The largest capital expense is the solvent extraction circuit consisting of over 1,000 mixer-settlers
, and makes up 33% of the total capital cost at US$101 million.
Recent projects include the installation of the world's largest reverse-flow mixer-settlers, and engineering and construction of one of the world's lowest unit cost copper facilities in Chile.
It has a conventional 2 x 1 SX circuit configuration and incorporates a novel, cost-effective reverse flow mixer-settler design.
The nickel-cobalt sulphate solution goes to a cobalt solvent extraction circuit, which employs Outokumpu's proprietary mixer-settlers
with helical stirrers, for cobalt extraction.
The most important operating criteria for an SX plant are its operating capacity and the stage efficiency of specific mixer-settlers.
The mixer-settlers were designed for solution flows and tenors determined in the feasibility study.
Clarified pregnant solution containing uranium and 2 g/l copper goes first to the copper solvent-extraction circuit which consists of three identical mixer-settlers.
The loaded organic is scrubbed with acidified water in three mixer-settlers before being stripped by aqueous ammonium sulphate solution and gaseous ammonia in four mixer-settlers.
VSF's only other commercial application to date is at Kokkola Chemicals' cobalt/nickel plant in Finland where 21 VSF mixer-settlers have been in operation since 1991.
The SX mixer-settler will recover 90% of the copper from the pregnant liquor, the remaining 10% of the copper will be returned to the heap leach in the raffinate with the addition of sulphuric acid.
Leach solution is fed to two 1st-stage mixer-settlers
Some of the spent electrolyte is pumped to the solvent-extraction strip mixer-settlers
via electrolyte interchangers.