CN116608061B

CN116608061B - Aftertreatment system and control method for ammonia fuel engine

Info

Publication number: CN116608061B
Application number: CN202310521145.5A
Authority: CN
Inventors: 陈镇; 项旭昇; 李鹏远; 李智; 冯坦; 赵文冉; 刘寰; 董才月; 何胜勇
Original assignee: Dongfeng Trucks Co ltd
Current assignee: Dongfeng Trucks Co ltd
Priority date: 2023-05-10
Filing date: 2023-05-10
Publication date: 2025-04-29
Anticipated expiration: 2043-05-10
Also published as: CN116608061A

Abstract

The invention relates to a post-treatment system and a control method for an ammonia fuel engine, wherein the post-treatment system comprises an engine, an ammonia cracker, an ammonia tank and a post-processor, hydrogen is produced through the pyrolysis of the ammonia cracker, the combustion of the engine is improved through the pyrolysis of the ammonia cracker, the ammonia cracker and the post-treatment system are integrated, the exhaust energy and tail gas purification are fully utilized, the whole system is efficient and compact, the control method for optimizing the conversion efficiency of the ammonia cracker and the post-treatment catalyst according to the exhaust temperature is realized, the high-temperature high-flow working condition of the engine is realized, a bypass booster fully utilizes a heat source to carry out the ammonia cracker, and the ammonia cracker is bypassed at low temperature, so that the conversion efficiency of the post-treatment is ensured.

Description

Aftertreatment system for ammonia fuel engine and control method

Technical Field

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

Background

The ammonia fuel engine is an internal combustion engine which is combusted by mixing pure ammonia gas or ammonia gas with diesel oil, ammonia gas with hydrogen gas or ammonia gas with other fuels, and the combustion product is green and low-carbon because the ammonia gas is mainly used as fuel. Although hydrogen is the cleanest energy source in all energy sources, the energy density is high, the burnt product is water, no pollutant is generated, and the hydrogen is very friendly to the environment, but the hydrogen is very active, the problems of explosion and the like are easily generated, and the equipment investment cost in the hydrogen transportation link, the hydrogen adding station and other storage links is very high. Ammonia gas is used as gas which can be synthesized manually at low cost, has high energy density, is easy to liquefy, store and transport, is convenient to transport, does not generate carbon dioxide after combustion, can be used as an alternative fuel for engine combustion, can also be used as a raw material for decomposing hydrogen and gas for catalytic reduction of a post-treatment system, and can improve ammonia combustion, improve combustion heat efficiency, reduce emission of pollutants such as nitrogen oxides generated by ammonia combustion and the like, and simultaneously can be used as a post-treatment reducing agent for catalytic reduction of nitrogen oxides in exhaust gas by using hydrogen generated by ammonia pyrolysis.

The prior art describes a method for producing hydrogen by ammonia cracking, but the method is not integrated with an engine and a post-treatment system, and the heat generated by engine combustion exhaust is not fully utilized.

Disclosure of Invention

In order to solve the problems, the invention provides a post-treatment system and a control method for an ammonia fuel engine, which can improve combustion and reduce emission pollutants by generating hydrogen through pyrolysis.

The technical scheme adopted by the invention is that the after-treatment system for the ammonia fuel engine is characterized by comprising an engine, an ammonia cracker, an ammonia tank and a post-processor, wherein an air outlet of the engine is divided into two paths, one path is communicated with a front exhaust pipe through a supercharger, and the other path is communicated with the front exhaust pipe through a first throttle valve and a first bypass pipe;

The ammonia tank is divided into three paths after passing through an ammonia filter, one path is communicated with an engine air inlet through a first electromagnetic valve, the other path is communicated with the engine air inlet after passing through an ammonia cracker, a hydrogen extraction device and a hydrogen metering pump, a fifth electromagnetic valve is arranged between the ammonia cracker and the hydrogen extraction device, a third electromagnetic valve is arranged between the ammonia filter and the ammonia cracker, the third path is communicated with a postprocessor after passing through an ammonia injection device and a nozzle, a fourth electromagnetic valve is arranged between the ammonia filter and the ammonia injection device, and a second electromagnetic valve is arranged between the ammonia tank and the ammonia filter.

Preferably, a first temperature sensor is arranged at the front end of the ammonia cracker.

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

Preferably, the ammonia cracker comprises an outer shell, a heat insulation material, an inner shell, a catalyst filling cavity, a low-temperature low-pressure catalyst, an ammonia conveying connector and a mixed gas conveying connector, wherein the heat insulation material is arranged between the outer shell and the inner shell, the catalyst filling cavity is arranged in the inner shell, the low-temperature low-pressure catalyst is filled in the catalyst filling cavity, the ammonia cracker is communicated with the ammonia filter through the ammonia conveying connector, and the ammonia cracker is communicated with an engine air inlet through the mixed gas conveying connector.

Preferably, the aftertreatment device comprises a DOC module, a DPF module, an SCR carrier module and a mixer which are sequentially arranged, wherein the DOC module, the DPF module, the SCR carrier module and the mixer are adjacently connected through a flange or a clamp.

Preferably, the mixer segment is provided with a front NOx sensor, and the rear end of the post-processor is provided with a rear NOx sensor.

The control method for the ammonia fuel engine aftertreatment system is characterized by comprising the following steps:

After the engine starts to burn, the first electromagnetic valve and the second electromagnetic valve are opened, ammonia in the ammonia tank transmits ammonia fuel to the engine through an ammonia pipe, the engine burns to generate waste gas, and the waste gas carries heat to pass 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, the second throttle valve is opened, the waste gas directly reaches the post-processor through the booster to carry out tail gas treatment, when the temperature of the third temperature sensor reaches more than 180 ℃, the electronic control unit ECU of the engine controls the fourth electromagnetic valve to be opened, ammonia in the ammonia tank reaches the ammonia filter through the gas pipe to be filtered, and then reaches the ammonia injection device through the gas pipe to carry out pressure stabilizing and regulating, the ammonia injection device contains a pressure sensor, the temperature sensor and a pressure stabilizing cavity, the pressure stabilizing cavity is used for accurately metering the ammonia along with the operation condition and the injection quantity requirement of the engine, the metered ammonia reaches the nozzle through the gas pipe to be injected into the post-processor to carry out catalytic reduction reaction, when the temperature of the third temperature sensor is lower than 180 ℃, the fourth electromagnetic valve is closed to stop conveying the ammonia for oxidation reduction NOx, when the temperature of the first temperature sensor reaches more than 350 ℃, the first throttle valve and the third throttle valve are opened, the first electromagnetic valve is closed, the engine ECU controls the third electromagnetic valve to be opened, the ammonia after the filtration is conveyed through the gas pipe to the ammonia pipe to the pyrolysis device to be sent into the pyrolysis device through the gas pipe to the pyrolysis device, the hydrogen gas is discharged from the pyrolysis device to the gas pipe to the pyrolysis device through the low-pressure mixing pipe, the hydrogen gas is separated from the pyrolysis device through the pyrolysis device, the hydrogen gas is discharged from the pyrolysis device through the pyrolysis gas pipe to the pyrolysis gas, and the mixed gas is discharged into the pyrolysis gas, and the mixed gas is discharged from the pyrolysis gas through the pyrolysis device through the low-phase gas through the pyrolysis device, the hydrogen metering pump is used for metering the hydrogen delivery quantity according to the combustion requirement of the engine, the hydrogen delivery quantity is delivered into an air inlet channel of the engine through a hydrogen pipe and is mixed with ammonia gas, the combustion efficiency is improved, the linkage control of the hydrogen delivery quantity of the hydrogen metering pump is realized through controlling different duty ratios of a fifth electromagnetic valve, engine exhaust reaches a post-processor through a rear exhaust pipe, unburned ammonia gas and hydrogen gas in the exhaust can be oxidized by the DOC module, part of NO can be oxidized into NO2, the second temperature sensor is used for monitoring the temperature in front of the DOC module, particulate matters are collected by the DPF module, ammonia gas sprayed by a nozzle is uniformly mixed in a mixer, a carrier catalyst of the SCR carrier module catalyzes the ammonia gas to react with nitrogen oxides, the front NOx sensor and the rear NOx sensor are used for detecting the condition of the change of NOx, the reaction temperature of the SCR carrier module is cooperatively judged by the third temperature sensor and the fourth temperature sensor, the ammonia gas injection quantity is closed-loop controlled through the MAP calibration of the engine working condition and the reading value of the front NOx sensor and the rear NOx sensor, and a detachable flange or clamp structure is designed between the modules on the post-processor, and the post-processor is convenient for post-market maintenance and replacement.

The aftertreatment system of the 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. The front end of the ammonia cracker is connected with a front exhaust pipe for receiving exhaust gas conveyed from an engine, the rear end of the ammonia cracker is connected with a rear exhaust pipe for exhausting the exhaust gas, an exhaust channel is arranged in the ammonia cracker and used for providing exhaust gas temperature required by ammonia cracking hydrogen production, a catalyst layer is also included, a low-temperature low-pressure high-efficiency catalyst for reducing the exhaust temperature and the pressure required by ammonia hydrogen production is filled, the required exhaust temperature can be reduced to about 200 ℃, meanwhile, the ammonia cracker is also provided with an air inlet pipe and an air outlet pipe and is used for receiving ammonia conveyed from an ammonia tank and conveying the cracked gas into a hydrogen extraction device, and a heat insulation material and a shell are arranged outside the ammonia cracker so as to reduce the loss of exhaust gas heat and realize better hydrogen production by cracking; the aftertreatment device comprises DOC, DPF, SCR carrier modules, a mixer, a temperature sensor, a front NOx sensor, a rear NOx sensor and a nozzle, wherein the DOC is used for oxidizing unburnt ammonia and hydrogen and improving the exhaust temperature, the DPF is used for collecting particulate matters generated by combustion, the SCR is used for catalyzing and reducing nitrogen oxides, the front NOx sensor is positioned at the front end of the nozzle and is used for measuring NOx generated by the oxidation of the NOx and ammonia generated by the NH3 quantity discharged by the undercombustion of the ammonia engine after the DOC is oxidized, the nozzle before the SCR is connected with ammonia conveyed from an ammonia tank through a jet pipe and is used for SCR catalytic reduction reaction, the mixer is positioned above the SCR and is used for mixing ammonia sprayed out of the nozzle, the uniformity requirement is achieved, and the SCR conversion efficiency is improved. The invention improves ammonia combustion and effectively reduces the exhaust pollutant emission of the engine. The invention has the following advantages:

1. the engine exhaust is used for heating and cracking ammonia gas to generate hydrogen, so that the combustion of the engine is improved;

2. The ammonia cracker is integrated with the post-treatment system, fully utilizes the exhaust energy and the tail gas purification, has high efficiency and compactness, optimizes the conversion efficiency of the ammonia cracker according to the exhaust temperature, and ensures the conversion efficiency of the post-treatment by the bypass booster under the working condition of high temperature and high flow of the engine.

Drawings

FIG. 1 is a schematic diagram of the structure of the present invention;

FIG. 2 is a control schematic diagram of the present invention;

In the figure, 1, an engine, 2, a front exhaust pipe, 3, an ammonia cracker, 4, a hydrogen extraction device, 5, a rear exhaust pipe, 6, an ammonia tank, 7, a post processor, 8, a nozzle, 9, a first bypass pipe, 10, a supercharger, 11, a second bypass pipe, an ammonia pipe (12, 13, 14, 15, 27), 16, a gas pipe, 17, a hydrogen metering pump, 18, a front NOx sensor, 19, a rear NOx sensor, 21, a first electromagnetic valve, 22, a second electromagnetic valve, 23, a third electromagnetic valve, 24, a fourth electromagnetic valve, 20, a fifth electromagnetic valve, 25, an ammonia injection device, 26, an ammonia filter, 28, a hydrogen pipe, 31, an outer shell, 32, a thermal insulation material, 33, an inner shell, 34, a catalyst filling cavity, 35, a low temperature low pressure catalyst, 36, an ammonia delivery joint, 37, a mixture gas delivery joint, 71, a DOC module, 72, a DPF module, 73, an SCR carrier module, 74, a mixer, a module connecting flange or a clip (75, 76, 77, 78);

T1, a first temperature sensor, T2, a second temperature sensor, T3, a third temperature sensor, T4, a fourth temperature sensor, P1, a first throttle valve, P2, a second throttle valve, P3 and a third throttle valve.

Detailed Description

The following description of the embodiments of the present invention will be made apparent and fully in view of the accompanying drawings, in which some, but not all embodiments of the invention are shown. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

In the description of the present invention, it should be noted that the directions or positional relationships indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. are based on the directions or positional relationships shown in the drawings, are merely for convenience of describing the present invention and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

In the description of the present invention, unless explicitly stated or limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected, mechanically connected, electrically connected, directly connected, indirectly connected via an intervening medium, or in communication between two elements. The specific meaning of the above terms in the present invention will be understood in specific cases by those of ordinary skill in the art.

As shown in fig. 1-2, the invention relates to an ammonia fuel engine aftertreatment system, which comprises an engine 1, an ammonia cracker 3, an ammonia tank 6 and a aftertreatment device 7, wherein an air outlet of the engine 1 is divided into two paths, one path is communicated with a front exhaust pipe 2 through a booster 10, the other path is communicated with the front exhaust pipe 2 through a first throttle valve P1 and a first bypass pipe 9, the other path is divided into two paths through the front exhaust pipe 2, one path is communicated with the aftertreatment device 7 through a second throttle valve P2, a second bypass pipe 11 and a rear exhaust pipe 5, and the other path is communicated with the aftertreatment device 7 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 an ammonia filter 26, one path is communicated with an air inlet of the engine 1 through a first electromagnetic valve 21, the other path is communicated with the air inlet of the engine 1 after passing through an ammonia cracker 3, a hydrogen extraction device 4 and a hydrogen metering pump 17, a fifth electromagnetic valve 20 is arranged between the ammonia cracker 3 and the hydrogen extraction device 4, a third electromagnetic valve 23 is arranged between the ammonia filter 26 and the ammonia cracker 3, the third path is communicated with the postprocessor 7 after passing through an ammonia injection device 25 and a nozzle 8, a fourth electromagnetic valve 24 is arranged between the ammonia filter 26 and the ammonia injection device 25, and a second electromagnetic valve 22 is arranged between the ammonia tank 6 and the ammonia filter 26.

In this embodiment, the front end of the ammonia cracker 3 is provided with a first temperature sensor T1.

In this embodiment, 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 section 74 of the post-processor 7 is provided with a third temperature sensor T3.

In this embodiment, the ammonia cracker 3 includes an outer shell 31, a heat insulating material 32, an inner shell 33, a catalyst filling cavity 34, a low temperature low pressure catalyst 35, an ammonia gas delivery connector 36 and a mixed gas delivery connector 37, the heat insulating material 32 is disposed between the outer shell 31 and the inner shell 33, the catalyst filling cavity 34 is disposed in the inner shell 33, the low temperature low pressure catalyst 35 is filled in the catalyst filling cavity 34, the ammonia cracker 3 is communicated with the ammonia gas filter 26 through the ammonia gas delivery connector 36, and the ammonia cracker 3 is communicated with the air inlet of the engine 1 through the mixed gas delivery connector 37.

In this embodiment, the post-processor 7 includes a DOC module 71, a DPF module 72, an SCR carrier module 73 and a mixer 73, which are sequentially arranged, and the DOC module 71, the DPF module 72, the SCR carrier module 73 and the mixer 74 are adjacently connected by flanges or clips (75, 76, 77, 78).

In this embodiment, the mixer 74 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.

The invention discloses a control method for an ammonia fuel engine aftertreatment system, which comprises the following steps:

When the engine 1 is started, the electromagnetic valve (the first electromagnetic valve 21 and the second electromagnetic valve 22) is opened, ammonia in the ammonia tank 6 is conveyed to the engine 1 through the ammonia pipe 12, waste gas is generated by engine combustion, heat carried by the waste gas passes through the front exhaust pipe 2, when the temperature of the first temperature sensor T1 is lower than 350 ℃, the throttle valve (the first throttle valve P1 and the third throttle valve P3) is closed, the second throttle valve P2 is opened, the exhaust gas directly reaches the post-treatment part through the supercharger 10 to carry out tail gas treatment, when the temperature of the third temperature sensor T3 reaches more than 180 ℃, the electronic control unit ECU of the engine 1 controls the fourth electromagnetic valve 24 to be opened, ammonia in the ammonia tank 6 reaches the ammonia filter 26 through the air pipe 13 to carry out filtration of impurity moisture and the like, then reaches the ammonia injection system 25 through the air pipe 14 to carry out pressure stabilizing and regulating, the ammonia injection device 25 contains a pressure sensor, a temperature sensor and a pressure stabilizing cavity, the ammonia is used for accurately metering control along with the running working condition and injection quantity requirement of the engine, the ammonia is injected into the post-treatment device 7 through the air pipe 15 to reach the position of the nozzle 8 to carry out catalytic reduction reaction, when the temperature of the ammonia reaches 180 ℃ is lower than 180 ℃, and the air delivery valve is closed for reducing NOx reduction when the ammonia is stopped, and the air delivery is stopped at the temperature of the air is lower than 180 ℃ than 24. When the temperature of the T1 exhaust temperature sensor 9 reaches above 350 ℃, the throttle valves P1 and P3 are opened, the P2 is closed, the engine ECU controls the electromagnetic valve 23 to be opened, filtered ammonia gas reaches the joint 36 of the cracker 3 through the ammonia gas conveying pipe 27 for cracking the ammonia gas, exhaust gas discharged from the front exhaust pipe 2 is heated through the low-temperature low-pressure catalyst 35 in the exhaust passage of the ammonia cracker 3 to generate hydrogen gas and nitrogen gas mixture, the mixture is conveyed to the gas conveying pipe 16 through the joint 37, the mixture in the gas pipe 16 is separated by the hydrogen gas extracting device 4, the hydrogen metering pump 17 is used for metering the hydrogen conveying amount according to the combustion requirement of the engine, the hydrogen is conveyed into the air inlet of the engine 1 through the hydrogen pipe 28 and mixed with the ammonia gas, the combustion efficiency is improved, and the linkage control of the hydrogen conveying amount with the hydrogen metering pump 17 is realized through controlling different duty ratios of the electromagnetic valve 20. The engine exhaust gas passes through the rear exhaust pipe 5 to reach the post-processor 7, unburned NH3, hydrogen and the like in the exhaust gas can be oxidized by the DOC71, part of NO can be oxidized into NO2, the temperature sensor T2 is used for monitoring the temperature before the DOC, the particulate matters are collected by the DPF72, ammonia gas sprayed by the nozzle 8 is uniformly mixed in the mixer 74, the carrier catalyst of the SCR73 catalyzes the reaction of the ammonia gas and nitrogen oxides, the front NOx sensor 18 and the rear NOx sensor 19 are used for detecting the change condition of the NOx, the temperature sensor T3 and the temperature sensor T4 cooperatively judge the reaction temperature condition of the SCR73, the ammonia gas spraying amount is calibrated through the engine working condition MAP and the reading values of the nitrogen-oxygen sensors (18 and 19) to realize closed loop control, and in addition, detachable flanges or clamp structures (75, 76, 77 and 78) are designed among all modules on the post-processor 7, so that the post-market maintenance and replacement are facilitated.

The foregoing has shown and described the basic principles and main structural features of the present invention. The present invention is not limited to the above examples, and various changes and modifications may be made therein without departing from the spirit and scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.

Here, it should be noted that the description of the above technical solution is exemplary, and the present specification may be embodied in different forms and should not be construed as being limited to the technical solution set forth herein. Rather, these descriptions will be provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. Furthermore, the technical solution of the invention is limited only by the scope of the claims.

Finally, it should be noted that the above embodiments are merely representative examples of the present invention. Obviously, the invention is not limited to the above-described embodiments, but many variations are possible. Any simple modification, equivalent variation and modification of the above embodiments according to the technical substance of the present invention should be considered to be within the scope of the present invention.

Claims

1. A post-treatment system for an ammonia fuel engine, characterized in that it comprises an engine (1), an ammonia cracker (3), an ammonia tank (6) and a post-treatment device (7), wherein 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-treatment device (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-treatment device (7) after passing through a third throttle valve (P3), an ammonia cracker (3) and a 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 is characterized in that a second temperature sensor (T2) is provided at the front end of the after-processor (7), a fourth temperature sensor (T4) is provided at the rear end, and a third temperature sensor (T3) is provided at the mixer (74) section of the after-processor (7).

3. The aftertreatment 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 arranged 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) through the ammonia delivery connector (36); and the ammonia cracker (3) is communicated with an air intake of the engine (1) through the mixed gas delivery connector (37).

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

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

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 is characterized in that: the ammonia injection device (25) contains a pressure sensor, a temperature sensor and a pressure stabilizing chamber for precise 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°C.

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