WO2008131573A1

WO2008131573A1 - Device and method for regenerating particle filters, use of a medium for regenerating particle filters, and refill pack comprising said medium

Info

Publication number: WO2008131573A1
Application number: PCT/CH2008/000176
Authority: WO
Inventors: Rainer Bunge
Original assignee: Hochschule Rapperswil
Priority date: 2007-04-25
Filing date: 2008-04-18
Publication date: 2008-11-06
Also published as: JP2010524669A; EP2140115A1; US20100175370A1

Abstract

The invention relates to the use of a fuel other than diesel or diesel fission products, particularly of monoethylene glycol and/or methanol, for the exhaust gas enrichment upstream of a particle filter (19) of a diesel engine (11), in order to heat the exhaust gas to a temperature sufficient for a regeneration of the particle filter (19) by means of a catalytic oxidation of said fuel. The invention further relates to the device allowing said use, which to this end comprises one fuel tank (25) and a fuel line (27) connected to an exhaust line (17) of a diesel engine (11). The fuel tank (25) of the exhaust line is not the diesel tank (15) of the diesel engine. The invention can further relate to the diesel engine (11) and the tank thereof (15), and the exhaust line (17) with the particle filter (19). The idea combining all the aspects of the invention is expressed by the method, which is characterized by the following steps: Fuel, particularly methanol and/or ethylene glycol, is added to the exhaust gas of a diesel engine (11) upstream of the particle filter (19) thereof such that said fuel oxidizes in the gaseous state on the surface of the catalyst (21), thus heating the exhaust gas to a temperature at which the regeneration of the particle filter can be carried out. Due to the fuel tank (25) being separate from the diesel tank (15), a fuel can be used that already reacts with the catalyst (21) at temperatures too low for diesel.

Description

Apparatus and method for the regeneration of particulate filters, and use of a medium for the regeneration of particulate filters, and refilling with the medium.

The invention relates to the regeneration of a particulate filter, or a method, the use of a medium and a device for the regeneration of the particulate filter.

Particulate filters are installed in diesel vehicles and diesel engines. Such particulate filters can become clogged. As a result, the back pressure in the exhaust system is greater. In the event of excessive pressure in the exhaust, the engine finally stops and can no longer be started.

In order to avoid this, particle filters have to be regenerated. To regenerate the particulate filter, the soot particles deposited therein must be burned. There are essentially two options for such regeneration. Both regeneration alternatives require a minimum operating temperature.

In a first way to achieve regeneration, the filter cake made of soot is oxidized by means of NO2 to CO2. The NO2 is oxidized by means of an oxidation catalyst from the NO contained in the exhaust gas and the residual oxygen contained in the exhaust gas. Such an oxidation catalyst is predominantly coated with platinum, but also contains proportions of palladium.

The oxidation catalyst is thus arranged as a component in the exhaust stream and upstream of the particulate filter. Particulate filters are "continuously produce" called. Namely, formed from an exhaust temperature of about 180 ⁰ C continuously NO2, which reacts with the soot in the particulate filter. The regeneration of the particulate filter is dependent on the operating temperature. It takes place from Temperatures around 220 ⁰ C take place, but increases exponentially with the increase in the operating temperature in the particulate filter.NO2 production, however, increases in the relevant temperature ranges in practice with the increase in temperature substantially linearly.

Increased emission of the strong oxidant and irritant gas NO2 is however not desired. The production of NO2 must therefore be continuous with these be matched as precisely as possible to the amount of soot regenerating particulate filters. By reducing the platinum doping of the catalysts, NO2 emissions are reduced. However, depending on the operation of the diesel engine different amounts of soot incurred, and the temperature-dependent conversion of NO2 with the soot is low to CO2 and NO at low temperatures, there is a risk of clogging of the particulate filter at high soot as well as at low operating temperatures, especially when this drops below 220 ° C. The conflict of objectives in continuously regenerating particulate filters is therefore that on the one hand as much NO2 as possible has to be produced in order to achieve regeneration of the filter even at low exhaust gas temperatures, and on the other hand an excess of NO2 has to be avoided for reasons of environmental protection.

A second way to achieve the regeneration of the particulate filter is called thermal. The filter cake is thermally burned off from time to time. It is usually heated to a temperature of 600 ° C. At this temperature, the soot burns off automatically. By a catalytic coating of the particulate filter, the ignition temperature of the soot can be lowered from 660 ⁰ C to 450 ⁰ C. Another possibility for reducing the ignition temperature is the addition of an additive to the diesel. This additive is mostly based on iron compounds. It passes through the engine into the exhaust gas and settles with the soot in the particulate filter. This mixture of soot and additive of the filter cake deposited in the particle filter has a lower ignition temperature than soot without additive, namely around 450 ^° C.

The filter cake built up in the particle filter is periodically burned off during thermal regeneration, usually as a function of the backpressure in the exhaust system. For this purpose, the filter cake is ignited and then burns off usually independently. There are four ways to ignite the filter cake:

• Ignition with an electric heater

• Ignition by interfering with engine operating conditions to increase exhaust temperature. This can be achieved, for example, by manipulating the combustion air supply (for example closing a throttle flap in the air intake nozzle).

• Ignition by combustion of fuel in open flame. For this purpose, a powered fuel burner is installed in the exhaust stream.

• Ignition by catalytic combustion of fuel. In catalytic combustion, the fuel is either injected directly into the exhaust gas stream or it is ejected by manipulating the engine control unburned fuel from the engine. In both cases, the fuel-enriched exhaust stream is passed over a catalytically coated surface, so that the fuel is catalytically (ie flameless) oxidized and thus leads to the exhaust gas heating. The injection of fuel in diesel engines has the disadvantage that the diesel must be very finely atomized because of its high boiling point by means of a compressed air nozzle. For this purpose, therefore, a compressed air supply must be set up. Practice shows that the injection nozzle located at the end of a feeding pipe is easily clogged by coking of the diesel, which requires special precautions to avoid this coking.

Catalysts used for thermal regeneration generally contain more palladium and less platinum than the catalysts used for continuous regeneration. This suppresses NO2 production on the catalyst. The catalyst used for the catalytic combustion of the fuel can be connected upstream of the particle filter as a component. But it can also be added as an additive to the diesel or the exhaust gas, so that it settles on the filter cake. Furthermore, the particle filter itself may be coated with a catalyst layer.

This thermal type of regeneration required in today's commercial catalysts exhaust temperatures upstream of the catalyst of more than 200 degrees, so that the injected diesel at least half is catalytically oxidized. The main constituents of the diesel fuel are predominantly alkanes, cycloalkanes and aromatic hydrocarbons having from about 9 to 22 carbon atoms per molecule and a boiling range between 15O ⁰ C and 390 ⁰ C. By Verdü- solution in very small droplets, the evaporation temperature of diesel under the lowered nominal boiling temperature. At exhaust gas temperatures below 200 ⁰ C, however, only a few of the diesel components volatilize. Although in some catalysts, at least in brand new condition, the light-off temperature can be reduced to 180 ⁰ C, however, the combustion of the diesel is then so incomplete that a cloud of unburned diesel is ejected from the exhaust ("blue smoke"), which in the It is only at temperatures above 200 ^° C. in the catalytic converter that the resulting heat converts so many constituents of the diesel into a reactive brought conditions that this can be used in practice for the regeneration of particulate filters.

There are attempts to further lower the reaction temperature of the catalyst by enriching the exhaust gas with fission products from the diesel. However, this requires technically very complex apparatuses for splitting the diesel into, in particular, shorter-chain alkanes with lower boiling points ("reformers") .This approach is currently not ready for the market and it is questionable whether such an on-board diesel splitting approach would be practicable at all will be.

In conclusion, at exhaust gas temperatures below 200 degrees Celsius no system for the regeneration of particulate filters by the catalytic oxidation of a fuel is known, which was not provided by the technically very complex splitting of diesel.

The need for regeneration of particulate filters at low exhaust gas temperatures is exacerbated when, e.g. for reasons of space, the filter must be mounted at a great distance from the engine. In order to reduce temperature losses in the exhaust gas, in such a case the long exhaust pipes between the engine and the catalytic converter must be laboriously isolated.

The object of the present invention is to propose a solution which allows regeneration of particulate filters to be achieved at low exhaust gas temperatures, for example below 200 ° C. A more specific task is to provide a retrofittable device with which this method can also be applied to existing vehicles equipped with particulate filters and units without having to intervene in the electric motor control.

The invention achieves the object by the features of the independent claims.

In a method for the regeneration of a particulate filter of a diesel-fueled internal combustion engine, the invention together with the prior art comprises the steps that enriched at a supply point upstream of the particulate filter with a catalytically oxidizable medium and by catalytic at low exhaust gas for regeneration Oxidation of the medium to an extent sufficient for the regeneration of the particulate filter. temperature is heated up. While in the prior art, this medium of the fuel, especially diesel, or in tests and diesel cracking products were applied, according to the invention, the exhaust gas is enriched with a different from the diesel and its fission products fuel.

While the prior art branches off the diesel fuel from the already existing diesel tank and adds it to the exhaust gas, the invention requires a second tank for the fuel. This has the disadvantage that two media must be refueled. However, it has the advantage that such a fuel can be selected from a wide range of combustible substances.

The range of possible fuels ranges from this inventive measure of gases such as hydrogen, propane or butane, over organic liquids such as kerosenes, gasoline or their constituents and fission products, to less common fuels. Advantageously, fuels are selected which are volatile at temperatures below 200 degrees, or oxidize on the catalyst at lower temperatures than the diesel. It is particularly advantageous if fuel oxidation does not compete with NO 2 production in the case of NO 2 regenerating particle filters.

It has been found that preferred fuels are found among the alcohols. Many alcohols have volatilization temperatures below 200 ^° C. and can therefore be introduced into the exhaust gas stream without complicated compressed-air atomization. They also evaporate without residue, so that there is no risk of coking, and at least some react at exhaust gas temperatures of 150 ⁰ C with the known catalyst surfaces. For example, (mono) ethylene glycol decomposes at temperatures above 165 ° C, releasing, among other things, glycolaldehyde, glyoxal, acetaldehyde, methane, formaldehyde, carbon monoxide and hydrogen. The less toxic propylene glycol has a boiling point of 187 ° C. The preferred methanol (methyl alcohol) even reaches 65 degrees Celsius.

Alcohols are common commercial goods in petrol station shops, so that no new distribution channels need to be created for the distribution of the fuel to be used according to the invention.

With the fuel, for example, by injecting methanol into the exhaust system and its catalytic oxidation, the exhaust gas temperature is directly on heated to the necessary temperature for regeneration. This is expedient for vehicles and units without diesel injection into the exhaust system.

In particular, in vehicles and units with a diesel injection into the exhaust line, the exhaust gas is advantageously heated by means of the additional fuel only to a temperature at which the diesel can be catalytically oxidized, e.g. to 240 ° C. Thereafter, the reaction temperature necessary for the regeneration can be achieved by enriching the exhaust gas with diesel in a conventional manner. This has the advantage that only small amounts of fuel are needed to initiate the regeneration process, but can be used for maintaining the appropriate for the regeneration temperature of diesel present in larger quantities.

The exhaust gas can be enriched with the fuel and diesel. The enrichment can take place successively or at the same time, with a mixture of fuel and diesel.

The process according to the invention is suitable for oxidation catalysts in general, but in particular for the commercially available platinum and / or palladium-coated catalysts. So it is neither specific for the regeneration by means of NO2, nor suitable exclusively for thermal regeneration.

Preferred alcohols are methanol (methyl alcohol, CH3OH) and monoethylene glycol (MEG, ethylene glycol, ethane-1,2-diol, C2H6O2). These two alcohols have a surprising effect in particle filters with nitric oxide regeneration in that they do not seem to hinder NO2 production by any means. Other fuels, however, appear to challenge the catalyst in competition with NO2 production.

In the case of exhaust-gas purification systems which manage without built-in catalyst surfaces or in which the catalytic surface is present in the particle filter and is largely covered by the soot, a catalytically oxidizing additive can be admixed. This can be added to the fuel or the fuel. In any case, it should serve as catalyst in the exhaust gas / fuel mixture.

In the meantime, however, a catalytic converter for the catalytic oxidation of the catalytic converter is installed between the feed point and the particle filter in the exhaust gas line Fuel used. Most filter pots contain a catalyst component upstream of the particulate filter component.

The enrichment of the exhaust gas with fuel can be carried out by measures before or in the internal combustion engine. Preferably, the enrichment of the exhaust gas between the engine and the particulate filter is made. This is particularly suitable for retrofit kits the appropriate place for the injection of fuel into the exhaust system. It is independent of the operating mode of the motor, so that in its control does not need to be intervened.

The use according to the invention of a catalytically oxidizable medium for enriching the exhaust gas of an internal combustion engine in order to heat the exhaust gas by catalytic oxidation of the medium to an exhaust gas temperature which is sufficient for the regeneration of the particulate filter is characterized in that the medium is substantially enriched by diesel, the fuel of the internal combustion engine, and its fission products contains different fuel, which is catalytically oxidizable at a lower temperature than the diesel.

In principle, gases can also be used as fuel. For ease of handling, it is preferred that the fuel is a liquid. Also suitable here are liquids which split on heating into oxidizable gases. Preferably, for the practice of our invention as fuels organic liquids into consideration, especially alcohols.

Thus, the fuel may be an alcohol or a mixture containing at least 40% alcohol. It may preferably be methyl alcohol or a mixture containing at least 10% of methyl alcohol. It may also be monoethylene glycol or a mixture containing at least 10% monoethylene glycol, with advantages over other fuels. It may further be propylene glycol or a mixture containing at least 10% propylene glycol, with advantages over other fuels. Glycols are inexpensive, frost-resistant, have a high flash point and are toxicologically relatively harmless. They are also water-soluble and safe to handle in this state. They are therefore particularly suitable as a fuel. Further advantageous fuels are glycerines, in particular in methanol-containing glycerol solutions, which are obtained as waste materials in the production of biodiesel and are therefore particularly inexpensive. The advantageous choice of fuels can also be described by the condition that the volatilization temperature of the fuel is lower than the volatilization temperature of substantial proportions of the diesel, in particular below 250 degrees Celsius. At devolatilizing temperature, both the decomposition temperature (as in the case of monoethylene glycol) and the boiling point (as in the case of methanol) are combined, at which the fuel becomes volatile. This has the advantage that at temperatures at which the diesel is still largely non-volatile, it can already be regenerated.

Unlike the preferred choice of the fuels can be limited by the feature that the volatilization temperature of the fuel is below the minimum necessary for a catalytic reaction of the diesel exhaust gas temperature, in particular below 200 degrees Celsius, preferably below 190 degrees Celsius, more preferably below 180 ⁰ C. This choice has the advantage that the fuel evaporates even if no reaction between diesel and catalyst is expected.

Surprisingly, the fuel may be mixed with water, or used in aqueous solution. This makes it easy to handle. A mixture of methyl alcohol and water, for example, is safe and can be traded in plastic bags. The content of water can be relatively large, without this having a strong effect on the heat development in the catalyst.

A device according to the invention comprising a fuel tank and a fuel line is used as an emergency regeneration device or regeneration start device on a device that has a diesel engine, a diesel fuel tank, an exhaust system, and a particulate filter in the exhaust system. In contrast to a windscreen washer system, which also fulfills the above-mentioned structural features, in an inventive use of the device, the fuel line is arranged upstream of the particulate filter in the exhaust line, so that the exhaust gas in front of the particulate filter with a fuel from the fuel tank ange- can be enriched. The device is used when there are insufficient temperatures in the exhaust gas line for regeneration of the particulate filter, but the regeneration is necessary. According to the invention, a device which has an internal combustion engine, a diesel tank for receiving a diesel fuel for the engine, and a diesel line from the diesel tank to the internal combustion engine, and in which an exhaust gas line and catalytic converter surfaces arranged therein and a particle filter are present are equipped with such a device. This added device according to the invention distinguishes the known system of the internal combustion engine. It comprises a fuel tank separate from the diesel tank for receiving a fuel different from the diesel and its fission products, a fuel line leading from the fuel tank to a feed point in the exhaust line upstream of the particulate filter and the catalytic surfaces, conveying means for conveying the fuel into the exhaust line Exhaust line and a circuit for activating the funding. As conveying means can be present: An overpressure in the fuel tank in combination with a valve, a pump or a pressure source, which presses a gas, in particular air or CO2 into the fuel tank, a liquid pump for the fuel in the fuel line or in the fuel tank, optionally in Combination with a valve in the fuel line.

For ease of assembly and handling, a liquid pump in the fuel line is preferred for pumping the fuel through the fuel line. An equally simple way of conveying fuel is by means of a self-priming injection nozzle in the exhaust stream (jet pipe or venturi).

The device may be directly connected to a controller or display device of the internal combustion engine device, which controller controls the regeneration of the particulate filter, and which display device indicates the need for regeneration of the particulate filter. An emergency regeneration, for example, can be triggered by this display device or the signal activating the display device. The device can also be equipped with its own sensor for monitoring the pressure and / or temperature conditions in the exhaust gas line, which gives the switching signal for activating the regeneration starting fuel supply to the exhaust line.

In narrow terms, the invention consists on the one hand in the use of glycol (preferably monoethylene glycol and / or propylene glycol) and / or methanol for enrichment of exhaust gases in front of a particle filter of a diesel engine in order to convert the exhaust gas by means of a catalytic oxidation of this fuel to one for regeneration. ration of the particulate filter to heat sufficient temperature. It therefore comprises commercial packings of a fuel for filling fuel tanks of a regeneration device. Such a refill pack is advantageously characterized by a content of at least 60% of a mixture of methanol and at least one glycol. Conveniently, the refill pack contains at least 20% methanol and at least 30% water.

On the other hand, the invention consists in the device which allows this use, comprising a fuel tank and a fuel line connected to an exhaust line of a diesel engine whose fuel tank is not the diesel engine diesel tank and whose fuel line is to be arranged in the exhaust tract. In an engine and the particulate filter with a comprehensive form, the invention therefore also includes the diesel engine and its tank, and the exhaust line with the particulate filter.

The idea common to all these aspects of the invention is expressed in the method that a fuel, in particular methanol and / or a glycol, (preferably monoethylene glycol and / or propylene glycol) is added to the exhaust gas of a diesel engine in front of its particle filter, so that the fuel Oxidized substance in the gaseous state on the catalyst surface while the exhaust gas heated to a temperature at which the regeneration of the particulate filter is feasible. Thanks to the separate from the fuel tank fuel tank, a fuel can be used, which reacts with too low exhaust gas temperatures for diesel with the catalyst.

The invention will be explained in more detail by means of specific experimental arrangements and the use of various selected fuels. 1 shows schematically a truck with engine and exhaust system, diesel tank and fuel tank for exhaust gas heating

2 is a schematic representation of a first test arrangement, with the diesel tank and internal combustion engine removed, FIG. 3 is a schematic representation of a second test arrangement, with the combustion engine being suppressed, FIG. 4 is a schematic representation of a third test arrangement, with the combustion engine being blanked out,

5 shows a diagram of the temperature increase by .DELTA.T an exhaust gas with temperature T via a first diesel oxidation catalyst (Her- controller: HJS) without injection (base line) and with injection of various media,

6 shows a corresponding diagram of the NO 2 concentration without and with injection of various media, FIG. 7 shows a diagram of the pressure and temperature development in the exhaust gas before and during the regeneration of the oxidation catalyst according to FIG. 1 by means of monoethylene glycol, FIG.

8 shows a diagram of the temperature increase over the oxidation catalyst as a function of the exhaust gas temperature before the oxidation catalyst and the composition of the injected medium water and

glycol,

9 shows a diagram of the temperature increase over the oxidation catalyst as a function of the exhaust gas temperature upstream of the oxidation catalyst and the composition of the injected medium of water and glycerol,

10 shows a container with a fuel for the regeneration of particulate filters.

11 shows a diagram of the temperature increase by ΔT of an exhaust gas at temperature T via a second diesel oxidation catalyst (manufacturer: Peugeot) without (base line) and with injection of different media,

12 is a corresponding diagram of the NO 2 concentration without and with injection of various media,

The truck shown schematically in Figure 1 has a diesel engine 11, which is supplied with a diesel pump 13 diesel fuel from a diesel tank 15. The diesel burns with the compressed air in the cylinders of the engine 11 lean with release of power and heat and with the formation of soot. The exhaust gases from this combustion flow into the exhaust gas line 17 and finally reach the particle filter 19. The particulate filter 19 is used to catch the soot particles and to filter them out of the exhaust gas. Due to the increase of soot particles in the particulate filter 19, its resistance increases. From a limiting resistance arises too high exhaust gas pressure in the exhaust line 17, so that the engine 11 turns off. Therefore, the particulate filter must be freed by a regeneration of the trapped soot before the engine 11 no longer runs economically or even turns off.

The particle filter 19 shown in FIG. 1 is preceded by an oxidation catalytic converter 21 in order to achieve regeneration. In general, the catalyst 21 and the particulate filter 19 are arranged in a common muffler. This can be referred to collectively as a particle filter. To obtain a clear language, the muffler is called together with the particulate filter 19 and the catalyst 21 in this document filter pot 23. With sufficient temperature of the exhaust gas upstream of the oxidation catalyst 21, NO contained in the exhaust gas on the surface of the catalyst 21 is converted into NO 2 together with the residual oxygen in the exhaust gas. This NO2 is an aggressive oxidant that is able to oxidize the soot in the particulate filter 19 to CO2. This reaction occurs even at low temperatures from 250 to 300 degrees, but increases significantly with increasing temperature. At a balance between soot production during combustion and the NO 2 production in the catalyst 21, this regeneration of the particulate filter is ensured continuously from a certain temperature of the exhaust gas.

For a safe regeneration, however, a certain excess of NO2 must be produced. This NO2 surplus leaves the exhaust system as polluting gas that should be avoided. Therefore, newer filter pots 23 are dimensioned so that the excess of NO 2 on average is very low, with the result that an average necessary regeneration of the particulate filter takes place only at temperatures from 250 to 450 degrees. Under certain driving conditions, the regeneration performance is therefore below average, in others above average. If the recovery performance is below average for a longer period of time, the particulate filter must become increasingly clogged.

The NO2 production also depends on the exhaust gas temperature. At exhaust gas temperatures below 220 degrees before the catalyst whose effectiveness is limited or even prevented. Therefore, the filter cake increases at low exhaust gas temperatures, although only enough NO and O2 would be present in the exhaust gas to produce an excess of NO2. This is the main reason why particulate filters become clogged. In order to be able to install filter pots 23 in the exhaust line of an internal combustion engine, which produce only a small excess of NO 2, it is necessary to be able to regenerate even if the continuous regeneration over long periods of time is insufficient. If the filter cake becomes too thick, regeneration is therefore forced. This has hitherto been done, for example, by injecting diesel into the exhaust line or passing unburnt diesel through the engine 11. Under the condition that the exhaust gas upstream of the catalyst is over 200 degrees hot, this diesel then catalytically burns on the catalyst and increases the exhaust gas temperature is about 450 degrees, so that the exhaust gas is hot enough that the catalyst can produce enough NO2 and regeneration of the particulate filter is achieved quickly.

But even for this catalytic combustion of diesel, a minimum exhaust gas temperature of 200 degrees is required. At lower temperatures, the combustion of unburned diesel is not guaranteed. Without catalytic combustion, however, the enrichment of the exhaust gas with diesel only causes an increased emission of hydrocarbons. The exhaust gas temperature does not rise and the particulate filter is not regenerated.

In order to still achieve regeneration of the particulate filter at exhaust gas temperatures below 200 degrees, it is proposed according to the invention to enrich the exhaust gas with a medium which differs from diesel. For this purpose, a fuel tank 25 separated from the diesel tank is required. This fuel tank has its own fuel line 27, which opens into the exhaust system, and a fuel pump 29th

The fuel can now be selected so that it reacts at lower temperatures than the diesel already catalytically with the residual oxygen in the exhaust gas, and therefore increases the exhaust gas temperature. This increase in the exhaust gas temperature is to be driven at least to such a temperature that allows catalytic oxidation of the diesel and therefore an effective enrichment of the exhaust gas with diesel.

A device for the regeneration of the particulate filter therefore necessarily comprises a fuel tank 25 separated from the diesel tank 15, a fuel line 27 and, for example, a pump as conveying means 29. In order to automate the function of this device, a control 31 shown in FIG. This control displays eg with a warning light 33 that the parameter Particle filter 23 must be regenerated. For this purpose, a sensor is arranged in the filter cup 23, for example a counter-pressure measuring device whose signal is evaluated by the controller. Due to a signal from this controller 31, the regeneration can now be initiated with the aid of the fuel. For example, the fuel pump 29 can be activated simultaneously or with a time delay with the warning light 33 lighting up.

2 shows only a section of the device described above, namely the fuel tank 25, the fuel line 27 with fuel pump 29, and the filter cup 23 with the oxidation catalyst 21 and the particulate filter 19th

In the fuel tank 25, an alcohol is filled. This is sprayed to Notregenerieren with the nozzle 35 into the exhaust gas. The sprayed alcohol evaporates quickly in the exhaust even if this is, for example, only 190 degrees hot. Even at these low temperatures (from 150 ⁰ C), it reacts on the catalyst surface with the residual oxygen with release of heat, so that the exhaust gas, depending on the supplied amount of the alcohol, is heated by 100 to 300 degrees. An illustration of the pressure development in the exhaust gas and the temperature after the oxidation catalyst is shown in FIG. 7 and will be discussed below. These measurements were made using a device according to FIG. 2, wherein monoethylene glycol was used to heat the exhaust gas.

Figure 3 shows an embodiment which is suitable for the injection of fuel and fuel. The pump 29 presses depending on the position of the valves 35 and 35 'fuel, diesel or fuel and diesel in the space in front of the catalyst component 21. A controller 31 operates the valves 35,35' and controls the shares of diesel and fuel for the Enrichment of the exhaust gas 37. A temperature sensor between catalyst 21 and particulate filter 19 provides the necessary information.

FIG. 4 shows an alternative embodiment which is suitable for retrofitting existing vehicles and units with particle filters which can heat the exhaust gas with diesel. The separate fuel tank may be a retrofit member or an existing container with a suitable fuel. Such an already existing fuel tank is the cooling water tank, if there is enough antifreeze in it. Another is the washerwash tank, if a detergent with sufficiently high alcohol content is used. part of it is present. The injection of fuel and fuel into the exhaust gas 37 can be done independently of each other.

The measurements shown in FIGS. 5 to 9 originate from a test arrangement with a Euro 3 industrial diesel engine (1.91 TDI from VW with turbocharger, direct injection and exhaust gas recirculation) and a commercially available continuously regenerating particle filter system from HJS (platinum doped oxidation catalyst). Various fuels were injected into the exhaust system. The injection was carried out according to the device shown in Figure 2, within the filter pot 23, upstream of the catalyst 21. The respective injection quantity was chosen so that at complete combustion, a temperature increase of about 100 ° C would be reached. The exhaust gas temperatures were set by engine speed and load (power brake).

From FIGS. 5 and 6 it can be seen what the effects of different organic liquids on the temperature increase (FIG. 5) and on the NO 2 production (FIG. 6) are via a commercially available platinum catalyst. It is surprising that the two alcohols methanol and monoethylene glycol already at 180 ° C in the exhaust gas trigger a significant increase in both the temperature and the NO2 production. The light-off temperatures at monoethylene glycol (MEG), methanol, and propylene glycol were 180 ⁰ C. In the case of methanol and MEG complete conversion was observed already at 190 degrees. In terms of temperature development, methanol and monoethylene glycol are about equally effective. As can be seen from FIG. 6, methanol is to be preferred in continuous regenerating systems, because the NO ² regeneration increases even at temperatures of about 20 ^° C. cooler than in the case of monoethylene glycol.

It is also notable that NO2 production does not increase in parallel with temperature evolution when using ethanol, 2-propanol and cyclohexanone. Compared to the increase in NO2 production as a function of the temperature without fuel injection (base line), the increase with injection of these fuels is significantly flatter. This is attributed inter alia to a competition between the oxidation of the fuel and the oxidation of the NO on the catalyst. It is also suspected that certain oxidation products of the longer chain alcohols, especially acetic acid and corresponding aldehydes, are responsible for the inactivation of the catalyst with respect to NO / NO 2 conversion. For comparison, diesel fuel was also injected. On the catalyst used, a temperature increase begins only above 220 ⁰ C (Fig. 5). However, NO2 production is largely suppressed (FIG. 6).

The experiments with methanol, monoethylene glycol, ethanol and diesel was also carried out on another filter pot (manufacturer Peugeot). This filter pot contains a presumably high platinum doped catalyst which produces NO2 and a downstream particulate filter which is also doped with a catalyst, presumably above all palladium. This filter is commercially available for automobiles from Peugeot, where a fuel additive is used. The filter cake formed from the additive and the soot is ignited in these vehicles by manipulating the engine control so that unburned diesel is discharged. This oxidizes on the catalyst and on the catalytically doped particle filter exothermic. The filter pot from Peugeot was used by us without any modifications, but the engine was not operated with the additized fuel, but with diesel. Instead of intervening in the engine control to direct unburned diesel from the engine into the filter pot, a fuel was introduced into the exhaust stream in our experiments. Although the start-up temperatures for the oxidation of the fuels were about 30-40 degrees lower in these tests, the quality was very similar to that of the first catalyst (HJS). Again, only methanol and monoethylene glycol were capable of raising the temperature even at very low exhaust gas temperatures (Figure 11) without suppressing NO 2 production (Figure 12).

The regeneration of the particulate filter (HJS) used in the above experiments was also investigated. The pressure curve shown in Figure 7 shows an increase in pressure during 5 ³ A hours in the exhaust line 37 according to Figure 2 to a good 140 millibars. The temperature of the exhaust gas after the catalyst 21 moves in this time by 200 degrees Celsius. At "start" is monoethylene glycol

(8.5 g / kg of exhaust gas) injected (nozzle 35). The evaporation of this fuel increases the pressure by 12 mbar. The vaporized MEG reacts with the oxygen in the exhaust gas 37 thanks to the catalytic surface of the catalyst component 21 (Figure 2) and therefore releases heat. Thanks to the now elevated temperature behind the catalogs lyst of about 350 ⁰ C starts the regeneration of the particulate filter and the pressure decreases steadily in the wake of Russ degradation. At injection of more fuel, a higher temperature and a faster degradation of the soot is effected. For faster regeneration of the particulate filter are in practice temperatures of to aim for over 450 degrees. With the end of the injection at "Stop", the exhaust gas pressure drops rapidly to a pressure below 100 mbar and begins to increase again .The renewed increase is the result of the temperature dropping abruptly after the end of the injection of the monoethylene glycol. Below 220 degrees, so no NO2 is produced and made of double

Reason (too low temperature and NO2 deficiency) no regeneration takes place anymore. By injecting MEG, the NO2 concentration in the exhaust gas was increased from 60ppm to 115ppm, providing sufficient NO2 for soot combustion.

To clarify whether the disadvantage of the invention, namely the need for a separate fuel tank from the fuel tank, the content of which can be injected as fuel in the exhaust stream, can be mitigated by the use of already carried in motor vehicles liquids were made tures, the existing Use container of a vehicle and enrich the media contained therein to enrich the exhaust gas with a catalytically oxidizable fuel. In principle, the cooling system with the coolant flowing therein is available, the glycol concentration of which is typically around 50 to 60%. Also available is the disc detergent in the appropriate container. Windscreen washes usually consist of 50/50% water and an alcohol or an alcohol mixture.

FIG. 8 therefore shows the effect of glycol 100% up to the aqueous solution of glycol with a glycol content of only 50% on the temperature increase over the catalyst. In the aqueous solutions takes the

As expected, the temperature increase decreases with increasing proportion of water, since the water absorbs evaporation energy. In the measurements shown, the water content was corrected and the dosage adjusted so that the same amount of alcohol was injected in each experiment. There were surprisingly small losses in temperature increase recorded.

Corresponding results are also shown in Figure 9 with respect to aqueous solutions of glycerol with a glycerol content of 75% and 50%. The same picture emerges here, namely that the temperature rise is sufficient even when using an aqueous solution to allow regeneration.

This realization has two aspects. On the one hand, cooling liquid or windshield washer fluid can be used to enrich the exhaust gas a catalytic oxidizable medium to raise the exhaust gas temperature to a sufficient for the regeneration of the particulate filter temperature. These liquids can be removed from the existing containers.

The second aspect is that apparently also an aqueous solution of a flammable alcohol, e.g. Methyl alcohol, can be used. This is harmless regarding trade and handling. It can be filled in specially provided for the regeneration of particulate fuel tanks and requires, in contrast to, for example, a gas tank, no safety precautions.

A preferred embodiment of the invention is the use of the fuel to "ignite" a filter cake of soot admixed with a catalyst added by fuel additive, which is an alternative to the known methods of electrically igniting such filter cake or ignition by manipulation of the engine control In a preferred variant, the exhaust gas enriched with the fuel is reacted on an oxidation catalytic converter arranged in front of the particle filter, and in this way heats the exhaust gas above the ignition temperature of the filter cake.

Depending on the selection of the fuel additive, instead of a catalyst element arranged in the exhaust gas stream, the catalyst present in the soot cake can itself be used for the oxidation of the added fuel (for example, platinum). A preferred variant is to use a conventional iron-containing fuel additive to iron the soot deposited in the particulate filter with iron and thus to reduce the ignition temperature of the filter cake. To initiate the regeneration, a platinum additive is added to the fuel instead of the iron additive, so that a platinum layer is formed on the surface of the filter cake. Then the required for the regeneration of fuel is injected, which reacts directly on the soot surface with the platinum catalyst and thus causes the ignition of the filter cake.

A device to be operated for installation in a vehicle or a unit with diesel engine and particulate filter, therefore, comprises a fuel tank for, for example, an aqueous alcohol solution, a pipe and a pump, and a nozzle for atomizing the fuel in the exhaust line. In the case of retrofit parts, the line can be provided with a collar with which an exhaust pipe can be enclosed. can be. The arrangement of the line with the nozzle in the exhaust pipe is thereby very simple. In addition, an electrical line between the pump motor and a switch is needed. The switch can also be operated manually.

Finally, FIG. 10 shows a canister containing a fuel which is provided for the regeneration of particle filters. The fuel may be, for example, an 80% aqueous solution of alcohol. The alcohol portion may comprise various components, in particular a major proportion of methanol for an early increase in NO2, and optionally a lower level of monoethylene glycol. Such a canister is available via existing distribution channels in gas station shops.

The inventive solution allows primarily an emergency regeneration, but can also be used for regular regeneration. An emergency regeneration is not triggered more frequently than every other regeneration cycle, preferably not more frequently than every fifth regeneration cycle. It is only triggered if, given the operating conditions of the lean-burn engine, the regular regeneration can not take place and regeneration is necessary for the further operation of the engine.

Claims

claims

1. A method for the regeneration of a particulate filter (19) of a lean-burn engine (ll), in particular a diesel engine, in which method at too low exhaust gas temperature, the exhaust gas (37) at a feed point upstream of the particulate filter (19) enriched with a catalytically oxidizable medium and is heated to a sufficient exhaust gas temperature for the regeneration of the particulate filter by catalytic oxidation of the medium, characterized in that the exhaust gas (37) is enriched with a fuel different from the fuel and its fission products, which oxidizes on the catalyst at lower temperatures than the fuel.

2. The method according to claim 1, characterized in that the exhaust gas temperature is heated with the fuel to a first temperature at which the fuel can be catalytically oxidized, and at the same time or subsequently the exhaust gas (37) is enriched with fuel.

3. Use of a catalytically oxidizable medium for enriching the exhaust gas (37) of a lean-burn engine (11) to heat the exhaust gas (37) by catalytic oxidation of the medium to a sufficient exhaust gas temperature for the regeneration of the particulate filter, characterized in that the medium from the Fuel of the lean-burn engine and its fission products is different fuel, which is catalytically oxidizable at a lower temperature than the fuel.

4. Use according to claim 3, characterized in that the fuel is or contains an organic liquid.

5. Use according to claim 4, characterized in that the fuel is an alcohol or is at least 40%, preferably at least 50% alcohol-containing mixture.

6. Use according to claim 4 or 5, characterized in that the fuel is methyl alcohol or a mixture containing at least 10% of methyl alcohol.

7. Use according to one of claims 4 to 5, characterized in that the fuel is a glycol, preferably monoethylene glycol or propylene glycol, or that the fuel is a mixture containing at least 10% glycol.

8. Use according to one of claims 3 to 7, characterized in that the volatilization temperature of the fuel is lower than the average volatilization temperature of the fuel, in particular below 250 degrees Celsius.

9. Use according to one of claims 3 to 8, characterized in that the volatilization temperature of the fuel is below the at least necessary for a catalytic lytic reaction of the exhaust gas temperatures, in particular below 220 degrees Celsius, preferably below 200 degrees Celsius, more preferably below 190 ⁰ C.

10. Use according to one of claims 3 to 9, characterized in that the fuel is dissolved in water.

11. Use of a device comprising a fuel tank (25) and a fuel line (27) and a conveyor (29), as Notregenerier- device in a device having a lean-burn engine (11), a fuel tank (15), an exhaust line ( 17), and a particulate filter (19) in the exhaust line comprises, in which use the fuel line (27) upstream of the particulate filter (19) is arranged in the exhaust line or opening, so that the exhaust gas (37) in front of the particulate filter (19) a fuel from the fuel tank (25) can be enriched.

12. Apparatus comprising:

a lean-burn engine (11), a fuel tank (15) and a fuel line from the fuel tank to the lean-burn engine,

- Subsequently to the lean-burn engine (11) an exhaust line (17) and arranged therein catalytic surfaces (21) and a particulate filter (19), characterized by

a fuel tank (25) separate from the fuel tank for receiving a fuel different from the fuel and its fission products, - A in the exhaust line (17) opening fuel line (27) from the fuel tank (25) to a feed point in the exhaust line (17) upstream of the particulate filter (19) and the catalytic surfaces (21), and

- Conveying means (29) for conveying the fuel into the exhaust line (17) and a circuit (31) for activating the conveying means (29).

13. The apparatus according to claim 12, characterized by a sensor (41) for monitoring the pressure and / or temperature conditions in the exhaust line (17) and for actuating the circuit (31).

14. The apparatus of claim 12, characterized by a connection of the circuit (31) to a warning device (33) of the lean-burn engine (11), which indicates the need for regeneration of the particulate filter (19).

15. Refill for a device for regenerating a particulate filter (19) of a diesel engine (11) containing a different diesel and diesel fuel split products fuel, in particular an alcohol.