Lane Xang Minerals Limited (LXML), a Lao
based company
jointly owned by Oxiana Resources NL (80 %) and Rio Tinto
(20 %), has awarded a US$161M contract to a joint venture between Bateman
BV and Ausenco Limited of Australia.
The contract concerns a copper hydrometallurgical
process plant and associated infrastructure for the Sepon Copper Project
in the Vilabouly District of Savannakhet province of Lao PDR and is
phase 2 of the development of the gold and copper resources in the Sepon
Project Development Area. The ore will be mined from the Khanong open-pit
deposit with an estimated copper reserve of 13,5M t at 5,1 % copper.
The definitive feasibility study (DFS) indicated
that the project will place Sepon in the lowest quartile of operating
costs, enabling it to tolerate lower copper prices than most global
copper producers. Nearby additional copper prospects have not been taken
into account in this forecast and provide Sepon with substantial upside
potential.
The Sepon plant will process 1,3M t/yr of chalcocite-clay
run-of- mine (ROM) ore at an average grade of about 5 % copper to produce
a nominal 60 000 t/yr of copper cathode. The design permits the treatment
of oxide-ore components, predominantly in the latter period of the projected
12-year mine life.
The plant design allows consistent copper recovery
from secondary sulphide minerals with an ability to accommodate high-carbonate
oxide ores, which are high consumers of acid. The remote location means
that acid and ferric reagents will have to be generated autogenously
on site. The process solution for the Khanong ore required extensive
batch testing with the selected flowsheet confirmed by continuous pilot
tests.
The resulting two-step leaching process is expected
to recover more than 90 % of the copper in the ore. The first stage,
in open agitated tanks with a ferric sulphate / sulphuric acid leach
medium, is the main copper recovery step. Following counter- current
decantation, the remaining sulphides (elemental sulphur, copper sulphides
and pyrite) are recovered by acidic flotation with the copper-rich portion
of the concentrate treated in medium-pressure autoclaves at 220°C.
The function of the autoclave is to generate reagents that are recycled
to the atmospheric-leach circuit. The key to the overall flowsheet is
the simple method of ferric generation that allows an aggressive approach
to copper recovery in the atmospheric leach circuit.
The dissolved copper in the clarified leach liquor
is recovered as copper cathode after passage through the solvent-extraction
(SX) and electrowinning (EW) circuits.
Generating the appropriate process route for the project
required integrated teamwork between LXML and BATEMAN with appropriate
consulting support.
The site team will face several challenges, amongst
which are logistics, complicated by a monsoon climate, the need to upgrade
the road to the site, obtaining electrical power from Thailand and managing
unexploded ordnance from bygone wars that must be cleared away before
site construction can commence.
Prior to the project, studies were also undertaken
to identify the main environmental and socio-economic consequences of
the project. These incorporated input from the International Finance
Corporation (the private lending arm of the World Bank) in consultation
with the Lao PDR government, local communities and non-governmental
organisations. The main conclusions were that the project would have
minimal impact on the traditional usage of the land around Sepon, that
potentially adverse impact on downstream users of the Nam Kok River
could be minimised and that the subsistence economy in the area would
move towards a cash economy. The Lao government enthusiastically supports
the project.
The DFS commenced in December 2001 and the project
was awarded in January 2003. Construction work up to September 2003
will be limited to the delivery of materials of construction and upgrading
the road to the site before the onset of the 2003 wet season. Site construction
is scheduled to commence in October 2003 and should be completed by
the end of 2004. After wet commissioning, the first copper is scheduled
to be produced in the first quarter of 2005. The contract also provides
for the joint venture to participate in the subsequent ramp-up period
to consistent design throughput.
For further details, please contact Tony Cau, BATEMAN
General Manager, Copper and Zinc, on +61-7-3320-3333 or email Tony.Cau@batepro.com.au.
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