CA1181350A

CA1181350A - Turbocharged i.c. engines

Info

Publication number: CA1181350A
Application number: CA000374271A
Authority: CA
Inventors: Bernard E. Enga; Edward R. Middleton; Graham A. Hards; Michael W. Saunders
Original assignee: Johnson Matthey PLC
Current assignee: Johnson Matthey PLC
Priority date: 1980-03-31
Filing date: 1981-03-31
Publication date: 1985-01-22
Also published as: FR2479323A1; GB2074888B; SE8102023L; IT1137322B; BR8101919A; FR2479323B1; MX7464E; GB2074888A; DE3112796A1; IT8120838A0

Abstract

ABSTRACT OF THE DISCLOSURE

This invention relates to a turbocharged diesel engine in combination with apparatus for oxidizing particles in the exhaust gas emitted from the engine. The chamber of the apparatus contains at least one interstitial catalyst system made of small diameter wire on which a layer of refractory metal oxide is disposed and on which in turn the catalyst is disposed. The catalyst comprises at least one of the metals platinum, palladium, rhodium, ruthenium or iridium. The apparatus significantly reduces the level of particulate matter and other pollutants from an exhaust gas emitted from a diesel engine.

Description

135~13 TUR8OCHARGED DIESEL ENGINE COMBINED WITH ~PPARATUS

FOR EXHAUST PVRIFICATION

This invention relates to a turbocharged diesel engine in combination with apparatus for oxidising particles i~ exhaust gas emieted from the engine.

Exhaust gas emit~ed from a diesel engine contains solid/liquid particles (ie solid particles having a liquid outer covering layer)~ Also prese~t are solid chain aggregate~ (in which spherical particles of between 100 to 800 x 10-1 m diameter link up together), liquid sulphates~ liquid hydrocarbons and '~ .

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~ 2 gaseous hydrocarbons such as aldehydes. The solid/liquid partlcles generally comprise carbon particles with adsorbed liquid hydrocarbons whereas the solid chain aggregates are generally composed of high molecular weight organic compounds and/or inorganic sulphates.

Abou~ 90Z of these particles have maximum dimensions of less than one micron which i8 within the respirable particle size and the maxlmum dlmensions of the remaining iO~ of these particles are le~s than four ~icrons. Usually, the catalytic oxidation of carbon particles takes place at about 400C whereas their normal (ie uncatalysed) temperature o~ combustion is 700 to 800C. For hydrocarbon par~icles cataly~lc oxidation will take place at ~e~peratures about 200C.

~ n ob~ect of the present inventlon is to reduce the quantity both of noxious gases and particles especially carbon particles present in exhaust gas emltted fro~ a turbocharged diesel engine. Noxious gases include hydrocarbons, oxide~ of nitrogen a~d carbon monoxide.

Accordingly this invention provides a turbocharged diesel engine in combination with apparatu~ suitable for oxidislng ,~ _ . , .

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particles in exhaust gas emitted from the engine wherein (a) the apparatus comprises ~alls defining a chamber havi.ng entry means for receiving exhaust gas from the engine and exit means through which the e~haust gas can leave the chamber, (b) the chamber contains at least one interstitial catalyst system comprising an interstitial support made from wire on -~llch is disposed a layer of refractory metal oxide and in turn there is disposed on or throughout the layer a catalyst comprising at least one of the metals platinum, palladium, rhodium, ruthen~um or iridium~

lS (c) the support is shaped 50 as to define an inner passageway within the support and i~ spaced fro~ -the chamber walls so as tG define an outer passageway outside the support, 20 (d) the inner passageway is closed in the region of one end of the support and the outer passageway is closed at least in the region of the other end and one oE the passageways communicates with the entry means and the other communicates with the exit means so that exhaust gas received through the entry means passes into one closed passageway and is then compelled to pass Phrough /

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the interstitital catalyst system into the other closed passgeway and (e) the inner and outer passage~ays are aligned relative to the entry mean~ such that exhaust glas flowing through the chamber is compelled to flo~ $n a direction transverse of the entry means during a portion of its passage through the chamber thereby increasing turbulence, lQ

~he catalyst comprises the metals platinum, palladium9 rhodi~m, ruthenium or iridium either alone or as an alloy or intermetallic compound containing at least 20 wt % o~ one or more of the metals.

The layer of refractory metal ogide is preferably a washcoat layer containing oxides o~ one or more members of the group consi~ting of Mg~ Ca, Sr, Ba, Sc, Y, the lanthanides, Ti, Zr, Hf, Th, Ta, V, Cr, ~n, Co, Ni, B, Al, Si and Sn~ Preferred washcoat material~ are A1203 and alumina hydrates and stabllsing oxides such as BaO and oxides promoting catalytic activity 8uch as TiO2, ZrO2, HfO2, ThO2, Cr203 and NiO are also preferably present.
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The wire from which the support is made is preferably formed from base metal alloys which are corrosion resistant and preferably oxidation resistant. Examples of such base metal alloys are nickel and chromill~ alloys having an aggregate Ni plus Cr content greater than 20% by weight and alloys of iro~ including at least one of the elements chromium (3 to 40) w~ %, aluminium (1 to 10) wt %, cobalt (trace to 5) wt %, nickel ~trace to 72) wt %
and carbon (trace to 0.5) wt %. Such supports are described in German DOS 2450664.

Other examples of base metals capable of withstanding the rigorous conditions required are iron-aluminium-chromium alloys which may also contaiD yttrium. The latter alloys may contain 0.5 to 12 wt-Z Al, 0.1 to 3.0 wt % Y, O to 20 ~t % Cr and balance Fe. These are described in United States Patent ~o. 302725Z.

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Alternatively the base metal alloys may have less corrosion resistance, eg mild steel, but with a protective coating compositlon covering the surface of the substrate as described in our co-pending British Patent application No. 7903817 dated

2 February 197g (now GB 2013517A).

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The thickness of the wire is pref~rably be~ween 0.254 to 508 mm and especially betwee~ 0.0254 to 0.305 mm~ Preferably prior to its fabrication into woven, knitted or crushed form, the wire is rolled down to a ribbon having two flat opposite surfaces.

The invention i6 further illustrated by the following specific embodiments described with reference to Figures 1 to 7 o~
the drawings and by the following Examples. In the drawings, Figure 1 show~ a section through an apparatus suitable for use in combination with a turbocharged diesel engine acording to the inventlon, Figures 2, each show on a larger scale sections 5, 6 and 7 through e~bodiments o~ alternative apparatus, Figure 3 shows in perspective an assembly of spaclng bars suitable for acting as a central framework to prevent the interstitial support collapsing in~ardly.

Figure 4 shows in perspective an alterna~ive central framework.

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~ 7 Figure 1 shows an apparatus 1 for use in combination with a turbocharged diesel engine (not shown~ in order to oxidise particles contained in exhaust gas emitted from the engine.
Apparatus 1 comprises walls 21a and 21b which define chamber 2 having entry ports 27 to 30 for receiving exhaust gas from the engine and having exit port 32 through which exhaust gas can leave chamber 2 and enter exhaust pipe 31. Entry ports 27 to 30 are suitable for mounting adjacent to and in communication wlth exhaust ports in the engine.

Chamber 2 contains interstitial catalyst system 23 comprising all interstitial support, a layer of refractory metal oxide and a catalyst. Interstitia1 catalyst system 23 is shaped around spacing tube 22 so as to define cylindrical inner passageway 3. Spacing tube 22 should be perforated or made from wire mesh so as to permit exhaust gas to flow from catalyst system 23 into inner passgeway 3, One end of inner passage~ay 3 is closed by disc 26 located at one end of catalyst system 23 and the other end of inner passageway 3 communicates with exit port 32.

Spaclng tube 22 i.9 supported centrally withl~ chamber 2 by means of annular disc 25 with the result that the support (not shown) within catalyst system 23 is spaced from chamber wall 21b '.~

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so as to define outer passageway 4 which communlcates with entry ports 27 to 30. Both ends of outer passageway 4 are closed by walls 21a. Inner and outer passage~ays 3 and 4 extend transversely of the direction of entry of exhaus~ gas into cha~ber 2 as shown by arrows F41 to F44.

Exhaust gas from the engine received by entry ports 27 to 30 passes into outer passagewy 4 and is then eompelled to pass through interstitial catalyst system 23 into inner passagew~y 3 where it ls compelled to execute a sharp turn as shown by arrow before leaving chamber 2 via exit port 32. Interstitial catalyst system 23 induces turbulence in the flow of exha~tst gas and the general direction of the turbulent flow through chamber 2 is indicated by arrows F41 to F45. In particular, flow ~ithin inner passa~eway 3 is transverse of the flow in entry ports F41 to F44.

The in~erstltial support in the catalyst system is preferably made of knitted wire mesh. This may be fabricated lnto a slngle monolith or it may be made up in annular secti.ons, The layer of reractory metal oxide ~7ashcoat and the catalyst may be applied to each sectlon of the wire support separately or after the sections have been linked together~ .

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3Sq3 _ 9 Figure 3 shows an alternative central structure in which in place of tube 22 ~here is provided a series of 5 rlgid spacing bars, 100 to 500, running the length of chamber 2~ Bars 100 to 500 are maintained in fixed spatial relationship to one another by spacing plates 600. Accordingly bars 100 to 500 hold catalyst system 23 rigidly in place within chamber 2. Spacing plates 600 in pairs connect thrae of the fi~e bars and are usually at right angles to each other thus being disposed along a diameter of central cylindrical passageway 3~ Two or more pairs of spacing plates 600 may be adapted to extend the whole leng~h of chamber 21b as shown in Figure 4 whereupon ~hey may be used as spacing means instead of bars 100 to 500.

Rods and spac~ng ~lates need to be constructed of a material resistant to oxidatlon up to at least 800C.

Figure 2 shows an alternative apparatus 5 in which a chamber 6 is defined by walls 100~ Chamber 6 has en~ry ports 101 and 102 comprising sleeves 106 and 107 adjacent to and in communication with engine exhaust ports ~not shown). Chamber 6 also has exit port 103 adjacent ~o an exhaust pipe (not shown).

Chamber 6 contains an interstitial catalyst system 104 (comprising a support, a layer of re~ractory metal oxide and a . ,~

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catalyst) shaped around spacing plates 105 as shown in Figure 4 so as to define an ~nner passageway 110. Catalyst system 104 is disposed centrally within chamber 6 and transversely of entry ports 101 and 102 so as to define an outer transverse passageway 104a. One end of inner passageway 110 is closed by disc 108 and one end of outer passageway 104a is closed by end ~all 104a.

Exhaust gas received by entry ports 101 and 102 flows into inner passageway 110 where it executes a sharp turn as lndicated by arrows Fg2 to Fgg and and is compelled to pass through interstit~al cataiyst system 104 into outer pasgeway 104a. In outer passageway 104a, the flow execu~es a further sharp turn so that the exhaus~ gas passes along outer pasageway 104a in a direction tra~sverse of its direction through entry ports 101 and 102. Passage through intersei~al catalyst system 104 imparts turbulence ~o the flow of exhaust gas and the ge~eral direction of turbulen~ flow through chamber 6 ls indicated by arrows FgO to Apparatus 5 would usually be used with more than two entry ports, but for simplicity only two are shown in Figure 2.

The support for the catalyst system 104 is preEerably of , ~8~3~i~

knitted wlre which may be made up into four sections or three units. If the support is in sections, eg of doughnut configuration, these are normally linked together before the support ~s placed in the chamber.

Figures 5 and 6 show a further alternative apparatus 7 in which walls 51 define a chamber 8 containing openiDgs 52 and 53. Chamber 8 contalns an interstitial catalyst sys~em 64 comprising a support 7 a layer of refractory metal oxide and a catalys~ and is shaped around spacing plates 65 so as to define innar passageway 60. Catalyst system 64 is spaced from walls 51 so as to define outer passageway 56. One end of inner passageway 60 is closed by disc 67 and the end of outer passageway 56 which is remote from disc 67 is closed by end wall 51 so that gas flowing from one passageway to the other is compelled to pass through interstitial catalyst system 64.

Figure 5 ShoW8 a chamber 8 sultable ~or yositioning between a turbocharger and an exhaus~ pipe ~neither shown).
Opening 52 i9 positioned ad~acent and in communication wlth the outlet from the turbocharger and so functlons as an entry por~
receiving exhaust gas. Opening 53 is positioned ad~acent the exhaust pipe and serves as an exit for the exhaust gas leavlng chamber 8. The ~low of exhaust gas ~hrough chamber 8 ls lndicated R~,

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by arrows Fsl to F66 from which it will be seen that the exhaust gas executes sharp turns and flows transversely of the axes of openings 52 and 53 during its passage through catalyst system 64.

Figure 6 lllus~rates the use of apparatus 7 downstream of a turbocharger whereupon opening 53 functions as the entry port . and o?ening 52 as the exit port. The flow of exhau3t gas is reversed as compared with th~t shown in Flgure 5. The flow is indicated by arrQW~ F71 to ~86-Figure 7 shows a modification of the embodiment show~ in Figure 5, the modification being suitable for use with large capacity engines.

The essential difference between the embodiment shown in Yigure 5 and the modiication is that chamber 9 of the modification contaLns a plural:Lty of ad~acent catalyst systems 203 to 205. System 204 is spaced apart from both systems 203 and 205 so as to define additional outer passageways between both systems 203 and 204 and systems 205 and 204.

Discs 209 to 211 close inner passageways in systems 203 to 205 and plate 212 closes ends of outer passagewaysO The flow ._4.,.~

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of exhaust gas through chamber 9 is indicated by arrows P20 to F24~.

~XAMPLE 1 In order to illustrate the per~ormance oE this lnvention, the exhaust syste~ leading from a turbocharged multicylinder engine of capacity 2000 cc and suitable for powering a commercially available diesel engined automobile was ~odified by fitting one of two alter~atlve e~haust-purification apparatus . dDwnstrea~ of the turbocharger between the outlet from the turbocharger and the exhaust pipe.. The alternative apparatus will be referred to as Apparatus A and Apparatus B~ Apparatus A was as described above with reference to Figure 6, tha~. is to say wlth e~haust gas flowing from central passageway 60 radially outwards into outer passageway 56. Apparatus B was as described above with reference to Figure 5, that is to say with exhaust gas flowlng radially i~ward~.

~ 1e inters~itial support for the catalyst was fabricated from knitted 310 stainless s~eel wire of diameter 0~254 mm which had been flattened. A layer of washcoat containlng alumina, barium oxide and ceria was applied at a loading of 0.34 g/g of B

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wire. The washcoated support was impregna~ed with 5.7% Rh, 94.5%
Pt at a loadlng of 918 g c~-3. The volume of support used was 2114.6 cm~3. The measurements were taken after the car had been driven 250 miles (400 km).
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The results were obtained by d~iving tha automobile through the LA4 diesel cycle. The L~4 cycla ~the Los Angeles cycle) is laid down by the Environmental Portection Age~cy (EPA~
in the United States aud is a standard tes-t cycle deivsed to simulate a dri~e to work in Los ~ngeles trafic conditions. It is furthermore a test which is used to show the effectiveness or otherwise of an exhaust-purification apparatus fitted to an automobile. The hydrocarbons, carbon monoxide, nitrogen oxides and particles present in the exhaust gas e~issions were measured in g/mile (or g/km). Baseline measure~ents were taken of the pollutant levels in the exhaust gas beore it passed through the apparatus.

The results are given in Table 1 as follows:-3~
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Baseline Apparatus Apparatus _ _ B
Particles 0.4 0.31 0032 g/mile (g/km) percen~age change (0.25) ~0,19) (0.20) NOX 1.75 2 2.1 g/mile (glkm) percen~age change (0.10) (1.24) (0.75) _ _ CO 1.25 0.2 0.46 g/mile (g/km) .
percentage change tO.76) (0~12) (0.29) ._ _ ..
Eydrocarbons 0.2 0.07 0.11 g/mile (g/bm) percentage change (0.12~ (0.04) (0.07) . . _ . _ Back ~axlmum~ 13545 22011 2268 Pressure percentage .
~m~2 difference ~ _ -62~5 -67.5 lS Minimum 3386 4402 4402 percentage .- difference -30 -30 . _ _ ___ A commercially available car with a 2.2 litre turbocharged diesel engine was fitted with Apparatus A downstream of the turbocharger as described above. The catalyst was supported on an interstitial support ~ade of knitted wire fabricated from 304 stainless steel wire of diameter 0.254 mm and B

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O.127 mm before being treated to produce flattened wire. Knitmesh fabricated from the small diameter wire was used to make up the inner portion of the support and the outer portion was made up from the knitmesh fabricated from the larger diameter wire. A
washcoat of alumina at a loading of 0.22 g/litre of the catalyst system. The catalytic metal used was 7-~ Rh 92~X Pt at a loading of 0.09% by weight~ The total volume of the catalyst system uas 2.6 litres~

With the car running through the LA4 cycle the baseline measurement of particles was 0.4 g/mile (0~25 g/~m3. After the exhaust had passed through the chamber the level of partlcles present was 0.19 gtmile (0.12 g¦km) which is a reduction o~
52.5%. The maximum back pressure over the whole system was 13545 ~2 EXAl~LE 3 A serles of tests were conducted using a diesel engine of capacity 14748 cm3 turbocharged to 1.6 bar. Apparatus was fitted 1.22 m from the turbocharger and contained catalyst systems arranged in parallel as shown in Figure 7 except that nine systems were used in parallel instead of three shown in Figure 7. The volume ;æ

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of the total catalyst system used was 21303 cm 3. The support, washcoat and catalytic metals used were the sa~e as for the catalyst system tested in Example 2.

The engine was run through the EPA 1980 new transient cycle test as laid dow~ by the EPA in the USA. Measurements of the lavel of particles present in the exhaust gas after tha catalyst chamber were taken at intervals of 5 hours, The results are given in Table 2 below.

Particles in g MLT-l BaselineAfter catalyst Percentage cha~ber change _ _ . _ 0~224 0.0745 66.7 0.0782 65 0.0745 66.7 0.1043 53.4 0.0820 63.4 0.0708 68.4 0.0782 65 - - ~ 58.4 B

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The level of hydrocarbons in the exhaust gas wa5 reduced from 600 ppm to 12 ppm by the apparatus. The maximum temperature of the exhaust through the apparatus was 388C. The ~aximum back pressure of the chamber was 249 ~m-2.

The examples show the effectiveness of the apparatus in removing particles and other pollutants from an exhaust gas emitted from a diesel e~gine even when the appartus is posi~ioned at a di~tance from the engine and has to operate at a }ower temperature.

Claims

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

1. A turbocharged diesel engine in combination with apparatus suitable for oxidizing particles contained in exhaust gas emitted from the engine to a turbocharger positioned to receive exhaust gas from the engine wherein:
(a) the apparatus comprises walls defining a chamber having entry means for receiving exhaust gas from the turbocharger and exit means through which the exhaust gas can leave the chamber, (b) the chamber contains at least one interstitial catalyst system suitable for oxidizing the particles en-trained in the exhaust gas comprising an interstitial support made from wire on which is disposed a layer of refractory metal oxide and in turn there is disposed on or throughout the layer a catalyst comprising at least one of the metals platinum, palladium, rhodium, ruthenium or iridium, (c) the support is shaped so as to define an inner passageway within the support and is spaced from the chamber walls so as to define an outer passageway outside the support, (d) the inner passageway is closed in the region of one end of the support and the outer passageway is closed at least in the region of the other end and one of the passageways communicates with the entry means and the other communicates with the exit means so that exhaust gas

Claim 1 con-t.

received through the entry means passes into one closed passageway and is then compelled to pass through the inter-stitial catalyst system into the other closed passageway and (e) the inner and outer passageways are aligned relative to the entry means such that exhaust gas flowing through the chamber is compelled to flow in a direction transverse of the entry means during a portion of its passage through the chamber thereby increasing turbulence.
2. A combination as claimed in claim 1 wherein the chamber contains a plurality of catalyst systems at least two of which are adjacent and spaced apart so as to define an outer passageway extending between them.
3. A combination according to claim 2 wherein the interstitial support is made from woven, knitted or crushed wire.
4. A combination according to claim 1, 2 or 3 wherein the inner and outer passageways extend transversely of the direction of entry of exhaust gas into the chamber.
5. A combination according to claim 1, 2 or 3 wherein the inner and outer passageways extend parallel to the di-rection of entry of the exhaust gas into the chamber so that in passing from one passageway to the other the exhaust gas is compelled to flow transversely of its direction of entry into the chamber.
6. A combination according to claim 1, 2 or 3 wherein the interstitial support comprises one or more sections having a doughnut configuration.
7. A combination according to claim 1, 2 or 3 wherein the wire from which the support is made is flat and has a thickness of from 0.0254 to 0.508 mm.
8. A combination according to claim 1, 2 or 3 wherein the apparatus is located downstream of a turbocharger.
9. A process for oxidizing particles in exhaust gas emitted from a turbocharged diesel engine wherein the exhaust gas is passed through an apparatus as defined in claim 1, 2 or 3 whereby combustion can begin at temperatures below 400°C.