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    • 专利摘要:
    A method for managing an SCR catalyst system composed of a first SCR catalyst (12) and a second SCR catalyst (13), comprising a step of controlling the NH3 mass flow rate downstream of the first SCR catalyst (12).
    公开号:FR3071010A1
    申请号:FR1858093
    申请日:2018-09-10
    公开日:2019-03-15
    发明作者:Frank Schweizer
    申请人:Robert Bosch GmbH；
    IPC主号:
    专利说明:

    Field of the invention
    The present invention relates to a method for managing an SCR catalyst system composed of a first SCR catalyst and a second SCR catalyst as well as a computer program and a machine-readable memory medium and a electronic control apparatus for implementing the method.
    State of the art
    To comply with the increasingly strict emission regulations (Euroô, Tier2Bin5 and other emission regulations) it is necessary to reduce the nitrogen oxides (NOx) of the exhaust gases of internal combustion engines, in particular diesel engines. For this, it is known to install an SCR catalyst (selective catalytic reduction catalyst) in the exhaust gas system of internal combustion engines to reduce the nitrogen oxides contained in the exhaust gases of the combustion engine. internally in the presence of a reducing agent to obtain nitrogen. This significantly reduces the nitrogen oxide content of the exhaust gas. To carry out the reduction, ammonia (NH3) is used, which is mixed with the exhaust gases. NH3 ammonia or reagents releasing NH3 ammonia are measured in the exhaust gas line. In general, an aqueous urea solution called HWL solution is used for this, which is injected into the exhaust gas pipe upstream of the SCR catalyst. This solution develops ammonia as a reducing agent. Such an aqueous 32.5% urea solution is known, marketed under the brand AdBlue®. For an SCR catalyst system ensuring a high conversion rate of nitrogen oxides, the SCR catalyst must be managed so that it is permanently filled to a certain level with the reducing agent ammonia. The efficiency of an SCR catalyst depends on the temperature, the space velocity (RG) and, quite decisively, also on the filling level NH3.
    SCR catalysts accumulate by absorption on their surface, a certain amount of ammonia. Thus, for NOx reduction in addition to the ammonia introduced directly by metering (in the form of HWL) there is also accumulated NH3 ammonia which increases the yield compared to an empty catalyst system. The capacity depends on the respective operating temperature of the catalyst. The lower the temperature, the greater the storage capacity. When the catalyst has completely filled its accumulator, there may be a slip of ammonia during sudden variations in charge, even if no more reducing agent is introduced by dosing. In the case of ammonia slip, only part of the ammonia contained in the reducing agent, upstream of the SCR catalyst in the exhaust gases, will be transformed by the SCR catalyst.
    To achieve as high a NOx conversion rate as possible, it is essential to operate the SCR system with a high NH3 filling level. To increase the SCR efficiency more quickly after a cold start, i.e. CO2 neutral, the SCR catalyst is installed closer to the engine and partly combined with a diesel particulate filter (filter DPF) thus forming an SCRF catalyst (designation of an SCR catalyst on a diesel particulate filter). However, also near the engine, the temperature gradient increases and the temperature level in the maximum load range reaches an absolute level, too high for the SCR operating mode. This is why, in general, we have a second SCR catalyst which is, if necessary, housed under the floor. For the operation of an SCRF / SCR system, especially when two metering valves are used, optimal cooperation is required between the SCRF catalyst and the second SCR catalyst to achieve very high efficiency of NOx separation. In the case of two metering valves, the first metering valve is installed upstream of the SCRF catalyst and the second metering valve is installed downstream of the SCR catalyst.
    In current systems for an SCRF catalyst, there are two set filling levels, a minimum difference for a reduced NOx yield without NH3 slip or a certain slip and a maximum filling level for a high NOx conversion for a low NH3 slip up to at around 200 ppm. First of all, the SCRF catalyst is operated with a maximum filling level, the NOx yield is very high, and the NH3 slip generated using the second SCR catalyst is absorbed. For a low NOx slip but a high NH3 slip of the SCRF catalyst, the filling level NH3 in the second SCR catalyst is quickly reached above the minimum level of the second SCR catalyst. The minimum filling level of the second SCR catalyst in itself produces a high NOx conversion but does not yet have the capacity of the filling level for NH3 sliding from the SCRF catalyst. If the NH3 filling level in the second SCR catalyst is above the minimum filling level and below the maximum filling level, the NH3 setpoint filling level in the SCRF catalyst is reduced according to an interpolation coefficient . If the filling level in the second SCR catalyst increases to or exceeds the maximum filling level, the NH3 setpoint filling level in the SCRF catalyst is lowered to the minimum filling level to avoid NH3 slippage. The process described works well and a system composed of two SCR catalysts can thus, in principle, be controlled. However, the method has the disadvantage of reacting only after the reaction of the NH3 slip, that is to say of the NH3 filling level of the second SCR catalyst and not as soon as a difference appears between the current NH3 slip and the NH3 slip desired. This means that the control system quickly tends to over-oscillate, causing the good NOx characteristic to be lost.
    Presentation and advantages of the invention
    The present invention aims to remedy these drawbacks and thus relates to a method for managing a system of SCR catalysts composed of a first SCR catalyst and a second SCR catalyst, comprising a step of regulating the mass flow NH3 in downstream of the first SCR catalyst.
    The expressions “NH3 mass flow” and “NH3 slip” are synonymous. Advantageously, the NH3 slip or the NH3 slip deviation from a set value upstream of the second SCR catalyst can be detected earlier, which makes it possible to influence the evolution of the NH3 filling level of the second catalyst earlier.
    SCR only if the regulation was made exclusively according to the filling level NH3 of the second SCR catalyst. This procedure avoids a large overshoot of the NH3 filling level in the second SCR catalyst and thus allows much more precise and more robust regulation.
    According to another preferred development, the regulation of the NH3 mass flow downstream of the first SCR catalyst is carried out by a first regulation of the actual value of the NH3 mass flow downstream of the first SCR catalyst on the reference value of the NH3 mass flow downstream of the first catalyst. This regulation is advantageously done by regulating the actual value over the set value.
    As in general there are only sensors between the first SCR catalyst and the second SCR catalyst, the expression "downstream of the first SCR catalyst" is synonymous with the expression "upstream of the second SCR catalyst".
    Preferably, the set value of the mass flow NH3 of the first catalyst is determined by a model of the second catalyst SCR. To determine the target value of the NH3 mass flow upstream of the second SCR catalyst, an appropriate catalyst model is used which is able to calculate an NH3 mass flow conforming to reality. As a variant or in addition to the model, the target value of the NH3 mass flow can be calculated analytically.
    Regardless of how the NH3 mass flow rate setpoint is calculated, the optimum NH3 mass flow can be sought. For stationary conditions and a regulated NH3 filling level in the first SCR catalyst, the NH3 filling level of the second SCR catalyst must not change. This means that the NH3 mass flow rate in the second SCR catalyst which is the sum of the NH3 mass flow rate leaving the first SCR catalyst and the quantity dosed upstream of the first SCR catalyst must be stoichiometrically equal to the NH3 consumption in the second SCR catalyst ; the latter is equal to the product of the mass flow NOx downstream of the first SCR catalyst and the current yield of the second SCR catalyst.
    If you want to increase the NH3 filling level of the second SCR catalyst, you can do this by increasing the NH3 mass flow rate leaving the first SCR catalyst or by injecting ammonia using a second metering valve. upstream of the second SCR catalyst if there is such a second metering valve.
    But if it is necessary to decrease the filling level NH3 in the second SCR catalyst, it is necessary to lower the NH3 slip leaving the first SCR catalyst. If the NH3 setpoint of the SCR model is used, it is possible to iterate the model data using iteration using simulation methods based on measurements. In this case, the maximum possible overall NOx performance must be reached for an acceptable NH3 slip downstream of the second SCR catalyst.
    According to a preferred development, if the NH3 filling level in the first SCR catalyst is stationary and regulated, the NH3 filling level in the second SCR catalyst is constant. This has the advantage of a steady state which can be achieved as already described above.
    According to another preferred development, the real value of the NH3 mass flow rate downstream of the first SCR catalyst is measured between this first SCR catalyst and the second SCR catalyst using a sensor. Preferably, the sensor is an NH3 sensor. This has the advantage of being able to determine the NH3 mass flow very precisely.
    Alternatively or in addition, the mass flow of ammonia between the two SCR catalysts can be determined using a NOx sensor (see document DE 10 2016 201 602 A1); this document describes a process for determining the mass flow rate of ammonia between two SCR catalysts installed one behind the other in the exhaust gas pipe. This solution has the advantage of saving an NH3 sensor. The use of an NH3 sensor has the advantage of giving a very precise value of the NH3 slip upstream of the second SCR catalyst and of thus being able to determine, from the sum signal of the NOx sensor sensitive transversely to the NH3 ammonia, the NOx mass flow upstream of the second SCR catalyst in an equally precise manner. In this case, the precise values of the mass flow rates of NOx and NH3 upstream of the second SCR catalyst are known.
    According to another advantageous characteristic, the set value of the mass flow NH3 downstream of the first SCR catalyst is the product of the current yield of the model of the second SCR catalyst and of the mass flow NOx upstream of the second SCR catalyst. This characteristic has the advantage that in this case, the NH3 mass flow rate downstream of the first SCR catalyst is exactly equal to the NH3 consumption modeled in the second catalyst. This NH3 mass flow setpoint corresponds to the NH3 consumption in the second SCR catalyst. The NOx mass flow upstream of the second SCR catalyst is preferably measured using a NOx sensor.
    The actual NH3 value can be changed quickly and simply, for example, according to the NOx efficiency demands of the catalyst model for the first SCR catalyst. Each SCR catalyst has a fixed relationship between the NOx conversion and the NH3 slip for a given NH3 filling level and an SCR temperature. For an increasing demand in NOx yield, the catalyst receives a higher quantity of dosage directly the quantity of prior order, increased and indirectly by the regulation process which, constantly compares, the mass flow NOx downstream of the second SCR catalyst with the model. The NH3 slip increases as a function of the physical filling level. The demand for NOx yield for the analytical catalyst model is modified as best as possible by modifying the frequency coefficient of NOx. The frequency coefficient can be used as an adjustment variable for regulation.
    According to another development, as a function of the regulation difference which corresponds to the difference between the actual value of the mass flow NH3 downstream of the first SCR catalyst and the set value of the mass flow NH3 downstream of the first SCR catalyst, the output of the first regulator changes the current performance of the second SCR catalyst model. Preferably, the regulation output regulates an updated yield of the model by modifying the frequency coefficient used in the model for NOx in the first SCR catalyst.
    The frequency coefficient A of the Arrhenius equation, according to collision theory, is the product of the number of collisions Z and the orientation coefficient P. In the particular case of monomolecular reactions, the Arrhenius equation described in chemical kinetics the quantitative dependence between the reaction rate constant k and the temperature. This equation is expressed as follows:
    F Λ k = A e "'Τ',
    In this formula:
    Ea is the activation energy, R is the universal constant of ideal gases, T is the temperature in K, and A is the pre-exponential factor.
    Preferably, if the temperature of the first SCR catalyst is lower than the lower temperature threshold or higher than the upper temperature threshold, the regulation output of the first regulation does not change. The lower temperature threshold is preferably equal to 250 ° C. The upper temperature threshold is preferably 550 ° C. At low temperatures, for example at temperatures below 250 ° C., the NH3 filling level in the first SCR catalyst is not raised as strongly to generate the NH3 slip, which is also not advantageous because of the reduction filling level required in the event of heating. On the other hand, for very high temperatures, for example above 550 ° C, parasitic influences result from oxidation. For these reasons, the correction quantity must be limited to an intermediate range, which is advantageously achieved by the characteristics indicated.
    Preferably, the above process has a second regulation of the filling level NH3 of the second SCR catalyst. In general, the NH3 slip downstream of the first SCR catalyst is a rapid regulation quantity. The significantly more inert NH3 filling level in general of the second SCR catalyst is preferably regulated by a second regulation loop. Preferably, the first regulation and the second regulation are coupled to each other.
    According to a preferred development, the second regulation regulates the filling level of the first SCR catalyst and of the second SCR catalyst between a minimum filling level and a maximum filling level. The filling level of the second SCR catalyst is regulated to its minimum filling level if the first SCR catalyst is at the maximum filling level. Preferably, the first SCR catalyst is regulated as a function of the overall filling level of the first and second SCR catalyst which is maximum if the first SCR catalyst is regulated on the maximum filling level and the second SCR catalyst is regulated on the level minimum filling. If the first SCR catalyst has a minimum filling level and the second SCR catalyst has a maximum filling level, then the overall yield is minimum.
    According to a preferred embodiment, the first SCR catalyst is managed to generate, on the stoichiometric level, a NOx mass flow rate as large as the NH3 mass flow rate, which has the advantage of keeping a constant NHR filling level in the second catalyst. SCR.
    According to another preferred embodiment, the set value of the NH3 mass flow rate downstream of the first SCR catalyst is multiplied with a multiplicative correction coefficient and an offset is added. Thus, both the multiplicative correction coefficient and the offset are chosen on a characteristic curve. The characteristic curve of the multiplicative correction coefficient as well as the characteristic curve of the offset have as parameter a second regulation deviation which corresponds to the difference between the reference value of the filling level NH3 of the second catalyst SCR and actual value of its filling level NH3. The modifications mentioned in the regulation circuit, that is to say the modification of the set value of the NH3 mass flow downstream of the first catalyst
    SCR in the first regulation circuit by multiplying with the correction coefficient and the possible addition of the offset is advantageously obtained by regulating the filling level NH3 of the second SCR catalyst.
    According to a preferred embodiment, if the reference value of the NH3 filling level of the second SCR catalyst is equal to the real value of its NH3 filling level, the multiplicative correction coefficient is equal to 1 and the offset is zero. In this case, the NH3 filling level of the second catalyst is regulated and there is no need to intervene any longer in the regulation of the first regulation circuit; this is why the multiplicative correction coefficient is equal to 1 and the offset is equal to 0.
    According to another preferred embodiment, if the reference value of the NH3 filling level of the second SCR catalyst is greater than the actual value of the NH3 filling level of the second SCR catalyst, the multiplicative correction coefficient is equal to 1 and the offset is greater than 0. In this case, the NH3 filling level of the second catalyst must be increased. For this, among other things, the multiplicative correction coefficient is fixed at 1 and the offset at a value greater than 0, which advantageously makes it possible to increase the real value of the filling level NH3.
    According to another preferred embodiment, if the reference value of the NH3 filling level of the second SCR catalyst is lower than the actual value of the NH3 filling level of the second SCR catalyst, the correction coefficient must be reduced and an equal offset must be applied to 0. In this case, the filling level of the second catalyst must be lowered and for this, a multiplicative correction coefficient of less than 1 is chosen because this advantageously lowers the set value of the mass flow NH3 downstream of the first SCR catalyst.
    The computer program is designed to apply the steps of the process, especially when the program is executed by an electronic control device or a computer. This allows the process to be implemented in the existing control device without having to make constructive changes. To do this, the computer program is saved on a machine-readable memory medium. Running the computer program on a regular electronic control device will keep the electronic control device designed to manage an SCR catalyst system composed of a first SCR catalyst and a second SCR catalyst.
    drawings
    The present invention will be described below in more detail with the aid of an exemplary embodiment of a catalyst system, shown in the accompanying drawings in which:
    Figure 1 is a diagram of a SCR catalyst system composed of two SCR catalysts for the implementation of the process of the invention, Figure 2 shows the NOx and NH3 emissions downstream of the SCR catalyst of a catalyst system for a certain temperature and as a function of the filling level NH3 of the SCR catalyst by describing different operating points of the catalyst used according to the method of the invention, FIG. 3 shows a diagram of the flow of signals for the operation of an example of embodiment of the method of the invention, FIG. 4 shows the results of measurements in a system of SCR catalysts composed of two SCR catalysts applying the method of the invention, FIG. 5 shows a simplified flowchart of the method of managing a system of SCR catalysts.
    Description of embodiments
    Figure 1 shows an example of the arrangement of components in the exhaust gas line of an internal combustion engine fitted with two SCR catalysts. Such an exhaust gas post-treatment installation advantageously applies the method of the invention. However, the process can also be applied in other exhaust aftertreatment plants that have two or more SCR catalysts. According to this embodiment of the exhaust gas post-treatment installation, in the direction of passage of the exhaust gases, there is first of all a Diesel oxidation catalyst (DOC) 10 followed downstream of a dosing installation 11 of the reagent used in SCR installations. Downstream of this, according to the direction of passage of the exhaust gases, a first SCR 12 catalyst functions as a particulate filter with an SCR coating (SCRF coating). Downstream of the first SCR catalyst 12, there is a second catalyst SCR catalyst 13. Finally, there is another catalyst which, in this case, is a cleaning catalyst (CuC) 14 to complete the post-treatment of the gases of 'exhaust. The arrow represents the direction of passage of the exhaust gases. Various sensors are provided, in particular nitrogen oxide sensors 15, an NH3 sensor 16 and temperature sensors 17. The values entered using sensors 15, 16, 17 are used for carrying out the process.
    Figure 2 shows the NOx sensor signal 20 downstream of the first SCR catalyst 12. As the NOx sensor is sensitive transversely to ammonia NH3, the NOx sensor signal 20 is the sum of the simple signal 22 corresponding to NOx and the signal simple 24 for NH3; these signals correspond to a parabolic curve. The simple signal 24 for NH3 was measured with an NH3 sensor. The simple signal 22 for NOx is calculated as the difference between the NOx sensor signal 20 and the simple signal 24 for NH3. The NOx sensor signal 20 has a characteristic trace for a conventional SCR catalyst at a certain temperature. The NOx sensor signal 20 is a function of the filling level NH3 of the first SCR catalyst 12. It is known, according to the state of the art, to manage a single SCR catalyst in the range D in which the SCR catalyst has a low NH3 fill level so that there is no NH3 slip. The operating point is certainly on the NOx side to have a stable adaptation of the system, that is to say of the NOx regulation. The setpoint or model value is far from the minimum of the sum curve to have the necessary regulation reserve.
    By managing a system with two SCR catalysts, when the stationary operating conditions are reached, it is possible to adjust the operating point B for which, downstream of the first SCR catalyst 12, as many nitrogen oxides are generated stoichiometrically NOx than NH3 slip. This means that the filling level NH3 will not change in the second SCR 13 catalyst because the nitrogen oxides NOx and the ammonia NH3 leaving the first catalyst are completely transformed. If due to a dynamic modification or a flow in the whole system, it is necessary to increase the filling level NH3 in the second catalyst SCR 13, which corresponds to a cooling of the second catalyst SCR 13, one can shift the operating point in direction C, which consists in supplying more ammonia NH3 than nitrogen oxides NOx.
    If it is necessary to reduce the NH3 filling level of the second SCR 13 catalyst, which corresponds to an increase in temperature of the second SCR 13 catalyst, the operating point can be shifted in direction A to have more oxides of NOx nitrogen than NH3 ammonia.
    The advantage is that at operating points A, B or C of the first SCR 12 catalyst of a global system composed of two SCR catalysts, the NOx performance is considerably increased compared to that of the usual operating point D. By optimizing the design, one can substantially halve the NOx slip, generally after the first SCR 12 catalyst relative to the operating point D used in the usual process.
    Figure 2 shows that the NH3 slip is the decisive quantity to determine where we really are. Points A, B, C have very little difference in efficiency because the simple signal 22 representing NOx is at this point very flat. The difference between the simple signal 24 for NH3 and which increases sharply with increasing NH3 fill level is much more significant. This means that by switching between points A, B, C, the NH3 mass flow emitted by the first SCR 12 catalyst can vary very quickly in percentage.
    Figure 3 shows the basic operation of the method of the invention in the form of a representation of the signal flow. The first regulation which regulates a real value 100 of the mass flow NH3, downstream of the first SCR catalyst 12 according to a setpoint 101 of the mass flow NH3 after the first catalyst, is carried out by determining the regulation difference 102 by the operator “minus” 104 and thus we obtain the characteristic curve 106. If, beforehand, the second regulation circuit 110 is not taken into account, the operator “minus” 104 subtracts the reference value 101 from the mass flow NH3 downstream of the first SCR 12 catalyst relative to the actual value 100 of the mass flow NH3 after the first SCR 12 catalyst, which gives the regulation deviation 102. The characteristic curve 106 assigns to the regulation deviation 102 a new efficiency model 108 which is then used mainly to adapt the setpoint 101 of the mass flow NH3 downstream of the first catalyst and thus recalculate it. The nominal value 101 of the mass flow NH3 downstream of the first catalyst is calculated as a product of the mass flow NOx 112 upstream of the second catalyst 13 and of the current-model output 114 of the second SCR catalyst 13. The new model output 108 is however corrected by a temperature-dependent correction 116 to obtain the new model yield 109. The temperature-dependent correction 116 has two inputs for an output from a limit characteristic curve 118 for a maximum correction coefficient and for an output from a curve limit characteristic 120 for a minimum correction coefficient; both the limit characteristic curve 118 of the maximum correction coefficient and the limit characteristic curve 120 of the minimum correction coefficient each have, as input variable, the average temperature 122 of the first SCR catalyst 12. The correction 116 depends on the temperature the fact that above an upper temperature threshold and below a lower temperature threshold, the model-current yield 114 does not continue to vary.
    The second regulation 110 modifies the first regulation presented above in the following manner. The “minus” operator 130 forms a second regulation deviation 136 as the difference between the reference value 132 of the filling level NH3 in the second SCR catalyst 13 and the actual value 134 of the filling level NH3 in the second catalyst SCR 13. The characteristic curve 140 applies a multiplication correction coefficient 142 to the second regulation difference 136 and a characteristic curve 144 applies an offset 146 to the second regulation difference 136. The reference value 101 of the mass flow NH3 downstream of the first catalyst SCR 12 is multiplied by the multiplicative correction coefficient 142 and to the result obtained, the offset 146 is added; a corrected reference value 150 is thus obtained of the NH3 mass flow downstream of the first SCR catalyst
    12.
    Taking into account the second regulation 110, the regulation difference 102 is formed as the difference between the corrected set value 150 of the mass flow NH3 downstream of the first SCR catalyst and the actual value 100 of the mass flow NH3 downstream of the first catalyst SCR 12.
    Each model yield corresponds to a certain frequency coefficient of the Arrhenius equation for NOx. As the regulation presented above however modifies the model efficiency, we do not obtain a determined frequency coefficient but a frequency range for the first SCR catalyst 12. This frequency range can be adapted in another main regulation circuit, when NH3 slip occurs downstream of the second SCR catalyst over the lifetime of the overall system.
    FIG. 4 shows the measurements of a method according to the invention in a critical situation. We enter a series of measured variables as a function of time. FIG. 4 has four measurement windows 190. In the measurement window 190 at the top, the temperature 200 in the first SCR catalyst 12 and the temperature 202 in the second SCR catalyst 13 is shown. In the second measurement window 190, we have the minimum NH3 filling level 204 in the first SCR 12 catalyst, the maximum NH3 filling level 206 in the first SCR 12 catalyst, the setpoint 208 of the NH3 filling level in the first SCR 12 catalyst as well as its level NH3 filling level 210. In the third measurement window 190, the minimum NH3 filling level 212 is shown in the second SCR 13 catalyst, the maximum NH3 filling level 214 in the second SCR 13 catalyst as well as the set value 132 of the filling level NH3 in the second SCR catalyst 13. In the fourth measurement window 190, the slip NH3 218 is shown downstream of the first SCR catalyst 12, the value of cons igne 220 of the NH3 slip downstream of the first SCR catalyst 12 and the multiplier correction coefficient 222.
    A high load point or operating point or a regeneration in the nitrogen oxide storage catalyst (also called NSC catalyst) develops a strong temperature gradient. This temperature threshold affects the first SCR 12 catalyst and increases the temperature of the first SCR 12 catalyst by about 25 seconds, which is just above 200 ° C to around 400 ° C. This temperature increase first of all lowers the setpoint 208 of the NH3 filling level in the first SCR catalyst 12 and also delayed the setpoint 132 of the NH3 filling level in the second SCR catalyst 13. The value of setpoint 220 of the NH3 slip downstream of the first SCR 12 catalyst is determined so that the NH3 filling level of the second SCR 13 catalyst remains if possible within the limits between the minimum NH3 filling level 212 and the maximum NH3 filling level 214. If the temperature 200 of the first SCR 12 catalyst is less than 280 ° C, the set value 220 of the NH3 slip and the actual value 218 of the NH3 slip are practically zero (see temperature 200) and the NH3 slip 218 downstream of the first catalyst SCR 12 and the NH3 slip setpoint 220 downstream of the first SCR 12 catalyst are in a range between 1675 and 1725 seconds. From around 280 ° C in the first SCR 12 catalyst, the limit characteristic curve 120 allows a minimum correction coefficient of the NH3 slip regulator. In the following (see the range after 1725 seconds), the NH32I8 slip after the first SCR 12 catalyst follows the setpoint 220 of the NH3 slip downstream of this first SCR 12 catalyst.
    FIG. 5 shows a method 300 for managing a system of SCR catalysts composed of a first SCR catalyst 12 and a second SCR catalyst 13. In the first step 310, the mass flow NH 3 is regulated downstream of the first catalyst SCR 12. Thus, in a first regulation, the actual value 100 of the mass flow NH3 downstream of the first catalyst SCR 12 is regulated to the setpoint 101 of the mass flow NH3 downstream of the first catalyst 12.
    The target value 101 of the NH3 mass flow downstream of the first SCR 12 catalyst is determined using a model of the second SCR 13 catalyst.
    The reference value 101 of the mass flow NH3 downstream of the first SCR catalyst 12 is calculated as a product of the current model output 114 of the second catalyst SCR 13 and of the mass flow NOx 112 upstream of the second catalyst SCR 13.
    In a second step 320, as a function of the regulatory difference 102 which is the difference between the actual value 100 of the mass flow NH3 downstream of the first SCR catalyst 12 and the set value 101 of the mass flow NH3 downstream of this first SCR catalyst 12, the regulator output 108 of the first regulation modifies the current model efficiency of the model of the second SCR catalyst 13.
    If the temperature of the first SCR catalyst 12 is lower than the lower temperature threshold or higher than the upper temperature threshold, the regulation output 108 of the first regulator remains unchanged.
    According to another step 330, the second regulation 110 regulates the filling level NH3 of the second SCR catalyst 13. The second regulation 110 regulates the filling levels of the first SCR catalyst 12 and of the second SCR catalyst 13 between each time a minimum filling level 204, 212 and a maximum filling level 206, 214; if the first SCR 12 catalyst is at the maximum filling level 206, the filling level of the second SCR 13 catalyst will be adjusted to the minimum filling level 212 of this second SCR 13 catalyst.
    Downstream of the first SCR catalyst 12, the target value 101 of the mass flow NH3 is multiplied by the multiplicative correction coefficient 142 and an offset 146 is added; both the multiplicative correction coefficient 142 and also the offset 146 will be chosen using a characteristic curve 140, 144; both the characteristic curve 140 for the multiplication correction coefficient 142 and also the characteristic curve 144 for the offset 146 will be considered as parameters of a second regulation deviation 136 representing the difference between the reference value 132 of the filling level NH3 of the second SCR 13 catalyst and of the actual value 134 of the filling level NH3 of the second SCR 13 catalyst.
    NOMENCLATURE OF MAIN ELEMENTS
    Diesel oxidation catalyst
    First SCR catalyst
    Second SCR catalyst
    Cleaning catalyst
    Nitrogen oxide sensor
    NH3 sensor
    Temperature sensor
    NOx sensor signal
    Simple NOx signal
    NH3 single signal
    100 Actual value of the NH3 mass flow downstream of the first SCR 12 catalyst
    101 NH3 mass flow rate setpoint downstream of the first SCR 12 catalyst
    102 Regulatory deviation
    104 "Less" operator
    106 Characteristic curve
    109 Model performance
    110 Second regulation circuit
    112 NOx mass flow upstream of the second SCR 13 catalyst
    114 Current model performance
    116 Temperature dependent correction coefficient
    118 Limiting characteristic curve
    120 Limiting characteristic curve
    122 Average temperature of the first SCR 12 catalyst
    130 "Less" operator
    132 NH3 filling level setpoint for the second SCR 13 catalyst
    136 Second regulation deviation
    140 Characteristic curve
    142 Multiplier coefficient
    144 Characteristic curve of the second regulation deviation 136
    146 Offset
    150
    190
    200
    202
    212
    214
    218
    220 ο
    222
    300
    Setpoint corrected for NHR mass flow Fourth measurement window
    Temperature in the first SCR 12 catalyst
    Temperature in the second SCR 13 catalyst
    Minimum NH3 filling level downstream of the first SCR 12 catalyst
    Maximum filling level
    NH3 slip value
    Set value for NH3 slip after the first SCR 12 catalyst
    Multiplicative correction coefficient
    Method for managing a catalyst system
    310,320, Steps of Method 300 for Managing a System of
    330 SCR catalysts
    权利要求:
    Claims (10)
    [1" id="c-fr-0001]
    1 °) Method (300) for managing a system of SCR catalysts composed of a first SCR catalyst (12) and a second SCR catalyst (13), method characterized in that it comprises a regulation step (310) NH3 mass flow downstream of the first SCR catalyst (12).
    [2" id="c-fr-0002]
    2) Method (300) according to claim 1, characterized in that the regulation of the NH3 mass flow downstream of the first SCR catalyst (12) comprises a first regulation of a real value (100) of the NH3 mass flow downstream of the first SCR catalyst (12) on a set value (101, 150) of the NH3 mass flow downstream of the first catalyst (12).
    [3" id="c-fr-0003]
    3 °) Method (300) according to claim 2, characterized in that the target value (101, 150) of the NH3 mass flow is determined downstream of the first catalyst (12) by a model of the second SCR catalyst (13) .
    [4" id="c-fr-0004]
    4 °) Method (300) according to claim 2 or 3, characterized in that the target value (101, 150) of the NH3 mass flow downstream of the first SCR catalyst (12) is calculated as a product of the current yield of the model (114) of the second SCR catalyst (13) and of the NOx mass flow (112) upstream of the second SCR catalyst (13).
    [5" id="c-fr-0005]
    5 °) Method (300) according to claim 4, characterized in that as a function of a regulation deviation (102) which corresponds to the difference of the actual value (100) of the mass flow NH3 downstream of the first SCR catalyst (12) and the set value (101, 150) of the NH3 mass flow downstream of the first SCR catalyst (12), the regulation output (108, 109) of the first regulation is modified according to the current efficiency of the model of the second SCR catalyst (13).
    [6" id="c-fr-0006]
    6 °) Process (300) according to the preceding claim, characterized in that if the temperature of the first SCR catalyst (12) is less than a lower temperature threshold or more than an upper temperature threshold, the output of regulation (108, 109) of the first regulation.
    [7" id="c-fr-0007]
    7 °) Method (300) according to one of the preceding claims, characterized by a second regulation (110) which regulates (330) the NH3 filling level of the second SCR catalyst (13).
    [8" id="c-fr-0008]
    8 °) Method (300) according to one of the preceding claims, characterized in that the second regulation (110) regulates the filling level of the first SCR catalyst (12) and of the second SCR catalyst (13) each time between a level minimum filling (204, 212) and a maximum filling level (206, 214), and in the case where the first SCR catalyst (12) has a maximum filling level (206), the filling level of the second is regulated SCR catalyst (13) on the minimum filling level (212) of the second SCR catalyst (13).
    [9" id="c-fr-0009]
    9 °) Process (300) according to claim 7 or 8, characterized in that the target value (101) of the NH3 mass flow rate downstream of the first SCR catalyst (12) is multiplied by a multiplicative correction coefficient (142) and adding an offset (146), the multiplicative correction coefficient (142) and the offset (146) being chosen respectively on a characteristic curve (140, 144), and at the same time the characteristic curve (140) for the coefficient multiplicative correction (142) and the characteristic curve (144) for the offset (146) have as parameter a second regulation deviation (136) which corresponds to the difference of the set value (132) 5 of the filling level NH3 of the second SCR catalyst (13) and the actual value (134) of the NH3 filling level of the second SCR catalyst (13).
    [10" id="c-fr-0010]
    10 °) computer program designed to execute the steps of method 10 (300) according to one of claims 1 to 9, and memory medium readable by a machine comprising the computer program, and electronic control apparatus for managing using the method (300) according to one of claims 1 to 9, an SCR catalyst system composed of a first SCR catalyst (12) and a second SCR catalyst (13).
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    同族专利:
    公开号 | 公开日
    DE102017216082A1|2019-03-14|
    FR3071010B1|2021-04-09|
    US10753255B2|2020-08-25|
    US20190078481A1|2019-03-14|
    CN109488421A|2019-03-19|
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    法律状态:
    2019-09-23| PLFP| Fee payment|Year of fee payment: 2 |
    2020-07-31| PLSC| Search report ready|Effective date: 20200731 |
    2020-09-21| PLFP| Fee payment|Year of fee payment: 3 |
    2021-09-27| PLFP| Fee payment|Year of fee payment: 4 |
    优先权:
    申请号 | 申请日 | 专利标题
    DE102017216082.9A|DE102017216082A1|2017-09-12|2017-09-12|A method of operating an SCR catalyst system comprising a first SCR catalyst and a second SCR catalyst|
    DE102017216082.9|2017-09-12|
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