distillation columns diameter

[mahmmoud30]

hi all
i want to know why
1. Atm. distillation columns have constant diameter from top to bottom while lighter cuts (e.g diesel ,naptha..etc have variable diameter from bottom to top?
2. why some absorbers are wide at top and narrow in the bottom?

 

[MortenA]

1) high liquid loads below a specific tray
2) Isnt this usually e.g. for demethanisers and similar that are re-boild absorbers? Here i think its because the feed point is near the top and that most of the feed is gas - and that the stripper section therefore dosnt need to have a large diameter

BEST REGARDS

mORTEN

 

[mahmmoud30]

thanks a lot mORTEN