Sintering Effect of Al and a Boron Source in High-Alumina Nano-Bonded Refractory Castables
Petrochemical refractory end-users face difficulties in finding commercial products with optimized thermo-mechanical properties for the low operational temperatures (<900°C) in fluid catalytic cracking units. Blending colloidal binders with sintering additives in castable compositions is an interesting alternative that may overcome the limited densification of conventional cement-bonded systems. This work investigated the effects associated with use of Al and/or boron sources added to high-alumina colloidal silica-bonded castables sintered at temperatures up to 1000°C. In situ measurements of hot elastic modulus and hot modulus of rupture, and XRD and SEM analyses were performed to explain the reaction mechanisms and phase evolution associated with Al and boron-based compound performance at high temperatures. The test results indicate that added boron induced formation of Al4B2O9 and generated liquid phase in the microstructure of the castables. Aluminium powder was oxidized (giving rise to alumina), which resulted in increased castable stiffness. This latter transformation was only observed in colloidal silica-containing compositions. The best thermo-mechanical performance in the 600–815°C range was obtained for castables containing both Al and boron.
Keywordscastable colloidal silica sintering additives alumina
Unable to display preview. Download preview PDF.
- Bittencourt, L.R.M., Fernandes, M.R., Da Silva, S.L.C., Rulff, B.M.: The effect of coke deposition on the mechanical and thermomechanical properties of dense and insulating castable used in FCC units, In Proceedings of UNITECR 2003, (2003) 549–552Google Scholar
- Luz, A.P., Braulio, M.A.L., Pandolfelli, V.C.: Refractory castable engineering. 1st Ed. Baden-Baden: Goller Verlag, (2015) 157–245Google Scholar
- Parr, C., Simonin, F., Touzo, B., Wohmeyer, C., Valdelievre, B., Namba, A.: The impact of calcium aluminate cement hydration upon the properties of refractory castables. In Proceedings of TARJ Meeting (2004) 1–17Google Scholar
- Ismael, M.R., Dos Santos, R.D., Salomão, R., Pandolfelli, V.C.: Colloidal silica as a nanostructured binder for refractory castables. Refractories Applications and News 11  (2006) 16–20Google Scholar
- Braulio, M.A.L., Morbioli, G.G., Medeiros, J., Gallo, J.B., Pandolfelli, V.C.: Nano-bonded wide temperature range designed refractory castables. J. Amer. Ceram. Soc. 95 (2012)  1100–1104Google Scholar
- Pileggi, R. G., Pandolfelli, V. C., Paiva, A.E., Gallo, J.: Novel rheometer for refractory castables. Amer. Ceram. Soc. Bull. 79 (2000)  54–58Google Scholar
- Pickett, G.: Equations for computing elastic constants from flexural and torsional resonant frequencies of vibration of prisms and cylinders. Proc. Amer. Soc. Testing Mater. 45 (1945) 846–865Google Scholar
- Siljan, O. J., Rian, G., Pettersen, D.G., Solheim, A., Shøning, C.: Refractories for molten aluminum contact, Part I: thermodynamics and kinetics, In Proceedings of UNITECR 2001, (2001) 531–550Google Scholar