Biotechnology and Bioprocess Engineering

, Volume 11, Issue 3, pp 245–250

Effects of hydrocarbon additions on gas-liquid mass transfer coefficients in biphasic bioreactors

  • Teresa Lopes da Silva
  • Vitor Calado
  • Nadia Silva
  • Rui L. Mendes
  • Sebastião S. Alves
  • Jorge M. T. Vasconcelos
  • Alberto Reis
Article

DOI: 10.1007/BF02932038

Cite this article as:
da Silva, T.L., Calado, V., Silva, N. et al. Biotechnol. Bioprocess Eng. (2006) 11: 245. doi:10.1007/BF02932038
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Abstract

The effects of aliphatic hydrocarbons (n-hexadecane andn-dodecane) on the volumetric oxygen mass transfer coefficient (kLa) were studied in flat alveolar airlift reactor and continuous stirred tank reactors (CSTRs). In the flat alveolar airlift reactor, high aeration rates (>2 vvm) were required in order to obtain efficient organic-aqueous phase dispersion and reliablekLa measurements. Addition of 1% (v/v)n-hexadecane orn-dodecane increased thekla 1.55-and 1.33-fold, respectively, compared to the control (superficial velocity: 25.8×10−3 m/s, sparger orifice diameter: 0.5 mm). Analysis of the gas-liquid interfacial areaa and the liquid film mass transfer coefficientkL suggests that the observedkLa increase was a function of the media's liquid film mass transfer. Addition of 1% (v/v)n-hexadecane orn-dodecane to analogous setups using CSTRs led to akLa increase by a factor of 1.68 and 1.36, respectively (superficial velocity: 2.1×10−3 m/s, stirring rate: 250 rpm). These results propose that low-concentration addition of oxygen-vectors to aerobic microbial cultures has additional benefit relative to incubation in purely aqueous media.

Keywords

flat alveolar airlift bioreactorCSTRoxygen-vectorkLa, dodecanehexadecane

Nomenclature

a

specific interfacial area (1/m)

C*

oxygen saturation concentration of the aqueous phase (g/L)

C

dissolved oxygen concentration of the aqueous phase (g/L)

d32

Sauter mean bubble diameter (m)

deqi

diameter of the volume-equivalent sphere (m)

D

impeller diameter (m)

E

bubble major axis in two-dimensional projection (m)

e

bubble minor axis in two-dimensional projection (m)

kL

liquid film mass transfer coefficient (m/h)

(kl)v

kL in the presence of an oxygen-vector (organic phase) (m/h)

(kL)w

kL in the absence of an oxygen-vector (aqueous phase) (m/h)

kLa

volumetric mass transfer coefficient (1/h)

(kLa)v

kLa in the presence of an oxygen-vector (organic phase) (1/h)

(kLa)w

kLa in the absence of an oxygen-vector (aqueous phase) (1/h)

N

impeller speed (1/s)

P

power (W)

t

time (h)

V

liquid volume (m3)

Greek symbols

δ

sparger orifice diameter (mm)

ε

gas hold up (dimensionless)

Vs

superficial gas velocity (m/s)

Copyright information

© The Korean Society for Biotechnology and Bioengineering 2006

Authors and Affiliations

  • Teresa Lopes da Silva
    • 1
  • Vitor Calado
    • 1
  • Nadia Silva
    • 1
  • Rui L. Mendes
    • 2
  • Sebastião S. Alves
    • 3
  • Jorge M. T. Vasconcelos
    • 3
  • Alberto Reis
    • 1
  1. 1.Instituto Nacional de Engenharia, Tecnologia e Inovação, Departamento de BiotecnologiaUnidade de Bioengenharia e BioprocessosLisboaPortugal
  2. 2.Instituto Nacional de Engenharia, Tecnologia e Inovação, Departamento de Energias RenováveisUnidade de BiomassaLisboaPortugal
  3. 3.Instituto Superior Técnico, Departamento de Engenharia Química e BiológicaCentro de Engenharia Biológica e QuímicaLisboaPortugal