Biomedical Engineering Reference
In-Depth Information
Degassing
column
FIGURE 5.3
Schematic diagram of a horizontal tubular reactor.
Framework
Degassing
column
Solar
collector
Heater
Pump
FIGURE 5.4
Schematic diagram of a helical tubular reactor.
the areal footprint of the reactor is smaller, but the angle to sunlight is also reduced.
Placing a light in the center of the coil can improve light penetration. A conical,
instead of helical, framework has also been suggested, as it improves the spatial
distribution of tubes for sunlight capture (Morita et al., 2000). However, scale-up is
then limited as the angle and height of the coil are defined. One of the most effective
designs is the Biocoil developed by Robinson (1987). It consists of a set of polyethyl-
ene plastic tubes (2.4 to 5 cm in diameter) wound helically around an open circular
framework. Parallel bands of tubes connect to a gas exchange tower. A centrifugal
pump is used to move culture to the top of the coil, which may not be suitable for
all species due to shear stress in sensitive cells and pump fouling in filamentous
species. A heat exchanger or evaporative cooling provides temperature control.
The system provides good mixing; minimal cell adhesion to the inside of tubes and
scale-up is easy, involving the addition of more parallel coils. Several marine species
and
Spirulina
have been successfully cultivated for more than 4 months in a 700 L
Biocoil (Borowitzka, 1999; Carvalho et al., 2006).
Search WWH ::
Custom Search