WO2012123643A1

WO2012123643A1 - Purification device

Info

Publication number: WO2012123643A1
Application number: PCT/FI2012/050247
Authority: WO
Inventors: Matti Härkönen; Pekka Matilainen; Olli-Pekka HYPPÖNEN; Hannu HÄNNINEN
Original assignee: Ecocat Oy
Priority date: 2011-03-16
Filing date: 2012-03-16
Publication date: 2012-09-20
Also published as: RU151051U1; WO2012123618A1; CN203867667U

Abstract

The invention relates to a purification device (PD) for removing impurities, such as carbon containing particles and hydrocarbons, from exhaust and waste gas. The invention also relates to a method for manufacturing and to a method to use and regenerate such a purification device. The purification device (PD) additionally comprises at least one ignition elements (IE) before said open particle separator (OPS) in flow direction for periodically igniting collected and flowing gas impurities, and there is at least one open channel or chamber (CHA) between said ignition element(s) (IE) and open particle separator (OPS).

Description

Purification device

Background art The invention relates to a purification device for removing impurities, such as carbon containing particles and hydrocarbons, from exhaust and waste gas. The invention also relates to a method for manufacturing and to a method to use and regenerate such a purification device.

Allowable limits in the exhaust emissions of vehicles, work machines and engines have will lower year by year such that it is necessary to use aftertreatment to keep the emission below limits. With diesel vehicles, the hardest to reach are particulate-matter (PM) and NO_x emission limits, but carbon monoxide and hydrocarbon emissions can be effectively eliminated by oxidation catalysts. For decreasing NO_x, it is possible to use engine modification methods (EGR = exhaust gas recirculation) which, however, have an effect increasing CO, HC and PM emissions. 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 inside the wall after the initial accumulation. The average pore diameter in the filter walls of these skin filtration based filters is about 8-25 μιη, which is enough with common design to remove over 95% of particulate mass. 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 energy, unlike conventional filters, where the main fraction of ashes and unburned material will remain on the surface of a filter. Therefore, the pressure drop of full-filters aims to increase during the use, although soot/carbon is removed completely in regenerations. By the filtration efficiency, deep filtration based filters are between skin and partial filters and the filtration efficiency is about 50-90%, the optimum being by practical aspects about 60-80%. The deep filters are prepared usually by ceramic or metallic fibers or foams or sintered metal. Fibers can be as a bed or folded mat in the filter. The ratio of efficiency and pressure drop can be optimized by maximizing the filtration surface area (thin mats folded like in oil and air filters).

Nets, fiber mats and perforated plates/foils are commonly used in partial filters and particles are accumulating on these structures due to pressure differences and turbulence. The reaction mechanism and design are different between deep and partial filters, even if the namely the same materials are used. For example, the fiber mat can act as a cell structure by the assembly, where fluid is forced to flow through the mat (deep filtration) or as a cell structure, where the main stream flows between the flow channel formed from straight and corrugated fiber mats and a part of particles remains however on the surface of walls (partial filtration). The filtration on fiber-based filters is based on the appropriate diameter of fibers. The void fraction is usually very high (>90%) in fiber layer or mat but the void fraction or porosity on typical skin-type filters (e.g. cordierite, SiC, Al titanate) is typically 40-50% and in particular high-porous skin filters even up to 60-70%. Also in deep filtration, particles start to accumulate more on the front part of by the flow direction, by the similar way like on skin filtration.

Usually, filtered carbon fraction (soot) in PM is thermally combusted by means of extra heat. Soot can be oxidised by an intensive combustion reaction with oxygen at a temperature higher than 550 °C or slowly at lower temperatures (250-350 °C) by means of N0₂. N0₂ being formed in the oxidation catalyst oxidises soot in reasonably low temperatures (>250-300 °C) when the oxidation catalyst is efficient enough.

With efficient oxidation catalysts, it is possible to remove a large part of the hydrocarbon-containing volatile fraction (VOF = volatile organic fraction or SOF = soluble organic fraction) of PM. The VOF fraction is usually 1 0-40%, 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 strongly on flow and linear speed. The filtration efficiency of deep filters is usually decreasing by the increasing flow rate but the efficiency of partial filters is increasing by the increasing flow rate (filtration based on enhanced mass transfer), which makes a clear difference on their operation principles. Many deep filters start to allow particles through with higher flow speeds. The separating efficiency is also dependent on particle size.

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 containing oxidation catalyst and following it an uncoated or catalyst-coated DPF (EP341832). Problems in the passive method with the conventional full filter are related to situations where the formation of N0₂ is not sufficient e.g. when driving in rush-hour city traffic, and the method requires a fuel with very low sulphur content (S<10 ppm) for minimising the formation of sulphate in the efficient and expensive Pt containing oxidation catalyst. If high-S fuel is used with Pt containing oxidation catalyst, the increasing formation of sulphates (S0₂ -> S0₃ -> S0₄, catalyzed by Pt) ruins the benefits of a filter, which is filled too fast, which increase the regeneration frequency and blocking risk. The blocking of the DPF cannot be accepted in any situation, because it will interrupt driving. Consequently, most particle filters include 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. It is possible to arrange an active regeneration by increasing temperature periodically usually up to 600-650 °C with modern cars. If enough soot is accumulated in the filter, the initiation of combustion creates additional heat to complete soot combustion. 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 maintenance operations.

In addition to the conventional cellular particle filter of the wall flow type, structures 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 scrubbers. In known filter structures, 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 material. 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. It exists also metallic full-filters, they have made e.g. of sintered metal or metal foams. 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 axial 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.

The regeneration of particulate filters has been conducted by combined engine throttling (air/fuel ratio adjusted near to stoichiometric values) and additional fuel injection, in addition electrical, plasma (SAE Paper 1 999-01 -3638) or burners, which create additional heat and soot will burn (EP 007061 9-1982 and Emissionminderung, Autobilabgase, Dieselmotoren, Nurnberg 1 5-1 7 Oct 1985, Kurzfassungen, VDI 1 985). Additional fuel can be injected into cylinders (post- injection) or into exhaust gas before an oxidation catalyst and/or catalyzed particulate filter. Combustion can be enhanced with the agents injected into exhaust gas. These compounds consist of e.g. Ce, Fe or Sr, which are dispersed on soot and decrease combustion temperature e.g. down to 500 °C and boosted also NO₂ assisted regeneration.

Electrical heating has been used various ways, it is an old invention ((SAE 900603, Hayashi et al. 1 990). Electrical heating is based usually on the use of different kinds of electrical resistance. The heating of whole exhaust gas amount up to the combustion temperature of soot requires during the driving high instantaneous powers of the vehicle's electrical units. It is possible to heat locally on selected positions at the separate times, when the needed energy is decreased down to the scale of vehicle electrical power (SAE paper 2005-01 -3703). Electrical heating has been used to guarantee the regeneration at low temperatures combined with the use of fuel-born catalysts (SAE Paper 2000-01 -1 924). It is possible to arrange a separate exhaust line with a filter for each cylinder which enables the temperature and regeneration control of each line separately (US 4,709,547, 1 987). Electrical resistance wires can locate partially inside the filter, which can also be electrically conductive (US 5,472,462, 1 995 and EP 0244061 , 1987). The use of glow plugs has been proposed in relation to full-filter regeneration (DE 20 2004 01 8993, 2004). A pressure sensor can be integrated into glow plug (US 7,214,908, 2005). The regeneration algorithms of full-filter with glow plugs can be controlled based on pressure drop responses (WO 201 0/015428, 2009). The system consisted of one or more glow plugs assembled directly to the contact to the front face of a wall-flow filter which initiates soot combustion. In general, the control of active regeneration is an own technical field, where exist a lot of patents and publications. The control is usually based on the responses of temperature, pressure or engine map variables, which are correlated to the accumulated particulate loading and appropriate regeneration conditions.

The catalytic coating of particulate filter promotes the catalytic combustion of soot (SAE Paper 850001 5, 1 985), NO₂ formation and the oxidation of hydrocarbons injected to get temperature to rise. The most efficient and durable catalysts for HC (originating from fuel), carbon monoxide (CO) and NO oxidation are based on the use of platinum (Pt). Particularly, the high NO₂ formation rate requires the presence of Pt but in HC and CO oxidation also palladium (Pd) is active. Different kind of coated catalysts have been utilized to catalytic soot combustion and they consist of for example vanadium, copper, potassium, molybdenum and compounds based on similar elements. Their catalytic reactions are typically based on their high mobility on soot surface or they form mobile oxygen species.

Opposite to full-filters, the regeneration of partial filters is based mainly on passive regeneration by NO₂. Partial filters have been used without blocking also with fuels containing more sulphur and ashes, because unburned impurities and sulphates are emitted immediately or later out of open filter. The requirement for regeneration is that temperature and NO_x/C ratio are high enough in average, when it is possible to form enough NO₂ and NO₂+C reaction is fast enough to prevent the cumulative accumulation of carbonaceous particulates. The structure and the filtration of particulates differs from those of full-filters, therefore the regeneration conditions are different. The efficiency of partial filters was at the beginning of the 2000's century slightly better than with oxidation catalysts but later the PM efficiency of these partial filters has been liked up to the level of 60- 70%. Even with that efficiency, the PM emissions are still over 5-20 times compared to full filters (conversion over 95-98%) and therefore these filters are understood to fall to separate categories. Due to these reasons, blocking tendency and regeneration are still completely different with partial filters than with skin filtration based filters. The pressure drop increase of filling full-filters is so significant that it can be measured with standard pressure gauges. Instead, the pressure drop is increasing clearly less and slower. A detectable pressure drop increase like with full-filters is already a sign about blocking. This pressure drop dependency makes a difference between partial and full filters. Thus, different kinds of control strategies for PM regeneration are optimal for these two types of filters. Description of invention

The object of this invention is to provide a purification device (PD), system and regeneration method operating in diesel or equivalent waste gases which substantially minimises the quantity of emission components, particularly particulate emissions and hydrocarbons. 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.

The purification device comprises at least one open particle separator (OPS) comprising permeable/semipermeable sheets and/or mats and having open channels for gas with impurities to flow between said sheets/mats/foils, and that said purification device additionally comprises at least one ignition element before said open particle separator in flow direction for periodically igniting collected and flowing gas impurities. Advantageously there is at least one open channel or chamber between said ignition element(s) and open particle separator. . Compared to normal filters based on prior art, the novel type of a purification device and regeneration method/system provides service-free operation, regeneration in all use conditions and a low energy consumption. The purification device according to the invention remains unblocked over the life-time causing a low pressure loss and it additionally has low manufacturing and operation costs. According to an object of the invention there is at least one post injector for injecting fuel or HCs to exhaust or waste gas for burning with said ignition element. This substantially minimises the quantity of emission components. According to an object of the invention there is at least one separate vaporization device after said post injector for vaporizing injected fuel or HCs. Also this substantially minimises the quantity of emission components.

According to an object of the invention there is at least one fuel circulation device for injecting fuel or HCs to exhaust gas from normal fuel/HC circulation devices of engine. This also substantially minimises the quantity of emission components.

According to an object of the invention purification device (PD) can utilize catalytic coating. The purification device can employ coatings which comprise catalytically active components active for the oxidation of carbon monoxide, hydrocarbons, nitrogen monoxide (NO), particles and the reduction of nitrogen oxides by any reductants. The oxidation of particles can be promoted directly or indirectly by means of NO₂ and parallel periodically and/or continuously with the ignition element to guarantee the regeneration.

Possible fields of usage of the invention are e.g. exhaust, flue gas and waste 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, biogas), liquid fuel (e.g. light or heavy fuel oil, diesel, petrol or biofuels) or/and solid fuel. The device 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 possible rise in temperature are carried out in order to regenerate the device or its units either completely or partially from adsorbents, accumulated poisons and/or particles. The mixture can be adjusted if the complete system consists also, in addition to the device in this invention, of other catalysts/units (like NO_x adsorption catalyst or full-filters) which require periodically stoichiometric or rich conditions or higher temperature for regeneration.

The use of open particle separators and partial filters has been expanded to the applications, where temperatures are very low for example in continuous city driving and the conditions are not applicable for regeneration and then the efficient partial filters start partly to block or particles are passing into exhaust gas while the partial filter remains still open. In these conditions, it has created a need to use also active regeneration methods which were originally not applied with them. This created an idea to use active regeneration methods with the open particulate separator. But are the benefits of open particulate separators then lost and is it then better to use full-filters with active regeneration? However, the use of active regeneration with open particulate separators leaves many advantages. The volume and mean pressure drop are still significantly lower than with full-filters (wall-flow), which have a key role in investment and operation costs over the time of the systems. An open particulate separator will not need service to remove ash. Partial filters and OPS have usually thin walls and structures (e.g. fibers, low heat capacity -> lower external energy needed for heating compared to full-filters like cordierite or silicon carbate) and metallic structures have a good thermal conductivity, when the local temperature peaks are created less during carbon combustion.

The active regeneration can be divided into categories by the magnitude and effect of additional heating : 1 ) Heating of whole exhaust or waste gas and filter up to the combustion temperature of soot (high energy/power requirement), 2) Heating parallel filter segments by controlled phases at the different times up to the combustion temperature of soot or 3) Igniting the accumulated carbon containing particles or injected fuel/HCs to burn with an ignition impulse (the lowest energy/power requirements). That third regeneration can be conducted also segment by segment locally in separate positions in the filter. In the regeneration by the invention, this third method is applied with the purification device and open particle separator, which differs essentially from those two other known methods used with full-filters.

According to an object of the invention, there is at least one metallic or ceramic particle collection unit (PCU) locating near said ignition element (I E) for collecting carbon containing particulates and/or hydrocarbons near said ignition element (I E) thus enhancing the ignition and combustion of impurities. According to an object of the invention, at least one ignition element (I E) is located at least partly in said particle collection unit (PCU) or in contact with said particle collection unit (PCU). According to an object of the invention, said particle collection unit (PCU) is located inside the channels of open particle separator (OPS), advantageously in the front part of open particle separator (OPS) by flow direction.

The design of one embodiment of invention is shown in fig. 1 and 2. Fluid (1 , 2, 3) (usually exhaust gas) flows into a reactor (4), where an open particle separator (5) (OPS) is located with one or more ignition elements (6) (I E). Front of this reactor can be also a separate purification catalyst (7), which is advantageously an oxidation catalyst.

The ignition element can be connected with the particle collection unit (8) (PCU), which collects particles efficiently near to the ignition element. The reactor is for example a conventional mantled catalyst converter, where the substrate can be non-insulated or wrapped in insulation/assembly mat and/or heat shields. The reactor can be integrated into muffler, where is possibly also other functional units (oxidation or deNO_x catalysts (SCR, LNT), full-filters and other additional unit related to the use of previous ones). The open particle separator is a structure, which has, instead of tight pore or fiber structures of full-filters, open channels, where the detachment of particles on flow channels has been enhanced by using tortuous, in places throttling and expanding channel shapes, where exist passing paths through channel walls, which balance the pressure differences between parallel channels. The essential difference between full filters and the open particle separator is the fact, that fluid is enforced completely through filtering/collecting layer in full filters but it exist also free, open route through the OPS. The open channels through OPS is corresponding a hydraulic diameter, or distance from wall to wall, above 50 μιτι, which pores or mean distance between filtration walls are smaller with full-filters. These conditions promote the attachment of particles on walls, which act as collection surfaces and which have been advantageously prepared by ceramic or metallic nets, membranes, fiber mats, screens or/and perforated foils or their combinations. Ceramic are inorganic non-metallic materials like metal oxides (alumina, silica and their mixtures; cordierite and other materials used a porous fibers or sheets). These wall materials in OPS are permeable or semipermeable and allow the fluid to pass through. The semipermeable walls allow gaseous compounds to penetrate it but solid or liquid particles are attached on the surface of that wall. Even if the wall was completely full of particles, it will remain permeable in respect of gas flow. Typical filtration efficiency is between 40-80%, which is clearly lower than with wall-flow filters. Even if the wall was completely full of particles, it will remain permeable in respect of gas flow. It is possible to prepare full-filters from the same material, if the fluid is forced completely through the structures/layers which are usually also thicker than as OPS walls, e.g. efficient fiber filters.

The walls of OPS can be flexible or frigid, advantageously metallic and ceramic sheets/fiber mats are made from flexible materials which are easy to roll for the final structure. The metallic structures are made from typical oxidation resistant steel or alloy materials, which can be used in normal use conditions without excessive oxidation. The presence of aluminium in alloy is preferred to form protecting alumina (Al₂0₃) layer in preparation or in use conditions. According to an object of the invention, said open particle separator (OPS) comprises permeable/semipermeable corrugated sheets/mats/foils forming an open particle separator (OPS) structure with open channels (CHA) having corrugation height between 0.2-200 mm, advantageously between 0.35-25 mm, such as 0.5-3 mm. According to an object of the invention, said open particle separator (OPS) comprises permeable/semipermeable metal wire meshes/sheets/mats having wire diameter between 0.01-5 mm, advantageously between 0.05-1 mm, and/or the holes in metal wire sheets which apparent diameter is between 0.02-10 mm, advantageously between 0.05-0.6 mm. According to an object of the invention, said open particle separator (OPS) comprises (semi)permeable ceramic fiber sheet/mats. According to an object of the invention, said open particle separator (OPS) comprises permeable/semipermeable metallic fiber sheet/mats. According to an object of the invention, said (semi)permeable sheets/mats are corrugated forming an open particle separator (OPS) structure with channels having corrugation angle in relation to the main flow in either direction between 1 -89 degree, advantageously between 10-80 degree, such as 20-60 degree.

According to an object of the invention, said particle collection unit (PCU) comprises fibres or/and wire mesh having wire diameter of 1 to 20 % compared to the wire diameters of the open particle separator (OPS). Correspondingly, the ratio of fiber/wire diameters is in the range of 5-100 (diameter of OPS wires /diameter of CPU fibers). As an example according to an object of the invention, an open particle separator is built from corrugated mesh (net, screen), where the corrugation shapes channels, which orientation differs from the main flow direction and parallel nets are mutually in a different angle compared to the main flow direction (Fig. 2 and 3). The corrugation height (hi and h2) in the mesh structure can be selected suitable for the target as regards the assembly, back pressure and emission limits. The corrugation height can be the same or different in various meshes/screens. The height can be varied between 0.2-200 mm, advantageously between 0.35-25 mm, such as 0.5-3 mm. According to an object of the invention, the corrugation angle in relation to the main flow in either direction is at least in one mesh 1 - 89 degrees, such as 10 - 80 degrees, such as advantageously between 20 - 60 degrees. The corrugation angle can also be varied between -89 - +89 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 slant 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 OPS according to the invention is provided of the same mesh. It is also possible to prepare special structures, where the corrugation angle is between 89- 90 degrees. 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. These slant meshes are prepared by driving a flat mesh through obliquely toothed wheels, which form the corrugation structure used for open particle separators in the invention. Between two corrugated meshes can be also flat mesh, fiber mat or perforated wall, when the decreased channel size improves mass transfer and particle accumulation capacity. It is also possible that between permeable/semipermeable sheets is non-permeable a foil or wall, which divides OPS for sectors which have not connection paths. For example, the non- permeable wall can substitute every, every second or every fourth flat sheets in the previous structure (flat sheet between two slant corrugated sheets). This structure has few advantages: non-permeable wall acts as a fire-wall during fast combustion of particles, the regeneration can be restricted in each sectors and it acts as mechanical support for the structure. According to an object of the invention, it is possible to optimize the peak heights by the targets: very dirty targets -> high peak height, very clean targets -> low peak height.

According to an object of the invention, the mesh/sheet structure in OPS comprises threads (wires) the thickness of which is 0.01 -5 mm, advantageously between 0.05-1 mm, and holes the size of which (apparent diameter/hydraulic diameter from mesh to mesh at the middle of the meshwork) is 0.02-10 mm, advantageously 0.05-0.6 mm. The mesh (sheet) can be a woven structure or a mesh matting or otherwise cohering. 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, e.g. thickness 0.2-0.5 mm and holes 0.1 -2 mm, and the corrugation height is high, e.g. 2-10 mm and, in clean targets, the mesh is denser, e.g. thickness 0.05-0.2 mm and holes 0.05-0.1 mm, and the corrugation height low, e.g. 0.5-2 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 metallic or ceramic fibre mats/sheets, membranes or perforated foils of which an equivalent structure is made and they partially allow fluid through. In addition, the structure shown in Fig. 2 and 3 can have additional or alternatively flow barriers, throttling/expanding shapes/elements, dead ends and blades, which still improve the mass transfer and collection efficiency and create open particle separator structure. The ignition element has a function to create local additional heat, energy or impulse, which initiate the combustion of collected particles on OPS. Particles consist mainly of carbon and hydrocarbons, which are potential to ignite by this kind of additional energy or spark. Hydrocarbons can locally ignite when temperature rises over 1 50-300 °C and carbon, when temperature rises locally over 400-600 °C depending on soot structure and possible catalytic effect on carbon oxidation. Simultaneous high NO₂ concentration may also enhance this ignition. The target is thus not to warm up the whole separator but only ignite combustion, while the energy to regenerate the whole separator is created in situ by the combustion of ignited carbon, not by external heat. According to an object of the invention, the ignition element (I E) is an ignition glow plug, a lighter and/or spark generator. The ignition element is typically a glow plug, lighter, burner, primer firing, ignitor, other spark source or electrical resistance, which power can be significantly lower compared to known external heating elements heating wholly or a segment in a filter. The number of ignition elements can be one or more parallel and/or in sequences depending on regeneration strategy. The power for ignition element is originating from an energy source (ES), which releases electrical power or fuel. In mobile applications, this source is usually a battery and/or fuel. A battery is able to release the required power for the ignition element, which needs not to heat the whole exhaust gas but only locally for a moment. The bottle neck of many known regeneration methods based on electricity is the power of batteries. This problem has been solved in the invention because the main energy for particle regeneration is created by the combustion of carbon and/or hydrocarbons on open particle separator or in this device, not from that external energy source. Advantageously in the direct vicinity of the ignition element is also located the particle collection unit (PCU), which has a role to add the collection of particles near to ignition element, when ignition will start best and burning material is accumulated preferably on the front/inlet part of OPS. Because OPS is not a closed filter, particles are not naturally on its inlet part or on face. The particle collection unit is able to promote the regeneration and ignition of OPS for example in the conditions, when the loading degree of OPS is not yet very high. By utilizing the collection unit, it is possible to install the ignition element on the inlet of OPS and the heat regenerated will not affect on the ignition element itself, which may suffer more if installed downstream farer in the positions being in the middle of particle combustion zones. This is a way to protect the ignition element from thermal stress.

The material of particle collection unit (PCU) can be inorganic (silica, alumina or their mixture or corresponding material) or organic fiber selected in the way that it stands the use conditions. Metallic PCU is advantageous in some embodiments because it is mechanically strong and conducts heat better than ceramic structures. The particle collection unit PCU is for example metallic or ceramic fiber mat or layer, which is behind of the ignition element in flow direction. This unit is advantageously inside OPS wholly or partly. PCU can be also a separate unit directly front of OPS (Fig. 4). The PCU can have also a supporting mantle or cover, which protects PCU mechanically and prevents an excessive cooling effect by exhaust gas. The same particle collection material can be applied also in other positions than near to the ignition element in purpose to enhance the particle collection and balance pressure drop over the OPS. The local collection efficiency of particulates is clearly higher in positions where the PCU material is present (e.g. inside OPS). Depending on the total amount of PCU material, this can have a small or significant effect on the PM efficiency of whole OPS, which can be utilized to also to improve OPS. If the PCU is not covering wholly the face of OPS, it is a risk that flow distribution in uneven. Filling PCU material about as the same amount in the separate radial sectors by flow direction, will the pressure drop over different radial positions be the same and no uneven accumulation of particles will happen (Fig. 5).

The function of PCU is also to bring carbonaceous particles near enough to each others in the way, that combustion zone will propagate in PCU. If PCU is made of fiber or wire mesh, the distance between threads of PCU material is essentially smaller than the distance between the channel walls in OPS. According to an object of the invention, said in particle collection unit PCU the thickness of fibers/threads in PCU is between 1 -1000 μιτι, advantageously 5-100 μιτι, which size differs essentially from the wire diameters of OPS screens (about 1/10 or less). The thinner fiber is used, the higher is the fiber surface area and thinner fibers are able to collect more and more efficiently particles per fiber weight than thicker fibers. Too thin fibers result in the limiting factor of mechanical strength and too thin fibers have negative health effects. The use of thin-fiber mat between the channel walls will result in a high PM efficiency with a low amount of additional material combined with OPS.

According to an object of the invention, the void fraction (porosity) of particle collection unit (PCU) is between 50-99.9 %, advantageously between 85-98 %. According to an object of the invention, OPS/CU -ratio (w/w) is between 2-1000, advantageously between 5-100, such as between 10-50. This differs clearly from the properties of wall-flow filter walls (40-50%), which is the corresponding filtration layer. Typically in this purification device, the weight ratio between OPS and CU components is between 2-1000, more typically between 5-100. Thus OPS forms the main weight and this additional element will not add essentially size or weight. A thin fiber mat in the inlet of OPS will not add the weight of OPS made e.g. from metallic screens. The other reason to use low void fraction and relative amount is to keep pressure drop and blocking tendency as low in this purification device. If the PCU is too dense, it will be blocked too fast and most of particles are on outer surface of PCU.

It also possible to use thicker (similar diameter than in OPS wires) wire mesh mats as PCU but then the void fraction of that layer is as defined advantageously between 85-98% and PCU is locate inside OPS channels. This results in the structure, where a wire mesh bed/mat is filling totally or partly the empty channels in OPS. Another difference between wires in OPS and PCU is the orientation of wires: OPS contains wires arranged to a sheet (wires in line, 2D sheet) but PCU contains wires as a mesh bed having 3D structure between OPS channels. Mechanically that kind of thicker wire mesh as PCU is better than fiber PCU solutions. PCU can be also full-filter or a part of it, while it collects carbon containing particles, which can be ignited with IE. IE can be adjusted inside blocked end of cellular wall-flow filter and the other structure around is OPS. PCU can be integrated into IE and can be installed and changed during IE service. If IE is e.g. a glow plug, the ash accumulated in PCU can be removed in service. The pressure and temperature sensors can be also integrated into IE, which is possible with the modern technology. This is a way to have direct information about the operation and ignition conditions of IE.

PCU can form also one, another or several of the channel walls in OPS, when a corrugated structure is metallic screen and another is fiber mat equipped with IE at the edge.

An application is a design, where PCU is located front of or inside purification catalyst, which application differs from the basic definition (Fig. 6). Then IE ignite HCs or other burning compounds, which are naturally in waste fluid or which are added in purpose during ignition moments, before it flows into purification catalyst. This design enables to ignite HCs in a HC-rich exhaust gas in any conditions if the light-off is otherwise too slow, e.g. low temperatures (<200°C), small purification catalyst, it is not possible to use too active purification catalysts due to high- sulphur fuel. The ignition element in this design could be used thus advantageously with high-S fuels possibly together with fuel injection and temperature increase with engine management.

The possible locations of PCU between OPS screens are shown Fig. 7. OPS structure contains angle corrugated screens which lock the PCU (e.g. fiber mat) between channels. Thus, the OPS structure also locks fibers in small spaces where the flow is not able to break a fiber mat as easily than as thick loose mats. It is important to observe the direction of flow through the structure. It exist certain structures with metallic nets and fibers (deep filters) but they have the flow forced completely though that structure. In this invention fluid flows in open channels between screens where PCU can locate in selected parts. The fluid may be partly forced on the surface of OPS and through OPS by mass transfer and pressure drop forces but it remains still that open channel through PD. An easy way to keep a part of channels free even from PCU is shown by Fig. 7C. This design increases significantly the particle collection capacity but still leaves a part of channels open which helps to keep the PD open in all conditions. When every second channel is not filled with PCU (fiber), the flow rate is higher in these channels which also enhances the mass transfer and pushes fluid and particle through the screen to fiber mat. The distribution of PCU inside OPS can be concentrated also on wider areas like shown in Fig. 4 and 5.

The mesh of OPS is fastened by welding, soldering or metal nails or pins pushed through meshes. IE can be integrated into these mechanical fitting elements (e.g. nails/pins with an option for IE). According to an object of the invention, said particle collection unit (PCU) is coated with catalytic coatings active for CO, HC, NO and particulate oxidation and/or NO_x reduction. According to an object of the invention, front of the said purification device (PD) is installed a purification catalyst (CAT), for catalyzing the oxidation of carbon monoxide, hydrocarbons, NO to NO₂ and /or reduction of NO_x by any reductants. According to an object of the invention, the OPS can be coated with porous support material which operates as a base for active compounds which oxidise CO, hydrocarbons, NO, hydrogen, ammonia or carbon. The hydrocarbons can also include functional groups containing oxygen, nitrogen or halogens. According to an object of the invention, said open particle separator (OPS) is coated with catalytic coatings active for CO, HC, NO and particulate oxidation and/or NO_x reduction. 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/screen. Advantageously in some embodiments, holes in meshes are substantially open (30-99.9% of holes in OPS), advantageously 70-99%. 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 to 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 open 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 oxidize 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 on OPS device using various slurries, sols and/or solutions by dipping, pumping, sucking and/or spraying methods. The meshes of OPS can be coated open when loose of its pair by spraying and, after that, wind the mesh and OPS 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 (CVD, 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 in OPS include platinum (Pt), palladium (Pd), rhodium (Rh), iridium and/or ruthenium to catalyze the oxidation and/or reduction reaction of exhaust and waste gases. The active components can be added in the coated catalyst structure by impregnation (dry, wet or chemisorption) or among coating slurry, 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 OPS 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. 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 for passive regeneration, whereby there the loading is lower. On the outlet side, there can also be other active components such as Pd, which is active for HC oxidation but not for NO oxidation. This structure and described loading distribution can be used together with the purification (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 device 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. The presence of Pt is not automatically catalyzing high NO₂ formation, e.g. if vanadium is added with Pt on catalyst, NO₂ formation will be very low. 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.

As promoters in the support material can be used e.g. vanadium (V), wolfram (W), iron (Fe), zirconium (Zr), cerium (Ce), lanthanum (La), manganese (Mn), cobalt (Co), barium (Ba), strontium (Sr) and/or nickel (Ni). The support material can also mainly consist of the compounds of these promoters. In the coating, it is possible to add typical NO_x adsorption compounds e.g. by impregnation, whereby nitrogen oxides can be adsorbed in lean mixture and reduced during rich mixture. In PCU by invention, it is possible to use similar coatings as on OPS or optimally a coating added as sol, which coat PCU's fibers and pores with thin coating without blocking the open spaces which blocking increases pressure drop in that position. Sol means a liquid where are dispersed small particles, which mean diameter is in the range of 5-1000 nm, advantageously between 15-100 nm, which particle size allows to coat evenly even the smallest pores and thin fibers. The particle in sol can be for example Al, Si Ti, Zr, Ce Mn, V, Cr, Co, Sr, La, Y and/or Pr compounds (oxides). The amount of coating is typically 0.1 -30% of the weight of PCU and the active component is typically noble metal like Pt, Pd, Rh or their mixture. Otherwise the same promoters, active metal loadings/addition methods and treatments can be used as for other catalytic coatings described in this application. Particularly, it is possible to use in PCU compounds (V, Cr, Mn, Co, Sr) promoting soot oxidation and thermally stable oxides (La, Y, Zr) which protect PCU against thermal stress. An application by the invention is design, where PCU is coated with sol based coating (small particle size) and OPS with normal catalyst slurry, where also larger particles can be present (»100 μιτι). Slurry coating of thin screens/mats leaves the eyes open in OPS. But a coating slurry having large particles blocks e.g. fiber or porous PCU material or coating is filtered on the top of PCU material, which is not a wanted product. The use of normal catalyst coating (oxidation catalyst) on OPS results in mechanically strong coating layer which leaves the eyes of mesh open. Therefore, the variation of coatings on OPS and PCU results in the optimal coatings on both catalyzed units.

An option by the invention is a coating strategy, where PCU is coated with thermally stable coating (catalyst) and OPS is coated with a catalyst active for soot oxidation directly or indirectly (by NO₂ reactions). Then the particle remains non- reacted better on PCU than on OPS which guarantee the presence of burning carbonaceous materials near to IE, which makes the ignitions easier.

In the purification catalyst (7) by invention, it is possible to use similar coating compositions like on OPS. The purification catalyst differs from typical OPS by the properties in the way that the typical coating amount is higher i.e. about 50-500 g/L and the amount of active compound is also higher, typically 1 -5 g/L. The substrate is ceramic or metallic one which cell density is between 1 -2000 cpsi (cells per square inch), advantageously 50-600 cpsi. The substrate structure may be conventional with negligible filtration properties compared to the structures used for OPS or it can have also certain structures defined for OPS. The operation target is to oxidize efficiently CO, HCs and NO to water, CO₂ and NO₂, which can be utilized in situ or on OPS. Typically, this catalyst is also active in NO_x reduction, which property is needed in addition to PM removal in common diesel applications.

An example about different coatings for the purification catalyst (CAT) and OPS/PCU is a case, where OPS/PCU is coated with a catalyst coatings active preferably for particle/carbon oxidation and purification catalyst has preferably a coating active for oxidation of CO, HCs and NO as well as the reduction of NO_x with any known reductants. If OPS/PCU contains Pt and e.g. V as promoter, it has negligible oxidation activity for NO and SO₂, opposite to other Pt containing oxidation catalysts. In this case, a lot of NO₂ is formed in CAT but not in OPS/PCU.

OPS, PCU and/or purification catalyst coated with catalysts 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 device according to the invention is thus able to purify waste gases particularly in respect of particles. By utilising sufficiently dense mesh, low corrugation height and several layers of the mesh or an equivalent structure in OPS, good particle separating efficiency is also provided. The device includes a novel kind of an open particle separator structure for diesel targets (among others), where accumulated particles are regenerated in addition of passive regeneration with the periodical ignitions, when the condition are not appropriate for passive carbon oxidation. This device is particularly well suited for the purification of the exhaust gases with very low temperatures where regeneration can not be guaranteed with passive ways. However, in the regeneration of OPS, passive methods are utilized as much as possible to optimize fuel economy. The device or its components may also replace normal elements used in sound damping. At its best, the units can be located in the same original sound damper/mufflers.

The particles accumulated in OPS are regenerated therefore passively and/or active regeneration is initiated using IE. In exhaust gases comprising an excess of oxygen, in front of the OPS can be installed a purification catalyst (e.g. DOC), which oxidises CO, HCs and NO. Forming NO₂ slowly oxidizes carbon-based particles. The DOC can be located in the same container or it is separate in front of an OPS according to the invention. The DOC can also be within the inlet or outlet pipe. 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. Therefore, it is possible to combine the ignition based method described in this invention and pure active regeneration in various ways depending e.g. on applications, use conditions and fuels.

The accumulation of particles can be promoted with electrostatic methods, by using mesh pairs as charged collection meshes and by insulating 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 regeneration control of device by the invention is conducted using timing, where the low-energy ignition is activated e.g. with the periods of 0.1 -900 sec, advantageously 2-300 sec, punctually, which intervals are usually about 0.2-100 hours, advantageously 1 -10 hours. This timing is decided by the amount of accumulating particles. An appropriate time to make an ignition is when the amount of carbonaceous particles is e.g about 2-20 g/dm³, advantageously about 4-10 g/dm³, when it is a suitably burning carbon amount to heat OPS up to regeneration conditions. The needed heat amount corresponds to energy, which is enough to heat OPS up to 500-600 °C, which is enough for thermal PM oxidation and which can be assisted of the catalysts; -> lower PM oxidation temperatures; present on OPS or added into exhaust gas. Thus, it is essential that particles are collected up to the loading, which is enough to heat and keep combustion for so long time that the OPS is regenerated fully or partly. Because OPS is often mainly regenerated slowly without this ignition passively, this timing is defined by the worst-case scenarios to guarantee regeneration in all conditions. If normal active methods were used instead of this ignition, the energy consumption will be clearly higher which ruins the energy economy of a vehicle or device. When glow plugs are used as IE, ignition of plug is kept on e.g. for mentioned 10- 500 s continuously or by on/off cycling. The target is to ignite the burning material in vicinity and/or increase the temperature in vicinity up to so high values that carbon and/or hydrocarbons start to burn. The power of plug (IE) in power-on conditions can be about 10-2000 W, advantageously about 50^100 W. Of course, depending on the design compared to the examples in this invention, the powers can be scaled up or down by the size of units in device. For example, if the vehicle has a battery of 12 V and a plug of 15 A is used, the nominal power is 180 W. It is possible to vary also the design by the way that low-power IE is used for longer time and high-power IE for a moment. The carbon fraction in PCU will be ignited by the additional energy or sparks from a plug (IE). The temperature is significantly high near to plug (»600°C), to ignite burning material even as instantaneous sparks but long-term ignition gives higher probabilities to ignition when the wider surroundings is warm. The ignition propagates better if surroundings are hotter. The top of plug (IE) can be in contact to the mesh of OPS or it can be faced to the open channel of OPS, where also is PCU material (e.g. fiber wool or mesh) between OPS's meshes. If no PCU is used, heat propagates particularly in metal sheets/meshes/foils fast and carbonaceous particles ignite and the combustion zone proceeds further towards to the other end. If a high heat conductive metal sheet is used as another pair of OPS and insulator-type fiber mat as another wall of OPS, IE can be connected to either. On insulator, IE creates a point high temperature, where soot is ignited. On heat conductive metal surface, the heat propagated wider. IE can locate also in the middle or at the end of OPS, when the combustion zone will proceed against flow direction. This is possible and device can have one or more IE to guarantee the regeneration of end parts of OPS. When the flow is stopped, the ignition can start as well from the rear as from front part of OPS. When initiating from rear part the thermal stress on OPS is lower but the thermal stress of IE and PCU higher than when starting from the front part.

The initiation of ignition can be focused on the moments, when exhaust gas or fluid is naturally warm enough (exhaust above 300 °C) but the gas flow of exhaust gas is decreasing. This is a case e.g. when it is first driven on roads about 100 km/h and then the speed is decreased (a foot taken away from gas pedal). Then OPS is warm and it s quite easy to ignite soot present and due to decreasing speed, a low amount of cooling exhaust gas is coming from engine. For this kind of applications, the regeneration strategy can be created based on timings and the known engine map. Primary ignitions will thus be focused on these moments, when OPS contains enough burning particles. Secondary, ignition will be focused on some other driving conditions, if the primary condition will be never reached during the defined regeneration (time) window. If system has no pressure sensors, ignitions are needed more often than for full-filters or with sensors, to guarantee ignition in appropriate conditions and over-loading of particle will be prevented. Because the energy consumed for ignition is so low, this will not cause significant harm for the energy economy or electrical equipments. Opposite to the way that ignition is activated always periodically or by defined engine map points, the ignitions can be varied by the type, power and timings. Short ignitions (e.g. 100-200 s) can be made periodically and more seldom a longer ignition (e.g 500 s), which is able regenerate OPS also in boundary conditions or if regenerations tend otherwise to stay insufficient. In addition, the power of IE can be varied or the device can have in different positions varying lEs by power or type. These control actions are done to optimize regeneration with the same power usage.

The ignitions of several ignition elements can be timed to happen at the same or different times. If many lEs are ignited at the same time, it gives a possibility to heat more widely the surface of OPS/PCU and burning zone may propagate widely but causes also a higher peak of energy consumption. The timings can be at different times, when the burning zone can spread also to the vicinity of other lEs but the energy consumption peaks are lower.

A device can be designed to have two or several OPS units in sequence, which system is not applicable with full-filters (Fig. 8). The filtration capacity of OPS can be added by increasing axially the length of total OPS system with several units based on the same particle separation mechanism which is different than with skin type filters. In this type solution, it is possible to install ignition elements also after 1 ^st OPS unit and before and/or after 2^nd OPS unit. Therefore, the particles in each unit can be ignited independently. PCU can be added in each units by the same principles shown earlier.

The device described in invention is designed for conditions, where exist solely low temperatures for long times and the passive regeneration of OPS is insufficient. A OPS with a right design will not be blocked even without ignition elements but the accumulation capacity is decreased and more particles may pass through. This is a condition e.g. with a vehicle in continuous city driving or other drivings with low speeds. By using IE, the regeneration can be initiated periodically even if speeds and/or loads are continuously low. The passive regeneration of OPS or full-filters requires quite high Pt loadings on the oxidation catalyst located front of filters or on filters itself. When the regeneration can be guaranteed by the use of I E, the amount of expensive Pt can be dropped significantly. The main fraction of Pt in current passively regenerating systems is needed to increase NO₂ concentration between 200-300 °C. By using clearly lower Pt loadings, OPS can be regenerated passively above 300 °C when I E guarantee regeneration over the use conditions. This results also in lower NO₂ emissions and a smaller oxidation catalyst (purification catalyst) creates lower pressure drop, which has a positive effect on fuel economy. A target in the invention is to combine the benefits of the passive method and the use of I E with or without PCU in particle regeneration (of OPS). When passive regeneration is working always when possible, it keeps pressure drop low and will not consume any external energy. The additional l Es consume slightly energy but clearly less than other active regenerations, where fluid is heated wholly. The use of ignition guarantees that OPS and CU are purified in all conditions.

Even if OPS or partial filters are not so sensitive like full-filters and particularly CRT systems for fuel-S (<1 0 ppm required), it is helpful if fuel-S is as low as possible. In every application this is not yet possible. The use of I E results in regeneration, where the efficiency of an oxidation catalyst can be decreased (lower Pt loading), while sulfate formation is also dropped. The device by the invention is operating better than known technology thus with fuels with higher sulphur concentrations. The control strategy needs to be designed by the driving and use conditions and fuel. An application is a device, where regeneration is solely based on the use of I E and passive one is not possible or not wanted. The control of full-filters has been based on pressure and optional temperature sensors before and after filters. By combining pressure drop response to engine map values, it has been possible to activate active regeneration at the moments when it easiest, possible and most fuel-economical. It is of course possible to use these methods with partial filters and with a device by the invention. The pressure drop over partial filters and OPS cause a significant low pressure drop even with high loadings, which results in the problem that the accuracy of pressure sensors will be a limiting factor. If the sensors are not able to detect a small increase in pressure drop, OPS may collect too much particles when then the ignition of particles and thermal combustion may to cause too high temperature peaks (>1 000 °C), which are harmful for OPS and its coatings. Therefore, it is advantageous to control the ignition timings by the pre-designed strategies and no additional sensors are needed. It is also possible that the system consists of pressure and temperature sensors, even if the control is not based on them. These sensors can be applied with the system of invention for OBD purposes, to detect e.g. when device and OPS is blocking or overheated and requires service. Based on this invention, it is obvious to build and utilize also the defined OPS in the invention for similar applications without I E and/or PCU (Fig. 9). It is also possible to use a combination of OPS and PCU without I E. The regeneration strategies based on ignition methods proposed here can be applied also to any full-filters (skin or deep filtration) or open partial filters. It is also possible to utilize the same regeneration methods with I E for the regeneration of NO_x adsorption catalysts (Lean NO_x Trap, LNT) from nitrates and sulfates or oxidation catalysts from poisons like sulfur. I E can be used to ignite the fuel injected for reduction and regenerations. The use of I E with these catalysts fastens the ignition of hydrocarbons and enhances the regeneration. The enrichments and fuel injections for PD regeneration can be made at the same time with ignitions (the use of ignition elements). The use of ignition principle enables the use of active regeneration at lower temperatures. The functional properties (deNO_x, particulate removal, oxidation reactions) can be integrated into the same structures (purification catalyst, OPS and/or PCU). Before the purification device, 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 purifier and adjust the stoichiometry of reactions. In Fig. 1 0 it is shown how post injection of fuel or HCs can be done during ignition period. Ignition element I E can be ignited periodically when needed. Additional fuel is injected to exhaust gas 2 after turbo device. Said post injection is advantageously done during ignition period. This post injection PIN can advantageously be done by leading fuel from normal fuel circulation by adding separate valve and pipes to it. It is advantageous to feed the post fuel just after the turbo because the temperature is there high enough, e.g. 1 50 to 1 70 °C, to vaporize the fuel. Also separate vaporization device can be used. This is especially true when the engine is used so that that the temperature in open particle separator, is low, e.g.1 20 to 1 30 °C. Fuel is then advantageously evaporating when flowing through the exhaust pipe or through the separate vaporization device. When the fuel or HC pulse reaches the ignition element it ignites and the temperature is rising. In this application there is an open chamber CHA between said ignition element IE and open particle separator OPS. This improves the burning of fuel and also adjusts the fluid of exhaust gas. It has been found that it is advantageous to use at least two post injection dosing, advantageously at least three post injection dosing of fuel or HCs having duration times 0.1 to 5 sec, such as 0.1 to 0.2 sec, 1 .0 to 3.0 sec. and 0.5 to 2.0 sec. This procedure can e.g. be as follows:

- 0 sec. ignition of ignition element

- 24 sec. first dosing 0.1 sec

- 26 sec. second dosing 1 .5 to 1 .9 sec

- 28 sec. third dosing 0.8 to 1 .2 sec

- 30 sec. stopping ignition.

The temperature in open particle separator OPS is found to rise with this procedure up to 500 to 600 °C and practically all soot is burned.

Example 1.

The examples about different kind of structure are shown in figures. As an example, the properties of a prototype are described here. Metallic (semi)permeable screen (wire diameter 1 10 μιτι, the diameter of holes about 0.2 mm (screens by MESH 87) was corrugated with the corrugation angle of 34 degree to form the slant corrugation, structure shown by Fig. 8. This structure had also a flat screen between slant corrugated screens, which increases the collection efficiency and narrowed the open channel compared to the design without that additional flat screen. The corrugation was made with toothed wheels corresponding to a cell density of 330 cpsi (corrugation height about 1 .3 mm). The screen was coated with slurry coating including also larger catalyst raw material particles (alumina and zeolite and a mixed oxide of ZrCe, (d₅o > 1 μιτι) together with small (d₅₀ « 1 μηι) Ti and Al sol particles, 10 g/m² of GSA, 0.07 g/dm³ Pt). The slant screens were rolled to the OPS in a way that the tops of corrugation support the next corrugated screen (angles +34 and -34 degrees in relation to main flow direction). Silica fiber (d₅o ~ 9 μιτι) mat (PCU) was added between these metallic screens for the first 30 mm from the inlet of OPS. Radial, all the spaces between screens were filled. The void fraction in that fiber layer was about 96- 97%. The fibers were coated by Pt containing sol coatings consisting of alumina and titania as small particles (<100 nm) which did not block the spaces between fibers and coat fiber mats evenly, which properties are advantages for filtering and regeneration. The amount of coating in fiber layer (PCU) as dry basis was about 2.5 g in fiber layer and Pt loading was about 1 .2 g (3.9 g/dm³). Thus, the Pt loading was higher on that fibrous PCU unit than on whole OPS. The length of OPS was 180 mm and the diameter was 1 15 mm. The addition of PCU layer inside OPS structure did not change the total volume of OPS without the fibre mats. Four glow plugs (1 10 W each) were installed geometrically systematic way on the contact to front face of OPS and PCU. The ignitions were controlled with the timings without the use of any pressure drop or temperature sensors. A common ignition interval was few hours (e.g. two) and each ignition took about 2 minutes. The ignitions were conducted at the same time with each plug (IE) in the first experiments. Ignition was able to initiate the PM combustions and both PCU and OPS were regenerated. It was important to start the regeneration at the stage when soot loading was below 10-20 g/L to avoid overheating.

In addition to this base example, the filling amount of PCU material was varied (filling of OPS channels completely, no PCU at all, no coating on PCU). Sol coating with Pt was applied also both for OPS and CPU. The number of plugs and regeneration periods and intervals were also varied by the principles told earlier in the text. The structure in Fig. 8 was also prepared without the flat (semi)permeable screen between corrugated screens.

The device without ignition element can be used as in the applications where temperatures are high enough to passive regeneration and/or the design does not need ignitions and/or active regeneration are in use (Fig. 9). The use of PCU enhances the particulate efficiency without increasing unnecessarily the volume or weight of the system. Metallic PCU is advantageous in some embodiments because it is mechanically strong and conducts heat better than ceramic structures.

Claims

1 . A purification device (PD) for removing impurities, such as carbon containing particles and hydrocarbons, from exhaust and waste gas, characterized in that said purification device (PD) comprises at least one open particle separator (OPS) comprising permeable/semipermeable sheets, mats and/or foils and having open channels (CHA) for gas with impurities to flow between said sheets/mats/foils, and that said purification device (PD) additionally comprises at least one ignition elements (IE) before said open particle separator (OPS) in flow direction for periodically igniting collected and flowing gas impurities, and there is at least one open channel or chamber (CHA) between said ignition element(s) (IE) and open particle separator (OPS).

2. A purification device (PD) according to claim 1 , characterized in that said purification device (PD) comprises two or more open particle separators (OPS) comprising permeable/semipermeable sheets and/or mats and having open channels (CHA) between said sheets/mats/foils,.

3. A purification device (PD) according to claim 1 or 2, characterized in that said purification device (PD) comprises two or more ignition element (IE) for (periodically) igniting collected and flowing gas impurities.

4. A purification device (PD) according to any of preceding claims, characterized in that that said open particle separator (OPS) is coated with catalytic coatings active for CO, HC, NO and particulate oxidation and/or NO_x reduction.

5. A purification device (PD) according to any of preceding claims, characterized in that there is at least one post injector (PIN) for injecting fuel or HCs to exhaust or waste gas (2) for burning with said ignition element (IE).

6. A purification device (PD) according to claim 5, characterized in that said there is at least one separate vaporization device after said post injector (PIN) for vaporizing injected fuel or HCs.

7. A purification device (PD) according to any of preceding claims, characterized in that there is at least one fuel circulation device for injecting fuel or HCs to exhaust gas (2) from normal fuel/HC circulation devices of engine.

8. A purification device (PD) according to any of preceding claims, characterized in that the said open particle separator (OPS) comprises permeable/semipermeable corrugated sheets/mats/foils forming an open particle separator (OPS) structure with open channels (CHA) having corrugation height between 0.2-200 mm, advantageously between 0.35-25 mm, such as 0.5-3 mm.

9. A purification device (PD) according to any of preceding claims, characterized in that the said open particle separator (OPS) comprises permeable/semipermeable metal wire meshes/sheets/mats having wire diameter between 0.01 -5 mm, advantageously between 0.05-1 mm, and/or the holes in metal wire sheets which apparent diameter is between 0.02-10 mm, advantageously between 0.05-0.6 mm.

10. A purification device (PD) according to any of preceding claims, characterized in that said open particle separator (OPS) comprises permeable/semipermeable ceramic fiber sheet/mats.

1 1 . A purification device (PD) according to any of preceding claims, characterized in that said open particle separator (OPS) comprises permeable/semipermeable metallic fiber sheet/mats.

12. A purification device (PD) according to any of preceding claims, characterized in that said (semi)permeable sheets/mats are corrugated forming an open flow particle separator (OPS) structure with channels having corrugation angle in relation to the main flow in either direction between 1 -89 degree, advantageously between 10-80 degree, such as 20-60 degree.

13. A purification device (PD) according to any of preceding claims, characterized in that the ignition element (IE) is an ignition glow plug, a lighter and/or spark generator.

14. A purification device (PD) according to any of preceding claims, characterized in that there is at least one metallic or ceramic particle collection unit (PCU) locating near said ignition element(s) (IE) for collecting carbon containing particulates and/or hydrocarbons near said ignition element (IE) thus enhancing the ignition and combustion of impurities.

15. A purification device (PD) according to claim 14, characterized in that at least one ignition element (IE) is located at least partly in said particle collection unit (PCU) or in contact with said particle collection unit (PCU).

16. A purification device (PD) according to claim 14 or 15, characterized in that said particle collection unit (PCU) comprises fibres or/and wire mesh having wire/fiber diameter between 1 -1000 μιτι, advantageously between 5-100 μιτι.

17. A purification device (PD) according to any of claims 14 to 16, characterized in that said particle collection unit (PCU) comprises fibres or/and wire mesh having wire diameter of 1 to 20 % compared to the wire diameters of the open particle separator (OPS).

18. A purification device (PD) according to any of claims 14 to 17, characterized in that the void fraction (porosity) of particle collection unit (PCU) is between 50- 99.9 %, advantageously between 85-98 %.

19. A purification device (PD) according to any of claims 14 to 18, characterized in that OPS/PCU -ratio (w/w) is between 2-1000, advantageously between 5-100, such as between 10-50.

20. A purification device (PD) according to any of claims 14 to 19, characterized in that said particle collection unit (PCU) is located inside the channels of open particle separator (OPS), advantageously in the front part of open particle separa- tor (OPS) by flow direction.

21 . A purification device (PD) according to any of claims 14 to 20, characterized in that said particle collection unit (PCU) is coated with catalytic coatings active for CO, HC, NO and particulate oxidation and/or NO_x reduction.

22. A purification device (PD) according to any preceding claims, characterized in that front of said purification device (PD) is installed a purification catalyst

(CAT), for catalyzing the oxidation of carbon monoxide, hydrocarbons, NO to NO₂ and /or reduction of NO_x by any reductants.

23. A method for manufacturing a purification device (PD) for removing impurities, such as carbon containing particles and hydrocarbons, from exhaust and waste gas, characterized in that in said purification device (PD) is installed at least one open particle separator (OPS) comprising permeable/semipermeable sheets and/or mats and having open channels for gas flow with impurities between said sheets/mats, and that at least one ignition element (IE) before said open particle separator (OPS) in flow direction for periodically igniting collected and flowing gas impurities, and there is installed at least one open channel or chamber (CHA) between said ignition element(s) (IE) and open particle separator (OPS).

24. A method for manufacturing a purification device (PD) according to claim 23, characterized in that that in said purification device (PD) is installed at least one particle collection unit (PCU) near said ignition element (IE) for collecting carbon containing particulates and/or hydrocarbons.

25. A method for manufacturing a purification device (PD) according to claim 23 or 24, characterized in that at least one ignition element (IE) is installed at least partly in said particle collection unit (PCU) or in contact with said particle collection unit (PCU).

26. A method for removing impurities, such as carbon containing particles and hydrocarbons, from exhaust and waste gas, characterized in that a purification device (PD) according to any of claims 1 to 22 is used for removing carbon containing particles and hydrocarbons.

27. A method for removing impurities according to claim 26, characterized in that the regeneration of particulates is controlled by the periodic use of the ignition element and the duration of a ignition period is 0.1 -900 sec, advantageously between 2-300 sec.

28. A method for removing impurities according to claim 26 or 27, characterized in that the regeneration of particulates is controlled by the periodic use of the ignition element and the ignition period comprises at least one post injection dosing of fuel or HCs during ignition period having duration times 0.1 -10 sec.

29. A method for removing impurities according to any of claims 26 to 28, characterized in that the regeneration of particulates is controlled by the periodic use of the ignition element and the ignition period comprises at least two post injection dosing, advantageously at least three post injection dosing of fuel or HCs having duration times 0.1 to 5 sec, such as 0.1 to 0.2 sec, 1 .0 to 3.0 sec. and 0.5 to 2.0 sec.

30. A method for removing impurities according to any of claims 26 to 29, characterized in that the regeneration of particulates is controlled by the periodic use of the ignition element and the period between ignition phase is between 0.2- 100 hours, advantageously between 1 -10 hours.

31 . A method for removing impurities according of any of claims 26 to 30, characterized in that the regeneration of particulates is controlled by the periodic use of the ignition element and the regeneration is initiated when particle amount in device is in the range of 1-40 g/dm³, advantageously in the range of 4-15 g/dm³.

32. A method for removing impurities according to any of claims 26 to 31 , characterized in that the regeneration of particulates is controlled by the periodic use of the ignition element and the regeneration is initiated and controlled by the calculated particle amount, which is based on time, pressure drop, speed, temperature, particle sensor, fuel consumption and engine map responses and data.

33. A method for removing impurities according to any of claims 26 to 32, characterized in that the regeneration of impurities, such as carbon containing particles, is based on passive regeneration by NO₂ formed on purification catalyst, open particle separator (OPS) and/or PCU and the controlled initiation of combustion by the use of ignition element.