Investigation of in-situ Chemical Reactions of Al₂O₃-SiC-SiO₂-C Refractory and Its Interactions with Slag

Abstract

Experiments were carried out to investigate in-situ reactions of refractory and its interactions with slag (composition: 45.4%SiO₂+36.6%CaO+15.9%Al₂O₃) using a horizontal furnace by detecting CO and CO₂ contents in off gas with an infrared (IR) analyzer. The composition of refractory is 69.4%Al₂O₃+7.3%SiO₂+10.6%SiC+12.7%C. Temperature was from 1 773 to 1 873 K. The samples after high temperature experiments were analyzed using X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM)-Energy Dispersive Spectrometer (EDS). Mullite was detected after refractory samples were maintained at high temperatures. The refractory/slag reaction was evaluated by calculating the carbon removed. Carbon removal process was a two-step reaction, in the beginning the carbon was removed very quickly (fast reaction stage) and both CO and CO₂ gases were detected by IR analyzer. Then after around 2 000 s the reaction slowed down and no CO₂ gas could be detected (slow reaction stage). The main in-situ reaction product was SiC rather than SiO. Slag showed good wetting with the refractory and penetrated into it through pores. Low melting point compounds, anorthite (CaAl₂Si₂O₈) and gehlenite (Ca₂Al₂SiO₇) were detected after heating refractory for 7 200 s while remaining in contact with slag.