Representing and interpreting the liberation spectrum in a processing context

The compositional distribution of a population of particles is often referred to as the liberation spectrum. The challenge is to sensibly represent the vast amount of information contained in the liberation spectrum in a format that can be interpreted in a processing context. This paper describes one approach that can be used to represent the liberation spectrum, from compositional data obtained from automated SEM-based systems, and discusses how ore characteristics, such as mineral grade and grain size and distribution, can be interpreted. Ores from five different locations are compared using pyrite as the mineral of interest to demonstrate the approach. How this data might be used in a mineral processing context is also discussed, specifically with reference to how this approach may be used to determine grinding targets for separation processes

The role of vein-type mineralisation in mineral liberation

This paper provides a further investigation of the role of vein structures in the ease of mineral liberation by random masking simulation of breakage. A copper porphyry ore with vein-type mineralisation underwent different methods of sample preparation for liberation analysis. A selected core was cut into semicircular slabs and another core underwent crushing. The slabs and the crushed particles were analysed in the MLA and subjected to simulated breakage from which the liberation of sulphides was determined. The result was linked with the liberation measured from particles of the same ore that have undergone actual breakage. The analysis further provided an indication of the significant contribution of veins in liberation. This information points out to a proper approach of texture and liberation analyses, and the better use of textural data from core scale logging relevant to mineral processing

Interactions of clay minerals in copper-gold flotation: Part 2 - Influence of some calcium bearing gangue minerals on the rheological behaviour

This paper describes the results of research investigating the interaction between clay minerals and calcium bearing gangue minerals using theological measurements. This study was motivated by the high viscosity values observed in a copper-gold ore from which the flotation response of copper and gold minerals was poor and follows on from previous research investigating the effect of pH modifiers such as lime, sodium hydroxide and soda ash on the rheology of clay minerals (Cruz et al., 2013). It was found that Ca2+ ions interacted strongly with kaolinite and illite in enhancing their rheological properties. Gypsum was found to have the highest solubility in water and released the largest quantity of Ca2+ ions resulting in a significant interaction with illite and kaolinite. Calcite and dolomite were found to be less soluble and exhibited a lower interaction with these clay minerals. This study also investigated the interaction of the three calcium bearing minerals with bentonite, a swelling clay mineral. Gypsum had the greatest interaction with bentonite as well but affected the rheological characteristics of bentonite in the opposite way to that observed with illite and kaolinite. Ca2+ ions released from gypsum dispersed bentonite slurries by preventing the swelling of this clay mineral. This study suggests that when looking at ores with clay minerals, it is important to consider the potential input from other gangue minerals for the interactions in determining the rheological behaviour. (C) 2015 Elsevier B.V. All rights reserved

Key ore textures influencing separation behaviour of ores

Ore texture displays the fundamental ore properties that significantly influences processing behavior of ores. Of all texture characteristics, mineral grain size and mineral association are expected to have the greatest influence. These textural features can be used to predict the separation performance of ores. To obtain such micro-scale textural information is costly and time-consuming to be applicable to the entire deposit. Recent work has shown the contribution of vein-type mineralization in the separation behavior of ores. Since veins can be identified during core logging, it provides a cost-effective means of acquiring textural information relevant to mineral processing for the entire deposit. This can then improve geometallurgical characterization of separation performance, providing better understanding of separation variability within the deposit

Relating mineralogical and testural characteristics to flotation behaviour

Having knowledge of the ore mineralogy and texture can provide valuable information for effective design of a concentrator flowsheet. Specifically, these characteristics help in setting the appropriate grind size to achieve liberation and minimise overgrinding, and assist in identifying suitable flotation parameters to achieve optimum separation. This paper aims to obtain an understanding of the flotation behaviour of an ore by examining its mineralogical and textural features, particularly grain size distribution. Four samples with varying copper recoveries were obtained from different locations in a copper porphyry deposit. The samples were crushed to 4 mm and measured using a Mineral Liberation Analyser to determine the mineralogical characteristics of each. The mineralogical characteristics that were found to vary included: copper deportment and grain size and copper mineral association. This information was used to interpret batch flotation behaviour particularly copper recovery. (C) 2015 Elsevier Ltd. All rights reserved

Flotation circuit optimisation - towards more sustainable practice

Understanding and improving flotation circuit performance has grown in maturity and detail over the past five years, coinciding with the significant improvement in commodity prices. With the global financial crisis in 2008 - 2009, there has been a stronger focus on improving efficiency and reducing costs, across all processing plants. During this time, the flotation circuit analysis technology has continued to develop as part of the AMIRA International P9 project, among others. Changes to the technology have made the cell characterisation sensors more robust and independent of the plant facilities (air, power, etc), and changes to the methodology have reduced the time spent on site and the number of samples generated. The understanding of plant performance has greatly improved over this time as well, with the inclusion of size-by-size analysis now standard in the flotation projects. These advancements in characterising and optimising flotation circuit operation have led to reductions in the time and effort required to understand fl otation circuit performance, fewer disruptions to and more timely optimisation of flotation circuits resulting in minimising waste production, and identification of opportunities to enhance energy efficiency. The ongoing development of the optimisation technology will continue to provide more understanding of flotation circuits and provide operations with tools to identify potential areas for improvement

Methods for improving the flotation recovery of the coarse fraction of a nickel ore

Coarse particle size fractions (100 - 150 μm) generally have a poor response to flotation. This is mainly due to the low prospect of the particle-bubble aggregates withstanding the shearing forces in the flotation cell. Since particle-bubble attachment and detachment are directly related to the hydrophobicity of the particle, the most practical way to improve the fl otation of coarse fractions is to enhance their hydrophobicity. In this study, diesel oil, in addition to Potassium Amyl Xanthate (PAX), was used as an extender collector to fl oat the coarse fraction of a nickel ore in a laboratory batch flotation cell. Two different methods of oil addition were explored: oil was either emulsified with water and added to the flotation cell, or emulsified together with water and xanthate and then added to the flotation cell. It was shown that in both cases the oil addition increased the nickel recovery compared to the base case, but at the expense of concentrate grade. A high degree of entrainment, which was associated with extremely high water recoveries, was typical for flotation tests with the oil addition. The addition of collector via aerosol was also tested, as a way of introducing the collector with the air phase. This improved the quality of concentrate in terms of the nickel grade, at the expense of the lower nickel recoveries. The flotation rates of particles from flotation tests using these different methods are compared and discussed

The hydrodynamics of an operating flash flotation cell

Key parameters for evaluating the hydrodynamic conditions within an operating flash flotation cell have been investigated. Profiles of the slurry at increasing depth within the cell have shown a strong trend of increasing slurry density (per cent solids) and coarseness (P-80), with a clear indication of segregation on the basis of particle specific gravity. Results of local gas dispersion measurements, taken with the Anglo-Platinum Bubble Sizer, show that bubble coalescence is occurring at shallower depths within the cell and there is a clear trend of decreasing gas velocity (J(g)) with increasing depth at the axial location of measurement. Due to access restrictions gas dispersion measurements were taken close to the cell wall, but all data obtained falls well below the recommended minimum values for mechanically driven conventional flotation cells. However, the flash flotation environment is significantly different to a conventional cell, with higher per cent solids and a significantly coarser feed material, making this comparison qualitative (as unfortunately within the literature, there exists no other flash flotation data sets of this nature on which to base a comparison). The residence time distribution of solids indicates a significant amount of short-circuiting and/or internal recycle within the cell. Yet despite these findings, this cell contributes up to half of the pyrite recovery to the final concentrate at a very high grade. (C) 2012 Elsevier Ltd. All rights reserved