DE102008017280B4 - Arrangement for influencing the conversion behavior of catalytic converters - Google Patents

Abstract

Arrangement for varying the exhaust-gas temperature and the exhaust-gas pressure as operating parameters of at least one catalytic converter (5) for changing the composition of the exhaust gas of an internal combustion engine (1), the arrangement comprising: at least two exhaust-gas-charged charging groups (4, 7) with at least two exhaust gas turbines, which are a high-pressure turbine (3) and a low-pressure turbine (6), which are arranged fluidically behind one another; at least one catalyst (5), which is fluidly mounted between the at least two exhaust gas turbines (3, 6); and at least one adjusting device for varying compressor powers, turbine efficiencies or compressor efficiencies of the charge groups, characterized in that the at least one catalyst (5) comprises an SCR catalyst and that fluidly between the high pressure turbine (3) and the SCR catalyst is ammonia or ammonia-releasing reducing agent can be supplied, and further comprising an electronic control unit, which is designed to control the applied to the SCR catalyst exhaust gas temperature and exhaust gas pressure by means of the adjusting device.

Description

The invention relates to an arrangement for influencing the sales behavior of an exhaust aftertreatment system in equipped with exhaust charging internal combustion engines, such as diesel engines and gasoline engines, according to the preamble of claim 1.

In order to comply with the statutory exhaust emission limits, almost all internal combustion engines are now equipped with catalytic after treatment systems such as three-way catalytic converters, NOx storage catalysts, catalysts for hydrocarbon and carbon monoxide oxidation, SCR catalysts or particulate filters.

All these systems have in common that they presuppose sufficiently high exhaust gas temperatures for the correct function. This is particularly problematic in exhaust-gas-charged internal combustion engines, since the exhaust-gas turbocharger extracts enthalpy from the exhaust gas to perform the compression work, which leads to a cooling of the exhaust gas. If the internal combustion engine is additionally used in lightly loaded vehicles, the necessary minimum temperatures for the aftertreatment systems are often not reached.

One possible solution is to increase the catalysts and / or to increase the active mass. However, this leads to significantly higher costs.

An increase in the exhaust gas temperatures by throttling the exhaust or fresh air system and / or a reduction in the air / fuel ratio and / or a change in the injection times are conceivable, but lead to an increase in consumption.

Another possibility is to arrange the catalysts upstream of the exhaust gas turbocharger, but this leads to a high thermal load of the catalysts, which can lead to their damage. The exhaust gas temperatures upstream of the turbocharger are up to 900 ° C.

In addition, in some types of catalysts, such as NO oxidation and NOx storage catalysts, at too high temperatures, a decline in the achievable revenues.

Another important operating parameter for changing sales is the pressure under which the catalysts operate. Since the partial pressures of the exhaust gas components to be converted increase with increasing pressure, the reactions are accelerated. This leads to higher conversions compared to lower operating pressures at the same temperatures. One way to increase the operating pressure would be to install a throttle downstream of the aftertreatment system and thereby increase the exhaust backpressure. However, this is usually not done in practice because it results in a significant increase in consumption.

NO oxidation catalysts are used both in the SCR (Selective Catalytic Reduction) process and for the improved regeneration of particulate filters.

At the mostly platinum-containing NO oxidation catalysts, the strong oxidant nitrogen dioxide is formed with the aid of oxygen contained in the exhaust gas from the nitrogen monoxide emitted by the engine. 2NO + O ₂ ⇔ 2NO ₂ (1)

The problem of these NO oxidation catalysts is that the maximum achievable NO ₂ levels are thermodynamically limited at high temperatures. This means that, in contrast to other catalytic converters, the desired conversions fall again after a rise at low temperatures at high temperatures and no pronounced, plateau-like sales maximum is formed.

Another problem is the sulfurization of the NO oxidation and NOx storage catalysts by sulfur contained in the fuel and / or in the engine oil. The storage of sulfur in the catalysts reduces their NO oxidation and / or NOx storage capacity. A regeneration of the catalysts can be carried out by raising the exhaust gas temperatures to over 500 ° C, but this temperature is hardly reached in the normal vehicle operation downstream of the turbocharger.

The use of SCR catalysts has been used for many years in power plants and more recently also in internal combustion engines. A detailed description of such methods is the DE 34 28 232 A1 refer to. As SCR catalysts, V ₂ O ₅ -containing mixed oxides, for example in the form V ₂ O ₅ / WO ₃ / TiO ₂ , can be used. Typical V ₂ O ₅ contents are between 0.2-3%.

As reducing agents, ammonia or ammonia releasing compounds, such as urea or ammonium formate, in solid or solution form are used in practical application.

One mole of ammonia is necessary for the reaction of one mole of nitrogen monoxide. 4NO + 4NH ₃ + O ₂ ⇒ 4N ₂ + 6H ₂ O (2)

For the decomposition of the reducing agent, in particular after the start of the internal combustion engine, or when operating the internal combustion engine in the lower power range, the exhaust gas temperature is too low to produce without the onset of problematic by-products ammonia.

In connection with the decomposition of urea ((NH ₂ ) ₂ CO) in ammonia (NH ₃ ), it is known that this occurs under optimal conditions (temperatures above 350 ° C) in two stages (NH ₂ ) ₂ CO ⇒ NH ₃ + HNCO (3) First, the thermolysis, ie the thermal decomposition of urea. Subsequently, after HNCO + H ₂ O ⇒ NH ₃ + CO ₂ (4) the hydrolysis, ie the catalytic decomposition of isocyanic acid (HNCO) into ammonia (NH ₃ ) and carbon dioxide (CO ₂ ).

If the reducing agent is present in aqueous form, such as, for example, as a eutectic urea solution (brand name AdBlue), this water must additionally evaporate before and during the actual thermal and hydrolysis.

If the temperatures in the above reaction according to (3) and (4) below 350 ° C or is heated only slowly, it is from the DE 40 38 054 A1 discloses that mainly solid infusible cyanuric acid by trimerization according to (7) isocyanic acid according to 3HNCO ^{<350 ° C →} _{←> 350 ° C} (HNCO) ₃ (5) arises, which leads to the blockage of the subsequent SCR catalyst. Remedy can, as in the mentioned DE 40 38 054 executed, be created by the exhaust gas flow laden with the reducing agent is passed through a hydrolysis or urea decomposition catalyst. The exhaust gas temperature, from which a quantitative hydrolysis is possible, can be lowered to 160 ° C. Structure and composition of a corresponding catalyst is described in the cited publication as well as structure and function of a equipped with a hydrolysis catalyst SCR catalyst system.

Is the SCR catalysts a platinum-containing NO oxidation catalyst upstream of the formation of NO ₂ 2NO + O ₂ ⇔ 2NO ₂ (1) Thus, the SCR reaction can be significantly accelerated and the low-temperature activity can be significantly increased. NO + 2NH ₃ + NO ₂ ⇒ 2N ₂ + 3H ₂ O (6)

Care should be taken to ensure that the NO ₂ content of the total nitrogen oxides does not exceed 50%, as otherwise the NO x conversion will decrease. To ensure this, a bypass can be attached to the NO oxidation catalyst ₂ is opened -Anteilen at too high NO to lower the NO formed ₂ amount. Described are such bypass solutions in EP 1495796A1 . EP 1217196A2 and DE 102005049656 , Bypass solutions for catalysts are also known from other applications ( JP 4 017 714 B2 . JP 3 275 924 B2 ). The disadvantage of these solutions is that with the bypass solution only the sales reduced, but can not be raised. This has the consequence that the catalysts are made larger than necessary and is then reduced by the bypass of too high turnover.

In internal combustion engines operated in vehicles, nitrogen oxide reduction with the aid of the SCR method is therefore difficult because there are changing operating conditions, which makes the metering of the reducing agent more difficult. Although on the one hand the highest possible conversion of nitrogen oxides is to be achieved, on the other hand it is important to ensure that the emission of unused ammonia does not occur. In order to remedy this situation, an ammonia blocking catalyst arranged downstream of the SCR catalyst is frequently used, which converts excess ammonia into nitrogen and water vapor. Further, the use of V ₂ O ₅ as the active material for the SCR catalyst may pose problems when the exhaust temperature at the SCR catalyst is above 650 ° C because V ₂ O ₅ then sublimates. Here, the use of Fe, Cu or Co-containing zeolites as SCR catalysts offers.

In order to minimize the fine particles, either so-called particle separators or particulate filters are used both in power plants and in vehicles. A typical arrangement for use in vehicles with Partikelabscheider is for example in the EP 1 072 765 A2 described. Such arrangements differ from those with particle filters in that the diameter of the channels of the particle separator is substantially larger than the diameter of the largest occurring particles, while in particle filters, the diameter of the filter channels is in the range of the diameter of the particles. As a result of this Difference are particulate filter clogging, which increases the exhaust back pressure and reduces engine performance. An arrangement and a method with particle filter is the EP 0 341 832 A2 refer to. The two aforementioned arrangements and methods are distinguished by the fact that the oxidation catalyst arranged upstream of the particle separator or particle filter-usually a catalyst with platinum as active material-oxidizes the nitrogen monoxide in the exhaust gas to nitrogen dioxide with the aid of the likewise contained residual oxygen, which in turn Particle filter or particle filter with the carbon particles to CO, CO ₂ , N ₂ and NO. In this way, a continuous removal of the accumulated fine particles, regeneration cycles, as they must be carried out consuming in other arrangements, thereby eliminating. 2NO ₂ + C ⇒ 2NO + CO ₂ (7) NO ₂ + C ⇒ NO + CO (8) 2C + 2NO ₂ ⇒ N ₂ + 2CO ₂ (9)

In order to comply with the future applicable exhaust gas regulations, the simultaneous use of both arrangements for the reduction of nitrogen oxide emission, as well as arrangements for reducing the particulate matter emission is required. Various arrangements and methods have already become known for this purpose.

In the DE 103 48 799 A1 an arrangement is described which consists of an oxidation catalyst, a downstream of this arranged in the exhaust gas flow SCR catalyst and in turn arranged downstream of this in the exhaust gas flow particle filter. The supply of the reducing agent for the selective catalytic reaction taking place in the SCR catalytic converter takes place immediately upstream of the SCR catalytic converter via a urea injection device controlled as a function of operating parameters of the internal combustion engine. A disadvantage of this arrangement is that the nitrogen dioxide generated in the oxidation catalyst is substantially completely consumed by the selective catalytic reduction in the SCR catalyst, that is, is not available for the implementation of the deposited in the downstream particulate filter fines. The regeneration of the particulate filter must therefore be accomplished consuming by cyclically heating the exhaust stream by the exhaust gas stream is enriched with unburned hydrocarbons. This is done either by enriching the combustion mixture or injecting fuel before the particulate filter. Such an arrangement for regenerating the particulate filter is on the one hand laborious and therefore expensive, on the other hand, the cyclic regeneration of the particle filter located at the end of the arrangement again generates pollutants which can no longer be removed from the exhaust gas.

Another combination of a particulate filter and a selective catalytic reduction arrangement is known from US Pat EP 1 054 722 A1 known. The arrangement described therein consists of a arranged in the exhaust stream oxidation catalyst which increases the proportion of nitrogen dioxide in the exhaust, a downstream downstream fines filter, a reservoir for the reducing liquid and an injection device for the reducing liquid, which is located behind the fines filter, and downstream of this in the exhaust stream arranged SCR catalyst.

Next it is from the DE 10 2005 043 060 A1 a turbocharger device for an internal combustion engine having at least a first exhaust gas turbocharger and a further exhaust gas turbocharger known. The turbine of the first exhaust gas turbocharger and the turbine of the further exhaust gas turbocharger are drivable in an exhaust pipe from the exhaust gas of the internal combustion engine and successively acted upon by the exhaust gas mass flow in the flow direction. It is envisaged that the turbine of the first exhaust gas turbocharger, a first exhaust aftertreatment device and the turbine of the further exhaust gas turbocharger in the exhaust line are connected in series, with a controllable bypass line, through which the exhaust gas mass flow can flow with a proportion of 0% to 100%, upstream the series circuit branches off from the exhaust pipe and opens into an outlet downstream of the turbine of the first exhaust gas turbocharger in the exhaust pipe again.

From the DE 103 19 594 A1 Finally, a turbocharger device for an internal combustion engine is known, with at least one exhaust gas turbocharger whose turbine is driven in an exhaust pipe from the exhaust gas of the internal combustion engine and the compressor is arranged in an air supply line and provided for compressing combustion air of the internal combustion engine. In series with the turbine is a first exhaust gas catalyst in the exhaust pipe. Likewise, a switchable bypass line, through which the exhaust gas mass flow can flow, is provided, which branches off from the exhaust gas line upstream of the series connection and re-opens into the exhaust gas line in a junction downstream of the series connection.

Starting from the above-described prior art, the object of the invention, while avoiding the disadvantages of known arrangements, is to control or regulate the operating conditions of at least one exhaust aftertreatment catalyst such that the desired conversions result.

This object is achieved according to the characterizing part of claim 1.

To change the operating parameters, such as temperature and / or operating pressure of at least one catalyst for changing the composition of the exhaust gas of an internal combustion engine and / or a particulate filter and / or Partikelabscheiders an arrangement is proposed which comprises at least two exhaust gas-driven Aufladegruppen, wherein at least two exhaust gas turbines arranged one behind the other in terms of flow and at least one catalyst and / or particulate filter and / or particle separator between the at least two exhaust gas turbines is mounted and the compressor outputs and / or the turbine efficiencies and / or the compressor efficiencies are changed by at least one adjusting device.

The turbine, which is closer to the engine in terms of flow, is referred to as a high-pressure turbine, which is located farther away, as a low-pressure turbine.

By changing the compressor capacity and / or the turbine efficiency and / or the compressor efficiency of at least one charging group, it is possible to change the exhaust gas enthalpy, which is extracted from the exhaust gas via the first high-pressure turbine, and thus the desired exhaust gas temperature at the catalyst and / or particulate filter to adjust. In addition, an optimization of the sales by changing the exhaust gas pressure between the turbines and thus the operating pressure of the catalyst is possible.

For example, if the temperature and / or the exhaust pressure to be lowered at the catalyst, the compressor power of the high pressure stage can be raised. As a result, more enthalpy is removed from the exhaust gas, which leads to a reduction in the exhaust gas temperature and the exhaust gas pressure between the high and low pressure turbine. Since the low-pressure stage is now less exhaust enthalpy available, their compressor power is reduced accordingly, so that the funded fresh air amount changes in total only slightly. If the amount of air supplied to the internal combustion engine is to be kept constant, it makes sense to deliberately lower the compressor power of the low-pressure stage by means of appropriate devices.

If, on the other hand, the exhaust-gas temperature and / or the exhaust-gas pressure on the catalytic converter are to be raised, the compressor output of the high-pressure stage is lowered and the low-pressure stage correspondingly raised. This is particularly useful when cold starting the engine to heat the catalysts as quickly as possible.

The compressor capacities and / or the turbine efficiencies and / or the compressor efficiencies can be changed by a plurality of devices which can also be combined with one another.

The simplest solution is to provide a bypass line parallel to the exhaust gas turbine and set with the aid of a shut-off device in the bypass over the bypass bypassing the turbine exhaust gas. The more exhaust gas that bypasses the turbine via this bypass, the less compressor work can be done by this charging group. Such a device is referred to as a "wastegate" and as such is prior art.

A second possibility is to vary the flow of the turbine blades via adjustable nozzles, which leads to a change in the compressor power and the turbine efficiency. Such devices are referred to as turbochargers with variable turbine geometry, in short "VTG", and are in DE 3541508C1 . US6167703B1 and EP1334262A1 described.

A third embodiment provides for a bypass line to be provided parallel to the compressor, via which fresh air can flow back from the high-pressure side of the compressor back to the low-pressure side or into the environment. By means of an adjustable shut-off device in the bypass, the amount of fresh air flowing back through the bypass can be adjusted or regulated, which alters the compressor capacity and the compressor efficiency.

A fourth possibility is to influence the compressor performance by throttling on the fresh air side. In this case, the throttles can be installed upstream and / or downstream of the first and / or second compressor.

It is also possible to combine the devices described above. An example of a so-called combined charge group is in EP1640583A2 given, however, here neither the exhaust gas temperature nor the exhaust back pressure, but the boost pressure and thus the amount of fresh air is used as a controlled variable.

An adjustable throttle device in the exhaust gas flow between the low and high pressure turbine is conceivable. If the internal combustion engine is installed in a vehicle, this throttle device can be designed such that it is closed in the braking mode, whereby it acts as a motor dust brake.

The exhaust gas temperatures and exhaust gas pressures for position or regulation of the system may be determined or determined by means of suitable sensors an electronic control unit stored models, ie tables or curves are estimated.

In addition, the target operating parameters for the catalytic converters mounted between the exhaust gas turbines are determined in the electronic control unit and the corresponding points are activated. This is also done via suitable models and / or sensors, whereby the raw emissions and / or the target emissions and / or the actual emissions according to the system and / or the exhaust mass and / or the air mass and / or the fuel / air ratio and / or or the boost pressure and / or the atmospheric pressure and / or the exhaust gas recirculation rate and / or the exhaust gas backpressure and / or the residual oxygen content in the exhaust gas and / or the service life of the internal combustion engine and / or the aftertreatment system are used to determine the desired parameters.

The method or an appropriately configured electronic control unit can also be used to raise the exhaust gas temperature in the short term to perform a regeneration of the exhaust aftertreatment system. This is useful, for example, when NO oxidation and / or NO x storage catalysts are used. In these catalysts, it is very easy to sulfation and consequent sales decline. If these catalysts are installed between the two turbines, a short-term change in the compressor capacity and / or the turbine efficiency and / or the compressor efficiency of at least one charging group can produce a significant increase in temperature on the catalysts, and thermal desulfation of these catalysts can be carried out very simply. Contrary to the state of the art, in which fuel is usually additionally added to the internal combustion engine and / or the exhaust system and / or the injection starts of the fuel are adjusted "late", the method according to the invention or the correspondingly configured electronic control unit leads to a much smaller increase of fuel consumption.

In the same way, a particulate filter installed between the turbines can be regenerated since, at high temperatures, oxidation of the carbonaceous soot deposited in the particulate filter with the aid of oxygen occurs. 2C + O ₂ ⇒ 2CO (10)

As exhaust aftertreatment components between the at least two exhaust gas turbines NO-oxidation catalysts and / or three-way catalysts and / or NOx storage catalysts and / or urea decomposition catalysts and / or hydrolysis catalysts and / or catalysts for the oxidation of hydrocarbons and / or catalysts for the oxidation of Carbon monoxide and / or catalysts for the oxidation of ammonia and / or SCR catalysts and / or particulate filter and / or particle are used.

These can also be combined into a structural unit.

Cordierite or silicon carbide or sintered metal or ceramic fibers or silicate fibers or metal knits or aluminum titanate are advantageously suitable as material for the particle filter.

Suitable active components for the NO oxidation, three-way and NH ₃ oxidation catalysts are elements of the platinum metal group and their oxides and / or zeolites.

Vanadium oxide and / or tungsten oxide and / or titanium dioxide and / or iron zeolites and / or copper zeolites and / or cobalt zeolites can be used as active components for the SCR catalysts. Carried out for NO _x conversion must reductant supply upstream of the SCR catalyst, advantageously between the high pressure stage and the SCR catalyst.

Barium oxide and platinum metals are conceivable as active components for the NO storage catalysts.

Suitable active components for the urea decomposition catalysts are TiO ₂ and / or TiO ₂ / SiO ₂ and / or TiO ₂ / SiO ₂ / Al ₂ O ₃ and / or zeolites.

When using an SCR and / or urea decomposition catalyst, it makes sense to add the required reducing agent downstream of the high pressure turbine and upstream of the SCR or urea decomposition catalysts.

The catalysts described above can be housed in a housing which simultaneously acts as an exhaust muffler. For this purpose, damping volume and / or insulating mats and / or perforated intermediate plates and / or perforated pipe sections can be used.

The invention will be explained in more detail with reference to the drawings with reference to some examples, in which:

1 Thermodynamic equilibrium between NO and NO ₂ and effect of a NO oxidation catalyst;

2 schematic structure of the inventive arrangement with a wastegate on the high-pressure turbine;

3 schematic structure of the arrangement according to the invention, each with a wastegate on the high-pressure and the low-pressure turbine;

4 schematic structure of the arrangement according to the invention, each with a bypass on the high-pressure and low-pressure compressor;

5 schematic structure of the arrangement according to the invention, each with a wastegate and variable turbine geometry at the high-pressure and low-pressure turbine and one bypass on the high-pressure and low-pressure compressor;

6 schematic structure of the arrangement according to the invention, each with a wastegate on the high-pressure and low-pressure turbine, an adjustable throttle upstream of the low-pressure supercharger and a NO Oxidationskatalyator and a particulate filter.

In 1 the formation of NO _{2 is} illustrated by the example of two differently active NO oxidation catalysts. It can be clearly seen that, although the catalyst 1 At low temperatures, significantly more NO is converted into NO ₂ than the catalyst 2 However, at high temperatures, the NO ₂ levels are thermodynamically limited, which means that from temperatures of about 400 ° C, there is no difference between the two catalysts. If the maximum possible NO conversion of the catalysts is to be represented, the temperatures should be determined by the method according to the invention or a correspondingly set up electronic control unit for the catalyst 1 to about 290 ° C and for the catalyst 2 be adjusted to about 350 ° C. If, on the other hand, the optimum 50% NO ₂ content for the SCR process is to be set, the result for the catalyst 1 as possible temperatures 220 ° C or 430 ° C, for the catalyst 2 290 ° C or 430 ° C again.

In 2 the schematic expansion of the arrangement according to the invention is shown: the exhaust gas 2 an internal combustion engine 1 flows through the high-pressure turbine 3 the first charging group 4 , then through a downstream mounted catalytic converter 5 and the low-pressure turbine 6 the second charging group 7 , About the compressor of the second charging group 7 gets fresh air 8th sucked, compressed and over the compressor of the first Aufladegruppe 4 the internal combustion engine 1 as compressed charge air 9 fed. To the compressor capacity of the first charging group 4 to change, is parallel to the high-pressure turbine 3 a bypass 10 in the form of a wastegate including a shut-off device 11 appropriate. By varying the means of the shut-off device 11 The exhaust gas flow rate via the wastegate can be used to control the turbine output and thus the temperature or pressure at the catalytic converter 5 to adjust.

With the catalyst 5 it may be an SCR catalyst and, optionally, an NO oxidation and / or NH ₃ oxidation and / or hydrocarbon oxidation and / or Kohlenmonoxidoxidations- and / or urea decomposition and / or hydrolysis and / or NOx Storage catalytic act.

Is it the catalyst 5 an SCR and / or urea decomposition and / or hydrolysis catalyst, the supply of a reducing agent is required. In the 2 Not shown supply then takes place between the high-pressure turbine and the catalyst. The reducing agent used is usually ammonia or an ammonia-releasing reducing agent, such as aqueous urea solution. If ammonia is supplied, it makes sense to use it in a downstream reducing agent processing unit, which may be arranged in a bypass to the turbine of the high-pressure turbocharger, from a reducing agent such. B. prepare aqueous urea solution. The above-described reducing agent supply can also be realized accordingly in the following examples, without this being mentioned separately.

The arrangement after 3 corresponds in many parts to the example 2 , however, is also on the low-pressure turbine 6 another bypass 10 with a shut-off device 11 ' connected in parallel. It is thus also the performance of the low-pressure turbine 6 directly influence, so that the controllability of the entire arrangement in particular also improves with respect to the temperature applied to the catalyst or the pressure.

Another way, the compressor capacity of the compressor 3 and 6 to influence is in 4 shown. Here are in an arrangement similar to the example according to 3 , in place of the wastegate on because turbines, bypasses 10 '' . 10 ''' arranged parallel to the compressors. By an adjustable shut-off device 11 '' . 11 ''' in the bypasses 10 '' . 10 ''' the amount of fresh air flowing back through this can be adjusted or adjusted, which changes the compressor capacity and the compressor efficiency. This also allows the performance of the turbines 3 and 6 influence, so that in this way temperature and pressure on the catalyst 5 are adjustable.

A combination of the arrangement according to 3 and according to 4 shows 5 , Here are bypasses 10 . 10 ' . 10 '' . 10 ''' in the form of controllable wastegates on all turbines 12 . 12 ' and compressors arranged. In addition, the turbines 12 . 12 ' equipped with variable turbine geometry. This arrangement allows the maximum controllability of the temperature or the pressure at the catalyst.

The in 6 The structure shown is similar to that in FIG 2 described, in addition, is between the two exhaust gas turbines 3 . 6 an adjustable throttle device 13 attached to change the compressor performance. With the help of the throttle device 13 In addition, by means of complete shut-off, an engine brake can be realized.

As in further 6 shown are between the high pressure turbine 3 and the low-pressure turbine 5 a catalyst for the oxidation of hydrocarbons and / or carbon monoxide and / or nitrogen monoxide 14 and a particle filter 15 arranged, these two aftertreatment systems form a structural unit. The temperature or the pressure at the catalyst 14 or on the particle filter 15 can be controlled in the manner already described in detail in the preceding examples by varying the compressor capacity.

When using an SCR and / or urea decomposition catalyst, it makes sense to add the required reducing agent downstream of the high pressure turbine and upstream of the SCR or urea decomposition catalysts.

Claims (13)

Arrangement for changing the exhaust gas temperature and the exhaust gas pressure as operating parameters of at least one catalytic converter ( 5 ) for changing the composition of the exhaust gas of an internal combustion engine ( 1 ), the arrangement comprising: at least two exhaust gas-driven charging groups ( 4 . 7 ) with at least two exhaust gas turbines, which a high-pressure turbine ( 3 ) and a low-pressure turbine ( 6 ), which are arranged fluidically behind one another; at least one catalyst ( 5 ), which fluidly between the at least two exhaust gas turbines ( 3 . 6 ) is attached; and at least one adjusting device for varying compressor capacities, turbine efficiencies or compressor efficiencies of the charging groups, characterized in that the at least one catalyst ( 5 ) comprises an SCR catalyst, and that fluidically between the high-pressure turbine ( 3 ) and the SCR catalyst ammonia or ammonia-releasing reducing agent can be fed, and further comprising an electronic control unit, which is designed to control the applied to the SCR catalyst exhaust gas temperature and exhaust gas pressure by means of the adjusting device. Arrangement according to claim 1, characterized in that the compressor outputs, the turbine efficiencies or the compressor efficiencies by means of a bypass ( 10 . 10 ' . 10 '' . 10 ''' ) at least one turbine and / or a compressor ( 3 ) mounted shut-off device ( 11 . 11 ' . 11 '' . 11 ''' ) are changeable. Arrangement according to one of the preceding claims, characterized in that the compressor outputs or the turbine efficiencies using a variable turbine geometry ( 12 . 12 ' ) are variable by adjusting the flow of the turbine blades. Arrangement according to one of the preceding claims, characterized in that an adjustable throttle device ( 13 ) in terms of flow, between or after the at least two exhaust gas turbines ( 3 . 6 ) is attached. Arrangement according to claim 4, characterized in that by means of the throttle device ( 13 ) is raised in engine braking operation, the exhaust back pressure to increase the engine braking power. Arrangement according to one of claims, characterized in that the at least one catalyst additionally a NO oxidation and / or a NH ₃ oxidation and / or a Kohlenwasserstoffoxidations- and / or a Kohlenmonoxidoxidations- and / or a urea decomposition and / or a hydrolysis and / or a NOx storage catalytic converter comprises. Arrangement according to one of the preceding claims, characterized in that between the two exhaust gas turbines additionally a particle filter or a particle separator is arranged. Arrangement according to claim 7, characterized in that the particle filter or particle separator made of cordierite, silicon carbide, ceramic fibers, silicate fibers, metal foils and / or sintered metal are made. Arrangement according to one of the preceding claims, characterized in that at least one catalyst, particulate filter and / or Partikelabscheider is installed in at least one housing and this housing is designed as an exhaust muffler. Arrangement according to claim 9, characterized in that for sound damping compensation volumes and / or insulating mats and / or perforated intermediate plates and / or perforated pipes are provided. Arrangement according to one of the preceding claims, characterized in that the electronic control unit is further adapted to determine the operating parameters of the exhaust aftertreatment system via sensors and / or tables or curves, which are stored in the electronic control unit, with the current actual values compare and adjust these by controlling the setting device to the desired values. Arrangement according to claim 11, characterized in that the electronic control unit is further adapted to determine the desired values of the operating parameters of the exhaust aftertreatment system by means of tables or curves and / or sensors, the raw emissions and / or the target emissions and / or actual emissions after the exhaust aftertreatment system and / or the exhaust mass and / or the air mass and / or the air / fuel ratio and / or the boost pressure and / or the atmospheric pressure and / or the exhaust gas recirculation rate and / or the exhaust backpressure and / or the operating time the internal combustion engine and / or the exhaust aftertreatment system are used for determining the desired values of the operating parameters. Arrangement according to one of claims 11 or 12, characterized in that the electronic control unit is further adapted to increase the exhaust gas temperature by changing the compressor powers, the turbine efficiencies or the compressor efficiencies briefly to desulfurize the exhaust aftertreatment system and / or when using a particulate filter to regenerate.

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