Fluidized beds play an important role in various engineering fields. To model these systems numerically, CFD coupled with DEM is widely used. However, the CFD-DEM approach is computationally very demanding. As for today, it is restricted to lab scale reactors with only a limited number of particles. Coarse grain approaches with coupled CFD-DEM have become popular over the last years to address the aforementioned issue. Particles of the original system are summarized into so-called grains. Thus, the number of particles can be reduced drastically, giving the opportunity to calculate industrial scale reactors in a realistic time frame . The goal of the coarse grain approach is to mimic the original system precisely. A very common approach for coarsening the particles is to assume the conservation of energy from the original to the coarse grained particle system. Thus, the forces in the system must be scaled in an appropriate way. An important parameter for scaling in coarse grained DEM is the coarse grain factor, which is the ratio of the grain radius to the particle radius: This study investigates first how coarse graining influences force predictions in mono- and bidisperse systems on a lab-scale. Various collision force models are evaluated against fine-scale CFD-DEM simulations. Additionally, drag forces are examined, with a brief assessment of sub-grid correction models designed to account for unresolved meso-scale structures. While such models can improve accuracy, they often lack generalizability across process conditions. The core focus of this work is the extension of coarse-grained CFD-DEM to simulate an industrial-scale bubbling fluidized bed. This transition from lab to industrial scale presents significant challenges, including altered flow regimes, broader particle size distributions, and scale-dependent instabilities. Furthermore, model assumptions valid at small scale such as homogeneous bed behavior often break down in large systems. By systematically varying operational parameters in the simulations, this study highlights the limitations and potentials of coarse-grained CFD-DEM for industrial applications. The final large-scale simulation is compared against experimental results and the lab-scale conclusions, providing critical insights into model transferability, accuracy, and the practical readiness of coarse-graining strategies for industrial deployment.