DE20122823U1 - Particle trap with hydrolysis function - Google Patents

Abstract

particulate trap (11), in particular in the form of a layered honeycomb body (1), forms the flow channels (2) and structures (3) to flow in a fluid passing through the particle trap flows, Create turbulence, sedation and / or dead zones (5), wherein the particulate trap (11) is at least partially open and in at least a part is carried out with a hydrolysis coating.

Description

The The invention relates to a particulate trap for particulate contaminated Fluid, especially for the exhaust gas of a diesel engine, the particulate trap being due to oxidation the particle is regenerable and placed in a tube, e.g. in the Exhaust line of a motor vehicle, can be installed.

One Fluid, e.g. the exhaust of a motor vehicle, contains beside gaseous Ingredients include particles. These are expelled with the exhaust gas or may be stored in the exhaust system and / or in a catalytic converter of a motor vehicle, at. With load changes They are then in the form of a particle cloud, such. a soot cloud, expelled.

Become conventional Sieves (also sometimes referred to as filters) used, the Collect particles. However, the use of sieves brings two significant Disadvantages, on the one hand they clog and on the other hand they cause an undesirably high Pressure drop. In addition, must legal values for Motor vehicle emissions are exceeded, which exceeded without particle reduction would. There is therefore a need to provide trapping elements for exhaust particles, which overcome the disadvantages of sieves, filters or other systems.

task the invention is to provide a particle trap for a fluid flow, which is regenerable and open, as well as having improved functionality. These Task is solved with a particulate trap according to the features of claim 1, wherein preferred embodiments of the invention in the dependent formulated claims are indicated.

object The invention has a particle trap with flow channels and structures to in a fluid flow, which flows through the particle trap, To create turbulence, sedation and / or dead zones, wherein the particle trap is at least partially open. In addition, subject the invention, a particle trap with flow channels and structures in order to Fluid flow, which flows through the particle trap, To create turbulence, sedation and / or dead zones, wherein the particulate trap is at least partially open and at least a part the flow channels at least a subarea with an elevated Heat capacity, z. B. through higher Wall thickness, larger number of cells or the like, so that during dynamic load changes with rapidly increasing fluid temperature for entrained particles in the fluid the effect of thermophoresis in these areas increases.

Further There are also coated areas of the particulate trap, so that the Particle trap is formed in one part as a catalyst carrier. in this connection the particle trap has besides the function as a trap for particles as well a function as a hydrolysis catalyst.

Besides, they are various uses of the particulate trap in various combinations with further modules subject of the invention.

In experiments with mixing elements made of metal foils, as used for example in the WO91 / 01807 or the WO91 / 01178 described and have been tested for better distribution of injected in exhaust systems additives, it has surprisingly been successful on the bare, ie uncoated metal of the films particles, such as the soot from a diesel engine, deposit and bring to oxidation.

The Particles are believed to be turbulent due to the inner walls of the channels hurled and stick there. The turbulences are through structures the channel inner sides generated, these structures not only turbulences, but also create calming or dead zones in the flow shadow. In the sedative and / or dead zones, the particles are probably quasi alluvial (comparable to a gravity separation) and then stick firmly. In the adhesion of particles plays a possible interaction metal soot and / or also the temperature gradient fluid / channel wall a role. It will also a strong agglomeration of the particles in the gas stream or at the walls observed.

When Calming zone becomes a zone in the channel with low flow velocity and referred to as a dead zone zone without fluid movement.

In contrast to closed systems, the particle trap is referred to as "open" because there are no flow back alleys.This property can also be used to characterize the particulate trap, eg an openness of 20% means that in a cross-sectional view about 20% With a carrier of 600 cpsi (cells per square inch) with a hydraulic diameter of the channels of about 0.8 mm this would correspond to an area of about 0.01 mm ² .

The Particle trap does not clog like a conventional filtration system where Can clog pores, because before the flow would entrain the part of the agglomerated particles, which due to its increased Demolish drag leaves.

To produce a particle trap, at least partially structured layers are layered or wound by known methods and joined by joining, in particular soldered. The Cell density of the particle trap depends on the curl of the layers. The corrugation of the layers is not necessarily uniform over an entire layer, but different flows and / or pressure conditions within the traversed particle trap can be produced by suitable production of the layer structure.

The Particulate trap can be monolithic or multiple slices, this means from one element or several individual elements connected in series be constructed.

To cover various (dynamic) load cases of the drive system of a motor vehicle, a system with conical channels or a cone-shaped element is preferred. Such systems, such as in the WO93 / 20339 have widening or narrowing channels, so that at any mass flow at any point of the channels, if they are provided with appropriate deflection or Verwirbelungsstrukturen, particularly favorable conditions for the capture of particles arise.

Cone-shaped doing both the versions, in the flow direction show a diameter extension as well as the versions, which have a diameter reduction. Also cylindrical honeycomb body with channels, some of which have narrowed and part have widened suitable properties.

To an embodiment the invention of several wound into a honeycomb body layers has a smooth layer lying between two Welllagen holes, so the existence Fluid exchange between the channels formed by the winding is possible. This is a radial flow through the particle trap, the not at a 90 ° deflection is bound, possible. In the embodiment the smooth position with holes these are preferably located at the outlet of flow guide vanes, So that the flow directly into the holes is directed. Instead of the smooth position with holes can also another penetrable material, such as e.g. a fiber material used become.

The Material of the layers is preferably metal (sheet), but it can also a substance of inorganic (ceramic, fiber material), organic or organometallic nature and / or a sintered material, as long as there is a surface has the adhesion of the particles succeeds without coating.

The Particle trap is subject in use large temperature fluctuations in a partially oxidative atmosphere (Air), and it will emerge on the surface of the layers when these off Metal are, different oxides, maybe even in shape acicular crystals, so-called whiskers, which cause a certain surface roughness. The Particles of the flow, which are basically similar to molecules Behavior, through different mechanisms, in particular Impaction or interception in turbulent flow or thermophoresis in laminar flow on this rough surface alluvial and held there, the adhesion being essentially determined by Van der Waals forces is caused.

Even though the deposition of the particles on the uncoated metal foil It is not excluded that there are also coated areas the particle trap is because the particulate trap, for example, too in one part as a catalyst support is trained.

The film thickness the layers are preferably in the range between 0.02 and 0.2 mm, particularly preferred between 0.05 and 0.08 mm, in areas with increased heat capacity preferably between 0.65 and 0.11 mm.

at the particle trap with several wound layers are these out same or dissimilar material or have the same or uneven film thickness.

The Particles in the exhaust gas of a diesel engine, which consist essentially of soot, can be charged by passing through an electric field and / or polarize so that they from their preferred flow direction (e.g., axial direction of the particle trap parallel to the flow channels) become. Thus, the probability of particle impact is increased on the walls of the Flow channels of the particle trap elevated, as they flow through The particle trap now also has a velocity component in one other direction, in particular perpendicular to the preferred direction of flow, exhibit. This leaves For example, with one of the particulate trap upstream Plasma reactor realize a polarization of the particles guaranteed. It is also particularly advantageous that the particle trap at least one Pol the polarization path forms, especially if the particle trap at least partially having a positive charge, and electrically Negatively polarized particles are thus actively attracted. so be the mechanisms through which particles from the flow inside to be flushed to the wall (e.g., interception and impaction), accelerated and amplified.

In the event that the particulate trap is charged, it is advantageous that tips are arranged on the layers and / or in the structure of the film forming the layers, which reinforce the charging effect. The particles of the fluid can, for example, by a polarization path for charging are passed through, while the particles are then polarized. However, the particulate trap can also be grounded and remain charge-neutral, in particular if suitable insulation with respect to the tips and / or the polarization path is provided.

The Polarization and / or charging takes place according to one embodiment also over a photoionization.

To an embodiment the particles are over a corona discharge charged and / or polarized.

To an embodiment the particle trap makes use of the knowledge that a temperature difference between the channel wall and the flow for increased migration of the particles the channel wall serves (thermophoresis). Accordingly, a thick and thus equipped with high heat capacity Channel wall (about by a corresponding film thickness of the Position at the location causes) with opposing structures (conductive structures), the particles to this wall (such as by creating turbulence in the flow) to turn, combined. The thick duct wall has a high heat capacity and therefore keeps with dynamic load changes and rising exhaust gas temperature Temperature difference between the flow and the channel wall longer upright as a thin one Canal wall and receives thus favoring the deposition Effect longer as a thin one Channel wall. The lead structures are structures for generating Turbulence, sedation and dead zones and cause a forced Mixing of the flow, so that particle-rich Zones inside the flow outward be brought and vice versa. Thus, more particles is the contact the walls possible through interception and impaction, which then also stick stay.

To an embodiment it uses the effect of thermophoresis by connecting in series several particle traps each with different thickness channel walls.

The Cell densities of the particulate trap are preferably in the range between 25 to 1000 cpsi, preferably between 200 and 400 cpsi.

A typical 200 cpsi particulate trap has a volume, based on a diesel engine of about 0.2 to 11 per 100 kW, preferably 0.4-0.851 / 100 kW. For the geometric surface results, for example 1.78 m ^2/100 kW. Compared with the volumes of conventional filters and screening systems, this is a very small volume or a very small geometric surface compared to a conventional design with about 4 m ² surface per 100 kW.

The particulate trap is regenerable, wherein in the case of soot deposition in the diesel engine exhaust system regeneration by the oxidation of the carbon black either by nitrogen dioxide (NO ₂ ) at a temperature above about 200 ° C or with air or oxygen (O ₂ ) thermally at eg Temperatures above 500 ° C or by injection of an additive (eg Cer) takes place.

The soot oxidation by means of NO ₂ , for example via the mechanism of the "continuous regeneration trap" (CRT) C + 2NO ₂ → CO ₂ + 2NO requires that before the particulate trap in the exhaust line an oxidation catalyst is set, which oxidizes NO to NO ₂ in sufficient quantity. However, the ratio of the reactants also depends significantly on the mixing of the fluids, so that depending on the configuration of the channels of the particle trap and different proportions should be used.

Especially Advantageous, the embodiment in which a means for thermal regeneration of the Particle trap is provided, so that e.g. the element at least partly electrically heated, or the element is an electrically heatable Auxiliary, such as a heating catalyst, upstream.

at an embodiment is provided that an aid depending from the occupancy / fill level the particle trap is switched on or off for regeneration, what about in the simplest case the pressure loss that the particle trap creates in the exhaust line, is measured.

To a preferred embodiment has an oxidation catalyst upstream of the particulate trap lower specific heat capacity per unit volume and cell number as the particulate trap itself. So does the oxidation catalyst For example, preferably a volume of 0.5 liters, a cell number of 400 cpsi and a film thickness of 0.05 mm, while the Particle trap at the same volume and same number of cells one Film thickness of 0.08 mm and a downstream SCR catalyst again a film thickness of 0.05 mm.

Also the combination of the particulate trap with at least one catalyst and a turbocharger or the combination of a particle trap with a turbocharger is advantageous. It can be the turbocharger Downstream particle trap close to the engine or in underbody position be arranged.

The particulate trap is also used in combination with an upstream or downstream soot filter, wherein the soot filter downstream can be substantially smaller than the conventional soot filter, because it should only provide additional protection that Particle emission is excluded. Preferably, a filter of size 0.5 m ² per 100 kW diesel engine is used up to a maximum of 1 m ² , (in downstream filter surface, the cross-sectional area of the filter is adapted to that of the particulate trap, both in the case of a cross-sectional constriction as well as in the case of Cross-sectional expansion) whereas without particle trap filter sizes of about 4 m ² per 100 kW are required.

Of the soot filter can also be in the form of directly before or after the storage / oxidation element installed filter material, wherein the filter material thereby directly, e.g. above a solder joint, with may be connected to the storage / oxidation element.

• A) Oxidationskatalysator – Turbolader – Partikelfalle, wobei die Partikelfalle motornah oder in Unterbodenposition angeordnet sein kann.
• B) Vorkatalysator – Partikelfalle – Turbolader
• C) Oxidationskatalysator – Turbolader – Oxidationskatalysator- Partikelfalle
• D) Heizkatalysator – Partikelfalle 1 – Partikelfalle 2 (wobei Partikelfalle 1 und 2 gleich oder ungleich sein kann)
• E) Partikelfalle 1 – Konusöffnung des Abgasstranges – Partikelfalle 2F ) Additivzugabe – Partikelfalle – Hydrolysekatalysator – Reduktionskatalysator
• G) Vorkatalysator – Oxidationskatalysator – Additivzugabe- (eventuell Rußfilter) – Partikelfalle z.B. in Konusform, ggf. mit Hydrolysebeschichtung – (eventuell Rußfilter) – (eventuell Konus zur Erhöhung des Rohrquerschnitts) Reduktionskatalysator

The following examples represent arrangements which prove the multitude of possible combinations of the particle trap with catalysts, turbochargers, soot filter and additive addition along an exhaust system of a motor vehicle:

• A) oxidation catalyst - turbocharger - particle trap, wherein the particulate trap can be located close to the engine or in underfloor position.
• B) Pre-catalyst - particle trap - turbocharger
• C) Oxidation Catalyst - Turbocharger - Oxidation Catalyst Particle Trap
• D) heating catalyst - particle trap 1 - particle trap 2 (particle trap 1 and 2 may be the same or different)
• E) Particle trap 1 - cone opening of the exhaust line - particle trap 2F) Addition of additive - particle trap - hydrolysis catalyst - reduction catalyst
• G) Pre-catalyst - Oxidation catalyst - Additive additive (possibly soot filter) - Particle trap eg in cone shape, if necessary with hydrolysis coating - (possibly soot filter) - (possibly cone to increase the tube cross-section) Reduction catalyst

In one embodiment, the particulate trap is used in combination with at least one catalyst. Suitable catalysts, electrocatalysts and / or precatalysts are in particular: oxidation catalyst, heating catalyst with upstream or downstream heating disk, hydrolysis catalyst and / or reduction catalyst. Also, as the oxidation catalyst, those which oxidize NO _x (nitrous gases) to nitrogen dioxide (NO ₂ ) will be used besides those which oxidize hydrocarbons and carbon monoxide to carbon dioxide. The catalysts are, for example, tubular or conical.

Preferably, a nitrogen dioxide (NO ₂ ) storage is used in front of the particulate trap, which provides NO ₂ in sufficient quantity for the oxidation of the carbon black in the particulate trap, if necessary. This memory can be eg an activated carbon storage eg with sufficient oxygen supply.

ever according to embodiment the particle trap can have different coatings in partial areas, each one functionality require. For example, the particulate trap in addition to the function as Trap for Particle a storage, mixing, oxidation, flow distribution function and also e.g. have a function as a hydrolysis catalyst.

By The use of a particulate trap can cause deposition rates of up to 90%.

It it was found that the Deposition of particles takes place especially at the inlet and outlet surfaces of the catalysts. Therefore, according to one embodiment the particle trap not in the form of an element, but in shape several successive narrow elements, as a multi-disc element used. It also can Particle traps, the Welllagen without structures for the production of Turbulence and settling zones and with coating (e.g. conventional catalysts), be used. It will be preferred up to 10 elements used. This design referred to as "disc assembly" or "disc catalyst" can be used, for example, when in the range of 10 to 20% (using conventional Catalysts) particle deposition is desired.

The present invention proposes a particulate trap which can replace conventional filtering and screening systems and offers major advantages over these systems:
First, it can not clog and the pressure drop generated by the system does not increase as fast with the operating time as with screens, because the particles adhere outside the fluid stream, and second, it causes relatively low pressure drops because it is an open system.

Further specific embodiments and advantages of the invention will become apparent explained in the following drawing. The embodiments shown in the drawings are as specific, exemplary and particularly preferred embodiments of the invention to understand the invention in its meaning and spirit should not restrict.

It show schematically:

1 a particle trap according to the invention in the form of a layered honeycomb body in perspective view,

2 a single layer with structures for generating turbulence, calming and / or dead zones,

3 a further embodiment of the particle trap according to the invention with a planar reactor,

4 a further embodiment of the structures for generating turbulence, sedation and / or dead zones,

5 a particle trap according to the invention, which can be flowed through radially,

6 a layer with structures for generating turbulence, sedation and / or dead zones 4 , and

7 a particle trap in a disc arrangement with further exhaust gas cleaning agents.

1 shows a particle trap according to the invention 11 , which are made of metallic layers 4 . 6 is constructed, the flow through channels for a fluid 2 having. The layers 4 . 6 are either as a Welllage 4 or as a smooth position 6 educated. The film thickness of the layers 4 . 6 is preferably in the range between 0.02 and 0.2 mm, in particular less than 0.05 mm.

2 schematically shows a detailed view of the corrugated layer 4 which structures 3 for generating turbulence, sedation and / or dead zones 5 having. The fluid flows along the arrow 16 indicated preferred flow direction.

3 shows a further embodiment of the particulate trap according to the invention 11 with an upstream plasma reactor 17 , The fluid or the particles contained therein will / will be with the plasma reactor 17 at least polarized, possibly even ionized, if the fluid in the preferred flow direction (arrow 16 ) through the plasma reactor 17 flows. The plasma reactor 17 is with the negative pole of a voltage source 20 connected. The positive pole of the voltage source 20 is with tips 18 the particle trap 11 connected as close as possible to the axis 19 are arranged so that a deflection of the particles due to Van der Waalsscher forces to the central region of the particle trap 11 he follows. The formed electrostatic field can be operated with a voltage of 3 to 9 kV. The tips 18 can be electrically conductive with the metallic layers of the particle trap 11 be connected.

4 shows an alternative embodiment of the corrugated sheets 4 ,

5 shows a particle trap that is radial (radius 21 ) can be flowed through (arrow 16 ). The flow channels 2 extend from a central channel 22 in the area of the honeycomb body 1 is made porous, radially outwardly toward a honeycomb body 1 surrounding, porous coat 23 , The honeycomb body 1 is made of segmented or annular smooth layers 6 and wells 4 educated.

6 shows a possible, segmented, embodiment of the Welllage 4 with structures 3 for generating turbulence, sedation and / or dead zones.

7 shows a particulate trap having cone-shaped channels and which comprises a plurality of, optionally narrow, elements which are particulate traps and / or catalysts. For this purpose, several honeycomb bodies 1 , which in each case widen conically or taper one behind the other. In front of the honeycomb body 1 is an additive addition 7 , a nitrogen storage 14 and an oxidation catalyst 8th , which nitrous gases (No _x ) are oxidized to nitrogen dioxide (NO ₂ ), in the exhaust line 12 upstream. A turbocharger 9 and a soot filter 10 are downstream. Advantageously, the particle trap 11 in combination with a tool for soot oxidation 15 used.

1

honeycombs

2

flow channel

3

structures

4

Well location

5

dead zones

6

smooth layer

7

additive addition

8th

oxidation catalyst

9

turbocharger

10

soot filter

11

particle trap

12

exhaust gas line

13

channel wall

14

nitrogen storage

15

aid for soot oxidation

16

arrow

17

plasma reactor

18

top

19

axis

20

voltage source

21

radius

22

Central channel

23

coat

Claims (16)

Particle trap ( 11 ), in particular in the form of a layered honeycomb body ( 1 ), the flow channels ( 2 ) and structures ( 3 ) in order, in a fluid flow flowing through the particulate trap, turbulence, sedation and / or dead zones ( 5 ), wherein the particle trap ( 11 ) is at least partially open and carried out in at least one part with a hydrolysis coating. Particle trap ( 11 ) according to claim 1, wherein the particulate trap ( 11 ) at least partially, preferably wound, metallic layers ( 4 . 6 ), which are in particular soldered together, wherein it is further preferred that between two corrugations a penetrable by the fluid flow smooth layer is provided, and the smooth layer is formed in particular with holes or a fiber material. Particle trap ( 11 ) with flow channels ( 2 ) and structures ( 3 ) in a fluid flow passing through the particulate trap ( 11 ) flows, swirling, calming and / or dead zones ( 5 ), wherein the particle trap ( 11 ) is at least partially open and at least part of the flow channels ( 2 ) at least in a portion of its channel walls ( 13 ) has a high heat capacity, so that with increasing fluid temperature, the effect of the thermophoresis for particles contained in the fluid flow occurs increasingly in these areas. Particle trap ( 11 ) according to one of the preceding claims, consisting of a first layer ( 6 ) and at least one further film which has a corrugated layer (in particular provided with conductive structures). 4 ) or a smooth position ( 6 ) can be manufactured. Particle trap ( 11 ) according to one of the preceding claims, which can be flowed through radially. Particle trap ( 11 ) according to one of the preceding claims, the cone-shaped channels ( 2 ) having. Particle trap ( 11 ), according to one of the preceding claims, which comprises a plurality of, possibly narrow, elements which trap particles ( 11 ) and / or catalysts ( 8th ) are included. Particle trap ( 11 ) according to claim 7, which has at least two elements with different heat capacities. Particle trap ( 11 ) according to any one of the preceding claims, wherein no Strömungssackgassen are formed, wherein preferably a cell density in the range of 200 to 400 cpsi is provided. Particle trap ( 11 ) according to any one of the preceding claims, wherein the particulate trap additionally has at least one of the following additional functions: storage function, mixing function, flow distribution function. Use of at least one particle trap ( 11 ) according to one of claims 1 to 10 in an exhaust gas line ( 12 ) of a motor vehicle. Arrangement comprising in the flow direction of the fluid at least: - an additive addition - a particle trap ( 11 ), in particular in the form of a layered honeycomb body ( 1 ), the flow channels ( 2 ) and structures ( 3 ) in a fluid flow passing through the particulate trap, turbulence, settling and / or dead zones (US Pat. 5 ), wherein the particle trap ( 11 ) is at least partially open and preferably designed according to one of the preceding claims. The assembly of claim 12, wherein the particulate trap a hydrolysis catalyst is arranged downstream. Arrangement according to claim 12 or 13, wherein the particle trap a reduction catalyst, in particular an SCR catalyst, downstream is. Arrangement according to one of claims 12 to 14, wherein the additive addition an oxidation catalyst is prefixed. The assembly of claim 15, wherein between additive addition and particulate trap and / or between particulate trap and reduction catalyst a soot filter is provided.