Evaluation of the physical and thermal properties of refractory ceramics produced with rice husk ash and calcined alumina

ABSTRACT

The rice husk appears as a by-product of great importance for energy generation due to its high calorific value, as well as the ashes resulting from the burning process which are rich in silica. The main objective of this assignment was to evaluate the effects of the incorporation of rice husk ash and calcined alumina on the physical and thermal properties of refractory ceramics. The raw-materials were characterized in terms of chemical composition by X-Ray Fluorescence, phase composition, by X-Ray Diffraction. The physical properties investigated were apparent porosity, water absorption, bulk density, linear retraction and mass variation. The thermal properties evaluated were thermal shock resistance at 500 ºC and thermal conductivity. The rice husk ash used in this research confirmed its potential as a ceramic precursor in the development of silicate refractories. After sintering, the presence of the cristobalite, alumina-α, mullite and quartz phases was observed. With the addition of 10 % of rice husk ash, there was an increase in the linear retraction of the ceramics. The apparent porosity, water absorption, thermal conductivity and thermal shock resistance increased with the addition of calcined alumina, in particular in the percentage of 30 %. The modifications in properties can be explained by the increase in porosity and the phases, in particular alumina-α. Resistance to thermal shock and thermal conductivity showed acceptable values for use in the steelworks industry.

Keywords
rice husk ash; calcined alumina; refractory ceramics; physical properties; thermal properties