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Electrochemical Iron Removal from Titanium Ore 電気化学的な手法を用いたチタン鉱石からの脱鉄

Study on removing iron from titanium ore using electrochemical methods to enhance titanium production process efficiency.

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Electrochemical Iron Removal from Titanium Ore 電気化学的な手法を用いたチタン鉱石からの脱鉄

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  1. 電気化学的な手法を用いた チタン鉱石からの脱鉄 Iron removal from titanium oreby electrochemical method 尾花 勲1・岡部 徹2 Isao Obana1, Toru. H. Okabe2 1 東京大学 大学院工学系研究科 1 Graduate School of Engineering, The University of Tokyo 2東京大学 生産技術研究所 2 Institute of Industrial Science, The University of Tokyo

  2. Introduction Feature of titanium Application Lightweight and high-strength Corrosion resistant Biocompatibility Some titanium alloys： shape-memory effect super elasticity Aircraft Spacecraft Chemical plant Implant Artificial bone etc. The Kroll process: Current Ti production process Mg & TiCl4 feed port Reaction container Sponge titanium MgCl2 Chlorination Ti ore + C + 2 Cl2 → TiCl4 (+ FeClx) + CO2 Reduction TiCl4 + 2 Mg → Ti + 2 MgCl2 Electrolysis MgCl2 → Mg + Cl2

  3. Upgrade FeClx Upgrading of Ti ore FeOx Others Others Chloride wastes FeOx TiOx TiOx Ti ore (Ilmenite, FeTiOx) Upgraded Ilmenite (UGI) Discarded This study Low grade Ti ore MClx Ti scrap (FeTiOX) (CaCl2) Selective chlorination Chlorine recovery Fe TiCl4 Upgraded Ti ore FeClx (+AlCl3) (TiO2) Ti smelting Ti metal Advantages: 1. Material cost can be reduced by using low grade ore. 2. Chlorine circulation in the Kroll process can be improved. • This process can also be applied tothe new Ti production processes, e.g. ,the direct electrochemical reduction of TiO2.

  4. Previous study Pyrometallurgical de-Fe process Vacuum pump FeOx (s, in Ore) + MgCl2 (s, l) 　　 → FeClx (l, g) + MgO (s) Condenser Deposit (FeClx) Susceptor CaCl2 (s, l) + H2O (g) → HCl (g) + CaO (s) Mixture of Ti ore and MClx FeOx (in Ore) + HCl (g) 　　　　　　→ FeClx (l, g) + H2O (g) RF coil Quartz flange T = 973 ~ 1373 K N2 or N2+H2O gas The selective-chlorination of Ti ore by MgCl2 or CaCl2 is found to be feasible. Ref. R. Matsuoka and T. H. Okabe:Symposium on Metallurgical Technology for Waste Minimization at the 2005 TMS Annual Meeting, [San Francisco, California] (2005.2.13-17).

  5. Objective Low grade Ti ore (FeTiOx) Application of electrochemical method Iron removal by selective chlorination TiO2 + flux ・・・・・ Electrochemical reduction Reduction or Ti powder Calciothermic reduction 1. Thermodynamic analysis of selective chlorination 2. Fundamental experiments of selective chlorination by electrochemical methods

  6. 0 -10 -20 -30 -40 -50 -60 -40 -30 -20 -10 0 Thermodynamic analysis (Ti ore chlorination) Ti ore : mixture of TiOx and FeOx. Fe-Cl-O and Ti-Cl-O system, T = 1100 K Potential region for selective chlorination of iron from titanium ore Fe2O3 (s) Fe3O4 (s) CO / CO2 eq. C / CO eq. TiO2 (s) H2O(g) / HCl (g) eq. FeO (s) Oxygen partial pressure, log pO2(atm) MgO(g) / MgCl2 (l) eq. CaO (s) / CaCl2 (l) eq. aCaO = 0.1 FeCl2 (l) TiO (s) Potential region for chlorination Of titanium Fe (s) FeCl3 (g) TiCl4 (g) TiCl3 (s) Ti (s) TiCl2 (s) Chlorine partial pressure, log pCl2 (atm) Fig. Chemical potential diagram for Fe-Cl-O and Ti-Cl-O system at 1100 K. The selective-chlorination of Ti ore by controlling chlorine partial pressure might be possible using an electrochemical technique.

  7. Refining process using FeClx Electrolysis Cathode： Fen+ + n e- → Fe Ca2+ + 2 e- → Ca Anode: 2 Cl- (in CaCl2) → Cl2 + 2 e- FeOx + Cl2 → FeClX↑ + O2- Chlorine chemical potential at anode in molten CaCl2 can be increased electrochemically. DC power source FeCl３, AlCl３, O2, CO2 gas e- Ti ore or upgraded Ti ore (e.g. FeTiOx) Molten salt (CaCl2, MgCl2, etc.)

  8. V1 V2 A2 A1 Experimental apparatus Electrochemical interface 10 A Power Source Electrochemical control unit Reaction chamber 100 mm Potential lead (Ni wire) Stainless steel tube (Electrode) Ar inlet Rubber plug Wheel flange Thermocouple Heater Mild steel crucible (Cathode) Nickel electrode Carbon crucible (Anode) Ti ore Molten salt (CaCl2) Ceramic insulator Fig. Schematic illustration of experimental apparatus in this experiment.

  9. Experiment 1 Experimental condition： Temp.: 1100 K Atmosphere: Ar Molten salt: CaCl2 (800 g) Cathode: Mild steel crucible (O.D 102 mm) Anode: Carbon crucible (O.D 19 mm) Mass of Ti ore (Ilmenite), w / g Voltage, E / V Time, t’ / h Exp. A 4.00 2.5 6 Exp. B 4.00 2.0 3 Exp. C 4.00 1.5 12 Voltage monitor / controller e- Mild steel crucible (Cathode) Molten CaCl2 Sample Carbon crucible containing Ti ore (Anode)

  10. Result 1 XRF analysis Table Analytical results of titanium ore (starting sample) and the sample obtained after electrochemical selective chlorination. Concentration of element i, Ci (mass %) Ti Fe Si Al V Fe / Ti (%) Ti ore (init.) 42.6 48.7 2.2 2.2 0.6 114 Exp. A 64.5 29.7 1.8 1.0 0.9 49.5 Exp. B 64.3 29.4 1.3 1.4 1.4 45.6 Exp. C 57.1 24.7 1.6 0.9 3.1 47.4 After the electrochemical treatment, Fe was selectively chlorinated and removed. To proceed iron removal reaction Lower half of sample was unreacted. e- Ti ore (Ilmenite, FeTiOx) Carbon crucible (Anode) Observed unreacted portion Molten CaCl2

  11. Experiment 2 Experimental condition： Temp.: 1100 K Atmosphere: Ar Molten salt: CaCl2 (800 g) Cathode: Mild steel crucible (O.D 102 mm) Anode: Carbon crucible (O.D 19 mm) Mass of element i, Ci (g) Voltage, E / V Time, t” / h Ti ore (Ilmenite) Carbon powder Ti ore : CaCl2 CaCl2 Exp. C 4.00 ー ー ー 1.5 12 Exp. D 0.74 2.17 ー 1 : 4 1.5 3 Exp. E 0.74 2.17 0.18 1 : 4 1.5 3 Voltage monitor / controller e- Mild steel crucible (Cathode) Molten CaCl2 Sample Carbon crucible containing Ti ore + CaCl2 mixture (Anode)

  12. Result 2 XRF analysis In this stage, it is successfully demonstrated that Fe / Ti ratio decreased to 7.2%. Table Analytical results of titanium ore (starting sample) and the sample obtained after electrochemical selective chlorination. Concentration of element i, Ci (mass %) Ti Fe Si Al V Fe / Ti (%) Ti ore (init.) 42.6 48.7 2.2 2.2 0.6 114 Exp. C 57.1 24.7 1.6 0.9 3.1 47.4 Exp. D 90.8 6.5 0.0 0.1 0.6 7.2 Exp. E 52.9 13.1 0.6 0.3 0.2 24.7 94% of Fe was successfully removed. XRD analysis In Exp. D, the Ilmenite sample changed from FeTiO3 to CaTiO3 and TiO2 after experiment. :CaTiO3 :TiO2 Angle, 2 θ (degree) Fig. XRD pattern of the sample obtained after Exp. D.

  13. e- A e- O2- e- Carbon electrode TiO2 Ti Ti crucible（Cathode） Molten CaCl2-CaO Ca-X alloy Ti reduction Production of reductant Disccusion Fe in FeTiO3 was selectively removed in carbon crucible. Cathode : Ca2+ + 2 e- → Ca Fen+ + n e- → Fe Anode : 2 Cl- (in CaCl2) → Cl2 + 2 e- FeTiO3 (s) + CaCl2 (l) → CaTiO3 (s) + FeClx (l, g) Increase in the chlorine potential facilitates selective chlorination reaction of Ti ore. Fig. Apparatus of EMR-MSE process. CaTiO3 can be utilized for material of direct TiO2 reduction processes (e.g. FFC, OS, EMR-MSE processes).

  14. Summary and future work Summary Selective chlorination of Ti ore by the electrochemical method was investigated, and 94 mass% Fe was successfully removed from low-grade Ti ore. Future work ・A more efficient process for producing Fe-free Ti ore by the electrochemical method will be investigated. ・Behavior of chlorine during selective chlorination will be investigated. ・Low-cost Ti production directly from low-grade Ti ore will be established.

  15. 以下　質問対策

  16. History of Titanium 1791 First discovered by William Gregor, a clergyman and amateur geologist in Cornwall, England 1795 Klaproth, a German chemist, gave the name titanium to an element re-discovered in Rutile ore. 1887 Nilson and Pettersson produced metallic titanium containing large amounts of impurities 1910 M. A. Hunter produced titanium with 99.9% purity by the sodiothermic reduction of TiCl4 in a steel vessel. (119 years after the discovery of the element) 1946 W. Kroll developed a commercial process for the production of titanium: Magnesiothermic reduction of TiCl4... Titanium was not purified until 1910, and was not produced commercially until the early 1950s.

  17. ◎高純度のチタンが得られる ◎塩素サイクルが確立している ○効率の良いＭｇの電解を利用 ○TiとMgCl2/Mgの分離が容易 ○還元と電解は同時に行う必要はない × バッチ（回分）式プロセス ×工程が複雑 ×還元反応が大きな発熱反応 Features of the Kroll process ・非常に遅い生産速度 （反応容器一基あたりの生産は～1 t /day ） ・エネルギー大量消費プロセス チタンの新しい製造プロセスの開発が必要 ⇒

  18. Electrolysis (a1) Cathode: TiO2 + 4 e- → Ti + 2 O2- (a2) Anode: C + x O2- → COx + 2x e- 実用化研究中の製造法 FFC Process (Fray et al., 2000) e- Carbon anode TiO2 preform CaCl2 molten salt OS Process (Ono & Suzuki, 2002) TiO2 powder e- Carbon anode Ca CaCl2 molten salt (b1) TiO2 + 2 Ca→ Ti + 2 O2- + Ca2+ Electrolysis Cathode: Ca2+ + 2 e- → Ca (b2) Anode: C + x O2- → COx + 2x e- (b3)

  19. 開発中の製造法 EMR / MSE Process(Electronically Mediated Reaction / Molten Salt Electrolysis) Current monitor / controller Carbon anode e- e- e- e- TiO2 CaCl2 -CaO molten salt Ca-X alloy (X = Ag, Ni, Cu,・・・) (a) TiO2 reduction (b) Reductant production (c1) Cathode: TiO2 + 4 e- → Ti + 2 O2- (c2) Anode: Ca → Ca2+ + 2 e- Electrolysis Cathode: (c3) Ca2+ + 2 e- → Ca (c4) Anode: C + x O2- → COx + 2x e- Over all reaction (d) TiO2 + C → Ti + CO2

  20. 各直接還元プロセスの特徴 FFC Process ×電解と還元を同時に行う必要あり ×メタルと反応浴の分離が困難 △炭素や鉄などの汚染に敏感 △電流効率が低い ◎プロセスがシンプル ○プロセスの連続化が可能 OS Process ×メタルと反応浴の分離が困難 △炭素や鉄などの汚染に敏感 △電流効率が低い ◎プロセスがシンプル ○プロセスの連続化が可能 EMR / MSE Process ×酸化物系の場合、 メタルと反応浴の分離が困難 ×セルの構造が複雑 △プロセスが複雑 ◎炭素や鉄などの汚染を防止できる ○還元と電解は同時に行う必要はない ○プロセスの連続化が可能 電力の安価な夜に還元剤を製造し、 日中にTiO2を還元することが可能

  21. Preform Reduction Process (PRP) M = Nb, Ta, Ti R = Mg, Ca… MOx + R → M + RO TIG weld Stainless steel cover Stainless steel reaction vessel Feed preform (MOｘ+ flux) Stainless steel plate R reductant Ti sponge getter Fig. Schematic illustration of the experimental apparatus for producing titanium powder by means of the preform reduction process (PRP). • Amount of flux (molten salt) is small. • Easy to prevent contamination from reaction vessel and reductant. • Highly scalable.

  22. Ilmenite Reductant (Heavy oil etc.) Reduction (in kiln) Reduced ore HCl aq. HCl vapor Leaching (in digestor) Leached ilmenite Water Spray acid Fuel Roasting Filtration HCl aq. Absorber TiO2 Calcination The Benilite process Fe2+ / TFe = 80~95% (18~20% HCl) 145C° (2.5 kg/cm2) *4 hr *2 step TiO2 Iron oxide HCl Sol. (90% purity) (Synthetic rutile) 95% TiO2 1% TiFe Fig. Flowsheet of the Benilite process.

  23. Iron oxide + Sol. Thickener The Beacher process (WLS) Ilmenite Air Coal (low ash) Reduction (in kiln) Reduced ore Gas + particle Particle Cyclone Gas Screen +1 mm -1 mm Mag. separator Waste (Non. mag.) Reduced ilmenite Air NH4Cl Leaching H2SO4 aq. TiO2 Acid Leaching TiO2 Iron oxide Sol. Filtering / Drying TiO2 (Synthetic rutile) TiO2 92~93% TiFe 2.0~3.5% Fig. Flowchart of the Beacher process.

  24. Selective chlorination using MgCl2 FeOx (s) + MgCl2 (l) = FeClx (l) + MgO (s) Vacuum pump Glass flange Glass beads Chlorides Condenser Stainless steel net Deposit (FeClx．．．) Stainless steel susceptor Carbon crucible Chlorination Reactor Mixture of Ti ore and MgCl2 (Fe-free Ti ore) RF coil Quartz flange Ceramic tube N2 or N2+H2O gas Fig. Experimental apparatus for selective-chlorination of titanium ore using MgCl2 as a chlorine source. Experimental condition T = 1100 K, t’= 1 h, Atmosphere : N2, Ti ore (UGI) : 4 g, MgCl2 : 2 g

  25. Table Analytical results of titanium ore, the residue after selective chlorination, and the sample after reduction. These values are determined by XRF analysis. Concentration of element i, Ci (mass %) Ti Fe Si Al V 2.29 0.41 0.12 0.75 Ti ore (UGI from Ind.) 95.10 0.43 0.44 0.37 1.50 After heating sample 96.45 98.30 0.05 0.38 0.12 0.52 After reduction sample Results of previous study FeOx (s) + MgCl2 (l) = FeClx (l,g) + MgO (s) XRD analysis Deposit obtained after selective-chlorination. → FeCl2 was generated. : FeCl2 Intensity, I (a. u.) 10 20 30 40 50 60 70 80 90 100 Angle, 2θ (deg.) Fig. XRD pattern of the deposit at chlorides condenser. The sample powder was sealed in Kapton film before analysis. XRF analysis Residue after selective-chlorination. → Fe was selective chlorinated.

  26. Table Analytical results of the samples before and after heating and the sample deposited on quartz tube and Si rubber. These values are determined by XRF analysis. Concentration of element i, Ci (mass %) Ti Fe Cl Residue before heating 18.4 45.3 36.2 Residue after heating 9.8 80.1 9.0 Dep. on quartz tube after heating 3.5 50.4 46.1 Dep. on Si rubber after heating 64.9 0.9 34.1 Chlorination of Ti using FeCl2 Ti (s) + 2 FeCl2 (s) = TiCl4 (g) + 2 Fe (s) Quartz tube Sample mixture: (e.g., FeCl2+Ti powder) Sample deposits (on Si rubber, NaOH gas trap and quartz tube) Heater Carbon crucible Fig. Experimental apparatus for chlorination of titanium using FeCl2 as a chlorine source. XRF analysis

  27. 各反応のポテンシャル @1100 K 2CaCl2 + O2 → 2CaO ＋ 2Cl2 log pCl22/pO2 = -8.29 2MgCl2 + O2 → 2MgO ＋ 2Cl2 log pCl22/pO2 = 0.48 4HCl + O2 → 2H2O ＋ 2Cl2 log pCl22/pO2 = 1.49 2CO + O2 → 2CO2 log pO2 = -17.74 2C + O2 → 2CO log pO2 = -19.85 e.g. FeO + MgCl2 → FeCl2 + MgO ΔG= -0.28 kJ < 0

  28. 0 -10 -20 -30 -40 -50 -60 -40 -30 -20 -10 0 Thermodynamic analysis (FeOx chlorination) Ti ore : mixture of TiOx and FeOx. Fe-Cl-O system, T = 1100 K CaO (s) / CaCl2 (l) aCaO = 0.1 Fe2O3 (s) Fe3O4 (s) H2O(g) / HCl (g) CO / CO2 eq. C / CO eq. FeO (s) Oxygen partial pressure, log pO2(atm) MgO(g) / MgCl2 (l) eq. FeCl2 (l) Fe (s) FeCl3 (g) Chlorine partial pressure, log pCl2 (atm) Fig. Chemical potential diagram for Fe-Cl-O system at 1100 K. FeOX (s) + MgCl2 (l) → FeClX (l, g)↑ + MgO (s, l) e.g. FeOx can be chlorinated by controlling oxygen and chlorine partial pressure.

  29. 0 -10 -20 -30 -40 -50 -60 -40 -30 -20 -10 0 Thermodynamic analysis (TiOx chlorination) Ti ore : mixture of TiOx and FeOx. Fe / FeCl2 eq. Ti-Cl-O system, T = 1100 K CaO (s) / CaCl2 (l) aCaO = 0.1 TiO2 (s) H2O(g) / HCl (g) CO / CO2 eq. C / CO eq. Ti4O7 (s) Ti3O5 (s) Oxygen partial pressure, log pO2(atm) Ti2O3 (s) MgO(g) / MgCl2 (l) eq. TiO (s) TiCl3 (s) Ti (s) TiCl4 (g) TiCl2 (s) Chlorine partial pressure, log pCl2 (atm) Fig. Chemical potential diagram for Ti-Cl-O system at 1100 K. Since TiCl4 is highly volatile species, chlorine partial pressure must be kept in the oxide stable region.

  30. 1. A large amount of chloride wastes (e.g., FeClx) are produced in the Kroll process. 2. Chloride waste treatment is costly, and it causes chlorine loss in the Kroll process. Others FeOx TiOx Upgrading Ti ore for minimizing chloride wastes Others FeOx Upgrade Chloride wastes TiOx Up-graded Ilmenite (UGI) Ti ore (eg. Ilmenite) Discarded Importance 1. Reduction of disposal cost of chloride wastes 2. Minimizing chlorine loss in the Kroll process 3. Improvement of environmental burden 4. Reduction of material cost using low grade ore

  31. Refining process using FeClx This study Low-grade Ti ore MClX FeClx Ti scrap (FeTiOX) (Cl2) Selective chlorination Chlorine recovery Upgraded Ti ore FeClx Fe TiCl4 (TiO2) (+AlCl3) Carbo-chlorination TiCl4 feed COx FeClx (+AlCl3) Ti metal or TiO2 production • Advantages: • Utilizing chloride wastes from the Kroll process • 2. Low cost Ti chlorination • 3. Minimizing chlorine loss in the Kroll process • caused by generation of chloride wastes Effective utilization of chloride wastes Development of a new environmentally sound chloride metallurgy

  32. Electrochemical Interface (Potentiostat / Galvanostat) V A Electrolysis cell (Fe crucible) Counter electrode (Fe or C rod) Reference electrode (Ca/Ca2+ ref.) Working electrode (Fe or C rod) Molten salt (CaCl2 (-CaO) ) サイクリックボルタンメトリー(CV)法 反応媒体である CaCl2-CaO溶融塩の 電気的性質を調べることが必要 サイクリックボルタンメトリー(CV) 法を用いる Fig. Structureof cyclic voltammetry.

  33. Iron removal process by electrochemical method Establishment of a new up-grading process of Ti ore by electrochemical method. Direct reduction process from Ti ore to Ti metal can be achieved.

  34. Iron removal process Selective chlorination・Iron removal process Cathode： Fen++n e-　 →　Fe Ca2++2 e- 　 →　Ca Anode　 ： 2 Cl-　→　Cl2+2 e- FeOx + C + Cl2 →FeClｘ(l, g) + COx A e- Ti ore（TiO2 + FeOｘ） V Reference electrode Mild steel crucible（Cathode） FeTiOX Molten CaCl2 Carbon crucible(Anode) A e- e- 2. TiO2 reduction process O2- e- (e.g. EMR-MSE process) Carbon electrode TiO2 Ti Cathode： TiO2+4 e-　→　Ti+O2- Ti crucible（Cathode） Molten CaCl2-CaO Anode　 ： Ca（or Ca-X） → Ca2++2 e- Ca-X alloy Ti reduction Production of reductant Available Low-grade Ti ore and Directly reduction method Low cost Ti production and Increase new application

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