Cyclone separators: which statement correctly reflects how dust collection efficiency varies with operating and particle variables?

Introduction / Context:
Cyclone separators remove particulates from gas streams by centrifugal action. Performance depends on inlet velocity, cyclone geometry, gas properties, and particle characteristics (size, density). Understanding these trends is crucial for setting realistic expectations and avoiding misstatements about proportionalities.

Given Data / Assumptions:

• Standard tangential-inlet reverse-flow cyclones.
• Single-phase gas with suspended solids.
• No unusual pre-separation devices altering inlet conditions.

Concept / Approach:
Collection efficiency generally increases with inlet velocity (up to a limit) and particle size/density because higher centrifugal accelerations improve radial migration toward the wall. However, none of the first three options capture this correctly: (a) states the opposite trend; (b) claims inverse proportionality to mass, which is false (larger/heavier particles are usually collected more efficiently); (c) invokes “radius of the particle path” without a standard proportional relation and ignores the multivariable nature of efficiency. Therefore, among the options provided, the only defensible choice is that none of the statements are correct as written.

Step-by-Step Reasoning:

Verification / Alternative check:
Empirical grade-efficiency curves and Stairmand-type designs clearly exhibit improved efficiency with increased inlet velocity and particle size, confirming the misstatements in (a), (b), and (c).

Why Other Options Are Wrong:

• (a) Opposite to practice.
• (b) Inverse proportionality is incorrect; trend is generally direct.
• (c) Oversimplified and not standard.

Common Pitfalls:
Driving velocity too high raises pressure drop and erosion, potentially reducing lifecycle performance; neglecting fines that may still need a downstream filter.

Final Answer:
None of these