Ray expansion boosts Asarco copper output

The Ray Complex, about 35 miles south of here, has been called a “rock-to-metal” operation. Owned by Asarco (NYSE), the complex encompasses mining and milling operations at the Ray mine site as well as the milling and smelting operations at the company’s Hayden smelter about 20 miles to the southeast.

Asarco has owned the Hayden smelter since building it in 1910. Operating as a custom smelter originally, the Ray mine and mill were purchased by the company in 1986 from Kennecott and transformed into a fully integrated metal producer. Asarco paid Kennecott US$72 million for the acquisition plus US$65 million in royalties, which should be completely paid out by the end of the first quarter of 1993.

Asarco completed a major expansion of the Ray operation this March at a total cost of US$224 million, boosting projected copper production 58% to 182,000 tons per year, or about 364 million lb.

The average cash cost of production at the Ray complex is expected to be about US60 cents per lb. next year, compared with about US67 cents in the first nine months of this year.

The completion of the Ray expansion marks the success-

ful conclusion of a plan to increase copper output from the company’s various mining operations to 100% of its smelter capacity from about 25% of capacity in 1985.

Permitting delays for a new tailings impoundment slowed the expansion process by about six months until final permits were received on Nov. 1, 1991. The expansion included the purchase of 22 new 240-ton haul trucks, two 41-cu.-yd. electric shovels, a 40-million-ton pre-strip and the construction of a 5,000-ton-per-hour in-pit crusher and a 4,100-ft.-long conveyor system. The company also completed the construction of a 30,000-ton-per-day concentrator at the mine site.

Proven and probable minable reserves at Ray were upgraded in concert with the expansion and now sit at 1.1 billion tons grading 0.63% copper at a copper cutoff grade of about 0.3%.

This compares with proven and probable reserves at the end of 1991 of about 609 million tons grading 0.68% copper.

The Ray operation now mines about 280,000 tons of ore and waste per day from a single open pit, measuring 1.5 miles across by about 2.5 miles in length. The ultimate pit will be huge, measuring about 2.5 miles wide and four miles long and extend a further 600 ft. in depth. The pit floor currently sits at about 600 ft. above sea level compared with an upper bench elevation of about 3,550 ft. above sea level.

The daily mined total includes about 39,000 tons of waste, 168,500 tons of low-grade material which is dump-leached, 12,500 tons of silicate ore which is crushed and heap-leached separately, and 60,000 tons of sulphide ore which reports to the in-pit crusher and conveyor system.

Primary sulphide ores are chalcopyrite and chalcocite while the silicate ore is a chrysocolla.

Of the 60,000 tons of sulphide ore mined per day, 30,000 tons are milled in the new Ray concentrator while the other 30,000 tons of daily production are hauled the 20 miles by rail to the existing Hayden mill and smelter. The new flotation mill, which utilizes semi-autogenous grinding, is currently reporting copper recoveries of about 87% compared with target levels of about 80%. The mill uses a re-grind circuit and cleaner flotation to boost the concentrate grade to about 30%.

Ray’s solvent extraction and electrowinning operation produces about 41,000 tons per year of cathode copper from the heap-leaching and dump-leaching operations.

The Hayden smelter, which has a concentrate feed capacity of about 720,000 tons per year, produces about 180,000 tons of copper anodes per year. The smelter also yields about 150,000 tons of 93% sulphuric acid. Ray’s leaching operations constitute the smelter’s largest acid customer at about 60% of yearly output.

With the expansion of the Ray operations this year as well as the production increases at the Mission open-pit copper mine near Tucson, Ariz., Asarco expects to produce almost 700 million lb. copper in 1993.

This compares with copper production in 1991 of 504.2 million lb. Cash production costs in 1993 at all of the company’s copper operations are expected to drop to about US62 cents per lb., down from the US69 cents reported for the first nine months of this year.