Preparation method and system for supercritical hydro-thermal synthesis of nano-composite tin oxide

Abstract

The invention relates to the technical field of chemical engineering and environmental protection, in particular to a preparation method and system for supercritical hydro-thermal synthesis of nano-composite tin oxide, and the system sequentially comprises a material blending and conveying module, a mixed reaction module, a temperature and pressure reduction module and a product post-processing module. The material blending and conveying module accurately conveys pure water, a precursor and an additive to the subsequent module through a high-pressure metering pump. The mixed reaction module is used for carrying out supercritical hydrothermal synthesis by utilizing a heater, a mixer and first, second and third tubular reactors which are connected in parallel to form a reaction fluid containing nano tin oxide. And the cooling and depressurizing module is used for cooling and depressurizing the reaction fluid to generate the nano tin oxide suspension. And the product post-processing module is used for separating, purifying, doping and coating the suspension to finally obtain the high-performance nano composite tin oxide solid material. By accurately controlling the reaction conditions, the product quality and the production efficiency are effectively improved.

Description

Technical Field

[0001] This invention relates to the fields of chemical and environmental protection technology, specifically to a method and system for preparing nanocomposite tin oxide through supercritical hydrothermal synthesis. Background Technology

[0002] Lithium-ion batteries have attracted much attention due to their excellent energy density, long lifespan, low self-discharge, and environmental friendliness. They are used in various fields, including electronic products such as mobile phones and digital cameras, and are increasingly being applied in electric vehicles, energy storage power stations, aerospace, and military industries. Among the many lithium-ion battery anode materials, SnO2 anode material has good electrochemical performance. It has a high theoretical specific capacity, more than twice that of carbon. In addition, it has a moderate lithium intercalation voltage, is easy to synthesize, non-toxic, has high safety performance, and low cost. It is considered to be a lithium-ion battery anode material with good commercial prospects.

[0003] Supercritical hydrothermal synthesis is an efficient and green method for preparing nanocomposite tin oxide anode materials. The basic principle involves using water or an organic solvent as the solvent during the reaction process. The reactants undergo rapid nucleation and crystallization in supercritical water under high temperature and pressure to synthesize nano-tin oxide powder. The chemical reaction equation for the synthesis of nano-tin oxide is as follows: The reaction raw materials for the supercritical hydrothermal synthesis of tin oxide are sodium stannate trihydrate (Na2SnO3·3H2O) and urea (CH4N2O) in a molar ratio of 1:3. The solid product is tin oxide powder, and the liquid product is a sodium hydroxide solution. Sodium hydroxide is extremely corrosive, and direct discharge will pollute the water environment and soil.

[0004] The amount of aqueous phase generated after the post-processing of supercritical hydrothermal synthesis of nano-tin oxide is substantial, and direct discharge would result in a waste of water resources. Currently, several problems remain in the supercritical hydrothermal synthesis of nano-tin oxide, including: In the material transport process, typically only a single high-pressure metering pump is used for each material transport route. In industrial production, when the high-pressure metering pump malfunctions, there is no timely replacement pump, affecting the smooth operation of production.

[0005] In the mixing reaction module, the reaction time is controlled and the particle size is changed by adjusting the flow rate of the high-pressure metering pump to reduce or increase the flow rate, without considering the influence of the reactor length and pipe diameter on the reaction time. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a method and system for preparing nanocomposite tin oxide nanoparticles by supercritical hydrothermal synthesis, which addresses the shortcomings of the prior art and solves the technical problems of high energy consumption, high pollution, inaccurate particle size control and low resource utilization in the preparation of nanomaterials.

[0007] The objective of this invention is achieved through the following technical solutions: In a first aspect, the present invention provides a preparation system for supercritical hydrothermal synthesis of nanocomposite tin oxide, comprising, in sequence, a material preparation and conveying module, a mixing and reaction module, a cooling and depressurization module, and a product post-processing module; The material preparation and conveying module includes a pure water storage tank, a precursor storage tank, and an additive storage tank; the pure water storage tank is connected to the cooling and depressurization module via a first high-pressure metering pump and a second high-pressure metering pump; the precursor storage tank is connected to the mixing and reaction module via a third high-pressure metering pump and a fourth high-pressure metering pump; and the additive storage tank is connected to the mixing and reaction module via a fifth high-pressure metering pump and a sixth high-pressure metering pump. The mixing reaction module includes a heater, a mixer, a first tubular reactor, a second tubular reactor, and a third tubular reactor. The inlet of the heater is connected to a cooling and depressurization module. The mixer is connected to a third, fourth, fifth, and sixth high-pressure metering pump and the outlet of the heater, respectively. The outlet of the mixer is connected to the first, second, and third tubular reactors, which are arranged in parallel. The mixing reaction module is used to mix the phase raw materials to carry out supercritical hydrothermal synthesis of nano-tin oxide and form a reaction fluid. The cooling and depressurization module is used to cool and depressurize the reaction fluid generated by the mixing reaction module to form a nano-tin oxide suspension; The product post-processing module is used to sequentially separate, purify, dope, and coat the nano-tin oxide product to obtain nano-composite tin oxide solid.

[0008] As a further improvement of the present invention, manual shut-off valves are respectively provided at the inlet of the first high-pressure metering pump, the second high-pressure metering pump, the third high-pressure metering pump, the fourth high-pressure metering pump, the fifth high-pressure metering pump and the sixth high-pressure metering pump.

[0009] As a further improvement of the present invention, manual shut-off valves are respectively provided at the inlet of the first tubular reactor, the second tubular reactor and the third tubular reactor.

[0010] As a further improvement of the present invention, the cooling and pressure reduction module includes a jacket cooler and a pressure reduction unit; One inlet of the shell-and-tube cooler is connected to the outlets of the first, second, and third tubular reactors, which are arranged in parallel. The other inlet of the shell-and-tube cooler is connected to the first and second high-pressure metering pumps, respectively. One outlet of the shell-and-tube cooler is connected to the inlet of the pressure reducer, and the other outlet is connected to the inlet of the heater.

[0011] As a further improvement of the present invention, the cooler is a shell-and-tube quench cooler, the inlet of the inner tube of the shell-and-tube quench cooler is connected to a pure water high-pressure metering pump, and the outlet is connected to the inlet of a heater. The shell-and-tube quench cooler is used to exchange heat with room temperature water.

[0012] As a further improvement of the present invention, the product post-processing module includes a gas-liquid separator, a washing separator, a coating treatment tank, a centrifuge device, a drying device, and a calcination device. The inlet of the gas-liquid separator is connected to the outlet of the pressure reducer, and the outlet of the gas-liquid separator is connected to the inlet of the cleaning separator; the outlet of the cleaning separator is connected to the first inlet of the coating treatment tank, and the outlet of the coating treatment tank is connected to the inlet of the centrifuge; one outlet of the centrifuge is connected to the inlet of the drying device, and the outlet of the drying device is connected to the calcining device.

[0013] As a further improvement of the present invention, the product post-processing module also includes a nitrogen source and carbon coating agent mixing tank, the outlet of which is connected to the second inlet of the coating treatment pool, for providing a mixture of nitrogen source and carbon coating agent to the coating treatment pool, thereby forming a nitrogen-doped and carbon-coated layer on the surface of the nano-composite tin oxide product.

[0014] As a further improvement of the present invention, it also includes a by-product recovery module for recovering the by-product sodium hydroxide; the by-product recovery module includes a wastewater buffer tank, a triple-effect evaporator, a drum scraper dryer, and a sodium hydroxide recovery device; The inlet of the wastewater buffer tank is connected to the outlet of the cleaning separator, and the outlet of the wastewater buffer tank is connected to the inlet of the triple-effect evaporator to buffer the by-products output by the cleaning separator; the first outlet of the triple-effect evaporator is connected to the inlet of the drum scraper dryer, and the second outlet is connected to the wastewater reuse module; one outlet of the drum scraper dryer is connected to the sodium hydroxide recovery device, and the other outlet is connected to the wastewater reuse module.

[0015] As a further improvement of the present invention, it also includes a wastewater reuse module for treating and reusing the reaction effluent; the wastewater reuse module includes a condenser and a pure water treatment device; The first inlet of the condenser is connected to one outlet of the drum scraper dryer, and the first inlet is also connected to the outlet of the triple-effect evaporator. The second inlet of the condenser is connected to the outlet of the drying device. The outlet of the condenser is connected to the inlet of the pure water treatment device. The outlet of the pure water treatment device is connected to the pure water storage tank.

[0016] Secondly, the present invention provides a method for preparing supercritical hydrothermal synthesis of nanocomposite tin oxide, applied to the above-mentioned supercritical hydrothermal synthesis of nanocomposite tin oxide, comprising: The tin source required for preparing the nano-composite tin oxide anode is added to the precursor tank, and the concentrated urea solution is added to the additive tank. Pure water is pressurized by a first or second high-pressure metering pump, preheated by a cooler, and then heated by a heater before entering the mixer. Tin source is pressurized by a third or fourth high-pressure metering pump before entering the mixer, and urea additive is pressurized by a fifth or sixth high-pressure metering pump before entering the mixer. Tin source, urea additive, and pure water are thoroughly mixed in the mixer before entering any reactor to react. After the reaction, the fluid was cooled sequentially by a shell-and-tube cooler to obtain a nano-tin oxide suspension. The synthesized nano-tin oxide suspension was sequentially separated by a gas-liquid separator and a washing separator to obtain a solid phase product and an aqueous phase. The concentrated nano-tin oxide solution, nitrogen source and carbon coating agent were processed in a coating treatment tank and sequentially passed through a centrifuge, a drying device and a calcination device to obtain nitrogen-doped and carbon-coated nano-tin oxide anode material.

[0017] The beneficial effects of this invention are as follows: The supercritical hydrothermal synthesis system for nanocomposite tin oxide provided by this invention solves the problems of high energy consumption, high pollution, inaccurate particle size control, and low resource utilization in the traditional manufacturing process of nano-tin oxide particle size and morphology preparation through the design and integration of key modules. Firstly, in the material preparation and conveying module, a dual-pump backup design strategy is adopted. A first and second high-pressure metering pump ensure a stable supply of pure water, while third, fourth, fifth, and sixth high-pressure metering pumps supply precursors and additives respectively. This effectively avoids the risk of production interruption due to single-pump failure, improving the system's reliability and continuous production capacity. Secondly, the mixing reaction module raises the mixture to a supercritical state through a heater, and then guides it to the parallel first, second, and third tubular reactors, achieving efficient hydrothermal synthesis of nano-tin oxide. The differentiated design of the tube diameter and length of the different reactors provides flexible control over reaction time and product particle size, which not only improves the controllability of the synthesis process but also greatly optimizes the product quality. Furthermore, the cooling and depressurization module promptly cools and depressurizes the reaction products, generating a stable nano-tin oxide suspension. This avoids excessive reaction or structural damage under high temperature and pressure, ensuring product stability. Finally, the product post-processing module further processes the nano-tin oxide into a high-performance nano-composite tin oxide solid material through a series of processes, including separation, purification, doping, and coating. This significantly improves the material's electrochemical performance, making it suitable for use as a lithium-ion battery anode material. In summary, the technical solution of this invention effectively solves a series of technical challenges in the supercritical hydrothermal synthesis process, achieving high-quality, large-scale production of nano-composite tin oxide anode materials and environmentally friendly byproduct management. This has significant technological and economic value in promoting the development of the lithium-ion battery industry. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the system and method for supercritical hydrothermal synthesis of nanocomposite tin oxide according to the present invention; In the diagram, 1. Pure water storage tank; 2. Precursor storage tank; 3. Additive storage tank; 4. First high-pressure metering pump; 5. Second high-pressure metering pump; 6. Third high-pressure metering pump; 7. Fourth high-pressure metering pump; 8. Fifth high-pressure metering pump; 9. Sixth high-pressure metering pump; 10. Heater; 11. Mixer; 12. First tubular reactor; 13. Second tubular reactor; 14. Third tubular reactor; 15. Shell-and-tube cooler; 16. Pressure reducer; 17. Gas-liquid separator; 18. Cleaning separator; 19. Wastewater buffer tank; 20. Triple-effect evaporator; 21. Rotary drum dryer; 22. Sodium hydroxide recovery unit; 23. Condenser; 24. Pure water treatment unit; 25. Nitrogen source and carbon coating agent mixing tank; 26. Coating treatment tank; 27. Centrifuge; 28. Drying unit; 29. ​​Calcination unit. Detailed Implementation

[0020] To make the objectives and technical solutions of this invention clearer and easier to understand, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention.

[0021] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. The described embodiments are only some embodiments of the present invention, and not all embodiments.

[0022] Example 1 This embodiment provides a supercritical hydrothermal synthesis system for preparing nanocomposite tin oxide, such as... Figure 1 As shown, the system sequentially includes a material preparation and conveying module, a mixing and reaction module, a cooling and depressurization module, a product post-processing module, a by-product recovery module, and a wastewater reuse module.

[0023] The material preparation and conveying module includes a pure water storage tank 1, a precursor storage tank 2, an additive storage tank 3, a first high-pressure metering pump 4, a second high-pressure metering pump 5, a third high-pressure metering pump 6, a fourth high-pressure metering pump, a fifth high-pressure metering pump 8, and a sixth high-pressure metering pump 9. Pure water storage tank 1 is connected to the cooling and depressurization module via a first high-pressure metering pump 4 and a second high-pressure metering pump 5; precursor storage tank 2 is connected to the mixing reaction module via a third high-pressure metering pump 6 and a fourth high-pressure metering pump; additive storage tank 3 is connected to the mixing reaction module via a fifth high-pressure metering pump 8 and a sixth high-pressure metering pump 9. Specifically, the inlet of pure water storage tank 1 is connected to the wastewater reuse module, the first outlet of pure water storage tank 1 is connected to the inlet of the first high-pressure metering pump 4 and the second high-pressure metering pump 5, and the second outlet is connected to the inlet of the cleaning separator; precursor storage tank 2 is connected to the inlet of the third high-pressure metering pump 6 and the fourth high-pressure metering pump; additive storage tank 3 is connected to the inlet of the fifth high-pressure metering pump 8 and the sixth high-pressure metering pump 9; the outlets of the first high-pressure metering pump 4 and the second high-pressure metering pump 5 are connected to the cooling and depressurization module; the outlets of the third high-pressure metering pump 6 and the fourth high-pressure metering pump are connected to the mixing reaction module; and the outlets of the fifth high-pressure metering pump 8 and the sixth high-pressure metering pump 9 are connected to the mixing reaction module.

[0024] In addition, a manual shut-off valve V2 is installed at the inlet of the first high-pressure metering pump 4, and a manual shut-off valve V1 is installed at the inlet of the second high-pressure metering pump 5, for backup of the high-pressure metering pump for pure water; a manual shut-off valve V4 is installed at the inlet of the third high-pressure metering pump 6, and a manual shut-off valve V3 is installed at the inlet of the fourth high-pressure metering pump, for backup of the high-pressure metering pump for the precursor solution; a manual shut-off valve V6 is installed at the inlet of the fifth high-pressure metering pump 8, and a manual shut-off valve V5 is installed at the inlet of the sixth high-pressure metering pump 9, for backup of the high-pressure metering pump for the additive solution. The manual shut-off valves allow for independent control of each pump during maintenance or flow adjustment, preventing downtime of the entire production line. In principle, the manual shut-off valves allow for precise adjustment of the fluid input, thereby controlling the stoichiometry during the reaction process and ensuring efficient reaction. In terms of effectiveness, the technology in this embodiment enhances the flexibility and controllability of the system, enabling operators to adjust reaction parameters according to actual needs and optimize product quality. In other embodiments, more precise flow control can be achieved through an automated valve control system, further improving the accuracy of the response and solving the error problems that may occur during manual operation.

[0025] The mixing reaction module is used to mix the phase raw materials to carry out supercritical hydrothermal synthesis of nano-tin oxide and form a reaction fluid. The mixing reaction module includes a heater 10, a mixer 11, a first tubular reactor 12, a second tubular reactor 13 and a third tubular reactor 14. The inlet of the heater 10 is connected to the cooling and depressurization module. The mixer 11 is connected to the third high-pressure metering pump 6, the fourth high-pressure metering pump, the fifth high-pressure metering pump 8, the sixth high-pressure metering pump 9 and the outlet of the heater 10 respectively. The outlet of the mixer 11 is connected to the first tubular reactor 12, the second tubular reactor 13 and the third tubular reactor 14 arranged in parallel.

[0026] The inlet of the first tubular reactor 12, the second tubular reactor 13, and the third tubular reactor 14 are respectively equipped with manual shut-off valves (i.e., manual shut-off valve V7, manual shut-off valve V8, and manual shut-off valve V9). Technically, by installing manual shut-off valves at the reactor inlets, the start-up and shutdown of the reactors can be flexibly controlled, facilitating system maintenance and debugging. In principle, the selection and control of the reactor directly affects the reaction time and product characteristics; the use of manual shut-off valves ensures the consistency and repeatability of reaction conditions. In terms of effectiveness, the technology in this embodiment allows operators to select appropriate reactors for different product requirements, improving product diversity and adaptability. In other embodiments, an automatically controlled valve system can be introduced to achieve dynamic switching of the reactors, responding more quickly to changes in production needs and solving the problem of slow response in traditional manual operation.

[0027] In addition, the three tubular reactors in the mixing reaction module have different diameters and lengths to control the reaction time. Technically, this embodiment, by connecting tubular reactors of different diameters and lengths in parallel, can precisely control the reaction time, thereby regulating the particle size and morphology of the product. In principle, the reaction time directly affects the product growth process; by adjusting the diameter and length of the tubular reactors, the residence time of the fluid within the reactor can be changed, thus affecting the final morphology of the product. In terms of effectiveness, the technology in this embodiment provides operators with a flexible means to adjust product characteristics, improving the product's market competitiveness. In other embodiments, the problem of product diversity being limited by a single reactor type can be solved by introducing more types of reactors, such as stirred tank reactors or microreactors, or by using intelligent control technology to dynamically adjust the reactor's operating state.

[0028] The cooling and depressurization module is used to cool and depressurize the reaction fluid generated by the mixing reaction module to form a nano-tin oxide suspension.

[0029] The cooling and pressure reduction module includes a shell-and-tube cooler 15 and a pressure reducer. One inlet of the shell-and-tube cooler 15 is connected to the outlets of the first tubular reactor 12, the second tubular reactor 13, and the third tubular reactor 14, which are arranged in parallel. The other inlet of the shell-and-tube cooler 15 is connected to the first high-pressure metering pump 4 and the second high-pressure metering pump 5, respectively. One outlet of the shell-and-tube cooler 15 is connected to the inlet of the pressure reducer, and the other outlet is connected to the inlet of the heater 10. Technically, this embodiment achieves efficient heat exchange through the shell-and-tube cooler 15, rapidly reducing the temperature of the reaction fluid, while the pressure reducer smoothly reduces the fluid pressure to the target value. In principle, the shell-and-tube cooler 15 uses pure water as the cooling medium, rapidly removing heat from the reaction fluid through heat conduction between the inner and outer tube walls. The pressure reducer reduces the pressure by decreasing the cross-sectional area of ​​the fluid channel. In terms of effectiveness, the technology in this embodiment ensures rapid cooling of the reaction fluid and a stable pressure reduction, which is beneficial for maintaining the microstructure of the nano-composite tin oxide and improving the quality of the product. In other embodiments, cooling efficiency and pressure control accuracy can be further improved by employing more advanced cooling technologies and pressure regulation devices, such as spiral coil coolers and electronic pressure controllers, to solve the efficiency problems of cooling and depressurization under extreme conditions.

[0030] In this embodiment, the cooler is a shell-and-tube quench cooler. The inlet of the inner tube of the shell-and-tube quench cooler is connected to a high-pressure metering pump for pure water, and the outlet is connected to the inlet of the heater 10. The shell-and-tube quench cooler is used for heat exchange with room temperature water. Technically, this embodiment utilizes the high-efficiency heat exchange characteristics of the shell-and-tube quench cooler to achieve effective preheating of room temperature water.

[0031] In addition to the casing quencher, the cooling and pressure reduction module is equipped with a capillary pressure reducer and a manual back pressure valve. The manual back pressure valve and the manual back pressure valve are connected in parallel, and a manual shut-off valve V10 and a manual shut-off valve V11 are respectively installed at the inlet.

[0032] The product post-processing module is used to sequentially separate, purify, dope, and coat the nano-tin oxide product to obtain nano-composite tin oxide solid. The product post-processing module includes a gas-liquid separator, a washing separator, a nitrogen source and carbon coating agent mixing tank 25, a coating treatment tank 26, a centrifuge device 27, a drying device 28, and a calcination device 29. The inlet of the gas-liquid separator is connected to the outlet of the pressure reducing device, and the outlet of the gas-liquid separator is connected to the inlet of the washing separator. The outlet of the washing separator is connected to the inlet of the coating treatment tank 26, and the outlet of the nitrogen source and carbon coating agent mixing tank 25 is connected to another inlet of the coating treatment tank 26. Another outlet of the coating treatment tank 26 is connected to the inlet of the centrifuge device 27, one outlet of the centrifuge device 27 is connected to the inlet of the drying device 28, and the other outlet is connected to the inlet of the pure water treatment device 24. The outlet of the drying device 28 is connected to the calcination device 29.

[0033] The byproduct recovery module is used to recover the byproduct sodium hydroxide. The byproduct recovery module includes a wastewater buffer tank 19, a triple-effect evaporator 20, a drum scraper dryer, and a sodium hydroxide recovery device 22. The inlet of the wastewater buffer tank 19 is connected to the outlet of the washing separator, and the outlet of the wastewater buffer tank 19 is connected to the inlet of the triple-effect evaporator 20, used to buffer the byproduct output from the washing separator. The first outlet of the triple-effect evaporator 20 is connected to the inlet of the drum scraper dryer, and the second outlet is connected to the wastewater reuse module. One outlet of the drum scraper dryer is connected to the sodium hydroxide recovery device 22, and the other outlet is connected to the wastewater reuse module. Technically, this embodiment achieves efficient recovery of sodium hydroxide through the byproduct recovery module, while also treating wastewater and reducing environmental pollution. In principle, the sodium hydroxide in the wastewater is concentrated by the triple-effect evaporator 20, then dried by the drum scraper dryer, and finally collected in the sodium hydroxide recovery device 22. In terms of effectiveness, the technology in this embodiment not only reduces production costs but also improves the environmental performance of the system. In other embodiments, the recovery rate of by-products can be further improved by employing more advanced evaporation and drying technologies, such as membrane evaporation and vacuum drying, thereby solving the problem of low efficiency in traditional recovery technologies.

[0034] The wastewater reuse module is used to treat and reuse the reaction effluent. The module includes a condenser 23 and a pure water treatment device 24. The first inlet of the condenser 23 is connected to one outlet of the drum scraper dryer, and also to the outlet of the triple-effect evaporator 20. The second inlet of the condenser 23 is connected to the outlet of the dryer 28. The outlet of the condenser 23 is connected to the inlet of the pure water treatment device 24. The outlet of the pure water treatment device 24 is connected to the pure water storage tank 1. Technically, this embodiment achieves the recycling of the reaction effluent through the wastewater reuse module, reducing water consumption. In principle, after evaporation, condensation, and purification, the wastewater is transformed back into pure water and re-enters the pure water storage tank 1 for subsequent reactions. In terms of effectiveness, the technology in this embodiment not only saves water resources but also reduces wastewater discharge, improving the system's sustainability. In other embodiments, more advanced wastewater treatment technologies, such as reverse osmosis and deep filtration, can be introduced to further improve water purity and solve the problem of residual impurities that may exist in traditional wastewater treatment technologies.

[0035] This embodiment, by setting up parallel high-pressure metering pumps, ensures seamless switching to backup pumps even in the event of pump failure, maintaining continuous production and improving system stability and reliability. In principle, by controlling the flow rate and pressure of the high-pressure metering pumps, the reaction conditions in the supercritical hydrothermal synthesis process are precisely controlled, thereby affecting the particle size and morphology of the product. In terms of effect, the technology in this embodiment ensures high-quality preparation of nano-composite tin oxide while simplifying the operation process and improving production efficiency. In other embodiments, adding more backup pumps and optimizing pump design can further enhance system redundancy and resilience, addressing potential material transport interruptions in large-scale production.

[0036] Example 2 This embodiment also discloses a preparation method for a preparation system for the supercritical hydrothermal synthesis of nanocomposite tin oxide, including the following steps: Preparation of reactants: The tin source and additives required for the preparation of nano-composite tin oxide are added to the precursor storage tank and the additive storage tank, respectively; Supercritical hydrothermal synthesis reaction: Reaction water is pressurized by a first or second high-pressure metering pump, preheated by a shell-and-tube cooler, and then enters the heater. The tin source is pressurized by a third or fourth high-pressure metering pump and then enters the mixer. The additives are pressurized by a fifth or sixth high-pressure metering pump and then enter the mixer. The above reaction materials are mixed in the mixer, and then sequentially passed through a tubular reactor, a shell-and-tube cooler, and a pressure reducing device to obtain a nano-tin oxide suspension.

[0037] Post-processing of the product: The synthesized nano-tin oxide suspension is passed through a gas-liquid separator and a washing separator to obtain water and solid products; the water enters a wastewater buffer tank for further processing and recovery, and the solid products enter a coating treatment tank to obtain coated nano-tin oxide; the coated nano-tin oxide enters a centrifuge to obtain nano-composite tin oxide powder and water; the nano-composite tin oxide powder is passed through a drying-calcining device to obtain nitrogen-doped and carbon-coated nano-composite tin oxide anode material; the water after centrifugation and dehydration is recycled into a pure water treatment device.

[0038] Sodium hydroxide recovery from effluent: The effluent from the washing-separation unit passes through a wastewater buffer tank, then enters a triple-effect evaporator-drum scraper dryer for drying, and finally enters a sodium hydroxide recovery unit to obtain sodium hydroxide powder, which can be used as a process by-product; the water vapor generated during the evaporation, concentration and drying processes is recovered by passing through a condenser.

[0039] Sodium hydroxide recovery from effluent: The effluent from the washing-separation unit passes through a wastewater buffer tank, then enters a triple-effect evaporator-drum scraper dryer for drying, and finally enters a sodium hydroxide recovery unit to obtain sodium hydroxide powder, which can be used as a process by-product; the water vapor generated during the evaporation, concentration and drying processes is recovered by passing through a condenser.

[0040] Preferably, the carbon coating agent can be any one or more of substances including but not limited to sucrose, glucose, and starch.

[0041] Preferably, the nitrogen source can be any one or more of substances including but not limited to sucrose urea, melamine and dicyandiamide.

[0042] Preferably, the pure water in the cleaning separator device comes from a pure water storage tank.

[0043] The following example illustrates the working process of the system and method for preparing nano-composite tin oxide powder using a conventional raw material and auxiliary material system via hydrothermal synthesis. In the supercritical hydrothermal synthesis of nano-tin oxide using conventional raw materials and auxiliary materials, the tin source and additives are sodium stannate trihydrate and urea, respectively.

[0044] 1) Add sodium stannate trihydrate and urea to the precursor storage tank and additive storage tank, respectively; 2) The reaction pure water is pressurized by the first or second high-pressure metering pump, preheated by the shell-and-tube cooler, and then enters the heater. The tin source is pressurized by the third or fourth high-pressure metering pump and then enters the mixer. The additives are pressurized by the fifth or sixth high-pressure metering pump and then enter the mixer. The above reaction raw materials are mixed in the mixer, and then sequentially passed through a tubular reactor, a shell-and-tube cooler, and a pressure reducer to obtain a nano-tin oxide suspension. 3) The synthesized nano-tin oxide suspension is passed through a gas-liquid separator and a washing separator to obtain water and solid products; the water enters a wastewater buffer tank for further treatment and recovery, and the solid products enter a coating treatment tank to obtain coated nano-tin oxide; the coated nano-tin oxide enters a centrifuge to obtain nano-composite tin oxide powder and water; the nano-composite tin oxide powder is passed through a drying-calcining device to obtain nitrogen-doped and carbon-coated nano-composite tin oxide anode material. The effluent from the cleaning and separation unit passes through a wastewater buffer tank, then enters a triple-effect evaporator-drum scraper dryer for drying, and finally enters a sodium hydroxide recovery unit to obtain sodium hydroxide powder, which can be used as a process by-product. The water vapor generated during the evaporation, concentration, and drying processes is recovered by passing through a condenser.

[0045] Water recovered from the washing separator, wastewater buffer tank, triple-effect evaporator, and drum scraper dryer enters the condenser and is condensed into pure water, which then enters the pure water treatment device. Water recovered from the centrifuge device also enters the pure water treatment device, and water recovered from the drying device is condensed in the condenser and then enters the pure water treatment device. The water entering the pure water treatment device then enters the pure water storage tank for recycling.

Claims

1. A system for preparing nanocomposite tin oxide through supercritical hydrothermal synthesis, characterized in that, It includes, in sequence, a material preparation and conveying module, a mixing and reaction module, a cooling and depressurization module, and a product post-processing module; The material preparation and conveying module includes a pure water storage tank, a precursor storage tank, and an additive storage tank; the pure water storage tank is connected to the cooling and depressurization module via a first high-pressure metering pump and a second high-pressure metering pump; the precursor storage tank is connected to the mixing and reaction module via a third high-pressure metering pump and a fourth high-pressure metering pump; and the additive storage tank is connected to the mixing and reaction module via a fifth high-pressure metering pump and a sixth high-pressure metering pump. The mixing reaction module includes a heater, a mixer, a first tubular reactor, a second tubular reactor, and a third tubular reactor. The inlet of the heater is connected to a cooling and depressurization module. The mixer is connected to a third, fourth, fifth, and sixth high-pressure metering pump and the outlet of the heater, respectively. The outlet of the mixer is connected to the first, second, and third tubular reactors, which are arranged in parallel. The mixing reaction module is used to mix the phase raw materials to carry out supercritical hydrothermal synthesis of nano-tin oxide and form a reaction fluid. The cooling and depressurization module is used to cool and depressurize the reaction fluid generated by the mixing reaction module to form a nano-tin oxide suspension; The product post-processing module is used to sequentially separate, purify, dope, and coat the nano-tin oxide product to obtain nano-composite tin oxide solid.

2. The preparation system for supercritical hydrothermal synthesis of nanocomposite tin oxide according to claim 1, characterized in that, Manual shut-off valves are respectively installed at the inlet of the first, second, third, fourth, fifth, and sixth high-pressure metering pumps.

3. The preparation system for supercritical hydrothermal synthesis of nanocomposite tin oxide according to claim 1, characterized in that, Manual shut-off valves are installed at the inlets of the first, second, and third tubular reactors, respectively.

4. The preparation system for supercritical hydrothermal synthesis of nanocomposite tin oxide according to claim 1, characterized in that, The cooling and pressure reduction module includes a jacket cooler and a pressure reduction unit; One inlet of the shell-and-tube cooler is connected to the outlets of the first, second, and third tubular reactors, which are arranged in parallel. The other inlet of the shell-and-tube cooler is connected to the first and second high-pressure metering pumps, respectively. One outlet of the shell-and-tube cooler is connected to the inlet of the pressure reducer, and the other outlet is connected to the inlet of the heater.

5. The preparation system for supercritical hydrothermal synthesis of nanocomposite tin oxide according to claim 4, characterized in that, The cooler is a shell-and-tube quench cooler. The inlet of the inner tube of the shell-and-tube quench cooler is connected to a high-pressure metering pump for pure water, and the outlet is connected to the inlet of a heater. The shell-and-tube quench cooler is used to exchange heat with room temperature water.

6. The preparation system for supercritical hydrothermal synthesis of nanocomposite tin oxide according to claim 1, characterized in that, The product post-processing module includes a gas-liquid separator, a washing separator, a coating treatment tank, a centrifuge, a drying device, and a calcination device. The inlet of the gas-liquid separator is connected to the outlet of the pressure reducer, and the outlet of the gas-liquid separator is connected to the inlet of the cleaning separator; the outlet of the cleaning separator is connected to the first inlet of the coating treatment tank, and the outlet of the coating treatment tank is connected to the inlet of the centrifuge; one outlet of the centrifuge is connected to the inlet of the drying device, and the outlet of the drying device is connected to the calcining device.

7. The preparation system for supercritical hydrothermal synthesis of nanocomposite tin oxide according to claim 6, characterized in that, The product post-processing module also includes a nitrogen source and carbon coating agent mixing tank. The outlet of the nitrogen source and carbon coating agent mixing tank is connected to the second inlet of the coating treatment pool to provide a mixture of nitrogen source and carbon coating agent to the coating treatment pool, forming a nitrogen-doped and carbon-coated layer on the surface of the nano-composite tin oxide product.

8. The preparation system for supercritical hydrothermal synthesis of nanocomposite tin oxide according to claim 1, characterized in that, It also includes a byproduct recovery module for recovering sodium hydroxide byproduct; the byproduct recovery module includes a wastewater buffer tank, a triple-effect evaporator, a drum scraper dryer, and a sodium hydroxide recovery device; The inlet of the wastewater buffer tank is connected to the outlet of the cleaning separator, and the outlet of the wastewater buffer tank is connected to the inlet of the triple-effect evaporator to buffer the by-products output by the cleaning separator; the first outlet of the triple-effect evaporator is connected to the inlet of the drum scraper dryer, and the second outlet is connected to the wastewater reuse module; one outlet of the drum scraper dryer is connected to the sodium hydroxide recovery device, and the other outlet is connected to the wastewater reuse module.

9. The preparation system for supercritical hydrothermal synthesis of nanocomposite tin oxide according to claim 8, characterized in that, It also includes a wastewater reuse module for treating and reusing the reaction effluent; the wastewater reuse module includes a condenser and a pure water treatment device; The first inlet of the condenser is connected to one outlet of the drum scraper dryer, and the first inlet is also connected to the outlet of the triple-effect evaporator. The second inlet of the condenser is connected to the outlet of the drying device. The outlet of the condenser is connected to the inlet of the pure water treatment device. The outlet of the pure water treatment device is connected to the pure water storage tank.

10. A method for preparing supercritical hydrothermal synthesis of nanocomposite tin oxide, applied to the preparation system for supercritical hydrothermal synthesis of nanocomposite tin oxide according to any one of claims 1 to 9, characterized in that, include: The tin source required for preparing the nano-composite tin oxide anode is added to the precursor tank, and the concentrated urea solution is added to the additive tank. Pure water is pressurized by a first or second high-pressure metering pump, preheated by a cooler, and then heated by a heater before entering the mixer. Tin source is pressurized by a third or fourth high-pressure metering pump before entering the mixer, and urea additive is pressurized by a fifth or sixth high-pressure metering pump before entering the mixer. Tin source, urea additive, and pure water are thoroughly mixed in the mixer before entering any reactor to react. After the reaction, the fluid was cooled sequentially by a shell-and-tube cooler to obtain a nano-tin oxide suspension. The synthesized nano-tin oxide suspension was sequentially separated by a gas-liquid separator and a washing separator to obtain a solid phase product and an aqueous phase. The concentrated nano-tin oxide solution, nitrogen source and carbon coating agent were processed in a coating treatment tank and sequentially passed through a centrifuge, a drying device and a calcination device to obtain nitrogen-doped and carbon-coated nano-tin oxide anode material.

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