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Extractive Metallurgy of Copper Part 4

Tham khảo tài liệu 'extractive metallurgy of copper part 4', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Matte Smelting Fundamentals 67 oxidize Eqn. 4.11 . The reactions are exothermic and the energy they generate heats and melts the products. The contact time between concentrate particles and the gas is short a few seconds so ensuring good reaction kinetics is essential. Nearly all smelters accomplish this by mixing the concentrate with the gas prior to injecting it into the smelting furnace. The use of oxygen-enriched air instead of air also improves reaction kinetics and is increasingly popular. Use of oxygen-enriched air or oxygen also makes the process more autothermal. Because less nitrogen is fed to the furnace less heat is removed in the offgas. This means that more of the heat generated by the reactions goes into the matte and slag. As a result less or no hydrocarbon fuel combustion is required to ensure the proper final slag and matte temperature 1250 C. A new method for contacting concentrate and 02 is being used in submerged tuyere smelting furnaces. In these furnaces concentrate is blown into a mixture of molten matte and slag and the oxidation process takes place indirectly. This is discussed in Chapters 7 and 8. b Letting the matte settle through the slag layer into the matte layer below the slag. Most smelting furnaces provide a quiet settling region for this purpose. During settling FeS in the matte reacts with dissolved Cu2O in the slag by the reverse of Reaction 4.12 FeS Cu2O FeO Cu2S 4 JJ. in matte in slag in slag in matte This further reduces the amount of Cu in the slag. The importance of low slag viscosity in encouraging settling has already been mentioned. Keeping the slag layer still also helps. A trade-off is at work here too. Higher matte and slag temperatures encourage Reaction 4.15 to go to completion and decrease viscosity but they cost more in terms of energy and refractory wear. c Periodically tapping the matte and slag through separate tap holes. Feeding of smelting furnaces and withdrawing of offgas is continuous. Removal of matte and