Browsing by Author "Franzidis, J-P"

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    A comparison of pyrrhotite rejection;passivation in two nickel ores
    (Elsevier, 2013) Chimbganda, T; Becker, M; Broadhurst, J L; Harrison, S T L; Franzidis, J-P
    The non-stoichiometric sulfide mineral pyrrhotite (Fe1-xS) occurs almost ubiquitously inter-grown with the principal nickel mineral, pentlandite ((Fe,Ni)9S8). During Ni processing, pyrrhotite is generally rejected to the tailings stream by flotation to produce a low tonnage, high grade (Ni) smelter feed and reduce SO2 emissions. In this study, the effect of different pyrrhotite flotation rejection strategies (artificial oxidation and TETA: SMBS addition) are evaluated on a magnetic (Ore A) and non-magnetic (Ore B) pyrrhotite ore to determine if either may effectively depress and potentially passivate the pyrrhotite surface during flotation to produce benign tailings without compromising pentlandite recovery. For both ores, the best pyrrhotite rejection (pentlandite/pyrrhotite recovery) was obtained using TETA: SMBS. Differences in the flotation performance of the two ores are considered more a function of BMS content, liberation and ore handling rather than a difference in sulfide passivation from the inherent pyrrhotite mineralogy (magnetic vs non-magnetic pyrrhotite). Pyrrhotite passivation could possibly provide a means of rendering the tailings non-reactive and thus mitigate acid rock drainage (ARD) formation.
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    Open Access
    Flotation of coal and sulphur from South African ultrafine colliery wastes
    (Southern African Institute of Mining and Metallurgy, 2013) Mbamba, C K; Franzidis, J-P; Harrison, S T L; Broadhurst, J L  
    Flotation of coal and sulphur from a typical South African ultrafine colliery waste has been achieved in laboratory-scale batch flotation tests, using dodecane, kerosene, and oleic acid as coal collectors, and xanthates to float the sulphide minerals (with the aid of dextrin as a coal depressant). The use of oleic acid as collector, in conjunction with MIBC frother, produced a coal yield of 56 per cent (much more than was obtained with dodecane or kerosene) at an ash content of 18 per cent, from a feed ash of 34.4 per cent; and a low- sulphur tailings. Sulphide flotation using potassium xanthate (PAX) recovered 26.3 per cent of the total sulphur in the concentrate. Staged addition of xanthate increased the total sulphur recovery to 42.1 per cent and reduced the sulphur content of the tailing further.
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    A mineralogical approach to evaluating laboratory scale acid rock drainage characterisation tests
    (Elsevier, 2015) Becker, M; Dyantyi, N; Broadhurst, J L; Harrison, S T L; Franzidis, J-P
    Effective management of the risks associated with acid rock drainage (ARD) requires the ability to identify material with a potential to generate ARD reliably. With the increasing prevalence of quantitative mineralogy (Quantitative XRD, auto-SEM), opportunity exists to use mineralogy at all stages in ARD characterisation and prediction. This study uses a mineralogical approach across the head grade samples and the residues obtained under leach conditions of several common ARD characterisation tests (Acid Neutralising Capacity, Net Acid Generation), as well as the University of Cape Town (UCT) biokinetic test to evaluate the extent to which acid-neutralising minerals react. The results show the contribution of the carbonates to the acid neutralising capacity, as well as the partial dissolution of intermediate weathering silicate minerals such as chlorite and mica.
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    Mitigating acid rock drainage risks while recovering low-sulfur coal from ultrafine colliery wastes using froth flotation
    (Elsevier, 2012) Mbamba, C Kazadi; Harrison, S T L; Franzidis, J-P; Broadhurst J L
    Ultrafine coal wastes contain sulfide minerals, particularly pyrite, which oxidize and give rise to acid rock drainage (ARD) resulting in extensive and prolonged contamination of local ground and surface waters. Currently, mining operations emphasise an end-of-pipe approach to ARD management using costly chemical or biological treatment techniques, which do not address the long term problem of achieving sustainable closure solutions within the resource lifetime. Eliminating ARD potential before waste disposal would have a major beneficial impact on water quality and facilitate long term closure solutions. Recovering a saleable coal product would be an added economic incentive. This paper presents the results of an investigation to establish the feasibility of a two-stage flotation process to produce: (i) a low-volume sulfide-rich concentrate, (ii) a high-volume benign (low sulfur) tailings, and (iii) a coal concentrate. Laboratory-scale batch flotation experiments were carried out using an oily collector to float coal from samples of coal ultrafines and a xanthate collector to recover acid-generating sulfides. The results of acid generating potential tests (both static and biokinetic) indicate that a low-sulfur tailings with low ARD potential may be produced, together with a coal ultrafine concentrate stream with a low ash content.
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    Open Access
    Modelling the influence of the froth phase on recovery in batch and continuous flotation cells
    (2001) Mathe, Z T; Franzidis, J-P
    To determine model parameters, a large data set was required. This is due to the semi-empirical nature of the proposed froth model. In this regard, the use of data obtained from continuously operated cells was therefore not suitable for deriving model parameters. It was thought that this could only be achieved by using data obtained from a batch flotation cell. A batch flotation cell has a distinct advantage of being suitable for generating, rapidly, large amount of data. However, the non-steady behaviour of froths found in this type of cell require a robust methodology for extracting the necessary parameters. In return this methodology was developed in this thesis. The main hypothesis of this methodology is that batch flotation performance, in terms of recovery, can be adequately approximated by treating a batch test as if it consists of a series of tests carried out in continuously operated flotation cells. Each flotation time interval is regarded as a single stage. Treating batch data in this manner allows for the derivation of desired kinetic parameters to describe flotation performance.
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    Use of X-ray computed tomography to investigate crack distribution and mineral dissemination in sphalerite ore particles
    (Elsevier, 2011) Ghorbani, Yousef; Becker, Megan; Petersen, Jochen; Morar, Sameer H; Mainza, Aubrey; Franzidis, J-P
    As the trends in mineral processing move towards the beneficiation of finer grained and more complex ore bodies, so too do the methods needed to understand and model these processes. During the heap leaching of low-grade ore bodies, the crack distribution and mineral dissemination in ore particles are important characteristics that determine the performance of sub-processes, such as the diffusion of reagents in and out of particle pores. Recent developments in X-ray computed tomography (CT) as an advanced diagnostic and nondestructive technique have indicated the potential for the technology to become a tool for the acquisition of 3-D mineralogical and structural data. The spatial distribution of cracks and mineral dissemination in particles derived from a sphalerite ore in the Northern Cape, South Africa, was characterized using a high-resolution industrial X-ray CT system. This paper describes the use of image analysis techniques including image segmentation, which uses a combination of thresholding and other methods to characterize and quantify crack and mineral dissemination in the sphalerite particles. The results are validated with those obtained using traditional techniques such as physical gas (with N2) adsorption, mercury intrusion porosimetry, SEM and QEMSCAN. A comparison of the effect of different comminution devices (HPGR and Cone crusher) on crack generation is also given.