WO2005024074A1 - Procede destine a extraire des oxydes de titane cristallins - Google Patents

Procede destine a extraire des oxydes de titane cristallins Download PDF

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WO2005024074A1
WO2005024074A1 PCT/AU2004/001188 AU2004001188W WO2005024074A1 WO 2005024074 A1 WO2005024074 A1 WO 2005024074A1 AU 2004001188 W AU2004001188 W AU 2004001188W WO 2005024074 A1 WO2005024074 A1 WO 2005024074A1
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molten slag
tio
slag
bearing material
titanium oxides
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PCT/AU2004/001188
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English (en)
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Christopher Raymond Ure
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Promet Engineers Pty Ltd
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Publication of WO2005024074A1 publication Critical patent/WO2005024074A1/fr

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    • 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
    • C22B34/00—Obtaining refractory metals
    • C22B34/10—Obtaining titanium, zirconium or hafnium
    • C22B34/12—Obtaining titanium or titanium compounds from ores or scrap by metallurgical processing; preparation of titanium compounds from other titanium compounds see C01G23/00 - C01G23/08
    • C22B34/1204—Obtaining titanium or titanium compounds from ores or scrap by metallurgical processing; preparation of titanium compounds from other titanium compounds see C01G23/00 - C01G23/08 preliminary treatment of ores or scrap to eliminate non- titanium constituents, e.g. iron, without attacking the titanium constituent
    • C22B34/1209—Obtaining titanium or titanium compounds from ores or scrap by metallurgical processing; preparation of titanium compounds from other titanium compounds see C01G23/00 - C01G23/08 preliminary treatment of ores or scrap to eliminate non- titanium constituents, e.g. iron, without attacking the titanium constituent by dry processes, e.g. with selective chlorination of iron or with formation of a titanium bearing 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
    • C22B5/00—General methods of reducing to metals
    • C22B5/02—Dry methods smelting of sulfides or formation of mattes
    • C22B5/10—Dry methods smelting of sulfides or formation of mattes by solid carbonaceous reducing agents
    • 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 relates to a process for extracting crystalline titanium oxides, in particular to extracting crystalline titanium oxides from titanium oxides-bearing material also containing ferrous oxides.
  • BACKGROUND OF THE INVENTION It is known to require the extraction of various titanium oxide species (Ti ⁇ O ⁇ ) in crystalline form from ores and other materials bearing these titanium oxides.
  • Known processes for extraction of titanium oxides include the Becher process, in which ilmenite is subjected to a reductive process to reduce the iron oxide content to metallic iron, and then reoxidising the metallic iron in an aqueous solution to separate the metallic iron from the ilmenite to produce a synthetic rutile product and separate iron oxide waste product; and the conventional titanium slag process where ferrous ores of titanium are reductively smelted to produce an enriched titanium oxide slag and a pig iron byproduct.
  • the Becher and conventional titanium slag processes both require feedstock that is low in CaO, MgO, Al 2 O 3 and SiO 2 in order to produce synthetic rutile and titanium slag that have a sufficiently low content of CaO, MgO, Al 2 O 3 and SiO 2 to be acceptable as feedstock in the chloride process for producing titanium dioxide pigment. Both processes enrich the titanium oxide content, and consequently the CaO, MgO, Al 2 O 3 and SiO 2 contents, only by depletion of the iron oxide content.
  • the chloride process generally requires a feedstock having a TiO 2 content above 75% and an auxiliary oxide content substantially no more than as follows: CaO 0.15%, MgO 1.0%, Al 2 O 3 1.5%, SiO 2 2.0%, MnO 1.8%, and V 2 O 5 0.7%.
  • the low CaO, MgO, Al 2 O 3 , and SiO 2 feedstock impurity concentration requirement means that only a minor portion of the available resources of titanium oxides-bearing materials are able to be exploited.
  • a titanium slag production process is practiced at Richards Bay Iron and Titanium (Republic of South Africa), QIT-Fer et Titane (Canada), and Tinfos (Norway).
  • the Becher process is practiced by Iluka. These production facilities produce a high TiO 2 content slag that has up to 85% TiO 2 and at least 10% FeO with only up to total of 10% CaO, MgO, Al 2 O 3 , and SiO 2 . Typically, these slags cannot be tapped from the furnace if the FeO content is too low.
  • the feedstocks and coal that is used in the process is chosen to minimise CaO, MgO, Al 2 O 3 , and SiO 2 .
  • the present invention attempts to provide an alternative method for extracting TiO 2 in a crystalline form from titanium oxides-bearing materials that have levels of CaO and/or MgO and/or Al 2 O 3 and/or SiO 2 that make them generally make them unacceptable as feedstock for either the Becher process or the conventional titanium slag process.
  • a process for extracting crystalline TiO 2 from a titanium oxides-bearing material comprising the steps of: a) providing a molten slag of a mixture of titanium oxides-bearing material comprising Ti x O y , and fluxing agents comprising SiO 2 and metal oxides from a group including CaO, MgO and Al 2 O 3 , wherein the fluxing agents are present in the molten slag in an amount to adjust the molar ratio of CaO, MgO, Al O 3 and SiO 2 in the molten slag to substantially favour formation of CaAl Si 2 O 8 or CaMgSi 2 O 6 or Mg 2 Si 2 O 6 or Mg 2 Al 4 Si 5 Oi8, or a mixture thereof subsequent to formation of crystalline TiO 2 when the molten slag is cooled, the TiO 2 concentration in the molten slag being sufficient to afford crystalline TiO 2 when the molten slag is
  • Figure 1 is a three-dimensional composition diagram of the range of relative % composition of CaO, MgO, Al 2 O 3 and SiO 2 , in the molten slag, exclusive of the TiO 2 concentration, which substantially favours formation of silicate mineral phases CaAl 2 Si 2 O 8 or CaMgSi 2 O 6 or Mg 2 Si 2 O 6 or Mg 2 Al Si 5 O 18 , or a mixture thereof in accordance with a preferred embodiment of the present invention;
  • Figure 2 is four scanning electron microscope (SEM) micrographs of slag samples A- D at low magnification from Example 1 in accordance with the present invention
  • Figure 3 is a SEM micrograph of slag sample A shown at higher magnification than in Figure 2
  • Figure 4 is six SEM micrographs of slag samples Al-G at low magnification from Example 2 in accordance with the present invention.
  • Figure 5 is a flow chart of the present invention conducted in relation to reductive smelting of titanium oxides-bearing material also containing ferrous oxides. DESCRIPTION OF THE INVENTION
  • the present invention is based on the discovery that a molten slag comprising a mixture of Ti x O y and CaO, MgO, Al 2 O 3 and SiO 2 , wherein CaO, MgO, Al 2 O 3 and SiO 2 are in particular molar ratios, will differentially solidify to afford a plurality of crystalline phases, where a primary crystalline phase comprises crystalline TiO in the form of rutile and a secondary silicate phase substantially comprises silicate mineral species CaAl 2 Si 2 O 8 or CaMgSi O 6 or Mg Si 2 O 6 or Mg 2 Al 4 Si 5 O 18 , or a mixture thereof, when the molten slag is cooled at a slow rate between the liquidus and the solidus of the molten slag, provided that the TiO 2 content of the molten slag composition is sufficiently high for crystalline TiO 2 to form.
  • crystalline TiO 2 can be produced from a titanium oxides-bearing material by heating a mixture of titanium oxides-bearing material comprising Ti x O y , and fluxing agents comprising SiO 2 and metal oxides from a group including CaO, MgO and Al 2 O 3 to high temperatures to afford a molten slag.
  • the fluxing agents are present in the molten slag in an amount to adjust the molar ratio of CaO, MgO, Al 2 O 3 and SiO 2 in the molten slag to substantially favour formation of silicate mineral species CaAl 2 Si 2 O 8 or CaMgSi 2 O 6 or Mg 2 Si 2 O 6 or Mg 2 Al 4 SisO 18 , or a mixture thereof subsequent to formation of crystalline TiO 2 when the molten slag is cooled.
  • the TiO concentration in the molten slag must also be sufficient to afford crystalline TiO 2 when the molten slag is cooled.
  • the minimum TiO 2 content of the molten slag sufficient for crystalline TiO 2 to form varies depending on the relative proportions of CaO, MgO, Al 2 O 3 and SiO 2 in the molten slag, and varies from about 25% to about 50%.
  • the molten slag comprises calcium oxide (CaO), magnesium oxide (MgO), aluminium oxide (Al 2 O 3 ), silicon dioxide (SiO 2 ), and titanium oxides (Ti ⁇ O y ).
  • the molten slag contains CaO, MgO, SiO 2 and Al 2 O 3 in the molar ratios of CaO, MgO, Al 2 O 3 and SiO 2 as provided in the polygonal prism defined by vertices A-N (see Table 1 below) in addition to at least the minimum concentration of TiO 2 for crystalline TiO 2 to form during slow cooling solidification.
  • the process of the present invention is a beneficial enhancement to a reductive smelting process performed with titanomagnetite utilised for ironmaking, for example the Waikato North Heads vanadiferous titanomagnetite iron sand concentrate processed by New Zealand Steel, wherein a low-grade non- conventional titanium oxides-bearing slag is produced as a byproduct of the production of pig iron.
  • a carbonaceous reductant such as coal is required to reduce any iron oxides contained in the feedstock.
  • the resultant ash of the coal or other carbonaceous reductant inherently contains CaO, MgO, Al 2 O 3 and SiO 2 .
  • any titanium oxides-bearing slag produced by the reductive smelting process will also contain additional amounts of CaO, MgO, Al 2 O 3 and SiO 2 as a result of ash entrainment, in addition to certain amounts of CaO, MgO, Al 2 O 3 and SiO 2 inherently present in the gangue of the titanium oxides-bearing material.
  • Addition of CaO and MgO fluxes can be made as oxides or carbonates, the latter subsequently needing to be burnt to the oxide form during either or both the iron oxide reduction and smelting steps of the reductive smelting process. Flux additions in the form of sulphates will be deleterious to the process of the present invention.
  • One or more or all of the fluxes may be subject to preparation by conventional treatments. These may include but are not limited to drying, grinding, burning of carbonate forms to oxide forms, and agglomeration.
  • Flux additions can be made at three successive stages in the process of the present invention, including but not limited to during blending of the TOBM feedstock (and optionally the reductant) for the process and/or during smelting and/or prior to slow cooling solidification of the molten slag. Staggering the addition of the fluxes may be beneficial.
  • the TiO 2 content of the molten slag is diluted by too much then crystalline rutile will not form when the molten slag is slow cooled.
  • the molten slag may contain oxide impurities that may have originated as accessory oxides or/and accessory minerals in the titanium oxides-bearing material or/and fluxing agents or/and ash from the carbonaceous reductant(s).
  • Typical oxides encountered include oxides of vanadium, chromium, manganese, zinc, sodium and potassium.
  • the present invention proposes, where practicable, binding these oxide impurities as impurities within the silicate mineral phases.
  • chromium is present as trivalent chromium oxide (Cr O 3 ) then it readily substitutes for Al 2 O 3 and may be accomodated by equating the number of moles of Cr 2 O 3 as the same number of moles of Al 2 O 3 and cause the trivalent chromium oxide to manifest itself as an impurity within the respective silicate mineral phase.
  • silicate mineral species may be further required to create other silicate mineral species to bind with particular metal oxides present, in order to preferentially retain these oxides within the silicate mineral phase, and thus prevent them becoming impurities within the TiO 2 crystals.
  • the preferred percentage proportions of CaO, MgO, Al 2 O 3 , and SiO 2 in the molten slag in which crystallisation of titanium oxide is evidenced is shown in Figure 1. It will be appreciated that the preferred percentage proportions of CaO, MgO, Al 2 O 3 , and SiO 2 in the composition diagram of Figure 1 is equivalent to 100%. In other words the minimum concentration of TiO 2 in the molten slag is understood to be in addition to the CaO, MgO, Al 2 O 3 , and SiO 2 components in the molten slag. It will be understood that location of the composition boundary shown within the composition diagram of Figure 1 is approximate.
  • titanium oxides-bearing materials that may be used in the process of the present invention include, but are not limited to non-ferrous ores of titanium such as rutile (naturally occurring or synthetic), anatase, brookite, perovskite, titanate (also known as sphene) or geikielite. Rutile, anatase and brookite are polymorphs of TiO 2 .
  • the process of the present invention can also be used in relation to titanium ores containing iron oxides including, but not limited to, leucoxene, ilmenite (conventional or altered), tilvospinel, titanomaghemite, titanomagnetite, and vanadiferous titanomagnetite provided that the titanium ores containing iron oxides undergo standard reduction and melting or smelting processes, and which may include subjecting the titanium ores containing iron oxides to an oxidising roast.
  • pig iron is tapped from a smelting furnace and processed according to known techniques.
  • Molten slag is also tapped from the smelting furnace, and it is this tapped molten slag which is subject to treatment according to the present invention.
  • the suitability of any titanium oxides-bearing material must be assessed on general criteria as described in more detail as follows.
  • the titanium oxides-bearing material is typically comprised of TiO 2 , iron oxides (but not always), and other oxides.
  • the other oxides are typically but not exclusively CaO, MgO, Al 2 O 3 and SiO 2 .
  • Three examples of TiO 2 source materials that do not specifically contain iron are the minerals perovskite [CaTiO 3 ], geikielite [MgTiO 3 ], and Titanate (also known as Sphene) [CaTiSiO 5 ].
  • Perovskite and titanate cannot be used solely as the addition of requisite fluxes would dilute their TiO 2 content to less than that required to adequately form crystalline TiO 2 on slow cooling solidification. However, they may be used as combined sources of TiO 2 and flux with other materials. Thus, in all titanium oxides-bearing material it is necessary that following any beneficiation the ratio of TiO 2 content be sufficiently high relative to the combined CaO, MgO, Al 2 O 3 and SiO 2 contents present naturally or as gangue in the source material and present as ash in the carbonaceous reductant so that the molten slag subsequently created together with any requisite fluxing additions of CaO, MgO, Al 2 O 3 and SiO 2 has sufficiently high TiO 2 content.
  • TiO 2 source material contains various other metal oxides then these may also have to be allowed for.
  • the molten slag is predominantly comprised of TiO 2 , CaO, Al 2 O 3 and SiO 2 then any Cr 2 O 3 content may be treated as equivalent to Al 2 O 3 .
  • a titanium oxides-bearing material that is by itself unsuitable for this process is the Waikato North Heads vanadiferous titanomagnetite ironsand concentrate currently utilised for ironmaking at New Zealand Steel.
  • the ratio of TiO 2 were to be raised sufficiently by blending with requisite quantities of one or more high grade sources of TiO 2 , such as Ilmenite, Leucoxene or Rutile, then it will be suited for the process of the present invention.
  • the fine concentrate that would be produced by conventional beneficiation of the hard rock vanadiferous titanomagnetite present at Balla Balla in Western Australia would be suitable as the titanium oxides-bearing material for the process of the present invention.
  • two or more TOBMs may be blended and used in the process of the present invention.
  • Blending of the CaO, MgO, Al 2 O 3 and SiO 2 contained in the TOBMs can advantageously minimise the addition of the fluxing agents.
  • the molten slag is cooled at a slow rate between the liquidus and the solidus of the molten slag.
  • the crystalline TiO 2 can then be extracted from the solidified slag by various separation techniques.
  • the TiO 2 rutile crystals will first be liberated from the solidified slag by breaking up, crushing and grinding the solidified slag to a particle size suitable to commence separation techniques.
  • the largest particle size at which separation of the rutile crystals from the silicate mineral phases of the solidified slag can commence is approximately 1mm, because usually the bulk of rutile crystals formed are less than 1mm in size. Breaking, crashing and grinding are performed by conventional means.
  • breaking up of the solidified body of slag can be performed with a pneumatic or hydraulic powered breaking tool to produce lumps of slag less than 1000mm in size. These lumps are then crashed in a jaw crasher to less than 150mm in size. These subsequent lumps are then crashed in a cone crusher to less than 32mm in size, then ground using high-pressure grinding rolls (HPGR) to less than 1mm in size.
  • HPGR has the beneficial characteristic of breaking materials along grain boundaries between phases. If the phases are similar in hardness then similar size particles of the different phases will be produced. If the phases have different hardnesses then the harder the phase the larger the relative particle size will be.
  • Separation of the ratile crystals from the silicate phase minerals in the ground slag will be performed by conventional mineral particle separation methods, and usually augmented with finer grinding at intermediate stages to further liberate the rutile crystals.
  • Mineral particle separation methods typically work by exploiting the physical properties as shown in Table 2 (size, density, electrical conductivity, magnetic susceptibility, etc.) of the minerals that are being separated. Table 2. Physical properties of primary and secondary mineral phases formed in the slag.
  • Gravity separation methods can be used to separate the denser ratile particles from the less dense silicate mineral phase particles.
  • Gravity separation methods that could be employed include wet separation methods such as cones, spirals and shaking tables and dry separation methods such as air tables.
  • the silicate mineral phase in the solidified slag is acid soluble then acid can be used to remove these phases, usually in a final liberation step.
  • the silicate mineral phase CaAl 2 Si 2 O 8 is known to be soluble in hydrochloric acid.
  • hydrochloric acid can be used to dissolve the residual CaAl 2 Si O 8 .
  • the crystals of mineral ratile formed by the process of the present invention are of relatively high purity although they typically comprise less than 100% TiO 2 .
  • Laboratory scale trials of the process of the present invention have produced ratile crystals with TiO 2 content in excess of 99.0% and as high as 99.8%. Size and conformation of the crystals of rutile vary with the TiO 2 content and the relative proportions of CaO, MgO, Al 2 O 3 and SiO 2 in the molten slag.
  • Laboratory- scale tests have produced ratile crystals as large as lOOO ⁇ m in length and smaller than lO ⁇ m in length.
  • rutile crystal conformation has been observed to vary from cubic to dendritic to approximately filamentous, as shown in Figures 2 and 3.
  • the molar ratios of CaO, MgO, Al 2 O 3 and SiO 2 in the molten slag that result in an optimum ratile crystal conformation (cubic) are not necessarily the same as the molar ratios of CaO, MgO, Al 2 O 3 and SiO 2 in the molten slag that maximise the rutile crystal size and in turn are not necessarily the same as the ratios that maximise TiO 2 recovery as crystalline rutile. Up to a point, higher TiO 2 content in the molten slag promotes the formation of larger rutile crystals.
  • the rate of cooling of the molten slag also affects the ratile crystal size. Cooling at a rate of approximately 2 degrees centigrade or less during solidification is advantageous but not mandatory. Quench cooling where solidification takes place in a few seconds or less will prevent the formation of crystals of ratile. Cooling at a rate well in excess of 2 degrees centigrade per minute, for example 5 degrees centigrade per minute, does not necessarily prevent formation of crystals of ratile but the faster rate of cooling will typically result in ratile crystals that are substantially smaller in size than would otherwise be obtained by slower cooling.
  • Diffusion rate will vary also with the relative proportions of CaO, MgO, Al 2 O 3 and SiO 2 in the molten slag.
  • fewer and larger rutile crystals can only form if the rate of diffusion of TiO 2 in the liquid slag surrounding the rutile crystals initially formed during the slow cooling period exceeds the rate of rutile crystal formation dictated by the rate at which the solidifying slag is cooling. If the cooling rate of the solidifying slag is too high then the liquid slag surrounding existing rutile crystals will become supersaturated in respect of its TiO 2 content and new ratile crystals will begin to form so as to restore the concentration of TiO 2 in the surrounding liquid slag to its equilibrium concentration.
  • Slow cooling of the molten slag may be effected by natural means or by controlled means, provided that the cooling rate is slow enough so as to promote the formation of ratile crystals.
  • Slow cooling practice may employ any technique that may be advantageous to improving rutile crystal morphology and/or size, including but not limited to direction solidification by means of directional cooling. It will be appreciated that the optimum rate at which the solidifying slag is cooled will be sensitive to the temperature difference between the liquidus and the solidus.
  • the presence of a minor amount of Fe 2 O 3 has little or no effect on the formation of crystals of ratile because at low concentrations Fe 2 O 3 will be analogous to Al 2 O 3 and can be incorporated as if it were Al 2 O 3 into the Al 2 O 3 -bearing mineral species that form subsequent to the formation of rutile crystals.
  • This substitutional behaviour is the method by which most if not all of the other common and sometimes uncommon minor quantities of accessory oxides that are attendant in the raw titanium oxides-bearing materials, reductant and fluxes are accommodated.
  • the efficiency of recovery of the rutile crystals from the solidified slag is highly dependant on crystal size and conformation.
  • One method of promoting fewer and larger crystals of ratile to form is to seed the liquid slag with rutile crystals and cool it at sufficiently slow rate so that only the seed crystals grow. If the slag is at its liquidus temperature then the TiO is at its saturation level. Decreasing the slag temperature will cause the slag to become supersaturated in TiO 2 and rutile crystals will begin to precipitate. Increasing the slag temperature will cause the slag to become under-saturated in TiO 2 . Any ratile seed crystals that are added to an under-saturated molten slag will be at least partially dissolved up to the point that the new TiO 2 equilibrium saturation level is achieved.
  • the TiO content of the molten slag in the furnace can be controlled such that at the operating temperature the slag is both saturated in TiO 2 and crystals of rutile will pre-exist in the slag before commencement of cooling.
  • a molten slag that is close to saturation can be produced and just prior to commencement of the slow cooling step it is possible to stir in some rutile crystals that where previously extracted, ensuring that sufficient seed crystals are added to the molten slag allow for any portion thereof that will be dissolved in saturating the molten slag with TiO 2 .
  • the slag can be allowed to cool, or be deliberately cooled, to just above its liquidus temperature and some ratile crystals could be stirred in.
  • the advantage of the first method is that it maximises the TiO 2 productivity, but the disadvantage is that the denser ratile crystals may stratify in the slag.
  • the disadvantage of the second method is that it is usually very difficult to control smelting processes to achieve a slag temperature in conjunction with a high TiO 2 content.
  • the disadvantage of the third method is that the TiO 2 productivity of the furnace will be lower and slag temperature will have to be monitored.
  • Example 1 Four slags, designated A, B, C and D, were prepared by mixing the prescribed proportions of pre-dried Reagent Grade Al 2 O 3 , CaCO 3 , MgO, TiO 2 and SiO 2 in accordance with Table 3 Table 3. Composition of slags A to D.
  • High purity Ar (99.997%) was then introduced into the furnace tube at a flow rate of 0.5 1/min to flush and maintain an inert atmosphere inside the furnace.
  • the samples were then heated at 3°C/min to 1550°C. After being held at 1550°C for 3 hours, the samples were cooled to 800°C at 2°C/min and the to room temperature at 3°C/min.
  • the solidified samples were then removed from the furnace and the crucibles cut away from the samples. Large crystals were observed on the surface of samples A, C and D and the resultant samples were quite porous and crumbly. Sample B had no visible crystals on the surface.
  • Example 2 Several slags were prepared by mixing the prescribed proportions of pre-dried Reagent Grade Al 2 O 3 , CaCO 3 , MgO, TiO 2 and SiO 2 in accordance with Table 5 Table 5. Composition of slag samples (in mass %) used for melting and cooling tests.
  • High purity Ar (99.997%) was then introduced into the furnace tube at a flow rate of 0.5 1/min for 30 minutes to flush the tube, then the flow was reduced to 0.1 1/min.
  • the samples were then heated at 3°C/min to 1600°C. After being held at 1600°C for 3 hours, the samples were cooled to 800°C at 2°C/min and the to room temperature at 3°C/min.
  • the solidified samples were then removed from the furnace and the crucibles cut away from the samples. Large crystals were observed on the surface of samples B, D, E and F.
  • slags D, C and B had successively less TiO 2 content.
  • the ratile crystals in slag C are smaller than in slag D and no ratile crystals are detectable in slag B.
  • Slag A has the same TiO 2 content as slag B, but because the proportions of CaO,
  • MgO, Al 2 O 3 and SiO 2 have been altered rutile crystals were able to form.
  • the ores that may be treated by this process come from a group comprising titanium and iron oxides, including titanomagnetite, titanomaghemite, ulvospinel, ilmenite, leucoxene, and vanadiferous titanomagnetite.
  • titanomagnetite titanomaghemite
  • ulvospinel ilmenite
  • leucoxene vanadiferous titanomagnetite
  • vanadiferous titanomagnetite A similar process may be employed with partially processed materials having an iron oxide content, such as titanium slags and beneficiated ilmenites.
  • these ores first undergo a standard reduction melting or smelting process to produce pig iron and a molten slag.
  • the process of the present invention is thus performed in relation to the molten slag so formed.
  • the TOBM feedstock is sampled, analysed and characterised by well-known techniques. Importantly, the relative concentrations of CaO, MgO, Al 2 O 3 and SiO 2 in the gangue of the TOBM are determined.
  • the TOBM may additionally undergo beneficiation and/or concentration to increase the titanium oxides content of the TOBM.
  • Carbonaceous reductant is required to reduce any iron oxides contained in the TOBM to pig iron.
  • the TOBM may also contain various other accessory metal oxides that will be partially reduced or wholly reduced to the metallic state including, but not limited to, V 2 O 5 or MnO.
  • the carbonaceous reductants typically comprise coal.
  • the carbonaceous reductant is also sampled, analysed and characterised at the outset of the process to, amongst other things, determine the relative concentrations of CaO, MgO, Al 2 O 3 and SiO 2 in the carbonaceous reductant. Accordingly, various coals or/and other carbonaceous reductants may be blended to achieve a desired composite molar ratios of Cao, MgO, Al 2 O 3 and SiO 2 .
  • fluxing agents can be added to the feedstock at the outset of the process to adjust the molar ratios of CaO, MgO, Al 2 O 3 and SiO 2 in the subsequent molten slag to appropriate values to afford a molten slag composition that favours formation of crystalline TiO 2 when the molten slag is slow cooled between the liquidus and the solidus of the molten slag, as described previously.
  • the molar ratios of CaO, MgO, Al 2 O 3 and SiO 2 will be adjusted in accordance with Figure 1.
  • titanium oxide(s) bearing material(s) and carbonaceous reductant(s) and all or some or none of the fluxing agents and any binders are then blended together in a controlled manner.
  • blended materials are to be formed into green balls or briquettes then it is usual to add one or more binder materials to improve cohesion and strength.
  • binder materials In the case of green balls binders might be added, and any CaO added as a fluxing agent, if present in a sufficient amount, will also act as a binder when the water is added. Blending is achieved by conventional methods, either on a continuous basis or a batch basis or a combination of both. Thus not all of the above listed materials will necessarily be mixed together at the same time.
  • the requisite reductant requirement for the TOBMs is determined on a semi-empirical basis. Carbonaceous reductants are characterised by their fixed carbon content.
  • the TOBMs will be characterised by their reducible oxide contents. For example in the case of an ilmenite the reducible oxide will be FeO and sometimes some accessory Fe 2 O 3 .
  • the requisite reductant requirement will also be dependent upon the type of equipment in which the oxide reduction is performed. By way of examples, if the blended mix is neither balled nor briquetted and the coal in the blended mix is devolatilised before oxide reduction is performed in a rotary kiln then a certain fixed carbon to reducible oxides ratio requirement, and thereby coal requirement, will be established. Alternatively, if the blended feed is briquetted, the coal is not devolatilised and oxide reduction is performed in a rotary hearth furnace then the fixed carbon requirement, and thereby coal requirement, will be lower than for the previous example.
  • coal or other reductant requirement can only be established on a case by case basis in accordance with the nature and composition of all the raw materials and the specific process route that is employed, bearing in mind that no one process route is uniquely advantageous as it too is usually tailored to suit the locally accessible raw materials.
  • the blended feedstock materials may themselves undergo sampling, analysis and determination of molar ratios of CaO, MgO, Al 2 O 3 and SiO 2 , these analytical results being used in conjunction with other relevant analyses to jointly determine the requisite additions of fluxing agents at later stages in the process.
  • the carbonaceous reductant is conventional lignite/brown coal (e.g. from the Latrobe Valley in Victoria, Australia)
  • an additional subsequent treatment process as described in Australian Patent No. 703821
  • Lignite has a very high moisture content, which is mainly inherent.
  • the lignite brown coal could be pre-processed as part of the carbonaceous reductant preparation/beneficiation step described earlier.
  • the mixture may undergo briquetting or balling depending on the means by which the iron oxide reduction is performed.
  • oxide reduction is to be performed in a rotary hearth furnace (RHF)
  • balling or briquetting of the feedstock materials is typically required.
  • RHF rotary hearth furnace
  • balling or briquetting of the feedstock materials is typically required.
  • the operating requirements of the RHF or other iron oxide reduction means as specified by the equipment supplier.
  • oxide reduction is performed in a rotary kiln, balling or briquetting are not usually required.
  • Balling is carried out on one or more balling discs and requires the addition of water and usually but not always a binder.
  • CaO fluxing agents can be used as a binder.
  • Briquetting is carried out in a briquetting machine and usually requires the addition of a binder and sometimes the addition of water.
  • the feedstock may then undergo a drying or pre-heating process step.
  • the moisture content of the feedstock is high, such as in green balls produced in balling, or in the case that high moisture content lignite/brown coal is used as the carbonaceous reductant, it may be advantageous or desirable to reduce the moisture content by drying before further processing.
  • Drying occurs in two stages because water is usually present as both free and inherent moisture. Free moisture can be driven off at temperatures below 100 degrees centigrade. Inherent moisture in coal must be driven off at temperatures in excess of 105 degrees centigrade. Water of hydration that might be present with other materials has to be driven off at the respective 'ignition temperatures', which are usually substantially higher and more likely to be performed during the subsequent oxide reduction step or/and smelting step. Drying may be achieved by means of (but not limited to) a travelling grate, rotary kiln, rotary hearth, or a multiple hearth.
  • Drying could even be done in more than one step so that low grade waste heat is used to drive off free moisture at temperatures below 105 degrees centigrade.
  • Inherent moisture in coal could then be driven of in a second dryer that is fired (using natural gas or combustible process by-product gas(es) such as volatiles that are driven off during devolatilisation) to raise the mixture temperature to above 105 degrees centigrade as required.
  • coal or any other carbonaceous reductant
  • This may be achieved by means of, but not limited to, a travelling grate, rotary kiln, rotary hearth, or a multiple hearth. Because drying and devolatilisation may be achieved in the same type of plant then it is possible to simultaneously combine these two process steps.
  • the proportion of volatiles driven off is dependant on the temperature.
  • the volatiles driven off, and other combustible process gases that might be produced in the subsequent smelting step, etc. can be utilised in a number of ways including, being burnt to provide process heat for drying, preheating, etc, being burnt to raise steam for power cogeneration to supply power for the process and auxiliary equipment ( eg. conveyors, crashers, electric furnace(s) if used, etc.). It is generally advantageous to reduce the iron oxide(s) (wholly or partially) prior to the smelting step. When the iron oxide(s) are to be reduced prior to smelting reduction can be achieved by conventional processing in a travelling grate, rotary kiln, rotary hearth, or a multiple hearth.
  • One of the above iron oxide reduction means is usually employed because iron oxide reduction using carbonaceous reductant is an energy intensive process and if reduction is completed together with the melting of the slag and the resultant pig iron during the smelting step with an electric furnace then the electricity requirement is usually prohibitively costly.
  • the process heat is provided by combusting some or all of the process gases, and sometimes some additional natural gas or pulverised coal.
  • the smelting step only requires enough energy input to complete any reduction and afford high enough temperatures to produce the molten slag and the liquid pig iron.
  • the reduced feedstock material may then be sampled, analysed and characterised for determination of relative molar quantities of CaO, MgO, Al 2 O 3 , and SiO .
  • Requisite amounts of fluxing agents can either be added to the reduced feedstock material before smelting commences or during smelting. Smelting may be batchwise or continuous..
  • pig iron is tapped from the smelting furnace and is processed according to known techniques.
  • Molten slag is also tapped from the smelting furnace, and it is this slag which is subject to treatment according to the present invention. It is envisaged that during tapping of the slag following smelting a sample of the molten slag will be taken. The sample of slag will be analysed by standard techniques to determine its composition. The actual composition of slag tapped will be compared with both the intended composition of slag prior to slow cooling solidification and the intended composition of slag tapped if that differs from the intended composition of slag prior to cooling.
  • any difference in the actual and intended composition of the slag tapped will be used as the basis for adjusting the relative molar amounts of CaO, MgO, Al 2 O 3 and SiO 2 in the molten slag being smelted to substantially favour formation of silicate mineral species CaAl 2 Si 2 O 8 or CaMgSi 2 O 6 or Mg 2 Si 2 O 6 or Mg 2 Al 4 Si 5 O ⁇ 8 , or a mixture thereof subsequent to formation of crystalline TiO 2 when the molten slag is cooled, by adjusting the addition of fluxing agents to the smelting vessel.
  • any difference in the actual and intended composition of slag prior to slow cooling solidification and the mass of slag will be used as the basis for determining the requisite mass additions of fluxing agents prior to slow cooling to substantially favour formation of silicate mineral species CaAl 2 Si 2 O 8 or CaMgSi 2 O 6 or Mg 2 Si 2 O 6 or Mg 2 Al Si 5 Oi8, or a mixture thereof subsequent to formation of crystalline TiO 2 when the molten slag is cooled.
  • the slag includes titanium oxides in a plurality of oxidation states, for instance TiO 2 , Ti 3 Os, Ti 2 O 3 , TiO, Ti 3 O 2 , Ti 2 O, and Ti 3 O, following the reduction of the iron oxides to metallic iron.
  • TiO 2 , Ti 3 Os, Ti 2 O 3 , TiO, Ti 3 O 2 , Ti 2 O, and Ti 3 O following the reduction of the iron oxides to metallic iron.
  • New Zealand Steel slag which typically contains 35% TiO 2 equivalent (and is insufficient to form Rutile crystals given the bulk slag composition)
  • up to one third of the TiO 2 can be reduced to Ti 2 O 3 during the smelting step.
  • Bubbling air, as an alternate source of oxygen, through the molten slag will be disadvantageous as the nitrogen content of air will result in the formation of Titanium Oxy Nitride (TiON).
  • TiON Titanium Oxy Nitride
  • other partially reduced oxides present in the slag will be oxidised.
  • any FeO will be oxidised to Fe 2 O 3 .
  • any VO or V 2 O 3 will be oxidised to V 2 Os.
  • any flux additions required to make final adjustments to achieve the intended proportions of CaO, MgO, Al 2 O 3 and SiO 2 in the molten slag can be made. There are three reasons to make flux additions at this point.
  • the requisite additions will be determined on the basis of the mass of the slag and the difference between the analysed composition of the slag sample taken before oxidation and the intended slag composition.
  • the present invention envisages that a portion of the crystalline titanium oxides which is extracted according to methods such as those described above may be recycled for seeding as previously described on the basis of mass of slag, composition and temperature.
  • the molten slag is now cooled in a controlled fashion, at a rate sufficiently slow to enable the formation of crystalline TiO 2 .
  • the slag solidifies into a primary crystalline titanium dioxide phase (rutile) and a secondary silicate phase substantially comprising silicate mineral species CaAl 2 Si 2 O 8 or CaMgSi 2 O 6 or Mg Si 2 O 6 or Mg 2 Al 4 Si5 ⁇ s, or a mixture thereof, when the molten slag is cooled at a slow rate between the liquidus and the solidus of the molten slag, provided that the TiO 2 content of the molten slag composition is sufficiently high enough for crystalline TiO 2 to form.
  • the molten slag is allowed to slow cool at a rate of approximately 2°C per minute substantially between the liquidus and the solidus of the molten slag. Cooling at these rates results in the formation of crystalline titanium oxide.
  • the crystalline ratile can be recovered by liberating and separating as described previously. Modifications and variations as would be apparent to a skilled addressee are deemed to be within the scope of the present invention.

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Abstract

L'invention concerne un procédé destiné à extraire du TiO2 cristallin à partir d'une matière renfermant des oxydes de titane. Premièrement, on produit un laitier en fusion comprenant du TixOy et des fondants comprenant du SiO2 et des oxydes métalliques à partir d'un groupe renfermant du CaO, du MgO et de l'Al2O3, les fondants étant présents dans le laitier en fusion dans une proportion permettant d'ajuster le rapport molaire du CaO, du MgO, de l'Al2O3 et du SiO2 dans le laitier en fusion, ce qui favorise sensiblement la formation d'une phase de silicate secondaire après la formation d'une phase de TiO2 cristallin primaire lorsque le laitier en fusion est refroidi. La concentration en TiO2 dans le laitier en fusion doit être suffisante pour permettre l'obtention d'un TiO2 cristallin lorsque le laitier en fusion est refroidi. Ensuite, on refroidit lentement le laitier en fusion entre la phase liquide et la phase solide du laitier en fusion de manière à favoriser la cristallisation du TiO2, le TiO2 cristallin ainsi formé étant alors libéré et séparé du laitier solidifié. Ce procédé convient particulièrement aux laitiers renfermant du titane obtenus sous la forme d'un sous-produit dans une opération de fusion réductrice destinée au traitement d'oxydes ferreux contenant des oxydes de titane.
PCT/AU2004/001188 2003-09-05 2004-09-03 Procede destine a extraire des oxydes de titane cristallins WO2005024074A1 (fr)

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AU2003904835A AU2003904835A0 (en) 2003-09-05 Crystallisation of Crystalline Titanium Oxides
AU2003904835 2003-09-05

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WO2011143703A1 (fr) 2010-05-18 2011-11-24 Technological Resources Pty. Limited Procédé de fusion directe
CN103108967A (zh) * 2010-09-15 2013-05-15 技术资源有限公司 直接熔炼方法
CN113979742A (zh) * 2021-11-30 2022-01-28 松山湖材料实验室 Magnéli相亚氧化钛陶瓷及其制备方法和惰性电极
CN115125471A (zh) * 2022-06-29 2022-09-30 武汉苏泊尔炊具有限公司 非晶不粘材料的制造方法及非晶不粘涂层的制造方法

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KR101852863B1 (ko) * 2010-05-18 2018-04-27 테크놀라지칼 리소시스 피티와이. 리미티드. 직접 제련 방법
AU2011256134B2 (en) * 2010-05-18 2014-12-11 Tata Steel Limited Direct smelting process
WO2011143703A1 (fr) 2010-05-18 2011-11-24 Technological Resources Pty. Limited Procédé de fusion directe
EP2572005B1 (fr) * 2010-05-18 2020-11-18 Tata Steel Limited Procédé de fusion directe
US10280489B2 (en) 2010-05-18 2019-05-07 Tata Steel Limited Direct smelting process
US20150038317A1 (en) * 2010-05-18 2015-02-05 Technological Resources Pty. Limited Direct Smelting Process
CN102906280B (zh) * 2010-05-18 2015-09-30 技术资源有限公司 直接熔炼方法
US10023945B2 (en) 2010-05-18 2018-07-17 Tata Steel Limited Direct smelting process
RU2573849C2 (ru) * 2010-05-18 2016-01-27 Текнолоджикал Ресорсиз Пти. Лимитед Способ прямой плавки
CN102906280A (zh) * 2010-05-18 2013-01-30 技术资源有限公司 直接熔炼方法
CN103108967A (zh) * 2010-09-15 2013-05-15 技术资源有限公司 直接熔炼方法
KR101903434B1 (ko) * 2010-09-15 2018-10-02 타타 스틸 리미티드 직접 제련 방법
US10000821B2 (en) * 2010-09-15 2018-06-19 Tata Steel Limited Direct smelting process
US20130180361A1 (en) * 2010-09-15 2013-07-18 Rodney James Dry Direct smelting process
CN113979742A (zh) * 2021-11-30 2022-01-28 松山湖材料实验室 Magnéli相亚氧化钛陶瓷及其制备方法和惰性电极
CN115125471A (zh) * 2022-06-29 2022-09-30 武汉苏泊尔炊具有限公司 非晶不粘材料的制造方法及非晶不粘涂层的制造方法
CN115125471B (zh) * 2022-06-29 2023-05-16 武汉苏泊尔炊具有限公司 非晶不粘材料的制造方法及非晶不粘涂层的制造方法

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