Investigation of fluid dynamic in a scale-down laboratory digester

Mixing is a crucial process in biogas plants and is required to maintain uniform concentrations of biomass in the digester. However, mixing requires high energy inputs and hence energy efficient design and operation of the mixing process is of vital importance. At the design stage the shape, number and placement of stirrers are important decision variables. At the operational stage the rotational speed and the switching sequence are important to guarantee substrate uniformity whilst avoiding unnecessary over-mixing. In our laboratories at the Technische Hochschule Ingolstadt we set-up a 1:12 scale digester model. The digester is made of transparent plexiglass allowing us to carry out optical measurements.