To cite this version:Lydie Rouchon, LoÏc Favergeon, Michèle Pijolat. Analysis of the kinetic slowing down during carbonation of CaO Keywords:Carbonation, Calcium oxide, Kinetics, Porosity, TG Abstract:In order to improve the capture capacity of CaO-based sorbents, it appears important to understand the mechanism of calcium oxide carbonation and to get details on kinetic law controlling the reaction, which has not been really studied up to now. To investigate this mechanism, CaO carbonation kinetics was followed by means of thermogravimetric analysis (TG) on divided materials, of textural and morphological characterizations and of an original kinetic approach devoted to look for the rate-determining step controlling the reaction rate.In order to better describe the reaction mechanism, the influence of intensive variables such as carbonation temperature and CO 2 partial pressure were investigated. TG curves obtained under isothermal (450-650°C) and isobaric conditions (2-30 kPa) show a strong slowing down of the conversion leading to incomplete reaction. This slowing down and the fractional conversion at which it appears depend on carbonation temperature and CO 2 partial pressure.To explain these results, particular attention has been paid to the evolution the textural properties of the solid during processing. The solid powder consists of porous aggregates in which the porosity changes along the reaction due to the difference in the molar volumes of CaO and CaCO 3 .Temperature jumps during TG experiments have put in evidence a complex kinetic behavior since three distinct domains must be distinguished, over all the conversion range, whatever 32 2 the temperature and CO 2 pressure could be. The discussion of the results emphasizes the role of the porosity on the kinetic non-Arrhenius behavior observed in the second domain.

To cite this version:Lydie Rouchon, Loïc Favergeon, Michèle Pijolat. A new kinetic model for the rapid step of calcium oxide carbonation by carbon dioxide. Journal of Thermal Analysis and Calorimetry, Springer Verlag, 2014, 116 (3) Keywords:Carbonation, Calcium oxide, Kinetic modeling, TG AbstractCarbonation of solid calcium oxide by gaseous carbon dioxide was monitored by thermogravimetry (TG). A kinetic model of CaO carbonation is proposed in order to interpret the first rapid step of the reaction. By taking into account the existence of large induction period as well as the sigmoidal shape of the kinetic curves in this kinetic-controlled region, a surface nucleation and isotropic growth kinetic model based on a single nucleus per particle is proposed and the expressions of the fractional conversion and the reaction rate versus time are detailed. The induction period is found to have a linear variation with respect to temperature and to follow a power law with respect to CO 2 partial pressure. The areic reactivity of growth decreases with temperature increase, and increases with CO 2 partial pressure increase. A mechanism of CaCO 3 growth is proposed to account for these results and to determine a dependence of the areic reactivity of growth on the temperature and the CO 2 partial pressure.