 Rand Refinery’s high tech pyrometallurgical smelter offers a major competitive advantage over most other refiners as it provides a means to recover gold, silver and platinum group metals not only from by-products of the refinery but also from low grade by-products of mining and the precious metals industries worldwide. In fact, the minimum gold grade that can be treated is 150g/t. It is the largest precious metal smelting operation in the Southern hemisphere, sourcing feed for the smelter from Africa, the Far East, North America and Australia to treat a combined tonnage of approximately 4000 tons per annum.
Recognised for its custom smelting, the smelter has expanded its services beyond mine by-products (slags, concentrates, carbon) to cater for new, sustainable industries (e.g. computer and electronic scrap). Since the composition and nature of these materials differs vastly, the processing requirements differ too. Hence the refinery has a wide range of treatment charges depending upon the classification of the material. Submerged arc furnace technology and a bottom-blown oxygen conversion technique ensure the economic recovery of precious metals. The smelter also has a spiral plant with a fluidised bed incinerator, which upgrades carbon-bearing material from 150g/t to 3000g/t. The ash product from the incineration process is then fed to the arc furnace via a blending process to ensure efficient recovery.
| Rand Refinery’s high tech pyrometallurgical smelter offers a major competitive advantage over most other refiners |
This combination of smelting processes enables Rand Refinery to offer its depositors competitive smelting fees and precious metal returns. The end product of the smelting process is doré, averaging 30% gold (Au) and 60% silver (Ag), which is further upgraded in the refining process.
The different types of smelter feed have been grouped together into classes as tabulated below with differing fees and metal returns depending upon which class depositor material falls into:
Smelter Class |
Material Description |
Class 1 |
Clean borax slag |
Class 2 |
Ash and clinker, baghouse sweeps, bricks, posts and liners, calcines, carbon ash, cementation sweeps, chippings, coarse iron (magnetics), dirty borax slag, fine iron, flue dust, fan dust, gravity concentrates, mill concentrates, mine site demolition material, miscellaneous concentrates, jewellers sweeps |
Class 3 |
Silver ash, film ash, silver chloride, silver concentrates, silver sulphide |
Class 4 |
Base bars containing < 30% gold, electronic/computer metallics (free of plastic), unmelted gold deposits containing < 30% gold |
Class 5 |
Fine carbon |
Class 6 |
All gold bearing material not listed above |
An additional levy is also applied for material that requires crushing, screening or sorting and all material must meet the requisite environmental and safety standards.
Reliable sampling of feed material is of particular importance to the smelter due to the heterogeneous nature of the feed. Rand Refinery has given this a large amount of attention, subjecting itself to a number of audits culminating in the implementation of parallel stream sampling using automatic cross cut samplers.
Materials such as computer scrap, jewellery sweeps and base bars are obviously not suited to blending and instead these deposits are melted down to ensure homogeneous samples.
The smelting process by its nature is more involved than the refining process and therefore it takes longer to produce final bullion from the feed material. From a customer perspective, the payment pipeline from receipt of material to customer payment is therefore also longer than for the refinery.
Committed to operating an environmentally responsible process and to ensure continual improvement, the smelter carefully measures, monitors and controls all potential impacts through an environmental management system.
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