Describe the basic operation of a gas scrubber used to remove impurities from gas streams.

• A. Gas scrubber contacts gas with a liquid in packed or tray columns; contaminants are absorbed by the liquid and carried away for treatment.
• B. Gas scrubber uses a cyclone separator to remove particles.
• C. Gas scrubber burns impurities.
• D. Gas scrubber filters with a dry cartridge.

Answer: (A)

Gas scrubbers remove impurities by bringing the gas into contact with a liquid so contaminants transfer into the liquid. In a typical wet scrubber, the gas moves upward through a packed bed or over tray plates while the liquid flows downward, creating countercurrent contact. The large surface area and mixing promote mass transfer, so soluble contaminants dissolve into the liquid (and may react chemically if needed). The contaminated liquid is then sent to treatment or recirculated, and the cleaned gas exits. The liquid choice depends on the pollutants: water can remove general soluble contaminants, while alkaline or other solvents target specific acids or gases.

This reflects the fundamental idea of scrubbing: purification through liquid absorption, as opposed to removing particles with a cyclone, burning impurities, or filtering with a dry cartridge.