Kinetics of the carbonation reaction of an SrO-Al2O3 composite for thermochemical energy storage

In framework of the thermochemical energy storage (TCES) in concentrating solar power (CSP) applications, great attention is focused on the SrCO/SrO system, which is characterized by remarkably high theoretical volumetric energy density (4 GJ m) and working temperatures (1200 °C). It has been shown that the incorporation of AlO in the SrO/SrCO system can successfully hinder the sintering and agglomeration phenomena, thus improving the performances of the system. Aiming at providing useful information for the design, simulation and scale up of a reactor for the energy storage, besides the multicycle carbonation conversion, the evaluation of the reaction kinetics is crucial. Thus, in this work, the kinetics of the carbonation of a SrO-AlO composite (34%wt of AlO) for TCES-CSP has been investigated for the first time using a two-stage kinetic model. In particular, tests have been performed in a thermogravimetric analyzer at operating conditions relevant for TCES, namely at 1 atm of CO partial pressure within the temperature range of 900-1050 °C. The reaction rate, the intrinsic carbonation kinetic constant, the characteristic product layer thickness and their dependence on the temperature has been evaluated in the temperature range 900-1000 °C; the activation energy has been found to be 52 kJ mol. Finally, comparison of the calculated conversion-time profiles, obtained from the applied kinetic models, with experimental data revealed a good agreement.