Modeling of the carbonation behavior of a calcium based sorbent for CO2 capture

Calcium based sorbents are effective for CO2 capture. In this work, a modified grain size model has been developed to simulate the carbonation behavior of a calcium–magnesium based sorbent used for CO2 capture in the calcium looping process. The sorbent particle is comprised of CaO fine particles supported on porous magnesium oxide (MgO) (CGMG) framework. The model is based on the reversible reaction between CaO and CO2 and can predict the overall calcium oxide (CaO) conversion and temperature variation inside the sorbent particle under the calcium looping conditions. The overall conversion obtained by the model shows good agreement with experimental data. The effect of several parameters is also numerically analyzed on the dynamics of CaO conversion inside the particle. The conversion of CaO mainly depends on particle size, reaction temperature, CaO content and its porosity for this particular CGMG sorbent. The carbonation reaction does not generate a significant temperature increase inside the particle with a maximum increment of below 20 K. Moreover, the CGMG particle carbonation shows a two stage control behavior while the heat transfer due to convection is significant.

► A modified grain size model for the carbonation of a calcium based sorbent.
► Particle size, reaction temperature, porosity and CaO content dominate conversion.
► Carbonation is under chemical reaction control in the initial stage.
► Two stage behaviors can be explained by the reduction of the radius of CaO grains.
► Convection heat transfer is significant during carbonation.