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WO2012032421A1 - Fours de type balai-arc et procédé de traitement de minerais - Google Patents

Fours de type balai-arc et procédé de traitement de minerais Download PDF

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Publication number
WO2012032421A1
WO2012032421A1 PCT/IB2011/052428 IB2011052428W WO2012032421A1 WO 2012032421 A1 WO2012032421 A1 WO 2012032421A1 IB 2011052428 W IB2011052428 W IB 2011052428W WO 2012032421 A1 WO2012032421 A1 WO 2012032421A1
Authority
WO
WIPO (PCT)
Prior art keywords
brush
electrodes
arc furnace
chamber
furnace
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/IB2011/052428
Other languages
English (en)
Inventor
Hendrik Willem Greyling
Frederik Petrus Greyling
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.)
Individual
Original Assignee
Individual
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 Individual filed Critical Individual
Publication of WO2012032421A1 publication Critical patent/WO2012032421A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27B—FURNACES, KILNS, OVENS OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
    • F27B3/00—Hearth-type furnaces, e.g. of reverberatory type; Electric arc furnaces ; Tank furnaces
    • F27B3/08—Hearth-type furnaces, e.g. of reverberatory type; Electric arc furnaces ; Tank furnaces heated electrically, with or without any other source of heat
    • F27B3/085—Arc furnaces
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
    • C21C5/52—Manufacture of steel in electric furnaces
    • C21C5/5211—Manufacture of steel in electric furnaces in an alternating current [AC] electric arc furnace
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
    • C21C5/52—Manufacture of steel in electric furnaces
    • C21C5/5264—Manufacture of alloyed steels including ferro-alloys
    • 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
    • Y02P10/20—Recycling

Definitions

  • This invention relates to brush-arc furnaces, more particularly for use in the production of ferrochrome and to a method of processing ferrochrome ores.
  • a known submerged-arc AC furnace comprises a generally cylindrical vessel comprising a closed roof through or from which three Soderberg electrodes extend axially into a chamber defined by the vessel.
  • the electrodes have a diameter of d and typically extend to between 0.5d and 2d into a burden held in the chamber.
  • the electrodes are connected to three single-phase furnace transformers, alternatively to a single three phase transformer that acts as AC power supply to the furnace.
  • the vessel is provided with a refractory lining to provide protection against high reaction temperatures caused by the electric arcs created by the furnace electrodes.
  • raw materials comprising in general a combination of metallic ores, reductants and fluxes are fed into the chamber on a continuous basis, utilizing devices such as feed chutes extending through the roof.
  • Molten alloy and molten slag (waste material) are periodically removed through one or more refractory lined tap holes in the refractory lined vessel.
  • Hot gases emanating from the reaction in the furnace vessel are drawn off via one or more off-take ducts extending through the roof.
  • it is generally required to have a permeable burden comprising raw materials to ensure that gasses generated during the process can flow to the top of the burden and therefore the raw materials are required to comprise a relatively large portion of lumpy ores and/or pelletized fine ores.
  • a large percentage of carbon fed into the furnace needs to be in the form of coke and char to ensure the formation of a permeable coke bed inside the burden.
  • a brush-arc furnace comprising:
  • a vessel defining a chamber holding a burden comprising a body and a layer on the body comprising slag, the layer having an upper surface; at least two electrodes, each having a diameter d;
  • each of the at least two electrodes extending into the chamber to a level between a first limit above the surface and a second limit below the surface;
  • the first limit being smaller than 0.5d and the second limit being smaller than 0.3d;
  • the at least two electrodes are driven into brush-arc operation, so that a short and somewhat diffused arc is maintained between the electrode and the burden.
  • the first limit may be smaller than 0.4d and preferably is smaller than 0.3d.
  • the second limit may be smaller than 0.2d.
  • the power supply may comprise an AC power supply and the furnace may comprise three electrodes, each having a diameter of d.
  • the AC power supply may comprise three single phase transformers connected in a delta configuration to the three electrodes.
  • the power supply may comprise a DC power supply for driving the at least two electrodes as anode and cathode respectively.
  • the vessel may comprise at least one feed port for charging raw materials into the chamber and at least one outlet for gasses.
  • the at least one feed port and the at least one outlet may be provided in a roof of the vessel.
  • the vessel may be cylindrical in shape and may comprise a steel shell having a bottom opposite the roof and the steel shell may be lined on an inside thereof with a refractory lining.
  • At least one of the steel shell and the burden in the vessel may be kept at earth or ground potential.
  • the electrodes may extend in an axial direction into the chamber through suitable openings in the roof.
  • the roof may be water-cooled.
  • the electrodes may be axially adjustable.
  • Each electrode may comprise a so-called self-baking electrode, such as the type of electrode known in the art under the name Soderberg electrodes.
  • each electrode may comprise a pre-baked graphite electrode.
  • the at least one feed port may comprise means for controlling at least one of the rate and volume of raw material fed into the chamber and the at least one outlet may comprise means for controlling at least one of the rate and volume of hot gas escaping from the chamber.
  • the at least two electrodes may be energized utilizing an AC voltage, alternatively the at least two electrodes may be energized utilizing a DC voltage.
  • the body of the burden may comprise a ferrochrome alloy.
  • a method of converting a conventional submerged arc furnace into a DC brush-arc furnace comprising the steps of:
  • figure 1 is a sectional view through an example embodiment of an
  • figure 2 is an electrical circuit diagram of the furnace in figure 1 ;
  • figure 3 is a sectional view through an example embodiment of DC brush-arc furnace.
  • figure 4 is an circuit diagram of the furnace in figure 3.
  • An example embodiment of an AC brush-arc furnace is generally designated by the reference numeral 10 in figures 1 and 2.
  • the furnace 10 comprises a vessel, in this example embodiment, a circular cylindrical vessel 12 comprising a steel shell 14 lined with a layer 16 or more of refractory bricks.
  • the furnace comprises a roof 18 and an opposed bottom 20.
  • Three electrodes 22.1 , 22.2, and 22.3 extend through the roof in an axial direction into a chamber 24 defined by the vessel.
  • the electrodes have a diameter d.
  • the electrodes are connected to an AC power supply 26 (shown in figure 2).
  • the chamber holds a burden 28 comprising a body 30 comprising a ferrochrome alloy and a layer 32 comprising slag on the body.
  • the layer has an upper surface 34.
  • the electrodes In use, the electrodes extend to between a first limit above the surface 34 and a second limit l 2 below the surface 34.
  • the first limit is preferably smaller than 0.3d and the second limit is preferably smaller than 0.2d.
  • a brush-arc 36 required for work or a reaction in the vessel in the form of a very short and somewhat diffused arc is maintained between the electrodes and the burden.
  • the length of the brush-arc may vary, depending on application and circumstances. With brush-arc operation, arcing characteristics are independent of burden resistance or porosity, but are determined by the electrode tip position and the applied voltage.
  • the electrodes 22.1 to 22.3 extend through suitable openings in the roof into the chamber 24. The electrodes are adjustable in an axial direction.
  • Each electrode may comprise a so-called self-baking electrode, such as the type of electrode referred to in the art as a S derberg electrode.
  • the vessel may further comprise at least one inlet port (not shown) for raw material to be fed into the vessel and at least one outlet (also not shown) from the chamber for hot gasses.
  • the at least one inlet port and the at least one outlet may be provided in the roof 18 of the vessel.
  • the inlet port and/or outlet may comprise a gate or valve controllable to control the rate and/or volume of material and/or hot gasses, as the case may be.
  • the vessel further comprises a molten metal and slag tapping hole 40 (shown in figure 2). In other embodiments separate, tapping holes (nor shown) for molten metal and for slag may be provided.
  • the tapping holes may be opened and closed by hydraulically powered drill and plugging apparatus. Refractory clay may be used as plugging material.
  • the electrodes 22.1 to 22.3 are connected to an AC power supply 26.
  • the power supply comprises three single phase transformers 42.1 to 42.3 connected in a delta configuration and to the electrodes 22.1 to 22.3.
  • the AC brush-arc operation will have a substantially higher arc resistance than a comparable AC submerged-arc furnace and it is therefore envisaged that furnace transformers will be replaced when converting an AC submerged-arc furnace to a brush-arc furnace, as hereinafter described.
  • FIGS 3 and 4 there is shown an example embodiment of a DC brush- arc furnace 100.
  • the furnace 100 comprises a circular cylindrical vessel 112 comprising a steel shell 114 lined with a layer 116 or more of refractory bricks.
  • the furnace comprises a roof 118 and an opposed bottom 120.
  • Two electrodes 122.1 and 122.2 extend through the roof in an axial direction into a chamber 124 defined by the vessel.
  • the electrodes have a diameter d.
  • the electrodes are connected to a DC power supply 126 (shown in figure 4).
  • the chamber holds a burden 128 comprising a body 130 comprising a product and a layer 132 comprising slag on the body.
  • the layer has an upper surface 134.
  • the electrodes In use, the electrodes extend to a level between a first limit above the surface 134 and a second limit l 2 below the surface 134.
  • the first limit is preferably smaller than 0.3d.
  • a brush-arc 136 required for work or a reaction in the vessel in the form of a very short and somewhat diffused arc is maintained between the electrodes and the burden.
  • the DC power supply 126 comprises an AC supply 140 connected to a rectifier arrangement, which may comprise an SCR bridge 42, a DC reactor 144 and a polarity switching circuit 146 having an output 148.
  • the output 148 is connected to the electrode pair 122.1 and 122.2 by water-cooled bus tubes 150.
  • the polarity switching circuit is manipulatable or automatically controllable intermittently, preferably periodically, to reverse the polarity of the DC voltage at the output 148, so that the first electrode 122.1 will be driven as anode for a first period of time, and thereafter as cathode and vice versa for the second electrode 122.2.
  • the invention also extends to a method of converting an existing known submerged arc AC furnace into a DC brush-arc furnace substantially as shown in figures 3 and 4.
  • the method comprises the steps of replacing the set of three electrodes of the existing furnace with an electrode pair. This may be done by removing the electrode 22.3 and moving the electrode 22.1 into line with the electrode 22.2 on the tap hole center line 152 of the vessel 24.
  • the electrode pair is then connected to a DC power supply 126 shown in figure 4, thereby, in use, to drive a first electrode of the pair as an anode and another electrode of the pair as a cathode.
  • the vessel may be rectilinear in configuration and a plurality of electrode pairs may extend into the chamber.
  • three pairs of electrodes may be provided, each pair being driven by a respective DC power supply.
  • the brush-arc furnaces and methods according to the invention may be used for processing raw materials, more particularly ferrochrome ores, with at least a reduced requirement for permeable lumpy or pelletized ores and for lumpy coke to form a coke bed.

Landscapes

  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Vertical, Hearth, Or Arc Furnaces (AREA)

Abstract

Un four de type balai-arc (10) comprend une cuve (12). La cuve définit une chambre (24). La chambre supporte une charge (28) comprenant un corps (30), comprenant de préférence un alliage de ferrochrome, et une couche (32) sur le corps comprenant des scories. La couche présente une surface supérieure (34). Au moins deux électrodes (22.1, 22.2) présentant chacune un diamètre (d) s'étendent dans la chambre à un niveau situé entre une première limite (I1) au-dessus de la surface (34) et une seconde limite (I2) au-dessous de la surface. La première limite est inférieure à 0,5d et la seconde limite est inférieure à 0,3d. Une alimentation en courant alternatif (26) ou une alimentation en courant continu (126) entraîne les deux ou plus de deux électrodes en fonctionnement de type balai-arc.
PCT/IB2011/052428 2010-09-09 2011-06-02 Fours de type balai-arc et procédé de traitement de minerais Ceased WO2012032421A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
ZA201006472 2010-09-09
ZA2010/06472 2010-09-09

Publications (1)

Publication Number Publication Date
WO2012032421A1 true WO2012032421A1 (fr) 2012-03-15

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Family Applications (1)

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PCT/IB2011/052428 Ceased WO2012032421A1 (fr) 2010-09-09 2011-06-02 Fours de type balai-arc et procédé de traitement de minerais

Country Status (1)

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WO (1) WO2012032421A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3464653B1 (fr) 2016-05-31 2021-12-15 Tenova S.p.A. Procédé de production de fonte

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4342511A1 (de) * 1993-12-08 1995-06-14 Mannesmann Ag Elektro-Reduktionsofen mit offenem Schlackebad
WO2009010266A2 (fr) * 2007-07-18 2009-01-22 Sms Siemag Ag Four électrique de réduction modulaire

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4342511A1 (de) * 1993-12-08 1995-06-14 Mannesmann Ag Elektro-Reduktionsofen mit offenem Schlackebad
WO2009010266A2 (fr) * 2007-07-18 2009-01-22 Sms Siemag Ag Four électrique de réduction modulaire

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
W.S. STEINBERG: "Development of a control strategy for the open slag bath furncase at Highveld Steel and Vanadium Corporation Ltd., MEng dissertation, University of Pretoria, Pretoria,", December 2008, XP002658237 *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3464653B1 (fr) 2016-05-31 2021-12-15 Tenova S.p.A. Procédé de production de fonte

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