Direct Production of Titanium Powder from Titanium Ore by Preform Reduction Process

1. –40 –30 –20 –10 0 5 m 5 m 5 m 5 m 1 cm Direct Production of Titanium Powder from Titanium Ore by Preform Reduction Process Haiyan Zheng 1and Toru H. Okabe 1 1 Institute of Industrial Science, University of Tokyo, Graduate Student Introduction The Kroll process Current commercial Ti production process Direct reduction of TiO2 Preform reduction process (PRP) (a) FFC process (Fray et al.) Current status of industrial production of Ti Mg & TiCl4 feed port e– Feed preform (TiO2 feed + flux) Metallic reaction vessel World production of Ti sponge (2003) Carbon anode Reductant vapor Mg & MgCl2 recovery port TiO2 preform China 4 kt Reductant (R = Ca or Ca-X alloy) CaCl2 molten salt Common features: ○Simple process ○Semi-continuous process ×Difficult to control the purity ×Large amount of molten salt Ti sponge (b) OS process (Ono & Suzuki) Ti/Mg/MgCl2 mixture USA 8 kt Russia 26 kt TiO2(s) + Ca(g) →Ti(s) + CaO(s) TiO2 powder Furnace Total 65.5 kt Features: → Simple and low-cost process ◎Suitable for uniform reduction ◎Flexible scalability ○Possible to control the morphology of the powder by varying the flux content in the preform ○Possible to prevent the contamination from the reaction container and control purity ○Amount of waste solution is minimized ○Molten salt as a flux can be reduced in comparison with the other direct reduction process △Leaching is required ×Difficult to produce calcium and control its vapor Chlorination Ti ore + C + 2 Cl2 → TiCl4 (+ MClx) + CO2 Reduction TiCl4 + 2 Mg → Ti + 2 MgCl2 Electrolysis MgCl2 → Mg + Cl2 e– Kazakhstan 9 kt Carbon anode Ca Japan 18.5 kt (28% share) CaCl2 molten salt (c) EMR/MSE process (Okabe et al.) Comparison with common metals Current monitor/ controller e– e– Features of the Kroll process: ◎High-purity Ti can be obtained. ◎Metal/salt separation is simple. ○Chlorine circulation is established. ○Efficient Mg electrolysis can be utilized. ○Reduction and electrolysis can be carried out independently. ×Process is complicated. ×Reduction process is batch type. ×Production speed is low. ×Chloride wastes are produced. Carbon anode CaCl2-CaO molten salt TiO2 Ca-X alloy (d) PRP Purpose of this study: Development of a new smelting process for producing Ti with high purity and productivity and low cost Feed preform (TiO2 feed + flux) Reductant vapor Production cost of Ti is high and its application is limited. Reductant (R = Ca or Ca-X alloy) 1/300 1/15000 Research work Experimental results 1 Experimental results 2 Typical experimental apparatus for the reduction process Exp. A, RCat./Ti = 0.2 Exp. B, RCat./Ti = 0.3 Flowchart of the PRP Photographs XRD patterns SEM images TIG welding (1) (1) (1) (2) : TiO2 : CaCl2 : CaCl2 (H2O)4 JCPDS # 21-1276 JCPDS # 74-0522 JCPDS # 01-0989 Stainless steel reaction vessel Preform after calcination TiO2 + CaCl2 Feed preform TiO2 + CaCl2 + Binder Feed preform TiO2 + CaCl2 + Binder Ti ore Flux Binder Ti ore: Rutile Flux: CaCl2 Binder: Collodion Stainless steel cover Feed preform after Fe removal Mixing Stainless steel net JCPDS # 21-1276 JCPDS # 74-0522 JCPDS # 01-0989 : TiO2 : CaCl2 : CaCl2 (H2O)4 Stainless steel holder (2) (2) Slurry (4) (3) Preform after reduction TiO2 + CaO + Ca Sample obtained after leaching Ti powder Preform after calcination TiO2 + CaCl2 Reductant (Ca) Ti sponge getter Preform fabrication Intensity, I(a.u.) Feed preform (1) Experimental conditions JCPDS # 44-1294 JCPDS # 23-0430 JCPDS # 48-1467 : Ti : Ca : CaO (3) (3) Preform after reduction TiO2 + CaO +Ca Table Analytical results of the obtained sample. Calcination/iron removal FeClx Table Experimental conditions in this study. Sintered feed preform (2) : Ti JCPDS # 44-1294 (4) (4) Reduction Ca vapor Sample obtained after leaching Ti powder (3) Reduced preform 20 40 60 80 100 Angle, 2 (deg.) Leaching Acid a: Determined by X-ray fluorescence analysis, and the value excludes carbon and gaseous elements. Waste solution Vacuum drying a: Natural rutile ore produced in South Africa after pulverization. b: Cationic molar ratio, RCat./Ti = NCat./NTi, where NCat. and NTi are the mole amounts of the cations in the flux and Ti, respectively. c: C powder was added to the preform during the fabrication step in experiments C and D. ・Metallic Ti exhibiting a coral-like structure was obtained. ・Purity of Ti was greater than 99 mass %. Metallic Ti was successfully obtained after the experiment. Powder (4) Conclusion Discussion Experimental results 3 Experimental results 4 Mechanism of iron removal (Ti ore chlorination) Exp. C, RCat./Ti = 0.2, C powder: 0.2 g Table Composition of the samples obtained after leaching and yield of Ti powder The feasibility of the preform reduction process (PRP), based on the calciothermic reduction of natural Ti ore, was demonstrated. ・ 90% of iron was successfully removed by selective chlorination during the calcination step. ・ When C powder was added to the preform, iron was removed more efficiently, and Ti powder with a purity of 98% and yield of 88% was obtained. ・ It was experimentally demonstrated that high-purity metallic Ti powder (greater than 99 mass %) was obtained directly from natural Ti ore (rutile ore) by the PRP. 0 CaO(s)/CaCl2(l) eq. Fe2O3(s) XRD pattern SEM image Region for Selective chlorination of iron Fe3O4(s) –10 FeO(s) TiO2(s) Ti powder obtained after leaching CO(g)/CO2(g) eq. (4) (4) : Ti JCPDS # 44-1294 Fe(s) C(s)/CO(g) eq. –20 Ti4O7(s) Ti2O3(s) Ti3O5(s) log pO2 (atm) TiO(s) –30 FeCl3(g) FeCl2(g) 5 m –40 H2O(g)/HCl(g) eq. 20 40 60 80 100 MgO(g)/MgCl2(g) eq. Ti(s) –50 TiCl4(g) Table Analytical results of the obtained sample. TiCl3(g) a: Cationic molar ratio, RCat./Ti = NCat./NTi, where NCat. and NTi are the mole amounts of the cations in the flux and Ti, respectively. b: Determined by X-ray fluorescence analysis, and the value excludes carbon and gaseous elements. c: Iron removal ratio: (CFe/CTi (Before) – CFe/CTi (After))/(CFe/CTi (Before)) –60 log pCl2 (atm) Fig. Combined chemical potential diagram of the Fe-Cl-O (dotted line) and Ti-Cl-O (solid line) systems at 1300 K. FeOx (FeTiOx,s) + HCl(g) →FeClx(g)↑ + H2O(g) FeOx (FeTiOx,s) + CaCl2(l) → FeClx(g)↑ + CaO (CaTiOx,s) aCaO << 1 Currently, the development of a more effective method for the direct removal of iron from Ti ore, analysis of the detailed mechanism of selective chlorination, and development of an efficient recycling system of CaCl2 flux and the residual Ca reductant are under investigation. ・High-purity metallic Ti powder was obtained directly from natural Ti ore. ・Iron removal ratio was enhanced when C powder was added to the preform. ・Ti powder with a yield of 88% was obtained. a: Determined by X-ray fluorescence analysis, and the value excludes carbon and gaseous elements. ・FeOx can be chlorinated using CaCl2 + H2O. ・TiOx cannot be chlorinated using CaCl2 or CaCl2 + H2O. Iron removal efficiency was improved when C powder was added to the preform.