Bifurca(onfeaturesofCOandHCsinDOC

RamaKrishnaDadi

Advisers

Dr.VemuriBalakotaiahandDr.DanLuss

UniversityofHouston

CLEERS2016

Introduc(on

DOCCO,HCs,NO

CO2,H20,NO2

Oxida;onreac;onsR1:CO+ 0.5O2 →CO2R2 :C3H6 + 4.5O2 → 3CO2 +3H2 0R3 :C2H6 +3.5O2 → 2CO2 +3H2 0

ΔH (R1) = −283kJΔH (R2) = −1925kJΔH (R3) = −1560kJ

Introduc(onandobjec(ves

•  DieselengineexhaustconsistsofCO,H2andseveralhydrocarbonswhichigniteatdifferenttemperatures.

•  Theheatgeneratedbytheoxida(onofeasilyigni(ngspeciescanbeusedtoignitelateigni(ngspecies.

Objec(ves•  Tostudythebifurca(onfeaturesofindividualoxida(onreac(onsandco-oxida(onreac(ons.

•  Toillustrateseparateandsimultaneousigni(onsduringco-oxida(on

Mathema(calmodel

Xjm,in − Xjm −

kc ( j)L< u > RΩ

(Xjm − Xjs ) = 0

§  Speciesbalanceinfluidphase

§  Speciesbalanceinsolidphase

§  Energybalanceinfluidphase

Tm,in −Tm −hf L

< u > ρ fCpf RΩ(Tm −Ts ) = 0

§  Energybalanceinsolidphase

hf (Tm −Ts )− ΔHl Rv,l (Ts,X)0δc∫

l=1

rgl

∑ = 0

Kine;cmodel

RCO =k1XCOXO2

(1+KCOXCO )2

RC3H6 =k2XC3H6XO2

(1+KC3H6XC3H6 )2

RC2H6 = k3XC2H6XO2

COandHCs

RC3H6 =k2XC3H6XO2

(1+KC3H6XC3H6 +KICOXCO )2

RC2H6 =k1XC2H6XO2(1+KCOXCO )

2

cTmDje∂2Xj∂y2

+ υljRv,l (Ts,Xs )l=1

rgl

∑ = 0

COoxida(on

•  Steady-statehysteresisregionexpandswithincreaseininletmolefrac(onofthereac(ngspecies.Nega(veordereffectismorepronouncedthanexothermeffect

Tf,in(K)100 200 300 400 500

Conversion

0

0.2

0.4

0.6

0.8

1

500ppm

1%3%

Tf,in(K)100 200 300 400 500

Solid

tem

pera

ture

(K)

300

350

400

450

500

550

600

650

700

500ppm

1%3%

COoxida(on

=(sec)10-4 10-3 10-2 10-1

y in(

%)

0.2

0.25

0.3

0.35

0.4

0.45

0.5

No steady state multiplicity

Steady state multiplicity exists

•  Steady-statemul(plicityexpandswithincreaseinresidence(me

Igni(on-ex(nc(onlocus Hysteresislocus

CO(%)0 0.5 1 1.5 2 2.5 3

T f,in(K)

150

200

250

300

350

400

450

==0.1s

COExtinction

==0.01s Ignition

Propyleneoxida(on

•  Propyleneoxida(onfollowsLangmuir-Hinshelwoodkine(cs

Tf,in(K)300 350 400 450 500

Conversion

0

0.2

0.4

0.6

0.8

1

200ppm

2000ppm

(a)

Tf,in(K)300 350 400 450 500

Solid

tem

pera

ture

(K)

300

350

400

450

500

550

600

200ppm

2000ppm

(b)

Propyleneoxida(on

Igni(on-ex(nc(onlocus Hysteresislocus

=(sec)10-4 10-3 10-2 10-1

C3H

6(%

)

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

No steady-statemultiplicity

Steady-state multiplicityexists

(b)

C3H6(%)0 0.1 0.2 0.3 0.4 0.5

T f,in(K)

150

200

250

300

350

400

450

==0.1s

==0.01s

Extinction

Ignition

Modelcalibra(on•  Kine(cmodelforCO-

C3H6istakenfromtheworkRajetal.[1]

•  Kine(cmodelforethaneiscalibratedusingexperimentaldata.[2]

1.Rajetal.,ChemicalEngineeringJournal281(2015)322-33312.Gare]oetal,AppliedCatalysisB:Environmental73.1(2007)65-72

ECOR

=14422;

EC3H6R

=11306;

EC2H6R

= 9262

Ethaneoxida(on

Tf,in(K)200 400 600 800 1000

Co

nve

rsio

n

0

0.2

0.4

0.6

0.8

1

500ppm C2H61.5% C2H6

Tf,in(K)200 400 600 800 1000

Sol

id te

mpe

ratu

re(K

)

200

400

600

800

1000

12001.5%500ppm

Ethaneoxida(on

Bifurca(onset Hysteresislocus

=(sec)10-3 10-2 10-1

C2H

6(%

)0.5

1

1.5

2

2.5

3

3.5

4

No steady-statemultiplicity

Steady-state multiplicityexists

C2H6(%)0.5 1 1.5 2

T f,in(K)

350

400

450

500

550

600

650

700

==0.1s

==0.01s

Ignition

Extinction

Co-oxida(onofCOandC3H6

Tf,in(K)200 300 400 500 600 700

Con

vers

ion

0

0.2

0.4

0.6

0.8

1

CO 500ppmC3H6 500ppm

Tf,in(K)200 300 400 500 600 700

Sol

id te

mpe

ratu

re(K

)250

300

350

400

450

500

550

600

650

Simultaneousigni(onofCOandC3H6

Co-oxida(onofCOandC3H6

Tf,in(K)200 300 400 500 600 700

Con

vers

ion

0

0.2

0.4

0.6

0.8

1CO 1%C3H6 2000ppm

•  COinhibitspropyleneoxida(ononPt/Al2O3.Igni(ontemperatureincreaseswithincreaseininletmolefrac(onofCOandC3H6

C3H6(%)0 0.1 0.2 0.3 0.4 0.5

T f,in

(K)

100

150

200

250

300

350

400

450

IgnitionNo CO

Extinction

CO 1%

Co-oxida(onofCOandC2H6

Tf,in(K)200 400 600 800 1000

Con

vers

ion

0

0.2

0.4

0.6

0.8

1

CO 500ppm

C2H6 500ppm

Co-oxida(onofCOandC2H6

C2H6(%)0.5 1 1.5 2

T(K

)

300

350

400

450

500

550

600

1% CO

Pure ethane

•  Theexothermgeneratedbytheoxida(onofCOincreasessolidtemperatureandthisriseinsolidtemperaturereducestheigni(ontemperatureofC2H6duringco-oxida(onofCOandC2H6

Separateandsimultaneousigni(ons

Tf,in(K)200 400 600 800 1000

Con

vers

ion

0

0.2

0.4

0.6

0.8

1

1% CO1.5% C2H6

Tf,in(K)200 400 600 800 1000

Solid

tem

pera

ture

(K)

200

400

600

800

1000

1200

1400MixtureCO 1%C2H6 1.5%

Tf,in(K)200 400 600 800 1000

Con

vers

ion

0

0.2

0.4

0.6

0.8

12.2% CO1.5% C2H6

Tf,in(K)200 400 600 800 1000

Solid

tem

pera

ture

(K)

200

400

600

800

1000

1200

1400

Mixture2.2% CO1.5% C2H6

Co-oxida(onofCOandC2H6

CO(%)0 0.5 1 1.5 2 2.5 3

T(K)

150

200

250

300

350

400

450

500

550

600

Ethane

CO

1.5%C2H6

CO(%)0 0.5 1 1.5 2 2.5 3

T(K

)

150

200

250

300

350

400

450

500

550

600

C2H6

CO

Ethane 1%

1.0%C2H6

Co-oxida(onofCOandC2H6

Tf,in(K)200 400 600 800 1000

Solid

tem

pera

ture

(K)

200

300

400

500

600

700

800

900

1000

1

Tf,in(K)200 400 600 800 1000

Solid

tem

pera

ture

(K)

200

300

400

500

600

700

800

900

1000

1100

2

Tf,in(K)200 400 600 800 1000

Solid

tem

pera

ture

(K)

200

400

600

800

1000

1200

3

Tf,in(K)200 400 600 800 1000

Solid

tem

pera

ture

(K)

200

400

600

800

1000

1200

1400

4

Tf,in(K)0 200 400 600 800 1000

Solid

tem

pera

ture

(K)

200

400

600

800

1000

1200

5

CO(%)0 0.5 1 1.5 2 2.5 3

C2H

6(%

)

0

0.5

1

1.5

2

2.5

3

3

21

4

double limit locus

5

Co-oxida(onofCO,C3H6andC2H6

Tf,in(K)200 400 600 800 1000 1200

Con

vers

ion

0

0.2

0.4

0.6

0.8

1

C2H6 500ppm

C3H6 500ppm

CO 500ppm

Co-oxida(onofCO,C3H6andC2H6

Tf,in(K)0 200 400 600 800 1000 1200

Con

vers

ion

0

0.2

0.4

0.6

0.8

1

CO 3%

C3H6 500ppm

C2H6 500ppm

Tf,in(K)0 200 400 600 800 1000 1200

Con

vers

ion

0

0.2

0.4

0.6

0.8

1

CO 500ppmC3H6 6000ppmC2H6 500ppm

•  Theheatgeneratedbytheoxida(onofCOorC3H6isusedtoignitelateigni(ngspecieswhichischaracterizedbyethaneinourstudy.

Co-oxida(onofCO,C3H6andC2H6

C2H6(%)0 0.5 1 1.5 2

"T a

d(°C

)

180

200

220

240

260

280

300

Simultaneous ignition

Separate ignition

ΔTad = 9433YCO + 64200YC3H6

•  Theexothermicityofalllowtemperatureigni(ngspeciesisusedtosimultaneouslyignitehightemperatureigni(ngspecies

•  Lowtemperatureigni(ngspeciescanbeCO,C3H6andH2

•  Hightemperatureigni(ngspeciescanbeC2H6orC6H14

Summary

•  Bifurca(onanalysisofmixturescontainingCOandHCsisdoneusingshort-monolithmodel.

•  Simultaneousigni(onisobservedduringco-oxida(onofCOandC3H6.

•  Twoseparateigni(onsareobtainedduringco-oxida(onofCOandC2H6.

•  COinhibitsC3H6oxida(onbutimprovesthelight-offperformanceofC2H6

Thankyou