Elucidation of Removal Mechanisifrof Impurities from Copper Scrap by Using Cu_2O-based Slag

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In order to elucidate mechanism of impurity removal from molten copper scrap by using Cu_2O-based slag, the following experiments were conducted. In the present study, Cu_2O, Cu_2O-CaO and Cu_2O-SiO_2 were picked up as a slag system, and Sn, Co and Pb were picked up as an impurity in copper scrap.(1) Measurements of Oxygen Solubilities on Molten Copper Equilibrated with Cu_2O-based Slags and Oxygen Dissolution Rates into Molten Copper from the Slags.Molten Cu-O alloy was held under coexistence of Cu_2O-based slag in Ar atmosphere at 1573 K.At an appropriate time interval, metallic sample was taken by using a quartz tube (Sampled method). Especially, in case of Cu_2O slag, the sampled methods with an alumina tube, stainless rod, etc., and an EMF method using ZrO_2 solid electrolyte to determine oxygen partial pressure were also conducted at 1573 K.Based on the results, the reaction rate at the slag-metal interface (Cu_20(in slag) = 2Cu(l) +O(in Cu)) is considered to be the rate-determin … More ing step for the oxygen dissolution rate.(2) Measurement of Impurity Removal Rate in Molten Copper by Using Cu_2O-based SlagBy a sampled method (same as the experiment (1)), not only impurity removal rate but also oxygen dissolution rate were measured at 1573 K.Under these experimental conditions, impurity removal rates are faster in order of Sn, Co and Pb for the same initial oxygen content. For initial oxygen content of 0.03 %, both oxygen dissolution rate and impurity removal rate are slower than those rates at an initial oxygen content higher than 0.8 %. From these experiments, the following results were obtained :The mass transfer in molten copper phase is considered to be the rate-determining step for the impurity removal rate.The active agent (ex. Oxygen) in molten copper phase, which changes the interface area between molten copper and the Cu_2O-based slag, seems to greatly affect the behaviors of impurity removal and oxygen dissolution in the copper scrap refining process by using Cu_2O-based slag. Less