CN111760510A

CN111760510A - Self-cleaning supercritical hydrothermal synthesis system capable of adjusting reactant concentration on line

Info

Publication number: CN111760510A
Application number: CN202010624317.8A
Authority: CN
Inventors: 王树众; 张宝权; 孙盼盼; 王栋; 刘璐
Original assignee: Xian Jiaotong University
Current assignee: Xian Jiaotong University
Priority date: 2020-07-01
Filing date: 2020-07-01
Publication date: 2020-10-13

Abstract

A self-cleaning supercritical hydrothermal synthesis system for online adjustment of reactant concentration, comprising: the supercritical fluid conveying module, the outlet of which is supercritical solvent; the reactant supply module comprises a precursor supply unit and an additive supply unit, wherein the precursor solution is arranged at an outlet of the precursor supply unit, and the additive solution is arranged at an outlet of the additive supply unit; and the system cleaning module is connected with the supercritical fluid conveying module, the precursor feeding unit and the additive feeding unit, collects waste liquid and provides cleaning water. The invention realizes the online adjustment of the supercritical hydrothermal synthesis reactant concentration, the online addition of the additive, the rapid and uniform mixing of three fluids, the control of the reaction time and the self-cleaning of the system by arranging a plurality of precursor feeding routes in parallel, arranging an additive feeding route, coupling a three-inlet swirl mixer, connecting a reactor with controllable reaction time and having a cleaning function.

Description

Self-cleaning supercritical hydrothermal synthesis system capable of adjusting reactant concentration on line

Technical Field

The invention belongs to the technical field of chemical industry and environmental protection, and particularly relates to a self-cleaning supercritical hydrothermal synthesis system for online adjustment of reactant concentration.

Background

Nanotechnology has important strategic position in the industrial revolution of the 21 st century, and is the leading-edge technology which is the most important and has the greatest development prospect in the 21 st century. The nano material has unique electrical, thermal, magnetic, optical and mechanical properties, and is applied to the fields of electronic information, high-end manufacturing, new energy, green chemical industry, life medicine, military science and technology and the like, so that the revolutionary technical breakthrough in the field is caused, and the nano material has extremely bright application prospect. The preparation of the nano material is the fundamental basis of the wide application of the nano technology, and the high point of the nano technology can be seized only by mastering the preparation technology of the high-end nano material.

The traditional preparation method of nano powder is divided into two main categories of physical method and chemical method. However, the traditional method has complex process equipment, low yield, difficulty in being below 100nm and high difficulty in large-scale production; generally, the subsequent treatment is carried out; meanwhile, organic solvents or highly toxic additive components can be added in some preparation methods, so that serious pollution is caused in production. The price of the nano material is quite high due to various problems faced by the traditional nano manufacturing method, for example, the price of nano titanium dioxide with the wavelength of about 50nm is 30-40 ten thousand per ton, so that the large-scale application of the nano material is severely restricted, and the development of related industries is also restricted.

Supercritical water (SCW) refers to water in a special state having a temperature and pressure higher than its critical point (T ═ 374.15 ℃, P ═ 22.12 MPa). Supercritical water has the properties of liquid water and gaseous water, only a small amount of hydrogen bonds exist in water in the state, the dielectric constant is similar to that of an organic solvent, and the supercritical water has a very high diffusion coefficient and very low viscosity. The supercritical hydrothermal synthesis technology is a green synthesis technology for preparing nano metal powder. The supercritical water heat synthesis technology adopts supercritical water as a reaction medium in a closed high-pressure vessel, and takes the supercritical water as the reaction medium, so that metal salt is subjected to hydrolysis and dehydration reaction in a hydrothermal medium, and then is nucleated, grown and finally forms nano powder with certain granularity and crystal form.

The particles prepared in the supercritical hydrothermal synthesis process have the advantages of uniform particle size distribution, complete crystal grain development, high purity, light particle agglomeration, applicability to cheap raw materials, low operation cost compared with the traditional preparation method, and the technical advantages of preparing the nano metal particles by supercritical hydrothermal synthesis mainly comprise the following aspects:

1. the nucleation rate is extremely high, and the formation of ultrafine particles (10-30 nm) is facilitated;

2. the reaction rate is extremely fast and is improved by several orders of magnitude compared with the conventional method;

3. the reaction space is closed, the medium is water, and the method is pollution-free and environment-friendly;

4. the particle size and the morphology of the product can be controlled by controlling the process parameters;

5. the process is simple, the production cost is low, and the production cost is 5-10% of that of the traditional production method.

In the supercritical hydrothermal synthesis process, substances participating in the reaction mainly comprise three substances:

1. precursor (raw material): generally, salt composed of target metal cation and inert acid radical ion is used as raw material, copper sulfate, copper formate and the like can be adopted for preparing nano copper, and titanium chloride and the like can be adopted for preparing nano titanium dioxide.

2. Additive (organic ligand): macromolecular organic substances are generally used as ligands. The ligands associate with the growing crystal surface, inhibiting further growth of the crystal. For preparing the nano metal, polyvinylpyrrolidone (PVP), hexylamine and the like can be used as the organic ligand.

3. Reaction solvent: supercritical water is generally used as a reaction solvent, and supercritical alcohols (ethanol, ethylene glycol, etc.) may be used as a reaction solvent.

In the supercritical hydrothermal synthesis process, the cold metal salt solution, the high-temperature supercritical water and the organic ligand additive are mixed and then quickly reach a supercritical state, and the inorganic salt reacts to form the nanometer ultrafine particles. In this process, the organic ligand generally associates with the particle surface and acts as a steric hindrance, inhibiting further growth and agglomeration of the grains.

In the research of technological parameters of supercritical hydrothermal synthesis, parameters such as reactant concentration, species and additive concentration need to be adjusted. The existing supercritical hydrothermal synthesis device only has two feeding routes of supercritical fluid and precursor solution, the adjustment of the concentration of the precursor can only be completed in a material blending stage before entering a system, and the online adjustment of the concentration, the online addition of additives and the concentration adjustment cannot be realized. On the other hand, the supercritical hydrothermal synthesis technology can also be used for synthesizing salt nanoparticles (such as lithium iron phosphate nanoparticles), wherein three precursors (a lithium source, an iron source and a phosphorus source) are required. The existing device for preparing the multi-precursor material can only be realized by premixing a plurality of precursors in advance and jointly entering a system, and the concentration ratio of the precursor material cannot be adjusted on line. Furthermore, when the precursor solution is in a solid suspension state (when lithium iron phosphate is prepared, lithium phosphate which is slightly soluble in water can be used as a precursor), the metering pump in the conventional supercritical hydrothermal synthesis device cannot realize feeding and does not have synthesis conditions.

How to realize the online adjustment of the types and the concentrations of the precursors and the additives and the preparation of the multi-precursor nano material and the online adjustment of the precursor proportion are technical problems. The excellent supercritical hydrothermal synthesis system has the functions of online adjustment of reactant concentration, realization of suspension feeding and self-cleaning, so that the system has the capability of synthesizing various nano materials and controls the quality of products.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention aims to provide a self-cleaning supercritical hydrothermal synthesis system for online adjustment of reactant concentration, which is provided with a plurality of precursor feeding routes in parallel, an additive feeding route in a coupling manner, a three-inlet cyclone mixer in a coupling manner, a reactor with controllable reaction time and a cleaning function, and realizes online adjustment of supercritical hydrothermal synthesis reactant concentration, online addition of additives, rapid and uniform mixing of three fluids, control of reaction time and self-cleaning of the system.

In order to achieve the purpose, the invention adopts the technical scheme that:

a self-cleaning supercritical hydrothermal synthesis system for online adjustment of reactant concentration, comprising:

the supercritical fluid conveying module, the outlet of which is supercritical solvent;

the reactant supply module comprises a precursor supply unit and an additive supply unit, wherein the precursor solution is arranged at an outlet of the precursor supply unit, and the additive solution is arranged at an outlet of the additive supply unit;

the mixing reaction module comprises a mixer 15 and a reactor 16, wherein the mixer 15 is provided with a supercritical fluid inlet N1, a precursor inlet N2, an additive inlet N3 and a mixer outlet N4, the supercritical fluid inlet N1 is connected with the outlet of the supercritical fluid conveying module, the precursor inlet N2 is connected with the outlet of the precursor feeding unit, the additive inlet N3 is connected with the outlet of the additive feeding unit, and the mixer outlet N4 is connected with the inlet of the reactor 16;

and the system cleaning module is connected with the supercritical fluid conveying module, the precursor supply unit and the additive supply unit, collects waste liquid and provides cleaning water.

The supercritical fluid conveying module comprises a solvent storage tank 2, a first high-pressure metering pump 3 and an electric heater 4 which are sequentially connected, an outlet of the electric heater 4 is connected with a supercritical fluid inlet N1 of the mixer 15, and the power of the electric heater 4 is stably controlled by a temperature measuring point 21 of the reactor in the reaction process.

The precursor supply unit comprises a precursor storage tank, a low-pressure metering pump, a precursor buffer tank 9, a second high-pressure metering pump 10 and a first piston material column 11 which are sequentially connected, wherein the outlet of the first piston material column 11 is connected with a precursor inlet N2 of the mixer 15; the additive feeding unit comprises an additive storage tank 12, a third high-pressure metering pump 13 and a second piston material column 14 which are connected in sequence, and the outlet of the second piston material column 14 is connected with an additive inlet N3 of the mixer 15.

The precursor storage tanks comprise a first precursor storage tank 5 and a second precursor storage tank 7 which are connected in parallel, and the low-pressure metering pump comprises a first low-pressure metering pump 6 connected with the first precursor storage tank 5 and a precursor cache tank 9 and a second low-pressure metering pump 8 connected with the second precursor storage tank 7 and the precursor cache tank 9.

All be provided with the agitator in solvent storage tank 2, first precursor storage tank 5, second precursor storage tank 7, precursor buffer tank 9 and the additive storage tank 12, blender 15 is the whirl blender, is provided with blender ultrasonic generator 19, reactor 16 is snakelike tubular reactor of arranging, is provided with reactor ultrasonic generator 27, and the intermediate position is equipped with the middle sample connection of several, is controlled by first proportion unloading valve 22, second proportion unloading valve 23 and first stop valve 24, second stop valve 25, and follow-up system 17 is inserted to the middle sample connection.

A valve V10 is arranged between the first high-pressure metering pump 3 and the electric heater 4, a valve V11 is arranged between the first low-pressure metering pump 6 and the precursor buffer tank 9, a valve V12 is arranged between the second low-pressure metering pump 8 and the precursor buffer tank 9, a valve V13 is arranged between the precursor buffer tank 9 and the second high-pressure metering pump 10, the outlet of the second high-pressure metering pump 10 is divided into two paths, one path is connected with the first piston material column 11 and is provided with a valve V14, the other path is connected with the precursor inlet N2 and is provided with a valve V16, a valve V15 is arranged between the first piston material column 11 and the precursor inlet N2, the outlet of the third high-pressure metering pump 13 is divided into two paths, one path is connected with the second piston material column 14 and is provided with a valve V17, the other path is connected with the additive inlet N3 and is provided with a valve V19, a valve V18 is arranged between the, the intermediate outlets of the reactor 16 are respectively provided with valves V20-V23 which are connected with a subsequent treatment system 17.

The system cleaning module comprises a tap water storage tank 1 and a waste liquid collecting tank 18, wherein the tap water storage tank 1 is connected with an outlet of a solvent storage tank 2 through a cleaning pipeline with valves V1 and V2, is connected with an outlet of a first precursor storage tank 5 through a cleaning pipeline with valves V1 and V4, is connected with an outlet of a second precursor storage tank 7 through a cleaning pipeline with valves V1 and V6, is connected with an outlet of an additive storage tank 12 through a cleaning pipeline with valves V1 and V8, and the waste liquid collecting tank 18 is connected with a bottom waste liquid discharge port of the solvent storage tank 2, the first precursor storage tank 5, the second precursor storage tank 7 and the additive storage tank 12.

The outlet of the first high-pressure metering pump 3 is provided with a cleaning branch connected to the solvent storage tank 2 with a valve V3, the outlet of the first low-pressure metering pump 6 is provided with a cleaning branch connected to the first precursor storage tank 5 with a valve V3, the outlet of the second low-pressure metering pump 8 is provided with a cleaning branch connected to the second precursor storage tank 7 with a valve V3, and the outlet of the third high-pressure metering pump 13 is provided with a cleaning branch connected to the additive storage tank 12 with a valve V3.

The invention also provides a synthesis method of the self-cleaning supercritical hydrothermal synthesis system based on the online adjustment of the reactant concentration, which comprises the following steps of online adjustment of the reactant concentration and self-cleaning of the system:

wherein the online adjustment of the reactant concentration comprises the following steps:

step 1, when a single precursor material is synthesized, a precursor solution is filled in a first precursor storage tank 5, water is filled in a second precursor storage tank 7, the precursor solution and the water are collected in a precursor cache tank 9 through a first low-pressure metering pump 6 and a second low-pressure metering pump 8 respectively, and online adjustment of the concentration of the precursor solution entering a mixer 15 is realized by adjusting the flow rates of the first low-pressure metering pump 6 and the second low-pressure metering pump 8 and keeping the total flow rate unchanged;

step 2, when synthesizing a multi-precursor material, different precursor solutions are respectively contained in the first precursor storage tank 5 and the second precursor storage tank 7, are collected in the precursor cache tank 9, and then enter the precursor inlet N2 of the mixer 15 through the second high-pressure metering pump 10, and the on-line adjustment of the concentration ratio of the multiple precursors entering the mixer 15 is realized by adjusting the flow rates of the first low-pressure metering pump 6 and the second low-pressure metering pump 8;

step 3, when the precursor is suspension, adding the suspension into the first piston material column 11, closing the valve V16, opening the valves V14 and V15, and pumping pure water into the first piston material column 11 by the second high-pressure metering pump 10 to realize the feeding of the suspension;

the self-cleaning of the system comprises the following steps:

step 1, cleaning a storage tank: opening a cleaning valve V1-V9, closing V10-V19, and starting the first low-pressure metering pump 6, the second low-pressure metering pump 8, the first high-pressure metering pump 3 and the third high-pressure metering pump 13;

step 2, cleaning the cache tank: opening valves V11, V12;

and 3, cleaning a mixed reaction system: valves V3, V5, V7, V9 are closed, valves V10, V13, V16, V19 are opened.

The method for realizing the online adjustment of the concentrations of the two precursors comprises the following steps: the first low pressure metering pump 6 and the second low pressure metering pump 8 are adjusted simultaneously to keep the total flow constant.

Compared with the prior art, the invention has the beneficial effects that:

1. precursor paths are arranged in parallel and collected into a precursor buffer tank through an accurate metering pump: the online adjustment of the precursor concentration in the system operation process can be realized through the matching adjustment of the two low-pressure metering pumps; when preparing the multi-precursor nano material, the plurality of precursors can be separately fed, and the concentration ratio of the multi-precursor can be adjusted on line through a low-pressure metering pump.

2. An additive feed line was set and coupled to a three-inlet swirl mixer: the additive feeding route can switch between pure water and additive solution on line; the flow rates of the additive solution and the precursor solution are close, so that the swirl can be realized in the swirl mixer, and the rapid and uniform mixing of the mixed fluid is effectively promoted; the mixer applies an ultrasonic field to the mixing area through the ultrasonic generator, and the uniformity of mixing is further ensured.

3. Coupling reactor capable of intermediate sampling: the reactor is a tubular reactor coiled in a snake shape, the flow distance of fluid in a certain flow and in a certain time is accurately calculated in a middle reaction pipe section, a plurality of middle sampling ports are arranged, the control of reaction time can be realized, and reaction intermediate products can be researched. An ultrasonic field is applied to a reflecting area in the reactor through an ultrasonic generator, so that the problem of uneven fluid components caused by gravity and change of flow direction in the pipe is effectively avoided, and the distribution range of the particle size of the product is narrowed.

4. The self-cleaning pipeline is innovatively arranged, the system can be self-cleaned by adopting the original power source of the system operation, the storage tank in front of the pump can be cleaned by opening and closing the valve, and the water pump does not need to be additionally arranged.

Drawings

FIG. 1 is a schematic diagram of the system of the present invention.

FIG. 2 is a schematic diagram of a cyclone mixer.

FIG. 3 is a sectional view of a part of the swirl mixer.

FIG. 4 is a schematic diagram of the structure of the reactor.

Wherein: the device comprises a deionized water storage tank 1, a solvent storage tank 2, a first high-pressure metering pump 3, an electric heater 4, a first precursor storage tank 5, a first low-pressure metering pump 6, a second precursor storage tank 7, a second low-pressure metering pump 8, a precursor cache tank 9, a second high-pressure metering pump 10, a first piston material column 11, an additive storage tank 12, a third high-pressure metering pump 13, a second piston material column 14, a mixer 15, a reactor 16, a post-treatment system 17, a waste liquid collection tank 18, a mixer ultrasonic generator 19, a reaction tube 20, a reaction temperature measuring point 21, a first proportional unloading valve 22, a first stop valve 23, a second proportional unloading valve 24, a second stop valve 25, a back pressure valve 26 and a reactor ultrasonic generator 27.

Detailed Description

In order to make the technical solutions of the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It should be noted that the terms "first," "second," and the like in the description and claims of the present invention and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the invention described herein are capable of operation in sequences other than those illustrated or described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.

In the description of the present invention, "a plurality" means two or more unless otherwise specified. Unless expressly stated or limited otherwise, the terms "mounted," "connected," and "connected" are intended to be inclusive and mean, for example, that they may be fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

The invention is described in further detail below with reference to the accompanying drawings:

as shown in fig. 1, the self-cleaning supercritical hydrothermal synthesis system for on-line adjustment of reactant concentration of the present invention comprises:

the supercritical fluid conveying module comprises a solvent storage tank 2, a first high-pressure metering pump 3 and an electric heater 4 which are sequentially connected, wherein the outlet of the electric heater 4 is connected with a supercritical fluid inlet N1 of a mixer 15, the power of the electric heater 4 is stably controlled by a temperature measuring point 21 of the reactor in the reaction process, a stirrer is arranged in the solvent storage tank 2, and when the system is started, water (or alcohol solvents and the like) in the solvent storage tank 2 enters a supercritical fluid inlet N1 of the mixer 15 through the first high-pressure metering pump 3 and the electric heater 4.

The reactant supply module comprises a precursor supply unit and an additive supply unit, wherein the precursor solution is arranged at an outlet of the precursor supply unit, and the additive solution is arranged at an outlet of the additive supply unit; in the invention, the precursor supply unit comprises a precursor storage tank, a low-pressure metering pump, a precursor buffer tank 9, a second high-pressure metering pump 10 and a first piston material column 11 which are connected in sequence, wherein the outlet of the first piston material column 11 is connected with a precursor inlet N2 of a mixer 15; preferably, an additive feeding circuit is provided in the embodiment, the additive feeding unit comprises an additive storage tank 12, a third high-pressure metering pump 13 and a second piston material column 14 which are connected in sequence, an outlet of the second piston material column 14 is connected with an additive inlet N3 of the mixer 15, and the additive in the additive storage tank 12 enters an additive inlet N3 of the mixer through the high-pressure metering pump 13 to form a rotational flow with the precursor solution from the inlet N2; when the additive is in suspension, feeding may be accomplished by a plunger material column 14. Preferably, two precursor feeding paths are arranged in parallel in this embodiment, each precursor storage tank includes a first precursor storage tank 5 and a second precursor storage tank 7 which are connected in parallel, the low-pressure metering pump includes a first low-pressure metering pump 6 which is connected with the first precursor storage tank 5 and the precursor cache tank 9 and a second low-pressure metering pump 8 which is connected with the second precursor storage tank 7 and the precursor cache tank 9, the two paths are collected into the precursor cache tank 9 together, a stirrer is arranged in the precursor cache tank 9, and precursor solution enters a precursor inlet N2 of the mixer 15 through the second high-pressure metering pump 10.

The mixing reaction module comprises a mixer 15 and a reactor 16, wherein the mixer 15 is provided with a supercritical fluid inlet N1, a precursor inlet N2, an additive inlet N3 and a mixer outlet N4, the supercritical fluid inlet N1 is connected with the outlet of the supercritical fluid conveying module, the precursor inlet N2 is connected with the outlet of the precursor feeding unit, the additive inlet N3 is connected with the outlet of the additive feeding unit, and the mixer outlet N4 is connected with the inlet of the reactor 16.

And the system cleaning module is connected with the supercritical fluid conveying module, the precursor supply unit and the additive supply unit, collects waste liquid and provides cleaning water, and comprises a tap water storage tank 1 and a waste liquid collecting tank 18.

Referring to fig. 2, the mixer 15 is provided with a mixer ultrasonic wave generating device 19, and an ultrasonic external field is applied to the mixing region in the mixer 15 through the ultrasonic wave generating device 19 to promote rapid and uniform mixing of the supercritical fluid, the precursor solution, and the additive in the fluid after mixing in the mixer 15, and then the fluid exits through a mixer outlet N4 and enters the reactor 16.

Referring to fig. 3, the mixer 15 is a cyclone mixer, and the precursor solution and the additive solution entering from the N2 and N3 inlets form a cyclone, and are mixed with the supercritical solvent from the N1 inlet to increase the temperature, so that the reaction occurs.

Referring to fig. 4, the reactor 16 is a tubular reactor arranged in a serpentine shape, a reactor ultrasonic wave generating device 27 is arranged, a temperature measuring point 21 is arranged on a reaction pipe section for monitoring the reaction temperature in real time, two groups of intermediate sampling ports are arranged on the reactor pipe section by accurately calculating the flow distance of fluid in a certain flow rate and in a certain time, each sampling port is composed of a proportional unloading valve 22(24) and a stop valve 23(25), and the control of the reaction time can be realized, wherein the intermediate sampling ports include but are not limited to 3 and are connected to a subsequent system 17. The reactor 16 applies an ultrasonic external field through the ultrasonic wave generating device 27 to avoid uneven flow of the reaction fluid in the reaction tube 20. The reacted fluid leaving the reactor enters a post-treatment system 17 for cooling and separation.

For convenient control, the invention arranges the valves as follows:

a valve V10 is arranged between the first high-pressure metering pump 3 and the electric heater 4, a valve V11 is arranged between the first low-pressure metering pump 6 and the precursor buffer tank 9, a valve V12 is arranged between the second low-pressure metering pump 8 and the precursor buffer tank 9, a valve V13 is arranged between the precursor buffer tank 9 and the second high-pressure metering pump 10, an outlet of the second high-pressure metering pump 10 is divided into two paths, one path is connected with the first piston material column 11 and is provided with a valve V14, the other path is connected with the precursor inlet N2 and is provided with a valve V16, a valve V15 is arranged between the first piston material column 11 and the precursor inlet N2, an outlet of the third high-pressure metering pump 13 is divided into two paths, one path is connected with the second piston material column 14 and is provided with a valve V17, the other path is connected with the additive inlet N3 and is provided with a valve V19, a valve V18 is arranged between the second piston material column 14 and the additive inlet N3, intermediate outlets of, the post-processing system 17 is connected.

Tap water storage tank 1 is connected with the outlet of solvent storage tank 2 through a cleaning pipeline with valves V1 and V2, connected with the outlet of first precursor storage tank 5 through cleaning pipelines with valves V1 and V4, connected with the outlet of second precursor storage tank 7 through cleaning pipelines with valves V1 and V6, connected with the outlet of additive storage tank 12 through cleaning pipelines with valves V1 and V8, and waste liquid collection tank 18 is connected with the bottom waste liquid discharge port of solvent storage tank 2, first precursor storage tank 5, second precursor storage tank 7 and additive storage tank 12.

the self-cleaning of the system comprises the following steps:

step 2, cleaning the cache tank: opening valves V11, V12;

In summary, the invention discloses a self-cleaning supercritical hydrothermal synthesis system for online adjustment of reactant concentration, and the online adjustment of precursor concentration and the online adjustment of concentration ratio among precursors during preparation of a multi-precursor material can be realized by arranging a parallel precursor path, and collecting a multi-precursor solution after accurate measurement into a precursor buffer tank. By arranging an additive feeding route and coupling a swirl mixer applying an ultrasonic field, the online addition of the additive can be realized, and the rapid and uniform mixing of the fluid is effectively promoted. Through setting up the self-cleaning pipeline, need not to realize the washing of full system under the condition of additionally setting up the water pump. The control of the reaction time is realized by coupling the middle sampling reactor, and the ultrasonic field is applied to the reaction area, so that the uneven components of the reaction fluid are avoided, and the quality of the nano-particle product is effectively ensured.

It will be appreciated by those skilled in the art that the above-described embodiments are exemplary and can be modified by those skilled in the art, and that the structures described in the various embodiments can be freely combined without conflict in structure or principle, thereby solving the technical problem of the present invention.

Having described the embodiments of the present invention in detail, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the scope and spirit of the appended claims, and the invention is not limited to the exemplary embodiments set forth in the specification.

Claims

1. A self-cleaning supercritical hydrothermal synthesis system for online adjustment of reactant concentration, comprising:

the mixing reaction module comprises a mixer (15) and a reactor (16), wherein the mixer (15) is provided with a supercritical fluid inlet N1, a precursor inlet N2, an additive inlet N3 and a mixer outlet N4, the supercritical fluid inlet N1 is connected with the outlet of the supercritical fluid conveying module, the precursor inlet N2 is connected with the outlet of the precursor feeding unit, the additive inlet N3 is connected with the outlet of the additive feeding unit, and the mixer outlet N4 is connected with the inlet of the reactor (16);

2. The self-cleaning supercritical hydrothermal synthesis system for online regulation of reactant concentration according to claim 1, wherein the supercritical fluid delivery module comprises a solvent storage tank (2), a first high-pressure metering pump (3) and an electric heater (4) which are connected in sequence, the outlet of the electric heater (4) is connected with a supercritical fluid inlet N1 of the mixer (15), and the power of the electric heater (4) is controlled and stabilized by a reactor temperature measuring point (21) during the reaction process.

3. The self-cleaning supercritical hydrothermal synthesis system according to claim 1, wherein the precursor supply unit comprises a precursor storage tank, a low pressure metering pump, a precursor buffer tank (9), a second high pressure metering pump (10) and a first piston material column (11) which are connected in sequence, and the outlet of the first piston material column (11) is connected with a precursor inlet N2 of the mixer (15); the additive feeding unit comprises an additive storage tank (12), a third high-pressure metering pump (13) and a second piston material column (14) which are sequentially connected, and an outlet of the second piston material column (14) is connected with an additive inlet N3 of the mixer (15).

4. The system of claim 1, wherein the precursor tanks comprise a first precursor tank (5) and a second precursor tank (7) connected in parallel, and the low-pressure metering pump comprises a first low-pressure metering pump (6) connected to the first precursor tank (5) and the precursor buffer tank (9), and a second low-pressure metering pump (8) connected to the second precursor tank (7) and the precursor buffer tank (9).

5. The self-cleaning supercritical hydrothermal synthesis system for online adjustment of reactant concentration according to claim 4, wherein stirrers are arranged in the solvent storage tank (2), the first precursor storage tank (5), the second precursor storage tank (7), the precursor buffer tank (9) and the additive storage tank (12), the mixer (15) is a cyclone mixer, a mixer ultrasonic generator (19) is arranged, the reactor (16) is a tubular reactor arranged in a serpentine shape, a reactor ultrasonic generator (27) is arranged, a plurality of intermediate sampling ports are arranged in the intermediate positions, and the intermediate sampling ports are controlled by a first proportional unloading valve (22), a first stop valve (23), a second proportional unloading valve (24) and a second stop valve (25), and are connected to the subsequent system (17).

6. The self-cleaning supercritical hydrothermal synthesis system for online adjustment of reactant concentration according to claim 4 or 5, characterized in that a valve V10 is provided between the first high-pressure metering pump (3) and the electric heater (4), a valve V11 is provided between the first low-pressure metering pump (6) and the precursor buffer tank (9), a valve V12 is provided between the second low-pressure metering pump (8) and the precursor buffer tank (9), a valve V13 is provided between the precursor buffer tank (9) and the second high-pressure metering pump (10), the outlet of the second high-pressure metering pump (10) is divided into two paths, one path is connected with the first piston material column (11) and provided with a valve V14, the other path is connected with the inlet N2 and provided with a valve V16, a valve V15 is provided between the first piston material column (11) and the precursor inlet N2, the outlet of the third high-pressure metering pump (13) is divided into two paths, one path is connected with the second piston material column (14) and is provided with a valve V17, the other path is connected with an additive inlet N3 and is provided with a valve V19, a valve V18 is arranged between the second piston material column (14) and the additive inlet N3, and each middle outlet of the reactor (16) is respectively provided with a valve V20-V23.

7. The self-cleaning supercritical hydrothermal synthesis system with on-line adjustment of reactant concentration according to claim 4 or 5, characterized in that the system cleaning module comprises a tap water storage tank (1) and a waste liquid collection tank (18), the tap water storage tank (1) is connected with the outlet of the solvent storage tank (2) through a cleaning pipeline with valves V1 and V2, the outlet of the first precursor storage tank (5) is connected through a cleaning pipeline with valves V1 and V4, the outlet of the second precursor storage tank (7) is connected through a cleaning pipeline with valves V1 and V6, the outlet of the additive storage tank (12) is connected through a cleaning pipeline with valves V1 and V8, and the waste liquid collection tank (18) is connected with the solvent storage tank (2), the first precursor storage tank (5), the second precursor storage tank (7) and the bottom waste liquid discharge port of the additive storage tank (12).

8. The system for supercritical hydrothermal synthesis with online adjustment of reactant concentration according to claim 7, characterized by the fact that the first high pressure metering pump (3) outlet is provided with a purge branch with valve V3 connected to solvent tank (2), the first low pressure metering pump (6) outlet is provided with a purge branch with valve V3 connected to first precursor tank (5), the second low pressure metering pump (8) outlet is provided with a purge branch with valve V3 connected to second precursor tank (7), the third high pressure metering pump (13) outlet is provided with a purge branch with valve V3 connected to additive tank (12).

9. The synthesis method of the self-cleaning supercritical hydrothermal synthesis system for regulating the concentration of the reactant on line according to claim 8 is characterized by comprising the following steps of regulating the concentration of the reactant on line and self-cleaning the system:

step 1, when a single precursor material is synthesized, a precursor solution is filled in a first precursor storage tank (5), water is filled in a second precursor storage tank (7), the precursor solution and the water are collected in a precursor cache tank (9) through a first low-pressure metering pump (6) and a second low-pressure metering pump (8), and online adjustment of the concentration of the precursor solution entering a mixer (15) is realized by adjusting the flow rates of the first low-pressure metering pump (6) and the second low-pressure metering pump (8) and keeping the total flow rate unchanged;

step 2, when a multi-precursor material is synthesized, different precursor solutions are respectively contained in a first precursor storage tank (5) and a second precursor storage tank (7), are collected in a precursor cache tank (9), then enter a precursor inlet N2 of a mixer (15) through a second high-pressure metering pump (10), and the concentration ratio of the multiple precursors entering the mixer (15) is adjusted on line by adjusting the flow rates of a first low-pressure metering pump (6) and a second low-pressure metering pump (8);

step 3, when the precursor is suspension, adding the suspension into the first piston material column (11), closing the valve V16, opening the valves V14 and V15, and pumping pure water into the first piston material column (11) by the second high-pressure metering pump (10) to realize the feeding of the suspension;

the self-cleaning of the system comprises the following steps:

step 1, cleaning a storage tank: opening a cleaning valve V1-V9, closing V10-V19, and starting a first low-pressure metering pump (6), a second low-pressure metering pump (8), a first high-pressure metering pump (3) and a third high-pressure metering pump (13);

step 2, cleaning the cache tank: opening valves V11, V12;

10. The synthesis process according to claim 9, characterized in that the first low-pressure metering pump (6) and the second low-pressure metering pump (8) are regulated simultaneously, keeping the total flow constant and realizing the on-line regulation of the concentrations of the two precursors.