Method for preparing metallic iron or iron alloy through microwave activation-molten salt electrolysis

Abstract

The invention discloses a method for preparing metallic iron or iron alloy through microwave activation-molten salt electrolysis, which comprises the following steps: (1) carrying out compression molding on iron ore powder or alloy ore powder to obtain an ore powder rod; (2) the mineral powder rod is placed in microwaves for irradiation activation; (3) wrapping the irradiated and activated mineral powder rod with a stainless steel mesh, and performing a molten salt electrolysis reaction in a molten salt electrolyte system with a protective atmosphere as a cathode; and (4) after the electrolytic reaction is finished, cooling the electrolytic system to obtain the metallic iron or the iron alloy. According to the method, through microwave pre-radiation activation, the raw mineral materials generate a series of microwave effects such as electric, thermal, magnetic and chemical effects, the reaction activity of subsequent molten salt electrolysis of the raw mineral materials is improved, and energy needed by molten salt electrolysis is reduced through the generated thermal effect; the method has the advantages of simple process, small environmental pollution, low energy consumption and the like, and solves the problems of long process flow, high cost and the like of the existing metal iron and iron alloy material preparation.

Description

Technical Field

[0001] The invention relates to the technical field of metallurgy, in particular to a method for preparing metallic iron or iron alloy by microwave activation-molten salt electrolysis. Background Art

[0002] Iron is one of the most important elements in human life and is a key raw material for the preparation of advanced steel materials. With the development of science and technology, human demand for iron materials is increasing. At present, the main iron extraction technologies are traditional blast furnace method, direct reduction method and smelting reduction method. The traditional blast furnace ironmaking process has the disadvantages of high energy consumption and serious environmental pollution; hydrogen metallurgical ironmaking (direct reduction method) has high requirements for iron ore grade and high cost; the energy consumption, investment and operation stability of smelting reduction ironmaking cannot be compared with traditional blast furnaces.

[0003] Ferroalloy is one of the essential raw materials for the steel industry and machine casting industry. It is mainly used as a deoxidizer to eliminate excess oxygen in molten steel and alloy element additives to improve the quality and performance of steel. There are many ways to produce ferroalloys, most of which are produced by pyrometallurgy, including blast furnace, electric furnace, converter and vacuum resistance furnace. There are generally problems such as high energy consumption and cost, and serious environmental pollution. The process of extracting metallic iron or ferroalloys by molten salt electrolysis is simple, with little environmental pollution, and can effectively reduce the preparation cost of iron materials.

[0004] The patent application with publication number CN113802149A provides a method for extracting metallic iron from zinc kiln slag. The method uses zinc kiln slag and graphite rods as cathode and anode respectively, and carries out electrolytic reaction in a sodium chloride and potassium chloride molten salt system to obtain metallic iron. The method is simple to operate, has a high metallic iron recovery rate, and has low environmental pollution. However, the zinc kiln slag as a cathode has poor conductivity, and the solid metallic iron product is difficult to separate. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a method for preparing metallic iron or iron alloy by microwave activation-molten salt electrolysis.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention comprises the following steps: (1) pressing iron ore powder or alloy ore powder into a shape to obtain an ore powder rod; (2) The mineral powder rod is placed in a microwave for irradiation activation; (3) Wrapping the irradiated activated mineral powder rod with a stainless steel mesh and using it as the cathode to carry out molten salt electrolysis in a molten salt electrolyte system with a protective atmosphere; (4) After the electrolysis reaction is completed, the electrolysis system is cooled to obtain metallic iron or iron alloy.

[0007] Furthermore, in the step (2), the microwave frequency for irradiation activation is 2430-2465 MHz, and the irradiation time is 0.5-2 h.

[0008] Furthermore, the components of the molten salt electrolyte system in step (3) are sodium chloride, potassium chloride and / or calcium chloride.

[0009] Furthermore, in step (3), the temperature of the molten salt during molten salt electrolysis is 700-950°C.

[0010] Furthermore, the electrolysis time of the molten salt electrolysis is 2 to 10 hours, and the voltage is 2 to 3.2V.

[0011] The beneficial effects of adopting the above technical solution are: (1) The present invention prepares metallic iron or ferroalloy by molten salt electroreduction. Compared with the traditional pelletizing-blast furnace ironmaking process, the process is simpler and the electrolysis temperature is lower than the 1250-1300°C of the traditional process, which reduces energy consumption and has less environmental pollution.

[0012] (2) The present invention activates the pressed mineral powder rods by penetrating microwave pre-radiation, so that the mineral raw materials produce a series of microwave effects such as electrical, thermal, magnetic and chemical effects, thereby increasing the reaction activity of subsequent molten salt electrolysis of the mineral raw materials and generating thermal effects that reduce the energy required for molten salt electrolysis.

[0013] (3) The electrolyte used in the present invention is a chloride salt system, which has the advantages of low reaction temperature, low reagent cost and low requirements for electrolysis equipment compared to oxide systems (CaO, MgO, SiO2, etc.).

[0014] (4) The present invention reduces iron ore powder and other minerals to obtain metallic iron or ferroalloys through microwave activation-molten salt electroreduction, which has the advantages of simple process, low environmental pollution, and low energy consumption, and solves the current problems of long process flow and high cost for the preparation of metallic iron and ferroalloy materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0016] Figure 1 It is a schematic diagram of the structure of preparing metallic iron according to the present invention; Figure 2 It is a schematic structural diagram of the method for preparing ferroalloy according to the present invention. DETAILED DESCRIPTION

[0017] Figure 1 , 2As shown, the method for preparing metallic iron or ferroalloy by microwave activation-molten salt electrolysis adopts the following steps: (1) when preparing metallic iron, iron ore powder is used as raw material; when preparing ferroalloy, alloy ore powder is used as raw material, and the alloy ore powder includes iron ore powder and other component ore powders, such as other component ore powders are carbon powder, titanium oxide powder or titanium powder, or chromium oxide powder; the iron content in the iron ore powder is ≥60wt%, and the particle size of the iron ore powder or alloy ore powder is ≤150μm; in the alloy ore powder, the mixing ratio of iron ore powder to other component ore powder is 1:0.2~1.5.

[0018] Iron ore powder or alloy ore powder is dried at high temperature, mixed evenly and then pressed into shape to obtain a ore powder rod; the ore powder rod is preferably cylindrical, with a length of 2 to 6 cm and a diameter of 1 to 3 cm; the drying temperature of the high temperature drying is 200 to 400°C, and the drying time is 6 to 20 hours; during the pressing process, a certain binder is added, the pressing pressure is 5 to 10 MPa, the pressing temperature is 200 to 800°C, and the pressing time is 0.5 to 2 minutes.

[0019] (2) The mineral powder rod is placed in a microwave for irradiation activation; the microwave frequency of the irradiation activation is 2430-2465 MHz, and the irradiation time is 0.5-2 hours.

[0020] (3) Wrapping the irradiated activated mineral powder rod with a stainless steel mesh and then connecting it to a molybdenum rod, the wrapped mineral powder rod is used as a cathode and the inert electrode is used as an anode, and the cathode and anode are respectively inserted into a molten salt electrolyte system with a protective atmosphere for molten salt electrolysis reaction; the inert electrode is a graphite rod, a nickel alloy rod or a tin dioxide rod; the protective gas used in the protective atmosphere is argon, nitrogen or helium; the components of the molten salt electrolyte system are sodium chloride, potassium chloride and / or calcium chloride; the molten salt temperature during the molten salt electrolysis is 700-950°C, the electrolysis time is 2-10 hours, and the voltage is 2-3.2V; The overall reaction of molten salt electrolysis is: when the inert electrode is a graphite rod, C+Fe2O3 / Fe2O3+C / Fe2O3+TiO2 / Fe2O3+CrO2→Fe / FeC / FeTi / FeCr+CO2; when the inert electrode is a nickel alloy rod or a tin dioxide rod, Fe2O3 / Fe2O3+C / Fe2O3+TiO2 / Fe2O3+CrO2→Fe / FeC / FeTi / FeCr+O2.

[0021] (4) After the electrolysis reaction is completed, the inert electrode is removed, and the electrolysis system is cooled, cleaned, and dried to obtain metallic iron or iron alloy; the electrolysis system is cooled to 15 to 35° C.; the cleaning process is firstly cleaned with distilled water, and then the water is poured out and then placed in distilled water for ultrasonic cleaning; the drying process is carried out at a drying temperature of 100 to 180° C. and a drying time of 1 to 2 hours.

[0022] (5) The above method is used to obtain metallic iron with an iron purity of ≥97% and a current efficiency of ≥95%. The obtained iron alloy is a carbon-iron alloy, a titanium-iron alloy or a chromium-iron alloy, with an iron alloy purity of ≥96% and a current efficiency of ≥94%.

[0023] Example 1: The method for preparing metallic iron or iron alloy by microwave activation-molten salt electrolysis is described as follows.

[0024] The iron ore used comes from Peru, and its main components and their mass percentages are FeO: 28.99%, Al2O3: 0.29%, V2O3: 0.09%, SiO2: 1.42%, CaO: 0.55%, MgO: 0.94%, TiO2: 0.29%, and TFe: 69.20%.

[0025] (1) Dry the iron ore powder with a particle size of 74 μm and accounting for 78% at 200°C for 10 h, and then press it into a powder rod; the pressing process pressure is 5 MPa, the pressing temperature is 800°C, and the shape after pressing is cylindrical, with a length of 2 cm and a diameter of 1 cm; (2) placing the mineral powder rod in a microwave for irradiation activation; the microwave frequency is 2430 MHz and the irradiation time is 2 h; (3) Wrap the microwave-activated mineral powder rod with a stainless steel mesh, connect a molybdenum rod as the cathode and a graphite rod as the anode, and insert the cathode and anode into a molten sodium chloride-potassium chloride electrolyte system in an argon atmosphere for molten salt electrolysis for 2 hours. The molten salt temperature is 700 °C and the voltage is 2.5 V. (4) After the electrolysis reaction is completed, the electrolysis system is cooled to 15°C, the cathode is washed with distilled water and ultrasonic waves in turn, and then dried at 100°C for 2 hours to obtain metallic iron.

[0026] The purity of the iron in the metallic iron obtained in this embodiment is 97%, and the current efficiency is 95%. A comparative test was conducted using the same mineral without microwave irradiation, and the purity of the iron was 90%, and the current efficiency was 88%.

[0027] Example 2: The method for preparing metallic iron or iron alloy by microwave activation-molten salt electrolysis is described as follows.

[0028] (1) Iron ore powder and carbon powder with a particle size of 74 μm and accounting for 75% were dried at 400°C for 6 h, and then the iron ore powder and carbon powder were uniformly mixed in a mass ratio of 1:0.2 and pressed into shape; the pressing process pressure was 10 MPa, the pressing temperature was 200°C, and the cylindrical ore powder rod after pressing had a length of 4 cm and a diameter of 2 cm; (2) placing the mineral powder rod in a microwave for irradiation; wherein the microwave frequency is 2465 MHz and the irradiation time is 0.5 h; (3) The cathode and anode were respectively inserted into a nitrogen atmosphere, wherein the inert anode was a nickel alloy, the molten electrolyte system was sodium chloride, the molten salt electrolysis reaction time was 6 h, the molten salt temperature was 800 ° C, and the voltage was 3.2 V; (4) The electrolytic system was cooled to 25°C, the drying temperature was 150°C, and the drying time was 1.5 h to obtain a carbon-iron alloy.

[0029] The purity of carbon iron in the carbon-iron alloy obtained in this embodiment is 96%, and the current efficiency is 94%. A comparative test was conducted using the same mineral without microwave irradiation, and the purity of carbon iron was 88%, and the current efficiency was 87%.

[0030] Example 3: The method for preparing metallic iron or iron alloy by microwave activation-molten salt electrolysis is described as follows.

[0031] (1) Iron ore powder and titanium oxide powder with a particle size of 74 μm and accounting for 82% were dried at 300°C for 20 h, and then the iron ore powder and titanium oxide powder were uniformly mixed in a mass ratio of 1:1 and pressed into a shape; the pressing process pressure was 7 MPa, the pressing temperature was 500°C, and the cylindrical mineral powder rod after pressing had a length of 6 cm and a diameter of 3 cm; (2) placing the mineral powder rod in a microwave for irradiation; wherein the microwave frequency is 2445 MHz and the irradiation time is 1 hour; (3) inserting the cathode and anode into a helium atmosphere respectively, wherein the inert anode is a nickel alloy, the molten electrolyte system is sodium chloride-potassium chloride-calcium chloride, the molten salt electrolysis reaction time is 10 hours, the molten salt temperature is 950°C, and the voltage is 2V; (4) The electrolytic system was cooled to 35°C, the drying temperature was 180°C, and the drying time was 1.0 h to obtain a titanium-iron alloy.

[0032] The purity of the titanium iron in the titanium-iron alloy obtained in this embodiment is 98%, and the current efficiency is 96%. A comparative test was conducted using the same mineral without microwave irradiation, and the purity of the carbon iron was 89%, and the current efficiency was 89%.

[0033] Example 4: The method for preparing metallic iron or iron alloy by microwave activation-molten salt electrolysis is described as follows.

[0034] (1) Iron ore powder and chromium oxide powder with a particle size of 74 μm and accounting for 82% were dried at 300°C for 20 h, and then the iron ore powder and titanium oxide powder were uniformly mixed in a mass ratio of 1:1.5 and pressed into a shape; the pressing process pressure was 8 MPa, the pressing temperature was 600°C, and the cylindrical mineral powder rod after pressing was 3 cm in length and 2.5 cm in diameter; (2) placing the mineral powder rod in a microwave for irradiation; the microwave frequency is 2450 MHz, and the irradiation time is 1.5 h; (3) inserting the cathode and anode into a helium atmosphere respectively, wherein the inert anode is tin dioxide, the molten electrolyte system is potassium chloride-calcium chloride, the molten salt electrolysis reaction time is 8 hours, the molten salt temperature is 850°C, and the voltage is 3V; (4) The electrolytic system was cooled to 35°C, the drying temperature was 140°C, and the drying time was 1.0 h to obtain a chromium-iron alloy.

[0035] The purity of the ferrochrome in the chromium-iron alloy obtained in this embodiment is 98%, and the current efficiency is 96%. A comparative test was conducted using the same mineral without microwave irradiation, and the purity of the ferrochrome was 89%, and the current efficiency was 88%.

Claims

1. A method for preparing metallic iron or iron alloy by microwave activation-molten salt electrolysis, characterized in that: The method comprises the following steps: (1) pressing iron ore powder or alloy ore powder into a shape to obtain an ore powder rod; (2) The mineral powder rod is placed in a microwave for irradiation activation; (3) Wrapping the irradiated activated mineral powder rod with a stainless steel mesh and using it as the cathode to carry out molten salt electrolysis in a molten salt electrolyte system with a protective atmosphere; (4) After the electrolysis reaction is completed, the electrolysis system is cooled to obtain metallic iron or iron alloy.

2. The method for preparing metallic iron or iron alloy by microwave activation-molten salt electrolysis according to claim 1, characterized in that: In the step (2), the microwave frequency for irradiation activation is 2430-2465 MHz, and the irradiation time is 0.5-2 h.

3. The method for preparing metallic iron or iron alloy by microwave activation-molten salt electrolysis according to claim 1, characterized in that: The components of the molten salt electrolyte system in step (3) are sodium chloride, potassium chloride and / or calcium chloride.

4. The method for preparing metallic iron or iron alloy by microwave activation-molten salt electrolysis according to claim 1, 2 or 3, characterized in that: In the step (3), the temperature of the molten salt during molten salt electrolysis is 700 to 950°C.

5. The method for preparing metallic iron or iron alloy by microwave activation-molten salt electrolysis according to claim 4, characterized in that: The electrolysis time of the molten salt electrolysis is 2 to 10 hours, and the voltage is 2 to 3.2V.

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