U.S. patent application number 12/430194 was filed with the patent office on 2010-10-28 for diesel aftertreatment system.
This patent application is currently assigned to Tenneco Automotive Operating Company Inc.. Invention is credited to Timothy Gardner, Arda Gundogan, Timothy E. Jackson, Adam J. Kotrba, Dervis A. Yetkin.
Application Number | 20100269492 12/430194 |
Document ID | / |
Family ID | 42990871 |
Filed Date | 2010-10-28 |
United States Patent
Application |
20100269492 |
Kind Code |
A1 |
Kotrba; Adam J. ; et
al. |
October 28, 2010 |
DIESEL AFTERTREATMENT SYSTEM
Abstract
A diesel exhaust gas aftertreatment system (10) is provided to
treat the exhaust (12) from a diesel combustion process (14), such
as a diesel compression engine (16). The system (10) includes a
burner (18) that selectively supplies the exhaust (12) at an
elevated temperature to the rest of the system (10), a diesel
particulate filter (20) connected downstream from the burner (18)
to receive the exhaust (12) therefrom, and a NO.sub.x reducing
device (22) connected downstream from the filter (20) to receive
the exhaust therefrom.
Inventors: |
Kotrba; Adam J.;
(Laingsburg, MI) ; Jackson; Timothy E.; (Dexter,
MI) ; Yetkin; Dervis A.; (Ann Arbor, MI) ;
Gundogan; Arda; (Ypsilanti, MI) ; Gardner;
Timothy; (Canton, MI) |
Correspondence
Address: |
WOOD, PHILLIPS, KATZ, CLARK & MORTIMER
500 W. MADISON STREET, SUITE 3800
CHICAGO
IL
60661
US
|
Assignee: |
Tenneco Automotive Operating
Company Inc.
|
Family ID: |
42990871 |
Appl. No.: |
12/430194 |
Filed: |
April 27, 2009 |
Current U.S.
Class: |
60/297 ; 60/300;
60/301 |
Current CPC
Class: |
F01N 2240/14 20130101;
F01N 3/0842 20130101; F01N 3/025 20130101; F01N 13/009 20140601;
Y02T 10/24 20130101; F01N 2610/04 20130101; F01N 3/0231 20130101;
F01N 3/035 20130101; F01N 2610/02 20130101; F01N 3/2066 20130101;
F01N 3/106 20130101; F01N 2610/03 20130101; Y02T 10/12 20130101;
F01N 3/0807 20130101 |
Class at
Publication: |
60/297 ; 60/300;
60/301 |
International
Class: |
F01N 3/035 20060101
F01N003/035; F01N 3/10 20060101 F01N003/10 |
Claims
1. A diesel exhaust gas treatment system to treat the exhaust from
a diesel combustion process, the system comprising: a burner to
receive the exhaust and selectively heat the exhaust with a flame
to supply the exhaust at an elevated temperature to the rest of the
system; a diesel particulate filter connected downstream from the
burner to receive the exhaust therefrom; and at least one of a
selective catalytic reduction catalyst and a NO.sub.x trap
connected downstream from the diesel particulate filters to receive
the exhaust therefrom
2. The system of claim 1 further comprising a diesel oxidation
catalyst connected downstream from the burner to receive the
exhaust therefrom and upstream from the diesel particulate filters
to deliver the exhaust thereto.
3. The system of claim 2 further comprising a diesel oxidation
catalyst connected downstream from the diesel particulate filters
to receive the exhaust therefrom and upstream from the selective
catalytic reduction catalyst to deliver the exhaust thereto.
4. The system of claim 2 further comprising a fuel injector located
downstream from the burner and upstream of the DOC.
5. The system of claim 1 wherein the burner comprises at least one
fuel injector and at least one igniter.
6. The system of claim 1 wherein the at least one of a selective
catalytic reduction catalyst and a NO.sub.x trap is a selective
catalytic reduction catalyst and further comprising a reductant
injector connected upstream from the catalyst.
7. A method of treating a diesel exhaust from a diesel combustion
process, the method comprising the steps of: (a) selectively
increasing the temperature of the exhaust by burning a fuel in the
exhaust flow downstream from the diesel combustion process; (b)
removing soot from a filter by oxidizing carbon into the increased
temperature exhaust provided from step (a); and (c) removing
NO.sub.x carried in the exhaust provided from step (b).
8. The method of claim 7 further comprising the step of producing
NO.sub.2 by passing the exhaust from step (a) through an oxidation
catalyst prior to step (b).
9. The method of claim 8 further comprising the step of producing
NO.sub.2 by passing the exhaust from step (b) through an oxidation
catalyst prior to step (c).
10. The method of claim 8 further comprising the step of injecting
fuel into the exhaust after step (a) and prior to step (b).
11. The method of claim 7 wherein step (a) comprises the steps of
injecting a fuel into the exhaust and igniting the fuel.
12. The method of claim 7 wherein step (c) comprises converting
NO.sub.x to N.sub.2 by passing the exhaust over a selective
catalytic reduction catalyst.
13. The method of claim 7 wherein step (c) comprises trapping
NO.sub.x.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] Not Applicable.
FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not Applicable.
MICROFICHE/COPYRIGHT REFERENCE
[0003] Not Applicable.
FIELD OF THE INVENTION
[0004] This invention relates to systems and methods for treating
exhaust gases from a diesel combustion process, such as a diesel
compression engine, and more particularly to systems for reducing
oxides of nitrogen (NO.sub.x) and particulate matter (PM) emissions
from diesel compression engines.
BACKGROUND OF THE INVENTION
[0005] Environmental regulations have called for increasing
emission limits that require reduction in the NO.sub.x and PM from
diesel combustion processes, and in particular from diesel
compression engines. While diesel particulate filters (DPF) are
capable of achieving the required reductions in PM, which is
typically carbonaceous particulates in the form of soot, there is a
continuing need for improved systems that can provide the required
reductions in NO.sub.x in connection with the particulate matter
reduction provided by a DPF.
[0006] In this regard, systems have been proposed to provide a
diesel oxidation catalyst (DOC) upstream from a DPF in order to
provide an increased level of NO.sub.2 in the exhaust which reacts
with the soot gathered in the DPF to produce a desired regeneration
of the DPF (often referred to as a passive regeneration). However,
such systems become limited at temperatures below 300.degree. C.
and typically produce a pressure drop across the oxidation catalyst
that must be accounted for in the design of the rest of the system.
Additionally fuel, such as hydrogen or hydrocarbon fuel, can be
delivered upstream of the DOC to generate temperatures greater than
600.degree. F. in the DPF (often referred to as active
regeneration).
SUMMARY OF THE INVENTION
[0007] In accordance with one feature of the invention, a diesel
exhaust gas treatment system is provided to treat the exhaust from
a diesel combustion process. The system includes a burner to
receive the exhaust and selectively heat the exhaust with a flame
to supply the exhaust at an elevated temperature to the rest of the
system, a diesel particulate filter (DPF) connected downstream from
the burner to receive the exhaust therefrom, and at least one of a
selective catalytic reduction catalyst (SCR) and a NO.sub.x trap
connected downstream from the diesel particulate filter to receive
the exhaust therefrom.
[0008] As one feature, the system further includes a diesel
oxidation catalyst connected downstream from the burner to receive
the exhaust therefrom and upstream from the DPF to deliver the
exhaust thereto. In a further feature, the system further includes
a fuel injector located downstream from the burner and upstream of
the DOC.
[0009] In one feature, the system further includes a diesel
oxidation catalyst connected downstream from the DPF to receive the
exhaust therefrom and upstream from the SCR to deliver the exhaust
thereto.
[0010] According to one feature, the burner includes at least one
fuel injector and at least one igniter.
[0011] As one feature, the at least one of a selective catalytic
reduction catalyst and a NO.sub.x trap is a selective catalytic
reduction catalyst and further includes a reductant injector
connected upstream from the catalyst.
[0012] In accordance with one feature of the invention, a method is
provided for treating a diesel exhaust from a diesel combustion
process. The method includes the steps of:
[0013] (a) selectively increasing the temperature of the exhaust by
burning a fuel in the exhaust flow downstream from the diesel
combustion process;
[0014] (b) removing soot from a filter by oxidizing carbon into the
increased temperature exhaust provided from step (a); and
[0015] (c) removing NO.sub.x carried in the exhaust provided from
step (b).
[0016] In one feature, the method further includes the step of
producing NO.sub.2 by passing the exhaust from step (a) through an
oxidation catalyst prior to step (b). As a further feature, the
method further includes the step of injecting fuel into the exhaust
after step (a) and prior to step (b).
[0017] In a further feature, the method of further includes the
step of producing NO.sub.2 by passing the exhaust from step (b)
through an oxidation catalyst prior to step (c).
[0018] According to one feature, step (a) includes the steps of
injecting a fuel into the exhaust and igniting the fuel.
[0019] As one feature, step (c) includes converting NO.sub.x to
N.sub.2 by passing the exhaust over a selective catalytic reduction
catalyst.
[0020] In one feature, step (c) includes trapping NO.sub.x.
[0021] Other objects, features, and advantages of the invention
will become apparent from a review of the entire specification,
including the appended claims and drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 is a diagrammatic representation of a diesel exhaust
gas treatment system embodying the invention in connection with a
diesel combustion engine; and
[0023] FIGS. 2-4 are a representations similar to FIG. 1, but
showing alternate embodiments of the diesel exhaust gas treatment
system.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0024] A diesel exhaust gas aftertreatment system 10 is provided to
treat the exhaust 12 from a diesel combustion process 14, such as a
diesel compression engine 16. The exhaust 12 will typically contain
oxides of nitrogen (NO.sub.x) such as nitric oxide (NO) and
nitrogen dioxide (NO.sub.2) among others, particular matter (PM),
hydrocarbons, carbon monoxide (CO), and other combustion
byproducts.
[0025] The system 10 includes a burner 18 that selectively supplies
the exhaust 12 at an elevated temperature to the rest of the system
10, a diesel particulate filter (DPF) 20 connected downstream from
the burner 18 to receive the exhaust 12 therefrom, and a NO.sub.x
reducing device 22, such as a selective catalytic reduction
catalyst (SCR) 24, as shown in FIG. 1, or a lean NO.sub.x trap 26,
as shown in FIG. 2, connected downstream from the DPF 20 to receive
the exhaust 12 therefrom. To overcome the lower operating
temperatures in the exhaust 12 of lean-burn engines, such as the
diesel compression engine 16, an active regeneration process for
the DPF 20 is employed wherein fuel is ignited in the burner 18 to
create a flame 28 that heats the exhaust 12 to an elevated
temperature that will allow for oxidation of the PM in the DPF 20.
Additionally, in connection with such active regeneration, or
independent thereof, the burner 18 can be used in a similar manner
to heat the exhaust 12 to an elevated temperature that will enhance
the conversion efficiency of the SCR 24. Advantageously, the burner
18 can provide such elevated temperatures, either selectively or
continuously, independent of any particular engine operating
condition, including operating conditions that produce a low
temperature (<300 C) in the exhaust 12 as it exits the engine
16. Thus, the system 10 can be operated without requiring
adjustments to the engine controls.
[0026] The burner 18 preferably will include one or more injectors
30 for injecting suitable fuel, a couple examples of which are
hydrogen and hydrocarbons, and an oxygenator, such as air, to be
ignited together with unburned fuel already carried in the exhaust
by one or more igniters, such as spark plugs 32. In this regard,
each injector 30 can either be a combined injector that injects
both the fuel and oxygenator, or a specific injector for one of the
fuel or the oxygenator. Preferably, a control system, shown
schematically at 34, is provided to monitor and control the flows
through the injectors 30 and the ignition by the igniters 32 using
any suitable processor(s), sensors, flow control valves, electric
coils, etc.
[0027] The DPF 20 can be of any suitable construction or type, many
of which are known.
[0028] Any suitable catalyst can be utilized for the SCR 24,
examples of which include Cu based, Iron based and Vandia based
catalysts of any suitable construction or type. Preferably, the
system 10 also includes an reductant injector 36, again of any
suitable construction and type, that can introduce a nitrogenous
reductant, such as ammonia, urea, hydrocarbons, hydrogen, or syngas
into the exhaust 12 to reduce the NO.sub.x content in the exhaust
12 by preferably at least 25% and by as much as 99% under the right
conditions. In this regard, the temperature in the SCR will be
highly dependent upon the type of reductant used. The injector 36
can be supplied by a pressurized reductant source (not shown) and
controlled by the controller 34 or an independent controller (not
shown).
[0029] With reference to FIG. 2, any suitable construction and type
of lean NO.sub.x trap 26 can be utilized and preferably will store
NO.sub.2 during operating conditions that utilize a lean fuel-air
mixture, and reduce the stored NO.sub.2 to N.sub.2 and O.sub.2
under operating conditions that utilize a rich fuel-air mixture. In
this regard, while not preferred, if required supplemental
hydrocarbon fuel can be injected upstream of the trap 26 to produce
a rich fuel-air condition in the trap 26 to assist in forming
N.sub.2, H.sub.2O and CO.sub.2. from the stored NO.sub.2.
[0030] In operation, the need for active regeneration of the DPF 20
by the system 10 can be determined by based on a number of
parameters or combination of parameters, such as the DPF pressure
drop, DPF soot mass, a predetermined operating time set point, and
fuel consumption rate. Similarly, the active regeneration of the
DPF 20 can be terminated based on a number of parameters or
combination of parameters, such as the DPF pressure drop, DPF soot
mass, and a predetermined regeneration time set point. During
active regeneration, the injection of fuel and air via the
injector(s) 30 can be based on a number of parameters or
combination of parameters, including the flow rate of the exhaust
12, the oxygen concentration in the exhaust 12 and, the inlet and
outlet temperatures of the exhaust 12 to and from the DPF 20, with
flame stability being monitored by igniter ionization detection or
by comparing the inlet and outlet temperatures of the exhaust 12 to
and from the burner 18.
[0031] Similar control schemes utilizing the corresponding and
suitable parameters for the SCR 24 and/or lean NO.sub.x trap 26 can
be utilized to provide active use of the burner 18 to improve
performance and/or provide regeneration.
[0032] It should be appreciated that the system 10 can provide
enhanced fuel efficiency in comparison to known aftertreatment
systems that require excess fuel injection into the engine or
system in order to obtain suitable regeneration of a DPF. It should
also be appreciated that the burner 18 can be designed for a
relatively low pressure drop in the exhaust 12 through the burner
18, particularly in comparison to systems that rely on passive or
active regeneration by passing the exhaust through a DOC upstream
of a DPF to provide sufficient NO.sub.2 for passive regeneration of
the DPF. It should further be appreciated that the passage of the
exhaust 12 through the DPF 20 upstream of the SCR 24 tends to
dampen the thermal fluctuations in the SCR 24 which can simplify
the control of the reductant injection.
[0033] With reference to FIG. 3, an alternate embodiment of the
system 10 is shown wherein a DOC 40 is connected between the burner
18 and the DPF 20 to provide NO.sub.2 in the exhaust 12 for passive
regeneration of the DPF 20 at some level during operating
conditions that are favorable to passive regeneration. This can
reduce the demand for active regeneration by the burner 18 and
thereby increase the overall fuel efficiency of the system 10.
[0034] FIG. 4 shows yet another embodiment of the system 10 similar
to FIG. 3, but having yet another DOC 42 added between DPF 20 and
the SCR 24 to provide additional NO.sub.2 to optimize the reactions
in the SCR 24. As further alternative for the system 10, a fuel
injector 44 can be added between the burner 18 and the DOC 40 to
selectively provide additional fuel, two examples of which are
hydrocarbon fuel and hydrogen, to enhance the reactions in the DOC
40 and produce additional quantities of NO.sub.2 in the exhaust
under certain operating conditions.
* * * * *