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Atmospheric acid leaching of oxidised and mixed copper cobalt ores mined in the Democratic Republic of the Congo

dc.contributor.advisorAkdogan, G.en_ZA
dc.contributor.advisorBradshaw, S. M.en_ZA
dc.contributor.authorPretorius, Petrus Johannesen_ZA
dc.contributor.otherStellenbosch University. Faculty of Engineering. Dept. of Process Engineering.en_ZA
dc.date.accessioned2019-02-27T12:20:26Z
dc.date.accessioned2019-04-17T08:29:31Z
dc.date.available2019-02-27T12:20:26Z
dc.date.available2019-04-17T08:29:31Z
dc.date.issued2019-04
dc.identifier.urihttp://hdl.handle.net/10019.1/106119
dc.descriptionThesis (MEng)--Stellenbosch University, 2019.en_ZA
dc.description.abstractENGLISH ABSTRACT: Kamoto-Oliveira-Virgule (KOV) located in the Democratic Republic of the Congo, operates its mining operation on the north-western boundary of the approximately 350km long Congolese copper belt. This deposit accounts for nearly half of all the Cu-Co resources within the DRC. The concentrator and refinery being studied was launched as a brownfields project, designed to receive concentrated copper oxides that feed the leaching circuit directly. Copper sulphide concentrate was received by the fluidized bed roasters after sulphide and oxide flotation. Current open pit operation has predominantly oxidised copper ore and mining the mineral resources from the open pit is considerably more economical than running the underground operation that produces predominantly copper sulphides. Consequently, the decision to build a Flotation Tailings Acid Leach (FTAL) plant was made which allows for the copper oxide flotation process to be eliminated completely by increasing the leach circuit capacity to process all the ore from the open pit operation, the ore will only undergo a pre-flotation process to recover the copper sulphides fraction. The justification for the FTAL plant lies with the mineral recovery gained by eliminating the copper oxide flotation circuit. The purpose of this study is to characterize the ideal leaching conditions of flotation tails for ore mined from KOV and its respective orebodies. Therefore, determining if the mining, concentration and refining operation can run a metal recovery process from mine to metal efficiently by evaluating the leach performance and characteristics of all the available resources including the ores containing dolomite and calcite. Core samples were received from FNSR, Oliveira, Virgule and Variant ore bodies in the KOV pit. The samples were crushed and milled to a desired P80 particle size followed by a 4-minute flotation step to remove the copper sulphide minerals present in the sample. The concentrate from this step was submitted to the laboratory for analysis. The flotation tailings were dried and sent for chemical analysis and labelled as the leach feed. The flotation tails were then re-pulped and vigorously agitated and leached at a controlled temperature using diluted sulphuric acid, at the desired pH for a period of 4 hours. After the leach process, the acidic slurry was filtered, and washed. The initial experimental results revealed that particle with a P80 of 75μm, 150μm and 212μm had leach recoveries of 91%, 89%, 89% respectively and average acid consumption values of 141, 132 and 128 kg/t respectively, but the sulphides fraction recovery dropped by 20% from 212μm to 150μm. The fresh acid consumption (FAC) decreased from 142kg/MT to 86kg/MT for leach tests performed at pH values of 1.0 and 2.0 respectively and leach recovery decreased from 95.4%CuOx to 93%CuOx respectively. The effect on cobalt however was much more pronounced as the total cobalt recovery dropped from 82% to 60% for pH values of 1.0 and 2.0 respectively. A change in the percentage solids in the leach slurry showed that the optimal leach conditions was at 30% solids with a copper leach recovery of 98.2%. Leaching at 30°C, 45°C and 60°C resulted in copper leach recoveries of 98.2%, 98.2% and 98.5% respectively. The leaching of cobalt was much more affected by the change in temperature, the total cobalt leach efficiency varied from 78.6% to 88.0% for tests conducted at 30°C and 60°C respectively. A very strong correlation between the contained calcium in the feed and the gangue acid consumption value was found, which would make it uncomplicated to create an advanced blending strategy if the operation would invest in online analysers placed on the conveyors that feed the stockpiles. Furthermore, the mineralogy revealed that the percentage cobalt in the ore had a profound precipitation effect on the already leached copper in solution due to the electron negativity of the Co3+ found in heterogenite. The optimised leaching conditions were used to leach a large quantity core samples to verify the results from the initial core samples.en_ZA
dc.description.abstractAFRIKAANSE OPSOMMING: Kamoto-Oliveira-Virgule (KOV) in die Demokratiese Republiek van die Kongo, bedryf sy mynbedryf op die Noord-Westelike grens van die ongeveer 350 km lang Kongolese koperbelt. Hierdie neerslag dra by tot bykans helfte van al die Cu-Co hulpbronne binne die DRC verantwoording doen. Die konsentrator en raffinadery wat bestudeer is, is bekendgestel as ʼn beboudprojek ontwerp om gekonsentreerde koperoksiede te ontvang wat die logingskring direk voer, en kopersulfiedkonsentraat is ontvang deur die fluïedbedroosters na sulfied- en oksiedflotasie. Huidige oopgroefmynbedrywighede het egter hoofsaaklik geoksideerde kopererts en om die mineraalhulpbronne vanuit die oopgroefmyn te myn is aansienlik meer ekonomies as om die ondergrondse operasies te bedryf wat hoofsaaklik kopersulfiedes produseer. Dus is daar besluit om ʼn FTAL-aanleg te bou wat toelaat dat die koperoksiedflotasieproses heeltemal geëlimineer word. Deur die logingskringkapasiteit te verhoog om al die erts van die oopgroefmynbedryf te prosesseer, sal die erts slegs ʼn voorflotasieproses ondergaan om die kopersulfiedfraksies te herwin. Die regverdiging vir die FTAL-aanleg lê daarin dat mineraal herwinning verkry word deur die koperoksiedflotasiekring te elimineer. Die doel van hierdie ondersoek is daarom om vas te stel of die myn, konsentraat en affineringbedryf ʼn metaalherwinningproses van myn tot metaal doeltreffend kan bedryf deur die loging werkverrigting en kenmerke van al die beskikbare hulpbronne, insluitend die erts wat dolomiet en kalsiet bevat, te evalueer. Die eksperimentele resultate het gewys dat partikel groottes van P80 van 75 μm, 150 μm en 212 μm loging herwinning van 91%, 89% en 89% onderskeidelik gehad het, en gemiddeld suur gebruik waardes van 141 kg/t, 132 kg/t en 128 kg/t onderskeidelik, maar die sulfiedfraksie herwinning het met 20% geval van 212 μm na 150 μm. Die vars suur gebruik (FAC) het van 142 kg/MT na 86 kg/MT verminder vir logingstoetse uitgevoer by pH-waardes van 1.0 en 2.0 onderskeidelik en loging herwinning het van 95.4%CuOx na 93%CuOx onderskeidelik, verminder. Die effek op kobalt was egter baie duideliker omdat die totale kobalt herwinning van 82% tot 60% vir pH-waardes van 1.0 en 2.0 onderskeidelik, geval het. ʼn Verandering in die persentasie vastestowwe in die logingslyk het gewys dat die optimale loging toestande by 30% vastestowwe met ʼn koper loging herwinning van 99.6% was. Loging by 30 °C, 45 °C en 60 °C het loging herwinning van 99.6%, 97.0% en 98.2% onderskeidelik, tot gevolg gehad. Dis bewys dat die loging van kobalt baie meer geraak word deur die verandering in temperatuur en pH wat gevarieer het van 78.6% tot 88.0% vir toetse uitgevoer by 30 °C en 60 °C onderskeidelik. ‘n Baie sterk korrelasie was gevind tussen die kalsium inhoud en die afvalers suur gebruik (GAC), dit stel die myn in staat om ‘n eenvoudige erts meng strategie te ontwikkel indien hulle in aan-lyn analiseerders sou belê wat op die vervoerbande wat die voorraad hope over geplaas kan word. En nog meer, het die mineralogie bekendgemaak dat die persentasie kobalt in die erts a merkwaardige presipitasie effek op die alreeds geloogde koper in oplosing het as gevolg van die electron negetiwiteites verskil van die Co3+ in die heterogeniet.en_ZA
dc.language.isoen_ZAen_ZA
dc.publisherStellenbosch : Stellenbosch Universityen_ZA
dc.subjectReduction of acid consumptionen_ZA
dc.subjectUCTDen_ZA
dc.subjectAtmospheric acid leachen_ZA
dc.subjectGangue acid consumptionen_ZA
dc.subjectHydrometallurgyen_ZA
dc.titleAtmospheric acid leaching of oxidised and mixed copper cobalt ores mined in the Democratic Republic of the Congoen_ZA
dc.typeThesisen_ZA
dc.rights.holderStellenbosch Universityen_ZA


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