U.S. patent application number 13/401737 was filed with the patent office on 2013-08-22 for method and system for improving the robustness of aftertreatment systems.
This patent application is currently assigned to CUMMINS INC.. The applicant listed for this patent is Krishna KAMASAMUDRAM, Shankar KUMAR. Invention is credited to Krishna KAMASAMUDRAM, Shankar KUMAR.
Application Number | 20130213008 13/401737 |
Document ID | / |
Family ID | 48981205 |
Filed Date | 2013-08-22 |
United States Patent
Application |
20130213008 |
Kind Code |
A1 |
KUMAR; Shankar ; et
al. |
August 22, 2013 |
METHOD AND SYSTEM FOR IMPROVING THE ROBUSTNESS OF AFTERTREATMENT
SYSTEMS
Abstract
A method for treating a catalyst in an internal combustion
engine is disclosed. The method comprises detecting the efficiency
of a catalyst; sending the catalyst efficiency to a threshold
monitor; and heating the catalyst when the detected catalyst
efficiency is below a predetermined percentage.
Inventors: |
KUMAR; Shankar; (Columbus,
IN) ; KAMASAMUDRAM; Krishna; (Columbus, IN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KUMAR; Shankar
KAMASAMUDRAM; Krishna |
Columbus
Columbus |
IN
IN |
US
US |
|
|
Assignee: |
CUMMINS INC.
Columbus
IN
|
Family ID: |
48981205 |
Appl. No.: |
13/401737 |
Filed: |
February 21, 2012 |
Current U.S.
Class: |
60/274 ;
60/286 |
Current CPC
Class: |
F01N 2610/00 20130101;
F01N 2550/02 20130101; F01N 3/2066 20130101; F01N 3/021 20130101;
F01N 2560/026 20130101; F01N 3/2006 20130101; Y02T 10/24 20130101;
F01N 2560/021 20130101; Y02T 10/26 20130101; Y02T 10/12
20130101 |
Class at
Publication: |
60/274 ;
60/286 |
International
Class: |
F01N 3/20 20060101
F01N003/20; F01N 3/36 20060101 F01N003/36 |
Claims
1. A method of treating a catalyst in an internal combustion engine
comprising: detecting efficiency of a catalyst; sending the
catalyst efficiency to a threshold monitor; and heating the
catalyst when the detected catalyst efficiency is below a
predetermined percentage.
2. The method of claim 1 comprising detecting the efficiency of the
catalyst based on the threshold monitor.
3. The method of claim 1 wherein the catalyst comprises a
copper-zeolite based catalyst.
4. The method of claim 2 wherein the threshold monitor comprises a
sulphur estimator.
5. The method of claim 2 wherein the threshold monitor comprises a
catalyst efficiency monitor.
6. The method of claim 2 wherein the threshold monitor comprises a
timing device.
7. The method of claim 2 wherein the threshold monitor comprises a
humidity monitor.
8. The method of claim 1 wherein heating the catalyst in response
to the predetermined percentage further comprises regenerating the
catalyst by applying a high temperature treatment.
9. The method of claim 7 wherein regenerating the catalyst by a
high temperature treatment further comprises temperatures of at
least 650.degree. C.
10. The method of claim 8 wherein the high temperature treatment
increases the oxidation functionality of the catalyst.
11. The method of claim 1 wherein heating the catalyst in response
to the predetermined percentage comprises a thermal event.
12. The method of claim 6 wherein the thermal event comprises a
system deSO.sub.x which removes sulphur from the internal
combustion engine.
13. The method of claim 6 wherein the thermal event comprises a
system desorb which removes unburned hydrocarbons from the internal
combustion engine.
14. A system for treating a catalyst in an internal combustion
engine comprising: a diesel exhaust fluid valve; and a plurality of
threshold monitors for initiating a catalyst regeneration.
15. The system of claim 14 further comprising a diesel particulate
filter (DPF).
16. The system of claim 14 wherein the catalyst comprises a DOC,
SCR, or AMO.sub.x catalyst.
17. The system of claim 14 wherein the threshold monitors comprise
a timing device, a sulphur estimator, a catalyst efficiency
monitor, or a humidity monitor.
18. The system of claim 14 wherein the catalyst regeneration
comprises heating the system to a temperature of at least
200.degree. C.
19. An engine system comprising: an engine; and a catalyst system
coupled to the engine; wherein the catalyst system comprises a
catalyst; a diesel exhaust fluid valve; and a plurality of
threshold monitors for initiating a catalyst regeneration.
20. The engine system of claim 19 further comprising a diesel
particulate filter (DPF).
Description
FIELD OF THE INVENTION
[0001] The present invention relates generally to diesel engines
and more specifically to improving the robustness of aftertreatment
systems of diesel engines.
BACKGROUND OF THE INVENTION
[0002] Diesel engines are known to emit pollutants such as sulphur,
nitrous oxide (NO.sub.x), particulate matter, and unburned
hydrocarbons. Despite new technologies and modern electronic
control devices that aid in reducing engine-out exhaust emissions,
these pollutants remain a subject of concern. In addition to
adversely affecting the environment, these contaminants also hinder
the overall performance of the diesel engine aftertreatment systems
they are linked with. The most commonly used catalytic converter in
today's modern diesel engines is the Diesel Oxidation Catalyst
(DOC), which uses oxygen (O.sub.2) in the exhaust gas stream to
convert carbon monoxide (CO) and unburned hydrocarbons to water and
to carbon dioxide (CO.sub.2). The DOC however, does not effectively
treat the nitrous oxide (NO.sub.x) emissions from the diesel
engines.
[0003] In addition to the DOC, selective catalytic reduction
converter (SCR) and ammonia oxidation (AMO.sub.x) catalysts are
both copper-zeolite and iron-zeolite based catalysts used in diesel
engine aftertreatment systems which decrease NO.sub.x and ammonia
(NH.sub.3) emissions to help achieve near-zero emissions standards.
However, a loss in oxidation functionality of the SCR and AMO.sub.x
catalysts often leads to a decrease in the intended catalyst
functions. The loss of catalysts' oxidation functionality, can some
times be linked to long idling periods of the diesel engine, or
exposure of the catalyst to ambient conditions for extended periods
of time.
[0004] The decrease in the catalyst's oxidation functionality (also
referred to as catalyst degradation) can adversely impact the
performance of the diesel engine aftertreatment system. For
example, in the SCR catalyst, a decrease in oxidation functionality
would lead to a decrease in the catalyst's ability to convert
NO.sub.x to NO.sub.2 and to adsorbed nitrogen oxides and also a
decrease in the catalyst's ability to convert unburned hydrocarbons
to CO.sub.2. The AMO.sub.x and DOC catalysts would be similarly
affected since each of these catalysts often have zeolite-based
components in its formulation. Therefore, the SCR, DOC, and
AMO.sub.x catalysts having copper-zeolite- or iron-zeolite based
catalysts that would experience a decline in the aftertreatment
system's feed gas quality while experiencing an increase in the
diesel exhaust emissions output. Each of these undesired affects
result from a loss of oxidation functionality of the copper-zeolite
or iron-zeolite catalysts.
[0005] Accordingly, what is needed is a system and method of
regenerating diesel engine aftertreatment catalysts in an internal
combustion engine.
SUMMARY OF THE INVENTION
[0006] The present invention satisfies this need, and presents a
method and system for treating a catalyst in an internal combustion
engine. To achieve the above object, the present method is
described as detecting the efficiency of a catalyst; sending the
catalyst efficiency to a threshold monitor; and heating the
catalyst when the detected catalyst efficiency is below a
predetermined percentage.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIG. 1 is an illustration of a typical diesel engine
aftertreatment system 10.
[0008] FIG. 2 is a graphical illustration of an SCR model-based
treatment of sulphur on an SCR catalyst.
[0009] FIG. 3 is a graphical illustration of the adsorption of
sulphur entering the SCR.
[0010] FIG. 4 illustrates nitric oxide (NO.sub.x) oxidation to
nitrogen dioxide (NO.sub.2).
[0011] FIG. 5 illustrates NO.sub.x conversion of a copper-zeolite
SCR catalyst in a selected temperature region.
[0012] FIG. 6 illustrates the logic flow for the proposed
deSO.sub.x controller.
[0013] FIG. 7 illustrates a feedforward block diagram of a proposed
deSO.sub.x controller 700 for use in a diesel engine aftertreatment
system.
[0014] FIG. 8 illustrates a feedforward block diagram of a proposed
desorb controller for use in a diesel engine aftertreatment
system.
DETAILED DESCRIPTION
[0015] The present invention relates generally to diesel fuel
engines and more specifically to the improved robustness of
aftertreatment catalysts.
[0016] The following description is presented to enable one of
ordinary skill in the art to make and use the invention and is
provided in the context of a patent application and its
requirements. Various modifications to the preferred embodiment and
the generic principles and features described herein will be
readily apparent to those skilled in the art. Thus, the present
invention is not intended to be limited to the embodiment shown but
is to be accorded the widest scope consistent with the principles
and features described herein.
[0017] A method and system in accordance with the present invention
improves the robustness of Cu-zeolite aftertreatment catalysts by
using a controller for predictive and corrective actions, and also
to detect and remove poisoning species from aftertreatment
catalysts.
[0018] FIG. 1 is an illustration of a typical diesel engine
aftertreatment system 10. The aftertreatment system 10 includes a
DOC catalyst 12, an SCR catalyst 14, an AMO.sub.x catalyst 16, a
diesel particulate filter (DPF) 18, and a diesel exhaust fluid
valve 20. In some diesel engine aftertreatment systems, a DPF 18 is
not utilized, which makes the overall system 10 more susceptible to
sulphur, humidity, and other contaminants which would otherwise be
prevented from entering the SCR catalyst 14. In addition, non-DPF
diesel aftertreatment engines have greater reliance on the DOC
catalyst 12 to provide the NO.sub.2/NO.sub.X ratios for the
aftertreatment system 10 to adhere to the emissions design target.
As discussed above, there are several contaminants which can
adversely impact the aftertreatment system 10 including humidity,
sulphur, and unburned hydrocarbons.
[0019] FIG. 2 is a graphical illustration of an SCR model-based
treatment of sulphur on an SCR catalyst although sulphur is
described as the contaminant, one of ordinary skill in the art
recognizes that other contaminants such as humidity and unburned
hydrocarbons could be present and addressed in a similar manner. In
the SCR model 200, temperature 202 is an input variable. Sulphur
204 is an inlet gas feed measured in kg/s. The stored sulphur 206
is an output of the SCR model 200. The outlet rate 208 is the rate
at which the sulphur is removed (desorbed) from the SCR model 200
and is measured in kg/s. The SCR model 200 shows that the storage
capacity 210 (y-axis) and the outlet rate 208 are both a function
of temperature. For example, the higher temperatures of 400.degree.
C. and 600.degree. C. show a lower storage capacity 210 (y-axis)
and a faster rate of sulphur removal (illustrated by the
incrementally larger control valves) than the 200.degree. C.
temperature.
[0020] FIG. 3 is a graphical illustration of the normalized
adsorption of sulphur entering the SCR catalyst as a function of
normalized pre-stored sulfur on the catalyst. The curve 300
depicted in FIG. 3 illustrates that the sulphur entering the SCR is
adsorbed (300) exponentially depending on the amount of sulfur
already present on the SCR catalyst. As discussed above in FIG. 2,
sulphur is a contaminant which adversely impacts the diesel engine
aftertreatment system 10. Humidity is described as another example
of a contaminant which adversely impacts the diesel engine
aftertreatment system 10.
[0021] FIG. 4 illustrates nitric oxide (NO.sub.x) oxidation at
selected temperatures on an SCR catalyst. Unused copper-zeolite
catalysts oxidation functionality (dotted curve) can be increased
(solid curve) by treating the catalyst to high temperatures, such
as 650.degree. C. In addition, further exposure of the 650.degree.
C. which currently has active oxidation functionality (solid
curve), to humidity at low temperatures such as 80.degree. C.,
decreases the Cu-zeolite oxidation ability (dashed curve). Finally,
the oxidation functionality change (dotted curve) is reversible
where the degrade Cu-zeolite is treated at high temperatures such
as 650.degree. C., which fully recovered the oxidation performance
(dashed curve) of the Cu-zeolite catalyst.
[0022] FIG. 5 illustrates NO.sub.x conversion with NH3 reductant on
a copper-zeolite SCR catalyst in a selected temperature region. The
Cu-zeolite catalyst lost its oxidation functionality due to
extended periods of storage under ambient conditions, humidity
exposure, or due to long idling conditions. Accordingly, the
performance of the Cu-zeolite catalyst decreases in the case of the
SCR reactions such asNOx reduction with NH3 (dotted curve) and NH3
oxidation reaction in the case of AMOx catalyst (not shown).
Finally, the NO.sub.x conversion of the degraded Cu-zeolite
catalyst can be recovered by high temperature treatment such as
600.degree. C. (solid curve and dashed curve). Cu-zeolite catalyst
regeneration can be achieved through various means of auxiliary or
engine management techniques.
[0023] FIG. 6 illustrates the logic flow for the proposed
deSO.sub.x controller 600. A deSO.sub.x is a thermal event where
the engine control levers (not shown) are manipulated to achieve a
catalyst temperature of approximately 550.degree. C. or above. The
engine control levers are activated by one of three triggers: a
contaminant load trigger 602, a timer-based trigger 604, or a
catalyst efficiencybased trigger 606. The contaminant load trigger
602 is activated when the amount of sulphur estimated by the model
exceeds a predetermined threshold. The timer-based trigger 604 is
activated when a predetermined time occurs. The catalyst efficiency
trigger 606 is activated when a drop in the catalyst's efficiency
is noted by the catalyst monitor (not shown). Long exposure of the
catalysts to low temperatures for example ambient conditions or
extended periods of idling could lead to poisoning of the
catalysts, for example Cu-zeolite. As illustrated with FIG. 4 and
FIG. 5, poisons arising from humidity cause loss of oxidation
function and could also lead to loss of NOx conversion efficiency.
A controller, similar to the one described in FIG. 6, that work
based on humidity contaminant load trigger, for example idling
time, timer based trigger and performance based trigger.
[0024] FIG. 7 illustrates a feedforward block diagram of a proposed
deSO.sub.x controller 700 for use in a diesel engine aftertreatment
system 10'. In this instance, sulphur is the contaminant to be
removed by the aftertreatment system 10'. The proposed deSO.sub.x
controller 700 comprises a DOC catalyst 12', an SCR catalyst 14'
and an AMO.sub.x catalyst 16'. First, engine-out sulphur 702 at a
predetermined temperature setpoint enters the DOC storage
estimator. In step 704, the amount of stored sulphur is calculated
as a function of the inlet exhaust temperature and mass flow rate.
The stored sulphur is then sent to the DOC release estimator in
step 706, which calculates the amount of sulphur released based on
the stored sulphur from 704, and also temperature, and timing
variables.
[0025] Next, in step 708, the amount of accumulated sulphur is
calculated as the difference between the sulphur stored (via step
704) and the amount of sulphur released (via step 706). The
accumulated sulphur from step 708 is then sent to the threshold
comparator via step 710, and is also the input variable 711 for the
SCR storage estimator in step 714. In step 710, the threshold
comparator compares the accumulated sulphur to a predetermined
threshold that is based upon NO.sub.2/NO.sub.x. The output of the
threshold comparator in step 710 is then sent to the deSO.sub.x
threshold monitor 712. In step 714, the inlet sulphur's temperature
and mass flow rate are utilized by the SCR storage estimator to
calculate stored sulphur, which is then sent to the SCR release
estimator via step 716. In step 716, the SCR release estimator
calculates the amount of sulphur released as a function of
temperature, storage, and timing variables. The sulphur released in
step 716 is then sent to step 718. In step 718, the amount of
accumulated sulphur is calculated as the difference between the
stored sulphur from step 714 and the released sulphur from step
716. The accumulated sulphur from step 718 is then sent to a
threshold comparator via step 720, and is also the input variable
721 for the AMO.sub.x storage estimator in step 722. In step 720,
the threshold comparator compares the accumulated sulphur to a
predetermined threshold that is based on SCR catalyst efficiency.
The output of the threshold comparator in step 720 is then sent to
the deSOx threshold monitor 712. Note that for aftertreatment
systems that do include a DPF, a suitable block needs to be
included to accommodate the storage, release dynamics of sulphur on
the DPF. The basic structure of the DPF block would remain the same
as that of the DOC or the SCR ones.
[0026] Next, in step 722, the AMO.sub.x storage estimator
calculates the amount of sulphur stored as a function of the inlet
sulphur temperature, and the mass flow rate. The stored sulphur
from step 722 is then sent to step 724, where the AMO.sub.x release
estimator calculates the amount of sulphur released as a function
of stored sulphur (from step 722), temperature, and timing
variables. The sulphur released from step 724 is then sent to step
726, where the accumulated sulphur is calculated as the difference
between the stored sulphur from step 722, and the sulphur released
from step 724. The accumulated sulphur of step 726 is then output
as system-out sulphur 728, and secondly, the accumulated sulphur of
step 726 is also input to the threshold comparator in step 730,
which compares the accumulated sulphur to a predetermined threshold
based upon performance of the AMO.sub.x catalyst.
[0027] FIG. 8 illustrates a feedforward block diagram of a proposed
desorb controller 800 for use in a diesel engine aftertreatment
system 10' without a DPF. In this instance, unburned hydrocarbons
is the contaminant to be removed by the aftertreatment system 10'.
The proposed desorb controller 800 comprises a DOC catalyst 12',
and SCR catalyst 14' and an AMO.sub.x catalyst 16'. First,
engine-out hydrocarbon 802 at a predetermined temperature setpoint
enters the DOC storage estimator. In step 804, the amount of stored
hydrocarbon is calculated as a function of the inlet hydrocarbon's
temperature and mass flow rate. The stored hydrocarbon is then sent
to the DOC release estimator in step 806, which calculates the
amount of hydrocarbon released based on the stored hydrocarbon from
804, and also temperature, and timing variables.
[0028] Next, in step 808, the amount of accumulated hydrocarbon is
calculated as the difference between the hydrocarbon stored (via
step 804) and the amount of hydrocarbon released (via step 806).
The accumulated hydrocarbon from step 808 is then sent to the
threshold comparator in step 810, and is also the input variable
811 for the SCR storage estimator in step 814. In step 810, the
threshold comparator compares the accumulated hydrocarbon to a
predetermined threshold that is based upon NO.sub.2/NO.sub.x. The
output of the threshold comparator in step 810 is then sent to the
desorb threshold monitor 812. In step 814, the inlet hydrocarbon's
temperature and mass flow rate are utilized by the SCR storage
estimator to calculate stored hydrocarbon, which is then sent to
the SCR release estimator via step 816. In step 816, the SCR
release estimator calculates the amount of hydrocarbon release as a
function of temperature, storage, and timing variables. The
hydrocarbon released in step 816 is then sent to step 818. In step
818, the amount of accumulated hydrocarbon is calculated as the
difference between the stored hydrocarbon from step 814 and the
released hydrocarbon from step 816. The accumulated hydrocarbon
from step 818 is then sent to a threshold comparator via step 820,
and is also the input variable 821 for the AMO.sub.x storage
estimator in step 822. In step 820, the threshold comparator
compares the accumulated hydrocarbon to a predetermined threshold
that is based on SCR catalyst efficiency. The output of the
threshold comparator in step 820 is then sent to the desorb
threshold monitor 812, and is also the input variable 821 for the
AMO.sub.x storage estimator.
[0029] Next, in step 822, AMO.sub.x storage estimator calculates
the amount of hydrocarbon stored as a function of temperature, and
mass flow rate. The stored hydrocarbon from step 822 is then sent
to step 824, where the AMO.sub.x release estimator calculates the
amount of hydrocarbon released as a function of temperature,
storage, and time. The released hydrocarbon in step 824 is then
sent to step 826, where the accumulated hydrocarbon is calculated
as the difference between the stored hydrocarbon from step 822, and
the hydrocarbon released from step 824. In addition, the
hydrocarbon released in step 824 also goes to the exotherm
predictor in step 827. The accumulated hydrocarbon of step 826 is
then output as system-out unburned hydrocarbon via step 830, and
secondly, the accumulated hydrocarbon of step 826 is then input to
the threshold comparator in 832, which compares the accumulated
hydrocarbon to a predetermined threshold based upon performance of
the AMO.sub.x catalyst.
[0030] One advantage of a system and method in accordance with the
present invention is that the system robustness is improved due to
the predictive and corrective actions produced by the proposed
controller.
[0031] A second advantage of a system and method in accordance with
the present invention is that the proposed controller enables the
virtual sensing of the catalyst poisons, which allows for removal
of the poisons from the aftertreatment system.
[0032] A third advantage of a system and method in accordance with
the present invention is that the proposed controller works
complementary to the existing sensor set currently available within
the existing architecture of a diesel engine.
[0033] Although the present invention has been described in
accordance with the embodiments shown, one of ordinary skill in the
art will readily recognize that there could be variations to the
embodiments and those variations would be within the spirit and
scope of the present invention. Accordingly, many modifications may
be made by one or ordinary skill in the art without departing from
the spirit and scope of the appended claims.
* * * * *