In case of firing pulverized coal in power steam boiler certain fuel preparation process has to be taken in order to ensure stable and optimal combustion in boiler furnace. Before entering furnace low caloric coal is introduced from coal bunker to the coal preparation system where milling/pulverization and drying processes of raw large coal particles are conducted. For the purpose of defining fineness of grinding of pulverized coal mill gaseous mixture at mill outlet is introduced to the separator where large coal particles, separated from outgoing mill gaseous mixture, are recirculated to mill for regrinding. In this paper character of two-phase flow in inertial separator at milling plant in TPP Nikola Tesla Unit B under various operating conditions has been analyzed. The CFD approach has been used for calculating two-phase flow in separators flow domain. Measurement data taken on site along with results of performed heat balance calculations of milling plant have been used for validating calculation model as well as for setting appropriate boundary conditions in CFD model. The CFD calculations has been performed for different positions of all regulating flaps, recirculation rates of gaseous phase and values of specific weight of solid phase in two-phase mixture. For evaluating separators operating performance at different operating regimes changes of milling capacity and fineness of grinding of pulverized coal at separators outlet have been observed. Additionally, deviation rate of trajectories of different-sized particles to the streamlines of gaseous phase has been examined.