Development of a methodology to estimate flotation separability from ore microtexture

Catherine Evans (2010). Development of a methodology to estimate flotation separability from ore microtexture PhD Thesis, Sustainable Minerals Institute, The University of Queensland.

       
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Author Catherine Evans
Thesis Title Development of a methodology to estimate flotation separability from ore microtexture
School, Centre or Institute Sustainable Minerals Institute
Institution The University of Queensland
Publication date 2010-11
Thesis type PhD Thesis
Supervisor Professor S.G. Walters
Professor D. Bradshaw
Professor E.V. Manlapig
Total pages 303
Total colour pages 64
Total black and white pages 239
Subjects 04 Earth Sciences
Abstract/Summary This thesis addresses the need for a suitable methodology to populate geometallurgical models of an ore deposit with recovery values for the valuable mineral(s) present in the ore. The approach taken in this research was to identify whether the processing characteristics of ores, in this case the recovery of the target mineral in flotation, could be estimated from quantitative measurements of the mineral microtexture made on coarse particulate samples of crushed ore. If this technique was feasible it would have the benefit of reducing the amount of physical flotation testing required in geometallurgical modelling programmes, together with corresponding reductions in analysis costs, turnaround time and sample mass requirements. The overall methodology developed is a key contribution of the work and comprises three sequential stages which generate an estimate of mineral and elemental recovery for each ore sample that can be used as an input in geometallurgical models of the ore deposit. The three stages in the overall methodology are: − the characterisation of ore microtexture using coarse particulate samples, − simulating the breakage of the microtexture as a means of ranking the liberation and separability of the ore samples, − simulating the flotation response of the ores based on the surface composition of the particles created when the ore microtexture is broken to the flotation feed size distribution and using the flotation kinetic response of the minerals measured under standard flotation conditions. In developing the methodology three hypotheses central to the methodology were tested, these being that: − the characteristics of ore particles which affect their separability by flotation can be estimated from measurements of mineral microtexture in the ore. − the flotation behaviour of ore particles in a given mineral surface composition and size class does not vary with the spatial location of the ore in the deposit. − the flotation behaviour of ores in batch rougher flotation can be estimated using a model which calculates mineral recovery based on the mineral composition of particle surfaces and flotation kinetic data. In this research, four ores from one drill hole in the Cadia East Cu-Au porphyry deposit located near Orange, New South Wales, were used in the development of the methodology and a further three ores from a wider range of spatial locations in the deposit were used to demonstrate the application of the methodology. A key contribution of this research is the development of a method which estimates the coefficient of variation for the measured ore microtextural characteristics such as mineral grain size; this method, which is based on the bootstrap resampling technique, can also be used to identify the most appropriate size of coarse particles for use in the microtextural analysis as well as the number of particles which must be measured to achieve the level of error required by the user. The method also provides estimates of the confidence limits for quantitative microtextural data such as mineral grain size distributions. A notable finding is that, for the ores analysed in this work, the grain size of chalcopyrite had a greater effect than copper head grade on the particle composition distribution after grinding. All of the ores studied were shown to break non-randomly when ground to flotation feed size distribution. Thus when breakage of the ore is simulated by imposing a random geometric breakage pattern onto images of the ore texture, the absolute value of chalcopyrite liberation is not accurately predicted by these simulations; in all cases the observed value of chalcopyrite liberation was higher than the predicted value. However, the relative ranking of the ores based on their chalcopyrite liberation is correct and this finding provides some support for the first hypothesis. In applying the overall methodology the simulated random breakage would be used to identify and group ores with similar microtextures; representative archetypes of each group would then be physically broken to provide accurate particle composition distribution information for use in predicting separability for all members of the group. An investigation of the batch flotation response of the Cadia East ores showed that while the flotation kinetic responses of chalcopyrite in ores from a limited range of spatial locations in one drill hole were not significantly different, this similarity did not extend to ores from a wider range of spatial locations in the ore body. These more-widely located ores contained significant proportions of chalcopyrite which exhibited slower flotation kinetics than the chalcopyrite from the single drill hole; one ore sample from the deeper regions of the deposit contained a proportion of chalcopyrite which was identified as non-floating since it was not recovered under the standard test conditions. Therefore the second hypothesis was not supported for ores from the Cadia East deposit. In testing a published model to predict mineral recovery in flotation from particle surface composition data, the results showed that this model accurately predicts chalcopyrite recovery in ores where this mineral is present only as a fast-floating form; in this case the third hypothesis is supported. For these ores there was a clear relationship in most particle size classes between the flotation rate of the particle and the chalcopyrite grade of the particle surface, with the flotation rate increasing as the particle chalcopyrite surface grade increased. However, when the ore also contains slow-floating and/or non-floating forms of chalcopyrite the particle surface composition model over-estimates the chalcopyrite recovery and therefore the third hypothesis is not supported for these ores. Further work is required to extend the model to account for the presence of fast-floating, slow-floating and non-floating forms of the target mineral. The overall methodology proposed here can provide a practical approach to estimate and rank the recovery of minerals in flotation separation in ores where the target mineral is present in a form which has one flotation rate.
Keyword mineral
Liberation
flotation
Separation
Texture
Geometallurgy
Additional Notes Colour pages 26 38 40 49 76 77 83 85 88 89 93 96 101 104 107 109 110 111 112 116 117 120 122 124 127 129 131 138 140 141 142 148 162 163 164 165 169 171 172 173 174 175 177 179 180 182 193 204 206 207 209 211 212 214 215 218 226 227 229 230 290 291 292 293

 
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Created: Wed, 04 May 2011, 19:43:00 EST by Mrs Catherine Evans on behalf of Library - Information Access Service