Hydraulic modeling of a confined gas recirculation mixing system for a CSTR anaerobic digester
Date
2016
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Abstract
ENGLISH ABSTRACT: Hydraulic numerical rnadelling and experimental werk was used to develop a mixing
system, that is able to satisfy the biologica! requirement of micro bacteria and create
a homogeneaus salution inside the digester.
A review was conducted on the different mixing methods used commercially for
CSTR's as well as the influence of mixing intensity and intervals on anaerobic
digesters. The gas recirculation method, eperating in a two-phase plug-flow regime
mixing method was selected and a one-dimensional explicit, transient numerical
model was developed that could predict the liquid mass displaced by a gas plug. An
experimental study foliowed the numerical rnadelling of the digester mixing system to
capture the effect of various geometrical constructions of the plug-flow generator in
two empirica! equations to predict the mass and frequency of plug released. With
the numerical model and experimental results a full scale mixing system was
developed for a 1 600 m3 digester. The benefits of the proposed mixing system over
the mechanica! draft tube methad include the following: no moving parts inside the
digester, tedious downtime of clogged rotating equipment is eliminated and only
requires 7 % more power per unit volume.
Description
Keywords
Anaerobic digestion (Sewage purification), Digester gas, Gas recirculation, Hydraulic models