2. INTRODUCTION…
typical motionless bioreactor where the internal
circulation and mixing are achieved by bubbling air.”
Employ forced/ pressurized air to circulate cells and
nutrient medium.
Can be used to culture cells that highly shear-sensitive.
gas stream facilitate exchange of material between the gas
phase and the medium.
oxygen is usually transferred to the liquid, products are
removed through exchange with the gas phase.
3. STRUCTURE/ DESIGN…
Entire reactor is divided into 2 halves by a Draft tube:
inner gassed region ( Riser)
outer ungassed region ( Down comer)
Riser has gas injection connected- air moves upwards.
Down comer region has degassed media and cells.
Mean density gradient between riser and downcomer
regions causes continuous circulation.
4.
5. PARTS OF ALR… upward air flow.
RISER: Connected gas injection-
DOWNCOMER: degassed media+cells.
BASE: Connected to Perforated nozzle bank/ plate/
Sparger to pump pressurized air.
HEAD SPACE: Gas release region, flocculation, foam
accumulation etc.
GAS SEPARATOR:
Facilitates gas/liquid recirculation
maximizes gas residence time
reduces gas friction in downcomer.
6. ALR TYPES DESCRIPTION
INTERNAL LOOP ALR:
baffles placed strategically in a single vessel create the
channels required for the circulation
shortest path that a bubble cover from the riser to the
downcomer is a straight line
EXTERNAL LOOP ALR: circulation takes place through
separate and distinct conduits
there is usually a minimum horizontal distance to be
covered, increases the chances of disengagement of the
bubbles
12. ALR features
Gas separator
Gas Holdup
a) Driving force circulation
Shear stress
Effect of liquid
a) Disengement of bubbles
• Free rising velocity, liquid velocity, residence time of bubbles in gas
separator
Measuring The Liquid Velocity.
use of tracers in the liquid. If a tracer is injected and two probes are installed in
a section of the tube
15. ADVANTAGES OF ALRs…
Hence, homogenous mixing/ distribution of gas/ oxygen.
Simple design with no moving parts or agitator for
less maintenance, less risk of defects.
Easier sterilization (no agitator shaft parts)
Low Energy requirement Homogenous distribution of
nutrients and shear force.
DISADVANTAGES
Greater air throughput and higher pressures needed
Inefficient break the foam when foaming occurs
NO bubbles breaker
16. USES….
Mammalian cell cultures.
Waste water treatment
Biological processes involving biocatalysts as solids
To produce biopharma proteins etc from fragile cells.