Crude Oil from storage tank is pumped through preheat exchangers to an electrostatic desalter using fresh water, which is preheated and mixed with crude oil. The desalted crude is further heated in exchangers with hot product streams before it enters the heater.
The preheated crude oil from desalter is then charged to the heater which is fired by off-gas or one of the product streams. Crude Oil enters the heater convection section, passes through the radiant section and exits the heater at suitable temperature for fractionation.
The heated Crude oil from the fired heater is flashed into vapor and liquid fractions in the flash zone of the distillation column. The vapor fraction rises through wash zone fractionating trays of the column, whereas liquid fraction flows down to bottom through stripping section. At certain operating temperature, diesel fraction in the vapor condenses and flows back into liquid phase and is drawn as product from the chimney trays under level control into a diesel stripper. The lighter fractions including gas goes up and condenses in overhead air-cooled condenser. Part of condensate is fed back as reflux and the balance is blended with the residue from the column bottom and mixed with the Crude Oil. The uncondensed gases are vented to the flare system.
