June/July 2006

Canadian technology reduces costs, raises productivity of foreign mines

By P. Caulfield

CVRD personnel watching CESL's Glenn Barr sample from the pilot plant autoclave

The current mining boom across Canada is reflected not only in increased production and exploration activity but also in the development of innovative technologies that reduce the costs of mining and boost productivity. Many of the innovations that have been conceived and commercialized in Canada are finding application outside the country.

For example, Vancouver-based Cominco Engineering Services Ltd. (CESL) has developed a hydrometallurgical process for the refining of copper and nickel from sulphide concentrates. CESL says the process is environmentally superior to smelting, the traditional refining process, because it does not produce sulphur dioxide gas or significant amounts of effluent.

CESL has licensed the process to Compania Vale do Rio Doce (CVRD), the world’s largest miner of iron ore, which is installing a plant to recover copper at a mine that is being built at the Salobo ore body. Situated in southwestern Brazil, the Salobo ore body is rich in copper, but the concentrate is difficult to process by smelter. It contains high levels of fluorine, which is very corrosive and can do a great deal of damage to smelting equipment.

Doug Magoon, general manager, technology, Teck Cominco Ltd., and president of CESL, says CVRD first approached CESL about hydrometallurgy in 1998.

“They did some extensive testing of the process and then went back to Brazil,” he said. “When we didn’t hear from them we assumed they weren’t interested in the process.”

But CVRD hadn’t lost interest in CESL’s hydrometallurgy; they had been checking out other methods for refining copper concentrate. In 2002, the Brazilian company came back to CESL and undertook more testing of the process. “At that point CVRD told us they were sold,” Magoon said. “They said they’d looked, but hadn’t been able to find a better technology.”

Site preparation, detailed engineering, and procurement have begun at Salobo. The plant is expected to go into production in mid-2007. Magoon says the capacity of the plant, which is being designed to operate for two years, will be 10,000 tonnes of copper metal produced per year. If all goes well with the plant, a much larger one, with a capacity of more than 200,000 tonnes per year, will be built.

“CVRD is spending $1.5 billion to develop Salobo,” Magoon said. “They want to be sure they do everything right.”

CESL’s hydrometallurgical refining processing eliminates many of the costs associated with smelting.

“CVRD doesn’t have to ship concentrate to a smelter,” Magoon said. “All the refining is done onsite. The chemistry of the process handles impurities in the concentrate more safely and efficiently than traditional smelting. That means big transportation savings for the company.”

Another benefit to CVRD of using CESL’s hydrometallurgy process is that it allows the Brazilian mining company to take an ore body that would be difficult to commercialize and turn it into a success. It produces a value-added product at the mine site that is 30 percent of the weight of concentrate. It also reduces the environmental impact of mining.

“There are no gasses or dust and no smokestacks,” Magoon described. “All that gets produced is metal and residue, and the residue is in liquid form.” The sludge residue can be put in a tailings pond or a lined impoundment facility.

Other advantages of CESL’s hydrometallurgical process over smelting include: capital cost of a CESL refinery is much lower than a smelter, and a CESL hydrometallurgical refinery can be built at a much smaller scale than a smelter and still be economic; permits for a CESL refinery are easier, in most cases, to obtain than for a smelter; the CESL process does not require modifications to treat arsenical concentrates, transforming arsenic into an environmentally stable ferric arsenate; and in addition to the recovered metals, produced gypsum can be sold to the wallboard industry.

Because the CESL process can refine low-grade concentrates, the mill can reduce its concentrate grade, increasing overall mill recovery.

Magoon said hydrometallurgy technology has been known about for some time. It hadn’t been successful at a commercial level, however, until recently. Hydrometallurgy for refining copper was developed into a commercial process by CESL chemist David Jones.

Noranda had developed the original process, but the patent expired in the 1960s. Later on, CESL picked it up and began sorting out its technical deficiencies. It took CESL 13 years, from 1992 to 2005, to get the technology right.

Post a comment


PDF Version