CHAPTER ONE
NEW METHODOLOGIES FOR
MULTIPHASE BIOREACTORS 1:
HYDRODYNAMIC AND MASS
TRANSFER CHARACTERISTICS OF
MULTISTAGE SLURRY REACTORS
JINDŘICH ZAHRADNÍK†
Institute of Chemical Process Fundamentals, Academy of Sciences of the
Czech Republic, Rozvojová 135, 165 02 Prague 6-Suchdol, Czech
RepublicABSTRACT
The advantageous features of multistage bubble column reactors for
aerated slurry systems have been illustrated by the results of an extensive
experimental study aimed at examining the effect of selected construction
and operating variables (number of reactor stages, distributing plate
geometry, gas and liquid flow rates, solid phase concentration) on
hydrodynamic and mass transfer characteristics of multistage aerated
slurry reactors. Experimental results proved the favourable effect of
column sectionalisation on gas holdup and kLaL values, and on the energy
effectiveness of gas-liquid contacting. The effect of increasing solid
concentration on these system characteristics was negative within the
whole region of experimental conditions. The relationship between kLaL
and gas holdup was independent of the solid phase concentration and gas
flow rate. However, the value of kLaL corresponding to the given gas
holdup ratio increased substantially with the increasing number of column
stages. Axial mixing of the liquid (slurry) phase was well described by the
model of perfectly mixed tanks in series with backflow, for the number of
series terms equal to the number of column stages. Evaluation of the
backflow coefficient stressed the importance of plate design optimisation
for particular flow conditions. Implications of the experimental findings
for the performance and applicability of multistage slurry reactors has
been discussed thoroughly. Recommendations for future research have
been given, aimed at clarifying particular aspects of multistage reactors
performance with slurry systems and ultimately at providing reliable basis
for the design and scale-up of such reactors.† deceased