The document summarizes the process of crude oil distillation. Crude oil is heated through heat exchangers to 550°F and then further heated to 750°F in a furnace before entering the flash zone of an atmospheric fractionator. Reboilers provide heat to the bottom of distillation columns by boiling the liquid to generate vapors that drive the separation process. Temperature above 370-380°F can cause cracking and coking in atmospheric columns, so residue is sent to vacuum distillation where pressure is reduced below vapor pressure to distill the most volatile liquids.

2.  After desalting, the crude oil is pumped
through a series of heat exchanger and its
temperature raised to about 550°F (288°C ) by
heat exchange with product and reflux
streams.
 It is then further heated to about 750°F
(399°C ) in a furnace and charged to flash
zone of atmospheric fractionators.

4. Rectifying section
Flash zone
Stripping section

5.  Reboilers are heat exchangers typically used
to provide heat to the bottom of
industrial distillation columns.
 They boil the liquid from the bottom of a
distillation column to generate vapors
which are returned to the column to drive
the distillation separation.

6.  In this reboiler type, steam flows
through the tube bundle and exits
as condensate.
 The liquid from the bottom of the
tower, commonly called
the bottoms, flows through the
shell side.
 There is a retaining wall separating
the tube bundle from the reboiler
section so that the tube bundle is
kept covered with liquid.

7.  The vapour moves up the
column, and as it exits the top of
the unit, it is cooled by
a condenser.
 The condensed liquid is stored
in a holding vessel known as the
reflux drum.
 Some of this liquid is recycled
back to the top of the column
called the reflux.
 The condensed liquid that is
removed from the system is
known as the top product.

9.  Temperature above 370-380 °C is not
favourable in atmospheric column as high
molecular weight compounds in crude will go
thermal cracking and form coke.
 Formation of coke will result in plugging
tubes
 Therefore residue from atm column is sent to
vacuum distillation column.

10.  In Vacuum distillation the pressure is reduced
to less than its vapor pressure (usually less
than atmospheric pressure) causing
evaporation of the most volatile liquid(s)
(those with the lowest boiling points).
 This distillation method works on the
principle that boiling occurs when the vapor
pressure of a liquid exceeds the ambient
pressure.