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.