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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 the extraction of heat by circulation of coolant in the shell.

The absorbing 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, descend 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.

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

 Sr. No. Nominal Size (mm) Absorber Area (m2) No. Of Tubes/Tube OD (mm) Max. Gas Absorption Rate (Pure HCL)* (Kg/hr) Max. Acid Prod. Rate (As 30% HCL)( Kg/hr) Height (m)
 1 80 1.00 4/20 30 100 4400
 2 10L 20L 40 10 20 40
 2 100 1.76 7/20 60 200 4500
 3 150 4.80 19/20 150 500 4600
 4 225 7.80 31/20 250 833 4920
 5 300 15.30 61/20 500 1667 5050
 6 400 36.00 143/2 1175 3917 5300
 7 450 47.00 187/20 1500 5000 5700
 8 600 84.00 333/20 2700 9000 5800