Hot reflux in a column

[sgoel]

We have a column with accumulator tray in the middle. There is a side draw from accumulator tray. There is a pump around provided to next tray from accumulator tray. This stream is just circulating from accumulator tray to next tray through pump around pump. This liquid could have just overflown from the accumulator tray rather than spending energy in pump around pump. What could be the reason for this scheme.

Thanking you in anticipation

Shashank

 

[sshep]

Hello sgoel,

An important feature of total trap out is the ability to measure (or insure) the flow from the accumulator tray to the lower section of the column if desired. This can provide important control opportunities that do not exist with a simple overflow such as:

It is possible to insure (by means of positive flow) that the lower section does not run dry- an important consideration when the side draw is high relative to the return flow;

As overflow from a compartment implies a constant inventory on the trap tray (although in rare cases we see slotted overflow designs where level determines flow). The total trap out design means the side draw can be taken off via level control in cases where this makes sense. When level can vary, the accumulator can also be used for the variable hold-up which is needed in closed system designs (i.e. recycles of solvent, catalyst, etc).

This is my experience anyway.

best wishes,
sshep

 

[EmmanuelTop]

sgoel,

When you say 'pumparound', it means that stream is drawn-off from the tower, subcooled by exchanging sensible heat in an external circuit, and then returned to the tower as colder liquid - for the purpose of maintaining overall tower heat balance. This would not be possible if this amount of liquid cascades on the tray below as internal reflux.

http://antwrp.gsfc.nasa.gov/apod/astropix.html

 

[dcasto]

You could take a side draw with a composition you want on the side draw.

Is the accumulator set up for three pahse ie, can you decant water on that tray.