Classifications

• • 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
  • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
  • C21C7/04—Removing impurities by adding a treating agent
  • C21C7/076—Use of slags or fluxes as treating agents
• • 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
  • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
  • C21C7/0037—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00 by injecting powdered material
• • 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
  • C21C1/00—Refining of pig-iron; Cast iron
  • C21C1/02—Dephosphorising or desulfurising
  • C21C1/025—Agents used for dephosphorising or desulfurising
• • 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
  • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
  • C21C7/04—Removing impurities by adding a treating agent
  • C21C7/064—Dephosphorising; Desulfurising
  • C21C7/0645—Agents used for dephosphorising or desulfurising
• • 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
  • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
  • C21C7/04—Removing impurities by adding a treating agent
  • C21C7/068—Decarburising
• • 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

• the present invention is a method for refining steel by introducing conditioned quicklime, in particulate form, into an oxygen stream for injecting into a molten metal and slag bath of a steel-making vessel.
• refining vessels which are utilized include Basic Oxygen Furnaces, (BOF), Electric Arc Furnaces and Argon-Oxygen Decarburization vessels (AOD).
• BOF Basic Oxygen Furnaces
• AOD Argon-Oxygen Decarburization vessels
• the slag layer provides a protective covering for the molten metal, as well as a source of material for reacting chemically with elemental components (such as phosphorus and sulfur), inclusions, and the like, found in the molten metal, in order to adjust their level of concentration.
• the molten slag is most often formed by reaction of the oxides of iron, silicon, manganese, and phosphorus, for example, with a slag-forming flux such as calcium oxide that is added to the furnace with the metallic charge.
• the level of carbon in steel is an important consideration, as many of the properties of steel result from the carbon content of the steel.
• To remove carbon from the molten metal in a steel-making vessel it is well known to direct oxygen into the molten bath so as to combine MStMe ⁇ ' aWo ⁇ l' ⁇ feinl-fc'lJf ⁇ lilcn-lxits the molten metal as a gas, thus reducing the carbon content of the steel.
• the oxygen is most often blown into the molten metal with use of a lance so as to allow the oxygen to penetrate the layer of slag covering the molten metal.
• High pressure oxygen gas acts to stir the molten metal so as to promote the chemical reactions of the oxygen with the carbon, and also promote chemical reactions of other materials found in the molten metal with the slag layer on top of the molten metal.
• a slag-forming flux such as quicklime (CaO)
• CaO quicklime
• One method of adding CaO is to top charge the CaO on top of the molten slag.
• a large pebble CaO is often used, and it is added by dropping the CaO through an opening in the top of the refining vessel. Due to dust accompanying the pebble CaO, such practice usually has an impact on dust emissions that are captured by an air scrubbing system or a baghouse, and chemical reactions are delayed due to particle size and location of the charged material.
• Another method for adding CaO to the molten metal and slag bath is to convey a particulate form of CaO with the oxygen being blown through the lance into the vessel. Although this method promotes better mixing and chemical reactions within the vessel, conveying the particulate form of CaO to the lance and through the lance itself has been difficult, as a particulate form of CaO is difficult to convey through conduits and the like.
• the present invention is for use with a method of producing steel using a steel-making vessel, where lime is used as a flux material that is blown, from above, into a steel-making bath along with an oxygen stream.
• it is a feature of the invention to provide a flux material composition of calcium oxide having a particle size of less than 250 mesh, which contains a flow aid material that is an organic siloxane, in an amount of less than 0.5 percent by weight of the calcium oxide, and injecting the flux material composition through a lance along with oxygen into the steel-making bath contained in the vessel.
• Fig. 1 is a cross-sectional view of a steel-making vessel having an oxygen injection lance for injecting oxygen into the steel-making bath;
• Fig. 2 is a cross-sectional view of a lower portion of an oxygen lance for use with conditioned CaO of the present invention; and 11 FIgIHS ⁇ 'k"lcyi ⁇ a ! iic ⁇ r ( ⁇ Kgf'aW l of a preferred process for producing a flux material of the invention.
• Fig. 1 is a cross-sectional view of one example of a steel-making vessel in which molten metal, primarily iron, is refined to produce steel having a specified carbon content and acceptable levels of various other elements.
• molten metal primarily iron
• the composition of the molten metal is adjusted by causing chemical reactions to take place between the elements of concern and materials which are made to come into contact with those elements. Additionally, various materials for supplying elements that are deficient in the molten metal can be added, however such operation is not presently of concern.
• the refining vessel depicted in Fig. 1 is a Basic Oxygen Furnace (BOF), it being just one example of a refining vessel suitable for use with the present invention.
• the vessel is indicated at 1 and at 2 a lance for injecting oxygen into the molten metal and slag bath is indicated.
• the molten metal is depicted at 3 and a layer of the molten slag, covering the surface of the molten steel, is indicated at 4.
• the oxygen lance 2 in practice of the present invention, must incorporate means for introducing CaO into the stream of oxygen 5 entering the molten metal and slag bath.
• Fig. 2 is an example of a lance suitable for use in carrying out the present invention.
• Fig. 2 depicts a lower end portion of an oxygen lance in which a particulate material is added to the oxygen stream.
• the lance of Fig. 2 is the subject of U.S. Patent No. 6,217,824, the contents of which are incorporated by reference, herein.
• the particulate material and high-pressure oxygen is supplied through channel 6 for introduction into the molten metal and slag bath of the steel-making vessel.
• the conditioned CaO of the present invention overcomes the conveying problems and provides a particulate material highly suitable for the chemical reactions in the steel-making bath.
• the CaO of the present invention is prepared to have a preferred particle size of about 250 mesh (Tyler screen scale) or less, with only a small amount of fines that could contribute to the above-discussed pollution concerns.
• Such CaO particulate material is preferably prepared with use of a pulverizing mill and then sized with use of screening equipment. Introduction of the preferred size CaO into the steel-making bath enables the particles to be driven down toward the molten metal and slag bath for fast dissolution.
• the particles are mixed with a flow aid material to reduce the particle attraction that exists between adjacent particles.
• a flow aid material causes adjacent particles to repulse each other so that they can flow with a low pressure carrier gas.
• the flow-aid material is added in an amount of less than 0.5 percent by weight of the CaO.
• the preferred flow-aid material is an organic siloxane, such as alkyl siloxane, including polydimethylsiloxane and polymethylhydrosiloxane, which has been used as a flow aid for pulverized lime.
• organic siloxane such as alkyl siloxane, including polydimethylsiloxane and polymethylhydrosiloxane, which has been used as a flow aid for pulverized lime.
• Fig. 3 depicts a preferred process for preparing the conditioned CaO of the invention.
• Tanks 7 and 8 are provided for storage of starting material of high calcium quicklime and dolomitic quicklime, respectively.
• the process is used to prepare the conditioned product as 100% high calcium quicklime flux material (in storage tank 9); 100% dolomitic quicklime flux material (in storage tank 10) or a blend of the flux materials (in storage tank 11).
• either screw conveyor 12 or 13, or both are activated to convey the desired starting material to surge hopper 14.
• the surge hopper is used to feed pulverizing mills 15 and 16, which can include sizing screens and the like for obtaining the preferred particle size for further processing.
• the pulverized material is conveyed through conduits 17 and 18, which are provided with means for coating the particles with the flow-aid material dispensed from a flow-aid dispenser tank 19 A, through conduits 20 and 21. Additional flow-aid material is stored in a flow-aid transfer point tank at 19B. Following coating of the particles, the conduits continue to deliver the conditioned material to cyclones 22 and 23 for dust removal. Dust from cyclones 22 and 23 is conveyed to exhauster fans 15A and 16A which are associated with pulverizing mills 15 and 16, respectively. Following exit from the cyclones the conditioned fluxing material is directed to the proper storage tank (9, 10 or 11) with use of gates 24 and 25, for later use.
• Airlocks 28 are fluidly connected with dus't ' coll ' ectbrs " i-l'& u an"d 1 27 ⁇ nWSeIlV 1 COnIToI the flow of material between dust collectors 26 and 27 and surge hopper 14.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Treatment Of Steel In Its Molten State (AREA)

Applications Claiming Priority (1)

Publications (2)

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Citations (7)

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• 2006
  • 2006-02-09 WO PCT/US2006/004410 patent/WO2007092006A1/en active Application Filing
  • 2006-02-09 US US10/583,007 patent/US20090013827A1/en not_active Abandoned
  • 2006-02-09 EP EP06734571.0A patent/EP1984526A4/de not_active Withdrawn
  • 2006-02-09 CA CA002640471A patent/CA2640471A1/en not_active Abandoned

Patent Citations (7)

Non-Patent Citations (2)

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