Operations: The Precious Side of Inco
Port Colborne Refinery
The Port Colborne, Ont., refinery began operations in 1918, on the northeast shore of Lake Erie.
It’s a very different operation today. It no longer refines nickel, but incorporates a cobalt and precious metals refining facility, and acts as Inco’s nickel packaging, warehousing and distribution centre. With only 200 employees, it continues to be a major supplier of nickel and cobalt products to the world markets.
The electrocobalt refinery produces 1,360 tonnes of high quality electrolytic cobalt per year. The feed–crude nickel cobalt carbonate from Inco’s Sudbury operations–is treated to remove impurities and produce cobaltic hydrate. This is leached and filtered to produce a cobalt sulphate solution, which is further purified by ion exchange and polish filtration. High purity cobalt metal is plated as rounds in the electrowinning circuit. The rounds are collected, degassed, cleaned and dried. The final product (>99.8% pure Co) is packed in 250-kg drums.
Precious metals have been refined at Port Colborne since the late 1920s; the current hydrometallurgical precious metal refining process began operations in 1986. The refinery processes 500,000 to 600,000 troy ounces of platinum group metals (PGMs) and gold, and another 400,000 troy ounces of silver each year.
The operations upgrade two precious metals residues from Inco’s Sudbury facilities: one from copper refining, and the other from nickel refining. The final product streams consist of gold and silver sands, and a PGM concentrate.
Gold sand is produced and then refined to pure gold bullion through a toll contract with the Royal Canadian Mint. The silver sand is sent back to Sudbury where it is refined into pure silver bars. The PGM concentrate (75% PGMs) is shipped to Inco’s precious metals refining operations in Acton, United Kingdom (see below).
Port Colborne is also the home to specialty shearing and packaging operations for nickel products from Inco’s Manitoba and Sudbury nickel refineries, handling about 27,000 tonnes of nickel per year.
Inco is currently dealing with an environmental legacy issue in Port Colborne stemming from elevated levels of metals, including nickel, that have been found in surface soils in the community as a result of historic refinery emissions.[continued on page 50]
Inco has accepted full responsibility for the surface soil nickel levels and is supporting and funding a community-based risk assessment (CBRA) process.
The Ontario Environment Ministry also undertook special testing and health risk assessment on a neighbourhood of 180 properties next to the plant, and found that in 25 of these properties, the soil had nickel concentrations exceeding their recommended intervention level. Subsequently, neighbourhood residents filed a class action suit against Inco and others. Inco believes there is no basis for the claims made in the lawsuit. Among other things, the company’s analysis shows that the nickel concentrations at depth did not come from the refinery stack, but rather from landfill deposited earlier in the century. In spite of this, the company volunteered to remediate the soils in the 25 properties, and has cleaned up the five properties where it was permitted access.
The Acton refinery was built by the International Nickel Co. (Inco) in 1924, in West London, U.K. It is one of only a handful of PGM refineries in the world. Forty percent of its feed today is PGM concentrate from the Port Colborne cobalt refinery, nearly 6,400 km away. The rest comes from toll refining of primary concentrates and secondary materials.
Acton has 125 highly trained employees and operates at close to capacity. In 2001, Acton produced a record production of close to 1.4 million ounces of precious metals.
The hydrometallurgical process originally installed has been considerably enhanced and developed. Today, Acton is a leader in applying solvent extraction to precious metal refining; it is recognized for its efficient operation and product purity. The operation gained ISO14001 accreditation some two years ago, and will be accredited with ISO17025 in 2002.
The feed is first sampled and assayed by both Inco and the client’s laboratory, to determine the precious metals content. It can then pass through the whole process or be introduced at an intermediate stage.
In the main hydrometallurgical process, precious metals are dissolved in hydrochloric acid and chlorine to give a solution containing a mixture of all precious metals and any base metals present in the feed material. Individual precious metals are separated sequentially from this solution using a variety of operations including distillation, solvent extraction and ion exchange. Eventually, each is isolated as a pure, solid “salt” or metallic “black”, which is ignited to metal.
Secondary operations are available to deal with insoluble material from the leaching operation and with low-grade intermediates and feed materials. These include the use of peroxide fusion, selective base metal dissolution operations and lead smelting.
Final products include gold and silver grain as well as PGMs as sponge–a grey granular product. Platinum and Pd may be converted into bullion by melting in a vacuum furnace. The guaranteed minimum purity of Pt, Pd and Au is 99.95%, while Rh, Ru, Ir and Ag purities are at least 99.90%.