Howes, MJ & Clarke, B 2007, 'The Granites Callie Mine - Justification and Design of a Mine Cooling Plant Suitable for Wet or Dry Condensing', in Y Potvin (ed.), Proceedings of the Fourth International Seminar on Deep and High Stress Mining
, Australian Centre for Geomechanics, Perth, pp. 451-461, https://doi.org/10.36487/ACG_repo/711_33
The justification for the amount of cooling currently installed and for future expansions at Callie mine at the
Granites is based on the application of a heat stress management strategy where a requirement to relocate
personnel or impose a work-rest regimen is limited to less than 10% of the summer period. A limiting wet
bulb temperature of 30.5°C generally means that the stop work condition of 32.5°C wet bulb does not occur
and interruptions to productive mining and development are reduced to acceptable values.
Callie mine in the Tanami desert has a water supply that is mainly bore water pumped from a palaeochannel
22 km from the mine and consequently subject to environmental pressures to minimise the amount used.
Over a typical summer, wet condensing heat rejection for the cooling plant using conventional methods has
a water consumption of between 9.0 Ml/MWR and 12.0 Ml/MWR from both evaporation and the bleed off
necessary to maintain the quality of water. Condensation of moisture in the bulk air cooler provides
approximately 1.8 Ml/MWR which helps to offset the water losses.
The capacity and integrity of the bore field water supply line is not sufficient to guarantee sufficient supply of
water to the refrigeration plant and captured rain water from adjacent pits is required as backup to meet the
wet condensing requirements. While the pit water is normally available, supply could be compromised due to
previous pit wall instability and potential loss of access to the pit pumps. Lack of rainfall could also result in
insufficient stored water to supply the plant. These issues encouraged a hybrid condenser design where both
wet and dry condensing was possible to allow the plant to continue to run if water was not available.
Dry condensing can eliminate water losses however, because the condensing temperature then depends on
dry bulb rather than wet bulb, the condensing temperature and therefore the compressor power is higher.
For a typical summer, the increased power is 0.25 million kWh/MWR which is a significant with generated
power costing up to A$ 0.28/kWh depending on the cost of diesel fuel. Normally, wet condensing would be
used with dry condensing as a back up in the event that there was insufficient stored water. With compressor
motors that are 25% larger than normal, the plant should be able to provide 87.5% of the summer mine
cooling load when operating dry.
Hemp, R. (1987) Air temperature increases in airways. Mine Ventilation Society of South Africa, Volume 40, pp. 1-11.
Howes, M.J. and Sedlacek, J. (2001) Kidd Creek mine – Ventilation and cooling planning for an extension to 3100 m.
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Congress, Brisbane, Australia (Melbourne: Australasian Institute of Mining and Metallurgy, 1988), pp. 257-264.
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