The effects of high voltage pulse treatment on ore characteristics and separation performances of a porphyry copper ore

Abstract

Technological advancement in large scale mining has changed little in the past 20 years.Increasing global energy demands and continuously decreasing ore grades are putting pressure on the mining industry to develop new, energy efficient technologies. Comminution has the highest energy consumption across the mining industry, and its energy demands continue to increase as finer grinding is required to liberate the valuable minerals in lower grade ores.Novel devices, such as high voltage pulse devices (HVP), have the potential to reduce the overall energy consumption, as they offer preferential breakage at the mineral grain boundaries. Good liberation occurs in coarser products and gangue can be removed upstream. HVP devices offer the opportunity to replace and change old inefficient comminution circuits or to be strategically incorporated within a current circuit. They also provide an opportunity for improving the downstream separation performances. However, to date, little research has been conducted on the direct effects of HVP treatment on these mineral separation processes.In this thesis the effects of HVP treatment on the characteristics and surface chemistry of a sample of Los Bronces porphyry copper ore were initially investigated to determine the potential for improved separation performance. A commercially available SELFRAG Lab device was used to HVP treat the ore either in batch-mode or using the single-particle/single pulse (SP/SP) method. The results showed that the ore responded well to SELFRAG batch treatment, with improvements seen in the ore's resistance to breakage and mineral liberation. Batch flotation and Wilfley shaking table tests therefore followed, using SELFRAG batch treated and mechanically crushed ore, to determine the differences in the grade-recovery curves. Further froth flotation tests were done using SELFRAG SP/SP treated ore for comparison.Results indicate that SELFRAG batch treatment of Los Bronces ore significantly reduced the ore's resistance to breakage when compared to conventional (mechanical) crushing. However, it consumed 21.8 kWh/t whereas mechanical crushing only consumed 1.5 kWh/t to produce the same extent of breakage. The SELFRAG SP/SP method was developed to reduce the consumed energy so that overall energy savings could be realised. In this method, SELFRAG treatment pre-weakens the particles with little to no breakage, so the JKRBT was used to break the particles ii to -3.35 mm. This method consumed 4.55 kWh/t and the product had the same resistance to breakage as the mechanically crushed product.Mineral liberation results showed that chalcopyrite was more liberated in the SELFRAG batch treated product than in the mechanically crushed product, noticeably in the coarser size fractions.This was confirmed in the preliminary float/sink gravity separation results where improved chalcopyrite recoveries were seen. Although SELFRAG batch treatment improved the valuable mineral liberation, it also led to noticeable surface chemistry changes. The surface chemistry of p...

Selective breakage of mineralised particles by high voltage pulses

“…The energy efficiency was determined to be relatively low attributed to the significant amount of energy loss for conversion of applied power into very narrow high voltage pulses besides the losses within the crushing chamber (Shuloyakov et al, 1995;Usov and Tsukerman, 2000). Recent research in JKMRC has also suggested lower efficiency for size reduction purposes using the selFrag Lab unit (Parker, 2015;Shi et al, 2014b;Wang et al, 2011). As an example, to produce the same extent of breakage on a Los Bronces porphyry Cu ore, it was reported that the selFrag machine consumed 21.8 kWh/t whereas the mechanical crushing method only used 1.5 kWh/t (Parker, 2015) to produce a -3.35 mm product from a nominal 10 mm feed size.…”

“…Recent research in JKMRC has also suggested lower efficiency for size reduction purposes using the selFrag Lab unit (Parker, 2015;Shi et al, 2014b;Wang et al, 2011). As an example, to produce the same extent of breakage on a Los Bronces porphyry Cu ore, it was reported that the selFrag machine consumed 21.8 kWh/t whereas the mechanical crushing method only used 1.5 kWh/t (Parker, 2015) to produce a -3.35 mm product from a nominal 10 mm feed size. As for preweakening purposes, specific energy inputs between 1 -3 kWh/t were usually applied to induce cracks/microcracks inside the particles using the selFrag lab (Shi et al, 2012;van der Wielen et al, 2014;Wang et al, 2011).…”