DE102014204307A1 - Method and arrangement for the treatment of exhaust gases of an internal combustion engine - Google Patents

Abstract

The present invention relates to a method and an arrangement for treating exhaust gases from an internal combustion engine of a motor vehicle. In a method according to the invention, in which exhaust gases from the internal combustion engine are fed to an SCR catalytic converter (120) for selective catalytic reduction, nitrogen oxides (NOx) contained in the exhaust gas on the SCR catalytic converter (120) by reaction with ammonia (NH3) to form nitrogen ( N2) are reduced, the ammonia (NH3) is at least partially obtained by reaction of urine provided in a storage tank (130) with a bacterial catalyst.

Description

The present invention relates to a method and an arrangement for the treatment of exhaust gases of an internal combustion engine.

The introduction of increasingly stringent NO _x limits has led to the development of a variety of exhaust aftertreatment technologies to control NO _x emissions (= nitrogen oxide emissions) in the exhaust of a diesel engine.

One of these solutions is the so-called NO _x trap (LNT = "Lean _NOx Trap"), whose operating principle is based on nitrogen oxides _(NOx) under lean exhaust conditions to first save, and then setting a rich, reducing exhaust gas mixture converted in a regeneration phase, ,

A second technology for the reduction of nitrogen oxides (NO _x ) is the selective catalytic reduction in a so-called SCR catalyst (SCR = "Selective Catalytic Reduction"). Here, in particular, a urea-SCR system is known in which an aqueous urea solution is injected into the exhaust gas stream at the SCR catalyst. The reaction of the urea ((NH ₂ ) ₂ CO) to ammonia (NH ₃ ) and water (H ₂ O) is used, the ammonia (NH ₃ ) formed on the SCR catalyst containing the nitrogen oxides (NO _x ) contained in the exhaust gas. reduced to nitrogen (N ₂ ).

A problem occurring in practice in the latter approach is the provision of a sufficient amount of reducing agents in order to achieve an effective vehicle-side reduction of the nitrogen oxides (NO _x ) contained in the exhaust gas.

The prior art is merely an example DE 44 25 420 A1 such as US 5,240,688 A directed.

It is an object of the present invention to provide a method and an arrangement for treating exhaust gases of an internal combustion engine, which allow effective reduction of nitrogen oxides (NO _x ) contained in the exhaust gas while utilizing existing natural resources.

This object is achieved by the method according to the features of the independent patent claim 1 and the arrangement according to the features of the independent claim 10.

In a method according to the invention for the treatment of exhaust gases of an internal combustion engine of a motor vehicle, exhaust gases of the internal combustion engine are fed to an SCR catalytic converter for selective catalytic reduction and wherein nitrogen oxides (NO _x ) contained in the exhaust gas are oxidised on the SCR catalytic converter by reaction with ammonia (NH ₃ ). is reduced to nitrogen (N ₂ ), the ammonia (NH ₃ ) is recovered at least in part by reaction of urine provided in a storage tank with a bacterial catalyst.

The invention is based in particular on the concept of producing ammonia (NH ₃ ), which is required in an exhaust aftertreatment system or process comprising a SCR catalyst for reducing NO _x emissions (= nitrogen oxide emissions), urine in conjunction with to use a bacterial catalyst.

For the purposes of the present invention, a "bacterial catalyst" means any bacterial substance which is suitable for bringing about an enzymatic conversion of the urea contained in the urine. The term "bacterial catalyst" is suitable insofar as each enzyme is a biochemical catalyst that helps to cleave or alter a substrate. In this case, the corresponding enzymes can be added in pure form or be provided via suitable starting materials, which contain the respective enzymes by way of a fermentation process or fermentation process z. B. are able to give by spontaneous fermentation in a position. In particular, the term "bacterial catalyst" should be understood to include so-called ureases which catalyze the cleavage of urea into carbon dioxide and ammonia while consuming water.

The above-mentioned fermentation process or fermentation process can, in particular, take place outside the motor vehicle, the ammonia (NH ₃ ) generated here at a typically slow rate, for example, being oxidized. B. gaseous and stored under pressure or dissolved in water to form an aqueous solution. However, the invention is not limited to this, wherein in further embodiments, a substance stored on the vehicle side can be used for the realization of an on-board fermentation or fermentation process. As explained below, the splitting of urea ((NH ₂ ) ₂ CO) contained in the urine can also be supported electrolytically.

According to one embodiment, the storage tank for receiving the urine to a sewer, in particular to the household sewer line of a user, connected.

The invention thus particularly includes the approach, as a waste product z. B. in the household to collect accumulating urine, with a direct filling from the sewer line of the household can be done in a preferably equipped with a suitable filter device storage tank. If necessary, the user can make a direct transfer to an on-board vehicle tank. In this case, unwanted irritations are avoided because the user does not even come into contact with the urine as a result of storing it in a closed container.

The invention thus differs from the cited prior art in particular in that urine as z. B. accumulated in the household waste product is collected and (especially without additional previous, eg., Thermal treatment) directly a memory for reaction with the bacterial condenser, resulting in an effective reduction of nitrogen oxides contained in the exhaust gas (NO _x ) simultaneous maximum utilization of existing natural resources is possible, preferably at the same time suitable measures are taken to avoid unwanted irritation, since the user himself does not come into contact with the urine as a result of storing it in a closed container.

The bacterial catalyst used according to the invention, which allows the production of ammonia (NH ₃ ) from the collected urine, can - as explained in more detail below - either on the vehicle side (eg in a suitable storage container) available or outside the vehicle (z B. using food waste).

The recovery of the bacterial catalyst using a fermentation process can be done in particular directly in the storage tank.

The invention provides the possibility to provide a sufficient amount of ammonia (NH ₃ ) for NO _x reduction and at the same time contribute to an improvement of the CO ₂ balance and to a better use of natural resources.

Considering that in the so-called New European Driving Cycle (NEDC), a reduction in NO _x emissions by 1 gram (g) for a driving time of 20 minutes consumes 0.3 grams (g) of ammonia (NH ₃ ), only a comparatively small amount of the naturally generated by-product is required to meet the system requirements, even taking into account any distillation of the salts and minerals which may be required to increase the life of the dosing system. Another advantage of the invention is thus that practically no additional on-board urea tank is required because only a small buffer tank with a volume of less than 50 ml is sufficient due to the direct connection to the household sewer system, which in turn due to the elimination of the requirement of larger on-board storage tanks results in lower fuel consumption and additional space gain.

According to one embodiment, furthermore, an electrolytic splitting of urea ((NH ₂ ) ₂ CO) contained in the urine takes place. In this case, the electrical energy required for this electrolytic splitting can be provided outside the motor vehicle (eg from the household of a user) or also on the motor vehicle side. In particular, the motor vehicle-side provision of the electrical energy required for the electrolytic splitting using the drive train, z. As a hybrid powertrain, provided electrical energy, in particular by regenerative braking done.

The invention further relates to an arrangement for the treatment of exhaust gases of an internal combustion engine, wherein the arrangement comprises an SCR catalyst for selective catalytic reduction of nitrogen contained in the exhaust gas supplied to the SCR catalyst, wherein nitrogen oxides (NO _x ) contained in the exhaust gas at the SCR catalyst which is reducible to nitrogen (N ₂ ) by reaction with ammonia (NH ₃ ) and which comprises a storage tank with urine provided therein and a bacterial catalyst, wherein the ammonia (NH ₃ ) is at least partially recovered by reacting the urine with the bacterial catalyst can be generated.

In particular, the arrangement may be configured to perform a method having the features described above. With regard to preferred embodiments and advantages of the arrangement, reference is made to the above statements in connection with the method according to the invention.

Further embodiments of the invention are described in the description and the dependent claims.

The invention will be explained below with reference to a preferred embodiment with reference to the accompanying drawings.

The only 1 schematically shows an arrangement 100 for the treatment of exhaust gases of an internal combustion engine of a motor vehicle, in which exhaust gases flowing from the internal combustion engine (not shown) 1 first by a diesel particulate Filter 110 and then through a downstream of this diesel particulate filter 110 arranged SCR catalyst 120 stream. In the exhaust gas contained nitrogen oxides (NO _x ) are on the SCR catalyst 120 reduced by reaction with ammonia (NH ₃ ) to nitrogen (N ₂ ).

The inventive arrangement 100 has a storage tank 130 with provided therein urine and a bacterial catalyst, wherein the reduction of the nitrogen oxides (NO _x ) on the SCR catalyst 120 required ammonia (NH ₃ ) at least partially by reaction of the in the storage tank 130 provided urine with the bacterial catalyst is generated. The storage tank 130 for receiving the urine is in the embodiment of a sewer 140 , in particular to the household sewer of a user, connected.

The bacterial catalyst used according to the invention, which is the production of ammonia (NH ₃ ) from the in the storage tank 130 provided urine may be provided either on-board or outside the motor vehicle (eg, using food waste). In particular, the provision of the bacterial catalyst can take place by utilizing a fermentation process taking place outside the motor vehicle. The ammonia (NH ₃ ) produced here at a comparatively slow rate can either be stored in gaseous form and under pressurization or dissolved in water to form an aqueous solution.

In the exhaust pipe section between the diesel particulate filter 110 and the SCR catalyst 120 is accordingly a supply line or injection device 125 for injecting the urine or already produced ammonia (NH ₃ ) to react with the exhaust gases at the SCR catalyst 120 arranged.

In one embodiment, an electrolysis-type catalyst may also be used, which generates by means of electrolytic decomposition of urea contained in the urine ((NH _{2) 2)} CO), hydrogen (H _2), said hydrogen (H ₂₎ in turn for the NO _x - Reduction via an SCR catalyst or a NO _x storage catalyst (LNT) can be used.

The electrical energy required by such an electrolyzer-type catalyst for electrolysis of urine to generate hydrogen (H ₂ ) may be provided outside the vehicle (eg, on the domestic side). In a further embodiment, the electrical energy required by such an electrolysis-type catalyst for electrolysis can also be provided on the vehicle side, wherein in a hybrid drive train z. B. generated by regenerative braking electrical energy can be used.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely 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.

Cited patent literature

• DE 4425420 A1 [0006]
• US 5240688 A [0006]

Claims (12)

A method for treating exhaust gases of an internal combustion engine of a motor vehicle, wherein exhaust gases of the internal combustion engine an SCR catalyst ( 120 ) are fed to the selective catalytic reduction and wherein in the exhaust gas contained nitrogen oxides (NO _x ) on the SCR catalyst ( 120 ) are reduced to nitrogen (N ₂ ) by reaction with ammonia (NH ₃ ), characterized in that the ammonia (NH ₃ ) is at least partly removed by reaction in a storage tank ( 130 ) provided urine with a bacterial catalyst is obtained. A method according to claim 1, characterized in that the bacterial catalyst is provided on the motor vehicle side. A method according to claim 1 or 2, characterized in that the bacterial catalyst is obtained using a fermentation process, in particular by converting food waste. A method according to claim 3, characterized in that the recovery of the bacterial catalyst using a fermentation process directly in the storage tank ( 130 ) he follows. Method according to one of the preceding claims, characterized in that the bacterial catalyst comprises urease. Method according to one of the preceding claims, characterized in that the storage tank ( 130 ) for receiving the urine to a sewer ( 140 ), in particular to the household sewer of a user, is connected. Method according to one of the preceding claims, characterized in that further comprises an electrolytic splitting of urea contained in the urine ((NH ₂ ) ₂ CO). A method according to claim 7, characterized in that electrical energy required for this electrolytic splitting is provided on the motor vehicle side. A method according to claim 8, characterized in that the motor vehicle side providing the required for electrolytic splitting electrical energy using the provided in the drive train, in particular a hybrid powertrain, electrical energy, in particular by using regenerative braking occurs. Arrangement for the treatment of exhaust gases of an internal combustion engine, the arrangement comprising an SCR catalytic converter ( 120 ) for selective catalytic reduction in the SCR catalyst ( 120 ) contains nitrogen oxides contained in the exhaust gas, wherein in the exhaust gas contained nitrogen oxides (NO _x ) at the SCR catalyst ( 120 ) are reducible to nitrogen (N ₂ ) by reaction with ammonia (NH ₃ ), characterized in that the arrangement comprises a storage tank ( 130 ) with urine provided therein and a bacterial catalyst, wherein the ammonia (NH ₃ ) is at least partially producible by reaction of the urine with the bacterial catalyst. Arrangement according to claim 10, characterized in that the storage tank ( 130 ) for receiving the urine to a sewer ( 140 ), in particular to the household's own sewer line, is connected. Arrangement according to claim 10 or 11, characterized in that it is configured to carry out a method according to one of claims 1 to 9.

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