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Lototskyy M.V.,University of the Western Cape | Tolj I.,University of the Western Cape | Tolj I.,University of Split | Parsons A.,University of the Western Cape | And 3 more authors.
Journal of Power Sources | Year: 2016

We present test results of a commercial 3-tonne electric forklift (STILL) equipped with a commercial fuel cell power module (Plug Power) and a MH hydrogen storage tank (HySA Systems and TF Design). The tests included: (i) performance evaluation of "hybrid" hydrogen storage system during refuelling at low (<185 bar) dispensing pressures; (ii) comparison of the forklift performances during heavy-duty operation when changing the powering in the series: standard battery - fuel cell power module (alone) - power module with integrated MH tank; and (iii) performance tests of the forklift during its operation under working conditions. It was found that (a) the forklift with power module and MH tank can achieve 83% of maximum hydrogen storage capacity during 6 min refuelling (for full capacity 12-15 min); (b) heavy-duty operation of the forklift is characterised by 25% increase in energy consumption, and during system operation more uniform power distribution occurs when operating in the fuel cell powering mode with MH, in comparison to the battery powering mode; (c) use of the fully refuelled fuel cell power module with the MH extension tank allows for uninterrupted operation for 3 h 6 min and 7 h 15 min, for heavy- and light-duty operation, respectively. © 2016 Elsevier B.V. All rights reserved.


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.


Ayres N.L.,Impala Platinum Ltd | Gardner L.J.,Impala Platinum Ltd
Journal of the Southern African Institute of Mining and Metallurgy | Year: 2014

Tendon support systems have been successfully used to stabilize excavations. Tendon support systems are routinely designed using the axial load-bearing capacity of tendons, namely the tensile strength. To attain tensile strength the tendon must be loaded along its length, which often does not occur in practice. Tendons should optimally be installed at 90° to the surface of the excavation to achieve maximum penetration depth, yet this is often not physically or practically possible, and installations at angles less than 90° occur. Furthermore, the intersection of geological features within the rock mass frequently results in complex loading situations on tendons. The position and angle at which loading occurs results in different combinations of tensile and shear forces acting on the tendon, which can impact on the support performance of each unit and ultimately the whole system. All factors that influence the support system should be understood and taken into account to ensure a sound support design. Combination loading situations are further investigated and tested to obtain a better understanding of the mechanisms involved and the effects on tendon load-bearing capacity. Tendon support units were tested at different installation angles to establish the tendon performance, mechanical behaviour, and load capacity during these loading situations. The results and outcomes are aimed at providing rock engineers with additional data and improved understanding of how tendons could perform under certain conditions. © The Southern African Institute of Mining and Metallurgy, 2014.


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.


Lototskyy M.V.,University of the Western Cape | Tolj I.,University of the Western Cape | Tolj I.,University of Split | Davids M.W.,University of the Western Cape | And 10 more authors.
International Journal of Hydrogen Energy | Year: 2016

A novel hydrogen storage system for a RX60-30L 3-tonne electric forklift (STILL), equipped with a GenDrive 1600-80A fuel cell power module (Plug Power) has been developed. The system combines a compressed H2 composite cylinder (CGH2) and a liquid-heated-cooled metal hydride (MH) extension tank which is thermally integrated with a power module. The MH extension tank comprises a MH bed formed according to an advanced solution to provide easy activation of the MH material and fast H2 charge/discharge. The system has the same hydrogen storage capacity (∼19 Nm3 H2 or 1.7 kg) as the separate CGH2 tank charged at P = 350 bar, but at a lower H2 charge pressure (≤185 bar). A 15 min cycle refuelling provides the forklift with full-load operation (according to VDI-60 protocol) during >3 h, or 2 to 4 working shifts in a real industrial environment. The work also presents a hydrogen refuelling station (dispensing pressure up to 185 bar) with integrated MH compressor which has been developed for forklift refuelling. © 2016 Hydrogen Energy Publications LLC


Bartlett H.E.,Hugh Bartlett Consulting | 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.


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.


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.


Fernandes N.D.,Impala Platinum Ltd | Gardner L.J.,Impala Platinum Ltd
Journal of the Southern African Institute of Mining and Metallurgy | Year: 2011

Labour-intensive narrow reef stoping, as traditionally practised in South African gold and platinum mines, is almost unique in the modern first-world mechanized mining environment. Shortcomings of the system include the ever increasing cost of labour, a cap on achievable productivity and a poor safety record, particularly in the field of rock-related accidents. In the absence of sustainable alternative technologies, the South African mining industry has spent millions of rands improving the present system, focusing on improving workplace safety. This paper details the changes to stope support at Impala Platinum's Rustenburg operations, and the impact on rock-related safety performance. © The Southern African Institute of Mining and Metallurgy, 2010.

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