a University of Innsbruck, Unit of Environmental Engineering
Discharging cattle manure as the waste of the livestock activities to the environment has resulted in biological and chemical contamination and methane emission that has concluded major large-scale impacts, such as global warming. Thus, anaerobic digesters are utilized to eliminate harmful micro-organisms, which occur in the cattle manure, in a chemical and organic process in absence of Oxygen. For improving the efficiency of anaerobic digester, it is necessary to mix all the feedstock within the tank of the digester, properly. In this study, the aim is to model the agitation of the material within an anaerobic digestion tank with a mixer established for stirring cattle manure in a livestock yard; and also is to analyze stagnant volume formation and velocity gradient. The CFD model is steady-state and rheological properties of the feedstock is considered. RNG turbulence model is employed and SIMPLE algorithm is used to achieve velocity and pressure field. The results are validated comparing the power consumption of the mixer with the CFD results. Therefore, it is concluded that the employed procedure is suitable to predict the behavior of the cattle manure feedstock in the digester.