Port Colborne Operations
Vale Canada Limited – Port Colborne Refinery (PCR) focuses on the production of electrocobalt, the processing of precious metals and the packaging and distribution of finished nickel products to market. These three product lines are processed at three distinct production areas at PCR: the Cobalt Refinery, the Precious Metals Refinery and Nickel Processing. There are also support services and utilities throughout PCR in support of the production areas.
Precious Metals Refinery
In the PMR, slurry feed shipments of residues or process intermediates are received from Vale’s Sudbury Operations, or other toll materials from clients. These feeds undergo batch hydrometallurigical processes to remove impurities and purify targeted metals (i.e. gold) or metallic compounds (i.e. platinum group metals). The feed is either charged to a pressure autoclave or an atmospheric leach tank to be leached in an oxygen atmosphere. The resultant copper-free filter cake is leached to remove lead, fed to a thickener and filtered again, producing a lead carbonate. The leach solution is treated with iron and chlorine to precipitate silver and silver chloride and to dissolve various other precious metals for further upgrading steps. The solids are further processed to separate and concentrate various precious metals. Several metallic compounds are also created as by-products. The PMR produces gold sand, silver sand and platinum group metal cake, which is sent off-site for further refining and processing. By-products such as lead carbonate cake, selenium cake and bismuth sand are sold to other refining operations. An additional process circuit, which will be commissioned in 2012, will produce a saleable tellurium-containing product.
Cobalt Refinery
Slurry feed is received from Vale Canada Limited – Copper Cliff Nickel Refinery containing nickel and cobalt carbonates and other impurities. This slurry is first dissolved with sulphuric acid and then pH adjusted with soda ash. The mixture is then filtered to remove calcium and iron along with other metals, such as copper, nickel, and cobalt, co-precipitated. The solid phase is rejected and liquid phase is sent through several other purification steps including zinc ion exchange and copper removal using powdered nickel. The resulting copper/nickel reject cake is filtered, air-dried and reverted to Sudbury Operations. The remaining liquid containing purified cobalt and nickel is treated with sodium hypochlorite (sodium carbonate and chlorine) to separate the cobalt from the nickel. The remaining nickel solution is treated with soda ash producing a nickel carbonate precipitate which is reverted in slurry form to the Copper Cliff Nickel Refinery. Cobalt hydrate is precipitated, filtered, and sent to the Electro Cobalt Refinery (ECR) building.
In the ECR, the cobalt hydrate feed is subjected to additional purification through ion exchange, settling and filtering. Soluble cobalt contained in acidic liquor is pumped into plating cells containing cathodes and a sacrificial lead anode. Passing an electric current through the cells, metallic cobalt is electrolytically deposited onto mandrels. Several hundred cobalt disks form on each mandrel to a size of about three centimetres in diameter. Once removed from the mandrel, the rounds are polished, degassed in an electrically heated kiln and packaged for market in 250 kg drums.
The process for the maintenance and refinishing of the mandrels that are used in the ECR involves a series of treatments including acid cleaning with both nitric acid and sulphuric acid and grit blasting with aluminum oxide. The mandrels are then coated with epoxy ink in a pattern specific for rounds formation, and dried.
Nickel Processing
Nickel products are received from Vale Canada Limited’s other operations. Nickel rounds go through a sulphuric acid dip for cleaning followed by screening, a water rinse and polishing. Nickel cathodes are sheared into squares of varying sizes. Nickel pellets and flats are also received in bulk containers for repackaging. The products are packaged into 10 kg bags, 250 kg drums or tonne bulk bags for shipment to market.
