CaCO3 decomposition for calcium-looping applications: Kinetic modeling in a fixed-bed reactor. (November 2020) - Scaltsoyiannes, Athanasios
Highlights: Intrinsic reaction kinetics parameters were obtained for CaCO3 decomposition. A non-linear effect of CO2 partial pressure was observed in a fixed-bed reactor. Different particle models were used to describe limestone's decomposition. CaCO3 decomposition follows a two-stage Langmuir-Hinshelwood mechanism. The validity of the kinetic model was checked in a wide range of conditions. Abstract: Calcium looping can be used in various environmental applications such as post-combustion CO2 capture, sorption-enhanced reforming and thermochemical energy storage. The calcination reaction mechanism and the effect of CO2 partial pressure have not been fully clarified yet justifying further efforts; this work focuses on kinetic modeling of the reaction. Herein, calcination kinetics of limestone were studied experimentally in a fixed-bed reactor, and theoretically using different models previously reported in the literature. The Uniform Conversion Model (UCM) and the Changing Grain Model (CGM) described better the conversion-time data than the Random Pore Model (RPM). A Langmuir-Hinshelwood mechanistic model, which included the decomposition of CaCO3, the desorption of CO2 and the CaO* relaxation fitted well the reaction rate values leading to an activation energy of 210 kJ/mol and the pre-exponential factor equal to 18, 860 kmol/(m 2 s). The model was validated by predicting adequately the decomposition rates measured by other authors under different conditions.