Investigation of mechanisms for heat transfer and reaction in indirectly heated CaCO3 thermochemical energy storage based on CFD-DEM

Abstract

Thermochemical energy storage (TCES) based on calcium looping is currently one of the most promising heat storage technologies. In this work, the heat transfer and reaction mechanisms of CaCO3 in TCES are revealed using a developed CFD-DEM coupled with thermochemical reaction model. The results show that an incomplete consideration of radiation modeling significantly affects heat transfer and calcination reaction. Wall conduction and radiation are the dominant heat transfer mechanisms, while chemical reaction also plays a significant role. The performances and pathways of heat transfer and reaction in the splash zone, the wall region and the intermediate region of the dense phase zone are given detailed insights. The intensive radiation in the splash zone results in excellent heat transfer performance. Heat transfer is predominant in the wall region, driven by wall conduction and radiation. The intermediate region is dominated by chemical reaction with poor heat transfer performance. The state parameters along the trajectory of particle are analyzed, showing that heating effectiveness and flow behavior of particle significantly influence the TCES process. The movement of particle clusters demonstrates that heat transfer rates in bubble phase exhibit sharp fluctuations compared to the emulsion phase, highlighting the significant impact of bubble dynamics on heat transfer and calcination reaction.