On-line version ISSN 2411-9717
J. S. Afr. Inst. Min. Metall. vol.111 n.2 Johannesburg 2011
Meeting the reduced availability and rising costs of electrical power: Anglo Platinum ventilation and cooling strategies
M. Biffi; D. Stanton
The reality of rising electrical power costs and the haunting prospect of decreasing electrical power availability are a threat to the growth of new projects and expansion programmes that could negatively affect the sustainability of mining operations. These threats require the adoption of effective power saving measures aimed at three principal objectives: the elimination of wastage, the reduction of power usage particularly during peak demand periods and, more importantly, improving the efficiency of high power-demand processes. It is reasonable to assume that the greatest impact will be achieved by concentrating on those processes that are large electrical power consumers.
For Anglo Platinum operations, mine ventilation and, currently to a lesser extent, mine cooling are two continuous processes that fall in this category. It is estimated that these may consume fifteen to thirtyfive per cent of the power delivered to the shaft head-depending on the shaft's design.
Mine ventilation systems suffer from inherent, historical inefficiencies that lead to excessive power consumption. Air cooling systems are designed to be energy-wise in terms of modulating refrigeration plant operation to meet the underground requirements while maximizing use of 'free' cooling from surface conditions. Currently about ninety-five per cent of the refrigeration capacity used in Anglo Platinum mines is dedicated to surface bulk air coolers. The net thermal efficiency of these systems is compromised as mines expand in depth and on strike. Looking to the future, this practice will be complemented by more energy demanding underground cooling tactics requiring considerably higher electrical power consumption per unit ton produced.
To counter this increase in power consumption, more energyefficient systems and advantageous transient strategies such as thermal storage and the use of ice-on surface and possibly even underground-are being considered.
This paper describes work currently undertaken and planned by Anglo Platinum operations to reduce power consumption by main fans during off-shift periods, the associated efforts currently introduced to reduce underground air leakage, the possibility of introducing more efficient auxiliary ventilation systems, the feasibility of thermal storage, and a brief look at energy recovery system as a means of countering the anticipated power demand associated with underground cooling.
Keywords: Mine ventilation, mine air cooling, energy efficiency, chilled service water, energy recovery, air wastage, fan selection
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KRAMERS, A.P. and BIFFI, M. Selective Mine Cooling. Chapter 64, Challenges in Deep High Stress Mining, Australian Centre of Geomechanics, Y. Potvin, T.R. Stacey, and J. Hadjigeorgiou (eds.), Perth, 2007. [ Links ]