Air pollution control: which device is best suited to purify fine dust-laden air streams?

Introduction / Context:
Industrial air streams often carry particulate matter. Device selection depends on particle size distribution, loading, gas temperature, and required outlet emissions. Fine dust removal requires high collection efficiency at small particle sizes.

Given Data / Assumptions:

• Air stream contains fine dust (sub-micron to tens of microns).
• We seek high efficiency and low outlet particulate concentration.
• Comparing cyclone, bag filter, gravity settler, and tubular centrifuge.

Concept / Approach:
Bag filters remove fine particles by filtration through a fabric medium, achieving high efficiencies across a broad size range. Cyclones rely on inertial separation and are better for coarse particles. Gravity settlers work only for very coarse particles with long residence times. Tubular centrifuges are typically used for liquid–solid separation in small liquid volumes, not for large air flows.

Step-by-Step Solution:
Match device principle to particle size: fine dust → surface filtration.Select bag filter for high-efficiency fine particulate capture.Eliminate cyclone/settler for fine cut sizes and centrifuge for gaseous streams.

Verification / Alternative check:
Emission standards in many plants are met using baghouses or electrostatic precipitators (ESPs); baghouses are robust for fine dust.

Why Other Options Are Wrong:
Cyclone/settler are low-efficiency at fine sizes; tubular centrifuge is not typical for air service.

Common Pitfalls:
Assuming cyclones suffice for all dust problems; fine PM requires filtration or electrostatic capture.

Final Answer:
Bag filter (fabric filter)