Practical Application of Sodium Carbonate Slag Treatment to the Copper Refining Process.

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1. Confirming of the Slag Consumpion EstimationBased on calculated distribution ratios of As, Sb, Fe, and Sn between Na_2CO_3 and molten copper, the slag consumption, defined as the consumed slag mass in kg per one ton of copper containing some content of an impurity, was estimated.Then, distribution experiments were conducted to confirm the above estimated slag consumption. Prescribed amount of Cu-X alloy and premelted Na_2CO_3 calculated from the slag consumption, were equilibrated in an alumina crucible under Ar-CO-CO_2 gas mixture to control the partial pressure of oxygen and CO_2 at 1523 K.Levels of each impurities could be successfully reduced as expected by the estimation by the sodium carbonate slag treatment.However, when a large-scale experiments was attempted by using the large sized induction furnace, the slag consumption could not be successfully confirmed. From viewpoints of experimental conditions and methods, this causes were cleared up. Then, some improvements were cla … More rified.2. Rate of As and Sb removal from molten copperThe removal rate of As and Sb from molten copper by using Na_2CO_3 slag under Ar gas atmosphere was successfully investigated at 1523 K.Initial contents of impurities in the melt were changed between 500 and 4000 mass ppm, while that of oxygen was varied in the range of 500 to 4000 mass ppm. Based on the experimental results, the following conclusions were achieved.(1) The overall reaction rate is controlled by mass transfer of oxygen and/or impurities, depending on their relative contents in the melt.(2) Overall rates of As removal reaction sre always larger than those of Sb under almost same experimental conditions.(3) In the simultaneous elimination of As and Sb, preferential elimination of As was observed at the initial stage under the relatively low oxygen content in the melt. Based on the information of (1) and (2), this phenomenon was discussed.3. Design of Sodium Carbonate Recycling and Valuable Metals Recovery ProcessBased on information reported, the flowsheet for the recycling of Na_2CO_3 and recovery of As, Sb, Fe, and Sn by hydrometallurgical methods was successfilly designed. Less