Abstract

Refractory linings used in incinerators for energy production have to adapt to the energy transition, where fossile fuels tend to be replaced by biomass, exposing the lining to different ranges of chemical compositions. The use of alternative combustibles impacts the life expectancy of the refractory products due to corrosion reactions, whose complexity originates in the variety of the biomass sources. Andalusite, Al2O3-Cr, or SiC based refractory products have been heretofore used in incinerators, however refractory containing hibonite (CaO·6Al2O3) could be an alternative, because of its high refractoriness and high resistance against alkali attack. This work aims to describe and understand the chemical resistance brought by the presence of hexaaluminate of lime in a Low Cement Castable (LCC).

In order to outline the degradation mechanisms induced by biomass, this study focuses on the impact of wood ash and aims to understand the effect of its main oxides, namely CaO, SiO2 and K2O on the high temperature corrosion. Therefore, model slags were synthetized to isolate the influence of the different chemical species and enable the comparison with the effects observed by corrosion with the original wood slag. The reaction of hibonite with the model slags were characterized by means of in situ HT-XRD performed on the ground refractory powder mixed with the slag. Furthermore, hibonite raw materials were conserved in molten slag at high temperature in order to study the dissolution behavior through post-mortem SEM examinations performed on quenched microstructures. The crucible test was performed on a formulation of LCC designed with the hibonite raw materials, whose grain size ranges from 0-3 mm, to evaluate the resistance to reactive infiltration of a calcium hexaaluminate based refractory product.

Due to its high chemical resistance against different biomass slag compositions, the use of hibonite in the formulation of refractory castables could be a solution to prevent early breakdown of refractory lining, with high performance against the aggressive environment of biomass incinerators.