A method of controlling the particle size of a sandy alumina
By controlling the parameters of the refining liquid in the decomposition tank, the problem of controlling the particle size of granular alumina under high organic matter conditions was solved, achieving particle size stability and improved filtration efficiency, reducing overflow in the decomposition tank, and increasing seed activity and yield.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- YUNNAN WENSHAN ALUMINUM CO LTD
- Filing Date
- 2023-11-22
- Publication Date
- 2026-06-19
AI Technical Summary
Under conditions of high organic matter, existing technologies struggle to effectively control the particle size of granular alumina, leading to problems such as decreased filter cloth permeability, reduced filtration efficiency, deteriorated seed crystal quality, and overflow of the decomposition tank.
By controlling parameters such as the solid content of the refining liquid, alumina concentration, first tank temperature, and decomposition time in the decomposition tank, bauxite is leached using the Bayer process. This ensures that the solid content of the refining liquid is ≥850 g/L, the alumina concentration is 155–160 g/L, the first tank temperature is 60–70℃, the decomposition rate is stable at 48–52%, and the relationship 221≤C+T≤222 is satisfied. The temperature difference between the first and last tanks of the decomposition tank is controlled to be ≥12.5℃.
It achieved a sand-like alumina particle size of -45um with a content of ≤15%, stabilized the decomposition rate and aluminum hydroxide particle size, improved the filter capacity, reduced the overflow of the decomposition tank, and enhanced the activity and yield of seed crystals.
Abstract
Description
Technical Field
[0001] This invention belongs to the field of alumina production technology, and more specifically, relates to a method for controlling the particle size of granular alumina. Background Technology
[0002] Alumina production involves a wide variety of organic compounds, primarily in acidic form: humic acid, oxalic acid, formic acid, acetic acid, propionic acid, butyric acid, succinic acid, glutaric acid, benzoic acid, tartaric acid, and butylene oleic acid. These can be broadly categorized into three types: naturally occurring substances (such as tree roots); and humic acid and bitumen formed from organic matter (plants) through chemical changes and microbial decomposition. The amount of organic carbon dissolved during leaching depends mainly on the chemical composition of the original humic substances in the bauxite. Organic carbon partially transforms into sodium oxalate, which is the most significant degradation product. When sodium oxalate exceeds its solubility, crystallization occurs, severely impacting the Bayer process.
[0003] Under conditions of high organic matter content, the main challenges in particle size control are threefold: First, the sodium oxalate from the organic matter forms scales on the vertical filter cloth, reducing its air permeability, lowering filtration efficiency, decreasing the thickness of the adsorbed filter cake, and drastically reducing the filtrate yield, making it difficult to pass liquid and impacting the company's output. Second, the organic matter mixed in the seed crystals degrades their quality, reduces their activity, and hinders their aggregation and growth. Third, the organic matter causes foaming in the sodium aluminate solution, resulting in excessive foam in the decomposition tank, leading to overflow and short-circuiting, affecting the decomposition and aggregation growth time of the seed crystals. Therefore, controlling the particle size of granular alumina is one of the urgent problems to be solved. Summary of the Invention
[0004] This application aims to solve the technical problem of difficulty in controlling the particle size of granular alumina under high organic matter conditions in the prior art.
[0005] Therefore, the first objective of this invention is to provide a method for controlling the particle size of granular alumina, which can effectively control the content of granular alumina particles with a particle size of -45um to ≤15%, and effectively solve the adverse effects of high organic matter on seed crystal decomposition.
[0006] Specifically, a method for controlling the particle size of granular alumina, employing the Bayer process for bauxite leaching, includes: slurry grinding, slurry leaching, red mud separation, crude liquor refining, seed crystal decomposition, and roasting to obtain alumina; the controlled conditions for seed crystal decomposition include:
[0007] Control the solid content of the refined liquid in the decomposition tank: the solid content of the refined liquid is ≥850g / L;
[0008] The alumina concentration of the refining solution in the decomposition tank is controlled to be 155–160 g / L.
[0009] Controlling the temperature of the first tank in the decomposition tank: The temperature of the first tank is 60-70℃.
[0010] Furthermore, the solid content of the refined liquid is 900-980 g / L.
[0011] Furthermore, the solid content of the refined liquid is 950 g / L.
[0012] Furthermore, the method also includes controlling the decomposition rate of the refined liquid to be stable at 48-52%.
[0013] Furthermore, the alumina concentration of the refined solution and the temperature of the first tank satisfy the following relationship:
[0014] 221≤C+T≤222
[0015] In the formula, C represents the alumina concentration of the refined solution, in g / L; T represents the temperature of the first tank, in °C.
[0016] Furthermore, when the alumina concentration of the refining solution is 157 g / L, the temperature of the first tank is 64–65 °C; when the alumina concentration of the refining solution is 159 g / L, the temperature of the first tank is 62–63 °C.
[0017] Furthermore, the method also includes controlling the decomposition time to be ≥45h.
[0018] Furthermore, the method also includes controlling the temperature difference between the first and last tanks of the decomposition tank to be ≥12.5℃.
[0019] Furthermore, the aluminum hydroxide particle size of -45µm in the decomposition tank is ≤18%.
[0020] The technical mechanism is as follows:
[0021] (1) Increased solids content in the decomposition tank reduces impurities in the solution, improves seed activity, and increases the seed ratio, which is beneficial for the aggregation of some newly precipitated fine aluminum hydroxide, thus reducing the number of nuclei formed in the decomposition slurry. Stabilizing the solids content in the decomposition tank is a prerequisite for controlling nucleation. Solids content and nucleation are highly negatively correlated.
[0022] (2) When controlling nucleation, the semen concentration and the initial tank temperature need to be coordinated. When the semen concentration is controlled too low, the initial tank temperature will be controlled slightly higher. When the semen concentration is controlled too high, the initial tank temperature can be controlled slightly higher. By using the corresponding relationship between semen concentration and initial tank temperature 221≤C+T≤222, the decomposition rate and aluminum hydroxide particle size can be stably controlled.
[0023] (3) When the decomposition rate is low, the number of crystal nuclei separated is relatively small. Under the same solid content, temperature, concentration, and other conditions, the proportion of these nuclei after the growth process is small. When the decomposition rate is high, the number of crystal nuclei separated is relatively large. Under the same conditions, the growth process cannot completely consume these nuclei, resulting in an increasing proportion of these nuclei and refining the particle size in the tank. A stable decomposition rate of 48-52% allows for control of the number of nuclei regardless of the specific range.
[0024] A second objective of the present invention is to provide a granular alumina obtained by the method for controlling the particle size of granular alumina as described in any embodiment of the first aspect, wherein the granular alumina particle size of -45 μm contains ≤15%.
[0025] The beneficial effects of this application are as follows:
[0026] This application provides a method for controlling the particle size of granular alumina. By improving the correlation between the solid content of the decomposition tank, the concentration of the concentrate, and the temperature of the first decomposition tank (221≤C+T≤222), the decomposition rate and the particle size of aluminum hydroxide are stably controlled. Using this particle size control method, the content of aluminum hydroxide particles with a particle size of -45µm in the decomposition tank is ≤18%, and the content of alumina particles with a particle size of -45µm is ≤15%. Detailed Implementation
[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.
[0028] First, the present invention provides a method for controlling the particle size of granular alumina, which can effectively control the content of granular alumina particles with a particle size of -45um to ≤15%, effectively solving the adverse effects of high organic matter on seed crystal decomposition.
[0029] Specifically, a method for controlling the particle size of granular alumina, employing the Bayer process for bauxite leaching, includes: slurry grinding, slurry leaching, red mud separation, crude liquor refining, seed crystal decomposition, and roasting to obtain alumina; the controlled conditions for seed crystal decomposition include:
[0030] Control the solid content of the refined liquid in the decomposition tank: the solid content of the refined liquid is ≥850g / L;
[0031] The alumina concentration of the refining solution in the decomposition tank is controlled to be 155–160 g / L.
[0032] Controlling the temperature of the first tank in the decomposition tank: The temperature of the first tank is 60-70℃.
[0033] In this invention, the solid content of the refined liquid is 900-980 g / L.
[0034] In this invention, the solid content of the refined liquid is 950 g / L.
[0035] In light of this, the applicant discovered that increasing the solid content in the decomposition tank reduces the impurity content in the solution, improves seed crystal activity, and increases the seed ratio. This facilitates the aggregation of some newly precipitated fine aluminum hydroxide, thus reducing the number of nuclei formed in the decomposition slurry. Maintaining a stable solid content in the decomposition tank is a prerequisite for controlling nucleation. Solid content and nucleation are highly negatively correlated. Furthermore, increased solid content in the decomposition tank leads to a decrease in the liquid phase volume per unit volume of the slurry, resulting in a reduction in the organic matter content per unit volume and less foaming in the decomposition tank. Simultaneously, increased solid content increases the number of seed crystals. Upon entering the decomposition tank, organic matter such as oxalates adsorbs onto the seed crystal surface, inhibiting foaming and preventing overflow except in the first tank, thus extending the decomposition time. Reduced foaming in the decomposition tank, with less foam floating on the surface, facilitates heat dissipation from the slurry and lowers the temperature of the decomposition tank. Furthermore, as the solid content in the decomposition tank increases, the density of the slurry inside the decomposition tank also increases, which in turn increases the density difference between the inside and outside of the decomposition tank's feed cylinder. This leads to increased decomposition output, reduced overflow from the decomposition tank, and decreased foam in the tail trough as the overflow decreases, thereby improving the capacity of the vertical disc filter and increasing production.
[0036] In this invention, the method further includes controlling the decomposition rate of the refined liquid to be stable at 48-52%.
[0037] In light of this, the applicant discovered that when the decomposition rate is low, the number of crystal nuclei separated is relatively small, and under the same solid content, temperature, and concentration conditions, their proportion after the adsorption process is small. When the decomposition rate is high, the number of crystal nuclei separated increases relatively. Under the same conditions, the adsorption growth process cannot completely consume these crystal nuclei, resulting in an increasing proportion of these crystal nuclei and thus refining the particle size within the tank. A stable decomposition rate of 48-52% allows for control of the number of nuclei regardless of the specific range.
[0038] In this invention, the alumina concentration of the refining solution and the temperature of the first tank satisfy the following relationship:
[0039] 221≤C+T≤222
[0040] In the formula, C represents the alumina concentration of the refined solution, in g / L; T represents the temperature of the first tank, in °C.
[0041] In this invention, when the alumina concentration of the refining solution is 157 g / L, the temperature of the first tank is 64-65°C; when the alumina concentration of the refining solution is 159 g / L, the temperature of the first tank is 62-63°C.
[0042] In view of this, the applicant discovered that, during nucleation control, the semen concentration and the initial tank temperature need to be coordinated. When the semen concentration is controlled too low, the initial tank temperature will be controlled slightly higher; conversely, when the semen concentration is controlled too high, the initial tank temperature can be controlled slightly higher. By using the corresponding relationship between semen concentration and the initial decomposition tank temperature, 221≤C+T≤222, the decomposition rate and aluminum hydroxide particle size can be stably controlled.
[0043] In this invention, the method further includes controlling the decomposition time to be ≥45h.
[0044] In this invention, the method further includes controlling the temperature difference between the first and last tanks of the decomposition tank to be ≥12.5℃.
[0045] In this invention, the content of aluminum hydroxide particles with a particle size of -45 μm in the decomposition tank is ≤18%.
[0046] A second objective of the present invention is to provide a granular alumina obtained by the method for controlling the particle size of granular alumina as described in any embodiment of the first aspect, wherein the granular alumina particle size of -45 μm contains ≤15%.
[0047] <Example>
[0048] Example 1
[0049] The Bayer process for leaching bauxite includes: slurry milling, slurry leaching, red mud separation, crude liquor refining, seed crystal decomposition, and roasting to obtain alumina; the controlled conditions for seed crystal decomposition include:
[0050] The solid content of the purified liquid in the decomposition tank was controlled at 926 g / L;
[0051] The alumina concentration of the refining solution in the decomposition tank is controlled at 157 g / L;
[0052] The initial temperature of the decomposition tank is controlled at 65℃.
[0053] The decomposition time in the decomposition tank is controlled to be 50 hours.
[0054] The decomposition rate is controlled at 50%;
[0055] The temperature difference between the first and last tanks of the decomposition tank is controlled at 12.5℃.
[0056] Example 2
[0057] The difference between this embodiment and Embodiment 1 is that the solid content of the purified liquid in the decomposition tank is 935 g / L;
[0058] Example 3
[0059] The difference between this embodiment and Embodiment 1 is that the solid content of the refined liquid in the decomposition tank is 858 g / L;
[0060] Example 4
[0061] The difference between this embodiment and Embodiment 1 is that the solid content of the purified liquid in the decomposition tank is 873 g / L.
[0062] Example 5
[0063] The difference between this embodiment and Embodiment 4 is that the solid content of the purified liquid in the decomposition tank is 855 g / L;
[0064] Example 6
[0065] The difference between this embodiment and Embodiment 4 is that the solid content of the purified liquid in the decomposition tank is 867 g / L;
[0066] Example 7
[0067] The difference between this embodiment and Embodiment 1 is that the solid content of the refined liquid in the decomposition tank is 891 g / L;
[0068] Example 8
[0069] The difference between this embodiment and Embodiment 7 is that the alumina concentration of the refined liquid in the decomposition tank is 159 g / L; and the initial temperature of the decomposition tank is controlled at 62°C.
[0070] <Comparative Example>
[0071] Comparative Example 1
[0072] The difference between this comparative example and Example 1 is that the solid content of the purified liquid in the decomposition tank is 742 g / L.
[0073] Comparative Example 2
[0074] The difference between this comparative example and Example 1 is that the solid content of the purified liquid in the decomposition tank is 661 g / L.
[0075] Comparative Example 3
[0076] The difference between this comparative example and Example 1 is that the solid content of the purified liquid in the decomposition tank is 619 g / L.
[0077] Comparative Example 4
[0078] The difference between this comparative example and Example 1 is that the alumina concentration of the refined liquid in the decomposition tank is 165 g / L; and the initial temperature of the decomposition tank is controlled at 75°C.
[0079] <Experimental Example>
[0080] Experimental Example 1
[0081] The content of aluminum hydroxide and alumina particles with a particle size of -45 μm in the decomposition tank and the amount of filtered semen were tested using the control methods of Examples 1-8 and Comparative Examples 1-4. The experimental results are shown in Table 1.
[0082] Table 1. Content of aluminum hydroxide and aluminum oxide particles (-45µm) in the decomposition tank and the volume of filtered semen.
[0083] Group Aluminum hydroxide particle size - 45µm content (%) Alumina particle size - 45µm content (%) <![CDATA[Filtered semen volume (m 3 / h)]]> Example 1 17.83 14.27 796 Example 2 17.53 14.20 800 Example 3 17.24 14.08 826 Example 4 17.49 14.15 807 Example 5 17.89 14.92 778 Example 6 17.91 14.94 771 Example 7 17.45 14.13 809 Example 8 17.85 14.42 790 Comparative Example 1 26.62 19.93 552 Comparative Example 2 30.52 21.26 495 Comparative Example 3 21.39 20.06 607 Comparative Example 4 19.30 18.30 720
[0084] As shown in Table 1, under basically stable process conditions such as alumina concentration, first tank temperature, decomposition time, and temperature difference between the first and last tanks in the decomposition tank, the solid content in the decomposition tank increases to ≥850g / L, the aluminum hydroxide particle size (-45μm) content in the decomposition tank is ≤18%, and the alumina particle size (-45μm) content is ≤15%. Furthermore, through the new process control method, foaming in the decomposition tank is effectively controlled, there is no overflow in the decomposition tank, the filter capacity is improved, and the activity of the seed crystals is increased, resulting in continuous improvement in both decomposition rate and particle size, achieving a dual improvement.
[0085] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. A method for controlling the particle size of granular alumina under high organic matter conditions, employing the Bayer process for leaching bauxite, comprising: The process involves grinding a slurry, dissolving the slurry, separating red mud, refining the crude liquid, decomposing the seed crystals, and calcining to obtain alumina; characterized in that the controlled conditions for the seed crystal decomposition include: Control the solid content of the refined liquid in the decomposition tank: the solid content of the refined liquid is ≥850g / L; The alumina concentration of the refining solution in the decomposition tank is controlled to be 155~160 g / L. Controlling the temperature of the first tank in the decomposition tank: the temperature of the first tank is 60~70℃; The alumina concentration of the refined solution and the temperature of the first tank satisfy the following relationship: 221≤C+T≤222 In the formula, C represents the alumina concentration of the refining solution, in g / L; T represents the temperature of the first tank, in °C. The method further includes controlling the decomposition rate of the refined liquid to be stable at 48-52%.
2. The method for controlling the particle size of granular alumina under high organic matter conditions according to claim 1, characterized in that, The solid content of the refined liquid is 900~980g / L.
3. The method for controlling the particle size of granular alumina under high organic matter conditions according to claim 2, characterized in that, The solid content of the refined liquid is 950 g / L.
4. The method for controlling the particle size of granular alumina under high organic matter conditions according to claim 1, characterized in that, When the alumina concentration of the refining solution is 157 g / L, the temperature of the first tank is 64~65℃; when the alumina concentration of the refining solution is 159 g / L, the temperature of the first tank is 62~63℃.
5. The method for controlling the particle size of granular alumina under high organic matter conditions according to claim 1, characterized in that, The method also includes controlling the decomposition time to be ≥45h.
6. The method for controlling the particle size of granular alumina under high organic matter conditions according to claim 1, characterized in that, The method further includes controlling the temperature difference between the first and last tanks of the decomposition tank to be ≥12.5℃.
7. The method for controlling the particle size of granular alumina under high organic matter conditions according to claim 1, characterized in that, The content of aluminum hydroxide particles with a particle size of -45µm in the decomposition tank is ≤18%.