Experimental Study on Oxidative Desulfurization of Molten Copper Slag by Different Oxidants
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UCTION
A large amount of copper slag is produced in the copper smelting process. Usually the copper content in the slag is between 1 and 5 pct.[1] Presently, copper slag is treated by flotation and electric furnace. Copper content in copper slag can be reduced to 0.3 pct by flotation. This method faces problems such as the complex process, large area and large investment, and it cannot effectively utilize the heat of hot slag. Although the electric furnace process has advantages in heat utilization and occupies a smaller area, the copper content in slag is still 0.5 to 1 pct after treatment.[2] In the process of reductive extraction of valuable metals from copper slag, the problem of excessive S content in raw materials will be faced. Some scholars have proposed the process of oxidizing copper slag first and then reducing copper slag to realize metal extraction from copper slag.[3] Several studies on the reduction and dilution mechanism of molten copper slag and desulfurization of copper slag have been conducted in the literature. Ueda and Roghani contributed a multiphase system of Cu-Fe-O-S-SiO2-(CaO-MgO-Al2O3) copper slag, including the distribution ratio and occurrence form of Cu and S in different phases at different temperatures, atmospheres and slag characteristics. Their results show that Cu2O is easily reduced by CO, while Cu2S can hardly be reduced.[8,9] Rajcevic and Zander proposed a method
HONGYANG WANG, RONG ZHU, and YU MI are with the School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, China. Contact e-mail: [email protected] YUN WANG is with the Chinese Enfei Engineering Technology Co. Ltd, Beijing 100038, China. Manuscript submitted June 23, 2019.
METALLURGICAL AND MATERIALS TRANSACTIONS B
enhancing the existing electric furnace dilution process by adding lime and coal, enhancing stirring, increasing temperature and adjusting the ratio of Fe/SiO2 in a slag. The copper content in diluted form is maintained at 0.3 to 0.6 pct.[10,11] Siwiec et al. used coal as a reducing agent to reduce and dilute the flash smelting slag (wCu = 11.6 pct, wS = 0.03 pct). The copper content in the slag after dilution was low (wCu = 0.15 to 0.34 pct).[12] Lei et al. studied the oxidative desulfurization of molten copper slag (wCu = 1.06 pct, wS = 0.52 pct) with CaO and CaF2 in a pure oxygen atmosphere.[13] It was found that low alkalinity and high temperature enhance the oxidative desulfurization process, and sulfur in slag can be reduced to 0.005 pct. According to the literature, high FeO and low alkalinity aid the removal of sulfur in the form of SO2 in the oxidation and desulfurization of slag.[4] The composition of copper slag is more conducive to the occurrence of oxidative desulfurization; thus, the removal of S is suitable before extraction of copper and iron. Experimental study of oxidative desulfurization is significant for subsequent higher copper depletion rate. In the process of copper slag oxidation, a large amount of Fe2+ is oxidized to Fe3+ resu
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