A marine SCR urea solution supply system and control method

Abstract

The invention discloses a marine SCR urea solution supply system, comprising an air compressor, an ultrasonic atomizer, an SCR post-processor, a collection unit and a controller, wherein the air compressor provides compressed air to the ultrasonic atomizer, the ultrasonic atomizer atomizes the urea solution, the urea atomized mixed gas is sent to the SCR post-processor, and the SCR post-processor uses the urea atomized mixed gas to purify the exhaust gas generated by the engine; the collection unit obtains the NOx concentration and NH3 concentration of the SCR post-processor and the exhaust flow rate of the engine; the controller controls the injection amount of the urea atomized mixed gas according to the information obtained by the collection unit; the invention uses the precise control of each unit and the real-time signal feedback of the sensor, so that the device can accurately inject the urea solution into the exhaust system with a very small particle size after ultrasonic atomization, so that the SCR post-processing system can achieve high conversion rate and non-crystallization performance.

Description

Technical Field

[0001] The present invention relates to the technical field of marine SCR systems, and in particular to a marine SCR urea solution supply system and a control method. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention, and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] Due to the implementation of the non-road National IV emission regulations, the market has put forward higher requirements for the limit of exhaust emissions from marine engines. The urea injection metering system is a key functional module in the SCR post-treatment system. Since urea solution is corrosive and easy to crystallize, and in order to avoid problems such as crystallization blockage and difficulty in evaporation of urea solution during actual use, it is necessary to inject urea solution into the post-treatment system through a metering urea solution supply system.

[0004] At present, the atomized particle size of urea solution sprayed by the urea spray system commonly used in the prior art is relatively large, which is easy to cause serious crystallization failure; at the same time, the existing urea spray system also has the problem of inaccurate urea solution injection amount, which affects the exhaust gas treatment efficiency. Therefore, there is an urgent need for a metering urea solution supply system with small atomized particle size, high evaporation efficiency and accurate injection amount. Summary of the invention

[0005] In view of the problems existing in the prior art, the present invention provides a marine SCR urea solution supply system and a control method, which can reduce the atomized particle size of the urea solution and improve the accuracy of the urea solution injection amount.

[0006] The technical solution of the present invention is as follows:

[0007] In a first aspect of the present invention, a marine SCR urea solution supply system is provided, comprising an air compressor, an ultrasonic atomizer, an SCR post-processor, a collection unit and a controller, wherein the air compressor provides compressed air to the ultrasonic atomizer, the ultrasonic atomizer atomizes the urea solution, and the urea atomized mixed gas is sent to the SCR post-processor, and the SCR post-processor uses the urea atomized mixed gas to purify the exhaust gas generated by the engine;

[0008] The acquisition unit acquires the NOx concentration, NH3 concentration of the SCR post-processor and the exhaust flow rate of the engine; the controller controls the injection amount of the urea atomized mixed gas according to the information acquired by the acquisition unit.

[0009] In some embodiments of the present invention, the air compressor is connected to the ultrasonic nebulizer via a gas pipeline, a pressure regulating valve and a flow meter are provided on the gas pipeline, and the gas pipeline is also connected to a compressed air bottle, which is provided in parallel with the air compressor.

[0010] In some embodiments of the present invention, the solution inlet of the ultrasonic atomizer is connected to the urea tank through a urea pump, and an ultrasonic generator, a liquid level sensor and a humidity sensor are arranged inside the ultrasonic atomizer.

[0011] In some embodiments of the present invention, the outlet of the ultrasonic atomizer is connected to the front end of the SCR post-processor through a urea pipeline, and a solenoid valve is provided on the urea pipeline.

[0012] In some embodiments of the present invention, the humidity sensor, the liquid level sensor and the solenoid valve are electrically connected to the controller.

[0013] In some embodiments of the present invention, the NOx concentration is obtained by a NOx sensor disposed at the front and rear ends of the SCR post-processor, and the NH3 concentration is obtained by an NH3 sensor disposed on the SCR post-processor.

[0014] In some embodiments of the present invention, the exhaust flow of the engine is obtained by the engine ECD.

[0015] In a second aspect of the present invention, a control method for a marine SCR urea solution supply system is provided, comprising the following steps:

[0016] Obtain NOx concentration, NH3 concentration and engine exhaust flow rate before and after the SCR post-processor;

[0017] Calculate the required injection amount of urea atomization mixture;

[0018] Adjust the opening degree of the solenoid valve so that the injection volume meets the requirements.

[0019] In some embodiments of the present invention, the method further includes obtaining the humidity of the urea atomized mixed gas in the ultrasonic atomizer, and adjusting the power of the ultrasonic generator according to the humidity so that the urea atomized mixed gas in the ultrasonic atomizer reaches a suitable concentration range.

[0020] In some embodiments of the present invention, the pressure of the compressed air injected into the ultrasonic atomizer is further adjusted by a pressure-stabilizing valve to keep the pressure stable.

[0021] One or more technical solutions of the present invention have the following beneficial effects:

[0022] (1) In the marine SCR urea solution supply system of the present invention, the injection amount of the urea atomized mixed gas is controlled by the controller according to the NH3 sensor, NO x The exhaust volume of the sensor and the engine is calculated, and the actual injection volume is accurately controlled by the on-off and opening degree of the solenoid valve.

[0023] (2) In the marine SCR urea solution supply system of the present invention, the concentration of the injected urea atomized mixed gas is achieved by the controller according to the signal of the humidity sensor and the power adjustment of the ultrasonic atomizer. Through the precise control of each unit and the real-time signal feedback of the sensor, the system can accurately inject the urea solution into the exhaust system with extremely small particle size after ultrasonic atomization, so that the SCR post-treatment system can achieve high conversion rate and crystallization-free performance.

[0024] (3) The marine SCR urea solution supply system of the present invention continuously injects compressed air with stable pressure into the ultrasonic atomizer through the provided air compressor and compressed air bottle under the action of the pressure regulating valve. The atomized urea solution is suspended in the air and injected into the SCR post-processor of the marine engine together with the compressed air, thereby reducing the atomized particle size of the urea solution and preventing the occurrence of crystallization. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a structural schematic diagram of the marine SCR urea solution supply system of the present invention;

[0026] Figure 2 The following is a working flow chart of the marine SCR urea solution supply system of the present invention.

[0027] In the figure: 1. air compressor; 2. compressed air bottle; 3. pressure regulating valve; 4. flow meter; 5. humidity sensor; 6. ultrasonic atomizer; 6.1 ultrasonic generator; 7. urea pump; 8. urea tank; 9. liquid level sensor; 10. solenoid valve; 11. controller; 12. first NOx sensor; 13. NH3 sensor; 14. second NOx sensor; 15. SCR post-processor; 16. marine engine. DETAILED DESCRIPTION

[0028] The present invention will be described below in conjunction with the accompanying drawings.

[0029] Example 1

[0030] In a typical embodiment of the present invention, a marine SCR urea solution supply system is provided, such as Figure 1 As shown, it includes an air compressor 1, an ultrasonic atomizer 6, an SCR post-processor 15, a collection unit and a controller 11.

[0031] The air compressor 1 is used to provide compressed air to the ultrasonic atomizer 6. The air compressor 1 is connected to the ultrasonic atomizer 6 through a gas pipeline. A pressure-stabilizing valve 3 and a flow meter 4 are arranged on the gas pipeline. The gas pipeline is also connected to a compressed air bottle 2. The compressed air bottle 2 is arranged in parallel with the air compressor 1. If only the air compressor 1 is used to directly supply air, it will take a certain amount of time to reach the corresponding pressure requirement. The compressed air bottle 2 can play a pressure-maintaining function and also provide a certain pressure storage capacity to protect the entire system and improve the safety of the system. The pressure-stabilizing valve 3 can adjust the pressure of the compressed air coming out of the compressed air bottle 2 and the air compressor 1, so that the pressure of the compressed air remains stable and is continuously injected into the ultrasonic atomizer 6.

[0032] The ultrasonic atomizer 6 is a closed box structure, which is used to atomize the urea solution. An ultrasonic generator 6.1 is arranged in the ultrasonic atomizer. Under the action of the high-frequency ultrasonic wave generated by the ultrasonic generator, the urea solution is oscillated and broken into mist, suspended in the compressed air to become urea atomized mixed gas, and sent to the SCR post-processor. The solution inlet of the ultrasonic atomizer 6 is connected to the urea tank 8 through the urea pump 7. Under the action of the urea pump 7, the urea solution in the urea tank 8 is pumped into the ultrasonic atomizer. The outlet of the ultrasonic atomizer is connected to the front end of the SCR post-processor 15 through the urea pipeline. The solenoid valve 10 is arranged on the urea pipeline, and the solenoid valve is used to control the injection amount of the urea atomized mixed gas. The ultrasonic atomizer is also internally provided with a liquid level sensor 9 and a humidity sensor 5. The liquid level sensor 9 is used to monitor the height of the urea solution in the ultrasonic atomizer in real time so as to replenish the urea solution into the ultrasonic atomizer in time. The humidity sensor is arranged at an upper position in the ultrasonic atomizer to monitor the concentration of the urea atomized mixed gas in the ultrasonic atomizer. The higher the humidity, the more urea solution is injected, so that the concentration of the urea atomized mixed gas entering the SCR post-processor is within a suitable range, thereby improving the exhaust gas treatment efficiency.

[0033] The SCR post-processor 15 uses urea atomized mixed gas to purify the exhaust gas generated by the engine, that is, the urea atomized mixer is mixed and ammoniolyzed with the engine exhaust gas in the SCR post-processor, participating in the catalytic reduction reaction of the SCR system to reduce the NOx concentration in the exhaust gas.

[0034] The acquisition unit includes a first NOx sensor 12 disposed at the front end of the SCR post-processor 15, a second NOx sensor 14 disposed at the rear end of the SCR post-processor 15, and an NH3 sensor 13 disposed on the SCR post-processor 15. The NOx concentration signal is obtained by the NOx sensors disposed at the front and rear ends of the SCR post-processor, the NOx concentration is obtained by the first NOx sensor 12 and the second NOx sensor 14, and the NH3 concentration is obtained by the NH3 sensor 13. The acquisition unit also includes the exhaust flow of the engine, and the exhaust flow of the engine is obtained according to the electronic control unit (ECD) of the engine.

[0035] The controller 11 is electrically connected to the first NOx sensor 12, the NH3 sensor 13, the second NOx sensor 14, and the solenoid valve 10. The controller 11 calculates the actual injection amount of the urea atomizing mixer required according to the NOx concentration, the NH3 concentration and the exhaust flow rate of the engine obtained by the acquisition unit, and controls the opening degree of the solenoid valve 10 according to the actual injection amount, so as to achieve precise control of the injection amount of the urea atomizing mixer.

[0036] The actual injection volume is calculated by the following formula:

[0037]

[0038] Where, Q represents the actual injection amount of urea, g / h; M urea represents the molar mass of urea, 60 g / mol; q m.exhaust Indicates the exhaust gas mass flow rate, kg / h, obtained according to ECD; NO x Indicates the NOx concentration obtained by the first NOx sensor, ppm; NSR indicates the concentration of NH3 and NO X Molar ratio; C urea It indicates that the mass concentration of urea aqueous solution is 32.5%; the molar mass of the exhaust gas is 28.9 g / mol.

[0039] The basic principle of this calculation is as follows:

[0040] According to the exhaust gas mass flow rate, the exhaust gas molar flow rate can be calculated. According to the exhaust gas molar flow rate and NOx emissions, the NOx emission molar flow rate can be calculated. According to the NOx emission molar flow rate and NSR, the required NH3 molar flow rate can be calculated. 1 mol urea can generate 2 mol NH3. At the same time, according to the molecular weight of urea of ​​60 and the concentration of urea aqueous solution of 0.325, the required urea mass flow rate can be calculated.

[0041] Furthermore, the controller 11 is also electrically connected to the humidity sensor 5, the liquid level sensor 9, the ultrasonic generator 6.1, and the urea pump 7. The controller 11 can adjust the power of the ultrasonic generator 6.1 according to the signal of the humidity sensor 5, so that the urea atomized mixed gas in the ultrasonic atomizer reaches a suitable concentration range, specifically: judging whether the urea in the tail gas reaches a suitable amount by humidity, if the humidity is too low, the power needs to be increased, otherwise it needs to be reduced, and the concentration value needs to be determined according to different working conditions. Usually, during the engine calibration process, the urea amount required under different working conditions has been clearly calibrated, and later it only needs to be judged whether the urea amount meets the standard. The controller 11 controls the opening and closing of the urea pump 7 according to the signal of the liquid level sensor 9 to ensure that there is always a certain height of urea solution in the ultrasonic atomizer.

[0042] In this embodiment, the materials of the urea tank, urea pipeline, and ultrasonic atomizer are polyethylene and 06Cr 19 Ni 10 The material can prevent corrosion from urea solution, thereby ensuring the corrosion resistance of the system.

[0043] The working process of the marine SCR urea solution supply system of this embodiment is as follows: Figure 2 As shown, the following steps are included:

[0044] The urea pump 7 extracts urea aqueous solution from the urea tank 8 and injects it into the ultrasonic atomizer through the urea pipeline;

[0045] The controller 11 adjusts the power of the ultrasonic generator 6.1 according to the signal of the humidity sensor 5, so that the urea atomized mixed gas in the ultrasonic atomizer 6 reaches a suitable concentration range;

[0046] The compressed air is injected into the ultrasonic atomizer stably and continuously through the air compressor 1 and the compressed air bottle 2 after the pressure is adjusted by the pressure regulating valve 3;

[0047] The controller 11 calculates the volume of the urea atomized mixed gas to be injected into the SCR post-processor 15 according to the signals of the first NOx sensor 12, the NH3 sensor 13, and the second NOx sensor 14 installed on the SCR post-processor 15 and the exhaust flow rate of the engine 16, and realizes it by controlling the opening and closing time and opening degree of the solenoid valve 10;

[0048] The urea atomized mixed gas enters the SCR post-processor 15 through the urea pipeline and reacts with the exhaust gas of the engine 16 to achieve standard emission of the engine exhaust gas.

[0049] Example 2

[0050] In a typical embodiment of the present invention, a control method for a marine SCR urea solution supply system is provided, comprising the following steps:

[0051] Obtain NOx concentration, NH3 concentration and engine exhaust flow rate before and after the SCR post-processor;

[0052] Calculate the required injection amount of urea atomization mixture;

[0053] Adjust the opening degree of the solenoid valve so that the injection volume meets the requirements.

[0054] Furthermore, the method also includes obtaining the humidity of the urea atomized mixed gas in the ultrasonic atomizer, and adjusting the power of the ultrasonic generator according to the humidity, so that the urea atomized mixed gas in the ultrasonic atomizer reaches a suitable concentration range.

[0055] Furthermore, the method also includes adjusting the pressure of the compressed air injected into the ultrasonic atomizer through a pressure-stabilizing valve to keep the pressure stable.

[0056] The embodiments described above provide a detailed description of the technical solutions of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, supplements or similar substitutions made within the scope of the principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A marine SCR urea solution supply system, characterized in that: It includes an air compressor, an ultrasonic atomizer, an SCR post-processor, a collection unit and a controller. The air compressor provides compressed air to the ultrasonic atomizer, the ultrasonic atomizer atomizes the urea solution, and the urea atomized mixed gas is sent to the SCR post-processor. The SCR post-processor uses the urea atomized mixed gas to purify the exhaust gas generated by the engine; The acquisition unit obtains the NO of the SCR post-processor X concentration, NH3 concentration and exhaust flow rate of the engine; the controller controls the injection amount of urea atomized mixed gas according to the information obtained by the acquisition unit; The injection amount of urea atomization mixed gas is: Wherein, Q represents the actual injection amount of urea, g / h; represents the molar mass of urea; Indicates the exhaust gas mass flow rate, kg / h; Indicates the first NO X The NOx concentration obtained by the sensor, ppm; NSR represents the concentration of NH3 and NO X Molar ratio; Indicates the mass concentration of urea aqueous solution; Indicates the molar mass of the exhaust gas; The air compressor is connected to the ultrasonic atomizer through a gas pipeline, a pressure regulating valve and a flow meter are arranged on the gas pipeline, and the gas pipeline is also connected to a compressed air bottle, and the compressed air bottle is arranged in parallel with the air compressor; the air compressor and the compressed air bottle are provided to continuously inject compressed air with stable pressure into the ultrasonic atomizer under the action of the pressure regulating valve, and the atomized urea solution is suspended in the air and injected into the SCR post-processor together with the compressed air, thereby reducing the atomized particle size of the urea solution; The solution inlet of the ultrasonic atomizer is connected to the urea tank through a urea pump, and an ultrasonic generator, a liquid level sensor and a humidity sensor are arranged inside the ultrasonic atomizer; and the method further includes obtaining the humidity of the urea atomized mixed gas in the ultrasonic atomizer, and adjusting the power of the ultrasonic generator according to the humidity, so that the urea atomized mixed gas in the ultrasonic atomizer reaches a suitable concentration range; The outlet of the ultrasonic atomizer is connected to the front end of the SCR post-processor through a urea pipeline. A solenoid valve is arranged on the urea pipeline, and the solenoid valve is used to control the injection amount of the urea atomized mixed gas.

2. The marine SCR urea solution supply system according to claim 1, characterized in that: The humidity sensor, the liquid level sensor and the solenoid valve are electrically connected to the controller.

3. The marine SCR urea solution supply system according to claim 1, characterized in that: The NO X The concentration is set by NO2 at the front and rear ends of the SCR post-processor. X The NH3 concentration is obtained by a NH3 sensor arranged on the SCR post-processor.

4. The marine SCR urea solution supply system according to claim 1, characterized in that: The exhaust flow of the engine is acquired by an engine electronic control unit.

5. A control method for a marine SCR urea solution supply system according to any one of claims 1 to 4, characterized in that: The following steps are involved: Get the NO of the front and back end of the SCR postprocessor X concentration, NH3 concentration and exhaust flow rate of the engine; Calculate the required injection amount of urea atomization mixture; Adjust the opening degree of the solenoid valve so that the injection volume meets the requirements.

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