A method for recovering iron and aluminum by direct reduction of high-iron bauxite, electric furnace smelting and magnetic separation

Abstract

The application discloses a method for directly reducing, electrically smelting and magnetically separating and recovering iron and aluminum from high-iron bauxite, and belongs to the technical field of ore smelting. The method comprises the following steps: (1) crushing and finely grinding high-iron bauxite and reduction coal and uniformly mixing the high-iron bauxite and the reduction coal; (2) directly reducing in a pipe furnace to obtain reduced ore; (3) weakly magnetically separating the reduced ore to screen out aluminum concentrate and iron concentrate, and spreading a layer of reduction coal powder on the surface of the iron concentrate; (4) strongly magnetically separating the aluminum concentrate to screen out high-quality bauxite and iron-aluminum spinel; (5) uniformly mixing the high-quality bauxite and the iron concentrate with the layer of reduction coal powder and feeding the mixture into an electric arc furnace for smelting, and taking out a copper pot for cooling after the smelting is completed; and (6) breaking and magnetically separating after the copper pot is naturally cooled to obtain ferrosilicon alloy and high-purity aluminum oxide. The method can effectively recover iron and aluminum in high-iron bauxite.

Description

Technical Field

[0001] This invention relates to the field of ore smelting technology, specifically to a method for the direct reduction of high-iron bauxite followed by electric furnace smelting and magnetic separation to recover iron and aluminum. Background Technology

[0002] With the exploitation and utilization of resources, high-quality bauxite resources are now scarce. However, low-quality, low-alumina, high-iron bauxite resources are currently abundant. The rational development and utilization of low-alumina, high-iron bauxite is one way to address the scarcity of high-quality bauxite resources. The microcrystalline structure of tightly cemented iron and aluminum in high-iron bauxite is one of the main technical challenges restricting its efficient utilization. In the development and application of bauxite, high iron content often leads to the ineffective utilization of its reserves and causes environmental and other problems.

[0003] Currently, the main processes for the comprehensive utilization of high-speed rail bauxite include two types: wet and dry methods. Wet processes mainly include acid and alkali methods. The acid method is the traditional method for comprehensive bauxite utilization. Its main process involves first dissolving aluminum, sodium, and other metal ions from the bauxite using leaching acid, followed by separation and purification using carbonate precipitation. The acid method has advantages such as simple operation, mature technology, and high product purity, but it also has disadvantages such as leaching wastewater treatment problems and high energy consumption. The core of the alkali method is to dissolve aluminum ions from the bauxite using sodium hydroxide, then neutralize them with acidic solutions such as hydrochloric acid, and finally separate and purify them using carbonate precipitation. The alkali method has advantages such as energy saving, environmental protection, and low wastewater discharge, but it also has disadvantages such as low product purity and low product yield. The dry process mainly relies on the thermal decomposition of bauxite, which decomposes bauxite at high temperatures to produce products such as aluminates and iron oxides. The advantages of the dry process are energy saving and environmental protection, no wastewater discharge, and no need for large amounts of chemical reagents. However, it also has disadvantages such as complex process, large equipment investment, and low product purity.

[0004] To address the above problems, this invention proposes a method for the direct reduction of high-iron bauxite followed by electric furnace smelting and magnetic separation to recover iron and aluminum. Summary of the Invention

[0005] The purpose of this invention is to provide a method for the direct reduction of high-iron bauxite followed by electric furnace smelting and magnetic separation to recover iron and aluminum, thereby solving the problems of environmental pollution, low product purity, and low product yield mentioned in the background art.

[0006] To achieve the above objectives, this invention provides a method for the direct reduction of high-iron bauxite, electric furnace smelting, and magnetic separation to recover iron and aluminum, specifically including the following steps:

[0007] S1. After crushing and finely grinding the high-speed iron bauxite and reduced coal ore, mix them evenly.

[0008] S2. The mixture of high-speed bauxite and reducing coal is placed into a tubular furnace filled with nitrogen for reduction.

[0009] S3. The reduced ore is subjected to weak magnetic separation to separate aluminum concentrate and iron concentrate, and carbon powder is spread on the surface and around the iron concentrate.

[0010] S4. Perform strong magnetic separation on the aluminum concentrate to separate high-quality bauxite and iron-aluminum spinel.

[0011] S5. Mix high-quality bauxite and iron concentrate covered with reducing coal powder evenly and put them into an electric arc furnace for smelting. After smelting and cooling, take them out.

[0012] S6. The solidified block is crushed and magnetically separated using a magnetic separator. After the magnetic separation is completed, magnetic materials ferrosilicon alloy and high-purity alumina are obtained.

[0013] Preferably, in S1, the portion of high-iron bauxite crushed to a particle size of <1cm and finely ground to a particle size of <0.1mm accounts for more than 50% of the total weight of high-iron bauxite; the portion of reduced coal finely ground to a particle size of <0.05mm accounts for more than 70% of the total weight of reduced coal.

[0014] Preferably, in S1, the mass ratio of high-iron bauxite to reduced coal is 100:2 to 10.

[0015] Preferably, in S1, the high-iron bauxite is Ghanaian gibbsite-type high-iron bauxite, which, by mass percentage, includes 45-55% Al2O3, 5-10% SiO2, 30% Fe2O3, and other unavoidable impurities.

[0016] Preferably, in S1, the reducing coal is semi-coke or anthracite.

[0017] Preferably, in step S2, direct reduction is carried out at 1100–1400°C for 60–180 min; the ratio of fixed carbon content in the reduced coal to oxygen content of iron oxides in iron-containing minerals is 1–3, and the nitrogen flow rate is 1.5 L / min.

[0018] Preferably, in step S3, the magnetic field strength of the weak magnetic separation is 90-160 mT, and the amount of carbon powder used is 5-10% of the amount of high-iron bauxite used in step S1.

[0019] Preferably, in step S4, the magnetic field strength is 1000–1600 mT.

[0020] Preferably, in step S5, the melting temperature is 2000–3000℃ and the melting time is 180–360 min.

[0021] Preferably, in step S6, the magnetic field strength is 100–200 mT.

[0022] In the grinding step, this invention uses high-energy mechanical equipment to grind high-iron bauxite, breaking down the iron-aluminum structure and promoting the separation of aluminum and iron, resulting in rapid phase reconstruction. During the reduction process, pulverized coal is used as a reducing agent to reduce iron ions in the high-iron bauxite to iron particles, thereby disrupting the tightly bound iron-aluminum structure and promoting iron-aluminum separation. For the reducing agents, materials with reducing properties such as coke, carbon black, and charcoal are typically used. Simultaneously, by adjusting the magnetic field strength, metallic iron, aluminum concentrate, and iron-aluminum spinel are separated sequentially, improving the bauxite grade to meet the requirements for alumina smelting in an electric arc furnace. During the electric arc furnace smelting process, SiO2 is reduced to elemental Si by coking coal. Si reacts with elemental iron to form ferrosilicon alloy, which sinks to the bottom of the molten material, while Al2O3 remains at the top. After crushing, magnetic separation effectively separates iron and aluminum, leaving high-purity alumina.

[0023] Therefore, this invention proposes a method for the direct reduction, electric furnace smelting, and magnetic separation and recovery of iron and aluminum from high-iron bauxite. Compared with existing methods for the comprehensive utilization of high-iron bauxite, the specific beneficial effects are as follows:

[0024] (1) Compared with separation processes such as magnetic separation, flotation, and suspension roasting, it can more effectively separate alumina and iron minerals in high-iron bauxite, and the separated alumina has a high purity and the ferrosilicon alloy has a high quality.

[0025] (2) The reduction of high-iron bauxite by direct reduction-dependent gas has higher heat transfer efficiency than conventional roasting methods.

[0026] (3) The process of this invention is simple, the equipment has a large processing capacity, the product properties are easy to control, and it is easy to industrialize and scale up.

[0027] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the process for the direct reduction of high-iron bauxite, electric furnace smelting, and magnetic separation and recovery of iron and aluminum according to the present invention. Detailed Implementation

[0029] This invention provides a method for the direct reduction of high-iron bauxite, electric furnace smelting, and magnetic separation to recover iron and aluminum. The process is as follows: Figure 1 As shown, the specific steps include:

[0030] S1. Crush the high-iron bauxite to a particle size of less than 1 cm, and then grind it further until the portion with a particle size of less than 0.1 mm accounts for more than 50% of the total weight. Grind the reduced coal to a particle size of less than 0.05 mm, and the portion with a particle size of less than 70% of the total weight. Mix the high-iron bauxite powder and the reduced coal powder evenly at a mass ratio of 100:2 to 10 to obtain a mixture. This ensures that the ratio of the fixed carbon content in the reduced coal to the oxygen content of iron oxides in the iron-containing minerals is 1 to 3.

[0031] In this invention, the high-iron bauxite is a Ghanaian gibbsite-type high-iron bauxite, whose main mineral component is gibbsite, and it also includes gangue minerals, mainly goethite, hematite, kaolinite, rutile, quartz, etc. By mass percentage, it includes 45-55% Al₂O₃, 5-10% SiO₂, 30% Fe₂O₃, and other unavoidable impurities. The reducing coal is semi-coke or anthracite; wherein, the chemical composition of the anthracite powder is: fixed carbon 80.12%, ash 9.37%, volatile matter 8.58%, and other unavoidable impurities.

[0032] S2. The mixture is placed in a tube furnace for direct reduction at a temperature of 1100–1400℃ for a time of 60–180 min. Nitrogen gas is introduced into the tube furnace at a flow rate of 1.5 L / min.

[0033] S3. Use a dry magnetic separator to perform a weak magnetic separation on the reduced ore after reduction. The magnetic field strength is 90-160mT. Screen out aluminum concentrate and iron concentrate. Spread a layer of carbon powder on the surface and around the iron concentrate. The amount of carbon powder accounts for 5-10% of the total amount of the initial high-iron bauxite to ensure that the metallic iron is not rapidly oxidized in the air.

[0034] S4. Perform a strong magnetic separation on the aluminum concentrate to separate high-quality bauxite and iron-aluminum spinel. The magnetic separator used here should be a dry magnetic separator with a magnetic field strength of 1000-1600mT.

[0035] In this invention, the sieved iron-aluminum spinel can be recycled in an S2 tube furnace. Note that an appropriate amount of pulverized coal should be added to the tube furnace each time to ensure that the ratio of fixed carbon content in the reducing coal to oxygen content of iron oxides in the iron-containing minerals is 1 to 3.

[0036] S5. Mix high-quality bauxite and iron concentrate covered with reducing coal powder evenly and put them into an electric arc furnace. Melt at 2000-3000℃ for 180-360 minutes. After melting, remove the copper pot after cooling. The electric arc furnace mentioned here is an electric arc melting furnace.

[0037] After the smelting process is completed, the molten material cools down and the ferrosilicon alloy is located in the lower part, while the alumina is located in the upper part. The material should be crushed into two parts at a certain dividing point in the middle and then finely ground separately. This improves the magnetic separation efficiency and makes the separation of iron and aluminum more thorough.

[0038] S6. Crush the solidified lumps and perform magnetic separation using a magnetic separator. The magnetic separator mentioned here is either a wet magnetic separator or a dry magnetic separator, with a magnetic field strength of 100-200 mT.

[0039] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the invention should be considered equivalent substitutions and are included within the scope of protection of the present invention. Furthermore, it should be understood that after reading the contents of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims and are all within the scope of protection of the present invention.

[0040] In this document, the term "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The term "embodiment" appearing in various places throughout the specification does not necessarily refer to the same embodiment, nor does it specifically limit its independence or connection with other embodiments. In principle, in this application, as long as there are no technical contradictions or conflicts, the technical features mentioned in each embodiment can be combined in any way to form corresponding implementable technical solutions.

[0041] Unless otherwise defined, the technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the use of related terms herein is merely for the purpose of describing particular embodiments and is not intended to limit this application.

[0042] Unless otherwise specified, the reagents, instruments, and equipment used in this invention are all commonly used by those skilled in the art.

[0043] Example 1

[0044] This embodiment provides a method for the direct reduction of high-iron bauxite, electric furnace smelting, and magnetic separation to recover iron and aluminum. The ore used in this embodiment is Ghanaian gibbsite-type high-iron bauxite, in which the useful mineral is gibbsite, and the gangue minerals are mainly goethite, hematite, kaolinite, rutile, quartz, etc. By mass percentage, it contains 51.5% Al2O3, 9.8% SiO2, 30.3% Fe2O3, and other unavoidable impurities, belonging to the gibbsite-type high-iron bauxite.

[0045] The specific steps are as follows:

[0046] High-iron bauxite ore was crushed to a particle size of less than 1 cm using a jaw crusher, and then finely ground in a high-speed multi-functional pulverizer until 50% of the ore was less than 0.1 mm by weight. Reduced coal was finely ground until 70% of the ore was less than 0.1 mm by weight, yielding reduced coal powder. High-iron bauxite and coal powder were then ground in a ball mill at a mass ratio of 100:3.7 until 50% of the ore had a particle size ≤0.074 mm, yielding a mixture. This mixture was placed in a tubular furnace for reduction. After evacuation to a vacuum, nitrogen was introduced at a flow rate of 1.5 L / min, and moderate direct reduction was carried out at 1100℃ for 180 min to obtain reduced ore. The reduced ore is placed in a magnetic separator for the first stage of weak magnetic separation with a magnetic field strength of 90 mT to obtain iron concentrate and aluminum concentrate. Carbon powder, accounting for 5% of the total mass of the initial ore powder, is spread on the surface and around the iron concentrate. The aluminum concentrate is then subjected to a second stage of strong magnetic separation with a magnetic field strength of 1000 mT. The iron concentrate and high-quality bauxite with coal powder are then fed into an electric arc melting furnace and smelted at 2200℃ for 360 min. After smelting, the copper crucible is cooled with the furnace. The molten material is then cooled, solidified, crushed, and subjected to magnetic separation through a magnetic separator with a magnetic field strength of 200 mT.

[0047] The final obtained alumina has a purity of 95.7% and is a high-quality ferrosilicon alloy with an Fe / Si ratio of 1.4.

[0048] Example 2

[0049] This embodiment provides a method for the direct reduction of high-iron bauxite, electric furnace smelting, and magnetic separation to recover iron and aluminum. The ore used in this embodiment is Ghanaian gibbsite-type high-iron bauxite, in which the useful mineral is gibbsite, and the gangue minerals are mainly goethite, hematite, kaolinite, rutile, quartz, etc. By mass percentage, it contains 49.5% Al2O3, 10.2% SiO2, 29.5% Fe2O3, and other unavoidable impurities, belonging to the gibbsite-type high-iron bauxite.

[0050] The specific steps are as follows:

[0051] High-iron bauxite ore was crushed to a particle size of less than 1 cm using a jaw crusher, and then finely ground in a high-speed multi-functional pulverizer until 50% of the ore was less than 0.1 mm by weight. Reduced coal was finely ground until 70% of the ore was less than 0.1 mm by weight, yielding reduced coal powder. High-iron bauxite and coal powder were then ground in a ball mill at a mass ratio of 100:5.2 until 60% of the ore had a particle size ≤0.074 mm, yielding a mixture. This mixture was placed in a tubular furnace for reduction. After evacuation to a vacuum, nitrogen was introduced at a flow rate of 1.5 L / min, and moderate direct reduction was carried out at 1200℃ for 150 min to obtain reduced ore. The reduced ore is placed in a magnetic separator for the first stage of weak magnetic separation with a magnetic field strength of 120 mT to obtain iron concentrate and aluminum concentrate. Carbon powder accounting for 5% of the total mass of the initial ore powder is spread on the surface and around the iron concentrate. The aluminum concentrate is then subjected to a second stage of strong magnetic separation with a magnetic field strength of 1200 mT. The iron concentrate and high-quality bauxite covered with coal powder are then fed into an electric arc melting furnace and smelted at 2500℃ for 300 minutes. After smelting, the copper crucible is cooled with the furnace. The molten material is then cooled and solidified, crushed, and subjected to magnetic separation through a magnetic separator with a magnetic field strength of 180 mT.

[0052] The final obtained alumina has a purity of 95.3% and is a high-quality ferrosilicon alloy with an Fe / Si ratio of 1.3.

[0053] Example 3

[0054] This embodiment provides a method for the direct reduction of high-iron bauxite, electric furnace smelting, and magnetic separation to recover iron and aluminum. The ore used in this embodiment is Ghanaian gibbsite-type high-iron bauxite, in which the useful mineral is gibbsite, and the gangue minerals are mainly goethite, hematite, kaolinite, rutile, quartz, etc. By mass percentage, it contains 48.9% Al2O3, 7.5% SiO2, 31.2% Fe2O3, and other unavoidable impurities, belonging to the gibbsite-type high-iron bauxite.

[0055] The specific steps are as follows:

[0056] High-iron bauxite ore was crushed to a particle size of less than 1 cm using a jaw crusher, and then finely ground in a high-speed multi-functional pulverizer until 50% of the ore was less than 0.1 mm by weight. Reduced coal was finely ground until 70% of the ore was less than 0.1 mm by weight, yielding reduced coal powder. High-iron bauxite and coal powder were then ground in a ball mill at a mass ratio of 100:6.7 until 70% of the ore had a particle size ≤0.074 mm, yielding a mixture. This mixture was then placed in a tubular furnace for reduction. After evacuation to a vacuum, nitrogen was introduced at a flow rate of 1.5 L / min, and a moderate direct reduction was carried out at 1300℃ for 90 minutes to obtain reduced ore. The reduced ore is placed in a magnetic separator for the first stage of weak magnetic separation with a magnetic field strength of 150 mT to obtain iron concentrate and aluminum concentrate. Carbon powder accounting for 5% of the total mass of the initial ore powder is spread on the surface and around the iron concentrate. The aluminum concentrate is then subjected to a second stage of strong magnetic separation with a magnetic field strength of 1400 mT. The iron concentrate and high-quality bauxite covered with coal powder are then fed into an electric arc melting furnace and smelted at 2700℃ for 240 min. After smelting, the copper crucible is cooled with the furnace. The molten material is then cooled and solidified, crushed, and subjected to magnetic separation through a magnetic separator with a magnetic field strength of 160 mT.

[0057] The final obtained alumina has a purity of 95.5% and is a high-quality ferrosilicon alloy with an Fe / Si ratio of 1.4.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for the direct reduction of high-iron bauxite, electric furnace smelting, and magnetic separation to recover iron and aluminum, characterized in that... Specifically, the following steps are included: S1. After crushing and finely grinding the high-speed iron bauxite and reduced coal ore, mix them evenly. S2. The mixture of high-speed bauxite and reducing coal is placed into a tubular furnace filled with nitrogen for reduction. S3. The reduced ore is subjected to weak magnetic separation to separate aluminum concentrate and iron concentrate, and carbon powder is spread on the surface and around the iron concentrate. S4. Perform strong magnetic separation on the aluminum concentrate to separate high-quality bauxite and iron-aluminum spinel. S5. Mix high-quality bauxite and iron concentrate covered with reducing coal powder evenly and put them into an electric arc furnace for smelting. After smelting and cooling, take them out. S6. The solidified block is crushed and magnetically separated using a magnetic separator. After the magnetic separation is completed, magnetic materials ferrosilicon alloy and high-purity alumina are obtained. In S3, the magnetic field strength of the weak magnetic separation is 90-160 mT; In S4, the magnetic field strength is 1000–1600 mT; In S6, the magnetic field strength is 100-200 mT.

2. The method for direct reduction of high-iron bauxite, electric furnace smelting, and magnetic separation for iron and aluminum recovery according to claim 1, characterized in that: In S1, the portion of high-iron bauxite crushed to a particle size of <1cm and finely ground to a particle size of <0.1mm accounts for more than 50% of the total weight of high-iron bauxite; the portion of reduced coal finely ground to a particle size of <0.05mm accounts for more than 70% of the total weight of reduced coal.

3. The method for direct reduction of high-iron bauxite, electric furnace smelting, and magnetic separation for iron and aluminum recovery according to claim 1, characterized in that: In S1, the mass ratio of high-iron bauxite to reduced coal is 100:2 to 10.

4. The method for direct reduction of high-iron bauxite, electric furnace smelting, and magnetic separation for iron and aluminum recovery according to claim 1, characterized in that: In S1, the high-iron bauxite is Ghanaian gibbsite-type high-iron bauxite, which, by mass percentage, includes 45-55% Al2O3, 5-10% SiO2, 30% Fe2O3, and other unavoidable impurities.

5. The method for direct reduction of high-iron bauxite, electric furnace smelting, and magnetic separation for iron and aluminum recovery according to claim 1, characterized in that: In S1, the reducing coal is semi-coke or anthracite.

6. The method for direct reduction of high-iron bauxite, electric furnace smelting, and magnetic separation for iron and aluminum recovery according to claim 1, characterized in that: In step S2, direct reduction is carried out at 1100–1400℃ for 60–180 min; the ratio of fixed carbon content in the reduced coal to oxygen content of iron oxides in iron-containing minerals is 1–3, and the nitrogen flow rate is 1.5 L / min.

7. The method for direct reduction of high-iron bauxite, electric furnace smelting, and magnetic separation for iron and aluminum recovery according to claim 1, characterized in that: The amount of carbon powder used is 5-10% of the amount of high-iron bauxite used in S1.

8. The method for direct reduction of high-iron bauxite, electric furnace smelting, and magnetic separation for iron and aluminum recovery according to claim 1, characterized in that: In S5, the melting temperature is 2000-3000℃ and the melting time is 180-360min.

Images