Electrical breakdown channel locality in high voltage pulse breakage

An experimental study was conducted, in which synthetic samples made of construction grout and pyrite grains were subjected to high voltage pulses in a single-particle and single-pulse mode, in order to investigate the effect of electrical breakdown channel locality on particle breakage behaviour. The data confirm that the locality of electrical breakdown channel dominates the breakage response of particles. When a breakdown channel passes along the axis of a particle, it generates a finer product and produces more cracks/microcracks on the fragments. The electrical breakdown channel locality is controlled by the grains of minerals with high conductivity/permittivity and their location in a particle under the identical machine settings. The outcomes using the synthetic samples are helpful in understanding the breakage behaviour of natural ore particles in electrical comminution

Progress and challenges in electrical comminution by high-voltage pulses

The recent progress in electrical comminution using high-voltage pulses and the technical challenges in order to bring this technology to the mining industry are outlined. Pre-weakening ore particles and preferential liberation of minerals at coarse sizes are the two major research outcomes that may have potential benefits for the industry. A particle pre-weakening characterization method by single-particle/single-pulse test has been developed. The emerging challenges for the mining industry to realize the benefits of this novel comminution technology include scale-up for industrial application, hybrid circuit design, maximization of pulse-induced cracks, and study of the downstream processing effects

Factors affecting electrical comminution performance

Factors affecting electrical comminution performance were investigated through experimental work and numerical simulations. The effects of feed size, under-sieve classification, incremental breakage and energy input level on particle pre-weakening and mineral liberation were tested with six ore samples. Using commercial software, COULOMB 3D, simulation was used to explore the trends between the electrical field distribution/intensity, and the ore particle electrical/mechanical properties. These results were used to interpret the differences in breakage and liberation for various ores. The results showed that the induced electrical field is strongly dependent on the electrical properties of minerals, the grain size, the location of the conductive minerals in rocks, and the particle shape/orientation. Understanding how the machine-related factors and ore-related factors affect the electrical comminution performance will assist in the machine scale up development

The effect of metalliferous grains on electrical comminution of ore

The effect of metalliferous grains on electrical comminution efficiency was investigated by comparative experiments using natural rocks and synthetic samples. The result indicated that the existence of metalliferous grains affects the breakage probability and product size distribution of electrical comminution. On average, metalliferous grains increased the breakage probability of particle in the first pulse discharge by 55% and generated finer product at the coarse end. As a result, particles with metalliferous grains exhibited higher energy efficiency than that without metalliferous grain in electrical comminution. A positive linear relation between product fineness and specific energy in electrical comminution was observed. With the assistance of numerical simulation on the electrical field distribution of ore particle, the role of metalliferous grains in electrical comminution is confirmed and the mechanism of metalliferous grains effect is elucidated. Understanding of the effect of metalliferous grains on electrical comminution is important to evaluate the feasibility of applying electrical comminution to ores with different mineral composition, and to understand the breakage behavior in electrical comminution

Experimental and numerical studies of selective fragmentation of mineral ores in electrical comminution

An experiment was conducted in which two sulphide ores and one platinum ore were each subjected to high voltage pulses and mechanical breakage, with the same specific energy input, in order to compare the mineral modal abundance and grade in the two comminution products. The data from this experiment has provided unambiguous evidence of greater enrichment of the minerals with high conductivity/permittivity in the less than 0.3 mm size fractions of the electrical comminution product. Numerical simulations using COULOMB 3D indicated that with the existence of an electrical potential difference in the system, a high electrical field intensity was created around the boundary of the minerals with high conductivity/permittivity, causing selective fragmentation, thereby elucidating and supporting the experimental findings

Pre-concentration of copper ores by high voltage pulses. Part 2: opportunities and challenges

The JKMRC has recently reported a novel ore pre-concentration method using high voltage electrical pulses (Part 1 of this paper). The technique utilises metalliferous grain-induced selective breakage under a controlled pulse energy input, and size-based screening to separate the feed ore into body breakage and surface breakage components, leading to ore grade splitting. This technique offers new opportunities for barren pebbles rejection from the AG/SAG mill pebble stream, coarse waste rejection at mine site to reduce the RoM haulage, pre-treatment of AG/SAG mill feed taking the combined advantages of pre-weakening and pre-concentration, and multi-grade comminution and recovery circuits. The challenges for industrial uptake of this technique include ore variation and machine scale up. A diagram describing the pulse energy input in relation to the mass yield, grade, and recovery for various feed particle sizes is proposed for the ore pre-concentration characterisation. The research gaps are discussed and the technical approach is suggested

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

A roadmap for simulation

For over 50 years the JKMRC has applied a unique education-based research strategy to develop modelling and simulation tools that are "fit for purpose" for industrial application. These tools are widely used for the analysis and optimisation of mining and mineral processing systems. As the mining industry context evolves to deal with declining head grades, falling commodity prices, professional skill shortages, and an exponential growth in the volume of data, a re-evaluation of what "fit for purpose" means in the future is required. It is contended that future industry needs for simulation-based decision support requires tools and systems that incorporate: • Multi-component modelling, • Models of complex sensor behaviour, • Integration across the physical value-chain e.g. resource to market, • Financial analysis including risk and uncertainty assessment, • Enabling multi-criterion decision making (technical, financial and environmental), • Ore-body knowledge at multiple scales, • The use of fundamental numerical models to provide insight for the development of practically useful models, and • Decision support delivered through remote operations centres. JKMRC and CRC-ORE are collaborating to develop a next-generation simulation-based decision support system that assists in addressing these challenges. The Integrated Extraction Simulator (IES) combines many years of pragmatic and successful work integrated with modern technology trends - in particular the rapid move to cloud-based computing

The effect of pH and collector dosage on the flotation performance of arsenopyrite and pyrite

Flotation reagent schemes applied to both greenfield projects and brownfields gold operations are derived from extensive bench scale testwork programs targeted at maximising the recovery of gold and gold-bearing minerals at an acceptable grade for downstream processing. The reagent schemes developed are specific to the ores tested and can vary greatly. A literature review shows xanthate dosages from 5 to 600 g/t have been applied as collectors for bulk flotation of gold-bearing sulfide minerals at a pH range from 3 to 11. Research shows pH influences the formation of dixanthogen and pyrite oxidation, consequently affecting the contacting angle and pyrite hydrophobicity, likewise increasing xanthate dosage promotes pyrite hydrophobicity by changing the contact angle resulting in increased pyrite recovery. This research involves performing experiments according to a Central Composite Rotatable Design using a synthetic pyrite and arsenopyrite ore system to identify flotation kinetic changes based on the xanthate dosage and pH of the slurry