Development and testing of sensor-based stirring systems in biogas plants to increase efficiency and process stability in load-flexible and demand-oriented biogas production
Topic
Efficient stirring in biogas plants is still a challenge: On the one hand, the material in the fermenter must be stirred to distribute the added substrates in the tank and to ensure a stable fermentation process. On the other hand, intensive agitation leads to high internal power consumption and impairs methane production due to mechanical stress. This dichotomy is further aggravated with regard to flexible biogas production when large amounts of substrates are added to the digester within a short period of time. So far, no practicable technical solution is available that can reliably and automatically detect the stirring requirement in the tank and derive the optimum stirring settings. Decisions to date have been made mainly on the basis of experience and by looking at the digestate surface.
Goals
Building on the "OptiFlex" and "FlexFeed" projects, the digesate rheology is being characterized in greater depth in "Sens-O-Mix", and the mixing is being optimized in laboratory and by means of CFD. Within the project, one of the two fermenters of the research biogas plant of the University of Hohenheim at Unterer Lindenhof was equipped with extensive sensor technology to determine the stirring requirements of the plant during constant and load-flexible operation. Self-learning methods are used to identify suitable parameters for the stirrer control and to quantify the influence of the pozess parameters on the methane yield. The existing models for the prediction of (flexible) biogas production are to be further developed and coupled with the measured variables obtained. The simulations and models will be validated and the stirrer control and the overall process will be evaluated by practical trials at Unterer Lindenhof.
