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WO2003037038A2 - Electrode destinee en particulier aux fours siderurgiques a arc electrique et procede de fonctionnement connexe - Google Patents

Electrode destinee en particulier aux fours siderurgiques a arc electrique et procede de fonctionnement connexe Download PDF

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Publication number
WO2003037038A2
WO2003037038A2 PCT/IT2002/000679 IT0200679W WO03037038A2 WO 2003037038 A2 WO2003037038 A2 WO 2003037038A2 IT 0200679 W IT0200679 W IT 0200679W WO 03037038 A2 WO03037038 A2 WO 03037038A2
Authority
WO
WIPO (PCT)
Prior art keywords
electrode
fluid
gaseous hydrocarbon
combustible
tip
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.)
Ceased
Application number
PCT/IT2002/000679
Other languages
English (en)
Other versions
WO2003037038A3 (fr
Inventor
Domenico Capodilupo
Vittorio Ratto
Eugenio Repetto
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.)
Rina Consulting Centro Sviluppo Materiali SpA
Original Assignee
Centro Sviluppo Materiali SpA
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 Centro Sviluppo Materiali SpA filed Critical Centro Sviluppo Materiali SpA
Priority to EP02788534A priority Critical patent/EP1446984B1/fr
Priority to DE60209146T priority patent/DE60209146T2/de
Priority to AU2002353509A priority patent/AU2002353509A1/en
Publication of WO2003037038A2 publication Critical patent/WO2003037038A2/fr
Anticipated expiration legal-status Critical
Publication of WO2003037038A3 publication Critical patent/WO2003037038A3/fr
Ceased legal-status Critical Current

Links

Classifications

    • 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

Definitions

  • the present invention refers to an electrode and related operation method, addressed in particular to siderurgical electric arc furnaces and the like.
  • Said arcs are generated by effect of the voltage between the graphite electrodes and the metal charge.
  • Electrodes whose bottom end, defined electrode tip, is located at a distance from the metal (scrap or bath) under melting which increases proportionally to the value of the voltage applied between the electrodes and the charge.
  • Conventional electrodes are subject, during their operation, to wear phenomena on the tip (tip consumption) and on the electrode sidewall (oxidative consumption).
  • tip consumption As it is inferrable from several technical papers, among which 'The Electric Arc Furnace - 1990' published by International Iron and Steel Institute, oxidative consumption depends up on the temperature and on the atmosphere surrounding the same electrodes, whereas tip consumption increases proportionally to the value of the current density crossing the electrodes.
  • electrodes were developed providing cooling of their outer surface by water sprays .
  • the latter fail to reach the electrode portion that is internal to the furnace.
  • electrodes having a duct coaxial thereto for introducing solid materials towards the bath and directly inside of the electric furnace.
  • solid materials like e.g. coal, have been used to generate foaming slags and to carry out the metallurgical reduction of the oxides present in the chemical composition of the slag produced during steelmaking.
  • the technical problem underlying the present invention is that of providing novel electrodes allowing to overcome the abovementioned drawbacks, in particular allowing to reduce the consumption thereof and therefore the maintenance interventions.
  • object of the present invention is an operation method of novel electrodes as highlighted above.
  • an electrode in particular for siderurgical electric arc furnaces and the like, comprising means for ejecting a fluid towards the metal bath thereof, characterized in that said fluid comprises a heat decomposable Carbon-rich combustible component, in particular a gaseous hydrocarbon selected from the group comprising methane, ethane, propane, butane and mixtures thereof, so as to produce a cloud which shields the electrode tip and coats with a solid layer the graphite surface of the electrode.
  • a heat decomposable Carbon-rich combustible component in particular a gaseous hydrocarbon selected from the group comprising methane, ethane, propane, butane and mixtures thereof, so as to produce a cloud which shields the electrode tip and coats with a solid layer the graphite surface of the electrode.
  • the present invention refers to an electrode operation method, in particular for siderurgical electric arc furnaces and the like, comprising a step of ejecting, from an electrode tip close to a metal bath, a fluid, characterized in that said fluid comprises a heat decomposable Carbon-rich combustible component, in particular a gaseous hydrocarbon selected from the group comprising methane, ethane, propane, butane and mixtures thereof, so as to produce a cloud which shields the electrode tip and coats with a solid layer the graphite surface of the electrode .
  • a heat decomposable Carbon-rich combustible component in particular a gaseous hydrocarbon selected from the group comprising methane, ethane, propane, butane and mixtures thereof, so as to produce a cloud which shields the electrode tip and coats with a solid layer the graphite surface of the electrode .
  • the main advantage of the electrode and of the related operation method according to the present invention lies in allowing a relevant reduction in the consumption, both the tip and the oxidative one, of the conductive bottom (graphite) component of the electrode, thereby increasing the service life and reducing the number of changeouts thereof .
  • the present invention will hereinafter be described according to a preferred embodiment thereof, given by way of a non-limiting example and with reference to the attached drawings, wherein: * figure 1 is a schematic view of a DC electric furnace incorporating a mono electrode according to the present invention;
  • figure 2 is a schematic view of the electrode of figure 1 in a longitudinal section thereof;
  • figure 3 shows an enlarged detail of the electrode shown in figure 2.
  • figure 4 shows an enlarged detail of the electrode tip from which two fluids are concomitantly injected.
  • figure 5 shows a temperature change diagram of an electrode cooled according to the present invention.
  • a siderurgical electric arc furnace is indicated by 1.
  • the furnace 1 is a DC mono electrode arc furnace, lying in a so-called flat bath operative section, and being continuously fed, e.g. scrap metal 2, via a feed duct 3.
  • the furnace 1 comprises a case bottom portion 4, consisting of a shaft 5, housing a metal bath 12 in which the scrap metal 2 is discharged, a conducting hearth 6 for current passing, whereat the resulting molten steel pools, and a case top portion 7.
  • the latter forms the crown of the melting chamber 8 and it has a port 9 apt to allow the insertion of an electrode 10.
  • the electrode 10 acts as the cathode (negative pole), and the conductive members 11 of the conducting hearth act as the anode (positive pole).
  • the electrode 10 and the conductive members 11 are electrically connected to a generator 13.
  • the electrode 10 comprises first means for ejecting at least one fluid towards the metal bath 12 contained in the electric furnace 1 , which will be detailed hereinafter.
  • the electrode 10 in its top portion comprises a cylinder- shaped column body 16 made of graphite or metallic conductive material.
  • the column body 16 is water-cooled and partially coated with a protective layer of ceramics insulating material 17.
  • the bottom portion 26 of the electrode 10, including the tip 14, is made of graphite.
  • the electrode 10 is provided with an axial hole 19, first means for ejecting a fluid comprising a nozzle 20 being housed therein.
  • the nozzle 20 water-cooled by means of a cooling duct 18 running therethrough, is slidable inside of the hole 19.
  • the lance 20 ends in a nozzle head 21 of a shape suitable to give the desired fluid dynamics characteristics, and preferably those of a compact jet, to a fluid 22 outletted therefrom.
  • the fluid 22 comprises at least one heat decomposable Carbon-rich combustible component, in particular a gaseous hydrocarbon selected from the group comprising methane, ethane, propane, butane and mixtures thereof, and it is denominated 'reactive fluid' as it is apt to carry out a reducing/combustible action, with metallurgic functions analogous to those of coal usually found inside of an electric furnace.
  • the fluid 22 exits the ejecting nozzle, crossing the end section of the axial hole of the electrode at a suitable rate, heating up, yet not slowly enough to undergo substantial chemical transformations, until reaching the tip 14 of the electrode 10 whereat its molecular breaking is carried out by the heat provided by an electric arc.
  • the arc 15 turns into a plasma arc AP (at very high temperatures, ranging from 15.000 to 20000°C) due to the presence of the gas at the ionic state which, departing from the tip 14 of the electrode 10, oxidizes in the furnace atmosphere, thermally contributing to the latter and thereby allowing a power-saving in steelmaking.
  • a plasma arc AP at very high temperatures, ranging from 15.000 to 20000°C
  • the electrode 10 (graphite and metallic material versions) further comprises second means 23 for ejecting a second fluid 24. Said means 23 is positioned onto the cylinder-shaped surface of the electrode 10, bottomwise to the body 16.
  • the second fluid 24 stands out for its antioxidant properties, and it may comprise, or be replaced by, Carbon-based combustible compositions, like e.g. combustible oil, coal dust and other carbides like carbides of Calcium, of Silica, of Aluminum.
  • Carbon-based combustible compositions like e.g. combustible oil, coal dust and other carbides like carbides of Calcium, of Silica, of Aluminum.
  • Combustible oils may comprise: gas oil, diesel oil, petrols, light oils from petrol refining, or even drain oils deriving from lubrication of mechanical components, sludges, cutting oils, Carbon- and Hydrogen-containing emulsions.
  • the ejected fluid 24 may wholly or partially comprise water. Said fluid interacts with the cylinder-shaped graphite surface, so as to carry out a protective action which strongly reduces the oxidation of the graphite onto the surface of the body 26.
  • the fluid 24 may also comprise, optionally suspended, highly stable oxides like, e.g.
  • the second means 23 for ejecting consist of a ring of peripheral nozzles which are fed separately with respect to the nozzle 20 by a suitable feeding loop indicated by 25 in figure 2.
  • a suitable feeding loop indicated by 25 in figure 2 With reference to figures 2, 3 and 4, via the nozzle head 21 there is ejected the first fluid 22, which reacts with the metal bath and with the atmosphere thereabove in an environment having a very high temperature.
  • the nozzle head 21 may comprise a single inlet, from which a fluid, optionally in a mixture formed with at least one fluid reactive component is injected, or it may comprise a plurality of outlets, each corresponding to a reactive fluid ejected and fed separately from the other fluids.
  • the nozzle head 21 can vary its position inside of the axial hole 19 in connection with the consumption of the tip 14. Hence, the nozzle 20 should be slidable along the hole 19 rather than stationary with respect to the electrode.
  • figure 4 depicts a section of the electrode tip 10 and of the nozzle head 20 when it be desirable to concomitantly inject a second fluid 24 (e.g., oil) and a first fluid 22 (gas) inside of the electrode hole, yet keeping the two fluids separate down to the lance tip.
  • a second fluid 24 e.g., oil
  • a first fluid 22 gas
  • the injecting of the first and of the second fluid produces a region 28 hosting chemical transformations, at the projection of the nozzle head 21 between the tip 14 of the electrode 10 and the bath surface 12, and a exhaust volume 29, generated by the reaction gas of the two fluids which carries solid/liquid particles captured by the free surface of the molten bath 12 and solid particles evolved from the molecular demolition of fluids. Rising back along the electrode, such exhaust volume 29 deposits said particles onto the surface thereof, forming a layer of solid material having a function analogous to that of said antioxidant barrier 27 and coating the entire surface of the bottom portion of the electrode 10 which comprises the tip 14.
  • Electrode consumption In order to reduce the oxidative consumption of the electrode, due to the presence of air or of oxygen, the following operation steps were carried out. generating, about the graphite electrode, a layer of reducing (or at least of non- oxidizing) gas extended to the full length of the electrode generating a thin solid material barrier 27, such as to physically and chemically separate the graphite surface of the electrode from the surrounding atmosphere.
  • the antioxidant barrier 27 can be made by the oxides present in the second ejection fluid 24, or by the gas resulting from the molecular demolition of the fluid formed by gases/liquids outletted from the nozzle 20 when said gases/liquids interact with the plasma arc 15 and with the free surface of the bath, where there generally is a slag. In this latter case, in order to generate the solid antioxidant barrier 27, the inletting of solid substances in the fluid 24 outletted from the nozzle 20 by the inlet 30 is unnecessary since said solid substances are already largely present in the slag.
  • the chemical reactions taking place in the region 28 underlying the nozzle 14 of the electrode 10 are valid for all hydrocarbons of suitable ratios, and are exemplified as follows making reference to the injection of methane fuel.
  • CH 4 ⁇ C + 2H 2 endothermic reaction (2) C + 2H 2 + 3/2O 2 ⁇ CO + 2H 2 O exothermic reaction
  • the first reaction (1) defining the breaking (crack) of the Carbon-Hydrogen bonds, allows a cooling of the tip 14, reducing its consumption.
  • the second reaction (2) occurring when the products of the first reaction (1) meet the Oxygen present in the furnace atmosphere or contained in the metal bath due to the reduction under way, concurs to heat the metal bath, most conveniently so when the latter is fed scrap.
  • the temperatures of the electric arc being very high, Oxygen required for carrying out the second reaction may partially be provided by the oxides (FeO, SiO 2 , MnO, etc.) present in the slag, the latter being thereby reduced.
  • This entails positive metallurgic effects, like steel desulfurization, Manganese, Chrome and Silica recovery, via the reduction of the corresponding slag oxides.
  • the reactions 1 and 2 generate the exhaust volume 29, which is opaque due to the presence of solid particles and is such as to limit also the radiation of the plasma arc 15 towards the tip 14, concurring to lower the temperature of the latter and therefore to reduce graphite consumption.
  • the water-cooled nozzle 20 concurs to reduce oxidative consumption as it lowers the average temperature of the electrode. To that lower temperature there corresponds a lower electrical resistivity of the graphite of the electrode 10 and hence, a lesser heating up thereof by Joule effect.
  • An exemplary computation shows the average temperature of the electrode 10 to be of about 250°C lower with respect to that of an uncooled electrode (figure 5). With this lower temperature value, the corresponding electrical resistance of the graphite, as well as the heating power, is of about 5% lower.
  • a further cooling of the electrode 10 may be attained extracting the electrode at the end of each casting, before it reaches its steady thermal state, and putting it in a container having a non-oxidizing atmosphere in which it is left to cool down prior to reuse.
  • a second electrode previously cooled or new and placed in a working position by a second electrode bearing arm independent from the first one.
  • the electrode set forth allows to attain an increase in furnace productivity by increasing the thermal power transferred to the metal bath and due to the option of using, current strengths being equal, higher voltages of the electric arc, and hence greater electrical powers.
  • the consumption of the electrode which depends on the temperature and is proportional to the current density admiring on the tip thereof and causing its heating, is reduced by virtue of the following three combined effects:
  • Electric arc length The injection of fluids through the electrode allows to attain a 20%-60% shortening of the electric arc 15.
  • the electric arc 15 radiates less towards the refractory walls of the furnace 1, reducing the entailed damage thereto and also improving heat transmission to the bath 12.
  • the mentioned results have been constantly sought in steelshop electric furnaces, during flat bath operation steps, by generating foaming slags or reducing the electrical power, entailing bath oxidation and productivity decrease, respectively.
  • the shortening of the electric arc attained by this method reduces the need to employ materials (C, CaCO 3 , carbides) to generate foaming slags.
  • foaming slag generation is extremely difficult and costly in terms of Cr yield, Cr being oxidized by the generation-required Oxygen.
  • the reaction products of the injected fluids mainly consisting of gases from hydrocarbon cracking
  • the Nitrogen ions generated by effect of the very high temperatures of the electric arc have a partial pressure (concentration) lower than that had with an open-air generated arc. This entails that also the steel that is being made be exposed to a lesser extent, at the electric arc impact zone, to Nitrogen inletting.
  • the advantage of this effect is that the final Nitrogen content of the steel made in the melting electric furnace may reach values comparable to those attainable in integrated cycle steelmaking (20 ⁇ 50 ppm).
  • the employ of the electrode subject-matter of the present invention allowed to generally decrease the environmental impact, owing to reduced:

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Vertical, Hearth, Or Arc Furnaces (AREA)
  • Discharge Heating (AREA)
  • Refinement Of Pig-Iron, Manufacture Of Cast Iron, And Steel Manufacture Other Than In Revolving Furnaces (AREA)
  • Electrical Discharge Machining, Electrochemical Machining, And Combined Machining (AREA)
  • Carbon And Carbon Compounds (AREA)
  • Furnace Details (AREA)

Abstract

La présente invention concerne une électrode et un procédé de fonctionnement connexe, destinés en particulier aux fours sidérurgiques à arc électrique et analogues, laquelle électrode comprend des moyens qui permettent de projeter un fluide vers le bain métallique, le fluide précité comprenant un composant combustible riche en carbone se décomposant à la chaleur, en particulier un hydrocarbure gazeux choisi dans le groupe composé du méthane, de l'éthane, du propane, du butane et de mélanges de ces derniers, de façon à produire un nuage qui protège le bout de l'électrode et qui revêt d'une couche solide la surface en graphite de cette dernière.
PCT/IT2002/000679 2001-10-26 2002-10-25 Electrode destinee en particulier aux fours siderurgiques a arc electrique et procede de fonctionnement connexe Ceased WO2003037038A2 (fr)

Priority Applications (3)

Application Number Priority Date Filing Date Title
EP02788534A EP1446984B1 (fr) 2001-10-26 2002-10-25 Electrode destinee en particulier aux fours siderurgiques a arc electrique et procede de fonctionnement connexe
DE60209146T DE60209146T2 (de) 2001-10-26 2002-10-25 Elektrode, insbesondere für elektrolichtbogenöfen der stahlindustrie und dergleichen, und entsprechende operationsmethode
AU2002353509A AU2002353509A1 (en) 2001-10-26 2002-10-25 Electrode, in particular for siderurgical electric arc furnaces and the like, and related operation method

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
IT2001RM000634A ITRM20010634A1 (it) 2001-10-26 2001-10-26 Elettrodo, in particolare per forni elettrici ad arco di tipo siderurgico e simili, e relativo metodo di esercizio.
ITRM2001A000634 2001-10-26

Publications (2)

Publication Number Publication Date
WO2003037038A2 true WO2003037038A2 (fr) 2003-05-01
WO2003037038A3 WO2003037038A3 (fr) 2004-05-06

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PCT/IT2002/000679 Ceased WO2003037038A2 (fr) 2001-10-26 2002-10-25 Electrode destinee en particulier aux fours siderurgiques a arc electrique et procede de fonctionnement connexe

Country Status (7)

Country Link
EP (1) EP1446984B1 (fr)
AT (1) ATE317630T1 (fr)
AU (1) AU2002353509A1 (fr)
DE (1) DE60209146T2 (fr)
ES (1) ES2260496T3 (fr)
IT (1) ITRM20010634A1 (fr)
WO (1) WO2003037038A2 (fr)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2015062956A1 (fr) * 2013-10-31 2015-05-07 Siemens Aktiengesellschaft Procédé pour faire fonctionner un four à arc et four à arc
WO2015062968A1 (fr) * 2013-10-31 2015-05-07 Siemens Aktiengesellschaft Procédé pour faire fonctionner un four à arc et four à arc
JP2016108575A (ja) * 2014-12-02 2016-06-20 新日鐵住金株式会社 直流アーク式電気炉による高純度鋼の製造方法
EP3433385A1 (fr) * 2016-03-25 2019-01-30 L'Air Liquide Société Anonyme pour l'Etude et l'Exploitation des Procédés Georges Claude Recouvrement d'électrodes au gaz inerte dans un four à arc électrique
CN112595093A (zh) * 2020-11-26 2021-04-02 天津水泥工业设计研究院有限公司 一种用于电弧炉可喷吹粉剂的加热电极工艺及装置

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102020005129B4 (de) 2020-08-21 2024-05-16 Technische Universität Bergakademie Freiberg, Körperschaft des öffentlichen Rechts Kohlenstoffärmere und kohlenstofffreie Elektroden für den Einsatz in der Stahlmetallurgie
DE102020005130B3 (de) 2020-08-21 2022-02-10 Technische Universität Bergakademie Freiberg, Körperschaft des öffentlichen Rechts Verfahren zur Herstellung von kohlenstoffärmeren und kohlenstofffreien Elektroden-Wabenkörper-Werkstoffverbunden für den Einsatz in der Metallurgie

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1334116A (en) * 1971-01-22 1973-10-17 British Steel Corp Arc furnace operation
GB1390351A (en) * 1971-02-16 1975-04-09 Tetronics Research Dev Co Ltd High temperature treatment of materials
GB1532075A (en) * 1976-08-24 1978-11-15 Karinsky V Electric arc heating vacuum apparatus
DE3443740A1 (de) * 1984-10-11 1986-04-17 Fried. Krupp Gmbh, 4300 Essen Verfahren und vorrichtung zum halten oder erhoehen der temperatur einer metallschmelze
DE3629055A1 (de) * 1986-08-27 1988-03-03 Kloeckner Cra Tech Verfahren zum gesteigerten energieeinbringen in elektrolichtbogenoefen

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2015062956A1 (fr) * 2013-10-31 2015-05-07 Siemens Aktiengesellschaft Procédé pour faire fonctionner un four à arc et four à arc
WO2015062968A1 (fr) * 2013-10-31 2015-05-07 Siemens Aktiengesellschaft Procédé pour faire fonctionner un four à arc et four à arc
CN105940765A (zh) * 2013-10-31 2016-09-14 首要金属科技德国有限责任公司 用于操作电弧炉的方法以及电弧炉
US20160273062A1 (en) * 2013-10-31 2016-09-22 Primetals Technologies Germany Gmbh Method for operating an electric arc furnace, and electric arc furnace
JP2016108575A (ja) * 2014-12-02 2016-06-20 新日鐵住金株式会社 直流アーク式電気炉による高純度鋼の製造方法
EP3433385A1 (fr) * 2016-03-25 2019-01-30 L'Air Liquide Société Anonyme pour l'Etude et l'Exploitation des Procédés Georges Claude Recouvrement d'électrodes au gaz inerte dans un four à arc électrique
CN112595093A (zh) * 2020-11-26 2021-04-02 天津水泥工业设计研究院有限公司 一种用于电弧炉可喷吹粉剂的加热电极工艺及装置
CN112595093B (zh) * 2020-11-26 2022-05-27 天津水泥工业设计研究院有限公司 一种用于电弧炉可喷吹粉剂的加热电极工艺及装置

Also Published As

Publication number Publication date
AU2002353509A1 (en) 2003-05-06
WO2003037038A3 (fr) 2004-05-06
DE60209146D1 (de) 2006-04-20
EP1446984B1 (fr) 2006-02-08
ITRM20010634A1 (it) 2003-04-28
EP1446984A2 (fr) 2004-08-18
ITRM20010634A0 (it) 2001-10-26
ATE317630T1 (de) 2006-02-15
DE60209146T2 (de) 2006-10-19
ES2260496T3 (es) 2006-11-01

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