3 replies to this topic

[jdk11]

Hi I'm currently researching packed columns and am understanding most things but I really do not understand the term liquid loading.

I am aware if its units of m3/(m2.s) but does that not just simplify to a velocity of liquid? In which case how does it relate to the rate at which liquid is held up in the column?

I'd really appreciate some help on this issue as I cant find any websites that explain this fully, only use the term to explain other things.

Thanks
Jonathan

[breizh]

Hi Jonathan,

Consider these papers to support .

Breizh

[katmar]

You are correct that the liquid loading simplifies to a superficial velocity. But remember that the superficial velocity does not correspond with any actual physical velocity you will find in the column.  It is the velocity that would be achieved if the liquid were flowing down as a plug covering the entire cross section of the column.  In fact the liquid flows in narrow streams at higher velocities than the superficial velocity and when these velocities are averaged with the areas where the liquid velocity is zero you get to the superficial velocity.

 

The liquid holdup is the m³ of liquid in a m³ of column volume at any given moment.  The holdup is a function of the liquid loading, but also a function of the packing characteristics and of the gas loading. For example, as the gas loading increases it will restrict the flow of liquid down the column and the holdup will increase. But the liquid loading remains the same because although any one droplet of liquid is flowing downwards more slowly (because of the gas restricting it) the superficial velocity remains the same (because the liquid is flowing in a "thicker" stream).

[jdk11]

Thanks very much!