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WO2007122366A1 - Co-production d'acier, de titane et d'oxyde de grande qualite - Google Patents

Co-production d'acier, de titane et d'oxyde de grande qualite Download PDF

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Publication number
WO2007122366A1
WO2007122366A1 PCT/GB2007/000568 GB2007000568W WO2007122366A1 WO 2007122366 A1 WO2007122366 A1 WO 2007122366A1 GB 2007000568 W GB2007000568 W GB 2007000568W WO 2007122366 A1 WO2007122366 A1 WO 2007122366A1
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Prior art keywords
melt
titanium
liquid
gas
oxycarbide
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PCT/GB2007/000568
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Noel Warner
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Priority to GB0821025A priority Critical patent/GB2451600B/en
Priority to AU2007242640A priority patent/AU2007242640B2/en
Priority to US12/226,302 priority patent/US20090230598A1/en
Publication of WO2007122366A1 publication Critical patent/WO2007122366A1/fr
Anticipated expiration legal-status Critical
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G23/00—Compounds of titanium
    • C01G23/02—Halides of titanium
    • C01G23/022—Titanium tetrachloride
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G23/00—Compounds of titanium
    • C01G23/04—Oxides; Hydroxides
    • C01G23/047—Titanium dioxide
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21B—MANUFACTURE OF IRON OR STEEL
    • C21B13/00—Making spongy iron or liquid steel, by direct processes
    • C21B13/0006—Making spongy iron or liquid steel, by direct processes obtaining iron or steel in a molten state
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21B—MANUFACTURE OF IRON OR STEEL
    • C21B13/00—Making spongy iron or liquid steel, by direct processes
    • C21B13/006—Starting from ores containing non ferrous metallic oxides
    • 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
    • C21C5/56—Manufacture of steel by other methods
    • C21C5/567—Manufacture of steel by other methods operating in a continuous way
    • 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
    • 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
    • C22B34/1218—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 obtaining titanium or titanium compounds from ores or scrap by dry processes
    • C22B34/1231—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 obtaining titanium or titanium compounds from ores or scrap by dry processes treatment or purification of titanium containing products obtained by dry processes, e.g. condensation
    • 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
    • C22B34/1263—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 obtaining metallic titanium from titanium compounds, e.g. by reduction
    • C22B34/1281—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 obtaining metallic titanium from titanium compounds, e.g. by reduction using carbon containing agents, e.g. C, CO, carbides
    • 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
    • C22B34/1263—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 obtaining metallic titanium from titanium compounds, e.g. by reduction
    • C22B34/1286—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 obtaining metallic titanium from titanium compounds, e.g. by reduction using hydrogen containing agents, e.g. H2, CaH2, hydrocarbons
    • 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
    • C22B34/129—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 obtaining metallic titanium from titanium compounds by dissociation, e.g. thermic dissociation of titanium tetraiodide, or by electrolysis or with the use of an electric arc
    • 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
    • C22B34/1295—Refining, melting, remelting, working up of titanium
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21B—MANUFACTURE OF IRON OR STEEL
    • C21B2100/00—Handling of exhaust gases produced during the manufacture of iron or steel
    • C21B2100/60—Process control or energy utilisation in the manufacture of iron or steel
    • C21B2100/66—Heat exchange
    • 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
    • C21C2100/00—Exhaust gas
    • C21C2100/02—Treatment of the exhaust gas
    • 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
    • Y02P10/10—Reduction of greenhouse gas [GHG] emissions
    • Y02P10/134—Reduction of greenhouse gas [GHG] emissions by avoiding CO2, e.g. using hydrogen
    • 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
    • Y02P10/10—Reduction of greenhouse gas [GHG] emissions
    • Y02P10/143—Reduction of greenhouse gas [GHG] emissions of methane [CH4]
    • 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
    • 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
    • Y02P20/00—Technologies relating to chemical industry
    • Y02P20/50—Improvements relating to the production of bulk chemicals
    • Y02P20/54—Improvements relating to the production of bulk chemicals using solvents, e.g. supercritical solvents or ionic liquids

Definitions

  • This patent provides a method for directly smelting titaniferous materials such as ilmenite mineral concentrates to liquid titanium metal and or pigment-grade titanium dioxide by a process with an energy consumption believed to be less than one third of that of the currently best available commercial technology and potentially superior to other new technologies currently being considered as viable alternatives to the Kroll pyrometallurgical process route.
  • Titanium has valuable mechanical and corrosion resistant properties but according to a recent study performed for the US Department of Energy and Oak Ridge National Laboratory (Summary of Emerging Titanium Cost Reduction Technologies, January 2004), although titanium is the fourth most abundant structural material in the earth's crust after aluminium, iron and magnesium, the total US titanium production including scrap recycle was only around 48,000 tonnes in 1997 based on available statistics for that year.
  • TiCl 4 titanium tetrachloride
  • a preferred electrolyte is a molten calcium halide, which exhibits high oxygen anion solubility.
  • WO 03/046258 A3 describes a method for electrowinning titanium metal or alloy from titanium oxide containing compounds in the liquid state, which is claimed to have significant advantages over other emerging technologies. It involves direct electrowinning of titanium from molten titanium mixed oxide compounds in which the deoxygenation step is performed using either a consumable carbon anode, or an inert dimensionally stable anode or a gas diffusion anode.
  • the preferred electrolyte is molten calcium fluoride.
  • droplets of liquid titanium metal are produced at the oxide/electrolyte interface and sink by gravity, settling to the bottom of the electrochemical reactor, forming after coalescence, a pool of liquid titanium metal or alloy.
  • the liquid metal is continuously siphoned or tapped under an inert atmosphere and cast into dense titanium metal ingots.
  • the teachings of WO 03/046258 A3 form the basis of the present invention.
  • a truly continuous process is not yet available, which is capable of accepting the electrically conductive titaniferous charge materials such as ilmenite mineral concentrates or titaniferous magnetite at one end of the spectrum right through to synthetic rutile or solid upgraded titanium slag at the other end of the spectrum.
  • Their transformation in-line to high purity liquid titanium ⁇ oxide as the preferred continuous feed for titanium metal production is the essence of the present invention.
  • This invention is an attempt to lead industry onwards into a new era and leave behind the conventional wisdom, which for so long, has thwarted development of a virile titanium metal industry.
  • the hitherto upper temperature limit for ilmenite smelting furnaces, for example, will have to be abandoned and more advanced engineering designs incorporated in future plants.
  • the present invention achieves this objective and thus paves the way for ultra-high temperature processing for ilmenite treatment in the future.
  • Anatase, rutile and synthetic rutile are the preferred raw materials for the synthesis of the oxycarbide linings.
  • the other reactant is preferably carbon black, again a material commercially available at reasonable prices and is used, for example, in formulating the mix for automobile tyres.
  • fabrication of the linings in-situ is preferable, particularly those associated with complex arrangements such as underflow and overflow weirs and linings or whole component parts associated with siphons and gas-lift pumping devices.
  • a material mix corresponding to the required solidus composition can be melted in specialist facilities away from site and quenched rapidly to capture the solidus phase composition.
  • the cooled material is then reground and then pressed and sintered in a controlled atmosphere with a CO/CO 2 ratio as indicated on the HSC4 program into refractory blocks from which the melt circulation reactor can be fabricated on site.
  • the titanium oxycarbide may in some cases be the inner lining of a composite lining with more conventional refractory mixtures backing on to outer steel/alloy shells.
  • the inner steel casing is removed, leaving the outer steel case in place and the whole volume enclosed is filled with material of the liquidus composition.
  • the whole mass is conductively heated with perhaps graphite electrodes also installed above to melt the inner material, whilst heat is extracted from the external walls and base.
  • PCT/GB2006/000302 relates to a melt circulation ratio in excess of 1500/1 in these terms, and of course electrical conductive heating can be applied in striving for temperature uniformity.
  • the energy implications of such high melt circulation ratios are minimal, provided the head to which the melt is being circulated is itself relatively low.
  • the first of the sub-processes is the formation and recovery of a molten iron alloy for subsequent continuous processing to liquid steel ready for continuous casting.
  • a gas phase and two liquid phases are involved. All of these must be essentially at equilibrium with each other throughout the associated melt circulation loop. If the three phases are in a state of thermodynamic equilibrium, then provided a phase diagram is available, the composition of a suitable solid phase can be identified. Ceramists and others skilled in the art can specify the so-called liquidus and solidus compositions for a particular operating temperature. If phase equilibrium data are not available, clearly experimentation may then be required.
  • the reactor hearth, walls and contact areas of equipment such as lances, snorkels, overflow and underflow weirs immersed in the melt must all be prefabricated from material of the solidus composition.
  • the generic melt circulation technology advocated by the inventor on many prior occasions is characterised by circulation of a single liquid phase.
  • the carrier melt is copper-saturated, so it is clearly advantageous to maintain a stationary pool of molten copper below the circulating copper matte.
  • each of these phases is preferably independently circulated under turbulent flow conditions to promote good mixing.
  • the lower phase (metal) is circulated and the upper phase (slag) subjected to intense top blowing and vice versa, if suitable tuyeres can be installed to provide good mixing throughout the lower phase (metal) with the upper liquid phase (slag) force circulated.
  • suitable tuyeres can be installed to provide good mixing throughout the lower phase (metal) with the upper liquid phase (slag) force circulated.
  • TMs invention does not prescribe a single preferred reductant for carbothermic processing of ilmenite, as individual locations throughout the world have different priorities and opportunities for accessing their own preferred reductant.
  • Natural gas, calcined anthracite coal, petroleum coke, carbon black or wood charcoal are among reductants chemically feasible, but hydrogen and carbon monoxide or indeed manufactured gas with low methane content are very much less efficient thermodynamically, unless used in conjunction with a carbon source at unit activity.
  • a prime requirement is very low sulphur content because of the detrimental effects of sulphur on attaining high quality products in the present case.
  • Natural gas of the purity specification supplied to power stations is ideal in terms of sulphur content. For other reductants some prior desulphurisation may be necessary. In terms of sustainability, wood charcoal is obviously a renewable resource and is attractive for avoiding carbon emission penalties.
  • Fossil feel decarbonisation for mitigating global warming and heralding in a hydrogen economy is a possible scenario for the future.
  • Thermal decomposition of methane is central to the approach.
  • the by-product carbon black could well become readily available for carbothermic reduction under these circumstances.
  • the inventive strategy is based on the ability to transfer carbon reliably at very high efficiency to the melt in order to sustain equilibria throughout without precipitation of oxycarbide or other solid phases in the bulk of the melt. Such precipitation would lead to uncontrolled deposition and accretion build-up as well as deterioration in the physical properties of the single phase melt, especially viscosity, which is important to avoid, to ensure that the various liquid phase transport processes are not impeded.
  • the thermochemical reduction requirements can be provided by solid carbon addition, carburisation by blowing natural gas onto the surface of the melt is instantly controllable and provides locally advantageous mass transfer conditions conducive to effective assimilation of dissolved carbide. This is all achieved without carry-over of solid carbon particles into the gas phase above the melt surface.
  • the essential prerequisites are turbulent flow in the bulk melt and carefully designed top blow nozzles so that the carbon utilisation efficiency is very close to the predicted 100% theoretical value.
  • Natural gas top blowing is also the foundation for satisfying other important issues, which dominate the potential viability of the new continuous processing technology.
  • health and safety issues demand that the process plant is fully under control at all times.
  • automatic control strategies must be in place to take over the operation without manual intervention.
  • Straightforward top blowing of the melt surface from above, coupled with controlled melt circulation rate simply by changing the inert gas flowrate to the gas-lift pump arrangement and electrical conductive heating to supply the thermal demands, are fail-safe measures which can be exploited collectively to safely implement automatic control procedures.
  • melt circulation loops cannot readily be heated radiatively by post- combustion of the gaseous products of reduction.
  • copper matte and titanium oxycarbide melts are strong parallels between the properties of copper matte and titanium oxycarbide melts. Both are electronic conductors with relatively high thermal conductivities and because post combustion cannot be used to heat oxycarbide or matte melts directly, conductive heating and melt circulation are mandatory requirements for both.
  • the ductile to brittle fracture transition for such materials is very favourable and they would appear to be able to operate over a temperature range from above 2000 0 C to say 800 0 C. This facilitates maintenance of the unmelted shell approach rather than attempting to use so-called "skull formation" with water-cooled hearths. According to the Handbook of Refractory Carbides and Nitrides
  • the transition metal carbides have the ability to deform plastically above a given temperature, referred to as the ductile-to-brittle transition temperature. Below that temperature titanium carbide fails in a brittle manner, while above it, it shows ductile behaviour and undergoes plastic deformation. For TiC this is in the region of 800 0 C and because of the cubic structure of titanium oxycarbide over the whole range of solid-state stability, high temperature linings of titanium oxycarbide can reasonably be expected to behave in a similar fashion.
  • Fig. 1 is an overview of the plant for continuous smelting of ilmenite concentrates employing three melt circulation loops in series to feed an electrochemical deoxygenalion reactor to produce titanium metal with the oxidic melt overflow then undergoing various processing options to produce either or both pigment-grade titanium dioxide product, or, if exceptionally high purity specifications so demand, a process intermediate of titanium tetrachloride by direct chlorination of the oxycarbide melt at high temperature.
  • Fig. 2 repeats the essentials of Fig. 1 except that electrochemical deoxygenation to titanium metal is carried out at the end of the in-line processing, rather than being upstream of the downstream processing options, so that the only melt undergoing electrochemical deoxygenation is that destined to be converted to titanium metal.
  • Fig. 3 is schematic general arrangement of the first of the melt circulation loops for carbothermic reduction of ilmenite using natural gas as the reductant, showing ilmenite distribution onto the top of the oxidic melt, natural gas distribution to headers for top blowing the melt surface, the means for quenching the off-gas with quench gas recycled by a turbocompressor after heat recovery in a waste heat boiler and hot gas filtration with a candle filter, circulation of the melt in a closed loop and its continual progression to downstream in-line processing stations and continuous production of liquid steel in advance of refining prior to continuous casting.
  • Fig. 4 is schematic half sectional elevation of one arm of a melt circulation loop containing a single oxidic melt liquid phase showing the "cavity-wall" type of construction comprised of an inner hot face lining of solidus composition titanium oxycarbide, a free space containing support skids to allow unimpeded thermal expansion and contraction of the arm, boiler tubes for steam raising, superheating or closed-loop steam reheating service as appropriate on safety grounds, so positioned that they receive direct thermal radiation from the cooler face of the oxycarbide lining, and an outer backing of conventional refractory and insulating materials, all encased externally in a gas-tight steel shell.
  • the "cavity-wall" type of construction comprised of an inner hot face lining of solidus composition titanium oxycarbide, a free space containing support skids to allow unimpeded thermal expansion and contraction of the arm, boiler tubes for steam raising, superheating or closed-loop steam reheating service as appropriate on safety grounds, so positioned that they receive direct
  • Fig. 5 is a schematic sectional elevation of one end of the reduction arm (typically 60-90 m in overall length), shown in cross-section across the width in Fig. 4, when operating at the full design temperature.
  • Fig. 6 is a schematic cross-sectional elevation of the two side-by-side arms of the first of the melt circulation loops, the top blown reactor (TBRl), which employs forced circulation of both the oxidic melt and denser molten metal, each based on gas injection from above with overhead lances or other gas sparger devices.
  • Fig. 6 shows the suspended flat arch roof construction and one row of an array of top blowing lances passing across the hot face lining of titanium oxycarbide, positioned very close to the top surface of the oxidic melt.
  • Fig. 7 is a schematic sectional elevation view of the first of the melt circulation loops, the top blown reactor (TBRl), which employs forced circulation of both the oxidic melt and denser molten metal, each based on gas injection from above with overhead lances or other gas sparger devices.
  • Fig. 8 is a comparison of three sectional elevations taken across the melt circulation loop constituting TBRl, moving from left to right beyond the ceiling/melt close proximity top- blow area of Fig.7:
  • (a) shows side-by-side arms of the loop separated longitudinally by a central partition of the cavity wall type of construction with titanium oxycarbide of solidus composition on both sides of the free space with support skids, steam tubes, etc., and cross-hatching all removed for clarity purposes
  • Fig. 9 is a schematic sectional plan (AA in Fig. 8) of the molten oxidic melt cross-over between the two principal side-by-side arms of the upper oxidic melt circulation loop of TBRl, comprising, in the direction of melt cross- flow, the overflow weir from the main bath (submerged not visible), a melt calming section followed by an underflow weir all of titanium oxycarbide of the solidus composition with cavity wall type of construction and then the active melt sump for gas-lifting the oxidic melt across and overflow weir of the same solidus composition as the underflow and principal linings back into the other principal arm and means for top lancing or sparging as required for gas admission to promote two-phase flow upstream of the overflow weir.
  • Fig. 10 is a schematic sectional plan (BB in Fig. 8) of the molten metal cross-over between the two principal side- by-side arms of the lower molten metal circulation loop of TBRl, comprising in the direction of melt cross-flow, the weir from the main bath (above section not shown), a melt calming section followed by an underflow weir of titanium oxycarbide of the solidus composition with cavity wall type of construction and the active melt sump for gas-lifting the molten metal across the overflow weir of the same solidus composition as the underflow and principal linings back into the other principal arm and means for top lancing or sparging as required for gas admission to promote two-phase flow upstream of the overflow weir.
  • Fig. 11 is schematic cross-sectional elevation of the two side-by-side arms of the melt circulation loop that constitutes in-line continuous vacuum refining (CVR) of the liquid titanium oxycarbide produced in TBR2, showing both arms of the loop contained within a single vacuum vessel.
  • CVR continuous vacuum refining
  • Fig. 12 shows the key features of chlorine-based technology seen to be included as one of the "downstream processing options" referred to in Figs. 1 and 2.
  • Fig. 1 in explanation of what is termed "downstream processing", it is necessary to know that in the chloride process, titanium dioxide feedstock is reacted with chlorine in the presence of coke in a fluidised bed at around 900 u C to produce impure titanium tetrachloride.
  • the existing carbon in the oxycarbide melt contributes to the overall carbon requirement for carbochlorination.
  • the preferred embodiment if chlorination is deemed necessary to reduce residual impurity levels even further than can be accomplished in-line by vacuum refining, is to complement the existing carbon in the melt after electrochemical deoxygenation, with additional carbon added to the melt either as elemental carbon in one of the forms, already referred to, for carbothermic reduction to permit carbochlorination to proceed by reaction (3).
  • TiO + C + 2Cl 2fg TiCl ⁇ fe) ⁇ COfe) (3)
  • the chlorine may by injected into the melt to avoid hydrogen chloride formation in advance of carbochlorination, but it is recognised that excess CI 2 will react to form HCl unless steps are taken to keep the gaseous reactants apart. Accordingly, top blowing with CI 2 an already carburised melt by natural gas as top blowing in an entirely separate compartment is the preferred approach and it is proposed that another melt circulation loop to conduct this carbochlorination operation is fully justified.
  • On one arm (the first arm) for reaction with natural gas and the other for top blowing with chlorine is the preferred embodiment.
  • the off-gas from the first arm is a further stream of hydrogen enriched "fuel gas" to be added to this exported commodity or used in-plant for power generation.
  • the present invention takes as received mineral concentrates and transforms them continuously to titanium oxide with impurity levels so low that the pigment requirement for minimal optical absorption at visible wave lengths is met for adequate whiteness and opacity.
  • titanium dioxide this in turn requires high chemical purity and in particular transition metal impurities must be virtually eliminated.
  • Small amounts of impurities such as iron, manganese, chromium or vanadium darken the pure titanium dioxide crystal. Therefore, the priority in the present invention is to reduce as far as is thermodynamically possible the concentration levels of these four deleterious metals. At the same time, it was considered worthwhile to aim for minimum concentration levels of all other contaminants.
  • the plant for continuous smelting of ilmenite concentrates employs at least one melt circulation loop at around atmospheric pressure, or perhaps somewhat higher pressure to secure benefits, feeding continuously into a continuous vacuum refining (CYR) melt circulation loop discharging downstream into various processing options in advance of the residual melt finally undergoing electrochemical deoxygenation.
  • CYR continuous vacuum refining
  • preheated ilmenite concentrates 1 are distributed onto the surface of the circulating oxidic melt 2 in the top blown reactor TBRl on either or both of the reactor arms 3.
  • Natural gas 4 preheated no hotter than 350 0 C to avoid carbon decomposition, is piped to an array of top blowing nozzles or jets 5.
  • the very hot off- gases 6 (raw fuel gas) are quenched by special means, which have been incorporated so that the copious fume generated on quenching does not form accretions on solid surfaces in the immediate vicinity.
  • the preferred method of quenching is to exit the gases through nozzles at relatively high velocity so that the quench gas 7 is entrained radially into the hot gas jets to effect cooling without intervention of solid surfaces.
  • the gases are then passed onwards to a waste heat boiler 8.
  • the quench gas itself is recycled hydrogen enriched "fuel gas” at say 400 - 500 0 C.
  • the hydrogen enriched "fuel gas” is exported to a nearby power station.
  • a turbocompressor 11 is installed both for recycling purposes as well as for onwards transmission of the low sulphur fuel gas 12 directly to either gas turbine combustors for combined cycle power generation or pipeline distribution to customers.
  • the solids 13 collected by the candle filter 10 are reverted to the process feed 14 so that no fine solid waste disposal problems arise and valuable iron units are recovered.
  • the equivalent amount of liquid steel 15a actually produced within TBRl has to be withdrawn from the melt circulation loop as unrefined product liquid steel 15a.
  • the equivalent amount of oxidic melt 16a formed within TBRl has to be withdrawn continuously from melt circulation.
  • the siphons can utilise a full vacuum if so required.
  • the width of the furnaces involved could be in excess of 8 metres, so suspended arch construction is necessary and for the physical configuration demanded in carbothermic reduction using natural gas.
  • the refractory roof or "arch” 22 has to be flat so as to maintain a small clearance 23, probably in the region of 10 cm between the liquid melt 16 and the flat refractory roof 22 immediately above it.
  • the furnace hearth cannot support this roof because it expands very considerably itself on being heated to operating temperature.
  • the full length of the flat refractory roof and its associated structural steel work 24 is supported on steel pontoons floating on liquid metal or fusible alloy contained in launders or troughs 28 on each side of the hearth (un-melted oxycarbide 18) containing the melt 16 and extending the full length of the furnace.
  • the pontoons 26 can be made to float and thus during heating up from room temperature to say 2000 0 C at the hot face of the lining, the structure is free to expand both longitudinally and laterally across the width of the hearth.
  • liquid metal 27 can be partially removed from the troughs 28 so that the pontoon supported structures no longer float but rather can bear down onto refractory fibreboard 29 in a controlled fashion to form a gas-tight seal, assisted by the positioning of load cell devices at appropriate locations.
  • the pontoons 26 can be floated again by pumping liquid metal 27 back into the troughs 28 so that the roof structure 25 and its associated refractory flat arch 22 can return eventually to the cold position.
  • the removable lid 30 covers the whole extent of the furnace and may be a single unit or multiplicity of units to achieve the same effect and affords the means for ready access.
  • the unsectioned area on the right illustrates the external hearth channel enclosure 17.
  • a skid-mounted system 19 permitting thermal expansion or contraction of the oxycarbide lining 18 and a row of steam raising boiler tubes 31 to stabilise the munelted oxycarbide 18 at a prescribed steady state thickness are shown schematically in this diagram.
  • a protective gas atmosphere is maintained at locations not already referred to as containing natural gas or products of combustion, in order to prevent carburisation or hydrogen embrittlement of steel or alloy components exposed to relatively high temperatures, such as the steam boiler tubes 31 and Hie metal 20 sheathing the cooler faces of the oxycarbide lining 18.
  • Fig. 5 Also apparent in Fig. 5 is the flat suspended arch 22 with its steel support joist girders 25, which are permitted to move independently of both the external enclosure 21 and the un-melted shell of oxycarbide 18 constituting the furnace hearth, side and end walls in order to accommodate differential expansion during warm-up.
  • the fusible alloy launder/pontoon system discussed in Fig. 4, in relation to the flat refractory arch 22 and its supporting steelwork, would be activated so that sufficient weight is bearing down to effect compression of fibreboard sealing arrangements and also enough force applied laterally on the fibreboard seal at 29 to compress it adequately for gas sealing purposes.
  • this particular drawing depicts operation somewhat above atmospheric pressure.
  • the higher-pressure gas region is associated with the gas space 23 and the corresponding gas off-take 45, whilst near to atmospheric pressure conditions prevail above the melt in the gas at 46.
  • Fig. 6 external furnace enclosures have been removed and the cavity-wall type of construction associated with the oxycarbide linings 18 is simplified by deleting cross-hatching, skid mounts, boiler tubes, etc.
  • the refractory suspended flat arch 22 and its associated steel joist girders 25 and supporting steelwork 24 is shown to span across both arms of the melt circulation loop.
  • an alternative is to have two independent support systems each with its own pair of steel pontoons 26 floating on liquid metal or fusible alloy 17 contained in launders or troughs 28 to permit individual expansion or contraction, if only one of the arms of the melt circulation loop is required to be shut down.
  • Fig.6 relates specifically to TBRl in which both the oxidic melt 16 and the lower steel melt 15 are circulated independently of each other. Also shown in this diagram is the narrow gap or clearance 23 between the oxidic melt 16 and the hot face of solidus composition titanium oxycarbide roof elements 22.
  • Individual lances or jets 32 that form an extensive top blown array for admitting natural gas are protected with at least one and preferably two or more cylindrical concentric radiation shields fabricated from the solidus composition oxycarbide and other ceramic materials as the temperature decreases.
  • Each of the top blow lances 32 is steam cooled on its outer surface at least over the relatively short length exposed to the highest temperature within the titanium oxycarbide facing of the suspended arch or ceiling immediately above the melt. By these means the temperature of the natural gas is maintained below 350 0 C to prevent methane decomposition and carbon deposition.
  • One option is that such cooling constitutes the initial reheating of a closed loop steam system in association with an advanced steam turbine for power generation.
  • Fig. 7 this relates specifically to TBRl, a melt circulation loop with both oxidic and metal phase independent melt circulation.
  • the rows of lances 33 and 34 or other appropriate gas sparging devices are beyond the plane of section in the sectional elevation shown.
  • Lance row 33 admits lift-gas into the two-phase flow region that establishes forced circulation of the top layer oxidic melt 16.
  • Lance row 34 extends into the lower metal phase region to provide the driving force for forced circulation of the bottom layer of molten steel 15.
  • 33 and 34 show a row containing three lances and typically the requirement is between two and four lances for smaller width arms, say below 5 m in width, and correspondingly larger numbers if wider arms are employed for increased smelting throughputs.
  • the lift gas employed is preferably the hydrogen-enriched fuel gas 12, already compressed by the turbocompressor 11 in preparation for export or in-plant usage to fire the gas turbine combustors of a combined cycle power plant.
  • the solidus composition titanium oxycarbide lining 18 is shown crosshatched in this diagram. Because of the absence of high gas velocities and thus inherently lower gas phase mass transfer coefficients involved, the roof area 35 is of baked carbon or graphite construction, backed with carbon-based insulation, which may if deemed necessary be faced with oxycarbide, but calculations reveal that baked carbon would have an acceptable life span in this region. Elsewhere, in the natural gas top-blown region, extending virtually the whole length of the furnace, oxycarbide facing of the ceiling 22 is mandatory.
  • a single row of top blowing lances 32 is shown as discharging natural gas directly into the narrow gas space 23 above the surface of the oxidic melt 16.
  • the associated gas jets emerging from the hot face of the ceiling 22 are effectively in what is termed the potential core jet region so that hot gas entrainment is minimal and very little opportunity for methane decomposition arises in advance of the jets impinging on the melt surface under precisely controlled non- splash conditions.
  • the structural steelwork and steel joist girder 25 system for supporting the refractory suspended flat arch extends upwards towards the removable lid 30 covering the length of the furnace to ensure gas tightness.
  • this diagram is specific to TBRl and in certain cases optionally to TBR2. It relates to the non-top blown area at the right hand end of the furnace shown in Fig. 7, where they are no high gas velocities and the roof 35 is of baked carbon or graphite construction.
  • the solidus composition titanium oxycarbide linings 18 of the cavity-wall type of construction are not crosshatched but are shown schematically, free of expansion skids, boiler tubes, etc.
  • the oxycarbide linings 18 of the cavity walls illustrated envelop all solid faces in contact with oxidic melt 16 and liquid steel 15, including the hearths, sides, end walls, central partitions 36 as well as overflow weirs 37 and underflow weirs 38.
  • the two-phase regions 39 and 40 are equivalent to a less dense arm of a U-type configuration resembling a manometer. Gas injection into one side of the U, if a homogeneous gas/liquid mixed phase is formed, lowers the density on one side of the U so that the two-phase gas/liquid rises and eventually overflows, if there is inadequate height available to reach a new equilibrium position. Now, if the static leg of the U is connected to a supply of the liquid phase and the whole system forms a closed loop, then liquid circulation will continue indefinitely as long as the two-phase flow region is maintained stable by gas injection.
  • the static region 41 of the hypothetical U configuration can be viewed as a calming region in advance of the active two-phase flow region on the other side of the U. Region 41 is especially useful in the case of the lower liquid metal phase melt circulation loop as it provides access for withdrawing continuously the product unrefined liquid steel 15 from TBRl using the aforementioned vacuum-assisted electrically conductive heating siphon arrangement.
  • the oxidic melt 16 is force circulated around a closed loop encased throughout with a solidus composition titanium oxycarbide lining 18 using cavity-wall type of construction with ancillaries, such as steam raising boiler tubes removed from view for clarity.
  • the lower liquid steel 15 is mainly obscured but this is also force circulated independently of the oxide melt circulation emphasised in this diagram. There is no particular merit in attempting countercurrent contacting of the oxidic melt 16 and the liquid steel 15 as they are both fully back-mixed.
  • both liquid phases it is preferable for both liquid phases to be moving co-currently, so that individual bulk phase mixing is promoted at higher turbulence levels by this means without incurring a penalty in terms of Helmholtz interfacial instability.
  • a row of three upwards removable vertical lances 33 admits the preferred lift-gas into the active sump 39 for gas lifting the oxidic melt 16 across the overflow weir 37 and thereafter the melt flows by gravity along the length of the furnace split into two by the central partition 36 and around the closed loop path highlighted by the large block arrows and then back to the underflow weir 38.
  • various components related to the analogous arrangement for forced circulation of the liquid steel which will be described in Fig 10.
  • the unrefined liquid steel 15 constituting the bottom layer of the two liquid phases in TBRl is circulated around a closed loop encased throughout with solidus composition titanium oxycarbide lining 18 using cavity wall type of construction with ancillaries such as steam tubes removed from view for clarity.
  • a row three upwards removable vertical lances 34 admits the preferred strip gas into the active sump 40 for gas lifting the liquid steel 15 across the overflow weir 37 positioned so that it is above the level of the top surface of the oxidic melt 16, thus causing the liquid steel to shower through the oxidic melt layer as it sinks through to the circulating bottom layer of liquid steel 15.
  • the pumping head requirements for circulating the liquid steel 15 are somewhat greater than that required for circulating the oxidic melt 16, so it is necessary to provide additional submergence in the liquid steel sump to facilitate this.
  • a rough guide used by those skilled in "air-lift” technology is that the submergence should be at least twice the head to be pumped, so this is duly taken into account.
  • conditions may be established in the process design so there is optionally no liquid steel melt in either TBR2 or in the melt circulation loop associated with continuous vacuum refining (CVR) of the titanium oxycarbide melt fed continuously using the aforementioned siphon arrangements from TBR2 into the fore hearth or sump of the CVR melt circulation loop.
  • CVR continuous vacuum refining
  • steam jet injector systems have been developed for exhausting large volumes of gases from degassing vessels typically down to 0.5 to 1 mbar pressure.
  • oxygen top blown decarburisation in association with circulating flow steel vacuum degassing is now established practice in batch steel refining and multiple steam jet ejectors backed up with water ring pumps are state-of-the-art with, for example, 1800 kg/h dry air equivalent pumping capacity at 1 mbar pressure. This is the technology on which CVR is dependent. Furthermore, as in the comparable steel degassing case, it is considered worthwhile to accommodate a degree of top blowing with reducing gas of the titanium oxycarbide melt, to ensure that gas phase mass transfer does not limit reaction rates in forced circulation "swimming pool" reactors.
  • the CVR melt circulation loop across which the sectional elevation of Fig. 11 is taken contains identical arms projected to be typically 50 metres or so in overall length, so that concerns already expressed about differential thermal expansion apply equally well to the CVR arrangement.
  • Each of the melt circulation arms could optionally be made vacuum tight with crossovers at both ends to interconnect the arms to form a closed loop comprised of two principal side-by-side furnaces.
  • the whole loop can be accommodated within a single pressure vessel 42.
  • high pressure fluidised bed coal combustors are enclosed within spherical or cylindrical pressure vessels to eliminate concerns about pressure tightness of the various individual components that make up a fluidised bed system. In the United States, for example, utilisation of such prefabricated pressure vessels is limited by the maximum diameter transportable on inland waterways, which is considered to be around 12 metres.
  • Thermal expansion and contraction of the titanium oxycarbide hearth lining 18 may be taken care of by skid mounts 19 bearing on heat resistant metal alloy sheathing 20 on the cooler feces of the oxycarbide lining in association with steam boiler tubes 31, etc. Alternatively, more sophisticated means maybe adopted. Differential expansion and contraction associated with the suspended refractory roof arches with hot faces around 2000 0 C fabricated from solidus composition titanium oxycarbide elements 22 suspended from structural steelwork comprising steel joist girders 25, etc., are accommodated by the aforementioned system employing fusible alloy or liquid metal 27 inside launders or troughs 28 on each side of the structure spanning the overall width, inside which steel pontoons 26 extend the full length of the furnace.
  • the pontoons 26 either fully support the structural steel and its associated suspended refractory arch, when sufficient depth of liquid metal 27 is contained within the troughs 28 during start-up or shutdown, or when liquid metal is drained or pumped out to pre-determined extent, a controlled pressure is exerted on the ceramic fibre board 29 to effect a gas tight seal, once differential movement has ceased. As before, access is provided by the removable lid 30 and elsewhere there is a fixed steel enclosure 21.
  • the gas freeboard 44 is of such height that the gas phase pressure drop is only a relatively small fraction of the total operating pressure, which for current steel vacuum degassing systems is typically around 0.5 to 1 mbar.
  • This refined oxycarbide melt is removed preferably continuously from the vacuum chamber back to atmospheric pressure using the aforementioned electrical conductive heating principles not by a siphon, but this time by a barometric leg of the melt sheathed in its protective lining of solidus composition titanium oxycarbide into an atmospheric pressure sump or tundish, from which a siphon can then be used for either continuous or intermittent passage of the melt to the next in-line processing stage, the electrochemical deoxygenation reactor, as per the flow sheet presented in Fig. 1 and 2, to produce titanium metal.
  • thermochemistry An insight into the thermochemistry is provided in Table 1, which lists the standard free energy and enthalpy changes for the key chemical reactions all at 2000 0 C.
  • iron oxide is the most easily reduced to the metallic state but clearly there is little prospect for reduction of thorium oxide to metal.
  • ⁇ G° listed are for reactants and products in their standard states. Obviously a very minor component, such as uranium oxide, will be so diluted that its thermodynamic activity is extremely small and thus is unlikely to be reduced.
  • the equations for magnesium and calcium also warrant comment.
  • Table 1 also gives background to the refining of impurities out of the principal titanium oxide phase but it must be appreciated that besides oxide reduction to metal, formation of carbides must also be taken into account at the same time.
  • the first oxycarbide loop at 2080 0 C and CVR conditions are 1920 0 C at 1 mbar pressure.
  • the impurity oxide levels in the final reduced titanium oxide product are computed as:
  • Product of SRR overflown or siphoned to the forehearth or tundish at atmospheric pressure with barometric leg withdrawal continuously to a single titanium oxycarbide melt circulation loop (CVR) operating under a vacuum of 1 mbar at 194O 0 C.
  • impurity levels in final reduced titanium oxidic melt assuming equilibrium established in both loops, are computed as follows:
  • Example 1 indicates that if the initial melt circulation loop to which preheated ilmenite concentrates are added, is operated with molten iron as the carrier medium at say 1540 0 C so that the unmelted steel shell region is operable, then the oxides of chromium, manganese and silicon can be reduced down to less than 1 ppm and iron down to around 5 ppm after continuous vacuum refining (CVR).
  • CVR continuous vacuum refining
  • aluminium, niobium and vanadium levels range from 860 to 1920 ppm.
  • white pigment is the desired ultimate product, is the relatively high level of vanadium, previously referred to as especially deleterious, which is around 0.19% in this example.
  • Example 2 the initial processing loop is operated with oxidic melt circulation at the higher temperature of 2080 0 C rather than 1540 0 C and this reduces the vanadium oxide and niobium oxide down to levels around 1350 ppm.
  • oxidic melt circulation at the higher temperature of 2080 0 C rather than 1540 0 C and this reduces the vanadium oxide and niobium oxide down to levels around 1350 ppm.
  • This extracts both V and Nb oxides from the molten oxide phase by reaction at the slag/metal interface and then diffusion into the molten iron phase, where V in particular has a large negative deviation from ideality and is thus retained at very low thermodynamic activity.
  • the reaction between 3SIbO and TiC is somewhat more favourable but at high dilution Nb forms an almost ideal solution in molten iron, so the effectiveness of extraction from the slag into the molten iron is comparable for both oxides.
  • thermodynamic aspects are enhanced very considerably at the ultra high temperatures implicit in the invention and are just not available to the same extent with current industrial practice for ilmenite smelting.
  • the same considerations are also very advantageous in lowering the aluminium oxide content by the analogous mechanism.
  • reversion of refined molten iron/steel back into the melt circulation loop also extracts additional titanium into the circulating metal phase with a corresponding decrease in ultimate Ti oxide or Ti metal product recovery.
  • Example 3 a possibly somewhat excessive amount of molten iron is reverted in Example 3, in which 10 l ⁇ nol Fe( ⁇ /kmol TiO 2 in feed is considered at the expense of marked decrease in ultimate Ti recovery to product (92.5% to 81.5%).
  • Example 3 is also used to reinforce another vitally important aspect. If high purity is the objective, it is essential to reduce sulphur levels associated with inputs down to an absolute minimum. This applies to the feed ilmenite concentrate and also of course to the reductant. As stated earlier, natural gas is available commercially with very low sulphur levels (single digit ppm range) and if high purity is the over-riding consideration, it is then difficult for coal-based and most other forms of commercially available carbon to compete in purity terms, unless given very special treatment at added expense.
  • the actual level of sulphur in ilmenite be reduced prior to charging by preheating preferably already low sulphur ilmenite concentrates under controlled conditions to oxidise sulphide sulphur to sulphur dioxide in the region of 1200 0 C.
  • the sulphur must be reduced to around 0.005 mass % in order to sustain production of exceptionally high purity products.
  • the aforementioned sulphur problem is due to calcium sulphide in particular being extremely stable in a reducing environment, so the problem is mitigated if the calcium content of the ilmenite concentrate is itself minimal.
  • the indicated levels of around 200 ppm "calcium oxide" equivalent are very largely due to the anticipated contamination of the reduced melt with dissolved calcium sulphide associated with a feed to the SRR containing 0.05% S.
  • Example 3 considers that the sulphur is reduced down to below 0.005% sulphur in the thermal treatment before preheated concentrates enter the circuit.
  • Ilmenite concentrates of the aforementioned typical composition and with a sulphur content of 0.05 wt% are heated in a fluid bed to 1200 0 C to drive off sulphide sulphur down to 25 ppm prior to charging the preheated concentrates to TBRl.
  • Some 10 kmol refined liquid steel per kmol TiO 2 is reverted to TBRl in order to enhance the removal of vanadium, niobium and aluminium in particular and also to generally assist in further removal of other reducible oxides.
  • TBRl is operated at 1 bar pressure and 1870 0 C with 2.45 kmol CH 4 per kmol TiO 2 being top blown under non-splash conditions onto the oxidic melt surface. It is assumed that both the oxide melt and the liquid steel are fully back-mixed, induced by melt circulation using gas lifting with the aforementioned hydrogen enriched "fuel gas" and the linings throughout are of the appropriate solidus composition titanium oxycarbide.
  • a further 0.60 kmol CH 4 per kmol TiO 2 is top blown onto the surface of the melt in TBR2, which is lined with its own appropriate solidus composition titanium oxycarbide.
  • TBR2 which is at 1 bar pressure and a temperature of 2150 0 C.
  • the principal function of TBR2 is to carburise the melt in advance of continuous vacuum refining (CVR).
  • CVR is conducted in the third melt circulation loop at 1 mbar pressure and 2060 0 C. Again there is no liquid steel phase in this melt circulation loop and the reactor is lined throughout with its individual appropriate solidus composition titanium oxycarbide.
  • Top blowing is retained at 2.45 kmol CH/kmol TiO 2 in TBRl and 0.6 kmol CHLi/kmol TiO 2 in TBR2 and again conditions are chosen such that a liquid steel phase is only present in TBRl, where it is circulated independently of the oxidic melt TBRl operates at 1870 0 C and 1 bar pressure; TBR2 is 2115 0 C and 1 bar pressure with CVR at 200O 0 C and 1 mbar pressure, in this example.
  • TiO 2 equivalent recovery equals 81.7% and the equivalent TiO 2 purity is 99.98%
  • TiO 2 equivalent recovery equals 93.1% and the equivalent TiO 2 purity is 99.97% Impurity levels in ascending order are computed as:-
  • U.S.Patent 6,375,923 again on a hydrometallurgical route, reports a final titanium dioxide that contains only 6 ppm Fe and states that the invention described does not require an extra processing step to meet market requirements.
  • U.S. Patent Application 0060051267 relating to purification of titanium tetrachloride, states that common metal chloride impurities in crude titanium tetrachloride include chlorides and complex chlorides of Al, Nb, Ta and V. It is asserted that "these metal chloride impurities are not susceptible to removal by distillation because of the proximity of their boiling points to that of titanium tetrachloride or their solubility in the titanium tetrachloride.
  • Examples 4 and 5 are now presented to demonstrate that the aforementioned impurities can be reduced to single digit ppm levels by in-line high temperature refining during direct smelting of ilmenite concentrates and four nines (99.99%) TiO 2 equivalent is attainable in the present invention.
  • Ilmenite concentrates of the typical composition and with a sulphur content of 0.05 wt% are heated in a fluid bed to 120O 0 C to drive sulphur down to ⁇ 10 ppm prior to charging to TBRl.
  • Natural gas-based smelting reduction with both oxidic melt and liquid steel melt independently circulated in TBRl and TBR2.
  • 3 kmol refined liquid steel per kmol TiO 2 is reverted to TBRl in order to enhance the removal of V, Nb and Al.
  • TBRl operated at 1 bar pressure and 1870 0 C with 2.15 kmol CH 4 per kmol TiO 2 top blown under non-splash conditions.
  • TBR2 kmol refined liquid steel per kmol TiO 2 reverted to TBR2, which is at 1 bar pressure and 2100 0 C.
  • Principal function of TBR2 is to carburise the melt in advance of continuous vacuum refining (CVR) and to further reduce VO and (NbO + NbO 2 ) by extraction into reverted liquid steel circulation.
  • CVR conducted in the third melt circulation loop at 1 mbar pressure and 1990 0 C. There is no liquid steel phase in this third melt circulation loop.
  • Impurity levels in ascending order are computed as: CrO 2 , MnO, SiO 2 , Al 2 O 3 ⁇ 1 ppm; FeO 1.9 ppm; M 8 O 2.2; VO 5.4 ppm; (NbO + NbO 2 ) 11.80 ppm; CaO 42.1 ppm.
  • so-called "coloureds" in elemental form Mn, Cr ⁇ 1 ppm; Fe 1.9 ppm; V 4.1 ppm.
  • Methane decomposition and the oxycarbide reduction together are highly endothermic as indeed are the reactions with carbon as the reductant.
  • methane With methane the initial cracking of the molecule to elemental carbon and hydrogen add to overall endothermicity.
  • electrical conductive heating is essential in the present invention to supply the energy needs. The furnaces involved are thus strictly speaking electric furnaces, but not submerged or open arc of the type used presently throughout pyrometallurgical industry.
  • the preferred embodiment avoids high intensity top blowing, as for example is characteristic in LD steelmaking. Instead it is preferable to spread out the top-blowing to cover the whole available surface of gas/melt interface, which in the present case, means both arms of the first melt circulation loop, the top-blown reactor (TBRl), with each jet staying comfortably below the onset of splashing and then rely on melt circulation and the turbulence of the melt to ensure good mixing in the bulk of the liquid phase.
  • TBRl top-blown reactor
  • Simpleite smelting with natural gas effectively results in carbon consumption at the expense of hydrogen leaving as off-gas what is effectively a medium LCV fuel gas, as compared to the very much larger LCV of natural gas itself. It is not difficult to see the attraction of this "by-product", if emission- trading schemes become universal as they already are in the European Union.
  • carbon capture and removal in the longer term for climate change reasons may be facilitated by recycling carbon dioxide to the combustors of gas turbines and the like to control exomermicity, if pure oxygen rather than air is used.
  • availability of a medium LCV gas is highly desirable in such a scenario.
  • the preferred embodiment sees as mandatory provision of low intensity top-blowing over the entire available area of gas/liquid interface to prevent reaction endothe ⁇ nicity from disrupting the over-riding requirement of proximity to temperature uniformity to ensure stability of the oxycarbide linings.
  • an elementary calculation rules out maintaining a cooled roof at a temperature of around 35O 0 C above the melt and passing the large number of nozzles or top-blow lances through this relatively cool environment before the methane emerges at high velocity into the gas space above the melt followed then by minimal clearance between the roof and the melt surface to substantially limit enlrainment of hot gas into the methane jet.
  • gas removal at relatively low velocities can be accomplished throughout the length of both arms on each side through a number gas off-takes with the hot faces fabricated from material of the solidus composition.
  • the bulk gas and the liquid phases are flowing in a cross-flow pattern with bulk gas flow in both directions from the centre line, so questions concerning interfacial stability even with the relatively small clearance between the melt and the flat ceiling of about 10 cm or so, do not arise.
  • Example 2 Consider now the oxidic melt in Example 2 being subjected to thermally balanced oxidation with a CO 2 /gas mixture at 1940 0 C in advance of electrochemical deoxygenation at 1860 0 C, so that greater than 97% of the contained titanium is recovered as metal, before the two-phase liquid/solid region is entered.
  • the equilibrium composition in mol % is: TiO 20.74%; Ti 2 O 3 32.0%; Ti 3 O 5 32.09%; TiO 2 14.75%; TiC 0.42%.
  • Ti metal production with this melt as feed going right through to completion would consume an estimated 4.91 kWh kg " *Ti of electricity, compared with 6.98 IcWh kg -1 Ti evaluated by the author for the Cardarelli conditions.
  • the recently proposed Plasma Powder Process according to Norgate ⁇ t al. has an estimated electricity consumption of 25.2 kWh kg ⁇ Ti to which a further 1 kWh kg ⁇ Ti has to be added for single stage VAR, giving an overall electricity consumption of 26.2 kWh kg "x Ti.
  • the corresponding gross energy requirement (GER) figure evaluated by Norgate et al. for the Kroll process is 361 GJB 1 /t Ti, including the gross energy involved in dredging and mineral processing.
  • the precise figures for the latter components are not given in the Norgate et al. 22 paper, but inspection of their graphical figures would suggest that the combined figure for both is somewhat less than say 6 GJm /t Ti, so a conservative estimate for the GER is 355 GJ Th /t Ti.
  • the PFE value for the Kroll process is in the vicinity of 355 GJn 1 /t Ti.
  • a preferred embodiment is thus to continue the in-line processing by direct carbochlorination of the refined oxycarbide melt immediately after continuous vacuum refining, when the melt is returned to atmospheric pressure.
  • This sub-process is best carried out at virtually the same temperature and melt composition, characteristic of the CVR step.
  • carbochlorination is preferably conducted in a melt circulation loop, which is fully back-mixed so that operation of the melt close to the liquidus temperature enables utilisation of oxycarbide linings of the solidus composition for the hearth, walls and ends of both arms of the melt circulation loop.
  • the preferred embodiment is to top blow with natural gas under relatively mild non-splash conditions uniformly over the whole area of one arm of the loop and then on the other arm to. add chlorine judiciously so that virtually all the melt surface area is exposed to relatively mild reaction intensity.
  • the ceiling can be fabricated from graphite, as this is resistant to chlorine, carbon monoxide and the metallic chloride vapours, which constitute the gas phase on this particular arm.
  • a very small gap probably purged with carbon monoxide or other inert gas, needs to be maintained between the oxycarbide unmelted shell and the graphite upper regions. It is obviously important that the temperature of the melt, being already close to the liquidus temperature in relation to the oxycarbide lining, is not permitted to decrease so that the two-phase solid/liquid region is entered, so careful control of temperature using balanced conductive heating and heat removal to steam raising or other appropriate heat removal means, is required for this purpose.
  • Molten potassium chloride is force circulated around a closed loop employing electric motor-driven mechanical rotors to generate the intensive splash conditions, characteristic of an ISF condenser, in order to absorb the gaseous thorium chloride into the fused salt.
  • ISF condenser rotors are of alloy steel construction but for the present case graphite construction would eliminate any concerns about corrosion or contamination of the fiised potassium chloride melt.
  • the aluminium industry has been well served by centrifugal pumps constructed of graphite at comparable temperature levels of operation. Commercially proven technology is therefore readily available for all aspects relating to fused salt splash "condenser" proposed in the current invention.
  • a small portion of the fused salt melt is withdrawn either continuously or intermittently to regenerate the potassium chloride content by electrolytic deposition of thorium (and probably calcium) or other appropriate chemical means before the withdrawn potassium chloride melt side stream is reverted back to the splash "condenser" melt circulation loop.
  • the thorium will be deposited in the solid state on a non-consumable electrode arrangement and can be recovered using well-established procedures.
  • Fig. 12 shows the two aforementioned melt circulation loops in plan view, one for carbochlorination and the other representing the splash "condenser", i.e. absorber, for removing gaseous thorium tetrachloride from the gas evolved in the chlorination arm of the carbochlorination melt circulation loop.
  • the flow sequence begins at the bottom left-hand corner of Fig.
  • the present invention offers a cost-effective means for supplying continuously the refined titanium tetrachloride either in gaseous or liquid form ready for incorporation into the Ginatta/Carter JR. et al. chlorine-based electrochemical approach to titanium melt production on a large scale. It can thus be seen to be the front end of truly continuous titanium metal production directly in-line from ilmenite or other titaniferous minerals.
  • Carbochlorination of this melt at 2035 0 C would consume per initial kmol TiO 2 in the ilmenite feed concentrates a total of 1.665 kmol Cl 2 and 0.486 kmol CH 4 , based on an equilibrium gas phase composition at say 775 0 C (mean temperature for the splash "condenser" melt circulation loop) of almost 100% TiGU(g) as the main chloride molecular species involved with principally CO as the other major gas phase component at this lower temperature level. This assumes that as the gases are cooled no carbon deposition occurs and reactions involving CO and CO 2 are effectively frozen once HOO 0 C is reached.
  • Rutile pigment material produced by the chloride and sulphate routes are basically similar and to improve dispersibility, dispersion stability, opacity, gloss and durability, both require finisliing, which includes coating with inorganic compounds by selective precipitation on milled aqueous suspensions of the titanium dioxide material. This invention is not directly concerned with these downstream finishing operations but it is anticipated that the finishing requirements will parallel those of existing pigment manufacture.

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  • Engineering & Computer Science (AREA)
  • Organic Chemistry (AREA)
  • Geology (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Environmental & Geological Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
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  • Inorganic Chemistry (AREA)
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Abstract

Selon la présente invention, de l'acier et TiO2 de qualité de pigment allant jusqu'à 99,99 % (TiO2 + ZrO2) sont produits de manière continue par une fusion directe de concentrés d'ilménite ou de magnétite titanifère à une température ultra-élevée. Les phases oxydante et métallique sont mises en circulation de force de manière indépendante dans des réacteurs à circulation de fusion en retromélange total. La proximité immédiate de l'équilibre thermodynamique permet aux bains de composition à l'état liquide d'être contenus dans des réacteurs avec des revêtements protecteurs de coquilles non-fondues consistées d'oxycarbure de composition à l'état solide. Les coquilles non-fondues sont maintenues au-dessus de la température critique de la transition de ductile à la rupture fragile par la génération de vapeur supercritique, tandis que la chaleur endothermique est assurée par un chauffage électroconducteur. La réduction de la fusion avec du gaz naturel ou du carbone avec une faible teneur en soufre, suivie par un raffinage sous vide de manière continue permet de proposer une alimentation continue de bain raffiné pour un traitement direct supplémentaire à des températures légèrement plus basses en utilisant des technologies naissantes connues pour la production de métal de titane.
PCT/GB2007/000568 2006-04-25 2007-02-21 Co-production d'acier, de titane et d'oxyde de grande qualite Ceased WO2007122366A1 (fr)

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GB0821025A GB2451600B (en) 2006-04-25 2007-02-21 Co-production of steel titanium and high grade oxide
AU2007242640A AU2007242640B2 (en) 2006-04-25 2007-02-21 Co-production of steel, titanium and high grade oxide
US12/226,302 US20090230598A1 (en) 2006-04-25 2007-02-21 Co-Production of Steel, Titanium and High Grade Oxide

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GBGB0608080.8A GB0608080D0 (en) 2006-04-25 2006-04-25 Co-production of steel, titanium and high-grade oxide
GB0608080.8 2006-04-25

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US (1) US20090230598A1 (fr)
AU (1) AU2007242640B2 (fr)
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Cited By (1)

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WO2014146682A1 (fr) * 2013-03-18 2014-09-25 Outotec (Finland) Oy Procédé et installation pour produire du laitier de titane à partir d'ilménite

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US8602103B2 (en) 2009-11-24 2013-12-10 Conocophillips Company Generation of fluid for hydrocarbon recovery
WO2011123888A1 (fr) * 2010-04-06 2011-10-13 Iluka Resources Limited Procédé a perfectionné pour la production de rutile synthétique
CN112414129B (zh) * 2020-11-04 2025-03-07 浙江华泰法瑞铝合金有限公司 一种熔炼炉铝合金棒料加料装置
CN114053970B (zh) * 2021-11-22 2023-09-26 天津闪速炼铁技术有限公司 一种甲烷裂解炉

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US3463472A (en) * 1963-02-21 1969-08-26 Conzinc Riotinto Ltd Apparatus for the direct smelting of metallic ores
US4701217A (en) * 1986-11-06 1987-10-20 University Of Birmingham Smelting reduction
US20030126943A1 (en) * 1993-07-22 2003-07-10 Schoukens Albert Francois Simon Production of high titania slag from ilmenite
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WO2004074524A1 (fr) * 2003-02-22 2004-09-02 Noel Alfred Warner Siphon a metal en fusion equipe de dispositifs de chauffage interne et externe
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Publication number Priority date Publication date Assignee Title
WO2014146682A1 (fr) * 2013-03-18 2014-09-25 Outotec (Finland) Oy Procédé et installation pour produire du laitier de titane à partir d'ilménite
AU2013383015B2 (en) * 2013-03-18 2016-09-08 Outotec (Finland) Oy Process and plant for producing titanium slag from ilmenite

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US20090230598A1 (en) 2009-09-17
AU2007242640B2 (en) 2012-01-19
GB0821025D0 (en) 2008-12-24
AU2007242640A1 (en) 2007-11-01
GB2451600B (en) 2011-10-05
GB2451600A (en) 2009-02-04
GB0608080D0 (en) 2006-05-31

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