For the calcination of CaCO 3 under CO 2 ‐containing atmospheres, a mathematical model taking into account the CO 2 ‐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 CO 2 strongly affects the overall calcination rate both at high temperature and CO 2 partial pressure, since under these conditions CaO densification considerably reduces the effective diffusivity of CO 2 within product layer. It is observed that for large particles, the CO 2 ‐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 CO 2 , because CO 2 causes a much greater increase of the CaO sintering rate than limestone impurities do. © 2018 American Institute of Chemical Engineers AIChE J , 64: 3638–3648, 2018