• Henao, Hector M.
• Jak, Evgueni
• Ushkov, Leonid A.

Abstract

This experimental study is a part of a collaborative research program between The University of Queensland and Kazzinc metallurgists aimed at optimisation of the Isasmelt copper smelting process currently being commissioned. Thermodynamic modelling of the copper smelting process performed using the FactSage computer package is experimentally validated and calibrated. A number of key thermodynamic parameters, in particular, liquidus temperatures and minor elements distribution between copper smelting slag and matte in the range of conditions of interest to the industrial process are experimentally determined. The laboratory and thermodynamic modelling results are then validated and calibrated against actual industrial process through targeted sampling and expert analysis study.The experimental methodologies are based on the use of high temperature equilibration at controlled temperatures and gas atmospheres followed by quenching and direct measurements of phase compositions using Electron Probe X-ray microanalysis (EPMA) with Wave-length Dispersive Detectors. This general experimental approach has been further significantly developed in this study to enable the slag / matte equilibria to be accurately measured at a given targeted matte grade. The slag / matte samples were equilibriated on a primary phase substrate (trydimite or spinel). The oxygen partial pressure PO2 was iteratively adjusted by mixtures prepared from pure gases to obtain the targeted matte grade close to the 60 wt pct Cu at fixed sulfur dioxide partial pressures PSO2. Liquidus temperatures, compositions of the matte and minor elements distributions were obtained from direct EPMA measurements of phase compositions in quenched samples. Special procedures involving vacuumed silica ampoule were developed and applied for investigation of distributions of the volatile minor elements such as As and Pb.The effects of variations of slag composition on slag liquidus temperature were evaluated using linear interpolation of the experimental results. The slag liquidus temperatures in the tridymite and spinel primary phase fields have then been constructed as binary plots vs Fe/SiO2 at fixed CaO=3.3, Al2O3=0.9 and ZnO=2.0 wt % in equilibrium with a matte of 60wt pct Cu grade for temperatures 1160 to 1200 0C at PSO2 of 0.28 atm. Experimental results for the distribution of As, Pb and Zn between matte and slag as a function of PO2 were obtained. These data are essential for appropriate adjustments into thermodynamic model.The next essential step is the implementation of the laboratory and theoretical thermodynamic modelling results into industrial process optimisation. This part of the research program is frequently overlooked, but is important and requires high level of research expertise to identify the actual conditions in the real process and relate them to the laboratory and theoretical tools. Both the industrial process analysis and the calibration relative to the results of the advanced research tools are crucial for the application to the actual copper smelting reactor. For this purpose, a series of quenching experiments directly from the tapped slag and matte streams were conducted with temperatures measured by disposable dipthermocouples at the time and in the place of sampling. Special precautions were made to ensure the slag and matte were not altered during sampling so that the quenched samples closely represent the compositions and phases in the slag and matte streams at the time just before the sampling. Expert analysis of the microstructures, phase morphologies,compositional profiles at microscopic level and other features in the industrial samples was performed with optical and scanning electron microscopy and with EPMA. This advanced analysis enabled the actual processes taking place in the reactor to be evaluated, examined and “de-convoluted”. This is an essential stage of the implementation of the laboratory equilibrium and theoretical thermodynamic research results that ensures that elemental reactions taking place in the actual process, non-equilibrium and kinetic aspects are evaluated and taken into account.

Topics

• impedance spectroscopy
• microstructure
• phase
• experiment
• Oxygen
• copper
• quenching
• electron probe micro analysis