APPARATUS FOR PRODUCING AMMONIA

Abstract

The invention relates to a device for generating ammonia from an ammonia precursor solution, having a reaction space with an inflow connector through which an exhaust-gas flow can flow into the reaction space, having an outflow connector through which an ammonia-containing gas flow can exit the reaction space, and having a supply device by way of which selectively an ammonia precursor solution or a fuel can be supplied into the reaction space.

Claims

1. A device for generating ammonia from an ammonia precursor solution, comprising: a reaction space with an inflow connector through which an exhaust-gas flow can flow into the reaction space, an outflow connector through which an ammonia-containing gas flow can exit the reaction space, and a supply device configured to selectively supply an ammonia precursor solution or a fuel into the reaction space.

2. The device as claimed in claim 1, wherein the supply device comprises a dosing valve which includes a first feed line for ammonia precursor solution and a second feed line for a fuel.

3. The device as claimed in claim 1, wherein, in the reaction space, there is arranged an impingement structure toward which the supply device is oriented and which is impinged on by the supplied ammonia precursor solution.

4. The device as claimed in claim 3, wherein the impingement structure is provided with a coating which catalyzes both a hydrolysis of ammonia precursor solution into ammonia and an exothermic reaction of fuel with oxygen.

5. The device as claimed in claim 1, wherein the supply device comprises a common nozzle configured to spray ammonia precursor solution and fuel into the reaction space, wherein the nozzle generates different spray patterns with ammonia precursor solution and with fuel.

6. The device as claimed in claim 1, wherein different impingement regions for ammonia precursor solution and for fuel are provided within the reaction space.

7. The device as claimed in claim 1, wherein an electric heater is arranged in the reaction space.

8. The device as claimed in claim 7, wherein the electric heater comprises an electrically heatable honeycomb body.

9. The device as claimed in claim 1, wherein the inflow connector is arranged tangentially at the reaction space.

10. The device as claimed in claim 1, wherein the reaction space is divided by a cylindrical diverting element into a cylindrical gap and a central chamber, wherein the cylindrical gap and the central chamber are connected to one another by a diverting region, wherein the inflow connector is arranged at the cylindrical gap, the exhaust-gas flow from the cylindrical gap is conducted into the central chamber through the diverting region, and the supply device supplies the precursor solution and the fuel in an axial direction into the central chamber through the diverting region.

11. An exhaust-gas treatment device for the purification of the exhaust gases of an internal combustion engine, comprising: a device for generating ammonia as claimed in claim 1, wherein the inflow connector is connected by a line branch to an exhaust line of the exhaust-gas treatment device, and the outflow connector is connected by a supply line to the exhaust line, wherein, through the inflow connector, between 0.1 percent and 5 percent of the exhaust gas from the internal combustion engine flows into the reaction space.

Description

[0044] The invention and the technical field will be explained in more detail below on the basis of the figures. The figures show particularly preferred exemplary embodiments, to which the invention is however not restricted. It is pointed out in particular that the figures, and in particular the dimensional relationships illustrated in the figures, are merely schematic. In the figures:

[0045] FIG. 1: shows a described device,

[0046] FIG. 2: shows a cross section through a first embodiment of a described device,

[0047] FIG. 3: shows a cross section through a second embodiment of a described device, and

[0048] FIG. 4: shows a motor vehicle having a described device.

[0049] FIG. 1 illustrates a device 1 which has a cylindrical housing 38. Situated on one face side of the cylindrical housing 38 of the device is the supply device 5 by way of which fuel (e.g. diesel fuel) and/or ammonia precursor solution (e.g. urea-water solution) can be supplied to the device. For this purpose, the supply device 5 has a first feed line 7 for the metering of ammonia precursor solution and a second feed line 8 for the metering of fuel. The supply device 5 also comprises a dosing valve 6 by way of which the fuel and the ammonia precursor solution can be (selectively) dosed. The supply device 5 supplies the fuel and/or the ammonia precursor solution into a reaction space 2 of the device 1 in an axial direction 22. Here, the fuel and/or the ammonia precursor solution is sprayed with a spray pattern 11.

[0050] The outflow connector 4 is arranged on the device 1 so as to be situated opposite the supply device 5, through which outflow connector an ammonia-containing gas flow can emerge from the device 1. The inflow connector 3 is arranged on the circumferential surface of the device 1, via which inflow connector and exhaust-gas flow can enter the device. The reaction space 2 of the device 1 is divided by a diverting element 18 into a cylindrical gap 19 and a central chamber 20. The cylindrical gap 19 and the central chamber 20 are connected to one another by way of a diverting region 21 in the region of the supply device 5. In the diverting region 21 there is also provided a perforated screen 36 which has a central opening through which the supply device 5 can supply ammonia precursor solution and/or fuel into the central chamber 20 of the reaction space 2. The perforated screen 36 furthermore has additional, relatively small openings (arranged around the central opening) through which the exhaust-gas flow can pass into the central chamber 20.

[0051] The inflow connector 3 is preferably arranged tangentially at the device 1. In this way, a vortex flow 28 is generated within the reaction space 2 or within the cylindrical gap 19 and the central chamber 20.

[0052] Within the device 1, an impingement structure 9 is arranged downstream of the diverting element 18 and the central chamber 20 as viewed in the exhaust-gas flow direction, which impingement structure forms a first impingement region 14 and a second impingement region 15, wherein the first impingement region 14 is provided for receiving ammonia precursor solution and the second impingement region 15 is provided for receiving fuel. In the present embodiment of a device 1, the impingement structure 9 is in the form of an electric heater 16, and particularly preferably in the form of an electrically heatable honeycomb body 17. Arranged downstream of the impingement structure 9 in the flow direction is at least one catalytic converter substrate body 32 which may comprise coatings for the chemical conversion of the ammonia precursor solution and/or of the fuel. Furthermore, a sensor 33 is also provided in the device 1, by way of which sensor the conversion of ammonia precursor solution into ammonia in the device 1 can be monitored. The sensor 33 may for example comprise a temperature sensor and/or a lambda probe by way of which an oxygen content in the gas can be determined.

[0053] FIGS. 2 and 3 each show sections through different embodiments of the device 1 from FIG. 1 in a section direction arranged perpendicular to the axial direction. It is possible in each case to see the tangentially arranged inflow connector 3 and the diverting element 18, the housing 38, the cylindrical 19 and the central chamber 20. It is also possible to see the first impingement region 14 and the second impingement region 15. In FIG. 2, the second impingement region 15 is arranged concentrically around the first impingement region 14. In FIG. 3, an alternative embodiment has been selected in which the first impingement region 14 and the second impingement region 15 in each case form quarters of a circular basic area. Such a division between the first impingement region 14 for ammonia precursor solution and the second impingement region 15 for fuel can be realized by way of a suitable embodiment of the supply device and in particular of the nozzle of the supply device. In the first impingement region 14 there is provided a first coating 12 which serves for the conversion of the ammonia precursor solution into ammonia. In the second impingement region 15 there is provided a second coating 13 which serves for the thermal conversion of the fuel.

[0054] FIG. 4 shows a motor vehicle 24 having an internal combustion engine 27 and having an exhaust-gas treatment device 23 for the purification of the exhaust gases of the internal combustion engine 27, which exhaust-gas treatment device is connected to the internal combustion engine 27 by way of an exhaust line 26. The internal combustion engine 27 furthermore has an intake line 34 via which the internal combustion engine 27 draws in air (from the surroundings). The motor vehicle 24 also has a turbocharger 29 by way of which the intake air of the internal combustion engine 27 can be supercharged or compressed. The turbocharger 29 is driven by the exhaust gases flowing through the exhaust line 26. A line branch 25 branches off from the exhaust line 26 upstream of the turbocharger 29, which line branch leads to a described device 1. The ammonia generated by the device 1 is supplied into the exhaust line 26, downstream of the turbocharger 29 as viewed in the exhaust-gas flow direction, via a supply line 35, such that the ammonia that is generated can be used in the exhaust-gas treatment device 23 for the purposes of exhaust-gas purification. An SCR catalytic converter 37 is arranged in the exhaust-gas treatment device 23, by way of which SCR catalytic converter nitrogen oxide compounds in the exhaust gas of the internal combustion engine 27 can be converted together with the ammonia from the device 1. The device 1 is supplied with fuel from a fuel tank 31 and with ammonia precursor solution from a precursor solution tank 30.

[0055] By way of the described device, the particularly reliable provision of ammonia for an exhaust-gas aftertreatment device is ensured even in the presence of particularly low exhaust-gas temperatures. At the same time, a particularly small amount of energy is required for this purpose, and ammonia can be provided in the form of an ammonia precursor solution and converted into ammonia by the device. The device is suitable in particular for the purification of diesel exhaust gases of internal combustion engines which are often operated in the part-load range.

LIST OF REFERENCE SYMBOLS

[0056] 1 Device

[0057] 2 Reaction space

[0058] 3 Inflow connector

[0059] 4 Outflow connector

[0060] 5 Metering device

[0061] 6 Dosing valve

[0062] 7 First feed line

[0063] 8 Second feed line

[0064] 9 Impingement structure

[0065] 10 Nozzle

[0066] 11 Spray pattern

[0067] 12 First coating

[0068] 13 Second coating

[0069] 14 First impingement region

[0070] 15 Second impingement region

[0071] 16 Electric heater

[0072] 17 Heatable honeycomb body

[0073] 18 Diverting element

[0074] 19 Cylindrical gap

[0075] 20 Central chamber

[0076] 21 Diverting region

[0077] 22 Axial direction

[0078] 23 Exhaust-gas treatment device

[0079] 24 Motor vehicle

[0080] 25 Line branch

[0081] 26 Exhaust line

[0082] 27 Internal combustion engine

[0083] 28 Vortex flow

[0084] 29 Turbocharger

[0085] 30 Precursor solution tank

[0086] 31 Fuel tank

[0087] 32 Catalytic converter substrate body

[0088] 33 Sensor

[0089] 34 Intake line

[0090] 35 Supply line

[0091] 36 Perforated screen

[0092] 37 SCR catalytic converter

[0093] 38 Housing