U.S. patent application number 11/306438 was filed with the patent office on 2007-06-28 for controlled regeneration system.
This patent application is currently assigned to HONEYWELL INTERNATIONAL INC.. Invention is credited to Soumitri N. Kolavennu, Syed M. Shahed.
Application Number | 20070144149 11/306438 |
Document ID | / |
Family ID | 38109548 |
Filed Date | 2007-06-28 |
United States Patent
Application |
20070144149 |
Kind Code |
A1 |
Kolavennu; Soumitri N. ; et
al. |
June 28, 2007 |
CONTROLLED REGENERATION SYSTEM
Abstract
A system for controlled regeneration of a lean NO.sub.x trap for
an internal combustion engine. The system may include regenerating
one trap or a portion of a lean NO.sub.x trap while using another
trap or portion of the lean NO.sub.x trap for an exhaust, and then
interchanging operations. The portions may be individual structures
or of one structure. The trap may be a rotating element that is
regenerated in part at a time. There may be valves that direct the
exhaust gas through one trap and regeneration gas through another
trap and vice versa. Also, an exhaust system with regeneration may
include temperature, pressure, NO.sub.x and differential pressure
sensors. A processor may be connected to the sensors. There may be
emission sampling lines connected to different parts of the system
and to a collector to take, store, detect and analyze samples. A
processor may be connected to the collector.
Inventors: |
Kolavennu; Soumitri N.;
(Minneapolis, MN) ; Shahed; Syed M.; (Rancho Palos
Verdes, CA) |
Correspondence
Address: |
HONEYWELL INTERNATIONAL INC.
101 COLUMBIA ROAD
P O BOX 2245
MORRISTOWN
NJ
07962-2245
US
|
Assignee: |
HONEYWELL INTERNATIONAL
INC.
101 Columbia Road
Morristown
NJ
|
Family ID: |
38109548 |
Appl. No.: |
11/306438 |
Filed: |
December 28, 2005 |
Current U.S.
Class: |
60/286 ; 60/295;
60/297; 60/301 |
Current CPC
Class: |
F01N 3/0878 20130101;
F01N 3/0842 20130101; F01N 2240/14 20130101; F01N 13/011 20140603;
F01N 2560/14 20130101; Y02T 10/40 20130101; F01N 2560/06 20130101;
F01N 2410/12 20130101; F01N 3/0814 20130101; F01N 3/106 20130101;
F01N 2570/14 20130101; F01N 3/0821 20130101; F01N 2560/08 20130101;
F01N 2290/06 20130101; F01N 2560/026 20130101; Y02T 10/12 20130101;
F01N 3/0871 20130101; F01N 2250/12 20130101; F01N 11/002 20130101;
Y02A 50/20 20180101 |
Class at
Publication: |
060/286 ;
060/297; 060/301; 060/295 |
International
Class: |
F01N 3/00 20060101
F01N003/00; F01N 3/10 20060101 F01N003/10 |
Claims
1. A regenerative system comprising: a catalytic converter having
an input and an output; a first valve connected to the output of
the catalytic converter; a first trap having an input connected to
a first output of the first valve; and a second trap having an
input connected to a second output of the first valve; a second
valve having an input connected to an output of the first trap; and
a third valve having an input connected to an output of the second
trap.
2. The system of claim 1, further comprising a multiple way
catalytic converter having a first input connected to an output of
the second valve and connected to an output of the third valve.
3. The system of claim 2, wherein the first and second traps are
first and second NO.sub.x traps, respectively.
4. The system of claim 3, further comprising: a burner having an
output; a fourth valve having an input connected to the output of
the burner, having a first output connected to the input of the
first NO.sub.x trap, and having a second output connected to the
input of the second NO.sub.x trap.
5. The system of claim 4, wherein each of the first, second, third
and fourth valves has an actuator.
6. The system of claim 5, further comprising a processor connected
to the actuators of the first, second, third and fourth valves.
7. The system of claim 6 wherein: each of the first, second, third
and fourth valves has at least a first position and a second
position; the first position provides for a flow of exhaust gas
from the catalytic converter to the first NO.sub.x trap, and a flow
of a regenerative gas to the second NO.sub.x trap; and the second
position provides for a flow of exhaust gas from the catalytic
converter to the second NO.sub.x trap, and a flow of a regenerative
gas to the first NO.sub.x trap.
8. The system of claim 7, wherein the first and second NO.sub.x
traps are lean NO.sub.x traps.
9. An instrumentation-equipped exhaust system comprising: a
pre-catalyst device having an output; a dual trap having an input
connected to the output of the pre-catalyst device, and having
outputs; a filter having an input connected to the outputs of the
dual trap.
10. The system of claim 9, wherein: the pre-catalyst device is an
oxidation catalyst device; the dual trap comprises NO.sub.x
adsorber catalyst devices; and the filter is a catalytic
particulate filter.
11. The system of claim 9, wherein: the pre-catalyst is for
altering a temperature of an exhaust gas; the dual trap is for
adsorbing NO.sub.x; and the filter is for trapping particulates
from the exhaust gas.
12. The system of claim 11, wherein while one trap of the dual trap
is trapping NO.sub.x, another trap of the dual trap is being
regenerated.
13. The system of claim 12, further comprising: a first temperature
sensor situated at an input of the pre-catalyst; and a second
temperature sensor situated at the output of the pre-catalyst.
14. The system of claim 13, further comprising a processor
connected to the first and second temperature sensors.
15. The system of claim 14, further comprising a third and fourth
temperature sensors situated between the outputs of the dual trap
and the input of the filter.
16. The system of claim 15, further comprising a fifth temperature
sensor situated at an output of the filter.
17. The system of claim 12, further comprising: a first pressure
sensor at the input of the pre-catalyst device; and a second
pressure sensor between the output of the pre-catalyst device and
the input of the dual trap.
18. The system of claim 17, further comprising: third and fourth
pressure sensors between the outputs of the dual trap and the input
of the filter; and a fifth pressure sensor at the output of the
filter.
19. The system of claim 17, further comprising differential
pressure sensors situated at the input and the output of the
filter.
20. The system of claim 17, further comprising: a first NO.sub.x
sensor situated at the output of the pre-catalyst device; and a
second and third NO.sub.x sensors situated at the outputs,
respectively, of the dual trap.
21. The system of claim 9, further comprising: a collector; a first
sampling line connected to the collector and between the output of
the pre-catalyst device and the input of the dual trap; and a
second sampling line connected to the collector and the input of
the filter.
22. The system of claim 21, further comprising a third sampling
line connected to the collector and the output of the filter.
23. The system of claim 22, further comprising a fourth sampling
line connected to the collector and the input of the pre-catalyst
device.
24. An emissions trap assembly comprising: a rotatable emissions
trap having a first end and a second end; a first section attached
to the first end of the rotatable emissions trap; and a second
section attached to the second end of the rotatable emissions
trap.
25. The assembly of claim 24, wherein: a first portion of the first
section is a catalyst device; a second portion of the first section
is a burner; a first portion of the second section is an emissions
trap; and a second portion of the second section is a multiple way
catalyst.
26. The assembly of claim 25, wherein: an exhaust gas may flow
through the first portion of the first section, at least a portion
of the rotatable emissions trap and the first portion of the second
section; and a regenerative gas may flow from the second portion of
the first section, through at least a portion of the rotatable
emissions trap and through the second portion of the second
section.
Description
BACKGROUND
[0001] The invention pertains to engine exhaust systems and
particularly to pollutant control from exhaust systems. More
particularly, the invention pertains to regeneration of pollutant
reduction systems of exhaust systems.
SUMMARY
[0002] The invention provides controlled regeneration of a lean
NO.sub.x trap for an engine exhaust system.
BRIEF DESCRIPTION OF THE DRAWING
[0003] FIGS. 1a and 1b show a dual trap catalytic system;
[0004] FIG. 2 is a diagram of a lean NO.sub.x regenerative system
with instrumentation;
[0005] FIG. 3 is a graph of injection rate control;
[0006] FIG. 4 is a graph showing management of exhaust
temperature;
[0007] FIG. 5 is a graph showing an example of a deterioration rate
of a catalyst;
[0008] FIG. 6a is a diagram of a chemical process for trapping;
[0009] FIG. 6b is a diagram of a regeneration using a rich, high
temperature fuel mixture;
[0010] FIG. 7a shows a device that may be placed in an exhaust
stream of a system;
[0011] FIG. 7b shows a regeneration storage device which may be
moved to a side stream with a low flow rate, high temperature and
low oxygen; and
[0012] FIGS. 8, 9 and 10 reveal various continuously rotating lean
NO.sub.x trap assemblies having an absorption element.
DESCRIPTION
[0013] Diesel engines and lean burn gasoline engines may offer
thirty to fifty percent and ten to fifteen percent fuel economy
benefit respectively compared to conventional gasoline engines in
automobiles. However, a lean NO.sub.x trap (LNT) system may be
needed to reduce NO.sub.x emissions. A conventional, full flow lean
NO.sub.x trap system representing the state of the art may reduce
NO.sub.x but has several disadvantages, which include a high fuel
penalty because the temperature of the full exhaust stream needs to
be raised periodically; the catalyst loading is tied to NO.sub.x
storage capacity; high desulfation temperatures of the LNT may
affect the durability to the catalyst; and the efficiency is
affected because NO.sub.x from downstream material has less chance
to encounter a catalyst. A controlled regeneration lean NO.sub.x
trap system may overcome these problems.
[0014] The present system may solve such problems by implementing
several principles. They are to separate the catalysis and NO.sub.x
storage functions, and to conduct regeneration of storage medium
using a separate, controlled stream of gases. There may be many
physical implementations of these principles.
[0015] Under "normal" operating conditions, an exhaust may flow
over an oxidation catalyst which oxidizes NO to NO.sub.2 and then
over an absorption system consisting of adsorption material such as
Ca or BaCO.sub.3. When the adsorption system is "saturated" and the
adsorption efficiency falls, flow may be diverted to a much smaller
adsorption canister. NO.sub.x sensor signals together with
appropriate computation may be used to trigger the diversion. While
the main engine exhaust flows through the smaller system, the
primary system may be regenerated using a flow stream of controlled
temperature, oxygen and CO/HC concentration. When the primary
system is regenerated to a pre-set level, the flow may be restored
to normal conditions and the smaller system may be regenerated. The
ratio of storage to regeneration times may determine the size ratio
of the two systems. Alternatively, a rotating adsorption element
may be used. Adsorption and regeneration functions may be carried
on continuously as the element rotates and maintain adsorption
efficiency. Desorbed NO.sub.2 may be reduced to N.sub.2 in a
downstream three way catalyst.
[0016] FIG. 1a shows a catalytic system 80 having a dual trap 30.
Dual trap 30 may include a primary lean NO.sub.x trap (P-LNT) 82
and a secondary lean NO.sub.x trap (S-LNT) 83. An exhaust pipe 78
may connect a catalytic converter 81 (O.sub.xC) to an exhaust
manifold of an engine 11 (FIG. 2). An exhaust 79 may enter the
catalytic converter 81 (O.sub.xC) having an oxidation catalyst for
converting NO to NO.sub.2. The catalyst material may be a precious
metal such as Pt or a comparable material. The exhaust 79 may go
from converter 81 to the primary lean NO.sub.x trap (P-LNT) 82
which may be sized for NO.sub.x storage capacity. The base material
of trap 82 may contain or may be a metal such as barium or calcium.
Alternatively, the exhaust 79 may go from converter 81 to the
secondary lean NO.sub.x trap (S-LNT) 83, which may be sized for a
short duration while the primary trap 82 is being regenerated. A
two-way valve 91 may direct exhaust gas 79 in one of two
directions, that is, to the primary trap 82 or to the secondary
trap 83, depending on whether the primary lean NO.sub.x trap 82 is
being generated or not. A burner (B) 84 may be used for generating
a low flow rate of gas 95 at a high temperature and a zero oxygen
for regeneration of the lean NO.sub.x trap 82 or 83. Burner 84 may
heat an exhaust gas or provide another heated gas for regeneration.
One trap may be regenerated while the other is functioning as a
trap. An output of a trap 82 or 83 may proceed through a three way
catalytic (TWC) device 85 having a precious metal catalyst such as
Pt or the like.
[0017] A two-way valve 92 may direct the low flow rate of gas 95
for regeneration to trap 82 or trap 83. A two-way valve 93 may
direct an output of trap 82 to an exhaust pipe 96 if it is an
exhaust gas 79 or to the TWC device 85 if it is a regenerative gas
95. A two-way valve 94 may direct an output of trap 83 to an
exhaust pipe 96 if it is an exhaust gas 79 or to the TWC device 85
if it is a regenerative gas 95. Valves 91-94 may be in one of two
positions, A and B, or in one of more than two positions (i.e., a
valve having a variable opening and closure). If the valves 91-94
are moved toward the A position, the P-LNT device 82 may be used as
an exhaust trap and the S-LNT device 83 may be in regeneration. If
the valves 91-94 are moved toward the B position, the P-LNT device
82 may be in regeneration and the S-LNT device 83 may be used as an
exhaust trap. The valves 91-94 may have actuators connected to a
processor 90, as shown in FIG. 1b, (and/or an ECU (engine control
unit)) which determines when the valves 91-94 should be in position
A or B, or in between, and when burner 84 should be functioning.
Such actuation may be determined according to the regenerative need
of devices 82 and 83, and possibly other factors.
[0018] The dual trap system 80 of FIGS. 1a and 1b may have
instrumentation at various places of the system as shown in FIG.
1b. There may be temperature sensors 131 and 132 at the input and
output, respectively, of converter 81. There may be pressure
sensors 141 and 142 at the input and output, respectively, of
converter 81. There may be sampling lines 161 and 162 at the input
and output, respectively, of converter 81. There may be an NO.sub.X
sensor 152 at the output of converter 81. There may be a
temperature sensor 133, a pressure sensor 143, an NO.sub.x sensor
153 and a sampling line 163 at the output of P-LNT 82. There may be
a temperature sensor 134, a pressure sensor 144, an NO.sub.x sensor
154 and a sampling line 164 at the output of S-LNT 83. There may be
similar sensors immediately positioned at the inputs of P-LNT and
S-LNT; however, the sensors 132, 142, 152 and 162 at the output of
converter 81 may be sufficient in lieu of the LNT input
sensors.
[0019] There may a temperature sensor 135, pressure sensor 145 and
sampling line 165 at the output of TWC 85 or a filter 85. If a
filter 85 is in place for regular exhaust 79 to go through it, then
valves 93 and 94 may be appropriately switched to effect a flow of
gas 79 through the filter. Filter 85 may be regenerated, for
instance, with a sufficiently hot gas (95 or 79). The filter 85
may, for example, be a particulate matter filter.
[0020] There may be a differential pressure sensor pair 146 and 147
at the input and output, respectively, of TWC or filter 85. There
may also be a temperature sensor 138 and a pressure sensor 148 at
the output of burner 84. The sensors may be connected to the
processor 90. The sensors and sampling lines may be upstream or
downstream of the respective proximate valves. The sampling lines
may be connected to a collection and detection apparatus which may
be a part of processor 90. The connections of the sensors and
sampling lines to the processor 90 are not shown in FIG. 1b. There
may be additional sensors and sampling lines situated in system 80.
Other kinds of sensors may be placed in system 80.
[0021] FIG. 2 shows an example of instrumentation-equipped exhaust
catalyst system 10. For many engines, such as diesel engines, the
most significant pollutants to control may be particulate matter
(PM), oxides of nitrogen (NO.sub.x), and sulfur (SO.sub.x). An
engine 11 may output an exhaust 12 to a pre-catalyst device 13 via
a manifold 97 and an exhaust pipe 14. The pre-catalyst device 13
may be primarily an oxidation catalyst. The pre-catalyst 13 may be
used to raise the temperature of the exhaust 12 for a fast warm-up
and to improve the effectiveness of a catalytic system downstream
when the engine exhaust temperatures are too low. The exhaust 12
may proceed on to an underbody NO.sub.x adsorber catalyst (NAC)
device 15 via an exhaust pipe 16.
[0022] The NAC may be primarily for adsorbing and storing NO.sub.x
in the form of nitrates. For instance, a diesel exhaust may tend to
have excess oxygen. Therefore, NO.sub.x might not be directly
reducible to N.sub.2. The NO.sub.x may be stored for a short period
of time (for about a 60 second capacity). A very short period
(i.e., about 2 to 5 seconds) of a very rich fuel air mixture
operation may be conducted to get the exhaust stream down to a near
zero oxygen concentration. The temperature may also be raised to a
desirable window. Under these conditions, NO.sub.x may react with
CO and HC in the exhaust to yield N.sub.2, CO.sub.2 and H.sub.2O. A
base and precious metal catalyst may be used.
[0023] The exhaust 12 may go from an NAC 15 to a catalytic diesel
particulate filter 17 via an exhaust pipe 18. This filter may
provide physical filtration of the exhaust 12 to trap particulates.
It may be composed of a precious metal. Whenever the temperature
window is appropriate, then oxidation of the trapped particulate
matter may take place. The exhaust 12 may exit the system 10 via an
exhaust pipe 19.
[0024] In addition to the 60/2-5 second lean/rich swing for
NO.sub.x adsorption/desorption reduction, there may be other
"forced" events. They include desulfurization and PM burn-off. The
NO.sub.x adsorption sites may get saturated with SO.sub.x. So,
periodically, the SO.sub.x should be driven off which may require a
much higher temperature than needed for NO.sub.x desorption. As to
PM burn-off, there may be a forced burn-off if driving conditions
(such as long periods of low speed or urban operation) result in
excessive PM accumulation. The accumulation period may be several
hours depending on the duty cycle of operation. The clean up may be
several minutes (about 10). Higher temperatures and a reasonable
oxygen level may be required.
[0025] It may be seen that the catalytic system 10 may involve a
complex chemical reaction process. This process may utilize
monitoring of flows, temperatures, pressures, and pollutants by
sensors connected to a processor or computer 20. The sensors may be
situated at various places in the catalytic exhaust system 10, and
be used to detect the capacity saturation point, the need to raise
the exhaust temperature, the end of the clean up, and the
restoration of normal operation.
[0026] A temperature sensor 21 and pressure sensor 22 may be
situated in exhaust pipe 14 and be connected to a computer or
processor 20. Situated in exhaust pipe 16 may be a temperature
sensor 23 and a pressure sensor 24 connected to processor 20. In
exhaust pipe 18 may be a temperature sensor 25 and a pressure
sensor 26. A temperature sensor 27 and pressure sensor 28 may be
situated in the exhaust pipe 19. A differential pressure sensor 29
may be connected to exhaust pipe 18 and exhaust pipe 19 to detect
the pressure difference between exhaust pipes 18 and 19. This
difference determination may be transmitted to the processor 20. An
NO.sub.x sensor 31 may be situated in the exhaust pipe 16 and
connected to processor 20. In exhaust pipe 18 may be an NO.sub.x
sensor 32 which may be connected to processor 20. Processor 20 may
be connected to an engine control unit (ECU) 65 at engine 11.
[0027] There also may be several emission sampling lines 41, 42, 43
and 44 from exhaust pipes 14, 16, 18 and 19, respectively, to a
collector 45 of samples for testing and evaluation. Collector 45
may be connected to processor 20. There may be additional sensors
46, 47, 48 and 49 in exhaust pipes or lines 14, 16, 18 and 19,
respectively, for testing of various parameters as desired or
needed of the exhaust system 10. The collector 45 may be connected
to processor 20.
[0028] Fuel injection systems may be designed to provide injection
events, such as the pre-event 51, pilot event 52, main event 53,
after event 54 and post event 55, in that order of time, as shown
in the graph of injection rate control in FIG. 3, which shows
injected fuel versus crankshaft position. After-injection and
post-injection events 54 and 55 do not contribute to the power
developed by the engine, and may be used judiciously to simply heat
the exhaust and use up excess oxygen. The pre-catalyst may be a
significant part of the present process because all of the
combustion does not take place in the cylinder. FIG. 4 is a graph
65 showing management of exhaust temperature. Line 56 is a graphing
of percent of total torque versus percent of engine speed. The
upper right time line shows a main injection event 57 near top dead
center (TDC) and a post injection event 58 somewhat between TDC and
bottom dead center (BDC). This time line corresponds to a normal
combustion plus the post injection area above line 56 in the graph
65. The lower right time line shows the main injection event 57
near TDC and a first post injection event 59 just right after main
event 57, respectively, plus a second post injection event 58. This
time line corresponds to a normal combustion plus two times the
post injection area below line 56 in the graph 65.
[0029] In some cases, when the temperature during expansion is very
low (as under light load conditions), the post injection fuel may
go out as raw fuel and become difficult to manage using the
pre-catalyst 13. Under such conditions, two post injections 59 and
58 may be used--one to raise temperatures early in the expansion
stroke and the second to raise it further for use in downstream
catalyst processes. There could be an impact on the fuel economy of
the engine.
[0030] One aspect of the present system may be based on information
from process control 20. Normally in a catalytic flow system, the
effectiveness of a catalyst may be reduced exponentially in the
direction of flow along the length of the catalyst as shown in FIG.
5. FIG. 5 is a graph 66 showing an example of a deterioration rate
of a catalyst. The graph shows a percent of absorption sites used
up versus the percent of the total length of the catalyst device.
Curves 61, 62, 63 and 64 are plots of sites used versus catalyst
length for different time periods with increasing time as shown by
line 70 in the graph.
[0031] The catalytic and storage operations may be different.
Downstream desorption may see less catalyst and thus have low
NO.sub.x conversion efficiency. If the lean NO.sub.x trap (LNT) and
the catalyst are separated in a conventional full-flow system, the
catalyst may be needed upstream for oxidation and downstream for
reduction. The catalyst (Pt) and storage material
(Ba.sub.2CO.sub.3) may be mixed in conventional, full flow LNT
systems. There may be issues about "mixed" full flow systems, which
include raising the temperature of the full exhaust system, tying
storage capacity to the high cost Pt, and high desulfication
temperatures causing catalyst deterioration.
[0032] FIG. 6a is a diagram of a chemical process for trapping
(lean fuel mixture). NO and O.sub.2 may join in with NO.sub.2 of
the Pt catalyst 67 which may result in NO.sub.3 going to the trap
68. FIG. 6b is a diagram of a regeneration using a rich, high
temperature fuel mixture. There may be fuel that is added to the
collected NO.sub.3 in a trap 69. A fuel from a rich exhaust may be
added to the NO.sub.3 thereby resulting in a combination going from
the trap 69 towards the Pt catalyst 71. In the case of the latter
action, the hot NO.sub.3 expunged from the trap may go to the
catalyst 71. Here, the NO.sub.3 may shed N.sub.2 and take on CO to
form NO in the catalyst.
[0033] The catalytic and storage processes and materials may be
separated. Multiple physical configurations are possible. FIG. 7a
shows a device 72 that may be placed in the exhaust stream of a
system. Device 72 may operate as a trap in normal lean operation
and correspond to a process of FIG. 6a. The Pt in a catalyst
section 73 may be sized for NO--NO.sub.2 conversion efficiency at a
full exhaust flow rate. The material in section 73 may be some
other comparable material. The trapping material Ba.sub.2CO.sub.3
in the trapping section 74 may be sized for an optimum storage
capacity/efficiency/space trade-off. FIG. 7b shows a regeneration
storage device which may be moved to a side stream with a low flow
rate, high temperature and low oxygen. A section 76 may contain
trapping material Ba.sub.2NO.sub.3. The NO.sub.3 from the
regenerated trap section 76 may go to a catalyst section 77 for
conversion to NO. The amount of Pt needed in section 77 may be
small because of a low flow rate. The catalyst material may be a
comparable material in place of Pt.
[0034] FIG. 8 reveals a continuously rotating lean NO trap (LNT) of
an assembly 40 having an absorption NO.sub.x element 109 in a
section 101. Section 102 may have an oxidation catalyst (O.sub.xC)
104 and a burner (B) 105. The burner 105 may provide a controlled
stream of hot, zero oxygen, controlled CO/HC concentration gases,
i.e., regeneration gases. End view 106 reveals the sectors of
O.sub.xC 104 and B 105. A section 103 has a sector of three way
catalyst (TWC) 108 using flow from the burner 105, as shown by end
view 107, going through a portion of the trap element for
regeneration of that portion, to the TWC 108. The trap 109 may
rotate so that all portions of it may eventually be
regenerated.
[0035] FIG. 9 shows a continuously rotating lean NO.sub.x trap
(LNT) assembly 50 having an adsorption element 114 in section 111.
Section 112 may have a sector which is a burner (B) 115 and an
oxidation catalyst (O.sub.xC) 116, as shown by end view 117.
Section 113 may have a sector which is a three way catalyst (TWC)
119 and a sector of the absorption element 114, as shown by end
view 118. The burner 115 may provide a controlled stream of hot,
zero oxygen, controlled CO/HC concentration gases. A balance
between the regeneration and rotation may maintain the required
adsorption efficiency of the main lean NO.sub.x trap 50.
[0036] FIG. 10 shows a continuously rotating lean NO.sub.x trap
(LNT) 127 assembly 60 having sections 121, 122 and 123. End view
124 of section 122 shows a sector of a burner (B) 126 and a
remaining sector 127 of the adsorption trap. End view 125 of
section 123 shows a sector of a three way catalyst (TWC) 128 and a
remaining sector 127 of the adsorption trap.
[0037] In the present specification, some of the matter may be of a
hypothetical or prophetic nature although stated in another manner
or tense.
[0038] Although the invention has been described with respect to at
least one illustrative example, many variations and modifications
will become apparent to those skilled in the art upon reading the
present specification. It is therefore the intention that the
appended claims be interpreted as broadly as possible in view of
the prior art to include all such variations and modifications.
* * * * *