Design 1:
The flat plate reactors are surely the most robust design.
Roughly speaking, two sheets have to be glued together to
make a flat plate reactor with any desired light path length d in
the range from a few mm up to 70 mm, resulting in SVR 5 1/d
for one single plate and about 50 m1 for practical installations.
While this reactor design has already been employed for
decades, a recent comprehensive process engineering characterisation
is available from Sierra [35]. Mixing and CO2-
supply is accomplished by sparging with CO2-enriched air. For
the pilot scale example reactor (0.07 m wide, 1.5 m height,
2.5 m length) the authors report air flow rates of 0.25 v/v/min
leading to a mixing time of the medium of 150 s. Others
[30, 36] reported even much higher aeration rates up to 2.0
v/v/min with positive effects. Power supply for bubbling was in
the range of 50 W/m3
. Even in quite compact arrangements of
several plates close to each other (e.g. 25 L/m2
) this value is not
too high for an economically feasible production of chemical
energy (biomass itself, biodiesel) by microalgae. Agitation only
by bubbles seems to be the most gentle way with respect to
shear stress for the algae. But this point has to checked carefully
in practical applications (e.g. [30]).
A kind of horizontal plate reactor has been invented by Sato
[36], Fig. 8B. The light distribution is achieved in this case by
deformation of the plate to cylinders or spheres. The so-called
dome shaped reactor aerated by bubbles. This is one of the rare
examples, where a design has been conducted from scratch by
CFD simulations. The performance has been claimed to be
more than PG420.5 g/m2
/d for one device and it is fairly
mentioned, that the overall productivity for an area with
several domes is only half of that value. Such specifications are
missing in many other publications.