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

Van Tonder, Willem (2010-03)

Thesis (MScEng (Industrial Engineering))--University of Stellenbosch, 2010.

Thesis

ENGLISH ABSTRACT: the potential to serve as a strategic economic driver for the country if a local processing and production industry could be successfully established. According to the US Geological Survey, conducted in January 2009, South Africa has approximately 14% of the world’s reserves in ilmenite and rutile, the two most important titanium-containing minerals, but no metal producing abilities. The only role players, Exxaro and Richards Bay Minerals, have smelting operations and produce an enriched titania slag, but all the slag is exported. The processing steps between titanium-containing minerals and the metal represent a significant portion of the total production costs and this study is chiefly concerned with recommending a more cost-effective alternative for these steps. The existing industrial process is archaic, cost and energy intensive, batch operated with unfavourable economics. A large number of internationally research initiatives are actively trying to address the problem 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 ranking and evaluation of these alternatives to produce titanium metal. A 2-Phase Filtering System, based on both qualitative and quantitative techniques, was designed to assess, evaluate and formulate a final ranking. This evaluation was followed by a detailed sensitivity analysis of both local and global parameters. A total of 26 process alternatives were selected to be evaluated in this techno-economic evaluation. The complete ranking is given in Table 8.8, and the four leading process alternatives, based on this evaluation and the findings of the sensitivity analysis, are as follows: 1. CardQIT: The Canadian affiliate of Rio Tinto, QIT, developed a high-temperature titanium extraction process based on an electrolysis reaction, where molten titania slag is the cathode. 2. ArmITP: The Armstrong process is a continuous process that produces titanium in a very 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 titanium powder as the reaction product. 3. Kroll: This process was developed in the 1950s and the reduction step remains very much similar to the original process used by the USBM (United States Bureau of Mines). Two criteria played a big part in the unexpected high ranking of the Kroll process, and that were academic coverage, with almost 60 years of research, and the commercial readiness of an industrial process. 4. FFC: Solid pre-forms are pressed and sintered from pigment grade TiO2, to be directly electrochemically reduced to metallic titanium in a molten electrolyte of CaCl2. For future work, it is recommended that an additional filtering stage, a detailed profitability analysis, 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 investment and production costs based on process, industrial and economic engineering fundamentals.

AFRIKAANSE OPSOMMING: Titaan is deur die Suid Afrikaanse regering geidentifiseer as 'n mineraalhulpbron met die potensiaal om te dien as 'n strategiese ekonomiese drywer, indien 'n plaaslike verwerkingen verwaardingsbedryf suksesvol op die been gebring kan word. Volgens die US Geological Survey, wat in Januarie 2009 gedoen is, het Suid Afrika ongeveer 14% van die wêreld se reserwes in ilmeniet en rutiel, die twee belangrikste titaanhoudende minerale. Suid Afrika het egter geen metaal-vervaardigingsaanlegte nie. Die enigste twee rolspelers, Exxaro en Richards Bay Minerals, het smelteraanlegte en vervaardig 'n verrykte titaandioksiedkonsentraat, wat alles uitgevoer word. Die waardetoevoegingsaktiwiteite tussen die titaanhoudende minerale en die metaal verteenwoordig ‘n groot gedeelte van die produksiekoste van titaanmetaal en hierdie studie is hoofsaaklik daarmee gemoeid om ‘n meer koste-effektiewe aanbeveling te maak, m.b.t. dié stappe. Die bestaande bedryfsproses is argaïes, koste- en energieintensief, en is ontwerp as ‘n lot proses met ongunstige ekonomiese eienskappe. 'n Groot aantal internasionale navorsingsinstansies is aktief besig om oplossings te soek vir die probleem van hoë verwerking- en vervaardigingkostes, deur alternatiewe opsies te ondersoek en te ontwikkel. Die doel van hierdie studie was om vir die besluitnemingsgesag 'n rangorde en vergelyking van die alternatiewe opsies om titaniummetaal te vervaardig, te gee. 'n Tweeledige Filter Stelsel, gebaseer op beide kwalitatiewe- en kwantitatiewe tegnieke, is ontwerp om die rangorde te vorm, te bereken en te formuleer. 'n Sensitiwiteitsanalise is gedoen om die besluitnemingsparameters se invloed op die finale rangorde en uitslag te toets. 'n Totaal van 26 prosesse is geidentifiseer en gekies om aan hierdie tegno-ekonomiese evaluasie, te onderwerp. Die volledige rangorde word in Table 8.8 getoon, en die vier leidende prosesalternatiewe, gebaseer op die uitkomste van dié evaluering en die bevindinge van die sensitiwiteitsanaliese, is as volg: 1. CardQIT: Die Kanadese filiaal van Rio Tinto, QIT, het ‘n hoë-temperatuur titaan ontginningsproses ontwikkel, gebaseer op ‘n elektrolitiese reaksie, waarin gesmelte titaandioksiedkonsentraat die katode vorm. 2. ArmITP: Die Armstrong proses is ‘n kontinue opsie wat titaan produseer op ‘n baie soortgelyke wyse as die Hunter proses, deur die reduksie van TiCl4 met natrium, Na. TiCl4 damp word in ‘n gesmelte stroom natrium ingespuit om titaanmetaalpoeier te vorm as die reaksie produk. 3. Kroll: Die proses is ontwikkel in die 1950s en die reduksie stap wat vandag gebruik word is steeds soortgelyk soos die oorspronklike proses, aan gebruik deur die USBM. Veral twee besluitnemingskriteria het ‘n belangrike rol gespeel om tot die onverwagte hoë plasing van die Kroll proses te lei. Eerstens, akademiese dekking en die feit dat omtrent 60 jaar se navorsing in hierdie opsie ingepomp is en tweedens, die kommersiële gereedheid van hierdie prosesalternatief as ‘n volskaalse bedryfsproses. 4. FFC: Gegoe vorms van pigmentgehalte TiO2, word gepers en gesinter om die katodes te vorm wat dan direk elektrochemies gereduseer word tot titaanmetaal in ‘n gesmelte bad van CaCl2, as die elektroliet. Vir toekomstige werk word aanbeveel dat ‘n addisionele filtervlak, ‘n winsgewendheidsanalise, by die besluitnemingsmodel gevoeg word. Die vier prosesalternatiewe, soos hierbo genoem, kan gebruik word en vir elk moet die kostebesparingspotensiaal, die kapitaal insetkoste en die produksiekostes bereken word. Hierdie berekeninge kan gebaseer word op proses-, bedryfs- en ekonomiese ingenieurswese beginsels.

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