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Liebenberg M.J.,Impala Platinum Ltd
Journal of the Southern African Institute of Mining and Metallurgy | Year: 2014

This paper deals with the sampling and mass measurement for ore delivered from a shaft to a processing plant and the contribution of the data from these measurements to the metal balances from shaft deliveries to final metal production. Accurate measurement of the grade and tonnage of run-of-mine ore is important for four main reasons; It enables the measurement of the production from different profit centres to within statistically determined confidence limits for daily, monthly, or annual averages. The profit centres could be individual shafts within a mining complex or ore treated on a toll basis The monthly production at shaft head is compared to the grades and tonnage determined from underground sampling and mass measurement in terms of a shaft call factor The sum of the production from the shafts is the input to concentrators. This input is a major part of the total input into a complex with concentrators, smelters, and refineries. In terms of the Codes of Practice for Metal Accounting the inputs are compared to outputs and inventory changes to assess the efficiencies and unaccounted losses or gains at the various stages in the flow of metal from source to market On a daily or daily moving average basis, the grades and tons from shafts are monitored and compared against these quantities from underground measurements. This acts as a control on off-reef mining, dilution, and other factors underground. Accurate measurement of grade of ore at the shaft head has been a challenge because of the large particle size. The conventional wisdom has been that ore can be sampled accurately only after it has been milled to give a slurry that is sampled as feed to a flotation process. However, when the ore fed to a flotation plant comes from multiple sources each source has to be sampled separately. So, relying on the grades determined using the sampling of concentrator input with cross-stream slurry samplers is not an option for determining the grade from an individual shaft. Impala has developed a system for sampling and weighing run-of-mine ore from multiple shafts. The system involves sampling the inputs to the plants using cross-belt (hammer) samplers and weighing the deliveries using in-motion railway weighing systems. Many samples are taken. Individually they have a high variance but, as a consequence of the averaging effect of large numbers and as shown by statistical analysis, the mean results are fit for the purposes of daily grade control for shafts and for monthly accounting of production from individual shafts. In the metal accounting systems at Impala, the measurement of input, including ore and toll-treated material is compared to the output in the form of final metal and tailings losses, as well as any inventory change that takes place, in order to determine a final metal balance from mill feed to product. The calculated inventory is compared to that measured, and the difference, or unaccounted- for metal, is then reported as a percentage of input. The balances obtained over several years yields balances for platinum that are below 1% imbalanced. © The Southern African Institute of Mining and Metallurgy, 2014. ISSN 2225-6253. Source


Lototskyy M.,University of the Western Cape | Tolj I.,University of the Western Cape | Davids M.W.,University of the Western Cape | Bujlo P.,University of the Western Cape | And 2 more authors.
Journal of Alloys and Compounds | Year: 2015

Abstract This paper describes the layout and presents the results of the testing of a novel prototype "distributed hybrid" hydrogen storage and supply system that has the potential to be used for Low Temperature Proton Exchange Membrane Fuel Cell (LT-PEMFC) applications. The system consists of individual Metal Hydride (MH) and Compressed Gas (CGH2) tanks with common gas manifold, and a thermal management system where heat exchanger of the liquid heated-cooled MH tank is integrated with the cooling system of the LT-PEMFC BoP. The MH tank is filled with a medium-stability AB2-type MH material (H2 equilibrium pressure of about 10 bar at room temperature). This innovative solution allows for (i) an increase in hydrogen storage capacity of the whole gas storage system and the reduction of H2 charge pressure; (ii) shorter charging times in the refuelling mode and smoother peaks of H2 consumption during its supply to the fuel cell stack; (iii) the use of standard parts with simple layout and lower costs; and (iv) adding flexibility in the layout and placement of the components of the hydrogen storage and supply system. © 2015 Elsevier B.V. Source


Gardner L.J.,Impala Platinum Ltd
Harmonising Rock Engineering and the Environment - Proceedings of the 12th ISRM International Congress on Rock Mechanics | Year: 2012

Tunneling in South African platinum mines has traditionally been conducted using hand-held drilling and blasting methods, with tunnels being supported using tendons installed on at regular intervals. Rocks can and do fall out between the individual tendons, often with fatal results. To reduce levels of rock-related risk in line with a "Zero Harm" policy, Impala Platinum has adopted a two-pronged strategy for mining project tunnels. This includes limiting the number of personnel in tunnels by the increased use of mechanization, while reducing their exposure to unsupported rock by using areal coverage with the tendon support. While presenting a minimum of technical detail, this paper attempts to explain how Impala has continually optimized its tunnel support system to reduce rock-related risk in a challenging environment. Although this story is by no means unique, it provides an example of how such changes should be ongoing, and the resulting improvements that can be brought about in both safety and productivity. © 2012 Taylor & Francis Group, London. Source


Lototskyy M.V.,University of the Western Cape | Davids M.W.,University of the Western Cape | Tolj I.,University of the Western Cape | Klochko Y.V.,University of the Western Cape | And 5 more authors.
International Journal of Hydrogen Energy | Year: 2015

Metal Hydrides (MH) provide efficient hydrogen storage for various applications, including Low Temperature PEM Fuel Cells (LT PEMFCs), when system weight is not a major and critical issue. Endothermic dehydrogenation of MH leading to decreased rates of H2 evolution eliminates the risk of accidents even in the case of rupture of the hydrogen storage containment. At the same time, it poses a number of challenges related to the constant, stable and sufficient H2 supply for stable FC operation.This paper reviews recent efforts in MH hydrogen storage and supply systems for LT PEMFC applications, including the ones developed at HySA Systems/SAIAMC/University of the Western Cape. The systems are characterised by a series of hydrogen storage capacities ranging from 10NL to ~10Nm3H2 in turns providing stable operation for stationary and mobile FC power modules (from a few W to several kW). The MH systems use unstable hydride materials (equilibrium H2 pressure at ambient temperature around 10bar) that, in combination with special engineering solutions of MH containers (both liquid- and air-heated-cooled), and optimised system layout, facilitates H2 supply to LT PEMFC stacks. © 2015 Hydrogen Energy Publications, LLC. Source


Lototskyy M.V.,University of the Western Cape | Tolj I.,University of the Western Cape | Davids M.W.,University of the Western Cape | Klochko Y.V.,University of the Western Cape | And 5 more authors.
20th World Hydrogen Energy Conference, WHEC 2014 | Year: 2014

Metal Hydrides (MH) provide efficient hydrogen storage for various applications, including Low Temperature PEM Fuel Cells (LT PEMFCs), when system weight is not a major and critical issue. Endothermic dehydrogenation of MH leading to decreased rates of H2 evolution eliminates the risk of accidents even in the case of rupture of the hydrogen storage containment. At the same time, it poses a number of challenges related to the constant, stable and sufficient H2 supply for stable FC operation. This paper reviews recent efforts in MH hydrogen storage and supply systems for LT PEMFC applications, including the ones developed at HySA Systems / SAIAMC / University of the Western Cape. The systems are characterised by a series of hydrogen storage capacities ranging from 10 L to ∼10 m3 H2 STP in turns providing stable operation for stationary and mobile FC power modules (from a few W to several kW). The MH systems use unstable hydride materials (equilibrium H2 pressure at ambient temperature around 10 bar) that, in combination with special engineering solutions of MH containers (both liquid- And air-heated-cooled), and optimised system layout, facilitates H2 supply to LT PEMFC stacks. Copyright © (2014) by the Committee of WHEC2014 All rights reserved. Source

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