Marine SCR (Selective Catalytic Reduction) system

Abstract

The invention discloses a marine SCR (Selective Catalytic Reduction) system which comprises a reaction system used for reacting urea with waste gas exhausted by an engine and comprising a main pipeline and a bypass pipeline, one end of the main pipeline is connected with the exhaust end of the engine, and a front butterfly valve, a spray gun, a mixer, a reactor and a rear butterfly valve are sequentially arranged on the main pipeline; waste gas exhausted by the engine and urea sprayed by the spray gun enter the mixer together to be fully mixed, then the mixture enters the reactor to be subjected to a catalytic reduction reaction, and finally the reduced waste gas is exhausted, one end of the bypass pipeline is connected to the front end of the front butterfly valve on the main pipeline, and the other end of the bypass pipeline is connected to the tail end of the rear butterfly valve. According to the marine SCR system, the mixing efficiency of a urea solution and waste gas can be effectively improved, the reaction is accelerated, meanwhile, accumulation of urea crystals in the pipelines is prevented after the reaction is finished, carbon deposition and dust accumulation in a reactor are avoided, and the working performance of the SCR system is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of diesel engine exhaust after-treatment, and particularly to a marine SCR system. Background Technique

[0002] With the gradual implementation of emission regulations such as IMO TierIII, national standard II for marine engines, and national standard IV for non-road applications, the control of emission requirements for engines used in inland waterways, coastal and ocean-going marine engine fields, and non-road application fields is becoming increasingly strict. Currently, the emission index of engine NOx can no longer meet the requirements of current regulations. And it is very difficult for the engine to meet the standard requirements by using the in-cylinder purification technology route of self-matching and optimization of the engine itself, and it is necessary to adopt the post-treatment SCR technology to achieve it.

[0003] Due to the increasingly strict requirements for engine emission limits and the increasing size of emission control areas, SCR, as a technical route for reducing NOx, has become an effective way to solve NOx emissions. However, the conventional SCR system only mixes the urea solution with the exhausted gas, and there are the following problems: (1) The mixing rate of the urea solution and the exhaust gas is slow; (2) After the reaction ends, there is still urea solution remaining in the pipeline. If the urea solution is not cleaned for a long time, it will crystallize in the pipeline, thus affecting the supply of urea; (3) After a long-term catalytic reduction reaction, there will be impurities such as carbon deposition and dust in the reactor. If not cleaned, it will affect the progress of the catalytic reduction reaction in the reactor. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the existing defects and provide a marine SCR system, which can effectively improve the mixing efficiency of the urea solution and the exhaust gas, accelerate the progress of the reaction, and at the same time prevent the accumulation of urea crystallization in the pipeline after the reaction ends, and avoid the accumulation of carbon deposition and dust in the reactor, and can effectively solve the problems in the background technique.

[0005] To achieve the above object, the present invention provides the following technical solution: A marine SCR system, comprising:

[0006] A reaction system for the reaction of urea with the exhaust gas discharged from the engine, including a main pipeline and a bypass pipeline. One end of the main pipeline is connected to the exhaust end of the engine. A front butterfly valve, a spray gun, a mixer, a reactor, and a rear butterfly valve are sequentially arranged on the main pipeline. The exhaust gas discharged from the engine and the urea sprayed by the spray gun enter the mixer together for full mixing, and then enter the reactor for catalytic reduction reaction, and finally the reduced exhaust gas is discharged. One end of the bypass pipeline is connected to the front end of the front butterfly valve on the main pipeline, and the other end of the bypass pipeline is connected to the rear end of the rear butterfly valve on the main pipeline. A bypass butterfly valve is arranged on the bypass pipeline;

[0007] The urea injection system is used to transport urea solution into the spray gun, and includes a urea tank, a urea pipeline, a cleaning pipeline, and a compressed air pipeline. One end of the urea pipeline is connected to the urea tank, and the other end of the urea pipeline is connected to the spray gun for transporting urea solution to the spray gun. The cleaning pipeline is arranged on the urea pipeline and is used to clean the residual urea in the urea pipeline after the reaction is completed. One end of the compressed pipeline is connected to an air compressor, and the other end of the compressed pipeline is connected to the spray gun for atomizing the urea entering the spray gun so that the atomized urea is fully mixed with the exhaust gas;

[0008] The soot blowing system has one end connected to an air compressor and the other end connected to the reactor, and is used to blow away the impurities accumulated in the reactor to ensure the full progress of the catalytic reduction reaction.

[0009] As a preferred technical solution of the present invention, an orifice flow meter and a front nitrogen oxide sensor are sequentially arranged on the main pipeline near the engine position, a rear nitrogen oxide sensor is arranged at the exhaust end of the reactor on the main pipeline, a temperature sensor is arranged on the main pipeline between the mixer and the reactor, and differential pressure sensors are connected to both ends of the reactor.

[0010] As a preferred technical solution of the present invention, a supply solenoid valve, a urea pump, a flow meter, a reducing agent solenoid valve, and a proportional solenoid valve are sequentially arranged on the urea pipeline starting from the urea tank end. After the supply solenoid valve is opened, the urea pump pumps out the urea in the urea tank, the flow of urea is detected by the flow meter, after entering the reducing agent solenoid valve, the opening or closing of the urea is controlled by the reducing agent solenoid valve, and then it enters the proportional solenoid valve, and the urea flow is controlled by the proportional solenoid valve, so as to enter the spray gun.

[0011] As a preferred technical solution of the present invention, a urea return line and a back pressure valve are arranged on the urea pipeline between the flow meter and the reducing agent solenoid valve. The other end of the urea return line is connected to the urea tank, a return valve is arranged on the urea return line, and the back pressure valve is used to control the urea return flow, thereby controlling the urea pressure to ensure the stability of the urea pressure.

[0012] As a preferred technical solution of the present invention, a first one-way valve is arranged on the urea pipeline between the supply solenoid valve and the urea tank, a first filter, a first pressure sensor, and a first leakage valve are sequentially arranged on the urea pipeline between the urea pump and the flow meter, and a second leakage valve and a first check valve are sequentially arranged on the urea pipeline between the proportional solenoid valve and the spray gun.

[0013] As a preferred technical solution of the present invention, the cleaning pipeline is connected to the urea pipeline between the supply solenoid valve and the urea pump. An electric three-way valve, a cleaning solenoid valve, a second one-way valve and a water tank are sequentially arranged on the cleaning pipeline. Two ends of the electric three-way valve are respectively connected to the supply solenoid valve and the urea pump, and a third end of the electric three-way valve is connected to the cleaning solenoid valve. Water in the water tank enters the urea pipeline through the second one-way valve, the cleaning solenoid valve and the electric three-way valve to clean the residual urea in the urea pipeline.

[0014] As a preferred technical solution of the present invention, on the compressed air pipeline, a supply air solenoid valve, a second filter, a voltage stabilizer, a second pressure sensor, a first safety valve, a third leakage valve and a second check valve are sequentially arranged starting from the air compressor end. The air compressed by the air compressor enters the spray gun through the supply air solenoid valve, the second filter, the voltage stabilizer, the second pressure sensor, the first safety valve, the third leakage valve and the second check valve to atomize the urea solution entering the spray gun, and the atomized urea is fully mixed with the waste gas.

[0015] As a preferred technical solution of the present invention, the soot blowing system includes a main soot blowing pipeline and two soot blowing branch pipelines connected in parallel with the main soot blowing pipeline. One end of the main soot blowing pipeline is connected to the air compressor, and the soot blowing branch pipeline is connected to the reactor.

[0016] As a preferred technical solution of the present invention, on the main soot blowing pipeline, a soot blowing solenoid valve, a fourth leakage valve, a third filter, a third pressure sensor and a second safety valve are sequentially arranged starting from the air compressor end. On the soot blowing branch pipeline, a branch soot blowing solenoid valve, a fourth pressure sensor and a diverter are sequentially arranged. A plurality of bellows are arranged between the diverter and the reactor, and a third check valve is arranged on the bellows.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) By arranging a cleaning pipeline in the urea injection system of the present marine SCR system, the residual urea in the urea pipeline can be flushed out by flushing water into the urea pipeline after the reaction is completed, avoiding urea crystallization; (2) By arranging a compressed air pipeline in the urea injection system, the compressed air can be injected into the spray gun to atomize the urea solution, improving the mixing efficiency with the waste gas; (3) By arranging a soot blowing system, air can be blown into the reactor to blow away the impurities in the reactor, ensuring the smooth progress of the catalytic reduction reaction. Brief Description of the Drawings

[0018] Figure 1 It is a schematic diagram of the system of the present invention.

[0019] In the figure: 1 engine, 2 orifice flowmeter, 3 front nitrogen oxide sensor, 4 bypass butterfly valve, 5 reactor, 6 differential pressure sensor, 7 rear butterfly valve, 8 front butterfly valve, 9 spray gun, 10 mixer, 11 temperature sensor, 12 rear nitrogen oxide sensor, 13 urea tank, 14 urea circuit, 15 first check valve, 16 supply solenoid valve, 17 electric three-way valve, 18 water tank, 19 second check valve, 20 cleaning solenoid valve, 21 urea pump, 22 first filter, 23 first pressure sensor, 24 first leakage valve, 25 flowmeter, 26 return valve, 27 back pressure valve, 28 reductant solenoid valve, 29 proportional solenoid valve, 30 second leakage valve, 31 first non-return valve, 32 air supply solenoid valve, 33 second filter, 34 voltage stabilizer, 35 second pressure sensor, 36 first safety valve, 37 third leakage valve, 38 second non-return valve, 39 soot blowing solenoid valve, 40 fourth leakage valve, 41 third filter, 42 third pressure sensor, 43 second safety valve, 44 branch soot blowing solenoid valve, 45 fourth pressure sensor, 46 diverter, 47 bellows, 48 third non-return valve. Detailed implementation

[0020] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the protection scope of the present invention.

[0021] Please refer to Figure 1 , the present invention provides a technical solution: a marine SCR system, including a reaction system, a urea injection system and a soot blowing system;

[0022] The reaction system includes a main pipeline and a bypass pipeline. One end of the main pipeline is connected to the exhaust end of the engine 1. A front butterfly valve 8, a spray gun 9, a mixer 10, a reactor 5 and a rear butterfly valve 7 are sequentially arranged on the main pipeline. An orifice flowmeter 2 and a front nitrogen oxide sensor 3 are sequentially arranged on the main pipeline near the engine 1. A rear nitrogen oxide sensor 12 is arranged at the exhaust end of the reactor 5 on the main pipeline. A temperature sensor 11 is arranged on the main pipeline between the mixer 10 and the reactor 5. A differential pressure sensor 6 is connected to both ends of the reactor 5;

[0023] The exhaust gas generated by the engine 1 passes through the orifice flowmeter 2. The orifice flowmeter 2 is used to measure the exhaust gas volume of the engine 1, and controls the urea pump 21 to spray an appropriate amount of urea according to the exhaust gas volume;

[0024] In order to verify the nitrogen oxide conversion efficiency of the SCR system, a front nitrogen oxide sensor 3 and a rear nitrogen oxide sensor 12 are installed in front of and behind the reactor 5 respectively, for detecting the nitrogen oxide values of the exhaust gas before and after the reactor 5;

[0025] Since it is necessary to detect the original exhaust of the engine 1, one end of the bypass pipeline is connected to the front end of the front butterfly valve 8 on the main pipeline, and the other end of the bypass pipeline is connected to the rear end of the rear butterfly valve 7 on the main pipeline. A bypass butterfly valve 4 is arranged on the bypass pipeline. When the front butterfly valve 8 and the rear butterfly valve 7 are opened and the bypass butterfly valve 4 is closed, the main pipeline is unobstructed and the bypass pipeline is closed; when the front butterfly valve 8 and the rear butterfly valve 7 are closed and the bypass butterfly valve 4 is opened, the main pipeline is closed and the bypass pipeline is opened;

[0026] The spray gun 9 is used to spray high-pressure atomized urea. The mixer 10 fully mixes the urea and enters the reactor 5 for catalytic reduction reaction. The temperature sensor 11 is used to detect the temperature before the reactor 5 to ensure that the reaction temperature in the reactor 5 is within the optimal temperature range of the catalytic reduction reaction. The differential pressure sensor 6 is used to measure the differential pressure before and after the reactor 5 to ensure that the pressure drop of the reactor 5 is within the technical requirements. After the catalytic reduction reaction, the nitrogen oxides in the exhaust gas are greatly reduced and then discharged into the atmosphere through the exhaust pipe.

[0027] The urea injection system is the key of the SCR system and is used to transport the urea solution into the spray gun 9. It includes a urea tank 13, a urea pipeline, a cleaning pipeline and a compressed air pipeline. One end of the urea pipeline is connected to the urea tank 13, and the other end of the urea pipeline is connected to the spray gun 9 to transport the urea solution to the spray gun 9. A liquid level sensor, a temperature sensor, a heater, etc. are installed in the urea tank 13 to facilitate the heating of urea and parameter monitoring. On the urea pipeline, a supply solenoid valve 16, a urea pump 21, a flow meter 25, a reductant solenoid valve 28 and a proportional solenoid valve 29 are arranged in sequence starting from the urea tank 13 end. A urea return circuit 14 and a back pressure valve 27 are arranged on the urea pipeline between the flow meter 25 and the reductant solenoid valve 28. The other end of the urea return circuit 14 is connected to the urea tank 13, and a return valve 26 is arranged on the urea return circuit 14. A first one-way valve 15 is arranged on the urea pipeline between the supply solenoid valve 16 and the urea tank 13. A first filter 22, a first pressure sensor 23 and a first leakage valve 24 are arranged in sequence on the urea pipeline between the urea pump 21 and the flow meter 25. A second leakage valve 30 and a first check valve 31 are arranged in sequence on the urea pipeline between the proportional solenoid valve 29 and the spray gun 9;

[0028] The urea pumped out by the urea pump 21 passes through the first one-way valve 15, the supply solenoid valve 16, the urea pump 21, the first filter 22, the first pressure sensor 23, the first leakage valve 24, the flow meter 25, the return valve 26, the back pressure valve 27 and the reductant solenoid valve 28 and enters the proportional solenoid valve 29;

[0029] The first one-way valve 15 prevents the urea from flowing back;

[0030] The supply solenoid valve 16 controls the supply and closing of the urea;

[0031] The function of the first filter 22 is to filter impurities in the urea;

[0032] The first pressure sensor 23 is used to detect the urea supply pressure;

[0033] The first leakage valve 24 is a manual ball valve, which is convenient for troubleshooting when a fault occurs in the pipeline;

[0034] The flowmeter 25 is used to detect the urea flow rate;

[0035] The reflux valve 26 is a three-way valve, which returns the excess urea to the urea tank 13 through the urea circuit 14. The urea return flow is controlled by the opening of the back pressure valve 27, so as to control the urea pressure and ensure the stability of the urea pressure;

[0036] The reducing agent solenoid valve 28 controls the opening and closing of the urea. The proportional solenoid valve 29 is a key component for controlling the urea flow rate. An appropriate amount of urea is output into the spray gun 9 by controlling the opening angle of the proportional solenoid valve 29;

[0037] The urea enters the spray gun 9 through the second leakage valve 30 and the first check valve 31. The second leakage valve 30 is a manual ball valve, which is convenient for troubleshooting when a fault occurs in the pipeline; the function of the first check valve 31 is to prevent the urea from flowing back.

[0038] The cleaning pipeline is connected to the urea pipeline between the supply solenoid valve 16 and the urea pump 21. An electric three-way valve 17, a cleaning solenoid valve 20, a second one-way valve 19 and a water tank 18 are sequentially arranged on the cleaning pipeline. The two ends of the electric three-way valve 17 are respectively connected to the supply solenoid valve 16 and the urea pump 21. The third end of the electric three-way valve 17 is connected to the cleaning solenoid valve 20. The water in the water tank 29 enters the urea pipeline through the second one-way valve 19, the cleaning solenoid valve 20 and the electric three-way valve 17 to clean the residual urea in the urea pipeline and prevent the urea from crystallizing and blocking the pipeline.

[0039] In order to facilitate the atomization of the urea sprayed from the spray gun 9, one end of the compressed air pipeline is connected to the air compressor, and the other end is connected to the spray gun 9. An air supply solenoid valve 32, a second filter 33, a voltage stabilizer 34, a second pressure sensor 35, a first safety valve 36, a third leakage valve 37 and a second check valve 38 are sequentially arranged on the compressed air pipeline starting from the air compressor end. The air compressed by the air compressor enters the spray gun 9 through the air supply solenoid valve 32, the second filter 33, the voltage stabilizer 34, the second pressure sensor 35, the first safety valve 36, the third leakage valve 37 and the second check valve 38;

[0040] The air supply solenoid valve 32 controls the opening and closing of the compressed air;

[0041] The function of the second filter 33 is to filter impurities in the compressed air;

[0042] The function of the voltage stabilizer 34 is to ensure the stable pressure of the compressed air;

[0043] The second pressure sensor 35 is used to detect the supply pressure of the compressed air;

[0044] The first safety valve 36 provides pressure safety protection;

[0045] The third leakage valve 37 is a manual ball valve, which is convenient for troubleshooting when a fault occurs in the pipeline;

[0046] The function of the second check valve 38 is to prevent the compressed air from flowing back. In this way, the urea after filtration and stabilization is atomized with the assistance of the compressed air, and the atomized urea is more likely to be fully mixed with the exhaust gas.

[0047] The exhaust gas undergoes a catalytic reduction reaction with urea in the reactor 5. During long-term operation, impurities such as carbon deposits and dust are likely to accumulate in the reactor 5. Therefore, a soot blowing system needs to be connected to the reactor 5 for soot blowing;

[0048] The soot blowing system includes a main soot blowing pipeline and two parallel soot blowing branch pipelines connected to the main soot blowing pipeline. One end of the main soot blowing pipeline is connected to the air compressor. The soot blowing branch pipeline is connected to the reactor 5. A soot blowing solenoid valve 39, a fourth leakage valve 40, a third filter 41, a third pressure sensor 42, and a second safety valve 43 are sequentially arranged on the main soot blowing pipeline starting from the air compressor end. A branch soot blowing solenoid valve 44, a fourth pressure sensor 45, and a diverter 46 are sequentially arranged on the soot blowing branch pipeline. A plurality of bellows 47 are arranged between the diverter 46 and the reactor 5, and a third check valve 48 is arranged on the bellows 47;

[0049] Among them, the soot blowing solenoid valve 39 controls the opening and closing of the compressed air;

[0050] The fourth leakage valve 40 is a manual ball valve, which is convenient for troubleshooting when a fault occurs in the pipeline;

[0051] The function of the third filter 41 is to filter impurities in the compressed air;

[0052] The third pressure sensor 42 is used to detect the soot blowing pressure of the compressed air;

[0053] The function of the bellows 47 is pressure deformation compensation;

[0054] The third check valve 48 prevents the compressed air from flowing back;

[0055] When the impurities in the reactor 5 accumulate to a certain extent, the soot blowing system is started. Air enters into two soot blowing branches through the soot blowing solenoid valve 39, the fourth leakage valve 40, the third filter 41, the third pressure sensor 42 and the second safety valve 43. The air in each soot blowing branch enters into multiple bellows 47 through the branch soot blowing solenoid valve 44 and the diverter 46, and then enters into the reactor 5 through the bellows 47 to blow away the impurities, ensuring the full progress of the catalytic reduction reaction.

[0056] The parts not detailed in the invention are the prior art. Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A marine SCR system, characterized in that: Comprising: A reaction system for the reaction of urea with the exhaust gas discharged from the engine (1), including a main pipeline and a bypass pipeline. One end of the main pipeline is connected to the exhaust end of the engine (1). A front butterfly valve (8), a spray gun (9), a mixer (10), a reactor (5) and a rear butterfly valve (7) are sequentially arranged on the main pipeline. The exhaust gas discharged from the engine (1) and the urea sprayed by the spray gun (9) enter the mixer (10) together for full mixing, then enter the reactor (5) for catalytic reduction reaction, and finally the reduced exhaust gas is discharged. One end of the bypass pipeline is connected to the front end of the front butterfly valve (8) on the main pipeline, and the other end of the bypass pipeline is connected to the rear end of the rear butterfly valve (7) on the main pipeline. A bypass butterfly valve (4) is arranged on the bypass pipeline; A urea injection system for delivering urea solution to the spray gun (9), including a urea tank (13), a urea pipeline, a cleaning pipeline and a compressed air pipeline. One end of the urea pipeline is connected to the urea tank (13), and the other end of the urea pipeline is connected to the spray gun (9) for delivering urea solution to the spray gun (9). The cleaning pipeline is arranged on the urea pipeline for cleaning the residual urea in the urea pipeline after the reaction is completed. One end of the compressed pipeline is connected to an air compressor, and the other end of the compressed pipeline is connected to the spray gun (9) for atomizing the urea entering the spray gun (9) so that the atomized urea is fully mixed with the exhaust gas; A soot blowing system, one end of which is connected to an air compressor and the other end is connected to the reactor (5) for blowing away the impurities accumulated in the reactor (5) to ensure the full progress of the catalytic reduction reaction.

2. The marine SCR system according to claim 1, characterized in that: An orifice flowmeter (2) and a front nitrogen oxide sensor (3) are sequentially arranged on the main pipeline near the engine (1). A rear nitrogen oxide sensor (12) is arranged at the exhaust end of the reactor (5) on the main pipeline. A temperature sensor (11) is arranged on the main pipeline between the mixer (10) and the reactor (5). Differential pressure sensors (6) are connected to both ends of the reactor (5).

3. The marine SCR system according to claim 1, wherein: A supply solenoid valve (16), a urea pump (21), a flowmeter (25), a reductant solenoid valve (28) and a proportional solenoid valve (29) are sequentially arranged on the urea pipeline starting from the urea tank (13) end. After the supply solenoid valve (16) is opened, the urea pump (21) pumps out the urea in the urea tank (13), detects the flow rate of the urea through the flowmeter (25), enters the reductant solenoid valve (28), and then controls the opening or closing of the urea through the reductant solenoid valve (28), and then enters the proportional solenoid valve (29). The proportional solenoid valve (29) controls the urea flow rate, and thus enters the spray gun (9).

4. The marine SCR system according to claim 3, characterized in that: A urea return line (14) and a back pressure valve (27) are provided on the urea pipeline between the flow meter (25) and the reducing agent solenoid valve (28). The other end of the urea return line (14) is connected to the urea tank (13). A return valve (26) is provided on the urea return line (14). The back pressure valve (27) is used to control the urea return flow rate, thereby controlling the urea pressure and ensuring the stability of the urea pressure.

5. The marine SCR system according to claim 3, wherein: A first one-way valve (15) is provided on the urea pipeline between the supply solenoid valve (16) and the urea tank (13). A first filter (22), a first pressure sensor (23) and a first leakage valve (24) are successively provided on the urea pipeline between the urea pump (21) and the flow meter (25). A second leakage valve (30) and a first check valve (31) are successively provided on the urea pipeline between the proportional solenoid valve (29) and the spray gun (9).

6. The marine SCR system according to claim 3, characterized in that: The cleaning pipeline is connected to the urea pipeline between the supply solenoid valve (16) and the urea pump (21). An electric three-way valve (17), a cleaning solenoid valve (20), a second one-way valve (19) and a water tank (18) are successively provided on the cleaning pipeline. Two ends of the electric three-way valve (17) are respectively connected to the supply solenoid valve (16) and the urea pump (21). A third end of the electric three-way valve (17) is connected to the cleaning solenoid valve (20). Water in the water tank (29) enters the urea pipeline through the second one-way valve (19), the cleaning solenoid valve (20) and the electric three-way valve (17) to clean the residual urea in the urea pipeline.

7. The marine SCR system according to claim 3, characterized in that: An air supply solenoid valve (32), a second filter (33), a voltage stabilizer (34), a second pressure sensor (35), a first safety valve (36), a third leakage valve (37) and a second check valve (38) are successively provided on the compressed air pipeline starting from the air compressor end. The air compressed by the air compressor enters the spray gun (9) through the air supply solenoid valve (32), the second filter (33), the voltage stabilizer (34), the second pressure sensor (35), the first safety valve (36), the third leakage valve (37) and the second check valve (38) to atomize the urea solution entering the spray gun (9), and the atomized urea is fully mixed with the waste gas.

8. The marine SCR system according to claim 1, wherein: The soot blowing system includes a main soot blowing pipeline and two soot blowing branch pipelines connected in parallel to the main soot blowing pipeline. One end of the main soot blowing pipeline is connected to the air compressor, and the soot blowing branch pipeline is connected to the reactor (5).

9. The marine SCR system according to claim 8, wherein: A soot blowing solenoid valve (39), a fourth leakage valve (40), a third filter (41), a third pressure sensor (42) and a second safety valve (43) are successively provided on the main soot blowing pipeline starting from the air compressor end. A branch soot blowing solenoid valve (44), a fourth pressure sensor (45) and a diverter (46) are successively provided on the soot blowing branch pipeline. A plurality of bellows (47) are provided between the diverter (46) and the reactor (5), and a third check valve (48) is provided on the bellows (47).

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