Thermodynamic Considerations for Eliminating P and Si from Molten Copper by Na<SUB>2</SUB>CO<SUB>3</SUB>&ndash;Based Slag

Effects of Coexisting Oxygen and Antimony in Molten Copper on Rate of Arsenic Elimination from the Copper Phase by the Use of Na<SUB>2</SUB>CO<SUB>3</SUB> Slag

“…In addition to As, Sb in the molten copper was also eliminated. The reason for this reduction in the concentrations of these two impurities despite the lack of oxygen in the molten copper is discussed based on the results reported by Yamauchi et al 2,3) According to their results, the oxygen partial pressure between the NaO 0:5 -CO 2 -SbO 2:5 slag and the molten copper at equilibrium lies between the oxygen partial pressure thermodynamically determined according to the thermal decomposition reaction of Na 2 CO 3 slag [reaction (12)] and the dissolution reaction of O 2 gas into molten copper [reaction (13)]:…”

“…From a thermodynamic viewpoint, reactions (12) and (13) are expected to be enhanced at relatively low initial oxygen concentrations, which corresponds to relatively low oxygen partial pressures at the slag-metal interface. Considering this fact, the dissociated O 2 gas by reactions (12) and (13) might contribute to the elimination of As and Sb after the consumption of the oxygen initially dissolved in the molten copper for the As preferential elimination in run AS-1. In order to confirm this, the dissolution of O 2 gas, dissociated by the thermal decomposition reaction of Na 2 CO 3 slag, into oxygen-free copper melt was examined by conducting run B-1.…”

“…9(a) and 10, it is clarified that for relatively low initial oxygen concentration, As and Sb in molten copper react not only with the oxygen initially dissolved in the molten copper but also with the oxygen generated according to reactions (12) and (13) so that they are transferred into the slag phase as oxides. In other words, it is necessary to raise the oxygen concentration in the molten copper in order not only to enhance the elimination rates of As and Sb but also to prevent the evaporation loss of the Na 2 CO 3 slag.…”

“…Several research groups have therefore been conducting fundamental studies on this slag treatment. Using a thermodynamic approach, Yamauchi and coworkers have investigated the distribution ratios of various impurities between the Na 2 CO 3 slag and the molten copper, L X , {defined as (mass% of X in slag)/[mass% of X in molten copper]}, where the impurity element X ¼ Sb, [1][2][3][4][5][6] As, 5,7) Sn, 8) Fe, 9,10) Te, 11) Se, 11) P, 12) Si, 12) Ni, 13) Zn, 13) S, 14) and have discussed the slag consumption of this refining process using a mathematical model. 15,16) From a kinetic viewpoint, the Sb elimination rate from molten copper by injecting soda ash into molten copper has been measured by Kozlowski et al 17) and Stapurewicz et al 18) However, the kinetic mechanism of impurity elimination during this injection process is too complicated and has not yet been clarified.…”

“…19) In the present study, As was selected as an impurity element, and its elimination rate and mechanism was investigated by a very similar kinetic analytical method as the one described in the previous paper. 19) It should be noted that all the previous studies [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] were conducted for the purpose of elucidating the elimination behavior of single impurity elements from molten copper. However, from the viewpoint of practical operations, multiple impurity elements coexist in crude copper and will simultaneously react with Na 2 CO 3 slag.…”