Study of Industrial Copper Matte Converting Using Micrography and Thermochemical Calculations

The converting of copper matte after the smelting process is one of the main steps in the copper-making industry. This work used microstructural analyses of samples collected at different stages of converting and thermochemical calculations to study a real converting batch in a Peirce-Smith converter at Atlantic Copper. The transformation of matte and slag produced during the converting was studied. The use of thermochemical calculations allowed a simulation of non-standard process conditions that provides valuable additional information on converting. The examined non-standard conditions were slag blow carried out in a single blow, the influence of the Fe/SiO2 slag ratio and over-oxidation at the end of the copper blow in the converting process. The micrographical investigation showed two predominant phases formed in the matte matrix after slow cooling, and their proportion varied along the slag blow. The slag presented two fayalitic olivine phases with different Fe/SiO2 ratios, the most abundant being the one with a higher Fe/SiO2 ratio. Magnetite crystals were identified in slags, and some of them were surrounded by fayalitic olivine. The analytical data of samples show that the measured copper in the slag is higher than in the theoretical thermochemical calculations. This indicates that the physical entrainment of matte/copper droplets in slag prevents a complete separation of the matte from the slag (residence time, agitation by blowing and viscosity). The final slag produced at the end of converting contains a high copper content, wherein copper is distributed after slow cooling into cuprite (Cu2O) and delafossite [(Cu,Fe)O] phases.