DE102021105395A1 - Purification device and method for removing substances from exhaust gases from an internal combustion engine - Google Patents

Abstract

According to the invention, the technology disclosed here relates to a cleaning device (15) for removing substances from exhaust gases of an internal combustion engine (20), the cleaning device (15) having a diesel oxidation catalyst (30) for reducing the oxygen content in the exhaust gases and a hydrogen SCR catalyst (40 ) for reducing nitrogen oxides in the exhaust gases by means of hydrogen, wherein the hydrogen SCR catalytic converter (40) is arranged downstream of the diesel oxidation catalytic converter (30).

Description

The technology disclosed herein relates to a purification device for removing substances from exhaust gases from an internal combustion engine and a method for removing substances from exhaust gases from an internal combustion engine.

The removal of nitrogen oxides from the exhaust gases of an internal combustion engine by means of a urea SCR catalytic converter that uses urea or an aqueous urea solution ( ^AdBlue® ) is known. A problem here is that the aqueous urea solution freezes at temperatures below approx. -11°C. Thus, when the outside temperatures are cold, no nitrogen oxides can be removed from the exhaust gases of the internal combustion engine of the motor vehicle by means of the urea SCR catalytic converter immediately after the motor vehicle has been started. The urea SCR catalytic converter also usually needs a relatively high temperature before the nitrogen oxides in the exhaust gases can be reduced. Only when the temperature of the urea solution and/or the urea SCR catalytic converter has been increased by the waste heat from the internal combustion engine and/or an additional electric heater can nitrogen oxides be removed from the exhaust gases of the motor vehicle's internal combustion engine by means of the urea SCR catalytic converter.

It is a preferred object of the technology disclosed herein to mitigate or obviate at least one disadvantage of a previously known solution or to propose an alternative solution. In particular, a preferred object of the technology disclosed here is to provide a cleaning device or a method by means of which substances, in particular nitrogen oxides, can be removed from the exhaust gases of the internal combustion engine of a motor vehicle even at low temperatures. Other preferred objects may arise from the beneficial effects of the technology disclosed herein. The object(s) is/are solved by the subject matter of patent claim 1 or by the subject matter of patent claim 12 of the independent patent claims. The dependent claims represent preferred embodiments.

In particular, the object is achieved by a cleaning device for removing substances from exhaust gases from an internal combustion engine, the cleaning device comprising a diesel oxidation catalyst for reducing the oxygen content in the exhaust gases and a hydrogen SCR catalyst for reducing nitrogen oxides in the exhaust gases by means of hydrogen, the hydrogen -SCR catalyst is arranged downstream of the diesel oxidation catalyst.

One advantage of this is that even at low temperatures, which are often present after starting the motor vehicle or the internal combustion engine, unwanted substances, in particular substances that are harmful to the environment, e.g. nitrogen oxides, are (partially) removed from the exhaust gases of the internal combustion engine using the hydrogen can become. Exhaust gases that are harmful to the environment can thus be removed from the exhaust gases immediately or shortly after the engine is started. As a result, a large number of legal standards can be met. The arrangement of the hydrogen SCR catalytic converter after the diesel oxidation catalytic converter ensures that the proportion of carbon monoxide and hydrocarbons in the exhaust gases is low when they reach the hydrogen SCR catalytic converter, so that the hydrogen is used particularly effectively to reduce nitrogen oxides can be. The cleaning device can be designed to be arranged in a motor vehicle.

The object is also achieved by a motor vehicle with a cleaning device as described above.

In particular, the object is also achieved by a method for removing substances from exhaust gases from an internal combustion engine, the method comprising the following steps: passing the exhaust gases through a diesel oxidation catalyst to reduce the oxygen content in the exhaust gases; After the exhaust gases have been passed through the diesel oxidation catalyst, conducting the exhaust gases through a first urea SCR catalyst for reducing nitrogen oxides in the exhaust gases using urea and/or a hydrogen SCR catalyst for reducing nitrogen oxides in the exhaust gases using hydrogen.

The advantage of this method is that at low temperatures of the cleaning device, which can be present after starting the internal combustion engine or the motor vehicle, undesirable substances, preferably environmentally harmful substances such as nitrogen oxides, are or can be removed from the exhaust gases. In this process, these substances can be (at least partially) removed from the exhaust gases by means of the hydrogen even at low temperatures. Consequently, this method makes it possible to reliably remove substances from the exhaust gases, for example nitrogen oxides, directly or shortly after starting the internal combustion engine or the motor vehicle. A large number of prescribed standards and/or current and/or future exhaust gas guidelines can thus be met by this method. Passing the exhaust gases first through the diesel oxidation catalyst ensures that the proportion of carbon monoxide and hydrocarbons in the exhaust gases when they pass the hydrogen SCR Reach catalyst is low, so that the hydrogen is used particularly effectively for the reduction of nitrogen oxides. Through the reduction by means of hydrogen and/or urea, the catalytic converter or the reducing agent can be selected in each case which reduces the nitrogen oxides particularly effectively.

According to one embodiment of the cleaning device, the cleaning device also includes a first urea SCR catalytic converter for reducing nitrogen oxides in the exhaust gases by means of urea. The advantage here is that, in addition to the reduction of nitrogen oxides by means of hydrogen, a reduction of nitrogen oxides in the exhaust gases by means of urea is possible. The reduction of nitrogen oxides using urea or AdBlue ^® is particularly effective, especially at higher temperatures of the urea SCR catalytic converter.

According to one embodiment of the cleaning device, the cleaning device is designed in such a way that nitrogen oxides are optionally removed from the exhaust gases by means of the first urea SCR catalytic converter and/or nitrogen oxides from the exhaust gases by means of the hydrogen SCR catalytic converter. One advantage of this is that it is technically easy to switch to removing substances from the exhaust gases using urea or AdBlue ^® . This means that the catalyst or reducing agent (hydrogen or urea) that is most effective in the respective situation can always be used.

According to one embodiment of the cleaning device, the cleaning device also has a control device, wherein the control device switches between the first urea SCR catalytic converter and the hydrogen SCR catalytic converter such that below a predetermined temperature of the exhaust gases and/or the urea and/or the first urea SCR catalytic converter, nitrogen oxides are first removed from the exhaust gases by means of the hydrogen SCR catalytic converter and when the specified temperature of the exhaust gases and/or the environment of the internal combustion engine and/or the environment of the internal combustion engine and/or the urea and/or the first urea is reached and/or exceeded -SCR catalytic converter Nitrogen oxides are removed from the exhaust gases by means of the hydrogen SCR catalytic converter. The advantage here is that when the urea is liquid again and the first urea SCR catalytic converter has reached or exceeded a predetermined minimum temperature, it is possible to switch from reduction using hydrogen to reduction using urea, so that the smallest possible amount of hydrogen is consumed. The predetermined temperature can be approximately 100°C or approximately 160°C, for example. From a temperature of the first urea SCR catalytic converter of approx. 160° C., the reduction using urea is typically particularly effective.

According to one embodiment of the purification device, the first urea SCR catalytic converter and the hydrogen SCR catalytic converter are parts of a common catalytic converter. One advantage of this is that the cleaning device can be designed to be particularly compact or space-saving.

According to one embodiment of the cleaning device, the cleaning device further comprises a moveable flap, the flap being switched between a first position in which the exhaust gases from the internal combustion engine are directed into the first urea SCR catalyst and essentially not into the hydrogen SCR catalyst. and a second position in which the exhaust gases from the internal combustion engine are directed into the hydrogen SCR catalyst and substantially not into the first urea SCR catalyst is reversibly moveable. The advantage of this is that it is technically easy and reliable to switch between SCR catalysis using hydrogen and using urea or ^AdBlue® . In addition, a flap has a particularly long service life. In addition, a flap is particularly inexpensive.

According to one embodiment of the cleaning device, the cleaning device further comprises a pressure vessel for storing the hydrogen. The advantage of this is that a particularly large amount of hydrogen can be stored in a small volume in the cleaning device. As a result, the hydrogen SCR catalytic converter can be operated for a particularly long time. This means that refueling operations to fill up the hydrogen in the cleaning device only have to be carried out infrequently.

According to one embodiment of the cleaning device, the cleaning device further comprises a second urea SCR catalyst, the second urea SCR catalyst being designed to reduce nitrogen oxides in the exhaust gases by means of urea, the second urea SCR catalyst downstream of the hydrogen SCR -Katalysator is arranged, in particular downstream of the first urea SCR catalyst and downstream of the hydrogen SCR catalyst is arranged. An advantage of this is that the nitrogen oxides can also be removed from the exhaust gases when the first urea SCR catalytic converter has a very high temperature (e.g. due to very sporty driving and/or due to a high load on the internal combustion engine) and the reduction of Nitrogen oxides in the first urea SCR catalyst is not very effective. The second urea SCR catalyst temperature is more typical way lower than the temperature of the first urea SCR catalyst.

According to one embodiment of the cleaning device, the first urea SCR catalytic converter includes a particle filter. The advantage here is that due to the integration of the particle filter, a particularly small volume is required and the cleaning device including the particle filter can be very compact.

According to one embodiment of the cleaning device, the cleaning device further comprises a second hydrogen SCR catalyst, wherein the second urea SCR catalyst can function as a second hydrogen SCR catalyst. An advantage of this is that if the first hydrogen SCR catalytic converter fails, hydrogen can continue to be used to reduce nitrogen oxides in the exhaust gases. In addition, if the introduction of urea does not work (e.g. because there is no more urea in the urea tank or because a pipe is clogged), it is possible to remove nitrogen oxides at the position of the second urea SCR catalyst using hydrogen. This makes sense, for example, when the (first) hydrogen SCR catalytic converter has a very high temperature and a reduction in the (first) hydrogen SCR catalytic converter is not effective.

According to one embodiment of the method, below a predetermined temperature of the exhaust gases and/or the urea and/or the first urea SCR catalyst, nitrogen oxides are first removed from the exhaust gases by means of the hydrogen SCR catalyst and when the predetermined temperature is reached or exceeded Exhaust gases and/or the urea and/or the first urea SCR catalyst, nitrogen oxides are removed from the exhaust gases using the hydrogen SCR catalyst. Consequently, the reduction of nitrogen oxides using hydrogen will be switched to a reduction using urea as soon as a reduction using urea is possible and effective. This process minimizes the consumption of hydrogen, so that little hydrogen has to be stored in the cleaning device.

According to one embodiment of the method, by reversibly moving a flap between a first position in which the exhaust gases from the internal combustion engine are directed into the first urea SCR catalytic converter and a second position in which the exhaust gases from the internal combustion engine are directed into the hydrogen SCR catalyst are routed, switched between the reduction of nitrogen oxides by means of hydrogen or urea. In this way, it is possible to change or switch over reliably and technically easily between an SCR catalysis using hydrogen and using urea or AdBlue ^® . Thus, the catalyst material can be used reliably in each case, by means of which substances can be removed particularly effectively from the exhaust gases.

According to one embodiment of the method, the method further comprises the following step: conducting the exhaust gases, after they have been conducted through the first urea SCR catalyst or the hydrogen SCR catalyst, through a second urea SCR catalyst to reduce nitrogen oxides in the Exhaust gases using urea. The advantage of this is that hydrogen can also be used to remove substances from the exhaust gases when the (first) hydrogen SCR catalytic converter is not working. It is also possible, when the introduction of urea, for example due to a blockage or due to the lack of urea in the urea tank, to remove substances from the exhaust gases at the position of the second urea SCR catalyst using hydrogen. The latter is advantageous, for example, if the temperatures of the (first) hydrogen SCR catalytic converter are too high and the removal of substances from the exhaust gases by means of these is not effective.

The pressure vessel can be, for example, a cryogenic pressure vessel or a high-pressure gas vessel.

High-pressure gas tanks are designed to permanently store fuel at ambient temperatures at a nominal operating pressure (also known as nominal working pressure or NWP) of at least 350 bar overpressure (= excess pressure compared to atmospheric pressure) or at least 700 bar overpressure. A cryogenic pressure vessel is suitable for storing the fuel at the aforementioned operating pressures even at temperatures that are significantly (e.g. more than 50 Kelvin or more than 100 Kelvin) below the operating temperature of the motor vehicle.

The technology disclosed herein relates to a motor vehicle (e.g. passenger car, motorcycle, commercial vehicle) comprising the system disclosed here.

The urea can in particular also be an aqueous urea solution. The urea can be, for example, an approximately 32% or approximately 31.8% to approximately 33.2% urea solution with demineralized water. The urea can in particular be ^AdBlue® .

The abbreviation SCR can in particular stand for selective catalyst reaction.

A hydrogen SCR catalytic converter can in particular be a device which has an SCR coating and into which hydrogen (H ₂ ) is introduced as a catalytic converter or as a reducing agent or as a medium for the selective catalytic reaction of the exhaust gases.

A urea SCR catalyst can in particular be a device that has an SCR coating and into which urea or ammonia generated from the urea by means of thermolysis and hydrolysis as a catalyst agent or as a reducing agent or as an agent for the selective catalytic reaction of the exhaust gases is introduced.

It is conceivable that the first hydrogen SCR catalyst and the first urea SCR catalyst is a device in which hydrogen as a catalyst or as a reducing agent and once by means of thermolysis and hydrolysis from the urea generated ammonia as a catalyst or as Reducing agent is introduced. This can mean in particular that a single first catalytic converter is present, which functions or functions as a hydrogen SCR catalytic converter and as a urea SCR catalytic converter. The same can apply correspondingly to the second hydrogen SCR catalytic converter and the second urea SCR catalytic converter.

In other words, the technology disclosed here relates to a cleaning device or a method for removing substances from exhaust gases from an internal combustion engine, in which or in which substances, in particular nitrogen oxides, can be removed from the exhaust gases using hydrogen. Since the reduction of nitrogen oxides takes place after the diesel oxidation catalytic converter, the reduction of nitrogen oxides using hydrogen is particularly effective.

• 1 eine schematische Ansicht eines Kraftfahrzeugs mit einer Reinigungsvorrichtung gemäß der hier offenbarten Technologie, wobei sich eine Klappe in einer ersten Position befindet;
• 2 eine schematische Ansicht des Kraftfahrzeugs mit der Reinigungsvorrichtung aus 1, wobei sich eine Klappe in einer zweiten Position befindet; und
• 3 eine schematische Ansicht eines weiteren Kraftfahrzeugs mit einer weiteren Reinigungsvorrichtung gemäß der hier offenbarten Technologie, wobei sich eine Klappe in einer ersten Position befindet.

The technology disclosed here will now be explained with reference to the figures. Show it:

• 1 a schematic view of a motor vehicle with a cleaning device according to the technology disclosed herein, wherein a flap is in a first position;
• 2 a schematic view of the motor vehicle with the cleaning device 1 wherein a flap is in a second position; and
• 3 a schematic view of another motor vehicle with another cleaning device according to the technology disclosed herein, wherein a flap is in a first position.

1 FIG. 12 shows a schematic view of a motor vehicle 10 with a cleaning device 15 according to the technology disclosed herein, with a flap 38 in a first position. 2 FIG. 1 shows a schematic view of the motor vehicle 10 with the cleaning device 15 1 , with a flap 38 in a second position.

The cleaning device 15 is arranged in a motor vehicle 10 . The cleaning device 15 is designed to remove substances from the exhaust gases of an internal combustion engine 20 of the motor vehicle 10 . The internal combustion engine 20 typically drives the motor vehicle 10 . The internal combustion engine 20 can be a diesel engine or a gasoline engine, for example.

The cleaning device 15 comprises, along the flow direction of the exhaust gases from the internal combustion engine 20, first a diesel oxidation catalytic converter 30, then a hydrogen SCR catalytic converter 40 and a first urea SCR catalytic converter 50, then a second urea SCR catalytic converter 90 and then a rear silencer 99

The exhaust gases of the internal combustion engine 20 are guided or guided by the internal combustion engine 20 via a line 25 through a diesel oxidation catalytic converter 30 (English diesel oxidation catalytic converter; DOC). In the diesel oxidation catalytic converter 30, hydrocarbons and carbon monoxide are partially removed or their proportion reduced. In particular, the proportion of oxygen (O ₂ ) in the exhaust gases is also reduced.

Thereafter, the exhaust gases from the diesel oxidation catalyst 30 are routed to and through either the hydrogen SCR catalyst 40 or the first urea SCR catalyst 50 .

A first urea injector 75 for introducing urea or an aqueous urea solution or ^AdBlue® into the exhaust gases is arranged in the line 35 between the diesel oxidation catalytic converter 30 and the hydrogen SCR catalytic converter 40 or the first urea SCR catalytic converter 50 . A first hydrogen injector 65 for introducing hydrogen (H ₂ ) into the exhaust gases is also arranged in said line 35 .

The urea is stored in a urea tank 70 as an aqueous urea solution. The urea tank 70 has a pump (not shown) for pumping the urea out of the urine cloth container 70 on. In addition, urea may be filled into the urea tank 70 from outside of the motor vehicle 10 via a urea filling pipe (not shown). For example, about 15 kg to about 20 kg of aqueous urea solution can be stored in the urea tank 70 . The urea is fed from the urea tank 70 via a first feed line 72 to the first urea injector 75 and via a second feed line 73 to the second urea injector 77 .

The hydrogen is stored in a hydrogen tank. The hydrogen tank can be a pressure tank 60 . For example, the pressure vessel 60 may be a cryogenic pressure vessel. The system pressure in the pressure vessel 60 can be 350 bar, for example. The pressure vessel 60 has a tank valve and a pressure regulator (not shown). Likewise, hydrogen can be introduced into the pressure vessel 60 for storing the hydrogen from outside the motor vehicle 10 via a hydrogen filling pipe (not shown). The pressure vessel 60 can store, for example, approximately 0.5 kg to approximately 1 kg of hydrogen. The hydrogen is fed from the pressure vessel 60 via a first feed line 62 to the first hydrogen injector 65 and via a second feed line 63 to the second hydrogen injector 67 .

The first urea SCR catalytic converter 50 can be a commercially available SCR catalytic converter for reducing nitrogen oxides (NO, NO ₂ , NO _x ) using urea. The first and second urea catalysts each convert the nitrogen oxides mainly into H ₂ O and nitrogen (N ₂ ).

The hydrogen SCR catalyst 40 converts nitrogen oxides into water (H ₂ O) and nitrogen (N ₂ ) using hydrogen. The hydrogen SCR catalyst 40 may include platinum and/or palladium, for example, in order to most effectively perform the conversion.

The hydrogen SCR catalyst 40 is arranged downstream of the diesel oxidation catalyst 30 . This reduces the oxygen content so that the hydrogen in the hydrogen SCR catalyst 40 reacts with nitrogen oxides in the exhaust gases and not with the elemental oxygen (O ₂ ).

The cleaning device 15 has a flap 38 or switching flap, is determined by the respective position, whether the exhaust gases from the line 35, in particular immediately after the diesel oxidation catalyst 30 (mainly or completely) to the hydrogen SCR catalyst 40 or to the get first urea SCR catalyst 50 or flow through this. The flap 38 has a hinge about which the flap 38 can be reversibly moved between a first position and a second position.

In the first position of the flap 38, which is in 1 is shown, the exhaust gases enter the first urea SCR catalyst 50, ie the flap 38 blocks the way into the hydrogen SCR catalyst 40. When the flap 38 is in the first position, urea through the first urea injector before first urea SCR catalyst 50 (and after the diesel oxidation catalyst 30) is injected into the exhaust gases, so that the first urea SCR catalyst 50 fulfills its function, namely, inter alia, removing nitrogen oxides from the exhaust gases.

In the second position of the flap 38, which is in 2 shown, the exhaust gases enter the (first) hydrogen SCR catalyst 40, ie the flap 38 blocks the path into the first urea SCR catalyst 50. When the flap 38 is in the second position, hydrogen is through the first Hydrogen injector 65 introduced into the exhaust gases before the hydrogen SCR catalyst 40 (and after the diesel oxidation catalyst 30), so that the hydrogen SCR catalyst 40 fulfills its function.

The hydrogen SCR catalyst 40 and the first urea SCR catalyst 50 can be two parts of a single catalyst, which are only separated from one another by a partition wall, for example.

It is also conceivable that layers of the hydrogen SCR catalytic converter 40 and layers of the first urea SCR catalytic converter 50 alternate regularly or irregularly in a common catalytic converter. In this case, there is no need for flap 38, but the only difference between operating the hydrogen SCR catalyst 40 and the first urea SCR catalyst 50 is whether hydrogen is introduced into the exhaust gases through the first hydrogen injector 65 or urea through the first urea injector 75 is introduced into the exhaust gases. It is also conceivable that layers are part of both the hydrogen SCR catalyst 40 and the first urea SCR catalyst 50, i.e. the same layer is used as a reaction surface for both catalytic reactions. Here too, the introduction of urea or hydrogen determines whether the catalyst is operated as a first urea SCR catalyst 50 (when urea is introduced) or as a hydrogen SCR catalyst 40 (when hydrogen is introduced).

Between the diesel oxidation catalyst 30 and the hydrogen SCR catalyst 40 or the first urea SCR catalyst 50 is a first ter temperature sensor 81 for detecting the temperature of the exhaust gases arranged at this point.

After the hydrogen SCR catalytic converter 40 or the first urea SCR catalytic converter 50, the exhaust gases reach a line, regardless of whether they were conducted through the hydrogen SCR catalytic converter 40 or through the first urea SCR catalytic converter 50 55 to the second urea SCR catalytic converter 90. A second urea injector 77 for introducing urea into the exhaust gases is arranged in said line 55. A second hydrogen injector 67 for introducing hydrogen into the exhaust gases is arranged in said line 55 .

The second urea SCR catalytic converter 90 is what is known as an underfloor catalytic converter, i.e. it is often arranged in the underfloor area of the motor vehicle 10 .

It is also conceivable that no second hydrogen injector 67 is arranged.

In the line 55 between the hydrogen SCR catalytic converter 40 or the first urea SCR catalytic converter 50 and the second urea SCR catalytic converter 90 there is a second temperature sensor 82 for detecting the temperature of the exhaust gases after the hydrogen SCR catalytic converter 40 and the first urea SCR catalyst 50 is arranged.

The second urea SCR catalytic converter 90 is also used to reduce nitrogen oxides in the exhaust gases. A third temperature sensor 83 for detecting the temperature of the exhaust gases is arranged after the second urea SCR catalytic converter 90 . The exhaust gases from the second urea SCR catalytic converter 90 reach the rear silencer 99 through a line 95. The exhaust gases are then released into the environment.

When hydrogen is introduced through the second hydrogen injector 67, the second urea SCR catalyst 90 is operated as a hydrogen SCR catalyst 40 or is a hydrogen SCR catalyst 40.

In addition to the temperature of the exhaust gases at the three points mentioned, the temperature of the urea in the urea tank 70 can be recorded.

The cleaning device 15 includes a control device. The control device can detect the temperatures from the temperature sensors 81 , 82 , 83 and the temperature of the urea in the urea tank 70 . Depending on the temperature of the exhaust gases, from which the temperature of the various catalytic converters can be inferred, nitrogen oxides are converted into nitrogen and water by means of the urea in the first urea SCR catalytic converter 50 or in the second urea SCR catalytic converter 90 . If the first urea SCR catalyst 50 is too hot or the exhaust gases that reach it, then urea is released via the second urea injector 77 and the second urea SCR catalyst 90 is used to reduce nitrogen oxides. If the temperature in the second urea SCR catalyst 90 is too low, the first urea SCR catalyst 50 is usually at a temperature at which the nitrogen oxides can be reduced by means of urea. If both urea SCR catalytic converters 50, 90 are too cold, the reduction of nitrogen oxides by means of hydrogen, preferably in the hydrogen SCR catalytic converter 40 or alternatively in the second urea SCR catalytic converter 90, which is operated as a hydrogen SCR catalytic converter 40 is carried out.

After starting the motor vehicle 10 at cold ambient temperatures, the urea or the aqueous urea solution or AdBlue ^® may be frozen or neither of the two urea SCR catalytic converters 50, 90 have a sufficiently high temperature at which the removal of nitrogen oxides from the Exhaust gases can be carried out effectively using urea. The urea and the urea SCR catalytic converters 50, 90 are heated by waste heat from the internal combustion engine 20 or the heat from the exhaust gases. A reduction of nitrogen oxides using urea is not possible as long as the urea is frozen. In order to ensure a reduction in nitrogen oxides even in the situation in which the urea is frozen or the urea SCR catalytic converters 50, 90 are not hot enough (eg more than approximately 160° C.), the hydrogen SCR catalytic converter 40 used to reduce nitrogen oxides. This is usually only necessary for a manageable time after starting the motor vehicle 10, since the waste heat from the internal combustion engine 20 or the hot exhaust gases quickly thaws the urea and/or an (electrical) heating device for heating the urea in the urea tank 70. so that the reduction of nitrogen oxides by urea can be carried out. The urea SCR catalytic converters 50, 90 are also heated relatively quickly by the exhaust gases. In particular, the first urea SCR catalyst 50 is also heated by thermal bridges, etc. when the exhaust gases are passed through the hydrogen SCR catalyst 40, ie when the flap 38 is in the second position. For this reason, typically significantly less hydrogen than urea has to be stored in the motor vehicle 10 . Most of the time of the Kraft's normal operation vehicle 10, urea is used to reduce nitrogen oxides.

It is possible that when the supply of urea on the urea tank 70 is not possible or the operation of the first urea SCR catalyst 50 and the second urea SCR catalyst 90 is not possible, the reduction of nitrogen oxides using the hydrogen is carried out, although the urea is liquid and the two urea SCR catalysts 50, 90 have a sufficient temperature. The reduction by means of hydrogen can thus be carried out in a type of emergency operation or fallback operation function. In particular, if the internal combustion engine 20 generates a particularly large amount of waste heat (e.g. due to very sporty driving of the motor vehicle 10), hydrogen can be introduced into the exhaust gases via the second hydrogen injector 67 in this emergency operation. Namely, in this case, the hydrogen SCR catalyst 40 may have too high a temperature to effectively perform the removal of nitrogen oxides.

Typically, the first urea SCR catalytic converter 50 only works effectively above a temperature of approximately 180° C., so that the reduction of nitrogen oxides by means of hydrogen or by means of the hydrogen SCR catalytic converter 40 is carried out until this temperature is reached.

When hydrogen is introduced by the first hydrogen injector 65 or when the hydrogen SCR catalytic converter 40 is in operation, the hydrogen reacts with excess atmospheric oxygen from the combustion and in this way heats the first urea SCR catalytic converter 50 and the second urea SCR catalytic converter 90

Instead of a flap 38, other devices (e.g. valves) for selectively directing the air flow into the hydrogen SCR catalytic converter 40 or into the first urea SCR catalytic converter 50 are also conceivable.

A mixer for mixing the urea with the exhaust gases can be arranged after the first urea injector 75 and/or after the second urea injector 77 or directly downstream of the injectors.

A NoX sensor for detecting the density or the proportion of nitrogen oxides in the exhaust gases can be arranged immediately downstream of the first urea SCR catalytic converter 50 and/or the second urea SCR catalytic converter 90 . Depending on the density or the proportion of nitrogen oxides, the control device can determine the amount of hydrogen that is supplied by first hydrogen injector 65 and/or second hydrogen injector 67 and/or the amount of urea that is supplied by first urea injector 75 and/or is supplied to the second urea injector 77, control or regulate accordingly. With more nitrogen oxides, more hydrogen or urea is required than with fewer nitrogen oxides in the exhaust gases.

In the following description of the 1 and 2 illustrated alternative embodiment are for features compared to the 1 and 2 illustrated first embodiment are identical and / or at least comparable in their design and / or mode of operation, the same reference numerals are used. If these are not explained again in detail, their configuration and/or mode of action corresponds to the configuration and/or mode of action of the features already described above.

3 shows a schematic view of another motor vehicle 10 with another cleaning device 15 according to the technology disclosed here, wherein a flap 38 is in a first position.

In the 3 The cleaning device 15 shown differs from that in 1 or. 2 Cleaning device 15 shown is that no second hydrogen injector 67 is present. Thus, hydrogen cannot be introduced immediately before the second urea SCR catalyst 90 . As a result, the cleaning device 15 is technically particularly simple. If neither of the two urea SCR catalysts 50, 90 can be operated with urea, the substances are removed from the exhaust gases by the hydrogen SCR catalyst 40 or by introducing hydrogen and positioning the flap 38 in the second position .

For reasons of legibility, the expression “at least one” has been partially omitted for the sake of simplicity. Where a feature of the technology disclosed herein is described in the singular or vague (e.g., hydrogen SCR catalyst 40, first urea SCR catalyst 50, diesel oxidation catalyst 30, door 38, etc.) the majority of them should also be disclosed at the same time (e.g. the at least one hydrogen SCR catalytic converter 40, the at least one first urea SCR catalytic converter 50, the at least one diesel oxidation catalytic converter 30, the at least one flap 38, etc.) .

In the context of the technology disclosed here, the term “essentially” (eg “essentially vertical axis”) includes the exact property or value (eg “vertical axis”) as well as deviations that are insignificant for the function of the property/value (e.g. "tolerable deviation from the vertical axis").

The foregoing description of the present invention is for illustrative purposes only and not for the purpose of limiting the invention. Various changes and modifications can be made within the scope of the invention without departing from the scope of the invention and its equivalents.

Reference List

10

motor vehicle

15

cleaning device

20

combustion engine

25

Line between internal combustion engine and diesel oxidation catalyst

30

diesel oxidation catalyst

35

Line between diesel oxidation catalyst and hydrogen SCR catalyst and urea SCR catalyst

38

flap

40

Hydrogen SCR catalyst

50

first urea SCR catalyst

55

Line between hydrogen SCR catalyst/first urea SCR catalyst and second urea SCR catalyst

60

pressure vessel

62

Supply line from the pressure vessel to the first hydrogen injector

63

Supply line from the pressure vessel to the second hydrogen injector

65

first hydrogen injector

67

second hydrogen injector

70

urea tank

72

Supply line from the urea tank to the first urea injector

73

Supply line from the urea tank to the second urea injector

75

first urea injector

77

second urea injector

80

first temperature sensor

81

second temperature sensor

82

third temperature sensor

85

control device

90

second urea SCR catalyst

95

Line between the second urea SCR catalytic converter and the rear silencer

99

rear silencer

Claims (15)

Cleaning device (15) for removing substances from exhaust gases from an internal combustion engine (20), wherein the cleaning device (15) a diesel oxidation catalyst (30) for reducing the oxygen content in the exhaust gases and comprises a hydrogen SCR catalytic converter (40) for reducing nitrogen oxides in the exhaust gases using hydrogen, wherein the hydrogen SCR catalyst (40) is located downstream of the diesel oxidation catalyst (30). Cleaning device (15) after claim 1 , further comprising a first urea SCR catalyst (50) for reducing nitrogen oxides in the exhaust gases by means of urea. Cleaning device (15) after claim 1 or 2 , wherein the cleaning device (15) is designed such that selectively nitrogen oxides from the exhaust gases by means of the first urea SCR catalyst (50) and / or nitrogen oxides from the exhaust gases by means of the hydrogen SCR catalyst (40) are removed. Cleaning device (15) according to one of the preceding claims, wherein the cleaning device (15) further comprises a control device (85), wherein the control device (85) is arranged between the first urea SCR catalyst (50) and the hydrogen SCR catalyst ( 40) switches so that below a specified temperature of the exhaust gases and/or the urea and/or the first urea SCR catalytic converter (50), nitrogen oxides are first removed from the exhaust gases by means of the hydrogen SCR catalytic converter (40) and when this is reached and /or exceeding the specified temperature of the exhaust gases and/or the environment of the internal combustion engine (20) and/or the urea and/or the first urea SCR catalytic converter (50) nitrogen oxides from the exhaust gases by means of the hydrogen SCR catalytic converter (40) be removed. Purification device (15) according to any one of the preceding claims, wherein the first urea SCR catalyst (50) and the hydrogen SCR catalyst (40) are parts of a common catalyst. A cleaning device (15) according to any one of the preceding claims, further comprising a moveable flap (38), the flap (38) being movable between a first position in which the exhaust gases from the internal combustion engine (20) flow into the first urea SCR catalytic converter (50 ) and essentially not into the hydrogen SCR catalyst (40), and a second position in which the exhaust gases from the internal combustion engine (20) into the hydrogen SCR catalyst (40) and essentially not into the first Urea SCR catalyst (50) are passed, is reversibly movable. Purification apparatus (15) according to any one of the preceding claims, further comprising a pressure vessel (60) for storing the hydrogen. A cleaning device (15) according to any one of the preceding claims, further comprising a second urea SCR catalytic converter (90), the second urea SCR catalytic converter (90) being designed to reduce nitrogen oxides in the exhaust gases by means of urea, wherein the second urea SCR catalyst (90) is arranged downstream of the hydrogen SCR catalyst (40), in particular downstream of the first urea SCR catalyst (50) and downstream of the hydrogen SCR catalyst (40). A purification device (15) according to any one of the preceding claims, wherein the first urea SCR catalyst (50) comprises a particulate filter. A purification device (15) according to any one of the preceding claims, further comprising a second hydrogen SCR catalyst (40), wherein the second urea SCR catalyst (90) can function as a second hydrogen SCR catalyst (40). Motor vehicle (10) with a cleaning device (15) according to one of the preceding claims. A method for removing substances from exhaust gases from an internal combustion engine (20), the method comprising the steps of: passing the exhaust gases through a diesel oxidation catalyst (30) to reduce the oxygen content in the exhaust gases; Conducting the exhaust gases, after the exhaust gases have been conducted through the diesel oxidation catalytic converter (30), through a first urea SCR catalytic converter (50) for reducing nitrogen oxides in the exhaust gases by means of urea and/or a hydrogen SCR catalytic converter (40) for reducing nitrogen oxides in the exhaust gases using hydrogen. procedure after claim 12 , wherein below a predetermined temperature of the exhaust gases and/or the urea and/or the first urea SCR catalytic converter (50) nitrogen oxides are first removed from the exhaust gases by means of the hydrogen SCR catalytic converter (40) and when the given temperature of the exhaust gases and/or the urea and/or the first urea SCR catalytic converter (50) nitrogen oxides are removed from the exhaust gases by means of the hydrogen SCR catalytic converter (40). procedure after claim 12 or 13 , wherein by means of reversibly moving a flap (38) between a first position in which the exhaust gases from the internal combustion engine (20) are directed into the first urea SCR catalyst (50) and a second position in which the exhaust gases from the Combustion engine (20) in the hydrogen SCR catalytic converter (40) are passed, is changed between the reduction of nitrogen oxides by means of hydrogen or by means of urea. Procedure according to one of Claims 12 - 14 , further comprising the step of: passing the exhaust gases, after passing through the first urea SCR catalyst (50) or the hydrogen SCR catalyst (40), through a second urea SCR catalyst (90) to reduce Nitrogen oxides in the exhaust gases using urea.

Images