has good mixing characteristics, and seems promising for application in an in situ
extraction bioprocess.
The aim of this chapter is to show that the application of a three-phase reactor system
for bioconversions strongly inhibited by product, will result in a higher degree of
conversion, compared to a conventional reactor system. Not all conditions favour a three-
phase system, but it will be shown that with the right combination of operating conditions
(fluxes of both liquids), and physical parameters (distribution coefficient and inhibition
constant), a three-phase system is always favourable.
Figure 12.1 summarises different aspects looked upon in this paper. First, possible
process lay-outs and different reactor configurations for a liquid-liquid-solid three-phase
system are discussed. Next, the focus is on one of the reactor configurations: a three-
phase fluidised-bed bioreactor. Then, a reactor model is developed, and characteristics of
this model are discussed. Thereafter, the conditions for which a three-phase fluidised-bed
gives a better performance than a liquid-solid fluidised bed are demonstrated.
- Reactor Configuration
1 Three phase liquid-liquid-solid fluidised-beds, both liquids flow co-currently
2 Three phase liquid-liquid-solid fluidised-beds, water flow counter-currently
3 Liquid-impelled loop reactors
• Model derivation for reactor configuration 1 (^)
Simulations for a batch operation
Profiles inside a gel bead
Different distribution coefficients
Different toxic product concentrations
Different fluxes of organic solvent
• Comparison between conventional reactor and reactor configuration 1 (^)
Evaluation of the distribution coefficient for which reactor configuration 1 performs equally
well^
Batch operation is studied extensively
Continuous operation is briefly discussed
Figure 12.1 Short overview of
different aspects looked upon
PROCESS LAY-OUT AND OPERATION
A schematic presentation of a possible plant is shown in Figure 12.2. The core of the
plant is the bioreactor, i.e. a three-phase fluidised bed. This column is fed by a continuous
medium flow, introduced at the bottom of this column. This up-flowing stream is also
Design of liquid-liquid-solid fluidised-bed bioreactors 355