South African titanium : techno-economic evaluation of the alternatives to the Kroll process

[摘要] ENGLISH ABSTRACT: the potential to serve as a strategic economic driver for the country if a local processing andproduction industry could be successfully established. According to the US GeologicalSurvey, conducted in January 2009, South Africa has approximately 14% of the world'sreserves in ilmenite and rutile, the two most important titanium-containing minerals, butno metal producing abilities. The only role players, Exxaro and Richards Bay Minerals, havesmelting operations and produce an enriched titania slag, but all the slag is exported.The processing steps between titanium-containing minerals and the metal represent asignificant portion of the total production costs and this study is chiefly concerned withrecommending a more cost-effective alternative for these steps. The existing industrialprocess is archaic, cost and energy intensive, batch operated with unfavourable economics.A large number of internationally research initiatives are actively trying to address theproblem of high production costs by searching for and developing alternative, more costeffective,processes.It was the purpose of this study to provide the decision making authorities with a rankingand evaluation of these alternatives to produce titanium metal. A 2-Phase Filtering System,based on both qualitative and quantitative techniques, was designed to assess, evaluateand formulate a final ranking. This evaluation was followed by a detailed sensitivity analysisof both local and global parameters.A total of 26 process alternatives were selected to be evaluated in this techno-economicevaluation. The complete ranking is given in Table 8.8, and the four leading processalternatives, based on this evaluation and the findings of the sensitivity analysis, are asfollows:1. CardQIT: The Canadian affiliate of Rio Tinto, QIT, developed a high-temperaturetitanium extraction process based on an electrolysis reaction, where molten titaniaslag is the cathode.2. ArmITP: The Armstrong process is a continuous process that produces titanium in avery similar fashion as with the Hunter process, by the reduction of TiCl4 with sodium. TiCl4 vapour is injected into a stream of molten sodium to form titaniumpowder as the reaction product.3. Kroll: This process was developed in the 1950s and the reduction step remainsvery much similar to the original process used by the USBM (United States Bureauof Mines). Two criteria played a big part in the unexpected high ranking of the Krollprocess, and that were academic coverage, with almost 60 years of research, andthe commercial readiness of an industrial process.4. FFC: Solid pre-forms are pressed and sintered from pigment grade TiO2, to bedirectly electrochemically reduced to metallic titanium in a molten electrolyte ofCaCl2.For future work, it is recommended that an additional filtering stage, a detailed profitabilityanalysis, be added to the decision model. The top 4 alternatives, as mentioned above,should be used to estimate the cost-reduction potential as well as the capital investmentand production costs based on process, industrial and economic engineering fundamentals.

[发布机构] Stellenbosch University