Kinetic Insight into the Effect of Self-Generated CO<sub>2</sub> on the Thermal Decomposition of Inorganic Carbonates in an Inert Gas Atmosphere: ZnCO<sub>3</sub> and CaCO<sub>3</sub>
Mito Hotta, Loïc Favergeon, Nobuyoshi Koga
Abstract
This study aims to parametrize the effect of self-generated gas on the thermal decomposition of inorganic solids in an inert gas atmosphere. The kinetics of reversible thermal decomposition should be described as a function of the temperature and partial pressure of the gaseous product in the reaction atmosphere; however, the partial pressure of evolved gas at the specific reaction site is difficult to measure because of the heterogeneous reaction nature. Extrapolation of the universal kinetic relationship established over different temperatures and partial pressures of the gaseous product in the reaction atmosphere to a reaction condition in an inert gas atmosphere is proposed as a possible method for estimating the effect of self-generated gas on such reactions in an inert gas atmosphere. This idea was practically demonstrated, as exemplified by the thermal decomposition of ZnCO 3 and CaCO 3 in a stream of dry N 2 and air. By setting the effective partial pressure of CO 2 ( p (CO 2 )) as a weighted sum of the atmospheric and self-generated p (CO 2 ), a universal kinetic description of these thermal decomposition reactions across different temperatures and p (CO 2 ) values including those in an inert gas atmosphere was achieved, and the contribution of self-generated p (CO 2 ) was parametrized. Furthermore, the change in the contribution of self-generated p (CO 2 ) as the reaction advanced was evaluated by using consecutive surface and phase-boundary-controlled reaction models. The proposed kinetic analysis approach addresses many issues in the conventional kinetic analysis approach and provides detailed kinetic insight into the reversible thermal decomposition of solids.