Modeling of CaCO3 decomposition under CO2/H2O atmosphere in calcium looping processes

Abstract

Steam is typically present in the calcination step in most calcium looping based processes for CO2 capture. However, its effect on CaCO3 decomposition has received little attention in the literature. This work applied a mathematical model to investigate the mechanism of the effect of steam in CaCO3 decomposition in two different applications (i.e., the typical calcium looping and the HotPSA processes). The HotPSA process is a novel calcium looping based process operating at nearly a constant temperature. The results show that the physical effect of H2O on the calcination rate is negligible. Also, the CaCO3 decomposition in the typical calcium looping process is affected by particle size, gas temperature, and CO2/H2O concentrations, but independent of initial solid temperature. Moreover, the reaction rate is less affected by H2O at 950°C when its concentration exceeds 5%, indicating that additional steam injection is redundant. Furthermore, the calcination mode in HotPSA is significantly affected by particle size and steam temperature. The energy loss analysis suggests that the calcination mode should operate at 600°C with 6mm CaCO3 particles. The findings would be helpful in optimizing the operating conditions for the calcium looping process and minimizing energy loss in the HotPSA process.