Immersion Calorimetric Method to Study Lime Surfaces Impurities and Particles Aggregate Morphologies

Abstract

A new application of the immersion calorimetric method has been developed to study the specific wetting heat of colloidal lime particles dispersed in liquid paraffin. This method, combined with SEM, EDAX and Hg porosimeter measurements, allows to evaluate the effects of the limestone impurities on the shape of the limes particles aggregates. These morphologies are dependent upon the limestone thermal decomposition conditions and upon the impurities of the limestone rocks. The impurities that influence the shape of individual and agglomerated limes particle, according to this study, are SiO2 and Al2O3, in percentages at least of 0.24 wt% and 0.12 wt% respectively. At the temperature of 1300°C these oxides, combined with CaO, they can form a viscous liquid-like phase that changes dramatically the shape of the lime particles. Rhombohedra or irregular grains of about 0.4–3 μm, change their shape into flat and large crystallites of 10×10×1 μm. For the platelet microstructure, the specific exothermic heat ξ [J/m 2 ] is equal to –8 ±2 J/m 2 , while, for the aggregates of rhombohedric grains, is in the average –0.9 ±0.1 J/m 2 . From a technological point of view this study can be used to optimise the thermal decomposition conditions of limestone rocks with a proper content of silica and alumina oxides.