Aftertreatment system and control method for ammonia fuel engine

Abstract

The present invention relates to a post-processing system and a control method for an ammonia fuel engine. The post-processing system comprises an engine, an ammonia cracker, an ammonia tank and a post-processor. The ammonia cracker is used to crack hydrogen to produce hydrogen. The ammonia cracker is used to crack hydrogen to improve engine combustion. The ammonia cracker and the post-processing system are integrated to fully utilize exhaust energy and tail gas purification. The overall system is efficient and compact. The control method optimizes the conversion efficiency of ammonia cracking and a post-processing catalyst according to the exhaust temperature. Under high-temperature and high-flow conditions of the engine, a bypass supercharger fully utilizes a heat source to crack ammonia. At low temperatures, the ammonia cracker is bypassed to ensure the conversion efficiency of the post-processing.

Description

Technical Field

[0001] The present invention relates to the technical field of engine cooling systems, and in particular to an after-treatment system and a control method for an ammonia fuel engine. Background Art

[0002] Ammonia-fueled engines are internal combustion engines that use pure ammonia or a mixture of ammonia and diesel, ammonia and hydrogen, or ammonia and other fuels. Because ammonia is primarily used as fuel, the combustion products are green and low-carbon. Although hydrogen is the cleanest of all energy sources, with high energy density and a combustion product of water, it produces no pollutants, making it very environmentally friendly. However, hydrogen is highly reactive and prone to explosions, leading to high investment costs for hydrogen transportation and storage, such as at hydrogen refueling stations. Ammonia, a gas that can be synthesized artificially and at low cost, has high energy density and is easily liquefied and transported, making it easy to transport. Its combustion does not produce carbon dioxide, making it suitable for use as an alternative fuel in engines, as a feedstock for hydrogen production, and as a gas for catalytic reduction in post-treatment systems. Using hydrogen produced by ammonia cracking and feeding it into engines can improve ammonia combustion, increase thermal efficiency, and reduce emissions of pollutants such as nitrogen oxides. Furthermore, ammonia, as a post-treatment reducing agent, can catalytically reduce nitrogen oxides in exhaust gas.

[0003] The prior art has documented methods for producing hydrogen by cracking ammonia, but none of them are integrated with the engine and post-processing system, and the heat generated by the engine combustion exhaust is not fully utilized. Summary of the Invention

[0004] To solve the above problems, the present invention provides an after-treatment system and control method for an ammonia fuel engine, which improves combustion and reduces pollutant emissions by generating hydrogen through cracking.

[0005] The technical solution adopted by the present invention is: an after-treatment system for an ammonia fuel engine, characterized in that it includes an engine, an ammonia cracker, an ammonia tank and a after-treatment device, wherein the engine outlet is divided into two paths, one path is connected to the front exhaust pipe through the supercharger, and the other path is connected to the front exhaust pipe through the first throttle valve and the first bypass pipe; after passing through the front exhaust pipe, the gas is divided into two paths, one path is connected to the after-treatment device through the second throttle valve, the second bypass pipe and the rear exhaust pipe, and the other path is connected to the after-treatment device through the third throttle valve, the ammonia cracker and the rear exhaust pipe;

[0006] The ammonia tank is divided into three paths after passing through the ammonia filter. One path is connected to the engine air intake through the first solenoid valve; another path is connected to the engine air intake after passing through the ammonia cracker, the hydrogen extraction device and the hydrogen metering pump. A fifth solenoid valve is provided between the ammonia cracker and the hydrogen extraction device, and a third solenoid valve is provided between the ammonia filter and the ammonia cracker; the third path is connected to the post-processor after passing through the ammonia injection device and the nozzle, and a fourth solenoid valve is provided between the ammonia filter and the ammonia injection device; a second solenoid valve is provided between the ammonia tank and the ammonia filter.

[0007] Preferably, a first temperature sensor is provided at the front end of the ammonia cracker.

[0008] Preferably, a second temperature sensor is provided at the front end of the post-processor, a fourth temperature sensor is provided at the rear end, and a third temperature sensor is provided at the mixer section of the post-processor.

[0009] Preferably, the ammonia cracker includes an outer shell, a thermal insulation material, an inner shell, a catalyst filling cavity, a low-temperature and low-pressure catalyst, an ammonia gas delivery connector and a mixed gas delivery connector. A thermal insulation material is provided between the outer shell and the inner shell. The catalyst filling cavity is provided in the inner shell. The low-temperature and low-pressure catalyst is filled in the catalyst filling cavity. The ammonia cracker is connected to the ammonia filter through the ammonia gas delivery connector, and the ammonia cracker is connected to the engine air intake through the mixed gas delivery connector.

[0010] Preferably, the post-processor comprises a DOC module, a DPF module, an SCR carrier module and a mixer which are arranged in sequence, and the DOC module, DPF module, SCR carrier module and mixer are connected to each other via flanges or clamps.

[0011] Preferably, the mixer section is provided with a front NOx sensor, and the rear end of the post-processor is provided with a rear NOx sensor.

[0012] The above-mentioned control method for an ammonia fuel engine after-treatment system is characterized by comprising the following steps:

[0013] After the engine is ignited, the first solenoid valve and the second solenoid valve are opened, and the ammonia in the ammonia tank is transported to the engine through the ammonia pipe. The engine combustion produces exhaust gas, and the exhaust gas carries heat through the front exhaust pipe; when the temperature of the first temperature sensor is lower than 350℃, the first throttle valve and the third throttle valve are closed, and the second throttle valve is opened, and the exhaust gas directly passes through the supercharger to the post-processor for exhaust treatment; when the third temperature sensor reaches above 180℃, the engine's electronic control unit ECU controls the fourth solenoid valve to open, and the ammonia in the ammonia tank passes through the gas pipe to the ammonia filter for filtration, and then passes through the gas pipe to the ammonia injection device for voltage stabilization and regulation. The ammonia injection device contains The pressure sensor, temperature sensor and pressure stabilizing chamber are used for precise metering and control of ammonia according to the engine operating conditions and injection quantity requirements. The metered ammonia reaches the nozzle through the gas pipe and is injected into the post-processor for catalytic reduction reaction. When the third temperature sensor is lower than 180℃, the fourth solenoid valve is closed and the delivery of ammonia for oxidation and reduction of NOx is stopped; when the temperature of the first temperature sensor reaches above 350℃, the first throttle valve and the third throttle valve are opened, the first throttle valve is closed, and the engine ECU controls the third solenoid valve to open. The filtered ammonia is sent to the ammonia cracker through the ammonia delivery pipe and the ammonia delivery joint for cracking ammonia. The exhaust gas discharged from the front exhaust pipe is discharged through the ammonia delivery pipe. The exhaust passage of the ammonia cracker is heated by the low-temperature and low-pressure catalyst in the ammonia cracker to produce a mixture of hydrogen and nitrogen. The mixture is transmitted to the gas pipeline through the mixture transmission joint. The mixture in the gas pipeline is separated by the hydrogen extraction device. The hydrogen metering pump is used to measure the hydrogen delivery amount according to the combustion needs of the engine. The hydrogen is delivered to the intake duct of the engine through the hydrogen pipe to mix with ammonia to improve the combustion efficiency. The linkage control of the hydrogen delivery amount with the hydrogen metering pump is achieved by controlling the different duty ratios of the fifth solenoid valve; the engine exhaust reaches the after-processor through the rear exhaust pipe. The unburned ammonia and hydrogen in the exhaust will be oxidized by the DOC module, and part of the NO will be oxidized to NO2. The second The temperature sensor is used to monitor the temperature in front of the DOC module. Particulate matter is collected by the DPF module. The ammonia injected through the nozzle is evenly mixed in the mixer. The carrier catalyst of the SCR carrier module catalyzes the reaction of ammonia and nitrogen oxides. The front NOx sensor and the rear NOx sensor are used to detect NOx changes. The third temperature sensor and the fourth temperature sensor work together to determine the reaction temperature of the SCR carrier module. The ammonia injection amount is closed-loop controlled through the engine operating condition MAP calibration and the readings of the front NOx sensor and the rear NOx sensor. In addition, a detachable flange or clamp structure is designed between the modules on the after-processor to facilitate after-market maintenance and replacement of parts.

[0014] The beneficial effects achieved by the present invention are: the post-processing system of the present invention can be applied to ammonia fuel engines, including but not limited to ammonia engines, ammonia diesel dual-fuel engines, ammonia hydrogen dual-fuel engines, dual-fuel or multi-fuel engines of ammonia and other fuels. By connecting the front exhaust pipe at the front end of the ammonia cracker to receive the exhaust gas delivered from the engine, and the rear end to the rear exhaust pipe to discharge the exhaust gas, the ammonia cracker contains an exhaust channel inside to provide the exhaust temperature required for ammonia cracking and hydrogen production, and also contains a catalyst layer filled with a low-temperature, low-pressure, and high-efficiency catalyst that reduces the exhaust temperature and pressure required for ammonia hydrogen production, which can reduce the required exhaust temperature to about 200°C. At the same time, the ammonia cracker is also provided with an inlet pipe and an outlet pipe to receive ammonia delivered from the ammonia tank for cracking and to deliver the cracked gas to the hydrogen extraction device. The ammonia cracker is provided with insulation material and a shell to reduce the loss of exhaust heat and better cracking and hydrogen production; the post-processor includes DOC, DPF , SCR carrier module, mixer, temperature sensor, front NOx sensor, rear NOx sensor, nozzle, DOC is used to oxidize incompletely burned ammonia and hydrogen and increase exhaust temperature, DPF is used to collect particulate matter produced by combustion, SCR is used to catalytically reduce nitrogen oxides, the front NOX sensor is located at the front end of the nozzle, and is used to measure the amount of NH3 discharged by the ammonia engine due to incomplete combustion, the NOx produced after oxidation by DOC, and the NOX produced by the combustion of ammonia, the nozzle in front of the SCR is connected to the ammonia transported from the ammonia tank through the injection pipe for the SCR catalytic reduction reaction, the mixer is located above the SCR, and is used to mix the ammonia sprayed from the nozzle to achieve uniformity requirements and improve the SCR conversion efficiency. The present invention improves ammonia combustion and effectively reduces the emission of engine exhaust pollutants. The present invention has the following advantages:

[0015] 1. Heat and crack ammonia through engine exhaust to produce hydrogen, improving engine combustion;

[0016] 2. The ammonia cracker and post-treatment system are integrated to fully utilize exhaust energy and tail gas purification. The overall system is efficient and compact, and the control method for the conversion efficiency of ammonia cracking and post-treatment catalyst is optimized according to the exhaust temperature. Under high-temperature and high-flow engine conditions, the bypass turbocharger fully utilizes the heat source for ammonia cracking, and at low temperatures, the ammonia cracker is bypassed to ensure the conversion efficiency of the post-treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a structural schematic diagram of the present invention;

[0018] Figure 2 This is a control principle diagram of the present invention;

[0019] In the figure: 1, engine; 2, front exhaust pipe; 3, ammonia cracker; 4, hydrogen extraction device; 5, rear exhaust pipe; 6, ammonia tank; 7, post-processor; 8, nozzle; 9, first bypass pipe; 10, supercharger; 11, second bypass pipe; ammonia pipe (12, 13, 14, 15, 27); 16, gas pipe; 17, hydrogen metering pump; 18, front NOx sensor; 19, rear NOx sensor; 21, first solenoid valve; 22, second solenoid valve; 23, third solenoid valve; 2 4. Fourth solenoid valve; 20. Fifth solenoid valve; 25. Ammonia injection device; 26. Ammonia filter; 28. Hydrogen pipe; 31. Outer shell; 32. Insulation material; 33. Inner shell; 34. Catalyst filling chamber; 35. Low-temperature, low-pressure catalyst; 36. Ammonia delivery connector; 37. Mixed gas delivery connector; 71. DOC module; 72. DPF module; 73. SCR carrier module; 74. Mixer; Module connecting flanges or clamps (75, 76, 77, 78);

[0020] T1, first temperature sensor; T2, second temperature sensor; T3, third temperature sensor; T4, fourth temperature sensor; P1, first throttle valve; P2, second throttle valve; P3, third throttle valve. DETAILED DESCRIPTION

[0021] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0022] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0023] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0024] like Figure 1-2 As shown, the present invention is an after-treatment system for an ammonia fuel engine, comprising an engine 1, an ammonia cracker 3, an ammonia tank 6 and an after-treatment device 7. The gas outlet of the engine 1 is divided into two paths, one path is connected to the front exhaust pipe 2 through the supercharger 10, and the other path is connected to the front exhaust pipe 2 through the first throttle valve P1 and the first bypass pipe 9; after passing through the front exhaust pipe 2, the gas is divided into two paths, one path is connected to the after-treatment device 7 through the second throttle valve P2, the second bypass pipe 11 and the rear exhaust pipe 5, and the other path is connected to the after-treatment device 7 through the third throttle valve P3, the ammonia cracker 3 and the rear exhaust pipe 5;

[0025] The ammonia tank 6 is divided into three paths after passing through the ammonia filter 26. One path is connected to the air intake of the engine 1 through the first solenoid valve 21; another path is connected to the air intake of the engine 1 after passing through the ammonia cracker 3, the hydrogen extraction device 4 and the hydrogen metering pump 17. A fifth solenoid valve 20 is provided between the ammonia cracker 3 and the hydrogen extraction device 4, and a third solenoid valve 23 is provided between the ammonia filter 26 and the ammonia cracker 3; the third path is connected to the post-processor 7 after passing through the ammonia injection device 25 and the nozzle 8, and a fourth solenoid valve 24 is provided between the ammonia filter 26 and the ammonia injection device 25; a second solenoid valve 22 is provided between the ammonia tank 6 and the ammonia filter 26.

[0026] In this embodiment, a first temperature sensor T1 is provided at the front end of the ammonia cracker 3 .

[0027] In this embodiment, a second temperature sensor T2 is provided at the front end of the post-processor 7 , a fourth temperature sensor T4 is provided at the rear end, and a third temperature sensor T3 is provided at the mixer section 74 of the post-processor 7 .

[0028] In this embodiment, the ammonia cracker 3 includes an outer shell 31, an insulating material 32, an inner shell 33, a catalyst filling cavity 34, a low-temperature and low-pressure catalyst 35, an ammonia delivery connector 36, and a mixed gas delivery connector 37. Insulating material 32 is provided between the outer shell 31 and the inner shell 33. The catalyst filling cavity 34 is provided in the inner shell 33. The low-temperature and low-pressure catalyst 35 is filled in the catalyst filling cavity 34. The ammonia cracker 3 is connected to the ammonia filter 26 through the ammonia delivery connector 36, and the ammonia cracker 3 is connected to the air intake of the engine 1 through the mixed gas delivery connector 37.

[0029] In this embodiment, the post-processor 7 includes a DOC module 71, a DPF module 72, an SCR carrier module 73 and a mixer 74 arranged in sequence. The DOC module 71, the DPF module 72, the SCR carrier module 73 and the mixer 74 are connected to each other by flanges or clamps (75, 76, 77, 78).

[0030] In this embodiment, a front NOx sensor 18 is provided at the mixer 74 section, and a rear NOx sensor 19 is provided at the rear end of the post-processor 7 .

[0031] A control method for an ammonia fuel engine after-treatment system of the present invention comprises the following steps:

[0032] When the engine 1 is ignited, the solenoid valves (the first solenoid valve 21 and the second solenoid valve 22) are opened, and the ammonia in the ammonia tank 6 is transported to the engine 1 through the ammonia pipe 12. The engine combustion produces exhaust gas, and the exhaust gas carries heat through the front exhaust pipe 2. When the temperature of the first temperature sensor T1 is lower than 350°C, the throttle valve (the first throttle valve P1 and the third throttle valve P3) is closed, and the second throttle valve P2 is opened. The exhaust gas passes through the supercharger 10 directly to the post-processing part for exhaust gas treatment. When the third temperature sensor T3 reaches above 180°C, the electronic control unit ECU of the engine 1 controls the first throttle valve P1 and the third throttle valve P3. When the fourth solenoid valve 24 is opened, the ammonia in the ammonia tank 6 reaches the ammonia filter 26 through the gas pipe 13 for filtration of impurities, moisture, etc., and then reaches the ammonia injection system 25 through the gas pipe 14 for pressure stabilization and regulation. The ammonia injection device 25 contains a pressure sensor, a temperature sensor and a pressure stabilizing chamber, which are used for precise metering and control of ammonia according to the engine operating conditions and injection volume requirements. The metered ammonia reaches the nozzle 8 through the gas pipe 15 and is injected into the post-processor 7 for catalytic reduction reaction. When the T3 temperature is lower than 180°C, the solenoid valve 24 is closed, and the supply of ammonia for NOx oxidation and reduction is stopped. When the temperature of the T1 exhaust temperature sensor 9 reaches above 350°C, the throttle valves P1 and P3 are opened, P2 is closed, and the engine ECU controls the solenoid valve 23 to open. The filtered ammonia passes through the ammonia delivery pipe 27 to the connector 36 of the cracker 3 for cracking the ammonia. The exhaust gas discharged from the front exhaust pipe 2 passes through the exhaust channel of the ammonia cracker 3 and is heated by the low-temperature and low-pressure catalyst 35 therein to produce a mixture of hydrogen and nitrogen. The mixture is transmitted to the gas delivery pipe 16 through the connector 37. The mixture in the gas pipe 16 passes through the hydrogen extraction device 4 to separate the hydrogen. The hydrogen metering pump 17 is used to measure the hydrogen delivery amount according to the engine combustion needs. The hydrogen is delivered to the intake duct of the engine 1 through the hydrogen pipe 28 to mix with the ammonia to improve combustion efficiency. The hydrogen delivery amount is linked to the hydrogen metering pump 17 by controlling the different duty cycles of the solenoid valve 20. The engine exhaust reaches the after-processor 7 through the rear exhaust pipe 5. The unburned NH3 and hydrogen in the exhaust will be oxidized by the DOC71, and part of the NO will be oxidized to NO2. The temperature sensor T2 is used to monitor the temperature before the DOC. The particulate matter is collected by the DPF72. The ammonia injected through the nozzle 8 is evenly mixed in the mixer 74. The carrier catalyst of the SCR73 catalyzes the reaction of ammonia and nitrogen oxides. The front NOx sensor 18 and the rear NOx sensor 19 are used to detect the change of NOx. The temperature sensor T3 and the temperature sensor T4 work together to determine the reaction temperature of the SCR73. The ammonia injection amount is closed-loop controlled by the engine operating condition MAP calibration and the readings of the nitrogen oxide sensors (18, 19). In addition, a detachable flange or clamp structure (75, 76, 77, 78) is designed between each module on the after-processor 7 to facilitate after-market maintenance and replacement of parts.

[0033] The above illustrates and describes the basic principles and main structural features of the present invention. The present invention is not limited to the above examples. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

[0034] It should be noted that the description of the above technical solutions is illustrative only. This specification may be embodied in various forms and should not be construed as limiting the technical solutions set forth herein. Rather, these descriptions are provided to ensure that the disclosure of the present invention is thorough and complete and to fully convey the scope of the disclosure to those skilled in the art. Furthermore, the technical solutions of the present invention are limited only by the scope of the claims.

[0035] Finally, it should be noted that the above embodiments are merely representative examples of the present invention. Obviously, the present invention is not limited to the above embodiments and is susceptible to numerous variations. Any simple modifications, equivalent variations, and modifications to the above embodiments based on the technical essence of the present invention shall be deemed to fall within the scope of protection of the present invention.

Claims

1. An aftertreatment system for an ammonia fuel engine, characterized in that: The invention comprises an engine (1), an ammonia cracker (3), an ammonia tank (6) and a post-processor (7); the gas outlet of the engine (1) is divided into two paths, one path is connected to the front exhaust pipe (2) through a supercharger (10), and the other path is connected to the front exhaust pipe (2) through a first throttle valve (P1) and a first bypass pipe (9); after passing through the front exhaust pipe (2), the gas outlet is divided into two paths, one path is connected to the post-processor (7) after passing through a second throttle valve (P2), a second bypass pipe (11) and a rear exhaust pipe (5), and the other path is connected to the post-processor (7) after passing through a third throttle valve (P3), the ammonia cracker (3) and the rear exhaust pipe (5); The ammonia tank (6) is divided into three paths after passing through the ammonia filter (26), one path being connected to the air inlet of the engine (1) through the first solenoid valve (21); the other path being connected to the air inlet of the engine (1) after passing through the ammonia cracker (3), the hydrogen extraction device (4) and the hydrogen metering pump (17); a fifth solenoid valve (20) is provided between the ammonia cracker (3) and the hydrogen extraction device (4); a third solenoid valve (23) is provided between the ammonia filter (26) and the ammonia cracker (3); the third path being connected to the post-processor (7) after passing through the ammonia injection device (25) and the nozzle (8); a fourth solenoid valve (24) is provided between the ammonia filter (26) and the ammonia injection device (25); and a second solenoid valve (22) is provided between the ammonia tank (6) and the ammonia filter (26); A first temperature sensor (T1) is provided at the front end of the ammonia cracker (3); When the temperature of the first temperature sensor (T1) is lower than the set temperature a, the first throttle valve (P1) and the third throttle valve (P3) are closed, the second throttle valve (P2) is opened, and the exhaust gas passes through the supercharger (10) and directly reaches the post-processor (7) for exhaust gas treatment; When the temperature of the first temperature sensor (T1) reaches above the set temperature a, the first throttle valve (P1) and the third throttle valve (P3) are opened, the second throttle valve (P2) is closed, and the third solenoid valve (23) is opened, and the filtered ammonia is sent to the ammonia cracker (3) through the ammonia delivery connector (36) for cracking the ammonia.

2. The after-treatment system for an ammonia fuel engine according to claim 1, characterized in that: The front end of the post-processor (7) is provided with a second temperature sensor (T2), the rear end is provided with a fourth temperature sensor (T4), and the mixer (74) section of the post-processor (7) is provided with a third temperature sensor (T3).

3. The after-treatment system for an ammonia fuel engine according to claim 1, characterized in that: The ammonia cracker (3) comprises an outer shell (31), a heat-insulating material (32), an inner shell (33), a catalyst filling cavity (34), a low-temperature and low-pressure catalyst (35), an ammonia delivery connector (36) and a mixed gas delivery connector (37); a heat-insulating material (32) is provided between the outer shell (31) and the inner shell (33); the catalyst filling cavity (34) is provided in the inner shell (33); the low-temperature and low-pressure catalyst (35) is filled in the catalyst filling cavity (34); the ammonia cracker (3) is communicated with an ammonia filter (26) via the ammonia delivery connector (36); and the ammonia cracker (3) is communicated with an air inlet of an engine (1) via the mixed gas delivery connector (37).

4. The after-treatment system for an ammonia fuel engine according to claim 1, characterized in that: The post-processor (7) comprises a DOC module (71), a DPF module (72), an SCR carrier module (73) and a mixer (74) which are arranged in sequence, and the DOC module (71), the DPF module (72), the SCR carrier module (73) and the mixer (74) are adjacently connected via flanges or clamps.

5. The after-treatment system for an ammonia fuel engine according to claim 4, characterized in that: The mixer (74) section is provided with a front NOx sensor (18), and the rear end of the post-processor (7) is provided with a rear NOx sensor (19).

6. A control method for an ammonia fuel engine aftertreatment system according to any one of claims 1 to 5, characterized in that: The following steps are involved: After the engine (1) is ignited, the first solenoid valve (21) and the second solenoid valve (22) are opened, and the ammonia in the ammonia tank (6) is transported to the engine (1) through the ammonia pipe (12). The engine burns to generate exhaust gas, and the exhaust gas carries heat through the front exhaust pipe (2); when the temperature of the first temperature sensor (T1) is lower than the set temperature a, the first throttle valve (P1) and the third throttle valve (P3) are closed, and the second throttle valve (P2) is opened, and the exhaust gas passes through the supercharger directly to the post-processor (7) for exhaust gas treatment; When the third temperature sensor (T3) reaches a set temperature b or above, the fourth solenoid valve (24) opens, and the ammonia in the ammonia tank (6) reaches the ammonia filter (26) through the gas pipeline for filtration, and reaches the ammonia injection device (25) for voltage stabilization and regulation. The metered ammonia reaches the nozzle (8) and is injected into the post-processor (7) for catalytic reduction reaction; When the third temperature sensor (T3) is lower than the set temperature b, the fourth solenoid valve (24) is closed, and the delivery of ammonia for oxidation-reduction is stopped; When the temperature of the first temperature sensor (T1) reaches above the set temperature a, the first throttle valve (P1) and the third throttle valve (P3) are opened, the second throttle valve (P2) is closed, and the third electromagnetic valve (23) is opened. The filtered ammonia is sent to the ammonia cracker (3) through the ammonia delivery connector (36) for cracking the ammonia. The exhaust gas discharged from the front exhaust pipe (2) passes through the exhaust channel of the ammonia cracker (3) and is heated by the low-temperature and low-pressure catalyst (35) in the ammonia cracker (3) to generate a hydrogen and nitrogen mixed gas. The mixed gas passes through the mixed gas delivery connector (37) and enters the hydrogen extraction device (4) for hydrogen separation. The hydrogen metering pump (17) meters the hydrogen delivery amount according to the combustion requirements of the engine. The separated hydrogen is delivered to the intake duct of the engine (1) to mix with the ammonia to improve the combustion efficiency. The fifth electromagnetic valve (20) is controlled at different duty ratios to achieve linkage control of the hydrogen delivery amount with the hydrogen metering pump (17). The exhaust gas of the engine (1) reaches the post-processor (7) through the rear exhaust pipe (5), the unburned ammonia and hydrogen in the exhaust gas are oxidized by the DOC module (71), and part of the NO is oxidized to NO2. The second temperature sensor (T2) is used to monitor the temperature before the DOC module (71), the particulate matter is collected by the DPF module (72), the ammonia injected through the nozzle (8) is uniformly mixed in the mixer (74), the carrier catalyst of the SCR carrier module (73) catalyzes the reaction of ammonia and nitrogen oxides, the front NOx sensor (18) and the rear NOx sensor (19) are used to detect the change of NOx, the third temperature sensor (T3) and the fourth temperature sensor (T4) cooperate to determine the reaction temperature of the SCR carrier module (73), and the ammonia injection amount is closed-loop controlled by the engine operating condition MAP calibration and the readings of the front NOx sensor (18) and the rear NOx sensor (19).

7. The control method for an ammonia fuel engine aftertreatment system according to claim 6, characterized in that: The ammonia injection device (25) contains a pressure sensor, a temperature sensor and a pressure stabilizing chamber, and is used for accurate metering control of ammonia according to the engine operating conditions and injection quantity requirements.

8. The control method for an ammonia fuel engine aftertreatment system according to claim 6, characterized in that: a is 350℃.

9. The control method for an ammonia fuel engine aftertreatment system according to claim 6, characterized in that: b is 180℃.

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