Catalytic Converter For Exhaust Gases

Abstract

A catalytic converter for treating exhaust gas streams which has a removable catalyst cartridge embodied therein and which is designed to be connected directly to the exhaust ports of an internal combustion engine.

Description

This invention relates to an improved form of a converter adapted to hold a bed of solid contact material to treat an exhaust gas stream. More specifically, the present apparatus provides the means for the catalytic conversion and purification of the exhaust gases from an internal combustion engine, with the utilization of a design that provides for easy placement and removal of the catalytic bed therein and also that overcomes the problem of heat losses by being adapted for direct connection to the exhaust ports of the engine.

The desirability for removing, or converting to harmless form, the noxious components of vehicular exhaust gases has been well established. The principle constituents of such gases include the several oxides, nitrogen, carbon monoxide, and unburned or partially burned hydrocarbons; these materials, upon being expelled into the atmosphere, are known to be harmful to human health. Under the action of sunlight these emissions can combine to produce a wide variety of noxious, irritating compounds popularly and generally referred to as "smog."

It has long been recognized that catalytic devices located in the exhaust system of an internal combustion engine can overcome the problem of smog and of atmospheric contamination. In the usual catalytic method, the hot gases issuing from the motor exhaust manifold are passed through a fixed catalytic bed which effects more or less complete oxidation of the carbon monoxide and unburned hydrocarbons present in the exhaust gases, converting them to carbon dioxide and water. Oxides of nitrogen are also converted to nitrogen and oxygen. Sometimes the exhaust gases are mixed with a quantity of secondary or combustion air before being introduced into the catalytic bed, but with modern fuel-air ratios in present carburetion systems, this requirement is no longer considered absolutely necessary. Generally, the use of a catalytic method and apparatus provides for the initiation of the oxidation reaction at lower temperatures than would be otherwise possible without the use of a catalytic agent, and its use will also eliminate the need for spark plugs or other ignition means which are necessary in most types of "afterburners" or other apparatus which depend strictly upon thermal conversion conditions.

It has been found that one of the difficulties encountered in the utilization of catalytic converters for affecting the oxidation of automotive exhaust gases arises by the necessity to achieve a high enough temperature in the catalyst bed to establish initial oxidation and also to supply adequate, sensible heat to the catalyst after engine warm up. In other words, when an automobile is initially started from a cold start, then for a period of from 2 to perhaps 10 minutes, depending upon the manner of operating the automobile, the catalyst may remain relative cool and be unable to burn the residual combustible components effectively within the converter, thus permitting high emissions of unburned hydrocarbons, etc., through the system into the atmosphere.

In addition, it has been found that in most cases, catalytic reactors will operate at higher levels of efficiency, if provided with an adequate supply of sensible heat. For instance, it has been found that certain fuel additives and/or lube oil compounds, containing tetraethyllead, lead alkyls, barium, and other metal constituents, will normally deactivate or poison emission control catalysts. High temperature operations will prevent this sort of catalyst poisoning by such metals or fuel additives.

Heretofore, catalytic reactors which have been used on automotive vehicles have usually been designed for installation somewhere near the normal spot reserved on the vehicle for the muffler. However, when the converter is placed near the normal spot reserved for a muffler, the performance of the converter suffers at the time of initial oxidation and after warmup mainly because of the heat losses from the piping which extends from the engine to the muffler-converter. Various schemes have been used to minimize heat losses, including insulation, heating of secondary combustion air, etc. Conventionally, all multicylinder engines have an exhaust manifold which functions as a collecting chamber for the exhaust gases which issue from the cylinders. These gasses are then conducted through a pipe to the converter muffler, after which an exhaust pipe conducts them to the atmosphere. The present invention is an attempt to remedy the problems due to heat loss and catalyst deactivation in that it provides for a catalytic converter that doubles as the exhaust manifold in the engine.

It is further noted that after a period of operating time, the catalyst employed in a converter may still become contaminated, especially within engine systems utilizing a leaded gasoline. After contamination, the efficiency of conversion drops to such an extend that the undesirable hydrocarbons and carbon monoxide are emitted to the atmosphere without being converted. Thus, this present invention attempts to include the desirous characteristics of a converter system which has an arrangement that permits easy removal of the catalytic bed therein, thereby allowing for the replacement of contaminated catalyst particles.

Also, high temperatures, substantially in excess of those encountered within conventional exhaust systems, are produced as a result of the exothermic oxidation reactions taking place within and around the catalyst bed. Depending upon the particular catalyst employed and the proximity to the exhaust ports of the engine and upon the operation of motor vehicle itself, converter temperatures may run as high as 1,200.degree. to 1,800.degree. F. Because of these high temperatures, converters have been rapidly, and virtually completely destroyed by deformation, split seams, etc., as a result of uneven thermal expansion. The converter disclosed herein therefore embodies a design that provides for equalization of thermal stresses, whereby differential stresses within its walls are kept well within the elastic limit of the material of construction.

Thus, it is a principal object of this invention to provide an efficient catalytic converter that is located in close proximity to the exhaust ports of the engine, thereby eliminating the need for insulated pipes and/or heating of secondary combustion air and thereby preventing deactivation of the catalyst particles by tetraethyllead and other metals. More specifically, it is an object of this invention to provide for a catalytic converter for the conversion of automotive exhaust gases that also serves as the exhaust manifold of an engine.

It is also an object of this invention to provide for a catalytic converter that encases a removable catalyst retaining cartridge, its use thus permitting easy placement and removal of the subdivided catalyst particles.

It is a further object of this invention to provide a catalytic muffler which is constructed in such a manner that the various components will be capable of expanding and contracting relative to each other as the temperature of the apparatus fluctuates.

In a broad aspect, the present invention provides for a catalytic converter for containing subdivided catalyst particles for treating an engine exhaust stream and adapted for direct connection to the exhaust ports of an engine, which comprises, in combination, an elongated outer housing having a removable cover plate, an interior perforated cartridge for containment of said catalyst particles having an inlet perforate wall section and an outlet perforate wall section to provide for exhaust stream flow therethrough, said perforated cartridge removably disposed in said housing and spaced with respect to the interior of said housing to form an inlet manifold section and an outlet manifold section therein, plural inlet means through said housing and having communication with said inlet manifold section and said inlet wall section, said inlet means spaced and sized for direct connection to the exhaust ports of an engine, and treated gas outlet means from said housing and having communication with said outlet wall section via said outlet manifold section.

In a preferred form, the elongated housing comprises a simply constructed cast unit. The plurality of inlet means are adapted to connect to the exhaust ports of the engine and are introduced into the elongated housing through a horizontal top portion thereof. The inlet means may be so designed so as to permit casting during the casting operation of the outer housing, thereby establishing a single unit construction. In this preferred form, the elongated housing has a narrower longitudinal section extending along its lower side, thus providing the outlet manifold section and a cartridge placement shelf. This section is also cast along with the outer housing as one piece. The outlet manifold may be provided with a pipe extension having flanged ends for connection to the downstream end of an exhaust system. One side of the outer housing is open ended with flanged edges, having threaded holes therein, to establish connecting means for a cover plate, which permits access to the catalyst cartridge. In one embodiment the catalyst cartridge is substantially rectangularly shaped with the side wall portions abutting the interior of the elongated housing. Its depth is shorter than that of the internal depth of the elongated housing, thereby providing the manifold section between the inlet perforate wall section and the inlet means. The cartridge is placed on the bottom shelf surface of the elongated housing, formed by the extending longitudinal section.

The outlet perforate wall section communicates with the longitudinal section extending along the one side of the housings. Transverse projections or other suitable holding means are located along the interior walls of the outer housing and cover plate, so as to hold the cartridge in place when installed and to prevent passing of untreated exhaust gases between the cartridge side wall portions and the walls of the housing. The perforate sections of the cartridge may be curved slightly to enhance their strength.

In another embodiment, the inlet perforate wall section is curved to a greater extent and in fact is of a segment-cylinder-form. By referring to "segment-cylinder-form" it is meant to encompass a portion of a cylinder; i.e., a cylinder being defined by a line moving parallel to a fixed line. A semi-circular-cylinder-form would be one special example of such a segment-cylinder-form. In this embodiment, the outlet perforate wall section is also of a segment-cylinder-form and is spaced inwardly from the inlet perforate wall section. Of course, to form the cartridge end partition means must be connected to the perforate sections for establishing the structure and also for preventing catalyst particles from flowing through the ends. In one embodiment utilizing the segment-cylinder-form perforate walls the convex surface of the inlet perforate wall section contacts the inlet manifold section. Preferably in this embodiment, the longitudinal ends of the resulting cartridge are placed on the cartridge placement shelf and thus the concave surface of the outlet perforate section communicates with the longitudinal section extending along the one side of the housing.

In another embodiment utilizing the segment-cylinder-form perforate sections, the concave surface of the inlet perforate section contacts the inlet manifold section. In this embodiment, the longitudinal ends of the resulting cartridge are attached to the housing near the inlet means. There is no need to have a longitudinal section extending along one side of the housing because there is no need for a placement shelf on the outlet side thereof.

In both of the embodiments using the segment-cylinder-form perforate sections, the resulting cartridge may be held in place by the utilization of a tongue and groove arrangement, whereby the cartridge may be slid into the housing and held in place by the tongues and grooves. Of course, other suitable holding means within the housing may be provided for maintaining the cartridge in place.

Although not contemplated as being necessary in all applications, a secondary air inlet means may be provided in conjunction with this particular manifold converter. Also baffle means may be located within the inlet manifold section to establish uniform flow across the perforate inlet wall section of the cartridge. These baffle means may take various forms, as for example, they may be perforated inserts or plugs that can be placed within each individual inlet means. The present improved design may be better explained, as well as further advantageous features set forth, by reference to the accompanying drawing and the following description thereof.

FIG. 1 is a longitudinal partial sectional view of one embodiment of the converter of this present invention.

FIG. 2 is a sectional view of the embodiment of FIG. 1 as taken through line 2--2.

FIG. 3 is a sectional view of an inlet conduit with a baffle plug inserted therein.

FIG. 4 is a sectional view of an embodiment of the converter of this invention utilizing an "in-to-out" segment-cylinder-form cartridge.

FIG. 5 is a sectional view of an embodiment of the converter of this invention utilizing an "out-to-in" segment-cylinder-form cartridge.

Referring now more particularly to FIGS. 1 and 2 of the drawings, there is indicated one embodiment of a catalytic converter apparatus shown embodied within a casing or outer housing 1. Outer housing 1 in this particular arrangement has been formed by a casting operation known to those skilled in the art, and is of a suitable material adapted for casting, such as an iron alloy. The front face of outer housing 1 has flanged edges 2 provided around its entire periphery. Flanged edges 2 are provided with spaced-apart threaded holes 3, to be used for connection of the cover plate thereon. The cover plate 4 is designed to completely enclose the space within housing 1 and has holes 5 thereon for inserting of bolts 6. A gasket or other suitable sealing means 7, made of a material capable of withstanding temperatures to 2,000.degree. F., is provided between cover plate 4 and the flanged surfaces or edges 2.

In this particular embodiment the outer housing 1 has a lower longitudinal section 10, which is of a narrower cross section than is the main rectangular portion of housing 1. Thus is provided an internal surface 11, which serves as the surface of placement for the catalyst cartridge. The space 12, established by lower longitudinal extension 10, provides the outlet manifold section for the treated exhaust gases. A narrower cross section outlet pipe means 13, having flanged portions 14 for direct connection to the conventional exhaust system of an internal combustion engine, is located at the left end of manifold section 12, although it may be disposed at any location thereof.

Located within outer housing 1 and designed to abut walls 20, 21, 22, and 23, thus preventing any quantity of exhaust gases from passing thereby, is catalytic cartridge 24, shown containing subdivided catalyst particles 25. For most efficient converter operations, the cartridge should be filled to capacity. It is not intended to limit this improved type of catalytic converter to any one particular type of oxidation catalyst, inasmuch as there are various known effective and efficient catalyst compositions. Suitable oxidation catalysts include the metals of Groups I, V, VI, VII, and VIII of the Periodic Table, particularly chromium, copper, iron, nickel, and platinum. These components may be used singularly, in combinations of two or more, etc., and will generally be composited with an inorganic refractory oxide support material, such as alumina, silica alumina, silica alumina zirconia, silica-thoria, silica-boria, and the like.

The cartridge, as shown in FIGS. 1 and 2, has imperforate sidewall portions abutting walls 20, 21, 22, and 23 of housing 1. The top and bottom walls 27 and 28, are perforate wall sections which have been attached permanently to the sidewalls, after the catalyst particles 25 were inserted. Although not shown, it is contemplated that the construction of cartridge 24 will be such that the construction will prevent buckling during the operation of the converter. This may be accomplished in various ways. For example, the walls of the cartridge may be accordioned along their length so as to absorb any expansion due to temperature differentials. Also contemplated as being within the scope of this present improvement is a cartridge-type construction that embodies slotted wall sections to permit the various sections to be slidably supported within each other. In addition, it is contemplated that instead of having permanent enclosed particles, the cartridge be constructed in such a way as to permit opening and closing of at least one wall portion, thereby permitting access to remove contaminated catalyst particles and replace them with rejuvenated particles.

The cartridge is inserted into housing 1 via the opening in the front of housing 1, and, as heretofore described, placed on surface 11 to abut housing 1 at 20, 22, and 23. Also noted are projections 29 located on cover plate 4 and projections 29' located on the inner walls of outer housing 1. These projections serve to hold the cartridge 24 onto surface 11 when outer housing 1 is sealed by cover plate 4 and serve also as a means to prevent exhaust gases from passing thereby. Gasket 7 is then inserted onto flanged pieces 2, cover 4 is inserted over this gasket, and both are bolted into place via bolts 6, to abut cartridge 24 at 21. It is to be noted that the cartridge should not be so tightly abutted against the walls of the housing as to foreclose any expansion.

Horizontal plate 28 has apertures 31 provided therein. It is also noted that, similarly, plate 27 has apertures 30 located along its length. Thus is established a cartridge having an inlet perforate wall section 27 and an outlet perforate wall section 28 to establish flow of the exhaust stream through the subdivided catalyst particles 25. The cartridge is disposed within housing 1 so that the top inlet perforate wall section 27 is spaced from the housing and particularly from the inlet means introducing the exhaust steam into the housing, thereby establishing an inlet manifold section 35.

The inlet means comprises in this particular embodiment four conduits 36, 37, 38, and 39, which are spaced apart so as to coincide with the exhaust ports of an internal combustion engine. Of course this particular spacing should not be considered as a limiting factor upon the present invention for, as shown, this spacing is merely a schematical representation, and, of course, the spacing will depend upon the model, make and type of engine the converter is to be used in conjunction therewith. Necessarily, flanged portions are provided on each conduit so as to establish a connecting means to the exhaust ports of the engine. It is noted that these conduits have been cast in this particular embodiment at the same time as the outer housing 1, thus establishing a one-piece construction. These conduits communicate with inlet manifold section 35 via ports 40, 41, 42 and 43 through the top of housing 1. Of course, the introduction into inlet manifold section 35 should not be considered limiting upon this present invention, for introduction into manifold section 35 can be brought about from the back of housing 1, or for that matter, from the top at an angle to the horizontal.

It is felt that in some cases the direct downward flow of exhaust gases into the catalytic bed through the apertures 30 and plate 27 may be too concentrated. In addition, it has been found that a converter should be arranged so that uniform distribution of exhaust gas flow through the catalyst bed is maintained in order to achieve maximum catalyst life and maximum conversion. Therefore, it is contemplated that baffle means may be utilized within the converter of this present invention. Such baffle means may take various forms. As for example in FIG. 3, one such form of a baffle means is illustrated. It consists of a plug or insert 50 with a plurality of apertures 51 distributed over its surface. Insert 50 is force fitted into a conduit 36 and thus provides a means whereby the velocity head of the exhaust gases, rushing through the conduit, is reduced to a pressure head, thereby establishing more uniform distribution within manifold 35, and, consequently, through the catalyst materials within cartridge 24. This particular form of baffle means shall not be considered limiting, for others are contemplated, e.g., a flat plate spaced from the inlet ports may be attached permanently to the interior walls of housing 1.

In FIGS. 4 and 5 there is indicated an alternate arrangement of the converter of this invention utilizing a segment-cylinder-form catalyst cartridge. In other words, the cartridges 24' and 24" have been formed by segment-cylinder-form perforate wall sections 60 and 61 in FIG. 4 and 62 and 63 in FIG. 5. In these embodiments, the wall sections have a semicircular shape with straight extensions 64 and 65. The cartridge is made rigid by end partition means 66 and 67 on longitudinal edges thereof and by other similar partition end means on the transverse ends thereof (not shown). These end partition means also serve to prevent the catalyst particles from falling out of the cartridge.

The use of a curved or segment-cylinder-form partition plate has two distinct advantages. First, it increases the strength of the cartridge and prevents the perforate sections from flexing laterally. Lateral flexure has been known to crush catalyst particles within a catalyst retaining bed. A second advantage is in the configuration of the bed itself. In other words, a curved bed will provide maximum amount of catalyst volume in a minimum-sized bed and therefore a more efficient converter.

In these embodiments, the cartridges are inserted through an open end of the outer housing 1' and 1". After insertion, cover plates 4' and 4" and corresponding sealing gaskets are secured to the flanged portions 2' and 2" of the housing. Actually, in these embodiments the cartridges are held in place by a tongue and groove system. In FIG. 4, the tongue and groove system is established by transverse pieces 80 and 81 which form a groove 82 on both sides of the inlets. The tongue portion of the system is formed by the end partition means 66 which overlap the imperforate partitions to form the tongues 83. Thus, the cartridge 24' is merely slipped into the groove 82 and is thus held in place. Of course, to hold the cartridge in a rigid manner it may be bolted to the housing at one of its ends. Thus, it is held in place in a rigid manner but since it is only bolted at one place, it is free to expand in the groove 82. Similarly, the cartridge 24" of FIG. 5 is held within the housing 1" by a system of tongues and grooves. In this instance, transverse projections 84 are located adjacent to the longitudinal extension 10' forming the outlet manifold section. These projections form a groove 85 on both sides of the longitudinal section 10'. Again, the end partitions 67 overlap the perforate partitions to form the tongue 86. Thus, cartridge 24" is merely slipped into the groove 85. It may also be bolted into place to maintain it in a rigid state.

It is also contemplated that the particular converter of this invention be supplied with a source of secondary air, although it is not considered necessary in most applications, especially in light of the recent use of carburetion systems that supply excess air initially to the engine. The supply of secondary air may be established by simply inserting a conduit having communication with exterior of the housing into the inlet manifold section or by a more sophisticated utilization of valves, pumps, etc.

From the foregoing description, it is seen that this present invention provides for a converter that because of its location, provides for high temperature, at the inlet of the catalyst section. High temperatures will permit lower net emissions of undesirable components in an exhaust stream and will also permit the use of small converter configurations, which is desirable in light of the relatively small dimensions of present day engine compartments. The removability of the cartridge also enables the quick and inexpensive replacement of catalyst particles. Such a design will enable the unskilled person to rejuvenate the system by mere removal and replacement of the cartridge. The old cartridge, thus removed, can either be discarded, or if its design permits, be sent to the manufacturer thereof and its contents removed and replaced. This particular invention also allows for installation of expansible cartridges, thus preventing damage due to temperature differentials. The slip-fit of the cartridge within housing 1 will also prevent expansion problems from developing.

It is also considered as within the scope of this present improved design and construction to provide for a covering of the outer housing 1 with a suitable insulating material, such as asbestos, mineral wool, or the like, in order to maintain the maximum amount of heat within the catalyst cartridge, although it is found that in utilizing the improved converter that the amount of insulation necessary will not be as great as was the case within the converter-muffler type reactors as were used heretofore at zones remote from the motor, and in most instances will be needed only as a heat protection means.

It may be understood that various minor modifications in the design and or location of the various portions of this apparatus may be made within the scope of the present invention. As for example, there may be a variation in the shape and spacing of the cartridge from that indicated on the drawing, or in locating and designing the outlet manifold section 12, as well as with respect to sizing and positioning of the ports into the inlet manifold section. It is also noted that in some instances the cartridge may be reinforced with stiffening members contained within the cartridge itself. The apertures 30 and 31 located on the horizontal plates of cartridge 24 will of course be sized in relation to the size of the catalyst particles which are to be maintained within the apparatus. The physical shape for catalyst particles may be such that they are in the form of spheres, cylinders, or pellets, typically having a dimension of 1/16 to 1/4 inch, although particles of larger or smaller dimensions may be employed where desirable. Mixed sizes of catalyst may well be utilized, especially as a means to start their initial oxidation process. Also, as indicated hereinbefore, it is not intended to limit the present invention to any one type of catalyst.

For most efficient operations the catalyst cartridge should be maintained full of catalyst particles to prevent bypass of exhaust gases. Thus, it is also contemplated that a reservoir means be provided connective with the catalyst cartridge for maintaining a filled cartridge. The embodiments of FIGS. 4 and 5 are especially well suited for embodying such a reservoir means. In these embodiments the reservoir means 90 and 91 have been formed by connecting transverse sections 92 and 93 and 94 and 95 within the catalyst cartridges. These sections are provided with a plurality of openings 100 and 101 along their length to provide communication of the catalyst particles from the reservoir means into the main body of the cartridge. Of course, the cartridges themselves do not have any perforations in their walls in the region of the reservoir means.

Claims

We claim:

1. A catalytic converter for containing subdivided catalyst particles for treating an engine exhaust stream and adapted for direct connection to the exhaust ports of an engine, which comprises, in combination, an elongated outer housing having a removable cover plate, an interior perforated cartridge for containment of said catalyst particles having an inlet perforate wall section and an outlet perforate wall section to provide for exhaust stream flow therethrough, said perforated cartridge being removably disposed in said housing and spaced with respect to the interior of said housing to form an inlet manifold section and an outlet manifold section therein, said elongated housing having a longitudinal section extending along one side, said longitudinal section having a narrower cross section than the main body thereof to form said outlet manifold section and to form a cartridge placement shelf in that said longitudinal section longitudinally opposes said outlet perforate wall section, plural inlet means through said housing and having communication with said inlet manifold section and said inlet wall section, said inlet means spaced and sized for direct connection to the exhaust ports of an engine, and treated gas outlet means from said housing having communication with said outlet wall section via said outlet manifold section.

2. The catalytic converter of claim 1 further characterized in that a baffle means is provided in the inlet manifold section thereof for establishing uniform gas flow from said plural inlet means through the catalyst cartridge.

3. The catalytic converter of claim 1 further characterized in that said perforated cartridge is substantially rectangularly shaped and has sidewall portions abutting the interior of said elongated outer housing.

4. The catalytic converter of claim 1 further characterized in that the inlet perforate wall section is of segment-cylinder-form, the outlet perforate wall section is of segment-cylinder-form, spaced inwardly from said inlet perforate wall section, end partition means are connected to said perforate sections for preventing catalyst particles from flowing through the ends thereof, and in that the convex surface of said inlet perforate wall section contacts the inlet manifold section.

5. The catalytic converter of claim 1 further characterized in that holding means is provided within said housing for maintaining said cartridge in place.

6. The catalytic converter of claim 1 further characterized in that said outlet perforate wall section is of a segment-cylinder-form, said inlet perforate section of segment-cylinder-form spaced inwardly from said outlet segment-cylinder-form section, end partition means are connected to said perforate sections for preventing catalyst particles from flowing through the ends thereof, and in that the concave surface of said inlet perforate section contacts the inlet manifold section.

7. The catalytic converter of claim 6 further characterized in that a holding means is provided within said housing for maintaining said cartridge in place.

8. The catalytic converter of claim 1 further characterized in that a reservoir means is provided connective with said catalyst cartridge for maintaining a filled cartridge.