Synthetic coal slag infiltration into varying refractory materials

The infiltrations of synthetic coal slag into 99%Al ₂O ₃, 85%Al ₂O ₃-15%SiO ₂, and 90%Cr ₂O ₃-10%Al ₂O ₃ refractories with a temperature gradient induced along the penetration direction were compared to one another. The infiltrating slag was synthesized with a composition that is representative of an average of the ash contents from U S coal feedstock. Experiments were conducted with a hot-face temperature of 1450°C in a CO/CO ₂ atmosphere. Minimal penetration was observed in the 90%Cr ₂O ₃-10%Al ₂O ₃ material because interactions between the refractory and the slag produced a protective layer of FeCr ₂O ₄, which impeded slag flow into the bulk of the refractory. After 5 h, the 99%Al ₂O ₃ sample exhibited an average penetration of 12.7 mm whereas the 85%Al ₂O ₃-15%SiO ₂ sample showed 3.8 mm. Slag infiltrated into the 99%Al ₂O ₃ and 85%Al ₂O ₃-15%SiO ₂ refractory systems by dissolving the respective refractories' matrix materials, which consist of fine Al ₂O ₃ particles and an amorphous alumino-silicate phase. Due to enrichment in SiO ₂, a network-former, infiltration into the 85%Al ₂O ₃- 15%SiO ₂ system yielded a higher viscosity slag and hence, a shallower penetration depth. The results suggest that slag infiltration can be limited by interactions with the refractory through the formation of either a solid layer that physically impedes fluid flow or a more viscous slag that retards infiltration.