Continuous powder production system and method of producing the same

Abstract

The present application relates to a kind of powder continuous preparation system and its preparation method, the powder continuous preparation system includes: raw material supply device, mixer, reaction device, concentration device and separation device.Raw material supply device is two groups, raw material supply device includes raw material tank, conveying assembly and preheater, raw material tank is communicated with preheater by conveying assembly, mixer has feed inlet and discharge port, feed inlet is two, and two feed inlets are communicated with the preheater of two groups of raw material supply device respectively, reaction device includes aging tank, discharge port is communicated with aging tank, concentration device is communicated with aging tank, concentration device is used to concentrate after aging reaction, separation device is communicated with concentration device, separation device is used to separate and form powder concentrate product.The powder continuous preparation system of the present application can be continuously mixed by raw material, to realize the continuous of powder, and production efficiency is higher, and the stability and consistency of powder same batch are better.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of powder preparation, in particular to a powder continuous preparation system and a preparation method thereof. BACKGROUND

[0002] In the face of the high dependence on imported conductive silver powder for photovoltaic cells, especially heterojunction cells, and the low degree of self-control, the application demand of high-performance photovoltaic cells cannot be met.

[0003] In the silver powder preparation process, there are mechanical grinding, chemical reduction, plasma and other technical routes, among which chemical reduction has the most widely used method due to its mild conditions and simple process, but there are problems such as poor controllability of micro-morphology and particle size distribution. For example, the traditional chemical reduction method often uses a batch process and a kettle mixer, which not only greatly reduces the production efficiency due to the auxiliary links such as loading and unloading, cleaning, and temperature rising and falling, but also seriously affects the product quality stability due to the poor batch consistency caused by the magnification effect of the mixer and the uneven mass transfer-reaction, and due to the strong reactivity of silver ions, the silver powder preparation reactor is usually made of glass or titanium, which greatly increases the difficulty and processing cost of the mixer magnification. SUMMARY

[0004] The present application aims to at least solve one of the technical problems in the related art to some extent.

[0005] To this end, an embodiment of the present application provides a powder continuous preparation system, which can continuously mix raw materials to continuously produce powder, has high production efficiency, and has good stability and consistency of the same batch of powder.

[0006] An embodiment of the present application also provides a powder continuous preparation method.

[0007] The powder continuous preparation system and the preparation method thereof according to the embodiments of the present application include: a raw material supply device, the raw material supply device is at least two groups, the raw material supply device includes a raw material tank, a conveying assembly and a preheater, the raw material tank is communicated with the preheater through the conveying assembly; a mixer, the mixer has a feeding port and a discharging port, the feeding port is at least two, and the two feeding ports are communicated with the preheaters of the two groups of raw material supply devices respectively; a reaction device, the reaction device includes an aging tank, the discharging port is communicated with the aging tank; a concentration device, the concentration device is communicated with the aging tank, and the concentration device is used for concentrating the reaction product after aging; a separation device, the separation device is communicated with the concentration device, and the separation device is used for separating and forming powder from the concentrated product.

[0008] The powder continuous preparation system according to the embodiments of the present application can save a large number of auxiliary operations in the batch process, realize continuous uninterrupted chemical reduction preparation of the powder, and improve the production efficiency of the powder. In addition, the powder continuous preparation system according to the embodiments of the present application can realize continuous uninterrupted production process, effectively eliminate the difference between batches in the traditional "one-pot method" batch process, and fundamentally solve the problems of batch stability and consistency of the product. Moreover, the powder continuous preparation system according to the embodiments of the present application adopts modular design, so that it can be repaired or replaced individually without affecting the operation of the whole system, thereby ensuring the economy of manufacturing and operation and maintenance of the system. Further, the powder continuous preparation system according to the embodiments of the present application can adjust the supply frequency of the powder continuous preparation system according to the size of the production load, so that the production capacity can be adjusted and controlled.

[0009] In some embodiments, the reaction device further comprises a buffer tank, the discharge port is in communication with the buffer tank, and the buffer tank is in communication with the aging tank.

[0010] In some embodiments, the mixer comprises a mixing cavity, a discharge pipe and two feed pipes, one end of the feed pipe is in communication with the mixing cavity, the other end of the feed pipe has the feed port, one end of the discharge pipe is in communication with the mixing cavity, the other end of the discharge pipe has the discharge port, and the angle θ between the feed pipe and the discharge pipe is adjustable, the value of the angle θ is greater than or equal to 60° and less than or equal to 120°.

[0011] In some embodiments, the concentration device comprises a concentration tank and a scraper, the scraper is arranged in the concentration tank, the concentration tank is provided with a discharge port and an overflow port, the discharge port is arranged at the bottom of the concentration tank for discharging the concentrated product, and the overflow port is located at the upper end of the concentration tank for overflowing the waste liquid.

[0012] In some embodiments, the lower end of the concentration tank has a tapered section, the tip of the tapered section is arranged downward, the taper of the tapered section is greater than or equal to 1 and less than or equal to 2, the height of the tapered section is L1, the total height of the concentration cylinder is L2, and the ratio of L2 / L1 is greater than or equal to 2 and less than or equal to 4.

[0013] In some embodiments, the separation device comprises a separation tank, a sprayer, a filter core, a scraper and a dryer, the filter core is arranged in the separation tank for filtering the concentrated product, the sprayer is located in the separation tank and arranged above the filter core for washing the concentrated product, the dryer is in communication with the separation tank for drying the concentrated product, and the scraper is used for dispersing the dried product to form the powder.

[0014] In some embodiments, the inner walls of the raw material tank, the mixer, the buffer tank, the aging tank, the concentration device and the connecting pipelines thereof are provided with a plastic protective layer.

[0015] The powder continuous preparation method according to another embodiment of the present application is applied to the powder continuous preparation system according to any one of the embodiments of the present application, and comprises the following steps:

[0016] The metal salt is put into one of the raw material tanks to form a precursor solution, and the reducing agent and the auxiliary agent are put into another of the raw material tanks to form a reducing agent solution;

[0017] The precursor solution and the reducing agent solution are heated to a preset temperature by the two preheaters respectively;

[0018] The heated precursor solution and the reducing agent solution are injected into the mixer through the two feed ports respectively and undergo a reduction reaction to generate a reaction mixture containing metal particles;

[0019] The reaction mixture is introduced into the aging tank and aged for a preset time;

[0020] The aged reaction mixture is introduced into the concentration device for sedimentation, so that waste liquid is discharged from the overflow port and the concentrated product is discharged from the bottom of the concentration device;

[0021] The concentrated product is introduced into the separation device for filtration, washing and drying, so that the concentrated product forms a powder.

[0022] The powder continuous preparation method according to the embodiments of the present application can save a large number of auxiliary operations in the batch process, realize continuous and uninterrupted chemical reduction preparation of the powder, and improve the production efficiency of the powder. In addition, the powder continuous preparation method according to the embodiments of the present application can realize continuous and uninterrupted production process, effectively eliminate the differences between batches in the traditional "one-pot method" batch process, and fundamentally solve the problems of batch stability and consistency of the product. Furthermore, the powder continuous preparation system according to the embodiments of the present application adopts modular design, so that it can be repaired or replaced individually without affecting the operation of the whole system, thereby ensuring the economy of manufacturing and operation and maintenance of the system. Further, the powder continuous preparation method according to the embodiments of the present application can realize the adjustable and controllable production capacity by means of raw material supply, local "one standby one use" and overall expansion of the powder continuous preparation system according to the size of the production load.

[0023] In some embodiments, the metal salt is a silver salt, and the auxiliary agent is a composite auxiliary agent composed of polyvinylpyrrolidone with different polymerization degrees, wherein the monomer molar ratio of polyvinylpyrrolidone K89-96 and polyvinylpyrrolidone K29-32 is between 1:1 and 1:3; or the monomer molar ratio of polyvinylpyrrolidone K60 and polyvinylpyrrolidone K29-32 is between 4:1 and 2:1; or the monomer molar ratio of polyvinylpyrrolidone K89-9, polyvinylpyrrolidone K60 and polyvinylpyrrolidone K29-32 is 2:1:1.

[0024] In some embodiments, the heating temperature of the preheater is greater than or equal to 30°C and less than or equal to 60°C.

[0025] In some embodiments, the Reynolds number of the precursor solution and the reducing agent solution at the inlet of the mixer is greater than or equal to 800 and less than or equal to 1800, and the mixing time of the precursor solution and the reducing agent solution in the mixer is greater than or equal to 0.1 s and less than or equal to 0.8 s.

[0026] In some embodiments, the residence time of the reaction mixture in the aging tank is greater than or equal to 25 min and less than or equal to 35 min; the residence time of the aged reaction mixture in the concentration device is greater than or equal to 25 min and less than or equal to 35 min; and the filtration, washing and drying time of the concentrated product in the separation device is greater than or equal to 30 min and less than or equal to 60 min. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is a schematic diagram of a powder continuous preparation system according to an embodiment of the present application.

[0028] Figure 2A is a schematic diagram of a mixer of a powder continuous preparation system according to a first embodiment of the present application.

[0029] Figure 2B is a schematic diagram of a mixer of a powder continuous preparation system according to a second embodiment of the present application.

[0030] Figure 2C is a schematic diagram of a mixer of a powder continuous preparation system according to a third embodiment of the present application.

[0031] Figure 3A is a schematic diagram of silver powder prepared by a powder continuous preparation method according to a first embodiment of the present application.

[0032] Figure 3B is a schematic diagram of silver powder prepared by a powder continuous preparation method according to a second embodiment of the present application.

[0033] Figure 3Cis a schematic diagram of silver powder prepared by the powder continuous preparation method of the third embodiment of the present application.

[0034] Figure 3D is a schematic diagram of silver powder prepared by the powder continuous preparation method of the fourth embodiment of the present application.

[0035] Figure 3E is a schematic diagram of silver powder prepared by the powder continuous preparation method of the fifth embodiment of the present application.

[0036] Figure 3F is a schematic diagram of silver powder prepared by the powder continuous preparation method of the fifth embodiment of the present application.

[0037] Reference Signs:

[0038] 1, raw material supply device; 11, raw material tank; 111, first raw material tank; 112, second raw material tank; 12, preheater; 121, first preheater; 122, second preheater; 13, conveying assembly; 131, pipeline; 132, pump group; 133, valve group;

[0039] 2, mixer; 21, feed pipe; 211, first feed port; 212, second feed port; 22, discharge pipe; 221, discharge port; 23, mixing cavity;

[0040] 3, reaction device; 31, aging tank; 311, first plastic stirring paddle; 32, buffer tank; 321, second plastic stirring paddle;

[0041] 4, concentration device; 41, concentration tank; 411, overflow port; 412, discharge port; 413, conical section; 42, scraper member;

[0042] 5, separation device; 51, separation tank; 52, sprayer; 53, filter core; 54, dryer; 541, gas supply assembly; 55, vacuum device. DETAILED DESCRIPTION

[0043] Embodiments of the present application are described in detail below, examples of which are shown in the accompanying drawings. The embodiments described below by reference to the accompanying drawings are exemplary and are intended to explain the present application, and cannot be understood as a limitation of the present application.

[0044] The following description refers to the accompanying drawings, which are meant to be exemplary and not limiting as to the scope of the application. Figure 1 A powder continuous preparation system and a preparation method thereof according to an embodiment of the present application are described below with reference to FIG. 3.

[0045] As Figure 1As shown in FIG. 2, the powder continuous preparation system according to the embodiment of the present application comprises a raw material supply device 1, a mixer 2, a reaction device 3, a concentration device 4 and a separation device 5. The raw material supply device 1 is at least two groups, and the raw material supply device 1 comprises a raw material tank 11, a conveying assembly 13 and a preheater 12, and the raw material tank 11 is communicated with the preheater 12 through the conveying assembly 13. The mixer 2 has a feeding port and a discharging port 221, the feeding port is at least two, and the two feeding ports are respectively communicated with the preheaters 12 of the two groups of raw material supply devices 1, and the reaction device 3 comprises an aging tank 31, and the discharging port 221 is communicated with the aging tank 31. The concentration device 4 is communicated with the aging tank 31, the concentration device 4 is used for concentrating the aged reaction material, and the separation device 5 is communicated with the concentration device 4, and the separation device 5 is used for separating and forming the powder from the concentrated product.

[0046] The powder continuous preparation system according to the embodiment of the present application can save a large number of auxiliary operations in the batch process by continuously mixing and reacting the raw materials, continuously aging and concentrating the materials, realize the continuous and uninterrupted chemical reduction preparation of the powder, and improve the production efficiency of the powder. In addition, the powder continuous preparation system according to the embodiment of the present application can realize the continuous and uninterrupted production process, effectively eliminate the differences between batches in the traditional "one-pot method" batch process, and fundamentally solve the problems of batch stability and consistency. Moreover, the powder continuous preparation system according to the embodiment of the present application adopts modular design, and thus can be individually repaired or replaced without affecting the operation of the whole system, thereby ensuring the economy of manufacturing and operation and maintenance of the system. Further, the powder continuous preparation system according to the embodiment of the present application can adjust the supply frequency of the powder continuous preparation system according to the size of the production load, so as to realize the adjustable and controllable production capacity.

[0047] It can be understood that the raw material supply device 1 is two groups or more than two groups. In the embodiment of the present application, the raw material supply device 1 is two groups, and the feeding port is two. The two raw material supply devices 1 correspond to the two feeding ports one by one. Specifically, one of the raw material supply devices 1 comprises a first raw material tank 111 and a first preheater 121, and the other raw material supply device 1 comprises a second raw material tank 112 and a second preheater 122, and the conveying assembly 13 is arranged between the first raw material tank 111 and the first preheater 121 and between the second raw material tank 112 and the second preheater 122.

[0048] As shown in FIG. 2, the powder continuous preparation system according to the embodiment of the present application comprises a raw material supply device 1, a mixer 2, a reaction device 3, a concentration device 4 and a separation device 5. The raw material supply device 1 is at least two groups, and the raw material supply device 1 comprises a raw material tank 11, a conveying assembly 13 and a preheater 12, and the raw material tank 11 is communicated with the preheater 12 through the conveying assembly 13. The mixer 2 has a feeding port and a discharging port 221, the feeding port is at least two, and the two feeding ports are respectively communicated with the preheaters 12 of the two groups of raw material supply devices 1, and the reaction device 3 comprises an aging tank 31, and the discharging port 221 is communicated with the aging tank 31. The concentration device 4 is communicated with the aging tank 31, the concentration device 4 is used for concentrating the aged reaction material, and the separation device 5 is communicated with the concentration device 4, and the separation device 5 is used for separating and forming the powder from the concentrated product. Figure 1As shown, the conveying assembly 13 between the first raw material tank 111 and the first preheater 121 is taken as an example, the conveying assembly 13 includes a pipeline 131, a pump set 132 and a valve set 133, one end of the pipeline 131 is in communication with the first raw material tank 111, the other end of the pipeline 131 is in communication with the first preheater 121, and the valve set 133 and the pump set 132 are both arranged on the pipeline 131. The pump set 132 is used for conveying and metering the precursor and the reducing agent solution, and can be a standard peristaltic pump or a diaphragm pump with a fluorine rubber and a polytetrafluoroethylene diaphragm, and has a built-in flow metering and recording assembly. The valve set 133 is used for controlling the conveying of the material, and is composed of ball valves and check valves made of polytetrafluoroethylene, polypropylene and polyether ether ketone.

[0049] Specifically, the preheater 12 is used for heating the precursor and the reducing agent solution to a target reaction temperature, and is composed of a thermostatic water tank and an immersed coil.

[0050] The mixer 2 is used for mixing the precursor solution and the reducing agent solution and providing a place for the raw material reduction reaction, and can be composed of a three-way mixer with a variable included angle and a thermostatic water tank.

[0051] The aging tank 31 is used for aging and fully completing the reaction of the reaction mixture, and can be made of commonly used plastics such as polytetrafluoroethylene, polypropylene and polyether ether ketone, and has a first plastic stirring paddle 311 driven by a motor arranged therein.

[0052] The concentration device 4 is used for concentrating the aged reaction mixture, and can be made of commonly used plastics such as polytetrafluoroethylene, polypropylene and polyether ether ketone.

[0053] In some embodiments, as shown, Figure 1 The reaction device 3 further includes a buffer tank 32, the discharge port 221 is in communication with the buffer tank 32, and the buffer tank 32 is in communication with the aging tank 31. It can be understood that the buffer tank 32 is used for buffering the reaction mixture output from the mixer 2, and can be made of commonly used plastics such as polytetrafluoroethylene, polypropylene and polyether ether ketone, and has a second plastic stirring paddle 321 driven by a motor arranged therein. The powder continuous preparation system of the embodiments of the present application can regulate the time and frequency of powder preparation by arranging the buffer tank 32, and improves the flexibility of the powder continuous preparation system in use.

[0054] Optionally, as shown, Figure 2A , Figure 2B and Figure 2CAs shown, the mixer 2 comprises a mixing cavity 23, a discharge pipe 22 and two feeding pipes 21, one end of the feeding pipe 21 communicates with the mixing cavity 23, the other end of the feeding pipe 21 has a feeding port, one end of the discharge pipe 22 communicates with the mixing cavity 23, the other end of the discharge pipe 22 has a discharge port 221, the angle θ between the feeding pipe 21 and the discharge pipe 22 is adjustable, and the angle θ is greater than or equal to 60° and less than or equal to 120°. It can be understood that the feeding pipe 21 is located above the discharge pipe 22, and the feeding port is located above the discharge port 221, so that the precursor solution and the reducing agent solution can be mixed under the action of gravity and discharged from the lower discharge port 221.

[0055] Since the angle θ between the feeding pipe 21 and the discharge pipe 22 is adjustable, the precursor solution and the reducing agent solution can be introduced into the mixing cavity 23 at different incident angles, so that the precursor solution and the reducing agent solution can be mixed more fully. And according to the physical properties of the raw liquid, the contact mode during mixing, the mutual impact strength of the two fluids and the flow pattern after mixing can be flexibly adjusted, realizing rapid mixing and homogenization of the reactants in a very short time, ensuring the time and space uniformity of the silver powder nucleation and growth microenvironment, and breaking through the inherent defects of the traditional "one-pot method" intermittent process, such as difficult homogenization, existence of mass transfer dead zone during amplification, poor product morphology, particle size and physical properties, and poor batch consistency.

[0056] For example, the angle θ between the feeding pipe 21 and the discharge pipe 22 can be 60°, 90° or 120°. The inventors of the present application have found through experiments that when the angle θ between the feeding pipe 21 and the discharge pipe 22 meets the above range, the mixing effect of the precursor solution and the reducing agent solution is better.

[0057] In some embodiments, as shown in Figure 1 As shown, the concentration device 4 comprises a concentration tank 41 and a scraper member 42, the scraper member 42 is arranged in the concentration tank 41, the concentration tank 41 is provided with a discharge port 412 and an overflow port 411, the discharge port 412 is arranged at the bottom of the concentration tank 41 for discharging the concentrated product, and the overflow port 411 is located at the upper end of the concentration tank 41 for overflowing the waste liquid. It can be understood that the aged reaction mixture is introduced into the concentration tank 41 for sedimentation, and the silver powder and the solution are preliminarily separated by the sedimentation effect, the clear liquid is discharged from the upper overflow port 411, and the concentrated liquid rich in silver powder is discharged from the lower discharge port 412, so as to realize continuous and uninterrupted concentration of the reaction mixture, greatly reduce the liquid content in the material and the load in the subsequent separation process, and significantly improve the silver powder production efficiency in the post-processing link.

[0058] Specifically, as shown in Figure 1As shown, the lower end of the thickening tank 41 has a tapered section 413, the tip of the tapered section 413 is arranged downward. In other words, the thickening tank 41 is a cylinder structure with a tapered bottom, the bottom of the tapered section 413 is provided with two scraper members 42 driven to rotate by a motor, to scrape and separate the thickening adhered to the inside of the thickening tank 41.

[0059] Optionally, the taper of the tapered section 413 is greater than or equal to 1 and less than or equal to 2, the height of the tapered section 413 is L1, the total height of the thickening cylinder is L2, and the ratio of L2 / L1 is greater than or equal to 2 and less than or equal to 4. For example, the taper of the tapered section 413 can be 1, 1.5 or 2. The ratio of L2 / L1 can be 2, 3 or 4. The powder continuous preparation system of the embodiment of the present application can make the thickening tank 41 discharge the thickening more smoothly and the thickening effect of the thickening is better by arranging the thickening tank 41 in the above structure.

[0060] In some embodiments, as Figure 1 shown, the separation device 5 includes a separation tank 51, a sprayer 52, a filter core 53, a scraper (not shown) and a dryer 54, the filter core 53 is arranged in the separation tank 51 for filtering the thickening product, the sprayer 52 is arranged in the separation tank 51 and above the filter core 53 for washing the thickening product, the dryer 54 is in communication with the separation tank 51 for drying the thickening product, and the scraper is used to disperse the dried product to form the powder. It can be understood that the separation device 5 can filter, wash and dry the thickening.

[0061] Specifically, as Figure 1 shown, the inlet of the separation tank 51 is in communication with the bottom of the thickening tank 41, and the scraper is arranged above the filter core 53 for peeling off the filter cake from the filter core 53 and preliminary breaking and dispersing. The bottom of the filter core 53 is connected with a vacuum device 55, which can provide negative pressure to the thickening tank 41 to realize the filtering and washing of the silver powder. The dryer 54 can be a gas supply assembly 541, which is in communication with the bottom of the separation tank 51, and can blow air into the separation tank 51 to dry the filter cake and provide the removal of the silver powder adhered to the filter core 53, so that the high-dispersed silver powder product can be directly obtained after the treatment of the device.

[0062] Optionally, the inner walls of the raw material tank 11, the mixer 2, the buffer tank 32, the aging tank 31, the thickening device 4 and the connecting pipelines thereof are provided with plastic protective layers, or the raw material tank 11, the mixer 2, the buffer tank 32, the aging tank 31, the thickening device 4 and the connecting pipelines thereof are all made of plastic materials, so that the chemical reaction between the preparation system and the raw materials can be avoided, and the reliability of the powder continuous preparation system in operation is improved.

[0063] The powder continuous preparation method according to another embodiment of the present application is applied to the powder continuous preparation system according to the embodiment of the present application, and comprises the following steps:

[0064] S1: metal salt is put into one raw material tank 11 to form a precursor solution, and a reducing agent and an auxiliary agent are put into another raw material tank 11 to form a reducing agent solution;

[0065] S2: the precursor solution and the reducing agent solution are heated to a preset temperature through two preheaters 12 respectively;

[0066] S3: the heated precursor solution and the reducing agent solution are respectively injected into the mixer 2 through two feeding ports and react to generate a reaction mixture containing metal particles;

[0067] S4: the reaction mixture is passed into the aging tank 31 and aged for a preset time;

[0068] S5: the aged reaction mixture is passed into the concentration device 4 to settle, so that waste liquid is discharged from the overflow port 411, and the concentrated product is discharged from the bottom of the concentration device 4;

[0069] S6: the concentrated product is passed into the separation device 5 to be filtered, washed and dried, so that the concentrated product forms a powder.

[0070] The powder continuous preparation method according to the embodiment of the present application can save a large number of auxiliary operations in the batch process by continuously mixing and reacting raw materials and continuously aging and concentrating materials, realizes continuous and uninterrupted chemical reduction preparation of the powder, and improves the production efficiency of the powder. In addition, the powder continuous preparation method according to the embodiment of the present application can realize continuous and uninterrupted production process, can effectively eliminate the differences between batches in the traditional “one-pot method” batch process, and fundamentally solves the problems of product batch stability and consistency. Furthermore, the powder continuous preparation system according to the embodiment of the present application adopts modular design, so that it can be repaired or replaced individually without affecting the operation of the whole system, thereby ensuring the economy of system manufacturing and operation maintenance. Further, the powder continuous preparation method according to the embodiment of the present application can realize the adjustable and controllable production capacity by means of raw material supply, local “one standby one use” and overall expansion of the powder continuous preparation system according to the size of the production load.

[0071] In some embodiments, the metal salt is a silver salt. For example, the silver salt can be silver nitrate or silver acetate (but since the photosensitivity of silver acetate is higher than that of silver nitrate, the operation process needs to add a light-proof link). The reducing agent includes but is not limited to ascorbic acid, hydroxylamine, hydrazine hydrate, other reagents that have reducing properties to silver ions, and mixed reagents described above. The auxiliary agent includes but is not limited to polyvinylpyrrolidone, polyvinyl alcohol, polyethylene glycol, cetyltrimethylammonium bromide, sodium cetyl sulfonate, amino acid, sodium citrate, ethylenediaminetetraacetic acid. The adjusting agent includes but is not limited to nitric acid, acetic acid, citric acid, sodium hydroxide, potassium hydroxide, ammonia, and the solvent includes but is not limited to water and ethanol, propanol, ethylene glycol, glycerol and aqueous solutions thereof.

[0072] Optionally, the auxiliary agent is a composite auxiliary agent composed of polyvinylpyrrolidone with different polymerization degrees, wherein the monomer molar ratio of polyvinylpyrrolidone K89-96 and polyvinylpyrrolidone K29-32 is between 1:1 and 1:3; or the monomer molar ratio of polyvinylpyrrolidone K60 and polyvinylpyrrolidone K29-32 is between 4:1 and 2:1; or the monomer molar ratio of polyvinylpyrrolidone K89-9, polyvinylpyrrolidone K60 and polyvinylpyrrolidone K29-32 is 2:1:1. The inventors of the present application have found through experimental research that when the auxiliary agent is a composite auxiliary agent composed of polyvinylpyrrolidone with different polymerization degrees, the high-molecular macromolecules and low-molecular micromolecules are alternately composed into a three-dimensional network structure, forming effective steric hindrance, effectively controlling the nucleation and growth of silver particles in high-concentration precursors and preventing the coalescence of silver powders, and forming surface coating by virtue of its good compatibility with the silver surface to ensure the dispersibility of the silver powder. In addition, polyvinylpyrrolidone has good water solubility and alcohol solubility, is easy to wash off, and is non-toxic and harmless, and the formula is environmentally friendly.

[0073] Further, in the embodiment of the present application for preparing silver powder, the adjusting agent is nitric acid and sodium hydroxide, and the solvent is water and ethylene glycol aqueous solution. Based on the basic principles of metal deposition-etching dissolution balance, material reaction-transportation restriction synergy, micro-particle transportation kinetics, crystal isotropy / anisotropy, etc., the reaction kinetics is controlled by the acid / base adjusting agent, and the transportation kinetics is controlled by the solvent viscosity, so as to induce different growth modes of silver crystals, and realize the controllable preparation of flaky and small-particle spherical silver powder.

[0074] Optionally, the silver salt concentration can be 0.2-1 mol / L, the molar ratio of silver salt to auxiliary agent monomer is 20:1-10:1, the molar ratio of silver salt to acid / base adjusting agent is 20:1-10:1, the reducing agent is added in an amount of 1 times the stoichiometric ratio, and the solvent is 0-50 vol% alcohol aqueous solution.

[0075] Optionally, the heating temperature of the preheater 12 is greater than or equal to 30℃ and less than or equal to 60℃.

[0076] Optionally, the Reynolds number of the precursor solution and the reducing agent solution at the liquid inlet of the mixer is greater than or equal to 800 and less than or equal to 1800, and the mixing time of the precursor solution and the reducing agent solution in the mixer is greater than or equal to 0.1 s and less than or equal to 0.8 s. The inventors of the present application have found through experimental research that the control of the convection type and the mixing intensity by adjusting the included angle between the liquid inlet and the liquid outlet of the mixer and the Reynolds number of the fluid can realize the rapid mixing and homogenization of different physical property raw materials, and effectively solve the problems of wide particle size distribution and uneven morphology in the batch process.

[0077] Optionally, the residence time of the reaction mixture in the aging tank is greater than or equal to 25 min and less than or equal to 35 min. The residence time of the aged reaction mixture in the concentration device is greater than or equal to 25 min and less than or equal to 35 min, and the filtering, washing and drying time of the concentrated product in the separation device is greater than or equal to 30 min and less than or equal to 60 min. The inventors of the present application have found through experimental research that when the reaction time of the material is in the above range, the reaction effect of the silver salt and the reducing agent is more sufficient, and the quality of the prepared silver powder is better.

[0078] The inventors of the present application use the powder continuous preparation system of the embodiments of the present application to prepare silver powder with silver nitrate as the silver source, ascorbic acid as the reducing agent, polyvinylpyrrolidone as the auxiliary agent, nitric acid and sodium hydroxide as the adjusting agent, and water and ethylene glycol solution as the solvent, and perform the following comparative test.

[0079] Example 1:

[0080] 6.79 kg of silver nitrate, 0.22 kg of polyvinylpyrrolidone (K88-96) and 0.22 kg of polyvinylpyrrolidone (K29-32) are weighed into the first raw material tank 111, 200 L of water is added and stirred until completely dissolved to form a precursor solution; 7.05 kg of ascorbic acid and 0.16 kg of sodium hydroxide are weighed into the second raw material tank 112, 200 L of water is added and stirred until completely dissolved to form a reducing agent solution. The preheater 12 and the mixer 2 are started, and the thermostat water tank is heated to 60°C, the pump group 132 is set to a flow rate such that the Reynolds number of the liquid at the inlet of the mixer 2 reaches 800, the two inlets of the mixer 2 are perpendicular to the outlet and arranged in a T shape (as shown in Figure 2B The reaction mixture is formed after the liquid is mixed and reacted in the mixer 2, and then passes through the buffer tank 32, the aging tank 31, the concentration device 4 and enters the separation device 5 (i.e. the filtering-washing-drying device), and the silver powder product is obtained by negative pressure filtration, sufficient washing and air drying and dispersion in the separation device 5, with a yield of 98.3%. The morphology, particle size and tap density of the silver powder are measured by a scanning electron microscope, a laser diffraction method and a mechanical vibration method respectively, and the results are shown inFigure 3A and Table 1.

[0081] Example 2:

[0082] Take 20.38 kg of silver nitrate, 0.44 kg of polyvinylpyrrolidone (K88-96) and 0.89 kg of polyvinylpyrrolidone (K29-32) into the first raw material tank 111, add 200 L of water and stir until completely dissolved to form a precursor solution; take 21.14 kg of ascorbic acid and 0.48 kg of sodium hydroxide into the second raw material tank 112, add 200 L of water and stir until completely dissolved to form a reducing agent solution. Start the preheater 12 and the constant temperature water tank of the mixer 2 to heat to 30°C, set the flow rate of the pump set 132 to make the Reynolds number of the liquid at the inlet of the mixer 2 reach 1700, the two inlets and the outlet of the mixer 2 are arranged in a Y shape (as shown in Figure 2A Figure 2) with an included angle of 120°, then start the pump set 132 to simultaneously transport the precursor solution and the reducing agent solution to the mixer 2, the liquid is mixed and reacted in the mixer 2 to form a reaction mixture, which is sequentially passed through the buffer tank 32, the aging tank 31 and the concentration device 4 into the filter-washing-drying device, where the silver powder product is obtained by negative pressure filtration, sufficient washing and air drying and dispersion, with a yield of 98.5%. The morphology, particle size and tap density of the silver powder are measured by scanning electron microscopy, laser diffraction method and mechanical vibration method respectively, and the results are shown in Figure 3B and Table 1.

[0083] Example 3:

[0084] Take 20.38 kg of silver nitrate, 0.44 kg of polyvinylpyrrolidone (K88-96) and 0.89 kg of polyvinylpyrrolidone (K29-32) into the first raw material tank 111, add 200 L of water and stir until completely dissolved to form a precursor solution; take 21.14 kg of ascorbic acid and 0.48 kg of sodium hydroxide into the second raw material tank 112, add 200 L of water and stir until completely dissolved to form a reducing agent solution. Start the preheater 12 and the constant temperature water tank of the mixer 2 to heat to 30°C, set the flow rate of the pump set 132 to make the Reynolds number of the liquid at the inlet of the mixer 2 reach 1700, the two inlets and the outlet of the mixer 2 are arranged in a Y shape (as shown in Figure 2C Figure 2) with an included angle of 120°, then start the pump set 132 to simultaneously transport the precursor solution and the reducing agent solution to the mixer 2, the liquid is mixed and reacted in the mixer 2 to form a reaction mixture, which is sequentially passed through the buffer tank 32, the aging tank 31 and the concentration device 4 into the filter-washing-drying device, where the silver powder product is obtained by negative pressure filtration, sufficient washing and air drying and dispersion, with a yield of 98.5%. The morphology, particle size and tap density of the silver powder are measured by scanning electron microscopy, laser diffraction method and mechanical vibration method respectively, and the results are shown in Figure 3C and Table 1.

[0085] Example 4:

[0086] Take 6.79 kg of silver nitrate, 0.3 kg of polyvinylpyrrolidone (K60) and 0.15 kg of polyvinylpyrrolidone (K29-32) into the first raw material tank 111, add 200 L of 20 vol% ethylene glycol aqueous solution and stir until completely dissolved to form a precursor solution; take 7.05 kg of ascorbic acid into the second raw material tank 112, add 200 L of 20 vol% ethylene glycol aqueous solution and stir until completely dissolved, then add 143 mL of 65 wt% nitric acid and mix uniformly to form a reducing agent solution. Start the preheater 12 and the constant temperature water tank of the mixer 2 to heat to 40°C, set the flow rate of the pump set 132 to make the Reynolds number of the liquid at the inlet of the mixer 2 reach 1800, and the two inlets of the mixer 2 are perpendicular to the outlet, arranged in a T shape (as shown in Figure 2B The reaction mixture is formed after the liquid is mixed and reacted in the mixer 2, and then enters the filter-washing-drying device through the buffer tank 32, the aging tank 31 and the concentration device 4, and the silver powder product is obtained by negative pressure filtration, sufficient washing and air drying and dispersion in the filter-washing-drying device, with a yield of 97.7%. The morphology, particle size and tap density of the silver powder are measured by scanning electron microscopy, laser diffraction method and mechanical vibration method respectively, and the results are shown in Figure 3D and Table 1.

[0087] Example 5:

[0088] Take 6.79 kg of silver nitrate, 0.3 kg of polyvinylpyrrolidone (K60) and 0.15 kg of polyvinylpyrrolidone (K29-32) into the first raw material tank 111, add 200 L of 20 vol% ethylene glycol aqueous solution and stir until completely dissolved to form a precursor solution; take 7.05 kg of ascorbic acid into the second raw material tank 112, add 200 L of 20 vol% ethylene glycol aqueous solution and stir until completely dissolved, then add 143 mL of 65 wt% nitric acid and mix uniformly to form a reducing agent solution. Start the preheater 12 and the constant temperature water tank of the mixer 2 to heat to 40°C, set the flow rate of the pump set 132 to make the Reynolds number of the liquid at the inlet of the mixer 2 reach 1800, and the two inlets of the mixer 2 are perpendicular to the outlet, arranged in a T shape (as shown in Figure 2BThe precursor solution and the reducing agent solution are transported to the mixer 2 simultaneously by starting the pump set 132, mixed and reacted in the mixer 2 to form a reaction mixture, and then sequentially pass through the buffer tank 32, the aging tank 31 and the concentration device 4 to the filter-washing-drying device, in which the silver powder product is obtained by negative pressure filtration, sufficient washing and air drying and dispersion, with a yield of 97.1%. The morphology, particle size and tap density of the silver powder are measured by using a scanning electron microscope, a laser diffraction method and a mechanical vibration method, respectively, and the results are shown in Figure 3E and Table 1.

[0089] Comparative Example:

[0090] 67.95 g of silver nitrate was weighed into a glass reaction kettle with a volume of 10 L, 2 L of water was added and stirred until completely dissolved to form a precursor solution; 70.45 g of ascorbic acid was weighed into a beaker with a volume of 5 L, 2 L of water was added and stirred until completely dissolved to form a reducing agent solution. The precursor solution in the glass reaction kettle and the reducing agent solution in the beaker were heated to 50°C using a circulating water and a water bath, respectively, the reaction kettle was started to stir, and the reducing agent solution was pumped into the glass reaction kettle at a rate of 50 mL min-1 using a peristaltic pump. After the feeding was completed, the stirring was continued for 20 min, and then the reaction mixture was discharged from the reaction kettle. After filtration, washing, drying and crushing, the silver powder was obtained, with a yield of 97.8%. The flowability, morphology, particle size and tap density of the silver powder were measured by using a Hall flowmeter, a scanning electron microscope, a laser diffraction method and a mechanical vibration method, respectively, and the results are shown in Figure 3F and Table 1.

[0091] Table 1 Particle size and tap density of silver powder

[0092]

[0093] In summary, the powder continuous preparation system and method of the embodiments of the present application have at least the following effective benefits.

[0094] (1) The powder continuous preparation system and method of the embodiments of the present application have high silver powder preparation efficiency. The present application realizes continuous and uninterrupted chemical reduction preparation of silver powder by continuously mixing and reacting raw materials, continuously aging and concentrating materials, which saves a large number of auxiliary operations in the intermittent process; the controllable preparation of silver powder in an ultra-high concentration precursor is realized by effectively controlling nucleation and growth and inhibiting particle coalescence through the design of composite additives, which greatly improves the production efficiency per unit time and per unit space.

[0095] (2) The silver powder quality controllability of the powder continuous preparation system and method of the embodiment of the present application is high. The present application effectively eliminates the difference between batches in the traditional "one-pot method" intermittent process through continuous uninterrupted process, fundamentally solves the problems of product batch stability and consistency; through the design of high-efficiency mixer and reactor, the rapid mixing and homogenization of reactants are realized, the amplification effect in the intermittent process is avoided, the uniformity of the particle nucleation and growth microenvironment is ensured, the isotropic / anisotropic growth mode of the crystal is controlled in a targeted manner based on the reaction kinetics and the transmission kinetics based on the solvent viscosity, thereby realizing the high uniformity and controllability of the particle size, morphology and other properties of the flaky and spherical silver powder at the same time.

[0096] (3) The silver powder purity and dispersibility of the powder continuous preparation system and method of the embodiment of the present application are high. The formula material of the present application is simple in composition, has no complex added components except necessary additives and adjusting agents, and has good additive solubility, good environmental compatibility, and good affinity with silver, which can meet the demand for silver powder surface coating, is easy to separate and purify, ensures the product purity, and through the integration of filtration-washing-drying, high dispersibility products are obtained in one step, wherein the gas backflushing drying method effectively avoids the silver powder caking problem in the traditional static drying method.

[0097] (4) The silver powder for heterojunction cells of the powder continuous preparation system and method of the embodiment of the present application can be directly prepared. The present application realizes the simultaneous preparation of flaky and small-particle spherical silver powder through formula design, kinetic control, preparation process condition adjustment and other comprehensive means, directly obtains the silver powder filler meeting the needs of heterojunction cells, and avoids the complex process of separately preparing flaky and spherical silver powder and then compounding in the traditional method.

[0098] (5) The powder continuous preparation system of the embodiment of the present application has high flexibility, high efficiency and low cost. The powder continuous preparation system of the present application can be integrated and processed by standard parts and common materials, avoids the design, processing and control difficulties of the large reaction kettle in the intermittent process, and each part can be modularized, which can be repaired or replaced without affecting the operation of the whole system, ensures the economy of the manufacturing and operation and maintenance of the system, and has very high adaptability to the production load. The production capacity expansion can be easily realized by increasing the raw material supply, duplicating the whole system, and using "one for one" for the local intermittent operation link.

[0099] In the description of the present application, it is to be understood that the orientations or positional relationships indicated by the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like are based on the orientations or positional relationships shown in the drawings, and are only for the purpose of facilitating the description of the present application and simplifying the description, and do not indicate or imply that the devices or elements indicated thereby must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0100] In addition, the terms "first", "second", "third", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated thereby. Therefore, the features defined with "first", "second", etc. can explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of "a plurality of" is at least two, such as two, three, etc., unless otherwise explicitly specified and limited.

[0101] In the present application, unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connecting", "fixing" and the like should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be mechanically connected, or it can be electrically connected or in communication with each other; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal communication or interaction relationship of two elements, unless otherwise explicitly limited. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0102] In the present application, unless otherwise explicitly specified and limited, the first feature is "on" or "under" the second feature, which can be direct contact between the first and second features, or indirect contact between the first and second features through an intermediate medium. Moreover, the first feature "above", "above" and "above" the second feature can be directly above or obliquely above the first feature, or only indicate that the horizontal height of the first feature is higher than that of the second feature. The first feature "below", "below" and "below" the second feature can be directly below or obliquely below the first feature, or only indicate that the horizontal height of the first feature is less than that of the second feature.

[0103] In this disclosure, the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" mean that a particular feature, structure, material, or characteristic is included in at least one embodiment or example of the present disclosure. The illustrative appearances of the above-mentioned terms in various places in the specification are not necessarily referred to the same embodiment or example. Moreover, the particular features, structures, materials, or characteristics can be combined in any suitable manner in one or more embodiments or examples. Furthermore, the terms "comprising", "containing", "having" or "including" and their derivatives, mean "including but not limited to". The terms "coupled" and "connected", along with their derivatives, mean "directly or indirectly connected".

[0104] Although the above-mentioned embodiments have been shown and described, it is to be understood that the above-mentioned embodiments are exemplary, and are not to be construed as limiting the present disclosure, and any change, modification, replacement, and variation made by those skilled in the art to the above-mentioned embodiments are within the protection scope of the present disclosure.

Claims

1. A continuous powder production system, characterized in that, The application relates to a powder continuous preparation system and a powder continuous preparation method. The system comprises: raw material supply devices, which are at least two groups, and comprise raw material tanks, conveying assemblies and preheaters, the raw material tanks being communicated with the preheaters through the conveying assemblies; a mixer, which has at least two feeding ports and one discharging port, the two feeding ports being respectively communicated with the preheaters of the two groups of raw material supply devices, the mixer comprising a mixing cavity, a discharging pipe and two feeding pipes, one end of the feeding pipe being communicated with the mixing cavity, the other end of the feeding pipe having the feeding port, one end of the discharging pipe being communicated with the mixing cavity, the other end of the discharging pipe having the discharging port, the angle between the feeding pipe and the discharging pipe being adjustable, and the angle being greater than or equal to 60 degrees and less than or equal to 120 degrees; a reaction device, which comprises an aging tank, the discharging port being communicated with the aging tank; a concentration device, which is communicated with the aging tank and is used for concentrating the reaction product after aging; a separation device, which is communicated with the concentration device and is used for separating and forming powder from the concentrated product.

2. The continuous powder production system of claim 1, wherein, The reaction device further comprises a buffer tank, the discharging port being communicated with the buffer tank, and the buffer tank being communicated with the aging tank.

3. The continuous powder production system of claim 1, wherein, The concentration device comprises a concentration tank and a scraper, the scraper being arranged in the concentration tank, the concentration tank being provided with a discharging port and an overflow port, the discharging port being arranged at the bottom of the concentration tank and being used for discharging the concentrated product, and the overflow port being arranged at the upper end of the concentration tank and being used for overflowing waste liquid.

4. The continuous powder production system of claim 3, wherein, The lower end of the concentration tank is provided with a tapered section, the tapered section being arranged downward, the taper of the tapered section being greater than or equal to 1 and less than or equal to 2, the height of the tapered section being L1, the total height of the concentration tank being L2, and the ratio of L2 / L1 being greater than or equal to 2 and less than or equal to 4.

5. The continuous powder production system of claim 1, wherein, The separation device comprises a separation tank, a sprayer, a filter core, a scraper and a dryer, the filter core being arranged in the separation tank and being used for filtering the concentrated product, the sprayer being arranged in the separation tank and being arranged above the filter core and being used for washing the concentrated product, the dryer being communicated with the separation tank and being used for drying the concentrated product, and the scraper being used for dispersing the dried product to form powder.

6. The continuous powder production system of claim 2, wherein, The raw material tank, the mixer, the buffer tank, the aging tank and the concentration device are all provided with plastic protective layers on the inner walls thereof.

7. A method for the continuous production of a powder material, characterized in that The powder continuous preparation method is applied to the powder continuous preparation system, and comprises the following steps: metal salt is put into one of the raw material tanks to form a precursor solution, and a reducing agent and an additive are put into another of the raw material tanks to form a reducing agent solution; the precursor solution and the reducing agent solution are heated to a preset temperature through the two preheaters respectively; the heated precursor solution and the heated reducing agent solution are injected into the mixer through the two feeding ports respectively and react to generate a reaction mixture containing metal particles; passing the reaction mixture into the aging tank to age for a preset time; passing the aged reaction mixture into the concentration device to settle, so that waste liquid is discharged from the overflow port and concentrated product is discharged from the bottom of the concentration device; passing the concentrated product into the separation device to filter, wash and dry, so that the concentrated product forms a powder.

8. The method of claim 7, wherein the powder is continuously produced. the metal salt is a silver salt, and the auxiliary agent is a composite auxiliary agent composed of polyvinylpyrrolidone with different polymerization degrees, wherein, the monomer molar ratio of polyvinylpyrrolidone K89-96 and polyvinylpyrrolidone K29-32 is between 1:1 and 1:3; alternatively, the monomer molar ratio of polyvinylpyrrolidone K60 and polyvinylpyrrolidone K29-32 is between 4:1 and 2:1; alternatively, the monomer molar ratio of polyvinylpyrrolidone K89-9, polyvinylpyrrolidone K60 and polyvinylpyrrolidone K29-32 is 2:1:

1.

9. The method of claim 8, wherein the powder is continuously produced. the heating temperature of the preheater is greater than or equal to 30℃ and less than or equal to 60℃.

10. The method of claim 7, wherein the powder is continuously produced. the Reynolds number of the precursor solution and the reducing agent solution at the liquid inlet of the mixer is greater than or equal to 800 and less than or equal to 1800, and the mixing time of the precursor solution and the reducing agent solution in the mixer is greater than or equal to 0.1s and less than or equal to 0.8s.

11. The method of claim 7, wherein the powder is continuously produced by a process comprising: the residence time of the reaction mixture in the aging tank is greater than or equal to 25min and less than or equal to 35min; the residence time of the aged reaction mixture in the concentration device is greater than or equal to 25min and less than or equal to 35min; the filtering, washing and drying time of the concentrated product in the separation device is greater than or equal to 30min and less than or equal to 60min.

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