Experimental study and modeling of CaO carbonation: Effects of operating conditions on the carbonation behaviors of the calcined limestone particles

Thermochemical energy storage has received wide attention recently due to its high energy storage density and power cycle efficiency. However, most researchers focus on synthesizing new calcium-based heat storage materials, and there is still a significant knowledge gap on the effects of operating conditions on the carbonation behaviors of the calcium-based particles. In this study, the effects of carbonation temperature, CO2 concentration and raw particle size on the carbonation rate, conversion ratio and particle diameter were experimentally investigated. The results showed that the carbonation rate peaked between 873 K and 973 K, and it decreased at 1023 K due to sintering. Increasing the CO2 concentration from 15 vol% to 50 vol% enhanced the carbonation rate, while the promotional effect was weaker at higher CO2 concentrations. The maximum conversion ratio of the CaO particles was independent of the CO2 concentration, and the particle diameter increased by 7.3 % after the carbonation process. Additionally, a carbonation model was developed and validated by the experimental results. Simulation results revealed that increasing the raw particle size from 0.1 mm to 0.5 mm caused the carbonation reaction to transition from a kinetic-controlled regime to a diffusion controlled regime, significantly reducing the carbonation rate.