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A case study of optimising UG2 flotation performance / Martyn P. Hay in Minerals engineering, Vol. 23 N° 11-13 (Octobre 2010) 

Public ISBD [article]  in Minerals engineering > Vol. 23 N° 11-13 (Octobre 2010) . - pp. 855–867 Titre : A case study of optimising UG2 flotation performance : Part 1: Bench, pilot and plant scale factors which influence Cr2O3 entrainment in UG2 flotation Type de document : texte imprimé Auteurs : Martyn P. Hay, Auteur ; Ravi Roy, Auteur Année de publication : 2011 Article en page(s) : pp. 855–867 Note générale : Génie Minier Langues : Anglais (eng) Mots-clés : Froth  flotation  Flotation  kinetics  Modelling  Process  optimisation Résumé : In the Platinum Group Minerals (PGM) industry, almost all UG2 deposits being currently developed are deep level and bankable feasibility studies must rely entirely on batch testwork of borecore samples. Since UG2 has a significant chromite (FeO·Cr2O3) content, minimising chromium oxide (Cr2O3) recovery into final concentrate has become a critical aspect of downstream smelting since % Cr2O3 in furnace feed has a practical upper limit of about 2.5%. In most cases concentrate is toll smelted but penalties are severe depending on chromite content. Together with PGMs, the characterisation of chromite floatability and prediction of recovery and concentrate grade in a production plant using bench-scale data is therefore a key component of UG2 ore analysis. The need to accurately predict chromite recovery and particularly to identify characteristics that indicate when % Cr2O3 in concentrate can be reduced has a significant impact on the project’s financials and subsequent plant design. The natural floatability of chromite is low and its passage into concentrate is almost entirely by entrainment in water carry-over into concentrate whereas PGMs are recovered by true flotation. Optimising flotation performance has to accommodate these two completely different flotation behaviours in an effort to reject chromite whilst at the same time maximise Platinum Group Minerals (PGM) recovery and grade. Incorporating extensive testwork conducted by Barrick Platinum South Africa and Northam and other plant data, the paper traces chromite, and to a lesser extent PGM, floatability in bench, pilot and plant scales and highlights that certain mechanisms of chromite entrainment are consistent irrespective of cell size and efficiency. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S0892687510001214 [article] A case study of optimising UG2 flotation performance : Part 1: Bench, pilot and plant scale factors which influence Cr2O3 entrainment in UG2 flotation [texte imprimé] / Martyn P. Hay, Auteur ; Ravi Roy, Auteur . - 2011 . - pp. 855–867. Génie Minier Langues : Anglais (eng) in Minerals engineering > Vol. 23 N° 11-13 (Octobre 2010) . - pp. 855–867 Mots-clés : Froth  flotation  Flotation  kinetics  Modelling  Process  optimisation Résumé : In the Platinum Group Minerals (PGM) industry, almost all UG2 deposits being currently developed are deep level and bankable feasibility studies must rely entirely on batch testwork of borecore samples. Since UG2 has a significant chromite (FeO·Cr2O3) content, minimising chromium oxide (Cr2O3) recovery into final concentrate has become a critical aspect of downstream smelting since % Cr2O3 in furnace feed has a practical upper limit of about 2.5%. In most cases concentrate is toll smelted but penalties are severe depending on chromite content. Together with PGMs, the characterisation of chromite floatability and prediction of recovery and concentrate grade in a production plant using bench-scale data is therefore a key component of UG2 ore analysis. The need to accurately predict chromite recovery and particularly to identify characteristics that indicate when % Cr2O3 in concentrate can be reduced has a significant impact on the project’s financials and subsequent plant design. The natural floatability of chromite is low and its passage into concentrate is almost entirely by entrainment in water carry-over into concentrate whereas PGMs are recovered by true flotation. Optimising flotation performance has to accommodate these two completely different flotation behaviours in an effort to reject chromite whilst at the same time maximise Platinum Group Minerals (PGM) recovery and grade. Incorporating extensive testwork conducted by Barrick Platinum South Africa and Northam and other plant data, the paper traces chromite, and to a lesser extent PGM, floatability in bench, pilot and plant scales and highlights that certain mechanisms of chromite entrainment are consistent irrespective of cell size and efficiency. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S0892687510001214

A case study of optimising UG2 flotation performance / Martyn P. Hay in Minerals engineering, Vol. 23 N° 11-13 (Octobre 2010) 

Public ISBD [article]  in Minerals engineering > Vol. 23 N° 11-13 (Octobre 2010) . - pp. 868–876 Titre : A case study of optimising UG2 flotation performance : Part 2: Modelling improved PGM recovery and Cr2O3 rejection at Northam’s UG2 concentrator Type de document : texte imprimé Auteurs : Martyn P. Hay, Auteur Année de publication : 2011 Article en page(s) : pp. 868–876 Note générale : Génie Minier Langues : Anglais (eng) Mots-clés : Froth  flotation  Flotation  kinetics  Modelling  Process  optimisation Résumé : In Part 1 of this 2 part series of papers the relationships between Platinum Group Metals (PGM), mass and water recovery and %Cr2O3 (as chromite) in concentrate were defined for laboratory, pilot and plant scales. The entrainment of chromite in final concentrate was shown to be related to its slow floating kinetics. In 2004, Northam Platinum mine embarked upon an upgrading program on its UG2 plant which included the installation of two column cells with external spargers as final cleaners. Optimisation resulted in a PGM recovery increase of 6% whilst %Cr2O3 in final concentrate was reduced from 4.0% to 2.2%. In this second paper, the Northam circuit is modelled before and after modification and installation of the final cleaner column cells. Simulation shows that the external sparger, driven by a dedicated recirculation pump, imparts energy into the system and provides the column with a PGM recovery capability equal to that of a mechanically driven cell. The deep froth bed of the columns enhances chromite rejection. As a result of this, greater operating flexibility has allowed PGM recovery at Northam to be increased by increasing mass pull whilst at the same time reducing %Cr2O3 in concentrate. Modelling shows that Northam’s reduction in %Cr2O3 can be fully described by reducing only the laboratory to plant scale-up factor for slow floating rate of chromite by 25%, whilst leaving the normal scale-up factors for fast floating fraction and rate unchanged. The improvement in PGM recovery was simulated using the same set of rougher and cleaner feed PGM kinetics and scale-up factors. This suggests that chromite entrainment is modelled via its slow floating rate and PGM recovery by true flotation is primarily modelled via its fast floating fraction and rate. Floatable gangue is modelled via its full set of fast and slow kinetics as its passage into final concentrate (and cleaner tailings circulating load) is a mix of true flotation and entrainment. This case study shows that a standard flotation circuit and one incorporating Northam’s column cell may be predicted from laboratory scale rate tests and flotation kinetics. The impact of Northam’s technology on other UG2 ores may be predicted by applying the change in chromite scale-up factors determined by simulation. The degree of improvement is dependant on the ore’s mineralogy and specifically its selectivity between PGM minerals, chromite and floatable gangue. This is illustrated by simulating the impact of the Northam column cell on Barrick’s Sedibelo UG2 ore. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S0892687510001482 [article] A case study of optimising UG2 flotation performance : Part 2: Modelling improved PGM recovery and Cr2O3 rejection at Northam’s UG2 concentrator [texte imprimé] / Martyn P. Hay, Auteur . - 2011 . - pp. 868–876. Génie Minier Langues : Anglais (eng) in Minerals engineering > Vol. 23 N° 11-13 (Octobre 2010) . - pp. 868–876 Mots-clés : Froth  flotation  Flotation  kinetics  Modelling  Process  optimisation Résumé : In Part 1 of this 2 part series of papers the relationships between Platinum Group Metals (PGM), mass and water recovery and %Cr2O3 (as chromite) in concentrate were defined for laboratory, pilot and plant scales. The entrainment of chromite in final concentrate was shown to be related to its slow floating kinetics. In 2004, Northam Platinum mine embarked upon an upgrading program on its UG2 plant which included the installation of two column cells with external spargers as final cleaners. Optimisation resulted in a PGM recovery increase of 6% whilst %Cr2O3 in final concentrate was reduced from 4.0% to 2.2%. In this second paper, the Northam circuit is modelled before and after modification and installation of the final cleaner column cells. Simulation shows that the external sparger, driven by a dedicated recirculation pump, imparts energy into the system and provides the column with a PGM recovery capability equal to that of a mechanically driven cell. The deep froth bed of the columns enhances chromite rejection. As a result of this, greater operating flexibility has allowed PGM recovery at Northam to be increased by increasing mass pull whilst at the same time reducing %Cr2O3 in concentrate. Modelling shows that Northam’s reduction in %Cr2O3 can be fully described by reducing only the laboratory to plant scale-up factor for slow floating rate of chromite by 25%, whilst leaving the normal scale-up factors for fast floating fraction and rate unchanged. The improvement in PGM recovery was simulated using the same set of rougher and cleaner feed PGM kinetics and scale-up factors. This suggests that chromite entrainment is modelled via its slow floating rate and PGM recovery by true flotation is primarily modelled via its fast floating fraction and rate. Floatable gangue is modelled via its full set of fast and slow kinetics as its passage into final concentrate (and cleaner tailings circulating load) is a mix of true flotation and entrainment. This case study shows that a standard flotation circuit and one incorporating Northam’s column cell may be predicted from laboratory scale rate tests and flotation kinetics. The impact of Northam’s technology on other UG2 ores may be predicted by applying the change in chromite scale-up factors determined by simulation. The degree of improvement is dependant on the ore’s mineralogy and specifically its selectivity between PGM minerals, chromite and floatable gangue. This is illustrated by simulating the impact of the Northam column cell on Barrick’s Sedibelo UG2 ore. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S0892687510001482