Corrosion Mechanism of Alumina-Chromia Refractory by SiO₂-Al₂O₃-CaO Based Slag from Iron Capture Process of Spent Automotive Catalyst

Metal smelting-collecting processes have been widely recognized as the prior technology for recycling spent automotive catalysts (SACs), which are generally accompanied by the formation of high content of aluminosilicate slag. Nevertheless, this type of slag can readily cause refractory corrosion and even accelerate its failure. In this work, the slag corrosion resistance of the alumina-chromia refractory was experimentally investigated through static-corrosion experiments. The results showed the refractory can maintain relatively complete shape without breaking after contacting with SiO₂-CaO-Al₂O₃-based slag at 1600°C for 4 h. Furthermore, the corrosion mechanism of refractory in slag was studied. The results indicated the dissolution of refractory component and formation of new phase were the main factors responsible for corrosion of the refractory. The metamorphic layers formed at the interface between slag and refractory accelerate the refractory wear. However, the Cr₂O₃ reacted with MgO and SiO₂ and formed new phases like magnesia chrome spinel, which acted as a protective layer against further corrosion. Moreover, the thermochemical simulation results revealed lower smelting temperature was favorable for improving the slag corrosion resistance of alumina-chromia refractory. This article provides useful information for developing new refractory materials and optimizing slag physicochemical properties and processing parameters of SAC smelting-collection process.