Aftertreatment system with two SCR catalysts

Abstract

A system and a process comprise an internal combustion engine capable of generating an exhaust gas stream and an aftertreatment system operationally connected to the exhaust gas stream. The aftertreatment system includes an upstream selective reduction catalyst (SCR) component and a downstream SCR component located in significantly different thermal environments. The upstream and downstream SCR components are sized to fully treat the entire exhaust gas stream under a low-temperature condition of highest NOx conversion, and the downstream SCR component is sized to fully treat the entire exhaust gas stream under a high-temperature condition of highest NOx conversion.

Description

Cross-reference to related registrations:

[0001] The present application claims the priority and effect of the filing date of the US patent application with entry number 13 / 626145, filed on September 25, 2012, and the provisional application with number 61 / 649880, filed on May 21, 2012, which is incorporated herein by reference. BACKGROUND

[0002] 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. SUMMARY

[0003] 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 to be able to fully treat the entire exhaust gas stream under a low-temperature condition of highest NOx conversion, and the downstream SCR component is dimensioned to be able to fully treat the entire exhaust gas stream under a high-temperature condition of highest NOx conversion. Reducing agent supply devices may be present upstream of the upstream SCR component and between the upstream and downstream SCR components.

[0004] The systems, methods, and apparatus also include evaluating a current system operating condition of an internal combustion engine generating an exhaust stream and determining an active SCR component from one of the upstream or downstream components in response to the current system operating condition. In response to the determination of the active SCR component, either a command for an upstream reducing agent supply device or a command for a downstream reducing agent supply device is issued to inject reducing agent.

[0005] These and other aspects, forms, properties, examples of implementation and components are described in more detail below. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Fig. Figure 1 is a schematic diagram of a system that includes an aftertreatment system with two SCR catalyst components.

[0007] 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.

[0008] Fig. Figure 3 is an example of a NOx conversion / temperature relationship.

[0009] Fig. Figure 4 is an example of an NH3 oxidation / temperature relationship. DESCRIPTION OF ILLUSTRATORY EXECUTION FORMS

[0010] 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.

[0011] Referring to Fig. 1 is schematically a system 100 The system is described for the treatment of NOx emissions from an internal combustion engine. 100 contains an internal combustion engine 102 , which produces an exhaust stream 112 generated by the internal combustion engine. 102It can be of any type, including but not limited to a diesel engine. The system 100 It also includes an aftertreatment system that is operationally effective with the exhaust gas stream. 112 is connected. The aftertreatment system includes an upstream SCR component. 104 and a downstream SCR component 106 The SCR components 104 , 106 They can contain the same or different catalyst formulations. The SCR components 104 , 106 The catalyst formulations can be 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.

[0012] In certain embodiments, the upstream SCR component 104formulated as part of a particulate filter. In one example, the upstream SCR component is 104 An SCR catalyst wash coat is present on a diesel particulate filter (DPF). In certain embodiments, the system includes 100 an oxidation catalyst 124 , which is between the engine 102 and the upstream SCR component 104 is arranged. An exemplary system 100 includes the upstream SCR component 104 and / or the oxidation catalyst 124 (where applicable) as a catalyst located close to the engine. "Close to the engine" is to be interpreted broadly in this document. "Close to the engine" can mean as close as practically possible at a point downstream of a turbine component. 114a a turbocharger 114a , 114b arranged within a certain distance downstream of the turbine 114a(for example, 12 inches) arranged, and / or within a specific heat transfer regime (for example, away from an area that is exposed to heat during operation of the system). 100 , such as when the vehicle is moving or subject to significant airflow).

[0013] The system 100 further includes an upstream reducing agent supply device 108 , which are upstream of the upstream SCR component 104 is arranged, and a downstream reducing agent supply device 110 , which are upstream of the downstream SCR component 106 is arranged. The reducing agent supply devices 108 , 110include any type of reducing agent injection nozzle or supply device known in the field, including a urea or ammonia injection nozzle, and further including an air-assisted injection nozzle, liquid-phase or gas-phase injection nozzle.

[0014] The exemplary system 100 It also contains an EGR circuit. 118 with an EGR valve 122 An air intake 116 into the system 100 is fluid-conducting with a compressor side 114b of the turbocharger 114a , 114b connected. The illustrative system 100 It 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 100It contains various sensors and actuators, which are not shown for clarity. The sensors can include, but are not limited to, various temperature sensors, pressure sensors, composition sensors (e.g., NH3, NOx, O2, etc.), and / or velocity sensors.

[0015] The system 100 It also includes a downstream SCR component 106 The downstream SCR component 106 is located opposite the upstream SCR component 104 A significantly different thermal environment. A thermal environment that is significantly different must be comprehensively defined. 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... 106heats 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 is moving, which affects the system). 100 (includes). Another exemplary, significantly different thermal environment is one in which, in a first range of engine operating conditions, the upstream SCR component 104 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 106within a desired operating temperature range. The first range of engine operating conditions and the second range of engine operating conditions can overlap or be completely separate; the only requirement is that the first range of engine operating conditions does not coincide with the second range of engine operating conditions. The desired operating temperature range for each of the SCR components 104 , 106 This can 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 the currently available NO:NO2 ratio at each SCR component 104 , 106 .

[0016] 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, and turbocharger operating characteristics. 114a , 114b (such as wastegate values, VGT position, etc.), operating characteristics of the EGR 118and / or positions or use of any cooler bypass devices (such as EGR cooler or charge air cooler bypasses – not shown). In case of overlap of the first and second ranges of engine operating conditions – for example, when both SCR components 104 , 106 Given operating conditions, the desired operating ranges can be achieved – the control system can 120 NOx emissions with one or both SCR components 104 , 106 to be treated according to any desired operating principles, including, without limitation, all principles contained in the Fig. Section 2, which refers to this section, describes the following: Exemplary operating principles include prioritizing one of the SCR components. 104 , 106 within the shared engine operating ranges (e.g. always using the upstream SCR component) 104within a given shared engine operating range), maintaining a given SCR component 104 , 106 , until a change is necessary because an engine operating range is reached in which only the opposite SCR component is used 104 , 106 is preferred, 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.

[0017] In some embodiments, each of the SCR components 104 , 106 dimensioned to reduce the engine's NOx emissions 102 can treat completely, at least under the engine operating conditions under which the corresponding SCR component 104 , 106is dominant or active. In some embodiments, the upstream SCR component is 104 It is dimensioned to treat the entire exhaust gas flow under conditions of maximum NOx conversion, corresponding to normal operating temperatures. In yet another embodiment, the upstream and downstream SCR components are 104 , 106 dimensioned so that both are fully used for NOx reduction under a first operating condition, such as normal operating temperatures, and the downstream SCR component 106It is dimensioned to be able to fully treat the entire exhaust gas flow under a second operating condition, such as at high operating temperatures. Normal operating temperatures include temperatures that are not high, temperatures that occur during periods when an aftertreatment component is not undergoing thermally based regeneration, temperatures that are not cold or warm-up temperatures, and / or temperatures that are typical for a partially loaded engine.

[0018] A maximum NOx conversion condition corresponds to a condition under 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 maximum NOx conversion condition. Additionally or alternatively, the highest total NOx output of the engine present at any normal operating temperature is a maximum NOx conversion condition. In certain embodiments, an operating condition requiring the highest NOx conversion percentage and / or an operating condition requiring the most difficult-to-achieve NOx conversion percentage is a maximum NOx conversion condition. Examples of maximum NOx conversion conditions include, but are not limited to, the highest NOx output condition of the engine, the highest required NOx conversion percentage (e.g.,93% conversion required) and / or the most difficult-to-achieve NOx conversion percentage (e.g., 85% conversion required at a space velocity value that provides the 85% most difficult-to-achieve NOx conversion percentage within operating conditions that deliver a normal operating temperature, even if higher NOx conversion percentages may be required at lower space velocities). In certain embodiments, the upstream SCR component is... 104 dimensioned so that the required NOx conversion can be achieved under every operating condition within the design limits that occur in the normal operating temperature range, in order to treat the entire exhaust gas flow under the condition of highest NOx conversion corresponding to normal operating temperatures.

[0019] In certain embodiments, the system contains 100 furthermore, a control system 120, which is designed to control certain operating processes for an aftertreatment system for the engine 102 can execute. In certain embodiments, the control system forms 120 A part of a processing subsystem that includes one or more computer devices with storage, processing, and communication hardware. The control system. 120 It can be a single device or a decentralized device, and the functions of the control 120 can be executed by hardware or software. The control 120 It communicates with all devices, sensors and / or actuators as required to perform the functions present in a given embodiment.

[0020] In certain embodiments, the control system includes 120 one or more modules designed to perform the functions of the control system's operating processes 120execute. In certain embodiments, the control includes 120 An operating regime module, an SCR selection module, and an SCR execution module. The description herein, which includes the modules, emphasizes the independent structure of the control aspects. 120 and illustrates a grouping of operational processes and control tasks 120 It is understood that other groupings performing similar general operating processes are within the scope of the present invention. Modules can be implemented as hardware and / or software on a computer-readable medium, and modules can be distributed across various hardware or software components. More detailed descriptions of specific embodiments of the control operating processes are provided in the [reference to be added]. Fig. 2 referenced sections included.

[0021] 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.

[0022] Fig. Figure 2 is a schematic representation of a processing subsystem. 200 with a controller 120 The control 120It includes an operating regime module that evaluates a current system operating condition. Current system operating conditions 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 engine was started, a cumulative operating parameter since the engine 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 an engine load parameter. A cumulative operating parameter since the engine was started includes, but is not limited to, the cumulative total fuel supply, the total engine power output, the vehicle's mileage, and / or the cumulative time spent above an engine load or power threshold.A cumulative operating parameter since a change in the active SCR component includes, without limitation, a cumulative total fuel supply, a total engine power output, a value of the vehicle's miles traveled, a cumulative 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.

[0023] The control 120 It also includes an SCR selection module that selects an active SCR component. 210 in response to the current system operating conditions 208 determines the active SCR component. 210 The SCR component is included 104 , 106 , which are responsible for carrying out NOx conversion processes for the system 100 under the current system operating conditions 208 is preferred. One example is, among others, the inclusion of the active SCR component. 210as an upstream SCR component 104 after a cold start or during operation at low temperatures. An additional or alternative example is, among others, the provision of an active SCR component. 210 than the downstream SCR component 106 during operation at high temperatures and / or during thermal regeneration of one of the aftertreatment components. An additional or alternative example is, among others, the provision of the active SCR component. 210 than the upstream SCR component 104 during operation at nominal temperatures and / or during operation where the downstream SCR component 106 compared to the upstream SCR component 104 not within a clearly preferred temperature range. An additional or alternative example is, among others, the provision of the active SCR component. 210 than the same active SCR component 210from a previous execution cycle of the control system 120 in response to the fact that neither or both of the SCR components 104 , 106 under the current system operating conditions 208 to be given preference.

[0024] The control 120 It also includes an SCR execution module 206 , which is in response to the active SCR component 210 either a command 214 for an upstream reducing agent supply device or a command 212 for a downstream reducing agent supply device. In certain embodiments, the SCR implementation module provides 206 both reducing agent supply device commands 214 , 212 , and furthermore, in certain embodiments, one or both of the reducing agent supply device commands may be 214 , 212 It should be zero. In certain embodiments, the SCR execution module delivers 206the reducing agent supply device command 214 , 212 , which provides the appropriate NOx reduction on the active SCR component 210 This results in certain embodiments where the SCR implementation module delivers 206 the reducing agent supply device commands 214 , 212 , which makes the system acceptable for delivering the appropriate NOx reduction on the active SCR component 210 lead (e.g., switching from the upstream SCR component) 104 to the downstream SCR component 106 as an active SCR component 210 , and shutdown of the upstream reducing agent supply device 108 , while the downstream reducing agent supply device 110 (is started up). In certain embodiments, the SCR execution module delivers 206 the reducing agent supply device command 214 , 212 , which provides the appropriate NOx reduction on the active SCR component210 results in, and furthermore 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 is, for example, to ensure an NH3 supply to storage locations on the SCR component that is the active SCR component. 210 is. The supplied reducing agent feed device commands 212 , 214 They may also be limited by other considerations known in the field, including, for example, limitations on NH3 slip, diagnostic procedures, settings to compensate for the aging of one or more system components, etc.

[0025] In certain embodiments, the SCR selection module 204 Furthermore, in response to a cold start of the engine, it was determined that the upstream SCR component 104 the active SCR component 210Additionally or alternatively, the SCR selection module specifies 204 furthermore, it was determined that the downstream SCR component 106 the active SCR component 210 This occurs 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 determines 206 established that the downstream SCR component 106 the active SCR component 210 is, in response to the fact that an inlet temperature of the upstream SCR component 104 a switching temperature 218 exceeds this limit. An exemplary and non-restrictive switching temperature is 400°C. Temperatures between 250°C and 450°C can be used as switching temperatures. 218can be used when a switching temperature 218 is used. In certain embodiments, the SCR selection module applies 204 Furthermore, a temperature hysteresis on the switching temperature 218 for example 5°C hysteresis, 10°C hysteresis, 25°C hysteresis, 50°C hysteresis or another value.

[0026] In certain embodiments, the operating regime module evaluates 202 furthermore, an upstream oxidative conversion of reducing agent (e.g., as part of the current system operating condition). 208 , or separately (not shown). The SCR selection mode further determines that the downstream SCR component 106 the active SCR component 210 is, in response to the fact that the upstream oxidative conversion of reducing agent reaches a conversion threshold 216exceeds. The upstream oxidative conversion of reducing agent is a measured or modeled occurrence of the oxidation of the reducing agent on the upstream SCR component. 104 The conversion threshold 216 includes any selected value at the upstream SCR component 104 , where example values ​​include 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 applied, which includes the value for the upstream oxidative conversion of reducing agent.

[0027] In certain embodiments, the conversion threshold 216 a dynamic value, which, for example, is determined according to the NOx conversion efficiency of the upstream SCR component 104 and / or the downstream SCR component 106is determined. In the example where the downstream SCR component 106 It is not yet working efficiently, the conversion threshold may be exceeded. 216 so that it is increased to a value that still results in more efficient consumption of reducing agent if NOx continues to be treated at the upstream SCR component. 104 is converted. Furthermore, the conversion threshold can be used in the example. 216 be reduced, while 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 reduced at the downstream SCR component 106 is converted. The conversion threshold 216 In addition to other factors, the certainty or uncertainty of a reducing agent oxidation model and / or NOx reduction models of the SCR components may also be considered. 104 , 106be hired.

[0028] With reference to Fig. 3 will be an example data set 300 The curve shows the NOx conversion of an SCR component as a function of temperature. 302 This document presents 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. 4 will be an example data set 400 The curve represents the NH3 oxidation rate on an SCR component as a function of temperature. 402This presents 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.

[0029] In certain embodiments, the SCR execution module commands 206 Never inject both the upstream and downstream reducing agent supply devices simultaneously if both injections are intended for immediate NOx conversion on the respective SCR component. In certain embodiments, the SCR implementation module commands 206to inject both the upstream reducing agent supply device and the downstream reducing agent supply device 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 is and / or the execution module 206 performs a diagnostic operation.

[0030] 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.

[0031] 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 under a low-temperature condition of highest NOx conversion, with reducing agent being supplied only by the upstream reducing agent supply device, and the downstream SCR component is dimensioned to fully treat the entire exhaust gas stream under a high-temperature condition of highest NOx conversion.

[0032] According to one embodiment of the system, the downstream SCR component is dimensioned to completely treat the entire exhaust gas flow under conditions 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.

[0033] 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 a current system operating condition, an SCR selection module designed to determine an active SCR component in response to the current system operating condition, 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.

[0034] In one embodiment of the control system, the current system operating condition includes at least one condition 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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 condition selected from the following operating conditions: 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.

[0039] From another perspective, 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 under a low-temperature condition of highest NOx conversion; and fully treating the entire exhaust gas stream with the downstream SCR component under a high-temperature condition of highest NOx conversion.

[0040] In one embodiment, the condition for maximum NOx conversion corresponds to normal operating temperatures. In another embodiment, the method involves evaluating a current system operating condition; setting an active SCR component in response to the current system operating condition; 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 condition 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 condition as 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.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 condition 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 the system operating condition is interpreted 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.

[0041] 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, or performing a diagnostic operation.

[0042] According to another aspect, the method involves evaluating a current system operating condition of an internal combustion engine generating an exhaust gas stream; determining an active SCR component in response to the current system operating condition, wherein the active SCR component is selected from either an upstream SCR component or a downstream SCR component located in an aftertreatment system receiving 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.

[0043] In one embodiment of the method, the current system operating condition comprises at least one condition selected from the following: an upstream SCR component temperature, a downstream SCR component temperature, a time elapsed since the engine was started, a cumulative operating parameter since the engine was started, a 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, defining the active SCR component includes defining that the upstream SCR component is the active SCR component when the current system operating condition 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 condition is interpreted as one or more of the following operating conditions: 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.

[0044] 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 condition 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 condition 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.

[0045] 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.

[0046] 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 to fully treat the entire exhaust gas stream under a low temperature condition of highest NOx conversion, wherein reducing agent is supplied only by the upstream reducing agent supply device, and the downstream SCR component is dimensioned to fully treat the entire exhaust gas stream under a high temperature condition of highest NOx conversion. [2] System according to claim 1, wherein the downstream SCR component is dimensioned to fully treat the entire exhaust gas flow under a condition of highest NOx conversion corresponding to normal operating temperatures. [3] System according to claim 1, wherein the upstream SCR component comprises a wash coat on a particle filter. [4] System according to claim 3, wherein the upstream SCR component is arranged close to the motor. [5] System according to claim 4, further comprising an oxidation catalyst arranged between the engine and the upstream SCR component. [6] System according to claim 1, wherein the upstream SCR component contains either a Ce zeolite or an Fe zeolite. [7] System according to claim 1, further comprising a control system, wherein the control system comprises: an operating regime module designed to evaluate a current system operating condition; an SCR selection module designed to determine an active SCR component in response to the current system operating condition; and an SCR execution module designed to provide, in response to the active SCR component, either an upstream reducing agent feed command and / or a downstream reducing agent feed command. [8] System according to claim 7, wherein the current system operating condition comprises at least one condition selected from the following conditions: 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. [9] System according to claim 7, 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. [10] System according to claim 9, wherein 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. [11] System according to claim 7, 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. [12] System according to claim 11, wherein the switching temperature is 400°C. [13] System according to claim 11, wherein the SCR selection module is further configured such that a temperature hysteresis is applied to the switching temperature. [14] System according to claim 7, 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 component in response to the upstream oxidative conversion of reducing agent exceeding a conversion threshold. [15] System according to claim 14, wherein the conversion threshold comprises a value selected from the following values: 5%, 10%, 25%, 30% and 50%. [16] System according to claim 14, 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. [17] System according to claim 7, 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. [18] System according to claim 7, wherein the SCR execution module 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 condition selected from the following operating conditions: 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, performing a diagnostic operation. [19] 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 under a low-temperature condition of highest NOx conversion; and Complete treatment of the entire exhaust gas stream with the downstream SCR component under a high-temperature condition of highest NOx conversion. [20] Method according to claim 19, wherein the condition of highest NOx conversion corresponds to normal operating temperatures. [21] The method of claim 19, further comprising: Evaluating a current system operating condition; Setting an active SCR component in response to the current system operating condition; and In response to the setting 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 reject a reducing agent. [22] Method according to claim 21, further comprising determining that the upstream SCR component is the active SCR component in response to the evaluation of the current system operating condition as a cold start operation of the engine. [23] The method of claim 21, further comprising determining that the downstream SCR component is the active SCR component in response to evaluating the current system operating condition as 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. [24] The method of claim 21, further comprising specifying that the downstream SCR component is the active SCR component in response to the fact that the interpretation of the current system operating condition includes an inlet temperature of the upstream SCR component exceeding a switching temperature. [25] The method of claim 21, further comprising: Evaluating an upstream oxidative conversion of reducing agent when the system operating condition is interpreted; and Determine that the downstream SCR component is the active component in response to the upstream oxidative conversion of reducing agent exceeding a conversion threshold. [26] The method of claim 19, further comprising preventing simultaneous injection of reducing agent with an upstream reducing agent supply device arranged upstream of the upstream SCR component and with a downstream reducing agent supply device arranged between the upstream and downstream SCR components. [27] The method of claim 19, further comprising preventing simultaneous injection of reducing agent with an upstream reducing agent supply device arranged upstream of the upstream SCR component and with a 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. [28] The method of claim 19, further comprising the injection of reducing agent with both an upstream reducing agent supply device arranged upstream of the upstream SCR component and a downstream reducing agent supply device arranged between the upstream and downstream SCR components, during at least one operating condition selected from the following operating conditions: 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, performing a diagnostic operation. [29] Procedures, including: Evaluating a current system operating condition of an internal combustion engine that generates an exhaust gas flow; Determining an active selective reduction catalyst (SCR) component in response to the current system operating condition, 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, the upstream SCR component being located in a significantly different thermal environment than the downstream SCR component; and In response to the setting of the active SCR component, either deliver an upstream reducing agent supply command to an upstream reducing agent supply device located upstream of the upstream SCR component, or deliver a downstream reducing agent supply command to a downstream reducing agent supply device located between the upstream and downstream SCR components. [30] Method according to claim 29, wherein the current system operating condition comprises at least one condition selected from the following conditions: 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. [31] Method according to claim 29, wherein determining the active SCR component includes determining that the upstream SCR component is the active SCR component when the current system operating condition is interpreted as cold start operation of the engine. [32] Method according to claim 29, wherein determining the active SCR component includes determining that the downstream SCR component is the active SCR component when the current system operating condition is interpreted as one or more of the following operating conditions: 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. [33] Method according to claim 29, wherein determining the active SCR component includes determining that the downstream SCR component is the active SCR component when the current system operating condition evaluates that an inlet temperature of the upstream SCR component exceeds a switching temperature. [34] Method according to claim 29, wherein evaluating the current system operating condition 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.