Lightweight design of bauxite-SiC composite refractories as the lining of rotary cement kiln using alternative fuels

To meet the demand of energy-saving and adapt to the change from coal to the alternative fuel in the rotary cement kiln, bauxite-SiC refractories were fabricated by the incorporation of silica sol coated lightweight mullite aggregates in order to achieve low thermal conductivity and superior alkali vapor attack resistance simultaneously. Furthermore, the mechanism of resistance to alkali vapor attach was investigated by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM). Results showed that the thermal conductivity of bauxite-SiC specimens decreased gradually with increasing amounts of silica sol coated lightweight mullite aggregates while changes in the alkali vapor attach were not detectable. The shell-covered structure with a silica sol coating on the surface of lightweight aggregates hindered alkali vapor diffusion into the aggregates at high temperature. Bauxite-SiC refractories possessed lower thermal conductivity, superior alkali attack resistance and higher mechanical properties compared with the specimens which contained pristine lightweight aggregates.