Experimental study on pressure effects on thermochemical energy storage performance of TiO2-doped Ca-based materials: From powder to pellet

The pressurization can significantly enhance the thermochemical energy storage performance of Ca-based materials. In this study, detailed experimental investigations were conducted in both fixed bed and fluidized bed on the performance of TiO 2 modified Ca-based materials ranged from 700 °C to 900 °C under pressurized conditions (0.1 MPa to 0.8 MPa) from powder to pellet, including the influence of inert dopants on the properties of CaO powder, the optimization of biomass pore-former agents' selection and the enhancement of pressurized fluidization states on the performance of pelletized materials. The findings indicated that the pressure intensity has a positive correlation with the energy storage density and cyclic stability of TiO 2 modified Ca-based materials. The results demonstrated that the properties of CaO powder intensified with the pressure and the energy storage density was increased by 31.4 % with 5 % TiO 2 doped at 0.8 MPa. And the energy storage performance of the pelletized CaO-5TiO 2 with 10 % bagasse added was also significantly improved at a higher-pressure condition. The energy storage performance of the determined 10B-CaO-5TiO 2 pellet under fluidization conditions at 0.8 MPa was 38.9 % higher than that of atmospheric pressure after 10 cycles. As the carbonation pressure increased, the average grain size of CaO exhibited a decline of 7.0 %, a slighter sintering and deeper reaction region were observed into the determined pellet. Furthermore, the specific surface area and pore volumes of the 10B-CaO-5TiO 2 pellets under high carbonation pressure were 382.8 % and 460.0 % higher than that of atmospheric pressure in the fluidized bed, respectively.