The characterization and carbothermic reduction of furnace dust from the TKZN heavy mineral sands operation
dc.contributor.advisor | Akdogan, G. | en_ZA |
dc.contributor.advisor | Bradshaw, S. M. | en_ZA |
dc.contributor.author | Khesa, Makhale Elia | en_ZA |
dc.contributor.other | Stellenbosch University. Faculty of Engineering. Dept. of Process Engineering. | en_ZA |
dc.date.accessioned | 2016-12-22T13:32:55Z | |
dc.date.available | 2016-12-22T13:32:55Z | |
dc.date.issued | 2016-12 | |
dc.description | Thesis (MEng)--Stellenbosch University, 2016. | en_ZA |
dc.description.abstract | ENGLISH ABSTRACT: Titaniferous ores serve as a major feedstock for the production of a white titanium dioxide pigment, a titanium metal and several other titanium-based products. Such ores exist mainly as heavy mineral sands. Ilmenite, which is a subset of those ores, is often upgraded to intermediate products namely synthetic rutile and titania slag through the synthetic rutile route and the reductive smelting route respectively. Like in most mineral sands operations, Tronox KwaZulu Natal Sands (Pty) Ltd recovers and disposes of a furnace dust, which is produced from the reductive smelting route, as a waste material. However, previous investigations have shown that such furnace dust can contain significant amount of titanium-bearing minerals. This study was therefore initiated to better understand the characteristics of this furnace dust and subsequently to investigate the potential of transforming such a metallurgical waste stream into a valuable stream through the production of a titania slag within the context of ilmenite smelting. The specific objectives of the study were to study the chemical and mineralogical characteristics of the furnace dust that was obtained from Tronox KwaZulu Natal Sands, to simulate the carbothermic reduction process of the furnace dust and to experimentally investigate the potential of producing a titania slag and a metallic iron from the furnace dust. The characteristics of the furnace dust were examined by several analytical techniques including x-ray fluorescence, x-ray diffraction, microscopy and laser-diffraction size analyses. The observations from the characterization work showed that the furnace dust was rich in the oxides of titanium and iron (49.39wt% ๐๐๐2 and 29.51wt% ๐น๐2๐3). However, these oxides were associated with significant amount of impurities, with silica being the largest of such impurities. In order to understand the thermodynamic feasibility of producing a titania slag and a metallic iron from the furnace dust, a series of thermodynamic simulations were performed using FactSage between 1500หC and 1700หC and at different carbon additions. The FactSage simulations showed that more than 85wt% of the equivalent titanium dioxide content within the slag could be obtained under relatively high carbon additions and at temperatures between 1650หC and 1700หC. However, such strongly reducing conditions favoured a significant reduction of the oxides of titanium to metallic titanium without significantly reducing the impurity oxides from the slag phase. On the other hand, the degree of iron metallization was found to be above 90wt% at carbon additions that favoured less titanium loss from the slag phase. The simulation work also showed that the extent of reduction of ๐น๐๐ from the slag phase was mainly influenced by the carbon addition, but less influenced by temperature. An experimental production of a titania slag and a metallic iron was investigated on a laboratory scale, PVT 18/75/350 Carboliteยฎ vertical tube furnace at 1500หC, 1600หC and 1650หC with the reduction times up to 10 minutes. From these experimental reduction tests, the slag samples with the equivalent titanium dioxide content ranging within 70.87-76.87wt% at 1600หC and 1650หC were obtained. Such equivalent titanium dioxide content was slightly lower than the 79wt% that was calculated in thermodynamic simulations. The ๐น๐ content of the metallic iron samples that were produced ranged within 93.03-97.13wt%. However, a titania slag sample that was produced at 1500หC for 10 minutes exhibited the equivalent titanium dioxide content of only 65.87wt%. That relatively lower content of the equivalent titanium dioxide was attributed to an insignificant removal of the impurity oxides and further insignificant removal of iron oxide from the slag as the slag was partially molten. The metallic iron sample that was produced at 1500หC showed the ๐น๐ content of 98.47wt%. The overall experimental reduction tests were in good agreement with the simulation results and both test works evidenced the potential of producing a titania slag and a metallic iron from the furnace dust. The production of both titania slag and metallic iron from this furnace dust demonstrated the potential of such material to supplement the natural titaniferous ores in order to meet the ever-increasing market demands in the white titanium dioxide pigment industry and to substantiate the feedstock into the foundry market. | en_ZA |
dc.description.abstract | AFRIKAANSE OPSOMMING: Titaanhoudende erts dien as โn belangrike grondstof vir die vervaardiging van โn wit titaandioksied pigment, โn titanium metaal en verskeie ander titanium gebaseerde produkte. Hierdie tipe erts kom hoofsaaklik voor as swaar minerale sand. โn Onderafdeling van hierdie tipe erts, Ilmeniet, word dikwels opgegradeer tot intermediรชre produkte; naamlik sintetiese rutiel en titania slakmeel deur onderskeidelik die sintetiese rutiel en reduktiewe smelting roetes. Soos in meeste sand mineraal bedrywighede, herwin en verwyder Tronox KwaZulul Natal (Pty) Ltd oond stof, wat geproduseer word van die reduktiewe smelting roete, as โn afval materiaal. Vorige ondersoeke het egter getoon dat hierdie oond stof โn beduidende hoeveelheid titanium-draende minerale kan bevat. Hierdie studie was dus onderneem om die eienskappe van hierdie oond stof beter te verstaan en om die potentiaal van die transformasie van so โn afval stroom na โn waardevolle stroom deur middle van die produksie van โn titania slakmeel en metaal yster van die oond stof. Die spesifieke doelwitte van hierdie studie was om die chemiese en mineralogiese eienskappe van die oond stof van Tronox Kwazulu Natal Sands te ondersoek, die karbotermiese reduksie van die oond stof te simuleer en om die potentiaal vir die produksie van โn titania slakmeel en metaal yster van die oond stof eksperimenteel te ondersoek. Die eienskappe van die oond stof is ondersoek deur verskeie analitiese tegnieke, insluitend x-straal-fluoressensie, x-straaldiffraksie, mikroskopie en laser-diffraksie grootte analise. Die waarnemings van die karakterisering werk het getoon dat die oond stof ryk was in die oksiede van titanium en yster (49.39 massa% ๐๐๐2 en 29.51 massa% ๐น๐2๐3). Alhoewel, onsuiwerhede was geassosieer met hierdie oksiede, met silika as die grootste van die sodanige onsuiwerhede. Met die oog op die termodinamiese haalbaarheid van die vervaardiging van 'n Titania slag en 'n metaal yster uit die oond stof, is 'n reeks van termodinamiese simulasies uitgevoer met behulp van FactSage tussen 1500 หC en 1700หC asook by verskillende koolstof toevoegings. Die FactSage simulasies het getoon dat meer as 85 massa% van die ekwivalent titaandioksied inhoud binne die slakmeel verkry kan word, onder relatiewe hoรซ koolstof toevoegings en by temperature tussen 1650หC en 1700หC. Die sterk reduksie toestand het 'n aansienlike vermindering van die oksiede van titanium tot metaal titanium bevoordeel, sonder die reduksie van die onsuiwerhede in die slakmeel. Aan die ander kant, die graad van yster metallisatie was gevind om bo 90 massa% te wees by laer koolstof toevoegings, wat die verlies van titanium in die slakmeel verminder het. Die simulasie werk het ook getoon dat die omvang van 'n verlaging van ๐น๐๐ uit die slag fase hoofsaaklik beรฏnvloed was deur die koolstof toevoeging maar minder beรฏnvloed was deur die temperatuur. Die eksperimentele produksie van โn titania slakmeel en yster was onderoek op โn laboratorium skaal, PVT 18/75/350 Carboliteยฎ vertikale buisoond, by 1500หC, 1600หC en 1650หC met reduksie tye tot 10 minute. Van hierdie eksperimentele reduksie toetse, was die slakmeel monsters met die wissellende ekwivalente titaandioksied inhoud binne 70.87-76.87 massa% by 1600หC en 1650หC gekry. Sulke ekwivalent titaandioksied inhoud was effens laer as die 79 massa% wat bereken is deur die termodinamiese simulasies. Die ๐น๐ inhoud van die metaal yster monsters wat geproduseer was het gewissel binne 93.03-97.13 massa%, maar die titania slakmeel monster wat geproduseer was in 1500หC vir 10 minute het โn ekwivalente titaandioksied inhoud van slegs 65.87wt% getoon. Die relatiewe laer inhoud van die ekwivalente titaandioksied is toegeskryf aan die onbeduidende verwydering van die onreinheid oksiede en die onbeduidende afname van ysteroksied, want die slakmeel was slegs gedeeltelik gesmelt. Die metaal yster monster wat geproduseer was by 1500 หC het โn ๐น๐ inhoud van 98.47 massa%. Die algehele eksperimentele reduksie toetse het ooreengestem met die simulasie resultate en beide toets werke bewys die potensiaal van die vervaardiging van 'n titania slakmeel en 'n metaal yster uit die oond stof. Die produksie van beide titania slakmeel en 'n metaal yster uit hierdie oond stof het die potensiaal gedemonstreer om as aanvulling te dien vir die natuurlike titaanhoudende yster erts, om ten einde die toenemende vereistes van die mark in die wit titaandioksied pigment bedryf te ontmoet en om die roumateriaal in die gietery mark te staaf. | af_ZA |
dc.format.extent | 133 pages : illustrations | en_ZA |
dc.identifier.uri | http://hdl.handle.net/10019.1/100259 | |
dc.language.iso | en_ZA | en_ZA |
dc.publisher | Stellenbosch : Stellenbosch University | en_ZA |
dc.rights.holder | Stellenbosch University | en_ZA |
dc.subject | Titanium dioxide | en_ZA |
dc.subject | UCTD | en_ZA |
dc.subject | Titanium metal powder | en_ZA |
dc.subject | Titania (Chemical) | en_ZA |
dc.subject | Metal wastes | en_ZA |
dc.title | The characterization and carbothermic reduction of furnace dust from the TKZN heavy mineral sands operation | en_ZA |
dc.type | Thesis | en_ZA |