Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
  • C22B7/00—Working up raw materials other than ores, e.g. scrap, to produce non-ferrous metals and compounds thereof; Methods of a general interest or applied to the winning of more than two metals
  • C22B7/04—Working-up slag
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
  • C22B7/00—Working up raw materials other than ores, e.g. scrap, to produce non-ferrous metals and compounds thereof; Methods of a general interest or applied to the winning of more than two metals
  • C22B7/02—Working-up flue dust
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
  • C22B7/00—Working up raw materials other than ores, e.g. scrap, to produce non-ferrous metals and compounds thereof; Methods of a general interest or applied to the winning of more than two metals
  • C22B7/005—Separation by a physical processing technique only, e.g. by mechanical breaking
• • 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 disclosure relates to methods of recovering valuable metals from slags, and more particularly, to methods of recovering valuable metals from slags produced in a converter or an electric furnace.
• Slag is a by-product of the steel refining process. Slag is formed from iron ore or coke in an iron-making process, and is formed from oxides produced by the oxidation and deoxidation of molten iron or molten steel or from auxiliary materials used for smelting in a steel-making process.
• Slag basically contains SiO 2 and CaO, and may also contain Al 2 O 3 , FeO, MgO, P 2 O 5 , CaS and the like depending on the type of refining.
• Slag produced in an iron-making process contains CaO, SiO 2 , and Al 2 O 3
• slag produced from the oxidation of molten iron or molten steel in a steel-making process basically contains CaO, SiO 2 , and FeO.
• An aspect of the present invention is to provide an efficient method of recovering a metal such as iron and the like from slags, which are by-products of steel-refining process, by utilizing the magnetic properties of the slags.
• An embodiment of the present invention provides a method of recovering a valuable metal from slag, the method comprising steps of: applying a magnetic field whose magnitude is increased in a stepwise fashion, to crushed slag to separate a magnetic material from the crushed slag; and introducing a reductant into the separated magnetic material to recover a valuable metal therefrom.
• Another embodiment of the present invention provides a method of recovering a valuable metal from slag, the method comprising steps of: transferring molten slag produced in a converter or an electric furnace into a slag pot and introducing a reductant into the slag pot to recover a valuable metal from the molten slag; cooling the molten slag, to form a solid slag and crushing the solid slag; applying a magnetic field, whose magnitude is increased in a stepwise fashion, to crushed slag to separate magnetic materials from the crushed solid slag; and introducing a reductant into the separated magnetic material to recover a valuable metal therefrom.
• the magnetic material may contain Fe, FeO, Fe 2 O 3 , and Fe 3 O 4 .
• the applied magnetic field may be in the range between 100 G and 1000 G.
• the reductant may be at least one material selected from carbon (C), aluminum (Al), silicon (Si), sodium (Na), calcium (Ca), magnesium (Mg), and carbon monoxide (CO) gas.
• the crushed slag may have a particle size of 100 mm or less.
• the molten slag may be cooled at a cooling rate of 5 ⁇ 50° C./sec.
• iron (Fe) which is a valuable metal
• Fe which is a valuable metal
• Embodiments of the present invention are advantageous in that valuable metals can be efficiently recovered from slag which may otherwise be wasted.
• the iron (Fe) recovered from slag has a purity of 95% or more, it can be reused as a raw material for making steel. Therefore, embodiments of the present invention are advantageous in that it is cost-effective and environment-friendly.
• a magnetic field whose magnitude is increased in a stepwise fashion, is applied to crushed slag to separate magnetic materials from the slag, and subsequently a reductant is introduced into the magnetic materials to recover valuable metals therefrom.
• the slag produced from a converter or an electric furnace contains a large amount of valuable metal oxides, such as FeO and the like.
• Slag produced in a converter or an electric furnace in a steel-making process may contain 20% or more of valuable metal oxides, and in particular, slag initially produced in an electric furnace contain 30% or more of valuable metal oxides.
• the embodiments of present invention provide a method of recovering valuable metals from slag produced in a converter, an electric furnace, or similar systems.
• the slag transferred into the slag pot is then water-cooled or air-cooled to convert it into a solid slag.
• the solid slag is subsequently crushed into small particles.
• the desired final particle size can be determined based on the cost of production.
• magnetic field whose magnitude is increased in a stepwise fashion, is applied to the crushed slag.
• the applied magnetic field is in a range of 100 G to 1000 G, where G symbolizes gauss, which is a unit representing the intensity of a magnetic field.
• the magnetic field may be applied to sequentially separate magnetic materials such as Fe, FeO, Fe 2 O 3 , and Fe 3 O 4 from the slag.
• Fe may be separated under a magnetic field of 100 G.
• Metal compounds such as FeO, Fe 2 O 3 and Fe 3 O 4 may be sequentially separated by gradually increasing the magnitude of the applied magnetic field.
• other compounds such as CaAl 2 SiO 7 , CaMgSiO 4 and the like may also be separated in addition to the above-mentioned magnetic materials, thus lowering the quality of the separated magnetic materials.
• the maximum intensity of the magnetic field to not exceed 1000 G.
• 100 G represents the approximate minimum magnetic field intensity at which magnetic materials may be preferably separated.
• the particle size of the separated magnetic materials is 100 mm or less, there is no significant difficulty in separating magnetic materials even when nonmagnetic materials are mixed with the magnetic materials.
• the separated magnetic materials (Fe, FeO, Fe 2 O 3 , Fe 3 O 4 ) are subsequently melted, and a reductant is introduced into the molten magnetic materials to recovering the valuable metal such as Fe.
• the reductant may be at least one material selected from carbon (C), aluminum (Al), silicon (Si), sodium (Na), calcium (Ca), magnesium (Mg), and carbon monoxide (CO) gas.
• the reductant may be introduced using a carrier gas (e.g., air).
• Aluminum (Al) may be introduced at a feed rate of 10 ⁇ 50 kg per 1 ton of slag.
• the amount of aluminum (Al) to be introduced is determined based on the targeted recovery rate of 50 ⁇ 100%, depending on operating conditions.
• the amount of aluminum (Al) to be introduced may be calculated based on the following reaction formula:
• the method of this embodiment addresses a problem that is encountered when a slag has high iron (Fe) content, in which case the slag cannot be easily crushed because of its high strength and malleability even when the particles are coarse.
• the molten slag produced in a converter or an electric furnace is transferred into a slag pot, followed by introduction of a reductant into the slag pot to separate valuable metals from the molten slag.
• the remaining molten slag is subsequently cooled into a solid slag, which is then crushed.
• a magnetic field whose intensity is increased in a stepwise fashion, is applied to the crushed slag to separate magnetic materials therefrom. Then, a reductant is introduced into the separated magnetic materials to recover valuable metals therefrom.
• the reductant introduced into the slag pot serves to reduce iron oxides in the molten slag.
• Carbon (C) and aluminum (Al), whose affinity for oxygen is high, may be used as reductants.
• Carbon (C) is supplied into the slag pot, and aluminum (Al) is directly introduced into the molten slag in the slag pot.
• Aluminum (Al) may be introduced together with a gas in order to enhance the reaction.
• the gas may be air or inert gas such as nitrogen or argon.
• the inner walls of the slag pot are made of a copper plate or iron plate having high thermal conductivity, Carbon (C) and aluminum (Al) are both used for reducing iron (Fe) oxides.
• the temperature of the molten slag as transferred into the slag pot is about 1600° C. However, the temperature drops at a rate of 200 ⁇ 300° C./hr as a result of the endothermic reduction reaction of iron (Fe) oxides to iron (Fe) by carbon (C), heat dissipation, and other processes.
• Aluminum (Al) is introduced in order to maintain the molten slag at high temperature.
• the amount of aluminum (Al) introduced into the molten slag is controlled so that the temperature of the molten slag is maintained at 1300 ⁇ 1600° C. It is advantageous to perform the reduction of iron oxide (FeO) to iron (Fe) is when the temperature of molten slag is high. However, when the temperature of the molten slag is greater than 1600° C., the slag pot may be excessively corroded. On the other hand, when the temperature is less than 1300° C., the reduction reaction of iron oxide (FeO) to iron (Fe) is rapidly decelerated.
• carbon (C) which is supplied through holes on the slag pot, serves as a reductant, and the reduction reaction represented by FeO+C ⁇ Fe+CO is conducted.
• the temperature of the molten slag can be lowered.
• Aluminum (Al) may be introduced at a feed rate of 10 ⁇ 50 kg per 1 ton of slag in order to maintain the temperature of the molten slag at 1300 ⁇ 1600° C.
• the amount of aluminum (Al) to be introduced is determined based on the targeted recovery rate of 50 ⁇ 100%, depending on operating conditions.
• the content of FeO in the molten slag, whose amount is necessary for introduction of a reductant, may be measured using a spectrometer or a wet process.
• iron (Fe) having a high specific gravity is located at the lower portion of the slag pot, and the molten slag is located at the upper portion thereof.
• the molten slag located at the upper portion of the slag pot is transferred into an additional pot, and the iron (Fe) remaining in the slag pot is recovered.
• iron (Fe) which is difficult to crush, may be recovered at a high recovery rate of 20% of the weight of slag.
• Porous solid slag can be easily crushed without relatively high force because it has a low iron (Fe) content.
• the cooling of the molten slag may be conducted by injecting a mixture of steam and gas into the molten slag. Air may be used as the gas.
• Steam is injected in order to cool the molten slag, and gas is injected in order to allow the steam to be sprayed into molten slag.
• Steam has high cooling efficiency because it lowers the temperature of the molten slag and simultaneously maintains low expansibility.
• water must not be used to cool high-temperature molten slag because water has high expansibility and creates a danger of explosion.
• the molten slag may be cooled to room temperature at a cooling rate of 1 ⁇ 50° C./sec.
• the cooling rate of the molten slag has the maximum value or the minimum value depending on the injection rate of gas at room-temperature and the steam and the pressure control thereof.
• the shape, strength, and the texture of the solid slag are influenced by this cooling rate.
• the injection rate and pressure of room-temperature gas and steam is controlled so that the cooling rate of the molten slag is maintained at 5 ⁇ 50° C./sec.
• the control of the cooling rate thereof is conducted in order to increase the crushing efficiency of the solid slag.
• the average particle size of solid slag may be 50 mm or less, whose value indicates that the crushing efficiency is high.
• the maximum value of the cooling rate is applied depending on the injection rate of room-temperature gas and steam and the pressure control thereof.
• porous solid slag After the molten slag is cooled into a porous solid slag, the porous solid slag is crushed.
• the porous solid slag is easily crushed because it has a low valuable metal (Fe) content and has a porous structure.
• the average particle size of the crushed solid slag is 50 mm or less, which is uniform.
• the magnetic materials included in slag such as Fe, FeO, Fe 2 O 3 and Fe 3 O 4 , are sequentially separated depending on the intensity of the magnetic field.
• the particle size of the separated magnetic materials is 100 mm or less, there is no difficulty separating the magnetic materials even when nonmagnetic materials are mixed with the magnetic materials.
• a reductant is introduced into the separated magnetic materials (Fe, FeO, Fe 2 O 3 , Fe 3 O 4 ) to recover valuable metals such as iron (Fe).
• the reductant may be at least one material selected from carbon, aluminum (Al), silicon (Si), sodium (Na), calcium (Ca), magnesium (Mg), and carbon monoxide (CO) gas.
• the above-mentioned method may be similarly applied to the slag discharged from a converter.
• Table 2 shows the recovery rates of iron (Fe) using the method of recovering valuable metals from slag.
• Fe is first recovered from molten slag by reduction, followed by further recovery from the remaining molten slag by cooling into a porous solid slag, and subsequently applying a stepwise magnetic field to crushed porous solid slag, it may be inferred that the recovery rate of a valuable metal (Fe) is further increased.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• General Life Sciences & Earth Sciences (AREA)
• Manufacturing & Machinery (AREA)
• Environmental & Geological Engineering (AREA)
• Materials Engineering (AREA)
• Life Sciences & Earth Sciences (AREA)
• Geology (AREA)
• Organic Chemistry (AREA)
• Manufacture And Refinement Of Metals (AREA)
• Furnace Details (AREA)
• Curing Cements, Concrete, And Artificial Stone (AREA)
• Refinement Of Pig-Iron, Manufacture Of Cast Iron, And Steel Manufacture Other Than In Revolving Furnaces (AREA)
• Carbon Steel Or Casting Steel Manufacturing (AREA)

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• 2009
  • 2009-12-30 KR KR1020090133771A patent/KR101175422B1/ko active IP Right Grant
• 2010
  • 2010-06-25 WO PCT/KR2010/004127 patent/WO2011081265A1/ko active Application Filing
  • 2010-06-25 JP JP2012513883A patent/JP5656172B2/ja active Active
  • 2010-06-25 CN CN2010800247606A patent/CN102471826A/zh active Pending
  • 2010-06-25 EP EP10841098.6A patent/EP2471962A4/en not_active Withdrawn
• 2011
  • 2011-12-02 US US13/310,117 patent/US20120073404A1/en not_active Abandoned

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