Particulate control for power plants: For removing fly ash from flue gas in a utility-scale thermal power station, which device is generally the most efficient and suitable primary collector?

Introduction / Context:
Coal-fired boilers generate fine fly ash that must be removed to meet air quality standards. Different collectors operate on gravity, inertia, filtration, or electrostatic forces. Selection depends on efficiency, pressure drop, temperature capability, and load variability. This question focuses on the widely adopted solution for large power plants.

Given Data / Assumptions:

• Gas stream: large volumetric flow at elevated temperature.
• Particulate: predominantly fine fly ash with a broad size distribution.
• Plant-scale reliability and low specific power loss are important.

Concept / Approach:
Electrostatic precipitators (ESPs) impart charges to particles and collect them on oppositely charged plates, achieving very high collection efficiencies (often > 99%) at modest pressure drop—critical for big boilers. Gravity chambers are low-efficiency precollectors; cyclones are effective for coarse particles but less so for fine sub-10 µm fractions. Fabric filters (baghouses) can also reach high efficiencies but may face temperature/condensation constraints and higher pressure drops in very large units; many utility plants historically standardized on ESPs for main collection.

Step-by-Step Solution:
Compare mechanisms: inertial vs. electrostatic vs. filtration.Assess efficiency and scale: ESP suits fine ash at utility scale with low pressure drop.Select “electrostatic precipitator.”

Verification / Alternative check:
Regulatory compliance reports and plant specifications show widespread ESP use in coal power; hybrid ESP–baghouse systems also exist but ESP remains the canonical answer for primary fly ash control at scale.

Why Other Options Are Wrong:
Gravity chamber: Very low efficiency; precleaner only.Cyclone: Limited for very fine ash.Bag filter: Highly efficient but not the typical “most suitable” primary in legacy large utility units due to pressure drop and temperature constraints.

Common Pitfalls:

• Assuming cyclone sufficiency for fine particulate.
• Ignoring scale and gas flow when choosing filtration systems.

Final Answer:
electrostatic precipitator