Apparatus and method for continuously producing rubber-grade modified nano-zinc oxide

Abstract

The application discloses a kind of equipment and method for continuously preparing rubber-grade modified nano-zinc oxide, belong to the technical field of surface treatment of rubber filler.Method utilizes micro-channel reactor to continuously synthesize basic zinc carbonate precursor and is handled on-line high shear;Through rotary flash drying and three-stage continuous rotary reaction furnace thermal decomposition, nano-zinc oxide particles are generated;High-temperature nascent particles directly enter vertical high-turbulence modification chamber, and through ultrasonic atomization nozzle, modifier vapor is sprayed to carry out in-situ modification in gas phase, and covalent bonding of modifier and nano-zinc oxide surface is realized.The application realizes the coupling of whole process of synthesis, calcination and surface modification, and the modified nano-zinc oxide has excellent reinforcing performance and industrial application value as rubber reinforcing filler.The method of the application is also suitable for surface treatment of high-purity sulfur, selenium, arsenic, tellurium and other semiconductor materials.

Description

Technical Field

[0001] This invention belongs to the field of surface treatment technology for rubber fillers, and specifically relates to an apparatus and method for continuously preparing rubber-grade modified nano zinc oxide. Background Technology

[0002] Nano zinc oxide, as a multifunctional inorganic activator in the high-performance rubber industry, is prone to spontaneous aggregation during preparation, storage and application due to its extremely high surface energy. This leads to uneven dispersion in the rubber matrix and deterioration of the overall performance of rubber products.

[0003] Patent CN107265493B proposes a method for preparing nano-zinc oxide through microwave radiation thermal decomposition. However, in large-scale production, uneven microwave energy distribution easily leads to localized overheating, causing instantaneous sintering of nanocrystals and compromising the requirement for narrow particle size distribution. Patent CN108842207A discloses a method for mixing modified nano-zinc oxide dispersion with a thickener, but it focuses on the downstream application rather than the synthesis process, failing to address the agglomeration problem caused by the rapid decline in surface activity of nano-zinc oxide after synthesis.

[0004] Currently, the field of rubber-grade nano-zinc oxide preparation faces an inherent contradiction: the mismatch between the high-throughput demand for large-scale continuous production and the precise requirements for controlling the surface properties of nanomaterials and preventing in-situ agglomeration. Existing batch or semi-continuous processes lack a complete process coupling mechanism from precursor decomposition and crystal growth regulation to in-situ chemical modification. Similarly, in the surface treatment of high-purity semiconductor materials such as sulfur, selenium, arsenic, and tellurium, the technical dilemma of achieving both continuous production and precise surface activity control is difficult to resolve simultaneously. Existing equipment mostly employs batch processing methods, which cannot meet the stringent requirements of high-purity semiconductor materials for surface cleanliness, uniformity, and batch consistency. Summary of the Invention

[0005] This invention solves the problems of high surface polarity, easy agglomeration, poor compatibility with rubber matrix, and low modification efficiency of existing nano zinc oxide fillers.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0007] This invention provides a method for the continuous preparation of rubber-grade modified nano zinc oxide, comprising the following steps:

[0008] Step 1: Continuous synthesis and online shearing of the precursor sol; Zinc salt solution and precipitant solution are respectively pumped to the first and second mixing zones of a microchannel reactor via high-pressure constant flow pumps. The zinc salt solution is a zinc nitrate, zinc acetate, or zinc sulfate solution with a mass fraction of 15%-30%, and the precipitant solution is an ammonium bicarbonate or sodium carbonate solution with a molar concentration of 2mol / L-5mol / L. Within the microchannel reactor, the volumetric flow ratio of the two phases is controlled at 1:1.2-1:1.5 to create a transitional or laminar flow state within the microchannels. The channel diameter of the microchannel reactor is... The flow rate is set to 0.5mm-2.0mm, and the internal structure is equipped with static mixing elements with a periodic staggered structure. Through repeated cutting, rotation and recombination of the fluid between the elements, efficient micro-mass transfer is achieved at a low flow rate, avoiding dependence on extremely high flow rates, thus reducing system energy consumption and channel wear. The resulting precursor slurry is continuously fed into an online high-shear disperser. Under the action of a shear field with a rotation speed of 5000r / min-12000r / min, the average particle size of the precursor particles is controlled between 100nm and 300nm. The wet basis moisture content of the slurry is reduced to below 30% through a continuous pressure filtration and dewatering process.

[0009] Step 2: Controlled dynamic thermal decomposition and nanocrystal growth regulation; the dehydrated precursor filter cake is continuously fed into a multi-stage temperature-controlled rotary flash dryer via a screw feeder; the rotary flash dryer is equipped with a high-speed rotating pulverizing impeller with a linear velocity of not less than 25 m / s, using hot air drying to dehydrate and dry the precursor and crush it into ultrafine powder; the dried precursor powder enters a three-stage continuous rotary reactor with the carrier gas; in the first stage preheating zone, the temperature is controlled at 200℃-300℃ to achieve the removal of physical water and partial removal of chemically bound water from the precursor; in the second stage decomposition zone, the temperature is controlled at 450℃-550℃, where the precursor undergoes thermal decomposition to generate zinc oxide crystal nuclei; by controlling the residence time of the material in the decomposition zone to 10 min-20 min, the lattice defect rate during the crystal nuclei growth process is ensured to be at a high activity level; in the third stage stabilization zone, the temperature is controlled at 3... The temperature is 00℃-350℃ to stabilize the crystal structure. The three-stage continuous rotary reactor is filled with a protective atmosphere composed of nitrogen and carbon dioxide, or further containing trace amounts of oxygen. In one embodiment, the protective atmosphere consists of 95% N2 and 5% CO2 by volume. In another embodiment, the protective atmosphere consists of nitrogen, carbon dioxide, and oxygen, wherein the nitrogen volume fraction is 94%-96.5%, the carbon dioxide volume fraction is 2.5%-5%, and the oxygen volume fraction is 0.5%-1.0%. The oxygen vacancy concentration on the surface of the nano-zinc oxide is controlled by dynamically adjusting the oxygen partial pressure. At high temperatures, carbon dioxide undergoes a reversible adsorption-desorption equilibrium with the zinc oxide surface, inhibiting excessive sintering of the grains and regulating the oxygen vacancy concentration on the surface of the nano-zinc oxide, providing suitable active sites for subsequent in-situ modification.

[0010] Step 3: In-situ chemical modification and surface energy regulation in the gas phase; nascent nano-zinc oxide particles, at a high temperature of 300℃-350℃, discharged from the three-stage continuous rotary reactor, enter the vertical high-turbulence modification chamber directly without cooling; at the inlet of the vertical high-turbulence modification chamber, modifier vapor is continuously injected into the material flow through ultrasonic atomizing nozzles; the modifier is one or more combinations of silane coupling agents, titanate coupling agents, or higher fatty acids; as a preferred compounding scheme, the modifier is composed of γ-glycidyl etheroxypropyltrimethoxysilane and stearic acid in a mass ratio of 1:1, and is injected separately in the vertical high-turbulence modification chamber through ultrasonic atomizing nozzles in series, forming a double-layer gradient interface structure; the modifier is sprayed... The nano-zinc oxide particles are preheated to above 200°C to vaporize. The nano-zinc oxide particles and modifier vapor are mixed in a gas-solid two-phase flow in a vertical high-turbulence modification chamber. The turbulence intensity in the vertical high-turbulence modification chamber is maintained by tangential auxiliary hot air introduced from the bottom, and the flow rate of the auxiliary hot air is 15m / s-25m / s. Under the high temperature environment, the modifier molecules undergo a highly efficient dehydration condensation reaction with the active hydroxyl groups on the surface of the nano-zinc oxide, forming a strong chemical bond. The amount of modifier added is 3%-8% of the mass of nano-zinc oxide. By adjusting the material concentration and residence time in the vertical high-turbulence modification chamber, the grafting rate of the modified nano-zinc oxide surface reaches 2.0-3.5 molecular chains / nm².

[0011] Step four: continuous graded collection and gas-solid separation; the modified material enters a multi-stage cyclone separator with the airflow; the first-stage cyclone separator is used to collect particles with a diameter greater than 100nm, which are insufficiently modified agglomerates or a small amount of coarse particles. These particles are returned to the inlet of the vertical high-turbulence modification chamber through a pneumatic conveying pipeline, where they are mixed with high-temperature nascent nano zinc oxide particles and then re-modified in situ in the gas phase. The thermal stress and airflow shearing action under high temperature conditions cause the agglomerates to deagglomerate simultaneously during the modification process, eliminating the need for a separate crushing process; the second-stage cyclone separator collects the target product with a particle size between 30nm and 80nm; the obtained target product passes through a cooling system composed of finned heat exchangers to reduce the temperature to below 50°C, achieves complete gas-solid separation through a bag filter, and is quantitatively packaged in a vacuum environment.

[0012] Furthermore, as a preferred embodiment of the present invention, in step one, the zinc salt solution is pre-dissolved with a crystal-directing agent of 0.5%-1.5% by mass; the crystal-directing agent is polyvinylpyrrolidone or polyethylene glycol; the crystal-directing agent selectively adsorbs onto specific crystal faces of the zinc oxide precursor crystal during the nucleation stage through the complexation of zinc ions by polar groups, thereby inhibiting excessive growth of the crystal along the c-axis direction, ensuring that the final generated nano-zinc oxide exhibits a regular spherical or near-spherical morphology, and the morphology regularity deviation coefficient is controlled within 5%.

[0013] Furthermore, the walls of the microchannel reactor are hydrophobically modified with a contact angle greater than 110° to prevent the nano-precursors from adhering and depositing on the channel walls, thus preventing channel blockage. The pressure inside the microchannel is maintained between 0.3MPa and 0.8MPa by a back pressure valve located at the outlet end, ensuring that the liquid phase reaction takes place in a constant hydrodynamic environment and eliminating the influence of pressure fluctuations on nucleation kinetics.

[0014] Furthermore, in step two, the inner wall of the three-section continuous rotary reactor is welded with a lifting plate structure. The cross-sectional shape of the lifting plate is L-shaped, and the tilt angle is dynamically adjusted according to the rotation speed of the furnace. Through the flipping action of the lifting plate, it is ensured that the material is in full contact with the heat carrier and protective atmosphere during the rotation process. The rotation speed of the three-section continuous rotary reactor is controlled at 3r / min-8r / min, and the furnace tilt angle is set at 2°-5°. This dynamic heating method solves the problem of excessive temperature gradient and hard agglomeration caused by local sintering of particles in the traditional static calcination process, so that the average original particle size deviation of nano zinc oxide is less than 5nm.

[0015] Furthermore, in step three, the specific chemical reaction logic of the gas-phase in-situ chemical modification is as follows: the vaporized silane coupling agent molecules diffuse to the surface of the nano zinc oxide particles, and their alkoxy groups undergo hydrolysis under the action of water molecules or hydroxyl groups adsorbed on the particle surface to generate silanol groups; the silanol groups undergo dehydration condensation reaction with the residual hydroxyl groups on the surface of the nano zinc oxide to form SiOZn covalent bonds; since the nano zinc oxide is modified immediately after leaving the three-stage continuous rotary reactor, the surface has not yet absorbed too much physically adsorbed water or carbon dioxide due to exposure to the external environment, and the surface energy is in a metastable state, which reduces the activation energy of the chemical reaction, so that the modification reaction can be completed within 3s-5s, achieving uniform coating at the molecular level.

[0016] Furthermore, the vertical high-turbulence modification chamber is equipped with an airflow guiding structure, which is a three-dimensional spiral baffle or a spirally arranged guide vane. The airflow guiding structure forces the gas-solid mixture to generate strong rotation and radial diffusion during its upward movement, increasing the collision frequency between nanoparticles and modifier vapor. The wall of the vertical high-turbulence modification chamber is equipped with a jacketed heating system to maintain the inner wall temperature and material balance, prevent the modifier vapor from physically condensing on the wall, and ensure that the effective conversion rate of the modifier is not less than 98%.

[0017] Furthermore, the continuous preparation method also includes an online quality monitoring and feedback control loop; a laser particle size analyzer and a surface hydroxyl density infrared monitoring device are installed at the outlet of the second-stage cyclone separator; the online quality monitoring system collects the particle size distribution data and surface grafting rate data of the product in real time, converts them into electrical signals and transmits them to the central control system; the central control system dynamically adjusts the material flow ratio in step one, the calcination temperature in step two, and the amount of modifier injected in step three through a preset PID control algorithm; when the particle size distribution is widened or the median diameter deviates from the set value, the system automatically increases the flow rate of the microchannel reactor or decreases the temperature of the calcination zone to achieve closed-loop precise control of the entire production process.

[0018] Furthermore, the cooling system used in step four employs a two-stage indirect cooling process; the first stage uses ambient temperature circulating water as the cooling medium to rapidly reduce the material temperature from 350°C to 150°C, preventing secondary agglomeration of the modified nanoparticles at high temperatures; the second stage uses low-temperature cold brine as the cooling medium to reduce the material temperature to below 50°C to meet the stability requirements of the finished product packaging; the entire collection system maintains negative pressure operation, with the pressure set at -500Pa to -1000Pa to prevent leakage of nanoparticles.

[0019] As a preferred embodiment of the present invention, the specific physicochemical properties of the nano zinc oxide are as follows: BET specific surface area of ​​50m² / g-80m² / g, native average particle size of 20nm-40nm, and surface hydrophobicity as indicated by a methanol titration value greater than 40%. In rubber application experiments, the modified nano zinc oxide prepared by the present invention achieves a dispersion grade of level seven or higher in nitrile rubber or EPDM rubber matrix (according to ASTM D2663 standard), which is superior to traditional intermittent modified products.

[0020] Furthermore, the method also includes an intelligent closed-loop predictive control step based on multi-source data fusion:

[0021] A first online near-infrared spectrometer is installed at the outlet of the microchannel reactor to collect near-infrared spectral data of the precursor slurry in real time; a second online near-infrared spectrometer and thermocouple array are installed at the outlet of the second decomposition zone of the three-stage continuous rotary reactor to collect near-infrared spectral data and temperature field distribution data of the calcined nano-zinc oxide in real time; a third online near-infrared spectrometer is installed at the outlet of the vertical high-turbulence modification chamber to collect the surface grafting rate and methanol titration value of the modified product in real time; and a laser particle size analyzer and surface hydroxyl density infrared monitoring device are installed at the outlet of the second-stage cyclone separator to collect the particle size distribution and surface hydroxyl density of the final product in real time.

[0022] The central control system incorporates a multi-source data fusion prediction model to predict the modification effect in real time based on precursor characteristics and calcination conditions. This multi-source data fusion prediction model is constructed based on a partial least squares regression algorithm. The input feature vector includes the average particle size of the precursor slurry, the standard deviation of the particle size distribution of the precursor slurry, the morphological regularity deviation coefficient of the precursor slurry, the concentration of the zinc salt solution, the concentration of the precipitant solution, the temperature in the microchannel reactor, the temperature in the second decomposition zone of the three-stage continuous rotary reactor, the oxygen partial pressure in the three-stage continuous rotary reactor, the residence time of the material in the second decomposition zone, the total amount of modifier added, the mass ratio of the first modifier to the second modifier, and the turbulence intensity in the vertical high-turbulence modification chamber. The output feature vector includes the BET specific surface area, surface grafting rate, methanol titration value, and dispersion grade in the rubber of the final product.

[0023] The central control system implements rolling time-domain optimization control based on a multi-source data fusion prediction model. By solving the optimization objective function, it dynamically adjusts the volumetric flow rate ratio of the two-phase fluid in the microchannel reactor, the temperature of the second decomposition zone of the three-stage continuous rotary reactor, the residence time of the material in the second decomposition zone, the oxygen partial pressure in the three-stage continuous rotary reactor, the total amount of modifier added, and the flow rate of the auxiliary hot air in the vertical high-turbulence modification chamber, so that the quality indicators of the final product approach the target value.

[0024] Furthermore, the optimization objective function is:

[0025] ;

[0026] in: To predict the time domain length, the value is 5-10; For the first The predicted output vector for each step; To output the target value vector; For the first The control increment vector for each step; To output the weight matrix; To control the incremental weight matrix.

[0027] Furthermore, the central control system also implements an adaptive model update strategy, which combines online data collected in the most recent 4 hours with offline detection data to form an update sample set every 4 hours. When the size of the update sample set reaches 50 sets, the model incremental update is triggered, and the regression coefficient matrix is ​​updated through a recursive partial least squares algorithm.

[0028] In addition, this invention also discloses an apparatus for the continuous preparation of rubber-grade modified nano zinc oxide, comprising:

[0029] High-pressure constant flow pumps are used to separately deliver zinc salt solutions and precipitant solutions;

[0030] A microchannel reactor is connected to a high-pressure constant flow pump. The microchannel reactor includes a first mixing zone, a second mixing zone, a static mixing element with a periodically staggered structure, and a back pressure valve. The first and second mixing zones are located at the inlet end of the microchannel reactor, the static mixing element is located downstream of the first and second mixing zones, and the back pressure valve is located at the outlet end of the microchannel reactor.

[0031] An online high-shear disperser, wherein the inlet of the online high-shear disperser is connected to the outlet of a microchannel reactor;

[0032] A continuous filter press, wherein the inlet of the continuous filter press is connected to the outlet of an online high-shear disperser;

[0033] A screw feeder, wherein the inlet of the screw feeder is connected to the outlet of a continuous filter press;

[0034] A multi-stage temperature-controlled rotary flash dryer, wherein the inlet of the multi-stage temperature-controlled rotary flash dryer is connected to the outlet of the screw feeder, and a pulverizing impeller is provided inside the multi-stage temperature-controlled rotary flash dryer;

[0035] The three-stage continuous rotary reactor has its inlet connected to the outlet of a multi-stage temperature-controlled rotary flash dryer. The three-stage continuous rotary reactor includes a first preheating zone, a second decomposition zone, and a third stabilization zone connected in sequence. The inner wall of the furnace cylinder of the three-stage continuous rotary reactor is welded with a lifting plate structure.

[0036] A vertical high-turbulence modification chamber, wherein the inlet of the vertical high-turbulence modification chamber is connected to the outlet of a three-stage continuous rotary reactor, a tangential auxiliary hot air inlet is provided at the bottom of the vertical high-turbulence modification chamber, an ultrasonic atomizing nozzle is provided at the inlet of the vertical high-turbulence modification chamber, an airflow guiding structure is provided inside the vertical high-turbulence modification chamber, the airflow guiding structure is a three-dimensional spiral baffle or a guide vane arranged in a spiral shape, and a jacketed heat tracing system is provided on the wall of the vertical high-turbulence modification chamber;

[0037] A multi-stage cyclone separator, wherein the inlet of the multi-stage cyclone separator is connected to the outlet of a vertical high-turbulence modification chamber, the multi-stage cyclone separator includes a first-stage cyclone separator and a second-stage cyclone separator, the bottom outlet of the first-stage cyclone separator is connected to the inlet of the vertical high-turbulence modification chamber through a pneumatic conveying pipe, and the bottom outlet of the second-stage cyclone separator is used to output the target product;

[0038] The cooling system has an inlet connected to the outlet of the second-stage cyclone separator. The cooling system is a two-stage indirect cooling system, comprising a first-stage finned heat exchanger and a second-stage finned heat exchanger connected in sequence.

[0039] A bag filter dust collector, wherein the inlet of the bag filter dust collector is connected to the outlet of the cooling system;

[0040] The central control system is electrically connected to the high-pressure constant flow pump, microchannel reactor, online high-shear disperser, continuous filter press, screw feeder, multi-stage temperature-controlled rotary flash dryer, three-stage continuous rotary reactor, vertical high-turbulence modification chamber, multi-stage cyclone separator, cooling system, and bag filter.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] This invention integrates a microchannel reactor, a three-stage continuous rotary reactor, and a vertical high-turbulence modification chamber in series to construct a fully coupled system for synthesis, calcination, and modification. In-situ gas-phase modification is carried out at the high-energy initial particle stage. By utilizing the high activity of the particle surface and the high-temperature environment, the modifier forms a high-density covalent bond with the particle surface, preventing secondary agglomeration during storage.

[0043] The microchannel reactor integrates static mixing elements, achieving precise decoupling of the nucleation process. Combined with an online high-shear disperser, the average particle size of the precursor is controlled at the nanoscale, providing a highly uniform material basis for subsequent thermal decomposition. The three-stage continuous rotary reactor, combined with a protective atmosphere containing carbon dioxide, regulates the oxygen vacancy concentration on the surface of nano zinc oxide through dynamic heating and reversible adsorption-desorption equilibrium, which is beneficial for controlling grain sintering and particle size distribution.

[0044] The modified nano zinc oxide prepared by this invention has a high surface grafting rate, narrow particle size distribution, and regular morphology, and exhibits good dispersibility in rubber matrix; the entire production system operates in a closed manner, with a high conversion rate of gas phase modifier, and has industrial application value. Attached Figure Description

[0045] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0046] Figure 1 This is the continuous synthesis and online shearing process of the precursor sol of the present invention.

[0047] Figure 2 This invention provides a process flow for controlled dynamic thermal decomposition and nanocrystal growth regulation.

[0048] Figure 3 This invention provides a process flow for in-situ chemical modification and surface energy regulation in the gas phase. Detailed Implementation

[0049] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the embodiments of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0050] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0051] See Figures 1-3 This embodiment discloses an apparatus and method for the continuous preparation of rubber-grade modified nano zinc oxide:

[0052] Step 1: Controlled synthesis of the precursor basic zinc carbonate sol; A precise material delivery system driven by a high-pressure constant flow pump is used to feed a zinc salt solution (such as zinc nitrate, zinc acetate, or zinc sulfate) with a mass fraction of 15%-30% and a precipitant solution (such as ammonium bicarbonate or sodium carbonate) with a molar concentration of 2mol / L-5mol / L into a microchannel reactor at a defined flow ratio; The internal structure of the microchannel reactor is designed according to the principle of extremely rapid microscopic mass transfer, and the first and second mixing zones are confined by micron-level flow channels, allowing the two phases of fluid to collide in a very small space; To achieve efficient micro-mixing under macroscopic flow velocity constraints, static mixing elements are periodically arranged inside the microchannel reactor. These elements consist of staggered blades with specific geometric curvatures, forcing the fluid to cut, fold, and recombine. When the mixture flows within channels with diameters of 0.5 mm to 2.0 mm, the forced convection induced by the static mixing elements creates a highly uniform supersaturation field throughout the entire space. This environment induces the generation of numerous primary nuclei of basic zinc carbonate precursors with extremely narrow particle size distributions. To further control crystal morphology, zinc salt solutions... The solution contains 0.5%-1.5% by mass of a crystal-directing agent, such as polyvinylpyrrolidone or polyethylene glycol. The polar groups on these polymer segments, such as pyrrolidone groups or ether bonds, form stable complexes with zinc ions in the liquid phase through electron cloud overlap. During crystal nucleation and growth, these complexes selectively adsorb onto the polar faces or specific side faces of the basic zinc carbonate crystals. This adsorption behavior increases the growth activation energy of that crystal face while inhibiting the preferred growth of the crystal along the c-axis, ensuring that the resulting precursor and subsequently generated zinc oxide exhibit a regular spherical shape. The microchannel reactor has a near-spherical morphology, with its morphology regularity deviation coefficient strictly locked within 5%. The microchannel reactor wall has been hydrophobically modified based on a fluorosilane coupling agent, resulting in a wall contact angle greater than 110°. This reduces the van der Waals forces and electrostatic attraction between polar precursor particles and the metal wall, solving the industry problem of scaling and clogging in microchannels. By adjusting the back pressure valve at the outlet, a constant back pressure of 0.3MPa-0.8MPa is maintained inside the microchannel, which not only improves the solubility of dissolved gases to eliminate bubble interference, but also ensures the absolute stability of the nucleation kinetic environment.

[0053] After the nucleation stage, the resulting precursor slurry is continuously fed into an online high-shear disperser. In this equipment, the rotor and stator, rotating at speeds of 5000 r / min to 12000 r / min, form a high-energy-density shear field. Within this region, the material not only endures extremely high shear strain but also experiences cavitation due to severe local pressure fluctuations. This composite force field rapidly disintegrates loose aggregates caused by concentration fluctuations, resulting in an average particle size distribution between 100 nm and 300 nm. The slurry after high-shear treatment enters a continuous filter press, where it is dewatered using a programmed stepwise pressurization method until the wet basis moisture content of the filter cake drops below 30%, providing a stable solid content guarantee for the subsequent pyrolysis stage.

[0054] Step two involves the precise control of controlled dynamic thermal decomposition and nanocrystal growth. The filter cake is metered and conveyed by a screw feeder into a multi-stage temperature-controlled rotary flash dryer. The pulverizing impeller at the bottom of the dryer rotates at a high speed of no less than 25 m / s, working in conjunction with the tangentially entering high-temperature hot air to achieve instantaneous heat and mass transfer of the material. Under the volumetric heat transfer coefficient, the free water in the precursor rapidly vaporizes, while the mechanical impact of the pulverizing impeller refines the filter cake into ultrafine powder. The dried powder is guided by the carrier gas flow field and continuously enters a three-stage continuous rotary reactor. The internal design of the furnace reflects the intervention in lattice dynamics: the temperature of the first preheating zone is set at 200℃-300℃, and the physically adsorbed water on the surface of the powder and some of the chemically bound water inside the lattice are removed through gentle heat input; the second decomposition zone is the core area of ​​crystal structure transformation, and the temperature is strictly controlled at 450℃-550℃. In this temperature zone, basic zinc carbonate undergoes thermal decomposition and rearranges to form zinc oxide crystals. By adjusting the tilt angle (2°-5°) and rotation speed (3r / min-8r / min) of the rotary kiln, the residence time of the material in the decomposition zone is controlled between 10min and 20min. This dynamic heat treatment method, combined with the L-shaped lifting plate structure arranged inside the furnace, allows the powder to form a waterfall-like falling trajectory under the combined action of gravity and the lifting force of the lifting plates. This ensures that each particle can fully contact the protective atmosphere composed of 95% N2 and 5% CO2 in three-dimensional space. The presence of carbon dioxide can inhibit the excessive removal of surface hydroxyl groups through chemical equilibrium shift and undergo reversible adsorption and desorption equilibrium with the zinc oxide surface at high temperature, regulating the oxygen vacancy concentration on the nano zinc oxide surface and providing suitable active sites for subsequent in-situ modification. In the third stable zone, the temperature is lowered to 300℃-350℃ to eliminate the internal stress generated by the crystals during rapid decomposition, making the nanocrystal structure tend to a metastable equilibrium, and providing the best thermodynamic starting point for subsequent surface modification.

[0055] Step three is the in-situ gas-phase chemical modification stage. The nano-zinc oxide particles discharged from the three-stage continuous rotary reactor enter the vertical high-turbulence modification chamber at a high-temperature active state of 300℃-350℃ without any cooling measures. Utilizing the metastable high-energy characteristics of the initial particle formation, the chemical bonds on the nanoparticle surface are unsaturated and exhibit a tendency to gain and lose electrons. At the inlet of the vertical high-turbulence modification chamber, preheated silane coupling agents, titanate coupling agents, or higher fatty acid vapors are sprayed into the high-temperature particle flow in the form of micron-sized droplet clusters through ultrasonic atomizing nozzles. The high-frequency vibration energy generated by ultrasonic atomization further breaks up the droplets, causing them to completely vaporize upon contact with the high-temperature airflow. Inside the vertical high-turbulence modification chamber, auxiliary hot air at 15m / s-25m / s is introduced tangentially from the bottom, combined with internally installed three-dimensional spiral baffles, forcing the gas-solid two-phase flow into high-speed swirling motion. The modifier molecules in the gas... In its phase state, it possesses a diffusion coefficient, enabling it to penetrate the boundary layer between particles and undergo dehydration condensation reactions with the active hydroxyl groups on the surface of nano-zinc oxide. The alkoxy groups of the coupling agent molecules undergo hydrolysis mediated by the residual hydroxyl groups, and the resulting silanol groups chemically graft onto the zinc-oxygen bonds on the zinc oxide surface, forming strong SiOZn covalent bonds. This reaction is completed within 3-5 seconds, and the amount of modifier added is controlled at 3%-8% of the mass of nano-zinc oxide, thus achieving uniform coating of a monolayer or quasi-monomolayer on the particle surface. The jacketed heating system of the vertical high-turbulence modifier chamber compensates for the heat loss caused by the gas-solid mixing process, prevents the physical condensation of the modifier on the wall surface, and ensures that its chemical conversion rate is not less than 98%. By adjusting the material concentration and residence time inside the vertical high-turbulence modifier chamber, the grafting rate of the modified nano-zinc oxide surface reaches 2.0-3.5 molecular chains / nm², realizing the transformation from hydrophilic to extremely hydrophobic.

[0056] Step four ensures product consistency through a continuous graded collection and gas-solid separation system. The modified gas-solid mixture enters a multi-stage cyclone separator. The first-stage cyclone separator uses centrifugal force to capture coarse particles larger than 100nm or a small amount of adhering agglomerates, which are then pneumatically conveyed back to the vertical high-turbulence modification chamber for reprocessing. The second-stage cyclone separator collects target products with particle sizes between 30nm and 80nm. To prevent van der Waals force-induced secondary agglomeration of the modified nanoparticles during cooling, the system is equipped with a cooling system. This system employs a two-stage indirect cooling process: the first-stage finned heat exchanger uses ambient temperature circulating water to rapidly reduce the material temperature from 350℃ to 150℃, freezing the surface state of the particles; the second stage uses low-temperature cold brine to further reduce the material temperature to below 50℃. The cooled powder undergoes complete gas-solid separation through a bag filter.

[0057] Throughout the process, the online quality monitoring and feedback control system integrated into the production line plays a core command role. A laser particle size analyzer and a surface hydroxyl density infrared monitoring device, installed at the outlet of the second-stage cyclone separator, collect the physical and chemical characteristic parameters of the product in real time and upload them to the central control system via electrical signals. The central control system incorporates a neural network PID algorithm. When the laser particle size analyzer detects that the median diameter exceeds the set range, the system automatically sends instructions to the control unit of the microchannel reactor to increase the fluid volumetric flow rate ratio or increase the output frequency of the high-pressure constant flow pump to enhance nucleation intensity. If the infrared monitoring device detects insufficient surface grafting rate, the system immediately adjusts the feeding rate of the ultrasonic atomizing nozzle or increases the heating temperature of the vertical high-turbulence modification chamber. This closed-loop control logic ensures the production process is highly immune to raw material fluctuations and environmental disturbances.

[0058] Example 1: In this example, a 20% zinc nitrate solution was used as the zinc source, and a 3 mol / L ammonium bicarbonate solution was used as the precipitant. The microchannel reactor had a channel diameter of 1.0 mm and was equipped with a static mixing element with a cross-V structure. The volumetric flow rate ratio of the two-phase fluids was set to 1:1.3. 1.0% polyethylene glycol (PEG2000) was pre-added to the zinc salt solution as a crystal guiding agent. The microchannel outlet back pressure was set to 0.5 MPa. The resulting precursor slurry was treated by an online high-shear disperser at 8000 r / min and dehydrated by pressure filtration until the wet basis moisture content was 2%. 8%; In the pyrolysis section, the linear velocity of the pulverizing impeller of the rotary flash dryer is set to 30 m / s; The temperatures of the preheating zone, decomposition zone, and stabilization zone of the three-stage continuous rotary reactor are set to 250℃, 500℃, and 320℃, respectively, the residence time of the material in the decomposition zone is 15 min, and the rotary furnace speed is 5 r / min; The protective atmosphere consists of nitrogen with a volume fraction of 95% and carbon dioxide with a volume fraction of 5%; In the in-situ modification stage, KH550 silane coupling agent is selected as the modifier, with an addition amount of 3.5% of the zinc oxide mass, and the vaporization temperature is set to 230℃; The auxiliary hot air velocity in the vertical high-turbulence modification chamber is 20 m / s.

[0059] Example 2: This example is basically the same as Example 1, except that in this example, a 25% zinc sulfate solution is used, and a 4 mol / L sodium carbonate solution is used as the precipitant; the channel diameter of the microchannel reactor is set to 0.8 mm; a 1.5% polyvinylpyrrolidone (PVPK30) is used as the crystal guiding agent; the back pressure at the microchannel outlet is set to 0.6 MPa; the rotation speed of the high-shear disperser is increased to 10000 r / min, and the moisture content of the wet basis after dehydration is 25%; the temperature of the decomposition zone of the three-stage continuous rotary reactor is set to 530℃, the temperature of the stabilization zone is set to 350℃, and the residence time is extended to 18 min; the modifier is a titanate coupling agent (NDZ101) with an addition amount of 4.5% and a vaporization temperature of 250℃; a strong gas-solid exchange field is generated in the vertical high-turbulence modification chamber through a three-dimensional spiral baffle.

[0060] Example 3: In this example, the zinc source is a 15% zinc acetate solution, the precipitant is 2 mol / L ammonium bicarbonate; the microchannel reactor diameter is 1.5 mm; the crystal guiding agent is 0.8% polyethylene glycol; the decomposition zone temperature is set at 480℃, the stabilization zone temperature is 300℃, and the residence time is 12 min; the modifier is stearic acid vapor, the addition amount is 2.5%, and the vaporization temperature is 260℃.

[0061] Example 4: In this example, a 20% zinc nitrate solution was used as the zinc source, and a 3 mol / L ammonium bicarbonate solution was used as the precipitant. The microchannel reactor had a channel diameter of 1.0 mm and was equipped with a static mixing element with a cross-V structure. The volumetric flow rate ratio of the two-phase fluids was set to 1:1.3. 1.0% polyethylene glycol (PEG2000) was pre-added to the zinc salt solution as a crystal guiding agent. The microchannel outlet back pressure was set to 0.5 MPa. The resulting precursor slurry was subjected to online high-pressure treatment. The shear disperser was used to process the material at a speed of 8000 r / min, and the material was dehydrated by pressure filtration to a wet basis moisture content of 28%. In the pyrolysis section, the linear velocity of the pulverizing impeller of the rotary flash dryer was set to 30 m / s. The temperatures of the preheating zone, decomposition zone, and stabilization zone of the three-stage continuous rotary reactor were set to 250℃, 500℃, and 320℃, respectively. The residence time of the material in the decomposition zone was 15 min, and the rotation speed of the three-stage continuous rotary reactor was 5 r / min. The protective atmosphere consisted of 95% nitrogen and 5% carbon dioxide by volume.

[0062] In the in-situ modification stage, nano-zinc oxide particles at 320°C discharged from the three-stage continuous rotary reactor directly enter the vertical high-turbulence modification chamber without cooling. At the inlet of the vertical high-turbulence modification chamber, two sets of ultrasonic atomizing nozzles connected in series are installed to continuously spray the first modifier vapor and the second modifier vapor, respectively. The first modifier is γ-glycidyl etheroxypropyltrimethoxysilane (KH560), which is preheated to 220°C to vaporize, and the addition amount is 2.5% of the mass of nano-zinc oxide. The second modifier is stearic acid, which is preheated to 260°C to vaporize, and the addition amount is 2.5% of the mass of nano-zinc oxide. The mass ratio of the first modifier to the second modifier is 1:1. The vertical high-turbulence modification chamber is equipped with four sets of spirally arranged guide vanes, replacing the original three-dimensional spiral baffles. The installation angle of the guide vanes is 15°-30°, which forces the gas-solid mixture to generate a three-dimensional composite motion of continuous rotation, radial diffusion and axial back mixing during the upward process. The bottom of the vertical high-turbulence modification chamber tangentially introduces auxiliary hot air with a flow velocity of 18m / s-22m / s and a temperature of 250℃. The top of the vertical high-turbulence modification chamber is equipped with a Venturi acceleration section, which increases the flow velocity of the gas-solid mixture to 30m / s-35m / s at the outlet. The turbulent shear force generated by the acceleration further promotes the uniform spreading of modifier molecules on the particle surface.

[0063] The reaction mechanism of the compound modified system is as follows: the epoxy group in the KH560 molecule undergoes ring-opening at high temperature, reacting with the hydroxyl groups on the surface of nano-zinc oxide to form ZnOSi covalent bonds, while the epoxy groups at the ends of the KH560 molecule retain their activity; the carboxyl group of the stearic acid molecule undergoes esterification with the hydroxyl groups formed after the ring-opening of the KH560 molecule, forming a cross-linked network structure; by adjusting the injection order and ratio of the two modifiers, a double-layer gradient interface structure is constructed on the surface of nano-zinc oxide: the inner layer is a silane coupling agent layer covalently bonded to the surface of zinc oxide, providing a strong anchoring effect; the outer layer is a long stearic acid chain chemically bonded to the silane coupling agent, providing excellent lipophilicity and steric hindrance effect; the double-layer gradient interface structure increases the surface grafting rate to 4.0-5.0 molecular chains / nm², and the methanol titration value to ≥62%.

[0064] Step four is the same as in Example 1.

[0065] The modified nano-zinc oxide prepared in this embodiment has a BET specific surface area of ​​70.2 m² / g, a native average particle size of 23.5 nm, a particle size distribution standard deviation of 2.5 nm, a methanol titration value of 64.5%, a surface grafting rate of 4.6 molecular chains / nm², a rubber dispersion grade of 9.5, a tensile strength of 30.1 MPa, an abrasion volume of 0.08 cm³ / 1.61 km, and a morphological regularity deviation coefficient of 2.8%.

[0066] Example 5: In this example, a 25% zinc sulfate solution was used, and a 4 mol / L sodium carbonate solution was used as the precipitant; the channel diameter of the microchannel reactor was set to 0.8 mm; a 1.5% polyvinylpyrrolidone (PVPK30) was used as the crystal guiding agent; the back pressure at the microchannel outlet was set to 0.6 MPa; the speed of the high-shear disperser was increased to 10,000 r / min, and the moisture content of the wet basis after dehydration was 25%.

[0067] In the pyrolysis section, the dehydrated precursor filter cake is continuously fed into a multi-stage temperature-controlled rotary flash dryer via a screw feeder for drying and crushing. The dried precursor powder is then carried by carrier gas into a three-stage continuous rotary reactor. The temperature of the first preheating zone of the three-stage continuous rotary reactor is controlled at 220℃-280℃, the temperature of the second decomposition zone is controlled at 480℃-520℃, and the temperature of the third stabilization zone is controlled at 310℃-340℃. The three-stage continuous rotary reactor is filled with a dynamically adjusted protective atmosphere, which consists of nitrogen, carbon dioxide, and trace amounts of oxygen, with volume fractions of N2: 94%–96.5%, CO2: 2.5%–5%, and O2: 0.5%–1.0%, respectively. The oxygen partial pressure of the protective atmosphere is monitored in real time by zirconia oxygen analyzers installed at the furnace inlet and outlet, and the oxygen supply is dynamically adjusted by a mass flow controller to maintain the oxygen partial pressure in the furnace at 10. -4 Pa-10 -6 Between Pa; the presence of trace amounts of oxygen is used to selectively oxidize the zinc oxide surface at high temperatures, precisely controlling the concentration and distribution of oxygen vacancies on the surface, so that the oxygen vacancy concentration is controlled at 10 Pa. 13 -10 15 Between 1 / nm².

[0068] In the in-situ modification stage, nano-zinc oxide particles at 330℃ discharged from the three-stage continuous rotary reactor directly enter the vertical high-turbulence modification chamber without cooling. At the inlet of the vertical high-turbulence modification chamber, a dielectric barrier discharge plasma generator is installed to pre-treat the nano-zinc oxide particle stream entering the chamber. The plasma generator has a discharge power of 100W-300W, a discharge frequency of 5000Hz-20000Hz, and a treatment time of 0.5s-2s. This plasma pre-treatment generates additional active sites on the surface of the nano-zinc oxide, including oxygen vacancies, zinc vacancies, and surface hydroxyl groups, increasing the surface active site density by more than 30%. The nano-zinc oxide particles, after plasma pretreatment, are immediately mixed with modifier vapor injected through an ultrasonic atomizing nozzle. The modifier is a titanate coupling agent (NDZ201), added at 4%-6% of the mass of the nano-zinc oxide, with a vaporization temperature of 240℃-260℃. A pulsed airflow disturbance device is installed in the vertical high-turbulence modification chamber, intermittently injecting high-pressure nitrogen pulses into the chamber at a frequency of 0.5Hz-2Hz. The pulse pressure is 0.1MPa-0.3MPa, and the pulse width is 0.1s-0.3s. This is used to break the steady-state distribution of the gas-solid two-phase flow in the vertical high-turbulence modification chamber and increase the collision probability and contact uniformity between the nanoparticles and the modifier vapor.

[0069] Step four is the same as in Example 2.

[0070] The modified nano-zinc oxide prepared in this embodiment has a BET specific surface area of ​​74.8 m² / g, a native average particle size of 22.9 nm, a particle size distribution standard deviation of 2.2 nm, a methanol titration value of 68.3%, a surface grafting rate of 5.1 molecular chains / nm², a rubber dispersion grade of 9.8, a tensile strength of 31.5 MPa, an abrasion volume of 0.07 cm³ / 1.61 km, and a morphological regularity deviation coefficient of 2.5%.

[0071] Example 6: In this example, the zinc source is a 15% zinc acetate solution, the precipitant is 2 mol / L ammonium bicarbonate, the microchannel reactor diameter is 1.5 mm, the crystal guiding agent is 0.8% polyethylene glycol, the decomposition zone temperature is set at 480℃, the stabilization zone temperature is 300℃, and the residence time is 12 min.

[0072] In the in-situ modification stage, nano-zinc oxide particles at 310℃ discharged from the three-stage continuous rotary reactor enter the vertical high-turbulence modification chamber directly without cooling. The vertical high-turbulence modification chamber consists of three series-connected modification units, with a height ratio of 1:0.8:0.6 for each unit. Conical transition sections with cone angles of 30°-45° are set between each unit. The first-stage modification unit has a tangential air inlet structure to introduce auxiliary hot air and form a swirling flow field with a swirling intensity (swirling number) of 0.6-0.8. The second-stage modification unit has a reverse air inlet nozzle to introduce auxiliary hot air in the opposite direction to the mainstream flow, forming a reverse flow field with a reverse flow velocity ratio of 0 to the mainstream flow velocity. 0.3-0.5; The third-stage modification unit is equipped with a static mixing element to further enhance gas-solid mixing; Each modification unit is independently equipped with an ultrasonic atomizing nozzle to spray different types of modifiers or different proportions of the same modifier to achieve gradient modification; The first-stage modification unit sprays γ-methacryloyloxypropyltrimethoxysilane (KH570) at 2% of the mass of nano zinc oxide; The second-stage modification unit sprays zinc stearate at 1.5% of the mass of nano zinc oxide; The third-stage modification unit sprays titanate coupling agent (NDZ101) at 1.5% of the mass of nano zinc oxide; The total amount of modifiers added is 5% of the mass of nano zinc oxide.

[0073] The working mechanism of the multi-stage tandem modification unit is as follows: In the first-stage swirling flow field, KH570 molecules uniformly coat the surface of nano-zinc oxide under the action of high-speed rotating airflow, forming preliminary chemical grafting; in the second-stage countercurrent flow field, zinc stearate molecules undergo an addition reaction with the double bonds in KH570 molecules to form a cross-linked structure; in the third-stage static mixing element, titanate coupling agent molecules further fill and modify surface defects, forming a dense composite modification layer; the synergistic effect of the three-stage modification units enables the modification layer thickness to reach 2.5nm-3.5nm, improving the density and uniformity of the modification layer.

[0074] Step four is the same as in Example 3.

[0075] The modified nano-zinc oxide prepared in this embodiment has a BET specific surface area of ​​58.6 m² / g, a native average particle size of 35.2 nm, a particle size distribution standard deviation of 3.8 nm, a methanol titration value of 53.6%, a surface grafting rate of 3.8 molecular chains / nm², a rubber dispersion grade of 8.8, a tensile strength of 27.5 MPa, an abrasion volume of 0.12 cm³ / 1.61 km, and a morphological regularity deviation coefficient of 3.6%.

[0076] Example 7: In this example, a 20% zinc nitrate solution was used as the zinc source, and a 3 mol / L ammonium bicarbonate solution was used as the precipitant. The microchannel reactor had a channel diameter of 1.0 mm and was equipped with a static mixing element with a cross-V structure. The volumetric flow rate ratio of the two-phase fluids was set to 1:1.3. 1.0% polyethylene glycol (PEG2000) was pre-added to the zinc salt solution as a crystal guiding agent. The microchannel outlet back pressure was set to 0.5 MPa. The resulting precursor slurry was treated by an online high-shear disperser at 8000 r / min and dehydrated by pressure filtration until the wet basis moisture content was 28%. In the pyrolysis section, the linear velocity of the pulverizing impeller of the rotary flash dryer is set to 30 m / s; the temperatures of the preheating zone, decomposition zone, and stabilization zone of the three-stage continuous rotary reactor are set to 250℃, 500℃, and 320℃, respectively, the residence time of the material in the decomposition zone is 15 min, and the rotation speed of the three-stage continuous rotary reactor is 5 r / min; the protective atmosphere consists of 95% nitrogen and 5% carbon dioxide by volume; in the in-situ modification stage, KH550 silane coupling agent is selected as the modifier, with an addition amount of 3.5% of the zinc oxide mass, and the vaporization temperature is set to 230℃; the auxiliary hot air velocity in the vertical high-turbulence modification chamber is 20 m / s.

[0077] Based on Example 1, this embodiment further introduces an intelligent closed-loop predictive control system based on multi-source data fusion to achieve real-time prediction of product quality and dynamic optimization of process parameters.

[0078] (I) The system architecture and data acquisition are as follows:

[0079] The continuous preparation system in this embodiment adds the following online detection device to the system in embodiment 1:

[0080] A first online near-infrared spectrometer is installed at the outlet of the microchannel reactor to collect near-infrared spectral data of the precursor slurry in real time, which is used to invert the particle size distribution, morphological regularity and impurity content of the precursor.

[0081] A second online near-infrared spectrometer and thermocouple array are installed at the outlet of the second decomposition zone of the three-stage continuous rotary reactor to collect near-infrared spectral data and temperature field distribution data of calcined nano zinc oxide in real time.

[0082] A third online near-infrared spectrometer is installed at the outlet of the vertical high-turbulence modification chamber to collect chemical indicators such as surface grafting rate and methanol titration value of the modified product in real time.

[0083] A laser particle size analyzer and a surface hydroxyl density infrared monitoring device are installed at the outlet of the second-stage cyclone separator to collect the particle size distribution and surface hydroxyl density of the final product in real time.

[0084] All of the above-mentioned online detection devices have a sampling frequency of 10 times / s, and the data is transmitted to the central control system in real time via industrial Ethernet.

[0085] (II) The prediction model construction and training are as follows:

[0086] The central control system incorporates a multi-source data fusion prediction model to predict the modification effect in real time based on precursor characteristics and calcination conditions. The prediction model is constructed based on the partial least squares regression algorithm, and the model construction process is as follows:

[0087] Step 1: Feature Variable Extraction

[0088] Define the input feature vector ;in: The average particle size of the precursor slurry was obtained by inversion using a first online near-infrared spectrometer. The standard deviation of the particle size distribution of the precursor slurry was obtained by inversion using a first online near-infrared spectrometer. The morphological regularity deviation coefficient of the precursor slurry is obtained by inversion using the first online near-infrared spectrometer. The concentration of the zinc salt solution is expressed as a percentage by mass, measured using an online refractometer. The concentration of the precipitant solution is expressed in mol / L and is measured using an online conductivity meter. The temperature inside the microchannel reactor, in °C, is measured by a thermocouple. The temperature of the second decomposition zone in a three-stage continuous rotary reactor, in °C, is measured by a thermocouple array. The oxygen partial pressure in the three-stage continuous rotary reactor, in Pa, is measured by a zirconia oxygen analyzer. The residence time of the material in the second decomposition zone, in minutes, is calculated based on the rotational speed of the screw feeder. The total amount of modifier added, expressed as a percentage by mass, is measured using a mass flow meter. The mass ratio of the first modifier to the second modifier is dimensionless. In this embodiment, only a single modifier (KH550) is used, so the mass ratio of the first modifier to the second modifier is recorded as 1:0. This input feature is processed as a separate variable during model training and does not affect the applicability of the model in other compound modification schemes. The turbulence intensity in a vertical high-turbulence modification chamber is measured by the auxiliary hot air velocity, in m / s.

[0089] Define the output feature vector ;in: The BET specific surface area of ​​the final product, in m² / g, is obtained by joint inversion using a laser particle size analyzer and a surface hydroxyl density infrared monitoring device. The surface grafting rate of the final product is expressed in units of molecular chains / nm², and is measured by an infrared monitoring device for surface hydroxyl density. The methanol titration value of the final product, expressed as a percentage, is measured using a surface hydroxyl density infrared monitoring device. The dispersion grade in the rubber of the final product is obtained through offline detection and online data correlation modeling.

[0090] Step 2: Construction of Partial Least Squares Regression Model

[0091] Collect N sets of historical production data and construct an input matrix. and output matrix By extracting the latent variables of the input and output using the partial least squares regression algorithm, the following prediction model is established: ;in: This is the regression coefficient matrix, with dimension 1. ; The residual matrix has dimensions of . Regression coefficient matrix The solution is obtained through the following iterative process:

[0092] 1. For the input matrix and output matrix Standardization is performed to obtain the standardized matrix. and ;

[0093] 2. Extract the first latent variable ,in Let be the weight vector, satisfying , Represents covariance;

[0094] 3. Calculation right load vector and right load vector ;

[0095] 4. Calculate the residual matrix , 5. Repeat steps 2-4 to extract subsequent latent variables until the norm of the residual matrix is ​​less than a preset threshold or the number of extracted latent variables reaches a preset upper limit; 6. Calculate the regression coefficient matrix based on all extracted latent variables. .

[0096] The regression coefficient matrix After the model training is completed, it is embedded in the central control system for online prediction.

[0097] Step 3: Model Training and Validation

[0098] Production data from 500 hours of continuous operation was collected, yielding 12,000 samples. 10,000 samples were used for model training, and 2,000 for model validation. Five-fold cross-validation was employed for model training, and the number of latent variables was optimized using grid search. Validation results show that the prediction model... The average absolute error of the prediction for (BET specific surface area) is 1.2 m² / g. The predicted mean absolute error for (surface grafting rate) is 0.15 molecular chains / nm². The predicted average absolute error of (methanol titration value) is 1.8%, which meets the accuracy requirements of industrial online control.

[0099] (III) The rolling time-domain optimization control strategy is as follows:

[0100] Based on the above prediction model, the central control system implements rolling time-domain optimization control and dynamically adjusts process parameters to make product quality indicators approach the target value.

[0101] Define the optimization objective function as follows: ;in: To predict the time domain length, the value is 5-10; For the first The predicted output vector of the step is calculated using the aforementioned partial least squares regression model; The output target value vector includes the target BET specific surface area, target surface grafting rate, target methanol titration value, and target dispersion grade; For the first The control increment vector for each step; To output the weight matrix, the dimension is... The diagonal elements are respectively , , , ; To control the incremental weight matrix, the dimension is... , The number of adjustable control variables, with diagonal elements taking values ​​of to .

[0102] The adjustable control variables include: The volumetric flow rate ratio of the two-phase fluids in the microchannel reactor is adjustable from 1:1.1 to 1:1.6. The temperature of the second decomposition zone in the three-stage continuous rotary reactor is adjustable from 450℃ to 550℃. The residence time of the material in the second decomposition zone is adjustable from 8 min to 25 min. The oxygen partial pressure in the three-stage continuous rotary reactor is adjustable within a range of 10. -5 Pa-10 -3 Pa; The total amount of modifier added can be adjusted within the range of 3%-8% of the mass of nano zinc oxide; The flow velocity of the vertical high-turbulence modified indoor auxiliary hot air is adjustable from 12m / s to 28m / s.

[0103] The rolling time-domain optimization control performs the following steps at each sampling time:

[0104] Step 1: State estimation; based on the measured input at the current moment. and output The system state is estimated using a Kalman filter.

[0105] Step 2: Prediction; Based on the current state, use a prediction model to calculate the future. Predicted output of step .

[0106] Step 3: Optimization; Solve the following optimization problem to obtain the optimal control sequence. ;in To control the length of the time domain, the value is set to 3-5: The constraints are: upper and lower limits for control variables: Control variable rate of change constraint: Output variable constraints: .

[0107] Step 4: Implementation; Set the first element of the optimal control sequence Apply to the production system.

[0108] Step 5: Roll; proceed to the next sampling time and repeat steps 1-5.

[0109] (iv) The adaptive model is updated as follows:

[0110] To address model mismatch caused by raw material fluctuations and equipment aging, the central control system also implements an adaptive model update strategy. Every 4 hours, the system combines online data collected within the last 4 hours with offline detection data to form an update sample set. When the update sample set reaches 50 sets, an incremental model update is triggered. The incremental update uses a recursive partial least squares algorithm to update the regression coefficient matrix while preserving the original model structure, using the following recursive formula. : ;in: This is the updated regression coefficient matrix; This is the regression coefficient matrix before the update; The input matrix for the newly added samples; The output matrix for the newly added samples; The Kalman gain matrix is ​​calculated using a recursive least squares algorithm.

[0111] (v) The control effect was verified as follows:

[0112] The key quality indicators of the product using the intelligent closed-loop predictive control system of this embodiment are as follows after 500 hours of continuous operation: the relative standard deviation (RSD) of BET specific surface area is 0.8%, the relative standard deviation of surface grafting rate is 1.2%, and the relative standard deviation of methanol titration value is 1.5%. Compared with the PID control of Example 1 (RSD of 1.2%, 2.1%, and 2.5% respectively), the product consistency of this embodiment is improved.

[0113] When the concentration of the zinc salt solution deviates by ±5% due to fluctuations in the raw material batches, the intelligent control system of this embodiment can automatically adjust the flow ratio and calcination temperature of the microchannel reactor within 30 minutes to keep the BET specific surface area of ​​the final product within the target range of 65-72 m² / g. In contrast, the PID control of Example 1 requires more than 2 hours to recover stability and produces about 8% defective products during the fluctuation period.

[0114] This embodiment achieves a leap from passive feedback to active prediction by fusing multi-source sensor data, constructing a partial least squares regression prediction model, implementing rolling time-domain optimization control, and adaptive model updates. This enhances the anti-interference capability of the production process and the consistency of product batches, providing an intelligent solution for the high-quality continuous production of rubber-grade modified nano zinc oxide.

[0115] Comparative Example 1: Produced using the traditional intermittent precipitation method; zinc nitrate and ammonium bicarbonate of the same concentration were mixed in a reactor with a stirrer, aged and filtered, and the filter cake was placed in a box drying oven for drying, and then calcined at 500°C in a muffle furnace for 2 hours; after cooling, it was modified by dry ball milling, and an equal proportion of KH550 silane coupling agent was added, and it was treated in a high-speed mixer for 30 minutes.

[0116] Comparative Example 2: A continuous synthesis and calcination process was adopted, but the gas-phase in-situ modification step was eliminated; after zinc oxide was discharged from a three-stage continuous rotary reactor and naturally cooled to room temperature, it was put into a liquid-phase modification vessel, and an equal proportion of KH550 silane coupling agent was added in ethanol medium. The mixture was refluxed at 80°C for 3 hours, followed by secondary drying; since the nano zinc oxide had already undergone surface contamination and hard agglomeration during the cooling stage, the subsequent liquid-phase modification could only act on the outer surface of the agglomerates, making it difficult to achieve uniform coating of the particles.

[0117] The physicochemical properties and application performance of the products obtained in the above embodiments and comparative examples were tested, and the comparative data are shown in Table 1. The test standards were as follows: BET specific surface area was measured by nitrogen adsorption method; native average particle size was statistically analyzed by transmission electron microscopy (TEM); hydrophobicity was tested by methanol titration method (the higher the methanol titration value, the higher the degree of surface organicification); dispersion grade was evaluated in nitrile rubber matrix according to ASTM D2663 standard (ten grades are full marks); tensile strength and abrasion volume were tested according to GB / T528 and GB / T1689 standards, respectively.

[0118] Table 1: Summary Table of Performance Parameters Comparison between Embodiments and Comparative Examples of the Invention

[0119]

[0120] This invention achieves full-process coupling of synthesis, calcination, and surface modification by constructing a precise nucleation system synergistically using a microchannel reactor and static mixing elements, a three-stage continuous rotary reactor combined with an oxygen vacancy control mechanism under a carbon dioxide protective atmosphere, and a synergistic process of in-situ gas-phase chemical modification in the nascent high-energy state and two-stage indirect cooling. It solves the problems of high surface polarity, easy agglomeration, poor compatibility with rubber matrices, and low modification efficiency of existing nano-zinc oxide fillers. It improves the particle size uniformity, surface grafting rate, and dispersion grade in the rubber matrix of the product. Example data shows that the modified nano-zinc oxide prepared by this invention achieves a tensile strength of 31.5 MPa, a wear volume as low as 0.07 cm³ / 1.61 km, and excellent batch-to-batch consistency, providing a complete continuous preparation solution for high-performance rubber industry nano-activators.

[0121] The continuous surface modification apparatus and method described in this invention, based on its gas-phase in-situ modification mechanism and high-turbulence mixing design, can also be extended to the field of surface treatment of semiconductor materials such as high-purity sulfur, selenium, arsenic, and tellurium.

[0122] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0123] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. It should be noted that any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for continuous preparation of rubber-grade modified nano-zinc oxide, characterized in that, Includes the following steps: Step 1: The zinc salt solution and the precipitant solution are respectively pumped to the first and second mixing zones of the microchannel reactor via a high-pressure constant flow pump. In the microchannel reactor, the mixture passes through a static mixing element with a periodically staggered structure in a transitional or laminar flow state to generate primary nuclei for basic zinc carbonate precursors. The resulting precursor slurry is continuously fed into an online high-shear disperser for shearing treatment, and the wet basis moisture content of the slurry is reduced to below 30% through a continuous pressure filtration dewatering process. Step 2: The dehydrated precursor filter cake is continuously fed into a multi-stage temperature-controlled rotary flash dryer by a screw feeder for drying and crushing. The dried precursor powder enters a three-stage continuous rotary reactor with the carrier gas and passes through the first preheating zone, the second decomposition zone and the third stabilization zone in sequence for thermal decomposition reaction to generate nano zinc oxide particles. Step 3: The nano-zinc oxide particles, which are at 300℃-350℃ and discharged from the three-stage continuous rotary reactor, enter the vertical high-turbulence modification chamber directly without cooling. At the entrance of the vertical high-turbulence modification chamber, modifier vapor, which is preheated to above 200℃ and vaporized, is continuously sprayed into the material flow through an ultrasonic atomizing nozzle. The nano-zinc oxide particles and the modifier vapor mix in the vertical high-turbulence modification chamber and undergo a dehydration condensation reaction to form chemical bonds. Step four: The modified material enters the multi-stage cyclone separator with the airflow. The first-stage cyclone separator collects particles with a diameter greater than 100nm and returns them to the vertical high-turbulence modification chamber for recycling. The second-stage cyclone separator collects the target product with a diameter between 30nm and 80nm. After the target product is cooled by the cooling system, it is separated into gas and solid by a bag filter.

2. The method for continuous preparation of rubber-grade modified nano-zinc oxide according to claim 1, characterized in that, In step three, the modifier is a combination of a first modifier and a second modifier. The first modifier is γ-glycidyl etheroxypropyltrimethoxysilane, and the second modifier is stearic acid. The mass ratio of the first modifier to the second modifier is 1:

1. The vertical high-turbulence modification chamber is equipped with four sets of spirally arranged guide vanes, and the installation angle of the guide vanes is 15°-30°.

3. The method for continuous preparation of rubber-grade modified nano-zinc oxide according to claim 2, characterized in that, The top of the vertical high-turbulence modification chamber is equipped with a Venturi acceleration section, which increases the flow velocity of the gas-solid mixture to 30m / s-35m / s at the outlet.

4. The method for continuous preparation of rubber-grade modified nano-zinc oxide according to claim 1, characterized in that, In step two, the three-stage continuous rotary reactor is filled with a dynamically adjusted protective atmosphere, which consists of nitrogen, carbon dioxide and oxygen, with volume fractions of 94%-96.5% nitrogen, 2.5%-5% carbon dioxide and 0.5%-1.0% oxygen, respectively.

5. The method for continuous preparation of rubber-grade modified nano-zinc oxide according to claim 4, characterized in that, When the protective atmosphere consists of nitrogen, carbon dioxide, and oxygen, the oxygen partial pressure of the protective atmosphere is monitored in real time by zirconia oxygen analyzers installed at the furnace inlet and outlet, and the oxygen supply is dynamically adjusted by a mass flow controller to maintain the oxygen partial pressure inside the furnace at 10. -4 Pa-10 -6 Between Pa.

6. The method for continuous preparation of rubber-grade modified nano-zinc oxide according to claim 1, characterized in that, In step three, a dielectric barrier discharge plasma generator is installed at the entrance of the vertical high-turbulence modification chamber to perform plasma pretreatment on the nano-zinc oxide particle flow entering the vertical high-turbulence modification chamber. The discharge power of the plasma generator is 100W-300W, the discharge frequency is 5000Hz-20000Hz, and the processing time is 0.5s-2s.

7. The method for continuous preparation of rubber-grade modified nano-zinc oxide according to claim 1, characterized in that, In step three, a pulsed airflow disturbance device is installed in the vertical high-turbulence modification chamber to intermittently inject high-pressure nitrogen pulses into the modification chamber at a frequency of 0.5Hz-2Hz. The pulse pressure is 0.1MPa-0.3MPa and the pulse width is 0.1s-0.3s.

8. The method for continuous preparation of rubber-grade modified nano zinc oxide according to claim 1, characterized in that, The vertical high-turbulence modification chamber consists of three series-connected modification units. The height ratio of each modification unit is 1:0.8:0.

6. A conical transition section with a cone angle of 30°-45° is provided between each modification unit. Each modification unit is independently equipped with the ultrasonic atomizing nozzle.

9. The method for continuous preparation of rubber-grade modified nano zinc oxide according to claim 8, characterized in that, The first-stage modification unit has a tangential air inlet structure to form a swirling flow field with a swirling number of 0.6-0.8; the second-stage modification unit has a reverse air inlet nozzle to form a reverse flow field with a reverse flow velocity ratio of 0.3-0.5 to the mainstream flow velocity; and the third-stage modification unit has a static mixing element.

10. An apparatus for the continuous preparation of rubber-grade modified nano zinc oxide, characterized in that, include: High-pressure constant flow pumps are used to separately deliver zinc salt solutions and precipitant solutions; A microchannel reactor is connected to a high-pressure constant flow pump. The microchannel reactor includes a first mixing zone, a second mixing zone, a static mixing element with a periodically staggered structure, and a back pressure valve. The first and second mixing zones are located at the inlet end of the microchannel reactor, the static mixing element is located downstream of the first and second mixing zones, and the back pressure valve is located at the outlet end of the microchannel reactor. An online high-shear disperser, wherein the inlet of the online high-shear disperser is connected to the outlet of a microchannel reactor; A continuous filter press, wherein the inlet of the continuous filter press is connected to the outlet of an online high-shear disperser; A screw feeder, wherein the inlet of the screw feeder is connected to the outlet of a continuous filter press; A multi-stage temperature-controlled rotary flash dryer, wherein the inlet of the multi-stage temperature-controlled rotary flash dryer is connected to the outlet of the screw feeder, and a pulverizing impeller is installed inside the multi-stage temperature-controlled rotary flash dryer; The three-stage continuous rotary reactor has its inlet connected to the outlet of a multi-stage temperature-controlled rotary flash dryer. The three-stage continuous rotary reactor includes a first preheating zone, a second decomposition zone, and a third stabilization zone connected in sequence. The inner wall of the furnace cylinder of the three-stage continuous rotary reactor is welded with a lifting plate structure. A vertical high-turbulence modification chamber, wherein the inlet of the vertical high-turbulence modification chamber is connected to the outlet of a three-stage continuous rotary reactor, a tangential auxiliary hot air inlet is provided at the bottom of the vertical high-turbulence modification chamber, an ultrasonic atomizing nozzle is provided at the inlet of the vertical high-turbulence modification chamber, an airflow guiding structure is provided inside the vertical high-turbulence modification chamber, the airflow guiding structure is a three-dimensional spiral baffle or a guide vane arranged in a spiral shape, and a jacketed heat tracing system is provided on the wall of the vertical high-turbulence modification chamber; A multi-stage cyclone separator, wherein the inlet of the multi-stage cyclone separator is connected to the outlet of a vertical high-turbulence modification chamber, the multi-stage cyclone separator includes a first-stage cyclone separator and a second-stage cyclone separator, the bottom outlet of the first-stage cyclone separator is connected to the inlet of the vertical high-turbulence modification chamber through a pneumatic conveying pipe, and the bottom outlet of the second-stage cyclone separator is used to output the target product; The cooling system has an inlet connected to the outlet of the second-stage cyclone separator. The cooling system is a two-stage indirect cooling system, comprising a first-stage finned heat exchanger and a second-stage finned heat exchanger connected in sequence. A bag filter dust collector, wherein the inlet of the bag filter dust collector is connected to the outlet of the cooling system; The central control system is electrically connected to the high-pressure constant flow pump, microchannel reactor, online high-shear disperser, continuous filter press, screw feeder, multi-stage temperature-controlled rotary flash dryer, three-stage continuous rotary reactor, vertical high-turbulence modification chamber, multi-stage cyclone separator, cooling system, and bag filter.

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