Fundamental Forces Driving Analogue Sinter Mix Reshaping

Abstract

Major structural change occurs during sintering on melt formation. Melts activate surface forces that drive coalescence processes, as surface energy is reduced. The extent to which coalescence occurs depends on the relationship between surface and viscous forces, which in turn are determined by composition and temperature. In this study, a coal ash fusion furnace was utilised to investigate the impact of composition and temperature on analogue sinter mix tablet reshaping over alumina tiles. Sinter mix compositions were comparable to small size fractions of plant sinter mixes; as they are the first to form melt during sintering operations. A factorial experiment showed basicity to be the dominant driver for reshaping with increasing temperature. Alumina was found to retard reshaping, but only at low sintering temperatures. Material properties, calculated using FactSage and published correlations, were determined as a way to investigate forces acting in the system. Results showed the main determinant of reshaping was apparent viscosity, which was primarily dependent on the amount of melt formed in the sinter mix. The study also used a novel experimental technique, which demonstrated the ability of surface forces to drive reshaping and surface energy reduction when the tablet was suspended from a downward facing tile. This study found that while melt surface tension and wetting behaviour drive system reshaping to reduce surface energy, the extent of sinter mix reshaping was predominately determined by resistance from viscous forces.