Integrated system for tail gas treatment and waste liquid purification of ammonia fuel ship

Abstract

The invention discloses an ammonia fuel ship tail gas treatment and waste liquid purification integrated system, which is an ammonia fuel ship tail gas integrated treatment and waste liquid nitrate recovery system based on hydrodynamic cavitation and oxidant wet denitration, and is suitable for working conditions of limited ship space, rich waste heat resources and on-site use of seawater. According to the method, NH3, NO, NO2 and N2O in the tail gas can be efficiently and synergistically removed, nitrogen elements are converted into recyclable nitrate crystals, and a green closed loop of pollution control and resource recovery is achieved. According to the method, efficient recycling of nitrate in the tail gas treatment process of the ammonia fuel ship can be achieved, a nitrogen fixation circulating system is formed, the resource utilization rate is increased, the operation cost is reduced, the potential pollution risk of waste liquid to the environment is reduced, and remarkable environmental benefits are achieved. Meanwhile, the device is reasonable in structural design, easy and convenient to operate and easy to integrate and apply in an actual ship tail gas treatment system.

Description

Technical Field

[0001] This invention relates to the field of ammonia fuel ship exhaust gas treatment and resource utilization technology, and in particular to an integrated system for ammonia fuel ship exhaust gas treatment and waste liquid purification. Background Technology

[0002] Ammonia-fueled ships are considered a core pathway for the shipping industry to achieve carbon neutrality. The International Maritime Organization's 2023 Greenhouse Gas Strategy requires a 40% reduction in international shipping carbon intensity by 2030 compared to 2008 levels, and aims to achieve net-zero emissions around 2050. The European Union has included shipping in its carbon emissions trading system and implemented the FuelEU Maritime regulation from 2025, requiring ships to continuously reduce their carbon intensity. Ammonia molecules contain no carbon, do not produce CO2 when burned, and have moderate energy density, are easily liquefied, and are suitable for long-distance ocean transport. Therefore, major engine manufacturers have identified ammonia fuel as the next-generation zero-carbon solution. The first large-bore, low-speed ammonia-fueled engines were delivered in 2025, and the number of ammonia-powered ships in operation and under construction globally is rapidly increasing.

[0003] However, ammonia fuel is effective in addressing CO2 and SO2 emissions. x Along with particulate matter emissions, new challenges in exhaust gas treatment have also arisen. Ammonia has a low combustion temperature and short residence time, resulting in unburned NH3 reaching thousands of ppm. Because NH3 is less dense than air, it easily diffuses and reacts with acidic gases in the atmosphere to form secondary aerosols, exacerbating PM2.5 pollution in port areas. 2.5 The pollution and reduced visibility are problems, and it is also highly irritating to the respiratory tract, eyes, and skin of crew members. Ammonia has an ample source of nitrogen; during the low-temperature combustion stage, fuel-type NO is produced, and in the high-temperature zone, thermal NO is generated, resulting in an overall NO content of [missing information]. x Increased emissions. While selective catalytic reduction can reduce NO... x However, the pure composition and extremely low sulfur content of ammonia fuel exhaust gas lead to a decrease in the acidity of the catalyst surface, an active side reaction pathway, and a significant increase in N2O generation. This potent greenhouse gas, with a global warming potential nearly three hundred times that of CO2, directly weakens the "zero carbon" advantage of ammonia.

[0004] Current ship exhaust aftertreatment technologies are inadequate to address this issue. The exhaust temperature after the turbocharger of marine low-speed engines is often below 250℃, resulting in insufficient low-temperature activity of SCR (Selective Catalytic Reduction). After urea injection, NH3 escapes and combines with N2O byproducts, forming a "NO3-free" mixture. xHowever, this increases the vicious cycle of "N2O / NH3," and the catalytic reduction unit is large and has high back pressure, which is detrimental to engine room layout and fuel consumption. Wet scrubbing is effective against SO2 and particulate matter, but almost ineffective against NO. Oxidation and absorption of NO alone requires high-concentration oxidants, which are costly and prone to rebound due to the presence of NO2 byproducts. Furthermore, the waste liquid contains pollutants such as chloride ions, heavy metals, and polycyclic aromatic hydrocarbons. Port receiving facilities are limited, and there is a problem of secondary transfer of pollution from the atmosphere to the ocean. Dry or semi-dry desulfurization and denitrification equipment has a large footprint and high investment, and its reliability is poor under ship space and rolling conditions. Currently, it is only piloted on special ship types such as luxury passenger ships or LNG ships. More importantly, existing wet systems directly discharge nitrates into the sea, which wastes nitrogen resources and may cause eutrophication. Ships lack compact, low-energy-consumption processes to recover nitrates from high-salt waste liquids, leading to a secondary transfer of pollution from treatment to treatment.

[0005] Therefore, the exhaust gas composition of ammonia-fueled ships has shifted from "complex and multi-component" to "high NH3 and high NO". x Due to its high "high" and "high N2O" characteristics, traditional "desulfurization + SCR" or single wet scrubbing methods cannot achieve efficient and synergistic removal of NH3, NO, NO2, and N2O simultaneously, and also waste the amino nitrogen element that can be efficiently utilized. Summary of the Invention

[0006] This invention discloses an integrated system for treating ammonia-fueled ship exhaust gas and purifying waste liquid to overcome the above-mentioned problems.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows: An integrated system for treating exhaust gas and purifying waste liquid from ammonia-fueled ships includes: an oxidant preparation tank, a hydraulic cavitation reactor, a gas-liquid separator, a heat exchange spiral coil, an atmospheric pressure evaporator, a cold desorption tube, and a nitrate recovery chamber. The oxidant preparation tank is equipped with a seawater inlet and an oxidant inlet. The outlet of the oxidant preparation tank is connected to a hydraulic cavitation reactor. The hydraulic cavitation reactor is equipped with a ship exhaust gas inlet to obtain a nitrate solution based on the ship exhaust gas, seawater, and oxidant. The outlet of the hydraulic cavitation reactor is connected to the inlet of a gas-liquid separator. The liquid phase outlet of the gas-liquid separator is connected to the oxidant preparation tank; a nitrate enrichment sensor is installed inside the gas-liquid separator to obtain the concentration of the nitrate solution; the nitrate-rich solution outlet of the gas-liquid separator is connected to the inlet of the heat exchange spiral coil; when the concentration of the nitrate solution is higher than the set nitrate enrichment threshold, the nitrate solution flows into the heat exchange spiral coil. The heat exchange spiral coil is wound around the outer wall of the main unit's exhaust pipe; the outlet of the heat exchange spiral coil is connected to the inlet of the atmospheric pressure evaporator and also connected to the inlet of the heat exchange spiral coil through a reflux branch; a temperature sensor is installed at the outlet of the heat exchange spiral coil to obtain the temperature of the soluble nitrate solution. When the temperature of the nitrate solution is not higher than the set temperature threshold, the nitrate solution returns to the inlet of the heat exchange spiral coil through the reflux branch; when the temperature of the nitrate solution is higher than the set temperature threshold, it enters the atmospheric pressure evaporator. The outlet of the atmospheric pressure evaporator is connected to the inlet of the cold precipitate tube; the nitrate recovery chamber is located below the outlet of the cold precipitate tube and is connected to the outlet of the cold precipitate tube. The nitrate enrichment sensor and temperature sensor are both connected to the CPU control unit.

[0008] Furthermore, the gas-liquid separator is provided with an exhaust gas outlet at the top, and a multi-component flue gas sensor is provided at the exhaust gas outlet.

[0009] Furthermore, the bottom of the atmospheric pressure evaporator is provided with a microporous aeration ring, which is connected to a marine low-pressure blower through a duct.

[0010] Furthermore, the atmospheric pressure evaporator is equipped with a densitometer.

[0011] Furthermore, the outlet of the cold precipitator tube is equipped with a turbidity meter and a crystal slurry discharge valve. Both the turbidity meter and the crystal slurry discharge valve are connected to the CPU control unit so that the crystal slurry discharge valve is opened when the monitoring data of the turbidity meter is higher than or equal to a set threshold.

[0012] Furthermore, the nitrate recovery chamber is equipped with a conveyor belt that transports nitrates from a lower to a higher position. The conveyor belt is located below the outlet of the cold precipitation tube; a partition wall is provided below the conveyor belt to divide the nitrate recovery chamber into a crystal compartment and a solution compartment; the crystal compartment is located on the higher side of the conveyor belt, and the solution compartment is located on the lower side of the conveyor belt. The top of the partition wall is provided with an elastic soft scraper, and the top of the elastic soft scraper abuts against the bottom of the conveyor belt.

[0013] Furthermore, the conveying surface of the conveyor belt is made of polypropylene monofilament satin fabric.

[0014] Furthermore, a nitrate ion concentration sensor is installed inside the nitrate recovery chamber to obtain the nitrate ion concentration in the nitrate solution; The nitrate recovery chamber is equipped with a filtrate circulation and purification branch and a drainage branch at the filtrate outlet. The other end of the filtrate circulation and purification branch is connected to the inlet of the heat exchange spiral coil; a circulation pump and a fourth electric regulating valve are installed on the filtrate circulation and purification branch; an electric valve is installed on the discharge branch. The nitrate ion concentration sensor, the fourth electric regulating valve, and the electric valve are all connected to the CPU control unit. When the nitrate ion concentration in the nitrate recovery chamber is higher than the set threshold, the nitrate solution in the nitrate recovery chamber flows into the heat exchange spiral coil through the filtrate circulation purification branch via the circulation pump and the fourth electric regulating valve. When the nitrate ion concentration in the nitrate recovery chamber is not higher than the set threshold, the nitrate solution in the nitrate recovery chamber is discharged through the drainage branch.

[0015] Furthermore, the oxidant preparation tank is equipped with a folding blade stirrer, and the stirring speed is steplessly adjusted by the CPU control unit according to the type and concentration signal of the oxidant.

[0016] Beneficial Effects: This invention provides an integrated system for treating ammonia-fueled ship exhaust gas and purifying wastewater. It is an integrated system for treating ammonia-fueled ship exhaust gas and recovering nitrates from wastewater based on hydrodynamic cavitation synergistic oxidant wet denitrification. Suitable for shipboard conditions with limited space, abundant waste heat resources, and readily available seawater, this system achieves efficient synergistic removal of NH3, NO, NO2, and N2O from exhaust gas, converting nitrogen into recyclable nitrate crystals, thus realizing a green closed loop of pollution control and resource recovery. This invention enables efficient recovery and utilization of nitrates during the treatment of ammonia-fueled ship exhaust gas, forming a nitrogen-fixing cycle system. This not only improves resource utilization and reduces operating costs but also reduces the potential environmental pollution risk of wastewater, resulting in significant environmental benefits. Furthermore, this invention has a reasonable structural design, is easy to operate, and is readily integrated and applied in actual ship exhaust gas treatment systems. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the overall structure of the integrated system for ammonia-fueled ship exhaust gas treatment and waste liquid purification according to the present invention. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] This embodiment introduces an integrated system for treating exhaust gas and purifying waste liquid from ammonia-fueled ships, such as... Figure 1 As shown, it includes: oxidant preparation tank 1, hydraulic cavitation reactor 5, gas-liquid separator 6, heat exchange spiral coil 10, atmospheric pressure evaporator 13, cold precipitation tube 18, and nitrate recovery chamber 19. The oxidant preparation tank 1 is provided with a seawater inlet 2 and an oxidant inlet 3. The outlet of the oxidant preparation tank 1 is connected to the hydraulic cavitation reactor 5. The hydraulic cavitation reactor 5 is provided with a ship exhaust gas inlet 7 to obtain a nitrate solution based on the ship exhaust gas, seawater and oxidant. A metering pump 29 is provided at the oxidant inlet 3. The outlet of the hydraulic cavitation reactor 5 is connected to the inlet of the gas-liquid separator 6. The liquid phase outlet 61 of the gas-liquid separator 6 is connected to the oxidant preparation tank 1; a nitrate enrichment sensor 11 is installed inside the gas-liquid separator 6 to obtain the concentration of the nitrate solution; the nitrate-rich solution outlet 62 of the gas-liquid separator 6 is connected to the inlet of the heat exchange spiral coil 10; an electric regulating valve 9 is installed between the nitrate-rich solution outlet 62 of the gas-liquid separator 6 and the heat exchange spiral coil 10, and the electric regulating valve 9 is opened when the nitrate concentration signal obtained by the nitrate enrichment sensor 11 is higher than the set concentration threshold. The heat exchange spiral coil 10 is wound around the outer wall of the main unit's exhaust pipe; the outlet of the heat exchange spiral coil 10 is connected to the inlet of the atmospheric pressure evaporator 13, and is also connected to the inlet of the heat exchange spiral coil 10 through a reflux branch; a temperature sensor 12 is installed at the outlet of the heat exchange spiral coil 10 to obtain the temperature of the soluble nitrate solution. When the temperature of the nitrate solution is not higher than the set temperature threshold, the nitrate solution returns to the inlet of the heat exchange spiral coil 10 through the reflux branch; when the temperature of the nitrate solution is higher than the set temperature threshold, it enters the atmospheric pressure evaporator 13. The outlet of the atmospheric pressure evaporator 13 is connected to the inlet of the cold precipitate tube 18; the nitrate recovery chamber 19 is located below the outlet of the cold precipitate tube 18 and is connected to the outlet of the cold precipitate tube 18.

[0021] Specifically, the oxidant is fed into the oxidant preparation tank 1 via metering pump 29, and its outlet is connected to the liquid inlet of the hydraulic cavitation reactor 5 via circulation pump 4, forming a seawater-oxidant mixture in the oxidant preparation tank. The gas-liquid mixture outlet of the hydraulic cavitation reactor 5 is connected to the inlet of the gas-liquid separator 6, and the liquid phase outlet 61 at the bottom of the gas-liquid separator 6 returns to the oxidant preparation tank 1 via a return pipeline, forming an oxidation-separation circulation loop.

[0022] Specifically, the oxidant solution is pumped from the oxidant preparation tank 1 to the hydraulic cavitation reactor via the circulation pump 4. In this embodiment, the hydraulic cavitation reactor 5 is a Venturi tube structure. Based on the traditional Venturi tube structure, a small hole is opened at the top to introduce ship exhaust gas, so that the ship exhaust gas and seawater-oxidant mixture are fully mixed in the cavitation jet zone of the hydraulic cavitation reactor. Cavitation occurs in the high-speed zone at the throat. The local high temperature and pressure generated by the collapse of cavitation bubbles and strong oxidizing free radicals such as •OH and •ClO are used to simultaneously oxidize ammonia, nitrogen oxides and nitrous oxide in the exhaust gas into soluble nitrates. This can improve the denitrification efficiency of the oxidant, realize the simultaneous removal of four nitrogen-containing pollutants by a single oxidant, and significantly reduce the concentration of the oxidant used. The solution after the reaction is returned to the oxidation reaction tank for circulation treatment. After the oxidant in the solution has completely reacted, it is transported to the subsequent treatment unit. The nitrate-rich mother liquor is sent to the heat exchange spiral coil to be preheated using the waste heat of the flue. After passing through the evaporator, the nitrate concentration is accelerated to enrich, creating favorable conditions for the crystallization process. The mother liquor after evaporation is cooled by heat exchange with seawater through the lower cooling tube. This helps nitrates crystallize out of the waste liquor while simultaneously lowering its temperature. The crystals and solution are separated by a filter cloth and conveyor belt. The solution returns to the preheating stage for recycling, while the crystals are collected in a crystallization container for subsequent washing and drying.

[0023] Preferably, the gas-liquid separator 6 is provided with an exhaust gas outlet 63 at the top, and a flue gas multi-component sensor 8 is provided at the exhaust gas outlet 63.

[0024] Specifically, the gas-liquid separator 6 separates the treated, pollution-free ship exhaust gas that meets emission standards from the reaction solution. A tail gas outlet 63 is located at the top, discharging the treated exhaust gas through an exhaust port. A multi-component flue gas sensor 8 is installed; when the concentration of nitric oxide, nitrogen dioxide, ammonia, or nitrous oxide in the exhaust gas exceeds a set value, the system immediately issues an alarm signal, prompting the crew to check the equipment. A nitrate-rich solution outlet 62 is located at the bottom, connected to the inlet of the heat exchange spiral coil 10 via an electric regulating valve 9. A nitrate enrichment sensor 11 is installed inside the gas-liquid separator 6. When the concentration of the nitrate solution is not higher than the set nitrate enrichment threshold, the reaction solution returns to the oxidant preparation tank 1 for circulation and nitrate enrichment. The nitrate enrichment sensor 11 is signal-connected to the CPU control unit 25, which controls the opening and closing of the electric regulating valve 9 based on the enrichment signal. When the concentration of the nitrate solution is higher than the set nitrate enrichment threshold, the electric regulating valve 9 is opened, and the nitrate solution flows into the heat exchange spiral coil 10. Specifically, in this embodiment, the heat exchange spiral coil enhances heat exchange by increasing the contact area; it is wound around the outer wall of the main unit's exhaust pipe, and a high-temperature resistant and corrosion-resistant coating is applied to the contact surface. Taking advantage of the characteristic that the solubility of nitrates increases significantly with temperature, the waste liquid is preheated to 80–95°C (sub-boiling state below the normal boiling point), which not only fully recovers waste heat, but also ensures that the nitrates are completely dissolved, preventing pipe blockage due to premature crystallization, and reducing the heat load of the subsequent evaporation unit.

[0025] Preferably, the bottom of the atmospheric pressure evaporator 13 is provided with a microporous aeration ring 14, which is connected to the marine low-pressure blower 15 through a duct.

[0026] Specifically, the heat exchange spiral coil 10 is wound around the outer wall of the main engine exhaust pipe, and a temperature sensor 12 is installed at the outlet. After the soluble nitrate solution is heated, it enters the atmospheric pressure evaporator 13. The bottom of the atmospheric pressure evaporator 13 is provided with a microporous aeration ring 14, which is connected to a marine low-pressure fan 15 through a duct to agitate the solution in the tank and assist in evaporation. The outer wall of the atmospheric pressure evaporator 13 is provided with a heating jacket, the inlet of which is connected to the main engine cylinder liner cooling water outlet 16, using the waste heat of the main engine cylinder liner cooling water as a heat source to continuously heat the solution in the tank. In this embodiment, the outer wall of the heat exchange spiral coil 10 is coated with a high-temperature resistant and corrosion-resistant coating to improve heat exchange efficiency and prevent corrosion.

[0027] Specifically, the atmospheric pressure evaporator 13 uses an ambient temperature evaporation tube to guide the heated waste liquid into a box with an open top and a conical bottom for water evaporation. A shallow water layer and microporous aeration rings are installed at the bottom of the box. The shallow water layer shortens the heat transfer path from the bottom to the liquid surface, enabling rapid heating and timely evaporation. The bubbles generated by the microporous aeration continuously carry the hot water from the bottom to the liquid surface during their ascent, allowing unevaporated water to flow back to the bottom and continue absorbing heat. After the bubbles burst at the liquid surface, they expand the gas-liquid interface area, accelerating the vaporization of water molecules. The main engine cylinder liner cooling water is used as a heat source to reheat the solution to 75-80°C. Maintaining the solution temperature close to the saturation temperature under atmospheric pressure, the nitrate concentration in the waste liquid gradually increases, approaching critical supersaturation, creating conditions for rapid nucleation during subsequent cooling.

[0028] Specifically, the outlet of the atmospheric pressure evaporator 13 is connected to the inlet of the cold precipitator tube 18 via the second electric regulating valve 17. The cold precipitator tube 18 has a double-layer sleeve structure, with the inner tube having a diameter greater than 1.5 times the median particle size of the crystals but less than 5 mm to ensure smooth passage of the crystal slurry and avoid blockage. The outer tube is circulated with low-temperature seawater (32), which exchanges heat with the seawater to cool the evaporated waste liquid. This achieves rapid cooling and crystallization of the concentrate. Utilizing the characteristic that the solubility of nitrate decreases sharply with decreasing temperature, it helps nitrate crystallize out of the waste liquid, while simultaneously reducing the temperature of the waste liquid to provide a suitable temperature environment for subsequent separation operations. A seawater temperature sensor 30 is installed at the seawater inlet of the outer tube of the cold precipitator tube 18. The CPU control unit 25 automatically adjusts the opening of the corresponding third electric regulating valve 31 according to the seawater temperature (32) to maintain the required cooling temperature difference.

[0029] Preferably, the outlet of the cold precipitator tube 18 is equipped with a turbidity meter 27 and a crystal slurry discharge valve 28. Both the turbidity meter 27 and the crystal slurry discharge valve 28 are connected to the CPU control unit 25 so that when the monitoring data of the turbidity meter 27 is higher than or equal to a set threshold, the crystal slurry discharge valve 28 is opened.

[0030] Preferably, the atmospheric pressure evaporator 13 is equipped with a densitometer 26; the CPU control unit 25 determines whether the solution has reached a crystallizable supersaturated state based on the signal from the densitometer 26, and adjusts the evaporation time or heating power accordingly, as well as controls the opening and closing of the second electric regulating valve 17.

[0031] Preferably, the nitrate recovery chamber 19 is equipped with a conveyor belt 20, which transports nitrates from a lower to a higher position. The conveyor belt 20 is located below the outlet of the cold precipitation tube 18; a partition wall 221 is provided below the conveyor belt 20 to divide the nitrate recovery chamber 19 into a crystal compartment 222 and a solution compartment 223; the crystal compartment is located on the higher side of the conveyor belt 20, and the solution compartment 223 is located on the lower side of the conveyor belt 20. The top of the partition wall 221 is provided with an elastic soft scraper 22, and the top of the elastic soft scraper 22 abuts against the bottom of the conveyor belt 20.

[0032] Preferably, the conveying surface of the conveyor belt 20 is made of polypropylene monofilament satin fabric.

[0033] Specifically, the outlet of the cold separation pipe 18 is connected to the inlet of the nitrate recovery chamber 19. An inclined conveyor belt 20 is installed inside the nitrate recovery chamber 19, moving upwards at an angle. Gravity helps retain as much water as possible within the container. A vacuum pump is installed below the conveyor belt to accelerate water filtration and improve separation efficiency. Above the conveyor belt, most crystals fall into the crystal compartments 222 due to gravity. A small portion of crystals adhering to the conveyor belt 20 falls into the crystal compartments 222 under the action of the flexible scraper 22, facilitating subsequent washing and drying operations. The filtered liquid then returns to the heating pipe to continue the recycling process.

[0034] Specifically, the surface of the conveyor belt 20 is made of hydrophilic synthetic fiber monofilament woven fabric, which serves as the filter cloth material. The filter cloth can effectively filter out water, leaving crystals on it. Its nominal pore size is smaller than the median particle size of the crystals, allowing the filtrate to pass through while the crystals are trapped. The vacuum pump 21 is connected to the cavity below the filter cloth in the nitrate recovery chamber 19 to accelerate water filtration. A crystal compartment 222 is provided below the high end of the conveyor belt 20, and an elastic soft scraper 22 that abuts against the conveyor belt 20 is used to scrape residual crystals into the crystal compartment 222.

[0035] Preferably, a nitrate ion concentration sensor 33 is installed in the solution compartment 223 within the nitrate recovery chamber 19 to obtain the nitrate ion concentration in the nitrate solution; The nitrate recovery chamber 19 is equipped with a filtrate circulation purification branch and a filtrate discharge branch at the filtrate outlet. The other end of the filtrate circulation and purification branch is connected to the inlet of the heat exchange spiral coil 10; a circulation pump 23 and a fourth electric regulating valve 34 are provided on the filtrate circulation and purification branch; an electric valve 24 is provided on the discharge branch. The nitrate ion concentration sensor 33, the fourth electric regulating valve 34, and the electric valve 24 are all connected to the CPU control unit 25. When the nitrate ion concentration in the nitrate recovery chamber 19 is higher than the set threshold, the nitrate solution in the nitrate recovery chamber 19 flows into the heat exchange spiral coil 10 through the filtrate circulation purification branch via the circulation pump 23 and the fourth electric regulating valve 34. When the nitrate ion concentration in the nitrate recovery chamber 19 is not higher than the set threshold, the nitrate solution in the nitrate recovery chamber 19 is discharged through the drainage branch.

[0036] Specifically, the filtrate outlet at the bottom of the nitrate recovery chamber 19 is connected to the inlet of the heat exchange spiral coil 10 via a circulation pump 23 to form a filtrate circulation and purification loop; the filtrate outlet pipeline is provided with a separate branch, which discharges waste liquid with nitrate concentration below the threshold via an electrically controlled valve 24. The nitrate recovery chamber 19 is equipped with a nitrate ion concentration sensor 33 at the filtrate outlet. The CPU control unit 25 adjusts the opening of the fourth electric regulating valve 34 according to the nitrate concentration signal of the filtrate to give priority to the use of the mother liquor.

[0037] Specifically, in this embodiment, the CPU control unit 25 is connected to the flue gas multi-component sensor 8, temperature sensor 12, density meter 26, turbidity meter 27, nitrate enrichment sensor 11, metering pump 29, circulation pump 4 and each electric regulating valve 9 to realize automatic closed-loop control of the entire process of oxidant addition, heating, evaporation and concentration, cooling and crystallization, filtration and separation, circulation concentration and liquid discharge.

[0038] Preferably, the oxidant preparation tank 1 is equipped with a folding blade stirrer 35, and the stirring speed is steplessly adjusted by the CPU control unit 25 according to the type and concentration signal of the oxidant.

[0039] This embodiment is designed for ammonia-fueled ships with "high NH3, high NO3" conditions. X Given the characteristics of "high N2O" exhaust gas, the proposed "integrated treatment-waste liquid resource utilization" coupled system integrates hydraulic cavitation synergistic oxidant wet denitrification and nitrate recovery processes into the same process, achieving simultaneous and efficient removal of NH3, NO, NO2, and N2O from the exhaust gas, and converting nitrogen into recyclable nitrate crystals, thus creating a green closed loop of "pollution control-nitrogen fixation-reuse".

[0040] This embodiment combines oxidant-assisted hydraulic cavitation with onboard nitrate crystallization recovery to achieve simultaneous oxidation of four nitrogen-containing pollutants (NH3, NO, NO2, and N2O) using a single oxidant. A closed-loop nitrogen resource system is formed through evaporation-cold precipitation-filtration-recirculation concentration. This invention offers high ammonia ion removal efficiency, eliminates the need for SCR and urea, and reduces reagent usage compared to conventional wet processes.

[0041] This embodiment uses seawater as the medium, waste heat as the power source, and cavitation as the enhancement method throughout the entire process, with no land-based chemical waste discharge, which conforms to the IMO's "zero pollution" direction; The ammonia-fueled ship of this embodiment can realize an integrated exhaust gas treatment and nitrate recovery unit, making full use of the ship's abundant seawater resources and converting exhaust nitrogen into recyclable nitrate crystals. Compared with traditional methods such as SCR, it occupies less space, consumes less energy, can operate continuously with the ship, and provides the shipping industry with a new green technology route of "pollution → nitrogen fixation → fertilizer → ecology".

[0042] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An integrated system for treating ammonia-fueled ship exhaust gas and purifying waste liquid, characterized in that, include: Oxidizing agent preparation tank (1), hydraulic cavitation reactor (5), gas-liquid separator (6), heat exchange spiral coil (10), atmospheric pressure evaporator (13), cold precipitator (18), nitrate recovery chamber (19). The oxidant preparation tank (1) is provided with a seawater inlet (2) and an oxidant inlet (3). The outlet of the oxidant preparation tank (1) is connected to the hydraulic cavitation reactor (5). The hydraulic cavitation reactor (5) is provided with a ship exhaust gas inlet (7) to obtain a nitrate solution based on the ship exhaust gas, seawater and oxidant. The outlet of the hydraulic cavitation reactor (5) is connected to the inlet of the gas-liquid separator (6). The liquid phase outlet (61) of the gas-liquid separator (6) is connected to the oxidant preparation tank (1); a nitrate enrichment sensor (11) is installed inside the gas-liquid separator (6) to obtain the concentration of the nitrate solution; the nitrate-rich solution outlet (62) of the gas-liquid separator (6) is connected to the inlet of the heat exchange spiral coil (10); when the concentration of the nitrate solution is higher than the set nitrate enrichment threshold, the nitrate solution flows into the heat exchange spiral coil (10). The heat exchange spiral coil (10) is wound around the outer wall of the main exhaust pipe; the outlet of the heat exchange spiral coil (10) is connected to the inlet of the atmospheric pressure evaporator (13) and to the inlet of the heat exchange spiral coil (10) through a reflux branch; a temperature sensor (12) is provided at the outlet of the heat exchange spiral coil (10) to obtain the temperature of the soluble nitrate solution. When the temperature of the nitrate solution is not higher than the set temperature threshold, the nitrate solution returns to the inlet of the heat exchange spiral coil (10) through the reflux branch. When the temperature of the nitrate solution is higher than the set temperature threshold, it enters the atmospheric pressure evaporator (13). The outlet of the atmospheric pressure evaporator (13) is connected to the inlet of the cold precipitate tube (18); the nitrate recovery chamber (19) is located below the outlet of the cold precipitate tube (18) and is connected to the outlet of the cold precipitate tube (18); The nitrate enrichment sensor (11) and temperature sensor (12) are both connected to the CPU control unit (25).

2. The integrated system for treating ammonia-fueled ship exhaust gas and purifying waste liquid according to claim 1, characterized in that, The gas-liquid separator (6) is provided with an exhaust gas outlet (63) at the top, and a flue gas multi-component sensor (8) is provided at the exhaust gas outlet (63).

3. The integrated system for treating ammonia-fueled ship exhaust gas and purifying waste liquid according to claim 1, characterized in that, The bottom of the atmospheric pressure evaporator (13) is provided with a microporous aeration ring (14), which is connected to a marine low-pressure blower (15) through a duct.

4. The integrated system for treating ammonia-fueled ship exhaust gas and purifying waste liquid according to claim 1, characterized in that, The atmospheric pressure evaporator (13) is equipped with a hydrometer (26).

5. The integrated system for treating ammonia-fueled ship exhaust gas and purifying waste liquid according to claim 1, characterized in that, The outlet of the cold precipitator tube (18) is equipped with a turbidity meter (27) and a crystal slurry discharge valve (28). Both the turbidity meter (27) and the crystal slurry discharge valve (28) are connected to the CPU control unit (25) so that when the monitoring data of the turbidity meter (27) is higher than or equal to the set threshold, the crystal slurry discharge valve (28) is opened.

6. The integrated system for treating ammonia-fueled ship exhaust gas and purifying waste liquid according to claim 1, characterized in that, The nitrate recovery chamber (19) is equipped with a conveyor belt (20) that transports nitrates from a low position to a high position. The conveyor belt (20) is located below the outlet of the cold precipitation tube (18); a partition wall (221) is provided below the conveyor belt (20) to divide the nitrate recovery chamber (19) into a crystal compartment (222) and a solution compartment (223); the crystal compartment is located on the higher side of the conveyor belt (20), and the solution compartment (223) is located on the lower side of the conveyor belt (20); The partition wall (221) is provided with an elastic soft scraper (22) at the top, and the top of the elastic soft scraper (22) abuts against the bottom of the conveyor belt (20).

7. The integrated system for treating ammonia-fueled ship exhaust gas and purifying waste liquid according to claim 6, characterized in that, The conveying surface of the conveyor belt (20) is made of polypropylene monofilament satin fabric.

8. The integrated system for treating ammonia-fueled ship exhaust gas and purifying waste liquid according to claim 1, characterized in that, The nitrate recovery chamber (19) is equipped with a nitrate ion concentration sensor (33) to obtain the nitrate ion concentration in the nitrate solution; The nitrate recovery chamber (19) is equipped with a filtrate circulation purification branch and a drainage branch at the filtrate outlet; The other end of the filtrate circulation purification branch is connected to the inlet of the heat exchange spiral coil (10); a circulation pump (23) and a fourth electric regulating valve (34) are provided on the filtrate circulation purification branch; an electric valve (24) is provided on the discharge branch. The nitrate ion concentration sensor (33), the fourth electric regulating valve (34), and the electric valve (24) are all connected to the CPU control unit (25). When the nitrate ion concentration in the nitrate recovery chamber (19) is higher than the set threshold, the nitrate solution in the nitrate recovery chamber (19) flows into the heat exchange spiral coil (10) through the filtrate circulation purification branch via the circulation pump (23) and the fourth electric regulating valve (34). When the nitrate ion concentration in the nitrate recovery chamber (19) is not higher than the set threshold, the nitrate solution in the nitrate recovery chamber (19) is discharged through the drainage branch.

9. The integrated system for treating ammonia-fueled ship exhaust gas and purifying waste liquid according to claim 1, characterized in that, The oxidant preparation tank (1) is equipped with a folding blade stirrer (35), and the stirring speed is steplessly adjusted by the CPU control unit (25) according to the oxidant type and concentration signal.

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