3 replies to this topic

[NoobMi]

Hi all,

i am interested in calculating flooding and weeping in packed column based on different reflux ratio, so as to determine operation range for the tower reflux ratio.

For flooding, i was able to use the flooding curve equation/graph from Kessler and Wankat 1988.But was unable to find details abt weeping.

So my qn is
1) Does weeping occurs in packed column? or it is generally termed as mal-disttibution?

2) Is there any correlation to determine this weeping/mal-distribution effect in packed column?

[katmar]

The term "weeping" is usually used in tray columns where the liquid leaks through the perforations or valves because of insufficient counter current gas flow.  Weeping is undesirable and the liquid should flow across the tray and down the downcomer.  In a packed column the liquid is intended to flow downwards across the entire cross section of the column, so weeping is not a relevant concept in a packed column.

 

The closest analogous concepts for packed columns would be mal-distribution (as you have suggested) or wetting rate.  Correct use of liquid distributors and re-distributors will guard against mal-distribution.  If you have insufficient liquid flow it is possible that some of the packing will not be wetted and it would be possible for gas to flow upwards without contacting the liquid.  Different packing styles and materials of construction require different minimum wetting rates.

[Pilesar]

Proper liquid distribution is key to packed column performance. Engineered distributors are designed for a specific range of liquid flows. The liquid distributors may have a more tightly constrained operating range than the theoretical operating range for the packing.

[Vinayak Chavan]

In Packed column you have channelling (liquid flows along the wall of the column after traveling certain height of packed bed) and in tray column you have weeping (vapour flow rate becomes insufficient to hold the liquid on tray).

 

i dont think there will be any correlation for calculating channelling in the packed bed but in order to avoid it you have to restrict the packing bed height.

 

Maximum bed height is dependent on the type and size of the packing.

 

vinayak chavan