1. 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 Current status of industrial production of Ti MetalIronAluminumTitanium SymbolFeAlTi Melting point (K)18099331939 Density (g/cm 3 at 298 K) 7.92.74.5 Specific strength ((kgf/mm 2 )/(g/cm 3 )) 4~73~68~10 Clarke no.439 Price (\/kg)506003000 Production volume (t/world in 2003) 9.6 x 10 8 2.2 x 10 7 6.6 x 10 4 1/15000 1/300 Comparison with common metals World production of Ti sponge (2003) China 4 kt USA 8 kt Russia 26 kt Total 65.5 kt Kazakhstan 9 kt Japan 18.5 kt (28% share) Introduction Chlorination Ti ore + C + 2 Cl 2 → TiCl 4 (+ MCl x ) + CO 2 Reduction TiCl 4 + 2 Mg→ Ti + 2 MgCl 2 Electrolysis MgCl 2 → Mg + Cl 2 The Kroll process Current commercial Ti production process 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. Mg & TiCl 4 feed port Mg & MgCl 2 recovery port Ti sponge Ti/Mg/MgCl 2 mixture Furnace Metallic reaction vessel Production cost of Ti is high and its application is limited. Direct reduction of TiO 2 e–e– CaCl 2 molten salt TiO 2 preform Carbon anode (a) FFC process (Fray et al.) TiO 2 powder Carbon anode e–e– CaCl 2 molten salt Ca (b) OS process (Ono & Suzuki) CaCl 2 -CaO molten salt Current monitor/ controller e–e– Carbon anode TiO 2 e–e– Ca-X alloy (c) EMR/MSE process (Okabe et al.) (d) PRP Reductant vapor Reductant (R = Ca or Ca-X alloy) Feed preform (TiO 2 feed + flux) Common features: ○Simple process ○Semi-continuous process ×Difficult to control the purity ×Large amount of molten salt Preform reduction process (PRP) 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 TiO 2 ( s ) + Ca( g ) → Ti( s ) + CaO( s ) Purpose of this study: Development of a new smelting process for producing Ti with high purity and productivity and low cost Reductant vapor Feed preform (TiO 2 feed + flux) Reductant (R = Ca or Ca-X alloy) Flowchart of the PRP Powder Feed preform Reduced preform Mixing Vacuum drying Ca vapor Acid Waste solution Slurry Preform fabrication Ti oreFluxBinder FeCl x Reduction Ti ore: Rutile Flux: CaCl 2 Binder: Collodion Sintered feed preform Leaching Calcination/iron removal (1) (2) (3) (4) Research work Exp. No. a Cationic molar ratio CalcinationReduction Temp.TimeTemp.Time R Cat./Ti b T cal. /Kt' cal. /hT red. /Kt' red. /h A0.212731 6 B0.312731 6 C c 0.212732 9 D c 0.312732 9 Experimental conditions a: Natural rutile ore produced in South Africa after pulverization. b: Cationic molar ratio, R Cat./Ti = N Cat. /N Ti, where N Cat. and N Ti 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. Table Experimental conditions in this study. Stainless steel net Reductant (Ca) Stainless steel reaction vessel Ti sponge getter Feed preform after Fe removal TIG welding Stainless steel cover Stainless steel holder Experimental results 1 Exp. A, R Cat./Ti = 0.2 Photographs (1) (2) (3) (4) Intensity, I (a.u.) : TiO 2 : CaCl 2 : CaCl 2 (H 2 O) 4 JCPDS # 21-1276 JCPDS # 74-0522 JCPDS # 01-0989 JCPDS # 44-1294: Ti Angle, 2  (deg.) 10080604020 (1) (2) (3) (4) XRD patterns : TiO 2 : CaCl 2 : CaCl 2 (H 2 O) 4 JCPDS # 21-1276 JCPDS # 74-0522 JCPDS # 01-0989 : Ti : Ca : CaO JCPDS # 44-1294 JCPDS # 23-0430 JCPDS # 48-1467 Metallic Ti was successfully obtained after the experiment. Feed preform TiO 2 + CaCl 2 + Binder Preform after calcination TiO 2 + CaCl 2 Preform after reduction TiO 2 + CaO +Ca Sample obtained after leaching Ti powder Experimental results 2 Exp. B, R Cat./Ti = 0.3 ・ Metallic Ti exhibiting a coral-like structure was obtained. ・ Purity of Ti was greater than 99 mass %. Table Analytical results of the obtained sample. a: Determined by X-ray fluorescence analysis, and the value excludes carbon and gaseous elements. 5  m (1) (3) (2) (4) SEM images 5  m Step Concentration of element i, C i a (mass %) TiFeAlCaCl (1)68.001.070.4411.6618.83 (2)60.680.420.3314.8823.70 (3)17.740.07(0.00)67.4214.76 (4)99.100.030.30 0.58(0.00) Feed preform TiO 2 + CaCl 2 + Binder Preform after calcination TiO 2 + CaCl 2 Preform after reduction TiO 2 + CaO + Ca Sample obtained after leaching Ti powder Experimental results 3 SEM image Exp. C, R Cat./Ti = 0.2, C powder: 0.2 g 5  m Table Analytical results of the obtained sample. a: Determined by X-ray fluorescence analysis, and the value excludes carbon and gaseous elements. Iron removal efficiency was improved when C powder was added to the preform. Step Concentration of element i, C i a (mass %) TiFeAlCaCl (1)67.641.360.5010.2020.29 (2)65.990.130.0811.6522.15 (3)18.790.10(0.00)67.9813.09 (4)98.230.230.56 0.98(0.00) XRD pattern (4) 20406080 100 JCPDS # 44-1294 : Ti (4) Experimental results 4 ・ 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. Exp. No. Cationic molar ratio R Cat./Ti a Concentration of Ti and Fe in the obtained Ti powder C b (mass %) Iron removal ratio c (%) Yield (%) TiFeothers A0.298.160.881.7659- B0.399.100.030.8756- C0.298.230.231.549079 D0.398.440.141.426588 Table Composition of the samples obtained after leaching and yield of Ti powder a: Cationic molar ratio, R Cat./Ti = N Cat. /N Ti, where N Cat. and N Ti 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: (C Fe /C Ti (Before) – C Fe /C Ti (After) )/(C Fe /C Ti (Before) ) Discussion FeO x (FeTiO x, s ) + HCl( g ) → FeCl x ( g )↑ + H 2 O( g ) FeO x (FeTiO x, s ) + CaCl 2 ( l ) → FeCl x ( g )↑ + CaO (CaTiO x, s ) a CaO << 1 ・ FeO x can be chlorinated using CaCl 2 + H 2 O. ・ TiO x cannot be chlorinated using CaCl 2 or CaCl 2 + H 2 O. Mechanism of iron removal (Ti ore chlorination) Fig. Combined chemical potential diagram of the Fe-Cl-O (dotted line) and Ti-Cl-O (solid line) systems at 1300 K. TiCl 4 ( g ) TiCl 3 ( g ) –40 –10 –30 –20 –50 –60 –40–10–30–200 CaO( s )/CaCl 2 ( l ) eq. H 2 O( g )/HCl( g ) eq. MgO( g )/MgCl 2 ( g ) eq. log p Cl 2 (atm) FeCl 3 ( g ) Ti 3 O 5 ( s ) Ti 4 O 7 ( s ) FeCl 2 ( g ) Fe 2 O 3 ( s ) Fe 3 O 4 ( s ) FeO( s ) TiO 2 ( s ) Fe( s ) Ti 2 O 3 ( s) TiO( s ) Ti( s ) Region for Selective chlorination of iron log p O 2 (atm) 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. 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 CaCl 2 flux and the residual Ca reductant are under investigation. Conclusion Ti powder obtained after leaching Typical experimental apparatus for the reduction process 0 1 cm C( s )/CO( g ) eq. CO( g )/CO 2 ( g ) eq.