Impeller Selection — Which impeller type is commonly used across a wide range of viscosities in mixing and bioprocess applications?

Introduction:
Selecting the right impeller ensures adequate mixing, mass transfer, and shear environment. Different impellers are optimized for different viscosity ranges and process objectives (suspension, gas dispersion, blending). Turbines are versatile and widely used across a broad viscosity spectrum in chemical and bioprocess industries.

Given Data / Assumptions:

• Baffled, cylindrical tanks typical of STRs.
• Need for flexibility from water-like to moderately viscous broths.
• Both gas–liquid and liquid–liquid duties may be present.

Concept / Approach:

Radial and pitched-blade turbines generate strong flow and turbulence suitable for gas dispersion and blending. Their performance degrades less severely than simple propellers as viscosity rises, and they can be paired with different blade geometries to tailor flow (radial or axial components). Paddles are inexpensive but generally limited to low-viscosity blending; propellers excel at bulk circulation in low-viscosity fluids but lose efficiency in higher-viscosity ranges compared to turbines.

Step-by-Step Solution:

Verification / Alternative check:

Vendor charts and scale-up case studies routinely show turbines specified for a broad window of viscosities and gas rates, confirming their versatility.

Why Other Options Are Wrong:

A: Paddles lack efficiency at higher viscosities. C: Propellers are excellent at low viscosity but are less suitable as viscosity increases. D and E are overly restrictive or incorrect generalizations.

Common Pitfalls:

Ignoring non-Newtonian behavior; some high-viscosity, yield-stress fluids may require anchors or helical ribbons, but those are special cases outside “wide range.”

Final Answer:

Turbines (for example, Rushton or pitched-blade turbines)