U.S. patent application number 11/373352 was filed with the patent office on 2006-09-14 for emission abatement systems and methods.
Invention is credited to Navin Khadiya.
Application Number | 20060201139 11/373352 |
Document ID | / |
Family ID | 36992264 |
Filed Date | 2006-09-14 |
United States Patent
Application |
20060201139 |
Kind Code |
A1 |
Khadiya; Navin |
September 14, 2006 |
Emission abatement systems and methods
Abstract
An emission abatement assembly includes a fuel reformer which
supplies reformate gas to a catalyst. Exhaust gas from an internal
combustion engine is advanced through the catalyst and into a
downstream SCR catalyst.
Inventors: |
Khadiya; Navin; (Columbus,
IN) |
Correspondence
Address: |
BARNES & THORNBURG
11 SOUTH MERIDIAN
INDIANAPOLIS
IN
46204
US
|
Family ID: |
36992264 |
Appl. No.: |
11/373352 |
Filed: |
March 10, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60660361 |
Mar 10, 2005 |
|
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|
Current U.S.
Class: |
60/286 ; 60/275;
60/301 |
Current CPC
Class: |
F01N 2240/28 20130101;
F01N 2610/03 20130101; F02M 27/042 20130101; F02M 25/12 20130101;
F01N 13/011 20140603; F01N 3/0842 20130101; F01N 2240/30 20130101;
F01N 3/0878 20130101; F01N 13/009 20140601; F01N 3/2073 20130101;
F01N 2410/12 20130101; F01N 2240/25 20130101; Y02T 10/12 20130101;
F01N 3/2066 20130101; F01N 3/035 20130101; F01N 3/0821 20130101;
F01N 2610/04 20130101; Y02T 10/24 20130101; Y02T 10/121 20130101;
F01N 2610/08 20130101 |
Class at
Publication: |
060/286 ;
060/275; 060/301 |
International
Class: |
F01N 3/00 20060101
F01N003/00; F01N 3/10 20060101 F01N003/10 |
Claims
1. An emission abatement assembly comprising: an ammonia-generating
catalyst positioned to receive exhaust gas from an internal
combustion engine, an SCR catalyst positioned downstream of the
ammonia-generating catalyst, and a fuel reformer configured to
generate a reformate gas comprising H.sub.2, the fuel reformer
being positioned to introduce the reformate gas into the
ammonia-generating catalyst.
2. The emission abatement assembly of claim 1, wherein the fuel
reformer comprises a plasma fuel reformer.
3. The emission abatement assembly of claim 1, further comprising
an oxidation catalyst positioned upstream of the ammonia-generating
catalyst.
4. The emission abatement assembly of claim 1, wherein the
ammonia-generating catalyst comprises platinum.
5. The emission abatement assembly of claim 1, wherein the
ammonia-generating catalyst comprises palladium.
6. The emission abatement assembly of claim 1, wherein: the
ammonia-generating catalyst is configured to utilize the reformate
gas from the fuel reformer to convert NO.sub.X to NH.sub.3 when the
temperature of the ammonia-generating catalyst is above a
predetermined value, and the ammonia-generating catalyst is
configured to utilize the reformate gas from the fuel reformer to
convert NO.sub.X to N.sub.2 when the temperature of the
ammonia-generating catalyst is below the predetermined value.
7. The emission abatement assembly of claim 6, wherein the SCR
catalyst is configured to utilize NH.sub.3 generated by the
ammonia-generating catalyst to convert NO.sub.X to N.sub.2.
8. The emission abatement assembly of claim 1, wherein the SCR
catalyst is configured to store NH.sub.3.
9. The emission abatement assembly of claim 1, wherein the
ammonia-generating catalyst is configured to store NO.sub.X.
10. A method of operating an emission abatement assembly, the
method comprising the steps of: operating a fuel reformer to
generate a reformate gas comprising H.sub.2, advancing exhaust gas
from an internal combustion engine and the reformate gas through an
ammonia-generating catalyst such that (i) a portion of the NO.sub.X
in the exhaust gas is converted into NH.sub.3 when the temperature
of the ammonia-generating catalyst is above a predetermined value,
and (ii) a portion of the NO.sub.X in the exhaust gas is converted
to N.sub.2 when the temperature of the ammonia-generating catalyst
is below the predetermined value, and advancing the exhaust gas
exiting the ammonia-generating catalyst through an SCR
catalyst.
11. The method of claim 10, further comprising the step of
converting NH.sub.3 and NO.sub.X into N.sub.2 in the SCR
catalyst.
12. The method of claim 10, further comprising the step of
advancing the exhaust gas and the reformate gas through an
oxidation catalyst prior to being introduced into the
ammonia-generating catalyst.
13. The method of claim 12, wherein the operating step comprises
operating the fuel reformer to generate a predetermined quantity of
the reformate gas such that exhaust gas exiting the
ammonia-generating catalyst has a predetermined ratio of NO.sub.X
and NH.sub.3.
14. A method of operating an emission abatement assembly, the
method comprising the steps of: advancing exhaust gas and a
reformate gas comprising H.sub.2 from a fuel reformer into a
ammonia-generating catalyst, generating NH.sub.3 with the
ammonia-generating catalyst when the temperature of the
ammonia-generating catalyst is above a predetermined value,
generating N.sub.2 with the ammonia-generating catalyst when the
temperature of the ammonia-generating catalyst is below the
predetermined value, and advancing the exhaust gas out of the
ammonia-generating catalyst and through an SCR catalyst.
15. The method of claim 14, further comprising the step of
advancing the exhaust gas and the reformate gas through an
oxidation catalyst prior to introduction into the
ammonia-generating catalyst.
16. The method of claim 14, further comprising the step of
converting NH.sub.3 and NO.sub.X into N.sub.2 with the SCR
catalyst.
17. An emission abatement assembly comprising: an
ammonia-generating catalyst positioned in a first parallel flow
path, a fuel reformer positioned to supply a reformate gas
comprising H.sub.2 to the ammonia-generating catalyst, an oxidation
catalyst positioned upstream of a point which splits an exhaust
flow of an internal combustion engine into the first parallel flow
path and a second parallel flow path which bypasses the first
parallel flow path, and an SCR catalyst positioned downstream of a
point which recombines the first parallel flow path and the second
parallel flow path.
18. The assembly of claim 17, wherein the fuel reformer comprises a
plasma fuel reformer.
19. The assembly of claim 17, further comprising a flow diverter
valve operable to divert the exhaust gas flow between the first
parallel flow path and the second parallel flow path.
20. A method of operating an emission abatement assembly, the
method comprising the steps of: advancing exhaust gas from an
internal combustion engine through an oxidation catalyst, splitting
the exhaust gas downstream of the oxidation catalyst into (i) a
first flow of exhaust gas which is advanced through a first
parallel flow path, and (ii) a second flow of exhaust gas which is
advanced through a second parallel flow path which bypasses the
first flow path, advancing the first flow of exhaust gas and a
reformate gas comprising H.sub.2 from a fuel reformer through an
ammonia-generating catalyst positioned in the first parallel flow
path, recombining the first flow of exhaust gas and the second flow
of exhaust gas, and advancing the exhaust gas through an SCR
catalyst subsequent to the recombining step.
21. The method of claim 20, wherein the splitting step comprises
operating a flow diverter valve to divert the exhaust gas into the
first parallel flow path and the second parallel flow path.
Description
[0001] This application claims priority under 35 U.S.C. .sctn.
119(e) to U.S. Provisional Patent Application Serial No.
60/660,361, entitled "Emission Abatement Systems and Methods" filed
on Mar. 10, 2005 by Navin Khadiya, Samuel N. Crane, Jr., and Robert
Iverson, the entirety of which is hereby incorporated by
reference.
FIELD OF THE DISCLOSURE
[0002] The present disclosure relates to generally to emission
abatement systems for internal combustion engines.
BACKGROUND
[0003] Plasma fuel reformers reform hydrocarbon fuel into a
reformate gas such as hydrogen-rich gas. In the case of a plasma
fuel reformer onboard a vehicle or stationary power generator, the
reformate gas produced by the reformer may be utilized as fuel or
fuel additive in the operation of an internal combustion engine.
The reformate gas may also be utilized to regenerate or otherwise
condition an emission abatement device associated with the internal
combustion engine (e.g., a NO.sub.X trap, particulate filter, or
SCR catalyst). The reformate gas may also be used as a fuel for a
fuel cell.
SUMMARY
[0004] According to one aspect of the present disclosure, an
emission abatement assembly includes a pair of NO.sub.X traps
arranged in a parallel arrangement. The NO.sub.X traps are operated
in tandem such that both traps are online (i.e., absorbing
NO.sub.X) during operation of the engine. Periodically, one of the
traps is taken offline for regeneration.
[0005] According to another aspect of the disclosure, an emission
abatement assembly includes a catalyst positioned upstream of a
urea SCR catalyst. Hydrogen from a fuel reformer is advanced into
the upstream catalyst. At operating temperatures below a
predetermined temperature, NO.sub.X is converted by the upstream
catalyst into N.sub.2 in a similar manner as a H-SCR catalyst. At
operating temperatures above the predetermined temperature, the
upstream catalyst converts some of the NO.sub.X in the exhaust gas
into NH.sub.3. The NH.sub.3 is advanced, along with the remaining
NO.sub.X in the exhaust gas, into the SCR catalyst wherein it
functions as a reductant fluid to covert the remaining NO.sub.X
into N.sub.2.
[0006] In certain embodiments, the upstream catalyst is embodied as
two separate catalysts--an oxidation catalyst, such as a diesel
oxidation catalyst, and an ammonia generating catalyst.
[0007] In certain embodiments, the ammonia generating catalyst is
positioned in a parallel flow path with a portion of the engine
exhaust gas bypassing the ammonia generating catalyst through a
second parallel flow path.
[0008] According to yet another aspect of the disclosure, a plasma
fuel reformer is operated to generate oxygenated hydrocarbons. The
oxygenated hydrocarbons are supplied to the intake of an internal
combustion engine such as an HCCI engine.
[0009] 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
[0010] FIG. 1 is a simplified block diagram of a fuel reforming
assembly having a plasma fuel reformer under the control of an
electronic control unit;
[0011] FIG. 2 is a diagrammatic cross sectional view of the plasma
fuel reformer of FIG. 1;
[0012] FIG. 3 is a simplified block diagram of an emission
abatement assembly;
[0013] FIG. 4 is a timing graph of a trap regenerating scheme;
[0014] FIG. 5 is a fragmentary perspective view of a diverter
valve;
[0015] FIGS. 6-8 are simplified diagrammatic views of the diverter
valve of FIG. 5 showing the valve in various valve positions;
[0016] FIGS. 9 and 10 are simplified block diagrams of another
emission abatement assembly;
[0017] FIGS. 11-15 are simplified block diagrams of systems for
generating oxygenated hydrocarbons by use of a fuel reformer;
[0018] FIGS. 16 and 17 are simplified block diagrams of an emission
abatement assembly that is similar to the assemblies of FIGS. 9 and
10; and
[0019] FIG. 18 is a simplified diagram similar of an emission
abatement assembly that is similar to the assembly of FIGS. 16 and
17.
DETAILED DESCRIPTION OF THE DRAWINGS
[0020] As will herein be described in more detail, a fuel reformer,
according to the concepts of the present disclosure, may be
utilized to regenerate or otherwise condition an emission abatement
assembly. For example, a fuel reformer may be operated to generate
and supply a reformate gas to a pair of NO.sub.X traps or to a
catalyst positioned upstream of an SCR catalyst. Reformate gas from
the fuel reformer may also be utilized as a fuel additive for an
internal combustion engine such as an HCCI engine.
[0021] The fuel reformer described herein may be embodied as any
type of fuel reformer such as, for example, a catalytic fuel
reformer, a thermal fuel reformer, a steam fuel reformer, or any
other type of partial oxidation fuel reformer. The fuel reformer of
the present disclosure may also be embodied as a plasma fuel
reformer. A plasma fuel reformer uses plasma to convert a mixture
of air and hydrocarbon fuel into a reformate gas which is rich in,
amongst other things, hydrogen gas and carbon monoxide. Systems
including plasma fuel reformers are disclosed in U.S. Pat. No.
5,425,332 issued to Rabinovich et al.; U.S. Pat. No. 5,437,250
issued to Rabinovich et al.; U.S. Pat. No. 5,409,784 issued to
Bromberg et al.; and U.S. Pat. No. 5,887,554 issued to Cohn, et al.
Additional examples of systems including plasma fuel reformers are
disclosed in: (1) copending U.S. patent application Ser. No.
10/158,615 which is entitled "Low Current Plasmatron Fuel Converter
Having Enlarged Volume Discharges," which was filed on May 30, 2002
by A. Rabinovich, N. Alexeev, L. Bromberg, D. Cohn, and A.
Samokhin, (2) copending U.S. patent application Ser. No. 10/411,917
which is entitled "Plasmatron Fuel Converter Having Decoupled Air
Flow Control," which was filed on Apr. 11, 2003 by A. Rabinovich,
N. Alexeev, L. Bromberg, D. Cohn, and A. Samokhin, and is hereby
incorporated by reference herein, (3) copending U.S. patent
application Ser. No. 10/452,623 which is entitled "Fuel Reformer
With Cap and Associated Method," which was filed on Jun. 2, 2003 by
Michael W. Greathouse and Jon J. Huckaby, (4) copending U.S. patent
application Ser. No. 10/843,776 which is entitled "Plasma Fuel
Reformer With One-Piece Body," which was filed on May 12, 2004 by
Michael W. Greathouse and Jason Zhang, and (5) copending U.S.
patent application Ser. No. 60/660,362 which is entitled "Plasma
Fuel Reformer," which was filed on Mar. 10, 2005 by Michael W.
Greathouse, Stephen Goldschmidt, Navin Khadiya, Samuel Crane,
Robert Iverson, Kendall Duffield, Michael Blackwood, William
Taylor, III, Rudolf Smaling, Michael Smith, Jon Huckaby,
Christopher Huffmeyer, and Granville Hayworth, II. Each of the
above-identified patents and patent applications are hereby
incorporated by reference.
[0022] For purposes of the following description, the concepts of
the present disclosure will herein be described in regard to a
plasma fuel reformer. However, as described above, the fuel
reformer of the present disclosure may be embodied as any type of
fuel reformer.
[0023] Referring now to FIGS. 1 and 2, there is shown an exemplary
embodiment of a plasma fuel reforming assembly 10 of an emission
abatement assembly 14. The plasma fuel reforming assembly 10
includes a plasma fuel reformer 12 and a control unit 16. The
plasma fuel reformer 12 reforms (i.e., converts) hydrocarbon fuels
into a reformate gas that includes, amongst other things, hydrogen
and carbon monoxide. As such, the plasma fuel reformer 12 may be
used in the construction of an onboard fuel reforming system of a
vehicle or a stationary power generator. In such a way, the
reformate gas produced by the onboard plasma fuel reformer 12 may
be utilized as a regenerating fluid to regenerate or otherwise
condition an emission abatement device associated with an internal
combustion engine (e.g., a diesel engine or a gasoline engine).
[0024] As shown in FIG. 2, the plasma fuel reformer 12 includes a
plasma-generating assembly 42 and a reactor 44. The
plasma-generating assembly 42 is secured to an upper portion of the
reactor 44. The plasma-generating assembly 42 includes an upper
electrode 54 and a lower electrode 56. The electrodes 54, 56 are
spaced apart from one another so as to define an electrode gap 58
therebetween. An insulator 60 electrically insulates the electrodes
from one another.
[0025] The electrodes 54, 56 are electrically coupled to an
electrical power supply 36 such that, when energized, an electrical
current is supplied to one of the electrodes thereby generating a
plasma arc (not shown) across the electrode gap 58 (i.e., between
the electrodes 54, 56). A fuel input mechanism such as a fuel
injector 38 injects a hydrocarbon fuel 64 into the plasma arc. The
fuel injector 38 may be any type of fuel injection mechanism which
injects a desired amount of fuel into plasma-generating assembly
42. In certain configurations, it may be desirable to atomize the
fuel prior to, or during, injection of the fuel into the
plasma-generating assembly 42. Such fuel injector assemblies (i.e.,
injectors which atomize the fuel) are commercially available.
[0026] As shown in FIG. 2, the plasma-generating assembly 42 has an
annular air chamber 72. Pressurized air is advanced into the air
chamber 72 and is thereafter directed radially inwardly through the
electrode gap 58 so as to "bend" the plasma arc inwardly. Such
bending of the plasma arc ensures that the injected fuel 64 is
directed through the plasma arc. Such bending of the plasma arc
also reduces erosion of the electrodes 56, 58. Moreover,
advancement of air into the electrode gap 58 also produces a
desired mixture of air and fuel ("air/fuel mixture"). In
particular, the plasma reformer 12 reforms or otherwise processes
the fuel in the form of a mixture of air and fuel. The air-to-fuel
ratio of the air/fuel mixture being reformed by the fuel reformer
is controlled via control of the fuel injector 38 and an air inlet
valve 40. The air inlet valve 40 may be embodied as any type of
electronically-controlled air valve. The air inlet valve 40 may be
embodied as a discrete device, as shown in FIG. 2, or may be
integrated into the design of the plasma fuel reformer 12. In
either case, the air inlet valve 40 controls the amount of air that
is introduced into the plasma-generating assembly 42 thereby
controlling the air-to-fuel ratio of the air/fuel mixture being
processed by the plasma fuel reformer 12.
[0027] Gas (either reformed or partially reformed) exiting the
plasma arc 62 is advanced into the reactor 44. A catalyst (not
shown) may be positioned in the reactor 44. The catalyst completes
the fuel reforming process, or otherwise treats the gas, prior to
exit of the reformate gas from the reactor 44. In particular, some
or all of the gas exiting the plasma-generating assembly 42 may
only be partially reformed, and the catalyst is configured to
complete the reforming process (i.e., catalyze a reaction which
completes the reforming process of the partially reformed gas
exiting the plasma-generating assembly 42). The catalyst may be
embodied as any type of catalyst that is configured to catalyze
such reactions. In one exemplary embodiment, the catalyst embodied
as a substrate having a precious metal or other type of catalytic
material disposed thereon. Such a substrate may be constructed of
ceramic, metal, or other suitable material. The catalytic material
may be, for example, embodied as platinum, rhodium, palladium,
including combinations thereof, along with any other similar
catalytic materials. The plasma fuel reformer 12 may be embodied
without the catalyst.
[0028] As shown in FIG. 1, the plasma fuel reformer 12 and its
associated components are under the control of the control unit 16.
In particular, the fuel injector 38 is electrically coupled to the
electronic control unit 16 via a signal line 20, the air inlet
valve 40 is electrically coupled to the electronic control unit 16
via a signal line 22, and the power supply 36 is electrically
coupled to the electronic control unit 16 via a signal line 24.
Moreover, as will herein be described in greater detail, a number
of other components associated with the emission abatement assembly
14 may also be under the control of the control unit 16, and, as a
result, electrically coupled thereto. For example, a flow diverter
valve 88 for selectively diverting an exhaust gas flow from an
internal combustion engine and a flow of reformate gas from the
plasma fuel reformer 12 between any number of components may be
under the control of the control unit 16. A number of sensors such
as NO.sub.X sensors and pressure sensors associated with the
emission abatement assembly 14 are also electrically coupled to the
control unit 16.
[0029] Although the signal lines 20, 22, 24 (and any of the signal
lines used to couple other devices associated with the emission
abatement assembly 14 to the control unit) are shown schematically
as a single line, it should be appreciated that the signal lines
may be configured as any type of signal carrying assembly which
allows for the transmission of electrical signals in either one or
both directions between the electronic control unit 16 and the
corresponding component. For example, any one or more of the signal
lines 20, 22, 24 (or any other signal line disclosed herein) may be
embodied as a wiring harness having a number of signal lines which
transmit electrical signals between the electronic control unit 16
and the corresponding component. It should be appreciated that any
number of other wiring configurations may also be used. For
example, individual signal wires may be used, or a system utilizing
a signal multiplexer may be used for the design of any one or more
of the signal lines 20, 22, 24 (or any other signal line).
Moreover, the signal lines 20, 22, 24 may be integrated such that a
single harness or system is utilized to electrically couple some or
all of the components associated with the plasma fuel reformer 12
to the electronic control unit 16.
[0030] The electronic control unit 16 is, in essence, the master
computer responsible for interpreting electrical signals sent by
sensors associated with the plasma fuel reformer 12 and for
activating electronically-controlled components associated with the
plasma fuel reformer 12 in order to control the plasma fuel
reformer 12, the flow of reformate gas exiting therefrom, and an
exhaust gas flow from an internal combustion engine. For example,
the electronic control unit 16 of the present disclosure is
operable to, amongst many other things, determine the beginning and
end of each injection cycle of fuel into the plasma-generating
assembly 42, calculate and control the amount and ratio of air and
fuel to be introduced into the plasma-generating assembly 42,
determine the power level to supply to the plasma fuel reformer 12,
and determine when to commence and end a regeneration cycle of each
of the emission components (e.g., NO.sub.X traps or a soot
filter).
[0031] To do so, the electronic control unit 16 includes a number
of electronic components commonly associated with electronic units
which are utilized in the control of electromechanical systems. For
example, the electronic control unit 16 may include, amongst other
components customarily included in such devices, a processor such
as a microprocessor 28 and a memory device 30 such as a
programmable read-only memory device ("PROM") including erasable
PROM's (EPROM's or EEPROM's). The memory device 30 is configured to
store, amongst other things, instructions in the form of, for
example, a software routine (or routines) which, when executed by
the processor 28, allows the electronic control unit 16 to control
operation of the plasma fuel reformer 12 and other devices
associated with the emission abatement assembly 14.
[0032] The electronic control unit 16 also includes an analog
interface circuit 32. The analog interface circuit 32 converts the
output signals from the various fuel reformer sensors (e.g., a
temperature sensor or gas composition sensor) or other sensors
associated with the with the emission abatement assembly (e.g., the
NO.sub.X sensor and the pressure sensors) into a signal which is
suitable for presentation to an input of the microprocessor 28. In
particular, the analog interface circuit 32, by use of an
analog-to-digital (A/D) converter (not shown) or the like, converts
the analog signals generated by the sensors into a digital signal
for use by the microprocessor 28. It should be appreciated that the
A/D converter may be embodied as a discrete device or number of
devices, or may be integrated into the microprocessor 28. It should
also be appreciated that if any one or more of the sensors
associated with the plasma fuel reformer 12 or the emission
abatement assembly 14 generate a digital output signal, the analog
interface circuit 32 may be bypassed.
[0033] Similarly, the analog interface circuit 32 converts signals
from the microprocessor 28 into an output signal which is suitable
for presentation to the electrically-controlled components
associated with the plasma fuel reformer 12 (e.g., the fuel
injector 38, the air inlet valve 40, the power supply 36), or other
system components associated with the emission abatement assembly
14 (e.g., the diverter valve 88). In particular, the analog
interface circuit 32, by use of a digital-to-analog (D/A) converter
(not shown) or the like, converts the digital signals generated by
the microprocessor 28 into analog signals for use by the
electronically-controlled components associated with the fuel
reformer 12 and the emission abatement assembly 14. It should be
appreciated that, similar to the A/D converter described above, the
D/A converter may be embodied as a discrete device or number of
devices, or may be integrated into the microprocessor 28. It should
also be appreciated that if any one or more of the
electronically-controlled components associated with the plasma
fuel reformer 12 or the emission abatement assembly 14 operate on a
digital input signal, the analog interface circuit 32 may be
bypassed.
[0034] Hence, the electronic control unit 16 may be operated to
control operation of the plasma fuel reformer 12, and components
associated therewith, and the components associated with the
emission abatement assembly 14. In particular, the electronic
control unit 16 executes a routine including, amongst other things,
a closed-loop control scheme in which the electronic control unit
16 monitors the outputs from a number of sensors in order to
control the inputs to the electronically-controlled components
associated therewith. To do so, the electronic control unit 16
communicates with the sensors associated with the fuel reformer 12
and the emission abatement assembly 14 to determine, amongst
numerous other things, the amount, temperature, and/or pressure of
air and/or fuel being supplied to the plasma fuel reformer 12, the
amount of hydrogen and/or oxygen in the reformate gas, the
temperature of the reformer or the reformate gas, the composition
of the reformate gas, the accumulation level within an emission
abatement device (e.g., a NO.sub.X trap or soot filter), etcetera.
Armed with this data, the electronic control unit 16 performs
numerous calculations each second, including looking up values in
preprogrammed tables, in order to execute algorithms to perform
such functions as determining when or how long the fuel reformer's
fuel injector or other fuel input device is opened, controlling the
power level input to the fuel reformer, controlling the amount of
air advanced through air inlet valve, controlling the position of a
flow diverter valve responsible for directing the flow of reformate
gas and exhaust gas to one component or the other, determining the
quantity and/or composition of reformate gas to generate and
deliver to a particular component, etcetera.
[0035] Referring now to FIG. 3, there is shown the emission
abatement assembly 14 in greater detail. The emission abatement
assembly 14 includes a pair of NO.sub.X traps 84, 86 for removing
and treating NO.sub.X present in the exhaust gas from an internal
combustion engine 82 such as a diesel engine, a gasoline engine, a
gasoline direct injection (GDI) engine, or natural gas engine. The
NO.sub.X traps 84, 86 are arranged in a parallel relationship with
one another. As such, for purposes of clarity of description, the
NO.sub.X trap 84 will herein be referred to as the right NO.sub.X
trap, whereas the NO.sub.X trap 86 will herein be referred to as
the left NO.sub.X trap. However, such use of directional terms
(i.e., right and left) is not intended to infer any particular
orientation, but rather is only used herein only for ease of
description.
[0036] The NO.sub.X traps 84, 86 may be any type of commercially
available NO.sub.X trap, including a lean NO.sub.X trap, which
facilitates the trapping and removal of NO.sub.X in the lean
conditions associated with exhaust gases from diesel engines, GDI
engines, or natural gas engines. Specific examples of NO.sub.X
traps which may be used as the NO.sub.X traps 84, 86 of the present
disclosure include, but are not limited to, NO.sub.X traps
commercially available from, or NO.sub.X traps constructed with
materials commercially available from, EmeraChem, LLC of Knoxville,
Tenn. (formerly known as Goal Line Environmental Technologies, LLC
of Knoxville, Tenn.).
[0037] The emission abatement assembly 14 may also include one or
more additional components downstream of the NO.sub.X traps 84, 86.
For example, a number of catalysts and/or soot filters may be
positioned downstream of the NO.sub.X traps 84, 86. It should be
appreciated that although a specific exemplary embodiment is
described herein in which an oxidation catalyst 94 and a catalyzed
soot filter 96 are positioned downstream of the NO.sub.X traps 84,
86, numerous other configurations may be used to fit the needs of a
given system. For example, two soot filters (instead of one) may be
used with each filter being positioned downstream from one of the
NO.sub.X traps 84, 86 in a parallel flow arrangement.
[0038] The catalyst 94 may be embodied as any type of catalyst that
is configured to catalyze oxidation reactions in an exhaust gas
stream. In one exemplary embodiment, the catalyst 94 is embodied as
substrate having a precious metal or other type of catalytic
material disposed thereon. Such a substrate may be constructed of
ceramic, metal, or other suitable material. The catalytic material
may be, for example, embodied as platinum, rhodium, palladium,
including combinations thereof, along with any other similar
catalytic materials. When positioned downstream of the NO.sub.X
traps 84, 86, the catalyst 94 may function to clean up any hydrogen
or hydrocarbon "slip" from the NO.sub.X traps 84, 86. For example,
the oxidation catalyst 94 may be used to oxidize any H.sub.2,
certain hydrocarbons, or H.sub.2S that may be present in the gases
exiting the traps 84, 86. Moreover, as will be discussed herein in
greater detail, when positioned upstream of the soot filter 96, the
catalyst 94 may be utilized during assisted regeneration of soot
filter 96.
[0039] The soot filter 96 may be embodied as any type of
commercially available particulate filter. For example, the soot
particulate filter may be embodied as any known exhaust particulate
filter such as a "deep bed" or "wall flow" filter. Deep bed filters
may be embodied as metallic mesh filters, metallic or ceramic foam
filters, ceramic fiber mesh filters, and the like. Wall flow
filters, on the other hand, may be embodied as a cordierite or
silicon carbide ceramic filter with alternating channels plugged at
the front and rear of the filter thereby forcing the gas advancing
therethrough into one channel, through the walls, and out another
channel.
[0040] The soot filter 96 is impregnated with a catalytic material.
The catalytic material may be, for example, embodied as platinum,
rhodium, palladium, including combinations thereof, along with any
other similar catalytic materials. By use of catalytic material,
the temperature at which soot particles trapped in the filter
combust is lowered such that regeneration of the soot filter 96 may
occur in the presence of the heat of the engine exhaust gas.
However, if the soot accumulation level within the soot filter 96
reaches a predetermined level (i.e., regeneration based on exhaust
gas heat alone is not sufficient to clear the filter), reformate
gas from the fuel reformer 12 may be used to regenerate the
filter.
[0041] As shown in FIG. 3, a diverter valve 88 selectively diverts
the flow of exhausts gas from the engine 82 between the traps 84,
86. In particular, the diverter valve 88 may be operated to divert
a flow of exhaust gas from the engine 82 between a right flow path
102 and a left flow path 104. The right NO.sub.X trap 84 is
positioned in the right flow path 102 such that exhaust gas or
reformate gas advancing through the right flow path 102 is advanced
through the right NO.sub.X trap 84. The left NO.sub.X trap 86 is
positioned in the left flow path 104 such that exhaust gas or
reformate gas advancing through the left flow path 104 is advanced
through the left NO.sub.X trap 86.
[0042] As also shown in FIG. 3, the right flow path 102 and the
left flow path 104 are recombined by a flow coupler 106. The flow
coupler 106 is positioned downstream of the NO.sub.X traps 84, 86
and upstream of oxidation catalyst 94 and the soot filter 96. As a
result, gas exiting the NO.sub.X traps 84, 86 is directed through
both the oxidation catalyst 94 and the soot filter 96.
[0043] In the exemplary embodiment described herein, a number of
fluid lines such as pipes, tubes, or the like are utilized to
create the various flow paths. In particular, an exhaust gas inlet
108 of the diverter valve 88 is fluidly coupled to an exhaust
manifold 110 of the engine 82 via a fluid line 112. A right outlet
114 of the diverter valve 88 is fluidly coupled to an inlet 116 of
the right NO.sub.X trap 84 via a fluid line 118, whereas a left
outlet 120 of the diverter valve 88 is fluidly coupled to an inlet
122 of the left NO.sub.X trap 86 via a fluid line 124. An outlet
126 of the right NO.sub.X trap 84 is fluidly coupled to the flow
coupler 106 via a fluid line 128, whereas an outlet 130 of the left
NO.sub.X trap 86 is fluidly coupled to the flow coupler 106 via the
fluid line 132. A fluid line 134 fluidly couples the flow coupler
106 to an inlet 136 of the oxidation catalyst 94. An outlet 138 of
the oxidation catalyst 94 is fluidly coupled to an inlet 140 of the
soot filter 96 via a fluid line 142. Via a fluid line 144, an
outlet 146 of the soot filter 96 is either open to the atmosphere
or coupled to an additional exhaust system component (not shown)
positioned downstream of the soot filter 96.
[0044] In such a configuration, exhaust gas from the engine 82 may
be routed through the emission abatement assembly 14 to remove,
amongst other things, NO.sub.X and soot therefrom. To do so,
exhaust gas may be selectively routed between the two NO.sub.X
traps 84, 86 to allow for both treatment of the exhaust gas and
trap regeneration. For example, exhaust gas may be routed through
the right NO.sub.X trap 84 while the left NO.sub.X trap 86 is
maintained "offline." While offline, the left NO.sub.X trap 86 may
undergo regeneration. In such a case, exhaust gas is advanced along
a fluid path which includes the fluid line 112 from the exhaust
manifold 110, the diverter valve 88, the fluid line 118 to the
right NO.sub.X trap 84, through the trap 84 and the fluid line 128
to the flow coupler 106, the fluid line 134 to the oxidation
catalyst 94, through the catalyst 94 and the fluid line 142 to the
soot filter 96, through the soot filter 96 and out the fluid line
144.
[0045] To regenerate the right NO.sub.X trap 84, the position of
the diverter valve 88 may be switched such that exhaust gas from
the engine 82 is routed through the left NO.sub.X trap 86 while the
right NO.sub.X trap 84 is offline for regeneration. In this case,
exhaust gas is advanced along a fluid path which includes the fluid
line 112 from the exhaust manifold 110, the diverter valve 88, the
fluid line 124 to the left NO.sub.X trap 86, through the trap 86
and the fluid line 132 to the flow coupler 106, the fluid line 134
to the oxidation catalyst 94, through the catalyst 94 and the fluid
line 142 to the soot filter 96, through the soot filter 96 and out
the fluid line 144.
[0046] As will be discussed herein in greater detail, in addition
to diverting exhaust gas from the engine 82 to the appropriate
NO.sub.X trap 84, 86, the diverter valve 88 is also configured to
divert reformate gas from the fuel reformer 12 to the appropriate
NO.sub.X trap 84, 86. In particular, the outlet 76 of the fuel
reformer 12 is fluidly coupled to a regenerating fluid inlet 148 of
the diverter valve 88 via a fluid line 150. The diverter valve 88
diverts reformate gas from the fuel reformer 12 to the offline
NO.sub.X trap 84, 86. In particular, as described above, engine
exhaust gas is routed by the diverter valve 88 through one of the
traps 84, 86 while the other trap is maintained offline for
regeneration. The diverter valve 88 routes engine exhaust gas
through one of the traps 84, 86, while routing reformate gas from
the fuel reformer 12 through the other trap 84, 86.
[0047] The diverter valve 88 is electrically coupled to the
electronic control unit 16 via a signal line 152. As such, the
position of the diverter valve 88 is under the control of the
electronic control unit 16. Hence, the electronic control unit 16,
amongst its other functions, selectively directs the flow of
exhaust gas from the engine 82 and the flow of reformate gas from
the fuel reformer 12 to either the right NO.sub.X trap 84 or the
left NO.sub.X trap 86, or a combination of both traps 84, 86.
[0048] The control scheme for controlling the position of the
diverter valve 88 may be designed in a number of different manners.
For example, a sensor-based control scheme may be utilized. In such
a case, the position of the diverter valve 88 is changed as a
function of output from one or more sensors associated with the
NO.sub.X traps 84, 86. For instance, regeneration of one of the
NO.sub.X traps 84, 86 may commence when the output from an
associated NO.sub.X sensor 154 is indicative of a predetermined
NO.sub.X accumulation level within one of the NO.sub.X traps 84,
86. More specifically, each of the NO.sub.X sensors 154 is
positioned to sense the NO.sub.X content of exhaust gas passing
through traps 84, 86. In such a downstream position relative to the
NO.sub.X traps 84, 86, the sensor 154 may be used to monitor the
NO.sub.X accumulation level of the NO.sub.X trap 84, 86. As such,
when the output from one of the NO.sub.X sensors 154 indicates that
a particular NO.sub.X trap 84, 86 is in need of regeneration, the
control unit 16 takes the trap 84, 86 in need of regeneration
offline.
[0049] Alternatively, a timing-based control scheme may be utilized
in which the position of the diverter valve 88 is changed as a
function of time. For instance, regeneration of the traps 84, 86
may be performed at predetermined timed intervals. In such a case,
the NO.sub.X sensor 154 may be all together eliminated, or used
merely as a "failsafe" to ensure that regeneration is not
prematurely needed during a timed interval.
[0050] One specific exemplary timing-based control scheme is shown
in FIG. 4. Unlike conventional arrangements in which one trap is
maintained offline during the entire absorption cycle of the other
trap, the control scheme demonstrated in FIG. 4 allows for both
traps to be maintained online for predetermined periods of time
thereby increasing the NO.sub.X absorption capability of the
system. To do so, the regeneration cycle of the NO.sub.X traps 84,
86 are staggered in a manner which allows for both traps NO.sub.X
traps 84, 86 to absorb NO.sub.X during a majority of the time
during operation of the engine 82.
[0051] For example, in the exemplary embodiment described, both
NO.sub.X traps 84, 86 absorb NO.sub.X during sixty seconds of a
given interval of seventy seconds. Indeed, as shown in FIG. 4, the
process may begin with the right NO.sub.X trap 84 being maintained
offline for regeneration for a predetermined period of time (e.g.,
five seconds) as shown by the arrow labeled t1. During this period
time, the entire flow exhaust gas is advanced through the left
NO.sub.X trap 86. After the right NO.sub.X trap 84 has been
regenerated, the left NO.sub.X trap 86 is maintained offline for
regeneration for a predetermined period of time (e.g., five
seconds) as shown by the arrow labeled t2. During this period time,
the entire flow exhaust gas is advanced through the right NO.sub.X
trap 84. Once regenerated, the left NO.sub.X trap 86 is put back
online to absorb NO.sub.X in tandem with the right NO.sub.X trap 84
for a predetermined period of time (e.g., sixty-five seconds) until
the right NO.sub.X trap 84 is again taken offline for regeneration
and the cycle repeats as shown by the arrow labeled t3.
[0052] It should be appreciated that the duration of the periods of
time noted above are exemplary in nature, and may be varied to fit
the needs of a given system. Of note is that by operating the two
NO.sub.X traps in tandem significantly extends the absorption cycle
of each trap when compared to conventional methodologies in the
which the traps are "toggled". In particular, in conventional
systems, one trap is maintained offline for the entire absorption
cycle of the other trap. When the online trap saturates, the two
traps are toggled with the saturated trap going offline for the
entire absorption cycle of the other trap. Depending on the type of
the NO.sub.X trap and the type of regeneration fluid, a NO.sub.X
trap may have a regeneration cycle of around five seconds and an
absorption cycle (i.e., time to saturation) of around thirty
seconds. This means that the offline trap is regenerated, and then
merely "waiting" for twenty-five seconds out of every thirty second
cycle.
[0053] However, when working in tandem according to the methods of
the present disclosure, the absorption cycle of each trap can be
extended to, for example, seventy seconds (versus thirty seconds),
and in some cases, upwards of ninety seconds. This is due to the
other trap sharing some of the work of NO.sub.X absorption. Another
benefit is that the exhaust gas velocity is lowered since the flow
is shared by both traps.
[0054] It should be appreciated that the flow-sharing method
described above is not limited to two NO.sub.X traps. Indeed, such
a method could be used in a system having any number of NO.sub.X
traps.
[0055] Referring now to FIGS. 5-8, there is shown the diverter
valve 88 in greater detail. The diverter valve 88 includes a valve
housing 164 having a valve chamber 166 defined therein. Note that
in FIG. 5, all but a small portion of the top plate 172 of the
valve housing 164 has been cut away for clarity of view into the
valve chamber 166.
[0056] The exhaust gas inlet 108, the regenerating fluid inlet 148,
the right outlet 114, and the left outlet 120 are also defined in
the valve housing 164. Although each of the inlets and outlets
associated with the diverter valve 88 are exemplary embodied as an
orifice defined in the walls of the valve housing 164, it should be
appreciated that any or all of such inlets and outlets may,
alternatively, be embodied to include a tube, coupling assembly, or
other structure which extends through the wall of the housing
164.
[0057] The fluid lines 112, 118, 124, and 150 are secured to the
valve housing 164 such that fluids conducted therein may be
advanced into or out of the valve chamber 166 thereby fluidly
coupling the valve chamber 166 to a particular component. In
particular, as shown in FIG. 5, one end of the fluid line 112
(shown as a pipe in FIG. 5) extends through the exhaust gas inlet
108 of the valve housing 164 thereby fluidly coupling the valve
chamber 166 to the exhaust manifold 110 of the engine 82. An end of
the fluid line 118 (shown as a pipe in FIG. 5) extends through the
right outlet 114 of the valve housing 164 thereby fluidly coupling
the valve chamber 166 to the inlet 116 of the right NO.sub.X trap
84, whereas one end of the fluid line 124 (shown as a pipe in FIG.
5) extends through the left outlet 120 of the valve housing 164
thereby fluidly coupling the valve chamber 166 to the inlet 122 of
the left NO.sub.X trap 86. An end of the fluid line 150 (shown as a
pipe in FIG. 5) extends through the regenerating fluid inlet 148 of
the valve housing 164 thereby fluidly coupling the valve chamber
166 to the outlet 76 of the fuel reformer 12.
[0058] A valve member 168 in the form of a movable plate or "flap"
is positioned in the valve chamber 166. The flap 168 is movable
between a number of valve positions to selectively divert both
exhaust gas from the engine 82 and reformate gas from the fuel
reformer 12 to either one of the NO.sub.X traps 84, 86.
Specifically, the flap 168 is positionable to direct engine exhaust
gas to one or both of the NO.sub.X traps 84, 86 (i.e., the "online"
trap(s)) while directing reformate gas from the fuel reformer 12 to
the one of the NO.sub.X traps 84, 86 (i.e., the "offline"
trap).
[0059] For example, when positioned in the valve position shown in
FIG. 6, the flap 168 diverts engine exhaust gas to the right
NO.sub.X trap 84, while also diverting reformate gas from the fuel
reformer 12 to the left NO.sub.X trap 86. Specifically, when
positioned in the valve position of FIG. 6, the flap 168 fluidly
couples the exhaust gas inlet 108 to the right outlet 114, but
fluidly isolates the exhaust gas inlet 108 from the left outlet
120. When positioned in the valve position of FIG. 6, the flap 168
also fluidly couples the regenerating fluid inlet 148 to the left
outlet 120, but fluidly isolates the regenerating fluid inlet 148
from the right outlet 114.
[0060] Conversely, when positioned in the valve position shown in
FIG. 7, the flap 168 diverts engine exhaust gas to the left
NO.sub.X trap 86, while also diverting reformate gas from the fuel
reformer 12 to the right NO.sub.X trap 84. Specifically, when
positioned in the valve position of FIG. 7, the flap 168 fluidly
couples the exhaust gas inlet 108 to the left outlet 120, but
fluidly isolates the exhaust gas inlet 108 from the right outlet
114. When positioned in the valve position of FIG. 7, the flap 168
also fluidly couples the regenerating fluid inlet 148 to the right
outlet 114, but fluidly isolates the regenerating fluid inlet 148
from the left outlet 120.
[0061] Additionally, when positioned in the valve position shown in
FIG. 8, the flap 168 splits or otherwise diverts the flow engine
exhaust gas between both the NO.sub.X traps 84, 86. Specifically,
when positioned in the valve position of FIG. 8, the flap 168
fluidly couples the exhaust gas inlet 108 to both the right outlet
114 and the left outlet 120. When positioned in the valve position
of FIG. 8, the flap 168 also fluidly couples the regenerating fluid
inlet 148 to both the right outlet 114 and the left outlet 120. The
fuel reformer 12 may be idled or otherwise operated to not supply
reformate gas to the valve 88 when the flap 168 is positioned in
the valve position shown in FIG. 8.
[0062] The diverter valve 88 also includes a valve actuator 170
which, as alluded to above, is electrically coupled to the control
unit 16 via the signal line 152. As such, the position of the
diverter valve 88 is under the control of the control unit 16. As a
result, the control unit 16, amongst its other functions, may
selectively direct the flow of exhaust gas from the engine 82 and
reformate gas from the plasma fuel reformer 12 to either the right
NO.sub.X trap 84 or the left NO.sub.X trap 86 (or both).
Specifically, the control unit 16 may generate control signals on
the signal line 152 which cause the valve actuator 170 to
selectively position the flap 168 in either the valve positions of
FIG. 6-8. The valve actuator 170 may be embodied as any type of
electrically-controlled actuator for moving the flap 168 in such a
manner. For example, the valve actuator may be embodied as a linear
solenoid or a stepper motor.
[0063] It should be appreciated that although the diverter valve 88
is herein described as a three position, other control
configurations of the diverter valve 88 are also contemplated. For
example, a variable flow configuration is also contemplated in
which a desired amount of engine exhaust gas may be directed
through the offline trap 84, 86 and/or a desired amount of
reformate gas may be directed through the online trap 84, 86.
[0064] The components of the diverter valve 88 may be constructed
with any type of material suitable for withstanding the operating
conditions to which the valve 88 is subjected. For example, the
components of the diverter valve 88 may be constructed with any of
the 300-series or 400-series stainless steels. In a specific
implementation, the components of the diverter valve 88 may be
constructed with either "304" stainless steel or "409" stainless
steel. The components of the diverter valve 88 may also be
constructed with other materials such as ceramic coated metals or
the like.
[0065] Referring now to FIGS. 9 and 10, there is shown another
emission abatement system 210. Note that the system 210 utilizes a
number of the same components as the system 10. Like reference
numerals are used for like components.
[0066] Exhaust gas containing NO.sub.X is advanced through a
catalyst 212. The catalyst 212 may be embodied as a substrate
having a precious metal or other type of catalytic material
disposed thereon. Such a substrate may be constructed of ceramic,
metal, or other suitable material. The catalytic material may be,
for example, embodied as platinum, rhodium, palladium, including
combinations thereof, along with any other similar catalytic
materials.
[0067] The output from the catalyst 212 is then advanced through an
SCR catalyst 214. The SCR catalyst 214 may be embodied as a
conventional urea SCR catalyst.
[0068] The output from the plasma fuel reformer 12 (i.e., reformate
gas containing hydrogen) is advanced into an inlet of the catalyst
212. This arrangement allows for the conversion of NO.sub.X to
N.sub.2 at the various operating temperatures of the system. For
example, as shown in FIG. 9, at operating temperatures above
200.degree. C., the catalyst 212 catalyzes a reaction which
converts the hydrogen in the reformate gas and some of the NO.sub.X
in the exhaust stream into ammonia (NH.sub.3) and water. The
ammonia is then subsequently used by the SCR catalyst 214 to
convert the remaining NO.sub.X into N.sub.2. As such, at
temperatures above 200.degree. C., use of the catalyst 212 allows
for the onboard production of ammonia for use as a reductant fluid
for the SCR catalyst 214 thereby eliminating the need for urea
storage.
[0069] It should be appreciated that both the operating parameters
of the plasma fuel reformer 12 and the design of the catalyst 212
may be configured to produce ammonia and NO.sub.X in a desired
ratio. For example, a conventional SCR catalyst efficiently
converts NO.sub.X when the ratio of NH.sub.3 to NO.sub.X is
.about.1:1. Operation of the plasma fuel reformer 12 and the design
of the catalyst 212 may be configured such that NO.sub.X and
NH.sub.3 exit the catalyst 212 in such a ratio.
[0070] As shown in FIG. 10, at operating temperatures below
200.degree. C., the catalyst 212 catalyzes a reaction which
converts the hydrogen in the reformate gas and the NO.sub.X in the
exhaust stream into nitrogen (N.sub.2) and water. In essence, at
operating temperatures below 200.degree. C., the catalyst 212
functions as a hydrogen-SCR catalyst.
[0071] It should be appreciated that the specific transition
temperature identified above (i.e., 200.degree. C.) at which the
production of ammonia begins is exemplary in nature, and is largely
based on the type of catalytic material(s) utilized in the
construction of the catalyst 212. For example, such a transition
temperature (i.e., 200.degree. C.) is indicative of use of a
platinum catalytic material. Other catalytic materials may produce
different transition temperatures. For example, the transition
temperature of a catalyst constructed with palladium catalytic
material or a rhodium may be around 230.degree. C. It should also
be appreciated that the gas composition of the reformate gas may
also affect the transition temperature of the catalyst.
[0072] Referring now to FIGS. 16 and 17, there is shown another
emission abatement system 250. Note that the system 250 utilizes a
number of the same components as the systems 10, 210. Like
reference numerals are used for like components. Note that the
chemical references in FIGS. 16 and 17 are not intended to connote
specific chemical reactions (i.e., they are not balanced (or even
unbalanced) chemical equations), but rather are used merely to show
some of the reactants going into a particular catalyst and some of
the products coming out of the catalyst.
[0073] In the system of 250, the single ammonia-generating catalyst
212 has been replaced with a pair of catalysts--an oxidation
catalyst 252 and a lean-NO.sub.X/ammonia-generating catalyst 254.
Although shown a separate devices in FIGS. 16 and 17, the two
catalysts 252, 254 may be disposed on the same structure, e.g., the
same substrate.
[0074] The oxidation catalyst 252 may be embodied as any type of
precious metal oxidation catalyst such as platinum catalyst or
palladium catalyst. One such oxidation catalyst is a commercially
available diesel oxidation catalyst.
[0075] The lean-NO.sub.X/ammonia-generating catalyst 254 may be
embodied as any type of catalyst which, as described in more detail
below, functions as a lean NO.sub.X catalyst that converts NO.sub.X
to N.sub.2 under certain temperature conditions and an ammonia
generating catalyst under others. Examples of such catalysts are
found in the following articles, the entirety of each of which is
hereby incorporated by reference: (1) Optimal promotion by rubidium
of the NO+CO Reaction over Pt/g-Al.sub.2O.sub.3 Catalysts. Michalis
Konsolakis, Iannis V. Yentekakis, Alejandra Palermo and Richard M.
Lambert, Applied Catalysis B (Environmental) 33 335 (2001), (2)
Lean NO.sub.X reduction with CO+H.sub.2 mixtures over
Pt/Al.sub.2O.sub.3 and Pd/Al.sub.2O.sub.3 catalysts. Norman Macleod
and Richard M. Lambert, Journal of Applied Catalysis B
(Environmental) 35 269 (2001), (3) Efficient low-temperature NOx
reduction with CO+H.sub.2 under fuel-lean conditions over a
Pd/TiO.sub.2/Al.sub.2O.sub.3 catalyst. Norman Macleod and Richard
M. Lambert, Catalysis Communications 3 (2002) 61, (4) Efficient
reduction of NO.sub.X by H.sub.2 under oxygen-rich conditions over
Pd/TiO.sub.2 catalysts: an in situ DRIFTS study. Norman Macleod,
Rachael Cropley and Richard M. Lambert, Catalysis Letters 86 69
(2003), (5) In situ ammonia generation as a strategy for catalytic
NO.sub.X reduction under oxygen rich conditions. Norman Macleod and
Richard M. Lambert, Chemical Communications 1300 (2003), (6) An in
situ DRIFTS study of efficient lean NO.sub.X reduction with
H.sub.2+CO over Pd/Al.sub.2O.sub.3: the key role of transient NCO
formation in the subsequent generation of ammonia. Norman Macleod
and Richard M. Lambert, Applied Catalysis B: Environmental 46
(2003) 483, (7) Exploiting the synergy of titania and alumina in
lean NO.sub.X reduction: in situ ammonia generation during the
Pd/TiO.sub.2/Al.sub.2O.sub.3--catalysed /CO/NO/O.sub.2 reaction.
Norman Macleod, Rachael Cropley, James M. Keel and Richard M.
Lambert, Journal of Catalysis 221 (2004) 20, (7) An Investigation
of catalysts for on-board synthesis of NH3. A possible route to low
temperature NO.sub.X reduction for lean burn engines. Breen, Burch,
and Lingaiah, Catalysis Letters, v. 79, 2002, and (8) In-Situ NH3
Generation for SCR NOx Applications. S. Ogunwumi, R. Fox, M. D.
Patil and L. He; SAE 2002-01-2872.
[0076] Exhaust gas containing NO.sub.X is advanced through the DOC
catalyst 252 and the lean NO.sub.X/ammonia generating catalyst 254.
The output from the catalysts 252, 254 is then advanced through the
SCR catalyst 214.
[0077] The output from the plasma fuel reformer 12 (i.e., reformate
gas containing H.sub.2 and CO) is advanced into an inlet of the
catalyst 252. This arrangement allows for the conversion of
NO.sub.X to N.sub.2 at the various operating temperatures of the
system. For example, as shown in FIG. 17, at higher operating
temperatures (e.g., above 250.degree. C.), the catalysts 252, 254
catalyze a reaction which converts the hydrogen in the reformate
gas and some of the NO.sub.X in the exhaust stream into ammonia
(NH.sub.3) and water. Specifically, some NO is oxidized to NO.sub.2
and CO is oxidized to CO.sub.2 by the DOC catalyst 252. These
reactions consume some of the free O.sub.2 in the exhaust gas. A
portion of the remaining NO.sub.X is converted to NH.sub.3 by the
lean-NO.sub.X/ammonia-generating catalyst 254. The dosage of
reformate gas provided the plasma fuel reformer 12 is controlled
such that NO.sub.X and NH.sub.3 exit the catalyst 254 in the
desired 1:1 ratio. The NH.sub.3 is then subsequently used by the
SCR catalyst 214 to convert the remaining NO.sub.X into N.sub.2. As
such, at temperatures above 250.degree. C., use of the catalysts
252, 254 allow for the onboard production of ammonia for use as a
reductant fluid for the SCR catalyst 214 thereby eliminating the
need for urea storage.
[0078] As shown in FIG. 16, at lower operating temperatures (e.g.,
below 150.degree. C.), the catalysts 252, 254 catalyze a reaction
which converts the hydrogen in the reformate gas and the NO.sub.X
in the exhaust stream into nitrogen (N.sub.2) and water.
Specifically, in the DOC catalyst 252, some NO is oxidized to
NO.sub.2 and CO is oxidized to CO.sub.2 by the DOC catalyst 252.
These reactions consume some of the free O.sub.2 in the exhaust
gas. The H.sub.2 supplied by the plasma fuel reformer 12 reacts
with NO and NO.sub.2 in the lean-NO.sub.X/ammonia-generating
catalyst 254 to form N.sub.2 using the principles of lean NO.sub.X
catalysis or hydrogen-SCR. Thereafter, the SCR catalyst 214 acts as
a pass through catalyst (i.e., without any chemical
participation).
[0079] In an intermediate range (e.g., between 150.degree.
C.-250.degree. C.), somewhat of a combination of the two conditions
occurs. In particular, in the DOC catalyst 252, some NO is oxidized
to NO.sub.2 and CO is oxidized to CO.sub.2 by the DOC catalyst 252.
These reactions consume some of the free O.sub.2 in the exhaust
gas. The H.sub.2 supplied by the plasma fuel reformer 12 reacts
with NO and NO.sub.2 in the lean-NO.sub.X/ammonia-generating
catalyst 254 to form N.sub.2 using the principles of lean NO.sub.X
catalysis or hydrogen-SCR. However, some of the NO.sub.X is
converted to NH.sub.3 in the lean-NO.sub.X/ammonia-generating
catalyst 254. The dosage of reformate gas provided the plasma fuel
reformer 12 is controlled such that not all of the NO.sub.X is
converted to NH.sub.3 so that enough NO.sub.X remains for reaction
with the NH.sub.3 in the SCR catalyst 214 (i.e., for conversion
into N.sub.2).
[0080] It should be appreciated that the specific temperature
ranges identified above in which the production of ammonia begins
is exemplary in nature, and is largely based on the type of
catalytic material(s) utilized in the construction of the
catalysts. Other catalytic materials may produce different
temperature ranges. It should also be appreciated that the gas
composition of the reformate gas may also affect the temperature
ranges.
[0081] It should be appreciated that the position of the oxidation
catalyst 252 may be altered based on the desired reaction products.
For example, in certain embodiments, it may be desirable to convert
NO to NO.sub.2 upstream of the lean-NO.sub.X/ammonia-generating
catalyst 254, but it may not be necessary, or even desirable, to
convert CO to CO.sub.2. In such a case, the oxidation catalyst 252
would be positioned upstream of the point at which reformate gas
from the plasma fuel reformer 12 is introduced into the system
(i.e., reformate gas is not advanced through the oxidation catalyst
252). This may be done based on the type of
lean-NO.sub.X/ammonia-generating catalyst 254 being used. For
example, certain types of lean-NO.sub.X/ammonia-generating
catalysts, such as those that are palladium-based, actually benefit
from the presence of CO. As such, it is desirable to not convert
the CO in the reformate gas to CO.sub.2. On the other hand, other
types of lean-NO.sub.X/ammonia-generating catalysts, such as those
that are platinum-based, are inhibited by the presence of CO.
Hence, it is desirable to convert the CO in the reformate gas to
CO.sub.2 in this case.
[0082] It should also be appreciated that the oxidation catalyst
252 may be embodied as two separate catalysts. In such a case, one
of such catalysts is positioned upstream of the point at which
reformate gas from the plasma fuel reformer 12 is introduced into
the system (i.e., reformate gas would not be advanced through the
first catalyst) to convert NO in the exhaust gas to NO.sub.2. The
other of such catalysts is positioned downstream of the point at
which reformate gas from the plasma fuel reformer 12 is introduced
into the system (i.e., reformate gas is advanced through the second
catalyst). If the lean-NO.sub.X/ammonia-generating catalyst 254 is
inhibited by CO, then the second catalyst may be embodied as a CO
oxidation catalyst such as the Pt/Al.sub.2O.sub.3 or
Pt/Ce.sub.XZr.sub.X-1O.sub.2 catalysts described in The Journal of
Catalysis, Volume 225, Issue 2, 25 July 2004, Pages 259-266, the
entirety of which is hereby incorporated by reference. In such a
case, the second catalyst will remove CO while preserving or
enhancing the H.sub.2 concentration of the reformate gas.
[0083] Moreover, in lieu of, or in addition to, a CO oxidation
catalyst, a water/gas shift catalyst may be utilized upstream of
the lean-NO.sub.X/ammonia-generating catalyst 254. In such an
arrangement, CO will react with H.sub.2O in the water/gas shift
catalyst to form H.sub.2 and CO.sub.2. This is particularly useful
in cases where the lean-NO.sub.X/ammonia-generating catalyst 254 is
inhibited by CO.
[0084] Referring now to FIG. 18, there is shown another emission
abatement system 260. Note that the system 260 utilizes a number of
the same components as the systems 10, 210, 250. Like reference
numerals are used for like components.
[0085] In the system 260, the exhaust gas flow is split into two
parallel flow paths 262, 264 such that approximately 50% of the
exhaust gas flows through the ammonia generating catalyst 254 and
the other 50% is bypassed around the ammonia generating catalyst
254. The exhaust gas flow is split at a point downstream of the DOC
catalyst 252, and then recombined at a point upstream of the SCR
catalyst 254. In this embodiment, the DOC catalyst 252 converts NO
to NO.sub.2 and CO to CO.sub.2 which enhances operation of the
ammonia generating catalyst 254 by removing O.sub.2 from the
exhaust gas. In certain embodiments, the DOC catalyst 252 may be
omitted.
[0086] The plasma fuel reformer 12 introduces reformate gas into
the flow path containing the ammonia generating catalyst 254 (i.e.,
the flow path 262). As with the other systems described herein, any
number of fluid lines such as pipes, tubes, or the like are
utilized to create the various flow paths.
[0087] In the system 260, ammonia generation is desired at all
temperatures, and the hydrogen-SCR function at low temperatures is
not needed. The formulation of the catalyst 254 may be adjusted
accordingly. A relatively high ammonia conversion efficiency is
desired so that the NH.sub.3 leaving the first parallel flow path
262 and the NO.sub.X leaving the second parallel flow path 264 are
near the desired .about.1:1 ratio.
[0088] A flow diverter valve 256 may be used to adjust the ratio of
the exhaust gas flowing through each of the flow paths 262, 264. In
this way, desired ammonia conversion efficiency may be provided. In
other words, the position of the valve 256 may be controlled to
produce a desired amount of NH.sub.3 while also allowing a desired
amount of NO.sub.X to reach the SCR catalyst 214 by virtue of
bypassing the ammonia generating catalyst 254. In lieu of the point
where the two flow paths are split, the valve 256 may also be
positioned at the point where the two flow paths are
recombined.
[0089] Optionally, a water/gas shift catalyst may be utilized
upstream of the ammonia generating catalyst 254. In such an
arrangement, CO will react with H.sub.2O in the water/gas shift
catalyst to form H.sub.2 and CO.sub.2. This is particularly useful
in cases where the ammonia generating catalyst 254 is inhibited by
CO. In lieu of, or in addition to, use of such a water/gas shift
catalyst, a CO oxidation catalyst may be utilized upstream of the
lean-NO.sub.X/ammonia-generating catalyst 254 to remove CO.
[0090] It should be appreciated that in the case of any of the
systems 210, 250, 260, the SCR catalyst 214 generally has some
ammonia storage capacity. As a result, during periods when excess
NH.sub.3 is made, such excess may be stored. During deficient
periods, stored NH.sub.3 can be utilized so that desired efficiency
is obtained under diverse conditions.
[0091] Moreover, the ammonia generation catalyst 254 can optionally
have NO.sub.X storage components (or a NO.sub.X adsorber catalyst
can be used as the ammonia generation catalyst in certain
embodiments). During periods when an excess H.sub.2:NO.sub.X ratio
exists, some adsorbed NO.sub.X can be desorbed and utilized for
NH.sub.3 production. In situations where the H.sub.2:NO.sub.X ratio
is too low, excess NO.sub.X may be stored.
[0092] Referring now to FIGS. 11-15, there is shown a number of
systems in which the plasma fuel reformer 12 is being utilized for
combustion enhancement. In such arrangements, the gas produced by
the plasma fuel reformer 12 is supplied to the intake of an
internal combustion engine such as an HCCI engine. Indeed, research
and calculations suggest that auto ignition of fuel can be enhanced
by the addition of a small amount of partially reformed fuel
molecules to the air/fuel mixture. In particular, partially
reformed fuels have been shown to alter the temperature
requirements for successful combustion in HCCI engines. Research
has shown that molecules such as oxygenated hydrocarbons are
particularly desirable partially reformed fuels. Examples of such
oxygenated hydrocarbons include Acetaldehyde, Propenal, Butanal,
and Butanone. As will be discussed below in greater detail, there
are a number of methods for using the plasma fuel reformer 12 to
attain these partially reformed molecules.
[0093] Referring now to FIG. 11, the plasma fuel reformer 12 may be
used in conjunction with a heat exchanger 310. In such an
arrangement, thermal energy could be removed from the hot H.sub.2
and CO mixture as it exits the plasma fuel reformer 12. This
thermal energy may be used to heat an ultra lean mixture of air and
fuel that is in a reservoir 312 that is remote from the fuel
reformer 12. If the lean air/fuel mixture is heated to temperatures
near 300.degree. C., the fuel will begin to break up and be
partially reformed. The air/fuel ratio of the ultra lean mixture
may be >25.
[0094] Another way to attain partially reformed molecules is shown
in FIG. 12. In this case, the reactions within the plasma fuel
reformer 12 are quenched before they go to completion (i.e., before
the H.sub.2 and CO is produced in large quantities). To do so, a
heat exchanger 314 or some other device is used to quickly cool the
gasses as they leave the fuel reformer 12 thereby freezing the
chemistry in such a way that the fuel molecule remains primarily
intact or is only slightly reformed. This arrangement differs from
the arrangement of FIG. 11 in that the normal operation of the fuel
reformer 12 is altered in order to manipulate the chemical
composition of the gasses as they leave the reformer.
[0095] Another arrangement for attaining partially reformed
molecules is shown in FIG. 13. Computations suggest that the
reformate gas exiting a normally operating fuel reformer 12
contains a small amount of partially reformed fuel fragments. The
hydrogen and CO, which inhibit auto ignition, may be separated from
the partially reformed fuel molecules which help enable auto
ignition by use of a separator 316 positioned downstream of the
fuel reformer 12. This would allow for a wide amount of control
over the effective octane number of a fuel. Hydrogen and CO could
be added to the intake of an engine when a high octane fuel is
required. Partially reformed fuel could be added to the intake of
the engine when auto ignition may be beneficial.
[0096] As shown in FIG. 14, the magnitude of the power supplied to
the plasma fuel reformer may be reduced to initiate a small number
of reactions in the plasma fuel reformer system without allowing
for enough initial energy release to trip the reaction into full
fuel reforming. For example, depending on, amongst other things,
the air/fuel ratio of the fuel being reformed and the operating
temperature of the reformer, full fuel reforming (i.e., the
production of significant quantities of H.sub.2 and CO) can be
achieved at power levels of 70-100 W. Oxygenated hydrocarbons may
be generated at lower power levels in the range of, for example,
25-100 W.
[0097] As shown in FIG. 15, a stoichiometric mixture of air and
fuel is processed in the fuel reformer 12 to generate a large
amount of heat (carbon dioxide and water would also be generated).
This high temperature mixture may then be directed into a mixing
chamber 318 along with an ultra lean mixture of air and some
secondary fuel which is at a very low temperature (room
temperature). By manipulating the flow rate of the stoichiometric
mixture and the mass of the ultra lean mixture, the resulting
temperature of the final mixture may be controlled to a temperature
of about 300.degree. C. This mixture will begin to react, thus
reforming the fuel. This method allows for control over the
temperature of the mixture, which also allows for control over the
amount of the secondary fuel that reforms.
[0098] While the disclosure is susceptible to various modifications
and alternative forms, specific exemplary embodiments thereof have
been shown by way of example in the drawings and has 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 falling within the
spirit and scope of the disclosure.
[0099] There are a plurality of advantages of the present
disclosure arising from the various features of the apparatus,
systems, and methods described herein. It will be noted that
alternative embodiments of the apparatus, systems, and methods 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 apparatus, systems, and methods
that incorporate one or more of the features of the present
disclosure and fall within the spirit and scope of the present
disclosure.
[0100] Moreover, although the diverter valve 88 is herein described
in regard to the directing of engine exhaust gas, along with a
regenerating fluid in the form of reformate gas from a fuel
reformer, it should be appreciated that the valve 88 may be used in
regard to other types of regenerating fluids. For example, the
diverter valve 88 may be used to direct regenerating fluids in the
form of reductant gases which originate from sources other than
onboard reformers such as tanks or other storage devices.
[0101] The diverter valve 88 may also be used to direct
regenerating fluids in forms other than gases. For example, in
certain embodiments, the diverter valve 88 may be used to direct
regenerating fluids in the form of liquid hydrocarbon fuels. For
instance, the diverter valve 88 may be used to direct regenerating
fluid in the form of untreated diesel fuel. In such a case, for
example, the untreated diesel fuel may be injected into the valve
88 (e.g., through the regenerating fluid inlet 148) by use of a
fuel injector assembly (including a fuel injector assembly that
atomizes the diesel fuel prior to or during injection thereof).
* * * * *