Transcript Scale-up of Aerobic bioreactors

Scale-up of Aerobic bioreactors
Aerobic bioreactors
• Most of the industrial bioprocesses are aerobic
• Oxygen is an important nutrient for microorganism for growth
• The oxygen transfer rate can control the overall rate of the
bioprocess in aerobic bioreactors
Widely used types are
Stirred tank reactor
Bubble column
Air lift column
Parameters affecting the Oxygen transfer rate
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the system physical properties
the biochemical properties
the operational conditions(gas flow rate, stirrer tip speed)
the geometrical parameters of bioreactor (kind and size of
bioreactor, design and number of stirrers, etc.)
The parameters in the first two groups are determined by the
nature of the system and can not be altered freely; the last
two groups depend on the process parameters and on the
device used
Steps of scale up…
• Find geometric parameters of the larger scale bioreactor
– Stirred tank reactor
Vessel diameter, Height, Impeller diameter
– Bubble column
Height, Diameter
• Use scale up criteria to determine operational parameters of
the larger scale
– Stirred tank reactor
Impeller speed, Air flow rate
– Bubble column
Air flow rate
Geometric correlations of a stirred tank reactor
For Turbine blade impellers
J
H
L
W
E
Di
D
Scale-up criteria
– Constant volumetric mass transfer coefficient(KLa)
– Constant power consumption per unit volume(P/V)
– Constant impeller tip speed(пND)
– Constant Reynolds number(Re)
– Constant dissolved oxygen concentration (CO2)
Scale-up criteria
P/V (30%)
Kla (30%)
пND(20%)
O2 con. (20%)
Percentage of each criteria used in fermentation industry
(Garcia & Gomez, 2009)
Scale-up criteria
(Garcia and Gomez,2009)
Constant tip speed
N1= Impeller speed of small bioreactor
N2= Impeller speed of Large bioreactor
Di1= Impeller diameter of small bioreactor
Di2= Impeller diameter of large bioreactor
Constant Reynolds number
N = Impeller speed
D = Impeller diameter
ρL= Density of the liquid
μL=Viscosity of the liquid
Constant Power consumption per unit volume
Ungassed power consumption ,
Np
(Rushton’s equation)
Constant Power consumption per unit volume
Ungassed power consumption ,
Gassed power consumption ,
(Rushton’s equation)
Constant Power consumption per unit volume
Constant volumetric mass transfer coefficient (kLa)
•There are large no.of empirical correlations
Ex: empirical correlations to determine Kla for Newtonian fluids in stirred tank reactors
(Garcia and Gomez,2009)