Abstract: The decomposition kinetics of 4 different limestones in air and 81% air-19% CO2 atmosphere have been investi- gated respectively.Results showed that the decomposition of limestones in air followed one-dimensional phase boundary reac- tion model G（α）=α.While in 81% air-19% CO2 atmosphere，the kinetic model of decomposition was nucleation and growth model G(α)=-ln(1-α).Under a higher CO2 partial pressure，the decomposition of limestone was delayed which led to the in- crease of initial decomposition temperature by 200 ℃ and the increase of activation energy by three times.Furthermore，when the particle size was big enough，the activation energy will get smaller.The presence of MgCO3 accelerated the decomposition of CaCO3.The appropriate particle size for the decomposition of limestone in 81% air-19% CO2 atmosphere was less than 0.105 mm， with the optimum temperature of 890 ℃.

Key words: limestone, kinetics, carbon dioxide, magnesium carbonate, thermogravimetric analysis