Optimising flow and mixing in a full-scale gas-mixed anaerobic digester by integrating sludge rheological data using computational fluid dynamics

Gas-mixing is commonly applied in anaerobic digesters, yet the resulting flow and hydraulic mixing are difficult to evaluate because of limited full-scale experimental data uncertainties integrating sludge rheological data. This study used computational fluid dynamics (CFD) assess impact treated rheology on characterisation a biogas-mixed digester. The CFD model, which was firstly validated using lab-scale setup, showed that predictions depended properties, especially at low shear rates. predicted dominant rate out effective shear-rate range Ostwald leading performance overestimation. results indicated there limitations applying model conventional approaches for determining dead-zone. Herschel-Bulkley more appropriate prevailing rates large viscosity gradients digester, indicating two distinct compartments with different behaviour based gas-sparging height: plug-flow compartment vertical convection above, dead-zone considerable segregation below. induced insufficient mixing, but contributed well-functioning To correctly should be agreement type Our indicate digester must increased various options achieving this proposed.