A method for upgrading bauxite by chemical beneficiation

Abstract

The application provides a method for upgrading bauxite by chemical beneficiation, which comprises the following steps: refining bauxite to obtain bauxite particles, and performing grinding and classification on the bauxite particles to obtain concentrate particles with a particle size of greater than or equal to 250 microns, middling particles with a particle size of greater than 150 microns and less than 250 microns, and tailing particles with a particle size of less than or equal to 150 microns; repeatedly performing grinding and classification on the obtained concentrate particles to obtain first concentrate; mixing the obtained middling particles and tailing particles to perform refining, and mixing the refined particles with an alkaline solution to perform a hydrothermal reaction, and then performing solid-liquid separation to obtain second concentrate and a silicon-containing solution; mixing a calcium agent with the obtained silicon-containing solution, and performing solid-liquid separation to obtain a liquid and a silicon-containing solid. The method provided by the application can be used to process bauxite with a low grade, and two kinds of concentrate with an aluminum-silicon ratio of greater than or equal to 5.07 and greater than or equal to 4.5 can be obtained, no impurity phase and harmful chemical reagent is introduced in the reaction, and the obtained liquid product can be recycled and used to synchronously prepare a silicon-based carbon sink material.

Description

Technical Field

[0001] This invention belongs to the field of bauxite beneficiation technology and relates to a method for chemical beneficiation and upgrading of bauxite. Background Technology

[0002] Bauxite is a crucial raw material for the aluminum materials industry, comprising minerals such as gibbsite and boehmite. Among these, boehmite-type bauxite is characterized by high aluminum and high silicon content, with most being low- to medium-grade bauxite having an aluminum-to-silicon ratio (A / S) of less than 4. Extensive research and practice have aimed to improve bauxite grade through flotation desilication, followed by the economical Bayer process for alumina production. This method has indeed effectively improved bauxite resource utilization. However, with the rapid development of the alumina industry, the grade of bauxite being processed has decreased from an A / S ratio greater than 5 to below 3.5, and this rate is expected to continue to decline in the coming years. Given the dwindling availability of high-grade bauxite resources and the need for energy conservation, emission reduction, and lower production costs, the technology for the economical and rational utilization of low- to medium-grade bauxite resources has become a significant industry demand.

[0003] Numerous studies have been conducted on bauxite beneficiation. For example, CN101927215B discloses a bauxite direct flotation method, the flotation process of which includes grinding, classification, and direct flotation including at least one scavenging step; CN102755925A discloses a separation method suitable for medium- and low-grade bauxite, capable of processing raw ore with an aluminum-silicon ratio of 4 or higher; CN102294304A discloses a bauxite flotation method. These disclosed beneficiation methods can only process raw ore with an aluminum-silicon ratio as low as 4, which no longer meets practical production requirements.

[0004] CN108554594A discloses a method for beneficiating low-grade bauxite. This method involves controlled grinding to crush or ball-mill monohydrate gibbsite-type bauxite with an A / S ratio less than 3 to obtain bauxite powder. Then, through classification, some fine particles are separated out; these separated fine particles are the low A / S ratio product, with an A / S ratio less than 1.7. The remaining bauxite powder has an A / S ratio greater than 3. While this method can process bauxite with a low A / S ratio, it requires grinding the raw ore to below 10 micrometers, a process with extremely high energy consumption. Furthermore, the concentrate produced has an A / S ratio not exceeding 4, while the tailings have an A / S ratio as high as 1.7.

[0005] CN101391237A discloses a new process for desilication of bauxite by positive flotation. The method includes grinding, classification, flotation and roughing underflow classification and regrinding, etc. The process is complicated, the auxiliary materials are redundant, and the addition of flotation reagents makes it difficult to utilize the tailings, which cause environmental problems due to long-term accumulation.

[0006] CN101439317A and CN102806146A both disclose a method for pre-desiliconization in bauxite beneficiation. These two methods have relatively simple processes, but they also have the problem of difficult utilization of tailings, and the aluminum-silicon ratio of the raw ore that can be processed is above 3.5.

[0007] Therefore, in view of the shortcomings of existing technologies, there is a need to provide a method for chemical beneficiation and upgrading of bauxite. Summary of the Invention

[0008] The purpose of this invention is to provide a method for chemical beneficiation and upgrading of bauxite, which can effectively improve the recovery rate of medium and low grade bauxite resources, reduce production costs, solve potential environmental problems, and create huge economic value.

[0009] To achieve this objective, the present invention adopts the following technical solution:

[0010] This invention provides a method for chemical beneficiation and upgrading of bauxite, the method comprising the following steps:

[0011] (1) Refine bauxite to obtain bauxite particles;

[0012] (2) Grind and classify the bauxite particles obtained in step (1) to obtain concentrate particles with a particle size ≥ 250 μm, medium ore particles with a particle size > 150 μm and < 250 μm, and tailings particles with a particle size ≤ 150 μm; repeat grinding and classification of the obtained concentrate particles to obtain the first concentrate; refine the obtained medium ore particles and tailings particles to obtain mixed ore particles;

[0013] (3) Mix the alkaline solution with the mixed mineral particles obtained in step (2) to obtain a mixed slurry;

[0014] (4) The mixed slurry obtained in step (3) is subjected to hydrothermal reaction, and solid-liquid separation is performed after the reaction to obtain the second concentrate and silicon-containing solution;

[0015] (5) Mix the calcium agent with the silicon-containing solution obtained in step (4), and perform solid-liquid separation after mixing to obtain a liquid and a silicon-containing solid.

[0016] This invention involves selectively grinding and classifying low- to medium-grade bauxite particles to obtain a first concentrate, middlings, and tailings. The resulting middlings and tailings are then refined to obtain mixed particles, which are then mixed with an alkaline solution and subjected to a hydrothermal reaction for selective leaching and desilication to obtain a second concentrate. The desilication solution is then mixed with a calcium agent and separated to obtain silicon-containing solids and liquids, respectively. The method provided by this invention ensures high concentrate grade and recovery rate; moreover, the method is simple, widely applicable, and easy to promote.

[0017] Preferably, the refining method in step (1) includes crushing and / or ball milling.

[0018] Preferably, in step (1), the mass percentage of particles with a diameter of 0.5-2 cm in the bauxite particles is 20-100 wt% of the bauxite particles, for example, it can be 20 wt%, 30 wt%, 40 wt%, 50 wt%, 60 wt%, 70 wt%, 80 wt%, 90 wt%, or 100 wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0019] Pre-refining bauxite helps with subsequent grinding. Direct grinding can cause the silica-rich and alumina-rich phases to become intertwined and difficult to separate, while also increasing grinding energy consumption and reducing efficiency.

[0020] Preferably, the grinding method in step (2) includes dry grinding and / or wet grinding.

[0021] For example, the grinding method includes any one of ball milling, rod milling, pebble milling or autogenous milling.

[0022] Preferably, the grinding in step (2) is carried out using a mill.

[0023] Preferably, the grinding time is 1-30 min, for example, it can be 1 min, 10 min, 15 min, 20 min or 30 min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0024] Choosing the right grinding time can ensure sufficient separation of minerals. If the grinding time is too short, the minerals will not be separated sufficiently; if the grinding time is too long, the mineral particles will be too small, making them difficult to separate, and the energy consumption will be high.

[0025] Preferably, the rotational speed of the mill is 5-600 r / min, for example, it can be 5 r / min, 100 r / min, 200 r / min, 400 r / min or 600 r / min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0026] Preferably, the media filling rate of the mill is 20-60%, for example, it can be 20%, 30%, 40%, 50% or 60%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0027] Preferably, the filling rate of the mill is 30-70%, for example, it can be 30%, 40%, 50%, 60% or 70%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0028] The selection of mill speed, media filling rate, and filling rate is the result of comprehensive consideration of cost and separation efficiency; too high or too low a value will affect the grinding effect.

[0029] Preferably, the grading method in step (2) includes dry grading and / or wet grading.

[0030] For example, the grading method in step (2) includes any one of screening, wind grading, hydrocyclone grading or chute grading.

[0031] Preferably, the number of repetitions in step (2) is 1-10 times, for example, 1 time, 3 times, 5 times, 7 times or 10 times, but not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 2-5 times.

[0032] This invention improves the separation efficiency of minerals through repeated grinding and classification. If the number of repetitions is too low, the grade difference between tailings, middlings and concentrate will be too small; if the number of repetitions is too high, the energy consumption will be too high and the process will be too long.

[0033] Preferably, the refining method in step (2) includes crushing and / or ball milling.

[0034] Preferably, in the mixed mineral particles described in step (2), the mass percentage of particles with a diameter of less than 150 μm is 50-100 wt% of the mixed mineral particles, for example, it can be 50 wt%, 60 wt%, 70 wt%, 80 wt%, 90 wt% or 100 wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0035] Preferably, the alkaline solution in step (3) includes sodium hydroxide solution and / or potassium hydroxide solution.

[0036] Preferably, the concentration of the alkaline solution in step (3) is 0.05-2.5 mol / L, for example, it can be 0.05 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L or 2.5 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 0.1-1 mol / L.

[0037] The preferred concentration of the alkaline solution used in this invention can better promote the dissolution reaction. When the concentration of the alkaline solution is too low, the subsequent reaction is difficult to complete. When the concentration of the alkaline solution is too high, other products will be generated during the reaction, reducing the aluminum recovery rate.

[0038] Preferably, the solid-liquid ratio of the mixed mineral particles to the alkaline solution in step (3) is 1:(10-40), for example, it can be 1:10, 1:20, 1:30 or 1:40, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable. Preferably, it is 1:(15-30). The unit of the solid-liquid ratio is g / mL.

[0039] The solid-liquid ratio is a key factor. An appropriate solid-liquid ratio is beneficial for the selective leaching of silicon and the subsequent recovery of alkaline solution. When the solid-liquid ratio is too high, it is difficult to mix the aluminum-rich phase and the alkaline solution evenly. At the same time, if the silicon content that the solution can accommodate is too low, sodium silicon slag will form, making subsequent separation difficult. When the solid-liquid ratio is too low, it will cause unnecessary energy consumption.

[0040] Preferably, the temperature of the hydrothermal reaction in step (4) is 100-250℃, for example, it can be 100℃, 150℃, 200℃ or 250℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 140-220℃.

[0041] If the temperature of the hydrothermal reaction is too low, the reaction kinetics will be insufficient, reducing the dissolution rate of silica; if the temperature is too high, it will increase energy consumption and raise costs.

[0042] Preferably, the hydrothermal reaction time in step (4) is 1-30h, for example, it can be 1h, 10h, 20h, 25h or 30h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 2-10h.

[0043] If the hydrothermal reaction time is too short, the reaction will be incomplete, and many raw materials will not be converted, resulting in waste of raw materials; if the reaction time is too long, it will lead to increased energy consumption and increase the cost of mineral processing.

[0044] The preferred hydrothermal reaction temperature and time of this invention can improve the utilization rate of raw materials, efficiently achieve selective leaching of silicon in bauxite, and at the same time reduce resource waste and energy consumption.

[0045] Preferably, the solid-liquid separation in step (4) is carried out using conventional methods in the art. For example, the solid-liquid separation method may be filtration, centrifugation or sedimentation.

[0046] Preferably, the calcium agent in step (5) includes any one or a combination of at least two of calcium oxide, calcium hydroxide, or calcium sulfate. Typical but non-limiting combinations include a combination of calcium oxide and calcium hydroxide, a combination of calcium hydroxide and calcium sulfate, or a combination of calcium oxide, calcium hydroxide, and calcium sulfate.

[0047] As a preferred technical solution of the present invention, from the perspective of economy and environmental protection, the calcium agent can be industrial raw materials or waste residue with calcium oxide, calcium hydroxide or calcium sulfate as the main components.

[0048] Preferably, the molar ratio of the calcium agent to the silicon dioxide in the silicon-containing solution in step (5) is (0.4-1.5):1, for example, it can be 0.4:1, 0.8:1, 1.0:1, 1.2:1 or 1.5:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably (0.8-1.2):1.

[0049] The preferred molar ratio of calcium agent to silicon dioxide used in this invention enables more efficient utilization of silicon components. When the molar ratio is too low or too high, it will affect the desilication effect of the silicon-containing solution, thereby reducing the quality of the obtained silicon-based carbon sink material.

[0050] Preferably, the initial temperature of mixing in step (5) is 50-95°C, for example, it can be 50°C, 60°C, 70°C, 80°C or 95°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 60-80°C.

[0051] The present invention has the following preferred technical solution: the mixing is carried out using the residual heat of the hydrothermal reaction in step (4).

[0052] Preferably, the mixing time in step (5) is 10-120 min, for example, it can be 10 min, 40 min, 70 min, 100 min or 120 min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 30-60 min.

[0053] The preferred mixing temperature and time of this invention can ensure thorough mixing. If the temperature is too low or the time is too short, it will affect the sedimentation efficiency and the purification effect of the waste liquid. If the temperature is too high or the time is too long, it will reduce the time efficiency.

[0054] Preferably, the solid-liquid separation in step (5) is carried out using conventional methods in the art. For example, the solid-liquid separation method may be filtration, centrifugation or sedimentation.

[0055] Preferably, the liquid obtained in step (5) is reused in step (3).

[0056] In this invention, the solid obtained in step (5) includes silicon-based carbon sink materials.

[0057] The silicon-based carbon sink material obtained by this invention is mainly composed of hydrated calcium silicate. It has the characteristics of low density, high specific surface area, good adsorption performance and high reactivity. It can be used as a general adsorption material, a soil heavy metal solidification and remediation material, and can also be used to improve degraded soils lacking trace elements and promote ecological carbon sink.

[0058] Compared with the prior art, the present invention has the following beneficial effects:

[0059] (1) The method provided by the present invention can process low-grade bauxite to obtain two concentrates with aluminum-silicon ratios of more than 5.07 and more than 4.5, respectively, which fully meets the technical requirements urgently needed for the sustainable development of my country's alumina industry.

[0060] (2) No impurity phases or harmful chemical agents will be introduced during the reaction. The resulting liquid product can be recycled and used to prepare silicon-based carbon sink materials simultaneously.

[0061] (3) After the aluminum-rich phase and silicon-rich phase are separated during the reaction, the aluminum-rich phase is activated in situ, and the surface energy is increased, which can reduce the energy consumption during the subsequent Bayer process dissolution. Detailed Implementation

[0062] The technical solution of the present invention will be further illustrated below through specific embodiments.

[0063] To clearly illustrate the technical solution, in a specific embodiment of the present invention, an inductively coupled plasma mass spectrometer (ICP-OES) is used to determine the content of silicon oxide and aluminum oxide in bauxite and the obtained concentrate, and then the aluminum-silicon ratio (A / S) is calculated.

[0064] Example 1

[0065] This embodiment provides a method for chemical beneficiation and upgrading of bauxite, the method comprising the following steps:

[0066] (a) The Luoyang monohydrate gibbsite type bauxite with an aluminum-silicon ratio (A / S) of 2.5 was crushed to obtain bauxite particles with a particle size of 0.5-2 cm and a content of 80 wt%.

[0067] (b) The bauxite particles obtained in step (a) are ball-milled for 10 min at a mill speed of 300 r / min, with a media filling rate of 30% and a filling rate of 50%. After ball milling, the particles are classified by sieve to obtain concentrate particles with a particle size ≥ 250 μm, medium particles with a particle size > 150 μm and < 250 μm, and tailings particles with a particle size ≤ 150 μm. The concentrate particles are ball-milled three times to obtain the first concentrate. The medium particles and tailings particles obtained by mixing are crushed to obtain mixed mineral particles with a particle size of less than 150 μm and a particle content of 80 wt%.

[0068] (c) A 0.5 mol / L sodium hydroxide solution with a solid-liquid ratio of 1:15 is mixed with the mixed mineral particles obtained in step (b) to obtain a mixed slurry;

[0069] (d) The mixture slurry obtained in step (c) is subjected to hydrothermal reaction in a reactor at a temperature of 180°C for 2 hours. After the reaction, solid and liquid are separated by filtration to obtain a solid and a silicon-containing solution. The solid is washed and dried to obtain a second concentrate.

[0070] (e) When the silicon-containing solution obtained in step (d) is cooled to 80°C, calcium hydroxide and silicon dioxide in the silicon-containing solution are mixed at a molar ratio of 1.0:1. After precipitation for 30 minutes, solid-liquid separation is performed to obtain a liquid and a silicon-containing solid. The liquid is an alkaline solution that can be reused in step (c). The silicon-containing solid is washed and dried to obtain a silicon-based carbon sink material.

[0071] The silicon-based carbon sink material obtained in this embodiment has a silicon activation rate of 85%, a calcium activation rate of 93%, and a water absorption rate of 314%.

[0072] The aluminum-silicon ratios of the first and second concentrates were calculated, and the results are listed in Table 1.

[0073] Example 2

[0074] This embodiment provides a method for chemical beneficiation and upgrading of bauxite, the method comprising the following steps:

[0075] (a) The Luoyang monohydrate gibbsite type bauxite with an aluminum-silicon ratio (A / S) of 2.5 was crushed to obtain bauxite particles with a particle size of 0.5-2 cm and a content of 80 wt%.

[0076] (b) The bauxite particles obtained in step (a) are ball-milled for 30 min at a mill speed of 5 r / min, with a media filling rate of 60% and a filling rate of 30%. After ball milling, the particles are classified by sieve to obtain concentrate particles with a particle size ≥ 250 μm, medium particles with a particle size > 150 μm and < 250 μm, and tailings particles with a particle size ≤ 150 μm. The concentrate particles are ball-milled repeatedly 10 times to obtain the first concentrate. The medium particles and tailings particles obtained by mixing are crushed to obtain mixed mineral particles with a particle size of less than 150 μm and a particle content of 80 wt%.

[0077] (c) Mix a 1 mol / L potassium hydroxide solution with the mixed mineral particles obtained in step (b) at a solid-liquid ratio of 1:20 to obtain a mixed slurry;

[0078] (d) The mixture slurry obtained in step (c) is subjected to hydrothermal reaction in a reactor at a temperature of 220°C for 5 hours. After the reaction, solid and liquid are separated by filtration to obtain a solid and a silicon-containing solution. The solid is washed and dried to obtain a second concentrate.

[0079] (e) When the silicon-containing solution obtained in step (d) is cooled to 70°C, lime is mixed with the silicon-containing solution at a molar ratio of calcium oxide to silicon dioxide in the silicon-containing solution of 0.8:1. After precipitation for 45 minutes, solid-liquid separation is performed to obtain a liquid and a silicon-containing solid. The liquid is an alkaline solution that can be reused in step (c). The silicon-containing solid is washed and dried to obtain a silicon-based carbon sink material.

[0080] The silicon-based carbon sink material obtained in this embodiment has a silicon activation rate of 88%, a calcium activation rate of 90%, and a water absorption rate of 320%.

[0081] The aluminum-silicon ratios of the first and second concentrates were calculated, and the results are listed in Table 1.

[0082] Example 3

[0083] This embodiment provides a method for chemical beneficiation and upgrading of bauxite, the method comprising the following steps:

[0084] (a) The Luoyang monohydrate gibbsite type bauxite with an aluminum-silicon ratio (A / S) of 2.5 was crushed to obtain bauxite particles with a particle size of 0.5-2 cm and a content of 80 wt%.

[0085] (b) The bauxite particles obtained in step (a) are ball-milled for 1 min at a mill speed of 600 r / min, with a media filling rate of 20% and a filling rate of 70%. After ball milling, the particles are classified by sieve to obtain concentrate particles with a particle size ≥ 250 μm, medium particles with a particle size > 150 μm and < 250 μm, and tailings particles with a particle size ≤ 150 μm. The concentrate particles are ball-milled twice to obtain the first concentrate. The medium particles and tailings particles obtained by mixing are crushed to obtain mixed mineral particles with a particle size of less than 150 μm and a particle content of 80 wt%.

[0086] (c) A 0.1 mol / L sodium hydroxide solution with a solid-liquid ratio of 1:30 is mixed with the mixed mineral particles obtained in step (b) to obtain a mixed slurry;

[0087] (d) The mixture slurry obtained in step (c) is subjected to hydrothermal reaction in a reactor at a temperature of 140°C for 10 hours. After the reaction, solid and liquid are separated by filtration to obtain a solid and a silicon-containing solution. The solid is washed and dried to obtain a second concentrate.

[0088] (e) When the silicon-containing solution obtained in step (d) is cooled to 60°C, phosphogypsum and silicon-containing solution are mixed with calcium sulfate at a molar ratio of 1.2:1 to silicon dioxide in the silicon-containing solution. After precipitation for 60 minutes, solid-liquid separation is performed to obtain liquid and silicon-containing solid. The liquid is an alkaline solution that can be reused in step (c). After washing and drying the silicon-containing solid, silicon-based carbon sink material is obtained.

[0089] The silicon-based carbon sink material obtained in this embodiment has a silicon activation rate of 90%, a calcium activation rate of 91%, and a water absorption rate of 317%.

[0090] The aluminum-silicon ratios of the first and second concentrates were calculated, and the results are listed in Table 1.

[0091] Example 4

[0092] This embodiment provides a method for chemical beneficiation and upgrading of bauxite. Compared with Example 1, step (a) is controlled to obtain bauxite particles with a particle size of 0.5-2 cm and a content of 20 wt%, while the rest are the same as in Example 1.

[0093] The silicon-based carbon sink material obtained in this embodiment has a silicon activation rate of 83%, a calcium activation rate of 87%, and a water absorption rate of 299%.

[0094] Example 5

[0095] This embodiment provides a method for chemical beneficiation and upgrading of bauxite. Compared with Example 1, step (b) is controlled to obtain a mixed mineral particle with a particle size of less than 150 μm and a particle content of 50 wt%. The rest are the same as in Example 1.

[0096] The silicon-based carbon sink material obtained in this embodiment has a silicon activation rate of 87%, a calcium activation rate of 89%, and a water absorption rate of 311%.

[0097] Example 6

[0098] This embodiment provides a method for chemical beneficiation and upgrading of bauxite. Compared with Embodiment 1, the bauxite in step (a) is controlled to be Sanmenxia gibbsite-type bauxite with an A / S ratio of 3.5, and the rest is the same as in Embodiment 1.

[0099] The silicon-based carbon sink material obtained in this embodiment has a silicon activation rate of 86%, a calcium activation rate of 96%, and a water absorption rate of 324%.

[0100] Example 7

[0101] This embodiment provides a method for chemical beneficiation and upgrading of bauxite. Compared with Example 1, the solid-liquid ratio in step (c) is controlled at 1:10, the concentration of sodium hydroxide solution is 2.5 mol / L, and the rest are the same as in Example 1.

[0102] The silicon-based carbon sink material obtained in this embodiment has a silicon activation rate of 84%, a calcium activation rate of 87%, and a water absorption rate of 304%.

[0103] Example 8

[0104] This embodiment provides a method for chemical beneficiation and upgrading of bauxite. Compared with Example 1, the solid-liquid ratio in step (c) is controlled at 1:40, the concentration of sodium hydroxide solution is 0.05 mol / L, and the rest are the same as in Example 1.

[0105] The silicon-based carbon sink material obtained in this embodiment has a silicon activation rate of 86%, a calcium activation rate of 91%, and a water absorption rate of 313%.

[0106] Example 9

[0107] This embodiment provides a method for chemical beneficiation and upgrading of bauxite. Compared with Example 1, the temperature of the hydrothermal reaction in step (d) is controlled at 100°C and the reaction time is controlled at 30h. All other steps are the same as in Example 1.

[0108] The silicon-based carbon sink material obtained in this embodiment has a silicon activation rate of 84%, a calcium activation rate of 86%, and a water absorption rate of 293%.

[0109] Example 10

[0110] This embodiment provides a method for chemical beneficiation and upgrading of bauxite. Compared with Example 1, the temperature of the hydrothermal reaction in step (d) is controlled at 250°C and the reaction time is 1 hour. All other steps are the same as in Example 1.

[0111] The silicon-based carbon sink material obtained in this embodiment has a silicon activation rate of 91%, a calcium activation rate of 92%, and a water absorption rate of 321%.

[0112] Example 11

[0113] This embodiment provides a method for chemical beneficiation and upgrading of bauxite. Compared with Example 1, the silicon-containing solution in step (e) is cooled to 50°C, the molar ratio of calcium hydroxide to silicon dioxide is 0.4:1, the precipitation time is 120 min, and the rest are the same as in Example 1.

[0114] The silicon-based carbon sink material obtained in this embodiment has a silicon activation rate of 87%, a calcium activation rate of 87%, and a water absorption rate of 293%.

[0115] Example 12

[0116] This embodiment provides a method for chemical beneficiation and upgrading of bauxite. Compared with Example 1, the silicon-containing solution in step (e) is cooled to 95°C, the molar ratio of calcium hydroxide to silicon dioxide is 1.5:1, the precipitation time is 10 min, and the rest are the same as in Example 1.

[0117] The silicon-based carbon sink material obtained in this embodiment has a silicon activation rate of 89%, a calcium activation rate of 92%, and a water absorption rate of 318%.

[0118] Comparative Example 1

[0119] This comparative example provides a method for chemical beneficiation and upgrading of bauxite. Compared with Example 1, the bauxite is not subjected to the crushing process in step (a), but all other steps are the same as in Example 1.

[0120] The silicon-based carbon sink material obtained in this comparative example has a silicon activation rate of 35%, a calcium activation rate of 78%, and a water absorption rate of 177%.

[0121] Comparative Example 2

[0122] This comparative example provides a method for chemical beneficiation and upgrading of bauxite. Compared with Example 1, the repeated ball milling described in step (b) is not performed, and all other steps are the same as in Example 1.

[0123] The silicon-based carbon sink material obtained in this comparative example has a silicon activation rate of 87%, a calcium activation rate of 93%, and a water absorption rate of 309%.

[0124] Comparative Example 3

[0125] This comparative example provides a method for chemical beneficiation and upgrading of bauxite. Compared with Example 1, step (b) is controlled to obtain a mixed mineral particle with a particle size of less than 150 μm and a particle content of 30 wt%, while the rest are the same as in Example 1.

[0126] The silicon-based carbon sink material obtained in this comparative example has a silicon activation rate of 61%, a calcium activation rate of 81%, and a water absorption rate of 249%.

[0127] Comparative Example 4

[0128] This comparative example provides a method for chemical beneficiation and upgrading of bauxite. Compared with Example 1, the sodium hydroxide solution in step (c) is not added, and all other steps are the same as in Example 1.

[0129] The silicon-based carbon sink material obtained in this comparative example has a silicon activation rate of 34%, a calcium activation rate of 78%, and a water absorption rate of 194%.

[0130] Table 1

[0131]

[0132] The following points can be obtained from Table 1:

[0133] (1) As can be seen from Examples 1-6, the average grade of the first concentrate can reach 6.5, the grade of the second concentrate is above 4.9, and the aluminum recovery rate is greater than 50%. The chemical beneficiation and upgrading method for bauxite provided by the present invention can obtain two high-grade concentrates with high aluminum recovery rate. The method is simple and has strong applicability.

[0134] (2) Examples 7-12 also achieved the separation of the first concentrate and the recovery of aluminum resources. Overall, they can still solve the current problem of the inability to utilize low-grade bauxite and have high economic and social value. However, compared with Example 1, the grade of the second concentrate obtained in the above examples decreased by more than 0.5, and the overall recovery rate decreased by 5%. It can be seen that by using the preferred alkaline solution concentration of 0.1-1 mol / L and solid-liquid ratio of 1:(15-30), hydrothermal reaction temperature of 140-220℃ and time of 2-10h, molar ratio of calcium agent to silica (0.8-1.2):1, mixing start temperature of 60-80℃ and time of 30-60min, two high-grade concentrates can be obtained and the best aluminum recovery rate can be achieved.

[0135] (3) Comparing Example 1 with Comparative Example 1, it can be seen that the grade of the first concentrate has dropped significantly. This shows that crushing is particularly important for the subsequent separation of the first concentrate. Comparing Example 1 with Comparative Example 2, it can be seen that the aluminum-silicon ratio of the first concentrate has not increased much. Repeated ball milling is an important means of concentrate separation. Reducing or eliminating the number of ball milling repetitions will not yield the first concentrate. Comparing Example 1 with Comparative Example 3, it can be seen that the aluminum-silicon ratio of the first concentrate also cannot meet the requirements. This shows that the initial particle size of the ball mill has a significant impact on the separation of the first concentrate. Controlling the ball mill inlet particle size can improve the grade of the first concentrate, reduce the feed amount, save energy, and reduce costs. Comparing Example 1 with Comparative Example 4, it can be seen that the grade of the obtained second concentrate is low. Alkali solution is an important reaction auxiliary material in the hydrothermal process and is indispensable. Otherwise, the grade of bauxite cannot be effectively improved.

[0136] In summary, the method provided by this invention can process low-grade bauxite to obtain two concentrates with aluminum-silicon ratios of 4.5 and 5.07 or higher, respectively, which fully meets the technical requirements urgently needed for the sustainable development of my country's alumina industry. The reaction does not introduce impurity phases or harmful chemical agents, and the resulting liquid product can be recycled and used to prepare silicon-based carbon sink materials simultaneously. After the aluminum-rich phase and silicon-rich phase are separated during the reaction, the aluminum-rich phase is activated in situ, and the increased surface energy can reduce the energy consumption during the subsequent Bayer process leaching.

[0137] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for chemical beneficiation and upgrading of bauxite, characterized in that, The method includes the following steps: (1) The bauxite is refined to obtain bauxite particles; the mass percentage of particles with a diameter of 0.5-2 cm in the bauxite particles is 20-100 wt% of the mass of the bauxite particles. (2) Grind and classify the bauxite particles obtained in step (1) to obtain concentrate particles with a particle size ≥ 250 μm, medium ore particles with a particle size > 150 μm and < 250 μm, and tailings particles with a particle size ≤ 150 μm; repeat grinding and classification of the obtained concentrate particles to obtain the first concentrate; refine the obtained medium ore particles and tailings particles to obtain mixed ore particles; in the mixed ore particles, the mass percentage of particles with a particle size of less than 150 μm is 50-100 wt% of the mixed ore particles. (3) Mix the alkaline solution with the mixed mineral particles obtained in step (2), wherein the alkaline solution includes sodium hydroxide solution and / or potassium hydroxide solution, the concentration of the alkaline solution is 0.05-2.5 mol / L, the solid-liquid ratio of the mixed mineral particles to the alkaline solution is 1:(10-40), and the unit of the solid-liquid ratio is g / mL, to obtain a mixed slurry; (4) The mixture slurry obtained in step (3) is subjected to hydrothermal reaction, and solid-liquid separation is performed after the reaction to obtain the second concentrate and silicon-containing solution; (5) Mix the calcium agent with the silicon-containing solution obtained in step (4). The calcium agent includes any one or a combination of at least two of calcium oxide, calcium hydroxide or calcium sulfate. The molar ratio of the calcium agent to the silicon dioxide in the silicon-containing solution is (0.4-1.5):

1. After mixing, perform solid-liquid separation to obtain a liquid and a silicon-containing solid.

2. The method according to claim 1, characterized in that, The refining methods described in step (1) and step (2) independently include crushing and / or ball milling, respectively.

3. The method according to claim 1 or 2, characterized in that, The grinding method described in step (2) includes dry grinding and / or wet grinding.

4. The method according to claim 1, characterized in that, The grading method described in step (2) includes dry grading and / or wet grading.

5. The method according to claim 1, characterized in that, The number of repetitions in step (2) is 1-10 times.

6. The method according to claim 5, characterized in that, The number of repetitions in step (2) is 2-5 times.

7. The method according to claim 1, characterized in that, The concentration of the alkaline solution in step (3) is 0.1-1 mol / L.

8. The method according to claim 1, characterized in that, In step (3), the solid-liquid ratio of the mixed mineral particles to the alkaline solution is 1:(15-30), and the unit of the solid-liquid ratio is g / mL.

9. The method according to claim 1, characterized in that, The temperature of the hydrothermal reaction in step (4) is 100-250℃.

10. The method according to claim 9, characterized in that, The temperature of the hydrothermal reaction in step (4) is 140-220℃.

11. The method according to claim 1, characterized in that, The hydrothermal reaction time in step (4) is 1-30 hours.

12. The method according to claim 11, characterized in that, The hydrothermal reaction time in step (4) is 2-10 hours.

13. The method according to claim 1, characterized in that, The molar ratio of the calcium agent to the silicon dioxide in the silicon-containing solution in step (5) is (0.8-1.2):

1.

14. The method according to claim 1, characterized in that, The initial temperature of the mixture in step (5) is 50-95℃.

15. The method according to claim 14, characterized in that, The initial temperature of the mixture in step (5) is 60-80℃.

16. The method according to claim 1, characterized in that, The mixing time in step (5) is 10-120 min.

17. The method according to claim 16, characterized in that, The mixing time in step (5) is 30-60 minutes.

18. The method according to claim 1, characterized in that, The liquid obtained in step (5) is reused in step (3).

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