Electrolytic aluminum roasting process
Bauxite ore is treated through ultrasonic assisted crushing and grinding, and combined with sodium hydroxide digestion and roasting processes, the problems of low extraction rate and low purity in traditional bauxite roasting processes are solved, and efficient and green aluminum oxide production is achieved.
Patent Information
- Application Number
- CN202411824494.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-12
- Publication Date
- 2025-03-18
AI Technical Summary
In the traditional bauxite roasting process, the extraction rate of aluminum oxides and the purity of the product are problems.
The bauxite ore is treated with ultrasonic assisted crushing and grinding, and mixed with sodium hydroxide for digestion reaction. Through centrifugation, ultrafiltration and calcination steps, an aluminum oxide product is formed.
It improves the yield and quality of aluminum oxide, reduces heat loss, and achieves energy-saving and green production.
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of electrolytic aluminum, and in particular to an electrolytic aluminum roasting process. Background Art
[0002] The electrolytic aluminum roasting process is one of the most critical links in the aluminum smelting process, which mainly involves the processing of bauxite and the extraction of aluminum. The main component of bauxite is hydrated aluminum oxide (Al2O 3· nH2O), after roasting, the moisture in the bauxite ore can be removed by high temperature, so that the aluminum cubic hydroxide is converted into soluble aluminate, and then aluminum oxide is extracted through oxidation-reduction processes. The extraction rate and purity of aluminum oxide are affected by the processing technology of bauxite and determine the quality of subsequent aluminum oxide electrolysis products. Therefore, how to efficiently convert bauxite into aluminum oxide is an important link in the development and utilization of aluminum ore. Summary of the invention
[0003] The purpose of the present invention is to solve the problems of low extraction rate of aluminum oxide and low product purity in the traditional extraction of aluminum oxide by roasting bauxite.
[0004] The present invention is achieved through the following technical solutions:
[0005] The present invention provides an electrolytic aluminum roasting process, comprising the following steps:
[0006] S1 collects bauxite, crushes it with ultrasound assistance, and then grinds it to obtain bauxite ore; then mixes the bauxite ore with sodium hydroxide, heats and pressurizes it, and performs a digestion reaction to obtain a mixed bauxite slurry;
[0007] S2 centrifuges and ultrafilters the mixed bauxite slurry to separate solid precipitates; then cools and adjusts the pH value, and allows the mixture to stand to obtain aluminum hydroxide precipitates;
[0008] S3 roasts the aluminum hydroxide precipitate to form an aluminum oxide product.
[0009] Preferably, the digestion reaction is carried out by heating to 150-250° C. and pressurizing to 0.3-0.8 MPa.
[0010] Preferably, the temperature is lowered to 60-80° C., the pH value is adjusted to 6-8, and the mixture is allowed to stand for 1-2 hours.
[0011] Preferably, the calcination temperature is 950-1000° C. and the calcination time is 2-3 h.
[0012] Preferably, the hot gas generated by the roasting in step 3 is transported to the heating and pressurizing process in step 1 for heat recycling.
[0013] Preferably, in step S1, during the digestion reaction, an organic acid and / or a fluoride is also added.
[0014] Preferably, the organic acid comprises one or more of citric acid, oxalic acid, acetic acid, lactic acid or succinic acid.
[0015] Preferably, the amount of organic acid added is 0.5-5% of the total mass of bauxite.
[0016] Preferably, the amount of fluoride added is 0.5-2% of the total mass of the bauxite.
[0017] The technical solution of the present invention has the following beneficial effects:
[0018] The electrolytic aluminum roasting process proposed in the present invention can extract and convert aluminum from bauxite into aluminum oxide to a greater extent, that is, improve the yield and quality of aluminum oxide. Specifically, by using ultrasonic-assisted crushing and grinding, the bauxite raw material is made into a granular bauxite ore with uniform and fine particle size, so that it can be fully combined with sodium hydroxide and an added organic acid, thereby improving the solubility of aluminum in the digestion system, so that it can be more fully and efficiently separated and extracted from the raw material of the earth ore; combined with the subsequent specific roasting temperature and time, the aluminum hydroxide can be fully dehydrated and converted into aluminum oxide, and in this process, the excessive decomposition of aluminum oxide can also be avoided; in addition, in the multi-step heating process, the roasting hot air in the high-temperature section is concentratedly transported to the digestion process in the low-temperature section, which can greatly reduce the heat loss and achieve energy-saving and green production. DETAILED DESCRIPTION
[0019] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. Where specific conditions are not specified in the embodiments, they are carried out under conventional conditions or conditions recommended by the manufacturer; where the manufacturers of the instruments, equipment, reagents and raw materials used are not specified, they are all conventional products that can be purchased commercially.
[0020] The present invention provides an electrolytic aluminum roasting process, comprising the following steps:
[0021] (1) Preparation of bauxite slurry:
[0022] Bauxite is collected from the mine, crushed with ultrasound assistance, and then ground and finely crushed to obtain bauxite with a particle size of less than 2.5 cm;
[0023] Bauxite ore is mixed with sodium hydroxide at a mass ratio of 1:1.5-3, placed in a reactor, heated to 150-250°C, pressurized to 0.3-0.8MPa, and digested to form a mixed bauxite slurry of soluble aluminum hydroxide and insoluble impurities.
[0024] When the digestion reaction is carried out under heating and pressure in the reactor, an organic acid and a fluoride may be added. The organic acid may be selected from citric acid, oxalic acid, acetic acid, lactic acid or succinic acid, and the fluoride may be selected from sodium fluoride, which may help to increase the solubility of aluminum and promote its extraction from bauxite.
[0025] Specifically, the amount of organic acid added is 0.5-5% of the total mass of bauxite, and the amount of fluoride added is 0.5-2% of the total mass of bauxite; when citric acid is selected as the organic acid, the amount of citric acid used is 1-5wt%; when oxalic acid is selected as the organic acid, the amount of oxalic acid used is 0.5-3wt%; when acetic acid is selected as the organic acid, the amount of acetic acid used is 1-4wt%; when lactic acid is selected as the organic acid, the amount of lactic acid used is 1-5wt%; when succinic acid is selected as the organic acid, the amount of succinic acid used is 0.5-2wt%.
[0026] (2) Separation and precipitation:
[0027] The mixed bauxite slurry is separated by a high-efficiency centrifuge, and the solid precipitate is separated by ultrafiltration; then the temperature is cooled to below 80°C, preferably about 60-80°C, and the pH value of the slurry is adjusted to 6-8 with sodium hydroxide solution or dilute hydrochloric acid. After reaching the above temperature and pH value, the slurry is kept standing for 1-2 hours to promote the full precipitation of aluminum hydroxide and improve the recovery rate and yield of aluminum hydroxide crystals.
[0028] (3) Calcination:
[0029] A rotary kiln is used to roast the aluminum hydroxide precipitate at a temperature of 950-1000°C for 2-3 hours to ensure that the aluminum hydroxide is completely dehydrated and converted into aluminum oxide, and to avoid excessive decomposition of the aluminum oxide. During this period, the hot gas after roasting is collected and used to heat the bauxite, achieving efficient use of energy and reducing the impact and harm to the environment.
[0030] Example 1
[0031] Step 1: Collect bauxite from the mine, first use ultrasonic assisted crushing, then grind and crush, and screen through a mesh plate with an aperture of 2.5 cm to obtain bauxite ore with a particle size of less than 2.5 cm, and pile it into 10 kg portions. The aluminum content of each pile of bauxite ore is measured, and high-grade bauxite with an aluminum content of more than 58wt% is selected as raw material for standby use.
[0032] Step 2: Place the above bauxite in a high-pressure reactor, add 20kg of sodium hydroxide, then add 3 times the volume of pure water, stir evenly, then add 220g of oxalic acid and 150g of sodium fluoride, mix well, heat to 220°C, control the pressure in the reactor to 0.5±0.1MPa, and digest for 3.5h. During this period, stir the materials in the reactor every 30min to finally obtain a mixed bauxite slurry.
[0033] Step 3: Use a high-efficiency centrifuge to separate the mixed bauxite slurry, and use ultrafiltration to separate the solid precipitate; then cool it to 70±5°C, and adjust the pH value of the slurry to 7.2 by adding sodium hydroxide solution, and then keep the slurry standing for 2 hours to precipitate aluminum hydroxide crystals.
[0034] Step 4: Place the precipitated sodium hydroxide solid in a rotary kiln, heat to 980±10°C, roast for 2.75h, and cool to room temperature to obtain an aluminum oxide product.
[0035] Example 2
[0036] Step 1: Collect bauxite from the mine, first use ultrasonic assisted crushing, then grind and crush, and screen through a mesh plate with an aperture of 2.5 cm to obtain bauxite ore with a particle size of less than 2.5 cm, and pile it into 10 kg portions. The aluminum content of each pile of bauxite ore is measured, and high-grade bauxite with an aluminum content of more than 58wt% is selected as raw material for standby use.
[0037] Step 2: Place the above bauxite in a high-pressure reactor, add 20kg of sodium hydroxide, then add 3 times the volume of pure water, stir evenly, then add 80g of oxalic acid and 65g of sodium fluoride, mix well, heat to 220°C, control the pressure in the reactor to 0.5±0.1MPa, and digest for 3.5h. During this period, stir the materials in the reactor every 30min to finally obtain a mixed bauxite slurry.
[0038] Step 3: Use a high-efficiency centrifuge to separate the mixed bauxite slurry, and use ultrafiltration to separate the solid precipitate; then cool it to 70±5°C, and adjust the pH value of the slurry to 7.2 by adding sodium hydroxide solution, and then keep the slurry standing for 2 hours to precipitate aluminum hydroxide crystals.
[0039] Step 4: Place the precipitated sodium hydroxide solid in a rotary kiln, heat to 980±10°C, roast for 2.75h, and cool to room temperature to obtain an aluminum oxide product.
[0040] Example 3
[0041] Step 1: Collect bauxite from the mine, first use ultrasonic assisted crushing, then grind and crush, and screen through a mesh plate with an aperture of 2.5 cm to obtain bauxite ore with a particle size of less than 2.5 cm, and pile it into 10 kg portions. The aluminum content of each pile of bauxite ore is measured, and high-grade bauxite with an aluminum content of more than 58wt% is selected as raw material for standby use.
[0042] Step 2: Place the above bauxite in a high-pressure reactor, add 16 kg of sodium hydroxide, then add 3 times the volume of pure water, stir evenly, then add 82 g of oxalic acid and 65 g of sodium fluoride, mix well, heat to 220 ° C, control the pressure in the reactor to 0.5 ± 0.1 MPa, digest for 3.5 hours, during which the materials in the reactor are stirred every 30 minutes to finally obtain a mixed bauxite slurry.
[0043] Step 3: Use a high-efficiency centrifuge to separate the mixed bauxite slurry, and use ultrafiltration to separate the solid precipitate; then cool it to 70±5°C, and adjust the pH value of the slurry to 7.2 by adding sodium hydroxide solution, and then keep the slurry standing for 2 hours to precipitate aluminum hydroxide crystals.
[0044] Step 4: Place the precipitated sodium hydroxide solid in a rotary kiln, heat to 980±10°C, roast for 2.75h, and cool to room temperature to obtain an aluminum oxide product.
[0045] Example 4
[0046] Step 1: Collect bauxite from the mine, first use ultrasonic assisted crushing, then grind and crush, and screen through a mesh plate with an aperture of 2.5 cm to obtain bauxite ore with a particle size of less than 2.5 cm, and pile it into 10 kg portions. The aluminum content of each pile of bauxite ore is measured, and high-grade bauxite with an aluminum content of more than 58wt% is selected as raw material for standby use.
[0047] Step 2: Place the above bauxite in a high-pressure reactor, add 20kg of sodium hydroxide, then add 3 times the volume of pure water, stir evenly, then add 250g of citric acid and 150g of sodium fluoride, mix well, heat to 220°C, control the pressure in the reactor to 0.5±0.1MPa, and digest for 3.5h. During this period, stir the materials in the reactor every 30min to finally obtain a mixed bauxite slurry.
[0048] Step 3: Use a high-efficiency centrifuge to separate the mixed bauxite slurry, and use ultrafiltration to separate the solid precipitate; then cool it to 70±5°C, and adjust the pH value of the slurry to 7.2 by adding sodium hydroxide solution, and then keep the slurry standing for 2 hours to precipitate aluminum hydroxide crystals.
[0049] Step 4: Place the precipitated sodium hydroxide solid in a rotary kiln, heat to 980±10°C, roast for 2.75h, and cool to room temperature to obtain an aluminum oxide product.
[0050] Example 5
[0051] Step 1: Collect bauxite from the mine, first use ultrasonic assisted crushing, then grind and crush, and screen through a mesh plate with an aperture of 2.5 cm to obtain bauxite ore with a particle size of less than 2.5 cm, and pile it into 10 kg portions. The aluminum content of each pile of bauxite ore is measured, and high-grade bauxite with an aluminum content of more than 58wt% is selected as raw material for standby use.
[0052] Step 2: Place the above bauxite in a high-pressure reactor, add 20kg of sodium hydroxide, then add 3 times the volume of pure water, stir evenly, then add 200g of acetic acid and 150g of sodium fluoride, mix well, heat to 220°C, control the pressure in the reactor to 0.5±0.1MPa, and digest for 3.5h. During this period, stir the materials in the reactor every 30min to finally obtain a mixed bauxite slurry.
[0053] Step 3: Use a high-efficiency centrifuge to separate the mixed bauxite slurry, and use ultrafiltration to separate the solid precipitate; then cool it to 70±5°C, and adjust the pH value of the slurry to 7.2 by adding sodium hydroxide solution, and then keep the slurry standing for 2 hours to precipitate aluminum hydroxide crystals.
[0054] Step 4: Place the precipitated sodium hydroxide solid in a rotary kiln, heat to 980±10°C, roast for 2.75h, and cool to room temperature to obtain an aluminum oxide product.
[0055] Example 6
[0056] Step 1: Collect bauxite from the mine, first use ultrasonic assisted crushing, then grind and crush, and screen through a mesh plate with an aperture of 2.5 cm to obtain bauxite ore with a particle size of less than 2.5 cm, and pile it into 10 kg portions. The aluminum content of each pile of bauxite ore is measured, and high-grade bauxite with an aluminum content of more than 58wt% is selected as raw material for standby use.
[0057] Step 2: Place the above bauxite in a high-pressure reactor, add 20kg of sodium hydroxide, then add 3 times the volume of pure water, stir evenly, then add 150g of succinic acid and 150g of sodium fluoride, mix well, heat to 220°C, control the pressure in the reactor to 0.5±0.1MPa, and digest for 3.5h. During this period, stir the materials in the reactor every 30min to finally obtain a mixed bauxite slurry.
[0058] Step 3: Use a high-efficiency centrifuge to separate the mixed bauxite slurry, and use ultrafiltration to separate the solid precipitate; then cool it to 70±5°C, and adjust the pH value of the slurry to 7.2 by adding sodium hydroxide solution, and then keep the slurry standing for 2 hours to precipitate aluminum hydroxide crystals.
[0059] Step 4: Place the precipitated sodium hydroxide solid in a rotary kiln, heat to 980±10°C, roast for 2.75h, and cool to room temperature to obtain an aluminum oxide product.
[0060] Example 7
[0061] Step 1: Collect bauxite from the mine, first use ultrasonic assisted crushing, then grind and crush, and screen through a mesh plate with an aperture of 2.5 cm to obtain bauxite ore with a particle size of less than 2.5 cm, and pile it into 10 kg portions. The aluminum content of each pile of bauxite ore is measured, and high-grade bauxite with an aluminum content of more than 55wt% is selected as raw material for standby use.
[0062] Step 2: Place the above bauxite in a high-pressure reactor, add 18.6 kg of sodium hydroxide, then add 3 times the volume of pure water, stir evenly, then add 200 g of oxalic acid and 135 g of sodium fluoride, mix well, heat to 220 ° C, control the pressure in the reactor to 0.5 ± 0.1 MPa, digest for 3.5 hours, during which the materials in the reactor are stirred every 30 minutes to finally obtain a mixed bauxite slurry.
[0063] Step 3: Use a high-efficiency centrifuge to separate the mixed bauxite slurry, and use ultrafiltration to separate the solid precipitate; then cool it to 70±5°C, and adjust the pH value of the slurry to 7.2 by adding sodium hydroxide solution, and then keep the slurry standing for 2 hours to precipitate aluminum hydroxide crystals.
[0064] Step 4: Place the precipitated sodium hydroxide solid in a rotary kiln, heat to 980±10°C, roast for 2.75h, and cool to room temperature to obtain an aluminum oxide product.
[0065] Example 8
[0066] Step 1: Collect bauxite from the mine, first use ultrasonic assisted crushing, then grind and crush, and screen through a mesh plate with an aperture of 2.5 cm to obtain bauxite ore with a particle size of less than 2.5 cm, and pile it into 10 kg portions. The aluminum content of each pile of bauxite ore is measured, and high-grade bauxite with an aluminum content of more than 58wt% is selected as raw material for standby use.
[0067] Step 2: Place the above bauxite in a high-pressure reactor, add 20kg of sodium hydroxide, then add 3 times the volume of pure water, stir evenly, then add 220g of oxalic acid and 150g of sodium fluoride, mix well, heat to 220°C, control the pressure in the reactor to 0.5±0.1MPa, and digest for 3.5h. During this period, stir the materials in the reactor every 30min to finally obtain a mixed bauxite slurry.
[0068] Step 3: Use a high-efficiency centrifuge to separate the mixed bauxite slurry, and use ultrafiltration to separate the solid precipitate; then cool it to 70±5°C, and adjust the pH value of the slurry to 7.2 by adding sodium hydroxide solution, and then keep the slurry standing for 2 hours to precipitate aluminum hydroxide crystals.
[0069] Step 4: Place the precipitated sodium hydroxide solid in a rotary kiln, heat to 955±5°C, roast for 3h, and cool to room temperature to obtain an aluminum oxide product.
[0070] Example 9
[0071] Step 1: Collect bauxite from the mine, first use ultrasonic assisted crushing, then grind and crush, and screen through a mesh plate with an aperture of 2.5 cm to obtain bauxite ore with a particle size of less than 2.5 cm, and pile it into 10 kg portions. The aluminum content of each pile of bauxite ore is measured, and high-grade bauxite with an aluminum content of more than 58wt% is selected as raw material for standby use.
[0072] Step 2: Place the above bauxite in a high-pressure reactor, add 20kg of sodium hydroxide, then add 3 times the volume of pure water, stir evenly, then add 220g of oxalic acid and 150g of sodium fluoride, mix well, heat to 220°C, control the pressure in the reactor to 0.5±0.1MPa, and digest for 3.5h. During this period, stir the materials in the reactor every 30min to finally obtain a mixed bauxite slurry.
[0073] Step 3: Use a high-efficiency centrifuge to separate the mixed bauxite slurry, and use ultrafiltration to separate the solid precipitate; then cool it to 70±5°C, and adjust the pH value of the slurry to 7.2 by adding sodium hydroxide solution, and then keep the slurry standing for 2 hours to precipitate aluminum hydroxide crystals.
[0074] Step 4: Place the precipitated sodium hydroxide solid in a rotary kiln, heat to 995±5°C, roast for 2.2h, and cool to room temperature to obtain an aluminum oxide product.
[0075] Comparative Example 1
[0076] Step 1: Collect bauxite from the mine, first use ultrasonic assisted crushing, then grind and crush, and screen through a mesh plate with an aperture of 2.5 cm to obtain bauxite ore with a particle size of less than 2.5 cm, and pile it into 10 kg portions for use as raw materials.
[0077] Step 2: Place the above bauxite in a high-pressure reactor, add 20kg of sodium hydroxide, then add 3 times the volume of pure water, stir evenly, heat to 220°C, control the pressure in the reactor to 0.5±0.1MPa, and digest for 3.5h. During this period, stir the materials in the reactor every 30min to finally obtain bauxite slurry.
[0078] Step 3: Use a high-efficiency centrifuge to separate the bauxite slurry, and use ultrafiltration to separate the solid precipitate; then cool it to 70±5°C, keep the slurry standing for 2 hours, and precipitate aluminum hydroxide crystals.
[0079] Step 4: Place the precipitated sodium hydroxide solid in a rotary kiln, heat to 900±10°C, roast for 5 hours, and cool to room temperature to obtain an aluminum oxide product.
[0080] Test example
[0081] Samples: Examples 1-9, Comparative Example 1
[0082] The aluminum oxide samples prepared in the above Examples 1-9 and Comparative Example 1 are all prepared by separating, extracting and roasting 10 kg of bauxite. By calculating the product yield, the extraction degree and effect of different production processes on aluminum ore can be compared. The mass of the raw materials and products is measured, and the yield is calculated. The aluminum content in the product is measured by weight method. The results are shown in Table 1 below:
[0083] Table 1 Yield determination and calculation results of different samples
[0084] Aluminum oxide samples Raw material (kg) Product (kg) Yield (%) Aluminum content (%) Example 1 10.06 9.48 94.23 99.77 Example 2 10.21 9.23 90.40 99.72 Example 3 10.03 8.83 88.04 99.73 Example 4 10.45 9.77 93.49 99.69 Example 5 10.40 9.72 93.46 99.75 Example 6 10.25 9.64 94.05 99.70 Example 7 10.32 9.27 89.83 99.61 Example 8 10.19 9.20 90.28 99.68 Example 9 10.22 9.28 90.80 99.70 Comparative Example 1 10.26 8.59 83.72 99.13
[0085] As shown in Table 1 above, it can be seen that the yield of the aluminum oxide samples prepared in Examples 1 to 9 is significantly higher than that of the aluminum oxide samples prepared in Comparative Example 1, and the aluminum content of the aluminum oxide samples prepared in Examples 1 to 9 is higher, that is, the product purity is higher. Therefore, it can be explained that the electrolytic aluminum roasting process proposed in the present invention can improve the yield and product quality of aluminum oxide in the process of extracting and roasting aluminum oxide from bauxite, and can better meet the needs of downstream processing production and product use.
[0086] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.
Claims
1. An electrolytic aluminum roasting process, characterized in that: The steps include: S1 collects bauxite, crushes it with ultrasound assistance, and then grinds it to obtain bauxite ore; then mixes the bauxite ore with sodium hydroxide, heats and pressurizes it, and performs a digestion reaction to obtain a mixed bauxite slurry; S2 centrifuges and ultrafilters the mixed bauxite slurry to separate solid precipitates; then cools and adjusts the pH value, and allows the mixture to stand to obtain aluminum hydroxide precipitates; S3 roasts the aluminum hydroxide precipitate to form an aluminum oxide product.
2. The electrolytic aluminum roasting process according to claim 1, characterized in that: In step S1, the temperature is heated to 150-250° C. and the pressure is increased to 0.3-0.8 MPa to perform a digestion reaction.
3. The electrolytic aluminum roasting process according to claim 1, characterized in that: In step S2, the temperature is lowered to 60-80°C, the pH value is adjusted to 6-8, and the mixture is allowed to stand for 1-2 hours.
4. The electrolytic aluminum roasting process according to claim 1, characterized in that: In step S3, the calcination temperature is 950-1000° C. and the calcination time is 2-3 hours.
5. The electrolytic aluminum roasting process according to claim 1, characterized in that: The hot gas generated by the roasting in step 3 is transported to the heating and pressurizing process in step 1 for heat recycling.
6. The electrolytic aluminum roasting process according to any one of claims 1 to 5, characterized in that: In step S1, during the digestion reaction, an organic acid and / or a fluoride is also added.
7. The electrolytic aluminum roasting process according to claim 6, characterized in that: The organic acid includes one or more of citric acid, oxalic acid, acetic acid, lactic acid or succinic acid.
8. The electrolytic aluminum roasting process according to claim 7, characterized in that: The amount of organic acid added is 0.5-5% of the total mass of bauxite.
9. The electrolytic aluminum roasting process according to claim 6, characterized in that: The amount of fluoride added is 0.5-2% of the total mass of bauxite.