Reaction performance of CaCO3/CaO thermochemical energy storage with TiO2 dopant and experimental study in a fixed-bed reactor

The CaCO3/CaO reversible reaction pair is a promising thermochemical energy storage (TCES) technology for concentrating solar power (CSP) plants. However, the reaction performance and cyclic stability of this reaction pair is compromised because of sintering. In this study, TiO2-doped in CaCO3/CaO TCES system are systematically investigated by synchronous thermal analyzer (STA). The reaction kinetics of decarbonation process with and without TiO2 doping are compared in N2 and CO2 atmospheres. Furthermore, the performance of CaCO3/CaO TCES system is analyzed in a fixed-bed reactor for future application. It is found that doping TiO2 can improve the anti-sintering ability and cyclic stability of CaCO3, and the optimal doping ratio is 2.5 mol %, whose energy storage density is 1256.68 kJ/kgsample at first and improved by 2.26 times after 30 cycles. Moreover, doping TiO2 decreases the activation energy and initial decarbonation temperature in CO2 atmospheres. In exothermic experiments of fixed-bed reactor, the maximum exothermic temperature difference is 309.83 °C at 550 °C, and the highest absolute temperature reaches 848.7 °C at 750 °C. TiO2 dopant promotes the decarbonation at lower temperature, and obtains a higher overall conversion (0.506) at 850 °C. Overall, CaCO3 with TiO2 dopant is of great significance for future industrial and commercial applications. © 2021