U.S. patent application number 13/041672 was filed with the patent office on 2011-06-30 for exhaust gas purification apparatus for diesel engine.
This patent application is currently assigned to UD TRUCKS CORPORATION. Invention is credited to Kiminobu HIRATA, Nobuhiko MASAKI, Masakazu YANO.
Application Number | 20110154808 13/041672 |
Document ID | / |
Family ID | 42005152 |
Filed Date | 2011-06-30 |
United States Patent
Application |
20110154808 |
Kind Code |
A1 |
HIRATA; Kiminobu ; et
al. |
June 30, 2011 |
EXHAUST GAS PURIFICATION APPARATUS FOR DIESEL ENGINE
Abstract
A DPF disposed in an exhaust passage of a diesel engine is
coated with a selective reducing catalyst, for selectively reducing
and purifying NOx by using a reducing agent, and a thin film,
having fine pores of size for allowing passage of the NOx and
preventing passage of PM, in this order. In regeneration treatment
of a DPF, the thin film prevents direct transmission of combustion
heat of the PM to the selective reducing catalyst and suppresses a
temperature rise of the selective reducing catalyst to thereby
suppress deterioration of an active component.
Inventors: |
HIRATA; Kiminobu; (Ageo-shi,
JP) ; MASAKI; Nobuhiko; (Ageo-shi, JP) ; YANO;
Masakazu; (Ageo-shi, JP) |
Assignee: |
UD TRUCKS CORPORATION
|
Family ID: |
42005152 |
Appl. No.: |
13/041672 |
Filed: |
March 7, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/JP2009/065521 |
Sep 4, 2009 |
|
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13041672 |
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Current U.S.
Class: |
60/297 |
Current CPC
Class: |
F01N 3/0821 20130101;
F01N 2510/02 20130101; B01D 2251/21 20130101; F01N 3/023 20130101;
F01N 3/029 20130101; B01D 2251/208 20130101; Y02T 10/12 20130101;
B01D 2251/2067 20130101; B01D 53/944 20130101; F01N 3/2066
20130101; Y02T 10/24 20130101; B01D 53/9431 20130101; F01N 2610/02
20130101; F01N 13/0097 20140603 |
Class at
Publication: |
60/297 |
International
Class: |
F01N 3/035 20060101
F01N003/035 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 9, 2008 |
JP |
2008-230820 |
Claims
1. An exhaust gas purification apparatus for a diesel engine,
comprising: a diesel particulate filter disposed in an exhaust
passage of the diesel engine; a selective reducing catalyst for
selectively reducing and purifying nitrogen oxides by using a
reducing agent; and a thin film, having fine pores of size for
allowing passage of the nitrogen oxides and preventing passage of
particulate matter, wherein the diesel particulate filter is coated
with the selective reducing catalyst and the thin film in this
order.
2. An exhaust gas purification apparatus for a diesel engine
according to claim 1, wherein the thin film is applied only on an
exhaust inflow face of the diesel particulate filter.
3. An exhaust gas purification apparatus for a diesel engine
according to claim 1, wherein the thin film is made of alumina or
zeolite.
Description
[0001] This application is a continuation of PCT/JP2009/065521,
filed on Sep. 4, 2009.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a technique for removing
nitrogen oxides (NOx) and particulate matter (PM) in exhaust gas in
an exhaust gas purification apparatus for a diesel engine.
[0004] 2. Description of Related Art
[0005] As an exhaust gas purification apparatus for simultaneously
removing NOx and PM included in exhaust gas of a diesel engine, an
apparatus including a diesel particulate filter (DPF) coated with a
NOx selective reducing catalyst as disclosed in Japanese Laid-Open
(Kokai) Patent Application Publication No. 2006-274986 has been
proposed. In this exhaust gas purification apparatus, the PM is
trapped and removed by the DPF while the NOx is selectively reduced
and purified in the NOx selective reducing catalyst by using
ammonia, produced from a urea aqueous solution injection-supplied
on an exhaust upstream side of the DPF, as a reducing agent.
[0006] In the DPF, if clogging develops as an amount of trapped PM
increases, exhaust pressure increases over an acceptable value to
result in low fuel economy. Therefore, regeneration treatment is
indispensable, in the regeneration treatment, the PM trapped by the
DPF is incinerated by the well-known method such as increasing
exhaust temperature by an engine control and actuating an electric
heater provided to the DPF. Because temperature of the DPF
increases due to incineration heat of the PM during the
regeneration treatment of the DPF, temperature of the NOx selective
reducing catalyst applied to the DPF increases as well. In the NOx
selective reducing catalyst, there is a possibility that an active
component is deteriorated by heat due to the excessive temperature
rise.
SUMMARY OF THE INVENTION
[0007] Therefore, in view of the above conventional problems, the
present technique has an object to provide an exhaust gas
purification apparatus for a diesel engine, in which it is possible
to prevent direct transmission of incineration heat of the PM to
the NOx selective reducing catalyst applied to the DPF to thereby
suppress deterioration of an active component.
[0008] In the exhaust gas purification apparatus, a DPF disposed in
an exhaust passage of a diesel engine is coated with a selective
reducing catalyst, for selectively reducing and purifying NOx by
using a reducing agent, and a thin film, having fine pores of size
for allowing passage of the NOx and preventing passage of PM, in
this order.
[0009] With this exhaust gas purification apparatus, the PM
included in exhaust gas of the diesel engine cannot pass through
the thin film and therefore is trapped in a surface of the thin
film. On the other hand, the NOx included in the exhaust gas passes
through the thin film, reaches the selective reducing catalyst, and
is selectively reduced and purified by the selective reducing
catalyst by using a reducing agent. During regeneration treatment
of the DPF, the thin film prevents direct transmission of
incineration heat of the PM to the selective reducing catalyst to
suppress a temperature rise of the selective reducing catalyst. As
a result, it is possible to suppress deterioration of an active
component.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is an overall block view illustrating an example of
an exhaust gas purification apparatus in which the present
technique is embodied;
[0011] FIG. 2 is an explanatory view of a state in which a DPF is
coated with a NOx selective reducing catalyst and a thin film;
and
[0012] FIG. 3 is an enlarged view of a portion A in FIG. 2.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0013] Hereunder is a detailed description of the present technique
with reference to the accompanying drawings.
[0014] FIG. 1 is a general block view of an exhaust gas
purification apparatus for purifying NOx and PM included in exhaust
gas of a diesel engine by using a urea aqueous solution which is a
reducing agent precursor.
[0015] In an exhaust pipe 14 (exhaust passage) connected to an
exhaust manifold 12 of a diesel engine 10, a DPF16 for trapping and
removing the PM in the exhaust gas is disposed. The DPF 16 has a
large number of cells formed substantially parallel to an exhaust
gas flow by partition walls formed of porous members such as
ceramics and inlets and outlets of the respective cells are
alternately sealed with sealing members in a staggered pattern.
When the exhaust gas in the cell with the sealed outlet flows into
the adjacent cell with the sealed inlet through the partition wall,
the PM in the exhaust gas is trapped by the porous member forming
the partition wall.
[0016] As illustrated in FIG. 2, an exhaust inflow face of the DPF
16 is coated with a NOx selective reducing catalyst 18, for
selectively reducing and purifying the NOx by using ammonia as a
reducing agent, and a thin film 20, having fine pores of size for
allowing passage of the NOx and preventing passage of the PM, in
this order. Here, as a method of applying the NOx selective
reducing catalyst 18, for example, an active component may be
directly supported on a surface of the DPF 16 or a washcoat of a
carrier having an active-component-impregnated layer may be applied
on the surface of the DPF 16. On the other hand, as the thin film
20, it is preferable to employ alumina or zeolite in order to make
it easy to form the thin film 20.
[0017] A spray nozzle 22 for spraying the urea aqueous solution is
disposed in the exhaust pipe 14 on an exhaust upstream side of the
DPF 16. The urea aqueous solution stored in a reducing agent tank
24 is supplied to the spray nozzle 22 via a reducing agent dosing
device 26 including a pump and a flow rate control valve.
[0018] As a control system of the exhaust gas purification
apparatus, in the exhaust pipe 14 on the exhaust upstream side of
the spray nozzle 22, a temperature sensor 28 for measuring
temperature (exhaust temperature) of the exhaust gas introduced
into the DPF 16 is disposed. An output signal of the temperature
sensor 28 is input to a reducing agent dosing control unit
(hereafter referred to as "DCU (Dosing Control Unit)") 30 including
a computer. The DCU 30 is connected to an engine control unit (ECU)
32 so as to be able to communicate with the ECU 32 through a
network such as a CAN (Controller Area Network) in order to
appropriately read in an engine rotation speed and an engine load
as engine operating states. As the engine load, a known state
quantity such as a fuel injection amount, torque, an accelerator
opening, a throttle opening, an intake flow rate, intake negative
pressure, and supercharging pressure may be used.
[0019] The DCU 30 executes a control program stored in ROM (Read
Only Memory) to compute the urea aqueous solution dosing flow rate
suitable to the exhaust temperature, the engine rotation speed, and
the engine load, to thereby output a control signal according to
the dosing flow rate to the reducing agent dosing device 26. In the
reducing agent dosing device 26, the pump and the flow rate control
valve are appropriately and electronically controlled based on the
control signal from the DCU 30, and the urea aqueous solution of
the flow rate according to the engine operating state is supplied
to the spray nozzle 22.
[0020] In this exhaust gas purification apparatus, the urea aqueous
solution sprayed from the spray nozzle 22 into the exhaust pipe 14
is hydrolyzed by exhaust heat and water vapor in the exhaust gas
and converted into ammonia and the ammonia flows in the exhaust
flow and is supplied to the DPF 16. The thin film 20 applied on the
exhaust inflow face of the DPF 16 has fine pores of size for
allowing passage of the NOx and preventing passage of PM, and thus,
as illustrated in FIG. 3, the PM 34 in the exhaust gas is trapped
in the surface of the thin film 20 and the NOx 36 in the exhaust
gas passes through the thin film 20 and reaches the NOx selective
reducing catalyst 18. The NOx selective reducing catalyst 18
selectively reduces and purifies the NOx 36 in the exhaust gas by
using the ammonia supplied while flowing in the exhaust flow.
[0021] Then, for example, even if the exhaust temperature is
increased by an engine control to ignite the PM 34 in order to
carry out regeneration treatment of the DPF 16, existence of the
thin film 20 prevents direct transmission of incineration heat of
the PM 34 to the NOx selective reducing catalyst 18. As a result,
it is possible to suppress a temperature rise of the NOx selective
reducing catalyst 18 to thereby suppress deterioration of the
active component.
[0022] At this time, because the NOx selective reducing catalyst 18
and the thin film 20 are applied only on the exhaust inflow face of
the DPF 16, exhaust-passing resistance of the DPF 16 coated with
the NOx selective reducing catalyst 18 and the thin film 20 can be
reduced and it is possible to suppress reduction in fuel economy
and output due to increase in exhaust pressure. The thin film 20 is
made of alumina or zeolite, and thus, it is easy to form the thin
film 20.
[0023] Although the exhaust gas purification apparatus described
above is based on the premise that the urea aqueous solution is
used as the reducing agent precursor, it is also possible to use
hydrocarbon, alcohol, diesel oil, solid urea, and the like as the
reducing agent or the precursor thereof according to a mechanism
for selectively reducing and purifying the NOx. The technique can
be applied not only to the device in which the reducing agent or
the precursor thereof is injection supplied into the exhaust pipe
14 but also to a device in which a catalytic converter is used to
produce a reducing agent from exhaust components. Furthermore, the
NOx selective reducing catalyst 18 and the thin film 20 may be
applied on an exhaust oufflow face as well as on the exhaust inflow
face of the DPF 16. Here, because the thin film 20 applied on the
exhaust oufflow face of the DPF 16 does not contribute to trapping
of the PM, it is preferable to apply only the NOx selective
reducing catalyst 18 on the exhaust outflow face of the DPF 16 from
a viewpoint of reduction of the exhaust-passing resistance.
[0024] It should be noted that the entire contents of Japanese
Patent Application No. 2008-230820, filed on Sep. 9, 2008, on which
the convention priority is claimed is incorporated herein by
reference.
[0025] It should also be understood that many modifications and
variations of the described embodiments of the technique will occur
to a person having an ordinary skill in the art without departing
from the spirit and scope of the present technique as claimed in
the appended claims.
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