The application of the discrete element method (DEM) for industrial process simulation is often limited to two-dimensional slot models for the purpose of reducing the number of particles and hence the computational effort. In this work, a three-dimensional (3D) sector model is proposed with circumferential periodic boundary conditions (PBC) to represent a full 3D model for cylindrical geometries. Two typical processes, i.e. hopper flow and piling, are used to test the sector model. This reveals that the simulated flow features in the 3D sector model with suitable PBC are consistent with those in the full 3D model qualitatively and quantitatively. The proposed sector model can be generally used to investigate granular flow in a full 3D cylindrical geometry in the DEM simulation.