Old bubble cap trays & modern sieve trays

[ww2i]

Is it true that ancient bubble cap trays are better than modern trays?
And if yes, in which ways are they better?

[sys1]

It is not entirely true that bubble cap trays are better across the board. In fact, modern sieve and valve trays have largely replaced older bubble cap designs in most industrial distillation columns due to their efficiency and lower cost. However, bubble cap trays do possess a few specific operational superpowers that make them superior for certain specialized, demanding applications.

[jeem]

if you're looking at an existing refinery/petrochemical column with old bubble-cap trays that someone wants to replace, don't approve the change merely because the bubble caps are "old technology." The existing tray hydraulics and actual operating history should be evaluated first. Sometimes the old trays are performing extremely well for the particular service.

[ivani1]

Bubble-cap trays are often better when operating flexibility and low-load performance are more important than pressure drop, capacity, cost and mechanical simplicity.
A bubble-cap tray maintains liquid on the tray and forces vapor through the risers/caps. Unlike a sieve tray, there are no simple open holes through which liquid can drain when vapor flow becomes very low.
So at low vapor rates:

• less tendency for tray weeping

• better vapor-liquid contact

• better operation at low load

• wider operating range in some applications

This is why old bubble-cap trays can sometimes continue operating reasonably well when a modern sieve tray would start experiencing severe weeping.