JP2000073742A - Method for feeding reductant to nitrogen-containing exhaust gas of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To optimize the measured feeding of reductant to nitrogen-containing exhaust gas to the operation dynamic change in an internal combustion engine by measuring the reductant speed from prescribed parameters, by correcting the reducer speed according to the loading state change in the internal combustion engine, and by adding the adapted reducer quantity to an exhaust gas flow. SOLUTION: Air is fed to an air feed conduit 4 of an internal combustion engine by a compressor of an exhaust gas turbo charger 2. The exhaust gas exhausted from an exhaust turbine 5 is fed to catalyst 8 through the exhaust gas conduit 7 and exhausted from a discharge conduit 9 in a purified state. A measuring and feeding device 11 measures and introduces reductant from a conduit 12 and a nozzle 13 to an exhaust gas flow in the front side of the catalyst 8 and an adjustment and control device 14 controls the measuring and feeding device 11 via a control lead wire 21 based on the measured values of various types of sensors 15-20. Then, the engine eigenvalue of the NOx concentration and the exhaust gas quantity, and the detected exhaust gas temperature and the reductant concentration are used as the adjustment parameters for measuring and feeding the reductant.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention provides, according to the general concept of the first aspect, at least partially having at least NO _x reduction activity, having a small heat capacity and a storage capacity for a reducing agent. The invention relates to a process for metering a reducing agent, in particular urea or an aqueous urea solution, into the nitrogen-containing exhaust gas of an internal combustion engine into an exhaust gas line before a small catalyst system.

[0002]

In the case of the selective catalytic reduction of the Related Art NO _x (SCR), in order to reduce NO _x to N _2, the internal combustion engine and SC
Depending on the operating conditions of the R catalyst, a certain amount of reducing agent has to be metered into the exhaust gas stream. If too little reducing agent is metered in, the degree of reduction is unnecessarily reduced. If too much reductant is metered in, reductant slip and undesirable intermediates and decomposition products are produced. In addition, this results in an unnecessarily high consumption of the reducing agent. When urea is used as a reducing agent,
If ammonia leaks or an oxidation catalyst is connected downstream of the SCR catalyst, release of nitrous oxide N ₂ O may occur.

[0003] EP 0 515 857 A1 and EP 0 697 062 B1
Both are methods concerning the storage capacity of the catalyst and the temporary metering of the stoichiometric excess of the reducing agent.

[0004] DE 43 10 961 A1 describes a method for measuring catalytic activity by using at least one temperature sensor in the catalyst.

[0005] All known processes have in common that they do not allow accurate metering into the exhaust gas under dynamic or highly dynamic operating conditions of the internal combustion engine. Or highly dynamic changes have never been considered before. In particular, an accurate measurement of the catalytic activity in the case of the aforementioned dynamic alternating loads of an internal combustion engine has hitherto been one of the unsolved problems.

[0006] In addition, some, but not all relevant state variables, have been considered in the case of known reducing agent-metering methods. Thus, in the case of the method known from DE 43 10 961 A1, it is proposed to incorporate a plurality of temperature sensors into the catalyst in order to measure the change in the state of the catalyst, ie the temperature. However, this appears to be of little utility and, moreover, of high expense.

An accurate measurement of the degree of reductant charge in the SCR catalyst is necessary, as is necessary in order to be able to carry out the reductant metering according to the proposals of EP 0 697 062 B1 and EP 0 515 857 A1. This was not possible due to the complex relationships of such catalyst systems. For this reason, metering is
Temporarily interrupted and the catalyst is thus idled in order to obtain the defined ratio again.
However, the disadvantage is that the NO _x conversion necessarily decreases.

[0008] Thus, the above-mentioned prior art documents start with a clear storage capacity of the catalyst in terms of reducing agent and heat in its metering strategy.

[0009] This method can in principle be envisaged for a complete catalyst known from the power plant art. The process mode consists entirely of the active material, which makes it possible to store the reducing agent at particularly low temperatures. Thanks to this storage capacity, reductant leakage in the case of dynamic or highly dynamic alternating loads can be largely avoided by the short-term storage of excess reductant, in particular NH ₃ , by the catalyst.

For example, the use of such systems under conditions of very limited locality in vehicles where significant reductions in emissions and weight of currently available systems are required.
Complete catalysts are hardly suitable, because
This is because the complete catalyst does not have sufficient development potential (Entwicklungspotential) for the above requirements.

For the above-mentioned reasons, coated catalysts are used, the number of cells of the coated catalyst (Zellenzahl) can be set very high, and the coated catalyst has a substantially reduced support wall. Larger open countercurrent area due to thickness
(freie Anstroemflaeche) and thus have a lower pressure drop (see FIG. 6).

[0012] However, such a catalyst system uses NH 3
It has a low storage capacity for ₃ , since essentially less active material can be used. Thus, the reducing agent peak cannot be trapped by adsorption, and undesired release of the reducing agent product readily occurs.

[0013] Therefore, metering, and operation parameters, the catalyst temperature, NO _x concentration, the amount of exhaust gas, catalytic activity, etc., for the accuracy of the detection, so far higher than those used in the unsupported catalysts request Conclusions Is done.

[0014]

The object of the present invention is, therefore, to provide a process according to the above-mentioned general concept, that is to say that it has at least NO _x reduction activity locally, has a low heat capacity and a storage capacity for the reducing agent. A method for metering a reducing agent, in particular urea or an aqueous urea solution, into the nitrogen-containing exhaust gas of the internal combustion engine into the exhaust gas conduit before the catalyst system with a small amount of
Is to provide an adapted strategy in the sense of optimized reductant rate adaptation to dynamic changes in internal combustion engine operation.

[0015]

The object is achieved according to the invention by the features of the method described in accordance with the features of claim 1, that is, in connection with a reference internal combustion engine. using the determined concentration of NO _x and the engine eigenvalue and at least Note Note reducing agent concentration by the temperature and the case of the exhaust gas which is actually detected during the operation of the internal combustion engine for exhaust gas amount as an adjustment parameter for the reducing agent metering,
The reductant speed is calculated from these parameters, and the thus obtained reductant speed is dynamically and / or highly dynamically modified as a function of the detected change in the load state of the internal combustion engine and is adapted accordingly. The problem is solved by a method for metering a reducing agent into a nitrogen-containing exhaust gas of an internal combustion engine, characterized in that the determined amount of reducing agent is added to the exhaust gas stream.

The method according to the invention is based firstly on the same internal combustion engine as the internal combustion engine used at the time of application, for example on a dynamic engine test bench (dynamischen Maschinenpruefstand).
In operating characteristics of detecting the engine eigenvalues for concentration of NO _x and amount of exhaust gas released in the exhaust gas and metering device
(Kennfeld)-or data storage (Datenspeicher)
Is based on writing to the controlling computer. This data / value is supplemented by the value of the actually sensed temperature of the exhaust gas at least during engine operation and is also commonly used as a regulating parameter for the reductant-metering. In this case, a constant reducing agent velocity is calculated from these at least three parameters, possibly taking into account the concentration of the reducing agent. The reducing agent rate calculated in this way is a steady-state ratio (stationaere Verhaeltniss
For e), depending on the detected change in the load state of the internal combustion engine, a dynamic or highly dynamic correction is carried out, so that a change having a deviated value of the exhaust gas at a high speed corresponding to the exhaust gas. The modified reductant rate can be metered in such a way that the exhaust gas quantity which has been adapted is nevertheless optimally converted by the catalyst,
No slipping of the reducing agent occurs and no undesirable intermediate or decomposition products are identified.

On the other hand, the above problem can be solved by the characterizing part of claim 2.

[0018] Thus, for example, concentration of NO _x during operation of the internal combustion engine is determined from the sensed data by the sensors arranged in the exhaust gas stream prior to the catalyst. The exhaust gas amount of the internal combustion engine is calculated from the engine specific value. During operation of the internal combustion engine, in the case of load changes that require a dynamic but not highly dynamic correction of the amount of reducing agent to be metered into the exhaust gas, the temperature of the exhaust gas detected by the sensor is In addition, the exhaust gas temperature at the catalyst inlet over a fixed, possibly variable, presettable time before the measurement time can be taken into account. This memory fetch allows an improved control strategy in anticipation of future engine operating modes and thus the demands placed on the catalyst system.

Advantageous details and individual steps of the method are set forth in the dependent claims 3 to 11.

In addition, the NO _x concentration in the exhaust gas is also controlled downstream of the catalyst and the use of the influence on the regulation of the amount of reducing agent to be metered into the exhaust gas with a detected / determined control value. It is advantageous to use for

It is also advantageous to carry out a setpoint-actual value comparison between the calculated amount of reducing agent and the amount of reducing agent actually metered in the exhaust gas, in which case the amount of reducing agent added is determined. The measured values are determined by sensors or measuring instruments located at appropriate locations.

In the case of a high dynamic load state change of the operating internal combustion engine which requires a high dynamic correction of the reducing agent speed to be metered into the exhaust gas, the load state change of the internal combustion engine Is also detected or measured and taken into account. In this way, a reaction that is well adapted to load changes is possible.

The actual temperature of the intake air is detected by a sensor as an indicator as to whether or not the actual amount of exhaust gas coincides with the stored reference value of the amount of exhaust gas during operation of the internal combustion engine, and a predetermined reference value is set. It is also advantageous to compare the value. If this set value-actual value comparison is required,
This value is taken into account in the control technology to correct the rate of the reductant to be metered into the exhaust gas. In this way,
The significantly different climatic conditions in which the internal combustion engine can be used and the effects on exhaust gas quantity and composition conditioned thereby are taken into account.

It is advantageous to control the quality of the stored reductant, especially when the reductant is in liquid form, under such use conditions with very different temperatures.
This is done, for example, by sensing the temperature of the stored reducing agent by means of a sensor and by inferring its concentration from this value, the measured value being compared with a preset reference value. According to the result of the comparison between the set value and the measured value, the amount of the reducing agent to be metered and introduced into the exhaust gas can be further corrected.

It is likewise advantageous to take into account the aging of the initially used catalyst and the accompanying decrease in activity. In this case, the operating time of the catalyst is derived from the operating time of the internal combustion engine. Furthermore, the increase in operating time and the aging of the catalyst as a function of the time interval can be taken into account in accordance with a corresponding change in the amount of reducing agent to be metered into the exhaust gas.

In addition, the measured reduction activity of the reference catalyst is used to optimize the metering of the reducing agent at different reducing agent concentrations.

[0027] The method according to the present invention comprises a stationary device or vehicle;
It is particularly suitable in connection with highly dynamically operated internal combustion engines which are incorporated as drive sources in motor vehicles, commercial vehicles, in particular trucks and rides of all types of construction and use.

In principle, the invention is based on the following considerations or theory.

The amount of reducing agent to be metered into the exhaust gas of the internal combustion engine depends on the one hand on the exhaust gas emission and on the other hand on the active capacity of the catalyst to reduce said exhaust gas emission.

The activity or reducing ability of the catalyst can be described by various formulas.

A simple example of such an equation is the following formalkinetische equation: E →
P, where E is the exhaust gas component to be reduced, for example NO _x , and P is the reduction product, for example N ₂ , if there is a hypothetical reaction, the time (if constant volume) The change in the concentration dc of the starting material E for (assuming) can be described as follows:

[0032]

(Equation 1)

R _E is the rate of change of the substance amount of E (mol / s)
And m is the order of the reaction [−].

The rate constant k is a measure for how fast the reaction proceeds and depends on the temperature as follows:

[0035]

(Equation 2)

At this time, E is an activation energy [J / mo.
l], and R is a general gas constant of 8314 J /
(Mol * K), T represents temperature [K], and ko represents a duty _cycle .

[0037] (1) integral method assuming n = 1 (temporary reaction) According to obtained as _{follows: (3) c = c o} · e -kl this case, c is the final concentration [mol / M ³ ].
_co represents the starting concentration [mol / m ³ ], and t represents the reaction time [s].

The reaction time is equal to the residence time τ in the reactor:

[0039]

(Equation 3)

At this time, V is a volume flow rate (Volumenstrom) [m
³ / s], and V _Kat represents the catalyst capacity [m ³ ].

From the above equation, it can be seen that the final concentration c is in this case definitely dependent on the starting concentration c _o , but not on the residence time, and thus the volume flow rate Does not depend on EP 0 for dynamic operation
As suggested in 697 062 B1, it is not at all sufficient to indicate only the NO _x mass flow or the NO _x volume flow, since this gives a unique assignment at the time of operation of the catalyst system. It is impossible. Thus, a higher NO _x mass flow rate
It can also be obtained from the high concentration of NO _x and low exhaust gas flow, may also be obtained from a low concentration of NO _x, but higher gas flow. This results in different NO _x conversions.

The reaction temperature has an effect on the rate of change in the amount of substance depending on the rate constant k.

In addition, the dependence on the reducing agent concentration is also taken into account, for which reference is made to equations 5 and 6.

Formal kinetic equation:

[0045]

(Equation 4)

Mechanistic formula (Mechanistischer Ansatz):

[0047]

(Equation 5)

At this time, K is the sorption equilibrium constant of NH ₃ [m ³
/ Mol].

If one wishes to make as accurate an estimate as possible of the activity of the catalyst, it is therefore necessary to monitor the respective effects which occur mutually and to combine the NO _x concentration and the amount of exhaust gas produced with respect to the NO _x flow. Is important.

Determining such a rate equation to achieve a reductant-metering using a general rate equation is:
It seems impossible and undesirable under actual conditions, since the reducing agent-metering does not, on the one hand, reproduce the reducing capacity exactly enough over the entire working area of the catalyst, and On the other hand, the association is not immediately clarified. Reductant-fine adjustment of metering (Feinjus
tage) is thus extremely difficult.

For the above reasons, according to the invention, the operating characteristics of the reference internal combustion engine are employed to determine the NO _x -reduction potential (aufein Kennfeld einer Referenz-Brennkraf).
tmaschine zugegriffen), this operating characteristic replaces the comprehensive mass change rate equation by the assignment (Zuordnung) of each mass change rate at certain operating times of the catalyst system.

[0052] The one or more operational characteristics, contains a concentration of the reducing agent by the major agent i.e. concentration of NO _x c, the working temperature T _A of the assumptions, the exhaust gas volume flow V _{exhaust gas} and the case. Residence time τ and film diffusion due to V _{exhaust gas}
The speed associated with the (Filmdiffusion) effect is taken into account.

Since the only operating characteristic taking into account the above factors must be at least ternary, it is advantageous to receive at least two operating characteristics of the reference internal combustion engine separately from one another, a combination of these. The NO _x -reduction ratio of the catalyst can subsequently be calculated, for which FIG. 2 is referred to.

In this way, for example, the first operation characteristic (Δ
c V _{gas = constant} - operating characteristics, the final concentration in the case of containing information about the amount of substance changing speed) is constant V _{exhaust gas} [m ³ / h], which can vary NO _x - inlet concentration c _o
[Ppm] and T _A [° C.] can be taken (ablegen). T _A is the assumed working temperature in this case. For the time being, c _o can be read out from engine-specific operating characteristics, which are plotted as a function of the speed n as well as a load-dependent signal (eg injection quantity Q _e ) or directly during operation of the internal combustion engine It can be measured by a NO _x sensor.

[0055] Assuming the working temperature T _A and V _{exhaust gas} [m ³ /
h], the second operating characteristic (ε−
Operating characteristics) to allow the dwell time to influence the calculation, but on the other hand countercurrent (Anstroemun
g), used to compensate for irregularities in the case of film diffusion effects, backflow, etc. This operating characteristic is based on the correction factor ε
including.

From the first operating characteristic, V _{exhaust gas = constant} = _co.
−c is calculated and multiplied by ε. From this, a concentration difference Δc _correction [ppm] that can be actually reduced is obtained if the highly dynamic effects due to the reducing agent concentration remain unconsidered. After multiplication with V _{exhaust gas} , a reducible NO _x -mass flow ΔNO _x [mol / h] is obtained. Subsequent conversion gives the required reductant velocity, the urea commonly used for this reductant velocity being m
_{(NH2) 2CO,} referred to as _feed [g / h].

Determining the Temperature with a Large Effect As is clear from the above, it is not possible to find the possibility of measuring the temperature as accurately as possible, since the reaction temperature T has a great influence on the reaction rate and thus on the conversion. It is inevitable. This is problematic in that the exhaust gas temperature always changes in dynamic operation. The use of temperature sensors before and after the catalyst cannot correctly reflect the temperature course in the catalyst, and mounting more temperature sensors is problematic and expensive.

If the internal combustion engine is operated at a low load, for example after a relatively high load, the catalytic cold front moves. The rear temperature sensor still indicates a high temperature, while the front temperature sensor
A lower temperature is detected at the catalyst inlet. When a load jump to a higher load (Lastsprung) is performed,
The sensor at the inlet already reports a high temperature, while the sensor at the end still shows a high temperature, however, the temperature in the catalyst is essentially low, see FIG. 8 for this. Due to the temperature assumed to be too high, in the case of such moments, too much reductant, which can no longer be converted, is metered into the exhaust gas. Reducing agent slip occurs. The solution to this is the consideration of the history of the catalyst temperature in the dosing strategy, see FIG. Because of this, increase or decrease in catalyst inlet temperature to capture temperature peaks (schleif
end) mean T _mean is formed. The average temperature, for example inlet and temperature at the outlet of the catalyst, by associated with other catalyst, to form a working temperature T _A of the assumptions, further read from the operating characteristics data using the working temperature T _A .

[0059] (7) T _A = y, T _{Mean + Σ (x i, T i} ) At this time, _{T i} represents the temperature (e.g., temperature at the catalyst inlet and outlet of the catalyst T _exit) associated with the catalyst, T _Mean Represents the average value of the temperature increase and decrease (Schleifend), and T _average = f (T
_Inlet, a V _gas), it is Sx _i + y = 1.

Weighting of each temperature by coefficients x _i and y
(Wichtung).

At higher exhaust gas volume flows, the catalyst is heated and cooled more rapidly than at lower exhaust gas volume flows. For this reason, the length of the time interval Δt, in this case averaged, is T
In order to be able to better adapt the response characteristic of the _average by the operation state of each case, V _gas
Fluctuates according to the characteristic curve.

Therefore, a certain number of time intervals must be reserved for calculating the temperature T _average .

For the acceptance cycle (Aufnahmefrequenz) f, f = n / Δt, where n is the number of time intervals [−], and Δt is
Represents the total accepted length of the mean (Gesammtaufnahmelaenge).

A fixed period can be given in advance, and the number of time intervals in each case can be varied.

Determination of Exhaust Gas Volume (for example, Exhaust Gas Volume Flow Rate) which has a Large Effect The theoretical air volume flow rate is determined from the stroke volume, rotation speed n, and suction pipe pressure pLL of the internal combustion engine. This corrects the engine-specific volumetric efficiency and, for the exhaust gas volume flow, combines with the fuel mass (Kraftstoffmasse) obtained from the speeds n and Qe for the intake conditions.

Plots for ε-operating characteristics (Auftragun
For g), the V _{exhaust, suction} can still be modified towards the defined operating temperature from the T _inlet .

[0067] inlet concentration determined NO _x of the NO _x concentration is affected Dai, from the engine-specific data according to claim 1, for example, be the can either be determined by the operating characteristics, according to claim 2, NO It can also be determined by the _x sensor.

[0068] Peak or drop of the NO _x concentration a short time in the case of highly dynamic operation of the internal combustion engine occurs, this is significantly deviated and concentrations determined for static engine operation, for which FIG. 7 is referred to. This behavior is taken into account together with the characteristic curve for the rate of change of load in the case of highly dynamic operation, for which reference is made to claim 6.

[0069] Some further notes are as follows:-An advantage over known designs is that only one continuous track (durchgehender Strang) is used for control. This allows for a simple handling of the application, since the response to the change can indeed be assigned to individual operating characteristics or calculation factors. In addition, maximal clarity is achieved by the use of the agents, i.e. temperature, inlet concentration, volume flow and, if appropriate, the reducing agent concentration and the assignment of these agents to at least two operating characteristics.

[0070] - NO _x and NO _x sensor by use of the density can be incorporated easily metered strategies (alternative operating characteristics _{c NO} by the sensor data). Moreover, it is possible to achieve control behind the catalyst by mounting a sensor, for which reference is made to claim 4.

-Sudden load alternation (ploetzlicher Lastwechse
peak or drop of the NO _x concentration is generated in the case of l),
This cannot be fixed and fixed. Thus it is possible to schedule the additional modifications to the advanced dynamic state changes, this modification can act to dosing control by the load change rate, i.e., toward the lower or on the C _NO And reference is made to claim 6.

The dynamic correction is made with an assumed working temperature T _A.

In the case of the calculation of V _{exhaust gas} and [pp
m] to [mol / m ³ ], the air temperature as the suction condition is evaluated. In this case, the temperature measurement position increases the accuracy, for which reference is made to claim 7.

To minimize metering errors due to concentration differences, a concentration correction for the urea-water-solution can be scheduled, for which reference is made to claim 8 .

[0075]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 2 to 5 show, in flow chart form, various schematic diagrams of each one of the dosing strategies described above.

In this case, FIG. 1 schematically shows an internal combustion engine and an exhaust gas aftertreatment device, which explain, for example, the metering method according to the invention.

FIG. 2 shows a dosing strategy for urea dosing with dynamic correction by assumed operating temperatures.

FIG. 3 shows the metering strategy for reducing agent metering using advanced dynamic correction with reducing agent amount.

FIG. 4 shows a metering strategy for reducing agent metering using a NO _x sensor.

FIG. 5 shows a metering strategy for reducing agent metering using a plurality of NO _x sensors.

FIG. 6 shows a comparison of a full catalyst-coated catalyst represented by various wall thicknesses.

FIG. 7 shows the occurrence of a NO _x peak in the case of a sudden load alternation.

FIG. 8 shows the movement of the cold front by the catalyst.

In this case, FIG. 1 shows the loaded internal combustion engine at 1 and the associated exhaust gas turbocharger at 2. The air supply (Ladeluft) is conveyed by the compressor 3 of the exhaust gas turbocharger 2 into the air supply conduit 4 of the internal combustion engine 1. Exhaust gas turbocharger 2
Of the internal combustion engine 1 is supplied with exhaust gases from an exhaust gas truck (Abgasstrang) 6 for driving purposes. From the outlet of the exhaust gas turbine 5, the exhaust gas reaches via an exhaust gas conduit 7 a catalyst 8 incorporated therein and leaves the catalyst via a discharge conduit 9 in a clean state. At 10 a storage container for the liquid reducing agent is shown, at 11 a metering device is shown, which feeds the reducing agent into a conduit 12.
And a nozzle 13 in the exhaust gas conduit, which is metered into the exhaust gas stream before the catalyst 8 and at 14 a regulating and control device is shown, which controls the metering device. The control and control unit 14 has a microprocessor as a central control unit, which is connected via a data bus system to input and output peripherals and operating characteristics or data storage and program storage. are doing. The adjustment philosophy (R) for the control of the metering device within the method according to the invention in the program storage is adapted to software.
egelphilosophie) and adjustment algorithms. Reference values and target values are stored in the operating characteristic or data storage device, which control the metering device within the scope of the method according to the invention. Reference numeral 15 denotes a temperature sensor, which detects the temperature of the exhaust gas before entering the catalyst 8. A temperature sensor is shown at 16, which measures the exhaust gas temperature at the catalyst outlet. 17
In sensors - or measuring device is shown, NO _x concentration or its substitute elements in the exhaust gas after the catalyst is detected by using this device. At 18 a temperature sensor is shown, which senses the temperature of the stored reductant and thus allows a recursive deduction to the actual concentration of the reductant. At 19, a sensor or measuring device is shown which detects the recirculation or metering (actual value) of the amount of reducing agent to be metered into the exhaust gas. At 20 a temperature sensor for detecting the actual intake or supply air temperature is shown. Sensor 15, 1
The measured values of 6, 17, 18, 19, 20 and the further sensor values which are important to the engine operation or which allow an inductive inference to these values are supplied to the control and control unit 14 by means of its input peripherals. And in this case used internally or evaluated. The calculated control commands are applied to the metering device 11 by means of an output peripheral or control line 21, which converts the control commands into the reducing agent speed to be metered into the exhaust gas.

According to the second aspect, the NO _x concentration is not measured by the internal combustion engine for reference, but by a sensor 22 arranged before the catalyst 8 and before the nozzle 13. The reference internal combustion engine is only used for measuring the amount of exhaust gas.

The individual steps for the dosing strategy for this can be seen from the diagrams of FIGS.

FIG. 6 shows a comparison of a catalyst used for NO _x reduction with a complete catalyst used, for example, in a power plant. This complete catalyst cannot be used in dynamic processes due to its thermal inertia.

FIG. 7 shows the occurrence of the NO _x peak in the case of the load alternation.

FIG. 8 shows the movement of the cold front by the catalyst.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an internal combustion engine and an exhaust gas aftertreatment device, which are illustrated for explaining a metering method according to the present invention.

FIG. 2 is a flow diagram illustrating a dosing strategy for urea dosing with dynamic correction by assumed operating temperatures.

FIG. 3 is a flow chart showing a dosing strategy of a reducing agent metering using advanced dynamic correction by reducing agent amount.

FIG. 4 is a flow chart showing a metering strategy for reducing agent metering using a NO _x sensor.

FIG. 5 is a flow chart showing a metering strategy for reducing agent metering using multiple NO _x sensors.

FIG. 6 shows a comparison of a complete catalyst and a coated catalyst with respective cross-sectional views.

FIG. 7 is a diagram showing the occurrence of a NO _x peak in the case of sudden load alternation.

FIG. 8 is a diagram showing movement of a cold front by a catalyst.

[Explanation of symbols]

 20,22 sensor

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Gerhard Enmarling Germany Sulzkirchen les Luchenweg 3 (72) Inventor Andreas Dering Germany Germany Neukirchen Hin Mergartenstrasse 2 F-term (reference) 3G091 AA02 AA06 AA10 AA28 AB04 BA01 BA14 BA32 BA33 CA16 CB02 DB02 DB05 DB06 DB10 DB13 EA01 EA06 EA14 EA15 EA17 EA33 FC02 GA06 GB01X GB17X HA36 HA37 HA42 HB06

Claims (11)

[Claims] 1. The method according to claim 1, wherein the catalyst has at least NO _x reducing activity, a low heat capacity and a low storage capacity for the reducing agent, into the exhaust gas conduit before the catalyst system.
In metering method of the reducing agent to the nitrogen-containing exhaust gas of an internal combustion engine, is determined in relation to the reference for an internal combustion engine the NO _x
The engine-specific values for the concentration and the amount of exhaust gas and at least the temperature of the exhaust gas which is still actually detected during operation of the internal combustion engine and possibly also the concentration of the reducing agent are used as regulating parameters for the metering of the reducing agent, from which the reducing agent And a dynamic or highly dynamic correction of the thus obtained reductant velocity in response to the detected load state change of the internal combustion engine, and a correspondingly adapted reductant amount is calculated. A method for metering a reducing agent into a nitrogen-containing exhaust gas of an internal combustion engine, which is added to an exhaust gas stream. 2. The method according to claim 1, wherein the catalyst has at least NO _x reduction activity, a low heat capacity and a low storage capacity for the reducing agent, in the exhaust gas conduit before the catalyst system.
In metering method of the reducing agent to the nitrogen-containing exhaust gas of an internal combustion engine, in conjunction with a reference internal combustion engine to measure engine eigenvalues for the exhaust gas quantity, NO _x concentration of the catalyst before the gas stream during engine operation And at least the temperature of the exhaust gas, and possibly also the concentration of the reductant, which is actually detected during operation of the internal combustion engine, and possibly also the concentration of the reductant, for the metering of the reductant. Used as parameters, calculate the reducing agent speed from these parameters, and make a dynamic or highly dynamic correction to the obtained reducing agent speed in response to the detected change in the load condition of the internal combustion engine; and A method for metering a reducing agent into a nitrogen-containing exhaust gas of an internal combustion engine, characterized in that a correspondingly adapted amount of reducing agent is added to the exhaust gas stream. 3. In the case of a dynamic correction of the reducing agent velocity, in addition to the temperature of the exhaust gas sensed by the sensor, the exhaust gas temperature during a constant and possibly variable time before the measurement point at the catalyst inlet is taken into account. The method according to claim 1 or 2, wherein 4. The method according to claim 1, wherein the measurement of the NO _x concentration in the exhaust gas is performed downstream of the catalyst for control and regulation purposes.
Or the method of 2. 5. A comparison between a set value and a measured value between the calculated amount of the reducing agent and the amount of the reducing agent added to the exhaust gas, wherein the measured value of the added amount of the reducing agent is arranged at an appropriate position. The method according to claim 1, wherein the method is confirmed by a sensor or a measuring device. 6. The method as claimed in claim 1, wherein the rate of change of the load state of the internal combustion engine is detected and taken into account in the case of a highly dynamic correction of the reductant speed. 7. An actual temperature of intake air during operation of an internal combustion engine is detected by a sensor (20) as an index as to whether or not the actual exhaust gas amount matches a stored reference value of the exhaust gas amount. 3. The method as claimed in claim 1, further comprising: comparing with a set reference value and, if necessary, controlling the correction of the reducing agent rate to be metered into the exhaust gas. 8. The concentration of the stored liquid reducing agent is detected by a sensor, compared with a preset reference value, and measured and introduced into the exhaust gas according to the result of the comparison between the set value and the actually measured value. 3. The method according to claim 1, wherein any necessary correction of the amount of reducing agent is made. 9. The aging induced by the continuation of the operation of the internal combustion engine and of the catalyst and the reduction of the activity of the catalyst associated therewith are taken into account in a controlled manner by a corresponding change in the rate of the reducing agent to be metered into the exhaust gas. The method according to claim 1 or 2, wherein 10. The process as claimed in claim 1, wherein the measured reduction activity of the reference catalyst at different reducing agent concentrations is used for optimizing the reducing agent metering. 11. Dynamically or highly dynamically driven stationary equipment or vehicles, motor vehicles, commercial vehicles, in particular lorries and shared vehicles of all types of construction and use which are incorporated as driving sources. 11. The method according to claim 1, which is used in connection with an internal combustion engine.