Rheological behavior of slag-melilite suspensions in pyrometallurgical secondary lead smelter systems

Pyrometallurgical processes often operate at subliquidus temperatures, making it essential to understand the rheology of slag-solid suspensions, which significantly impacts various phenomena such as metal droplet settlement and slag tapping. However, the individual effects of solid particle characteristics, such as volume fraction, size, and aspect ratio (AR), remain poorly quantified at high temperatures due to difficulties in isolating single variables under harsh experimental conditions. While some high-temperature studies have explored the role of AR, they often did so without accounting for the particle size, limiting the understanding of how these parameters interact. This study addresses this gap by systematically investigating the combined influence of particle size and elongation on rheological behavior. This study presents a reliable viscosity dataset for slag-melilite suspensions, focusing on the influence of melilite particle elongation compared to equiaxed spinel. All melilite-containing samples showed shear thinning, demonstrating that this phenomenon is multifaceted and requiring the consideration of both the particle size and AR, as known in the basic rheological theory. While previous high-temperature studies examined the role of AR, they often overlooked the combined influence of particle size, which this study explicitly addresses. Melilite particles exhibited more pronounced shear thinning than similarly sized spinel particles, attributed to their elongated shape and stronger alignment of individual particles within the fluid. Additionally, melilite samples showed greater viscosity increase with rising particle fractions compared to spinel samples, reinforcing the role of particle elongation in viscosity behavior. Experimentally obtained micrographs after rheological measurements further confirmed the alignment of melilite particles with the flow direction.