Study of Decarbonation of CaCO3 for High Temperature Thermal Energy Storage.

In order to develop a high temperature heat storage and temperature upgrading system using the CaO/CaCO3 reaction, decarbonation of CaCO3 has been carried out with thermogravimetry in the ranges of 1073–1193 K and 3–55 kPa.Calcium carbonate virtually did not decompose under the condition where the partial pressure of CO2, P, is higher than half of the equilibrium decomposition pressure of CaCO3, Pe. It implies that the present heat storage system has to be operated in pressure regions lower than half of Pe. Most decarbonation occurred during the chemical reaction-controlling period. A rate expression, employing a fractional pressure term, (Pe – P)/Pe, is proposed for the reaction-controlling period by assuming the presence of a reaction intermediate. It is found that the dependency of pressure on reaction rate is non-linear, and the reaction is strongly influenced by the change in P.