The carbonation behaviors of K2CO3 generated by calcination of KHCO3 were investigated with a pressurized therm gravimetric apparatus, and the shrinking-core model in the noncatalytic heterogeneous reaction systems was used to explain the kinetics of the reaction between K2CO3, CO2, and H2O using analysis of the experimental breakthrough data The carbonation reaction process can be divided into two stage-controlled regions, one is the surface chemical reaction-controlled region at the initial stage and another is the internal diffusion-controlled region at the last stage. The total amount of carbonation conversion is mainly dependent on the first stage. The reaction rate of this stage decreases as the reaction temperature increases. It increases in the same temperature when the CO2 and H2O concentrations increase. The total carbonation conversion decreases as the pressure increases. On the basis of the Arrhenius equation, the apparent activation energy and pre-exponential factor for these two stages are calculated, when the temperature is in the range of 55-80 degrees C and the pressure is 0.1 MPa. They are 33.4 kJ/mol and 3.56 cm/min for the surface chemical reaction-controlled region and 99.1 kJ/mol and 4.01 x 10(-22) cm(2)/min for the internal diffusion-controlled region. This paper provides theoretical basis for the further study on the capture of CO2 from flue gas using dry potassium-based sorbents.