A process for preparing alpha-phase alumina powder by using a sand mill

Abstract

The invention discloses a process for preparing α-phase alumina powder by a sand mill, comprising the following steps: S1. preparing α-phase alumina powder raw materials, water and dispersant in a stirring kettle in proportion to form slurry, and then stirring; S2. using a diaphragm pump to pump the slurry into a basket sand mill with a magnetic filtration device for grinding, so that the average particle size of the alumina powder in the slurry is ground to 2-5 μm; S3. using a diaphragm pump to pump the slurry ground in step S2 into a horizontal rod sand mill with a magnetic filtration device for grinding, so that the alumina powder in the slurry is ground to a target particle size; S4. drying the slurry ground to the target particle size in step S3 to obtain α-phase alumina powder. The process for preparing α-phase alumina powder by a sand mill of the invention improves grinding efficiency, improves the quality of alumina products, and solves the problem of sand mill screen clogging.

Description

Technical Field

[0001] The invention relates to the technical field of alumina powder preparation, and in particular to a process for preparing alpha-phase alumina powder by a sand mill. Background Art

[0002] As the most widely used ceramic powder, high-quality ultrafine alumina has excellent properties such as high temperature resistance, corrosion resistance, and wear resistance. It is unique in the fields of sapphire, lithium battery diaphragm coating, polishing powder, grinding media, etc. However, there is still a big gap between our domestic high-quality alumina and foreign ones, mainly in that the purity, particle size, particle size distribution and dispersibility of domestic products cannot meet market demand. Therefore, the research and development of high-quality ultrafine alumina powder preparation technology is very urgent.

[0003] At present, domestic alumina powder is often crushed by ball milling and basket sand milling, which has problems such as wide particle size distribution, difficulty in reaching submicron or even nanometer level, and low grinding efficiency. In the patent CN100553918C, coarse particles of alumina are refined to about 3 microns by a basket sand mill, but its particle size and particle size are wide, which cannot meet the physical and chemical performance requirements of high-quality ultrafine alumina required by the market. If the average particle size of alumina is crushed to submicron level, the grinding efficiency of the basket ball mill will be greatly reduced, and its high cost performance is difficult to achieve. In the patent CN104741176A, it is pointed out that the rod pin sand mill has advantages in grinding efficiency, micronization of grinding products, narrow distribution of product particle size and particle size, and reduction of product slurry viscosity. In the patent CN111704813A, a horizontal rod sand mill is used for wet grinding to prepare submicron alumina. During the grinding process, the alumina particles block the screen of the sand mill discharge port, resulting in slow discharge or even no discharge. This phenomenon occurs because the alumina particle size distribution is wide. When preparing the slurry, large particles of alumina are easy to agglomerate, resulting in large particles of alumina causing the sand mill to be blocked, which will eventually affect the grinding efficiency and product quality. Therefore, it is necessary to design a process method and equipment to prepare submicron alumina, obtain a narrow particle size distribution, eliminate the screen that blocks the sand mill outlet, and improve the grinding efficiency and product quality. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a process for preparing α-phase alumina powder by a sand mill unit, so as to solve the problem of slurry blocking the screen of the discharge port of the horizontal rod sand mill, improve the grinding efficiency, reduce the damage of the equipment and the grinding medium, and be used for the production of high-quality ultrafine powder.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0006] The present invention provides a process for preparing α-phase alumina powder by a sand mill, comprising the following steps:

[0007] S1. The α-phase alumina powder raw material, water and dispersant are prepared into a slurry in a stirred tank according to the proportion, and then stirred;

[0008] S2. The slurry is pumped into a basket sand mill with a magnetic filtration device using a diaphragm pump for grinding, so that the average particle size of the alumina powder in the slurry is ground to 2 to 5 μm;

[0009] S3. The slurry ground in step S2 is pumped into a horizontal rod sand mill with a magnetic filtration device using a diaphragm pump for grinding, so that the alumina powder in the slurry is ground to a target particle size;

[0010] S4. Dry the slurry that has been ground to the target particle size in step S3 to obtain alumina powder.

[0011] In the prior art, when alumina particles are ground, the slurry is first passed through a sieve with a certain mesh size to filter out large particles of alumina, and then ground through a sand mill. The large particles of alumina filtered by this technical process are not effectively utilized, the sieve filtration efficiency is slow, and it has little effect on the particle size distribution of the alumina particles. Therefore, there is a problem of large particles clogging the sand mill screen due to agglomeration.

[0012] Basket sand mills generally use alumina particles with an average particle size of 10-60μm, and horizontal rod sand mills generally use alumina particles with an average particle size of 1-3μm. If a single basket sand mill is used to grind alumina particles, it can only be refined to about 3 microns, but its particle size and particle size are wide, and it cannot meet the physical and chemical performance requirements of high-quality ultrafine alumina required by the market; if a single horizontal rod sand mill unit is used to grind alumina particles, the alumina particles that need to be purchased are small, and the production cost is high. In the grinding process provided by the present invention, a basket sand mill is first used to coarsely grind the alumina powder to refine the particle size distribution, and then fine grinding is performed by a horizontal rod sand mill, which can not only improve the grinding efficiency, improve the quality of alumina products and solve the problem of sand mill screen clogging, but also reduce production costs.

[0013] Furthermore, in step S1, the average particle size of the α-phase alumina powder raw material is 10-100 μm.

[0014] Furthermore, in step S1, the solid content of the slurry is 10-40wt.%.

[0015] Furthermore, in step S1, the dispersant is ammonium citrate, and the mass fraction of the ammonium citrate in the α-phase alumina powder is 0.05-2wt.%.

[0016] Furthermore, in step S1, the stirring time after preparing the slurry is 10-60 minutes.

[0017] Step S2 of the present invention is rough grinding, the purpose of which is to grind large α-phase alumina particles with a wide particle size distribution into smaller particles and reduce the particle size and particle size distribution of the particles. Through the magnetic filtration device, the sand grinding process can preliminarily remove the Fe element in the slurry and the pipeline. Further, in step S2, the size of the grinding medium used in the basket sand mill is Φ1-3mm.

[0018] Step S3 of the present invention is fine grinding, the purpose of which is to grind the alumina particles cyclically ground by the basket sand mill unit again into the required ultrafine particles, reduce the particle size distribution again, and optimize the product quality. The slurry after coarse grinding is ground in a horizontal rod sand mill, which can greatly improve the grinding efficiency, obtain products with narrower particle size and particle size distribution, and solve the problem of screen clogging caused by slurry agglomeration in the horizontal rod sand mill. The magnetic filtration device provided therein can completely remove the Fe element in the final slurry, thereby improving the performance of the alumina product. Furthermore, in step S3, the size of the grinding medium used in the horizontal rod sand mill is φ0.1-0.6mm.

[0019] In steps S2 and S3 of the present invention, the slurry ground by the basket sand mill or the horizontal rod sand mill is sent to the basket sand mill or the horizontal rod sand mill again for cyclic grinding until the aluminum oxide in the slurry reaches the desired particle size and particle distribution.

[0020] Furthermore, in step S4, the drying method is: the slurry is powdered by a spray drying device. The powdering by spray drying can avoid the phase change of α-phase alumina during sand grinding, which leads to a decrease in product whiteness.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. The process of the present invention first uses a basket sand mill to perform coarse grinding to refine the particle size distribution, and then uses a horizontal rod sand mill for fine grinding, which can improve the grinding efficiency, improve the quality of alumina products and solve the problem of sand mill screen clogging.

[0023] 2. The process of the present invention is an automated or semi-automated production process, which can reduce labor costs and improve product quality; at the same time, the method of the present invention is simple and easy to implement, can reduce production costs, improve product quality, and is suitable for promotion and use. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the process flow of preparing α-phase alumina powder by a sand mill unit of the present invention;

[0025] Figure 2: is the particle size distribution diagram of aluminum oxide in the embodiment of the present invention: wherein a is the particle size distribution diagram of the aluminum oxide raw material; b is the particle size distribution diagram after grinding by a basket ball mill; c is the particle size distribution diagram after grinding by a horizontal rod sand mill;

[0026] Figure 3 These are SEM images of alumina according to embodiments of the present invention: a is a SEM image after grinding with a basket ball mill; b is a SEM image after grinding with a horizontal rod sand mill. DETAILED DESCRIPTION

[0027] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0029] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods, and the materials, reagents, etc. used are all available from commercial sources unless otherwise specified.

[0030] Example 1

[0031] This embodiment provides a process for preparing α-phase alumina powder by a sand mill. The process flow diagram is shown in Figure 1 , specifically including the following steps:

[0032] (1) Pre-dispersion

[0033] 50 kg of α-phase alumina powder with an average particle size of 10-100 μm, deionized water and dispersant ammonium citrate were fully dispersed in a stirring tank in a mass ratio of 1:9:0.003.

[0034] (2) Coarse grinding

[0035] The dispersed slurry in the stirring kettle flows into the operating dispersion kettle, and then the slurry is pumped into the basket sand mill through a diaphragm pump for cyclic grinding. The specific process parameters of the cyclic grinding are: the grinding medium is alumina balls of φ1-3mm; the speed of the basket sand mill is 800-1400rpm; the cyclic grinding time is 1-4h; the slurry ground by the basket sand mill passes through a magnetic filtration device to achieve a preliminary Fe removal effect; and the particle size distribution of the slurry is tested using a laser particle size analyzer.

[0036] (3) Fine grinding

[0037] The slurry after rough grinding is pumped into the horizontal rod sand mill through a diaphragm pump for cyclic grinding. The specific process parameters of the cyclic grinding are: the grinding medium is alumina balls of φ0.1-0.6 mm; the rotation speed of the horizontal rod sand mill is 500-1200 rpm; the cyclic grinding time is 5-10 hours; the slurry ground by the horizontal rod sand mill passes through a magnetic filtration device to achieve the effect of removing Fe impurity elements; and the particle size distribution of the slurry is tested using a laser particle size analyzer.

[0038] (4) Flour milling

[0039] After multiple cycles of grinding in step (3), the slurry that reaches the desired particle size is dried into powder by a spray drying device. The spray drying device dynamically and quickly dries the alumina slurry at high temperature. This process can increase the whiteness of the product and prevent agglomeration between particles.

[0040] Example 2

[0041] This embodiment is basically the same as Embodiment 1, except that:

[0042] In this embodiment, step (1) is:

[0043] (1) Pre-dispersion

[0044] 50 kg of α-phase alumina powder with an average particle size of 10-100 μm, deionized water and dispersant ammonium citrate were fully dispersed in a stirring tank at a mass ratio of 1:4:0.005.

[0045] Example 3

[0046] This embodiment is basically the same as Embodiment 1, except that:

[0047] In this embodiment, step (1) is:

[0048] (1) Pre-dispersion

[0049] 50 kg of α-phase alumina powder with an average particle size of 10-100 μm, deionized water and dispersant ammonium citrate were fully dispersed in a stirring tank at a mass ratio of 1:2.3:0.007.

[0050] Example 4

[0051] This embodiment is basically the same as Embodiment 1, except that:

[0052] In this embodiment, step (1) is:

[0053] (1) Pre-dispersion

[0054] 50 kg of α-phase alumina powder with an average particle size of 10-100 μm, deionized water and dispersant ammonium citrate were fully dispersed in a stirring tank at a mass ratio of 1:1.5:0.009.

[0055] Performance Testing

[0056] Figure 2 The particle size distribution diagram of alumina raw material, after being ground by a basket ball mill and after being ground by a horizontal rod sand mill. It can be seen from the figure that the particle size of the alumina raw material without ball milling is in the range of 0.5 to 100 μm, D10 = 1.094 μm, D50 = 11.73 μm, D90 = 44.22 μm; after ball milling by a basket ball mill, the particle size range of the alumina powder is reduced, D10 = 0.836 μm, D50 = 3.604 μm, D90 = 18.35 μm; after ball milling by a horizontal rod ball mill, the particle size range of the alumina powder is greatly reduced, D10 = 0.295 μm, D50 = 0.464 μm, D90 = 0.798 μm.

[0057] Figure 3 The SEM images of aluminum oxide after being ground by a basket ball mill and a horizontal rod sand mill are shown in Figure 1. As can be seen from the figure, after being ground by a basket ball mill, the size of the aluminum oxide powder particles is larger and the particle size is uneven; after being ground by a horizontal rod sand mill, the size of the aluminum oxide powder particles is smaller and the size is more uniform.

[0058] XRF test was performed on the alumina before and after grinding in the above example. The results are shown in Table 1.

[0059] Table 1 XRF test results of alumina before and after grinding

[0060]

[0061] By comparing the metal elements in the samples of Examples 1-5 through XRF analysis, it can be seen that impurities Fe and Na elements exist in the products, among which Fe disappears after grinding, mainly because the Fe removal device plays a role in removing Fe elements during the grinding process; the Na element in the product always remains the same as the content in the raw material.

[0062] In summary, the present invention provides a process for preparing α-phase alumina powder by a sand mill unit, by first using a basket sand mill for coarse grinding to refine the particle size distribution, and then using a horizontal rod sand mill for fine grinding, submicron-level alumina powder is successfully ground. This method can improve grinding efficiency, enhance the quality of alumina products, and solve the problem of sand mill screen clogging.

[0063] The above-described embodiments are only preferred embodiments for fully illustrating the present invention, and the protection scope of the present invention is not limited thereto. Equivalent substitutions or changes made by those skilled in the art based on the present invention are within the protection scope of the present invention. The protection scope of the present invention shall be subject to the claims.

Claims

1. A process for preparing α-phase alumina powder by a sand mill, characterized in that: The following steps are involved: S1. The α-phase alumina powder raw material, water and ammonium citrate were prepared into a slurry in a stirring tank at a ratio of 1:4:0.005 or 1:1.5:0.009, and then stirred; S2. The slurry is pumped into a basket sand mill with a magnetic filtration device using a diaphragm pump for grinding, so that the average particle size of the alumina powder in the slurry is ground to 2 to 5 μm; the size of the grinding medium used in the basket sand mill is Φ1 to 3 mm; S3. The slurry ground in step S2 is pumped into a horizontal rod sand mill with a magnetic filtration device using a diaphragm pump for grinding, so that the alumina powder in the slurry is ground to a target particle size; the size of the grinding medium used in the horizontal rod sand mill is Φ0.1 to 0.6 mm; S4. Dry the slurry that has been ground to a target particle size in step S3 to obtain α-phase alumina powder.

2. The process for preparing α-phase alumina powder by a sand mill assembly according to claim 1, characterized in that: In step S1, the average particle size of the α-phase alumina powder raw material is 10 to 100 μm.

3. The process for preparing α-phase alumina powder by a sand mill assembly according to claim 1, characterized in that: In step S1, the solid content of the slurry is 10-40 wt.%.

4. The process for preparing α-phase alumina powder by a sand mill assembly according to claim 1, characterized in that: In step S1, the stirring time after preparing the slurry is 10 to 60 minutes.

5. The process for preparing α-phase alumina powder by a sand mill assembly according to claim 1, characterized in that: In step S4, the drying method is: the slurry is powdered by a spray drying device.

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