Mechanism for the Reduction of Oxides in Copper-Smelting Slag under Blowing with CO–CO2 Gas Mixtures
А. А. Komkov, Р. И. Камкин
Abstract
A mechanism is proposed for the joint reduction of oxides from multicomponent copper-smelting slag when they are blown with CO–CO2 gas mixtures and an algorithm is developed for its implementation in the form of a mathematical model. The first feature of the proposed mechanism is that the total rate of the overall reduction process is determined by CO consumption in the course of its interaction with oxygen ions formed owing to the dissociation of slag oxides. The second feature is that the equilibrium between the slag, alloy, and gas phase is achieved in accordance with the oxidation potential of the system occurring at each moment of time. It is shown that there is a satisfactory agreement between the calculated and experimental data obtained in the course of the reduction of the industrial copper-smelting slag at a temperature of 1300°C and at a ratio of CO/CO2 = 4, 6, and 156. In this case, a first-order kinetic equation is valid with respect to the difference between the initial and equilibrium CO content in the gas phase. A generalized rate constant for the reduction of multicomponent slag has been calculated amounting to k = 2.6 × 10–7 molCO/(cm2 s%) at a temperature of 1300°С. It is shown that, under the reduction of industrial multicomponent slag, the reduction rates for copper oxide and magnetite are rather high, being close to the maximum value at the very beginning of the slag blowing with the reducing gas. At the same time, the reduction rates for ferrous oxide and for the oxides of zinc and lead in the first minutes of the process are insignificant and exhibit a gradual increase before reaching a maximum, after which they again decrease almost to zero values as the system approaches the equilibrium between the supplied gas and the melt. In general, the reduction rate of oxides decreases when the equilibrium between the initial gas and the liquid phase is approached, and this should be taken into account when organizing the processes of continuous slag depletion.