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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
DEER. Emission Control TechnologiesAugust 4th, 2009. Dearborn, MI 3
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
DEER. Emission Control TechnologiesAugust 4th, 2009. Dearborn, MI 4
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
DEER. Emission Control TechnologiesAugust 4th, 2009. Dearborn, MI 5
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
DEER. Emission Control TechnologiesAugust 4th, 2009. Dearborn, MI 6
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.
DEER. Emission Control TechnologiesAugust 4th, 2009. Dearborn, MI 7
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
DEER. Emission Control TechnologiesAugust 4th, 2009. Dearborn, MI 8
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
DEER. Emission Control TechnologiesAugust 4th, 2009. Dearborn, MI 9
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
DEER. Emission Control TechnologiesAugust 4th, 2009. Dearborn, MI 10
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%
DEER. Emission Control TechnologiesAugust 4th, 2009. Dearborn, MI 11
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
DEER. Emission Control TechnologiesAugust 4th, 2009. Dearborn, MI 12
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
DEER. Emission Control TechnologiesAugust 4th, 2009. Dearborn, MI 13
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
DEER. Emission Control TechnologiesAugust 4th, 2009. Dearborn, MI 14
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.
DEER. Emission Control TechnologiesAugust 4th, 2009. Dearborn, MI 15
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
DEER. Emission Control TechnologiesAugust 4th, 2009. Dearborn, MI 16
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
DEER. Emission Control TechnologiesAugust 4th, 2009. Dearborn, MI 17
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.
DEER. Emission Control TechnologiesAugust 4th, 2009. Dearborn, MI 18
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.
DEER. Emission Control TechnologiesAugust 4th, 2009. Dearborn, MI 19
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.