US 3169836 A
Description (OCR text may contain errors)
Feb. 16, 1965 w. M. DAVIS amusr GAS TREATING APPARATUS 2 Sheets-Sheet 1 Filed May 18, 1961 INVENTOR Waizfer M. Dcwz's ATTORNEY:
Feb. 16, 1965 w. M. DAVIS EXHAUST GAS TREATING APPARATUS 2 Sheets-Sheet 2 Filed May 18, 1961 INVENTOR Walter M flavzls' EXHAUST GAS TREATENG APPARATUE Waiter M. Davis, pt. Louis, Mo, assignor to Monsanto Company, a corporation of Delaware Filed May 18, 196i, Ser. No. 11%,932 '12 Qiaims. (fl. 2328$) is that automobile exhaust gases be made nonobnoxious by catalytically oxidizing the combustible constituents therein. Numreous efforts have been made to produce a catalytic oxidizer for the treatment of exhaust gases which could suitably take the place of a conventional automobile muiiier but no completely satisfactory device of this type has yet been produced.
A primary objection to catalytic devices heretofore proposed is that they usually result in operative temperatures above about 1500" F. and such high operating temperatures are very undesirable for a number of reasons. For example, such temperatures require the use of stainless steel or the like in the fabrication of the muffler shell, frequently result in damage to the catalyst, and usually necessitate the use of a heavy thickness of noninfiammable insulation between the mutiier and the passenger compartment of a vehicle upon which it is mounted. In addition, radiation from pipes carrying exhaust gases at such high temperatures underneath the vehicle frequently interfere with the proper operation of solenoids or the like in the vicinity of which they are passed and may interfere with the proper or safe operation of the car if they are passed in the proximity of a brake line carrying hydraulic fluid or a gasoline tank or fuel line.
In addition to being objectionable because of the high operating temperatures involved, catalytic mufliers heretofore proposed have been objectionable in many instances for the further reasons that they could not be satisfactorily manufactured in the shape or size of a conventional automobile mufiler or could not be fabricated by conventional metal working techniques. In other instances, such mufliers' have been objectionable for the reason that the catalyst bed developed thin spots as a result of shrinkage and mechanical vibration so that the mutiler rapidly lost operating efiiciency. In still other instances such mufders have been objectionable for the reason that they resulted in undesirably large engine back pressures, and for numerous other reasons.
It is a primary object of this invention to provide an apparatus for treating a'fiowing stream of gas which can be employed in lieu of a conventional automobile muffler and which when thus employed is largely free of the disadvantages as abo e set forth of catalytic automobile mufilers "heretofore available.
It is another object of the invention to provide apparatus for catalytically oxidizing cornbustile constituents in a gaseous stream which dissipates the heat generated by oxidation predominantly in a selected direction, which can'be fabricated by standard metal working techniques and which results'in operating temperatures insufliciently high to require the use-of-other than soft steel as a material of construction forthe shell of the apparatus.
It isstill anotherobject of this invention to provide a arenas Patented Feb. 16, 11%65 catalytic automobile muffler highly efiicient in operation, which requires only a relatively short time to reach operating temperatures and which results in exhaust noises being mufiled to an excellent degree.
It is a further object of the invention to provide a catalytic element for an automobile muflier which can, if desired, be mounted in a conventional automobile muflier shell.
The above as well as other objects of the invention are accomplished by the provision of apparatus comprising means for retaining two beds of catalyst in spaced relationship, means for directing a stream of gases such as automobile exhaust gases through a first one of the two beds of catalyst and into heat exchange relationship with a heat dissipation member which can be a portion of the external wall of the apparatus, and means for thereafter directing the stream of gas through a second bed of catalyst material. Preferably the two beds of catalyst are in superimposed relationship and the exhaust gases are introduced between the two beds so that the beds of catalyst serve as sound insulation and produce an excellent sound muflling etfect' With this preferred arrangement the exhaust gases can be directed first through the lower bed of catalyst 50- that when the apparatus is mounted on the underside of an automobile or the like the hot gases following their passage through the first bed of catalyst contact the external wall of the apparatus remote from the automobile and a large portion of the heat is dissipated in a downward direction.
One particularly preferred embodiment of the invention will now be described with reference to the accompanying drawings in which:
FIG. 1 is a cross-sectional view, taken in a horizontal plane substantially along the line 1--I of FIG. 2, of apparatus in accordance with this invention suitable for use as an automobile exhaust mufiier.
FIG. 2 is a cross-sectional view of the apparatus of FIG. 1 taken in a vertical plane substantially along the line 22 of FIG. 1.
FIG. 3 is a vertical cross-sectional view taken substantially along the line 33 of FIG. 2 of the drawings.
With reference to the drawings, there is illustrated an elongated, generally cylindroidal container indicated by the reference numeral 10, which comprises end members 12 and 14 and an external wall 16 formed of a thermally conductive material such as a suitable metal. It is an advantage of the invention that container 10 can suitably be formed of soft steel or the like since it is not necessary for the container to reach operating temperatures above about 600 to 800 F. The external wall 15 of container 16 is uninsulated and serves as a heat dissipating member in a-manner to be subsequently described, and to increase its external surface area and its efiiciency in dissipating heat by convection, at least the bottom portion thereof can suitably be undulated as indicated by reference numeral 18 in the drawings. Alternatively, the container it can be a conventional automobile muflier shell.
Disposed within container 10 is a catalytic element, generally indicated by the numeral 29, which is preferably formed of a heat resistant material such as stainless steel. The element 20 comprises a pair of vertically extending imperforate support plates 22 and 24 extending substantially the full length of container 10, and a pair of .gas permeable catalyst retaining plates or screens 26 and 28 extending between the support plates 22 and 24. The plates 22 and 24 are retained in spaced relationship to the inner surface of wall 16 by a plurality of spacing members or tabs 25 which are best seen in FIGS. 2 and 3' of the drawings, and which can be integral parts of the plates 22 and 24. Screens 26 and 28 can be secured to plates 22 and 24 by any suitable means such as by welding, and it is an advantage of the invention that the entire apparatus, except for any catalyst employed, can be fabricated by conventional metal working techniques.
Secured between the screens 26 and 28 and in spaced relationship to the screens and the support plates 22 and 24 is a generally rectangular parallelepiped shaped catalyst positioning member generally indicated by the reference numeral 30, which is coextensive in length but is slightly narrower in width than the screens 26 and 28, and is of less depth than the width of support plates 22 and 24. The member 30 is retained in position by a pair of end plates 32 and 34 which are secured to support plates 22 and 24 and screens'26 and 28.
Catalyst positioning member 30 is formed of two impervious side members 36 and 38 and upper and lower gas permeable plates or screens 4% and 42. An elongated spacer 44 extends between the screens 26 and 40 V to add rigidity and insure that the screens are operatively retained a constant selective distance from each other. A similar spacer 46 extends between screen 28 and screen 42.
With particular reference to FIG. 3 of the drawings, it will be seen that the member 30, in cooperation with support plates 22 and 24 and screens 26 and 28, provides catalyst retaining means for a pair of superimposed catalyst beds 48 and 50 which are illustrated as being filled with particulate catalyst 52. It will be seen that each of catalyst beds 48 and 50 has a relatively large surface area and can be almost as long and as wide as container 10. This results in an advantageously low pressure drop across the muffler and makes possible relatively low exhaust manifold pressures.
Member 30 does not extend on either side to support plates 22 and 24, and this results in the upper catalyst bed 50 being spatially connected to the lower catalyst bed 48 so that the catalyst in the upper bed is induced by gravity to feed into the lower catalyst bed. This insures that the lower catalyst bed is retained in a completely filled condition at all times even though some shrinkage of the catalyst is'incurred as a result of being heated to elevated temperatures or some catalyst is lost as a result of attrition.
In the illustrated embodiment of the invention, a particulate catalyst is advantageous because of the feature described above which enables catalyst from the upper bed to feed into the lower bed. It will be understood, however, that the beds 48 and 50 of particulate catalyst can satisfactorily be replaced with beds of catalyst in any other suitable form. For example, the catalyst beds can in each instance be formed from a plurality of layers of screen wire coated with catalytic material such that a stream of gas can readily pass through the screens, or the catalyst beds can in each instance suitably comprise a molded, gas permeable mass of catalytic material or the like. With such beds of catalyst there is no advantage in the beds being interconnected and they are preferably completely isolated from each other except for being in series gas flow relationship.
Extending through an opening in plate 12 is a funnel shaped member 54. The enlarged end of member 54 corresponds in size and shape to one end of member 30 and extends into a corresponding opening in end plate 32, thus providing means for introducing a stream of exhaust gases into the container 10 and between the catalyst beds 48 and 50. This arrangement produces an excellent mufliing effect since the beds of catalyst serve as sound absorbing layers and reduce the amplitude of the sound which would otherwise be produced by the release of the exhaust gases. shaped member 56, generallysimilar to member 54,
extends through end member 14 and plate 34 and provides a means fordischarging the streamof gases from intermediate the two catalyst beds and out of the end A second funnel of the mufiier remote from that through which the stream of exhaust gases was introduced.
Disposed within member 30 and extending between side members 36 and 38 is a baffle means 58 secured obliquely with respect to the longitudinal axis of container 10. Baflie means 58 abuts at one end against funnel shaped member 54 and at the other against funnel shaped member 56, thereby dividing the interior of member 30 into two chambers each triangular in crosssection. This an exceedingly advantageous arrangement because the permissible thickness of an automobile muffler is limited in most instances to the thickness of the frame of the automobile and the oblique mounting of baffle 58 provides for a smooth flow of the exhaust gases with near minimum space requirements. This arrangement of the baffle 58 also provides a uniformly distributed flow of gases through the catalyst beds.
In operation the container 10 is mounted in any convenient location where it is desired to effect oxidation of combustible constituents in a stream of gases. It
is an advantage of the invention that the container 10 can correspond in size and shape to a conventional muffler and can be mounted on the underside of a vehicle propelled by a gasoline engine the exhaust gases of which are to be treated. When so mounted the muflier should be positioned with the short transverse axis of container 10 disposed in a vertical plane so that catalyst bed 43 is remote from the underside of the vehicle.
The gases to be treated usually contain insuflicient oxygen to' burn the combustible constituents thereof and in such instances air must be supplied to provide the necessary oxygen. In the case of gasoline engine exhaust gases, the provision of additional oxygen is almost always necessary. For the introduction of air there can suitably be employed a pump or an aspirator such as .one utilizing a venturi tube. When used with a gasoline engine the air to be supplied to the exhaust gases is preferably withdrawn from between the air cleaner and the carburetor of the gasoline engine and this is particularly true in instances where a venturi type aspirator is employed; With this arrangement, if the exhaust passageway becomes blocked subsequent to the point where the secondary air is introduced, the exhaust gases are fed through the aspirator air intake into the carburetor thus stalling the engine and preventing possible carbon monoxide poisoning.
When a mixture of exhaust gases and secondary air is introduced interiorly of the container 10 through mem ber 54, the mixture is forced by baffle 58 to flow first through the lower catalyst bed 58 which is always retained in a completely filled condition as previously explained. As will be seen best in FIG. 3, the area available for the exhaust gases to enter into catalyst bed 48 is less than the area available for the gases to exit from the catalyst bed because the surface area of screen or perforate plate 40 is less than the surface area of screen 26 due to the narrower width of the former. Restricting the area of entry in this manner is advantageous for the reason that it results in a more rapid heating of the catalyst disposed adjacent screen 40 so that the bed of catalyst reaches a satisfactory operating temperature in a shorter time than would otherwise be required. The heat insulating eifect of the upper catalyst bed 50 also contributes to bed 48'reaching a satisfactory operating temperature in an advantageously short time.
Catalyst bed 48 can be made relatively thin since it is I not required that all of the combustible constituents be oxidized within this'bed of catalyst. This is a. major'advantage. When a stream of exhaust gases heavily laden with combustible constituents is passed through a catalyst bed of sufficient thickness to result in substantially all of such constituents being oxidized, the catalyst near'the area where the exhaust gases depart from the catalyst bed frequently becomes overheated and is thereby'made inefiective. With a thin primary catalyst bed and'a secondary catalyst bed, as in the apparatus of this invention,
the gases exiting from the primary bed can suitably be at a temperature far below that at which damage to the catalyst or the soft steel elements of the apparatus is encountered.
Upon departing from lower catalyst bed 48 the hot exhaust gases are brought into heat exchange relationship with the lower section of wall 16 which is undulated as at 18. Since wall 16 is uninsulated and is in open contact with the air moving past the vehicle on which the mutller is normally mounted, the undulations in wall 16 act in the manner of cooling fins and transform wall 16 into an excellent heat dissipating means so that the gases departing from catalyst bed 48 are cooled substantially. It will be seen that with this arrangement the hottest portion of wall 16 is normally remote from the vehicle upon which container is mounted and a major portion of the heat dissipated from wall 16 is released in a downward direction so that the need for excessively heavy insulation between the mufiier and the interior of the vehicle is avoided.
The stream of exhaust gases which has been cooled by contact with wall 16 must now flow transversely of the longitudinal axis of the container 10 to the upper portion of the container and then pass downwardly through catalyst bed 50. This is because plates 22, 24, 32 and 34 revent the gases from reaching the discharge outlet except by passage through the upper bed of catalyst material. As the partially cooled gases pass through the upper catalyst bed, further oxidation of combustible constituents is etfected without the temperature of the gases reaching excessively high levels.
Following passage through upper bed 50 the gases are forced by baffie 58 through the funnel shaped member 56 and can then be carried by a conventional tail pipe to a safe place of discharge. It will be noticed that the heat generated by the oxidation eifected in the upper catalyst bed is at least partially prevented from being dissipated on the upper side of the container 10 by the insulating effect of the catalyst bed 50 and the direction of flow of the gas stream.
Having thus described my invention and one specific embodiment thereof, what I desire to claim and secure by Letters Patent is:
1. Apparatus for mounting on the underside of a vehicle and for catalytically oxidizing combustible constituents in the exhaust gases from a gasoline engine carried by said vehicle, said apparatus comprising an elongated container having an uninsulated, heat dissipating external wall formed of a thermally conductive material, a pair of superimposed beds of catalytic material disposed within said container, said beds being in spaced apart relationship with respect to each other, means for introducing a gaseous stream of said exhaust gases interiorly of said container, means for directing said stream of exhaust gases downwardly through the lower one of said pair of catalyst beds and into heat exchange relationship with said heat dissipating wall, and means for thereafter directing said stream of gases interiorly of said container and in contact with said wall to the upper surface of the upper catalyst bed and thereafter through said upper catalyst bed.
2. Apparatus according to claim 1 wherein said catalyst beds comprise a particulate catalyst material.
3. Apparatus according to claim 2 wherein said catalyst beds are interconnected so that particulate catalyst in the upper bed is induced by gravity to feed into the lower catalyst bed whereby said lower bed is retained in a completely filled condition at all times.
4. Apparatus according to claim 1 wherein at least the downwardly facing portion of said heat dissipating wall is provided with external undulations to increase its surface area and the rate at which heat is removed from said wall by convection.
5. Apparatus according to claim 1 wherein the area provided for gases to enter the said lower catalyst bed is less than the area provided for said gases to exit from said lower bed.
6. Apparatus according to claim 1 wherein said ex haust gases are introduced through one end of said con tainer to between said catalyst beds, whereby said beds serve to mufile sound waves carried by said gases.
7. Apparatus according to claim 1 including a baflie plate disposed obliquely with respect to the longitudinal axis of said container and secured intermediate said catalyst beds.
8. A catalytic element suitable for mounting in an automobile mufiler shell, said element comprising catalyst retaining means to retain first and second beds of catalyst material in spaced apart relationship and in spaced relationship to a muffler shell in which said element is mounted, means for operatively introducing a stream of exhaust gases intermediate said two catalyst beds, baffle means to direct said stream of exhaust gases through a selected one of said two catalyst beds, means for discharging said stream of gases from intermediate said two catalyst beds subsequent to the passage of said stream through said other catalyst bed, and means limiting, except by passage through said other catalyst bed, the passage of said stream of exhaust gases to said discharging means.
9. Apparatus for catalytic-ally oxidizing combustible constituents in the exhaust gases from an internal combustion gasoline engine comprising a metallic, generally cylindroidal container for mounting on the underside of a gasoline engine propelled vehicle with its shorter transverse axis in a vertical plane, a pair of vertically extending imperforate support plates disposed Within said container in spaced relationship to the walls thereof, upper and lower gas permeable catalyst retaining screens extending between said support plates, a generally rectangular parallelepiped shaped catalyst positioning member having a perforated top and bottom secured between said screens in spaced relationship to said screens and said support plates, a pair of end plates secured to said catalyst positioning member to form spatially connected upper and lower catalyst chambers, said chambers containing, in each instance, a particulate oxidation catalyst, a longitudinally extending baffle secured within said catalyst positioning member, means for introducing a stream of exhaust gases through one end of said container to a space between said bafile and said lower catalyst chamber, and means for discharging said stream of exhaust gases through the other end of said container from a space between said bafile and said upper catalyst chamber, whereby exhaust gases introduced into said apparatus pass through the bed of catalyst in said lower chamber, flow into contact with the wall of said container, and thereafter flow through the bed of catalyst in said upper chamber.
10. Apparatus according to claim 9 wherein at least a lower portion of said container wall is undulated to increase its surface area and the rate at which heat is removed from said wall by convection.
11. Apparatus for catalytically oxidizing combustible constituents in the exhaust gases from an internal combustion engine comprising a heat-conductive, generally cylindroidal container for mounting on the underside of a gasoline engine propelled vehicle with its shorter transverse axis in a vertical plane, a first generally rectangular parallelepiped shaped catalyst bed disposed such that the plane of its short axis is parallel to the plane of the short axis of said cylindroidal container, a second substantially rectangular parallelepiped shaped catalyst bed disposed in spaced superimposed relationship to said first catalyst bed with its short axis generally parallel to the short axis of said first bed, a bafile plate extending from one end of the uppermost of said catalyst beds to the opposite end of the lower catalyst bed, imperforate support plate means extending from the upper side edges '3 8 of said uppermost catalyst bed to the corresponding References Cited in the file of this patent lower side edges of the lower catalyst bed in contact UNITED STATES PATENTS with said baffle such that a tapered chamber is formed above said lower catalyst bed and a similar chamber is 1,422,211 Lamb July 11, 1922 formed immediately below said upper catalyst bed, means 5 1,522,111 FIaQCkPhmPSOH 1925 supporting said catalyst beds in spaced relationship to 1,867,325 Navlue y 12, 1932 the inside surface of said cylindroidal container, means Kryzanowsky 1933 for introducing exhaust gases into the tapered chamber 2,071,119 f 1937 immediately above said lower catalyst bed and means 72,198,796 Tlflestad P 1940 for withdrawing gases from the tapered chamber im- 10 2,329,847 Mccausland Sept 1943 mediately below said upper catalyst bed, whereby when 2684932 Berg y 1954 exhaust gases are fed into said first named chamber, 2,742,437 Houdry P 1956 they pass through said lower catalyst bed in a, uniform 2,772,147 Bowan et 27, 1956 manner, flow in contact with said inside surface of said 2,816,010 Shabaker 10, 1957 cylindroidal container to the upper side of said upper 15 28982O2 Houdry et 1959 catalyst bed, flow uniformly through said upper catalyst 290L109 i g et Sept 1959 bed and into said second named tapered chamber from 2,956,865 Wllhams 1960 which they are then exhausted from said cylindroidal 2,974,020 Kassel 7, 1961 container 2:991:160 Claussen July 4, r U y p 3,050,935 Eastwood Aug, 28, 1962 12. Apparatus accol'din to claim 11 wherein the wall 20 3,090,677 Scheitlin at al- May 21 1963 of said cylindroidal container immediately below said lower catalyst bed is undulated to increase its surface area.