Corrosion behaviour of chromium-free ceramics for liquid slag removal in Pressurized Pulverized Coal Combustion

The corrosion behaviour of HfO2, HfSiO4, ZrSiO4, NiAl2O4 and, for comparison, a commercial Cr2O3-containing ceramic was investigated under Pressurized Pulverized Coal Combustion (PPCC) conditions at 1450 °C in the presence of liquid slag. Although Cr2O3-containing ceramics show sufficient corrosion resistance, they have the main disadvantage of vaporisation of toxic Cr(VI)-species. Among the investigated chromium-free ceramics, HfO2 and HfSiO4 showed relatively good corrosion resistance in laboratory investigations. The stability of the latter one depends not only on the microstructure of the ceramic but also on the slag composition. Technically produced ceramic balls of HfO2 and ZrSiO4 performed very well in the liquid slag separator of a PPCC test facility.