Determination of the hydration and carbonation kinetics of CaO for low-temperature applications

In this work, the reaction kinetics of CaO were investigated with interest in its application as a sorbent in the sorption-enhanced methanation process. Therefore, hydration and carbonation kinetics were studied under operating conditions analogous to those required by the process (i.e. atmospheric pressure and temperature range between 200 °C and 350 °C). Two different CaO-based materials were considered in this study. The experimental results indicated that a shrinking core model with chemical reaction control successfully predicted hydration and carbonation conversion for both CaO-based sorbents. The activation energy obtained was similar for both sorbents, being 1.69 kJ/mol and 1.76 kJ/mol for the hydration reaction and 22.27 kJ/mol and 21.60 kJ/mol for the carbonation reaction. Additionally, the present study investigated the impact of simultaneous hydration and carbonation reactions. Both sorbents showed a reduction in hydration capacity when CO2 was introduced into the reaction atmosphere due to the formation of a CaCO3 product layer.