Fine particulate control below dew point:\nFor removing submicron dust (< 1 µm) from air that is below its dew point, which equipment is most suitable?

Introduction / Context:
Capturing very fine particulates from gas streams requires high-efficiency devices. Gas temperature relative to dew point affects equipment selection due to condensation risks. This item tests recognition of the device that combines high fine-particle efficiency with tolerance for saturated conditions when properly designed.

Given Data / Assumptions:

• Particle size: less than 1 micrometre.
• Gas temperature: at or below dew point (saturated conditions).
• Industrial-scale removal is required.

Concept / Approach:
Electrostatic precipitators (ESPs) excel at collecting submicron particles by imparting charge and using an electric field to drive them to collection plates. While fabric filters also capture fines well, operation below dew point risks condensation on bags, blinding, and corrosion. Cyclones and settling chambers are ineffective for submicron particles. Wet scrubbers remove fines less efficiently without special enhancements and may face plume and wastewater issues. Properly designed ESPs (including wet ESPs when handling saturated/corrosive gas) are preferred for submicron control in saturated conditions.

Step-by-Step Solution:

Verification / Alternative check:
Air pollution control texts specify ESPs—especially wet ESPs—for fine mists and submicron particulates in saturated streams, such as acid mists and SO3 aerosols.

Why Other Options Are Wrong:

• Bag filter: vulnerable to condensation; not ideal below dew point.
• Cyclone/settling chamber: poor efficiency at < 1 µm.
• Wet scrubber: may need very high energy (venturi) to approach ESP efficiency.

Common Pitfalls:
Ignoring dew-point effects on baghouses; saturated gas can rapidly foul filters.

Final Answer:
Electrostatic precipitator