Skip to content
Licensed Unlicensed Requires Authentication Published by De Gruyter February 17, 2015

Studies on Computer-Aided Design and Analysis of Three-Phase Semifluidized Bed Bioreactors

C. M. Narayanan

Abstract

Attempts have been made to perform computer-aided analysis and simulation of the performance of a three-phase semifluidized bed bioreactor. The bioreactor is of biofilm type. Cocurrent operation with liquid (substrate solution) forming the continuous phase has been considered. Both air and feed solution are thus admitted from the bottom, the air moving up as tiny bubbles. Being semifluidized, the bioreactor is composed of a fully fluidized bed at the bottom and a packed bed at the top. The performance of the bioreactor is analysed by assuming it to be equivalent to two plug flow dispersion reactors (PFDRs) in series, each with a different value of dispersion number/axial dispersion coefficient. The performance equations (assuming dispersed flow) for both sections are written separately and then solved numerically using fourth-order Runge–Kutta method/successive over-relaxation method, based on appropriate boundary conditions. The specific case considered is the aerobic synthesis of Xanthan gum from cheese whey permeate, which follows Contois-type kinetic equation. The fractional gas holdup in both sections, height ratio of fluidized section to packed section and the semifluidization velocity are computed at the outset from selected experimental correlations (compiled from available literature). The results obtained from the developed software package, after verifying experimentally, are used to study and illustrate the performance characteristics of the bioreactor. It is observed that the three-phase semifluidized bed biofilm reactor of proposed design provides substantially large fractional conversion of substrate at large capacities, with relatively low reactor volume requirement.

Acknowledgements

This paper has been presented in the International conference on Bioprocess Engineering (Bioprocess-2014) held at Valencia, Spain, during June 26–27, 2014 and has been modified based on the discussion and interactions during the conference. The author is thankful to all the participants of the conference, to all of his fellow members of IRG (International Research Group), to a large number of consultancy firms and software companies of India and abroad for their valuable assistances towards the successful completion of this project.

Nomenclature

A

cross-sectional area of reactor column, m2

CS (z)

substrate concentration at any z, g/L

CSb

substrate concentration at the exit of the fluidized section (or entrance to the packed section) of the bioreactor, g/L

CSe

substrate concentration in product solution leaving the bioreactor, g/L

CS0

substrate concentration in feed solution entering the bioreactor, g/L

CSP

substrate concentration at the biofilm–liquid interface, g/L

dP

diameter of the support particle, m

dPm

diameter of particle-biofilm aggregate, m

D

diameter of reactor column, m

DLf

axial dispersion co-efficient for the fluidized section of bioreactor, m2/s

DLP

axial dispersion co-efficient for the packed section of bioreactor, m2/s

F

volume fraction of biofilm in particle-biofilm aggregate, dimensionless

fD

drag coefficient, dimensionless

kC

kinetic constant, dimensionless

KC (app)

parameter defined in eqs (27) and (28), g/L

L

height of initial static bed, m

L*

characteristic dimension (see eq. (35)), m

Lf

height of fluidized section of bioreactor, m

LP

height of packed section of bioreactor, m

LSf

total height of semifluidized bed, m

Q0

volumetric flow rate of substrate solution, m3/s

rSint

intrinsic rate of biochemical reaction, g/(L.s)

R

bed expansion ratio, dimensionless

Rem

modified Reynolds number (see eq. (6)), dimensionless

ReP

particle Reynolds number, dimensionless

Ug

superficial velocity of gas, m/s

Umf

minimum fluidization velocity for a liquid–solid fluidized bed, m/s

USL

operating superficial velocity of liquid through the bioreactor (liquid phase semifluidization velocity), m/s

xf

cell mass concentration in biofilm, g/L

xfL

parameter defined in eq. (29), g/L

xfP

parameter defined in eq. (30), g/L

Y

overall yield coefficient for cell mass production, g/g

z

axial coordinate, m

α

fractional conversion of substrate, dimensionless

β(z)

parameter defined in eq. (36), dimensionless

δ

thickness of biofilm, m

ϵf

total voidage of fluidized section of bioreactor, dimensionless

ϵfg

fractional gas holdup in the fluidized section of the bioreactor, dimensionless

ϵfL

fractional liquid holdup in the fluidized section of the bioreactor, dimensionless

ϵP

total voidage of packed section of bioreactor, dimensionless

ϵPg

fractional gas holdup in the packed section of the bioreactor, dimensionless

ϵPL

fractional liquid holdup in the packed section of the bioreactor, dimensionless

ηd

parameter defined in eq. (33), dimensionless

η(z)

effectiveness factor at any z, dimensionless

μL

viscosity of substrate solution, kg/(m.s)

μm

kinetic constant, s–1

μm (app)

parameter defined in eqs (25) and (26), g/(L.s)

ρL

density of substrate solution, kg/m3

ρm

density of microbial solution, kg/m3

ρm

density of support particle, kg/m3

ρSm

density of particle-biofilm aggregate, kg/m3

ϕ

Thiele-type modulus, dimensionless

References

1. JenaHM. Hydrodynamics of gas-liquid-solid fluidized and semi-fluidized beds. PhD Thesis, National Institute of Technology, Rourkela, India, 2009.Search in Google Scholar

2. DakshinamurtyP, SubrahmanyamV, RaoJN. Bed porosities in gas-liquid fluidization. Ind Eng Chem Proc Des Dev2007;11:31819.10.1021/i260042a031Search in Google Scholar

3. DartonRC, GasHD. Liquid holdup in three-phase fluidization. Chem Eng Sci1975;50:5816.Search in Google Scholar

4. BegovichJM, WatsonJS. Hydrodynamic characteristics of three-phase fluidized beds. In: DavisonJF, KeairnsDL, editors. Fluidization. Cambridge: Cambridge University Press; 1978.10.2172/6919977Search in Google Scholar

5. KatoY, UchindaK, KagoT, MorokaS. Liquid holdup and heat transfer coefficient in liquid-solid and gas–liquid-solid fluidized beds. Powder Technol1981;28:1739.10.1016/0032-5910(81)87040-4Search in Google Scholar

6. FanLS, MatsuraA, ChernSH. Hydrodynamic characteristics of a gas–liquid-solid fluidized bed containing binary mixture of particles. AIChE J1985;31:180110.10.1002/aic.690311106Search in Google Scholar

7. Saberian-BroudjenniM and others. Contribution to hydrodynamics study of gas –liquid-solid fluidized bed reactors. Int Chem Eng1987;27:42340.Search in Google Scholar

8. SongGH, BavarianF, FanLS. Hydrodynamics of three-phase fluidized bed containing cylindrical hydrotreating catalysts. Can J Chem Eng1989;67:26575.10.1002/cjce.5450670213Search in Google Scholar

9. HanJH, WildG, KimSD. Phase hold-up characteristics in three-phase fluidized beds. Chem Eng J1990;43:6773.10.1016/0300-9467(90)80002-TSearch in Google Scholar

10. NacefS, PoncinbS, BouguettouchaaA, WildG. Drift flux concept in two and three phase reactors. Chem Eng Sci2007;62:75308.10.1016/j.ces.2007.08.031Search in Google Scholar

11. WenCY, YuYH. Mechanics of fluidization. Chem Eng Symp Ser1966;62:10011.Search in Google Scholar

12. ChernSH, FanLS, MuroyamaK. Hydrodynamics of cocurrent gas –liquid-solid semi-fluidization with liquid as continuous phase. AIChE J1984;30:28894.10.1002/aic.690300218Search in Google Scholar

13. NarayananCM, ManekaB, SayaniH. Performance analysis of immobilized enzyme semi-fluidized bed bioreactors. Int J Chem Reactor Eng2011;9:11118.10.2202/1542-6580.2670Search in Google Scholar

14. NarayananCM. Performance analysis of semi-fluidized bed biofilm reactors with liquid phase oxygen utilization. In: Proc 14th Int Conf on Fluidization – from Fundamentals to Products. ECI Symp Ser. Available at: http://dc.engconfintl.org/fluidization_xiv/12, 2013.Search in Google Scholar

15. ZabotGL and others. Hybrid modeling of xanthan gum bioproduction in batch bioreactor. Bioprocess Biosyst Eng2011;34:97586.10.1007/s00449-011-0548-5Search in Google Scholar

16. GottifrediJC, GonzoEE. Approximate expression for effectiveness factor estimation. Chem Eng J2005;109:837.10.1016/j.cej.2005.03.012Search in Google Scholar

Published Online: 2015-2-17
Published in Print: 2015-3-1

©2015 by De Gruyter