The Ernest Henry Mine is a copper-gold open pit operation situated in northwest Queensland, Australia. It is owned and operated by Xstrata Copper, with a current throughput of 11 Mtpa, however, open pit operations are scheduled to cease in mid 2011. The deposit dips approximately 45º and extends for at least another 400 m vertically below the final 530 m deep pit design.
Construction and development of a sublevel caving (SLC) operation beneath the open pit was approved in December 2009. The feasibility design requires 39 km of development to be completed prior to production, which will commence in the fourth quarter of 2011. Initial ore production will be trucked and will increase to 3 Mtpa by the end of 2012, after which a hoisting shaft will be used. Ore production will then increase to 5 Mtpa in 2013 and ultimately to 6 Mtpa in 2016.
Two 3000 kilo watt of refrigeration (kW(R)) modular refrigeration plants will be installed, as well as two 1600 kW mixed-flow fans capable of a combined flow rate of 780 m3/s at a total pressure loss across the mine of 2000 Pa. The main fans will be installed underground and will exhaust into the base of the pit.
The following challenges were faced in the development of the ventilation and refrigeration network:
•a relatively steep geothermal gradient,
•tropical ambient conditions,
•working under a wide pit shell, and
•a large underground trucking fleet prior to shaft commissioning.
A considerable number of ventilation studies were conducted with later studies extensively using Ventsim Visual™ mine ventilation software to complete the design process of the ventilation and refrigeration networks, including the comparison of several alternative designs.
The paper focuses on design challenges prior to the
commissioning of the hoisting shaft, and discusses resistance optimisation and
occupational hygiene-related design parameters, such as heat and diesel
emissions, production level ventilation, main fan selection and location, and
van Baalen, O and
Stewart, C, 2011. Starting-up the Ernest Henry
underground mine – thermal and occupational hygiene challenges, in Proceedings 11th AusIMM Underground Operators’
, pp 151 (The Australasian Institute of Mining and Metallurgy: