U.S. patent application number 09/767004 was filed with the patent office on 2001-06-28 for device and method for post-treatment of exhaust gases of an internal combustion engine.
Invention is credited to Konig, Axel.
Application Number | 20010004831 09/767004 |
Document ID | / |
Family ID | 26047825 |
Filed Date | 2001-06-28 |
United States Patent
Application |
20010004831 |
Kind Code |
A1 |
Konig, Axel |
June 28, 2001 |
Device and method for post-treatment of exhaust gases of an
internal combustion engine
Abstract
An exhaust gas treatment device has a cylindrical body with
axial passages having a catalyst and a central cavity. A filter is
provided in the cavity and the cylindrical body is mounted for
rotation in a housing through which the exhaust gas flows.
Inventors: |
Konig, Axel; (Wolfsburg,
DE) |
Correspondence
Address: |
BAKER & BOTTS
30 ROCKEFELLER PLAZA
NEW YORK
NY
10112
|
Family ID: |
26047825 |
Appl. No.: |
09/767004 |
Filed: |
January 22, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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09767004 |
Jan 22, 2001 |
|
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PCT/EP99/04187 |
Jun 17, 1999 |
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Current U.S.
Class: |
60/274 ; 60/276;
60/285; 60/288 |
Current CPC
Class: |
Y02T 10/22 20130101;
Y02T 10/123 20130101; F01N 3/0885 20130101; Y02T 10/12 20130101;
B01D 53/9454 20130101; F01N 2610/03 20130101; B01D 53/885 20130101;
F01N 3/0214 20130101; F02B 2075/125 20130101; F01N 2240/16
20130101; F01N 3/0814 20130101; F01N 2570/04 20130101; F01N 3/0871
20130101; F01N 2290/06 20130101; F01N 3/0842 20130101 |
Class at
Publication: |
60/274 ; 60/288;
60/285; 60/276 |
International
Class: |
F01N 003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 31, 1998 |
DE |
198 34 576.3 |
Nov 4, 1998 |
DE |
198 50 762.3 |
Claims
In the claims:
1. Apparatus for treatment of exhaust gases of an internal
combustion engine comprising a housing having a gas inlet and a gas
outlet and a chamber arranged between said inlet and said outlet, a
gas permeable body at least partially coated with a catalyst for
reduction of pollutant gases, and arranged for rotation in said
chamber about an axis transverse to a direction corresponding to
flow of gas between said inlet and said outlet, said gas permiable
body having a central cavity having a filter arranged therein, said
gas permeable body being arranged in said chamber such that gases
entering said gas inlet flow through a first region of said body,
through said filter in said central cavity and through a second
region of said body to said gas outlet.
2. Apparatus as specified in claim 1 wherein said gas inlet of said
housing is in flow communication with channels in said first region
of said body.
3. Apparatus as specified in claim 1 wherein said filter is
arranged to rotate with said body.
4. Apparatus as specified in claim 1 wherein said body has a
cylindrical shape and includes radially extending gas flow
channels.
5. Apparatus as specified in claim 4 wherein said cavity comprises
a cylindrical recess extending along the axis of said cylindrical
body.
6. Apparatus as specified in claim 1 further including a heating
element.
7. Apparatus as specified in claim 1 wherein said body is arranged
to rotate about a cylindrical axis within said housing.
8. Apparatus as specified in claim 7, wherein said housing is made
of a nonmetallic material.
9. Apparatus as specified in claim 1 wherein said body is rotated
by a drive unit.
10. Apparatus as specified in claim 9, wherein said drive unit is
an electric motor.
11. Apparatus as specified in claim 9, wherein said drive unit is
formed by providing an magnetic field and magnets arranged within
the housing.
12. Apparatus as specified in claim 1 wherein said body is arranged
to rotate a speed of about 0.3 to 10 rpm.
13. Apparatus as specified in claim 1 wherein said body comprises
ceramic.
14. Apparatus as specified in claim 1 wherein said body is
fabricated using metal.
15. Apparatus as specified in claim 1 wherein said body is a
monolith.
16. Apparatus as specified in claim 1 wherein said body comprises
segments that are traversed by channels.
17. Apparatus as specified in claim 1 further including an inlet
for the introduction of additional fuel.
18. Apparatus as specified in claim 17 wherein said inlet apparatus
for the introduction of additional fuel is arranged at the axis of
rotation of the body.
19. A method for post-treatment of an exhaust gust gas stream of an
internal combustion engine comprising: providing a body having a
catalyst in portions thereof and having a cavity with a filter;
passing said exhaust gas through channels in a first region of said
body, through said filter and through channels a second region of
said body whereby soot particles are retained in said filter; and
rotating said body to interchange said first and second regions of
said body.
20. A method as specified in claim 19 wherein said body is rotated
at a speed which causes a maximum temperature region of said body
to be located at said filter thereby to cause combustion of said
soot particles.
21. A method as specified in claim 19 wherein reducing agents are
added to cause continuous reduction of Nox accumulation in said
body.
22. A method as specified in claim 19 further providing
desulfurigation of said body, comprising periodically increasing
the pollutant quantity of supplied exhaust gas and retarding or
interrupting rotation of said body until a maximum temperature
region is in said second region, and wherein said body is
thereafter rotated so that second region assumes the original
position of said first region and said maximum temperature region
is predominantly in said repositioned first region and thereafter
reducing the pollutant quantity.
23. Method according to claim 22, wherein said retardation or
interruption of rotation is repeated a number of times, until said
body is substantially desulfurized.
24. Method according to claim 22, wherein that continuous rotation
of said body is resumed when the temperature maximum is located at
approximately the interface of the first and second regions.
Description
BACKGROUND OF THE INVENTION
[0001] The invention relates to a device and method for
post-treatment of exhaust gases of an internal combustion engine,
and in particular relates to a device and method for post-treatment
of soot particles and/or nitrogen oxides in the exhaust gas
stream.
[0002] Known NOx catalysts absorb nitrogen oxides produced during
lean operation of an engine and reduce accumulated NOx during rich
operation of the engine, where the known methods are discontinuous
and accumulation and reduction of nitrogen oxides takes place at
different times. In order to be able to carry out such a method,
the accumulator must be emptied after a certain period of time
because of its finite absorption capacity. This is done after a
fixed predetermined time has elapsed or else the degree of fill of
the catalyst must be determined. If the accumulator is regenerated
after a fixed predetermined time, this has the disadvantage that
for safety reasons the accumulating capacity of the catalyst is not
fully utilized, so that optimal engine operation with regard to
fuel consumption and exhaust gas behavior is not possible. If the
accumulator is regenerated when a given degree of fill of the
accumulator has been reached, this has the disadvantage that an
additional device is required, to determine the degree of fill of
the NOx-accumulating catalyst. There, exact determination of the
degree of fill of the accumulator is difficult, so that here too a
switch to regenerative operation is made when the accumulator is
not yet completely full. In the end, this likewise leads to less
than optimal operation of the engine. In addition, in both these
methods optimal exhaust gas behavior is not obtained during rich
operation of the engine and a complicated engine control system is
required for cyclical engine operation.
[0003] In addition, a minimum temperature of about 250.degree. C.
is required for effective function of a NOx-accumulating catalyst.
If the exhaust gas coming from the engine is too cold, the method
can only function when the catalyst is heated to this minimum
temperature. Then heat losses occur, as a result of which the
energy requirement is greatly increased.
[0004] In addition, soot particles that should not be allowed to
escape into the environment are present in the exhaust gas of
diesel engines. For post-treatment of such exhaust gases carrying
soot particles, in one well known device the soot particles are
retained and cyclically, as a given degree of fill of the soot
filter is reached, they are either removed or the retained soot
particles are ignited with a suitable heating device and burned.
Both of these procedures are unsatisfactory for continuous use.
[0005] The object of the invention therefore is to develop a device
and method for treatment of the exhaust gas stream of an internal
combustion engine that permit optimal engine operation.
SUMMARY OF THE INVENTION
[0006] The device according to the invention for post-treatment of
exhaust gases of an internal combustion engine has a body or
monolith with channels through which the exhaust gas flows and
which is arranged to rotate in the exhaust gas stream. Here, a
monolith is understood to mean a body that may consist of one piece
that is made of ceramic, of metallic carrier materials or of
ceramic or metallic segments, which are arranged in an
accommodating support structure.
[0007] The device has an inflow channel that is in flow
communication with a part (B1) of the channels of the body.
Additionally provided is a flow connection that is in communication
on the output side with the part B1 of the channels approached by
the inflow channel and connects said part with a part B2 of the
channels that is not in flow communication with the inflow
channel.
[0008] The body or monolith preferably is divided into two regions
B1, B2, where the exhaust gas enters the first region B1 at the
front face of the body, exits at the rear face of the first region
B1, flows through the filter mounted there, enters a face of the
second region B2 and leaves the second region B2 at the other face,
while during flow the body rotates about an axis substantially
perpendicular to the direction of flow of the exhaust gas
stream.
[0009] The body preferably has a cylindrical shape, and the
channels extend in the radial direction. The body has a cylindrical
recess in the axial direction, in other words, the cylinder is
hollow in the axial direction. The body may consist of metal or
ceramic, and may be built in one piece or of segments fitted
together. If the body consists of segments, the latter are
traversed by channels in such a way that after the segments are
assembled the channels extend in the radial direction with respect
to the axis of symmetry of the cylinder.
[0010] The device preferably comprises a filter, which may be
arranged for rotation, and the filter may in particular rotate with
the monolith, while in the case of the cylindrical body with the
axial recess the filter is arranged in the latter. There, the
filter may be stationary or may rotate along with the body, where
its speed of rotation need not be identical to the speed of
rotation of the body.
[0011] In addition, the internal combustion engine preferably has
direct fuel injection into the combustion chamber and/or is a
diesel engine.
[0012] The filter preferably has a heating element that serves to
bring the filter to operating temperature after a cold start. When
the required temperature has been reached, the heating element may
be shut off. In principle, extra heating is provided only when
engine conditions (exhaust gas temperature) do not lead to soot
burnup.
[0013] In particular, the required temperature for pollutant
conversion may alternatively or secondarily also be rapidly
obtained by suitably selected engine parameters (injection
quantity, injection course, reinjection), and here too the engine
parameters are restored to their normal conditions when the desired
temperature has been reached.
[0014] In addition, for pollutant reduction, in particular for the
reduction of NOx, HC and/or CO, the body may be at least partially
catalytically coated.
[0015] In addition, the device may have a stationary housing (10),
having a chamber in which is arranged the body rotating about its
longitudinal axis. The housing preferably is made of a nonmetallic
material.
[0016] Rotation of the body preferably is effected by a drive unit.
The drive unit may be an electric motor. It is alternatively
possibly for the drive unit to be formed by an outer magnetic field
source and magnets arranged within the housing. In addition, the
body may alternatively be rotated in the manner of a turbine by the
exhaust gas stream. The speed of rotation of the body (4)
preferably is about 0.3 to 10 rpm, and the speed of rotation is
selected so that the maximum of the temperature distribution
obtained remains within the body, preferably at the site of the
filter.
[0017] In addition, the device may have a means for the
introduction of additional fuel in order to produce a reduction of
the NOx exhaust gas component when the engine can be operated lean.
The means for introducing additional fuel is arranged in the axis
of rotation of the body.
[0018] The method according to the invention provides for
post-treatment of exhaust gases of an internal combustion engine,
wherein a body is arranged in the exhaust gas stream, which body is
traversed by channels in the direction of flow of the exhaust gas
and is divided into two regions, has the following steps:
[0019] Passing of the exhaust gas stream into the front face of the
first region,
[0020] Passing of the exhaust gas stream at the rear face of the
first region into a face of a second region and discharge of the
exhaust gas stream at the other face of the second region, and
[0021] Rotation of the body during operation about an axis, so that
the channels shift from the first region into the second
region.
[0022] Preferably, the body is rotated about its axis at a speed
such that heating of the second region by the exhaust gas stream
leads to heating of the exhaust gas stream through the first
region.
[0023] Soot particles in the exhaust gas stream preferably are
retained in a filter, which is arranged between the exhaust gas
outlet-side face of the first region and the exhaust gas inlet-side
face of the second region, and the speed of rotation is selected so
that the maximum of the temperature region is located approximately
at the filter.
[0024] The body used in the method preferably is at least partially
catalytically coated, so that NOx accumulation of the exhaust gas
is effected during the lean phases of internal combustion engine
operation. A continuous NOx-accumulating regeneration method can be
effected by addition of reducing agents into the body.
[0025] The method according to the invention for desulfurization of
the device according to the invention for post-treatment of exhaust
gases of an internal combustion engine, where the device is
designed as a NOx accumulator, has the following steps:
[0026] at the start of desulfurization retardation or interruption
of rotation of the body, with simultaneous increase of pollutant
quantity in the exhaust gas, until a resulting temperature maximum
has migrated into or through the second region, in particular near
the exhaust gas exit-side face of the second region,
[0027] rotation of the body until the second region at least
predominantly assumes the place of the first region, so that the
temperature maximum lies predominantly in the first region, and
interruption of rotation until the temperature maximum has moved
into at least the relocated first region,
[0028] reduction of reinjection and restored rotation of the
body.
[0029] At the same time it may be necessary for retardation or
interruption of rotation to be repeated a number of times, until
all regions have been substantially desulfurized. Continuous
rotation of the body is resumed when the temperature maximum is
located at approximately the interface of the two regions.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] FIG. 1a shows a horizontal cross-sectional view through a
first embodiment of the device according to the invention for
post-treatment of the exhaust gas of an internal combustion
engine.
[0031] FIG. 1b shows a vertical cross section through the device of
FIG. 1a.
[0032] FIG. 2a shows horizontal cross-sectional view through a
second embodiment of the device according to the invention for
post-treatment of the exhaust gas of an internal combustion
engine.
DESCRIPTION OF THE INVENTION
[0033] FIG. 1a shows a horizontal cross section through a first
preferred embodiment of a device according to the invention for
post-treatment of the exhaust gas of an internal combustion engine.
A cylindrical body is arranged in a chamber within a housing 10.
Untreated exhaust gas of an engine (not illustrated) flows through
an exhaust gas inlet 1 in to an outer face 2 of a first region B1
of a cylindrical body 4 that is traversed by channels 3. Channels 3
run in the radial direction with respect to the axis of rotation 9
formed by the axis of symmetry of the cylinder. The channels 3,
arranged perpendicular to the axis of rotation 9, are at least
partially catalytically coated, as has already been described
above. After exit of the exhaust gas from the inner face 5 of the
body 4, which forms an axial cavity 7 located centrally in the
body, the exhaust gas goes through a particle filter 6 arranged in
the cavity 7, through the inner face 5, enters an opposite second
region B2, leaves region B2 through outer face 2 and enters a
discharge channel 8. In FIG. 1a, it is shown that the first region
and the second region are each limited to 3 channels by the inflow
channel 1 and the discharge channel 8. This is not mandatory. In
another design of the housing 10 surrounding the body 4, the waste
gas flowing in and out in each instance reaches a first and second
region B1, B2 of at most 180.degree.. In other words, the first and
second region may comprise at most one-half of the body 4.
[0034] FIG. 1b shows a vertical section through the device
according to the invention. The filter 6, which in general rotates
synchronously with the body 4, is arranged in the interior cavity
of the body 4 which is traversed by channels 3. The body 4 and the
filter 6 are arranged in a chamber formed by a suitable housing 10.
Rotation takes place about an axis of rotation 9, which may serve
as inlet for additional fuel for combustion in a catalytically
active filter or in the rotor matrix, i.e., the body 4.
[0035] Owing to flow through the body 4 with the filter 6, the
temperature rises at the inlet side due to catalytic conversion of
CO and HC present in the exhaust gas during passage through the
catalytically coated channels 3. At the same time, nitrogen oxides
can be absorbed chemically if the channels 3 are coated with a
NOx-absorbing catalyst. The temperature maximum is reached in the
center of the device, in the particle filter 6. Upon continued
passage through the body 4 or rotor the exhaust gas again gives off
its heat and leaves the rotor 4 at about the same temperature as on
the inlet side. Without rotation the temperature front, i.e., the
maximum temperature, would be driven out of the device. Owing to
rotation of the rotor 4 the temperature front is always driven back
into the system. A periodically stationary temperature profile,
whose maximum lies in the region of the filter 6, is produced in
the body.
[0036] FIG. 2 shows a horizontal cross-sectional view through a
second embodiment of the device according to the invention for
post-treatment of exhaust gases of an internal combustion engine,
in which the device is operated as a pure NOx-accumulating
catalyst.
[0037] FIG. 2 shows a body 4, rotating about its longitudinal axis,
which is coated as a NOx-accumulating catalyst and which is used as
a regenerative heat exchanger. The body 4 has a great plurality of
fine channels 3 in the radial direction and exhaust gases flow
through it radically, specifically, exhaust gases are supplied to
it through an inflow channel 1 and are carried away through a
discharge channel 8, whereby first and second regions B1, B2 are
formed as in the case of the first embodiment. In addition, the
body has an axial cavity 7, which is bounded by the inner face 5 of
the body 4. The axial cavity serves for flow communication of the
channels 3 of the first and of the second region B1, B2.
Advantageously, no flow deflection takes place, whereby pressure
loss is kept low. The inner part of the channels 3, represented as
a ring-shaped area T1, is coated with a NOx-accumulating catalyst.
The outer part of the channels, represented by a ring-shaped area
T2, is not coated and does not participate in catalysis, having the
function only of heat exchange. The radial flow with simultaneous
rotation allows a temperature profile to be established in the body
4, which at the inlet and outlet sides of the outer face 2 of the
body is at about exhaust gas temperature and toward the center
rises steeply to about 350 to 400.degree. C. As a result, part of
the catalyst is always in an optimal temperature region for NOx
accumulation. The rotating arrangement of the catalyst, i.e., the
body 4, provides for best possible heat recovery by the
regeneration principle. With ideal heat insulation and correct
dimensioning and rotational speed, the heat once brought in will
not leave the system. The heat losses actually occurring are offset
by the heat of reaction that is released upon pollutant oxidation
in the region T1.
[0038] For starting up the cold system, the ignition temperature of
about 200.degree. C. must be reached in the catalytically active
region T2. For this purpose, an electric heating element 11 may be
provided in the center of the body 4. Alternatively and/or
secondarily, the temperature required for pollutant conversion may
also be obtained by suitably selected engine parameters
(particularly in the case of common-rail injection, for example, by
variation of injection timing, injection course, injection
quantity, and/or reinjection). After the ignition temperature has
been reached, such measures are ended. Additional temperature
increase takes place only through a brief increase in pollutant
concentrations, which raises the catalyst temperature through the
heat of reaction released upon conversion of pollutants in the
region T1. This increase in pollutant concentration may take place
either through separate fuel introduction in the center of the body
4, or may also be brought about through modifications of engine
parameters.
[0039] Rotation of the body 4 is realized by a suitable electric or
mechanical drive (not represented). For this purpose, the body 4 is
mounted on a shaft rotatable about its axis of rotation 9, which is
put into rotation by the abovementioned drive. The additional
introduction of fuel may also be effected through this shaft 9.
When an electric motor is used, the speed of rotation may be
adapted to the operating condition of the vehicle engine by means
of suitable information from the engine-control device. In
addition, the body 4 is arranged in a suitable stationary housing
10.
[0040] Regeneration of the NOx-accumulating catalyst is effected in
known fashion by engine enrichment of the exhaust gas.
[0041] When sulfurous fuel is used, desulfurization of the catalyst
must be carried out from time to time, as has already been
described above. This is done thermally at temperatures above
600.degree. C. As already mentioned above, in the system described
a temperature rise of almost any degree may be obtained by
increasing the concentration of pollutant or by its oxidation. By
appropriate control of the speed of rotation and pollutant
concentration, the catalyst can be kept at the necessary high
temperatures for the required time of several minutes. As already
described above, the consumption of energy is distinctly lower than
in conventional systems.
[0042] Therefore, the following embodiments of the device described
above by means of two examples are possible:
[0043] Device with a body 4, capable of rotation in the exhaust gas
stream, without catalytic coating and without filter, for producing
a temperature maximum in the device;
[0044] Device with a body 4, capable of rotation in the exhaust gas
stream and a filter 6 arranged in the body 4, for burnup of soot
particles;
[0045] Device with a body 4, capable of rotation in the exhaust gas
stream and having an at least partial catalytic coating of the body
4;
[0046] Device with a body 4, capable of rotation in the exhaust gas
stream, as well as a filter 6 arranged in the body 4, and having an
at least partial catalytic coating of the body.
[0047] While there has been described what are believed to be the
preferred embodiment of the present invention, those skilled in the
art will recognize that other and further changes and modifications
may be made thereto without departing from the spirit of the
invention, and it is intended to claim all such changes and
modifications as fall within the true scope of the invention.
LIST OF REFERENCE NUMERALS
[0048] 1 Inflow channel
[0049] 2 Outer face
[0050] 3 Channels
[0051] 4 Body or rotor
[0052] 5 Inner face
[0053] 6 Filter
[0054] 7 Axial cavity
[0055] 8 Discharge channel
[0056] 9 Axis of rotation
[0057] 10 Housing
[0058] 11 Electric heating element
[0059] B1 First region
[0060] B2 Second region
[0061] T1 Inner ring-shaped area
[0062] T2 Outer ring-shaped area
* * * * *