U.S. patent application number 13/271706 was filed with the patent office on 2012-04-19 for method to reduce the ignition temperature of soot being accumulated on a particulate trap.
This patent application is currently assigned to HJS EMISSION TECHNOLOGY GMBH & CO. KG. Invention is credited to Jan Margraf, Klaus Schrewe, Simon Steigert.
Application Number | 20120090299 13/271706 |
Document ID | / |
Family ID | 44651499 |
Filed Date | 2012-04-19 |
United States Patent
Application |
20120090299 |
Kind Code |
A1 |
Margraf; Jan ; et
al. |
April 19, 2012 |
Method to reduce the ignition temperature of soot being accumulated
on a particulate trap
Abstract
A method for lowering the ignition temperature of soot
accumulated on a particulate filter 2 installed in exhaust tract 1
of an internal combustion engine is described. In this method, a
precursor of a catalyst which lowers the oxidation temperature of
soot is introduced into exhaust tract 1 downstream from the
internal combustion engine and upstream from particulate filter 2.
The precursor introduced into exhaust tract 1 is converted to its
gaseous phase within exhaust tract 1 prior to contacting the soot
accumulated on particulate filter 2. The gaseous catalyst precursor
is adsorbed by the soot accumulated on particulate filter 2.
Subsequently the catalyst responsible for lowering the ignition
temperature is formed from the gaseous precursor in a reaction with
at least one other component contained in the exhaust gas flow.
Inventors: |
Margraf; Jan; (Dortmund,
DE) ; Schrewe; Klaus; (Ruthen, DE) ; Steigert;
Simon; (Menden, DE) |
Assignee: |
HJS EMISSION TECHNOLOGY GMBH &
CO. KG
Menden
DE
|
Family ID: |
44651499 |
Appl. No.: |
13/271706 |
Filed: |
October 12, 2011 |
Current U.S.
Class: |
60/274 |
Current CPC
Class: |
F01N 9/002 20130101;
F01N 2610/12 20130101; F01N 2610/01 20130101; Y02T 10/40 20130101;
F01N 2610/1453 20130101; F01N 3/0293 20130101; F01N 2610/06
20130101; Y02T 10/47 20130101; F01N 2610/08 20130101 |
Class at
Publication: |
60/274 |
International
Class: |
F01N 3/18 20060101
F01N003/18 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 13, 2010 |
DE |
10 2010 038 143.8 |
Claims
1. A method for lowering the ignition temperature of soot
accumulated in a particulate filter installed in an exhaust tract
of an internal combustion engine comprising: providing a precursor
of a catalyst, said catalyst functioning to lower an ignition
temperature of the soot; introducing the catalyst into the exhaust
tract downstream from the internal combustion engine and upstream
from the particulate filter; wherein the precursor introduced into
the exhaust gas tract is converted within the exhaust gas tract
into its gaseous phase before it contacts the soot accumulated on
the particulate filter; said gaseous catalyst precursor being
absorbed by the soot accumulated on the particulate filter; and
said catalyst precursor forming the catalyst responsible for
lowering the ignition temperature in a reaction with at least one
other gaseous component contained in the exhaust gas flow.
2. The method as recited in claim 1, wherein an oxide is used as
the catalyst, which is formed from the gaseous precursor and the
oxygen contained in the exhaust gas flow.
3. The method as recited in claim 1 wherein to convert the
precursor installed in the exhaust tract into its gaseous phase,
the precursor is entrained in the exhaust gas flow over a certain
dwell time.
4. The method as recited in claim 2 wherein to convert the
precursor installed in the exhaust tract into its gaseous phase,
the precursor is entrained in the exhaust gas flow over a certain
dwell time.
5. The method as recited in claim 1 wherein a material whose vapor
pressure favors a change of the aggregate state into the gaseous
phase is introduced into the exhaust tract as precursor.
6. The method as recited in claim 2 wherein a material whose vapor
pressure favors a change of the aggregate state into the gaseous
phase is introduced into the exhaust tract as precursor.
7. The method as recited in claim 3 wherein a material whose vapor
pressure favors a change of the aggregate state into the gaseous
phase is introduced into the exhaust tract as precursor.
8. The method as recited in claim 4 wherein a material whose vapor
pressure favors a change of the aggregate state into the gaseous
phase is introduced into the exhaust tract as precursor.
9. The method as recited in claim 1 wherein the precursor is
introduced into the exhaust tract in a dissolved form or a gaseous
form.
10. The method as recited in claims 2 wherein the precursor is
introduced into the exhaust tract in a dissolved form or a gaseous
form.
11. The method as recited in claims 5 wherein the precursor is
introduced into the exhaust tract (1) in a dissolved form or a
gaseous form.
12. The method as recited in claim 7 wherein the precursor is
introduced into the exhaust tract (1) in a dissolved form or a
gaseous form.
13. The method as recited in claim 1 wherein the precursor is
introduced into the exhaust tract as dissolved or gaseous
ferrocene.
14. The method as recited in one of claim 3, wherein the precursor
is introduced into the exhaust tract as dissolved or gaseous
ferrocene.
15. The method as recited in claim 5, wherein the precursor is
introduced into the exhaust tract as dissolved or gaseous
ferrocene.
16. The method as recited in claim 1 wherein the method is carried
out within the scope of a regeneration of the particulate filter
with sufficient advance timing before an intended regeneration so
that the catalyst may form from the precursor and another gaseous
component in the exhaust gas flow.
17. The method as recited in claim 2 wherein the method is carried
out within the scope of a regeneration of the particulate filter
with sufficient advance timing before an intended regeneration so
that the catalyst may form from the precursor and another gaseous
component in the exhaust gas flow.
18. The method as recited in claim 16, wherein the mixing-in of the
precursor is terminated before the regeneration process is started
or triggered
Description
CROSS REFERENCE APPLICATIONS
[0001] This application claims priority from German application
number 10 2010 038 148.8 filed Oct. 13, 2010, which is hereby
incorporated in its entirety for all purposes.
BACKGROUND
[0002] To purify the exhaust gases emitted from an internal
combustion engine such as a diesel engine, it is sometimes
necessary that the exhaust gas or the exhaust gas purification unit
must have a certain minimum temperature. The exhaust gas is
sometimes heated using additional measures such as connecting an
exhaust gas burner so that the exhaust gas treatment operation can
be preformed even if the exhaust gas and thus the exhaust gas
purification unit is not yet at the minimum temperature.
[0003] Diesel engines are equipped with exhaust gas purification
systems for reducing harmful emissions. The exhaust gas expelled
from such a diesel engine is passed through an exhaust gas
purification system for this purpose. The exhaust gas purification
system includes an exhaust tract in which one or more exhaust gas
purification units are installed. A particulate filter may be
installed in the exhaust tract to remove the soot in the exhaust
gas. The soot in the exhaust gas accumulates on the inflow-side
surface of the particulate filter. The soot is burned off when the
soot load on the filter is sufficiently high to clog the filter to
prevent the exhaust gas counterpressure from increasing excessively
during the successive soot accumulation. The particulate filter is
regenerated when a soot burn-off is completed. A non-combustible
ash residue remains on the filter. For the soot burn-off to occur
the soot must have a specific temperature, called soot ignition
temperature. The required temperature for triggering soot burn-off
is not always attained by the inflowing exhaust gas depending on
the operation of the diesel engine. Additional measures must be
taken for triggering a regeneration process in these circumstances.
This can be done by heating the filter body or its inflow-side
surface with the aid of electrical heating elements or by heating
the exhaust gas flowing to the filter by using burners and/or
oxidation catalysts, which are brought into contact with fuel to
increase the exhaust gas temperature.
[0004] It is also known to lower the soot ignition temperature is
by supplying a catalyst. Such catalysts are used in the form of an
additive containing a precursor of the catalyst. Additives of this
type are typically mixed into the fuel. The additive is supplied to
the internal combustion engine with the fuel. The catalyst is
formed from the precursor during the combustion process and
deposited on the soot being formed at the same time. The catalyst
flows with the soot through the exhaust tract until the soot
particles are captured by a particulate filter.
[0005] Ferrocene is used in many cases as additive. In addition to
supplying ferrocene as additive and the iron oxide Fe.sub.xO.sub.y
for example Fe.sub.2O.sub.3, formed therefrom during the conversion
in the internal combustion engine, it is known from EP 0 543 477 B1
to supply ferrocene in the gaseous form to the combustion chamber
of the internal combustion engine. In these methods, the catalyst
is also formed together with the soot during the process of
combustion of the fuel by the internal combustion engine. In the
two above-described methods, the soot emitted by the internal
combustion engine already has a lowered ignition temperature.
Accordingly, the soot accumulated in a particulate filter installed
in the exhaust tract has a lowered ignition temperature within the
entire filter cake.
[0006] In the above methods, a known problem is that the additive
introduced into the combustion chamber can have a disadvantageous
impact at the time of the injection or in the units used for fuel
injection when supplying the catalyst to the soot by converting the
catalyst precursor in the engine compartment of the internal
combustion engine. Against this background, methods have been
developed in which the catalyst precursor is introduced into the
exhaust tract downstream from the internal combustion engine. Such
a method is known, for example, from EP 1 741 886 A1. In this
method, a dissolved metal colloid is injected into the exhaust
tract as catalytic precursor for the purpose of evaporating the
solvent and then depositing the catalyst contained therein on the
soot particles entrained in the exhaust gas flow before these are
deposited from the exhaust gas flow on the surface of the
particulate filter.
[0007] In addition to this previously known method, it is also
known to introduce a catalyst precursor into the exhaust tract so
it contacts the soot already deposited on the particulate filter.
Metal colloids in solutions are also used as catalyst precursor in
this method. The disadvantage of these methods is that the catalyst
precursor must be supplied continuously or quasi-continuously for
the entire quantity of the soot accumulated on the particulate
filter to have a lowered ignition temperature. Yet EP 1 741 886 A1
also refers to a discontinuous operation of supplying the catalyst
precursor. However, such an operation as described in this document
is only possible when switching between operating states of the
internal combustion engine at a higher load and lower or no load
takes place or is possible at all. If the internal combustion
engine is operated in such states, which are very different
regarding their load, the catalyst precursor is supplied only in
the high load range against the background that most the of soot to
accumulate on the filter is formed in that case.
[0008] Of course, an effort is made to keep the quantity of
additive to be supplied (catalyst or catalyst precursor) which is
used for the purposes mentioned as low as possible. Since the
quantities of catalyst precursor are rather small anyway, it
requires a non-negligible effort to meter the catalyst precursor
sufficiently accurately and not provide too great an excess amount.
It must also be kept in mind in this context that metering takes
place in a hot environment.
[0009] Based on this above-discussed prior art, an aspect of the
present disclosure is to refine an above-described method such that
the metering of a catalyst precursor into the exhaust tract
simplified and an effort is made for all, or at least a predominant
portion of the soot accumulated on a particulate filter to have an
ignition temperature lowered by the catalyst.
[0010] The foregoing example of the related art and limitations
related therewith are intended to be illustrative and not
exclusive. Other limitations of the related art will become
apparent to those of skill in the art upon a reading of the
specification and a study of the drawings.
SUMMARY
[0011] The present disclosure relates to a method for lowering the
ignition temperature of soot accumulated on a particulate filter
installed in the exhaust tract of an internal combustion engine.
The disclosed method uses a precursor of a catalyst which lowers
the ignition temperature of the soot is introduced into the exhaust
tract downstream from the internal combustion engine and upstream
from the particulate filter.
[0012] The following embodiments and aspects thereof are described
and illustrated in conjunction with systems, tool and methods which
are meant to be exemplary and illustrative, not limiting in scope.
In various embodiments, one or more of the above described problems
have been reduced or eliminated, while other embodiments are
directed to other improvements.
[0013] Disclosed is a method in which the precursor introduced into
the exhaust tract is converted into its gaseous phase within the
exhaust tract prior to impinging on the soot accumulated on the
particulate filter. The gaseous catalyst precursor adsorbs the soot
accumulated on the particulate filter. The catalyst responsible for
lowering the ignition temperature is subsequently formed from the
catalyst precursor in a reaction with at least one other gaseous
component contained in the exhaust gas flow.
[0014] In contrast with the previously known methods, in this
method the catalyst is formed from a catalyst precursor in its
gaseous phase. The catalyst is formed with the participation of at
least one other gaseous component contained in the exhaust gas
flow. This reaction for forming the catalyst takes place in or on
the soot, and thus in situ, i.e.: directly at the one place where
the catalyst is needed. In the above-described concept, use is made
of the adsorbing characteristics of the soot accumulated on the
particulate filter, which has adsorption characteristics like
activated carbon. The gaseous catalyst precursor is adsorbed by the
soot due to its above-described characteristics. The catalyst
needed for lowering the ignition temperature is thus formed from
the accumulated gaseous catalyst precursor by combining with at
least one other gaseous component contained in the exhaust gas
flow.
[0015] Furthermore, the gaseous characteristic of the catalyst
precursor is used for distributing same within the soot accumulated
on the particulate filter. The catalyst precursor penetrates into
the soot layer due to its gaseous aggregate state and may thus be
supplied to all the soot. It is assumed that this describes, for
the first time, the active percolation of a catalyst precursor
through a soot cake. In contrast to previously known methods, in
which the catalyst is continuously deposited together with the soot
particles on the inflow side surface of the particulate filter,
with the subject matter of the claimed method this allows the
supply of the catalyst precursor be carried out discontinuously.
Due to the above-described characteristics of the claimed method,
the catalyst precursor may be introduced into the exhaust tract
only when a particulate filter regeneration is to be triggered.
This has advantages in metering, as it is described below, as well
as in monitoring and control of a particulate filter regeneration.
The point in time of a particulate filter regeneration is also
better determined and unintended regeneration processes are avoided
because in this operation the soot ignition temperature is lowered
only directly before a regeneration process. This is true mainly
when soot oxidation and thus soot burn-off is to be avoided when
the accumulated quantity of soot is not yet sufficiently large for
performing an optimum soot burn-off.
[0016] The catalyst precursor is introduced into the exhaust tract
downstream from the internal combustion engine and upstream from
the particulate filter. Use is made of the circumstance that the
catalyst precursor is in the exhaust tract for a certain dwell time
and changes its aggregate state into the gaseous phase during this
dwell time. The supplied gaseous catalyst precursor is brought into
contact with all, or nearly all, soot particles which then adsorb
the catalyst due to the permeability of the soot cake accumulated
on the particulate filter. It is not required that the soot
particles have a lowered ignition temperature during the process of
deposition from the exhaust gas flow. Rather, in this method the
catalyst precursor may be supplied discontinuously. Typically the
precursor is supplied in connection with a regeneration process of
the particulate filter. The catalyst precursor is supplied in
advance of the actual regeneration process being started or
triggered. The advance timing is chosen such that sufficient time
is available for the catalyst to be formed from the gaseous
catalyst precursor adsorbed by the soot particles. This reaction
may take several minutes.
[0017] In such a discontinuous operation of the supply of the
catalyst precursor the quantity to be metered is exponentially
higher compared to metering when the catalyst precursor must be
supplied continuously to the exhaust tract during the entire
operation of the internal combustion engine. As an example, if a
quantity of 60 mL of catalyst precursor is needed for providing
sufficient quantity of catalyst for the desired lowering of the
ignition temperature of a soot accumulated on a particulate filter,
in the claimed method 6 mL/min of the catalyst precursor is
introduced into the exhaust tract approximately 10 minutes prior to
the regeneration process. In this example, the quantity of soot
accumulated on the particulate filter corresponds to the quantity
of soot that is accumulated during an operation of the internal
combustion engine for 20 hours. In conventional methods, the same
quantity of catalyst precursor must be introduced continuously into
the exhaust tract over the 20 hours of operation at a metering rate
of 0.05 mL/min.
[0018] Advantageously, the method may be carried out if a metal
oxide, for example an iron oxide, is used as catalyst for the
purpose of lowering the ignition temperature of soot. Ferrocene,
which is typically introduced into the exhaust tract in dissolved
form, is well suited as catalyst precursor for forming an iron
oxide as catalyst. Due to the temperature typically prevailing in
the exhaust tract during the operation of the internal combustion
engine, the solvent quickly evaporates. Toluene may be used as
solvent, for example. Ferrocene, which remains in the solid form
after the solvent is evaporated, is then converted into its gaseous
form. When using ferrocene, this process is supported by the
relatively high vapor pressure of ferrocene. Ferrocene is initially
present in the solid form and has changed its aggregate state to
the gaseous phase after a relatively short flow path in the exhaust
tract. The oxygen contained in the exhaust gas flow is used as a
further gaseous component for forming the desired iron oxide
catalyst. Research has shown that when ferrocene is used as
catalyst precursor, in its gaseous phase it is very effectively
adsorbed by the soot accumulated on the particulate filter. In
particular before the gaseous ferrocene, together with oxygen, has
reacted to form the iron oxide catalyst it is absorbed by the soot.
The reaction is slowed down by the typically relatively small
oxygen content in the exhaust gas flow. This slow-down is used in
the method to ensure that sufficient gaseous ferrocene has been
adsorbed by the soot particles before the catalyst is actually
formed. Of course, the process of forming the catalyst from the
gaseous catalyst precursor goes hand-in-hand with the supply of the
catalyst precursor.
[0019] The description of the method makes it clear that, despite
the discontinuous supply of a catalyst precursor, it is ensured
that the ignition temperature of all the soot accumulated by a
particulate filter, or at least of a sufficient quantity thereof,
is lowered to allow controlled and full regeneration (soot
burn-off) to be carried out.
[0020] In addition to the exemplary aspects and embodiments
described above, further aspects and embodiments will become
apparent by reference to the accompanying drawings forming a part
of this specification wherein like reference characters designate
corresponding parts in the several views.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 is a schematic view of a particulate filter installed
in exhaust tract of a diesel engine (not illustrated).
[0022] Before explaining the disclosed embodiment of the present
invention in detail, it is to be understood that the invention is
not limited in its application to the details of the particular
arrangement shown, since the invention is capable of other
embodiments. Exemplary embodiments are illustrated in referenced
figures of the drawings. It is intended that the embodiments and
figures disclosed herein are to be considered illustrative rather
than limiting. Also, the terminology used herein is for the purpose
of description and not of limitation.
DETAILED DESCRIPTION OF THE DRAWINGS
[0023] In the illustrated exemplary embodiment, particulate filter
2 has a plurality of filter pockets 3 made of sintered metal. Soot
is deposited from the exhaust gas flow on the inflow-side top of
filter pocket 3 during operation of the internal combustion engine.
It accumulates successively during the operation of the diesel
engine on the inflow-side surfaces of filter pockets 3. Of course,
while the exhaust gas counterpressure increases with the successive
accumulation of soot in particulate filter 2, the accumulated soot
layer continues to be permeable to the exhaust gas flow.
[0024] Downstream from the diesel engine (not shown) and upstream
from particulate filter 2, a port 4 is installed in exhaust tract
1. Material may be introduced into the exhaust tract via port 4.
Port 4 includes a nozzle 5 located in the exhaust tract, whose
supply line leads out of exhaust tract 1. A metering pump 7 is
installed in supply line 6. The inlet side of the metering pump 7
is connected, in a manner not illustrated in detail, to a storage
container for storing the material to be injected into the exhaust
gas flow. An air supply line 8 opens into supply line 6 downstream
in the pumping direction of metering pump 7. A valve may be
installed therein if desired (not shown). The material pumped
during the operation of metering pump 7 and enriched with air, may
thus be introduced into exhaust tract 1.
[0025] In the section of an exhaust gas purification system
illustrated in FIG. 1, port 4 and the units related thereto, are
used to mix in a catalyst precursor into the exhaust gas flowing
through exhaust tract 1. The catalyst forming from the precursor is
used for lowering the ignition temperature of the soot accumulated
on particulate filter 2. In the depicted embodiment, ferrocene
dissolved in toluene is thus mixed into the exhaust gas flowing in
exhaust tract 1 through the port 4 during operation of the diesel
engine as shown by the block arrow in FIG. 1. Supported by the
temperatures prevailing in exhaust tract 1 (270.degree. C. to
300.degree. C.) during operation of the diesel engine, the toluene
atomized from nozzle 5 and introduced into exhaust tract 1
evaporates almost immediately, so that small ferrocene particles
are entrained in the exhaust gas flow even after a short flow path
of the supplied catalyst precursor. Ferrocene is converted from its
solid state into its gaseous phase due to the temperature in
exhaust tract 1 and supported by its sublimation, which takes place
at relatively low temperatures. Therefore, gaseous ferrocene is
subsequently entrained in the exhaust gas flow. The configuration
illustrated in FIG. 1 is dimensioned regarding the length of the
exhaust gas flow path in such a way that when dissolved ferrocene
is injected during operation of the diesel engine, ferrocene is
converted into its gaseous state prior to reaching particulate
filter 2. The droplets introduced into exhaust tract 1 and the
solid particles present after the evaporation of toluene are shown
larger than scale only to elucidate the mode of operation.
Actually, the liquid is atomized by nozzle 5 into minute droplets.
The air introduced through air supply line 8 into the liquid flow
pumped by metering pump 7 supports this atomizing process.
[0026] During an operation for supplying the catalyst precursor
into the exhaust gas flow via port 4, the soot layer accumulated on
the inflow-side surface of particulate filter 2 is exposed to the
gaseous ferrocene contained in the exhaust gas flow. The
accumulated soot acts as an active carbon filter and adsorbs the
gaseous ferrocene. Since in each inflow-side filter pocket 3, the
exhaust gas flows through the soot layer on the inflow-side surface
of particulate filter 2, in this way gaseous ferrocene is
introduced into the entire soot layer, including the soot particles
directly on the filter surface of particulate filter 2.
[0027] Oxygen is also transported in the exhaust gas flow.
Therefore, an iron oxide is formed from the gaseous ferrocene
absorbed by the soot, which is a catalyst for lowering the
activation energy of a soot oxidation necessary for filter
regeneration. If a sufficient quantity of gaseous ferrocene has
been introduced into the accumulated soot and the catalytic iron
oxide has been formed, regeneration of particulate filter 2 may be
triggered at substantially lower temperatures compared to the
ignition temperature of soot without such a catalyst addition.
[0028] A special feature of the above-described method is that the
catalyst needed for lowering the oxidation temperature of soot is
formed in situ at the location where the catalyst is actually
needed. If the catalyst were entrained in the exhaust gas flow in
its oxide form, it would deposit only on the uppermost soot layer,
but would not be able to penetrate to the soot particles
therebelow
[0029] The above-described mode of operation allows the catalyst
precursor to be introduced into exhaust tract 1 via port 4 for the
purpose of regenerating particulate filter 2 only shortly before an
intended regeneration, for example when sufficient soot
accumulation has been detected. The quantity of catalyst precursor
introduced into exhaust tract 1 over a certain period of time is
such that the catalyst formed therefrom is sufficient for lowering
the oxidation temperature of all the soot accumulated on
particulate filter 2. Finally, this quantity corresponds to the
quantity that would be necessary to add in continuous supply of a
catalyst precursor over the same time of operation of the diesel
engine between two regeneration periods.
[0030] Due to the special characteristics of the method described
with reference to FIG. 1, discontinuous introduction of the
catalyst precursor is possible, whereby the needed quantity of
catalyst is supplied in the form of the precursor may be metered in
much larger quantities due to the short time period in which the
quantity of catalyst precursor needed for the entire soot cake is
supplied. Metering larger quantities is considerably less demanding
regarding the systems needed for metering, making metering much
more accurate and therefore more effective.
[0031] Of course, for carrying out the method, the catalyst
precursor may be mixed into the exhaust tract also in its solid
form instead of the liquid form described in the exemplary
embodiment. A catalyst precursor may also be supplied in the
gaseous form, for example gaseous ferrocene.
[0032] The present invention was described with reference to an
exemplary embodiment. The claimed method may also be used in
exhaust gas purification systems in which additional units are
provided, for example for increasing the temperature in the exhaust
tract or other components used in connection with an exhaust gas
purification system.
[0033] While a number of exemplary aspects and embodiments have
been discussed above, those of skill in the art will recognize
certain modifications, permutations, additions and sub-combinations
therefore. It is therefore intended that the following appended
claims hereinafter introduced are interpreted to include all such
modifications, permutations, additions and sub-combinations are
within their true spirit and scope. Each apparatus embodiment
described herein has numerous equivalents.
[0034] The terms and expressions which have been employed are used
as terms of description and not of limitation, and there is no
intention in the use of such terms and expressions of excluding any
equivalents of the features shown and described or portions
thereof, but it is recognized that various modifications are
possible within the scope of the invention claimed. Thus, it should
be understood that although the present invention has been
specifically disclosed by preferred embodiments and optional
features, modification and variation of the concepts herein
disclosed may be resorted to by those skilled in the art, and that
such modifications and variations are considered to be within the
scope of this invention as defined by the appended claims. Whenever
a range is given in the specification, all intermediate ranges and
subranges, as well as all individual values included in the ranges
given are intended to be included in the disclosure.
LIST OF REFERENCE NUMERALS
[0035] 1 exhaust tract [0036] 2 particulate filter [0037] 3 filter
pocket [0038] 4 port [0039] 5 nozzle [0040] 6 supply line [0041] 7
metering pump [0042] 8 air supply line
* * * * *