Effect of steam on heat storage and attrition performance of limestone under fluidization during CaO/CaCO3 heat storage cycles

Abstract

In a CaO/CaCO₃ heat storage system, steam as a calcination medium can be easily separated from CO₂. In this work, the exothermic process of the calcined limestone was simulated with a CFD–DEM model, and the effect of steam on heat storage and attrition performance of the limestone was tested in a bubbling fluidized bed reactor. The results show that under the same carbonation atmosphere, the limestone calcined under steam exhibits better heat storage performance but worse attrition resistance than that calcined under CO₂. After 10 cycles, the effective conversion and attrition rate of the limestone calcined under steam and carbonated under CO₂ are 0.3 and 1.39 μm per cycle, respectively. The attrition rate drops to 1.2 μm per cycle when 20% CO₂ is introduced into the steam calcination atmosphere after 10 cycles. Furthermore, the introduction of the low-concentration steam in the carbonation atmosphere increases the effective conversion of the limestone, but it decreases the exothermic temperature. A mixture of high-concentration steam and CO₂ is suitable as a calcination atmosphere, which provides a simple way for gas separation for a CaO/CaCO₃ heat storage system.