Scrubbers – Wet and Dry - Environmental Scientist- TNPSC

-

 

Scrubbers – Wet and Dry: Air Pollution Control Devices

🌍 Introduction

Scrubbers are air pollution control devices used to remove gases, vapors, and particulates from industrial exhaust streams before they are released into the atmosphere. They are particularly effective in removing sulfur dioxide (SO₂), acidic gases, and fine particles. Scrubbers are classified into two major types based on the method of pollutant removal: Wet Scrubbers and Dry Scrubbers.

                         

💧 1. Wet Scrubbers

Definition:

Wet scrubbers use a liquid (usually water or a chemical solution) to capture and neutralize airborne pollutants from exhaust gas streams.

Working Principle:

  • Polluted gas enters the scrubber chamber.

  • It is sprayed or bubbled through a liquid (e.g., water, lime slurry).

  • Pollutants are absorbed, dissolved, or chemically reacted with the scrubbing liquid.

  • The cleaned gas exits, and the contaminated liquid is collected for treatment or disposal.

Types:

  • Spray Towers: Spray liquid into a vertical chamber.

  • Venturi Scrubbers: Use high-velocity gas through a narrow throat with scrubbing liquid.

  • Packed Bed Scrubbers: Gas passes through a bed of packing material with liquid sprayed over it.

Advantages:

  • Effective at removing acidic gases (e.g., SO₂, HCl, NH₃) and particulate matter.

  • Can cool hot gases as well (acts as a quenching system).

  • Some can also capture heavy metals and odorous compounds.

Disadvantages:

  • Produces wastewater/sludge that needs treatment.

  • Higher maintenance and operating costs.

  • Not suitable for all types of pollutants (e.g., dry dust without soluble gases).

Applications:

  • Coal-fired power plants

  • Chemical manufacturing

  • Metal processing industries

  • Waste incinerators

🌬️ 2. Dry Scrubbers

Definition:

Dry scrubbers remove pollutants from exhaust gases using dry sorbent materials without any liquid medium.

Working Principle:

  • A dry powder (like lime or sodium bicarbonate) is injected into the flue gas stream.

  • The sorbent reacts with acidic gases (e.g., SO₂, HF, HCl), forming solid salts.

  • The mixture of clean gas and solid by-products passes through a filter or baghouse, where particulates are captured.

Types:

  • Dry Injection Systems (DIS)

  • Spray Dry Absorbers (SDA) – also known as semi-dry scrubbers (use a fine mist of sorbent slurry that dries rapidly)

Advantages:

  • No liquid waste produced

  • Lower water usage

  • Simpler handling and disposal of dry residues

  • Compact and easier to operate

Disadvantages:

  • Lower removal efficiency compared to wet scrubbers (especially for SO₂)

  • Only suitable for specific pollutants

  • Sorbent consumption may be high

Applications:

  • Cement plants

  • Municipal waste incineration

  • Glass manufacturing

  • Smaller industrial boilers

⚖️ Comparison Table

Feature                 Wet ScrubbersDry Scrubbers
Uses LiquidYesNo
Water ConsumptionHighLow/None
Waste TypeLiquid/SludgeDry solid residue
EfficiencyHigher for gasesLower for gases
CostHigher (O&M)Lower (O&M)
Common UseHeavy industrySmall/medium industry
Download this Material as PDF
Click here to download

Other Topics

Components of Environment - TNPSC - Env Scientist

 Atmosphere

Segments of Environment

Lithosphere

Hydrosphere


Popular posts from this blog

TNPSC Environmental Scientist - Environment: Components – Study Notes

-
Image
            Environment: Components – Study Notes Syllabus: Unit I: Introduction to Environment (30 Questions) Environment: Components – Segments – Atmosphere: Troposphere – Stratosphere – Mesosphere – Thermosphere – Lithosphere: Crust – Mantle – Core – Hydrosphere: Fresh water and saline water - Biosphere – Ecology: Autecology – Synecology – Ecosystem: Structure and Function – Energy Flow – Food Chain – Food web – Ecological pyramids – Biogeochemical cycles (C,N, P, S and water) - Ecological successions: Primary and Secondary succession – Ecological interactions: Symbiosis - Commensalism – Mutualism - Proto-cooperation – Amensalism – Predation – Parasitism – Natural resources: Classificationrenewable and non-renewable - Status and challenges. Water resources: Types – Availability – Issues - Conflicts over water. Soil and mineral resources - Mineral exploitation and Environmental impacts; Forest resources. Energy resources: Conventional and Non-convent...
Read more

Environmental Scientist - TNPSC - Ecological Interactions MCQs

-
Image
       🌱 Ecological Interactions – MCQs Answers are given below.... 1. Which type of ecological interaction benefits both species involved? A) Predation B) Parasitism C) Mutualism D) Commensalism 2. In parasitism, the organism that is harmed is called the: A) Predator B) Host C) Parasite D) Vector 3. The interaction in which one organism benefits while the other is neither harmed nor benefited is called: A) Mutualism B) Amensalism C) Commensalism D) Competition 4. Which of the following is an example of interspecific competition ? A) Lions competing with each other for mates B) Trees shading out understory plants C) Two bacteria cells dividing D) An eagle preying on a rabbit 5. Which ecological interaction is detrimental to both species involved? A) Predation B) Mutualism C) Competition D) Commensalism 6. Mycorrhizal fungi associated with plant roots illustrate what type of interaction? A) Parasitism B) Mutualism C) Predation D) Amensalism 7. A...
Read more

Environmental Scientist - TNPCB - Hydrosphere

-
Image
  Hydrosphere –   Study Notes Unit I: Introduction to Environment (30 Questions) Environment: Components – Segments – Atmosphere: Troposphere – Stratosphere – Mesosphere – Thermosphere – Lithosphere: Crust – Mantle – Core – Hydrosphere: Fresh water and saline water   Introduction The Hydrosphere encompasses all the water found on, under, and above the surface of the Earth. It includes oceans, seas, rivers, lakes, glaciers, groundwater, and atmospheric water vapor. Water is essential for all forms of life, and the hydrosphere plays a critical role in shaping weather, climate, landforms, and sustaining ecosystems. Definition and Components   Definition: The Hydrosphere is defined as the combined mass of water found on, under, and over the surface of a planet.   Major Components of the Hydrosphere: Component Percentage of Total Water Oceans and Seas 97.2% Icecaps and ...
Read more