A system and control method for supercritical hydrothermal and solvothermal synthesis of nano-zirconia

Abstract

This invention discloses a system and control method for supercritical hydrothermal and solvothermal synthesis of nano-zirconia, including a material conveying system, a mixing reaction unit, a post-processing unit, and an emergency tank unit. The entire system can achieve quality control, precise temperature and pressure control, large flow rate system control, and safety control in supercritical hydrothermal / solvothermal synthesis of nano-composite zirconia. It solves key problems such as rapid heating and pressurization and cooling and depressurization, safe and reliable operation, and quality control in supercritical hydrothermal / solvothermal synthesis of nano-composite zirconia systems, and achieves system optimization, laying the foundation for the industrialization of continuous supercritical hydrothermal / solvothermal synthesis.

Description

Technical Field

[0001] This invention belongs to the field of energy and chemical technology, specifically relating to a system and control method for supercritical hydrothermal synthesis and solvothermal synthesis of nano-zirconia. Background Technology

[0002] Nanoceramics are ceramic materials with nanoscale phases in their microstructure. Zirconia-based nanoceramics have attracted much attention due to their excellent properties. Compared with ordinary micron-sized zirconia, the toughness, strength, and high-temperature resistance of nano-zirconia are greatly improved with decreasing particle size. Zirconia has three crystal types: monoclinic (room temperature to 1175℃), tetragonal (1175 to 2370℃), and cubic (2370 to 2680℃). The tetragonal and cubic phases can be stabilized at room temperature using various techniques (such as adjusting the pH value or doping with yttrium, lanthanum, cerium, etc.). Due to its excellent physical properties such as high strength, high temperature resistance, and adjustable coefficient of thermal expansion, as well as its chemical properties such as corrosion resistance and strong oxygen ion conductivity, nano-zirconia has been widely used in many fields such as thermal barrier coatings, dental materials, catalysts, luminescent materials, fuel cells, and shape memory ceramics.

[0003] Currently, the main methods for synthesizing nano-zirconia include chemical vapor deposition (CVD), chemical vapor phase synthesis, solid-state combustion, spray pyrolysis, sol-gel method, and co-precipitation. However, these methods have many drawbacks, including the need for subsequent heat treatment at high temperatures, easy agglomeration at room temperature, poor dispersibility, uneven particle size distribution, and low specific surface area and activity. Continuous supercritical hydrothermal and solvothermal synthesis flow reaction systems offer significant advantages due to their high nucleation density, short reaction time, high reaction rate, high product purity, stable distribution, and controllable particle size, crystal form, and morphology. Furthermore, the cost of instruments, energy, and precursors used in this system is much lower, making it more environmentally friendly. The process flow of continuous supercritical hydrothermal and solvothermal synthesis mainly includes a material conveying unit, a heating and pressurizing unit, a mixing / reaction unit, a cooling and depressurizing unit, and a post-processing unit. However, in the process of synthesizing nano-zirconia using continuous supercritical hydrothermal and solvothermal synthesis flow reaction systems, many problems still exist.

[0004] (1) The material conveying unit only has a simple solvent path and a precursor path, without considering the particle size control, crystal stability and anti-agglomeration of zirconium oxide; in the design of the whole system, the purity control problem is not considered, and the materials are mostly stainless steel 304 or 316, which has a great risk of corrosion.

[0005] (2) The reactors used in the current systems for synthesizing nano-zirconia are all batch reactors or simple continuous reactors, without considering the precise control of heating and pressurization, and cooling and pressurization during industrial scale-up.

[0006] (3) Current systems for synthesizing nano-zirconia cannot control multiple flow rates and are usually limited to small flow rate systems because heating and depressurization are achieved in one step and large flow rate systems are not considered.

[0007] (4) Supercritical hydrothermal / solventricular synthesis reaction is a high temperature and high pressure reaction that raises the temperature and pressure of the material to a supercritical state. Existing heating systems do not take into account the control of major safety accidents such as overpressure and explosion.

[0008] The aforementioned problems directly limit the synthesis of nanocomposite zirconia using supercritical hydrothermal / solvothermal methods, severely hindering its further promotion. Therefore, establishing a systematic and control method for the supercritical hydrothermal and solvothermal synthesis of nanocomposite zirconia is crucial. Summary of the Invention

[0009] In order to overcome the shortcomings of the prior art, the present invention aims to provide a system and control method for supercritical hydrothermal synthesis and solvothermal synthesis of nano-zirconia, so as to solve the technical problems of existing technologies for preparing nano-zirconia that cannot achieve multi-flow system control, have hidden dangers in safe operation, and cannot regulate the quality of nano-zirconia.

[0010] To achieve the above objectives, the present invention employs the following technical solution:

[0011] This invention discloses a system for supercritical hydrothermal synthesis and solvothermal synthesis of nano-zirconia, comprising a material conveying unit, a mixing reaction unit, a post-processing unit, and an emergency tank unit;

[0012] The material conveying unit includes a precursor storage tank, a solvent storage tank, an additive storage tank, and a composite storage tank. The precursor storage tank and the composite storage tank are connected to the inlet of high-pressure pump one after they are combined. The solvent storage tank and the additive storage tank are connected to the inlets of high-pressure pump two and high-pressure pump three, respectively. Pressure gauges PIC1, PIC2, ​​and PIC3 are respectively installed at the outlets of high-pressure pump one, high-pressure pump two, and high-pressure pump three. The pressure gauges are interlocked with the motors of the high-pressure pumps at the corresponding positions.

[0013] The mixing reaction unit includes a heater, a mixing unit, and a reaction unit. The outlet of high-pressure pump two is connected to the inlet of the heater. The outlet of the heater, the outlet of high-pressure pump one, and the outlet of high-pressure pump three are respectively connected to the mixing unit. The outlet of the mixing unit is connected to the inlet of the reaction unit. Temperature sensors TIC2 and TIC3 are respectively installed at the inlet and outlet of the reaction unit. Temperature sensor TIC1 is installed on the heater. The average value of temperature sensors TIC2 and TIC3 is interlocked with the reading of temperature sensor TIC1.

[0014] The post-processing unit includes a cooling unit, a slow cooling unit, a capillary pressure reducer, a gas-liquid separation unit, a solid-liquid separation unit, a drying unit, and a nano-product storage unit connected in sequence. The gas-liquid separation unit is also connected to a waste gas treatment unit, and the solid-liquid separation unit is also connected to a waste liquid treatment unit. Temperature sensors are installed at the inlet and outlet of the cooling unit, and temperature sensors TIC4 and TIC5 are installed at the inlet and outlet of the slow cooling unit, respectively. A temperature reduction unit is interlocked between temperature sensors TIC4 and TIC5. A pressure control valve is installed on the pipeline connecting the capillary pressure reducer and the gas-liquid separation unit.

[0015] The emergency tank unit acts on the mixing reaction unit through interlocking with the first safety valve, and acts on the material conveying unit through interlocking with the second safety valve.

[0016] Preferably, a flow meter FIC1 is installed at the outlet of the composite storage tank to regulate the ratio of stabilizer, ligand and precursor.

[0017] Preferably, the reaction unit includes several reactors arranged in series or in parallel, and each reactor is provided with a valve at its inlet and outlet. The reactors are either reaction vessels or tubular reactors.

[0018] Preferably, the cooling unit includes several coolers arranged in series or in parallel, and each cooler is provided with a valve at its inlet and outlet. The coolers are coil coolers, shell-and-tube coolers, or finned coolers.

[0019] Preferably, the mixing unit is also equipped with an online pH monitoring device, which is interlocked with the flow meter FIC1 at the outlet of the composite storage tank.

[0020] Preferably, pressure sensors PIC4, PIC5, PIC6, and PIC7 are respectively provided at the outlets of the reaction unit, cooling unit, slow cooling unit, and capillary pressure reducer.

[0021] Preferably, a steam user circuit is also provided on the slow cooling unit.

[0022] Preferably, the composite storage tank is not limited to two or more; the heater is not limited to electromagnetic heaters, infrared heaters, or resistance heaters; the mixing unit is not limited to T-type three-way mixers, coaxial countercurrent mixers, or cross-type jet mixers; reaction unit one and reaction unit two are not limited to tubular reactors or batch reactors, etc., one or more connected in series or parallel, and their length or flow rate is set according to the reaction time requirements; the heat exchange form of cooling unit one, cooling unit two, and slow cooling unit is not limited to coil type or coaxial type, etc., and their number is not limited to one or more connected in series or parallel; the waste liquid treatment unit is not limited to filtration membranes such as forward osmosis, RO reverse osmosis, or ultrafiltration membranes, or evaporation forms such as MVR and triple-effect evaporation; the form of the pressure control valve V9 is not limited to back pressure valves, proportional unloading valves, electric pressure regulating valves, etc.; the material of the integral components is not limited to nickel-based alloys, titanium-lined stainless steel, or non-metallic coatings, etc.

[0023] This invention also discloses a controlled method for preparing nano-zirconia using the above-described system for supercritical hydrothermal synthesis and solvothermal synthesis of nano-zirconia, characterized in that it includes:

[0024] Material conveying and mixing / reaction stage:

[0025] The precursor in the precursor storage tank is mixed with the stabilizer and ligand in the composite storage tank and then transported to the mixing unit by high pressure pump one. The additive in the additive storage tank is transported to the mixing unit by high pressure pump three. The solvent in the solvent storage tank is transported to the heater by high pressure pump two and then transported to the mixing unit. The three materials are fully mixed in the mixing unit and then enter the reaction unit to react.

[0026] Post-processing stage:

[0027] The hot fluid generated by the reaction enters the cooling unit. The cooled medium-temperature fluid is further cooled by the slow cooling unit. The cooled fluid passes through the capillary pressure reducer and flows into the gas-liquid separation unit. The gas enters the waste gas treatment unit for treatment. The solid-liquid phase enters the solid-liquid separation unit. The liquid phase is recovered to the waste liquid treatment unit. The solid phase is processed by the drying unit and then stored in the nano-product storage unit.

[0028] Preferably, the regulation process includes:

[0029] Ingredient control: The ratio of stabilizer and ligand to precursor in the composite storage tank is controlled by the reading of flow meter FIC1, and the pumping volume of high pressure pump 1, high pressure pump 2 and high pressure pump 3 is controlled to achieve precise ingredient control.

[0030] Flow control: When the system needs to switch from a small flow rate to a large flow rate, the flow rate is increased by changing the power of high-pressure pump one, high-pressure pump two, and high-pressure pump three, and the temperature is increased by increasing the power of the heater. During the cooling and depressurization process, temperature sensors TIC4 and TIC5 are interlocked with the desuperheating unit. The desuperheating water in the desuperheating unit acts on the cooling unit and the slow cooling unit by increasing the desuperheating water flow rate to achieve matching of rapid cooling at a large flow rate. The stepwise depressurization of the reaction unit, cooling unit, slow cooling unit, capillary pressure reducer, and pressure control valve achieves matching of rapid depressurization at a large flow rate.

[0031] Temperature control: When the temperature of the reaction unit does not reach the supercritical condition, the average value of temperature sensors TIC2 and TIC3 is interlocked with temperature sensor TIC1 to control the heater power and achieve reaction heat replenishment; when incomplete cooling is detected during the cooling process, temperature sensors TIC4 and TIC5 are interlocked with the de-cooling unit, which increases the de-cooling water flow rate to act on the cooling unit and the slow cooling unit to achieve rapid cooling.

[0032] Pressure regulation: Pressure sensors PIC4, PIC5, PIC6, and PIC7 are respectively installed at the outlets of the reaction unit, cooling unit, slow cooling unit, and capillary pressure reducer to monitor the pressure drop during the cooling stage. When the pressure cannot be completely reduced during the cooling process, the pressure control valve V9 is adjusted to completely release the pressure, thereby realizing step-by-step pressure control of the entire system.

[0033] Nano-zirconia quality control: The stabilizer and ligand materials in the composite storage tank are regulated by interlocking the pH value online monitoring device with the flow meter FIC1 at the outlet of the composite storage tank to achieve crystal stability and prevent agglomeration; the particle size of nano-zirconia is controlled by changing the electric heating power, the pump input pressure, the length of the reaction unit or the flow path to change the temperature, pressure and reaction time.

[0034] Safety Control: Pressure gauges PIC1, PIC2, ​​and PIC3 are interlocked with the motors of high-pressure pumps 1, 2, and 3, respectively. When any material supply pipeline experiences overpressure, operation is stopped to achieve Level 1 safety control. When the reaction unit experiences overpressure, the pressure control valve is opened to release pressure, achieving Level 2 safety control. When the system experiences overheating, blockage, or leakage of high-temperature fluid, the emergency tank unit is activated. The first safety valve acts on the reaction unit, the second safety valve acts on the material conveying unit, and the cooling unit continues to operate until the system cools and depressurizes, achieving Level 3 safety control.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] This invention discloses a system for the supercritical hydrothermal and solvothermal synthesis of nano-zirconia, comprising a material conveying unit, a mixing and reaction unit, a post-processing unit, and an emergency tank unit. First, in the material conveying unit, precise batching is achieved by adjusting the material ratio in the composite storage tank and controlling the pumping rate of several high-pressure pumps. In the mixing and reaction unit, temperature sensors and a de-cooling unit are interlocked, and pressure sensors, pump motors, and pressure control valves work together to achieve step-by-step heating and pressurization and rapid and reliable cooling and de-pressurization of the entire system, precisely controlling the system's temperature and pressure. Second, through the interlocking of pressure gauges and high-pressure pumps, operation is stopped when any material supply pipeline experiences overpressure, achieving first-level safety control; when the reaction... When a unit experiences overpressure, pressure is released by opening the pressure control valve, achieving secondary safety control. When the system experiences overheating, blockage, or leakage of high-temperature fluid, the emergency tank unit is activated. The first safety valve acts on the reaction unit, the second safety valve acts on the material conveying unit, and the cooling unit continues to operate until the system cools and depressurizes, achieving tertiary safety control and improving system reliability. Third, by interlocking flow meters to control the ratio of stabilizers and ligands to precursors, and by changing the electric heating power, pump input pressure, and the length or flow path of the reaction unit, temperature, pressure, and reaction time can be altered. This makes operating parameters easier to control and adjust, achieving crystal stabilization, particle size control, and anti-agglomeration of nano-zirconia particles. Therefore, this invention achieves system optimization, laying the foundation for the industrialization of continuous supercritical hydrothermal / solvothermal synthesis.

[0037] Furthermore, a steam user loop is also set up on the slow cooling unit to supply the waste heat of the slow cooling unit to the steam user, which improves the waste heat utilization efficiency of the supercritical hydrothermal synthesis / solvent thermal synthesis of nano-zirconia and reduces the system operating cost. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the system and control method for the supercritical hydrothermal synthesis and solvothermal synthesis of nano-zirconia of the present invention.

[0039] The tank is as follows: 1 is the precursor storage tank; 2 is the solvent storage tank; 3 is the additive storage tank; 4 is the composite storage tank; 5 is high-pressure pump one; 6 is high-pressure pump two; 7 is high-pressure pump three; 8 is the heater; 9 is the mixing unit; 10 is the online pH monitoring unit; 11 is the reaction unit one; 12 is the reaction unit two; 13 is the cooling unit one; 14 is the cooling unit two; 15 is the slow cooling unit; 16 is the steam user; 17 is the capillary pressure reducer; 18 is the gas-liquid separation unit; 19 is the waste gas treatment unit; 20 is the solid-liquid separation unit; 21 is the waste liquid treatment unit; 22 is the drying unit; 23 is the nano-product storage unit; 24 is the emergency tank unit; 25 is the de-icing unit. Detailed Implementation

[0040] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0041] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0042] The present invention will now be described in further detail with reference to the accompanying drawings:

[0043] See Figure 1 A system for supercritical hydrothermal synthesis and solvothermal synthesis of nano-zirconia includes a material conveying system, a mixing reaction unit, a post-processing unit, and an emergency tank unit 24.

[0044] In the material conveying unit, the precursor storage tank 1 and the composite storage tank 4 are connected to the inlet of the high-pressure pump 5 after merging. The solvent storage tank 2 and the additive storage tank 3 are connected to the inlets of the high-pressure pump 6 and the high-pressure pump 7, respectively. The pressure gauges PIC1, PIC2 and PIC3 are connected to the outlets of the high-pressure pump 5, the high-pressure pump 6 and the high-pressure pump 7, respectively.

[0045] The mixing reaction unit includes a heater 8, a mixing unit 9, an online pH monitoring unit 10, a reaction unit 11, and a reaction unit 2 12. The outlet of the high-pressure pump 2 6 is connected to the inlet of the heater 8. The outlet of the heater 8 merges with the outlets of the high-pressure pump 1 5 and the high-pressure pump 3 7 in the mixing unit 9. The outlet of the mixing unit 9 is divided into two paths: one path is connected to the online pH monitoring unit 10, and the other path is connected to the reaction unit. Temperature sensors TIC2 and TIC3 are installed at the inlet and outlet of the reaction unit.

[0046] The post-reaction processing unit includes a cooling unit 13, a cooling unit 2 14, a slow cooling unit 15, a steam user 16, a capillary pressure reducer 17, a gas-liquid separation unit 18, a waste gas treatment unit 19, a solid-liquid separation unit 20, a waste liquid treatment unit 21, a drying unit 22, and a nano-product storage unit 23. The outlet of the gas-liquid separation unit 18 is divided into two paths, one of which is connected to the waste gas treatment unit 19, and the other is connected to the solid-liquid separation unit 20. Temperature sensors TIC3, TIC4, PIC4, and PIC5 are installed at the inlet and outlet of the cooling unit 13 and the cooling unit 2 14.

[0047] The emergency tank unit 24 is interlocked with the components in the material conveying unit and the mixing reaction unit via safety valves V10 and V11.

[0048] Preferably, the heater 8 is equipped with a temperature sensor TIC1, and the average readings of temperature sensors TIC2 and TIC3 are interlocked with TIC1. The average of the inlet and outlet temperature readings is taken as the actual reaction temperature inside the reactor, and the heater temperature is adjusted to ensure that the reaction temperature reaches the expected set temperature.

[0049] Preferably, pressure gauges PIC1, PIC2 and PIC3 are interlocked with the motors of high-pressure pump 5, high-pressure pump 6 and high-pressure pump 7, respectively.

[0050] Preferably, a flow meter FIC1 is installed at the bottom of the composite storage tank 4.

[0051] Preferably, valves V1 and V3 are respectively provided at the front and rear of reaction unit 11, and valves V2 and V4 are respectively provided at the front and rear of reaction unit 12. The reaction units are not limited to two, but can be composed of multiple modules connected in series or in parallel, and their form is not limited to tubular or kettle type.

[0052] Preferably, valves V5 and V7 are respectively provided at the front and rear of cooling unit 13, and valves V6 and V8 are respectively provided at the front and rear of cooling unit 14. The cooling units are not limited to two, but can be composed of multiple modules connected in series or in parallel, and their forms are not limited to coil type, sleeve type or finned type, etc.

[0053] Preferably, temperature sensors TIC4 and TIC5 are respectively provided at the outlets of the cooling unit and the slow cooling unit 15, and are interlocked with the cooling unit 25.

[0054] Preferably, pressure sensors PIC4, PIC5, PIC6 and PIC7 are respectively provided at the outlets of the reaction unit, cooling unit, slow cooling unit 15 and capillary pressure reducer 17, and a pressure control valve V9 is provided between the capillary pressure reducer 17 and the pressure sensor PIC7.

[0055] Preferably, the composite storage tank 4 is not limited to one, but can be two or more depending on the substances added to the reaction; the heater 8 is not limited to electromagnetic heaters, infrared heaters, or resistance heaters; the mixing unit 9 is not limited to T-type three-way mixers, coaxial countercurrent mixers, or cross-type jet mixers; the reaction unit 11 and reaction unit 22 are not limited to tubular reactors or batch reactors, etc., one or more connected in series or parallel, and their length or flow rate is set according to the reaction time requirements; the heat exchange form of cooling unit 13, cooling unit 24, and slow cooling unit 15 is not limited to coil type or coaxial type, etc., and their number is not limited to one or more connected in series or parallel; the waste liquid treatment unit 21 is not limited to filtration membranes such as forward osmosis, RO reverse osmosis, or ultrafiltration membranes, or evaporation forms such as MVR or triple-effect evaporation; the form of the pressure control valve V9 is not limited to back pressure valves, proportional unloading valves, electric pressure regulating valves, etc.; the material of the integral components is not limited to nickel-based alloys, titanium-lined stainless steel, or non-metallic coatings, etc.

[0056] The method for synthesizing nano-zirconia using the above-mentioned system for supercritical hydrothermal synthesis and solvothermal synthesis is as follows:

[0057] A mixture containing one or more ligands (such as PVP, EDTA, etc.) and one or more stabilizers (such as yttrium salts, lanthanides, cerium salts, etc.) is stored in composite storage tank 4. This mixture is then transferred to precursor storage tank 1 and stirred with zirconium-based precursors (zirconium oxynitrate, zirconium acetate, zirconium nitrate, or zirconium oxychloride, etc.) and stored in precursor storage tank 1. The precursor mixture is pressurized by high-pressure pump 5 to reach the critical pressure value for supercritical hydrothermal synthesis. The pressurized material is then pumped into mixing unit 9, while alkali in additive storage tank 3... The solution (sodium hydroxide, potassium hydroxide, ammonia, etc., which can provide hydroxide ions) is pressurized by high-pressure pump 7 and then pumped into mixing unit 11. Pure water or other solvents (ethanol, methanol, etc.) in solvent storage tank 5 are pressurized by high-pressure pump 7 and then pumped into heater 8. The pure water or other solvents are rapidly heated to supercritical temperature and then mixed with the alkaline solution and precursor mixture in mixing unit 9. The mixer type is not limited to countercurrent mixing or cross-jet mixing, but can increase the mixing area and improve mixing efficiency. The ratio of stabilizer and ligand to precursor in composite storage tank 4 is controlled by the reading of flow meter FIC1. Simultaneously, high-precision metering pumps 5, 6, and 7 are used to achieve precise control of the batching.

[0058] The thoroughly mixed solution then enters reaction unit 11 or reaction unit 2 12 for rapid hydrolysis and dehydration. The reaction time of the reaction unit can be adjusted according to actual conditions. Afterwards, the solution is cooled in stages through cooling unit 13 or cooling unit 2 14 and slow cooling unit 15. The form of the slow cooling unit is not limited to shell-and-tube, coil, or finned heat exchangers, used to increase the heat exchange area and improve heat exchange efficiency. Slow cooling unit 15 utilizes waste heat to generate steam for steam user 16, which is further cooled before entering capillary pressure reducer 17.

[0059] When valves V2 and V4 are closed and valves V1 and V3 are opened, the mixed supercritical fluid enters reaction unit 11. When valves V1 and V3 are closed and valves V2 and V4 are opened, the mixed supercritical fluid flows into reaction unit 22. When the temperature of the reaction unit does not reach the supercritical condition, the average values ​​of temperature sensors TIC2 and TIC3 are transmitted to the control system for controlling the power of electric heater 8 to achieve reaction reheating. When valves V6 and V8 are closed and valves V5 and V7 are opened, the post-reaction fluid enters cooling unit 13. When valves V5 and V7 are closed and valves V6 and V8 are opened, the post-reaction fluid enters cooling unit 24. The cooled intermediate-temperature fluid is further cooled by slow cooling unit 15. When incomplete cooling is detected during the cooling process, temperature sensors TIC4 and TIC5 are interlocked with desuperheating unit 25. The desuperheating water in the desuperheating unit acts on the cooling unit and slow cooling unit 15 by increasing the desuperheating water flow rate, achieving rapid cooling. Thus, temperature control of the supercritical hydrothermal synthesis or solvothermal synthesis system is achieved.

[0060] Pressure sensors PIC4, PIC5, PIC6 and PIC7 are respectively installed at the outlets of the reaction unit, cooling unit, slow cooling unit 15 and capillary pressure reducer 17 to monitor the pressure drop during the cooling stage. When the system cannot completely reduce the pressure during the cooling process, the pressure control valve V9 is adjusted to completely release the pressure, thereby realizing the step-by-step pressure control of the entire system.

[0061] The solid-liquid-gas three-phase mixture is divided into two paths in the gas-liquid separation unit 18. One path is the gas phase, which enters the waste gas treatment unit 19. The waste gas can be used to supply the gas heater 8, converting harmful gases into clean gases such as CO2, N2, and H2O and releasing them. It can also be used for other purposes. The other path is the solid-liquid phase, which enters the solid-liquid separation unit 20 for separation. The solid phase enters the drying unit 22 for drying, obtaining nano-composite zirconia powder with small particle size, good dispersion, and high purity, and is stored in the nano-product storage unit 23. The liquid phase enters the waste liquid treatment unit 21, where it can be directly discharged in compliance with standards or generate high-value by-products such as acetates, nitrates, and chlorides.

[0062] When the low-flow system finishes running and needs to be switched to the high-flow system, the flow rate is increased by changing the power of high-pressure pump 5, high-pressure pump 6, and high-pressure pump 7. The heating process can be matched by increasing the power of electric heater 8. During the cooling and depressurization process, temperature sensors TIC4 and TIC5 are interlocked with the desuperheating unit 25. The desuperheating water of the desuperheating unit acts on the cooling unit and the slow cooling unit 15 by increasing the desuperheating water flow rate, which can match the high-flow-rate rapid cooling. The stepwise depressurization of the reaction unit, cooling unit, slow cooling unit 15, capillary pressure reducer 17, and pressure control valve V9 can match the high-flow-rate rapid depressurization.

[0063] If any of the precursor, solvent, or additive paths experiences overpressure, pressure gauges PIC1, PIC2, ​​and PIC3 are interlocked with the high-pressure pump motor, triggering an overpressure warning and automatic shutdown of the high-pressure pump, achieving Level 1 safety control. When the reaction unit experiences overpressure, pressure control valve V9 opens and releases pressure, achieving Level 2 safety control. If the system experiences overheating, system blockage, malfunction of the pressure relief valve, or leakage of high-temperature fluid, emergency tank unit 24 opens, and safety valves V10 and V11 act on the reaction unit and the precursor, solvent, and additive paths, respectively. Cooling water continues to act until the system cools and depressurizes, achieving Level 3 safety control. Of course, the safety control in this patent is not limited to three or more levels.

[0064] The control processes involved in the above-mentioned supercritical hydrothermal / solvothermal synthesis of nano-zirconia include:

[0065] 1) Batching control: The ratio of stabilizer and ligand to precursor in composite storage tank 4 is controlled by the reading of flow meter FIC1. At the same time, high-pressure pump 5, high-pressure pump 6 and high-pressure pump 7 adopt high-precision metering pumps to achieve precise batching control.

[0066] 2) Flow control: When the small flow system is completed and a large flow system needs to be switched, the power of high-pressure pump 5, high-pressure pump 6, and high-pressure pump 7 is changed to increase the flow rate. The heating process can be matched by increasing the power of electric heater 8. During the cooling and depressurization process, temperature sensors TIC4 and TIC5 are interlocked with the desuperheating unit 25. The desuperheating water of the desuperheating unit acts on the cooling unit and the slow cooling unit 15 by increasing the flow rate of the desuperheating water, which can match the rapid cooling of the large flow rate. The stepwise depressurization of the reaction unit, cooling unit, slow cooling unit 15, capillary pressure reducer 17 and pressure control valve V9 can match the rapid depressurization of the large flow rate.

[0067] 3) Temperature Control: Valves V2 and V4 are closed, and valves V1 and V3 are opened, allowing the mixed supercritical fluid to enter reaction unit 11. Valves V1 and V3 are closed, and valves V2 and V4 are opened, allowing the mixed supercritical fluid to enter reaction unit 22. When the reaction unit temperature does not reach supercritical conditions, the average values ​​of temperature sensors TIC2 and TIC3 are transmitted to the control system for controlling the power of electric heater 8, achieving reaction heat replenishment. Valves V6 and V8 are closed, and valves V5 and V7 are opened, allowing the post-reaction fluid to enter cooling unit 13. Valves V5 and V7 are closed, and valves V6 and V8 are opened, allowing the post-reaction fluid to enter cooling unit 24. The cooled intermediate-temperature fluid is further cooled by slow cooling unit 15. If incomplete cooling is detected during the cooling process, temperature sensors TIC4 and TIC5 are interlocked with desuperheating unit 25. The desuperheating water in the desuperheating unit increases its flow rate and acts on the cooling unit and slow cooling unit 15, achieving rapid cooling. This achieves temperature control for the supercritical hydrothermal or solvothermal synthesis system.

[0068] 4) Pressure regulation: Pressure sensors PIC4, PIC5, PIC6, and PIC7 are respectively installed at the outlets of the reaction unit, cooling unit, slow cooling unit 15 and capillary pressure reducer 17 to monitor the pressure drop during the cooling stage. When the system cannot completely reduce the pressure during the cooling process, the pressure control valve V9 is adjusted to completely release the pressure, so as to realize the step-by-step pressure control of the entire system.

[0069] 5) Quality Control of Nano-Zirconium Oxide: The pH value of the reaction solution is monitored online via pH monitor 10. If the pH value is lower than the optimal value, pH monitor 10 is interlocked with flow meter FIC1 to increase the input of stabilizer and ligands in composite storage tank 4, achieving complete stabilization of the tetragonal and cubic phases and reducing the agglomeration of nano-zirconia, thus achieving crystal form stabilization and preventing agglomeration. Temperature, pressure, and reaction time can be changed by altering the electric heating power, pump input pressure, and the length or flow path of the reaction unit, optimizing process parameters and achieving particle size control. The entire system uses titanium-lined stainless steel, nickel-based alloys, or high-temperature resistant non-metallic coatings to reduce pipe corrosion. Furthermore, forward and reverse flushing devices can be designed for each component, including pumps, storage tanks, reactors, and mixers, to reduce batch impact and achieve purity control of nano-zirconia particles. Thus, overall quality control of nano-zirconia particles is achieved.

[0070] 6) Safety Control: Pressure gauges PIC1, PIC2, ​​and PIC3 are interlocked with the motor of the high-pressure pump. If any of the precursor, solvent, or additive circuits experiences overpressure, the high-pressure pump will automatically stop operating, achieving Level 1 safety control. When the reaction unit experiences overpressure, the safety relief valve will open and release pressure, achieving Level 2 safety control. If the system overheats, the system becomes blocked, the pressure relief valve malfunctions, or the system leaks high-temperature fluid, the emergency tank unit 24 will open, and safety valves V10 and V11 will act on the reaction unit and the precursor, solvent, and additive circuits. Cooling water will continue to act until the system cools down and depressurizes, achieving Level 3 safety control.

[0071] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A system for supercritical hydrothermal and solvothermal synthesis of nano-zirconia, characterized in that, It includes a material conveying unit, a mixing and reaction unit, a post-processing unit, and an emergency tank unit (24); The material conveying unit includes a precursor storage tank (1), a solvent storage tank (2), an additive storage tank (3), and a composite storage tank (4). The precursor storage tank (1) and the composite storage tank (4) are connected to the inlet of high-pressure pump one (5) after they merge. The solvent storage tank (2) and the additive storage tank (3) are connected to the inlets of high-pressure pump two (6) and high-pressure pump three (7), respectively. Pressure gauges PIC1, PIC2, ​​and PIC3 are respectively installed at the outlets of high-pressure pump one (5), high-pressure pump two (6), and high-pressure pump three (7). The pressure gauges are interlocked with the motors of the high-pressure pumps at the corresponding positions. A flow meter FIC1 is installed at the outlet of the composite storage tank (4) to regulate the ratio of stabilizer, ligand, and precursor. The mixing reaction unit includes a heater (8), a mixing unit (9), and a reaction unit. The outlet of high-pressure pump 2 (6) is connected to the inlet of the heater (8). The outlet of the heater (8), the outlet of high-pressure pump 1 (5), and the outlet of high-pressure pump 3 (7) are respectively connected to the mixing unit (9). The outlet of the mixing unit (9) is connected to the inlet of the reaction unit. Temperature sensors TIC2 and TIC3 are respectively installed at the inlet and outlet of the reaction unit. Temperature sensor TIC1 is installed on the heater (8). The average value of temperature sensors TIC2 and TIC3 is interlocked with the reading of temperature sensor TIC1. A pH online monitoring device (10) is also installed on the mixing unit (9). The pH online monitoring device (10) is interlocked with the flow meter FIC1 at the outlet of the composite storage tank (4). The post-processing unit includes a cooling unit, a slow cooling unit (15), a capillary pressure reducer (17), a gas-liquid separation unit (18), a solid-liquid separation unit (20), a drying unit (22), and a nano-product storage unit (23) connected in sequence. The gas-liquid separation unit (18) is also connected to a waste gas treatment unit (19), and the solid-liquid separation unit (20) is also connected to a waste liquid treatment unit (21). The inlet and outlet ends of the cooling unit are respectively equipped with temperature sensors. The inlet and outlet ends of the slow cooling unit (15) are respectively equipped with temperature sensors TIC4 and TIC5. A temperature reduction unit (25) is interlocked between temperature sensors TIC4 and TIC5. A pressure control valve V9 is provided on the pipeline connecting the capillary pressure reducer (17) and the gas-liquid separation unit (18). The accident tank unit (24) acts on the mixing reaction unit through interlocking with the first safety valve V10, and acts on the material conveying unit through interlocking with the second safety valve V11.

2. The system for supercritical hydrothermal and solvothermal synthesis of nano-zirconia according to claim 1, characterized in that, The reaction unit includes several reactors arranged in series or in parallel. Each reactor has a valve at its inlet and outlet. The reactors are either reaction vessels or tubular reactors.

3. The system for supercritical hydrothermal and solvothermal synthesis of nano-zirconia according to claim 1, characterized in that, The cooling unit includes several coolers arranged in series or in parallel. Each cooler has a valve at its inlet and outlet. The coolers are coil coolers, shell-and-tube coolers, or finned coolers.

4. The system for supercritical hydrothermal and solvothermal synthesis of nano-zirconia according to claim 1, characterized in that, Pressure sensors PIC4, PIC5, PIC6, and PIC7 are respectively installed at the outlets of the reaction unit, cooling unit, slow cooling unit (15), and capillary pressure reducer (17).

5. The system for supercritical hydrothermal and solvothermal synthesis of nano-zirconia according to claim 1, characterized in that, A steam user (16) circuit is also provided on the slow cooling unit (15).

6. The system for supercritical hydrothermal and solvothermal synthesis of nano-zirconia according to claim 1, characterized in that, The composite storage tank (4) is provided in two or more; the heater (8) is an electromagnetic heater, an infrared heater or a resistance heater; the mixing unit (9) is a T-type three-way mixer, a sleeve-type countercurrent mixer or a cross-type jet mixer; the pressure control valve V9 is a back pressure valve, a proportional unloading valve or an electric pressure regulating valve.

7. A controlled method for preparing nano-zirconia using the system for supercritical hydrothermal synthesis and solvothermal synthesis of nano-zirconia as described in any one of claims 1 to 6, characterized in that, include: Material conveying and mixing / reaction stage: The precursor in the precursor storage tank (1) is mixed with the stabilizer and ligand in the composite storage tank (4) and then transported to the mixing unit (9) by high pressure pump one (5). The additive in the additive storage tank (3) is transported to the mixing unit (9) by high pressure pump three (7). The solvent in the solvent storage tank (2) is transported to the heater (8) by high pressure pump two (6) for heating and then transported to the mixing unit (9). The three materials are fully mixed in the mixing unit (9) and then enter the reaction unit to react. Post-processing stage: The hot fluid generated by the reaction enters the cooling unit. The cooled medium-temperature fluid is further cooled by the slow cooling unit (15). The cooled fluid passes through the capillary pressure reducer (17). The depressurized fluid flows into the gas-liquid separation unit (18). The gas enters the waste gas treatment unit (19) for treatment. The solid-liquid phase enters the solid-liquid separation unit (20). The liquid phase is recycled to the waste liquid treatment unit (21). The solid phase is processed by the drying unit (22) and then stored in the nano-product storage unit (23).

8. The control method according to claim 7, characterized in that, The regulation process includes: Ingredient control: The ratio of stabilizer and ligand to precursor in composite storage tank (4) is controlled by the reading of flow meter FIC1, and the pumping output of high pressure pump one (5), high pressure pump two (6) and high pressure pump three (7) is controlled to achieve precise ingredient control; Flow regulation: When the system needs to switch from a small flow rate to a large flow rate, the flow rate is increased by changing the power of high pressure pump 1 (5), high pressure pump 2 (6) and high pressure pump 3 (7), and the temperature is increased by increasing the power of heater (8). During the cooling and depressurization process, temperature sensors TIC4 and TIC5 are interlocked with the de-cooling unit (25). The de-cooling water of the de-cooling unit (25) acts on the cooling unit and the slow cooling unit (15) by increasing the de-cooling water flow rate to achieve the matching of rapid cooling of large flow rate. The reaction unit, cooling unit, slow cooling unit (15), capillary pressure reducer (17) and pressure control valve V9 achieve the matching of rapid depressurization of large flow rate. Temperature control: When the temperature of the reaction unit does not reach the supercritical condition, the average value of temperature sensors TIC2 and TIC3 is interlocked with temperature sensor TIC1 to control the power of heater (8) and realize reaction heat replenishment; when incomplete cooling is detected during the cooling process, temperature sensors TIC4 and TIC5 are interlocked with the cooling unit (25), and the cooling unit (25) increases the cooling water flow rate to act on the cooling unit and the slow cooling unit (15) to achieve rapid cooling; Pressure regulation: Pressure sensors PIC4, PIC5, PIC6 and PIC7 are respectively installed at the outlets of the reaction unit, cooling unit, slow cooling unit (15) and capillary pressure reducer (17) to monitor the pressure drop during the cooling stage. When the pressure cannot be completely reduced during the cooling process, the pressure control valve V9 is adjusted to completely release the pressure, so as to realize the step-by-step pressure control of the entire system. Nano-zirconia quality control: The stabilizer and ligand materials in the composite storage tank (4) are controlled by interlocking the pH value online monitoring device (10) with the flow meter FIC1 at the outlet of the composite storage tank (4) to achieve crystal stability and prevent agglomeration; the temperature, pressure and reaction time are changed by changing the electric heating power, the pump input pressure, the length of the reaction unit or the flow path to achieve nano-zirconia particle size control. Safety control: Pressure gauges PIC1, PIC2 and PIC3 are interlocked with the motors of high-pressure pump one (5), high-pressure pump two (6) and high-pressure pump three (7) respectively. When any material supply pipeline is over-pressurized, the operation is stopped to achieve first-level safety control. When the reaction unit is over-pressurized, the pressure is released by opening the pressure control valve V9 to achieve second-level safety control. When the system is over-temperature, blocked or there is a high-temperature fluid leakage, the emergency tank unit (24) is opened, and the first safety valve V10 acts on the reaction unit, the second safety valve V11 acts on the material conveying unit, and the cooling unit continues to act until the system is cooled and depressurized to achieve third-level safety control.

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