Aftertreatment system with two SCR catalysts

Abstract

System, with: an internal combustion engine that can generate an exhaust stream; an aftertreatment system that is operationally connected to an exhaust gas stream, wherein the aftertreatment system comprises an upstream selective reduction catalyst (SCR) component and a downstream SCR component, wherein the upstream SCR component is located in a significantly different thermal environment than the downstream SCR component when the internal combustion engine generates an exhaust gas stream; an upstream reducing agent supply device located upstream of the upstream SCR component, and a downstream reducing agent supply device located between the upstream and downstream SCR components; and wherein the upstream SCR component and the downstream SCR component are dimensioned such that in a first state of highest NOx conversion, corresponding to at least one of the cold start and warm-up operating conditions of the system, they completely treat the entire exhaust gas flow, with reducing agent being supplied only by the upstream reducing agent supply device, and the downstream SCR component is dimensioned such that in a second state of highest NOx conversion, corresponding to the operating conditions of the system during at least one of a regeneration event of an aftertreatment component and a regeneration event of a particulate filter, it completely treats the entire exhaust gas flow,wherein, during at least one of the regeneration events of the aftertreatment component and the regeneration event of the particulate filter, reducing agent is supplied only from the downstream reducing agent supply device and reducing agent supply from the upstream reducing agent supply device is prevented.

Description

BACKGROUND

[0001] Modern emissions regulations have led to many internal combustion engine applications that use SCR systems to reduce NOx to detection limits. SCR catalyst formulations have a preferred operating temperature range in which NOx conversion is most efficient. Beyond the fact that high efficiency is desirable, higher efficiencies may be required to meet emissions targets, depending on the system design. At very high temperatures, parasitic oxidation reactions of the reducing agent reduce the overall conversion achievable by the SCR system and increase operating costs due to inefficient losses of the reducing agent. Following a cold start, a significant amount of time may be required before the SCR catalyst reaches an effective operating temperature.During operating periods in which another aftertreatment component is being regenerated, for example a particulate filter, the engine outlet temperatures can reach very high temperatures, which are well within the temperature regime of reducing agent oxidation.

[0002] From US 2005 / 0069476 A1, a method for the selective catalytic reduction of NOx in the exhaust gas flowing in the exhaust system of an internal combustion engine is known. The exhaust system has an upstream and a downstream SCR catalyst as well as an upstream and a downstream reducing agent supply device.

[0003] From US 2010 / 0180580 A1, an exhaust gas treatment system for treating an exhaust gas stream containing NOx and particulate matter is known, wherein the exhaust gas system comprises a particulate filter and a flow-through substrate downstream of it. The particulate filter includes a first SCR catalyst for NOx conversion, and the flow-through substrate is provided with a second SCR catalyst for NOx conversion.

[0004] From DE 10 2006 016 906 A1 a device for monitoring an exhaust gas catalyst in the exhaust system of an internal combustion engine is known.

[0005] From US 2012 / 0023905 A1, an exhaust aftertreatment process is known in which an SCR catalyst is provided in the exhaust stream of an internal combustion engine, it is determined that the temperature of the exhaust stream is not within an NH3-based SCR range, and a quantity of unburned hydrocarbon is provided, responding to the fact that the temperature of the exhaust stream is not within the NH3-based SCR range. SUMMARY

[0006] Various systems, devices, and methods for treating an exhaust gas stream generated by an internal combustion engine are disclosed. An upstream selective reduction catalyst (SCR) component and a downstream SCR component are arranged in significantly different thermal environments within the exhaust system. The upstream and downstream SCR components are dimensioned such that, in a first state of highest NOx conversion, corresponding to at least one of the system's cold-start and warm-up operating conditions, they can be used to treat the entire exhaust gas stream. The downstream SCR component is dimensioned such that, in a second state of highest NOx conversion, corresponding to the system's operating conditions during at least one of an aftertreatment component regeneration event and a particulate filter regeneration event, it can also treat the entire exhaust gas stream.Reducing agent supply devices are located upstream of the upstream SCR component and between the upstream and downstream SCR components. During at least one of the regeneration events of the aftertreatment component and the regeneration event of the particulate filter, reducing agent is only supplied from the downstream reducing agent supply device, and the supply of reducing agent from the upstream reducing agent supply device is prevented.

[0007] The systems, methods, and apparatus also include evaluating the current operating state of an internal combustion engine generating an exhaust stream and selecting an active SCR component from one of the upstream or downstream components in response to the current operating state. In response to the selection of the active SCR component, either an upstream reducing agent supply device command is sent to the upstream reducing agent supply device, or a downstream reducing agent supply device command is sent to the downstream reducing agent supply device to inject reducing agent.

[0008] These and other aspects, forms, properties, examples of implementation and components are described in more detail below. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a schematic diagram of a system that includes an aftertreatment system with two SCR catalyst components. Fig. Figure 2 is a schematic diagram of a processing subsystem with a controller that functionally performs operational processes to control a post-treatment system. Fig. Figure 3 is an example of a NOx conversion / temperature relationship. Fig. Figure 4 is an example of an NH3 oxidation / temperature relationship. DESCRIPTION OF ILLUSTRATORY EXECUTION FORMS

[0009] To facilitate a better understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings, which will be described using specific terms. It is understood, however, that this is not intended to limit the scope of the invention, and that all variations and further modifications of the illustrated embodiments, as well as all further applications of the principles of the invention presented therein, which would normally occur to a person skilled in the art in the field relating to the invention, are considered herein.

[0010] Referring to Fig. Figure 1 schematically depicts a system 100 for treating NOx emissions from an internal combustion engine. The system 100 includes an internal combustion engine 102, which generates an exhaust gas stream 112. The internal combustion engine 102 can be of any type, including, but not limited to, a diesel engine. The system 100 further includes an aftertreatment system that is operationally connected to the exhaust gas stream 112. The aftertreatment system includes an upstream SCR component 104 and a downstream SCR component 106. The SCR components 104 and 106 can contain the same or different catalyst formulations. The SCR components 104 and 106 can have catalyst formulations of any type known in the prior art, including, for example, a zeolite-copper formulation and / or a zeolite-iron formulation. Other formulations are conceivable, including vanadium and base metal catalysts, etc.

[0011] In certain embodiments, the upstream SCR component 104 is formulated as part of a particulate filter. In one example, the upstream SCR component 104 is an SCR catalyst wash coat present on a diesel particulate filter (DPF). In certain embodiments, the system 100 includes an oxidation catalyst 124 arranged between the engine 102 and the upstream SCR component 104. An exemplary system 100 includes the upstream SCR component 104 and / or the oxidation catalyst 124 (if present) as a close-coupled catalyst. "Close-coupled" is to be interpreted comprehensively in this document.Proximally close to the engine can mean as close as practically possible to a location downstream of a turbine part 114a of a turbocharger 114a, 114b, located within a certain distance downstream of the turbine 114a (for example, 12 inches), and / or located within a certain heat transfer regime (for example, away from an area that is subject to significant flow during operation of the system 100, such as when the vehicle is moving).

[0012] System 100 further comprises an upstream reducing agent supply device 108, which is arranged upstream of the upstream SCR component 104, and a downstream reducing agent supply device 110, which is arranged upstream of the downstream SCR component 106. The reducing agent supply devices 108 and 110 include any type of reducing agent injection nozzle or supply device known in the trade, including a urea or ammonia injection nozzle, and further including an air-assisted injection nozzle, liquid-phase or gas-phase injection nozzle.

[0013] The exemplary system 100 further includes an EGR circuit 118 with an EGR valve 122. An air inlet 116 into the system 100 is fluidly connected to a compressor side 114b of the turbocharger 114a, 114b. The illustrative system 100 contains certain features and components that may not be present in some embodiments, and other features or components not shown may be present in some embodiments. The system 100 contains various sensors and actuators, which are not shown for clarity. The sensors may include, but are not limited to, various temperature sensors, pressure sensors, composition sensors (e.g., NH3, NOx, O2, etc.), and / or speed sensors.

[0014] System 100 further includes a downstream SCR component 106. The downstream SCR component 106 is located in a thermal environment that is significantly different from that of the upstream SCR component 104. A thermal environment that is significantly different must be comprehensively designed. An example of a significantly different thermal environment is one that varies according to a temperature observed over a period of time after an engine start event, for example, when the downstream SCR component 106 heats up more slowly and / or heats up to a different final temperature than the upstream SCR component 104. Another example of a significantly different thermal environment is one with a differential heat transfer environment, either a static heat transfer environment and / or a dynamic heat transfer environment (e.g., when a vehicle containing System 100 is in motion).Another exemplary, significantly different thermal environment is one in which, in a first range of engine operating conditions, the upstream SCR component 104 is located within a desired temperature operating range (e.g., between 200 °C and 400 °C), and in a second range of engine operating conditions, the downstream SCR component 106 is located within a desired temperature operating range. The first and second ranges of engine operating conditions may overlap or be completely separate; the only requirement is that the first and second ranges of engine operating conditions do not coincide.The desired temperature operating range for each of the SCR components 104, 106 may be the same temperature range or a different temperature range and depends on one or more different factors understood in the field, including, but not limited to: catalyst formulations, space velocity and / or catalyst volume considerations, currently stored amounts of reducing agent at each SCR component 104, 106 and / or currently available NO:NO2 ratio at each SCR component 104, 106.

[0015] Conditions defining a range of “engine operating conditions” are to be interpreted comprehensively and may include information on engine speed, but may alternatively or additionally, without limitation, include vehicle load (such as weight, road gradient, etc.), ambient temperature, ambient pressure, ambient wind speed and direction, vehicle speed, transient or constant operation, injection timing and other characteristics of the engine fuel supply (e.g., post- and / or pilot fuel supply events), the availability and use of hydrocarbon dosing into the aftertreatment system, operating characteristics of turbocharger 114a, 114b (such as wastegate values, VGT position, etc.), operating characteristics of EGR 118 and / or positions or use of any cooler bypass devices (such as EGR cooler or charge air cooler bypasses - not shown).In the event of an overlap between the first and second ranges of engine operating conditions – for example, if both SCR components 104, 106 are within the desired operating ranges for a given operating condition – the control unit 120 can treat NOx emissions with one or both SCR components 104, 106 according to any desired operating principles, including, without limitation, all principles specified in the [reference to be added]. Fig. Section 2 refers to the operating principles described below. Exemplary operating principles include favoring one of the SCR components 104, 106 within the shared motor operating ranges (e.g., always using the upstream SCR component 104 within a given shared motor operating range), maintaining a given SCR component 104, 106 until a switch is necessary because a motor operating range is reached in which only the opposite SCR component 104, 106 is favored, and subsequent switching, and / or applying a hysteresis value to each switch. The hysteresis value can have any unit known in the field, for example, time-based hysteresis, temperature-based hysteresis, motor load-based hysteresis, etc.

[0016] In some embodiments, each of the SCR components 104, 106 is dimensioned to completely treat NOx emissions from the engine 102, at least under the engine operating conditions in which the corresponding SCR component 104, 106 is dominant or active. In some embodiments, the upstream SCR component 104 is dimensioned to treat the entire exhaust gas flow in a state of maximum NOx conversion, corresponding to normal operating temperatures. In yet another embodiment, the upstream and downstream SCR components 104, 106 are dimensioned such that both are fully utilized for NOx reduction in a first operating condition, such as at normal operating temperatures, and the downstream SCR component 106 is dimensioned to completely treat the entire exhaust gas flow in a second operating condition, such as at high operating temperatures.Normal operating temperatures include operating temperatures that are not high operating temperatures, operating temperatures that exist during periods when an aftertreatment component is not undergoing thermally based regeneration, operating temperatures that are not cold or warm-up operating temperatures, and / or operating temperatures that are the operating temperatures of a not fully loaded engine.

[0017] A state of maximum NOx conversion corresponds to a state in which the greatest degree of NOx conversion is expected in the aftertreatment system for the system to comply with emissions regulations and / or achieve the planned emissions target. For example, the highest total NOx output of the engine can be the state of maximum NOx conversion. Additionally or alternatively, the highest total NOx output of the engine present at any normal operating temperature is a state of maximum NOx conversion. In certain embodiments, an operating state requiring the highest NOx conversion percentage and / or an operating state requiring the most difficult NOx conversion percentage to achieve is a state of maximum NOx conversion. Examples of states of maximum NOx conversion include, but are not limited to, the highest NOx output state of the engine, the highest required NOx conversion percentage (e.g., 93% conversion required), and / or the most difficult NOx conversion percentage to achieve.B. 85% conversion is required at a space velocity value that achieves the 85% NOx conversion percentage that is most difficult to achieve within the operating conditions that provide a normal operating temperature (even if higher NOx conversion percentages may be required at lower space velocities). In certain embodiments, the upstream SCR component 104 is dimensioned such that the required NOx conversion can be achieved in every operating condition within the design limits that occur in the normal operating temperature range, in order to treat the entire exhaust gas flow in the state of highest NOx conversion, which corresponds to normal operating temperatures.

[0018] In certain embodiments, the system 100 further includes a controller 120, which is configured to execute certain operating processes for controlling an aftertreatment system for the engine 102. In certain embodiments, the controller 120 forms part of a processing subsystem that includes one or more computer devices with storage, processing, and communication hardware. The controller 120 can be a single device or a distributed device, and its functions can be performed by hardware or software. The controller 120 communicates with all devices, sensors, and / or actuators as necessary to perform the functions present in a given embodiment.

[0019] In certain embodiments, the controller 120 includes one or more modules configured to perform the functions of the controller's operating operations. In certain embodiments, the controller 120 includes an operating regime module, an SCR selection module, and an SCR execution module. The description herein, which includes modules, emphasizes the independent structure of the controller 120's aspects and illustrates a grouping of operating operations and tasks of the controller 120. It is understood that other groupings performing similar general operating operations are within the scope of the present invention. Modules may be implemented as hardware and / or software on a computer-readable medium, and modules may be distributed across different hardware or software components. More detailed descriptions of certain embodiments of the controller's operating operations are provided in the reference to Fig. 2 referenced sections included.

[0020] Certain operating procedures described herein include operations that evaluate one or more parameters. Evaluation, as used in this document, includes receiving values ​​by any method known in the prior art, including at least receiving values ​​from a data link or network communication, receiving an electronic signal (e.g., voltage, frequency, current, or PWM signal) indicative of the value, receiving a software parameter indicative of the value, reading the value from a memory location on a computer-readable medium, receiving the value as a runtime parameter by any means known in the field, and / or receiving a value from which the evaluated parameter can be calculated, and / or referencing a predefined value that is evaluated as the parameter value.

[0021] Fig. Figure 2 is a schematic representation of a processing subsystem 200 with a controller 120. The controller 120 contains an operating regime module that evaluates a current system operating state. The current system operating states include, but are not limited to, the temperature of the upstream SCR component, the temperature of the downstream SCR component, the time elapsed since the motor was started, a cumulative operating parameter since the motor was started, the time elapsed since a change in the active SCR component, and / or a cumulative operating parameter since a change in the active SCR component, and a motor load parameter.An accumulated operating parameter since an engine was started includes, but is not limited to, an accumulated total fuel supply, a total engine power output, a value for the vehicle's miles traveled, and / or an accumulated time above an engine load or power threshold. An accumulated operating parameter since a change in the active SCR component includes, but is not limited to, an accumulated total fuel supply, a total engine power output, a value for the vehicle's miles traveled, an accumulated time above an engine load or power threshold, a total amount of injected reducing agent, and / or a total amount of NOx emitted from the engine.

[0022] The controller 120 further includes an SCR selection module that defines an active SCR component 210 in response to the current system operating state 208. The active SCR component 210 includes the SCR component 104, 106, which is preferred for carrying out NOx conversion processes for the system 100 in the current system operating states 208. One example is, among others, designating the active SCR component 210 as the upstream SCR component 104 after a cold start or during operation at low temperatures. An additional or alternative example is, among others, designating the active SCR component 210 as the downstream SCR component 106 during operation at high temperatures and / or during thermal regeneration of one of the aftertreatment components.The provision of the active SCR component 210 as the upstream SCR component 104 during operation at nominal temperatures and / or during operation in which the downstream SCR component 106 is not in a clearly preferred temperature range compared to the upstream SCR component 104. An additional or alternative example is, inter alia, the provision of the active SCR component 210 as the same active SCR component 210 from a previous execution cycle of the controller 120 in response to the fact that neither or both of the SCR components 104, 106 are preferred in the current system operating states 208.

[0023] The controller 120 further includes an SCR execution module 206, which, in response to the active SCR component 210, provides either an instruction 214 for an upstream reducing agent supply device or an instruction 212 for a downstream reducing agent supply device. In certain embodiments, the SCR execution module 206 provides both reducing agent supply device instructions 214 and 212, and in further embodiments, one or both of the reducing agent supply device instructions 214 and 212 may be zero. In certain embodiments, the SCR execution module 206 provides the reducing agent supply device instruction 214 or 212 that results in the appropriate NOx reduction at the active SCR component 210. In certain embodiments, the SCR execution module 206 provides the reducing agent supply device commands 214, 212, which enable the system to acceptably deliver the appropriate NOx reduction to the active SCR component 210 (e.g.Switching from the upstream SCR component 104 to the downstream SCR component 106 as the active SCR component 210, and shutting down the upstream reducing agent supply device 108 while the downstream reducing agent supply device 110 is powered on). In certain embodiments, the SCR execution module 206 provides the reducing agent supply device command 214, 212, which results in the appropriate NOx reduction on the active SCR component 210, and further provides a reducing agent supply device command 214, 212, which supplies reducing agent to the SCR component that is not the active SCR component 210, for example, to provide an NH3 supply to storage locations on the SCR component that is the active SCR component 210.The supplied reducing agent supply device commands 212, 214 may also be restricted by other considerations known in the field, including, for example, restrictions on NH3 slip, diagnostic procedures, settings to compensate for the aging of one or more system components, etc.

[0024] In certain embodiments, the SCR selection module 204 further specifies that the upstream SCR component 104 is the active SCR component 210 in response to a cold start of the engine. Additionally or alternatively, the SCR selection module 204 further specifies that the downstream SCR component 106 is the active SCR component 210 in response to one or more operating conditions such as: a regeneration event of an aftertreatment component or an impending regeneration event, a regeneration event of a particulate filter or an impending regeneration event, and a high engine load or an impending high engine load. In certain embodiments, the SCR selection module 206 specifies that the downstream SCR component 106 is the active SCR component 210 in response to an inlet temperature of the upstream SCR component 104 exceeding a switching temperature 218.An exemplary and non-restrictive switching temperature is 400 °C. Temperatures between 250 °C and 450 °C can be used as the switching temperature 218 if a switching temperature 218 is used. In certain embodiments, the SCR selection module 204 further applies a temperature hysteresis to the switching temperature 218, for example, 5 °C hysteresis, 10 °C hysteresis, 25 °C hysteresis, 50 °C hysteresis, or another value.

[0025] In certain embodiments, the operating regime module 202 further evaluates upstream oxidative conversion of reducing agent (e.g., as part of the current system operating state 208, or separately – not shown). The SCR selection mode further determines that the downstream SCR component 106 is the active SCR component 210 in response to the upstream oxidative conversion of reducing agent exceeding a conversion threshold 216. The upstream oxidative conversion of reducing agent is a measured or modeled occurrence of the oxidation of the reducing agent at the upstream SCR component 104. The conversion threshold 216 includes any selected value at the upstream SCR component 104, with example values ​​including 5%, 10%, 25%, 30%, and 50% oxidative conversion of the reducing agent.In certain embodiments, a hysteresis value is applied to the conversion threshold 216, which includes the value for the upstream oxidative conversion of reducing agent.

[0026] In certain embodiments, the conversion threshold 216 is a dynamic value, determined, for example, according to the NOx conversion efficiency of the upstream SCR component 104 and / or the downstream SCR component 106. In the example where the downstream SCR component 106 is not yet operating efficiently, the conversion threshold 216 can be increased to a value such that more efficient consumption of reducing agent still occurs when NOx continues to be converted at the upstream SCR component 104. Furthermore, in the example, the conversion threshold 216 can be decreased as the downstream SCR component 106 warms up and reaches a more efficient operating range; and at a certain point, it is determined that more efficient consumption of reducing agent occurs when NOx is converted at the downstream SCR component 106.The conversion threshold 216 can be set in addition to other factors according to a certainty or uncertainty of a reducing agent oxidation model and / or NOx reduction models of the SCR components 104, 106.

[0027] With reference to Fig. Figure 3 presents an exemplary data set 300 for NOx conversion of an SCR component as a function of temperature. Curve 302 provides illustrative data that can be used to determine the NOx conversion efficiency of an SCR component as a function of the SCR component's temperature. Data such as those in Fig. The three values ​​shown are generally known and / or can be easily determined for a specific catalyst and a specific aftertreatment component. With reference to Fig. Figure 4 presents an exemplary data set 400 for NH3 oxidation on an SCR component as a function of temperature. Curve 402 provides illustrative data that can be used to determine the conversion efficiency of the parasitic reducing agent oxidation of an SCR component as a function of the SCR component's temperature. Data such as those in Fig. The four values ​​shown are generally known and / or can be easily determined for a specific catalyst and a specific aftertreatment component.

[0028] In certain embodiments, the SCR execution module 206 never commands both the upstream and downstream reducing agent supply devices to inject simultaneously if both injections are intended for immediate NOx conversion on the respective SCR component. In certain embodiments, the SCR execution module 206 commands both the upstream and downstream reducing agent supply devices to inject during at least one of the following operating conditions: injection overlap during a switchover of the active component 210 (e.g.,from the upstream SCR component 104 to the downstream SCR component 106), preloading either the upstream SCR component 104 or the downstream SCR component 106 if the component to be preloaded is not the active SCR component 210 and / or the execution module 206 is performing a diagnostic operation.

[0029] As can be seen from the illustrations and text presented above, a multitude of aspects and embodiments thereof are conceivable according to the present disclosure.

[0030] According to one aspect, a system comprises an internal combustion engine capable of generating an exhaust gas stream and an aftertreatment system operationally connected to that exhaust gas stream. The aftertreatment system includes an upstream SCR component and a downstream SCR component. The upstream SCR component is located in a significantly different thermal environment than the downstream SCR component during the operation of the internal combustion engine. An upstream reducing agent supply device is located upstream of the upstream SCR component, and a downstream reducing agent supply device is located between the upstream and downstream SCR components.The upstream SCR component and the downstream SCR component are dimensioned to fully treat the entire exhaust gas stream in a low-temperature state of highest NOx conversion, with reducing agent supplied only by the upstream reducing agent supply device, and the downstream SCR component is dimensioned to fully treat the entire exhaust gas stream in a high-temperature state of highest NOx conversion.

[0031] According to one embodiment of the system, the downstream SCR component is dimensioned to completely treat the entire exhaust gas flow in a state of maximum NOx conversion, corresponding to normal operating temperatures. In another embodiment, the upstream SCR component comprises a wash coat on a particulate filter. In a further development of this embodiment, the upstream SCR component is located close to the engine. In a further development of this embodiment, the system includes an oxidation catalyst located between the engine and the upstream SCR component. In yet another embodiment of the system, the upstream SCR component comprises either a copper zeolite or an iron zeolite.

[0032] According to another aspect, a control system is provided that is operational with a system that includes the internal combustion engine. The control system includes an operating regime module designed to evaluate the current system operating state, an SCR selection module designed to specify an active SCR component in response to the current system operating state, and an SCR execution module designed to provide a command for an upstream reducing agent supply device and / or a command for a downstream reducing agent supply device in response to the active SCR component.

[0033] In one embodiment of the control system, the current system operating states include at least one state selected from the following: a temperature of the upstream SCR component, a temperature of the downstream SCR component, a time period since the engine was started, a cumulative operating parameter since the engine was started, a time period since a change in the active SCR component, a cumulative operating parameter since a change in the active SCR component, and an engine load parameter.

[0034] In another embodiment of the control system, the SCR selection module is further configured to determine, in response to a cold start of the engine, that the upstream SCR component is the active SCR component. In another embodiment of the control system, the SCR selection module is further configured to determine, in response to one or more operating conditions selected from: a regeneration event of an aftertreatment component or an impending regeneration event, a regeneration event of a particulate filter or an impending regeneration event, a high engine load, or an impending high engine load.

[0035] In yet another embodiment of the control system, the SCR selection module is further configured to determine that the downstream SCR component is the active SCR component, selected in response to one or more operating conditions from: a regeneration event of an aftertreatment component or an impending regeneration event, a regeneration event of a particulate filter or an impending regeneration event, a high engine load, or an impending high engine load. In another embodiment of the control system, the SCR selection module determines that the downstream SCR component is the active SCR component in response to an inlet temperature of the upstream SCR component exceeding a switching temperature. In a further development of this embodiment, the switching temperature is 400 °C.The SCR selection module can also be designed in such a way that a temperature hysteresis is applied to the switching temperature.

[0036] In another embodiment of the control system, the operating regime module is further configured to evaluate upstream oxidative conversion of reducing agent, and the SCR selection module is further configured to determine that the downstream SCR component is the active component in response to the upstream oxidative conversion of reducing agent exceeding a conversion threshold. In a further development of this embodiment, the conversion threshold comprises a value selected from the following: 5%, 10%, 25%, 30%, and 50%. The SCR selection module can further be configured to apply hysteresis to the upstream oxidative conversion of reducing agent and the conversion threshold.

[0037] In another embodiment of the control system, the SCR execution module of the control system is designed such that the upstream reducing agent supply device and the downstream reducing agent supply device are never ordered to inject reducing agent simultaneously when both injections are intended for immediate NOx conversion on the respective SCR component.In another embodiment of the control, the SCR execution module of the control is configured to command both the upstream reducing agent supply device and the downstream reducing agent supply device to inject reducing agent during at least one operating state selected from the following operating states: injection overlap during an active component switchover, preloading either the upstream SCR component or the downstream SCR component when that upstream SCR component or downstream SCR component is not the active SCR component, and performing a diagnostic operation.

[0038] According to another aspect, a process comprises: operating an internal combustion engine to generate an exhaust gas stream; feeding the exhaust gas stream to an aftertreatment system comprising an upstream SCR component and a downstream SCR component, the upstream SCR component being located in a significantly different thermal environment than the downstream SCR component; fully treating the entire exhaust gas stream with the upstream SCR component and the downstream SCR component in a low-temperature state of highest NOx conversion; and fully treating the entire exhaust gas stream with the downstream SCR component in a high-temperature state of highest NOx conversion.

[0039] In one embodiment, the state of highest NOx conversion corresponds to normal operating temperatures. In another embodiment, the method involves evaluating a current system operating state; setting an active SCR component in response to the current system operating state; and, in response to setting the active SCR component, either delivering a command to an upstream reducing agent supply device located upstream of the upstream SCR component to inject a reducing agent, or delivering a command to a downstream reducing agent supply device located between the upstream and downstream SCR components to reject a reducing agent.In a further development of this embodiment, the method includes specifying that the upstream SCR component is the active SCR component, in response to an evaluation of the current system operating state as a cold start operation of the engine. In another further development of the embodiment, the method includes specifying that the downstream SCR component is the active SCR component, in response to an evaluation of the current system operating state as one or more operating states selected from: a regeneration event of an aftertreatment component or an impending regeneration event, a regeneration event of a particulate filter or an impending regeneration event, a high engine load, or an impending high engine load.In a further refinement of this embodiment, the method involves determining that the downstream SCR component is the active SCR component in response to the fact that the evaluation of the current system operating state reveals that the inlet temperature of the upstream SCR component exceeds a switchover temperature. In another refinement of this embodiment, the method involves evaluating upstream oxidative conversion of reducing agent when interpreting the system operating state and determining that the downstream SCR component is the active SCR component in response to the fact that the upstream oxidative conversion of reducing agent exceeds a conversion threshold.

[0040] In another embodiment, the method involves preventing the simultaneous injection of reducing agent by an upstream reducing agent supply device located upstream of the upstream SCR component and by a downstream reducing agent supply device located between the upstream and downstream SCR components. In yet another embodiment, the method involves preventing the simultaneous injection of reducing agent by an upstream reducing agent supply device located upstream of the upstream SCR component and by a downstream reducing agent supply device located between the upstream and downstream SCR components when both injections are intended for immediate NOx conversion on the respective SCR component.In yet another embodiment, the method involves injecting reducing agent with both an upstream reducing agent supply device located upstream of the upstream SCR component and a downstream reducing agent supply device located between the upstream and downstream SCR components, during at least one operating condition selected from the following: injection overlap during a switchover of the active SCR component, preloading either the upstream SCR component or the downstream SCR component when that upstream SCR component or downstream SCR component is not the active SCR component, and performing a diagnostic operation.

[0041] According to another aspect, the method involves evaluating a current system operating state of an internal combustion engine that generates an exhaust gas stream; determining an active SCR component in response to the current system operating state, wherein the active SCR component is selected from either an upstream SCR component or a downstream SCR component located in an aftertreatment system that receives the exhaust gas stream, the upstream SCR component being located in a significantly different thermal environment than the downstream SCR component;and in response to the activation of the active SCR component, either delivering an upstream reducing agent supply command to an upstream reducing agent supply device located upstream of the upstream SCR component, or delivering a downstream reducing agent supply command to a downstream reducing agent supply device located between the upstream and downstream SCR components.

[0042] According to one embodiment of the method, the current system operating state comprises at least one state selected from the following: the temperature of the upstream SCR component, the temperature of the downstream SCR component, the time elapsed since the engine was started, a cumulative operating parameter since the engine was started, the time elapsed since a change in the active SCR component, a cumulative operating parameter since a change in the active SCR component, and an engine load parameter. In another embodiment of the method, determining the active SCR component involves specifying that the upstream SCR component is the active SCR component when the current system operating state is interpreted as the engine being cold-started.In yet another embodiment of the method, determining the active SCR component involves specifying that the downstream SCR component is the active SCR component when the current system operating state is interpreted as one or more of the following operating states: a regeneration event of an aftertreatment component or an impending regeneration event, a regeneration event of a particulate filter or an impending regeneration event, a high engine load or an impending high engine load.

[0043] In another embodiment of the method, determining the active SCR component is determining that the downstream SCR component is the active SCR component in response to the current system operating state evaluating that an inlet temperature of the upstream SCR component exceeds a switchover temperature. In yet another embodiment of the method, evaluating the current system operating state involves evaluating an upstream oxidative conversion of reducing agent, and determining the active SCR component involves determining that the downstream SCR component is the active SCR component in response to the upstream oxidative conversion of reducing agent exceeding a conversion threshold.

[0044] While the invention has been illustrated and described in detail in the drawings and the preceding description, this must be considered illustrative and non-limiting, since it is understood that only certain exemplary embodiments have been shown and described. It is understood by those skilled in the art that many variations are possible in the exemplary embodiments without substantially departing from this invention. Accordingly, all such variations are to be included within the scope of this disclosure, as defined in the following claims.

[0045] When reading the claims, it is understood that the use of words such as "a," "an," "at least one," or "at least a part" is not intended to limit the claim to only one item, unless expressly stated otherwise in the claim. When terms such as "at least a part" and / or "a part" are used, the item may comprise a part and / or the entire item, unless expressly stated otherwise.

Claims

[1] System, with: an internal combustion engine that can generate an exhaust stream; an aftertreatment system that is operationally connected to an exhaust gas stream, wherein the aftertreatment system comprises an upstream selective reduction catalyst (SCR) component and a downstream SCR component, wherein the upstream SCR component is located in a significantly different thermal environment than the downstream SCR component when the internal combustion engine generates an exhaust gas stream; an upstream reducing agent supply device located upstream of the upstream SCR component, and a downstream reducing agent supply device located between the upstream and downstream SCR components; and wherein the upstream SCR component and the downstream SCR component are dimensioned such that in a first state of highest NOx conversion, corresponding to at least one of the cold start and warm-up operating conditions of the system, they completely treat the entire exhaust gas flow, with reducing agent being supplied only by the upstream reducing agent supply device, and the downstream SCR component is dimensioned such that in a second state of highest NOx conversion, corresponding to the operating conditions of the system during at least one of a regeneration event of an aftertreatment component and a regeneration event of a particulate filter, it completely treats the entire exhaust gas flow,wherein, during at least one of the regeneration events of the aftertreatment component and the regeneration event of the particulate filter, reducing agent is supplied only from the downstream reducing agent supply device and reducing agent supply from the upstream reducing agent supply device is prevented. [2] System according to claim 1, wherein the downstream SCR component is dimensioned to fully treat the entire exhaust gas flow in a third state of highest NOx conversion, which corresponds to normal operating temperatures. [3] System according to claim 1, further comprising an oxidation catalyst upstream of the upstream SCR component, wherein the upstream SCR component comprises a wash coat on a particulate filter, wherein the upstream SCR component is arranged close to the engine, and the upstream reducing agent supply device is arranged downstream of the oxidation catalyst. [4] System according to claim 1, wherein the upstream SCR component contains either a Ce zeolite or an Fe zeolite. [5] System according to claim 1, further comprising a control system, wherein the control system comprises: an operating regime module designed to evaluate the current system operating state; an SCR selection module designed to determine an active SCR component in response to the current system operating state; and an SCR execution module designed to provide a command for the upstream reducing agent supply device and / or a command for the downstream reducing agent supply device in response to the active SCR component. [6] System according to claim 5, wherein the current system operating state comprises at least one state selected from the following states: a temperature of the upstream SCR component, a temperature of the downstream SCR component, a time period since the engine was started, a cumulative operating parameter since the engine was started, a time period since a change in the active SCR component, a cumulative operating parameter since a change in the active SCR component, an engine load parameter. [7] System according to claim 5, wherein the SCR selection module is further configured to determine, in response to a cold start operation of the engine, that the upstream SCR component is the active SCR component. [8] System according to claim 7, wherein the SCR selection module is further configured to determine that the downstream SCR component is the active SCR component in response to a high engine load operating condition or an impending high engine load. [9] System according to claim 5, wherein the SCR selection module determines that the downstream SCR component is the active SCR component in response to an inlet temperature of the upstream SCR component exceeding a switching temperature. [10] System according to claim 9, wherein the switching temperature is 400 °C. [11] System according to claim 10, wherein the SCR selection module is further configured such that a temperature hysteresis is applied to the switching temperature. [12] System according to claim 5, wherein the operating regime module is further configured to evaluate an upstream oxidative conversion of reducing agent, and wherein the SCR selection module is further configured to determine that the downstream SCR component is the active SCR component in response to the upstream oxidative conversion of reducing agent exceeding a conversion threshold, wherein the conversion threshold changes in the opposite direction to the NOx conversion efficiency of the downstream SCR component. [13] System according to claim 12, wherein the conversion threshold comprises a value selected from the following values: 5%, 10%, 25%, 30% and 50%. [14] System according to claim 12, wherein the SCR selection module is further configured such that hysteresis is applied to the upstream oxidative conversion of reducing agent and the conversion threshold. [15] System according to claim 5, wherein the SCR implementation module is designed such that the upstream reducing agent supply device and the downstream reducing agent supply device are never ordered to inject reducing agent simultaneously when both injections are intended to perform immediate NOx conversion on the respective SCR component. [16] System according to claim 5, wherein the SCR implementation module is configured to command both the upstream reducing agent supply device and the downstream reducing agent supply device to inject reducing agent during a diagnostic operation. [17] Procedures, including: Operating an internal combustion engine to generate an exhaust stream; Feeding the exhaust gas stream to an aftertreatment system comprising an upstream selective reduction catalyst (SCR) component and a downstream SCR component, wherein the upstream SCR component is located in a significantly different thermal environment than the downstream SCR component; Complete treatment of the entire exhaust gas stream with the upstream SCR component and the downstream SCR component in a first state of highest NOx conversion, corresponding to a warm-up operating state of the internal combustion engine; and Complete treatment of the entire exhaust gas stream with the downstream SCR component in a second state of highest NOx conversion, which corresponds to operating conditions during at least one regeneration event of an aftertreatment component and a regeneration event of a particulate filter, wherein reducing agent is supplied only from a downstream reducing agent supply device located between the upstream and downstream SCR components, while simultaneous supply of reducing agent from an upstream reducing agent supply device is prevented upstream of the upstream reducing agent supply device. [18] Method according to claim 17, wherein a third state of highest NOx conversion corresponds to normal operating temperatures. [19] The method of claim 17, further comprising: Evaluating the current system operating state; Setting an active SCR component in response to the current system operating state; and In response to the activation of the active SCR component, either a command for an upstream reducing agent supply device to an upstream reducing agent supply device located upstream of the upstream SCR component to inject a reducing agent, or a command for a downstream reducing agent supply device to a downstream reducing agent supply device located between the upstream and downstream SCR components to inject a reducing agent. [20] The method of claim 19, further comprising specifying that the upstream SCR component is the active SCR component in response to the fact that the current system operating state is a cold start operation of the engine. [21] The method of claim 19, further comprising specifying that the downstream SCR component is the active SCR component in response to a high engine load operating condition or an impending high engine load. [22] Method according to claim 19, further comprising specifying that the downstream SCR component is the active SCR component in response to the interpretation of the current system operating state that an inlet temperature of the upstream SCR component exceeds a switching temperature. [23] The method of claim 19, further comprising: Evaluating an upstream oxidative conversion of reducing agent when interpreting the system operating state; and Specify that the downstream SCR component is the active SCR component in response to the upstream oxidative conversion of reducing agent exceeding a conversion threshold, where the conversion threshold changes in the opposite direction to the NOx conversion efficiency of the downstream SCR component. [24] The method of claim 17, further comprising preventing the simultaneous injection of reducing agent with the upstream reducing agent supply device arranged upstream of the upstream SCR component and with the downstream reducing agent supply device arranged between the upstream and downstream SCR components when both injections are intended to effect immediate NOx conversion on the respective SCR component. [25] The method of claim 17, further comprising the injection of reducing agent with both the upstream reducing agent supply device arranged upstream of the upstream SCR component and the downstream reducing agent supply device arranged between the upstream and downstream SCR components during a diagnostic operation. [26] Procedures, comprehensive: Evaluating the current system operating state of an internal combustion engine that generates an exhaust gas stream; Determining an active selective reduction catalyst (SCR) component in response to the current system operating state, wherein the active SCR component is selected from either an upstream SCR component or a downstream SCR component arranged in an aftertreatment system receiving the exhaust gas stream, wherein the upstream SCR component is located in a significantly different thermal environment than the downstream SCR component; wherein Determining the active SCR component includes determining that the upstream SCR component is the active SCR component when the current system operating state is evaluated as a cold start operation of the engine; Determining the active SCR component includes determining that the downstream SCR component is the active SCR component when the current system operating state is evaluated as one or more regeneration events of an aftertreatment component and a particulate filter; and In response to the determination that the downstream SCR component is the active SCR component, a command is provided for a downstream reducing agent supply device to a downstream reducing agent supply device located between the upstream and downstream SCR components, while preventing simultaneous reducing agent supply from an upstream reducing agent supply device located upstream of the upstream SCR component. [27] Method according to claim 26, wherein the current system operating state comprises at least one state selected from the following states: a temperature of the upstream SCR component, a temperature of the downstream SCR component, a time period since the engine was started, a cumulative operating parameter since the engine was started, a time period since a change in the active SCR component, a cumulative operating parameter since a change in the active SCR component, an engine load parameter. [28] Method according to claim 26, wherein determining the active SCR component includes determining that the upstream SCR component is the active SCR component when the current system operating state is evaluated as the engine warm-up operation. [29] Method according to claim 26, wherein determining the active SCR component further includes determining that the downstream SCR component is the active SCR component when the current system operating state is evaluated as a high engine load or an impending high engine load. [30] Method according to claim 26, wherein determining the active SCR component includes determining that the downstream SCR component is the active SCR component when the current system operating state is evaluated as an inlet temperature of the upstream SCR component that exceeds a switching temperature. [31] Method according to claim 26, wherein evaluating the current system operating state includes evaluating an upstream oxidative conversion of reducing agent, and determining the active SCR component includes determining that the downstream SCR component is the active SCR component in response to the upstream oxidative conversion of reducing agent exceeding a conversion threshold, wherein the conversion threshold changes in the opposite direction to a NOx conversion efficiency of the downstream SCR component. [32] Method according to claim 17 or 26, further comprising an oxidation catalyst upstream of the upstream SCR component, wherein the upstream SCR component comprises a wash coat on a particulate filter, wherein the upstream SCR component is located close to the engine, and the upstream reducing agent supply device is located downstream of the oxidation catalyst.

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