fuels and thermochemistry

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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&ethods 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.

fuels and thermochemistry

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