Microwave preheating mineral powder-molten salt electrolysis ironmaking co-production system and co-production method

Abstract

The invention provides a microwave preheating mineral powder-molten salt electrolysis ironmaking co-production system and a co-production method, and relates to the technical field of green low-carbon ironmaking systems and methods. The system comprises a feeding unit, a microwave preheating device, a molten salt electrolytic bath, a product treatment device and a gas circulation unit which are sequentially connected through a pipeline. The microwave preheating device is provided with a reducing gas inlet, preheated mineral powder is directly fed into a molten salt electrolytic bath, direct current is introduced into a molten salt medium for electrolysis, metal iron liquid is obtained at a cathode, and a gas product is separated out at an anode; and anode gas generated by electrolysis and tail gas generated by preheating are purified and separated by the gas circulating unit and then are recycled. According to the method, the high efficiency of microwave preheating and the greenness of molten salt electrolysis are combined, so that the energy consumption is obviously reduced, the method is green and low-carbon, the process is short, the production efficiency is high, the raw material adaptability is wide, high-value products are co-produced, and industrial large-scale production, popularization and application are facilitated.

Description

Technical Field

[0001] This invention relates to the technical field of green and low-carbon ironmaking systems and methods, and in particular to a microwave preheating ore powder-molten salt electrolytic ironmaking co-production system and method. Background Technology

[0002] The steel industry is a pillar industry of the national economy, but it is also a major energy consumer and carbon emitter. Currently, the mainstream blast furnace-converter long-process ironmaking technology heavily relies on coke, and the production process generates large amounts of CO2 and SO2. x NO x Pollutants such as these pose enormous environmental pressures.

[0003] To address these challenges, green metallurgy technology has become a research hotspot. Existing green metallurgy technologies include molten salt electrolysis and microwave heating.

[0004] Molten salt electrolysis is a promising emerging technology. Its principle involves using iron oxides as raw materials and passing a direct current through a molten salt medium to directly reduce them to metal. Theoretically, this method can avoid the use of carbonaceous reducing agents, and if an inert anode is used, the anode product is oxygen, potentially solving the CO2 emission problem at its source.

[0005] For example, the "Method for Extracting Metallic Iron from Zinc Kiln Slag" provided by Chinese Patent CN113802149A employs molten salt electrolysis technology, using zinc kiln slag and graphite rods as the cathode and anode, respectively, to electrolyze and recover metallic iron in a chloride salt system. While this method is simple to operate and causes minimal environmental pollution, its core drawbacks are: using solid waste slag directly as the cathode results in poor conductivity and low electrolysis efficiency; furthermore, the metallic iron product adheres to the cathode skeleton in solid form, making its separation and extraction steps cumbersome and difficult to implement in continuous production, thus limiting its industrial application prospects.

[0006] On the other hand, microwave heating technology, with its unique advantages such as bulk heating, selective heating, rapid heating rate, and high energy efficiency, has shown great potential in the field of material pretreatment. Recently, some studies have attempted to combine microwave heating with metallurgical processes.

[0007] For example, Chinese patent CN114410873A discloses a "pure hydrogen vertical shaft furnace ironmaking device based on microwave preheating of iron-containing furnace charge," the core of which lies in preheating lumpy or pelletized iron-containing furnace charge with microwaves to reduce the energy consumption of the subsequent hydrogen reduction process. This scheme cleverly utilizes the thermal effect of microwaves, but its overall process still falls under the category of gas-based solid-phase reduction, failing to break free from the framework of traditional vertical shaft furnaces. Furthermore, its product is solid direct reduced iron (DRI), which still requires subsequent electric furnace smelting to obtain liquid metal, meaning the process is not fundamentally shortened.

[0008] Chinese patent CN119194533A discloses a method for preparing metallic iron or iron alloys by microwave activation-molten salt electrolysis. Microwave activation is applied to mineral powder rods that have been pressed into shape. After activation, the rods are wrapped with stainless steel mesh and connected to a molybdenum rod as the cathode for molten salt electrolysis. The final product is metallic iron attached to the cathode. Obviously, microwave activation and molten salt electrolysis are applied to mineral powder rods. The pressed mineral powder rods are very likely to break or be damaged during the electrolysis process due to environmental influences, which will affect the quality stability and purity of the electrolyzed products.

[0009] In summary, existing technologies do not consider how to deeply integrate the advantages of microwave activation pretreatment and molten salt electrolytic reduction to create a new process route that can directly process powdered raw materials, is highly efficient and low-carbon, and can continuously produce metallic iron. This process route requires abandoning the principle of gas-based solid-phase reduction, which goes beyond the framework of traditional vertical shaft furnaces. Summary of the Invention

[0010] The main objective of this invention is to address the bottlenecks in existing technologies, such as poor cathode conductivity, high energy consumption, and difficulty in product separation when using molten salt electrolysis to process powdered raw materials. Furthermore, microwave preheating technology is primarily used in traditional vertical shaft furnace reduction processes and has not been effectively coupled with more advanced electrochemical reduction technologies. Therefore, this invention proposes a microwave preheating ore powder-molten salt electrolysis ironmaking co-production system and method that can solve the aforementioned problems.

[0011] A microwave preheating iron ore powder-molten salt electrolysis co-production system is disclosed, comprising: a feeding unit, a microwave preheating device, a molten salt electrolysis cell, a product processing device, and a gas circulation unit; wherein...

[0012] The outlet of the feeding unit is connected to the inlet of the microwave preheating device for feeding mineral powder into the microwave preheating device; the microwave preheating device is provided with a reducing gas inlet and a preheating exhaust gas outlet for preheating and pre-reducing the mineral powder in a reducing atmosphere; the outlet of the microwave preheating device is connected to the inlet of the molten salt electrolytic cell for feeding the preheated mineral powder into the molten salt electrolytic cell.

[0013] The molten salt electrolysis cell is equipped with an anode, a cathode, and a molten salt system. The anode and cathode are connected to an external DC power supply. The molten salt electrolysis cell has an iron outlet at the bottom and an anode gas outlet at the top.

[0014] The product processing device is connected to the iron outlet of the molten salt electrolytic cell and is used to further process the produced molten iron. The inlet of the gas circulation unit is connected to the preheating tail gas outlet and the anode gas outlet, respectively, and its outlet is connected to the reducing gas inlet, which is used to purify the tail gas, adjust its composition, and then recycle it.

[0015] Optionally, the feeding unit includes a ore bin for storing mineral powder and a screw feeder for quantitatively and uniformly conveying the mineral powder to the microwave preheating device, the screw feeder being disposed below the ore bin.

[0016] Optionally, the microwave preheating device is a microwave rotary kiln or a microwave fluidized bed reactor, and its internal working atmosphere is a reducing atmosphere composed of CO, H2 or a mixture thereof.

[0017] Optionally, the anode of the molten salt electrolytic cell is an inert metal oxide anode or a carbon material anode; the cathode is made of refractory metal or conductive ceramic material.

[0018] Optionally, the cathode may be made of a refractory metal such as molybdenum or tungsten.

[0019] Optionally, the molten salt system in the molten salt electrolysis cell is a CaCl2-based, NaCl-based, or CaCl2-NaCl mixed molten salt, and the operating temperature is 800-950℃.

[0020] Optionally, the gas circulation unit includes a dust removal device, a dehydration device, a CO2 separation / absorption device, and a gas mixing tank connected in sequence; the gas circulation unit is also provided with a branch for exporting the separated CO2-rich gas and performing carbon capture, utilization, or storage.

[0021] Optionally, the outer surfaces of the microwave preheating device, the molten salt electrolysis cell, and the connecting pipeline are all covered with thermal insulation material. The thickness of the thermal insulation material is 50-200mm, and the thermal insulation material is one or more composite structures selected from ceramic fiber, aluminum silicate cotton, or nanoporous thermal insulation material.

[0022] A co-production method using the microwave preheating ore powder-molten salt electrolytic ironmaking co-production system as described above, the ironmaking co-production method comprising the following steps:

[0023] S1. Microwave preheating and pre-reduction: Iron ore powder is fed into the microwave preheating device through the feeding unit, and reducing gas is introduced through the reducing gas inlet. Under the action of microwave, the ore powder is heated to rapidly remove crystal water, volatile matter and partially pre-reduction reaction, to obtain preheated and pre-reduced ore powder and preheated tail gas. The preheated tail gas is discharged from the preheated tail gas outlet.

[0024] S2, Molten Salt Electrolysis: The preheated and pre-reduced ore powder obtained in S1 is continuously added to the molten salt electrolysis cell. A DC voltage is applied to the molten salt system to carry out the electrolysis reaction. Molten iron is deposited at the cathode and gaseous products are deposited at the anode. The deposited molten iron is discharged from the iron outlet of the molten salt electrolysis cell.

[0025] S3. Product collection: Collect the molten iron discharged from the tapping port of the molten salt electrolysis cell in S2, and transport the collected molten iron to the product processing unit for ingot casting or refining.

[0026] S4. Gas Circulation: The preheated exhaust gas generated by S1 and the gas products from the anode of S2 are introduced into the gas circulation unit. After purification, CO2 separation and component adjustment, they are returned to the microwave preheating device of S1 as reducing gases for recycling.

[0027] Optionally, the reducing atmosphere in S1 is provided by mixing CO and H2 in a volume ratio of (0.5-2):1, and the pre-reduction degree of the mineral powder is controlled at 10-40%; the mineral powder is heated to 600-850°C under microwave action at a frequency of 900MHz to 3.0GHz for 10-30 minutes.

[0028] Optionally, the microwave frequency in S1 is 2.45 GHz ± 50 MHz.

[0029] Optionally, the DC cell voltage in S2 is 2.5-3.5V, and the current density is 0.5-2.0A / cm²; the temperature of the molten salt system is 800-950℃, and the electrolysis time is 30-120min; when a carbon anode is used, the anode gas is a CO / CO2 mixture; when an inert anode is used, the anode gas is high-purity oxygen.

[0030] The above technical solution has at least the following advantages compared with the existing technology:

[0031] The above-mentioned solution proposes a microwave preheating ore powder-molten salt electrolysis ironmaking co-production system and method, which can solve the bottlenecks in the existing technology when processing powdered raw materials by the single molten salt electrolysis method, such as poor cathode conductivity, high energy consumption and difficult product separation; and the technical problems that the single microwave preheating technology is mostly used to serve the traditional vertical furnace reduction process and has failed to form an effective coupling with the more advanced electrochemical reduction technology.

[0032] This invention utilizes microwaves for bulk heating of mineral powder, resulting in extremely high efficiency. The preheated hot mineral powder is directly fed into the electrolytic cell, significantly reducing the heating load on the cell and lowering the overall system energy consumption by more than 20% compared to direct cold mineral powder electrolysis.

[0033] This invention employs molten salt electrolysis technology. If an inert anode is used, the main product is oxygen, thus avoiding CO2 emissions at the source. If a carbon anode is used, the anode gas is CO / CO2, the concentration and composition of which are controllable and easy to collect, utilize or store. Compared with the blast furnace process, carbon emissions are reduced by more than 50%.

[0034] This invention tightly couples the preheating and electrolysis unit operations, eliminating the long processes of sintering and coking in traditional processes and simplifying the process.

[0035] The microwave pretreatment of this invention can effectively remove crystal water and harmful impurities from ores, improve the stability of subsequent electrolysis and the purity of iron products, and can process low-grade and complex ores.

[0036] The oxygen or syngas (CO) generated at the anode of this invention can be used as a high-value byproduct, improving the economics of the entire process.

[0037] In summary, compared with traditional ironmaking methods, the present invention creatively processes powdered raw materials directly through a feeding unit, microwave preheating device, molten salt electrolytic cell, product processing device, and gas circulation unit connected in sequence by pipelines. This method is highly efficient, low-carbon, and can continuously produce metallic iron. It significantly reduces energy consumption, is green and low-carbon, has a short process, high production efficiency, wide raw material adaptability, and can co-produce high-value products, which is conducive to large-scale industrial production and widespread application. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 This is a schematic diagram of the structure of a microwave preheating ore powder-molten salt electrolytic ironmaking co-production system according to the present invention; wherein: mark 1 is the feed pipe, mark 2 is the screw conveyor, mark 3 is the microwave preheating device, mark 4 is the reducing gas inlet, mark 5 is the first gas outlet, mark 6 is the anode, mark 7 is the heating device, mark 8 is the molten salt system, mark 9 is the cathode, mark 10 is the DC power supply, mark 11 is the protective gas inlet, mark 12 is the molten iron, and mark 13 is the second gas outlet. Detailed Implementation

[0040] The technical solution of the present invention will now be described with reference to the accompanying drawings.

[0041] In embodiments of the present invention, words such as "exemplarily," "for example," etc., are used to indicate that something is an example, illustration, or description. Any embodiment or design described as "exemplary" in the present invention should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of the word "exemplary" is intended to present the concept in a concrete manner. Furthermore, in embodiments of the present invention, the meaning expressed by "and / or" can be both, or either one.

[0042] In the embodiments of the present invention, the terms "image" and "picture" may sometimes be used interchangeably. It should be noted that when the distinction is not emphasized, their intended meanings are consistent.

[0043] In this embodiment of the invention, sometimes a subscript such as W1 may be written in a non-subscript form such as W1. When the difference is not emphasized, the meaning they express is the same.

[0044] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with the accompanying drawings and specific embodiments.

[0045] A microwave preheating iron ore powder-molten salt electrolysis co-production system is disclosed, comprising: a feeding unit, a microwave preheating device, a molten salt electrolysis cell, a product processing device, and a gas circulation unit; wherein...

[0046] The outlet of the feeding unit is connected to the inlet of the microwave preheating device for feeding mineral powder into the microwave preheating device; the microwave preheating device is provided with a reducing gas inlet and a preheating exhaust gas outlet for preheating and pre-reducing the mineral powder in a reducing atmosphere; the outlet of the microwave preheating device is connected to the inlet of the molten salt electrolytic cell for feeding the preheated mineral powder into the molten salt electrolytic cell.

[0047] The molten salt electrolysis cell is equipped with an anode, a cathode, and a molten salt system. The anode and cathode are connected to an external DC power supply. The molten salt electrolysis cell has an iron outlet at the bottom and an anode gas outlet at the top.

[0048] The product processing device is connected to the iron outlet of the molten salt electrolytic cell and is used to further process the produced molten iron. The inlet of the gas circulation unit is connected to the preheating tail gas outlet and the anode gas outlet, respectively, and its outlet is connected to the reducing gas inlet, which is used to purify the tail gas, adjust its composition, and then recycle it.

[0049] Specifically, the feeding unit includes a ore bin for storing mineral powder and a screw feeder for quantitatively and uniformly conveying the mineral powder to the microwave preheating device, the screw feeder being disposed below the ore bin.

[0050] Specifically, the microwave preheating device is a microwave rotary kiln or a microwave fluidized bed reactor, and its internal working atmosphere is a reducing atmosphere composed of CO, H2 or a mixture thereof.

[0051] Specifically, the anode of the molten salt electrolytic cell is an inert metal oxide anode or a carbon material anode; the cathode is made of refractory metal or conductive ceramic material.

[0052] Specifically, the cathode is made of refractory metals such as molybdenum and tungsten.

[0053] Specifically, the molten salt system in the molten salt electrolysis cell is a CaCl2-based, NaCl-based, or CaCl2-NaCl mixed molten salt, and the operating temperature is 800-950℃.

[0054] Specifically, the gas circulation unit includes a dust removal device, a dehydration device, a CO2 separation / absorption device, and a gas mixing tank connected in sequence; the gas circulation unit is also provided with a branch for exporting the separated CO2-rich gas and for carbon capture, utilization, or storage.

[0055] Specifically, the outer surfaces of the microwave preheating device, the molten salt electrolysis cell, and the connecting pipes are all covered with thermal insulation material, the thickness of which is 50-200mm, and the thermal insulation material is one or more composite structures selected from ceramic fiber, aluminum silicate cotton, or nanoporous thermal insulation material.

[0056] A co-production method using the microwave preheating ore powder-molten salt electrolytic ironmaking co-production system as described above, the ironmaking co-production method comprising the following steps:

[0057] S1. Microwave preheating and pre-reduction: Iron ore powder is fed into the microwave preheating device through the feeding unit, and reducing gas is introduced through the reducing gas inlet. Under the action of microwave, the ore powder is heated to rapidly remove crystal water, volatile matter and partially pre-reduction reaction, to obtain preheated and pre-reduced ore powder and preheated tail gas. The preheated tail gas is discharged from the preheated tail gas outlet.

[0058] S2, Molten Salt Electrolysis: The preheated and pre-reduced ore powder obtained in S1 is continuously added to the molten salt electrolysis cell. A DC voltage is applied to the molten salt system to carry out the electrolysis reaction. Molten iron is deposited at the cathode and gaseous products are deposited at the anode. The deposited molten iron is discharged from the iron outlet of the molten salt electrolysis cell.

[0059] S3. Product collection: Collect the molten iron discharged from the tapping port of the molten salt electrolysis cell in S2, and transport the collected molten iron to the product processing unit for ingot casting or refining.

[0060] S4. Gas Circulation: The preheated exhaust gas generated by S1 and the gas products from the anode of S2 are introduced into the gas circulation unit. After purification, CO2 separation and component adjustment, they are returned to the microwave preheating device of S1 as reducing gases for recycling.

[0061] Specifically, the reducing atmosphere in S1 is provided by mixing CO and H2 in a volume ratio of (0.5-2):1, and the pre-reduction degree of the mineral powder is controlled at 10-40%; the mineral powder is heated to 600-850°C under microwave action at a frequency of 900MHz to 3.0GHz for 10-30 minutes.

[0062] Specifically, the microwave frequency in S1 is 2.45 GHz ± 50 MHz.

[0063] Specifically, the DC cell voltage in S2 is 2.5-3.5V, and the current density is 0.5-2.0A / cm²; the temperature of the molten salt system is 800-950℃, and the electrolysis time is 30-120min; when a carbon anode is used, the anode gas is a CO / CO2 mixture; when an inert anode is used, the anode gas is high-purity oxygen.

[0064] Example 1

[0065] A co-production method using the microwave preheated ore powder-molten salt electrolytic ironmaking co-production system as described above, employing hematite powder (TFe 68%) with a particle size of less than 100 mesh, is shown in the schematic diagram below. Figure 1 As shown.

[0066] The iron smelting co-production method includes the following steps:

[0067] S1. Microwave Preheating and Pre-reduction: Hematite powder is continuously and stably fed into the microwave preheating device 3 through the feed pipe 1 and screw conveyor 2; at the same time, a reducing gas composed of CO and H2 in a volume ratio of 1:1 is introduced into the device through the reducing gas inlet 4; the microwave power is adjusted so that the powder is rapidly heated to 750°C within 10-15 minutes; during this process, the hematite powder undergoes a partial reduction reaction (Fe2O3→Fe3O4→FeO), and the pre-reduction degree reaches about 30%, resulting in preheated and pre-reduced powder; at the same time, the water of crystallization is completely removed, and the tail gas after the reaction is discharged from the first outlet 5.

[0068] S2, Molten Salt Electrolysis: The preheated and pre-reduced mineral powder obtained in S1 is directly fed into a molten salt electrolysis cell maintained at the working temperature (900℃) through a sealed, insulated pipe. The molten salt system 8 in the electrolysis cell is CaCl2, the anode 6 is a SnO2-based inert anode, and the cathode 9 is molybdenum metal. A DC voltage of 3.0V is applied through a DC power supply 10, and the current density is controlled at 1.0 A / cm² for electrolysis. At the cathode 9, iron ions are reduced to molten iron 12, which collects at the bottom of the cell and is discharged from the iron outlet of the molten salt electrolysis cell. At the anode 6, high-purity oxygen is released and discharged from the second gas outlet 13.

[0069] S3. Product collection: The molten iron 12 that is periodically discharged from the tapping port of the molten salt electrolysis cell is sent to the continuous casting machine to be cast into iron ingots.

[0070] S4, Gas Circulation: The preheated tail gas generated from the first outlet 5 by S1 and the anode evolution gas product discharged from the second outlet 13 by S2 are introduced into the gas circulation unit. After dust removal, dehydration, amine washing to remove CO2 and component adjustment, they are returned to the microwave preheating device 3 as reducing gas for recycling. The separated high-purity CO2 can be sealed or used to produce chemical products.

[0071] Example 2

[0072] A co-production method using the microwave preheated ore powder-molten salt electrolytic ironmaking co-production system as described above, employing hematite powder (TFe 68%) with a particle size of less than 100 mesh, is shown in the schematic diagram below. Figure 1 As shown.

[0073] The iron smelting co-production method includes the following steps:

[0074] S1. Microwave Preheating and Pre-reduction: Hematite powder is continuously and stably fed into the microwave preheating device 3 through the feed pipe 1 and screw conveyor 2; at the same time, a reducing gas composed of CO and H2 in a volume ratio of 1:1 is introduced into the device through the reducing gas inlet 4; the microwave power is adjusted so that the powder is rapidly heated to 750°C within 10-15 minutes; during this process, the hematite powder undergoes a partial reduction reaction (Fe2O3→Fe3O4→FeO), and the pre-reduction degree reaches about 30%, resulting in preheated and pre-reduced powder; at the same time, the water of crystallization is completely removed, and the tail gas after the reaction is discharged from the first outlet 5.

[0075] S2, Molten Salt Electrolysis: The preheated and pre-reduced mineral powder obtained in S1 is directly fed into a molten salt electrolysis cell maintained at the working temperature (900℃) through a sealed and insulated pipe. The molten salt system 8 in the electrolysis cell is CaCl2, the anode 6 uses a high-density graphite electrode, and the cathode 9 uses molybdenum metal. A DC voltage of 3.0V is applied through a DC power supply 10, and the current density is controlled at 1.0 A / cm² for electrolysis. At the cathode 9, iron ions are reduced to molten iron 12, which collects at the bottom of the cell and is discharged from the iron outlet of the molten salt electrolysis cell. At the anode 6, the anode reaction is the oxidation of carbon, generating a CO / CO2 mixed gas (volume ratio approximately 2:1) which is discharged from the second gas outlet 13.

[0076] This mixed gas is a high-quality chemical synthesis gas that can be collected for methanol synthesis or used as fuel. Although the use of carbon anodes will produce CO2, its high concentration and concentrated emission make it easy to separate and store through the CO2 capture device in the gas circulation unit. Compared with the decentralized emissions of blast furnaces, it still has significant advantages in carbon emission reduction and resource utilization.

[0077] S3. Product collection: The molten iron 12 that is periodically discharged from the tapping port of the molten salt electrolysis cell is sent to the continuous casting machine to be cast into iron ingots.

[0078] S4. Gas Circulation: The preheated exhaust gas generated from the first outlet 5 and the CO / CO2 mixed gas (volume ratio of about 2:1) discharged from the second outlet 13 by S2 are introduced into the gas circulation unit. After dust removal, dehydration, amine washing to remove CO2 and component adjustment, they are returned to the microwave preheating device 3 as reducing gas for recycling. The separated high-purity CO2 can be sealed or used to produce chemical products.

[0079] Example 3

[0080] Magnetite powder with a particle size of less than 200 mesh (TFe 62%) was used. The volume ratio of CO to H2 in the reducing gas was 2:1. Microwave heating was carried out at 700℃ for 15 minutes, and the pre-reduction degree was controlled at 20%. Molten salt electrolysis was performed using a mixed molten salt of CaCl2-NaCl (mass ratio 7:3), with an operating temperature of 850℃, a cell voltage of 2.8V, and a current density of 0.8A / cm².

[0081] Example 4

[0082] Limonite powder with a particle size of less than 150 mesh (TFe 55%, moisture content 12%) was used. Pure H2 was used as the reducing gas. Microwave heating to 600℃ and holding for 25 minutes was used to completely remove the water of crystallization. Molten salt electrolysis was performed using NaCl-based molten salt at an operating temperature of 820℃, a cell voltage of 3.2V, and a current density of 1.2A / cm².

[0083] Example 5

[0084] Titanium magnetite powder with a particle size of less than 100 mesh is used. The reducing gas has a CO to H2 volume ratio of 0.5:1, and is microwave-heated to 800℃ and held for 20 minutes. Molten salt electrolysis uses CaCl2-based molten salt, operates at 920℃, has a cell voltage of 3.5V, a current density of 1.5A / cm², and uses conductive ceramic material for the cathode.

[0085] The above-mentioned solution proposes a microwave preheating ore powder-molten salt electrolysis ironmaking co-production system and method, which can solve the bottlenecks in the existing technology when processing powdered raw materials by the single molten salt electrolysis method, such as poor cathode conductivity, high energy consumption and difficult product separation; and the technical problems that the single microwave preheating technology is mostly used to serve the traditional vertical furnace reduction process and has failed to form an effective coupling with the more advanced electrochemical reduction technology.

[0086] This invention utilizes microwaves for bulk heating of mineral powder, resulting in extremely high efficiency. The preheated hot mineral powder is directly fed into the electrolytic cell, significantly reducing the heating load on the cell and lowering the overall system energy consumption by more than 20% compared to direct cold mineral powder electrolysis.

[0087] This invention employs molten salt electrolysis technology. If an inert anode is used, the main product is oxygen, thus avoiding CO2 emissions at the source. If a carbon anode is used, the anode gas is CO / CO2, the concentration and composition of which are controllable and easy to collect, utilize or store. Compared with the blast furnace process, carbon emissions are reduced by more than 50%.

[0088] This invention tightly couples the preheating and electrolysis unit operations, eliminating the long processes of sintering and coking in traditional processes and simplifying the process.

[0089] The microwave pretreatment of this invention can effectively remove crystal water and harmful impurities from ores, improve the stability of subsequent electrolysis and the purity of iron products, and can process low-grade and complex ores.

[0090] The oxygen or syngas (CO) generated at the anode of this invention can be used as a high-value byproduct, improving the economics of the entire process.

[0091] In summary, compared with traditional ironmaking methods, the present invention creatively processes powdered raw materials directly through a feeding unit, microwave preheating device, molten salt electrolytic cell, product processing device, and gas circulation unit connected in sequence by pipelines. This method is highly efficient, low-carbon, and can continuously produce metallic iron. It significantly reduces energy consumption, is green and low-carbon, has a short process, high production efficiency, wide raw material adaptability, and can co-produce high-value products, which is conducive to large-scale industrial production and widespread application.

[0092] It should be understood that the term "and / or" in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. Additionally, the character " / " in this article generally indicates an "or" relationship between the preceding and following related objects, but it can also represent an "and / or" relationship. Please refer to the context for a more accurate understanding.

[0093] In this invention, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of a single item or a plurality of items. For example, at least one of a, b, or c can represent: a, b, c, ab, ac, bc, or abc, where a, b, and c can be a single item or multiple items.

[0094] It should be understood that, in various embodiments of the present invention, the order of the above-mentioned process numbers does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0095] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A microwave preheating ore powder-molten salt electrolytic ironmaking co-production system, characterized in that, The microwave preheating ore powder-molten salt electrolysis ironmaking co-production system includes: a feeding unit, a microwave preheating device, a molten salt electrolysis cell, a product processing device, and a gas circulation unit; wherein... The outlet of the feeding unit is connected to the inlet of the microwave preheating device. The microwave preheating device is provided with a reducing gas inlet and a preheating exhaust gas outlet. The outlet of the microwave preheating device is connected to the inlet of the molten salt electrolytic cell. The molten salt electrolysis cell is equipped with an anode, a cathode, and a molten salt system. The anode and cathode are connected to an external DC power supply. The molten salt electrolysis cell has an iron outlet at the bottom and an anode gas outlet at the top. The product processing device is connected to the iron outlet of the molten salt electrolysis cell, the inlet of the gas circulation unit is connected to the preheating tail gas outlet and the anode gas outlet respectively, and its outlet is connected to the reducing gas inlet.

2. The microwave preheating ore powder-molten salt electrolytic ironmaking co-production system according to claim 1, characterized in that, The feeding unit includes a ore bin for storing mineral powder and a screw feeder for quantitatively and uniformly conveying the mineral powder to the microwave preheating device. The screw feeder is located below the ore bin.

3. The microwave preheating ore powder-molten salt electrolytic ironmaking co-production system according to claim 1, characterized in that, The microwave preheating device is a microwave rotary kiln or a microwave fluidized bed reactor, and its internal working atmosphere is a reducing atmosphere composed of CO, H2 or a mixture thereof.

4. The microwave preheating ore powder-molten salt electrolytic ironmaking co-production system according to claim 1, characterized in that, The anode of the molten salt electrolytic cell is an inert metal oxide anode or a carbon material anode; the cathode is made of refractory metal or conductive ceramic material.

5. The microwave preheating ore powder-molten salt electrolytic ironmaking co-production system according to claim 1, characterized in that, The molten salt system in the molten salt electrolysis cell is a CaCl2-based, NaCl-based, or CaCl2-NaCl mixed molten salt, and the operating temperature is 800-950℃.

6. The microwave preheating ore powder-molten salt electrolytic ironmaking co-production system according to claim 1, characterized in that, The gas circulation unit includes a dust removal device, a dehydration device, a CO2 separation / absorption device, and a gas mixing tank connected in sequence; the gas circulation unit is also provided with a branch for exporting the separated CO2-rich gas and performing carbon capture, utilization, or storage.

7. The microwave preheating ore powder-molten salt electrolytic ironmaking co-production system according to claim 1, characterized in that, The outer surfaces of the microwave preheating device, molten salt electrolysis cell, and connecting pipelines are all covered with thermal insulation material.

8. A co-production method using the microwave preheating ore powder-molten salt electrolytic ironmaking co-production system as described in any one of claims 1-7, characterized in that, The iron smelting co-production method includes the following steps: S1. Microwave preheating and pre-reduction: Iron ore powder is fed into the microwave preheating device through the feeding unit, and reducing gas is introduced through the reducing gas inlet. Under the action of microwave, the ore powder is heated to rapidly remove crystal water, volatile matter and partially pre-reduction reaction, to obtain preheated and pre-reduced ore powder and preheated tail gas. The preheated tail gas is discharged from the preheated tail gas outlet. S2, Molten Salt Electrolysis: The preheated and pre-reduced ore powder obtained in S1 is continuously added to the molten salt electrolysis cell. A DC voltage is applied to the molten salt system to carry out the electrolysis reaction. Molten iron is deposited at the cathode and gaseous products are deposited at the anode. The deposited molten iron is discharged from the iron outlet of the molten salt electrolysis cell. S3. Product collection: Collect the molten iron discharged from the tapping port of the molten salt electrolysis cell in S2, and transport the collected molten iron to the product processing unit for ingot casting or refining. S4. Gas Circulation: The preheated exhaust gas generated by S1 and the gas products from the anode of S2 are introduced into the gas circulation unit. After purification, CO2 separation and component adjustment, they are returned to the microwave preheating device of S1 as reducing gases for recycling.

9. The co-production method according to claim 8, characterized in that, The reducing atmosphere described in S1 is provided by mixing CO and H2 in a volume ratio of (0.5-2):1, and the pre-reduction degree of the mineral powder is controlled at 10-40%. The mineral powder is heated to 600-850℃ under the action of microwaves with a frequency of 900MHz to 3.0GHz for 10-30min.

10. The co-production method according to claim 8, characterized in that, The DC cell voltage described in S2 is 2.5-3.5V, and the current density is 0.5-2.0A / cm²; the temperature of the molten salt system is 800-950℃, and the electrolysis time is 30-120min; when a carbon anode is used, the anode gas is a CO / CO2 mixture; when an inert anode is used, the anode gas is high-purity oxygen.

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