For a cyclone separator handling dusty gas, the overall dust-collection efficiency most strongly depends on which geometric and operating factors?

Introduction / Context:
Cyclone separators remove particulates by imparting a high tangential velocity, creating a centrifugal field that drives particles to the wall. Geometry and operating conditions together determine cut size and fractional efficiency curves.

Given Data / Assumptions:

• Standard reverse-flow cyclone.
• Goal: maximize overall collection efficiency at a given pressure drop.
• Particles span a distribution of sizes and densities.

Concept / Approach:
Smaller body diameter increases angular velocity for a given volumetric flow, improving separation of fine particles. Higher inlet gas velocity raises centrifugal acceleration. Adequate height and proper proportions increase residence time and reduce short-circuiting, improving capture across the size spectrum.

Step-by-Step Solution:
Relate separation to centrifugal force: F_c ∝ m * v_tangential^2 / r.Decrease r (smaller diameter) → higher F_c at same v_tangential.Increase v_tangential (via inlet velocity) → higher F_c and better fine capture, mindful of erosion/pressure drop.Set proportions/height to avoid re-entrainment and ensure adequate residence time for particles to migrate to the wall and drop out.

Verification / Alternative check:
Empirical models (e.g., Stairmand, Lapple) show explicit dependencies of cut size on gas velocity and characteristic dimensions, validating the multi-factor influence on efficiency.

Why Other Options Are Wrong:
Any single factor alone does not guarantee high efficiency; cyclone performance is a coupled function of geometry and velocity.

Common Pitfalls:
Over-increasing inlet velocity causing erosion and excessive pressure drop; using oversized cyclones that reduce centrifugal acceleration and degrade fine capture.

Final Answer:
all (a), (b) & (c)