Woody biomass cofiring with coal at existing pulverized-coal boilers is known to be a green energy source and is a low-expense alternative for pure coal combustion. Co-milling woody biomass particles (15 wt%) with coal particles (85 wt%) before burning at a boiler is a complex problem because large woody biomass particles (> 300 mu m) exit the milling system along with the fine particles. A Computational Particle Fluid Dynamics (CPFD) is used in this paper to present a novel analysis about the behavior of woody biomass particles as they are mixed with coal particles inside the classifier. To meet this objective, a model of SolidWorks of the milling system is defined using the Barracuda VR 17.1.0 software package. We made a C# programming code to analyze the post processing files of this simulation (base simulation); it showed that approximately none of the large particles of woody biomass nor any of the coal particles that exit along with fine particles swirl inside the classifier, and they exit the system in the product stream immediately after getting through the vanes. More importantly, only a few numbers of the exiting particles, regardless of their size, swirl inside the classifier. Manipulation of hardware can improve the classifier performance and leads to changes in the behavior of particles inside the classifier. However, changes in operating conditions cannot improve it significantly. Particle size distribution and the average flow rate of the product stream of the experiment and the base simulation match well.