Method and device for treating exhaust gases, as well as vehicle

Abstract

Method for treating exhaust gases from an internal combustion engine, comprising a first step in reducing the level of nitrogen oxides (NOx). X in the exhaust gases by treatment in a first catalyst under the reducing influence of a reducing agent, and a second step in further reducing the level of nitrogen oxides (NOx). X in the exhaust gases by treating the exhaust gases previously treated in the first catalyst (5) in at least one further catalyst (7) arranged in series with the first catalyst (5) under the reducing influence of a reducing agent, characterized by Steps of metering the supply of reducing agent for each catalyst (5, 7) based on the results of the treatment in the respective catalyst by means of control systems (9, 10) which are each connected to sensors arranged downstream of the associated catalyst (5, 7) which detect the content of representative parameters in the exhaust gases and thereby provide information about relevant parameters, where urea or ammonia is used as the reducing agent, and where the treatment result is expressed as NO X -Content and is determined as excess reducing agent in the exhaust gases.

Description

[0001] The present invention relates to a method for treating exhaust gases from an internal combustion engine according to the preamble of appended claim 1. The invention further relates to a device for treating exhaust gases according to the preamble of appended claim 5. The invention also relates to a vehicle according to claim 10.

[0002] In internal combustion engine technology, a high combustion temperature is often associated with better performance, lower fuel consumption, and lower emissions of both particulates and hydrocarbons and carbon monoxide. However, a high combustion temperature also produces undesirably high emissions of nitrogen oxides (NO X ).

[0003] Already known technology for cleaning the exhaust gases of combustion engines such as diesel engines involves, among other things, the removal of nitrogen oxides (NO X) and particulate emissions.

[0004] For example, Austrian patent AT 412 845 B describes an exhaust gas treatment system for reducing NO X Emissions from heat engines using a fuel-derived reducing agent are known. The exhaust gas treatment system includes a high-temperature and a low-temperature catalyst connected in series in the exhaust stream.

[0005] Furthermore, a method and a device for supplying a reducing agent into a catalyst device are known from German patent application DE 100 38 741 A1.

[0006] Under current and even more so under the expected future legislation regarding exhaust emissions, high NO X Proportions are not acceptable. Techniques for selective catalytic reduction, so-called SCR (Selective Catalytic Reduction) technology, have been developed, in which nitrogen oxides (NO X) in exhaust gases are reduced by means of ammonia, e.g. in the form of urea as in the AdBlue ® traded type, which is fed in liquid form to an SCR unit.

[0007] However, current SCR technology is not sufficiently effective to achieve the low emissions of NO required for future legislation. X to achieve, so that development is now focused on reducing NO X -content from the engine by using a combination of SCR technology with exhaust gas recirculation, so-called EGR (Exhaust Gas Recirculation), in which recirculated exhaust gases are in most cases also cooled before being returned to the engine. EGR reduces the temperature in the combustion chamber, and the lower temperature leads to lower NO X-contents in the exhaust gases, which are subsequently cleaned by SCR technology. A major disadvantage, however, is that EGR results in a low exhaust temperature, making it difficult for the SCR catalyst to operate at sufficiently high levels of efficiency, as SCR catalysts require a certain temperature to function satisfactorily. Existing EGR technology also reduces engine efficiency by requiring a certain amount of energy to function properly.

[0008] The object of the present invention is to provide a more effective form of exhaust gas purification for internal combustion engines, in particular for diesel engines.

[0009] The above-mentioned object is achieved by a method, a device, and a vehicle having features according to independent claims 1, 5, and 10, respectively. Further advantages are achieved with the features of the dependent claims.

[0010] The invention will be described in more detail below with reference to embodiments and the accompanying drawings, in which: Fig. 1 schematically shows in the form of a block diagram a first embodiment of a device according to the invention.

[0011] Fig. Figure 1 shows an internal combustion engine, exemplified by a turbocharged diesel engine 1, which, in the embodiment shown, includes a charge air cooler 2 and a conventional turbo unit 3. Versions without a charge air cooler 2 are conceivable and exist.

[0012] The exhaust gases from the engine, represented by an arrow 4, are guided through the exhaust line to a first SCR catalyst 5 for selective catalytic reduction under the reducing influence of a reducing agent in a known manner, which according to the invention is urea or ammonia, whereby NO Xto N2 and / or N2O. The preferred form of urea is the substance AdBlue ® , which is a 32.5% solution of urea in water and is specified in the standard DIN V 70 070.

[0013] A device 6 for metering and adding urea to the exhaust gases is arranged upstream of the catalyst 5 in the exhaust line. The schematic diagram shows the device 6 and the catalyst 5 as separate, but alternative embodiments are also conceivable in which they are combined to form a single unit.

[0014] A second SCR catalyst 7 is arranged in the exhaust line in series with the first SCR catalyst 5 in order to subject the exhaust gases already treated in the first SCR catalyst 5 to a treatment in order to reduce their NO XA device 8 for metering and adding urea is arranged upstream of the second SCR catalyst 7 in a similar manner to the arrangement relating to the first catalyst 5. Again, embodiments are also conceivable in which the device 8 and the catalyst 7 are combined to form a single unit.

[0015] For each of these catalysts 5, 7, there is a control system 9, 10, which is designed to control the metering of urea for the respective catalyst by means of the associated metering and mixing device 6, 8 based on the results of the treatment in the respective catalyst. For this purpose, sensors are located downstream of the respective catalysts 5, 7 to measure the content of representative parameters in the exhaust gases. The sensors are connected to the respective control systems 9, 10 and thus provide information about relevant parameters. It is important that the sensors assigned to the respective catalysts are arranged at locations where the exhaust gases are homogeneously distributed with regard to the measured parameters so that they are able to record correct values.It is advantageous if the exhaust line is equipped with a relatively large distance between the catalyst and the sensor, so that the exhaust gases are thoroughly mixed after leaving the catalyst. In some cases, it may be necessary to further mix them using guide rails, pipe bends, and other exhaust gas mixing devices.

[0016] The treatment result is detected as an excess of reducing agent, urea, in the exhaust gases and the associated control system is designed to control the metering with respect to a predetermined content of reducing agent such as urea in the exhaust gases, e.g. a minimization of the reducing agent content in the exhaust gases.

[0017] Furthermore, the treatment result is measured as the NO content X in the exhaust gases and the associated control system is designed to control the metering with reference to a predetermined NO content X in the exhaust gases.

[0018] In both cases, excess reducing agent or NO X -content, adaptive control systems are conceivable in which the metering is based on empirical values ​​for excess reducing agent or NO X -salary is regulated.

[0019] Thus, the treatment outcome is captured by a combination of the above described, ie both the NO X-content and the excess of reducing agent in the exhaust gases, making the associated control systems suitable for regulating the metering with reference to a predetermined result for one or both of these variables. It is therefore possible to take into account deficiencies in a catalyst. For example, it may happen that urea accumulates, or even accumulates locally in the catalyst, with the result that a detected zero excess of urea in the exhaust gases does not necessarily mean that the supplied urea has been consumed.

[0020] It is therefore possible that a detected NO X -content provides information useful for achieving more effective and appropriate metering control while taking into account technical deficiencies of the type described above.

[0021] It is conceivable that different types of detection are used for different catalysts.

[0022] Embodiments of the device are conceivable in which at least one further SCR catalyst is connected in series with the first two.

[0023] According to preferred embodiments, the exhaust gas treatment is effected without recirculating the engine's exhaust gases to the engine intake according to known EGR technology. The engine will therefore not have a recirculation line connecting its exhaust side to its intake side. This makes it impossible, under certain circumstances, for the exhaust gas treatment according to the invention to be combined with an engine that also uses EGR technology to reduce exhaust emissions.

[0024] The method for treating exhaust gases and the operation of the device according to the invention are perhaps already essentially indicated by the above part of the description.

[0025] The exhaust gases from the engine are first directed to the first SCR catalyst 5, where they undergo a first treatment step in which urea injected by the device 6 reacts with the nitrogen oxides in the exhaust gases, thereby reducing their content. This step certainly reduces the NO content. X in the exhaust gases, but a certain residual amount still remains. The exhaust gases treated in the first step are then passed on to the second SCR catalyst 7, which is arranged in series with the first catalyst, and in which the exhaust gases are subjected to a second treatment step in which urea injected by the device 8 reacts with the nitrogen oxides in the exhaust gases to reduce their NO X -content to be further reduced.

[0026] At each step, the metering of urea is carried out by the control systems 9, 10, at each step on the basis of the results of the respective step, the results being recorded as a NO X -content and / or an excess of reducing agent in the exhaust gases can be detected after the respective step.

[0027] The invention offers advantages in the form of effective exhaust gas treatment.

[0028] Eliminating the need for EGR brings benefits in the form of accepting high exhaust temperatures, leading to more effective catalytic converter performance. It also reduces engine power requirements by reducing the need to tolerate high cylinder pressures. Eliminating EGR, of course, eliminates the need for an EGR system and also results in the vehicle's existing cooling capacity being sufficient to allow more power to be extracted from the engine.

[0029] There is also an intrinsic technical value in that the use of SCR catalysts in series results in a uniform treatment technology that does not affect the engine.

[0030] The invention is described above in connection with preferred embodiments and examples.

[0031] Further examples and minor modifications and additions are of course conceivable without deviating from the basic idea of ​​the invention.

[0032] Two or more SCR catalysts can be combined with associated metering and mixing devices to form a single unit.

[0033] The above description uses urea as an example of a reducing agent at certain points, but in the case of a reducing agent other than urea, the description is still applicable, e.g., with regard to metering and mixing devices, etc.

[0034] Embodiments are conceivable in which the reducing agent used is not the same in all SCR catalysts.

[0035] Furthermore, the control systems can be an integral part of the vehicle's overall control and monitoring system. A common control system controlling both / all of the catalytic converters is also conceivable.

[0036] It has been assumed herein that SCR catalysts and metering and mixing devices are familiar components with known functionality to a person skilled in the art. This also applies to technology for measuring NOx and reductant levels in exhaust gases.

[0037] Therefore, the invention is not to be considered as limited to the embodiments given above, but may be varied within its scope given by the appended claims.

Claims

[1] A method for treating exhaust gases from an internal combustion engine, comprising a first step in reducing the level of nitrogen oxides NO X in the exhaust gases by treatment in a first catalyst under the reducing influence of a reducing agent, and a second step of further reducing the content of nitrogen oxides NO X in the exhaust gases by treating the exhaust gases previously treated in the first catalyst (5) in at least one further catalyst (7) arranged in series with the first catalyst (5) under the reducing influence of a reducing agent, characterized by steps of metering the supply of reducing agent for each catalyst (5, 7) on the basis of the results of the treatment in the respective catalyst by means of control systems (9, 10) each connected to sensors arranged downstream of the associated catalyst (5, 7) which detect the content of representative parameters in the exhaust gases and thereby provide information on relevant parameters, wherein urea or ammonia is used as reducing agent, and wherein the treatment result is NO X -content and as excess reducing agent in the exhaust gases. [2] Method according to claim 1, characterized by that the urea in the form of AdBlue ® is used. [3] Method according to claim 1 or 2, characterized by the step of providing information about the NO X-content of the exhaust gases behind at least one catalyst (5, 7) as a basis for metering reducing agent for the catalyst (5, 7), and the step of metering reducing agent for the catalyst (5, 7) with reference to a predetermined content of NO X in the exhaust gases. [4] Method according to claim 1 or 2, characterized by the step of providing information about the excess reducing agent in the exhaust gases downstream of at least one catalyst (5, 7) as a basis for metering reducing agent for the catalyst (5, 7), and the step of metering reducing agent for the catalyst (5, 7) such that the excess reducing agent is minimized. [5] Device for treating exhaust gases from an internal combustion engine, comprising Devices for reducing the content of nitrogen oxides NO Xin the exhaust gases by treatment in a first catalyst under the reducing action of a reducing agent, and at least one further catalyst (7) for subjecting the exhaust gases previously treated in the first catalyst (5) to a treatment under the reducing action of a reducing agent, the further catalyst (7) being arranged in series with the first catalyst (5), characterized by Devices (6, 8) for metering reducing agent for supply to the respective catalyst (5, 7) on the basis of the result of the treatment in the respective catalyst (5, 7) by means of a control system (9, 10) which is connected to sensors arranged downstream of the associated catalyst (5, 7) which detect the content of representative parameters in the exhaust gases and thereby provide information about relevant parameters, using urea or ammonia as reducing agent, and with devices for determining the treatment result as NO X -content and as excess reducing agent in the exhaust gases. [6] Device according to claim 5, characterized by that the urea in the form of AdBlue ® is present. [7] Device according to claim 5 or 6, characterized by Devices for providing information about the NO X -content of the exhaust gases as a basis for metering reducing agent for at least one catalyst (5, 7), and in that the control system (9, 10) is suitable for metering reducing agent for the relevant catalyst (5, 7) with reference to a predetermined content of NO X in the exhaust gases. [8] Device according to claim 5 or 6, characterized byDevices for providing information on the reducing agent content of the exhaust gases as a basis for metering reducing agent for at least one catalyst (5, 7), and in that the control system (9, 10) is suitable for metering reducing agent for the relevant catalyst (5, 7) so that an excess of reducing agent is minimized. [9] Device according to one of claims 5 to 8, characterized by that at least two catalysts (5, 7) are arranged in series as a unit for treating the exhaust gases. [10] Vehicle, characterized by that it comprises devices according to one of claims 5 to 9.

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