A safe recycling ammonia fuel main engine ammonia gas leakage treatment system

Abstract

The application discloses a safe recycling ammonia fuel main engine leakage ammonia gas treatment system, which utilizes a high-pressure selective catalytic reduction (SCR) system already equipped on a ship, and directs leakage ammonia gas to an SCR mixing pipeline through a special spray gun, so that the leakage ammonia gas participates in a catalytic reduction reaction. x In the process, the leakage ammonia gas can completely replace traditional urea solution as a reducing agent, and reacts with nitrogen oxides (NOx) in exhaust gas to generate non-toxic and harmless nitrogen and water vapor. After the reaction, the ammonia gas is completely decomposed and no longer has combustibility and toxicity, so that potential threats to the environment and personnel health are eliminated from the source. Since the leakage ammonia gas has assumed part of the reducing agent function, the system can intelligently adjust the urea injection amount through a urea metering unit to realize dynamic reduction of urea consumption, thereby reducing operation cost, reducing the demand for urea storage and supply, and improving system economy and operation efficiency.

Description

Technical Field

[0001] This invention belongs to the field of marine shipbuilding and design, and specifically relates to a safe and reusable ammonia treatment system for leaked ammonia from an ammonia fuel main engine. Background Technology

[0002] As the International Maritime Organization (IMO) engages in in-depth discussions on the details of the carbon pricing mechanism, the European Parliament has voted to include ship greenhouse gas emissions in the EU Emissions Trading System (EU-ETS). This means that the shipping industry will be included in a mandatory carbon cost system for the first time, and ship operators will have to bear direct economic responsibility for their carbon emissions in the future.

[0003] Currently, mainstream dual-fuel engines can only achieve greenhouse gas emission reductions of 0% to 24% in actual operation, far from meeting the deep decarbonization level required by the IMO's 2050 net-zero emissions target for the shipping industry. Therefore, developing non-fossil fuels has become an industry consensus and an inevitable trend. The market generally expects LPG and LNG to play a key role as transitional low-carbon fuels, while ammonia fuel (NH3) is considered a core solution for achieving shipping decarbonization in the medium to long term.

[0004] Ammonia-fueled main engines, as an important technological approach, have received active research and development and promotion from major main engine manufacturers, including WinGD. However, according to the ammonia-fueled main engine structure designed by WinGD, there is an inherent risk of trace ammonia fuel leakage in the main engine nozzle area—this leakage stems from the system's operating characteristics and is difficult to completely eliminate through structural optimization. Therefore, how to safely and efficiently recover or dispose of leaked ammonia has become a key safety issue that urgently needs to be addressed before the practical application of ammonia-fueled main engines on ships, directly affecting ship operational safety, crew health, and regulatory compliance. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a safe and reusable ammonia fuel engine leakage treatment system. The system aims to recover leaked ammonia fuel on-site and participate in the high-pressure SCR catalytic reduction reaction, achieving a closed-loop treatment objective of "leakage as conversion, waste as reducing agent." The technical solution adopted is as follows: A safe and reusable ammonia gas recovery system for ammonia fuel generator leaks ammonia gas. The ammonia fuel generator is equipped with an ammonia gas vent and a high-pressure exhaust outlet. The ammonia gas vent is connected to a high-pressure SCR mixing pipe via a pipeline and an NH3 spray gun. The high-pressure SCR mixing pipe is connected to a high-pressure SCR reactor. The leaked ammonia gas from the ammonia fuel generator is directly injected into the high-pressure SCR mixing pipe through the NH3 spray gun.

[0006] The high-pressure flue gas outlet is connected to the high-pressure SCR reactor via a pipeline through a high-pressure SCR mixing pipe. The flue gas from the main unit enters the high-pressure SCR mixing pipe through the pipeline, mixes thoroughly with the leaked ammonia gas, and then enters the high-pressure SCR reactor to participate in the catalytic reduction reaction.

[0007] The urea cabinet is connected to the high-pressure SCR mixing pipe via a pipeline through the urea metering unit.

[0008] The urea metering unit is connected to the main unit and the high-pressure SCR reactor. The urea metering unit receives the main unit power signal and calculates and dynamically adjusts the injection amount of supplementary urea based on the leakage ammonia amount and the main unit flue gas flow rate corresponding to the current power, so that it can participate in the catalytic reduction reaction in conjunction with the leakage ammonia.

[0009] The urea metering unit receives NO at the outlet of the high-pressure SCR reactor in real time. x Concentration feedback signal, when NO is detected at the outlet x When the concentration exceeds 2 ppm, the system determines that the denitrification efficiency is abnormal or the reaction is insufficient. The urea metering unit automatically starts the compensation mechanism, adds urea injection, strengthens the reduction reaction, until the flue gas concentration is stably lower than the limit, and ultimately ensures that the main unit's flue gas continuously meets the IMO Tier III emission standards.

[0010] The aforementioned ammonia treatment system for safe recycling and reuse of ammonia fuel from main engine leaks can be further categorized into IMO Tier II emission standards and Tier III emission standards based on the emission limit levels of the ship's navigation area.

[0011] When implementing the IMO Tier II emission standard, urea is not required. Instead, the leaked ammonia from the main engine mixes with the exhaust gas from the main engine and then enters the high-pressure SCR reactor for reaction.

[0012] Furthermore, in the aforementioned safe recycling and reuse system for treating leaked ammonia from an ammonia fuel generator, the pressure of the ammonia fuel before entering the ammonia fuel generator is 80 bar.

[0013] Furthermore, in the aforementioned safe recycling and reuse system for treating leaked ammonia from an ammonia fuel generator, the leaked ammonia pressure from the ammonia fuel generator is 30 bar.

[0014] Furthermore, the aforementioned ammonia gas leakage treatment system for ammonia fuel main unit that allows for safe recycling and reuse has a double-walled structure in the pipeline between the main unit's vent and the NH3 spray gun. The inner pipe transports ammonia gas, while the outer pipe is equipped with a leakage monitoring and safe collection channel.

[0015] Furthermore, in the aforementioned safe recycling and reuse system for treating leaked ammonia from an ammonia fuel main unit, a sensor is installed at the outlet of the high-pressure SCR reactor to monitor the NO at the reactor outlet.x The concentration is measured, and the monitored signal is fed back to the urea metering unit.

[0016] Furthermore, in the aforementioned safe recycling and reuse system for treating leaked ammonia from an ammonia fuel generator, a urea metering unit is connected to a urea spray gun, through which urea is sprayed into the high-pressure SCR mixing pipe.

[0017] Furthermore, in the aforementioned safe recycling and reuse system for treating leaked ammonia from an ammonia fuel main unit, the urea tank is equipped with a urea transfer pump, which transfers the urea to the urea metering unit.

[0018] This invention utilizes the high-pressure selective catalytic reduction (SCR) system already equipped on ships. Leaking ammonia gas is directionally injected into the SCR mixing pipeline via a dedicated spray gun, allowing it to participate in the catalytic reduction reaction. In this process, the leaking ammonia gas can completely replace the traditional urea solution (AUS 32) as a reducing agent, reacting with nitrogen oxides (NOx) in the exhaust gas. x Ammonia undergoes a catalytic reaction to produce non-toxic and harmless nitrogen (N2) and water vapor (H2O). After the reaction, ammonia is completely decomposed and no longer possesses flammability and toxicity, thus eliminating the potential threat to the environment and human health at the source.

[0019] In addition, since the leaked ammonia has already served as a reducing agent, the system can intelligently adjust the urea injection volume through the urea metering unit to achieve dynamic reduction of urea consumption. This not only reduces operating costs but also reduces the need for urea storage and replenishment, thereby improving the system's economy and operational efficiency.

[0020] This invention cleverly integrates safety protection and resource recycling, requires no new large-scale equipment, is compatible with existing high-pressure SCR architecture, and has advantages such as high engineering feasibility, low modification cost, and significant safety benefits, providing key safety assurance and technical support for the practical application of ammonia fuel main engines on ships. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the system of the present invention; Among them, 1-ammonia fuel main unit, 2-ammonia fuel vent, 3-high pressure flue gas outlet, 4-NH3 spray gun, 5-urea spray gun, 6-high pressure SCR mixing pipe, 7-high pressure SCR reactor, 8-main unit flue gas outlet, 9-urea metering unit, 10-urea transfer pump, 11-urea cabinet. Detailed Implementation

[0022] The invention will be further described with reference to the accompanying drawings.

[0023] like Figure 1The system shown is a safe and reusable ammonia fuel main unit leakage treatment system. Due to the structural characteristics of the WinGD ammonia fuel main unit 1, there is an inherent leakage phenomenon during the combustion process of ammonia fuel injected into the cylinder through the nozzle. This leaked ammonia cannot flow back to the storage tank and must be treated on-site in the engine room. After the leaked ammonia is discharged through the ammonia fuel vent 2 of the ammonia fuel main unit 1, it is directly injected into the high-pressure SCR mixing pipe 6 through the NH3 spray gun 4, where it is fully mixed with the main unit exhaust gas and enters the high-pressure SCR reactor 7 to participate in the catalytic reduction reaction. The main unit exhaust gas is discharged from the high-pressure exhaust outlet 3 and enters the high-pressure SCR mixing pipe through the pipeline.

[0024] The ammonia fuel is at a pressure of approximately 80 bar before entering the main unit, and the pressure remains at approximately 30 bar even after leakage, providing sufficient kinetic energy to drive the injection. Therefore, this system can achieve stable atomization and precise injection of ammonia gas in the NH3 spray gun 4 without the need for additional pressurization devices or compressed air assistance, reducing system complexity and energy consumption.

[0025] Given that ammonia is easily vaporized and toxic at normal temperature and pressure, in order to prevent leakage and spread, the pipeline from the ammonia fuel vent 2 to the NH3 spray gun 4 adopts a double-wall structure. The inner pipe transports ammonia, and the outer pipe is equipped with a leakage monitoring and safety collection channel to ensure zero leakage during the transportation process and protect the safety of the cabin personnel.

[0026] After the leaked ammonia gas is uniformly mixed with the flue gas from the main unit in the high-pressure SCR mixing pipe 6, it enters the high-pressure SCR reactor 7, where the following main reduction reactions occur under the action of a catalyst: 4NO + 4NH3 + O2 → 4N2 + 6H2O 2NO + 2NO₂ + 4NH₃ + O₂ → 4N₂ + 6H₂O 2NO2 + 4NH3 + O2 → 3N2 + 6H2O The reaction products are only nitrogen (N2) and water vapor (H2O), which are non-toxic, harmless, and non-flammable. This completely eliminates the harm of leaked ammonia to the environment and human health, achieving a safe conversion with "zero residue and zero emissions." Finally, the ammonia is discharged into the atmosphere through the main unit's exhaust outlet 8.

[0027] The urea tank 11 is connected to the high-pressure SCR mixing pipe 6 via a pipeline through the urea metering unit 9. The urea tank is equipped with a urea transfer pump, and the urea metering unit 9 is connected to a urea spray gun 5. Urea is sprayed into the high-pressure SCR mixing pipe 6 through the urea transfer pump and the urea spray gun.

[0028] The urea metering unit is connected to the ammonia fuel main unit 1 and the high-pressure SCR reactor signal 7. The urea metering unit receives the main unit power signal and calculates and dynamically adjusts the injection amount of supplementary urea based on the leakage ammonia gas volume and the main unit flue gas flow rate corresponding to the current power, so that it can participate in the catalytic reduction reaction in conjunction with the leakage ammonia gas.

[0029] This system intelligently adjusts its operating strategy based on the emission limit levels of the ship's navigation area. Tier II emission zones: No mandatory NO control required. x The leakage can be neutralized simply by the participation of the leaked ammonia in the SCR reaction. At this point, the system's primary function is "safe recovery of leaked ammonia," and some NO will still remain after the reaction. x It is discharged with the exhaust gas and meets Tier II standards.

[0030] Tier III emission zones: NO2 must be strictly controlled. x Emission limits. At this time, the urea transfer pump 10 draws urea solution from the urea tank 11 and delivers it to the urea metering unit 9.

[0031] Because the leakage of ammonia fuel nozzles and the exhaust volume of the main unit change dynamically under different power conditions, in order to ensure that the denitrification efficiency of the SCR system always meets the Tier III emission requirements, the urea metering unit 9, after receiving the main unit power signal, will intelligently calculate and dynamically adjust the injection amount of supplementary urea based on the leakage ammonia and exhaust flow rate corresponding to the current power. This urea will then work in conjunction with the leaking ammonia to participate in the catalytic reduction reaction, thereby controlling excess NO. x Precise neutralization.

[0032] Meanwhile, the urea metering unit 9 also receives the NO from the outlet of the high-pressure SCR reactor 7 in real time. x Concentration feedback signal. When NO is detected at the outlet. x When the concentration exceeds 2 ppm, the system determines that the denitrification efficiency is abnormal or the reaction is insufficient. To ensure emission compliance, the metering unit will automatically activate the compensation mechanism, increase the urea injection volume, and enhance the reduction reaction until the flue gas concentration is stably lower than the limit, ultimately ensuring that the main unit's flue gas continuously meets the IMO Tier III emission standards.

[0033] This dual closed-loop control strategy—"power prediction + concentration feedback"—effectively improves system response accuracy and emission stability, while balancing economy and compliance. It is a key guarantee for the safe, efficient, and compliant operation of ammonia fuel main units under complex operating conditions.

[0034] This invention cleverly utilizes the ship's existing high-pressure SCR system, enabling the safe recovery and resource utilization of leaked ammonia from the main engine without the need for any additional auxiliary equipment. Leveraging the high-pressure characteristics of ammonia fuel (maintaining approximately 30 bar pressure even after leakage), it can be directly injected into the SCR mixing pipeline via a spray gun, eliminating the need for additional pressurization, compression, or atomization auxiliary systems, significantly reducing system complexity and energy consumption.

[0035] Meanwhile, upon entering the mixing pipe, the leaked ammonia gas, due to the higher ambient temperature and lower pressure, can naturally vaporize and thoroughly mix with the main engine exhaust. It then participates in the high-pressure SCR catalytic reduction reaction, efficiently converting into non-toxic and harmless nitrogen and water vapor. This process not only eliminates the risk of ammonia leakage but also achieves a substantial reduction of approximately 1.76% in urea injection within the Tier III emission control area through the mechanism of "leaked ammonia replacing part of the urea," thereby reducing ship operating costs and the frequency of urea replenishment, and improving economic efficiency and maintenance convenience.

[0036] This invention has a simple structure, strong adaptability, and low modification cost. It is applicable to all ships that are already equipped with ammonia fuel main engines and high-pressure SCR systems, and has broad engineering promotion value and industry application prospects.

Claims

1. A system for safely recycling and reusing ammonia gas leaking from a main ammonia fuel engine, characterized in that, The ammonia fuel main unit is equipped with an ammonia vent and a high-pressure exhaust outlet. The ammonia vent is connected to the high-pressure SCR mixing pipe via a pipeline through an NH3 spray gun. The high-pressure SCR mixing pipe is connected to the high-pressure SCR reactor. Leaking ammonia from the ammonia fuel main unit is directly injected into the high-pressure SCR mixing pipe through the NH3 spray gun. The high-pressure flue gas outlet is connected to the high-pressure SCR reactor via a pipeline through a high-pressure SCR mixing pipe. The flue gas from the main unit enters the high-pressure SCR mixing pipe through the pipeline, mixes thoroughly with the leaked ammonia gas, and then enters the high-pressure SCR reactor to participate in the catalytic reduction reaction. The urea cabinet is connected to the high-pressure SCR mixing pipe via a pipeline through the urea metering unit. The urea metering unit is connected to the ammonia fuel main unit, the high-pressure SCR mixing pipe, and the high-pressure SCR reactor. The urea metering unit receives the power signal of the ammonia fuel main unit and calculates and dynamically adjusts the injection amount of supplementary urea based on the leakage ammonia gas volume and the flue gas flow rate of the main unit corresponding to the current power, so that it can participate in the catalytic reduction reaction in conjunction with the leakage ammonia gas. The urea metering unit receives NO at the outlet of the high-pressure SCR reactor in real time. x Concentration feedback signal, when NO is detected at the outlet x When the concentration exceeds 2 ppm, the system determines that the denitrification efficiency is abnormal or the reaction is insufficient. The urea metering unit automatically starts the compensation mechanism, adds urea injection, strengthens the reduction reaction, until the flue gas concentration is stably lower than the limit, and ultimately ensures that the main unit's flue gas continuously meets the IMO Tier III emission standards.

2. The ammonia gas leakage treatment system for ammonia fuel main unit that allows for safe recycling and reuse according to claim 1, characterized in that, Based on the emission limit level of the navigation area, the emission standards can be divided into IMO Tier II emission standards and Tier III emission standards. When implementing the IMO Tier II emission standard, urea is not required. Instead, the leaked ammonia from the main engine mixes with the exhaust gas from the main engine and then enters the high-pressure SCR reactor for reaction.

3. The ammonia gas leakage treatment system for ammonia fuel main unit that allows for safe recycling and reuse according to claim 1, characterized in that, The pressure of ammonia fuel before entering the ammonia fuel main unit is 80 bar.

4. The ammonia gas leakage treatment system for ammonia fuel main unit that allows for safe recycling and reuse according to claim 1, characterized in that, The leaking ammonia pressure in the ammonia-fueled main unit is 30 bar.

5. The ammonia gas leakage treatment system for ammonia fuel main unit that allows for safe recycling and reuse according to claim 1, characterized in that, The pipeline between the main unit's vent and the NH3 spray gun adopts a double-wall structure, with the inner pipe transporting ammonia and the outer pipe equipped with a leak monitoring and safety collection channel.

6. The ammonia gas leakage treatment system for ammonia fuel main unit that allows for safe recycling and reuse according to claim 1, characterized in that, A sensor is installed at the outlet of the high-pressure SCR reactor to monitor the NO at the outlet of the high-pressure SCR reactor. x The concentration is measured, and the monitored signal is fed back to the urea metering unit.

7. The ammonia gas leakage treatment system for ammonia fuel main unit that allows for safe recycling and reuse according to claim 1, characterized in that, The urea metering unit is connected to a urea spray gun, through which urea is sprayed into the high-pressure SCR mixing pipe.

8. The ammonia gas leakage treatment system for ammonia fuel main unit that allows for safe recycling and reuse according to claim 1, characterized in that, The urea cabinet is equipped with a urea transfer pump, which transfers urea to the urea metering unit.

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