Market Survey on Copper - Indian Bureau of Mines

Production and expansions
1993 and 1994 expansion increased capacity from the initial level of 320,000t/y
of copper-in-concentrates to 480,000t/y. Further expansion in 1996 took output
capacity to 800,000t/y. In November 1998, concentrator expansion was completed,
increasing capacity to 127,000t/d of ore. A new oxide ore processing plant then began
operation, reaching its design rate of 125,000t/y of electrolytic copper metal in mid-
1999. The $1.044bn 110,000t/d Phase 4 concentrator was completed in September
2002 using retained earnings.
Escondida’s proved and probable reserves are currently 3,900Mt; including the
addition of 1,200Mt from the Escondida Norte project.
The project partners have invested $400m for opening the new Escondida Norte
pit, 5km north of the existing mine. By the end of 2004, 126Mt of material had been
moved during pre-stripping operations.
Meanwhile, the Escondida sulphide leach project, designed to produce
180,000t/y of cathode copper cathode, is costing $870m to commission. The process
will use bacterially assisted leaching on low-grade run-of-mine ore from both the
Escondida and Escondida Norte pits, with solvent-extraction and electrowinning to
produce the copper. Production at the plant began in 2007.
Open-pit mining
Escondida is a conventional open-pit operation processing sulphide and
oxide ores. Run-of-mine ore is hauled to two semi-mobile, in-pit crushers for primary
reduction before being conveyed to the coarse ore stockpiles. The stripping ratio will
average around 1.7:1 over the full life of the project. In-pit truck dispatching and
monitoring is handled by a system from Wenco International Mining Systems, while
project materials, maintenance and costing control is achieved using Mincom’s mine
information management system.
Ore processing
The sulphide concentrator employs crushing, milling and flotation circuits.
12m-high, 4m-square column cells are used for cleaning the bulk sulphide
concentrate. The new concentrator uses 94 Wemco 160m³ cells for rougher and
cleaner flotation. The separate oxide ore plant uses solvent extraction-electrowinning
technology to produce cathode copper metal directly from leached ore. Oxide ore is
crushed and sized then heap leached, the dissolved copper being recovered directly by
electrolysis.
Concentrate transport and handling
Copper concentrates from the Escondida mill are pumped through a 170kmlong,
nine-inch-diameter pipeline to the coastal port of Coloso where concentrates are
dewatered and dried for export. Concentrate dewatering employs three Larox style PF
and four ceramic hyperbaric filters, which reduce the moisture content to an average
of 9% after arrival at the pipeline discharge. Effluent is treated before discharge deep
into the Pacific Ocean.
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