Modeling Mixing in Anaerobic Digesters with Computational Fluid Dynamics Validated by Experiments

To keep biogas production competitive against alternatives in the energy sector, operating costs of biogas plants must be reduced. Up to 50 % of the energy consumption in biogas plants is contributed by mixing of biomass slurry. Thus, optimization of the mixing system is a promising approach to increase the overall efficiency of biogas plants. Investigations to find the optimal conditions of mixing are challenging in full-scale biogas digesters. Two main strategies to study biomass mixing in laboratories are to build a scale-down digester using an artificial substrate to mimic biomass, and to develop a computational fluid dynamics (CFD) model to simulate the mixing process. In this paper, a combined approach is carried out: a CFD model is presented and verified experimentally.