5 replies to this topic

[swethaneelagiri]

Can anyone tell me the relation between % flooding, foaming factor and safety factor. How does flooding affect column? what do you mean by equivalent flooding?

Thank you

[Padmakar Katre]

Dear,
Refer any of the Mass Transfer Handbook or Distillation System Design Handbook for to get the definations and the better understandings of these terms or just google the terms and the get the right information.

[siroos]

Dear,
Refer any of the Mass Transfer Handbook or Distillation System Design Handbook for to get the definations and the better understandings of these terms or just google the terms and the get the right information.

the flooding which i know is:when the liquid(clear liquid+foam) level on trays increases due to :(outlet or product<input or feed,reboiler duty>required duty(increasing the foam on trays,reflux is too high with respect to product) then the DP of the tower begins to increase.th dp indicate the liquid level on tray.the level increases on each tray from the bottom of the tower.the first tray becomes full of liquid.the liquid reaches to next tray.(from bottom to top).at this point the flooding begins on first tray and if there is no action ,it transfer to top of the tower .then we have flooding in tower.the trays will not work.because of liquid contact.tower becomes like one step separator.

[Zauberberg]

% of flooding is that design/operational point of tower/tray section which gives you the information how close you are to the hydraulic limit of existing tower internals - whether it is downcomer liquid capacity handling (downcomer flood), or tray vapor capacity handling (jet flood). Columns are usully designed with max. 85% of flooding at their rated capacity, so you can consider 15% to be the safety factor. For smaller diameter towers, maximum percent of flooding is somewhat lower.

Foaming factor is a quantitative description of phase separation inside the tower. The lower the foaming factor, the more difficult is to separate vapor from liquid - and more time is required for proper phase separation. This results in lower flooding velocities and lower downcomer handling capacities, which means that you have to go for larger tower diameter and increased tray spacing - as compared to the same system/application if the foaming factor is equal to 1. Highly foaming systems require higher tray residence time, to allow for good phase separation.

[Qalander (Chem)]

Nice, Fairly accurate response indeed! Dear Zauberberg.
Qalander

[smalawi]

Hi,

Go to google books and search for distillation operation / design by H Kister

These books are simple excellent and you will understand the "many" types of flood cases possible.

Cheers,

SM