Comparison of mixing efficiency of different impellers for agitation of slurry in anaerobic digester

Adequate mixing is one of prominent factors which can enhance the biogas production. Uniform distribution of velocity and viscosity at lower impeller speeds is biggest challenge. Correspondingly, in this study CFD simulations of Rushton turbine, anchor impeller and disc mixer were carried out using SC tetra program. The rotational speed of the mixers was kept between 40 to 100 rpm. The average velocity of the slurry particles in case of Rushton turbine, anchor impeller and disc impeller were noted as 0.054, 0.091 and 0.14 ms−1 respectively. The results demonstrated that the disc mixer performed best as compared to other impellers in terms of better distribution of velocity and lesser number of dead zones. Lower mixing intensities are best to enhance biogas production rates in actual experiments by using appropriate impeller geometry and lower rpm.