In BOF steelmaking process, high-activity lime has been widely used to form an appropriate slag as a medium for the removal of non-volatile impurities from the hot metal treated. In recent years, however, great attention has been paid to the possibility of directly using limestone instead of lime in the furnace. Despite laboratory experiments and industrial trials have proven the feasibility of the technique, a list of underlying issues still require more considerations, e.g., thermodynamics and kinetics of steelmaking reactions and limestone evolution during blowing under the new condition. The main motivation behind this paper is to establish a kinetic model for limestone decomposition under BOF steelmaking condition on the basis of shrinking core hypothesis. The Kozeny-Carman equation that correlates pressure gradient with the corresponding velocity is integrated into the model in order to account for the CO₂ flow through the lime layer packed with small grains. The model is demonstrated using a set of experimental data and is finally verified by comparing the obtained thermal conductivity and grain size with available values in the literature.