Nox-Sources and Control Methods

8/9/2019 Nox-Sources and Control Methods

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NOxNOxSources and Control MethodsPresented byKOMAL AROOSHKOMAL AROOSH

(2010-2012)

CENTRE FOR COALCENTRE FOR COALTECHNOLOGY TECHNOLOGY

UNIVERSITY OF THEUNIVERSITY OF THEUN!A"UN!A" 1


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CONTENTSCONTENTS• Specific sources of NO x• NO x Effects• Characteristics of NO x compounds• NO x Regulation• NO x Formation

• Control Technologies & Techniques• Combustion odification• !dd"On Controls #Flue $as Treatment %


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SpecificSpecificsources ofsources ofNONO

'


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1! "o#bustion sources• Automobiles• Boilers• Incinerators

2! Hi$%-te#per&ture industri&' oper&tions• Metallurgical furnaces• Blast furnaces• Plasma furnaces• Kilns

! Ot%er sources• Nitric acid plants• Industrial processes that use nitric

acid (


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)

NONO ffectsffects


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It is one of the main ingredients involved in theformation of ground-level ozone, hich can trigger

serious respirator! problemscontributes to nutrient overload that deteriorates ater"ualit!contributes to atmospheric particles that cause

visibilit! impairment most noticeable in national par#sreacts to form nitrate particles, acid aerosols, as ellas N$ %, hich also cause respirator! problems

contributes to formation of acid rain

reacts to form to&ic chemicalscontributes to global arming

*


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"%&r&cteristics"%&r&cteristicsof NOof NO

co#poundsco#pounds


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NO * Nitric o ide• 'olorless and odorless gas• Insoluble in ater ()emember this for later on*+• o&ic

NO 2 * Nitro$en dio ide• suall! e&ists as a dimer compound (N %$ . + at lo

/ '

• 0as distinct reddish-bro n color • Moderatel! soluble in a"ueous li"uids• o&ic• 'ontributes to bro n haze that occurs ith smog

,


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NONORe$u'&tionRe$u'&tion


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NO concentr&tions &re re'&ti+e'y 'o,in t%e &t#osp%ere so ,%y &re t%eyre$u'&ted.

N$ and N$ % react rapidl! ith othercompounds, creating ozone and otherundesirable compounds1 he N$ and N$ %

ma! never reach high concentrations, but arecreating other air pollutants1

1.


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NONOxx

FormationFormation


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• 2ormed at elevated temperatures duringcombustion of fuel in the presence of air1

• Appro&imatel! 3/ to 345 of the nitrogen

o&ides generated in combustionprocesses are in the form of nitric o&ide(N$+1 ()emember this for later on*+

• $nce in the atmosphere, the N$ reactsin a variet! of photochemical and thermalreactions to form N$ %1

1


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• /%er#&' NO/%er#&' NO formed b! reactionbet eenN % and $ % in the air6 sensitive to

temperature• ue' (or Pro#pt) NOue' (or Pro#pt) NO formed fromcombustion of fuel containing organicnitrogen6 dependent on local combustionconditions and nitrogen content in the fuel1

Not all of the fuel nitrogen compounds arereleased during combustion1 nli#e sulfur,a significant fraction of the fuel nitrogenremains in the bottom ash or in the fl! ash1

1'


14/36Location of NoLocation of No xx formation in a Boilerformation in a Boiler 1(


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1)

"ontro'"ontro'/ec%no'o$ies/ec%no'o$ies

/ec%ni3 es/ec%ni3ues


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N$& control technologiesN$& control technologies

1*


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1. Modify combustion to suppress NOx formation

• 7o e&cess air operation• $ff-stoichiometric combustion• 2lue gas recirculation

• Natural gas reburning

2. Reduce No x to molecular nitrogen throughcontrols (also kno n as flue gas treatment!

• 8elective Non-'atal!tic )eduction (8N')+• 8elective 'atal!tic )eduction (8')+• 9r! 8orption

1+

NO contro' /ec%ni3uesNO contro' /ec%ni3ues


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8trategies for 'ombustion Modification8trategies for 'ombustion Modification

)educe pea#te#per&tures othe flame zone)educe gasresidence ti#e in the flame

zone

1,


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4ou'd ,et scrubbers be & $ood contro'

tec%ni3ue for NO e#issions.:et scrubbers ould not be a goodcontrol techni"ue for N$ & emissions1

Re&son N$ is mainl! formed during the

combustion process and N$% is formed

in the atmosphere1 8ince N$ isinsoluble in ater, et scrubbing ouldnot or# ver! ell*

1-


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.

"o#bustion"o#bustionModific&tionsModific&tions


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Lo, e cess &ir oper&tion Involves a reduction in thetotal "uantit! of air used in the combustion process1 B!using less o&!gen, the amount of N$& produced is not asgreat1

1


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Off-stoic%io#etric co#bustion ; Involves the mi&ing ofthe fuel and air in a a! that reduces the pea#gas temperatures and pea# o&!gen concentrations1

Lo, NO burners ; Keeps temperatures

do n and dissipates heat "uic#l! O+erfire &ir (O A) ; Keeps mi&ture fuel rich

and completes combustion process using airin


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O#$Sto%ch%o&etr%c Co&'ust%on %n "urnerO#$Sto%ch%o&etr%c Co&'ust%on %n "urner(Lo) No(Lo) No xx "urner*"urner*

'


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O#$Sto%ch%o&etr%c Co&'ust%onO#$Sto%ch%o&etr%c Co&'ust%on

(O+er,re A%r*(O+er,re A%r*

(


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O#$Sto%ch%o&etr%c Co&'ust%onO#$Sto%ch%o&etr%c Co&'ust%on

("urners$Out$o-$Ser+%ce*("urners$Out$o-$Ser+%ce* )


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'ue $&s recircu'&tion'ue $&s recircu'&tion

Involves the return of cooled

combustion gases to the burner areaof the boiler1 )educed temperaturesproduce less N$&1 he processre"uires a recirculation fan and ducts!stem1

*


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Involves the operation of the main burners in aboiler at ver! lo e&cess air (fuel richconditions+1 A series of overfire air ports are used in thisupper region to provide all of the air needed for

complete combustion1

ue' Reburnin$ue' Reburnin$

+


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ue' Reburnin$ ,


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-

Add-OnAdd-On

"ontro's"ontro's( 'ue 6&s( 'ue 6&s/re&t#ent/re&t#ent !!


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Se'ecti+e non-c&t&'ytic reduction syste#s

(SN"R)Involves the in


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Se'ecti+e Nonc&t&'ytic Reduction (SN"R) Re&ctions

O H NOO NH

O H N O NO NH

'

'

*()(

*(((

+→+

+→++

!bo/e 1... oC

'1


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Example SNCR System for NoExample SNCR System for No xx Control in aControl in a '


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Se'ecti+e c&t&'ytic reduction (S"R) Involves using beds containing ammonia or urea toreduce nitrogen o&ides to molecular nitrogen and ater1

o or three catal!sts (usuall! tungsten and vanadium+are arranged in hone!comb shapes in the beds so aircan flo through1 N$& reduction efficiencies rangingfrom ?4 to 3/5 are possible hen the amount ofcatal!st is sufficient, the catal!st is in good condition,the ammonia reagent flo is sufficient, and theammonia is ade"uatel! distributed across the gasstream1

''


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Se'ecti+e "&t&'ytic Reduction (S"R) Re&ctions

O H N O NH NO

O H N O NH NO

&&catal0stsupportedO1orTiO

&'&

&&catal0stsupportedO1orTiO

&'

*'(&

*((()&&

)&&

+ → ++

+ → ++

Temperature 2 '.. " (.. oC

'(


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Exapmle SCR System for NoExapmle SCR System for No xx Control in aControl in a ')


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7ry Sorption7ry Sorption◦ Activated carbon (220 ~ 2 0 oC!◦ S"ell #l$e %as &reatin' System (~ 00 oC!

◦ Al)ali *etal and Al)ali Eart" *etal based sorbents

CuOOCu

O H SOCu H CuSO

O H N O NH NO

CuSOSOOCuO

→+

++→+

+ → ++

→++

(

catal0stsasCuSOorCuO'

(

)3.

&&

*(((

)3.(

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Nox-Sources and Control Methods