BHP is the world's largest copper concentrate producer with production
from mines at Escondida (Chile), Ok Tedi (Papua New Guinea), and
Island Copper (Canada). The entire concentrate production is further
processed into refined copper by third-party smelters around the world. In
anticipation of an expansion in the global copper concentrate production
capacity and a corresponding increase in treatment and refining charges
by copper smelters, BHP has continuously evaluated various
opportunities for downstream copper processing. An expansion in the
Escondida mine production, combined with BHP's interest in processing
some of its concentrate production on-shore in Chile, ultimately resulted
in the development of the Escondida Leach Process. This process was
specifically developed for higher grade concentrates, such as from
Escondida. An ammoniacal lixiviant and air are used under ambient conditions to
leach less than one-half of the contained copper values. After solid-liquid
separation, the solution is subjected to solvent extraction regenerating the
ammoniacal lixiviant and the copper loaded organic phase is stripped in
spent electrolyte returned from the electrowinning plant where ultra-high
quality SX-EW copper is produced. The solid leach residue can, if
required, be upgraded by flotation to produce a high-grade copper
concentrate with improved fuel values and a pyrite tail for disposal. After an 18-month bench and pilot plant scale program and an
engineering feasibility study, Minera Escondida Limitada decided to build
an 80 000 tonnes of copper per year facility near Antofagasta, Chile. The
installed investment cost amounted to around $160 million. The plant
went into commercial production in November 1994 and better than
99.9995 per cent Cu cathodes were produced right from the start. BHP believes that the process and the commercial plant are an
excellent example of a novel approach advancing the science of copper
metallurgy in harmony with present demands for environmentally sound
processes and high quality products.