MASS TRANSFER IN SYNGAS FERMENTATION BIOREACTORS
Mohsen Karimi & Henrik Ström
Marine Technology and Fluid Dynamics Workshop
March 2020
| 122020-03-16 Marine Technology and Fluid Dynamics Workshop 2
FINAL RESULTS
0
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5 6 7 8 9 10
Coe
ffici
ent o
f Var
iatio
n, (-
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Time, (s)
Injection
90% mixing
99% mixing
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CONTEXT
Converting syngas (H2, CO, CO2) into fuels using microorganisms
augmented with electrical field to improve selectivity of target
products and increase carbon efficiency.
What is syngas fermentation?
Modeling approach
Macro-scale
Micro-scale
• Tool: ANSYS Fluent
• Target: Mass transfer coefficient
• Tool: OpenFOAM• Target: Sub-gird model to resolve the
mass boundary layer
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MACRO-SCALE𝑘!𝑎 Flow field Mixing time Representation of mixing
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MACRO-SCALEMixing representations 30 probes 5 probes
𝐶𝑜𝑉 =𝜎
𝐶!"#$
𝛾# = 1−Σ 𝐶% − *𝐶% 𝐴%2 �̅�% Σ𝐴%
𝑈!#&/!%$ =𝐶!#& 𝑡 − 𝐶!%$(𝑡)
𝐶!"#$
Δ!#& = max 𝐶!#& −𝐶!"#$, 𝐶!"#$ −𝐶!%$
𝑈 𝑡 = 1−Δ!#& 𝑡Δ!#&(0)
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MACRO-SCALE
rpmExperiments
CFD ̅𝑡" 𝑠𝑡𝑑
300 3.1 0.804 2.1500 1.9 0.141 1.8800 1.2 0.271 1.41
Mixing time:
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MICRO-SCALE
COCO2H2
Problem formulation:
Extremely thin mass boundary layer that should be resolved:
1. Fine mesh
2. Sub-grid scale model
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MICRO-SCALE2D, Half a bubble with axis of symmetry
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MICRO-SCALEScaling boundary layer thickness
𝛿 ∝1𝑆𝑐
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MICRO-SCALEIdea of sub-grid model
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MICRO-SCALE
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CONCLUDING REMARKS• Modeling mass transfer for syngas fermentation bioreactor
o Macro-scale:
§ Flow characteristics by mixing time
§ Volumetric mass transfer coefficient (ongoing)
o Micro-scale
§ Resolving the mass boundary layer utilizing fine mesh
§ Developing sub-grid scale models (ongoing)