hr vdu process
TRANSCRIPT
Vacuum Distillation Unit
- Process
Sujit K Ghosh
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Introduction: Refinery Overview
• Refining Objective:
High volume Fuels / Lube production
Flexible operation for different crudes
Proactive on environmental issues
Maximize higher value distillate yield
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Introduction: Refinery Overview
• RefineryTypes: Simple:
Processing specific range of crude to middle distillatesCDU & VDU, FCCU / Hydrocracker, Catalytic Reformer,
Hydrogen Plant Complex:
Processing variety of crude making a range of high value added products
CDU & VDU, Visbreaker, Lube extraction, FCCU, Delayed Coker, Catalytic Reformer, Sulphur Plant, Bitumen Plant
Integrated:Refinery + Petrochemical
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Refinery Feed Stock
• Crude Oil:– mixture of large number of hydrocarbons
1. Paraffins : normal and iso paraffins Methane, Ethane, Butane, iso-butane
2. Napthenes : Cycloalkanes / Sat. ring structure Methyl cyclo pentane
3. Aromatics : Benzene Ring & its derivatives Benzene, Toluene
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Refinery Feed Stock
• Crude Assay:– Used to evaluate crude for processing
Crude assay Determines Refinery Configuration Product Yield Analysis
– Assay Content: Key Crude oil properties Boiling Point curve including properties of
fractions Chracterization factor (k) Density Curve Sulphur & Nitrogen content Other contaminants
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Vacuum Distillation
• Why Vacuum unit ?– Further fractionation of Reduced Crude Oil
(RCO) ex ADU/CDU residue to get heavier distillates :1. For Lube feed stock 2. For Cracking for high value fuel distillates.
• Recovery of distillates from RCO without Vacuum leads to coking/ cracking and quite energy intensive.
• Higher temperature operation requires :
- Special metallurgy & higher cost.
- Higher protection for equipment & personnel
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Vacuum Distillation
Product Routings:Distillates:
HSD Pool FCC Feed Hydrocracker Feed Lube Processing
Vacuum Residue Lube Processing ( PDA extraction) Visbreaker / Thermal cracker Feed Bitumen
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Vacuum Distillation
• VDU Types:
Fuel Based Lube BasedPrepares feedstock for FCC, Hydrocracker
Prepares feedstock for Lube Processing
Products:1. Diesel
2. LVGO
3. HVGO
4. Slop
5. Vacuum Residue
Products:1. Gas Oil/Diesel
2. Spindle Oil
3. Light Oil
4. Intermediate Oil
5. Heavy Oil
6. Vacuum Residue
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Vacuum Distillation
• Vacuum Column Types:
Dry Damp WetTop/Flash Press (mm Hga) 8 / 24 25 / 42 75 /95
Heater Outlet Temp (oC) 420 405 395
Steam Nil Medium Highest
Column Dia Highest Medium Least
Transfer Line Highest Least Medium
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Vacuum Distillation: Column Types
• Dry Vacuum Features: Higher Heater Outlet temp (COT) More ejector steam
• Wet Vacuum Features: Used for Lube Stocks where Flash Point of Products
are to be met Reduces Heater Outlet temp (COT) requirement due
to partial pressure of steam Lesser Ejector steam Marginally better yield of distillates and
controllability due to steam Economics normally in favour of Damp Vacuum
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Vacuum Distillation: Distillate Specification
• Lube VDU Columns are typically wet vacuum as:
Products need to meet Flash Point spec Better product separation (Sharp Cut) required
KV ([email protected])
Flash Point (oC)
CCR (Wt %)
Gas Oil 1.3-1.6 120 -
Spindle Oil 3.5-3.6 160+ -
Light Oil 6.0 min 200+ -
Inter Oil 9.0-11.0 230-240 -
Heavy Oil 19.0-24.0 240-260 2.4 max
Short Residue 1200+ 300-320 18-20
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VDU: Process Description
Block Diagram:
Pre-heat Train
Furnace
Vacuum Column
SO
IOLO
HO
OSBL
Feed PumpFeed BoosterGO
LN
IN
HN
SR
SO
Ejector
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What is Vacuum Distillation?
Distillation under vacuum Condition
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What is Vacuum?
• Any pressure below atmospheric.
How is it expressed?
760 mmHg (a) 1 Atm 0 Kg/cm2 (g)
76 mmHg vac ? (760-76) mmHg absolute
76 mmHg abs ? (760-76) mmHg vac
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Process Description
Five main sections
• The Pre-heat Train
• The Furnace
• The Vacuum Column
• The Side Strippers
• Auxilliary Systems
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Process DescriptionBlock Flow Diagram
Pre-heat Train
Furnace
Vacuum Column
SO
IOLO
HO
Feed PumpFeed BoosterGO
LN
IN
HN
SR
SO
Ejector
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Process Description
The Pre-heat Train configuration is based on
• Heat recovery plan & Product R/D temp before cooler
• Heat Exchanger network configuration as per heat/ temperature potential of streams
• Fouling characteristics, Corossivity of the liquid, flow, viscosity, metallurgy, etc
To Furnace
RCO Feed
SRIOGas Oil
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Process Description
The Furnace
• The required temperature for distillation is achieved in the furnace, the outlet of which directly goes to to the Flash zone of the vacuum distillation column.
• The furnace is a balanced draft type and has the facility of dual firing (both Fuel gas & Fuel oil). Its has got two passes with flow control in each.
• The feed stream from the pre-heat train enters the convection zone followed by the radiation zone.
• Major part of the oil feed to the furnace gets vaporized before entering the vacuum column.
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Process DescriptionVacuum Column features :
• The distillation and stripping takes place in the vacuum column.• Internals are normally packing/ tray type or both.• Bottom section (stripping) are typically with trays (sieve).• Downcomers are either side/central or both based on liquid load.• Transfer line enters tangentially with impingement plate to reduce impact.• Multi Product Draw.• Side draws are provided with strippers to control flash point• Typical turn down 60-65%• Top and bottom section are SS cladded based on crude property.• Top temperature maintained 15-20 C above the Dew Point• Column Diameter higher as compared to ADU columns (?)• Diameter fixed by capacity and height depends on degree of rectification.
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Process DescriptionThe Vacuum Column
• Two reflux :• Top reflux• Bottom Reflux (Known as Pump Around).
• Pump Around: To remove heat from the column• Key parameters:
– Flash zone temperature/ pressure, – Top temperature/pressure, – Side draw temperatures– PA return flow and tempearure– Bottom tempearture
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Process Description
The Vacuum Column
Vacuum Distillation
Column
RCO From Furnace
Stripping Steam
To Ejectors
Gas oil
Reflux
S O
LO
IO
HO
Vacuum Slop
SR/VR
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Process Description
The Side Draw Strippers• Different cuts drawn from the vacuum column are
routed to their respective Stripper columns.• Lighter components in the draws are stripped off
the main product by using superheated steam. ```` Draw Temperatures
• Spindle Oil stripper----- 210-240 C• Light Oil stripper-------- 250-280 C• Inter Oil stripper--------- 300-320 C• Heavy Oil Stripper------ 340-360 C
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Process Description
The Side Draw Strippers• The bottom products from the Strippers are routed to their
respective storage tanks after exchanging heat with the RCO Feed in the Pre- Heat exchanger Train and then Cooling Water Exchangers.
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Process Flow Diagrams
Haldia Refinery Vacuum Distillation Unit PFD(furnace and fractionator circuit)
F-1
P-113/113R
SR to E-11R
CO
ex F-1/F-2
CW
To Ejectors
VS STEAM
GO as refluxex E-2A/B/C
#1
#4
#5
#8
#12
#16
#19
#22
#26
C-1
F-2
Burners
Fuel gas
IFO supply
IFO returnAtomising steam
Fuel gas
IFO supplyIFO returnAtomising steam
RCO Ex E-11
P-10/10R
#4
#1
#1
#1
#1
#4
#4
#4
P-8/7R
P-12/12R
P-5/5R
P-7/7R
HO draw
IO draw
LO draw
PA draw
SO draw
GO draw
SR draw
P-9/9R
Vac slop to E-9
Over Flash
HO Ex P-8/7Ras Demister Wash
Bot Quench Ex H-1A/B
Burners
Furnace recycle Ex p-9/9r
VB steam VS steam
Comb. air To burners
Turbulising steam
Turbulising steam
Turbulising steam
Turbulising steam
Combustion airEx APH
Com
bustion airE
x APH
P-6/6R
E-6A/B/C
P-3/3R
E-128A/B
GO to E-1A/B/C/D
SO toE-123
VS steam
VS steam
VS steam
VS steam
LO to E-121
IO to E-7
HO to E-9
LC-101
LC-03
FC-11
LC-04
LC-05FC-10B
FC-13
FC-12
FC-10AFC-10B
FC-4
FC-5
FC-8
FC-9
FC-102
PC-06 HV-01
DPC-03
FC-209
FC-216FC-217
FC-201
FC-202
C-105
C-2
C-3
C-4
Haldia RefineryVacuum Distillation Unit PFD
(Feed preheat and product cooling section )
P-1/1R
B-1
E-121
E-1A
E-1B
E-1C
E-1D
E-2AE-2B
E-2C
E-123
E-127
E-14A/B
E-6A
E-6BE-6C
E-4B
E-4A E-122A/B
E-7
E-9
E-11
RCO Ex tanks
LO Ex P-5/5R
GO Ex P-3/3R
SO Ex P-7/7R
PA Ex P-6/6R
IO Ex P-12/12R
HO Ex P-8/7R
SR Ex P-10/10R
H-1A H-1B
DM water
To VB steamheader
CW To TK-761
GO to R/D
GO to top reflux
CWCW
CW
CW
RCO to P-113/113R suction
SO to R/D
E-10
TW
E-125A/B IO to R/D
HO to R/D TW
TW
TW
SR to R/D
E-126A/B
E-124A/B
Pump Around To # 18 of C-1
IO to VBU
FC-20
FC-21LO R/D
To Tar
To VBU
FC-15
FC-19 FC-23A
FC-22FC
-23
To HSD
To Tar
To TK-761
To VBU
FC-25
FC-24
FC-27
FC-26
To R/D
To VBU
FC-12FC-28
LC-02
TC-06
Vac slop to PDA
Vac slop Ex P-9/9R
HO Ex P-8/7R
To PDA
To VBU
Bot quench
Haldia RefineryVacuum Distillation Unit PFD
(Vacuum System)
E-128A
CW
#19
#22#26
E-128B
E-129E-130
31C-1
Cooling Water Inlet Header
Cooling Water Return Header
VM Steam to Ejectors
PEJSEJ
B-2
B-7seal pot
Vent
oil waterBarometric legs
P-101/101R P-102/102R
B-3coaleser
Hot well gas oil to HSD pool
Hot well water to OWS/ DesalterHot well
PC-05
PC-121
VB steam
DM water
P-114A/B/C
E-116A/B/C
E-124A/B/C
E-126A/B
E-125A/B
E-10
Tempered water circuit
B-105SR
HO
IO
Vac Slop
CW
Tempered water
CW CW
CWCW
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Auxilliary Systems
The VDU has following auxilliary systems
1. The tempered water system
2. Steam generation and SR Cooling
3. Balanced Draft Furnace
4. Battery Limit product lines
5. Pumping systems
6. Vacuum System
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Auxiliary SystemsThe Tempered Water System :Why?
• Run down temperature @80 C
• Product congealing in nature.
• C/W higher scaling nature above 55 C.
• Less corrosive due to DM water/ Condensate
.
TW vessel
TW pump
SR SR IO HN
TW cooler
C/WMake Up DM Water
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Auxiliary SystemsSteam Generation and SR cooling
• Steam generation reboilers from SR stream.
• SR after Exchanging heat with RCO in 31 E 11 and 31 E 122 A/B enters 31-H- 1A/B where DM water recovers the heat from SR and generates steam at ~5 Kg/ Cm2 g and 151 C.
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Auxiliary SystemsBalance Draft Furnace
Main Features:Process circuit: PHE Convection zone Radiation
ZoneColumnFlue gas Circuit: Radiation Zone, Convection Zone,
APH , ID fan, StackCombustion Air Circuit: FD fan, SCAPH, APH,
BurnersFuel Oil Circuit & Fuel gas circuit
Turbo Steam
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Auxiliary SystemsBattery Limit and Product lines
Feed, Products and utilities are routed through the Battery Limit.
The product lines are provided with Flow control valves, Level control valves and necessary instrumentations like Temperature Transmitters, Pressure Transmitters, Pressure/ Temperature Gauges etc.
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Auxiliary SystemsVacuum System
Precondensers
Primary ejectors
Secondary ejectors
Seal pot
Barometric legs
Hot Well (HW)
Gas oil recovery system from HW
Haldia RefineryVacuum Distillation Unit PFD
(Vacuum System)
E-128A
CW
#19
#22
#26
E-128B
E-129
E-130
31C-1
Cooling Water Inlet Header
Cooling Water Return Header
VM Steam to Ejectors
PEJSEJ
B-2
B-7seal pot
Vent
oil waterBarometric legs
P-101/101R P-102/102R
B-3coaleser
Hot well gas oil to HSD pool
Hot well water to OWS/ DesalterHot well
PC-05
PC-121
CW CW
CW
CW