Which of the following particulate control devices has the poorest removal efficiency for particles in the sub-micron size range?

Correct option is C

Explanation:
Cyclones are particulate control devices that utilize centrifugal force to separate particles from a gas stream. They are most effective at removing larger particles due to their design, which relies on the inertia of the particles to throw them against the wall of the cyclone. As the air stream spirals down, larger particles are more likely to be forced out due to their mass. However, for sub-micron size particles (typically less than 1 micron), cyclones are significantly less effective.
1. Sub-Micron Particles: These particles have low inertia and can easily follow the flow of air, which means they are less likely to be separated by centrifugal force in a cyclone.
2. Comparison with Other Devices:
· Electrostatic Precipitator: This device uses electrical forces to attract and collect sub-micron particles effectively.
· Fabric Filter: Also known as baghouses, these are highly efficient at capturing both large and small particles, including sub-micron sizes.
· Venturi Scrubber: This device captures particles through scrubbing liquid, and it also performs well with smaller particles.
Therefore, among the options provided, the cyclone is the least efficient in removing sub-micron particles.
Information Booster:
· Efficiency Factors: The efficiency of particulate control devices varies significantly based on particle size, with larger devices generally performing better for larger particles.
· Applications: Cyclones are often used as a pre-cleaner for larger particles before finer filtration systems.
· Pressure Drop: Cyclones have lower pressure drops compared to other filtration systems, making them energy-efficient for larger particles.
· Maintenance: Cyclones typically require less maintenance than baghouses or electrostatic precipitators.
· Limitations: The main limitation of cyclones is their inefficiency for smaller particles, which necessitates additional filtration methods for comprehensive air quality control.
Additional Information:
· Option (a) Electrostatic Precipitator: Highly efficient for sub-micron particles due to the electrical charges applied to the particles.
· Option (b) Fabric Filter: Offers high efficiency for all particle sizes, including sub-micron.
· Option (d) Venturi Scrubber: Effective in capturing small particles through liquid scrubbing, performing better than cyclones for sub-micron sizes.