Kinetics of the flash converting of MK (chalcocite) concentrate

The chemical kinetics and mechanism of the flash converting reaction of MK concentrate (approximately 93 pct chalcocite and 7 pct pentlandite) in oxygen-containing atmospheres were determined. The reaction path of individual particles undergoing flash oxidation in a laminar flow furnace was followed by observing the particle temperature and changes in apparent particle diameter with a fast response, two-wavelength pyrometer; and these observations were compared to the predictions of a mathematical model of a single reacting particle. Flash reaction products were examined under a scanning electron microscope to determine chemical composition and particle morphology. A dust generation mechanism was elucidated, whereby preferential evaporation of copper from the surface of the particle leaves it encased in a nickel-rich shell. Continued oxidation of sulfides and metallic copper leads to ongoing particle heating and the generation of gas (sulfur dioxide and copper vapor) which either vents through a rupture or causes catastrophic fragmentation of the nickel-rich shell.