SE530028C2 - Method and apparatus for the treatment of exhaust gases and vehicles - Google Patents

Description

550 028 2 technology with exhaust gas recirculation, so-called EGR (exhaust gas recirculation), whereby the recirculated exhaust gases in most cases are also cooled before it is returned to the engine.

EGR lowers the temperature in the combustion chamber and the lower temperature achieves lower NOx levels in the exhaust gases, which are then purified by SCR technology. A significant disadvantage, however, is that EGR causes low temperatures on the exhaust gases, which makes it difficult for the SCR catalyst to work with sufficiently high efficiencies, since SCR catalysts require a certain temperature in order to function satisfactorily.

In addition, known EGR technology lowers the engine's efficiency as some energy is used for the EGR function.

The present invention has for its object to achieve an efficient and cost-effective exhaust gas purification for internal combustion engines, and then in particular for diesel engines, which in addition entails, among other things, lower strength requirements for the engine components such as cylinders etc.

Brief description of the invention The object according to the above is achieved with a method, a device and a vehicle with features according to the independent claims 1, 6 and 12, respectively. Further advantages are achieved with features according to the respective dependent claims.

Brief description of the drawings The invention is described in more detail below in connection with exemplary embodiments and accompanying drawings, in which Fig. 1 schematically shows a first embodiment of a device according to the invention in the form of a block diagram. 530 028 Description example Fig. 1 shows an internal combustion engine exemplified by a supercharged diesel engine 1, which according to the embodiment shown comprises a charge air cooler 2 and a turbocharger 3 of conventional types. Designs without charger fl cooler 2 are conceivable and occur.

The exhaust gases from the engine, represented by an arrow 4, are led in the exhaust line to a first SCR catalyst 5 for selective cathalytic reduction under the reducing action of a reducing agent, preferably urea in a manner known per se, wherein NOx reduced to N; and / or N 2 O. Other reducing agents, such as ammonia, may also be used. Preferred is urea in the form of the substance AdBlue®, which is a 32.5% solution of urea in water, which substance is specified in DIN standard DIN V 70 070.

A device 6 for dosing and mixing urea into the exhaust gases is arranged upstream of the catalyst 5 in the exhaust line. In the schematic figure the device 6 and the catalyst 5 are shown separated, but alternative embodiments are conceivable where these are assembled into one unit.

A second SCR catalyst 7 is arranged in the exhaust line in series with the first SCR catalyst 5 for treating the exhaust gases already treated in the first SCR catalyst 5 in order to further reduce the NOx content in the exhaust gases. A device 8 for dosing and mixing urea is previously arranged upstream of the second SCR catalyst 7 analogously to that arranged at the first catalyst 5. Also in this case embodiments are conceivable where the device 8 and the catalyst 7 are integrated into one unit.

For each catalyst 5, 7 there is a feedback control system 9, 10 respectively, arranged to control the dosing of urea by means of the respective dosing and mixing device 6, 8 to 4 and the respective catalyst, based on the outcome of the treatment in each catalyst. For this purpose, according to the respective catalyst 5, 7 there are sensors which sense the content of representative parameters in the exhaust gases, and which sensors are connected to the respective control system 9, 10 and thereby provide information regarding current parameters. In order for the sensors to be able to detect correct values, it is important that the sensors from each catalyst are arranged in positions where the exhaust gases are homogeneously distributed with regard to the parameters that are sensed. It is therefore an advantage if the exhaust line is designed with a relatively long distance from the catalyst to the current sensor so that the exhaust gases have time to mix well after the outlets from the catalyst. In some cases, it may be necessary to mix them further with the help of guide rails, pipe bends or other ways of mixing the exhaust gases.

According to preferred embodiments, the outcome is detected as excess reducing agent, urea, in the exhaust gases, the respective feedback control system being arranged to control the dosage towards a predetermined content of reducing agent, for example urea, in the exhaust gases, for example a minimization of the reducing agent content

Embodiments are also conceivable where the outcome is detected as the content of NOx in the exhaust gases, wherein the respective control system is arranged to control the dosage towards a predetermined content of NOx in the exhaust gases.

In both cases, reduction of excess funds resp. NOx content, adaptive control systems are conceivable where the dosage is controlled based on experience values of excess and NOx content, respectively.

According to an in some cases particularly preferred form of agitation, the outcome is detected by a combination of the previously described, ie. as well as NOx content and excess reducing agent in the exhaust gases, whereby the respective feedback control system is arranged to control the dosage towards a predetermined outcome with regard to one or both of these quantities. In this case, imperfections of a catalyst can be taken into account. Thus, it occurs that urea accumulates, even accumulates locally, in the catalyst, 530 0128, whereby a detected zero excess of urea in the exhaust gases does not unambiguously mean that the supplied urea is consumed.

At the same time, detected NOx content can add information to be used to achieve a more efficient and more adequate control of the dosage and enable consideration of device technical imperfections of the type described above.

It is conceivable that different embodiments of detection are used for different catalysts.

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

According to preferred embodiments, the treatment of the exhaust gases is intended to be carried out without the engine exhaust gases being recycled to the engine inlet according to known EGR technology.

The engine thus lacks a return line which connects its exhaust side to its inlet side. However, this does not prevent the treatment of exhaust gases according to the invention under certain conditions from being combined with an engine which also uses EGR technology to reduce exhaust emissions.

The method for the treatment of the exhaust gases as well as the function of the device according to the invention should to a substantial part already have been stated in the above part of the description.

The exhaust gases from the engine are first passed to the first SCR catalyst 5 where the exhaust gases in a first treatment step by reaction with the urea injected from the device 6 react with the nitrogen oxides in the exhaust gases to reduce their content.

The content of NOx in the exhaust gases has admittedly been reduced at this stage, but a certain amount of residue still remains. The exhaust gases treated in the first stage are then passed on to the second SCR catalyst 7, which is arranged in series with the first catalyst, where the exhaust gases in a second treatment step by reaction with the urea injected from the device 8 react with the nitrogen oxides in the exhaust gases for further reduction of the NOx content.

Dosage of urea in each step is controlled by means of the feedback control systems 9, 10 in each step based on the outcome in each step, where the outcome can be detected as NOx content and / or excess reducing agent in the exhaust gases after each step.

The invention offers advantages in the form of efficient exhaust gas treatment.

Elimination of the need for EGR offers advantages in the form of acceptance of high exhaust gas temperatures, which leads to more efficient catalyst function. Furthermore, the strength requirements of the motor decrease due to reduced need for durability for high cylinder pressures.

Eliminated EGR naturally eliminates the required EGR system and also means that the vehicle's considerable cooling capacity is sufficient to allow extraction of higher effects. of SCR catalysts.

The invention has been described above in connection with preferred embodiments and embodiments.

Of course, more embodiments as well as minor changes and additions are conceivable without departing from the basic idea of invention.

Thus, two or more SCR catalysts, including dosing and mixing devices, can be assembled into one unit.

UW (N CD CD P »3 G3 7 In the description above, urea has been used as an example of a reducing agent in some cases. - ningarna etc.

Embodiments are conceivable where the same reducing agent is not used in all SCR catalysts.

Furthermore, the feedback control systems can be included as an integral part of the vehicle's overall control and monitoring system. It is also conceivable that a common control system exists for both / all the catalysts.

It has been assumed here that SCR catalysts and dosing and mixing devices are components known to those skilled in the art with known function. The same applies to technology for measuring NOx levels and reducing agent levels in the exhaust gases.

The invention should thus not be considered limited to the above-mentioned embodiments but can be varied within the scope specified by the appended claims.

Claims (12)

10 15 20 25 30 (fl (JJ CD CD iQ! PATENTKRAV A method of treating exhaust gases from an internal combustion engine comprising a first step of reducing the content of nitrogen oxides, NOx, in the exhaust gases by treatment in a first catalyst under the reducing action of reducing agent, and a second step of further reducing the content of nitrogen oxides. , NOx, in the exhaust gases by treating the exhaust gases thus treated in the first catalyst (5) in at least one further catalyst (7) connected in series with the first catalyst (5) under the reducing action of reducing agent characterized by the steps of metering the feed of reducing agents for each catalyst (5, 7) based on the outcome of the treatment in each catalyst by means of feedback control systems (9, 10), which control systems are for this purpose connected to sensors arranged after the respective catalyst (5, 7) and which sense the content of parameters representing in the exhaust gases and thereby provide information regarding current parameters. Method according to claim 1, characterized by the step of determining the outcome as NOx content and / or excess reducing agent in the exhaust gases. Method according to Claim 1 or 2, characterized in that urea is used as reducing agent, preferably in the form of AdBlue®. Method according to claim 1, 2, or 3, characterized by the step of providing information regarding the NOx content in the exhaust gases after at least one catalyst (5, 7) as a basis for dosing reducing agents for that catalyst (5, 7). and the step of dosing a reducing agent for the catalyst (5, 7) against a predetermined content of NOX in the exhaust gases. Method according to claim 1, 2, or 3, characterized by the step of providing information concerning the excess reducing agent in the exhaust gases after at least one catalyst (5, 7) as a basis for dosing reducing agent for that catalyst. Üilšš 9 (5, 7) and the step of dosing a reducing agent for the catalyst (5, 7) so that the excess of reducing agent is minimized. Apparatus for treating exhaust gases from an internal combustion engine, comprising means for reducing the content of nitrogen oxides, NOx, in the exhaust gases by treatment in a first catalyst under the reducing action of reducing agent, and at least one further catalyst (7) for treatment under reducing action of reducing agent of the exhaust gases thus treated in the first catalyst (5), which further catalyst (7) is connected in series with the first catalyst (5), characterized by devices (6, 8) for dOSCIa ICÖUKÜOHSIHCÖCI for supply for each catalyst (5, 7) based on the outcome of the treatment in each catalyst (5,7) by means of feedback control systems (9, 10), which control systems (9, 10) are for this purpose connected to sensors arranged after each catalyst (5, 7) and which senses the content of parameters representing in the exhaust gases and thereby provides information regarding current parameters. Device according to Claim 6, characterized by devices for determining the outcome as NOx content and / or excess of reducing agent in the exhaust gases or catalyst (5, 7), respectively. Device according to claim 6 or 7, characterized in that said reducing agent is urea, preferably in the form of AdBlue®. Device according to claim 6, 7 or 8, characterized by devices for providing information regarding the NOx content in the exhaust gases as a basis for dosing reducing agents to at least one catalyst (5, 7) and for the control system (9, 10) is arranged to dose reducing agent for the catalyst in question (5, 7) against a predetermined content of NOx in the exhaust gases. 10 * CO 550 02 10 Device according to claim 6, 7 or 8, characterized by devices for providing information concerning the content of reducing agent in the exhaust gases as a basis for dosing reducing agent to at least one catalyst (5, 7) and for the control system (9, 10 ) is arranged to dose reducing agent for the catalyst in question (5, 7) so that excess reducing agent is minimized. Device according to Claim 7, 8, 9e11er 10, characterized in that at least two catalysts (5, 7) are arranged as a unit for serial treatment of the exhaust gases. Vehicle, characterized in that it comprises devices according to any one of claims 6-11.