System and method for supercritical hydro-thermal synthesis of superfine nano barium titanate powder

Abstract

The invention discloses a system and a method for supercritical hydro-thermal synthesis of superfine nano barium titanate powder, and belongs to the technical field of supercritical hydro-thermal synthesis equipment. Barium / titanium precursors are evenly mixed under the supercritical condition through the structural synergistic effect of the multi-stage mixers, specifically, a first outlet of the material blending unit and a second outlet of the material blending unit are both connected with the first-stage mixer, so that the barium precursors and the titanium precursors can be preliminarily premixed firstly, and uneven initial distribution is reduced; the first-stage mixer is connected to a first inlet of the second-stage mixer, the pre-mixed precursor is conveyed to the second-stage mixer, meanwhile, the multi-stage cooling unit is connected with the second-stage mixer through the heater, the heated supercritical water enters and is mixed with the pre-mixed precursor for the second time, dispersion of the precursor is promoted through the characteristics of the supercritical water, and local over-concentration is avoided; and finally, the outlet of the second-stage mixer is connected with a supercritical hydrothermal reactor, and precursors subjected to two-stage mixing can react quickly, so that impure phases are reduced, and the purity of a product is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of supercritical hydrothermal synthesis equipment, in particular to a system and method for supercritical hydrothermal synthesis of superfine nanometer barium titanate powder. BACKGROUND

[0002] Nanomaterials have shown great application potential in many fields such as electronics, energy, catalysis, and biomedicine due to their unique quantum size effect, surface effect, and macroscopic quantum tunneling effect, and have become one of the core driving forces for promoting industrial upgrading. However, there are many bottlenecks in the current traditional nanometer powder preparation methods. The physical method for preparing nanometer powder, such as mechanical ball milling and vapor deposition, can avoid chemical pollution, but the equipment structure is complex, the energy consumption is high, and it is difficult to prepare nanometer powder with uniform particle size. At the same time, the high cost seriously restricts its application in large-scale production. The chemical method for preparing nanometer powder, such as sol-gel and chemical precipitation, can control the particle morphology to a certain extent, but organic solvents or toxic additives are needed in the preparation process, which will result in high concentration of organic matter and heavy metal ions in the generated wastewater, and the subsequent wastewater treatment cost is very high. Moreover, most chemical methods also need subsequent high-temperature calcination or centrifugal purification treatment, which is easy to introduce impurities and cause particle agglomeration, thereby affecting the quality of nanometer powder.

[0003] Supercritical hydrothermal synthesis technology, as a green synthesis method using supercritical water as a reaction medium, brings new hope to solve the above problems. The core principle is to quickly promote the hydrolysis, nucleation and crystallization of metal salt precursors by taking advantage of the unique physical and chemical properties of supercritical water, thereby efficiently preparing nanomaterials. However, during the popularization and application of supercritical hydrothermal synthesis technology, researchers found that this technology has some defects: under supercritical conditions, barium / titanium precursors are prone to uneven mixing, which leads to local over-reaction to form impurities, resulting in a decrease in product purity.

[0004] Therefore, how to realize the uniform mixing of barium / titanium precursors under supercritical conditions and improve the product purity has become a technical problem that needs to be solved by the technical personnel in the field. SUMMARY

[0005] The purpose of the present application is to provide a system and method for supercritical hydrothermal synthesis of superfine nanometer barium titanate powder to overcome the problem of uneven mixing of barium / titanium precursors under supercritical conditions in the prior art, which leads to local over-reaction to form impurities and a decrease in product purity.

[0006] The present application solves the above technical problems by the following technical solutions: The system for synthesizing superfine nano barium titanate powder by supercritical hydrothermal method comprises a material preparation unit, a supercritical reaction unit, a multi-stage cooling unit, a product post-processing unit and a by-product recovery unit, wherein the supercritical reaction unit comprises a first mixer, a heater, a second mixer and a supercritical hydrothermal reactor. The first outlet of the material preparation unit and the second outlet of the material preparation unit are connected to the first inlet of the second mixer through the first mixer, the outlet of the second mixer is connected to the first inlet of the multi-stage cooling unit through the supercritical hydrothermal reactor, the first outlet of the multi-stage cooling unit is connected to the second inlet of the second mixer through the heater, the second outlet of the multi-stage cooling unit is connected to the second inlet of the multi-stage cooling unit through the first inlet of the material preparation unit, the third outlet of the multi-stage cooling unit is connected to the inlet of the by-product recovery unit through the product post-processing unit, and the outlet of the by-product recovery unit is connected to the second inlet of the material preparation unit.

[0007] The material preparation unit comprises a titanium precursor storage tank, a barium precursor storage tank, a pure water storage tank, a first high-pressure delivery pump, a second high-pressure delivery pump and a third high-pressure delivery pump. The outlet of the titanium precursor storage tank is connected to the inlet of the first high-pressure delivery pump, the first outlet of the barium precursor storage tank is connected to the inlet of the second high-pressure delivery pump, the outlet of the first high-pressure delivery pump and the outlet of the second high-pressure delivery pump are connected to the first inlet of the second mixer through the first mixer, the second outlet of the multi-stage cooling unit is connected to the second inlet of the multi-stage cooling unit through the barium precursor storage tank, and the outlet of the by-product recovery unit is connected to the heater through the pure water storage tank, the third high-pressure delivery pump, the third inlet of the multi-stage cooling unit and the first outlet of the multi-stage cooling unit in sequence.

[0008] The multi-stage cooling unit comprises a water spray cooler, a quencher, a slow cooler, a pressure reducer, a cooling water storage tank and a fourth high-pressure delivery pump. The supercritical hydrothermal reactor is connected to the first inlet of the quencher through the water spray cooler, the third high-pressure delivery pump is connected to the second inlet of the quencher, the first outlet of the quencher is connected to the first inlet of the slow cooler, the second outlet of the quencher is connected to the heater, the first outlet of the slow cooler is connected to the product post-processing unit through the pressure reducer, and the second outlet of the slow cooler is connected to the second inlet of the slow cooler through the barium precursor storage tank, the cooling water storage tank and the fourth high-pressure delivery pump in sequence.

[0009] The quencher is one of a jacketed heat exchanger, a coil heat exchanger and a spiral fin tube heat exchanger, and the pressure reducer adopts a capillary tube.

[0010] The product post-processing unit comprises a first-stage centrifugal device, a second-stage centrifugal device, a third-stage centrifugal device, an ultrasonic washing device, a vacuum drying device and a nano barium titanate product storage tank. The outlet of the pressure reducer is sequentially connected to the inlet of the second-stage centrifugal device through the first-stage centrifugal device and the third-stage centrifugal device, and the solid-phase product outlet of the third-stage centrifugal device is sequentially connected to the inlet of the nano barium titanate product storage tank through the ultrasonic washing device and the vacuum drying device.

[0011] The product post-processing unit further comprises a standby centrifugal device, a first valve, a second valve and a third valve. The outlet of the pressure reducer is divided into two paths, the first path is sequentially connected to the inlet of the second-stage centrifugal device through the first valve and the first-stage centrifugal device, and the second path is sequentially connected to the inlet of the second-stage centrifugal device through the second valve, the standby centrifugal device and the third valve.

[0012] The product post-processing unit further comprises a standby centrifugal device, a first valve, a second valve and a third valve.

[0013] The membrane separation device adopts one of a reverse osmosis membrane and a nanofiltration membrane.

[0014] The first-stage mixer is one of a jet collision mixer and a Laval mixer, the second-stage mixer is one of a jet collision mixer and a Laval mixer, and the heater is one of an electromagnetic induction heater, an infrared heater, an electric resistance heater and a natural gas heater.

[0015] The application further provides a preparation method of the supercritical hydrothermal synthesis of superfine nano barium titanate powder. The temperature of the barium precursor is raised by the multi-stage temperature lowering unit, the titanium precursor and the barium precursor are transported to the first-stage mixer through the material distribution unit to obtain the pre-mixed reaction precursor, and the reaction precursor is transported to the second-stage mixer; the pure water is transported to the multi-stage temperature lowering unit through the material distribution unit to be preheated to obtain the preheated pure water, the preheated pure water is transported to the heater to be heated to obtain the supercritical pure water, and the supercritical pure water is transported to the second-stage mixer. Mixing the reaction precursors and the supercritical state pure water in a secondary mixer to obtain fluid and the reaction precursors after temperature rising, and sending the reaction precursors after temperature rising into a supercritical hydrothermal reactor to synthesize superfine nano barium titanate powder; Cooling the fluid through the multi-stage cooling unit to obtain normal pressure fluid; separating the normal pressure fluid into solid phase product and liquid phase product; storing the solid phase product through the product post-processing unit and recycling the liquid phase product through the by-product recycling unit.

[0016] Compared with the prior art, the positive progress effect of the present application is that: The system for supercritical hydrothermal synthesis of superfine nano barium titanate powder provided by the present application realizes uniform mixing of barium / titanium precursors under supercritical conditions through the synergistic effect of the structure of the multi-stage mixer. Specifically, the first outlet of the material preparation unit and the second outlet of the material preparation unit are both connected to a primary mixer, so that the barium precursor and the titanium precursor can be preliminarily mixed, the physical separation of the two precursors in the initial state is broken, and the local concentration difference caused by uneven distribution of the initial materials is reduced; the primary mixer is connected to the first inlet of a secondary mixer, so that the premixed precursors are sent to the secondary mixer; at the same time, the multi-stage cooling unit is connected to the secondary mixer through a heater, so that the heated supercritical water enters the secondary mixing with the premixed precursors; the characteristics of the supercritical water promote the dispersion of the precursors and avoid local over-concentration; finally, the outlet of the secondary mixer is connected to a supercritical hydrothermal reactor, so that the precursors mixed by two stages can quickly react and reduce impurities, thereby improving the purity of the product.

[0017] Further, the multi-stage cooling system composed of a water spray cooler, a quenching heat exchanger and a slow cooling pressure reducer can quickly reduce the high-temperature reaction product to an appropriate temperature, avoid particle agglomeration caused by slow cooling, and ensure product quality.

[0018] Further, by providing a standby centrifugal device, a first valve, a second valve and a third valve, two parallel material processing paths are formed at the outlet of the pressure reducer. When the primary centrifugal device fails or needs maintenance, the first valve can be closed and the second valve and the third valve can be opened, so that the material enters the secondary centrifugal device through the standby centrifugal device, which can effectively avoid production interruption caused by failure of a single centrifugal device, thereby improving production efficiency and equipment utilization. BRIEF DESCRIPTION OF DRAWINGS

[0019] The accompanying drawings are included to provide a further understanding of the present application, and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions serve to explain the present application, and do not constitute an improper limitation on the present application.

[0020] Figure 1 The system for supercritical hydrothermal synthesis of superfine nano barium titanate powder is connected to a schematic diagram. 1 - titanium precursor storage tank; 2 - barium precursor storage tank; 3 - pure water storage tank; 4 - first high-pressure delivery pump; 5 - second high-pressure delivery pump; 6 - third high-pressure delivery pump; 7 - first mixer; 8 - heater; 9 - second mixer; 10 - reactor; 11 - water spray desuperheater; 12 - quencher; 13 - slow cooler; 14 - cooling water storage tank; 15 - fourth high-pressure delivery pump; 16 - pressure reducer; 17 - first centrifugal device; 18 - backup centrifugal device; 19 - second centrifugal device; 20 - third centrifugal device; 21 - ultrasonic washing device; 22 - vacuum drying device; 23 - nano barium titanate product storage tank; 24 - membrane separation device; 25 - by-product recovery storage tank; V1 - first valve; V2 - second valve; V3 - third valve. DETAILED DESCRIPTION

[0021] In order to make the objects, technical solutions, and advantages of the embodiments of the present application clearer, the following will be combined with the accompanying drawings for the embodiments of the present application to make a clear and complete description of the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the accompanying drawings can be arranged and designed in various different configurations.

[0022] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. All other embodiments obtained by a person of ordinary skill in the art without creative labor based on the embodiments in the present application are within the scope of protection of the present application.

[0023] It should be noted that: similar reference numerals and letters represent similar items in the following drawings, therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0024] In the description of the embodiments of the present application, it should be noted that, if the orientation or position relationship indicated by the terms "upper", "lower", "horizontal", "inner", and the like is based on the orientation or position relationship shown in the drawings, or is the orientation or position relationship when the product of the present application is usually placed, which is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the indicated device or element must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second", and the like are only used for differentiation in description, and cannot be understood as indicating or implying relative importance.

[0025] In addition, it needs to be explained that, unless otherwise explicitly specified and limited, if the terms "arrange", "install", "connect", "connect" appear, they should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected, it can be mechanically connected, or it can be electrically connected, it can be directly connected, or it can be indirectly connected through an intermediate medium, it can be the communication inside two elements. For ordinary skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0026] The present application will be further described in detail below in combination with the drawings and specific embodiments, which are an explanation of the present application rather than a limitation.

[0027] A system for supercritical hydrothermal synthesis of superfine nanometer barium titanate powder comprises a material preparation unit, a supercritical reaction unit, a multi-stage cooling unit, a product post-processing unit and a by-product recovery unit, wherein the supercritical reaction unit comprises a first-stage mixer 7, a heater 8, a second-stage mixer 9 and a supercritical hydrothermal reactor 10. The first outlet of the material preparation unit and the second outlet of the material preparation unit are both connected to the first inlet of the second-stage mixer 9 through the first-stage mixer 7, the outlet of the second-stage mixer 9 is connected to the first inlet of the multi-stage cooling unit through the supercritical hydrothermal reactor 10, the first outlet of the multi-stage cooling unit is connected to the second inlet of the second-stage mixer 9 through the heater 8, the second outlet of the multi-stage cooling unit is connected to the second inlet of the multi-stage cooling unit through the first inlet of the material preparation unit, the third outlet of the multi-stage cooling unit is connected to the inlet of the by-product recovery unit through the product post-processing unit, and the outlet of the by-product recovery unit is connected to the second inlet of the material preparation unit.

[0028] The system for supercritical hydrothermal synthesis of superfine nanometer barium titanate powder provided by the present application realizes uniform mixing of barium / titanium precursors under supercritical conditions through the synergistic effect of the structure of the multi-stage mixer. Specifically, the first outlet of the material preparation unit and the second outlet of the material preparation unit are both connected to the first-stage mixer, so that the barium precursor and the titanium precursor can be preliminarily premixed, the physical separation of the two precursors in the initial state is broken, and the local concentration difference caused by uneven distribution of the initial materials is reduced; the first-stage mixer is connected to the first inlet of the second-stage mixer, the premixed precursors are sent to the second-stage mixer, and at the same time, the multi-stage cooling unit is connected to the second-stage mixer through the heater, so that the heated supercritical water enters the second-stage mixer for secondary mixing with the premixed precursors, the characteristics of the supercritical water promote the dispersion of the precursors and avoid local over-concentration; finally, the outlet of the second-stage mixer is connected to the supercritical hydrothermal reactor, the precursors after two-stage mixing can quickly react and reduce impurities, thereby improving the purity of the product.

[0029] Specifically, the material preparation unit comprises a titanium precursor storage tank 1, a barium precursor storage tank 2, a pure water storage tank 3, a first high-pressure delivery pump 4, a second high-pressure delivery pump 5 and a third high-pressure delivery pump 6. The outlet of the titanium precursor storage tank 1 is connected to the inlet of the first high-pressure delivery pump 4, the first outlet of the barium precursor storage tank 2 is connected to the inlet of the second high-pressure delivery pump 5, and the outlets of the first high-pressure delivery pump 4 and the second high-pressure delivery pump 5 are both connected to the first inlet of the secondary mixer 9 through a primary mixer 7; the second outlet of the multi-stage cooling unit is connected to the second inlet of the multi-stage cooling unit through the barium precursor storage tank 2; and the outlet of the by-product recovery unit is connected to the heater 8 in sequence through the pure water storage tank 3, the third high-pressure delivery pump 6, the third inlet of the multi-stage cooling unit, the first outlet of the multi-stage cooling unit.

[0030] Specifically, the multi-stage cooling unit comprises a water spray cooler 11, a quenching device 12, a slow cooling device 13, a pressure reducer 16, a cooling water storage tank 14 and a fourth high-pressure delivery pump 15. The supercritical hydrothermal reactor 10 is connected to the first inlet of the quenching device 12 through the water spray cooler 11, the third high-pressure delivery pump 6 is connected to the second inlet of the quenching device 12, the first outlet of the quenching device 12 is connected to the first inlet of the slow cooling device 13, the second outlet of the quenching device 12 is connected to the heater 8, the first outlet of the slow cooling device 13 is connected to the product post-processing unit through the pressure reducer 16, and the second outlet of the slow cooling device 13 is connected to the second inlet of the slow cooling device 13 in sequence through the barium precursor storage tank 2, the cooling water storage tank 14 and the fourth high-pressure delivery pump 15.

[0031] The multi-stage cooling system composed of the water spray cooler, the quenching heat exchanger and the slow cooling pressure reducer can quickly reduce the high-temperature reaction product to an appropriate temperature, avoid particle agglomeration caused by slow cooling and ensure product quality.

[0032] Specifically, the quenching device 12 is one of a jacketed heat exchanger, a coil heat exchanger and a spiral fin tube heat exchanger; and the pressure reducer 16 adopts a capillary tube.

[0033] Specifically, the product post-processing unit comprises a first centrifugal device 17, a second centrifugal device 19, a third centrifugal device 20, an ultrasonic washing device 21, a vacuum drying device 22 and a nano barium titanate product storage tank 23. The outlet of the pressure reducer 16 is connected to the inlet of the third centrifugal device 20 in sequence through the first centrifugal device 17 and the second centrifugal device 19, the solid-phase product outlet of the third centrifugal device 20 is connected to the inlet of the nano barium titanate product storage tank 23 in sequence through the ultrasonic washing device 21 and the vacuum drying device 22, and the liquid-phase product outlet of the third centrifugal device 20 is connected to the inlet of the by-product recovery unit.

[0034] The three-stage centrifugal connection combined with the ultrasonic washing technology can achieve high solid-liquid separation efficiency.

[0035] Specifically, the product post-treatment unit further comprises a standby centrifugal device 18, a first valve V1, a second valve V2 and a third valve V3. The outlet of the pressure reducer 16 is divided into two paths, the first path is connected to the inlet of the secondary centrifugal device 19 in sequence through the first valve V1, the primary centrifugal device 17, and the second path is connected to the inlet of the secondary centrifugal device 19 in sequence through the second valve V2, the standby centrifugal device 18, the third valve V3.

[0036] By arranging the standby centrifugal device, the first valve V1, the second valve V2 and the third valve V3, two parallel material processing paths are formed at the outlet of the pressure reducer. When the primary centrifugal device fails or needs to be maintained, the first valve V1 can be closed, and the second valve V2 and the third valve V3 can be opened, so that the material enters the secondary centrifugal device through the standby centrifugal device, which can effectively avoid the production interruption caused by the failure of a single centrifugal device, thereby improving the production efficiency and equipment utilization.

[0037] Specifically, the by-product recovery unit comprises a membrane separation device 24 and a by-product recovery tank 25; the liquid phase product outlet of the tertiary centrifugal device 20 is connected to the inlet of the membrane separation device 24, the first outlet of the membrane separation device 24 is connected to the by-product recovery tank 25, and the second outlet of the membrane separation device 24 is connected to the inlet of the pure water tank 3.

[0038] The pure water is recycled through the membrane separation device, and the high-value-added by-products are sold or resourcefully utilized, so as to realize zero discharge of waste liquid.

[0039] Specifically, the membrane separation device 24 adopts one of a reverse osmosis membrane and a nanofiltration membrane.

[0040] Specifically, the primary mixer 7 is one of a jet collision mixer and a Laval mixer; the secondary mixer 9 is one of a jet collision mixer and a Laval mixer; and the heater 8 is one of an electromagnetic induction heater 8, an infrared heater 8, an electric resistance heater 8 and a natural gas heater 8.

[0041] Based on the same inventive concept, the application further provides a preparation method of supercritical hydrothermal synthesis of superfine nano barium titanate powder, which adopts the system for supercritical hydrothermal synthesis of superfine nano barium titanate powder as described above, and comprises the following steps: The temperature of the barium precursor is raised by the multi-stage cooling unit, the titanium precursor and the barium precursor are transported to a first mixer 7 by the material deployment unit to obtain a pre-mixed reaction precursor, and the reaction precursor is transported to a second mixer 9; pure water is transported to the multi-stage cooling unit by the material deployment unit for preheating to obtain preheated pure water, the preheated pure water is transported to a heater 8 for heating to obtain supercritical pure water, and the supercritical pure water is transported to the second mixer 9; The reaction precursor and the supercritical pure water are mixed in the second mixer 9 to obtain a fluid and a heated reaction precursor, and the heated reaction precursor is fed into a supercritical hydrothermal reactor 10 to synthesize superfine nano barium titanate powder; The fluid is cooled by the multi-stage cooling unit to obtain an atmospheric fluid; the atmospheric fluid is subjected to solid-phase and liquid-phase separation to obtain a solid-phase product and a liquid-phase product; the solid-phase product is stored by a product post-processing unit, and the liquid-phase product is recovered by a by-product recovery unit.

[0042] Example One Referring to Figure 1 A system for supercritical hydrothermal synthesis of superfine nano barium titanate powder includes a material deployment unit, an outlet of the material deployment unit being connected to a supercritical reaction unit; the supercritical reaction unit, a reaction fluid outlet of the supercritical reaction unit being connected to a multi-stage cooling unit; the multi-stage cooling unit, outlets of the multi-stage cooling unit being connected to the material deployment unit and a product post-processing unit respectively; the product post-processing unit, a liquid-phase product outlet of the product post-processing unit being connected to a by-product recovery unit; the by-product recovery unit, a pure water outlet of the by-product recovery unit being connected to the material deployment unit.

[0043] The material deployment unit includes a titanium precursor storage tank 1, a barium precursor storage tank 2 and a pure water storage tank 3; an outlet of the titanium precursor storage tank 1 is connected to an inlet of a first high-pressure delivery pump 4, an outlet of the first high-pressure delivery pump 4 is connected to the supercritical reaction unit; an inlet of the barium precursor storage tank 2 is connected to the multi-stage cooling unit, an outlet is connected to an inlet of a second high-pressure delivery pump 5, an outlet of the second high-pressure delivery pump 5 is connected to the supercritical reaction unit; an inlet of the pure water storage tank 3 is connected to the by-product recovery unit, an outlet is connected to an inlet of a third high-pressure delivery pump 6, an outlet of the third high-pressure delivery pump 6 is connected to the multi-stage cooling unit; The supercritical reaction unit includes a first mixer 7, a heater 8, a second mixer 9 and a supercritical hydrothermal reactor 10; an inlet of the first mixer 7 is connected to an outlet of the titanium precursor first high-pressure delivery pump 4 and an outlet of the barium precursor second high-pressure delivery pump 5 respectively, an outlet is connected to the second mixer 9; an inlet of the heater 8 is connected to the multi-stage cooling unit, an outlet is connected to the second mixer 9; an outlet of the second mixer 9 is connected to an inlet of the supercritical hydrothermal reactor 10; an outlet of the supercritical hydrothermal reactor 10 is connected to the multi-stage cooling unit; The multi-stage cooling unit comprises a water spray desuperheater 11, a quencher 12, a slow cooler 13, a pressure reducer 16, a cooling water storage tank 14 and a fourth high-pressure delivery pump 15; the reaction fluid inlet of the water spray desuperheater 11 is connected with the reaction fluid outlet of the supercritical water thermal reactor 10, and the reaction fluid outlet is connected with the inlet of the water spray desuperheater 11; the outlet of the water spray desuperheater 11 is connected with the reaction fluid inlet of the quencher 12; the cold fluid inlet of the quencher 12 is connected with the outlet of the pure water third high-pressure delivery pump 6, the hot fluid outlet is connected with the inlet of the heater 8, and the reaction fluid outlet is connected with the reaction fluid inlet of the slow cooler 13; the inlet of the cooling water storage tank 14 is connected with the outlet of the barium precursor storage tank 2, the outlet is connected with the inlet of the fourth high-pressure delivery pump 15, and the outlet of the fourth high-pressure delivery pump 15 is connected with the cold fluid inlet of the slow cooler 13; the hot fluid outlet of the slow cooler 13 is connected with the barium precursor storage tank 2, and the reaction fluid outlet is connected with the inlet of the pressure reducer 16; the outlet of the pressure reducer 16 is connected with the product post-processing unit; The product post-processing unit comprises a first centrifuge 17, a standby centrifuge 18, a second centrifuge 19, a third centrifuge 20, an ultrasonic washing device 21, a vacuum drying device 22 and a nano barium titanate product storage tank 23, and each step of the unit adopts manual transfer. The inlet of the first centrifuge 17 is connected with the outlet of the pressure reducer 16 and the outlet of the standby centrifuge 18 respectively, and the outlet is connected with the inlet of the standby centrifuge 18 and the inlet of the second centrifuge 19 respectively; the outlet of the second centrifuge 19 is connected with the inlet of the third centrifuge 20; the solid-phase product outlet of the third centrifuge 20 is connected with the inlet of the ultrasonic washing device 21, and the liquid-phase product outlet is connected with the by-product recovery unit. The outlet of the ultrasonic washing device 21 is connected with the inlet of the vacuum drying device 22; the outlet of the vacuum drying device 22 is connected with the inlet of the nano barium titanate product storage tank 23; The by-product recovery unit comprises a membrane separation device 24 and a by-product recovery storage tank 25. The inlet of the membrane separation device 24 is connected with the liquid-phase product outlet of the third centrifuge, and the outlet is connected with the inlet of the by-product recovery storage tank 25 and the outlet of the pure water storage tank 3 respectively; The mixer adopts a jet collision mixer or a Laval mixer, and the mixing type is divided into pre-mixing of barium precursors and titanium precursors, and pre-mixing of barium-titanium precursors and supercritical water; the heater 8 adopts an electromagnetic induction heater, an infrared heater, a resistance heater or a natural gas heater.

[0044] The quencher 12 and the slow cooler 13 adopt a jacketed heat exchanger, a coil heat exchanger or a spiral fin tube heat exchanger; the pressure reducer 16 adopts a capillary tube; and the membrane separation device 24 adopts a reverse osmosis membrane or a nanofiltration membrane.

[0045] The supercritical hydrothermal reactor 10 is provided with multiple groups of parallel reactors, and high-temperature and high-pressure stop valves are arranged between the supercritical hydrothermal reactors 10 and between the supercritical hydrothermal reactors 10 and the water spray desuperheater 11, so as to control the reaction time of the reaction fluid.

[0046] Through the multiple groups of parallel reactors and the high-temperature and high-pressure stop valves, the reaction residence time is accurately controlled to adapt to different particle size requirements; and the standby centrifugal design ensures continuous production without interruption.

[0047] Embodiment two A preparation method of supercritical hydrothermal synthesis of superfine barium titanate powder, comprising the following steps: Material preparation, preheating and mixing: the titanium precursor and the barium precursor are respectively conveyed from the titanium precursor storage tank 1 and the barium precursor storage tank 2 to the first mixer 7 by the first high-pressure conveying pump 4 and the second high-pressure conveying pump 5 for pre-mixing of the reaction precursors; the barium precursor needs a long dissolution time, and the temperature in the barium precursor storage tank 2 is raised by the circulation of cooling water in the cooling water device 14 using the waste heat of the slow cooling device 13; the pure water is conveyed from the pure water storage tank 3 to the quenching device 12 by the third high-pressure conveying pump 6 for preheating, and then heated to a supercritical state by the heater 8 and then mixed in the second mixer 9 and rapidly heated; the mixed hot fluid enters the supercritical hydrothermal reactor 10 for supercritical hydrothermal reaction to generate nano barium titanate powder, and the residence time of the hot fluid can be adjusted by controlling the stop valve of the supercritical hydrothermal reactor module to control the duration of the reaction.

[0048] Reaction fluid cooling and pressure reduction: the reaction fluid enters the water spray desuperheater 11 for preliminary cooling and leaves the supercritical state; then enters the quenching device 12 for secondary cooling, terminates the reaction by rapid cooling, and avoids further growth and agglomeration of the product; then enters the slow cooling device 13 for tertiary cooling to ensure that the fluid temperature is reduced to a safe pressure relief temperature range; and the completely cooled reaction fluid enters the pressure reducer 16 to reduce the pressure from supercritical pressure to normal pressure.

[0049] Reaction fluid separation: the reaction product at normal temperature and pressure is completely separated into solid and liquid products by three-stage centrifugation, 70-80% of the solid product is separated by the first centrifuge 17, 10-20% of the solid product is separated by the second centrifuge 19, and 1-10% of the solid product is separated by the third centrifuge 20, a standby centrifuge 18 is arranged at the first centrifuge 17 to realize seamless switching of continuous separation; the solid product is prepared into nano barium titanate powder by ultrasonic washing 21 and vacuum drying 22, and stored in the nano barium titanate powder storage tank 23; the liquid product is separated by the membrane separation device 24, the pure water is recycled to the pure water storage tank 3 for recycling, and the separated high-value byproduct 25 is sold to realize liquid zero emission.

[0050] In summary, the present application provides a high-efficiency, energy-saving, and environmentally friendly method and system for supercritical hydrothermal synthesis of superfine nano-barium titanate powder. By integrating material preparation, supercritical reaction, multi-stage cooling, product post-processing, and byproduct recovery units, a complete continuous production system for superfine nano-barium titanate powder is established. The core of the system lies in: 1. Multi-stage mixing and precise temperature control: the first mixer realizes the premixing of barium / titanium precursors, and the second mixer combines with supercritical water rapid heating to ensure reaction uniformity; 2. Energy recycling: the preheating of pure water in the quencher and the use of waste heat from the quencher for barium precursor dissolution significantly reduce external energy input; 3. Rapid cooling to terminate the reaction: the synergistic effect of the water spray cooler and the quencher avoids secondary growth of the product, ensuring the morphology of nano-sized particles; 4. Modular design: parallel reactors and standby centrifuges are configured to improve system fault tolerance and production continuity, suitable for industrialization. The method not only improves the market competitiveness of barium titanate powder, but also provides a technical reference for the green synthesis of other nanomaterials, with industrial application value and social and economic benefits.

[0051] Finally, it should be noted that the above examples are only one or more specific manifestations of the technical solutions of the present application. Their purpose is to clearly explain the concept, principle and application mode of the present application through specific examples, and are not intended to limit the scope of protection of the present application to these specific examples. In fact, the true value of the present application lies in its proposed technical ideas and innovations, not its forms or means of implementation.

[0052] For ordinary skilled persons in the art, after thoroughly reading and understanding the technical solutions of the present application, they have the ability to make various forms of changes, modifications or equivalent replacements to the specific embodiments of the invention based on their own professional knowledge and skills. These changes may include but are not limited to adjusting the value range of technical parameters, optimizing the algorithm process to improve efficiency, replacing part of the technical components to achieve better compatibility or reduce costs, etc. As long as the technical solutions after these changes still maintain the technical features required by the original invention, i.e. still can realize the core functions and effects of the present application, these changes should be considered as falling within the scope of protection of the claims of the present application.

[0053] In addition, with the continuous progress and development of technology, new technical means and methods are constantly emerging, which also provides a broad space for further improvement and perfection of the present application. Therefore, the scope of protection of the present application should also include those reasonable and foreseeable improvements and extensions based on the existing technology, as long as these improvements and extensions do not deviate from the basic principles and core ideas of the present application, they should be considered as equivalents of the present application and also be protected by the patent right.

Claims

1. A system for supercritical hydrothermal synthesis of ultrafine nano-barium titanate powder, characterized in that, The device comprises a material preparation unit, a supercritical reaction unit, a multi-stage cooling unit, a product post-processing unit and a by-product recovery unit, wherein the supercritical reaction unit comprises a first mixer (7), a heater (8), a second mixer (9) and a supercritical hydrothermal reactor (10); The first outlet of the material preparation unit and the second outlet of the material preparation unit are both connected to the first inlet of the second mixer (9) through the first mixer (7), the outlet of the second mixer (9) is connected to the first inlet of the multi-stage cooling unit through the supercritical hydrothermal reactor (10), the first outlet of the multi-stage cooling unit is connected to the second inlet of the second mixer (9) through the heater (8), the second outlet of the multi-stage cooling unit is connected to the second inlet of the multi-stage cooling unit through the first inlet of the material preparation unit, the third outlet of the multi-stage cooling unit is connected to the inlet of the by-product recovery unit through the product post-processing unit, and the outlet of the by-product recovery unit is connected to the second inlet of the material preparation unit.

2. The system for supercritical hydrothermal synthesis of superfine barium titanate nanopowder according to claim 1, characterized in that, The material preparation unit comprises a titanium precursor storage tank (1), a barium precursor storage tank (2), a pure water storage tank (3), a first high-pressure delivery pump (4), a second high-pressure delivery pump (5) and a third high-pressure delivery pump (6); The outlet of the titanium precursor storage tank (1) is connected to the inlet of the first high-pressure delivery pump (4), the first outlet of the barium precursor storage tank (2) is connected to the inlet of the second high-pressure delivery pump (5), the outlet of the first high-pressure delivery pump (4) and the outlet of the second high-pressure delivery pump (5) are both connected to the first inlet of the second mixer (9) through the first mixer (7), the second outlet of the multi-stage cooling unit is connected to the second inlet of the multi-stage cooling unit through the barium precursor storage tank (2), and the outlet of the by-product recovery unit is connected to the third inlet of the multi-stage cooling unit, the first outlet of the multi-stage cooling unit and the heater (8) in sequence through the pure water storage tank (3), the third high-pressure delivery pump (6).

3. The system for supercritical hydrothermal synthesis of superfine barium titanate nanopowder according to claim 2, characterized in that, The multi-stage cooling unit comprises a water spray cooler (11), a quencher (12), a slow cooler (13), a pressure reducer (16), a cooling water storage tank (14) and a fourth high-pressure delivery pump (15); The supercritical hydrothermal reactor (10) is connected to the first inlet of the quencher (12) through the water spray cooler (11), the third high-pressure delivery pump (6) is connected to the second inlet of the quencher (12), the first outlet of the quencher (12) is connected to the first inlet of the slow cooler (13), the second outlet of the quencher (12) is connected to the heater (8), the first outlet of the slow cooler (13) is connected to the product post-processing unit through the pressure reducer (16), and the second outlet of the slow cooler (13) is connected to the second inlet of the slow cooler (13) in sequence through the barium precursor storage tank (2), the cooling water storage tank (14) and the fourth high-pressure delivery pump (15).

4. The system for supercritical hydrothermal synthesis of superfine barium titanate nanopowder according to claim 3, characterized in that, The quencher (12) is one of a jacketed heat exchanger, a coil heat exchanger and a spiral fin tube heat exchanger, and the pressure reducer (16) adopts a capillary tube.

5. The system for supercritical hydrothermal synthesis of superfine barium titanate nanopowder according to claim 3, characterized in that, The product post-processing unit comprises a first centrifugal device (17), a second centrifugal device (19), a third centrifugal device (20), an ultrasonic washing device (21), a vacuum drying device (22) and a nano barium titanate product storage tank (23). The outlet of the pressure reducer (16) is connected to the inlet of the first centrifugal device (17) in sequence, the second centrifugal device (19) is connected to the inlet of the third centrifugal device (20) in sequence, the solid phase product outlet of the third centrifugal device (20) is connected to the inlet of the ultrasonic washing device (21) in sequence, the vacuum drying device (22) is connected to the inlet of the nano barium titanate product storage tank (23) in sequence; the liquid phase product outlet of the third centrifugal device (20) is connected to the inlet of the by-product recovery unit.

6. The system for supercritical hydrothermal synthesis of superfine barium titanate nanopowder according to claim 5, characterized in that, The product post-processing unit further comprises a standby centrifugal device (18), a first valve (V1), a second valve (V2) and a third valve (V3); The outlet of the pressure reducer (16) is divided into two paths, the first path is connected to the inlet of the second centrifugal device (19) in sequence through the first valve (V1) and the first centrifugal device (17), and the second path is connected to the inlet of the second centrifugal device (19) in sequence through the second valve (V2), the standby centrifugal device (18) and the third valve (V3).

7. The system for supercritical hydrothermal synthesis of superfine barium titanate nanopowder according to claim 6, characterized in that, The by-product recovery unit comprises a membrane separation device (24) and a by-product recovery storage tank (25); the liquid phase product outlet of the third centrifugal device (20) is connected to the inlet of the membrane separation device (24), the first outlet of the membrane separation device (24) is connected to the by-product recovery storage tank (25), and the second outlet of the membrane separation device (24) is connected to the inlet of the pure water storage tank (3).

8. The system for supercritical hydrothermal synthesis of superfine barium titanate nanopowder according to claim 7, characterized in that, The membrane separation device (24) uses one of a reverse osmosis membrane and a nanofiltration membrane.

9. The system for supercritical hydrothermal synthesis of superfine barium titanate nanopowder according to claim 1, characterized in that, The first mixer (7) is one of a jet collision mixer and a Laval mixer; the second mixer (9) is one of a jet collision mixer and a Laval mixer; and the heater (8) is one of an electromagnetic induction heater (8), an infrared heater (8), an electric resistance heater (8) and a natural gas heater (8).

10. A method for preparing supercritical hydrothermal synthesis of superfine nano-barium titanate powder, characterized in that, The system for supercritical hydrothermal synthesis of superfine nano barium titanate powder according to any one of claims 1-9 comprises the following steps: The temperature of the barium precursor is raised by the multi-stage cooling unit, the titanium precursor and the barium precursor are transported to the first mixer (7) through the material allocation unit to obtain the pre-mixed reaction precursor, and the reaction precursor is transported to the second mixer (9); the pure water is transported to the multi-stage cooling unit through the material allocation unit to obtain the preheated pure water, the preheated pure water is transported to the heater (8) to obtain the supercritical state pure water, and the supercritical state pure water is transported to the second mixer (9); The reaction precursor and the supercritical state pure water are mixed in the second mixer (9) to obtain the fluid and the heated reaction precursor, and the heated reaction precursor is sent into the supercritical hydrothermal reactor (10) to synthesize the superfine nano barium titanate powder; The fluid is cooled by the multi-stage cooling unit to obtain the normal pressure fluid, the normal pressure fluid is separated into the solid phase product and the liquid phase product, the solid phase product is stored by the product post-processing unit, and the liquid phase product is recovered by the by-product recovery unit.

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