APPARATUS AND METHOD FOR PRODUCING AMMONIA FOR EXHAUST GAS AFTERTREATMENT

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 a gas flow can flow into the reaction space, with an outflow connector through which an ammonia-containing gas flow can exit the reaction space, and with a supply device by way of which an ammonia precursor solution can be supplied into the reaction space, wherein the inflow connector is connected to a first connecting line through which air can flow from an intake line of an internal combustion engine into the reaction space, and wherein the inflow connector is furthermore connected to a second connecting line through which exhaust gas can flow from an exhaust line of the internal combustion engine 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 a gas flow can flow into the reaction space, with an outflow connector through which an ammonia-containing gas flow can exit the reaction space, and with a supply device configured to supply ammonia precursor solution into the reaction space, wherein the inflow connector is connected to a first connecting line through which air can flow from an intake line of an internal combustion engine into the reaction space, and wherein the inflow connector is furthermore connected to a second connecting line through which exhaust gas can flow from an exhaust line of the internal combustion engine into the reaction space.

2. The device as claimed in claim 1, wherein, between the first connecting line and the second connecting line, there is arranged a valve configured to supply selectively exhaust gas or air to the reaction space.

3. The device as claimed in claim 2, wherein the valve, is configured to generate a mixture of air and exhaust gas which can be supplied to the reaction space.

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

5. The device as claimed in claim 4, wherein the electric heater comprises an electrically heatable honeycomb body.

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

7. 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 way of 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 in an axial direction into the central chamber through the diverting region.

8. 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, and an SCR catalytic converter which is arranged downstream of the device as viewed in the exhaust-gas flow direction, such that an ammonia-containing gas flow which emerges from the outflow connector flows through the SCR catalytic converter, wherein the inflow connector is connected by a line branch to an exhaust line of the internal combustion engine, wherein, through the inflow connector, between 0.1% and 5% of the exhaust gas from the internal combustion engine flows into the reaction space.

9. The exhaust-gas treatment device as claimed in claim 8, comprising a particle filter which is arranged downstream of the device as viewed in the exhaust-gas flow direction, such that a gas flow emerging from the outflow connector of the device flows through the particle filter.

10. A method for operating an exhaust gas treatment device for the purification of the exhaust gases of an internal combustion engine comprising a device as claimed in claim 1 and a particle filter, the method comprising: supplying air from an intake line of the internal combustion engine into the device through the inflow connector; generating ozone in the device such that an ozone-containing gas flow is generated in the device and emerges from the device at the outflow connector; supplying the ozone to the particle filter via a supply line; regenerating particle filter, wherein soot deposits in the particle filter are converted using ozone.

Description

[0042] The invention and the technical field of the invention will be explained in more detail below on the basis of the figures. In particular, it should be noted that the figures and in particular the proportions illustrated in the figures are merely schematic. In the figures:

[0043] FIG. 1: shows a device for generating ammonia from an ammonia precursor solution,

[0044] FIG. 2: shows a cross section through a device of said type for generating ammonia, and

[0045] FIG. 3: shows a motor vehicle having a device for generating ammonia.

[0046] FIG. 1 shows a device 1 which has a cylindrical housing 20. On a face side of the device 1, there is arranged a supply device 5 by way of which an ammonia precursor solution (e.g. a urea-water solution) can be supplied into a reaction space 2 of the device 1. On the opposite face side of the device 1, there is situated an outflow connector 4 at which an ammonia-containing gas flow can flow out of the device 1. On the circumferential surface of the device 1, there is arranged, in a tangential orientation, an inflow connector 3 via which a gas flow can flow into the reaction space 2 of the device 1. The inflow connector 3 is connected to a first connecting line 6 via which an exhaust-gas flow that is branched off from an exhaust line can be supplied into the device 1. The inflow connector 3 is furthermore connected to a second connecting line 7, via which an air flow, which may for example be branched off from an intake line of an internal combustion engine, can flow into the device 1. A diverting element 15 is provided in the (single) reaction space 2 of the device 1, which diverting element separates a cylindrical gap 16 from a central chamber 17 in the reaction space 2. The gas flow entering through the inflow connector 3 firstly enters the cylindrical gap 16 and is subsequently diverted, in a diverting region 18, into the central chamber 17.

[0047] The supply device 5 preferably comprises a nozzle 28 which sprays the ammonia precursor solution in a spray cone 29 onto an impingement region 32 arranged within the reaction space 2. In the diverting region 18, there is also provided a perforated screen 31 through which the spray cone 29 of the supply device 5 extends. For this purpose, the perforated screen 31 has a central opening. Furthermore, the perforated screen 31 has a multiplicity of relatively small openings (arranged around the central opening) through which the exhaust-gas flow can pass from the cylindrical gap 16 into the central chamber 17. Owing to the tangential arrangement of the inflow connector 3 at the reaction space 2 or at the device 1, a vortex flow 30 of the gas flow is generated within the reaction space 2.

[0048] An impingement region 32 for the ammonia precursor solution that is supplied by way of the supply device 5 is arranged on an electric heater 13 in the form of an electrically heatable honeycomb body 14, which, as viewed in the exhaust-gas flow direction and in the axial direction 19, is situated downstream of the supply device 5 proceeding from the inflow connector 3 and the supply device 5. It is also possible for yet further components (such as for example a catalytic converter substrate body 26 or a sensor 27), by way of which the reactions within the device 1 can be monitored or influenced in a controlled manner, to be provided in the device 1 downstream of the electric heater 13 as viewed in the exhaust-gas flow direction.

[0049] FIG. 2 shows a cross section through the device from FIG. 1, in which the tangentially arranged inflow connector 3, the diverting element 15, the cylindrical gap 16 and the central chamber 17, and also the impingement region 32 and the housing 20, are visible.

[0050] FIG. 3 shows a motor vehicle 33 having an internal combustion engine 9 and having an exhaust-gas treatment device 11 which is configured for the purification of the exhaust gases of the internal combustion engine 9. The exhaust-gas treatment device 11 is connected via an exhaust line 10 to the internal combustion engine 9. The internal combustion engine 9 furthermore has an intake line 8 via which the internal combustion engine draws in air (from the surroundings). The air that passes via the intake line 8 to the internal combustion engine 9 is supercharged and/or compressed by a turbocharger 34, wherein the turbocharger 34 is driven by the exhaust-gas flow in the exhaust line 10. An SCR catalytic converter 21 for performing a selective catalytic reduction and a particle filter 23 for filtering particles in the exhaust-gas flow are arranged in the exhaust-gas treatment device 11. The motor vehicle 33 also has a device 1 by way of which an ammonia-containing gas flow can be generated. The device 1 is preferably also suitable for generating ozone by way of which particles deposited in the particle filter 23 can be reduced. The device 1 is supplied with air from the intake line 8 via a first connecting line 6. The device 1 is furthermore supplied with exhaust gas from the exhaust line 10 via a second connecting line 7. The device 1 has a valve 12 by way of which the exhaust gas from the second connecting line 7 and the air from the first connecting line 6 can be mixed in targeted fashion and supplied to the device 1. The device 1 is furthermore supplied with ammonia precursor solution from a precursor solution tank 22.

[0051] The described device is particularly advantageous because it firstly makes it possible for ammonia for performing the SCR method in an SCR catalytic converter to be provided in an effective manner. At the same time, the device also makes it possible to provide ozone by way of which soot deposits in a particle filter can be burned off in an effective manner.

LIST OF REFERENCE SYMBOLS

[0052] 1 Device [0053] 2 Reaction space [0054] 3 Inflow connector [0055] 4 Outflow connector [0056] 5 Supply device [0057] 6 First connecting line [0058] 7 Second connecting line [0059] 8 Intake line [0060] 9 Internal combustion engine [0061] 10 Exhaust line [0062] 11 Exhaust-gas treatment device [0063] 12 Valve [0064] 13 Electric heater [0065] 14 Electrically heatable honeycomb body [0066] 15 Diverting element [0067] 16 Cylindrical gap [0068] 17 Central chamber [0069] 18 Diverting region [0070] 19 Axial direction [0071] 20 Housing [0072] 21 SCR catalytic converter [0073] 22 Precursor solution tank [0074] 23 Particle filter [0075] 24 Exhaust-gas flow direction [0076] 25 Supply line [0077] 26 Catalytic converter substrate body [0078] 27 Sensor [0079] 28 Nozzle [0080] 29 Spray cone [0081] 30 Vortex flow [0082] 31 Perforated screen [0083] 32 Impingement structure [0084] 33 Motor vehicle [0085] 34 Turbocharger