Granular flows are extremely important for the pharmaceutical and chemical industry, as well as for other scientific areas. Thus, the understanding of the impact of particle size and related effects on the mean, as well as on the fluctuating flow field, in granular flows is critical for design and optimization of powder processing operations. We use a specialized simulation tool written in C and CUDA (Compute Unified Device Architecture), a massive parallelization technique which runs on the Graphics Processing Unit (GPU). We focus on both, a new implementation approach using CUDA/GPU, as well as on the flow fields and mixing properties obtained in the million-particle range. We show that using CUDA and GPUs, we are able to simulate granular flows involving several millions of particles significantly faster than using currently available software. Our simulation results are intended as a basis for enhanced DEM simulations, where fluid spraying, wetting and fluid spreading inside the powder bed is considered. (C) 2010 Elsevier Ltd. All rights reserved.