U.S. patent application number 14/292688 was filed with the patent office on 2014-09-18 for exhaust gas purification apparatus and method for increasing corrosion resistance of exhaust gas purification apparatus.
This patent application is currently assigned to UD TRUCKS CORPORATION. The applicant listed for this patent is UD TRUCKS CORPORATION. Invention is credited to Satoshi SUGIYAMA.
Application Number | 20140260204 14/292688 |
Document ID | / |
Family ID | 48574031 |
Filed Date | 2014-09-18 |
United States Patent
Application |
20140260204 |
Kind Code |
A1 |
SUGIYAMA; Satoshi |
September 18, 2014 |
EXHAUST GAS PURIFICATION APPARATUS AND METHOD FOR INCREASING
CORROSION RESISTANCE OF EXHAUST GAS PURIFICATION APPARATUS
Abstract
An exhaust gas purification apparatus includes a SCR converter
selectively reducing and purifying NOx in exhaust gas upon being
supplied with ammonia generated from urea aqueous solution and an
injection nozzle injection-supplying the urea aqueous solution on
exhaust gas upstream side of the SCR converter. At least a part of
an exhaust pipe located between the injection nozzle and the SCR
converter has a double-pipe structure including inner and outer
pipes, each having a welded portion, and the welded portion of the
outer pipe was welded from an inside of the outer pipe. Thus, the
outer pipe has fine welded portion on an inner peripheral surface
where a welding temperature is high and the coarse welded portion
on an outer peripheral surface where the welding temperature is
low, resulting in an ordered atomic arrangement and thus improved
corrosion resistance of the inner peripheral surface, which may be
exposed to ammonia.
Inventors: |
SUGIYAMA; Satoshi;
(Ageo-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
UD TRUCKS CORPORATION |
Ageo-shi |
|
JP |
|
|
Assignee: |
UD TRUCKS CORPORATION
Ageo-shi
JP
|
Family ID: |
48574031 |
Appl. No.: |
14/292688 |
Filed: |
May 30, 2014 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
PCT/JP2012/078937 |
Nov 8, 2012 |
|
|
|
14292688 |
|
|
|
|
Current U.S.
Class: |
60/274 ;
60/299 |
Current CPC
Class: |
F01N 2450/22 20130101;
F01N 3/2066 20130101; Y02T 10/12 20130101; F01N 2530/02 20130101;
B23K 9/0284 20130101; F01N 13/16 20130101; F01N 2610/02 20130101;
F01N 3/20 20130101; B23K 9/0253 20130101; F01N 13/141 20130101;
B23K 9/167 20130101; F01N 13/08 20130101; Y02T 10/24 20130101 |
Class at
Publication: |
60/274 ;
60/299 |
International
Class: |
F01N 3/20 20060101
F01N003/20 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 6, 2011 |
JP |
2011-266472 |
Claims
1. An exhaust gas purification apparatus comprising: a selective
catalytic reduction converter which is disposed in an exhaust pipe
of an engine and that selectively reduces and purifies nitrogen
oxide contained in exhaust gas upon being supplied with ammonia
generated from a urea aqueous solution; and an injection nozzle
that supplies by injection the urea aqueous solution on an exhaust
gas upstream side of the selective catalytic reduction converter,
wherein at least a part of the exhaust pipe located between the
injection nozzle and the selective catalytic reduction converter
has a double-pipe structure including an inner pipe and an outer
pipe, each of which has a welded portion, wherein the welded
portion of the outer pipe is produced by welding performed from an
inside of the outer pipe.
2. The exhaust gas purification apparatus according to claim 1,
wherein the welding comprises tungsten inert gas welding.
3. The exhaust gas purification apparatus according to claim 1,
wherein each of the inner pipe and the outer pipe has a welded
portion extending in a direction in which an axis thereof
extends.
4. The exhaust gas purification apparatus according to claim 1,
further comprising an oxidation catalytic converter disposed on an
exhaust gas downstream side of the selective catalytic reduction
converter and that oxidizes ammonia.
5. The exhaust gas purification apparatus according to claim 1,
further comprising a diesel particulate filter disposed on the
exhaust gas upstream side of the selective catalytic reduction
converter and that collects and removes particulate matter
contained in the exhaust gas.
6. The exhaust gas purification apparatus according to claim 5,
further comprising a diesel oxidation catalytic converter disposed
on an exhaust gas upstream side of the diesel particulate filter
and that oxidizes nitrogen monoxide contained in the exhaust gas to
nitrogen dioxide.
7. A method for increasing corrosion resistance of an exhaust gas
purification apparatus in which at least a part of an exhaust pipe
located between a selective catalytic reduction converter, that
selectively reduces and purifies nitrogen oxide contained in an
exhaust gas upon being supplied with ammonia generated from a urea
aqueous solution, and an injection nozzle, that supplies by
injection the urea aqueous solution on an exhaust gas upstream side
of the selective catalytic reduction converter, has a double-pipe
structure including an inner pipe and an outer pipe, each of which
has a welded portion, the method comprising the step of producing
the welded portion of the outer pipe by welding performed from an
inside of the outer pipe.
8. The method for increasing corrosion resistance of the exhaust
gas purification apparatus according to claim 7, wherein each of
the inner pipe and the outer pipe is welded by tungsten inert gas
welding.
9. The method for increasing corrosion resistance of the exhaust
gas purification apparatus according to claim 7, wherein each of
the inner pipe and the outer pipe is welded in a direction in which
an axis thereof extends.
Description
[0001] This application is a continuation application of
PCT/JP2012/078937, filed on Nov. 8, 2012.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to an exhaust gas purification
apparatus that selectively reduces and purifies nitrogen oxide
(NOx) contained in exhaust gas of an engine and relates to a method
for increasing corrosion resistance of the exhaust gas purification
apparatus.
[0004] 2. Description of Related Art
[0005] As a catalytic purification system for removing NOx
contained in exhaust gas of an engine, an exhaust gas purification
apparatus disclosed in Japanese Laid-open Patent Application
Publication No. 2005-226528 has been proposed. Such an exhaust gas
purification apparatus supplies by injection a liquid reducing
agent or a precursor thereof according to an engine operation state
on the exhaust gas upstream side of a selective catalytic reduction
(SCR) converter, which is disposed in an exhaust pipe, to thereby
selectively cause a reduction reaction between NOx and the reducing
agent in the SCR converter, so that the NOx is purified into
harmless components. Furthermore, in such an exhaust gas
purification apparatus, a double-pipe structure including an inner
pipe and an outer pipe is applied to the exhaust pipe, in which the
liquid reducing agent or the precursor thereof is supplied by
injection, to prevent the reducing agent or the precursor thereof
from being cooled and deposited.
[0006] In an exhaust gas purification apparatus mounted on a
vehicle, a urea aqueous solution that has advantages in safety and
ease of handling may be used as a precursor of a liquid reducing
agent. In this case, exhaust gas, in which the urea aqueous
solution is mixed, not only passes through an inner pipe of a
double-pipe structure, but also passes between the inner pipe and
an outer pipe. Since an outer peripheral surface of the outer pipe
is exposed to outer air, a temperature in the outer pipe may be
easily decreased to a low temperature, compared to that in the
inner pipe. Furthermore, when the temperature in the outer pipe
becomes less than approximately 200.degree. C. in accordance with
an engine operation state or the like, droplets of the urea aqueous
solution adhering to an inner peripheral surface of the outer pipe
generate biuret while generating ammonia, and thus, the biuret may
be deposited on the inner peripheral surface of the outer pipe. The
biuret deposited on the inner peripheral surface of the outer pipe
generates cyanuric acid and ammonia when a temperature of the
exhaust gas increases according to a change in engine operation
state. Ammonia is corrosive on metals, and accordingly, when a
concentration thereof locally increases, the outer pipe,
particularly a welded portion made thereon, may be corroded. In
addition, the corrosion of the outer pipe may occur not only by the
biuret, but by any precipitate derived from urea.
SUMMARY OF THE INVENTION
[0007] Thus, an object of the present invention is to provide an
exhaust gas purification apparatus, in which an outer pipe has an
improved corrosion resistance, and a method for increasing
corrosion resistance of the exhaust gas purification apparatus.
[0008] The exhaust gas purification apparatus includes: an SCR
converter which is disposed in an exhaust pipe of an engine and
that selectively reduces and purifies nitrogen oxide contained in
exhaust gas upon being supplied with ammonia generated from a urea
aqueous solution; and an injection nozzle that supplies by
injection the urea aqueous solution on an exhaust gas upstream side
of the SCR converter. At least a part of the exhaust pipe located
between the injection nozzle and the SCR converter has a
double-pipe structure including an inner pipe and an outer pipe,
each of which has a welded portion, and the welded portion of the
outer pipe is produced by welding performed from an inside of the
outer pipe.
[0009] In the exhaust pipe having the double-pipe structure
including the inner pipe and the outer pipe, since the outer pipe
is welded from the inside of the outer pipe, grain boundaries of
the welded portion can be fine on an inner peripheral surface and
can be coarse on an outer peripheral surface. Thus, since the grain
boundaries of the welded portion on the inner peripheral surface of
the outer pipe are made finer, an atomic arrangement can be put in
order, and accordingly, corrosion resistance of the inner
peripheral surface, that may be exposed to ammonia, can be
improved, so that occurrence of corrosion can be reduced.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a plan view illustrating an example of an exhaust
gas purification apparatus;
[0011] FIG. 2 is a perspective view illustrating the example of the
exhaust gas purification apparatus;
[0012] FIG. 3 is an explanatory view illustrating the inside of the
example of the exhaust gas purification apparatus;
[0013] FIG. 4 is a cross-sectional view of an exhaust pipe having a
double-pipe structure including an inner pipe and an outer
pipe;
[0014] FIG. 5 is an enlarged view of an X portion of FIG. 4 and an
explanatory view illustrating a state of grain boundaries of welded
portions when the outer pipe is welded from the outside
thereof;
[0015] FIG. 6 is an enlarged view of the X portion of FIG. 4 and an
explanatory view illustrating a state of grain boundaries of the
welded portions when the outer pipe is welded from the inside
thereof; and
[0016] FIG. 7 is an explanatory view illustrating the inside of
another example of the exhaust gas purification apparatus.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0017] Hereinbelow, embodiments for carrying out the present
invention will be described with reference to the accompanying
drawings.
[0018] FIGS. 1 to 3 illustrate an example of an exhaust gas
purification apparatus.
[0019] The exhaust gas purification apparatus includes a first
casing 10 having a tubular shape, a second casing 20, which also
has a tubular shape, and a communication pipe 30 by which far-end
portions of the first casing 10 and the second casing 20
communicate with each other. The first casing 10 and the second
casing 20 are arranged to be close to each other in a manner such
that an axis 10A thereof and an axis 20A thereof are arranged to be
substantially parallel to each other (as used herein, "parallel"
may be confirmed by measuring with the eye). In addition, the
communication pipe 30 is also arranged in a manner such that an
axis 30A thereof is substantially parallel to the axis 10A of the
first casing 10 and the axis 20A of the second casing 20. Here, the
first casing 10, the second casing 20 and the communication pipe 30
correspond to a part of an exhaust pipe of an engine.
[0020] The first casing 10 is provided with an inlet 12 formed on
an exhaust gas upstream end thereof and an outlet 14 formed on an
exhaust gas downstream end thereof. In the present embodiment, the
inlet 12 is formed on an end face of the exhaust gas upstream end,
and the outlet 14 is formed on a side face of the exhaust gas
downstream end. Furthermore, between the inlet 12 and the outlet
14, a diesel oxidation catalytic (DOC) converter 16 that oxidizes
at least NO (nitrogen monoxide) to NO.sub.2 (nitrogen dioxide), and
a diesel particulate filter (hereinbelow, referred to as "DPF") 18
that collects and removes particulate matter (PM) are disposed in a
manner such that the DOC converter 16 is arranged on the exhaust
gas upstream side of the DPF 18.
[0021] The second casing 20 is provided with an inlet 22 formed on
an exhaust gas upstream end thereof and an outlet 24 formed on an
exhaust gas downstream end thereof. In the present embodiment, both
of the inlet 22 and the outlet 24 are formed on side faces of the
ends. Furthermore, between the inlet 22 and the outlet 24, an SCR
converter 26 that selectively reduces and purifies NOx using
ammonia as a reducing agent, and an oxidation catalytic converter
28 that oxidizes ammonia which has been passed through the SCR
converter 26 are disposed in a manner such that the SCR converter
26 is arranged on the exhaust gas upstream side of the oxidation
catalytic converter 28.
[0022] The communication pipe 30 communicates far-end portions of
the first casing 10 and the second casing 20 with each other, that
is, communicates the outlet 14 of the exhaust gas downstream end of
the first casing 10 with the inlet 22 of the exhaust gas upstream
end of the second casing 20, which are the end portions located
opposite to and far from each other. Thus, exhaust gas of the
engine flows into the first casing 10 via the inlet 12, and passes
through the DOC converter 16 and the DPF 18, and then, enters the
communication pipe 30 via the outlet 14. Then, through the
communication pipe 30, the exhaust gas flows into the second casing
20 via the inlet 22, and then, the exhaust gas is discharged from
the outlet 24, passing through the SCR converter 26 and the
oxidation catalytic converter 28. That is, a passage of the exhaust
gas from the first casing 10 to the second casing 20 through the
communication pipe 30 is made to turn once by the communication
pipe 30.
[0023] Furthermore, the communication pipe 30 is a linearly formed
straight pipe, both ends of which are formed to be bent portions
for connecting the communication pipe 30 to the outlet 14 of the
first casing 10 and the inlet 22 of the second casing 20. To the
bent portion for the outlet 14, an injection nozzle 32 is attached,
to supply by injection a urea aqueous solution toward an inside of
the straight portion of the pipe. Thus, a length of the straight
portion required to uniformly diffusing the urea aqueous solution
in the exhaust gas can be obtained. Here, to facilitate the uniform
diffusion of the urea aqueous solution, for example, a diffusing
member in a mesh shape or the like may be disposed in the
communication pipe 30.
[0024] According to such an exhaust gas purification apparatus,
since the first casing 10 and the second casing 20 are arranged to
be close and in parallel to each other, the outline thereof can be
as small in size as a box-shaped muffler. Furthermore, since the
communication pipe 30 communicates the far-end portions of the
first casing 10 and the second casing 20 with each other, the pipe
length required to uniformly diffuse the urea aqueous solution can
be obtained, and the communication pipe 30 can be placed within the
outline defined by the first casing 10 and the second casing 20, so
that reduction in size in a direction from the exhaust gas upstream
side to the exhaust gas downstream side can be achieved.
[0025] The straight portion of the communication pipe 30 extending
between the bent portions, that is, at least a part of the exhaust
pipe located between the injection nozzle 32 and the SCR converter
26 has a double-pipe structure, in which an inner pipe 34 and an
outer pipe 36 are concentrically arranged, as illustrated in FIG.
4, in order to improve a heat retaining property of the
communication pipe 30 and to facilitate hydrolysis of the urea
aqueous solution supplied by injection from the injection nozzle
32, for example. In this case, when exhaust gas mixed with the urea
aqueous solution passes between the inner pipe 34 and the outer
pipe 36, a temperature thereof may be decreased since an outer
peripheral surface of the outer pipe 36 is exposed to outside air,
so that droplets of the urea aqueous solution adhering to an inner
peripheral surface of the outer pipe 36 may form precipitates
derived from urea, such as biuret, and may be deposited thereon.
Then, when the temperature of exhaust gas passing between the inner
pipe 34 and the outer pipe 36 increases, the precipitates deposited
on the inner peripheral surface of the outer pipe 36 locally
generate ammonia at high concentration.
[0026] Furthermore, each of the inner pipe 34 and the outer pipe 36
may be, for example, formed by butting ends of a rectangular plate
material on each other and by being welded by tungsten inert gas
(TIG) welding or the like, and may be welded by the TIG welding or
the like on the inner peripheral surface thereof to secure a
bracket or the like. In this case, each of the inner pipe 34 and
the outer pipe 36 includes a welded portion 38 extending in a
direction in which an axis thereof extends. Accordingly, the welded
portion 38 produced on the outer pipe 36 is exposed to ammonia,
that is corrosive.
[0027] When the outer pipe 36 is welded from the outside thereof,
as illustrated in FIG. 5, grain boundaries of the welded portion
become coarse on the inner peripheral surface in which a welding
temperature is low, while the grain boundaries become fine on the
outer peripheral surface in which the welding temperature is high.
Since the welded portion 38 with the coarse grain boundaries has a
random atomic arrangement comparing with that of the welded portion
38 with the fine grain boundaries, intergranular corrosion may
easily occur.
[0028] Thus, by welding the outer pipe 36 from the inside thereof,
as illustrated in FIG. 6, the grain boundaries can be produced so
that the grain boundaries become fine on the inner peripheral
surface in which the welding temperature is high, while the grain
boundaries become coarse on the outer peripheral surface in which
the welding temperature is low. Furthermore, since the grain
boundaries of the welded portion 38 on the inner peripheral surface
of the outer pipe 36 can be made finer, the atomic arrangement can
be put in order, and accordingly, the corrosion resistance of the
inner peripheral surface, which may be exposed to ammonia at high
concentration, can be improved, so that occurrence of corrosion can
be reduced.
[0029] Here, as a welding method of the inner pipe 34 and the outer
pipe 36, the TIG welding may be employed, to produce a
high-quality, beautiful weld bead (trace of a welding pass).
[0030] As illustrated in FIG. 7, the exhaust gas purification
apparatus may be obtained by aligning in a straight line the first
casing 10, in which the DOC converter 16 and the DPF 18 are placed,
and the second casing 20, in which the SCR converter 26 and the
oxidation catalytic converter 28 are placed. Furthermore, as the
exhaust gas purification apparatus, at least the SCR converter 26
may be provided therein. Still further, the welding method is not
limited to the TIG welding, and may be any arc welding, such as
metal inert gas (MIG) welding or metal active gas (MAG)
welding.
[0031] It should be noted that the entire contents of Japanese
Patent Application No. 2011-266472, filed on Dec. 6, 2011, on which
convention priority is claimed, is incorporated herein by
reference.
[0032] It should also be understood that many modifications and
variations of the described embodiments of the invention will be
apparent to a person having an ordinary skill in the art without
departing from the spirit and scope of the present invention as
claimed in the appended claims.
* * * * *