Evaluation of hydraulic mixing performance in a full-scale anaerobic digester with an external liquid recirculation system using CFD and experimental validation

Rosario Arnau, Javier Climent, Raúl Martínez-Cuenca, Jorge Rodríguez, Sergio Chiva

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6 Scopus citations

Abstract

Anaerobic digestion (AD) has become an essential process for sludge treatment and its optimum performance is related to its mixing degree. In this study, a full-scale Anaerobic Digester (ADer) with an external recirculation mixing system was studied via single-phase 3D-CFD simulations to assess the influence of recirculation flow and a 3-blade propeller. The model was validated with inert tracer tests. The design and mixing parameters were studied to characterise the mixing efficiency in different scenarios. The design parameters were assessed first, but wide deviations from the recommended values were found. Local mixing parameters were found to be useful for defining the degree and type of mixing, and are highly recommended in the CFD studies of ADers. A second-order statistical moment was proposed as a global mixing parameter to describe geometrical and local mixing, and to state a reliable homogenisation time.

Original languageBritish English
Article number117392
JournalChemical Engineering Science
Volume251
DOIs
StatePublished - 6 Apr 2022

Keywords

  • Anaerobic digester
  • CFD
  • Homogeneity
  • Mixing degree
  • Tracer

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