SE542085C2 - Exhaust gas treatment system and method for treating an exhaust gas stream - Google Patents

Abstract

An exhaust gas treatment system (350) arranged to treat an exhaust gas stream (303) is presented. According to the present invention, the exhaust gas treatment system comprises: - a first oxidation catalyst (310), - a first dosing device (371) arranged downstream of said first oxidation catalyst and arranged to supply a first additive in said exhaust gas stream; arranged to reduce nitrogen oxides in said exhaust gas stream by utilizing said first additive; - a particulate filter (320) arranged downstream of said first reduction catalyst device; - a second dosing device (372) arranged downstream of said particle filter and arranged to supply a second additive in said exhaust stream; and - a second reduction catalyst device (332) 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 catalytically oxidizing coating, which is arranged downstream of said first reduction catalyst device and upstream of said second reduction catalyst device.

Description

TECHNICAL FIELD The present invention relates to an exhaust gas treatment system according to the preamble of claim 1 and a method of 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 is 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 NOx, hydrocarbons CxHy, 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 standards for these applications limit the emissions from the internal combustion engines.

In an effort 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, so vehicles equipped with an internal combustion engine usually include at least one catalyst. There are different types of catalysts, where the different and different types may be suitable depending on, for example, which combustion concepts, combustion strategies and / or fuel 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 NOx, vehicles often include a catalyst in which an additive is added to the exhaust gas stream resulting from the combustion engine combustion to effect a reduction of nitrogen oxides NOx mainly to nitrogen gas and water. This is described in more detail below.

A common type of catalyst for this type of reduction, especially for heavy vehicles, is 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 NOxi the exhaust gases. The additive is injected into the exhaust gas stream resulting from the internal combustion engine upstream of the catalyst. The additive fed to the catalyst is adsorbed (stored) in the catalyst, in the form of ammonia NH3, whereby a redox reaction can take place between nitrogen oxides NOXi 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 influence between the engine and exhaust gas treatment. In particular, there is a link between the ability to reduce nitrogen oxides NOX 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 fuel efficiency / efficiency and its produced nitrogen oxides NOx. This relationship indicates that for a given system there is a positive connection between produced nitrogen oxides NOx and the fuel efficiency, ie an engine that is allowed to emit more nitrogen oxides NOx can be made to consume less fuel by, for example, the injection time can be chosen more optimally, which can give a higher combustion efficiency. Correspondingly, there is a negative link between a produced particulate mass PM and the fuel efficiency, ie an increased emission of particulate matter PM from the engine links to an increase in fuel consumption. These relationships form the background to the widespread use of exhaust gas treatment systems including an SCR catalyst, which are intended to optimize fuel and particulate matter for the engine against a relatively larger amount of nitrogen oxides produced NOx. A reduction of these nitrogen oxides NOx is then carried out in the exhaust gas treatment system, which may thus include 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 fuel efficiency can therefore be achieved together with low emissions of both PM particles and NOx nitrogen oxides.

Brief description of the invention To a certain extent, the performance of the exhaust gas treatment systems can be increased by increasing the substrate volumes included 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 fuel efficiency from the higher degree of conversion. Larger substrate volumes also mean an increased cost. It is thus important to be able to make optimal use of the exhaust gas treatment systems, for example by avoiding oversizing and / or by limiting the spread of the exhaust gas treatment systems in size and / or manufacturing cost.

The function and efficiency of catalysts in general, and of reduction catalysts in particular, are strongly dependent on the temperature above the reduction catalyst. In this document, a temperature above the reduction catalyst means a temperature in / at / for the exhaust gas flow 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 is NOx typically inefficient. The NO2 / NOx content in the exhaust gases represents a certain possibility to increase the catalytic activity, even at lower exhaust gas temperatures. However, the temperature above the reduction catalyst and the NO2 / NOx content are generally difficult to control, as they largely depend on previously unknown factors, for example on how the driver drives the vehicle. For example, the temperature across the reduction catalyst depends on the torque requested 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 driving style.

Prior art exhaust treatment systems, such as the system described in detail below which many manufacturers have used to meet the Euro VI emission standard (hereinafter referred to as the "EuroVI system"), include a first oxidation catalyst, a diesel particulate filter and a reduction catalyst, presenting problems related to the large thermal 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, mufflers and various connections. For example for cold starts, when both engine and exhaust gas treatment system are cold, and for load applications from low exhaust temperatures, when more torque is required than before, for example when light city driving turns into highway driving or after idle and power take-off operation, the diesel particulate filter's large thermal mass / inertia the temperature of the reduction catalyst is only slowly increased in such prior art exhaust treatment systems. This impairs, for example in cold starts and in vehicle operation with temperature and / or flow transient elements, the function of the reduction catalyst, and thereby the reduction of nitrogen oxides NOx. This deterioration can result in substandard exhaust gas purification, which risks unnecessarily polluting the environment.

In addition, the deterioration of the reduction catalyst's function increases the risk of not meeting the requirements set by the authorities for exhaust gas purification. Fuel consumption can also be negatively affected by the deteriorating function, as fuel energy may then need to be used to, via various temperature-raising measures, 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, while at the same time the conditions for achieving a higher fuel 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 also achieved by the above-mentioned method according to the characterizing part of claim 12. The object is also achieved 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, the first reduction catalyst device at cold starts and applications from low temperatures here reaches previous operating temperatures at which an effective reduction of nitrogen oxides NOx is maintained. Thus, according to the invention, the available heat is utilized in a more energy-efficient manner, which results in an earlier and / or more efficient reduction of nitrogen oxides NOx, for example at cold starts and at start-ups from low exhaust temperatures, than has been possible with the previously known exhaust gas treatment systems described above. .

In certain other operating types, similarly, the second downstream mounted catalyst catalyst device may operate at more favorable temperatures than the temperatures of the first downstream mounted catalyst catalyst device.

By utilizing the invention, different thermal inertia are obtained for the first and for the second reduction catalyst device, which means that these first and 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, i.e. from a perspective that looks at the function of the entire exhaust gas treatment system, and can therefore be used to provide an overall more efficient purification of the exhaust gases than the separately optimized catalysts could provide . 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 units other 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 of 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. Thereby, by the present invention, an interaction / symbiosis is obtained between the first reduction catalyst device, which is optimized for the first thermal mass and the first temperature function / temperature profile 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, i.e. the utilization of the first oxidation catalyst mounted upstream of the first reduction catalyst device and of the particulate filter mounted downstream of the downstream first reduction catalyst device, provides an increased proportion of nitrogen dioxide NO . In this way, the proportion of the total conversion of nitrogen oxides NOX that takes place via a fast reaction path, i.e. via fast SCR ("solid SCR") where the reduction takes place via reaction paths over both nitrogen monoxide NO and nitrogen dioxide NO2, can be increased. The increased proportion of conversion through rapid SCR means that the response with which the NOx conversion takes place is increased and that the requirements for the catalyst volume are reduced. Quick SCR is described in more detail below.

The first oxidation catalyst mounted upstream of the 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 set up, among other things, to oxidize hydrocarbon compounds in the exhaust stream, which creates heat. According to one embodiment, this generated heat can be used in regeneration of any exhaust gas treatment component, such as for example of a reduction catalyst device or of the particle filter in the exhaust gas treatment system, whereby a robust regeneration can be achieved 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, of the second reduction catalyst device and / or the first reduction catalyst device. For example, here 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 such a way that it does not have to 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 gas purifier which is suitable for emissions which occur in substantially all types of driving falls, especially for strongly transient operation which gives a varying temperature and / or flow profile. . Transient operation can, for example, include relatively many starts and decelerations for the vehicle or relatively many up and down slopes. Since relatively many vehicles, such as buses which often stop at stops and / or vehicles which are driven in city traffic or hilly topography, experience such transient operation, the present invention provides an important and very useful exhaust gas purification, which overall reduces the emission from the vehicles in which it implemented.

The present invention thus utilizes the previously problematic thermal mass and heat exchange of primarily the particulate filter in the EuroVI system as a positive property. The exhaust gas treatment system of the present invention may, similarly to the EuroVI system, contribute heat to the exhaust gas stream and the downstream mounted catalytic converter device for shorter periods of towing or other low temperature operation if this low temperature operation has been preceded by operation with higher operating temperatures. The particulate filter is then, due to its thermal inertia, hotter than the exhaust gas stream, so the exhaust gas stream can be heated by the particulate filter.

In addition, this good property is thus supplemented by the fact that the upstream first reduction catalyst device, especially in transient operation, can utilize the higher temperature which arises during start-up. Thus, the first reduction catalyst device experiences a higher temperature after application 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 a NOx conversion upstream of a large thermal inertia and a NOx conversion downstream of a large thermal inertia. The exhaust gas treatment system according to the present invention can then make maximum use of available heat in an energy efficient manner.

The first oxidation catalyst also creates heat during the oxidation of, among other things, hydrocarbon compounds. By 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 of 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 of the present invention can be made compact when the constituent units, for example the reduction catalyst devices, do not have to be large in volume. As the size of these units is kept down 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 purification 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 substrate means that a larger volume within the predetermined size for the exhaust gas purification device can be used for distribution, mixing and turning. the exhaust gas flow within 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 predetermined external geometry if the performance per substrate volume unit is increased. Thus, the total volume of the exhaust gas treatment system according to the invention can be reduced compared to at least some previously known 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 recirculation systems has, among other things, advantages 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 of nitrogen oxides to soot (??? / soot 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 sites, 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 sensitive to these poisonings than catalysts of greater physical length. When, for example, noble metal, such as Platinum, is applied to the physically long diesel particulate filter DPF, instead of to the physically shorter first oxidation catalyst DOC1, 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 / NOX 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 can then 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 NOX in the first reduction catalyst device via so-called "fast SCR", as described in more detail above / below.

The present invention also has an advantage in that two dosing devices are cooperatively used in combination for dosing the reducing agent, for example urea, upstream of the first and second reducing catalyst devices, which relieves and facilitates mixing and possible evaporation of the reducing agent, since the injection of the reducing agent is divided between two physically . 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 also reduced when the injection of the reducing agent is distributed between two positions. It is also possible with the present invention to switch off dosing in one dosing position in order to then heat away any precipitates that may occur. Hereby, 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 are met by the second reduction catalyst device in the meantime. This larger / richer dosage can be seen as a more aggressive dosage, which gives dosage amounts closer to / above a dosage limit value at which a risk of precipitation / crystallization of additives arises. As a non-limiting example, if the single dosing device in the EuroVI system had been optimized to provide an evaporation and distribution of the reducing agent giving 98% NOx conversion, then the NOX conversion of the two respective reduction catalyst devices in the exhaust gas treatment system of the present invention invention is reduced, for example to 60% and 95%, respectively. The amounts of reducing agent which must then be evaporated in the respective two positions become lower, and the distributions of the reducing agent need not 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 evaporation / mixing must be used when the reducing agent is to be mixed with the exhaust gases, ie with the nitrogen oxides NOx. Since not as 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 to lower the exhaust back pressure when the present invention is used.

The two dosing positions used in the present invention thus enable a total of more additives to be supplied to the exhaust gas stream than if only one dosing position had been used in the system. This allows an improved performance to be provided.

The present invention thus provides a relief of the mixture and the possible evaporation. On the one hand, the double dosing positions mean that the reducing agent is 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 mean that lower conversion rates, and thus dosing with less unfavorable gear ratio, can be used. The influence of the size of the conversion rates and the dosage ratio 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 dosing in the position where residues of additives may occur if necessary can be reduced / closed 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 also provides robustness against failure in the 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 the conversion rates and emissions that result from a 10% dosing error for the reducing agent for a case of 10 g / kWh NOx. 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 can be seen from the table, a system with a reduction step, such as in the Euro-VI system, gives the emission 1.18 g / kWh. Instead, two reduction steps, as in a system according to the present invention, give the emission 0.67 g / kWh according to the example. This significantly 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 allows this to correct for the dosing error at the first dosing device when dosing with the second dosing device is made.

Image available on "Original document" This embodiment can be implemented with a low addition in complexity, as a NOx sensor that is already present in today's 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 the nitrogen oxides NOxur the exhaust stream, the first reduction catalyst device and its first dosage may possibly survive without measured information on nitrogen oxides NOx upstream of the first reduction catalyst device.

However, accurate information, i.e. information with relatively high accuracy, about nitrogen oxides NOx upstream of the second reduction catalyst device is important to obtain, since the emission in the second reduction catalyst device must be reduced to low levels, often to levels close to zero. This position, i.e. the position at or upstream of the second reduction catalyst device, should therefore according to an embodiment of the invention be suitably provided with a NOX sensor. This NOx sensor can thus, according to the embodiment of the invention, be placed downstream of the particle filter, which is also a less aggressive environment from a chemical poisoning perspective, compared to the environment upstream of the particle filter.

In addition, an adaptation / calibration of several NOx sensors in the exhaust gas treatment system can be easily performed in the system of 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 too high during, and also 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 NOx conversion corresponding to the two respective dosing devices in the exhaust gas treatment system of the present invention may be 60% and 95%, respectively, the exhaust gas treatment system of the invention theoretically requires an equal total volume of the first and second reduction catalyst devices. in the EuroVI system requires to provide a NOx conversion corresponding to 98% with only one reduction catalyst.

In practice, however, the requirements of the EuroVI system for the high conversion rate of 98% will require a larger catalyst volume than the catalyst volumes corresponding to the sum of the lower conversion rates 60% and 95%, respectively, according to the present invention. This is due to a non-linear relationship between volume and conversion rate. At high conversion rates, such as, for example, 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 greater storage / coverage of reducing agent on the catalyst surface. This stored reducing agent then risks desorbing under certain exhaust gas conditions, ie 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, ie the slope / derivative, for the degree of conversion (y-axis to the left) decreases in relation to stoichiometry (x- axis) at high conversion rates, ie the curve for the conversion rate flattens out for high conversion rates, which is partly due to imperfections in the distribution of exhaust gases 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 values higher than one (1) for stoichiometry, more reducing agents are added than are theoretically needed, which also increases the risk of NH3 grinding.

According to one embodiment, the present invention also enables a control of a NO2 / NOX ratio between the amount of nitrogen dioxide NO2 and the amount of nitrogen oxides NOX before the second reduction step, which means that the system can avoid too high values of this ratio, for example avoid NO2 / NOx> 50%. , by increasing the dosage, may increase the value of the NO2 / NOX ratioWhen the value is too low, for example if NO2 / NOx <50%. The value of the NO2 / NOX ratio here, for example by utilizing an embodiment of the present invention, can be increased by reducing the level of nitrogen oxides NOx.

In addition, by utilizing the present invention, the value of the NO2 / NOX ratio for the first reduction step can also be controlled by controlling the level of the nitrogen oxides NOx at the first oxidation step by motor measures.

The NO2 / NOX ratio can assume lower values, for example after the system has aged for some time. The present invention thus provides an opportunity to counteract the time-degraded, and for the system negative property, which gives too low values for the NO2 / NOX ratio. Thus, by utilizing the present invention, the content of nitrogen dioxide NO2 can be actively controlled, which is made possible by the NOx level being adjusted upstream of the catalytically oxidizing coating, for example including noble metal, in the particulate filter 320. This control of the NO2 / NOxcan ratio, in addition to catalytic performance advantages provide the opportunity to reduce emissions of nitrogen dioxide NO2, which gives a very toxic and strongly foul-smelling emission. This can provide benefits in the event of the 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 influenceable in the exhaust gas treatment system itself.

In other words, the active control of the nitrogen dioxide NO2 content is made possible by utilizing the present invention, where the active control can be used to increase the nitrogen dioxide NO2 content in the driving cases for which it is necessary. In this way, an exhaust gas treatment system can be selected / specified, which, for example, requires less precious metal and thus is also cheaper to manufacture.

If the proportion of the total conversion of nitrogen oxides NOx which takes place via a fast reaction path, i.e. via fast SCR ("solid SCR") where the reduction takes place via reaction paths over both nitrogen oxide NO and nitrogen dioxide NO2, can be increased by the active control of the nitrogen dioxide content NO2, as described above, the requirements for the catalyst volume can also be 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. As an example, it can be mentioned that the nitrogen dioxide-based sotoxidation in the particle filter DPF can take place at temperatures exceeding 275 ° C. As a result, the reduction of nitrogen oxides NOxi in the first reduction catalyst device does not significantly compete with the sotoxidation in the particulate filter DPF because they are active in at least partially different temperature ranges. Tox. For example, a well-chosen and optimized first reduction catalyst device can provide a significant conversion of nitrogen oxides NOX even at 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 NH 3 and / or nitrous oxide (nitrous oxide) N 2 O 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 a certain selectivity towards, for example, nitrous oxide N2O, which means that the NOx level is lowered. by utilizing the additional reduction step of the present invention also switches down the resulting levels of nitrous oxide N2O. The resulting levels of ammonia NH 3 can be lowered accordingly as 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 which: Figure 1 shows an exemplary vehicle which may include the present invention, Figure 2 shows a traditional exhaust treatment system; 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 including 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 in a conventional manner, via a shaft 102 emanating on the internal combustion engine 101, usually via a flywheel, to a gearbox 103 via a clutch 106.

The internal combustion engine 101 is controlled by the control system of the vehicle via a control unit 115. Likewise, the clutch 106 and the gearbox 103 can be controlled by the control system of the vehicle 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 a conventional automatic transmission, of a type with a hybrid driveline, etc.

A shaft 107 emanating from the gearbox 103 drives the drive wheels 113, 114 via an end gear 108, such as e.g. a conventional differential, and drive shafts 104, 105 connected to said final gear 108.

The vehicle 100 further includes an exhaust gas treatment / exhaust purification system 150 for treating / purifying exhaust emissions resulting from combustion in the combustion chamber of the internal combustion engine 101, which may be cylinders.

Figure 2 shows a previously known exhaust gas treatment system 250, which can illustrate the above-mentioned EuroVI system, and which with an exhaust line 202 is connected to an internal combustion engine 201, where the exhaust gases generated during combustion, i.e. the exhaust gas flow 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 here 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 residual hydrocarbons CxHy (also called HC) and carbon monoxide CO in the exhaust stream 203 to carbon dioxide CO2 and water H2O 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 gas stream to nitrogen dioxide NO2. The oxidation of nitrogen monoxide NO to nitrogen dioxide NO2 is important for the nitrogen dioxide-based sotoxidation in the filter and is further advantageous in the event of a subsequent reduction of nitrogen oxides NOx. 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 ammonia can be generated / formed, such as e.g. urea, as an additive to reduce the amount of nitrogen oxides NOxi 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, so the reaction of the reduction is positively affected by the previous oxidation of NO to NO2 in the oxidation catalyst DOC. This applies up to a value corresponding to approximately 50% for the molar ratio NO2 / NOx. For higher proportions for the molar ratio NO2 / NOx, ie for values exceeding 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, for example, nitrogen oxides NOxi 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 can for example consist of AdBlue, which in principle constitutes urea mixed with water. Urea forms ammonia partly by heating (thermolysis) and partly by heterogeneous catalysis on an oxidizing surface (hydrolysis), which may for example consist of titanium dioxide TiO 2, within the SCR catalyst. The exhaust gas treatment system may also include a separate hydrolysis catalyst.

The exhaust gas treatment system 250 is also provided with an Ammonia Slip Catalyst (ASC) which is 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. Thereby, the grinding catalyst ASC can provide an opportunity to improve the system's total NOx conversion / reduction.

The exhaust gas treatment system 250 is also provided with one or more sensors, such as one or more NOx and / or temperature sensors 261, 262, 263, 264 for determining nitrogen oxides and / or temperatures in the exhaust gas treatment system.

The prior art exhaust treatment system shown in Figure 2, i.e. the 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 attenuation and various connections, have a large thermal mass / inertia. At starts when the catalyst temperature is below its optimum operating temperature, which can be around 300 ° C, for example, and at start-ups from low exhaust temperatures, which can occur when light city driving turns into 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 of the reduction of, for example, nitrogen oxides NOxhos SCR catalyst 230, which can cause a substandard exhaust gas purification provided by the system shown in Figure 2. This allows a smaller amount of nitrogen oxides NOx emitted from the engine 101 than 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 precipitates. This risk of precipitation downstream of the injection increases if the amount of reducing agent injected must be large.

Among other things, to compensate for the limited supply of heat / temperature in, for example, cold starts and low-load operation, so-called fast SCR ("fixed SCR") can be used, in which the reduction is controlled to take place as far as possible via reaction paths over both nitric 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 NO2 / NOx molar ratio is close to 50%.

For certain catalyst temperature and flow 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 / NOx ratio exceeds 50%, which can be a real problem for exhaust gas purification. An optimization of the NO2 / NOx ratio for the above-mentioned critical low-temperature operating phage thus risks giving an excessively high proportion of nitrogen dioxides NO2 in other operating cases at, for example, higher temperatures. This higher proportion of nitrogen dioxides NO2 results in greater volume requirements for the SCR catalyst and / or in a limitation of the amount of nitrogen oxides emitted from the engine and thus in a poorer fuel efficiency for the vehicle. In addition, there is a risk that the higher proportion of nitrogen dioxides NO2 also results in emissions of nitrous oxide N2O. These risks of a non-beneficial proportion of nitrogen dioxide NO2 also exist due to the aging of the system.

For example, the NO2 / NOx ratio can be lower values when the system has aged, which can mean that a catalyst specification that in the unaged state gives too high proportions of NO2 / NOx must be used to take into account, and be able to compensate for, aging. 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 also be a problem for the exhaust gas treatment system at high NOx conversion rates.

In the prior art solution described in US2005 / 0069476 it is proposed that the exhaust system should consist of a closely connected SCR catalyst (ccSCR), which should be connected close, less than 1 meter, from the engine or turbine exhaust outlet, downstream followed by an SCRT system. The SCRT system is defined by the authors of US2005 / 0069476 as a prior art 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 in the flow direction of the exhaust stream consists of the following separate components: the closely coupled ccSCR catalyst, the DOC catalyst, the DPF filter, and the SCR catalyst; ccSCR-DOC-DPF-SCR.

According to the solution in US2005 / 0069476, the closely coupled ccSCR catalyst must be mounted close to the engine and / or turbo to minimize the impact of the thermal mass / inertia of the exhaust pipe and / or the exhaust gas treatment system, as this thermal mass / inertia impairs the exhaust gas purifying properties of the exhaust gas treatment system. Nevertheless, there is a risk that the solution described in US2005 / 0069476 will have performance problems because neither the closely coupled 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 cooperating with ccSCR.

In US2005 / 0069476 the closely coupled ccSCR catalyst is added to the exhaust gas treatment system to take care of problems related to the cold start, which provides a costly solution aimed only at cold starts.

These problems of the system described in US2005 / 0069476 are solved at least in part by the present invention.

Figure 3 schematically shows an exhaust gas treatment system 350 according to the present invention which is connected with an exhaust line 302 to an internal combustion engine 301. Exhaust gases generated during combustion in the engine 301 and the exhaust gas stream 303 (indicated by arrows) are led to a first oxidation catalyst DOC1310, which is arranged to oxidize nitrogen compounds, carbon compounds and / or hydrocarbon compounds in the exhaust gas stream 303 of the exhaust gas treatment system 350.

The particulate filter 320 is described below. During the oxidation in the first oxidation catalyst DOC1310, a part of the nitrogen monoxides NO in the exhaust gas stream 303 is oxidized to nitrogen dioxide NO2. A first metering device 371, which is arranged downstream of the first oxidation catalyst DOC1310 and is arranged to supply a first additive in the exhaust stream 303. A first reduction catalyst device 331 is arranged downstream of the first metering device 371. The first reduction catalyst stream 33 utilizing the first additive added to the exhaust stream by the first metering device 371. In more detail, the first reduction catalyst device 371 uses an additive, for example ammonia NH 3 or urea, from which ammonia can be generated / formed / released, in the reduction of the nitrogen oxides NO may, for example, consist of the above-mentioned AdBlue.

According to an embodiment of the invention, a first hydrolysis catalyst, which may consist of substantially 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 then used to increase the rate of degradation of urea to ammonia and / or to mix the additive with the emissions and / or to evaporate the additive.

The increased proportion of nitrogen dioxides NO2 in the exhaust gas stream 303, which is obtained by using the first oxidation catalyst DOC1310 placed upstream of the first reduction catalyst device, means that a larger proportion of the total conversion of nitrogen oxides NOx occurs via the fast reaction path. both nitric oxide NO and nitrogen dioxide NO2.

The first oxidation catalyst mounted upstream of the 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 NO2 / NOx ratio between the amount of nitrogen dioxide NO2 and the amount of nitrogen oxides NOx before the first reduction step, by adjusting / adjusting the level / amount of the nitrogen oxides NOxatalate reaching the first oxidation by engine and / or combustion measures. In other words, if necessary, an adjustment of a ratio NO2_SCR1 / NOx_SCR1 is performed here between the first amount of nitrogen dioxide NO2_SCR1 and the first amount of nitrogen oxides NOx_SCR1 which reach the first reduction catalyst device 331.

The adjustment is effected by an active control by means of engine and / or combustion measures of an amount of nitrogen oxides NOX_DOC1 which is emitted from the engine and then reaches the first oxidation catalyst 310. Indirectly an active control is also obtained of the first amount of nitrogen oxides NOx first amount of nitrogen oxides NOx_SCR1 depends on the amount of nitrogen oxides NOx_DOC1 emitted from the engine.

According to one embodiment, the present invention also enables a control of a NO2 / NOx ratio between the amount of nitrogen dioxide NO2 and the amount of nitrogen oxides NOx before 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 comprises 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 is arranged to capture soot particles. The oxidizing coating is arranged to oxidize soot particles and one or more of nitric oxide NO and incompletely oxidized carbon compounds in the exhaust stream 303. This document describes the exhaust treatment system for pedagogical reasons mainly according to the embodiment where the particle filter 320 at least partially 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 catalytically oxidizing coating is disposed between the first and second reduction catalyst devices.

The exhaust stream 303 is passed here 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 stream 303 reaches after passing 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 SCR1, or a first selective catalytic reduction catalyst SCR1 downstream followed by a first slip catalyst ASC1 / AMOX1. Since the particulate filter 320 is the first exhaust gas treatment system component that the exhaust gas stream 303 reaches after passing the first reduction catalyst device 331, for this embodiment substantially no oxidation of nitric oxide NO and / or incompletely oxidized carbon compounds occurs between the first reduction catalyst device 3201 and the particulate filter device 331.

An advantage of connecting the particulate filter 320 downstream of the reduction catalyst device 331 without intermediate exhaust gas treatment system components, apart from any pipe connections, is that the number of substrates in the exhaust gas treatment system 350 will be less than, for example, a second oxidation catalyst DOC2 would have been to 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 particle filter 320. In other words, the second oxidation catalyst DOC2 is arranged downstream of the first reduction catalyst device 331 and thus extruded therefrom. the 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 an 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 particle filter DPF 320 lacking catalytic oxidizing coating.

The catalytic oxidizing coating may, according to another embodiment when 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.

When 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. That is, the particulate filter 320 may be at least partially coated with one or more noble metals, such as platinum.

The particulate filter cDPF 320 comprising the oxidizing coating has several advantages over a classic particulate filter DPF without oxidizing coating.

The particle filter cDPF 320 comprising the oxidizing coating gives an improved NO2-based regeneration of the filter, i.e. 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, i.e. 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 intends, by utilizing the catalytic oxidizing coating, 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. During active regeneration, the exhaust gas treatment system according to the invention has an advantage in that the first reduction catalyst device itself can handle a certain NOx conversion while the second reduction catalyst device arranged downstream of the filter, due to the regeneration, experiences such a high temperature that it is difficult to reach 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 comprises the oxidizing coating also provides 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 coating and / or of the second oxidation catalyst DOC2 allows the value of the NO2 / NOx ratio, i.e. the NO2 content, to be controlled.

Downstream of the particulate filter 320, the exhaust gas treatment system 350 is provided with a second metering device 372, which is arranged to supply a second additive in the exhaust stream 303, this second additive comprising 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, i.e. 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 tanks.

In addition, according to an embodiment of the invention, 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 first mixer.

The exhaust gas treatment system 350 also includes a second reduction catalyst device 332, which is disposed downstream of the second metering device 372. The second reduction catalyst device 332 is arranged to reduce nitrogen oxides NOx in the exhaust stream 303 by utilizing the second additive and, if the first additive stream is present, 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 failure in metered amount of reducing agent can be achieved by an embodiment of the invention, where a NOx sensor 363 is placed between the two dosing devices 371, 372, and preferably between the particle filter 320 and the second dosing device 372, in the exhaust gas treatment system 350. it is possible to correct 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 particle 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 372, also makes it possible to correct the amount of additives dosed by the second dosing device 372 for nitrogen oxides NOx which can be created over the particle filter cDPF. 320 of excess residues of the additive from that dosing performed by 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 reducing nitrogen oxides NOx and / or with respect to volumes of the first 331 and second 332 reduction catalysts, respectively. By the present invention, the particulate filter 320 is utilized to the advantage of the function by taking into account how its thermal mass affects the temperature of the second reduction catalyst 332 and how the catalytic coating affects the NO2 / NOx content upstream of the second reduction catalyst 332 in the exhaust gas purification.

By taking into account the thermal inertia of the particle 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 are arranged to co-purify the exhaust gases of the present invention, the exhaust gas treatment system 350, or at least some of its components, can be made compact. When the space set aside for the exhaust gas treatment system 350, for example in a vehicle, is limited, it is a great advantage 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 provides 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 NOxi the exhaust stream at substantially all driving cases, including especially cold starts and load applications, i.e. increased required torque, from low exhaust 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 driving cases that give rise to a transient temperature course in the exhaust gas treatment. An example of such a driving case can be city driving, which includes many starts and decelerations.

The prior art problems associated with an excessive proportion of nitrogen dioxides NO2 can be solved at least in part by utilizing the present invention, since two reduction catalyst devices 371, 372 are included in the exhaust gas treatment system 350. The problem can be addressed by combining the present invention with the insight the proportion of nitrogen dioxides NO2 obtained downstream of a filter / substrate coated with a catalytic oxidizing coating, i.e. the amount of nitrogen oxides NOx can be used to control the value of the NO2 / NOx ratio. By reducing the nitrogen oxides NOx above the first reduction catalyst device 371 in low temperature operation, a requirement for a given ratio of nitrogen dioxide to nitrogen oxides NO2 / NOxi the exhaust gases reaching the second reduction catalyst device 372 can be met with a smaller, and thus less expensive, amount of oxidizing coating between the first 331 and second 332 the reduction catalyst device, i.e. on the second oxidation catalyst DOC2 and / or on the particle filter cDPF.

According to one embodiment, the first reduction catalyst device 331 in the exhaust gas treatment system 350 is active at a lower reduction temperature range. 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 NOxi the first reduction catalyst device 331. Thus the reduction of nitrogen oxides NOxi the first reduction catalyst device 331 does not necessarily in the particulate filter 320 because they are active in at least partially different temperature ranges; Three? Tox.

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 then achieved at the expense of reducing the engine's overall efficiency with regard to 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 made to react more quickly to this heat generated than has been possible for, for example, the Euro VI system. Therefore, less fuel is consumed overall by utilizing the present invention.

According to an embodiment of the present invention, the engine is controlled to create such heat to an extent so that the first reduction catalyst device reaches a certain given temperature / performance. Thus, an efficient exhaust gas purification can then be obtained by the first reduction catalyst device being able to operate at a favorable temperature, while at the same time an unnecessarily large heating, and thus fuel efficiency, is avoided.

Unlike the above-mentioned prior art solutions, the first reduction catalyst device 331 according to the present invention does not have to be closely connected to the engine and / or turbo. The fact that the first reduction catalyst device 331 according to the present invention can be mounted further from the engine and / or turbo, and for example can 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 turbo 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 of having the possibility of reducing nitrogen oxides NOx both upstream and downstream of the thermally inert filter cDPF.

A further advantage of the present invention can be deduced from the fact that the first oxidation catalyst DOC1310 and the second reduction catalyst device 332 are situated / placed in thermally different positions. This means, for example, during a load application that the first oxidation catalyst DOC1310 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 is then given, as mentioned above, the possibility of reducing nitrogen oxides NOx before the second reduction catalyst device 332. In addition, the layout / configuration of the exhaust gas treatment system 350 will also lead to the second reduction catalyst device 332 being able to perform the reduction according to fast SCR. SCR ") when the first oxidation catalyst DOC1310 can begin to convert nitrogen monoxide NO to nitrogen dioxide NO2 at an early stage. At the critical load application, when there is a 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 DOC had been part of 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 SCR1, · a first selective catalytic reduction catalyst SCR1 downstream integrated with a first slip catalyst ASC1 / AMOX1, where the first slip catalyst ASC AMOX1 is arranged to oxidize a residue of additives, where the residue may consist, for example, of urea, ammonia NH3 or isocyanic acid HNCO and / or to be SCR1 helpful in further reducing nitrogen oxides NOxi the exhaust gas stream 303; a first selective catalytic reduction catalyst SCR1 downstream followed by a separate first grinding catalyst ASC1, wherein the first grinding catalyst ASC1 is arranged to oxidize a residue of additives, the residue may consist for example of urea, ammonia NH3 or isocyanic acid HNCO and / or to be SCR1-assisted by further reducing nitrogen oxides NOxi the exhaust gas stream 303; and - a first slip catalyst ASC1, which is primarily arranged for reduction of nitrogen oxides NOx and secondarily for 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.

According to various embodiments, the second reduction catalyst device 332 is constituted by 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 is arranged to oxidize a residue of additives and / or to be SCR2 helpful with a further reduction of the nitrogen gas NOx3 ; 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 be SCR2 helpful with a further reduction of nitrogen oxides NOxi 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 2 O 5 / WO 3 / TiO 2. Metals such as iron and / or copper can also be included in the first 331 and / or second 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 where each unit DOC1, DOC2, SCR1, SCR2, (c) DPF, ASC1, ASC2 has the respective characteristics set out throughout this document. The particulate filter 320 with the at least partially catalytic oxidizing coating is referred to herein as cDPF. A particulate filter 320, which as described above may have, but does not have to have, a catalytic oxidizing coating is referred to below and in this document (c) DPF. Thus, in this document, the term DPF includes a particulate filter that is not coated with oxidizing coating. The term cDPF includes a particulate filter that is at least partially coated with oxidizing coating, the term (c) DPF includes both DPF and cDPF, which means that particulate filter termed (c) DPF can be either a particulate filter DPF without oxidizing coating or a particulate filter cDPF with oxidizing coating. The catalytic oxidizing coating can be adapted to its properties of oxidizing nitric oxide NO and oxidizing incompletely oxidized carbon compounds.

Incompletely oxidized carbon compounds can, for example, consist of 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. That is, the exhaust gas treatment system 350 comprises a first oxidation catalyst DOC1, downstream followed by a first selective catalytic reduction catalyst SCR1, downstream followed by a particle filter with an at least partially catalytic oxidizing coating cDPF, downstream followed by a second selective catalytic catalytic reductionR2. For the above-described embodiment where also a second oxidation catalyst DOC2 is arranged between SCR1 and (c) DPF, the system has the structure DOC1-SCR1-DOC2- (c) DPF-SCR2. A symbiotic utilization of both the first selectively catalytic reduction catalyst SCR1 together with the second selectively catalytic reduction catalyst SCR2i in the exhaust gas treatment system 350 may enable a second abrasive catalyst ASC2 to be omitted in the exhaust gas treatment system 350 for certain limited application requirements, 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 omitting 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. That is, the exhaust gas treatment system 350 comprises a first oxidation catalyst DOC1, downstream followed by a first selective catalytic reduction catalyst SCR1, downstream followed by a first slip catalyst ASC1, downstream followed by a particulate filter with an at least partially catalytic oxidizing coating followed by cDPF, second selective catalytic reduction catalyst SCR2.For the above-described embodiment where also a second oxidation catalyst DOC2 is arranged between SCR1 and (c) DPF, the system has the structure DOC1-SCR1-DOC2-ASC1- (c) DPF-SCR2. As mentioned above, the use of both the first selectively catalytic reduction catalyst SCR1 and the second selectively catalytic reduction catalyst SCR2i in the exhaust treatment system 350 allows a second slip catalyst ASC2 to be omitted in the exhaust gas treatment system 350 for certain applications, which reduces the production cost. The utilization of the first slip catalyst ASC1 enables a greater load and thus a better utilization of the first selective catalytic reduction catalyst SCR1 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. That is, the exhaust gas treatment system 350 comprises a first oxidation catalyst DOC1, downstream followed by a first selective catalytic reduction catalyst SCR1, downstream followed by a particle filter with an at least partially catalytic oxidizing coating cDPF, downstream followed by a second selective catalytic catalytic reduction. second grinding catalyst ASC2.For the above-described embodiment where also a second oxidation catalyst DOC2 is arranged between SCR1 and (c) DPF, the system gets the structure DOC1-SCR1- DOC2- (c) DPF-SCR2-ASC2 .This exhaust treatment system 350 enables emission levels for nitrogen ox zero, since the second reduction catalyst SCR2 can be heavily loaded, for example by increasing the dosage of the second additive, as it is followed downstream by the second abrasive catalyst ASC2.

According to a configuration according to the invention, the exhaust gas treatment system has the structure DOC1-SCR1-ASC1-cDPF-SCR2-ASC2. That is, the exhaust gas treatment system 350 comprises a first oxidation catalyst DOC1, downstream followed by a first selective catalytic reduction catalyst SCR1, a downstream catalyst followed by a first downstream catalyst. , downstream followed by a particle filter with an at least partially catalytic oxidizing coating cDPF, downstream followed by a second selective catalytic reduction catalyst SCR2, downstream followed by a second grinding catalyst ASC2. c) DPF gets the system structure DOC11 SCR1-ASC1-DOC2- (c) DPF-SCR2-ASC2 .This exhaust gas treatment system 350 enables emission levels for nitrogen oxides NOx near zero, it is followed downstream by the second slip catalyst satorn ASC2.

The utilization of the first slip catalyst ASC1 also enables a lowering of the starting temperature ("light off" temperature) for the NOx reduction and can also give a greater load and thus a better utilization of the first selective catalytic reduction catalyst SCR1.

According to a configuration according to the invention, the exhaust gas treatment system has the structure DOC1-ASC1-cDPF-SCR2. That is, the exhaust gas treatment system 350 comprises a first oxidation catalyst DOC1, downstream followed by a first grinding catalyst ASC1, downstream followed by a particulate filter with an at least partially catalytic oxidizing coating cDPF, downstream followed by a second selective catalytic reduction catalyst described above. the embodiment where also a second oxidation catalyst DOC2 is arranged between SCR1 and (c) DPF, the system has the structure DOC1-ASC1-DOC2- (c) DPF-SCR2. the reduction catalyst SCR2, the second grinding catalyst ASC2 is omitted in the exhaust gas treatment system 350 for certain applications. The use of the first abrasive catalyst ASC1 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-ASC1-cDPF-SCR2-ASC2. That is, the exhaust gas treatment system 350 comprises a first oxidation catalyst DOC1, downstream followed by a first grinding catalyst ASC1, downstream followed by a particulate filter with an at least partially catalytic catalyst surface. coating cDPF, downstream followed by a second selective catalytic reduction catalyst SCR2, downstream followed by a second abrasive catalyst ASC2. For the above-described embodiment where also a second oxidation catalyst DOC DPF-SCR2-ASC2. This exhaust gas treatment system 350 enables emission levels for nitrogen oxides close to zero, as the second reduction catalyst SCR2 can be heavily loaded, i.e. with a relatively high dosage of the second additive, as it is followed downstream by the second grinding catalyst ASC2.

The use of the first slip catalyst ASC1 enables 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 SCR1 and the first grinding catalyst ASC1 may consist of an integrated unit comprising both SCR1 and ASC1, or may consist of separate units for SCR1 and ASC1.

Correspondingly, the second reduction catalyst SCR2 and the second grinding catalyst ASC2anting may be an integrated unit comprising both SCR2 and ASC2, or may consist of separate units for SCR2 and ASC2.

According to an embodiment of the present invention, the exhaust gas treatment system 350 comprises an additive supply system 370, which comprises at least one pump 373 arranged to supply the first 371 and second 372 dosing devices with additives, i.e. 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. Liquid additives 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 that both the first and the second dosing device are used. for dosing in different types of operation. The optimized utilization, for example, is then not limited to the fact that the first dosing device is only used for cold starts. There is thus already an existing distribution network for liquid additives, which ensures access to additives where 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, gaseous additive is also 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 nitrogen dioxide NO2 during normal operation of the internal combustion engine, i.e. not only in cold starts, can be reduced by using an embodiment of the present invention by dosing the additive at both the first 371 and second 372 metering devices. 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 is sufficient without interruption for service, since liquid additives are available for purchase at regular gas stations. In this way, substantially continuous dosing with both the first 371 and second 372 dosing devices can be done during normal service intervals for 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 guaranteed availability of additives also means that a reliable control of the NO2 content NO2 / NOx can always be performed, ie during the entire service intervals.

Utilizing additives in liquid form for dosing with both the first 371 and second 372 dosing devices means that the complexity of the system 370 is kept low, since a common tank can be used for storing the additive.

Liquid additives 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 H2.

An example of such an additive supply system 370 is shown schematically in Figure 3, where the system comprises the first dosing device 371 and the second dosing device 372, which are arranged upstream of the first reduction catalyst 331 and upstream of the second reduction catalyst 332. The first and second dosing devices 371, 372, which are often dispensing nozzles that dispense additives to, 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 here that the additive may be in liquid and / or gaseous form, as described above. When the additive is in liquid form, the pump 373 is a liquid pump and the one or more tanks 376 are liquid containers. When the additive is 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, where at least one tank and pump are arranged for the supply of liquid additives and at least one tank and pump are arranged for the supply of 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 additive, 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 additives, respectively. The specific function of the additive system 370 is well described in the prior art, and the exact method of injecting additives is therefore not described in more detail here. In general, however, the injection point / SCR catalyst temperature should be above a lower limit temperature to avoid precipitation and the formation of undesirable by-products, such as ammonium nitrate NH4NO3. An example of a value for such a lower limit temperature may be about 200 ° C. According to an embodiment of the invention, the system 370 for supplying additives comprises a dosing control unit 374 arranged to control the at least one pump 373, so that additives are supplied to the exhaust gas stream. Dosing control unit 374 according to one embodiment 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. Dosing control unit 374 also comprises a second pump control unit 379 arranged to control the at least one pump 373 in such a way that a second dose of the second additive is supplied to the exhaust gas stream 303 via the second dosing device 372.

The first and second additives are usually 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, which means that the dosage of each of the first 331 and second 332 reduction catalyst devices, and thus also the function of each and one of the first 331 and second 332 reduction catalyst devices can also be optimized 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 different types of additives to the first dosing device 371 and the second dosing device 372. As mentioned above, the one or more tanks and the one or more pumps are adapted to the condition of the additive, i.e. to if the additive is 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 gas stream 303 by means of the first 371 and second 372 metering devices upstream of the first 331 and second 332 reduction catalyst devices. 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 gas stream 303 via the first dosing device 371. The second pump control unit 379 is arranged to control either a common pump, or a pump dedicated to the second metering device 372, whereby the second metering is controlled to be supplied to the exhaust gas 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 herein by means 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 is fed to a first additive by utilizing a first metering device 371 disposed downstream of said first oxidation catalyst 310. In a third stage 403 of the process, a reduction of nitrogen oxides NOxi to the exhaust stream is performed by utilizing this first additive in a first reducing agent. 331, which may comprise a first selective catalytic reduction catalyst SCR1 and / or a first abrasive catalyst ASC1, arranged downstream of the first dosing device 371. The first abrasive catalyst ASC1 oxidizes here a residue of additives, the remainder may consist of for example urea, ammonia NH3 or isocyanic acid HNCO, and / or provides a further reduction of NOx nitrogen oxides in the exhaust gas stream 303. It should be noted that the reduction of NOx nitrogen oxides by the first reduction catalyst device 331 in this document may include partial oxidation as long as the total reaction constitutes a reduction in v nitrogen oxides NOx.

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 catalytically 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 supplied to the exhaust gas stream 303 using a second metering device 372. In a sixth step 406 of the process, a reduction of the nitrogen oxides NOxi to the exhaust gas stream 303 is performed by using at least the second additive in a second reduction catalyst 33, which catalyst catalyst may comprise a second selective catalytic reduction catalyst SCR2 and in some configurations a second grinding catalyst ASC2, arranged downstream of the second dosing device 371. The second grinding catalyst here oxidizes an excess of ammonia and / or gives a further reduction of nitrogen oxides NOxi the exhaust gas stream 303. that the reduction of nitrogen oxides NOx by the second reduction catalyst device 332 in this document may include partial oxidation as long as the total reaction constitutes a reduction of nitrogen oxides NOx.

It can be seen that a first temperature T1 to which the first reduction catalyst device 331 is exposed and a second temperature T2 to which the second reduction catalyst device 332 is exposed are of great importance for the operation of the exhaust gas treatment system 350. However, it is difficult to regulate these temperatures T1, T2, as they largely depend on how the driver drives the vehicle, i.e. the first T1 and second 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 become considerably more efficient than a traditional system (as shown in Figure 2) in that the first temperature T1 of the first reduction catalyst device 331, for example at start-up processes, previously reaches higher values of the first temperature T1, and thereby higher efficiency in the reduction of nitrogen oxides NOx by the process of the present invention. Thus, a more effective reduction of nitrogen oxides NOx is obtained here, for example at cold starts and at start-ups from low exhaust temperatures, which gives a smaller increase in fuel consumption in such driving cases. In other words, the present invention utilizes the difficult-to-control first T1 and second T2 temperatures to its advantage in 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 using 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 nitric 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 NOx conversion can be obtained via rapid SCR, i.e. by means of nitric oxide NO and nitrogen dioxide NO2. to a greater extent takes place via reaction pathways over both nitrogen monoxide NO and nitrogen dioxide NO2, the total claim for catalyst volume can be reduced at the same time as the transient response is improved for the NOx reduction.

In addition, the upstream first reduction catalyst device 331 mounted first oxidation catalyst 310 can also be used to generate heat in downstream mounted components, which according to one embodiment can be used for a robust initiation of regeneration of the particulate filter 320 in the exhaust gas treatment system 350 and / or can be used to optimize NOx 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 the first reduction catalyst device 331 to take place within a reduction temperature range Tred, which differs at least in part from an oxidation temperature range Toxinom in which a significant sotoxidation by the particle filter 320 takes place, Tred? Tox, whereby the reduction of nitrogen oxides NOxi the first reduction catalyst device does not significantly compete with the nitrogen dioxide-based sotoxidation in the particle filter cDPF because they are active in at least partially different temperature ranges Tred? Tox.

According to an embodiment of the method according to the present invention, the supply of additives to the first dosing device 371 and / or the second dosing device 372 is increased to a level of added additive at which residues / precipitates / crystallization can occur. This level can be determined, for example, by comparison with a predetermined limit 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 here can mean that the supply is completely interrupted. Hereby, for example, a larger dosing 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 here 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 need not be arranged to be able to shut down the supply by means of the first dosing device 371 for 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 may also be optimized based on properties, such as catalytic properties, of 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 that 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 second 372 reduction catalyst device, a catalyst type of the first 371 and / or second 372 reduction catalyst device, a temperature range within which the first 371 and / or second 372 reduction catalyst device is active, a degree of ammonia coverage for the first 371 and / or second 372 reduction catalyst device 372.

According to an embodiment of the present invention, the first reduction catalyst device 371 and the second reduction catalyst device 372, respectively, are optimized based on 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 / NOx in the first reduction catalyst device 371. This has an advantage in the first metering device 371 can then be controlled so that the exhaust gas stream contains a proportion of nitrogen dioxide NO2 when it reaches the particulate filter 320, enabling efficient reaction kinetics over the first reduction catalyst device 331 by rapid SCR, and some nitrogen dioxide-based (NO2-based) sotoxidation. In other words, access to nitrogen dioxide NO2 here can be guaranteed by 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 remaining in the exhaust stream 303 when it reaches the particulate filter 320. nitrogen oxides NO2 / NOx, upstream of the first reduction catalyst device 371 can be determined, for example, based on predetermined data for the first oxidation catalyst 310, for example in the form of mapped values for nitrogen dioxide NO2 after the first oxidation catalyst 310. With such control of the dosage of the first additive comes all dosed additive, and the entire NOx conversion over the first reduction catalyst device, is consumed by rapid SCR, which has the advantages mentioned in this document.

As a non-limiting example, the control here can be performed so that the dosage of the first additive very rarely corresponds to a NOx conversion exceeding the value of 2 times the ratio between the proportion of nitrogen dioxide NO2 and the proportion of nitrogen oxides NOx, i.e. the dosage of the first additive corresponds to a NOx conversion less than (NO2 / NOx2 *. If, for example, NO2 / NOx = 30%, then the dosage of the first additive can be controlled to correspond to a NOx conversion less than 60% (2 * 30% = 60%), e.g. a NOx conversion equal to about 50%, which would guarantee that the reaction rate over the first reduction catalyst device is fast and that 5% nitrogen dioxide NO2 remains for NO2-based sotoxidation by the particulate filter 320.

According to an embodiment of the process of the present invention, an active control of the reduction performed by the first reduction catalyst device 331 is performed based on a ratio between the amount of nitrogen dioxide NO2_SCR2 and the amount of nitrogen oxides NOx_SCR2 reaching the second reduction catalyst device 332. In other words, a ratio of NO the reduction in the second reduction catalyst device 332 suitable value, whereby a more efficient reduction can be obtained. Thus, in more detail here, the first reduction catalyst device 331 performs a first reduction of a first amount of nitrogen oxides NOx_SCR1 reaching the first reduction catalyst device 331. At the second reduction catalyst device 332, a second reduction of a second amount of nitrogen oxides NOx_SCR2 is performed. is performed by the ratio NO2_SCR2 / NOx_SCR2 between the amount of nitrogen dioxide NO2_SCR2 and the second amount of nitrogen oxides NOx_SCR2 which reach the second reduction catalyst device 332.

This adjustment is performed here by utilizing an active control of the first reduction based on a value for the ratio NO2_SCR2 / NOx_SCR2, with the intention of giving the ratio NO2_SCR2 / NOx_SCR2 a value which makes the second reduction more effective. The value for the NOx_SCR2 / NOx_SCR2 ratio can here consist 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 / NOx ratio for the first reduction stage 331 can also be controlled by controlling the level of the nitrogen oxides NOx 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 gas according to the present invention may additionally be implemented in a computer program, which when executed in a computer causes the computer to perform the method. 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 computer-readable non-volatile / durable / durable / permanent medium consists of a suitable memory, such as for example: 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 may be constituted by substantially any suitable type of processor or microcomputer, e.g. a Digital Signal Processor (DSP), or an Application Specific Integrated Circuit (ASIC).

The computing unit 501 is connected to a memory unit 502 arranged in the control unit 500, which provides the computing unit 501 e.g. the stored program code and / or the stored data calculation unit 501 is needed to be able to perform calculations. The calculation unit 501 is also arranged to store partial or final 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 computing unit 501. These signals are then provided to the computing 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 are intended.

Each of the connections to the devices for receiving and transmitting input and output signals, respectively, may consist of 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.

In general, control systems in modern vehicles consist of a communication bus system consisting of one or more communication buses for interconnecting a number of electronic control units (ECUs), or controllers, and various components located on the vehicle. Such a control system can comprise a large number of control units, and the responsibility for a specific function can be divided into more than one control unit. Thus, vehicles of the type shown often comprise significantly more control units than shown in Figure 5, which is well known to those skilled in the art.

As will be appreciated by those skilled in the art, the controller 500 of Figure 5 may include one or more of the controllers 115 and 160 of Figure 1, the controller 260 of Figure 2, the controller 360 of Figure 3, and the controller 374 of Figure 3.

In the embodiment shown, the present invention is implemented in the control unit 500. However, the invention can also 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 according to the invention, such as for instance a vehicle or a voltage / current generator.

The present invention is not limited to the above-described embodiments of the invention but relates to and encompasses all embodiments within the scope of the appended independent claims.

Claims (30)

Patent claims Exhaust gas treatment system (350) arranged to treat an exhaust gas stream (303) which results 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 dosing device (371) arranged downstream of said first oxidation catalyst (310) and arranged to supply a first additive in said exhaust gas stream (303); a first reduction catalyst device (331) arranged downstream of said first dosing device (371) and arranged to reduce nitrogen oxides NOxi said exhaust gas stream (303) by using said first additive, said first reduction catalyst device (331) comprising at least one firstC catalyst ), which is arranged to first carry out reduction of nitrogen oxides NOx and secondly to carry out oxidation of a residue of additives in said exhaust gas stream (303); a particulate filter (320) at least partially comprising a catalytic oxidizing coating, which is arranged downstream of said first reduction catalyst device (331) and is arranged to capture and oxidize soot particles in said exhaust stream (303), and to oxidize one or more of nitric oxide NO and incompletely oxidized carbon compounds in said exhaust stream (303) and; - a second dosing device (372) arranged downstream of said particle filter (320) and arranged to supply a second additive in said exhaust stream (303); and - a second reduction catalyst device (332) arranged downstream of said second dosing device (372) and arranged to reduce nitrogen oxides NOxi said exhaust gas stream (303) by using at least one of said first and said second additives. The exhaust gas treatment system (350) of claim 1, wherein at least one of said first and second additives comprises ammonia or a substance from which ammonia can be recovered and / or released. An exhaust gas treatment system (350) according to any one of claims 1-2, wherein said first reduction catalyst device (331) comprises any of the group of: - a first selective catalytic reduction catalyst (SCR1) downstream integrated with said first slip catalyst (ASC1); a first selective catalytic reduction catalyst (SCR1) downstream followed by said first grinding catalyst (ASC1), said first grinding catalyst (ASC1) being arranged separately; and - said first slip catalyst (ASC1) · An exhaust gas treatment system (350) according to any one of claims 1-3, wherein said second reduction catalyst device (332) comprises someone in the group of: - a second selective catalytic reduction catalyst (SCR2); - 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 (SCR2) with a further reduction of nitrogen oxides NOxi said exhaust stream (303) ; and - a second selective catalytic reduction catalyst (SCR2) downstream followed by a separate second grinding catalyst (ASC2), said second grinding catalyst (ASC2) being arranged to oxidize a residue of additives and / or to assist said second selective catalytic reduction catalyst (SCR2) with a further reduction of nitrogen oxides NOXi in said exhaust gas stream (303). An exhaust gas treatment system (350) according to any one of claims 1-4, wherein said particulate filter (320) is the first exhaust gas treatment system component said exhaust gas stream (303) reaches after passing said first reduction catalyst device (331). 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, comprising at least one pump (373) arranged to supply said first (371) and second (371). 372) dosing device with said first and second additives, respectively. 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). An exhaust gas treatment system (350) according to claim 6, wherein said additive supply system (370) comprises a dosing control unit (374) comprising: - a first pump control unit (378) arranged to control said at least one pump (373), wherein a first dosing of said first additive, said exhaust gas is supplied by using said first dosing device (371); and - a second pump control unit (379) arranged to control said at least one pump (373), a second dose of said second additive being supplied to said exhaust stream by utilizing said second dosing device (372). An exhaust gas treatment system according to any one of claims 1-8, wherein said first reduction catalyst device (331) is arranged to reduce said nitrogen oxides NOXinom a reduction temperature range Trevil which at least partially differs from an oxidation temperature range Toxinom which an oxidation of said incomplete oxides (320) can happen; Third? Tox. An exhaust gas treatment system according to any one of claims 1-9, wherein said first oxidation catalyst (310) is arranged to create heat for downstream mounted components. A process for treating an exhaust stream (303) which results from a combustion in an internal combustion engine (301), characterized by - 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 of nitrogen oxides NOxi in said exhaust stream. first additive in at least one first reduction catalyst device (331) arranged downstream of said first dosing device (371), said first reduction catalyst device (331) comprising at least one first grinding catalyst (ASC1), which primarily performs reduction of nitrogen oxides NOx and secondly performs NOx. oxidation of a residue of additives in said exhaust stream (303); capturing and oxidizing soot particles in said exhaust stream (303), and oxidizing one or more of nitric oxide NO and incompletely oxidized carbon compounds in said exhaust stream (303), by utilizing a particulate filter (320) at least partially comprising a catalytic oxidizing coating, which is 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 particulate filter (320), said supply of said second additive affecting a reduction of nitrogen oxides NOxi 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). The method of claim 11, wherein said internal 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) reaches a predetermined performance spirit. conversion of nitrogen oxides NOx. A process according to any one of claims 11-12, wherein said reduction by means of said first reduction catalyst device (331) is controlled to take place within a reduction temperature range Three which at least partially differs from an oxidation temperature range Toxin happen; Third? Tox. A method according to any one of claims 11-13, wherein said supply of at least one of said first and second additives by using 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. A method according to any one of claims 11-13, wherein said supply of at least one of said first and second additives by using one of said first dosing device (371) and said second dosing device (372), respectively, is reduced, after which residues of at least one of said first and second additives are eliminated by heat of said exhaust stream, said reduction of said feed being performed if required total catalytic function for an exhaust gas treatment system (350) performing said process may be provided after said decreasing. The method of claim 15, wherein said required catalytic function depends on current and / or predicted operating conditions of said internal combustion engine (301). A method according to any one of claims 15-16, wherein said reduction of said supply constitutes an interruption of said supply. A process according to any one of claims 11-17, wherein said effect on said reduction of nitrogen oxides NOx for said first reduction catalyst device (371) is controlled based on one or more properties and / or operating conditions of said first reduction catalyst device (371). A process according to any one of claims 11-17, wherein said effect on said reduction of nitrogen oxides NOx 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). The method of any of claims 11-17, wherein said influence 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). The method of any of claims 11-17, wherein said influence 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). A process according to any one of claims 18-21, wherein said properties of said first (371) and second (372) reduction catalyst devices are related to one or more in the group of: - catalytic properties of said first reduction catalyst device (371); - catalytic properties of said second reduction catalyst device (372); a catalyst type for said first reduction catalyst device (371); a catalyst type for said second reduction catalyst device (372); a temperature range within which said first reduction catalyst device (371) is active; a temperature range within which said second reduction catalyst device (372) is active; - an ammonia coverage of said first reduction catalyst device (371); and - a degree of ammonia coverage for said second reduction catalyst device (372). A process according to any one of claims 18-21, wherein said operating conditions of said first (371) and second (372) reduction catalyst devices are related to one or more in the group of: - a temperature of said first reduction catalyst device (371); - a temperature of said second reduction catalyst device (372); - a temperature trend of said first reduction catalyst device (371); and - a temperature trend for said second reduction catalyst device (372). A method according to any one of claims 11-23, wherein said supply of said first additive by utilizing said first dosing device (371) is controlled based on a distribution of the ratio between nitrogen dioxide and nitrogen oxides NO2 / NOx upstream of said first reduction catalyst device (371). A process according to any one of claims 11-24, wherein - said first reduction catalyst device (331) performs a first reduction of a first amount of said nitrogen oxides NOx_SCR1 which reaches said first reduction catalyst device (331); and - an adjustment of a NO2_SCR1 / NOx_SCR1 ratio between a first amount of nitrogen dioxide NO2_SCR1 and said first amount of nitrogen oxides NOx_SCR1 which reach said first reduction catalyst device (331) is performed as needed, an active control of said first amount of nitrogen oxides and NOx is carried out. A process according to any one of claims 11 to 25, wherein - 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 - adjusting a ratio of NCgSCR2 / NOx_SCR2 between a second amount of nitrogen dioxide NCg SCR2 and said second amount of nitrogen oxides NO2_SCR2 for said ratio NO2_SCR2 / NOx_SCR. A method according to claim 26, wherein said value for said ratio NO2_SCR2 / NOx_SCR2 is constituted by one in the group of: - a measured value; - a modeled value; - a predicted value. A process according to any one of claims 11-27, wherein said first oxidation catalyst (310) and / or a second oxidation catalyst creates heat for downstream mounted components. 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 one of claims 11-28. A computer program product comprising a computer readable medium and a computer program according to claim 29, wherein said computer program is included in said computer readable medium.