Silver powder continuous production device and method

Abstract

The invention provides a continuous silver powder production device and method. A liquid storage tank in the production device overflows a solution A to the rolling water dam body, a high-pressure atomization pipeline atomizes a solution B and sprays the solution B to the overflowed solution A, the overflowed solution A makes contact with the atomized solution B, the solution A and the atomized solution B can flow to the bottom of a mixed liquid tank along the rolling water dam body after making contact, and the mixed liquid is sprayed to the rolling water dam body. A mixed liquid vortex is formed in the mixed liquid tank, so that a silver source and a reducing agent in the solution A and the solution B are fully reacted to synthesize a silver powder crude product, and the silver powder crude product is precipitated and falls on the bottom of the crude product conveying belt; and the silver powder crude product is conveyed to the top of the crude product conveying belt, blown away by the high-pressure spraying device and sprayed into the cleaning tank for cleaning and precipitation, and the finished wet silver powder is obtained. Therefore, by combining the overflow dam principle, energy-saving, rapid, full-process, continuous and green production of the silver powder is achieved, and meanwhile the problems that the quality of the silver powder is unstable and the like are solved.

Description

Technical Field

[0001] This invention relates to the field of silver powder production technology, specifically to a continuous silver powder production apparatus and method. Background Technology

[0002] In the electronics industry, silver powder is an important conductive material, widely used in the manufacture of conductive plastics, conductive coatings, and conductive adhesives. Although silver powder preparation technology is quite mature both domestically and internationally, most still use traditional silver powder synthesis systems (including raw material reactors, synthesis reactors, cleaning reactors, filtration, and other complete systems) for batch production.

[0003] Invention patent application CN119525479 A discloses a method for preparing silver powder that can be continuously synthesized, including the following steps: (1) preparing silver nitrate solution, surface treatment solution and ascorbic acid solution; (2) using deionized water, surface treatment solution and ascorbic acid solution as base liquid, and then adding silver nitrate solution and ascorbic acid solution in a certain proportion for reaction, and using pH adjuster to adjust the pH value of the reaction solution to be maintained at 4-6 during the reaction process; (3) when the total volume of liquid in the reactor in step (2) accounts for 80% of the reactor volume, stopping the feeding and turning off the stirring, releasing the bottom material after sedimentation, releasing the material until the remaining liquid in the reactor accounts for 30-40% of the reactor volume, and restarting the stirring and feeding after the material is released; (4) after centrifugation, washing and drying of the material released from the bottom, silver powder is obtained. From the perspective of the entire process of silver powder production, the above invention patent application mainly discloses the continuous and stable production of silver powder by the synthesis system, but does not involve cleaning, filtration and other systems, and still belongs to intermittent production. The existing intermittent production has the following significant problems: I. Inability to Conduct Continuous Production: The reaction vessel typically uses a mechanical pump to add liquid from a raw material vessel (usually containing three or more raw materials (silver source, dispersant, reducing agent, pH adjuster, etc.)) to the reaction vessel. The reaction is then stirred by a stirrer to complete the silver powder synthesis. Afterwards, a centrifuge or filter press separates the silver powder from the mother liquor, forming a thick filter cake. This filter cake is then broken up and sent to a washing vessel for cleaning. The washing liquid and silver powder are then separated, and this process is repeated multiple times to obtain pure silver powder. This operating method dictates that it can only be used for intermittent production. Each batch requires shutdown, cleaning, and re-batch preparation, which not only affects production efficiency but also exacerbates silver powder losses during various transportation stages, increasing production costs. Currently, some silver powder companies have achieved automated production, enabling partially continuous production. However, this only involves connecting various devices together and transporting via pipelines, and does not solve the fundamental problem.

[0004] II. Unstable Silver Powder Quality: There are three main reasons: 1) During the chemical reduction synthesis of silver powder, the concentrations of the silver source, reducing agent, and dispersant have a significant impact on the morphology and particle size of the silver powder. Traditional reactors use agitators to chemically reduce silver powder, and the concentrations of these components change in real time during the reaction. This leads to poor morphology and inconsistent particle size in the synthesized silver powder. Industrially, larger reactors are often used to minimize the impact of concentration changes on silver powder synthesis by reducing the concentration of the reaction solution; 2) Because large reactors use mechanical stirring, the linear velocities of the solution at the center of the agitator and at the outer edge differ, resulting in inconsistent mixing speeds. This leads to uneven concentration throughout the reactor, significantly affecting the particle size consistency of the synthesized silver powder; 3) Intermittent production makes it difficult to ensure completely consistent reaction conditions for each batch, resulting in fluctuations in the quality of the silver powder.

[0005] Third, high energy consumption: The silver powder synthesis system requires a large amount of electrical energy during the production process due to the need for various equipment for stirring, centrifugation, etc. In addition, since the chemical reduction of silver powder is an exothermic reaction, a constant temperature water bath / oil bath is required to heat or cool the equipment in order to maintain a constant temperature in the reaction vessel, which leads to a sharp increase in electricity consumption.

[0006] IV. Environmental Issues: Traditional intermittent production methods require more water to wash the caked silver powder in the filter cake. To achieve a good cleaning effect, the water consumption in industrial production can reach 1:100. The resulting wastewater, exhaust gas, and solid waste are difficult to treat effectively, causing certain environmental pollution. Furthermore, since some aspects require human intervention, the resulting pollution seriously affects the health of the operators.

[0007] Although some new preparation methods have emerged in recent years, such as vapor phase evaporation condensation, grinding and atomization, most of these methods have problems such as high cost, complex process or low production efficiency, making it difficult to promote on a large scale. Summary of the Invention

[0008] In view of this, the purpose of the present invention is to provide a continuous silver powder production device and method, which mainly utilizes the mixing liquid vortex formed by the principle of a rolling dam to generate silver powder in situ, and then filters and cleans it in a timely manner, thereby realizing energy-saving, rapid, continuous and green production of silver powder throughout the entire process, while solving problems such as unstable silver powder quality.

[0009] To achieve the above objectives, the present invention provides the following technical solution: A continuous silver powder production apparatus includes: a storage tank for holding solution A, a dam body, a mixing tank, a high-pressure atomizing pipe for supplying solution B, a coarse product conveyor belt, a high-pressure spraying device, and a cleaning tank. The dam body is connected to both the storage tank and the mixing tank. One end of the coarse product conveyor belt is connected to the mixing tank, and the other end is connected to the high-pressure spraying device. The cleaning tank is located below the high-pressure spraying device. Solution A and solution B are, respectively, silver source solution and reducing agent solution. The storage tank includes a liquid receiving cavity, a liquid level adjustment unit, and a solution A overflow port. The liquid receiving cavity can hold the solution A, and the liquid level adjustment unit can adjust the liquid level of the solution A in the liquid receiving cavity so that the solution A continuously overflows from the solution A overflow port. The dam body includes a dam crest and a dam body ramp. The bottom of the dam body ramp extends to the mixing tank. The height of the dam crest is not higher than the overflow port of solution A. Solution A overflowing from the overflow port of solution A can flow from the dam crest along the dam body ramp to the mixing tank. The high-pressure atomizing pipe can atomize and spray solution B near the bottom of the dam slope, and it flows with solution A into the mixing tank, forming a vortex of the mixing liquid near the bottom of the dam slope. This allows solution A and solution B to react fully and synthesize crude silver powder. The crude silver powder falls onto the crude product conveyor belt and is transported to the high-pressure spraying device. The high-pressure spraying device can blow and spray the crude silver powder into the cleaning tank for cleaning, and after sedimentation, the finished wet silver powder is obtained.

[0010] Furthermore, the liquid level adjustment unit includes a movable base plate, above which the liquid receiving cavity is formed, and below which a lifting structure is installed to move the movable base plate up and down to continuously adjust the liquid level of solution A contained in the liquid receiving cavity, so that solution A continuously overflows from the solution A overflow port; this helps to ensure the continuity of the silver powder synthesis reaction and the stability of the reactant concentration in the mixing tank.

[0011] Furthermore, the liquid level adjustment unit also includes a bottom feeding pipe that can continuously fill the liquid receiving cavity with solution A, thus enabling continuous addition of solution A.

[0012] Furthermore, a flow controller is installed at one end of the bottom feeding pipe, and the other end passes through the movable base plate and extends to the liquid receiving cavity; in this way, solution A can be accurately supplied to the liquid receiving cavity, thereby regulating the flow rate of solution A overflowing from the solution A overflow port.

[0013] Furthermore, baffles are provided above the storage tank, the sluice gate, and the mixing tank to prevent the reaction raw material solution from escaping and being wasted during the movement.

[0014] Furthermore, the high-pressure atomizing pipe is equipped with several fan-shaped atomizers facing the dam slope. The high-pressure atomizing pipe is installed on the baffle plate at the intersection of the rolling dam and the mixing tank. This facilitates the rapid formation of a vortex after the mixture of solution A and solution B, and also helps to ensure the stability of the flow rate of solution A.

[0015] Furthermore, an anti-scouring base is installed at the bottom of the mixing tank, with one end of the anti-scouring base extending to the bottom of the dam slope. The vortex formed in the mixing tank is located above the anti-scouring base, which helps the silver powder generated by the reaction of the silver source and reducing agent in the vortex to quickly leave the vortex under the action of centrifugal force.

[0016] Furthermore, the coarse product conveyor belt is installed on the other side of the anti-surge base, and a filter screen is mounted on it. Under the action of the vortex formed at the bottom of the dam slope, the coarse silver powder is filtered through the filter screen and falls onto the coarse product conveyor belt, then conveyed to the next process. This ensures the timely discharge of coarse silver powder that has formed flocculent precipitates, preventing the physical agglomeration of silver powder into larger particles and achieving continuous production of silver powder. The mesh size of the filter screen is 1000 mesh or higher, preferably 2000 mesh or higher.

[0017] Furthermore, the bottom of the mixing tank is provided with a mixing outlet, which facilitates the discharge of the mixed liquid after the reaction. This helps to maintain a constant volume of the mixing tank during the reaction process, thereby ensuring the consistency of the synthesis environment for the crude silver powder and ensuring the stability of the silver powder quality.

[0018] Furthermore, the cleaning tank is installed on the finished product conveyor belt, facilitating the transfer of the cleaning tank containing wet silver powder to the next process. The cleaning tank is also equipped with a cleaning liquid discharge port for easy discharge of cleaning waste liquid.

[0019] Furthermore, the production apparatus also includes a support frame for mounting the liquid storage tank, the sluice gate, and the mixing tank, and the bottom of the coarse product conveyor belt is mounted on the support frame.

[0020] A continuous silver powder production method, utilizing the aforementioned production apparatus to produce finished silver powder, includes the following steps: Supply of raw materials: Solution A is injected into the storage tank and overflows from the overflow port of Solution A, and the overflowing Solution A flows down the dam slope; at the same time, near the bottom of the dam slope, Solution B is atomized and sprayed out from the high-pressure atomizing pipe, and the atomized Solution B comes into contact with the overflowing Solution A. Crude silver powder is synthesized: According to the principle of a dam, after the overflowing solution A and the atomized solution B come into contact, they will flow along the dam slope to the bottom of the mixing tank and form a vortex in the mixing tank. After a full reaction, crude silver powder is synthesized. The crude silver powder precipitates and falls onto the crude product conveyor belt, which then conveys it to the next process. Cleaning silver powder: After the coarse silver powder reaches the top of the coarse product conveyor belt, the coarse silver powder is blown apart by the high-pressure spray device and falls into the cleaning tank for cleaning and gradual sedimentation to obtain the finished wet silver powder.

[0021] Therefore, the technical solution provided by the present invention has the following advantages: 1) Energy saving: Utilizing the principle of a spillway dam, by controlling the amount of solution A and solution B added, and by controlling the height of the overflow outlet of solution A, the height of the dam crest, and the slope of the dam slope, the flow velocity of the overflowing solution A and the atomized solution B on the dam slope is controlled, thereby forming a stable vortex in the mixing tank and controlling the intensity of the vortex, thus achieving thorough mixing and uniform reaction of the reactants; this method does not require additional heating and pressurization equipment, reducing energy consumption; 2) Rapid and continuous production: The production apparatus and method provided by the present invention can achieve rapid and continuous preparation of wet silver powder by continuously injecting the reactant solution and using the shear force of the vortex to fully mix the reactants; the method does not require shutdown, cleaning and re-mixing, which greatly improves production efficiency; 3) Stable quality of silver powder: By using the production device provided by the present invention, and continuously injecting the reactant solution and continuously discharging the mixed waste liquid, parameters such as the concentration, flow rate and vortex intensity of the silver source and reducing agent can be adjusted. This allows for precise control of the particle size, morphology and dispersibility of silver powder, ensuring complete consistency of reaction conditions for each batch, avoiding or reducing the impact of factors such as changes in reactant concentration on silver powder synthesis, ensuring the consistency of the formed silver powder particle size, and thus obtaining stable quality wet silver powder.

[0022] Therefore, the continuous silver powder production apparatus and method provided by the present invention not only solves the problems existing in the prior art, but also has the advantages of high production efficiency, low energy consumption, good environmental protection and stable silver powder quality. The promotion and application of the technical solution provided by the present invention will help improve the overall level of the silver powder preparation industry and promote the sustainable development of the electronics industry. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the operating state of the continuous silver powder production device provided in an embodiment of the present invention; Figure 2 The diagram shows the structure (left) and usage status (right) of the high-pressure atomizing pipe used in the embodiments of the present invention. Figure 3 SEM morphology images of silver powder produced using the method provided in this embodiment of the invention (left) and the conventional method (right).

[0024] The components in the diagram are as follows: 001-Liquid storage tank; 002-Modible base plate; 003-Bottom feeding pipe; 004-Liquid receiving cavity; 005-Overflowing solution A; 006-Rolling dam body; 007-Baffle plate; 008-High-pressure atomizing pipe; 009-Atomized solution B; 010-Mixed liquid vortex; 011-Mixed liquid; 012-Crude silver powder; 013-Filter screen; 014-High-pressure jetting device; 015-Cleaning tank; 016-Cleaning liquid outlet; 017-Finished product conveyor belt; 018-Mixed liquid tank; 019-Mixed liquid outlet; 020-Crude silver powder conveyor belt; 021-Anti-impact base; 022-Equipment support; 023-Fan-shaped atomizer. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention.

[0026] Unless otherwise specified, the terminology used in this invention is a common term in the relevant field, and the raw materials, equipment, preparation processes, testing methods, etc., used are all prior art in the relevant field unless otherwise specified.

[0027] Example 1 Please see Figure 1 and Figure 2 This embodiment provides a continuous silver powder production device, including: a storage tank 001, a dam 006, a high-pressure atomizing pipe 008, a mixing tank 018, a coarse product conveyor belt 020, a high-pressure spraying device 014, a cleaning tank 015, and a device support 022. The device support 022 is mainly used to support the storage tank 001, the dam 006, the mixing tank 018, and the coarse product conveyor belt 020. The dam 006 is connected to the storage tank 001 and the mixing tank 018 respectively. The bottom of the coarse product conveyor belt 020 is installed on the device support 022 and passes through the mixing tank 018, and the high-pressure spraying device 014 is installed on the top. The cleaning tank 015 is installed below the high-pressure spraying device 014.

[0028] The storage tank 001 is mainly used to diffuse solution A into the dam body 006. The high-pressure atomizing pipe 008 is mainly used to atomize solution B and spray it onto the diffused solution A 005, so that the diffused solution A 005 comes into contact with the atomized solution B 009. After contact, they flow along the dam body 006 to the bottom of the mixing tank 018, forming a mixing vortex 010 in the mixing tank 018. This allows the silver source and reducing agent in solution A and solution B to react fully and quickly synthesize crude silver powder 012. Since the density of crude silver powder 010 is greater than that of the mixed solution, it will precipitate and fall onto the bottom of the crude product conveyor belt 017. The crude silver powder 012 is then conveyed to the top of the crude product conveyor belt 020, blown apart by the high-pressure spray device 014, and sprayed into the cleaning tank 015 for cleaning and precipitation to obtain the finished wet silver powder. One of the solutions, A and B, is a silver source solution, and the other is a reducing agent solution.

[0029] Specifically, the storage tank 001 includes a liquid receiving cavity 004, a liquid level adjustment unit, and an overflow port for solution A (not shown in the figure). The liquid receiving cavity 004 can hold solution A, and the liquid level adjustment unit can adjust the liquid level of solution A in the liquid receiving cavity 004, allowing solution A to continuously overflow from the overflow port, providing a basis for utilizing the principle of a dam. In one specific embodiment, the overflow port for solution A (not shown in the figure) is located near the top of the storage tank 001.

[0030] In one specific embodiment, the liquid level adjustment unit includes a movable base plate 002, above which a liquid receiving cavity 004 is formed for holding solution A 004. A precision hydraulic lifting device is installed below the movable base plate 002, which allows the movable base plate 002 to move up and down to adjust the liquid level of solution A in the liquid receiving cavity 004, causing solution A to continuously overflow from the solution A overflow port. In short, the flow rate of solution A overflowing from the solution A overflow port can be controlled by controlling the movable base plate 002. In other embodiments, a precision gear lifting device can be used instead of a precision hydraulic lifting device.

[0031] In another specific embodiment, the movable base plate 002 is also provided with a bottom feeding pipe 003 that continuously fills the liquid receiving cavity 004 with solution A. The continuous supply of solution A to the liquid receiving cavity 004 through the bottom feeding pipe 003 is beneficial to the continuous production of silver powder.

[0032] In another specific embodiment, a flow controller (not shown) is installed at one end of the bottom feeding pipe 003, and the other end passes through the movable base plate 002 and extends to the liquid receiving cavity 004, facing the solution A therein, thereby enabling a continuous and accurate supply of solution A to the liquid receiving cavity 004. Thus, by controlling the speed and flow rate of adding solution A to the liquid receiving cavity 004 through the bottom feeding pipe 003, or by controlling the speed at which the movable base plate 002 moves upward, the speed and flow rate of solution A overflowing from the solution A overflow port can be controlled.

[0033] The spillway dam 004 includes a dam crest and a dam ramp. The bottom of the dam ramp extends to the mixing tank 018. The height of the dam crest is no higher than the overflow port of solution A. Solution A 005 overflows from the overflow port of solution A and flows from the dam crest along the dam ramp to the mixing tank 018. By adjusting the height of the dam crest and the slope of the dam ramp, the flow velocity of the overflowing solution A 005 and the atomized solution B 009 from the dam ramp and the flow velocity of their mixture reaching the bottom of the dam ramp can be controlled, thereby controlling the intensity of the mixing vortex 010.

[0034] The high-pressure atomizing pipe 008 is equipped with several fan-shaped atomizers 023 facing the dam slope. The fan-shaped atomizers 023 can atomize the solution B to form an atomized solution B that can be sprayed near the bottom of the dam slope. After the atomized solution B comes into contact with the solution A, it flows into the mixing tank and forms a mixing vortex 010 near the bottom of the dam slope.

[0035] The mixing tank 018 includes an anti-scour base 021 installed at the bottom. One end of the anti-scour base 021 extends to the bottom of the dam slope. The anti-scour base 021 has an arc-shaped upper surface, one end of which is connected to the dam slope. The mixing vortex 010 is formed above the arc-shaped upper surface of the anti-scour base 021. This design of the anti-scour base 021 has three advantages: 1) It helps the mixed solution formed by the overflowing solution A and the atomized solution B to form a circular vortex, making the mixing more uniform; 2) It prevents the mixed solution from rushing to the bottom, causing the flow rate of the mixed solution to be turbulent; 3) It helps the silver powder generated by the reaction of the silver source and the reducing agent in the vortex to quickly leave the vortex under the action of centrifugal force.

[0036] The mixing tank 018 is provided with a mixing liquid discharge port 019 on the side wall near the bottom, which facilitates the real-time discharge of the mixed waste liquid after the reaction in the mixing tank 018, so as to maintain a constant volume of the mixed solution in the mixing tank during the reaction process, thereby ensuring the consistency of the synthesis environment of the crude silver powder and ensuring the stability of the silver powder quality.

[0037] In one specific embodiment, the continuous silver powder production apparatus further includes a filter screen 013 installed on the coarse product conveyor belt 020, which is installed on the other side of the anti-impact base 021. Thus, the flocculent precipitate formed by the reaction of the silver source and the reducing agent is filtered by the filter screen 013 and discharged with the coarse product conveyor belt 020, minimizing the physical agglomeration of silver powder to form larger particles and achieving continuous silver powder production. The mesh size of the filter screen is 1000 mesh or higher; in this embodiment, the mesh size is 2000 mesh or higher.

[0038] In one specific embodiment, the continuous silver powder production device further includes a baffle plate 007 disposed above the storage tank, the dam, and the mixing tank to prevent the reaction raw material solution from escaping and being wasted during the flow, spraying, and vortexing processes, especially to prevent solution A from being wasted during the flow process. The high-pressure atomizing pipe 008 is installed on the baffle plate 007 at the intersection of the dam slope and the mixing tank 018. This design has two main functions: first, the overflowing solution A has the highest flow velocity at this point, allowing it to quickly mix with the atomized solution B and enter the mixing vortex; second, it ensures the stability of the overflowing solution A flow velocity.

[0039] In one specific embodiment, the continuous silver powder production device further includes a finished product conveyor belt 017, and the cleaning tank 015 is installed on the finished product conveyor belt 017 to facilitate the conveying of the cleaning tank containing wet silver powder to the next process.

[0040] In one specific embodiment, the side wall of the cleaning tank 015 is also provided with a cleaning liquid discharge port 016 to facilitate the discharge of the upper clear liquid waste liquid in the cleaning tank and obtain wet silver powder. In addition, the upper clear liquid waste liquid discharged from the cleaning liquid discharge port 016 can be discharged into a settling tank for further sedimentation to recover the synthesized silver powder to a greater extent.

[0041] Example 2 This embodiment provides a method for continuous production of silver powder using the production apparatus provided in Embodiment 1, including the following steps: Raw material supply: Solution A is injected into the liquid receiving cavity 004 in the storage tank through the bottom feeding pipe 003. After the solution A in the liquid receiving cavity 004 stabilizes, the movable bottom plate 002 is controlled to move upward so that the liquid level of solution A is not lower than the overflow port of solution A and overflows from the overflow port of solution A. The overflowing solution A 005 flows steadily down the dam slope. At the same time, near the bottom of the dam slope, solution B is atomized and sprayed out from the high-pressure atomizing pipe 008. The atomized solution B 009 comes into contact with the overflowing solution A 005. Crude silver powder synthesis: Based on the principle of a dam, the overflowing solution A 005 and the atomized solution B 009 come into contact and flow along the dam slope to the anti-scour base 021 at the bottom of the mixing tank, forming a mixing vortex 010 above the anti-scour base 021. After sufficient reaction, silver powder is synthesized. Since the density of the silver powder is greater than that of the solution, it will precipitate to form crude silver powder 012. The crude silver powder 012 is filtered by the filter screen 013 and falls onto the crude product conveyor belt 020, which then conveys it to the next process. At the same time, part of the mixed solution in the mixing tank 018 is discharged through the mixed solution outlet 019 to maintain a constant volume of the mixed solution in the mixing tank 018. Cleaning silver powder: After the coarse silver powder 012 reaches the top of the coarse product conveyor belt 020, the high-pressure spray device 014 can both blow the coarse silver powder 012 into the cleaning tank 015 and gradually settle it down, and also clean the surface of the silver powder of excess organic matter; after the upper clear liquid is discharged from the cleaning liquid outlet 016, the settled silver powder can be output through the finished product conveyor belt 017, dried and shaped to obtain the wet silver powder finished product.

[0042] The silver source solution and reducing agent solution described in this invention are both existing technologies. Factors such as the flow rate and volume of the overflow solution A 005 and the atomized solution B 009, the silver source concentration, the reducing agent concentration, and the vortex intensity of the mixed solution all affect the quality and consistency of the wet silver powder product. Regardless of the specific settings of the parameters for these influencing factors, their values ​​can be determined based on actual process requirements, as long as the Ag content in the silver source in the mixing tank 018 is guaranteed. + The silver powder can be completely reduced to Ag elemental particles. Preferably, the silver source solution may include a silver source with a concentration of 0.1-1 mol / L and a dispersant with a concentration of 0.001-0.1 mol / L, and the reducing agent solution may include a reducing agent with a concentration of 0.2-2 mol / L and an additive with a concentration of 0.01-0.1 mol / L. In the step of synthesizing crude silver powder, the flow rate ratio of the overflow solution A 005 to the atomized solution B 009 is 1:2-10. The silver source can be silver nitrate, silver ammonia, etc. The dispersant can be polyvinylpyrrolidone (PVP-K15), etc. The reducing agent can be ascorbic acid, formaldehyde, sodium borohydride, etc. The additive can be nitric acid, sulfuric acid, sodium hydroxide, sodium carbonate, sodium bicarbonate, etc., used to adjust the pH value of solution A or solution B. The flow rate of the overflowing solution A 005 is preferably 0.4-0.6 L / min, and the flow rate of the atomized solution B 0095 is preferably 0.4-2 L / min.

[0043] The continuous silver powder production apparatus and method provided in this embodiment of the invention can not only realize the continuous production of silver powder throughout the entire process, but also has the advantages of high production efficiency, low energy consumption, good environmental protection and stable silver powder quality; this is specifically verified through the following test scheme.

[0044] Application example: The method provided in Example 2 is used to produce silver powder, including the following steps: (1) Prepare 1 mol / L silver nitrate solution, 0.3 mol / L ascorbic acid solution, 10 g / L polyvinylpyrrolidone PVP-K15 dispersant solution, dilute nitric acid solution, and sodium hydroxide solution respectively; and premix the 1 mol / L silver nitrate solution and the 10 g / L polyvinylpyrrolidone PVP-K15 dispersant solution at a volume ratio of 1:2, and prepare 10 L of solution A with pH=3 by combining with dilute nitric acid solution; mix the 0.3 mol / L ascorbic acid solution and sodium hydroxide solution to prepare 30 L of solution B with pH=3; (2) 10 L of solution A is injected into the liquid receiving cavity 004 through the bottom feeding pipe 003. After solution A stabilizes, the upper level of solution A is made higher than the top surface of the spillway 006. The overflowing solution A 005 can flow down steadily along the dam slope with a flow rate of 0.5 L / min. (3) The high-pressure atomizing pipe 008 contains a high-pressure solution B, which is atomized by the fan-shaped sprayer 023 and comes into contact with the overflowing solution A 005. The flow rate is 1.5 L / min. (4) After the overflowing solution A 005 comes into contact with the atomized solution B 009, it reaches the bottom anti-impact base 021 and forms a mixed liquid vortex 010 on the upper part of the anti-impact base 021. After the reaction is complete, silver powder is synthesized. Since the density of the silver powder is greater than that of the solution, it will precipitate to obtain crude silver powder 012, which is then conveyed to the next stage by the crude product conveyor belt 020 with filter screen 013. (5) After the coarse silver powder 012 reaches the top of the coarse product conveyor belt 020, the high-pressure spray device 014 can both blow the coarse silver powder into the cleaning tank 015 and gradually settle it down, and also clean the excess organic matter on the surface of the silver powder; after the upper clear liquid is discharged from the cleaning liquid outlet 016, the settled silver powder can be output through the finished product conveyor belt 017 to obtain the wet silver powder finished product, such as Figure 3 As shown on the left.

[0045] Comparative Example (Traditional Method): This comparative example provides a method for generating silver powder, including the following steps: (1) Prepare 1 mol / L silver nitrate solution, 0.3 mol / L ascorbic acid solution, 10 g / L polyvinylpyrrolidone PVP-K15 dispersant solution, dilute nitric acid solution, and sodium hydroxide solution respectively; and premix the 1 mol / L silver nitrate solution and the 10 g / L polyvinylpyrrolidone PVP-K15 dispersant solution at a volume ratio of 1:2, and prepare 10 L of pH=3 solution A with dilute nitric acid solution; mix the 0.3 mol / L ascorbic acid solution and sodium hydroxide solution to prepare 30 L of pH=3 solution B, and place them in a chemical drum; (2) Solution B is added to solution A in the reactor by means of a pump at a flow rate of 1.5 L / min. The reactor rotation speed is 300 rpm / min. At this time, the solution changes color. (3) Since the pH changes continuously during the silver powder reduction reaction, dilute nitric acid solution or sodium hydroxide solution needs to be added to the solution to keep the pH change in the reaction solution within ±0.3; at the same time, since the redox reaction is highly exothermic, a high and low temperature device needs to be started to ensure that the internal temperature change of the reactor is less than ±2℃. (4) After the reaction solution has completely turned colorless and transparent, and after reacting for 1 hour, the reaction vessel can be stopped. The mixed mother liquor containing silver powder is injected into a centrifuge / filter press for the first solid-liquid separation; then the filter cake is removed, crushed, and placed back into the washing vessel for washing (the theoretical yield for each washing is 99.5%). After repeating the solid-liquid separation operation 4 times, the wet silver powder product is obtained, such as... Figure 3 As shown on the right.

[0046] The methods for producing wet silver powder provided in the application examples and comparative examples were each repeated three times. The actual amount of silver powder obtained, the actual yield, the time taken, the water consumption, and the particle size (laser particle size analyzer) are shown in Tables 1 and 2. Specifically, the actual amount of silver powder obtained was obtained by the following method: the wet silver powder product after being washed with water was first washed with ethanol (to remove moisture and a small amount of residual organic matter), and then dried in a 60°C forced-air drying oven for 12 hours to obtain dry silver powder; then the mass of the dry silver powder was weighed.

[0047] Actual yield: is the actual amount of silver powder obtained divided by the theoretical amount of silver powder obtained.

[0048] Table 1 Comparison of Silver Powder Production type Theoretically obtained quality of crude silver powder Theoretical yield after washing Actual amount of silver powder obtained Actual harvest rate Water consumption (L) Time taken (h) Comparative Example 1078.67 98.015% 1056.13 97.91% 70～120 6～8 Application examples 1078.67 99.5% 1071.66 99.35% 30～50 2～4 The "theoretical yield of crude silver powder" in the table above is obtained by theoretical calculation based on the original amount of silver nitrate used; the "theoretical yield after washing" in the comparative example is obtained by the cumulative yield of four washings (0.95×0.95×0.95×0.95).

[0049] Table 2. Statistical Comparison of Particle Size of Wet Silver Powder Obtained from Three Repeated Experiments

[0050] As can be seen from Tables 1-2, compared with the traditional comparative examples, the application examples using the method provided in the embodiments of the present invention significantly improve the actual yield of wet silver powder, while greatly reducing water consumption and production time, thus effectively lowering the production cost of wet silver powder. Furthermore, the differences in particle sizes D10, D50, and D90 of the silver powder synthesized using the method provided in the embodiments of the present invention (application examples) are significantly smaller. Figure 3 As shown, the wet silver powder synthesized using the method provided in this embodiment of the invention has a relatively concentrated particle size, which effectively improves the consistency and quality of the silver powder particle size.

[0051] In summary, the continuous silver powder production apparatus and method provided in this embodiment of the invention, combined with the principle of a rolling dam, realizes energy-saving, rapid, continuous, and green production of silver powder throughout the entire process, while solving problems such as unstable silver powder quality. In addition, the above-mentioned production apparatus and method also have the advantages of high production efficiency, low energy consumption, and good environmental protection. Its promotion and application will help improve the overall level of the silver powder preparation industry and promote the sustainable development of the electronics industry.

[0052] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them; although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications can still be made to the specific implementation of the present invention or equivalent substitutions can be made to some technical features without departing from the spirit of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the technical solutions claimed in the present invention.

Claims

1. A continuous production apparatus for silver powder, comprising: The storage tank for containing solution A, the rolling water dam body, the mixed liquid tank, the high-pressure atomizing pipeline for supplying solution B, the coarse product conveying belt, the high-pressure spraying device and the cleaning tank are provided, and the rolling water dam body is in communication with the storage tank and the mixed liquid tank respectively, one end of the coarse product conveying belt is connected with the mixed liquid tank, and the other end is connected with the high-pressure spraying device; the cleaning tank is arranged below the high-pressure spraying device; Wherein, one of the solution A and the solution B is a silver source solution, and the other is a reducing agent solution; The storage tank comprises a liquid containing cavity, a liquid level adjusting unit and a solution A overflow port, wherein the liquid containing cavity can contain the solution A, the liquid level adjusting unit can adjust the liquid level of the solution A in the liquid containing cavity, and the solution A continuously overflows from the solution A overflow port; The rolling water dam body comprises a dam top and a dam body slope, the bottom of the dam body slope extends to the mixed liquid tank, and the height of the dam top is not higher than the solution A overflow port; the solution A overflowing from the solution A overflow port can flow along the dam body slope to the mixed liquid tank from the dam top; The high-pressure atomizing pipeline can atomize and spray the solution B near the bottom of the dam body slope, and the solution B flows to the mixed liquid tank with the solution A, and forms a mixed liquid vortex near the bottom of the dam body slope, so that the solution A and the solution B fully react to synthesize silver powder coarse product; the silver powder coarse product falls on the coarse product conveying belt and is transmitted to the high-pressure spraying device; the high-pressure spraying device can blow and spray the silver powder coarse product into the cleaning tank for cleaning to obtain finished product wet silver powder.

2. The production apparatus according to claim 1, characterized by The liquid level adjusting unit comprises a movable bottom plate, the upper part of the movable bottom plate forms the liquid containing cavity, and the lower part is provided with a lifting structure, so that the movable bottom plate moves up and down to continuously adjust the liquid level of the solution A contained in the liquid containing cavity, so that the solution A continuously overflows from the solution A overflow port.

3. The production apparatus according to claim 2, characterized by The liquid level adjusting unit further comprises a bottom filling pipeline which can continuously fill the solution A into the liquid containing cavity.

4. The production apparatus according to claim 1, characterized by The upper parts of the storage tank, the rolling water dam and the mixed liquid tank are provided with a material blocking plate.

5. The production apparatus according to claim 1, characterized by A plurality of fan-shaped atomizers are installed on the high-pressure atomizing pipeline and face the dam body slope; the high-pressure atomizing pipeline is installed on the material blocking plate at the intersection of the rolling water dam and the mixed liquid tank.

6. The production apparatus according to claim 1, wherein A scouring prevention base is installed at the bottom of the mixed liquid tank, one end of the scouring prevention base extends to the bottom of the dam body slope, and the vortex formed in the mixed liquid tank is located above the scouring prevention base.

7. The production apparatus according to claim 1, wherein The coarse product conveying belt is installed on the other side of the scouring prevention base, and a filter screen is installed on the coarse product conveying belt; the silver powder coarse product formed by the vortex at the bottom of the dam body slope is filtered through the filter screen and falls on the coarse product conveying belt and is transmitted to the next process.

8. The production apparatus according to claim 1, wherein A mixed liquid discharge port is arranged at the bottom of the mixed liquid tank, so as to facilitate the discharge of the mixed liquid after reaction and keep the volume of the mixed liquid tank constant during the reaction process.

9. The production apparatus according to claim 1, wherein The cleaning tank is installed on the finished product conveying belt, so as to facilitate the transmission of the cleaning tank containing wet silver powder to the next process.

10. A continuous production method of silver powder, using the production device of any one of claims 1-9 to produce silver powder products, comprising the steps of: feeding raw materials: injecting solution A into the storage tank and making it overflow through the overflow port of the solution A, and the overflowed solution A flows down along the dam slope; at the same time, near the bottom of the dam slope, solution B is sprayed from the high-pressure atomizing pipeline, and the atomized solution B contacts with the overflowed solution A; synthesizing silver powder crude products: according to the principle of the rolling dam, after the overflowed solution A and the atomized solution B contact, they flow to the bottom of the mixing tank along the dam slope and form a vortex in the mixing tank, and after sufficient reaction, silver powder crude products are synthesized, and the silver powder crude products fall and deposit on the crude product conveyor belt, and are conveyed to the next process by the crude product conveyor belt; washing silver powder: after the silver powder crude products reach the top of the crude product conveyor belt, the silver powder crude products are blown away by the high-pressure spraying device, fall into the washing tank, and gradually deposit after washing to obtain wet silver powder products.

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