Thermally induced carbonation of Ca(OH)2 in a CO2 atmosphere: kinetic simulation of overlapping mass-loss and mass-gain processes in a solid–gas system

Abstract

Thermally induced carbonation of Ca(OH)₂ in a CO₂ atmosphere is a reaction exhibiting particular features, including stoichiometric completeness to form CaCO₃ and a kinetic advantage over the carbonation of CaO particles. This study aims to gain further insight into the reaction mechanisms of CO₂ capture by Ca(OH)₂ and CaO. It focuses on the kinetic modeling of the carbonation of Ca(OH)₂ as a consecutive reaction in a solid–gas system. The kinetic behaviors of the thermal decomposition of Ca(OH)₂ in an inert gas atmosphere and of the overall process of thermally induced carbonation of Ca(OH)₂ in a CO₂ atmosphere were investigated using thermal analyses and other complementary techniques. Based on kinetic results, the overall reaction of the thermally induced carbonation of Ca(OH)₂ in a CO₂ atmosphere was separated by a kinetic deconvolution analysis into two consecutive reaction steps: the thermal decomposition of Ca(OH)₂ and the subsequent carbonation of the CaO intermediate. The relationship between the two component reaction processes was well illustrated by a consecutive shrinkage of the dual reaction interfaces of Ca(OH)₂–CaO and CaO–CaCO₃. The continuous supply of water vapor and CO₂ to the CaO–CaCO₃ interface from different directions was suggested to be the physico-geometrical advantageous feature of the carbonation of Ca(OH)₂.