Kinetic investigation and numerical modelling of CaCO3/Al2O3 reactor for high-temperature thermal energy storage application

• Published in: Solar energy Vol. 241; pp. 262 - 274
• Main Authors: Mathew, Arun, Nadim, Nima, Chandratilleke, Tilak. T., Paskevicius, Mark, Humphries, Terry D., Buckley, Craig E.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 15.07.2022
• Subjects: Calcium carbonate; Numerical modelling; Reaction kinetics; Thermochemical energy storage; Thermochemical energy storage; Numerical modelling; Calcium carbonate; Reaction kinetics
• ISSN: 0038-092X; 1471-1257
• DOI: 10.1016/j.solener.2022.06.005

•Carbonation reaction kinetics of limestone-based CaCO3/Al2O3 mixture is estimated.•Numerical modelling of CaCO3 based reactor for thermal storage application is performed.•The influence of operating parameters on the reactor's performance is examined.•The effect of incorporating graphite fin into the CaCO3 reactor is studied. This study conducts kinetic analyses of the carbonation reaction of CaCO3 (doped with Al2O3) as well as parametric analyses of the performance of a thermochemical reactor, which can act as a thermal battery. Kinetic measurements of CO2 release and absorption were carried out using thermogravimetric analysis (TGA) at 815, 830 and 845 °C on a CaCO3/Al2O3 sample that had been previously cycled over 500 times. The rapid reaction kinetics revealed that the Avrami nucleation growth model with exponent 3 fits well to explain the carbonation reaction. The numerical study considered a cylindrical reactor with a height and diameter of 100 mm. According to numerical analysis, at an applied CO2 pressure of 1 bar, increasing the thermal conductivity of the reactor bed from 1.33 to 5 W/m.K increases the rate of carbonation reaction by 74%. When the applied CO2 pressure is increased from 1 to 2 bar, the performance of the reactor bed with thermal conductivity of 1.33 W/m.K improves by 42%; however, when the applied CO2 pressure is increased from 2 to 3 bar, the performance improves by only 18%. Additionally, when the boundary temperature of the reactor was lowered by 30 °C, performance was enhanced by 43% at an applied CO2 pressure of 1 bar. This study also examined the effect of using a graphite fin as a heat extraction system. The graphite fin allowed for more rapid heat extraction and increased the carbonation reaction by 44% in the reactor bed with poor thermal conductivity (1.33 W/m.K) but had no effect in the reactor with modest thermal conductivity of (5 W/m.K) due to its ability to already transfer heat effectively to the reactor shell.