Technology Unit

: Vacuum Distillation Unit
: Generic VDU
Short Name: VDU
Description: The VDU operates at a vacuum pressure to help in separating Heavy Hydrocarbons and allows lower temperatures for Distillation than are possible in the ADU. The vacuum pressure is typically 18 kPa at the Vacuum Column Flash Zone and 10 kPa at the Column Top. The vacuum is created by placing a series of Ejectors in service. The VDU uses the same operating principles as the ADU but with fewer Trays and Side Cuts. The Superheated Steam is introduced from the Bottom of the Column at about 350°C, so as to reduce the partial pressure in the Column and thus enhance Vaporization and Separation of the Heavy Hydrocarbons. The temperature profile is designed so that the lowest temperature is well above the dew point temperature of the Steam at Column Pressure, to ensure it will not condense in the Column. Steam is typically supplied at about 1 kg steam/100 kg Hydrocarbons.
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