Exhaust gas treatment system and method for treating an exhaust gas stream

专利摘要:
An exhaust gas treatment system arranged for the treatment of an exhaust gas stream is presented. According to the present invention, the exhaust gas treatment system comprises: a first oxidation catalyst 310 arranged to oxidize nitrogen and / or hydrocarbon compounds in said exhaust stream; a first dosing device arranged downstream of said first oxidation catalyst and arranged to supply a first additive in said exhaust gas stream; a first reduction catalyst device arranged downstream of said first dosing device and arranged to reduce nitrogen oxides in said exhaust gas stream by utilizing said first additive; a particulate filter arranged downstream of said first reduction catalyst device and arranged to capture soot particles in said exhaust stream; a second dosing device arranged downstream of said particle filter and arranged to supply a second additive in said exhaust gas stream; and - a second reduction catalyst device arranged downstream of said second dosing device and arranged for a reduction of nitrogen oxides in said exhaust gas stream by using at least one of said first and said second additives; and - a catalytic oxidizing coating, which is arranged downstream of said first reduction catalyst device and upstream of said second reduction catalyst device and is arranged to oxidize soot particles and one or more of nitric oxide and incompletely oxidized carbon compounds in said exhaust stream. 3
公开号:SE1450230A1
申请号:SE1450230
申请日:2014-02-28
公开日:2015-08-29
发明作者:Magnus Nilsson；Henrik Birgersson
申请人:Scania Cv Ab；
IPC主号:

专利说明:

TECHNICAL FIELD The present invention relates to an exhaust gas treatment system according to the preamble of claim 1 and a method for exhaust gas treatment according to the preamble of claim 12.
The present invention also relates to a computer program and a computer program product, which implement the method according to the invention.
Background The following background description constitutes a description of the background of the present invention, and thus does not necessarily constitute prior art.
Due to increased government interests regarding pollution and air quality, especially in urban areas, emission standards and emission rules for internal combustion engines have been developed in many jurisdictions.
Such emission or emission standards often constitute sets of requirements which define acceptable limits on exhaust emissions from internal combustion engines in, for example, vehicles. For example, levels for emissions of nitrogen oxides NOR, hydrocarbons CRHy, carbon monoxide CO and PM particles are often regulated for most types of vehicles in these standards. Vehicles equipped with internal combustion engines typically give rise to these emissions to varying degrees. This document describes the invention mainly for its application in vehicles. However, the invention can be used in essentially all applications where internal combustion engines are used, for example in vehicles, such as in ships or aircraft / helicopters, whereby rules and / or 2 standards for these applications limit the emissions from the internal combustion engines.
In a penalty to meet such emission standards, the exhaust gases caused by the combustion engine's combustion are treated (purified).
A common way of treating exhaust gases from an internal combustion engine consists of a so-called catalytic purification process, for which vehicles equipped with an internal combustion engine usually comprise at least one catalyst. There are different types of catalysts, where the different and different types can be suitable depending on, for example, which combustion concepts, combustion strategies and / or industry types are used in the vehicles and / or which types of compounds in the exhaust stream are to be purified. For at least nitrous gases (nitrogen monoxide, nitrogen dioxide), referred to in this document as nitrogen oxides NOR, vehicles often include a catalyst in which an additive is supplied to the exhaust stream resulting from the combustion engine combustion to achieve a reduction of nitrogen oxides NO mainly to nitrogen gas and water vapor. This is described in more detail below.
A common type of catalyst for this type of reduction, especially for heavy vehicles, Or SCR (Selective Catalytic Reduction) catalysts. SCR catalysts usually use ammonia NH3, or a composition from which ammonia can be generated / formed, as an additive which is used for the reduction of the nitrogen oxides NO in the exhaust gases. The additive is injected into the exhaust stream resulting from the internal combustion engine and tightened on the catalyst. The additive fed to the catalyst is adsorbed (stored) in the catalyst, in the form of ammonia NH3, whereby a redox reaction 3 can take place between nitrogen oxides NO in the exhaust gases and ammonia NH3 available through the additive.
A modern internal combustion engine is a system where there is a collaboration and mutual impact between the engine and exhaust gas treatment. In particular, there is a link between the ability to reduce nitrogen oxides NO in the exhaust gas treatment system and the fuel efficiency of the internal combustion engine. For the internal combustion engine, there is also a connection between the engine's industry efficiency / efficiency and its produced nitrogen oxides NOR. This connection indicates that for a given system there is a positive connection between produced nitrogen oxides NO and the fuel efficiency, it viii to say that an engine that is allowed to emit more nitrogen oxides NO can be phased to consume less fuel by, for example, the injection time can be chosen more optimally. a higher combustion efficiency. Correspondingly, there is a negative connection between a produced particulate mass PM and the fuel efficiency, which means that an increased emission of particulate mass PM from the engine is linked to an increase in fuel consumption. These relationships form the background for the widespread use of exhaust gas treatment systems including an SCR catalyst, where it is intended to optimize the industry and particulate matter against a relatively larger amount of nitrogen oxides NOR produced. A reduction of these nitrogen oxides NO is then carried out in the exhaust gas treatment system, which may therefore comprise an SCR catalyst. Through an integrated approach to the design of the engine and exhaust gas treatment system, where engine and exhaust gas treatment complement each other, a high industry efficiency can therefore be achieved together with legal emissions of both PM and nitrogen oxides NOR. Brief Description of the Invention To some extent, the performance of the exhaust gas treatment systems can be increased by increasing the substrate volumes contained in the exhaust gas treatment systems, which in particular reduces the losses due to uneven distribution of the exhaust gas flow through the substrates.
At the same time, a larger volume of substrate gives a greater back pressure, which to some extent can counteract gains in industry efficiency from the higher degree of conversion. Larger substrate volumes also entailed an increased cost. It is therefore important to be able to make optimal use of the exhaust gas treatment systems, for example by avoiding oversizing and / or by limiting the size and / or manufacturing cost of the exhaust gas treatment systems.
The function and efficiency of catalysts in general, and of reduction catalysts in particular, are strongly dependent on the temperature of the reduction catalyst. In this document, a temperature Over reduction catalyst meant a temperature in / at / for the exhaust stream through the reduction catalyst. The substrate will assume this temperature due to its ability to heat exchange. At a low temperature above the reduction catalyst, the reduction of nitrogen oxides NO is typically inefficient. The NO2 / NOx content in the exhaust gases constitutes a certain possibility of increasing the catalytic activity, even at lower exhaust gas temperatures. However, the temperature above the reduction catalyst and the NO2 / NOx content are generally responsive to control, as they largely depend on factors unknown in advance, for example on how the driver drives the vehicle. For example, the temperature above the reduction catalyst depends on the torque required by a driver and / or a cruise control, on the appearance of the road section on which the vehicle is located and / or on the driver's cross style.
Previously known exhaust gas treatment systems, such as the system described in detail below which many manufacturers have used to meet the Euro VT emission standard (hereinafter referred to as the "EuroVI system"), include a primary oxidation catalyst, a diesel particulate filter and a reduction catalyst. the mass / inertia of catalysts / filters and the large thermal mass / inertia of the rest of the exhaust gas treatment system, including for example exhaust pipes, silencers and various connections. For example, for cold starts, both engine and exhaust gas treatment systems are cold, and for load paths from low exhaust temperatures, when more torque than before is required, for example cid ldtt city corn overgring in country road corn or after idle and power take-off operation, above all the diesel particulate filter's large thermal mass / fidelity the temperature of the reduction catalyst is only slowly increased in such previously known exhaust gas treatment systems. This improves, for example in cold starts and in vehicle operation with temperature and / or river transient elements, the function of the reduction catalyst, and thereby thereby the reduction of nitrogen oxides NOR. This accumulation can result in substandard exhaust gas purification, which risks further polluting the environment. In addition, the deterioration of the function of the reduction catalyst increases the risk of non-compliance with requirements set by the authorities on exhaust gas purification. Fuel consumption can also be negatively affected by the impaired function, as fuel energy death may need to be used to, via various temperature-raising Atgarder, increase the temperature and efficiency of the reduction catalyst.
It is an object of the present invention to improve the purification of the exhaust gases in an exhaust gas treatment system, at the same time as the hazardous exposures for achieving a higher industry efficiency are improved.
These objects are achieved by the above-mentioned exhaust gas treatment system according to the characterizing part of claim 1. The object is achieved above by the above-mentioned method according to the characterizing part of claim 12. The object is achieved above by the above-mentioned computer program and the computer program product.
By utilizing the present invention, a more temperature-efficient treatment of the exhaust gases is obtained in that the upstream-mounted first reduction catalyst device in the exhaust gas treatment system according to the invention can operate at more favorable temperatures than the temperatures of the downstream-mounted second reduction catalyst device. For example, when the first reduction catalyst device at cold starts and path pulls from low temperatures has previous operating temperatures at which an effective reduction of nitrogen oxides NO is obtained. Thus, according to the invention, the available heat is utilized in a more energy-efficient way, which results in an earlier and / or more efficient reduction of nitrogen oxides NOR, for example at cold starts and at pathways from low exhaust temperatures, than has been possible with the previously known exhaust gas treatment systems. .
Correspondingly, in certain other operating types, the second downstream mounted reduction catalyst device may operate at more favorable temperatures than the temperatures of the first upstream mounted reduction catalyst device.
By utilizing the invention, different thermal inertia is obtained for the first and the second reduction catalyst device, which means that these first 7 and the second reduction catalyst devices can be optimized differently with respect to activity and selectivity. Thereby, the first and second reduction catalyst devices can be optimized from a system perspective, the viii saga from a perspective that looks at the function of the entire exhaust gas treatment system, and can therefore be used together to provide an overall more efficient purification of the exhaust gases than the separately optimized catalysts could have provided . These optimizations of the first and second reduction catalyst devices according to the invention can be used to provide this overall more efficient purification in, for example, cold start, but also in substantially all vehicle operation, since temperature and / or flow transient elements often occur even in normal vehicle operation. As mentioned above, the invention can also be used for exhaust gas purification in other units than vehicles, such as in different types of vehicles, whereby an overall more efficient purification of the exhaust gases from the unit is obtained.
The present invention utilizes the thermal inertia / mass having the particulate filter to an advantage of the function by, based on this inertia, optimizing the operation of both the first and second reduction catalyst devices. The present invention thereby provides an interaction / symbiosis between the first reduction catalyst device, which is optimized for the first thermal mass and the first temperature function / temperature gradient to which it is exposed, and the second reduction catalyst device, which is optimized for the second thermal mass and the second temperature course. to which it is exposed.
In addition, the utilization of two oxidizing steps in the exhaust gas treatment system of the present invention provides the viii saga utilization of the first oxidation catalyst mounted upstream of the upstream first reduction catalyst device and of the particulate filter mounted downstream of the downstream first reduction catalyst device, respectively. the second reduction catalyst device. As a result, the proportion of the total conversion of nitrogen oxides NO that takes place via a fast reaction wave, the viii saga via fast SCR ("solid SCR") (Jar reduction takes place via reaction waves over both nitrogen monoxide NO and nitrogen dioxide NO2, Okas. The increased proportion of conversion through fast SCR means that the response with which the NOR conversion takes place Okas and that the requirements in the catalyst volume are reduced.Speed SCR is described in more detail below.
The first oxidation catalyst mounted upstream of the upstream first reduction catalyst device can also be used to create heat in the exhaust gas treatment system of the present invention. The first oxidation catalyst can create this heat because it is designed, among other things, to oxidize hydrocarbon compounds in the exhaust stream, which creates heat. This generated heat can, according to one embodiment, be used in regenerating any exhaust gas treatment component, such as for example by a reduction catalyst device or by the particulate filter in the exhaust gas treatment system, whereby a robust regeneration can be effected by utilizing the present invention.
The first reduction catalyst device and / or the second reduction catalyst device can thus be optimized based on properties, for example catalytic properties, for the second reduction catalyst device and / or the first reduction catalyst device. For example, the second reduction catalyst device can be designed / selected so that its catalytic properties at low temperatures become less efficient, which enables its catalytic properties at high temperatures to be optimized. If these catalytic properties of the second reduction catalyst device are taken into account, then the catalytic properties of the first reduction catalyst device can then be optimized in that it need not be as efficient at high temperatures.
These possibilities for optimizing the first reduction catalyst device and / or the second reduction catalyst device mean that the present invention provides an exhaust purifier which is lamped for emissions which occur in essentially all types of caftan, especially for highly transient operation which gives a varying temperature and / or river profile. . Transient operation may, for example, include relatively few starts and decelerations for the vehicle or relatively few uphill and downhill slopes. Since relatively few vehicles, such as buses that often stop at hillside locations and / or vehicles that drive in city traffic or hilly topography, experience transient operation, the present invention provides an important and very useful exhaust gas purification, which overall reduces emissions from the vehicles in which it implemented.
The present invention therefore utilizes the previously problematic thermal mass and the wire exchange has primarily the particle filter in the EuroVI system as a positive property. The exhaust gas treatment system of the present invention can, in a manner similar to the EuroVI system, contribute heat to the exhaust stream and the downstream mounted catalytic converter device for shorter periods of slack or other bed temperature operation if this bed temperature operation has been carried out by operation with higher operating temperatures. Due to its thermal inertia, the particulate filter is hotter than the exhaust stream, so the exhaust stream can be heated by the particulate filter.
In addition, this good property is supplemented by the fact that the first reduction catalyst device located upstream, especially in transient operation, can utilize the higher temperature which arises at path. Thus, the first reduction catalyst device experiences a higher temperature after the path than the second reduction catalyst device experiences. This higher temperature of the first reduction catalyst device is utilized by the present invention to improve the NOx reduction of the first reduction catalyst device. The present invention, which utilizes two reduction catalyst devices, can utilize both of these positive properties by providing an opportunity for NOx reduction with a small thermal inertia, i.e. the exhaust gas treatment system according to the invention comprises both an NOx conversion upstream of a star thermal inertia and a NOx conversion downstream of a star thermal inertia. The exhaust gas treatment system according to the present invention can, in an energy-efficient manner, make maximum use of available heat.
The first oxidation catalyst creates Oven heat during the oxidation of, among other things, hydrocarbon burns. By means of the present invention, this heat can also be used to improve the NOx reduction of the first reduction catalyst device. Thus, according to the present invention, the various components of the exhaust gas treatment system and their products from the exhaust gas purification can be used to provide an overall efficient exhaust gas treatment system. The exhaust gas treatment system according to the present invention has the potential to meet the emission / emission requirements of the Euro VI emission standard. In addition, the exhaust gas treatment system of the present invention has the potential to meet the emission / emission requirements of several other existing and / or future emission standards.
The exhaust gas treatment system according to the present invention can be made compact as the input units, for example the reduction catalyst devices, do not have to be large in volume. As the size of these units is reduced by the present invention, the exhaust back pressure can also be limited, which results in lower fuel consumption for the vehicle. Catalytic performance per unit volume of substrate can be exchanged for a smaller volume of substrate to obtain some catalytic purification. For an exhaust gas cleaning device with a predetermined size and / or a predetermined external geometry, which is often the case in vehicles with limited space for the exhaust gas treatment system, a smaller volume of a larger volume than the exhaust gas purification device for the predetermined size can be used for distribution and distribution. the exhaust gas stream with the exhaust gas purification device. This means that the exhaust back pressure can be reduced for an exhaust gas cleaning device with a predetermined size and / or a danger-driven external geometry if the performance per substrate volume unit is increased. Thus, the total volume of the exhaust gas treatment system of the invention can be reduced as compared with at least some prior art systems. Alternatively, the exhaust back pressure can be reduced by utilizing the present invention.
By utilizing the present invention, the need for an Exhaust Gas Recirculation (EGR) system can also be reduced or completely eliminated. Reducing the need for utilization of exhaust gas pipeline systems has, among other things, 12 components related to robustness, gas exchange complexity and power output.
In order to achieve a sufficient nitrogen dioxide-based (NO2-based) soot oxidation, the engine ratio between nitrogen oxides and soot (NOdsot ratio), as well as the control of the reducing agent dosing by means of the first upstream mounted dosing device in the exhaust gas treatment system according to the invention, must meet certain criteria.
The oxidizing coating, for example comprising noble metal, which in EuroVI systems is in the oxidation catalyst DOC can according to an embodiment of the invention be at least partially implemented for example in the diesel particulate filter DPF, whereby conditions for a sufficient NO2-based sotoxidation can be obtained. By using a diesel particulate filter DPF with oxidation catalyst properties, an increased predictability for the formation of nitrogen dioxides NO2 can also be obtained. This is because deactivation of the catalytically active states, such as, for example, deactivation caused by phosphorus, often has an axial concentration gradient. This means that catalysts of relatively short physical length may be more susceptible to these poisonings than catalysts of greater physical length. Since, for example, noble metal, such as Platinum, is deposited on the physically long diesel particulate filter DPF, instead of on the physically shorter first oxidation catalyst DOC], more stable levels of nitrogen dioxide NO2 can potentially be obtained over time.
According to an embodiment of the present invention, the supply of the first additive is controlled by using the first dosing device based on a distribution of the ratio between nitrogen dioxide and nitrogen oxides NO2 / NO x in the first reduction catalyst device. This has an advantage in that the dosing of the first additive by means of the first dosing device cid can be controlled so that the exhaust gas stream always contains a proportion of nitrogen dioxide NO2 when it reaches the particle filter. This enables a good nitrogen dioxide-based (NO2-based) sotoxidation in the particle filter and an effective reduction of nitrogen oxides NO in the first reduction catalyst device via so-called "rapid SCR", as described in more detail above / below.
The present invention also has an advantage in that two dosing devices cooperating are used in combination for dosing the reducing agent, for example urea, upstream of the first and second reduction catalyst devices, which relieves and facilitates mixing and possible evaporation of the reducing agent, since the injection of the reducing agent is distributed between two positions. . This reduces the risk of the reducing agent locally cooling down the exhaust gas treatment system, which can potentially form deposits at the positions where the reducing agent is injected, or downstream of these positions.
The relief of the evaporation of the reducing agent means that the exhaust back pressure can potentially be reduced as the requirement for NOx conversion per reduction step is reduced, whereby the amount of reducing agent that must be evaporated is reduced by injecting the reducing agent between two positions, compared to the previous single dosing position. It is also possible with the present invention to switch off dosing in one dosing position in order to then heat away any precipitates which may occur. Thereby, for example, a larger dosage amount (a more abundant dosage) in the first dosing position of the first reduction catalyst device can be allowed, since any precipitates can be heated away at the same time as the emission requirements 14 are met by the second reduction catalyst device in the meantime. This larger / more abundant dosage can be seen as a more aggressive dosage, which gives dosage amounts closer / above a dosage limit value at which a risk of precipitation / crystallization of additives arises. As a non-limiting example, if the only dosing device in the EuroVI system had been optimized to provide an evaporation and distribution of the reducing agent which gives 98% NOR conversion, then the NOR conversion for the two respective reduction catalyst devices in the exhaust gas treatment system according to the present invention is collected, for example to 60% and 95%, respectively. The amounts of reducing agent that must be evaporated in the respective two positions become lower, and the distributions of the reducing agent also do not need to be as optimized in the system according to the invention as in the EuroVI system. An optimal and homogeneous distribution of the reducing agent, as required by the EuroVI system, often gives a high exhaust back pressure because an advanced fermentation / mixing must be used when the reducing agent is to be mixed with the exhaust gases, ie with the nitrogen oxides NOR. Since less high demands on optimal and homogeneous distribution of the reducing agent are placed on the system according to the present invention, there is a possibility of lowering the exhaust back pressure according to the present invention.
The two dosing positions used in the present invention thus mean that in total more additives can be supplied to the exhaust stream than if only one dosing position had been used in the system. This means that a improved performance can be provided.
The present invention thus provides a relief of the mixture and the possible evaporation. On the one hand, the double dosing positions allow the reducing agent to be mixed and possibly evaporated in two positions instead of in a position as in the EuroVI system, and on the other hand, the double dosing positions allow lower conversion rates, and clamed dosing with less adverse exchange can be used.
The influence of the size of the conversion rates and the dosage variation is described in more detail below.
For embodiments which use additives in liquid form, the evaporation is also improved when the system according to the invention is used. This is partly due to the fact that the total amount of additives to be supplied to the exhaust gas stream is divided into two physically separate dosing positions and partly because the system can be loaded harder than systems with only one dosing position. The system can be loaded harder because the dosage in the position where residues of additives may arise if necessary can be reduced / shut down with the system according to the invention, at the same time as criteria for the total emissions can be met.
The exhaust gas treatment system of the present invention provides the oven with robustness against failure of a metered amount of reducing agent.
According to an embodiment of the present invention, a NOx sensor is placed between the two dosing devices in the exhaust gas treatment system. This makes it possible to correct a possible dosing error in the first dosing device during dosing with the second dosing device.
Table 1 below shows a non-limiting example of which conversion rates and emissions are the result of a 10% dosing error for the reducing agent for a case of 10 g / kWh NOR. In the system with a reduction step, 98% NOx conversion is requested according to the example. To provide 98% NOx conversion in the two-stage exhaust gas treatment system, 60% NOx conversion is required for the first reduction catalyst device and 95% NOx conversion for the second reduction catalyst device. As shown in the table, a system with a reduction step, as for example in the Euro-VI system, gives the emission 1.18 g / kWh. Two reduction steps, as in a system according to the present invention, per figure according to the example emission 0.67 g / kWh. This considerably lower resulting emission for the system of the present invention is the mathematical result of utilizing the two dosing points / reduction steps, as shown in Table 1. The NOx sensor placed between the two dosing devices per this possibility to correct for the dosing error at the first dosing device when dosing with the second dosing device gars.
Required conversion rate Achieved conversion. degree with 10% dose error Achieved Emission [g / kWh] One red. Step 98% 88.2% 1.18 Two red. Step I98% Step 1 - 60% 54.0% 4.60 Step 2 - 95% 85.5% I.
Table 1 This embodiment can be implemented with an added addition in complexity, since a NOx sensor that already exists in the current EuroVI system can be used for the correction. The NOx sensor is normally located in the muffler inlet. Since the first reduction catalyst device and its first dosage in the present invention do not necessarily have to remove all nitrogen oxides NO from the exhaust stream, the first reduction catalyst device and its first dosage may optionally clear sip without measured information on nitrogen oxides NO the first reduction catalyst catalyst is generated. 17 Correct information, the viii saga information with relatively high accuracy, about nitrogen oxides NO upstream of the second reduction catalyst device is important to obtain, however, since the emission in the second reduction catalyst device is to be reduced to low levels, often to near zero levels. This position, that is to say the position at or upstream of the second reduction catalyst device, therefore, according to an embodiment of the invention, should suitably be equipped with a NOR sensor. This NOR sensor can thus, according to the embodiment of the invention, be placed downstream of the particulate filter, which Oven Or a less aggressive environment from a chemical poisoning perspective, compared to one million upstream of the particulate filter.
In addition, an adaptation / calibration of several NOR sensors in the exhaust gas treatment system can easily be performed in the system according to the present invention, since the sensors can be exposed to the same NOx level while the emission levels can be kept at reasonable levels during the adaptation / calibration. For the EuroVI system, for example, the adaptation / calibration has often meant that the emissions have become increasingly favorable during, and even partly after, the actual adaptation / calibration.
As mentioned above, the first and second reduction catalyst devices can be optimized individually, and taking into account the operation of the entire exhaust gas treatment system, which can provide an overall very efficient purification of the exhaust gases. This individual optimization can also be used to reduce one or more of the volumes occupied by the first and second reduction catalyst devices, whereby a compact exhaust gas purification system is obtained. For the above-mentioned non-limiting example, where the NOR conversion corresponding to the two respective dosing devices in the exhaust gas treatment system according to the present invention can be constituted by 60% and 95%, respectively. The exhaust gas treatment system according to the invention theoretically requires an equally strong total volume for the first and second reduction catalyst devices as the reduction catalyst device in the EuroVI system requires to provide a NOx conversion corresponding to 98% with only one reduction catalyst.
In practice, however, the EuroVI system's requirement of the 98% high conversion rate will require a larger catalyst volume than the catalyst volumes corresponding to the sum of the lower conversion rates of 60% and 95%, respectively, according to the present invention. This is due to a joke lines relationship between volume and conversion rate. At high conversion rates, such as 98%, imperfections in the distribution of exhaust gases and / or reducing agents affect the requirement for catalyst volume to a greater extent. High conversion rates further require a larger catalyst volume as the high conversion rates result in a higher degree of storage / filling of reducing agent on the catalyst surface. This stored reducing agent then risks desorbing in certain exhaust gas conditions, it is said that a so-called ammonia slip can occur. An example of the effect of distribution of the reducing agent and the effect of increasing NH3 slip is shown in Figure 6. The figure shows that the gear ratio, the viii saga slope / derivative, for the degree of conversion (y-axis to left) decreases in relation to stachiometry (x- axis) at high conversion rates, i.e. the curve for the conversion rate flattens out for high conversion rates, which is due, among other things, to imperfections in the distribution of exhaust gases 19 and / or reducing agents. The figure also shows that an increase in NH3 slip (y-axis to the right) occurs at higher conversion rates. At higher values than one (1) for stoichiometry, more reducing agents are added than what is theoretically behaved, which also increases the risk of NH3 slip.
According to an embodiment, the present invention also enables a control of a NO2 / NOR ratio between the amount of nitrogen dioxide NO2 and the amount of nitrogen oxides NO for the second reduction step, which enables the system to avoid too high a value of this ratio, for example to avoid NO2 / NOR> 50%. and that the system, by increasing the dosage, can increase the value for the ratio NO2 / NOR when the value Or is set, for example am NO2 / NOR <50%. The value of the NO2 / NOR ratio can be increased, for example by using an embodiment of the present invention, by reducing the level of nitrogen oxides NOR.
In addition, by utilizing the present invention, the above value of the NO2 / NOR ratio for the first reduction stage can be controlled by controlling the level of the nitrogen oxides NO at the first oxidation stage by motor guards.
The NO2 / NOR ratio can assume the storage value, for example after the system has aged for some time. The present invention thus provides an opportunity to counteract the time accumulated, and gives the system a negative property, which gives the father the right value for the NO2 / NOR ratio. Thus, by utilizing the present invention, the content of nitrogen dioxide NO2 can be actively controlled, which is made possible by the NOR level being adjusted upstream of the catalytically oxidizing coating, for example including noble metal, in the particulate filter 320. This control of the NO2 / NOR ratio can, in addition to advantages in catalytic performance , also provide an opportunity to reduce the emission of nitrogen dioxide NO2, which produces a very toxic and strongly foul-smelling emission. This can provide benefits in the event of a future introduction of a separate legal requirement for nitrogen dioxide NO2, as well as the opportunity to reduce harmful emissions of nitrogen dioxide NO2. This can be compared with, for example, the EuroVI system, in which the proportion of nitrogen dioxide NO2 provided during exhaust gas purification is not affectable in the exhaust gas treatment system itself.
In other words, the active control of the content of nitrogen dioxide NO2 is made possible by utilizing the present invention, where the active control can be used to increase the content of nitrogen dioxide NO2 at the caftans for which it is necessary. As a result, an exhaust gas treatment system can be selected / specified, which, for example, requires less precious metal and thus Oven Or cheaper to manufacture.
If the proportion of the total conversion of nitrogen oxides NO that takes place via a fast reaction wave, ie via fast SCR ("solid SCR") where the reduction takes place via reaction waves Over both nitrogen oxide NO and nitrogen dioxide NO2, can be increased by the active control of the content nitrogen dioxide NO2 as described above The requirements for catalyst volume are also reduced.
According to one embodiment of the present invention, the first reduction catalyst device in the exhaust gas treatment system is active at a lower reduction temperature range, including the oxidation temperature range Tox required for the nitrogen dioxide-based sotoxidation in the cDPF particulate filter. As an example, it can be mentioned that the nitrogen dioxide-based sotoxidation in the particle filter DPF can take place at temperatures exceeding 27 ° C. As a result, the reduction of nitrogen oxides NO in the first reduction catalyst device 21 does not compete significantly with the sotoxidation in the particulate filter DPF because they are active at least partially different temperature ranges Txxxj 0 T. For example, a selected and optimized first reduction catalyst device can give NO significant oxides. even about 200 ° C, which means that this first reduction catalyst device does not have to compete with the sotoxidation performance of the particulate filter.
By utilizing the present invention, secondary emissions such as emissions of ammonia NH3 and / or nitrous oxide (nitrous oxide) N2O can also be reduced in relation to a given degree of conversion and / or a given NOx level. A catalyst, for example an ASC (Ammonia Slip Catalyst), which may be included in the second reduction step if the emissions for certain jurisdictions are to be reduced to very low levels, may have some selectivity towards, for example, nitrous oxide N20, which causes the NOx level to decrease by utilizing the additional reduction step of the present invention, the resulting levels of nitrous oxide N2 are also reduced. The resulting levels of ammonia NH 3 can be lowered in the corresponding manner in which the present invention is utilized.
BRIEF DESCRIPTION OF THE DRAWINGS The invention will be further elucidated below with reference to the accompanying drawings, in which like reference numerals are used for like parts, and in: Figure 1 shows an exemplary vehicle which may include the present invention, Figure 2 shows a traditional exhaust gas treatment system, Figure 3 shows an exhaust gas treatment system. according to the present invention, Figure 4 shows a flow chart of the exhaust gas treatment process of the present invention, Figure 5 shows a control unit according to the present invention, Figure 6 shows, inter alia, a relationship between NOx conversion and NH3 grinding.
Description of Preferred Embodiments Figure 1 schematically shows an exemplary vehicle 100 comprising an exhaust gas treatment system 150, which may be an exhaust gas treatment system 150 according to an embodiment of the present invention. The driveline comprises an internal combustion engine 101, which is connected to a shaft 103 via a shaft 102, usually via a flywheel motor, usually via a flywheel, via a flywheel 103.
The internal combustion engine 101 is controlled by the control system of the vehicle via a control unit 115. Like the clutch 106 and the gear unit 103, the control system of the vehicle can be controlled by means of one or more applicable control units (not shown). Of course, the vehicle's driveline can also be of another type, such as of a type with conventional automatic transmission, of a type with a hybrid driveline, etc.
A shaft 107 extending from the shaft shaft 103 drives the drive wheels 113, 114 via an end shaft 108, which e.g. a conventional differential, and drive shafts 104, 105 connected to said final shaft 108. The vehicle 100 further comprises an exhaust gas treatment system / exhaust purification system 150 for treating / purifying exhaust emissions resulting from combustion in the combustion chamber of the combustion engine 101, which may be discharged from cylinders.
Figure 2 shows a previous edge of the exhaust gas treatment system 250, which may illustrate the above-mentioned EuroVI system, and which is indicated by an exhaust line 202 or connected to an internal combustion engine 201, where the exhaust gases generated during combustion, i.e. the exhaust stream 203, are indicated by arrows. The exhaust stream 203 is led to a Diesel Particulate Filter (DPF) 220 via a Diesel Oxidation Catalyst (DOC) 210. During combustion in the internal combustion engine, soot particles are formed, and the DPF 220 particulate filter is used to capture these soot particles. The exhaust stream 203 is passed through a filter structure where soot particles are captured from the passing exhaust stream 203 and stored in the particulate filter 220.
The oxidation catalyst DOC 210 has several functions and is normally used primarily to oxidize the remaining hydrocarbons CHy (also called HC) and carbon monoxide CO the exhaust gas stream 203 to carbon dioxide CO2 and water H 2 O during the exhaust gas treatment. The oxidation catalyst DOC 210 can also oxidize a large proportion of the nitrogen monoxides NO present in the exhaust stream to nitrogen dioxide NO2. The oxidation of nitrogen monoxide NO to nitrogen dioxide NO2 Or is important for the nitrogen dioxide-based sotoxidation in the filter and Or further advantageous in the event of a subsequent reduction of nitrogen oxides NOR. In this regard, the exhaust gas treatment system 250 further comprises a SCR (Selective Catalytic Reduction) catalyst 230 arranged downstream of the particulate filter DPF 220. SCR catalysts use ammonia NH 3, or a composition from which 24 ammonia can be generated / formed, such as e.g. urea, as an additive to reduce the amount of nitrogen oxides NOx the exhaust gas stream. However, the reaction rate of this reduction is affected by the ratio of nitrogen monoxide NO to nitrogen dioxide NO2 in the exhaust stream, whereupon the reaction of the reduction is positively affected by the previous oxidation of NO to NO2 in the oxidation catalyst DOC. This (Jailer up to a value corresponding to approximately 50% for the molar ratio NO2 / NO. For higher proportions for the molar ratio NO2 / NO, ie if the value exceeds 50%, the reaction rate is strongly negatively affected.
As mentioned above, the SCR catalyst 230 requires additives to reduce the concentration of a compound such as nitrogen oxides NO in the exhaust stream 203. This additive is injected into the exhaust stream upstream of the SCR catalyst 230 (not shown in Figure 2). This additive is often ammonia and / or urea based, or consists of a substance from which ammonia can be extracted or released, and may for example consist of AdBlue, which in principle consists of urea mixed with water. Urea forms ammonia partly by heating (thermolysis) and partly by heterogeneous catalysis on an oxidizing surface (hydrolysis), which can be formed, for example, of titanium dioxide TiO 2, including the SCR catalyst. The exhaust gas treatment system may also include a separate hydrolysis catalyst.
The exhaust gas treatment system 250 Or is also provided with an slip catalyst (Ammonia Slip Catalyst; ASC) which Or arranged to oxidize an excess of ammonia which may remain after the SCR catalyst 230 and / or to assist the SCR catalyst with further NOx reduction. As a result, the grinding catalyst ASC can provide an opportunity to improve the system's overall NOx conversion / reduction.
The exhaust gas treatment system 250 is also equipped with one or more sensors, such as one or more NOR and / or temperature sensors 261, 262, 263, 264 for determining nitrogen oxides and / or temperatures in the exhaust gas treatment system.
The previously known exhaust gas treatment system shown in Figure 2, the viii saga EuroVI system, has a problem in that catalysts are efficient heat exchangers, which together with the rest of the exhaust system, including for example the exhaust line 202 and materials and space for sound evaporation and various connections, have a large thermal mass / inertia.
At start-up when the catalyst temperature is below its optimum working temperature, which can be around 300 ° C, for example, and at start-up from low exhaust gas temperatures, which can occur when light city driving passes during highway driving or after idle and power take-off operation, the exhaust temperature is filtered by this large thermal mass . This affects the function, and thereby the efficiency for the reduction of, for example, nitrogen oxides NO of the SCR catalyst 230, which may mean that an inferior exhaust gas purification is provided by the system shown in Figure 2. This means that a smaller amount of nitrogen oxides NO released can be allowed out of the engine. 101 if the exhaust gas purification had been efficient, which could lead to requirements for a more complex engine and / or a lower fuel efficiency.
In the previously known exhaust gas treatment system, there is also a risk that the relatively cold reducing agent locally cools down the exhaust pipe parts and thus can give rise to precipitations. This risk of discharges downstream of the injection increases if the amount of reducing agent injected must be large. 26 Among other things, to compensate for the limited supply of heat / temperature in, for example, cold starts and operation with low loads, so-called fast SCR ("fixed SCR") can be used, in which the reduction is controlled to the same extent as possible via reaction waves over both nitrogen oxide NO and nitrogen dioxide NO2. In rapid SCR, the reaction uses equal parts nitrogen monoxide NO and nitrogen dioxide NO2, which means that an optimal value of the molar ratio NO2 / NO x is close to 50%.
For certain catalyst temperature and ft: 3rd conditions, i.e. for a certain residence time in the catalyst ("Space Velocity"), there is a risk that a non-advantageous proportion of nitrogen dioxides NO2 is obtained. In particular, there is a risk that the NO2 / NO x ratio exceeds 50%, which can be a real problem for exhaust gas purification. An optimization of the NO2 / NO x ratio for the above-mentioned critical low-temperature operating cases thus risks giving an excessively high proportion of nitrogen dioxide NO2 in other operating cases at, for example, higher temperatures. This higher proportion of nitrogen dioxides NO2 results in greater volume performance for the SCR catalyst and / or in a limitation of the amount of nitrogen oxides emitted from the engine and thus in a lower fuel efficiency for the vehicle. In addition, there is a risk that the higher proportion of nitrogen dioxide NO2 also results in emissions of nitrous oxide N20. These risks that a non-beneficial proportion of nitrogen dioxide NO2 arises also exist due to Aging of the system.
For example, the NO2 / NO x ratio can assume lower values when the system has Aged, which may mean that a catalyst specification which in an unaged state gives too high proportions of NO2 / NO x must be used to stop, and be able to compensate for, aging.
Also a lack of control robustness against dosing errors for the amount of reducing agent and / or a lack of control robustness against a sensor error display can at hag-a NOx conversion rates constitute a problem for the exhaust gas treatment system.
In the previous solution described in 1JS2005 / 0069476 it is proposed that the exhaust system should consist of an anesthetized SCR catalyst (ccSCR), which should be connected close, less than 1 meter, from the engine or turbo exhaust outlet, downstream followed by an SCRT system. The SCRT system is defined by the authors of US2005 / 0069476 as a previous edge system in the direction of the exhaust stream which includes a DOC catalyst, a DPF filter, a urea dosing device, and an SCR catalyst. Thus, the exhaust gas treatment system described in US2005 / 0069476 in turn consists in the flow direction of the exhaust stream of the following separate components: the anesthetized ccSCR catalyst, the DOC catalyst, the DPF filter, and the SCR catalyst; ccSCR-DOC-DPF-SCR.
According to the solution in US2005 / 0069476, the anesthetized ccSCR catalyst must be mounted close to the engine and / or turbo in order to minimize the impact of the thermal mass / inertia on the exhaust pipe and / or on the exhaust gas treatment system, as this thermal mass / inertia impairs the exhaust gas treatment properties. Nevertheless, there is a risk that the solution described in US2005 / 0069476 will have performance problems because neither the uncoupled ccSCR catalyst nor the subsequent SCR catalyst are optimized for cooperating exhaust gas purification. The subsequent SCR catalyst is in US2005 / 0069476 the same catalyst that has previously been used in the SCRT system, which means that this subsequent SCR catalyst can be both unnecessarily expensive and not optimized for exhaust gas purification with ccSCR.
In US2005 / 0069476 the anesthetized ccSCR catalyst is added to the exhaust gas treatment system to deal with problems 28 related to the cold start, providing a costly solution aimed only at cold starts.
These problems for the system described in US2005 / 0069476 are at least partially solved by the present invention.
Figure 3 schematically shows an exhaust gas treatment system 3 according to the present invention which with an exhaust line 302 Or connected to an internal combustion engine 301. Exhaust gases generated during the combustion in the engine 301 and the exhaust stream 303 (indicated by arrows) are led to a first oxidation catalyst DOC1 310, which Or. oxidize nitrogen compounds, carbon compounds and / or hydrocarbon compounds in the exhaust stream 303 of the exhaust gas treatment system 350. The particulate filter 320 is described below. During the oxidation in the first oxidation catalyst DOC1 310, a part of the nitrogen monoxides NO in the exhaust stream 303 is oxidized to nitrogen dioxide NO2.
A first metering device 371, which Or is arranged downstream of the first oxidation catalyst DOC1 310 and is arranged to supply a first additive in the exhaust stream 303. A first reduction catalyst device 331 Or is arranged downstream of the first metering device 371. The first reduction catalyst is arranged below the NO. 303 by utilizing the first additive supplied to the exhaust gas stream by the first metering device 371. In more detail, the first reduction catalyst device 371 uses an additive, for example ammonia NH3 or urea, from which ammonia can be generated / formed / released, in the reduction of nitrogen oxides NO in exhaust gas 303. This additive may, for example, consist of the above-mentioned AdBlue.
According to an embodiment of the invention, a first hydrolysis catalyst, which may consist essentially of any suitable hydrolysis coating, and / or a first mixer may be arranged in connection with the first dosing device 371. The first hydrolysis catalyst and / or the first mixer is used for to increase the rate of degradation of urea to ammonia and / or to mix the additive with the emissions and / or to purge the additive.
The increased proportion of nitrogen dioxides NO2 in the exhaust stream 303, which is obtained by utilizing the first oxidation catalyst DOC1 310 placed upstream of the upstream, means that a larger proportion of the total conversion of nitrogen oxides NO takes place via the fast reaction path, i.e. reduction via fast SCR via reaction scales Over bide nitric oxide NO and nitrogen dioxide NO2.
The first oxidation catalyst mounted upstream of the upstream first reduction catalyst device also creates heat during oxidation of any hydrocarbon compounds in the exhaust gas stream, which means that this heat can be used for, for example, optimization of the NOx reduction.
According to one embodiment, the present invention enables a control of a ratio of NO2 / NO x between the amount of nitrogen dioxide NO2 and the amount of nitrogen oxides NO for the first reduction step, by adjusting / adjusting the level / amount of the nitrogen oxides NO which reach the first by means of engine and / or combustion devices. the oxidation catalyst. In other words, if necessary, an adaptation of a precipitating NO2 SCR1 / NOx SCR1 between the first amount of nitrogen dioxide NO2scR1 and the first amount of nitrogen oxides NOxscR1 as air has the first reduction catalyst device 331.
The adaptation is effected by an active control by means of engine and / or combustion actuators of a quantity of nitrogen oxides NOx DOC1 which are emitted from the engine and thereafter when the first oxidation catalyst 310. Indirectly an active control is thereby obtained of the first quantity of nitrogen oxides. , since the level of the first amount of nitrogen oxides NOxscill depends on the amount of nitrogen oxides NO. DOC1 emitted from the engine.
The present invention makes it possible, according to one embodiment, to control a NO2 / NO x ratio between the amount of nitrogen dioxide NO2 and the amount of nitrogen oxides NO for the second reduction step, by adjusting the dosage of additives in the first reduction catalyst device.
The exhaust gas treatment system 350 of the present invention includes downstream of the first reduction catalyst device 331 a particulate filter 320. The particulate filter 320 may comprise a catalytic oxidizing coating. The particulate filter 320 Or arranged to capture soot particles. The oxidizing coating Or arranged to oxidize soot particles as well as one or more of nitric oxide NO and incompletely oxidized carbon compounds in the exhaust stream 303. This document describes the exhaust gas treatment system of pedagogical shells mainly according to the embodiment day. the particulate filter 320 At least in part comprises the catalytically oxidizing coating. However, according to various embodiments described in more detail below, the catalytic oxidizing coating may also be located in other components of the exhaust gas treatment system 350, provided that the catalytic oxidizing coating is disposed between the first and second reduction catalyst devices. The exhaust stream 303 is passed through the filter structure of the particulate filter, which according to one embodiment is at least partially coated with a catalytic oxidizing material. Soot particles are captured in the filter structure from the passing exhaust stream 303 and stored and oxidized in the particulate filter.
According to one embodiment of the invention, the particulate filter 320 is arranged so that the particulate filter 320 is the first exhaust gas treatment system component that the exhaust gas stream 303 passes through the first reduction catalyst device 331. In other words, the particulate filter 320 according to the embodiment is connected downstream. the reduction catalyst device 331 and the particulate filter 320.
As described in more detail below, according to one embodiment, the first reduction catalyst device 331 may comprise a first selective catalytic reduction catalyst SCR ', or a first selective catalytic reduction catalyst SCR' downstream followed by a first slip catalyst ASCIAMOX1. Since the particulate filter 320 is the first exhaust gas treatment system component that the exhaust gas stream 303 passes through the first reduction catalyst device 331 for this embodiment, essentially no oxidation of nitrogen oxide NO and / or incompletely oxidized carbon compounds occurs between the first reduction catalyst particle device 33.
An advantage of connecting the particulate filter 320 downstream of the reduction catalyst device 331 without intermediate 32 exhaust gas treatment system components, apart from any rudder connections, is that the number of substrates in the exhaust gas treatment system 350 becomes smaller if, for example, a second oxidation catalyst DOC2 were arranged between the particulate filter filter and the substrate reduction filter. provides the possibility of a more compact exhaust gas treatment system 350 with lower back pressure, which is easier and cheaper to manufacture and / or assemble.
According to one embodiment, the exhaust gas treatment system 350 also includes a second oxidation catalyst DOC2, which is disposed between the first reduction catalyst device 331 and the particulate filter 320. In other words, the second oxidation catalyst DOC2 is disposed downstream of the first reduction catalyst device 331. the oxidizing coating at least partially in the second oxidation catalyst DOC2, where this oxidizing coating may comprise at least one noble metal.
The catalytic oxidizing coating may, according to one embodiment where the exhaust gas treatment system 350 comprises the second oxidation catalyst DOC2, be arranged only in the second oxidation catalyst DOC2, the downstream particulate filter DPF 320 lacking catalytic oxidizing coating.
The catalytic oxidizing coating may, according to another embodiment where the exhaust gas treatment system 350 comprises the second oxidation catalyst DOC2, be arranged both to some extent in the second oxidation catalyst DOC2 and to some extent in the downstream particle filter cDPF. The catalytic oxidizing coating, according to an embodiment mainly described in this document, can also be arranged only in the particle filter cDPF.
Since the particle filter cDPF 320 is at least partially coated with a catalytic oxidizing coating, this oxidizing coating may comprise at least one noble metal. It will be appreciated that the particulate filter 320 may be at least partially coated with one or more noble metals, for example platinum. The particle filter cDPF 320 comprising the oxidizing coating has several advantages over a classic particle filter DPF without oxidizing coating.
The particle filter cDPF 320 comprising the oxidizing coating gives an improved NO2-based regeneration of the filter, that is to say an improved NO2-based sotoxidation, which can also be called passive regeneration of the filter. An exhaust gas treatment system comprising a particle filter DPF, the viii saga without oxidizing coating, and which does not have a second oxidation catalyst DOC2 between the reduction catalyst and the classic particle filter DPF, provides a very limited NO2-based oxidation of soot in the filter.
The system according to the embodiment of the present invention, by utilizing the catalytically oxidizing coating, intends to purify the filter from soot by the NO 2 -based oxidation. However, the present invention can also be used to advantage in active regeneration / oxidation of the filter, for example by using an injector, which supplies fuel upstream of the filter. In the case of active regeneration, the exhaust gas treatment system according to the invention has the advantage that the first reduction catalyst device itself can handle a certain NO2 conversion while the second reduction catalyst device arranged downstream of the filter, due to the regeneration, experiences such a high temperature that it has difficulty reaching a high degree of conversion.
When using the engine injection system in a regeneration of the particle filter cDPF, or of another exhaust gas treatment component, such as for example the first reduction catalyst device, the first oxidation catalyst device can be used to create the necessary heat.
The particle filter cDPF 320 which includes the oxidizing coating gives Oven more stable conditions for the nitrogen dioxide level NO2 at the second reduction catalyst device 332.
In addition, the use of the particle filter cDPF 320 comprising the oxidizing precipitate and / or of the second oxidation catalyst DOC2 allows the value of the NO2 / NO ratio, the said NO2 content, to be controlled.
Downstream particle filter 320 Or the exhaust gas treatment system 3 provided with a second metering device 372, which is arranged to supply a second additive in the exhaust stream 303, where this second additive comprises ammonia NH3, or a substance, for example AdBlue, from which ammonia can be generated / formed / released. as described above. The second additive may here consist of the same additive as the above-mentioned first additive, it being said that the first and second additives are of the same type and may possibly also come from the same tank. The first and second additives may also be of different types and may come from different thoughts.
According to an embodiment of the invention, in addition, a second hydrolysis catalyst and / or a second mixer may be arranged in connection with the second dosing device 372. The function and design of the second hydrolysis catalyst and / or the second mixer correspond to those described above for the first hydrolysis catalyst and the understand the mixer.
The exhaust gas treatment system 350 also includes a second reduction catalyst device 332, which is located downstream of the second metering device 372. The second reduction catalyst device 332 is arranged to reduce nitrogen oxides NO in the exhaust stream 303 by utilizing the second additive and, if the first additive is present, ndr the second reduction catalyst device 332, also by utilizing the first additive.
The exhaust gas treatment system 350 may also be provided with one or more sensors, such as one or more NOx sensors 361, 363, 364 and / or one or more temperature sensors 362, 363, which are arranged for determining NOx concentrations and of temperatures in the exhaust gas treatment system 350, respectively. A robustness against errors in metered amount of reducing agent can be achieved by an embodiment of the invention, where a NOR sensor 363 is placed between the two dosing devices 372, and preferably between the particle filter 320 and the second dosing device 372, in the exhaust gas treatment system 350. This makes it possible correcting by means of the second dosing device 372 a possible dosing error which has created unforeseen emission levels downstream of the first reducing device 371 and / or the particulate filter 320.
This placement of the NOx sensor 363 between the two dosing devices 371, 372, and preferably between the particle filter cDPF 320 and the second dosing device also makes it possible to correct the amount of additive 36 dosed by the second dosing device 372 for nitrogen oxides NO which can be created over the particle filter cDPF. 320 of excess residues of the additive from the dosing challenge of the first dosing device 371.
The NOx sensor 364 downstream of the second reduction catalyst device 332 can be used in feedback of dosing of the additive.
By utilizing the exhaust gas treatment system 350 shown in Figure 3, both the first reduction catalyst device 331 and the second reduction catalyst device 332 can be optimized with respect to a choice of catalyst characteristics for reduction of nitrogen oxides NO and / or with respect to volumes of the first 331 and second 332 reduction catalyst, respectively. By the present invention, the particulate filter 320 is utilized to the advantage of the function by considering how its thermal mass affects the temperature of the second reduction catalyst 332 and how the catalytic coating affects the NOx / NOx content upstream of the second reduction catalyst 332 in the exhaust gas purification.
By taking into account the thermal inertia of the particulate filter 320, the first reduction catalyst device 331 and the second reduction catalyst device 332, respectively, can be optimized with respect to the specific temperature function they will each experience. Since the optimized first 331 and second 332 reduction catalyst devices Or are designed to co-clean the exhaust gases of the present invention, the exhaust gas treatment system 350, or at least some of its components, can be compacted. Since the space set aside is limited by the exhaust gas treatment system 350, for example in a vehicle Or 37, it is a rigid part to provide a compact exhaust gas treatment system by a high degree of utilization of the catalysts used according to the present invention. This high degree of utilization, and the associated smaller volume language, also gives the opportunity for a reduced back pressure and thus also for a lower fuel consumption.
The present invention provides an exhaust gas treatment system 350 which effectively reduces the amount of nitrogen oxides NO in the exhaust stream at substantially all choirs, including especially cold starts and load deductions, i.e. increased starting torque, from low exhaust gas temperature and load deduction, i.e. reduced required torque. Thus, the exhaust gas treatment system 350 of the present invention is suitable for substantially all choruses that give rise to a transient temperature course in the exhaust gas treatment. An example of such a choir fall can be city driving which includes many starts and decelerations.
The prior art problems associated with a high proportion of nitrogen dioxide NO2 can be solved At least in part by utilizing the present invention, since two reduction catalyst devices 371, 372 are present in the exhaust gas treatment system 350. The problem can be solved by combining the present invention with the realization that the amount of nitrogen oxides NO controls the proportion of nitrogen dioxides NO2 obtained downstream of a filter / substrate coated with a catalytic oxidizing coating, ie the amount of nitrogen oxides NO can be used to control the value of the NO2 / NO ratio. By reducing the nitrogen oxides NO Over the first reduction catalyst device 371 when operating at low temperature, a requirement of a given ratio between nitrogen dioxide and nitrogen oxides NO2 / NO x in the exhaust gases when the second reduction catalyst device 372 can be met with a 38 smaller, and thus less expensive, amount of oxidizing coating between the first 331 and second 332 reduction catalyst devices, i.e. on the second oxidation catalyst DOC2 and / or on the particle filter cDPF.
The first reduction catalyst device 331 in the exhaust gas treatment system 350 is in one embodiment active at a lower reduction temperature range. Third is the oxidation temperature range Tox at which the nitrogen dioxide-based sotoxidation, i.e. the oxidation of incompletely oxidized carbon compounds 320 in the particulate filter. In other words, the temperature of a so-called "light-off" for the sotoxidation in the particulate filter 320 is higher than the "light-off" for the reduction of nitrogen oxides NO in the first reduction catalyst device 331. As a result, the reduction of nitrogen oxides NO in the first reduction catalyst device 331 does not. with the sotoxidation in the particulate filter 320 since the Or active mom at least partially different temperature ranges; 'redTox.
The exhaust gas treatment system sometimes requires the engine to generate heat in order for the exhaust gas treatment system to achieve sufficient efficiency with respect to exhaust gas purification. This heat generation is thus achieved at the expense of reducing the engine's overall efficiency in terms of fuel consumption. An advantageous feature of the exhaust gas treatment system according to the present invention is that the first reduction catalyst device upstream of the filter can be phased to react more quickly to this generated heat than has been possible for, for example, the Euro VI system. Therefore, there is less industry overall by utilizing the present invention. According to an embodiment of the present invention, the engine is controlled to generate such heat to an extent such that the first reduction catalyst device reaches a certain given temperature / performance. Thus, efficient exhaust gas purification can be obtained by operating the first reduction catalyst device at a favorable temperature, while avoiding unnecessary heating, and thus fuel efficiency.
Unlike the aforementioned prior art solutions, the first reduction catalyst device 331 of the present invention need not be anesthetized to the engine and / or turban. The fact that the first reduction catalyst device 331 according to the present invention can be mounted further from the engine and / or turban, and can for instance sit in the muffler, has an advantage in that a longer mixing distance for additives can be obtained in the exhaust stream between the engine and / or the turban and the first The reduction catalyst device 331. This results in a better utilization rate for the first reduction catalyst device 331. At the same time, the present invention provides the many advantages mentioned in this document with the possibility of reducing nitrogen oxides NO both upstream and downstream of the thermally faithful filter cDPF.
A further advantage of the present invention can be deduced from the fact that the first oxidation catalyst DOC] 310 and the second reduction catalyst device 332 are situated / placed in thermally different positions. This means, for example, in the case of a loading path that the first oxidation catalyst DOC1 310 and the first reduction catalyst device 331 will reach a higher exhaust temperature before the second reduction catalyst device 332 reaches a higher temperature.
The first reduction catalyst device 331 will then, as mentioned above, be given the possibility of reducing nitrogen oxides NO before the second reduction catalyst device 332. In addition, the layout / configuration of the exhaust gas treatment system 3 will also lead to the second reduction catalyst device 332 having greater ability to perform. SCR ") since the first oxidation catalyst DOC1 3 can start early to convert nitrogen monoxide NO to nitrogen dioxide NO2. In the critical loading path, due to the racial lack of higher exhaust temperatures, by utilizing the present invention, a more favorable environment is obtained for the second reduction catalyst device 332 via a more advantageous mixture of nitrogen dioxide and nitrogen oxides NO2 / NOx than would have been the case with the first oxidation catalyst. 3 had not been in the exhaust gas treatment system 350.
According to various embodiments of the present invention, the first reduction catalyst device 331 comprises any of: a first selective catalytic reduction catalyst SCR; a first selective catalytic reduction catalyst SCR1 is down-tightened integrated with a first slip catalyst ASC1 / AMOX1, where the first slip catalyst ASC1 / AMOXlar is arranged to oxidize a residue of additives, where the residue may consist of, for example, urea, ammonia NE3 or isocyanic acid HNCO and / or to be SCR1 helpful in further reducing nitrogen oxides NO in the exhaust stream 303; a first selective catalytic reduction catalyst SCR1 downstream followed by a separate first grinding catalyst ASC1, where the first grinding catalyst ASC1 is arranged to oxidize a residue of additives, where the residue may consist of, for example, urea, ammonia NH3 or isocyanic acid ENCO and / or to assist the SCR 'in further reducing nitrogen oxides NO in the exhaust gas stream 303; and a first slip catalyst ASC1, which is arranged primarily for the reduction of nitrogen oxides NO and secondarily for the oxidation of a residue of additives, where the residue may consist, for example, of urea, ammonia NH3 or isocyanic acid HNCO in the exhaust stream 303.
In various embodiments, the second reduction catalyst device 332 is comprised of any of: a second selective catalytic reduction catalyst SCR2; a second selective catalytic reduction catalyst SCR2 downstream integrated with a second grinding catalyst ASC2 / AMOX2, wherein the second grinding catalyst ASC2 / AMOX2 Or is arranged to oxidize a residue of additives and / or to be SCR2 helpful with a further reduction of nitrogen oxides NOx the exhaust stream 303; and a second selective catalytic reduction catalyst SCR2 downstream followed by a separate second grinding catalyst ASC2, wherein the second grinding catalyst ASC2 is arranged to oxidize a residue of additives and / or to assist SCR2 with a further reduction of nitrogen oxides NO in the exhaust stream 303 .
For both the first 331 and second 332 reduction catalysts, its catalytic properties can be selected based on the environment to which it is, or will be, exposed. In addition, the catalytic properties of the first 331 and second 332 reduction catalyst devices can be adjusted so that they can be allowed to operate in symbiosis with each other. The first 331 and second 332 reduction catalyst devices may further comprise one or more materials which provide the catalytic property. For example, transition metals such as Vanadium and / or Tungsten can be used, for example in a catalyst comprising V / V10 3/10 2 O 2. Even metals such as iron 42 and / or copper can not be present in the first 331 and / or other 332 reduction catalyst device, for example in a zeolite-based catalyst.
The exhaust gas treatment system 350 shown schematically in Figure 3 can thus, according to different embodiments, have a variety of structures / configurations, which can be summarized according to the following paragraphs, and the respective units DOC1, DOC2, SCR ', SCR2, (c) DPF, ASC1, ASC2 have the respective characteristics that appear throughout this document. The particulate filter 320 with the at least partially catalytic oxidizing coating is designated cDPF. A particulate filter 320, which as described above may have, but must not have, a catalytic oxidizing coating is referred to below and in this document (c) DPF. In this document, therefore, the term DPF includes a particulate filter which is not coated with oxidizing coating. The term cDPF includes a particulate filter that is at least partially coated with oxidizing coating. the name (c) DPF includes both DPF and cDPF, which means that particle filter named (c) DPF can be formed either by a particle filter DPF without oxidizing coating or by a particle filter cDPF with oxidizing coating. The catalytic oxidizing coating can be adapted to its properties of oxidizing nitrogen oxide NO and oxidizing incompletely oxidized carbon compounds. Incompletely oxidized carbon compounds can, for example, be fuel residues created by the engine's injection system.
According to a configuration according to the invention, the exhaust gas treatment system has the structure DOC1-SCR1-cDPF-SCR2. It is said that the exhaust gas treatment system 350 comprises a first oxidation catalyst DOC1, downstream followed by a first selective catalytic reduction catalyst SCR, downstream followed by a particle filter with an at least partially catalytic oxidizing coating cDPF, downstream followed by a second catalyst reductive catalytic catalyst. For the cyan described embodiment, a second oxidation catalyst DOC2 is also arranged between SCR ash (c) DPF and the system has the structure DOC1-SCR1-DOC2- (c) DPF-SCR2. A symbiotic use of both the first selectively catalytic reduction catalyst SCR 1 together with the second selectively catalytic reduction catalyst SCR2 exhaust gas treatment system 350 may enable a second abrasive catalyst ASC2 to be fired in the exhaust gas treatment system 3 for certain applications, e.g. . This is an advantage, for example, compared with the above-mentioned EuroVI system, in which the grinding catalyst is in practice a requirement. Since an SCR catalyst is typically cheaper than an ASC catalyst, this embodiment of the invention can reduce the manufacturing cost by depleting the second grinding catalyst ASC2. According to an inventive configuration, the exhaust gas treatment system has the structure DOC1-SCR1-ASC1-cDPF-SCR2.
It is said that the exhaust gas treatment system 350 comprises a first oxidation catalyst DOC1, downstream followed by a first selective catalytic reduction catalyst SCR, downstream followed by a first slip catalyst ASC1, downstream followed by a particle filter with an at least partially catalytic oxide or DP second selective catalytic reduction catalyst SCR2. For the above-described embodiment, a second oxidation catalyst DOC2 is arranged between SCR-2 and (c) DPF for the system structure DOC1-SCR1-DOC2-ASC1- (c) DPF-SCR2. As mentioned above, the use of both the first selective catalytic reduction catalyst SCR 1 and the second selective catalytic reduction catalyst SCR2 in the exhaust gas treatment system 350 allows a second slip catalyst ASC2 to be omitted in the exhaust gas treatment system 350 for certain applications. The utilization of the first slip catalyst ASC1 allows a greater load and thus a better utilization of the first selective catalytic reduction catalyst SCR 'and also enables a lowering of the starting temperature ("light off" temperature) for the NOx reduction.
According to a configuration according to the invention, the exhaust gas treatment system has the structure DOC1-SCR1-cDPF-SCR2-ASC2.
It is said that the exhaust gas treatment system 350 comprises a first oxidation catalyst DOC1, downstream followed by a first selective catalytic reduction catalyst SCR, downstream followed by a particulate filter with an at least partially catalytic oxidizing coating cDPF, downstream followed by a second selective catalytic catalyst second slip catalyst ASC2. For the embodiment described above, a second oxidation catalyst DOC2 is arranged between SCR-2 and (c) DPF for the system structure DOC-- SCR1- DOC2- (c) DPF-SCR2-ASC2. This exhaust gas treatment system 3 emits levels of nitrogen oxides NOx close to zero, since the second reduction catalyst SCR2 can be loaded rapidly, for example by increasing the dosage of the second additive, which is followed downstream by the second grinding catalyst ASC2.
According to a configuration according to the invention, the exhaust gas treatment system has the structure DOC1-SCR1-ASC1-cDPF-SCR2-ASC2. It is said that the exhaust gas treatment system 350 comprises a first oxidation catalyst DOC1, downstream followed by a first selective catalytic reduction catalyst SCR ', downstream followed by a first slip catalyst ASC1, downstream followed by a particulate filter with an at least partially catalytic oxidizing coating. a second selective catalytic reduction catalyst SCR2, downstream of a second slip catalyst ASC2. For the embodiment described above, a second oxidation catalyst DOC2 is arranged between SCR and (c) DPF for the system structure DOC1-SCR1-ASC1-DGC2- (c) DPF-SCR2-ASC2. This exhaust gas treatment system 350 emits emission levels of nitrogen oxides NO near the nail, since the second reduction catalyst SCR2 can be driven hard, for example by increased dosing of the second additive, which is followed downstream of the second grinding catalyst ASC2.
The utilization of the first slip catalyst ASC1 allows Oven to lower the starting temperature ("light off" temperature) for the NOx reduction and can give Oven a greater load and clamed a better utilization of the first selective catalytic reduction catalyst SCR '.
According to a configuration according to the invention, the exhaust gas treatment system has the structure DOC1-ASC1-cDPF-SCR2. It is said that the exhaust gas treatment system 350 comprises a first oxidation catalyst DGC1, downstream followed by a first slip catalyst ASC1, downstream followed by a particle filter with an at least partially catalytic oxidizing coating cDPF, downstream followed by a second selective catalytic SC reduction catalyst. In the embodiment described above, a second oxidation catalyst DOC2 is arranged between the SCR and (c) DPF for the system structure DOC1-Asci-DOC2- (c) DPF-sCR2. Also, due to the utilization of both the first grinding catalyst ASC1 and the second selectively catalytic reduction catalyst SCR2, the second grinding catalyst ASC2 can be omitted in the exhaust gas treatment system 3 for certain applications. The utilization of the first grinding catalyst ASC1 makes it possible to lower the starting temperature ("light off" temperature) for the NOx reduction. According to a configuration according to the invention, the exhaust gas treatment system has the structure DOC2-ASC2-cDPF-SCR2-ASC2. It is said that the exhaust gas treatment system 350 comprises a first oxidation catalyst DOC2, downstream followed by a first slip catalyst ASC2, downstream followed by a particle filter with at least one catalytic oxidizing coating cDPF, downstream folded by a second selective catalyst of a second grinding catalyst ASC2. For the above-described embodiment (Jar Oven a second oxidation catalyst DOC2 Or arranged between SCR 'and (c) DPF for the system structure DOC2-ASC2-D ° C2- (c) DPFSCR2-ASC2. This exhaust gas treatment system 350 allows emission levels for nitrogen oxides NO near nail , since the second reduction catalyst SCR2 can be loaded hard, i.e. with a relatively high dosage of the second additive, in which it is followed downstream of the second grinding catalyst ASC2. The use of the first grinding catalyst ASC2 allows a lowering of the starting temperature ("light"). off "temperature) for the NOx reduction.
In the above-listed configurations according to the embodiments, as described above, the first reduction catalyst SCR and the first grinding catalyst ASC2 may be composed of an integrated unit comprising both SCR and ASC2, or may consist of separate units for SCR2 and ASC2.
Similarly, the second reduction catalyst SCR2 and the second grinding catalyst ASC2 may either be an integrated unit comprising both SCR2 and ASC2, or may be separate units for SCR2 and ASC2.
According to an embodiment of the present invention, the exhaust gas treatment system 350 comprises a system 370 for supplying additives, which comprises at least one pump 373 47 arranged to fill the first 371 and second 372 dosing devices with additives, the viii saga with for example ammonia or urea. The system 370 according to one embodiment provides at least one of the first 371 and second 372 dosing devices additives in liquid form.
Additives in liquid form can be refueled at many filling stations / gas stations where fuel is provided, so that the filling of the additive, and thus an optimized utilization of the two reduction steps in the exhaust gas treatment system can be ensured, where the optimized utilization can mean, for example, for dosing in different types of operation. The optimized utilization, for example, is not limited to the first dosing device being used only for cold starts. Today, therefore, there is already an existing distribution channel for liquid additives, which ensures the addition of additives when the vehicle is driven.
In addition, vehicles only need to be supplemented with an additional dosing device, the first 371 dosing device, if only liquid additives are available for use. This minimizes the addition in complexity by using only liquid additives. If, for example, the gaseous additive is used in addition to the liquid additive, the exhaust gas treatment system needs to be equipped with a complete system for supplying the gaseous additive. In addition, a distribution network and / or logistics for the supply of the gaseous additive need to be built up.
The secondary emission treatment system's secondary emissions of, for example, ammonia NH3 and / or carbon dioxide NO2 during normal operation of the internal combustion engine, i.e. not only at 48 cold starts, can be reduced by using an embodiment of the present invention by dosing the additive at both the first 371 and other 372 dosing device. However, when utilizing the embodiment, this presupposes that a substantially continuous dosage is possible to provide. Utilizing additives in liquid form means that the additive racks are serviced without interruption, as additives in liquid form can be bought at regular gas stations. As a result, substantially continuous dosing with both the first 371 and second 372 dosing devices can be done throughout normal service intervals of a vehicle.
The possibility of continuous dosing with both the first 371 and second 372 dosing devices means that the exhaust gas treatment system can be utilized to its full potential. Thus, the system can be controlled so that robust and very high total degrees of NOx conversion can be obtained over time, without the system having to take height for the additive to run out. The factual availability of additives also means that a reliable control of the NO2 content NO2 / NOx can always be carried out, that is to say during the entire service intervals.
Utilizing additives in liquid form for dosing with both the first 371 and second 372 dosing devices allows the complexity of the system 370 to be maintained, since a common tank can be used for storing the additive. Additives in liquid form can be refueled at many filling stations / gas stations where fuel is provided, so that the filling of the additive, and thus an optimized utilization of the two reduction steps in the exhaust gas treatment system, can be ensured. According to another embodiment, the system 370 provides at least one of the first 371 and second 372 dosing devices in gaseous additives. According to one embodiment, this additive may be hydrogen gas H2.
An example of such an additive supply system 370 is shown schematically in Figure 3, where the system comprises the first metering device 371 and the second metering device 372, which are arranged upstream of the first reduction catalyst 331 and upstream of the second reduction catalyst 332. The first and second metering devices 371, 372, which are often dispensing nozzles that dispense additives into, and mix this additive with, the exhaust stream 303, additives are provided by the at least one pump 373 via additive lines 375. The at least one pump 373 receives the additive from one or more additive tanks 376 via one or more lines 377 between the tank (s) 376 and the at least one pump 373. It will be appreciated that the additive may be in liquid and / or gaseous form, as described above. Since the additive Or in liquid form, the pump 373 is a liquid pump and the one or more tanks 376 Or are liquid containers. Dd the additive Or in gaseous form, the pump 373 is a gas pump and the one or more tanks 376 are gas containers. If both gaseous and liquid additives are used, several tanks and pumps are provided, at least one tank and pump Or being provided for supplying liquid additives and at least one tank and pump Or being provided for providing gaseous additives.
According to an embodiment of the invention, the at least one pump 373 comprises a common pump which feeds both the first 371 and the second 372 dosing device with the first and second additives, respectively. According to another embodiment of the invention, the At least one pump comprises a first and a second pump, which feed the first 371 and the second 372 dosing device, respectively, with the first and second additive, respectively. The specific function of the additive system 370 is described in the prior art, and the exact procedure for injecting additives is therefore not further described. In general, however, the temperature at the injection point / SCR catalyst should be above a lower limit value temperature to avoid precipitation and the formation of joke by-product by-products, such as ammonium nitrate NH4NO3. An example of a value for such a lower limit value temperature may be about 200 ° C. According to an embodiment of the invention, the system 370 for supply of additives comprises a dosing control unit 374 arranged to control it At least one pump 373, so that additives are supplied to the exhaust gas stream. According to one embodiment, the dosing control unit 374 comprises a first pump control unit 378 arranged to control the At least one pump 373, in such a way that a first dosing of the first additive is supplied to the exhaust gas stream 303 via the first dosing device 371. At least one pump 373 IDA sAdant provided that a second dose of the second additive is supplied to the exhaust stream 303 via the second metering device 372.
The first and second additives usually consist of the same type of additive, for example urea. However, according to an embodiment of the present invention, the first additive and the second additive may be of different types, for example urea and ammonia, giving the dosage to each of the first 331 and second 332 reduction catalyst devices, and thus the function 51 for each of the first 331 and second 332 reduction catalyst devices can be optimized above with respect to the type of additive. If different types of additives are used, the tank 376 comprises several sub-tanks, which contain the different respective types of additives.
One or more pumps 373 may be used to provide the various types of additives to the first metering device 371 and the second metering device 372. As mentioned above, the one or more tanks and the one or more pumps are adapted to the condition of the additive, am the additive Or gaseous or liquid.
The one or more pumps 373 are thus controlled by a metering control unit 374, which generates control signals for controlling the supply of additives so that the desired amount is injected into the exhaust stream 303 by means of the first 371 and second 372 metering devices upstream of the first 331 and second 332 reduction catalyst, respectively. In more detail, the first pump control unit 378 is arranged to control either a common pump, or a pump dedicated to the first dosing device 371, whereby the first dosing is controlled to be supplied to the exhaust stream 303 via the first dosing device 371. The second pump control unit 379 is arranged to control a common pump, or a dedicated pump for the second metering device 372, whereby the second metering is controlled to be supplied to the exhaust stream 303 via the second metering device 372.
According to one aspect of the present invention, there is provided a method of treating an exhaust stream 303 emitted by an internal combustion engine 301. This method is described with the aid of 52 of Figure 4, in which the process steps follow the flow of the exhaust stream through the exhaust treatment system 350.
In a first step 401 of the process, an oxidation of nitrogen compounds, carbon compounds and / or hydrocarbon compounds is performed in the exhaust stream 303. This oxidation is performed by a first oxidation catalyst 310 arranged so that the exhaust stream 303 passes through it.
In a second step 402 of the process, the exhaust gas stream is fed to a first additive by utilizing a first metering device 371 disposed downstream of said first oxidation catalyst 310. In a third step 403 of the process, a reduction of nitrogen oxides NOx is carried out to the exhaust stream by using this first additive reducing agent. 331, which may comprise a first selective catalytic reduction catalyst SCR 'and / or a first grinding catalyst ASC1, arranged downstream of the first dosing device 371. The first grinding catalyst ASC1 oxidizes has a residue of additives, the remainder may consist of, for example, urea, ammonia NH3 or isocyanic acid HNCO, and / or gives a further reduction of nitrogen oxides NO in the exhaust stream 303. It should be noted that the reduction of nitrogen oxides NO by the first reduction catalyst device 331 in this document may include partial oxidation as long as the total reaction constitutes a reduction. n of nitrogen oxides NOR.
In a fourth step 404 of the process, the exhaust gas stream is filtered, whereby soot particles are captured by a particle filter 320, which according to one embodiment may at least partially comprise a catalytic oxidizing coating. In addition, soot particles and one or more incompletely oxidized nitrogen and / or carbon compounds are oxidized. In a fifth step 405 of the process, a second additive is fed to the exhaust stream 303 using a second metering device 372. In a sixth step 406 of the process, a reduction of the nitrogen oxides NO in the exhaust stream 303 is performed by using at least the second additive in a second reducing catalyst 33 , which may comprise a second selective catalytic reduction catalyst SCR2 and in some configurations a second grinding catalyst ASC2, arranged below the second dosing device 371. The second grinding catalyst oxidizes has an excess of ammonia and / or gives a further reduction of nitrogen oxides NO in the exhaust gas stream 303. It should be noted that the reduction of nitrogen oxides NO by the second reduction catalyst device 332 in this document may include partial oxidation sd lange as the total reaction constitutes a reduction of nitrogen oxides NOR.
It can be seen that a first temperature Ti to which the first reduction catalyst device 331 is exposed and a second temperature 12 to which the second reduction catalyst device 332 is exposed are of great importance to the operation of the exhaust gas treatment system 350. However, it is difficult to regulate these temperatures T1, T2, since they largely depend on how the driver drives the vehicle, it can be said that the first T1 and other T2 temperatures depend on the actual operation of the vehicle and on input via, for example, an accelerator pedal in the vehicle.
The exhaust gas treatment process and the exhaust gas treatment system 350 itself are considerably more efficient than a traditional system (as shown in Figure 2) in that the first temperature Ti before the first reduction catalyst device 331, for example at start-up cycle, previously reaches the value of the first temperature T1. and thereby higher efficiency in the reduction of nitrogen oxides NO by the process of the present invention. Assume that a more effective reduction of nitrogen oxides NOR is obtained here, for example in cold starts and at paddles from low exhaust gas temperatures, which results in less increase in fuel consumption in saclana vessels. In other words, the present invention utilizes the response-controlled first Ti and other 12 temperatures to its advantage in such a way that they contribute to increasing the overall efficiency of the exhaust gas purification system.
The above-mentioned advantages of the exhaust gas treatment system 350 are also obtained for the process of the present invention.
By utilizing two oxidizing steps in the exhaust gas treatment system of the present invention, i.e. in the first process step 401, in which oxidation of nitrogen compounds, carbon compounds and / or hydrocarbon compounds is carried out by the first oxidation catalyst 310, and in the fourth process step, in which the oxidation of a or more of nitrous oxide NO and incompletely oxidized carbon compounds are carried out by means of the particulate filter 320 and / or a second oxidation catalyst DOC2, an increased proportion of the total NOR conversion phase can take place via rapid SCR, i.e. nitrous oxide NO and nitrogen dioxide NO2. When the reduction to a greater extent takes place via reaction waves over both nitrogen monoxide NO and nitrogen dioxide NO2, the total claim on catalyst volume can be reduced at the same time as the transient response is improved for the NOR reduction.
In addition, the first oxidation catalyst 310 mounted upstream of the upstream first reduction catalyst device 331 can also be used to create heat in downstream mounted components, which according to one embodiment can be used for a robust initiation of particle filter regeneration 320 in the exhaust gas treatment system 350 and / or can be used to optimize NO the reduction in the exhaust gas treatment system 350.
According to one embodiment of the process of the present invention, the reduction is controlled by means of the first reduction catalyst device 331 to occur at a reduction temperature range, which is at least partially different from an oxidation temperature range of Lox, which a significant sotoxidation by the particle filter 3 occurs. NO in the first reduction catalyst device does not significantly compete with the nitrogen dioxide-based sotoxidation in the particle filter cDPF because they are active at least in part different temperature ranges' redTo. According to one embodiment of the process of the present invention, the supply of additives to the first dosing device 371 and / or 372 to a level of added additive at which residues / precipitates / crystallization may occur. This level can be determined, for example, by comparison with a predetermined spruce value for the supply. Utilization of this embodiment can thus result in residues / precipitates / crystals of additives being created.
According to an embodiment of the method according to the present invention, the supply of additives to the first dosing device 371 and / or to the second dosing device 372 is reduced when precipitates / residues of the additive have formed, whereby these precipitates can be heated away. The reduction may have meant that the supply is completely interrupted. As a result, for example, a larger dosage in the first dosing position of the first reduction catalyst device can be allowed, since any precipitates / residues can naturally be heated away at the same time as the emission requirements are met by the second reduction catalyst device in the meantime.
The reduction / interruption of the supply may be due to current and / or predicted operating conditions for the internal combustion engine and / or the exhaust gas treatment system. Thus, for example, the second reduction catalyst device 332 must not be designed to handle a shutdown of the supply by means of the first dosing device 371 in all operating cases. An intelligent control therefore enables a smaller system which can be used when appropriate and when this system can provide a required catalytic function.
According to one embodiment of the present invention, the first reduction catalyst device 371 is optimized based on properties, such as catalytic properties, for the first 371 and / or second 372 reduction catalyst device. In addition, the second reduction catalyst device 372 can also be optimized based on properties, such as catalytic properties, for the first 371 and / or second 372 reduction catalyst device. These possibilities for optimizing the first reduction catalyst device and / or the second reduction catalyst device provide an overall efficient exhaust gas purification which better takes into account the conditions of the complete exhaust gas treatment system.
The above-mentioned properties of the first 371 and / or second 372 reduction catalyst device may be related to one or more of the catalytic properties of the first 371 and / or other 372 reduction catalyst device, a catalyst type of the first 371 and / or other 372 57 reduction catalyst device, a temperature range at which the first 371 and / or second 372 reduction catalyst device is active, a degree of ammonia filling for the first 371 and / or second 372 reduction catalyst device 372.
According to one embodiment of the present invention, the first reduction catalyst device 371 and the second reduction catalyst device 372, respectively, are optimized based on the operating conditions of the first 371 and second 372 reduction catalyst devices, respectively. These operating conditions may be related to a temperature, i.e. a static temperature, for the first 371 and the second 372 reduction catalyst device, respectively, and / or to a temperature trend, i.e. a change in temperature, for the first 371 and the second 372 reduction catalyst device, respectively.
According to an embodiment of the present invention, the supply of the first additive is controlled by using the first dosing device 371 based on a distribution of the ratio between nitrogen dioxide and nitrogen oxides NO2 / NO x in the first reduction catalyst device 371. This has an advantage in that the dosage of the first additive the first metering device 371 can then be controlled so that the exhaust stream contains a proportion of nitrogen dioxide NO2 when it reaches the particulate filter 320, which enables efficient reaction kinetics over the first reduction catalyst device 331 by rapid SCR, as well as some nitrogen dioxide-based (NO2-based) sotoxidation. In other words, access to nitrogen dioxide NO2 may have been guaranteed during the sotoxidation of the particulate filter 320, since the dosage of the first additive can be controlled so that there is always nitrogen dioxide NO2 left in the exhaust stream 303 when it is nay. 58 the particle filter 320. The amount of nitrogen dioxide NO2, and with the distribution of the ratio between nitrogen dioxide and nitrogen oxides NO2 / NO, the first reduction catalyst device 371 is tightened can be determined based on predetermined data for the first oxidation catalyst 310, for example in the form of mapped NO2 the first oxidation catalyst 310. With such a control of the dosage of the first additive comes alit dosed additive, and the whole NOx conversion Over the first reduction catalyst device, is consumed by fast SCR, which has in this document mentioned parts.
As a non-limiting example, the control may have been carried out so that the dosage of the first additive very much corresponds to a NOx conversion exceeding the value of twice the ratio between the proportion of nitrogen dioxide NO2 and the proportion of nitrogen oxides NO, which means that the dosage of the first additive corresponds to a NOx conversion less than (NO2 / NOx) * 2. If, for example, NO2 / NO x = 30%, then the dosage of the first additive can be controlled to correspond to a NOx conversion less than 60% (2 * 30% = 60%), for example a NOx conversion equal to about 50%, which would guarantee that the reaction rate Over the first reduction catalyst device Or is fast and that 5% nitrogen dioxide NO2 remains if NO2-based sotoxidation by means of the particulate filter 320.
According to one embodiment of the process of the present invention, an active control of the reduction challenge is performed by the first reduction catalyst device 331 based on a ratio between the amount of nitrogen dioxide NO2SCR2 and the amount of nitrogen oxides NOx SCR2 reaching the second reduction catalyst device 332. In other words, the NOx2 to have a father the reduction in the second reduction catalyst device 332 appropriate, 59 whereby a more effective reduction can be obtained. In more detail, therefore, the first reduction catalyst device 331 has a first reduction of a first amount of nitrogen oxides NOxscpa which reaches the first reduction catalyst device 331. At the second reduction catalyst device 332, a second reduction of a second amount of nitrogen oxidants2 is performed which NOx2 an adjustment is made to the NO2scR2 / NOx SCR2 ratio between the amount of nitrogen dioxide NO2SCR2 and the other amount of nitrogen oxides NO. SCR2 which reach the second reduction catalyst device 332.
This adjustment is performed by utilizing an active control of the first reduction based on a value for the proportional NO2sca2 / NOx sca2, with the intention of giving the ratio NO2 SCR2 / NOx SCR2 a value which makes the second reduction more efficient. The value for the ratio NO2 SCR2 / NOx SCR2 may have consisted of a measured value, a modeled value and / or a predicted value.
According to an embodiment of the present invention, the value of the NO2 / NO2 ratio for the first reduction stage 331 can also be controlled by controlling the level of the nitrogen oxides NO at the first reduction stage 331 by controlling / adjusting engine and or combustion measures taken for the engine.
Those skilled in the art will appreciate that a method of processing an exhaust stream according to the present invention may additionally be implemented in a computer program, which when executed in a dater causes the computer to perform the procedure. The computer program usually forms part of a computer program product 503, wherein the computer program product comprises a suitable digital non-volatile / durable / permanent / permanent storage medium on which the computer program is stored. The said computer-readable non-volatile / durable / durable / permanent medium consists of a 60 light memory, such as: ROM (Read-Only Memory), PROM (Programmable Read-Only Memory), EPROM (Erasable PROM), Flash memory, EEPROM (Electrically Erasable PROM ), a hard disk drive, etc.
Figure 5 schematically shows a control unit 500. The control unit 500 comprises a computing unit 501, which can be constituted by essentially any suitable type of processor or microcomputer, e.g. a Digital Signal Processor (DSP), or an Application Specific Integrated Circuit (ASIC).
The calculation unit 501 is connected to a memory unit 502 arranged in the control unit 500, which provides the calculation unit 501 e.g. the stored program code and / or the stored data calculation unit 501 needs to be able to perform calculations. The calculation unit 501 is also arranged to store partial or end results of calculations in the memory unit 502.
Furthermore, the control unit 500 is provided with devices 511, 512, 513, 514 for receiving and transmitting input and output signals, respectively. These input and output signals may contain waveforms, pulses, or other attributes, which of the input signals receiving devices 511, 513 may be detected as information and may be converted into signals which may be processed by the calculating unit 501. These signals are then provided to the calculating unit 501. The devices 512 , 514 for transmitting output signals are arranged to convert calculation results from the calculation unit 501 into output signals for transmission to other parts of the vehicle control system and / or the component (s) for which the signals Or are intended.
Each of the connections to the devices for receiving and transmitting input and output signals, respectively, may be formed 61 by one or more of a cable; a data bus, such as a CAN bus (Controller Area Network bus), a MOST bus (Media Orientated Systems Transport bus), or any other bus configuration; or by a wireless connection.
One skilled in the art will appreciate that the above-mentioned computer may be constituted by the computing unit 501 and that the above-mentioned memory may be constituted by the memory unit 502.
General control systems in modern vehicles consist of a communication bus system consisting of one or more communication buses which can connect a number of electronic control units (ECUs), or controllers, and various components located on the vehicle. Such a control system may comprise a large number of control units, and the responsibility for a specific function may be divided into more than one control unit. Vehicles of the type shown thus often comprise considerably more control units than what is shown in Figure 5, which is a choice for those skilled in the art.
As will be appreciated by those skilled in the art, the control unit 500 of Figure 5 may include one or more of the control units 115 and 160 of Figure 1, the control unit 260 of Figure 2, the control unit 360 of Figure 3 and the control unit 374 of Figure 3.
The present invention is in the embodiment shown implemented in the control unit 500. However, the invention may be implemented in whole or in part in one or more other control units already existing with the vehicle or in a control unit dedicated to the present invention.
Those skilled in the art will also appreciate that the above exhaust gas treatment system may be modified according to the various embodiments of the method of the invention. In addition, the invention relates to the motor vehicle 100, for example a passenger car, a truck or a bus, or another unit comprising at least one exhaust gas treatment system 62 according to the invention, such as for example a vehicle or a voltage / tension generator.
The present invention is not limited to the above-described embodiments of the invention but relates to and includes all embodiments within the scope of the appended independent claims. 63

权利要求:
Claims (34)
[1]
An exhaust gas treatment system (350) arranged to treat an exhaust stream (303) resulting from a combustion in an internal combustion engine (301), characterized by - a first oxidation catalyst (310) arranged to oxidize compounds comprising one or more of nitrogen, carbon and hydrogen in said exhaust stream; A first metering device (371) arranged downstream of said first oxidation catalyst (310) and arranged to supply a first additive into said exhaust stream (303); A first reduction catalyst device (331) arranged downstream of said first dosing device (371) and arranged to reduce nitrogen oxides NO in said exhaust gas stream (303) by using said first additive; a particulate filter (320) arranged downstream of said first reduction catalyst device (331) arranged to capture soot particles in said exhaust stream; A second metering device (372) arranged downstream of said particle filter (320) and arranged to supply a second additive into said exhaust stream (303); A second reduction catalyst device (332) arranged downstream of said second metering device (372) and arranged to reduce nitrogen oxides NO in said exhaust stream (303) by using at least one of said first and said second additives; and 5. a catalytic oxidizing coating, which is arranged downstream of said first reduction catalyst device (331) and upstream of said second reduction catalyst device (332) and is arranged to oxidize soot particles and to oxidize one or more of nitric oxide NO and incompletely oxidized carbon gases. ). 64
[2]
An exhaust gas treatment system (350) according to claim 1, wherein at least one of said first and second additives comprises ammonia or a substance from which the ammonia is recovered and / or released.
[3]
An exhaust gas treatment system (350) according to any one of claims 1-2, wherein said first reduction catalyst device (331) comprises any one of the group of: 1. a first selective catalytic reduction catalyst (SCR); a first selective catalytic reduction catalyst (SCR) downstream integrated with a first slip catalyst (ASC2), wherein said first slip catalyst (ASC1) is arranged to oxidize a residue of additives and / or to assist said first selective catalytic reduction catalyst (SCR2). ) with a further reduction of nitrogen oxides NO in said exhaust stream (303); A first selective catalytic reduction catalyst (SCR) downstream followed by a separate first grinding catalyst (ASC2), wherein said first grinding catalyst (ASC1) is arranged to oxidize a residue of additives and / or to assist said first selective catalytic reduction catalyst (SCR) with a further reduction of nitrogen oxides NO in said exhaust stream (303); and 3. a first slip catalyst (ASC1), which is arranged firstly for the reduction of nitrogen oxides NOx and secondarily for the oxidation of a residue of additives in said exhaust gas stream (303).
[4]
An exhaust gas treatment system (350) according to any one of claims 1-3, wherein said second reduction catalyst device (332) comprises any one of the group of: 1. a second selective catalytic reduction catalyst (SCR2); 6 - a second selective catalytic reduction catalyst (SCR2) downstream integrated with a second grinding catalyst (ASC2), wherein said second grinding catalyst (ASC2) is arranged to oxidize a residue of additives and / or to assist said second selective catalytic reduction catalyst (ASC2). SCR2) with a further reduction of nitrogen oxides NO in said exhaust stream (303); and - a second selective catalytic reduction catalyst (SCR2) downstream followed by a separate second slip catalyst (ASC2), wherein said second slip catalyst (ASC2) is arranged to oxidize a residual of additives and / or to assist said second selective catalytic reduction catalyst. (SCR2) with a further reduction of nitrogen oxides NO in said exhaust gas stream (303).
[5]
An exhaust gas treatment system (350) according to any one of claims 1 to 4, wherein said particulate filter (320) is the first exhaust gas treatment system component said exhaust gas stream (303) after passing said first reduction catalyst device (331).
[6]
An exhaust gas treatment system (350) according to any one of claims 1-5, wherein said exhaust gas treatment system (350) comprises a system (370) for supplying additives, which comprises at least one pump (373) arranged to supply said first (371) and others (371). 372) dosing device with said first and second additives, respectively.
[7]
The exhaust gas treatment system (350) of claim 6, wherein said additive supply system (370) comprises a metering control unit (374) arranged to control said at least one pump (373).
[8]
The exhaust gas treatment system (350) of claim 6, wherein said additive supply system (370) comprises a metering control unit (374) comprising: 1. a first pump control unit (378) arranged to control said at least one pump (373), wherein a first metering of said first additive is supplied to said exhaust stream using said first metering device (371); and 2. a second pump control unit (379) arranged to control said at least one pump (373), wherein a second dose of said second additive is supplied to said exhaust stream by utilizing said second metering device (372).
[9]
An exhaust gas treatment system according to any one of claims 1 to 8, wherein said first reduction catalyst device (331) is arranged to reduce said nitrogen oxides NO with a reduction temperature range, which is at least partially different from an oxidation temperature range of Lox with which an oxidation of incompletely oxidized oxides said particle filter (320) can be done; 'redTox.
[10]
An exhaust gas treatment system according to any one of claims 1 to 9, wherein said first oxidation catalyst (310) is arranged to create heat for downstream mounted components.
[11]
An exhaust gas treatment system according to any one of claims 1 to 10, wherein said catalytic oxidizing coating is arranged according to one of the group of: 1. included in said particulate filter (320); 2. comprising partly in said particle filter (320) and partly in a second oxidation catalyst arranged downstream of said first reduction catalyst device (331) and tightening said particle filter (320); and 3. included in a second oxidation catalyst disposed downstream of said first reduction catalyst device (331) and upstream of said particulate filter (320). 67
[12]
A process for treating an exhaust stream (303) which results from a combustion in an internal combustion engine (301), characterized by 1. an oxidation of compounds comprising one or more of nitrogen, carbon and hydrogen in said exhaust stream by using a first oxidation catalyst (310); Controlling a supply of a first additive in said exhaust stream by utilizing a first metering device (371) disposed downstream of said first oxidation catalyst (310), said supply of said first additive affecting a reduction in the amount of nitrogen in of said first additive in At least one first reduction catalyst device (331) arranged downstream of said first dosing device (371); A capture of soot particles in said exhaust stream (303) by utilizing a particulate filter (320) arranged downstream of said first reduction catalyst device (331); and - controlling the supply of a second additive in said exhaust stream (303) by using a second dosing device (372) arranged downstream of said particle filter (320), said supply of said second additive influencing a reduction of nitrogen oxides NO in said exhaust stream ( 303) by utilizing at least one of said first and said second additives in a second reduction catalyst device (332) arranged downstream of said second dosing device (372); and 4. an oxidation of soot particles and the oxidation of one or more of nitrous oxide NO and incompletely oxidized carbon compounds in said exhaust stream (303) by utilizing a catalytic oxidizing coating, which is arranged downstream of said first reduction catalyst and second catalyst (681). (332).
[13]
The method of claim 12, wherein said combustion engine (301) is controlled to generate heat for heating at least one of said oxidation catalyst (310) and said first reduction catalyst device (331) to such an extent that said first reduction catalyst device (331) predetermines a performance conversion of nitrogen oxides NOR.
[14]
A process according to any one of claims 12-13, wherein said reduction by means of said first reduction catalyst device (331) is controlled to take place at a reduction temperature range, which is at least partially different from an oxidation temperature range Tc, which an oxidation of incompletely oxidized carbon compounds in said particle filter (320) can be done; 'red
[15]
A method according to any one of claims 12-14, wherein said supply of at least one of said first and second additives by utilizing one of said first dosing device (371) and said second dosing device (372) is increased to a level at which there is a risk for precipitations of said additives to occur.
[16]
The process of claim 15, wherein said first reduction catalyst device (331) comprises a first slip catalyst (ASC1), which primarily performs reduction of nitrogen oxides NO and secondarily performs oxidation of a residue of additives in said exhaust stream (303). .
[17]
A method according to any one of claims 12-14, wherein said supply of at least one of said first and second additives by utilizing one of said first 69 dosing device (371) and said second dosing device (372), respectively, is reduced, after which residues of at least one of said first and other additives are eliminated by said exhaust gas stream, where said reduction of said feed is performed at the required total catalytic function of an exhaust gas treatment system (350) which said said process may be provided after said reduction.
[18]
The method of claim 17, wherein said required catalytic function depends on current and / or predicted operating conditions for said internal combustion engine (301).
[19]
A method according to any of claims 17-18, wherein said reduction of said supply constitutes an interruption of said supply.
[20]
A method according to any of claims 12-19, wherein said effect on said reduction of nitrogen oxides NO for said first reduction catalyst device (371) is controlled based on one or more properties and / or operating ratios of said first reduction catalyst device (371).
[21]
A method according to any of claims 12-19, wherein said effect on said reduction of nitrogen oxides NO for said first reduction catalyst device (371) is controlled based on one or more properties and / or operating conditions of said second reduction catalyst device (372).
[22]
A method according to any one of claims 12-19, wherein said effect on said second reduction catalyst device (372) is controlled based on one or more properties and / or operating conditions of said second reduction catalyst device (372).
[23]
A method according to any of claims 12-19, wherein said effect on said second reduction catalyst device (372) is controlled based on one or more properties and / or operating conditions of said first reduction catalyst device (371).
[24]
A process according to any one of claims 20-23, wherein said properties of said first (371) and second (372) reduction catalyst devices, respectively, are related to one or more in the group of: 1. catalytic properties of said first reduction catalyst device (371); 2. catalytic properties of said second reduction catalyst device (372); A catalyst type for said first reduction catalyst device (371); 4. a catalyst type for said second reduction catalyst device (372); a temperature range in which said first reduction catalyst device (371) is active; A temperature range in which said second reduction catalyst device (372) is active; 6. a degree of ammonia filling for said first reduction catalyst device (371); and 7. a degree of ammonia filling for said second reduction catalyst device (372).
[25]
A method according to any one of claims 20-23, wherein said operating conditions of said first (371) and second (372) reduction catalyst devices Or are related to one or more in the group of: 71 1. a temperature of said first reduction catalyst device (371); A temperature of said second reduction catalyst device (372); a temperature trend called the first reduction catalyst device (371); and 3. a temperature trend called said second reduction catalyst device (372).
[26]
A method according to any one of claims 12-25, wherein said supply of said first additive by using said first dosing device (371) is controlled based on a distribution of the ratio between nitrogen dioxide and nitrogen oxides NO2 / NO x upstream of said first reduction catalyst device (371).
[27]
A process according to any one of claims 12 to 26, wherein 1. said first reduction catalyst device (331) performs a first reduction of a first amount of said nitrogen oxides NOx scRi which reaches said first reduction catalyst device (331); and - an adaptation of a ratio of NO2scRiNOx SCR1 between a first amount of nitrogen dioxide NO2scRi and said first amount of nitrogen oxides NOx SCR1 which when said first reduction catalyst catalyst device (331) is carried out when necessary, an active control of said first amount of nitrogen oxides NO, scR and / or incinerators.
[28]
A process according to any one of claims 12-27, wherein 1. said second reduction catalyst device (332) performs a second reduction of a second amount of said nitrogen oxides NOx scR2 which reaches said second reduction catalyst device (332); and 2. an adaptation of a NO2scR2 / NOx SCR2 ratio between a 72 second amount of nitrogen dioxide NO2SCR2 and said second amount of nitrogen oxides NOx SCR2 which is performed when said second reduction catalyst device (332) if necessary, an active control of said first reduction of said first amount nitrogen oxides NO.scR1 are carried out based on a value for the said ratio NO2 SCR2 / NOx SCR2 •
[29]
The method of claim 28, wherein said value for said ratio NO2scR2 / NOx SCR2 is one of the group of: - a measured value; 1. a modeled value; 2. a predicted value.
[30]
A process according to any one of claims 12-29, wherein said first oxidation catalyst (310) and / or a second oxidation catalyst creates heat for downstream mounted components.
[31]
A process according to any one of claims 12-30, wherein an oxidation of nitrogen and / or hydrocarbon compounds in said exhaust stream is carried out using a second oxidation catalyst arranged downstream of said first reduction catalyst device (331) and upstream of said catalytic oxidizing coating.
[32]
A method according to any one of claims 12 to 30, wherein said catalytically oxidizing coating Or is arranged according to one of the group of: 1. comprising in a particulate filter (320) comprising said catalytically oxidizing coating; 2. comprised partly in a particulate filter (320) comprising said catalytically oxidizing coating and partly in a second oxidation catalyst arranged downstream of said first reduction catalyst device (331) and upstream of said 73 particulate filters (320); and - included in a second oxidation catalyst arranged downstream of said first reduction catalyst device (331) and upstream of a particulate filter (320).
[33]
A computer program comprising program code, which when said program code is executed in a computer, causes said computer to perform the method according to any of claims 12-32.
[34]
A computer program product comprising a computer readable medium and a computer program according to claim 33, wherein said computer program is included in said computer readable medium. 91. 901. "- '1. 01. LOI. 901. 91. 901. ---' LO £ 01. 1701. ---- # £ 1. r4 I- 'Old 2/201 00000 260 2 I

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