Caractérisation hydrodynamique des réacteurs anaérobies produisant du biogaz et fonctionnant en batch et en continu

Abstract : This work is devoted to an in-depth study on the anaerobic process for wastewater treatment and sewage sludge treatment in order to intensifier the biogas production. Firstly, the hydrodynamic in an internal circulation (IC) reactor was characterized by experimental simulation. The relative importance of the three phases is ordered as gas > solid > liquid for the liquid circulation velocity. The bubble size affects not only the shear rate but also the types of interaction between bubbles and granules. Then the effect of mean shear rate was investigated in an anaerobic stirred tank reactor. With the increase of mean shear rate, the flow rate of biogas passes through a maximum at the shear rate of 6.8 s-1, while the methane content decreases continuously. The deformation of granules is induced by shear stress and collisions; nevertheless the granules’ density remains unchanged. At micro-scale, a local deformation in the shape of crater located at the extremity of biogas channel was detected for the first time. The cater diameter is proportional to the size of gas exit pore, and the compression pressure of the microbubble estimated by the Young-Laplace equation compares favorably with the mechanical resistance of granule measured by penetrometry. Finally, the study focused on the rheological properties of the highly concentrated digested sludge. A shear thinning behavior with a yield stress and a viscoelastic property were characterized. The effect of solid content is much more significant than that of temperature. Furthermore, the experiments of a sphere impacting on the highly concentrated digested sludge were carried out to reveal its transient dynamics. A simplified drag force model was established to estimate the elasticity modulus and the impact viscosity
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Jian Kai Jiang. Caractérisation hydrodynamique des réacteurs anaérobies produisant du biogaz et fonctionnant en batch et en continu. Alimentation et Nutrition. Université de Lorraine, 2014. Français. ⟨NNT : 2014LORR0142⟩. ⟨tel-01751145⟩

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