U.S. patent application number 10/054443 was filed with the patent office on 2002-11-07 for device for introducing an additive into an exhaust gas.
Invention is credited to Ganzmann, Ingo, Langer, Werner, Ritter, Hartmut, Zwack, Jurgen.
Application Number | 20020162322 10/054443 |
Document ID | / |
Family ID | 7915691 |
Filed Date | 2002-11-07 |
United States Patent
Application |
20020162322 |
Kind Code |
A1 |
Ganzmann, Ingo ; et
al. |
November 7, 2002 |
Device for introducing an additive into an exhaust gas
Abstract
A reducing agent or an additive that releases an agent is often
added to an exhaust gas from engines in order to chemically convert
constituents, in particular nitrogen oxides, in the exhaust gas. To
achieve intimate mixing of the exhaust gas with the reducing agent
or additive over a short section of the gas duct, at least one
mixer and at least one nozzle for introducing the additive into the
exhaust gas are structurally and functionally combined with one
another.
Inventors: |
Ganzmann, Ingo; (Erlangen,
DE) ; Langer, Werner; (Neustadt, DE) ; Ritter,
Hartmut; (Kronach, DE) ; Zwack, Jurgen;
(Sesslach, DE) |
Correspondence
Address: |
LERNER AND GREENBERG, P.A.
Post Office Box 2480
Hollywood
FL
33022-2480
US
|
Family ID: |
7915691 |
Appl. No.: |
10/054443 |
Filed: |
January 22, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10054443 |
Jan 22, 2002 |
|
|
|
PCT/DE00/02402 |
Jul 21, 2000 |
|
|
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Current U.S.
Class: |
60/286 |
Current CPC
Class: |
B01D 53/92 20130101;
Y02T 10/12 20130101; F01N 3/2066 20130101; F01N 2240/20 20130101;
B01D 53/79 20130101; F01N 2610/02 20130101; B01F 25/3131 20220101;
B01F 2025/931 20220101; F01N 2470/24 20130101; F01N 2610/1453
20130101 |
Class at
Publication: |
60/286 |
International
Class: |
F01N 003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 22, 1999 |
JP |
199 34 413.2 |
Claims
We claim:
1. A device for introducing an additive into an exhaust gas, the
exhaust gas being introduced into an exhaust gas line from a diesel
engine and having a flow direction, the device comprising: at least
one nozzle; and at least one mixer for mixing the exhaust gas with
the additive, said mixer and said nozzle combined with one another
to form a structural and functional unit, said mixer having a
tubular body disposed approximately parallel in terms of the flow
direction of the exhaust gas and housing said nozzle, said tubular
body having an upstream end with a first opening formed therein and
a downstream end with a second opening formed therein and
communicating with said first opening, said mixer having lamellae
supported by said tubular body, and said lamellae, with regard to
the flow direction of the exhaust gas, face upstream at said
upstream end of said tubular body and face downstream at said
downstream end of said tubular body.
2. The device according to claim 1, wherein said tubular body has a
cross section that is circular.
3. The device according to claim 1, wherein said tubular body has a
diameter in a range of 0.2 to 0.5 times a diameter of the exhaust
gas line.
4. The device according to claim 1, wherein said tubular body has a
length that is approximately 0.2 to 0.5 times a diameter of the
exhaust gas line.
5. The device according to claim 1, wherein said mixer has a
tubular connection piece projecting into the exhaust gas line and
guided onto said tubular body, said mixer further having a tube
serving as a feed line and as a support for said nozzle, said tube
extending into said tubular body through said tubular connecting
piece.
6. The device according to claim 1, wherein mixer has a center axis
and said nozzle lies on said center axis in such a manner that the
additive can be sprayed in the flow direction of the exhaust
gas.
7. The device according to claim 1, wherein said tubular body has
an axis, and said lamellae supported by said upstream end and said
downstream end of said tubular body form an angle of 30.degree. to
60.degree., with said axis of said tubular body and, said lamellae
for support, have free ends directed onto an inner side of the
exhaust gas line.
8. The device according to claim 1, wherein said lamellae have root
ends connected to said tubular body and free ends being
approximately twice as wide as said root ends.
9. The device according to claim 1, wherein said lamellae have a
given width, and between adjacent ones of said lamellae free spaces
are formed having a width approximately as wide as said given width
of said lamellae.
10. The device according to claim 1, wherein said lamellae that
face upstream are disposed staggered with respect to said lamellae
that face downstream.
11. The device according to claim 1, wherein a number of said
lamellae facing upstream is equal to a number of said lamellae
facing downstream.
12. The device according to claim 1, wherein said tubular body
bears a same number of said lamellae at both of said upstream end
and said downstream end.
13. The device according to claim 1, wherein said lamellae include
planar metal sheets.
14. The device according to claim 12, wherein said tubular body
bears between four and eight of said lamellae at both of said
upstream end and said downstream end.
15. The device according to claim 7, wherein said angle is
45.degree..
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation of copending
International Application PCT/DE00/02402, filed Jul. 21, 2000,
which designated the United States.
BACKGROUND OF THE INVENTION
Field of the Invention
[0002] The invention relates to a device for introducing an
additive into an exhaust gas or gas stream, which can be introduced
into a gas duct, in particular into an exhaust gas line from a
diesel engine. The device has at least one nozzle and at least one
mixer. The additive may be a reducing agent or a compound that
releases such an agent.
[0003] A device of this type is known, for example, from Published,
Non-Prosecuted German Patent Application DE 36 42 612 A. The device
introduces a reducing agent into a NOx-containing exhaust-gas duct
with intensive mixing. The device is intended to achieve a
homogeneous mixing of the reducing agent and the exhaust gas over a
relatively short section of duct.
[0004] High levels of efficiency are desired during the conversion
of fossil fuel or of fuel obtained from plants into mechanical
and/or thermal energy. The conversion temperatures are often so
high that significant amounts of nitrogen oxides (NOx) are formed
during the conversion (combustion). This applies in particular to
diesel engines, which are operated, for example with mineral oil or
with rapeseed oil.
[0005] Since a release of the nitrogen oxide is extremely
undesirable and is therefore to be avoided, the nitrogen oxides are
usually catalytically reduced. However, this requires the presence
of a reducing agent in the exhaust gas from an energy conversion
installation, for example, in a diesel engine. It has proven
expedient to admix a reducing agent of this type or an additive
that releases it as a reducing-agent carrier, in particular ammonia
or urea (dissolved in water), to the exhaust gas only after it has
emerged from the energy conversion installation.
[0006] During operation of a device of this type or of a flue-gas
cleaning device, it is often difficult to achieve sufficiently
intimate mixing of the exhaust gas or gas stream with the reducing
agent. The reason for this is that the length of the gas or exhaust
gas duct which is inherently required to achieve this, being of the
order of magnitude of approximately 50 times the duct diameter, is
not realistic. For relatively small installations, such as for
example diesel engines with an output of up to a few 100 kW, it is
in principle possible to feed a reducing agent carrier into the
exhaust-gas duct via an injection device, for example via a single
nozzle, and a reducing-agent generator which lies close behind the
engine. However, as the rated output rises, this entails
disproportionately high costs.
[0007] In relatively large installations, for example, in a
combined heat and power plant or a drive of a ship, with
exhaust-gas duct diameters of over 200 mm, therefore, it is usual
for at least two static mixers to be disposed downstream of an
atomization system, which represents a complex injection device.
The distances between the atomization system and the mixers are in
each case to be at least equal to twice the diameter of the
exhaust-gas duct. However, space for the resulting length of
exhaust-gas duct is often not available.
SUMMARY OF THE INVENTION
[0008] It is accordingly an object of the invention to provide a
device for introducing an additive into an exhaust gas which
overcomes the above-mentioned disadvantages of the prior art
devices of this general type, which allows the use both of an
injection device or at least one nozzle for an additive and of a
number of necessary mixers in an exhaust-gas duct in which, at the
same time, the duct length is as short as possible. It should be
possible for the device to be used in particular in a round gas
duct whose diameter is between approximately 200 mm and
approximately 1000 mm.
[0009] With the foregoing and other objects in view there is
provided, in accordance with the invention, a device for
introducing an additive into an exhaust gas. The exhaust gas is
introduced into an exhaust gas line from a diesel engine and has a
flow direction. The device contains at least one nozzle, and at
least one mixer for mixing the exhaust gas with the additive. The
mixer and the nozzle combined with one another form a structural
and functional unit. The mixer has a tubular body disposed
approximately parallel in terms of the flow direction of the
exhaust gas and houses the nozzle. The tubular body has an upstream
end with a first opening formed therein and a downstream end with a
second opening formed therein and communicates with the first
opening. The mixer has lamellae supported by the tubular body, and
the lamellae, with regard to the flow direction of the exhaust gas,
face upstream at the upstream end of the tubular body and face
downstream at the downstream end of the tubular body.
[0010] For this purpose, the mixer and the nozzle for atomizing the
additive or the reducing agent itself are combined to form a
structural and functional unit. The combination can be introduced
into the gas duct, i.e. can be fitted into the duct when the
structural unit is operating as intended.
[0011] This immediately eliminates the length of the distance from
the nozzle to the mixer of a first mixer stage, so that the duct
length can preferably be shortened to only two to four times the
duct diameter (two to four duct diameters). Neither the action nor
the efficiency of each individual functional part, namely the
injection function, on the one hand, and the static mixer function,
on the other hand, is impaired.
[0012] According to an expedient refinement, the mixer has a
tubular body which is open at both ends, is parallel in terms of
flow, is advantageously, in the installed state, coaxial with
respect to the gas duct and at one end bears lamellae which face
upstream and at the other end bears lamellae which face downstream.
In this case, the tubular body, in a gas duct that is circular in
cross section, is likewise circular in cross section. The diameter
of the gas duct into which the structural unit containing the mixer
and the nozzle can be fitted should expediently be no less than
approximately 200 mm and no greater than approximately 1000 mm.
[0013] In advantageous configurations of the tubular body, its
diameter is approximately 0.5 to 0.2 times the diameter of the gas
duct. The length of the tubular body approximately corresponds to
0.2 to 0.5 times the diameter of the gas duct. In this case, the
tubular body is expediently supported by a tubular connection piece
that projects into the gas duct transversely with respect to the
gas stream and through which a tube, which serves as a feed line
and as a support for the nozzle or the injection device, extends as
far as the center axis of the tubular body.
[0014] The nozzle is advantageously disposed in the region of the
center axis of the tubular body, and therefore, in the installed
state, of the center axis which is common to the gas duct and the
tubular body. In this position, the nozzle or the injection device
atomizes the additive, for example ammonia as the reducing agent or
urea solution as the additive, in the direction of flow of the gas
stream. A spray cone that emerges from the nozzle includes an angle
of 20.degree. to 60.degree., preferably an angle of 30.degree., at
its cone tip.
[0015] Lamellae that are supported at the ends of the tubular body
preferably form an angle of from 30.degree. to 60.degree., in
particular an angle of 45.degree., with the axis of the tubular
body. The lamellae are oriented in such a manner that, in the
installed state of the device, they are supported on the inner side
of walls of the gas duct by their free ends. In this case, the
lamellae are approximately twice as wide at their free ends as at
their root ends that are connected to the tubular body. Free spaces
between adjacent lamellae are in this case approximately as wide as
the lamellae themselves.
[0016] Expediently, the lamellae which face upstream are staggered
with respect to the lamellae which face downstream, so that every
partial stream of the gas stream is made turbulent, in each case an
identical number of the lamellae which face downstream and the
lamellae which face upstream are provided. The tubular body
expediently bears in each case four to eight lamellae at both end
sides, the lamellae preferably are formed of planar metal
sheets.
[0017] The advantages which are achieved with the invention consist
in particular in the fact that, on account of the spatial and
functional combination of at least one mixer and the nozzle in a
device which has these functional components for the introduction
of an additive, such as for example ammonia or urea solution, into
an exhaust gas, it is possible to achieve a particularly short
configuration of an exhaust-gas duct accommodating the device,
without the risk of the mixer becoming encrusted, even when using
urea solution.
[0018] The reason for this is that only a short trailing section in
the exhaust-gas duct is required even though, at the same time, it
is ensured that the temperature and velocity are made more uniform
over the entire cross section of the duct.
[0019] Moreover, the small number of components in the overall
system leads to a reduction in manufacturing costs.
[0020] Other features which are considered as characteristic for
the invention are set forth in the appended claims.
[0021] Although the invention is illustrated and described herein
as embodied in a device for introducing an additive into an exhaust
gas, it is nevertheless not intended to be limited to the details
shown, since various modifications and structural changes may be
made therein without departing from the spirit of the invention and
within the scope and range of equivalents of the claims.
[0022] The construction and method of operation of the invention,
however, together with additional objects and advantages thereof
will be best understood from the following description of specific
embodiments when read in connection with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIG. 1 is a diagrammatic, partially, longitudinal
sectional-view of a flue-gas cleaning device with a combined mixing
and injection device according to the invention;
[0024] FIG. 2 is a partially sectional plan view of the cleaning
device;
[0025] FIG. 3 is a front-elevational view of the cleaning
device;
[0026] FIG. 4 is a sectional view of the cleaning device taken
along the line IV-IV shown in FIG. 1; and
[0027] FIG. 5 is a sectional view of the cleaning device taken
along the line V-V shown in FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0028] In all the figures of the drawing, sub-features and integral
parts that correspond to one another bear the same reference symbol
in each case. Referring now to the figures of the drawing in detail
and first, particularly, to FIG. 5 thereof, there is shown a gas or
exhaust-gas duct 1 with a diameter d1 of, for example, 200 mm to
1000 mm is connected, by a flange 2 (FIG. 1) to a preferably
non-illustrated stationary diesel engine. An exhaust gas A flows
through it in the direction indicated by an arrow 3. A tubular
connection piece 4 penetrates through a wall of the exhaust-gas
duct 1 and projects into the exhaust-gas duct 1 transversely with
respect to the direction of flow 3 of the exhaust-gas A and
therefore at right angles to a duct axis 5. If the duct cross
section is circular, as in the exemplary embodiment, therefore, the
tubular connection piece 4 runs in a radial direction. Outside the
exhaust-gas duct 1, the tubular connection piece 4 bears a flange 6
at its free end, on which an end plate 7 rests in a sealed manner,
thus closing off an interior of the tubular connection piece 4 with
respect to the outside.
[0029] That end of the tubular connection piece 4 which lies in the
exhaust-gas duct 1 bears a tubular body 8 which is open at both end
sides and is disposed coaxially with respect to the exhaust-gas
duct 1. The duct axis 5 therefore forms the center axis of both the
exhaust-gas duct 1 and the tubular body 8. The tubular body 8 has a
diameter d2 (FIG. 5) that corresponds to 0.2 to 0.5 times the
diameter d1 of the exhaust-gas duct 1.
[0030] The tubular body 8 has a length that is approximately equal
to 0.2 to 0.5 times the diameter d1 of the exhaust-gas duct 1.
[0031] A number of first lamellae 9, which face upstream with
respect to the direction of flow 3 of the exhaust gas A, are
secured to an inflow-side end of the tubular body 8. A preferably
identical number of second lamellae 10, which correspondingly
extend downstream, are secured to an outflow-side end of the
tubular body 4. The lamellae 9 and the lamellae 10 are disposed
staggered with respect to one another, i.e. each of the lamellae 9
lies between in each case two lamellae 10, and vice versa, as seen
in the direction of the duct axis 5. This can be seen relatively
clearly from FIGS. 3 to 5.
[0032] The lamellae 9 and 10 in each case form an angle .alpha.
from 30.degree. to 60.degree., preferably of .alpha.=45.degree.
(see FIG. 1), with the duct axis 5 and are supported, by their free
ends 9a and 10a, respectively, on the inner side or inner wall 1'
of the exhaust-gas duct 1. The free ends 9a, 10a of the lamellae 9
and 10 are approximately twice as wide as their root ends 9b and
10b, respectively, which are secured to the tubular body 8. By way
of example, four to eight lamellae 9, 10 are secured to each end of
the tubular body 8, the lamellae 9, 10 contain planar metal sheets.
Consequently, they cause particularly powerful turbulence in the
flowing exhaust gas A.
[0033] The tubular connection piece 4 contains a tube 11 that is
supported by the end plate 6 and on which, at a free end side in
the tubular body 8, a nozzle 12 is held. The tube 11 is connected
via a line, in a manner which is not illustrated in more detail, to
a reservoir for an additive which releases a reducing agent or for
a reducing-agent carrier R, for example for an aqueous urea
solution, and expediently, in addition, to an air connection for
cooling and atomizing the urea solution which is, for example,
aqueous. A non-illustrated pump forces the reducing-agent carrier
R, e.g. the aqueous urea solution, or a corresponding reducing
agent, e.g. ammonia, through the tube 11 and through the nozzle
12.
[0034] The geometric dimensions of the nozzle 12 are such that, at
the delivery pressure of the reducing-agent carrier R which is
reached, a spray cone 13 is formed by the carrier R when it emerges
from the nozzle 12, the tip of which cone includes an angle .beta.
of from 20.degree. to 60.degree., preferably of .beta.=30.degree.
to 45.degree.. The nozzle 12 and the tubular body 8 with the
lamellae 9 and 10 therefore form a structural and functional unit,
the tubular body 8 and the lamellae 9, 10 attached thereto
representing, in functional terms, a static mixer or a mixing
stage. The nozzle 12 in this case lies on the common center axis of
the exhaust-gas duct 1 and of the mixer 8, 9, 10, which corresponds
to the duct axis 5.
[0035] In operation, the hot exhaust gas A from the diesel engine
flows through the exhaust-gas duct 1 in the direction of flow 3. In
the process, a small proportion of the exhaust gas A, and therefore
at least one exhaust-gas partial stream, flows through the tubular
body 8. When a predetermined operating state is reached, the
reducing-agent carrier R is sprayed or injected through the nozzle
12 into the flowing exhaust gas A.
[0036] In the region of the tubular body 8, considerable turbulence
caused by the lamellae 9 and 10 occurs in the flowing exhaust gas
A, which turbulence also acts on the spray cone 13, thus ensuring
very intimate mixing of the exhaust gas A with the reducing-agent
carrier R.
[0037] In the state which prevails in the exhaust-gas duct 1, the,
for example, aqueous urea solution is broken down by hydrolysis
into gaseous ammonia and water, so that in the gas mixture which is
formed in this way, when a catalytic converter which is suitable
and provided for this purpose, but is not shown, is reached,
nitrogen oxides contained in the exhaust gas A are virtually
completely reduced to form nitrogen.
* * * * *