Vacuum Distillation Process Steps
The function of a VDU is separation of the atmospheric crude tower residue to produce heavy, medium, and light gas oil as well as a vacuum residue.
Vacuum Distillation Unit (VDU) Process Steps
The typical process steps involved are as follows:
- The reduced crude oil is pumped through a series of heat exchangers and a crude furnace until reaching the desired temperature (350°C – 390°C)
- The reduced crude oil is flashed to separate the desired fractions. Light vapors rise to the top and heavier hydrocarbon liquids fall to the bottom.
- Steam injection at the bottom of the column improves the separation of lighter boiling components
- The vacuum column uses a series of pump arounds to maintain temperature at the correct level at certain points along the tower
- Light vapour gases are removed at the top of the tower, condensed and recycled back to the column as reflux. Light Naphtha is drawn off and excess gases sent to flare.
- Vacuum gas oil (VGO) and lubricating oils are drawn off and routed for further treatment in Hydrotreating units
- Vacuum residue from the bottom is sent to intermediate storage or typically to be further processed in a FCC or delayed coking unit.