DE102008030307A1 - Catalyst arrangement for purifying exhaust gas flow of internal combustion engine in motor vehicle, has electrical heater for heating catalyst and/or exhaust gas flow, and another heater for heating another catalyst and/or exhaust gas flow - Google Patents

Abstract

The arrangement (1) has a catalyst (15) arranged downstream of an internal combustion engine (5). Another catalyst (27) is arranged downstream to the catalyst (15). An electrical heater (11) is assigned to the catalyst (15) to heat the catalyst (15) and/or exhaust gas flow (3). Another heater (23) is assigned to the catalyst (27) to heat the catalyst (27) and/or the flow. The catalyst (15) is designed as oxidation catalyst, the catalyst (27) is designed as a selective catalytic reduction catalyst or both the catalysts are designed as nitrogen oxide storage catalysts (17, 29). An independent claim is also included for a method for purifying exhaust gas flow of an internal combustion engine of a motor vehicle with catalyst arrangement.

Description

Catalyst arrangements can have one or more catalysts and serve for the aftertreatment or purification of pollutants entrained in the exhaust gas stream of the internal combustion engine, for example particles, in particular soot particles, hydrocarbons and / or nitrogen oxides. The catalyst or catalysts generally have a conversion rate for the pollutants, which is temperature-dependent. It is known to influence the temperature of the exhaust gas stream and / or the catalyst by means of an electric heater. The DE 199 33 654 A1 shows an arrangement for electrically heating a catalyst and the DE 196 40 577 A1 an electrically heated catalyst for a motor.

task the invention is to provide an improved catalyst arrangement, in particular an improved conversion rate of pollutants in to enable the catalyst arrangement.

The Task is with a catalyst arrangement for purifying an exhaust gas stream an internal combustion engine of a motor vehicle, with a combustion engine downstream first catalyst, a first catalyst arranged downstream of the second catalyst, one of the first Catalyst associated with the first electric heater for heating the first and / or second catalyst and / or the exhaust stream and a second electric power associated with the second catalyst Heating for heating the second catalyst and / or dissolved the exhaust stream. Advantageously, the catalyst arrangement two catalysts, each separated by means of the electric Heaters are heated and thus start faster (light off temperature) and / or better in one for one Conversion of pollutants to maintain optimal functional range are. This results in a significantly improved implementation rate. It is possible for each of the catalysts separately Define functional area and this as quickly as possible to adjust by means of separate electric heaters. additionally can increase motoring measures a temperature of the exhaust gas flow are performed. Of the first catalyst is located close to the engine and the second this downstream, for example in an underbody of the motor vehicle. Under close to the engine, for example, an arrangement directly behind an exhaust manifold of the internal combustion engine to be understood.

at an embodiment of the catalyst arrangement is provided that the first electric heater to the first catalyst and the second electric heater upstream of the second catalyst is. By means of the electric heaters can each of the exhaust gas flow heated upstream of the associated catalyst become.

at a further embodiment of the catalyst arrangement it is provided that the first and the second catalyst each are designed as NOx catalyst. Under NOx catalyst can in this application, a NOx storage catalyst (NSK) understood become. By means of the first and second heating, the necessary for operating the NOx storage catalytic converter temperatures or functional areas are set faster and better. NOx storage catalysts can be used in particular for Internal combustion engines that operate with an excess of air are to be used.

at Another embodiment provides that the first catalyst as the oxidation catalyst (Ox-Kat) and the second catalyst are designed as SCR catalyst. Under oxidation catalyst In this application, a catalyst can be understood which in the presence of an oxidizing agent, for example oxygen, in particular with a lean mixture composition of the internal combustion engine and / or by means of a secondary air injection present is, pollutants of the exhaust stream by oxidation in innocuous Converts components, such as water and / or carbon dioxide. Under SCR catalyst can be understood in this application, a catalyst which are pollutants by means of a selective catalytic reaction reduced contrary to an actually existing reaction equilibrium, in particular Converts nitrogen oxides into nitrogen. This can be done, for example a presence of oxygen with the addition and / or release of a additional reagent, especially ammonia, the also participates in the reaction happen. By means of the assigned Electric heaters can both the oxidation catalyst as also the SCR catalyst better and / or faster in a respective Function range or temperature range brought for optimal conversion rates and / or kept.

at a further embodiment of the catalyst arrangement is provided that the first catalyst downstream of a particulate filter is. By means of the particulate filter can be advantageous in Exhaust gas entrained particles, in particular soot particles, be removed from the exhaust stream. Advantageously, it is possible the necessary for a regeneration of the particulate filter Temperature increase to burn off the soot particles too ignite, faster by means of the first electric heater initiate.

In a further embodiment of the catalyst arrangement is provided that the second catalyst nachge a barrier catalyst is switched. By means of the barrier catalyst unwanted pollutant breakthroughs, in the case of selective catalytic reaction, such as ammonia breakthroughs can be avoided.

In a further exemplary embodiment of the catalyst arrangement, it is provided that a motor controller (for controlling and / or regulating) ( 75 ) is provided. By means of the engine control parameters of the internal combustion engine and / or the catalyst arrangement can be controlled and / or regulated, for. As temperatures of the exhaust stream and / or the catalysts.

The Task is also with a method for cleaning an exhaust gas stream of an internal combustion engine of a motor vehicle solved with a catalyst arrangement described above. The method includes raising an exhaust gas temperature of the exhaust stream by means of the electric heater and / or raising the exhaust gas temperature the exhaust gas flow by means of the second electric heater and / or raising the exhaust gas temperature of the exhaust gas stream by means of a catalytic Implementation of motor generated by means of the internal combustion engine hydrocarbons (HC) and / or driving a functional area of a NOx storage by means of the temperature increase and / or a driving of a functional area a desulfurization by means of the temperature increase. Advantageous can by means of the first and second heating functional areas for the catalysts of the catalyst arrangement separately be set.

The Task is further with a motor vehicle with a previously described Catalyst arrangement solved. It results in the advance described advantages.

Further Advantages, features and details emerge from the following Description, in reference to the drawing, an embodiment is described in detail. Same, similar and / or functionally identical parts are provided with the same reference numerals. Show it:

1 a catalyst arrangement for purifying an exhaust gas stream of an internal combustion engine of a motor vehicle;

2 another catalyst arrangement;

3 a graph of a temperature increase in comparison of a catalyst assembly with electric heating and without electrical heating; and

4 different measurement curves over a time axis of a urea dosing, a temperature profile and a NOx emission, in each case in comparison with and without electrical auxiliary heating.

1 shows a catalyst arrangement 1 for cleaning an exhaust gas stream 3 an internal combustion engine 5 a motor vehicle 7 , The catalyst arrangement 1 can be part of an internal combustion engine 5 Downstream, only schematically illustrated exhaust system 9 of the motor vehicle 7 be. The catalyst arrangement 1 has a first electric heater 11 with a first electrical catalyst disk 13 on.

The first electric catalyst disk 13 is arranged close to the engine, for example, directly on the exhaust side of the internal combustion engine 5 downstream. The first electric catalyst disk 13 is a first catalyst 15 downstream. The first catalyst 15 has a NOx storage catalyst 17 (NSK). The NOx storage catalyst 17 is a particle filter 19 downstream. By means of the NOx storage catalyst 17 can nitrogen oxides of the exhaust stream 3 be withheld. By means of the particle filter 19 can in the exhaust stream 3 entrained particles, in particular soot particles are retained. The first electric heater 11 with the first electric catalyst disk 13 , the downstream first catalyst 15 with the NOx storage catalyst 17 and this downstream particle filter 19 are arranged close to the engine, ie directly to the internal combustion engine 5 downstream. Further downstream, for example in an in 1 only schematically indicated subsoil 21 of the motor vehicle 7 are further downstream components. This is a second electric heater 23 holding a second electrical catalyst disk 25 having. The catalyst discs 13 and 25 are from the exhaust stream 3 flows through and can by means of energization by means of an electrical energy source, such as an on-board battery of the motor vehicle 7 and / or other energy sources, such as capacitors, the exhaust stream 3 Warm up. It is conceivable that the catalyst disks 13 . 25 even have a catalyst or catalytically active material and thus for the catalytic conversion of the in the exhaust stream 3 contributing pollutants. In the second electric catalyst disk 25 is a second catalyst 27 with a second NOx storage catalyst 29 downstream. The second electric catalyst disk 25 and the downstream second catalyst 27 form a second purification stage. The second purification stage is a barrier catalyst 31 downstream.

2 shows a further catalyst arrangement 1 for cleaning the exhaust stream 3 , The same parts are provided with the same reference numerals, with only the differences to 1 will be received. In contrast, the catalyst arrangement 1 according to 2 or the first catalyst 15 an oxidation catalyst 33 (Ox-kat) on. Also in contrast, the second catalyst 27 an SCR catalyst 35 on. The SCR catalyst 35 is to a selective catalytic reaction to purify the exhaust stream 3 designed. For this purpose, the catalyst arrangement 1 one in 2 Not shown Zudosiereinheit, for example, for an aqueous urea solution, the upstream of the SCR catalyst 35 can be arranged. Any existing ammonia breakthroughs of the SCR catalyst 35 can by means of the barrier catalyst 31 be converted back into NOx emissions.

3 shows a graph 37 a temperature of the exhaust gas flow 3 , The graph 37 shows over a timeline 39 a first temperature profile 41 in comparison to a dotted temperature curve 43 , Accordingly, on a Y-axis 45 of the chart 37 a temperature of the exhaust stream 3 of the internal combustion engine 5 applied. At the temperature gradients 41 and 43 It can be a means of one of the first electric heater 11 or the second electric heater 23 act downstream temperature actable downstream measuring point. The first temperature profile 41 shows the course after a cold start, as it results in switched off electric heaters 13 and 23 , In comparison, the second temperature curve shows 43 the temperature behavior of the exhaust stream 3 when the first electric heater is switched on 11 and / or second electric heater 23 , To save electrical energy, it is conceivable, the first and / or second electric heater 11 . 23 operate only for a limited time. In the comparison of the temperature gradients 41 and 43 this can be seen, being in a right half of the temperature gradients 41 and 43 these approach each other. In a first half, in 3 shown on the left, the temperature curves 41 and 43 it can be seen that the second temperature profile 43 right at the beginning of a very steep temperature rise 47 learns, so the first temperature history 41 much faster than the second temperature profile 43 a functional area 49 reached in 3 is indicated by a dashed line.

4 shows another graph 53 with a first partial diagram 55 , a second partial diagram 57 and a third part diagram 59 , each over a time axis 39 , The timeline 39 may be in a time interval between 0 and 1000 seconds, for example. On a first Y-axis 61 of the first part diagram 55 a cumulative NOx emission is plotted. On a second Y axis 63 of the second partial diagram 57 is a temperature of the exhaust stream 3 , similar to the illustration in 3 , applied. On the third Y-axis 65 of the third partial diagram 59 an amount of urea dosing is applied. The graph 53 of the 4 can, for example, measured values of in 2 illustrated catalyst arrangement 1 include.

Measured values are shown in each case with the aid of the first electric heater 11 and / or the second electric heater 23 , By comparison, symbolized by solid lines, measured values are plotted without the electric heaters 11 and or 23 result.

Based on the first part of the diagram 55 it can be seen that a first accumulated NOx emission 67 significantly steeper than a second accumulated NOx emission 69 how they look when switched on electric heaters 11 and or 23 results. In the second partial diagram 57 are a first temperature profile 41 how he turned off electric heaters 11 . 23 results and a second temperature profile 43 how he turned on with electric heaters 11 and or 23 results. It can be seen that the dotted second temperature profile 43 right at the beginning, for example after a cold start of the internal combustion engine 5 , a very steep temperature rise 47 having. In the third part of the diagram 59 are by solid lines a first urea dosing 71 and by dotted lines a second urea dosing 73 applied. The second urea dosing amount 73 corresponds to the second temperature profile 43 and the second cumulative NOx emission 69 how they look when switched on electric heaters 11 and or 23 result.

Based on the second urea dosing quantity 73 can be seen that these due to the rapid increase of the second temperature profile 43 can start much earlier, which is a sign of a much higher conversion rate and thus a significantly reduced NOx emission, which is also based on the second NOx emission 69 of the first part diagram 55 can be seen.

The peculiarity of the catalyst arrangement 1 is that the first catalyst 15 the first electric heater 11 close to the engine upstream and this in combination with the downstream in the subsoil 21 arranged second electric heater 23 is arranged. For controlling and / or regulating the electric heaters 11 and or 23 and the entire remaining catalyst arrangement 1 and the internal combustion engine 5 is one in the 1 and 2 illustrated engine control 75 intended. To enter the functional area of the in 1 illustrated NOx storage catalyst 17 and / or the NOx storage catalyst 29 In addition, the temperature of the exhaust gas flow can be reached via engine measures 3 be raised. To support this temperature For a short time, the first electric catalyst disk can be used 13 and / or the second electric catalyst disk 25 be turned on. A corresponding control can be done by means of the motor control 75 and / or amplifiers not shown in detail. This can be advantageous both during a cold start of the internal combustion engine 5 as well as in a low-load engine operation of the internal combustion engine 5 to achieve faster reaching the necessary for the storage or regeneration temperatures. Advantageously, the first and or second electrical catalyst disk 13 and or 25 also be used to motorized hydrocarbons (HC) on one of the NOx storage catalytic converters 17 and or 29 to achieve a further increase in temperature.

To the first and or second NOx storage catalyst 17 and or 29 To desulphurise can also be raised by means of engine measures, the exhaust gas temperature and advantageously additionally support by means of an electric catalyst discs 13 and or 25 respectively.

• 1. Anhebung der Abgastemperatur des Abgasstroms 3 in dem Funktionsbereich 49 einer NOx-Speicherung.
• 2. Anhebung der Abgastemperatur des Abgasstroms 3 in einen Funktionsbereich einer Entschwefelung.
• 3. Anhebung der Abgastemperatur des Abgasstroms 3 um in Verbindung mit der katalytischen Umsetzung der motorisch erzeugten Kohlenwasserstoffe eine weitere Steigerung der Abgastemperatur des Abgasstromes 3 zur Erweiterung des Funktionsbereichs 49 der NOx-Speicherkatalysatoren 17 und oder 29 (1) bzw. der Abgasreinigung mittels einer selektiven katalytischen Reaktion mittels des SCR-Katalysators 35 der in 2 dargestellten Katalysatoranordnung 1.

The electronically controlled, in particular by means of the engine control 75 , first catalyst disc 13 before the oxidation catalyst 33 ( 2 ) in combination with the second upstream electric catalyst disk 25 in the subsoil 21 of the motor vehicle 7 can be used as follows:

• 1. raising the exhaust gas temperature of the exhaust stream 3 in the functional area 49 NOx storage.
• 2. raising the exhaust gas temperature of the exhaust stream 3 into a functional area of desulfurization.
• 3. raising the exhaust gas temperature of the exhaust stream 3 in order in connection with the catalytic conversion of the engine-generated hydrocarbons, a further increase in the exhaust gas temperature of the exhaust gas stream 3 for expanding the functional area 49 the NOx storage catalysts 17 and or 29 ( 1 ) or the exhaust gas purification by means of a selective catalytic reaction by means of the SCR catalyst 35 the in 2 illustrated catalyst arrangement 1 ,

1

catalyst assembly

3

exhaust gas flow

5

internal combustion engine

7

motor vehicle

9

exhaust system

11

First electric heating

13

First electric catalyst disk

15

first catalyst

17

NOx storage catalytic converter

19

particulate Filter

21

underbody

23

Second electric heating

25

Second electric catalyst disk

27

second catalyst

29

second NOx storage catalytic converter

31

blocking catalytic converter

33

oxidation catalyst

35

SCR catalyst

37

graph

39

timeline

41

first temperature curve

43

second temperature curve

45

Y-axis

47

rise

49

functional area

51

line

53

graph

55

first Part diagram

57

second Part diagram

59

third Part diagram

61

First Y-axis

63

Second Y-axis

65

third Y-axis

67

First Cumulative NOx emission

69

Second Cumulative NOx emission

71

First Harnstoffzudosierung

73

Second Harnstoffzudosierung

75

motor control

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 19933654 A1 [0001]
• - DE 19640577 A1 [0001]

Claims (9)

Catalyst arrangement ( 1 ) for purifying an exhaust gas stream ( 3 ), an internal combustion engine ( 5 ), of a motor vehicle ( 7 ) with: - an internal combustion engine ( 5 ) downstream of the first catalyst ( 15 ), - a first catalyst ( 15 ) arranged after second catalyst ( 27 ), - one of the first catalyst ( 15 ) associated first electrical heater ( 11 ) for heating the first catalyst ( 15 ) and or the exhaust stream ( 3 ), - one the second catalyst ( 27 ) associated second heating ( 23 ) for heating the second catalyst ( 27 ) and or the exhaust stream ( 3 ). Catalyst arrangement according to the preceding claim, wherein the first electric heater ( 11 ) the first catalyst ( 15 ) and the second electric heater ( 23 ) the second catalyst ( 27 ) is connected upstream. Catalyst arrangement according to one of the preceding claims, wherein the first catalyst ( 15 ) and the second catalyst ( 27 ) as NOX storage catalysts ( 17 . 29 ) (NSK) are formed. Catalyst arrangement according to one of the preceding claims 1 or 2, wherein the first catalyst ( 15 ) as oxidation catalyst ( 33 ) (Ox-Cat.) And the second catalyst ( 27 ) as an SCR catalyst ( 35 ) are formed. Catalyst arrangement according to one of the preceding claims, wherein the first catalyst ( 15 ) a particle filter ( 19 ) is connected downstream. Catalyst arrangement according to one of the preceding claims, wherein the second catalyst ( 27 ) a barrier catalyst ( 31 ) is connected downstream. Catalyst arrangement according to one of the preceding claims, wherein for controlling and / or regulating a motor control ( 75 ) is provided. Process for purifying an exhaust gas stream ( 3 ) of an internal combustion engine ( 5 ) of a motor vehicle ( 7 ) with a catalyst arrangement ( 1 ) according to one of the preceding claims, with at least one of the following steps: raising an exhaust gas temperature ( 41 . 43 ) of the exhaust gas stream ( 3 ) by means of the first electric heater ( 11 ), - raising an exhaust gas temperature ( 41 . 43 ) of the exhaust gas stream ( 3 ) by means of the second electric heater ( 23 ), - raising an exhaust gas temperature ( 41 . 43 ) by means of a catalytic conversion by motor means of the internal combustion engine ( 5 ) generated hydrocarbons (HC), - driving a functional area ( 49 ), a NOx storage by means of the temperature increase, - controlling a functional area, a desulfurization of the catalyst arrangement ( 1 ) by means of the temperature increase. Motor vehicle ( 7 ) with a catalyst arrangement ( 1 ) according to one of the preceding claims 1 to 7.