Bingham Canyon Copper Mine, UT, USA

Located near Salt Lake City, Utah, USA, Bingham Canyon celebrated its 100th anniversary in June 2003. The Bingham Canyon mine, Copperton concentrator and Garfield smelter comprise one of the largest and most up-to-date integrated copper operations in the world: major investments during the past 15 years have ensured economically and environmentally sound operation. Cumulative copper output is now about 17Mt, more than any other mine.

For much of its life, Bingham Canyon was owned by Kennecott Copper Corp. However, during the post-1973 oil crisis shake-out, the company was acquired by British Petroleum, then sold on to Rio Tinto, which operates Bingham Canyon through its 100% subsidiary, Kennecott Utah Copper Corp. The facilities employ about 1,400 people.

In early 2005, Rio Tinto committed $170m to the East 1 pushback project, which will extend the life of the open pit at Bingham Canyon until 2017. Various open-pit and underground alternatives will also be considered in relation to development of the mine after that.

GEOLOGY AND RESERVES

The classic copper porphyry orebody is not only huge but also enjoys a fairly uniform distribution of sulphide mineralisation, mainly chalcopyrite. The existing pit will be worked out by 2013, but open pit and then underground mining will continue after that. As of end-2005, proven and probable open-pit reserves totalled 667Mt grading 0.54% copper, 0.043% molybdenum, 0.32g/t gold and 2.59g/t silver. Total open-pit and underground mineral resources were 960Mt at 0.7% copper, 0.3g/t gold, 0.03% moly and 3.1g/t silver.

OPEN-PIT MINING

The Bingham Canyon pit is now 4km across and very deep. Mining uses a rotary drilling/blasting – shovel/truck – in-pit crushing system, with two to four blasts per day. To contain costs, management has been quick to utilise the most cost-effective drilling, loading and haulage equipment and management tools available.

One of the first of the recent series of major investments was an in-pit, semi-mobile gyratory crushing unit linked to the Copperton Concentrator by an 8km conveyor system. This reduced haulage distances from the working faces substantially but even so the mine needs a large fleet of Caterpillar mechanical drive and Komatsu electric-drive trucks, mostly of 218t-capacity, to service ten P&H electric rope shovels.

Dispatching is by the Modular Mining computerised system and Bingham also utilises Thunderbird Pacific's drill monitoring and logging systems. Both GPS and Glonass are used for precise drill positioning. Germany's MAN Takraf has upgraded and relocated the semi-mobile in-pit crushing plant and conveyor system to keep trucking distances down.

ORE PROCESSING

The Copperton concentrator was expanded in 1992 and fitted with some of the world’s largest SAG and ball mills, and large flotation cells. There are four grinding and flotation lines, sequentially yielding a copper and molybdenum concentrate. The copper concentrate is piped about 27km to the smelter. Until its closure in mid-2001, the older North plant still supplied about 20% of the copper concentrate for smelting.

The current smelting facilities are the result of major investment, comprising a new primary flash smelter and flash converter system, designed by Outokumpu with input from Kennecott, plus a slag treatment plant. The converter treats matte that has been granulated and powdered. The 98.6% copper from the new converter is refined to 99.5% copper in two anode furnaces. Smelter off-gas is treated in a 1Mt/y Monsanto sulphuric acid plant.

Cast anodes are railed about 3km to the refinery’s electrolytic tankhouse, where marketable high-purity copper is produced and the gold and silver content of the concentrate is also recovered.

PRODUCTION

In 2006, Bingham Canyon mined 47.8Mt of ore grading 0.63% Cu, 0.057% Mo, 0.49 g/t Au and 3.5 g/t Ag. The Copperton concentrator yielded 1.02Mt of concentrates containing 265,600t of copper, 16,800t of molybdenum, 523,000oz of gold and 4.2Moz of silver. The smelter-refinery complex converted 918,000t of concentrate to 217,900t of copper, 462,000oz of gold and 4.15Moz of silver.

Having been regarded as a minor contributor to income at Bingham Canyon, increased world demand for molybdenum has now made it very important. Income from moly sales was just US$30m in 2002, but rose to US$700m in 2005. The mine plan has been modified to include areas of higher moly content, even at the expense of copper, while the concentrator has also been fine-tuned to optimise moly recoveries, with a second expansion of the moly-recovery circuit having been commissioned in mid-2006.

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