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Shi F.,Julius Kruttschnitt Mineral Research Center | Weh A.,SELFRAG AG | Manlapig E.,Julius Kruttschnitt Mineral Research Center | Wang E.,Julius Kruttschnitt Mineral Research Center
26th International Mineral Processing Congress, IMPC 2012: Innovative Processing for Sustainable Growth - Conference Proceedings | Year: 2012

In the current energy-sensitive world, sustainable development in the mineral industry will require new, better and more efficient processes. Novel comminution methods, which offer the prospect of achieving the required outcomes of size reduction and mineral liberation at lower energy consumption, are continually being sought. In the past five years, extensive research using high voltage pulse electrical comminution technology has been carried out at the Julius Kruttschnitt Mineral Research Centre (JKMRC), in collaboration with selFrag AG. The major outcome of this research is the development of the concept of pre-weakening ore particles by electrical comminution procedures to reduce the energy consumption in the downstream grinding circuit. The research has also verified the preferential liberation of valuable minerals by electrical comminution. Given the advantages, several potential applications of electrical comminution in the mineral industry are proposed, including AG/SAG mill feed pre-weakening, pebble treatment, ball mill feed pre-weakening, early recovery of the liberated valuable minerals, crack/micro crack generation for improved leaching, and smelter slag treatment. For the mineral industry to utilize electrical comminution, two emerging issues identified from the research need to be address. They are the energy consumption by electrical comminution in the locked cycle treatment and the facilities scale up necessary to move this technology from the laboratory to the plant.


Smith V.C.,University of Oxford | Mark D.F.,Scottish Universities Environmental Research Center | Staff R.A.,University of Oxford | Blockley S.P.E.,Royal Holloway, University of London | And 7 more authors.
Quaternary Science Reviews | Year: 2011

The varved Suigetsu (SG06) sediment core is potentially one of the most important and well-constrained mid-latitude palaeoclimate archives, recording continuous deposition during the last ∼150 kyrs. Numerous visible and non-visible volcanic ash layers form unique age markers within SG06. These ash layers are too fine and crystal-poor to be directly dated using the 40Ar/39Ar technique so the tephra were correlated to proximal volcanic deposits using their glass shard compositions. A high-precision 40Ar/39Ar sanidine age of 10.0 ± 0.3 ka (1σ, n = 34, MSWD = 0.71, p = 0.89) was obtained for the SG06-1288 (U-Oki) proximal tephra (Ulleungdo U4). 40Ar/39Ar yields a precision of ±3% near the younger limit of the method, with improved precision possible for older SG06 samples. Such 40Ar/39Ar ages for tephra layers can provide invaluable tie-points within the Lake Suigetsu SG06 sequence, giving independent verification of the core's varve chronology, allowing for the calibration of cosmogenic nuclide production, and providing a precise chronology beyond the varve limit. © 2011 Elsevier Ltd.


Van Der Wielen K.P.,University of Exeter | Pascoe R.,University of Exeter | Weh A.,SELFRAG AG | Wall F.,University of Exeter | Rollinson G.,University of Exeter
Minerals Engineering | Year: 2013

High voltage breakage is a novel comminution method that relies on highly energetic electrical pulses to weaken or fully fragment rocks. The potential of this technology to improve liberation and increase the grindability of ores has been demonstrated previously, but the fragmentation process is not fully understood. In this study a total of 20 rock types were treated in a SELFRAG Lab device to determine the influence of equipment parameters on breakage. Rock mass properties and Bond Work Index were determined for each rock type to identify their relation to breakage behaviour. Results show how, by influencing total applied energy, the number of discharges and voltage are the two major influences on the resultant product size. It has also been shown that coarser feed sizes are more amenable to high voltage breakage. Acoustic impedance, porosity and quartz content were found to relate to breakage but Bond Work Index only correlates loosely. © 2013 Elsevier Ltd. All rights reserved.


Shi F.,Julius Kruttschnitt Mineral Research Center | Krishnan N.,Newcrest Mining | Von Der Weid F.,SELFRAG AG | Van Der Wielen K.,Julius Kruttschnitt Mineral Research Center | And 2 more authors.
IMPC 2014 - 27th International Mineral Processing Congress | Year: 2014

Laboratory study has identified a new application of high voltage electrical pulse technology for preweakening ores. In recent years, the Julius Kruttschnitt Mineral Research Centre (JKMRC), Newcrest Mining and SELFRAG AG have conducted joint research in validation of pre-weakening of SAG mill feed through the pilot scale tests and comminution circuit simulations. Ten tons of SAG mill feed with a top particle size 150 mm were tested with two pilot scale SELFRAG machines installed in Switzerland. A simulation study using JKSimMet software was carried out to find where the high voltage pulses preweakening technique can be best applied in a gold-copper ore comminution circuit, based on the data of the pilot scale SELFRAG tests. A novel comminution circuit was designed, which incorporated SELFRAG to pre-condition part of SAG mill feed (9.5 to 150 mm) and to treat the circulating SAG mill pebbles. The high voltage pulse technology effectively reduced the amount of 'critical size' particles in the SAG mill and pre-weakened particle strength for grinding. Attributing to the nature of bi-modal size distribution and the significantly reduced F80, the simulations showed that the SAG mill had spare capacity to process part of hydrocyclone underflow from the secondary ball mill grinding circuit. The simulations indicated that the novel comminution circuit had the potential to remove two MP1000 pebble crushers and one 10 MW ball mill from the existing 2000 t/h grinding circuit. A 5 kWh/t energy reduction by adopting the novel comminution circuit in a gold-copper operation may be realized. This would result in substantial savings in operation costs.


Futterer M.A.,European Commission | Van Der Weid F.,European Commission | Kilchmann P.,European Commission | Kilchmann P.,SELFRAG AG
International Congress on Advances in Nuclear Power Plants 2010, ICAPP 2010 | Year: 2010

This paper describes results from experimental proof-of-principle tests to liberate coated particles and to fragment them. These tests were performed with surrogate fuel and coated particles in commercially available high voltage (HV) discharge installations. The product to be fragmented is poured into a vessel which is filled with water. An electrode delivering repetitive HV discharges under water is plunged into the vessel creating shock waves. Coated particles were liberated intact from their matrix and subsequently they were fragmented to sub-millimeter dimensions. The energy consumption is low and the installation is suitable for a hot cell environment and industrially relevant material streams. A process is proposed for the separation of the coated particles from the fuel element matrix. After further fragmentation of the coated particles, the fragmentation product can be directly fed into classical aqueous reprocessing.

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