DE102004062897A1 - Exhaust gas treatment system for internal combustion engine has at least one time switched device to collect carbon-oxygen compounds before converter - Google Patents

Abstract

The exhaust gas treatment system includes an oxidation catalytic converter (4), to which a diesel particle filter (5) is connected. It includes at least one time-switched device (8) in the exhaust flow to collect carbon-oxygen compounds in gaseous and/or aerosol form. The time-switched device is located before the catalytic converter.

Description

The This invention relates to a system and method for aftertreatment of exhaust gases from internal combustion engines, in particular diesel engines, In the exhaust stream at least one diesel particulate filter arranged is, through which the exhaust gas to be discharged to the environment must be performed. She is in particular for the retrofit from already commissioned corresponding internal combustion engines and also for suitable for mobile use.

It is known that in diesel engines in addition to other pollutant components In the exhaust gas leaving the engine also soot particles are included, the according to applicable and in the future even more aggravated statutory regulations are no longer readily available to the environment allowed to be there they damage your health lead to organisms can.

Around such diesel soot particles to separate from the exhaust, are very different diesel particulate filter already used.

At the Operation of such appropriately equipped exhaust aftertreatment systems but is more or less large intervals, the also from the respective pre-run operating conditions of a Diesel engines are affected, a regeneration of the diesel particulate filter perform. A Such regeneration is achieved by a corresponding increase in temperature, such that oxidation of the carbon present in carbon black form, the throttle effect when flowing through the exhaust gas through the particulate filter with simultaneous increase the exhaust backpressure causes, is performed.

There are temperatures for this in the range around 600 ° C required, especially in part-load operation of a diesel engine when exiting the diesel engine exhaust gas can not be achieved can, without that extra activities be taken.

For the implementation of Such regenerations on diesel particulate filters are very different Solution approaches known.

So For example, additives are added with which for a regeneration required temperature can be reduced. Such additives have to but kept in separate containers and carried in mobile use become. Furthermore is at least a monitoring over that Presence of additives required.

In Another form of regeneration is initiated by the fact that the Diesel particulate filter from the outside additionally be heated, with the necessary temperatures a considerable energy requirement, which are additionally provided must, require.

Of Further is the use of such exhaust aftertreatment systems of oxidation catalysts also an already proven means especially hydrocarbons, carbon monoxide as well as nitric oxide, which are contained in the untreated exhaust gas stream to catalytically oxidize. Such a catalytic surface coating having oxidation catalysts are also known per se and commercially available in a variety of forms.

All known technical solutions for a corresponding Exhaust after-treatment with diesel particulate filters, which are regenerated must show but especially then disadvantages if they already existing Internal combustion engines are to be retrofitted. Besides that is the required effort for the purchase and for the operation frequently significant or effectiveness for the corresponding Required regeneration only small.

The latter Aspect particularly concerns such solutions in which regeneration the diesel particulate filter with corresponding increase in the exhaust gas temperature should be made by intervening in the engine management, by an electronic control operating states are set, the an increased Exhaust gas temperature for Regeneration is sufficient to cause.

One such intervention in the engine management, so the electronic Control of the diesel engine but also carries a significant risk potential in itself, if such operating conditions in unfavorable situations of the be aimed at electronic control.

It It is therefore an object of the invention to propose a solution that is simple and cost-effective is. In this case, a regeneration of diesel particulate filters reliable and can be done without an intervention in the engine management, as well the possibility for the retrofitting already in operation / internal combustion engines (diesel engines) be given.

According to the invention, this object is achieved with a system having the features of claim 1. The exhaust aftertreatment can according to the invention by a method according to claim 16 be performed.

advantageous Embodiments and developments of the invention can with in the subordinate claims designated characteristics can be achieved.

The inventive system also uses, as known from the prior art, an oxidation catalyst, in the flow direction the exiting the internal combustion engine exhaust before a Diesel particulate filter is arranged. It can be known per se Elements used and accordingly for the invention also different oxidation catalysts or Diesel particulate filter are used, which also for the corresponding Internal combustion engine out chooses and in particular can be dimensioned.

at The invention can be advantageously exploited that on a Oxidation catalyst by an oxidation of hydrocarbon compounds exothermic Reactions initiated, which raise the respective Lead exhaust gas temperature.

at but modern internal combustion engines will be particularly under consideration high efficiencies a complete Combustion of the hydrocarbons contained in the fuels achieved, so that the proportion of hydrocarbons in the exhaust gas, the can be exothermally oxidized by means of an oxidation catalyst, is very low and therefore only a slight increase in temperature of the Exhaust gas is achieved.

A significant increase in temperature the exhaust gas by exothermic oxidation of hydrocarbons on However, oxidation catalyst can already with a share of 1 to 5 vol .-% of hydrocarbons in the exhaust gas can be achieved.

to targeted influencing, it is therefore provided according to the invention, in the flow direction of Exhaust gas upstream of the oxidation catalyst at least one temporarily switchable Arrange device. about This device can then the exhaust gas at least one hydrocarbon compound in Supplied gas or aerosol so that's the extra Hydrocarbon compounds contained in the exhaust gas by means of Oxidation catalyst and in the exhaust gas still contained oxygen oxidized and by the exothermic oxidation the exhaust gas temperature up above the for the regeneration of the downstream diesel particulate filter raised so in the form of soot oxidize carbon contained in the diesel particulate filter. After successful sufficient regeneration of the diesel particulate filter can then Add the respective hydrocarbon compound (s) over the temporary switchable device can be stopped.

The Activation of the system according to the invention for one Regeneration of diesel particulate filters is usually required whenever if the respective internal combustion engine operated for longer periods in partial load operation has been at the respective exhaust gas temperature significantly below the for the regeneration required exhaust gas temperature is.

Especially It is advantageous, the system of the invention similar to a modular system different modules to make composable. So can oxidation catalyst and diesel particulate filters form individual modules for each Internal combustion engine can be selected in an optimized form from known solutions. For the device about the the hydrocarbon compounds are fed into the exhaust stream can, can also be part of a separate module, but also with be combined with a module with oxidation catalyst.

The inventive system can be operated so that an activation leading to regeneration always after expiry of predefinable time intervals, independent of Loading condition of a diesel particulate filter is performed. Alone or in addition But it can also be an activation in regulated form for a regeneration of the diesel particulate filter. For such Regulation can For example, used exhaust gas temperature sensors and exhaust pressure sensors become.

So is it safe for you, the respective exhaust gas temperature within the exhaust system and preferred before the oxidation catalyst with a corresponding arranged there To detect exhaust gas temperature sensor. With this can be considered How much of a difference in exhaust gas temperature from that for the regeneration required temperature is present or not. Is the current one Exhaust gas temperature sufficiently high, it can be an activation of the system according to the invention be omitted. The temperature determination also has meaning for the functionality of the oxidation catalyst. Such is the conventional oxidation catalysts at least the achievement of a catalyst activation temperature (usually above 200 ° C) required to exothermically oxidize hydrocarbon compounds and this as possible Completely implement (avoid HC slippage), so that possible no unburned hydrocarbons remain in the exhaust gas.

In the invention, however, an exhaust gas pressure difference between inlet and outlet of the exhaust gas can be determined at the diesel particulate filter. If this provision is exceeded by a detected predetermined threshold of the respective exhaust pressure difference, so the diesel particulate filter is already loaded to a considerable extent with soot, an activation of the system, by releasing the device and corresponding supply of hydrocarbon compounds in the exhaust stream, which then exothermally oxidized by means of the oxidation catalyst and thereby the corresponding exhaust gas temperature can be raised to within the range that is sufficient for regeneration of the diesel particulate filter.

Accordingly The regulation can be determined solely by determining the respective exhaust gas temperature or the exhaust gas pressure difference, but also in combination of these measured values carried out become.

The inventive system can advantageously diesel fuel, as a suitable form of hydrocarbon compounds, the over the device can be supplied to the exhaust gas flow operated become. This is particularly advantageous in that No additional Containers for appropriate Hydrocarbon compounds are carried or be present have to.

Becomes Diesel fuel as a suitable form of hydrocarbon compounds used in the solution according to the invention, should this be supplied by means of the device so the exhaust stream, that he is either already complete gaseous, partially gaseous and at least but in the form of finely divided droplets aerosol in enters the exhaust stream. So can a nearly 100% oxidation hydrocarbons at exhaust gas temperatures> 200 ° C guaranteed be, so that the limits of the system according to the invention discharged into the environment can be met and Furthermore the energy content for the increase the exhaust gas temperature can be exploited.

Accordingly can the facility, about which are supplied to the hydrocarbon compounds are heated. The temperature increase, for example, diesel fuel or others in liquid form present hydrocarbon compounds to above the vaporization temperature of at least one hydrocarbon compound carried out is, so that at least a portion of the exhaust gas stream supplied hydrocarbons is already present in the gas phase, which clearly shows the conditions for the exothermic oxidation favorably influenced.

The warming the over the device in the hydrocarbon stream (s) to be supplied to the exhaust stream can be performed on different form within the element. So it is possible an electric heating, over Resistance elements inside the corresponding device are arranged and the flowing electric current a generate sufficiently high temperature, which leads to a temperature increase of Carbon-hydrogen compounds within the element leads.

Of the for one warming the hydrocarbon compound (s) Required energy requirement can be reduced, in the the facility, about the hydrocarbon compound (s) is / are supplied so formed and arranged to at least partially in the exhaust stream protrudes and flows around the exhaust is, so that at least a preheating is achievable and only an additional Heating up to the possibly necessary achievement of the Evaporation temperature is necessary.

In front should exit the respective hydrocarbon compound (s) from the device a filter can be arranged by the respective hydrocarbon compound (s) is passed through, to prevent the ingress of unwanted extra To avoid particles in the exhaust stream.

The Facility, about the hydrocarbon compound (s) supplied to the exhaust gas is to be connected to a pump, with the one advancement and precompressing the respective hydrocarbon compound (s), independently of it, whether it is liquid or gaseous hydrocarbon compounds, be achieved. Between such a pump and the device should be possible then a valve may be connected in the connection line to prevent backflow the device and optionally also a modifiable supply of To ensure hydrocarbon compounds.

The However, respective (hydrocarbon) compounds) can also have a Container, e.g. a pressurized gas container, be supplied to the institution, in which the respective hydrocarbon compound (s) in compressed form is / are included.

So can be used as a hydrocarbon compound a correspondingly compressed Gas in a compressed gas tank be used. Suitable gases are, for example, the low molecular weight Propane, butane and, for example, methane or natural gas.

In such an embodiment, the device to be used in a system according to the invention may be designed as a simple valve, which then only has to be opened or closed in a controlled manner in order, if necessary, to use the hydrocarbons required for the exothermic oxidation substance connection to be able to supply the exhaust gas stream.

Should such compressed gas tank with gaseous Hydrocarbon compounds can be used on conventional Compressed gas tank, the for example, available in exchange are used be, especially in mobile use for redundancy then at least two such gas cylinders should be carried.

Independently of, whether the hydrocarbon compounds used already gaseous or in advance still fluid It may be advantageous to have more than one equivalent facility over which the Hydrocarbon compounds are supplied to a system according to the invention provided. It should then the appropriate facilities be arranged clearly separated from each other locally, to a more even distribution the supplied Hydrocarbon compound (s) to reach within the exhaust stream.

Hydrocarbon compounds but can also sequentially, ie offset in time from each other from several Means are supplied to the exhaust gas stream, for. a sufficient Amount for the exothermic oxidation available to be able to make.

at the system according to the invention can but also next to the for the exothermic oxidation of useful hydrocarbon compounds additionally the known additives that are used to reduce the for the regeneration of particulate filters required temperature can be used.

Especially when using in originally liquid Form present hydrocarbon compounds that over the Device supplied to the exhaust stream can be, in addition to the already mentioned and described warming also an increase pressure within the device. This can be done accordingly for one such compression appropriate elements within the device can be arranged and used, corresponding to the internal volume to reduce. In an advantageous manner, such elements can be made from a Piezoceramic be formed, which expands or contracts accordingly can be and thereby particularly advantageous, the outlet of the respective hydrocarbon compound (s) supports the element and over a period equalized if, for example the compression after opening the facility for the exit of the hydrocarbon compound (s) has been reduced.

Of the Exit of the gaseous and / or hydrocarbon compound (s) present in aerosol form from the device into the exhaust stream can via at least one metering and / or a corresponding tax or adjustable outlet valve.

In the case, that the respective hydrocarbon compound (s) at least can be partially fed in aerosol form the exhaust stream, can in an injection range the exhaust system before the oxidation catalyst an additional ignition device be arranged. Such an ignition device For example, an annealing or spark plug be, in particular in the latter case, such an ignition device preferably should be located close to the oxidation catalyst.

The inventive system can be modular in a compact design and to different Applications, with regard to mobile or stationary use or different Are adapted internal combustion engines. The individual components / modules are tunable to each other in a wide range and possibly also steplessly.

One Safe operation of the internal combustion engine can be achieved through regeneration be achieved by diesel particulate filters under all operating conditions.

The respective for Regenerations of the diesel particulate filter required time and Regeneration speed can specifically influenced become.

The inventive system Can be used at least in almost all diesel engines, to these customized and so also retrofitted become.

following the invention will be explained in more detail by way of example.

there demonstrate:

1 in schematic form with a block diagram an example of a system according to the invention and

2 two sectional views through an example of a heated device for the supply of hydrocarbon compounds in the exhaust stream.

With the in 1 shown block diagram is to be exemplified an inventive system.

This comes from a diesel engine 1 , as used here internal combustion engine exiting exhaust via an exhaust pipe 3 into an injection zone for hydrocarbon compounds and then to an oxidation catalyst 4 , with which the oxidation of not or not completely oxidized exhaust gas components as well as via a device 8th additionally supplied hydrocarbons are oxidized. The already partially pretreated by appropriate oxidation of such pollutant components exhaust gas is then through a diesel particulate filter 5 and then, at least almost completely freed from pollutants, can be released to the environment.

The device 8th , can be fed via the hydrocarbon compounds in addition to the exhaust gas flow, in this example, to the respective diesel fuel-containing tank 6 connected. The diesel fuel is pumped 7 in the facility 8th promoted, with a particularly advantageous embodiment of such a device 8th , in the description of the 2 will come back yet.

Furthermore, this system additionally includes an exhaust gas temperature sensor 10 in the exhaust pipe 3 as well as two exhaust pressure sensors 9 and 9a available. The exhaust pressure sensors 9 and 9a are in front of and behind the diesel particulate filter 5 arranged so that a determination of the exhaust gas differential pressure before and after the diesel particulate filter 5 can be carried out.

Exhaust gas temperature sensor 10 as well as the exhaust pressure sensors 9 and 9a are to the electronic control unit 2 connected. Furthermore, there are also connections to the fuel tank 6 and are to the electronic control unit 2 , the pump 7 to the electronic control unit 2 guided.

Thus, the respective exhaust gas temperature with the exhaust gas temperature sensor 10 be constantly determined, as well as for the respective exhaust pressure difference with the exhaust pressure sensors 9 and 9a can be determined to be used for the control of the system according to the invention.

If, for example, an increase in the exhaust gas pressure difference, which exceeds a predefinable threshold, with the exhaust pressure sensors 9 and 9a detects and at the same time an exhaust gas temperature value with the exhaust gas temperature sensor 10 determined below that for the regeneration of the diesel particulate filter 5 required temperature is, so the device can 8th be manipulated so that gas and / or aerosol-shaped diesel fuel fed through the exhaust gas stream and the hydrocarbons with the aid of the oxidation catalyst 4 be oxidized exothermic to raise the exhaust gas temperature, so that for the regeneration of the diesel particulate filter 5 required exhaust gas temperature is reached or even significantly exceeded, by oxidation of the soot form by means of the diesel particulate filter 5 separated carbon to regenerate this.

Thus, an effective control depending on the detected measurement signals of exhaust gas temperature sensor 10 and the exhaust pressure sensors 9 and 9a and by appropriate regulation of the institution 8th supplied volume flow of hydrocarbon compounds and a timing of the supply optimized regeneration of the diesel particulate filter 5 be achieved.

With 2 is intended in particular an advantageous example of a device 8th , can be supplied via the hydrocarbon compounds to the exhaust stream, be clarified.

There is a supply line 21 for diesel fuel from the fuel tank, not shown here 6 via a pump 22 , The administration 23 in the facility 8th available. In the line 23 between facility 8th and pump 22 If there is an additional valve, not shown here, with which the supply of diesel fuel in the device can be temporarily blocked or released, be present.

The diesel fuel can over the line 23 by means of the pump 22 in cavities 8a in the facility 8th reach. It should be the cavities 8a have a volume with which a diesel fuel volume can be filled, which is sufficiently large for a complete regeneration process of the diesel particulate filter.

In the facility 8th are additional heating elements 16a present, over the electrical connections 14 and 15 Resistance be heated. The heating elements 16 are accordingly formed of an electrically conductive material and have the largest possible surface area available for heating the diesel fuel.

In this case, the heating elements 16 be formed in the form of a loose bed or open-cell foam of an electrically conductive material and the cavities between a bed of forming more or less large particles or balls or the open pores of the cavity 18 form for the diesel fuel to be heated. The electrical connections can then be designed and connected differently than in 2 shown.

In this example of means for supplying hydrocarbon compound (s) into the exhaust stream is within the device 8th between the cavities 18 for the absorption of diesel fuel and the heating elements and a dosing jet 10 , from the heated, optionally partially gas and possibly also partially aerosol diesel fuel exiting into the exhaust stream, a filter 19 arranged. The cavities are channel-shaped in the example shown. There are also several cavities 18 for a more effective heating of the diesel fuel available.

In the 2 in a sectional view indicated device 8th can advantageously be arranged within the exhaust system that an area of the device 8th For example, at least one third of the facility 8th protrudes into the exhaust system and can flow around the exhaust, so that the exhaust gas temperature for heating of the diesel fuel in the device 8th can be exploited and the energy required for the additional heating by means of the heating elements 16 can be reduced accordingly.

Claims (19)

System for the aftertreatment of exhaust gases from internal combustion engines, in which in an exhaust system in the flow direction of the exhaust gas, an oxidation catalyst and, following this, a diesel particulate filter are arranged, characterized in that in the flow direction of the exhaust gas upstream of the oxidation catalyst ( 4 ) at least one temporarily switchable device ( 8th ) is arranged for the addition of gaseous and / or present in aerosol hydrocarbon compounds in the exhaust stream. System according to claim 1, characterized in that the oxidation catalyst ( 4 ), the facility ( 8th ) and the diesel particulate filter ( 5 ) are formed as interconnectable modules. System according to claim 1 or 2, characterized in that in / on the exhaust pipe at least one exhaust gas temperature sensor ( 10 ) and / or two exhaust pressure sensors ( 9 . 9a ), for determining the differential pressure before and after the diesel particulate filter ( 5 ), for a regulation of the institution ( 8th ) are arranged. System according to one of the preceding claims, characterized in that the device ( 8th ) Diesel fuel is supplied. System according to one of the preceding claims, characterized in that the device ( 8th ) is heated. System according to one of the preceding claims, characterized in that the device ( 8th ) Is heated to above the evaporation temperature of the respective hydrocarbon compound (s). System according to one of the preceding claims, characterized in that the device ( 8th ) is at least partially flowed around by the exhaust gas. System according to one of the preceding claims, characterized in that in the device ( 8th ) before exiting for the respective hydrocarbon compound (s) a filter ( 19 ) is arranged. System according to one of the preceding claims, characterized in that the device ( 8th ) to a pump ( 22 ) or a container containing compressed hydrocarbon compound (s) is connected. System according to one of the preceding claims, characterized characterized in that in an injection region for gas and / or aerosol-supplied hydrocarbon compounds an ignition device is arranged. System according to one of the preceding claims, characterized in that the device ( 8th ), the temperature sensor ( 10 ), the exhaust pressure sensors ( 9 . 9a ) and / or the pump ( 7 ) to an electronic control unit ( 2 ) is / are connected. System according to one of the preceding claims, characterized in that in the device ( 8th ) there is at least one element for increasing the pressure on the hydrocarbon compound (s). System according to one of the preceding claims, characterized in that the element (s) consist of a piezoceramic material is formed / are. System according to one of the preceding claims, characterized in that on the device ( 8th ) at least one metering nozzle ( 10 ) and / or an outlet valve is present. System according to one of the preceding claims, characterized in that the device ( 8th ) is electrically heated. Method for the aftertreatment of exhaust gases from internal combustion engines with a system according to one of claims 1 to 15, characterized in that after expiration of specifiable time intervals and / or the detection of a predetermined threshold exceeding exhaust gas differential pressure before and after the diesel particulate filter ( 5 ) at least one hydrocarbon compound in gas or aerosol form the exhaust gas flow upstream of the oxidation catalyst ( 4 ) is supplied. Method according to claim 16, characterized in that that the volume flow and / or the time in which the hydrocarbon compound (s) is / are supplied, is regulated. Method according to one of claims 16 or 17, characterized that the hydrocarbon compound (s) prior to delivery in the exhaust stream is compressed and / or heated. Method according to claim 18, characterized that the hydrocarbon compound (s) is / are evaporated.