Application: Separates and recovers the relatively lighter fractions (e.g., naphtha, kerosine, diesel and cracking stock) from a fresh crude oil charge. The vacuum flasher processes the crude distillation bottoms to produce an increased yield of liquid distillates and a heavy residual material.
Description: The charge is preheated (1), desalted (2) and directed to a preheat train (3) where it recovers heat from product and reflux streams. The typical crude fired heater (4) inlet temperature is on the order of 550 ° F, while the outlet temperature is on the order of 675°F to 725°F. Heater effluent then enters a crude distillation column (5) where light naphtha is drawn off the tower overhead (6); heavy naphtha, kerosine, diesel and cracking stock are sidestream drawoffs. External reflux for the tower is provided by pumparound streams (7–10). The atmospheric residue is charged to a fired heater (11) where the typical outlet temperature is on the order of 725 °F to 775°F.
From the heater outlet, the stream is fed into a vacuum tower (12), where the distillate is condensed in two sections and withdrawn as two sidestreams. The two sidestreams are combined to form cracking feedstock. An asphalt base stock is pumped from the bottom of the tower. Two circulating reflux streams serve as heat removal media for the tower.
Yields: Typical for Merey crude oil:
Crude unit products wt% °API Pour, °F
Overhead & naphtha 6.2 58.0 —
Kerosine 4.5 41.4 – 85
Diesel 18.0 30.0 – 10
Gas oil 3.9 24.0 20
Lt. vac. gas oil 2.6 23.4 35
Hvy. vac. gas oil 10.9 19.5 85
Vac. bottoms 53.9 5.8 (120)*
Total 100.0 8.7 85
Licensor: Foster Wheeler USA Corp.