Hydrogen engine exhaust system

Abstract

Exhaust line for hydrogen engine. The invention relates to an exhaust line (1) for a hydrogen engine, comprising an injection and mixing device (5) for a reducing agent, and a reduction catalyst (6). Figure for the abstract: 1

Description

Description Title of the invention: Exhaust line for engine hydrogen technical field The invention relates to an exhaust system for a hydrogen engine. Prior art A hydrogen engine produces during combustion an exhaust gas comprising polluting components including nitrogen oxides or NOx, carbon monoxide CO and unburned hydrocarbons HC. Depending on the anti-pollution standard adopted, it is necessary to remove all or part of these pollutants from the exhaust gases before they exit the exhaust line into the open air. Also, the invention proposes exhaust line architectures integrating the necessary purification / pollution devices. Summary of the invention The invention relates to an exhaust line for a hydrogen engine, comprising, between the inlet of the exhaust line connected to the outlet of the engine and the outlet of the exhaust line, in this order: an injection and mixing device for a reducing agent, and a reduction catalyst. Specific characteristics or embodiments, usable alone or in combination, are: - the exhaust line also includes, upstream of the injection and mixing device (5), a first particulate filter, - the exhaust system still includes an oxidation catalyst or OC, - the first particulate filter incorporates the oxidation catalyst, - the reduction catalyst is a selective reduction catalyst or SCR, - the reduction catalyst is a selective reduction catalyst incorporating the first particulate filter or SCRF, - the exhaust line also includes, downstream of the reduction catalyst, an ammonia oxidation catalyst or ASC, - the ammonia oxidation catalyst is integrated into the reduction catalyst, - the exhaust line also includes, upstream of the reduction catalyst, a heating element or EHC, - the device for injecting and mixing a reducing agent is capable of heating said reducing agent, - the reducing agent is urea or hydrogen, - the exhaust line also includes, downstream of the reduction catalyst, a second particulate filter. Brief description of the drawings The invention will be better understood upon reading the following description, given solely by way of example, and with reference to the figures in the appendix in which: [Fig.1] [Fig.1] shows, in schematic view, a first embodiment of an exhaust line, [Fig.2] [Fig.2] shows, in schematic view, another embodiment of an exhaust line, [Fig.3] [Fig.3] shows, in schematic view, another embodiment of an exhaust line, [Fig.4] [Fig.4] shows, in schematic view, another embodiment of an exhaust line, [Fig. 5] [Fig. 5] shows, in schematic view, another embodiment of an exhaust line, [Fig. 6] [Fig. 6] shows, in schematic view, another embodiment of an exhaust line, [Fig.7] [Fig.7] shows, in schematic view, another embodiment of an exhaust line, [Fig.8] [Fig.8] shows, in schematic view, another embodiment of an exhaust line, [Fig.9] [Fig.9] shows, in schematic view, another embodiment of an exhaust line. Description of the implementation methods The invention relates to an exhaust system 1 for a hydrogen engine. Such an exhaust system 1 comprises a pipe adapted to carry exhaust gas. This pipe extends from an inlet 2 to an outlet 3. The inlet 2 of the exhaust system 1 is connected to the outlet of the hydrogen engine, so as to recover the combustion residues or exhaust gases. The outlet 3 of the exhaust system 1 terminates either in an acoustic module or in an exhaust nozzle open to the atmosphere. Along the exhaust line 1 are arranged, across the pipeline, so as to be crossed by the exhaust gases of the purification devices 4-10. The purification devices 4-10 are always listed, from upstream to downstream, from inlet 2 to outlet 3, represented from left to right in the diagrams of the figures. In all figures, the escape line | is shown by a line. The escape line 1 extends from an inlet 2 located on the left in the figures to an exit 3 located on the right in the figures. One of the major pollutants is NOx. According to a first, minimalist embodiment, illustrated in particular in [Fig. 1], an exhaust system 1 according to the invention comprises the purification components for purifying NOx, namely, in this order: an injection and mixing device 5 for a reducing agent, and a reduction catalyst 6. These two components work together. The reduction catalyst 6 is capable of reducing NOx, provided that it has been previously mixed with a reducing agent. Furthermore, an injection and mixing device S is arranged upstream of the reduction catalyst 6 and is capable of injecting a reducing agent into the exhaust gases and mixing the reducing agent with the exhaust gases before they pass through the reduction catalyst 6. Such a minimalist architecture is suitable for NOx purification with a vehicle having CO and HC emissions below the thresholds to be respected. If the purification of fine particles is necessary, according to another characteristic, more particularly illustrated in [Fig. 2], the preceding exhaust line 1 also includes a first particulate filter 4. It is possible to use a GPF (gasoline) or a DPF (diesel). Such a particulate filter 4 is capable of retaining fine particles. This first particulate filter 4 can be located at any point in the exhaust line 1. According to a preferred characteristic, the first particulate filter 4 is located at the top of the exhaust line 1, i.e., upstream of the injection and mixing device 5. Such a placement near the engine is advantageous in that it facilitates cleaning of the first particulate filter 4. If CO and HC purification is required, according to another characteristic, the exhaust line 1 also includes an oxidation catalyst 7 or OC. Such an oxidation catalyst 7 is capable of trapping and / or oxidizing CO and HC. Oxidation transforms carbon monoxide (CO) into carbon dioxide (CO2) and hydrocarbons (HC) into carbon dioxide (CO2) and water (H2O). An oxidation catalyst 7 comprises a brick through which the exhaust gases pass and which is coated with a deposit of catalytic material. Such an oxidation catalyst 7 can be disposed at any point in the exhaust line 1, except between the injection and mixing device S and the reduction catalyst 6, where it would oxidize the reducing agent. As illustrated in Figure 3, the oxidation catalyst 7 can be disposed upstream of the injection and mixing device 5 or downstream of the oxidation catalyst 6. Preferably, the oxidation catalyst 7 is disposed upstream of the optional first particulate filter 4. According to another characteristic, more particularly illustrated in [Fig. 4], the first Particulate filter 4 incorporates oxidation catalyst 7. It has been observed that oxidation catalyst 7 is produced by deposition. Therefore, in this particular case, particle filter 4 has a portion of its surface coated with such a deposit of catalytic material, thereby enabling it to function as oxidation catalyst 7. As illustrated in [Fig. 4], the same purifying element 4 / 7 performs both functions. It has been seen that both the first particulate filter 4 and the oxidation catalyst 7 can be disposed substantially at any point in the exhaust line 1. Also, a combined element 4 / 7 can also be disposed at any point in the exhaust line 1, except between the injection and mixing device 5 and the reduction catalyst 6, and preferably before the injection and mixing device 5. According to another characteristic, reduction catalyst 6 is a selective reduction catalyst, more commonly known by the acronym SCR (from the English "Selective Catalytic Reduction" meaning selective reduction catalyst). According to another characteristic, an alternative to the previous one, the reduction catalyst 6 is a selective reduction catalyst that also integrates the first particulate filter 4. Such an integrated element is more commonly known by the acronym SCRF (from the English "Selective Catalyst Reduction Filter"). As illustrated in [Fig. 5], such an integrated element is represented by a 6 / 4 element. This particulate filter 4 integrated into the reduction catalyst 6 can be an alternative to, or a complement to, the first particulate filter 4 described previously. For the reduction catalyst 6 to function, a reducing agent must be added to the exhaust gases. As described earlier, this reducing agent provides ammonia (NH3), typically in the form of a precursor: urea in aqueous solution. Ammonia is necessary for the reduction reaction, and to avoid the risk of shortages, it may be added in excess. However, it is not desirable to release this ammonia into the atmosphere. Furthermore, according to another characteristic, the exhaust line 1 also includes an ammonia oxidation catalyst 8, or ASC (from the English "Ammonia Slip Catalyst"). Such an ammonia oxidation catalyst 8 is capable of converting residual ammonia NH3 into nitrogen N2 and water H2O, both of which can be released into the atmosphere. Therefore, as illustrated in [Fig. 6], such an ammonia oxidation catalyst 8 is advantageously added to the exhaust line 1. In order to process the ammonia not used by the reduction catalyst 6, the ammonia oxidation catalyst 8 is preferentially located downstream of the reduction catalyst 6. According to another feature, more particularly illustrated in [Fig. 7], the ammonia oxidation catalyst 8 can be integrated with the reduction catalyst 6, in the same purification element 6 / 8. In such a case, the two catalytic deposits are deposited evenly on the surfaces of the purification element. The reduction catalyst 6 is placed on the first (upstream) part of the integrated purification element 6 / 8 and the ammonia oxidation catalyst 8 on the second (downstream) part of this element 6 / 8. It has been observed that a reduction catalyst 6 is capable of catalytically reacting a mixture of exhaust gases with a reducing agent. Furthermore, this reaction requires a high temperature, known as the ignition temperature, to occur. Under steady-state conditions, this high temperature is obtained and maintained by the heat of the exhaust gases passing through the reduction catalyst 6. However, at engine start-up, the exhaust line 1 and the exhaust gases are cold. Therefore, according to another characteristic, it is advantageous to add a heating element 9 or EHC to the exhaust line 1. To efficiently heat the reduction catalyst 6 by heating the exhaust gases, said heating element 9 is advantageously positioned upstream of the reduction catalyst 6, and preferably, as illustrated in [Fig. 8], immediately upstream of the reduction catalyst 6. Another way to improve the reduction reaction taking place within the reduction catalyst 6 is, alternatively or in addition to heating by a heating element 9, to heat the reducing agent during its injection into the exhaust line 1. Also, according to another feature, more particularly illustrated in [Fig. 9], the injection and mixing device 5 for a reducing agent is capable of heating said reducing agent. This is achieved by an element 5 / 9 combining the two functions. This can, for example, be achieved by means of an injection and mixing device 5 in which the reducing agent injector is a heated injector. It is also possible to preheat the reducing agent in a chamber located upstream of the injector. According to another characteristic, the reducing agent is urea. A common solution is to use an aqueous urea solution, known as AUS32 or DEF, or commercially as AdBlue®. This aqueous urea solution acts as a precursor to gaseous ammonia, which is essential for the reduction reaction. Alternatively, according to another characteristic, the reducing agent is hydrogen. According to another feature, more particularly illustrated in [Fig.6], the exhaust line 1 also includes a second particulate filter 10. Said second particulate filter 10 can be used alternatively or in addition to the first particulate filter 4. The invention has been illustrated and described in detail in the drawings and the preceding description. This description should be considered illustrative and given by way of example, and not as limiting the invention to this single description. Numerous variations implementation options are possible. List of reference signs 1: exhaust line, 2: entrance, 3: Exit, 4: first particle filter, 5: Injection and mixing device, 6: reduction catalyst, 7: oxidation catalyst, 8: ammonia oxidation catalyst, 9: heating element, 10: Second particle filter

Claims

Claims

1. Exhaust line (1) for a hydrogen engine, characterized in that which it includes, between the inlet (2) of the exhaust line (1) connected to the output of a motor and the output (3) of the line exhaust (1), in this order: an injection device and mixture (5) of a reducing agent, and a reduction catalyst (6).

2. Exhaust line (1) according to claim 1, further comprising, upstream of the injection and mixing device (5), a first filter particles (4).

3. Exhaust line (1) according to any one of claims 1 or 2, further comprising an oxidation catalyst (7) or OC.

4. Exhaust line (1) according to claim 3, where the first filter particles (4) integrates the oxidation catalyst (7).

5. Exhaust line (1) according to any one of claims 1 to 4, where the reduction catalyst (6) is a reduction catalyst selective or SCR.

6. Exhaust line (1) according to any one of claims 1 to 4, where the reduction catalyst (6) is a reduction catalyst selective integrating the first particulate filter (4) or SCRF.

7. Exhaust line (1) according to any one of claims 1 to 6, further comprising, downstream of the reduction catalyst (6), a ca- ammonia oxidation catalyst (8) or ASC.

8. Exhaust line (1) according to the preceding claim, where the ca- ammonia oxidation catalyst (8) is integrated into the catalyst of reduction (6).

9. Exhaust line (1) according to any one of claims 1 to 8, further comprising, upstream of the reduction catalyst (6), a heating element (9) or EHC.

10. Exhaust line (1) according to any one of claims 1 to 9, where the device (5) for injecting and mixing a reducing agent is capable of heating said reducing agent.

11. | Exhaust line (1) according to any one of claims 1 to 10, where the reducing agent is urea or hydrogen.

12. Exhaust line (1) according to any one of claims 1 to 11, further comprising, downstream of the reduction catalyst (6), a second particle filter (10).

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