Fuel Oils(Npti)

8/20/2019 Fuel Oils(Npti)

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FUEL OILS

• Liquid fuels are ideal source of energy for

industry for following reasons:

High Heating Value

Constant Heating Value

Relative Ease in burning

Easy handling and storage


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• Crude Petroleum is the raw material for Fuel

ils!

•

"t has been #roduced by decay of minutemarine organisms with #lant life by the

action of Heat and Pressure or by

decom#osition!

• $he oil #oc%ets are usually found tra##ed in

folds of im#ervious roc%s brought about by

u#heavals in the earth&s crust!

• $here is salt water below the oil and gasabove it!

• $he #ressure of gas #ushes the oil out of

the well when drilling ta%es #lace!


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Figure


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il can also be tra##ed in a formation where a

fault has occurred 'Fig!()!

Petroleum is a mi*ture of many com#ounds ofCarbon + Hydrogen! $hese vary widely, as

atoms of C + H are arranged in widely differing

#atterns in their molecules!

$he com#ound having larger no! of C atoms in

its molecule has High -oiling Point!

$his fact is made use of in se#arating differentoils!

$he crude oil refining is normally done by

Fractional .istillation 'F!.!) Process!


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$his is so called as it se#arates different

fractions of oil! $he crude mineral oil is

se#arated into:

a! Petrol

b! /olvent s#irits

c! Paraffins

d! 0as oils

e! Lubrication oils

f! /olid #araffin wa*es

g! .istillates and residual oils!


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"n F!.! il is first heated

in a furnace, totem#erature u#to 122oC

and then #asses to tall

steel cylinders or

Fractionating $owers!

$hese have trays at

different levels, on

which the va#oursgiven off by heating are

condensed and run off

as liquids


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•

$he heavy fractions which do notva#ourise, dro# to the bottom of the tower!

• $he va#ours condense in trays at different

levels according to their -!P!

• $he lowest -!P! liquid se#arate out at to#

level trays and high -!P! liquids at low level

trays!

• 0ases do not condense and are ta%en out

from to#!


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3fter refining, 4 main oils are #roduced! $hese

are then mi*ed to form various grades of oilsused commercially!

$hese are:

5o!6, 5o!(, 5o!4, 5o!7 'Light), 5o!7 'Heavy) and5o! 1

First two are distillates!

Last is a residual oil

thers are mi*ture of refinery #roducts!


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Distillate

Straight Run Cracked

1. Obtained directly from

Crude by heating it and

then condensing vapours

at various temperaturesand atmospheric pressure

2. Contain Paraffins.

1. Cracking involves

heating to higher

temperature and pressure

or presence of a catalyst.

2. Contain aromatic

compounds


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5o!6 and 5o!( 'straight run) are va#ori8ed from

crude at relatively lower tem#eratures '6729

72o

C) and are used for home heating ; lightindustrial use!

5o!1 oil is basically the residue left after lightvolatile #roducts have been distilled! "t is a

heavy oil with viscosity range from


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5o!7 oil comes in ( classes, light 'or

cold) with viscosity range of 672922

/=/ at >!?oC and heavy 'hot) with

viscosity of 729>72 /=/ at >!?oC!

Reason for two classes is that light oilshould be ca#able at atomi8ation without

#reheating, heavy oil needs #reheating!


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C5/$"$=E5$/ F "L

3 ty#ical fuel oil may contain ?( to ?7

#ercent carbon and 62 to 6 #ercent

hydrogen! ther constituents are :

/ul#hur: /ul#hur content of fuel oil varies

from 2! to 4!7@ .istillates 'light oils) have

lower sul#hur than residual oils

'light oil A 2! to 6!7@, Heavy oil A (94!7@)!

6@ rise in sul#hur decrease 0CV of oil by ?

Bcal;%g! /ul#hur is undesirable from the

#oint of view of acid corrosion of 3PH!


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3sh: 3#art from hydrocarbons with

small amounts of (, 5(, / and C(,fuel oils contain traces of im#urities

classified as organo9metallic

com#ounds!

.uring Combustion these im#urities

#roduce a metallic o*ide ash in thefurnace!


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3sh #roducing com#ounds that are

#resent in crude oil, normally end u#

concentrated in Residual fuel oils! $heyare chemically bound in the oil and can

not be removed by #hysical methods of

se#aration li%e centrifuging and filtering!


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3sh content of light oil varies from 2 to 2!6@

3sh content of heavy oil varies from 2!( to

6!7@


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/ome (7 metals can be found in oil ash!

Vanadium, "ron, 5ic%el, Calcium,

3luminum and /odium are the most#revalent!

3sh containing sodium, nic%el and

vanadium are es#ecially trouble some!


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$hey can cause accelerated corrosion of

boiler tubes 'act as catalyst for

converting /o( to /o), fouling of /!H!tubes and damage to refractories!


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/odium: $he sodium com#ounds can cause a

significant degree of fouling and thus reduce

efficiency and affect availability, if they are#resent in amounts a greater than 622 ##m!

"n crude oils, sodium #ercentage is low, but

this can be increased by contamination withsea water in tan%ers which carry crude to the

refineries!

3 neutralisation #rocess carried out in the

refineries, if not carefully controlled, can

significantly add to the sodium content of the

fuel oil! /odium in H is of the order of 42 to

672 ##m!

V di V di d f 2


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Vanadium: Vanadium com#ounds vary from 72 to

(72 ##m in Heavy oils!

$hese are im#ortant because of their corrosive

action on boiler tubes above 711DC!

For this reason, the final tem#erature in oil fired

boilers does not e*ceed 742DC!

"t has been seen that the de#osit formation is

minimum when the ratio of Vanadium ; /odium

'both calculated as the metal) is within the range

of 4;6 to 6(;6!

However this ratio becomes less significant with

decreasing Vanadium and /odium content so that

with low Vanadium and /odium content a ratio of6;6 could be tolerated!


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3$ER 35. /E."E5$/:

"n light oils 9 u#to 2!( to 2!7@

"n heavy fuel oils from 2!6@ to (@


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ater:

=sually comes from condensation,

lea%ing tan%s and lea%ing manholes or

lea%ing heating coils for Fuel ilHeating!


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/ediments: /ediments are usually dirts

#ic%ed u# during refining, trans#ortation

or storage!

5ormal amount of sediments #ic%u# do

not cause any #roblem!

-ut #ic%u# of accumulated tan% bottoms

can #roduce large amount of these

contaminations and can cause, line

#lugging, strainer cho%ing, burner

cho%ing and even flame failure!


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/ludges: /ludges found in some heavy oils

are wrongly classified as sediments! 3ctually

they are a mi*ture of organic com#ounds that

have #reci#itated after different oils have

been blended! ost notable are as#haltene

grou# of Hydrocarbons and wa*!

=nfortunately they are not detected withnormal test methods, because the solvents

used in these tests dissolve them! $he

#resence of these com#ounds is %nown onlywhen they cause #roblem! Heat can eliminate

wa*, but as#haltenes require a solvent for

dissolution, and this generally is im#ractical


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Coal fired boilers require oil for initial

light u# of boilers, during shutting off of

boiler and in emergencies! Very rarelyoil is used for load carrying #ur#oses

when coal is not available and demand

have to be met! ost commonly usedfuel oils are:

6! L!! or .iesel used during light u#,

shutting down and in emergencies!0!C!V A 62>(2 %cal;Bg!


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(! H!F!! Highly viscous '


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! Heavy #etroleum sto%e 'HP/) ; low

sul#hur heavy sto%e 'L/H/)! 5ow a

days, heavy fuel oil is also becomingscarse for Power /tation use! Power

/tations now receive, still viscous heavy

#etroleum stro%e and low sul#hur heavy

sto%e! $hese have to be heated to a

minimum tem#erature of 662oC 9 6(2oC

before burners! L/H/ contains low

sul#hur '2!1 to 6!2@) and its #our #oint is4977oC! HP/ contains 497@ sul#hur

and is slightly less viscous then L!/!H!/!


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PRPER$"E/ F F=EL "L/

Viscosity: "t is a measure of relative

ease or difficulty with which an oilflows! Low viscosity fluids flow easily

and highly viscous fluid flow with

difficulty!

=nits of Viscosity:

6! /ay bolt universal seconds '/=/)

(! /ay bolt Furol seconds '/F/)


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/=/: Viscosity is measured as time in

seconds that it ta%es 12 CC of oil to

flow through a standard si8ed orific ata s#ecific tem#erature of >!?oC!

/F/: Furol viscosity meter which has a

larger orific o#ening and which uses72oC! as standard tem#erature!


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Pour Point: Pour #oint is the lowest

tem#erature at which a liquid flows

under standard conditions! "t is anindicative of oil handling tem#erature!

"n a controlled laboratory environment,

the #our #oint is about (!4oC abovesolidification tem#erature! For heavy

fuel oil it is about (2oC to ?oC and for

light oil it is about 67oC!


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Pour #oint is influenced by oil&s wa*

content! $he more the wa*, higher the

#our #oint!

3 standard #our #oint test is only an

indicative of what can be e*#ected in

actual service, for handling, storageand use of oil also de#end on other

factors li%e tan% si8e, #i#e line si8e, oil

#ressure and structure of wa* crystalswhen solidifying!

High #our #oint oils #resent a delicate


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High #our #oint oils #resent a delicate

handling #roblem! $hey also do not

have uniform #hysical #ro#ertiesG

some follow normal viscosity ;tem#erature curves on heating, others

become highly fluid only a few degrees

above #our #oint! $his result in needfor greater attention to burner #reheat

tem#erature to #revent viscosity from

dro##ing too low at the no88le forefficient combustion!


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Flash Point: Flash Point is the

tem#erature at which heated oil

va#ours flash when an e*ternal heatsource is brought near it! However

there is no continuous burning! $his is

a measure of oils volatility and

indicates ma*imum tem#erature forsafe handling

Flash Point of .iesel =#to 12oC

Flash Point of H!F! 9 11oC to


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Flash #oint of H!! being high, they do

not #resent fire ha8ard at ambient

tem#erature unless they arecontaminated with a volatile #roduct!

Fire Point: Fire Point is the tem#erature

at which sufficient va#ours are drivenoff to #roduce continuous burning of

oil!


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$R35/PR$3$"5 F "L

il trans#ortation to #ower station

de#ends on rate of oil consum#tion +location of Plant! "t is done mainly by

6! /ea $an%er: ainly in case of

im#orts or where both refineries and#ower station are situated by the side

of sea!


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(! -arge: -arges of about 722 $

ca#acity are used to trans#ort fuel oils

from refineries to Power /tationssituated on rivers! $hese are easier to

manouvre than tan%ers and do not

require dee# berthing facilities,

however they can not carry large

quantities of oil!


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!Rail: Here oil is trans#orted in closed

wagons 'of ca#acity (2 to 12$) with two

outlet valves at its bottom forunloading! H!F!!;H!P!/! and L!/!H!/! in

our country are mostly trans#orted in

this way!

4!Road: "n lorries of about 64BL

ca#acity! Light oil, which is consumed

in lesser quantity is usuallytrans#orted in this way and is directly

unloaded in the storage tan%s!


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7! .irect Pum#ing: $his method of oil

trans#ortation is least e*#ensive,

convenient and is used when the#ower station is u#to about 42 %ms!

away from refinery! $he heavy fuel oil

have to be heated before it can be

#um#ed! ith #ro#er insulation, a

tem#erature dro# of only about 4oC

over a distance of over 42 %ms! can be

achieved ma%ing oil trans#ort by#um#ing very attractive! nly little

further heating is required for easy

handling!

$he requirements of an adequate direct


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$he requirements of an adequate direct

su##ly are:

a! Reliable #um#s at the refinery endca#able of o#erating at variable s#eeds

and controlled by fuel #ressure signals

from the #um#ing and heating units!

b! /uitable trace heating to %ee# an

agreed fuel tem#erature when there is

no flowc! 3 #i#e #urging system

d! verall o#erational control in the

station control room!


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/3PL"50 "L

Fuel oil received by the Power /tation

must meet the required s#ecificationsfor #ro#er handling and good

combustion! $he entire oil can not be

analysed for this! /o re#resentative

sam#les must be carefully #re#ared

and must re#resent the entire su##ly!


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E$H./ F /3PL"50 "L

6! .ri# /am#ling: 3 dri# sam#le is the

accumulated com#osite obtained by

continuous dri##ing through a small

ni##le on the unloading line! $he

sam#le si8e is usually 6;4 to one

gallon!

( /lug /am#les: are small quantities


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(! /lug /am#les: are small quantities

'6;4 to litre a##ro*imately) ta%en

#eriodically from unloading line! $he

number and frequency of sam#lesde#end on unloading time! ith an oil

tan%er, many thousand gallons are

unloaded in a few hours time, so a slugsam#le can be ta%en every 2 mnts!

For a truc% su##ly it can be ta%en every

7 mnts! 3 no! of se#arate sam#les arethen mi*ed to form a com#osite!


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! /am#les from storage tan%s: 3tleast

three sam#les are ta%en one from near

to#, one from middle and one fromnear bottom! $o# sam#le should be

ta%en atleast a foot below surface, to

avoid #ic%ing light or stratified oil

floating at surface and bottom one

about a ft! from the tan% bottom to

avoid sludge lying at bottom!

F=EL "L H35.L"50 /I/$E


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F=EL "L H35.L"50 /I/$E

$he movement of oil, from its arrival #oint in

P!/! till it reaches the burners, falls under Fuel

il Handling /ystem or Fuel il /ystem! 3nim#ortant consideration in design of a F!!/

is the Fle*ibility to handle a wide range of

oils! 3 system designed for a H!F!! offersthis advantage while that designated for L!!

is restricted to that grade only! Fle*ibility is

im#ortant to ta%e any #rice advantage, a#articular grade might offer and also because

of uncertainty about ty#e of oil the #ower

station might use in future because of

international oil situation!

/ome other factors to be considered while designing


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/ome other factors to be considered while designing

F!!/! are:

6! Rate of fuel consum#tion

(! .istance from the source of fuel to the

#lant

! /#ace available for storage tan%s and

di%es

4! Ca#acity of storage tan%s

7! .istance from storage tan%s

9 "t will affect heating ; #um#

ca#acity etc!


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1! 3vailability of stm! ; electricity

9 $he system should be so arranged such that

equi#ments are easily accessible for o#eration andmaintenance!

9 3utomatic control should be avoided as

e*#erience show that transfer systems receive little

attention from #lant #ersonnel! "f neglected,

com#le* controls may cause more #roblems than

they solve!

3"5 /$R30E $35B/


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3"5 /$R30E $35B/

/i8ing: $an% ca#acity including a safe

inventory margin de#ends on:

6! Rate of fuel consum#tion

(! ethod of delivery

! .istance from fuel

su##ly de#ot!

4 -ad weather delivery delays stri%es


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4! -ad weather, delivery delays, stri%es,

fuel shortage! 3##ro*imately 42 days

su##ly of oil in storage tan%s should be

maintained! $he tan%s are equi##ed

with gauges to indicate the quantity of

oil! "t can be a float cou#led to an

e*ternal scale calibrated and mar%ed toindicate the contents of the tan%!

5o of tan%s: $he number of storage


49/56

5o! of tan%s: $he number of storage

tan%s and their si8es varies in various

#ower stations, de#ending not only on

the method of fuel delivery but on the

soil condition also which affect the

foundations and ground area of the

tan%s! 3 single tan% cost less,o#eration is chea#er and maintenance

is low!

- t ith lti l t %


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-ut with multi#le tan%s

6! Re#airs can be made to equi#ments

and heater in one tan% while other isbeing used! "t also allows time for

sludge and moisture to settle in a tan%

while other is being used!

(! $an% can be switched if oil #resents

a firing #roblem!

LC3$"5


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LC3$"5

"t should be close to the unloading area

and sufficient s#ace must be availablefor concrete di%es 'earth emban%ments

to confine s#illage of oil in case of tan%

lea%age)! $he tan%s should be built

away from buildings, ha8ardousequi#ments and materials and #ower

lines!


52/56

$he oil inlet #i#e to tan% should e*tend to

within 1 inches of the tan% bottom, otherwise

s#lashing may lead to #roduction of staticelectricity with subsequent danger of fire!

3lso there should be a vent at tan% to# for

dis#lacement of air during filling and to

#revent formation of internal vacuum, and

#ossible consequent colla#se of the tan%!

Roof manholes should be hinged so that they

fold bac% beyond the #oint of balance! $hetan%s should also be #rotected from the effect

of lighting by #roviding connections to

earthing electrodes!

P"PE L"5E/ $R3CE HE3$"50


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P"PE L"5E/ $R3CE HE3$"50

Pi#e lines are heated by low #ressure

steam or electric surface heaters! 3

small bore steam #i#e of about (7mm

diameter is run along the full length of

oil #i#e and the whole is encased in a

lagging! Here relief valves must be#rovided at suitable #laces to ta%e care

of e*#ansion of the oil! .uring shut

down #eriod fuel oil increases itsvolume by about > #ercent as it is

heated from ?oC 672oC!

$R35/FER P=P/


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$R35/FER P=P/

$ransfer Pum#s are either of

centrifugal or Rotary $y#e! Centrifugal

Pum#s have easy control, are reliable

and need not much maintenance!

However, they can not handle highly

viscous fuel oils efficiently and aree*#ensive!


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Rotary #um#s can either be screw or

gear design! $hese #um#s are very

efficient, can o#erate with negativesuction and have a relative low ca#ital

cost! Relief valves are #rovided to

#revent overloading of motor in case of

discharge sto##age!

3=J"L"3RI /$E3 -"LER/


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3=J"L"3RI /$E3 -"LER/

3u*iliary /team -oilers are used for

generating steam for fuel oil, tan%

heating, steam tracing! "n com#osite

#ower stations having many units,these are not being #rovided!

Fuel Oils(Npti)

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