Process for extracting iron from red mud

Abstract

The application discloses a method for extracting iron from red mud, and aims to provide a method for recovering iron from red mud. The technical scheme of the application is that red mud, calcium fluoride, calcium oxide, sodium carbonate, cryolite and reducing carbon are mixed and balling in a mass ratio of 100:0-3:0.1-5:0.1-5:0.1-5:8-18, and then are sent into a reduction furnace, and are heated to 1100-1450 DEG C and kept for 0.5-4 hours, so that a blocky silicon-iron mixture is obtained after cooling; the reducing carbon is formed by mixing graphite powder with semi-coke or with coal, the carbon content in the reducing carbon is greater than or equal to 85%, and the content of the graphite powder in the reducing carbon is greater than 50%; the purity of the calcium fluoride is greater than or equal to 80%, the purity of the calcium oxide is greater than or equal to 85%, the purity of the sodium carbonate is greater than or equal to 90%, the purity of the cryolite is greater than or equal to 90%, and the purity of the graphite powder is greater than or equal to 90%; the blocky silicon-iron mixture is ball milled into powder; and the iron in the powder is extracted by magnetic separation. The application has the advantages of high grade of the extracted iron and low consumption of raw coal, and is a method for recycling red mud resources.

Description

Technical Field

[0001] This invention relates to a method for extracting iron from red mud, belonging to the field of industrial solid waste resource utilization and metallurgical technology. Background Technology

[0002] Red mud is a waste product generated during the alumina refining process from bauxite, named for its reddish-brown slurry appearance. Red mud contains large amounts of metals such as iron, aluminum, sodium, and calcium. Large-scale stockpiling of red mud not only occupies significant amounts of land and farmland, incurring substantial construction and maintenance costs for stockpiles, but also causes severe water pollution and wastes substantial amounts of metal resources.

[0003] Currently, the main method for extracting iron from red mud is roasting-magnetic separation. However, this method generally suffers from low iron grade and low iron recovery rate, and there is still considerable room for improvement in the iron extraction method. Summary of the Invention

[0004] In view of the above-mentioned defects in the existing technology, the present invention aims to provide a method for extracting iron from red mud that has good treatment effect, high iron extraction rate and low coal consumption.

[0005] To achieve the above objectives, the method of the present invention includes roasting, ball milling, and magnetic separation, and the specific steps are as follows: 1) Mix red mud, calcium fluoride, calcium oxide, sodium carbonate, cryolite, and reduced carbon in a mass ratio of 100:0~3:0.1~5:0.1~5:0.1~5:8~18, form pellets, and feed them into a reduction furnace. Heat the mixture to 1100~1450℃, hold it at that temperature for 0.5~4h, and then cool it to obtain a blocky ferrosilicon mixture. The reduced carbon is composed of graphite powder and semi-coke, or a mixture of graphite powder and coal, with a carbon content ≥85% and a graphite powder content >50%; the purity of the calcium fluoride is ≥80%, the purity of the calcium oxide is ≥85%, the purity of the sodium carbonate is ≥90%, the purity of the cryolite is ≥90%, and the purity of the graphite powder is ≥90%. 2) The blocky ferrosilicon mixture is ball-milled into powder; 3) Magnetic separation is used to extract iron from the powder.

[0006] Preferably, in the above technical solution, the mass ratio of red mud, calcium fluoride, calcium oxide, sodium carbonate, cryolite, and reduced carbon is 100:0.5:2:2:2:12.

[0007] Furthermore, the above technical solution also includes ferrosilicon powder, red mud, calcium fluoride, calcium oxide, sodium carbonate, cryolite, reduced carbon, and ferrosilicon powder in a mass ratio of 100:0~3:0.1~5:0.1~5:0.1~5:8~18:0.1~2, wherein the purity of the ferrosilicon powder is ≥95%.

[0008] Furthermore, in the above technical solution, the mass ratio of red mud, calcium fluoride, calcium oxide, sodium carbonate, cryolite, reduced carbon, and ferrosilicon powder is 100:0.5:2:2:2:12:0.5.

[0009] Furthermore, in the above technical solution, the heat treatment temperature is 1350℃ and the holding time is 1 hour.

[0010] In the above technical solution, calcium fluoride and calcium oxide mainly remove impurities such as silicon and aluminum from the tailings. The reaction principle is CaF2 + SiO2 = CaSiO3 + 2HF, CaO + SiO2 = CaSiO3, and 3CaO + Al2O3 = Ca3(AlO3)2. Sodium carbonate and calcium oxide work synergistically to react with the generated silicates to form low-melting-point substances, based on the principle of NaCO3 + CaSiO3 = NaSiO3 + CaCO3. Cryolite acts as a melting aid, lowering the reaction temperature. Ferrosilicon powder can improve the conversion rate of reduced iron. The addition of graphite powder increases the melting point of the material, effectively alleviating the problem of ring formation at 900–1100℃. At the same time, the layered structure of graphite powder has a lubricating effect, which can effectively reduce the adhesion problem of the material. Under the synergistic effect of the above two, the addition of graphite powder can effectively solve the ring formation problem in rotary kilns.

[0011] Compared with existing technologies, the method of this invention can not only achieve an iron powder recovery rate of >90% and a grade of 85-93%, effectively solving the problem of low iron grade extraction by traditional methods, but also reduce raw coal consumption (coal powder consumption of 0.14 tons / ton, lower than the industry average of 0.35 tons / ton). Detailed Implementation

[0012] The present invention will be further described below with reference to specific embodiments: Example

[0013] 1) Mix 50 kg of calcium fluoride, 200 kg of sodium carbonate and 200 kg of calcium oxide, add 200 kg of cryolite and 1200 kg of reduced carbon and mix well to obtain a purifying agent; mix the purifying agent with 10000 kg of red mud and pelletize to obtain pretreated red mud. 2) The pretreated red mud is fed into a reduction furnace and heat-treated at 1350°C for 1 hour, then cooled to obtain a blocky ferrosilicon mixture; 3) The blocky ferrosilicon mixture is ball-milled into powder and magnetically separated to obtain an iron powder mixture with a grade of 93%.

[0014] In this example, the reduced carbon is composed of graphite powder and semi-coke, or graphite powder and coal, and the carbon content in the reduced carbon is ≥85%, and the graphite powder content in the reduced carbon is >50%.

[0015] Example 2, the steps are the same as in Example 1. The amount of calcium fluoride is 0 kg, and the resulting iron powder mixture has a purity of 91%.

[0016] Example 3, the steps are the same as in Example 1. The amount of calcium fluoride is 300 kg, and the resulting iron powder mixture has a purity of 92%.

[0017] Example 4, the steps are the same as in Example 1. The amount of sodium carbonate is 10 kg, and the resulting iron powder mixture has a purity of 88%.

[0018] Example 5, the steps are the same as in Example 1. The amount of sodium carbonate is 500 kg, and the resulting iron powder mixture has a purity of 85%.

[0019] Example 6, the steps are the same as in Example 1. The amount of calcium oxide is 10 kg, and the resulting iron powder mixture has a purity of 81%.

[0020] Example 7 follows the same steps as in Example 1. The amount of calcium oxide is 500 kg, and the resulting iron powder mixture has a purity of 91%.

[0021] Example 8, the steps are the same as in Example 1. The cryolite used is 10 kg, and the resulting iron powder mixture has a purity of 90%.

[0022] Example 9, the steps are the same as in Example 1. The cryolite used is 500 kg, and the resulting iron powder mixture has a purity of 92%.

[0023] Example 10 follows the same steps as Example 1. The heat treatment temperature is 1100℃, and the resulting iron powder mixture has a purity of 81%.

[0024] Example 11, the steps are the same as in Example 1. The heat treatment temperature is 1200℃, and the grade of the resulting iron powder mixture is 86%.

[0025] Example 12 follows the same steps as Example 1. The heat treatment temperature is 1300℃, and the resulting iron powder mixture has a purity of 91%.

[0026] Example 13 follows the same steps as Example 1. The heat treatment temperature is 1450℃, and the resulting iron powder mixture has a purity of 93%.

[0027] Example 14 follows the same steps as Example 1. However, 20 kg of ferrosilicon powder was added, resulting in an iron powder mixture with a purity of 93%, increasing the iron powder reduction rate from 77% to 84%.

[0028] Example 15 follows the same steps as Example 14. The amount of ferrosilicon powder used is 30 kg, the resulting iron powder mixture has a purity of 93%, and the iron powder reduction rate is increased from 77% to 87%.

[0029] Example 16 follows the same steps as Example 14. The amount of ferrosilicon powder is 40 kg, the resulting iron powder mixture has a purity of 93%, and the iron powder reduction rate is increased from 77% to 90%.

[0030] Example 17 follows the same steps as Example 14. The amount of ferrosilicon powder is 50 kg, the resulting iron powder mixture has a purity of 93%, and the iron powder reduction rate is increased from 77% to 94%.

[0031] Example 18, the steps are the same as in Example 14. The amount of ferrosilicon powder is 60 kg, the grade of the resulting iron powder mixture is 93%, and the iron powder reduction rate is increased from 77% to 94%.

[0032] Example 19 follows the same steps as Example 14. The amount of ferrosilicon powder is 80 kg, the resulting iron powder mixture has a purity of 93%, and the iron powder reduction rate is increased from 77% to 94%.

[0033] Example 20 follows the same steps as Example 14. The amount of ferrosilicon powder used is 100 kg, the resulting iron powder mixture has a purity of 93%, and the iron powder reduction rate is increased from 77% to 95%.

[0034] Example 21 follows the same steps as Example 14. The amount of ferrosilicon powder used is 200 kg, the resulting iron powder mixture has a purity of 93%, and the iron powder reduction rate is increased from 77% to 95%.

[0035] Example 22, the steps are the same as in Example 17. The reduced carbon is 800 kg (containing 400 kg of graphite powder), and ring formation was found inside the rotary kiln after 45 days of continuous operation.

[0036] Example 23 follows the same steps as Example 17. In this example, 1200 kg of reduced carbon contains 600 kg of graphite powder, and no ring formation occurs after 90 days of continuous operation of the rotary kiln.

[0037] Example 24, all steps are the same as in Example 17. The reduced carbon is 1800 kg (containing 900 kg of graphite powder), and no ring formation is produced after the rotary kiln has been running continuously for 100 days.

[0038] Comparative Example 1: The steps were the same as in Example 17. In this example, 1200 kg of reduced carbon contained 0 kg of graphite powder, and ring formation was observed inside the rotary kiln after 7 days of continuous operation.

[0039] Comparative Example 2: The steps were the same as in Example 17. In this example, 1200 kg of reduced carbon contained 200 kg of graphite powder. After the rotary kiln was run continuously for 15 days, ring formation was observed inside the kiln.

[0040] Comparative Example 3: The steps were the same as in Example 17. In this example, 1200 kg of reduced carbon contained 400 kg of graphite powder. After the rotary kiln was run continuously for 30 days, ring formation was observed inside the kiln.

[0041] In the above embodiments, the purity of the calcium fluoride is ≥80%, the purity of the calcium oxide is ≥85%, the purity of the sodium carbonate is ≥90%, the purity of the cryolite is ≥90%, and the purity of the graphite powder is ≥90%.

Claims

1. A method for extracting iron from red mud, comprising roasting, ball milling, and magnetic separation, characterized in that... The method is as follows: 1) Mix red mud, calcium fluoride, calcium oxide, sodium carbonate, cryolite, and reduced carbon in a mass ratio of 100:0~3:0.1~5:0.1~5:0.1~5:8~18, form pellets, and feed them into a reduction furnace. Heat the mixture to 1100~1450℃, hold it at that temperature for 0.5~4h, and then cool it to obtain a blocky ferrosilicon mixture. The reduced carbon is composed of graphite powder and semi-coke, or a mixture of graphite powder and coal, with a carbon content ≥85% and a graphite powder content >50%; the purity of the calcium fluoride is ≥80%, the purity of the calcium oxide is ≥85%, the purity of the sodium carbonate is ≥90%, the purity of the cryolite is ≥90%, and the purity of the graphite powder is ≥90%. 2) The blocky ferrosilicon mixture is ball-milled into powder; 3) Magnetic separation is used to extract iron from the powder.

2. The method for extracting iron from red mud according to claim 1, characterized in that: The mass ratio of red mud, calcium fluoride, calcium oxide, sodium carbonate, cryolite, and reduced carbon is 100:0.5:2:2:2:

12.

3. The method for extracting iron from red mud according to claim 1, characterized in that: It also includes ferrosilicon powder, red mud, calcium fluoride, calcium oxide, sodium carbonate, cryolite, reduced carbon, and ferrosilicon powder in a mass ratio of 100:0~3:0.1~5:0.1~5:0.1~5:8~18:0.1~2, wherein the purity of the ferrosilicon powder is ≥95%.

4. The method for extracting iron from red mud according to claim 3, characterized in that: The mass ratio of red mud, calcium fluoride, calcium oxide, sodium carbonate, cryolite, reduced carbon, and ferrosilicon powder is 100:0.5:2:2:2:12:0.

5.

5. The method for extracting iron from red mud according to any one of claims 1 to 4, characterized in that: The heat treatment temperature is 1350℃ and the holding time is 1 hour.