Pressure Dependence of the Low Temperature Carbonation Kinetics of Calcium Oxide for Potential Thermochemical Energy Storage Purposes and Sustainable CO2 Fixation

Abstract

The pressure effect on the carbonation behavior of CaO as model compound is studied under mild hydrothermal conditions, as relevant to sustainable geological CO2 sequestration and for potential utilization in thermochemical energy storage. Reaction yields are determined experimentally by means of in situ powder X-ray diffraction using CaO powder samples in a controlled reaction with CO2 under gas pressures between 1.0 and 5.0 MPa and at temperatures between 298 and 373 K. The results show a two-step conversion of CaO to CaCO3, involving Ca(OH)2 as a reactive intermediate, with differing influences of the microstructures on the individual reaction sub-steps. A kinetic evaluation of the experimental data delivers a high rate-enhancing effect of temperature on the hydration reaction, whereas the CaCO3 formation is strongly dependent on the available CO2 gas pressure. With this systematic investigation the optimal pressure and temperature conditions for this reaction system can be determined delivering a contribution to a sustainable climate and energy management.