Embed Size (px)
Citation preview
1 | P a g e
SUMMER TRAINING REPORT 2011
(23rd MAY-15th JULY)
INDIAN OIL CORPORATION LIMITED
PANIPAT REFINERY
ATMOSPHERIC AND VACCUM DISTILLATION UNIT
SUBMITTED BY
RAVI VERMA (08112028)
DEPARTMENT OF CHEMICAL ENGINNERING
Dr. B.R. AMBEDKAR NATIONAL INSTITUTE OF TECHNOLOGY
JALANDHAR
2 | P a g e
ACKNOWLEDGEMENT
My sincere thanks to Mr.Y.B.Joshi and Mr. Ravi Sharma for allowing me to
do training under their guidance. I am grateful for their cooperation.
I express my sincere gratitude to Mr. K.S.Shukla and Mr. Subhajit Sarkar for
providing invaluable support and guidance.
My acknowledgement especially to Mr.Vikas kashyap (Process Engineer) who
helped me to understand the practical aspects of my project and in giving the
useful data necessary for the project.
The various guidelines and information given to me by Mr. BARDAN LAMA,
Mr. PRATEEK and Mr. GAGAN were of extreme help during project.
I would like to appreciate the time taken out by them for clarifying my doubts
and helping me at various steps.
RAVI VERMA
08112028 ------------------------------
DEPARTMENT OF CHEMICAL ENGINNERING
NATIONAL INTITUTE OF TECHNOLOGY
JALANDHAR
(2008 – 2012)
3 | P a g e
CONTENTS
SECTION -1 IOCL
1. An Introduction To INDIAN OIL CORPORATION
2. IOCL PANIPAT
SECTION -2 ATMOSPHERIC AND VACCUM DISTILLATION
UNIT
1. INTRODUCTION
2. PRODUCTS OF UNIT
3. CRUDE AND PRODUCT SPECIFICATION
4. LIST OF EQUIPMENTS
5. PROCESS DESCRIPTION
6. CRUDE DISTILLATION UNIT
7. NAPTHA STABILIZER SECTION
8. NAPTHA SPLITTER SECTION
9. MTO SPLITTER SECTION
10. VACCUM DISTILLATION UNIT
11. LPG AMINE & CAUSTIC WASH SECTION
12. FUEL GAS TRAETMENT SECTION
13. CHEMICALS REQUIRED
14. UTILITIES REQUIRED
SECTION -3 PROJECTS
1. INTRODUCTION
2. FLOW DIAGRAM
3. CALCULATION
4. RESULT
SECTION -4 REFRENCES AND BIBLOGRAPHY
4 | P a g e
SECTION 1:
IOCL
5 | P a g e
INDIAN OIL CORPORATION
Indian Oil Corporation Ltd. is India’s largest commercial enterprise, with a
sales turnover of Rs.2,85,337 crore and a net profit of Rs.2,950 crore for
the year 2008 – 09. Indian Oil is also the highest ranked Indian company
in the prestigious Fortune Global 500 listing ( 116 to position in 2008).
Indian Oil Company Ltd. established as an Oil marketing entity on 30th
June 1959, and was renamed Indian Oil Corporation Ltd. on 1st September
1964 following the merger of the refining entity ,Indian Refineries Ltd.
Since then, the Indian Oil people with their dedication and determination
have nurtured the integrated downstream petroleum company into India’s
No. 1 company and the country’s largest commercial enterprise . It is the
ceaseless efforts of several generations of the Indian oil family that has
today placed the corporation firmly among the world’s largest corporate ,
with the distinction of being 18th largest petroleum company in the
world .
Set up with a clear mandate for achieving self-sufficiency in petroleum
refining ,pipelines transportation and marketing operations for a nascent
nation set on the path of economic growth and prosperity , Indian Oil is
proud to account for nearly half of India’s petroleum consumption today .
Indian Oil and its subsidies account for 49% petroleum products market
share , 40.4 % refining capacity and 69 % downstream
Sector pipelines capacity in India. The Indian Oil Group of companies owns
and operates 10 of India’s 20 refineries with a combined refining
capacity of 60.2 MMPTA. i.e. 1.2 barrels per day. The Corporation’s cross –
country network of crude oil and product pipelines ,spanning about 9,300
km and the largest in the country, meets the vital energy needs of the
consumers in an efficient, economical and environmental – friendly manner.
6 | P a g e
To achieve the next level of growth, Indian Oil is currently forging
ahead on a well laid – out road map through vertical integration -
upstream into oil Exploration & Production and downstream into
petrochemicals and diversification into natural gas marketing, besides
globalization of its downstream operations .
As the leading public sector enterprise of India, Indian Oil has
successfully combined its corporate social responsibility agenda with its
business offerings, meeting the energy needs of millions of people
everyday across the length and breadth of the country , traversing a
diversity of cultures , difficult terrains and harsh climatic conditions . The
corporation takes pride in its continuous investments in innovative
technologies and solutions for sustainable energy flow and economic
viable and environment- friendly products & services for the benefit of its
consumers.
IOCL PANIPAT
Panipat Refinery is the 7th refinery of Indian Oil commissioned in 1998.
Referred to, as country’s technically advanced refinery is situated in the village
Baholi in Panipat District of Haryana. Built at the cost of Rs.3, 868 crore, it has
an installed capacity of 15 MMTPA now. Backed by global, state-of-the-art
technologies from IFP-France, Haldor Topsoe-Denmark, UNOCAL/UOP-USA,
Stone & Webster-USA, and Delta-Hudson-Canada. The refinery is designed for
processing both indigenous and imported crudes. It receives crude oil through
the chaksu-Kamal branch pipeline of the Salaya-Mathura pipeline Vadinar
Gujarat coast to Panipat through a 1339 km long pipeline.
The various products of the refinery are:
01. Liquefied Petroleum Gas
02. Naphtha
03. Motor Spirit
04. Aviation Turbine Fuel
05. Mineral Turpentine Oil
06. Superior Kerosene
07. High Speed Diesel
08. Heavy Petroleum Stock
09. Bitumen
10. Sulphur
7 | P a g e
Around 66% of these products are transported through environment-friendly
pipelines, while both rail and road account for 17% each.
Panipat Refinery meets demands of petroleum products not only of Haryana but
also the entire Northwest Region including Punjab, J&K, Himachal,
Chandigarh, Western U.P. and part of Rajasthan and Delhi.
Indian Oil Corporation Limited (IOCL) at Panipat consists of various units.
Among them major once are:
1. Atmospheric and Vacuum Distillation Unit(AVU)
2. Continuous Catalytic Reformer Unit(CCRU)
3. Visbreaking Unit(VBU)
4. Hydrogen Generation Unit(HGU)
5. Resid Fluidized Catalytic Cracking Unit(RFCCU)
6. Once Through Hydrocracker Unit(HCU)
7. Diesel Hydro Desulphurisation Unit(DHDS)
8. Amine Regeneration Unit(ARU)
9. Sour Water Stripper Unit(SWSU)
10. Bitumen Blowing Unit(BBU)
11. Recovery Unit(SRU)
8 | P a g e
Atmospheric and Vacuum Distillation Unit(AVU)
SH Steam
Crude Filter Desalter
Furnace
Atmospheric
Column
Unstablised Gasoline
Inter Naphtha
Heavy Naphtha
Kerosene/ATF
Light Gas Oil
Heavy Gas
Oil
SH Steam
Atmospheric Residue
Non-Condensable
Vacuum Residue
Heavy Vacuum
Gas Oil
Light Diesel Oil
Light Vacuum
Gas OilVacuum
Column
AVU is designed to process 6.0 MMTPA Bombay High and Arab Mix crudes in
blocked out operation. AVU, a fully integrated unit, consists of the following
sections. Crude Distillation Unit, Vacuum Treating Units for Fuel Gas, LPG and
9 | P a g e
Naphtha. The Unit was mechanically completed in February 1998 and trial
operation of the various sections started in phases starting from May 1998. The
Unit was commissioned on 2nd
October 1998
Continuous Catalytic Reformer Unit(CCRU)
LPG
Reformate
H2 Rich Gas
Fuel Gas
LPG
Absorber
StabliserRecontacting
Drum
Hydrotreater Recycle
Gas Compressor
Hydrotreater
Naphtha
Feed
Seperator Stripper
Reforming
Reactors
Seperator
Purge to
ATU
Recycle Gas
Compressor
H2 Rich Gas
Compressor
Hydrotreated
Naphtha
Storage
M/s. IFP, FRANCE licenses the CCRU. This unit is designed to process 0.5 MMTPA
of SR Naphtha from Arab mix and/or Bombay High crude. This unit consists of
Naphtha Hydro Treating, Catalytic Reforming and Catalyst Circulation and
10 | P a g e
Regeneration Sections. Catalytic Reforming is a major conversion process that
transforms low octane Naphtha feed stock to high octane reformate (RON : 98)
for use as a gasoline blending component to make lead free petrol (MS). A rich
hydrogen gas (about 90% purity) and LPG are obtained as valuable by- products. The
reformer can also be run for production of reformate rich in benzene, toluene, and
xylenes (BTX).
Visbreaking Unit(VBU)
SHS
Soaker
AR
Quench
Fractionator
Unstablised
Gasoline
VB Gas Oil
Visbreaking Unit (VBU) is designed to process 0.4 MMTPA Arab mix vacuum
residue. This unit is a soaker Visbreaker, which reduces the viscosity of feed at
lower temperature. The unit was mechanically completed in March 1998 and
the trial operation started in July, 98. The unit was commissioned on 29th
11 | P a g e
October 1998.The visbreaker is designed to process 400000 MTPA of Arab mix
vacuum residue from a crude mix of 50:50 Arab heavy and Arab light crudes.
The unit consists of a two pass heater and separation system. The products from
the unit are fuel oil, gasohol, and naphtha and fuel gas.
Products
VB Gas 8200 MTPA
VB Naphtha 13600 MTPA
VB Gasohol 44800 MTPA
VB Tar (350 C) 333400 MTPA
Hydrogen Generation Unit
Recycle H2
Light NaphthaHydro-
Desulphurisat ion
Sulphur
Absorber 1 & 2
Pre-ReformerTubular ReformerMT-Shift
Converter
Pressure Shift
Adsorber
Product H2
Off Gases
The Panipat Refinery Hydrogen Unit is designed to produce 38,000 MTPA of
high purity (99.99%) hydrogen gas Hydrogen is produced in the unit by Steam
12 | P a g e
Reforming of Naphtha based on the technology from M/S Haldor Topsoe A/S,
Denmark.
The process for hydrogen generation involves the following four major
steps.
Sulphur removal from Naphtha.
Steam reforming of Naphtha
Medium and low temperature shift conversions.
Hydrogen purification in a PSA unit.
Residue Fluidised Catalytic Cracking Unit
HP
Receiver
Na
ph
tha
Sp
litte
r
LCN
HCN
De
bu
ten
ise
r
Compressor
HCO
Flue Gas
to Stack
Main
Column
Air
Blowe
r
Reactor
RG-2
RG-1
DCO
O/H
Receiver
LCO
LPG
Str
ipp
er
Pri
ma
ry
Ab
so
rbe
r
Sp
on
ge
Ab
so
rbe
r
Off
Gas
Rich
Oil
Feed
Slurry +
HCO
13 | P a g e
The demand of the petroleum products in the world is shifting more towards
light distillates because of increasing demand of LPG and Gasolene as a result
of the steady growth in private transportation system and shift towards the
cooking gas in the developing countries. The declining market for fuel oil
coupled with anticipated changes in the future crude quality and the shift in
product demand in favour of light distillate placed and additional emphasis on
upgrading the bottom of the barrel i.e. the heavier residues into more and more
light distillates
Diesel Hydrodesulphurisation Unit
Hydrogen
Make up gas
Compressor
Section
Hydrogen
Reactor
Heater
System
Reactor
Section
Recycle gas
Compressor
Section
Feed
System
Stripper
Section
Naphtha
Stabilizer
Section
HP Amine
Absorber
Section
LP Amine
Absorber
Section Rich Amine
to ARU
Naphtha to
Storage
Gas Oil to
Storage
Separation
Section
Feed
Preheating
System
14 | P a g e
The DHDS unit is set up to reduce sulfur content in the diesel and produce
diesel with 0.25% Sulphur.
The unit treats the following gas-oils fractions.
1. S.R.Gas oil
2. Vacuum Diesel
3. Vis-Breaker Gas Oil
4. Total Cycle Oil
DHDS unit has been designed to reduce the sulphur content in High Speed
Diesel to less than 0.05% wt. The process technology for this unit was built
within the record time on LUM SUM TURN key (LSTK) basis by M/s.
L&T. The capacity of the unit is 0.7 MMTPA. The unit was mechanically
completed in March’99 and commissioned on the 12th
July.
Amine Regeneration Unit(ARU)
ARU is designed to process Hydrogen Sulfide rich amine from amine
Absorption units and recover amine after releasing the acid gas to the Sulphur
Recovery Unit. This unit was mechanically completed in February’99 and was
commissioned on 6th
March’99.
Sour Water Stripper Unit(SWSU)
The unit consists of 2 Sour Water Stripping Units, one for the sour water from
the Hydrocracker unit and the other for the sour water from the remaining units.
This unit was mechanically completed in December’98 and was commissioned
on 15th
February’99.
15 | P a g e
Bitumen Blowing Unit (BBU)
Bitumen Blowing Unit (BBU) has been designed to produce 3 grades of
Bitumen, viz.: 80-100, 60-70 and 30-49 from vacuum residue of high Sulfur
Crudes. The capacity of the unit is 0.5 MMTPA. This unit was mechanically
completed in March 1998; trial run of the unit was taken in July 1998 and was
commissioned on 12th December 1998.
Sulfur Recovery Unit (SRU)
SRU is designed to process Hydrogen Sulfide rich acid gas recover elemental
sulfur. The unit was designed by M/s. EIL for a capacity of 84tonnes per day
96% recovery efficiency, which has further been revamped to 115 tonnes per
day and 99% recovery efficiency based on the process technology of M/s. Delta
Hudson, Canada. This unit was mechanically completed in March’99 and was
commissioned on 30th March’99.
Other Facilities:
Off sites
The off sites facilities at Panipat Refinery are spread over an area of 115 acres.
There are 77 Storage tanks having storage capacity of 400,000KL Crude Oil
and 830,000KL of Petroleum products. There are 7 nos. of pump stations, a
blending station and connecting pipelines. There are 7 nos. of LPG Horton
Spheres each of 1500KL capacity. The off sites operation is controlled from the
centralized DCS control room of OM&S. The special feature of offsite
operation is that Tank Truck loading (TTL) and Tank Wagon Loading (TWL)
facilities are provided at the Marketing Terminal, which is adjacent to the
refinery. Offsite operation of the Refinery started with the receiving of the first
batch of crude oil in Refinery Storage Tanks on 30th
November’97.
16 | P a g e
Thermal Power Station & Utilities
The Power and Steam requirement of the refinery is met from the Captive
Power Plant designed and constructed by BHEL in consultation with NTPC.
Capacity of the power plant is:
Steam Turbine Generator – 3 x 25 MW.
Gas Turbine Generator – 30 MW.
Steam boiler – 3 x 160 T/hr.
Heat Recovery Steam Generator: 125 T/hr.
The first boiler was commissioned in May’97 and first TG was commissioned
in August’97.
Nitrogen Plant
Nitrogen is produce in a cryogenic separation plant by air distillation after
liquefying the same. M/s. BHPV constructed the plant on a turnkey basis. The
capacity of the plant is 800 NM3/hr. The plant was commissioned on
December’97.
Miscellaneous
One raw water reservoir of capacity 200,000KL
Raw water treatment plant of capacity 2100KL/hr.
Four chains of DM Water treatment plant
Compressed air system with 4 nos. of compressors and 3 nos. air drier.
Cooling tower with 5 cells for TPS and 8 cells for process units
17 | P a g e
SECTION 2
ATMOSPHERIC AND VACCUM
DISTILLATION UNIT
18 | P a g e
INTRODUCTION
Atmospheric, Vacuum and Naphtha Splitter unit of Panipat Refinery is designed
to process 100% Bombay High Crude and 100% Arab Mix Crude (consisting of
light and heavy crude in 50:50 proportion by weight) in blocked out operation
without loss of throughput @ 7.5 MMTPA. Unit is located in an area of 24800
square meters & was commissioned with 6.0 MMTPA in May 1998 and
revamped to 7.5 MMTPA in October 2010. In actual practice various low
sulphur crude and high sulphur crude are being processed since commissioning
of the plant.
AVU is called a mother unit as it provides feed to other secondary units like
hydrogen unit, CRU, HCU, FCC, Bitumen unit and VBU.
In addition to crude processing, AVU also maintains Fuel Gas amine wash
system and LPG vaporiser to maintain refinery fuel gas header pressure.
SECTIONS IN THE UNIT :
a) Crude Desalting section.
b) Preflash section.
c) Atmospheric Distillation section.
d) Stabiliser section.
e) Naphtha splitters for HGU, CCRU and PX feed
f) Naphtha Caustic wash section.
g) MTO splitter section.
h) Vacuum Distillation section.
i) LPG Amine & caustic wash section.
j) Centralised Sour Fuel gas Amine treatment section.
k) LPG vaporiser section.
CAPACITIES :
1) Crude Distillation Unit 7.50 MMTPA
2) Vacuum Distillation Unit. 4.125 MMTPA
3) Naphtha stabiliser. 1.525 MMTPA
4) Pre-topping column. 1.375 MMTPA
19 | P a g e
5) MTO splitter. 0.03 MMTPA
0.03 MMTPA production from ATF/KERO stream of Arab Mix with
4000 Hrs. operation.
6) Naphtha caustic wash
C5-90ºC cut. 0.48 MMTPA
90-120º C cut. 0.6MMTPA
S.N
O SHORT
NAME
LONG NAME CUT RANGE º
C USAGE
1. GAS
Fuel gas C1-C2 Internal fuel
2. LPG Liquefied Petroleum
Gas
C3-C4 Domestic/Auto
fuel
3. NAPH Naphtha C5-120 MS Component
4. HN Heavy Naphtha 120-150 HSD
Component
5. KERO Kerosene 140-270 Domestic fuel
6. ATF Aviation Turbine Fuel 140-240 Aeroplanes
7. LGO Light Gas Oil 240/270-320 HSD/
DHDS/DHDT
feed
8. HGO Heavy Gas Oil 320-370 HSD/
DHDS/DHDT
feed
20 | P a g e
2. PRODUCTS OF THE UNIT
3 . CRUDE AND PRODUCT SPECIFICATION
SPECIFICATION OF CRUDE :
1) Gravity 30-40 º C API
2) Viscosity 3-24 Cst @ 36 º C
3) Pour point (-) 30 – (+) 30 º C
4) RVP 0.34-0.67 Kg/cm2 (max.)
5) Salt content 165 ppm (max.)
6) BS & W 2.0% vol. (max.)
7) Total Sulphur 0.17-2.35 % Wt.
8) Wax Content 10.68-2.8% wt.
SPECIFICATION OF PRODUCT :
9. VD Vacuum Diesel 370 HSD/
DHDS/DHDT
feed
10. LVGO Light Vacuum gas Oil 370-425 Feed to
HCU/FCCU
11. HVGO Heavy Vacuum Gas
Oil
425-550 Feed to
HCU/FCCU
12. V.SLOP Vacuum Slop 550-560 IFO Component/
feed to RFCCU
13. VR Vacuum Residue 560+ Bitumen/ VBU
feed/ DCU feed /
RFFCU feed
14. C5-90º C cut NAPTHA C5-90 HGU
feed/ISOM Feed
21 | P a g e
1) LPG Confirm to IS-4576 to general and
following specifications in
particular.
a) Vapour pressure @ 65º C not to
exceed 16.87 Kg/cm2 (a)
b) Weathering 95% vol. Minimum
at 2º C and 760 mm HG
pressure.
c) Not more than 1% of C5
components.
2) STABILISED NAPHTHA RVP not to exceed 0.7 Kg/Cm2 (a)
3) HN Flash : >15 C
Distillation : 120-140 º C
4) KERO Confirm to IS : 1459-
1974
FBP : 300º C (max.)
Flash : 38º c (min)
5) ATF Flash : 38º C (min)
Freezing : (-) 50º C (min)
Silver strip : Nil
Corrosion.
Density @ : 0.775 to 0.84
6) MTO Confirm to BIS-1440 in general and to
the
22 | P a g e
Following specifications in particular.
ASTM D-86 IBP : 145º C
FBP : 200º C
Flash : 38º C
7) LGO Flash : 35º C (min)
Pour : As per instruction.
8) HGO Flash : 35º C (min.)
Pour : As per instruction
Recovery : 90% @360 º C
9) RCO Flash : 150º C
Density : As reported
Recovery : 10% at 370º C
10) Vac. Diesel Flash : >125º C
Pour : (+6) to (+) 18º
Recovery : 90% @360 º
C
11) LVGO CCR :
0.50wt.%max.
12) HVGO Pour : (+) 27 to (+)
42º C
23 | P a g e
4. LIST OF EQUIPMENTS:
A. COLUMNS:
1. Crude Distillation column
2. Heavy Naphtha stripper
3. KERO/ATF Stripper
4. LGO stripper
5. HGO stripper
6. Naphtha stabilizer
7. Naphtha splitter
8. MTO Splitter
9. Vacuum Distillation column
10. LPG Amine Absorber
11. Fuel Gas Amine Absorber
A. VESSELS
B. PUMPS
C. FURNACES (Crude furnace, Naphtha Splitter Furnace and Vacuum
furnace)
D. EJECTORS
E. AIR FIN COOLERS
F. AIR FIN COOLER FANS
G. EXCHANGERS
H. REBOILERS
I. DESALTERS (Crude Desalter 1st stage, 2
nd stage and 3
rd stage)
5. PROCESS DESCRIPTION
Crude oil from crude charge pumps is charged to preheat exchanger trains in
two parallel streams.
24 | P a g e
1st PREHEAT TRAIN
The first crude stream passes through Crude v/s vacuum diesel CR and
picks up heat from Vacuum Diesel CR coming at 142-166º c. Vacuum
Diesel CR is cooled to 91-99º C, whereas crude is getting heated upto 56-
61º C.
Crude outlet from above enters Crude v/s Hy. Naphtha CR exchanger.
Crude gets heated upto 87-103º C whereas Hy. Naphtha CR gets cooled
from 122-147º C to 94-108º C.
After that, Crude enters Crude v/s VR exchanger. Crude gets heated upto
113º C whereas VR gets cooled from 237-242º C to 178-128º C.
The second crude steam passes through Crude v/s Kero/ATF where it is
picking up heat from Kero/ATF coming at 124-125º c & getting cooled to
95-98º C whereas crude is getting heated upto 55-58º C.
After this, crude enters crude v/s Kero/ATF CR exchanger. Crude gets
heated upto 107-115º C, whereas Kero/ATF CR gets cooled from 154-
171º C to 115 º C.
After that, crude enters crude v/s Kero/ATF exchanger. Crude gets heated
upto 132-135º C, whereas Kero/ATF CR gets cooled from 163-174º C to
124-125 º C.
Crude oil from both streams is combined to average the temperature @ 136-
141º c and enters crude desalters 03-LD-001 & 03-LD-002 in series.
Provision has been kept to inject wash water and demulsifier.
ELECTRIC DESALTING
The desalter is an electrostatic coalescer used for purification of crude from
sludge, salts and corrosion inducing salts. Sludge and salts like NaCl
generally gets deposited on the tubes of exchangers and thus reduce preheat
temperature. Salt if not removed will cause corrosion in distillation column.
Salts may vary widely in the ratio of metal ions and brine concentration
though 75% Na, 15% Mg and 10% Ca are common averages. Chloride is the
source of the indices of corrosion potential of the crude. MgCl2 is the most
specific producer of HCI with Ca and Na in descending order. In desalting,
the electric field is a powerful tool for overcoming the resistance of
stabilising films. The collision and coalescence of drops is accomplished by
25 | P a g e
an induced dipole attraction between them. That is the electrical charges
inherent in each droplet are separated so that positive charges move to one
end of the droplet and negative charges move to the other end.
As droplets then approach each other, the force between them becomes very
great. The stabilizing films are squeezed between drops and coalescence is
rapid. In a 5% emulsion, drops average about two diameters apart;
coalescence proceeds almost instantaneously. The distance between drops
then increases as drops fall due to gravity. For a 1% emulsion, drops are four
diameters apart and coalescence slows. When the emulsion content is 0.1%,
drops are eight diameters apart on the average. The forces of dipole
attraction, diminished by a factor of 250, are insignificant at this distance and
the final emulsion content shall depend on this to about 0.1%.
Crude from second desalter, bypassing crude pump (03-P—003 A/B/C)
discharge, is divided into parallel heat exchanger trains
2ND
PREHEAT TRAIN
The first desalted Crude stream passes through Crude v/s HGO where
it is picking up heat from HGO coming at 185-194º C and getting cooled
to 140-144º C whereas crude is getting heated up to 140-142º C.
After this, crude enters Crude v/s LVGO exchanger. Crude gets heated up
to 166-174º C whereas LVGO gets cooled from 265-268º C to 147-152º
C.
Subsequently, crude enters Crude v/s HGO exchanger. Crude gets heated
up to 185-194 º C.
The second desalted crude stream passes through 03-E-021 (Crude v/s
Kero/ATF) where it is picking up heat from Kero/ATF coming at 195-
205º c and getting cooled to 163-174º C whereas crude is getting heated
upto 146-153º C.
Further, crude enters Crude v/s LGO CR where it is picking up heat from
LGO CR coming at 185-190º C and getting cooled to 170-180º C
whereas crude is getting heated upto 155-162º C.
26 | P a g e
After that, crude enters Crude v/s HVGO where it is picking up heat from
HVGO coming at 248-291º C and getting cooled to 204-211º C whereas
crude is getting heated up to 173-176º C.
Crude oil from both streams is combined to average the temperature @ 179-
180º C and enters pre-flash drum where 3-4% wt. of light ends are removed.
Crude after flashing in the preflash drum is pumped by through 3rd
preheat train,
after being further divided into two parallels preheat circuits.
3rd
PREHEAT TRAIN
The first crude stream passes through Crude v/s LGO CR where it is
picking up heat from LGO-CR coming at 241-249º C and getting
cooled to 185-190º C whereas crude is getting heated upto 210-213º
C.
Crude then enters Crude v/s HVGO CR exchanger. Crude gets heated
up to 218-228º C whereas HVGO CR gets cooled from 259-271º C to
239-258º C.
After that, crude enters Crude v/s HGO CR exchanger. Crude gets
heated up to 223-249º C whereas HGO CR gets cooled from 302-311º
C to 275-303º C.
Subsequently, crude enters Crude v/s HVGO CR exchanger. Crude
gets heated up to 241-277º C whereas HVGO CR gets cooled from
238-298º C to 239-271º C.
Further, crude enters Crude v/s HVGO exchanger. Crude gets heated
up to 251-283º C whereas HVGO gets cooled from 298-306º C to
201-248º C.
After that, crude enters Crude v/s HGO exchanger. Crude gets heated
up to 259-289º C whereas HGO gets cooled from 323-325º C to 291-
260º C.
The second crude stream passes through Crude v/s LGO where it is
picking up heat from LGO coming at 226-258º C and getting cooled to
179-197º C whereas crude is getting heated up to 184-198º C.
After that, crude enters Crude v/s LVGO CR exchanger. Crude gets
heated up to 218-236º C whereas LVGO CR gets cooled from 258-
265º C to 204-214º C.
Further, crude enters Crude v/s VR exchanger. Crude gets heated up to
248-265º C whereas VR gets cooled from 350/350º C to 237-242º C.
27 | P a g e
After this, crude enters Crude v/s vacuum slop exchanger. Crude gets
heated up to 258-288º C whereas vac slop gets cooled from 353/370º
C to 298-353º C.
Crude is combined to average the temperature @ 259-289º C .This
temperature is called preheat temperature or coil inlet temperature (CIT).
FIRED HEATERS :
The preheated crude is further heated and partially vaporized in Atmospheric
Heater having eight passes. (Four sections with 6 inches sch. 40 tubes).
The atmospheric heater is a box-type vertical furnace with up firing burners,
8 Nos. of burners in each section are provided on the floor with FG and FO
firing facilities. A total 32 nos. of burners have been provided in CDU
heater. Out of 32 burners, 28 nos. of burners have both FO and FG firing
facility and 4 burners, called LP burners have facility to fire off- gas from
VDU column and FG (called support burners).
This heater is having two distinct heating sections i.e.
A) Radiant Section: It houses the burners and forms the combustion
chamber or fire box. Tubes are arranged in a vertical arrangement
along the walls of each cell with tube arrangement itself forming the
cell.
B) Covection Sections: It receives heat from hot flue gases leaving the
radiant section. Tubes are arranged in horizontal bank and positioned
above radiant section.
28 | P a g e
6. CRUDE DISTILLATION SECTION
The column is provided with 56 trays of which 10 are baffle trays in the
stripping section. In addition 6 nos. of chimney trays are also provided in the
column. Feed to the column is on tray # 10. The vaporized portion of the feed
along with the light ends from the Pre-topping Vessel are fractionated on trays
above the flash zone to yield liquid side draw products, pump arounds
(circulating refluxes) and overhead vapor stream.
Heated and partly vaporized crude feed coming from fired heater enters the
flash zone of the column at tray no. 10 at 360-370 º C (LS crude)/370-380º C
(HS crude). Hydrocarbon vapors flash in this zone and get liberated. Non
flashed liquid moves down which is largely bottom product, called RCO.
Certain degree of over flashing of crude is desirable for proper stabilisation of
RCO and fractionation of gas oil components. Over flash is achieved by setting
up COT at slightly higher value than actually required. This over flashed
material mostly condenses on 11th
tray. The condensed liquid withdrawn from
11th tray is put back on 10
th tray into the column. Over flash liquid travels down
form tray 11 to tray 10. It strips out heavier vapour components coming up from
RCO stock collected at column bottom and which otherwise could move and
cause coloration of gas oil stream. Flow of over flash liquid could be increased
by either increasing COT and condensing more material on 11th
tray or by
reducing HGO draw off and dropping more HGO components on 11th
tray.
However, this will result is less gas oil yield and higher energy consumption
without any advantage. Too large flow of over flash liquid may result in drop in
bottom temperature and lighter bottom product, RCO.
The optimum over flash flow is about 4-5 % on crude throughput. MP steam
having some degree of superheat is introduced in the column below tray 1, at
approximately 3.5 Kg/Cm2 (g) and 290º C for stripping of RCO. Steam
stripping helps to remove lighter constituents from the bottom product RCO by
reducing their partial pressure and helping them vaporize without requiring
additional heat. Hydrocarbon vapours liberated by flashing move up along with
steam in the column for further mass transfer at trays in upper section.
29 | P a g e
Steam flow to column is regulated based on outgoing RCO quantity to Vacuum
Heater. To reduce pressure drops at column entry nozzle and achieve
homogenous distribution, steam is introduced through two nozzles.
Reduced crude oil product is collected at bottom of the column. Column bottom
level control can be done either by manipulating RCO flow to vacuum heater or
by manipulating VR+Quench rundown flow (in case of only CDU run when
VDU is not operating).
OVERHEAD SECTION :
The overhead vapors are totally condensed in Crude Overhead Air Condensers.
This condensed overhead product is separated as Hydrocarbon and water in a
Reflux Drum. Water is drawn out under inter-phase level control and sent to
sour water stripper or to ETP by a pump. Unstabilised naphtha containing Fuel
Gas, LPG and Naphtha is partially refluxed and partially pumped to the
Stabilizer.
HEAVY NAPHTHA SECTION:
Heavy Naphtha is withdrawn as side product from tray # 44 to the Side Stripper.
Light ends in Hy. Naphtha is stripped in the Hy. Naphtha Reboiler using LGO
as the hot medium. Stripped vapors from the side stripper are routed to tray # 46
of the Atmospheric Column. The bottom product is cooled in Hy Naphtha
/BFW Exchangers followed by a trim cooler and sent to storage.
KERO SECTION:
Kero is withdrawn as side product from tray # 31 to the Kero side stripper .
Light ends in Kero are stripped in the Kero Reboiler using HVGO CR as the hot
medium. Stripped vapors from the side stripper are routed to tray # 33 of the
Atmospheric Column. The bottom product is routed to MP Steam Generator
followed by LMP Steam Generator and Crude Preheat exchanger (to reduce
30 | P a g e
vapour pressure & hence increase available NPSH) before being pumped. The
discharge of routed to crude preheats exchangers and finally cooled before
being routed under flow control to storage.
LIGHT GAS OIL SECTION :
LGO is withdrawn as side product from tray # 22 to the LGO side Stripper.
Light ends in LGO are stripped using MP steam. Stripped vapors from the side
stripper are routed to tray # 24 of the Atmospheric Column. The bottom product
is pumped by 03-P-12 A/B under flow control through Hy. Naphtha Reboiler,
Crude preheat exchangers and finally cooled in tempered water exchanger, air
coolers and trim cooler before being routed to storage.
Facility has been provided to supply hot LGO to DHDS.
HEAVY GAS OIL SECTION:
HGO is withdrawn from tray # 15 to the HGO side stripper 03. Light ends in
HGO are stripped using MP steam. Stripped vapors from the side stripper are
routed to tray # 18 of the Atmospheric Column. The bottom product is routed to
preheat exchangers, tempered water exchanger and coolers before being finally
routed to storage on Flow Control to DHDS/DHDT feed tanks through blending
station at OM&S.
Facility has been provided to supply hot HGO to DHDS.
REDUCED CRUDE OIL :
Stripped RCO drawn from the bottom is pumped to the Vacuum heater of
vacuum Distillation Unit on Level control. Single pump will operate during
turndown operation for both AM/BH operations. Starts up lines connect RCO to
VR pump discharge line. Provision to route RCO to VR, and to route RCO
through HVGO PDT & CR circuit and finally through VR product cooler is also
provided to cater to short period of operation of CDU without VDU operation.
31 | P a g e
CIRCULATING REFLUXES
In order to maximize heat recovery and balance tower loadings, heat is removed
by way of circulating reflux (or pump around) from each of the sections. These
pump around are withdrawn and pumped through preheat train for maximum
heat recovery, thus cooling these streams. Duty controllers are provided for
removing the requisite duty. HGO CR is used to reboil the Stabilizer Bottom.
LGO CR is used for generating LP Steam. For turndown operations single
pump will operate for HN/Kero/LGO/HGO CR pumps.
7. NAPHTHA STABLIZER SECTION
Unstabilised Naphtha from Crude Column overhead is pumped to the Naphtha
Stabilizer after preheating with stabilizer bottoms in the Feed/Bottom
exchanger. A bypass has been provided to maintain NSU feed temperature in
the range of 85-90 º C and stabiliser feed temperature about 125- 128 º C. This
column has 40 trays with feed entering on the 21st tray. Necessary heat to reboil
is provided by HGO-CR to the Horizontal Thermosyphon Reboiler on Flow
control (opposite acting). Temperature on tray # 3 regulates HGO CR flow
through the reboiler.
A. LPG:
Stabiliser overhead vapors are condensed in the overhead condenser and then
flow into the reflux drum. The stabilizer works either on partial condensation
mode or total condensation mode. During full condensation is under control
action and under control operation. Any water present with the overheads and
separated in the Reflux drum and part of Hydrocarbons is refluxed. The balance
(LPG) is pumped to Caustic & Amine treating Unit for treatment on LIC/FIC
control by pumps provided with double mechanical seal with methanol as seal
fluid releasing to flare on pressurization.
32 | P a g e
Fuel Gas generated during BH/AM operation is routed to Amine Treatment
Unit (located within CDU/VDU unit) to remove H2S before being routed to the
Fuel gas KO Drum and then to the plant Fuel Gas Distribution Header.
B. STABILIZED NAPHTHA:
Naphtha from stabiliser bottom after exchanging heat with feed Naphtha is
routed to the Naphtha Splitter Unit. In case naphtha splitter is shutdown, the
stabilized naphtha is cooled and sent to rundown through CRU naphtha caustic
wash system.
Provision is also made to divert unsterilized Naphtha to slop header during start
up.
8. NAPHTHA SPLITTER SECTION
In the Naphtha Splitter, stabilized Naphtha is split to C5-65/90º C and 115/165
ºC cuts as overhead and bottom product respectively. This column has four
packing beds with single feed entering above the 2nd
bed.
A) NAPHTHA SPLITTER OVERHEAD PRODUCT :
The overhead vapour is condensed in Air cooler and the condensed product
flows to the reflux drum from where a part is refluxed back to the column. This
overhead product is further cooled to 40º C before being routed to storage via
Caustic Wash. Min. flow bypass has been provided for pumps for turndown
operations. Provision of partial or total C5-90 Naphtha diversion has given to
caustic and water wash (as no need of caustic/water wash of bottom stream).
This is done due to high production of C5-90 Naphtha and inadequate capacity
of the vessel.
33 | P a g e
B) NAPHTHA SPLITTER BOTTOM PRODUCT :
The bottom product is cooled in two air coolers, to 40 º C before being routed to
storage via a separate caustic wash. Two control valves were provided in
parallel to cater to the wide variations in flow between the various operations.
C) NAPHTHA SPLITTER REBOILER (FURNACE) :
The heat for reboiling is provided by a fired heater 03-F-002. The heater can be
fired with FO/FG or combination fuel. Vacuum heater and Naphtha Splitter
fired reboiler share a common Air preheating system. Firing is controlled by
temperature on the 3rd
tray. For better control Coil Outlet Temperature, the
principles of pass balancing is used. This is a vertical cylindrical Heater having
six flows passes. The radiant section is provided with 6” Sch. 40 tubes having
two 8” Sch. 40 tubes as last and second last tubes at the outlet of each pass
while the pass while the connection section is provided with 6” Sch. 40 tubes.
The radiant section tubes are disposed in a vertical arrangement along the walls
of the combustion chamber.
The heater is provided with 12 forced drafts, low NOx combination fuel fired
burners (fuel oil & Refinery fuel gas). These burners are arranged in a circle and
are fired vertically upward from the floor.
The convection section of Naphtha Splitter Reboiler has 8 Nos. of soot blowers,
which are controlled by automatic sequential control panel provided at grade
level.
A combined air preheater system containing one cast Air preheater and one
Glass Air preheater along with two forced draft fans and one induced draft fan
is provided for both Vacuum Heater and Splitter Reboiler.
The turndown factors are as follows: -
For AM, C5-90º C overhead product with max. Reflux, 75/55/65% on
FO/FG/Comb Fuel is possible with vacuum Heater also in operation. With NSU
heater operating in isolation no turndown is possible.
34 | P a g e
For BH, C5-90º C overhead product, 50% turndown is achievable with or
without Vacuum Heater in operation.
D) NAPHTHA CAUSTIC WASH SYSTEM :
The Naphtha Splitter overhead Product & the Bottom product are Caustic
washed to remove H2S, phenols and mercaptans in two separate wash facilities.
Caustic wash consists of mixer settler unit with 12-15% caustic followed by
mixer settler unit of water wash with Service water to remove Caustic traces.
The Naphtha cuts flow separately from the Splitter to the Caustic wash vessels
through mixing valves where it is mixed with 25 vol. % of 12-15 wt %
circulating Caustic on flow control. The thorough mixing given in the mixing
valve transfers the H2S, part of phenols (from stripped sour water through the
desalter), and part of mercaptans from Naphtha cuts to the caustic. The mixture
is given adequate residence time in the vessels for the Hydrocarbon and Caustic
phases to separate. The Hydrocarbon phase leaves at the top of the vessel and
the Caustic phase from the bottom. As the circulation goes on, the strength of
the Caustic goes down and when Caustic is 75% spent the entire Caustic is
drained out.. Shorter batch times may be required with heavier feed mercaptans.
The Hydrocarbon phase is then sent for water wash in vessels to remove
entrained Caustic, water is circulated by pumps for the overhead and bottom
products, and the hydrocarbon is thoroughly mixed with water in the mixing
valve upstream of the wash water vessel. Here again 25-vol. % of service water
is circulated on flow control. The washed Naphtha cuts are routed to storage.
Presently both naphtha splitter streams go to rundown without caustic and water
circulation.
35 | P a g e
9. MTO SPLITTER SECTION
Part of Kero/ATF, upstream of the Product Rundown Control Valve is pumped
to the MTO Splitter after exchanging heat with MTO bottom product (Hy.
Kero). The balance heat required is provided by HVGO CR in the Horizontal
Thermosyphon Reboiler on flow control (opposite acting). Temperature on the
3rd
tray regulates HVGO CR flow through the Reboiler.
The column is designed with 26 trays with feed entering on the 10th tray.
Provision to route the feed to the 8th tray is also provided.
A.MTO SPLITTER OVERHEAD:
The overheads are condensed in tempered water Exchanger and routed to the
Reflux Drum from where a part of the condensed products is refluxed and the
rest pumped to Kero/ATF rundown line after cooling.
B.MTO PRODUCT:
This product is drawn from a total draw tray below tray # 19. A part is refluxed
and the balance cooled, before being rundown to storage. During BH operation
this stream is blended with Kero/ATF rundown line.
C.HEAVY KERO (MTO SPLITTER BOTTOM):
The bottom product is pumped by and finally cooled and routed to storage on
flow control. During AM operation this product is blended with Kero/ATF in
the rundown line.
One provision is made to route Light Kero, MTO and Heavy Kero together to
route to ATF R/D at MEROX ATF R/D.
36 | P a g e
10. VACUUM DISTILLATION UNIT
VACUUM FURNACE:
Hot RCO from the atmospheric column bottom at 355/365º C is mixed with
slop recycle from Vacuum Column, heated and partially vaporized in the 8-pass
Vacuum Furnace and introduced to the flash zone of the Vacuum Column. The
flash zone pressure is 57MM. Velocity Steam (MP) is injected into individual
passes and regulated manually. 3-injection points have been provided on each
pass. This is to maintain required velocities in the heater passes and to prevent
coking at high coil outlet temperatures. The heater can be Fuel Gas, Fuel Oil or
Combination fuel fired.
This is a twin cell cabin heater provided with eight flow passes. The radiant
sections of 5: sch. 40 tubes having 8” Sch. 40 tubes as last tubes and 6” Sch. 40
as second last tube at the outlet of each pass while the convection section is
provided with 5” Sch. 40 tubes. The radiant section tubes are arranged
horizontally along the side walls and arch of each cell of combustion chamber.
The common convection section has horizontal bank of tubes positioned above
the combustion chamber.
The heater consists of 24 forced draft, low NOx combination fuel fired burners
(both fuel oil and refinery fuel gas). Each cell is provided with 12 burners fired
vertically upshot from furnace floor along the centreline of the cell. Convection
section is provided with 16 nos. of soot blowers, which are controlled by
automatic sequential control panel from grade level.
A combined air preheating system has been envisaged for Vacuum heater and
Naphtha Splitter Reboiler Furnace for maximum energy recovery. Turndown
restrictions of furnace are governed by burner and FD fan limitations.
Turndown facilities are as follows: -
37 | P a g e
50% turndown for operation of AM with or without Naphtha Splitter
Reboiler operating.
For BH operation the turndown possible are 80/60/70% for FO/FG/Comb
Fuel with NSU heater also in operation and max. Slop recycle. For Vacuum
Heater operation without NSU heater 60% is possible with max. slop recycle
VACUUM COLUMN:
The vaporised portion entering the flash zone of the column along with stripped
light ends from the column bottoms, rise up in the Vacuum column and is
fractionated into four side stream products in 5 packed sections. The
Hydrocarbon vapours are condensed in the HVGO, LVGO, and Vac. Diesel
sections by circulating refluxes to yield the side draw products. One utility
provision is made at VDU column to evacuate Oxygen by Nitrogen during start-
up of the unit to save the unit start-up time.
The column has been provided for achieving low-pressure drop. Random
packing’s have been provided inside the column with combination bed in the
slop (wash) section. Demister pads have been provided above the wash zone to
prevent asphaltenes carry over and at the top, to minimise carryover of
hydrocarbons to the ejector section.
The stripping section is provided with 10 baffle trays.
The following features have been incorporated to ensure quality of
Hydrocracker Unit feed stock: -
Provision of de-entrainment baffles in the bottom section.
Maintaining reasonable vapour velocities in the flash zone (corresponding to
vapour capacity factor of 0.2-0.3).
Providing adequate vapour of stages in the wash zone.
Providing adequate vapour of stages in the wash zone.
38 | P a g e
Ensuring adequate liquid flows in the wash section.
Providing suitable metallurgy to ensure that iron pick up on account of
corrosion is less than 1PPM.
VACUUM DIESEL:
Vac. Diesel is drawn from the top most packed section along with Circulating
Reflux (CR) and internal Reflux (IR) from Chimney tray below the Bed # 1 .IR
is returned to the LVGO section (bed#2) through spray nozzle distribution. The
CR is returned to the top of the Vac. Diesel packing (Bed#1) after exchanging
heat with crude to maintain overhead temperature of 60-65º C. Higher overhead
temperature would lead to high Hydrocarbon carry over to ejector.
Vac Diesel product exchanges heat with a tempered water exchanger and water
cooler before going to storage on flow control. Slop oil from hot well is also
joining to the vacuum diesel at rundown. Facility has also been provided to
route hot vac. diesel to DHDS feed.
LIGHT VACUUM GAS OIL:
This section comprises of two beds # 2, and # 3, for fractionation and heat
transfer respectively. LVGO is drawn along with CR and IR from Chimney tray
# 2. It is combined with HVGO CR & routed to the HVGO packing bed # 4
through spray nozzle distributor. CR is returned to the top of the bed # 3 after
exchanging heat with Crude.
HEAVY VACUUM GAS OIL:
HVGO is drawn from the Chimney tray # 3 below bed # 4 along with CR and
IR. The IR is returned to the wash zone (Bed#5) through spray distribution
nozzles, on flow control to maintain the required irrigation rate of 0.7-0.3
gpm/ft2 on the wash bed. The CR is used to reboil MTO and kero stripper and
crude preheat train exchangers, before being returned to the top of HVGO
39 | P a g e
section on flow control.HVGO product goes through crude preheat exchangers
and TW exchanger before being routed to storage.
VACUUM SLOP:
This section is a combination bed with demister pad provided above the wash
zone to prevent asphaltenes carry over. Slop distillate is withdrawn from
chimney tray # 4 below bed # 5 along with slop recycle. Slop recycle is routed
to Vacuum Heater. The slop product and quench is routed through crude preheat
exchanger and MP stream generator and tempered water exchanger. A part of
this stream is routed to the slop quench vessel and remaining portion is routed to
final storage. Two controls valves in parallel provided to eater to wide
variations in flow between AM/BH operations. Provision to run down slop
product to FCCU feed tanks or blend with HVGO or VR in run down lines is
also provided. One provision is made to route Vac slop partly or fully to FCC
feed surge drum directly.
VACUUM RESIDUE:
The liquid portion of the feed drops into the bottom section of the tower and is
withdrawn as Vacuum Residue. MP Steam is used for stripping. In view of
steam requirement for BH operation being very low, separate control valves are
provided in parallel for AM and BH operations. The tower bottom temperature
is kept at 350º C to reduce possible cracking during holdup in the tower by
quenching with cooled VR. Quenching is achieved by returning a quench
stream to the tower at a temp of 250º C after heat exchanges with crude in
preheat train on TIC/FIC cascade. Two parallel Control Valves are provided for
proper controllability during BH and AM operation due to wide variations in
flow.
Vacuum Residue is withdrawn and sent for heat exchange with incoming crude
in the crude preheats train. Split range Control Valve TIC-1106 is bypassed
during AM operation. During BH operation it ensures rundown temperature of
40 | P a g e
120º C. VR is used to generate LP Steam, before being cooled in TW
exchangers and finally sent to storage.
One stream after is routed to Vacuum Column as VR quench whose flow is
cascaded with bottom temperature.
VACUUM COLUMN OVERHEAD SYSTEM:
Vacuum is maintained by a 3-stage ejector system with surface condensers.
The Vacuum column overhead vapours are routed to the 1st stage ejectors. The
outlet from the 1st stage goes directly to the 1
st stage inter condenser.
Uncondensed vapours from 1st stage inter condenser are routed to 2
nd stage
ejector. The outlet from the 2nd
stage ejector is routed to the 2nd
stage inter
condenser from where the uncondensed vapours are sent to the 3rd
stage ejector
system. The discharge of the 3rd
stage goes to the after condenser.
The condensed portion from the condensers are routed to the hot well from
where the non condensable are sent to the Crude furnace low pressure burners
or vented to the atmosphere. Condensate from the hot well is pumped to the
sour water stripper unit or to WWTP. Any oil which is carried over along with
the steam condensate is pumped to the Vacuum diesel run down line, after
removing any traces of water in the coalesce. Provision has also been provided
to route the hot well slop oil to DHDS feed tank.
11. LPG AMINE & CAUSTIC WASH SECTION
LPG AMINE SECTION:
Straight run LPG is fed to the 1st tray of 19-C-001.Lean amine ex LPG Merox
(strength @15-25% wt.) is fed through 19-FIC -1101 at the 10th tray. Both the
streams follow counter current operation.
41 | P a g e
Maximum RSH content in LPG to be considered for LPG Caustic wash is 1000
Mole PPM
From the bottom of, Rich Amine goes to Amine Regeneration Unit. LPG goes
out ex top to Caustic wash section. Carried over Amine is drained. Pressure &
Temp. in the column is maintained @ 16.0 Kg/cm2 (g), and 40º C respectively.
LPG CAUSTIC WASH SECTION:
It is carried out in two-stage batch operation. Fresh Caustic (Strength=15% wt)
enters the 2nd
stage drum where as the LPG enters the 1st stage drum. Spent
Caustic is sent to spent Caustic drum. Caustic inventory is replenished by 15%
wt. fresh Caustic. Caustic from second stage drum is pumped to 1st stage drum.
Treated LPG which contains less than 5 PPM (wt) RSH (mercaptans) is passed
through a sand filter to remove entrained caustic.
Under Back Press C/V 19-PV-2101 @ 13.5 Kg/Cm2 (g), LPG is sent to storage
in Horton Spheres.
12. FUEL GAS TREATMENT SECTION:
The unit is having absorber column, which is designed to absorb H2S/CO2 from
sour gases of Crude Distillation unit, Visbreaker unit, Hydrocracker unit and
Catalytic Reformer unit.
PRE FILTRATION:
Off gases from CDU/VBU/OHCU/FCCU/CRU are routed to Sour Gas Filter
Separator under flow measurement. Liquid particles in fuel gases are separated
in Sour Fuel Gas Filter Separator and drained to CBD/Flare periodically
depending upon the liquid level in it. Provision is there to automatically shut
down the draining in case of very low liquid level in filter separator.
42 | P a g e
If the pressure drop in Filter Separator exceeds 0.20 Kg/Cm2 the equipment is
by passed and cartridges in filter separator are changed before taking it again on
line.
A.ABSORPTION:
From the sour gas filter separator the gases are routed to the bottom of the Fuel
Gas Amine absorber 19-C-002. The Fuel Gas Amine absorber is provided with
valve trays and a demister pad above the top tray.
The absorber operates at a top pressure of 4.0 Kg/Cm2 (g) and temperature of
45º C. Lean Amine from ARU is introduced on the top tray under flow control.
Hydrogen sulphide and CO2 from the sour gas gets absorbed into DEA and
because of the chemical reaction the temperature of DEA solution rises to 57º
C. The rich DEA containing H2S/CO2 is pumped to ARU for the regeneration
and reused in Absorber. Differential pressure indicators measure their pressure
drop across trays.
B.POST FILTRATION:
From the top of the Absorber, the sweetened Fuel Gas under Absorber pressure
control is passed to Sweet Fuel Gas Filter separator where any Amine which is
entrained in the gas is trapped and sweet Fuel Gas is routed to Fuel Gas system.
Liquid collected in sweet Fuel Gas Filter separator is periodically drained to
Amine Sump. The operation of sweet Fuel Gas Filter separator is similar to sour
fuel gas filter separator.
Start up Fuel Gas demand of the unit is supplied by LPG vaporiser, which is a
vertical drum with submerged-in Reboiler heated by LP Steam.
13. CHEMICALS REQUIRED
1) AMMONIA
To neutralize the HCL (Hydrochloric Acid) formed due to the decomposition
of mainly calcium and magnesium chloride present in the crude oil at the initial
condensation point of water i.e. at crude & vacuum over head system
2) NEUTRALIZING AMINE
43 | P a g e
3) CORROSION INHIBITOR
Corrosion inhibitors are amine compounds which forms a thin protective layer
in the column over head line to protect the line from corrosion by acidic
compounds present in the column overhead vapours..
4) FILMING AMINE
5) DEMULSIFIER
Demulsifier is used for breaking stable crude water emulsions to ensure proper
desalting and minimum carryover of oil along with brine
6) CAUSTIC SOLUTION (pre- & post desalter)
Caustic (NaOH) is dosed in pre- desalter crude to neutralise free Napthenic
acid present in crude. It is dosed in post- desalter crude to neutralise the acids
formed due to hydrolysis of calcium and magnesium salts in desalter.
7) TSP (Tri-Sodium Phosphate)
It is used to increase the pH from Acidic to Neutral and to protect the steam
generating exchangers/ vessel from corrosion. In CDU/VDU it is used in steam
generating vessel (03-V-23/24/E-54).
Handling of hazardous Chemicals:-
Hazardous chemicals used in AVU are Caustic , Ammonia ,Corrosion
Inhibitor & Demulsifier .These are to be handled carefully since unsafe
operation can lead to personal injury. Always use face shield, safety goggles,
safety gloves & rubber boots during preparation of these chemicals. Avoid
contact with eyes, skin & clothing. Avoid breathing vapors or mist. Never use
cutting torch on or near the container, since vapors may travel away from the
container & explosion may result.
If in case of physical contact with these chemicals, wash the affected portion
with water immediately, remove the person to fresh air & seek medical advice.
Threshold Limit Value for Ammonia & Corrosion Inhibitor is 25 ppm & that of
caustic is 2.5 mg/m3.
44 | P a g e
Filled Ammonia cylinders should always be stored in vertical position & empty
cylinders in horizontal position in separate area. At any point of time more than
5 filled cylinders should not be kept at the site.
14. UTILITIES REQUIRED :
LP Steam Pressure: 3.5 kg/cm2
MP Steam Pressure: 14 kg/cm2
Instrument air : 6.0 kg/cm2
Cooling Water: 4.0 kg/cm2
FG Pressure : 3.0 kg/cm2
FO Pressure: 9.0 kg/cm2
45 | P a g e
SECTION 3
PROJECT
46 | P a g e
INTRODUCTION
A fired heater is a direct-fired heat exchanger that uses the hot gases of
combustion to raise the temperature of a feed flowing through coils of tubes
aligned throughout the heater. Depending on the use, these are also called
furnaces or process heaters. Some heaters simply deliver the feed at a
predetermined temperature to the next stage of the reaction process; others
perform reactions on the feed while it travels through the tubes.
Fired heaters are used throughout hydrocarbon and chemical processing
industries such as refineries, gas plants, petrochemicals, chemicals and
synthetics, olefins, ammonia and fertilizer plants. Most of the unit operations
require one or more fired heaters as start-up heater, fired Reboiler, cracking
furnace, process heater, process heater vaporizer, crude oil heater or reformer
furnace.
Sankey diagram of reheating furnace
47 | P a g e
There are majorly four sections in furnace:
Radiant Section: The radiant tubes, either horizontal or vertical, are located
along the walls in the radiant section of the heater and receive radiant heat
directly from the burners or target wall. The radiant zone with its refractory
lining is the costliest part of the heater and most of the heat is gained there. This
is also called the firebox.
48 | P a g e
Convection Section: The feed charge enters the coil inlet in the convection
section where it is preheated before transferring to the radiant tubes. The
convection section removes heat from the flue gas to preheat the contents of the
tubes and significantly reduces the temperature of the flue gas exiting the stack.
Too much heat picked up in the convection section is a sign of too much draft.
Tube temperature is taken in both convection and radiant sections.
Stack and Breeching: The transition from the convection section to the stack is
called the breeching. By the time the flue gas exits the stack, most of the heat
should be recovered and the temperature is much less. From a measurement
point of view, this location places fewer demands on the analyzer but is much
less desirable for the ability to control the process. Measurement of stack
emissions for compliance purposes is normally made here.
Shield Section: Just below the convection section is the shield (or shocktube)
section, containing rows of tubing which shield the convection tubes from the
direct radiant heat. Several important measurements are normally made just
below the shield section. The bridge wall or break wall temperature is the
temperature of the flue gas after the radiant heat is removed by the radiant tubes
and before it hits the convection section.
CALCALUTION:
DATA REQUIRED FOR FURNACE EFFICIENCY
BASED ON RAD.LOSS OF 1.0
LHV OF FG 11200.00
LHV OF FUEL OIL 9998.00
AMBIENT TEMP 14.00
HGU-I PSA OFF GAS 1291.00
HGU-II PSA OFF GAS 1156.00
NAPTHA 10531.00
C/H WT FO 7.00
C/H WT FG 4.00
HUMIDITY OF AIR KG/KG 0.022
49 | P a g e
For CDU furnace, THE DESIGN EFFICIENCY IS 91%.
Practical CDU furnace efficiency is calculated by following method:-
Fuel gas(FG) used = 35 MT/D
Fuel oil(FO) used = 112 MT/D
Heat released by fuel gas =
= 11200 x 35 / 24 x 1000
= 16.33 MMKCAL/HR
Heat released by fuel oil =
= 9998 x 112 / 24 x 1000
= 46.65 MMKCAL/HR
TOTAL HEAT RELEASED =Heat released by fuel gas + Heat
released by fuel oil
= 62.98 MMKCAL/HR
O2 content in STACK = 4.0
CO2 content in STACK = 10.64
STACK TEMPERATURE = 188 ° C
Atomizing steam= 1.86 T/HR
Atomizing steam = 1.86 x 24 = 44.64 T/HR
50 | P a g e
Theoretical air for fuel oil =
= (7 + 3) x 1000/ (7 +1) x 12 x 0.21
= 496 KGMOLES
Theoretical air for fuel gas =
= (4+ 3) x 1000/ (4 +1) x 12 x 0.21
= 556 KGMOLES
Total theoretical air required
=
= 112 x 496 + 35 x 556
= 75012 KGMOLES
Total CO2 =
= ((7) x 112 / (7) +1) + (4) x 35 / (4) +1)) x 1000/12
= 10500 KGMOLES
51 | P a g e
Total H2O =
= (112 / 7 +1) + 35 / 4 +1) x 1000/4
= 5250 KGMOLES
Total theoretical N2 =
= 75012x0.79
= 59259.48 KGMOLES
Flue gas O2 =
= 4 x (10500 + 5250 + 59259.8)/ (100-4/0.21)
= 3706.35 KGMOLES
Actual air required =
= 75012 + 3706.35/0.21
= 92661.28 KGMOLES
Air average mol. Wt = 29
Total air (normal condition) = 92661.28 x 22.4/ 24
= 86483.87 NM3/HR
Total air (given condition) at 35 ° C = 86483 x (273+35)/273
= 97571.54 M3/HR
52 | P a g e
% EXCESS AIR = TOTAL AIR - TOTAL THEO. AIR REQUIRED x 100
TOTAL THEO. AIR REQUIRED
= (92661.28 – 75012) x 100 / 75012
= 23.53 %
H2O moles due to humidity =
= 0.022 x 92661.28 x29 /18
= 3284.32 KGMOLES
Total flue gas =
= 10500+5250+59259.48+3706.25/0.21+44.64 x 1000/18
= 98423.085 KGMOLES
Flue gas average mol. Wt =
------------------------------------------------------------------------------------------------
(Total Flue gas)
= 29
53 | P a g e
Total flue gas (normal condition) = total flue gas x 22.4 / 24
= 91861.5 NM3/HR
Total flue gas (given condition) at 188 ° C = 91861.5 x (273+188)/273
= 155121.43 M3/HR
Flue gas heat loss = m *Cp * ΔT
Where m= total flue gas
=
= 98423.085 x 29/1000 + 1000 x 0.245 x (188-14) x 10^-6
= 5.069 MMKCAL/HR
% HEAT LOSS TO FLUE GAS =
= 5.069/62.98 x100
= 8.048%
Setting loss =
= 62.98 x 1 / 100
= .63 MMKCAL/HR
% Setting heat loss = 4%
54 | P a g e
Actual furnace efficiency = 100 - % setting loss – % heat loss flue gas
= 100 – 8.048 - 4
= 87.95 %
RESULT:
For CDU furnace, THE DESIGN EFFICIENCY IS 91%.
ACTUAL EFFICIENCY IS 87.95 %
55 | P a g e
SECTION 4
REFRENCES AND BIBLOGRAPHY
56 | P a g e
REFERNCES:
1. www.google.com
2. www.wikipedia.com
3. www.iocl.co.in
4. Training AVU manual
5. Perry’s handbook of Chemical Engineering
6. www.cleanboiler.org
7. Industrial Furnace, Volume 1 and Volume 2, John Wiley &
Sons – Trinks
8. Improving furnace efficiency, Energy Management Journal
