Optimizing entrained-flow reactors for biomass gasification: a novel framework for controlling slag–refractory interactions and enhancing durability

Biomass-fed entrained-flow reactors are promising for syngas production, but slag formation and refractory degradation remain major challenges for their reliable operation. This study investigates the coupled effects of biomass ash chemistry, slag phase evolution, heat transfer, and slag–refractory interactions, with particular emphasis on the cold-crucible concept. Thermodynamic modelling and laboratory-scale experiments were combined to characterize inorganic species transformation, slag liquidus temperature, and the interaction of miscanthus-derived slag with silicon carbide (SiC) refractory. Alkali- and chlorine-containing species were found to play a major role in deposit formation, with KCl identified as a potentially corrosive species. The experimentally determined liquidus temperature of miscanthus ash was approximately 1230 °C, compared with 1324 °C predicted by thermodynamic calculations, highlighting limitations in existing databases for alkali-rich systems. At 1300 °C, molten slag caused limited SiC infiltration and dissolution, with penetration restricted to approximately 100 µm. Under a controlled thermal gradient, a stable 8 mm solid slag layer developed, providing thermal protection to the refractory. The liquid slag/solid slag and solid slag/SiC interfaces stabilized at 1231 °C and 1130 °C, respectively, corresponding to a heat flux of 12.9 kW m −2 . These results support the potential of cooled SiC linings and self-forming slag layers for improving wall stability and provide a basis for optimizing reactor operating conditions.