U.S. patent application number 11/885602 was filed with the patent office on 2008-02-21 for method for exhaust-gas treatment for diesel engines or the like, and apparatus for implementing this method.
Invention is credited to Thorsten Duesterdiek, Achim Freitag, Carsten Jutka, Martina Koesters.
Application Number | 20080041041 11/885602 |
Document ID | / |
Family ID | 36007394 |
Filed Date | 2008-02-21 |
United States Patent
Application |
20080041041 |
Kind Code |
A1 |
Duesterdiek; Thorsten ; et
al. |
February 21, 2008 |
Method for Exhaust-Gas Treatment for Diesel Engines or the Like,
and Apparatus for Implementing This Method
Abstract
In a method for exhaust-gas treatment for diesel engines, the
exhaust gas is conducted through a regenerable particulate filter
as well as an NOx catalytic converter, each disposed in exhaust
branch. The exhaust gas is first conducted through the NOx
catalytic converter of the carbamide SCR type situated close to the
engine, and subsequently through the particulate filter of the CSF
type, the energy necessary for regenerating the particulate filter
being supplied to it from outside. Fuel is used as regenerating
agent, which is taken from fuel tank provided for the operation of
the diesel engine.
Inventors: |
Duesterdiek; Thorsten;
(Hannover, DE) ; Freitag; Achim; (Wolfenbuettel,
DE) ; Jutka; Carsten; (Isenbuettel, DE) ;
Koesters; Martina; (Hannover, DE) |
Correspondence
Address: |
KENYON & KENYON LLP
ONE BROADWAY
NEW YORK
NY
10004
US
|
Family ID: |
36007394 |
Appl. No.: |
11/885602 |
Filed: |
January 24, 2006 |
PCT Filed: |
January 24, 2006 |
PCT NO: |
PCT/EP06/00591 |
371 Date: |
October 17, 2007 |
Current U.S.
Class: |
60/295 ;
60/299 |
Current CPC
Class: |
F01N 2340/02 20130101;
F01N 3/0253 20130101; F01N 3/2066 20130101; F01N 2610/02 20130101;
F01N 3/025 20130101; Y02A 50/2325 20180101; F01N 13/009 20140601;
Y02A 50/20 20180101; F01N 3/035 20130101; Y02T 10/12 20130101; Y02T
10/24 20130101; F01N 3/20 20130101 |
Class at
Publication: |
060/295 ;
060/299 |
International
Class: |
F01N 3/10 20060101
F01N003/10 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 3, 2005 |
DE |
10 2005 009 686.7 |
Claims
1-6. (canceled)
7. A method for exhaust-gas treatment for a diesel engine,
comprising: first conducting the exhaust gas through an NOx
carbamide SCR catalytic converter disposed in an exhaust branch of
the diesel engine and close to the diesel engine; subsequently
conducting the exhaust gas through a CSF particulate filter
disposed in the exhaust branch; and supplying energy from an
outside to the particulate filter to regenerate the particulate
filter.
8. The method according to claim 7, further comprising injecting
fuel into the exhaust branch upstream of the particulate
filter.
9. An apparatus for exhaust-gas treatment for a diesel engine,
comprising: an NOx carbamide SCR catalytic converter disposed in an
exhaust branch of the diesel engine and close to the diesel engine;
a CSF particulate filter disposed in the exhaust branch and
downstream of the catalytic converter; and a device configured to
supply energy to the particulate filter to regenerate the
particulate filter.
10. The apparatus according to claim 9, further comprising a device
configured to inject fuel into the exhaust branch upstream of the
particulate filter.
11. The apparatus according to claim 10, wherein the device
configured to inject fuel is connected to a fuel tank of the diesel
engine.
12. The apparatus according to claim 9, wherein the particulate
filter is disposed in an underbody area of a motor vehicle.
13. The apparatus according to claim 9, wherein the apparatus is
configured to perform the method according to claim 7.
14. An apparatus for exhaust-gas treatment for a diesel engine,
comprising: NOx carbamide SCR catalytic converting means disposed
in an exhaust branch of the diesel engine and close to the diesel
engine; CSF particulate filtering means disposed in the exhaust
branch and downstream of the catalytic converting means; and means
for supplying energy to the particulate filtering means to
regenerate the particulate filtering means.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a method for exhaust-gas
treatment for diesel engines, etc., in which the exhaust gas is
conducted through a regenerable particulate filter as well as an
NOx catalytic converter, each disposed in the exhaust branch. The
present invention also relates to an apparatus for implementing
this method. Diesel engines include engines whose exhaust gases
contain not insignificant quantities of soot particulates or
similar residues from combustion.
BACKGROUND INFORMATION
[0002] It is conventional to reduce the content of soot
particulates and nitrogen oxides in the exhaust gas using separate
aggregates, to the extent that the exhaust gas complies with the
exhaust-gas limiting values determined by law.
[0003] One technology proven for years for decreasing NOx is the
carbamide SCR technology (SCR=selective catalytic reduction). In
that case, carbamide or an aqueous carbamide solution is introduced
via a metering system into the exhaust branch upstream of the NOx
catalytic converter. Ammonia develops in two chemical steps in the
NOx catalytic converter, and the ammonia reacts with the nitrogen
oxides collected in the NOx catalytic converter to form nitrogen.
The advantage of using carbamide is that its handling during
transport and storage is completely problem-free, since carbamide
is colorless, odorless, non-toxic and biologically safe.
[0004] Particulate filters of the CSF type (CSF=catalyzed soot
filter) have proven to be reliable for filtering soot particulates
out of the exhaust gas. They are particulate filters which have a
catalytic coating in order to improve or permit the soot burn-off.
Particulate filters of the CSF type are passive, that is, are
continuously operating systems having high durability. A further
advantage is their modest space requirement.
[0005] Therefore, NOx catalytic converters of the SCR type on one
hand, and particulate filters of the CSF type on the other hand are
particularly suitable for use in motor vehicles. Systems have
already been discussed in the literature, in which a particulate
filter of the CSF type and an NOx catalytic converter of the SCR
type are disposed in the exhaust branch one behind the other
relative to the direction of flow of the exhaust gas. Because of
the relatively high exhaust-gas temperature, disposing the
particulate filter close to the engine ensures a reliable soot
burn-off. However, a problem results from disposing the SCR
catalytic converter far from the engine. The carbamide SCR
technology can first be used with sufficient stability starting
from an exhaust-gas temperature of more than 200.degree. C. Below
this temperature, no fresh reducing agent can be injected into the
exhaust branch, since a complete dissolution of the carbamide
solution in the exhaust branch is not guaranteed at temperatures
below 200.degree. C. Namely, polymerization of the carbamide may
occur, which leads to irreversible deposits in the exhaust branch
and clogs it in the course of time.
[0006] This means that a significant removal of nitrogen oxide from
the exhaust gas can only begin after the SCR catalytic converter
has been heated up to a sufficient temperature after a certain
operating time. Therefore, in an MVEG test cycle (MVEG=motor
vehicle emissions group) in which the exhaust-gas temperature at
the downstream SCR catalytic converter remains below 200.degree. C.
for a very long time, only a relatively low rate of nitrogen-oxide
reduction can be expected.
SUMMARY
[0007] Example embodiments of the present invention provide a
method, as well as an apparatus for implementing the method, in
which the efficiency of the SCR catalytic converter may be improved
in all operating ranges, while ensuring proper operation of the CSF
particulate filter.
[0008] The method provides that the exhaust gas is first conducted
through an NOx catalytic converter of the carbamide SCR type
disposed close to the engine, and subsequently through a
particulate filter of the CSF type, the energy necessary for
regenerating the particulate filter being supplied to it from
outside.
[0009] Because the SCR catalytic converter is located close to the
engine, the work window of the catalytic converter is better
utilized as a result of the higher exhaust-gas temperature. The
conversion of the nitrogen oxides begins earlier, leading to an
increase in the rate of nitrogen-oxide removal over the entire
operating time (e.g., an MVEG test cycle). The carbamide necessary
for the regeneration is injected into the exhaust branch upstream
of the SCR catalytic converter.
[0010] To ensure proper operation of the CSF particulate filter
despite being disposed at a distance from the engine, the energy
necessary for its regeneration is supplied to it from outside. This
energy may be supplied in different manners, namely, for instance,
in the form of thermal energy with the aid of microwave- or
electro-heating devices, or in the form of fuels which react with
the oxygen surplus included in the exhaust gas. The fuel provided
for the operation of the engine may be used as a regenerating agent
for the CSF particulate filter, since this fuel is always available
during operation and, for example, does not require a separate
tank. In this context, however, the particulate filter cannot be
regenerated using a mixture enrichment controlled by the engine
management, since the exhaust-gas temperatures of more than
650.degree. C. resulting therefrom--which are obtained, somewhat
reduced, in the SCR catalytic converter as well--would clearly lie
at its tolerance limits. Moreover, an increased hydrocarbon
concentration caused by postinjection, upon passing over certain
types of SCR catalysts, would lead to contamination of the
catalyst, and therefore to losses in efficiency.
[0011] Therefore, the fuel is injected into the exhaust branch
upstream of the particulate filter (HCl method).
[0012] Using the method according to example embodiments of the
present invention, a good utilization of the work window of the SCR
catalytic converter may therefore be achieved on one hand, as well
as an engine-protecting particulate-filter regeneration on the
other hand.
[0013] In example embodiments of the present invention, an
apparatus includes an NOx catalytic converter of the carbamide SCR
type disposed close to the engine, and a particulate filter of the
CSF type downstream therefrom, and by a device assigned to the
particulate filter for supplying the energy necessary for its
regeneration. As already explained above, a device may be provided
to inject fuel into the exhaust branch upstream of the particulate
filter. For example, the fuel provided for the operation of the
diesel engine may be used as fuel, so that the device for injecting
fuel may be connected directly to the fuel tank of the diesel
engine, and a separate fuel tank is not necessary.
[0014] When the apparatus described for exhaust-gas treatment is
used in a motor vehicle, the particulate filter is disposed in the
underbody area of the motor vehicle, where the heat output by it
can be dissipated directly to the surroundings.
[0015] Example embodiments of the present invention are shown in
the drawing and described in more detail below.
BRIEF DESCRIPTION OF THE DRAWING
[0016] The FIGURE schematically illustrates a motor vehicle having
a combustion engine, in the exhaust branch of which, an SCR
catalytic converter and a CSF particulate filter are situated one
behind the other.
DETAILED DESCRIPTION
[0017] Motor vehicle 2 shown schematically in the FIGURE is powered
by a diesel engine 4. As shown schematically, diesel engine 4 is
equipped with an exhaust-gas turbocharger 6 which uses the exhaust
gases of diesel engine 4 in a conventional manner to supercharge
it.
[0018] The exhaust gases are carried away through an exhaust
branch, denoted as a whole by numeral 8, into the surroundings. In
this exhaust branch 8, directly behind diesel engine 4, an SCR
catalytic converter 10 is situated, in which nitrogen oxide is
removed from the exhaust gases in a first method step. SCR
catalytic converter 10 works with carbamide or an aqueous carbamide
solution as a reducing agent, which is taken from a carbamide tank
12 located, for example, in the rear end of the vehicle, and is
injected into exhaust branch 8 upstream of SCR catalytic converter
10. Carbamide SCR catalytic converter 10 functions at an
exhaust-gas temperature clearly within the heat-tolerance limits of
the SCR catalytic converter in an effective range of the SCR work
window.
[0019] Disposed in the exhaust branch downstream of the SCR
catalytic converter is a regenerable particulate filter 14 which
removes soot particulates from the exhaust gas. Particulate filter
14 is a particulate filter of the CSF type, which is coated with a
catalytically active material. Particulate filter 14 is regenerated
by fuel that is taken from fuel tank 16 of motor vehicle 2 and
injected into exhaust branch 8 upstream of particulate filter 14.
By a regulated metering of the fuel injection, it is possible to
operate the particulate filter at a temperature optimal for the
soot burn-off.
LIST OF REFERENCE NUMERALS
[0020] 2 motor vehicle [0021] 4 diesel engine [0022] 6 exhaust-gas
turbocharger [0023] 8 exhaust branch [0024] 10 SCR catalytic
converter [0025] 12 carbamide tank [0026] 14 particulate filter
[0027] 16 fuel tank
* * * * *