SCR (Selective Catalytic Reduction) system for marine ammonia fuel main engine

Abstract

The SCR system for the marine ammonia fuel main engine comprises a pressure regulating unit, an ammonia metering unit, a mixing pipe and a reactor, wherein the pressure regulating unit is connected with the ammonia fuel supply system, one end of the ammonia metering unit is connected with the pressure regulating unit, the other end is connected with the mixing pipe, one end of the mixing pipe is connected with a waste gas outlet of the main engine, the other end is connected with the reactor, the reactor is provided with a waste gas outlet, and the control system of the marine ammonia fuel main engine is respectively connected with the pressure regulating unit and the ammonia metering unit; the pressure regulating unit is used for regulating the pressure of ammonia from the ammonia fuel supply system according to a pressure calibration value given by the control system and inputting the pressure into the ammonia metering unit, the ammonia metering unit is used for regularly and quantitatively spraying the ammonia into the mixing pipe according to an instruction of the control system and a calibrated MAP, and the ammonia is mixed with waste gas of a main machine in the mixing pipe and then enters the reactor; and taking the waste gas as a reducing agent to participate in oxidation-reduction reaction to complete waste gas treatment of the marine ammonia fuel main engine. The requirement of Tier3 on NOx emission is met, and the effects of simplifying the structure of the SCR system and reducing the cost are achieved.

Description

Technical Field

[0001] The invention relates to a marine low-speed dual-fuel engine using ammonia fuel, and in particular to an SCR system for a marine ammonia fuel main engine, belonging to the technical field of internal combustion engines. Background Art

[0002] With the development of the shipping market, the exhaust emissions of marine diesel engines fueled by petroleum products have seriously polluted the current environment. At the same time, due to the increasingly stringent emission regulations, in order to reduce carbon emissions, various new marine engines using environmentally friendly fuels have been continuously launched. Among them, the marine ammonia fuel main engine refers to a dual-fuel marine engine that can use not only fuel oil (diesel / heavy oil) as fuel, but also ammonia as fuel.

[0003] However, marine ammonia fuel main engine cannot directly meet the Tier 3 emission requirements, and an exhaust gas treatment system needs to be added. The SCR system is one of the most commonly used exhaust gas treatment systems. The SCR (selective catalytic reduction) device is an emission reduction device for treating ship engine exhaust. Its principle is to collect the exhaust gas generated by the main engine combustion through the exhaust manifold, mix it with urea solution through a mixer, and then convert NOx into nitrogen through an oxidation-reduction reaction in the reactor, thereby reducing the content of nitrogen oxides in the exhaust gas, and finally discharge it through the supercharger to achieve the effect of emission reduction.

[0004] The SCR system of the main engine using conventional fuel needs to use urea to prepare ammonia, and usually requires special ammonia preparation systems such as urea cabinets, urea pumping stations, and urea decomposition units. However, the marine ammonia fuel main engine itself is already equipped with an ammonia fuel supply system, and ammonia is the reducing agent of the SCR system. Therefore, this creates conditions for the structural optimization of the SCR system of the marine ammonia fuel main engine. Summary of the invention

[0005] The purpose of the present invention is to overcome the defect of complex structure of conventional SCR system, and provide an SCR system specially used for marine ammonia fuel main engine according to the characteristics of marine ammonia fuel main engine, so as to meet the requirements of Tier 3 for NOx emission and achieve the effect of simplifying the structure and reducing the cost of the SCR system of marine ammonia fuel main engine.

[0006] Based on the above purpose, the technical solution provided by the present invention is as follows:

[0007] An SCR system for a marine ammonia fuel main engine, the marine ammonia fuel main engine comprising an exhaust gas outlet, an ammonia fuel supply system and a control system, characterized in that: the SCR system comprises a pressure regulating unit, an ammonia metering unit, a mixing tube and a reactor; the pressure regulating unit is connected to the ammonia fuel supply system through a pipeline, one end of the ammonia metering unit is connected to the pressure regulating unit, and the other end is connected to the mixing tube, one end of the mixing tube is connected to the exhaust gas outlet of the marine ammonia fuel main engine, and the other end is connected to the reactor, the reactor is provided with an exhaust gas outlet, and the control system of the marine ammonia fuel main engine is respectively connected to the pressure regulating unit and the ammonia metering unit;

[0008] The pressure regulating unit adjusts the pressure of ammonia from the ammonia fuel supply system according to the pressure calibration value given by the control system, and inputs the pressure into the ammonia metering unit. The ammonia metering unit sprays ammonia into the mixing tube in a timely and quantitative manner according to the calibrated MAP diagram according to the instructions of the control system. The ammonia is mixed with the exhaust gas from the main engine in the mixing tube and then enters the reactor, and participates in the redox reaction as a reducing agent to complete the exhaust gas treatment of the marine ammonia fuel main engine.

[0009] Furthermore, according to the requirement of the suction port pressure of the ammonia metering unit, the pressure calibration of the pressure regulating unit is completed, and the pressure calibration value is stored in the control system.

[0010] Furthermore, the pressure calibration value can be adjusted to match the pressure loss of different systems.

[0011] Furthermore, the MAP chart calibration of the ammonia metering unit is completed through bench testing, and the obtained calibration value and its tolerance are stored in the control system.

[0012] Furthermore, the pressure regulating unit is a set of pressure regulating valve groups.

[0013] Furthermore, the SCR system also serves as an ammonia capture system for the exhaust gas of the marine ammonia fuel main engine, and is used to reduce the ammonia escape concentration in the exhaust gas.

[0014] Furthermore, the SCR system is applicable to both the high-pressure SCR system and the low-pressure SCR system of the marine ammonia fuel main engine.

[0015] Compared with conventional SCR systems, the present invention achieves the following beneficial effects:

[0016] 1. The present invention eliminates the urea cabinet, urea pump station, urea decomposition unit and other equipment in the conventional SCR system, adds a branch pipe to the ammonia fuel supply system of the ammonia fuel host, connects ammonia to the ammonia metering unit of the SCR system through the pressure regulating valve group, directly sprays ammonia into the SCR mixing pipe to mix with the host exhaust gas, and enters the SCR reactor as a reducing agent to participate in the reaction, thereby optimizing the ammonia supply link of the SCR system, reducing unnecessary SCR equipment, making the SCR system structure more concise and reliable, and reducing equipment costs and layout space requirements.

[0017] 2. The SCR also serves as an ammonia capture system for the ammonia fuel main engine, thereby reducing the concentration of ammonia escape in the exhaust gas without the need for repeated installation of similar equipment. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0019] In the figure,

[0020] 1—pressure regulating unit, 2—ammonia metering unit, 3—mixing tube, 4—reactor. DETAILED DESCRIPTION

[0021] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0022] The present invention is specially used for marine ammonia fuel main engine that uses ammonia as fuel, so that it can meet the Tier 3 NOx emission requirements. The present invention eliminates the urea cabinet, urea pump station, urea decomposition unit and other equipment in the conventional SCR system, adds a branch in the ammonia fuel supply system of the main engine, and directly supplies ammonia to the ammonia metering unit of the SCR system through a set of pressure regulating valve groups. The ammonia metering unit supplies ammonia to the ammonia spray gun on the SCR mixing tube in a timely and quantitative manner according to the requirements of the control system. Ammonia is mixed with exhaust gas in the SCR mixing tube, and enters the SCR reaction after passing through the ammonia spray grid, completing the exhaust gas treatment of the ammonia fuel main engine.

[0023] See also Figure 1 The SCR system includes a pressure regulating unit 1, an ammonia metering unit 2, a mixing tube 3 and a reactor 4.

[0024] The pressure regulating unit 1 is a set of pressure regulating valve groups, which are connected to the ammonia fuel supply system of the marine ammonia fuel main engine through pipelines. One end of the ammonia metering unit 2 is connected to the pressure regulating unit 1, and the other end is connected to the mixing tube 3. One end of the mixing tube 3 is connected to the exhaust gas outlet of the marine ammonia fuel main engine, and the other end is connected to the reactor 4. The reactor 4 is provided with an exhaust gas outlet directly leading to the outside. The control system of the marine ammonia fuel main engine (not shown in the figure) is respectively connected to the pressure regulating unit 1 and the ammonia metering unit 2.

[0025] The SCR system needs to be calibrated before operation, as follows:

[0026] Step 1: According to the suction port pressure requirement of the ammonia metering unit 2, the pressure calibration of the pressure regulating unit 1 is completed, and the pressure calibration value is stored in the control system. At the same time, the pressure calibration value of the pressure regulating unit 1 can be adjusted to match different system pressure losses of different system layouts.

[0027] Step 2: Complete the MAP chart calibration of the ammonia metering unit 2 through bench tests to ensure that the ammonia metering unit 2 can spray ammonia reducing agent into the mixing tube 3 in a timely and quantitative manner according to the emission reduction requirements. The calibration value plus the tolerance is included in the emission file as the IMO value and stored in the control system to ensure the consistency of the emission performance of the SCR system after loading.

[0028] When the SCR system is running, the pressure regulating unit 1 adjusts the pressure of ammonia from the ammonia fuel supply system according to the pressure calibration value given by the control system, and inputs the pressure into the ammonia metering unit 2. The ammonia metering unit 2 sprays ammonia into the mixing tube 3 in a timely and quantitative manner according to the instructions of the control system and the calibrated MAP diagram. Ammonia is mixed with the exhaust gas from the main engine in the mixing tube 3 and then enters the reactor 4, and participates in the redox reaction as a reducing agent to complete the exhaust gas treatment of the marine ammonia fuel main engine.

[0029] When the marine ammonia fuel main engine operates in the specified emission control area, the pressure regulating unit 1 adjusts the ammonia in the ammonia fuel supply system to the corresponding pressure as required and transmits it to the ammonia metering unit 2. The ammonia metering unit 2 sprays ammonia into the mixing pipe 3 in a timely and quantitative manner according to the control command of the control system and the calibrated MAP diagram, and fully mixes the ammonia with the exhaust gas of the ammonia fuel main engine, and then enters the reactor 4 to complete the NOx reduction reaction, thereby achieving NOx emission reduction.

[0030] When the marine ammonia fuel main engine operates outside the emission control area, the SCR system stops running (not intervened), that is, the ammonia metering unit 2 does not work, and the exhaust gas of the marine ammonia fuel main engine can maintain the original path, wherein a small amount of escaped ammonia can still undergo oxidation-reduction reaction with NOx in the exhaust gas when passing through the reactor 4, thereby achieving ammonia capture on the one hand and reducing NOx emissions to a certain extent on the other hand, that is to say, the SCR system can also serve as an ammonia capture system for the exhaust gas of the marine ammonia fuel main engine, and is used to reduce the ammonia escape concentration in the exhaust gas.

[0031] The SCR system of the present invention is applicable to both the high-pressure SCR system of the marine ammonia fuel main engine and the low-pressure SCR system of the marine ammonia fuel main engine.

[0032] The protection scope of the present invention is not limited to the above-mentioned embodiments, but should also include other obvious changes and substitutions for the present invention.

Claims

1. An SCR system for a marine ammonia fuel main engine, the marine ammonia fuel main engine comprising an exhaust gas outlet, an ammonia fuel supply system and a control system, characterized in that: The SCR system comprises a pressure regulating unit, an ammonia metering unit, a mixing tube and a reactor; the pressure regulating unit is connected to the ammonia fuel supply system through a pipeline, one end of the ammonia metering unit is connected to the pressure regulating unit, and the other end is connected to the mixing tube, one end of the mixing tube is connected to the exhaust gas outlet of the marine ammonia fuel main engine, and the other end is connected to the reactor, the reactor is provided with an exhaust gas outlet, and the control system of the marine ammonia fuel main engine is respectively connected to the pressure regulating unit and the ammonia metering unit; The pressure regulating unit adjusts the pressure of ammonia from the ammonia fuel supply system according to the pressure calibration value given by the control system, and inputs the pressure into the ammonia metering unit. The ammonia metering unit sprays ammonia into the mixing tube in a timely and quantitative manner according to the calibrated MAP diagram according to the instructions of the control system. The ammonia is mixed with the exhaust gas from the main engine in the mixing tube and then enters the reactor, and participates in the redox reaction as a reducing agent to complete the exhaust gas treatment of the marine ammonia fuel main engine.

2. The SCR system for a marine ammonia fuel main engine according to claim 1, characterized in that: According to the requirement of the suction port pressure of the ammonia metering unit, the pressure calibration of the pressure regulating unit is completed, and the pressure calibration value is stored in the control system.

3. The SCR system for a marine ammonia fuel main engine according to claim 2, characterized in that: The pressure calibration value can be adjusted to match the pressure loss of different systems.

4. The SCR system for a marine ammonia fuel main engine according to claim 1, characterized in that: The MAP chart calibration of the ammonia metering unit is completed through bench testing, and the obtained calibration value and its tolerance are stored in the control system.

5. The SCR system for a marine ammonia fuel main engine according to claim 1, characterized in that: The pressure regulating unit is a set of pressure regulating valve groups.

6. The SCR system for a marine ammonia fuel main engine according to claim 1, characterized in that: The SCR system also serves as an ammonia capture system for the exhaust gas of the marine ammonia fuel main engine, and is used to reduce the ammonia escape concentration in the exhaust gas.

7. The SCR system for a marine ammonia fuel main engine according to claim 1, characterized in that: The SCR system is applicable to both the high-pressure SCR system of the marine ammonia fuel main engine and the low-pressure SCR system of the marine ammonia fuel main engine.

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