DE10347134A1 - Diesel exhaust aftertreatment systems - Google Patents

Abstract

A method for controlling a temperature of a heated element of a reductant supply system for an exhaust gas aftertreatment device for lean burn engines arranged downstream of an internal combustion engine is presented. The method teaches reaching a desired temperature of a heating element by selecting a control signal to the heating element from a predetermined temperature map based on engine operating conditions, such as. Exhaust gas temperature, engine speed, engine load, etc. Accordingly, the life of the heating element and its power consumption are improved, for example, by controlling its temperature to prevent overheating and by the ability to turn off the heating element when the exhaust gas temperatures are sufficiently high.

Description

The present invention relates refer to a system and method to improve performance an exhaust gas aftertreatment device and in particular on its use an airborne heated reductant delivery system, to improve system performance and fuel economy disadvantage reduce.

Current exhaust gas regulations require the use of catalysts in the exhaust systems of motor vehicles in order to convert carbon monoxides (CO), hydrocarbons (HC) and nitrogen oxides (NOx), which are generated during engine operation, into non-compliant exhaust gases. Vehicles equipped with diesel or lean gasoline engines offer the advantage of improved fuel consumption behavior. Such vehicles must be equipped with exhaust gas aftertreatment systems for lean-burn engines, such as Active Lean NO _x catalysts (ALNC), which can continuously reduce NO _x emissions even in an oxygen-rich environment. To maximize NO _x reduction in the ALNC, a hydrocarbon based reductant, such as fuel (HC), must be added to the exhaust gas entering the device. However, the introduction of fuel as a reductant fuel worsens the overall fuel economy of the vehicle. In order to achieve high levels of NO _x conversion in the ALNC and at the same time to minimize the fuel consumption disadvantage, it is important to optimize the use of injected reductant.

In this regard, it is known per se that improved NO _x conversion can be achieved by introducing the reductant in vapor rather than liquid form. The introduction of the reductant in vapor form enables a better distribution and mixing of the reductant with the exhaust gas entering the NO _x reduction device.

Such a system is described in the US patent 5,771,689, in which a reductant enters the exhaust system via a Evaporator device introduced which is a hollow body with a heating element extending into its interior. The evaporator device extends into the wall of the exhaust pipe upstream of the catalyst. The reductant is introduced in such a way that it the narrow space between the hollow body and the heating element flows, until it reaches the top of the heating element, from where it is in vapor form enters the exhaust pipe and gets into the catalytic converter entering exhaust gas mixed.

The inventors recognized several disadvantages this approach. If namely the feeder was turned off or reduced by reductant, as by operating conditions can force some reductant in the ring-shaped Space remain in contact with the heating element and consequently around the annular opening block the heater by charring the remaining fuel. Such carbon buildup can block the passage lead at the top over the the vaporized fuel enters the exhaust stream. Furthermore it comes with the introduction of the reductant in the exhaust gas flow due to a delay due to the time the reductant needs to get over the length to move the heating element. About that in addition, the life of the heating element is reduced because of its Temperature is not regulated and adjusted based on the operating conditions and soot contamination comes. Another disadvantage of the state of the art Technology is that due of the above In the absence of temperature control, additional electricity is consumed.

The present invention teaches System and procedure for introducing vaporized reductant into an exhaust gas stream enters an exhaust gas aftertreatment device for lean-burn engines and the those mentioned above Eliminate disadvantages of the prior art procedures.

According to the invention, a reductant supply system comprises: an evaporator unit having at least one heating element, a Mixing device which has at least one inlet and at least one outlet, said outlet with the evaporator unit is connected, and a control unit for the introduction of reductant and air into the said mixing device through the named inlet opening, injecting a mixture of said reductant and said air through said outlet into said evaporator unit, said control device a temperature of said heater for the evaporation of said Adapts mixture.

According to another feature of the present Invention includes a procedure for the operation of a reductant delivery system for one Exhaust aftertreatment device, wherein the system at least one Heating element has the following: operating in a first mode, where a reductant and air mixture into the reductant supply system injected and the heating element is turned on, and operating in a second mode, in which the said reductant and air mixture into the reductant delivery system injected and the heating element is switched off.

The present invention offers a number of advantages. In particular, the creation improves ner mixture of reductant and air the efficiency of the exhaust gas aftertreatment device due to the improved mixing of the reductant with the main exhaust gas stream and improved catalyst effect compared to the use of reductant in the liquid phase. In addition, the mixing of reductant and air breaks the reductant into small particles, which leads to a correspondingly faster evaporation process. Furthermore, the injection of air into the evaporator unit prevents paint and soot deposits on the surface of the heating element. Furthermore, the inventors recognized that dynamically regulating the temperature of the heating element to benefit from the heat provided by the exhaust gases prevents overheating, improves the life of the heating element, and reduces power consumption.

A still further advantage of the present invention is that the temperature of the heating element can be controlled so that the injected reductant and air mixture ignites and thus carbon monoxide (CO) is produced, which further improves the NO _x reduction in the ALNC.

Another advantage of the present invention is that the CO production (and thus the NO _x conversion efficiency) is improved _by placing an oxidation catalyst in the way of the reductant and air mixture before it is mixed with the exhaust gases.

Further features essential to the invention emerge from the description below, in which with reference on the drawings embodiments explained become. The drawings show:

1A and 1B schematic diagrams of an engine in which the invention is advantageously used;

2 an example of an embodiment of an exhaust gas purification system in which the present invention is advantageously used;

3A . 3B and 3C Examples of reductant delivery systems according to the present invention;

4 FIG. 5 is a high level flow chart of an exemplary routine for controlling a temperature of the heating element of the reductant delivery system according to the present invention;

5 and 6 the description of an exemplary routine and a change curve for determining an amount of reductant to be supplied to the exhaust gas aftertreatment device according to the present invention.

description preferred embodiments

An internal combustion engine 10 , which has a plurality of cylinders, one cylinder in 1 is shown by an electronic engine control unit 12 controlled. The motor 10 has a combustion chamber 30 and cylinder walls 32 with a piston arranged therein and connected to the crankshaft 40 36 on. The combustion chamber 30 stands above the respective inlet valves 52 and exhaust valves 54 with an intake manifold 44 and an exhaust manifold 48 in connection. The intake manifold 44 is further shown so that a fuel injector 80 is connected to be proportional to the pulse width of a signal FPW from the control unit 12 Add fuel. Both the amount of fuel regulated by the FPW signal and the injection timing can be adapted. Fuel becomes the fuel injector 80 through a fuel system (not shown) that includes a fuel tank, a fuel pump, and a fuel rail (not shown).

The control unit 12 is in 1 shown as a microcomputer known per se, which comprises: a microprocessor unit 102 , Input / output connections 104 , a non-erasable read-only memory 106 , a random access memory 108 and a conventional data bus. The control unit 12 receives various signals from those with the motor in addition to the signals discussed above 10 connected sensors, including: engine coolant temperature (ECT) through the one with the cooling jacket 114 connected temperature sensor 112 , a measurement of manifold pressure (MAP) by the one with the intake manifold 44 connected pressure sensor 116 , a measurement (AT) of the manifold temperature by the temperature sensor 117 ; an engine speed signal (RPM) through the crankshaft 40 connected engine speed sensor 118 ,

An emission control system 20 that with an exhaust manifold 48 is explained in detail below using the 2 described.

With reference to 1 B is now shown an alternative embodiment in which the engine 10 is a direct injection engine, the injector 80 is arranged so that it fuel directly into the cylinder 30 injects.

With reference to 2 an example of an exhaust gas purification system according to the present invention is described. The emission control system 20 is downstream of an internal combustion engine 10 connected and is referenced to 1 described. The catalyst 14 is an Active Lean NO _x catalyst (ALNC), which can reduce NO _x in an oxygen-rich environment. The oxidation catalyst 13 is connected upstream of the ALNC and can be a noble metal catalyst, preferably a platinum-containing catalyst. The oxidation catalyst burns exothermic hydrocarbons (NC) in the exhaust gas arriving from the engine and thus supplies heat for the rapid heating of the Active Lean NO _x catalyst (ALNC) 14 , Additionally improved as a result of HC combustion in the oxidation catalyst 13 carbon monoxide (CO) the NO _x reduction in the ALNC. The particle filter 15 is connected downstream of the ALNC and is able to store carbon particles from the exhaust.

A reductant delivery system 16 is connected to the exhaust manifold between the oxidation catalyst and the ALNC. Alternative embodiments of the reductant delivery system are described later herein with particular reference to FIG 3A to 3C described.

The diagram of the 3A generally represents an embodiment of a reductant delivery system according to the invention. The system comprises an evaporator unit 21 which is an elongated heating element 22 includes. In this example, the heating element is an electrically heated cylindrical heating element. Alternatively, the heating element could be rectangular in shape to increase its surface contact area with the injected reductant and air mixture.

In yet another alternative embodiment, an oxidizing catalytic coating can be added to the evaporator unit, such as a coating on the inner surface of the heater housing and a catalytic cap at the point where the vaporized reductant and air mixture enters the exhaust manifold to around the Facilitate CO production. The catalytic coating can be a coating of noble metal, preferably a coating containing platinum or palladium. The control unit 12 regulates the temperature of the heating element by supplying a PWM signal with different switch-on cycles. The switch-on cycle of the PWM control signal to the heating element is determined on the basis of a stored table based on operating conditions in order to achieve the desired heating element temperature. The mixing unit 23 has a reductant inlet and an air inlet and an outlet 24 on, which is connected to the evaporator unit and via which a mixture of reductant and air is injected into the housing and then to the surface of the heating element 22 comes into contact.

In an alternative embodiment (not shown), both air and reductant can be injected through a single inlet. The reductant can the mixing unit 23 can be supplied from the fuel tank or from a storage container. The air pump 25 delivers compressed air to the mixing unit 23 , creating a mixture of reductant and air. The outlet 24 is designed so that it supplies the reductant and air mixture to a certain surface on the surface of the heating element. Alternatively, the outlet could be 24 be designed so that the reductant and air mixture is supplied to more than one surface on the surface of the heating element. The control unit 12 Depending on operating conditions, such as engine speed, engine load, exhaust gas temperature, etc., it can optionally activate and deactivate the injection of the mixture into these areas. For example, if the required amount of reductant is large, such as under high load conditions, it may be necessary to activate the supply of the reductant and air mixture to more than one area on the surface of the heating element.

3B shows an alternative construction of the heating element housing. As can be seen in the drawing, the heating element is enclosed by a feed tube, the inner diameter of which is large enough to accommodate the heating element. The feed pipe has a narrow channel drilled in the same which serves as a passage for the air and reductant mixture. The air and reductant mixture is injected into the narrow channel and is quickly evaporated by the heat supplied by the enclosed heating element without coming into direct contact with its surface. In this embodiment, the life of the heating element is further improved because the reductant and air mixture never comes into direct contact with its surface. The feed pipe has one or more openings at its end through which the vaporized reductant and air mixture enters the exhaust manifold.

3C shows an alternative embodiment of the in 3B The heating element housing shown, in which a porous oxidizing catalytic insert, preferably a platinum or palladium-containing insert, is arranged at the head of the feed pipe in order to facilitate the conversion of the vaporized hydrocarbons into carbon monoxide. In addition, one or more openings can be drilled along the length of the feed tube and sealed with porous oxidizing catalytic material to further facilitate the conversion of hydrocarbons to carbon monoxide.

Accordingly, according to the invention, an improved one Reduktantzuführsystem and presented an improved process. Mixing reductant with air causes that Reductant is well distributed within the reductant delivery system, and thus the evaporation process is accelerated. Furthermore, the lifespan of the system by reducing paint and soot deposits due to better distribution of the reductant and faster Evaporation process improved. The system performance is determined by the addition of an oxidizing catalytic coating further improved.

As is readily apparent to those skilled in the art, the following can be seen from the 3 and 4 The routines described represent one or more of any number of processing strategies, such as event-driven, interrupt-driven, multi-tasking, multi-threading, and similar strategies. Accordingly, various steps or functions shown in the sequence shown or par allelic or in some cases omitted. Similarly, the order of processing does not have to be strictly followed to achieve the objectives, features and advantages of the invention, these are provided for purposes of illustration and description only. Although this has not been expressly shown, those skilled in the art will recognize that one or more of the steps or functions shown may be performed multiple times depending on the particular strategy used.

With reference to 4 An exemplary routine for controlling the temperature of the heating element of the reductant delivery system according to the present invention will now be described. First, the desired heating element _{temperature Tdes is} determined in step 100. This determination is based on which function the reductant evaporator system performs, for example whether the mixture has to be evaporated or burned. Next, the routine proceeds to step 200 where operating conditions known to have an effect on heater temperature, such as the exhaust gas temperature upstream of the ALNC, are evaluated. The exhaust gas temperature can be determined on the basis of a temperature sensor arranged in the exhaust manifold or can be estimated on the basis of parameters such as engine speed, engine load, engine temperature, ignition timing, etc. Next, in step 300, an optimal switch-on cycle for achieving the desired heating element temperature for the heating element is determined on the basis of operating conditions, such as, for example, the exhaust gas temperature in the present example, and on the basis of a stored temperature map which has been developed by tests. The routine then proceeds to step 400 where the heater control signal turn-on cycle is adjusted to achieve the desired heater temperature. The routine is then complete.

By building a map the heating element temperature due to operating conditions such as e.g. the exhaust gas temperature, or any parameter, of who knows that he affects the temperature of the heating element, it is accordingly possible, to regulate the temperature of the heating element dynamically in order to achieve an optimal one Delivery of reductant and air mixture to achieve and at the same time minimize power consumption and overheat the heating element to prevent. In other words, it is possible to get the heat from that through the reductant delivery system flowing Exhaust gas is delivered to use when the temperature of the heating element is regulated. For example, leads a higher one Exhaust gas temperature to low power consumption, while a lower exhaust gas temperature to higher Electricity demand leads. It is also possible, the power supply is complete turn off when the exhaust gas temperature is high enough to the heating element at the one you want Maintain temperature, e.g. in a state with high engine load.

worin RA_{f g} die Menge an Reduktant in der in die Vorrichtung eintretenden Abgasmischung ist, die auf der Grundlage von Motorbetriebsbedingungen bestimmt werden kann. Diese anfängliche Reduktantmenge RA_{inj_1} wird bei konstanten Be dingungen evaluiert und ergibt eine Basisreduktantmenge, welche für jeden Motordrehzahl- und Motorlastpunkt einzuspritzen ist. Die Menge wird kalibriert, um ein bestimmtes Reduktant/NO_x-Verhältnis R_des in dem aus dem Motor ausströmendem Abgas zu erreichen. Das Verhältnis wird typischerweise als Ergebnis einer Abwägung zwischen NO_x-Umwandlung und Kraftstoffverbrauchsnachteil aufgrund der Reduktanteinspritzung bestimmt, und in diesem Beispiel wird es auf ungefähr 10 eingestellt. Anschließend wird im Schritt 700 die Basis-Reduktanteinspritzmenge RA_{inj_1} bei konstanten Bedingungen modifiziert, um Motorbetriebsbedingungen, wie Motorkühlmitteltemperatur T_c, Abgastemperatur T_eg, EGR-Ventilstellung EGR_pos, Beginn der Einspritzung SOI und sonstige Parameter, zu berücksichtigen:

With reference to 5 An exemplary routine of controlling the injection of a reductant into the exhaust gas stream using a reductant evaporator system as shown in FIG 3A described, presented. First, the amount of entering into the apparatus NO _x in the exhaust gas mixture _fg NOx is estimated on the basis of engine operating conditions in step 500th These conditions may include engine speed, engine load, exhaust gas temperatures, exhaust gas aftertreatment device temperatures, injection timing, engine temperature, and other parameters known to those skilled in the art to be suitable for indicating the amount of NO _x produced by the combustion pressures. Alternatively, a NO _x sensor can be used to measure the amount of NO _x in the exhaust mixture. Next, in step 600, the reductant _{injection amount} RA _{inj_1 is calculated at constant conditions based on the} following equation:

where RA _{f g is} the amount of reductant in the exhaust gas mixture entering the device that can be determined based on engine operating conditions. This initial reductant _quantity RA _{inj_1} is evaluated under constant conditions and results in a basic reductant _{quantity which} is to be injected for each engine speed and engine load point. The amount is calibrated to achieve a certain reductant / NO _x ratio R _of the exhaust gas flowing out of the engine. The ratio is typically determined as a result of trade-off between NO _x conversion and fuel consumption due to the disadvantage Reduktanteinspritzung, and in this example, it is adjusted to approximately 10x. Then, in step 700, the basic reductant _{injection quantity} RA _{inj_1 is modified} under constant conditions in order to take engine operating conditions into account, such as engine coolant temperature T _c , exhaust gas temperature T _eg , EGR valve position EGR _pos , start of injection SOI and other parameters:

worin T_s die Samplingrate ist und pps(t) die Gaspedalstellung beim Zeitpunkt t angibt. Als nächstes wird im Schritt 900 ein Tiefpaßfilter angewandt, um Störeinflüsse zu dämpfen:

worin k_f die Rate der Filterung regelt. Die Routine geht dann weiter zum Schritt 1000, wo die Reduktantmenge weiter modifiziert wird, um transientes Motorverhalten zu berücksichtigen, wie dies durch die Veränderungen bei der Gaspedalstellung dargestellt wurde:

worin die Funktion f₅ gebildet wird, um ein verstärktes Einspritzen von Reduktant während des Niedertretens des Gaspedals und ein vermindertes Einspritzen von Reduktant während des Loslassens des Gaspedals zu erlauben. Bei diesem alternativen Ausführungsbeispiel können anstelle der Gaspedalstellung die Motordrehzahl oder der Kraftstoffbedarfssensor oder jeder andere Parameter, von dem der Fachmann weiß, daß er geeignet ist, eine Messung des transienten Motorverhaltens zu liefern, verwendet werden, um RA_{inj_3} zu erhalten. Als nächstes wird im Schritt 1100 die gewünschte Temperatur des Heizelements wie unter besonderer Bezugnahme auf 4 beschrieben erhalten, um dadurch eine optimale Temperatur für die Reduktant- und Luftmischungsverdampfung zu erreichen. Die Routine geht dann weiter zum Schritt 1200, bei dem die Bereiche an der Oberfläche des Heizelements, in die eine Reduktant- und Luftmischung eingespritzt wird, aufgrund von Betriebsbedingungen ausgewählt werden. Diese Bereiche werden auf der Grundlage von Parametern, wie der Menge des zuzuführenden Reduktants, Motorlast, Drehzahl, Abgastemperatur, Katalysatortemperatur, Drosselklappenstellung usw., aus einem abgespeicherten Kennfeld ausgewählt. Beispielsweise kann es bei hohen Motorlasten wünschenswert sein, die Reduktant- und Luftmischung schneller einzuspritzen als bei niedrigen Motorlasten, und demzufolge wird in diesem Fall die Zuführung zu mehreren Bereichen aktiviert. Die Routine ist damit beendet. Ein Beispiel von f₅ wird mit besonderer Bezugnahme auf 6 gezeigt.The routine then continues to step 800, where the current change in accelerator pedal position is calculated as follows:

where T _{s is} the sampling rate and pps (t) indicates the accelerator pedal position at time t. Next, a low pass filter is applied in step 900 to dampen interference:

where k _f controls the rate of filtering. The routine then continues to step 1000, where the amount of reductant is further modified to account for transient engine behavior, as illustrated by the changes in accelerator pedal position:

wherein function f _{5 is} formed to allow increased reductant injection during accelerator pedal depression and reduced reductant injection during accelerator pedal release. In this alternative embodiment, engine speed or fuel _{demand sensor} or any other parameter known to those skilled in the art to be capable of providing a measure of transient engine _behavior may be used in place of accelerator pedal _position to obtain RA _{inj_3} . Next, in step 1100, the desired temperature of the heating element is as with particular reference to FIG 4 described in order to achieve an optimal temperature for the reductant and air mixture evaporation. The routine then proceeds to step 1200, where the areas on the surface of the heating element into which a reductant and air mixture is injected are selected based on operating conditions. These ranges are selected on the basis of parameters, such as the amount of the reductant to be supplied, engine load, speed, exhaust gas temperature, catalytic converter temperature, throttle valve position, etc., from a stored map. For example, at high engine loads, it may be desirable to inject the reductant and air mixture faster than at low engine loads, and as a result, delivery to multiple areas is activated. This ends the routine. An example of f ₅ is given with particular reference to FIG 6 shown.

Accordingly, the amount of reductant to be injected should be adapted to achieve an improved efficiency of the exhaust gas aftertreatment device in order to take into account increases or decreases in the amount of NO _x in the exhaust gas entering the device. This can be supplemented by continuously monitoring the engine parameters, which make it possible to provide a measurement of the transient engine behavior, such as, for example, an accelerator pedal position sensor, and continuously adapting the amount of reductant to be injected as a function of filtered instantaneous changes in these parameters. Since NO _x production is typically increased when the accelerator pedal is depressed and decreased when the accelerator pedal is released, the result of such an operation would be to increase the basic injection quantity in the former case and to decrease the basic injection quantity in the latter case. Furthermore, the use of a reductant evaporator unit ensures a quick system response, more efficient system operation, better exhaust gas cleaning and improved fuel consumption behavior.

This is the description of the invention completed. Your reading by the specialist to discover numerous changes and modifications without departing from the spirit and scope of the invention. Accordingly, it is intended that the Framework of the invention defined by the following claims becomes.

Claims (32)

Reductant delivery system, which system is characterized in that it comprises: an evaporator unit having at least one heater; a mixing device having at least one inlet and at least one outlet connected to said evaporator unit; and a controller for introducing reductant and air into said mixer through said inlet, injecting a mixture of said reductant and said air through said outlet into said evaporator unit, said controller adjusting the temperature of said heater that said mixture is evaporated. System according to claim 1, characterized in that the reductant Is urea. System according to claim 1, characterized in that the reductant Is hydrocarbon. System according to claim 1, characterized in that said Reduktantzuführsystem a container for the Housing the injected reductant and air mixture includes, wherein said reductant and air mixture inside said container evaporates without directly touching a surface of the heating element to come into contact. System according to claim 1, characterized in that said Heater an electrically heated elongated heating element insert is. System according to claim 5, characterized in that said Heating element insert is cylindrical. System according to claim 5, characterized in that said Heating element insert is of rectangular shape. System according to claim 2, characterized in that said Evaporator unit also a hydrolyzing catalyst includes. System according to claim 3, characterized in that said Evaporator unit further comprises an oxidation catalyst. System according to claim 1, characterized in that this called control unit a pulse width modulated signal of a predetermined turn-on cycle supplies to adjust the said temperature of the heater. System according to claim 10, characterized in that this called control unit turns off the power to the heater when the said temperature of the heater above a predetermined temperature lies. Method for controlling a temperature of a heating element a reductant delivery system for an exhaust gas aftertreatment device, wherein the device is connected downstream of an internal combustion engine which method is characterized by comprising: estimating Operating conditions, and adjusting the temperature of the heating element based on the above operating conditions. A method according to claim 12, characterized in that the operating conditions are engine operating conditions. A method according to claim 12, characterized in that the mentioned operating conditions include at least the engine speed. A method according to claim 12, characterized in that the mentioned operating conditions at least one exhaust gas mixture temperature include. A method according to claim 12, characterized in that the mentioned operating conditions include at least the engine load. A method according to claim 12, characterized in that the Engine is a diesel engine. A method according to claim 17, characterized in that the Exhaust aftertreatment device is an ALNC. A method according to claim 17, characterized in that the Exhaust aftertreatment device is an SCR catalytic converter. Procedure for the operation of a reductant delivery system for one Exhaust aftertreatment device, wherein the system at least one Has heating element, which method is characterized that it comprising: business in a first mode in which a reductant and air mixture into the reductant delivery system is injected and the heating element is switched on, and business in a second mode, in which the said reductant and air mixture into the reductant delivery system is injected and the heating element is switched off. A method according to claim 20, characterized in that this Reductant is urea. A method according to claim 21, characterized in that the Exhaust aftertreatment device is an SCR catalytic converter. A method according to claim 20, characterized in that the called reductant is hydrocarbon. A method according to claim 23, characterized in that the Exhaust aftertreatment device is an ALNC. A method according to claim 20, characterized in that this Heating element is switched off when a temperature of the exhaust gas aftertreatment device is above a predetermined threshold. Procedure for the control of a reductant delivery system for one Exhaust aftertreatment device connected downstream of an internal combustion engine exhaust, which method is characterized in that it comprises: injecting a mixture of reductant and air into the reductant delivery system; Customize one Temperature of a heating element which is inside the reductant supply system is housed, causing the evaporation of said mixture is caused, and Introduce said vaporized mixture in the exhaust gas aftertreatment device. A method according to claim 26, characterized in that the Engine is a diesel engine. A method according to claim 27, characterized in that the Exhaust aftertreatment device is an ALNC. A method according to claim 28, characterized in that the called mixture of reductant and air a mixture of hydrocarbon and air is. A method according to claim 27, characterized in that the Exhaust aftertreatment device is an SCR catalytic converter. A method according to claim 30, characterized in that the called mixture of reductant and air a mixture of urea and air is. Procedure for the operation of a reductant delivery system for one Exhaust aftertreatment device connected downstream of an internal combustion engine, wherein the system has at least one heating element, which method is characterized in that it comprising: business of the system in a first mode in which a reductant and air mixture is injected into the system and a temperature of the said Adjusted heating element to evaporate the said reductant and air mixture, and Operation of the system in a second mode, in which the called reductant and Air mixture is injected into the system and the temperature mentioned of the said heating element is adapted to the said reductant and burn air mixture.