# Computational fluid dynamics (CFD) analysis of airlift bioreactor: effect of draft tube configurations on hydrodynamics, cell suspension, and shear rate

- 373 Downloads
- 4 Citations

## Abstract

The biomass productivity of microalgae cells mainly depends on the hydrodynamics of airlift bioreactor (ABR). Thus, the hydrodynamics of concentric tube ABR was initially studied using two-phase three-dimensional CFD simulations with the Eulerian–Lagrangian approach. The performance of ABR (17 L) was examined for different configurations of the draft tube using various drag models such as Grace, Ishii–Zuber, and Schiller–Naumann. The gas holdups in the riser and the downcomer were well predicted using E–L approach. This work was further extended to study the dispersion of microalgae cells in the ABR using three-phase CFD simulations. In this model (combined E–E and E–L), the solid phase (microalgae cells) was dispersed into the continuous liquid phase (water), while the gas phase (air bubbles) was modeled as a particle transport fluid. The effect of non-drag forces such as virtual mass and lift forces was also considered. Flow regimes were explained on the basis of the relative gas holdup distribution in the riser and the downcomer. The microalgae cells were found in suspension for the superficial gas velocities of 0.02–0.04 m s^{−1} experiencing an average shear of 23.52–44.56 s^{−1} which is far below the critical limit of cell damage.

## Keywords

Microalgae cultivation CFD modeling Three-phase flow Airlift photobioreactor Discrete phase model## List of symbols

*A*_{d}Cross-sectional area of downcomer (m

^{2})*A*_{r}Cross-sectional area of the riser (m

^{2})*C*_{cd}Interphase momentum transfer coefficient for the interphase drag force

*C*_{D}Drag coefficient

*C*_{L}Lift coefficient

*C*_{wl}Wall lubrication coefficient

*D*Diameter of the reactor (m)

*d*_{b}Bubble diameter (m)

*Eo*Eotvos number

*F*_{B}Buoyancy force acting on the particle (N)

*F*_{D}Drag force acting on particle (N)

*F*_{P}Pressure gradient force (N)

*F*_{VM}Virtual (or added) mass force (N)

*g*Gravity vector (m s

^{−2})*k*Turbulent energy (m

^{2}s^{−2})*M*Interfacial momentum transfer term between gas–liquid phases

*Mo*Morton number

*m*_{b}Mass of single bubble (kg)

*P*Pressure (Pa)

*P*_{k}Turbulence production due to viscous forces (kg m

^{−1}s^{−3})*P*_{kb}Turbulence production due to buoyancy effect (kg m

^{−1}s^{−3})*P*_{εb}Turbulence dissipation due to buoyancy effect (kg m

^{−1}s^{−3})*Re*Reynold’s Number

*Re*_{ω}Vorticity Reynolds’s Number

*t*Time (s)

*U*Averaged liquid-phase velocity (m s

^{−1})*U*_{b}Bubble velocity (m s

^{−1})*U*_{c}Continuous phase velocity (m s

^{−1})*U*_{p}Particle velocity (m s

^{−1})*U*_{t}Bubble terminal velocity (m s

^{−1})*V*Velocity (m s

^{−1})*V*_{g}Superficial gas velocity (m s

^{−1})*V*_{ld}Liquid circulation velocity (m s

^{−1})

## Subscript

- b
Bubble phase

- c
Continuous phase

- p
Particle (solid) phase

- eff
Effective

- g
Gas phase

- l
Liquid phase

- lam
Laminar

- t
Turbulent

- OV
Overall

- r, R
Riser

- d, D
Downcomer

## Greek letters

*µ*Viscosity of liquid phase (kg m

^{−1}s^{−1})*ρ*Density of phase (kg m

^{−3})*ε*Turbulent energy dissipation (m

^{2}s^{−3})*σ*Surface tension (N m

^{−1})*σ*_{ρ}Turbulent Schmidt number

- α
Gas holdup

*Ω*Rotation vector

## Notes

### Acknowledgements

The author is very grateful to the Department of Science and Technology, New Delhi for their financial support for this research work under the scheme of DST Inspire Faculty Award (IFA13-ENG63). The author is also very thankful to the Director, CSIR–NEERI Nagpur for providing enough infrastructure facilities to carry out this research.

### Compliance with ethical standards

### Conflict of interest

The author declares that there is no conflict of interest.

## Supplementary material

## References

- 1.Merchuk JC (2003) Airlift bioreactors: review of recent advances. Can J Chem Eng 81:324–337CrossRefGoogle Scholar
- 2.Chisti MY, Moo-Young M (1987) Airlift reactors: characteristics, applications and design considerations. Chem Eng Commun 60:195–242CrossRefGoogle Scholar
- 3.Miron AS, Camacho FG, Gomez AC, Grima EM, Chisti Y (2000) Bubble column and airlift photobioreactor for algal culture. AIChE J 46:1872–1887CrossRefGoogle Scholar
- 4.Krichnavaruk S, Loataweesup W, Powtongsook S, Pavasant P (2005) Optimal growth conditions and the cultivation of
*Chaetoceros calcitrans*in airlift photobioreactor. Chem Eng J 105:91–98CrossRefGoogle Scholar - 5.Pangarkar VG (2015) Design of multiphase reactors. John Wiley & Sons Inc, HobokenGoogle Scholar
- 6.Pawar SB (2016) Process engineering aspects of vertical column photobioreactors for mass production of microalgae. ChemBioEng Rev 3:101–115CrossRefGoogle Scholar
- 7.Chen F, Chen H, Gong X (1997) Mixotrophic and heterotrophic growth of
*Haematococcus lacustris*and rheological behaviour of the cell suspensions. Bioresour Technol 62:19–24CrossRefGoogle Scholar - 8.Wongsuchoto P, Charinpanitkul T, Pavasant P (2003) Bubble size distribution and gas–liquid mass transfer in airlift contactors. Chem Eng J 92:81–90CrossRefGoogle Scholar
- 9.Luo HP, Al-Dahhan MH (2010) Local gas holdup in a draft tube airlift bioreactor. Chem Eng Sci 65:4503–4510CrossRefGoogle Scholar
- 10.Luo H, Al-Dahhan MH (2012) Airlift column photobioreactors for
*Porphyridium*sp. culturing: part I: effects of hydrodynamics and reactor geometry. Biotechnol Bioeng 109:932–941CrossRefGoogle Scholar - 11.Klein J, Vicente AA, Teixeira JA (2003) Hydrodynamics of a three-phase airlift reactor with an enlarged separator—application to high cell density systems. Can J Chem Eng 81:433–443CrossRefGoogle Scholar
- 12.Darmana D, Deen NG, Kuipers JAM (2005) Detailed modeling of hydrodynamics, mass transfer and chemical reaction in a bubble column using a discrete bubble model. Chem Eng Sci 60:3383–3404CrossRefGoogle Scholar
- 13.Joshi JB (2001) Computational flow modeling and design of bubble column reactors. Chem Eng Sci 56:5893–5933CrossRefGoogle Scholar
- 14.Pourtousi M, Sahu JN, Ganesan P (2014) Effect of interfacial forces and turbulence models on predicting flow pattern inside the bubble column. Chem Eng Process 75:38–47CrossRefGoogle Scholar
- 15.Simonnet M, Gentric C, Olmos E, Midoux N (2008) CFD simulation of the flow field in a bubble column reactor: importance of the drag force formulation to describe regime transitions. Chem Eng Process 47:1726–1737CrossRefGoogle Scholar
- 16.Mohajerani M, Mehrvar M, Ein-Mozaffari F (2012) CFD analysis of two-phase turbulent flow in internal airlift reactors. Can J Chem Eng 90:1611–1630Google Scholar
- 17.Rodriguez GY, Valverde-Ramirez M, Mendes CE, Bettega R, Badino AC (2015) Global performance parameters for different pneumatic bioreactors operating with water and glycerol solution: experimental data and CFD simulation. Bioprocess Biosyst Eng 38:2063–2075CrossRefGoogle Scholar
- 18.McClure DD, Kavangh JM, Fletcher DF, Barton GW (2014) Development of a CFD model of bubble column bioreactor: part two—comparison of experimental data and CFD predictions. Chem Eng Technol 37:131–140CrossRefGoogle Scholar
- 19.ANSYS Inc. Release 15 (2014) Particle Transport Modeling, CFX, Ansys Documentation, Canonsburg, USAGoogle Scholar
- 20.Amooghin AE, Jafari S, Sanaeepur H, Kargari A (2015) Computational fluid dynamics simulation of bubble coalescence and breakup in an internal airlift reactor: analysis of effects of a draft tube on hydrodynamics and mass transfer. Appl Math Model 39:1616–1642CrossRefGoogle Scholar
- 21.Pawar SB (2017) CFD analysis of flow regimes in airlift reactor using Eulerian–Lagrangian approach. Can J Chem Eng 95:420–431CrossRefGoogle Scholar
- 22.Van Baten JM, Ellenberger J, Krishna R (2003) Using CFD to describe the hydrodynamics of internal air-lift reactors. Can J Chem Eng 81:660–668CrossRefGoogle Scholar
- 23.Simcik M, Mota A, Ruzicka MC, Vicente A, Teixeira J (2011) CFD simulation and experimental measurement of gas holdup and liquid interstitial velocity in internal loop airlift reactor. Chem Eng Sci 66:3268–3279CrossRefGoogle Scholar
- 24.Clift R, Grace JR, Weber ME (1978) Bubbles, drops and particles. Academic Press, San DiegoGoogle Scholar
- 25.Shang Z, Lou J, Li H (2015) CFD analysis of bubble column reactor under gas–oil–water–solid four-phase flows using Lagrangian algebraic slip mixture model. Int J Multiph Flow 73:142–154CrossRefGoogle Scholar
- 26.Azargoshasb H, Mousavi SM, Jamialahmadi O, Shojaosadati SA, Mousavi SB (2016) Experiments and a three-phase computational fluid dynamics (CFD) simulation coupled with population balance equations of a stirred tank bioreactor for high cell density cultivation. Can J Chem Eng 94:20–32CrossRefGoogle Scholar
- 27.Wongsuchoto P, Pavasant P (2004) Internal liquid circulation in annulus sparged internal loop airlift reactor. Chem Eng J 100:1–9CrossRefGoogle Scholar
- 28.Blazej M, Glover GMC, Generalis SC, Markos J (2004) Gas–liquid simulation of an airlift bubble column reactor. Chem Eng Process 43:137–144CrossRefGoogle Scholar
- 29.Ebrahimifakhar M, Mohsenzadeh E, Moradi S, Moraveji M, Salimi M (2011) CFD simulation of the hydrodynamics in an internal air-lift reactor with two different configurations. Front Chem Sci Eng 5:455–462CrossRefGoogle Scholar
- 30.Lestinsky P, Vecer M, Vayrynen P, Wichterle K (2015) The effect of the draft tube geometry on mixing in a reactor with an internal circulation loop—a CFD simulation. Chem Eng Process 94:29–34CrossRefGoogle Scholar
- 31.Luo H, Al-Dahhan MH (2011) Verification and validation of CFD simulation for local flow dynamics in a draft tube airlift bioreactor. Chem Eng Sci 66:907–923CrossRefGoogle Scholar
- 32.Rengel A, Zoughaib A, Dron D, Clodic D (2012) Hydrodynamic study of an internal airlift reactor for microalgae culture. Appl Microbiol Biotechnol 93:117–129CrossRefGoogle Scholar
- 33.Pfaffinger CE, Schone D, Trunz S, Lowe H, Botz-Weuster D (2016) Model based optimization of microalgae areal productivity in flat-plate gas-lift photobioreactors. Algal Res 20:153–163CrossRefGoogle Scholar
- 34.Van Benthum WAJ, Van der Lans RGJM, Van Loosdrecht MCM, Heijnen JJ (1999) Bubble recirculation regimes in an internal-loop airlift reactor. Chem Eng Sci 54:3995–4006CrossRefGoogle Scholar
- 35.Miron AS, Sanchez A, Garcia MCC, Gomez AC, Camacho FG, Grima EM, Chisti Y (2003) Shear stress tolerance and biochemical characterization of
*Phaeodactylum tricornutum*in quasi steady-state continuous culture in outdoor photobioreactors. Biochem Eng J 16:287–297CrossRefGoogle Scholar - 36.Contreras A, Garcia F, Molina E, Merchuk JC (1999) Influence of sparger on energy dissipation, shear rate, and mass transfer to sea water in a concentric-tube airlift bioreactor. Enzyme Microb Technol 25:820–830CrossRefGoogle Scholar
- 37.Meng C, Huang J, Ye C, Cheng W, Chen J, Li Y (2015) Comparing the performances of circular ponds with different impellers by CFD simulation and microalgae culture experiments. Bioprocess Biosyst Eng 38:1347–1363CrossRefGoogle Scholar
- 38.Michels MHA, van der Goot AJ, Norsker NH, Wijffels RH (2010) Effects of shear stress on the microalgae
*Chaetoceros muelleri*. Bioprocess Biosyst Eng 33:921–927CrossRefGoogle Scholar - 39.Xu Y, Luo L, Yuan J (2011) CFD simulations to portray the bubble distribution and the hydrodynamics in an annulus sparged air-lift bioreactor. Can J Chem Eng 89:360–368CrossRefGoogle Scholar