A horizontal rotating tumbler provided with internal baffles and containing a mixture of two types of particles is investigated by discrete element method (DEM) simulations. The main objective of this study is to characterize the dynamics of a rotary kiln containing spherical steel balls and wood particles, investigating the effect of internal baffles and wood chip particle shape on segregation. The results show that the presence of baffles imposes a cyclic behavior to the solid bed and that the magnitude of this cyclic behavior depends on the solid holdup. The wood particle shape effects are analyzed considering two different approaches: a spherical approximation and a multisphere approximation. The differences between these two approaches are mitigated at relatively high velocity. This type of simulation can also serve for baffle sizing.