Buffer Tank Vented to Vacuum Tower

[gte682n]

thread124-420364

Hello, this question is related to my previous post above. For the buffer tank that has a dip pipe on the liquid fill line and a vent to a vacuum tower, what is the consequence of not sealing the dip pipe? I would imagine gas being drawn back to the tower via both the vent and liquid fill line. But if my liquid fill line is sized to be self venting, is this an issue? I would also think that it would be optimal to control the level at some minimum required submergence of the dip pipe to avoid excessive back pressure on the product leaving the tower to the buffer tank. Comments on that thought?

Thanks,

 

[georgeverghese]

There is a total differential height of more than 36+54 = 90inches between the level in the buffer tank and the elevation of the balance vent line below the draw tray at T3, so that should be more than adequate to be in excess of the tray dp and any frictional losses even if there was no feed dip pipe at the buffer vessel.

There may be some other reason why you have usteady flow at this sidedraw pump set:
a) Pockets in the vent line where condensed liquids could collect?
b) Corrosion in this vent line or some waxy / viscous deposits building up? Is this line suitably insulated and preferably heat traced ? - cannot read the descriptor label on this line in your diagram - may be due to low resolution on your scanner
c) Presume you've got adequate residence time at LAL-NLL level range in this buffer tank to enable adequate degassing of the exit stream to the pump ?