investigation on continuous soot oxidation and nox ... · investigation on continuous soot...

DEER. Emission Control TechnologiesAugust 4th, 2009. Dearborn, MI

Investigation on continuous soot oxidation and NOx reduction by SCR coated DPF

Phillip Bush, EminoxSvetlana Iretskaya, Catalytic Solutions, Inc.Ted Tadrous, Engine Control Systems

DEER. Emission Control TechnologiesAugust 4th, 2009. Dearborn, MI 2

Outline

•

Requirements for combined SCR-DPF catalyst•

Evaluation of CSI catalyst for NOx

removal and soot oxidation

•

Engine tests on continuous soot oxidation and NOx

reduction by combined SCR-DPF•

Summary


SCR-DPF. Two Functions: NOx

reduction and Soot oxidation

SCR with ammonia (urea)

4NO + 4NH3

+ O2

4N2

+ 6H2

O (standard SCR

reaction)NO + NO2

+ 2NH3

2N2

+ 3H2

O (fast SCR reaction)

NO + ½

O2

→ NO2

6 NO2

+ 8 NH3

→7 N2

+ 12 H2

O (slow SCR reaction)

SOOT OXIDATION

C + O2 CO2

C + ½

O2

CO

C + NO2

CO + NO

C + 2 NO2

CO2

+ 2NO

Urea Injector

SCRDPF/CDPF

Urea Injector

SCRDPF/CDPF

C

Urea Injector

SCR-DPFC

Urea Injector

SCR-DPFC

Urea Injector

SCR-DPF


CSI SCR catalysts activity on Flow-Through substrates More than 90% NOx reduction

Engine aged at 500 C for 250 hrs

0

10

20

30

40

50

60

70

80

90

200 250 350 400 450Temperature, C

% /

ppm

NOx conversion,% Ammonia slip, ppm SCR Inlet NO2/NOx, %

Practically 100% efficiency had been measured at every tested point on DOC SCR systems aged on engine for 250 hrs at 500 oC.

Engine aged at 500 C for 250 hrs

0

10

20

30

40

50

60

70

80

90

200 250 350 400 450Temperature, C

% /

ppm

NOx conversion,% Ammonia slip, ppm SCR Inlet NO2/NOx, %

Practically 100% efficiency had been measured at every tested point on DOC SCR systems aged on engine for 250 hrs at 500 oC.

FTP Hot Start

0

50

100

150

200

250

300

350

400

100 200 300 400 500 600 700 800 900 1000 1100 1200Time (s)

Tem

pera

ture

(Deg

C)

0

10

20

30

40

50

60

70

80

90

NO

x C

once

ntra

tion

(ppm

)

Exhaust Temp Catalyst Temp NOx_Tailpipe NOx Engine Out

EO NOx = 1.98 g/bhp*h

TP NOx = 0.182 g/bhp*h

Max NH3 slip 4 ppm

FTP Hot Start

0

50

100

150

200

250

300

350

400

100 200 300 400 500 600 700 800 900 1000 1100 1200Time (s)

Tem

pera

ture

(Deg

C)

0

10

20

30

40

50

60

70

80

90

NO

x C

once

ntra

tion

(ppm

)

Exhaust Temp Catalyst Temp NOx_Tailpipe NOx Engine Out

EO NOx = 1.98 g/bhp*h

TP NOx = 0.182 g/bhp*h

Max NH3 slip 4 ppm

Re: “Two Catalyst Formulations –

One solution for NOx after-

treatment systems”

DEER 2008, August 6th.

Various steady state and transient tests:

> 90% NOx reduction


TermoGravimetric/DerivativeThermalAnalysis

(TG/DTA) test Lab tool to evaluate catalysts soot oxidation quality

Gas composition: 0 or 400 ppm NO210% O2N2

–

balance Temperature: 20oC 500/700 oC at 10 oC/minSoot (from engine) mixed with Catalyst at 5/95 wt/wt

0

2

4

6

8

10

12

14

16

18

20 120 220 320 420 520 620 720Temperature, deg C

DTA

(mV/

10)

-2.5

-2

-1.5

-1

-0.5

0

0.5

TG(m

g)D

TG(m

g/se

c)

DTA: No catalyst

TG: No catalyst

DTG: No catalyst

596 C

660C

Soot Oxidation without catalyst: peak of oxidation:

660 oC

= soot combustion

660oC


Soot oxidation by LT-SCR. TG/DTA tests (@TCC) Catalytic soot oxidation

-4

-2

0

2

4

6

8

10

12

14

16

20 70 120 170 220 270 320 370 420 470

Temperature, deg C

DTA

(mV/

10)

-2.5

-2

-1.5

-1

-0.5

0

TG (m

g); D

TG (m

g/se

c)

DTA: SCR w/out NO2TG: SCR w/out NO2DTG: SCR w/out NO2

364 C

433 C

-2

0

2

4

6

8

10

12

14

16

18

20 70 120 170 220 270 320 370 420 470

Temperature, degC

DTA

(mV/

10)

-3

-2.5

-2

-1.5

-1

-0.5

0

TG (m

g), D

TG (m

g/se

c)

DTA: SCR with NO2TG: SCR with NO2DTG: SCR with NO2

363 C

425 C Soot Oxidation with LT-SCR catalyst:

with NO2

in feedgas peak of oxidation: 425 oC

without NO2

in feedgas peak of oxidation: 433 oC

425oC

433oC

Catalytic Soot oxidation had been observed with and without NO2

in feed gas.


Balance Point Temperature Test (@ ECS) No urea injection. 5.9L engine. 14L SCR-DPF.

4 grams/lit Soot Loading - Cummins ISB 5.9 - ULSD

100

150

200

250

300

350

400

450

500

Exh

Tem

p [d

eg-C

]

0.02

0.03

0.04

0.05

0.06

0.07

0.08

SBP

["H

2O/a

cfm

]

Temperature - Pre Muffler SBP

BPT ~ 300 oC

> 90% soot regeneration ~ 440o


SCR-DPF: NOx

Reduction and Soot oxidation

•

CSI Low-temperature SCR catalyst showed –

good SCR activity at various conditions and –

also soot oxidation properties:•

TG/DTA –

lowering peak of soot oxidation by > 200 oC•

Balance Point Temperature on engine test was found to be around 300 oC (in presence of NO2

)

•

Big Question: would LT-SCR catalyst keep SCR and Soot oxidation properties simultaneously?

•

Questions addressed in the current study:–

does presence of soot on filter affect SCR performance–

does urea-injection affect soot oxidation properties–

does NO2

concentration limit SCR or soot performance


Test Set Up (@ Eminox)

Test substrate

Injection

~ 1000mm

Fully insulated pipeworkall test system

2 3 400mm 400mm

4

min 800mm

1. NOx, NO,NO2, T, P static (emissions measured with CL)2. Adblue injection rate3. T, P static, exh flow rate4. T, P static, NOx, NO, NO2, NH3 (emissions measured with FTIR)

<7

1200mm

1

10.5x6 Oxicat

> 500mm

Bleed off valve for flow control

Mixer

10.5x12 Filter

To silencer

Valve to control

NO/NO2 ratio

Test substrate

Injection

~ 1000mm

Fully insulated pipeworkall test system

2 3 400mm 400mm

4

min 800mm

1. NOx, NO,NO2, T, P static (emissions measured with CL)2. Adblue injection rate3. T, P static, exh flow rate4. T, P static, NOx, NO, NO2, NH3 (emissions measured with FTIR)

<7

1200mm

1

10.5x6 Oxicat

> 500mm

Bleed off valve for flow control

Mixer

10.5x12 Filter

To silencer

Valve to control

NO/NO2 ratio

Set up enables to control:-

temperature, -

flow rate, -

injection stoichiometry- NO/NO2

ratio

Engine: Cummins N14 Eu2 525 hp

SCR-DPF: CS-585 on 9”x12”

300/12 high-

porosity cordierite


Example of a Test on soot loaded SCR-DPF (340oC; 35Khr-1; NO2

/NOx

= 0.3, 4.9 g/L soot) NOx

conversion; Ammonia slip; ANR

T=340C.SV=35K. NO2/NOx = 0.3

0

10

20

30

40

50

60

70

80

90

100

0 5 10 15 20 25Time (min)

Am

mon

ia s

lip (p

pm) N

Ox

conv

ersi

on,

%

-0.1

0.1

0.3

0.5

0.7

0.9

1.1

1.3

1.5

AN

R

ConvNH3_outANR

97.6%


Details of a test on soot loaded SCR-DPF (340oC; 35Khr-1; NO2

/NOx

= 0.3, 4.9 g/L soot) NO,NO2

–

inlet and outlet; ANRT=340C, SV=35K

0

200

400

600

800

1000

1200

1400

1600

1800

5 15 25 35 45 55Time, min

Tem

pera

ture

(deg

C) N

O, N

O2

(ppm

)

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

AN

R

NO In NO Out

NO2 in NO2 Out

Temp Cat-In ANR - -

Switched both analysers

to downstream locationto check correlation


Details of a test on soot loaded SCR-DPF (@ Eminox) (340oC; 35Khr-1; NO2

/NOx

= 0.3, 4.9 g/L soot) NO,NO2

outlet; Backpressure

T = 340 C; SV=35K; NO2/NOx=0.3

3

3.5

4

4.5

5

5.5

6

6.5

7

7.5

8

10 20 30 40 50 60Time (min)

dP (k

Pa)

0

150

300

450

600

750

900

1050

1200

1350

1500

NO

x (p

pm)/T

empe

ratu

re (d

egC

)

dPNO OutNO2 OutTemp

urea is injected

18% soot removal based on weight of

the filter


SCR activity with and without soot No effect of soot was observed

0

100

200

300

400

500

600

700

800

900

1000

5 15 25 35 45

Time, min

NO

x (p

pm)

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

NO_in 5 g sootNO2_in 5 g sootNO_out 5 g sootNO2_out 5 g sootNH3_out 5 g SootANR

T = 310 oC, SV=32K hr-1, NO2

/NOx

= 0.5, 0 g sootT = 310 oC, SV=32K hr-1,

NO2

/NOx

= 0.5, 5.3 g soot

0

100

200

300

400

500

600

700

800

900

1000

0 10 20 30 40 50 60

Time, min

NO

x (p

pm)

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

AN

R

NO_in 0 g sootNO2_in 0 g sootNO_out 0 g sootNO2_out 0 g sootNH3_out 0 g sootANR

NO2

to NO conversion due to soot oxidation did not affect SCR performance –

the same high (>97%) NOx

conversion at 10 ppm NH3

was observed during the tests


SCR activity with and without soot Monitoring Back Pressure

T = 310 oC, SV=32K hr-1, NO2

/NOx

= 0.5, 0 g sootT = 310 oC, SV=32K hr-1,

NO2

/NOx

= 0.5, 5.3 g sootT=300C, SV=32K, NO2/NOx=0.5, 5.3 g/L soot

7

7.5

8

8.5

9

9.5

10

10.5

11

11.5

12

10 15 20 25 30 35 40 45 50Time, min

dP (k

Pa)

0

200

400

600

800

1000

1200

1400

NO

x (p

pm)/T

empe

ratu

re (d

eC)

dPNO_outNO2_outT2

T=300K, 32K, 50%NO2, 0 g/L soot

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

0 10 20 30 40 50Time, min

dP (k

Pa)

0

100

200

300

400

500

600

700

800

900

NO

x (p

pm),

Tem

pera

ture

(deg

C)

dP kPaNO_out - ppmNO2_out - ppmT2 Cat-In degC

Soot oxidation was relatively low at these conditions –

BP lowered about 0.5 kPa

BP during 45 min of the test.


Evaluating effect of NO2

/NOx

ratio SCR performance was not influenced by NO2

/NOx

ratio at 300oC

0

100

200

300

400

500

600

700

800

900

1000

5 15 25 35 45

Time, min

NO

x (p

pm)

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

AN

R

NO_in 5 g sootNO2_in 5 g sootNO_out 5 g sootNO2_out 5 g sootNH3_out 5 g SootANR

T = 310 oC, SV=32K hr-1, NO2

/NOx

= 0.5,

5.3 g sootT = 300 oC, SV=32K hr-1,

NO2

/NOx

= 0.3,

4.6 g soot

Competition for NO2

between soot oxidation reaction and SCR reaction did not affect SCR performance –

the same high NOx

conversion (>98% at 10 ppm ammonia slip) was observed during the tests

0

200

400

600

800

1000

1200

1400

15 25 35 45 55 65Time (min)

NO

x, N

H3

(ppm

)

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

AN

R

NO_in - ppmNO2_in - ppmNO_out - ppmNO2_out - ppmNH3_out - ppmANR - -

T=300C, SV=32K, NO2/NOx=0.3


Evaluating effect of NO2

/NOx

ratio Soot oxidation –

no clear effect

T=300C, SV=32K, NO2/NOx=0.5, 5.3 g/L soot

7

7.5

8

8.5

9

9.5

10

10.5

11

11.5

12

5 10 15 20 25 30 35 40 45 50Time, min

dP (k

Pa)

0

200

400

600

800

1000

1200

1400

NO

x (p

pm)/T

empe

ratu

re (d

eC)

dPNO_outNO2_outT2

T = 310 oC, SV=32K hr-1, NO2

/NOx

= 0.5,

5.3 g soot50’

test: % soot removal –

n/aT=300C, SV=32K, NO2/NOx=0.3

8

8.5

9

9.5

10

10.5

11

11.5

12

12.5

13

30 35 40 45 50 55 60 65 70Time (min)

dP (k

Pa)

0

200

400

600

800

1000

1200

NO

x (p

pm)/T

empe

ratu

re (d

egC

)

dP kPaNO_out - ppmNO2_out - ppmT2 Cat-In degC

T = 300 oC, SV=32K hr-1, NO2

/NOx

= 0.3,

4.6 g soot70’

test: 33.3% soot removal

Based on BP measurements no difference in soot oxidation had been observed at 300 C for both tests. Based on weight of the filter 33.3% soot was removed during 70 min of the test with 30% NO2


Ammonia slip vs. NOx conversion for SCR-DPF More than 90% NOx

@ 10 ppm NH3

slip

0

5

10

15

20

0 10 20 30 40 50 60 70 80 90 100Conversion, %

Am

mon

ia s

lip, p

pm

NH3-Out 340 C-32K-30%NO2NH3-Out 300 C-32 -50%NO2NH3-Out 300C-32K-50%NO2NH3-Out 340 C-32K-30%NO2NH3-Out 210 C-35K-50%NO2NH3-Out 340C-48K-50%NO2NH3-Out 290C - 32K-30%NO2 NH3-Out 300 C-48K-30%NO2

More than 90% of NOx

reduction

at 10 ppm NH3

slip had been observed for all tests regardless soot loading, SV,

NO2

/NOx

ratio and temperatures within evaluated range of conditions.

Significant soot removal at T> 300 C.


Summary of Observations Simultaneous NOx

and Soot removal

•

No negative effect of soot loading (up to 6 g/L) was observed on

NOxoxidation function of SCR-DPF

•

SCR performance was not affected by concentration of NO2

in feed gas (within 0.3-0.5 NO2

/NOx

range)•

Competition for NO2

between SCR and passive soot oxidation did not affect rate of soot removal (within 0.3-0.5 NO2

/NOx

range)•

We did not observe slowing down in rate of soot oxidation due to

urea injection. •

Soot removal was continued when NOx

reduction was higher than 90% and no NO2

was available for soot oxidation

•

Overall: simultaneous NOx

and soot removal had been confirmed.


People working on the project

ECS: Ted Tadrous

TCC DW: Kikuhara-san

CSI DW: Shannon

CSI DW: Tiffany

TCC DW: Kagawa-san

Eminox: Jon Bradley

CSI DW: Sen

Eminox: Phil Bush

CSI: Andrew

CSI Diesel Warriors:Jiho, Svetlana, Dylan

Santa Monica Mtns. Pt. Diesel.

investigation on continuous soot oxidation and nox ... · investigation on continuous soot...

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