Method for monitoring the conversion of ammonia to nitrogen and water in an exhaust line of a motor vehicle

Abstract

The invention relates to a method for monitoring the conversion of ammonia to nitrogen and water in an exhaust line (100) of a motor vehicle, the vehicle comprising an internal combustion engine (1), a first catalytic converter (2) and a second catalytic converter (3), the first catalytic converter (2) being configured to produce a quantity of ammonia, characterized in that the method comprises the following steps: a step of measuring the second oxygen concentration; a step of detecting an ammonia conversion defect when the oxygen concentration is below a threshold value; a step of activating the oxygen regeneration device causing the injection of fuel into the internal combustion engine (1) to stop, the stopping of the injection of fuel resulting in an increase in the quantity of oxygen in the second catalytic converter; and a step of the second catalytic converter (3) completely converting the ammonia.

Description

DESCRIPTION TITLE OF THE INVENTION: METHOD FOR MONITORING THE CONVERSION OF AMMONIA INTO NITROGEN AND WATER IN AN EXHAUST LINE OF A MOTOR VEHICLE

[0001] The present invention claims priority from French application No. 2401072 filed on 05.02.2024, the content of which (text, drawings and claims) is incorporated herein by reference.

[0002] The invention relates to the treatment of exhaust gases from a motor vehicle comprising a heat engine, and more particularly to the management of the ammonia produced during the conversion of nitrogen oxides present in these exhaust gases.

[0003] An international patent application WO2022167431 is known from the prior art, which describes an exhaust gas treatment system for a gasoline engine. The treatment system is designed to reduce ammonia emissions. Ammonia is formed in the exhaust gas when hydrogen reacts with nitrogen oxides. The gasoline engine comprises a first three- or four-way catalyst. The first catalyst comprises a particulate filter. The treatment system comprises a second catalyst for the reduction of ammonia. The second catalyst itself comprises a selective catalytic reduction catalyst and / or an ammonia oxidation catalyst. The selective catalytic reduction catalyst corresponds to the catalytic reduction of nitrogen oxides with a reducing agent in the presence of oxygen.An ammonia oxidation catalyst is a catalyst comprising at least one suitable metal for converting excess ammonia in the exhaust gases into nitrogen. Ammonia reacts with oxygen to produce nitrogen. However, there is a drawback. The presence of each of these catalysts adds weight to the exhaust system. Furthermore, this represents an additional production cost. Exhaust system assembly time is also increased. Furthermore, the presence of oxygen in the catalysts is necessary for ammonia reduction. However, in a... In a gasoline engine, a large portion of the oxygen is consumed during fuel combustion.

[0004] The objective of the present invention is to remedy these drawbacks, and in particular to reduce ammonia emissions from the exhaust line of a motor vehicle.

[0005] To achieve this objective, the invention proposes a method for monitoring the conversion of ammonia into nitrogen and water in an exhaust line of a motor vehicle, said vehicle comprising an internal combustion engine capable of receiving a fuel, said internal combustion engine being configured to generate exhaust gases, said internal combustion engine comprising an oxygen regeneration device, said exhaust line being configured to evacuate the exhaust gases, said exhaust line comprising a first catalyst and a second catalyst, the first catalyst having a first temperature, said first catalyst being configured to produce a quantity of ammonia as a function of the composition of the exhaust gases and the first temperature, said second catalyst having an oxygen concentration and a second temperature,said second catalyst comprising a sensor for measuring the oxygen concentration, the second catalyst being positioned downstream of the first catalyst, remarkable in that said method comprises the following steps:, - a step of measuring the oxygen concentration, the oxygen concentration being dependent on the second temperature; - a step of detecting an ammonia conversion defect when the oxygen concentration is lower than a predetermined oxygen concentration threshold value; - a step of activating said oxygen regeneration device when the fault is detected, the activation of the oxygen regeneration device causing a stoppage of the fuel injection into the internal combustion engine, the stoppage of the fuel injection causing an increase in the quantity of oxygen in the second catalyst; - a step of complete conversion of ammonia into nitrogen and water by the second catalyst.

[0006] Thanks to this invention, ammonia emissions are reduced, or even eliminated, at the exhaust line. Thus, the environment and human health are not impacted.

[0007] Advantageously, the second catalyst comprises a sensor for measuring the quantity of ammonia, said method comprising a step of measuring the quantity of ammonia, the ammonia conversion defect being detected when the oxygen concentration is lower than the threshold value of the predetermined oxygen concentration and when the quantity of ammonia is higher than a threshold value of the predetermined quantity of ammonia.

[0008] The presence of an ammonia quantity measuring sensor is an additional means of monitoring ammonia conversion.

[0009] Advantageously, the second catalyst comprises a sensor for measuring the quantity of nitrogen oxides, said method comprising a step of measuring the quantity of nitrogen oxides, the ammonia conversion defect being detected when the oxygen concentration is lower than the threshold value of the predetermined oxygen concentration and when the quantity of nitrogen oxides is higher than a threshold value of the predetermined quantity of nitrogen oxides.

[0010] A sensor measuring the quantity of nitrogen oxides makes it possible to confirm that the oxygen deficiency is due to a reaction defect in the conversion of nitrogen oxides into ammonia.

[0011] Preferably, the first catalyst comprises a sensor for measuring the oxygen concentration.

[0012] Thus, it is possible to detect a decrease in the oxygen concentration at the first catalyst, which will allow early detection of a decrease in the oxygen concentration at the second catalyst.

[0013] Furthermore, the invention relates to a computer program comprising instructions which, when the program is executed by a computer, cause the latter to implement the steps of the method for monitoring the conversion of ammonia into nitrogen and water in an exhaust line of a motor vehicle.

[0014] The invention also relates to a motor vehicle comprising an internal combustion engine configured to implement said method for monitoring the conversion of ammonia into nitrogen and water in an exhaust line of a motor vehicle.

[0015] The invention will be further detailed by the description of non-limiting embodiments, and on the basis of the appended figures illustrating variants of the invention, in which: - [Fig.1] schematically illustrates an exhaust line of a motor vehicle according to one embodiment of the invention; - [Fig.2] schematically illustrates, in the form of a flowchart, a process for monitoring the conversion of ammonia into nitrogen and water in an exhaust line of a motor vehicle.

[0016] An exhaust line 100 of a motor vehicle is schematically illustrated in Figure 1. The motor vehicle comprises an internal combustion engine 1. The internal combustion engine 1 is a mechanical device into which a fuel is injected, enabling, through its combustion, the generation of mechanical energy. For example, the gasoline engine and the diesel engine are two internal combustion engines 1. The combustion of the fuel causes the emission of exhaust gases. The exhaust gases generally comprise carbon dioxide, water and nitrogen oxides. The exhaust line 100 comprises a first catalyst 2. The first catalyst 2 has a first temperature. The role of the first catalyst 2 is to carry out a chemical reaction transforming the nitrogen oxides into nitrogen and water. The reaction takes place in the presence of oxygen, i.e. in the presence of oxygen.A reaction intermediate in the reaction described above is ammonia. The first catalyst 2 therefore produces a quantity of ammonia depending on the composition of the exhaust gases and the first temperature. Thus, the nitrogen oxides are transformed into ammonia, nitrogen and water. The presence of ammonia is temporary because, when the reaction is carried out in an oxygen-rich environment, the reaction continues until the complete conversion of the nitrogen oxides and ammonia into nitrogen and water. However, a large part of the oxygen is consumed at the internal combustion engine 1 . The first catalyst 2 is therefore susceptible. to have a partial oxygen deficiency causing the accumulation of ammonia in the exhaust line 100. In addition, ammonia emissions contribute to air and water pollution. Ammonia emissions also pose a health risk because they are likely to cause respiratory problems. It is therefore necessary to eliminate ammonia in the exhaust line 100. The exhaust line 100 according to the invention comprises a second catalyst 3. The second catalyst 3 has a second temperature and an oxygen concentration. The second catalyst 3 comprises a sensor for measuring the oxygen concentration. The second catalyst 3 is positioned downstream of the first catalyst 2. Thus, the ammonia produced by the first catalyst 2 is discharged to the second catalyst 3. The oxygen concentration in the second catalyst 3 must be sufficient to complete the reaction transforming the ammonia into nitrogen and water.Preferably, the first catalyst also comprises a sensor for measuring the oxygen concentration. Thus, if a decrease in the oxygen concentration is detected at the first catalyst, this indicates a future decrease in the oxygen concentration at the second catalyst. In addition, the internal combustion engine 1 comprises an oxygen regeneration device whose role is to stop the injection of fuel into said internal combustion engine 1. Stopping the injection of fuel into the internal combustion engine 1 causes oxygen to enter the exhaust line 100. The circulation of oxygen is illustrated by two arrows in FIG. 1.

[0017] Figure 2 schematically illustrates, in the form of a flowchart, a method for monitoring the conversion of ammonia into nitrogen and water in the exhaust line 100 of said vehicle. During a measurement step E1, the oxygen concentration in the second catalyst 3 is measured. The oxygen concentration is dependent on the second temperature. During a detection step E2, an ammonia conversion defect is detected when the oxygen concentration previously measured during the measurement step E1 is lower than a predetermined oxygen concentration threshold value. During an activation step E3, said oxygen regeneration device is activated when an ammonia conversion defect is detected previously during the detection step E2. The injection of fuel into the internal combustion engine 1 is therefore interrupted, which causes the increase in the quantity of oxygen in the exhaust line 100, and more particularly in the second catalyst 3. During a conversion step E4, the addition of oxygen causes the complete conversion of the ammonia into nitrogen and water. Preferably, the second catalyst 3 comprises a sensor for measuring the quantity of ammonia and the method comprises a step of measuring the quantity of ammonia. Thus, during the detection step E2, the ammonia conversion defect is detected when the oxygen concentration is lower than the threshold value of the predetermined oxygen concentration and when the quantity of ammonia is higher than a threshold value of the predetermined quantity of ammonia.In fact, the increase in the quantity of ammonia measured in the second catalyst 3 is a sign of an excessive accumulation of ammonia in the first catalyst 2, the oxygen concentration of which will decrease rapidly in the event of an accumulation of ammonia. Alternatively, the second catalyst 3 comprises a sensor for measuring the quantity of nitrogen oxides and the method comprises a step of measuring the quantity of nitrogen oxides. In this way, the ammonia conversion defect is detected when the oxygen concentration is lower than the predetermined oxygen concentration threshold value and when the quantity of nitrogen oxides is higher than a predetermined threshold value of the quantity of nitrogen oxides. In fact, if nitrogen oxides are detected at the second catalyst 3, this means that there is a nitrogen oxide conversion defect at the first catalyst 2.The defect in the conversion of nitrogen oxides means that there is most likely also a defect in the conversion of ammonia.

[0018] Furthermore, the invention relates to a motor vehicle comprising an internal combustion engine configured to implement the method for monitoring the conversion of ammonia into nitrogen and water in an exhaust line of a motor vehicle. Finally, the invention also relates to a computer program comprising instructions directing a computer to implement the previously described steps of said method.

Claims

CLAIMS 1. Method for monitoring the conversion of ammonia into nitrogen and water in an exhaust line (100) of a motor vehicle, said vehicle comprising an internal combustion engine (1) capable of receiving a fuel, said internal combustion engine (1) being configured to generate exhaust gases, said internal combustion engine (1) comprising an oxygen regeneration device, said exhaust line (100) being configured to evacuate the exhaust gases, said exhaust line (100) comprising a first catalyst (2) and a second catalyst (3), the first catalyst (2) having a first temperature, said first catalyst (2) being configured to produce a quantity of ammonia as a function of the composition of the exhaust gases and the first temperature, said second catalyst (3) having an oxygen concentration and a second temperature,said second catalyst (3) comprising a sensor for measuring the oxygen concentration, the second catalyst (3) being positioned downstream of the first catalyst (2), characterized in that said method comprises the following steps:, - a step (E1) of measuring the oxygen concentration, the oxygen concentration being dependent on the second temperature; - a step (E2) of detecting a defect in the conversion of ammonia when the oxygen concentration is lower than a predetermined threshold value of the oxygen concentration; - a step of activating (E3) said oxygen regeneration device when the fault is detected, the activation of the oxygen regeneration device causing a stoppage of the fuel injection into the internal combustion engine (1), the stoppage of the fuel injection causing an increase in the quantity of oxygen in the second catalyst; - a complete conversion step (E4) of ammonia into nitrogen and water by the second catalyst (3).

2. Method according to claim 1 characterized in that the second catalyst (2) comprises a sensor for measuring the quantity of ammonia, said method comprising a step of measuring the quantity of ammonia, the defect in conversion of the ammonia being detected when the concentration in oxygen is less than the predetermined oxygen concentration threshold value and when the amount of ammonia is greater than a predetermined ammonia amount threshold value.

3. Method according to claim 1 characterized in that the second catalyst (3) comprises a sensor for measuring the quantity of nitrogen oxides, said method comprising a step of measuring the quantity of nitrogen oxides, the ammonia conversion defect being detected when the oxygen concentration is lower than the threshold value of the predetermined oxygen concentration and when the quantity of nitrogen oxides is higher than a threshold value of the predetermined quantity of nitrogen oxides.

4. Method according to any one of claims 1 to 3, characterized in that the first catalyst comprises a sensor for measuring the oxygen concentration.

5. Computer program comprising instructions which, when the program is executed by a computer, cause the latter to implement the steps of the method for monitoring the conversion of ammonia into nitrogen and water in an exhaust line (100) of a motor vehicle according to any one of claims 1 to 4.

6. Motor vehicle comprising an internal combustion engine (1) configured to implement said method for monitoring the conversion of ammonia into nitrogen and water in an exhaust line (100) of a motor vehicle according to any one of claims 1 to 4.

Images