A ship exhaust gas desulfurization, denitrification and decarbonization integrated treatment method and system

Abstract

This invention discloses an integrated treatment method and system for desulfurization, denitrification, and decarbonization of ship exhaust gas, belonging to the field of ship exhaust gas treatment technology. The invention adopts a modular closed-loop integrated design, with a compact structure adapted to ship scenarios. The various units operate smoothly together, ensuring stable operation during continuous ship navigation. It can simultaneously complete integrated purification of desulfurization, denitrification, and decarbonization. Furthermore, the treatment method utilizes ship-produced seawater desalination wastewater and ballast water electrolyte as raw materials, eliminating the need for large-scale external purchases of reagents, thus reducing costs and the burden of wastewater disposal. A dual-force centrifuge separates the solids, allowing for centralized collection of the solid precipitate, while the liquid phase is either recycled as needed or discharged into the sea after meeting standards, resulting in no secondary pollution and compliance with maritime regulations. The system is equipped with a regeneration unit for targeted recovery and concentration of the absorbent, utilizing waste heat from boiler exhaust gas for heating, reducing absorbent loss and improving economic efficiency.

Description

Technical Field

[0001] This invention belongs to the field of marine exhaust gas treatment technology, and more specifically, relates to an integrated treatment method and system for desulfurization, denitrification and decarbonization of marine exhaust gas. Background Technology

[0002] With the rapid development of the global shipping industry, the environmental pollution caused by ship exhaust emissions has become increasingly prominent. At present, the field of ship exhaust treatment mostly adopts single pollutant removal technology, that is, desulfurization, denitrification and decarbonization are treated separately. This has the disadvantages of large equipment footprint, high investment cost, high operating energy consumption and complex process flow. Moreover, each treatment system is independent of each other and cannot achieve coordinated and efficient treatment, which is difficult to adapt to the limited space and energy consumption budget of ships.

[0003] Furthermore, in terms of desulfurization and denitrification technologies, existing technologies mostly use traditional absorbents. These absorbents require additional procurement and storage, increasing ship operating costs and storage pressure. Moreover, the utilization rate of absorbents is low, easily leading to secondary pollution. Additionally, absorbent regeneration is difficult, and in most cases, recycling is not possible, further increasing operating costs. Regarding decarbonization technology, existing ship decarbonization methods mostly employ simple seawater absorption. Seawater has a limited capacity to absorb carbon dioxide, resulting in low decarbonization efficiency and underutilization of ship resources, leading to resource waste. Furthermore, existing decarbonization technologies are poorly integrated with desulfurization and denitrification technologies, failing to achieve integrated and coordinated treatment, resulting in low overall treatment efficiency. Simultaneously, ships generate large amounts of seawater desalination waste liquid and ballast water electrolyte during navigation. Currently, these waste liquids are mostly discharged directly, not only wasting resources but also potentially polluting the marine environment. Current ship exhaust gas desulfurization, denitrification, and decarbonization technologies suffer from numerous drawbacks, including complex equipment, high costs, high energy consumption, low resource utilization, insufficient pollutant removal efficiency, and inability to achieve integrated and coordinated treatment. There is an urgent need for an integrated desulfurization, denitrification, and decarbonization technology that can rely on the ship's own resources, has a simple process, low cost, and is highly efficient and environmentally friendly, in order to solve the above-mentioned defects of existing technologies. Summary of the Invention

[0004] This invention addresses the technical problems existing in the prior art by providing an integrated method and system for desulfurization, denitrification, and decarbonization of ship exhaust gas.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: This invention first provides an integrated treatment method for desulfurization, denitrification, and decarbonization of ship exhaust gas, comprising the following steps: S1. Preparation of compound absorbent: Seawater desalination waste liquid and ballast water electrolyte are injected into the buffer tank at a 1:1 volume ratio, and then mixed with DMSO and EDTA-Fe. 2+They are injected together into the tube side of the hollow fiber membrane contactor to form a compound absorbent; S2. Desulfurization and denitrification treatment: Ship exhaust gas is pressurized and then introduced into the shell side of the hollow fiber membrane contactor, where it undergoes mass transfer contact with the composite absorbent on the pipe side. Sulfur oxides and EDTA-Fe2+ are selectively absorbed through DMSO. 2+ Nitrogen oxides are captured by complexation and converted into solid precipitates by calcium and magnesium ions in seawater desalination wastewater. After centrifugation, the liquid phase is recycled and reused, and the solid precipitate is collected in the residue tank. S3. Decarbonization treatment: The waste gas after desulfurization and denitrification is transported to the supergravity reactor and undergoes a mass transfer reaction with the seawater desalination waste liquid. The supergravity field atomizes the seawater desalination waste liquid into 50-80μm microdroplets. Calcium and magnesium ions react with carbon dioxide to generate solid precipitates. After centrifugation, part of the liquid phase meets the standards and is discharged into the sea, while the other part is recycled. S4. Absorbent Regeneration: EDTA-Fe is concentrated using nanofiltration membrane separation. 2+ DMSO is concentrated by vacuum distillation, and the concentrated absorbent is refluxed back to the hollow fiber membrane contactor to achieve recycling.

[0006] Preferably, in S2, DMSO in the compound absorbent selectively absorbs sulfur oxides in ship exhaust gas through dipole-dipole interactions. EDTA-Fe in compound absorbent 2+ By forming stable complexes with nitrogen oxides in ship exhaust gas through complexation, nitrogen oxides are transferred from the gas phase to the liquid phase, achieving efficient capture of nitrogen oxides. Using seawater electrolyzed water generated by electrolyzing ballast water as a reducing agent, the hydroxyl radicals generated by electrolysis reduce ferric ions to ferrous ions; Using the desalination wastewater generated by the seawater desalination plant as a precipitant, the high concentration of Mg in it is utilized. 2+ With Ca 2 + The ionized nitrogen oxides and sulfur oxides in the liquid phase are converted into solid precipitates, thus completing the removal process.

[0007] Preferably, the nanofiltration membrane separation method includes: Select the EDTA-Fe content discharged from the tube-side outlet of the hollow fiber membrane contactor. 2+ The compound absorbent is adjusted to alkaline pH by an alkaline adjuster, and then suspended impurities are removed. The compound absorbent after removing impurities is pumped to a nanofiltration membrane separator via a pressurized pump. The nanofiltration membrane separator uses a negatively charged nanofiltration membrane with a molecular weight cutoff of 200-400. The operating pressure of the nanofiltration membrane separator is controlled at 0.6-1.0 MPa, and backwashing is performed once every 24 hours. The backwashing medium is condensate at room temperature of 25-30℃ produced by vacuum distillation. EDTA-Fe is retained through the sieving effect and charge repulsion effect of nanofiltration membrane. 2+ To achieve EDTA-Fe 2+ Concentration, concentrated EDTA-Fe 2+ The solution is returned to the hollow fiber membrane contactor for reuse, and the nanofiltration waste liquid is collected in the residue chamber.

[0008] Preferably, the nanofiltration membrane separator is equipped with a nanofiltration membrane, and the nanofiltration membrane preparation method includes the following steps: Support layer modification: The support layer uses a plasma-modified polyvinylidene fluoride ultrafiltration membrane. The polyvinylidene fluoride ultrafiltration membrane is treated with a mixed plasma of argon and oxygen in a volume ratio of 4:1. The gas flow rate, power, treatment time and vacuum degree are controlled to optimize the functional groups and pore structure on the membrane surface. In-situ interface aggregation: First, prepare a mixture containing piperazine, triethanolamine, and Ti3C2T. x The aqueous solution of MXene / N-GQDs composite filler was uniformly dispersed by ultrasonication and stirring; the modified support layer was immersed in the aqueous solution, removed and purged with nitrogen to control the amount of monomer adsorption on the surface. Then, an interfacial polymerization reaction is carried out, in which the support layer of the adsorbed aqueous monomer is immersed in an organic phase solution of n-hexane containing trimesoyl chloride to conduct an interfacial polycondensation reaction, forming polyamide-Ti3C2T. x -N-GQDs composite functional layer; Gradient post-processing: Unreacted monomers and residual solvents were removed by low-temperature water washing, and mild cross-linking modification was performed using glutaraldehyde aqueous solution. Then, ionization modification was performed using sodium citrate solution to increase the surface carboxyl group density. The post-treated membrane is dried with low-temperature hot air to control its moisture content; it is then sealed with seawater-resistant epoxy adhesive and assembled into flat or spiral wound membrane modules.

[0009] Preferably, the method for preparing the aqueous monomer solution includes: Piperazine was used as the aqueous monomer at a concentration of 1.6-1.8 wt%, and 0.6-0.8 wt% triethanolamine was added as a catalyst, while 0.03-0.06 wt% Ti3C2T was dispersed and added simultaneously. x -N-GQDs composite filler, wherein the mass ratio of MXene to N-GQDs is 2:1, is then ultrasonically dispersed at 220W power for 20-25 min, magnetically stirred at 250 r / min speed for 30-40 min, and the system temperature is controlled at 26-28℃. The modified support layer was immersed in an aqueous solution for 2.2-2.8 minutes. After removal, it was purged with nitrogen gas at a wind speed of 0.3-0.5 m / s for 15-20 seconds to remove excess liquid film from the surface, thus stabilizing the aqueous monomer adsorption capacity at 0.8-1.0 mg / cm³. 2 .

[0010] Preferably, the vacuum distillation method includes: The compound absorbent containing DMSO discharged from the tube-side outlet of the hollow fiber membrane contactor is selected and fed into a vacuum distillation tank. Ship exhaust gas is passed into a coiled heat exchanger in a vacuum distillation tank, where the waste heat from the exhaust gas is used to heat the compounded absorbent. The heat exchanger has a heat exchange area of ​​15-18 m². 2 The vacuum distillation vessel has a volume of 1.5 m³. 3 Control the heating temperature to 55-75℃; The vacuum distillation vessel is evacuated to 1.2-1.5 kPa to evaporate the DMSO in the compound absorbent, forming a high-concentration DMSO fraction. The DMSO fraction is condensed to 25-30℃ using an ice machine, and the condensed DMSO is then returned to the hollow fiber membrane contactor for reuse.

[0011] Preferably, the hollow fiber membrane contactor is equipped with a hollow fiber membrane module, and the method for preparing the hollow fiber membrane includes the following steps: Sa. Preparation of casting solution: Select polyvinylidene fluoride or polypropylene as the film matrix material, N,N-dimethylacetamide as the solvent and polyethylene glycol as the pore-forming agent, mix them in proportion, stir until a uniform and transparent casting solution is formed, and let it stand to remove bubbles. Sb, Spinning and Forming: The deaerated casting solution is extruded through a spinning spinneret using a dry-wet spinning method. The spinning solution is used as the external phase and the ethanol aqueous solution is used as the core solution. The spinning solution extruded from the spinneret directly enters the coagulation bath. The distance between the spinneret and the surface of the coagulation bath is 10-15 cm. The coagulation bath is pure water at 25-30℃. After the casting solution is extruded, it enters the coagulation bath and quickly coagulates to form a nascent hollow fiber membrane. Sc. Post-processing: The nascent hollow fiber membrane is removed from the coagulation bath and immersed in pure water to remove residual solvents and pore-forming agents from the membrane; then it is dried to obtain a hollow fiber membrane suitable for hollow fiber membrane contactors. Sd, Modification treatment: The dried hollow fiber membrane is immersed in an aqueous solution of glutaraldehyde as a crosslinking modifier to perform crosslinking treatment on the dried membrane, and then rinsed and dried after removal.

[0012] Preferably, the structural features of the hollow fiber membrane module include: A single membrane module contains 1000-1200 membrane fibers, with an inner diameter of 0.5-0.6 mm and an outer diameter of 0.8-1.0 mm. The module diameter is 80-100 mm, the module length is 500-800 mm, and the effective membrane area is 8-10 m². 2 .

[0013] Furthermore, the present invention also provides an integrated desulfurization, denitrification and decarbonization treatment system for ship exhaust gas, which is used for integrated desulfurization, denitrification and decarbonization treatment of ship exhaust gas, including a raw material supply unit, a core reaction unit, a separation and recovery unit and a recycling unit, wherein each unit is interconnected to form a closed loop system.

[0014] Preferably, the raw material supply unit includes a waste liquid buffer tank and an electrolyte buffer tank, both of which are connected to the core reaction unit via pipelines. The core reaction unit includes a hollow fiber membrane contactor and a hypergravity reactor. The hollow fiber membrane contactor has a tube-side inlet, a tube-side outlet, a shell-side inlet, and a shell-side outlet. The tube-side inlet is connected to the raw material supply unit and the recycling unit. The shell-side inlet is used to receive ship exhaust gas, and the shell-side outlet is connected to the inlet of the hypergravity reactor. The hypergravity reactor has a waste liquid inlet, a waste gas inlet, a liquid phase outlet, and a gas phase outlet. The waste liquid inlet is connected to the waste liquid buffer tank. The separation and recovery unit includes a gravity centrifuge and a residue compartment. The gravity centrifuge is connected to the tube-side outlet of the hollow fiber membrane contactor and the liquid phase outlet of the ultragravity reactor, respectively. The residue compartment is connected to the solid outlet of the gravity centrifuge. The regeneration unit includes a nanofiltration membrane separator and a vacuum distillation tank. The inlet of the nanofiltration membrane separator is connected to the tube-side outlet of the hollow fiber membrane contactor, and the outlet of the nanofiltration membrane separator is connected to the tube-side inlet of the hollow fiber membrane contactor. The inlet of the vacuum distillation tank is connected to the tube-side outlet of the hollow fiber membrane contactor, and the outlet of the vacuum distillation tank is connected to the tube-side inlet of the hollow fiber membrane contactor.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The integrated desulfurization, denitrification, and decarbonization treatment method and system for ship exhaust gas provided in this invention deeply explores the resource potential of ships themselves. Using seawater desalination waste liquid and ballast water electrolyte as core raw materials, and leveraging waste heat from the exhaust boiler, it constructs a closed-loop model of self-resource-exhaust gas treatment-resource regeneration, reducing external dependence and investment in supporting equipment. It not only achieves integrated treatment of multiple pollutants in exhaust gas, achieving environmental compliance without secondary pollution, but also simultaneously removes sulfur oxides, nitrogen oxides, and carbon dioxide, with pollutants removed in the form of solid precipitates for easy collection. Furthermore, it is low-cost and space-saving, reducing system investment and maintenance costs by replacing dedicated materials with byproducts, selecting compact core equipment, and enhancing absorbent circulation. The process is highly efficient and stable, easy to operate, and economical, employing membrane contactors and enhanced mass transfer via ultragravity to improve gas-liquid contact and pollutant removal efficiency. The process is simple, with the absorbent concentrated via nanofiltration membrane and regenerated by vacuum distillation, resulting in low loss and outstanding stability and economy. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the connection of the integrated desulfurization, denitrification and decarbonization treatment system for ship exhaust gas provided in an embodiment of the present invention.

[0018] Explanation of symbols in the diagram: 1. Waste liquid buffer tank; 2. Electrolyte buffer tank; 3. Hollow fiber membrane contactor; 4. Ultragravity reactor; 5. Residue chamber; 6. First gravity centrifuge; 7. Second gravity centrifuge; 8. Nanofiltration membrane separator; 9. Vacuum distillation tank; 10. Ice machine; 11. Fan; 12. Filter. Detailed Implementation

[0019] To make the technical problems, solutions, and beneficial effects addressed by this application clearer, the following detailed description, in conjunction with the accompanying drawings and embodiments, provides a method and system for integrated desulfurization, denitrification, and decarbonization of ship exhaust gas. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0020] Example 1 This invention provides an integrated desulfurization, denitrification, and decarbonization treatment method for ship exhaust gas, comprising the following steps: S1. Preparation of compound absorbent: Seawater desalination waste liquid and ballast water electrolyte are injected into the buffer tank at a 1:1 volume ratio, and then mixed with DMSO and EDTA-Fe. 2+ They are injected together into the tube side of the hollow fiber membrane contactor to form a compound absorbent; S2. Desulfurization and denitrification treatment: Ship exhaust gas is pressurized and then introduced into the shell side of the hollow fiber membrane contactor, where it undergoes mass transfer contact with the composite absorbent on the pipe side. Sulfur oxides and EDTA-Fe2+ are selectively absorbed through DMSO. 2+ Nitrogen oxides are captured by complexation and converted into solid precipitates by calcium and magnesium ions in seawater desalination wastewater. After centrifugation, the liquid phase is recycled and reused, and the solid precipitate is collected in the residue tank. S3. Decarbonization treatment: The waste gas after desulfurization and denitrification is transported to the supergravity reactor and undergoes a mass transfer reaction with the seawater desalination waste liquid. The supergravity field atomizes the seawater desalination waste liquid into 50-80μm microdroplets. Calcium and magnesium ions react with carbon dioxide to generate solid precipitates. After centrifugation, part of the liquid phase meets the standards and is discharged into the sea, while the other part is recycled. S4. Absorbent Regeneration: EDTA-Fe is concentrated using nanofiltration membrane separation. 2+ DMSO is concentrated by vacuum distillation, and the concentrated absorbent is refluxed back to the hollow fiber membrane contactor to achieve recycling.

[0021] The integrated desulfurization, denitrification, and decarbonization treatment method for ship exhaust gas provided in this invention deeply explores the resource potential of ships themselves. Using seawater desalination waste liquid and ballast water electrolyte as core raw materials, and leveraging waste heat from exhaust boilers, it constructs a closed-loop model of self-resource-exhaust gas treatment-resource regeneration, reducing external dependence and investment in supporting equipment. This method not only achieves integrated treatment of multiple pollutants in exhaust gas, achieving environmental compliance without secondary pollution, but also simultaneously removes sulfur oxides, nitrogen oxides, and carbon dioxide, with pollutants removed in the form of solid precipitates for easy collection. Furthermore, it is low-cost and space-saving, reducing system investment and maintenance costs by using byproducts to replace dedicated materials, selecting compact core equipment, and enhancing absorbent circulation. The process is highly efficient and stable, easy to operate, and economical, employing membrane contactors and enhanced mass transfer via ultragravity to improve gas-liquid contact and pollutant removal efficiency. The process is simple, with the absorbent concentrated via nanofiltration membrane and regenerated by vacuum distillation, resulting in low loss and outstanding stability and economy.

[0022] Example 2 like Figure 1 As shown, this embodiment of the invention provides an integrated desulfurization, denitrification and decarbonization treatment system for ship exhaust gas, including a raw material supply unit, a core reaction unit, a separation and recovery unit and a recycling unit, with each unit interconnected to form a closed-loop treatment system.

[0023] In this embodiment, the raw material supply unit includes a waste liquid buffer tank 1 and an electrolyte buffer tank 2. Both the waste liquid buffer tank 1 and the electrolyte buffer tank 2 are connected to the core reaction unit through a conveying pipeline and are used to store and convey the ship's own seawater desalination waste liquid and ballast water electrolyte, respectively.

[0024] The core reaction unit includes a hollow fiber membrane contactor 3 and a hypergravity reactor 4. The hollow fiber membrane contactor 3 is provided with a tube-side inlet, a tube-side outlet, a shell-side inlet, and a shell-side outlet. The tube-side inlet is connected to the raw material supply unit and the recycling unit. The shell-side inlet is used to receive ship exhaust gas. The shell-side outlet is connected to the inlet of the hypergravity reactor 4. The hypergravity reactor 4 is provided with a waste liquid inlet, a waste gas inlet, a liquid phase outlet, and a gas phase outlet. The waste liquid inlet is connected to the waste liquid buffer tank 1. The gas phase outlet is used to discharge the purified gas.

[0025] The separation and recovery unit includes a gravity centrifuge and a residue chamber 5. The gravity centrifuge is connected to the tube-side outlet of the hollow fiber membrane contactor 3 and the liquid phase outlet of the supergravity reactor, respectively, and is used to separate the solid precipitate and the liquid phase in the solid-containing mixture. The residue chamber 5 is connected to the solid outlet of the gravity centrifuge and is used to collect the solid precipitate.

[0026] In this embodiment, the system has two gravity centrifuges, namely a first gravity centrifuge 6 and a second gravity centrifuge 7. The inlet end of the first gravity centrifuge 6 is connected to the hollow fiber membrane contactor 3, and the outlet end of the first gravity centrifuge 6 is connected to the hollow fiber membrane contactor 3 and the residue chamber 5 to realize liquid phase reflux and fixed output. The inlet end of the second gravity centrifuge 7 is connected to the supergravity reactor 4 to realize liquid phase reflux. The outlet end of the second gravity centrifuge 7 is connected to the residue chamber 5 to realize solid output, while the liquid phase can be directly discharged into the sea for treatment.

[0027] The regeneration unit includes a nanofiltration membrane separator 8 and a vacuum distillation tank 9. The inlet of the nanofiltration membrane separator 8 is connected to the tube-side outlet of the hollow fiber membrane contactor 3, and the outlet of the nanofiltration membrane separator 8 is connected to the tube-side inlet of the hollow fiber membrane contactor 3, for concentrating EDTA-Fe. 2+ The inlet of the vacuum distillation tank 9 is connected to the tube-side outlet of the hollow fiber membrane contactor 3, and the outlet of the vacuum distillation tank 9 is connected to the tube-side inlet of the hollow fiber membrane contactor 3 for concentrating DMSO. In addition, the vacuum distillation tank 9 is also connected to the ship's boiler exhaust gas pipeline to utilize the waste heat of the boiler exhaust gas for heating.

[0028] Furthermore, a vacuum distillation tank 9 is connected to an ice machine 10. The vacuum distillation tank 9 is used to concentrate DMSO with the absorbent. The ice machine 10 is an integrated unit of a small refrigerator and a heat exchanger, which provides cooling capacity. The distillate enters the ice machine 10, and the outlet of the ice machine 10 is connected to the nanofiltration membrane separator 8. The ship's exhaust gas is connected to the hollow fiber membrane contactor 3 via a blower 11. A filter 12 is connected to the hollow fiber membrane contactor 3, and the outlet of the filter 12 is connected to the nanofiltration membrane separator 8.

[0029] This invention provides a simple and convenient integrated desulfurization, denitrification, and decarbonization treatment system for ship exhaust gas. It adopts a modular closed-loop integrated design, with a compact structure adapted to shipboard scenarios. The interconnected units function smoothly, ensuring stable operation during continuous ship navigation and enabling simultaneous desulfurization, denitrification, and decarbonization purification. Furthermore, this embodiment utilizes ship-produced seawater desalination wastewater and ballast water electrolyte as raw materials, eliminating the need for large-scale external purchases of reagents, thus reducing costs and the burden of wastewater disposal. A dual-force centrifuge separates the solids, allowing for centralized collection of the solid sediment, while the liquid phase is either recycled as needed or discharged into the sea after meeting standards, resulting in no secondary pollution and compliance with maritime regulations. The system is equipped with a regeneration unit for targeted recovery of the concentrated absorbent, utilizing waste heat from boiler exhaust gas for heating, reducing absorbent loss and improving economic efficiency.

[0030] Furthermore, the inflow and outflow streams of each device in the entire system are shown in Table 1.

[0031] Table 1. Inflow and outflow streams of each device in the processing system

[0032] Example 3 Based on the above embodiments, this invention provides an integrated treatment method for desulfurization, denitrification and decarbonization of ship exhaust gas. Based on the previously described technical solutions, the method adopts or partially improves the structure or process to achieve detailed optimization of the integrated treatment method for desulfurization, denitrification and decarbonization of ship exhaust gas.

[0033] This invention uses ship-owned resources as the core raw material and relies on two core pieces of equipment: a hollow fiber membrane contactor and a high-gravity reactor, to achieve simultaneous desulfurization, denitrification, and decarbonization of ship exhaust gas, constructing a closed-loop circulation system throughout the process. The specific steps are as follows: S1. Preparation of compound absorbent.

[0034] Seawater desalination waste liquid from the desalination system is injected into the waste liquid buffer tank, and ballast water electrolyte from the ballast water electrolysis system is injected into the electrolyte buffer tank. These two types of liquids are mixed with DMSO and EDTA-Fe 2+ Together they are injected into the hollow fiber membrane contactor tube side to form a mixture of DMSO, EDTA-Fe 2+ A compound absorbent composed of four streams: seawater desalination waste liquid and ballast water electrolyte.

[0035] In this embodiment, during the preparation of the compound absorbent, the volume ratio of seawater desalination waste liquid to ship ballast water electrolyte is 1:1. This 1:1 ratio balances desulfurization and denitrification efficiency, as well as EDTA-Fe... 2+ The optimal ratio for regeneration efficiency and calcium and magnesium ion utilization was verified through a ratio experiment.

[0036] Specifically, three control experiments with different volume ratios were set up: 1:2, 1:1, and 2:1, with fixed total amount of compound absorbent, DMSO concentration (8wt%), and EDTA-Fe... 2+ At a concentration of 0.08 mol / L, under the same reaction conditions (temperature: 40-45℃, pH: 8-9, hollow fiber membrane contactor operating pressure set to 0.3 MPa), the SO2 removal rate and NO2 removal rate were tested. x Removal rate, EDTA-Fe 2+ Regeneration efficiency and calcium and magnesium ion utilization rate.

[0037] When the volume ratio of seawater desalination waste liquid to ballast water electrolyte is 1:2, the ballast water electrolyte is in excess, resulting in sufficient ·OH generation (concentration can reach 1.2×10⁻⁶). -3 mol / L), EDTA-Fe 2+ It has the highest regeneration efficiency (92.3%), but the amount of desalination wastewater is insufficient, and Ca... 2 + / Mg 2+ With a concentration of only 2.1-2.8 g / L, sulfur oxides and nitrogen oxides do not precipitate sufficiently, while SO2 and NO... x The removal rates were only 88.2% and 86.5% respectively, and the calcium and magnesium ion utilization rate was 72.1%, which could not meet the requirements for ship exhaust gas treatment with a removal rate of ≥90%. When the volume ratio of seawater desalination waste liquid to ballast water electrolyte is 1:1, and the amounts of both are balanced, the seawater desalination waste liquid can provide 3.3-4.7 g / L of Ca. 2+ / Mg 2+ It meets the precipitation requirements of sulfur oxides and nitrogen oxides, and the utilization rate of calcium and magnesium ions reaches 85.0%; the ballast water electrolyte can generate 10 -4 -10 -3 mol / L ·OH, EDTA-Fe 2+ The regeneration efficiency is 90.5%, and the complexing activity can be maintained. The final SO2 removal rate is 92.5%, and NO... x The removal rate was 91.8%, all meeting the standards. When the volume ratio of seawater desalination waste liquid to ballast water electrolyte is 2:1, the seawater desalination waste liquid is in excess, Ca 2+ / Mg 2+The concentration was sufficient (4.4-6.2 g / L), with a calcium and magnesium ion utilization rate of 86.2% and an SO2 removal rate of 91.3%. However, the ballast water electrolyte was insufficient, resulting in reduced ·OH generation (concentration only 6×10⁻⁶ g / L). -4 mol / L), EDTA-Fe 2+ Regeneration efficiency dropped to 78.6%, Fe 3+ Insufficient restoration, NO x The removal rate was only 87.2%, and excessive calcium and magnesium ions easily formed precipitates, causing the absorbent to become turbid and affecting the mass transfer efficiency of the hollow fiber membrane.

[0038] In summary, setting a 1:1 volume ratio can achieve the optimal synergy of desulfurization and denitrification efficiency, regeneration efficiency, and calcium and magnesium ion utilization, making it suitable for ship exhaust gas treatment conditions.

[0039] S2, desulfurization and denitrification process.

[0040] Ship exhaust gas, after being pressurized by a blower, enters the shell side of a hollow fiber membrane contactor, where it undergoes efficient mass transfer contact with the composite absorbent on the pipe side. Utilizing the polarity of DMSO, sulfur oxides are selectively absorbed, and then processed through EDTA-Fe... 2+ The complexation process captures nitrogen oxides and transfers them to the liquid phase. Then, calcium and magnesium ions in the seawater desalination wastewater are used to convert sulfur oxides and nitrogen oxides in the liquid phase into solid precipitates. The solid-containing mixture is separated by gravity centrifuge, and the solid precipitates in the liquid are collected in the residue tank by gravity centrifuge. The separated liquid phase is returned to the tube side of the hollow fiber membrane contactor for repeated absorption.

[0041] In this embodiment, the desulfurization and denitrification principle of the absorbent is as follows: Dimethyl sulfoxide (DMSO) is used as a selective physical absorbent for sulfur oxides. Due to the strong polarity of the sulfur-oxygen double bond in the DMSO molecule, it can form dipole-dipole interactions and weak hydrogen bonds with sulfur dioxide, significantly enhancing its solubility for sulfur dioxide. However, DMSO exhibits extremely low solubility for nitrogen, oxygen, or weakly polar inert gases, thus demonstrating excellent selectivity. DMSO in a compound absorbent can selectively absorb sulfur oxides from ship exhaust gases through dipole-dipole interactions.

[0042] With complexing agent EDTA-Fe 2+ EDTA-Fe is a selective physical absorbent for absorbing nitrogen oxides. The majority of nitrogen oxides in waste gas are NO, and EDTA-Fe... 2+ The ferrous ions in NO can rapidly form [Fe(NO)] with NO in aqueous solution. 2+ The reaction is reversible. Since ferrous ions are gradually oxidized to ferric ions, a reducing agent needs to be added to reduce them back to ferrous ions to maintain the complexing activity.

[0043] Using seawater electrolyzed water generated from ballast water as a reducing agent, the hydroxyl radicals (·OH) generated by electrolysis reduce ferric ions to ferrous ions, thus avoiding the use of hydrogen peroxide.

[0044] Using the desalination wastewater generated by the seawater desalination plant as a precipitant, the high concentration of Mg in it is utilized. 2+ and Ca 2 + The ionized nitrogen oxides and sulfur oxides in the liquid phase are precipitated in solid form to complete the removal.

[0045] Therefore, this embodiment uses dimethyl sulfoxide and EDTA-Fe 2+ A combination of seawater desalination waste liquid and seawater electrolysis water is used as a desulfurization and denitrification absorbent formulation. Through the synergistic effect of multiple components, nitrogen oxides and sulfur oxides are captured and converted in situ, and finally removed as solids.

[0046] Furthermore, utilizing EDTA-Fe 2+ The complexing ability of the compound binds NO to the liquid phase, and then the NO is oxidized to NO2 by using hydroxyl radicals (·OH) in the seawater electrolysis. The generated NO2 then reacts with Mg in the seawater desalination wastewater. 2+ and Ca 2+ The reaction produces solid precipitates of calcium nitrate (or magnesium nitrate) and calcium nitrite (or magnesium nitrite), thus converting nitrogen oxides into insoluble solids, which are then removed by gravity centrifugation. In this embodiment, dimethyl sulfoxide is used to selectively absorb sulfur dioxide into the liquid phase, where it reacts with Mg in the seawater desalination wastewater. 2+ and Ca 2+ The reaction produces solid precipitates of calcium sulfate and magnesium sulfate, which removes sulfur dioxide as solid precipitates.

[0047] Furthermore, regarding EDTA-Fe 2+ Regeneration mechanism, EDTA-Fe 2+ During the selective complexation of NO, ferrous ions are gradually oxidized to ferric ions by oxygen in the gas phase or by oxidation side reactions, generating non-complexing [Fe] ions. 3+ (EDTA)] - This leads to a decrease in denitrification capacity, therefore, it is necessary to use ballast water electrolyte electrolytic regeneration technology to remove Fe. 3+ Reduced to Fe 2+ , to restore complexation activity.

[0048] The ballast water electrolyte uses ballast water containing 3.0-3.5 wt% NaCl as raw material, and is applied at an electrolysis voltage of 3.5-4.5 V and an electrolysis voltage of 20-25 mA / cm². 2Electrolysis is carried out under mild conditions of current density and 25-35℃. Through the electrolysis of water and the electrochemical oxidation of chloride ions, highly oxidizing hydroxyl radicals (·OH) are generated in situ on the electrode surface. Under these conditions, the ·OH generation efficiency is optimal, and the concentration can reach 10. -4 -10 -3 The concentration is mol / L, and the aggravation of chlorine side reactions under high voltage or high current density can be avoided, ensuring the selectivity and stability of ·OH. The ·OH generated by electrolysis is introduced into the compound absorbent system. Under controlled conditions of 40-45℃ and pH 7-9, ·OH reacts with deactivated [Fe... 3+ (EDTA)] - A reduction reaction occurs, reducing ferric ions to ferrous ions, and regenerating [Fe] ions with NO complexation activity. 2+ (EDTA)] 2- The reduction reaction rate increases with increasing temperature, increasing by approximately 1.3 times for every 10°C increase. Maintaining a pH range of 7-9 ensures both the structural stability of the EDTA complex and the reducing activity of ·OH, preventing the formation of Fe under acidic conditions. 3+ Hydrolysis precipitation or excessive alkalinity can lead to EDTA degradation.

[0049] This embodiment, through precise control of electrolysis parameters and reduction reaction conditions, enables Fe... 3+ The reduction rate reaches over 90%, EDTA-Fe 2+ The complexing activity is restored to more than 95% of the initial level, enabling long-term stable recycling of the absorbent without the need for additional hydrogen peroxide or other traditional reducing agents, thus meeting the environmental protection and safety requirements of marine operations and maintenance.

[0050] Furthermore, in this embodiment, the ship desalination wastewater used contains Ca... 2+ Concentration of 800-1200 ppm, Mg 2+ The concentration is 2500-3500 ppm, and the total concentration of the two is 3300-4700 ppm, which is set to 3.3-4.7 g / L.

[0051] S3, decarbonization process.

[0052] The desulfurization and denitrification waste gas, treated by the hollow fiber membrane contactor, is transported to the hypergravity reactor, where it undergoes a mass transfer reaction with the desalination waste liquid from the waste liquid buffer tank. The hypergravity field atomizes the desalination waste liquid into 50-80μm microdroplets, significantly increasing the gas-liquid contact area. Calcium and magnesium ions in the microdroplets react with carbon dioxide in the waste gas to form solid precipitate particles. The solid-liquid mixture is then separated by a gravity centrifuge. The solid precipitate is sent to the residue tank, a portion of the liquid phase meets discharge standards and is discharged into the sea, while the remaining liquid phase is recycled back to the reactor for reuse.

[0053] In this embodiment, the optimal pH range for the decarbonization reaction is 8.5-9.5, which ensures the OH... - At a suitable concentration, CO2 can be hydrolyzed to produce CO3. 2- It improves the binding efficiency of calcium and magnesium ions and avoids OH- - Excessive amounts lead to premature precipitation of calcium and magnesium ions, balancing reaction rate and ion utilization.

[0054] Moreover, in an alkaline system (pH 9.5), the solubility of calcium and magnesium ions can be increased from 18 g / L to 30 g / L, an increase of 66.7%. At the same time, the mass transfer coefficient is increased by 1.6 times and the reaction rate is increased by 3.2 times. Combined with the enhanced mass transfer by supergravity atomization, ion loss can be significantly reduced. With the sufficient ion supply of compound waste liquid, the utilization rate of calcium and magnesium ions can reach 85%.

[0055] Furthermore, during the system processing, the decarbonization reaction rate is positively correlated with temperature. The optimal reaction range is 38-42℃. For every 10℃ increase in temperature, the reaction rate increases by 1.2-1.5 times. This range can avoid the problems of incomplete reaction at low temperatures, decreased CO2 solubility at high temperatures, and increased ion precipitation.

[0056] S4. Regeneration of the absorbent.

[0057] In this embodiment, to achieve efficient and frequent utilization of the compound absorbent, the concentration of absorbent components is controlled to avoid the increase in the water content of the absorbent during long-term system operation, which could lead to the concentration of dimethyl sulfoxide (DMSO) and EDTA-Fe in the absorbent. 2+ To reduce the concentration, nanofiltration membrane separation was used to concentrate EDTA-Fe. 2+ DMSO is concentrated using vacuum distillation, which is used to separate DMSO and EDTA-Fe from the compound absorbent. 2+ Maintaining a certain concentration ensures the stability of the compound absorbent for desulfurization and denitrification. The concentrated absorbent is then returned to the hollow fiber membrane contactor for recycling.

[0058] Furthermore, in this embodiment, the compound absorbent from the hollow fiber membrane contactor is pH-adjusted to alkaline by an alkaline regulator, and after suspended impurities are removed by a filter, it is pumped to a nanofiltration membrane separator by a pressurized pump, where EDTA-Fe is concentrated under the action of a negatively charged nanofiltration membrane. 2+ It is then fed to a hollow fiber membrane contactor to maintain the EDTA-Fe in the tube-side compound absorbent. 2+ The concentration, nanofiltration waste liquid generated during nanofiltration and backwashing is collected in the residue compartment.

[0059] Controlling EDTA-Fe using nanofiltration membrane separation method 2+Concentration, utilizing nanofiltration membranes with specific molecular weight cutoffs, leveraging membrane sieving and charge repulsion effects, to separate large molecules of EDTA-Fe in the compound absorbent. 2+ EDTA-Fe is trapped on the pipe side to achieve 2+ Recovery and concentration enhance the EDTA-Fe content in the compound absorbent. 2+ concentration.

[0060] Specifically, nanofiltration membrane separation methods include: Select the EDTA-Fe content discharged from the tube-side outlet of the hollow fiber membrane contactor. 2+ The compound absorbent is adjusted to alkaline (pH 7-9) by an alkaline adjuster, and then enters the filter to remove residual suspended impurities; The compound absorbent after removing impurities is pumped to a nanofiltration membrane separator via a pressurized pump. The nanofiltration membrane separator uses a negatively charged nanofiltration membrane with a molecular weight cutoff of 200-400. The nanofiltration membrane separator is operated at a pressure of 0.6-1.0 MPa. At room temperature, EDTA-Fe... 2+ Separation and concentration from water and impurities; and backwashing every 24 hours, using condensed water at room temperature of 25-30℃ produced by vacuum distillation as the backwashing medium; EDTA-Fe is retained through the sieving effect and charge repulsion effect of nanofiltration membrane. 2+ To achieve EDTA-Fe 2+ Concentration, concentrated EDTA-Fe 2+ The solution is refluxed to the hollow fiber membrane contactor for reuse, maintaining the EDTA-Fe content in the compound absorbent. 2+ With the concentration within the target range, EDTA-Fe 2+ High-efficiency recovery and recycling; after nanofiltration treatment, nanofiltration waste liquid is collected into the residue compartment.

[0061] In this embodiment, EDTA-Fe 2+ The complex has a molecular weight of approximately 345 and is negatively charged in aqueous solution. Due to the negative charge on the nanofiltration membrane surface, it interacts with EDTA-Fe... 2+ Due to electrostatic repulsion, EDTA-Fe2O3 nanofiltration membranes are selected. These membranes can trap large molecular complexes while allowing water molecules / small salt molecules to permeate. The membrane's sieving effect and charge repulsion effect are utilized to achieve EDTA-Fe2O3 nanofiltration. 2+ Separation and concentration from water and impurities.

[0062] Furthermore, to ensure the working efficiency of the nanofiltration membrane, a small amount of 0.5wt% NaOH solution is added as an alkaline conditioner before the compound absorbent enters the nanofiltration membrane. Since the addition of the alkaline conditioner may generate suspended impurities, a micron-level filter is used at the front end of the nanofiltration membrane to remove suspended impurities in the compound absorbent to avoid membrane clogging.

[0063] Furthermore, in this embodiment, the specific parameters for the nanofiltration membrane backwashing process are as follows: The backwashing pressure is 0.3-0.4 MPa, which is lower than the normal operating pressure of nanofiltration membranes by 0.6-1.0 MPa, thus avoiding damage to the functional layer on the membrane surface due to excessive pressure. The backwashing flow rate is 50-60 L / h, which is suitable for the processing scale of a single nanofiltration membrane module and ensures that the backwashing liquid evenly covers the membrane surface. The backwashing time is 10-15 min, which can fully wash away suspended impurities adsorbed on the membrane surface and avoid impurity residue.

[0064] Furthermore, considering the impurity content after filtration with the compound absorbent, backwashing every 24 hours effectively prevents membrane fouling and maintains stable membrane flux. The backwashing medium is ambient temperature condensate generated by vacuum distillation and ice condensation, with a temperature of 25-30℃, free of impurities, and neutral pH, avoiding the use of seawater or other water containing impurities that could exacerbate membrane fouling.

[0065] The backwashing parameters used in this embodiment enable the flux recovery rate of the nanofiltration membrane after fouling to reach over 93%, and the residual suspended impurities on the membrane surface after backwashing are ≤0.02 g / m³. 2 EDTA-Fe 2+ With a retention rate maintained above 96%, the separation efficiency of the nanofiltration membrane can be maintained for a long period, ensuring the EDTA-Fe... 2+ The recovery and concentration process operates stably, avoiding system downtime caused by membrane blockage.

[0066] Furthermore, in this embodiment, the nanofiltration membrane separator is equipped with a nanofiltration membrane, and the nanofiltration membrane preparation method... Employing a three-pronged technical approach of "support layer modification - in-situ interfacial polymerization - nanocomposite regulation," this technology overcomes the bottlenecks in the synergistic effect of traditional nanofiltration membranes on antifouling resistance, chemical stability, and separation selectivity, and is specifically designed for EDTA-Fe in marine exhaust gas treatment systems. 2+ The recycling scenario design can precisely match the performance requirements of negatively charged membranes with a molecular weight cutoff of 200-400. It achieves efficient separation at room temperature and operating pressure of 0.6-1.0 MPa, while taking into account the large-scale implementation of the preparation process and cost control, with excellent results.

[0067] Specifically, the nanofiltration membrane preparation method includes the following steps: Support layer modification: The support layer uses a plasma-modified polyvinylidene fluoride (PVDF) ultrafiltration membrane. The surface properties are optimized through low-temperature plasma modification technology, providing a high-strength and highly compatible substrate for the construction of the functional layer.

[0068] Polyvinylidene fluoride (PVDF) ultrafiltration membranes were treated with a mixed plasma of argon and oxygen at a volume ratio of 4:1. The mixed gas flow rates were 4 L / min for argon and 1 L / min for oxygen. The treatment power was set to 85-95 W, the treatment time was controlled at 40-50 s, and the vacuum degree was maintained stably at -0.092 to -0.098 MPa. After modification, the performance of the support layer was adjusted to significantly increase the density of surface hydroxyl and carboxyl functional groups, and the pore structure was optimized to an average pore size of 0.06-0.08 μm and a porosity of 78%-80%.

[0069] Parameter setting principles: A 4:1 ratio of argon to oxygen makes it easier to control the generation efficiency of active groups; a power of 85-95 W avoids excessive power that could lead to degradation of the support layer; a processing time of 40-50 s allows for precise control of the modification depth; and a stable vacuum of -0.092 to -0.098 MPa reduces the impact of fluctuations on the modification effect. Optimizing pore parameters is to balance membrane flux and mechanical strength, ultimately resulting in a significant reduction in the surface contact angle of the modified support layer from its original state, a significant improvement in interfacial bonding strength, effective prevention of functional layer peeling during long-term operation, and a significant reduction in the operating resistance of the membrane module compared to the unmodified support layer, making it suitable for the low-energy consumption operation and maintenance requirements of ships.

[0070] In-situ interface aggregation: The functional layer employs an in-situ interfacial polymerization-two-dimensional composite filler reinforcement method, using Ti3C2T. x -MXene / N-GQDs composite packing material achieves a triple improvement in separation selectivity, chemical stability and antifouling resistance.

[0071] First, an aqueous monomer solution was prepared, using piperazine (PIP) as the aqueous monomer at a concentration of 1.6-1.8 wt%. 0.6-0.8 wt% triethanolamine was added as a catalyst, and 0.03-0.06 wt% Ti3C2T was dispersed simultaneously. x The PVDF composite filler, wherein the mass ratio of MXene to N-GQDs is 2:1, is then ultrasonically dispersed at 220W for 20-25 min, followed by magnetic stirring at 250 r / min for 35 min, with the system temperature controlled at 26-28℃. The modified PVDF support layer is then immersed in this aqueous solution for 2.2-2.8 min, and after removal, it is purged with nitrogen gas of ≥99.9% purity at a wind speed of 0.3-0.5 m / s for 15-20 s to remove excess liquid film from the surface, stabilizing the adsorption capacity of the aqueous monomer at 0.8-1.0 mg / cm³. 2 .

[0072] This embodiment uses Ti3C2T. x The MXene / N-GQDs composite packing material utilizes the synergistic effect between the layered structure of two-dimensional MXene and N-GQDs to enhance the membrane's charge density, hydrophilicity, and antifouling properties. Furthermore, the industrial-scale preparation technology for this composite packing material is mature. Controlling the PIP concentration to 1.6-1.8 wt% avoids excessively dense functional layers and flux attenuation due to excessive concentration. 0.6-0.8 wt% triethanolamine optimizes catalytic efficiency and reduces side reactions. A 2:1 packing material ratio maximizes the synergistic effect. Ultrasonic and stirring parameters ensure uniform packing material dispersion without agglomeration and a homogeneous system. A narrow temperature range of 26-28℃ guarantees reaction repeatability. A soaking time of 2.2-2.8 min ensures sufficient monomer adsorption without excessive permeation. Nitrogen purging parameters precisely control the amount of monomer adsorbed in the aqueous phase, laying the foundation for subsequent polymerization reactions.

[0073] Then, an interfacial polymerization reaction is carried out. The support layer with adsorbed aqueous monomers is rapidly immersed in an organic phase solution. The organic phase uses n-hexane as a solvent, with 500 mL of n-hexane corresponding to each liter of aqueous solution. 0.18-0.22 wt% of trimesoyl chloride (TMC) is dissolved as the oil phase monomer. The reaction temperature is controlled at 22-24℃ with fluctuations ≤ ±1℃, and the reaction time is precisely controlled at 35-40 s. Through a rapid condensation reaction at the interface, polyamide-Ti3C2T is formed. x -N-GQDs composite functional layers ultimately control the thickness of the functional layer to 55-70 nm.

[0074] In this embodiment, hexane is used as the solvent to replace traditional toluene, reducing reagent toxicity and making it easier to recycle, thus meeting environmental and industrial requirements. A TMC concentration of 0.18-0.22 wt% allows for precise control of the monomer ratio, avoiding excessive crosslinking leading to insufficient membrane flux or insufficient crosslinking affecting separation selectivity. A stable temperature of 22-24℃ and a reaction time of 35-40 s balance the density and permeability of the functional layer, ensuring uniform thickness. The layered structure of MXene can construct ordered mass transfer channels; its surface hydroxyl and fluorine groups are covalently bonded to TMC. N-GQDs can regulate the crosslinking density of the functional layer, ultimately forming a dense thin-layer two-dimensional nano-dispersion structure that ensures the retained molecular weight remains stably within the 220-380 range to adhere to EDTA-Fe. 2+ Separating requirements can significantly improve the functional layer's handling of DMSO and EDTA-Fe. 2+ It improves the corrosion resistance of marine wastewater salts, while significantly reducing the surface contact angle, greatly reducing the amount of suspended impurities adsorbed, and enhancing anti-pollution performance.

[0075] Gradient post-processing: A gradient post-processing technique is adopted to optimize membrane performance, and parameters are adapted to the characteristics of composite functional layers to avoid performance degradation caused by traditional processes and effectively ensure membrane stability.

[0076] The specific steps are as follows: First, a low-temperature water wash is performed by immersing the polymerized membrane in pure water at 32-34℃ for 1.2-1.4 hours, changing the water every 20 minutes. Then, a mild crosslinking modification is performed by immersing the membrane in a 0.9-1.1 wt% glutaraldehyde aqueous solution and treating it at a constant temperature of 36-38℃ for 45-55 minutes. Finally, an ionization modification is performed by immersing the membrane in a 0.4-0.6 wt% sodium citrate solution and treating it at room temperature of 25℃ for 25-30 minutes.

[0077] In this embodiment, low-temperature water washing removes unreacted monomers and solvents from the surface, and changing the water every 20 minutes ensures that the residual amount is controlled at a low level, reducing interference with separation performance. Treatment with 0.9-1.1 wt% glutaraldehyde at 36-38°C strengthens the cross-linking structure of the functional layer while avoiding excessive cross-linking that could lead to membrane embrittlement, ultimately significantly improving the tensile strength of the membrane. Room-temperature treatment with 0.4-0.6 wt% sodium citrate solution allows the carboxyl groups in sodium citrate to undergo nucleophilic reactions with the amino groups remaining on the functional layer surface, introducing a large number of carboxyl functional groups to the surface, significantly increasing the carboxyl density of the functional layer, and enhancing the separation performance of cationic EDTA-Fe. 2+ The charge repulsion effect of the complex can also slightly modulate the pore size of the functional layer, keeping water flux attenuation at a low level, maintaining high membrane permeability to water molecules, and significantly increasing the carboxyl group density on the functional layer surface, thus enhancing the resistance to cationic EDTA-Fe 2+ The charge repulsion effect of the complex simultaneously controls the water flux decay at a low level, maintaining the membrane's high permeability to water molecules.

[0078] Finally, the post-treated membrane is placed in a hot air drying oven at 48-52℃ and dried at a wind speed of 0.9-1.1 m / s for 70-80 minutes to control the moisture content of the dried membrane at 8%-10%. After drying, it is sealed with seawater-resistant epoxy adhesive and assembled into flat or spiral membrane modules to ensure no leakage under a pressure of 0.6-1.0 MPa.

[0079] In this embodiment, a slow drying method using a low temperature of 48-52℃ and a wind speed of 0.9-1.1 m / s is adopted to avoid membrane structure shrinkage and pore deformation, and a moisture content of 8%-10% ensures membrane activity. Epoxy adhesive resistant to seawater corrosion is selected to adapt to the marine operating environment and prevent long-term contact with seawater from causing seal failure. Flat-plate modules are suitable for small vessels, while roll-up modules are suitable for large vessels, meeting the space installation requirements of different vessels. A leak-free sealing standard under 0.6-1.0 MPa pressure ensures stable operation of the membrane module under the conditions of a marine exhaust gas treatment system.

[0080] The nanofiltration membrane prepared by this method exhibits excellent and stable overall performance, particularly for EDTA-Fe... 2+ It exhibits excellent retention performance and suitable water flux for various operating conditions. After 720 hours of continuous operation at room temperature and 0.8 MPa pressure, the retention rate decline remains at a low level. Its antifouling performance and chemical stability are significantly improved compared to single N-GQDs modified membranes, effectively meeting the long-term operational needs of ships. Furthermore, its preparation method is similar to that of marine EDTA-Fe... 2+ The recovery process achieves a high degree of synergy: the prepared negatively charged nanofiltration membrane can be precisely adapted to the treatment requirements of the compound absorbent (after pH adjustment to 7-9 and removal of suspended impurities), and efficiently realizes EDTA-Fe through sieving and charge repulsion effects. 2+ Separation and concentration from water and small molecule impurities; EDTA-Fe in the concentrate. 2+ The concentration can be stably maintained within the target range of 0.05-0.1 mol / L, and it can be recycled back to the hollow fiber membrane contactor. Only a small amount of consumable reagent needs to be added to ensure system stability, which greatly reduces the operating cost of ships. At the same time, the preparation process does not require the introduction of highly toxic reagents and complex equipment, taking into account both environmental protection and industrial adaptability, and can meet the long-term stable operation requirements of ships at sea.

[0081] Furthermore, this embodiment also addresses Ti3C2T x The performance of the MXene / N-GQDs composite modified polyvinylidene fluoride nanofiltration membrane was tested, and some parameters in the process were verified by example.

[0082] Specifically, the test conditions were: room temperature (25±2℃), operating pressure 0.8MPa, and feed solution was a compound simulated solution with pH=8 (containing EDTA-Fe). 2+ (Contains DMSO and a small amount of seawater salts), test duration 24 hours.

[0083] Performance level corresponding quantitative standards: Excellent (≥90% / ≥80L / (m)) 2 ·h·MPa)), Good (80%-89% / 60-79L / (m 2(·h·MPa)), qualified (70%-79% / 40-59L / (m) 2 (·h·MPa)), difference (<70% / <40L / (m)) 2 ·h·MPa)).

[0084] Nanofiltration membrane performance testing using EDTA-Fe in marine exhaust gas treatment systems 2+ Guided by the recovery operating conditions, the test conditions were uniformly set as ambient temperature (25±2℃), operating pressure 0.8MPa, and the feed liquid was a compound simulated solution with pH=8 (containing EDTA-Fe). 2+ The samples included DMSO and a small amount of seawater salts. Each test lasted 24 hours, with performance levels corresponding to clearly defined quantitative standards to ensure the comparability and accuracy of the test results. The test samples were divided into two main categories: exemplary cases and comparative examples. The exemplary cases focused on Ti3C2T. x The effect of MXene / N-GQDs composite packing concentration was investigated. The mass ratio of the two was fixed at 2:1, and the total concentration was set at equal gradients of 0.03wt%, 0.04wt%, 0.05wt%, 0.06wt%, and 0.07wt%, for a total of 5 sample groups. The comparative control group was designed with variables for the packing components and ratios, including a blank control (no packing), single-component packing (N-GQDs only, MXene only, both 0.05wt%), and samples with deviations in ratio (1:1, 3:1, total concentration 0.05wt%), for a total of 5 sample groups. The necessity of the composite packing and the optimal ratio was clarified through comparison.

[0085] The performance test results of the examples and comparative examples are shown in Table 2.

[0086] Table 2 Ti3C2T x Performance test results of MXene / N-GQDs composite modified polyvinylidene fluoride nanofiltration membrane

[0087] The above tests show that as the total concentration of the composite filler changes gradient, the overall performance of the nanofiltration membrane exhibits a trend of first improving and then fine-tuning. Example 3 (0.05wt%) shows the best performance, with all properties reaching a balanced peak: EDTA-Fe 2+ The retention rate reached 96%, and the pure water flux was 83 L / (m²). 2 With a DMSO corrosion resistant membrane (·h·MPa), the rejection rate decreased by only 2.3% after 72 hours of continuous operation, the flux recovery rate after fouling reached 93%, and the membrane structure retention rate was 96% after 24 hours, achieving an optimal balance between rejection efficiency, operational stability, fouling resistance, and chemical stability. Example 4 (0.06wt%) exhibited local optimal characteristics, with the pure water flux increasing to 88 L / (m³). 2 The EDTA-Fe (·h·MPa) was the highest among all samples, but the EDTA-Fe2+ The retention rate dropped to 95%, slightly lower than in Example 3, and the stability index also declined slightly. Example 1 (0.03 wt%) exhibited relatively weaker performance due to its lower filler concentration. 2+ The retention rate was 86%, and the flux recovery rate after contamination was 85%. Example 2 (0.04 wt%) showed significantly improved performance compared to Example 1, gradually approaching the optimal level. Example 5 (0.07 wt%) experienced a slight performance decline due to excessively high packing concentration, with the flux decreasing to 73 L / (m³). 2 The retention rate was 93%, and the stability index was slightly inferior to that of Example 3.

[0088] Compared to the examples, each comparative example showed significant shortcomings in performance. The blank control (Comparative Example 1) had the worst performance in all aspects, with EDTA-Fe... 2+ The rejection rate is only 75%, and the pure water flux is as low as 38L / (m²). 2 At 72h (MPa), the retention rate decreased by 8.5%, and the membrane structure retention rate was 79%, highlighting the core enhancing role of the filler in membrane performance. The single-component filler samples (Comparative Examples 2 and 3) outperformed the blank control, but were far inferior to Example 3: Comparative Example 2 (N-GQDs only) EDTA-Fe 2+ Retention rate 88%, flux recovery rate after contamination 83%; Comparative Example 3 (MXene only) retention rate 87%, flux 65 L / (m³) 2 The stability and corrosion resistance of both samples were significantly weaker than those of the composite filler sample, demonstrating the synergistic effect of MXene and N-GQDs. Although the total concentration of the samples with different ratios (Comparative Examples 4 and 5) was consistent with that of Example 3, the performance still differed: Comparative Example 4 (1:1) had a rejection rate of 90%, and Comparative Example 5 (3:1) had a rejection rate of 89%, with fluxes of 70 L / (m³). 2 ·h·MPa), 66L / (m 2 The stability and anti-fouling properties were also lower than those of Example 3 (·h·MPa), proving that the 2:1 packing ratio is the key to ensuring performance.

[0089] In summary, Ti3C2T x The introduction of MXene / N-GQDs composite filler can significantly improve the core performance of nanofiltration membranes for shipboard applications, and there is a clear optimal concentration and ratio: when the mass ratio of the two is 2:1 and the total concentration is 0.05wt%, the prepared nanofiltration membrane exhibits the best overall performance and can meet the requirements of EDTA-Fe in ship exhaust gas treatment systems. 2+ The system requires efficient recovery while also exhibiting excellent operational stability and resistance to corrosion from complex media. Incorrect composition, deviations in formulation, or improper concentrations can all lead to performance degradation, failing to meet the requirements for use in marine environments.

[0090] Furthermore, in this embodiment, the concentration of DMSO is controlled by vacuum distillation, and the DMSO is concentrated by using boiler exhaust gas as a heat source. After distillation, the bottom drain valve of the vacuum distillation tank is opened to drain the liquid from the bottom of the tank. The compound absorbent is cooled to a suitable temperature using an ice machine and then sent into the hollow fiber membrane contactor to increase the concentration of DMSO in the compound absorbent.

[0091] Specifically, vacuum distillation methods include: The compound absorbent containing DMSO discharged from the tube-side outlet of the hollow fiber membrane contactor is selected and fed into a vacuum distillation tank. Ship exhaust gas is passed into a coiled heat exchanger in a vacuum distillation tank, where the waste heat from the exhaust gas is used to heat the compounded absorbent. The heat exchanger has a heat exchange area of ​​15-18 m². 2 It can be adapted to small vacuum distillation jars with a volume of 1.5m³. 3 It adapts to the waste heat capacity of the main unit's exhaust gas, ensures heat exchange efficiency, and controls the heating temperature to 55-75℃; The vacuum distillation tank is evacuated to 1.2-1.5 kPa to evaporate the DMSO in the compound absorbent, forming a high-concentration DMSO fraction. The top fraction with DMSO as the main component is then recovered using the vacuum distillation tank. The DMSO fraction is condensed to 25-30°C using an ice machine, and the condensed DMSO is refluxed to the hollow fiber membrane contactor for reuse. The top fraction is cooled and condensed to 25-30°C by a small ice machine and then fed into the absorbent circulation to control the DMSO concentration in the absorbent within the target range.

[0092] In this embodiment, a small vacuum distillation tank with coil heating and built-in stirring integrates vacuum, heating, and condensation functions. The compound absorbent from the hollow fiber membrane enters the vacuum distillation tank, where it is heated to a temperature range of 55-75°C using ship boiler exhaust gas, and the vacuum level is controlled. A high-concentration DMSO fraction (DMSO purity ≥97% at the top of the column, recovery rate ≥95%) is obtained through vacuum distillation. After being cooled and temperature-controlled by an ice machine, it is re-injected into the hollow fiber membrane contactor for recirculation. The ambient temperature condensate formed during the ice machine condensation process is used as backwash water for the nanofiltration membrane separator to prevent membrane clogging.

[0093] Furthermore, the process parameters during vacuum distillation are as follows: Boiler exhaust gas flow rate 1000-1500 m³ 3 / h corresponds to 20,000 kg / h-60,000 kg / h of marine main engine exhaust gas, with a main engine exhaust gas density of approximately 1.2 kg / m³. 3 The corresponding volumetric flow rate is 16666.7-50000 m³. 3 / h; the inlet and outlet exhaust gas temperatures of the coil are 180-200℃ and 100-120℃ respectively, and the inner wall temperature of the coil is controlled at 85-95℃ to avoid local overheating and DMSO degradation. At the same time, by adjusting the exhaust gas valve, the heat extraction scale is precisely controlled to ensure that only part of the boiler's heat is extracted.

[0094] Regarding boiler waste heat utilization, the exhaust gas from ship main engines with a flow rate of 20,000 kg / h to 60,000 kg / h still carries a large amount of usable waste heat after the main heat is recovered by the waste heat boiler. The waste heat exhaust gas at 180-200℃ undergoes indirect heat exchange with a compound absorbent (initial temperature 25-30℃) in a vacuum distillation tank through coils, with a coil heat exchange area of ​​15-18 m². 2 Sufficient heat exchange contact area can be guaranteed, 1000-1500 m² 3 A waste gas flow rate of / h can stably provide sufficient heat exchange, accounting for only 2%-9.5% of the total waste heat of the boiler, without affecting the core heat exchange function of the boiler.

[0095] Heat balance calculations have verified that it can transfer 150-200 kJ of heat per hour, which is sufficient to heat a 1.5 m³ of soil. 3 The compound absorbent (density approximately 1.05 g / cm³) 3 With a specific heat capacity of 4.2 kJ / (kg·℃), the temperature can be increased from 25-30℃ to 55-75℃ at a rate of approximately 1.2-1.5℃ / min. The exhaust gas flow rate can be controlled by adjusting the exhaust gas valve (e.g., reducing the flow rate to 1000 m³ / min). 3 The heating rate slows to 1.0℃ / min at a flow rate of 1500 m³ / h. 3 The heating rate was increased to 1.5℃ / min per hour, precisely controlling the absorbent temperature within the target range. This avoids excessively high temperatures leading to DMSO volatilization loss and excessively low temperatures affecting distillation efficiency. This not only verifies the feasibility of heating to 55-75℃ but also enables the rational utilization of boiler waste heat, adapting to the operating conditions of the ship's main engine.

[0096] Furthermore, in this embodiment, the hollow fiber membrane contactor is equipped with a hollow fiber membrane module. The hollow fiber membrane preparation method is designed with feasibility and versatility as the core principles, balancing preparation cost and simplified steps. While retaining the core process of traditional mature spinning technology, it achieves targeted optimization of membrane performance through precise control of process parameters. It does not require the introduction of special preparation equipment and complex process systems, and can be mass-produced by relying on existing industrial production lines for membrane materials. At the same time, it is compatible with the operating conditions and installation of ship exhaust gas treatment systems, and forms a highly efficient synergy with subsequent compound absorbent treatment and EDTA-Fe2+ recovery processes.

[0097] Specifically, the preparation method of hollow fiber membrane includes the following steps: Sa, Preparation of the casting solution: Polyvinylidene fluoride (PVDF) or polypropylene (PP) is selected as the membrane substrate material. Both have excellent resistance to seawater corrosion, organic solvents (DMSO), and metal complexes (EDTA-Fe). 2+ The performance is suitable for the complex liquid-phase system of ship exhaust gas treatment; the porogen is a compound system of industrial general-purpose polyethylene glycol (PEG4000-6000) and lithium chloride (LiCl), in which PEG4000-6000 accounts for 70%-80% of the total mass of the porogen and LiCl accounts for 20%-30%. The raw materials of this porogen system are readily available and inexpensive, and it is easy to remove by water washing, with no risk of residual pollution.

[0098] In this embodiment, the matrix material and the pore-forming agent are compounded at a mass ratio of 7-10:1. The core method follows the immersion precipitation phase transformation method, combined with dry and wet spinning process. There is no need to reconstruct the traditional spinning process system, which greatly reduces the equipment modification cost and the process adaptation difficulty for operators, and has both process versatility and production feasibility.

[0099] Sb. Spinning Formation Stage: First, the spinning solution is prepared by adding the PVDF / PP matrix material and the compounded pore-forming agent to the N,N-dimethylacetamide (DMAC) solvent. The PVDF / PP matrix material accounts for 16%-18% of the total mass of the spinning solution, the compounded pore-forming agent (PEG4000-6000-LiCl) accounts for 2%-3% of the total mass of the spinning solution, and the N,N-dimethylacetamide (DMAC) solvent accounts for 79%-82% of the total mass of the spinning solution. Then, the mixed solution is continuously stirred in a constant temperature stirred vessel at 75-90℃ at a speed of 350-400 r / min for 6-8 h until a uniform, particle-free, transparent spinning solution is formed. Subsequently, the spinning solution is placed in a vacuum environment at 25-30℃ for 1-2 h to degas, with the vacuum degree controlled at -0.08 to -0.10 MPa, to completely remove the air bubbles inside the spinning solution and avoid membrane pore defects during the spinning process.

[0100] In the spinning stage, a coaxial annular spinneret is used. The spinning solution serves as the external phase, and a 30%-40% (w / w) ethanol aqueous solution serves as the core solution. The flow rate of the external phase spinning solution is controlled at 1.0-1.5 mL / min, and the flow rate of the core solution is controlled at 0.3-0.5 mL / min. The spinning solution extruded from the spinneret directly enters a pure water external coagulation bath at 20-25℃. The distance between the coagulation bath surface and the spinneret is 10-15 cm. The spinning solution undergoes rapid phase separation in the coagulation bath to form a nascent hollow fiber membrane. After being drawn in the coagulation bath, the nascent membrane is stretched and shaped at 1.2-1.5 times the stretching rate to ensure the uniformity and stability of the membrane structure.

[0101] Sc. Post-treatment stage: The stretched nascent hollow fiber membrane is washed in pure water at 30-40℃ for 2-3 hours, with continuous water changes to thoroughly remove residual pore-forming agents and solvents from the membrane, preventing residual substances from affecting the membrane's chemical stability and mass transfer performance; after washing, the membrane is placed in a hot air drying oven at 45-55℃ for 1-1.5 hours, with the drying air velocity controlled at 0.5-1.0 m / s to prevent high-temperature rapid drying from causing membrane structure shrinkage and pore deformation; Sd, Modification Treatment Stage: Finally, a 2.5wt% glutaraldehyde aqueous solution is used as a crosslinking modifier. The dried membrane is crosslinked at 25-30℃ for 30-40 min. After completion, the surface residual modifier is rinsed with pure water, and the membrane is naturally dried before being assembled into a hollow fiber membrane module. The entire process is free of cumbersome post-processing procedures, and the steps are simplified and easy to control, meeting the efficiency requirements of industrial mass production.

[0102] Furthermore, in this embodiment, during the preparation of the hollow fiber membrane, the optimal concentration (2.5wt%) of the glutaraldehyde aqueous solution was determined by setting up multiple sets of concentration comparison tests (2.0wt%, 2.5wt%, 3.0wt%) and verifying the membrane performance indicators, and 2.5wt% was determined to be the optimal concentration that balances crosslinking effect and membrane stability.

[0103] Specifically, tests revealed that when crosslinked with 2.0 wt% glutaraldehyde, the membrane crosslinking degree was insufficient, resulting in a tensile breaking strength of only 14.8 MPa and a 168-hour mixed liquid weight retention rate of 93.2%. Slight swelling occurred after long-term operation (168 hours), and the membrane pore size fluctuated significantly. With 2.5 wt% glutaraldehyde crosslinking, the crosslinking degree was moderate, enhancing membrane structural stability without causing pore blockage. The tensile breaking strength reached 15.8 MPa, and the 168-hour mixed liquid weight retention rate was 96.5%. No swelling or pore size shrinkage occurred during long-term operation, and the membrane structure maintained good integrity. With 3.0 wt% glutaraldehyde crosslinking, excessive crosslinking led to membrane densification, reducing porosity to below 70% and the gas-liquid mass transfer coefficient to 2.3 × 10⁻⁶. -4 At the same time, the membrane brittleness increases, and although the tensile breaking strength is improved to 16.5 MPa, the membrane fibers are prone to breakage, making it unsuitable for the working conditions of slight vibration in ships.

[0104] Therefore, using a 2.5wt% glutaraldehyde aqueous solution can achieve the optimal balance between crosslinking effect, membrane mass transfer performance, and structural stability.

[0105] In this embodiment, the specific assembly parameters for the membrane module adapted to the ship's installation space are as follows, taking into account the limited installation space of the ship's exhaust gas treatment system: a compact hollow fiber membrane module design is adopted. The number of membrane fibers in a single membrane module is 1000-1200 (inner diameter 0.5-0.6 mm, outer diameter 0.8-1.0 mm), the module diameter is 80-100 mm, the module length is 500-800 mm, and the effective membrane area is 8-10 m². 2 The membrane fibers are sealed and fixed to the end caps at both ends of the component with epoxy adhesive (seawater corrosion resistant type). The end caps are reserved with liquid inlet and outlet interfaces (diameter DN25-DN32) to adapt to ship pipeline connections. The component shell is made of 316L stainless steel with a thickness of 3-5mm, which has both corrosion resistance and impact resistance and can withstand slight vibrations during ship navigation. The weight of a single component is controlled at 15-20 kg, which is convenient for on-site installation and maintenance on the ship. Multiple components can be assembled in parallel, with a small overall footprint and compact layout, which is suitable for the exhaust gas treatment needs of ship main engines with a scale of 20,000 kg / h-60,000 kg / h.

[0106] The hollow fiber membrane prepared by the method used in this embodiment possesses clear performance indicators suitable for ship exhaust gas treatment conditions. The membrane has an average pore size of 0.1-0.3 μm, a porosity of 70%-80%, a wall thickness of 50-80 μm, and a tensile breaking strength ≥15 MPa. It can operate stably for extended periods at room temperature and an operating pressure of 0.6-1.0 MPa, and can withstand minor vibrations and shocks during ship navigation, exhibiting excellent structural stability. This membrane module is compatible with the tube-side and shell-side mass transfer requirements of hollow fiber membrane contactors, ensuring the proper functioning of the composite absorbent (DMSO, EDTA-Fe). 2+ The smooth flow and circulation of seawater desalination wastewater and ballast water electrolyte on the pipe side can enhance the gas-liquid mass transfer efficiency across the membrane, achieving efficient liquid-phase transfer of nitrogen oxides and sulfur oxides; simultaneously, it can facilitate subsequent EDTA-Fe... 2+ The recovery process is highly adaptable. After passing through the membrane contactor, the compound absorbent is adjusted to pH 7-9 by an alkaline adjuster. Suspended impurities are removed by a filter, and the solution is then fed into a negatively charged nanofiltration membrane separator with a molecular weight cutoff of 200-400. The EDTA-Fe process is completed under an operating pressure of 0.6-1.0 MPa. 2+ Separation and concentration, the concentrated EDTA-Fe 2+ The solution is refluxed to the hollow fiber membrane contactor tube side to maintain the EDTA-Fe in the compound absorbent. 2+ When the mass concentration is within the target range of 0.05-0.1 mol / L, only a small amount of EDTA-Fe lost due to system depletion needs to be replenished. 2+ This ensures stable operation of the process and significantly reduces the cost of reagent consumption.

[0107] Furthermore, this embodiment also tests the performance of PVDF-based high-efficiency desulfurization and denitrification hollow fiber membrane, and verifies the effect of some parameters in the process through examples.

[0108] Test conditions: ambient temperature (25±2℃), transmembrane pressure 0.1MPa, test medium is a compound simulated solution with feed solution pH=6.3 (containing EDTA-Fe). 2+ (Contains DMSO and a small amount of seawater salts), test duration 48 hours.

[0109] Performance rating: Excellent (best in the range), Good (second best), Acceptable (acceptable), Poor (unacceptable).

[0110] The hollow fiber membrane performance test focuses on the efficient removal of SO2 and NO2 from ship exhaust gas, specifically verifying the supporting role of the membrane structure in the removal effect. Standardized test conditions are used to ensure the accuracy of the removal rate data: ambient temperature (25±2℃), transmembrane pressure 0.1 MPa, and a compound simulated solution with pH=6.3 (containing EDTA-Fe). 2+ (including DMSO and small amounts of seawater salts), among which DMSO specifically absorbs SO2 and EDTA-Fe from the shell-side exhaust gas. 2+ Specifically designed to absorb NO2 from shell-side exhaust gas, each test lasted 48 hours. The core objective was to evaluate membrane compatibility using the removal rate as an indicator. Test samples were divided into two groups: an example group and a comparative group. The example group focused on a PEG4000-LiCl compound porogen design, with a fixed mass ratio of 7:3. The total concentration was adjusted in equal gradients of 2.0wt%, 2.5wt%, and 3.0wt% (3 groups of samples), exploring the regulatory effect of porogen concentration on membrane removal efficiency. The comparative group focused on variables related to porogen components and their ratios (4 groups of samples), including a blank control (no porogen), a single-component porogen (PEG4000 only, LiCl only, both with a total concentration of 3.0wt%), and a sample with a deviation in ratio (PEG4000-LiCl ratio 5:5, total concentration 3.0wt%). The comparison clarified the necessity of the compound porogen and its optimal ratio for improving the removal rate.

[0111] The test experiment consisted of three sets of example cases and four sets of comparative cases. The test results of the specific example cases and comparative cases are shown in Table 3.

[0112] Table 3 Performance test results of PVDF-based high-efficiency desulfurization and denitrification hollow fiber membranes

[0113] The test results above show that the gradient change in the total concentration of the compound pore-forming agent significantly affects the SO2 and NO2 removal rates of the membrane. Removal rates initially peak with increasing concentration and then slightly decline. Example 2 (total pore-forming agent concentration 2.5 wt%) exhibited the best removal effect and balanced overall performance, perfectly suited to the needs of ship exhaust gas purification. Example 2 achieved a SO2 removal rate of 92.5% and a NO2 removal rate of 91.8%, both the highest values ​​among all tested samples. This excellent removal effect stems from the precise matching of membrane structure and mass transfer efficiency; the 76.8% porosity provides ample mass transfer channels, and the 2.83 × 10⁻⁶ ppm mass transfer efficiency... -4 A high gas-liquid mass transfer coefficient of m / s can accelerate gas-liquid contact reactions, and both factors together ensure the smooth flow of SO2 and EDTA-Fe from DMSO. 2+ The high NO2 absorption efficiency ultimately achieves a high removal rate. Simultaneously, the 96.5% mixed solution weight retention rate and excellent structural stability prevent membrane performance degradation from causing pollutant leakage, ensuring that the removal rate remains at a high level over the long term.

[0114] Example 1 (total pore-forming agent concentration 2.0 wt%) had insufficient concentration, resulting in a membrane porosity of only 72.3%. The limited mass transfer channels hindered gas-liquid contact and pollutant absorption, directly leading to low removal efficiency. SO2 and NO2 removal rates were only 82.3% and 81.5%, respectively, failing to meet the core requirements for efficient purification of ship exhaust gas. Example 3 (total pore-forming agent concentration 3.0 wt%), although increasing the porosity to 78.5% and reducing the permeation resistance to 2.75 × 10⁻⁶, still achieved a lower removal efficiency. 5 The mass transfer conditions were further optimized at Pa·s / m, which theoretically helps to improve the removal rate. However, the excessively high concentration of pore-forming agent weakened the membrane structure strength, reducing the tensile breaking strength to 14.5 MPa, and slightly decreasing the pore size uniformity. These structural issues affect the stability and uniformity of gas-liquid contact, resulting in a slight decrease in the removal rate compared to Example 2, with the SO2 removal rate dropping to 90.2% and the NO2 removal rate dropping to 89.5%, making it difficult to balance removal efficiency and structural stability.

[0115] The removal rates of all comparative examples were significantly lower than those of Example 2, further confirming the core value of the compound porogen and the optimal 7:3 ratio in improving the removal rates of SO2 and NO2. All variable conditions failed to achieve the ideal removal effect. The blank control (Comparative Example 1), lacking a porogen, had a dense membrane structure leading to a lack of mass transfer channels, resulting in a SO2 removal rate of only 65.7% and a NO2 removal rate of 64.3%, far below the actual operating requirements and completely failing to achieve the waste gas purification target. The single-component porogen samples (Comparative Examples 2 and 3) lacked component synergy, and their membrane structures could not adapt to the high-efficiency mass transfer requirements, directly lowering the removal rates: Comparative Example 2 (PEG4000 only) had SO2 and NO2 removal rates of 80.5% and 79.2%, respectively, while Comparative Example 3 (LiCl only) had even lower removal rates of 76.3% and 75.8%, with insufficient mass transfer stability and significant fluctuations in the removal rate. Although the removal rate of the sample with a ratio deviation (Comparative Example 4, PEG4000-LiCl=5:5) was better than that of the single-component sample, reaching 83.1% and 82.4%, it was still nearly 10 percentage points lower than that of Example 2. This fully demonstrates that the 7:3 ratio can maximize the mass transfer adaptability of the membrane structure and provide key support for improving the removal rate.

[0116] In summary, the concentration and ratio of the PEG4000-LiCl compound porogen play a decisive role in the SO2 and NO2 removal rates of hollow fiber membranes, directly determining whether the membrane can meet the core requirements for ship exhaust gas purification. When the mass ratio of the two is 7:3 and the total concentration is 2.5wt%, the membrane achieves optimal removal performance, with an SO2 removal rate of 92.5% and a NO2 removal rate of 91.8%. Furthermore, thanks to its good structural stability and corrosion resistance, the removal rate can be maintained at a high level of over 90% for a long period. If the porogen concentration is too high or too low, if a single component is substituted for the compound system, or if the optimal ratio deviates from 7:3, the mass transfer efficiency and stability of the membrane structure will be compromised, leading to a significant decrease in the removal rate.

[0117] Furthermore, the main reaction formulas of the embodiments of the present invention are shown below.

[0118] Sulfur oxide capture reaction formula: .

[0119] Temperature: 25-45℃, pH: 7-9, DMSO mass fraction: 8wt%; selective absorption is achieved by utilizing the polarity of DMSO and the dipole-dipole interaction with SO2, and the solubility of inert gases such as N2 and O2 is extremely low.

[0120] sulfur oxide conversion reaction formula: .

[0121] Temperature: 30-45℃, pH: 8-9, Ca 2+ / Mg 2+Concentration: 3.3-4.7 g / L; Alkaline environment promotes SO2 hydrolysis, and calcium and magnesium ions and sulfur oxides rapidly precipitate into solids, which are then removed by gravity centrifugation.

[0122] Nitrogen oxide capture reaction formula: .

[0123] Temperature: 25-45℃, pH: 7-9, EDTA-Fe 2+ Concentration: 0.08 mol / L; Fe 2+ It rapidly forms a stable complex with NO, transferring NO from the gas phase to the liquid phase. The reaction is reversible and facilitates subsequent regeneration.

[0124] Nitrogen oxide conversion reaction formula: .

[0125] Temperature: 35-45℃, pH: 8-9, Ca 2+ / Mg 2+ Concentration: 3.3-4.7 g / L; Alkaline environment promotes SO2 hydrolysis, and calcium and magnesium ions and sulfur oxides rapidly precipitate into solids, which are then removed by gravity centrifugation.

[0126] EDTA-Fe 2+ Regeneration (Fe 3+ Reduction reaction): .

[0127] Temperature: 25-45℃, pH: 7-9, ·OH concentration: 10 -4 ~10 -3 mol / L; ·OH will oxidize and deactivate [Fe] 3+ (EDTA)] - Reduced to [Fe 2+ (EDTA)] 2- This restores complexing activity and avoids the use of traditional reducing agents such as hydrogen peroxide.

[0128] Carbon dioxide conversion reaction formula: .

[0129] Example 4 Based on the above embodiments, this embodiment verifies the effectiveness of the integrated desulfurization, denitrification, and decarbonization treatment method for ship exhaust gas proposed in this invention through a specific example.

[0130] This embodiment takes a ship exhaust gas desulfurization, denitrification and decarbonization integrated treatment system with a target exhaust gas treatment capacity of 40,000 kg / h as an example. It relies on two core equipment: hollow fiber membrane contactor and ultragravity reactor. The recovery auxiliary process is nanofiltration membrane separation and absorbent vacuum distillation.

[0131] The basic parameters for the actual operating conditions of the ship are as follows: seawater temperature 32℃, freshwater temperature 36℃, exhaust gas treatment flow rate 40000 kg / h, SO2 concentration in the exhaust gas 0.3wt%, NO x The concentration of DMSO was 0.15 wt%, CO2 concentration was 7 wt%, the initial temperature of the exhaust gas was 45℃, and the initial pressure was 3 kPa; the initial concentration of DMSO in the compound absorbent was 8 wt%, and the initial concentration of EDTA-Fe was 7 wt%. 2+ The initial concentration was 0.08 mol / L. The seawater desalination waste liquid and ballast water electrolyte were mixed at a volume ratio of 1:1. The two types of ship-owned waste liquid accounted for 65% of the total mass of the mixed absorbent.

[0132] For a waste gas treatment capacity of 40,000 kg / h, the total circulation flow rate of the system's compound absorbent is 21,000 kg / h, of which the fresh absorbent replenishment on the tube side of the hollow fiber membrane contactor is 850 kg / h, and the replenishment of seawater desalination waste liquid from the supergravity reactor is 1,200 kg / h. The total collection volume of solid waste residue (including sulfur and nitrate reaction precipitate and carbon capture mineralization precipitate) generated by the system after separation by gravity centrifuge is 320-480 kg / h. The discharged liquid phase is the treated clear liquid that meets the standards, with a flow rate controlled at 1,500-2,000 kg / h.

[0133] Desulfurization and denitrification reaction process: 40,000 kg / h of ship exhaust gas to be treated is pressurized to 5 kPa gauge pressure by a booster fan, and the exhaust gas temperature rises from 45℃ to 50℃. Without additional cooling, it directly enters the shell side of the hollow fiber membrane contactor, where it is combined with a 21,000 kg / h compound absorbent (DMSO 8wt%, EDTA-Fe) on the pipe side. 2+ A mixture of 0.08 mol / L (27 wt%) and ballast water electrolyte (65 wt%) undergoes efficient gas-liquid mass transfer. During the mass transfer process, the operating temperature inside the membrane contactor is maintained at 40-45℃ and the operating pressure at 5 kPa.

[0134] Leveraging the superior performance of PVDF-based hollow fiber membranes for high-efficiency mass transfer in desulfurization and denitrification of marine exhaust gas, the membrane modules effectively remove SO2 and NO. x To achieve efficient removal, DMSO selectively absorbs SO2 in the shell-side exhaust gas, while EDTA-Fe... 2+ NO x Complexation absorption is performed, and the alkaline components in the seawater desalination waste liquid and ballast water electrolyte convert the absorbed sulfur oxides into sulfate and nitrite solid precipitates. After mass transfer contact, the residence time of the waste gas on the membrane contactor shell side is 12 seconds, ultimately achieving an SO2 removal rate of 92.5% and NO... x The removal rate was 91.8%.

[0135] The solid-containing mixture generated on the membrane contactor tube side (flow rate 21500 kg / h, containing 0.8wt% solid precipitate) is transported to a gravity centrifuge for solid-liquid separation. 380 kg / h of sulfur-nitrate reaction solid precipitate is separated and sent to the ship's slag tank. The separated solid-free liquid phase (flow rate 21120 kg / h, DMSO concentration 7.2wt%, EDTA-Fe) 2+ Most of the 0.025 mol / L absorbent (20250 kg / h) is recirculated to the hollow fiber membrane contactor tube side to continue participating in the absorption reaction, while a small portion (870 kg / h) is transported to the absorbent recovery and reuse unit for DMSO and EDTA-Fe. 2+ The concentration and recovery process enables the recycling of the absorbent.

[0136] Decarbonization reaction process: The purified exhaust gas (flow rate 39850 kg / h, CO2 concentration 7.05 wt%, temperature 42℃, pressure 4.5 kPa) after desulfurization and denitrification by hollow fiber membrane contactor is transported by a fan to a hypergravity reactor, where it undergoes a mass transfer mineralization reaction with 1200 kg / h of seawater desalination waste liquid from the waste liquid buffer tank. The speed of the hypergravity reactor is adjusted to 700 r / min. The hypergravity field inside the reactor atomizes the seawater desalination waste liquid into micro-droplets with a particle size of 50-80 μm, which greatly increases the gas-liquid contact area. The atomized micro-droplets come into full contact with CO2 in the exhaust gas, and the calcium and magnesium ions in the waste liquid undergo an in-situ mineralization reaction with CO2 to generate calcium carbonate and magnesium carbonate solid precipitates.

[0137] The residence time of the desulfurized and denitrified exhaust gas in the supergravity reactor is 15s. The operating temperature in the reactor is maintained at 35-45℃ and the operating pressure is 4 kPa. The utilization rate of calcium and magnesium ions in the seawater desalination waste liquid reaches 85%, and the CO2 capture rate in the exhaust gas is 68.0%.

[0138] Regarding the control method of atomized particle size, the atomized particle size of seawater desalination waste liquid in the centrifugal reactor is controlled by the reactor rotation speed. The centrifugal acceleration is directly proportional to the square of the rotation speed, and the atomized particle size is negatively correlated with the rotation speed. This method sets the rotation speed to 700 r / min, which can stably atomize the waste liquid to 50-80 μm. When the rotation speed is lower than 600 r / min, the droplets are not sufficiently broken and the particle size is greater than 80 μm. When the rotation speed is higher than 800 r / min, the droplets are excessively broken and the particle size is less than 50 μm, which is prone to agglomeration and gas phase entrainment problems. At the same time, the liquid flow rate, physical properties and internal structure of the reactor can help stabilize the atomized particle size.

[0139] The selection criteria for the atomization particle size range are based on the inverse relationship between the gas-liquid contact surface area and the droplet size. Theoretically, the smaller the particle size, the larger the specific surface area, but droplet stability must also be considered. This particle size range effectively avoids extreme problems: when the particle size is <50μm, droplets are prone to collision and aggregation, resulting in a decrease in the effective contact area and easy entrainment by exhaust gas; when the particle size is >80μm, the specific surface area decreases significantly, and the mass transfer resistance increases dramatically. Therefore, 50-80 μm can maintain a high effective specific surface area while ensuring droplet stability, thus maximizing the gas-liquid contact area.

[0140] In this embodiment, to demonstrate the rationality of the decarbonization efficiency, and in conjunction with the ship exhaust gas treatment conditions of the embodiment, focusing on the calcium and magnesium ion utilization rate of 85% and the effect of solution alkalinity enhancement, the rationality of the CO2 capture rate of 68.0% is verified through formula calculation and quantitative analysis. The core verification process is as follows.

[0141] Key parameters of the example: exhaust gas flow rate 39850 kg / h, CO2 concentration 7.05 wt%; replenishment of seawater desalination waste liquid in the supergravity reactor 1200 kg / h, the compound waste liquid is an alkaline system (pH=9.5), calcium and magnesium ion utilization rate 85%; reactor residence time 15 s, atomized particle size 50-80 μm.

[0142] Verification using the formula yields: CO2 mass flow rate in exhaust gas: 63850.68 mol / h; Effective calcium and magnesium ion concentration: 29.15 kg / h; Effective ion concentration of the entire system: 36907.85 mol / h; Solubility improvement rate: 77.8%; Ion solubility ratio: 85%; Mass transfer coefficient improvement factor: 1.6; Theoretical capture rate: 57.8%, actual capture rate calculated: 68%, which perfectly matches the measured value in the example, thus verifying the validity.

[0143] The solid-containing mixed liquid discharged from the supergravity reactor (flow rate 41,000 kg / h, containing 0.25 wt% solid precipitate) is transported to a gravity centrifuge for solid-liquid separation. Approximately 100 kg / h of carbon capture mineralization solid precipitate is separated and sent to the ship's slag hold, where it is combined with the sulfur and nitrate reaction precipitate for collection. The separated solid-free liquid phase is divided into two parts: one part (39,000 kg / h) is returned to the supergravity reactor to continue participating in the mineralization reaction, and the other part (2,000 kg / h), after passing quality tests, is discharged into the sea as a clear liquid. The CO3 in the discharged liquid phase... 2- HCO3 - The concentrations were all below the limits for marine emissions from ships, and there was no secondary pollution.

[0144] Absorbent recovery and reuse process: In this embodiment, the system unit uses nanofiltration membrane separation to concentrate EDTA-Fe. 2+ DMSO is concentrated using vacuum distillation, enabling efficient recovery of low-concentration absorbent from the reflux liquid phase of the hollow fiber membrane contactor. This maintains a stable concentration of the effective components in the compound absorbent and significantly reduces absorbent loss. The nanofiltration membrane used is Ti3C2T. x -MXene / N-GQDs composite modified polyvinylidene fluoride nanofiltration membrane utilizes waste heat from ship boiler exhaust gas through vacuum distillation, eliminating additional steam consumption and meeting the low-cost operation and maintenance needs of ships.

[0145] Nanofiltration membrane separation and concentration of EDTA-Fe 2+ The low-concentration liquid phase (870 kg / h) fed from the membrane contactor reflux liquid phase is adjusted to pH 8.0 with an alkaline adjuster (NaOH solution), and then filtered through a precision filter with a filtration accuracy of 0.2 μm to remove suspended impurities. It is then pumped by a pressurized pump to the nanofiltration membrane separator, operating at an operating pressure of 0.8 MPa and an operating temperature of 25℃. The nanofiltration membrane is used to separate EDTA-Fe... 2+ With a retention rate of ≥96%, EDTA-Fe in the liquid phase will be removed. 2+ The concentration was increased from 0.025 mol / L to 0.085 mol / L, resulting in a high concentration of EDTA-Fe at a flow rate of 218 kg / h. 2+ The solution is directly refluxed to the hollow fiber membrane contactor tube side to replenish the EDTA-Fe in the absorbent. 2+ The concentration was reduced to an initial 0.08 mol / L; the 652 kg / h nanofiltration waste liquid generated during the nanofiltration separation process was collected in the ship's slag hold, with no external pollution discharge.

[0146] DMSO Concentration via Vacuum Distillation: The liquid phase separated by the nanofiltration membrane is combined with another portion of the low-concentration reflux liquid from the membrane contactor, and a total of 1200 kg / h is transported to the vacuum distillation tank. Waste heat from the ship's boiler is used to heat the liquid phase in the tank to 65°C, while simultaneously evacuating the tank to -1.3 kPa to achieve vacuum distillation of DMSO. During distillation, the DMSO in the liquid phase is concentrated from 7.2 wt% to a 98.5% DMSO fraction at the top of the tank (105 kg / h). This fraction is transported to an ice machine heat exchanger for condensation and cooling to 25°C, forming a high-concentration DMSO liquid, which is directly refluxed to the hollow fiber membrane contactor tube side to replenish the DMSO concentration in the absorbent to the initial 8 wt%. The 15 kg / h of ambient temperature condensate generated during distillation is collected and used specifically for backwashing the nanofiltration membrane. Backwashing is performed every 4 hours to effectively prevent membrane clogging caused by impurities adsorbed onto the nanofiltration membrane surface, ensuring long-term stable operation of the nanofiltration membrane.

[0147] Through nanofiltration membrane separation and vacuum distillation combined, the overall recovery rate of DMSO in the system reached 92%, and EDTA-Fe 2+ With a comprehensive recovery rate of 96%, the effective components in the compound absorbent do not require large-scale replenishment; only a small amount needs to be added to maintain a stable concentration, significantly reducing the procurement and loss costs of the absorbent.

[0148] In summary, for a ship exhaust gas treatment capacity of 40,000 kg / h, this integrated desulfurization, denitrification, and decarbonization treatment method leverages the core equipment advantages of hollow fiber membrane contactors and high-gravity reactors, combined with auxiliary processes such as absorbent recovery and reuse. It also fully utilizes existing resources such as ship desalination wastewater, ballast water electrolyte, and boiler exhaust heat to achieve simultaneous and efficient treatment of sulfur, nitrate, and carbon pollutants, with an SO2 removal rate of 92.5% and NO... x With a removal rate of 91.8% and a CO2 capture rate of 68.0%, the treatment efficiency of the three pollutants is highly consistent with the optimal performance test results of the core equipment and membrane components.

[0149] During overall system operation, no additional large-scale supporting equipment is required. Both the hollow fiber membrane contactor and the high-gravity reactor are compact devices, effectively reducing the overall system footprint. The absorbent achieves efficient recycling through a recovery and reuse process, utilizing DMSO and EDTA-Fe... 2+ The loss rate is reduced to less than 0.5% of the system's processing capacity. Simultaneously, the system utilizes the ship's own resources to replace specialized absorbents and mineral raw materials, eliminating the procurement and storage costs of specialized materials. The system's energy consumption relies entirely on the ship's own waste heat and low-pressure energy, with no additional steam or electricity consumption. The cost per ton of waste gas treated is reduced by 45% compared to traditional processes.

[0150] The system generates a total solid residue collection capacity of 480 kg / h, which is all collected in the ship's residue tank for unified treatment. The discharged liquid phase is a qualified clear liquid, and the flow rate is controlled within 2000 kg / h. This achieves the harmless and resource-based treatment of ship exhaust gas, adapts to the working conditions of ships at sea, and combines high efficiency, economy and environmental friendliness.

[0151] Example 5 This embodiment verifies the applicability of the system and method provided in the above embodiments to the ship exhaust gas range.

[0152] Specifically, using integrated desulfurization, denitrification, and decarbonization treatment systems for ship exhaust with target waste gas treatment capacities of 20,000 kg / h, 40,000 kg / h, and 60,000 kg / h as core implementation cases, this study leverages two core pieces of equipment—a hollow fiber membrane contactor and a high-gravity reactor—along with nanofiltration membrane separation and absorbent vacuum distillation as auxiliary processes, to comprehensively verify the adaptability of the technical solution under different treatment scales. Simultaneously, through multi-dimensional comparisons with traditional combined desulfurization, denitrification, and decarbonization processes and single-membrane waste gas treatment processes, the efficiency, cost, and energy consumption advantages of this technology are highlighted. Furthermore, long-term stability data from 30 days of continuous system operation is supplemented to verify the reliability of the technology in long-term marine operations.

[0153] The ship's actual operating parameters are as follows: seawater temperature 32℃, freshwater temperature 36℃, initial exhaust gas temperature 45℃, initial pressure 3 kPa; initial concentration of DMSO in the compound absorbent is 8wt%, EDTA-Fe 2+ The initial concentration was 0.08 mol / L. The seawater desalination waste liquid and ballast water electrolyte were mixed at a volume ratio of 1:1. The two types of ship-owned waste liquid accounted for 65% of the total mass of the mixed absorbent.

[0154] For three typical operating conditions of ship main engine exhaust gas treatment capacity of 20,000 kg / h, 40,000 kg / h, and 60,000 kg / h, system operation tests were carried out respectively. The core operating parameters and treatment effects are shown in the table below, which fully verifies the adaptability of the technology under different treatment scales.

[0155] Table 4. Core operating parameters and treatment effects for different ship main engine exhaust gas treatment capacities.

[0156] Based on the above results, a multi-condition adaptability analysis was conducted. Regarding the adaptability of processing efficiency, the SO2 removal rate remained stable at 92.3%-92.6% under the three conditions, and the NO removal rate was [missing information]. x The removal rate remained stable at 91.6%-91.9%, the CO2 capture rate remained stable at 67.5%-68.3%, and the calcium and magnesium ion utilization rate remained at 84.8%-85.2%, with no significant fluctuations in treatment efficiency. This proves that the method of this invention is adaptable to the treatment scale of marine main engine exhaust gas in the full range of 20,000-60,000 kg / h. The core equipment and process parameters do not require significant adjustments; only proportional matching of the absorbent circulation flow rate and replenishment amount is needed to achieve stable and efficient treatment. Regarding resource utilization adaptability, as the exhaust gas treatment volume increases, the total circulation flow rate of the compound absorbent and the replenishment amount of seawater desalination waste liquid are increased synchronously in a 1:2:3 ratio. DMSO and EDTA-Fe... 2+ The concentration and nanofiltration waste liquid volumes also increased proportionally, while the absorbent recovery rate remained stable at 92% (DMSO) / 96% (EDTA-Fe). 2+ The utilization rate of ship-owned waste liquids (seawater desalination waste liquid and ballast water electrolyte) has remained above 65%, and there has been no waste of resources or insufficient supply due to the expansion of the treatment scale.

[0157] Solid waste and marine discharge compatibility: The total amount of solid waste residue collected is positively correlated with the amount of waste gas treated, and the flow rate of the treated clear liquid discharged into the sea increases proportionally. Furthermore, under all operating conditions, the CO3 concentration in the discharged liquid phase is [missing information]. 2- HCO3 - The concentrations are all below the limits for marine emissions from ships, with no secondary pollution, and are suitable for the solid waste storage and marine discharge management needs of ships of different sizes.

[0158] Furthermore, this embodiment selects the traditional desulfurization, denitrification and decarbonization combined process (alkaline solution absorption + activated carbon adsorption + calcium decarbonization) and the single membrane waste gas treatment process (PVDF membrane absorption + physical decarbonization) as controls, and conducts a comparison from the dimensions of treatment efficiency, operating cost, energy consumption, absorbent loss and system footprint. Specific data are shown in Table 5.

[0159] Table 5. Parameter comparison between the present invention and traditional processing methods

[0160] In summary, the treatment system and method provided by this invention take the efficient mass transfer of hollow fiber membranes, enhanced mineralization under hypergravity, and resource utilization of ship's own waste liquid as the core synergistic route. Targeting the special working conditions of ship exhaust gas treatment, it breaks through the dual bottlenecks of large efficiency fluctuations and high costs of traditional desulfurization, denitrification, and decarbonization processes, as well as insufficient selectivity and weak stability of single membrane decarbonization methods, and constructs a highly efficient, economical, and highly adaptable integrated treatment solution.

[0161] In terms of pollutant removal efficiency, the multi-unit synergistic effect achieves simultaneous and efficient purification of sulfur, nitrate, and carbon: the SO2 removal rate is stable at 92.3%-92.6%, significantly higher than that of single membrane processes (85%-88%), and avoids efficiency fluctuations caused by alkali fluctuations in traditional processes; NO x The removal rate reaches 91.6%-91.9%, a significant improvement over traditional processes (55%-85%), and comparable to and more stable than single membrane methods (90%-92%). The CO2 capture rate reaches 67.5%-68.3%, an improvement of 12.5%-18.3% over traditional processes and 7.5%-13.3% over single membrane methods, solving the technical pain points of insufficient gas-solid contact in traditional processes and limited physical separation selectivity in single membrane methods.

[0162] In terms of cost control and energy consumption optimization, this technology achieves cost reduction and low-energy operation across the entire chain by using ship-owned waste liquid to replace specialized reagents and absorbents in a highly efficient closed-loop recycling strategy. The unit waste gas treatment cost is only 4.2-4.7 yuan / ton, a reduction of 41%-65% compared to traditional processes (8-12 yuan / ton) and 21%-42% compared to single membrane methods (6-8 yuan / ton). The absorbent loss rate is only 0.4%-0.6%, far lower than traditional processes (3%-5%) and single membrane methods (2%-3%). Relying on modular compact design and full utilization of ship waste heat, the unit energy consumption is only 35-42 kWh / ton of waste gas, a reduction of 58%-77% compared to traditional processes and 48%-65% compared to single membrane methods. The total system footprint is only 30-38 m². 2 / 10000kg / h of waste gas, reducing it by 53%-75% compared to traditional processes and by 37%-60% compared to single membrane methods, and is suitable for ship equipment installation space.

[0163] In terms of long-term operational stability, thanks to the synergistic protection of the corrosion-resistant structure of the hollow fiber membrane, the high-efficiency solid-liquid separation under ultra-gravity, and the closed-loop recovery of the absorbent, this technology exhibits extremely strong adaptability to marine operating conditions: the efficiency decay rate after 30 days of continuous operation is only 0.8%-1.2%, which is far lower than that of traditional processes (3%-5%) and single membrane processes (<3%). It can effectively resist the interference of complex operating conditions such as ship vibration and corrosion, and avoid the sudden drop in performance caused by the decay of reagents in traditional processes and the membrane fouling of single membrane processes, providing a reliable guarantee for exhaust gas treatment for long-term marine operations.

[0164] Therefore, the technical approach of hollow fiber membrane, ultragravity, and self-owned resources in the various embodiments of the present invention not only takes into account the high efficiency of pollutant removal and the optimal cost throughout the entire life cycle, but also meets the core requirements of low energy consumption, small footprint, and long-term reliable operation of ships. It is the optimal technical path for the integrated treatment of desulfurization, denitrification and decarbonization of ship exhaust gas.

[0165] Example 6 To verify the reliability of the system under long-term offshore operation scenarios, this embodiment conducted a 30-day continuous operation test under the baseline condition of 40,000 kg / h exhaust gas treatment capacity. The test focused on monitoring the performance of core equipment, pollutant treatment efficiency, absorbent loss, and system operating status. The test results are shown in Tables 6-8. All data are daily averages.

[0166] Table 6 Changes in the Removal Rate of Core Pollutants

[0167] Table 7 Performance Changes of Core Equipment

[0168] Table 8 Absorbent Loss and System Operating Status

[0169] The experimental results above demonstrate that the treatment method of this invention is suitable for ships in terms of treatment efficiency, equipment performance, and absorbent consumption. Regarding treatment efficiency, after 30 days of continuous operation, SO2 and NO... x The CO2 removal rates decreased by only 0.43%, 0.49%, and 0.61%, respectively, and the calcium and magnesium ion utilization rate decreased by less than 0.5%. The core treatment efficiency showed no significant decline, fully meeting the treatment standards for long-term ship operations. Regarding equipment performance, the performance degradation rates of the core equipment (hollow fiber membrane, ultragravity reactor, nanofiltration membrane, and vacuum distillation tank) were all below 4%. As a key mass transfer element, the porosity and tensile strength of the hollow fiber membrane remained within acceptable limits, with no issues such as membrane fiber breakage or a sharp drop in mass transfer efficiency, making it suitable for the complex operating conditions of shipboard vibration and corrosion. Regarding absorbent loss, the 30-day DMSO and EDTA-Fe... 2+ The total losses are only 18.6 kg and 8.2 kg respectively, and the absorbent loss rate is controlled below 0.6%. Relying on the recovery process of nanofiltration membrane and vacuum distillation, only a small amount of fresh replenishment is needed to maintain the stability of the absorbent concentration, which greatly reduces the operation and maintenance costs. For system operation, the energy consumption relies entirely on the ship's own resources, without any additional external energy dependence. The overall system has good long-term stability and is suitable for the operation and maintenance needs of ships sailing at sea for a long time.

[0170] This invention provides an integrated desulfurization, denitrification, and decarbonization treatment method and system for ship exhaust gas. It deeply leverages the ship's own resource potential, using seawater desalination waste liquid and ballast water electrolyte as core raw materials. Utilizing waste heat from the exhaust boiler, it constructs a closed-loop model of self-resource-exhaust gas treatment-resource regeneration, reducing external dependence and investment in supporting equipment. This not only achieves integrated treatment of multiple pollutants in exhaust gas, meeting environmental standards without secondary pollution, but also simultaneously removes sulfur oxides, nitrogen oxides, and carbon dioxide, with pollutants removed in the form of solid precipitates for easy collection. Furthermore, it is low-cost and space-saving, reducing system investment and maintenance costs by using byproducts to replace dedicated materials, selecting compact core equipment, and enhancing absorbent circulation. The process is highly efficient and stable, easy to operate, and economical, employing membrane contactors and enhanced mass transfer via ultragravity to improve gas-liquid contact and pollutant removal efficiency. The process is simple, with the absorbent concentrated via nanofiltration membrane and regenerated by vacuum distillation, resulting in low loss and outstanding stability and economy. Moreover, the method of this invention achieves integrated desulfurization, denitrification, and decarbonization. After two-stage treatment, the pollutant emission concentration of the exhaust gas discharged from the hull side meets the marine environmental protection standards, avoiding penalties for exceeding emission standards. The solid precipitates generated by the method are collected in the residue tank and can be disposed of uniformly after docking in port, eliminating the problem of random discharge of solid waste at sea. Some liquid phases are treated before being discharged into the sea, and the water quality meets the standards for ship discharge into the sea, preventing secondary pollution to the marine environment. Furthermore, the raw materials adopt the ship waste recycling model, reducing the environmental pressure of direct waste discharge. It fully complies with marine environmental compliance requirements and is suitable for navigation restrictions in various sea areas around the world.

[0171] Specifically, this invention directly uses the wastewater generated by the ship's seawater desalination system as the core raw material for the decarbonization process, eliminating the need for additional procurement of dedicated decarbonization mineralization raw materials. The ship's ballast water electrolyte is efficiently reused, serving as a regenerated raw material for the desulfurization and denitrification absorbent components, ensuring the absorbent's recycling, and also acting as an oxidizing raw material for target components in the exhaust gas, aiding in pollutant conversion and removal. Simultaneously, the small amount of steam generated by the ship's exhaust boiler is utilized to provide the necessary heat source for the regeneration process of the desulfurization absorbent, eliminating the need for additional heating equipment. Through multi-dimensional and efficient utilization of the ship's existing resources, the large-scale addition of external additives is avoided from the source, while also eliminating the need for additive storage, preparation, and supporting auxiliary equipment, significantly improving the process's ship adaptability and environmental friendliness.

[0172] This invention balances economic efficiency and spatial adaptability, perfectly meeting the core needs of ships with limited space and sensitive operating costs. Firstly, on the raw material side, it utilizes the ship's own resources to replace specialized materials, directly applying seawater desalination waste liquid and ballast water electrolyte to the entire process of desulfurization, denitrification, and decarbonization of waste gas. This eliminates the need for investment in purchasing specialized mineral raw materials and also eliminates the need for storage tanks, pipelines, and other supporting equipment for these materials. This significantly reduces upfront equipment investment and subsequent raw material procurement costs, while also minimizing the space required for auxiliary equipment, fully demonstrating the economic applicability and spatial compatibility of the process in a shipboard setting. Secondly, the system optimizes the selection of core devices at each equipment end, specifically employing hollow fiber membrane contactors as the core equipment for desulfurization and denitrification. Leveraging their high mass transfer efficiency and compact structure, these devices significantly reduce the footprint compared to traditional tower-type equipment. Simultaneously, a high-gravity reactor is selected for decarbonization, utilizing its enhanced mass transfer and small size to further reduce the overall system footprint, effectively solving the problem of limited space on ship decks and in cabins, and significantly improving the system's spatial adaptability. Finally, the absorbent at the consumable end of this invention is recovered and reused through a DMSO distillation process with EDTA-Fe. 2+ The synergistic application of nanofiltration recovery technology enables the recycling and reuse of most of the desulfurization and denitrification absorbent raw liquid, significantly reducing absorbent loss, reducing the frequency of absorbent replenishment and procurement costs, and further improving the economic applicability of the process from the operational perspective, forming the core advantages of low cost, low loss and high adaptability.

[0173] Moreover, this invention boasts the dual advantages of simplicity and readily available raw materials. Firstly, the treatment method uses a hollow fiber membrane contactor coupled with a high-gravity reactor as the core treatment unit. Each step is tightly integrated and easy to operate. From waste gas pressurization and mass transfer, solid-liquid reaction and precipitation, to gravity centrifugal separation and liquid-phase reflux, the entire process involves no complex operational steps or equipment control requirements. The process is simple, easy to implement, and suitable for the actual operation and maintenance scenarios of ships at sea. Secondly, the core reaction and absorption consumables of the treatment method are seawater desalination waste liquid and ballast water electrolyte produced by the ship's own operations. These are byproducts of ship operation, eliminating the need to purchase large quantities of specialized treatment agents. The raw materials are readily available, and the resource utilization of ship waste is achieved. DMSO and EDTA-Fe, which play a complexation and transfer role in the process, are used in this method. 2+ Because it participates in the liquid-phase reflux throughout the entire process and repeatedly completes the absorption process, the loss within the system is extremely low. In actual operation, only a small amount of DMSO and EDTA-Fe needs to be added. 2+ This ensures stable process operation, significantly reduces the consumption and procurement costs of special additives, and reflects the process characteristics of readily available raw materials and low operation and maintenance costs.

[0174] In the description of this invention, it should be understood that terms such as “length”, “width”, “upper”, “lower”, “front”, “rear”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inner”, and “outer” indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0175] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0176] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for integrated desulfurization, denitrification, and decarbonization of ship exhaust gas, characterized in that, Includes the following steps: S1. Preparation of compound absorbent: Seawater desalination waste liquid and ballast water electrolyte are injected into the buffer tank at a 1:1 volume ratio, and then mixed with DMSO and EDTA-Fe. 2+ They are injected together into the tube side of the hollow fiber membrane contactor to form a compound absorbent; S2. Desulfurization and denitrification treatment: Ship exhaust gas is pressurized and then introduced into the shell side of the hollow fiber membrane contactor, where it undergoes mass transfer contact with the composite absorbent on the pipe side. Sulfur oxides and EDTA-Fe2+ are selectively absorbed through DMSO. 2+ Nitrogen oxides are captured by complexation and converted into solid precipitates by calcium and magnesium ions in seawater desalination wastewater. After centrifugation, the liquid phase is recycled and reused, and the solid precipitate is collected in the residue tank. S3. Decarbonization treatment: The waste gas after desulfurization and denitrification is transported to the supergravity reactor and undergoes a mass transfer reaction with the seawater desalination waste liquid. The supergravity field atomizes the seawater desalination waste liquid into 50-80μm microdroplets. Calcium and magnesium ions react with carbon dioxide to generate solid precipitates. After centrifugation, part of the liquid phase meets the standards and is discharged into the sea, while the other part is recycled. S4. Absorbent Regeneration: EDTA-Fe is concentrated using nanofiltration membrane separation. 2+ DMSO is concentrated by vacuum distillation, and the concentrated absorbent is refluxed back to the hollow fiber membrane contactor to achieve recycling.

2. The integrated desulfurization, denitrification, and decarbonization treatment method for ship exhaust gas according to claim 1, characterized in that, In S2, DMSO in the compound absorbent selectively absorbs sulfur oxides in ship exhaust gas through dipole-dipole interactions. EDTA-Fe in compound absorbent 2+ By forming stable complexes with nitrogen oxides in ship exhaust gas through complexation, nitrogen oxides are transferred from the gas phase to the liquid phase, achieving efficient capture of nitrogen oxides. Using seawater electrolyzed water generated by electrolyzing ballast water as a reducing agent, the hydroxyl radicals generated by electrolysis reduce ferric ions to ferrous ions; Using the desalination wastewater generated by the seawater desalination plant as a precipitant, the high concentration of Mg in it is utilized. 2+ With Ca 2+ The ionized nitrogen oxides and sulfur oxides in the liquid phase are converted into solid precipitates, thus completing the removal process.

3. The integrated desulfurization, denitrification, and decarbonization treatment method for ship exhaust gas according to claim 1, characterized in that, The nanofiltration membrane separation method includes: Select the EDTA-Fe content discharged from the tube-side outlet of the hollow fiber membrane contactor. 2+ The compound absorbent is adjusted to alkaline pH by an alkaline adjuster, and then suspended impurities are removed. The compound absorbent after removing impurities is pumped to a nanofiltration membrane separator via a pressurized pump. The nanofiltration membrane separator uses a negatively charged nanofiltration membrane with a molecular weight cutoff of 200-400. The operating pressure of the nanofiltration membrane separator is controlled at 0.6-1.0 MPa, and backwashing is performed once every 24 hours. The backwashing medium is condensate at room temperature of 25-30℃ produced by vacuum distillation. EDTA-Fe is retained through the sieving effect and charge repulsion effect of nanofiltration membrane. 2+ To achieve EDTA-Fe 2+ Concentration, concentrated EDTA-Fe 2+ The solution is returned to the hollow fiber membrane contactor for reuse, and the nanofiltration waste liquid is collected in the residue chamber.

4. The integrated desulfurization, denitrification, and decarbonization treatment method for ship exhaust gas according to claim 3, characterized in that, The nanofiltration membrane separator is equipped with a nanofiltration membrane, and the nanofiltration membrane preparation method includes the following steps: Support layer modification: The support layer uses a plasma-modified polyvinylidene fluoride ultrafiltration membrane. The polyvinylidene fluoride ultrafiltration membrane is treated with a mixed plasma of argon and oxygen in a volume ratio of 4:

1. The gas flow rate, power, treatment time and vacuum degree are controlled to optimize the functional groups and pore structure on the membrane surface. In-situ interface aggregation: First, prepare a mixture containing piperazine, triethanolamine, and Ti3C2T. x The aqueous solution of MXene / N-GQDs composite filler was uniformly dispersed by ultrasonication and stirring; the modified support layer was immersed in the aqueous solution, removed and purged with nitrogen to control the amount of monomer adsorption on the surface. Then, an interfacial polymerization reaction is carried out, in which the support layer of the adsorbed aqueous monomer is immersed in an organic phase solution of n-hexane containing trimesoyl chloride to conduct an interfacial polycondensation reaction, forming polyamide-Ti3C2T. x -N-GQDs composite functional layer; Gradient post-processing: Unreacted monomers and residual solvents were removed by low-temperature water washing, and mild cross-linking modification was performed using glutaraldehyde aqueous solution. Then, ionization modification was performed using sodium citrate solution to increase the surface carboxyl group density. The post-treated membrane is dried with low-temperature hot air to control its moisture content; it is then sealed with seawater-resistant epoxy adhesive and assembled into flat or spiral wound membrane modules.

5. The integrated desulfurization, denitrification, and decarbonization treatment method for ship exhaust gas according to claim 4, characterized in that, Methods for preparing aqueous monomer solutions include: Piperazine was used as the aqueous monomer at a concentration of 1.6-1.8 wt%, and 0.6-0.8 wt% triethanolamine was added as a catalyst, while 0.03-0.06 wt% Ti3C2T was dispersed and added simultaneously. x -N-GQDs composite filler, wherein the mass ratio of MXene to N-GQDs is 2:1, is then ultrasonically dispersed at 220W power for 20-25 min, magnetically stirred at 250 r / min speed for 30-40 min, and the system temperature is controlled at 26-28℃. The modified support layer was immersed in an aqueous solution for 2.2-2.8 minutes. After removal, it was purged with nitrogen gas at a wind speed of 0.3-0.5 m / s for 15-20 seconds to remove excess liquid film from the surface, thus stabilizing the aqueous monomer adsorption capacity at 0.8-1.0 mg / cm³. 2 .

6. The integrated desulfurization, denitrification, and decarbonization treatment method for ship exhaust gas according to claim 1, characterized in that, The vacuum distillation method includes: The compound absorbent containing DMSO discharged from the tube-side outlet of the hollow fiber membrane contactor is selected and fed into a vacuum distillation tank. Ship exhaust gas is passed into a coiled heat exchanger in a vacuum distillation tank, where the waste heat from the exhaust gas is used to heat the compounded absorbent. The heat exchanger has a heat exchange area of ​​15-18 m². 2 The vacuum distillation vessel has a volume of 1.5 m³. 3 Control the heating temperature to 55-75℃; The vacuum distillation vessel is evacuated to 1.2-1.5 kPa to evaporate the DMSO in the compound absorbent, forming a high-concentration DMSO fraction. The DMSO fraction is condensed to 25-30℃ using an ice machine, and the condensed DMSO is then returned to the hollow fiber membrane contactor for reuse.

7. The integrated desulfurization, denitrification, and decarbonization treatment method for ship exhaust gas according to claim 1, characterized in that, The hollow fiber membrane contactor is equipped with a hollow fiber membrane module, and the method for preparing the hollow fiber membrane includes the following steps: Sa. Preparation of casting solution: Select polyvinylidene fluoride or polypropylene as the film matrix material, N,N-dimethylacetamide as the solvent and polyethylene glycol as the pore-forming agent, mix them in proportion, stir until a uniform and transparent casting solution is formed, and let it stand to remove bubbles. Sb, Spinning and Forming: The deaerated casting solution is extruded through a spinning spinneret using a dry-wet spinning method. The spinning solution is used as the external phase and the ethanol aqueous solution is used as the core solution. The spinning solution extruded from the spinneret directly enters the coagulation bath. The distance between the spinneret and the surface of the coagulation bath is 10-15 cm. The coagulation bath is pure water at 25-30℃. After the casting solution is extruded, it enters the coagulation bath and quickly coagulates to form a nascent hollow fiber membrane. Sc. Post-processing: The nascent hollow fiber membrane is removed from the coagulation bath and immersed in pure water to remove residual solvents and pore-forming agents from the membrane; then it is dried to obtain a hollow fiber membrane suitable for hollow fiber membrane contactors. Sd, Modification treatment: The dried hollow fiber membrane is immersed in an aqueous solution of glutaraldehyde as a crosslinking modifier to perform crosslinking treatment on the dried membrane, and then rinsed and dried after removal.

8. The integrated desulfurization, denitrification, and decarbonization treatment method for ship exhaust gas according to claim 7, characterized in that, The structural features of the hollow fiber membrane module include: A single membrane module contains 1000-1200 membrane fibers, with an inner diameter of 0.5-0.6 mm and an outer diameter of 0.8-1.0 mm. The module diameter is 80-100 mm, the module length is 500-800 mm, and the effective membrane area is 8-10 m². 2 .

9. An integrated desulfurization, denitrification, and decarbonization treatment system for ship exhaust gas, characterized in that, The integrated desulfurization, denitrification and decarbonization treatment method for ship exhaust gas as described in any one of claims 1-8 includes a raw material supply unit, a core reaction unit, a separation and recovery unit and a recycling unit, with each unit interconnected to form a closed-loop system.

10. The integrated desulfurization, denitrification, and decarbonization treatment system for ship exhaust gas according to claim 9, characterized in that, The raw material supply unit includes a waste liquid buffer tank and an electrolyte buffer tank, both of which are connected to the core reaction unit via pipelines. The core reaction unit includes a hollow fiber membrane contactor and a hypergravity reactor. The hollow fiber membrane contactor has a tube-side inlet, a tube-side outlet, a shell-side inlet, and a shell-side outlet. The tube-side inlet is connected to the raw material supply unit and the recycling unit. The shell-side inlet is used to receive ship exhaust gas. The shell-side outlet is connected to the inlet of the hypergravity reactor. The hypergravity reactor has a waste liquid inlet, a waste gas inlet, a liquid phase outlet, and a gas phase outlet. The waste liquid inlet is connected to the waste liquid buffer tank. The separation and recovery unit includes a gravity centrifuge and a residue compartment. The gravity centrifuge is connected to the tube-side outlet of the hollow fiber membrane contactor and the liquid phase outlet of the ultragravity reactor, respectively. The residue compartment is connected to the solid outlet of the gravity centrifuge. The regeneration unit includes a nanofiltration membrane separator and a vacuum distillation tank. The inlet of the nanofiltration membrane separator is connected to the tube-side outlet of the hollow fiber membrane contactor, and the outlet of the nanofiltration membrane separator is connected to the tube-side inlet of the hollow fiber membrane contactor. The inlet of the vacuum distillation tank is connected to the tube-side outlet of the hollow fiber membrane contactor, and the outlet of the vacuum distillation tank is connected to the tube-side inlet of the hollow fiber membrane contactor.

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