1 資源･素材 2005( 室蘭 ); September 25, 2005 電気化学的な手法を用いた チタン鉱石からの脱鉄 尾花 勲 1 ・岡部 徹 2 1 東京大学 大学院工学系研究科 1 Graduate School of Engineering, The University of Tokyo Iron removal from titanium ore by electrochemical method Isao Obana 1, Toru. H. Okabe 2 2 東京大学 生産技術研究所 2 Institute of Industrial Science, The University of Tokyo

2 資源･素材 2005( 室蘭 ); September 25, 2005 Aircraft Spacecraft Chemical plant Implant Artificial bone etc. Application Lightweight and high-strength Corrosion resistant Biocompatibility Some titanium alloys ： shape-memory effect super elasticity Feature of titanium Introduction Ti ore + C + 2 Cl 2 → TiCl 4 (+ FeCl x ) + CO 2 Chlorination TiCl Mg Reduction MgCl 2 Electrolysis The Kroll process: Current Ti production process Mg & TiCl 4 feed port Sponge titanium → Ti + 2 MgCl 2 → Mg + Cl 2 Reaction container MgCl 2

3 資源･素材 2005( 室蘭 ); September 25, 2005 (CaCl 2 ) Ti ore (Ilmenite, FeTiO x )Upgraded Ilmenite (UGI) TiO x FeO x Others TiO x FeO x Others Upgrade Chloride wastes Discarded Upgrading of Ti ore Ti metal Ti smelting This study Low grade Ti ore Upgraded Ti oreFeCl x (+AlCl 3 ) (FeTiO X ) (TiO 2 ) MCl x Chlorine recoverySelective chlorination Fe FeCl x TiCl 4 Ti scrap Advantages: 1. Material cost can be reduced by using low grade ore. 2. Chlorine circulation in the Kroll process can be improved. 3.This process can also be applied to the new Ti production processes, e.g., the direct electrochemical reduction of TiO 2.

4 資源･素材 2005( 室蘭 ); September 25, 2005 Previous study Ref. R. Matsuoka and T. H. Okabe: Symposium on Metallurgical Technology for Waste Minimization at the 2005 TMS Annual Meeting, [San Francisco, California] ( ). FeO x ( s, in Ore) + MgCl 2 ( s, l ) → FeCl x ( l, g ) + MgO ( s ) CaCl 2 ( s, l ) + H 2 O ( g ) → HCl ( g ) + CaO ( s ) FeO x (in Ore) + HCl ( g ) → FeCl x ( l, g ) + H 2 O ( g ) The selective-chlorination of Ti ore by MgCl 2 or CaCl 2 is found to be feasible. Susceptor RF coil Vacuum pump Quartz flange Deposit Mixture of Ti ore and MCl x N 2 or N 2 +H 2 O gas Pyrometallurgical de-Fe process Condenser (FeCl x ) T = 973 ~ 1373 K

5 資源･素材 2005( 室蘭 ); September 25, 2005 Objective Application of electrochemical method Ti powder Reduction Low grade Ti ore TiO 2 + flux (FeTiO x ) Iron removal by selective chlorination 1. Thermodynamic analysis of selective chlorination 2. Fundamental experiments of selective chlorination by electrochemical methods Electrochemical reduction ・・・・・ or Calciothermic reduction

6 資源･素材 2005( 室蘭 ); September 25, 2005 TiCl 4 ( g ) TiCl 3 ( s ) CaO ( s ) / CaCl 2 ( l ) eq. a CaO = 0.1 Fig. Chemical potential diagram for Fe-Cl-O and Ti-Cl-O system at 1100 K. Fe-Cl-O and Ti-Cl-O system, T = 1100 K Potential region for selective chlorination of iron from titanium ore Potential region for chlorination Of titanium Oxygen partial pressure, log p O 2 (atm) Chlorine partial pressure, log p Cl 2 (atm) C / CO eq. CO / CO 2 eq. The selective-chlorination of Ti ore by controlling chlorine partial pressure might be possible using an electrochemical technique. Thermodynamic analysis (Ti ore chlorination) Ti ore : mixture of TiO x and FeO x. H 2 O ( g ) / HCl ( g ) eq. MgO ( g ) / MgCl 2 ( l ) eq. TiCl 2 ( s ) FeO ( s ) Fe 2 O 3 ( s ) FeCl 2 ( l ) Fe 3 O 4 ( s ) FeCl 3 ( g )Fe ( s ) TiO ( s ) TiO 2 ( s ) Ti ( s )

7 資源･素材 2005( 室蘭 ); September 25, Cl - (in CaCl 2 ) → Cl e - Anode: Chlorine chemical potential at anode in molten CaCl 2 can be increased electrochemically. Cathode ： Ca e - → Ca Electrolysis Fe n+ + n e - → Fe FeO x + Cl 2 → FeCl X ↑ + O 2- Refining process using FeCl x e-e- Molten salt (CaCl 2, MgCl 2, etc.) DC power source Ti ore or upgraded Ti ore (e.g. FeTiO x ) FeCl ３, AlCl ３, O 2, CO 2 gas

8 資源･素材 2005( 室蘭 ); September 25, 2005 Experimental apparatus Electrochemical interface Reaction chamber Fig. Schematic illustration of experimental apparatus in this experiment. Ceramic insulator Thermocouple Heater Rubber plug Ar inlet Wheel flange Stainless steel tube (Electrode) Molten salt (CaCl 2 ) Potential lead (Ni wire) Nickel electrode Mild steel crucible (Cathode) V1V1 V2V2 A1A1 A2A2 Carbon crucible (Anode) Ti ore 10 A Power Source Electrochemical control unit 100 mm

9 資源･素材 2005( 室蘭 ); September 25, 2005 Experimental condition ： Temp.:1100 K Atmosphere: Ar Molten salt: CaCl 2 (800 g) Cathode:Mild steel crucible (O.D 102 mm) Anode:Carbon crucible (O.D 19 mm) Experiment 1 Sample Molten CaCl 2 Mild steel crucible (Cathode) Carbon crucible containing Ti ore (Anode) e-e- Voltage monitor / controller Mass of Ti ore (Ilmenite), w / g Exp. A4.00 Exp. B4.00 Exp. C Voltage, E / V Time, t’ / h

10 資源･素材 2005( 室蘭 ); September 25, 2005 Result 1 XRF analysis After the electrochemical treatment, Fe was selectively chlorinated and removed. Table Analytical results of titanium ore (starting sample) and the sample obtained after electrochemical selective chlorination. Concentration of element i, C i (mass %) VTiFeSiAl Ti ore (init.) Exp. A Fe / Ti (%) To proceed iron removal reaction Ti ore (Ilmenite, FeTiO x ) Molten CaCl 2 Carbon crucible (Anode) e-e- Observed unreacted portion Lower half of sample was unreacted. Exp. B Exp. C

11 資源･素材 2005( 室蘭 ); September 25, 2005 Experiment 2 Sample Molten CaCl 2 Mild steel crucible (Cathode) Carbon crucible containing Ti ore + CaCl 2 mixture (Anode) e-e- Voltage monitor / controller Mass of element i, C i (g) Ti ore (Ilmenite) CaCl 2 Carbon powder 4.00 ーーー Exp. C Ti ore : CaCl 2 Exp. D Exp. E ー 0.18 Voltage, E / V Time, t” / h 1 : Experimental condition ： Temp.:1100 K Atmosphere: Ar Molten salt: CaCl 2 (800 g) Cathode:Mild steel crucible (O.D 102 mm) Anode:Carbon crucible (O.D 19 mm)

12 資源･素材 2005( 室蘭 ); September 25, 2005 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, C i (mass %) VTiFeSiAl Fe / Ti (%) % of Fe was successfully removed. Exp. C Exp. D Exp. E XRD analysis In Exp. D, the Ilmenite sample changed from FeTiO 3 to CaTiO 3 and TiO 2 after experiment. Fig. XRD pattern of the sample obtained after Exp. D. :CaTiO 3 :TiO 2 Angle, 2 θ (degree) Ti ore (init.)

13 資源･素材 2005( 室蘭 ); September 25, 2005 FeTiO 3 ( s ) + CaCl 2 ( l ) → CaTiO 3 ( s ) + FeCl x ( l, g ) Fe in FeTiO 3 was selectively removed in carbon crucible. 2 Cl - (in CaCl 2 ) → Cl e - Anode : Cathode : Ca e - → Ca Fe n+ + n e - → Fe Disccusion Increase in the chlorine potential facilitates selective chlorination reaction of Ti ore. CaTiO 3 can be utilized for material of direct TiO 2 reduction processes (e.g. FFC, OS, EMR-MSE processes). A e-e- TiO 2 Ti e-e- e-e- O 2- Ca-X alloy Molten CaCl 2 -CaO Carbon electrode Ti crucible （ Cathode ） Ti reductionProduction of reductant Fig. Apparatus of EMR-MSE process.

14 資源･素材 2005( 室蘭 ); September 25, 2005 Summary and future work Selective chlorination of Ti ore by the electrochemical method was investigated, and 94 mass% Fe was successfully removed from low-grade Ti ore. ・ 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. Summary Future work

15 資源･素材 2005( 室蘭 ); September 25, 2005 以下 質問対 策

16 資源･素材 2005( 室蘭 ); September 25, 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 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 TiCl 4 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 TiCl 4... Titanium was not purified until 1910, and was not produced commercially until the early 1950s. History of Titanium

17 資源･素材 2005( 室蘭 ); September 25, 2005 ・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 × 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 ◎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 MgCl 2 /Mg の分離が容易 ○ 還元と電解は同時に行う必要はな い チタンの新しい製造プロセスの開発が必要 ⇒ Features of the Kroll process

18 資源･素材 2005( 室蘭 ); September 25, 2005 FFC Process (Fray et al., 2000) C + x O 2- → CO x + 2x e - Anode: Cathode:TiO e - → Ti + 2 O 2- Electrolysis (a1) (a2) OS Process (Ono & Suzuki, 2002) C + x O 2- → CO x + 2x e - Anode: TiO Ca → Ti + 2 O 2- + Ca 2+ Cathode:Ca e - → Ca Electrolysis (b1) (b2) (b3) e-e- CaCl 2 molten salt TiO 2 preform Carbon anode e-e- TiO 2 powder CaCl 2 molten salt Carbon anode Ca 実用化研究中の製造法

19 資源･素材 2005( 室蘭 ); September 25, 2005 EMR / MSE Process (Electronically Mediated Reaction / Molten Salt Electrolysis) (a) TiO 2 reduction(b) Reductant production e-e- Carbon anode TiO 2 e-e- Ca-X alloy (X = Ag, Ni, Cu, ・・・ ) e-e- e-e- CaCl 2 -CaO molten salt Current monitor / controller TiO 2 + C → Ti + CO 2 Over all reaction (d) Ca → Ca e - Anode: Cathode: TiO e - → Ti + 2 O 2- C + x O 2- → CO x + 2x e - Ca e - → Ca Cathode: Anode: Electrolysis (c4) (c1) (c2) (c3) 開発中の製造法

20 資源･素材 2005( 室蘭 ); September 25, 2005 ◎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 FFC Process OS Process EMR / MSE 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 × 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 × 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 ◎プロセスがシンプル ○ 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 TiO 2 を還元することが可 能 各直接還元プロセスの特徴

21 資源･素材 2005( 室蘭 ); September 25, 2005 Stainless steel cover Stainless steel plate R reductant Stainless steel reaction vessel Ti sponge getter Feed preform (MO ｘ + flux) TIG weld Fig. Schematic illustration of the experimental apparatus for producing titanium powder by means of the preform reduction process (PRP). MO x + R → M + RO 1.Amount of flux (molten salt) is small. 2.Easy to prevent contamination from reaction vessel and reductant. 3.Highly scalable. M = Nb, Ta, Ti R = Mg, Ca… Preform Reduction Process (PRP)

22 資源･素材 2005( 室蘭 ); September 25, 2005 Reduction (in kiln) Fe 2+ / TFe = 80~95% 145C° (2.5 kg/cm 2 )*4 hr *2 step (90% purity) IlmeniteReductant (Heavy oil etc.) Reduced oreHCl vapor Leached ilmeniteWaterSpray acidFuel (Synthetic rutile) 95%TiO 2 1%TiFe TiO 2 HCl aq. Leaching (in digestor)Filtration Roasting HCl Sol. TiO 2 Iron oxide Calcination Absorber HCl aq. (18~20% HCl) Fig. Flowsheet of the Benilite process. The Benilite process

23 資源･素材 2005( 室蘭 ); September 25, 2005 Gas + particleParticle Ilmenite Gas Reduced ilmenite TiO 2 (Synthetic rutile) TiO 2 92~93% TiFe2.0~3.5% TiO 2 Reduction (in kiln) Leaching WasteMag. separator Acid Leaching Filtering / Drying Screen -1 mm +1 mm Cyclone Reduced ore Coal (low ash) Air NH 4 Cl H 2 SO 4 aq. Air Iron oxide + Sol. Iron oxideSol. Thickener Fig. Flowchart of the Beacher process. (Non. mag.) The Beacher process (WLS)

24 資源･素材 2005( 室蘭 ); September 25, 2005 FeO x ( s ) + MgCl 2 ( l ) = FeCl x ( l ) + MgO ( s ) T = 1100 K, t’ = 1 h, Atmosphere : N 2, Ti ore (UGI) : 4 g, MgCl 2 : 2 g Experimental condition Fig. Experimental apparatus for selective-chlorination of titanium ore using MgCl 2 as a chlorine source. Carbon crucible Stainless steel susceptor Glass beads Stainless steel net RF coil Ceramic tube Glass flange Vacuum pump Quartz flange Deposit Mixture of Ti ore and MgCl 2 Chlorides Condenser Chlorination Reactor (FeCl x ．．． ) (Fe-free Ti ore) N 2 or N 2 +H 2 O gas Selective chlorination using MgCl 2

25 資源･素材 2005( 室蘭 ); September 25, 2005 FeO x ( s ) + MgCl 2 ( l ) = FeCl x ( l,g ) + MgO ( s ) Intensity, I (a. u.) Fig. XRD pattern of the deposit at chlorides condenser. The sample powder was sealed in Kapton film before analysis. XRD analysis Deposit obtained after selective-chlorination. → FeCl 2 was generated : FeCl 2 XRF analysis Residue after selective-chlorination. → Fe was selective chlorinated. Angle, 2θ (deg.) 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, C i (mass %) Ti ore (UGI from Ind.) After heating sample V Ti Fe Si Al After reduction sample Results of previous study

26 資源･素材 2005( 室蘭 ); September 25, 2005 Fig. Experimental apparatus for chlorination of titanium using FeCl 2 as a chlorine source. Heater Quartz tube Sample deposits (on Si rubber, NaOH gas trap and quartz tube) Carbon crucible Sample mixture: (e.g., FeCl 2 +Ti powder) Ti ( s ) + 2 FeCl 2 ( s ) = TiCl 4 ( g ) + 2 Fe ( s ) XRF analysis 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, C i (mass %) Residue before heating Residue after heating Ti Fe Cl Dep. on quartz tube after heating Dep. on Si rubber after heating Chlorination of Ti using FeCl 2

27 資源･素材 2005( 室蘭 ); September 25, K 2CaCl 2 + O 2 → 2CaO ＋ 2Cl 2 2MgCl 2 + O 2 → 2MgO ＋ 2Cl 2 4HCl + O 2 → 2H 2 O ＋ 2Cl 2 2CO + O 2 → 2CO 2 FeO + MgCl 2 → FeCl 2 + MgO 2C + O 2 → 2CO log p Cl 2 2 / p O 2 = log p O 2 = log p O 2 = e.g. ΔG = kJ < 0 log p Cl 2 2 / p O 2 = 1.49 log p Cl 2 2 / p O 2 = 0.48 各反応のポテンシャル

28 資源･素材 2005( 室蘭 ); September 25, 2005 e.g Fe-Cl-O system, T = 1100 K CaO ( s ) / CaCl 2 ( l ) a CaO = 0.1 C / CO eq. CO / CO 2 eq. Oxygen partial pressure, log p O 2 (atm) Chlorine partial pressure, log p Cl 2 (atm) FeO ( s ) Fe 2 O 3 ( s ) FeCl 2 ( l ) Fe 3 O 4 ( s ) FeCl 3 ( g ) Fig. Chemical potential diagram for Fe-Cl-O system at 1100 K. FeO x can be chlorinated by controlling oxygen and chlorine partial pressure. Ti ore : mixture of TiO x and FeO x. H 2 O ( g ) / HCl ( g ) MgO ( g ) / MgCl 2 ( l ) eq. Fe ( s ) FeO X ( s ) + MgCl 2 ( l ) → FeCl X ( l, g )↑ + MgO ( s, l ) Thermodynamic analysis (FeO x chlorination)

29 資源･素材 2005( 室蘭 ); September 25, 2005 Fig. Chemical potential diagram for Ti-Cl-O system at 1100 K TiO ( s ) TiO 2 ( s ) TiCl 4 ( g ) Ti 2 O 3 ( s ) TiCl 3 ( s ) Ti 3 O 5 ( s ) Oxygen partial pressure, log p O 2 (atm) Ti-Cl-O system, T = 1100 K Chlorine partial pressure, log p Cl 2 (atm) CaO ( s ) / CaCl 2 ( l ) a CaO = 0.1 C / CO eq. CO / CO 2 eq. Fe / FeCl 2 eq. Ti ore : mixture of TiO x and FeO x. Since TiCl 4 is highly volatile species, chlorine partial pressure must be kept in the oxide stable region. TiCl 2 ( s ) H 2 O ( g ) / HCl ( g ) MgO ( g ) / MgCl 2 ( l ) eq. Ti 4 O 7 ( s ) Ti ( s ) Thermodynamic analysis (TiO x chlorination)

30 資源･素材 2005( 室蘭 ); September 25, 2005 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 Upgrading Ti ore for minimizing chloride wastes Ti ore (eg. Ilmenite) Up-graded Ilmenite (UGI) TiO x FeO x Others TiO x FeO x Others Upgrade Chloride wastes Discarded 1. A large amount of chloride wastes (e.g., FeCl x ) are produced in the Kroll process. 2. Chloride waste treatment is costly, and it causes chlorine loss in the Kroll process.

31 資源･素材 2005( 室蘭 ); September 25, 2005 Refining process using FeCl x Advantages: 1.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 Development of a new environmentally sound chloride metallurgy Effective utilization of chloride wastes Ti metal or TiO 2 production TiCl 4 feedFeCl x (+AlCl 3 ) Carbo-chlorination CO x This study Low-grade Ti ore Upgraded Ti oreFeCl x (+AlCl 3 ) (FeTiO X ) (TiO 2 ) MCl X Chlorine recoverySelective chlorination (Cl 2 ) Fe FeCl x TiCl 4 Ti scrap

32 資源･素材 2005( 室蘭 ); September 25, 2005 反応媒体である CaCl 2 -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. Structure of cyclic voltammetry. V Counter electrode (Fe or C rod) Working electrode (Fe or C rod) Reference electrode (Ca/Ca 2+ ref.) Electrolysis cell (Fe crucible) Molten salt (CaCl 2 (-CaO) ) A Electrochemical Interface (Potentiostat / Galvanostat) サイクリックボルタンメトリー (CV) 法

33 資源･素材 2005( 室蘭 ); September 25, 2005 Iron removal process by electrochemical method Direct reduction process from Ti ore to Ti metal can be achieved. Establishment of a new up-grading process of Ti ore by electrochemical method.

34 資源･素材 2005( 室蘭 ); September 25, 2005 Iron removal process Low cost Ti production and Increase new application Available Low-grade Ti ore and Directly reduction method Ti ore （ TiO 2 + FeO ｘ ） Molten CaCl 2 V Mild steel crucible （ Cathode ） Carbon crucible(Anode) A FeTiO X A e-e- TiO 2 Ti e-e- e-e- O 2- Reference electrode Ca-X alloy Molten CaCl 2 -CaO Carbon electrode e-e- Ti crucible （ Cathode ） Ti reductionProduction of reductant Selective chlorination ・ Iron removal process Fe n+ + n e - → Fe 2 Cl - → Cl e - FeO x + C + Cl 2 Cathode ： Anode ： Ca e - → Ca → FeCl ｘ (l, g) + CO x 2. TiO 2 reduction process TiO e - → Ti + O 2- Ca （ or Ca- X ） Cathode ： Anode ： (e.g. EMR-MSE process) → Ca e -