Packed tower performance: stage efficiency in packed columns varies primarily with which set of factors?

Introduction / Context:
Stage efficiency (often expressed as HETP, height equivalent to a theoretical plate) is a key design parameter for packed towers used in absorption, stripping, and distillation. It links the actual packed height to an equivalent number of ideal equilibrium stages. Many interacting variables control efficiency in practice.

Given Data / Assumptions:

• Random or structured packing with appropriate liquid distributors.
• Steady operation away from flooding, loading, and weeping regimes.
• Gases and liquids with known properties (viscosity, surface tension, diffusivity).

Concept / Approach:
Efficiency depends on interfacial area, film renewal, and mass-transfer coefficients in both phases. Packing geometry (surface area per volume, corrugation, void fraction) and size directly affect these. Fluid rates set hydrodynamics and wetting; properties influence film thickness and diffusivity. Pressure changes the gas density and, thus, superficial velocities and transfer rates. Column diameter affects maldistribution tendencies and wall effects.

Step-by-Step Solution:

Verification / Alternative check:
Vendor rating programs and correlations (e.g., Onda, Billet–Schultes) embody these variables explicitly, confirming their collective impact on efficiency.

Why Other Options Are Wrong:

• Choosing only one factor ignores the multi-variable nature of packed column performance.

Common Pitfalls:
Poor liquid distribution overshadowing packing selection; extrapolating pilot data to large diameters without correcting for maldistribution; operating too close to flooding.

Final Answer:
All (a), (b) and (c)