CA1157780A

CA1157780A - Catalyst reactors

Info

Publication number: CA1157780A
Application number: CA000360754A
Authority: CA
Inventors: Edward R. Middleton; Bernard E. Enga
Original assignee: Johnson Matthey PLC
Current assignee: Johnson Matthey PLC
Priority date: 1979-09-20
Filing date: 1980-09-22
Publication date: 1983-11-29
Also published as: DE3035472A1; SE8006534L; JPS5696111A; FR2465875A1

Abstract

ABSTRACT

This invention relates to the purification of gases and in particular of waste gases. This invention is especially concerned with at least reducing the quantity of pollutants such as carbon monoxide and smoke in gases emitted from internal combustion engines.
In more detail an internal combustion engine includes apparatus for reducing pollutants contained in exhaust gases emitted from the engine having at least one exhaust port, the apparatus comprising a chamber, means for cooling the chamber and a catalyst supported within the chamber, the catalyst including a substrate, a layer of refractory metal oxid?
applied to at least a part of the surface of the substrate and a catalytic material applied to the layer of refractory metal oxide, the chamber also including an inlet in communication with the said exhaust port via which exhaust gas emitted from the engine is led into the chamber and passed through the catalyst prior to passage through an exhaust system to atmosphere.

Description

This invention relates to the purification of gases and in particular of waste gases. This invention is especially con-cerned with at least reducing the quantity of pollutants such as carbon monoxide and smoke in gases emitted from internal com~
bustion engines.
Gases from internal combustion engines often contain finely divided particles of hydrocarbons and/or carbon and/or other solid matter which emerge in the form of smoke. The smoke from a diesel engine, for example, is composed of solid/liquid particles, solid chain aggregates in which essentially spherical particles of between 100-800~ diameter, link up together liquid sulphates, liquid hydrocarbons and gaseous hydrocarbons. The solid/liquid particles generally comprise carbon particles with adsorbed liquid hydrocarbons and the solid chain aggregates are generally composed of high molecular weight organic compounds and/or inorganic sulphates.
Three different types of smoke are commonly observed issuing from diesel engine exhaust pipes. These are "white smoke"
"black smoke" and "blue smoke". White smoke is produced when the engine first starts up and results from the condensation of water vapor on to particles contained in the exhaust gas so that a fine mist is formed. Black smoke is produced when the engine has warmed up and contains a relatively high proportion of carbon particles. In blue smoke there is some carbon with a relatively high proportion of gaseous hydrocarbons such as aldehydes.

Throughout the remainder of this specification the particles referred to above will be described as "smoke forming particles". About 90% of these smoke forming particles have maxi-mum dimensions of less than one micron which is within the respirable particle size and the maximum dimension of the remain-ing 10% of these smoke forming particles is less than four microns.
Other undesirable components present in exhaust gases are noxious gases such as carbon monoxide and hydrocarbons. In this specification the word "pollutants" is to be taken to mean smoke forming particles and noxious gases.
Catalytic oxidation of carbon particles takes place at about 400C whereas the normal temperature of combustion of these particles is 700-800C. For hydrocarbon particles catalytic oxi-dation will take place at temperatures about 200C. The effect of a catalyst on the temperature at which catalytic oxidation of particulates entrained in the exhaust gas stream of a diesel engine took place were studied. A number of sample catalysts were prepared. The catalysts comprised a substrate fabricated from 310 stainless steel wire of diameter 0.010 inch, rolled down to ribbon 0.004 inch thick, a layer of alumina and a layer of one or more platinum group metal(s) at a loading of 2.46 mg/g of alumina. A portion of coated wire was cut from a catalyst and heated gradually raising the temperature together with particu-late matter, collected from the exhaust gas stream of a diesel engine, in the sample pan of a differential scanning colorimeter (a DSC) in an atmosphere of 1% oxygen in argon. Samples of the atmosphere above the sample pan were taken via a heated capillary tube to a mass spectrometer. Four mass numbers were traced:
carbon monoxide (44), double charged argon (20), oxygen (32) and water (18) or nitrogen and carbon monoxide (28). The temperature at which the differential plot of the DSC peaked was taken to be the temperature at which combustion of the particulates took place. This temperature can be referred to as the "light-off~
temperature. The results are given below:

Alumina Loading CatalYtic metal(s) Light-off (g/g of wire) temperature (C) 0.33 5.7% Rh 94.3% Pt 235 0.28 67% Pt 33~ Pd 207 0.30 Pd 265 0.28 Pt 220 The light-off temperature of particulates from the exhaust gas stream of a diesel engine, 207-265C, is csnsiderably lower than the temperature for combustion to take place when no catalyst is present. Since the presence of a catalyst enables oxidation of the smoke for~ing particles in a gas to take place at a lower temperature than the normal temperature at which combustion takes place, little or no heating of the exhaust gas from an internal combustion engine should be required when it is desired to effect the catalytic oxidation of any smoke forming particles in the gas. For example, a diesel engine runs at about 400C when operating at medium to full power so that no preheating of the exhaust gas issuing from the diesel engine would be required before passing the said exhaust gas over a catalyst to remove the smoke.

forming particles from the gas by catalytic oxidation, provided the catalyst is close to the engine.
Internal combustion engines are often used in areas where there are stringent regulations on their use such as in mines. Diesel engines which are to be used in a NCB mine are modified to comply with regulations controlling the use of diesel machinery in mines. The engine is surrounded by a water jacket so that the temperature of any exterior part of the engine which comes into contact with the atmosphere is less than 120C. The exhaust gas of the engine is passed through a water conditioner and flame traps before finally being emitted to the atmosphere.
The water conditioner may be a container of the water through which the exhaust gas is bubbled or water may be sprayed into the stream of exhaust gas. Any chamber containing a catalyst, for treating the exhaust gas, will have to comply with regulations but still keep the temperature of the exhaust gas up to enable catalytic removal of the pollutants to take place.
An object of the present invention is to at least reduce the quantity of the smoke contained in exhaust gas by effecting catalytic oxidation of smoke forming particles in the gas.
A further object of the present invention is to reduce the quantity of noxious gases and particulates present in the exhaust gas from an internal combustion engine.

1 1~7780 Another ob~ect of the present invention is to provide a modlfied diesel or petrol driven internal co~bustion engine such that a considerably reduced quantity of noxious gases and particulates is produced.
In accordance with the present invention there is provlded a diesel engine comprising one or more cylinders which can generate exhaust gas containing carbon particles when the engine is in operation, each cylinder having an exhaust port for discharglng the exhaust gas, and the engine is provided with an exhaust pipe for venting the exhaust gas to atmosphere and in co~bination with the engine an apparatus suitable for oxidising the carbon particles wherein (a) the apparatus comprises a chamber and means for cooling the chamber and the chamber ha~ at least one entry port in communication with an exhaust port and an exlt port ln communlcatlon with the exhaust plpe so that exhaust gas can pass from the exhaust port through the chamber and lnto the exhaust pipe, (b) the chamber contains an interstitial catalyst system comprising a catalytic metal, a layer of refractory metal oxide and a substrate made from filamentary metallic material in a knitted or woven form, the catalyst being disposed on or throughout the layer of refractory metal oxide which in turn 1~ tlsposed on the surface of the ~ubstrate;
(c) the substrate i8 mounted within the chamber spaced from the inner walls of the chamber so as to create an outer passageway, and is shaped so as to define a central passageway within the substrate, (d) wherein one of the passageways communicates with the entry port or ports and the other conununicates with the exit port and the substrate is positioned so that substantially all the exhaust gas discharged from the or each cylinder ls caused to pass through one passageway, then through the interstitial catalyst system and then thr,~gh the other passageway, and (e) the outer and central passageways and the substrate are aligned relative to the entry port or ports such that exhaust gas passing through the chamber is caused to flow in a direction transverse to the entry port or ports during a portion of lts pa~sage through the chamber thereby increasing turhulence within the interstitial catalyst system.
The catalytic metal may be selected from the group consisting of Ru, Rh, Pd, Ir, Pt, Fe, Co, Ni, V, Cr, Mo, W, Y, Ce and alloys and intermetallic compounds containing at least 20Z by weight of one or more of these metals disposed upon the surface of or throughout the refractory metal oxide washcoat layer.
The refractory metal oxide washcoat layer preferably contains in the form of their oxides one or more members of the group consisting of Mg, Ca, Sr, Ba, Sc, Y, the lanthanides, Ti, Zr, Hf, Th, V, Cr, Mn, Co, Ni, B, Al, Si and Sn.
A preferred layer material is A12O3 and alumina hydrates but stabilising oxideæ such as BaO and oxides promoting catalytic activity such a8 TiO2, ZrO2, HfO2, ThO2, Cr2O3 and~iO may also be present.
The structure of knitted or woven form used as the substrate makes the exhaust gas flow through the catalyst turbulent. Metals or alloys used in the fabrication of the substrate are preterably oxidation resistant and should be thermally stable up to at least 600C.
Suitable base metal alloys are nickel and chromium alloys having an aggregate Ni plus Cr content greater than 20% by weight and alloys of iron including at least one of the elements chromium (3-40) wt %, aluminum (1-10) wt %, cobalt (trace-5) wt %, nickel (trace-72) wt % and carbon (trace-0.5) wt ~. Such substrates are described ln German DOS 2450664.
Other examples of base metal alloys capable of withstandlng the rigorous conditions required are iron-alumlnium-chromium alloys which may I 1577~Q

also contain yttrium. The latter alloys may contain 0.5-12 wt % Al, 0.1-3.0 wt % Y, 0-20 wt ~ Cr and balance Fe. These are described in United States Patent No. 3298826. Another range of Fe-Cr-Al-Y alloys contain 0.5-4 wt X Al, 0.5-3.0 wt X Y, 20.0-95 wt ~ Cr and balance Fe and these are described in United States Patent No. 3027252.
Alternatively the base metal alloys may have less corrosion resistance, e.g., mild steel, but with a protective coating composition covering the surface of the substrate as described in our co-pending Britlsh Patent Application No. GB 2,013 517A published 15 August 1979, corresponding to Canadian Patent 1,128,031.
Where wlre is used as substrate lts thlckness is preferably between 0.0254 and 0.508 mm dlameter and more preferably between 0.254 and 0.305 mm diameter.
Specific embodiments of the inventlon will now be described wlth reference to the accompany drawings in which: `
Figure 1 and 2 show catalytlc systems ad~acent the exhaust ports of cylinders of an internal combustion engine;
Figure 3 is a diagra~matic repre~entation of an apparatus containing a catalyst system shown in section;

Figure 3A is a diagrammatic representation of an alternative apparatus containing a catalyst system shown in section;
Figure 4 is a perspective view of a spacer unit suitable for use in the apparatus shown in Figure 3;
Figure 5, on the same sheet as Figure 1, ls a perspective view of an alternative spacer unit suLtable for use In the apparatus shown in Figure 3A;
Figure h to 45 are graphs illustrating the performance of the catalyst systems described; and ~ - h -Figure 46 to 49 are histograms illustratil~ the performance of catatyst systems comprising catalysts A or B as described in Example 2.
In Figure 1, the outer wall, 7, of a catalyst chamber has openings, 10 and 11, which are adjacent to and continuous with the exhaust ports of the cylinders of the engine and one exit, 12, ad~acent to the exhaust pipe, 13. Catalysts, 1, 2, 8 and 9 are positioned as shown. The catalyst chamber has an inner wall, 5 and two outer walls, 6 and 7, with an air gap between the walls S and 6 and the gaps between 6 and 7 filled with circulating water. The water is provided from the water ~acket surrounding the engine.
The ....
~ _ f,~ _ 1 15778~

exhaust gas flow is generally indicated by the labelled arrows Fl, F2, F3, F4, F5 and F6. Exhaust gas flows from the cylinders, through the exhaust ports and through into the openings, 10 and 11, into the chamber and makes contact with catalysts 1 or 2 and then catalyst 8 and possibly catalyst 9 before passing through the opening, 12, to the exhaust pipe.
The substrate may be a monolith or a structure of wire.
If a wire substrate is used one unit for each catalyst may be used or a number of small units linked together.
In Figure 2, the catalyst chamber has openings, 10 and 11, adjacent to and continuous with the exhaust ports of the cylinders and one exit, 12, adjacent to the exhaust pipe, 13.
Between the inner wall, 25, and outer wall, 27, of the catalyst chamber, water from the cooling water jacket of the engine circu-lates. An inner chamber, 24, containing two catalysts, 1 and 2, is arranged in the catalyst chamber as shown in Figure 2 such that the exhaust gas on entering the catalyst chamber has to pass through an inner chamber, 24, and makes contact with the cata-lysts before leaving the chamber and entering the exhaust pipe.
Part of the inner chamber, 29, is perforated with holes or slots to allow the exhaust gas therein to pass from the inner chamber to the catalyst chamber and thence to the exhaust pipe. Exhaust gas entering the catalyst chamber at opening, 10, flows through the chamber as indicated by the labelled arrows F21, F23, F25, F27, F28 and F31 while gas entering at the other opening, 11, flows through as indicated by the labelled arrows F22, F24, F26, F29, F30 and F31 The support may be a monolith or fabricated from metal-lic wire. The two catalysts are positioned in the catalyst chamber as shown in Figure 2 so that approximately the same amount of exhaust gas passes through each catalyst, the exhaust gas from one cylinder passing through one catalyst.
An embodiment of the invention is depicted in Figure 3, in which one or more catalysts with optional spools are utilised.
The catalyst chamber has openings, 50 and 51, adjacent to and con-tinuous with the exhaust ports of the cylinders and one exit, 52, adjacent to the exhaust pipe, 53. The catalysts, 41, 42 and 43, comprising a support, a washcoat layer and a catalyst metal, are disposed so that the exhaust gas on entering the catalyst chamber is compelled to pass through the interstices of at least one catalyst before leaving the chamber and entering the exhaust pipe.
The exhaust gas flows through the chamber as indicated by the labelled arrows, F41, F42~ F43~ F44~ F4s~ F46~ F47~ F48~ 49~
F50, F51, F52, F53~ F54~ F55 and F56- The exhaust gas enters the catalyst chamber through a sleeve arrangement, 45, which is set into the chamber, and is deflected by a spool, 47, before passing through the catalyst.
In this embodiment the substrate for the catalyst is preferably of knitted wire which may be unitary or in sections.
Sections, for example, of doughnut configuration, are normally linked together before being placed in the chamber. Annular discs, 48, may be used to secure the catalyst to the walls of the chamber. In the centre of catalysts, there is a spacer unit, 45, which supports the catalysts and spools and forms an exit tube 1 1577~

through which the exhaust gas passes to enter the exhaust pipe.
The spools are not essential and one long catalyst may be used.
Figure 4 depicts one form of a spacer unit in which a series of 5 rigid bars 100-500 running the length of the chamber are used. These are maintained in fixed spatial relationship to one another, thus holding the supported catalyst rigidly in place within the chamber, by the use of spacing plates 600. The spac-ing plates in pairs connect three of the five bars and are usual-ly at right angles to each other thus being disposed along a dia-meter of the central cylindrical exit tube. Two or more pairs ofspacing plates may be used and they are usually positioned at regular intervals in the length of the chamber. Alternatively the spacing plates may be used instead of rods where they would be continuous throughout the length of the chamber as shown in Figure 5. Rods and spacing plates need to be constructed of a material resistant to oxidation up to 800 C.
A further embodiment will be described with reference to Figure 3A. The catalyst chamber has openings 82 and 83 adjacent to and continuous with the exhaust ports of the cylinders and one exit 84 adjacent to the exhaust pipe. Water from the cooling water jacket of the engine circulates between the inner wall 81 and the outer wall 80 of the catalyst chamber. The catalyst 85 comprising a support, a washcoat layer and a catalytic metal is so disposed that the exhaust gas has to flow through the catalyst before leaving the chamber. The catalyst is disposed in the chamber using spacing plates 86 as described above. One end of the spacing plates 89 is fixed to the chamber wall 81 and a disc 1 1577gO

or metal plate 90 is attached to the other end of the spacing plates to ensure that no exhaust gas can leave the chamber with-out passing through the catalyst. The exhaust gas flows into the chamber through the openings 82 and 83 down through sleeves 87 and 88 and through intermediate chambers 92 and 93 into the inner space 91 provided by the spacing plates 86. The exhaust gas then flows through the catalyst outwards and then through ~0 - 9a -1 1577~

the exit 84. The flow of the exhaust gas is indicated by the labelled arrows F60-F79. The intermediate chambers 92 and 93 comprise a hollow cylinder with integral end flanges having sub-stantially centrally positioned holes to allow the spacing plates 86 to pass through and a sleeve, either 87 or 88, is fitted radially into the cylinder wall such that the joint is gas tight.
The support for the catalyst is preferably of knitted wire which may be made up into four sections or three units. If the support is in sections, e.g. of doughnut configuration, these are normally linked together before the support is placed in the chamber.
A Perkins 4.236 diesel engine, a low emissions diesel engine, modified for mine use was used to demonstrate the results obtained in operation.
Example 1 A catalyst chamber as outlined in the first embodiment, Figure 1, was fitted to the engine. The substrate W2S a monolith of cell density 400 cell/sq. in. made from an alloy of the following composition:-% wt Cr 15 Al 4 Y 0.3 Fe balance ~ 1 157780 ~ -- 11 -A washcoa~ Or alumina stabilised with ceria at a loading of 1.5 g~cu ft was applied. The cat~lytic metal layer comprising Pt and Pd in the ratio of ~:1 was applied at a loading of 80 g~cu ft. The variation of the amount of hydrocarbons, carbon monoxide, nitrogen oxides ~nd particulates, presen~ in the exhaust gas, with the load ~f the diesel engine as brake mean effective pressure was measured at 1,0QO rpm and 2200 rpm. The results of these measurements are given in graphical form in the attached figures 5-21. Table 1 below gives the deta-ls of the measurements taken and tne figures giving the results.

~ 10 Table 1 ) Speed of Figure Pollutant in exhaust gas measured engine in rpm Carbon monoxide. CO, in ppm 1,000 6 " 1,400 7 1,800 8 ~ 2,200 9 Hydrocarbons, HC, in ppm 1,000 10 1~ 1,400 11 n 1,800 12 ., 2,200 t3 Nitrogen oxides, NOx, in ppm 1,0G0 1~

~, 1.400 15 - - - 1,800 t~

- 2,200 17 Particulates in g/hr 1,000 18 ~ 1,400 19 ,. 1,800 20 2,200 ~1 ... . .. . . .. . . ..

The two lines show the difference between the pollutants present in the exhaust gas when no catalyst cha~ber is used, ('baseline'), represented in the figures by X X ~ , and after the exhaust gas has passed through a catalyst chamber, represented by the figures by _ . A high sulphur containing fuel with 0.7% sulphur was the fuel for the engine.
A further set of results were obtained using the catalyst fitted to the engine as described above. The results were ob-tained with the engine running at 1,400 rpm for Figures 36, 37, 38, 39 and 40 and at 2,200 rpm for Figures 41, 42, 43, 44 and 45.
Example 2 Further experiments were carried out using a catalyst chamber as described in Figure 3. A knitted mesh substrate was fabricated from wire of diameter 10 thou". Two catalysts were prepared. The substrate for catalyst A was fabricated from wire of an alloy of the following composition.
% wt Cr 15 Al 4 Y 0.3 Fe balance The washcoat of alumina stablished with ceria was present at a loading of 0.13 g/g of wire substrate. The catalytic metal layer comprising 7~% Hr, 92~% Pt was applied at a loading of 80 g/cu ft.
Catalyst B had a washcoat of alumina at a loading of 0.2 g/g of wire onto which was applied the catalytic metal layer of 5~% Rh, 94.5% Pt with a loading of 7 g of catalytic metal over the three catalyst units. The substrate was fabricated from 310 stainless steel which was treated with a protective coating composition as described in our co-pending British Patent Application No.
GB 2,013 517A published August 15, 1979.

- 12a -~ 13 ~

The variation o~ the amount of hydrocarbo.ls, carbon monoxide, nitrogen oxides and particulates, present in the exhaust gas, with the Load of the .~.iesel engint as brake ~ean effective pressure was meas~red at 11~(!0 rpm and 2200 rpm for catalyst A. The fuci ~Ised ir. the engine ~as a high sulphur fuel containing 0.7% sulphur. Th~ variation of the partic~la,.os ~resent in the exhaust gas with the power of the engine was measured usir.g a low sulphur fuel containing 0.07~ sulphur in the engine with catalyst A in the catalyst chamber.

Using catalyst B the variation of the particulates ~ith the po-.~er o~ the engine was me~.sured with the engine running on h-gh and low s-~lphur fuels.

~ The results are given in graphical form in the a~tached Figures 22-35. Table 2 below gives the details of the mea~urements taken.

Table 2 ~pe~d of Pollutant in exhaust gas measured Catalyst engine in Fuel . Fig~-e rpm .

Hydrocarbons HC in ppm A 1,~00Hi~h S 22 Carbon monoxide C0 in ppm A 1,400 " 23 Particulates in g/hr A 1,400 " 24 Nitrogen oxides in p~m A 1,400 " 25 Hydrocarbons HC in ppm A 2,200 " 2~
Carbon monoxid~ C0 in ppm A 2,200 " 27 Particulates in g/hr A 2,200 " 28 Nitrogen oxides in ppm A 2,200 " 29 Particulates in g/hr A 1,400 Lo~ S 30 Particulates in g/hr A 2,200 " 31 B 1, 4 00Low and 32 high S
" . B 2,200" 33 B 1, 4 00High ~ 34 . " B 2,2Q0 " 35 1~

The two iines in Figures 22-31 sho~ the difference between the pollutants present in the exhaust gas when no catalyst chamber is used, 'ba.~eline', and after the exhaust gac has passed through a catalyst chamber.

y~ denotes b~seline measurements ,, denotes measurements alter exhaust gas lows passed through . the catalyst ~hamber In figures 32 and 33 -. denotes high sulphur fuel baseline measurement - denotes " " " after catalyst ~ denotes low " " baseline measurement 7 1~ denotes " " ". after catalyst ~ ' In Figures 34 and 3~

I Y~ ~ denotes baseline measurement denotes prellminary test after catalyst ~ , denotes after catalyst after 7 hours.
J " denotes after catalyst after 50 hours l Figures 34 and 35 show the effect of time on the properties of the ¦ catalyst.

The maximum temperature on the flange of the catalyst chamber when the engine is running at a speed of 2,200 rpm and 107 brake mean effect , pressure lb/in was 103 C and on the outer wall of the chamber was 75 C.
f The back pressure was negligible.

i5 The weight of particulates present in the exhaust gas was measured by passin~ a known volume of exhaust through a dilution tunnel where it W2S diluted with a set volu~.e of air to ~revent the solids settlin~
before passing the gases through a filter pad. The weight of particulates enables a value for the par~iculates in g/hr to be calculated. The particulates present ir the exhaust gas were analysed further to give thermogravimetric weight, and the weight of volatile components, hydrocarbons, carbon and sulphate. Using t~e above method a number o~ filter pads were obtained for analysis. The weight of sulphate in the particulates was measured by wet chemical analysis of the particulates. Another sample was placed in a thermo~ravimetric balance where the sample was heated in an inert atmosphere to a temperature of 780 C until the wei~'ht ~, was constant. The weight loss between the initial weight and the new gives the weight of volatile components present. A~r was introduc~3d and heating cont-nued until the weight was again constant. ~he difference in this weight and the value for the previous constant weight gives the weight of carbon components present. The re~ainder was ash and non-comoustible materials such as iron.
~.
' The results of the analysis of the partic~ tes present in the exhaust gas for an engine usin~ high and low sulphur fuels are given in Figures 46-49 Figurcs 46and 4iare with catalyst A in the catalyst ~hamber and Figures 4ga~ld4g are with catalyst B in the catalyst chamber.
'. .
Table 3 gives sulphate leYels in g/h~ in the particulates using a high and low sulphur fuel in the engine.

, Table 4 below gives sul~)hate levels in g/hr in the exhaust gas using a high sulphur fuel in the engine with catalyst B in the catalyst \ ~ _ 16 _ chamber. Measureme~ts were taken after 7 and 50 hours.

`
, _ 17 -. ~ . _ - Q~
E~
~ CO~ V~
¢ 2 ~ ~ ~ ~ o ¢ O O .,1 .rl O
C~ ~ Z Z ~ ~ "~
' ~1:' E~ 3 .
U~ ~
e~ OCn a~ ~ ~ ~r E~ Zo ~ O ~_l _ . ~ ~ N Z

Z ~
~U~
~ O =~ ~ ~ O~
V~ Z ~o o o o 0~ 0 t-m c~ m m o o J
_ ~ H V~ .
s o ,~ a~, ~ o ~
E~ ~~D . . . t_ ~ c~ . . t_ ~ a:~ -.~ . _ ~ U~
' ` ~ .
! ~ov~
.~ ~ ~ o~ ~ u~
~, ~ Cl . . ~. o~ ~ .
.
.
. H ~ ~q ~d S ~ ~ ~ U~ ~ O O
c/~ bl)1~ OC~
. m ~ :~ ~ _ ~ _ ~ ~ N

¦ . a~ H O
W IS~ 0 :~ ~ N
m ~~-- '~= - ~ ~
E~
' " ` ~
`

~ ~57783 _ 18 _ Table 4 _ .............. _ 1400 REV/MIN INITIAL LEVEL g/h AFTER 7 nOUR~ ~. TER 50 HOURS
STABLISING g/h STABLISING g/h load 2 3.60 0.67 0.6 " 50 2.64 1.32 0.9 " 100 37.68 22.80 9.6 . - , .' _ .
% load 100 53.28 36.20 55.7 " 50 18.00 21.10 15.1C
" 2 5.76 6I~o 2.3

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed, are defined as follows:

1. A diesel engine comprising one or more cylinders which can generate exhaust gas containing carbon particles when the engine is in operation, each cylinder having an exhaust port for discharging the exhaust gas, and the engine is provided with an exhaust pipe for venting the exhaust gas to atmosphere and in combination with the engine an apparatus suitable for oxidising the carbon particles wherein (a) the apparatus comprises a chamber and means for cooling the chamber and the chamber has at least one entry port in communication with an exhaust port and an exit port in communication with the exhaust pipe so that exhaust gas can pass from the exhaust port through the chamber and into the exhaust pipe, (b) the chamber contains an iterstitial catalyst system comprising a catalytic metal , a layer of refractory metal oxide and a substrate made from filamentary metallic material in a knitted or woven form , the catalyst being disposed on or throughout the layer of refractory metal oxide which in turn is disposed on the surface of the substrate;
(c) the substrate is mounted within the chamber spaced from the inner walls of the chamber so as to create an outer passageway, and is shaped so as to define a central passageway within the substrate, (d) wherein one of the passageways communicates with the entry port or ports and the other communicates with the exit port and the substrate is positioned so that substantially all the exhaust gas discharged from the or each cylinder is caused to pass through one passageway, then through the interstitial catalyst system and then through the other passageway, and (e) the outer and central passageways and the substrate are aligned relative to the entry port or ports such that exhaust gas passing through the chamber is caused to flow in a direction transverse to the entry port or ports during a portion of its passage through the chamber thereby increasing turbulence within the interstitial catalyst system.

2. A combination according to claim 1, wherein the outer and central passageways and the substrate extend in a direction transverse to the entry port or ports whereby exhaust gas passing through the passageways flows in a direction transverse to the entry port or ports.

3. A diesel engine according to claim 1 wherein the chamber has a number of entry ports corresponding to the number of cylinder exhaust ports.

4. A diesel engine according to claim 1 wherein the apparatus is disposed adjacent the cylinder exhaust ports.

5. A diesel engine according to claim 1 wherein the refractory metal oxide is selected from the group consisting of oxides of Mg, Ca, Sr, Ba, Sc, Y, the lanthanides, Ti, Zr, Hf, Th, Ta, V, Cr, Mn, Co, Ni, B, Al, Si and Sn.

6. A diesel engine according to claim 5, wherein the first layer is made from A12O3, alumina hydrates, BaO, TiO2, zrO2, HfO2, ThO2, or CrO2O3.

7. A diesel engine according to claim 1, wherein the substrate is made from a corrosion-resistant alloy containing a base metal.

8. A diesel engine according to claim 7, wherein the substrate is made from an alloy containing nickel and chromium, having an aggregate nickel plus chromium content greater than 20 weight precent.

9. A diesel engine according to claim 8, wherein the substrate is made from an alloy of iron including at least one of the elements:- chromium (3 to 40) wt %, aluminium (1 to 10) wt %, cobalt (trace to 5) wt %, nickel (trace to 72) wt % and carbon (trace to 0.5) wt %.

10. A diesel engine according to claim 8, wherein the base metal alloy includes yttrium in an amount of 0.1 to 3.0 wt %.

11. A diesel engine according to claim 1, wherein the substrate is made from a filamentary metallic material having a thickness falling within the range 0.0254 and 0.508 mm.

12. A diesel engine according to claim 1, wherein the catalytic metal is a metal selected from the group consisting of Ru, Rh, Pd, Ir, Pt, Fe, Co, Ni, V, Cr, Mo, W, Y, Ce, alloys containing at least one of said metals and intermetallic compounds containing at least 20 wt % of one or more of the said metals.

13. A diesel engine according to claim 1, wherein the means for cooling the chamber comprises a water jacket.

14. A diesel engine according to claim 13, wherein the water jacket is part of a water jacket covering substantially the whole of the engine