Thermal synthesis of black coal fly ash and gibbsite

Abstract

Mullite is an aluminosilicate mineral with exceptional properties, and plays an important role in refractory ware production.

Its occurrence in nature is very rare; it is therefore synthesized from various natural, primary raw minerals (sillimanite, andaluzite, cyanite, etc.), but the main source is kaolinite.

The process of mullite formation is connected with the transformation of alumina minerals into 3 Al2O3SiO2. The effectiveness of transformation of aluminum compounds into mullite is not adequate to the theoretical content of Al2O3 in the material. The transformation process depends on the presence of mineralizers, temperature, time of firing, etc.

The aim of this work was the assessment of potential uses of energetic waste including such components as Si and Al. To correct the material composition, an Al additive in the form of gibbsite was used. This study also investigated the influence of different mixture ratios of fly ash and gibbsite, and the influence of trans­formation temperature on the phase composition of the prepared mullite type composite.