A method for green electrochemical extraction of metallic iron from iron-containing ores

Abstract

This invention discloses a green electrochemical method for extracting metallic iron from iron-bearing ore, belonging to the field of electrochemical technology. The invention uses solid iron oxide as the cathode, iron with a purity greater than 99.5% as the anode, and a halide molten salt containing an oxygen ion source as the electrolyte to form an electrolytic circuit. Electrolysis is performed at the electrolysis temperature using a constant current or constant voltage method, causing the iron oxide at the cathode to be electrochemically reduced to metallic iron, while an oxygen evolution reaction occurs at the anode. By controlling the composition of the molten salt electrolyte, this invention significantly reduces the corrosiveness of the high-temperature molten salt to the pure iron anode, enabling the low-cost pure iron anode to operate stably for extended periods, achieving efficient reduction of iron at the cathode. Compared with traditional processes, the method provided by this invention has lower carbon emissions, a shorter process flow, simpler operation, and stronger raw material adaptability. It can process iron-bearing ores of different grades and is a green, low-carbon, and efficient method for extracting metallic iron.

Description

Technical Field

[0001] This invention relates to the field of electrochemical technology, and in particular to a green electrochemical method for extracting metallic iron from iron-bearing ores. Background Technology

[0002] Blast furnace ironmaking is currently the main process for extracting metallic iron from iron ore. This process uses coke as a reducing agent to reduce iron oxides to metallic iron at high temperatures, while simultaneously generating a large amount of carbon dioxide. Statistics show that carbon dioxide emissions from blast furnace ironmaking account for more than 80% of the total carbon emissions from the entire steel production process. Therefore, developing low-carbon / zero-carbon ironmaking technologies is of significant practical importance.

[0003] Molten salt electrochemical metallurgy is a green and clean metal extraction technology. This technology uses electrons as a reducing agent to directly reduce metal oxides to metals, offering advantages such as a short process and environmental friendliness. High-temperature molten salts possess high ionic conductivity, low vapor pressure, a wide electrochemical window, and excellent thermal conductivity and stability, making them widely used in metal electrochemical extraction and refining, molten salt thermal storage, spent fuel reprocessing, and battery energy. In metal extraction, molten salt electrolysis can directly reduce active metal ions in molten salts, such as aluminum, magnesium, alkali / alkaline earth metals, rare earth metals, and refractory metals like titanium and vanadium, making it one of the most important modern metallurgical methods. Theoretically, if an inert anode is used, the molten salt electrochemical reduction process can achieve near-zero carbon emissions. However, current research mostly uses chloride molten salts, which are highly corrosive at high temperatures, making them difficult for conventional metal materials to withstand. Inert anodes in high-temperature molten salts must meet the following basic conditions: 1. Good electronic conductivity and low resistivity; 2. Good electrochemical and chemical stability, with no anodic dissolution or extremely low corrosion rate, strong oxidation resistance, and the ability to release oxygen on the surface; 3. Low anodic oxygen evolution overpotential; 4. No impact on cathode product quality; 5. Strong thermal shock resistance, easy processing and forming, and conductive connection; 6. Inexpensive and readily available. Currently accepted inert anode materials (such as tin oxide and iridium-tantalum coatings) suffer from high cost, difficult processing, and susceptibility to poisoning and failure, making them unsuitable for industrial applications.

[0004] Therefore, how to construct a molten salt electrochemical system with controllable corrosion, low anode cost, and stable oxygen evolution is a key technical challenge for realizing the industrialization of green electrochemical extraction of metallic iron. Summary of the Invention

[0005] The purpose of this invention is to overcome the aforementioned shortcomings of existing technologies and provide a green electrochemical method for extracting metallic iron from iron-bearing ores. This invention uses solid iron oxide as the cathode, pure iron as the anode, and a halide molten salt containing an oxygen ion source as the electrolyte to form an electrolytic circuit for electrolysis. Compared to traditional iron ore extraction processes, this invention achieves long-term application of the pure iron inert anode through weakly corrosive molten salt electrolysis. The anode continuously releases oxygen, fundamentally avoiding carbon dioxide emissions caused by the use of carbonaceous reducing agents, thus achieving a near-zero carbon emission green metallurgical process. Simultaneously, this method has the advantages of simple operation and high cathode reduction efficiency.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: This invention provides a method for green electrochemical extraction of metallic iron from iron-bearing ore, comprising the following steps: Step 1: In the electrolysis device, a solid iron oxide is used as the cathode, iron with a purity greater than 99.5% is used as the anode, and a halide molten salt containing an oxygen ion source is used as the electrolyte to form an electrolysis circuit. Step 2: Electrolyze the electrolytic circuit at the electrolysis temperature, so that the solid iron oxide is electrochemically reduced to metallic iron at the cathode, while an oxygen evolution reaction occurs at the pure iron anode. Step 3: After electrolysis is complete, remove the cathode product.

[0007] Preferably, in step 1, the solid iron oxide is an iron ore block obtained by molding and sintering iron ore powder, and the porosity of the iron ore block is 5-70%.

[0008] Preferably, the method for preparing the iron ore block includes the following steps: Iron ore powder with a particle size of 0.05-1mm, pore-forming agent and binder are ball-milled and mixed, and then pressed into blocks; the blocks are placed in a high-temperature furnace for sintering, and the pore-forming agent and binder are removed to obtain iron ore blocks.

[0009] Preferably, the iron-bearing ore is selected from at least one of iron ore, red mud, laterite nickel ore, and vanadium-titanium magnetite; the iron grade of the iron-bearing ore is 30-70%.

[0010] Preferably, the pore-forming agent is selected from at least one of potassium chloride, sodium chloride, and ammonium bicarbonate.

[0011] Preferably, the adhesive is selected from at least one of polyvinyl alcohol and polyvinyl chloride.

[0012] Preferably, the weight ratio of the pore-forming agent to the iron ore powder is 1:(0.5-9); the amount of the binder added is 0.5-2% of the total weight of the pore-forming agent and the iron ore powder.

[0013] Preferably, the ball milling time is 12-24 hours and the ball-to-material ratio is 1:(4-12).

[0014] Preferably, the molding method is isostatic pressing, with a pressure of 5-30 MPa, a block diameter of 10-150 mm, and a thickness of 1-20 mm.

[0015] Preferably, the high-temperature furnace is a muffle furnace, with a sintering temperature of 300-1300℃ and a sintering time of 2-10h.

[0016] In a further description of the present invention, in the above-mentioned method for preparing iron ore blocks, the pore-forming agent and binder can be removed at a sintering temperature of 300-600℃ to obtain iron ore blocks with certain strength and porosity.

[0017] Preferably, in step 1, the metal wire is selected from one of iron wire, nickel wire, molybdenum wire, and tungsten wire, and the metal guide rod is made of stainless steel.

[0018] Preferably, in step 1, the halide molten salt is selected from at least one of chloride-based molten salt and bromide-based molten salt.

[0019] More preferably, the chloride-based molten salt comprises a chloride salt, an oxide, and an oxyacid salt; the chloride salt is selected from at least one of sodium chloride, potassium chloride, lithium chloride, calcium chloride, barium chloride, and magnesium chloride; the oxide is selected from at least one of sodium oxide, potassium oxide, lithium oxide, and calcium oxide, and the amount of the oxide added is 0.5-18 wt%; the oxyacid salt is selected from at least one of carbonate, borate, vanadate, sulfate, and phosphate, and the amount of the oxyacid salt added is 0.5-10 wt%.

[0020] More preferably, the bromide-based molten salt comprises bromide salts, oxides, and oxyacid salts; the bromide salt is selected from at least one of sodium bromide, potassium bromide, lithium bromide, calcium bromide, barium bromide, and magnesium bromide; the oxide is selected from at least one of sodium oxide, potassium oxide, lithium oxide, and calcium oxide, and the amount of the oxide added is 0.5-18 wt%; the oxyacid salt is selected from at least one of carbonate, borate, vanadate, sulfate, and phosphate, and the amount of the oxyacid salt added is 0.5-10 wt%.

[0021] In a further description of the present invention, in chloride-based molten salts, chloride salts are used as the base electrolyte, and oxides and oxyacid salts are used as additive electrolytes; in bromide-based molten salts, bromide salts are used as the base electrolyte, and oxides and oxyacid salts are used as additive electrolytes; wherein, the oxide or oxyacid salt additive electrolyte can provide the necessary oxygen ions for the anodic reaction, and in bromide-based molten salts, it can also reduce the volatilization of bromide salts.

[0022] Preferably, in step 2, the electrolysis temperature is 400-800℃.

[0023] Preferably, in step 2, the electrolysis is performed using constant current electrolysis or constant voltage electrolysis, and the electrolysis time is 4-600 hours. During the electrolysis process, the cathode can be selectively removed and replaced with a new cathode according to experimental requirements and cathode reduction status to maintain semi-continuous electrolysis.

[0024] More preferably, the cathode current density used in the constant current electrolysis is 0.05-1.5 A / cm². 2 The anode current density is 0.1-1 A / cm². 2 .

[0025] More preferably, the cell voltage range used in the constant voltage electrolysis is 1.5-5.0V.

[0026] Preferably, after step 3, the method further includes: when the iron content of the solid iron oxide is not less than 60%, using the cathode product as direct reduced iron; or when the iron content of the solid iron oxide is less than 60%, performing melting and separation treatment on the cathode product to obtain molten iron.

[0027] Regarding a further explanation of the present invention, in step 3, after electrolysis, the obtained cathode product can be processed using different methods depending on the iron grade of the raw material, all of which ultimately yield high-purity metallic iron. When the raw material is iron-bearing ore with an iron content of not less than 60%, it is considered high-grade iron-bearing ore. The cathode product is obtained directly by electrolysis, and its metallization rate is not less than 90%. It can be used as direct reduced iron for electric arc furnace steelmaking, or melted and used for converter steelmaking. When the raw material is iron-bearing ore with an iron content of less than 60%, it is considered low-grade iron-bearing ore, and the cathode product is a mixture of metallic iron and incompletely reduced iron oxides. In this case, the cathode product needs to be further processed in an electric arc furnace to separate slag and iron, obtaining molten iron with a purity of not less than 99%. This molten iron can be used for steelmaking in an electric arc furnace or converter.

[0028] The beneficial effects of this invention are as follows: 1. Compared to existing technologies, this invention provides a green electrochemical method for extracting metallic iron from iron-bearing ore. By precisely introducing specific oxides and oxyacids into halide molten salts, a weakly corrosive molten salt electrolyte system is constructed, significantly reducing the corrosion of pure iron anodes by high-temperature molten salts. This allows extremely low-cost industrial pure iron to function as a quasi-inert anode, operating stably at industrial-grade current densities, with continuous oxygen evolution reaction and an extremely low corrosion rate. Compared to traditional blast furnace ironmaking, this invention uses electrons instead of carbon as a reducing agent and oxygen evolution reaction instead of carbon evolution reaction, fundamentally avoiding carbon dioxide generation and achieving near-zero carbon emissions in green metallurgy. Compared to hydrogen metallurgy that relies on green hydrogen, this invention eliminates the need for high-cost reducing gas, has higher energy efficiency, and uses extremely low-cost anode materials that can be used and reused for extended periods without polluting cathode products.

[0029] 2. Compared with existing technologies, this invention prepares iron ore into a bulk material with a specific porosity as the cathode. By controlling the porosity, it ensures efficient transport and removal of oxygen ions during electrolysis, significantly improving the cathode reduction efficiency. Furthermore, this invention proposes a differentiated processing path based on raw material grade: for high-grade iron ore, the metallization rate of the cathode product obtained from electrolysis can reach over 90%, which can be directly used as high-quality direct reduced iron for electric arc furnace steelmaking; for low-grade iron ore, the electrolysis product undergoes simple electric arc furnace melting and separation to achieve efficient slag-iron separation, obtaining clean molten iron with a purity of not less than 99%, which can be used for subsequent steelmaking. This method overcomes the stringent limitations of traditional processes on raw material grade, has a short process flow, is simple to operate, and can achieve semi-continuous production by changing the cathode, showing broad prospects for industrial application. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0031] Figure 1 This is a schematic diagram of the electrolysis system of this application; Figure 2 The following are the analysis results of the cathode products and photographs after anodic electrolysis in Example 1 of this application; Figure 3 The following are the analysis results of the cathode products and photographs after anodic electrolysis in Example 2 of this application; Figure 4 The following are the analysis results of the cathode products, photographs after anodic electrolysis, and molten iron beads from Example 3 of this application; Figure 5The following are the analysis results of the cathode products and SEM images after anodic electrolysis for Comparative Example 1 of this application; Figure 6 The following are the analysis results of the cathode products and SEM images after anodic electrolysis in Comparative Example 2 of this application; Figure 7 This is a SEM image of Comparative Example 3 after anodic electrolysis in this application; Figure 8 The results of the cathode product analysis are for Comparative Example 4 of this application.

[0032] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0033] The technical solutions described below in conjunction with the embodiments will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the 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.

[0034] This invention provides a method for green electrochemical extraction of metallic iron from iron-bearing ore, comprising the following steps: Step 1: In the electrolysis device, a solid iron oxide is used as the cathode, iron with a purity greater than 99.5% is used as the anode, and a halide molten salt containing an oxygen ion source is used as the electrolyte to form an electrolysis circuit. Step 2: Electrolyze the electrolytic circuit at the electrolysis temperature, so that the solid iron oxide is electrochemically reduced to metallic iron at the cathode, while an oxygen evolution reaction occurs at the pure iron anode. Step 3: After electrolysis is complete, remove the cathode product.

[0035] Preferably, in step 1, the solid iron oxide is an iron ore block obtained by molding and sintering iron ore powder, and the porosity of the iron ore block is 5-70%.

[0036] Specifically, the porosity of the iron ore block is any one of 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, and 70%, and any two of them.

[0037] Preferably, the method for preparing the iron ore block includes the following steps: Iron ore powder with a particle size of 0.05-1mm, pore-forming agent and binder are ball-milled and mixed, and then pressed into blocks; the blocks are placed in a high-temperature furnace for sintering, and the pore-forming agent and binder are removed to obtain iron ore blocks.

[0038] Preferably, the iron-bearing ore is selected from at least one of iron ore, red mud, laterite nickel ore, and vanadium-titanium magnetite; the iron grade of the iron-bearing ore is 30-70%.

[0039] Specifically, the iron grade of the iron ore is any one of 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70% and any two of them.

[0040] Preferably, the pore-forming agent is selected from at least one of potassium chloride, sodium chloride, and ammonium bicarbonate.

[0041] Preferably, the adhesive is selected from at least one of polyvinyl alcohol and polyvinyl chloride.

[0042] Preferably, the weight ratio of the pore-forming agent to the iron ore powder is 1:(0.5-9); the amount of the binder added is 0.5-2% of the total weight of the pore-forming agent and the iron ore powder.

[0043] Specifically, the weight ratio of the pore-forming agent to the iron ore powder is any one or any two of 1:0.5, 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, and 1:9; the amount of binder added is any one or any two of 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, and 2% of the total weight of the pore-forming agent and the iron ore powder.

[0044] Preferably, the ball milling time is 12-24 hours and the ball-to-material ratio is 1:(4-12).

[0045] Preferably, the molding method is isostatic pressing, with a pressure of 5-30 MPa, a block diameter of 10-150 mm, and a thickness of 1-20 mm.

[0046] Preferably, the high-temperature furnace is a muffle furnace, with a sintering temperature of 300-1300℃ and a sintering time of 2-10h.

[0047] Specifically, the sintering temperature is any one of 300℃, 500℃, 800℃, 1000℃, and 1300℃, or any two of these; and the sintering time is any one of 2h, 5h, 8h, and 10h, or any two of these.

[0048] In a further description of the present invention, in the above-mentioned method for preparing iron ore blocks, the pore-forming agent and binder can be removed at a sintering temperature of 300-600℃ to obtain iron ore blocks with certain strength and porosity.

[0049] Preferably, in step 1, the metal wire is selected from one of iron wire, nickel wire, molybdenum wire, and tungsten wire, and the metal guide rod is made of stainless steel.

[0050] Preferably, in step 1, the halide molten salt is selected from at least one of chloride-based molten salt and bromide-based molten salt.

[0051] More preferably, the chloride-based molten salt comprises a chloride salt, an oxide, and an oxyacid salt; the chloride salt is selected from at least one of sodium chloride, potassium chloride, lithium chloride, calcium chloride, barium chloride, and magnesium chloride; the oxide is selected from at least one of sodium oxide, potassium oxide, lithium oxide, and calcium oxide, and the amount of the oxide added is 0.5-18 wt%; the oxyacid salt is selected from at least one of carbonate, borate, vanadate, sulfate, and phosphate, and the amount of the oxyacid salt added is 0.5-10 wt%.

[0052] Specifically, the amount of oxide added is any one or any two of 0.5wt%, 1wt%, 3wt%, 5wt%, 7wt%, 9wt%, 11wt%, 13wt%, 15wt%, and 18wt%; the amount of oxyacid salt added is any one or any two of 0.5wt%, 1wt%, 2wt%, 4wt%, 6wt%, 8wt%, and 10wt%.

[0053] More preferably, the bromide-based molten salt comprises bromide salts, oxides, and oxyacid salts; the bromide salt is selected from at least one of sodium bromide, potassium bromide, lithium bromide, calcium bromide, barium bromide, and magnesium bromide; the oxide is selected from at least one of sodium oxide, potassium oxide, lithium oxide, and calcium oxide, and the amount of the oxide added is 0.5-18 wt%; the oxyacid salt is selected from at least one of carbonate, borate, vanadate, sulfate, and phosphate, and the amount of the oxyacid salt added is 0.5-10 wt%.

[0054] Specifically, the amount of oxide added is any one or any two of 0.5wt%, 1wt%, 3wt%, 5wt%, 7wt%, 9wt%, 11wt%, 13wt%, 15wt%, and 18wt%; the amount of oxyacid salt added is any one or any two of 0.5wt%, 1wt%, 2wt%, 4wt%, 6wt%, 8wt%, and 10wt%.

[0055] In a further description of the present invention, in chloride-based molten salts, chloride salts are used as the base electrolyte, and oxides and oxyacid salts are used as additive electrolytes; in bromide-based molten salts, bromide salts are used as the base electrolyte, and oxides and oxyacid salts are used as additive electrolytes; wherein, the oxide or oxyacid salt additive electrolyte can provide the necessary oxygen ions for the anodic reaction, and in bromide-based molten salts, it can also reduce the volatilization of bromide salts.

[0056] Preferably, in step 2, the electrolysis temperature is 400-800℃.

[0057] Specifically, the electrolysis temperature is any one of 400℃, 500℃, 600℃, 700℃, and 800℃, or any two of them.

[0058] Preferably, in step 2, the electrolysis is performed using constant current electrolysis or constant voltage electrolysis, and the electrolysis time is 4-600 hours. During the electrolysis process, the cathode can be selectively removed and replaced with a new cathode according to experimental requirements and cathode reduction status to maintain semi-continuous electrolysis.

[0059] Specifically, the electrolysis time is any one of 4h, 10h, 20h, 50h, 100h, 200h, 300h, 400h, 500h, and 600h, or any two of them.

[0060] More preferably, the cathode current density used in the constant current electrolysis is 0.05-1.5 A / cm². 2 The anode current density is 0.1-1 A / cm². 2 .

[0061] Specifically, the cathode current density is 0.05 A / cm or 0.1 A / cm. 2 0.3A / cm 2 0.5A / cm 2 0.7A / cm 2 0.9A / cm 2 1.0A / cm 2 1.2A / cm 2 1.5A / cm 2 The range between any one of the above and any two of the above; the anode current density is 0.1 A / cm, 0.3 A / cm, 0.5 A / cm, 0.7 A / cm, 0.9 A / cm, 1 A / cm. 2 The range between any one of them and any two of them More preferably, the cell voltage range used in the constant voltage electrolysis is 1.5-5.0V.

[0062] Specifically, the cell voltage range used in the constant voltage electrolysis is any one of 1.5V, 2.5V, 3.5V, 4.5V, and 5.0V, or any two of them.

[0063] Preferably, after step 3, the method further includes: when the iron content of the solid iron oxide is not less than 60%, using the cathode product as direct reduced iron; or when the iron content of the solid iron oxide is less than 60%, performing melting and separation treatment on the cathode product to obtain molten iron.

[0064] Regarding a further explanation of the present invention, in step 3, depending on the iron grade of the raw material, different processing paths can be adopted for the obtained cathode product, all of which ultimately yield high-purity metallic iron: When the raw material is iron-bearing ore with an iron content of not less than 60%, it is considered high-grade iron-bearing ore. The cathode product is obtained directly by electrolysis, and its metallization rate is not less than 90%. It can be used as direct reduced iron for electric arc furnace steelmaking, or melted and used for converter steelmaking. When the raw material is iron-bearing ore with an iron content of less than 60%, it is considered low-grade iron-bearing ore, and the cathode product is a mixture of metallic iron and incompletely reduced iron oxides. In this case, the cathode product needs to be further processed in an electric arc furnace to separate slag and iron, obtaining molten iron with a purity of not less than 99%. This molten iron can be used for steelmaking in an electric arc furnace or converter.

[0065] In a preferred embodiment, the method for green electrochemical extraction of metallic iron from iron-bearing ore includes the following steps: Step 1: The solid iron oxide is bound and fixed to the metal guide rod with metal wire to obtain the pre-made solid iron oxide; iron with a purity greater than 99.5% is used as the anode, two pre-made solid iron oxides are used as the cathode, and a halide molten salt containing an oxygen ion source is used as the electrolyte; the above cathode and anode are arranged in parallel in the electrolytic cell in the form of cathode / anode / cathode to form an electrolytic circuit. Step 2: Seal and evacuate the assembled electrolytic cell, and perform vacuum drying at 180-220℃ for 10-13 hours; after drying, introduce an inert gas as a protective atmosphere and heat the system to 400-800℃ to melt the molten salt; immerse the cathode and anode in the molten salt, and electrolyze the electrolytic circuit at the electrolysis temperature, so that the solid iron oxide is electrochemically reduced to metallic iron at the cathode to obtain the cathode product, while an oxygen evolution reaction occurs at the anode; Step 3: After electrolysis, remove the cathode product from the molten salt, cool and clean it.

[0066] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0067] Example 1 A method for green electrochemical extraction of metallic iron from iron-bearing ore includes the following steps: Step 1: Tie the iron ore blocks to a stainless steel guide rod with iron wire to obtain pre-made iron ore blocks; use 99.8% pure iron as the anode, two pre-made iron ore blocks as the cathode, and LiCl-KCl-Li2CO3-Li2O chloride-based molten salt as the electrolyte, wherein the molar ratio of LiCl to KCl is 1:1, the amount of Li2O added is 5wt%, and the amount of Li2CO3 added is 2.5wt%; arrange the above cathode and anode in parallel in the electrolytic cell in a cathode / anode / cathode manner to form an electrolytic circuit, wherein the anode is cylindrical with a diameter of 5mm; Step 2: Seal and evacuate the assembled electrolytic cell, and vacuum dry it at 200℃ for 12 hours. After drying, introduce argon gas as a protective atmosphere and heat the system to 600℃ to melt the molten salt. Immerse the cathode and anode in the molten salt and perform electrolysis using a constant current electrolysis mode, controlling the electrolysis temperature at 600℃ and the anode current density at 0.3 A / cm². 2 The cathode current density is 0.1 A / cm². 2 The electrolysis time is 20 hours. During this process, the cathode is electrochemically reduced to metallic iron to obtain cathode products, while the oxygen evolution reaction occurs at the anode. Step 3: After electrolysis, the cathode product is removed from the molten salt, cooled, and cleaned. Testing showed that the metallization rate of the cathode product obtained in this embodiment was 96%, meaning that metallic iron accounted for 96% of the total iron content in the cathode product by mass. According to the present invention, this cathode product has a high metallization rate and can be used as direct reduced iron.

[0068] In step 1, the method for preparing the iron ore block includes the following steps: Iron ore powder with an iron content of 67% was mixed with potassium chloride at a weight ratio of 0.5:1. Then, polyvinyl alcohol, accounting for 1% of the total weight of the iron ore powder and potassium chloride, was added. The mixture was ball-milled for 18 hours with a ball-to-material ratio of 1:8 to obtain a mixture. The mixture was then pressed into blocks with a diameter of 20 mm and a thickness of 4 mm under a pressure of 15 MPa using isostatic pressing. The formed blocks were then placed in a muffle furnace and sintered at 900℃ for 5 hours to obtain iron ore blocks with a porosity of 60%. The particle size of the iron ore powder was 0.1 mm.

[0069] In step 2, during the electrolysis process, the cathode is removed and replaced with a new cathode after 10 hours of electrolysis to maintain semi-continuous electrolysis. Electrolysis is stopped when the cathode is replaced, and electrolysis continues after the replacement is completed. There is no need to disconnect the power during this period.

[0070] The cathode products of this embodiment were characterized, and the anode after electrolysis was observed. The results are as follows: Figure 2 As shown; Figure 2 The analysis results of the cathode products and the photographs after anodic electrolysis in this embodiment show that the 67-grade iron ore is transformed into metallic iron elemental phase after cathode reduction. SEM and EDS analysis show that the cathode products are mainly composed of Fe element (Fe: 97.484wt%), indicating that the cathode reduction is sufficient. The anode shows no obvious corrosion and no significant loss in diameter, exhibiting excellent corrosion resistance.

[0071] Example 2 A method for green electrochemical extraction of metallic iron from iron-bearing ore includes the following steps: Step 1: Iron ore blocks are bound and fixed to stainless steel guide rods with iron wire to obtain pre-formed iron ore blocks; 99.8% pure iron is used as the anode, two pre-formed iron ore blocks are used as cathodes, and LiBr-KBr-LiBO2-Li2O bromide-based molten salt is used as the electrolyte, wherein the molar ratio of LiBr to KBr is 1:1, the amount of Li2O added is 5wt%, and the amount of LiBO2 added is 1.5wt%; the above cathodes and anodes are arranged in parallel in the electrolytic cell in a cathode / anode / cathode configuration to form an electrolytic circuit; wherein the anode is cylindrical with a diameter of 5mm; Step 2: Seal and evacuate the assembled electrolytic cell, and vacuum dry it at 200℃ for 12 hours. After drying, introduce argon gas as a protective atmosphere and heat the system to 600℃ to melt the molten salt. Immerse the cathode and anode in the molten salt and perform electrolysis using a constant current electrolysis mode, controlling the electrolysis temperature at 600℃ and the anode current density at 0.3 A / cm². 2 The cathode current density is 0.1 A / cm². 2 The electrolysis time is 12 hours. During the electrolysis process, the iron ore at the cathode is electrochemically reduced to metallic iron, yielding cathode products, while an oxygen evolution reaction occurs at the anode. Step 3: After electrolysis, the cathode product is removed from the molten salt, cooled, and cleaned. Testing showed that the metallization rate of the cathode product obtained in this embodiment was 90%, meaning that metallic iron accounted for 90% of the total iron content in the cathode product by mass. According to the present invention, this cathode product has a high metallization rate and can be used as direct reduced iron.

[0072] The method for preparing the iron-bearing ore block includes the following steps: Iron ore powder with an iron content of 61% was mixed with potassium chloride at a weight ratio of 2:1. Then, 1% polyvinyl alcohol (PVA) was added, and the mixture was ball-milled for 18 hours at a ball-to-material ratio of 1:8 to obtain a mixture. The mixture was then pressed into blocks with a diameter of 15 mm and a thickness of 5 mm under a pressure of 15 MPa using isostatic pressing. The formed blocks were then placed in a muffle furnace and sintered at 900 °C for 5 hours to obtain iron ore blocks with a porosity of 30%. The particle size of the iron ore powder was 0.1 mm.

[0073] The cathode products of this embodiment were characterized, and the anode after electrolysis was observed. The results are as follows: Figure 3 As shown; Figure 3 The analysis results of the cathode products and the photographs after anodic electrolysis in this embodiment show that the 61-grade iron ore is transformed into metallic iron elemental phase after cathode reduction. SEM and EDS analysis show that the cathode products are mainly composed of Fe element (Fe: 94.287%), indicating that the cathode reduction is sufficient. The anode shows no obvious corrosion and no significant loss in diameter, exhibiting excellent corrosion resistance.

[0074] Example 3 A method for green electrochemical extraction of metallic iron from iron-bearing ore includes the following steps: Step 1: Iron ore blocks are bound and fixed to stainless steel guide rods with iron wire to obtain pre-formed iron ore blocks; 99.8% pure iron is used as the anode, two pre-formed iron ore blocks are used as cathodes, and NaBr-KBr-LiBO2-Li2O bromide-based molten salt is used as the electrolyte, wherein the molar ratio of NaBr to KBr is 1:1, the amount of Li2O added is 5wt%, and the amount of LiBO2 added is 1wt%; the above cathodes and anodes are arranged in parallel in the electrolytic cell in a cathode / anode / cathode configuration to form an electrolytic circuit; wherein the anode is cylindrical with a diameter of 5mm; Step 2: Seal and evacuate the assembled electrolytic cell, and vacuum dry it at 200℃ for 12 hours. After drying, introduce argon gas as a protective atmosphere and heat the system to 600℃ to melt the molten salt. Immerse the cathode and anode in the molten salt and perform electrolysis using a constant current electrolysis mode. Control the electrolysis temperature at 800℃ and the anode current density at 0.3 A / cm². 2 The cathode current density is 0.2 A / cm². 2 The electrolysis time is 16 hours. During the electrolysis process, the iron ore at the cathode is electrochemically reduced to metallic iron, yielding cathode products, while an oxygen evolution reaction occurs at the anode. Step 3: After electrolysis, the cathode product is removed from the molten salt, cooled, and cleaned. Testing showed that the metallization rate of the cathode product obtained in this embodiment was 82%, meaning that metallic iron accounted for 82% of the total iron content in the cathode product by mass.

[0075] The method for preparing the iron-bearing ore block includes the following steps: Iron ore powder with an iron content of 54% was mixed with potassium chloride at a weight ratio of 1:1. Then, polyvinyl alcohol accounting for 1% of the total weight of iron ore powder and potassium chloride was added. The mixture was ball-milled for 18 hours with a ball-to-material ratio of 1:8 to obtain a mixture. The mixture was then pressed into blocks with a diameter of 50 mm and a thickness of 10 mm under a pressure of 15 MPa using isostatic pressing. The formed blocks were then placed in a muffle furnace and sintered at 900℃ for 5 hours to obtain iron ore blocks with a porosity of 45%. The particle size of the iron ore powder was 0.1 mm.

[0076] The cathode products of this embodiment were characterized, and the anode after electrolysis was observed. The results are as follows: Figure 4 As shown; by Figure 4 It can be seen that the cathode products are composed of elemental iron phase and Fe3O4, indicating that the 54 grade iron ore was not completely reduced. SEM and EDS analysis showed that the cathode products had a high content of O element and uneven distribution, indicating that the cathode reduction was uneven and contained a large amount of iron oxide. The anode showed no obvious corrosion and no significant loss in diameter, exhibiting excellent corrosion resistance.

[0077] Since the raw material in this embodiment is low-grade iron ore (iron grade 54%), the cathode product still contains residual iron oxides, requiring further melting and separation in an electric arc furnace to achieve slag-iron separation. After melting and separating the cathode product obtained in this embodiment in an electric arc furnace, molten iron with a purity of 99% is obtained. Upon cooling, molten iron beads are obtained, such as... Figure 4 As shown, for low-grade iron ore, the subsequent cathode products can be processed by electric arc furnace melting to separate iron from oxides, thereby obtaining high-purity metallic iron elemental phase.

[0078] Comparative Example 1 A method for green electrochemical extraction of metallic iron from iron-bearing ore, differing from Example 1 only in step 1, which specifically involves: Iron ore blocks are bound and fixed to stainless steel guide rods with iron wire to obtain pre-formed iron ore blocks; iron with a purity of 99.8% is used as the anode, two pre-formed iron ore blocks are used as the cathode, and LiCl-KCl-Li2O chloride-based molten salt is used as the electrolyte, wherein the molar ratio of LiCl to KCl is 1:1, and the amount of Li2O added is 5wt%; the above cathode and anode are arranged in parallel in the electrolysis device in a cathode / anode / cathode manner to form an electrolysis circuit; wherein the anode is cylindrical with a diameter of 5mm.

[0079] The cathode product and the anode after electrolysis in this comparative example were characterized, and the results are as follows: Figure 5 As shown; Figure 5The analysis results of the cathode products and the SEM images after anodic electrolysis in this comparative example show that the cathode products contain a large amount of oxygen, indicating that the reduction is insufficient; the anode is significantly corroded, with the anode diameter being corroded from 5 mm to 4.127 mm.

[0080] Comparative Example 2 A method for green electrochemical extraction of metallic iron from iron-bearing ore, differing from Example 1 only in step 1, which specifically involves: Iron ore blocks are bound and fixed to stainless steel guide rods with iron wire to obtain pre-formed iron ore blocks; iron with a purity of 99.8% is used as the anode, two pre-formed iron ore blocks are used as the cathode, and LiCl-KCl-Li2O chloride-based molten salt is used as the electrolyte, wherein the molar ratio of LiCl to KCl is 1:1, and the amount of Li2O added is 10wt%; the above cathode and anode are arranged in parallel in the electrolysis device in a cathode / anode / cathode manner to form an electrolysis circuit; wherein the anode is cylindrical with a diameter of 5mm.

[0081] The cathode product and the anode after electrolysis in this comparative example were characterized, and the results are as follows: Figure 6 As shown; Figure 6 The analysis results of the cathode products and the SEM images after anodic electrolysis for this comparative example show that the cathode products contain some oxygen, indicating that the reduction does not replenish it; the anode is significantly corroded, with the anode diameter being corroded from 5 mm to 3.127 mm.

[0082] Comparative Example 3 A method for green electrochemical extraction of metallic iron from iron-bearing ore, differing from Example 1 only in step 1, which specifically involves: Iron ore blocks are bound and fixed to stainless steel guide rods with iron wire to obtain pre-formed iron ore blocks; iron with a purity of 99.8% is used as the anode, two pre-formed iron ore blocks are used as the cathode, and LiCl-KCl-Li2CO3 chloride-based molten salt is used as the electrolyte, wherein the molar ratio of LiCl to KCl is 1:1, and the amount of Li2CO3 added is 10wt%; the above cathode and anode are arranged in parallel in the electrolysis device in a cathode / anode / cathode manner to form an electrolysis circuit; wherein the anode is cylindrical with a diameter of 5mm.

[0083] The anode of this comparative example was characterized after electrolysis. The SEM images of the anode after electrolysis are shown below. Figure 7 As shown, the anode has undergone significant corrosion, with its diameter decreasing from 5 mm to 4.146 mm.

[0084] Comparative Example 4 A method for green electrochemical extraction of metallic iron from iron-bearing ore, differing from Example 1 only in step 1, which specifically involves: Iron ore blocks are bound and fixed to stainless steel guide rods with iron wire to obtain pre-formed iron ore blocks; iron with a purity of 99.8% is used as the anode, two pre-formed iron ore blocks are used as the cathode, and LiCl-KCl-Li2CO3-Li2O chloride-based molten salt is used as the electrolyte, wherein the molar ratio of LiCl to KCl is 1:1, the amount of Li2O added is 5wt%, and the amount of Li2CO3 added is 2.5wt%; the above cathodes and anodes are arranged in parallel in the electrolysis device in a cathode / anode / cathode manner to form an electrolysis circuit; wherein the anode is cylindrical with a diameter of 5mm.

[0085] The method for preparing the cathode block includes the following steps: Iron ore powder with an iron content of 61% was mixed with polyvinyl alcohol accounting for 1% of the total weight of the iron ore powder. The mixture was ball-milled for 18 hours with a ball-to-powder ratio of 1:8 to obtain a mixture. The mixture was then pressed into blocks with a diameter of 50 mm and a thickness of 10 mm under a pressure of 15 MPa using isostatic pressing. The formed blocks were then placed in a muffle furnace and sintered at 900℃ for 5 hours to obtain a cathode block with a porosity of 1%. The particle size of the iron ore powder was 0.1 mm.

[0086] The cathode products of this comparative example were characterized, and the results are as follows: Figure 8 As shown; Figure 8 The analysis results of the cathode products in this comparative example show that the cathode products contain some oxygen and a large number of other metal elements besides Fe, indicating that the cathode reduction effect is not good.

[0087] In summary, this invention provides a green electrochemical method for extracting metallic iron from iron-bearing ore. This method uses a solid iron oxide bulk as the cathode and low-cost pure iron as the anode, and electrolysis is carried out in a halide molten salt system containing an oxygen ion source. Through precise design of the molten salt composition, the corrosiveness of the high-temperature molten salt to the pure iron anode is significantly reduced, achieving stable oxygen evolution at industrial-grade current densities and eliminating carbon emissions at the source. Simultaneously, by controlling the porosity of the cathode bulk and developing differentiated post-processing strategies based on the raw material grade, not only is the high purity of the final iron product ensured, but the process's adaptability to raw materials is also significantly broadened. The method provided by this invention overcomes the stringent limitations of traditional processes on raw material grade, has a short process flow, and is simple to operate. It is a method for extracting metallic iron that integrates green, low-carbon, low-cost, highly adaptable, and semi-continuous production, and has broad prospects for industrial application.

[0088] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for green electrochemical extraction of metallic iron from iron-bearing ore, characterized in that, Includes the following steps: Step 1: In the electrolysis device, a solid iron oxide is used as the cathode, iron with a purity greater than 99.5% is used as the anode, and a halide molten salt containing an oxygen ion source is used as the electrolyte to form an electrolysis circuit. Step 2: Electrolyze the electrolytic circuit at the electrolysis temperature, so that the solid iron oxide is electrochemically reduced to metallic iron at the cathode, while an oxygen evolution reaction occurs at the pure iron anode. Step 3: After electrolysis is complete, remove the cathode product.

2. The method according to claim 1, characterized in that, Step 3 is followed by: when the iron content of the solid iron oxide is not less than 60%, the cathode product is used as direct reduced iron; or when the iron content of the solid iron oxide is less than 60%, the cathode product is subjected to melting and separation treatment to obtain molten iron.

3. The method according to claim 1, characterized in that, In step 1, the solid iron oxide is an iron ore block obtained by molding and sintering iron ore powder; the porosity of the iron ore block is 5-70%.

4. The method according to claim 3, characterized in that, The iron-bearing ore is selected from at least one of iron ore, red mud, laterite nickel ore, and vanadium-titanium magnetite, and the iron grade of the iron-bearing ore is 30-70%.

5. The method according to claim 1, characterized in that, In step 1, the halide molten salt is selected from at least one of chloride-based molten salt and bromide-based molten salt.

6. The method according to claim 5, characterized in that, The chloride-based molten salt comprises chloride salts, oxides, and oxyacid salts; the chloride salt is selected from at least one of sodium chloride, potassium chloride, lithium chloride, calcium chloride, barium chloride, and magnesium chloride; the oxide is selected from at least one of sodium oxide, potassium oxide, lithium oxide, and calcium oxide, and the amount of the oxide added is 0.5-18 wt%; the oxyacid salt is selected from at least one of carbonates, borates, vanadates, sulfates, and phosphates, and the amount of the oxyacid salt added is 0.5-10 wt%.

7. The method according to claim 5, characterized in that, The bromide-based molten salt comprises bromide salts, oxides, and oxyacid salts; the bromide salt is selected from at least one of sodium bromide, potassium bromide, lithium bromide, calcium bromide, barium bromide, and magnesium bromide; the oxide is selected from at least one of sodium oxide, potassium oxide, lithium oxide, and calcium oxide, and the amount of the oxide added is 0.5-18 wt%; the oxyacid salt is selected from at least one of carbonate, borate, vanadate, sulfate, and phosphate, and the amount of the oxyacid salt added is 0.5-10 wt%.

8. The method according to claim 1, characterized in that, In step 2, the electrolysis temperature is 400-800℃.

9. The method according to claim 1, characterized in that, In step 2, the electrolysis is performed using constant current electrolysis or constant voltage electrolysis, and the electrolysis time is 4-600 hours.

10. The method according to claim 8, characterized in that, The cathode current density used in the constant current electrolysis is 0.05-1.5 A / cm². 2 The anode current density is 0.1-1 A / cm². 2 The cell voltage range used in the constant voltage electrolysis is 1.5-5.0V.

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