System and method for electrically reducing iron ore fines

Abstract

The present application belongs to the field of energy and metallurgy. Specifically, the present application discloses a system and method for electric reduction of iron ore fines. Iron concentrate is filtered through acidolysis to obtain a saturated iron salt solution, and then iron salt crystals are obtained through crystallization. The iron salt crystals are purified and dissolved into a cathode liquid circulation system to supplement the iron ions consumed in the electrochemical iron smelting process; through an energy-saving and environment-friendly process, the tailings are recycled, sulfur is recycled, and heat is used in a cascade manner. Through the electrochemical iron smelting process, the valence state of iron ions is adjusted to ensure that the liquid into the iron electrodeposition device is divalent iron, high-purity iron is prepared, and the system is recycled, water is recycled, and hydrogen and oxygen are recycled. Through the circulation of the anode liquid and the cathode liquid, cross contamination is avoided, and the production efficiency is improved. The present application is suitable for large-scale and continuous processing of electric reduction of iron ore fines, and has the advantages of high efficiency, low energy consumption, no pollution, and good economic efficiency.

Description

Technical Field

[0001] This invention belongs to the fields of energy and metallurgy, and specifically relates to a system and method for producing iron from iron ore powder by electroreduction. Background Technology

[0002] In 2021, my country's crude steel production was approximately 1 billion tons, emitting about 1.8 billion tons of CO2, accounting for about 16% of the country's total emissions. my country's steel industry primarily utilizes a long process, such as blast furnace-converter furnace production (accounting for as much as 90%), with blast furnace ironmaking being the main source of CO2 emissions, accounting for about 70% of the entire process. Blast furnace ironmaking uses coke as a reducing agent to remove oxygen from iron ore to obtain molten iron, releasing large amounts of CO2. The steel industry urgently needs to develop transformative low-carbon ironmaking technologies.

[0003] Currently developed ultra-low carbon ironmaking technologies mainly focus on replacing coke. These include hydrogen reduction as a substitute for carbon reduction and electroreduction as a substitute for carbon reduction.

[0004] The "hydrogen reduction" route, namely, hydrogen production through water electrolysis and hydrogen reduction of iron, is described in patent CN112159880B. This method and apparatus for hydrogen iron smelting involves using microwave irradiation to smelt iron ore in a hydrogen or hydrogen-rich gas atmosphere to obtain directly reduced iron. This solves the problem of significant carbon dioxide emissions still occurring when using hydrogen-rich gas to reduce iron oxides in existing hydrogen iron smelting processes. Patent application CN102586527A discloses a new hydrogen-carbon molten reduction iron smelting process. The heat required for the entire process is provided by the combustion of oxy-coal and the secondary combustion of reducing gases. Compared with existing processes, this process reduces CO2 emissions by approximately 10%. Patent application CN105886688A discloses a green circular production system where hydrogen replaces carbon in reducing iron ore to elemental iron during metal smelting. No CO2 is produced in the process; the steam generated during smelting generates electricity, and the H2 produced from water electrolysis is recycled. However, current industrial-scale hydrogen production via water electrolysis primarily uses alkaline aqueous solutions, with an energy efficiency of around 60%, and the efficiency of hydrogen production is also relatively low. In the process of hydrogen reducing iron, due to limited thermodynamic equilibrium, the single-cycle conversion rate is low, requiring multiple cycles and increasing energy consumption. Simultaneously, the thermal effect of hydrogen reducing iron is poor, requiring a significant amount of additional thermal energy. Overall, "hydrogen metallurgy" essentially consumes green electrical energy; it is electrometallurgy. Developing a step-by-step electrochemical reduction of iron is also of great significance.

[0005] Iron ore can be decomposed into metallic iron and release oxygen under electrochemical action. This process is generally carried out in three typical systems: a high-temperature molten salt / molten iron oxide system, an alkaline system, and an acidic system. High-temperature molten salt / molten iron oxide system: Patent application CN114232033A discloses a method for preparing high-purity iron by high-temperature molten salt electroreduction, using a CaCl2-Fe2O3-CaO molten salt system. Under a certain current density and an inert argon atmosphere at 850℃, molten salt electroreduction yields a high-purity iron product with a purity of 99.94%. Patent CN101906646B discloses a method for producing metallic iron from iron ore by molten salt electrolysis, using a Fe2O3-Al2O3-SiO2 molten salt system. Under a certain current density and electrolysis temperature (1580-1620℃), metallic iron is obtained through molten salt electroreduction. Patent CN109477232B discloses a method for preparing iron by electrolytic deposition of molten oxide. It employs a Na2O2-B2O3-Fe2O3 molten salt system, and obtains metallic iron with a purity of 97% through molten salt electroreduction at a specific voltage (1.5V / 2.5V) and electrolysis temperature (1000℃). Currently, the main challenges of high-temperature molten salt / molten iron oxide systems are the development of economical inert anode materials, suitable electrolyte systems, and the purification of raw materials.

[0006] An alkaline solution electroreduction technique for producing iron. Allanore A et al. (DOI:10.1149 / 1.2790285) experimentally demonstrated that electrolysis of suspended iron oxide particles in a sodium hydroxide solution (50% mass concentration, 110℃) (iron ion concentration 2.6 × 10⁻⁶) yields iron. -3 The invention mentions the possibility of iron formation (M), but also notes the low solubility of hematite in this system, leading to extremely low reduction efficiency. Patent CN101696510B discloses a method and apparatus for preparing high-purity iron powder through electrolytic deoxygenation, involving an electrochemical method for obtaining high-purity iron from solid iron oxide. Solid iron oxide is a sintered body or ore composed of single or mixed Fe2O3, Fe3O4, and FeO. The anode and cathode are located at opposite ends of an electrolytic cell. The electrolytic cell contains an ion-conducting membrane and a high-temperature hydroxide solution (sodium hydroxide or potassium hydroxide, at 700-800℃). A preset voltage is applied between the electrodes to drive oxygen ions to diffuse from the iron oxide in the cathode basket to the anode, where high-purity iron can be obtained. However, in this patent, the anode must be a solid material with strong alkali resistance, corrosion resistance, and good conductivity, and the solid oxygen ion-conducting membrane must also possess alkali resistance and corrosion resistance, resulting in high costs. In addition, to prevent impurities in solid iron oxide from dissolving in high-temperature alkaline solutions and adversely affecting electrolyte performance, iron oxide needs to undergo impurity removal pretreatment, which will lead to a significant increase in economic and environmental costs.

[0007] Acidic Solution Electroreduction Technology for Iron Production. Researchers have conducted extensive work on the electroreduction of iron from acidic iron-containing solutions, primarily aiming to prepare high-purity metallic iron and pure iron powder. The most common electrolyte solutions used in this process are ferrous chloride and ferrous sulfate. Acidic FeCl2 solution: Patent application CN107955952A discloses a method for producing high-purity iron powder from iron slag. This involves leaching (leaching solution composition: 15-19 parts sodium hydroxide, 5-9 parts sodium methyl methacrylate, 260-300 parts water) to remove inorganic components such as silica from the iron slag, increasing the iron particle content in the filter residue. An electrolyte solution containing 6-9 parts (15% by volume) of hydrochloric acid, 10-14 parts (magnesium sulfate), and 900-1000 parts (water) is then added for electrolysis. Finally, the surface of the iron powder is cleaned using an 18-22% (w / w) ethylenediaminetetraacetic acid solution to obtain high-purity iron powder. The patented method consumes large amounts of sodium hydroxide and hydrochloric acid during leaching and electrolysis. Furthermore, due to impurities and concentration, these leachates and electrolytes cannot be recycled, making subsequent processing difficult. Patent CN101517129B discloses an electrochemical method for recovering iron and chlorine from an iron-rich metal chloride solution, with a cathode electrolyte pH of 0.9-1.1, an electroreduction temperature of 80-85℃, and a cathode current density of 200-500 A / m. 2 The current efficiency is 96.4%-97.9%, and the purity of iron prepared by electroreduction is 99.99%. This patent has high requirements for the control of impurity content and pH in the solution. The ferric chloride solution needs to be adjusted to a relatively low pH value to prevent the pH value on the cathode surface from rising to a level higher than the precipitation pH value of other impurities, causing co-precipitation. However, it cannot be too low to prevent the release of hydrogen gas as a byproduct.

[0008] Acidic FeSO4 electrolyte solution. Patent application CN113481540A discloses a method for preparing high-purity iron, using a soluble anode, an electrolyte mainly containing FeSO4 and a small amount of stabilizer, and a cathode current density of 100-230 A / m. 2The electrolyte pH is 1.00-4.00, the electrolyte temperature is 20-100℃, the purity of the iron prepared by electrolysis is 99.90%-99.99%, and the deposition thickness is 20μm-3cm. This patent uses a sulfuric acid system, and the soluble anode is industrial pure iron, low carbon steel, etc., so the purity of the electrolyte solution is high. However, if the purity of the electrolyte decreases, it will lead to a series of problems such as more side reactions, reduced current efficiency, and contamination by impurities. Patent CN102084034B discloses an electrochemical method for recovering metallic iron or iron-rich alloys, oxygen, and sulfuric acid from iron-rich metal sulfate waste (byproduct of the ilmenite sulfate process). The electrolyte is an iron-rich metal sulfate solution, the electrolyte pH is 1.4-3.5, the electrolyte temperature is 25-60℃, and the cathode current density used is 300-1000A / m. 2 The purity of iron produced by electrolysis can reach 99.99%, with a current efficiency of 95%-98%. In this patent, the iron-rich metal sulfate solution must undergo pretreatment (such as pH adjustment) before electroreduction, and the acidic insoluble solids produced in this process are also difficult to handle. Furthermore, E. Mostad et al. (DOI:10.1016 / j.hydromet.2007.07.014) mentioned that a Norwegian smelter conducted a semi-industrial electroreduction experiment between 1947 and 1957 using pyrite (FeS2) as raw material in a pilot plant, conducting electroreduction experiments on FeSO4 solutions produced from calcination and sulfuric acid leaching processes, ultimately obtaining high-purity metallic iron. This process was the first to use iron ore (pyrite) as raw material for electroreduction to produce metallic iron, producing a total of 1.5 × 10⁻⁶ tons of iron between 1955 and 1957. 5A study by WD Badenhorst et al. (DOI: 10.3390 / membranes9110137) found that using a novel BM-5AEM anion exchange membrane could achieve a current efficiency of 95% in iron electrolysis with an energy consumption of 3.53 kWh / kg iron, which is superior to the existing Pyror process and also shows better stability and lower energy consumption than commercially available AEM membranes. The study also found that when the iron concentration in the solution is below 5 g / L, cathode side reactions lead to a decrease in process efficiency. However, these studies mainly use pyrite or ferrous sulfate as raw materials, with limited research on the broader applications of hematite or magnetite. Patent applications WO2022204379A1 and WO2022197954A1 disclose a method for producing pure iron from iron ore and removing impurities from the solution. This method first involves thermally reducing one or more non-magnetic iron oxide components in the iron ore to form magnetite in the presence of a reducing agent. Then, the magnetite is dissolved in acid to form an acidic iron salt solution. Undissolved impurities are separated and processed. Subsequently, the acidic iron salt is electrolyzed to obtain high-purity iron, and the remaining solution is returned to the acidolysis tank for recycling. However, the reducing agent mentioned in these patents is mainly hydrogen, which is generated through a chemical reaction between iron metal and acid. This method requires the addition of iron metal, increasing costs. Furthermore, this exothermic reaction easily generates a large amount of hydrogen and heat instantaneously, significantly impacting equipment and safety. Furthermore, this method reduces iron ore to magnetite through thermal reduction, specifically by lowering the valence state of some iron in the ore to promote dissolution. This is primarily because a higher degree of iron reduction in the ore results in a higher leaching rate (DOI: 10.3321 / j.issn:1005-3026.2008.12.017). However, the patent does not mention how to achieve efficient iron ore reduction, nor does it address the failure to recover and utilize the heat generated during this process. Additionally, the acid used to dissolve magnetite in this method is highly acidic, while the acidity of the solution recycled back to the acidolysis tank after electrolysis is relatively low, potentially leading to an acidity mismatch that hinders magnetite dissolution. Patent applications WO2022204387A1, WO2022204391A1, and WO2022204394A1 disclose a method for dissolving, converting, and systematically utilizing iron ore. This method involves dissolving iron-containing ore into an acidic iron salt solution, followed by reacting Fe in a first electrolytic cell. 3+ Reduction to form Fe 2+ The Fe that will be formed subsequently 2+The iron is transferred from the first electrolytic cell to the second electrolytic cell and reduced to high-purity iron, with the remaining solution returned to the dissolving tank. In this method, the first and second electrolytic cells employ proton exchange membranes (PEM) and anion exchange membranes (AEM), respectively. The use of two different types of ion-exchange membranes increases the variety of membranes used in the electrolytic cells, thus increasing operating costs. Furthermore, the patent mentions that the volume of solution entering the cathode chamber in the second electrolytic cell is smaller than the volume entering the anode chamber, increasing process complexity and potentially reducing iron utilization efficiency. Since the patent also uses hydrochloric acid to dissolve magnetite, the introduction of chloride ions can lead to a competing reaction at the anode, increasing the risk of chlorine gas evolution and potentially exacerbating wear on the ion-exchange membrane, further increasing costs. Additionally, the patent does not address the recovery and reuse of the evolved oxygen.

[0009] Currently, the iron-containing electrolyte in acidic solution electroreduction for iron production is generally based on ferrous iron (Fe2+), with raw materials mainly derived from pyrite and ilmenite, which contain ferrous iron. When using more widely available hematite or magnetite as raw materials, there are fewer reports on this, and a series of new challenges arise: mismatch between the acid produced at the electroreduction anode and the leaching acidity, mismatch between the final leaching acid and the electroreduction cathode acidity, leading to difficulties in circulating the sulfuric acid medium, intensified acidolysis, water circulation in diaphragm (ion-exchange membrane) electroreduction, purification of the ferric sulfate solution, and the utilization of acidolysis / purification residues. In summary, current hydrogen reduction or electroreduction iron production technologies still face bottlenecks. Therefore, developing systematic low-carbon electrometallurgical technologies for iron ore through process technology innovation is of great significance. Summary of the Invention

[0010] To address the aforementioned problems, this invention proposes a system and method for producing iron from iron ore powder by electroreduction, thereby achieving the preparation of high-purity iron and the recycling of by-product resources.

[0011] To achieve this objective, the present invention employs the following technical solution:

[0012] A system for producing iron from iron ore powder by electroreduction, the system comprising an acid leaching purification process 1, an electrochemical ironmaking process 2, and an energy-saving and environmentally friendly process 3;

[0013] The acid hydrolysis purification process 1 includes a sulfuric acid heat exchange device 1-1, an acid hydrolysis filtration device 1-2, an acid hydrolysis liquid heat exchange device 1-3, an iron salt crystallization device 1-4, an iron salt purification device 1-5, and an iron salt dissolution device 1-6.

[0014] The electrochemical ironmaking process 2 includes a valence state control device 2-1, an iron electrodeposition device 2-2, a cathode liquid heat exchanger 2-3, and an anolyte heat exchanger 2-4;

[0015] The energy-saving and environmentally friendly process 3 includes a sulfur dioxide heat exchanger 3-1, a high-temperature desulfurization device 3-2, a purification device 3-3, and a solar furnace 3-4;

[0016] The inlet of the sulfuric acid heat exchanger 1-1 is connected to the anode outlet of the iron electrodeposition device 2-2, the outlet of the sulfuric acid heat exchanger 1-1 is connected to the inlet of the acid hydrolysis filter device 1-2, the air inlet of the sulfuric acid heat exchanger 1-1 is connected to the high-temperature air outlet of the sulfur dioxide heat exchanger 3-1, and the air outlet of the sulfuric acid heat exchanger 1-1 supplies low-temperature air for venting.

[0017] The iron concentrate inlet of the acidolysis filtration device 1-2 is connected to the outlet of the iron concentrate storage device; the liquid inlet of the acidolysis filtration device 1-2 is connected to the sulfuric acid solution main pipe; the pipe connecting the liquid inlet of the acidolysis filtration device 1-2 to the sulfuric acid solution main pipe is connected to the low-temperature sulfur dioxide outlet of the sulfur dioxide heat exchanger 3-1; the slag outlet of the acidolysis filtration device 1-2 is connected to the inlet of the high-temperature desulfurization device 3-2; the liquid outlet of the acidolysis filtration device 1-2 is connected to the inlet of the acidolysis liquid heat exchanger 1-3; the liquid outlet of the acidolysis liquid heat exchanger 1-3 is connected to the inlet of the iron salt crystallization device 1-4; the iron salt crystallization device 1- The outlet of device 4 is connected to the inlet of purification device 3-3; the outlet of iron salt crystallization device 1-4 is connected to the inlet of iron salt purification device 1-5; the tail slag outlet of iron salt purification device 1-5 is connected to the inlet of high-temperature desulfurization device 3-2; the outlet of iron salt purification device 1-5 is connected to the inlet of iron salt dissolving device 1-6; the inlet of iron salt dissolving device 1-6 is connected to the cathode outlet of electrodeposition iron device 2-2; the outlet of iron salt dissolving device 1-6 is connected to the inlet of cathode liquid heat exchanger 2-3; and the outlet of cathode liquid heat exchanger 2-3 is connected to the cathode inlet of valence state control device 2-1.

[0018] The air inlet of the acid hydrolysis heat exchange device 1-3 is connected to the high-temperature air outlet of the sulfur dioxide heat exchanger 3-1, and the air outlet of the acid hydrolysis heat exchange device 1-3 sends low-temperature air to be discharged.

[0019] The anode inlet of the valence state control device 2-1 is connected to the outlet of the anolyte heat exchanger 2-4, and the inlet of the anolyte heat exchanger 2-4 is connected to the outlet of the purification device 3-3; the anode outlet of the valence state control device 2-1 is connected to the anode inlet of the electrodeposition iron device 2-2; the valence state control device 2-1 The anode outlet of the electrodeposition device 2-1 is connected to the oxygen product pipeline; the cathode outlet of the valence state control device 2-1 is connected to the cathode inlet of the electrodeposition iron device 2-2; the cathode outlet of the electrodeposition iron device 2-2 is connected to the hydrogen inlet of the high-temperature desulfurization device 3-2; pure iron is obtained from the cathode of the electrodeposition iron device 2-2; the anode outlet of the electrodeposition iron device 2-2 is connected to the oxygen product pipeline; the anode of the valence state control device 2-1 is connected to the positive electrode of the green electricity via a conductive copper beam; the cathode of the valence state control device 2-1 is connected to the negative electrode of the green electricity via a conductive copper beam; the anode of the electrodeposition iron device 2-2 is connected to the positive electrode of the green electricity via a conductive copper beam; the cathode of the electrodeposition iron device 2-2 is connected to the negative electrode of the green electricity via a conductive copper beam.

[0020] The air inlet of the cathode liquid heat exchanger 2-3 is connected to the high-temperature air outlet of the sulfur dioxide heat exchanger 3-1, and the air outlet of the cathode liquid heat exchanger 2-3 sends low-temperature air to be discharged.

[0021] The air inlet of the anolyte heat exchanger 2-4 is connected to the high-temperature air outlet of the sulfur dioxide heat exchanger 3-1, and the air outlet of the anolyte heat exchanger 2-4 supplies low-temperature air for venting.

[0022] The air inlet of the sulfur dioxide heat exchanger 3-1 is connected to an air source, and the high-temperature sulfur dioxide inlet of the sulfur dioxide heat exchanger 3-1 is connected to the high-temperature outlet of the high-temperature desulfurization device 3-2; the high-temperature medium inlet of the high-temperature desulfurization device 3-2 is connected to the high-temperature medium outlet of the solar furnace 3-4, and the low-temperature medium outlet of the high-temperature desulfurization device 3-2 is connected to the low-temperature medium inlet of the solar furnace 3-4.

[0023] The solid material outlet of the high-temperature desulfurization device 3-2 is connected to the cement clinker discharge pipe through a pipeline; the purification slag outlet of the purification device 3-3 is connected to the feed inlet of the high-temperature desulfurization device 3-2.

[0024] The solar furnace 3-4 receives solar radiation through its light inlet.

[0025] The present invention also provides a method for producing iron from iron ore powder by electroreduction based on the above system, comprising the following steps:

[0026] Iron concentrate powder enters the acid filtration device 1-2, where it undergoes acid lysis with concentrated sulfuric acid solution from sulfuric acid heat exchanger 1-1, sulfuric acid solution from the sulfuric acid solution main pipe, and low-temperature sulfur dioxide from sulfur dioxide heat exchanger 3-1 to obtain acid lysis solution and acid lysis residue. The acid lysis solution is preheated by acid lysis solution heat exchanger 1-3 and then enters the iron salt crystallization device 1-4 to obtain iron salt and dilute sulfuric acid solution. The iron salt passes through iron salt purification device 1-5 to obtain pure iron salt and purification residue. The pure iron salt and dilute ferrous sulfate solution pass through iron salt dissolution device 1-6 to obtain iron salt solution. The iron salt solution is heated by cathode liquid heat exchanger 2-3 and then sent to the cathode chamber of valence state control device 2-1. After crystallization, the dilute sulfuric acid solution passes through purification device 3-3 to obtain purified dilute sulfuric acid solution. The purified dilute sulfuric acid solution is sent to the anode chamber of the valence state control device 2-1 after heat exchange in the anolyte heat exchanger 2-4; the purified residue, acidolysis residue, purified residue and hydrogen are sent to the high-temperature desulfurization device 3-2 to obtain high-temperature sulfur dioxide and cement clinker; the cement clinker is discharged for reuse; the high-temperature sulfur dioxide is mixed with the sulfuric acid solution after heat exchange in the sulfur dioxide heat exchanger 3-1 and sent to the acidolysis filtration device 1-2; the sulfuric acid solution is only used during the first start-up; the solar furnace converts solar energy into heat energy to raise the temperature of the medium, and the high-temperature medium circulates to provide heat for the high-temperature desulfurization device 3-2; ambient temperature air is heated by the sulfur dioxide heat exchanger 3-1, and the resulting high-temperature air is used to heat the cathode liquid, anolyte, concentrated sulfuric acid solution and acidolysis solution.

[0027] Ferrous salt solution is reduced at the cathode by valence state control device 2-1 to obtain ferrous sulfate solution; ferrous sulfate solution enters the cathode chamber of electrodeposition iron device 2-2; dilute sulfuric acid solution is anolyzed by valence state control device 2-1 to obtain oxygen and sulfuric acid; sulfuric acid solution enters the anode chamber of electrodeposition iron device 2-2; oxygen is discharged for treatment; ferrous sulfate solution is reduced at the cathode by electrodeposition iron device 2-2 to obtain pure iron, dilute ferrous sulfate solution, and hydrogen as a byproduct; dilute ferrous sulfate solution is sent to iron salt dissolution device 1-6; pure iron is the final product; part of the hydrogen is passed into high-temperature desulfurization device 3-2, and the remaining hydrogen is used as a product; sulfuric acid solution is anolyzed by electrodeposition iron device 2-2 to obtain concentrated sulfuric acid solution and oxygen; concentrated sulfuric acid solution is heated by sulfuric acid heat exchange device 1-1 and then sent to acidolysis filtration device 1-2; oxygen is collected as a product.

[0028] Preferably, the iron concentrate powder is hematite or magnetite, with an iron oxide grade of not less than 90%, and the iron concentrate powder is directly leached with high-concentration concentrated sulfuric acid generated at the anode of the iron electrodeposition device 2-2.

[0029] Preferably, in the acid hydrolysis filtration device 1-1, acid hydrolysis is used, with a reaction temperature of 100℃-200℃, a pressure of 0.1MPa-1.6MPa, and the concentration of concentrated sulfuric acid solution is not less than 100g / L.

[0030] Preferably, in the acid hydrolysis filtration device 1-2, the ferric ions generated during the acid hydrolysis process are reduced to ferrous ions under the chemical reduction of sulfur dioxide, thereby achieving reductive acid hydrolysis, improving the acid hydrolysis efficiency, and the acid hydrolysis rate is above 98%.

[0031] Preferably, in the acid hydrolysis filtration device 1-2, the filtration equipment adopts plate and frame filter press, belt filter or centrifugal filter.

[0032] Preferably, the high-temperature desulfurization device 3-2 adopts a fluidized bed or rotary kiln reactor, with a reaction temperature of 1000℃-1500℃ and a desulfurization rate of over 99%.

[0033] Preferably, in the valence state control device 2-1, the diaphragm material is an ion exchange membrane or a porous membrane, wherein the permeation rate of the porous membrane is 1%-40% and the current density is 50A / m. 2 -1000A / m 2 The anode is a lead alloy or titanium-based ruthenium-iridium-tantalum coated electrode, the cathode is made of iron or titanium, and the temperature is 20℃-100℃;

[0034] In the electrodeposition iron device 2-2, the diaphragm material is an ion-exchange membrane or a porous membrane, wherein the permeation rate of the porous membrane is 1%-40%, and the current density is 100 A / m. 2 -2000A / m 2 The anode is a lead alloy or titanium-based ruthenium-iridium-tantalum coated electrode, and the cathode is made of iron, copper, titanium or stainless steel. The reaction temperature is 60℃-100℃, the current efficiency is above 95%, the cathode iron purity is above 99%, and the DC power consumption per ton of iron is less than 3500kWh.

[0035] Preferably, the solar furnace 3-4 converts solar energy into thermal energy, which is a solar heating medium. The medium can be molten salt and / or gas. The molten salt is a molten salt composed of one or more of silicon, sodium, oxygen, calcium, and aluminum. The gas includes nitrogen and / or argon.

[0036] One of the features of this invention is that the iron concentrate powder is hematite or magnetite, and the iron concentrate powder is directly leached with high-concentration concentrated sulfuric acid generated at the anode of the iron electrodeposition device 2-2.

[0037] The second feature of this invention is as follows: An iron salt solution is fed into the cathode chamber of the valence state control device for electrolysis. After electrolysis, a concentrated ferrous sulfate solution is fed into the cathode chamber of the iron electrodeposition device. The resulting dilute ferrous sulfate solution is then fed into the iron salt dissolution chamber as a solvent for crystallizing the iron salt. The resulting iron salt solution is then returned to the cathode chamber of the valence state control device, thus completing the independent circulation of the cathode solution. The dilute sulfuric acid solution obtained from the iron salt crystallization device is purified and fed into the anode chamber of the valence state control device as an electrolyte. The resulting sulfuric acid solution is fed into the anode chamber of the iron electrodeposition device. The resulting concentrated sulfuric acid solution is used as an acidolysis solvent for the iron ore. After the acidolysis solution undergoes iron salt crystallization, the resulting crystallized solution, which is then purified, is fed into the anode chamber of the valence state control device, thus completing the independent circulation of the anode solution. The separate and independent circulation of the anode and cathode solutions avoids cross-contamination and improves production efficiency.

[0038] The third feature of this invention is that the cathode liquid of the valence state control device is electrolyzed with a near-saturated high-concentration iron salt solution, which can improve the current density and efficiency.

[0039] The fourth feature of this invention is that: iron ore is leached with a high acid solution of anolyte to obtain a saturated iron salt solution, and iron salt crystals are obtained by cooling and crystallization.

[0040] The fifth feature of this invention is that the iron salt crystals are purified and transported to the catholyte system, ensuring that the catholyte is a nearly saturated high-concentration iron salt solution.

[0041] The sixth feature of this invention is that the acid hydrolysis residue, purification residue, and cleaned residue are desulfurized at high temperature to obtain a cement clinker substitute, and the sulfur dioxide generated is sent to the acid hydrolysis purification process.

[0042] The seventh feature of this invention is that the sulfur dioxide generated during high-temperature desulfurization is passed through an acid hydrolysis and filtration process after heat exchange. The sulfur dioxide has a reducing effect, improving the acid hydrolysis efficiency. Hematite or magnetite is directly leached with low acid, achieved through sulfur dioxide reduction leaching.

[0043] The eighth feature of this invention is that the purpose of the valence state control device is to adjust the valence state to ensure that the feed liquid to the iron electrodeposition device is always ferrous iron (Fe2+). Part of the hydrogen produced as a byproduct of the electrodeposition process is used as a reducing agent in the high-temperature desulfurization process, and the remainder is used as a hydrogen product. The electrochemical ironmaking process employs a two-step method of valence state control and iron electrodeposition to address the influence of ferric ions in the iron electrodeposition process and improve production efficiency.

[0044] The ninth feature of this invention is that a high-temperature medium obtained by heating with a solar furnace 3-4 provides heat for high-temperature desulfurization. High-temperature air is obtained by exchanging heat between air and high-temperature sulfur dioxide, which then heats the cathode solution, anolyte, sulfuric acid solution, and acidolysis solution, achieving cascaded energy utilization. The entire process is carbon-free.

[0045] The tenth feature of this invention is that it obtains oxygen as a byproduct.

[0046] The eleventh feature of this invention is the recovery and utilization of hydrogen.

[0047] The twelfth feature of this invention is that the tailings are completely recycled.

[0048] The thirteenth feature of this invention is: a complete sulfur recycling system. Iron concentrate reacts with concentrated sulfuric acid solution to obtain acidolysis solution and acidolysis residue. The sulfur element in the acidolysis solution is recycled through an electrochemical ironmaking process, and the sulfur element in the acidolysis residue is recycled through high-temperature desulfurization. Sulfuric acid solution is added during the initial startup of the system, and thereafter the sulfur element is recycled throughout the entire system.

[0049] The fourteenth feature of this invention is that the tailings can be used in cement clinker, etc.

[0050] The fifteenth feature of the present invention is that the battery separator of the valence state control device 2-1 and the iron electrodeposition device 2-2 is an ion-exchange membrane or a porous membrane, wherein the permeation rate of the porous membrane is 1%-40%.

[0051] The sixteenth feature of this invention is that a high-temperature medium obtained by heating with a solar furnace 3-4 provides heat for high-temperature desulfurization.

[0052] The seventeenth feature of this invention is that: this invention uses a sulfur dioxide heat exchanger to exchange heat between the high-temperature sulfur dioxide generated by high-temperature desulfurization and air, and then the obtained high-temperature air is respectively passed into a sulfuric acid heat exchanger, an acid hydrolysis solution heat exchanger, a cathode liquid heat exchanger and an anolyte heat exchanger to heat the concentrated sulfuric acid solution, acid hydrolysis solution, cathode liquid and anolyte. While completing heat recovery, the temperature of the electrolyte is increased, which further improves the electrolysis efficiency. The heat generated in the system forms a closed loop, which has high utilization rate, saves energy and does not pollute the environment.

[0053] Compared with the prior art, the present invention has the following outstanding advantages:

[0054] (1) Electrolysis of water to produce hydrogen is powered by green electricity, and the hydrogen and oxygen produced can be recycled and reused.

[0055] (2) Sulfuric acid solution and sulfur dioxide gas can be recycled within the system without emission, making it safe and environmentally friendly;

[0056] (3) The iron ore is leached with high acid from the anolyte to obtain a saturated iron salt solution. The solution is then cooled and crystallized to obtain iron salt crystals, which are then purified and transferred to the catholyte system.

[0057] (4) Zero carbon emissions throughout the entire process;

[0058] (5) The anolyte and catholyte solutions of this system are circulated separately;

[0059] (6) The tailings produced can be fully utilized to make cement clinker.

[0060] (7) The process is simple, the production cost is low, and the product purity is high;

[0061] This invention involves acid leaching and filtration of iron concentrate to obtain a saturated iron salt solution, followed by crystallization to obtain iron salt crystals. The iron salt crystals are purified and dissolved before entering the cathode liquid circulation system to replenish the iron ions consumed in the electrochemical ironmaking process. Through energy-saving and environmentally friendly processes, the system achieves resource utilization of tailings, sulfur recycling, and cascade utilization of heat. The electrochemical ironmaking process adjusts the valence state of iron ions, ensuring that the feed liquid to the iron electrodeposition device is always divalent iron, thus achieving the preparation of high-purity iron. This, in turn, enables the recycling of sulfuric acid, water, and the recovery and reuse of hydrogen and oxygen. The iron ore powder electroreduction ironmaking technology using this invention not only yields high-purity iron but also achieves zero carbon emissions throughout the entire process, separate recycling of anolyte and cathode solutions, complete resource utilization of tailings, recycling of byproducts such as sulfuric acid and sulfur dioxide, and recovery and reuse of hydrogen and oxygen. This invention is suitable for large-scale, continuous processing of iron ore powder electroreduction ironmaking, offering advantages such as high efficiency, low energy consumption, no pollution, and good economic benefits. Attached Figure Description

[0062] Figure 1 This is a schematic diagram of the configuration of the iron ore powder electroreduction iron production system of the present invention.

[0063] Figure label:

[0064] Acid hydrolysis purification process 1:

[0065] Sulfuric acid heat exchanger 1-1, acid hydrolysis filtration device 1-2, acid hydrolysis liquid heat exchanger 1-3, iron salt crystallization device 1-4, iron salt purification device 1-5, iron salt dissolution device 1-6;

[0066] Electrochemical ironmaking process 2:

[0067] Valence control device 2-1, iron electrodeposition device 2-2, cathodic liquid heat exchanger 2-3, anodic liquid heat exchanger 2-4;

[0068] Energy-saving and environmentally friendly process 3:

[0069] Sulfur dioxide heat exchanger 3-1, high-temperature desulfurization device 3-2, purification device 3-3, solar furnace 3-4. Detailed Implementation

[0070] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. It is worth noting that the embodiments are only used to illustrate the technical solutions of the present invention, and not to limit it. Figure 1 This is a schematic diagram of a system for producing iron from iron ore powder by electroreduction according to the present invention.

[0071] Example 1

[0072] Combination Figure 1 A system for producing iron from iron ore powder by electroreduction, the system comprising an acid leaching purification process 1, an electrochemical ironmaking process 2, and an energy-saving and environmentally friendly process 3;

[0073] The acid hydrolysis purification process 1 includes a sulfuric acid heat exchanger 1-1, an acid hydrolysis filtration device 1-2, an acid hydrolysis liquid heat exchanger 1-3, an iron salt crystallization device 1-4, an iron salt purification device 1-5, and an iron salt dissolution device 1-6.

[0074] The electrochemical ironmaking process 2 includes a valence state control device 2-1, an iron electrodeposition device 2-2, a cathode liquid heat exchanger 2-3, and an anolyte heat exchanger 2-4;

[0075] The energy-saving and environmentally friendly process 3 includes a sulfur dioxide heat exchanger 3-1, a high-temperature desulfurization device 3-2, a purification device 3-3, and a solar furnace 3-4;

[0076] The iron concentrate inlet of the acidolysis filtration device 1-2 is connected to the outlet of the iron concentrate storage device. The liquid inlet of the acidolysis filtration device 1-2 is connected to the liquid outlet of the sulfuric acid heat exchange device 1-1 and the outlet of the sulfuric acid solution storage device, respectively. The pipe connecting the liquid inlet of the acidolysis filtration device 1-2 to the outlet of the sulfuric acid solution storage device is connected to the low-temperature sulfur dioxide outlet of the sulfur dioxide heat exchanger 3-1. The slag outlet of the acidolysis filtration device 1-2 is connected to the inlet of the high-temperature desulfurization device 3-2. The liquid outlet of the acidolysis filtration device 1-2 is connected to the liquid inlet of the acidolysis liquid heat exchange device 1-3. The gas inlet of the acidolysis liquid heat exchange device 1-3 is connected to the sulfur dioxide heat exchanger 3-1. The low-temperature sulfur dioxide outlet of the acid hydrolysis heat exchange device 1-3 is connected to the liquid outlet of the iron salt crystallization device 1-4, and the outlet of the acid hydrolysis heat exchange device 1-3 supplies low-temperature air for venting; the outlet of the iron salt crystallization device 1-4 is connected to the liquid outlet of the purification device 3-3, and the outlet of the iron salt crystallization device 1-4 is connected to the inlet of the iron salt purification device 1-5; the tailings outlet of the iron salt purification device 1-5 is connected to the inlet of the high-temperature desulfurization device 3-2, and the outlet of the iron salt purification device 1-5... The inlet of the iron salt dissolving device 1-6 is connected to the feed inlet of the iron salt dissolving device 1-6; the liquid inlet of the iron salt dissolving device 1-6 is connected to the cathode liquid outlet of the iron electrodeposition device 2-2; the liquid outlet of the iron salt dissolving device 1-6 is connected to the liquid inlet of the cathode liquid heat exchanger 2-3; the liquid inlet of the sulfuric acid heat exchanger 1-1 is connected to the anode liquid outlet of the iron electrodeposition device 2-2; the air inlet of the sulfuric acid heat exchanger 1-1 is connected to the high-temperature air outlet of the sulfur dioxide heat exchanger 3-1; and the air outlet of the sulfuric acid heat exchanger 1-1 supplies low-temperature air for venting.

[0077] The anode inlet of the valence state control device 2-1 is connected to the outlet of the anolyte heat exchanger 2-4; the cathode inlet of the valence state control device 2-1 is connected to the outlet of the catholyte heat exchanger 2-3; the anode outlet of the valence state control device 2-1 is connected to the anode inlet of the electrodeposition iron device 2-2; the anode outlet of the valence state control device 2-1 is connected to the oxygen product pipeline; the cathode outlet of the valence state control device 2-1 is connected to the cathode inlet of the electrodeposition iron device 2-2; the anode of the valence state control device 2-1 is connected to the positive electrode of green electricity via a conductive copper beam; the valence state control device... The cathode of electrodepositing iron device 2-1 is connected to the negative electrode of green electricity via a conductive copper beam; the cathode outlet of electrodepositing iron device 2-2 is connected to the inlet of high-temperature desulfurization device 3-2; pure iron is obtained from the cathode of electrodepositing iron device 2-2; the anode outlet of electrodepositing iron device 2-2 is connected to the oxygen product pipeline; the anode of electrodepositing iron device 2-2 is connected to the positive electrode of green electricity via a conductive copper beam; the cathode of electrodepositing iron device 2-2 is connected to the negative electrode of green electricity via a conductive copper beam; the inlet of cathode liquid heat exchanger 2-3 is connected to the high-temperature air outlet of sulfur dioxide heat exchanger 3-1; the cathode liquid heat exchanger 2-3... The outlet of the anolyte heat exchanger 2-4 is connected to the outlet of the purification device 3-3, the inlet of the anolyte heat exchanger 2-4 is connected to the high-temperature air outlet of the sulfur dioxide heat exchanger 3-1, and the outlet of the anolyte heat exchanger 2-4 is connected to the outlet of the purification device 3-3.

[0078] The air inlet of the sulfur dioxide heat exchanger 3-1 is connected to an air source; the high-temperature sulfur dioxide inlet of the sulfur dioxide heat exchanger 3-1 is connected to the high-temperature outlet of the high-temperature desulfurization device 3-2; the high-temperature medium inlet of the high-temperature desulfurization device 3-2 is connected to the high-temperature medium outlet of the solar furnace; the low-temperature medium outlet of the high-temperature desulfurization device 3-2 is connected to the low-temperature medium inlet of the solar furnace 3-4; the solid material outlet of the high-temperature desulfurization device 3-2 is connected to the cement clinker substitute via a pipeline; the purified slag outlet of the purification device 3-3 is connected to the feed inlet of the high-temperature desulfurization device 3-2; and the solar furnace's light inlet can receive solar radiation.

[0079] Example 2

[0080] This embodiment uses the iron ore powder electroreduction method for iron production described in Embodiment 1, including the following steps:

[0081] Iron concentrate powder enters the acid leaching and filtration device 1-2, where it undergoes acid leaching with concentrated sulfuric acid solution from sulfuric acid heat exchanger 1-1, sulfuric acid solution from the sulfuric acid solution main pipe, and low-temperature sulfur dioxide from sulfur dioxide heat exchanger 3-1 to obtain acid leaching solution and acid leaching residue. The acid leaching solution is preheated by acid leaching solution heat exchanger 1-3 and then enters the iron salt crystallization device 1-4 to obtain iron salt and dilute sulfuric acid solution. The iron salt passes through iron salt purification device 1-5 to obtain pure iron salt and purification residue. The pure iron salt and dilute ferrous sulfate solution pass through iron salt dissolution device 1-6 to obtain iron salt solution. The iron salt solution is heated by cathode liquid heat exchanger 2-3 and then sent to the cathode chamber of valence state control device 2-1. After crystallization, the dilute sulfuric acid solution is purified by purification device 3-3. Dilute sulfuric acid solution and purification residue; the purification liquid is sent to the anode chamber of valence state control device 2-1 after heat exchange in anolyte heat exchanger 2-4; the purification residue, acidolysis residue, purification residue and hydrogen are sent to high-temperature desulfurization device 3-2 to obtain high-temperature sulfur dioxide and cement clinker; the cement clinker is discharged for reuse; the high-temperature sulfur dioxide is mixed with sulfuric acid solution after heat exchange in sulfur dioxide heat exchanger 3-1 and sent to acidolysis filtration device 1-2; the sulfuric acid solution is only used during the first start-up; the solar furnace converts solar energy into heat energy to raise the temperature of the medium, and the high-temperature medium circulates to provide heat for the high-temperature desulfurization device; room temperature air is heated by sulfur dioxide heat exchanger 3-1, and the resulting high-temperature air is used to heat the cathode liquid, anolyte, concentrated sulfuric acid solution and acidolysis solution.

[0082] Ferrous salt solution is reduced at the cathode by valence state control device 2-1 to obtain ferrous sulfate solution; ferrous sulfate solution enters the cathode chamber of electrodeposition iron device 2-2; dilute sulfuric acid solution is anolyzed by valence state control device 2-1 to obtain oxygen and sulfuric acid; sulfuric acid solution enters the anode chamber of electrodeposition iron device 2-2; oxygen is discharged for treatment; ferrous sulfate solution is reduced at the cathode by electrodeposition iron device 2-2 to obtain pure iron, dilute sulfuric acid solution, and hydrogen as a byproduct; dilute ferrous sulfate solution is sent to iron salt dissolving device 1-6; pure iron is the final product; part of the hydrogen is passed into high-temperature desulfurization device 3-2, and the remaining hydrogen is used as a product; sulfuric acid solution is anolyzed by electrodeposition iron device 2-2 to obtain concentrated sulfuric acid solution and oxygen; concentrated sulfuric acid solution is heated by sulfuric acid heat exchange device 1-1 and then sent to acidolysis filtration process; oxygen is collected as a product.

[0083] Example 3

[0084] This embodiment uses the system and method of Examples 1-2, taking hematite concentrate from a certain enterprise as the treatment object, with an iron oxide grade of 90%. In the acid hydrolysis filtration device 1-2, the reaction temperature is 100℃ and the pressure is 0.1MPa. The sulfuric acid solution is used for the initial start-up of the system, with a concentration of 150g / L and an acid hydrolysis rate of 98%. The filtration equipment adopts plate and frame filter press. The high-temperature desulfurization device 3-2 adopts a fluidized bed reactor, with a reaction temperature of 1000℃ and a desulfurization rate of 99%. In the valence state control device 2-1, the diaphragm material is an ion exchange membrane, and the current density is 50A / m.2 The reaction temperature is 20℃; the anode is a lead alloy electrode, and the cathode is made of iron; in the iron electrodeposition apparatus 2-2, the diaphragm material is an ion-exchange membrane, and the current density is 100 A / m. 2 The reaction temperature is 60℃, the current efficiency is 95%, the cathode iron purity is 99%, and the DC power consumption per ton of iron is 3500kWh; the anode is a lead alloy electrode, and the cathode is made of iron; the solar furnace 3-4 converts solar energy into heat energy, and the solar heating medium is a mixed molten salt of sodium aluminosilicate and calcium aluminosilicate.

[0085] Example 4

[0086] This embodiment uses the system and method of Examples 1-2, taking magnetite concentrate from a certain enterprise as the processing object, with an iron oxide grade of 95%; in the acid hydrolysis filtration device 1-2, the reaction temperature is 200℃ and the pressure is 1.6MPa; the sulfuric acid solution is used for the initial start-up of the system, with a concentration of 160g / L and an acid hydrolysis rate of 99%; the filtration equipment adopts a belt filter; the high-temperature desulfurization device 3-2 adopts a rotary kiln reactor, with a reaction temperature of 1500℃ and a desulfurization rate of 99%; in the valence state control device 2-1, the diaphragm material is a porous membrane with a permeation rate of 1% and a current density of 1000A / m 2 The reaction temperature is 100℃; the anode is a lead alloy electrode, and the cathode is made of iron; in the iron electrodeposition apparatus 2-2, the diaphragm material is a porous membrane with a permeation rate of 1% and a current density of 2000 A / m³. 2 The reaction temperature is 100℃, the current efficiency is 95%, the cathode iron purity is 99%, and the DC power consumption per ton of iron is 3400kWh; the anode is a lead alloy electrode, and the cathode is made of iron; the anode is a lead alloy electrode, and the cathode is made of iron; the solar furnace 3-4 converts solar energy into thermal energy, and the solar heating medium is a mixture of nitrogen and argon gas.

[0087] Example 5

[0088] This embodiment uses the system and method of Examples 1-2, taking magnetite concentrate from a certain enterprise as the processing object, with an iron oxide grade of 95%; in the acid hydrolysis filtration device 1-2, the reaction temperature is 150℃; sulfuric acid solution is used for the initial start-up of the system, with a concentration of 160g / L and an acid hydrolysis rate of 99%; centrifugal filtration is used for filtration; the high-temperature desulfurization device 3-2 uses a rotary kiln reactor, with a reaction temperature of 1200℃ and a desulfurization rate of 99%; in the valence state control device 2-1, the diaphragm material is a porous membrane with a permeation rate of 40% and a current density of 500A / m³. 2 The reaction temperature is 60℃; the anode is a lead alloy electrode, and the cathode is made of iron; in the iron electrodeposition apparatus 2-2, the diaphragm material is a porous membrane with a permeation rate of 40% and a current density of 500 A / m³. 2The reaction temperature is 80℃, the current efficiency is 96%, the cathode iron purity is 99%, and the DC power consumption per ton of iron is 3400kWh; the anode is a lead alloy electrode, and the cathode is made of iron; the solar furnace 3-4 converts solar energy into thermal energy, and the solar heating medium is a mixture of nitrogen and argon gas.

[0089] The parts of this invention not described in detail are well-known in the field.

[0090] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the disclosure of the present invention, but these corresponding changes and modifications should all fall within the protection scope of the claims of the present invention.

Claims

1. A system for electroreduction of iron ore powder to produce iron, characterized in that, The system includes an acid hydrolysis purification process (1), an electrochemical ironmaking process (2), and an energy-saving and environmental protection process (3). The acid hydrolysis purification process (1) includes a sulfuric acid heat exchange device (1-1), an acid hydrolysis filtration device (1-2), an acid hydrolysis liquid heat exchange device (1-3), an iron salt crystallization device (1-4), an iron salt purification device (1-5), and an iron salt dissolution device (1-6). The electrochemical ironmaking process (2) includes a valence state control device (2-1), an iron electrodeposition device (2-2), a cathode liquid heat exchanger (2-3), and an anolyte heat exchanger (2-4). The energy-saving and environmentally friendly process (3) includes a sulfur dioxide heat exchanger (3-1), a high-temperature desulfurization device (3-2), a purification device (3-3), and a solar furnace (3-4). The inlet of the sulfuric acid heat exchanger (1-1) is connected to the anode outlet of the iron electrodeposition device (2-2), the outlet of the sulfuric acid heat exchanger (1-1) is connected to the inlet of the acid hydrolysis filter device (1-2), the air inlet of the sulfuric acid heat exchanger (1-1) is connected to the high-temperature air outlet of the sulfur dioxide heat exchanger (3-1), and the air outlet of the sulfuric acid heat exchanger (1-1) sends low-temperature air for venting. The iron concentrate inlet of the acidolysis filtration device (1-2) is connected to the outlet of the iron concentrate storage device; the liquid inlet of the acidolysis filtration device (1-2) is connected to the sulfuric acid solution main pipe; the pipe connecting the liquid inlet of the acidolysis filtration device (1-2) to the sulfuric acid solution main pipe is connected to the low-temperature sulfur dioxide outlet of the sulfur dioxide heat exchanger (3-1); the slag outlet of the acidolysis filtration device (1-2) is connected to the inlet of the high-temperature desulfurization device (3-2); the liquid outlet of the acidolysis filtration device (1-2) is connected to the inlet of the acidolysis liquid heat exchanger (1-3); the liquid outlet of the acidolysis liquid heat exchanger (1-3) is connected to the inlet of the iron salt crystallization device (1-4); the iron salt crystallization device (1-4)... The outlet of the iron salt crystallization device (1-4) is connected to the inlet of the purification device (3-3), and the outlet of the iron salt crystallization device (1-4) is connected to the inlet of the iron salt purification device (1-5). The tail slag outlet of the iron salt purification device (1-5) is connected to the inlet of the high-temperature desulfurization device (3-2), and the outlet of the iron salt purification device (1-5) is connected to the inlet of the iron salt dissolving device (1-6). The inlet of the iron salt dissolving device (1-6) is connected to the cathode outlet of the electrodeposition iron device (2-2), and the outlet of the iron salt dissolving device (1-6) is connected to the inlet of the cathode liquid heat exchanger (2-3). The outlet of the cathode liquid heat exchanger (2-3) is connected to the cathode inlet of the valence state control device (2-1). The air inlet of the acid hydrolysis heat exchange device (1-3) is connected to the high-temperature air outlet of the sulfur dioxide heat exchanger (3-1), and the air outlet of the acid hydrolysis heat exchange device (1-3) sends low-temperature air to be discharged. The anode inlet of the valence state control device (2-1) is connected to the outlet of the anolyte heat exchanger (2-4), and the inlet of the anolyte heat exchanger (2-4) is connected to the outlet of the purification device (3-3); the anode outlet of the valence state control device (2-1) is connected to the anode inlet of the electrodeposition iron device (2-2); the anode outlet of the valence state control device (2-1) is connected to the oxygen product pipeline; the cathode outlet of the valence state control device (2-1) is connected to the cathode inlet of the electrodeposition iron device (2-2); the cathode of the electrodeposition iron device (2-2)... The outlet is connected to the hydrogen inlet of the high-temperature desulfurization device (3-2); the cathode of the electrodeposition iron device (2-2) produces pure iron; the anode outlet of the electrodeposition iron device (2-2) is connected to the oxygen product pipeline; the anode of the valence state control device (2-1) is connected to the positive electrode of the green electricity via a conductive copper beam; the cathode of the valence state control device (2-1) is connected to the negative electrode of the green electricity via a conductive copper beam; the anode of the electrodeposition iron device (2-2) is connected to the positive electrode of the green electricity via a conductive copper beam; the cathode of the electrodeposition iron device (2-2) is connected to the negative electrode of the green electricity via a conductive copper beam. The inlet of the cathode liquid heat exchanger (2-3) is connected to the high-temperature air outlet of the sulfur dioxide heat exchanger (3-1), and the outlet of the cathode liquid heat exchanger (2-3) sends low-temperature air to be discharged. The air inlet of the anolyte heat exchanger (2-4) is connected to the high-temperature air outlet of the sulfur dioxide heat exchanger (3-1), and the air outlet of the anolyte heat exchanger (2-4) sends low-temperature air to be discharged. The air inlet of the sulfur dioxide heat exchanger (3-1) is connected to an air source, and the high-temperature sulfur dioxide inlet of the sulfur dioxide heat exchanger (3-1) is connected to the high-temperature outlet of the high-temperature desulfurization device (3-2); the high-temperature medium inlet of the high-temperature desulfurization device (3-2) is connected to the high-temperature medium outlet of the solar furnace (3-4), and the low-temperature medium outlet of the high-temperature desulfurization device (3-2) is connected to the low-temperature medium inlet of the solar furnace (3-4). The solid material outlet of the high-temperature desulfurization device (3-2) is connected to the cement clinker discharge pipe through a pipeline; the purification slag outlet of the purification device (3-3) is connected to the feed inlet of the high-temperature desulfurization device (3-2). The solar furnace (3-4) receives solar radiation through its light inlet.

2. A method for producing iron from iron ore powder by electroreduction based on the system described in claim 1, comprising the following steps: Iron concentrate powder enters the acid filtration device (1-2), where it is acidified with concentrated sulfuric acid solution from the sulfuric acid heat exchange device (1-1), sulfuric acid solution from the sulfuric acid solution main pipe, and low-temperature sulfur dioxide from the sulfur dioxide heat exchanger (3-1) to obtain acid lysis solution and acid lysis residue. The acid lysis solution is preheated by the acid lysis liquid heat exchange device (1-3) and then enters the iron salt crystallization device (1-4) to obtain iron salt and dilute sulfuric acid solution. The iron salt is purified by the iron salt purification device (1-5) to obtain pure iron salt and purification residue. The pure iron salt and dilute ferrous sulfate solution are dissolved by the iron salt dissolving device (1-6) to obtain iron salt solution. The iron salt solution is heated by the cathode liquid heat exchanger (2-3) and then sent to the cathode chamber of the valence state control device (2-1). After crystallization, the dilute sulfuric acid solution is purified by a purification device (3-3) to obtain purified dilute sulfuric acid solution and purification residue. The purified dilute sulfuric acid solution is then sent to the anode chamber of the valence state control device (2-1) after heat exchange in the anolyte heat exchanger (2-4). The purification residue, acidolysis residue, purification residue and hydrogen are then sent to the high-temperature desulfurization device (3-2) to obtain high-temperature sulfur dioxide and cement clinker. The cement clinker is discharged for reuse. The high-temperature sulfur dioxide is mixed with the sulfuric acid solution after heat exchange in the sulfur dioxide heat exchanger (3-1) and sent to the acidolysis filtration device (1-2). Sulfuric acid solution is only used during the initial startup; the solar furnace converts solar energy into heat energy to raise the temperature of the medium, and the high-temperature medium circulates to provide heat for the high-temperature desulfurization device (3-2); ambient temperature air is heated by the sulfur dioxide heat exchanger (3-1), and the resulting high-temperature air is used to heat the cathode liquid, anolyte, concentrated sulfuric acid solution, and acid hydrolysis solution; The iron salt solution is reduced at the cathode by the valence state control device (2-1) to obtain ferrous sulfate solution; the ferrous sulfate solution enters the cathode chamber of the iron electrodeposition device (2-2); the dilute sulfuric acid solution is anoly oxidized at the valence state control device (2-1) to obtain oxygen and sulfuric acid; the sulfuric acid solution enters the anode chamber of the iron electrodeposition device (2-2); the oxygen is discharged and sent for treatment; the ferrous sulfate solution is reduced at the cathode of the iron electrodeposition device (2-2) to obtain pure iron, dilute ferrous sulfate solution, and hydrogen gas as a byproduct; the dilute ferrous sulfate solution is sent to the iron salt dissolution device (1-6); Pure iron is the final product; part of the hydrogen is passed into the high-temperature desulfurization unit (3-2), and the remaining hydrogen is used as a product; the sulfuric acid solution is anoly oxidized by the electrodeposition iron unit (2-2) to obtain concentrated sulfuric acid solution and oxygen; the concentrated sulfuric acid solution is heated by the sulfuric acid heat exchange unit (1-1) and then sent to the acid hydrolysis filtration unit (1-2); the oxygen is collected as a product.

3. The method for producing iron from iron ore powder by electroreduction according to claim 2, characterized in that, The iron concentrate powder is hematite or magnetite, with an iron oxide grade of not less than 90%. The iron concentrate powder is directly leached with high-concentration concentrated sulfuric acid generated at the anode of the iron electrodeposition device (2-2).

4. The method for producing iron from iron ore powder by electroreduction according to claim 2, characterized in that, In the acid hydrolysis filtration device (1-2), the reaction temperature is 100℃-200℃, the pressure is 0.1 MPa-1.6 MPa, and the concentration of concentrated sulfuric acid solution is not less than 150 g / L.

5. The method for producing iron from iron ore powder by electroreduction according to claim 2, characterized in that, In the acid hydrolysis filtration device (1-2), the ferric ions generated during the acid hydrolysis process are reduced to ferrous ions under the chemical reduction of sulfur dioxide, thereby achieving reductive acid hydrolysis, improving the acid hydrolysis efficiency, and the acid hydrolysis rate is above 98%.

6. The method for producing iron from iron ore powder by electroreduction according to claim 2, characterized in that, In the acid hydrolysis filtration device (1-2), the filtration equipment adopts plate and frame filter press, belt filter or centrifugal filter.

7. The method for producing iron from iron ore powder by electroreduction according to claim 2, characterized in that, The high-temperature desulfurization device (3-2) adopts a fluidized bed or rotary kiln reactor, with a reaction temperature of 1000 ℃-1500 ℃ and a desulfurization rate of over 99%.

8. The method for producing iron from iron ore powder by electroreduction according to claim 2, characterized in that, In the valence state control device (2-1), the diaphragm material is an ion-exchange membrane or a porous membrane, wherein the permeation rate of the porous membrane is 1%-40% and the current density is 50 A / m. 2 - 1000 A / m 2 The anode is a lead alloy or titanium-based ruthenium-iridium-tantalum coated electrode, and the cathode is made of iron or titanium. The temperature range is 20 ℃-100℃. In the electrodeposition iron device (2-2), the diaphragm material is an ion-exchange membrane or a porous membrane, wherein the permeation rate of the porous membrane is 1%-40% and the current density is 100 A / m. 2 - 2000 A / m 2 The anode is a lead alloy or titanium-based ruthenium-iridium-tantalum coated electrode, and the cathode is made of iron, copper, titanium or stainless steel. The reaction temperature is 60 ℃-100 ℃, the current efficiency is above 95%, the purity of the cathode iron is above 99%, and the DC power consumption per ton of iron is less than 3500 kWh.

9. The method for producing iron from iron ore powder by electroreduction according to claim 2, characterized in that, The solar furnace (3-4) converts solar energy into thermal energy. The solar heating medium can be molten salt and / or gas. The molten salt is composed of one or more of the elements silicon, sodium, oxygen, calcium, and aluminum. The gas includes nitrogen and / or argon.

10. The method for producing iron from iron ore powder by electroreduction according to claim 2, characterized in that, The cathode liquid and anolyte in the electroreduction ironmaking process are circulated separately.

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