Effects of particle size distribution on calcium-looping energy storage characteristics and thermochemical behaviors in fluidized reactor

Calcium looping based on fluidized reactors is promising for large-scale long-duration energy storage and industrial decarbonation. However, the correlation between energy conversion and thermochemical behaviors in the reactor remains unclear, with particle size distribution (PSD) playing a significant role. The aim of this study is to investigate the effect of PSD on energy storage characteristics and thermochemical behaviors in the fluidized reactor. Energy storage and release processes can be categorized into feed, main reaction and reaction completion phases. The energy storage characteristics of different PSD are investigated. 0.1–0.3 mm show rapid heat transfer and stable reaction, but its low reactivity and extremely long conversion time hinder efficient energy utilization. 0.3–0.7 mm exhibit relatively superior heat transfer and reaction performance. 0.7–0.9 mm demonstrate good reactivity but poor temperature uniformity. The thermochemical behavior of different PSD is further revealed. 0.1–0.5 mm is dominated by sintering, and the probability of fragmentation increases above 0.5 mm. In 0.7–0.9 mm, agglomeration dominates due to the highest temperature inhomogeneity. To better match industrial applications, 0.3–0.5 mm requires enhanced sintering resistance, while 0.5–0.7 mm needs to further improve mechanical performance. Moreover, 0.3–0.7 mm shows the highest energy storage density exceeding 1380 kJ/kg, with peak particle temperature exceeding 850 °C and being well-matched to the release process.