NaO0.5-CO2-SnO2系スラグの熱力学と本系スラグ-溶銅間のSnの分配比の推算

福山 博之, 霜鳥 潤, 藤澤 敏治, 山内 睦文

doi:10.2320/jinstmet1952.57.8_905

In view of the application of sodium carbonate slag to the elimination of Sn from molten copper, the thermodynamic properties of NaO_0.5-CO₂-SnO₂ slag have been studied by conducting the following experiments: (1) Activities of NaO_0.5 in the slag were determined by the EMF method using β^′′-alumina as a solid electrolyte over the composition range of 1>N≥0.795{N=n_Na+(n_Na⁄n_Sn),n:the number of moles}under the partial pressures of CO₂ of 0.001∼0.08 MPa at 1423∼1523 K. It was found that the activity of NaO_0.5 did not depend on the slag composition for the constant partial pressure of CO₂ and the slag was saturated with Na₂SnO₃(s). (2) Then the solubility of Na₂SnO₃(s) into the sodium carbonate melt was measured under the various partial pressures of CO₂ at 1523 K. With decreasing the partial pressure of CO₂ the solubility increased, but the partial pressure of oxygen had no effect. (3) Activities of SnO₂ were determined by the distribution equilibrium measurements for Sn between the Na₂SnO₃(s)-saturated slag and molten copper. From the activity of SnO₂ combined with that of NaO_0.5, the standard free energy change for the following reaction was determined as: (This article is not displayable. Please see full text pdf.) \oindentThe activity of SnO₂ in the homogeneous liquid region of the slag was also evaluated by the distribution equilibrium measurements. Based on the results obtained, the distribution ratios of Sn between the slag and molten copper were estimated. The ratios decrease with decreasing SnO₂ content in the Na₂SnO₃(s)-saturated slag. The higher oxygen partial pressure and the lower CO₂ partial pressure are more preferable for the removal of Sn from molten copper.

NaO<SUB>0.5</SUB>-CO<SUB>2</SUB>-SnO<SUB>2</SUB>系スラグの熱力学と本系スラグ-溶銅間のSnの分配比の推算

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