CFD Simulation of Mixing by Maxblend Impeller in a Lab-Scale Anaerobic Digester

Abstract

Mixing is the most prominent factor, undeviatingly determines the consequences of an anaerobic digester with higher solid content. This paper presents the Computational Fluid Dynamic model using Ansys SC tetra software that characterize the mechanical mixing by maxblend impeller in an anaerobic digester. Effect of impeller geometry is studied on the flow pattern, dead volume and particle velocity distribution. Geometry of maxblend is analyzed along with varying mixing speeds of impeller. Mixing was analyzed at three different speeds i.e. 40, 80 and 100 rpm. It was observed that higher mixing intensity resulted in increased particle velocity. Uniform distribution of velocity was observed and mixing speed of 80 and 100 rpm seems optimal. This paper recommends the strategy for modelling mechanically mixed slurry at lab scale. Keyword: anaerobic digestion, mixing, CFD, maxblend impeller Acronyms CFD Computational fluid dynamics K Consistency index AD Anaerobic digestion MI Marine impeller RPM Revolution per minute AI Anchor impeller RT Rushton turbine PI Pelton impeller HR Helical ribbon HEB High efficiency blade DFB Disc mounted flat blade TS Total solid