ITMI20011747A1 - DEVICE AND PROCEDURE TO TREAT THE EXHAUST GASES OF AN ENDOTHERMAL ENGINE - Google Patents

Description

Description

The invention relates to a device and a method for treating the exhaust gases of an internal combustion engine, especially of a Diesel engine, with a particle filter in accordance with the introductory definition of the independent claims.

State of the art

In accordance with the advanced state of knowledge for the protection of health and the environment, legal regulations governing vehicle emissions are continually being unapplied. To meet these requirements, for example, in addition to the use of correspondingly modified propellants, solid particles are removed from the exhaust gas by means of filters.

Diesel drive devices in particular produce large quantities of carbon black, where there is a suspicion that diesel exhaust gases have carcinogenic potential. Thus, many provisions have already been proposed for dealing with diesel engine exhaust gases. In general these arrangements are formed by filtration systems which retain the particulate contents. An efficient filter in this respect fully effectively retains carbon black particles especially with a diameter of approx. 10 up to 5000 nanometers.

However, the particles retained by corresponding filters as a result of the engagement of the filter or its surface causes a reduction in the gas flow rate and thus lead to an increase in the filtration resistance. This resistance leads to a greater consumption of propellant until the engine stops, so that regeneration phases must be provided. Regeneration generally takes place by means of an almost residue-free combustion of the stored carbon black. The temperatures of around 200 ° C that exist in the exhaust gas of diesel engines are generally not sufficient in this regard, so that additional systematic aids must be provided.

Without additional precautions, the carbon black oxidizes starting from approx. 550 up to 600 ° C. The lower temperature threshold for carbon black oxidation can be lowered to approx. 250 up to 350 ° C. However, these temperatures for modern diesel engines are still higher than the usual temperatures of the exhaust gas, so that measures to increase the temperature are necessary for the safe regeneration of the filters.

In order to increase the temperature of the exhaust gas, up to now, for example, additional electric heaters, microwave heaters or internal devices have been provided for in the engines, where these, for example, due to the necessary high heating power, may require additional batteries, if necessary, have a high expenditure of the system, involve a considerable greater consumption of propellant or are not able to guarantee the necessary temperature increase for sure.

Thus, for example, it is known that by throttling the sensor of the intake air mass, it is possible to increase the temperature of the process or the temperature of the exhaust gas. Document EP 0010 384 illustrates, for example, a device which varies the intake air by means of an adjustable throttle valve system. However, the required ignition temperature can only be achieved in the higher load and speed range. For driving situations with a predominantly low load and speed range, in practice, the conditions required for regeneration of the filter are rarely met.

One embodiment, likewise described in EP 0 010 384, reaches the process temperature high enough to clean by combustion the low-load, low-speed carbon black combustion filter by means of an exhaust gas recycle comprising between other a relatively compact unit. This embodiment is also suitable only to a limited extent for regenerating the filter, since for a perfect functioning of the combustion engine the percentage of exhaust gases in the supply air cannot exceed 30%. In this way, reaching the temperature of the exhaust gas, necessary for regeneration of the filter, is not possible in all driving situations. A heating device is additionally required for this, which additionally increases the construction effort.

Basically, in the device of the document EP 0 010 384, an outlet temperature as high as possible is required from the particle filter, so that among other things the intake air can be preheated as strongly as possible.

Furthermore, document DE 35 22 431 illustrates a device which increases the temperature of the exhaust gas due to the fact that a heat exchanger, located downstream of the carbon black filter, preheats the intake air of the combustion engine. In this way, in the first place, the hot operation phase is reduced and, on the other hand, the temperature of the process gas is increased, even in the case of low load, sufficiently to allow a regeneration of the filter. For this purpose, a setting valve is provided in particular, which ensures that at full load or when an upper limit temperature at the carbon black filter is exceeded, the intake air stream is made to pass in front of the heat exchanger. This firstly reduces the power reductions caused by the heat exchanger at full load and on the other hand protects the carbon black filter from overheating.

The disadvantage of the illustrated device is that the necessary ignition temperature for regeneration of the filter can be added only when the engine has undergone the hot operating phase. In addition, it is particularly disadvantageous that the heat exchanger is arranged in the intake region, whereby a pressure drop occurs during operation of the engine. The aforementioned setting valve, involving an additional expenditure on equipment, is therefore mandatory to maintain the power density in the full load operating range.

Thus, the hitherto known exhaust gas filtration systems are generally relatively expensive, where in part it is necessary to accept a particularly critical pressure drop in the intake area for operation of the engine, or a reduction in the power density in the range of full load operation.

Advantages of the invention

Differently from this, the invention has the task of proposing a device and a method for treating the exhaust gas of an internal combustion engine, especially of a Diesel engine, with a particle filter, where a regeneration of the particle filter is envisaged. significantly reducing the expenditure depending on the system, where moreover, at the same time, there is no pressure drop in the intake area or there is no reduction in the power density of the internal combustion engine.

Starting from a device or from a method of the kind mentioned in the introduction, this problem is solved by means of the characteristics of the independent claims. Advantageous embodiments and further developments of the invention are possible with the expedients mentioned in the sub-claims.

Accordingly, a device according to the invention is characterized in that at least one heat exchanger is provided for heating the exhaust gas to be filtered at least by means of the dissipated heat of the filtered exhaust gas. Advantageously in this regard, the heat exchanger of the exhaust gas is recovered by means of the heat exchanger according to the invention for regeneration of the filter, so that the energy expenditure for obtaining the regeneration temperature is substantially reduced and no power reductions are caused. endothermic engine. For example, for the most varied operating conditions of the internal combustion engine, among other things through the exothermic reaction of the catalytic oxidation of the burnt hydrocarbon components, still present in the exhaust gas, an additional heating of the particle filter takes place and therefore of the exhaust gas to be filtered with the aid of the heat exchanger according to the invention. In this way the construction effort of a device according to the invention for the treatment of the exhaust gas is minimized.

Preferably, a collector duct for feeding the entire exhaust gas stream into the heat exchanger is arranged upstream of this, so that the largest possible and therefore effective heat supply can be achieved by means of the exhaust gas to be filtered. in the heat exchanger.

In a further particular development of the invention at least the particle filter and the heat exchanger are designed as a construction unit. In this way it is advantageously possible to obtain an implementation of the device according to the invention as small as possible, effective and therefore economically convenient. In this connection, the waste heat of the filter is generally used, which develops with the regeneration of the waste heat of the exhaust gas to be filtered along the entire heat exchanger, so that a relatively low exhaust gas temperature can be achieved at the same time. outlet of the heat exchanger. In this way, according to the invention, the maximum possible preheating of the exhaust gas to be filtered is obtained.

Preferably, at least one heating device is provided, so that even for example for very extreme operating or atmospheric conditions a safer regeneration of the filter is guaranteed. The heating device can advantageously be arranged integrated either between the both gas zones of the heat exchanger and / or in the heat exchanger. Thus in this way it is advantageously possible to carry out a regeneration of the filter even before the internal combustion engine has reached its operating temperature.

In a preferred embodiment of the invention, a control dependent at least on temperature, time, gas composition, or pressure is provided. With this, for example, it is possible to realize an automatic ignition of the heating device when a defined pressure difference between the inlet of the filter and the outlet of the filter is exceeded. In addition, it is also possible to monitor the temperature of the filter or the heat exchanger if necessary. Overheating of the filter, among other things in the case of full load operation of the internal combustion engine, can be avoided, for example, by bypassing the heat exchanger. Likewise, it is possible to control the amount of heat of the heating device as a function of the temperature of the filter. According to the invention, the particle filter with corresponding conditions is possibly also regenerated in advance, i.e. even before regeneration is required, without a heating device. In particular, the control preferably comprises a management system which, for example, monitors almost all components of the vehicle.

Advantageously, means are provided for introducing at least air into the exhaust gas stream, so that, depending on the composition of the exhaust gas, it is possible to carry out an additional blowing of air, which improves, for example, the exothermic reaction of the catalytic oxidation of the hydrocarbon components. unburnt, still present of the exhaust gas, or the oxidation of the carbon black. In this way, an injection of, for example, hydrocarbons into the exhaust gas stream is also advantageous. In a preferred embodiment of the invention the heat exchanger has a surface enlargement structure. Thus, for example, by means of a parallel connection of several heat exchange units or by means of coplanar heat transfer walls, structural or of similar effect, it is possible to advantageously carry out the transmission of heat from the filter or from the filtered exhaust gas to the gas. drain to be filtered.

In a further preferred embodiment, the exhaust gas section arranged between the internal combustion engine and the heat exchanger has a branch point through which the exhaust gases can be divided into a main stream and a secondary stream. During regeneration of the particle filter, only a partial stream of the exhaust gas is fed to the heat exchanger or to the heating device, so that rapid heating of the particle filter with minimum heat energy consumption is ensured.

Basically, all embodiments of the invention lead to a marked reduction in the amount of heating energy as well as in the construction expenditure, so that a substantially cheaper and more environmentally friendly operation is possible than in the current state of the art.

Examples of realization

More embodiments of the present invention are shown in the drawing and are illustrated in more detail on the basis of the following figures.

In particular:

figure 1 shows a block diagram of a device according to the invention together with an internal combustion engine,

figure 2 shows a schematic representation of a device according to the invention, figure 3 shows a schematic representation of a further device according to the invention,

figure 4 shows a schematic representation of a device according to the invention with several heat exchange units,

figure 5 shows a basic temperature trend in a device according to the invention,

Figure 6 shows a schematic representation of a device according to the invention with a branch point in the exhaust gas section,

figure 7 shows a schematic representation of a device according to the invention with a heat exchanger having a catalytically active coating,

figure 8 shows a schematic representation of a device according to the invention with two heat exchangers, and

Figure 9 shows a schematic representation of a device according to the invention with two subsequent treatment plants of the exhaust gas.

Figure 1 in block diagram representation shows a heat exchanger 1 according to the invention which by means of a connection pipe 2 is connected to an internal combustion engine 3. Furthermore, Figure 1 shows an intake pipe 4 of the internal combustion engine 3 as well as an exhaust gas outlet duct 5.

The exhaust gas outlet in the embodiment example of FIG. 1 can be brought to the exhaust gas outlet 5 either via an exhaust pipe 6 of the heat exchanger or via an optionally mounted butterfly valve 7. By means of the throttle valve 7, it may be possible to bypass the structure of the heat exchanger 1, so that, especially in full load operation of the internal combustion engine 3, overheating of the heat exchanger 1 or of a particle filter not shown in more detail is prevented. Figure 1.

The device shown in Figure 1 also comprises a heating device 8 as well as a control unit 9. Temperature sensors or pressure sensors not shown in more detail, for example, determine the pressure upstream and downstream of the heat exchanger 1 or of the filter. During the operation of the internal combustion engine 3 the carbon black contained in the exhaust gas is deposited on the filter, so that the control unit 9 by means of the aforementioned pressure sensors determine a pressure difference upstream and downstream of the heat exchanger 1 with progressive covering of the filter with carbon black. If the determined pressure difference exceeds a settable threshold value, then for example the heating device 8 is switched on to start the regeneration of the filter.

Figure 2 shows a heat exchanger 1 including a filter 10 during an operating phase of the heating device 8. In this connection, the heating device 8 is shown schematically as a burner, where, however, electrical and other chemical transformations are also possible. for example catalytic, of a heating material. In this case, both separate heating devices 8 and also integrated heating devices can be used. For example, it is possible to provide for electroconductive ceramics or for the integration of heating wires in an electro-insulating sintered ceramic. The ceramic can advantageously be provided in this regard simultaneously as a filter, where it is possible to use catalytically coated as well as non-catalytically coated ceramics. Furthermore, it is optionally possible to feed additional thermal energy into the gas flow case or onto the heat exchanger case.

The heating of an inlet stream 11, i.e. of exhaust gas flowing from the internal combustion engine 3 via the connection pipe 2 in the heat exchanger 1, takes place by means of the dissipated heat of the exhaust gas filtered through a wall 12 of the heat exchanger. According to the invention, the conduction of the heat takes place both in an inlet zone B respectively in a zone of the filter D and also in an outlet zone E or in an inlet zone A of the heat exchanger 1. In the outlet zone E An exhaust stream 13 extends including the filter region D. In this regard, according to the invention, the greatest possible cooling of the exhaust stream 13 by means of the heat exchanger 1 is provided.

The highest temperature of the filter 10 respectively of the exhaust stream 13 is obtained for example by means of an exothermic reaction for the catalytic oxidation of residual hydrocarbons, present in the supply stream 11, in the zone D of the filter 10 and, or by means of the heating device 8.

Figure 1 illustrates by way of example a basic temperature trend in the heat exchanger 1. Figure 5 illustrates the fact that the inflow stream 11 in the heat exchanger 1 is conducted with an inlet temperature Te. In the inlet zone A, B the inlet stream 11 is strongly preheated, so that the exhaust gas in a heating zone C by means of the heating device 8 additionally has to be heated relatively little. To be brought to an ignition temperature Tz. Above the ignition temperature Tz, an automatic ignition of the exhaust gas stream takes place, so that regeneration of the filter 10 takes place. The regeneration of the filter 10 in the heat exchanger 11 with suitable dimensioning of the filter or heat exchanger can take place in an exothermic or at least autothermic manner, so that the emission of further heating energy can be terminated by means of the heating device 8.

Corresponding to the temperature trend in filter zone D, the exhaust gas temperature decreases slightly. Especially in the outlet area E relatively much heat is removed from the exhaust stream 13, so that it leaves the heat exchanger 1 with a comparatively low outlet temperature Ta. Figure 5 in particular illustrates the fact that it is advantageous to reduce the outlet temperature Ta as large as possible for the preheating of the inlet stream 11 and thus for the regeneration of the filter 10.

The heat exchanger 1 in Figure 3 with respect to the heat exchanger 1 of Figure 2 has a butterfly valve 7 which allows a partial or complete bypassing of the structure of the heat exchanger, i.e. the recovery of heat to heat the exhaust gas to be filtered. In this way, for example, in the full load operation of the internal combustion engine 3 it is possible to prevent overheating of the filter 10 or of a further filter 14.

As already mentioned, the exhaust gas of an internal combustion engine 3, operating in full load operation, already has temperatures above the ignition temperature Tz of the filter 10.14, so that it is possible to do without heat recovery by means of the exchanger. of heat 1 respectively it is advantageous to avoid overheating of the filters 10,14. In the embodiment of Figure 3, the inlet stream 11 flows almost completely through the throttle valve 7 as outflow stream 15. Since the filter 10 is bypassed in this case, the filter 14 is therefore required to filter the gas stream. at full load.

Figure 4 schematically represents a heat exchanger 16 having a parallel circuit of several heat exchanger 1 of figure 2. The parallel connection of the heat exchangers 1 increases in particular the overall surface of the wall 12 of the heat exchanger, so that better heat recovery is achieved. Several openings 17 are provided to discharge the outflow currents 13.

Basically, in an unlimited number it is possible to connect heat exchanger units 1 to each other. Furthermore, it is possible to carry out both a direct supply of the inflow currents 11 from individual cylinders of the internal combustion engine 3, as well as a supply of more than one collecting pipe and subsequent division into individual pipes. It is also possible to use a single heating device 8 as well as to use several heating devices in the heat exchanger 16. The openings 17 are advantageously combined in a single exhaust gas duct 5 downstream of the heat exchanger. 16.

Furthermore, for all devices according to the invention, as a control mechanism for successful ignition of the carbon black filter, it is possible to arrange a temperature sensor at a suitable point of the heat exchanger 1.16, especially in or directly downstream of the filter 10, 14. The measured temperature can be used by means of the control unit 9 so that the heating power of the heating device 8 is controlled and possibly switched off. In the case of an engine with a strong production of carbon black or when sufficient hydrocarbons are contained in the inflow stream 11 and at the same time the filter 10.14 catalytically actively allows the transformation of hydrocarbons, the oxidation of carbon black and hydrocarbons can also occur continuously after a single ignition of the heating device 8.

Figure 6 shows a further example of embodiment of the present invention. In this connection, the connection line 2 has a three-way exhaust gas valve 20, by means of which the exhaust gas stream 11 leaving the combustion engine 3 can be divided into a main stream and a secondary stream. During a cold start phase of the internal combustion engine 3 or during a regeneration process of the filter 10, for example, the three-way exhaust gas valve 20 is set so that only a small part of the exhaust gas as a secondary stream reaches the heat exchanger 1 and subsequently to the heating device 8 respectively to the filter 10. This is advantageous since during a cold start the temperature of the exhaust gas is too low for a regeneration of the filter 10 and the exhaust gas will have to be heated by means of the heating device 10. Since only a small amount of the exhaust gas has to be heated by splitting the flue gas stream at this time, a higher flue gas temperature is achieved with comparatively low heat energy consumption. Meanwhile, the main stream of the exhaust gas via the exhaust gas line 22 is led in front of the heat exchanger 1 and released directly into the ambient air.

As soon as the flue gas reaching the heater 8 has a sufficiently high temperature, the three-way flue gas valve 20 is set so that the entire flue gas stream via the connection line 2 is fed to the exchanger heat 1.

If it is intended to prevent overheating of the filter 10 with the appearance of very hot exhaust gases 11, then the main exhaust gas stream, discharged via the exhaust gas line 22 in accordance with Figure 7, preferably upstream of the filter 10 bypassing the heat exchanger 1 can be combined again with the secondary current. By bypassing the heat exchanger 1, further heating of the hot exhaust gases is avoided and the exhaust gas back pressure is reduced. In this embodiment, the heating device provides for an injection of the fuel at a delivery point 28 in the connection pipe 2. Subsequently, a preferably catalytic transformation of the fuel injected takes place in correspondence with a catalytically active layer 30, integrated for example in the heat exchanger 1, with residual oxygen contained in the exhaust gas.

Figure 8 shows a further example of embodiment of the present invention which presents two systems formed respectively by the supply point 28.29, heat exchanger 1.21, catalytically active coating 30.32 and filter 10.40. Here, the exhaust gas stream 11 which leaves the internal combustion engine 3 via the three-way exhaust gas valve 20 can be divided according to the regeneration requirements of the filters 10,40 so that, for example, during a regeneration process of the filter 10 only a secondary stream of the exhaust gas via the connection line 2 is fed to the heat exchanger 1 and the main flow via the exhaust gas line 22 is fed to the heat exchanger 21 and vice versa.

During a cold start phase, the main stream of the exhaust gas is preferably conducted on the first filter 10 which retains the particles contained in the exhaust gas, and yet due to the modest temperature of the passing exhaust gases it cannot undergo regeneration. In this case, a secondary stream of the exhaust gas is fed to the second filter 40 and is heated by fuel injection at the delivery point 29 and catalytic transformation at the catalytically active layer 32. As soon as the exhaust gases at the second filter 40 have a sufficient temperature for regeneration, the main exhaust gas stream is fed to the second filter 40 via the three-way exhaust gas valve 20 and the first filter 10 to for example, by injection of fuel at the adduction point 28 and by means of its catalytic transformation at the catalytically active layer 30, it is subjected to a regeneration.

Since the resistance of a second heat exchanger 21 is not necessarily required for this process, according to a further embodiment shown in Figure 9 it is actually possible to pre-insert, for example, a heat exchanger 1, preferably with a catalytic coating 30, to the first filter 10. active, and yet the second filter 40 can only be connected via the exhaust gas line 22 with the integrated heating device 8 to the three-way exhaust gas valve 20. The three-way exhaust gas valve 20 can alternatively be replaced by two block valves inserted consecutively.

Basically, the described embodiments can also be transferred to systems for the subsequent treatment of the exhaust gas, in which a NOx storage catalyst is used additionally or instead of the particle filter.

Claims (1)

Claims 1.-Device for treating the exhaust gas of an internal combustion engine, especially of a Diesel engine, with a particle filter, where a regeneration of the particle filter is envisaged, characterized in that at least one heat exchanger is provided (1 , 16,21) to heat the exhaust gas (11) to be filtered, at least by the dissipated heat of the filtered exhaust gas (13). 2. Device according to Claim 2, characterized in that a collector unit for supplying the entire exhaust gas stream (11) is arranged in the heat exchanger (1,16,21) upstream from this. 3. Device according to one of the aforementioned claims, characterized in that at least the particle filter (10,14,40) and the heat exchanger (1) are designed as a construction unit (1). 4. Device according to one of the aforementioned claims, characterized in that at least one heating device (8) is provided. 5. Device according to one of the preceding claims, characterized in that a control (9) is provided which depends at least on temperature, time, gas composition and / or pressure. 6. Device according to one of the aforementioned claims, characterized in that means are provided for feeding at least air into the exhaust gas stream. 7. Device according to one of the aforementioned claims, characterized in that the heat exchanger (1.16) has a surface enlargement structure (16). 8. Device according to one of the aforementioned claims, characterized in that in the direction of the flue gas flow (11) upstream of the heat exchanger (1.21) the connection pipe (2) has a branch point ( 20) to divide the exhaust gas stream into a main stream and a secondary stream. 9. A device according to Claim 8, characterized in that two particle filters (10,14,40) are provided. 10. Device according to one of claims 8 to 8, characterized in that two heat exchangers (1,16,21) are provided. 11. Device according to one of the aforementioned claims, characterized in that the heat exchanger (1,21) has a catalytic coating (30,32) at least in a partial area. 12.-Process for regenerating an exhaust gas subsequent treatment system, especially a particle filter, characterized in that during the regeneration the exhaust gas (11) is divided into a main stream and a partial stream and the current partial is heated and fed to the subsequent exhaust gas treatment system (10,14,40). 13. Process according to Claim 12, characterized in that the main stream of the exhaust gas during the regeneration is fed to a second subsequent exhaust gas treatment system. 14. Process according to Claim 12 or 13, characterized in that it is carried out during the cold starting phase of an internal combustion engine (3). 15. Process according to one of the claims 12 to 13, characterized in that it is carried out by means of a device according to one of the claims 1 to 11.