U.S. patent application number 11/262669 was filed with the patent office on 2007-05-03 for method and apparatus for emissions trap regeneration.
This patent application is currently assigned to Arvin Technologies, Inc.. Invention is credited to Samuel N. JR. Crane, Navin Khadiya.
Application Number | 20070095053 11/262669 |
Document ID | / |
Family ID | 37994520 |
Filed Date | 2007-05-03 |
United States Patent
Application |
20070095053 |
Kind Code |
A1 |
Crane; Samuel N. JR. ; et
al. |
May 3, 2007 |
Method and apparatus for emissions trap regeneration
Abstract
An apparatus comprises an emissions trap and a trap regenerator
fluidly coupled to the emissions trap to advance a regenerative
agent thereto to regenerate the emissions trap. The trap
regenerator is configured to change a concentration of the
regenerative agent advanced to the emissions trap from a first
trap-regenerating level to a second trap-regenerating level
different from the first trap-regenerating level. An associated
method is disclosed.
Inventors: |
Crane; Samuel N. JR.;
(Columbus, IN) ; Khadiya; Navin; (Columbus,
IN) |
Correspondence
Address: |
BARNES & THORNBURG LLP
11 SOUTH MERIDIAN
INDIANAPOLIS
IN
46204
US
|
Assignee: |
Arvin Technologies, Inc.
|
Family ID: |
37994520 |
Appl. No.: |
11/262669 |
Filed: |
October 31, 2005 |
Current U.S.
Class: |
60/295 ; 60/285;
60/286 |
Current CPC
Class: |
F01N 13/011 20140603;
F01N 3/0842 20130101; F01N 2240/30 20130101; F02D 41/0275 20130101;
F02D 41/0035 20130101; F02D 41/027 20130101; F01N 3/0828 20130101;
F01N 3/0871 20130101; F01N 3/085 20130101; F01N 3/0878
20130101 |
Class at
Publication: |
060/295 ;
060/285; 060/286 |
International
Class: |
F01N 3/00 20060101
F01N003/00 |
Claims
1. A method of regenerating an emissions trap, comprising the steps
of: advancing a regenerative agent to the emissions trap for a
first predetermined period of time, and changing a concentration of
the regenerative agent advanced to the emissions trap in response
to expiration of the first predetermined period of time, the
concentration of the regenerative agent changing from a first
trap-regenerating level to a second trap-regenerating level
different from the first trap-regenerating level.
2. The method of claim 1, wherein: the regenerative agent has an
air-to-fuel ratio, and the changing step comprises changing the
air-to-fuel ratio from the first trap-regenerating level to the
second trap-regenerating level.
3. The method of claim 2, wherein: the first trap-regenerating
level is fuel rich and the second trap-regenerating level is more
fuel-rich than the first trap-regenerating level, and the advancing
step comprises advancing to the emissions trap the regenerative
agent with the first trap-regenerating level for the first
predetermined period of time and then advancing to the emissions
trap the regenerative agent with the second trap-regenerating level
for a second predetermined period of time.
4. The method of claim 1, wherein the advancing step comprises
advancing to the emissions trap the regenerative agent with the
first trap-regenerating level for the first predetermined period of
time and then advancing to the emissions trap the regenerative
agent with the second trap-regenerating level for a second
predetermined period of time, further comprising releasing
emissions trapped by the emissions trap at a first release rate
during the first predetermined period of time and releasing
emissions trapped by the emissions trap at a second release rate
faster than the first release rate during the second predetermined
period of time.
5. The method of claim 1, wherein: the emissions trap is a NOx
trap, the advancing step comprises advancing the first regenerative
agent to the NOx trap, and the changing step comprises changing the
concentration of the regenerative agent advanced to the NOx trap
from the first trap-regenerating level to the second
trap-regenerating level.
6. The method of claim 1, wherein the changing step comprises
varying the position of an exhaust valve.
7. The method of claim 1, wherein the changing step comprises
varying operation of a fuel reformer.
8. The method of claim 1, wherein the changing step comprises
varying flow of air or fuel to an engine.
9. An apparatus, comprising; a first emissions trap, and a trap
regenerator fluidly coupled to the first emissions trap to advance
a regenerative agent thereto in response to expiration of a first
predetermined amount of time to regenerate the first emissions
trap, the trap regenerator configured to change a concentration of
the regenerative agent advanced to the first emissions trap from a
first trap-regenerating level to a second trap-regenerating level
different from the first trap-regenerating level.
10. The apparatus of claim 9, wherein: the regenerative agent has
an air-to-fuel ratio, and the trap regenerator is configured to
change the air-to-fuel ratio of the regenerative agent advanced to
the first emissions trap from the first trap-regenerating level to
the second trap-regenerating level.
11. The apparatus of claim 10, wherein: the first trap-regenerating
level is fuel-rich and the second trap-regenerating level is more
fuel-rich than the first trap-regenerating level, and the trap
regenerator is configured to provide the first trap-regenerating
level to the first emissions trap during the first predetermined
period of time and to provide the second trap-regenerating level to
the first emissions trap during a second predetermined period of
time subsequent to the first predetermined period of time.
12. The apparatus of claim 9, further comprising a second emissions
trap flow-parallel to the first emissions trap, wherein: the trap
regenerator is fluidly coupled to the second emissions trap to
advance the regenerative agent thereto to regenerate the second
emissions trap, and the trap regenerator is configured to change
the concentration of the regenerative agent advanced to the second
emissions trap from the first trap-regenerating level to the second
trap-regenerating level.
13. The apparatus of claim 9, wherein: the trap regenerator
comprises (i) at least one component configured to provide at least
a portion of the regenerative agent, and (ii) a controller
electrically coupled to the at least one component, the controller
comprising (i) a processor, and (ii) a memory device electrically
coupled to the processor, the memory device having stored therein a
plurality of instructions which, when executed by the processor,
cause the processor to: operate the at least one component in a
first mode establishing the first trap-regenerating level, and
operate the at least one component in a second mode establishing
the second trap-regenerating level.
14. The apparatus of claim 13, wherein the at least one component
comprises either (1) an air valve electrically coupled to the
controller and configured to control flow of air to an exhaust gas
producer, or (2) a fuel injector electrically coupled to the
controller and configured to control flow of fuel to an exhaust gas
producer.
15. The apparatus of claim 13, wherein the at least one component
comprises a fuel reformer electrically coupled to the
controller.
16. The apparatus of claim 13, wherein the at least one component
comprises a first exhaust valve electrically coupled to the
controller and configured to control flow of exhaust gas to the
first emissions trap.
17. The apparatus of claim 16, further comprising a second exhaust
valve electrically coupled to the controller, wherein the first
exhaust valve is positioned upstream from the first emissions trap
and the second exhaust valve is positioned downstream from the
first emissions trap.
18. The apparatus of claim 9, wherein the first emissions trap is a
NOx trap.
19. The apparatus of claim 9, wherein the first emissions trap is a
sulfur trap.
20. The apparatus of claim 9, wherein the first emissions trap is
an ammonia trap.
Description
FIELD OF THE DISCLOSURE
[0001] The present disclosure relates to methods and apparatus for
removal of emissions from exhaust gas.
BACKGROUND OF THE DISCLOSURE
[0002] There are emissions traps used to trap emissions in an
effort to prevent discharge of the emissions into the atmosphere.
From time to time, these traps need to be regenerated to remove the
emissions trapped thereby for further use of the traps.
SUMMARY OF THE DISCLOSURE
[0003] According to an aspect of the present disclosure, there is
provided an apparatus comprising an emissions trap and a trap
regenerator. The trap regenerator is fluidly coupled to the
emissions trap to advance a regenerative agent thereto to
regenerate the emissions trap. The trap regenerator is configured
to change a concentration of the regenerative agent advanced to the
emissions trap from a first trap-regenerating level to a second
trap-regenerating level different from the first trap-regenerating
level. In this way, the amount of emissions discharged into the
atmosphere can be reduced. An associated method is disclosed.
[0004] The emissions trap may be any one of a number of different
types of emissions traps. For example, the emissions trap may be
configured as a NOx (i.e., nitrogen oxides) trap, a sulfur trap,
and/or an ammonia trap, to name just a few.
[0005] The above and other features of the present disclosure will
become apparent from the following description and the attached
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 is a simplified block diagram showing a trap
regenerator for regenerating an emissions trap;
[0007] FIG. 2 is a simplified block diagram showing an exemplary
embodiment of the trap regenerator; and
[0008] FIG. 3 is a simplified block diagram showing another
exemplary embodiment of the trap regenerator.
DETAILED DESCRIPTION OF THE DRAWINGS
[0009] While the concepts of the present disclosure are susceptible
to various modifications and alternative forms, specific exemplary
embodiments thereof have been shown by way of example in the
drawings and will herein be described in detail. It should be
understood, however, that there is no intent to limit the
disclosure to the particular forms disclosed, but on the contrary,
the intention is to cover all modifications, equivalents, and
alternatives following within the spirit and scope of the invention
as defined by the appended claims.
[0010] Referring to FIG. 1, there is shown an apparatus 10
comprising an emissions trap 12 configured to trap emissions
present in an exhaust system associated with a producer of exhaust
gas ("EG" in the drawings) such as an internal combustion engine
14. From time to time, the emissions trap 12 needs to be
regenerated so as to remove the trapped emissions therefrom for
further use of the trap 12. To do so, there is a trap regenerator
16 fluidly coupled to the emissions trap 12 to advance a
regenerative agent thereto to regenerate the emissions trap 12. The
trap regenerator 16 is configured to change a concentration of the
regenerative agent advanced to the emissions trap 12 from a first
trap-regenerating level to a second trap-regenerating level
different from the first trap-regenerating level. In doing so, the
amount of emissions discharged into the atmosphere can be reduced
as discussed in more detail below.
[0011] It is believed that trap regeneration may be a two-step
process involving (1) release of emissions from the trap 12 (i.e.,
desorption), and (2) conversion of the released emissions to a more
environmentally acceptable form. In some cases, the conversion rate
may occur more slowly than the release rate at least for some
initial period of time during trap regeneration. In such a case,
this could result in undesirable spikes in the amount of
unconverted emissions discharged into the atmosphere.
[0012] To address this issue, the trap regenerator 16 may be
operated to slow the release rate during this initial period of
time. In particular, the trap regenerator 16 may be operated to
provide the first trap-regenerating level to the trap 12 during a
first period of time and the second-trap regenerating level to the
trap 12 during a second period of time subsequent to (e.g.,
immediately or shortly after) the first period of time, the first
and second trap-regenerating levels being selected so that the
release rate during the first period of time is slower than the
release rate during the second period of time. Upon expiration of
the first period of time, the conversion rate is able to "handle"
the faster release rate of the second period of time, thereby
allowing an increase in the overall speed of trap regeneration
during the second period of time.
[0013] Illustratively, the trap regenerator 16 comprises at least
one component 18 configured to provide at least a portion of the
regenerative agent and an electronic controller 20 electrically
coupled to the at least one component 18. The controller comprises
a processor 22 and a memory device 24 electrically coupled to the
processor 22. The memory device 24 has stored therein a plurality
of instructions which, when executed by the processor 22, cause the
processor 22 to operate the at least one component 18 in a first
mode establishing the first trap-regenerating level, and operate
the at least one component 18 in a second mode establishing the
second trap-regenerating level.
[0014] The emissions trap 12 may be embodied as any number of
different types of emissions traps. For example, the trap 12 may
be, but is not limited to, a NOx trap for trapping NOx present in
exhaust gas of the engine 14, a sulfur trap for trapping sulfur
(e.g., in the form of SOx, sulfur oxides) present in the exhaust
gas, and/or an ammonia trap for trapping ammonia that may have been
introduced into the exhaust gas to facilitate reduction of NOx at a
selective catalytic reduction device.
[0015] A fuel-rich environment may be created about the emissions
trap 12 to regenerate the trap 12. This is particularly useful
where the emissions trap 12 includes a NOx trap, a sulfur trap,
and/or an ammonia trap. As such, the regenerative agent may have an
air-to-fuel ratio and the trap regenerator 16 may change the
air-to-fuel ratio from the first trap-regenerating level to the
second trap-regenerating level, both trap-regenerating levels being
fuel-rich. To change the air-to-fuel ratio from the first
trap-regenerating level to the second trap-regenerating level, the
amount of exhaust gas (which contains O.sub.2) and/or fuel supplied
to the trap 12 can be varied in a variety of ways (discussed in
more detail below). What is meant herein by the term "fuel-rich" is
that the air-to-fuel ratio is less than the stoichiometric
air-to-fuel ratio of the fuel (stated quantitatively, the lambda
value of a fuel-rich mixture is less than 1.0).
[0016] Considering for a moment the particular case where the trap
12 is a NOx trap, it is believed that NOx-trap regeneration is a
two-step process involving (1) release of NOx from the trap 12
(i.e., NOx desorption), and (2) chemical reduction of the released
NOx to N.sub.2 by a NOx reductant of the regenerative agent. During
NOx trap regeneration, NOx is released from the surface nitrate
storage sites faster than it is initially reduced to N.sub.2 by
reaction with the reductant, which, in some cases, may result in
spikes in the amount of NOx discharged to the atmosphere. As such,
the trap regenerator 16 may be operated so that, although both
trap-regenerating levels is fuel-rich to effect NOx reduction, the
first trap-regenerating level is less fuel-rich than the second
trap-regenerating levels. As a result, the NOx-release rate is
slower during the first period of time than during the second
period of time, allowing the NOx-reduction rate time to increase to
an amount to handle the increased NOx-release rate of the second
period of time. In this way, the amount of NOx discharged into the
atmosphere during a trap regeneration event can be reduced.
[0017] Referring to FIG. 2, the trap regenerator 16 may be embodied
as the trap regenerator 116. The regenerator 1 16 comprises the
controller 20 that controls operation of one or more of the
components illustrated in FIG. 2 to change the concentration, or
more particularly the air-to-fuel ratio, of the regenerative agent
advanced to the trap 12 from the first trap-regenerating level to
the second trap-regenerating level.
[0018] Illustratively, the regenerator 116 may include an air valve
26, a fuel injector 28, and/or a fuel reformer 30 electrically
coupled to and under the control of the controller 20 to change the
air-to-fuel ratio of the regenerative agent supplied to the trap
12. The controller 20 may be electrically coupled to the air valve
26, the fuel injector 28, and the fuel reformer 30 via electrical
lines 32, 34, and 36, respectively.
[0019] The air valve 26 may be, for example, the throttle valve
that controls the amount of air introduced into the engine 14. In
such a case, the position of the air valve 26 may be varied to
change the amount of 02 in, and thus the air-to-fuel ratio of, the
exhaust gas that flows to the trap 12.
[0020] The fuel injector 28 may be, for example, one or more of the
fuel injectors that injects fuel into the engine 14. In such a
case, the position of the fuel injector 28 may be varied to change
the amount of fuel in, and thus the air-to-fuel ratio of, the
exhaust gas that flows the to the trap 12.
[0021] The fuel reformer 30 may be used to dose the exhaust gas
with a reformate gas comprising, for example, hydrogen (H.sub.2)
and/or carbon monoxide (CO) so as to change the air-to-fuel ratio
provided to the trap 12. In the case where the trap 12 is a NOx
trap, such fuel acts as a NOx reductant.
[0022] The air valve 26, the fuel injector 28, the fuel reformer
30, or any combination thereof may be included in the trap
regenerator 116 to change the air-to-fuel ratio of the regenerative
agent advanced to the trap 12.
[0023] Referring to FIG. 3, the trap regenerator 16 may be embodied
as the trap regenerator 216. The regenerator 216 comprises the
controller 20 which controls operation of one or more of the
components illustrated in FIG. 3 to change the concentration, or
more particular the air-to-fuel ratio, of the regenerative agent
advanced to the trap 12 from the first trap-regenerating level to
the second trap-regenerating level.
[0024] Illustratively, there are two emissions traps 12a and 12b
positioned in a dual-leg arrangement of the exhaust system. The
first trap 12a is positioned in a first leg 38 and the second trap
12b is positioned in a parallel second leg 40. As such, the traps
12a, 12b are flow-parallel to one another.
[0025] An exhaust valve arrangement is used to control flow of the
regenerative agent to the traps 12a, 12b. The regenerative agent
comprises exhaust gas from the engine 14, or more particularly the
O.sub.2 present therein, and a reformate gas (e.g., H.sub.2 and/or
CO) generated by the fuel reformer 30. In the case where the trap
12a or 12b is a NOx trap, the reformate gas acts as a NOx
reductant. The exhaust valve arrangement is thus configured to
control flow of the exhaust gas and the reformate gas to the traps
12a, 12b.
[0026] Illustratively, the exhaust valve arrangement comprises a
first exhaust valve 52, a second exhaust valve 54, and a third
exhaust valve 56. The first exhaust valve 52 is positioned upstream
from the traps 12a, 12b at an upstream junction of the legs 38, 40
so as to be able to control flow of exhaust gas and the agent
component to the traps 12a, 12b. The second exhaust valve 54 is
positioned in the first leg 38 downstream from the first trap 12a.
The third exhaust valve 56 is positioned in the second leg 40
downstream from the second trap 12b.
[0027] The controller 20 is electrically coupled to each valve 52,
54, 56 and the fuel reformer 30 via electrical lines 58, 60, 62,
36, respectively, to control operation of these components and thus
regeneration of the traps 12a, 12b. Normally, both traps 12a, 12b
are "on-line" such that they trap emissions present in exhaust gas
advanced through both traps 12a, 12b. To establish this
configuration, the first exhaust valve 52 is positioned to allow
exhaust gas to flow to both legs 38, 40 and each of the second and
third exhaust valves 54, 56 is opened the position shown in solid
in FIG. 3 to allow exhaust gas to flow freely therethrough. The
fuel reformer 30 is not operated when both traps 12a, 12b are
on-line.
[0028] As alluded to above, each trap 12a, 12b is regenerated in
two phases, the first phase occurring during a first period of time
and the second phase occurring during a second period of time
subsequent to the first period of time. In the first phase (i.e.,
during the first period of time), the first trap-regenerating level
is advanced to the trap 12a, 12b, and, in the second phase (i.e.,
during the second period of time), the second trap-regenerating
level is advanced to the trap 12a, 12b.
[0029] Each of the valves 52, 54, 56 allows a certain amount of
exhaust gas to leak past it even when it is "closed." More
particularly, the first exhaust valve 52 has a higher leakage rate
than each of the second and third exhaust valves 54, 56.
Exemplarily, the first exhaust valve 52 may allow about 3% leakage
when it assumes either the solid or phantom position shown in FIG.
3 and each of the second and third exhaust valves 54, 56 may allow
about 1% leakage when it assumes the solid position shown in FIG.
3. Such a difference in leakage rates facilitates establishment of
the first and second trap-regenerating levels during regeneration
of the traps 12a, 12b.
[0030] To regenerate the first trap 12a while the second trap 12b
remains on-line, the controller 20 signals the first exhaust valve
52 to move to the position shown in solid in FIG. 3 and signals the
fuel reformer 30 to produce the reformate gas. As such, the first
exhaust valve 52 directs most of the exhaust gas away from the
first leg 38 into the second leg 40, thereby taking the first trap
12a "off-line" while the second trap 12b remains on-line. The
controller 20 signals the third exhaust valve 56 to remain open in
the solid position of FIG. 3 to allow passage of reformate gas
supplied thereto to the first leg 38.
[0031] The controller 20 operates the second exhaust valve 54 to
establish the first and second trap-regenerating levels of the
first and second phases of trap regeneration. In particular, in the
first phase, the controller 20 signals the second exhaust valve 54
to assume its opened position shown in solid in FIG. 3. In this
way, the amount of leakage of exhaust gas into the first leg 38 is
established by the larger leakage rate of the first exhaust valve
52. The O.sub.2 of the leaked exhaust gas mixes with the reformate
gas from the fuel reformer 30 to provide the regenerative agent of
the first phase which has an air-to-fuel ratio at the first
trap-regenerating level. The trap 12a is thus exposed to the first
trap-regenerating level so as to reduce the amount of discharged to
the atmosphere during the first phase.
[0032] Upon expiration of the first period of time, the controller
20 signals the second exhaust valve 54 to assume its "closed"
position shown in phantom in FIG. 3 to commence the second phase.
In this way, the amount of leakage of exhaust gas into the first
leg 38 is established by the smaller leakage rate of the second
exhaust valve 52. As a result, less O.sub.2 enters the first leg 38
than in the first phase so that the regenerative agent becomes more
fuel-rich and the trap 12a is exposed to the second
trap-regenerating level.
[0033] A process similar to what has just been discussed in
connection with the regeneration of trap 12a may be used to
regenerate trap 12b. In particular, the controller 20 signals the
first exhaust valve to assume the position shown in phantom in FIG.
3 so as to direct most of the exhaust gas away from the second leg
40 to the first leg 38 and to direct reformate gas supplied by the
fuel reformer 30 to the second leg 40. In the first phase, the
controller 20 signals the third exhaust valve to assume its open
position shown in solid in FIG. 3 so that the exhaust gas leakage
rate into the second leg 40 is established by the larger leakage
rate of the first exhaust valve 52 to expose the second trap 12b to
the first trap-regenerating level. Upon expiration of the first
period of time, the controller 20 signals the third exhaust valve
56 to assume its "closed" position shown in phantom in FIG. 3 so
that the exhaust gas leakage rate into the second leg 40 is
established by the smaller leakage rate of the second exhaust valve
56 to expose the trap 12b to the second trap-regenerating
level.
[0034] In some embodiments, the second and third valves 54, 56 may
be eliminated. In such a case, the first exhaust valve 52 may be
variable in the sense that its position can be varied in small
amounts by the controller 20 so as to change the leakage rate of
exhaust gas into a leg 38, 40 from the higher leakage rate (e.g.,
3%) establishing the first trap-regenerating level to the lower
leakage rate (e.g., 1%) establishing the second trap-regenerating
level. The first exhaust valve 52 may be, for example, a
proportional valve. In other examples, a stepper motor or other
valve actuator may be used to vary the position of the valve 52 in
this way.
[0035] In other embodiments where the second and third valves 54,
56 have been eliminated, the controller 20 may vary operation of
the fuel reformer 30 while the first exhaust valve 52 remains
stationary. In other words, the amount of reformate gas may be
varied while the leakage rate of exhaust gas past the valve 52 is
generally fixed. In such a case, the fuel reformer 30 may be
operated to produce more reformate gas during the second phase than
during the first phase to establish the first trap-regenerating
level during the first phase and the more fuel-rich second
trap-regenerating level during the second phase. It is within the
scope of this disclosure to control the fuel-richness of the
regenerative agent by a combination of varying the leakage rate of
exhaust gas into the respective leg 38, 40 and varying the amount
of reformate gas supplied by the fuel reformer 30.
[0036] In still other embodiments, the second NOx trap 12b and the
third exhaust valve 56 may be eliminated from the apparatus. In
such a case, the second leg 40 may act simply as a bypass of the
first leg 38.
[0037] The fuel reformer 30 may be configured in a variety of ways.
For example, it may include a catalytic reformer and/or a plasma
fuel reformer. A catalytic reformer may be embodied as any of a
steam reformer catalyst, a partial oxidation catalyst, and/or a
water-shifting catalyst, to name just a few. A plasma fuel reformer
generates an electrical arc (i.e., a plasma) to initiate partial
oxidation of a fuel (e.g., diesel, gasoline) into reformate gas
including, for example, H.sub.2 and/or CO. In some cases, the fuel
reformer 30 may include a combination of a plasma fuel reformer and
a catalyst.
[0038] It is to be understood that the fuel reformer 30 may be
replaced by a fuel source in any of the regenerators 16, 116, 216.
As such, the fuel source may supply fuel (rather than reformate
gas) such as diesel fuel, gasoline, etc. for use in regeneration of
the traps.
[0039] The duration of the first period of time and the second
period of time may depend on a number of factors (e.g., trap
composition, final air-to-fuel ratio of interest). Exemplarily,
each of the first and second periods of time may be on the order of
1 to 5 seconds.
[0040] While the concepts of the present disclosure have been
illustrated and described in detail in the drawings and foregoing
description, such illustration and description is to be considered
as exemplary and not restrictive in character, it being understood
that only illustrative embodiments have been shown and described
and that all changes and modifications that come within the spirit
of the disclosure are desired to be protected.
[0041] There are a plurality of advantages of the concepts of the
present disclosure arising from the various features of the systems
described herein. It will be noted that alternative embodiments of
each of the systems of the present disclosure may not include all
of the features described yet still benefit from at least some of
the advantages of such features. Those of ordinary skill in the art
may readily devise their own implementations of a system that
incorporate one or more of the features of the present disclosure
and fall within the spirit and scope of the invention as defined by
the appended claims.
* * * * *