Thesis

Modélisation, optimisation dynamique et commande d’un méthaniseur par digestion anaérobie

Thesis for: Master, Advisor: Grégory François and Monique Polit

ABSTRACT Today, anaerobic bioreactors are high-performance industrial facilities that are able to remove polluted wastewaters of the food-processing industries. Their capability to transform pollutant is interesting on an ecologic and energetic perspective, since biogases are deemed to be renewable energy sources. However, anaerobic digestion is often performed in a suboptimal manner, notably during the starting phases since biomass concentration transitory profiles are not correctly modelled. A tendency model has been developed on the basis of an existing dynamic model to predict independently bacteria in the solution and bacteria that are bound together in a biofilm. Model parameter identification has been performed using data obtained on the bioreactor of the Environmental Biotechnology Laboratory of the INRA of Narbonne. With this tendency model, optimal control profiles have been found, in terms of dilution rate and organic substrate inlet concentration. Applying this optimal profile to the system leads to a reducing of the time needed to reach a pre-specified yield. In addition, dilution rate was used to control the purification yield. This case study raised a good compromise between high purification rate and a significant final time reduction of the start-up phase.

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