Ammonia fuel ship tail gas denitration system

Abstract

The utility model relates to an ammonia fuel ship tail gas denitration system, which is characterized in that an ammonia supply pipeline of an ammonia fuel engine in the system adopts a double-wall pipe, an inner pipe of the double-wall pipe is used for conveying liquid ammonia, and an outer pipe of the double-wall pipe is connected with an ammonia treatment system through a fan so as to suck leaked ammonia gas to the ammonia treatment system; the ammonia treatment system is connected with the buffer tank through a fan and is used for conveying the discharged gas to the buffer tank after pressurizing the discharged gas through the fan; the ammonia treatment system is connected with a reducing agent tank through a pump; the reducing agent tank receives ammonia water of the ammonia treatment system through the pump; the SCR reducing agent supply system is connected with the reducing agent spray gun through the reducing agent tank and the buffer tank and used for conveying the discharged gas to the reducing agent spray gun through the SCR reducing agent supply system to assist in atomizing ammonia water. According to the tail gas denitration system for the ammonia fuel ship, ammonia water generated in the ammonia treatment system is used as a reducing agent of the SCR system, and discharged gas of the ammonia treatment system is used as auxiliary atomization gas of the reducing agent, so that waste is recycled, and the denitration efficiency is improved.

Description

Technical Field

[0001] This utility model relates to ship exhaust gas treatment technology, specifically an exhaust gas denitrification system based on ammonia-fueled ships. It utilizes waste ammonia gas to generate high-concentration ammonia water as a reducing agent for the SCR system, while using vented gas to assist atomization, thereby achieving energy-saving and efficient denitrification. Background Technology

[0002] Selective catalytic reduction (SCR) systems are aftertreatment technologies used to address nitrogen oxide (NOx) emissions from engines. They require urea solution or ammonia as a reducing agent to react with NOx and reduce emissions. Diesel SCR systems typically use urea solution, while ammonia-fueled ships, using liquid ammonia, require a liquid ammonia storage tank. This tank generates boil-off gas (BOG), which has a high ammonia concentration and purity. BOG is processed by a BOG recovery and reuse system, which compresses, condenses, liquefies, and separates it for reuse. The engine ammonia fuel supply pipeline uses a double-walled pipe; the inner pipe transports liquid ammonia, while the outer pipe is vented by a blower. In case of a leak, ammonia is extracted by the blower and collected by the ammonia treatment system. When switching between ammonia and diesel operating modes, nitrogen is used to purge the ammonia fuel supply system to remove residual ammonia. The purging gas is then introduced into the ammonia treatment system. Ammonia treatment systems use water as the medium for absorbing ammonia. As the concentration of ammonia in the water gradually increases, the ammonia water reaches saturation at the operating temperature and pressure, and can no longer absorb more ammonia. In this case, the ammonia water in the treatment system needs to be released and stored, and then treated again when the ship docks. Therefore, the stored ammonia water occupies cabin space and increases management costs.

[0003] Traditional SCR systems rely on urea solution or liquid ammonia, resulting in high storage costs and energy consumption. Ammonia-fueled ships require the treatment of boil-off gas (BOG) and leaked ammonia; existing technologies necessitate the additional release of ammonia-containing wastewater, occupying shipboard space. Patent CN118526944A mentions using low-concentration ammonia water for denitrification, but it does not address the issues of ammonia water generation and atomization optimization. This invention integrates an ammonia treatment system with an SCR system, enabling waste reuse and improving denitrification efficiency. Summary of the Invention

[0004] The present invention proposes an ammonia-fueled ship exhaust gas denitrification system that utilizes the waste gas generated during the operation of the ammonia-fueled engine (the vent gas from the ammonia treatment system, mainly composed of air and nitrogen) as the ammonia-water auxiliary atomizing gas, thereby achieving waste reuse and improving denitrification efficiency.

[0005] To achieve the above objectives, the technical solution of this utility model is: an ammonia-fueled ship exhaust gas denitrification system, comprising: an ammonia-fueled engine, a liquid ammonia storage tank, an ammonia fuel supply system, an ammonia fuel valve group unit, an ammonia treatment system, and an SCR reducing agent supply system. The ammonia supply pipeline of the ammonia-fueled engine adopts a double-walled pipe. The inner pipe of the double-walled pipe is used to transport liquid ammonia, and the outer pipe is connected to the ammonia treatment system through a fan to draw leaked ammonia gas to the ammonia treatment system. The ammonia treatment system is connected to a buffer tank through a fan to pressurize the vented gas and then transport it to the buffer tank. The ammonia treatment system is connected to a reducing agent tank through a pump. The SCR reducing agent supply system is connected to a reducing agent spray gun through the reducing agent tank and the buffer tank to transport the vented gas to the reducing agent spray gun through the SCR reducing agent supply system, thereby assisting in the atomization of ammonia water.

[0006] Furthermore, the ammonia treatment system is also connected to the ammonia fuel storage silo via valves.

[0007] Furthermore, the ammonia treatment system is also equipped with a regulating valve.

[0008] Furthermore, the ammonia fuel engine is connected to the ammonia fuel valve assembly unit via a double-walled pipe, and the ammonia fuel valve assembly unit is connected to the ammonia treatment system and the ammonia fuel supply system.

[0009] Furthermore, the ammonia treatment system adopts a scrubbing tower or dispersion tank structure.

[0010] Furthermore, one or more pumps and reducing agent tanks are provided for storing ammonia water at the required concentration.

[0011] Furthermore, one or more blowers and buffer tanks are provided for storing vent gas from the ammonia treatment system.

[0012] The beneficial effects of this utility model are:

[0013] This invention provides a denitrification system and method for ammonia-fueled ship exhaust gas. It uses ammonia water generated in the ammonia treatment system as the reducing agent in the SCR system, and uses the vent gas from the ammonia treatment system as the auxiliary atomizing gas for the reducing agent. The decomposition of ammonia water into ammonia gas requires only a physical evaporation process, not a chemical decomposition process. Therefore, compared to urea solution, using ammonia water as the reducing agent is more conducive to the full generation of ammonia gas before the SCR catalyst, improving the SCR denitrification efficiency. When the engine is running in diesel mode, the ammonia supply system stops working, and air is used as a supplement to the reducing agent auxiliary atomizing gas. To obtain sufficient ammonia water for the SCR system, a portion of the ammonia BOG from the liquid ammonia storage tank is introduced into the ammonia treatment system to generate ammonia water with a mass fraction of 20% or higher. This invention reuses waste materials from ammonia-fueled engines, saving energy consumption of the auxiliary atomizing compressed air in the SCR system; saving urea reducing agent and improving the denitrification efficiency of the SCR system; and eliminating the need for a urea storage tank, thus saving ship space.

[0014] The core innovation of this utility model is:

[0015] I. System Composition:

[0016] (1) The ammonia treatment system 7 absorbs leaked ammonia gas and purges ammonia gas to generate high-concentration ammonia water;

[0017] (2) The SCR system uses ammonia instead of urea and venting gas instead of compressed air atomization;

[0018] (3) Dynamically adjust the pressure of the ammonia treatment system to maintain ammonia saturation.

[0019] II. Technical Effects:

[0020] (1) Save urea and compressed air, reduce energy consumption;

[0021] (2) Eliminate the need for ammonia wastewater storage and optimize cabin space;

[0022] (3) Improve ammonia generation efficiency and enhance SCR denitrification performance. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the exhaust gas denitrification system for ammonia-fueled ships according to this utility model;

[0024] In the diagram: 1. Ammonia fuel engine; 2. Liquid ammonia storage tank; 3. Ammonia fuel supply system; 4. Ammonia fuel valve unit; 5. Double-walled pipe; 6. Fan; 7. Ammonia treatment system (scrubbing tower / dispersion tank); 8. Pump; 9. Reducing agent tank; 10. Fan; 11. Buffer tank; 12. SCR reducing agent supply system; 13. Reducing agent spray gun; 14. Valve; 15. Control valve; 16. Control valve.

[0025] The arrows indicate the connection relationships of each pipeline. Line A is the ammonia water pipeline, line B is the liquid ammonia pipeline, line C is the ventilation air pipeline, line D is the ammonia evaporation gas pipeline, line E is the ammonia depressurization and nitrogen purging pipeline, line F is the nitrogen purging pipeline, and line G is the air pipeline. Detailed Implementation

[0026] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0027] like Figure 1As shown in the figure, an embodiment of this utility model provides an ammonia-fueled ship exhaust gas denitrification system, including an ammonia-fueled engine 1, a liquid ammonia storage tank 2, an ammonia fuel supply system 3, an ammonia fuel valve assembly unit 4, a double-walled pipe 5, a blower 6, an ammonia treatment system 7, a pump 8, a reducing agent tank 9, a blower 10, a buffer tank 11, an SCR reducing agent supply system 12, a reducing agent spray gun 13, valves 14, regulating valves 15 and 16. The ammonia-fueled ship is equipped with an ammonia-fueled engine 1, an ammonia fuel storage tank 2, an ammonia fuel supply system 3, and an ammonia fuel valve assembly unit 4.

[0028] The ammonia supply pipeline of the ammonia fuel engine 1 adopts a double-walled pipe 5. The inner pipe is used to transport liquid ammonia, and the outer pipe is connected to the ammonia treatment system 7 via a blower 6 to draw leaked ammonia gas to the ammonia treatment system 7. The ammonia treatment system 7 is connected to a buffer tank 11 via a blower 10, which pressurizes the vent gas and delivers it to the buffer tank 11. The buffer tank 11 stores the vent gas from the ammonia treatment system 7 and assists in atomizing ammonia water after pressurization by the blower 10. The reducing agent tank 9 is connected to the ammonia treatment system 7 via a pump 8, and receives ammonia water from the ammonia treatment system 7 via the pump 8. The reducing agent tank 9 and the buffer tank 11 are connected to the reducing agent spray gun 13 via an SCR reducing agent supply system 12. When the SCR system is working, the vent gas is delivered to the reducing agent spray gun 13 through the reducing agent supply system 12 to assist in atomizing ammonia water. This system utilizes waste ammonia gas from the ship to generate high-concentration ammonia water as the SCR reducing agent, saving urea and compressed air and improving denitrification efficiency.

[0029] In addition, the ammonia treatment system 7 is connected to the ammonia fuel storage tank 2 via valve 14. Opening valve 14 allows a portion of the ammonia BOG to be introduced into the ammonia treatment system 7. The ammonia treatment system 7 is also equipped with a regulating valve 15, which determines the working pressure based on the online temperature of the ammonia water detected internally. The opening degree of the regulating valve 15 controls the working pressure of the ammonia treatment system 7, ensuring that the mass fraction of the ammonia water inside the ammonia treatment system 7 can reach 20% or more under the working temperature and working pressure.

[0030] The ammonia fuel engine 1 is connected to the ammonia fuel valve assembly unit 4 via a double-walled pipe 5. The ammonia fuel valve assembly unit 4 is connected to the ammonia treatment system 7 and the ammonia fuel supply system 3. When switching between ammonia and diesel operating modes, the ammonia fuel engine 1 uses nitrogen to purge the ammonia fuel valve assembly unit 4 and the ammonia fuel engine 1 to remove residual ammonia. The ammonia contained in the purging nitrogen is collected by the ammonia treatment system 7.

[0031] Preferably, the ammonia treatment system 7 adopts a scrubbing tower or dispersion tank structure.

[0032] Preferably, one or more pumps 8 and reducing agent tanks 9 are provided for storing ammonia water with the required concentration.

[0033] Preferably, one or more blowers 10 and buffer tanks 11 are provided for storing the vent gas from the ammonia treatment system 7.

[0034] Preferably, the ammonia treatment system 7 is used to absorb leaked ammonia from the double-walled pipe 5 and to purge residual ammonia with nitrogen to generate ammonia water with a mass fraction ≥20%.

[0035] This invention also provides a method for denitrification of ammonia-fueled ship exhaust gas. Based on the aforementioned ammonia-fueled ship exhaust gas denitrification system, ammonia water produced in the ammonia treatment system 8 is used as the reducing agent in the SCR system, and the vent gas from the ammonia treatment system 8 is used as the auxiliary atomizing gas for the reducing agent. The decomposition of ammonia water to generate ammonia gas requires only a physical evaporation process, without a chemical decomposition process. Therefore, compared to urea solution, using ammonia water as the reducing agent is more conducive to the full generation of ammonia gas before the SCR catalyst, thereby improving the SCR denitrification efficiency.

[0036] Diesel SCR systems typically use urea solution as a reducing agent, while ammonia-fueled ships, using liquid ammonia as fuel, are equipped with liquid ammonia storage tanks. These liquid ammonia storage tanks generate ammonia vapor (BOG), which has a high ammonia concentration and purity. This BOG is processed through a BOG recovery and reuse system, which compresses, condenses, liquefies, and separates the BOG for reuse.

[0037] The ammonia supply pipeline of the ammonia fuel engine 1 adopts a double-walled pipe 5. The inner pipe is used to transport liquid ammonia, and the outer pipe is connected to the fan 6. In the event of a leak, the ammonia gas is extracted by the fan 6 and collected in the ventilation air through the ammonia treatment system 7.

[0038] The ammonia treatment system 7 uses water as the medium for absorbing ammonia. When the concentration of ammonia in the water gradually increases and the mass fraction of ammonia reaches 20% or more, the ammonia water in the ammonia treatment system is pumped to the reducing agent tank 9 by pump 8. When the SCR system is working, the ammonia water in the reducing agent tank 9 is pumped to the reducing agent spray gun 13 through the SCR reducing agent supply system 12.

[0039] The vent gas from the ammonia treatment system 7 is pressurized by the blower 10 and then sent to the buffer tank 11. When the SCR system is working, the vent gas is sent to the reducing agent spray gun 13 through the reducing agent supply system 12 to assist in atomizing ammonia water.

[0040] When the engine is running in diesel mode, the ammonia supply system stops operating, valve 16 opens, and blower 10 draws in air as a supplement to the reducing agent atomizing gas. To collect sufficient concentration of ammonia water for SCR system operation, ammonia treatment system 7 opens valve 14 connected to ammonia fuel storage tank 2, allowing a portion of the ammonia BOG to be introduced into ammonia treatment system 7. When the ammonia water mass fraction in ammonia treatment system 7 reaches 20% or higher, valve 14 is closed, and all BOG is then processed by the BOG recovery and reuse system.

[0041] The SCR reducing agent supply system 12 determines the required amount of ammonia water for the SCR system based on the mass fraction and density of ammonia water in the reducing agent tank 9, which are monitored online. The calculation formula is as follows:

[0042]

[0043] m: Ammonia water usage, l / h

[0044] C: NOx concentration in exhaust gas, ppm

[0045] V: Exhaust volumetric flow rate under standard conditions, Nm3 / h

[0046] α: Ammonia-to-nitrogen ratio, dimensionless

[0047] ρ: Density of ammonia solution, g / l

[0048] w: Mass fraction of ammonia solution, %

[0049] The ammonia treatment system 7 determines its required operating pressure (online detected gas pressure) based on its internal operating temperature (the temperature of the ammonia solution monitored online). The operating pressure of the ammonia treatment system 7 is controlled by adjusting the opening of valve 15 to ensure that the mass fraction of ammonia solution inside the ammonia treatment system 7 reaches 20% or higher at the operating temperature and pressure. The relationship between the operating temperature, operating pressure, and mass fraction of ammonia solution in the ammonia treatment system 7 is as follows:

[0050]

[0051] Example: The temperature of the ammonia water in the ammonia treatment system 7 is 25℃, and the density is 0.91 g / cm³. 3 According to the table interpolation, at 25°C and 100 kPa, the ammonia concentration can reach 31.65%, meeting the minimum requirement of 20%. Therefore, regulating valve 15 is fully open, and the ammonia treatment system 7 can meet the ammonia concentration requirements of the SCR system by operating at atmospheric pressure. If the actual ammonia concentration in the ammonia treatment system 7 is much less than 31.65% at this time, it indicates that the ammonia in the ammonia treatment system 7 is not yet saturated and can continue to absorb ammonia. When the ammonia concentration is between 20% and 31.65%, pump 8 is operated in a timely manner according to the SCR system operation to deliver the ammonia to the reducing agent tank for use by the reducing agent supply system 12.

[0052] Example 1:

[0053] (1) Ammonia water generation: Ammonia gas leaking from the double-walled pipe 5 is drawn into the ammonia treatment system 7 by the fan 6 and mixed with the spray water to generate ammonia water. When the mass fraction of the ammonia water reaches 20%, the pump 8 delivers it to the reducing agent tank 9.

[0054] (2) Atomization control: After being pressurized by the blower 10, the vent gas is temporarily stored in the buffer tank 11. When the SCR is running, it is mixed with ammonia water and atomized into the tail gas pipe.

[0055] (3) Diesel mode adaptation: After shutting off the ammonia fuel supply, open valve 16, and blower 10 draws in air as a supplement to the reducing agent atomizing gas. Open valve 14 to introduce BOG into the ammonia treatment system 7 until the ammonia water meets the standard.

[0056] (4) Dynamic adjustment: The ammonia mass fraction can be adjusted to 20% or more by means of temperature sensor and regulating valve 15 (e.g., 31.65% mass fraction at 100kPa when the temperature is 25℃).

Claims

1. An ammonia-fueled ship exhaust gas denitration system characterized by comprising: The application relates to an ammonia fuel engine, a liquid ammonia storage bin, an ammonia fuel supply system, an ammonia fuel valve group unit, an ammonia treatment system, an SCR reducing agent supply system, and a double-wall pipe for ammonia supply of the ammonia fuel engine, wherein the inner pipe of the double-wall pipe is used for conveying liquid ammonia, and the outer pipe is connected with the ammonia treatment system through a fan to suck leaked ammonia gas to the ammonia treatment system; the ammonia treatment system is connected with a buffer tank through the fan to convey the leaked gas to the buffer tank after the leaked gas is pressurized by the fan; the ammonia treatment system is connected with a reducing agent tank through a pump; the SCR reducing agent supply system is connected with a reducing agent spray gun through the reducing agent tank and the buffer tank to convey the leaked gas to the reducing agent spray gun through the SCR reducing agent supply system to assist atomization of ammonia water. The ammonia treatment system is further connected with the ammonia fuel storage bin through a valve.

2. The ammonia-fueled marine vessel exhaust gas denitration system according to claim 1, characterized by, The ammonia treatment system is further provided with an adjusting valve.

3. The ammonia-fueled ship exhaust gas DeNOx system according to claim 1, characterized by, The ammonia fuel engine is connected with the ammonia fuel valve group unit through the double-wall pipe, the ammonia fuel valve group unit is connected with the ammonia treatment system and the ammonia fuel supply system.

4. The ammonia-fueled ship exhaust gas DeNOx system according to claim 1, characterized by, The ammonia treatment system adopts a washing tower or a dispersion tank structure.

5. The ammonia-fueled ship exhaust gas DeNOx system according to claim 1, characterized by, The pump and the reducing agent tank are provided with one or more to store ammonia water with a concentration up to a standard.

6. The ammonia-fueled marine vessel exhaust gas denitration system according to claim 1, characterized by, The fan and the buffer tank are provided with one or more to store the leaked gas of the ammonia treatment system.

7. The ammonia-fueled marine vessel exhaust gas denitration system according to claim 1, characterized by, ​

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