There are several types of scrubbers commonly used in waste gas treatment to effectively remove pollutants from industrial exhaust gases. Let's explore these different types and their mechanisms for pollutant removal:

Wet Scrubbers:

Wet scrubbers, also known as wet scrubbing systems or wet air scrubbers, use a liquid, typically water, to capture and remove pollutants from the exhaust gas stream. They work through the following mechanisms:

Absorption: Pollutants dissolve or react with the liquid scrubbing medium. This can occur through physical absorption or chemical reactions, depending on the nature of the pollutants and the scrubbing liquid used.

Impaction: Larger particles or droplets in the gas stream collide with the liquid droplets in the scrubber, resulting in their capture and removal.

Condensation: Certain pollutants may undergo condensation when exposed to the cooler temperature of the liquid scrubbing medium, allowing for their removal.

Different designs of wet scrubbers include packed bed scrubbers, spray towers, venturi scrubbers, and bubble plate scrubbers. Each design has specific advantages and suitability for different pollutant types and concentrations.

Dry Scrubbers:

Dry scrubbers, also known as dry air scrubbers or dry sorbent injection systems, utilize solid or liquid sorbents to capture and remove pollutants from the exhaust gas stream. They operate through the following mechanisms:

Adsorption: Pollutants adhere to the surface of the solid or liquid sorbent material through physical or chemical adsorption.

Reaction: Some pollutants may undergo chemical reactions with the sorbent material, resulting in their capture and conversion to less harmful compounds.

Filtration: Particulate pollutants are captured by physical filtration mechanisms, such as fabric filters or electrostatic precipitators, before they can be released into the atmosphere.

Dry scrubbers can be particularly effective for the removal of acid gases, such as sulfur dioxide (SO2) and hydrogen chloride (HCl), as well as particulate matter.

Biological Scrubbers:

Biological scrubbers, also known as biofilters or biotrickling filters, use microbial activity to remove pollutants from the exhaust gas stream. The key mechanism involved is biodegradation, where microorganisms present in the biofilter media metabolize and break down the pollutants into harmless byproducts, such as carbon dioxide and water. Biological scrubbers are commonly used for the treatment of volatile organic compounds (VOCs) and certain odorous compounds.

Adsorption Scrubbers:

Adsorption scrubbers utilize adsorbent materials, such as activated carbon or zeolite, to capture and remove pollutants from the exhaust gas stream. The adsorbent materials have a high surface area, allowing for the physical adsorption of pollutants onto their surfaces. Adsorption scrubbers are effective for the removal of a wide range of organic compounds, including VOCs and hazardous air pollutants.

In conclusion, different types of scrubbers, such as wet scrubbers, dry scrubbers, biological scrubbers, and adsorption scrubbers, are used in waste gas treatment to effectively remove pollutants from industrial exhaust gases. These scrubbers employ various mechanisms, including absorption, impaction, adsorption, biodegradation, and chemical reactions, to capture and remove pollutants, ensuring cleaner emissions and improved air quality. The selection of the appropriate scrubber type depends on the specific pollutants present, their concentrations, and the desired emission standards.