WO2011001027A1

WO2011001027A1 - Purifier assembly

Info

Publication number: WO2011001027A1
Application number: PCT/FI2010/050555
Authority: WO
Inventors: Teuvo Maunula; Erkki NÄRHI; Toni Kinnunen; Kati Lehtoranta; Juha-Matti ÅSENBRYGG; Mikko Sorsa
Original assignee: Ecocat Oy
Priority date: 2009-06-29
Filing date: 2010-06-28
Publication date: 2011-01-06
Also published as: EP2448656A1; FI20095735A0; EP2448656A4; EA201270064A1; EA021434B1; CN203235421U

Abstract

The invention relates to a purifier assembly used in the treatment of fluids. The invention also relates to a method for manufacturing and using such a purifier assembly. The purifier assembly comprises a perforated structure (4) arrangeable in an inlet pipe (2) and/or an outlet pipe (3) around which is installed at least one mesh structure (5) contained by an open channel, formed by a spiral-like flow channel which comprises at least two meshes in the flow channels between which and through the mesh structure the fluid (1, 7) is arranged to flow, and that at one end of the perforated structure (4) there are one or more blocking elements (6, 9) in order to control the flow of the fluid (1, 7) through the perforated structure (4) to the mesh structure (5) and/or vice versa.

Description

Purifier assembly

Background art

The invention relates to a purifier assembly used in the treatment of exhaust or waste gases. The invention also relates to a method for manufacturing and using such a purifier assembly.

Allowable limits in the exhaust emissions of vehicles, work machines and engines have lowered and will lower in 2005-2016 such that it is necessary to use after- treatment to reach the emission limits. With diesel vehicles, the hardest to reach are particu late-matter (PM) and NOχ emission limits, but carbon monoxide and hydrocarbon emissions can be effectively eliminated by oxidation catalysts. For decreasing NO_x, it is possible to use in various work machines engine-technical methods (combustion temperature, cylinder conditions, EGR = exhaust gas recirculation) which, however, have an effect increasing CO, HC and PM emissions. In targets provided with smaller engines (passenger cars, small work machines), NO_x emissions are conventionally adjusted engine-technically and unburned emissions are removed by an oxidation catalyst. Diesel particulate filters (DPF) are particularly utilised in vehicle targets to decrease the quantity of particles detrimental to health with conversions of over 90%. These conventional filters are of the wall flow type (forced flow through a porous wall) based on skin filtration in which a particle cake starts to build up on the wall of the flow channel and no great numbers of particles are accumulated within the wall after the initial accumulation. Instead of these, it is possible to use partially filtering filters (partial filters) which are also known with the name POC (partial oxidation catalyst) and their filtering capacity is about 40-70%. An advantage of partial filters is that they are maintenance-free as unburned ashes and the excess of particles are able to exit the assembly without using external power, unlike conventional filters. Usually, filtered PM soot (coal material) is thermally combusted by means of extra heat. Soot can be oxidised by an intensive combustion reaction with oxygen at a temperature higher than 550⁰C or slowly at lower temperatures (250-350⁰C) by means of NO₂. NO₂ being formed in the oxidation catalyst oxidises soot in reasonably low temperatures (>250- 300⁰C) when the oxidation catalyst is efficient enough.

With efficient oxidation catalysts, it is possible to remove a large part of the hydrocarbon-bearing volatile fraction (VOF = volatile organic fraction or SOF = soluble organic fraction) of PM. The VOF is usually 10-40%, but with some engines and in some driving conditions the VOF of particles can be even 70-90%. Such conditions are provided in urban traffic, with old engines and/or specific fuels. Thus, it is not unambiguously possible to classify the oxidation catalyst, partial filter and full filter according to separating efficiency, but their separating efficiencies overlap as conversion figures depending on operating conditions. Furthermore, the separating efficiency of filters in which particles accumulate within the filter phase and not on the channel surfaces is dependent on flow and linear speed in a known manner. The separating efficiency is also dependent on particle size. Many deep- filtering filters start to allow particles through with higher flow speeds.

The removal of the carbon fraction requires a longer residence time in the filter or the catalyst. A known continuous regenerating trap (CRT) method includes a Pt- bearing oxidation catalyst and following it an uncoated or catalyst-coated DPF (EP341832). Problems in the passive method with the conventional filter are re- lated to situations where the creation of NO₂ is not sufficient e.g. when driving in rush-hour traffic, and the method requires a fuel with very low sulphur content (S<10 ppm) for minimising the creation of sulphate in the efficient and expensive Pt-bearing oxidation catalyst. The blocking of the DPF cannot be accepted in any situation, because it will interrupt driving. Consequently, most particle filters in- elude active regeneration, which principle has already been applied for several decades. The use of modern adjusting technique with engine control enables active regeneration in the DPF. Irrespective of the regeneration of carbon, unburned ashes are accumulated in the DPF the quantity of which must be taken into account as regards dimensioning, lubricant recommendations and possible mainte- nance operations.

In addition to the conventional cellular particle filter of the wall flow type, assemblies are also known made of steel wool, of ceramic foam, as a tapered structure, as a pipe structure coated with fibre, using electrostatic separation or wet cleaners. In known filter assemblies, on top of perforated pipe structures is wrapped fibre matting or metal wool and one or more of these structures can be installed in the whole filter assembly. It is typical that the fibre structure is uniform without intermediate spaces and the flow is controlled in the structure randomly avoiding fibre threads, the average main direction being radial. This is typical for filters based on deep filtration in which particles partially accumulate within the filter ma- terial. Usually, exhaust gas flows in these filters in the radial direction towards the inside of the pipe, whereby particles have sufficient room to accumulate within, on the surface of and in the open space of the assembly before the filter.

The assembly of partial filters has been modified of the oxidation catalyst such that the separation of particles is promoted by using, instead of a ceramic or metal cell, assemblies which include various pass-through openings, claws or projections on the walls as well as throttles or filtering elements in the flow channels of the cell. The pass-through openings or filtering elements'have been provided by employing ceramic or metal meshes, wools or porous materials instead of the normal metal or ceramic walls. Partial filters usually have a cellular structure which includes ax- ial open channels in the main flow direction. The main flow is similar to the one of normal catalyst assemblies, but particle separation has been enhanced by forcing the flow to partially travel in the radial direction via meshes, fibres or holes in the wall controlled by a pressure difference. However, the radial flow is usually random in different directions, whereby a vector in the direction of the main flow is on average axial. The basic principle is also that the flow enters from one end and exits on the opposite side from the other end of the cell which is usually circular or rectangular.

Description of invention

The object of this invention is to provide a purifier assembly operating in diesel or equivalent waste gases which substantially minimises the quantity of emission components in refuse gas and induces a small pressure loss.

To reach this object, the invention is characterised by features which are presented in the independent claims. The other claims present some advantageous embodiments of the invention. Compared to normal filters based on prior art, the novel type of a purifier assembly provides smaller pressure loss, reasonable operating efficiency, smaller volume (smaller material consumption) and low manufacturing costs. The purifier assembly can employ a coating which comprises catalytically active components. The catalyst coating enhances the oxidation of carbon monoxide, hydrocarbons, nitro- gen monoxide (NO) and particles. The oxidation of particles can be promoted directly or indirectly by means of NO₂.

A further advantage of the purifier assembly is that, due to its technically simple structure, the manufacturing and operating costs are low. The purifier assembly according to the invention is arranged with a perforated structure in an inlet pipe and/or an outlet pipe of the purifier. Around the perforated structure is arranged at least one mesh structure contained by an open channel, formed by a spiral-like flow channel which structure comprises at least two meshes in the flow channels between which and through the mesh structure a fluid is arranged to flow. The perforated structure is arranged e.g. from its one end in the fluid inlet pipe and/or outlet pipe and the other end of the perforated structure including one or more blocking elements to control the flow of the fluid through the perforated structure to the mesh structure and/or vice versa. The invention is thus based on the fact that the purifier assembly comprises the perforated structure, such as a perforated pipe, around which is installed the mesh structure made of e.g. corrugated mesh or other porous sheet or membrane, by means of which is provided the spiral-shaped, open flow channel which forces the flow to partially travel through the holes of the mesh structure. Consequently, an efficient purifier assembly is provided to remove particles and gaseous impurities.

The purifier assembly according to the invention also provides an efficient catalytic structure in which the flow is forced to circulate spirally between the mesh sheets around the perforated structure but is also able to travel through the mesh.

Possible fields of usage of the invention are e.g. exhaust, flue gas and refuse gas applications in mobile or stationary targets. Usually, the gas mixture comprises an excess of oxygen, either continuously or on average. In the combustion creating exhaust gas, it is possible to use any gaseous fuel (e.g. methane, propane, bio- fuels), liquid fuel (light or heavy fuel oil, diesel, petrol or biofuels) or solid fuel. The assembly can also be employed for the treatment of fluids liquiform or in gas-liquid phase, e.g. as a purifier to separate solid impurities from liquids or liquids from gas. Furthermore, the assembly can be used for some synthesis processes.

The filter according to the invention can thus be used in completely lean conditions (excess of oxygen) or in conditions where the mixture ratio is adjusted from time to time to stoichiometric or rich for a short time. The adjustment of the mixture ratio and the resulting rise in temperature are carried out in order to regenerate the catalysed filter either completely or partially from particles and accumulated toxins or adsorbents.

Advantageously, the fluid flow direction is in some embodiments from the perforated structure through the mesh structure. Advantageously, the fluid flow direction is in some embodiments through the mesh structure to the perforated structure. In a basic assembly according to the invention, the flow of the fluid, usually exhaust gas, can be either from within the perforated structure through the wall outwards through the mesh structure to the housing or the other way round from the purifier housing through the mesh structure through the holes in the wall of the perforated structure within the perforated structure. The mesh structure can be e.g. around a perforated pipe at the end of the inlet pipe and/or outlet pipe and the other end of the perforated structure comprises a blocking element to control the flow of the fluid through the perforated structure to the mesh structure and/or vice versa. The blocking element of the perforated structure can be a separate part, e.g. a detach- able pipe plug, or it can be a fixed part of the perforated structure, e.g. a fixed pipe end.

Advantageously, at the end/ends of the mesh structure there are one or more blocking elements in order to at least partially prevent the flow of the fluid. The blocking elements at both ends block the by-pass flow totally or partially along the surface of the perforated pipe out or after the first mesh layers. The blocking element blocks up and clamps the mesh or an equivalent structure. The blocking element is advantageously made of the mesh structure surrounding the perforated pipe. The blocking element can clamp the channel only partially, whereby a narrow flow channel remains between the meshes. It is possible to adjust pressure differ- ences with the size of the channel such that gas is forced to circulate on the spiral route but, as counterpressure rises, there is also a by-pass channel for the flow the temperature, flow volume or number of accumulated particles increasing, which prevents too high a counterpressure or clogging. One end of the mesh structure can also be totally open. Then, the holes of the perforated pipe are ad- vantageously mainly on the other edge in order to prevent too direct a by-pass.

If the purifier assembly is in the inlet pipe, the temperature is higher and the purifier housing is the cleaner side. Then, particles accumulate in the pipe and in the purifier assembly on the inlet side. A possible clogging risk can be relieved by using a sufficiently sparse mesh and by wrapping less mesh around the pipe. If the purifier assembly is on the outlet side around the channel exiting the housing, there is more accumulation volume for the particles, but the temperature is lower than in the former version. The temperature is relevant when starting the oxidation of components being purified (CO, HC, NO).

Usually, the purifier housing is a normal sound-damper structure in which can also be integrated other catalyst structures (cells and/or particle filters in which oxidation, three-way, NH₃-SCR, HC-SCR, NO-degrading, N₂O-removing and/or NO_x- trap catalyst on the surface). Before or after the purifier of the invention, there can be one or more of these catalyst structures in a separate container. A way is to combine the purifier according to the invention with a filter and/or a partial filter successively either in the same or different housing. The basic assembly thus comprises the perforated structure arrangeable in the fluid inlet pipe and/or outlet pipe within the purifier housing which is made e.g. of a readily perforated pipe or holes are drilled in the pipe. The shape of the holes can be e.g. circular or oval or they can be e.g. elongated slots. The diameter of the holes, the hydraulic diameter if not a circular hole, in the perforated structure is 0.1-100 mm, such as advantageously 1-50 mm, such as e.g. 10-40 mm. The area of the holes is 1-95%, such as advantageously 10-70%, such as e.g. 20- 60%, of the area of the whole perforated structure. The holes are evenly or unevenly distributed in the perforated structure. There are holes at the point of the whole mesh structure or only in part against it. In addition to the perforated struc- ture against part of the mesh structure, there can be a closed pipe or the fluid is able to access part of the catalyst structure directly (no pipe at that point but at both ends as support). The mesh structure can also be installed around some other than the circular perforated structure. Instead of the perforated sheet/pipe, the used perforated structure can be e.g. a sturdy mesh structure or a wall made of sintered metal. The perforated structure is arrangeable of its one end in the fluid inlet pipe and/or outlet pipe. Advantageously, the fluid flow pipes and the perforated structure are connectable concentrically and parallelly, whereby the pressure losses of the flow are as small as possible. The perforated structure is advantageously simply connectable directly to the inlet pipe and/or outlet pipe. It can also include a separate connector part with which it is easily connectable. Advantageously, the diameters of the perforated structure as well as the inlet pipe and/or outlet pipe are equal or close to each other, such as e.g. pipes installable abutting or within each other, whereby connecting is technically simple and simultaneously the pressure loss of the connection is as small as possible. Advantageously, the perforated structure forms a uniform wall through the holes of which the fluid is able to flow. The perforated structure has to be sturdy/rigid enough and/or its material thickness has to be sufficient to connect it to the inlet pipe and/or outlet pipe in order to provide a durable assembly. The mesh structure of the purifier assembly can again be relatively light-structured as there is no need to connect it to the inlet pipe and/or outlet pipe. The fluid inlet pipe and outlet pipe can be pipes or other structures, such as channels, sleeves or fittings, via which the fluid is controllable within the purifier assembly or out of it. The inlet pipe and/or outlet pipe can also be e.g. assembly openings in the purifier housing. According to an object of the invention, the perforated structure is arranged as a part of the fluid inlet pipe and/or outlet pipe or the other way round a part of the inlet pipe and/or outlet pipe is arranged to simultaneously form the perforated structure. Then, e.g. the conven- tional inlet pipe and/or outlet pipe is replaced by a purifier assembly according to the invention in which part of the pipe is a pipe section not perforated and coated with mesh which is connectable e.g. to the purifier housing, and part of the pipe is a section perforated on top of which the mesh structure is wrapped. This further simplifies and makes the structures more solid. The catalyst structure comprises at least two meshes which form open channels between the meshes. The two meshes can be two separate meshes or they can formed from e.g. a structurally continuous mesh wrapped around itself. The greatest volume and thus the easiest fluid flow channel in the structure is the space between the meshes. Because a corrugation angle of at least one mesh is advanta- geously diverging from the main flow, the fluid is able to circulate the open channel spirally around the perforated structure and the mesh structure. In some embodiments, the mesh structure comprises channels formed by a mesh pair in which the flow is also able to travel sideways. If both meshes are corrugated and at least one mesh has a corrugation angle diverging from the main flow, the fluid is able to openly flow to one of the channels between the corrugation peak. By using a straight mesh between the corrugated meshes, it is possible to force the fluid to circulate in the curved channels and to penetrate the mesh before the blocking element.

According to an object of the invention, by changing the hole size and thread thickness of the mesh, it is possible to adjust the flow direction i.e. how much of it goes spirally around and how much of it goes directly through the mesh. When more particles accumulate in the structure, the holes of the meshes can clog but the spiral route is still open. Instead of the mesh, it is possible to use some other perforated sheet, mesh coated with sintered metal, fibre matting, membrane or filter paper by means of which it is possible to form an equivalent flow channel. In this specification, this element is designated with the general term of mesh structure. Holes in these materials are equivalent to the eyes of the mesh in the later examples. Instead of the mesh, it is also possible to combine two or more materials to provide the structure. For example, it is possible to combine mesh and per- forated sheet/foil which are corrugated and wound fast in each other around a perforated structure, such as a perforated pipe. According to an object of the invention, the mesh structure also comprises one or more non-corrugated mesh foils, perforated foils, perforated sheets, meshes, fibre mattings, paper sheets and/or membranes. Instead of the mesh pair, it is possible to wrap the structure of several different meshes or structures, one or more of which can also be non-corrugated. Instead of one mesh, there can be a whole foil which forces the flow to totally circulate on the spiral route. If many meshes are used, they can start at different points of the perforated structure, whereby gas is able to access directly two or more spiral-like channels from which the fluid can also be carried through the mesh. Pressure difference at different points of the structure decides the flow route of the fluid. One or more mesh structures can be located in parallel with each other, whereby a very long structure can be provided. Parallel meshes can also partially overlap or there is a separate clamping and blocking element between them, whereby the fluid circulates separately in each element. According to an object of the invention, it is possible to use a greater corrugation height in the inner circle than in the outer circle. Then, the mesh of the inner circle is first wrapped and then continued by wrapping the mesh of the outer circle having a different corrugation height. The mesh can also be wrapped in an inverse way. The object is to install a mesh of greater corrugation height on the inlet side of the fluid and, equivalent^, a lower mesh on the outlet side. Then, space is obtained for the accumulating soot and it does not accumulate in other structures and the flow has possibilities to spread wider in the mesh structure.

According to an object of the invention, the corrugation height in the mesh structure can be selected suitable for the target as regards the assembly, counterpres- sure and emission limits. The corrugation height can be the same or different in various meshes. The height can be varied between 0.2-200 mm, advantageously it is between 0.8-3 mm. Even a small corrugation angle creates an open flow channel, which differs from the case of mesh having been wrapped directly as a sheet around the pipe. According to an object of the invention, the corrugation an- gle in relation to the main flow in either direction is at least in one mesh 1-90 degrees, such as 10-80 degrees, such as advantageously between 20-60 degrees. The corrugation angle can also be varied between -90 - +90 degrees, advantageously it is between -60 - -20 and +20 - +60 degrees. The minus and plus angles mean angles in the opposite directions in relation to the main flow direction. It is practical to use the same slantly corrugated mesh material, make a mesh pair of them by turning one of the meshes inside out such that the corrugation peaks are in different directions and carrying against each other. Then, an assembly according to the invention is provided of the same mesh. By using the mesh structure, it is possible to wrap the slantly corrugated cell partially against the corrugation peaks directly against the perforated structure. The ratio of the height and width of the corrugation can be varied at a very large range, using either low and wide corrugations or high and narrow corrugation peaks.

According to an object of the invention, the peak height of the corrugated mesh is between 0.2-200 mm, advantageously 0.8-3 mm. Within the advantageous range, the counterpressure, the cohesion and the volume of the corrugated mesh are provided suitable for practical targets. According to an object of the invention, it is possible to use other peak heights in special targets: very dirty targets -> large peak height, very clean targets and when using little meshes -> small peak height. It is also possible to optimise in a small space with a very small peak height an efficient purifier assembly in which the counterpressure in the open channel is considerably higher than with greater peak height. The higher counterpressure in the open channel provides that a greater part of the fluid goes through the holes of the mesh.

According to an object of the invention, the mesh structure comprises threads the thickness of which is 0.1-5 mm, advantageously between 0.1-1 mm, and holes the size of which (apparent diameter/hydraulic diameter from mesh to mesh at the middle of the meshwork) is 0.05-10 mm, advantageously 0.1-2 mm. The mesh can be a woven structure or a mesh matting or otherwise cohering.

According to an object of the invention, the size of the holes in the mesh is between 0.05-10 mm, advantageously between 0.1-2 mm. The great variation is due to the fact that there are very different targets of usage or intended uses. In very dirty targets, the mesh is coarser and the corrugation height is great and, in clean targets, the mesh is denser and the corrugation height small. As it is also possible to use various layers around the perforated sheet, very different properties are required. If using foil or perforated foil instead of metal mesh, its thickness is in the same range as the thickness of the thread i.e. between 0.01-5 mm, advantageously between 0.02-0.2 mm. According to an object of the invention, it is possible to use a mesh made of a very thin thread and/or large eyes for the corrugated mesh and a very dense mesh for the straight mesh, whereby it is possible to wind the mesh at a very large corrugation angle (40-80 degrees). Instead of or together with the mesh, it is also possible to use above-mentioned fibre sheets or membranes of which an equivalent structure is made and they partially allow fluid through.

An embodiment is an assembly in the inner circle of which the mesh is clamped and closed and the flow thus cannot immediately access the housing from beside the pipe. In the outer circle, the mesh is then partially open to the housing, whereby clogging is prevented in specific situations. One or both of the ends can obviously be not closed, but then the fluid is easily able to by-pass mainly the spiral structure immediately beside the pipe out or in, the counterpressure controlling the relative flow volumes. According to an object of the invention, both ends of the mesh are totally closed, one fast in the perforated sheet and the other in the outer circle. Then, the fluid is forced to penetrate the mesh and cannot circulate the open spiral channel, but a space remains between the meshes in which particles can accumulate. Another advantage is that a great part of the mesh threads are not fast in each other but regularly separated from each other by corrugation. The fluid has a better possibility to touch the threads and more volume (collection volume, turbulent volume) is provided in the structure than by wrapping the mesh matting directly around the pipe. In open spaces, turbulence is created which enhances, inter alia, the separation of particles. An embodiment is to construct a very elongated perforated structure, in the example a perforated pipe, around which is wrapped a mesh structure. Consequently is provided a large open flow area which correlates with the surface area of the perforated pipe. Thus, fluid (exhaust gas) is able to circulate between the meshes in a wide area, which can decrease relative counterpressure. In such a case, the di- ameter of the housing does not have to be larger than the outer diameter of the catalyst and so many mesh layers are not required as in the narrower version. If the same catalyst quantity is installed as in the narrow version, the number of layers around the perforated pipe is equivalent^ decreased. The conversions of gaseous components coarsely follow the catalyst quantity. The long and narrow structure can also be integrated into the piping and it mostly looks like a pipe with a casing. The length of the structure could be e.g. 30-200 cm for an engine of about two litres. The long structure can also be assembled of parallel elements welded/connected together. There can be clamping rings at the end of each element or not until the ends of the whole mesh. The mesh of the purifier assembly is fastened around the perforated structure with the above clamping rings, but additionally it is possible to use welding, soldering, a thicker support mesh around the mesh coil or a metal nail or pin pushed through a larger mesh which can be fast in the inner pipe. Instead of the clamping and blocking ring, the ends can have been welded. The clamping ring is usually welded to the other structure.

According to an object of the invention, the mesh structure can be coated with porous support material which operates as a base for active compounds which oxidise CO, hydrocarbons, NO, hydrogen, ammonia or coal. The hydrocarbons can also include functional groups containing oxygen, nitrogen or halogens. According to an object of the invention, the coating is made such that the mesh holes remain at least partially open at least in one mesh. Advantageously in some embodiments, all the holes are substantially open. This provides the advantage that in the open channel the fluid is able to go through the mesh at every point, whereby particles remain on the surface of the mesh with great filtering efficiency. The fluid is driven to change to the other channel by the pressure difference between the channels, which provides efficient mass transport past the catalyst surface on the surface of the mesh.

An assembly according to an object of the invention does not have a coating at all, whereby it only operates as a particle separator and sound damper. Furthermore or alternatively, the catalyst can catalyse the reduction of NO_x with hydrocarbons or ammonia, adsorb nitrogen oxides (reduction in rich conditions) or oxidise ammonia. Typically, the catalyst comprises in the support material aluminium, silicon, titanium oxides and/or zeolites. The thickness of the coating is between 1-500 micrometres, advantageously between 5-40 micrometres. The area of the coating is determined by used materials and is between 1-700 m²/g, usually between 20- 300 m²/g. The coating can be added to the purifier assembly of various sludges, sols and/or solutions by dipping, pumping, sucking and/or spraying. The meshes can be coated open when loose of its pair by spraying and, after that, wind the mesh and catalyst structure. Consequently, it is possible to ensure that the eyes of the mesh remain open. The coating can also be made totally or partially by means of volatile starting materials (CVD₁ ALE techniques).

According to an object of the invention, at least part of the mesh structure is coated with support material in which is added catalytically active compounds.

According to an object of the invention, the catalytically active compounds catalyse the oxidation and/or reduction reaction of exhaust and waste gases. According to an object of the invention, the support material comprises aluminium oxide, silicon oxide, titanium oxide, zeolite, zirconium oxide and/or cerium oxide.

According to an object of the invention, the catalytically active compounds include platinum, palladium, rhodium, iridium, ruthenium and/or vanadium, catalyse the oxidation and/or reduction reaction of exhaust and waste gases.

According to an object of the invention, there are in the flow direction upstream or downstream of the purifier assembly one or more catalysts or operational units such as an oxidation catalyst, a particle filter, a reduction catalyst of nitrogen oxides and/or some other unit used for purifying refuse gases. As active metals can be used e.g. noble metals such as platinum (Pt), palladium (Pd), iridium (Ir) and/or rhodium (Rh) and/or ruthenium (Ru). The active components can be added in the coated catalyst structure by absorbing (dry, wet or chemisorption) or among coating sludge, solution or sol. The active components can be pre-matched in the particles of materials before coating. The coatings and/or absorptions employ water or other solvents or their mixtures usually in the liquid phase.

There can be active metal (e.g. noble metal) in the purifier assembly for 0.01-10 g/dm³, advantageously 0.1-3 g/dm³. If there are several structures successively in the flow direction, the first can include active metal advantageously for 0.8-3 g/dm³ and the latter 0-0.8 g/dm³. It is also possible to make an assembly the inner circle of which comprises a mesh containing active component and the outer circle including very little active component or not at all on the surface of the mesh (can also be without coating). The division of the active component in the mesh can also be inversed: Pt more in the outer circle and less in the inner circle. The aim is to add to the same structure e.g. Pt more on the inlet side in the direction of the flow where it is possible to make more NO2. On the outlet side, Pt cannot catalyse the oxidation of NO as much, whereby there the charge is lower. On the outlet side, there can also be other active components such as Pd. This structure can be used together with the oxidation catalyst being upstream. The active component is selected according to the use. Platinum-bearing catalyst coatings can enhance the formation of NO₂, which promotes the combustion of particles and the regeneration of the purifier e.g. in diesel targets. Decreasing the formation of NO₂ is an object in targets in which the regeneration is done totally actively (fuel injection and/or engine throttling) and when wishing to minimise NO₂ emissions. Pd can be employed as an active component when the object of the catalyst coating is to catalyse the oxidation of CO and HCs and the temperatures are high in the operating or regeneration conditions. When the gas mixture is stoichiometric or rich (λ<1), rhodium and/or palladium is used for stability, selectiv- ity and NO_x reduction.

As promoters in the support material can be used e.g. vanadium (V), wolfram (W), iron (Fe), zirconium (Zr), cerium (Ce)₁ lanthanum (La), manganese (Mn)₁ cobalt, barium, strontium and/or nickel (Ni). The support material can also mainly consist of these promoters. In the coating, it is possible to add typical NO_x adsorption compounds e.g. by absorbing, whereby nitrogen oxides can be adsorbed in lean mixture and reduced during rich mixture.

A purifier coated with catalyst according to the invention can be treated during manufacture in static or dynamic conditions with oxidising and/or reducing gas mixtures which can include air, oxygen, hydrogen, carbon monoxide, ammonia, exhaust gas, hydrocarbons, water or inert gas. With the treatments, it is also possible to form various mixed oxides between the coating compounds by employing suitable starting materials, particle sizes and finishing conditions.

The purifier according to the invention is thus able to decrease the emissions of refuse gases. By utilising sufficiently dense mesh, low corrugation height and sev- eral layers of the mesh or an equivalent structure, good particle separating efficiency is also provided. The assembly is a novel kind of a partial filter structure for diesel targets, among others. This assembly is particularly well suited for the purification of the exhaust gases of small diesel engines in which it is integrateable directly to the sound-damper structure. The purifier also replaces normal elements used in sound damping. At its best, the purifier can be located in the same original sound damper, whereby no change is visible on the outside and no redesigning problems occur in the target of usage. As the flow has been forced onto the spiral route, the filtering capacity is better with the same total volume than when the same meshes were wound as a cell and the flow conveyed through the created cell from one end to the other. The assembly according to the invention provides great separating efficiency for the used mesh material and with relatively great corrugation height due to the forced spiral route.

For the regeneration of particles accumulated in the purifier, it is possible to use passive or active methods. In exhaust gases comprising an excess of oxygen, in front of the purifier assembly can be installed an oxidation catalyst (DOC) which oxidises CO, HCs and NO. Forming NO₂ slowly oxidises coal-based particles. The DOC can be located in the same container or it is separate in front of a container according to the invention. The DOC can also be within the inlet or outlet pipe. The oxidation catalyst coating can also be in a structure in an inlet according to the invention and another structure uncoated or containing less active compounds according to the invention in the outlet. The temperature of the catalyst can also be increased externally by combusting hydrocarbons or by utilising other exothermic (heat-forming) reactions. Additional heat is provided by feeding fuel among the exhaust gas and/or by post-injection in the engine. At the same time, it is possible to decrease the volume of combustion air (by decreasing A/F ratio). It is also possible to provide additional heat for the regeneration of the catalyst structure by electric heating, burners and/or plasma and/or some other method heating the structure and/or soot. The accumulation of particles can be promoted with electrostatic methods, by using mesh pairs as charged collection meshes and by insulat- ing the meshes from the other structure and each other. For the regeneration of particles, it is also possible to use additives which enhance the combustion of soot (FBC = fuel-born catalyst) which include e.g. Fe, Sr and/or Ce-based compounds. The purifier assembly can also be coated with known compounds catalysing the combustion of soot in which the chemical element is e.g. vanadium, manganese, copper, cerium, iron or alkali/alkali earth metal.

Before the purifier assembly, it is possible to feed in addition to hydrocarbons and known fuels also other oxidising or reducing compounds such as ammonia, urea, ozone, hydrogen peroxide, air, oxygen and/or water as clean or in mixtures. These can promote the reaction of NO_x and/or particles and the maintenance of the puri- fier and adjust the stoichiometry of reactions.

Particular description of invention

Some embodiments of the invention are described in the following figures and example.

Figs. 1A-1C show some structures according to the invention.

Fig. 2 shows a cross-sectional view at the point of a catalyst structure.

Fig. 3 shows channels formed by a mesh pair in which the flow is also able to travel sideways.

Fig. 4 shows meshes with different starting points.

Fig. 5 shows a mesh structure formed by the mesh pair or several walls. Fig. 6 shows a special structure.

Fig. 7 shows an elongated purifier assembly.

In Figs. 1A-1C: 1= incoming fluid, 2= inlet pipe, 3= outlet pipe, 4= perforated structure, 5= catalyst structure, 6, 9= blocking elements, 7= outgoing fluid, 8= purifier housing. The flow of the fluid 1 ,7, usually exhaust gas, can either be from within the pipe outwards through the mesh structure 5 or inversed from the purifier housing 8. The purifier assembly is within the purifier housing 8 and it is arranged in the inlet pipe 2 (Figs. 1A₁ 1C) or the outlet pipe 3 (Fig. 1B). At one end of the perforated structure 4, around which there is the spiral-like mesh structure 5, there is the blocking element 6, 9 to control the flow of the fluid 1 , 7 through the perforated structure 4 to the mesh structure 5 and/or vice versa. At the end of the mesh structure 5, there is the blocking element 6 in order to at least partially prevent the flow of the fluid 1 , 7. The blocking elements 6 at both edges block the by-pass flow totally or partially along the outer surface of the perforated pipe 4 out or after the first mesh layers. The blocking element 6 blocks up and clamps the mesh or an equivalent structure. The perforated pipe 4 is totally closed with the blocking element 6, 9, whereby the flow is forced through the perforated and catalyst structure 4, 5. The case is of the block of the inlet or outlet pipe 2, 3 depending on which way the flow goes through the purifier assembly (Fig. 1A or 1B). At the end of the pipe i.e. the perforated structure 4 can be welded a plug 9 of the same material as the perforated structure 4. The plug can also be integrated into the closest blocking element 6 clamping the mesh structure 5. Fig. 1C clarifies the structure for the part of the blocking elements 6, 9. The perforated structure 4 of Fig. 1C is from one end an open and from the other end a closed pipe. In Fig. 2, arrows point the alternative flow directions of the fluid. In Fig. 3, in the channels of the mesh structure 5 formed by the mesh pair the fluid 1 incoming in the axial direction is also advantageously able to travel sideways. The greatest volume and thus the easiest flow channel of the fluid 1 in the mesh structure 5 is a space formed by corrugations h-L between the meshes. In Fig. 4, the mesh structure 5 is wrapped around the perforated structure 5 of several different meshes or structures one or more of which are non-corrugated. A whole foil forces the flow to totally circulate on the spiral route. If many meshes are used, they can start at different points of the perforated structure, whereby gas is able to access directly two or more spiral-like channels from which the fluid can also be carried through the mesh. Fig. 5 describes some of the concepts. A corrugation width L and height (e.g. hi relative high peak, h2 relatively low peak) in the corrugated foil can be selected suitable for the target in relation to the assembly, counterpressure and emission limits. The corrugation height can be the same or different in various meshes. The wall is usually a mesh or a foil. The foil can also be a smooth foil hθ. Fig. 5 also shows a width D of the mesh. The direction of peaks h3, h4 of the corrugated foil is selected advantageously such that it is at an angle with the fluid flow direction. Fig. 5 shows two corrugated foils h3, h4 which are both at an angle with the flow direction of the fluid 1 and, furthermore, at an angle in relation to each other h3/h4. In Fig. 6: 1= incoming fluid, 2= inlet pipe, 3= outlet pipe, 4= perforated structure, 5= catalyst structure, 6= blocking elements, 7= outgoing fluid, 8=purifier housing. The purifier assembly of Fig. 6 is a specific special structure in which the blocking ring 6 only closes the inner circle of the mesh structure 5 and from the outer circle the fluid is able to exit from the side to the housing 8. The flow can also be in- versed i.e. from the housing 8 through the mesh structure 5 to the perforated structure 4.

In Fig. 7: 1= incoming fluid, 2= inlet pipe, 3= outlet pipe, 4= perforated structure, 5= catalyst structure, 6= blocking elements, 7= outgoing fluid, 8=purifier housing. The purifier assembly of Fig. 7 is an elongated purifier assembly within the purifier housing 8 which comprises a relatively great open flow area which correlates with the surface area of the perforated structure 4.

Example 1

The purifier assembly according to the invention (code NOC) was manufactured by using a slantly corrugated mesh foil which was wound for five overlapping meshes around the perforated pipe such that the outer diameter of the structure was 90 mm and its length 130 mm. The pipe diameter was 55 mm, holes were 10 x 50 mm, the area of the holes was about 45% of the total area of the perforated pipe. The corrugation height was about 1.3 mm, width about 2.5 mm and the volume of the catalyst layer was 0.52 litres. The thread thickness was about 110 μm and there were about 34 threads at the distance of one centimetre (87 mesh). The structure was coated by spraying in the mesh support material having a large area in which the main component was aluminium oxide and it further contained as promoters ZSM-5 and Beta zeolite (Si/AI₂ >25), TiO₂, CeO₂ and ZrO₂, for the total of about 40%. The support material included particles of both small (<2 μm) and large (>2 μm) particle size. The eyes of the mesh remained totally open, because the quantity of the coating was about 10 g/litre and the eye diameter (from mesh edge to mesh edge) before coating about 180 μm. As an active component, Pt was absorbed in the support material for 0.53 g/litre i.e. the total of about 0.27 g of Pt. As the eyes of the mesh remained open in coating, exhaust gas is able to travel in the assembly also through the mesh, which intensifies particle separation. The perforated pipe was connected

In the tests, a Fiat Doblo (1.9 I) was the vehicle which was driven within the European passenger-car test cycle (EDC) settings. In front of the structure according to the invention, immediately following the engine, there was an oxidation catalyst (DOC) the cellular structure of which was made of metal foil, the volume was 0.52 litres, the cell number was 120 cpsi (cells per in²), the coating volume was about 110 g/l and Pt charge 3.2 g/l. The consistency of the coating was similar to the one in the catalyst according to the invention. The purpose of the oxidation catalyst is to intensify the operation of gaseous components (the oxidation of CO, HC and NO), because the assembly according to the invention solely has quite little coating and Pt. The assembly according to the invention was tested using both flow directions of Fig. 1.

Table 1. Emissions and conversions with oxidation catalyst (DOC) and novel structure according to the invention

The catalyst according to the invention with the oxidation catalyst provided the conversions of 63% of CO, 55% of THC and 53% of PM with the assembly according to Fig. 1A. The assembly according to Fig. 1 B with the oxidation catalyst provided the conversions of 63% of CO, 59% of THC and 45% of PM. With the sole oxidation catalyst the conversions were: CO 56%, THC 37% and PM 26%. NO_x conversions cannot be considerable in these conditions and the measuring result was even negative which can result from measurement variation. The PM, THC and CO conversions are good when keeping in mind that the temperatures are clearly below 200⁰C for the first 800 seconds in the cycle with the duration of about 1 ,200 s.

Claims

1. A purifier assembly employed in the treatment of fluids to be arranged in the purifier to an inlet pipe (2) and/or an outlet pipe (3) of fluid (1 , 7), characterised in that the purifier assembly comprises a perforated structure (4) arrangeable in the inlet pipe (2) and/or the outlet pipe (3) around which is installed at least one mesh structure (5) contained by an open channel, formed by a spiral-like flow channel, which comprises at least two meshes in the flow channels between which and through the mesh structure the fluid (1 , 7) is arranged to flow, and that in the perforated structure (4) is arranged one or more blocking elements (6, 9) to control the flow of the fluid (1 , 7) through the perforated structure (4) to the mesh structure (5) and/or vice versa.

2. A purifier assembly according to claim 1 , characterised in that the diameter/hydraulic diameter of the holes of the perforated structure (4) is 0.1-100 mm, such as advantageously 1-50 mm, such as e.g. 10-40 mm, and/or the area of the holes is 1-95% of the total area of the whole perforated structure, such as advantageously 10-70%, such as e.g. 20-60%.

3. A purifier assembly according to claim 1 or 2, characterised in that the mesh structure (5) comprises holes the size/apparent diameter of which is 0.05-10 mm, such as advantageously 0.1-2 mm.

4. A purifier assembly according to any one of preceding claims, characterised in that at the ends of the mesh structure (5) there are one or more blocking elements (6) in order to at least partially prevent the flow of the fluid (1 , 7).

5. A purifier assembly according to any one of preceding claims, characterised in that the mesh structure (5) installed around the perforated structure (4) formed by a spiral-like flow channel is formed from one or more slantly corrugated mesh foils, perforated foils, perforated sheets, meshes, fibre mattings, paper sheets and/or membranes.

6. A purifier assembly according to any one of preceding claims, characterised in that the mesh structure (5) also comprises at least one non-corrugated mesh foil, perforated foil, perforated sheet, mesh, fibre matting, paper sheet and/or membrane.

7. A purifier assembly according to any one of preceding claims, characterised in that the mesh structure (5) comprises threads the thread thickness of which is 0.1-5 mm, advantageously between 0.1-1 mm.

8. A purifier assembly according to any one of preceding claims, characterised in that the mesh structure (5) comprises at least one slantly corrugated mesh the corrugation angle of which in relation to the main flow in either direction is 1-90 degrees, advantageously 20-60 degrees.

9. A purifier assembly according to any one of preceding claims, characterised in that the mesh structure (5) comprises at least one slantly corrugated mesh the peak height of which is 0.2-200 mm, advantageously 0.8-3 mm.

10. A purifier assembly according to any one of preceding claims, characterised in that at least part of the mesh structure (5) is coated with support material in which is added catalytically active compounds.

11. A purifier assembly according to claim 10, characterised in that the mesh structure (5) is coated with the support material such that the eyes of the mesh remain at least partially open.

12. A purifier assembly according to claim 10 or 11 , characterised in that the mesh structure (5) comprises catalytically active compounds which catalyse the oxidation and/or reduction reaction of exhaust and waste gases.

13. A purifier assembly according to any one of claims 10-12, characterised in that the mesh structure (5) comprises support material which contains aluminium oxide, silicon oxide, titanium oxides, zeolite, zirconium oxide and/or cerium oxide.

14. A purifier assembly according to any one of claims 10-13, characterised in that the mesh structure (5) comprises catalytically active compounds which con- tain platinum, palladium, rhodium, iridium, ruthenium and/or vanadium, catalyse oxidation and/or reduction reaction of exhaust and waste gases.

15. A purifier assembly according to any one of preceding claims, characterised in that the flow direction of the fluid (1 , 7) is arranged from the perforated structure through the mesh structure.

16. A purifier assembly according to any one of preceding claims, characterised in that the flow direction of the fluid (1 , 7) is arranged through the mesh structure to the perforated structure.

17. A purifier assembly according to any one of preceding claims, characterised in that there are in the flow direction upstream or downstream of the purifier assembly one or more catalysts or operational units such as an oxidation catalyst, a particle filter, a reduction catalyst of nitrogen oxides and/or some other unit used for purifying refuse gases.

18. A method for manufacturing a purifier assembly used in the treatment of fluids, characterised by forming in the purifier assembly a perforated structure (4) arrangeable in an inlet pipe (2) and/or outlet pipe (3) of fluid (1, 7) around which arranging at least one mesh structure (5) contained by an open channel, formed by a spiral-like flow channel which comprises at least two meshes in the flow channels between which and through the mesh structure the fluid (4, 6) is arranged to flow, and by arranging in the perforated structure (4) one or more blocking elements (6, 9) to control the flow of the fluid (1 , 7) through the perforated structure (4) to the mesh structure (5) and/or vice versa.

19. The use of a purifier assembly in the treatment of exhaust or waste gases, characterised in that any purifier assembly according to claims 1-17 is employed in the treatment of gases comprising an excess of oxygen by controlling the fluid (1 , 7) to the purifier assembly.