Fundamentals of Combustions and Combustion Equipment

7/24/2019 Fundamentals of Combustions and Combustion Equipment

1/18

Fundamentals of

Combustions andCombustion equipment

Lecture # 9 to 12

Mujahid Mehdi Abro Indus University Karachi


2/18

FUNDAMENTALS

The purpose of any combustion contro system is tosafey and e!cienty maintain the desired boieroutput "ithout the need for constant operatorattention Therefore$ the combustion process inside

the furnace must be controed "hie the boier outputchan%es in response to oad demands The basicprincipe of combustion contro is to meet the boieroad re&uirements re%uatin% the &uantities of fue andair "hie achievin% optimum combustion and

maintainin% safe conditions for operators ande&uipment


3/18

Combustion Pin!iples

'ombustion is the rapid o(idation of materia )the fue* toreease ener%y )heat* The fue can be a soid$ i&uid or %as$and the amount of heat reeased is normay e(pressed in+TUs )+ritish therma units*

The o(y%en re&uired to reease the ener%y from the fuenormay comes from the air and represents 2,9- of thenorma atmosphere

'ombustion is a rapid chemica combination of o(y%enand

the combustibe eements of a fue"ith a resutin% reeaseof heat 'ombustion is an e(othermic )heat producin%*reaction .f the three major combustibe eements in anyfossi fue$ carbon$ hydro%en$ and sufur$ ony the /rst t"ohave si%ni/cance as a source of heat
https://www.myodesie.com/index.php/wiki/index/returnEntry/id/3054#Fuelhttps://www.myodesie.com/index.php/wiki/index/returnEntry/id/3054#Heathttps://www.myodesie.com/index.php/wiki/index/returnEntry/id/3054#Oxygenhttps://www.myodesie.com/index.php/wiki/index/returnEntry/id/3054#Airhttps://www.myodesie.com/index.php/wiki/index/returnEntry/id/3054#Oxygenhttps://www.myodesie.com/index.php/wiki/index/returnEntry/id/3054#Fuelhttps://www.myodesie.com/index.php/wiki/index/returnEntry/id/3054#Heathttps://www.myodesie.com/index.php/wiki/index/returnEntry/id/3054#Heathttps://www.myodesie.com/index.php/wiki/index/returnEntry/id/3054#Fuelhttps://www.myodesie.com/index.php/wiki/index/returnEntry/id/3054#Oxygenhttps://www.myodesie.com/index.php/wiki/index/returnEntry/id/3054#Airhttps://www.myodesie.com/index.php/wiki/index/returnEntry/id/3054#Oxygenhttps://www.myodesie.com/index.php/wiki/index/returnEntry/id/3054#Heathttps://www.myodesie.com/index.php/wiki/index/returnEntry/id/3054#Fuel


4/18

Combustion Po!essAs the combustion process ta0es pace in thefurnace$ o(y%enin the combustion aircombines

chemicay "ith the carbon and hydro%en in thefue to produce heat The amount of air thatcontains enou%h o(y%en to combine "ith a thecombustibe matter in the fue is caed the

stoichiometric vaue or theoretica air

It is improbabe for every moecue of fue thatenters the furnace to combine chemicay "ith

o(y%en or this reason$ it is necessary toprovide more air than the stoichiometricre&uirement or most boiers$ it is customary toprovide 3 to 2, percent more air that thestoichiometric re&uirement to ensure competecombustion This additiona air is caed e(cess
https://www.myodesie.com/index.php/wiki/index/returnEntry/id/3054#Oxygenhttps://www.myodesie.com/index.php/wiki/index/returnEntry/id/3054#Airhttps://www.myodesie.com/index.php/wiki/index/returnEntry/id/3054#Fuelhttps://www.myodesie.com/index.php/wiki/index/returnEntry/id/3054#Heathttps://www.myodesie.com/index.php/wiki/index/returnEntry/id/3054#Heathttps://www.myodesie.com/index.php/wiki/index/returnEntry/id/3054#Fuelhttps://www.myodesie.com/index.php/wiki/index/returnEntry/id/3054#Airhttps://www.myodesie.com/index.php/wiki/index/returnEntry/id/3054#Oxygen


5/18

Combustion Po!ess

Three basic eements are re&uired forcombustion to occur4

ue)a combustibe materia*

.(y%enin su!cient &uantity to supportcombustion

5u!cient heatto brin% the fue to itsi%nition temperature and 0eep it there

If an# of t"ese !onditions $eeemo%ed& t"ee $ould no lon'e be a(e) T"is is t#pi!all# demonstatedusin' a (e tian'le)
https://www.myodesie.com/index.php/wiki/index/returnEntry/id/3054#Fuelhttps://www.myodesie.com/index.php/wiki/index/returnEntry/id/3054#Oxygenhttps://www.myodesie.com/index.php/wiki/index/returnEntry/id/3054#Heathttps://www.myodesie.com/index.php/wiki/index/returnEntry/id/3054#Heathttps://www.myodesie.com/index.php/wiki/index/returnEntry/id/3054#Oxygenhttps://www.myodesie.com/index.php/wiki/index/returnEntry/id/3054#Fuel


6/18

*equiements

fo Boiles5impy stated$ to be%in the combustion process re&uires fue$ heat and )air* o(y%en "ith the

ma0e6up of the air bein% about 21- o(y%en$ 78- nitro%en$ and appro(imatey 1-misceaneous %ases 5o it is ony the o(y%en that is used in combustion$ and the baance ofthe air is aon% for the ride This is "hy it is important to imit the amount of e(cess air$ butsti have enou%h to compete o(idation eavin% enou%h e(cess to 0eep the combustionprocess safe

To do this$ "e need a su!cient air suppy to support combustion "hie 0eepin% the boier roompositive reative to atmospheric pressure e don:t "ant the room to %o ne%ative as this coudimpact the chemica reaction$ not ao"in% for fu o(idation$ resutin% in considerabe carbonmono(ide )'.* formation rather than the formation of carbon dio(ide )'.2* referenced above

hen determinin% boier room air re&uirements foo"in% parameters must be revie"ed4

The si;e of the room

Air


7/18

COMBUSTION*EACTIONS

2C + O2 2CO + LESS HEAT

C

OO

C

C OC O

COMBUSTION INCOMPLETE


8/18

COMBUSTION*EACTIONS

C + O2 CO2+ HEAT

C

O

O

C

O

O

2H2 + O2 2H20 + HEAT

H H

OO

H H

H

H

OH

H

O

COMBUSTION COMPLETE


9/18


10/18

Bunes and Contols

+urners are the devices responsibe for4

>roper mi(in% of fue and air in the correctproportions$ for e!cient and competecombustion

?eterminin% the shape and direction of the


11/18

Bunes t#pe

Oil BunesAs previousy mentioned$ oi must beatomi;ed for optima combustion

The abiity to burn fue oi e!cientyre&uires a hi%h fue surface area6to6voume ratio

@ach of the burner types uses a no;;eto provide the spray of i&uid fue Therate of combustion is imited byvapori;ation of the i&uid fue The%reater the surface area of the fue$the %reater the combustion capabiity
https://www.myodesie.com/index.php/wiki/index/returnEntry/id/3054#Fuelhttps://www.myodesie.com/index.php/wiki/index/returnEntry/id/3054#Fuel


12/18

Pessue +et Bunes

A pressure jet burner is simpy an o;;e atthe end of a pressuri;ed tube

In the operatin% ran%e$ the substantiapressure drop created over the no;;e "hen

the fue is dischar%ed into the furnaceresuts in atomi;ation of the fue

Ad%anta'es of pessue ,et bunes-

Beativey o" cost

5impe to maintain


13/18

*ota# Cup Bunes

In a rotary cup burner $ fue oi issuppied do"n a centra tube$ and

dischar%es onto the inside surface of arapidy rotatin% cone +ecause the

atomi;ation is produced by the rotatin%cup$ rather than by some function of the

fue oi )e%$ pressure*$ the turndo"nratio is much %reater than the pressure

jet burner

5ome advanta%es of rotary cup burners

are that they are robust$ have a %oodturndo"n ratio$ and fue viscosityis esscritica The major disadvanta%e of

rotary cup burners is they are more

e(pensive to buy and maintain
https://www.myodesie.com/index.php/wiki/index/returnEntry/id/3054#Fuelhttps://www.myodesie.com/index.php/wiki/index/returnEntry/id/Hydraulic%20Theory#Pressurehttps://www.myodesie.com/index.php/wiki/index/returnEntry/id/Lubrication%20Concepts#Viscosity%202https://www.myodesie.com/index.php/wiki/index/returnEntry/id/Lubrication%20Concepts#Viscosity%202https://www.myodesie.com/index.php/wiki/index/returnEntry/id/Hydraulic%20Theory#Pressurehttps://www.myodesie.com/index.php/wiki/index/returnEntry/id/3054#Fuel


14/18

.asBunes

At present$ %as is probaby the most common fue used in thefaciities Atomi;ation is not an issue "ith a %as$ and proper mi(in% of%as "ith the appropriate amount of air is a that is re&uired forcombustion T"o types of %as burners in use are o"6pressure andhi%h6pressure

Lo$/Pessue BuneThese operate at o"6pressure$ usuay bet"een 23 and 1, mbar Theburner is a simpe venturi device "ith %as introduced in the throatarea and combustion airbein% dra"n in from around the outside
https://www.myodesie.com/index.php/wiki/index/returnEntry/id/3054#Fuelhttps://www.myodesie.com/index.php/wiki/index/returnEntry/id/3054#Airhttps://www.myodesie.com/index.php/wiki/index/returnEntry/id/3054#Airhttps://www.myodesie.com/index.php/wiki/index/returnEntry/id/3054#Airhttps://www.myodesie.com/index.php/wiki/index/returnEntry/id/3054#Airhttps://www.myodesie.com/index.php/wiki/index/returnEntry/id/3054#Fuel


15/18

0i'"/Pessue Bune

These operate at hi%her pressures$ usuay bet"een 12 and 173mbar$ and may incude a number of no;;es to produce a particuar


16/18

Daft

An ade&uate


17/18

Fo!ed Daftorced draft boiers operate "iththe air and combustion products

maintained above atmosphericpressure ans at the inet to theboier system$ caed forced draft)?* fans$ provide su!cient

pressure to force the air and


18/18

Balan!e Daft

+aanced draft boiers have a forced draftfan at theboier inet and an induced draft fan at the systemoutet This reduces both

Documents

Fundamentals of Combustions and Combustion Equipment