Kirti Vardhan Project

8/9/2019 Kirti Vardhan Project

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CHAPTER 1

GENERAL

1.1 INTRODUCTION

The Crude Distialltion Unit of Bongaigaon Refinery and Petrochemicals Ltd is designed to

process 1.35 million tonnes per year of crude oil mi comprising !ahar"atiya#La"$a#

Rudrasagar in %&'1('13 ratio )y $eight. The Unit ia also capa)le of handling any of the

follo$ing feeds'

i*La"$a and Rudrasagar crudes in %+',+ ratio )y $eight.

ii*!ahar"atiya crude alone.

-u)se uent necessary modifications in the units ha/e )een done for processing of lo$

sulphur imported light Crude. Because of this0 the units are capa)le of processing lo$

sulphur Ra//a Crude as $ell.

The unit consists of the follo$ing sections'

Topping0-ta)ili ation and !aptha -plitters. The product of the unit are 2uel as0 -R !aptha0

LP 0 Reformer feed !aptha0 4ero component0 "ero# 0 4ero# 0 as 6il and Reduced Crude

oil. 2uel as is used as a fuel in the process heaters. 6ther unit products are either further

processed or )lended to produce finished products.

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1.2 STREAM FACTOR:

The on#stream hours for the operation of the Crude Distillation Unit is &+++ hours per

year.

1.3 DESIGN DATA:

The Crude Distillation Unit has )een designed to process 1.35 77TP8 of 8ssam crude. The

unit is also capa)le of handling lo$ sulphur crude li"e Ra//a crude0 Bonny light crude0La)uan crude etc.

Table 1.1 Typical Fee C!a"ac#e"i$#ic$

-l. !o Characteristics Units 8ssamcrude

Ra//a crude

1 Density 915 oC gm:cc +.&;


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Table 1.1 %c&'# .(

13 Charc. 2actor 4U6P 11.3; 11.(

1, ield Pattern Typical*C1 # C,C5 # 11+6C11+ # 1,56C1,5 # 1&+6C1&+ #


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PROCESS DESCRIPTION

2.1 GENERAL

Crude distillation unit is designed to process 1.3577TP8 of 8ssam Crude 6il produced

)y 6il ndia Limited 6! C.

Design TEput ,+5+ 7T:day

7inimum TEput


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4ero# CR is used as heating medium for sta)iliser re)oiler.The purpose of sta)ili er is to

sta)ili e naptha and to produce li uefied petroleum gas LP *.

LP $ithdra$n from -ta)iliser reflu drum is first $ashed $ith caustic and then $ashed

$ith $ater and then sent to Forton sphere for storage.

The sta)ili ed naptha is further split into light naptha 5+#11+*deg.C and hea/y naptha 11+#

1&+* deg.C in -plitter# . Feating medium for splitter# is 4ero# CR.

-plitter# )ottom is further split into reformer feed naptha 11+#1,;* deg.C and 4ero

component.Re)oiler heating medium for splitter# is Reduced Crude 6il from main

fractionator column.

8 uous ammonia is inGected in o/erhead /apour in main fractionator to com)at corrosion due

to hydrochloric acid /apour.

-ide strippers are used for "ero# 0"ero# and gas oil for stripping lighter ends. -tripping

steam superheated to a)out ,++deg. C is used as stripping media in all three strippers.

2.2 FEED SUPPL)

Crude oil is recei/ed )y pipeline and stored in four floating roof storage tan"s T4#18:B:C:D

each ha/ing a nominal capacity of


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rude oil to the Unit. !ormally only one feed pump $ill run. 2ailure of the feed pump $ill

cause a drop in discharge line pressures $hich $ill )e indicated in the control room audio#

/isually0 hence the spare feed pump $ill start automatically. There is a pro/ision also for

stopping any of these feed pumps through a push )utton and selector s$itch.

Temperature ndicator0 2lo$ Recorder and a 2lo$ ntegrator are pro/ided on the feed line

$ithin the )attery limit ahead of the crude preheat e changer train.

2.3 FEED PREHEATING

Crude oil is first preheated in a series of ele/en Feat e changers /i H#310H#330H#,0H#


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2., DESALTER

The Crude Desalter is a process /essel that remo/es $ater and there)y salt from the

crude. The $ash $ater is mi ed $ith crude $itd into the Crude Desalter. Demulsifying

chemicals are also added at this stage to pre/ent formation of ne$ emulsion and to assist in

)rea"ing do$n any emulsions that e ist $ith the crude. Thus0 Desalter /essel0 in addition to

allo$ing a certain residence time for the crude oil that allo$s separation of the $ater $ith the

help of gra/ity0 also pro/ides an electrostatic field to assist the )alance of $ater particles to

coalesce under the electrical charge and thus separates from the crude oil. The effluent $ater is $ithdra$n from the /essel under interface Le/el Control and the desalted and dehydrated

crude is $ithdra$n from the /essel under )ac"pressure.

2.,.1 C"- e De$al#i'

Crude oil )rings salts along $ith it. Particularly those of sodium0 7agnesium etc.0metals li"e

8rsenic0 =anadium etc and mud. 8lthough these are present only in small amounts0 their

presence can result in serious pro)lem in do$n stream e uipments /i . heat e changers0

heaters and columns. Fence the need of their remo/al is important )efore processing.

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8t high temperatures0 7agnesium chloride decomposes and forms Fydrochloric acid0 $hich

corrodes trays in the top section of column and tu)es of o/erhead Condensers etc. The

presence of calcium and -odium salts can cause plugging of heat e changers and heater

tu)esI there)y rapidly reducing heat transfer coefficients. The presence of 8rsenic acts as a

poison to Platinum catalysts that may )e used in do$n stream process units.

Presence of these salts also promotes co"e formation in heater tu)es $hich results in

increased pressure drop as $ell as less heat transfer rates. The e cessi/e co"e formation

result in escalation of hot spots on heater tu)es $hich can ha/e serious and disastrous

conse uences for heater tu)es. 8t high temperatures0 salts in crude oil sho$ a tendency to

deposit along heat e change surface of the e uipment.

Caustic inGection in crude is done to neutrali e acids present in crude and con/ert them into

salts. These salts are then remo/ed )y Desalter $ater in Desalter. Brine is also associated $ith

crude as emulsions. To )rea" these light emulsions0 Demulsifier is added. n fact )oth caustic

solution and Demulsifier is added into the crude )efore the preheat train.

Desalter utilises electronic elements at ,15 /olts to coalesce and separate $ater from oil for

reducing the salt content in crude oil so that it is $ithin accepta)le and specified limits in

desalted crude. ?hen oil $ater mi ture enters the high /oltage electric field0 it separates intot$o phases in Desalter. The oil phase floats on top and o/erflo$s. ?hile $ater $ith its

dissol/ed salts0 metals0 mud and ron o ides settles do$n at the )ottom. Thus oil from

Desalter flo$s to the rest of the preheat train.

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2.,.2 De$al#e" e$$el De$c"ip#i&'

This is a single stage Desalter unit.Performance of it is as follo$s'

Hlectrical po$er re uirement J ,15=:5+ hert : 3 phase

Po$er Demand J ;54/a ma *

6perating Temperature:Pressure J 1


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2.* FURNANCE

Crude 6il from preheating e changers is further heated and partially /apori ed in

furnace 2#10 the temperature rising from


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2eed coming from the furnace enters the column in the flash one under tray 5. The flash

one temperature is maintained at 35& deg .C .-tripping steam is introduced at the )ottom of

the column to remo/e lighter fractions from the )ottom product i.e reduced crude oil.

2ractionator flash one temperature and pressure is normally maintained at a)out 35+

deg. C and 1.3 4g : s cm respecti/ely .

n Crude distillation column C# * 0the crude oil fractionates into num)er of distillates and

)ottom product .

Table 2.1 CDU P"& -c# a' i#$ #&p$ i$#illa#i&' "a' e$ '

PRODUCT RANGES2uel gas +#5+ deg.C

LP %+#%5 deg.C-R! 55#1++ deg.CR2! 11+#1,5 deg.C

4ero comp 1,5#1&+ deg.C4ero# 1&+#


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column from tray K


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2.0 STA4ILI5ER

The Crude Column o/erhead product BP# 1&+deg.C cut* is sta)ili ed )y remo/ing the gas

fraction up to C, in the sta)ili er column C#5.The -ta)ili er column has 3+ )u))le caps

/al/e trays . The tray material is of car)on steel and /al/es are of Cr steel.

The feed to the sta)ili er is preheated in 4# heat e changer H#(8 and 4# heat e changer H#

1+ and H#


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2. .1 Fi"$# Nap#!a Spli##e"

The sta)ili ed naptha is split in the 1 st !aptha -plitter C#% into an o/erhead light naptha

and a )ottom product. The 1 st !aptha -plitter C#% has 3+ )u))le caps /al/e type trays.

The tray material is of car)on steel . -ta)ili ed naptha from the )ottom of the -ta)ili er is fed

to C#% at tray 15.

The o/erhead /apors at a temperature of (,#(& deg.C are condensed in H#1%. The condenser

li uid is ta"en from the reflu drum and a part is sent to the top of the column as reflu and

)alance is routed through cooler H#


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preheating the crude and cooled in H#1( and routed as 4ero component to storage C#;

)ottom.

2. LPG CAUSTIC 6ASH

Caustic is inGected into crude to con/ert all the chlorides eg. 7gCl


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CHAPTER 3

OPERATION OF CDU

3.1 INTRODUCTION

There is a large amount of preparatory $or" performed )y the operating cre$ to operate the

plant efficiently. 8 planned chec" of all units not only ensures smooth start up )ut also

ac uaintance $ith the operations of /arious sections comprising of /aried /ariety e uipments

to run them. -tart up is critical and includes operation of each e uipment .6peration includes

proper inspection of /essels 0columns 0piping and instruments.

3.2 FUNCTIONAL TESTS

8ll motors and pumps including dosing pumps $ill undergo functional test to chec" their

performance.

3.2.1 M&"$

Hach motor should )e chec"ed and started to ensure that it has the correct direction of

rotation .The motor speed should )e chec"ed to ensure that rpm is correct. 8fter a short run

each )earing should )e felt to ensure that it is free and not o/erheated.

3.2.2 P-7p$

enerally the pump is opened and chec"ed to ensure that it contains no foreign material.

Cleanliness of suction line and installation of fine strainer should )e ensured.

1+


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3.3.3 I'$#"-7e'#$

% i ( C&'#"&l al8e$ '

?e should ma"e certain that the de)ris are not lodged in the control

/al/e.Hach control /al/e installation should )e chec"ed for full tra/el of the

/al/e. t should also )e ensured that each control /al/e is at proper position

close or open* at right air pressure.

% ii( Di99e"e'#ial p"e$$-"e #"a'$7i##e"$ a' "ecei8e"$:

6rdinarily these should )e cali)rated locally against a $ater column and the

cali)ration chec"ed at the recei/er 0$hich may )e recorder or indicator.

% iii( Ti !#'e$$ #e$#:

The purpose of this test is to chec" the tightness of flanges0 Goints0 manholes

etc. This test $ill )e done $ith steam. Before conducting this test0 all the

safety /al/es should )e placed in position and properly lined up only after

testing.

3., OPERATING PROCEDURE

The Crude Distillation Unit is steam purged in sections to free all /essel and piping of air.

8fter displacing air from the system0 the hydrocar)on feed $ill )e ta"en in the unit.

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Unit charge pump located in offsites ta"es suction from crude oil tan"s and deli/ers into the

crude distillation column. 8fter )uilding up ade uate le/el in the column0 circulation is

esta)lished.

Feater is fired and transfer temperature gradually raised to normal /alue of 355 deg.C.

=arious product streams are $ithdra$n and circulating reflu is adGusted according to the

temperature in the column.

6/erhead naptha product is routed to sta)ili er $here lighter ends up to )utane are

remo/ed. The sta)ili ed naptha is routed to 1 st splitter.C5#11+deg.C cut is o)tained as

o/erhead and sent to naptha storage. The )ottom product is routed to < nd splitter $hich also

$or"s in a similar manner. Feating medium of re)oiler $ill )e reduced crude.11+#1,5 deg.C

cut is o)tained as o/erhead product of < nd splitter and pumped to storage as Reformer feed.0

the )ottom product is 1,5#1&+deg.C cut $hich is routed to 4ero# storage tan". 8fter

sta)ilising the unit 0the inGection of chemicals is started.

3.* E UIPMENT OPERATING PROCEDURE

Fi . 3.1 Ce'#"i9- al P-7p

1( CENTRIFUGAL PUMPS:

8 centrifugal pump is a rotodynamic pump that uses a rotating impeller toincrease the /elocity of a fluid. Centrifugal pumps are commonly used to mo/e

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li uids through a piping system. The fluid enters the pump impeller along or near to

the rotating a is and is accelerated )y the impeller0 flo$ing radially out$ard into a

diffuser cham)er0 from $here it e its into the do$nstream piping system.

8 centrifugal pump $or"s )y the con/ersion of the rotational "inetic energy0typically from an electric motor or tur)ine0 to an increased static fluid pressure. This

action is descri)ed )y Bernoulli s principle. The rotation of the pump impeller

imparts "inetic energy to the fluid as it is dra$n in from the impeller eye centre* and

is forced out$ard through the impeller /anes to the periphery. 8s the fluid e its the

impeller0 the fluid "inetic energy /elocity* is then con/erted to static* pressure due

to the change in area the fluid e periences.Centrifugal pumps are used in the crude distillation unit e cept Crude oil charge

pump0 -ta)ili er feed pump and sta)ili er reflu pump. 8ll mechanical Go)s are

completed. Cooling $ater pro/ision and steam is opened for any dead cooling in the

pumps. Then oil le/el is chec"ed and flushing is done if oil is dirty or contains any

foreign material. The suction /al/e is opened and motor is energi ed .Pump is started

and stopped immediately. Discharge pressure is chec"ed and opened slo$ly.

2( HEAT E;CHANGERS

8 heat e changer is a de/ice )uilt for efficient heat transfer from onemedium to another. The follo$ing are the /arious type of heat e changers0 in

CDU.

1a* Feat H changers'

)* Re)oilers'c* Condensers'd* Coolers'


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Ope"a#i' $#ep$ '

Cooling medium /ent /al/e is opened. Drain /al/e and flushing oil /al/es areclosed. !o$ cooling medium /ent /al/e is opened0 li uid is allo$ed to come out thenagain closed. Then open the cooling medium outlet /al/e and fully open the inlet/al/e also. Feating side /ent /al/e is opened and all flashings are shut off. 2inally thenormal inlet and outlet temperatures are chec"ed

3.+ NORMAL OPERATING CONDITIONS

FURNANCE E UIPMENT NO: 11F< 1(

Table 3.1 Ope"a#i' 8a"iable Da#a$ &9 9-"'ace

SER ICE CRUDE OIL STEAM

Total duty0774Cal:Fr

1(.3 +. /( Te7pe"a#-"e p"&9ile:

Column top temperature 15, deg.CRe)oiler outlet temperature 1(% deg.C

2eed temperature 1;< deg.C

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2ig 3.1 =arious 6perational e uipments


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Differential pressure transmitter Differential pressure recei/ers

Centrifugal pump Control /al/e

Feat e changer

2,

CHAPTER ,


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UALIT) CONTROL OF CDU PRODUCTS

-amples are ta"en at regular inter/als to see if the desired specifications are met or some

correcti/e solutions are necessary .-ometimes samples are ta"en to find out the effect of

certain changes )rought a)out in the operating conditions. The samples ha/e to undergo

chemical and physical tests.

,.1 TESTS ON LPG

2ollo$ing tests are carried out'

1. Density test


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2or copper strip corrosion0 LP samples are chec"ed )y la)oratory. To ensure cu strip

uality 0 LP samples are chec"ed $ith lead acetate solution in e/ery shift. n the LP $ash

section 0 replenishment of spent caustic $ith fresh caustic is done as per La).Report.

?hene/er LP fails in Cu strip0 different parameters are adGusted. 8lso0 the

recirculation caustic and $ater is replaced $ith fresh ma"e#up )ased on cu strip.

,.2 TESTS ON SRN

1. Density test


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C

Cu#corfrosion 9 3& deg. C for 1hr.0 deg. C

!ot $orse than 1


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Table *.2 Typical U#ili#ie$ C&'$-7p#i&' pe" 7&'#! :

-l. !o. UT L T H- C6!-U7PT 6!

1. 2uel 6il (&& 7T


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3. Caustic -trength 1+@? -


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Study of Process andOperations of Crude DistillationUnit of IOCL-BGR

Kirti Vard an

A4STRACT


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Crude distillation unit of BRPL has an annual crude processing capacity of 1.35 77TP8.

The main products of CDU are LP 0 -traight Run !aptha0 Reformer 2eed !aptha0 4ero# 0

4ero# 0 4ero component0 as oil and Reduced Crude

6il. t $as commissioned in 1(;(.

This report discusses the /arious aspects of an operating refinery /i ' process0 operations0

maintenance 0 uality control 0 of crude distillation unit CDU* of B.R.P.L I supported )y

/arious ta)les0 data and figures.

During the proGect $or"0 understood the $or"ing and operation of this unit. Plant

operations included operating procedures of distillation columns0 pumps0

2urnaces0 control /al/es and /arious instruments.

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Kirti Vardhan Project