Vacuum Distillation column working process in oil and gas refineries

Vacuum Distillation column
Atmospheric resid is further fractionated in a Vacuum Distillation tower. Products that exist as a liquid at atmospheric pressure will boil at a lower temperature when pressure is significantly reduced. Absolute operating pressure in a Vacuum Tower can be reduced to 20 mm of mercury or less (atmospheric pressure is 760 mm Hg). In addition, superheated steam is injected with the feed and in the tower bottom to reduce hydrocarbon partial pressure to 10 mm of mercury or less.

Atmospheric resid is heated to approximately 750˚F (400˚C) in a fired heater and fed to the Vacuum Distillation tower where it is fractionated into light gas oil, heavy gas oil and vacuum resid.

Typical products and their true boiling points (TBP) from crude oil distillation (i.e., both atmospheric and vacuum tower products) are:

Initial TBP - ˚F (˚C)
Final TBP - ˚F (˚C)
Light Naphtha
80 (27)
200 (95)
Heavy Naphtha
200 (95)
380 (195)
355 (180)
500 (260)
Light Gas Oil
470 (245)
650 (345)
Heavy Gas Oil
630 (330)
800 (425)
Vacuum Gas Oil
775 (410)
1000 (540)
Vacuum Resid
1000 (540)

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