Fluidized grinding ball device

Abstract

This invention discloses a fluidized bed grinding device, belonging to the field of ceramsite preparation technology. This fluidized bed grinding device is used to shape and / or grind particles into spherical shapes using a fluidized bed method. The device includes: a first screen, positioned at the lower part of the device; a cover, comprising a frustum-shaped barrel and a cylindrical barrel joined together, with the outer periphery of the smaller radius end of the frustum-shaped barrel connected to the outer periphery of the first screen; a grinding rod assembly, comprising multiple grinding rods with rough surfaces, vertically fixed on the first screen and located inside the cover; and a fluidizing device for introducing fluidizing air to continuously collide the particles with the grinding rods. The fluidized bed grinding device provided by this invention can grind particles of different shapes into spherical particles according to different particle size requirements, and the resulting spherical particles have high particle size uniformity.

Description

[0001] This application is a divisional application of the patent application filed on September 6, 2024, with application number 202411245058.2 and entitled "Fluorescent Grinding Ball Apparatus and Grinding Ball Method Using the Same". Technical Field

[0002] This invention belongs to the field of ceramic particle preparation technology, specifically relating to a fluidized grinding ball device. Background Technology

[0003] Spherical ceramic particles are used in numerous industrial processes. For example, zirconium oxide and silicon carbide microspheres are used as grinding media in ball milling, while alumina, silica, titanium oxide, and zirconium oxide microspheres are used as catalyst supports in industrial catalysis. Many applications require high particle size uniformity of spherical ceramic particles: for example, ball milling requires uniform particle size of the grinding media, otherwise, the particle size uniformity of the milled products is easily poor. Catalyst supports with poor particle size uniformity affect the uniformity of catalyst loading and catalytic reaction, which is particularly significant for the uniformity of catalytic reactions in moving beds and fluidized beds, ultimately reducing the yield or selectivity of the catalytic reaction.

[0004] The main industrial method for preparing spherical ceramsite is the rolling forming method. This involves first obtaining strip-shaped plastic particles through extrusion, then rolling the plastic particles in a pellet rounding machine to reshape them into spheres. This method has high output, is simple, and is widely used. However, the rolling time in the pellet rounding method is short (usually no more than 5 minutes, rarely exceeding 10 minutes). Individual plastic particles have high moisture content and good internal cohesion, making them less prone to powder loss due to grinding during rolling. Their mass remains essentially unchanged during rolling, and multiple particles easily aggregate and adhere together.

[0005] Therefore, the length of the extruded plastic body determines the particle size of the product spheres, and uneven extrusion length will directly lead to uneven particle size. The relative deviation of the length distribution of the strip extruder increases as the target particle size decreases, so this method is more suitable for producing particles larger than 5 mm, while the particle size uniformity is poor when the target particle size is small (e.g., less than 5 mm). Summary of the Invention

[0006] In view of this, the present invention aims to provide a fluidized bed grinding ball device and a grinding ball method using the fluidized bed grinding ball device. This fluidized bed grinding ball device and grinding method can grind particles of different shapes into spherical particles according to different particle size requirements, and the resulting spherical particles have high particle size uniformity. The technical solution is as follows:

[0007] According to one aspect of the present invention, a fluidized grinding ball apparatus is provided.

[0008] The fluidized bed grinding ball device is used to shape and / or grind particles into spherical shapes in a fluidized bed manner; the fluidized bed grinding ball device includes:

[0009] A first screen is configured to be located at the lower part of the fluidized grinding ball device;

[0010] The cover includes a frustum-shaped barrel and a cylindrical barrel joined together, with the outer periphery of the smaller radius end of the frustum-shaped barrel connected to the outer periphery of the first screen.

[0011] A polishing rod assembly comprising multiple polishing rods with roughened surfaces, the multiple polishing rods being vertically fixed on a first screen and located inside a shroud; and,

[0012] A fluidizing device for introducing fluidizing air that causes the particles to be processed to continuously collide with multiple grinding rods.

[0013] In some embodiments, the combination of the fluidization device and the grinding rod assembly is used to shape and grind the particles to be processed; the number of grinding rods is not less than 10, the grinding rods are arranged in a hexagonal pattern, the distance between the grinding rods is 0.2 to 3 cm, and the grinding rods are higher than the upper plane of the frustum-shaped barrel, but not higher than the upper plane of the cylindrical barrel.

[0014] In some embodiments, the plurality of grinding rods are higher than the height of the frustum-shaped barrel but do not exceed 3 / 4 of the height of the cylindrical barrel; the fluidized grinding ball device also includes a second screen, which is disposed directly below the first screen, and the periphery of the second screen is movably connected to the periphery of the first screen; the second screen is used to prevent the particles to be processed from falling into the fluidization device.

[0015] According to another aspect of the present invention, a method for grinding balls using the above-described fluidized grinding ball apparatus is provided. The grinding ball method includes the following steps:

[0016] Pour the particles to be processed into the hopper of the fluidized grinding ball device;

[0017] Fluidizing air of the first volume is introduced until the sphericity of the particles reaches the preset target. The first volume of fluidizing air is used to make the particles to be treated continuously collide with the rough outer walls of multiple grinding rods. The highest height to which the particles to be treated are blown up does not exceed the height of the multiple grinding rods.

[0018] In some embodiments, in the first stage, the particles to be treated are wet, non-spherical plastic particles. The fluidization device causes the non-spherical plastic particles to gradually be shaped into spheres as they continuously collide with multiple grinding rods and the wall of the hood in a turbulent fluidized state. In the second stage, as the particles to be treated dry from the surface inward, the surface of the particles to be treated gradually wears down, the mass of a single particle to be treated decreases, and the height of the particles blown up in the fluidization device gradually increases until ground particles are produced, wherein the moisture content of the particles to be treated is 25% to 70%.

[0019] In some embodiments, when the sphericity of the ground particles does not meet the expected target, water is sprayed from the top of the fluidized grinding ball device into the hood to slow down the drying speed of the particles to be treated and prolong the shaping time; by controlling a predetermined proportion of the particles to be treated to be blown to a higher height, the wear rate of larger particles to be treated is faster, so that larger particles to be treated are ground faster and smaller particles to be treated are ground slower, and the size of the particles to be treated gradually converges as the fluidization process proceeds; during the grinding process, samples are taken at any time to detect the particle size, particle size distribution span, and aspect ratio of the particles to be treated; during the fluidization process, the fluidization device dries the particles to be treated from the outside to the inside, so that the particles to be treated that are dried on the outside do not stick together.

[0020] In some embodiments, the first air volume is calculated according to the following formula:

[0021] A1 = 5.29 - a + 8.73 × D 50 +20.0×ρ;

[0022] Where A1 is the first air volume, D 50 ρ is the average particle size of the particles to be treated, ρ is the average bulk density of the particles to be treated, and a is a constant greater than 2;

[0023] The larger the aspect ratio of the particles to be processed, the smaller the first air volume should be set; the larger the bed thickness of the particles to be processed, the larger the first air volume should be set.

[0024] In some embodiments, the percentage of particles to be processed that are higher than the tops of the multiple grinding rods is equal to the sampling weight of the bottom sampler / (the sampling weight of the bottom sampler + the sampling weight of the middle sampler in the same time interval) × 100%, wherein the bottom sampler takes samples from the bottom of the cover barrel, and the middle sampler takes samples from inside the cover barrel that are higher than the height of the multiple grinding rods.

[0025] In some embodiments, the grinding method further includes the following steps:

[0026] The air volume of the fluidizing air is continuously adjusted to maintain a preset percentage of the particles to be treated being blown to a height exceeding the height of multiple grinding rods.

[0027] Once the particles to be processed meet the preset particle size target, the fluidization air is stopped.

[0028] The preset percentage is 20% to 30%.

[0029] In some embodiments, the air volume of the fluidizing air is continuously adjusted by first increasing the air volume to a second air volume, and then gradually decreasing it to a third air volume.

[0030] The fluidized grinding ball apparatus and grinding ball method using the present invention provided by embodiments of the present invention have at least one or a portion of the following advantages:

[0031] (1) The fluidized grinding ball device provided in the embodiments of the present invention adopts a combination of fluidization process and grinding rod to achieve the shaping (first stage) and grinding (second stage) of the particles to be processed. In the first stage, when the particles to be processed are freshly extruded non-spherical plastic particles (such as strips), due to the high water content (usually in the range of 25% to 70%), the non-spherical particles in the turbulent fluidization state are gradually shaped into spherical shapes as they continuously collide with the grinding rod, other particles and the wall of the cover. In this stage, when the non-spherical plastic particles are relatively wet, the deformation is mainly plastic, and grinding occurs less. In the second stage, as the particles gradually dry from the surface to the inside, the adhesion between the dried outer wall and the particles decreases, and the particles... As the particle surface gradually wears down, the edges are further smoothed, the mass of individual particles decreases, and the height of the particles in the fluidized bed gradually increases until they are ground into particles (particles with the required particle size). The ultrafine particles generated by particle wear are blown out of the grinding ball device from the top by the fluidizing air and collected by a cyclone or bag filter. If only the shaping of non-spherical particles (to a certain degree of sphericity) is required, only the first stage needs to be completed. If the sphericity is insufficient, water can be continuously sprayed through the top atomizing nozzle to slow down the drying speed of the plastic body and extend the time of the sphericification (shaping) stage. If the particles are dried non-plastic bodies, the grinding stage can be directly entered from the start of fluidization. This method is applicable to particles of any shape and has a wide range of applications.

[0032] (2) The grinding ball method provided in the embodiments of the present invention controls a certain percentage of particles to be blown higher, which causes a faster rate of wear on larger particles. As fluidization continues, larger particles, due to their heavier mass, are blown to a lower height in the fluidized bed (the highest blown height should not exceed the height of the top of the grinding rod), and thus will be continuously ground by the grinding rod, resulting in more wear. The mass of the particles gradually decreases with grinding. Smaller particles, due to their smaller mass, are blown to a higher height in the fluidized bed and have more time to be blown above the top of the grinding ball device. Therefore, smaller particles are less worn by the grinding rod. On the other hand, larger particles shuttle through the narrow gap between the grinding rods and have more opportunities to collide with the grinding rod than smaller particles. Moreover, larger particles, due to their greater weight, will produce more powder when ground. For the above reasons, larger particles are ground faster and smaller particles are ground slower, so that the particle size gradually becomes more uniform as the fluidization process proceeds, thereby improving particle size uniformity, i.e., reducing the particle size distribution span.

[0033] (3) The grinding method provided in the embodiments of the present invention can precisely control the particle size to achieve the target particle size. Through the fluidization device, samples can be taken at any time during the grinding process (the amount of each sample is usually in the range of 5 to 20g). The sample is taken out and the particle size, particle size distribution span and aspect ratio are detected by an image particle size analyzer such as CamSize. The total time is no more than 20 minutes. By comparing the detection results with the target, it can be quickly confirmed whether the particles meet the standard. Since the method can achieve the particle size gradually decreases with the increase of fluidization time, the particle size, particle size distribution span and other parameters can be quickly detected by sampling detection. Based on this, the fluidization time can be controlled to fine-tune the particle size. When the target is reached, the machine can be stopped quickly to achieve precise control of the particle size and particle size distribution span. Such fine-tuning cannot be achieved in the ball rolling mechanism because the particle mass remains unchanged during the ball rolling process.

[0034] (4) The ball grinding method provided in the embodiments of the present invention can avoid the aggregation and adhesion of multiple particles commonly found in the ball rolling machine; during the fluidization process, the extrusion pressure between particles is significantly less than the extrusion pressure in the ball rolling machine, making it difficult for particles to agglomerate; and the fluidization process dries the particles from the outside to the inside, while the particles with dry outer surfaces will not agglomerate.

[0035] (5) The main parameters of the grinding ball method provided in the embodiments of the present invention can be quantitatively or semi-quantitatively determined by experimental methods. Combined with actual experiments, it has high operability. For example, the air volume affects the height of the particles being blown up, the collision with the grinding rod, the frequency and intensity of friction, etc., which are crucial for obtaining the target particle size, particle size distribution and aspect ratio. Therefore, it is necessary to set the air volume quantitatively and continuously adjust it during the processing. The appropriate air volume setting is significantly positively correlated with the average particle size and particle density. Attached Figure Description

[0036] These and / or other aspects and advantages of the present invention will become apparent and readily understood from the following description of preferred embodiments taken in conjunction with the accompanying drawings, in which:

[0037] Figure 1 This is a schematic diagram of a fluidized grinding ball device according to an embodiment of the present invention;

[0038] Figure 2 for Figure 1 The diagram shows a modified example of a fluidized grinding ball apparatus.

[0039] The reference numerals in the attached figures are explained as follows:

[0040] 100-Fluidized grinding ball device;

[0041] 10-First screen; 20-Cover barrel; 21-Frustum-shaped barrel; 22-Cylindrical barrel; 30-Grinding rod assembly; 40-Second screen; 50-Bottom barrel sampler; 60-Middle barrel sampler; 70-Atomizing nozzle;

[0042] 200 - Particles to be processed;

[0043] 210 - Initial particles to be processed; 220 - Larger particles to be processed; 230 - Smaller particles to be processed. Detailed Implementation

[0044] The features of the present invention are further illustrated below through specific embodiments. The following description of the embodiments of the present invention with reference to the accompanying drawings is intended to explain the overall concept of the present invention and should not be construed as a limitation thereof.

[0045] In this invention, the particle size distribution span is defined as (D 90 -D 10 ) / D 50 (×100%), where D is the particle diameter, and the subscript number indicates the percentage of particles smaller than that diameter. The percentage is calculated as a volume fraction, and the same applies below; for example, D 50 The particle size that represents the proportion of particles smaller than this size in the particle distribution, which accounts for 50% of the total volume, is also often referred to as the average particle size. D 90 D 10 and D 50 All of these measurements can be obtained using a CamS i zer image particle size analyzer.

[0046] like Figure 1As shown, one embodiment of the present invention provides a fluidized grinding ball device 100 for shaping particles 210 to be processed into spherical shapes and / or grinding them into spherical particles with a particle size that meets the target requirements in a fluidized manner. The fluidized grinding ball device 100 includes four main components: a fluidizing device (not shown), a first screen 10, a cover 20, and a grinding rod assembly 30.

[0047] The cover 20 comprises two parts: a frustum-shaped barrel 21 and a cylindrical barrel 22. Specifically, it is assembled from the frustum-shaped barrel 21 and the cylindrical barrel 22 from bottom to top, and may also include other necessary components. The outer periphery of the smaller radius end of the frustum-shaped barrel 21 is connected to the outer periphery of the first screen 10. The grinding rod assembly 30 includes multiple grinding rods with rough surfaces. The multiple grinding rods are vertically fixed on the first screen 10, and are higher than the upper plane of the frustum-shaped barrel 21, but not exceeding the upper plane of the cylindrical barrel 22. The fluidization device is used to introduce fluidizing air that causes the particles 200 to be treated (including the initial particles 210, larger particles 220, and smaller particles 230) to continuously collide with each grinding rod assembly 30.

[0048] Furthermore, the fluidized grinding ball apparatus 100 may also include a collection device (not shown) for collecting ultrafine particulate waste generated during grinding that is blown out from the top of the cylindrical barrel 22 by fluidizing air.

[0049] In one embodiment, the first screen 10 is used to prevent the particles 200 to be processed during the grinding process from falling into the bellows below the fluidizing device. If the first screen 10 cannot meet the requirement of preventing the particles 200 to be processed from falling into the bellows below the fluidizing device during the grinding process, the fluidized grinding ball device 100 can also provide a second screen 40 according to the particle size requirement of the particles 200 to be processed. The second screen 40 is located directly below the first screen 10, and the periphery of the second screen 40 is movably connected to the periphery of the first screen 10. The second screen 40 is a replaceable part used to adapt to the particle size of the target particles, that is, the mesh diameter of the second screen 40 is smaller than the mesh diameter of the first screen 10, i.e., it is comparable to the particle size of the target particles.

[0050] The main specifications of the fluidized grinding ball device 100 used in this embodiment of the invention are as follows:

[0051] The inner diameter of the bottom of the frustum-shaped barrel 21 is 10 cm, the inner diameter of the top of the frustum-shaped barrel 21 is 20 cm, and the height is 18 cm.

[0052] The cylindrical barrel 22 has an inner diameter of 20 cm and a height of 40 cm.

[0053] The fluidized bed grinding apparatus 100 is suitable for processing particles 200 weighing between 100 and 1500 grams. The first screen 10 is, for example, a 200-mesh stainless steel screen, with a circular perimeter. The collection device, i.e., the fine powder collection device, employs a single-stage cyclone separator with a tail-end filter bag. The blown air is at room temperature, and the maximum blower volume is, for example, approximately 2 cubic meters per minute, with an airflow setting range of, for example, 0 to 100. Of course, those skilled in the art will understand that the values ​​of the above parameters can be set as needed.

[0054] The polishing rod assembly 30 may, for example, use 19 polishing rods, although the number of polishing rods in the assembly 30 can be set as needed. Further, the polishing rods can be arranged in a hexagonal (e.g., regular hexagon) configuration. Alternatively, the spacing between two adjacent polishing rods is 0.8 cm, and each polishing rod has a diameter of 1.2 cm and a length of 35 cm. After installation, the tops of the polishing rods in the assembly 30 are higher than the frustum-shaped barrel 21 but do not exceed half the length of the cylindrical barrel 22. The polishing rod closest to the edge of the first screen 10 is 0.4 cm from the edge of the first screen 10. The first screen 10 has drilled holes in its ring, allowing screws to securely connect the frustum-shaped barrel 21 to the first screen 10. As described above, those skilled in the art can set specific values ​​for the above parameters as needed, and are not limited to the values ​​exemplified in the present invention.

[0055] Another embodiment of the present invention provides a grinding method using the above-described fluidized grinding ball apparatus 100, comprising the following steps:

[0056] Step 1: Pour the particles 200 to be processed directly into the fluidized grinding ball device 100, such as the cover tank 20, or add them into the fluidized grinding ball device 100 through a feeder such as an auger or pneumatic conveyor.

[0057] Step 2: Introduce the first volume of fluidizing air to start fluidizing the particles 200 to be treated (usually controlled in a turbulent fluidization state). The first volume of fluidizing air is used to keep the particles 200 to be treated in a turbulent fluidization state and the highest height they are blown up does not exceed the height of multiple grinding rods. The particles 200 to be treated continuously collide with multiple grinding rods, other particles and the wall of the cover 20. All the particles 200 to be treated gradually transform into spherical shapes until the sphericity of the particles reaches the preset target, and spherical particles are obtained.

[0058] The particles 200 to be processed (especially the initial particles 210) are usually freshly extruded non-spherical plastic particles. Due to their high water content (typically in the range of 25% to 70%), the non-spherical particles in the turbulent fluidization state are gradually shaped into spherical shapes through continuous collisions with multiple grinding rod components 30, other particles, and the wall of the shroud 20, but their volume does not decrease. Figure 2 As shown, in this stage, if the moisture content of the particles 200 to be processed is insufficient, the atomizing nozzles 70 positioned directly above the multiple grinding rod assemblies 30 can be used to maintain a certain moisture content in the particles 200 to be processed.

[0059] To determine the airflow setting where >99% of the particles are blown to a maximum height below the top of the multiple grinding rod assemblies 30, alternatively, embodiments of the present invention use a fluidized grinding ball device 100 of the above specifications to conduct airflow experiments and obtain 104 sets of experimental data. Experimental verification shows that the airflow setting (A, range 0-100) where >99% of the particles are blown to a maximum height below the top of the multiple grinding rod assemblies 30 is consistent with the average particle size (D). 50 (unit: mm) and average bulk density of particles (ρ, unit: g / cm³). 3 The empirical formula is:

[0060] A = 5.29 - a + 8.73 × D 50 +20.0×ρ;

[0061] Where A is the air volume, and D is the air volume. 50 ρ is the average particle size of the particles 200 to be processed, and ρ is the average bulk density of the particles 200 to be processed.

[0062] The t-test results show that for D 50 The statistical values ​​for ρ and t are 8.7 and 4.8 respectively, therefore A and D... 50 Both ρ and ρ are significantly correlated; Adjusted R 2 =0.75, therefore the setting of A is 75% determined by the above two parameters.

[0063] In practice, the particles 200 to be processed during the particle fluidization process are relatively dry and their density will decrease. Therefore, a slightly lower air velocity needs to be set to avoid the particles being blown too high.

[0064] In an embodiment of the present invention, based on experience, the first air volume is set as follows:

[0065] A1 = 5.29 - a + 8.73 × D 50 +20.0×ρ;

[0066] Where A1 is the first air volume, D 50 ρ is the average particle size of the particles 200 to be processed, ρ is the average bulk density of the particles 200 to be processed, and a is a constant greater than 2, preferably 3 in this embodiment.

[0067] In addition, the first air volume is also affected by other factors: the larger the aspect ratio of the particles 200 to be treated (the lower the sphericity), the smaller the air volume should be set, so as to avoid the particles with low sphericity being blown too high and thus less polished; the larger the bed thickness (total weight of particles) of the particles 200 to be treated, the larger the first air volume should be set, because the thicker bed causes greater air resistance.

[0068] To achieve better particle size separation and allow smaller particles to be blown higher than the top of the grinding rod, the airflow should be increased based on the A value obtained above. The more pronounced the required separation effect, the higher the initial airflow should be. The influence of these factors on the initial airflow setting can also be obtained through empirical formulas combined with actual experiments.

[0069] Step 3: After shaping the particles 200 to be processed into spherical particles, increase the air volume from the first air volume to the second air volume, and then gradually decrease it to the third air volume. The purpose is to keep the maximum height of the particles 200 to be processed exceeding the height of the multiple polishing rod components 30.

[0070] like Figure 1 As shown, smaller particles 230 have more time to be blown above the top of the fluidized grinding ball device 100 and are worn less by the multiple grinding rod assemblies 30; smaller particles 220 are at a lower height within the shroud 20 (not exceeding the upper height of the multiple grinding rod assemblies 30) and are ground more frequently. The ground ultrafine particle waste generated by particle wear is blown out of the fluidized grinding ball device 100 from the top by fluidizing air and collected by a collection device such as a cyclone and / or a bag filter. In an embodiment of the invention, alternatively, the second air volume, the third air volume, and the adjustment speed should all be obtained by continuously adjusting the air volume through sampling in conjunction with the above formulas.

[0071] The percentage of particles whose height exceeds the top of multiple grinding rod components 30 = the sampling weight of the bottom barrel sampler 50 / (the sampling weight of the bottom barrel sampler 50 + the sampling weight of the middle barrel sampler 60 in the same time interval) × 100%.

[0072] Step 4: After all the particles to be processed 200 have reached the preset target size, stop the fluidizing air and end the fluidized grinding process to obtain uniform spherical particles with a small particle size distribution range and a low aspect ratio.

[0073] The method for determining whether the particle size meets the preset target in this invention is as follows: During the grinding process, samples are taken, for example, 5-20g each time. The particle size, particle size distribution span, and aspect ratio are then detected using an image particle size analyzer such as CamSizer. The total time taken is no more than 5 minutes. By comparing the detection results with the target, it can be quickly (within 5 minutes) determined whether the target has been met. Alternatively, the bottom sampler 50 and / or the middle sampler 60 are cylindrical hollow tubes that can be pulled out / pushed forward and rotated, with a groove at the bottom. During sampling, the cylindrical hollow tube is rotated 180 degrees so that the groove opening faces upward, allowing the particles to fall into the groove and be collected; pulling out the cylindrical hollow tube and rotating it 180 degrees so that the groove opening faces downward allows the particles to fall out.

[0074] Similarly, other equipment parameters, such as the size of the grinding rods in the multiple grinding rod assembly 30, the density of the multiple grinding rods, and the gap width, can also be obtained by a similar method.

[0075] Example 1:

[0076] The objective of this embodiment is to obtain uniform spherical particles with an average particle size of 2.7 mm using the fluidized grinding ball device 100.

[0077] The raw material composition for the extruded plastic body was alumina: peanut shell powder pore-forming agent: starch: latex: water = 100:30:5:0.5:78. The moisture content, measured by a halogen moisture analyzer (endpoint temperature set to 105℃), was 40.3%. After thorough mixing (mixing time 8 minutes), the mixture was extruded through a die with a 3.0 mm inner diameter channel to obtain a cylindrical strip-shaped plastic body. Corn flour with a particle size of 35 to 60 mesh was used as a dispersant to prevent excessive aggregation and adhesion of the plastic body.

[0078] Using vernier calipers, randomly measure the cross-sectional diameter and length of 50 strip-shaped plastic bodies, and calculate d. 90 d 50 d 10 l 90 l 50 l 10 Where d represents the cross-sectional diameter of the strip-shaped plastic body, and the subscript numbers indicate percentiles (percentages are calculated as length fractions rather than volume fractions); for example, d 50 This represents the diameter when the sum of the diameters of particles smaller than this diameter accounts for 50% of the total diameter of all particles; l represents the length of the strip-shaped plastic body, and the subscript numbers indicate percentiles; e.g., l 50 This represents the length when the total length of particles shorter than this value accounts for 50% of the total length of all particles. (Based on d) 90 d 50 d 10 The calculated diameter distribution span is:

[0079] (d 90 -d 10 ) / d 50 = (3.10 - 2.81) / 2.96 = 10%;

[0080] According to l 90 l 50 l 10 The length distribution span was calculated as follows:

[0081] (l 90 -l 10 ) / l 50 = (3.42 - 2.33) / 2.86 = 38%.

[0082] The D of this strip-shaped plastic body was measured by the CamS izer image particle size analyzer. 90 D 50 and D 10 The particle size distribution span is (D 90 -D 10 ) / D 50 = (3.65-2.82) / 3.32 = 25%. Where D represents the diameter of the equivalent sphere calculated by the instrument, and the subscript numbers indicate the percentile (percentages are calculated as volume fractions). The image particle size analyzer also measured the average aspect ratio to be 1.23. The aspect ratio is the ratio of the length to the width of the circumscribed rectangle of the two-dimensional image of the particle taken by a high-speed camera. It can be used to characterize the degree of deviation of the particle from a perfect sphere; the closer the value is to 1, the closer the particle morphology is to a sphere.

[0083] In Example 1, under the initial conditions D 50 The diameter is 3.32 mm, and the density is 0.82 g / cm³. 3 According to A1 = 5.29 - 3 + 8.73 × D 50 +20.0×ρ; we can find that A1 is 48.

[0084] Pour 500 grams of extruded strip plastic body into the bed. Turn on the fluidizing air device to introduce fluidizing air, so that the strip plastic body is in a turbulent fluidization state. The initial air volume is set to 48.

[0085] During the shaping stage (first stage), which in this embodiment is the first 15 minutes of the fluidization process, the strip-shaped plastic body moves within a range below the height of the multiple grinding rods (the highest position of the strip-shaped plastic body does not exceed the top of the multiple grinding rods). The yellow corn flour, due to its small particle size, is mostly carried away by the fluidizing air in the first minute of the fluidization process. The small amount of corn flour adhering to the plastic body particles is also detached from the plastic body and carried away by the fluidizing air during the remaining time as the plastic body particles dry, fluidize, and are ground. During this stage, it can be observed that the plastic body particles gradually dry, and the strip-shaped plastic body gradually transforms into a spherical shape due to collisions. Sampling was performed at the end of the plasticization stage. The moisture content of the particles was measured to be 5.3% by a halogen moisture analyzer, and the average particle size D was measured by an image particle size analyzer. 50 The particle size is 3.35 mm, the particle size distribution range is (3.70-2.92) / 3.35=23%, ​​and the average aspect ratio is 1.11.

[0086] After shaping, increase the airflow to 58 and enter the polishing stage (second stage). At this point, approximately 25% by weight of particles will be blown up to a height exceeding the tips of multiple polishing rods.

[0087] During the remaining hour, the airflow was adjusted to maintain the highest blowing height of 25% by weight particles above the tips of multiple grinding rods; the airflow was gradually reduced from 58 to 51. During this stage, the particles gradually abraded, and a large number of white, smoky particles were observed forming within the bed. These were ultrafine particle wastes generated by particle abrasion, carried out from the top by the fluidizing air. At the end of the hour, the fluidizing air was stopped, ending the fluidized bed grinding process, and residual powder was removed using a sieve. The resulting particles had a moisture content of 3.3%, an average particle size of 2.91 mm, a particle size distribution span of (3.12-2.68) / 2.91 = 15%, and an average aspect ratio of 1.08. The particles were calcined at 650℃ for 3 hours to obtain the final ceramsite product. Its average particle size was 2.72 mm, the particle size distribution span was (2.90-2.52) / 2.72 = 14%, and the average aspect ratio was 1.08.

[0088] Example 2:

[0089] The objective of this embodiment is to obtain uniform spherical particles with an average particle size of 6 mm using a fluidized bed grinding device 100. The fluidized bed grinding device 100 and the raw material composition and dispersant used for extruding the plastic body are the same as in Example 1. The plastic body is extruded through a die with a 6.2 mm inner diameter channel by an extruder to obtain a strip-shaped plastic body.

[0090] The diameter and length of the cross-sections of 50 strip-shaped plastic bodies were randomly measured using vernier calipers to obtain the diameter distribution span:

[0091] (d 90 -d 10 ) / d 50= (6.49 - 6.05) / 6.26 = 7%;

[0092] Length distribution span:

[0093] (l 90 -l 10 ) / l 50 = (7.22 - 5.25) / 6.22 = 32%.

[0094] The equivalent spherical particle size distribution span of this strip-shaped plastic body, measured by the CamS i zer image particle size analyzer, is (D 90 -D 10 ) / D 50 = (7.67-6.40) / 7.07 = 18%, and the average length-to-diameter ratio is 1.20.

[0095] In Example 2, under the initial conditions D 50 The diameter is 7.07 mm, and the density is 0.80 g / cm³. 3 The first air volume A1 can be calculated to be 80.

[0096] Pour 500 grams of extruded strip plastic body into the bed. Turn on the fluidizing air device to introduce fluidizing air, so that the strip plastic body is in a turbulent fluidization state, and the initial air volume is set to 80.

[0097] During the shaping stage (first stage), specifically the first 20 minutes of the fluidization process in this embodiment, the strip-shaped plastic body moves within a range below the height of the multiple grinding rods (the highest point of the strip-shaped plastic body does not exceed the tops of the multiple grinding rods). The yellow cornstarch, due to its small particle size, is mostly carried away by the fluidizing air during the first minute of the fluidization process. A small portion of the cornstarch adhering to the plastic body particles is also detached from the plastic body and carried away by the fluidizing air during the remaining time as the plastic body particles dry, fluidize, and are ground. During this stage, it can be observed that the plastic body particles gradually dry, and the strip-shaped plastic body gradually transforms into a spherical shape due to collisions. Sampling at the end of the plasticization stage revealed a particle moisture content of 10.5%, a particle size distribution span of (7.55-6.46) / 6.99 = 16%, and an average aspect ratio of 1.12.

[0098] After shaping, increase the airflow to 95 and enter the polishing stage (second stage). At this point, approximately 25% by weight of particles will be blown up to a height exceeding the tips of multiple polishing rods.

[0099] During the remaining 1 hour and 20 minutes, the airflow was adjusted to maintain the highest blowing height of 25% by weight particles above the tips of multiple grinding rods; the airflow was gradually reduced from 95 to 87. During this stage, the particles gradually abraded, and a large number of white, smoky particles were observed to form within the bed. These were ultrafine particle wastes generated by particle abrasion, carried out from the top by the fluidizing air. After 1 hour and 20 minutes, the fluidizing air was stopped, ending the fluidized bed grinding process, and residual powder was removed using a sieve. The resulting particles had a moisture content of 2.9%, an average particle size of 6.37 mm, a particle size distribution span of (6.77-6.00) / 6.371 = 12%, and an average aspect ratio of 1.09. The particles were calcined at 650℃ for 3 hours to obtain the final ceramsite product. Its average particle size was 5.89 mm, the particle size distribution span was (6.23-5.52) / 5.89 = 12%, and the average aspect ratio was 1.09.

[0100] Example 3:

[0101] The objective of this embodiment is to obtain uniform spherical particles with an average particle size of 0.8 mm using the fluidized grinding ball device 100.

[0102] The fluidized bed grinding equipment is the same as in Example 1. The added particles are dried (4.7% moisture content) uncalcined silica microspheres with an average particle size D. 50 The particle size is 0.978 mm, the particle size distribution span is (1.063-0.881) / 0.978=19%, and the aspect ratio is 1.10.

[0103] 500 grams of small balls were poured into the barrel 20 of the fluidized grinding ball device 100. The fluidizing air was turned on and the airflow was set to 31, so that the particles 200 to be processed were in a turbulent fluidized state. During the 30-minute grinding time, the airflow was gradually reduced from 31 to 28 to maintain the maximum blowing height of the particles 200 (approximately 25% by weight) above the tops of the grinding rods. The fluidizing air was then stopped, ending the fluidized grinding process. The resulting particles had a particle size distribution span of (0.924-0.802) / 0.862 = 14% and an average aspect ratio of 1.09. The particles were calcined at 650℃ for 3 hours to obtain the final ceramsite product. Its average particle size was 0.820 mm, and the particle size distribution span was (0.872-0.757) / 0.820 = 14%.

[0104] Comparative Example 1:

[0105] The raw material composition used for extruding the plastic body was the same as in Example 1. After thorough mixing (mixing time 8 minutes), the mixture was extruded through a die with a 2.6 mm inner diameter channel to obtain a cylindrical strip-shaped plastic body. Corn flour with a particle size of 35 to 60 mesh was used as a dispersant to prevent excessive aggregation and adhesion of the plastic body.

[0106] According to d 90 d 50 d 10 The calculated diameter distribution span is:

[0107] (d 90 -d 10 ) / d 50 = (2.78 - 2.48) / 2.63 = 11%;

[0108] According to l 90 l 50 l 10 The length distribution span was calculated as follows:

[0109] (l 90 -l 10 ) / l 50 = (3.27 - 2.21) / 2.74 = 39%.

[0110] The equivalent spherical particle size distribution span of this strip-shaped plastic body, measured by the CamS i zer image particle size analyzer, is (D 90 -D 10 ) / D 50 = (3.40-2.66) / 3.04 = 24%, and the average aspect ratio is 1.21.

[0111] Add 500g of extruded granules to a rounding machine, along with approximately 20g of corn flour (35-60 mesh) as a dispersant. Round the granules for 3 minutes until they are spherical. The optimal running time of 3 minutes is determined empirically; stop the machine when the granules are observed to be free of sharp edges, have high sphericity, and show no significant aggregation, adhesion, or deformation (such as flattening). Alternatively, the rounding machine can be stopped every half minute, and the aspect ratio of the resulting granules measured using a CamS zer. The total running time corresponding to the minimum aspect ratio is obtained. The optimal running time obtained in this experiment is consistent with the empirically determined 3-minute running time. The resulting particle size distribution span is (D 90 -D 10 ) / D 50 = (3.34-2.65) / 2.99 = 23%, with an average aspect ratio of 1.12. The obtained particles were dried at 120℃ and then calcined at 650℃ to obtain the final ceramsite product, with a particle size distribution span of (D...). 90 -D 10 ) / D 50 = (3.13-2.47) / 2.78 = 24%, and the average aspect ratio is 1.11.

[0112] Comparative Example 2:

[0113] The raw material composition used for the extruded plastic body was the same as in Example 1. After thorough mixing (mixing time 8 minutes), the mixture was extruded through a die with a 2.6 mm inner diameter channel to obtain a cylindrical strip-shaped plastic body. Corn flour with a particle size of 35 to 60 mesh was used as a dispersant.

[0114] According to d 90 d 50 d 10 The calculated diameter distribution span is:

[0115] (d 90 -d 10 ) / d 50 = (5.78 - 5.31) / 5.58 = 8%;

[0116] According to l 90 l 50 l 10 The length distribution span was calculated as follows:

[0117] (l 90 -l 10 ) / l50=(6.32-4.74) / 5.54=29%.

[0118] The equivalent spherical particle size distribution span of this strip-shaped plastic body, measured by the CamS i zer image particle size analyzer, is (D 90 -D 10 ) / D 50 = (7.07-5.79) / 6.45 = 20%, and the average length-to-diameter ratio is 1.19.

[0119] Add 500 grams of extruded granules to a rounding machine, and add approximately 20 grams of corn flour with a particle size of 35 to 60 mesh as a dispersant. Round the granules in the machine for 3 minutes until they are spherical. The resulting particle size distribution span is (D 90 -D 10 ) / D 50 = (7.01-5.85) / 6.49 = 18%, with an average aspect ratio of 1.13. The obtained particles were dried at 120℃ and then calcined at 650℃ to obtain the final ceramsite product, with a particle size distribution span of (D...). 90 -D 10 ) / D 50 = (6.61-5.50) / 6.07 = 18%, and the average aspect ratio is 1.12.

[0120] Comparative Example 3:

[0121] The added particles are dried (4.2% moisture content) uncalcined silica microspheres with an average particle size D. 50The particle size is 0.866 mm, the particle size distribution span is (0.938-0.767) / 0.866=20%, and the aspect ratio is 1.10.

[0122] Add 500 grams of the granules to a rounding machine, along with approximately 20 grams of corn flour with a particle size of 35 to 60 mesh as a dispersant. Round the granules in the machine for 3 minutes. The resulting particle size distribution span is (D 90 -D 10 ) / D 50 = (0.943-0.785) / 0.855 = 18%, with an average aspect ratio of 1.09. The obtained particles were dried at 120℃ and then calcined at 650℃ to obtain the final ceramsite product. Its particle size distribution span is (D... 90 -D 10 ) / D 50 = (0.889-0.738) / 0.810 = 19%, and the average length-to-diameter ratio is 1.09.

[0123] As shown in Example 1, when the particle size is small (less than 5 mm), the length uniformity of the extruded plastic body is very poor. As shown in Example 2, when the particle size increases, the length uniformity of the extruded plastic body improves. Comparing Examples 1 and 2, it is clear that the smaller the plastic body particle size, the worse the length uniformity of the extruded plastic body. Conventional ball milling methods (spheronizing machines) are unlikely to improve the length uniformity of the plastic body (compared to Comparative Examples 1 and 2), especially for plastic bodies with relatively small particle sizes.

[0124] By comparing Example 1 and Comparative Example 1, and by comparing Example 2 and Comparative Example 2, it can be seen that the fluidized grinding ball device 100 provided in the embodiments of the present invention can achieve adjustment of particle size. During the grinding process, D 90 Compared to D 10 The greater decrease indicates that the grinding method in this embodiment can selectively grind larger particles more, thereby reducing the particle size distribution range and improving particle size uniformity. A comparison of Stage 1 before and after in Examples 1 and 2 demonstrates that the shaping stage can effectively mold particles into spherical shapes, achieving a sphericity effect similar to that of a spheroidizing machine. A comparison of Example 3 and Comparative Example 3 shows that for dried but uncalcined particles, the fluidized bed grinding device 100 can still reduce the average particle size and particle size distribution range, thereby improving particle size and particle size uniformity.

[0125] The fluidized grinding ball apparatus and grinding ball method using the present invention provided by embodiments of the present invention have at least one or a portion of the following advantages:

[0126] (1) The fluidized grinding ball device provided in the embodiments of the present invention adopts a combination of fluidization process and grinding rod to achieve the shaping (first stage) and grinding (second stage) of the particles to be processed. In the first stage, when the particles to be processed are freshly extruded non-spherical plastic particles (such as strips), due to the high water content (usually in the range of 25% to 70%), the non-spherical particles in the turbulent fluidization state are gradually shaped into spherical shapes as they continuously collide with the grinding rod, other particles and the wall of the cover. In this stage, when the non-spherical plastic particles are relatively wet, the deformation is mainly plastic, and grinding occurs less. In the second stage, as the particles gradually dry from the surface to the inside, the adhesion between the dried outer wall and the particles decreases, and the particles... As the particle surface gradually wears down, the edges are further smoothed, the mass of individual particles decreases, and the height of the particles in the fluidized bed gradually increases until they are ground into particles (particles with the required particle size). The ultrafine particles generated by particle wear are blown out of the grinding ball device from the top by the fluidizing air and collected by a cyclone or bag filter. If only the shaping of non-spherical particles (to a certain degree of sphericity) is required, only the first stage needs to be completed. If the sphericity is insufficient, water can be continuously sprayed through the top atomizing nozzle to slow down the drying speed of the plastic body and extend the time of the sphericification (shaping) stage. If the particles are dried non-plastic bodies, the grinding stage can be directly entered from the start of fluidization. This method is applicable to particles of any shape and has a wide range of applications.

[0127] (2) The grinding ball method provided in the embodiments of the present invention controls a certain percentage of particles to be blown higher, which causes a faster rate of wear on larger particles. As fluidization continues, larger particles, due to their heavier mass, are blown to a lower height in the fluidized bed (the highest blown height should not exceed the height of the top of the grinding rod), and thus will be continuously ground by the grinding rod, resulting in more wear. The mass of the particles gradually decreases with grinding. Smaller particles, due to their smaller mass, are blown to a higher height in the fluidized bed and have more time to be blown above the top of the grinding ball device. Therefore, smaller particles are less worn by the grinding rod. On the other hand, larger particles shuttle through the narrow gap between the grinding rods and have more opportunities to collide with the grinding rod than smaller particles. Moreover, larger particles, due to their greater weight, will produce more powder when ground. For the above reasons, larger particles are ground faster and smaller particles are ground slower, so that the particle size gradually becomes more uniform as the fluidization process proceeds, thereby improving particle size uniformity, i.e., reducing the particle size distribution span.

[0128] (3) The grinding method provided in the embodiments of the present invention can precisely control the particle size to achieve the target particle size. Through the fluidization device, samples can be taken at any time during the grinding process (the amount of each sample is usually in the range of 5 to 20g). The sample is taken out and the particle size, particle size distribution span and aspect ratio are detected by an image particle size analyzer such as CamSize. The total time is no more than 20 minutes. By comparing the detection results with the target, it can be quickly confirmed whether the particles meet the standard. Since the method can achieve the particle size gradually decreases with the increase of fluidization time, the particle size, particle size distribution span and other parameters can be quickly detected by sampling detection. Based on this, the fluidization time can be controlled to fine-tune the particle size. When the target is reached, the machine can be stopped quickly to achieve precise control of the particle size and particle size distribution span. Such fine-tuning cannot be achieved in the ball rolling mechanism because the particle mass remains unchanged during the ball rolling process.

[0129] (4) The ball grinding method provided in the embodiments of the present invention can avoid the aggregation and adhesion of multiple particles commonly found in the ball rolling machine; during the fluidization process, the extrusion pressure between particles is significantly less than the extrusion pressure in the ball rolling machine, making it difficult for particles to agglomerate; and the fluidization process dries the particles from the outside to the inside, while the particles with dry outer surfaces will not agglomerate.

[0130] (5) The main parameters of the grinding ball method provided in the embodiments of the present invention can be quantitatively or semi-quantitatively determined by experimental methods. Combined with actual experiments, it has high operability. For example, the air volume affects the height of the particles being blown up, the collision with the grinding rod, the frequency and intensity of friction, etc., which are crucial for obtaining the target particle size, particle size distribution and aspect ratio. Therefore, it is necessary to set the air volume quantitatively and continuously adjust it during the processing. The appropriate air volume setting is significantly positively correlated with the average particle size and particle density.

[0131] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above-described embodiments. Those skilled in the art will understand that changes can be made to these embodiments without departing from the overall concept and spirit of the present invention, and such changes should also be considered to fall within the scope of protection of the present invention. The scope of the present invention is defined by the claims and their equivalents.

Claims

1. A fluidized bed grinding ball device, characterized in that, The fluidized grinding ball device is used to shape and / or grind particles to be processed into spherical shapes in a fluidized manner, and the fluidized grinding ball device includes: A first screen is configured to be located at the lower part of the fluidized grinding ball device; The cover barrel includes a frustum-shaped barrel and a cylindrical barrel joined together, with the outer periphery of the smaller radius end of the frustum-shaped barrel connected to the outer periphery of the first screen. A polishing rod assembly, comprising a plurality of polishing rods with rough surfaces, the plurality of polishing rods being vertically fixedly disposed on the first screen and located inside the cover barrel; and A fluidizing device, wherein the fluidizing device is used to introduce fluidizing air that causes the particles to be processed to continuously collide with the plurality of grinding rods; The fluidizing airflow introduced into the fluidizing device is a first airflow that allows the particles to be processed to reach a preset target sphericity, so that the highest height to which the particles to be processed are blown up does not exceed the height of multiple grinding rods. The fluidized grinding ball device causes the particles to be processed to undergo a first stage and a second stage. In the first stage, the particles to be processed are wet, non-spherical plastic particles. The fluidization device causes the non-spherical plastic particles to gradually be shaped into spheres as they collide with the multiple grinding rods and the wall of the cover in a turbulent fluidization state. In the second stage, as the particles dry from the surface inward, the surface of the particles gradually wears down, the mass of each individual particle decreases, and the height of the particles blown up in the fluidization device gradually increases until they are ground into particles. The moisture content of the particles to be treated is 25% to 70%. The fluidized grinding ball device also includes an atomizing nozzle positioned directly above multiple grinding rods. The atomizing nozzle enables water to be sprayed from the top of the fluidized grinding ball device into the hood when the sphericity of the ground particles does not meet the expected target, thereby slowing down the drying speed of the particles to be processed and extending the shaping time. The fluidization device dries the particles to be processed from the outside to the inside during the fluidization process, so that the particles to be processed with the dried surface will not stick together. The first air volume is calculated according to the following formula: A1= 5.29 - a + 8.73×D 50 + 20.0×ρ; Where A1 is the first air volume, D 50 Let ρ be the average particle size of the particles to be processed, ρ be the average bulk density of the particles to be processed, and a be a constant greater than 2. The larger the aspect ratio of the particles to be processed, the smaller the initial air volume should be set. The greater the bed thickness of the particles to be processed, the greater the initial airflow should be.

2. The fluidized grinding ball apparatus according to claim 1, characterized in that, The combination of the fluidizing device and the grinding rod assembly is used to shape and grind the particles to be processed. The number of polishing rods is no less than 10, the polishing rods are arranged in a hexagonal pattern, and the distance between the polishing rods is 0.2 to 3 cm. The plurality of polishing rods are above the upper plane of the frustum-shaped barrel, but do not exceed the upper plane of the cylindrical barrel.

3. The fluidized grinding ball apparatus according to claim 2, characterized in that, The plurality of polishing rods are higher than the height of the frustum-shaped barrel but do not exceed 3 / 4 of the height of the cylindrical barrel; The fluidized grinding ball device further includes a second screen, which is disposed directly below the first screen, and the periphery of the second screen is movably connected to the periphery of the first screen; the second screen is used to prevent the particles to be processed from falling into the fluidization device.

4. The fluidized grinding ball apparatus according to claim 1, characterized in that, The percentage of particles to be processed whose height exceeds the top of multiple grinding rods = sampling weight of the bottom barrel sampler / (sampling weight of the bottom barrel sampler + sampling weight of the middle barrel sampler in the same time interval) × 100%, wherein the bottom barrel sampler takes samples from the bottom of the cover barrel, and the middle barrel sampler takes samples from inside the cover barrel at a height higher than the multiple grinding rods.

5. The fluidized grinding ball apparatus according to claim 4, characterized in that, The fluidizing device continuously adjusts the airflow of the fluidizing air to maintain a preset percentage of the particles to be treated being blown to a height exceeding the height of multiple grinding rods; and once the particles to be treated meet the preset particle size target, the fluidizing airflow is stopped. The preset percentage is 20% to 30%.

6. The fluidized grinding ball apparatus according to claim 5, characterized in that, In order to continuously adjust the air volume of the fluidizing air, the fluidizing device first increases the air volume to a second air volume, and then gradually decreases it to a third air volume. The fluidized grinding ball device also includes a collection device for collecting ultrafine particulate waste generated during grinding that is blown out from the top of the cylindrical barrel by fluidizing air.

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