Corrosion of phosphate added high-chrome refractory materials in an entrained-flow gasifier

Durability of the refractory liner located in an entrained-flow gasifier is one of the main factors affecting the efficiency and cost of gasification process. This study investigates the corrosion mechanism of phosphate added high-chrome refractories in a commercial entrained-flow gasifier and the effect of phosphate additives on the improvement of service life combining thermodynamic simulation calculations. The microstructures, chemical compositions, and mineral phases of the corroded samples were analyzed by scanning electron microscopy (SEM and EDS) and X-ray powder diffraction (XRD). The results demonstrated that chemical corrosion mainly occurred at the slag-matrix interface and the junction of aggregates and matrix regions. Complex spinel solid solutions were formed at the slag-refractory interface. Phosphate additives decomposed into gaseous products (such as O₂, P₂O₃) and diffused into the interior of refractories at or close to the slag-refractory interface, not only causing an oxidizing environment but also increasing the phosphate contents in the interior of refractories. Phosphate additives in the infiltration layer occupied the gaps between crystal grains of (Cr, Al)₂O₃ solid solutions, reduced the infiltration of silicate phases, and absorbed Ca and Na in the slag, which subsequently increased the viscosity of the slag.