Damage Mechanism of High Chromia Refractory in the Slag Tapping Hole of Commercial Entrained-Flow Gasifiers
The service life of refractory bricks in the slag tapping hole of entrained-flow gasifiers is a critical bottleneck for long-term stable operation. This study investigated the damage mechanism of high chromia refractories in four commercial coal-water slurry gasifiers by analyzing gasification coal samples and corroded refractory bricks. Slag characteristics, including crystallization and viscosity-temperature behavior, were evaluated. Results revealed that low-viscosity slag induces more severe refractory damage. To mitigate slag crystallization risk, a safe slag tapping temperature range is recommended as tICT−t2.5 when tICT exceeds t25. Interior morphology of corroded bricks exhibited cracks, primarily attributed to molten slag penetration and subsequent reactions with refractory material. SEM-EDS analysis of slag-aggregate and slag-matrix interfaces identified reduction in Cr2O3 content as the earliest damage characteristic. XRD detected no zirconium-containing spinel in cracks, indicating that thermal expansion mismatch between newly formed phases and the refractory matrix drives crack propagation. A damage mechanism is proposed: initial Cr2O3 depletion compromises both matrix and aggregate, facilitating slag ingress and new phase formation, ultimately leading to structural failure. Early detection or prevention of Cr2O3 reduction is essential to prolong refractory service life.