For the calcination of CaCO3 under CO2-containing atmospheres, a mathematical model taking into account the CO2-catalyzed sintering of the CaO product layer is developed. In this model, a modified shrinking core model is coupled with a population balance-based sintering model. By comparing model predictions with experimental data, it is found that CO2 strongly affects the overall calcination rate both at high temperature and CO2 partial pressure, since under these conditions CaO densification considerably reduces the effective diffusivity of CO2 within product layer. It is observed that for large particles, the CO2-catalyzed sintering of CaO can produce the die off phenomenon, which takes place when the reaction stops due to the blockage of pores within product layer. Finally, it was determined that limestone impurities do not significantly affect the calcination reaction under atmospheres containing CO2, because CO2 causes a much greater increase of the CaO sintering rate than limestone impurities do. (c) 2018 American Institute of Chemical Engineers AIChE J, 64: 3638-3648, 2018