Question

What is the primary function of an Electrostatic Precipitator (ESP)?

• A. To remove particulate matter from air or gas streams
• B. To neutralize acidic pollutants
• C. To reduce nitrogen oxide emissions
• D. To remove volatile organic compounds (VOCs)

Hint:

• Electrostatic Precipitators (ESPs) are used to control particulate matter (PM) emissions.
• They work by electrostatically charging particles in a gas stream and then collecting them on oppositely charged plates.
• ESPs are effective for a wide range of particle sizes and are common in large industrial applications.
• They do not primarily target gaseous pollutants like acidic gases, NOx, or VOCs.

Answer 1

The Correct Option is A

The primary function of an Electrostatic Precipitator (ESP) is to remove particulate matter from air or gas streams.

Step-by-Step Explanation:

Step 1: Understanding Particulate Matter

Particulate matter (PM) refers to solid or liquid particles suspended in the air or gas. These can include dust, ash, smoke, soot, and aerosols. In industrial processes (like power plants, cement factories, or steel mills), large quantities of particulate matter can be generated and released into the atmosphere, contributing to air pollution and health problems.

Step 2: How an Electrostatic Precipitator (ESP) Works

An ESP operates on the principle of electrostatic forces to collect particulate matter. The process typically involves three main steps:

1. Charging: The dirty gas stream enters the ESP, and the particulate matter within it passes through a strong electric field generated by discharge electrodes (typically negatively charged). These electrodes emit electrons that attach to the particles, giving them an electrical charge (usually negative).
2. Collection: The charged particles then move towards collecting electrodes (typically positively charged plates or surfaces). Due to the electrostatic attraction between the charged particles and the oppositely charged collecting plates, the particles are pulled out of the gas stream and adhere to the plates.
3. Removal (Rapping/Washing): Periodically, the collected particulate matter is dislodged from the collecting plates. This is often done by mechanically "rapping" (vibrating or hitting) the plates, causing the accumulated dust to fall into hoppers below, from where it is removed. In some applications, the plates are washed with water.

Step 3: Evaluating the Other Options

• To neutralize acidic pollutants: Neutralizing acidic pollutants (like SO₂ or HCl) typically involves gas scrubbers that use alkaline solutions (e.g., lime or caustic soda). ESPs are not designed for this chemical reaction.
• To reduce nitrogen oxide emissions: Nitrogen oxides (NOx) are gaseous pollutants reduced through technologies like Selective Catalytic Reduction (SCR) or Selective Non-Catalytic Reduction (SNCR), which involve chemical reactions, often with ammonia or urea. ESPs do not target NOx.
• To remove volatile organic compounds (VOCs): VOCs are gaseous organic compounds that contribute to air pollution. Their removal usually involves adsorption (e.g., activated carbon), thermal oxidation, or catalytic oxidation, which convert or capture the gaseous compounds. ESPs are designed for particulate matter, not gaseous pollutants like VOCs.

Step 4: Conclusion

Therefore, the fundamental and primary role of an Electrostatic Precipitator (ESP) in pollution control is to efficiently remove particulate matter from air or gas streams, making it a crucial technology in industries to comply with air quality regulations.