heat and hot gases by a refractory cement 19 and therefore is not corroded.
  • the carbon deposits in the voids between the carbon granules.
  • the casing 14, the support means 15 and the tubular member 16 are each constructed of carbon steel.
  • the heat insulating material 19 is a high alumina content refractory cement having a thermal conductivity coefidcient of about 3 and undergoes a hydraulic set outside the furnace housing and a ceramic set inside the furnace when the temperature of the cement reaches about 700 C.
  • the casing 14 is the first of the members to be consumed since it is subjected to the hot gases inside the furnace throughout the period of time which requires for the electrode to be completely consumed and carries a large portion of the electric current.
  • the heat insulating material 19 is later consumed because it is more stable to the higher temperatures than is carbon steel and does not carry the electric current.
  • the carbon steel tubular shell 16 is consumed after it is directly exposed to the high temperatures by the consumption of the heat insulating material 19.
  • the paste 1''] which has partially thermally decomposed forms a carbon which is extremely resistant to the high temperatures and to the corrosive gases contained within the furnace 10. An increased electrode life over any electrode heretofore known is achieved.
  • an electrode having an outside diameter of about 70 inches and operating at a current density of from about 2 to 4 amperes per square centimeter is consumed at the rate of about /3 inch per hour in a phosphorus furnace in which the temperature of the electrode tip is about 2000 C.
  • an electric furnace 20 is provided with a hollow electrode 21.
  • a carbon steel inner tubular member 22 (shown in FIGURE provides a passage 23 throughout the length of the electrode 21 for the introduction of a burden to the furnace.
  • an electric current is supplied to the electrode 21 through conduit 24.
  • the other elements of the electrode 21, that is the casing 25, the .support means 26 (shown in FIGURE 5), the tubular shell 27, the refractory cement 28 and the paste 29 are each constructed from the same materials and each function in the manner as described in reference to FIGURES 1, 2 and 3.
  • the electrode is sealed in the furnace by a conventional sealing means 30.
  • the burden supplied to the furnace is about 150 F., thus the temperature of the carbon steel inner tubular member 22 thereby is below about 1200 C. for the major portion of the electrode 21. At the temperature no appreciable corrosion of the carbon steel inner tubular member occurs.
  • the size of the electrode, the thickness of the casing, shell and tubular member, if a hollow electrode is desired will be dependent upon the particular furnace design and can be determined from engineering guidelines established for electric furnaces. Additionally, the width of the space between the casing and the shell will be dependent upon the temperature outside the electrode, the heat insulating material used and the materials of construction used for the shell. These factors, of course, will be dependent upon the particular furnace and electrode design and the process in which the electric furnace is being used.
  • an electrode having a tubular carbon steel casing, having a diameter of about 6 feet and a thickness of about 0.2 to about 0.3 inch, and a space of from about 2.2 to about 3.0 inches between the casing and a carbon steel shell (having a thickness of from about 0.08 inch to about 0.12 inch), which space is filled with a high alumina content refractory cement having a thermal conductivity coeificient of about 2 B.t.u./hr./sq. ft./ F./in. at about 500 F.
  • An electrode for an electric furnace comprising (a) an electrically conductive casing, (b) an electrically and thermally conductive tubular shell positioned inside said casing to form an annular space between said shell and said casing, (c) electrically and thermally conductive support means connecting said casing and said shell, (d) a heat insulating material filling said space between said shell and said casing and (e) an electrically and thermally conductive, thermally sensitive, carbon-forming paste inside said tubular shell.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Discharge Heating (AREA)
  • Furnace Details (AREA)
  • Vertical, Hearth, Or Arc Furnaces (AREA)
  • Carbon And Carbon Compounds (AREA)
US618175A 1967-02-23 1967-02-23 Continuous electrodes Expired - Lifetime US3365533A (en)

Priority Applications (6)

Application Number Priority Date Filing Date Title
US618175A US3365533A (en) 1967-02-23 1967-02-23 Continuous electrodes
NL6802049A NL6802049A (fi) 1967-02-23 1968-02-13
FR1556531D FR1556531A (fi) 1967-02-23 1968-02-15
BE710976D BE710976A (fi) 1967-02-23 1968-02-19
DE19681608031 DE1608031A1 (de) 1967-02-23 1968-02-20 Elektrode fuer einen Elektroofen
GB8677/68A GB1172941A (en) 1967-02-23 1968-02-22 Continuous Electrodes

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US618175A US3365533A (en) 1967-02-23 1967-02-23 Continuous electrodes

Publications (1)

Publication Number Publication Date
US3365533A true US3365533A (en) 1968-01-23

Family

ID=24476617

Family Applications (1)

Application Number Title Priority Date Filing Date
US618175A Expired - Lifetime US3365533A (en) 1967-02-23 1967-02-23 Continuous electrodes

Country Status (6)

Country Link
US (1) US3365533A (fi)
BE (1) BE710976A (fi)
DE (1) DE1608031A1 (fi)
FR (1) FR1556531A (fi)
GB (1) GB1172941A (fi)
NL (1) NL6802049A (fi)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3524004A (en) * 1968-12-03 1970-08-11 Ohio Ferro Alloys Corp Non-metal reinforced self-baking electrode for electric furnaces
US4575856A (en) * 1984-05-18 1986-03-11 Pennsylvania Engineering Corporation Iron free self baking electrode
US6590926B2 (en) 1999-02-02 2003-07-08 Companhia Brasileira Carbureto De Calcio Container made of stainless steel for forming self-baking electrodes for use in low electric reduction furnaces
US6625196B2 (en) 1999-02-02 2003-09-23 Companhia Brasileira Carbureto De Calcio Container made of aluminum and stainless steel for forming self-baking electrodes for use in low electric reduction furnaces
WO2020043314A1 (de) 2018-08-31 2020-03-05 Max Aicher Gmbh & Co. Kg Verfahren zur herstellung eines verkokungsprodukts

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2725537A1 (de) * 1977-06-06 1978-12-14 Korf Stahl Elektrode fuer lichtbogenoefen
DE2845367C2 (de) * 1978-10-18 1981-01-22 Korf & Fuchs Syst Tech FlUssigkeitsgekühlte Halterung für die Spitze einer Elektrode eines Lichtbogenschmelzofens

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1640735A (en) * 1923-05-16 1927-08-30 Norske Elektrokemisk Ind As Process of making channeled continuous electrodes
US1691505A (en) * 1925-05-15 1928-11-13 Norske Elektrokemisk Ind As Electrode
DE529118C (de) * 1925-06-06 1931-07-10 Josias Rees Metallarmierte kontinuierliche Kohlenelektrode fuer elektrische OEfen
US2764539A (en) * 1952-08-21 1956-09-25 Frank H Morse Carbon electrodes

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1640735A (en) * 1923-05-16 1927-08-30 Norske Elektrokemisk Ind As Process of making channeled continuous electrodes
US1691505A (en) * 1925-05-15 1928-11-13 Norske Elektrokemisk Ind As Electrode
DE529118C (de) * 1925-06-06 1931-07-10 Josias Rees Metallarmierte kontinuierliche Kohlenelektrode fuer elektrische OEfen
US2764539A (en) * 1952-08-21 1956-09-25 Frank H Morse Carbon electrodes

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3524004A (en) * 1968-12-03 1970-08-11 Ohio Ferro Alloys Corp Non-metal reinforced self-baking electrode for electric furnaces
US4575856A (en) * 1984-05-18 1986-03-11 Pennsylvania Engineering Corporation Iron free self baking electrode
US6590926B2 (en) 1999-02-02 2003-07-08 Companhia Brasileira Carbureto De Calcio Container made of stainless steel for forming self-baking electrodes for use in low electric reduction furnaces
US6625196B2 (en) 1999-02-02 2003-09-23 Companhia Brasileira Carbureto De Calcio Container made of aluminum and stainless steel for forming self-baking electrodes for use in low electric reduction furnaces
WO2020043314A1 (de) 2018-08-31 2020-03-05 Max Aicher Gmbh & Co. Kg Verfahren zur herstellung eines verkokungsprodukts

Also Published As

Publication number Publication date
BE710976A (fi) 1968-08-19
GB1172941A (en) 1969-12-03
FR1556531A (fi) 1969-02-07
DE1608031A1 (de) 1970-09-24
NL6802049A (fi) 1968-08-26

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