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Processing Plant Debottlenecking to 7.0 – 7.5 Mtpa
In parallel with the cessation of grade streaming, AngloGold Ashanti is pursuing opportunities to debottleneck the processing
plant throughput from its nameplate capacity of 5.8Mtpa to a throughput in the range of 7.0 – 7.5Mtpa. The debottlenecking
will involve ongoing work to reduce planned maintenance downtime by improving the design of high wear areas, speeding up
conveyors and pumps and potentially supplementing the existing leach tank capacity.
AngloGold Ashanti has already demonstrated that the processing plant can operate at a rate of 6.6Mtpa over periods of a
month at a time and has achieved throughput rates of about 7Mtpa over shorter periods. Therefore, the goal of 7.0 – 7.5Mtpa on
a sustainable basis is considered highly achievable with minimal incremental capital expenditure.
The higher throughput rates are achievable due to the inherent overdesign of key equipment items such as the primary crusher,
high pressure grinding rolls (HPGR), and ball mill. The HPGR has performed extremely well and is operating at ~60% of capacity
with wear rates on the HPGR surface being about half that expected. AngloGold Ashanti expected the wear life for the HPGR to
be about 7,000 hours, however the first change-out was at 14,000 hours delivering a significant benefit in reduced downtime
and reduced cost.
At these higher processing plant throughput rates and average reserve grade, the sustainable gold production rate is expected
to be about 400,000 oz/year from 2016.
The current low grade stockpile Reserve at Tropicana, which is currently estimated to be approximately 8.4Mt at an average
grade of 1.09 g/t Au, and which is expected to grow to about 10Mt by the end of the grade streaming period, will be processed
at the end of mine life, as contemplated in the BFS.
Conceptual Mining Study
As part of a conceptual mining study, the joint venture partners are evaluating the depth and strike extensions of the Tropicana
mineralised system. The study is also considering opportunities to use larger scale equipment and alternative mining methods,
such as strip mining and in-pit waste disposal. This would potentially deliver substantially lower mining costs than traditional
open cut methods, which were the basis of the mining options in the Havana Deeps study.
If the concept can be demonstrated, mine life would be significantly extended. The joint venture partners expect to carry out
a substantial drilling program, utilising data generated by last year’s 3D seismic survey to test for extensions to the Tropicana,
Boston Shaker and Havana South mineralisation. Subject to positive results from this mine-life extension study and the resource
drilling, it is expected that the work would progress to a feasibility study in 2016.