Air Pollution Control techniques applied to reduce gaseous pollutants in the ambient atmosphere are: (A) Cyclone collectors (B) Limestone Injection multistage Burner in thermal Power Plants (C) Selective Catalytic Reduction (SCR) in thermal power plants (D) Electrostatic Precipitators in thermal Power Plants (E) Fabric bag filters
Choose the most appropriate answer from the options given below:

Correct option is C

The correct answer is (c) B, C, and E only. These techniques are specifically used to reduce gaseous pollutants in the ambient atmosphere, particularly in thermal power plants.
Breakdown of Techniques:
1. (B) Limestone Injection Multistage Burner:
· Used in thermal power plants to reduce sulfur dioxide (SO₂) emissions by injecting limestone (CaCO₃) during combustion. The sulfur reacts with limestone to form calcium sulfate (CaSO₄), which is a solid and less harmful.
2. (C) Selective Catalytic Reduction (SCR):
· An effective method in thermal power plants for reducing nitrogen oxides (NOₓ) emissions. Ammonia (NH₃) is injected into the flue gas, and the reaction over a catalyst converts NOₓ into nitrogen (N₂) and water (H₂O).
3. (E) Fabric Bag Filters:
· Although primarily used for removing particulate matter, these filters can also capture some gaseous pollutants when combined with other techniques, making them relevant for air pollution control systems.
Why Other Options Are Incorrect:
1. (A) Cyclone Collectors:
· Designed to remove large particulate matter (dust), not gaseous pollutants.
2. (D) Electrostatic Precipitators (ESPs):
· Effective for removing particulate matter rather than gaseous pollutants. ESPs work by charging particles and collecting them on plates, but they don’t directly address gaseous emissions.
Information Booster 1. Techniques for Gaseous Pollutant Control:
· SO₂ Control:
· Limestone Injection and Flue Gas Desulfurization (FGD) are used to reduce sulfur dioxide emissions.
· NOₓ Control:
· Selective Catalytic Reduction (SCR) and Selective Non-Catalytic Reduction (SNCR) are effective methods.
· VOC Control:
· Techniques like activated carbon adsorption can capture volatile organic compounds.
2. Particulate Matter Control:
· Cyclone Collectors and Fabric Bag Filters are used to remove solid particles from emissions.
3. Combinations in Power Plants:
· Modern thermal power plants often use multi-stage pollution control systems that combine techniques for gaseous and particulate emissions.
Additional Knowledge · Limestone Injection:
· Reduces sulfur emissions during combustion by reacting with SO₂.
· SCR (Selective Catalytic Reduction):
· One of the most effective technologies for reducing NOₓ emissions in thermal power plants.
· Fabric Bag Filters:
· Common in industrial processes for capturing fine particulates and, in some cases, gaseous pollutants.