Mechanisms of SiC Refractory High Temperature Corrosion by Molten Salts (Na,K,Ca,Cl,S) in Waste to Energy Facilities

Damage of SiC oxide bonded refractories in waste-to-energy facilities (WtE) has been characterized. Different phenomena were observed: wear by slag phases, volume expansion of tiles and fracture in different locations. These results are in agreement with laboratory experiments. The role of gas composition and tiles temperature profile on deposit composition, on condensation of gaseous alkali chloride and on formation of liquid phase inside the porosity of the refractories has been emphasized. Gaseous alkali species are involved, not only in the formation of liquid phases, but also as a precursor of cristoballite formation around the SiC grains as well as in the rich alumina-silica matrix. On the hot face of the refractories, oxo-reduction reactions produce the formation of wollastonite. Post-mortem analysis after several thousand hours of operation point to three main corrosion mechanisms: