Mass Transfer

Gas-Liquid Mass Transfer:

Ever wonder how do petrochemical industries reduce their air pollutions emitted by their machinery to abide by the laws imposed on them and to prevent acid rain/global warming? This is done by using a unit operation called the Gas-Liquid Mass Transfer using the Gas Absorption towers. 

So what does Gas Absorption towers do?

Packings for Gas Absorption

Gas Absorption Towers

It involves 2 phases (gas and liquid) which are brought together intimately with the presence of packing in the tower, where the solute will diffuse from the gas phase to the liquid phase. Basically this means that the gas that is harmful will be diffused into the liquid so that it is extracted out when the industrial machine releases the gases.

Liquid-Gas Mass Transfer:

Whenever a heat exchanger is used, there will be warm water that will be discharged. As the warm water has to be cooled down before sending it back to the heat exchanger. This is achieved by using a unit operation called the Liquid-Gas Mass Transfer by using cooling towers.

So what does Cooling towers do? 

Condenser attached to a boiling flask

A cooling tower is just like a condenser that you use in a lab. The driving force of gas phase is due to difference in humidity where water evaporates to gas phase by latent heat of evaporation. The driving forces for the temperature in the liquid phase and for the gas phase. The sensible heat will be transferred from the bulk liquid to the interface in the liquid and from the interface to bulk gas. In simple terms, the water phase is cooled down as water vapour diffuses into the gas phase by evaporating.

Trays for Cooling Towers

Cooling Tower