In gas treatment, what is the unit operation that uses countercurrent gas and liquid flow to remove soluble components?

In gas treatment, what is the unit operation that uses countercurrent gas and liquid flow to remove soluble components?

• A. Distillation column
• B. Absorber
• C. Scrubber
• D. Separator

Answer: (B)

Gas absorption is the process of removing soluble components from a gas by dissolving them into a liquid solvent. In an absorber, the gas and liquid flow countercurrently, which maintains a high driving force for mass transfer across the interface. As the gas stream contacts the liquid solvent that’s moving in the opposite direction, soluble species diffuse into the liquid because the gas is rich in solute at the inlet while the liquid entering is relatively lean. The cleaned gas exits, and the liquid leaves as a rich solution carrying the dissolved components. The countercurrent arrangement is key because it sustains a strong concentration gradient throughout the column, improving the removal efficiency. Distillation relies on differences in volatility and heat-driven phase change, not simply dissolving solutes into a liquid. A separator mainly separates immiscible liquids or phases. A scrubber is a related gas-cleaning device that uses liquid contact, but the specific operation described—removing soluble components from a gas by countercurrent mass transfer into a liquid—is best described as an absorber.

Gas absorption is the process of removing soluble components from a gas by dissolving them into a liquid solvent. In an absorber, the gas and liquid flow countercurrently, which maintains a high driving force for mass transfer across the interface. As the gas stream contacts the liquid solvent that’s moving in the opposite direction, soluble species diffuse into the liquid because the gas is rich in solute at the inlet while the liquid entering is relatively lean. The cleaned gas exits, and the liquid leaves as a rich solution carrying the dissolved components. The countercurrent arrangement is key because it sustains a strong concentration gradient throughout the column, improving the removal efficiency.

Distillation relies on differences in volatility and heat-driven phase change, not simply dissolving solutes into a liquid. A separator mainly separates immiscible liquids or phases. A scrubber is a related gas-cleaning device that uses liquid contact, but the specific operation described—removing soluble components from a gas by countercurrent mass transfer into a liquid—is best described as an absorber.