CFD Simulation Study on Mixing Experiment of Anaerobic Digestion Tank

Abstract

The anaerobic fermentation produces biogas with the participation of sensitive microorganisms. The smooth fermentation needs to ensure good heat transfer and mass transfer effects. Stirring is very important to create these fermentation conditions. In this paper, the computational fluid dynamics method is used to simulate the flow field inside a fully-mixed stirred anaerobic reactor. It is divided into a single-layer six-leaf open-type turbine with baffles and two-layer four-leaf inclined 45-degree paddles. Group conditions, and quantitative calculation and analysis of the internal flow field of the simulated reactor. The effects of different blades and different stirring speeds are investigated. The results show that the double-layer oblique upward paddle can produce a better axial velocity distribution, which is more conducive to the formation of a large fluid loop structure that circulates up and down. The average speed of double-layer agitation at 125-320 rpm is less than the average speed of a single layer, but the speed of double-layer agitation at 60 rpm is greater than the speed of a single layer.