$2 millio plan a Campbel wil cu emission – `Pressur oxidation was

A new $24-million plant to treat refractory gold ores from Placer Dome’s (TSE) Campbell Red Lake mine at Balmertown, Ont., will result in the elimination of sulphur dioxide gas emissions from the site. The new plant, known as a pressure oxidation circuit, is under construction at the mill and should be fully operational by the fall of 1991, the company said.

The circuit, designed to handle about 60 tons of refractory sulphide concentrates per day, will replace the current roasting operation which processes sulphide concentrates for later gold recovery. Up until now the old roaster had been operating under controlled conditions with occasional shutdowns necessary when the wind direction is unfavorable. About 35% of the mine’s annual gold output (248,000 oz.) is extracted from refractory ore.

By employing modern technology, all sulphur dioxide emissions will be eliminated, and the mill’s effluent products will be treated as part of the process. The new circuit will have significant environmental benefits from both water effluent and air emission standpoints.

“We felt that pressure oxidation was the best available technology for our sulphide concentrate,” said mill superintendent John Frostiak.

He said the company examined a number of alternatives for treating its refractory concentrate, including upgrading of the existing roaster, and bioleaching which uses bacteria to liberate gold.

“Everybody with refractory ore is looking at the types of technology available,” said Frostiak.

The Campbell Red Lake mine is the highest-grade gold mine in Canada and has sufficient reserves for at least another 15 years of production. Grades mined last year averaged about 0.67 oz. gold per ton.

Meanwhile, concentrates from the nearby Arthur White mine of Dickenson Mines (TSE) are being stockpiled while the company evaluates the feasibility of using bioleach technology. A spokesman for Dickenson said pressure oxidation is not an economical alternative for the White operation.

According to a Sept. 20 article in the Wall Street Journal, dozens of U.S. mining companies have lab- scale bioleaching experiments under way and some pilot projects are also planned.

“U.S. miners desperately need new technology to release hard-to- refine gold reserves economically, but no one has come up with it,” said the New York-based daily newspaper.

Elsewhere in Ontario, Consolidated Professor Mines (TSE) has been considering the use of pressure oxidation to treat sulphide concentrates from its Duport gold deposit at Shoal Lake.

However, development of the $53-million mine has been delayed by a number of factors including the project’s designation under Ontario’s Environmental Assessment Act.

Meanwhile, Deak Resources (TSE) is contemplating the use of an autoclave pressure-leach system to replace a roaster at the old Kerr mill near Virginiatown, Ont. If successfully implemented, that operation could custom treat refractory concentrates from various projects including Consolidated Professor.