In Figure 1 -4, the crude oil received from off-site storage tanks through booster pumps is pumped by charge pump P-101 and preheated in parallel trains of preheat exchangers with hot intermediate streams and products. A small quantity of water and demulsifier chemicals are added before preheating. The hot crude is mixed with washwater and fed to electric desalters V-106 A and B to reduce the salt content by an electric desalting process. The water phase, containing most of the dissolved salts contained in the crude, separates out. The desalted crude is dosed with an NaOH solution to a fixed chloride content. The desalted crude is further heated through two parallel trains of heat exchangers and fed to preflash tower V-l 17. The preflash tower overhead vapor is cooled by exchanging heat with crude oil and condensed in an overhead drum V-l 18. Part of this liquid naphtha is used as reflux in the column; the rest of the liquid and the vapor from the drum are sent to the naphtha processing unit.
Atmospheric distillation. K.O. = knockout; C.W. = cooling water; B.L. = battery limits.
The crude from the bottom of the preflash tower is pumped through the heat exchangers, recovering heat from vacuum tower bottoms and side-stream HVGO, and sent to fired atmospheric heater H-101. The crude is partially vaporized in the fired heater before entering the flash zone of the atmospheric tower V-101. Superheated stripping steam is introduced through the bottom of the column.
The tower overhead vapor is cooled by exchanging heat with crude oil, condensed in air cooler E-109, and routed to overhead product accumulator V-105. The overhead gases from this accumulator are compressed in compressor C-101 to about 40psig pressure and sent to the refinery gas recovery system. The condensed naphtha in the accumulator is separated from water. A part of this naphtha is sent back to the column by reflux pump P-102 and the rest is withdrawn as an intermediate product for processing in naphtha fractionation unit.
Kerosene and light diesel cuts are withdrawn as sidestreams from the atmospheric distillation tower. These are steam stripped in steam strippers V-102 and V-103, respectively. The kerosene and light diesel product streams exchange heat with crude oil feed in the crude preheat train and finally cooled in air fin coolers E-106 and E-lll and sent to storage.
The hot atmospheric bottoms or reduced crude, at approximately 660°F, is transferred by P-107 to vacuum tower heater H-102.
Was this article helpful?