U.S. patent application number 12/066604 was filed with the patent office on 2009-10-29 for exhaust emission control device.
This patent application is currently assigned to HINO MOTORS, LTD.. Invention is credited to Mitsuru Hosoya, Mori Ishii, Masatoshi Shimoda.
Application Number | 20090266056 12/066604 |
Document ID | / |
Family ID | 37864919 |
Filed Date | 2009-10-29 |
United States Patent
Application |
20090266056 |
Kind Code |
A1 |
Hosoya; Mitsuru ; et
al. |
October 29, 2009 |
EXHAUST EMISSION CONTROL DEVICE
Abstract
Fuel added to exhaust gas is uniformly afforded to catalytic
surfaces of a NO.sub.x-adsorption reduction catalyst so that
overall regeneration of the NO.sub.x-adsorption reduction catalyst
proceeds efficiently. The invention is directed to an exhaust
emission control device with the NO.sub.x-adsorption reduction
catalyst incorporated in an exhaust pipe (exhaust flow passage) for
guidance of the exhaust gas 9 from an engine 1 and with an fuel
addition device (fuel addition means) 13 arranged for addition of
fuel as a reducing agent to the exhaust pipe (exhaust flow passage)
11 upstream of the reduction catalyst 12 (exhaust flow passage) 11,
a dispersion plate 15 being arranged between a position of adding
the fuel by the fuel addition device 13 and the NO.sub.x-adsorption
reduction catalyst 12 for dispersing the exhaust gas 9 to stimulate
dispersion of the added fuel.
Inventors: |
Hosoya; Mitsuru; ( Tokyo,
JP) ; Shimoda; Masatoshi; (Tokyo, JP) ; Ishii;
Mori; (Tokyo, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND MAIER & NEUSTADT, L.L.P.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
HINO MOTORS, LTD.
Hino-shi, Tokyo
JP
|
Family ID: |
37864919 |
Appl. No.: |
12/066604 |
Filed: |
September 12, 2006 |
PCT Filed: |
September 12, 2006 |
PCT NO: |
PCT/JP2006/318019 |
371 Date: |
March 12, 2008 |
Current U.S.
Class: |
60/286 ; 60/295;
60/297; 60/301; 60/310 |
Current CPC
Class: |
F01N 3/2892 20130101;
Y02C 20/10 20130101; Y02A 50/20 20180101; F01N 2240/20 20130101;
F01N 2570/14 20130101; F01N 2610/03 20130101; F01N 3/0814 20130101;
F01N 13/0097 20140603; B01D 53/9431 20130101; Y02A 50/2344
20180101; F01N 3/0842 20130101; F01N 3/0821 20130101 |
Class at
Publication: |
60/286 ; 60/301;
60/297; 60/310; 60/295 |
International
Class: |
F01N 9/00 20060101
F01N009/00; F01N 3/10 20060101 F01N003/10; F01N 3/035 20060101
F01N003/035; F01N 3/04 20060101 F01N003/04; F01N 3/023 20060101
F01N003/023 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 13, 2005 |
JP |
2005-265289 |
Claims
1. An exhaust emission control device wherein a NO.sub.x-adsorption
reduction catalyst is incorporated in an exhaust flow passage for
guiding exhaust gas from an engine, fuel addition means for
addition of fuel as reducing agent being provided in the exhaust
flow passage upstream of the reduction catalyst, a dispersion plate
being provided between a position of adding fuel by the fuel
addition means and the reduction catalyst so as to disperse the
exhaust gas to stimulate dispersion of the added fuel.
2. An exhaust emission control device according to claim 1, wherein
the dispersion plate is composed of at least either of punching
metal and metal mesh.
3. An exhaust emission control device according to claim 1, wherein
a catalytic regenerative particulate filter is arranged just behind
the NO.sub.x-adsorption reduction catalyst.
4. An exhaust emission control device according to claim 2, a
catalytic regenerative particulate filter is arranged just behind
the NO.sub.x-adsorption reduction catalyst.
Description
TECHNICAL FIELD
[0001] The present invention relates to an exhaust emission control
device.
BACKGROUND ART
[0002] Conventionally, exhaust emission control has been attempted
using an exhaust emission control catalyst incorporated in an
exhaust pipe. Known as such exhaust emission control catalyst is a
NO.sub.x-adsorption reduction catalyst having a feature of
oxidizing NO.sub.x in exhaust gas for temporary adsorption in the
form of nitrate salt when air/fuel ratio of exhaust is lean, and
decomposing and discharging NO.sub.x through intervention of
unburned HC, CO and the like for reduction and purification when
O.sub.2 concentration in the exhaust gas is lowered.
[0003] Since no further NO.sub.x can be adsorbed once an adsorbed
NO.sub.x amount increases into saturation in the
NO.sub.x-adsorption reduction catalyst, it is periodically required
to lower the O.sub.2 concentration in the exhaust gas flowing into
the reduction catalyst to decompose and discharge NO.sub.x.
[0004] For example, in application to a gasoline engine, lowering
the operational air/fuel ratio in the engine (operating the engine
with rich air/fuel ratio) can lower the O.sub.2 concentration and
increase the reduction components such as unburned HC and CO in the
exhaust gas for facilitation of decomposition and discharge of
NO.sub.x. However, in use of a NO.sub.x-adsorption reduction
catalyst in an exhaust emission control device for a diesel engine,
it is difficult to operate the engine with rich air/fuel ratio.
[0005] Thus, it has been necessary that, while an operation with
low .lamda. (.lamda.: air excessive ratio) through fuel injection
control is conducted as much as possible at engine side, fuel (HC)
is added to the exhaust gas upstream of a NO.sub.x-adsorption
reduction catalyst, the added fuel being reacted as reducing agent
with O.sub.2 on the reduction catalyst so as to lower the O.sub.2
concentration in the exhaust gas (see, for example, Reference
1).
[0006] [Reference 1] JP 2001-73748A
SUMMARY OF THE INVENTION
Problems to be Solved by the Invention
[0007] However, in such fuel (HC) addition upstream of the
NO.sub.x-adsorption reduction catalyst, mist in the fuel added to
the exhaust gas is led to the reduction catalyst without dispersed
satisfactorily and tends to nonuniformly hit on catalytic surfaces,
so that there may occur a situation that the regenerative reaction
locally proceeds only around catalytic surfaces on which the mist
of the fuel has been attached, and overall regeneration of the
catalyst does not effectively proceed, disadvantageously resulting
in lowering of recovery ratio of NO.sub.x-adsorption sites occupied
in volume of the reduction catalyst and failing in educing maximal
NO.sub.x reduction performance in the NO.sub.x-adsorption reduction
catalyst
[0008] The invention was made in view of the above and has its
object to uniformly afford fuel added in exhaust gas to catalytic
surfaces of a NO.sub.x-adsorption reduction catalyst so that
overall regeneration of the reduction catalyst may proceed
efficiently.
Means or Measures for Solving the Problems
[0009] The invention is characterized in that a NO.sub.x-adsorption
reduction catalyst is incorporated in an exhaust flow passage for
guiding exhaust gas from an engine, fuel addition means for
addition of fuel as reducing agent being provided in the exhaust
flow passage upstream of the reduction catalyst, a dispersion plate
being provided between a position of adding fuel by the fuel
addition means and the reduction catalyst so as to disperse the
exhaust gas to stimulate dispersion of the added fuel.
[0010] The dispersion plate may be composed of, for example, at
least either of punching metal and metal mesh.
[0011] Thus, the exhaust gas added with fuel by the fuel addition
means passes through the dispersion plate to be dispersed, which
stimulates the dispersion of the added fuel to equalize mist
dispersion in the exhaust flow passage. As a result, uniform fuel
supply to the catalytic surfaces of the NO.sub.x-adsorption
reduction catalyst is realized so that overall regeneration of the
reduction catalyst proceeds efficiently.
[0012] Dispersion of the mist in the fuel added to the exhaust gas
through its passing through the dispersion plate stimulates
refinement or hyperfination of the mist in the fuel. This action of
stimulating the hyperfination of the mist also enhances reactivity
on the catalytic surfaces of the NO.sub.x-adsorption reduction
catalyst in comparison with before to attain improvement of
regeneration efficiency.
[0013] Preferably, in the invention, a catalytic regenerative
particulate filter is arranged just behind the NO.sub.x-adsorption
reduction catalyst, which makes it possible to capture the
particulates entrained in the exhaust gas having passed through the
reduction catalyst to attain concurrent reduction in amount of
NO.sub.x and the particulates.
[0014] The unifomization in reaction of the added fuel in the
front-end NO.sub.x-adsorption reduction catalyst brings about
elevation in temperature of the overall back-end particulate filter
with no localization through resultant reaction heat, so that the
particulates captured are satisfactorily burned off to attain early
regeneration of the particulate filter.
[0015] Excessive fuel for use to regeneration of the front-end
NO.sub.x-adsorption reduction catalyst is oxidized in the back-end
particulate filter, so that HC finally remaining in the exhaust gas
and discharged out of a vehicle is substantially reduced.
EFFECTS OF THE INVENTION
[0016] According to the above exhaust emission control device of
the invention, the following excellent features and advantages can
be obtained.
(I) The fuel added to the exhaust gas can be satisfactorily
dispersed, which can bring about the equalization in mist
dispersion in the added fuel and the refinement or hyperfination of
the mist, so that highly reactive hyperfine fuel mist is uniformly
afforded to the catalytic surfaces of the NO.sub.x-adsorption
reduction catalyst. As a result, effective regeneration of the
NO.sub.x-adsorption reduction catalyst can be realized to educe the
maximal NO.sub.x reduction performance of the NO.sub.x-adsorption
reduction catalyst. (II) When a catalytic regenerative particulate
filter is arranged just behind the NO.sub.x-adsorption reduction
catalyst, the particulates entrained in the exhaust gas having
passed through the NO.sub.x-adsorption reduction catalyst can be
captured to realize concurrent reduction in amount of NO.sub.x and
the particulates. The particulates captured can be efficiently
burned off using the heat from equalized reaction in the front-end
NO.sub.x-adsorption reduction catalyst, and excessive combustible
components for use to the regeneration of the front-end
NO.sub.x-adsorption reduction catalyst can be oxidized to
substantially reduce HC remaining finally in the exhaust gas and
discharged to outside of a vehicle.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a schematic view showing an embodiment of the
invention;
[0018] FIG. 2 is a graph showing differences between the NO.sub.x
reduction ratio whether the dispersion plate exists or not in FIG.
1; and
[0019] FIG. 3 is a graph showing differences in regenerative
treatment time whether the dispersion plate exists in FIG. 1 or
not.
EXPLANATION OF THE REFERENCE NUMERALS
[0020] 1 engine [0021] 9 exhaust gas [0022] 11 exhaust pipe
(exhaust flow passage) [0023] 12 NO.sub.x-adsorption reduction
catalyst [0024] 13 fuel addition device (fuel addition means)
[0025] 14 casing (exhaust flow passage) [0026] 15 dispersion plate
[0027] 16 particulate filter
BEST MODE FOR CARRYING OUT THE INVENTION
[0028] An embodiment of the invention will be described in
conjunction with the drawings.
[0029] FIG. 1 shows an embodiment of the invention. In FIG. 1,
reference numeral 1 denotes a diesel engine, the engine 1
comprising a turbocharger 2 with a compressor 2a and a turbine 2b.
Intake air 4 from an air cleaner 3 is fed via an intake pipe 5 to
the compressor 2a of the turbocharger 2, the intake air 4
pressurized being fed to and cooled by an intercooler 6, the cooled
intake air 4 from the intercooler 6 being further fed to an intake
manifold 7 and dispersed into respective cylinders 8 in the engine
1.
[0030] Exhaust gas 9 discharged from the respective cylinders 8 of
the engine 1 is fed via an exhaust manifold 10 to the turbine 2b of
the turbocharger 2, the exhaust gas having driven the turbine 2b
being guided to the exhaust pipe (exhaust flow passage) 11 and
passing through a NO.sub.x-adsorption reduction catalyst 12
incorporated in the exhaust pipe 11, the gas with reduced NO.sub.x
there being discharged outside of a vehicle.
[0031] Arranged in the exhaust pipe 11 and at an entry side of the
NO.sub.x-adsorption reduction catalyst 12 is a fuel addition device
13 as fuel addition means for injection of the fuel into the
exhaust pipe 11, the fuel added by the fuel addition device 13
being utilized as reducing agent for regeneration of the
NO.sub.x-adsorption reduction catalyst 12.
[0032] Arranged in the exhaust pipe 11 and in an entry portion of a
casing (exhaust flow passage) 14 carrying the NO.sub.x-adsorption
reduction catalyst 12 is a dispersion plate 15 which disperses the
exhaust gas 9 to stimulate dispersion of the added fuel, the
dispersion plate 15 being a ventilation structure composed of, for
example, punching metal and/or metal mesh.
[0033] In the embodiment shown, arranged in the casing 14 and just
behind the NO.sub.x-adsorption reduction catalyst 12 is a catalytic
regenerative particulate filter 16 carrying an oxidation catalyst
so as to capture the particles entrained in the exhaust gas having
passed through the front-end reduction catalyst 12.
[0034] In the figure, reference numeral 17 denotes an EGR pipe; 18,
an EGR valve; and 19, an EGR cooler.
[0035] Thus, with the exhaust emission control device as
constructed in the above, the exhaust gas 9 added with the fuel by
the fuel addition device 13 passes through the dispersion plate 15
to be dispersed to thereby stimulate dispersion of the added fuel
into uniformization of the mist distribution in the casing (exhaust
flow passage) 14. As a result, uniform fuel supply to the catalytic
surfaces of the NO.sub.x-adsorption reduction catalyst 12 is
realized so that the overall regeneration of the
NO.sub.x-adsorption reduction catalyst 12 proceeds efficiently.
Dispersion of the mist of the fuel through its passing through the
dispersion plate 15 stimulates refinement or hyperfination of the
mist in the fuel, so that, through such action of stimulating the
hyperfination of the mist, the reactivity on the catalytic surfaces
of the NO.sub.x-adsorption reduction catalyst 12 is enhanced in
comparison with before to improve the regeneration efficiency.
[0036] Especially in the embodiment, the catalytic regenerative
particulate filter 16 is arranged just behind the
NO.sub.x-adsorption reduction catalyst 12, so that the particles
entrained in the exhaust gas 9 having passed through the front-end
NO.sub.x-adsorption reduction catalyst 12 can be captured by the
back-end particulate filter 16 to attain concurrent reduction in
amount of NO.sub.x and the particulates.
[0037] Moreover, the uniformization in reaction of the added fuel
in the front-end NO.sub.x-adsorption reduction catalyst 12 brings
about elevation in temperature of the overall back-end particulate
filter 16 without localization through the resultant reaction heat,
so that the particulates captured are satisfactorily burned off to
attain early regeneration of the particulate filter 16.
[0038] Thus, according to the embodiment, the fuel added to the
exhaust gas 9 can be satisfactorily dispersed to attain
unifomization of mist dispersion in the added fuel and
hyperfination of the mist, so that the highly reactive hyperfine
fuel mist can be uniformly afforded to the catalytic surfaces of
the NO.sub.x-adsorption reduction catalyst 12 to realize the
effective regeneration of the reduction catalyst 12 and educe
maximal NO.sub.x reduction performance of the reduction catalyst
12.
[0039] In fact, it has been ascertained by validation experiments
conducted by the inventors that, as shown in the graph of FIG. 2,
the NO.sub.x reduction ratio is enhanced in a case where a
dispersion plate 15 is arranged in comparison with a case no
dispersion plate 15 is arranged.
[0040] Especially in the embodiment, the particles entrained in the
exhaust gas 9 having passed through the NO.sub.x-adsorption
reduction catalyst 12 can be captured to realize concurrent
reduction in amount of NO.sub.x and the particulates and, moreover,
the particulates captured can be efficiently burned off using the
heat from the uniformized reaction on the front-end reduction
catalyst 12.
[0041] FIG. 3 shows experimental results in validation on
regenerative treatment time to the particulate filters 16
(treatment time necessary for forced burning-off of the captured
particulates through positive addition of fuel); it has been
ascertained that the regenerative treatment time can be
substantially reduced in a case where the dispersion plate 15 is
provided than in a case where no dispersion plate 15 is
provided.
[0042] When the catalytic regenerative particulate filter 16 is
provided in back-end, any excessive combustibles in use to
regeneration of the front-end NO.sub.x-adsorption reduction
catalyst 12 can be oxidized to substantially reduce HC remaining
finally in the exhaust gas 9 and discharged outside of a
vehicle.
[0043] It is to be understood that an exhaust emission control
device according to the invention is not limited to the above
embodiment and that various changes and modifications may be made
without leaving the spirit of the invention. For example, the
dispersion plate may be composed of any material other than
punching metal and metal mesh.
* * * * *