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8/17/2019 Fuels and Thermochemistry
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Fuels&
Thermochemistry
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FUELS
A combustible substance whichon proper burning in air liberates
huge amount of heat, that can beused economically for domestic
and industrial purposes
e.g. coe, coal, charcoal,petroleum diesel etc
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!LASS"F"!AT"#$
Fuels
%rimary or natural Secondary or deried
Solid li'uid (aseous
)ood crude oil $atural gas
!oal
*ung
solid li'uid gaseous
coe tar coal gas
charcoal erosene water gas
diesel oil gas
%etrol bio gas
L%(
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!+AA!TE"ST"!S #F A
(##* FUEL1. High Calorific value
2. Low moisture contents
3. Moderate ignition temperature4. Low ash content
5. No harmful comustion product formation
!. Moderate rate of comustion". low cost
#. $as% to transport
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!omparison between solid,
li'uid and gaseous fuels%roperties Solid fuels Li'uid fuels (aseous
fuels
Price Cheap andeasilyavailable
Costly Costly exceptnatural gas
Transport and
storage
easy Transported
easily thoughpipelines butmust be storedin closedcontainerscarefully
Transported
throughpipelines andare stored inleak prooftanks
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Combustion slow quick Very fast
Fire hazards ess risk !reaterrisk
"ven greaterthan liquidfuels
#moke andash
$lwaysproducedand reducescalori%c
value
$sh is notproducedbut smokeis produced
&either ash norsmoke isproduced
Calori%cvalue
least higher 'ighest
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%etroleum
Petroleum is a mixture of thousands of di(erent types of hydrocarbons)
ight Crude *il 'eavy Crude *il
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+here +e !et *il,
The world-s top %ve crude oil.producing countries are/ – #audi $rabia
– 0ussia
– 1nited #tates
– 2ran
– China
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%etroleum +ydrocarbon Structures
• Para3ns• $romatics
• &aphthenes
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!omposition of petroleum
• C / 45.467• ' / 897
• #:&:* / 87
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Composition of Crude Oil
CRUDE OIL
HYDROCARBONS NON-HYDROCARBONS
ALIPHATICS AROMATICS NAPHTHENES SULFURS NITROGENS OXYGENS METALLIC
25% 17% 50%
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Fractional *istillation of%etroleum
• Petroleum can be separated intodi(erent fractions by fractional
distillation)
• This separation can take place
because petroleum is a mixture ofsubstances with di(erent boilingpoints)
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!onditions for #il e-ning
• Petroleum is heated to ;
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Question
Why is petroleum vaporized in the absence of air at360°C?
It !" #!t#$ %&'( !n) #!*+( !n (,-./+&/n0
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!AL#"F"! ALUE1g &rg. compound ' &2 C&2 'H2&( )H* +
Here( )H * calorific value
UNITS
1. Calorie, for 1g of water % 1o
C 1calorie * 4.1#4 -oule * 4.1#5 1/" ergs
2. K.Calorie, for 1 0g of water % 1oC
3. British Thermal Unit (B.Th.U.), for 1 pound of
water % 1o
4. Centigrade heat unit (C.H.U.), for 1 pound % 1oC
1k.cal = 1Cal = !."#$ B.Th.U. = %.% C.H.U.
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(#SS # +"(+E !AL#"F"!
ALUE /+!0Heat evolved when a unit uantit% of a fuel is
completel% urnt and the products of comustion are
allowed to cool at room temperature.
' &2 C&2 ' H2&v ( )H1*
H2&v H2&l ( )H2 * %% * latent heat of steam
6o( HC7 * 8otal )H * ' %
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L#)E # $ET !AL#"F"! ALUE
/L! or $!0 Heat evolved when a unit uantit% of a fuel is completel%
urnt and the products of comustion are allowed to escape at
room temperature. ' &2 C&2 ' H2&v ( )H1*
LC7 *
* HC7 9 latent heat of water vapours formed
LC7 * HC7 9 /./: H 5#" cal;gwhere( H * < of h%drogen in the fuel
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*i1erences between (ross and$et calori-c alue
S.$o (! $!
8 The amount of heatreleased when unitquantity of fuel is burntcompletely and theproducts of combustionare allowed to cool atroom temperature)
The amount of heatreleased when unitquantity of fuel is burntcompletely and theproducts of combustionare allowed to escapeat room temp)
= Latent heat ofcondensation of steam isincluded
Latent heat ofcondensation of steam isnot included
; 2t is also known as 'igher
Calori%c Value
2t is also known as ower
Calori%c Value
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?*@? C$*02@"T"0
2etal 3omb
"nstrumental setup
Schematic *iagram
!AL!ULAT"#$
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!AL!ULAT"#$ mass of fuel ta0en in calorimeter * m g
mass of water ta0en in calorimeter*=g
water euivalent of calorimeter om( thermometer(stirrer etc * w g
>nitial temp. of water in calorometer * t1
final temp. of water in calorimeter * t2
higher calorific value * HC7
heat lierated % urning of fuel * m HC7
heat gained % water( calorimeter etc * ='wt2?t1
heat lierated * heat gained m HC7 * = ' wt2?t1
HC7 * ='wt2?t1 cal;g or 0cal;0g
m
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Let H e the < of h%drogen in the fuel(thenLC7 * HC7 9 /./:H 5#" cal;g or 0cal;0g
Corrections
i use wire correction C , should e sutracted.ii cid correction C , should e sutracted.
iii Cooling correction CC , should e added.
6o( HC7 * = ' wt2?t1'CC?C'C cal;g
m
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!#AL SA2%LE A$AL4S"S
8) Proximate analysis
=) 1ltimate analysis
$&$A#2# *F C*$ #$@P"
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$&$A#2# *F C*$ #$@P"
Coal is a highl% caronaceous matter that has een
formed from fossilised remains of plants undersuitale conditions.
ANALYSIS ? 2 t%pes
1) P0*B2@$T" $&$A#2# . includes thedetermination of moisture( volatile matter( ash and
fied caron
i &oisture, at 11/oC for an hour
< of moisture * Loss in wt. 1//
wt of coal sample
ii ' l il :25 ; 25 C f " i
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ii 'olatile matter , at :25';? 25oC for " minutes
< of volatile matter * Loss of wt due to removal of
volatile matter 1//
wt of coal sample ta0en
iii sh content, at "//?"5/oC for half an hour
< of ash * wt of ash 1// wt of coal sample ta0en
iv i*ed car+on * 1//? < of moisture ' ash '
volatile matter6>@N>>CNC$,
Higher < of fied caron Higher calorific
value etter fuel
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Solid Fuels (Phsi!"l #$o#e$%ies&
P$o'i"%e ")"lsis
T#i!"l #$o'i"%e ")"lsis o* +"$ious !o"ls
(,&IndianCoal
IndonesianCoal
South AfricanCoal
Mois%u$e -./0 /.12 0.-
Ash 20.32 42.// 45
6ol"%ile"%%e$
78.58 7/.5/ 72.70
Fi'ed C"$9o) 21.3/ 13.5/ -4.77
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U,TI&T- N,SIS /
C/,>ncludes the estimation of < of elements in the
fuel
i0etermination o C 2 H
C ' &2 C&
H2 ' &2 H2& 2A&H ' C&2 A 2C&3 ' H2&
CaCl2 ' "H2& CaCl2."H2&
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< of C *>ncrease in the wt of A&H tue 12 1//
=t of coal sample ta0en 44
< of H * >ncrease in the wt of CaCl2 tue 2 1//
=t of coal sample ta0en 1#
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iiD Eetermination of &/ ABeldahl method
uel= g ' H26&4 NH426&4
NH426&4 ' Na&H NH3 'Na26&4 ' H2&
Anown amount of HCl
NH3 is neutralised $cess HCl
8itrated against al0ali
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Mass of fuel * = g
7olume of acid used to neutralie NH3 * 7 ml Normalit% of HCl * N
$. of HCl * $. of NH3 * $. of N
N7 wt of Nw * w 1/// $ of N 14
< of N * 1.4 N7
=
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iiiD E"T"0@2&$T2*& *F #/
# *= #*=
#*= '=* '=#*>
7 of # G wt of ?a#*> formed x ;= x 855
wt of coal sample x =;;
ivD E"T"0@2&$T2*& *F $#'/by proximate analysis
VD E"T"0@2&$T2*& *F *
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VD E"T"0@2&$T2*& *F */7 of * G 855 . 7 of C ' & # ashD
Solid Fuels (Chei!"l P$o#e$%ies&
Ul%i"%e ")"lsis
T#i!"l ul%i"%e ")"lsis o* !o"l (,&
3arameter Indian Coal4 5 Indonesian Coal4 5
Moisture 5.:# :.43
Mineral Matter 1.1 sh 3#.!3 13.::
Caron 41.11 5#.:!
H%drogen 2."! 4.1! Nitrogen 1.22 1./2
6ulphur /.41 /.5!
&%gen :.#: 11.##
!CV kCalHkgD >555 9955
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/CTN- NU&B-6
• &.N. signifies the ignition ualit% of gasoline in
automoile engines.
• or grading gasolineDetrol
>sooctane * 1//
n?heptane * /
• 8he < of isooctane present in the miture of isooctane
and n?heptane which has the same 0noc0ing propert% asthe fuel itself.
• More the octane numer( etter the fuel efficienc%.
6easons or o7ting the +lend o iso octane 2 n
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6easons or o7ting the +lend o iso8octane 2 n8
he7tane9
• 8he different h%drocaron in gasoline,6traight chain paraffin
>so?paraffins
Naphthenes
romatics
• or the same Caron NoE straight chain paraffin have lowest octane No.
• Franched chain paraffin isomers( Naphthenes have higher octane No.
• &lefins also have high &.N. ut the% cause gum deposits in the fuel
tan0 and are not desirale.• romatic have high &.N. ut their content is eing restricted due to
their carcinogenic nature.
/ctane n m+ers o e h drocar+ons9
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!arbon +ydrocarbon #ctane
$o.C
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ðods to increase octane num+er9
1. F% adding the anti0noc0ing agent, e.g. 8$L aout 1./?3./
ml ;gallon petrol along with some eth%lene diromide.
2. F% iso?merisation3. F% al0%lation
4. F% aromatisation
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C-TN- NU&B-6
• or grading diesel oil
• Normal paraffinGs have highest cetane no. followed %
naphthenes( isoparaffins( olefins and aromatics.
• or grading diesel oil.Headecane cetane * 1//
? meth%l naphthalene * /
• 8he < of cetane present in the miture of cetane and
?meth%l naphthalene which has the same ignition
propert% as the fuel itself.
• More the cetane numer( etter the fuel efficienc%.
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,SH 3/INT
8he flash point of a volatile liuid is the lowest
temperature at which it can vaporise to form an
ignitale miture in air.
t the flash point( the vapour ma% cease to urn when
the source of ignition is removed.&r
8he minimum temperature( at which the sample gives
sufficient vapours( which forms an ignition miturewith air( giving a flash when a flame is applied to it(
is called flash point.