2012 Volume 52 Issue 10 Pages 1801-1808
An investigation was carried out on recycling spent refractories comprising of Al2O3–12.9%C refractory substrate after 30 minutes of interactions with molten iron at 1823 K. XRF results showed that the spent refractory was contaminated with iron (0.798 wt%). Spent refractories in 10, 20 and 30 wt% proportions were mixed with virgin refractory composition of Al2O3–10%C. High temperature interactions of recycled refractory substrates with liquid iron were investigated at 1823 K to understand chemical reactions occurring in the metal/refractory interface as well as in the bulk of the refractory. The sessile drop technique was used to determine the interfacial wetting behaviour and the phase transformations during interactions with molten iron were determined using SEM and EDS. These investigations determined the role of spent refractory constituents which contains degraded alumina, carbon and iron. The presence of iron and reactive alumina in the refractory substrates was seen to affect both physical and chemical interactions, contact angles and carbon pick-up. The drop in contact angles was in direct correspondence with an increase in carbon pickup. The structural integrity and bonding of the recycled refractory was also compromised, and interfacial cracks were observed along with increases in the interfacial area of contact of metal droplet with refractory. Video images also showed whisker formation on metal droplets during 30 minutes of reaction time. The results from this study have shown that metal contaminated spent refractories tend to enhance refractory degradation during recycling and therefore may be unsuitable for steelmaking applications.