Calcite precipitation by a high-pressure CO2 carbonation route

The formation of powdered calcite from slurries containing a calcium source and carbon dioxide (industrial carbonation route) is a complex process of considerable importance nowadays. In the absence of additives, the rhombohedral morphology can be obtained in precipitation processes by using solution routes, but rarely by the industrial method where the most common morphology of precipitated calcite is the scalenohedral one. In this work, the conditions and mechanisms for producing calcite particles with various shapes and sizes have been investigated in a reaction between aqueous calcium hydroxide and compressed carbon dioxide (compressed vapour, liquid or supercritical). Influence of pressure, temperature and reaction time were analyzed. Rhombohedral calcite with a very low degree of agglomeration was obtained under supercritical conditions. The carbonation process was also applied to the in situ precipitation of calcite inside of the pores of cellulose paper.