Corrosion resistance mechanism of postmortem corundum-mullite refractories used in hot stoves

ABSTRACT Alkali attack of aluminosilicate refractories has been a long-term problem in the industry. In this paper, XRD, SEM, and CT scanning methods were used to analyze the phase and structure characteristics of postmortem corundum-mullite refractory used in hot stoves for more than 10 years, and the anti-corrosion mechanism of the refractory was explored. Results show that the corundum-mullite refractory after long-term corrosion by hot stove gas maintains excellent physical properties, and its cold compressive strength can still reach 92.7 MPa. The mullite network formed by the interpenetration of short columnar mullite endows the corundum-mullite refractory with excellent resistance to gas corrosion: Under the working conditions of the hot stoves, mullite network plays a role in dispersing impurities in refractory, so that the CaO entrained in hot stove gas can be transformed into high melting point CAS2 instead of low melting point phase with high Ca content in the working layer of refractory; CAS2 has good resistance to alkaline gases such as K2O(g) and Na2O(g), and the blocking of pores in the working layer of refractory by CAS2 finally makes the refractory free from the corrosion of hot stove gas.