Process for extracting iron by reducing red mud through electric furnace

Abstract

The invention relates to the technical field of metallurgical solid waste treatment, in particular to a process for extracting iron by reducing red mud through an electric furnace. In the converter steelmaking process, the dephosphorizing agent is a CaO-FeO-SiO2 slag system basically, and the red mud contains a proper amount of Al2O3, Na2O and the like, so that the dephosphorizing agent containing the red mud is changed into CaO-SiO2-FeO-Al2O3-Na2O slag, and the solubility of P is improved. The cost of the cost step is 350 yuan / steel, and the cost price of molten iron is more than 1300 yuan / steel. The price of the molten iron spindle is about 2400 yuan / ton. And the earnings of 2000 yuan / ton are higher. In the short-process smelting process of stainless steel, the high-iron red mud is directly reduced to extract iron by adding coke into the electric furnace to strike arc and blowing carbon powder, so that an iron water resource can be supplemented for the electric furnace, the problem that the red mud pollutes the environment is solved, and waste is turned into wealth. And a novel idea is provided for subsequent electric furnace smelting. According to the method, a novel thought and pioneering practice for treating the metallurgical solid waste by the stainless steel refining furnace are developed, considerable profits are created, and the competitiveness is improved.

Description

Technical Field

[0001] The invention relates to the technical field of metallurgical solid waste treatment, and in particular to a process for extracting iron by reducing red mud in an electric furnace. Background Art

[0002] The stainless steel wire of the first steelmaking plant currently uses all scrap steel for smelting. The molten iron is far away and cannot be smelted with molten iron. If molten iron can be made by ourselves, the cost reduction of stainless steel wire electric furnace and medium frequency furnace power consumption will be greatly improved; the second is the control of p content in the metallurgical industry. At present, the metallurgical industry uses a lot of low-cost materials such as scrap steel and slag steel, resulting in a high p content. Low-p materials are currently a major problem that plagues the operation area. The third is that the smelted steel cannot be smelted due to the limitation of molten iron, and the quality of the steel cannot be guaranteed.

[0003] Red mud is the solid residue after alumina is leached from bauxite with strong alkaline solution. After aluminum is leached from the alumina process, the iron oxide content is enriched, causing the red mud to appear red from a distance, which is difficult to distinguish from red soil and is commonly known as "red mud". After alumina is extracted from bauxite with a high iron content, the remaining slag is called high-iron red mud. my country's alumina industry discharges more than 100 million tons of red mud each year. Due to the high alkali content, it is difficult to achieve large-scale utilization and can only be stored for treatment; Bayer red mud storage will cause problems such as occupying farmland, polluting the air and groundwater. In extreme weather, the collapse of the red mud yard will cause a devastating blow to downstream farmland. Applying red mud to an electric furnace, using carbon powder and coke to reduce it can extract the rich iron resources, and the molten iron can be directly used and produced. This method not only uses free raw materials but also effectively converts hematite into molten iron, and solves the environmental pollution problem of red mud, which can reduce energy consumption and pollutant emissions, and has great potential value.

[0004] Red mud contains a large amount of iron and has high alkalinity. It is also a non-ferrous metal solid waste, containing iron, aluminum and other elements. At present, the research on red mud is mainly used for iron extraction and building materials. Red mud solid waste is a key issue of national concern. If one ton of red mud is treated under a national project, there will be certain environmental treatment costs. Red mud has high alkalinity and contains almost no phosphorus. Shanxi aluminum plants are mostly located in the Bayer process, and the stock of red mud is large, so the problem of red mud storage needs to be solved urgently.

[0005] The present invention adopts the process route of "electric furnace → small ingot mold casting", which is the first domestic electric furnace reduction red mud iron production process, realizing the full utilization of high-iron red mud solid waste resources, solving the dependence on molten iron resources in the short-process production of stainless steel, and under the premise of ensuring product quality, the process technology of smelting high-grade molten iron resources from red mud effectively solves the problem of molten iron raw materials in short-process steelmaking. The comprehensive utilization of solid waste resources is realized, and the dependence on molten iron resources in the production of stainless steel is reduced; in the steel industry, red mud + carbon powder + SiC are mixed and loaded into the material tank; large pieces of coke or scrap steel are loaded into the material tray, ensuring that they are added under the electrode for arc starting. By continuing to spray carbon powder to directly reduce and roast red mud to extract iron, the Fe grade can reach more than 85% and the Fe recovery rate can reach 90%; by using carbon powder for reduction in the steelmaking process, the cost is relatively low, and lime is used as an additive, the iron separation effect is better and the iron element recovery rate is high. It can turn waste into treasure and make full use of iron resources in red mud; the stacking of red mud pollutes the soil and environment, and the treatment of red mud stacking solves the environmental protection problem and promotes the sustainable development of soil environmental protection. The present invention provides a new idea and pioneering practice for stainless steel electric furnaces to treat metallurgical solid waste. Summary of the invention

[0006] The purpose of the present invention is to provide a process for reducing red mud to extract iron in an electric furnace in view of the above problems.

[0007] The object of the present invention is achieved as follows: A process for reducing red mud to extract iron in an electric furnace, comprising the following steps: Step 1: raw materials for the electric furnace: Na2O: 3-5%, Al2O3: 22-27%, SiO2: 6-9%, CaO: 1-3%, TiO2: 4-8%, Fe2O3: 53-56%, and the rest are unavoidable impurities; loading weight 58-62t, electric furnace tapping temperature: 1550-1600℃; Step 2: after loading is completed, confirm Is the arc starting material covered under the electrode? Step 3: Use low gear ≤5 to start the arc, supply 3000-5000kwh of power, and gradually increase the gear according to the stability of the arc; Step 4: Observe the changes in current and voltage at any time during the power supply process, and adjust to the range of step 3 at any time if there is an abnormality. If there is no abnormality, the power supply process will not be stopped; Step 5: No auxiliary materials are added during the entire power supply process, and no oxygen is blown; Step 6: Steel is discharged after all the raw materials entering the furnace are dissolved; Step 7: After steel is discharged, enter the slag removal station for slag removal and sampling.

[0008] In step 3, the gear is gradually increased according to the stability of the arc: arc starting gear 1, voltage 260V, power supply to 200-300 degrees, and 100-150kg of ferrosilicon is added during the process; up to gear 3, voltage is 380V, power is continuously supplied to 8500-9000 degrees, and 150-200kg of ferrosilicon is added during the process; up to gear 4, voltage is 500V, power is supplied to 14500-15500 degrees, VCB is closed, up to gear 5, voltage is 620V, and red mud is added 1-1.2t during the process; power is supplied to 39000-41000 degrees, up to gear 6, voltage is 740V, and power is continuously supplied to 42000 degrees; start blowing nitrogen at the furnace door oxygen gun for 1000h / m³ for 3-5 minutes, spray carbon powder 150-200kg, and add 300-400kg of ferrosilicon to produce steel.

[0009] The beneficial effects of the present invention are as follows: the present invention uses electric furnace "red mud" to start arc, sprays carbon powder after electric furnace cleaning, and controls the temperature at 1550℃-1600℃ during electric furnace smelting to carry out medium frequency furnace iron extraction, which can increase the iron content in red mud to more than 85%, solves the problem of electric furnace dependence on molten iron raw materials, and realizes self-production and self-sufficiency of molten iron resources. At the same time, it solves the pollution of red mud to the environment, turns waste into treasure, realizes the full utilization of high-speed rail red mud iron resources, and produces huge economic benefits.

[0010] (1) The present invention realizes the process technology of producing high-grade iron resources by smelting red mud while ensuring product quality, effectively solving the problem of molten iron raw materials for short-process steelmaking. It realizes the comprehensive utilization of solid waste resources and reduces the dependence on molten iron resources in the production process of stainless steel.

[0011] (2) In the steel industry, the present invention can increase the Fe grade to more than 85% and the Fe recovery rate to 90% by adding carbon powder and coke to directly reduce and roast red mud to extract iron.

[0012] (3) At present, the composition of molten iron made from iron ore is more than 90% iron, about 0.11% phosphorus, about 4% carbon, and about 0.5% silicon. After iron extraction from red mud, the iron content is more than 90%, phosphorus can be less than 0.01%, carbon is about 2.5%, and silicon is about 1%. Low phosphorus, high silicon, and high-grade molten iron can be produced.

[0013] (4) The dumping of red mud pollutes the soil and the environment. The treatment of red mud also solves environmental problems and promotes the sustainable development of soil environmental protection. At the same time, a certain amount of environmental protection fee will be subsidized for each ton of red mud treated.

[0014] (5) In the converter steelmaking process, the slag is basically CaO-FeO-SiO2, and red mud contains appropriate amounts of Al2O3, Na2O, etc., so the dephosphorization agent containing red mud becomes CaO-SiO2-FeO-Al2O3-Na2O slag, which increases the solubility of P.

[0015] The cost of the process is 350 yuan per ton of steel, while the cost of molten iron is more than 1,300 yuan per ton of steel. The price of molten iron ingots is about 2,400 yuan / ton. The cost price of raw materials is 0, and the profit is 2,000 yuan / ton, which is a relatively high profit. DETAILED DESCRIPTION

[0016] The concept of the present invention is: the present invention aims to provide a process method for extracting iron from red mud by reducing it in an electric furnace. To reduce production costs and solve the dependence on molten iron resources, high-iron red mud, a solid waste of alumina produced by the Bayer process, is used as raw material, and the process route involved is: electric furnace → small ingot casting. Through the unique process route setting, the full reduction of high-iron red mud is achieved; through this iron extraction process, the iron grade in high-iron red mud can be increased to more than 85%, solving the dependence on short-process smelting molten iron resources, and at the same time developing a low-cost comprehensive utilization of solid waste resources, treating red mud stacking to solve environmental protection problems, and promoting the sustainable development of soil environmental protection.

[0017] For every ton of alumina produced by high-iron bauxite, about 1.2-1.4 tons of high-iron red mud will be produced. After red mud is extracted to make molten iron, the iron content is greater than 90%, P can be less than 0.01%, carbon is about 2.5%, and silicon is about 1%. Low-P, high-silicon, high-grade molten iron can be prepared. The stacking of red mud pollutes the soil and the environment. The treatment of red mud stacking solves environmental protection problems and promotes the sustainable development of soil environmental protection. Specifically as follows: The composition of molten iron made of iron ore is greater than 90% iron, P ranges from 0.1-0.2%, carbon 3-5%, silicon 0.2-1%, and the iron content of red mud after iron extraction is greater than 90%, P can be less than 0.01%, carbon 2-3%, silicon 0.5-2%. In the converter steelmaking process, the slag is basically CaO-FeO-SiO2, and red mud contains appropriate amounts of Al2O3, Na2O, etc., so the dephosphorization agent containing red mud becomes CaO-SiO2-FeO-Al2O3-Na2O slag, which increases the solubility of P.

[0018] Red mud contains high silicon and high iron content, so the slag has better fluidity, which solves the problem of adding fluorite. Future potential: Replace iron ore and achieve self-sufficiency in molten iron. Exploratory attempts have been made with good results. Cost-effectiveness issue: Profit per ton of steel: The process cost is 350 yuan per ton of steel, and the cost price of molten iron is more than 1,300 yuan per ton of steel. The price of Taiyuan iron ingots is about 2,400 yuan / ton. The processing cost of red mud per ton of steel is 3 yuan / ton, which can offset the freight; compared with the molten iron in the iron smelting plant, the price of iron ore is saved by 774 yuan / ton. 1 ton of molten iron requires 1.6 tons of iron ore.

[0019] The present invention realizes the process technology of producing high-grade iron resources by smelting red mud under the premise of ensuring product quality, effectively solves the problem of molten iron raw materials for short-process steelmaking, realizes the comprehensive utilization of solid waste resources, handles environmental problems, and solves the dependence on molten iron resources in the production process of stainless steel.

[0020] 1. The conductivity problem in the arc starting stage of the electric furnace, because red mud is not conductive, the solution is to change the feeding method, add a layer of carbon powder in the middle and upper layers of the charge cup for power supply and arc starting. The amount of power supply and the injection of carbon powder. The raw materials entering the electric furnace: Na2O: 3-5%, Al2O3: 22-27%, SiO2: 6-9%, CaO: 1-3%, TiO2: 4-8%, Fe2O3: 53-56%, and the rest are unavoidable impurities; the loading weight is 58-62t, and the steel tapping temperature of the electric furnace is 1550-1600℃; after the loading is completed, confirm whether the arc starting material is covered under the electrode. The arc starting material is 3.5 tons of carbon powder and 3 tons of arc starting coke to ensure conductivity.

[0021] 2. Key points for power supply and electrode height control during smelting: gradually increase the gear according to the stability of the arc. Specifically: arc starting gear 1, voltage 260V, power supply to 200-300 degrees, add 100-150kg of ferrosilicon during the process; 3 gears, voltage 380V, continuous power supply to 8500-9000 degrees, add 150-200kg of ferrosilicon during the process; 4 gears, voltage 500V, power supply to 14500-15500 degrees, VCB closed, 5 gears, voltage 620V, add 1-1.2t of red mud during the process; power supply to 39000-41000 degrees, 6 gears, voltage 740V, continuous power supply to 42000 degrees; start blowing nitrogen 1000h / m³ from the oxygen gun at the furnace door for 3 minutes, spray 150-200kg of carbon powder, add 300-400kg of ferrosilicon for steel production.

[0022] 3. There is no flame at the steel outlet. Turn the power to 50,000 degrees and shake the furnace back to 18 degrees to open the steel outlet. Then turn it back and turn the power to 50,840 to produce steel.

[0023] 4. Use low gear (≤5 gears) to start the arc when transmitting power. When transmitting 3000-5000kwh, increase the gear according to the arc stability. After the arc is stable, adjust the voltage to a high current. The power supply curve needs to be designed.

[0024] 5. No auxiliary materials are added during the whole process, and no oxygen is blown. If necessary, if materials accumulate at the furnace door, a small amount of oxygen can be blown to melt the materials at the furnace door. After a large amount of molten pool is formed, nitrogen can be blown for stirring.

[0025] The specific implementation of the method of the present invention is described in detail below in conjunction with examples, but the specific implementation of the present invention is not limited to the following examples. Example 1

[0026] This example is a 90t electric furnace → small ingot mold. The specific implementation is as follows: the electric furnace uses coke to start the arc and sprays carbon powder to directly reduce high-iron red mud to extract iron. The process route involved is: 90t electric furnace → small ingot mold (the nominal capacity of each metallurgical furnace).

[0027] The operating steps of this embodiment are as follows: 1. The raw materials put into the electric furnace are as shown in the following table.

[0028]

[0029] The rest are inevitable impurities; loading weight 60t; electric furnace tapping temperature: 1558℃. 2. After loading, check the furnace conditions, especially whether the arc starting material is covered under the electrode.

[0030] 3. Use low gear (≤5 gears) to start the arc when transmitting power. When transmitting 3000-5000kwh, increase the gear according to the arc stability. After the arc is stable, adjust the current to a low voltage.

[0031] 4. During the power transmission process, the main control monitors the changes in current and voltage at any time, and makes adjustments at any time if there is an abnormality. If there is no abnormality, the power transmission process will not be interrupted.

[0032] 5. No auxiliary materials are added and no oxygen is blown during the whole process.

[0033] 6. Steel is tapped after all is dissolved.

[0034] 7. Slag removal and sampling at the slag removal station.

[0035] The final sampling component analysis results of the implementation case are: Fe 88%; C 2.45%; Si 0.28%; S 0.001%; ​​P0.008%; the rest are unavoidable impurities. Example 2

[0036] This example is a 90t electric furnace → small ingot mold. The specific implementation is as follows: the electric furnace uses coke to start the arc and sprays carbon powder to directly reduce high-iron red mud to extract iron. The process route involved is: 90t electric furnace → small ingot mold (the nominal capacity of each metallurgical furnace).

[0037] The operating steps of this embodiment are as follows: 1. The raw materials put into the electric furnace are as shown in the following table.

[0038]

[0039] The rest are inevitable impurities; loading weight 60t; electric furnace tapping temperature: 1558℃. 2. After loading, check the furnace conditions, especially whether the arc starting material is covered under the electrode.

[0040] 3. Use low gear 1 to start the arc when transmitting power. When transmitting 3000-5000kwh, increase the gear according to the arc stability. After the arc is stable, adjust the current to a high level with low voltage.

[0041] 4. During the power transmission process, the main controller observes the changes in current and voltage at any time, and the power is not cut off during the power transmission process.

[0042] 5. No auxiliary materials are added and no oxygen is blown during the whole process.

[0043] 6. Steel is tapped after all is dissolved.

[0044] 7. Slag removal and sampling at the slag removal station.

[0045] The final sampling composition analysis results of the implementation case are: Fe 89.5%; C 2.77%; Si 0.17%; S 0.001%; ​​P0.005%; the rest are unavoidable impurities.

[0046] The above description is only a specific embodiment of the present invention, but the structural features of the protection scope of the present invention are not limited thereto. Any changes or modifications made by any technician in the field of the present invention are all covered by the patent scope of the present invention.

Claims

1. A process for extracting iron from red mud by reducing it in an electric furnace, characterized in that: The following steps are involved: Step 1: Raw materials for electric furnace: Na2O: 3-5%, Al2O3: 22-27%, SiO2: 6-9%, CaO: 1-3%, TiO2: 4-8%, Fe2O3: 53-56%, and the rest are inevitable impurities; loading weight 58-62t, electric furnace tapping temperature: 1550-1600℃; Step 2: After loading, check whether the arc starting material is covered under the electrode; Step 3: Use low gear ≤5 to start the arc, supply 3000-5000kwh of power, and gradually increase the gear according to the arc stability; Step 4: Observe the changes of current and voltage at any time during the power transmission process. If there is any abnormality, adjust it to the range of step 3 at any time. If there is no abnormality, the power transmission process will not be stopped; Step 5: No auxiliary materials or oxygen blowing are added during the whole process of power transmission; Step 6: After all raw materials are dissolved, steel is tapped; Step 7: After steel is tapped, enter the slag removal station for slag removal and sampling.

2. The process for extracting iron from red mud by electric furnace reduction according to claim 1, characterized in that: In step 3, the gear is gradually increased according to the stability of the arc: arc starting gear 1, voltage 260V, power supply to 200-300 degrees, and 100-150kg of ferrosilicon is added during the process; up to gear 3, voltage is 380V, power is continuously supplied to 8500-9000 degrees, and 150-200kg of ferrosilicon is added during the process; up to gear 4, voltage is 500V, power is supplied to 14500-15500 degrees, VCB is closed, up to gear 5, voltage is 620V, and red mud is added 1-1.2t during the process; power is supplied to 39000-41000 degrees, up to gear 6, voltage is 740V, and power is continuously supplied to 42000 degrees; start blowing nitrogen at the furnace door oxygen gun for 1000h / m³ for 3-5 minutes, spray carbon powder 150-200kg, and add 300-400kg of ferrosilicon to produce steel.