Ultrasonic flow field measurement in agitated lab-scale reactors for optimization of anaerobic digesters

Abstract

In this article, an ultrasonic flow field measurement is coupled with an evaluation similar to a particle image velocimetry (PIV). This Echo-PIV is executed to evaluate the flow in a mechanical agitated laboratory scaled reactor representing a real-life cylindrical digestion tower. The resulting flow field inside the reactor with the corresponding power demand of the stirring device gives a foundation for energetic process optimization. To represent different amounts of total solids concentration as found in real digestion towers, distinctive mixing ratios of water and glycerol are used. Furthermore, two different agitation devices are investigated with different operation parameters. Findings highlighted the applicability and constraints of an ultrasonic measuring approach for investigating flow fields inside a reactor using low- to high viscous fluids. Both the agitation speed as well as the choice of agitation device have an impact on the overall mixing with predominant influence reached with the latter one.