The chemical CO capture by carbonation-decarbonation cycles.

The abatement of CO emitted from combustion is a hot research topic. Current CO capture techniques of adsorption, absorption, membrane separation and cryogenics involve high investment and operation costs. For moderate and high temperature exhaust gas, carbonation/decarbonation cycles offer an attractive alternative. An objective assessment method (screening index) was applied to select the most appropriate chemical reactions, with MgO and Mg(OH) being screened as having the highest potential. Macro-thermogravimetric experiments determined a CO capture yield between 60 and 70% for Mg(OH) at temperatures between 260 and 330 °C, and from 85 to 98% for MgO at temperatures of 400-440 °C. Reaction rates were measured for both MgO-CO and Mg(OH)-CO. The reaction kinetics are best fitted by the Jander 3D-diffusion approach. The Arrhenius equation is applied to the reaction rate constant, and both its activation energy and pre-exponential factor are determined. Integrating the Jander expression in the reaction rate equation enables to predict the CO-capture conversion for any selected temperature and/or contact time.