Hydrogen-Assisted Calcination of CaCO ₃ : Kinetics and Mechanistic Insights under Desorption-Enhanced Reverse Water Gas Shift Conditions

High Resolution Image Download MS PowerPoint Slide This study investigates the kinetics of CaCO 3 calcination in H 2 under conditions relevant to the desorption-enhanced reverse water–gas shift (DERWGS) process. Thermogravimetric experiments performed with natural limestone between 600 and 800 °C showed that H 2 markedly accelerates calcination, enabling decomposition at temperatures about 150 °C lower than in conventional calcination environments. As a consequence, the CaO obtained under DERWGS conditions exhibited significantly improved cyclic performance, with nearly double the residual CO 2 carrying capacity of sorbents calcined under standard Ca-looping conditions. For small particles, CaCO 3 conversion followed a homogeneous pattern and was well described by an Avrami–Erofeev kinetic expression with n = 2. The derived kinetic model, which accounts for temperature, H 2 partial pressure, and the thermodynamic driving force associated with the equilibrium CO 2 partial pressure, accurately reproduced conversion curves obtained at different temperatures, calcination cycles, and gas compositions. The apparent activation energy was 184 ± 4 kJ mol –1, consistent with literature values for reductive calcination. CO 2 was the only gas-phase species found to directly inhibit calcination, whereas CO and H 2 O had no measurable independent effect. These findings support a sequential calcination–RWGS mechanism and provide a kinetic basis for the design and scale-up of DERWGS systems for low-carbon lime production and CO 2 utilization.