U.S. patent application number 13/836725 was filed with the patent office on 2014-09-18 for exhaust aftertreatment system.
This patent application is currently assigned to Caterpillar Inc.. The applicant listed for this patent is Caterpillar Inc.. Invention is credited to Mirza P. Baig, Kurtis E. Chenoweth, Raymond U. Isada, Rick E. Jeffs, Thomas W. Manning, Kevin J. Weiss.
Application Number | 20140260198 13/836725 |
Document ID | / |
Family ID | 51521031 |
Filed Date | 2014-09-18 |
United States Patent
Application |
20140260198 |
Kind Code |
A1 |
Baig; Mirza P. ; et
al. |
September 18, 2014 |
EXHAUST AFTERTREATMENT SYSTEM
Abstract
An exhaust aftertreatment module is provided. The exhaust
aftertreatment module includes a housing having a first end and a
second end. The at least one inlet is disposed between the first
end and the second end and is configured to introduce an exhaust
into the housing. A mixing tube is disposed downstream of the at
least one inlet. The mixing tube is configured to direct the
exhaust towards the second end of the housing. The exhaust
aftertreatment module further includes a single bank of Selective
Catalytic Reduction (SCR) catalysts disposed at an oblique angle to
a longitudinal axis of the mixing tube. The single bank of SCR
catalysts is configured to receive the exhaust redirected from the
second end of the housing.
Inventors: |
Baig; Mirza P.; (Peoria,
IL) ; Weiss; Kevin J.; (Peoria, IL) ; Isada;
Raymond U.; (Peoria, IL) ; Manning; Thomas W.;
(Metamora, IL) ; Jeffs; Rick E.; (Peoria, IL)
; Chenoweth; Kurtis E.; (Ipava, IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Caterpillar Inc.; |
|
|
US |
|
|
Assignee: |
Caterpillar Inc.
Peoria
IL
|
Family ID: |
51521031 |
Appl. No.: |
13/836725 |
Filed: |
March 15, 2013 |
Current U.S.
Class: |
60/274 ;
60/301 |
Current CPC
Class: |
F01N 13/017 20140601;
F01N 3/106 20130101; F01N 2470/16 20130101; F01N 2330/36 20130101;
Y02T 10/12 20130101; F01N 3/2066 20130101; Y02T 10/24 20130101 |
Class at
Publication: |
60/274 ;
60/301 |
International
Class: |
F01N 3/18 20060101
F01N003/18 |
Claims
1. An exhaust aftertreatment module comprising: a housing having a
first end and a second end; at least one inlet disposed between the
first end and the second end, the at least one inlet configured to
introduce exhaust into the housing; a mixing tube disposed
downstream of the at least one inlet, the mixing tube configured to
direct the exhaust towards the second end of the housing; and a
single bank of Selective Catalytic Reduction (SCR) catalysts
disposed at an oblique angle to a longitudinal axis of the mixing
tube, the single bank of SCR catalysts configured to receive the
exhaust redirected from the second end of the housing.
2. The exhaust aftertreatment module of claim 1 further comprising
at least one diesel oxidation catalyst (DOC) device disposed
proximate to the at least one inlet.
3. The exhaust aftertreatment module of claim 1 further comprising
a reductant injector located at an inlet of the mixing tube.
4. The exhaust aftertreatment module of claim 1 further comprising
at least one outlet located downstream of the single bank of SCR
catalysts and proximate to the at least one inlet, the at least one
outlet configured to allow the exhaust to exit from the
housing.
5. The exhaust aftertreatment module of claim 1 further comprising
a sound attenuation chamber disposed downstream of the at least one
inlet and proximate to the mixing tube, the sound attenuation
chamber configured to receive the exhaust from the at least one
inlet.
6. The exhaust aftertreatment module of claim 5, wherein the sound
attenuation chamber comprises a plurality of compartments.
7. The exhaust aftertreatment module of claim 6, wherein at least
one of the plurality of compartments has a trapezoidal shaped
configuration.
8. The exhaust aftertreatment module of claim 7, wherein at least
one of the plurality of compartments has a triangular shaped
configuration and is disposed adjacent to and is in fluid
communication with the at least one of the plurality of
compartments having the trapezoidal shaped configuration.
9. An exhaust aftertreatment module comprising: a housing having a
first end and a second end; at least one inlet disposed between the
first end and the second end, the at least one inlet configured to
introduce exhaust into the housing; a sound attenuation chamber
disposed downstream of the at least one inlet, the sound
attenuation chamber configured to receive the exhaust from the at
least one inlet; a mixing tube disposed downstream of the sound
attenuation chamber, the mixing tube configured to direct the
exhaust towards the second end of the housing; and a single bank of
Selective Catalytic Reduction (SCR) catalysts disposed at an
oblique angle to a longitudinal axis of the mixing tube, the single
bank of SCR catalysts configured to receive the exhaust redirected
from the second end of the housing.
10. The exhaust aftertreatment module of claim 9 further comprising
at least one diesel oxidation catalyst (DOC) device disposed
between the at least one inlet and the sound attenuation
chamber.
11. The exhaust aftertreatment module of claim 9 further comprising
at least one outlet located downstream of the single bank of SCR
catalysts and proximate to the at least one inlet the at least one
outlet configured to allow the exhaust to exit from the
housing.
12. The exhaust aftertreatment module of claim 9, wherein the sound
attenuation chamber comprises a plurality of compartments.
13. The exhaust aftertreatment module of claim 12, wherein at least
one of the plurality of compartments has a trapezoidal shaped
configuration.
14. The exhaust aftertreatment module of claim 13, wherein at least
one of the plurality of compartments has a triangular shaped
configuration and is disposed adjacent to and is in fluid
communication with the at least one of the plurality of
compartments having the trapezoidal shaped configuration.
15. A method comprising: introducing exhaust into at least one
inlet disposed between a first end and a second end of a housing;
receiving the exhaust into a mixing tube disposed downstream of the
at least one inlet; directing the exhaust towards the second end of
the housing; and receiving the exhaust redirected from the second
end of the housing into a single bank of Selective Catalytic
Reduction (SCR) catalysts disposed at an oblique angle to a
longitudinal axis of the mixing tube.
16. The method of claim 15 further comprising allowing the exhaust
to exit from the housing through at least one outlet, the at least
one outlet located downstream of the single bank of SCR catalysts
and proximate to the at least one inlet.
17. The method of claim 15 further comprising receiving the exhaust
into a sound attenuation chamber disposed downstream of the at
least one inlet and proximate to the mixing tube.
Description
TECHNICAL FIELD
[0001] The present disclosure relates to an exhaust system, and
particularly to an exhaust aftertreatment system for large engine
applications.
BACKGROUND
[0002] Growing concern for environment pollution has created new
challenges for manufacturers. Improvement in exhaust systems are
required in order to comply with the current pollution regulatory
norms. More specifically, exhaust aftertreatment systems are
utilized to treat exhaust containing relatively harmful pollutants,
such as nitrogen oxides (NO.sub.x). The exhaust aftertreatment
systems are known to employ selective catalytic reduction (SCR) for
such treatment. In the SCR process, a reductant, for example urea
((NH.sub.2).sub.2CO) or a water/urea solution, is selectively
injected into the exhaust and adsorbed onto a downstream substrate.
The injected urea solution decomposes into ammonia (NH.sub.3),
which reacts with NO.sub.x in the exhaust gas to form water
(H.sub.2O) and diatomic nitrogen (N.sub.2). Hence, the SCR process
effectuates a reduction in harmful emissions.
[0003] A variety of designs for the exhaust aftertreatment system
exist. These designs may vary based on the type of application.
Known exhaust aftertreatment system designs typically occupy space.
However, there may be space constraints in certain large engine
applications to accommodate the exhaust aftertreatment system.
Therefore, there is a need to provide an improved design for the
exhaust aftertreatment system.
[0004] For example, U.S. Published Application No. 2011/0146253
relates to an aftertreatment module for use with an engine. The
aftertreatment module includes a plurality of inlets configured to
direct exhaust in a first flow direction into the aftertreatment
module. The aftertreatment module also has a mixing duct configured
to receive exhaust from the plurality of inlets, and a branching
passage in fluid communication with the mixing duct. The branching
passage may be configured to redirect exhaust from the mixing duct
into separate flows that exit the aftertreatment module in a second
flow direction opposite the first flow direction. However, the
disclosed aftertreatment system has a relatively large design.
SUMMARY OF THE DISCLOSURE
[0005] In one aspect of the present disclosure an exhaust
aftertreatment module is provided. The exhaust aftertreatment
module includes a housing having a first end and a second end. At
least one inlet is disposed between the first end and the second
end. The at least one inlet is configured to introduce exhaust into
the housing. Further, a mixing tube is disposed downstream of the
at least one inlet. The mixing tube is configured to direct the
exhaust towards the second end of the housing. The exhaust
aftertreatment module further includes a single bank of Selective
Catalytic Reduction (SCR) catalysts disposed at an oblique angle to
a longitudinal axis of the mixing tube. The single bank of SCR
catalyst is configured to receive the exhaust redirected from the
second end of the housing. In one embodiment, a sound attenuation
chamber is provided in the aftertreatment module. The sound
attenuation chamber is disposed downstream of the at least one
inlet and proximate to the mixing tube. The sound attenuation
chamber is configured to receive the exhaust from the at least one
inlet.
[0006] In another aspect, a method is provided. The method
introduces exhaust into at least one inlet disposed between a first
end and a second end of a housing. The method receives the exhaust
into a mixing tube disposed downstream of the at least one inlet.
Further, the method directs the exhaust towards the second end of
the housing. Thereafter, the method receives the exhaust redirected
from the second end of the housing into a single bank of Selective
Catalytic Reduction (SCR) catalysts disposed at an oblique angle to
a longitudinal axis of the mixing tube.
[0007] Other features and aspects of this disclosure will be
apparent from the following description and the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is an exemplary power system, according to one
embodiment of the disclosure;
[0009] FIG. 2 is a cutaway perspective view of an exemplary exhaust
aftertreatment module; and
[0010] FIG. 3 is a cutaway top view of the exhaust aftertreatment
module shown in FIG. 2.
DETAILED DESCRIPTION
[0011] FIG. 1 illustrates an exemplary power system 100. The power
system 100 is depicted and described as a generator set including a
generator 102 powered by a multi-cylinder internal combustion
engine 104. The generator 102 and engine 104 are generally
contained within and supported by an external frame 106. It is
contemplated, however, that the power system 100 may embody another
type of power system, if desired, such as one including a diesel,
gasoline, or gaseous fuel-powered engine associated with a mobile
machine such as a locomotive, or a stationary machine such as a
pump.
[0012] Multiple separate sub-systems may be included within the
power system 100 to promote power production. For example, the
power system 100 may include, among other things, an air induction
system 108 and an exhaust system 110. The air induction system 108
may be configured to direct air or an air/fuel mixture into the
power system 100 for subsequent combustion. The exhaust system 110
may treat and discharge byproducts of the combustion process to the
atmosphere. The exhaust system 110 may include components that
condition and direct exhaust from cylinders of the engine 104 to
the atmosphere. For example, the exhaust system 110 may include an
aftertreatment module 112 connected to receive and treat exhaust
from the engine 104. The aftertreatment module 112 may treat,
condition, and/or otherwise reduce constituents of the exhaust
before the exhaust is discharged to the atmosphere.
[0013] The aftertreatment module 112 includes a housing 114. FIG. 2
depicts a cutaway perspective view of the housing 114, according to
one embodiment of the disclosure. As illustrated, the housing 114
may have a plurality of side walls 202, 204, 206, and 208. Further,
the housing 114 may include a first end 210 and a second end 212
located on opposite sides of the housing 114. In one exemplary
case, a distance between the side wall 202 and the side wall 206 is
approximately about 2235 mm and a distance between the side wall
204 and the side wall 208 is approximately about 1736 mm.
[0014] Referring to FIG. 2, at least one inlet 214 may be disposed
between the first end 210 and the second end 212. In the present
disclosure, two inlets 214 are shown placed side by side each other
and proximate to the first end 210 of the housing 114. It should be
noted that both these inlets may have a similar configuration in
terms of size and orientation within the housing 114. The inlet 214
is configured to introduce the exhaust into the housing 114. The
inlet 214 may have a tube like structure with perforations. The
design of the inlet 214 may facilitate ease of uniform flow of the
exhaust into the housing 114. As shown, the inlet 214 may be
provided on a bottom surface of the housing 114, such that a
longitudinal axis of the inlet 214 is substantially transverse to
the bottom surface of the housing 114. More specifically, in one
situation a diameter of the inlet 214 is approximately about 127
mm.
[0015] Further, the aftertreatment module 112 may include at least
one oxidation catalyst, for example a diesel oxidation catalyst
(DOC) 216 within the housing 114. The illustrated embodiment
depicts two DOCs 216 located downstream of the inlet 214. The DOC
216 is configured to receive the exhaust from the inlet 214. It
should be understood that the DOC 216 may include a porous ceramic
honeycomb structure, a metal mesh, a metal or ceramic foam, or
another suitable substrate coated with or otherwise containing a
catalyzing material, in order to catalyze a chemical reaction. The
chemical reaction may alter a composition of the exhaust passing
through the DOC 216. Exemplary materials used to make the DOC 216
may include palladium, platinum, vanadium, or a mixture thereof
that may facilitate a conversion of NO present in the exhaust into
NO.sub.2. In one embodiment, the DOC 216 may alternatively or
additionally perform particulate trapping functions, hydro-carbon
reduction functions, carbon-monoxide reduction functions, and/or
other functions known in the art for the treatment of the
exhaust.
[0016] In one embodiment, a sound attenuation chamber 218 may be
disposed downstream of the DOC 216. The sound attenuation chamber
218 may receive the exhaust from the DOC 216. It should be noted
that parameters related to the sound attenuation chamber 218 such
as, shape, size and dimension may vary as per requirement. The
sound attenuation chamber 218 may include one or more compartments.
In one exemplary embodiment, as shown in FIG. 2, the sound
attenuation chamber 218 may include a trapezoidal shaped
compartment 220. A first separation wall 222 may be disposed within
the trapezoidal shaped compartment 220. Further, the sound
attenuation chamber 218 may additionally include a substantially
rectangular shaped compartment 224 located downstream of the
trapezoidal shaped compartment 220. The rectangular shaped
compartment 224 may be formed by the sidewall 204 of the housing
114 and a second separation wall 226 positioned proximate to one
side of a mixing tube 228.
[0017] Referring closely to FIG. 2, the sound attenuation chamber
218 may additionally include a triangular shaped compartment 230,
which may be formed adjacent to the trapezoidal shaped compartment
220 and the rectangular shaped compartment 224. In one exemplary
embodiment, the triangular shaped compartment 230 may include at
least one opening 232 configured to allow the exhaust received into
the trapezoidal shaped compartment 220 to flow in and out of the
triangular shaped compartment 230, for the purpose of sound
attenuation. Further, in another exemplary embodiment, at least one
opening (not shown in figures) may be provided on the first
separation wall 222, to provide fluid communication between the
triangular shaped compartment 230 and the rectangular shaped
compartment 224. This arrangement may facilitate in further
reduction in noise present in the exhaust.
[0018] Further, the sound attenuation chamber 218 may fluidly
connect an outlet of the DOC 216 with an upstream open end of the
mixing tube 228. As shown, the mixing tube 228 may have a hollow
tubular structure. A longitudinal axis X-X of the mixing tube 228
may be substantially parallel to the bottom surface of the housing
114. The mixing tube 228 may be supported within the housing 114
using suitable supporting structures. In an exemplary case, a
diameter of the mixing tube 228 is approximately about 216 mm.
[0019] A reductant injector (not shown) may be located at or near
the upstream open end of the mixing tube 228. The reductant
injector is configured to inject a reductant into the exhaust
flowing through the mixing tube 228. A gaseous or liquid reductant,
most commonly a water/urea solution, ammonia gas, liquefied
anhydrous ammonia, ammonium carbonate, an ammine salt, or a
hydrocarbon such as diesel fuel, may be sprayed or otherwise
advanced into the exhaust passing through the mixing tube 228. In
an embodiment, a mixer (not shown) may be located within mixing
tube 228 in order to enhance incorporation of the reductant with
the exhaust flowing through the mixing tube 228. The mixer may be
located downstream of reductant injector.
[0020] Referring to FIG. 2, a downstream open end of the mixing
tube 228 may open into a compartment 234 near the second end 206 of
the housing 114. The compartment 234 may be formed by relevant
surfaces of the rectangular shaped compartment, the side surfaces
206, 208 of the housing 114, a third separation wall 236, and a
single bank of selective catalytic reduction (SCR) catalysts 238
disposed within the housing 114. It should be noted that the single
bank of SCR catalysts 238 is arranged within the housing 114 in a
space efficient manner. As shown, the single bank of SCR catalysts
238 is disposed an oblique angle .alpha. (see FIG. 3) with respect
to the longitudinal axis X-X of the mixing tube 228. For example,
in one implementation, the single bank of SCR catalysts 238 is
disposed at the oblique angle .alpha. of approximately about 12
degrees with respect to the longitudinal axis XX of the mixing tube
228.
[0021] The single bank of SCR catalysts 238 may include a number of
SCR catalysts. Each of the SCR catalysts 238 may have similar
dimensions and properties. In the illustrated embodiment, the
single bank of SCR catalysts 238 includes four cylindrical shaped
SCR catalysts. A person of ordinary skill in the art will
appreciate that the number of SCR catalysts 238 may vary based on
the application. Moreover, each of the of SCR catalysts 238 has a
corresponding SCR inlet 240 and an SCR outlet 242. As shown in
accompanying figures, each of the SCR catalysts 238 is arranged
side by side with the respective SCR inlets 240 oriented proximate
to the sidewall 242.
[0022] The single bank of SCR catalysts 238 is configured to
receive the redirected exhaust from the second end of the housing
214. It should be noted that the orientation of the single bank of
SCR catalyst 238 relative to the sidewalls 206, 208 of the housing
may cause a restriction in the exhaust flow entering the single
bank of SCR catalysts. To this end, each of the SCR catalysts 238
may receive an equal distribution of the exhaust flow. More
specifically, each of the plurality of SCR catalysts 238 may
include a generally cylindrical substrate fabricated from or
otherwise coated with a ceramic material such as titanium oxide, a
base metal oxide such as vanadium and tungsten, zeolites, and/or a
precious metal. With this composition, decomposed reductant
entrained within the exhaust redirected into the single bank of SCR
catalysts 238 may be adsorbed onto the surface and/or absorbed
within the single bank of the SCR catalysts 238. The reductant may
react with NO.sub.x (NO and NO.sub.2) present in the exhaust to
form water (H.sub.2O) and diatomic nitrogen (N.sub.2).
[0023] The exhaust may exit the single bank of SCR catalysts 238
via the SCR outlet 242. Further, the housing 114 may include at
least one outlet 244 proximate to the first end 202 of the housing
114. As shown, the outlet 244 may be provided on the sidewall 202
of the housing 114. The exhaust leaving the single bank of SCR
catalysts 238 may exit the exhaust aftertreatment module 112 via
the outlet 244. In one case, the outlet 244 has a diameter of
approximately about 254 mm. It should be noted that the housing 114
may additionally include a number of compartments or divisions in
order to assist in directing the exhaust flow within the housing.
These compartments may be created using any suitable material.
[0024] In one embodiment, a NO.sub.x sensor may be provided in
order to detect a NO.sub.x concentration in the exhaust exiting the
bank of SCR catalysts 238 through the SCR outlet 242. The location
of the NO.sub.x sensor within the housing 114 may vary. For
example, the NO.sub.x sensor may be located on an outer surface of
mixing tube 228. Alternatively the NO.sub.x sensor may be located
upstream of the single bank of SCR catalysts 238 on an inner
surface of mixing tube 228.
[0025] The NO.sub.x sensor may generate a signal indicative of the
concentration of NO.sub.x present in the exhaust flowing through a
given region or area within the housing 114. In one embodiment, the
signal may be received by an exhaust or power system controller
(not shown). The controller may then responsively adjust parameters
of the engine 104 and/or aftertreatment operation, such as, for
example, adjusting the amount of the reductant being injected in
order to maintain a concentration of NO.sub.x below regulated
limits.
[0026] FIG. 3 depicts a cutaway top view of the aftertreatment
module 112 of FIG. 2, according to an embodiment of the disclosure.
More specifically, FIG. 3 includes arrowheads which illustrate the
flow of the exhaust within the exhaust aftertreatment module 112.
The exhaust flow from the engine 104 may be directed through
turbines and passages (not indicated) to the exhaust aftertreatment
module 112. This exhaust may contain a complex mixture of air
pollutants, which can include, among other things, the oxides of
nitrogen (NO.sub.x) requiring treatment. Further, the exhaust may
be introduced into the housing 114 of the aftertreatment module 112
via the inlet 214.
[0027] The exhaust may then pass through the DOC 216. In one
embodiment, NO present in the exhaust may be converted to NO.sub.2
within the DOC 216. Alternatively or additionally, particulate
matter, hydrocarbons, and/or carbon monoxide present in the exhaust
may be trapped, converted, and/or reduced within the DOC 216.
[0028] In one embodiment, the exhaust may be received by the sound
attenuation chamber 218. As the exhaust passes through the
plurality of compartments of the sound attenuation chamber 218,
sound associated with the flow may reverberate therein and
dissipate. As shown by the arrowheads, the exhaust may flow into
the trapezoidal shaped compartment 220. In one exemplary
embodiment, the exhaust may flow in and out of the triangular
shaped compartment 230 provided adjacent to the trapezoidal shaped
compartment 220 via the at least one opening 232. In another
exemplary embodiment, the exhaust may further flow in and out of
the rectangular shaped compartment 224 via the opening (not shown).
It should be noted that an extension of the mixing tube 228 into
the sound attenuation chamber 218 may enhance the attenuation
effects of the sound attenuation chamber 218.
[0029] Further, the exhaust may enter into the mixing tube 228. In
one embodiment, turbulence of the exhaust flowing through the
mixing tube 228 may be promoted by the mixer. Also, the reductant
may be injected into the exhaust upstream of the mixer located in
the mixing tube 228. As the turbulent flow of the exhaust mixed
with the reductant passes along a length of the mixing tube 228,
the mixture may continue to homogenize and the reductant may begin
to decompose. It should be noted that a bulk of the reductant may
be decomposed in this process.
[0030] Subsequently, the exhaust may flow out of the mixing tube
228 and collide against the sidewalls 206, 208 of the housing 114.
The construction of the housing 114 and more particularly the
arrangement of the sidewalls 206, 208 relative to the mixing tube
228 and the single bank of SCR catalysts 238 may cause a reversal
in the flow of the exhaust, causing the exhaust to be redirected
towards the SCR inlet 240. Moreover, in one embodiment, a
decreasing flow area defined between the mixing tube 228, the
sidewalls and the bank of SCR catalysts may cause the a uniform
distribution of the exhaust entering the SCR inlets 240.
[0031] Within the single bank of SCR catalysts 238, the NO.sub.x
present in the exhaust may be reduced to water and diatomic
nitrogen. The exhaust may then flow out of the single bank of the
SCR catalysts 238 via the SCR outlet 242. The treated exhaust may
then flow towards the outlet 244 and exit the exhaust
aftertreatment module 112 therefrom.
INDUSTRIAL APPLICABILITY
[0032] Typically in known exhaust systems, the use of a catalytic
convertor may cause problems in some situations. In particular, the
catalytic convertor may restrict the exhaust flow to some extent
and thereby cause an increase in a back pressure of the exhaust. If
the exhaust back pressure is too high, breathing ability and
subsequent performance of the engine could be negatively impacted.
As a general rule, increased back pressure results in lower fuel
efficiency, decreased performance and a more limited altitude range
for any given engine.
[0033] Further, the exhaust systems of many internal combustion
engines may also be equipped with noise attenuation devices, such
as mufflers. The mufflers are typically located downstream of the
catalytic converter to dissipate noise in the exhaust gases.
Although these mufflers assist in reduction of noise, the inclusion
of these serially located devices often increases the size of the
exhaust system.
[0034] The present disclosure provides the aftertreatment module
112 having a compactly designed housing 114. The housing 114 may
contain the sound attenuation chamber 218 for reduction in noise
associated with the exhaust. The sound attenuation chamber 218 may
function similar to the known muffler. The incorporation of the
sound attenuation chamber within the aftertreatment module 112 to
form a single unit may further enhance design compactness. Also,
the single bank of SCR catalysts 224 located proximate to the
mixing tube 220 may provide an improved flow path for the exhaust,
causing uniform redirection of the exhaust flow towards the single
bank of SCR catalysts 224. The aftertreatment module 112 may also
provide the necessary backpressure required for large engine
applications. Additionally, the DOC 216 and/or the bank of SCR
catalysts may be replaced as per requirement.
[0035] Although the embodiments of this disclosure as described
herein may be incorporated without departing from the scope of the
following claims, it will be apparent to a person skilled in the
art that various modifications and variations to the above
disclosure may be made. Other embodiments will be apparent to those
skilled in the art from consideration of the specification and
practice of the disclosure. It is intended that the specification
and examples be considered as exemplary only, with a true scope
being indicated by the following claims and their equivalents.
* * * * *