In the context of gaseous pollutants control using packed towers, consider the following statements:
(A) The flow of the effluent gas through a packed tower is countercurrent.

(B) The packing material should have a large surface to volume ratio.

(C) The packing material is used to increase the contact time between the gaseous pollutant and liquid.

Which of the above statements are correct?

Correct option is C

In the context of packed towers used for gaseous pollutant control, let's analyze each statement:

(A) The flow of the effluent gas through a packed tower is countercurrent.
This statement is correct. In packed towers, the flow of gas is typically countercurrent to the flow of liquid. This countercurrent flow maximizes the contact between the gas and liquid phases, enhancing the efficiency of pollutant removal.

(C) The packing material is used to increase the contact time between the gaseous pollutant and liquid.
This statement is correct. The primary purpose of the packing in a packed tower is to increase the surface area available for interaction between the gas and liquid, which, in turn, increases the contact time and enhances the absorption of pollutants.

Information Booster:

1. Countercurrent flow in packed towers is essential because it promotes efficient mass transfer by ensuring that the gas and liquid phases move in opposite directions, increasing the driving force for absorption.
2. Surface-to-volume ratio of packing material plays a crucial role in the performance of packed towers. Materials like ceramics, plastic, and metal are used for packing because they offer high surface area to volume ratios, which improve mass transfer rates.
3. Packing material should be selected based on factors like chemical compatibility, resistance to clogging, and surface area. Common packing materials include raschig rings, berl saddles, and structured packing.
4. Gas-liquid contact is crucial in packed towers for effective removal of pollutants. The increased contact time helps to ensure that pollutants are absorbed into the liquid phase.
5. Tower design (e.g., the choice of packing material, tower height, and liquid flow rate) must be optimized to achieve the desired removal efficiency for specific pollutants.
6. Efficiency factors like gas flow rate, liquid flow rate, and packing material design must be carefully balanced to achieve optimal pollutant removal.