DE102018212193A1 - Exhaust gas treatment device for a diesel internal combustion engine and corresponding diesel internal combustion engine - Google Patents

Abstract

The invention relates to an exhaust gas aftertreatment device (1) for a diesel internal combustion engine, with a diesel oxidation catalytic converter (3) arranged in an exhaust pipe (2) and an SCR catalytic converter (4) arranged downstream of the diesel oxidation catalytic converter (3) in the exhaust pipe for carrying out a selective catalytic reduction. It is provided that a three-way catalytic converter (9) is additionally arranged in the exhaust pipe (2). The invention further relates to a diesel internal combustion engine with an exhaust gas aftertreatment device (1).

Description

The invention relates to an exhaust gas aftertreatment device for a diesel internal combustion engine, having a diesel oxidation catalytic converter arranged in an exhaust pipe, and an SCR catalytic converter arranged downstream of the diesel oxidation catalytic converter in the exhaust pipe for carrying out a selective catalytic reduction. The invention further relates to a diesel internal combustion engine.

The publication is, for example, from the prior art WO 2015/040047 A2 known. This relates to an exhaust gas aftertreatment device for an internal combustion engine. The device has a catalyst chamber containing a catalyst. One or more exhaust gas inlets are provided to guide exhaust gas from the internal combustion engine into the catalyst chamber. Furthermore, an exhaust gas outlet is provided in order to supply exhaust gas from the catalytic converter to an exhaust gas turbocharger. There is also an injection nozzle for introducing a reducing agent into the exhaust gas between the catalytic converter and the turbocharger. The reducing agent and the exhaust gas can be mixed as they pass through the exhaust gas turbocharger. The catalyst may have a three-dimensional open structure to improve the flow of the exhaust gas.

It is an object of the invention to propose an exhaust gas aftertreatment device for a diesel internal combustion engine which has advantages over known exhaust gas aftertreatment devices, in particular enables a reliable conversion of nitrogen oxides contained in the exhaust gas. This is achieved according to the invention in that a three-way catalytic converter is additionally arranged in the exhaust line.

The diesel engine is operated with a fuel, namely diesel fuel, and generates exhaust gas during its operation. This exhaust gas is fed to the exhaust gas aftertreatment device, preferably completely. In other words, the entire exhaust gas generated by the diesel engine is fed to the exhaust gas aftertreatment device. With the help of the exhaust gas aftertreatment device, the exhaust gas is removed from the diesel internal combustion engine, in particular in the direction of an external environment. For example, the exhaust gas aftertreatment device is connected on its side facing away from the flow of the diesel internal combustion engine to an end pipe via which the exhaust gas is released into the outside environment. The exhaust gas aftertreatment device primarily serves to convert pollutants contained in the exhaust gas. In this context, the pollutants include in particular nitrogen oxides, that is to say nitrogen monoxide and / or nitrogen dioxide, carbon dioxide, in particular carbon monoxide and / or carbon dioxide, and hydrocarbon, that is to say unburned fuel.

The exhaust gas aftertreatment device has the exhaust gas line, to which the exhaust gas generated by the diesel internal combustion engine is fed on the input side. The exhaust gas flows through the exhaust gas line and emerges from it on its end facing away from the diesel internal combustion engine. For example, the exhaust pipe is connected on this side to the end pipe already mentioned above. The diesel oxidation catalytic converter and the SCR catalytic converter are available in the exhaust pipe for exhaust gas aftertreatment or exhaust gas purification. The diesel oxidation catalytic converter (DOC) converts in particular carbon monoxide (CO) and hydrocarbon (C _n H _m ) into less dangerous products, in particular by oxidation.

The diesel oxidation catalytic converter is designed, in particular, to operate the diesel internal combustion engine with excess air, that is to say to operate the diesel internal combustion engine more than stoichiometrically. As a catalyst, the diesel oxidation catalyst preferably has platinum, palladium or platinum and palladium, preferably exclusively. Finally, the diesel oxidation catalyst is provided and designed, in particular exclusively, for the oxidation of carbon monoxide and hydrocarbon. The diesel oxidation catalyst is expressly not designed to reduce nitrogen oxide, such as nitrogen monoxide and / or nitrogen dioxide.

For this reason, the SCR catalytic converter is arranged in the exhaust pipe downstream of the diesel oxidation catalytic converter. The SCR catalyst is used to carry out a selective catalytic reduction of nitrogen oxide. For this purpose, a reducing agent is introduced into the SCR catalytic converter or upstream of the SCR catalytic converter into the exhaust pipe. Ammonia, for example, is used as the reducing agent, which reacts with the nitrogen oxide contained in the exhaust gas to form elemental nitrogen and water. During the operation of the exhaust gas aftertreatment device, the reducing agent may be introduced excessively, so that not all of the reducing agent in the SCR catalytic converter reacts with nitrogen oxide, but rather emerges downstream of the SCR catalytic converter.

In order to remove this excess reducing agent from the exhaust gas, an SCR blocking catalytic converter is particularly preferably arranged downstream of the SCR catalytic converter in the exhaust pipe. The SCR lock catalyst is used to implement the excess reducing agent in less dangerous products, in particular the reducing agent reacts with remaining nitrogen oxide. If ammonia is used as a reducing agent, the SCR blocking catalyst can also be referred to as an ammonia blocking catalyst.

The diesel oxidation catalyst preferably has a nitrogen oxide storage or a nitrogen oxide storage component. For example, an alkaline earth metal or an alkaline earth metal compound such as barium carbonate or barium oxide is used as the nitrogen oxide storage. During lean operation of the diesel internal combustion engine, i.e. with excess air, the nitrogen oxide is temporarily stored in the nitrogen oxide store until sufficiently reducing components, in particular hydrocarbon and / or carbon monoxide, are available during rich operation of the diesel internal combustion engine, i.e. with a lack of air.

A strong nitrogen oxide emission occurs in particular in the case of unsteady processes within the diesel internal combustion engine, for example when the load is increased rapidly. Due to the simultaneously occurring high exhaust gas mass flows, the diesel oxidation catalytic converter and the SCR catalytic converter are “run over”, so that the nitrogen oxide conversion performance of the exhaust gas aftertreatment device drops considerably. Such an increase in load often occurs during substoichiometric operation of the diesel internal combustion engine because a high injection quantity and lack of air occur simultaneously. Under these conditions, a three-way catalytic converter can convert a high proportion of nitrogen oxide while maintaining a sufficient temperature. For example, the three-way catalyst can convert at least 90%, at least 92.5% or at least 95% of the nitrogen oxide from a temperature of at least 300 ° C.

For this reason, the three-way catalytic converter is also arranged in the exhaust pipe. This prevents that when the diesel oxidation catalytic converter and the SCR catalytic converter are “run over” as described above, an impermissibly large amount of nitrogen oxide passes through the exhaust gas aftertreatment device and exits from it. In addition, the three-way catalyst can be used to convert carbon oxide and / or hydrocarbon. Against this background, the exhaust gas aftertreatment device with the diesel oxidation catalyst, the SCR catalyst and the additional three-way catalyst is able to ensure a reliable conversion of nitrogen oxide over a wide operating range.

A further embodiment of the invention provides that the three-way catalytic converter is arranged upstream of the diesel oxidation catalytic converter or in terms of flow between the diesel oxidation catalytic converter and the SCR catalytic converter. The arrangement of the three-way catalytic converter upstream of the diesel oxidation catalytic converter is advantageous because of the arrangement close to the engine, because the three-way catalytic converter quickly reaches its operating temperature, from which it reliably reduces the nitrogen oxide contained in the exhaust gas. The arrangement of the three-way catalytic converter located in terms of flow between the diesel oxidation catalytic converter and the SCR catalytic converter, on the other hand, is advantageous with regard to the conversion of carbon oxide and / or hydrocarbon.

Another embodiment of the invention provides that an exhaust gas turbine of an exhaust gas turbocharger is arranged in the exhaust line upstream of the diesel oxidation catalytic converter. The exhaust gas turbocharger serves to increase the specific power and / or the efficiency of the diesel internal combustion engine. The exhaust gas turbocharger has the exhaust gas turbine, through which exhaust gas flows, from which enthalpy and / or flow energy is removed. The energy generated in the exhaust gas turbine is used to drive a compressor of the exhaust gas turbocharger. For example, the exhaust gas turbine is directly coupled to the compressor for this purpose, in particular mechanically coupled. The compressor serves to compress fresh gas which is supplied to the diesel internal combustion engine after the compression. The use of the exhaust gas turbocharger enables a higher performance or a higher efficiency of the diesel internal combustion engine.

A preferred further embodiment of the invention provides that the three-way catalytic converter is arranged upstream of the exhaust gas turbine or in terms of flow between the exhaust gas turbine and the diesel oxidation catalytic converter. This in turn corresponds to an arrangement of the three-way catalytic converter close to the engine, so that it quickly reaches its operating temperature.

In the context of a further embodiment of the invention, it can be provided that the distance between the three-way catalytic converter and the exhaust gas turbine is less than the distance between the exhaust gas turbine and the diesel oxidation catalytic converter, as seen in the flow direction. To this extent, an arrangement close to the engine is provided for the three-way catalytic converter and the exhaust gas turbine, whereas in terms of flow technology the diesel oxidation catalytic converter is arranged significantly further away from the diesel internal combustion engine. With such an arrangement, both the three-way catalyst and the diesel oxidation catalytic converter are each operated in an optimal temperature range.

A further development of the invention provides that a diesel particle filter is arranged in the exhaust pipe. The diesel particle filter serves to filter out particles contained in the exhaust gas, in particular soot particles. The use of the diesel particle filter enables a further reduction in the pollutants present in the exhaust gas after passing through the exhaust gas aftertreatment device.

A further embodiment of the invention provides that the diesel particle filter and the SCR catalytic converter are integrated with one another, a catalytic coating of the SCR catalytic converter being applied to a honeycomb body of the diesel particle filter. The diesel particulate filter has a honeycomb body to filter the exhaust gas. The catalytic coating of the SCR catalytic converter is additionally applied to these, so that a particularly advantageous integration of the diesel particle filter and SCR catalytic converter is realized. In particular, the diesel particle filter and the SCR catalytic converter are arranged in a common particle filter housing.

Finally, it can be provided within the scope of a further embodiment of the invention that the diesel oxidation catalytic converter and the three-way catalytic converter are arranged in a common housing. To this extent, a particularly advantageous integration can also be provided for the diesel oxidation catalytic converter and the three-way catalytic converter. In particular, they are arranged one after the other in terms of flow technology, so that when the exhaust gas flows through the housing, it first completely flows through the diesel oxidation catalytic converter and then flows into the three-way catalytic converter or vice versa. Despite the arrangement in the common housing, the diesel oxidation catalytic converter and the three-way catalytic converter are formed separately, for example they consist of separate substrates, to which the actual catalytic converter is respectively applied. The described configuration enables a particularly high conversion performance of the exhaust gas aftertreatment device with a small space requirement.

The invention further relates to a diesel internal combustion engine with an exhaust gas aftertreatment device, in particular an exhaust gas aftertreatment device according to the explanations in the context of this description, which has a diesel oxidation catalytic converter arranged in an exhaust pipe and an SCR catalytic converter arranged downstream of the diesel oxidation catalytic converter in the exhaust pipe for carrying out a selective catalytic reduction. It is provided that a three-way catalytic converter is additionally arranged in the exhaust pipe.

The advantages of such a configuration of the diesel internal combustion engine or the exhaust gas aftertreatment device have already been pointed out. Both the diesel internal combustion engine and the exhaust gas aftertreatment device can be further developed in accordance with the statements in the context of this description, so that reference is made to them in this respect.

A further embodiment of the invention provides that the diesel oxidation catalytic converter is connected to an exhaust manifold in terms of flow technology via an exhaust gas turbine of an exhaust gas turbocharger. The diesel internal combustion engine has the exhaust manifold, which is connected to the cylinders of the diesel internal combustion engine via exhaust valves. The exhaust manifold is used to bring together the exhaust gas generated in the cylinders. In other words, the exhaust gas from one of the cylinders enters the exhaust manifold separately from the exhaust gas of the other cylinders and is combined there with the exhaust gas from the other cylinders.

The exhaust gas which emerged from the cylinders and is subsequently brought together in the exhaust manifold exits through an outlet of the exhaust manifold to which the exhaust gas aftertreatment device, in particular its exhaust pipe, is connected in terms of flow technology. The exhaust gas emerging from the exhaust manifold flows in the direction of the diesel oxidation catalytic converter. Here, it passes through the exhaust gas turbine of the exhaust gas turbocharger, which is arranged between the exhaust manifold and the diesel oxidation catalytic converter in terms of flow.

• Figur eine schematische Darstellung einer Abgasnachbehandlungseinrichtung für eine Dieselbrennkraftmaschine.

The invention is explained in more detail below with reference to the exemplary embodiments shown in the drawing, without the invention being restricted. The only one shows

• Figure is a schematic representation of an exhaust gas aftertreatment device for a diesel engine.

The figure shows a schematic representation of an exhaust gas aftertreatment device 1 for an internal combustion engine. The exhaust gas aftertreatment device 1 has an exhaust pipe 2 , in which in the flow direction of the exhaust gas a diesel oxidation catalyst 3 and an SCR catalyst 4 available. Upstream of the SCR catalytic converter 3 or in terms of flow between the diesel oxidation catalyst 3 and the SCR catalyst 4 is an insertion device 5 for introducing a reducing agent into the exhaust pipe 2 provided and arranged.

Downstream of the SCR catalytic converter 4 is, however, an SCR blocking catalyst 6 in the exhaust pipe 2 arranged, which an exit of the introduced reducing agent from the exhaust gas aftertreatment device 1 at least partially or even completely prevented. Upstream of the diesel oxidation catalyst 3 is an exhaust gas turbine 7 of an exhaust gas turbocharger 8th arranged. Again upstream of the exhaust gas turbocharger 8th or the exhaust gas turbine 7 is a three-way catalyst 9 in front. The flow direction of the exhaust pipe 2 is through the arrow 10 indicated.

As an alternative to the arrangement of the three-way catalytic converter shown and described here 9 this could also be fluidly between the exhaust gas turbine 7 and the diesel oxidation catalyst 3 or fluidically between the diesel oxidation catalyst 3 and the SCR catalyst 4 be arranged. In both arrangements, the diesel oxidation catalyst is preferred 3 and the three-way catalyst 9 arranged in a common housing, so that a particularly space-saving design of the exhaust gas aftertreatment device 1 is achieved.

With the configuration of the exhaust gas aftertreatment device described here 1 there is a breakdown of nitrogen oxide through the diesel oxidation catalyst 3 and / or the SCR catalytic converter 4 effectively prevented, namely by the three-way catalyst 9 is additionally realized. Without the three-way catalyst 9 Such a breakdown could occur, for example, in the case of a rapid increase in the load of the diesel internal combustion engine, which is associated with high exhaust gas mass flows and lack of air.

QUOTES INCLUDE IN THE DESCRIPTION

This list of documents listed by the applicant has been generated automatically and is only included for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• WO 2015/040047 A2 [0002]

Claims (10)

Exhaust gas aftertreatment device (1) for a diesel internal combustion engine, with a diesel oxidation catalytic converter (3) arranged in an exhaust pipe (2) and an SCR catalytic converter (4) arranged downstream of the diesel oxidation catalytic converter (3) for carrying out a selective catalytic reduction, characterized in that in addition, a three-way catalytic converter (9) is arranged in the exhaust line (2). Exhaust aftertreatment device after Claim 1 , characterized in that the three-way catalytic converter (9) is arranged upstream of the diesel oxidation catalytic converter (3) or in terms of flow between the diesel oxidation catalytic converter (3) and the SCR catalytic converter (4). Exhaust gas aftertreatment device according to one of the preceding claims, characterized in that an exhaust gas turbine (7) of an exhaust gas turbocharger (8) is arranged in the exhaust line (2) upstream of the diesel oxidation catalyst (3). Exhaust gas aftertreatment device according to one of the preceding claims, characterized in that the three-way catalytic converter (9) is arranged upstream of the exhaust gas turbine (7) or in terms of flow technology between the exhaust gas turbine (7) and the diesel oxidation catalyst (3). Exhaust gas aftertreatment device according to one of the preceding claims, characterized in that, viewed in the direction of flow, the distance between the three-way catalytic converter (9) and the exhaust gas turbine (7) is less than the distance between the exhaust gas turbine (7) and the diesel oxidation catalyst (3). Exhaust aftertreatment device according to one of the preceding claims, characterized in that a diesel particle filter is arranged in the exhaust line (2). Exhaust gas aftertreatment device according to one of the preceding claims, characterized in that the diesel particle filter and the SCR catalytic converter (4) are integrated with one another, a catalytic coating of the SCR catalytic converter (4) being applied to a honeycomb body of the diesel particle filter. Exhaust gas aftertreatment device according to one of the preceding claims, characterized in that the diesel oxidation catalyst (3) and the three-way catalyst (9) are arranged in a common housing. Diesel internal combustion engine, with an exhaust gas aftertreatment device (1), in particular an exhaust gas aftertreatment device (1) according to one or more of the preceding claims, which has a diesel oxidation catalyst (3) arranged in an exhaust gas line (2) and a downstream of the diesel oxidation catalyst (3) in the exhaust gas line (2 ) arranged SCR catalytic converter (4) for carrying out a selective catalytic reduction, characterized in that a three-way catalytic converter (9) is additionally arranged in the exhaust pipe. Diesel engine after Claim 9 , characterized in that the diesel oxidation catalytic converter (3) is connected in terms of flow technology to an exhaust manifold via an exhaust gas turbine (7) of an exhaust gas turbocharger (8).

Images