Preparation method of special aluminum hydroxide for corundum

Abstract

The invention relates to a preparation method of aluminum hydroxide special for corundum, and belongs to the technical field of aluminum hydroxide preparation. The method comprises the following steps: obtaining sodium aluminate fine liquid; mixing the sodium aluminate fine solution with a seed crystal to obtain a mixed solution; carrying out decomposition reaction on the mixed solution at a set temperature to obtain an aluminum hydroxide solution; and carrying out rotational flow grading on the aluminum hydroxide solution to obtain the finished product aluminum hydroxide. The method comprises the following steps: adding seed crystals with specific particle sizes and quantity into a reaction system, taking the seed crystals as crystallization cores, preferentially adsorbing solutes in a solution, and continuously growing crystals on the surfaces of the seed crystals along with the proceeding of a reaction, so that aluminum hydroxide crystals with different particle sizes grow around the seed crystals with different particle sizes, thereby establishing a reasonable particle size gradient; and the sodium adsorption is reduced. The graded temperature control of the decomposition tank adjusts the reaction temperature of the solution according to different stages of the reaction so as to optimize the reaction conditions, promote crystal growth and reduce impurities, so that the sodium content of the final product is obviously reduced.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of aluminum hydroxide preparation, and in particular to a preparation method of corundum special-purpose aluminum hydroxide. BACKGROUND

[0002] In the field of corundum production, the quality of raw materials has a crucial impact on the performance of corundum. As an important industrial material, corundum is widely used in abrasives, refractory materials, and other high-tech fields. The improvement of its performance is directly related to the quality and efficiency of related products. However, traditional aluminum hydroxide raw materials have exposed a series of problems that need to be solved in the production process of corundum.

[0003] Firstly, the production process of traditional aluminum hydroxide is complex and difficult to control accurately. The multi-stage production process not only increases the production steps, but also leads to energy loss and time extension in the transfer process of materials, which directly affects the improvement of production efficiency. At the same time, the complex production process also puts higher requirements on the stability and maintenance of equipment, increasing the production cost. Secondly, the sodium content in traditional aluminum hydroxide products is high, which seriously affects the sintering performance of corundum and the quality of the final product. The presence of sodium elements can interfere with the sintering process of corundum, leading to an increase in sintering temperature and a decrease in sintering rate, thereby affecting the density and overall performance of corundum. For the industry that pursues high-quality corundum products, this problem cannot be ignored. In addition, the particle size distribution of traditional aluminum hydroxide is also not reasonable. The uniformity of particle size distribution is crucial for the bulk density and strength of corundum products. However, the aluminum hydroxide produced by traditional processes often has uneven particle size distribution, which leads to the fact that the performance of corundum products cannot reach the optimal state. Therefore, it is of great practical significance and research value to develop a new special-purpose aluminum hydroxide for corundum to solve the above problems and improve the performance and quality of corundum. SUMMARY

[0004] The application provides a preparation method of corundum special-purpose aluminum hydroxide to solve the technical problem of how to effectively reduce the sodium content in aluminum hydroxide products.

[0005] The application provides a preparation method of corundum special-purpose aluminum hydroxide, which comprises the following steps:

[0006] obtaining sodium aluminate concentrate;

[0007] mixing the sodium aluminate concentrate with seed crystals to obtain a mixed solution;

[0008] performing a decomposition reaction on the mixed solution at a set temperature to obtain an aluminum hydroxide solution;

[0009] performing cyclone classification on the aluminum hydroxide solution to obtain finished aluminum hydroxide.

[0010] Optionally, the mass concentration of the NK in the sodium aluminate liquor is 144 g / L to 146 g / L.

[0011] Optionally, the decomposition reaction of the mixed liquor at the set temperature comprises:

[0012] The mixed liquor is gradually discharged into a plurality of decomposition tanks for reaction, wherein the plurality of decomposition tanks comprise a decomposition first tank, a plurality of intermediate growth tanks, and a decomposition last tank.

[0013] Optionally, the temperature of the decomposition first tank is 72 DEG C to 73 DEG C, the temperature of the decomposition last tank is 55 DEG C to 56 DEG C, and the temperature difference between the plurality of decomposition tanks is less than 3 DEG C.

[0014] Optionally, the solid content of the decomposition first tank is 700 g / L to 750 g / L.

[0015] Optionally, the solid content of the decomposition last tank is 750 g / L to 800 g / L.

[0016] Optionally, the particle size of the crystal seed is 5 μm to 8 μm, and the volume of the crystal seed is 0.6% to 1.6% of the volume of the sodium aluminate liquor.

[0017] Optionally, the time of the decomposition reaction is 44 h to 46 h.

[0018] Optionally, the D50 of the underflow of the cyclone classification is 80 μm to 85 μm.

[0019] Optionally, in the finished product of aluminum hydroxide, the mass fraction of sodium oxide is less than 0.2%, and the mass fraction of crystalline alkali is 0.16% to 0.18%.

[0020] The above technical solution provided by the embodiments of the present application has the following advantages compared with the prior art:

[0021] The embodiments of the present application provide a preparation method of corundum special aluminum hydroxide, which comprises: obtaining a sodium aluminate liquor; mixing the sodium aluminate liquor with a crystal seed to obtain a mixed liquor; performing a decomposition reaction on the mixed liquor at a set temperature to obtain an aluminum hydroxide solution; and performing cyclone classification on the aluminum hydroxide solution to obtain a finished product of aluminum hydroxide. By adding a crystal seed with a specific particle size and quantity to the reaction system, the crystal seed as a crystal core preferentially adsorbs solutes in the solution, and continuously grows crystals on the surface of the crystal seed as the reaction proceeds, so that different particle sizes of aluminum hydroxide crystals grow around the crystal seeds with different particle sizes, thereby establishing a reasonable particle size gradient and reducing the adsorption of sodium. The temperature control of the decomposition tank is adjusted according to different stages of the reaction to optimize the reaction conditions, promote the growth of crystals, and reduce impurities, so that the sodium content of the final product is significantly reduced. BRIEF DESCRIPTION OF DRAWINGS

[0022] The accompanying drawings, which are incorporated herein and constitute part of the specification, illustrate embodiments consistent with the application and, together with the description, serve to explain the principles of the application.

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the accompanying drawings needed to be used in the embodiments or prior art description will be briefly introduced as follows. Obviously, those skilled in the art can obtain other drawings according to these drawings without any creative effort.

[0024] Figure 1 A flowchart of a preparation method of corundum special-purpose aluminum hydroxide provided by the embodiments of the present application. DETAILED DESCRIPTION

[0025] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without any creative effort fall within the scope of protection of the present application.

[0026] The range descriptions described herein, such as numerical range, ratio range, etc., include all possible sub-ranges and single values within the range, for example, the range description of "1 to 6" or "1-6" covers all sub-ranges (such as 1 to 3, 2 to 5, etc.) and single values (such as 1, 2, 3, 4, 5, 6) between 1 and 6. Unless otherwise specified, the terms "include", "contain" and the like used herein mean "include but not limited to"; the relationship terms "first", "second" and the like are only used to distinguish different entities or operations, and do not imply actual sequence or relationship; "and / or" means that multiple cases can exist independently or simultaneously; "at least one", "multiple", "at least one" and the like refer to any combination of the corresponding objects, including single or multiple combinations of the objects. The ratio relationships involved herein, such as mass ratio, molar ratio, etc., should be understood as the corresponding relationship between the front and rear terms in the ratio. The raw materials, reagents, instruments and equipment used herein can be purchased or prepared by existing methods.

[0027] Figure 1 A flowchart of a preparation method of corundum special-purpose aluminum hydroxide provided by the embodiments of the present application.

[0028] Please refer to Figure 1The embodiment of the present application provides a preparation method of corundum special-purpose aluminum hydroxide, and the method comprises the following steps:

[0029] S1, obtaining sodium aluminate concentrate;

[0030] In some embodiments, the mass concentration of NK in the sodium aluminate concentrate is 144g / L-146g / L.

[0031] In the embodiment of the present application, NK refers to the mass concentration of caustic alkali (NaOH) in the sodium aluminate concentrate in the form of Na2O, which is a key parameter for measuring the strength of the solution. The NK concentration of the sodium aluminate concentrate needs to be strictly controlled in the range of 144g / L-146g / L, which directly affects the seed decomposition rate and the crystalline morphology of aluminum hydroxide. If the NK concentration is higher than 146g / L, the precipitation of Al(OH)3 will be inhibited, resulting in incomplete decomposition; if the NK concentration is lower than 144g / L, the stability of the solution may be reduced, and spontaneous decomposition may occur. For example, the mass concentration of NK in the sodium aluminate concentrate can be 144g / L, 144.4g / L, 144.8g / L, 145.2g / L, 145.6g / L, 146g / L, etc.

[0032] S2, mixing the sodium aluminate concentrate with seed crystals to obtain a mixed solution;

[0033] In some embodiments, the particle size of the seed crystals is 5-8μm, and the volume of the seed crystals is 0.6%-1.6% of the volume of the sodium aluminate concentrate.

[0034] Seed crystals with a particle size of 5-8μm have a high specific surface area to volume ratio, which can provide sufficient effective nucleation sites. This particle size range matches the lattice constant of Al(OH)3 in the sodium aluminate solution (about ), which can reduce the nucleation activation energy. Compared with smaller particle sizes (such as <5μm), 5-8μm seed crystals can reduce the overlapping effect of surface hydroxyl groups, avoiding the agglomeration of grains caused by non-uniform nucleation; compared with larger particle sizes (such as >8μm), the surface defect density is moderate, which is conducive to the directional growth of the grains along the (001) crystal plane. For example, the particle size of the seed crystals can be 5μm, 5.5μm, 6μm, 6.5μm, 7μm, 7.5μm, 8μm, etc.

[0035] The volume ratio of 0.6%-1.6% of the seed crystals corresponds to a total surface area of the seed crystals in the range of 6.3x10 3 -1.7x10 4 cm 2 / L. This parameter makes the aluminum aluminate ions (Al(OH)4 -The adsorption-desorption rate of the seed crystal and the crystal growth rate reach a dynamic balance, and the induction period of the decomposition reaction can be shortened. For example, the volume of the seed crystal can be 0.6%, 0.8%, 1.0%, 1.2%, 1.4%, 1.6%, etc. of the volume of the sodium aluminate slurry.

[0036] The synergistic effect of the particle size and the proportion can reduce the physical adsorption amount of sodium oxide. The specific surface area of the 5 μm seed crystal is 1.2 m 2 / g, and the specific surface area of the 8 μm seed crystal is 0.75 m 2 / g. When the volume proportion is 0.6% to 1.6%, the total adsorption site number is controlled to be 3.5×10 18 ~9.3×10 18 sites / L, which just meets the monolayer adsorption requirement of Na + ions, and avoids the over-standard (more than 0.2%) of the mass fraction of sodium oxide caused by multilayer adsorption.

[0037] S3, performing a decomposition reaction on the mixed solution at a set temperature to obtain an aluminum hydroxide solution;

[0038] In some embodiments, the performing a decomposition reaction on the mixed solution at a set temperature comprises:

[0039] gradually discharging the mixed solution into a plurality of decomposition tanks for reaction, wherein the plurality of decomposition tanks comprise a decomposition first tank, a plurality of intermediate growth tanks, and a decomposition last tank.

[0040] The decomposition first tank, the plurality of intermediate growth tanks, and the decomposition last tank have clear functional division:

[0041] The decomposition first tank: as an initial reaction unit, a higher temperature (72°C to 73°C) is set to accelerate the dissolution of the seed crystal and the diffusion of the solute, and the solid content in the first tank is controlled to be 700 g / L to 750 g / L to promote the formation of crystal nuclei.

[0042] The intermediate growth tank: a step-by-step temperature reduction design (temperature difference between adjacent tanks <3°C) is adopted, and the crystal is grown along the (001) crystal plane through gradient temperature reduction to inhibit the generation of defects such as twinning. The solid content in the tank is gradually increased to 750 g / L to 800 g / L to ensure the densification of the crystal structure. The number of intermediate growth tanks can be adjusted according to the production capacity requirement.

[0043] The decomposition last tank: the temperature is finally reduced to 55°C to 56°C, at which time the supersaturation of the solution is reduced to below the critical value, and mainly performs crystal surface reconstruction to reduce the physical adsorption of sodium oxide.

[0044] In some embodiments, the temperature of the decomposition first tank is 72°C to 73°C, the temperature of the decomposition last tank is 55°C to 56°C, and the temperature difference between the plurality of decomposition tanks is <3°C.

[0045] As the initial stage of the decomposition reaction, higher temperature (72℃-73℃) can accelerate the dissolution of the seed crystal and the diffusion of solutes in the sodium aluminate solution, which helps to increase the concentration of aluminate ions (Al(OH)4 - ) in the solution, providing sufficient raw materials for subsequent crystal growth. Under the condition of high temperature (72℃-73℃) in the first tank, the supersaturation of the sodium aluminate solution will increase, which is conducive to the rapid formation of aluminum hydroxide nuclei. The increase of supersaturation can shorten the induction period of the decomposition reaction, and make the crystal growth process enter the stable state earlier. Finally, the high temperature environment (72℃-73℃) of the first tank provides a favorable environment for the initial growth of aluminum hydroxide crystals. At such a temperature, the crystal can more easily overcome the nucleation energy barrier, forming a large number of uniformly distributed crystal nuclei, laying a good foundation for the subsequent crystal growth stage. By controlling the temperature of the first tank within the range of 72℃-73℃, the rate of the decomposition reaction can be accelerated, thereby shortening the entire production cycle. This has a significant effect on improving production efficiency and reducing production costs. For example, the temperature of the first decomposition tank can be 72℃, 72.2℃, 72.4℃, 72.6℃, 72.8℃, 73℃, etc.

[0046] As the late stage of the decomposition reaction, lower temperature (55℃-56℃) helps the oriented growth of aluminum hydroxide crystals along specific crystal planes (such as the (001) plane), which can form crystals with dense structure and excellent performance, which is of great significance to improve the strength and thermal stability of corundum products. At a temperature of 55℃-56℃, the physical adsorption on the surface of aluminum hydroxide crystals will weaken, thereby reducing the adsorption amount of sodium oxide (Na2O) on the crystal surface, which helps to reduce the content of sodium oxide in the finished aluminum hydroxide and improve the purity and performance of the product. The low temperature environment (55℃-56℃) of the last tank helps to control the particle size distribution of aluminum hydroxide crystals, making the crystal particles more uniform. Uniform particle size distribution not only improves the appearance quality of the product, but also helps to improve the bulk density and strength of corundum products. Through the low temperature treatment (55℃-56℃) of the last tank, the structure of aluminum hydroxide crystals can be further stabilized, and the performance fluctuations caused by unstable crystal structure can be reduced, which has a positive effect on ensuring the stability and reliability of corundum products during long-term use. For example, the temperature of the last decomposition tank can be 55℃, 55.2℃, 55.4℃, 55.6℃, 55.8℃, 56℃, etc.

[0047] The small temperature difference between the tanks (<3°C) can ensure that the decomposition reaction is carried out under the condition of a smooth transition of the temperature gradient, avoiding crystal structure defects (such as twinning, dislocation, etc.) caused by sudden changes in temperature. This linear cooling mode helps the aluminum hydroxide crystal to complete the phase change process from non-steady state to steady state under controlled thermodynamic conditions, thereby improving the structural integrity and performance stability of the crystal. In addition, precise temperature gradient control can inhibit the generation of impurities (such as aluminum silicates), ensuring that the mass fraction of sodium oxide in the finished product is <0.2%, while reducing the adhesion of alkali on the surface of the crystal caused by long-term residence in the high-temperature region. Compared with the traditional single-tank decomposition process, the staged cooling system can reduce the additional heat input and maintain system heat balance through the exothermic decomposition reaction. The limiting value of the temperature difference <3°C can also prevent temperature shock caused by convection of materials between different decomposition tanks, ensuring the stability of continuous operation of the production line. This is particularly important for industrial production, as it can ensure smooth production and reduce production accidents or product quality problems caused by temperature fluctuations. For example, the temperature difference between the tanks can be 0.5°C, 1°C, 1.5°C, 2°C, 2.5°C, 3°C, etc.

[0048] In some embodiments, the solid content of the first decomposition tank is 700g / L-750g / L.

[0049] The "solid content" refers to the content of solid substances in the solution, which is usually expressed in grams per liter of solution. The high solid content environment (700g / L-750g / L) of the first tank significantly increases the crystal nucleation rate by increasing the supersaturation of sodium aluminate solution. This concentration range can maintain the surface energy of aluminum hydroxide seed crystals in the solution at an optimal state, promoting directional grain growth rather than disorderly nucleation. The upper limit of 750g / L for solid content is based on the critical threshold for the adsorption of alkali on the surface of Al(OH)3 crystals. When this value is exceeded, the amount of physically adsorbed sodium oxide on the surface of the crystal will increase nonlinearly, resulting in a mass fraction of sodium oxide in the final product exceeding the control limit of 0.2%. The lower limit of 700g / L for solid content can ensure the production efficiency of the unit volume reactor. For example, the solid content of the first decomposition tank can be 700g / L, 710g / L, 720g / L, 730g / L, 740g / L, 750g / L, etc.

[0050] In some embodiments, the solid content of the last decomposition tank is 750g / L-800g / L.

[0051] The last tank is in the late stage of the decomposition reaction, at which time the aluminum hydroxide crystals in the solution have basically completed the nucleation process. The solid content of the last tank is 750 g / L-800 g / L, which may be because during the decomposition process, as the reaction proceeds, the solid product gradually increases, so the solid content of the last tank naturally rises. For example, the solid content of the decomposition last tank can be 750 g / L, 760 g / L, 770 g / L, 780 g / L, 790 g / L, 800 g / L, etc.

[0052] In some embodiments, the time of the decomposition reaction is 44 h-46 h.

[0053] The time of the decomposition reaction of 44 h-46 h enables the aluminum hydroxide crystals to complete the complete phase transition process in the staged cooling system. After the rapid formation of crystal nuclei at a high temperature (72℃-73℃) in the first tank, the crystals complete the transition from non-stable γ-Al(OH)3 to stable α-Al(OH)3 at a temperature of 55℃-56℃ in the last tank through 44 h-46 h of continuous reaction, avoiding crystal structure defects (such as twin crystals, dislocations) caused by insufficient reaction time. A sufficiently long reaction time (44 h-46 h) is conducive to the full sedimentation and separation of impurities such as aluminosilicates, and in combination with the high concentration environment of the solid content of the last tank of 750 g / L-800 g / L, the physical adsorption amount of sodium oxide on the surface of the crystals can be reduced to a control threshold of <0.2% by mass fraction. Finally, the time of the decomposition reaction of 44 h-46 h matches the temperature gradient control between the decomposition tanks (temperature difference between tanks <3℃), so that the reaction system maintains thermal balance through its own heat release, reducing the input of external heat. For example, the time of the decomposition reaction can be 44 h, 44.4 h, 44.8 h, 45.2 h, 45.6 h, 46 h, etc.

[0054] S4, performing cyclone classification on the aluminum hydroxide solution to obtain finished aluminum hydroxide.

[0055] In the decomposition process of the Bayer process for producing aluminum oxide, after the decomposition is complete, a portion of the aluminum hydroxide solution will first be directly returned to the cyclone. The cyclone is a device that uses centrifugal force to separate solids from liquids, and can classify particles in the solution according to size. Through the classification action of the cyclone, aluminum hydroxide particles can be separated according to particle size, providing convenience for subsequent processing. The cyclone separates coarse particles (underflow) and fine particles (overflow), and the underflow is used as a product, while the aluminum hydroxide in the overflow is filtered to remove excess liquid. The filtered aluminum hydroxide particles are returned to the artificial decomposition tank for further decomposition or recycling, which helps to improve resource utilization and product purity.

[0056] In addition to the portion that is refluxed to the cyclone for classification, the remaining aluminum hydroxide solution does not need to be classified and can be directly introduced into the seed filtration process. The purpose of the seed filtration process is to thoroughly separate the solid particles in the aluminum hydroxide solution from the liquid, obtaining aluminum hydroxide solids, which will act as seeds and play an important role in the subsequent decomposition process. The aluminum hydroxide solids obtained from the seed filtration process will be mixed as seeds into the new sodium aluminate liquor and then returned to the first tank of the artificial decomposition tank. The addition of seeds can accelerate the crystallization process of aluminum hydroxide and improve the decomposition efficiency. By mixing seeds into the new liquor and returning them to the first tank, a continuous decomposition cycle can be formed, ensuring the stability and continuity of the production process. After the seeds are mixed and returned to the first tank, the next stage of the decomposition process will be carried out. This process is similar to the previous decomposition process and also requires temperature and time control to ensure the quality of the crystallization of aluminum hydroxide and the production efficiency. Through continuous decomposition cycles, high-quality aluminum hydroxide products can be continuously produced.

[0057] In some embodiments, the D50 of the underflow of the cyclone classification is 80-85 pm.

[0058] Controlling the D50 of the cyclone classification underflow to be 80-85 pm has the following positive effects: D50 (median particle size) represents the particle size of 50% of the volume of the particle group. The D50 range of 80-85 pm is regulated by the centrifugal field of the cyclone, which can effectively separate aluminum hydroxide crystals of the target particle size and reduce the inclusion of fine particles (<50 pm), ensuring that the particle size distribution of the finished product is concentrated. This narrow distribution characteristic is beneficial for the directional arrangement of crystals in the corundum sintering process, reducing porosity and improving the thermal stability of the refractory material. Coarse particles (D50 of 80-85 pm) have a lower specific surface area, which can reduce the physical adsorption of sodium oxide (Na2O) on the crystal surface. By removing fine particles (high specific surface area carriers) through cyclone classification, the mass fraction of sodium oxide in the finished product is stably controlled at <0.2%, and the crystalline alkali content is maintained at 0.16%-0.18%. This characteristic is crucial for the corrosion resistance and high temperature strength of corundum products. For example, the D50 of the underflow of the cyclone classification can be 80 pm, 81 pm, 82 pm, 83 pm, 84 pm, 85 pm, etc.

[0059] In some embodiments, the mass fraction of sodium oxide in the finished aluminum hydroxide product is <0.2%, and the mass fraction of crystalline alkali is 0.16%-0.18%.

[0060] The traditional aluminum hydroxide raw material has a high sodium content, which affects the sintering performance of corundum and the product quality, and the sodium content is reduced by the one-stage high-temperature control process and the added crystal seeds. The mass fraction of sodium oxide (Na2O) in the finished aluminum hydroxide is less than 0.2%, and the mass fraction of crystalline alkali is 0.16%-0.18%. The crystalline alkali refers to the sodium compound (such as NaAlO2) combined by chemical bonds on the surface or in the crystal lattice of the aluminum hydroxide crystal, and the content directly affects the sintering activity and the final purity of corundum. For example, the mass fraction of sodium oxide in the finished aluminum hydroxide can be 0.1%, 0.12%, 0.14%, 0.16%, 0.18%, 0.2%, etc.; and the mass fraction of crystalline alkali can be 0.16%, 0.164%, 0.168%, 0.172%, 0.176%, 0.18%, etc.

[0061] The application will be further described below in combination with specific examples. The experimental methods not specified in the following examples are generally determined according to the national standards / industry standards; if there is no corresponding national standard / industry standard, the international standard, the conventional condition or the condition suggested by the manufacturer is used.

[0062] Example 1

[0063] Aluminum source: sodium aluminate concentrate 384 m 3 / h (NK is 144.67 g / L).

[0064] Crystal seeds: added aluminum hydroxide crystal seeds (particle size 5 μm-8 μm), and the addition amount is 0.8% of the sodium aluminate concentrate.

[0065] The temperature of the first decomposition tank is 72.83°C, the temperature of the last decomposition tank is 55.23°C, and the temperature difference between the tanks is less than 3°C. The decomposition reaction time is 44.2 h. The particle size of the discharged material less than 45 μm accounts for 8.63%, the mass fraction of sodium oxide in the finished aluminum hydroxide is 0.195%, and the mass fraction of crystalline alkali is 0.175%.

[0066] Example 2

[0067] Aluminum source: sodium aluminate concentrate 391 m 3 / h (NK is 145.36 g / L).

[0068] Crystal seeds: added aluminum hydroxide crystal seeds (particle size 5 μm-8 μm), and the addition amount is 1.0% of the sodium aluminate concentrate.

[0069] The temperature of the first decomposition tank is 72.15°C, the temperature of the last decomposition tank is 55.63°C, and the temperature difference between the tanks is less than 3°C. The decomposition reaction time is 45.1 h. The particle size of the discharged material less than 45 μm accounts for 6.97%, the mass fraction of sodium oxide in the finished aluminum hydroxide is 0.193%, and the mass fraction of crystalline alkali is 0.180%.

[0070] Example 3

[0071] Aluminum source: sodium aluminate liquor 397m 3 / h (NK is 144.95 g / L).

[0072] Seed crystal: added aluminum hydroxide seed crystal (particle size 5-8 μm), and the addition amount is 1.2% of the sodium aluminate liquor.

[0073] The temperature of the first decomposition tank is 72.38℃, the temperature of the last decomposition tank is 55.74℃, and the temperature difference between the tanks is less than 3℃. The decomposition reaction time is 44.7h. The particle size of the discharge is less than 45 μm, accounting for 7.31%, the mass fraction of sodium oxide in the finished product aluminum hydroxide is 0.189%, and the mass fraction of crystalline alkali is 0.177%.

[0074] Comparative Example 1

[0075] Aluminum source: sodium aluminate liquor 415m 3 / h (NK is 148.37 g / L).

[0076] Seed crystal: added aluminum hydroxide seed crystal (particle size 5-8 μm), and the addition amount is 0.8% of the sodium aluminate liquor.

[0077] The temperature of the first decomposition tank is 71.22℃, the temperature of the last decomposition tank is 49.23℃, and the temperature difference between the tanks is not controlled. The decomposition reaction time is 44.2h. The particle size of the discharge is less than 45 μm, accounting for 13.42%, the mass fraction of sodium oxide in the finished product aluminum hydroxide is 0.231%, and the mass fraction of crystalline alkali is 0.213%.

[0078] One or more technical solutions in the embodiments of the present application have at least the following technical effects or advantages:

[0079] The method provided by the embodiments of the present application significantly reduces the sodium content in the aluminum hydroxide product. Low-sodium aluminum hydroxide can effectively reduce the sintering temperature and improve the sintering rate in corundum production, making it easier for corundum to reach a dense state, thereby improving the overall performance of corundum products.

[0080] The embodiments of the present application adopt a one-stage process, abandoning the traditional multi-stage complex process, which not only reduces the production links and the transfer of intermediate materials, but also shortens the production cycle, thereby reducing production costs and equipment investment and maintenance costs.

[0081] The foregoing detailed description of the application has been presented for purposes of illustration and description. Various modifications to the description will be readily apparent to those skilled in the art, and the generic principles defined herein can be applied to other implementations without departing from the spirit or scope of the application. Accordingly, the application is not intended to be limited to the implementations described herein but is to be accorded the widest scope consistent with the principles and novel features to the application.

Claims

1. A method for preparing aluminum hydroxide specifically for corundum, the method comprising: Sodium aluminate semen was obtained; The sodium aluminate concentrate is mixed with seed crystals to obtain a mixed solution; The mixture is decomposed at a set temperature to obtain an aluminum hydroxide solution; The aluminum hydroxide solution was subjected to hydrocyclone classification to obtain the finished aluminum hydroxide product.

2. The method according to claim 1, characterized in that, The mass concentration of NK in the sodium aluminate semen is 144 g / L to 146 g / L.

3. The method according to claim 1, characterized in that, The step of decomposing the mixture at a set temperature includes: The mixture is fed into multiple decomposition tanks in stages for reaction, wherein the multiple decomposition tanks include a first decomposition tank, multiple intermediate long tanks, and a final decomposition tank.

4. The method according to claim 3, characterized in that, The temperature of the first decomposition tank is 72℃~73℃, the temperature of the last decomposition tank is 55℃~56℃, and the temperature difference between the multiple decomposition tanks is <3℃.

5. The method according to claim 1, characterized in that, The solid content of the first decomposition tank is 700 g / L to 750 g / L.

6. The method according to claim 1, characterized in that, The solid content of the final decomposition tank is 750 g / L to 800 g / L.

7. The method according to claim 1, characterized in that, The seed crystals have a particle size of 5 μm to 8 μm and a volume of 0.6% to 1.6% of the volume of the sodium aluminate concentrate.

8. The method according to claim 1, characterized in that, The decomposition reaction takes 44 to 46 hours.

9. The method according to claim 1, characterized in that, The D50 of the underflow in the swirl classification is 80 μm to 85 μm.

10. The method according to claim 1, characterized in that, In the finished aluminum hydroxide, the mass fraction of sodium oxide is <0.2%, and the mass fraction of crystalline alkali is 0.16% to 0.18%.

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