Post mortem study of refractory lining used in FCC units

•Post mortem study of refractory lining used in FCC units.•Samples also collected from an unused refractory lining for comparison purposes.•Samples obtained from hot side regions usually show higher volume fractions of coke.•Coke observed in samples collected from used linings is a carbon black-like material.•The presence of coke led to a partial obstruction of the refractory pores.

In this work we performed a structural characterization of samples obtained at the end-of-life of refractory lining used in REGAP #2 FCC unit (Petrobras/Brazil). Samples collected from an unused lining were also used for comparison purposes. They were examined by X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray microtomography (μ-CT), mercury intrusion porosimetry (MIP), Raman spectroscopy (RS), and Fourier transform infrared spectroscopy (FTIR). We observed that alpha- and sodium beta-alumina are the major phases in the samples used in this work. SiO2, CaAl2O4, and CaAl4O7 were observed in significant amounts in samples obtained from an unused lining. Al(OH)3 was detected in minor amounts in these materials. CaAl2O4 and CaAl4O7 were observed as minor components in samples collected from a coked lining. Nonetheless, CaCO3 is present in significant amounts in these materials. Raman tests revealed that the coke observed in samples collected from used linings is a carbon black-like material. It was observed by MIP and μ-CT that the presence of coke led to a partial blockage of the refractory pores. We noticed that samples collected from hot side regions usually show higher volume fractions of coke than those obtained from cold side regions.