Noranda’s CEZ adding silver recovery circuit

Celebrating 25 years of production, Canadian Electrolytic Zinc (CEZ) is adding a silver recovery circuit to its zinc reduction plant located just outside Montreal.

A pilot plant has been installed and a process permitting the recovery of silver from low grade ores (under 3 oz per ton) is to be tested. Success with the pilot program could see CEZ coming “on line” with its silver recovery system within two years, D. D. Rodier, plant manager, told The Northern Miner during a tour of operations.

Recovery of silver would add to the list of byproducts the Noranda Inc. (TSE) company now produces and which includes sulphuric acid, cadmium and copper residue. In 1987, the plant turned out 405,500 tonnes of sulphuric acid, 508 tonnes of cadmium and 4,300 tonnes of copper residue.

Zinc production last year totalled 220,400 tonnes. (The plant’s rated capacity is 230,000 tonnes zinc per year.) More than half of the zinc output is exported to the U.S., with the North American market absorbing about 75% of the plant’s production. Near the St. Lawrence

The CEZ plant stands on a 300-acre site near the St. Lawrence River and an adequate supply of hydro-electric power. The plant began producing zinc in September, 1963, construction of the facilities having been started the year before. Seeking a means to process the zinc-bearing ores from its mining projects in northwestern Quebec and Ontario, Noranda chose to build its own refinery, and today the CEZ plant handles about half of the parent company’s total mined zinc output.

Geographic location was important for the operation of the refinery, which uses 58 million cubic metres of cooling water per year. Its peak electrical power demand is 115,000 kW, enough electricity, Rodier said, to meet the needs of a city of 100,000 people. (CEZ is Hydro Quebec’s third largest customer.)

Delivery of its products was also a consideration. In 1963 CEZ shipped to within a 500-mile radius of its plant. Today, CEZ does business with 20 different countries and is the second largest (rated capacity) zinc refiner in Canada (after Cominco Ltd. and its Trail, B.C., operation). New cell house

Every five years the plant seems to undergo some sort of expansion, Rodier said. Next major job being considered is replacement of the two cell houses (electrolysis department) with a single unit incorporating state-of-the-art equipment. To be decided is whether to increase the current capacity.

The No 1 cell house uses manual cathode stripping techniques and has a daily capacity of 420 tonnes. The No 2 cell house, started up in 1976, features a mechanized conveying system and can produce up to 280 tonnes of cathodes daily. Cost of a new cell house, Rodier said, would be well over $100 million. The existing two-cell-house operation involves 200 workers, whereas the new unit would employ about 65 people.

Recently announced by CEZ were plans to build a new facility at the plant site to produce zinc battery powder for the alkaline battery market, at a capital cost exceeding $5 million. The new facility, which the company hopes to have in operation by fall 1989, is expected to have a capacity of more than 25-million lbs of powder annually and employ 14 people. Research and development

CEZ, like Noranda’s Canadian Copper Refiners in Montreal, makes good use of the Noranda Research Centre, also located in the Montreal area. The new silver recovery process mentioned above is one example of a co-operative effort, as were the developments of technology to produce specialized zinc powder for alkaline batteries and of a water-atomized zinc dust plant. Other ventures include development of zinc pellets for new steel sheet electrogalvanizing lines. Also playing an important role in CEZ’s ongoing success, at the marketing end, is the Noranda Sales division.

Zinc’s resistance to corrosion and its steel galvanizing ability allow the metal to be used in a variety of applications. Also, the metal can be cast at a relatively low cost and it has use in compounds such as zinc oxide and zinc dust which go into making chemical coatings, rubber products and plastic stabilizers.

Supply of zinc-bearing ore to CEZ is not considered a problem into the near future at current plant capacity. In New Brunswick, Noranda-controlled Brunswick Mining and Smelting (TSE), which operates a zinc-lead-silver mine at Bathurst, retains a sizeable mineral inventory. And in northwestern Quebec, while Noranda is closing its Matagami mine after 25 years of operation, the nearby Isle Dieu mine is stepping in to replace it. (The Matagami mine concentrator will be used to treat the Isle Dieu ore.) Extraction and refining

Ore from the mine site arrives at the CEZ plant in concentrated form, comprising about 50% zinc. Extraction and refining occurs in four main stages: roasting, leaching and purification, electrolysis and casting. The sulphuric acid byproduct, about 10% of which is consumed internally and which is marketed to a number of different industries, is produced from the sulphur dioxide drawn off at the roasting stage.

The aforementioned atomized zinc dust plays a role in the purification process where cadmium, along with copper and smaller amounts of cobalt, nickel and other elements, are recovered. Cadmium has a variety of applications, including in paint pigmentations, electroplating and nickel-cadmium rechargeable batteries.

On the labor front, CEZ, with a payroll of 750 people, has embarked on a “preventive mediation” plan by which the company hopes to be able to solve any labor problems at the lowest possible level and which involves opening up the lines of communication between management and worker. The plant workforce is stable, with a less than 1% turnover, Rodier said.