Process for producing silicon dioxide micro powder by wet method

Abstract

The invention discloses a process and a system for producing silicon dioxide micro powder by a wet method. The process comprises the following steps: preparing a glue solution by using pure water and chemical polymer glue accounting for 0.1-1% of the solution; mixing silicon dioxide powder with D50 of 0-8 [mu] m with the glue solution to prepare slurry with the solid content of 5-70%; carrying out stepped defoaming treatment on the slurry by adopting a stepped vacuum standing defoaming device; and finally, carrying out spray drying on the defoamed slurry to obtain the product. The stability and formability of the slurry are guaranteed from the source through the specific polymer glue solution; by means of the stepped defoaming system integrating primary buffer tank coarse defoaming, secondary vacuum tank deep segmentation defoaming and tertiary surge tank undisturbed storage, various bubbles from the millimeter level to the submicron level in the slurry are efficiently removed, the defoaming problem of the high-solid-content slurry is thoroughly solved, the treated slurry is subjected to spray drying, and then the slurry is subjected to spray drying, so that the high-solid-content slurry is obtained. The silicon dioxide micro powder with regular particle morphology, narrow particle size distribution, good fluidity, large apparent density and excellent batch consistency can be obtained, and the high-end application requirement is comprehensively met.

Description

Technical Field

[0001] This invention relates to the field of silica micro powder production processes, specifically to a wet process for producing silica micro powder. Background Technology

[0002] In the wet process for producing silica micron powder, ultrafine silica powder is typically mixed with a liquid medium and polymeric additives to form a slurry, which is then spray-dried to obtain a free-flowing micron powder product. One of the key challenges of this process lies in the pretreatment of the slurry: silica powder has a large specific surface area and high surface energy, making it prone to agglomeration and entrainment of numerous air bubbles in the slurry. If these air bubbles are not effectively removed, they will cause the gas within the atomized droplets to expand and rupture during the subsequent spray drying process, resulting in problems such as internal porosity, incomplete surface, excessively wide particle size distribution, and irregular particle morphology in the final product, severely affecting the product's bulk density, flowability, and application performance.

[0003] In existing technologies, defoaming of slurries often involves simple mechanical stirring, settling, or the addition of chemical defoamers. While mechanical stirring can break up some large bubbles, high-speed shearing introduces more air and may compromise slurry stability. Simple settling is time-consuming and inefficient, failing to meet the demands of continuous production, and has minimal effect on removing submicron-sized microbubbles. Adding chemical defoamers may introduce impurities, affecting product purity and interfering with the bonding performance of subsequent polymer adhesives. Furthermore, while conventional single-stage vacuum degassing devices can remove some dissolved gases and larger bubbles, for high-solids, high-viscosity silica slurries, the microbubbles encased within them are difficult to escape effectively within a limited time and under a single vacuum environment.

[0004] Therefore, there is an urgent need in this field to develop an efficient, stable, and continuous slurry defoaming process and apparatus that can deeply remove various types of bubbles from silica slurry without introducing secondary pollution or compromising slurry stability, thereby providing a reliable guarantee for obtaining high-quality silica micropowder products. This invention is proposed based on the aforementioned problems. Summary of the Invention

[0005] The purpose of this invention is to solve the problems in the background art and provide a wet process for producing silica micro powder.

[0006] The above-mentioned technical objective of the present invention is achieved through the following technical solution: A wet process for producing silica micro powder includes the following steps: S1, Preparation of adhesive solution: Prepare an adhesive solution using pure water and chemical polymer adhesive, with the polymer adhesive accounting for 0.1%-1% of the solution; S2, Slurry mixing: Mix silica powder with D50 of 0~8μm with the glue solution in step S1 to prepare a silica slurry with a solid content of 5%-70%. S3, Step-by-step defoaming: The silica slurry prepared in step S2 is subjected to step-by-step defoaming treatment using a step-by-step vacuum static defoaming device. S4, Spray granulation: The defoamed slurry is sent to a spray drying device for drying to obtain silica micro powder.

[0007] This invention utilizes a specific ratio of polymer adhesives to formulate a slurry, providing a dispersion medium and structural binder for subsequent ultrafine silica powder production. This lays the foundation for slurry stability and final particle formation from the outset. Furthermore, by feeding the formulated slurry into a dedicated stepped vacuum static defoaming device, it creatively solves the industry problem of deep removal of microbubbles from slurries with high solids content and high specific surface area. This device achieves deep defoaming of microbubbles in slurries with high solids content and high specific surface area through a stepped synergistic effect of gravity-fed coarse defoaming, fine segmentation defoaming under vacuum, and undisturbed pressure-stabilized feeding, without introducing secondary shearing or contamination. The efficient and thorough removal of air bubbles ranging from millimeters to submicrons from the slurry eliminates defects such as droplet breakage and morphological distortion caused by air bubbles during spray drying. Finally, the slurry, which has undergone this deep defoaming and has highly uniform and stable performance, is spray-granulated, allowing the drying process to be carried out under optimal thermodynamic conditions. The resulting silica micropowder product exhibits regular particle morphology, smooth surface, narrow particle size distribution, excellent flowability, high bulk density, and good batch consistency. It fully meets the stringent requirements of high-end application fields for the physical properties of silica micropowder, realizing a reliable transformation from raw materials to high-quality products.

[0008] Preferably, the spray drying equipment includes an air supply system, a material supply system, a drying tower, and a gas-solid separation system connected sequentially along the process flow. The air supply system includes an air filter, a blower, and a heat exchanger connected sequentially. The material supply system is a paddle feeder used to transport silica slurry to an atomizer located at the top of the drying tower. The atomizer is a high-speed centrifugal atomizer with a dispersion disc linear velocity of 100-200 m / s. The gas-solid separation system includes an induced draft fan and at least one-stage cyclone separator. A hot air distributor is provided at the top of the drying tower, and the hot air distributor is connected to the output end of the heat exchanger. The gas-solid separation system also includes a secondary collection unit located downstream of the cyclone separator. The secondary collection unit is a bag filter or a secondary cyclone separator, with its inlet connected to a pipe before the induced draft fan and its outlet connected to the inlet of the induced draft fan.

[0009] This invention provides a clean, stable, and uniformly distributed high-temperature thermal field for material drying through an air supply system consisting of an air filter, blower, and heat exchanger, in conjunction with a hot air distributor at the top of the drying tower. This fundamentally ensures the uniformity and controllability of the heat and mass transfer process. Furthermore, by employing a linear velocity as high as 100-200... A high-speed centrifugal atomizer with a speed of m / s instantly breaks down the homogeneous slurry after deep defoaming into fine droplets with uniform size and height. Precise matching with a uniform thermal field ensures that each droplet undergoes a nearly identical drying kinetic process, thus laying the core foundation for the formation of micro powder products with regular particle morphology, smooth surface, and good dispersibility. Finally, by constructing a multi-stage high-efficiency gas-solid separation system consisting of at least one cyclone separator and a downstream bag filter, and scientifically linking it with an induced draft fan, not only is rapid and efficient collection of mainstream dried products achieved, ensuring a high yield, but also deep capture of ultrafine powder entrained in the exhaust gas. On the one hand, this further improves the overall product yield and economy, and on the other hand, it achieves clean exhaust gas emission. This enables gentle, rapid, and uniform drying of silica slurry containing polymer adhesives, ultimately obtaining high-quality silica micro powder with excellent flowability and outstanding comprehensive performance.

[0010] The fuels used in spray drying equipment include natural gas, propane, and acetylene. The natural gas flow rate is 4-20 m3 / h, the feed rate is 100-250 kg / h, and the dispersion disc rotation speed is 100-200 m / s.

[0011] Preferably, the stepped vacuum defoaming device includes a primary buffer tank, a secondary vacuum defoaming tank, and a tertiary pressure stabilizing tank arranged sequentially along the slurry flow direction and connected by pipelines. The primary buffer tank is used for preliminary defoaming and homogenization of the slurry, and has an inlet and an outlet at the top. The secondary vacuum defoaming tank is a sealed tank with a vacuum system connected to its top for deep defoaming of the slurry under negative pressure. The tertiary pressure stabilizing tank is used to store the defoamed slurry and stably supply it to subsequent processes, and has a discharge pump connected to its outlet. The installation height of the secondary vacuum defoaming tank is lower than the bottom outlet of the primary buffer tank, and the installation height of the tertiary pressure stabilizing tank is lower than the bottom outlet of the secondary vacuum defoaming tank, so that the slurry can flow from the upper tank to the lower tank at least partially by gravity.

[0012] The secondary vacuum defoaming tank is equipped with a porous conical tray inside, and the top of the porous conical tray has an arc-shaped impact section.

[0013] This invention guides the slurry to form a zigzag shape, extending its flow path. Without relying on external mechanical energy, it efficiently and gently separates and removes large air bubbles entrained in the slurry, creating stable fluid conditions for subsequent deep processing. Then, in the negative pressure environment of the secondary vacuum defoaming tank, the slurry flows through multiple porous trays and is repeatedly divided into thin liquid films or fine liquid columns. The micron- and submicron-sized microbubbles encased within are deeply exposed and completely removed under the synergistic effect of vacuum expansion and the large gas-liquid interface. Finally, the slurry is smoothly transferred by gravity to a tertiary pressure tank with nitrogen protection, completely eliminating the risk of secondary foaming and oxidation caused by disturbance, impact, or contact with air during temporary storage and transportation of the defoamed slurry. Thus, the entire system continuously provides high-quality silica slurry with low gas content, uniform solid content, stable rheology, and no secondary pollution for subsequent spray drying processes. This provides an irreplaceable pretreatment guarantee for preparing final silica micropowder products with regular particle morphology, concentrated particle size distribution, and excellent flowability.

[0014] Preferably, the primary buffer tank has at least two layers of inclined baffles in the vertical direction inside. Each layer of inclined baffle is an annular notch fixed to the inner wall of the tank, with its surface at an angle of 15°-30° to the horizontal plane. The notches of two adjacent layers of inclined baffles are staggered by 60°-120° in the horizontal circumferential direction.

[0015] This invention forcibly transforms the vertically falling slurry flow into a slow laminar flow along the plate surface by setting at least two layers of inclined baffles at an angle of 15°-30° to the horizontal plane. The flow is driven by the component of gravity, thus significantly extending the effective residence path and time of the slurry in the tank without introducing mechanical shearing. This provides a fundamental time guarantee for the upward separation of bubbles. Furthermore, by employing a specific shape of annular notched plates and arranging the notches of the upper and lower baffles to be staggered horizontally by 60°-120°, a zigzag three-dimensional path for the slurry flow is creatively constructed. This design, on the one hand, forces the slurry to constantly change its horizontal direction as it flows between layers, ensuring the uniformity of the entire tank cross-section and completely eliminating dead zones in the flow. On the other hand, the non-aligned channels formed by the staggered notches allow the slurry falling from the upper layer to be reliably received by the solid surface of the lower baffle, perfectly avoiding fluid short-circuiting. At the same time, it provides unobstructed escape space for bubbles that detach from the surface and rise to the surface. Ultimately, this structure works together to achieve efficient and gentle pre-separation of large bubbles in the slurry and provides stable and homogeneous feeding conditions for the subsequent vacuum deep defoaming process.

[0016] Preferably, an umbrella-shaped dispersion disc is provided below the primary buffer tank. The umbrella-shaped dispersion disc includes a central guide column, the upper end of which is used to connect to the feed inlet, and the lower end is shaped like a funnel. A conical or spherical dispersion block is provided inside the funnel. The cone angle or radius of curvature of the block is set to convert the vertically falling slurry flow into a radially spreading liquid film. A slurry flow channel is formed between the conical dispersion block and the funnel. An annular guide skirt is provided around the outer edge of the conical dispersion block to regulate the edge of the liquid film, so that it smoothly detaches and falls into the buffer tank in the form of a continuous annular curtain. Several supporting ribs are connected between the conical dispersion surface and the central guide column, and a conductive channel is formed between two adjacent supporting ribs.

[0017] This invention uses a central guide column to receive the vertically falling slurry flow. Through a slurry flow channel formed by a conical dispersion block and a funnel-shaped opening at its lower end, the high-kinetic-energy concentrated jet is smoothly guided and transformed into a thin liquid film spreading radially along the surface of the dispersion block. This process effectively dissipates the impact energy of the slurry, completely eliminating splashing and new bubbles caused by direct drop. Furthermore, an annular guide skirt surrounding the outer edge of the dispersion block regulates and constrains the liquid film spreading to the edge, allowing it to overcome surface tension and smoothly detach in a continuous, uniform annular curtain shape. This achieves a gentle, all-encompassing distribution of the slurry into the lower tank space. In addition, several supporting ribs connecting the conical dispersion surface and the central guide column ensure structural strength, while the conductive channels formed between adjacent ribs provide a diversion path for some slurry, further promoting the uniform distribution of the liquid film and preventing the formation of flow dead zones or negative pressure zones on the back of the dispersion block. The entire structure works together to provide an ideal and stable initial slurry distribution for the efficient operation of the subsequent inclined baffles, ensuring the uniformity and reliability of the bubble pre-separation effect from the source.

[0018] Preferably, the secondary vacuum defoaming tank is equipped with a porous tray clogging early warning and self-cleaning system, which includes a monitoring unit, an execution unit, and a control unit. The monitoring unit includes a differential pressure transmitter spanning the upper and lower layers of a multi-layered porous tray, a flow meter installed on the feed pipeline, and an absolute pressure transmitter installed on the top of the tank. The execution unit includes: a first quick-cut-off valve on the feed pipe of the secondary vacuum defoaming tank, a second quick-cut-off valve on the discharge pipe, a clean air source injection circuit on the top of the secondary vacuum defoaming tank, and a clean discharge valve on the side wall of the secondary vacuum defoaming tank; the clean air source injection circuit is provided with a pulse gas storage tank and a high-speed switching injection valve in sequence; The control unit is configured to perform the following steps: S1, based on the real-time data of the flow meter and absolute pressure transmitter and the preset benchmark model, calculate the theoretical pressure difference through the multi-layer porous tray; S2, compare the theoretical pressure difference with the actual pressure difference measured by the differential pressure transmitter in real time. When the actual pressure difference continuously exceeds the first preset percentage of the theoretical pressure difference, generate an early warning signal; when it exceeds the second preset percentage, generate a self-cleaning command, wherein the second preset percentage is greater than the first preset percentage. S3, in response to the self-cleaning command, control the closure of the first quick-cut-off valve and the second quick-cut-off valve to isolate the secondary vacuum defoaming tank; at the same time, control the opening of the cleaning discharge valve; S4, control the opening of the high-speed switch injection valve to inject the gas in the pulse gas storage tank into the top of the first-stage buffer tank, forming a high-speed clean airflow from top to bottom, which flows sequentially through the multi-layer porous tray in the second-stage vacuum defoaming tank for unidirectional flushing, and the flushed gas and dirt are directly discharged through the clean discharge valve. S5, after cleaning is completed, control the closing of the high-speed switch injection valve and the cleaning discharge valve, restore the system to normal production state, and reopen the first and second quick shut-off valves.

[0019] This invention utilizes a multi-sensor fusion monitoring system, including differential pressure transmitters, high-precision flow meters, and absolute pressure transmitters installed across multiple layers, to capture and calculate the differential pressure signal that characterizes the actual flow resistance of the porous tray in real time. The control unit intelligently compares this signal with a theoretical benchmark value dynamically calculated based on real-time flow and vacuum, thereby achieving early and accurate warning of micro-blockage trends and objective quantitative diagnosis of blockage severity. When the algorithm determines that intervention is needed, the execution unit and control unit immediately respond in concert, isolating the defoaming tank through a rapid shut-off valve to create an independent clean environment. Subsequently, the system activates a cleaning circuit consisting of a pulse gas storage tank and a high-speed switching injection valve, injecting clean gas into the top of the primary buffer tank, forming a high-speed clean airflow from top to bottom. This airflow sequentially flows through the multi-layer porous tray in the secondary vacuum defoaming tank, using its stable shearing and carrying force to efficiently flush the deposits in the pores in the same direction. The flushed gas and detached contaminants are directly discharged from the system through a clean discharge valve located on the side wall of the defoaming tank. The entire cleaning process is completed fully automatically within a closed system, requiring no human intervention and introducing no liquid cleaning media, resulting in no secondary pollution or wastewater generation. The successful application of this system revolutionizes equipment maintenance from traditional post-failure shutdown and disassembly repair to status-based early warning and online proactive self-maintenance. This fundamentally eliminates performance degradation and unplanned downtime caused by blockages, significantly improving the continuity, stability, and overall intelligence of the production process, providing a solid guarantee for the long-term, reliable, and efficient performance of the core deep defoaming process.

[0020] Preferably, the outlet of the primary buffer tank is connected to the inlet of the secondary vacuum defoaming tank via a first transfer pump. No transfer pump is installed between the outlet of the secondary vacuum defoaming tank and the inlet of the tertiary pressure stabilizing tank; they are directly connected only by a pipeline. The slurry flows by gravity and the pressure difference between the tanks. The transfer of the slurry from the secondary vacuum defoaming tank to the tertiary pressure stabilizing tank is achieved entirely by gravity and the pressure difference between the tanks, without passing through a transfer pump in between.

[0021] This invention uses a first delivery pump to smoothly pump the pre-defoamed slurry from the primary buffer tank into the secondary vacuum defoaming tank. This controllable mechanical delivery provides the necessary power for the slurry to enter the vacuum environment. Simultaneously, the pump's stable characteristics prevent the generation of new bubbles due to pulsating flow. Then, in the most crucial step, the outlet of the secondary vacuum defoaming tank is directly connected to the inlet of the tertiary pressure stabilizing tank via a pump-free pipeline. Utilizing the preset height and pressure differences between the two tanks—the secondary tank being under negative pressure and the tertiary tank under normal or slightly positive pressure—the slurry, having undergone deep vacuum defoaming, is driven entirely by gravity and pressure difference. The gravity-fed transfer design completely eliminates the unavoidable risks of shearing, agitation, and pulsation caused by using mechanical pumps during the most sensitive stage of slurry, when it has been deeply degassed but not yet stably stored. It fundamentally eliminates secondary foaming and energy input caused by pumping, perfectly maintaining the high-quality, low-aeration state of the slurry obtained in the secondary tank. This gravity-fed design not only simplifies the system structure and reduces energy consumption and failure points, but also acts as a protective valve for the entire defoaming process, ensuring zero-loss transmission of defoaming effect and providing an absolutely stable slurry source for subsequent spray drying.

[0022] Preferably, the top of the three-stage pressure stabilizing tank is provided with a gas balance port, which is connected to a nitrogen source. The three-stage pressure stabilizing tank is provided with a submerged feed pipe, and the outlet of the submerged feed pipe is located in the lower middle part of the side wall of the tank.

[0023] This invention effectively solves the core problem of secondary bubble generation in the slurry during transfer and storage after defoaming by setting the feed inlet of the three-stage pressure tank to a submerged type and extending it to the lower middle part of the side wall, combined with top nitrogen protection. The submerged feed allows the slurry to enter the tank with a soft landing, completely avoiding new bubbles generated by impact and splashing; the top nitrogen micro-positive pressure protection isolates the slurry from air, preventing oxygen from dissolving in. The synergistic effect of these two features ensures that the deeply degassed slurry maintains absolute stability during the final storage and output stages, providing bubble-free, uniform raw materials for subsequent spray drying and guaranteeing the high quality of the final product.

[0024] In summary, the beneficial effects of this invention are as follows: 1. This invention uses a specific ratio of polymer adhesives to formulate a slurry, providing a dispersion medium and structural binder for subsequent ultrafine silica powder. This lays the foundation for slurry stability and final particle formation from the outset. Furthermore, by feeding the formulated slurry into a dedicated stepped vacuum static defoaming device, it creatively solves the industry problem of deep removal of microbubbles in slurries with high solids content and high specific surface area. This device achieves this through the synergistic effect of gravity-fed coarse defoaming, fine segmentation defoaming under vacuum, and undisturbed pressure-stabilized feeding, without introducing secondary shearing or contamination. The efficient and thorough removal of air bubbles ranging from millimeters to submicrons in the slurry eliminates defects such as droplet breakage and morphological distortion caused by air bubbles during spray drying. Finally, the slurry, which has undergone this deep defoaming and has highly uniform and stable performance, is spray granulated, allowing the drying process to be carried out under optimal thermodynamic conditions. The prepared silica micro powder products exhibit regular particle morphology, smooth surface, narrow particle size distribution, excellent flowability, high bulk density, and good batch consistency, fully meeting the stringent requirements of high-end application fields for the physical properties of silica micro powder, and realizing a reliable transformation from raw materials to high-quality products. 2. This invention guides the slurry to form a zigzag shape to extend the flow path, achieving efficient and gentle initial separation and removal of large air bubbles entrained in the slurry without relying on external mechanical energy. This creates stable fluid conditions for subsequent deep processing. Furthermore, in the negative pressure environment of the secondary vacuum defoaming tank, the slurry flows through multiple porous trays and is repeatedly divided into thin liquid films or fine liquid columns. The micron- and submicron-sized microbubbles encased within are deeply exposed and completely removed under the synergistic effect of vacuum expansion and the huge gas-liquid interface. Finally, the slurry is smoothly transferred by gravity to a tertiary pressure stabilizing tank with nitrogen protection, completely eliminating the risk of secondary foaming and oxidation of the defoamed slurry during temporary storage and transportation due to disturbance, impact, or contact with air. Thus, the entire system ultimately provides high-quality silica slurry with low gas content, uniform solid content, stable rheology, and no secondary pollution for the subsequent spray drying process. This provides an irreplaceable pretreatment guarantee for the preparation of final silica micro powder products with regular particle morphology, concentrated particle size distribution, and excellent flowability. 3. This invention utilizes multi-sensor fusion monitoring, including differential pressure transmitters, high-precision flow meters, and absolute pressure transmitters installed across multiple layers, to capture and calculate the differential pressure signal characterizing the true flow resistance of the porous tray in real time. The control unit intelligently compares this signal with theoretical benchmark values ​​dynamically calculated based on real-time flow and vacuum, thereby achieving early and accurate warnings of micro-blockage trends and objective quantitative diagnosis of blockage severity. When the algorithm determines that intervention is needed, the execution unit and control unit immediately respond collaboratively, isolating the defoaming tank through a rapid shut-off valve to create an independent clean environment. Subsequently, the system activates the cleaning circuit consisting of a pulse gas storage tank and a high-speed switching injection valve, injecting clean gas into the top of the primary buffer tank, forming a high-speed clean airflow from top to bottom. This airflow sequentially flows through the multi-layer porous tray in the secondary vacuum defoaming tank, utilizing its stable shearing and carrying force to efficiently flush the deposits in the pores in the same direction. The flushed gas and detached contaminants are directly discharged from the system through a clean discharge valve located on the side wall of the defoaming tank. The entire cleaning process is completed fully automatically within a closed system, requiring no human intervention and introducing no liquid cleaning media, resulting in no secondary pollution or wastewater generation. The successful application of this system revolutionizes equipment maintenance from traditional post-failure shutdown and disassembly repair to status-based early warning and online proactive self-maintenance. This fundamentally eliminates performance degradation and unplanned downtime caused by blockages, significantly improving the continuity, stability, and overall intelligence of the production process, providing a solid guarantee for the long-term, reliable, and efficient performance of the core deep defoaming process. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the process of the present invention; Figure 2 This is a schematic diagram of the stepped vacuum static defoaming device of the present invention; Figure 3 This is a three-dimensional schematic diagram of the primary buffer tank of the present invention; Figure 4 This is the present invention. Figure 1 An enlarged view of point A; Figure 5 This is a three-dimensional schematic diagram of the umbrella-shaped dispersion disk of the present invention; Figure 6 This is a cross-sectional schematic diagram of the umbrella-shaped dispersion disk of the present invention; Figure 7 This is a three-dimensional schematic diagram of the porous conical tray of the present invention. Detailed Implementation

[0026] The following specific embodiments are merely illustrative of the present invention and are not intended to limit the invention. After reading this specification, those skilled in the art can make modifications to these embodiments without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of the present invention.

[0027] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0028] Example 1

[0029] like Figure 1 As shown, a wet process for producing silica micro powder includes the following steps: S1, Preparation of adhesive solution: Prepare an adhesive solution using pure water and chemical polymer adhesive, with the polymer adhesive accounting for 0.1% of the solution; S2, Slurry mixing: Mix silica powder with D50 of 8μm with the glue solution in step S1 to prepare a silica slurry with a solid content of 5%. S3, Step-by-step defoaming: The silica slurry prepared in step S2 is subjected to step-by-step defoaming treatment using a step-by-step vacuum static defoaming device 1. In the primary buffer tank 11, the slurry undergoes gentle pre-defoaming through an umbrella-shaped dispersion plate 113 and two layers of inclined baffles 111 at an angle of 15° with the gaps staggered by 60°. Subsequently, the slurry is pumped into the secondary vacuum defoaming tank 12, where it flows through a porous conical tray 121 for deep defoaming. Finally, the slurry flows by gravity into the tertiary pressure stabilizing tank 13, where it is temporarily stored and stably output under micro-positive pressure nitrogen protection.

[0030] S4, Spray granulation: The defoamed slurry is fed into spray drying equipment 2 at a lower feed rate of 100 kg / h, matching the low solids content. A high-speed centrifugal atomizer with a linear velocity of 100 m / s is used, and the dried product is collected by a cyclone separator.

[0031] The specific process of defoaming treatment is as follows: 3a. The slurry from step 2 is fed into the primary buffer tank. Inside the tank, the slurry is guided by inclined baffles to extend the flow path and achieve the initial separation of large bubbles. 3b. The slurry is smoothly delivered from the primary buffer tank to the secondary vacuum defoaming tank via a transfer pump. Under vacuum conditions, the slurry flows through multiple porous trays and is divided into liquid films to achieve deep defoaming. 3c. After defoaming, the slurry flows into the three-stage pressure stabilizing tank by gravity, where it is temporarily stored under slight positive pressure or nitrogen protection, and then stably transported to the spray drying equipment.

[0032] like Figure 1As shown, the spray drying equipment 2 includes an air supply system 21, a material supply system 22, a drying tower 23, and a gas-solid separation system 24 connected in sequence along the process flow. The air supply system 22 includes an air filter 211, a blower 212, and a heat exchanger 213 connected in sequence. The material supply system is a paddle feeder 4, which is used to transport silica slurry to an atomizer located at the top of the drying tower 6. The atomizer is a high-speed centrifugal atomizer with a linear velocity of 100-200 m / s for its dispersion disc. The gas-solid separation system 24 includes an induced draft fan 241 and at least one stage cyclone separator 242. A hot air distributor 241 is provided at the top of the drying tower 23, and the hot air distributor 241 is connected to the output end of the heat exchanger 3. The gas-solid separation system 24 also includes a secondary collection unit located downstream of the cyclone separator 242; the secondary collection unit is a bag filter or a secondary cyclone separator, the inlet of which is connected to the pipe before the induced draft fan 8, and the outlet is connected to the inlet of the induced draft fan 8. The spray drying equipment is also equipped with a cooling pipe.

[0033] like Figure 2 As shown, the stepped vacuum defoaming device 1 includes a primary buffer tank 11, a secondary vacuum defoaming tank 12, and a tertiary pressure stabilizing tank 13, which are arranged sequentially along the slurry flow direction and connected by pipelines. The primary buffer tank 11 is used for preliminary defoaming and homogenization of the slurry, and has an inlet and an outlet at the top. The secondary vacuum defoaming tank 12 is a sealed tank with a vacuum system connected to its top for deep defoaming of the slurry under negative pressure. The tertiary pressure stabilizing tank 13 is used to store the defoamed slurry and stably supply it to subsequent processes. Its outlet is connected to a discharge pump 131. The installation height of the secondary vacuum defoaming tank 12 is lower than the bottom outlet of the primary buffer tank 11, and the installation height of the tertiary pressure stabilizing tank 13 is lower than the bottom outlet of the secondary vacuum defoaming tank 12, so that the slurry can be... The slurry flows from the upper tank to the lower tank at least partially by gravity. The outlet of the primary buffer tank 11 is connected to the inlet of the secondary vacuum defoaming tank 12 through the first transfer pump 110. There is no transfer pump between the outlet of the secondary vacuum defoaming tank 12 and the inlet of the tertiary pressure stabilizing tank 13; they are directly connected by a pipeline. The slurry flows by gravity and the pressure difference between the tanks. The transfer of the slurry from the secondary vacuum defoaming tank 12 to the tertiary pressure stabilizing tank 13 is achieved entirely by gravity and the pressure difference between the tanks, without passing through a transfer pump. The top of the tertiary pressure stabilizing tank 13 is provided with a gas balance port 131, which is connected to a nitrogen source. The tertiary pressure stabilizing tank 13 is provided with a submerged feed pipe 131, and the outlet of the submerged feed pipe 131 is located in the lower middle part of the side wall of the tank.

[0034] like Figure 3 As shown, the first-stage buffer tank 11 has at least two layers of inclined baffles 111 arranged vertically inside. Each layer of inclined baffle 111 is an annular notch 112 fixed to the inner wall of the tank. Its surface forms an angle of 15°-30° with the horizontal plane, and the notches of the two adjacent layers of inclined baffles are staggered by 60°-120° in the horizontal circumferential direction.

[0035] like Figures 4-6 As shown, an umbrella-shaped dispersion disk 113 is provided below the primary buffer tank 11. The umbrella-shaped dispersion disk 113 includes a central guide column 1131, the upper end of which is used to connect to the feed inlet, and the lower end is a funnel-shaped opening. A conical or spherical dispersion block 1134 is provided inside the funnel-shaped opening. Its cone angle or radius of curvature is set to convert the vertically falling slurry flow into a radially spreading liquid film. A slurry flow channel 1130 is formed between the conical dispersion block 1134 and the funnel-shaped opening. An annular guide skirt 1135 is provided around the outer edge of the conical dispersion block 1134 to regulate the edge of the liquid film, so that it smoothly detaches and falls into the buffer tank in the form of a continuous annular curtain. Several supporting ribs 1136 are connected between the conical dispersion surface 1134 and the central guide column 1131. A connecting channel 1137 is formed between two adjacent supporting ribs 1136.

[0036] like Figure 7 As shown, the interior of the secondary vacuum defoaming tank 12 is provided with a porous conical tray 121, and the top of the porous conical tray is an arc-shaped impact part 122.

[0037] The secondary vacuum defoaming tank 12 is equipped with a porous tray clogging warning and self-cleaning system, which includes a monitoring unit, an execution unit and a control unit. The monitoring unit includes a differential pressure transmitter 123 spanning the upper and lower parts of the multi-layer porous tray 121, a flow meter 124 installed on the feed pipeline, and an absolute pressure transmitter installed on the top of the tank. The execution unit includes: a first quick-cut-off valve 125 located on the feed pipe of the secondary vacuum defoaming tank 12, a second quick-cut-off valve 125 located on the discharge pipe, a clean air source injection circuit 127 located at the top of the secondary vacuum defoaming tank 12, and a clean discharge valve 128 located on the side wall of the secondary vacuum defoaming tank 12; a pulse gas storage tank and a high-speed switching injection valve are sequentially provided on the clean air source injection circuit 127. The control unit is configured to perform the following steps: S1 calculates the theoretical pressure difference through the multi-layer porous tray based on real-time data from the flow meter and absolute pressure transmitter and a preset benchmark model. S2 compares the theoretical differential pressure with the actual differential pressure measured by the differential pressure transmitter in real time. When the actual differential pressure continues to exceed the first preset percentage of the theoretical differential pressure, an early warning signal is generated; when it exceeds the second preset percentage, a self-cleaning command is generated. The second preset percentage is greater than the first preset percentage. S3, in response to the self-cleaning command, controls the closure of the first quick-shut-off valve and the second quick-shut-off valve to isolate the secondary vacuum defoaming tank 12; at the same time, controls the opening of the cleaning discharge valve; S4, control the opening of the high-speed switch injection valve to inject the gas in the pulse gas tank into the top of the first-stage buffer tank 11, forming a high-speed clean airflow from top to bottom, which flows sequentially through the multi-layer porous tray 121 in the second-stage vacuum defoaming tank 12 for unidirectional flushing. The flushed gas and dirt are directly discharged through the clean discharge valve. S5, after cleaning is completed, control the closing of the high-speed switch injection valve and the cleaning discharge valve, restore the system to normal production status, and reopen the first and second quick shut-off valves.

[0038] The algorithm continuously collects the feed flow rate (Q), the absolute pressure inside the tank (P_vac), and the actual pressure difference (ΔP_actual) across multiple porous pallets. First, based on the real-time Q and P_vac, the theoretical pressure difference (ΔP_theoretical) that the cleaning pallet should have under the current operating conditions is calculated by interpolation from a preset benchmark model using a lookup table or formula. Then, the core of the algorithm compares the actual pressure difference with the theoretical pressure difference in real time and calculates the deviation rate.

[0039] The system has two threshold levels for status management and decision-making: when the deviation rate continues to exceed the first warning threshold, it is determined to be a slight blockage trend and the system issues an early warning; when the deviation rate further increases and continues to exceed the second cleaning threshold, it is determined to be a significant blockage and the system automatically generates a self-cleaning command.

[0040] Once the instruction is generated, the algorithm immediately coordinates the execution unit to enter the automatic cleaning process: First, it quickly closes the quick-shutdown valves on the inlet and outlet pipelines to isolate the tank, and simultaneously opens the cleaning discharge valve located on the side wall of the tank; then, it controls the high-speed switch injection valve to open, rapidly injecting gas from the pre-pressurized pulse gas tank, forming a high-speed cleaning airflow from top to bottom. This airflow flows sequentially through the multi-layer porous tray, using its stable shearing and carrying force to efficiently flush the deposits in the channels in the same direction. The flushed gas and dirt are directly discharged from the system through the cleaning discharge valve. After cleaning, the system automatically closes the cleaning inlet and outlet valves, restores the system to normal production status, and reopens the process valves. The entire process is completed automatically within tens of seconds without manual intervention. This algorithm revolutionizes the traditional passive shutdown maintenance after a fault into predictive maintenance and online proactive cleaning based on condition monitoring, significantly improving the continuity, reliability, and intelligence level of equipment operation.

[0041] Working principle: such as Figures 1-7 As shown, the slurry preparation involves dissolving the chemical polymer adhesive in pure water at a mass ratio of 0.1%-1% to prepare a homogeneous adhesive solution. Subsequently, this adhesive solution is thoroughly stirred with silica powder with a D50 of 0-8μm in a mixing device to form a silica slurry with a solid content of 5%-70%. In this stage, the polymer adhesive plays a role in stabilizing dispersion and providing structural bonding.

[0042] Primary Buffer Tank Coarse Defoaming and Homogenization: The prepared slurry is transported through pipelines to the primary buffer tank 11 of the stepped vacuum settling defoaming device 1. The slurry first flows through the umbrella-shaped dispersion plate 113 inside the tank, where the central guide column 1131 receives the vertically falling slurry. Through the slurry flow channel 1130 formed by the lower conical dispersion block 1134 and the funnel mouth, the concentrated jet is transformed into a thin liquid film that spreads radially along the surface of the dispersion block. This process effectively eliminates the impact kinetic energy. Subsequently, the slurry flows sequentially through at least two layers of staggered inclined baffles 111. These annular notches 112, which are at an angle of 15°-30° to the horizontal plane, guide the slurry to flow slowly along a zigzag three-dimensional path through their staggered 60°-120° notch design. During the laminar flow of the slurry along the inclined plate surface, the large air bubbles larger than millimeters entrained inside have sufficient time to rise, merge, and escape from the exhaust port at the top of the tank, achieving efficient and gentle pre-separation and homogenization.

[0043] Deep defoaming in a secondary vacuum defoaming tank: The slurry, after initial defoaming, is smoothly pumped into the secondary vacuum defoaming tank 12, which is installed at a lower position, by the first delivery pump 110. A stable negative pressure environment is maintained inside the tank by a vacuum system. After entering the tank, the slurry first impacts and flows through the porous conical tray 121 with an arc-shaped impact section 122 at the top, and is repeatedly divided into numerous thin liquid films or columns by the dense through-holes on its conical surface. Under vacuum conditions, the micron- and submicron-sized microbubbles encased within these liquid films / columns expand rapidly, their buoyancy greatly increasing, allowing them to quickly detach from the slurry bulk and be continuously removed by the vacuum system. This process of division, expansion, and degassing, repeated by the multiple layers of conical trays, achieves deep and thorough removal of microbubbles from the slurry.

[0044] Disturbance-free transfer and pressure-stabilized storage: The slurry, after deep defoaming, flows entirely by gravity into the tertiary pressure-stabilized tank 13 via a directly connected pipeline, relying on the installation height difference and pressure difference between the secondary vacuum defoaming tank 12 and the tertiary pressure-stabilized tank 13 (negative pressure in the secondary tank and normal or slightly positive pressure in the tertiary tank), without the intervention of any transfer pump. This design completely avoids the risks of shearing, pulsation, and secondary foaming that may be caused by mechanical conveying. The slurry is temporarily stored in the tertiary pressure-stabilized tank 13 under slightly positive pressure or nitrogen protection, and is stably and continuously supplied to subsequent processes by the discharge pump 131 through its side wall outlet, ensuring the perfect maintenance of the obtained high-quality, low-aeration slurry state.

[0045] Spray Drying and Product Collection: The slurry output from the pressure tank is stably conveyed to the spray drying equipment 2 by the paddle feeder 4. At the top of the drying tower 23, the slurry is atomized into fine droplets of uniform size and height by a high-speed centrifugal atomizer with a linear velocity of 100-200 m / s. Simultaneously, clean hot air provided by the air filter 211, blower 212, and heat exchanger 213 forms a uniform and stable high-temperature flow field at the top of the tower via the hot air distributor 241. The droplets undergo instantaneous heat and mass exchange with the hot air inside the tower, causing rapid evaporation of moisture and the formation of silica micropowder. The dried gas-solid mixture enters the gas-solid separation system 24. First, most of the product is separated by at least one cyclone separator 242. Subsequently, the exhaust gas containing fine powder enters a downstream bag filter or a secondary cyclone separator for deep purification, achieving final product collection and compliant exhaust gas emission, resulting in high-quality silica micropowder with regular particle morphology, concentrated particle size distribution, and excellent flowability.

[0046] Intelligent Online Maintenance: To ensure the long-term efficient operation of the core components of the deep defoaming tank, the secondary vacuum defoaming tank incorporates a built-in porous tray clogging warning and self-cleaning system. The system monitors the actual pressure difference of the slurry flowing through the porous tray in real time using a cross-layer differential pressure transmitter, a feed flow meter, and an absolute pressure transmitter at the tank top. It then combines real-time flow rate and tank vacuum level to intelligently calculate the theoretical pressure difference based on a preset benchmark model. By comparing the actual pressure difference with the theoretical pressure difference, the system determines the clogging status in real time: when the actual pressure difference continuously exceeds the first threshold of the theoretical pressure difference, a warning signal is issued; when it exceeds a higher threshold, the cleaning process is automatically triggered.

[0047] After the cleaning command is generated, the control unit automatically performs the following operations: First, it closes the quick-shutdown valves on the inlet and outlet pipelines to isolate the defoaming tank; simultaneously, it opens the tank-side cleaning discharge valve; then, it opens the high-speed switch injection valve, causing gas from the pulse gas storage tank to be rapidly injected into the top of the tank, forming a high-speed cleaning airflow from top to bottom, sequentially flushing the porous tray channels of each layer and removing adhering substances; the contaminated airflow is then quickly discharged from the system through the cleaning discharge valve. After cleaning is completed, the system automatically closes the cleaning air path and discharge valve, restores the vacuum, and reopens the process valves. The entire process is completed automatically within tens of seconds, without the need for machine shutdown or manual intervention.

[0048] This system transforms traditional post-fault maintenance into predictive maintenance and online cleaning based on real-time status, significantly improving the continuous operation capability, reliability, and intelligence level of equipment, and ensuring stable production and consistent processes.

[0049] Example 2

[0050] Unlike Example 1, S1, Preparation of adhesive solution: Prepare an adhesive solution using pure water and chemical polymer adhesive, with the polymer adhesive accounting for 0.5% of the solution; S2, Slurry mixing: Mix silica powder with D50 of 4μm with the glue solution in step S1 to prepare a silica slurry with a solid content of 40%. S3, Step-by-step defoaming: The silica slurry prepared in step S2 is subjected to step-by-step defoaming treatment using a step-by-step vacuum static defoaming device 1; the primary buffer tank 11 is equipped with three layers of inclined baffles 111 with an inclination angle of 22.5° and a notch staggered by 90°.

[0051] S4, Spray granulation: The defoamed slurry is fed into the spray drying equipment at a feed rate of 180 kg / h. A high-speed centrifugal atomizer with a linear velocity of 150 m / s is used. The dried product is collected by a primary cyclone separator and a bag filter.

[0052] Example 3

[0053] Unlike Example 1, S1, Preparation of adhesive solution: Prepare an adhesive solution using pure water and chemical polymer adhesive, with the polymer adhesive accounting for 1.0% of the solution; S2, Slurry mixing: Mix silica powder with D50 of 0.5μm with the glue solution in step S1 to prepare a silica slurry with a solid content of 70%. S3, Step-by-step defoaming: The silica slurry prepared in step S2 is subjected to step-by-step defoaming treatment using a step-by-step vacuum static defoaming device 1; the primary buffer tank 11 is equipped with three layers with an inclination angle of 30°.

[0054] S4, Spray granulation: The defoamed slurry is fed into the spray drying equipment at a rate of 250 kg / h. A high-speed centrifugal atomizer with a linear velocity of 200 m / s is used. The dried product is collected by a primary cyclone separator and a bag filter. Comparative example: A wet process for producing silica micro powder includes the following steps: S1, Preparation of adhesive solution: Prepare an adhesive solution using pure water and chemical polymer adhesive, with the polymer adhesive accounting for 0.1% of the solution; S2, Slurry mixing: Mix silica powder with D50 of 8μm with the glue solution in step S1 to prepare a silica slurry with a solid content of 5%. S3, Spray granulation: The defoamed slurry is fed into spray drying equipment 2 at a lower feed rate of 100 kg / h, matched with low solids content. A high-speed centrifugal atomizer with a linear velocity of 100 m / s is used, and the dried product is collected by a cyclone separator.

[0055] Performance Comparison Data Table

Claims

1. A wet process for producing silica micro powder, characterized in that, Includes the following steps: S1, Preparation of adhesive solution: Prepare an adhesive solution using pure water and chemical polymer adhesive, with the polymer adhesive accounting for 0.1%-1% of the solution; S2, Slurry mixing: Mix silica powder with D50 of 0~8μm with the glue solution in step S1 to prepare a silica slurry with a solid content of 5%-70%. S3, Step defoaming: The silica slurry prepared in step S2 is subjected to step defoaming treatment using a step vacuum static defoaming device (1). S4, Spray granulation: The defoamed slurry is sent to a spray drying device (2) for drying to obtain silica micro powder.

2. The process for wet production of silica micro powder according to claim 1, characterized in that, The spray drying equipment (2) includes an air supply system (21), a material supply system (22), a drying tower (23), and a gas-solid separation system (24) connected in sequence along the process flow. The air supply system (22) includes an air filter (211), a blower (212), and a heat exchanger (213) connected in sequence. The material supply system is a paddle feeder (4) used to transport silica slurry to an atomizer located at the top of the drying tower (6). The atomizer is a high-speed centrifugal atomizer with a linear velocity of 100-200 m / s for its dispersion disc. The gas-solid separation system (24) includes an induced draft fan (241) and at least one stage cyclone separator (242).

3. The process for wet production of silica micro powder according to claim 2, characterized in that, The top of the drying tower (23) is provided with a hot air distributor (241), which is connected to the output end of the heat exchanger (3).

4. The process for wet production of silica micro powder according to claim 2, characterized in that, The stepped vacuum static defoaming device (1) includes a first-stage buffer tank (11), a second-stage vacuum defoaming tank (12), and a third-stage pressure stabilizing tank (13) arranged sequentially along the slurry flow direction and connected by pipes. The first-stage buffer tank (11) is used for the initial defoaming and homogenization of the slurry. It has an inlet and an outlet at the top. The second-stage vacuum defoaming tank (12) is a sealed tank with a vacuum system connected to its top for deep defoaming of the slurry under negative pressure. The third-stage pressure stabilizing tank (13) is used to store the defoamed slurry and stably supply it to subsequent processes. Its outlet is connected to a discharge pump (131). The installation height of the second-stage vacuum defoaming tank (12) is lower than the bottom outlet of the first-stage buffer tank (11), and the installation height of the third-stage pressure stabilizing tank (13) is lower than the bottom outlet of the second-stage vacuum defoaming tank (12), so that the slurry can flow from the upper tank to the lower tank at least partially by gravity.

5. The process for wet production of silica micro powder according to claim 4, characterized in that, The primary buffer tank (11) has at least two layers of inclined baffles (111) arranged vertically inside. Each layer of the inclined baffle (111) is an annular notch (112) fixed to the inner wall of the tank. Its surface forms an angle of 15°-30° with the horizontal plane, and the notches of the two adjacent layers of the inclined baffle are staggered by 60°-120° in the horizontal circumferential direction.

6. The process for wet production of silica micro powder according to claim 4, characterized in that, Below the primary buffer tank (11) is an umbrella-shaped dispersion disc (113), the umbrella-shaped dispersion disc (113) comprising: A central guide column (1131) has an upper end for connecting to the feed inlet and a lower end that is shaped like a horn. A conical dispersing block (1134) is provided inside the horn. The cone angle is set to convert the vertically falling slurry flow into a radially spreading liquid film. A slurry flow channel (1130) is formed between the conical dispersing block (1134) and the horn. An annular guide skirt (1135) is provided around the outer edge of the conical dispersing block (1134). Several supporting ribs (1136) are connected between the conical dispersing surface (1134) and the central guide column (1131). A connecting channel (1137) is formed between two adjacent supporting ribs (1136).

7. The process for wet production of silica micro powder according to claim 4, characterized in that, The secondary vacuum defoaming tank (12) is provided with a porous conical tray (121) inside, and the top of the porous conical tray is an arc-shaped impact part (122).

8. The process for wet production of silica micro powder according to claim 7, characterized in that, The secondary vacuum defoaming tank (12) is equipped with a porous tray clogging early warning and self-cleaning system, which includes a monitoring unit, an execution unit and a control unit. The monitoring unit includes a differential pressure transmitter (123) spanning the upper and lower parts of the multi-layer porous tray (121), a flow meter (124) installed on the feed pipeline, and an absolute pressure transmitter installed on the top of the tank. The execution unit includes: a first quick-cut-off valve (125) on the feed pipe of the secondary vacuum defoaming tank (12), a second quick-cut-off valve (125) on the discharge pipe, a clean air source injection circuit (127) on the top of the secondary vacuum defoaming tank (12), and a clean discharge valve (128) on the side wall of the secondary vacuum defoaming tank (12); the clean air source (127) injection circuit is provided with a pulse gas storage tank and a high-speed switching injection valve in sequence; The control unit is configured to perform the following steps: (S1) Based on the real-time data of the flow meter and absolute pressure transmitter and the preset benchmark model, calculate the theoretical pressure difference through the multi-layer porous tray; (S2) The theoretical pressure difference is compared with the actual pressure difference measured by the differential pressure transmitter in real time. When the actual pressure difference continues to exceed the first preset percentage of the theoretical pressure difference, an early warning signal is generated; when it exceeds the second preset percentage, a self-cleaning command is generated, wherein the second preset percentage is greater than the first preset percentage. (S3) In response to the self-cleaning command, control the closing of the first quick-cut-off valve and the second quick-cut-off valve to isolate the secondary vacuum defoaming tank (12); at the same time, control the opening of the cleaning discharge valve; (S4) Control the opening of the high-speed switch injection valve so that the gas in the pulse gas storage tank is injected into the top of the first-level buffer tank (11) to form a high-speed clean airflow from top to bottom. The airflow flows sequentially through the multi-layer porous tray (121) in the second-level vacuum defoaming tank (12) for unidirectional flushing. The flushed gas and dirt are directly discharged through the clean discharge valve. (S5) After cleaning is completed, the high-speed switch injection valve and the cleaning discharge valve are closed to restore the system to normal production status, and the first and second quick shut-off valves are reopened.

9. The process for wet production of silica micro powder according to claim 7, characterized in that, The outlet of the primary buffer tank (11) is connected to the inlet of the secondary vacuum defoaming tank (12) via the first transfer pump (110). There is no transfer pump between the outlet of the secondary vacuum defoaming tank (12) and the inlet of the tertiary pressure stabilizing tank (13), but they are directly connected by a pipeline. The slurry flows by gravity and the pressure difference between the tanks. The transfer of the slurry from the secondary vacuum defoaming tank (12) to the tertiary pressure stabilizing tank (13) is achieved entirely by gravity and the pressure difference between the tanks, without passing through a transfer pump.

10. The process for wet production of silica micro powder according to claim 9, characterized in that, The top of the three-stage pressure stabilizing tank (13) is provided with a gas balance port (131), which is connected to a nitrogen source. The three-stage pressure stabilizing tank (13) is provided with a submerged feed pipe (131), and the outlet of the submerged feed pipe (131) is located in the lower middle part of the side wall of the tank.

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