Characterization of Accelerated Sole Degradation by Speiss Infiltration in a Flash Smelting Furnace

The infiltration of speiss—a copper—and arsenic—rich metallic phase with a low melting point, high density, and low viscosity—has been identified as the primary cause of accelerated degradation of the sole in the flash smelting furnace at the Chuquicamata Smelter. This study examines the speiss infiltration process in the furnace’s sole refractory bricks, employing optical microscopy, X-ray diffraction, X-ray fluorescence, and SEM-EDS to characterize the infiltrated phases in a comprehensive and traditional “post-mortem” analysis. Microstructural analysis, alongside predictions of liquidus temperature and solidification range for the multicomponent speiss system, enables a theoretical assessment of the infiltration phenomena and the chemical interactions between speiss and oxidized structural constituents of the brick, such as periclase and chromite. Findings reveal that speiss readily penetrates the open porosity of the brick, inducing structural damage due to spalling, with additional chemical interactions proposed. The implications of these observations are discussed for the design of refractory materials that are more resistant to infiltration, including the consideration of alternative chrome-alumina bricks and low-porosity monolithic materials. A technical criterion for selecting refractory materials could be proposed to consider a simple infiltration test using the sessile drop technique. This work provides a scientific basis for improving the durability of the furnace lining and extending its operational life.