versão On-line ISSN 2411-9717
J. S. Afr. Inst. Min. Metall. vol.111 no.3 Johannesburg 2011
Titanium production via metallothermic reduction of TiCl4in molten salt: Problems and products
D.S. van VuurenI; S.J. OosthuizenI; M.D. HeydenrychII
IMaterials Science and Manufacturing, CSIR, Pretoria
IIDepartment of Chemical Engineering, University of Pretoria
Industrial production of titanium occurs via the batch-wise reduction of titanium tetrachloride (TiCl4) with a reducing metal, being magnesium in the Kroll process, or sodium in the Hunter process. In the search for low cost titanium, the CSIR is developing a continuous process to produce titanium powder directly via metallothermic reduction of TiCl4 in molten salt, dubbed the CSIR-Ti process.
The move to a continuous process has been attempted by a number of organizations, but was until now always met with failure, due in no small part to challenges inherent in the process chemistry. The reaction between TiCl4 and the reducing metal can occur directly, when TiCl4 or any titanium sub-chlorides present, comes into contact with suspended or dissolved reducing metal. The reaction can also occur indirectly, without any physical contact between the reacting species, via an electronically mediated mechanism. The reaction mechanism via electronic mediation can cause TiCl4 to react at the outlet of the feed port, rapidly causing blockages of the TiCl4 feed line. The electrical conductivity of the metal reactor can also cause the electronically mediated reaction to favour the formation of titanium sponge on the reactor walls and internals, rather than titanium powder.
Various methods were investigated to overcome the problem of blockages in the TiCl4 feed line, e.g. mechanical removal, sonic velocities, dilution of the TiCl4 and the use of ceramic feed lines.
This article discusses problems experienced with the continuous feeding of reagents, and various methods attempted are shown and discussed. Information is also given on the morphology, chemical composition and suitability of the final titanium powder for powder metallurgical application as presently produced by the CSIR-Ti process.
Keywords: Titanium dioxide, titanium nitride, carbo-thermic reduction, ilmenite, slag, tunnel kiln, residence time
“Full text available only in PDF format”
1. VAN VUUREN, D.S. A Critical Evaluation of Processes to Produce Primary Titanium, Journal of The Southern African Institute of Mining and Metallurgy, vol. 109, August 2009, pp. 455-461. [ Links ]
2. TZ MINERALS INTERNATIONAL AND EHK TECHNOLOGIES. Ti-Metal: The Global Titanium Metal Industry, 2007, p. 171. [ Links ]
3. EHK TECHNOLOGIES. Summary of emerging titanium cost reduction technologies, A study for US Department of Energy and Oak Ridge National Laboratory, Subcontract 4000023694. 2003. [ Links ]
4. FROES, F.H. Developments in titanium P/M, University of Idaho, www.webs1.uidaho.edu/imap/MPR%20Paper.pdf#search=%22%22Developments%20in%20Titanium%20P%2FM%22%22. 1 September 2006. [ Links ]
5. SUZUKI, R.O., HARADA, T.N., MATSUNAGA, T., DEURA, T.N., and ONO, K. Titanium Powder Prepared by Magnesiothermic Reduction of Ti2+ in Molten Salt, Metallurgical and Materials Transactions, vol. 30B, June 1999, p. 403. [ Links ]
6. WINTER, C.H. Production of Metals, US Patent 2,607,674, 19 Aug. 1952. [ Links ]
7. WHITE, J.C. and ODEN, L.L. Continuous Production of Granular Ti, Zr and Hf or Their Alloy Products, US Patent 5,259,862, 9 Nov. 1993. [ Links ]
8. ARMSTRONG, D.R., BORYS, S.R., and ANDERSON, R.P. Titanium and Titanium Alloy, US Patent 7,445,658, 4 Nov. 2008. [ Links ]
9. SEON, F. and NATAF, P. Production of Metals by Metallothermia, US Patent 4,725,312, 16 Feb. 1988. [ Links ]
10. KELLER, W.H and ZONIS, I.S. Method of Producing Titanium, US Patent 2,846,303, 5 August 1958. [ Links ]
11. FINLAY, W.L. (Chairman) Titanium: Past, Present and Future, Publication NMAB-392, National Academy Press, Washington D.C., p. 208 http://www.nap.edu/openbook.php?record_id=1712&page=R1 [7 January 2010]. 1993. [ Links ]