Friedman method kinetic analysis of CaO-based sorbent for high-temperature thermochemical energy storage

Abstract

A CaO-based sorbent synthesized using the Pechini method is shown to have improved stability and cyclability over commercial calcium carbonates and other Ca-based sorbents for thermochemical energy storage and other chemical looping processes under N2 and a 100%–CO2 atmosphere. The improved performance is ascribed to the greater surface area and smaller grain and particle sizes of the synthesized material. A modified isoconversional approach (the Friedman method) was used to model the kinetics of the decomposition and carbonation reaction under different atmospheres. The model accounts for the dependence of the reaction rate on equilibrium pressure under different atmospheres, including a CO2 atmosphere similar to reactor conditions. For calcination, values of energy of 164 kJ mol−1 (under N2) and 307 kJ mol−1 (under CO2) were found for the calcination of Pechini-synthesized CaCO3. For the carbonation of the synthesized CaO, approximate values of 200 kJ mol−1 (25% v/v CO2) and 450 kJ mol−1 (100% CO2) were obtained for the activation energies of the chemical reaction regions. Further research into Pechini-synthesized Ca-based sorbents with supports will be carried out to further improve energy storage density and cyclic stability of sorbents.