Types of Impeller(Propeller & Turbines)pptx

1. Types of Impeller &
Configuration(Placement)

2. Impeller
Turbines
Propeller
Combination

5. 1.Marine Propeller
 Marine propellers are relatively simple in design and require minimal maintenance.
 The angled blades generate a powerful upward or
downward thrust, pushing gas bubbles efficiently
throughout the liquid volume.
 The strong axial flow helps prevent stagnant zones in
the bioreactor, ensuring good mixing and gas distribution
throughout the liquid.
 They may be operated for either downward or upward pumping
of the fluid; downward pumping is more common.
 They are used with low-to-medium viscosity fluids and are usually installed with diameter
around one-third the tank diameter.
Types of Impeller

6. 2.Rushton Disc Turbine
 The most frequently used impeller in the fermentation industry is the six-flat-blade disc-mounted turbine
 It is the best choice for fermentation has been well studied and characterised,
it is very effective for gas dispersion.
 larger impellers of size up to one-half the tank diameter provide considerable
benefits for improved mixing and gas distribution in Aerobic fermentation.
 The Rushton turbine is a radial-flow impeller. Flat disc with 4-6 flat,
vertical blades.
 Provides moderate top-to-bottom circulation and good radial mixing.
 Effective for dispersing gas due to turbulence and shear created by the blades
(exception in turbines)
 Generates moderate to high shear forces, depending on operating conditions.
 Relatively high power consumption compared to some other designs.
 Simple design, readily available, well-studied and characterized.
 May not be optimal for highly viscous liquids, can lead to some solids settling at the bottom.

7. 3.Pitch Blade Turbine
 It offers both i.e. radial and axial flow patterns. The specific flow
pattern depends on the blade angle(30° to 45°) and operating
conditions.
 Features 3-6 curved blades attached to a central hub.
 Blade angle can be fixed or adjustable.
 Generates moderate shear forces, less than high-shear impellers but
more than axial flow impellers.
 PBT diameter is generally keep around 1/3 to 1/2 the diameter of the
vessel for optimal performance.
 Application in Fermenters,Bioreactors,Blending tanks,Chemical
reactors,Wastewater treatment

8. 4.Anchor Impeller
 Generates primarily top-to-bottom circulation(axial flow), mixing the
liquid along the vessel height and poor radial flow.
 Immersed deep within the liquid to ensure proper bottom circulation
and avoid settling of solids.
 It’s Performance decreases with increasing viscosity.
 Single or multiple flat blades attached to a central shaft.
 Not ideal for gas dispersion-Requires additional components like
spargers for efficient gas introduction.
 May not be suitable for highly viscous liquids-High viscosity can
interfare proper flow and mixing.
 Mixing time-Might require longer mixing times compared to some
high-shear impellers.
 Used in processes where there is a need of gentle mixing, efficient solid
suspension, and low shear forces.

9. 5.Helical Ribbon
 The helical ribbon impeller, also known as a helical screw impeller, possesses a
unique design that offers several notable properties, making it suitable for specific
mixing applications.
 Primarily generates top-to-bottom circulation, effectively suspending solids
And weaker radial flow component, contributing to some horizontal mixing across
the tank volume.
 Due to its gentle, low-shear mixing action, it handles high viscosities better than
some other impellers. Efficiently prevents settling of solids throughout the tank.
 Not ideal for applications requiring vigorous gas introduction due to the low shear
and limited surface area interaction but good for shear sensitive cells.
 Mostly useful in the mixing applications for fermentation,bioreactors and mixing
of viscous liquids.

10. Configuration(Placement) of Impeller
in Bioreactor

11. Configuration
 This refers to the design and characteristics of the impeller itself.It includes,
 Number of blades: More blades generally create more flow but also higher shear stress.
 Blade geometry: Different shapes (curved, angled, etc.) influence flow direction and intensity.
 Material: Chosen based on factors like chemical compatibility, strength, and weight.
Placement
 This refers to the physical location and orientation of the impeller within the bioreactor,It includes,
 Height from bottom: Affects how well the bottom of the vessel is mixed and potential dead zones.
 Distance from vessel walls: Influences flow patterns and potential vortex formation.
 Angle of inclination: Can be used to direct flow towards specific areas or enhance mixing patterns.
 Number of impellers: Using multiple impellers can improve mixing uniformity in larger vessels.

12. 1.Desired Mixing Regime
 Mixing regime referes to the pattern of mixing of any fluid in the container
1.1Suspension-Uniformly suspend cells or particles throughout the vessel.
 Impeller Configuration:
• Type: Marine impeller, pitched blade turbine, or hydrofoil impeller for gentler mixing.
• Number: One or two, depending on vessel size.
 Placement:
• Height: Off the bottom to avoid sediment resuspension.
• Distance from walls: Centralized to avoid dead zones.
• Angle: Flat or slightly inclined for axial flow.
1.2.Shear Sensitive Culture-Minimize shear stress to protect delicate cells or biomolecules
•Impeller Configuration:Type: Low shear impellers like marine impellers or hydrofoils.
•Number: One or two, with lower rotational speeds.
Configuration and Placement of Impeller is depends on

13.  Placement:
• Height: Off the bottom but not too high to maintain mixing.
• Distance from walls: Centralized to avoid high shear regions near walls.
• Angle: Flat to minimize tangential flow and shear.

14. 2. Volume and geometry of the bioreactor
 The volume and geometry or shape of the bioreactor also desides what should be the placement and
configuration of the impeller
2.1.Large Cylindrical Bioreactor with Shear-Sensitive Cells
 Type: Marine impeller with curved blades for lower shear.
 Number: Two impellers placed vertically, one near the top and one near the bottom.
 Placement: Off the bottom to avoid resuspending settled cells. Spaced strategically to create circulation loops
throughout the vessel, avoiding stagnant zones.
 Angle: Flat to promote axial flow with minimal tangential shear.
 2.2. Shallow Rectangular Bioreactor with High Oxygen Demand Culture
 Type: Rushton turbine with multiple flat blades for strong radial flow.
 Number: Two impellers positioned near the bottom, facing opposite directions.
 Placement: Slightly off the bottom, angled downwards to direct flow towards the gas sparger location.
 Angle: Tilted at an angle to create turbulence and enhance gas dispersion.

15. 3. Rheological properties of the culture broth
 The rheological properties of a culture broth, such as its viscosity, greatly influence the optimal impeller
configuration and placement in a bioreactor.
3.1. High Viscosity:
 Impeller configuration:
 Type: Rushton turbine or other high-shear impellers for strong mixing power to overcome the high viscosity.
 Number: Multiple impellers might be needed for large vessels.
 Placement:
 Height: Off the bottom to avoid resuspending settled cells/particles.
 Distance from walls: Spaced strategically to create multiple flow loops and avoid dead zones.
 Angle: Flat or slightly tilted for balanced mixing and vortex prevention.

16. 3.2.Low Viscosity
 Type: Rushton turbines: These offer moderate shear and good mixing for general applications.
 Disc impellers: They provide axial flow and are good for homogenizing suspensions.
 Gas-inducing impellers: If oxygen transfer is crucial, these designs with integrated spargers can be efficient.
 Number: Low-viscosity broths generally require fewer impellers compared to viscous ones. One or two
strategically placed impellers are often sufficient for adequate mixing.
 Height: Placing it slightly off the bottom is sufficient to avoid resuspending settled materials.
 Distance from walls: Dead zones near the walls are less of a concern due to the easier flow in low-viscosity
broths. However, avoid positioning the impeller too close to prevent excessive vortex formation.
 Angle: Flat or slightly inclined angles (45° or less) are generally preferred for balanced mixing and efficient
flow patterns.

17. 4. Mass Transfer Requirements
 Optimizing impeller design and placement is crucial for maximizing mass transfer in bioreactors.
4.1.Gas-Liquid Mass Transfer
 Type: Gas-inducing impeller with integrated sparger (e.g., hollow disc impeller). This design directly
disperses gas bubbles into the liquid, increasing interfacial area for mass transfer.
 Number: Multiple impellers depending on vessel size and oxygen demand. This creates more flow paths and
turbulence, enhancing gas dispersion and contact with the liquid.
 Height: Strategically positioned near the gas sparger to ensure immediate bubble entrainment and dispersion
throughout the bulk liquid.
 Distance from walls: Spaced to avoid dead zones and create flow patterns that maximize bubble contact with
the liquid.
 Angle: Slightly tilted to promote both axial and radial flow, increasing the gas-liquid interfacial area.

18. Apart from this there are also some additional points which desides placement and
configuration of the bioreactor.
1.Heat transfer needs: Depending on the process, efficient heat transfer might be required. Impeller selection and
placement can influence heat transfer by generating flow patterns.
2.Minimizing dead zones: Stagnant areas where mixing is poor can negatively impact culture growth. Impeller
configuration and number are chosen to minimize these zones.
3.Maintenance and cleaning: Ease of access and cleaning the impeller and surrounding areas are important
considerations.
4.Cost and availability: Balancing desired performance with cost-effectiveness influences impeller selection.
Readily available options might be preferred.
5.Scale-up: Designing for future scale-up requires considering factors like power draw per unit volume, which can
change with scale.
6.Specific culture characteristics: Some cultures might have specific sensitivities or requirements that influence
impeller choice.