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
  • C22B11/00—Obtaining noble metals
  • C22B11/02—Obtaining noble metals by dry processes
• • 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
  • C22B1/00—Preliminary treatment of ores or scrap
• • 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
  • C22B34/00—Obtaining refractory metals
  • C22B34/30—Obtaining chromium, molybdenum or tungsten
  • C22B34/32—Obtaining chromium
• • 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
  • C22B5/00—General methods of reducing to metals
  • C22B5/02—Dry methods smelting of sulfides or formation of mattes
• • 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
  • C22B9/00—General processes of refining or remelting of metals; Apparatus for electroslag or arc remelting of metals
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C33/00—Making ferrous alloys
  • C22C33/04—Making ferrous alloys by melting
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
• • 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
  • F27B19/00—Combinations of furnaces of kinds not covered by a single preceding main group
  • F27B19/04—Combinations of furnaces of kinds not covered by a single preceding main group arranged for associated working
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F9/00—Making metallic powder or suspensions thereof
  • B22F9/02—Making metallic powder or suspensions thereof using physical processes
  • B22F9/06—Making metallic powder or suspensions thereof using physical processes starting from liquid material
  • B22F9/08—Making metallic powder or suspensions thereof using physical processes starting from liquid material by casting, e.g. through sieves or in water, by atomising or spraying
  • B22F9/082—Making metallic powder or suspensions thereof using physical processes starting from liquid material by casting, e.g. through sieves or in water, by atomising or spraying atomising using a fluid
• • 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 invention relates to a method and an ap ⁇ paratus for recovering platinum group metals and fer- rochrome from PGM bearing chromite ore.
• Platinum group metals include platinum, rhodium, palladium, ruthenium, iridium, osmium. PGMs frequently occur together with chromites.
• the platinum industry in South Africa is increasingly moving from traditional Meren- sky reef to UG2 reef as a raw material.
• the UG2 reef contains most of the world's known PGM reserves, and it also has high chromite content.
• the UG2 concentration process used by the platinum industry in South Africa produces lots of chromite-containing tailings. Ferrochrome producers can use these tailings as raw material. South Africa suffers from shortage of electricity, which is why lo ⁇ cal producers cannot use all chromite-containing tail ⁇ ings of platinum industry but tailings are exported to China. The Chinese are building a lot of ferrochrome capacity now, which is worrying for the South African producers.
• One of the targets of the present invention is to provide a process that allows the South Africans to use their UG2 reserves more completely in their own country .
• US 6,699,302 Bl disclos ⁇ es a method for processing metal sulfide concentrate that contains at least one metal selected from the group consisting of the PGMs, nickel, cobalt and zinc.
• the method comprises dead-roasting the metal sulfide concentrate, smelting the dead-roasted concentrate un ⁇ der reducing conditions in an electrically stabilized open-arc furnace, and collecting the metals from the smelting step in the form of an alloy or vapor. Chrome is an unwanted element and it is removed from the met ⁇ al alloy in a converter.
• the purpose of the present invention is to eliminate or at least reduce the problems of the prior art .
• a further purpose is to provide a new process for effective utilization of PGM bearing chromite ore.
• the new method comprises preparing a concen ⁇ trate that contains most of the PGMs and chromite of the ore, subjecting the concentrate to a heating step to dry and/or preheat the concentrate, and smelting the concentrate under reducing conditions in a DC smelting furnace to produce molten metal alloy that contains the PGMs of the feed and molten slag that contains the chromium of the feed.
• the molten slag is tapped from the smelting furnace into an AC slag fur ⁇ nace, where reduction of the oxides of iron and chro ⁇ mium contained in the slag takes place so that ferro ⁇ chrome is produced.
• the heating step additionally comprises roasting the concentrate to remove sulfur and/or volatiles con ⁇ tained in the concentrate.
• the slag properties are controlled with flux.
• the method comprises adding flux and/or reductant into the smelting furnace and/or into the slag furnace.
• the reducing conditions in the smelting furnace and/or in the slag furnace are controlled with the addition of reductant.
• the slag properties in the smelting furnace and/or in the slag furnace are controlled with the addition of flux .
• Advantageously molten metal alloy is tapped from the smelting furnace, after which PGMs are recovered from the metal alloy by hydrometallurgical pro- Derivatives or a combination of pyrometallurgical and hy ⁇ drometallurgical processes.
• molten metal alloy from the smelting furnace is tapped to a Peirce-Smith converter, after which the converted metal alloy is subjected to atomization and hydromet ⁇ allurgical process steps.
• molten metal alloy is tapped from the smelting furnace directly to an atomizer, after which the atom- ized metal alloy is subjected to hydrometallurgical process steps.
• the new apparatus comprises a DC smelting furnace for producing a molten metal alloy containing the PGMs of the feed and a molten slag containing the chromium of the feed, and an AC slag furnace for pro ⁇ ducing a ferrochrome alloy from the molten slag tapped from the DC smelting furnace.
• the apparatus further comprises a heating unit for drying and/or preheating the concentrate before it is fed to the smelting furnace.
• the heating unit is pref ⁇ erably selected from a group comprising a fluidized bed reactor, a rotary kiln, a drying tower, or similar .
• the slag furnace can be an open bath alterna ⁇ tive current furnace, or similar.
• the apparatus further comprises a Peirce-Smith converter for removing iron from the molten metal alloy tapped from the smelting furnace.
• the apparatus further comprises an atomizer for atomizing the molten metal alloy tapped from the smelting furnace or from the converter.
• the present invention proposes using molten slag from a PGM smelter as a raw material in ferro ⁇ chrome production.
• both PGMs and ferrochrome are produced at the same time, which gives flexibility for the use of raw material and makes the concentration of PGM and chromite con- taining ore easier.
• the process also saves energy com ⁇ pared to current recovery processes.
• the ferrochrome containing slag fraction need not to be cooled and re ⁇ heated before introduction into ferrochrome process.
• the present invention allows adjusting the Cr/Fe ratio in the ferrochrome by controlling how much iron is reduced in the smelting furnace.
• Typical use of pure UG2 ore results in Cr/Fe ratio of around 1.35, which means that the Cr content in the ferrochrome is below 50%.
• Higher Cr contents are preferred by the end users of ferrochrome, i.e. stainless steel industry.
• the enclosed Figure 1 is a flow chart illus ⁇ tration of one embodiment of a process according to the present invention.
• PGM bearing chromite ore is fine grinded to liberate the PGM particles.
• the fine grinded ore is concentrated in a concentrator 10, where the target is to remove gangue while keeping iron, chromium, base metals and PGMs in the concentrate.
• the process is simpler than the concentration processes currently used in PGM recovery, because there is no need to sep- arate chrome and iron from the base metals and PGMs.
• the concentrate is subjected to heat treat ⁇ ment in a heating unit 12, where the concentrate is dried, if necessary, and possibly preheated before it is fed to a smelting furnace 14.
• the heating unit 12 can be, for instance, a fluidized bed reactor, a rota ⁇ ry kiln, or a drying tower. If the raw material contains lots of sulfides and/or volatiles, roasting can be carried out in the heating unit 12 to oxidize the metal sulfides. CO gas generated in subsequent smelt- ing and slag furnaces 14, 16 can be used as a heat source in the heating unit 12.
• the preheated concentrate is charged as a feed into a DC smelting furnace 14.
• carbonaceous reductant such as anthracite or coke
• some flux may be charged, if necessary.
• the concentrate is melted and the PGMs, base metals and part of the iron contained in the feed are reduced to elemental metal, which is separated as a molten metal alloy be ⁇ low the lighter slag phase.
• most of the feed goes into the slag phase.
• all Cr and most of Fe, AI 2 O 3 , S 1O 2 , MgO and CaO of the feed go in ⁇ to the slag phase.
• Reduction in the smelting furnace 14 is limited by controlling the amount of carbon charged to the furnace 14. The target is only to get the PGMs into metal phase together with just a part of the iron. Iron droplets capture the PGMs and other base metals, forming molten metal alloy. Ni and Cu can also be present in the molten metal alloy produced in the smelting furnace 14.
• Liquid slag is tapped from the DC smelting furnace 14 to an AC slag furnace 16.
• Liquid metal al ⁇ loy is tapped from the bottom of the DC smelting fur- nace 14 to further refining steps in pyrometallurgical and/or hydrometallurgical processes.
• the slag furnace 16 is preferably an open bath alternative current furnace where electrodes are buried in a burden of lumpy materials comprised of molten slag received from DC smelting furnace. Carbo ⁇ naceous reductant and flux are charged to the AC fur ⁇ nace to control the reduction reactions and to opti ⁇ mize the amount and quality of slag.
• Typical ferro- chrome furnace operations comprise reduction of oxides of iron and chromium into metal phase.
• the resulting slag mainly contains AI 2 O 3 , MgO, CaO and S i0 2 - Metal alloy received from the slag furnace 16 contains Fe, Cr, some C and Si. All the rest of the feed is re ⁇ tained in the slag.
• Products received from the slag furnace 16 are ferrochrome metal and slag.
• the temperature of the slag tapped from the AC slag furnace 16 is 1650-1750°C and the temperature of the ferrochrome tapped from the AC slag furnace 16 is 1550-1600°C.
• PGM rich metal alloy tapped from the smelting furnace 14 can either be directly passed to hydromet- allurgical treatment steps or it can be converted in a Peirce-Smith converter 18 before passing to hydromet- allurgical treatment.
• the purpose of converting is to remove iron and other impurities from the metal alloy.
• the recovery of PGMs can comprise, for instance, atom- ization in an atomizer 20 and leaching.
• the basic idea of the present innovation is to smelt the concentrate in a DC smelting furnace 14, where PGMs are reduced, and then to produce FeCr alloy from the slag of the DC smelting furnace in a separate AC slag furnace 16. This gives flexibility as regards the raw materials and simplifies the concentrating process 10.
• Benefits of the new process comprise simplic ⁇ ity of the preceding concentration process as there is no need to remove chromite at an early stage.
• FeCr and PGMs are produced at the same time, less concen ⁇ tration, cooling and melting is needed and the process is more energy efficient.
• the safety of the process is improved as there is no risk of crust formation or ex- plosion.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Mechanical Engineering (AREA)
• Organic Chemistry (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Manufacturing & Machinery (AREA)
• Life Sciences & Earth Sciences (AREA)
• Environmental & Geological Engineering (AREA)
• General Life Sciences & Earth Sciences (AREA)
• Geology (AREA)
• Geochemistry & Mineralogy (AREA)
• General Engineering & Computer Science (AREA)
• Manufacture And Refinement Of Metals (AREA)

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• 2013
  • 2013-03-25 FI FI20135284A patent/FI125099B/fi not_active IP Right Cessation
• 2014
  • 2014-03-25 EP EP14720990.2A patent/EP2978866A1/en not_active Withdrawn
  • 2014-03-25 CA CA2907005A patent/CA2907005C/en not_active Expired - Fee Related
  • 2014-03-25 BR BR112015024481A patent/BR112015024481A2/pt not_active IP Right Cessation
  • 2014-03-25 CN CN201480017592.6A patent/CN105164285A/zh active Pending
  • 2014-03-25 EA EA201591659A patent/EA029428B1/ru not_active IP Right Cessation
  • 2014-03-25 WO PCT/FI2014/050214 patent/WO2014154945A1/en active Application Filing
• 2015
  • 2015-09-21 ZA ZA2015/07020A patent/ZA201507020B/en unknown

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