Oxidizing Roasting of Sulphide Copper-Nickel Concentrate: Thermodynamic Simulation

The process of oxidizing roasting of sulphide concentrates in fluidized bed furnaces finds a wide application when it comes to the processing of sulphide copper, copper-nickel and pyrite concentrates. The roasted product is then smelted or hydrometallurgically processed. The literature describes results of various laboratory studies and the industrial practice of sulphide roasting. This paper focuses on the thermodynamic modelling of roasting process in application to copper-nickel concentrate. Thermodynamic modelling was done with the help of the FactSage software. Thus, the simulation for coppernickel concentrate was performed in the temperature range of 300–1,200 oC and at lgpO2 from –20 to –2. Areas are shown where possible products of roasting – i.e. sulphates, oxides, sulphides and non-ferrous metals – can exist. The simulation results show that sulphates of non-ferrous metals tend to form in the low temperature region, and the region of their existence tends to move towards higher temperatures as the oxidizing power of the gas phase rises. Oxide phases (including ferrites) were observed in the medium temperature region, while sulphide and metallic phases existed at the upper limit of the temperature range studied. The simulation results were compared with the data obtained after actual roasted products had been examined by means of scanning electron microscopy and X-ray microanalysis. It is obvious that roasting processes can be simulated based on the bulk thermodynamic equilibrium assumption. It is established that the FactSage algorithms and databases for oxidation process simulation deliver coherent results. Thus, they can be used for building control systems for industrial furnaces.The authors would like to thank L. Sh. Tsemekhman and L. B. Tsymbulov for their contribution to this paper.