Discrete element method (DEM) is widely used in industrial and environmental applications for numerical modelling of mixing and transport of lumpy materials. However, it is computationally expensive for a large number of particles. To reduce this cost, we have implemented a revision approach for traditional coarse graining as proposed by Bierwisch et al. J. Mech. Phys. and Solids, 57, 31, 2009. We introduce the use of variable coarse grain ratio instead of the uniform one to provide faster computation compare to the traditional coarse graining giving more flexibility to reduce the number of particles. To overcome the problem of violation of geometrical similarity derived from this method, we implement a correction parameter to measure overlap distance between parcels containing small and large particles. The results show fairly good agreement between the revision model, reference DEM simulations and the experimental data of W. Sui et al. Nature Sci. Reports, 7, 8, 2017. Display omitted •Introducing a faster alternative tool for poly disperse granular flow simulation.•The simulation results are validated with respect to experimental data.•Better accuracy in particle distribution compare to traditional coarse graining.•Providing a prediction method for the revision parameter.