REACTION OF COPPER MATTE DROPLETS WITH AN OXIDIZING SLAG

Abstract

<p>Reaction kinetics of copper sulphide matte (Cu₂S) with an oxidizing slag was investigated. Silica-saturated fayalite (2FeO.SiO₂) slag was synthesized by melting powder mixtures of iron, silica and hematite with respective ratios of 1:2:3.6 at high temperatures. Experiments were performed in an inert atmosphere using a high-temperature furnace equipped with X-ray fluoroscopy and pressure transducer. The effect of temperature (1400 – 1475 °C) and matte droplet size (0.5 – 2 g) on desulphurization rate was evaluated. Chemical titration was performed on quenched slag samples synthesized at different temperatures in order to determine the amounts of Fe²⁺ and Fe³⁺ in the slags. Slag/matte samples quenched from high temperatures were extensively analyzed by means of optical microscope as well as scanning electron microscope (SEM), the latter equipped with an energy dispersive X-ray spectrometer (EDS). EDS analysis of the quenched samples showed that some areas of pure Cu were formed inside the matte droplets. It indicated that desulphurization reaction indeed has taken place and copper was formed as the product. In addition, EDS showed that some Fe-rich areas were formed inside the matte droplets. Gas halo formation around the droplets was confirmed by X-ray fluoroscopy observations. Additionally, it was seen that dome-like bubbles formed during high-temperature experiments on top of the matte droplets with mass equal to 0.75-gram or larger. In contrast to Fe-C metal droplets in contact with oxidizing slags, no droplet swelling was detected in this study. Reaction kinetics investigations showed that initial desulphurization rate increased with increasing temperature and matte droplet size. In fact, it was shown that rate increased linearly with matte droplet surface area. Finally, mass transfer in the slag phase and mass transfer in the gas halo formed around the droplet were found to be the rate-controlling mechanisms prior to and after gas halo formation, respectively.</p>