APPROACH TO REFINING PROCESSES - petrofed.winwinho...

APPROACH TO
REFINING PROCESSES
1

Beginning of Petroleum Refining in India
In 1890s Crude Oil used to be
distilled in DIGBOI in Cast
Iron pans – called ‘Stills’.
Bottom portion of one such
still of 9 feet dia is still kept at
Digboi Refinery.
A refinery was commissioned
in 1901 at Digboi with 500
Barrels per Day capacity
THE FIRST STILL LIES STILL

OUTLINE
1. Introduction
2. Physical Processes
3. Thermal Processes
4. Catalytic Processes
5. Conversion of Heavy Residues
6. Treatment of Refinery Gas Streams

INTRODUCTION
Oil refining is a key activity in the CPI.
Over 600 refineries worldwide have a total
annual capacity of more than 3500 x 10 6
tonnes.
Goal of oil refining is mainly twofold:
i. production of fuels for transportation, power
generation and heating; and
ii.
production of raw materials for the CPI.
Oil refineries are complex plants, but are
relatively mature and highly integrated.

Overview
After desalting and dehydration, crude is
separated into fractions by distillation.
The distilled fractions can not be used directly.
The reason for such a complex set of
processes is the difference between the crude
oil properties and the needs of the market.
Another reason for complexity is
environmental. Legislation demands cleaner
products and is the major drive for process
improvement and development of novel
processes.

Quality
Control
COMPLETE REFINERY
Marketing
Power &
Utilities
OM&S (Product Blending &
Dispatch)
Finishing
Units
Crude
Oil
Jetty /
Pipeline
OM&S
Separation
Units
OM&S
(Intermediates)
Waste
Treatment
Round the clock operation
Conversion
Units
Welfare /
Admn.

Physical and Chemical processes
Physical
Thermal
Chemical
Catalytic
Distillation
Solvent extraction
Propane deasphalting
Solvent dewaxing
Blending
Visbreaking
Delayed coking
Flexicoking
Hydrotreating
Catalytic reforming
Catalytic cracking
Hydrocracking
Catalytic dewaxing
Alkylation
Polymerization
Isomerization

Flow scheme of a modern refinery

Desalting/dehydration
Crude oil often contains water, inorganic salts, suspended
solids, and water-soluble trace metals.
Step 0 in the refining process is to remove these contaminants
so as to reduce corrosion, plugging, and fouling of equipment
and to prevent poisoning catalysts in processing units.
The typical method of crude-oil desalting is electrostatic
separation.
In desalting, water
and chemical
surfactant
(demulsifiers) are
added to the crude,
which is heated so that
salts and other
impurities dissolve or
attach to the water;
then held in a tank to
settle out.

Desalting/dehydration
The crude oil feedstock is heated to 110 – 150 °C to
reduce viscosity and surface tension for easier mixing
and separation of the water. The temperature is limited
by the vapor pressure of the crude oil.
High-voltage electrostatic charges are applied at the
settling tank to concentrate suspended water globules
in the bottom of the settling tank.

Crude distillation
Step 1 in the refining process is the separation of crude oil
into various fractions or straight-run cuts by distillation. The
main fractions or "cuts" obtained have specific boilingpoint
ranges and can be classified in order of decreasing
volatility into gases, light distillates, middle distillates,
heavy vacuum distillates and residuum.
The desalted crude feedstock is preheated using
recovered process heat.
The feedstock then flows to a direct-fired crude charge
heater then into the vertical distillation column just above
the bottom, at pressure slightly above atmospheric and at
temperatures ranging from 340-370°C (above these
temperatures undesirable thermal cracking may occur).
All but the heaviest fractions flash into vapor at the feedentry
location of the column.

Liquid and vapor flows in a tray column

Crude distillation
As the hot vapor rises in the tower, portions of the vapor are
condensed at successively higher stages in the tower, and
the various products – e.g., diesel, kerosene, gasoline – are
drawn off as liquids (through side-draw strippers).
Uncondensed vapours leave column
overhead, are condensed outside and
stored in overhead accumulator drum.
Part of this liquid is refluxed back to the
column at top, and part is withdrawn as
the ‘top’ fraction.
Heavy residuum is drawn out from
column bottom.
To further distill the residuum from the
atmospheric tower, without thermal
cracking, reduced pressure is required.
The process takes place in vacuum distillation tower. The principles
of vacuum distillation are same, except that larger diameter
columns are used to maintain comparable vapor velocities at the
reduced pressures.

Atmospheric & Vacuum Distillation Unit
S
LPG
T
A
Pr= 40-60 mm Hg a
T=200 Deg C
Pre-topping
Unstabilised
Naphtha
B
Stabilized Naphtha
Light Naphtha
Heavy Naphtha
To Steam Ejector
LVGO
LDO
Crude Oil
Desalter
T=130-140
Deg C
Furnace
T= 370 oC
RCO
Atmospheric
Kero / ATF
LGO
HGO
Furnace
T= 415 oC
Vacuum
HVGO
Vac Slop
VR

Streams from Atm. Distillation
Crude
oil
Stream
b.p.,
o
C
Application
Key
Property
Treatment
Gas Refinery fuel H 2 S Amine
scrubbing
LPG Domestic /
Industrial fuel
Naphtha 30 – 140 MS blend,
feed for
Petrochemical
/ fertilzer
Kerosine
/ ATF
140 – 270
140 – 240
Domestic fuel /
Jet fuel
Cu corrosion,
Weathering
Cu corrosion,
Component
analysis
(PIONA)
Smoke pt. /
Freeze pt.,
Ag corr.
Gas Oil 240 – 370 Diesel fuel ‘S’ content,
Cetane no.
Caustic
wash,
Merox
Catalytic
reforming /
isomerization
Merox /
Hydrotreatment
Hydrotreatment
Reduced
crude
> 370 Further
conversion,
Furnace Oil
Vacuum
distillation

Catalytic Reforming Reactions

Semi-regenerative Catalytic Reforming Unit
Flow Scheme

Effect of process variables on Reforming

Continuous Catalytic Reforming Unit
Flow Scheme
LSRN (85-160)
VBN
NHDT
Off Gas to
FG system
H2 RICH
GAS TO PSA
Off Gas to
FG system
COL OVHD
RECEIVER
Pr. 17.0
kg/cm2g
RGC
SEPARATOR
Pr. 17.0
kg/cm2g
T =-10 deg c
Recontacting drum
S
T
A
B
I
L
I
S
E
R
LPG
T=520-540 Deg C
Regenerator
Reformate to MS Pool
via RSU

Diesel Hydro Desulphurisation (DHDS) Unit
Fuel gas
Off. gas
H2 Recycle
H2 Make
Up
Temp. 350
Deg C
High Pr.
Separator
Pr. 35-40
kg/cm2g
A
b
s
or
b
er
Lean
Amine
Rich
Amine
S
T
R
I
P
P
E
R
COL OVHD
RECEIVER
Wild
naphtha
Steam
Feed
Furnace
Reactor
Desulphurized
Diesel

DHDS / DHDT :
Product Yields & Operating Conditions
1. Typical Product Yields, wt.% on feed
No. Products DHDS DHDT End Use
1. Off Gas 1.4 1.8 Refinery Fuel Gas
after Amine Wash
2. Wild
Naphtha
1.3 2.0 Naphtha after
stabilization
3. Diesel 97.2 96.1 Diesel Pool
2. Typical Operating Conditions
DHDS
DHDT
Temperature, o C 340 – 390 330 – 370
System Pressure, kg/cm 2 (g) 40 – 50 90 – 105

Secondary processing of VDU streams
No VDU Product Quality Processing
1. VGO & SO High ‘S’. Low
Cetane no.
Hydrotreatment (DHDT) for Sulphur and
Cetane No./LOBS
2. LO High ‘S’. Heavy
Hydrocarbons
3. IO High ‘S’. Heavy
Hydrocarbons
4. HVGO High ‘S’. Heavy
Hydrocarbons
5. Vacuum Slop Heavy
Hydrocarbons,
Fuel oil Product
Fluid Catalytic Cracking (FCC) unit /
Hydro-Cracking Unit(HCU) / LOBS
Fluid Catalytic Cracking (FCC) unit /
Hydro-Cracking Unit(HCU) / LOBS
Fluid Catalytic Cracking (FCC) unit /
Hydro-Cracking Unit(HCU) / LOBS
Visbreaker unit / Coker/ Fluid Catalytic
Cracking (FCC) unit
6. Vacuum
Residue
Residue
Bitumen Blowing Unit / VBU / Coker/
Propane De-Asphalting (PDA) unit

Lube Base Oil Processing
Crude Selection
Multi-step manufacturing process

BASE OIL COMPONENT PROPERTIES
PROPERTY
N-
PARAFFINS
ISO-
PARAFFINS
NAPHTHENES
AROMATICS
VI HIGH HIGH MEDIUM LOW
POUR PT HIGH LOW LOW LOW
OXIDATION
STABILITY
GOOD GOOD FAIR LOW
THERMAL
STABILITY
GOOD GOOD FAIR LOW

Lube Base Oil Processing Philosophy
Crude
oil
Atmospheric distillation
Gas
Naphtha
Kero
Diesel
RCO
VGO
Vacuum distillation
VR
Propane De-
Asphalting
Properties controlled by Process Units
KV,
Flash Point
VI, CCR Pour Point
Vacuum
Distillates
DAO
Solvent Extraction
(Furfural & NMP)
Waxy
Raffinate
De-waxed
oils
Colour &
Stability
H 2
Solvent
Dewaxing
Unit
VI,Pour Point,
Colour&Stability
100N
Catalytic 150N
Dewaxing 500N
H Unit 150BS
2
Hydrofinishing
Group I
LOBS
150N
500N
HN
BN/150BS
Group II LOBS

EXTRACTION UNIT
Feed stock: - Vac. Distillates
ex VDU
-DAO ex PDA
Purpose : Extraction of
aromatics – using Furfural as
solvent – to improve VI of
LOBS.
Products : - Raffinate
- Aromatic extract.
Quality Monitoring:
Raffinate: K.V (100 oC), RI,
Extract : Density.

FURFURAL EXTRACTION SCHEME
TREATING SECTION
EXTRACT E RECOVERY
SECTION
RAFFINATE RECOVERY
SECTION
SOLVENT PURIFICATION
DEAERATED
FEEDSTOCK
E
X
T
R
C
T
O
R
HP
MP
LP
Flash
Tower
STEAM
VAC
S
T
R
I
P
P
E
R
STEAM
VAC
FURFURAL
A
T
O
W
E
R
B
T
O
W
E
R
WASTE
WATER
R/D RAFFINATE
R/D EXTRACT
FURFURAL

SOLVENT DE-WAXING UNIT
Objective
To remove paraffinic
hydrocarbons so that
LOBS is suitable for low
temp. application
The Process
Extraction and
crystallization to achieve
de-waxing, followed by
Filtration & Solvent
Recovery
Solvent : MEK & Toluene in
equal proportions.
Toluene is oil solvent &
MEK is anti wax solvent.
Feed characterized by
Density, Kin. Visc & RI
LOBS characterized by KV,
P.Pt., VI, Fl.Point,

General Effects of Refining on Main
Characteristics of Lube Oil Fractions
Main
Characteristics
General Range of Changes Brought about
Solvent
Refining
Dewaxing
Hydro
finishing
Viscosity ↓ --
V.I. ↓ --
Pour Point ↓ →
C.C.R ↓ -- ↓
Acidity ↓ -- ↓
Sulphur ↓ -- ↓
Colour ↓ -- ↓

CATALYTIC DE-WAXING UNIT
SIMPLIFIED PROCESS SCHEME
RECYCLE
HYDROTREATING
MSDW
PURGE
HYDROFINISHING
FEED
SEPARATOR
MAKE UP
HYDROGEN
HDT. EFFLUENT
STRIPPING & SCRUBBING
NAPHTHA
DIESEL
PRODUCT
FRACTIONATION
SECTION
GROUP II / GROUP III LOBS PRODUCT

Fluidized Catalytic Cracking Unit (FCCU)
Objective : To convert Heavy Vacuum Gas Oil
to valuable distillates like LPG, Gasoline, Diesel
by catalytic cracking in fluidized bed.
Feed : VGO/RCO/VR/HydroCracker Bottom.
Catalyst : Silica & Alumina Zeolite Structure

FCCU Product Qualities & End Uses
No Product Qualities End Use
1. Gas H2S rich Off. Gas Refinery Fuel Gas after
Amine scrubbing
2. LPG H2S, Mercaptons,
olefins like
Propylene/Butylene
3. Gasoline High Octane No. and
high Olefin contents
To LPG Pool/
Petrochemical feedstock
MS Pool
4. HNaphtha
+ LCO
Low Cetane no. High
‘S’, Unsaturates
Diesel Pool after
Hydrotreatment
5. CLO High Aromatics, Good
Cutter Stock
Fuel Oil

Yield pattern of Different Types of FCC
VGO FCC RFCC INDMAX PETROFCC
FEED VGO VGO+VR VGO+VR VGO
FEED QUALITY
CCR, WT% 0.74 4.06

Hydro-cracking Unit
Objective
: To convert Heavy Vacuum
Gas Oil to valuable distillates like LPG, Naphtha, ATF,
Kerosene and Diesel.
Feed
: VGO / Coker Products
Operating Conditions
- Temperature range : 370 – 420 o C
- System Pressure : 160 – 170 kg/cm 2 (g)
Catalyst : - Ni/Mo oxides for hydro-treating
- Ni/Mo/W(Tungsten) for Hydro-cracking

Hydro Cracker Unit Flow Scheme
Ex
MPU
Makeup H2
MUC
R-1 R-2
RGC
HP Amine
Gas & LN to Light
End
Recovery Section
PSA
G-1
V-1
F-1
Wash Water
Amine
Scrubber
Heavy
Naphtha
HVGO
Feed
Filter
E-1
Feed Preheat Ex
Hydrocracking
Reactor
PRT
V-2 V-3
V-8
V-9
MPU
To MUG
F-2
CR
Unconverted
Oil
ATF/Kero
Diesel

HCU Product Qualities & End Uses
No. Product Qualities End Uses
1. Gas H 2 S rich Off. Gas Refinery Fuel Gas
after Amine Wash
2. LPG H 2 S Contents LPG Pool after caustic
wash
3. Naphtha low Octane No. and low
‘S’ contents
Hydrogen Unit Feed /
CRU feed/ Naphtha
4. ATF /
Kero
Low ‘S’ and Low
Aromatics
ATF/ Kero.
5. Diesel Low ‘S’ and High Cetane Euro – IV/ III Diesel
6. Unconverted
Oil
Low ‘S’, High Saturates
FCCU Feed

Delayed Coking Process
Feedstock
: Vacuum Residue
Good process for increasing distillates and minimizing
black oil production.
Products Yields :
Gas+loss 8%
LPG 4%
Naphtha 6%
Gas oil 43%
FO 11%
RPC 28%
Gas oil & Naphtha need further treatment.

Delayed Coking Unit (DCU) flow scheme
Gas/LPG
FEED
F
SR
A
O
C
AT
KI
O
EN
RA
T
O
R
Naphtha
Kero
Gas Oil
Fuel Oil
S
E
P
A
R
A
T
O
R
RFO
C
O
K
E
C
H
A
M
B
E
R
C
O
K
E
C
H
A
M
B
E
R
Pre heat Exchanger
Furnace
T=505 0 C

Delayed Coker
Products Qualities & End Uses
No Product Qualities End Uses
1. Gas H2S rich Off Gas Refinery FG after
Amine Wash
2. LPG Mercaptons, unsaturates LPG after Merox /
Caustic wash
3. Naphtha Low Octane, High Olefins NHDT / DHDT feed
4. Kerosene High unsatuartes DHDT Feed
5. Gas Oil Low Cetane No. and high DHDT / HCU feed
unsaturates
6. Fuel Oil Good cutter stock Fuel Oil
7. Coke Low ash, Sulphur content
depends on feed ‘S’
Gasification/ cement
ind. /Electrode
Preparation

Sulphur Recovery - schematic

Flow scheme of a modern refinery

Thank you
Thank you

BASIC REFINERY OPERATIONS
Hydrocarbon molecules in crude do NOT meet customer needs
SEPARATION PROCESSES
(Primary Processes)
Segregate the molecules
CONVERSION PROCESSES
(Secondary Processes)
Rearrange the molecules
FINISHING PROCESSES
(Secondary Processes)
Remove Contaminants
MARKETABLE PRODUCTS