Thermodynamic Evaluation of Distribution Behaviour of Arsenic in Copper Smelting

Abstract

Distribution behaviour of minor elements has important implications for copper making processes. The arsenic distribution among the three phases of gas, slag and matte was evaluated thermodynamically and is described in this article.
The arsenic distribution is basically dependent on the process factors such as the arsenic content of charge, the amount of waste gas, the degree of vapour saturation with arsenic or temperature. The thermodynamic quantities such as the activity coefficient of arsenic in matte, the activities of iron and copper, SO₂ or O₂ potentials and the ratio of arsenic distribution between slag and matte phases L_As^s/m are decisive factors for the arsenic distribution, and the behaviours in various smelters could be explained systematically and reasonably by considering changes in these quantities during smelting.
In oxidizing smelting at 10.1 or 101.1 kPa (0.1 or 1 atm) SO₂, the proportion of arsenic in gas phase is predominant in both the smelting and the converting stages, the degree of vapour saturation with arsenic seriously affecting the distribution behaviour. The arsenic content of final matte does not change too much even if the content of charge or of starting matte increases substantially. Furthermore, the proportion of arsenic in matte does not decrease appreciably even if L_As^s/m gets extremely large.
In reducing smelting at 10⁻¹¹ of p_O2, the proportions in gas and slag phases decrease remarkably, owing to a small activity coefficient of arsenic in matte and also to extremely small L_As^s/m.