WO2007086781A1 - Exhaust gas aftertreatment system - Google Patents

Exhaust gas aftertreatment system Download PDF

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Publication number
WO2007086781A1
WO2007086781A1 PCT/SE2006/000113 SE2006000113W WO2007086781A1 WO 2007086781 A1 WO2007086781 A1 WO 2007086781A1 SE 2006000113 W SE2006000113 W SE 2006000113W WO 2007086781 A1 WO2007086781 A1 WO 2007086781A1
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WO
WIPO (PCT)
Prior art keywords
catalytic converter
scr
exhaust gas
soot
injector
Prior art date
Application number
PCT/SE2006/000113
Other languages
French (fr)
Inventor
Gert-Ove WAHLSTRÖM
Paulina Ramfelt
Original Assignee
Volvo Lastvagnar Ab
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Volvo Lastvagnar Ab filed Critical Volvo Lastvagnar Ab
Priority to CNA200680051744XA priority Critical patent/CN101336337A/en
Priority to US12/159,406 priority patent/US20090007551A1/en
Priority to BRPI0621003-1A priority patent/BRPI0621003A2/en
Priority to EP06701333A priority patent/EP1979586A4/en
Priority to PCT/SE2006/000113 priority patent/WO2007086781A1/en
Priority to JP2008551215A priority patent/JP2009524758A/en
Publication of WO2007086781A1 publication Critical patent/WO2007086781A1/en

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Classifications

    • 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
    • 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
    • F01N1/00—Silencing apparatus characterised by method of silencing
    • F01N1/003—Silencing apparatus characterised by method of silencing by using dead chambers communicating with gas flow passages
    • F01N1/006—Silencing apparatus characterised by method of silencing by using dead chambers communicating with gas flow passages comprising at least one perforated tube extending from inlet to outlet of the silencer
    • 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
    • F01N1/00—Silencing apparatus characterised by method of silencing
    • F01N1/02—Silencing apparatus characterised by method of silencing by using resonance
    • F01N1/023—Helmholtz resonators
    • 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
    • F01N13/00—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00
    • F01N13/009—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00 having two or more separate purifying devices arranged in series
    • 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
    • F01N13/00—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00
    • F01N13/009—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00 having two or more separate purifying devices arranged in series
    • F01N13/0097—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00 having two or more separate purifying devices arranged in series the purifying devices are arranged in a single housing
    • 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
    • F01N13/00—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00
    • F01N13/011—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00 having two or more purifying devices arranged in parallel
    • F01N13/017—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00 having two or more purifying devices arranged in parallel the purifying devices are arranged in a single housing
    • 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
    • F01N3/0335—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 exhaust silencers in a single housing
    • 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
    • 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
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/105—General auxiliary catalysts, e.g. upstream or downstream of the main catalyst
    • F01N3/106—Auxiliary 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
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/18—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control
    • F01N3/20—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control specially adapted for catalytic conversion ; Methods of operation or control of catalytic converters
    • F01N3/2066—Selective catalytic reduction [SCR]
    • 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
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/24—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by constructional aspects of converting apparatus
    • F01N3/28—Construction of catalytic reactors
    • F01N3/2882—Catalytic reactors combined or associated with other devices, e.g. exhaust silencers or other exhaust purification devices
    • F01N3/2885—Catalytic reactors combined or associated with other devices, e.g. exhaust silencers or other exhaust purification devices with exhaust silencers in a single housing
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
    • F02B37/00—Engines characterised by provision of pumps driven at least for part of the time by exhaust
    • 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
    • F01N1/00—Silencing apparatus characterised by method of silencing
    • F01N1/003—Silencing apparatus characterised by method of silencing by using dead chambers communicating with gas flow passages
    • 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
    • F01N2610/00—Adding substances to exhaust gases
    • F01N2610/02—Adding substances to exhaust gases the substance being ammonia or urea
    • 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
    • Y02T10/12—Improving ICE efficiencies

Definitions

  • the present invention relates to an exhaust gas aftertreatment system for treating exhaust gases from an internal combustion engine, comprising a soot catalytic converter and an SCR catalytic converter, which reduces NOx-emissions by means of a reagent delivered via a nozzle located upstream of the SCR catalytic converter.
  • SCR Selective Catalytic Reduction
  • a reagent in the form a urea/water solution, for example, is injected upstream of an SCR catalytic converter.
  • DPF Diesel Particulate Filters
  • NO 2 is another system which reduces engine particulate emissions (which consist primarily of carbon) .
  • NO 2 is produced by means of an oxidation catalytic converter located upstream of the particulate filter.
  • particulate filter Various types exist, of which the so-called “wall flow” cordierite filter has been the most commonly used. Another type of filter that has emerged of late is the so-called “flow-through” filter. The latter is characterized in that it has a lower - - particulate reduction and is ash-permeable, thereby requiring no servicing.
  • Variants exist in which a hydrolysis catalytic converter may also be incorporated, primarily into the SCR catalytic converter, and the particulate filter may be catalytically coated, thereby avoiding the first oxidation catalytic converter downstream of the engine. They are all characterized, however, in that the particulate filter is located upstream of the urea injection. This has been essential where "wall flow" cordierite filters were used, due among other things to the fact that these collect ash, primarily calcium sulfate (i.e. gypsum), which presents problems if urea/water solution is injected upstream. They are further characterized by a considerable porous mass, which absorbs the ammonia formed and thereby makes transient urea dosing more difficult.
  • An object of the invention is therefore to provide an effective exhaust gas aftertreatment system which is more compact that known systems.
  • the exhaust gas aftertreatment system according to the invention for treating exhaust gases from an internal combustion engine comprises a soot catalytic converter and an SCR catalytic converter, which reduces NOx- emissions by means of a reagent delivered via a nozzle located upstream of the SCR catalytic converter and is characterized in that the soot catalytic converter is located between the nozzle and the SCR catalytic converter.
  • FIG. 1 shows a schematic representation of an internal combustion engine having an exhaust gas aftertreatment system according to the invention
  • Fig. 2 shows in more detail a longitudinal section through a treatment unit forming part of the exhaust gas aftertreatment system according to
  • Fig. 3 correspondingly shows a cross-section through the treatment unit according to Fig. 2. - -
  • the internal combustion engine 10 represented schematically in Fig. 1 comprises an engine block 11 having six piston cylinders 12 with an inlet manifold 13 and an exhaust manifold 14. Exhaust gases from the engine are led via an exhaust line 15 to a turbine rotor 17 of a turbocharger unit 16.
  • the turbine shaft 18 drives the compressor wheel 19 of the turbocharger unit, which via an inlet line 20 compresses intake air and delivers it via an intercooler 21 to the inlet manifold 13.
  • Fuel is fed to each cylinder 12 via injection devices (not shown) .
  • injection devices not shown
  • Exhaust gases that have passed through the turbocharger unit 16 are led onwards via the exhaust line 22 to an oxidation catalytic converter 23 for the production of NO 2 for the exhaust gas flow.
  • a unit 24 for removing soot particles and NO x from the exhaust gas flow Downstream of the oxidation catalytic converter is a unit 24 for removing soot particles and NO x from the exhaust gas flow, which unit will be described with reference to Fig. 2.
  • the unit 24 comprises an oval cylindrical casing 26 having two end walls 27, 28 and three internal dividing walls 29, 30, 31.
  • An inlet pipe 32 extends from the side in through the casing 26 and via a pipe bend onwards in the longitudinal direction of the casing through the three dividing walls 29-31 to a distributing space 33 at the end wall 27.
  • Two catalytic converter units 34, 35 are fitted in parallel, each in its pipe in the casing, said pipes extending through the three dividing walls 29-31 with internal sealing in relation to said walls and external sealing in relation to the outer casing 26, in order to form two separate internal spaces 36, 37 in the casing.
  • the space 36 situated nearest the distributing space 33 communicates via perforations 38 with the exhaust inlet 32.
  • the space 36 therefore communicates with the distributing space 33 via the inlet pipe 32.
  • a further connection between the distributing space 33 and the space 36 is provided via a pipe 39, which extends between the distributing space 33 and the space 37, by the side of the other pipes in the casing 26.
  • the pipe 39 is provided with perforations into the space 36 on the one hand and into the space 37 on the other. The provision of the pipe 39 allows the otherwise enclosed space 37 to serve as a sound-damping
  • the pipe 39 forms a flow path from the space 36 to the distributing space 33 via said perforations, the flow path reducing the pressure gradient into the distributing space and furthermore increasing the scope for gasifying of the reagent in the exhaust gas flow.
  • the distributing space 33 distributes the exhaust gas flow entering via the inlet pipe 32 and the pipe 39 to the two catalytic converter units 34, 35, which are both identically fitted each with its particulate filter 40 of the soot catalytic converter type.
  • the exhaust gas flow from this particulate filter thereafter passes through an SCR-catalytic converter - -
  • the embodiment of the aftertreatment unit 24 according to the invention in which the exhaust gas flow passes through the particulate filter 40 before it reaches the SCR catalytic converter 41, allows the injector 25 to be located advantageously close to the unit 24. Distribution and gasification of the reagent in the exhaust gas flow occurs in the pipes 32, 39, the distributing space 33 and the particulate filter 40. At the same time it becomes possible to locate the particulate filter, the SCR-catalytic converter and the oxidation catalytic converter as a common unit 24 in one and the same casing 26. If the injector 25 were instead to be located between the particulate filter and SCR- catalytic converter, the entire exhaust gas aftertreatment system would have to be configured differently, taking up more space.
  • the aftertreatment unit 24 need not be provided with multiple catalytic converter units arranged in parallel.

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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)
  • Toxicology (AREA)
  • Materials Engineering (AREA)
  • Exhaust Gas After Treatment (AREA)

Abstract

The invention relates to an exhaust gas after treatment system for treating exhaust gases from an internal combustion engine (10) . The system comprises a soot catalytic converter (40) and an SCR catalytic converter (41) , which reduces NOx- emissions by means of a reagent delivered via an injector located upstream of the SCR catalytic converter. According to the invention the soot catalytic converter (40) is located between the injector (25) and the SCR-catalytic converter (41).

Description

TITLE:
Exhaust gas aftertreatment system
FIELD OF THE INVENTION:
The present invention relates to an exhaust gas aftertreatment system for treating exhaust gases from an internal combustion engine, comprising a soot catalytic converter and an SCR catalytic converter, which reduces NOx-emissions by means of a reagent delivered via a nozzle located upstream of the SCR catalytic converter.
BACKGROUND OF THE INVENTION: Increasing requirements aimed at reducing exhaust emissions from heavy trucks and buses are leading to ever more advanced systems of exhaust gas aftertreatment. SCR (Selective Catalytic Reduction) is one such system for reducing NOx emissions, in which a reagent, in the form a urea/water solution, for example, is injected upstream of an SCR catalytic converter. DPF (Diesel Particulate Filters), in which the soot is burned by means of NO2 (so-called CRT or Continuously Regenerating Trap) , is another system which reduces engine particulate emissions (which consist primarily of carbon) . NO2 is produced by means of an oxidation catalytic converter located upstream of the particulate filter.
Various types of particulate filter exist, of which the so-called "wall flow" cordierite filter has been the most commonly used. Another type of filter that has emerged of late is the so-called "flow-through" filter. The latter is characterized in that it has a lower - - particulate reduction and is ash-permeable, thereby requiring no servicing.
The more stringent emission requirements are leading to a need to combine these two types of exhaust gas aftertreatment system, which often presents problems of insufficient installation space.
In hitherto known combined exhaust gas aftertreatment systems (SCR + DPF) , the systems comprise components fitted in the following order:
Figure imgf000003_0001
Variants exist in which a hydrolysis catalytic converter may also be incorporated, primarily into the SCR catalytic converter, and the particulate filter may be catalytically coated, thereby avoiding the first oxidation catalytic converter downstream of the engine. They are all characterized, however, in that the particulate filter is located upstream of the urea injection. This has been essential where "wall flow" cordierite filters were used, due among other things to the fact that these collect ash, primarily calcium sulfate (i.e. gypsum), which presents problems if urea/water solution is injected upstream. They are further characterized by a considerable porous mass, which absorbs the ammonia formed and thereby makes transient urea dosing more difficult. SUMMARY OF THE INVENTION:
An object of the invention is therefore to provide an effective exhaust gas aftertreatment system which is more compact that known systems.
The exhaust gas aftertreatment system according to the invention for treating exhaust gases from an internal combustion engine comprises a soot catalytic converter and an SCR catalytic converter, which reduces NOx- emissions by means of a reagent delivered via a nozzle located upstream of the SCR catalytic converter and is characterized in that the soot catalytic converter is located between the nozzle and the SCR catalytic converter. This embodiment of the arrangement makes it possible to assemble multiple system components into one compact unit.
Advantageous exemplary embodiments of the invention are set forth in the following dependent claims .
BRIEF DESCRIPTION OF THE DRAWINGS:
The invention will be described in more detail below with reference to exemplary embodiments shown in the drawings attached, in which Fig. 1 shows a schematic representation of an internal combustion engine having an exhaust gas aftertreatment system according to the invention,
Fig. 2 shows in more detail a longitudinal section through a treatment unit forming part of the exhaust gas aftertreatment system according to
Fig. 1, and
Fig. 3 correspondingly shows a cross-section through the treatment unit according to Fig. 2. - -
DESCRIPTION OF PREFERRED EMBODIMENTS:
The internal combustion engine 10 represented schematically in Fig. 1 comprises an engine block 11 having six piston cylinders 12 with an inlet manifold 13 and an exhaust manifold 14. Exhaust gases from the engine are led via an exhaust line 15 to a turbine rotor 17 of a turbocharger unit 16. The turbine shaft 18 drives the compressor wheel 19 of the turbocharger unit, which via an inlet line 20 compresses intake air and delivers it via an intercooler 21 to the inlet manifold 13. Fuel is fed to each cylinder 12 via injection devices (not shown) . Although the figure illustrates a six-cylinder engine, the invention may also be used in conjunction with other cylinder configurations.
Exhaust gases that have passed through the turbocharger unit 16 are led onwards via the exhaust line 22 to an oxidation catalytic converter 23 for the production of NO2 for the exhaust gas flow. Downstream of the oxidation catalytic converter is a unit 24 for removing soot particles and NOx from the exhaust gas flow, which unit will be described with reference to Fig. 2. An injector 25 for mixing a reagent, such as urea or ammonia, for example, into the exhaust gas flow, is located upstream of the unit 24.
The unit 24 comprises an oval cylindrical casing 26 having two end walls 27, 28 and three internal dividing walls 29, 30, 31. An inlet pipe 32 extends from the side in through the casing 26 and via a pipe bend onwards in the longitudinal direction of the casing through the three dividing walls 29-31 to a distributing space 33 at the end wall 27. Two catalytic converter units 34, 35 are fitted in parallel, each in its pipe in the casing, said pipes extending through the three dividing walls 29-31 with internal sealing in relation to said walls and external sealing in relation to the outer casing 26, in order to form two separate internal spaces 36, 37 in the casing. The space 36 situated nearest the distributing space 33 communicates via perforations 38 with the exhaust inlet 32. The space 36 therefore communicates with the distributing space 33 via the inlet pipe 32.
A further connection between the distributing space 33 and the space 36 is provided via a pipe 39, which extends between the distributing space 33 and the space 37, by the side of the other pipes in the casing 26. The pipe 39 is provided with perforations into the space 36 on the one hand and into the space 37 on the other. The provision of the pipe 39 allows the otherwise enclosed space 37 to serve as a sound-damping
Helmholtz resonator for sound waves that occur in the exhaust gas flow from the engine 10. In addition, the pipe 39 forms a flow path from the space 36 to the distributing space 33 via said perforations, the flow path reducing the pressure gradient into the distributing space and furthermore increasing the scope for gasifying of the reagent in the exhaust gas flow.
The distributing space 33 distributes the exhaust gas flow entering via the inlet pipe 32 and the pipe 39 to the two catalytic converter units 34, 35, which are both identically fitted each with its particulate filter 40 of the soot catalytic converter type. The exhaust gas flow from this particulate filter thereafter passes through an SCR-catalytic converter - -
41, in which ammonia reacts with NOx to form N2. Finally the exhaust gas flow passes through an oxidation - catalytic converter 42, which removes any residual ammonia from the exhaust gas flow. The exhaust gas flow is then led via an outlet space 43 to an exhaust outlet 44.
The embodiment of the aftertreatment unit 24 according to the invention, in which the exhaust gas flow passes through the particulate filter 40 before it reaches the SCR catalytic converter 41, allows the injector 25 to be located advantageously close to the unit 24. Distribution and gasification of the reagent in the exhaust gas flow occurs in the pipes 32, 39, the distributing space 33 and the particulate filter 40. At the same time it becomes possible to locate the particulate filter, the SCR-catalytic converter and the oxidation catalytic converter as a common unit 24 in one and the same casing 26. If the injector 25 were instead to be located between the particulate filter and SCR- catalytic converter, the entire exhaust gas aftertreatment system would have to be configured differently, taking up more space.
The invention must not be regarded as being limited to the exemplary embodiments described above, a number of further variants and modifications being feasible without departing from the scope of the following patent claims. For example, the aftertreatment unit 24 need not be provided with multiple catalytic converter units arranged in parallel.

Claims

- -CLAIMS
1. An exhaust gas aftertreatment system for treating B exhaust gases from an internal combustion engine (10) , comprising a soot catalytic converter (40) and a SCR- catalytic converter (41) , which reduces NOx-emissions by means of a reagent delivered via an injector (25) located upstream of the SCR catalytic converter, 0 characterized in that the soot catalytic converter (40) is located between the injector (25) and the SCR catalytic converter (41) .
2. The system as claimed in claim 1, characterized in 5 that an oxidation catalytic converter (42) is located downstream of the SCR-catalytic converter (41) .
3. The system as claimed in claim 2, characterized in that the soot catalytic converter (40), the SCR 0 catalytic converter (41) and the oxidation catalytic converter (42) are arranged in series inside a common casing (26) .
4. The system as claimed in any one of claims 1 to 3 , 5 characterized in that the casing (26) is divided by means of internal dividing walls (29-31) to form distributing spaces (33, 43) at the ends of the casing and an acoustically active space (42) situated between these spaces . 0
5. The system as claimed in any one of claims 1 to 4, characterized in that the injector (25) for delivering reagent is located alongside a connection (32) for an admission line (15) for exhaust gases from the internal 5 combustion engine (10) . - -
6. The system as claimed in claim 5, characterized in that an oxidation catalytic converter (23) is located in the admission line (15) upstream of the nozzle (25) .
PCT/SE2006/000113 2006-01-24 2006-01-24 Exhaust gas aftertreatment system WO2007086781A1 (en)

Priority Applications (6)

Application Number Priority Date Filing Date Title
CNA200680051744XA CN101336337A (en) 2006-01-24 2006-01-24 Exhausted gas post-processing system
US12/159,406 US20090007551A1 (en) 2006-01-24 2006-01-24 Exhaust Gas Aftertreatment System
BRPI0621003-1A BRPI0621003A2 (en) 2006-01-24 2006-01-24 exhaust gas aftertreatment system
EP06701333A EP1979586A4 (en) 2006-01-24 2006-01-24 Exhaust gas aftertreatment system
PCT/SE2006/000113 WO2007086781A1 (en) 2006-01-24 2006-01-24 Exhaust gas aftertreatment system
JP2008551215A JP2009524758A (en) 2006-01-24 2006-01-24 Exhaust gas aftertreatment system

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/SE2006/000113 WO2007086781A1 (en) 2006-01-24 2006-01-24 Exhaust gas aftertreatment system

Publications (1)

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WO2007086781A1 true WO2007086781A1 (en) 2007-08-02

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PCT/SE2006/000113 WO2007086781A1 (en) 2006-01-24 2006-01-24 Exhaust gas aftertreatment system

Country Status (6)

Country Link
US (1) US20090007551A1 (en)
EP (1) EP1979586A4 (en)
JP (1) JP2009524758A (en)
CN (1) CN101336337A (en)
BR (1) BRPI0621003A2 (en)
WO (1) WO2007086781A1 (en)

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Also Published As

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EP1979586A4 (en) 2010-03-10
US20090007551A1 (en) 2009-01-08
EP1979586A1 (en) 2008-10-15
BRPI0621003A2 (en) 2011-11-29
CN101336337A (en) 2008-12-31
JP2009524758A (en) 2009-07-02

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