Development of energy efficient mixing strategies in egg-shaped anaerobic reactors through 3D CFD simulation

ABSTRACT

This work describes a 3D computational fluid dynamic model, which characterizes the hydrodynamic behavior of a mixing strategy applied to egg-shaped reactors that lack a mechanical stirring device. The model is based on Navier-Stokes and material balance equations without a chemical reaction. To describe the behavior of mixing, initial water feed flows of 6, 7.5 and 9 mL s⁻¹ were used. An experimental validation was subsequently carried out using a pulse technique, with NaCl as a tracer. The residence time distributions were quantitatively determined. Then, the degradation process of the wastewater sludge was characterized by studying the time dependence of the dynamic viscosity, the concentration of volatile solids and the density of wastewater sludge. The data resulting were introduced into the validated model, and five feed flows from 9 to 13 mL s⁻¹, the best performance found was with feed flow of 11 mL s⁻¹.

KEYWORDS:

• 3D CFD
• egg-shaped reactor hydrodynamics
• mixing
• rheology

Funding

Juan M. Méndez-Contreras, Eduardo Hernández as well as the entire team of Instituto Tecnológico de Orizaba and Universidad Veracruzana acknowledge the PhD scholarship from Dirección General de Educación Superior Tecnológica (DGEST) No. 20120000590. In addition, they acknowledge the support of the project financed by DGEST with registration number 4591.12-P.