GB2486196A - Reducing exhaust emissions by controlling the exhaust composition entering a filter - Google Patents

Reducing exhaust emissions by controlling the exhaust composition entering a filter Download PDF

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Publication number
GB2486196A
GB2486196A GB1020595.3A GB201020595A GB2486196A GB 2486196 A GB2486196 A GB 2486196A GB 201020595 A GB201020595 A GB 201020595A GB 2486196 A GB2486196 A GB 2486196A
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United Kingdom
Prior art keywords
engine
filter
carbon
containing particles
exhaust
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
GB1020595.3A
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GB201020595D0 (en
Inventor
Annika C Kristoffersson
Per Ericsson
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GM Global Technology Operations LLC
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GM Global Technology Operations LLC
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Priority to GB1020595.3A priority Critical patent/GB2486196A/en
Publication of GB201020595D0 publication Critical patent/GB201020595D0/en
Publication of GB2486196A publication Critical patent/GB2486196A/en
Withdrawn legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
    • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
    • B01D53/9404—Removing only nitrogen compounds
    • B01D53/9409—Nitrogen oxides
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/0025—Controlling engines characterised by use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
    • F02D41/0047—Controlling exhaust gas recirculation [EGR]
    • F02D41/005—Controlling exhaust gas recirculation [EGR] according to engine operating conditions
    • F02D41/0052—Feedback control of engine parameters, e.g. for control of air/fuel ratio or intake air amount
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
    • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
    • B01D53/9459—Removing one or more of nitrogen oxides, carbon monoxide, or hydrocarbons by multiple successive catalytic functions; systems with more than one different function, e.g. zone coated catalysts
    • B01D53/9463—Removing one or more of nitrogen oxides, carbon monoxide, or hydrocarbons by multiple successive catalytic functions; systems with more than one different function, e.g. zone coated catalysts with catalysts positioned on one brick
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
    • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
    • B01D53/9495—Controlling the catalytic process
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/02—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust
    • F01N3/021—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters
    • F01N3/023—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters using means for regenerating the filters, e.g. by burning trapped particles
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/02—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust
    • F01N3/021—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters
    • F01N3/033—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters in combination with other devices
    • F01N3/035—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters in combination with other devices with catalytic reactors, e.g. catalysed diesel particulate filters
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/02—Circuit arrangements for generating control signals
    • F02D41/021—Introducing corrections for particular conditions exterior to the engine
    • F02D41/0235—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus
    • F02D41/024—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus to increase temperature of the exhaust gas treating apparatus
    • F02D41/025—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus to increase temperature of the exhaust gas treating apparatus by changing the composition of the exhaust gas, e.g. for exothermic reaction on exhaust gas treating apparatus
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2255/00—Catalysts
    • B01D2255/10—Noble metals or compounds thereof
    • B01D2255/102—Platinum group metals
    • B01D2255/1021—Platinum
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2255/00—Catalysts
    • B01D2255/20—Metals or compounds thereof
    • B01D2255/204—Alkaline earth metals
    • B01D2255/2042—Barium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2255/00—Catalysts
    • B01D2255/90—Physical characteristics of catalysts
    • B01D2255/91—NOx-storage component incorporated in the catalyst
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2255/00—Catalysts
    • B01D2255/90—Physical characteristics of catalysts
    • B01D2255/912—HC-storage component incorporated in the catalyst
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
    • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
    • B01D53/9404—Removing only nitrogen compounds
    • B01D53/9409—Nitrogen oxides
    • B01D53/9431—Processes characterised by a specific device
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
    • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
    • B01D53/944—Simultaneously removing carbon monoxide, hydrocarbons or carbon making use of oxidation catalysts
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/02—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust
    • F01N3/021—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters
    • F01N3/023—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters using means for regenerating the filters, e.g. by burning trapped particles
    • F01N3/0231—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters using means for regenerating the filters, e.g. by burning trapped particles using special exhaust apparatus upstream of the filter for producing nitrogen dioxide, e.g. for continuous filter regeneration systems [CRT]
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D2200/00—Input parameters for engine control
    • F02D2200/02—Input parameters for engine control the parameters being related to the engine
    • F02D2200/08—Exhaust gas treatment apparatus parameters
    • F02D2200/0806—NOx storage amount, i.e. amount of NOx stored on NOx trap
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D2200/00—Input parameters for engine control
    • F02D2200/02—Input parameters for engine control the parameters being related to the engine
    • F02D2200/08—Exhaust gas treatment apparatus parameters
    • F02D2200/0808—NOx storage capacity, i.e. maximum amount of NOx that can be stored on NOx trap
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/02—Circuit arrangements for generating control signals
    • F02D41/021—Introducing corrections for particular conditions exterior to the engine
    • F02D41/0235—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus
    • F02D41/027—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus to purge or regenerate the exhaust gas treating apparatus
    • F02D41/0275—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus to purge or regenerate the exhaust gas treating apparatus the exhaust gas treating apparatus being a NOx trap or adsorbent
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/02—Circuit arrangements for generating control signals
    • F02D41/021—Introducing corrections for particular conditions exterior to the engine
    • F02D41/0235—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus
    • F02D41/027—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus to purge or regenerate the exhaust gas treating apparatus
    • F02D41/029—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus to purge or regenerate the exhaust gas treating apparatus the exhaust gas treating apparatus being a particulate filter
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/02—Circuit arrangements for generating control signals
    • F02D41/14—Introducing closed-loop corrections
    • F02D41/1438—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor
    • F02D41/1444—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases
    • F02D41/146—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases the characteristics being an NOx content or concentration
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02C—CAPTURE, STORAGE, SEQUESTRATION OR DISPOSAL OF GREENHOUSE GASES [GHG]
    • Y02C20/00—Capture or disposal of greenhouse gases
    • Y02C20/10—Capture or disposal of greenhouse gases of nitrous oxide (N2O)
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/40—Engine management systems

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Health & Medical Sciences (AREA)
  • Biomedical Technology (AREA)
  • Environmental & Geological Engineering (AREA)
  • Analytical Chemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Exhaust Gas After Treatment (AREA)

Abstract

A method of reducing emissions in the exhaust system 20 of an engine 40 by providing a filter 10 for trapping carbon-containing particles and oxides of nitrogen and by controlling the composition of the exhaust supply to the filter so that the amount of carbon containing particles therein is equal to or excesses of the amount required for the reduction of the nitrogen oxides to nitrogen at all times. Preferably the required amount of carbon containing particles is provided by using an exhaust gas recirculation EGR system 24 or a direct injection arrangement to produce a stoichiometric ratio. An engine and exhaust system is also claimed as well as a filter for an exhaust system having a coating comprising a uniform mixture of platinum and barium oxide.

Description

Exhaust Sy!tems The present invention relates to filtering arrangements for, in particular, automotive exhaust systems and to an apparatus for dealing with carbon emissions and emissions of oxides of nitrogen.
Numerous proposals have been made to reduce such emissions.
US 6,753,294 discloses a filter in which diesel exhaust gas entering a reactor undergoes oxidation of HO, 00 and NO in the presence of a platinum coating. Soot in the gas is collected on the filter walls and is combusted by NO2 derived from the oxidation of NO. The gas, containing soot combustion products, passes through the wall of the filter and contacts a separate NOx trap coating of barium oxide, which absorbs NO. When sufficient NO2 is stored (as the nitrate, for example), which can be ascertained by the on-board diagnostics of the vehicle, the NOx-trap-coating is regenerated with a rich pulse of gaseous exhaust i.e. gas including excess reductant such as HO. The rich/lean cycling can be controlled using the vehicle's engine management system. The resulting NOx-rich gas contacts coating NOx-trap coating including the NOx reduction catalyst, which effects oxidation of HO and 00 and reduction of NOx to N2.
A disadvantage of the above-described arrangement is the periodic need for regeneration of the trap coating.
Other systems for reducing exhaust emissions are disclosed in US 2006/0133969, US 6,912,847 and EP 1079084.
Aspects of the present invention seeks to overcome or at least reduce the above disadvantage.
According to a first aspect of the present invention there is provided a method of reducing emissions in the exhaust system of an engine comprising providing a filter for trapping carbon-containing particles and oxides of nitrogen and controlling the composition of the exhaust supply to the composition of the exhaust supply to the reactor so that the amount of carbon-containing particles therein is equal to or in excess of the amount required for the reduction of the nitrogen oxides to nitrogen at substantially all times.
An advantage of the above-described method is that normal operation of the engine does not need to be interrupted to remove excess nitrogen oxides. Moreover, emissions can be reduced and there can be improvements in fuel economy.
Preferably, an exhaust gas recirculation arrangement is provided, the arrangement being so controlled that it provides a required amount of carbon-containing particles.
This arrangement permits a well-balanced control of the filter and avoids build-up of NOx emissions, on the one hand, and carbon-containing particles on the other.
According to a second aspect of the present invention, there is provided an engine having an exhaust system comprising a filter incorporating a medium arranged to trap carbon-containing particles and to receive oxides of nitrogen for reaction with the trapped carbon-containing particles, the engine being arranged to supply an amount of carbon- containing particles such that there are excess carbon-containing particles with respect to the amount needed for the reduction of the nitrogen oxides to nitrogen.
The engine preferably has an associated exhaust gas recirculating arrangement having a valve which is controlled to produce a required amount of carbon-containing particules.
The valve may be controlled by a NOx sensor positioned in the exhaust pipe downstream of the filter. Alternatively, or in addition, the valve may be controlled by an NOx sensor located upstream of the filter and/or by a temperature sensor. The more sensors there are used to control the operation of the valve, the more precisely the arrangement can be controlled.
The filter preferably has a coating comprising a substantially uniform mixture of platinum and barium oxide.
This has the advantage of facilitating a balance of polluting components at all locations of the filter.
According to a third aspect of the present invention there is provided a filter for an exhaust system for trapping carbon-containing particles and oxides of nitrogen, the filter having a coating comprising a substantially uniform mixture of platinum and barium oxide.
Preferred embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings of which; Figure 1 shows a sectional view of a catalytic wall-flow filter, for a diesel engine exhaust system in accordance with a first embodiment of the present invention; Figure 2 shows a schematic diagram of an engine and an exhaust system in accordance with a second embodiment of the present invention.
Referring to the drawings, Figure 1 shows a filter or reactor 10 for an exhaust emission reducing system for an automotive diesel engine. The filter 10 has the same general configuration as that disclosed in US 6,753,294 and comprises porous walls 12 plugged at the downstream end. The walls carry a coating 16 which is a washcoat comprising a substantially uniform mixture of barium oxide (BaO) and platinum (Pt) . The platinum serves to oxidise NO to NO2 and the barium oxide serves to store the NO2 as Ba (NO3)2. The soot, or other particulate matter trapped in the filter is oxidised by the NO2 to gaseous 00, which is then further cxidised by the platinum to relatively harmless 002. Thus the system comprises a particulate filter 10 with NOx storage capability to continuously reduce NOx by the trapped particulates. The particulates comprise carbon in the form of soot. The walls 12 have barium oxide deposited thereon or therein in order to trap the NOx for the purposes of oxidising the soot, the NOx itself being reduced to nitrogen.
Platinum deposited on or in the walls 12 produces the NOx from the original exhaust supply including NO. Instead of having NOx in excess, as in prior art arrangements, the operating conditions of the engine are set so that there is always arranged to be an excess of soot particles with respect to the amount needed for reduction of the NOx.
An advantage of the above-described system is that is operates uniformly and that no periods of rich operation are required to remove excess NOx. Thus there is no interruption to normal operation of the engine. Also, since no NOx reduction regeneration is necessary, this leads to advantages of fuel economy. The system meets the requirements of European emission standard 5 (euro 5) Arrangements according to the invention may operate with or without an associated exhaust gas recycling (EGR) system.
In arrangements without EGR, the engine separates both NOx and particulates in normal mode. Since both the washcoat and the filter have the potential to store a certain amount of NOx and soot, the ratio of the quantities thereof produced can vary over the cycle. However, if the washcoat is filled up with NOx there will be NOx slip through the system and if they system fills up with soot, the filter becomes clogged.
Accordingly, preferred embodiments of the present invention incorporate an EGR system to provide a balancing effect. If the NOx stage approaches a maximum threshold value, the soot emissions must be raised by increasing EGR. If on the other hand, the filter contains too much soot, the EGR is reduced so that more NOx is created to oxidise the soot particles.
A second embodiment of the present invention constitutes an exhaust emission reducing system for an automotive direct injected petrol engine operating stoichiometrically. Here, the air-to-fuel balancing can be performed so that soot in the particulate filter is continuously reduced by the NOx.
Figure 2 shows an engine 40 and an exhaust system 20 in accordance with a second embodiment of the present invention, which takes into account the above factors. A trap or filter 10, as shown in Figure 1 for example is connected in an exhaust pipe 22. An exhaust gas recycling (EGR) path 24 is connected from the exhaust pipe 22 to a point located upstream of engine 40. The directions of the flows of exhaust gases are shown by arrows. The amount of exhaust gas recycled through path 24, the EGR rate, is controlled by a continuously variable valve 26 which is operated in an opening or closing direction in dependence on the output of a NOx sensor 28 connected in the exhaust pipe 22 downstream of the filter 10.
The NC and particulate emissions strongly depend on the EGR rate. A low EGR rate or value gives low particulate and high NO emissions, whereas a high EGR rate gives an increase in particulates and reduction of NOR. If the NOx conversion is low for the trap 10, this means the system is full and no particulates are present for reduction of NOx stored in the washcoat as Ba(NO3)2. An increase of the EGR rate creates particulates which regenerate the NOx trap 10. Increased EGR also lowers the NOx-concentrating which minimizes the NOx release or slip out from the trap 10. The operating temperature of the system 20 is approximately 200-500°C, where soot oxidation in the presence of NO2 takes place.
Storage of NO2 in the BaO is less critically dependent on temperature.
The second embodiment has similar advantages to the first embodiment. Furthermore, both embodiments can be operated so that there is maximum conversion of both soot and NOx so as to provide minimal levels of overall pollution.
Instead of, or in addition to, the NO sensor 28, the valve 26 may also be dependent on the output of a NOx sensor 30 located upstream of the filter 10. In any of the above cases the operation cf the valve 26 may also be dependent on the output of a temperature sensor 32 located upstream of the trap 10. Valve 26 may be controlled in dependence on the output of a suitable lock-up table.
A system in accordance with the second embodiment may be used in connection with a diesel engine operating in accordance with European emission standard 6 and beyond.

Claims (15)

  1. CLAIMS1. A method of reducing emissions in the exhaust system (20) of an engine (40) comprising providing a filter (10) for trapping carbon-containing particles and oxides of nitrogen and controlling the composition of the exhaust supply to the composition of the exhaust supply to the reactor so that the amount of carbon-containing particles therein is equal to or in excess of the amount required for the reduction of the nitrogen oxides to nitrogen at substantially all times.
  2. 2. A method according to claim 1, wherein an exhaust gas recirculation arrangement (24) is provided, the arrangement being so controlled that it provides a required amount of carbon-containing particles.
  3. 3. A method according to claim 1 or 2, wherein the engine (40) is a diesel engine.
  4. 4. A method according to claim 1, wherein a direct injection arrangement is provided to produce a stoichiometric ratio, the arrangement being so controlled that it produces a required amount of carbon-containing particles.
  5. 5. A method according to claim 4, wherein the engine (40) is a direct-injected petrol engine.
  6. 6. An engine (40) having an exhaust system (20) comprising a filter (10) incorporating a medium (16) arranged to trap carbon-containing particles and to receive oxides of nitrogen for reaction with the trapped carbon-containing particles( the engine being arranged to supply an amount of carbon-containing particles such that there are excess carbon-containing particles with respect to the amount needed for the reduction of the nitrogen oxides to nitrogen.
  7. 7. An engine according to claim 6, wherein the medium (16) is a mixture comprising platinum and barium oxide.
  8. 8. An engine according to claim 7 wherein the mixture is in the form of a coating on the filter.
  9. 9. An engine according to any of claims 6 to 8 having an exhaust gas recirculating arrangement (24) having a valve (26) which is controlled to produce a required amount of carbon-containing particules.
  10. 10. An engine according to claim 9, wherein the valve (26) is controlled by a NOx sensor (28) positioned in the exhaust pipe (22) downstream of the filter (10)
  11. 11. An engine according to claim 9 or 10, wherein the valve (26) is controlled by a NOx sensor (30) positioned in the exhaust pipe (22) upstream of the filter (10)
  12. 12. An engine according to any of claims 6 to 11 which is a diesel engine.
  13. 13. An engine according to any of claims 6 to 8 having a direct injection arrangement which is arranged to produce a stoichiometric ratio and to produce a required amount of carbon-containing particles.
  14. 14. An engine according to claim 6 or 13 which is a direct-injected petrol engine.
  15. 15. A filter (10) for an exhaust system (20) for trapping carbon-containing particles and oxides of nitrogen, the filter having a coating (16) comprising a substantially uniform mixture of platinum and barium oxide.
GB1020595.3A 2010-12-06 2010-12-06 Reducing exhaust emissions by controlling the exhaust composition entering a filter Withdrawn GB2486196A (en)

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1108862A2 (en) * 1999-12-17 2001-06-20 Volkswagen Aktiengesellschaft Method and apparatus for reducing harmful constituents of exhaust gas of a combustion engine
EP1273779A2 (en) * 2001-06-22 2003-01-08 Nissan Motor Co., Ltd. Regeneration of diesel particulate filter for diesel engine
US7062904B1 (en) * 2005-02-16 2006-06-20 Eaton Corporation Integrated NOx and PM reduction devices for the treatment of emissions from internal combustion engines
GB2460397A (en) * 2008-05-19 2009-12-02 Ford Global Tech Llc Controlling the operation of an engine
EP2128393A1 (en) * 2008-05-29 2009-12-02 Hyundai Motor Company Exhaust gas post-processing apparatus and regeneration method thereof

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1108862A2 (en) * 1999-12-17 2001-06-20 Volkswagen Aktiengesellschaft Method and apparatus for reducing harmful constituents of exhaust gas of a combustion engine
EP1273779A2 (en) * 2001-06-22 2003-01-08 Nissan Motor Co., Ltd. Regeneration of diesel particulate filter for diesel engine
US7062904B1 (en) * 2005-02-16 2006-06-20 Eaton Corporation Integrated NOx and PM reduction devices for the treatment of emissions from internal combustion engines
GB2460397A (en) * 2008-05-19 2009-12-02 Ford Global Tech Llc Controlling the operation of an engine
EP2128393A1 (en) * 2008-05-29 2009-12-02 Hyundai Motor Company Exhaust gas post-processing apparatus and regeneration method thereof

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