Towards chrome-free lining for plasma gasifiers using the CA6-SiC castable based on high-temperature water vapor corrosion

Abstract This paper focuses on the water vapor corrosion mechanisms of calcium hexaluminate (CA 6 )-SiC, SiC, and MgAl 2 O 4 -Cr 2 O 3 castables. The weight and linear change, mechanical performance, sintering properties, and pore-size distribution of the three castables were investigated before and after corrosion. Morphologies, chemical bonds, and phases were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) respectively. Thermodynamic analysis was used to explain the chemical reaction during corrosion. The results show that the CA 6 aggregates remain stable after 1000 °C × 100 h in wet air. However, SiC and Cr 2 O 3 can react with the wet air. First, SiC reacts with O 2 to form SiO 2 , then the siloxane network (Si-O-Si) of the SiO 2 can be corroded to form silanol groups (Si-OH). The MgAl 2 O 4 -Cr 2 O 3 castable exhibits weight loss and forms large pores after vapor corrosion because Cr 2 O 3 reacts with H 2 O (g) and O 2 (g) to form CrO 2 (OH) 2 (g).