Iron-air battery-denitrification and phosphorus removal system coupled with multiple scenarios in coastal areas and its application

Abstract

The application discloses a coastal multi-scene coupled iron-air battery and denitrogenation and dephosphorization system and application thereof, and relates to the technical field of iron-air battery and combined denitrogenation and dephosphorization of sewage. The system comprises an iron anode, an air cathode, an electrolyte, a wind-solar power coupling interface, a power supply interface and a charging and discharging control module. The iron anode comprises an iron base body and a hydrogen evolution inhibitor loaded on the surface of the iron base body. The air cathode comprises a cathode base body, and the surface of the cathode base body is loaded with Co3O4-Ni heterojunction or Fe-doped Co3O4 nanosheet. The electrolyte is pretreated mariculture tail water. The charging and discharging control module is used for switching of a discharging dephosphorization mode, a charging denitrogenation mode and a mixed operation mode. The application realizes energy storage, denitrogenation and dephosphorization functions, integrates the energy storage battery and mariculture tail water treatment, couples wind-solar power generation, energy storage peak regulation, mariculture, tail water treatment and island / data center power supply, and forms a five-in-one collaborative development mode.

Description

Technical Field

[0001] This invention relates to the field of iron-air batteries and wastewater denitrification and phosphorus removal technology, and particularly to iron-air battery-denitrification and phosphorus removal systems coupled in multiple coastal scenarios and their applications. Background Technology

[0002] With the rapid development of renewable energy sources such as offshore wind power and photovoltaics, the intermittency and volatility of these renewable energy sources have become prominent issues, necessitating long-term energy storage technologies. Iron-air batteries, with their advantages of low cost (theoretically only 1 / 10 the cost of lithium batteries), high safety, and long energy storage time (supporting 10-100 hours of discharge), have become an important technological route for large-scale long-term energy storage.

[0003] However, the development of iron-air battery technology still faces the following two thorny issues:

[0004] (1) Energy storage and water treatment are independent of each other, resulting in low system efficiency.

[0005] Existing iron-air batteries are used solely for pure energy storage (e.g., Form Energy's iron-air battery and Shanghai University's iron-air battery prototype) and do not possess any water treatment capabilities. Electrochemical water treatment equipment (such as electrocoagulation and electrooxidation equipment) requires additional electrical energy. These two approaches operate independently, resulting in large system investments, high operating costs, and an inability to achieve synergistic efficiency.

[0006] (2) The electrolyte of iron-air batteries is expensive and the maintenance is complicated.

[0007] Traditional iron-air batteries use alkaline electrolytes such as KOH, which are costly to prepare and maintain, and suffer from problems such as carbonation and electrolyte evaporation, resulting in poor long-term operational stability. Although there is research on seawater batteries (such as aluminum-seawater batteries and magnesium-seawater batteries), they are all disposable batteries and only utilize the conductivity of seawater, without water treatment capabilities.

[0008] my country's marine aquaculture industry is enormous, accounting for over 60% of global production. However, nitrogen and phosphorus emissions from aquaculture wastewater are a major cause of eutrophication in nearshore waters. Existing electrochemical wastewater treatment technologies (such as electrocoagulation for phosphorus removal and electro-oxidation for nitrogen removal) are all independent water treatment devices requiring external power grid connection, resulting in high operating costs that are difficult for small and medium-sized aquaculture enterprises to afford. Although some patents propose using solar power, these still require separate photovoltaic and water treatment systems, resulting in low integration. These problems lead to traditional marine aquaculture wastewater treatment methods requiring large investments and incurring high operating costs, placing a heavy burden on aquaculture enterprises and hindering their widespread adoption.

[0009] Currently, coastal wind and solar power generation, energy storage for peak shaving, mariculture, wastewater treatment, and power supply for islands / data centers are still operating independently, without synergistic optimization of energy and material flows, resulting in low resource utilization efficiency. Although the concept of "wind-data synergy" (offshore wind power + seabed data center) has been proposed, it only involves power supply and does not form a closed loop with energy storage, aquaculture, and water treatment, lacking a system-level multi-scenario coupling solution.

[0010] For example, Chinese patent CN110902781B provides a device for treating phosphorus-containing wastewater and recovering phosphorus resources using an iron-air battery. It uses ferrous ions generated in situ by an iron electrode as a phosphorus removal agent, achieving phosphorus removal from wastewater without introducing other impurity ions, while also recovering phosphorus resources and electrical energy from the wastewater. However, this patented technology only operates on a single-cycle discharge mode, removing only phosphorus but not nitrogen, and cannot achieve rechargeable energy storage, resulting in a limited functionality. It is only applicable to phosphorus-containing industrial wastewater, not to marine aquaculture tailwater, and does not consider the impact of high salinity or complex water quality. It lacks a system coupling design, being only a single water treatment device and not integrated with scenarios such as wind and solar power generation or data centers. The air cathode only catalyzes the oxygen reduction reaction (ORR) and does not possess the ammonia oxidation reaction (AOR) function, thus failing to achieve recharge-based nitrogen removal.

[0011] Therefore, there is an urgent need to develop an iron-air battery system that can simultaneously achieve multi-functional coupling of energy storage, nitrogen removal, and phosphorus removal, enabling it to be deeply integrated with various coastal scenarios and fill this technological gap. Summary of the Invention

[0012] This invention provides a coastal multi-scenario coupled iron-air battery-denitrification and phosphorus removal system and its application. It proposes for the first time a bidirectional water treatment mechanism of "discharge phosphorus removal + charge denitrification," directly using mariculture wastewater as the electrolyte. This achieves the coupling of four major functions: wind and solar power generation, energy storage and peak shaving, mariculture wastewater treatment, and data center power supply, filling a gap in existing technologies. Specifically, this invention is achieved through the following technologies.

[0013] This invention provides a coastal multi-scenario coupled iron-air battery-denitrification and phosphorus removal system, including an iron anode, an air cathode, an electrolyte, a wind-solar coupling interface, a power supply interface, and a charge-discharge control module;

[0014] The iron anode includes an iron substrate and a hydrogen evolution inhibitor loaded on the surface of the iron substrate; the air cathode includes a cathode substrate and a Co3O4-Ni heterojunction and / or Fe-doped Co3O4 nanosheet array structure loaded on the surface of the cathode substrate.

[0015] The electrolyte is pretreated seawater aquaculture wastewater; the wind-solar coupling interface is used to connect wind power equipment and / or photovoltaic equipment; the power supply interface is used to connect electrical equipment; the charge-discharge control module is used to switch between discharge phosphorus removal mode, charge denitrification mode and hybrid operation mode.

[0016] In the aforementioned iron-air battery-phosphorus removal system, the iron anode module employs a three-dimensional porous structure, which significantly increases the number of reactive sites. During discharge, iron oxidizes to form Fe. 2+ / Fe 3+ The iron oxide reacts with phosphate ions in the electrolyte to form precipitates such as ferric phosphate and lapis lazuli, thus achieving phosphorus removal. During charging, the iron oxide is reduced to elemental iron, completing the energy storage cycle. A surface-loaded hydrogen evolution inhibitor suppresses the hydrogen evolution side reaction during charging, improving coulombic efficiency.

[0017] The air cathode used has a Co3O4-based hydrogen evolution inhibitor loaded on its surface. The air cathode can simultaneously perform three catalytic functions: (1) catalyzing the oxygen reduction reaction (ORR) during discharge; (2) catalyzing the ammonia oxidation reaction (AOR) during charging to achieve denitrification; and (3) catalyzing the oxygen evolution reaction (OER) as a backup charging mode when necessary. The air cathode forms a self-supporting electrode through electron redistribution and doping regulation at the heterostructure interface, which improves conductivity and stability; at the same time, it optimizes the active sites of the three reactions ORR, AOR and OER, thereby realizing "one electrode for three uses".

[0018] The pretreated seawater aquaculture wastewater is used as the electrolyte in the iron-air battery. The salt content provides ionic conductivity, while the nitrogen and phosphorus pollutants it contains can be treated by the electrochemical reaction.

[0019] The selected charge / discharge control module can intelligently switch between discharge phosphorus removal mode, charging denitrification mode, and hybrid operation mode based on energy storage demand, power supply status of wind and solar power equipment, and electrolyte water quality, achieving coordinated optimization of energy flow and material flow. These functions can be switched and implemented using currently known power generation technologies and PLC control chips.

[0020] The selected wind-solar coupling interface connects to renewable energy sources such as offshore wind power equipment and coastal photovoltaic equipment, and utilizes abandoned electricity for charging to achieve wind and solar power consumption and energy storage peak regulation.

[0021] The reserved power supply interface can provide power to various scenarios such as island residents, underwater data centers, and aquaculture facilities, providing long-term backup power and peak-shaving services.

[0022] Furthermore, the iron matrix is ​​one or more of the following: porous sponge iron structure, foamed iron structure, carbonyl iron powder, ordinary iron powder, and rolled iron foil.

[0023] Furthermore, the porosity of the iron matrix is ​​60%-85%, and the specific surface area is not less than 5 m². 2 / g.

[0024] Furthermore, the hydrogen evolution inhibitor is one or more of Bi2O3, SnO2, PbS, CuS, FeS, and MoS2.

[0025] The specific method for loading hydrogen evolution inhibitors such as Bi2O3 and SnO2 onto the iron matrix surface is as follows:

[0026] (1) Synthesis of hydrogen evolution inhibitor powder: The hydrogen evolution inhibitor powder is stirred and mixed in a mixer for 1 h; placed in a high-temperature furnace and sintered at 750°C for 2 h under an inert atmosphere or a reducing atmosphere; cooled to room temperature, crushed and sieved to obtain the hydrogen evolution inhibitor powder.

[0027] (2) Mixing with iron active materials to form a slurry: Add hydrogen evolution inhibitors at a ratio of 5-10 wt% to the negative electrode active iron materials and mix with one or more binders (such as carboxymethyl cellulose CMC, hydroxypropyl methyl cellulose HPMC, polyvinyl alcohol PVA, polytetrafluoroethylene PTFE, etc.) to form a slurry.

[0028] (3) Coating onto iron substrate current collector: The slurry is coated onto the iron substrate current collector, and after drying and rolling, an electrode sheet is formed.

[0029] Furthermore, the cathode substrate is one or more of the following: carbon cloth, nickel foam current collector, conductive ceramic gas diffusion layer, stainless steel mesh, activated carbon-PTFE sintered body, and carbon nanofibers.

[0030] Furthermore, the pretreatment method for the electrolyte involves filtering to remove particulate suspended solids from the seawater aquaculture effluent and adjusting the pH value to 7.5-9.0. For example, a pretreatment unit can be installed to remove large particulate suspended solids through a grid filter and remove fine particulate matter through microfiltration, preventing electrode clogging. Alternatively, a pH adjustment unit can be installed to adjust the pH value of the seawater aquaculture effluent to the optimal range of 7.5-9.0, balancing battery performance and treatment efficiency.

[0031] Furthermore, the discharge phosphorus removal mode is as follows: when the total phosphorus concentration in the mariculture tailwater exceeds a preset threshold, or there is a power supply demand, or the power supply from wind power equipment and / or photovoltaic equipment is insufficient, the charge-discharge control module controls the discharge to oxidize the iron anode into Fe(OH)2, while partially dissolving Fe. 2+ / Fe 3+ Phosphorus is removed by the formation of precipitate with phosphate ions, and the iron-air battery outputs electrical energy.

[0032] The charging and denitrification mode is as follows: when the ammonia nitrogen concentration in the marine aquaculture tailwater is higher than the preset threshold, or when there is a surplus of power supply from wind power equipment and / or photovoltaic equipment, the charging and discharging control module controls the charging process, causing the air cathode to undergo an ammonia oxidation reaction, oxidizing ammonia nitrogen into harmless N2, and reducing Fe(OH)2 generated by the iron anode during the discharge process into elemental iron, thus completing the iron-air battery energy storage.

[0033] The hybrid operation mode is as follows: the discharge phosphorus removal mode and the charging denitrification mode are performed alternately.

[0034] Furthermore, the operating voltage of the discharge phosphorus removal mode is 0.6-1.0 V, and the current density is 5-50 mA / cm². 2 The charging voltage for the charging-to-denitrification mode is 1.2-1.8 V, and the current density is 5-30 mA / cm². 2 .

[0035] Furthermore, it also includes wind power equipment and / or photovoltaic equipment, marine aquaculture modules and power load modules (such as island resident loads and / or subsea data centers).

[0036] This invention also provides a method for nitrogen and phosphorus removal using an iron-air battery coupled in multiple coastal scenarios, employing the aforementioned iron-air battery-nitrogen and phosphorus removal system for nitrogen and phosphorus removal, such as... Figure 5 As shown, it includes the following steps:

[0037] The pretreated effluent from seawater aquaculture is used as an electrolyte and introduced into the iron-air battery-denitrification and phosphorus removal system.

[0038] The iron anode undergoes an oxidation reaction to generate Fe. 2+ Further oxidized to Fe 3+ The phosphorus is removed by reacting with phosphate to form a precipitate, while the oxygen reduction reaction occurs simultaneously at the air cathode, which outputs electrical energy.

[0039] The iron-air battery is charged using surplus wind and solar power. The air cathode undergoes an AOR reaction to oxidize ammonia nitrogen into nitrogen gas, thus achieving denitrification. At the same time, the iron anode undergoes a reduction reaction to reduce iron oxides to elemental iron, thus completing energy storage.

[0040] Periodically drain the precipitates from the iron-air battery denitrification and phosphorus removal system to recover phosphorus-containing compounds;

[0041] The quality of the effluent from the electrolyte is tested regularly, and once it meets the standards, it is discharged or reused in seawater aquaculture.

[0042] This invention relates to the interdisciplinary field of electrochemical energy storage and environmental engineering, specifically to a rechargeable iron-air battery system, and particularly to an integrated system and method that utilizes marine aquaculture wastewater as an electrolyte, simultaneously achieves nitrogen and phosphorus removal during the charging and discharging process, and can be coupled with coastal wind and solar power generation, marine aquaculture, and data center power supply.

[0043] Compared with the prior art, the advantages of the present invention are:

[0044] 1. Bidirectional charging and discharging treatment, simultaneous removal of nitrogen and phosphorus.

[0045] During discharge, phosphorus is removed by dissolution at the iron anode, and nitrogen is removed by ammonia oxidation at the air cathode during charging. Both the charging and discharging processes are used to treat wastewater, and the water treatment efficiency is more than twice that of the traditional single mode. This is the core innovation of this invention.

[0046] 2. Synergistic integration of wind and solar energy consumption with energy storage for peak shaving.

[0047] By utilizing surplus wind and solar power for charging, the intermittency of wind and solar power is solved, the energy consumption cost of water treatment is reduced, and the renewable energy consumption rate is increased by more than 15%.

[0048] 3. Zero cost of electrolyte, turning waste into treasure; phosphorus resource recovery, realizing resource utilization.

[0049] By directly using seawater aquaculture wastewater as the electrolyte, there is no need to prepare expensive alkaline electrolytes. This solves the cost problem of electrolytes and treats aquaculture wastewater, truly achieving "waste treatment with waste." The precipitates such as iron phosphate and lapis lazuli generated during discharge can be recycled as phosphate fertilizers or chemical raw materials, realizing the resource utilization of pollutants and further improving economic benefits.

[0050] 4. Multifunctional coupling and multi-scenario system integration significantly improve system efficiency and effectiveness.

[0051] This invention simultaneously achieves energy storage, nitrogen removal, and phosphorus removal within a single electrochemical system, integrating an energy storage battery with a marine aquaculture wastewater treatment device. It organically couples five scenarios: wind and solar power generation, energy storage for peak shaving, marine aquaculture, wastewater treatment, and power supply for islands / data centers, forming a synergistic development model integrating "energy, environment, agriculture, and digital economy." Ultimately, the overall system investment is reduced by more than 40%, the overall investment payback period is shortened to 6-8 years, and operating costs are reduced by more than 60%.

[0052] 5. Intrinsically safe and widely applicable.

[0053] The iron-air battery of this invention uses a water-based electrolyte, is inherently safe, and has no risk of explosion; it is particularly suitable for scenarios with high safety requirements, such as seabed data centers, islands, and aquaculture areas. Attached Figure Description

[0054] Figure 1 The following is a diagram of the overall architecture of the iron-air battery denitrification and phosphorus removal system of the present invention, which includes multi-scenario coupling of wind and solar power, energy storage, aquaculture and data center.

[0055] Figure 2 and 3 The diagram illustrates the bidirectional denitrification and phosphorus removal principle of the iron-air battery-denitrification and phosphorus removal system of the present invention during charging and discharging.

[0056] Figure 4 The present invention relates to a catalyst structure of an air cathode in an iron-air battery-denitrification and phosphorus removal system, and a schematic diagram of the charging and discharging catalytic principle.

[0057] Figure 5 Here is a process flow diagram of the nitrogen and phosphorus removal process of this invention using an iron-air battery-denitrification and phosphorus removal system. Detailed Implementation

[0058] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0059] Example 1: Laboratory Small-Scale Experiment of Iron-Air Battery-Nitrogen and Phosphorus Removal System

[0060] The iron-air battery denitrification and phosphorus removal system coupled to multiple coastal scenarios provided by the present invention includes an iron anode, an air cathode, an electrolyte, and also includes wind power equipment and / or photovoltaic equipment, a marine aquaculture module and an electrical load module.

[0061] The assembly method for the laboratory-scale iron-air battery-denitrification and phosphorus removal system is as follows: The prepared iron anode and air cathode are fixed onto electrode clamps, ensuring an effective reaction area of ​​4 cm × 4 cm. 250 mL of pretreated simulated seawater aquaculture wastewater is injected as the electrolyte. The two electrodes are connected to an electrochemical workstation (or DC power supply / load) via wires, and a data acquisition device is connected in series in the circuit to monitor voltage, current, and charge changes during charging and discharging. After assembly, the system is allowed to stand for 10 minutes until the open-circuit potential stabilizes before starting the experiment.

[0062] The effective electrolyte reaction volume of this system is 250 mL, and the specific parameters of each structure are as follows.

[0063] (1) Iron anode: Three-dimensional porous sponge iron, size 5 cm × 5 cm × 0.5 cm, porosity 75%, surface coated with Bi2O3 hydrogen evolution inhibitor.

[0064] In this embodiment, the method for preparing the above-mentioned iron anode is as follows:

[0065] Synthesizing hydrogen evolution inhibitor powder: The hydrogen evolution inhibitor powder is stirred and mixed in a mixer for 1 h; placed in a high-temperature furnace and sintered at 750℃ for 2 h under an inert atmosphere or a reducing atmosphere; cooled to room temperature, pulverized and sieved to obtain the hydrogen evolution inhibitor powder.

[0066] Mixing with iron-active materials to form a slurry: Add hydrogen evolution inhibitors at a ratio of 5-10 wt% to the negative electrode active iron materials and mix with one or more binders (such as carboxymethyl cellulose CMC) to form a slurry.

[0067] Electrode sheet coated on iron substrate current collector: The slurry is coated on the iron substrate current collector, and after drying and rolling, it forms an electrode sheet.

[0068] (2) Air cathode: such as Figure 4 As shown, the carbon cloth-supported Co3O4-Ni heterojunction catalyst has a catalyst loading of 2 mg / cm³. 2 .

[0069] In this embodiment, the method for preparing the air cathode is as follows:

[0070] ① Cut the carbon cloth to the required size, and ultrasonically clean it in acetone, anhydrous ethanol and deionized water for 15-30 min each (e.g. 30 min). Then treat it in a concentrated nitric acid bath at 60℃ for 2 h to introduce oxygen-containing functional groups to enhance hydrophilicity. After washing, vacuum dry it for later use.

[0071] ② Co3O4 nanowire arrays were grown on pretreated carbon cloth using a hydrothermal method: 2 mmol Co(NO3)2·6H2O, 10 mmol NH4F and 25 mmol CO(NH2)2 were dissolved in 70 mL of deionized water. The carbon cloth was immersed in the solution and then subjected to a hydrothermal reaction at 120℃ for 6-8 h (e.g., 8 h). After cooling, cleaning and drying, the carbon cloth was calcined in air at 400℃ for 2 h to obtain carbon cloth-supported Co3O4 nanowires (CC / Co3O4).

[0072] ③ Next, NiO nanosheets were coated by chemical bath deposition: 5 mmol Ni(NO3)2·6H2O and 10 mmol hexamethylenetetramine were dissolved in 50 mL of deionized water, and CC / Co3O4 was immersed in the solution and heated in a water bath at 90℃ for 4-6 h (e.g., 6 h) to uniformly coat the surface of Co3O4 nanowires with NiO nanosheets, forming a core-shell structure Co3O4@NiO array.

[0073] ④ After cleaning, calcine in air at 300℃ for 2 hours to strengthen the Co3O4-Ni heterojunction coupling. This is achieved by controlling the Ni... 2 + / Co 2+ The electronic structure was optimized proportionally. The final catalyst loading was controlled by the mass difference of the carbon cloth before and after calcination, and was approximately 2 mg / cm³. 2 If insufficient, the deposition step can be repeated.

[0074] The air cathode prepared above has three catalytic activities: ORR, AOR, and OER.

[0075] The Co3O4-based modified catalyst can simultaneously possess three catalytic functions: catalyzing the oxygen reduction reaction (ORR) during discharge; catalyzing the ammonia oxidation reaction (AOR) during charging to achieve denitrification; and catalyzing the oxygen evolution reaction (OER) as a backup charging mode.

[0076] (3) Electrolyte: simulated seawater aquaculture tailwater, with a salinity of 30‰, ammonia nitrogen concentration of 50 mg / L, total phosphorus concentration of 10 mg / L, and pH=8.0.

[0077] (4) Charge and discharge control module.

[0078] Used for switching between discharge phosphorus removal mode, charging denitrification mode, and hybrid operation mode. Specifically:

[0079] Discharge phosphorus removal mode: salinity 30‰, ammonia nitrogen concentration 50 mg / L, total phosphorus concentration 10 mg / L, pH=8.0. Constant current discharge, current density 10 mA / cm². 2 Discharge to 0.6 V and monitor the total phosphorus removal rate and discharge voltage. Figure 3 As shown, at this time, Fe dissolves from the iron anode. 2+ / Fe 3+ Phosphorus is removed by the formation of precipitate with phosphate ions, and the iron-air battery outputs electrical energy.

[0080] Nitrogen removal charging mode: salinity 30‰, ammonia nitrogen concentration 50 mg / L, total phosphorus concentration 10 mg / L, pH=8.0. Constant current charging, current density 10 mA / cm². 2 Charge to 1.6 V and monitor ammonia nitrogen removal rate and charging voltage. Figure 2 As shown, at this time, an ammonia oxidation reaction occurs at the air cathode, oxidizing ammonia nitrogen into harmless N2 and reducing iron oxide into elemental iron, thus completing the iron-air battery energy storage.

[0081] Hybrid operation mode: Five cycles of cyclic discharge phosphorus removal and charging denitrification, with each cycle lasting 2 hours. Stability and degradation patterns were investigated.

[0082] The experimental results are shown in Table 1 below. The small-scale laboratory experiment verified the feasibility of bidirectional nitrogen and phosphorus removal during charge and discharge, with both nitrogen and phosphorus removal efficiency and battery performance meeting expectations.

[0083] Table 1

[0084]

[0085] Example 2: Pilot-scale system design of iron-air battery-denitrile and phosphorus removal system

[0086] like Figure 1 As shown, the iron-air battery-denitrification and phosphorus removal system used in this embodiment has been adjusted as follows based on Embodiment 1:

[0087] (1) Iron-air battery stack: 20 individual cells are connected in series, with a plate and frame structure. The battery stack power is 10 kW and the energy storage capacity is 100 kWh (10 hours of discharge).

[0088] (2) Set up a pretreatment unit for seawater aquaculture wastewater: including a screen, microfiltration and pH adjustment functions, used to remove particulate matter and adjust pH value respectively; the daily treatment capacity of seawater aquaculture wastewater is 100 m³. 3 / d, applicable farming scale: approximately 100 mu of shrimp farming ponds.

[0089] (3) An electrolyte circulation system was added, including a centrifugal pump, pipelines and a storage tank.

[0090] (4) A solid-liquid separation unit was added, including an inclined plate sedimentation tank and a plate and frame filter press. During the phosphorus removal process in the iron-air battery discharge, Fe dissolved from the iron anode... 2+ / Fe 3+ Phosphate reacts with phosphate ions in the electrolyte to form insoluble precipitates such as FePO4 and Fe3(PO4)2·xH2O (blue iron ore). These precipitates have fine particle sizes and densities close to water; if directly discharged, they will flow out with the effluent, causing secondary pollution and making it impossible to recover phosphorus resources. Therefore, an inclined plate sedimentation tank combined with a plate and frame filter press is used to remove these precipitates.

[0091] (5) A wind-solar coupling interface has been added for connecting wind power equipment and / or photovoltaic equipment.

[0092] This system uses an FL-800DC bidirectional DC / DC energy storage converter (with an EMS-2000 energy management system) as the wind-solar coupling interface. The wind power equipment connected via an 800 V DC bus is a China Shipbuilding Industry Corporation H210-10MW offshore wind turbine (rated power 10 MW, rotor diameter 210 m, suitable for nearshore and deep-sea areas). The photovoltaic equipment is Chint New Energy ASTRO N5-72 n-type TOPCon photovoltaic modules (single module peak power 600 W, module efficiency 23.2%, with excellent salt spray resistance). The DC power output from the wind and solar power generation unit is connected to the 800 V DC bus via a bidirectional DC / DC converter. The iron-air battery energy storage system is connected to the same DC bus via another bidirectional DC / DC converter, realizing energy routing and coordinated scheduling between wind and solar power generation, energy storage, and load.

[0093] (6) A power supply interface has been added. The power supply interface is used to connect the power load module.

[0094] (7) An electrical load module and a battery management module have been added.

[0095] The power supply interface includes a 35 kV fiber optic composite submarine cable (directly connected to the submarine data center) and a 400 V AC power distribution bus (connected to island residents and aquaculture facilities).

[0096] The power load modules cover three typical coastal scenarios:

[0097] ①The submarine data center adopts a submarine data module with a single module power of 2.3 MW and a PUE of ≤1.15. It is provided with long-term backup power of ≥10 hours by this system.

[0098] ② For the load of island residents, referring to the standard of offshore fish raft microgrid, the single-point power supply capacity is increased to 100 kW, covering living, monitoring and electric boat charging;

[0099] ③ Marine aquaculture facilities, including aerators, circulating water pumps and feeding systems, with a total load of approximately 150 kW.

[0100] The battery management module (BMS) is customized for the characteristics of iron-air batteries:

[0101] ①Single-cell monitoring: Real-time monitoring of the iron negative electrode potential, setting a critical threshold to prevent dendrite growth;

[0102] ② Current diversion control: When a cell is fully charged, the excess current is transferred to the remaining cells through a controllable impedance to achieve continuous adjustment of the analog quantity;

[0103] ③System protection: Integrated monitoring of total voltage, current, electrolyte pH and temperature, with multiple protections including overvoltage and overtemperature;

[0104] ④ Mode scheduling: Based on wind and solar power output, load demand and tailwater quality (ammonia nitrogen, total phosphorus concentration), intelligently switch between discharge phosphorus removal, charging nitrogen removal and mixed operation modes; ⑤ Collaborative management: Link with the energy management system (EMS) to achieve optimal control of peak-valley regulation and new energy consumption.

[0105] (8) Charge / discharge control module. Used for switching between discharge phosphorus removal mode, charge denitrification mode, and mixed operation mode.

[0106] (9) Water quality online monitoring system: used to monitor the ammonia nitrogen, total phosphorus, pH, conductivity and other properties of the electrolyte in real time.

[0107] The expected performance indicators set in the online water quality monitoring system of this embodiment are shown in Table 2 below.

[0108] Table 2

[0109]

[0110] Application Example 1: Coastal Multi-Scenario Coupled Demonstration Application of Iron-Air Battery-Denitrification and Phosphorus Removal System

[0111] This application example uses a marine aquaculture demonstration area in a coastal province as the experimental demonstration area. The iron-air battery-denitrification and phosphorus removal system used is configured as follows, based on Example 2:

[0112] 1. Offshore wind power equipment: generating capacity of 10 MW.

[0113] One H210-10MW offshore wind turbine generator set from China Shipbuilding Industry Corporation (CSIC) was selected, with a rated power of 10 MW, a rotor diameter of 210m, and a hub center height of 130m. It is capable of withstanding typhoons in Class I wind zones. The generator set's output voltage is 1.14 kV, which is locally stepped up to 35 kV via a 10 MVA step-up transformer built into the bottom of the tower, and then connected to the onshore control station via a 35 kV fiber optic composite submarine cable. The wind power output is rectified by AC / DC and connected to the site's 800 V DC bus for grid connection on the DC side.

[0114] 2. Iron-air battery energy storage system: 2 MW / 20 MWh (10-hour discharge).

[0115] It adopts a containerized modular architecture, consisting of four independent 5 MWh energy storage units, with a total footprint of approximately 800m². 2 .

[0116] (1) Battery stack structure: Each energy storage unit contains 10 plate-and-frame single stacks, with a rated power of 500 kW per stack. The single stack adopts a bipolar plate design and is composed of 200 individual cells connected in series, with an effective reaction area of ​​50 cm × 50 cm and a sealing pressure of 0.5 MPa.

[0117] (2) Electrical architecture: The battery stack is connected to the DC bus via a bidirectional DC / DC converter (input range 400-800 V, output 800 V DC); and is converted to 400 V AC power by two 1 MW bidirectional DC / AC converters (PCS) and connected to the microgrid.

[0118] (3) Liquid flow pipeline system: Equipped with 2 corrosion-resistant centrifugal pumps (one for use and one for standby, with a flow rate of 250 m³ / h). 3 / h), with a supporting 500 m 3 The electrolyte buffer tank (made of PE material) enables forced circulation of electrolyte between the battery stack and the solid-liquid separation unit through PVC pipelines.

[0119] (4) Thermal management and fire protection: The container is equipped with a negative pressure ventilation system and a salt spray filter on the top; the interior is equipped with a VESDA very early smoke detection system and a perfluorohexanone automatic fire extinguishing device.

[0120] 3. Marine aquaculture wastewater treatment line (5000 m³ / s of marine aquaculture wastewater treatment capacity) 3 / d): An integrated wastewater treatment workshop will be built for a 1,000-mu (approximately 67 hectares) Litopenaeus vannamei (white shrimp) farming area.

[0121] (1) Pretreatment unit: A rotary mechanical bar (5 mm gap) is installed at the inlet to intercept large particles of uneaten food and shrimp shells. Then, the water enters a bag microfilter (50 μm filtration accuracy) to remove fine suspended solids, and the SS in the effluent is reduced to below 20 mg / L.

[0122] (2) pH adjustment unit: Two 50 m units are installed. 3 The pH adjustment tank is equipped with an online pH monitor and an alkaline dosing pump to automatically add NaOH solution and stabilize the pH of the effluent at 8.0±0.2.

[0123] (3) Solid-liquid separation unit: The effluent after the reaction enters the inclined tube sedimentation tank (surface loading 1.0 m). 3 / m 2 The bottom sludge is pumped by a screw pump to a plate and frame filter press (filtration area 100 m²). 2 After dehydration, the mud cake (moisture content <70%) is collected as raw material for phosphate fertilizer, and the filtrate is returned to the equalization tank.

[0124] (4) Online monitoring: A multi-parameter water quality analyzer is installed at the outlet to monitor ammonia nitrogen, total phosphorus, COD and turbidity in real time, and the data is uploaded to the central control system.

[0125] 4. Supporting submarine data center and power supply system: Long-term plan includes access to a 5 MW submarine data center load, using a second-generation submarine data cabin architecture.

[0126] (1) Data cabin configuration: Initially, two standard data cabins will be deployed, with a rated power of 2.3 MW per cabin and accommodating 24 standard 42U racks with a power density of 15 kW per rack.

[0127] (2) Power supply connection: A dual-redundant power supply mode is adopted. The main power supply circuit is directly supplied by the offshore wind farm through a 35 kV fiber optic composite submarine cable; the backup power supply circuit is connected to the 400 V AC bus of the iron-air battery energy storage system and connected through a step-up transformer. The iron-air battery can provide long-term backup power of ≥10 hours when wind power is interrupted.

[0128] (3) Heat dissipation system: Natural cooling is achieved by utilizing the low temperature environment of the seabed. Liquid cooling backplate technology is used inside the data center, and the PUE value is controlled below 1.15, eliminating the need for additional cooling towers.

[0129] 5. Central Energy Management and Control System (EMS)

[0130] A three-story control center was constructed to deploy a Supervisory Control and Data Acquisition (SCADA) system. The system communicates with wind turbines, energy storage converters, battery management systems (BMS), water treatment PLCs, and the data center's environmental monitoring system via the OPC protocol. Based on wind and solar power output forecasts, electricity price signals, and water quality models, the EMS executes a multi-objective optimization scheduling algorithm to automatically generate charging and discharging commands, achieving integrated coordinated operation of the "source-grid-load-storage-pollution" system.

[0131] (1) Nighttime “charging and denitrification + low-cost energy storage” mode (00:00-08:00)

[0132] ①Scenario determination: Based on ultra-short-term wind power forecast data, EMS determined that the nighttime wind power output was greater than the data center's basic load (approximately 2 MW), and the on-grid electricity price was at a low point.

[0133] ② Charging and denitrification process:

[0134] EMS issues a command to control the iron-air battery to enter the constant current charging denitrification mode.

[0135] Power allocation: The charging power is set at 1.5 MW (with some power reserved for data center operation). The charging current density is controlled at 10-15 mA / cm². 2 The charging voltage is maintained at 1.4-1.6 V.

[0136] Water quality linkage: At this time, the electrolyte circulation pump runs at full speed, pumping the marine aquaculture tailwater at a rate of 200 m³ / h. 3A flow rate of [amount] / h is pumped into the battery stack. The air cathode undergoes an ammonia oxidation reaction (AOR) at a high potential, oxidizing ammonia nitrogen in the effluent to N2. The system monitors the effluent ammonia nitrogen concentration in real time to ensure a stable removal rate of over 75%.

[0137] ③ Energy storage target: Utilize cheap wind power at night to increase the battery's SOC (state of charge) from 30% to 90%, thus storing energy for peak discharge the following day.

[0138] (2) Daytime “discharge phosphorus removal + peak adjustment” mode (09:00-17:00)

[0139] ①Scenario determination: EMS monitoring shows that wind power output is weakening during the day, while the data center enters its peak business period (load climbs to 4-5 MW), and the power grid is in its peak price period.

[0140] ② Discharge phosphorus removal procedure:

[0141] The EMS sends a command to control the iron-air battery to switch from charging mode to constant current discharge phosphorus removal mode.

[0142] Peak shaving method: The discharge power is set at 1.0 MW, and the discharge continues for 8 hours. At this time, the battery, as one of the main power sources, shares the load of the data center with wind power, reducing the peak power demand and achieving "peak shaving and valley filling".

[0143] Water quality linkage: The electrolyte is switched to the phosphorus removal process, and Fe is oxidized and dissolved during the discharge process at the iron anode. 2+ / Fe 3+ It combines with phosphate ions in the effluent to form FePO4 precipitate. The discharge voltage is kept stable at 0.7-0.9 V to ensure that the total phosphorus removal rate is maintained above 90%.

[0144] ③ End-of-line treatment: The electrolyte containing ferric phosphate precipitate flows into the inclined plate sedimentation tank for solid-liquid separation, and the precipitate is recovered after pressure filtration.

[0145] (3) Real-time optimized charging and discharging strategy of energy management system (EMS)

[0146] EMS employs a rolling optimization + feedback correction mechanism, performing a global optimization every 5 minutes. The specific logic is as follows:

[0147] ① Multi-objective optimization function:

[0148] EMS uses "minimizing operation and maintenance costs" and "maximizing the probability of water quality meeting standards" as its objective functions. The weighting coefficients are dynamically adjusted according to the season (water quality weighting is increased in summer due to higher water temperature and more algae; power supply reliability weighting is increased in winter due to higher load).

[0149] ②Constraint handling:

[0150] Safety constraints: Real-time monitoring of the iron negative electrode potential; once it approaches the hydrogen evolution potential threshold (-0.95 V vs. SHE), shunt control is immediately activated or the charging current is reduced to prevent dendrite growth.

[0151] Water quality constraints: Ammonia nitrogen >40 mg / L or total phosphorus >8 mg / L is set as the "emergency treatment" trigger line. Once triggered, regardless of the electricity price, the corresponding mode (charging for nitrogen removal or discharging for phosphorus removal) will be activated first until the water quality meets the standards.

[0152] ③ Coping with the uncertainty of scenery:

[0153] Prediction deviation correction: If the actual wind power output is more than 20% lower than the predicted value, the EMS will automatically reduce the charging power or suspend charging to prioritize the power supply to the data center; if the actual output is surplus, the "overcharge protection" logic will be activated to consume the excess power through the braking resistor or through the water electrolysis hydrogen production module.

[0154] Load fluctuation response: When the submarine data center experiences a sudden high load, the EMS instantly (<100 ms) increases the discharge power of the iron-air battery to fill the power gap and ensure the continuity of power supply to the data center.

[0155] ④ Seasonal strategy fine-tuning:

[0156] Summer (peak aquaculture season): The nitrogen and phosphorus concentrations in the effluent are high. The EMS will appropriately extend the single operation time of discharge phosphorus removal and charging denitrification (from 2 hours to 3 hours), sacrificing some peak-valley price difference revenue, and prioritizing the quality of the effluent.

[0157] In winter (when wind resources are abundant): the concentration of pollutants in the tailwater is relatively low. EMS focuses on energy storage and peak shaving, utilizing surplus wind power for full-power charging to maximize the absorption of clean energy.

[0158] The recovered iron phosphate precipitate is sold as phosphate fertilizer to surrounding farmland.

[0159] The expected comprehensive benefits of the above-mentioned iron-air battery-denitrification and phosphorus removal system are:

[0160] (1) According to calculations, the annual renewable energy consumption rate will increase by more than 15%, and the annual consumption of abandoned wind power will be approximately 8.0 × 10⁻⁶. 7 kWh, the wind power self-consumption rate has increased to over 95%.

[0161] (2) It is estimated that approximately 1.8 million cubic meters of aquaculture wastewater will be treated annually. 3 This will reduce ammonia nitrogen emissions by approximately 60 tons and total phosphorus emissions by approximately 15 tons annually.

[0162] (3) It is estimated that about 12 tons of iron phosphate will be recovered annually, resulting in an additional income of about 300,000 yuan.

[0163] (4) According to calculations, the backup power supply time of the data center is ≥10 hours, which is much longer than the 2-4 hours of lithium batteries.

[0164] (5) According to calculations, the annual operating cost of the project has been reduced from RMB 9.85 million to RMB 3.9 million, a reduction of more than 60%.

[0165] (6) The overall investment in the system is reduced by 72%, and even a conservative estimate can reduce it by 40%. Considering the high cost of the pilot stage of iron-air batteries and the time required for the implementation of the wastewater treatment fee policy, the investment payback period is conservatively estimated to be shortened to about 6-8 years, which has good economic benefits.

[0166] The above detailed embodiments describe the implementation of the present invention; however, the present invention is not limited to the specific details described in the above embodiments. Within the scope of the claims and technical concept of the present invention, various simple modifications and changes can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

Claims

1. A coastal multi-scenario coupled iron-air battery-denitrification and phosphorus removal system, characterized in that, Includes iron anode, air cathode, electrolyte, wind and solar coupling interface, power supply interface, and charge / discharge control module; The iron anode includes an iron substrate and a hydrogen evolution inhibitor loaded on the surface of the iron substrate; the air cathode includes a cathode substrate and a Co3O4-Ni heterojunction and / or Fe-doped Co3O4 nanosheet array structure loaded on the surface of the cathode substrate. The electrolyte is pretreated seawater aquaculture wastewater; the wind-solar coupling interface is used to connect wind power equipment and / or photovoltaic equipment; the power supply interface is used to connect electrical equipment; the charge-discharge control module is used to switch between discharge phosphorus removal mode, charge denitrification mode and hybrid operation mode.

2. The coastal multi-scenario coupled iron-air battery-denitrification and phosphorus removal system according to claim 1, characterized in that, The iron matrix is ​​one or more of the following: porous sponge iron structure, foamed iron structure, carbonyl iron powder, ordinary iron powder, and rolled iron foil; Furthermore, the porosity of the iron matrix is ​​60%-85%, and the specific surface area is not less than 5 m². 2 / g.

3. The coastal multi-scenario coupled iron-air battery-denitrification and phosphorus removal system according to claim 1, characterized in that, The hydrogen evolution inhibitor is one or more of Bi2O3, SnO2, PbS, CuS, FeS, and MoS2.

4. The coastal multi-scenario coupled iron-air battery-denitrification and phosphorus removal system according to claim 1, characterized in that, The cathode substrate is one or more of the following: carbon cloth, nickel foam current collector, conductive ceramic gas diffusion layer, stainless steel mesh, activated carbon-PTFE sintered body, and carbon nanofiber.

5. The coastal multi-scenario coupled iron-air battery-denitrification and phosphorus removal system according to claim 1, characterized in that, The pretreatment method for the electrolyte is to filter out particulate suspended solids in the effluent from seawater aquaculture and adjust the pH value to 7.5-9.

0.

6. The coastal multi-scenario coupled iron-air battery-denitrification and phosphorus removal system according to claim 1, characterized in that, The discharge phosphorus removal mode is as follows: when the total phosphorus concentration in the effluent from the marine aquaculture exceeds a preset threshold, or when there is a power demand, or when the power supply from the wind power equipment and / or photovoltaic equipment is insufficient, the charge-discharge control module controls the discharge to oxidize the iron anode into Fe(OH)2, while partially dissolving Fe. 2+ / Fe 3+ Phosphorus is removed by the formation of precipitate with phosphate ions, and the iron-air battery outputs electrical energy. The charging and denitrification mode is as follows: when the ammonia nitrogen concentration in the marine aquaculture tailwater is higher than the preset threshold, or when there is a surplus of power supply from wind power equipment and / or photovoltaic equipment, the charging and discharging control module controls the charging process, causing the air cathode to undergo an ammonia oxidation reaction, oxidizing ammonia nitrogen into harmless N2, and reducing Fe(OH)2 generated by the iron anode during the discharge process into elemental iron, thus completing the iron-air battery energy storage. The hybrid operation mode is as follows: the discharge phosphorus removal mode and the charging denitrification mode are performed alternately.

7. The coastal multi-scenario coupled iron-air battery-denitrification and phosphorus removal system according to claim 6, characterized in that, The operating voltage of the discharge phosphorus removal mode is 0.6-1.0 V, and the current density is 5-50 mA / cm². 2 ; The charging voltage for the charging-to-denitrification mode is 1.2-1.8 V, and the current density is 5-30 mA / cm². 2 .

8. The coastal multi-scenario coupled iron-air battery-denitrification and phosphorus removal system according to claim 1, characterized in that, It also includes wind power equipment and / or photovoltaic equipment, marine aquaculture modules and power load modules.

9. A method for nitrogen and phosphorus removal from an iron-air battery coupled in multiple coastal scenarios, characterized in that, The nitrogen and phosphorus removal process using the iron-air battery-denitrification and phosphorus removal system according to any one of claims 1-8 includes the following steps: The pretreated effluent from seawater aquaculture is used as an electrolyte and introduced into the iron-air battery-denitrification and phosphorus removal system. The iron anode undergoes an oxidation reaction to generate Fe. 2+ Further oxidized to Fe 3+ The phosphorus is removed by reacting with phosphate to form a precipitate, while the oxygen reduction reaction occurs simultaneously at the air cathode, which outputs electrical energy. The iron-air battery is charged using surplus wind and solar power. The air cathode undergoes an AOR reaction to oxidize ammonia nitrogen into nitrogen gas, thus achieving denitrification. At the same time, the iron anode undergoes a reduction reaction to reduce iron oxides to elemental iron, thus completing energy storage. Periodically drain the precipitates from the iron-air battery denitrification and phosphorus removal system to recover phosphorus-containing compounds; The quality of the effluent from the electrolyte is tested regularly, and once it meets the standards, it is discharged or reused in seawater aquaculture.

Images