System for supercritical hydro-thermal synthesis of nano barium titanate and quality regulation and control method

Abstract

The invention provides a system for supercritical hydro-thermal synthesis of nano barium titanate and a quality regulation and control method, and belongs to the technical field of energy and chemical industry. Aiming at the problems of poor reaction uniformity, wide product particle size distribution, uncontrollable morphology, long reaction period and the like in the traditional hydrothermal synthesis process, the invention provides a modular reaction system based on supercritical hydrothermal synthesis, which comprises a raw material pretreatment module, a multi-section reaction module, a rapid cooling crystallization module and a product collection module. The system integrates performance improvement, doping modification and directional regulation and control, gradient utilization of heat energy, additional product recovery and material cyclic utilization are achieved, the particle size, morphology, crystal form and structure of nano barium titanate are precisely regulated and controlled, an effective anti-agglomeration technology is combined, and the system has the advantages of being high in reaction efficiency, excellent in product performance and low in energy consumption; and a foundation is laid for the industrial process of continuous supercritical hydro-thermal synthesis of nano materials.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of energy and chemical industry, and particularly relates to a system for supercritical hydrothermal synthesis of nano-barium titanate and a quality control method. BACKGROUND

[0002] Traditional hydrothermal synthesis method usually utilizes high-temperature aqueous solution to promote the hydrolysis and crystallization of inorganic precursors in a sealed high-pressure container, and has been widely used for the preparation of nanomaterials, including functional ceramic materials such as barium titanate. This method has mild reaction conditions and relatively simple operation. However, the traditional hydrothermal method also has obvious shortcomings. First, due to the limitation of static kettle type reaction environment, the mass transfer and heat transfer efficiency of the reaction system is low, which easily leads to uneven reaction, obvious local concentration and temperature gradient, and the composition and structure of the product often lack consistency. Second, the particle size distribution of the nanoparticles synthesized by the traditional hydrothermal method is wide, and it is difficult to achieve precise control of the particle size. During the reaction process, nucleation and growth are difficult to separate, and a large number of particles of different sizes may exist in the same batch, resulting in poor product uniformity. In addition, the morphology of the generated particles is often uncontrollable, and agglomerated or irregularly shaped particles are easily generated, which poses a challenge to applications requiring regular morphology.

[0003] Supercritical hydrothermal synthesis technology is an improved method proposed to solve the above problems. When water is in a supercritical state beyond the critical point, its physical and chemical properties change significantly: the viscosity decreases, the diffusion coefficient increases, it is similar to a gas but the density is still high, and the dielectric constant decreases, changing its solubility for inorganic salt precursors. These characteristics enable the reactants to mix instantaneously and nucleate rapidly in a supercritical hydrothermal environment, greatly shortening the nucleation induction period and reaction time. Compared with the traditional hydrothermal method, supercritical hydrothermal synthesis can complete the preparation of nanomaterials in a few seconds to a few minutes, significantly improving the reaction efficiency. In addition, the product particles generated under supercritical conditions are often smaller and more uniform, which helps to obtain nanocrystals with narrow particle size distribution. More importantly, supercritical hydrothermal synthesis is suitable for the use of continuous flow reactors, enabling continuous production of the reaction, breaking through the capacity limit of traditional batch kettle reactions. In a supercritical continuous flow reaction system, by precisely controlling the flow rate, pressure and temperature, the reaction conditions can be kept constant, ensuring the quality of the products in each batch to be stable and consistent, and the continuous process is easy to scale up, which is beneficial to industrialization. However, supercritical hydrothermal technology also faces some challenges. For example, the harsh supercritical conditions require high-temperature and high-pressure resistance and corrosion resistance of the equipment materials; the rapid generation of solid-phase products during the reaction process easily causes pipeline blockage, and optimization of mixing and cooling strategies is needed to avoid particle aggregation or deposition. Therefore, how to design an efficient and stable supercritical hydrothermal reaction system to fully utilize its advantages of rapid nucleation and limited growth while overcoming equipment and process difficulties is the key to the industrial application of this technology.

[0004] Barium titanate is the core dielectric material for manufacturing multilayer ceramic capacitors. With the development of electronic components towards miniaturization and high performance, higher requirements are put forward for the quality of barium titanate powder. On the one hand, barium titanate particles are required to have nanoscale size and narrow particle size distribution to improve the dielectric constant and ensure the reliability of the device. On the other hand, the crystal phase composition and dielectric temperature stability of barium titanate are often adjusted by doping modification or surface coating. This requires uniform introduction of the second component and accurate control of its content during synthesis. These composite modification methods require higher requirements for the process, and need to achieve uniform distribution of different components on a nanoscale. In summary, the existing technology cannot meet the requirements of high-efficiency continuous production and high-quality product control, and an innovative synthesis strategy is needed to simultaneously improve reaction uniformity and efficiency, achieve precise control of the particle size, morphology and structure of barium titanate nanoparticles, and be suitable for large-scale continuous production. SUMMARY

[0005] The purpose of the present application is to overcome the above-mentioned deficiencies and provide a system for supercritical hydrothermal synthesis of nanometer barium titanate and a quality control method.

[0006] In order to achieve the above-mentioned purpose, the present application adopts the following technical solutions: In a first aspect, the present application provides a system for supercritical hydrothermal synthesis of nanometer barium titanate, comprising a raw material pretreatment module, the raw material pretreatment module comprising a titanium precursor storage tank, a barium precursor storage tank, a deionized water storage tank, a ligand / dopant storage tank, an additive storage tank and a cooling water storage tank, the outlet of the cooling water storage tank being connected to a rapid cooling crystallization module through a fifth high-pressure metering pump, the heat being reused to the barium precursor storage tank, the outlet of the ligand / dopant storage tank and the outlet of the additive storage tank converging with each other, being connected to inlet one of a labofuge mixer through a first high-pressure metering pump, the outlet pipes of the titanium precursor storage tank and the barium precursor storage tank being provided with a second high-pressure metering pump and a third high-pressure metering pump respectively, being connected to the inlet of a jet impingement mixer, the outlet of the jet impingement mixer being connected to inlet two of the labofuge mixer, the outlet pipe of the deionized water storage tank being provided with a fourth high-pressure metering pump, being connected to the inlet of a heater after being affected by a rapid cooling crystallization module, the outlet of the heater being connected to inlet three of the labofuge mixer, forming three converging mixtures, the labofuge mixer being connected to a pH detector, the outlet of the labofuge mixer being connected to a multi-section reaction module; The multi-section reaction module comprises a plurality of reactors connected in sequence, and a three-way ball valve is arranged at the outlet of each reactor, and the three-way ball valve is connected to a rapid cooling crystallization module; The rapid cooling crystallization module is used for gradient cooling and pressure reduction of the material reacted in the reactor to produce solid and liquid products, and the outlet of the rapid cooling crystallization module is connected to a product collection module; The product collection module is used for processing the solid and liquid products.

[0007] The multi-section reaction module comprises a first reactor, a second reactor, a third reactor and a fourth reactor connected in sequence.

[0008] The rapid cooling and crystallization module comprises a water spray cooler, a quenching heat exchanger, a slow cooling heat exchanger and a capillary pressure reducer connected in sequence, the outlet of the quenching heat exchanger is divided into two paths, one path is connected with the inlet of the heater, and the other path is connected with the inlet of the slow cooling heat exchanger, the outlet of the slow cooling heat exchanger is divided into two paths, one path is connected with the inlet of the capillary pressure reducer, and the other path is connected with the inlet of the barium precursor storage tank; the outlet of the capillary pressure reducer is connected with the product collection module.

[0009] The product collection module comprises a first centrifuge, a second centrifuge and a third centrifuge connected in sequence, the outlet of the third centrifuge is divided into two paths, one path is for solid phase product treatment, and the other path is for liquid phase product treatment.

[0010] The solid phase product treatment comprises an ultrasonic washing device, a vacuum dryer and a nano barium titanate storage tank connected in sequence.

[0011] The liquid phase product treatment comprises a liquid phase product membrane separator connected in sequence, the outlet of the liquid phase product membrane separator is connected with a by-product recovery device in one path and with a deionized water storage tank in the other path.

[0012] The liquid phase product membrane separator adopts a reverse osmosis membrane or a nanofiltration membrane.

[0013] The heater adopts an electromagnetic induction heater, an infrared heater, a resistance wire heater or a natural gas heater.

[0014] In the second aspect, the application provides a quality control method for synthesizing nano barium titanate by supercritical hydrothermal synthesis, comprising the following steps: The fourth high-pressure metering pump increases the system pressure to the critical pressure value of the supercritical hydrothermal synthesis, the anti-agglomerating ligand or the doping modified dopant is stored in the ligand / dopant storage tank, the additive with mineralization or pH adjustment is stored in the additive storage tank, is directly sent to the inlet of the Laval mixer through the first high-pressure metering pump for pre-mixing, the titanium precursor in the titanium precursor storage tank and the precursor in the barium precursor storage tank are respectively converged in the jet collision mixer through the second high-pressure metering pump and the third high-pressure metering pump for precursor pre-mixing, the mixed cold fluid enters the Laval mixer together, is mixed with the supercritical hot fluid preheated by the system and heated by the heater, the Laval mixer is connected with the pH detector to ensure that the reaction environment is stable and maintains the required pH value, after the three-way material is fully mixed in the Laval mixer, the material enters the reactor for hydrolysis and dehydration reaction, then realizes gradient stable cooling and pressure reduction through the water spray desuperheater, the quenching heat exchanger, the slow cooling heat exchanger and the capillary pressure reducer, the solid phase and the liquid phase products after the gradient cooling and pressure reduction are separated under the centrifugal action of the three-stage centrifugal separator, the solid phase product is stripped of dirt on the surface by the impact force of the ultrasonic washing device, and then enters the vacuum dryer for drying, the dried material is sent into the nano barium titanate storage tank for storage; the liquid phase product is separated into by-products and water molecules through the liquid phase product membrane separator, the by-products enter the by-product recovery device for storage, and the water molecules enter the deionized water storage tank for reaction.

[0015] By changing the ratio of the ligand, the dopant or the additive in the ligand / dopant storage tank and the additive storage tank to the titanium precursor, the particle morphology and the anti-agglomeration are controlled, the content of the doping element is adjusted, and the crystal form of the product is controlled; by changing the ratio of the precursors in the barium precursor storage tank and the titanium precursor storage tank, the defect content of the reaction product is controlled, and the dielectric property of the product is changed; by controlling the electric heating power and the pressure setting value, the reaction temperature and the reaction pressure are changed, the particle size and the crystallinity of the product are adjusted; by controlling the three-way valve, the number and the connection form of the reactors in the multi-stage reaction module are changed, and then the reaction time is changed, the particle size of the nano barium titanate particles is controlled; by the online feedback of the pH detector, the concentration and the flow of the additive are adjusted in real time, and the reaction environment of different precursors is controlled.

[0016] Compared with the prior art, the present application has the following beneficial effects: (1) Structural design innovation: the modular system architecture is adopted, and the raw material pretreatment, the multi-stage reaction, the rapid cooling crystallization and the product collection and other functional units are organically combined. Through the double mixing design of the jet collision mixer and the Laval mixer, the high-speed and uniform mixing of the reactants is realized, the reaction uniformity is significantly improved, and the performance fluctuation caused by insufficient local mixing in the traditional process is avoided. The overall structure is compact and easy to control, and embodies the unique design idea for the optimization of the synthesis of nano materials.

[0017] (2) Process continuous and efficient: A continuous flow supercritical hydrothermal reaction system is constructed, which greatly improves the production efficiency and process stability compared with the traditional batch hydrothermal method. The reactants continuously enter the multi-stage reactor under the drive of high-pressure metering pumps, and the products are continuously produced after the reaction reaches a steady state, eliminating the fluctuations and downtime caused by batch processing. This continuous production method not only improves the output per unit time, but also ensures consistent product quality, facilitating industrial scaling and long-term stable operation.

[0018] (3) Precise control of particle size and morphology: Through the integration of multiple means, precise control of the size and morphology of barium titanate nanoparticles is achieved. By adjusting the number of reactors in series or parallel in the multi-stage reaction module or changing the residence time of the material, the particle size can be adjusted. By monitoring the pH online and adjusting the amount of additives in real time, the ideal reaction environment is maintained to control the crystal growth rate and morphology. At the same time, by changing the ratio of titanium and barium precursors and the type and amount of ligand / dopant added, the nucleation rate and growth mechanism can be affected, resulting in a narrower particle size distribution and more controllable morphology. Compared with existing technologies that can only passively control particle size through methods such as sieving after the reaction, the present invention actively and precisely adjusts the particle size and morphology during the synthesis process.

[0019] (4) Heat energy cascade recovery: In the system design, the energy utilization efficiency is fully considered, and heat is recovered through staged heat exchange and circulation cooling. The rapid cooling crystallization module uses a quenching heat exchanger and a slow cooling heat exchanger to transfer the heat of the high-temperature reaction fluid in stages: part of the heat is transferred to the deionized water before entering the heater through the quenching heat exchanger, preheating the feed to reduce the main heating load; another part of the heat is returned to the barium precursor solution through the slow cooling heat exchanger, achieving raw material preheating. At the same time, the cooling water circulation is involved in the heat exchange process, further absorbing and utilizing the waste heat. Through the above heat integration design, the external energy consumption of the system is minimized, reflecting the green and energy-saving process advantage.

[0020] (5) Stable and reliable product quality: The present invention ensures the quality stability of barium titanate nanoparticles through multiple measures. The continuous process mode combined with online monitoring ensures that the reaction conditions are maintained within the set range for a long time, avoiding the performance differences caused by environmental fluctuations in traditional batch processes. At the same time, the in-situ addition of ligands prevents agglomeration, allowing nanoparticles to be surface-modified and isolated immediately after formation, preventing secondary aggregation and growth, resulting in highly dispersed powders. The multi-stage centrifugation, ultrasonic washing, and vacuum drying in the product collection module further remove impurities and prevent agglomeration, ensuring that the final powder is pure and uniform in size. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 The system structure diagram of the present invention; Figure labeling: 1. Titanium precursor tank; 2. Barium precursor tank; 3. Deionized water tank; 4. Ligand / dopant tank; 5. Additive tank; 6. First high-pressure metering pump; 7. Second high-pressure metering pump; 8. Third high-pressure metering pump; 9. Fourth high-pressure metering pump; 10. Jet collision mixer; 11. Heater; 12. Laval mixer; 13. pH detector; 14. Primary reactor; 15. Secondary reactor; 16. Tertiary reactor 17. Quadruple reactor; 18. Water spray desuperheater; 19. Rapid cooling heat exchanger; 20. Slow cooling heat exchanger; 21. Cooling water storage tank; 22. Fifth high-pressure metering pump; 23. Capillary pressure reducer; 24. First-stage centrifuge; 25. Backup centrifuge; 26. Second-stage centrifuge; 27. Third-stage centrifuge; 28. Ultrasonic washer; 29. ​​Vacuum dryer; 30. Nano-barium titanate storage tank; 31. Liquid phase product membrane separator; 32. By-product recovery unit. Detailed Implementation

[0022] To further understand the content of this invention, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the embodiments are merely illustrative and not limiting of the invention.

[0023] Example 1 like Figure 1 As shown, a system for the supercritical hydrothermal synthesis of nano-barium titanate includes a raw material pretreatment module, a multi-stage reaction module, a rapid cooling crystallization module, and a product collection module connected in sequence.

[0024] The raw material pretreatment module's outlet is connected to a multi-stage reaction module, including a titanium precursor storage tank 1, a barium precursor storage tank 2, a deionized water storage tank 3, a ligand / dopant storage tank 4, an additive storage tank 5, and a cooling water storage tank 21. The outlet of the cooling water storage tank 21 is connected to the slow-cooling heat exchanger 20 of the rapid cooling crystallization module via a fifth high-pressure metering pump 22, recovering heat to the barium precursor storage tank 2. The outlets of the ligand / dopant storage tank 4 and the additive storage tank 5 converge and are connected to the inlet of the Laval mixer 12 via a first high-pressure metering pump 6. The outlet pipelines of the titanium precursor storage tank 1 and the barium precursor storage tank 2 are respectively equipped with a second high-pressure metering pump 7 and a third high-pressure metering pump 8, both used for material conveying. The outlets of the second high-pressure metering pump 7 and the third high-pressure metering pump 8... The outlet is connected to the inlet of the jet collision mixer 10, and the outlet of the jet collision mixer 10 is connected to the second inlet of the Laval mixer 12. The outlet pipeline of the deionized water storage tank 3 is also equipped with a fourth high-pressure metering pump 9. After heat exchange through the rapid cooling crystallization module's quench heat exchanger 19, it is connected to the inlet of the heater 11. The outlet of the heater 11 is then connected to the third inlet of the Laval mixer 12, forming a three-way convergence mixing. One end of the Laval mixer 12 is connected to the pH detector 13, and the outlet of the Laval mixer 12 is connected to the multi-stage reaction module.

[0025] The outlet of the multi-stage reaction module is connected with the rapid cooling and crystallization module, the multi-stage reaction module comprises a first-stage reactor 14, a second-stage reactor 15, a third-stage reactor 16 and a fourth-stage reactor 17 connected in sequence, and a three-way ball valve is arranged at the outlet of each reactor and connected with the rapid cooling and crystallization module.

[0026] Preferably, the reactors are tubular reactors in the form of straight pipes or coils, which are connected in series or in parallel.

[0027] The outlet of the rapid cooling and crystallization module is connected with the product collection module, the rapid cooling and crystallization module comprises a water spray cooler 18, a quenching heat exchanger 19, a slow cooling heat exchanger 20 and a capillary pressure reducer 23 connected in sequence, the outlet of the quenching heat exchanger 19 is divided into two paths, one of which is connected with the inlet of the heater 11, and the other of which is connected with the inlet of the slow cooling heat exchanger 20, the outlet of the slow cooling heat exchanger 20 is also divided into two paths, one of which is connected with the inlet of the capillary pressure reducer 23, and the other of which is connected with the inlet of the barium precursor storage tank 2; the outlet of the capillary pressure reducer 23 is connected with the product collection module.

[0028] Preferably, the heater 11 is an electromagnetic induction heater, an infrared heater, a resistance wire heater or a natural gas heater.

[0029] The product collection module is used for processing the solid-phase and liquid-phase products of the reaction, and comprises a first-stage centrifugal machine 24, a second-stage centrifugal machine 26 and a third-stage centrifugal machine 27 connected in sequence, the outlet of the third-stage centrifugal machine 27 is divided into two paths, one of which is for processing the solid-phase product and comprises an ultrasonic washing machine 28, a vacuum dryer 29 and a nano barium titanate storage tank 30 connected in sequence, and the other of which is for processing the liquid-phase product and comprises a liquid-phase product membrane separator 31, the outlet of the liquid-phase product membrane separator 31 is connected with a by-product recovery device 32 on one path and with a deionized water storage tank 3 on the other path, and the first-stage centrifugal machine 24 is connected in parallel with a standby centrifugal machine 25.

[0030] Preferably, the liquid-phase product membrane separator 31 is a reverse osmosis membrane or a nanofiltration membrane.

[0031] Preferably, the pipes and elements of each module are made of nickel-based alloy or stainless steel titanium lining material to prevent impurities from being generated due to corrosion of the system.

[0032] It can be seen that the various functional modules in the application are connected with each other, and the whole system is integrated and optimized to realize the whole-process regulation and control of product quality. The raw material pretreatment module accurately proportionally mixes the components to create uniform and stable initial conditions for the reaction; the multi-stage reaction module ensures that the hydrothermal reaction is fully carried out and the reaction process is controllable through the adjustable reaction path and residence time, so as to avoid overgrowth or incomplete reaction; the rapid cooling and crystallization module implements gradient cooling and pressure reduction on the reaction fluid at the appropriate time, on the one hand to terminate the grain growth in time, and on the other hand to recover waste heat and improve energy utilization efficiency; finally, the product collection module efficiently separates and purifies the nanoparticles, and recycles the by-products and water, forming a closed production loop. The modules are organically combined and supplemented with real-time feedback control, so that the key parameters in the whole process from raw material input to product harvesting of the barium titanate nanoparticles are strictly regulated and controlled, and the product quality is accurately controllable.

[0033] Example 2 The application provides a quality regulation and control method for nanometer composite barium titanate based on the above system, which comprises the following steps: The fourth high-pressure metering pump 9 increases the system pressure to the critical pressure value of the supercritical hydrothermal synthesis, the anti-agglomeration ligand or the doping modified dopant is stored in the ligand / dopant storage tank 4, the additive with mineralization or pH adjustment is stored in the additive storage tank 5, the dopant and the additive converge with each other, and are directly sent to the inlet one of the Laval mixer 12 through the first high-pressure metering pump 6 for pre-mixing; the titanium precursor in the titanium precursor storage tank 1 and the barium precursor in the barium precursor storage tank 2 converge in the jet collision mixer 10 through the second high-pressure metering pump 7 and the third high-pressure metering pump 8 respectively for precursor pre-mixing, the mixed cold fluid enters the inlet two of the Laval mixer 12 together, is mixed with the supercritical hot fluid preheated by the system and heated by the heater 11, and enters the inlet three of the Laval mixer 12, the Laval mixer 12 is connected with the pH detector 13 to ensure that the reaction environment is stable and maintains the required pH value, after the three-way material is fully mixed in the Laval mixer 12, the material enters the multi-stage reactor for hydrolysis and dehydration reaction, the reactors are connected with each other through the three-way ball valves, the reaction tube length can be set by adjusting the three-way ball valve V2, the three-way ball valve V3 and the three-way ball valve V4, so as to adjust the reaction time and control the particle size of the barium titanate nanoparticles, then gradient stable cooling and pressure reduction are realized through the water spray temperature reducer 18, the rapid cooling heat exchanger 19, the slow cooling heat exchanger 20 and the capillary pressure reducer 23, the barium precursor is preliminarily preheated by the heat recovery of the slow cooling heat exchanger 20 using the cooling water of the cooling water storage tank 21, while the dissolution of the barium precursor is accelerated, and the deionized water is preheated by the heat recovery of the rapid cooling heat exchanger 19, so that the heating process in the heater 11 is more gentle, and the energy consumption of the heater 11 is further reduced.

[0034] The solid phase and liquid phase products after gradient cooling and pressure reduction are separated by centrifugation of the three-stage centrifugal separator, the solid phase product is stripped of surface dirt by the impact force of the ultrasonic washing device 28, and then enters the vacuum dryer 29 for drying, and the dried material is sent to the nano barium titanate storage tank 30 for storage; the liquid phase product is separated from by-products and water molecules through the liquid phase product membrane separator 31, the by-products enter the by-product recovery device 32 for storage, and the water molecules enter the deionized water storage tank 3 for reaction.

[0035] By changing the ratio of ligands, dopants or additives in the ligand / dopant storage tank 4 and the additive storage tank 5 to the titanium precursor, the particle morphology and anti-agglomeration are controlled, the content of doped elements is adjusted, and the crystal form of the product is controlled; by changing the ratio of the precursors in the barium precursor storage tank 2 and the titanium precursor storage tank 1, the defect content of the reaction product is controlled, and the dielectric properties of the product are changed; by controlling the electric heating power and the pressure setting value to change the reaction temperature and the reaction pressure, the particle size and crystallinity of the product are adjusted; by controlling the valves to change the number and connection form of the reactors in the multi-stage reaction module, the reaction time is changed, and the particle size of the nano barium titanate particles is controlled; by the online feedback of the pH detector 13, the concentration and flow of the additives are adjusted in real time, and the reaction environment of different precursors is controlled.

[0036] In summary, the present application provides a system for supercritical hydrothermal synthesis of nano barium titanate and a quality control method, which has overall advantages such as continuous and efficient, precise and controllable, energy saving and environmental protection, and excellent product performance. From the structure to the process, the innovative design effectively overcomes the bottlenecks of traditional hydrothermal method such as uneven reaction, difficult particle size control, high energy consumption, poor batch stability of products, etc., significantly improving the quality and efficiency of nano material preparation. The technical scheme of the present application is particularly suitable for the preparation of high-performance barium titanate-based powder in the field of electronic ceramics, such as continuous production of MLCC dielectric powder, PTC thermosensitive ceramic materials, etc., meeting the urgent needs of the industry for consistency and scale of nano powder. At the same time, the design concept and architecture of the system are universal, which can be applied to other nano material synthesis processes that require precise control of particle size and morphology, providing a new idea for the application of supercritical fluid technology in functional material industry, and having significant application prospect and industrial promotion significance.

[0037] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, but not to limit it, although the present application has been described in detail with reference to the above examples, those skilled in the art should understand that: the specific embodiments of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the present application, any modification or equivalent replacement within the scope of the claims of the present application should be covered.

Claims

1. A system for supercritical hydrothermal synthesis of nano-barium titanate, characterized in that, The raw material pretreatment module comprises a titanium precursor storage tank (1), a barium precursor storage tank (2), a deionized water storage tank (3), a ligand / dopant storage tank (4), an additive storage tank (5) and a cooling water storage tank (21), the outlet of the cooling water storage tank (21) is connected with the rapid cooling crystallization module through the fifth high-pressure metering pump (22), the heat is reused to the barium precursor storage tank (2), the outlet of the ligand / dopant storage tank (4) and the outlet of the additive storage tank (5) converge with each other, and are connected with the inlet one of the raffinate mixer (12) through the first high-pressure metering pump (6), the outlet pipelines of the titanium precursor storage tank (1) and the barium precursor storage tank (2) are respectively provided with the second high-pressure metering pump (7) and the third high-pressure metering pump (8), and are connected with the inlet of the jet collision mixer (10), the outlet of the jet collision mixer (10) is connected with the inlet two of the raffinate mixer (12), the outlet pipeline of the deionized water storage tank (3) is provided with the fourth high-pressure metering pump (9), and is connected with the inlet of the heater (11) after the action of the rapid cooling crystallization module; the outlet of the heater (11) is connected with the inlet three of the raffinate mixer (12), and three-way convergence mixing is formed, the raffinate mixer (12) is connected with the pH detector (13), and the outlet of the raffinate mixer (12) is connected with the multi-section reaction module. The multi-section reaction module comprises a plurality of reactors connected in sequence, and a three-way ball valve is arranged at the outlet of each reactor and connected with the rapid cooling crystallization module through the three-way ball valve. The rapid cooling crystallization module is used for gradient cooling and pressure reduction of the material reacted in the reactor, so as to generate solid-phase and liquid-phase products, and the outlet of the rapid cooling crystallization module is connected with the product collection module. The product collection module is used for processing the solid-phase and liquid-phase products.

2. The system for supercritical hydrothermal synthesis of nano-barium titanate according to claim 1, characterized in that, The multi-section reaction module comprises a first reactor (14), a second reactor (15), a third reactor (16) and a fourth reactor (17) connected in sequence.

3. The system for supercritical hydrothermal synthesis of nano-barium titanate according to claim 1, characterized in that, The rapid cooling crystallization module comprises a water spray cooler (18), a rapid cooling heat exchanger (19), a slow cooling heat exchanger (20) and a capillary pressure reducer (23) connected in sequence, the outlet of the rapid cooling heat exchanger (19) is divided into two paths, one path is connected with the inlet of the heater (11), and the other path is connected with the inlet of the slow cooling heat exchanger (20), the outlet of the slow cooling heat exchanger (20) is divided into two paths, one path is connected with the inlet of the capillary pressure reducer (23), and the other path is connected with the inlet of the barium precursor storage tank (2); and the outlet of the capillary pressure reducer (23) is connected with the product collection module.

4. The system for supercritical hydrothermal synthesis of nano-barium titanate according to claim 1, characterized in that, The product collection module comprises a first centrifugal separator (24), a second centrifugal separator (26) and a third centrifugal separator (27) connected in sequence, the outlet of the third centrifugal separator (27) is divided into two paths, one path is used for processing the solid-phase product, and the other path is used for processing the liquid-phase product.

5. The system for supercritical hydrothermal synthesis of nano-barium titanate according to claim 4, characterized in that, The solid-phase product processing comprises a ultrasonic washer (28), a vacuum dryer (29) and a nano barium titanate storage tank (30) connected in sequence.

6. The system for supercritical hydrothermal synthesis of nano-barium titanate according to claim 4, characterized in that, The liquid product treatment includes a liquid product membrane separator (31) connected in sequence, an outlet of the liquid product membrane separator (31) connected to a by-product recovery device (32) in one way and to a deionized water storage tank (3) in another way.

7. The system for supercritical hydrothermal synthesis of nano-barium titanate according to claim 6, characterized in that, The liquid product membrane separator (31) adopts a reverse osmosis membrane or a nanofiltration membrane.

8. The system for supercritical hydrothermal synthesis of nano-barium titanate according to claim 1, characterized in that, The heater (11) adopts an electromagnetic induction heater, an infrared heater, a resistance wire heater or a natural gas heater.

9. The method according to any one of claims 1 to 8, wherein the method is a method for quality control of the synthesis of nano-barium titanate by supercritical hydrothermal synthesis. It comprises: The fourth high-pressure metering pump (9) increases the system pressure to the critical pressure value of the supercritical hydrothermal synthesis, the anti-agglomerated ligand or the doped modified dopant is stored in the ligand / dopant storage tank (4), the additive with mineralization or pH adjustment is stored in the additive storage tank (5), and is directly sent to the inlet of the Laval mixer (12) for pre-mixing through the first high-pressure metering pump (6), the titanium precursor in the titanium precursor storage tank (1) and the barium precursor in the barium precursor storage tank (2) are respectively converged in the jet collision mixer (10) for precursor pre-mixing through the second high-pressure metering pump (7) and the third high-pressure metering pump (8), the mixed cold fluid enters the Laval mixer together, is mixed with the supercritical hot fluid preheated by the system and heated by the heater (11), the Laval mixer (12) is connected to the pH detector (13) to ensure that the reaction environment is stable and maintains the required pH value, after the three-way material is fully mixed in the Laval mixer (12), it enters the reactor for hydrolysis and dehydration reaction, and then realizes gradient stable cooling and pressure reduction through the water spray cooler (18), the quenching heat exchanger (19), the slow cooling heat exchanger (20) and the capillary tube pressure reducer (23), and the solid phase and the liquid phase product after the gradient cooling and pressure reduction are separated under the centrifugal action of the three-stage centrifugal separator, the solid phase product is stripped of the dirt on the surface of the material by the impact force of the ultrasonic washing device (28), and then enters the vacuum dryer (29) for drying, and the dried material is sent to the nano barium titanate storage tank (30) for storage. The liquid product is separated from by-products and water molecules through the liquid product membrane separator (31), the by-products enter the by-product recovery device (32) for storage, and the water molecules enter the deionized water storage tank (3) for reaction. 10.The quality control method of synthesizing nano-barium titanate by supercritical hydrothermal synthesis according to claim 9, characterized in that, By changing the ratio of the ligand / dopant in the ligand / dopant storage tank (4) and the additive in the additive storage tank (5) to the titanium precursor, the particle morphology and anti-agglomeration, the content of the doped element, and the crystal form of the product are controlled; by changing the ratio of the precursor in the barium precursor storage tank (2) to the titanium precursor in the titanium precursor storage tank (1), the defect content of the reaction product is controlled, and the dielectric properties of the product are changed; by controlling the electric heating power and the pressure setting value, the reaction temperature and the reaction pressure are changed, and the particle size and the crystallinity of the product are adjusted; by controlling the three-way valve, the number and connection form of the reactors in the multi-stage reaction module are changed, and then the reaction time is changed, and the particle size of the nano barium titanate particles is controlled; by the online feedback of the pH detector (13), the concentration and flow of the additive are adjusted in real time, and the reaction environment of different precursors is controlled.

Images