Hydrogen fuel engine exhaust after-treatment method and device

Abstract

The present application provides a method and device for after-treatment of exhaust gas from a hydrogen fuel engine, the method comprising: when the original exhaust temperature of the hydrogen fuel engine is greater than a first temperature threshold, controlling the exhaust gas to enter a first pipeline for after-treatment, wherein the first pipeline is provided with a hydrogen-oxygen catalyst and an ammonia selective catalytic reduction device, and the hydrogen-oxygen catalyst is located upstream of the ammonia selective catalytic reduction device; when the original exhaust temperature of the hydrogen fuel engine is less than or equal to a second temperature threshold, controlling the exhaust gas to enter a second pipeline for after-treatment, wherein the second temperature threshold is less than or equal to the first temperature threshold, and the second pipeline is provided with a hydrogen selective catalytic reduction device. Through the present application, a reasonable selection of exhaust after-treatment methods is made based on the original exhaust temperature of the hydrogen fuel engine, thereby effectively suppressing nitrogen oxide and hydrogen emissions under all operating conditions.

Description

Technical Field

[0001] The present application relates to the technical field of exhaust gas aftertreatment, and in particular to a method and device for aftertreatment of exhaust gas from a hydrogen fuel engine. Background Art

[0002] As a clean energy technology, hydrogen fuel engine has relatively few pollutants in its exhaust gas, but they still exist. The main pollutants are nitrogen oxides (NO x ) This is because during the hydrogen fuel combustion process, due to the high temperature conditions, a certain amount of nitrogen oxides, including nitric oxide (NO) and nitrogen dioxide (NO2), may be produced. In addition, the exhaust gas emitted by hydrogen fuel engines may also contain unburned hydrogen. Although relevant regulations do not impose emission control requirements for hydrogen as a pollutant, hydrogen is a flammable and explosive gas and should be removed from the exhaust gas as much as possible for safety reasons.

[0003] Currently, there are two main technology approaches for engine exhaust aftertreatment: NH3-SCR, which removes nitrogen oxides from exhaust gas through an ammonia selective catalytic reduction device; and H2-SCR, which removes nitrogen oxides from exhaust gas through a hydrogen selective catalytic reduction device. However, when applied to hydrogen-fueled engines, neither of these technology approaches can effectively suppress nitrogen oxide and hydrogen emissions under all operating conditions. Summary of the Invention

[0004] The present application provides a method and device for after-treatment of exhaust gas from a hydrogen fuel engine, which can solve the technical problem in the prior art of being unable to effectively suppress nitrogen oxide and hydrogen emissions under all operating conditions.

[0005] In a first aspect, an embodiment of the present application provides a method for after-treatment of exhaust gas from a hydrogen fuel engine, the method comprising:

[0006] When the exhaust temperature of the hydrogen fuel engine is greater than a first temperature threshold, the exhaust gas is controlled to enter a first pipeline for post-processing, wherein the first pipeline is provided with a hydrogen-oxygen catalyst and an ammonia selective catalytic reduction device, and the hydrogen-oxygen catalyst is located upstream of the ammonia selective catalytic reduction device;

[0007] When the original exhaust temperature of the hydrogen fuel engine is less than or equal to a second temperature threshold, the exhaust gas is controlled to enter the second pipeline for post-processing, wherein the second temperature threshold is less than or equal to the first temperature threshold, and the second pipeline is provided with a hydrogen selective catalytic reduction device.

[0008] Furthermore, in one embodiment, the second temperature threshold is equal to the first temperature threshold;

[0009] The first temperature threshold is the original exhaust temperature when the hydrogen fuel engine is operating at the target operating point;

[0010] Among the different test operating points, the emission quantification value corresponding to the target operating point is the lowest;

[0011] The emission quantification value is the weighted calculation result of the nitrogen oxide concentration and hydrogen concentration in the exhaust gas entering the first pipeline and participating in the after-treatment when the hydrogen fuel engine is operating at the corresponding test operating point;

[0012] The test operating point is a common operating point of the hydrogen fuel engine. When the hydrogen fuel engine is operating at the test operating point, the absolute value of the difference between the original exhaust temperature of the hydrogen fuel engine and the reference temperature is less than or equal to the preset span;

[0013] When the exhaust temperature of the hydrogen fuel engine is equal to the reference temperature, the theoretical conversion efficiencies of the ammonia selective catalytic reduction device and the hydrogen selective catalytic reduction device for nitrogen oxides are equal.

[0014] Furthermore, in one embodiment, the second temperature threshold is less than the first temperature threshold;

[0015] The hydrogen fuel engine exhaust post-processing method further comprises:

[0016] When the original exhaust temperature of the hydrogen fuel engine is less than or equal to the first temperature threshold and greater than the second temperature threshold, and the hydrogen concentration in the exhaust gas after participating in the post-processing is less than or equal to the first concentration threshold, the exhaust gas is controlled to enter the first pipeline for post-processing;

[0017] When the original exhaust temperature of the hydrogen fuel engine is less than or equal to the first temperature threshold and greater than the second temperature threshold, and the hydrogen concentration in the exhaust gas after post-processing is greater than the first concentration threshold, the exhaust gas is controlled to enter the second pipeline for post-processing.

[0018] Furthermore, in one embodiment, the hydrogen fuel engine exhaust post-processing method further includes:

[0019] When the original exhaust temperature of the hydrogen fuel engine is less than or equal to the second temperature threshold, and the nitrogen oxide concentration in the exhaust gas after post-processing is greater than the second concentration threshold, the hydrogen concentration in the exhaust gas before post-processing is increased.

[0020] Furthermore, in one embodiment, the step of increasing the hydrogen concentration in the tail gas before post-processing includes:

[0021] The amount of hydrogen injected into the cylinder by the first hydrogen injector after the power stroke is increased, wherein the first hydrogen injector is a hydrogen injector of a hydrogen fuel engine.

[0022] Furthermore, in one embodiment, the step of increasing the hydrogen concentration in the tail gas before post-processing includes:

[0023] The amount of hydrogen injected into the second pipeline by the second hydrogen injector is increased, wherein the second pipeline is further provided with a second hydrogen injector, and the second hydrogen injector is located upstream of the hydrogen selective catalytic reduction device.

[0024] Furthermore, in one embodiment, the hydrogen fuel engine exhaust post-processing method further includes:

[0025] When the original exhaust temperature of the hydrogen fuel engine is less than or equal to the second temperature threshold, and the hydrogen concentration in the exhaust gas after post-processing is greater than the third concentration threshold, the hydrogen concentration in the exhaust gas before post-processing is reduced.

[0026] Furthermore, in one embodiment, the step of lowering the hydrogen concentration in the tail gas before post-processing includes:

[0027] When the amount of hydrogen injected into the cylinder by the first hydrogen injector after the power stroke is greater than zero, reducing the amount of hydrogen injected into the cylinder by the first hydrogen injector after the power stroke, wherein the first hydrogen injector is a hydrogen injector of a hydrogen fuel engine;

[0028] When the amount of hydrogen injected into the cylinder by the first hydrogen injector after the power stroke is equal to zero, the amount of hydrogen injected into the cylinder by the first hydrogen injector before the power stroke starts is reduced.

[0029] Furthermore, in one embodiment, the step of lowering the hydrogen concentration in the tail gas before post-processing includes:

[0030] When the amount of hydrogen injected into the second pipeline by the second hydrogen injector is greater than zero, reducing the amount of hydrogen injected into the second pipeline by the second hydrogen injector, wherein the second pipeline is further provided with a second hydrogen injector, and the second hydrogen injector is located upstream of the hydrogen selective catalytic reduction device;

[0031] When the amount of hydrogen injected into the second pipeline by the second hydrogen injector is equal to zero, the amount of hydrogen injected into the cylinder by the first hydrogen injector before the start of the power stroke is reduced, wherein the first hydrogen injector is a hydrogen injector of a hydrogen fuel engine.

[0032] In a second aspect, an embodiment of the present application further provides a hydrogen fuel engine exhaust gas after-treatment device, the hydrogen fuel engine exhaust gas after-treatment device comprising:

[0033] a first flow direction control module, configured to control exhaust gas to enter a first pipeline for post-processing when the original exhaust temperature of the hydrogen fuel engine is greater than a first temperature threshold, wherein the first pipeline is provided with a hydrogen-oxygen catalyst and an ammonia selective catalytic reduction device, and the hydrogen-oxygen catalyst is located upstream of the ammonia selective catalytic reduction device;

[0034] The second flow direction control module is used to control the exhaust gas to enter the second pipeline for post-processing when the original exhaust temperature of the hydrogen fuel engine is less than or equal to the second temperature threshold, wherein the second temperature threshold is less than or equal to the first temperature threshold, and the second pipeline is provided with a hydrogen selective catalytic reduction device.

[0035] In this application, when exhaust gas enters the first pipeline for post-treatment, hydrogen is first removed from the exhaust gas by a hydrogen-oxygen catalyst, and then nitrogen oxides are removed from the exhaust gas by an ammonia selective catalytic reduction device. This ensures high conversion efficiency under medium and high temperature operating conditions. When exhaust gas enters the second pipeline for post-treatment, nitrogen oxides and hydrogen are removed from the exhaust gas by a hydrogen selective catalytic reduction device, ensuring high conversion efficiency under medium and low temperature operating conditions. Through this application, a reasonable choice of exhaust post-treatment method is made based on the original exhaust temperature of the hydrogen fuel engine, thereby effectively suppressing nitrogen oxide and hydrogen emissions under all operating conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a flow chart of a method for after-treatment of exhaust gas from a hydrogen fuel engine according to one embodiment of the present application;

[0037] Figure 2 Schematic diagram of temperature-conversion efficiency curves of an ammonia selective catalytic reduction device and a hydrogen selective catalytic reduction device in one embodiment of the present application;

[0038] Figure 3 This is a schematic structural diagram of an exhaust gas after-treatment system for a hydrogen fuel engine in one embodiment of the present application;

[0039] Figure 4 Schematic diagram of the functional modules of the exhaust gas after-treatment device of a hydrogen fuel engine in one embodiment of the present application.

[0040] Description of reference numerals:

[0041] 1. Exhaust pipe; 11. Intake main line; 12. First parallel line; 13. Second parallel line; 14. Exhaust main line; 2. Temperature sensor; 3. Three-way valve; 4. Hydrogen-oxygen catalyst; 5. Ammonia selective catalytic reduction device; 51. Urea injector; 52. Catalyst; 53. Ammonia slip catalyst; 6. Hydrogen selective catalytic reduction device; 7. Nitrogen oxide sensor; 8. Hydrogen sensor. DETAILED DESCRIPTION

[0042] In order to enable those skilled in the art to better understand the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0043] In order to make the objectives, technical solutions and advantages of this application clearer, the implementation methods of this application will be further described in detail below with reference to the accompanying drawings.

[0044] In a first aspect, an embodiment of the present application provides a method for after-treatment of exhaust gas from a hydrogen fuel engine.

[0045] Figure 1 A schematic flow chart of a method for after-treatment of exhaust gas from a hydrogen fuel engine in one embodiment of the present application is shown.

[0046] Reference Figure 1 In one embodiment, a method for post-processing exhaust gas from a hydrogen fuel engine comprises the following steps:

[0047] S1. When the exhaust temperature of the hydrogen fuel engine is greater than a first temperature threshold, the exhaust gas is controlled to enter a first pipeline for post-processing, wherein the first pipeline is provided with a hydrogen-oxygen catalyst and an ammonia selective catalytic reduction device, and the hydrogen-oxygen catalyst is located upstream of the ammonia selective catalytic reduction device.

[0048] Specifically, the raw exhaust temperature refers to the temperature of the exhaust gas generated by the combustion of fuel in the engine combustion chamber when it is just discharged into the exhaust system. The hydrogen-oxygen catalyst (HOC) mainly uses a specific catalyst to promote the oxidation reaction of hydrogen and oxygen to produce water, thereby achieving the purpose of reducing hydrogen emissions. The ammonia selective catalytic reduction device (NH3-SCR) uses ammonia as a reducing agent. Under the action of the catalyst, it selectively reacts chemically with nitrogen oxides in the exhaust gas, reducing them to nitrogen and water, thereby achieving the purpose of reducing nitrogen oxide emissions. The ammonia selective catalytic reduction device has a high conversion efficiency for nitrogen oxides under medium and high temperature conditions, and a low conversion efficiency for nitrogen oxides under low temperature conditions (for example, the raw exhaust temperature is 0-150°C). The hydrogen-oxygen catalyst cannot ignite under low temperature conditions.

[0049] In this embodiment, the purpose of placing the hydrogen-oxygen catalyst upstream of the ammonia selective catalytic reduction device is to utilize the exothermic heat of the reaction in the hydrogen-oxygen catalyst to increase the temperature of the exhaust gas entering the ammonia selective catalytic reduction device, thereby improving the conversion efficiency of nitrogen oxides. The first temperature threshold is used to eliminate low-temperature operating conditions to ensure the conversion efficiency of the exhaust gas entering the first pipeline for post-processing.

[0050] S2. When the exhaust temperature of the hydrogen fuel engine is less than or equal to a second temperature threshold, the exhaust gas is controlled to enter the second pipeline for post-processing, wherein the second temperature threshold is less than or equal to the first temperature threshold, and the second pipeline is provided with a hydrogen selective catalytic reduction device.

[0051] Specifically, the hydrogen selective catalytic reduction device (H2-SCR) uses hydrogen as a reducing agent. Under the action of a catalyst, it selectively reacts chemically with nitrogen oxides in the exhaust gas, reducing them to nitrogen and water, thereby achieving the purpose of reducing nitrogen oxide emissions. Since the above reaction also requires the consumption of hydrogen, the purpose of reducing hydrogen emissions can also be achieved by rationally controlling the amount of hydrogen. The hydrogen selective catalytic reduction device has a high conversion efficiency for nitrogen oxides under medium and low temperature conditions. Under high temperature conditions (for example, the original exhaust temperature is between 200-300°C), the reaction activity under oxygen-rich conditions is relatively low. The competitive reaction between hydrogen and oxygen inhibits the effect of selective catalytic reduction of nitrogen oxides, resulting in a low conversion efficiency.

[0052] In this embodiment, the second temperature threshold is used to exclude high-temperature conditions to ensure the conversion efficiency of the exhaust gas when it enters the second pipeline for post-processing. When the second temperature threshold is set equal to the first temperature threshold, the original exhaust temperature is the only basis for selecting the exhaust gas post-processing method. Considering that there is a certain temperature range, the conversion efficiency of the two exhaust gas post-processing methods is not much different and is within an acceptable range. Therefore, the second temperature threshold can also be set to be less than the first temperature threshold. When the original exhaust temperature is less than or equal to the first temperature threshold and greater than the second temperature threshold, any exhaust gas post-processing method can be used, or other bases can be introduced for selection.

[0053] Therefore, in this embodiment, when the exhaust gas enters the first pipeline for post-treatment, hydrogen is first removed from the exhaust gas by the hydrogen-oxygen catalyst, and then nitrogen oxides are removed from the exhaust gas by the ammonia selective catalytic reduction device, ensuring high conversion efficiency under medium and high temperature operating conditions. When the exhaust gas enters the second pipeline for post-treatment, nitrogen oxides and hydrogen are removed from the exhaust gas by the hydrogen selective catalytic reduction device, ensuring high conversion efficiency under medium and low temperature operating conditions. Through this application, the exhaust gas post-treatment method is reasonably selected based on the original exhaust temperature of the hydrogen fuel engine, thereby effectively suppressing nitrogen oxide and hydrogen emissions under all operating conditions.

[0054] Furthermore, in one embodiment, the second temperature threshold is equal to the first temperature threshold;

[0055] The first temperature threshold is the original exhaust temperature when the hydrogen fuel engine is operating at the target operating point;

[0056] Among the different test operating points, the emission quantification value corresponding to the target operating point is the lowest;

[0057] The emission quantification value is the weighted calculation result of the nitrogen oxide concentration and hydrogen concentration in the exhaust gas entering the first pipeline and participating in the after-treatment when the hydrogen fuel engine is operating at the corresponding test operating point;

[0058] The test operating point is a common operating point of the hydrogen fuel engine. When the hydrogen fuel engine is operating at the test operating point, the absolute value of the difference between the original exhaust temperature of the hydrogen fuel engine and the reference temperature is less than or equal to the preset span;

[0059] When the exhaust temperature of the hydrogen fuel engine is equal to the reference temperature, the theoretical conversion efficiencies of the ammonia selective catalytic reduction device and the hydrogen selective catalytic reduction device for nitrogen oxides are equal.

[0060] In this embodiment, the second temperature threshold is set equal to the first temperature threshold, and a method for determining the first temperature threshold is provided. This embodiment allows for reasonable determination of the temperature threshold serving as the switching point when the exhaust gas aftertreatment method is selected solely based on the original exhaust temperature, thereby improving the suppression of nitrogen oxide and hydrogen emissions under all operating conditions.

[0061] Figure 2 A schematic diagram showing temperature-conversion efficiency curves of an ammonia selective catalytic reduction device and a hydrogen selective catalytic reduction device in one embodiment of the present application is shown.

[0062] For example, refer to Figure 2 First, find the intersection of the temperature-conversion efficiency curves of the ammonia selective catalytic reduction device and the hydrogen selective catalytic reduction device. Figure 2 The temperature T0 corresponding to the intersection in is the reference temperature. Then, among the commonly used operating points of the hydrogen fuel engine, find the operating point where the original exhaust temperature is close to the reference temperature (for example, T0±20°C) as the test operating point. Next, obtain the nitrogen oxide concentration and hydrogen concentration in the exhaust gas after entering the first pipeline for post-processing when the hydrogen fuel engine is working at different test operating points, and perform weighted calculation to obtain the emission quantification value. The weight is set as needed. For example, nitrogen oxides are pollutants defined by relevant regulations, and their weight can be set relatively higher. The lower the emission quantification value, the better the effect of exhaust gas post-treatment. Finally, the test operating point with the lowest emission quantification value is determined as the target operating point, and the original exhaust temperature of the hydrogen fuel engine when the hydrogen fuel engine is working at the target operating point is determined as the first temperature threshold.

[0063] Furthermore, in one embodiment, the second temperature threshold is less than the first temperature threshold;

[0064] The hydrogen fuel engine exhaust post-processing method further comprises:

[0065] When the original exhaust temperature of the hydrogen fuel engine is less than or equal to the first temperature threshold and greater than the second temperature threshold, and the hydrogen concentration in the exhaust gas after participating in the post-processing is less than or equal to the first concentration threshold, the exhaust gas is controlled to enter the first pipeline for post-processing;

[0066] When the original exhaust temperature of the hydrogen fuel engine is less than or equal to the first temperature threshold and greater than the second temperature threshold, and the hydrogen concentration in the exhaust gas after post-processing is greater than the first concentration threshold, the exhaust gas is controlled to enter the second pipeline for post-processing.

[0067] In this embodiment, the second temperature threshold is set to be lower than the first temperature threshold. When the original exhaust temperature is less than or equal to the first temperature threshold but greater than the second temperature threshold, the hydrogen concentration in the exhaust gas after post-treatment is introduced as an additional reference. When the hydrogen concentration is high, it is considered that the first pipeline cannot effectively control hydrogen emissions and the second pipeline is required for exhaust post-treatment. Through this embodiment, the exhaust post-treatment method can be reasonably selected in the intermediate temperature range based on the hydrogen removal situation during actual operation, thereby improving the suppression effect of nitrogen oxides and hydrogen under all operating conditions.

[0068] Furthermore, in one embodiment, the hydrogen fuel engine exhaust post-processing method further includes:

[0069] When the original exhaust temperature of the hydrogen fuel engine is less than or equal to the second temperature threshold, and the nitrogen oxide concentration in the exhaust gas after post-processing is greater than the second concentration threshold, the hydrogen concentration in the exhaust gas before post-processing is increased.

[0070] In this embodiment, the nitrogen oxide concentration of the exhaust gas after entering the second pipeline for post-treatment is monitored. If the nitrogen oxide concentration is too high, it means that there is insufficient hydrogen for post-treatment. It is necessary to increase the hydrogen concentration in the exhaust gas before post-treatment until the nitrogen oxide concentration is reduced to an acceptable range.

[0071] As an optional embodiment, the step of increasing the hydrogen concentration in the tail gas before post-processing includes:

[0072] The amount of hydrogen injected into the cylinder by the first hydrogen injector after the power stroke is increased, wherein the first hydrogen injector is a hydrogen injector of a hydrogen fuel engine.

[0073] In this embodiment, the hydrogen injected into the cylinder by the hydrogen injector of the hydrogen fuel engine after the power stroke does not participate in combustion, but will all be used as part of the exhaust gas for post-processing to achieve precise regulation of the hydrogen concentration. In this way, there is no need to set up a separate hydrogen injector for the hydrogen selective catalytic reduction device, which helps to simplify the structure and reduce costs.

[0074] As another optional embodiment, the step of increasing the hydrogen concentration in the tail gas before post-processing includes:

[0075] The amount of hydrogen injected into the second pipeline by the second hydrogen injector is increased, wherein the second pipeline is further provided with a second hydrogen injector, and the second hydrogen injector is located upstream of the hydrogen selective catalytic reduction device.

[0076] In this embodiment, a hydrogen injector is separately provided for the hydrogen selective catalytic reduction device in the second pipeline to achieve precise regulation of the hydrogen concentration.

[0077] Furthermore, in one embodiment, the hydrogen fuel engine exhaust post-processing method further includes:

[0078] When the original exhaust temperature of the hydrogen fuel engine is less than or equal to the second temperature threshold, and the hydrogen concentration in the exhaust gas after post-processing is greater than the third concentration threshold, the hydrogen concentration in the exhaust gas before post-processing is reduced.

[0079] In this embodiment, the hydrogen concentration of the exhaust gas after entering the second pipeline for post-processing is monitored. If the hydrogen concentration is too high, it means that there is excessive hydrogen participating in the post-processing. The hydrogen concentration in the exhaust gas before participating in the post-processing needs to be lowered until the hydrogen concentration drops to an acceptable range.

[0080] As an optional embodiment, the step of lowering the hydrogen concentration in the tail gas before post-processing includes:

[0081] When the amount of hydrogen injected into the cylinder by the first hydrogen injector after the power stroke is greater than zero, reducing the amount of hydrogen injected into the cylinder by the first hydrogen injector after the power stroke, wherein the first hydrogen injector is a hydrogen injector of a hydrogen fuel engine;

[0082] When the amount of hydrogen injected into the cylinder by the first hydrogen injector after the power stroke is equal to zero, the amount of hydrogen injected into the cylinder by the first hydrogen injector before the power stroke starts is reduced.

[0083] In this embodiment, the hydrogen in the exhaust gas prior to post-processing comes from two sources: a portion of the hydrogen injected into the cylinder by the first hydrogen injector before the start of the power stroke, i.e., the remaining portion from the combustion reaction; and all of the hydrogen injected into the cylinder by the first hydrogen injector after the completion of the power stroke. Because each combustion reaction is influenced by numerous factors, the amount of remaining hydrogen is difficult to precisely control. Therefore, when it is necessary to reduce the hydrogen concentration in the exhaust gas prior to post-processing, the amount of hydrogen injected into the cylinder by the first hydrogen injector after the completion of the power stroke is preferentially reduced. After this amount is reduced to zero, the amount of hydrogen injected into the cylinder by the first hydrogen injector before the start of the power stroke is then reduced.

[0084] As an optional embodiment, the step of lowering the hydrogen concentration in the tail gas before post-processing includes:

[0085] When the amount of hydrogen injected into the second pipeline by the second hydrogen injector is greater than zero, reducing the amount of hydrogen injected into the second pipeline by the second hydrogen injector, wherein the second pipeline is further provided with a second hydrogen injector, and the second hydrogen injector is located upstream of the hydrogen selective catalytic reduction device;

[0086] When the amount of hydrogen injected into the second pipeline by the second hydrogen injector is equal to zero, the amount of hydrogen injected into the cylinder by the first hydrogen injector before the start of the power stroke is reduced, wherein the first hydrogen injector is a hydrogen injector of a hydrogen fuel engine.

[0087] Specifically in this embodiment, the hydrogen injected into the cylinder by the first hydrogen injector before the start of the power stroke will participate in the combustion, and the hydrogen injected into the second pipeline by the second hydrogen injector will not participate in the combustion. Therefore, the amount of the former is lowered first, and after it is lowered to zero, the amount of the latter is lowered.

[0088] It is understood that the above embodiment describes how to properly control the amount of hydrogen involved in the post-processing of exhaust gas entering the second pipeline. In practice, the amount of ammonia involved in the post-processing of exhaust gas entering the first pipeline also needs to be properly controlled. Since ammonia selective catalytic reduction technology is very mature, relevant literature can be referenced and will not be elaborated on here.

[0089] Figure 3 A schematic structural diagram of an exhaust gas after-treatment system for a hydrogen fuel engine in one embodiment of the present application is shown.

[0090] Reference Figure 3 The exhaust after-treatment system of a hydrogen fuel engine includes an exhaust pipe 1, a temperature sensor 2, a three-way valve 3, a hydrogen-oxygen catalyst 4, an ammonia selective catalytic reduction device 5, a hydrogen selective catalytic reduction device 6, a nitrogen oxide sensor 7 and a hydrogen sensor 8.

[0091] The exhaust gas pipeline 1 includes an intake main pipeline 11, a first parallel pipeline 12, a second parallel pipeline 13 and an outlet main pipeline 14. The air inlet of the intake main pipeline 11 is connected to the air outlet of the hydrogen fuel engine (not shown in the figure), the air outlet of the intake main pipeline 11 is connected to the air inlets of the first parallel pipeline 12 and the second parallel pipeline 13, and the air inlet of the outlet main pipeline 14 is connected to the air outlet of the first parallel pipeline 12 and the second parallel pipeline 13.

[0092] The temperature sensor 2 is provided on the main air intake line 11. The air inlet of the three-way valve 3 is connected to the air outlet of the main air intake line 11, the first air outlet of the three-way valve 3 is connected to the air inlet of the first parallel line 12, and the second air outlet of the three-way valve 3 is connected to the air inlet of the second parallel line 13.

[0093] The hydrogen-oxygen catalyst 4 is disposed in a first parallel line 12. The ammonia selective catalytic reduction device 5 is disposed in the first parallel line 12, downstream of the hydrogen-oxygen catalyst 4. The hydrogen selective catalytic reduction device 6 is disposed in a second parallel line 13. The nitrogen oxide sensor 7 is disposed in the main outlet line 14. The hydrogen sensor 8 is disposed in the main outlet line 14.

[0094] Specifically, the ammonia selective catalytic reduction device 5 includes a urea injector 51, a catalyst 52, and an ammonia slip catalyst 53. The urea injector 51 is used to inject urea aqueous solution into the exhaust gas, hydrolyzing it to produce ammonia. The catalyst 52 provides a reaction environment and the necessary catalytic action for the selective catalytic reduction reaction of ammonia and nitrogen oxides. The ammonia slip catalyst 53 removes excess ammonia that does not participate in the reaction.

[0095] The hydrogen fuel engine exhaust after-treatment method of the present application is applicable to Figure 3 The hydrogen fuel engine exhaust after-treatment system shown uses the first parallel pipeline 12 as the first pipeline and the second parallel pipeline 13 as the second pipeline. The original exhaust temperature of the hydrogen fuel engine is collected by the temperature sensor 2, and the exhaust gas flow to the first pipeline or the second pipeline is controlled by the three-way valve 3. When the original exhaust temperature of the hydrogen fuel engine is less than or equal to the second temperature threshold, the nitrogen oxide concentration in the exhaust gas after the after-treatment is collected by the nitrogen oxide sensor 7, and the hydrogen concentration in the exhaust gas after the after-treatment is collected by the hydrogen sensor 8.

[0096] It should be noted that Figure 3 This is only an example of the system structure to facilitate a more intuitive understanding of how the various operations required by this application can be implemented, but it is not intended to limit the system structure. For example, assuming that the nitrogen oxide sensor and the hydrogen sensor are set in the second parallel pipeline 13, located downstream of the hydrogen selective catalytic reduction device 6, the corresponding collection work can also be completed. For another example, the first pipeline and the second pipeline are not necessarily Figure 3 The simple parallel relationship shown.

[0097] In a second aspect, an embodiment of the present application also provides a hydrogen fuel engine exhaust gas after-treatment device.

[0098] Figure 4 A schematic diagram of the functional modules of a hydrogen fuel engine exhaust after-treatment device in one embodiment of the present application is shown.

[0099] Reference Figure 4 In one embodiment, the exhaust gas after-treatment device of a hydrogen fuel engine includes:

[0100] A first flow direction control module 10 is configured to control exhaust gas to enter a first pipeline for post-processing when the exhaust temperature of the hydrogen fuel engine is greater than a first temperature threshold, wherein the first pipeline is provided with a hydrogen-oxygen catalyst and an ammonia selective catalytic reduction device, and the hydrogen-oxygen catalyst is located upstream of the ammonia selective catalytic reduction device;

[0101] The second flow direction control module 20 is used to control the exhaust gas to enter the second pipeline for post-processing when the original exhaust temperature of the hydrogen fuel engine is less than or equal to the second temperature threshold, wherein the second temperature threshold is less than or equal to the first temperature threshold, and the second pipeline is provided with a hydrogen selective catalytic reduction device.

[0102] Furthermore, in one embodiment, the second temperature threshold is equal to the first temperature threshold;

[0103] The first temperature threshold is the original exhaust temperature when the hydrogen fuel engine is operating at the target operating point;

[0104] Among the different test operating points, the emission quantification value corresponding to the target operating point is the lowest;

[0105] The emission quantification value is the weighted calculation result of the nitrogen oxide concentration and hydrogen concentration in the exhaust gas entering the first pipeline and participating in the after-treatment when the hydrogen fuel engine is operating at the corresponding test operating point;

[0106] The test operating point is a common operating point of the hydrogen fuel engine. When the hydrogen fuel engine is operating at the test operating point, the absolute value of the difference between the original exhaust temperature of the hydrogen fuel engine and the reference temperature is less than or equal to the preset span;

[0107] When the exhaust temperature of the hydrogen fuel engine is equal to the reference temperature, the theoretical conversion efficiencies of the ammonia selective catalytic reduction device and the hydrogen selective catalytic reduction device for nitrogen oxides are equal.

[0108] Furthermore, in one embodiment, the second temperature threshold is less than the first temperature threshold;

[0109] The hydrogen fuel engine exhaust after-treatment device further includes a third flow direction control module 30, which is used to:

[0110] When the original exhaust temperature of the hydrogen fuel engine is less than or equal to the first temperature threshold and greater than the second temperature threshold, and the hydrogen concentration in the exhaust gas after participating in the post-processing is less than or equal to the first concentration threshold, the exhaust gas is controlled to enter the first pipeline for post-processing;

[0111] When the original exhaust temperature of the hydrogen fuel engine is less than or equal to the first temperature threshold and greater than the second temperature threshold, and the hydrogen concentration in the exhaust gas after post-processing is greater than the first concentration threshold, the exhaust gas is controlled to enter the second pipeline for post-processing.

[0112] Furthermore, in one embodiment, the hydrogen fuel engine exhaust after-treatment device further includes a hydrogen injection control module 40, which is used to:

[0113] When the original exhaust temperature of the hydrogen fuel engine is less than or equal to the second temperature threshold, and the nitrogen oxide concentration in the exhaust gas after post-processing is greater than the second concentration threshold, the hydrogen concentration in the exhaust gas before post-processing is increased.

[0114] Furthermore, in one embodiment, the hydrogen injection control module 40 is configured to:

[0115] The amount of hydrogen injected into the cylinder by the first hydrogen injector after the power stroke is increased, wherein the first hydrogen injector is a hydrogen injector of a hydrogen fuel engine.

[0116] Furthermore, in one embodiment, the hydrogen injection control module 40 is configured to:

[0117] The amount of hydrogen injected into the second pipeline by the second hydrogen injector is increased, wherein the second pipeline is further provided with a second hydrogen injector, and the second hydrogen injector is located upstream of the hydrogen selective catalytic reduction device.

[0118] Furthermore, in one embodiment, the hydrogen fuel engine exhaust after-treatment device further includes a hydrogen injection control module 40, which is used to:

[0119] When the original exhaust temperature of the hydrogen fuel engine is less than or equal to the second temperature threshold, and the hydrogen concentration in the exhaust gas after post-processing is greater than the third concentration threshold, the hydrogen concentration in the exhaust gas before post-processing is reduced.

[0120] Furthermore, in one embodiment, the hydrogen injection control module 40 is configured to:

[0121] When the amount of hydrogen injected into the cylinder by the first hydrogen injector after the power stroke is greater than zero, reducing the amount of hydrogen injected into the cylinder by the first hydrogen injector after the power stroke, wherein the first hydrogen injector is a hydrogen injector of a hydrogen fuel engine;

[0122] When the amount of hydrogen injected into the cylinder by the first hydrogen injector after the power stroke is equal to zero, the amount of hydrogen injected into the cylinder by the first hydrogen injector before the power stroke starts is reduced.

[0123] Furthermore, in one embodiment, the hydrogen injection control module 40 is configured to:

[0124] When the amount of hydrogen injected into the second pipeline by the second hydrogen injector is greater than zero, reducing the amount of hydrogen injected into the second pipeline by the second hydrogen injector, wherein the second pipeline is further provided with a second hydrogen injector, and the second hydrogen injector is located upstream of the hydrogen selective catalytic reduction device;

[0125] When the amount of hydrogen injected into the second pipeline by the second hydrogen injector is equal to zero, the amount of hydrogen injected into the cylinder by the first hydrogen injector before the start of the power stroke is reduced, wherein the first hydrogen injector is a hydrogen injector of a hydrogen fuel engine.

[0126] Among them, the functional implementation of each module in the above-mentioned hydrogen fuel engine exhaust gas after-treatment device corresponds to the various steps in the above-mentioned hydrogen fuel engine exhaust gas after-treatment method embodiment, and their functions and implementation processes will not be repeated here one by one.

[0127] It should be noted that the serial numbers of the above-mentioned embodiments of the present application are for description only and do not represent the advantages or disadvantages of the embodiments.

[0128] The terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned drawings are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally includes steps or units that are not listed, or optionally includes other steps or units inherent to these processes, methods, products or devices. The terms "first", "second" and "third" are used to distinguish different objects, etc., and do not represent a sequence, nor do they limit the "first", "second" and "third" to different types.

[0129] In the description of the embodiments of this application, the words "exemplary," "for example," or "for example" are used to indicate examples, illustrations, or descriptions. Any embodiment or design described as "exemplary," "for example," or "for example" in the embodiments of this application should not be construed as being preferred or advantageous over other embodiments or designs. Rather, the use of words such as "exemplary," "for example," or "for example" is intended to present the relevant concepts in a concrete manner.

[0130] In the description of the embodiments of the present application, unless otherwise specified, “ / ” means or, for example, A / B can mean A or B; “and / or” in the text is merely a description of the association relationship of associated objects, indicating that three relationships may exist, for example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. In addition, in the description of the embodiments of the present application, “multiple” refers to two or more than two.

[0131] In some processes described in the embodiments of the present application, multiple operations or steps are included that appear in a specific order. However, it should be understood that these operations or steps may not be performed in the order in which they appear in the embodiments of the present application or may be performed in parallel. The sequence numbers of the operations are only used to distinguish between different operations, and the sequence numbers themselves do not represent any order of execution. In addition, these processes may include more or fewer operations, and these operations or steps may be performed in sequence or in parallel, and these operations or steps may be combined.

[0132] Through the description of the above implementation methods, those skilled in the art can clearly understand that the above-mentioned embodiment methods can be implemented by means of software plus the necessary general hardware platform, of course, it can also be implemented by hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of the present application, or the part that contributes to the prior art, can be embodied in the form of a software product, which is stored in a storage medium (such as ROM / RAM, magnetic disk, optical disk) as described above, and includes a number of instructions for enabling a terminal device to execute the methods described in each embodiment of the present application.

[0133] The above are only preferred embodiments of the present application and do not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A method for post-processing exhaust gas from a hydrogen fuel engine, characterized in that: The hydrogen fuel engine exhaust post-processing method comprises: When the exhaust temperature of the hydrogen fuel engine is greater than a first temperature threshold, the exhaust gas is controlled to enter a first pipeline for post-processing, wherein the first pipeline is provided with a hydrogen-oxygen catalyst and an ammonia selective catalytic reduction device, and the hydrogen-oxygen catalyst is located upstream of the ammonia selective catalytic reduction device; When the exhaust temperature of the hydrogen fuel engine is less than or equal to a second temperature threshold, the exhaust gas is controlled to enter the second pipeline for post-processing, wherein the second temperature threshold is less than the first temperature threshold, and the second pipeline is provided with a hydrogen selective catalytic reduction device; When the original exhaust temperature of the hydrogen fuel engine is less than or equal to the first temperature threshold and greater than the second temperature threshold, and the hydrogen concentration in the exhaust gas after participating in the post-processing is less than or equal to the first concentration threshold, the exhaust gas is controlled to enter the first pipeline for post-processing; When the original exhaust temperature of the hydrogen fuel engine is less than or equal to the first temperature threshold and greater than the second temperature threshold, and the hydrogen concentration in the exhaust gas after post-processing is greater than the first concentration threshold, the exhaust gas is controlled to enter the second pipeline for post-processing.

2. The method for post-processing exhaust gas from a hydrogen fuel engine according to claim 1, wherein: The hydrogen fuel engine exhaust post-processing method further comprises: When the original exhaust temperature of the hydrogen fuel engine is less than or equal to the second temperature threshold, and the nitrogen oxide concentration in the exhaust gas after post-processing is greater than the second concentration threshold, the hydrogen concentration in the exhaust gas before post-processing is increased.

3. The method for post-processing exhaust gas from a hydrogen fuel engine according to claim 2, wherein: The step of increasing the hydrogen concentration in the tail gas before participating in the post-processing comprises: The amount of hydrogen injected into the cylinder by the first hydrogen injector after the power stroke is increased, wherein the first hydrogen injector is a hydrogen injector of a hydrogen fuel engine.

4. The method for post-processing exhaust gas from a hydrogen fuel engine according to claim 2, wherein: The step of increasing the hydrogen concentration in the tail gas before participating in the post-processing comprises: The amount of hydrogen injected into the second pipeline by the second hydrogen injector is increased, wherein the second pipeline is further provided with a second hydrogen injector, and the second hydrogen injector is located upstream of the hydrogen selective catalytic reduction device.

5. The method for post-processing exhaust gas from a hydrogen fuel engine according to claim 1, wherein: The hydrogen fuel engine exhaust post-processing method further comprises: When the original exhaust temperature of the hydrogen fuel engine is less than or equal to the second temperature threshold, and the hydrogen concentration in the exhaust gas after post-processing is greater than the third concentration threshold, the hydrogen concentration in the exhaust gas before post-processing is reduced.

6. The method for post-processing exhaust gas from a hydrogen fuel engine according to claim 5, wherein: The step of lowering the hydrogen concentration in the tail gas before participating in the post-processing comprises: When the amount of hydrogen injected into the cylinder by the first hydrogen injector after the power stroke is greater than zero, reducing the amount of hydrogen injected into the cylinder by the first hydrogen injector after the power stroke, wherein the first hydrogen injector is a hydrogen injector of a hydrogen fuel engine; When the amount of hydrogen injected into the cylinder by the first hydrogen injector after the power stroke is equal to zero, the amount of hydrogen injected into the cylinder by the first hydrogen injector before the power stroke starts is reduced.

7. The method for post-processing exhaust gas from a hydrogen fuel engine according to claim 5, wherein: The step of lowering the hydrogen concentration in the tail gas before participating in the post-processing comprises: When the amount of hydrogen injected into the second pipeline by the second hydrogen injector is greater than zero, reducing the amount of hydrogen injected into the second pipeline by the second hydrogen injector, wherein the second pipeline is further provided with a second hydrogen injector, and the second hydrogen injector is located upstream of the hydrogen selective catalytic reduction device; When the amount of hydrogen injected into the second pipeline by the second hydrogen injector is equal to zero, the amount of hydrogen injected into the cylinder by the first hydrogen injector before the start of the power stroke is reduced, wherein the first hydrogen injector is a hydrogen injector of a hydrogen fuel engine.

8. A hydrogen fuel engine exhaust gas post-processing device, characterized in that: The hydrogen fuel engine exhaust after-treatment device comprises: a first flow direction control module, configured to control exhaust gas to enter a first pipeline for post-processing when the original exhaust temperature of the hydrogen fuel engine is greater than a first temperature threshold, wherein the first pipeline is provided with a hydrogen-oxygen catalyst and an ammonia selective catalytic reduction device, and the hydrogen-oxygen catalyst is located upstream of the ammonia selective catalytic reduction device; a second flow direction control module, configured to control the exhaust gas to enter a second pipeline for post-processing when the original exhaust temperature of the hydrogen fuel engine is less than or equal to a second temperature threshold, wherein the second temperature threshold is less than the first temperature threshold, and the second pipeline is provided with a hydrogen selective catalytic reduction device; The third flow direction control module is used to control the exhaust gas to enter the first pipeline for post-processing when the original exhaust temperature of the hydrogen fuel engine is less than or equal to the first temperature threshold, greater than the second temperature threshold, and the hydrogen concentration in the exhaust gas after participating in post-processing is less than or equal to the first concentration threshold; when the original exhaust temperature of the hydrogen fuel engine is less than or equal to the first temperature threshold, greater than the second temperature threshold, and the hydrogen concentration in the exhaust gas after participating in post-processing is greater than the first concentration threshold, control the exhaust gas to enter the second pipeline for post-processing.

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