Granulation forming equipment and method for manufacturing sandy silicon dioxide by granulation forming equipment

Abstract

The invention discloses granulation forming equipment and a method for manufacturing sandy silicon dioxide by using the granulation forming equipment, and belongs to the field of new material synthesis. The invention aims to solve the problems of high energy consumption, pollution, particle damage and the like in a crushing link in the traditional sandy silicon dioxide production, and provides a novel granulation forming device and process. The preparation method comprises the following steps: mixing sol and an accelerant to prepare wet gel, carrying out solvent removal and aging control under the protection of an inert atmosphere, and utilizing granulation equipment made of a high-purity quartz material to realize primary crushing, atomized water vapor assisted cracking and rounded forming of gel particles. And finally, roasting to obtain the sandy silicon dioxide with a closed pore structure, low hydroxyl content, high purity and excellent circularity. According to the method, the wet gel preparation and granulation technology is optimized, the traditional crushing and rounding process is avoided, the material purity and yield are remarkably improved, and a new way is provided for efficient and environment-friendly industrial production of the high-purity sandy silicon dioxide.

Description

Technical Field

[0001] This invention belongs to the field of new material synthesis, specifically relating to a granulation molding device and a method for manufacturing granular silica. Background Technology

[0002] Conventional granular silica is mainly derived from natural ores, produced through electrolytic crushing, or from silicon tetrachloride (SiCl4) which is hydrolyzed in an oxyhydrogen flame followed by electrolytic crushing. Neither of these methods utilizes clean energy, and the purity of natural ores is limited to 5N to 6N, making further improvements difficult. In contrast, liquid-phase synthesis methods using organosilicon alkoxides and chlorosilanes offer lower reaction temperatures, simpler equipment, and lower energy consumption, achieving product purity of 7N or even 9N. These methods demonstrate higher purity, lower energy consumption, and greater potential for industrial applications, making them a more promising production method.

[0003] Liquid-phase synthesis, especially the sol-gel process, is a highly efficient route for preparing granular silica. Inorganic systems utilize raw materials such as water glass and silicon tetrachloride, forming a sol through hydrolysis and system conditioning. Organic systems use alkoxysilane raw materials such as tetramethoxysilane, generating a sol under the catalysis of alcohol dispersants and acid / base. Regardless of whether the method is inorganic or organic, the sol must undergo drying and calcination after formation to remove the solvent and densify the structure, finally breaking it down into granular silica with the required particle size. This process is simple and efficient, making it a preferred solution for industrial production.

[0004] Therefore, the granulation process faces significant technical bottlenecks in the existing production of granular silica. The brittleness of the gel makes it difficult to precisely control the particle morphology, and in the subsequent crushing stage, traditional crushers not only easily generate a large amount of dust but also lead to excessive energy consumption and environmental pollution. In addition, after drying and calcination, the particles become denser and their hardness increases significantly, resulting in more fine powder during the later rounding process, reducing product yield, and making the particles more susceptible to contamination. Summary of the Invention

[0005] To address the shortcomings of existing technologies and problems with existing equipment, this invention discloses a granulation molding device and a method for manufacturing granular silica. The invention involves mixing a sol with an accelerator to prepare a wet gel. Subsequently, under an inert atmosphere, the wet gel undergoes solvent removal while its aging process is strictly controlled to maintain a unique state that is neither hard nor soft. Then, using the granulation molding device described in this invention, the wet gel can be oriented and molded into approximately spherical gel particles. Finally, sintering yields a high-purity granular silica product with a closed pore structure, low hydroxyl content, high purity, excellent sphericity, and suitable particle size.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a granulation and molding device, the device including a rotating drum 1, with an inlet and an outlet at both ends, the inlet being higher than the outlet. A feeder 13 is provided at the inlet. The outlet of the feeder 13 is inserted into the rotating drum 1. A baffle 11 is provided below the outlet. The baffle 11 is connected to the feeder 13 through a support body 12. The feeder 13 is designed to be inclined to facilitate control of the descent speed of the gel block, disperse the accumulation of gel blocks, and enhance the shear force in contact with the baffle 11. An atomizer 7 is provided at the outlet. The atomizer 7 is a straight tube with a blind end design. The blind end is inserted into the outlet and passes through the rotating cylinder 1 to above the baffle plate 11. A nozzle 15 is provided at the end of the atomizer 7 near the inlet. Guide rail rings are fixed to the outer walls of both ends of the rotating drum 1. The guide rail rings are placed on rollers 10 to achieve rotation. The rollers 10 are fixed on the support platform 14. A sprocket 4 is provided between the guide rail rings, and the chain is driven by the motor 9, which in turn drives the rotating drum 1 to rotate.

[0007] Furthermore, the sprocket 4 divides the rotating drum 1 into a first heating zone 2 and a second heating zone 3 in the axial direction, and the length of the first heating zone 2 is greater than the length of the second heating zone 3.

[0008] Furthermore, the length ratio of the first heating zone 2 to the second heating zone 3 is 2:1.

[0009] Furthermore, a circular weir 17 is provided at the discharge port, and the ratio of the inner diameter to the outer diameter of the weir 17 is (0.3~0.5):1. An opening 16 is provided on the side wall of the rotating cylinder 1 near the weir 17.

[0010] Furthermore, the number of openings 16 is 2 to 4, and they are distributed in a circular pattern.

[0011] Furthermore, the number of nozzles 15 is 4 to 8, the orifice size is 0.9 to 3 mm, the spacing between each nozzle is 2.5 to 15 cm, and the flow rate of the nozzles is precisely controlled by a pure water pump.

[0012] Furthermore, the atomizer 7 is provided with a filler 8 inside the second heating zone 3, which is used to heat the pure water inside the atomizer 7 tube.

[0013] Furthermore, the rotating drum 1 forms an inclination angle of 0.5° to 4° with the horizontal plane.

[0014] Furthermore, the folding plate 11 forms an angle of 120° to 150° with the feeding direction.

[0015] Furthermore, the outlet is covered with a gas collecting hood 5 to collect the steam generated during the drying process. Below the gas collecting hood 5, a discharge device 6 is provided to collect the approximately spherical dry gel particles brought out when the tilted tail end of the rotating drum 1 rotates.

[0016] All components of the granulation molding equipment described in this invention are made of high-purity quartz.

[0017] The present invention also provides a method for manufacturing granular silica, the method comprising gelation, drying, granulation, and calcination, wherein the granulation is performed using the aforementioned equipment.

[0018] Furthermore, the gel comprises mixing and stirring a sol with an accelerator to obtain a wet gel; The sol is an inorganic silica sol or an organosilicon sol. The inorganic silica sol includes sols formed by exchanging or hydrolyzing water glass, silicon tetrachloride, or chlorosilane as raw materials through a strong acid resin. The organosilicon sol includes sols formed by hydrolyzing alkoxysilanes and their oligomers as raw materials under the action of a dispersant through alkaline or acid-catalyzed hydrolysis. The accelerator is selected from at least one of nitric acid, hydrochloric acid, acetic acid, formic acid, lactic acid, lysine, ammonia, and amine organic bases.

[0019] Furthermore, the molar ratio of the sol to the accelerator is 1: (0.005~0.05).

[0020] Furthermore, the reaction temperature of the wet gel is 20~95℃, and the reaction time is 0.5~48h.

[0021] Furthermore, the drying temperature is 20~200℃, and the time is 0.5h~24h.

[0022] Furthermore, the calcination temperature is 800~1400℃, and the time is 10~35h.

[0023] Furthermore, during granulation, the rotational speed of the rotating drum is 0.5~6 r / min.

[0024] Furthermore, the temperature of the first heating zone is 20~100℃.

[0025] Furthermore, the temperature of the second heating zone is 20~200℃.

[0026] Furthermore, the pure water feed rate in the atomizer is 5~75L / min.

[0027] Furthermore, the method for manufacturing granular silica according to the present invention includes the following steps: Step 1: In a stirrer, mix the sol and the accelerator, let it stand to prepare a wet gel, and then turn on the stirrer again to obtain blocky gel particles.

[0028] Step two involves drying the blocky gel particles under an inert atmosphere to remove some of the moisture, resulting in gel particles. Simultaneously, the aging process is strictly controlled to maintain them in a unique state that is neither too hard nor too soft.

[0029] Step three: The obtained gel particles are continuously fed into the rotating drum 1 through the feeder 13. Under the action of gravity, the gel particles first impact the baffle 11, achieving primary crushing and forming smaller particles. The pure water in the atomizer 7 is heated sequentially and forms hollow cone-shaped atomized water vapor through the nozzle 15. After the particles are initially crushed, they break apart instantly upon contact with the atomized water vapor, achieving further crushing. Driven by the rotating drum 1, the particles move forward in a spiral shape at a certain linear velocity. During this process, the particle surface becomes rounded, forming approximately spherical microparticles. When the microparticles pass through the second heating zone 3, they are further dried and finally recovered by the discharger 6.

[0030] Step four: The recovered microparticles are loaded into a quartz crucible and sent to a roasting furnace for roasting treatment to finally obtain high-purity sandy silica.

[0031] The present invention also provides a granular silica prepared by the above method, wherein the granular silica has a purity of 5N (99.999%) or higher, a particle size range D50 of 60~255µm, a roundness of 0.82~0.9, and a hydroxyl number of 5~60ppm.

[0032] The beneficial effects of this invention include: This invention aims to solve the problems of high energy consumption, pollution, and particle damage in the crushing process of traditional granular silica production. It proposes a novel granulation and forming device and process to precisely address issues such as particle surface damage, residual hydroxyl groups, and poor roundness. By mixing a sol with an accelerator to prepare a wet gel, followed by solvent removal and aging control under an inert atmosphere, and utilizing a high-purity quartz granulation device, the gel particles undergo primary crushing, atomized water vapor-assisted pyrolysis, and rounding. Finally, calcination yields granular silica with a closed-pore structure, low hydroxyl content, high purity, and excellent roundness. This method optimizes wet gel preparation and granulation technology, cleverly bypassing traditional crushing and grinding processes, significantly improving material purity and yield (target mesh size > 85%), providing a new approach for the efficient, environmentally friendly, and industrialized production of high-purity granular silica. Attached Figure Description

[0033] Figure 1 This is a process flow diagram of the method for preparing granular silica according to the present invention.

[0034] Figure 2This is a structural diagram of the granulation and molding equipment of the present invention.

[0035] In the diagram, 1. Rotary drum; 2. First heating zone; 3. Second heating zone; 4. Sprocket; 5. Gas collection hood; 6. Discharge device; 7. Atomizer; 8. Packing material; 9. Motor; 10. Roller; 11. Baffle plate; 12. Support body; 13. Feeder; 14. Support platform; 15. Nozzle; 16. Opening; 17. Dike. Detailed Implementation

[0036] The following description, in conjunction with the accompanying drawings and embodiments, aims to make the advantages and features of the present invention more readily understood by those skilled in the art, thereby providing a clearer and more explicit definition of the scope of protection of the present invention.

[0037] like Figure 1 As shown, a method for manufacturing granular silica includes the following steps: Step 1: In a stirrer, mix the sol and accelerator at a molar ratio of 1:0.0005~0.05, let stand for 0.5~48h to obtain a wet gel, then turn on the stirrer to obtain a gel block of 10~100mm.

[0038] Step two involves introducing an inert atmosphere for drying, during which the wet gel breaks down into 5-20mm particles. Simultaneously, the aging process is strictly controlled to maintain a unique state that is neither too hard nor too soft.

[0039] The rigidity of the gel was evaluated by assessing its mechanical properties. Specifically, the gel was cut into cubic blocks with a side length of 10±0.2mm using a grid cutter, and stress was tested using an FG-20KG tensile and compressive strength tester with a probe cross-section diameter of D8±0.5mm. The stress area was obtained as S=π(D / 2). 2 The probe is pressed down, and the maximum stress value F when the gel block breaks is recorded. The corresponding pressure P is then calculated using the pressure calculation formula (P=F / S) to accurately characterize and evaluate the state of the wet gel. In this invention, when the calculated pressure P is in the range of 1.5~6MPa, the wet gel is considered to be in a unique state that is neither hard nor soft, and can be granulated.

[0040] Step 3: Feed the sample into the granulation and molding equipment described in this invention for granulation and molding to obtain approximately spherical silica particles.

[0041] Step four involves further calcining to obtain high-purity, dense, sand-like silica with closed pores, low hydroxyl content, high purity, and suitable particle size.

[0042] In this invention, Specific surface area (m²) 2 / kg): The amount of nitrogen adsorbed on sandy silica was measured using a Mack physical adsorption analyzer in the United States.

[0043] Hydroxyl group number (ppm): Analyzed by FTIR of sandy silica at a wavelength of 3600 cm⁻¹ -1 The infrared absorption intensity at the left and right sides is calculated using the Lambert-Beer law.

[0044] Circularity: Tested using a dynamic image particle size and shape analyzer, using the formula: Circularity = 4πS / L 2 Calculate. Where S is the projected area of ​​the particle, and L is the projected perimeter of the particle. Example 1

[0045] like Figure 2 As shown, a granulation molding device is made entirely of high-purity quartz material to ensure the purity of the materials in contact. The device includes a rotating drum 1, with a feed inlet and a discharge outlet at both ends. The feed inlet is higher than the discharge outlet, and the rotating drum 1 forms a 2° inclination angle with the horizontal plane.

[0046] The feed inlet is provided with a feeder 13, the outlet of the feeder 13 is inserted into the rotating drum 1, and a baffle 11 is provided below the outlet. The baffle 11 is connected to the feeder 13 through a support body 12, and the baffle 11 forms a 125° angle with the feeding direction.

[0047] An atomizer 7 is provided at the outlet. The atomizer 7 is a straight tube with a blind end design. The blind end is inserted from the outlet and passes through the rotating cylinder 1 to the top of the baffle plate 11. A nozzle 15 is provided at one end of the atomizer 7 near the inlet. There are 4 nozzles 15 with an orifice size of 1mm and a spacing of 12cm between each nozzle. The atomizer 7 is provided with a filler 8 inside the second heating zone 3.

[0048] The outer walls at both ends of the rotating drum 1 are fixed with guide rail rings, which are placed on rollers 10 to achieve rotation. The rollers 10 are fixed on the support platform 14. A sprocket 4 is arranged between the guide rail rings, and a chain is driven by a motor 9, thereby driving the rotating drum 1 to rotate. The sprocket 4 divides the rotating drum 1 into a first heating zone 2 and a second heating zone 3 in the axial direction. The length ratio of the first heating zone 2 to the second heating zone 3 is 2:1, and electric heating is used.

[0049] A circular weir 17 is provided at the discharge port. The ratio of the inner diameter to the outer diameter of the weir 17 is 0.35:1. An opening 16 is provided on the side wall of the rotating cylinder 1 near the weir 17. There are two openings 16, which are distributed diagonally around the circumference.

[0050] The outlet is covered with a gas collecting hood 5, and a discharge device 6 is provided below the gas collecting hood 5. Example 2

[0051] Using the equipment described in Example 1, purified tetraethyl orthosilicate and ultrapure water were stirred for 4.5 h in a stirrer lined with polytetrafluoroethylene to prepare a viscous sol at room temperature. Then, electronic-grade lactic acid was added as an accelerator. The molar ratio of tetraethyl orthosilicate, ultrapure water and lactic acid was 1:15:0.014. Stirring was continued for 15 min, and the mixture was allowed to stand at room temperature for 24 h to obtain a wet gel. Stirring was then turned on to obtain a wet gel block.

[0052] Under nitrogen protection, the temperature was raised to 200℃ and dried to obtain gel particles, with a breaking strength of 4.2 MPa.

[0053] The rotational speed of the drum is controlled at 4 r / min, the temperature of the first heating zone is set at 80℃, and the temperature of the second heating zone is set at 160℃.

[0054] The resulting gel particles are continuously fed into the impactor through the feeder, impacting the baffle plate to form particles of 0.5~1mm. Pure water enters the atomizer at a pump flow rate of 25L / min and is sequentially heated, forming hollow cone-shaped atomized water vapor through the four sets of nozzles. Upon contact with the atomized water vapor, the particles instantly break apart and are further fragmented. Driven by the rotating drum, the particles move forward in a spiral at a certain linear velocity. During this process, the particle surface becomes rounded, forming approximately spherical microparticles. When the microparticles pass through the second heating zone, they are further dried and finally collected by the discharger.

[0055] Finally, the silica particles were placed into a quartz crucible and calcined in a calcination furnace at 300℃ for 4.5 hours, 500℃ for 4.5 hours, 700℃ for 4.5 hours, 900℃ for 6 hours, and 1200℃ for 28 hours to obtain 5N8 (99.9998%) high-purity granular silica with a particle size (D50) of 254µm and a specific surface area of ​​42m². 2 / kg, hydroxyl count 25ppm, and roundness 0.84. Example 3

[0056] The same synthesis process was carried out according to Example 2, with the following specific difference: the molar ratio of purified methyl silicate, ultrapure water, and electronic grade ammonia as an accelerator was 1:16:0.005 to obtain a wet gel.

[0057] After drying, the crushing strength was measured to be 3.8 MPa. The resulting silica particles, obtained using the granulation equipment described in Example 1, were placed in a quartz crucible and calcined in a calcination furnace under the same calcination conditions to obtain 5N7 (99.9997%) high-purity granular silica with a particle size (D50) of 221 µm and a specific surface area of ​​38 m². 2 / kg, hydroxyl count 32ppm, and roundness 0.83. Example 4

[0058] The same synthesis process was carried out according to Example 2, with the following specific differences: water glass was used to dilute the silica content to 6.5 wt%, and after treatment with a strong acid ion exchange resin, the pH was adjusted to 5-6 with 0.1 mol / L ammonia water as an accelerator while stirring. Stirring was continued for 10 min, the temperature was controlled at 35°C, and the mixture was allowed to stand for 24 h to obtain a wet gel.

[0059] After drying, the crushing strength was measured to be 3.5 MPa. The resulting silica particles, obtained using the granulation equipment described in Example 1, were placed in a quartz crucible and calcined in a calcination furnace under the same calcination conditions to obtain 5N (99.999%) high-purity granular silica with a particle size (D50) of 213 µm and a specific surface area of ​​28 m². 2 / kg, hydroxyl count 27ppm, and roundness 0.83. Comparative Example 1

[0060] Following Example 2, the wet gel was prepared and dried in the same manner. The resulting silica particles were crushed into 0.5-1 mm gel particles using a roller mill. The particles had low saturation, poor roundness, and a high content of fine powder, resulting in a low yield. The gel particles were then placed in a quartz crucible and calcined in a calcining furnace under the same calcining conditions to obtain 4N8 (99.998%) high-purity granular silica with a particle size (D50) of 127 µm and a specific surface area of ​​48 m². 2 / kg, hydroxyl count 75ppm, and roundness 0.63. Comparative Example 2

[0061] Following Example 3, the wet gel was prepared and dried in the same manner. The resulting silica particles were then crushed into 0.5-1 mm particles in a disc mill. The particles had low saturation. After sieving, particles of different mesh sizes were further processed in a grinding mill and then fed into a calcination furnace for calcination under the same calcination conditions. This yielded 4N2 (99.992%) high-purity granular silica with a particle size (D50) of 143 µm and a specific surface area of ​​25 m². 2 / kg, hydroxyl count 65ppm, and roundness 0.80.

[0062] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A granulation and molding equipment, characterized in that, The device includes a rotating drum (1), with a feed inlet and a discharge outlet at both ends, the feed inlet being higher than the discharge outlet. A feeder (13) is provided at the feed inlet. The outlet of the feeder (13) is inserted into the rotating drum (1). A baffle plate (11) is provided below the outlet. The baffle plate (11) is connected to the feeder (13) through a support body (12). An atomizer (7) is provided at the outlet. The atomizer (7) is a straight tube with a blind end design. The blind end is inserted from the outlet and passes through the rotating cylinder (1) to the top of the baffle plate (11). A nozzle (15) is provided at one end of the atomizer (7) near the inlet. The outer walls at both ends of the rotating drum (1) are fixed with guide rail rings, which are placed on rollers (10) to achieve rotation. The rollers (10) are fixed on the support platform (14). A sprocket (4) is provided between the guide rail rings, and the chain is driven by the motor (9), which in turn drives the drum (1) to rotate.

2. The device according to claim 1, characterized in that, The sprocket (4) divides the drum (1) into a first heating zone (2) and a second heating zone (3) in the axial direction. The length of the first heating zone (2) is greater than the length of the second heating zone (3). Preferably, the length ratio of the first heating zone (2) to the second heating zone (3) is 2:

1.

3. The device according to claim 1 or 2, characterized in that, The discharge port is provided with a circular weir (17), the ratio of the inner diameter to the outer diameter of the weir (17) is (0.3~0.5):1, and the side wall of the rotating cylinder (1) near the weir (17) is provided with an opening (16). Preferably, the number of openings (16) is 2~4, and they are distributed in a circle.

4. The device according to any one of claims 1 to 3, characterized in that, The number of nozzles (15) is 4 to 8, the orifice size is 0.9 to 3 mm, and the distance between each nozzle is 2.5 to 15 cm; And / or, the atomizer (7) is provided with filler (8) inside the second heating zone (3); And / or, the rotating drum (1) forms an inclination angle of 0.5° to 4° with the horizontal plane; And / or, the folding plate (11) forms an angle of 120°~150° with the feeding direction; And / or, the outlet is covered with a gas collecting hood (5), and a discharge device (6) is provided below the gas collecting hood (5).

5. A method for manufacturing granular silica, characterized in that, The method includes gelation, drying, granulation, and calcination, wherein the granulation is performed using the equipment described in any one of claims 1 to 4.

6. The method according to claim 5, characterized in that, The gel is obtained by mixing and stirring a sol with an accelerator to obtain a wet gel. The sol is an inorganic silica sol or an organosilicon sol. The inorganic silica sol includes sols formed by exchanging or hydrolyzing water glass, silicon tetrachloride, or chlorosilane as raw materials through a strong acid resin. The organosilicon sol includes sols formed by hydrolyzing alkoxysilanes and their oligomers as raw materials under the action of a dispersant through alkaline or acid-catalyzed hydrolysis. The accelerator is selected from at least one of nitric acid, hydrochloric acid, acetic acid, formic acid, lactic acid, lysine, ammonia, and amine organic bases.

7. The method according to claim 6, characterized in that, The molar ratio of the sol to the accelerator is 1: (0.005~0.05). And / or, the reaction temperature of the wet gel is 20~95℃, and the reaction time is 0.5~48h.

8. The method according to any one of claims 5 to 7, characterized in that, The drying temperature is 20~200℃, and the time is 0.5h~24h; And / or, the calcination temperature is 800~1400℃, and the time is 10~35h.

9. The method according to any one of claims 5 to 8, characterized in that, During granulation, the rotational speed of the rotating drum is 0.5~6 r / min; And / or, the temperature of the first heating zone is 20~100℃; And / or, the temperature of the second heating zone is 20~200℃; And / or, the pure water feed rate in the atomizer is 5~75L / min.

10. A granular silica prepared by the method according to any one of claims 5 to 9, characterized in that, The granular silica has a purity of 5N (99.999%) or higher, a particle size range (D50) of 60-255µm, a roundness of 0.82-0.9, and a hydroxyl number of 5-60ppm.

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