The document provides information on the operation of a crude and vacuum distillation unit. It separates crude oil into different products based on boiling point differences and prepares the feed for secondary processing units. Key features include two kerosene draw-off flexibilities to meet changing specifications and a heavy gas oil draw off to minimize load on the vacuum heater and vacuum column. The crude distillation unit processes various crude oil cases to produce products like fuel gas, LPG, naphtha, kerosene, light gas oil, heavy gas oil, and reduced crude oil.

1. PRESENTATION ON
OPERATION OF
CRUDE AND VACUUM
DISTILATION UNIT

2. Objective
To separate crude into different products by
boiling point differences.
Prepare feed for secondary processing units
Key Features
Two kerosene draw-off flexibility to meet
changing market and product specifications.
Heavy gas oil (HGO) draw off minimizes load
on Vacuum Heater and Vacuum column
Over flash facility provided in atmospheric
and vacuum column as part of advance
process control.
Crude Distillation Unit

3. Case - 1
31500 MT/D - 70/30 Arab Light / Arab
Heavy
Case - 2
31500 MT/D - 50/50 Arab Light / Arab
Heavy
Case - 3
27000 MT/D - Bombay High
Licensor - ABB LUMMUS CREST Ltd.
Detailed engineering - ENGINEERS INDIA
Ltd
Crude Distillation Unit

4. Distillation of Crude Oil to produce :
Product Name Cut Range Usage
Fuel Gas C1 - C2 Internal Fuel
LPG C3 - C4 Domestic Fuel
Overhead Naphtha C5 - 120 Feed for
NHT/CCR
Heavy Naphtha 120 - 140 Diesel
Component
Kerosene 140 - 270 Domestic Fuel
ATF 140 - 240
Aviation Fuel
Light Gas Oil 240/320 Diesel
Component
Heavy Gas Oil 320 - 370 Diesel
Component
Reduced Crude Oil 370 - 560+ VDU Feed /
IFO
ATMOSPHERIC DISTILATION UNIT

5. CRUDE SPECIFICATION
Properties Case 1 Case 2 Case 3
Specific gravity 60/60 0.864 0.87 0.832
Density at 20oC kg/m3 862 867 830
Sulfur wt% 2.2 2.4 0.17
Pour point Below ambient
Below
ambient 30 deg C
Viscosity at 20oC cSt 18 24 4.8
Viscosity at 50oC cSt 7.5 9 2.6
Viscosity at 100oC cSt 2.8 3.2 1.3
Nickel ppm wt% 8.4 10.5 1.15
Vanadium ppm wt% 31 38 0.44
CCR value wt% 5.35 6.14 1.29
UOP K 11.89 11.88 11.93
oAPI 32.27 31.14 38.57
B S&W (vol %) 0.5 0.5 0.5

6. AtmosphericDistillationProcess
16000 M3X2
Desalter-I
Desalter-II
Preflash
Off Gas / Ovhd Naphtha - SGU
Heavy Naphtha -NHT
L Kero - KMU,FO
H Kero - KMU, FO
LGO -DHDS, FO
HGO - DHDS, FO
RCO to VDU
3640C
280 0C
20 0C
20kg/cm2 g
125 0C
130 0C
11kg/cm2 g

7. Process Description
• Crude is pumped from day tanks to Desalters
• After preheating with product streams crude enters in
to Desalters.
• Two stage desalting is done to remove salts
• Salt removal from crude helps in prevention of
• Heat exchangers fouling
• Corrosion of atm column from hydrolyzing of salts
• Desalter outlet is sent to Pre-flash vessel
• For removal of lighter fractions
• Removal of lighter fractions helps in
• Reduction of vapor phase and two phase flow in preheat
exchangers and fired heater
• Facilitates higher throughput and optimum equipment sizing
• Pre flashed vapors are directly fed to Atm Column

8. Process Description…
• Pre flashed liquid sent for further preheating.
• Preheating of crude with hot product streams Helps in
• Heat optimization
• Lower loads on fired heaters
• Lower cooling water requirement for products cooling
• Preheated crude comes to Fired Heaters
• Where it is further heated to 364 0C
• Heated crude finally enters Atm Column.
• Where it is fractionated as per required specifications
• Product streams are sent to storage / secondary
processing

9. DESALTER OPERATION
 FUNCTION OF DESALTER IS TO REMOVE SALT FROM CRUDE.
 OPERATING VARIABLES
TEMPERATURE : 130 DEG. C
OUTLET CRUDE SALT CONTENT : <0.5 ptb
PRESSURE: 8-11 kg/cm2
BRINE OIL CONTENT: 165 ppm (max)
WATER INJECTION RATE: 4 - 6 % Vol. Of Crude
INTERFACE LEVEL: 40 - 50%
DEMULSIFIER INJECTION: 6 - 8 ppm on crude
DESALTER - 1 DESALTER - 2
MIXING VALVE
CRUDE
DEMULSIFIER DEMULSIFIER
WATER WATER

10. PREFLASH VESSEL
• Pre flash vessel helps to remove around 3-4% of lighter ends from the
crude and send them to the main fractionating column by-passing the
furnace, thus reducing un-necessary furnace load.
• Pre flash vessel is also acting as a surge vessel for CDU Heater Feed.
• Pre-flashed vapors is introduced in the Crude Column LK section.
PREFLASH
VESSEL
PV
PRE-FLASHED VAPOURS
PRE-FLASHED
CRUDE
DESALTED
CRUDE
(3-4% OF CRUDE)

11. CRUDE HEATERS
• Crude heater
• 24 burners in each heater.
• Dual fired burners arranged into 6 groups.
• Each group has four burners.
• Each groups has two pilot flame detectors.
• Pilot flame detractors are arranged on alternate burners.
• Two FD fans and one ID fan.
• MP steam is generated in convection section.
• 8 Pass flows in each heater.

12. CRUDE COLUMN OPERATION
• FLASH ZONE : Partially vaporized crude from heater at 364 °C enters the flash zone of
the crude column. Here the vapors travel upward and the liquid travel downward. The
section of the column below the flash zone is the stripping section and the one above is
the rectifying section.
• STRIPPING SECTION : Here the liquid traveling downwards is stripped off its lighter
components by the stripping steam traveling upwards. There are 6 fixed valve trays in this
section.
• RECTIFYING SECTION : Here the hydrocarbon vapors traveling upwards are rectified
through mass transfer, whereby its heavier components are condensed by the
comparatively cold circulating reflux, which travel down and in turn the lighter components
of the down-coming liquid are taken up by the hot vapors.
There are 63 nos. valve trays and 6 nos. chimney trays in the rectifying section.

13. CRUDE COLUMN OPERATION
 REFLUXES : Refluxes serve two purposes - provide liquid in the
rectifying section to cause liquid and vapour contact for fractionation
- maintain temperature gradient in the column
 OVERFLASH : The flashed vapors of the crude which condenses on
the first tray above the flash zone are dropped down to the stripping
section. This is known as over flash and it helps in (a) stabilizing the
bottom product and (b) proper fractionation of Gas Oil. Over flash
should be ideally 3-5% of crude vol.
 STRIPPING STEAM : This helps in removing the lighter ends from the
bottom product by decreasing the partial pressure. It is introduced
below the valve trays in the stripping section.

14. CRUDE COLUMN FLASH ZONE
• Combined heater outlet enters flash zone.
• A vane type feed inlet and a large empty space allows
vapor/liquid separation by gravity with minimum
entrainment.
• Flash zone is large enough to contain foaming.
• The incoming vapor from the heater produces significant
turbulence
• This is controlled by passing the vapor from the flash zone through a
chimney collector tray 69 which also serves as vapor distributor.
Hot Crude

15. Bottom Section
• Liquid from flash zone and gas oil from the collector tray 69 is
collected on tray 70
• Routed to the stripping section.
• In the stripping section (trays 70 to 75) hydrocarbon vapors are stripped out from
the residue by medium pressure stripping steam injected at the bottom of this
section.
• Atmospheric residue or Reduced Crude Oil (RCO) is drawn
from the bottom
• Pumped to vacuum Distillation Unit.
• Where it is further heated in fired heaters before vacuum distillation process.

16. Overhead Section..1
• Two-stage condensation with wash water circulation.
• First stage condensation
• In Crude / overhead exchanger, 10E-102,
• Then in air fin exchanger, 10EA-301, to 90 0C
• To avoid corrosion by strong acids
• Wash water is circulated and injected at the inlet of 10E-102.
• Corrosion inhibitors injected in overhead vapor.
• After air cooler it is sent to the reflux vessel,10V-301,
• For separation of vapor, hydrocarbon liquid and water.
• Second Stage Condensation
• Uncondensed vapor from the reflux vessel is sent to
• Air cooler 10EA-302
• Then to exchanger 10E-301(cooling water) to 40 0C where the
overhead naphtha product is condensed .
• The mixed phase this exchanger is sent to naphtha vessel 10V-
302.
Neutralizers &
corrosion
inhibitors are
added in vapor
line

17. • From the reflux Vessel
• Naphtha is sent by the reflux pump 10P-302 to column.
• Sour water is sent to battery limit
• In Naphtha Vessel
• water, hydrocarbons and uncondensed vapor are
separated.
• Liquid naphtha sent to the battery limit as overhead
naphtha product.
• Water, is preheated against the sour water going to
battery limit, and sent back as recycled wash water to the
inlet of the overhead exchanger.
• uncondensed off gas sent to off gas compressor 10K-301
• Compressed to 10 kg/cm2a and sent to saturated gas separation
unit.
Overhead Section…2

18. Col Ovhd
Air Fin Air Fin
Exch
OFF Gas
COMP
Treating
Nap Prod
Crude Pht
Reflux Vessel
Nap Vessel
Wash Water
Overhead Circuit
Reflux

19. Heavy Naphtha section
• Fractionation between heavy naphtha and lighter
fractions of crude occurs between tray 1 and 11.
• Product is drawn from tray 12 to H naphtha
stripper, 10C-401 under level control.
• In the stripper light components are removed by
thermo siphon reboiling against Top Pump Around.
• Stripper vapors are sent back to column
• Product is cooled in air fin cooler followed by CW
cooling and sent to storage.

20. Light kerosene section
• Fractionation between Lkero H- naphtha between tray 13 & 24.
• Product is drawn from tray 25 to Lkero stripper, 10C-501 under level
control.
• Light components are removed from the light kerosene by reboiling with LGO
PA.
• Use of steam is avoided for stripping to prevent presence of water in product
• From Stripper it is sent to crude preheat exchangers
• Followed by cooling in air fin cooler and CW cooler.
• Cooled product is sent for treatment / storage.

21. Heavy kerosene Section
• Fractionation between Hkero & Lkero
between trays 26 & 40.
• Drawn from tray 41 to Stripper 10C-
601 under Level Control
• Steam is injected to strip out lighter
components
• Hkero is pumped with 10P 601 to
10E105 (crude)
• Then to 10EA 601 air fin cooler
• and then to Hkero Dryer 10C602
• Dryer vapor outlet is connected to ejector
inlet of vacuum column
• Moisture is removed by vacuum
• Then to 10EA 602 before sending to
storage/treating
Storage
HK/Crude
37
Stripper
Air Fin
Dryer
Air Fin
41

22. Hkero Pump Around
• Hkero pumparound is provided from tray 41 to
37.
• Medium pressure steam is generated in
exchanger 10E-903.
• Hkero is then sent to the stabilizer reboiler in
the SGU unit
• HK PA from SGU is preheat the dry crude in
10E-155 and then it is returned back to the
crude column.

23. TOP Pump Around
• Provided from tray 30 to 26.
• The top pumparound is first used as
heating medium in the heavy naphtha
reboiler, 10E-401
• Subsequently to preheat crude.
• Purpose
• Heat removal from tower which helps
in
• Maintaining temperature profile
• Draw off temperatures and product quality
control
TPA/HNAP
TPA/Crude
30
26

24. LGO Stripping & Rundown
• Fractionation between LGO/ Hkero in trays 42 & 57.
• LGO Drawn from tray 52 to stripper 10C 701 under Level
Control 10LV-104
• Steam is injected to remove lighter fractions
• Then pumped to 10E-902 to generate MP steam.
• Subsequently sent to LGO/Crude exchanger 10E-109.
• Then to cooler 10EA-701 and to 10E-701 trim cooler.
• Finally sent to HDS/storage/blending

25. LGO Pump Around
• LGO PA is provided from tray 48 to
52
• The duty is utilized to generate MP
steam in exchanger 10E-901.
• LGO from 10E-901 is sent to the
light kerosene reboiler 10E-501, as
a heating medium
• Finally returned back to the crude
column 10C-201.
LGO/LKero
48
52
LGO/MPst

26. HGO stripper & rundown
• Fractionation between HGO and LGO occur between tray
53 to 58.
• HGO product is drawn from tray 63 under level control
• After steam stripping product sent to 10E-905 to
generate MP steam.
• HGO is further cooled in Crude preheat exchanger 10E-
108
• Finally through air cooler 10EA-801 Product HGO is sent
to HDS unit/ storage/ blending.

27. HGO Pump Around
• HGO pump around is provided from tray 59 to 63.
• heat is utilized to preheat crude before the furnace in exchanger 10E-
153 A/B.
• Subsequently HGO is used to generate MP steam in 10E-904
• Finally sent back to crude column as pump around.

28. VACUUM DISTILLATION UNIT

29. Vacuum Distillation Unit
Crude
Atmospheric
Distillation
Middle
Distillates
RCO
TO VDU
Blending
Secondary
Processing
Storage

30. Process Description-1
• Feed to vacuum heater is
received from atmospheric
column bottom
• Which is further separated into
middle and heavy distillates
under vacuum
• Feed flow is cascaded with
crude column level.
• The atmospheric residue feed
to the unit is combined with
recycle HHVGO and (in case of
Bombay high feed) recycle
vacuum residue.
• The joint feed is sent to
heaters 11F-101 A/B.
F-101 A/B
FC
LC
Recycle
HHVGO(AL/AH) /
VR (BH)

31. VACUUM HEATERS
• Velocity steam is mixed in the radiant section of heater
• to start vaporization by lowering hydrocarbon partial pressure.
• Here most of the heat is absorbed as heat of vaporization as opposed to
temperature increase.
• Thus rise in COT temperature is prevented.
• It also helps in slowing down coking process
• Vacuum heater
• Sixteen burners in each heater.
• Dual fired burners arranged into four groups.
• Each group has four burners.
• Each groups has two pilot flame detectors.
• Pilot flame detractors are arranged on alternate burners.
• Two FD fans and one ID fan.
• LP steam is generated in convection section.
• LP superheater coil is also given to superheat LP steam.
Velocity
Steam

32. Vacuum Column-1
• Combined heaters outlet goes
to vacuum column at 403 0C
• Height 50 m
• Diameter
• Top 8.2 m
• Middle 12.5 m
• Bottom 6.8 m.
• Four structured packed bed.
• COT - Coil Outlet Temperature is
kept below 420 0C
• To avoid cracking which may
cause coking and overload
vacuum system
50 m
6.8 m
12.5 m
8.2 m

33. Flash Zone and Stripping
• Liquid from flash zone is collected on a
chimney tray and passed to the stripping
section.
• Vapors are passed through chimney tray
and packed bed no 4
• Light hydrocarbon are stripped on valve
trays with superheated LP steam.
• Residue is quenched to 360oC with cooled
vacuum residue in order to prevent
cracking in the bottom section.
Feed
Flash Zone -
vane type
inlet
Stripping
Section
Chimney
Tray
Bed 4
Steam
Valve
Trays

34. VDU Products
Vacuum Distillate
FEED
LVGO
HVGO
HHVGO
VR
Ejectors and
Vacuum Pump
BED-1
BED-2
BED-3
BED-4
Reflux
Air Cooled TPA
HVGO - PA
HVGO - Reflux

35. Overhead Section
VDU
Over
head
Vapor
from CDU
Dryers
Ejector Package
Steam
Condensation
and Vapor
Liquid
Separation
Vacuum Pump
Package
Uncondensed vapor
Vent
Gas
Seal
Vessel
Water / Slop Oil
Slop Oil
Storage
Sour Water
Stripper Unit
Vent Gases
incinerated

36. Vacuum pulling is done with steam ejectors. The load on the ejectors
is determined by the overhead vapours, which comprise :
- Non condensibles like cracked gas from furnace and air leaks
- Condensible hydrocarbon vapours
- Entrainment
- Furnace velocity steam
- Tower stripping steam
PRESSURE PROFILE ( Not To Scale)
100 psig
DISCHARGE
NOZZLE
DIFFUSER
SUCTION
MOTIVE
STEAM
1.16 psig
0.1 psig
EJECTOR SYSTEM

37. Ejectors convert pressure energy of motive steam into supersonic
velocity from the motive nozzle, thereby creating a low pressure zone for
pulling the suction load into the ejector.
OIL WATER
FROM
VAC. COL.
1st Stage 2nd Stage 3rd Stage
HOT WELL
OFF GAS
THEORY OF EJECTOR SYSTEM

38. BAROMETRIC LEG : The drain line from condensers to hot well is the
barometric leg. Draining is by gravity, so barometric legs should be
high enough to avoid flooding of the condenser tubes. Hot well
pressure is atmospheric. Hence minimum barometric height should
be 34ft in case of pure water and 45ft in case of hydrocarbon.
Various barometric arrangements are shown below :
HOT WELL HOT WELL HOT WELL
45 deg.
(min.)
PREFERRED ACCEPTABLE INCORRECT
THEORY OF EJECTOR SYSTEM

39. VACUUM DISTILLATE
Storage
Vac
Dist
Vesse
l
FC
TC
FC
• Bed 2 Temp is
controlled by Vac
Rest goes to
storage
Air Fin Cooler
Crude/ Vac
Distillate
exchangers
Reflux
PA
142 0C
60 0C
142 0C
60 0C
BED-1
BED-2
Vac Dist

40. LVGO
• Drawn off from chimney tray below
bed no 2 into LVGO Vessel
• Vessel level is controlled by adjusting
rundown flow
• From vessel it is pumped through MP
steam generator exchanger of CDU
• Then to crude preheat exchangers
• Finally cooled with tempered water
and sent to storage / FCC feed
LVGO
Vesse
l
MP Steam Generator
Crude
Tempered
Water
LVGO Product
Return
Return
BED-1
BED-2
238 0C
80 0C

41. HVGO
• Drawn off from
chimney tray
below bed - 3
• Vessel level is
controlled by
adjusting rundown
flow
• Pump discharge
goes back as
reflux
• Remaining goes
as pump around,
FCC/Storage after
cooling with crude
/ tempered water.
Crude
BED-2
BED-3
BED-4
Reflux
FC
Crude
Storage
Tempered
Water
Supply
FCCU
Return
HVGO
293 0C
230 0C
293 0C
170 0C
80 0C

42. HHVGO
• Draw off is from below
Bed-4 into HHVGO vessel.
• Vessel level is cascaded
with rundown flow control.
• HHVGO is first cooled by
MP steam generation
(CDU)
• Then split in two
• First part goes as quench to
HHVGO vessel.
• Quench flow is regulated by
pump discharge temperature
• Second Part goes for LP
steam generation (VDU),
then to FCCU / Storage.
HVGO
BED-4
MP Steam
Generator
TC
LP Steam
Generator
Storage
FCCU
HHVGO
FC
Quench
390 0C
230 0C
170 0C

43. VACUUM
RESIDUE
• Vac Residue is the bottom product -
first pumped through Crude preheat
train to cool it down to 290 0C
• Then
• Sent back to tower as quench, to control
cracking
• Cooled further against crude to 190 0C
• Vac residue finally leaves the unit as
• VBU Feed
• Storage
• VBU Blending
Crude
Crude
TC
FC
Superheated
LP Steam
Quench
VBU Feed
Bitumen unit
Storage
360 0C
290 0C
190 0C

44. •Introduce stripping steam before
pulling vacuum so that sudden
expansion is not there
•While stripping steam is introduced,
care should be taken so that column
bottom level is not too high
•Vacuum pulling / vacuum breaking
should be done gradually
PRECAUTIONS & TROUBLE SHOOTING

45. START UP SEQUENCE FOR
CDU/VDU

46. •Flushing of all the Process and utility Systems
•Chemical Cleaning of Compressor piping
•Alkali boil out of the Steam generation drums
•Leak test of all the Process and Utility Systems
•Pump no load and Load trials
•Commissioning of Utilities system inside the unit
•Refractory dry out of the Furnaces
•Vacuum hold test of the Vacuum column section
•Removal of air from the system by Steaming out the unit
•Backing-in fuel gas into all the systems
•Draining water from the system
•Preparation for cold oil circulation in CDU
START UP SEQUENCE

47. START UP SEQUENCE
•Charging crude for cold oil circulation in CDU
•Preparation for crude heaters light up
•Crude heaters burner light up:
•Raising temperature for hot oil circulation
•Stripping steam injection in crude column
•Routing of atmospheric residue to VDU
•Chemical injection in crude column overhead
section

48. START UP SEQUENCE
•Establishing pump around and product circuit
(I )Heavy Naphtha Product Circuit
(II) Light kerosene Product Circuit
(III) Top Pump around Circuit
(IV) Heavy Kerosene Pump around Circuit
(V) Heavy Kerosene Product Circuit
(VI) LGO Pump around Circuit
(VII) LGO Product Circuit
(VIII) HGO Pump around Circuit
(IX) HGO Product Circuit

49. VDU START UP SEQUENCE
•Preparation for cold oil circulation in VDU
•Charge LDO for circulation in VDU bottom
•LDO circulation in HHVGO system
•Vacuum heaters light up and hot oil circulation
•Replacement of LDO with RCO after raising
temperature
•Fill up of vacuum distillate and LVGO system with LGO
and HGO from CDU
•Introduction of stripping steam and vacuum pulling
•Switch over of atmospheric residue to vacuum column
•Rising of vacuum heater O/L temperature to 350 °c and
injection of turbulizing steam in to heater coil
•Vacuum furnace cot raising and product routing

50. SHUTDOWN SEQUENCE FOR
CDU/VDU

51. CDU/VDU SHUT DOWN SEQUENCE
•General
•Through Put Reduction
•Vacuum Furnace COT reduction and Vacuum product
routing to off spec
•Stripping steam cut off in Vacuum column
•Vacuum breaking in Vacuum column
•Velocity steam cut off and Vacuum column product
thinning with Wash oil
•CDU Off Gas compressor Shutdown
•Crude Heater COT reduction and Routing Crude
products to Off spec

52. CDU/VDU SHUT DOWN SEQUENCE
•Stripping steam cut off in Crude Column and Switching
off of Chemical injections in Crude column overhead
•Shutdown of Sat Gas Unit
•Desalters Isolation and Switching off Chemical injections
•Establishing hot oil circulation in bottom loop
•Deinventoring

53. EMERGENCY SHUTDOWN

54. EMERGENCY SHUTDOWN
•Loss Of Feed
•Power Failure
•Power Dip
•Instrument Air Failure
•Cooling Water Failure
•Sea Cooling Water Failure
•LP Steam Failure
•MP Steam Failure
•DCS Failure
•Heater Tube Rupture
•Crude Charge Pump Failure

55. THANK YOU