A zero-carbon power generation and value-added system and method for reducing iron oxide to iron powder by electrolytic hydrogen production

Abstract

The application discloses a zero-carbon power generation and value-added system and method for reducing iron oxide to iron powder by electrolytic hydrogen production. The system comprises an electrolytic water hydrogen production unit, a hydrogen purification and buffering unit, an iron oxide reduction unit, an iron powder passivation and superfine unit, a sealed storage and inert explosion-proof conveying unit, an iron powder boiler power generation unit, a combustion product capture and grading unit, and a collaborative control unit. Green electricity is used to electrolyze water to produce hydrogen, which reduces iron oxide at 500-800 DEG C to produce metal iron powder, and the tail gas is dehydrated for hydrogen recycling. The iron powder is passivated and stored in a sealed environment with an oxygen volume fraction of not more than 2% and a relative humidity of not more than 30%, and is conveyed to the iron powder boiler by dense-phase pneumatic conveying with nitrogen as the carrier gas. The iron oxide in the flue gas is efficiently captured, part of which is returned to the reduction unit for recycling, and the other part is graded and purified for sale. The application converts intermittent green electricity into solid zero-carbon fuel that can be stored for a long time, and there is no carbon dioxide emission in the whole process.

Description

Technical Field

[0001] This invention relates to the field of zero-carbon energy and hydrogen metallurgy, specifically to a system and method that uses renewable electricity to electrolyze water to produce hydrogen as a reducing agent, reduces iron oxide to metallic iron powder and uses it as zero-carbon fuel to generate electricity, while simultaneously recovering and increasing the value of the combustion product ferric oxide and enabling a closed-loop cycle of iron elements. Background Technology

[0002] In recent years, wind power and photovoltaic installations have grown rapidly, but their output has significant diurnal and seasonal fluctuations. Wind and solar curtailment and peak power shortages coexist, creating an urgent need for long-term, large-capacity energy storage and energy carriers that can be transported across regions.

[0003] Currently, mainstream energy storage and energy conversion routes each have their own limitations: lithium-ion batteries are suitable for short-term peak shaving of 2 to 4 hours, but due to resource, safety and recycling constraints, they are difficult to support cross-seasonal energy storage; pumped hydro storage is limited by geographical conditions; high-pressure gaseous hydrogen storage, cryogenic liquid hydrogen and pipeline hydrogen transportation face problems such as high storage and transportation costs, hydrogen embrittlement, leakage and safety risks, and require entirely new infrastructure.

[0004] Metal fuel cycling offers a new approach to addressing these issues. Iron powder is chemically stable at room temperature and pressure, can be stored for extended periods, and has a volumetric energy density approximately 1.5 to 2 times that of bituminous coal, making it suitable for transport by ordinary trucks, railways, and freight ships. The combustion products of iron powder are solid oxide particles, which can be efficiently captured using cyclone separation and filtration, and then regenerated through reduction reactions, thus forming a closed loop of "combustion-reduction-recombustion." Demonstrations have been conducted both domestically and internationally: Rift in the Netherlands has built 100kW and 1MW iron-fueled boilers for brewery heating and community heating; German research institutions have proposed converting decommissioned coal-fired power plants into iron-fueled boilers, retaining the turbines and grid connection; simulations based on energy system models from the Karlsruhe Institute of Technology show that the iron fuel cycle can complement the green hydrogen route in long-term energy storage scenarios.

[0005] In the reduction stage, the technological foundation for green hydrogen reduction of iron oxide has been established: a 10,000-ton-scale green electricity and green hydrogen fluidized bed hydrogen metallurgy demonstration line uses green electricity to electrolyze water to produce hydrogen, and then uses hydrogen to reduce iron concentrate, stably producing direct reduced iron with a metallization rate of over 95%, with the complete reduction time of particles shortened to less than 10 minutes; the metallization rate of the pure hydrogen vertical furnace route has also reached over 96%. These advancements provide an engineering basis for the energy conversion of "green electricity—green hydrogen—metallic iron".

[0006] However, existing technologies and literature still have the following shortcomings: (1) Research focuses on iron powder burners or boiler bodies, lacking integrated system integration of the whole chain of "hydrogen production - reduction - storage and transportation - combustion - recovery", each unit is designed independently, and the energy flow and material flow are mismatched; (2) The reduction link either relies on fossil-based reducing agents or is not dynamically coupled with green electricity electrolysis to produce hydrogen, making it difficult to achieve zero carbon throughout the process; (3) Ultrafine iron powder has a large specific surface area and high chemical activity, and there is a risk of spontaneous combustion and dust explosion during storage and transportation. Existing solutions lack inertization explosion-proof and safety interlock design in coordination with the front-end reduction and the back-end combustion; (4) Combustion product iron oxide is mostly simply returned to the furnace or stockpiled, without graded purification and high-value utilization, resulting in poor system economy; (5) There is a lack of coordinated control strategies for green electricity fluctuations, and the electrolysis load, reduction furnace thermal regime and boiler load cannot be optimized in a coordinated manner.

[0007] Therefore, there is an urgent need for a system and method to convert intermittent green electricity into solid zero-carbon fuel that can be stored and transported safely for a long time, and to couple energy conversion with iron element material cycling and product value-added. Summary of the Invention Technical problems to be solved

[0008] The technical problems to be solved by this invention are: (1) how to convert intermittent and fluctuating renewable electrical energy into zero-carbon fuel that can be stored for a long time, has high volumetric energy density, and can be transported across regions; (2) how to avoid the use of fossil reducing agents in the reduction process so that there is no carbon dioxide emission throughout the process; (3) how to solve the risk of spontaneous combustion and dust explosion of ultrafine iron powder during storage and transportation; (4) how to improve the utilization value of the combustion product ferric oxide and improve the economic efficiency of the system; (5) how to achieve coordinated control of the electrolysis, reduction, storage and transportation, combustion and recycling units under all working conditions. Technical solution

[0009] To achieve the above objectives, the present invention provides a zero-carbon power generation and value-added system for producing iron powder by electrolysis of hydrogen to reduce iron oxide, comprising a green electricity-driven water electrolysis hydrogen production unit, a hydrogen purification and buffering unit, an iron oxide reduction unit, an iron powder passivation and ultrafine refining unit, a sealed storage and inerting explosion-proof conveying unit, an iron powder boiler power generation unit, a combustion product collection and classification unit, and a collaborative control unit.

[0010] The water electrolysis hydrogen production unit uses an alkaline electrolyzer or a proton exchange membrane electrolyzer. Power is supplied from surplus electricity from wind farms or photovoltaic power plants, or from off-peak electricity grid power. The DC power consumption is 4.0~5.0 kW·h / Nm³. 3 The power can be adjusted within the range of 10% to 110% of the rated value, and the load response time is no more than 10s to adapt to the intermittent nature of green electricity. The oxygen produced by electrolysis is separated into gas and liquid and dried. Part of it is sent to the iron powder burner as oxygen-enriching combustion air, and the rest is sold as industrial or medical oxygen.

[0011] The hydrogen purification and buffering unit includes a deoxygenator, a dryer, a hydrogen compressor, and a hydrogen buffer tank, ensuring that the hydrogen entering the reduction unit has a purity of not less than 99.99% and a dew point of not more than -40°C, thereby providing a stable hydrogen source for the reduction reaction.

[0012] The iron oxide reduction unit is a fluidized bed reduction furnace or a vertical reduction furnace. The iron oxide raw material is ferric oxide powder, including iron ore powder, rolled steel scale, iron extraction products from red mud, or combustion products returned by the system itself. The reduction reaction proceeds according to the sequence Fe2O3 + 3H2 → 2Fe + 3H2O, with a reaction temperature of 500~800℃. The molar ratio of hydrogen to ferric oxide is 3.5~6, i.e., a relative stoichiometric excess of 1.2~2.0 times. The reduction tail gas is purified by a condenser to remove water and a hydrogen recovery device before being returned to the hydrogen inlet for recycling. The recovery rate of unreacted hydrogen in a single pass is not less than 90%, and the metallization rate of the product is not less than 92%, preferably not less than 95%.

[0013] The iron powder passivation and ultrafine processing unit includes a passivator and an ultrafine pulverizer and classifier. The passivator introduces an inert gas containing trace amounts of oxygen into the high-temperature metallic iron powder, causing a dense oxide film with a thickness of several nanometers to tens of nanometers to form on its surface, thus preventing spontaneous combustion in room temperature air; the ultrafine pulverizer and classifier processes the iron powder to a D50 of 5~50μm, taking into account both ignition stability and pneumatic conveying flowability.

[0014] In the sealed storage silo and inerting explosion-proof conveying unit, the top of the sealed storage silo is equipped with a feed inlet, a breather valve, and an explosion relief device. The lower part is a conical unloading section with a nitrogen air cushion anti-arch device. The silo is equipped with an oxygen content sensor, a temperature sensor, a level gauge, and a CO concentration sensor. The inerting replacement circuit adopts a "vacuum-nitrogen replacement" method: first, the sealed storage silo is evacuated to an absolute pressure not exceeding 10 kPa, and then nitrogen is introduced to a slight positive pressure of 0.5~2 kPa. This process is repeated at least twice to reduce the oxygen volume fraction in the silo to not exceeding 2%. The circulating purification branch is equipped with dehumidification and deoxygenation devices to ensure that the circulating nitrogen dew point is not higher than -20℃ and the relative humidity in the silo is not higher than 30%. The loss-in-weight metering and feeding unit consists of a weighing hopper and a variable frequency screw feeder, with a feeding accuracy of not less than ±1%. A rotary discharge valve and a fireproof and explosion-proof valve are installed at the outlet. The dense phase pneumatic conveying pipeline uses nitrogen as the carrier gas, with a solid-to-gas mass ratio of 20~80 and an apparent gas velocity of 2~8m / s. Wear-resistant liners, electrostatic bridging, and pipeline flame arresters are installed at bends. An explosion suppression device with a jet lag time of not more than 50ms is installed on the pipeline. The explosion relief device has an operating pressure of 0.01~0.02MPa. All equipment and pipelines are equipped with electrostatic elimination and grounding devices.

[0015] The iron pulverized iron boiler power generation unit includes an iron pulverized iron burner, a boiler body, and a steam turbine generator set. Iron pulverized iron is injected into the furnace as a dense-phase gas stream, achieving a combustion flame temperature exceeding 1800℃. The iron pulverized iron burnout rate is no less than 98%. The generated heat is used to produce high-temperature, high-pressure, or supercritical steam to drive the steam turbine generator set for power generation. It can also provide industrial steam as needed for combined heat and power (CHP). This system can be retrofitted from existing coal-fired power plants, retaining the plant buildings, turbines, generators, and transmission lines, while only replacing the combustion system, powder conveying, and product collection devices.

[0016] The combustion product collection and classification unit includes a cyclone separator, a bag filter or electrostatic precipitator, and an air classifier connected in series, with a total ferric oxide collection efficiency of not less than 99.5%. The collected ferric oxide is divided into two paths according to the ratio set by the co-control unit: the first path returns to the ferric oxide reduction unit via a return pipeline, realizing a closed-loop circulation of iron elements with a circulation rate of not less than 80%; the second path enters the product warehouse, where it is classified and purified to obtain a product with a Fe2O3 mass fraction of not less than 95%, which is then sold externally as ferric oxide red pigment, soft or hard magnetic ferrite raw material, catalyst carrier, or steelmaking coolant to add value.

[0017] The coordinated control unit realizes unified scheduling of energy flow and material flow: in energy storage mode, it increases electrolysis power, increases reduction load and raises storage bin level according to the power prediction of renewable power station and grid electricity price signal; in power generation mode, it adjusts the feed rate and solid-gas mass ratio according to grid load command so that the feed rate deviation of a single burner is no more than ±5%; at the same time, it executes three-level safety interlocks and performs priority actions of "nitrogen replenishment inerting - cutting off feed - starting explosion suppression" when oxygen volume fraction, temperature or CO concentration exceeds the limit. Beneficial effects

[0018] Compared with the prior art, the present invention has the following beneficial effects: (1) Zero carbon emissions throughout the entire process. Hydrogen is produced by electrolyzing water with green electricity as the only reducing agent. The only byproduct of the reduction reaction is water. The combustion of iron powder does not produce carbon dioxide or sulfur oxides. The carbon emissions of the system come from the purchased electricity, which can achieve near-zero emissions. (2) Achieve long-term, cross-seasonal energy storage and cross-regional energy transmission. Iron powder can be stored for months or even years without self-degradation under normal temperature and pressure. Its volumetric energy density is about 1.5 to 2 times that of bituminous coal. It can be transported by rail and ship to transmit surplus electricity from new energy bases in the Northwest and other regions to load centers in the east in the form of solid fuel, overcoming the dependence of hydrogen storage and transportation on high-pressure containers, pipelines and underground gas storage facilities. (3) The system combines closed-loop material recycling with product value enhancement. After the combustion product ferric oxide is efficiently captured, part of it is returned to the reduction unit to form a closed-loop iron element cycle, and the other part is purified in stages and sold as a chemical product. At the same time, by-product oxygen, waste heat recovery and recycled hydrogen are generated, forming diversified revenue and significantly improving the system's economic efficiency. (4) Intrinsic safety. Through inerting by vacuuming and nitrogen purging, sealed storage, dense nitrogen transport, static electricity elimination and grounding, explosion relief and suppression devices, and three-level safety interlocks, the risk of spontaneous combustion and dust explosion of ultrafine iron powder is transformed from passive protection to active suppression. (5) Facilitates the retrofitting of existing units. Iron powder has similar combustion characteristics to pulverized coal, allowing for the retrofitting of combustion systems, powder conveying and product collection units on the basis of existing coal-fired power plants, while retaining turbines, generators and transmission lines, thus significantly reducing the sunk costs of zero-carbon transition. (6) Full-condition coordinated control. The coordinated control unit incorporates green power prediction, electrolysis load, reduction furnace thermal regime, storage silo level and boiler load into unified scheduling, so that the system can smoothly switch between the two operating conditions of abandoned power storage and peak power generation, thereby improving equipment utilization and overall round-trip efficiency. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the overall flow and material and energy flow of the system described in this invention;

[0020] Figure 2 This is a schematic diagram of the iron oxide reduction unit described in this invention;

[0021] Figure 3 This is a schematic diagram of the structure of the sealed storage silo and the inerted explosion-proof conveying unit described in this invention;

[0022] Figure 4 This is a flowchart of the method described in this invention.

[0023] The reference numerals in the attached figures are as follows: 1-Electrolysis of water to produce hydrogen; 11-Electrolyzer; 12-Gas-liquid separator; 13-Deoxygenator dryer; 14-Oxygen branch; 2-Hydrogen purification and buffer unit; 3-Iron oxide reduction unit; 31-Reduction furnace body; 32-Iron oxide feed port; 33-Hydrogen distribution device; 34-Tail gas outlet; 35-Condenser; 36-Hydrogen recovery device; 37-Metallic iron outlet; 38-Heat exchanger; 4-Iron powder passivation and ultrafine grinding unit; 5-Sealed storage and inerting explosion-proof conveying unit; 51-Sealed storage; 52-Inerting replacement circuit; 521-Vacuuming branch 522-Nitrogen replenishment branch; 523-Circulating purification branch; 53-Loss-in-weight metering feeding unit; 54-Dense phase pneumatic conveying pipeline; 55-Explosion relief device; 56-Explosion suppression device; 57-Static elimination and grounding device; 58-Oxygen content sensor; 59-Temperature sensor; 510-Level gauge; 511-CO concentration sensor; 512-Nitrogen air cushion arch-breaking device; 513-Shut-off valve; 514-Fireproof explosion-proof valve; 515-Pipeline flame arrester; 6-Iron powder boiler power generation unit; 7-Combustion product collection and classification unit; 71-Cyclone separator; 8-Cooperative control unit. Detailed Implementation

[0024] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings. The following examples are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. Example 1: System Composition and Operation Process

[0025] like Figure 1 As shown, the system in this embodiment includes, in order of material flow direction: water electrolysis hydrogen production unit (1), hydrogen purification and buffering unit (2), iron oxide reduction unit (3), iron powder passivation and ultrafine processing unit (4), sealed storage and inert explosion-proof conveying unit (5), iron powder boiler power generation unit (6), combustion product collection and classification unit (7), and collaborative control unit (8).

[0026] During operation, surplus electricity from wind farms or photovoltaic power stations is fed into the electrolytic cell (11), where hydrogen is generated at the cathode and oxygen at the anode. After being processed by a gas-liquid separator (12) and a deoxygenation dryer (13), the hydrogen is pressurized to 0.5~3.0 MPa by a hydrogen compressor and stored in a hydrogen buffer tank. A portion of the oxygen is sent to an iron powder burner via an oxygen branch (14) for oxygen-enriched combustion, and the remainder is sold externally. Hydrogen and ferric oxide from the return pipeline enter the reduction furnace body (31) at a molar ratio of H2 / Fe2O3 of 3.5~6 and undergo a reduction reaction at 500~800℃. The generated metallic iron is discharged through the metallic iron outlet (37). The tail gas is purified by a condenser (35) to remove water and a hydrogen recovery device (36) before being recycled. The metallic iron forms a dense oxide film in the passivator and is then processed by an ultrafine pulverizer and classifier to a D50 of 5~50 μm before being sent to a sealed storage silo (51). The sealed storage silo (51) undergoes at least two "vacuuming-nitrogen filling" replacements via a vacuuming branch (521) and a nitrogen replenishment branch (522), ensuring that the oxygen volume fraction in the silo is no higher than 2% and the relative humidity is no higher than 30%. During feeding, the iron powder is metered by the loss-in-weight metering feeding unit (53) and then enters the dense phase pneumatic conveying pipeline (54). Using nitrogen as the carrier gas and a solid-to-gas mass ratio of 20-80, it is transported to the iron powder burner, where it burns and releases heat in the boiler body. The generated steam drives the steam turbine generator set to generate electricity. The ferric oxide in the flue gas is collected by a cyclone separator (71) and a bag filter, and then classified by an air classifier: fine particles are returned to the reduction furnace body (31) for circulation, while the remainder is sold outside the product silo. Example 2: Main process parameters of a 100MW system

[0027] A 100MW iron powder power generation system is equipped with a 40MW water electrolysis hydrogen production unit and corresponding reduction, storage and transportation units. Its main process parameters are shown in Table 1. Table 1 Main process parameters DC power consumption for hydrogen electrolysis <![CDATA[4.0~5.0 kW·h / Nm 3 ]]> Alkaline or PEM electrolyzers, calculated in LHV Electrolysis load adjustment range 10%~110% Rated Response time no more than 10 seconds, adaptable to green electricity fluctuations. Hydrogen purity / dew point ≥99.99% / ≤-40℃ After deoxygenation and drying, it enters the buffer tank. Reduction reaction temperature 500~800 ℃ Fluidized bed temperature is preferably 600~750℃, and the anti-adhesion temperature can reach 900℃. <![CDATA[H₂ / Fe₂O₃ molar ratio]]> 3.5~6 The stoichiometric ratio is 3, and the excess coefficient is 1.2~2.0. Metallization rate ≥95% Comparable to the level of a 10,000-ton-level green hydrogen fluidized bed demonstration line Iron powder particle size D50 5~50 μm Balancing fire stability and transport fluidity Storage oxygen volume fraction ≤2% Evacuate to ≤10kPa, then purge with nitrogen to 0.5~2kPa, repeat ≥2 times. relative humidity of storage ≤30% Circulating nitrogen dew point ≤ -20℃ Solid-to-gas mass ratio 20~80 Nitrogen carrier gas, apparent gas velocity 2~8 m / s Explosion relief action pressure 0.01~0.02 MPa Detonation suppression injection delay time ≤50ms Iron powder burnout rate ≥98% Flame temperatures can reach over 1800℃ Ferric oxide collection efficiency ≥99.5% Cyclone separator + bag filter / electrostatic precipitator Iron closed-loop circulation rate ≥80% The remainder will be sold externally as products. <![CDATA[Fe2O3 content of commercially sold products]]> ≥95% Pigments / Magnetic Materials / Steelmaking Raw Materials Example 3: Time-sharing operation mode of power abandonment drive

[0028] During peak wind power generation or photovoltaic output periods (such as off-peak hours at night), the coordinating control unit (8) increases the electrolysis power to 90%~110% of the rated value, the reduction furnace operates at full load, the iron powder output exceeds the boiler consumption, and the surplus iron powder is stored in a sealed storage silo (51), with the silo level rising from 30% to 90%. During peak grid periods, the electrolysis unit is reduced to the minimum stable operating load or shut down, and the iron powder boiler generates electricity at full output according to the grid load command, with the silo level decreasing from 90% to 30%. During transition periods, the solid-gas mass ratio and feed rate are adjusted according to the silo level and load prediction, so that the feed rate deviation of a single burner is no more than ±5%. Under this mode of operation, the annual utilization hours of the electrolysis unit are no less than 3000h, and the proportion of green energy storage in the system's annual power generation is no less than 60%. Example 4: Collaborative Control and Three-Level Safety Interlock

[0029] The collaborative control unit (8) collects the available power of electrolysis, the temperature of the reduction furnace and the hydrogen content of the tail gas, the oxygen content of the storage silo, the temperature, the material level and the CO concentration, and the unit load signal. It adjusts according to the principle of "energy storage priority and safety priority" and implements three-level interlocking: Level 1: When the oxygen volume fraction is higher than 2% or the temperature inside the chamber is higher than 60℃, open the nitrogen replenishment valve to perform inerting replacement; Level 2: Temperature above 80℃ or CO volume fraction above 200×10⁻⁶ -6 At this time, close the shut-off valve (513) and stop feeding; Level 3: When a sudden pressure rise or flame signal is detected, the explosion suppression device (56) is activated to spray inert powder or high-pressure nitrogen, and at the same time the explosion relief device (55) is activated to release pressure.

[0030] The above three actions are executed in the order of "nitrogen replenishment and inerting - material cut-off - explosion suppression activation". Any action at any level will trigger an alarm and be recorded to the superior monitoring system.

[0031] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made in accordance with the claims of the present invention shall fall within the protection scope of the present invention.

Claims

1. A zero-carbon power generation and value-added system for producing iron powder by electrolytic hydrogen reduction of iron oxide, characterized in that, include: The green-electric-driven water electrolysis hydrogen production unit (1) has its power input terminal connected to a renewable power station and / or the power grid, and is equipped with a hydrogen outlet and an oxygen outlet; the hydrogen purification and buffering unit (2) is connected to the hydrogen outlet and is used to remove moisture and residual oxygen and pressurize and buffer the hydrogen; the iron oxide reduction unit (3) has its hydrogen inlet connected to the hydrogen purification and buffering unit (2) and its solid inlet connected to the iron oxide silo, and performs a gas-based reduction reaction of iron oxide inside to generate metallic iron and water-containing reduction tail gas; the iron powder passivation and ultrafine processing unit (4) has its inlet receiving The metallic iron discharged from the iron oxide reduction unit (3) is passivated iron powder with a D50 of 5~50μm and a dense oxide film on the surface; the sealed storage and inerting explosion-proof conveying unit (5) includes a sealed storage silo (51), an inerting replacement circuit (52), a loss-in-weight metering feeding unit (53), a dense phase pneumatic conveying pipeline (54), an explosion relief device (55), an explosion suppression device (56), and a static electricity elimination and grounding device (57). The sealed storage silo (51) maintains an oxygen volume fraction of no more than 2% and a relative humidity of no more than 30%. The pneumatic conveying pipeline (54) uses nitrogen as the carrier gas and the solid-to-gas mass ratio is 20-80; the iron powder boiler power generation unit (6) includes an iron powder burner, a boiler body and a steam turbine generator set, and the outlet of the dense phase pneumatic conveying pipeline (54) is connected to the feed port of the iron powder burner; the combustion product collection and classification unit (7) has its inlet connected to the flue gas channel of the boiler body, and is used to collect ferric oxide powder in the flue gas and classify it. Its first outlet is connected to the solid inlet of the iron oxide reduction unit (3) through the return pipeline, and its second outlet is connected to the outer surface of the iron oxide product. The sales line is connected; and the collaborative control unit (8) has its input terminals connected to the available power signal terminal of the water electrolysis hydrogen production unit (1), the temperature and tail gas hydrogen content detection terminal of the iron oxide reduction unit (3), the oxygen content, temperature and CO concentration detection terminal of the sealed storage tank (51), and the load signal terminal of the steam turbine generator set, respectively. Its output terminals are connected to the power regulator of the water electrolysis hydrogen production unit (1), the hydrogen regulating valve of the iron oxide reduction unit (3), the nitrogen replenishment valve and the shut-off valve (513) of the sealed storage tank (51), and the feed regulating valve of the iron powder burner, respectively.

2. The system according to claim 1, characterized in that, The iron oxide reduction unit (3) is a fluidized bed reduction furnace or a vertical reduction furnace. The reduction reaction temperature is 500~800℃, the molar ratio of hydrogen to ferric oxide is 3.5~6, and the reduction tail gas is returned to the hydrogen inlet for recycling after being treated by the condenser (35) to remove water and the hydrogen recovery device (36). The metallization rate of the product is not less than 92%.

3. The system according to claim 1, characterized in that, The water electrolysis hydrogen production unit (1) is an alkaline electrolyzer or a proton exchange membrane electrolyzer, and its oxygen outlet is connected to the combustion air pipeline or oxygen product pipeline of the iron powder burner; the power adjustment range of the water electrolysis hydrogen production unit (1) is 10% to 110% of the rated power, and the load response time is no more than 10s.

4. The system according to claim 1, characterized in that, The sealed storage chamber (51) is equipped with an inlet and a breathing valve at the top and an outlet at the bottom. An oxygen content sensor (58), a temperature sensor (59), a level gauge (510), and a CO concentration sensor (511) are installed inside the chamber. The inerting replacement circuit (52) includes a vacuuming branch (521), a nitrogen replenishment branch (522), and a circulation purification branch (523). The replacement method is as follows: first, the sealed storage chamber (51) is evacuated to an absolute pressure not higher than 10 kPa, and then nitrogen is introduced to a slight positive pressure of 0.5~2 kPa. This is repeated at least twice to reduce the oxygen volume fraction in the chamber to not higher than 2%.

5. The system according to claim 1, characterized in that, The lower part of the sealed storage silo (51) is a conical unloading section, and a nitrogen air cushion arch-breaking device (512) is installed on the conical wall. The gas supply branch of the nitrogen air cushion arch-breaking device (512) is connected to the nitrogen replenishment branch (522) and is equipped with a one-way valve. The loss-in-weight metering feeding unit (53) includes a weighing hopper and a variable frequency screw feeder. Its feeding accuracy is not less than ±1%, and its outlet is equipped with a rotary unloading valve and a fireproof and explosion-proof valve (514).

6. The system according to claim 1, characterized in that, The nitrogen carrier gas in the dense phase pneumatic conveying pipeline (54) is recycled after being deoxygenated and dehydrated. The apparent gas velocity inside the pipeline is 2~8m / s. Wear-resistant lining, electrostatic bridging and pipeline flame arrester (515) are installed at the pipeline bends. The operating pressure of the explosion relief device (55) is 0.01~0.02MPa. The injection lag time of the explosion suppression device (56) is no more than 50ms. The explosion suppression medium is inert powder or high-pressure nitrogen.

7. The system according to claim 1, characterized in that, The combustion product collection and classification unit (7) includes a cyclone separator (71), a bag filter or electrostatic precipitator and an air classifier connected in series, with a total ferric oxide collection efficiency of not less than 99.5%; the collaborative control unit (8) adjusts the ratio of ferric oxide return amount to external sales amount according to the boiler load command and the amount of iron powder in storage, so that the iron element closed-loop circulation rate is not less than 80% and the Fe2O3 mass fraction of the externally sold ferric oxide products is not less than 95%.

8. A zero-carbon power generation and value-added method for producing iron powder by electrolytic hydrogen reduction of iron oxide, characterized in that, The system according to any one of claims 1 to 7 comprises the following steps: S1 Energy Storage: Using the abandoned electricity from renewable power plants or off-peak electricity from the power grid to drive the water electrolysis hydrogen production unit (1) to produce hydrogen and produce oxygen as a byproduct; S2 Reduction: After purification and pressurization, hydrogen is sent to the iron oxide reduction unit (3) to reduce ferric oxide to metallic iron powder at 500~800℃. The reduction tail gas is condensed and dehydrated before hydrogen is recovered and recycled. S3 Passivation storage: The metal iron powder is surface passivated and ultra-finely processed, and then sent to a closed storage silo (51) with an oxygen volume fraction of no more than 2% and a relative humidity of no more than 30% for long-term storage. S4 Inerting Conveying: After being metered by weight loss, iron powder in a sealed storage silo is conveyed in a dense phase pneumatic manner using nitrogen as the carrier gas. The solid-to-gas mass ratio is 20-80. Static grounding, explosion relief and explosion suppression protection are provided throughout the conveying process. S5 Combustion Power Generation: Iron powder is burned in an iron powder boiler to release heat, generating high-temperature and high-pressure steam to drive a steam turbine generator set to generate electricity. The feed rate is adjusted according to the grid load command to ensure that the feed rate deviation of a single burner is no more than ±5%. S6 Product Value-Added: Ferric oxide powder is captured in flue gas. A portion of it is returned to step S2 in a set ratio to achieve a closed-loop cycle of iron elements, while the other portion is purified through classification and sold as iron oxide pigment, magnetic material, catalyst carrier or steelmaking raw material.

9. The method according to claim 8, characterized in that, In step S1, the collaborative control unit (8) allocates power between electrolysis power, reduction load, and storage level according to the power forecast of the renewable power plant and the grid load command, so that the annual utilization hours of the water electrolysis hydrogen production unit (1) are not less than 3000h and the hydrogen production power consumption is not higher than 4.8kW·h / Nm 3 .

10. The method according to claim 8, characterized in that, The collaborative control unit (8) performs a three-level safety interlock: Level 1 is when the oxygen volume fraction in the sealed storage chamber (51) is higher than 2% or the temperature inside the chamber is higher than 60°C, the nitrogen replenishment valve is opened; Level 2 is when the temperature is higher than 80°C or the CO volume fraction is higher than 200×10⁻⁶. -6 The shut-off valve (513) is closed and feeding is stopped; the third level is to activate the explosion suppression device (56) when a sudden pressure rise or flame signal is detected.

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