Increased Treatment of Secondary Raw Materials in the PS Converter Operation at Toyo Smelter and Refinery

Since 2003, Toyo Smelter and Refinery has been working on developing the technologies to improve the smelting capacity of the concentrate burner in the flash furnace process. In order to cope with the increasing amount of treated copper concentrate in the flash furnace, one converter furnace was added, and the converter operation pattern was shifted from 2-hot-2-blowing to 3-hot-2-blowing in 2005. In 2016, cathode copper production reached 450,000 tons per year. In addition, with the aim of achieving a closed loop process and reducing greenhouse gas (GHG) emissions, continued efforts have been made to increase the amount of secondary raw materials treated in the converter process. As a result, the ratio of copper produced from secondary raw materials exceeded 20% in recent years. In the converter process, both the slag making stage and the copper making stage involve exothermic reactions, requiring the addition of cooling materials to maintain the appropriate operating temperature. Secondary raw materials are part of these cooling materials. This includes not only high-grade materials with a copper content exceeding 90%, but also low-grade materials such as electronic scrap. In the past, increasing the treatment of secondary raw materials in converters decreased the fluidity of converter slag and increased the copper loss in the converter slag. Various investigations revealed that the variation in the composition of secondary raw materials caused deterioration of converter slag when the processing amount of secondary raw materials was increased. Therefore, by focusing on the composition of secondary raw materials and working on improving the processing methods, it has become possible to significantly increase the secondary raw materials processing while preventing the deterioration of converter slag properties.