text: The South African company Rand Refinery Limited rebuilt its smelter in 1986, incorporating two 1.5 t TBRCs and a small static reverberatory furnace for cupellation to produce doré bullion containing gold and silver. The original concept was to produce doré bullion directly from the TBRCs, but this proved impossible, as it was found impossible to take the oxidation stage to completion while maintaining temperatures at which the doré would remain molten. Consequently, the reverberatory cupellation furnace was necessary to complete the process.
  In January 1993, the management team of Rand Refinery decided to review alternate technologies to replace the TBRC–reverberatory furnace circuit, with the objective of having cupellation undertaken in a single stage. After evaluating the possibility of modifying the existing TBRCs by replacing the existing lance–burner combination with a separate lance and burner, and considering complete replacement of the TBRCs with an Ausmelt top-submerged lance furnace, Rand Refinery decided to replace one of the TBRC with a 4 t BBOC. The remaining TBRC is used to treat litharge slag to recover the lead for sale.
  The Rand Refinery BBOC was commissioned in 1994. The operators reported a 28% reduction in the operating costs when the BBOC’s costs were compared with those of the TBRC–reverberatory furnace combination. This included a 45% reduction in bulk oxygen costs and halving the number of operators required to run the plant. The BBOC’s refractory life was 13 weeks, compared to an average refractory life of 2 weeks for the TBRCs. Other maintenance costs also fell.