Efficient gas absorption depends on the following:

This is achieved in a Falling Film Absorber which is essentially a shell & tube heat exchanger in which both gas to be absorbed and absorbing liquid flow co-currently downward with extraction of heat by circulation of coolant in the shell. The abssorbing liquid is circulated through a tank till desired concentration is achieved. The liquid flows at such a rate that the tubes do not flow full of the liquid but instead, descends by gravity along the inner walls of the tubes as a thin film. Obviously, this produces a much greater linear velocity for a giver rate flow than could be obtained if the tube flowed full.

The equipment works as a number of water cooled-wall columns in parallel and each tube is provided with distribution system on top to effect uniform distribution of both liquid and gas and also formation of a thin liquid film on the inner surface of the tube.

Salient Features

• The heat of absorption is continuously removed. This ensures better absorption and product concentration as compared with conventional packed tower.
• Low residence time and operating temperature ideally suited to heat sensitive materials.
• Borosilicate glass and PTFE contact parts ensure corrosion/ contamination free operation.
• Both standard and custom built units are available.
• Capable of operating from zero to maximum gas flow rate.
• Ease of installation due to light weight.
• Trouble free and consistent performance with minimal attention.
• Wide application e.g. HCl, HBr, NH3, SO2, H2S, Br2 etc.
• Less cost.
• Negligible pressure drop compared to conventional columns.
• Compact design Sleek and slender.
• Both heat and mass transfer operations are incorporated in a single equipment.
• Very high heat transfer coefficient as the liquid falls instead of flowing.
• Scaling of process fluid is minimal due to high velocity and ease of cleaning by simple acid circulation.
• Hot conditions are eliminated at all stages namely pipe, tanks and pumps etc.

Limitations

• Not recommended for gases containing high proportion of inert (insoluble).
• Not applicable if the gases are not highly soluble.