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Tham khảo tài liệu 'extractive metallurgy of copper 4th ed. w. davenport et. al. (2002) episode 6', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Copper Loss in Slag 177 Others accept converter slag in addition to smelter slag requiring more emphasis on reduction. Most commonly these furnaces are fed only smelting-furnace slag and are used primarily as a final settling furnace. Fig. 11.1 illustrates a typical electric slag-clcaning furnace Barnett 1979 Higashi el al. 1993 Kucharski 1987 . Heat is generated by passing electric current through the slag layer. AC power is used supplied through three carbon electrodes. This method of supplying heat generates the least amount of turbulence which improves settling rates. The furnace sidewalls are cooled by external water jackets to minimize refractory erosion. Table 11.2 compares the operating characteristics of seven electric furnaces. Required capacities are set by the size of the smelting operation and the choice of input slags. Settling times are usually on the order of one to five hours. Typical energy use is 15-70 kWh per tonne of slag depending upon furnace inputs target Cu temperature and residence time. While some electric slag-cleaning furnaces process only smelting furnace slag others are fed a variety of materials. Several furnace operators input converter slag or solid reverts in addition to smelting slag. When this is done a reducing agent is often required to reduce Cu oxide in the slag to Cu metal or Cu sulfide. Coal or coke is often added for this reduction. Pyrite may also be added if additional sulfur is needed to form matte Ponce and Sanchez 1999 c Cu2O - CO 2Cu 11.4 c Cu2O FeS2 - Cu2S FeS co 11.5 . Carbon additions also reduce solid magnetite in the slag to liquid FeO c Fe3O4 s - CO 3FeO 11.6 . This decreases slag viscosity and improves settling rates. Ferrosilicon is occasionally used as a reducing agent Shimpo and Toguri 2000 especially in the Mitsubishi slag-cleaning furnace Chapter 13. Recent initiatives in slag-cleaning furnace practice have involved lance injection of solid reductants or gaseous reducing agents such as methane to improve
