CN105813715A - Particulate filter designed as a wall-flow filter - Google Patents

Particulate filter designed as a wall-flow filter Download PDF

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Publication number
CN105813715A
CN105813715A CN201380081133.XA CN201380081133A CN105813715A CN 105813715 A CN105813715 A CN 105813715A CN 201380081133 A CN201380081133 A CN 201380081133A CN 105813715 A CN105813715 A CN 105813715A
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CN
China
Prior art keywords
substrate
filter
particulate filter
porosity
waste gas
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Pending
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CN201380081133.XA
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Chinese (zh)
Inventor
K.施赖韦
S.斯泰格特
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HJS Emission Technology GmbH and Co KG
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HJS Emission Technology GmbH and Co KG
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Publication of CN105813715A publication Critical patent/CN105813715A/en
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
    • B01D46/24—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies
    • B01D46/2403—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies characterised by the physical shape or structure of the filtering element
    • B01D46/2418—Honeycomb filters
    • B01D46/2425—Honeycomb filters characterized by parameters related to the physical properties of the honeycomb structure material
    • B01D46/24491—Porosity
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
    • B01D46/24—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies
    • B01D46/2403—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies characterised by the physical shape or structure of the filtering element
    • B01D46/2418—Honeycomb filters
    • B01D46/2425—Honeycomb filters characterized by parameters related to the physical properties of the honeycomb structure material
    • B01D46/2429—Honeycomb filters characterized by parameters related to the physical properties of the honeycomb structure material of the honeycomb walls or cells
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
    • B01D46/24—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies
    • B01D46/2403—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies characterised by the physical shape or structure of the filtering element
    • B01D46/2418—Honeycomb filters
    • B01D46/2425—Honeycomb filters characterized by parameters related to the physical properties of the honeycomb structure material
    • B01D46/24492—Pore diameter
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
    • B01D46/24—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies
    • B01D46/2403—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies characterised by the physical shape or structure of the filtering element
    • B01D46/2418—Honeycomb filters
    • B01D46/2451—Honeycomb filters characterized by the geometrical structure, shape, pattern or configuration or parameters related to the geometry of the structure
    • B01D46/2474—Honeycomb filters characterized by the geometrical structure, shape, pattern or configuration or parameters related to the geometry of the structure of the walls along the length of the honeycomb
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
    • B01D46/24—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies
    • B01D46/2403—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies characterised by the physical shape or structure of the filtering element
    • B01D46/2418—Honeycomb filters
    • B01D46/2451—Honeycomb filters characterized by the geometrical structure, shape, pattern or configuration or parameters related to the geometry of the structure
    • B01D46/2482—Thickness, height, width, length or diameter
    • 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
    • F01N3/022—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 characterised by specially adapted filtering structure, e.g. honeycomb, mesh or fibrous
    • F01N3/0222—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 characterised by specially adapted filtering structure, e.g. honeycomb, mesh or fibrous the structure being monolithic, e.g. honeycombs
    • 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
    • F01N3/18—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
    • F01N3/2803—Construction of catalytic reactors characterised by structure, by material or by manufacturing of catalyst support
    • F01N3/2825—Ceramics
    • F01N3/2828—Ceramic multi-channel monoliths, e.g. honeycombs
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2255/00—Catalysts
    • B01D2255/90—Physical characteristics of catalysts
    • B01D2255/903—Multi-zoned catalysts
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2255/00—Catalysts
    • B01D2255/90—Physical characteristics of catalysts
    • B01D2255/92—Dimensions
    • B01D2255/9205—Porosity
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2258/00—Sources of waste gases
    • B01D2258/01—Engine exhaust gases
    • B01D2258/012—Diesel engines and lean burn gasoline engines
    • 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
    • F01N2330/00—Structure of catalyst support or particle filter
    • F01N2330/06—Ceramic, e.g. monoliths
    • 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
    • F01N2330/00—Structure of catalyst support or particle filter
    • F01N2330/30—Honeycomb supports characterised by their structural details
    • F01N2330/32—Honeycomb supports characterised by their structural details characterised by the shape, form or number of corrugations of plates, sheets or foils
    • 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
    • F01N2330/00—Structure of catalyst support or particle filter
    • F01N2330/60—Discontinuous, uneven properties of filter material, e.g. different material thickness along the longitudinal direction; Higher filter capacity upstream than downstream in same housing
    • 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

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Geometry (AREA)
  • Physics & Mathematics (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Health & Medical Sciences (AREA)
  • Ceramic Engineering (AREA)
  • Toxicology (AREA)
  • Biomedical Technology (AREA)
  • Environmental & Geological Engineering (AREA)
  • Analytical Chemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Filtering Materials (AREA)
  • Exhaust Gas After Treatment (AREA)
  • Processes For Solid Components From Exhaust (AREA)

Abstract

A particulate filter designed as a wall-flow filter is used for removing soot particles entrained in the exhaust gas of an internal combustion engine, in particular a diesel engine. The particulate filter comprises a porous substrate 1 that has a plurality of filter ducts 3 surrounded by filter walls 2. The substrate 1 has at least two substrate zones P1, P2, P3 that have different porosities and follow each other in the direction in which the exhaust gas flows through the substrate 1.

Description

It is designed as the particulate filter of wall type flow filter
The present invention relates to a kind of particulate filter, it is designed as wall type flow filter, for removing carbon black granules contained in the exhaust gas of an internal combustion engine, described particulate filter has the substrate of porous, and described substrate has the filter passages that multiple filtered wall is surrounded.
In order to reduce the discharge of internal combustion engine, first herein relate to Diesel engine, exhaust steam passage is connected to particulate filter.This particulate filter is for removing granule in the waste gas being included combustion engine, especially carbon black granules.At this, people are devoted to suppress as far as possible completely the discharge of carbon black granules in all cases, are therefore full filter by particulate filter design under many circumstances.This full filter is wall type flow filter, that is: medium to be filtered in the filter (in this case the carbon black granules contained by granule and waste gas) must flow through filter wall, for arriving downstream (purification side) from the upstream side of substrate.The substrate of this particulate filter include multiple filtered wall extended parallel to each other around filter passages.Multiple ceramic material can as application material.At this, filter passages is disposed adjacent to cellular and mutually separate respectively through filter wall.Filter passages is alternately closed at upstream side or downstream.The cross section of upstream passageway and downstream passage can be designed as symmetry or asymmetric.The full filter of granule is it is also known that ground has other the filter passages geometry being made up of sintered metal materials.
This particulate filter design, for the operation of exhaust gas cleaning system, will not improve exhaust back pressure power further from there through particulate filter when carbon black gathers increase.Thus need the reducing base when reaching carbon black loaded amount.In this reduction process, the carbon black gathered is oxidized, and this is also referred to as controlled carbon black after-flame.This reduction can be passive and thus when carbon black reaches the temperature determined automatically or actively by input heat be triggered.In this passive reduction, the upstream side at the carbon black gathered inputs NO2, thus can start the oxidation of carbon black at a lower temperature and thus need not carry out the intensification added.In order to meet aforementioned claim, it has the relatively small pore-size of usual 5 μm to 15 μm and is significantly less than the porosity of 50% largely.Additionally, substrate design is, the substrate never loaded starts filter process and is adjusted to surface filtration as quickly as possible.Before at least starting surface filtration with discernible value, the hole being in filter wall has been attached carbon black, and thus the effective porosity of this substrate is further reduced.When lasting depth-type filtration, the desired degree of filtering more than 98% cannot be realized with this filter.Therefore, people are devoted to design this particulate filter so that it arrives the surface filtration state preparing to realize rapidly.
In some applications, it is not necessary to carry out completely or largely completely carbon black discharge reduction.In this applications, the carbon black discharge of internal combustion engine is reduced 50% or only 20% to 25% and is sufficient to.
For this, have developed so-called stage filter.Stage filter has maximum nominal degree of filtering in desired magnitude.It means that this filter can obtain a part for the granule especially carbon black granules in the waste gas being included combustion engine corresponding with degree of filtering.Stage filter can be designed as wall type flow filter.In this case, substantial amounts of bypass passageways one or more, usual is formed by different measures.Bypass passageways achieves the mobility from the upstream side of substrate to downstream, flows through filter wall without making waste gas.This connection being bypassed through the filter wall closed in the downstream filter wall open with one or more upstream sides realizes.Can the cross section of percolation being so designed that of bypass flow so that a part of waste gas stream does not flow through with filtering.Can the cross section of percolation determine by the degree of filtering that this stage filter realizes according to bypass flow.
Particulate filter design is the wall type flow filter with channel design, and great majority gather the carbon black carrying out comprising in waste gas in the filter passages that downstream is closed.When carbon black gathers, along with the intensification of filter passages, carbon black is piled up also more big.Thus, carbon black loaded amount is constantly increased from the approaching side of filter passages to the closing of side downstream.Exist in the end regions in the downstream of particulate filter and the amount of carbon blacks relatively large relative to approaching side can cause occurs thermal problem when reduction at the end regions of particulate filter or its basic downstream.It is overheated that this can cause in the generation of this region, thus damages or possibly even damages particulate filter.First this be applicable to the particulate filter that its substrate is made up of ceramic material such as cordierite material.
From discussed prior art, the technical problem to be solved is, Curve guide impeller is the particulate filter of the wall type flow filter with channel design, is prevented effectively from overheated in substrate regions owing to reduction causes.
Described technical problem is solved by the particulate filter of a kind of aforementioned type according to the present invention, wherein, and substrate regions that described substrate has at least two percolation direction arranged in succession along the waste gas described substrate of traverse, that possess different aperture degree.
In this particulate filter, substrate and at least there is along waste gas through the flow direction of substrate the region with different aperture degree of two arranged in succession around the filter wall of filter passages.The scheme with the substrate in the region of different aperture degree makes can regulate in that region the different percolation characteristic of waste gas traverse filter wall.Relative to shortcoming described in the prior art discussed above, can be effectively prevented in the end regions in the downstream of substrate by the program and sometimes occur that bigger carbon black gathers in the filter passages closed in the direction.This is achieved in, and namely arranges porosity more less than the main carbon black accumulation region that upstream side is arranged in the end regions that the downstream of substrate is arranged.Relatively low porosity in this end regions makes the carbon black granules being included in waste gas have the more highly porous one or more regions being arranged in upstream owing to relatively low flow resistance flows through more, and the carbon black granules thus comprised accumulates in the filter wall of upstream side according to favourable flow path in these one or more regions.Can be effectively prevented from by this way making particulate filter impaired owing to occurring undesirable overheated in outlet end region when reduction.
First manufacturing substrate with single or unified porosity, without carrying out corresponding porosity subregion during fabrication, by the coating in the one or more regions to substrate, these regions have relative to other less porosity in porosity region.This coating is preferably implemented as the coating increasing surface area, namely usually by being coated with so-called carrier material (Washcoat) realization.The combination of this carrier material or composition and application are sufficiently known.This carrier material is generally used for increasing the substrate surface area of catalyst converter.It should be understood that the porosity in region is conditioned in a simple way by the coating with identical or different carrier material of one or many.
The similarly end regions of the as the aforementioned substrate of particulate filter, it is possible to independently to this or can also additionally make, compared with the adjacent pore region that entry zone arranges in downstream with it, there is relatively low porosity.
As a rule, the whole cross section of substrate defines pore region.But porositys different in its porosity for adjacent pore region only can also be limited in the subrange of cross section of substrate.Thus can also use the program, when substrate is anisotropically flow through by waste gas to be cleaned, for being advantageously carried out being uniformly distributed of carbon black loaded on the cross section of substrate.The filtration device structure being made up of various piece can particularly simple realize.
The scheme that previous designs is the porosity subregion of the particulate filter of wall type flow filter is equally applicable to full filter device and stage filter.It is interesting that the program is so initially used for being designed as the particulate filter of wall type flow filter, because in an advantageous embodiment for having the substrate of Higher porosity, especially porosity is more than 50%.Higher porosity is preferably approximately between 60% to 70%, it is preferable that also have relatively large pore-size and between 15 μm to 30 μm.According to being advantageously improved scheme, pore-size is striven for less than 25 μm.This substrate is made up of carbofrax material, it is particularly advantageous due to higher porosity, in order to begun through the coating being coated with the coating of one or more increase surface areas, especially carrier material form to realize porosity subregion by the substrate with unified porosity.Carrier material used herein so adjusts so that the porosity of substrate declines about 5% to 10% in coating procedure.This is thus configured to the porosity difference between the pore region that the enough substrates of described purpose are adjacent.At this it will be appreciated that in the first step, substrate is generally with carrier material coating, for forming the void area of multiple porositys with reduction in a subsequent step compared with the first unified porosity set.
When using carrier material, it is preferable that the substrate of the more porous used is also in its hole undercoating so that the reduction of porosity reaches pore-size also by certain reduction.
In improvement project, this carrier material exists in whole substrate or only exists in the region of coating, in order to use carrier material as the carrier of catalyst coatings.It is understood that activating substance is integrated in carrier material in this case, or it is coated on the surface provided by carrier material in ensuing process steps.In both cases, the carrier material coating used for the porosity subregion of substrate can be used simultaneously as the carrier for catalyst coatings increasing surface area.The coating of oxidation catalysis is such as related at this.It is also feasible that the substrate of this entirety or topical application carrier material has the coating of effective catalysis for NOx reduction, for instance can be the SCR of nitrogen oxides according to so-called SCR (SCR) technique.In this case, being provided with entry zone, it has the catalyst coatings for implementing hydrolysis.It is subsequently used as the region support package of hydrolysis catalyst containing carbamide microdroplet in the offgas as reducing agent presoma, for discharging its NH contained3As reducing agent.This NOx reduction carried out on SCR catalytic washcoat for the downstream in substrate is required.
The granule wall type flow filter being designed as stage filter has aforesaid porosity and preferred particle size, wherein has been provided for the feature of the particulate filter being made up of substrate in the design of substrate.The percolation that the relatively low porosity of substrate makes filter wall have lower resistance.Thus, in the stage filter being designed as the wall type flow filter with channel design, this form has been obviously prolonged depth-type filtration effect.
Thus, bypass percolation can have less size relative to the aforesaid particulate filter being designed as wall type flow filter by the cross section of the opening of property.In same substrate volume, this achieves the improvement of degree of filtering efficiency.Meanwhile, by the considerably higher porosity of substrate, the weight of substrate is not strongly reduced relative to aforesaid substrate.
The degree of filtering of this particulate filter is determined also by filter passages density.This is also referred to as chamber density, and it is preferably between about 100cpsi to 350cpsi, especially between 180cpsi to 225cpsi (chamber number per square inch).Particularly effective particulate filter is about 200cpsi when considering aforesaid design standard.
Thus filter passages density can consider the purpose for substrate.When filter channel density is less so that be of a relatively high by the flowing velocity of filter wall, and in the design of this particulate filter, thus reduce desired depth-type filtration, and thus reduce degree of filtering.Additionally, bypass percolation is relatively large by the cross-sectional area of property.When higher chamber density, bypass percolation is relatively small by the cross-sectional area of property.Additionally, depth-type filtration in filter wall only more be realize from possession, this causes that quick carbon black from the teeth outwards gathers.
In the particulate filter of this design, due to desired depth-type filtration effect, first filter wall also serves as this for filtering the granule comprised in waste streams.Particularly advantageously, wall thickness is between 0.3mm to 0.7mm, be especially about 0.4mm, in order to realize set requirement on this stage filter.
Below in conjunction with embodiment shown in the drawings, the present invention is described.In the accompanying drawings:
Fig. 1 illustrates the longitudinal section of a filter passages of a plurality of this filter passages of the particulate filter according to the present invention, and particulate filter has the filter wall loading carbon black,
Fig. 2 illustrates the longitudinal section of a filter passages of a plurality of this filter passages of the particulate filter according to prior art, and particulate filter has the filter wall loading carbon black, and
Fig. 3 illustrates by two by catalyst coating, waste gas cleaning equipment that the particulate filter that is designed as wall type flow filter is constituted.
The substrate 1 being made up of the carbofrax material of porous for formed multiple wall that extend parallel to each other, filtered around filter passages.Particulate filter design is stage filter so that the first filter passages group is closed in downstream in this embodiment, and second channel group is not closed simultaneously, and thus provides the one bypass percolation property passed through.The porosity of the carbofrax material constituting substrate 1 is approximately 65% in the embodiment shown.Fig. 1 illustrates the cutting longitudinal section round filter wall 2,2.1,2.2 gained of filter passages 3.Filter passages 3 is closed by obturator 4 in downstream, and obturator forms stopper relative to filter passages 3.The filter passages adjacent with filter passages 3 is not closed in the embodiment shown.Thus, the particulate filter being made up of substrate 1 relates to granule stage filter.
In an illustrated embodiment, after only multiple pore region being set in the longitudinal extension section of substrate, just install obturator 4 and by obturator 4 install all other respectively at the stopper of downstream enclosed filters passage.In the embodiment shown in fig. 1, three pore region P it are provided with1、P2、P3.They pass the percolation direction of substrate 1 along waste gas, are successively arranged as shown in by block arrows.Three pore region P1、P2、P3By the reducing accordingly of primary porosity of substrate 1 being adjusted after substrate is manufactured.For this, substrate 1 overall loaded body material in the first step covers.This and in ensuing coating step advantageously, obturator 4 is not yet installed.Thus, carrier material can by substrate 1 is immersed carrier material solvent and from carrier material solvent take out carrier material implement preferably.It is also advantageous that similarly, for drying up of the ensuing carrier material to covering.The carrier material arranged is known, traditional catalyst coat as carrier.In substrate 1, people but first with the characteristic increasing surface area of the carrier material covered, are used for reducing porosity.By the first carrier material process, the pore region P in the middle of adjusting2Porosity.It has dropped about 7% relative to primary porosity.In a subsequent step, in terminal area, i.e. pore region P3In, porosity is reduced about 7% again by Second support material coating procedure.Similarly, at pore region P1In in the entrance region shown in Fig. 1, porosity again by Second support material coating procedure such as pore region P2In porosity be lowered.For this, again arrange identical carrier material so that substrate 1 is at pore region P1、P3Inside there is the porosity of about 51% and at pore region P2Inside there is the porosity of about 58%.This for the percolation of substrate 1 it is meant that due to different porositys, waste gas preferably flows through pore region P2。
In an illustrated embodiment, at pore region P2And P3The carrier material of middle existence is implemented as the catalyst coatings of selective reduction NOx.It means that the substrate 1 of particulate filter is at region P2And P3The middle form according to SCR catalyst, except its filter function, work when existing as the ammonia of reducing agent.It is positioned at pore region P1In carrier material be implemented as play hydrolysis coating.It is for accelerating to comprise the hydrolysis of carbamide microdroplet in the offgas, in order to therefrom discharge for SCR catalysis as NH necessary to reducing agent3.Thus, the substrate 1 of particulate filter, except the filter function of itself, is also equipped with the function of SCR catalyst.It should be understood that in order to SCR catalyst sprays carbamide in the upstream of substrate in waste gas stream.
The compartmentalization of the above described holes porosity of substrate 1 is produced as a result, carbon black contained in waste gas farthest accumulates in pore region P in the side of the filter passages 3 closed by obturator 42In.Reason is in that, with pore region P1And P3Compare, pore region P2There is the relatively low percolation resistance determined by bigger porosity.Schematically show the typical configuration loading carbon black of filter passages 3 in FIG.Carbon black is identifiably labeled as accompanying drawing labelling 5 wherein.Substantially it will be seen that have porosity P3End regions in, it is reduce that carbon black gathers the direction towards obturator 4.Meanwhile, in an illustrated embodiment, by pore region P3In additional carrier material, be used for reducing this region P3Relative to region P2Porosity, and implemented additional coated weight.At pore region P3In relatively low carbon black gather and the additional coated weight implemented by carrier material protects pore region P3(end regions of substrate 1), it is prevented that it is undesirable overheated to occur when substrate 1 reduces, this overheated meeting causes the carbon black 5 gathered oxidized.When add carbamide waste gas enter substrate 1 time, carbamide as reducing agent presoma at pore region P1Surface on hydrolysis, for discharging contained NH3.Meanwhile, by the filtration occurred, also at pore region P1Interior accumulation carbon black.Due at pore region P2In relatively low flow resistance, most of amount of carbon blacks are at pore region P2Inner accumulated.This first relates to the thickness of the carbon black gathered.Because pore region P2Occupying the longest region relative to the longitudinal extension section of substrate 1 and be about the 70% of substrate 1 length, this additionally makes, and most of amount of carbon blacks are at this pore region P2Inner accumulated.Gather along with carbon black, by the latest at pore region P1Hydrolysis catalyst on release NH3, contained NOx is at pore region P2And P3Catalytic surface on be reduced.
Fig. 2 illustrates the view of the known corresponding substrate in its longitudinal extension section with uniform bore porosity according to prior art.Filter passages F shown in Fig. 2 has the carbon black loaded R being gradually increased towards obturator V.The typical carbon black that traditional substrate of particulate filter is formed gathers owing to there is overheated danger when the relatively large amount of carbon blacks existed in end regions causes and reducing in the end regions in downstream.Owing to one fixes on this region memory in relatively large amount of carbon blacks, thus further increase reduction temperature and first persistently longer compared with only having the region gathered compared with low carbon black wherein reduction process.
Fig. 3 illustrates the waste gas cleaning equipment with the substrate 1 constituting particulate filter.In the housing 7 with substrate 1, jointly there is other substrate 8, be likewise constructed to particulate filter.Substrate 8 is directed to this substrate as described in substrate 1.With substrate 1 the difference is that, substrate 8 only has two pore region P4、P5.Pore region P4、P5Be equivalent to the pore region P of substrate 12、P3.Thus, in the substrate 8, porosity is at pore region P5Internal ratio is at pore region P4Interior decline.The overall carrier material of substrate 8 is implemented by oxidation catalyst coating.This is used for Hydrocarbon and the carbon monoxide of removing in waste gas stream, and for being generated NO by the NO contained in waste gas2.At the outlet side relative to substrate 8, the desired NO:NO in waste gas stream2Ratio be 1:2 to 2:1.This NO:NO2Ratio promote SCR catalysis in substrate 1.Similarly as in substrate 1, the pore region P that porosity reduces5It is overheated to be used in the substrate 8 preventing occurring when reduction.
Between two substrates 8,1, there is injection apparatus 9, for the carbamide as reducing agent presoma of infusion fluid form.By injection apparatus 9, the carbamide of liquid form input is atomized, and it is the latest at the pore region P of substrate 11It is decomposed during inherent contact hydrolyzation catalysis coating.
The pore-size provided in the present embodiment, refers to medium pore-size in principle.At this, the preferred standard deviation of scope of pore-size is maximum is 70%.
Two of waste gas cleaning equipment shown in Fig. 3 purify level, it is possible to be made up of the filter substrate of one or more series connection.Because monobasal only has relatively short length along the flow direction of waste gas, so being formed the structure of total substrate by multiple monobasals is significant for reduction, because this effectively avoids the damage relevant to calorifics.In this design, wherein more than one substrate forms a purification level, monobasal layer folded form ground mutually is arranged.In the design of this laminated advantageously, each monobasal is respectively provided with the region of relatively low-porosity in end range, as described in an embodiment.
The structure producing eddy current can be provided with, for instance be designed as eddy current fence between each filter substrate.
The advantage of preceding solution is in that, particulate filter design as wall type flow filter is the substrate for being coated with catalyst coatings thereon, owing to having relatively higher porosity and relatively large pore-size compared with monolithic filter, thus for the coating of carrier material with provide the surface that can contact more greatly for catalyst coatings.Finally, due to the design of this stage filter, it is ensured that also by catalyst coat in pore volume.Thus, by this substrate in tight space, compared with the surface being designed as pure catalyst converter, it is provided that king-sized catalyst converter surface.
Exhaust gas cleaning scheme cleaning in conjunction with diesel engine, the waste gas of such as Diesel engine in the present embodiment is described.Similarly, the program is also applied for the cleaning of petrolic waste gas.
Described waste gas cleaning equipment can also be called four stroke waste gas cleaning equipments or four stroke catalyst converters.
The present invention describes in conjunction with the embodiments.As long as no departing from scope of the claims, technical staff can be accomplished in several ways the present invention.
Reference numerals list
1 substrate
2,2.1,2.2 filter wall
3 filter passages
4 obturators
5 carbon blacks
6 waste gas cleaning equipments
7 housings
8 substrates
9 injection apparatus
P1-P5Pore region
F filter passages
R carbon black loaded thing
V obturator

Claims (14)

1. a particulate filter, it is designed as wall type flow filter, for removing carbon black granules contained in the exhaust gas of an internal combustion engine, described particulate filter has the substrate (1,8) of porous, described substrate (1,8) has the filter passages (3) that multiple filtered wall (2,2.1,2.2) is surrounded, it is characterized in that, substrate regions (P that described substrate (1,8) has at least two percolation direction arranged in succession along the waste gas described substrate of traverse (1,8), that possess different aperture degree1、P2、P3、P4、P5)。
2. the particulate filter described in claim 1, it is characterised in that relative to another substrate regions (P2、P4) there is a substrate regions (P of relatively low-porosity1、P3、P5) in, described substrate (1,8) is increased surface area ground coating by one or many, in order at this substrate regions (P1、P3、P5) middle reduction porosity.
3. the particulate filter described in claim 2, it is characterised in that the coating reducing porosity is the coating applying carrier material.
4. according to the particulate filter one of claims 1 to 3 Suo Shu, it is characterized in that, described substrate (1,8) has the end regions comprising side downstream, and the substrate regions adjacent relative to the upstream side of the flow direction along waste gas, this end regions has the porosity of reduction.
5. the particulate filter described in claim 4, it is characterised in that the longitudinal length of described end regions less than described substrate (1,8) length 20%.
6. according to the particulate filter one of claim 1 to 5 Suo Shu, it is characterised in that described substrate (1) has entrance region, the substrate regions (P adjacent relative to the downstream of the flow direction along waste gas2), this entrance region has the porosity of reduction.
7. the particulate filter described in claim 6, it is characterised in that described entrance region is by catalytically coating, for the moisture drop being included in waste gas stream is hydrolyzed.
8. the particulate filter described in claim 6 or 7, it is characterised in that the flow direction along waste gas follows at least one substrate regions in described entrance region closely by catalytically coating, for carrying out the reduction of NOx.
9. according to the particulate filter one of claim 1 to 8 Suo Shu, it is characterised in that described substrate (1,8) is the ceramic material of porous, such as carbofrax material, cordierite material or material of aluminum titanate.
10. according to the particulate filter one of claim 1 to 9 Suo Shu, it is characterised in that described particulate filter is designed to stage filter.
11. the particulate filter described in claim 10, it is characterised in that a number of filter passages was not both closed also without in downstream at upstream side.
12. the particulate filter described in claim 11, it is characterised in that described substrate (1,8) not coated part has the pore-size between the porosity more than 50% and 15 μm to 30 μm.
13. according to the particulate filter one of claim 10 to 12 Suo Shu, it is characterised in that at least one substrate in described substrate (1,8) or multiple substrate is by catalytically coating, for instance be coated with oxidation catalyst coating.
14. according to the particulate filter one of claim 10 to 13 Suo Shu, it is characterised in that the wall thickness of described filter wall (2,2.1,2.2) is between 0.3mm to 0.7mm, especially equal to about 0.4mm.
CN201380081133.XA 2013-11-21 2013-11-21 Particulate filter designed as a wall-flow filter Pending CN105813715A (en)

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