U.S. patent number 3,656,915 [Application Number 05/033,359] was granted by the patent office on 1972-04-18 for catalytic exhaust gas treatment apparatus.
This patent grant is currently assigned to Chemical Construction Corporation. Invention is credited to John F. Tourtellotte.
United States Patent |
3,656,915 |
Tourtellotte |
April 18, 1972 |
CATALYTIC EXHAUST GAS TREATMENT APPARATUS
Abstract
An apparatus for catalytically treating the exhaust gas from
internal combustion engines in two stages, with the first catalyst
stage reducing nitrogen oxides, and the second stage oxidizing
hydrocarbons and carbon monoxide. Preheated air is injected into
the exhaust gas stream between the stages, and the final hot fully
reacted exhaust gas serves to preheat the air. The entire apparatus
is disposed in a single container having flat inclined catalyst
beds and a central co-axial heat exchange section.
Inventors: |
Tourtellotte; John F.
(Westfield, NJ) |
Assignee: |
Chemical Construction
Corporation (New York, NY)
|
Family
ID: |
21869960 |
Appl.
No.: |
05/033,359 |
Filed: |
April 30, 1970 |
Current U.S.
Class: |
422/171; 60/308;
423/213.2; 60/298; 60/301; 422/172; 423/213.7 |
Current CPC
Class: |
F01N
3/34 (20130101); B01J 8/048 (20130101); F01N
3/2846 (20130101); F01N 3/2882 (20130101); F01N
3/2889 (20130101); F01N 3/32 (20130101); F01N
2510/06 (20130101); F01N 2370/04 (20130101); Y02T
10/20 (20130101); F01N 2330/08 (20130101); Y02T
10/12 (20130101); F01N 2240/02 (20130101) |
Current International
Class: |
B01J
8/04 (20060101); F01N 3/28 (20060101); F01N
3/32 (20060101); F01N 3/34 (20060101); F01N
3/30 (20060101); B01j 009/04 () |
Field of
Search: |
;23/288F,2E
;60/3R,31 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Wolk; Morris O.
Assistant Examiner: Richman; Barry S.
Claims
I claim:
1. An apparatus for catalytically treating the exhaust gas from an
internal combustion engine which comprises a container, a first
inclined catalyst bed disposed in said container, means to pass an
exhaust gas stream from an internal combustion engine into said
container, whereby said exhaust gas stream flows through said first
catalyst bed and at least a portion of the nitrogen oxides in said
exhaust gas stream are catalytically reduced, means within said
container to pass a preheated air stream into the exhaust gas
stream discharged from said first catalyst bed, means to pass the
resulting exhaust gas-air mixture through a second inclined
catalyst bed disposed in said container, whereby said exhaust gas
stream containing injected air flows through said second catalyst
bed and at least a portion of the hydrocarbons and carbon monoxide
in said exhaust gas stream are catalytically oxidized and a final
hot exhaust gas stream substantially free of noxious components is
discharged from said second catalyst bed, means within said
container to pass said final hot exhaust gas stream in indirect
heat exchange with an air stream, whereby said air stream is heated
to form said preheated air stream, and means to remove the
resulting cooled final exhaust gas stream from said container.
2. The apparatus of claim 1, in which said container is
horizontally oriented and provided with substantially vertical
front and rear end walls, said exhaust gas is passed through the
front end wall of said container adjacent to said first bed, said
first catalyst bed is disposed above and spaced from said second
catalyst bed, said means to pass a preheated air stream into the
exhaust gas stream discharged from said first catalyst bed within
said container is disposed adjacent to said rear end wall of said
container, and said means to pass said final hot exhaust gas stream
in indirect heat exchange with an air stream within said container
is disposed between said first catalyst bed and said second
catalyst bed.
3. The apparatus of claim 2, in which said first catalyst bed and
said second catalyst bed are inclined and slope upwards from said
front end wall to said rear end wall.
4. The apparatus of claim 3, in which said first catalyst bed and
said second catalyst bed are inclined at an angle in the range of
2.degree. to 45.degree. from the horizontal.
5. An apparatus for catalytically treating the exhaust gas from an
internal combustion engine which comprises a horizontally oriented
container, an upper exhaust gas inlet at one end of said container,
means to pass an exhaust gas stream from an internal combustion
engine to said exhaust gas inlet, whereby said exhaust gas stream
flows into the top portion of said container, a first flat inclined
catalyst bed disposed in the upper section of said container, said
first catalyst bed being inclined at an angle in the range of
2.degree. to 45.degree. from the horizontal and extending upwards
from below said exhaust gas inlet at said one end of said container
to the opposite other end of said container, whereby said exhaust
gas stream flows downwards through said first catalyst bed and at
least a portion of the nitrogen oxides in said exhaust gas stream
are catalytically reduced, a substantially horizontal partition
disposed in said container below said first catalyst bed, said
partition extending from one fluid-impervious terminus contiguous
with said one end of said container to another terminus spaced from
and adjacent to said other end of said container, whereby said
exhaust gas stream flowing downwards from said first catalyst bed
is diverted horizontally towards said other end of said container
by said partition and flows downwards between said other terminus
of said partition and said other end of said container, means to
inject a preheated air stream into said downflowing exhaust gas
stream adjacent to said other terminus of said partition, a second
flat inclined catalyst bed disposed in the lower section of said
container below said partition, said second catalyst bed being
inclined at an angle in the range of 2.degree. to 45.degree. from
the horizontal and extending upwards from the lower portion of said
one end of said container to a terminus adjacent to said other
terminus of said partition, whereby said exhaust gas stream
containing injected air flows upwards through said second catalyst
bed and at least a portion of the hydrocarbons and carbon monoxide
in said exhaust gas stream are catalytically oxidized and a hot
exhaust gas stream substantially free of noxious components is
formed above said second catalyst bed at said one end of said
container, means to pass said hot fully reacted exhaust gas stream
coaxially from said one end of said container, and between said
first catalyst bed and said second catalyst bed, through said
container to an exhaust gas outlet at said other end of said
container, and means to pass air from said one end of said
container through said container between said first catalyst bed
and said second catalyst bed and in indirect heat exchange with
said hot fully reacted exhaust gas stream, whereby said air is
heated by said hot exhaust gas stream and is discharged into said
exhaust gas stream between said first catalyst bed and said second
catalyst bed as said preheated air stream.
6. The apparatus of claim 5, in which said container is
substantially elliptical in vertical cross-section, said elliptical
cross-section having a vertical axis which is longer than the
horizontal axis.
7. The apparatus of claim 5, in which said container is rectangular
in vertical cross-section, said partition is an upper partition
which defines the upper side of a central rectangular passage for
flow of said hot fully reacted exhaust gas stream between said
first catalyst bed and said second catalyst bed, a second
horizontal partition is spaced below said upper partition to define
the lower side of said central rectangular passage for flow of said
hot fully reacted exhaust gas stream, and said air is preheated by
passing air through at least one pipe disposed within said central
rectangular passage, said pipe discharging preheated air into the
partially reacted exhaust gas stream discharged from said first
catalyst bed adjacent to said other end of said container.
8. The apparatus of claim 5, in which said first bed and said
second bed are inclined at substantially the same angle to the
horizontal and are substantially parallel.
9. The apparatus of claim 5, in which said hot fully reacted
exhaust gas stream flows centrally and axially through said
container from said one end of said container to discharge at said
other end of said container through a first central substantially
horizontal duct, said first duct being coaxial with said container
and disposed between said first catalyst bed and said second
catalyst bed, and said air is preheated by providing a second outer
duct concentrically disposed external to said first duct, and
providing means to pass said air through the annular passage
defined between said first duct and said second duct.
10. The apparatus of claim 9, in which said means to pass air into
the annular passage defined between said first duct and said second
duct is substantially tangential to said annular passage, and the
resulting preheated air is tangentially removed from said annular
passage by said means to inject a preheated air stream into said
exhaust gas stream, whereby said air is preheated while flowing in
a spiral flow path through said annular passage.
11. The apparatus of claim 5, in which said first catalyst bed and
said second catalyst bed are composed of the same active catalytic
agent, deposited on a suitable carrier.
12. The apparatus of claim 11, in which said active catalytic agent
is selected from the group consisting of zinc, nickel, platinum,
copper, manganese, vanadium, cobalt, chromium, iron, catalytically
promoted mixtures thereof, and catalytically promoted oxides
thereof, deposited on a suitable carrier.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to the elimination of deleterious components
present in the exhaust gas from internal combustion engines such as
diesel engines or gasoline-burning automobile engines, so as to
prevent the discharge of these noxious components such as nitrogen
oxides, unburned hydrocarbon vapors and carbon monoxide into the
atmosphere, and thereby prevent air pollution.
Description of the Prior Art
In recent years it has been recognized that the exhaust gas
discharged from internal combustion engines is a serious source of
air pollution, especially in metropolitan areas. In some areas a
so-called smog is generated due to atmospheric inversions and
accumulation of such exhaust gases in the atmosphere. Recent
attempts to prevent such air pollution have concentrated on the
destruction or elimination of noxious components by catalysis,
especially by admixture of secondary air into the exhaust gas
followed by catalytic oxidation of residual hydrocarbons, carbon
monoxide, etc., in various types of apparatus specially designed
for this purpose. Improvements in active catalytic agents for this
function are described in U.S. Pat. Nos. 3,053,773; 3,429,656;
3,316,057; 3,398,101; 3,477,893 and 3,476,508 and prior art
apparatus for carrying out the procedure are described in U.S. Pat.
Nos. 3,380,810, 3,325,256; 3,255,123; 3,222,140; 3,186,806;
3,180,712; 3,169,836; 3,168,806, 3,146,073 and 3,086,839.
SUMMARY OF THE INVENTION
In the present invention, a catalytic apparatus for treating
exhaust gas from internal combustion engines is provided, in which
catalysis is effected in two stages within the same unitary
container, which also accommodates for preheating of air which is
then employed as an additive to the exhaust gas between the initial
reduction stage, in which nitrogen oxides are catalytically
reduced, and the second catalytic stage in which residual
hydrocarbons and carbon monoxide are catalytically oxidized to
innocuous components such as carbon dioxide and water vapor. The
apparatus includes inclined upper and lower catalyst beds for first
and second stage reactions, and conventional catalysts may be
employed for each stage, such as those described in the U.S.
patents mentioned supra. Different catalysts may be used for each
stage, but the same catalytic agent is preferably employed in both
catalytic stages, for reasons of economy and simplicity. The flat
inclined catalyst beds are aligned within the same container and
are preferably substantially parallel, and the indirect heat
exchange section, for preheating of reaction air by indirect heat
exchange with hot fully reacted exhaust gas, is disposed centrally
in the container and aligned coaxially with the central axis of the
substantially horizontal container.
The principal advantage of the apparatus of the present invention
is that a unitary apparatus combination is provided which is
readily fabricated and easy to assemble, and which accomplishes in
a single apparatus unit the combined functions of catalytic
reduction, preheating of air, injection of preheated air into the
catalytically reduced exhaust gas, and catalytic oxidation. Another
advantage is that the apparatus has a low overall gas pressure
drop, and thus does not entail the provision of a high initial
exhaust gas pressure or high back pressure. A further advantage is
that the apparatus also has a dampening effect on sounds and
pulsations of exhaust gas from the internal combustion engine, and
thus the apparatus also functions as a muffler.
It is an object of the present invention to provide an improved
apparatus for catalytically treating the exhaust gas from internal
combustion engines.
Another object is to remove the noxious components from engine
exhaust gases by means of an improved apparatus.
An additional object is to prevent air pollution by preventing the
discharge of engine exhaust gases, containing deleterious
components such as nitrogen oxides, carbon monoxide and residual
hydrocarbons, into the atmosphere.
A further object is to provide an improved catalytic apparatus for
removing noxious components from the exhaust gas from internal
combustion engines, using two stage catalysis with interstage
injection of preheated air.
These and other objects and advantages of the present invention
will become evident from the description which follows.
DESCRIPTION OF THE DRAWINGS AND PREFERRED EMBODIMENTS
Referring now to the drawings,
FIG. 1 is a sectional elevation view of one embodiment of the
invention,
FIG. 2 is an elevation view of one end of the FIG. 1 embodiment,
taken on section 2--2 and showing internals,
FIG. 3 is a sectional elevation view of an alternative embodiment
of the invention,
FIG. 4 is an elevation view of one end of the FIG. 3 embodiment,
taken on section 4--4 and showing exhaust gas and air inlet
members,
FIG. 5 shows the two air inlet pipes in plan view, and is taken on
section 5--5 of FIG. 4,
FIG. 6 is a sectional elevation view of the FIG. 3 embodiment,
taken on section 6--6 and showing internals.
Referring now to FIG. 1, hot exhaust gas stream 1 is derived from
an internal combustion engine such as a gasoline-burning automobile
or truck engine or the like. Stream 1 typically contains noxious
components such as nitrogen oxides, residual hydrocarbon vapor, and
carbon monoxide, as well as carbon dioxide and nitrogen. Stream 1
is passed via inlet pipe 2 into the generally horizontally oriented
container defined by one end wall 3, side or top and bottom wall 4
and the other end wall 5. A vertically oriented fluid closure
partition 6 depends from the top wall 4 external to pipe 2, and
directs the exhaust gas stream 1 through enclosure screen 7 and
into the initial catalyst bed 8, in which the selective reduction
of all or most of the nitrogen oxides in the gas stream to
elemental nitrogen takes place. Catalyst bed 8 may typically
consist of any known catalytic agent for the treatment of exhaust
gases, such as those agents, compounds or compositions described in
the U.S. patents cited supra. Bed 8 preferably consists of
elemental metallic zinc, nickel, platinum, copper, manganese,
vanadium, cobalt, chromium or iron, or mixtures thereof, or
mixtures including oxides thereof, which may be suitably promoted
by alkali or alkaline earth metal oxides or carbonates or the like,
such as the oxides or carbonates of sodium, potassium, calcium,
magnesium, etc., and which are preferably deposited on a suitable
carrier such as kaolin, silica, alumina, zeolite or the like. A
catalytic reduction of nitrogen oxides takes place by the reaction
of nitrogen oxides in bed 8 with reducing components in the gas
stream, to yield nitrogen and water vapor and/or carbon dioxide.
Bed 8 is preferably substantially flat and inclined at an angle of
2.degree. to 45.degree. to the horizontal, and extends upwards from
partition 6 to a terminus at end wall 5.
The downflowing hot partially reacted gas stream is discharged
below bed 8 and is now substantially free of nitrogen oxides,
however the gas stream contains other noxious components as
mentioned supra which are destroyed by a high temperature oxidation
reaction. The downflowing gas stream is diverted horizontally and
laterally below bed 8 by the substantially horizontal partition 9,
which extends through the container from a fluid-impervious
connection with the lower end of partition 6. A preheated hot air
stream is discharged into the partially reacted exhaust gas between
wall 5 and the end of partition 9 adjacent to and spaced from the
wall 5, via the flared outlet of transition duct 10. The resulting
hot mixture of exhaust gas and air flows downwards between wall 5
and the gas diversion baffle 11, which depends from the end of the
partition or baffle 9 adjacent to wall 5. The hot gaseous mixture
next flows through catalyst retention screen 12 and upwards through
oxidation catalyst bed 13, which is of known composition to
catalyze the oxidation of hydrocarbon vapor, carbon monoxide etc.
in the exhaust gas to innocuous components such as carbon dioxide
and water vapor, and which may be one of the compositions or
catalysts mentioned supra, such as those described in the U.S.
patents cited supra.
The resulting hot fully reacted exhaust gas stream discharged
upwards from bed 13 is now of a suitable composition substantially
free of noxious components, and may be safely discharged to
atmosphere without causing air pollution. The hot fully reacted gas
is diverted laterally and horizontally towards end wall 3 below
partition 9, and the hot gas next flows into the substantially
horizontal duct 14 which is generally coaxial with the
substantially horizontal container defined by the wall 4 and end
walls 3 and 5. As will appear infra, the hot gas flowing through
duct 14 is cooled by indirect heat exchange with air flowing
external to duct 14 and the cooled fully reacted and innocuous
exhaust gas is discharged from duct 14 via stream 15, which may
pass via a tailpipe to an auxiliary muffler, not shown, or directly
to atmospheric discharge.
The air stream which is preheated in accordance with the present
invention is derived as stream 16 from a suitable blower or the
like, not shown, which may be driven by a pulley rotated by the
fanbelt of the motor or engine. In any case, stream 16 is passed
into the device, via transition pipe or element 17, which passes
the preferably ambient air stream 16 tangentially via a tangential
transition piece into an annular passage defined between duct 14
and outer concentric duct 18, so that the air flows through the
annular passage between ducts 14 and 18 in a spiral flow path. The
spirally flowing air is heated by indirect heat exchange with the
hot fully reacted exhaust gas flowing within duct 14, and the
resulting preheated air is removed from the annular passage between
ducts 14 and 18 via a tangential transition piece or section of
pipe 10, with tangential removal of preheated air via 10 aiding in
maintaining the spiral flow pattern of the air. The heated air is
discharged from the pipe or duct 10 into the partially reacted
exhaust gas, as described supra.
Referring now to FIG. 2, a sectional elevation view of the front
end of the FIG. 1 device is shown, with selected internal elements
being illustrated as seen through front wall 3. FIG. 2 shows the
generally elliptical cross-section of the device via wall element
4, with the vertical axis of elliptical element 4 being longer than
the horizontal axis. Tangential entry of stream 16 via pipe 17 into
the annular passage between ducts 14 and 18 is shown, as well as
tangential removal of preheated air from the tangential passage via
pipe 10. Finally, FIG. 2 shows horizontal partition 9 extending
between outer duct 18 and wall 4. Portions of the catalyst bed 8
and screen 7 have been omitted in FIG. 2, in the interest of
clarity. In this respect, it will be evident from FIG. 2 that
elements 8 and 7 may extend downwards laterally between the upper
half of duct 18 and wall 4 to a lower terminus of partition 9.
Similar considerations apply to the upper rear section of catalyst
bed 13 and screen 12, which may extend to an upper terminus which
is contiguous to partition 9 on each side between the lower half of
duct 18 and wall 4, adjacent to baffle 11.
FIG. 3 shows an alternative and simplified embodiment of the
invention, in which rectangular elements and passages are provided.
Unit 19 is an internal combustion engine or motor such as the motor
of a gasoline-burning automobile, and exhaust gas stream 20 passes
from unit 19 into pipe 21, which extends through front wall 22 and
discharges the exhaust gas into the rectangular device of this
embodiment of the present invention, which is defined by front wall
22, top wall 23, bottom wall 24 and rear wall 25. The exhaust gas
passes downwards through flat inclined inlet screen 26, which
extends upwards between walls 22 and 25 at an angle which is
typically 2.degree. to 45.degree. from the horizontal. Reducing
catalyst bed 27 extends between screen 26 and lower screen 28 which
is preferably substantially parallel with screen 26, and the
nitrogen oxides content of the hot exhaust gas flowing downwards
through bed 27 is catalytically reduced to innocuous components
such as elemental nitrogen and water vapor and/or carbon
dioxide.
The resulting exhaust gas discharged downwards from screen 28 is
diverted laterally and horizontally by the substantially horizontal
partition 29 and towards the rear of the device, where the exhaust
gas flows downwards between the end of partition 29 and wall 25,
and external to discharge pipe 30 and downwards between the
substantially vertical baffle 32 and wall 25. Baffle 32 depends
from the end of partition 29. A preheated air stream is injected
into the downflowing exhaust gas via pipe 31. The resulting
downflowing mixture of hot exhaust gas and preheated air flows
downwards and horizontally below the lower end of baffle 32, and is
diverted upwards by floor or bottom wall 24. The hot gaseous
mixture next flows laterally and upwards through screen 33 and
oxidizing catalyst bed 34, in which noxious components such as
hydrocarbon gases or vapors and carbon monoxide are oxidized to
innocuous components such as water vapor and carbon dioxide. The
resulting hot gaseous mixture flows upwards from catalyst bed 34
through upper retention screen 35. Screens 34 and 35 are preferably
parallel, and may be inclined at a greater angle to the horizontal
than screens 26 and 28, or screens 34 and 35 may in some cases be
substantially parallel to screens 26 and 28. In any case, screens
34 and 35 extend from the lower front end wall 22 upwards and
laterally to the lower end of baffle 32.
The hot gaseous mixture discharged upwards from screen 35 is now
suitable for discharge to the atmosphere, and may be discharged
without causing air pollution, however the hot gaseous mixture is
utilized in accordance with the present invention to preheat
reaction air by indirect heat exchange. The rising hot gaseous
mixture is diverted horizontally below the lower substantially
horizontal partition 36, and flows upwards between the end of
partition 36 and front wall 22. The hot gaseous mixture next flows
horizontally through the passage defined between partitions 36 and
29, and heats the air flowing within pipe 31, which is disposed
between horizontal partitions 36 and 29, so that preheated air is
discharged from pipe 31 as described supra. The somewhat cooled
gaseous mixture is discharged from the passage between partitions
36 and 29 via pipe 30, which discharges the gaseous mixture 37 to
atmosphere or to an auxiliary muffler or tailpipe, not shown.
The preheated air is derived from ambient air stream 38, which is
passed via fan or blower 39 as stream 40 to the main inlet pipe 41,
from which a portion of the air is conducted by shoulder pipe
connection 42 to pipe 31, for preheating and usage as described
supra.
Referring now to FIG. 4, an elevation view of the front end, or
exhaust gas and air inlet end of the device is shown. FIG. 4 shows
top wall 23, bottom wall 24, and side walls 43 and 44 of the
rectangular device of FIG. 3. In addition, FIG. 4 illustrates a
second air preheating pipe or tube 45, which is parallel with pipe
31 and receives air for preheating via central pipe 41 and shoulder
pipe connection 46.
FIG. 5 is a sectional plan view of FIG. 4, taken on section 5--5,
and shows the parallel air preheat pipes 31 and 45 which receive
air stream 40 via pipe 41 and shoulder pipe connections or
transition members 42 and 46, and which discharge hot air into the
partially reacted hot exhaust gas between baffle or partition 32
and the rear wall 25. One or more than two air preheat pipes such
as elements 31 and 45 may be provided in practice. Pipe 30, which
serves to discharge the fully reacted and innocuous exhaust gas
from the device external to rear wall 25, is also shown.
FIG. 6 is a sectional elevation view of a portion of the FIG. 3
device, taken on section 6--6, and shows the arrangement of pipes
31 and 45, central exhaust gas discharge pipe 30, all disposed
between horizontal partitions 29 and 36.
Numerous alternatives within the scope of the present invention,
besides those alternatives mentioned supra, will occur to those
skilled in the art. As mentioned supra, the air blower may be
driven by the fan belt of the motor, thus the fan belt or auxiliary
gearing of motor 19 may drive blower 39. The catalyst beds could be
inclined in the opposite direction, sloping downwards from the
front wall of the device to the rear wall.
An example of testing of a fabricated device according to FIG. 1,
as applied to a commercial gasoline-burning truck engine, will now
be described.
EXAMPLE
The device according to FIG. 1 was fabricated and tested on a
commercial truck engine. The reducing section catalyst area was
0.625 square feet, catalyst volume was 0.156 cubic feet. The
oxidizing section catalyst area was 0.58 square feet, catalyst
volume was 0.144 cubic feet. The catalyst composition was composed
of a reduced mixture of the oxides of nickel, cobalt and manganese
deposited on particles of alpha alumina, with the preliminary
reduction by means of hydrogen serving to reduce a portion of the
oxides to the metallic state. The same catalyst composition was
used in both the reducing and oxidizing catalyst beds. Following
are the test results. ##SPC1##
In the test runs, all surfaces were insulated with 0.5 inches of
insulation.
The inlet exhaust gas contained 1,040 ppm of nitrogen oxides, which
was reduced to less than 75 ppm in the final exhaust gas.
Essentially complete destruction of hydrocarbon vapors and carbon
monoxide was attained in the oxidizing section, and the final
exhaust gas was essentially devoid of these components.
* * * * *