Sub-micronic dust control from blast-furnace gas: which device is the most efficient for removing particles in the sub-micron range?

Introduction / Context:
Blast-furnace top gas contains a wide particle-size spectrum. Achieving very low particulate emissions, especially in the sub-micron regime, requires high-efficiency control equipment that does not rely solely on inertial effects.

Given Data / Assumptions:

• Target: sub-micron particulate removal.
• Industrial-scale gas flows and temperatures.
• Device choices: ESP, cyclone, gravity chamber, venturi-type device (listed as atomiser).

Concept / Approach:
Cyclones and gravity chambers depend on inertia and gravity and are ineffective for sub-micron fines. Wet scrubbers (e.g., venturi scrubbers) can capture very fine particles but at high pressure drop; the listed option “venturi atomiser” is not the standard scrubber. Electrostatic precipitators (ESPs) impart charge to particles and drive them to collecting plates with an electric field, achieving very high efficiencies even for sub-micron particles at reasonable pressure drop.

Step-by-Step Solution:
Identify device physics: electrostatic force is effective for very small particles.Compare alternatives: inertia/gravity insufficient; unspecified atomiser is not the classic high-ΔP venturi scrubber.Choose ESP as the best available option.

Verification / Alternative check:
Steel plants commonly use cyclones or wet scrubbers as precleaners and ESPs for final polishing of blast-furnace gas to very low dust levels.

Why Other Options Are Wrong:
Gravity chamber: low efficiency for fines.Cyclone: good for > 5–10 micron particles; weak for sub-micron.Venturi atomiser: not the standard term for high-efficiency venturi scrubber; ESP remains superior in this list.

Common Pitfalls:
Confusing venturi scrubbers with ordinary spray devices; only high-ΔP venturi scrubbers approach ESP performance for sub-micron capture.

Final Answer:
electro-static precipitator