Optimization of bioreactor operating conditions using computational fluid dynamics techniques

Abstract

High hydraulic retention times are commonly used in bioreactors, as they provide greater contact time between substrate and biomass. These reactors also operate at low flow rates to minimize damage to the biomass due to shear stress and drag. However, a high flow rate provides greater mixing, and thus the optimal operation condition is difficult to estimate. In this study, the effect of different flow rates on the behaviour of the phases in an anaerobic sequencing batch bioreactor is evaluated numerically. Fluent 15 code was used, considering the two‐phase, transient, and turbulent flow in a three‐dimensional mesh. The turbulence, the drag of the biomass flocs to the recirculation system, and the shear stress in the remaining solids were evaluated. For the reactor evaluated in this study, the flow rate of 189.4 g/s was found to be the most suitable, not only for the operation of the reactor, but also to provide energy savings in the operation of the recirculation pump.

CFD Simulations in Mechanically Stirred Tank and Flow Field Analysis: Application to the Wastewater (Sugarcane Vinasse) Anaerobic Digestion

“…The anaerobic digestion occurs at the mesophilic regime at 37°C. As previously said, it is assumed that the sugarcane vinasse is Newtonian [6] and the fluid is isothermal and incompressible. The rheological properties of the medium are related to the total solid (TS) content of the substrates.…”

“…Viscosity is the term to express the resistance of a fluid to flow and motion. It is assumed that the sugarcane vinasse is Newtonian [6]. In order to model the flows within a digester, it is therefore necessary to know both its technical characteristics (geometry, stirring mode) and the fluid properties.…”

Hydrodynamic Evaluation of Five Influent Distribution Systems in a Cylindrical UASB Reactor Using CFD Simulations

“…Similarly, Wongnoi et al [36] modified a GLSS using a model-based design approach, obtaining a more efficient structure that reduced the premature exit of solids from the reactor. Other studies using the technique have revealed, for instance, the presence of a discontinuity in the flow within the reaction zone [37] or that the water inlet velocity directly relates to the height of the sludge layer [38]. However, there is an information gap on the relationship between IDS configurations and their potential for granule production.…”

A novel quasi plug‐flow reactor design for enzymatic hydrolysis of cellulose using rheology experiment and CFD simulation

“…In addition, high viscosity of lignocellulose slurry constrains mixing results, and the impeller is the main structure that determines the mixing effect and power consumption. Many impeller designs are mainly focused on optimization of height‐to‐tank diameter ratio, impeller types such as energy efficiency on pitched blades, helical ribbon impeller and Rushton and others, and operation conditions like critical stirring speed are investigated . Ahead of developing an appropriate reactor, the rheological properties of the enzymatic hydrolysis slurry should be studied .…”

“…Many impeller designs are mainly focused on optimization of height-to-tank diameter ratio, [22] impeller types such as energy efficiency on pitched blades, [23] helical ribbon impeller and Rushton [24] and others, [25] and operation conditions like critical stirring speed are investigated. [26][27][28] Ahead of developing an appropriate reactor, the rheological properties of the enzymatic hydrolysis slurry should be studied. [29] Direct measurement by rheometer and indirect representation by model are two common approaches to characterize the rheology of liquid.…”