Effects of CaCl2 on Cyclic Carbonation-Calcination Kinetics of CaO-based Composite for Potential Application to Solar Thermochemical Energy Storage

Abstract

The calcium looping (CaL) process is a promising thermochemical energy storage option for concentrated solar power systems due to its great advantages of high energy density and low material cost. However, CaO-based sorbents often suffer from continuous degradation in their reversibility due to the formation of a passivation layer and evolution of a sintering effect. In this work, we focused on the effects of CaCl2 as an additive to CaO sorbents with the aim to enhance reversibility by addressing the mass-transfer issue. A variety of CaO-based sorbents with CaCl2 were synthesized, characterized, and examined their reaction patterns during cyclic carbonation-calcination. The experimental results show that the addition of CaCl2 enhances the rate of the carbonation reaction, based on enhanced reactant diffusion. The CaCl2 causes reduction of surface area; however, the addition of MgO effectively delays sintering. Therefore, CaO-based sorbents with CaCl2 and MgO achieved high reversibility with enhanced durability. © 2020