A method for beneficiating and improving the quality of bauxite

Abstract

The present invention provides a method for beneficiation and upgrading of bauxite, comprising the following steps: refining bauxite into bauxite particles, wherein the bauxite has an aluminum-silicon ratio of ≤4; mixing a calcium agent with the bauxite particles to obtain a solid mixture; mixing an alkaline solution with the solid mixture to obtain a mixed slurry; subjecting the mixed slurry to a hydrothermal reaction, followed by solid-solid separation to obtain a bauxite concentrate and a slurry containing tailings; and subjecting the slurry containing tailings to solid-liquid separation to obtain tailings. The method provided by the present invention can process lower-grade bauxite ore to obtain a concentrate with an aluminum-silicon ratio of 5.0 or greater, fully meeting the technical requirements urgently needed for the sustainable development of the alumina industry. During the reaction, the aluminum-rich phase is refined and activated in situ, reducing energy consumption during subsequent Bayer process dissolution; and no impurity phases or harmful chemicals are introduced.

Description

Technical Field

[0001] The invention belongs to the technical field of bauxite beneficiation and relates to a method for beneficiating and improving the quality of bauxite. Background Art

[0002] Bauxite, including minerals such as gibbsite and diaspore, is a key raw material for the aluminum materials industry. Diaspore-type bauxite is characterized by high aluminum and silicon content, and the majority of bauxite is medium- to low-grade, with an aluminum-to-silicon ratio (A / S) of less than 4. With the rapid development of the alumina industry leading to a decrease in high-grade bauxite resources and the need to reduce energy consumption and production costs, technologies for the economical and rational utilization of medium- and low-grade bauxite resources have become a major industry need.

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

[0004] CN108554594A discloses a low-grade bauxite beneficiation method. This method uses controlled grinding to crush or ball-mill diaspore-type bauxite with an A / S ratio of less than 3 to obtain bauxite powder. The fine particles are then separated by classification. The separated fine particles are a low aluminum-silicon ratio product with an A / S ratio of less than 1.7. The remaining bauxite powder is a product with an A / S ratio of greater than 3. Although this method can process bauxite with a lower aluminum-silicon ratio, it requires fine grinding of the ore to less than 10 microns. This process consumes extremely high energy, and the aluminum-silicon ratio of the selected concentrate does not exceed 4, while the aluminum-silicon ratio of the tailings is as high as 1.7.

[0005] CN101391237A discloses a new process for desiliconization of bauxite by direct flotation. The method includes the steps of grinding, classification, flotation, and roughing underflow classification and regrinding. The process is complicated, the auxiliary materials are redundant, and the addition of flotation reagents makes the tailings difficult to utilize. Long-term accumulation causes environmental problems.

[0006] CN101439317A and CN102806146A both disclose a method for pre-desiliconization of bauxite beneficiation. The processes of these two methods are relatively simple, but there is also the problem that the tailings are difficult to utilize, 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 the existing technology, it is necessary to provide a method for beneficiation and quality improvement of bauxite. Summary of the Invention

[0008] The purpose of the present invention is to provide a method for 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; and the method is simple, highly applicable and easy to promote.

[0009] To achieve this object, the present invention adopts the following technical solutions:

[0010] The present invention provides a method for beneficiation and upgrading of bauxite, which comprises the following steps:

[0011] (1) refining bauxite into bauxite particles, wherein the aluminum-silicon ratio of the bauxite is ≤4;

[0012] (2) mixing a calcium agent with the bauxite particles obtained in step (1) to obtain a solid mixture;

[0013] (3) mixing the alkaline solution with the solid mixture obtained in step (2) to obtain a mixed slurry;

[0014] (4) subjecting the mixed slurry obtained in step (3) to a hydrothermal reaction, and performing solid-solid separation after the hydrothermal reaction to obtain a slurry containing bauxite concentrate and tailings;

[0015] (5) subjecting the tailings-containing slurry obtained in step (4) to solid-liquid separation to obtain tailings.

[0016] The present invention mixes medium- and low-grade bauxite particles with a calcium agent, adds alkali solution, and then realizes a directional reaction through a hydrothermal reaction. During the directional conversion process, the silicon-rich ore phase of the bauxite is selectively dissolved by active alkali ions, and then combined with calcium ions and directionally converted into tailings with low density. The tailings are then separated from the aluminum-rich ore phase with high density through solid-solid separation, thereby obtaining a bauxite concentrate with a high aluminum-silicon ratio.

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

[0018] Preferably, the mass percentage of the bauxite particles with a particle size of 150-250 μm obtained in step (1) is 30-100 wt% of the mass of the bauxite particles.

[0019] Preferably, the calcium agent in step (2) comprises 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.

[0020] As a preferred technical solution of the present invention, from the perspective of economy and environmental protection, the calcium agent of the present invention can be industrial raw materials or waste residues with calcium oxide, calcium hydroxide or calcium sulfate as the main components.

[0021] Preferably, the molar ratio of the calcium agent in step (2) to the silicon dioxide in the bauxite particles is (0.4-1.5):1, for example, it can be 0.4:1, 0.7:1, 1.0:1, 1.2:1 or 1.5:1, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable, preferably (0.8-1.2):1.

[0022] The preferred molar ratio of calcium agent to silicon dioxide in bauxite particles of the present invention can make more effective use of the silicon component in the bauxite. When the molar ratio is too low or too high, the dissolution effect of the silicon-rich ore phase will be affected.

[0023] Preferably, the alkaline solution in step (3) comprises sodium hydroxide solution and / or potassium hydroxide solution.

[0024] Preferably, the concentration of the alkaline solution in step (3) is 0.05-2.5 mol / L, for example, 0.05 mol / L, 0.5 mol / L, 1.0 mol / L, 1.5 mol / L, 2.0 mol / L or 2.5 mol / L, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable, preferably 0.1-1 mol / L.

[0025] The preferred concentration of the alkaline solution of the present invention can better promote the dissolution reaction. When the concentration of the alkaline solution is too low, the subsequent reaction is difficult to proceed completely. When the concentration of the alkaline solution is too high, other products will be generated during the reaction, reducing the aluminum recovery rate.

[0026] Preferably, the solid-liquid ratio of the solid mixture to the alkaline solution in step (3) is 1:(2.5-40), and the unit of the solid-liquid ratio is g / mL, for example, it can be 1:2.5, 1:10, 1:20, 1:30 or 1:40, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable, preferably 1:(5-20).

[0027] The solid-liquid ratio of the solid mixture to the alkaline solution is a key factor in selective dissolution. When the solid-liquid ratio is too high, the mixture of the mixture and the alkaline solution is difficult to mix evenly, and the volume of the reaction product will expand rapidly, making the reaction difficult to proceed. When the solid-liquid ratio is too low, it will cause unnecessary energy consumption.

[0028] Preferably, the temperature of the hydrothermal reaction in step (4) is 100-250°C, for example, 100°C, 150°C, 200°C or 250°C, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable, preferably 140-220°C.

[0029] When the temperature of the hydrothermal reaction in step (4) is too low, the reaction kinetics is insufficient, which reduces the conversion rate of the silicon-rich mineral phase; when the temperature of the hydrothermal reaction in step (4) is too high, the energy consumption is increased, which increases the cost.

[0030] Preferably, the hydrothermal reaction time in step (4) is 1-30 h, for example, 1 h, 10 h, 15 h, 20 h, 25 h or 30 h, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable, preferably 2-10 h.

[0031] If the reaction time of the hydrothermal reaction in step (4) is too short, the reaction will not be complete and many raw materials cannot be converted, resulting in a waste of raw materials; if the reaction time of the hydrothermal reaction in step (4) is too long, it will lead to increased energy consumption and increase the mineral processing cost.

[0032] The above-mentioned preferred temperature and time can improve the utilization rate of raw materials, achieve efficient and directional conversion of silicon in bauxite, and at the same time reduce resource waste and lower energy consumption.

[0033] Preferably, the solid-solid separation method in step (4) comprises sedimentation and / or centrifugation.

[0034] The solid-solid separation is performed based on the difference in density between the bauxite concentrate and the tailings. The separated material with a high density is the concentrate, and the separated material with a low density is the tailings.

[0035] As a preferred technical solution of the present invention, the solid-solid separation can be performed using equipment that utilizes density difference for separation. Exemplarily, the separation equipment includes a sedimentation tank, a hydrocyclone, a chute, or a centrifuge.

[0036] In the present invention, the solid-liquid separation in step (5) is performed by conventional means in the art. Exemplary separation methods include filtration or centrifugation.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] (1) By using the method provided by the present invention to separate lower-grade bauxite ore through aluminum-silicon separation, the aluminum-silicon ratio of the obtained concentrate can reach above 5.0, and the aluminum-silicon ratio of the tailings is lower than 1.7, which fully meets the technical requirements urgently needed for the sustainable development of the alumina industry;

[0039] (2) After the aluminum-rich phase and the silicon-rich phase are separated during the reaction, the interwoven ore is opened, the aluminum-rich phase is refined and activated in situ, and the surface energy is increased, which can reduce the energy consumption of the subsequent Bayer process dissolution;

[0040] (3) No impurities or harmful chemicals will be introduced during the reaction. DETAILED DESCRIPTION

[0041] The technical solution of the present invention is further illustrated below through specific implementation methods.

[0042] In order 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 respectively determine the contents of silicon oxide and aluminum oxide in bauxite, the concentrate obtained by the present invention, and the obtained tailings, and then calculate the aluminum-silicon ratio (A / S).

[0043] Example 1

[0044] This embodiment provides a method for beneficiation and upgrading of bauxite, the method comprising the following steps:

[0045] (a) crushing Luoyang diaspore-type bauxite having an aluminum-silicon ratio (A / S) of 2.5 to obtain bauxite particles having a particle size of 150-250 μm and a particle content of 80 wt %;

[0046] (b) mixing calcium hydroxide and bauxite particles at a molar ratio of calcium hydroxide to silicon dioxide in the bauxite particles obtained in step (a) of 1.0:1 to obtain a solid mixture;

[0047] (c) mixing a 0.5 mol / L sodium hydroxide solution with the solid mixture obtained in step (b) at a solid-to-liquid ratio of 1:5 to obtain a mixed slurry;

[0048] (d) subjecting the mixed slurry to a hydrothermal reaction in a reactor at a reaction temperature of 180° C. for a reaction time of 2 h, subjecting the slurry after the reaction to solid-solid separation by sedimentation to obtain a solid with high density and a residual slurry, and washing the solid to obtain a bauxite concentrate;

[0049] (e) filtering the remaining slurry obtained in step (d) to separate the solid from the liquid, and the obtained solid is the tailings.

[0050] The aluminum-silicon ratios of the concentrate and tailings were calculated and the results are listed in Table 1.

[0051] Example 2

[0052] This embodiment provides a method for beneficiation and upgrading of bauxite, the method comprising the following steps:

[0053] (a) crushing Luoyang diaspore-type bauxite having an aluminum-silicon ratio (A / S) of 2.5 to obtain bauxite particles having a particle size of 150-250 μm and a particle content of 80 wt %;

[0054] (b) mixing lime and bauxite particles at a molar ratio of calcium oxide to silicon dioxide in the bauxite particles obtained in step (a) of 1.2:1 to obtain a solid mixture;

[0055] (c) mixing a 0.1 mol / L sodium hydroxide solution with the solid mixture obtained in step (b) at a solid-to-liquid ratio of 1:20 to obtain a mixed slurry;

[0056] (d) subjecting the mixed slurry to a hydrothermal reaction in a reactor at a reaction temperature of 140° C. for a reaction time of 10 h, subjecting the reacted slurry to solid-solid separation by centrifugation to obtain a high-density solid and a residual slurry, and washing the solid to obtain a bauxite concentrate;

[0057] (e) filtering the remaining slurry obtained in step (d) to separate the solid from the liquid, and the obtained solid is the tailings.

[0058] The aluminum-silicon ratios of the concentrate and tailings were calculated and the results are listed in Table 1.

[0059] Example 3

[0060] This embodiment provides a method for beneficiation and upgrading of bauxite, the method comprising the following steps:

[0061] (a) crushing Luoyang diaspore-type bauxite having an aluminum-silicon ratio (A / S) of 2.5 to obtain bauxite particles having a particle size of 150-250 μm and a particle content of 80 wt %;

[0062] (b) mixing phosphogypsum and bauxite particles at a molar ratio of calcium sulfate to silicon dioxide in the bauxite particles obtained in step (a) of 0.8:1 to obtain a solid mixture;

[0063] (c) mixing a 1 mol / L potassium hydroxide solution with the solid mixture obtained in step (b) at a solid-to-liquid ratio of 1:10 to obtain a mixed slurry;

[0064] (d) subjecting the mixed slurry to a hydrothermal reaction in a reactor at a reaction temperature of 220° C. for a reaction time of 5 hours, subjecting the reacted slurry to solid-solid separation by hydrocyclone to obtain a high-density solid and a residual slurry, and washing the solid to obtain a bauxite concentrate;

[0065] (e) filtering the remaining slurry obtained in step (d) to separate the solid from the liquid, and the obtained solid is the tailings.

[0066] The aluminum-silicon ratios of the concentrate and tailings were calculated and the results are listed in Table 1.

[0067] Example 4

[0068] This embodiment provides a method for beneficiation and upgrading of bauxite. Compared with Example 1, Sanmenxia monohydrate bauxite with an aluminum-silicon ratio (A / S) of 3.5 is used in step (a), and the rest is the same as Example 1.

[0069] Example 5

[0070] This embodiment provides a method for beneficiation and upgrading of bauxite. Compared with Example 1, the bauxite in step (a) is crushed to obtain bauxite particles with a particle size of 150-250 μm and a particle content of 30 wt%. The rest is the same as Example 1.

[0071] Example 6

[0072] This embodiment provides a method for beneficiation and upgrading of bauxite. Compared with Example 1, the molar ratio of calcium hydroxide to silicon dioxide in step (b) is 0.4:1, and the rest is the same as Example 1.

[0073] Example 7

[0074] This embodiment provides a method for beneficiation and upgrading of bauxite. Compared with Example 1, the molar ratio of calcium hydroxide to silicon dioxide in step (b) is 1.5:1, and the rest is the same as Example 1.

[0075] Example 8

[0076] This embodiment provides a method for beneficiation and upgrading of bauxite. Compared with Example 1, the concentration of the sodium hydroxide solution in step (c) is 0.05 mol / L, the solid-liquid ratio is 1:40, and the rest is the same as Example 1.

[0077] Example 9

[0078] This embodiment provides a method for beneficiation and upgrading of bauxite. Compared with Example 1, the concentration of the sodium hydroxide solution in step (c) is 2.5 mol / L, the solid-liquid ratio is 1:2.5, and the rest is the same as Example 1.

[0079] Example 10

[0080] This embodiment provides a method for beneficiation and upgrading of bauxite. Compared with Example 1, the temperature of the hydrothermal reaction in step (d) is 100° C. and the reaction time is 30 h. The rest is the same as Example 1.

[0081] Example 11

[0082] This embodiment provides a method for beneficiation and upgrading of bauxite. Compared with Example 1, the temperature of the hydrothermal reaction in step (d) is 250° C. and the reaction time is 1 h. The rest is the same as Example 1.

[0083] Comparative Example 1

[0084] This comparative example provides a method for beneficiation and upgrading of bauxite. Compared with Example 1, the sodium hydroxide solution in step (c) is not added, and the rest is the same as Example 1.

[0085] Comparative Example 2

[0086] This comparative example provides a method for beneficiation and upgrading of bauxite. Compared with Example 1, calcium hydroxide is not added in step (b), and the rest is the same as Example 1.

[0087] Comparative Example 3

[0088] This comparative example provides a method for beneficiation and upgrading of bauxite. Compared with Example 1, step (d) solid-solid separation is not performed, and the rest is the same as Example 1.

[0089] Table 1

[0090]

[0091]

[0092] The following points can be drawn from Table 1:

[0093] (1) As can be seen from Examples 1-5, the grade of the concentrate selected by the method provided by the present invention is greater than 5.5, the aluminum-silicon ratio of the tailings is less than 1.7, and the recovery rate is greater than 57%, thereby achieving the improvement of bauxite grade and the recycling of aluminum resources.

[0094] (2) As can be seen from Examples 6-11, the grade of the obtained concentrates is higher than 5.0, which can still solve the current problem of low-grade bauxite being unable to be utilized as a whole, and has high economic and social value. Compared with Example 1, the aluminum-silicon ratio of the concentrate selected in the above embodiment decreased by about 0.5, and the aluminum resource recovery rate decreased by about 10%. It can be seen that the use of the preferred molar ratio of calcium agent to silicon dioxide (0.8-1.2):1 of the present invention can make calcium dissolve the silicon-rich phase in the bauxite better; the use of the preferred alkaline solution concentration of 0.1-1 mol / L and the solid-liquid ratio of 1: (5-20) of the present invention can fully mix the bauxite material with the alkaline solution and make the reaction proceed smoothly without producing other products, thereby achieving the best dissolution effect; the use of the preferred hydrothermal reaction temperature of 140-220°C and the reaction time of 2-10h of the present invention can achieve directional and efficient conversion of silicon in bauxite, thereby improving the utilization rate of raw materials.

[0095] (3) Comparing Example 1 with Comparative Examples 1 and 2, it can be seen that the grade of the concentrates obtained in Comparative Examples 1 and 2 is greatly reduced. Alkaline solution and calcium agent are important reaction auxiliary materials for hydrothermal reaction, and neither of them can be missing. Otherwise, the silicon-rich phase in the bauxite cannot be completely dissolved and separated, and the concentrate with a grade that meets the use requirements cannot be obtained; Comparing Example 1 with Comparative Example 3, it can be seen that the aluminum-silicon ratio of the obtained concentrate is almost not improved. Solid-solid separation is a necessary step in the mineral processing and quality improvement process. Otherwise, the grade of bauxite cannot be effectively improved, and it is difficult to achieve aluminum recycling.

[0096] In summary, the method for beneficiation and upgrading of bauxite provided by the present invention can ensure the grade of the concentrate, has a high recovery rate, is simple in method, and has strong applicability.

[0097] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above are only 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 in the scope of protection of the present invention.

Claims

1. A method for beneficiation and upgrading of bauxite, characterized in that: The method comprises the following steps: (1) refining bauxite into bauxite particles, wherein the aluminum-silicon ratio of the bauxite is ≤4; (2) mixing a calcium agent with the bauxite particles obtained in step (1), wherein the molar ratio of the calcium agent to the silicon dioxide in the bauxite particles is (0.4-1.5):1, to obtain a solid mixture; (3) mixing an alkaline solution with the solid mixture obtained in step (2) to obtain a mixed slurry; wherein the concentration of the alkaline solution is 0.05-2.5 mol / L; (4) subjecting the mixed slurry obtained in step (3) to a hydrothermal reaction at a temperature of 100-250° C., and performing solid-solid separation after the hydrothermal reaction to obtain a slurry containing bauxite concentrate and tailings; (5) The slurry containing tailings obtained in step (4) is subjected to solid-liquid separation to obtain tailings.

2. The method according to claim 1, characterized in that The refinement method in step (1) includes crushing and / or ball milling.

3. The method according to claim 1, characterized in that The mass percentage content of the bauxite particles with a particle size of 150-250 μm obtained in step (1) is 30-100 wt% of the mass of the bauxite particles.

4. The method according to claim 1, wherein The calcium agent in step (2) includes any one of calcium oxide, calcium hydroxide or calcium sulfate, or a combination of at least two of them.

5. The method according to claim 1, wherein The molar ratio of the calcium agent in step (2) to the silicon dioxide in the bauxite particles is (0.8-1.2):

1.

6. The method according to claim 1, wherein The alkaline solution in step (3) includes sodium hydroxide solution and / or potassium hydroxide solution.

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 The solid-liquid ratio of the solid mixture to the alkaline solution in step (3) is 1:(2.5-40), and the unit of the solid-liquid ratio is g / mL.

9. The method according to claim 8, characterized in that The solid-liquid ratio of the solid mixture to the alkaline solution in step (3) is 1:(5-20), and the unit of the solid-liquid ratio is g / mL.

10. The method according to claim 1, characterized in that The temperature of the hydrothermal reaction in step (4) is 140-220°C.

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

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, wherein The solid-solid separation method in step (4) includes sedimentation and / or centrifugation.

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