Preparation method and device of high specific surface area porous zinc powder

Abstract

This invention relates to the field of zinc powder preparation technology, specifically to a method and apparatus for preparing high specific surface area porous zinc powder. The method for preparing high specific surface area porous zinc powder includes the following steps: mixing zinc powder raw materials, dispersant, binder, pore-forming agent, and solvent, and stirring evenly to obtain a slurry; spray granulating the slurry to obtain precursor particles; subjecting the precursor particles to a degreasing stage: heating to 150-250°C at a heating rate of 5-10°C / min and holding for 10-120 min; a medium-temperature sintering stage: heating to 300-380°C at a heating rate of 3-5°C / min and holding for 20-180 min; and a high-temperature setting stage: heating to 385-410°C at a heating rate of 2-3°C / min and holding for 10-60 min, followed by cooling, sieving, and vacuum drying to obtain high specific surface area porous zinc powder. By constructing porous precursors through spray granulation and combining them with a low-temperature segmented sintering degreasing process, the pore structure can be controlled to achieve efficient and large-scale preparation of porous zinc powder with high specific surface area, meeting the needs of downstream high-end applications.

Description

Technical Field

[0001] This invention relates to the field of zinc powder preparation technology, specifically to a method and apparatus for preparing high specific surface area porous zinc powder. Background Technology

[0002] Zinc powder, as an important metal powder material, has broad application prospects in various fields such as aqueous zinc-ion batteries, high-end anti-corrosion coatings, catalyst carriers, and adsorption materials due to its excellent electrochemical activity, corrosion resistance, catalytic performance, and biodegradability. With the high-end development of downstream industries, higher requirements are being placed on the performance of zinc powder. Among these, high specific surface area is one of the core performance indicators—high specific surface area can significantly improve the reactivity, adsorption capacity, and coating uniformity of zinc powder, effectively improving the charge-discharge efficiency of aqueous zinc batteries, the protective performance of anti-corrosion coatings, and the catalytic activity of catalyst materials.

[0003] Currently, the mainstream methods for preparing zinc powder in industry include mechanical ball milling, water atomization, gas atomization, and chemical reduction. However, these methods all have inherent defects, making it difficult to prepare porous zinc powder with both high specific surface area and high batch stability, as detailed below: 1) Mechanical ball milling breaks zinc blocks into powder through mechanical impact. Its advantages include low equipment investment, simple process, and the ability to increase the specific surface area of ​​zinc powder to a certain extent. However, the zinc powder prepared by this method has irregular morphology, wide particle size distribution, and poor flowability; moreover, oxidation is easily generated during ball milling, resulting in a high oxygen content in the zinc powder; in addition, the stress generated by ball milling easily causes zinc powder particles to agglomerate, making it impossible to stably obtain a high specific surface area, which is difficult to adapt to high-end application scenarios.

[0004] 2) Water atomization and gas atomization are currently the main routes for large-scale zinc powder preparation. Specifically, high-pressure water or gas is used to impact molten zinc, breaking it into droplets, which are then cooled and solidified to form zinc powder. These methods produce zinc powder with high yield and moderate cost, but the powder particles are dense and non-porous, resulting in a low specific surface area and limited reactivity and adsorption capacity. This fails to meet the rigid requirements for high specific surface area in applications such as aqueous zinc batteries and advanced catalysis.

[0005] 3) The chemical reduction method uses a reducing agent to reduce zinc salts to zinc powder. This method can produce zinc powder with a high specific surface area, but it has obvious shortcomings: impurities are easily introduced during the reduction process, resulting in low purity and high oxygen content of zinc powder; the reaction conditions are difficult to control, resulting in poor batch stability; and the preparation cost is high, making it impossible to achieve large-scale mass production. It is only suitable for small-batch preparation in the laboratory and cannot meet the needs of industrial applications.

[0006] In summary, existing zinc powder preparation technologies cannot simultaneously address the core challenges of "high specific surface area, high stability, and scalability," leaving a significant market gap for high-end porous zinc powder with high specific surface area.

[0007] Therefore, developing a method and apparatus that is adapted to the characteristics of zinc powder, has a simple process, can be scaled up, and can stably prepare porous zinc powder with high specific surface area has become an urgent problem to be solved. Summary of the Invention

[0008] The purpose of this invention is to provide a method and apparatus for preparing porous zinc powder with high specific surface area, aiming to solve the technical problem that existing zinc powder preparation methods cannot simultaneously achieve high specific surface area and high batch stability.

[0009] To achieve the above objectives, this invention proposes a method for preparing high specific surface area porous zinc powder, comprising the following steps: mixing zinc powder raw materials, dispersant, binder, pore-forming agent and solvent and stirring evenly to obtain a slurry; spray granulating the slurry to obtain precursor particles; and subjecting the precursor particles to segmented sintering degreasing, cooling, sieving and vacuum drying to obtain the high specific surface area porous zinc powder. Degreasing section: Heat to 150-250℃ at a heating rate of 5-10℃ / min and hold for 10-120min; Medium-temperature sintering section: Heat to 300-380℃ at a heating rate of 3-5℃ / min and hold for 20-180min; High-temperature setting section: Heat to 385-410℃ at a heating rate of 2-3℃ / min and hold for 10-60min.

[0010] Preferably, the slurry comprises, by mass percentage: 60-80% zinc powder raw material, 0.5-2% dispersant, 2-8% binder, 5-15% pore-forming agent, and 5-15% solvent.

[0011] Preferably, the dust cover is provided with fixing ears on both sides, and at least one of the fixing ears is connected to the telescopic member.

[0012] Preferably, the segmented sintering and debinding of the precursor particles includes the following steps: Degreasing section: Under a pressure of 0 to 0.3 MPa, the temperature is raised to 180 to 220°C at a heating rate of 6 to 8°C / min, and held for 80 to 100 minutes; Medium-temperature sintering section: Under a pressure of 0.2 to 0.6 MPa, the temperature is raised to 320 to 340°C at a heating rate of 3.5 to 4.5°C / min, and held for 120 to 150 min; High-temperature setting section: Under a pressure of 0.5 to 1.0 MPa, the temperature is raised to 405 to 408°C at a heating rate of 2.3 to 2.8°C / min, and held for 40 to 50 minutes.

[0013] Preferably, the dispersant is at least one of polyethylene glycol and sodium dodecylbenzenesulfonate; the binder is at least one of polyvinyl alcohol and sodium carboxymethyl cellulose; the pore-forming agent is at least one of starch, PMMA, and ammonium bicarbonate; and the solvent is at least one of deionized water and ethanol.

[0014] Preferably, the slurry spray granulation process includes the following steps: the slurry is fed into a spray dryer, and an inert gas is simultaneously introduced into the spray dryer to maintain the pressure inside the spray dryer at 0.01 to 0.03 MPa. After atomization and drying, spherical and porous precursor particles are obtained. The spray dryer has an inlet hot air temperature of 100–380°C, an outlet hot air temperature of 60–100°C, and a feed rate of 5–50 kg / h.

[0015] Preferably, before preparing the slurry, the zinc powder raw material undergoes the following pretreatment steps: selecting zinc powder raw material with a purity of ≥99% and drying it to remove surface moisture, thereby obtaining zinc powder raw material with a particle size of 1-90μm.

[0016] Preferably, the temperature during vacuum drying is 50–120°C, and the drying time is 2–4 hours.

[0017] In addition, the present invention also proposes a preparation apparatus for high specific surface area porous zinc powder, using the above-mentioned preparation method for high specific surface area porous zinc powder. The preparation apparatus includes a slurry preparation system, a spray granulation system, a sintering and degreasing system, a cooling system, and a collection system connected in sequence. The control system is electrically connected to the slurry preparation system, the spray granulation system, the sintering and degreasing system, the cooling system, and the collection system, respectively.

[0018] Preferably, the slurry preparation system includes a preparation tank, which is equipped with a stirring mechanism and a temperature control device. The temperature control device is used to control the temperature inside the preparation tank to be 25-50°C. The spray granulation system includes a spray dryer, which is connected to a first inert gas supply device and a preparation tank; The sintering and degreasing system includes an atmosphere sintering furnace and a heating device. The atmosphere sintering furnace is connected to a second inert gas supply device. The atmosphere sintering furnace is equipped with a temperature sensor and a flow control device. The flow control device is used to control the flow rate of the inert gas introduced into the atmosphere sintering furnace to be 0.5 to 2 L / min. The cooling system is provided with a cooling chamber, which is connected to the atmosphere sintering furnace and a third inert gas supply device to introduce inert gas at -5 to 10°C into the cooling chamber. The collection system includes a powder collection tank, which is equipped with a sieving mechanism and a dust removal device. The sieving mechanism is used to sieve zinc powder to obtain porous zinc powder with a high specific surface area and a particle size of 20-200 μm.

[0019] Preferably, the powder collection tank is connected to the preparation tank and is used to recover high specific surface area porous zinc powder with a particle size not in the range of 20-200 μm to the preparation tank for re-preparation of slurry.

[0020] The method and apparatus for preparing high specific surface area porous zinc powder disclosed in this invention have the following beneficial effects: 1. Technological innovation to overcome existing technical bottlenecks: The composite process of "spray granulation + segmented sintering and debinding" is adopted. Spray granulation constructs spherical porous precursors, laying the foundation for high specific surface area; segmented sintering and debinding achieves complete removal of binders and pore-forming agents. At the same time, low-temperature sintering (below the melting point of zinc) technology is used to maintain the porous skeleton from collapsing and melting agglomeration, solving the problem that a single process cannot obtain stable high specific surface area zinc powder. 2. Excellent and stable product performance: The prepared porous zinc powder is spherical / quasi-spherical with a uniform particle size distribution in the range of 20-200μm, and the specific surface area is increased by 1.5-8 times compared with conventional atomized zinc powder; the entire preparation process is protected by an inert atmosphere with an oxygen content ≤100ppm; the porous structure of the zinc powder provides sufficient channels for reaction and adsorption, significantly improving reaction activity and adsorption capacity, and is suitable for high-end needs in multiple fields; 3. Simple process and scalable: It adopts general and mature equipment, without the need for customized special equipment. The slurry preparation, spray granulation and sintering debinding are integrated into continuous production with a capacity of 50-1000 kg / day. The preparation cost is lower than that of chemical reduction method, which is suitable for industrial-scale promotion. 4. High adaptability: The specific surface area, pore size distribution and particle size of zinc powder can be flexibly controlled by adjusting the slurry formula, spray granulation parameters and sintering degreasing parameters to adapt to different downstream scenarios such as water-based zinc batteries, anti-corrosion coatings, and catalyst carriers. 5. Environmentally friendly and with high resource utilization: The preparation process has no harmful gas emissions, and dust is treated by a dust removal device, which meets environmental protection requirements; the coarse powder after sintering and degreasing can be recycled and reused, reducing raw material waste and improving resource utilization. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0022] Figure 1 This is a scanning electron microscope image of the untreated zinc powder raw material in Example 1; Figure 2 This is a scanning electron microscope image of the high specific surface area porous zinc powder prepared in Example 1; Figure 3 This is a connection block diagram of the apparatus for preparing high specific surface area porous zinc powder according to the present invention; Figure 4 This is a schematic diagram of the slurry preparation system in the apparatus for preparing high specific surface area porous zinc powder of the present invention; Figure 5 This is a schematic diagram of the sintering and degreasing system in the apparatus for preparing high specific surface area porous zinc powder of the present invention; Figure 6 This is a partial structural diagram of the cooling system in the preparation apparatus for high specific surface area porous zinc powder of the present invention; Figure 7 This is a schematic diagram of the sieving mechanism in the preparation device for high specific surface area porous zinc powder of the present invention.

[0023] In the attached diagram: 1-slurry preparation system, 11-preparation tank, 12-stirring mechanism, 2-spray granulation system, 3-sintering and degreasing system, 31-atmosphere sintering furnace, 32-heating device, 4-cooling system, 41-cooling chamber, 5-collection system, 51-powder collection tank, 52-screening mechanism, 6-control system.

[0024] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0026] It should be noted that if the embodiments of the present invention involve directional indication, the directional indication is only used to explain the relative positional relationship and movement of the components in a certain specific posture. If the specific posture changes, the directional indication will also change accordingly.

[0027] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. If the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0028] A method for preparing high specific surface area porous zinc powder includes the following steps: mixing zinc powder raw materials, dispersant, binder, pore-forming agent and solvent and stirring evenly to obtain a slurry; spray granulation of the slurry to obtain precursor particles; the precursor particles are subjected to segmented sintering degreasing, cooling, sieving and vacuum drying to obtain the high specific surface area porous zinc powder. In this process, after introducing inert gas, the furnace atmosphere flow rate is maintained at 0.5–2 L / min. The precursor particles undergo the following segmented sintering and degreasing steps: in the degreasing stage, the temperature is increased to 150–250°C at a rate of 5–10°C / min and held for 10–120 min; in the medium-temperature sintering stage, the temperature is increased to 300–380°C at a rate of 3–5°C / min and held for 20–180 min; and in the high-temperature setting stage, the temperature is increased to 385–410°C at a rate of 2–3°C / min and held for 10–60 min.

[0029] In this scheme, zinc powder raw materials, dispersants, binders, pore-forming agents and solvents are first uniformly mixed through a mixing and stirring slurry preparation process to form a stable slurry. Then, the slurry is spray-granulated to obtain spherical precursor particles. Next, under the protection of inert gas, the temperature is raised and held in three stages to complete the segmented sintering and degreasing process. Finally, after cooling, sieving and vacuum drying, high specific surface area porous zinc powder finished product is obtained.

[0030] This invention first mixes zinc powder raw material with dispersant, binder, pore-forming agent, and solvent to form a slurry, and then obtains spherical or near-spherical precursor particles through spray granulation. These steps significantly improve the morphological regularity and flowability of the initial zinc powder raw material, and uniformly distribute the pore-forming agent and organic template within the precursor, laying the foundation for the subsequent formation of porous structures. Compared with existing mechanical ball milling or irregular morphology methods, spray granulation allows for controllable precursor particle size and good batch-to-batch consistency, solving the problems of poor morphology and wide distribution in traditional methods.

[0031] It should be noted that spray granulation can achieve various morphological controls of powders and improve flowability. However, spray granulation alone can only produce agglomerated precursor particles. The precursor contains organic matter such as binders and dispersants. Without subsequent processing, the particles have low strength, are easily broken, and have unstable pore structures, making it difficult to form a stable porous structure and obtain a high specific surface area. In addition, zinc has a low melting point of -419.5℃, is easily oxidized, and is easily volatilized. Conventional sintering processes cannot simultaneously "preserve pores" and "prevent oxidation and melting," making existing composite processes unsuitable for the preparation requirements of zinc powder. Therefore, addressing the challenges of zinc powder's low melting point (419.5℃), easy oxidation, and high volatility, this invention does not employ the conventional high-temperature densification sintering path. Instead, it designs a special three-stage low-temperature sintering and degreasing process: In the degreasing stage (150–250℃), the temperature is increased by 5–10℃ / min to gently remove the solvent, binder, and dispersant, preventing rapid vaporization of organic matter that could lead to cracking of the green body or collapse of the pores, thus initially forming interconnected pores. In the medium-temperature sintering stage (300–380℃), the temperature is controlled below the zinc melting point, and the heating rate is reduced to 3–5℃ / min. This allows sintering necks to begin forming between zinc particles to obtain mechanical strength, while the pore-forming agent (and residual binder) completely decomposes, leaving uniform pores and ensuring that the pore structure is not destroyed by high-temperature melting. The high-temperature setting stage (385–410℃) involves heating at a slow rate of 2–3℃ / min within a temperature window close to but not exceeding the melting point of zinc, followed by a short holding time. This stage further strengthens the bonding between particles, stabilizes the formed porous structure, and, combined with inert gas protection, prevents oxidation and effectively inhibits zinc volatilization. This segmented temperature-time control strategy allows zinc powder to achieve a balance between "retaining a high specific surface area" and "obtaining sufficient particle strength." Compared to the difficulty and instability of chemical reduction methods, this approach offers a clear process window and good batch consistency.

[0032] After the aforementioned segmented sintering and degreasing, the zinc powder undergoes cooling, sieving, and vacuum drying to obtain a high specific surface area porous zinc powder with a regular spherical morphology, uniform pore structure, low oxygen content, and high batch stability. The entire process utilizes conventional equipment and is capable of large-scale production. It addresses the core challenge of existing technologies that cannot simultaneously achieve high specific surface area, high stability, and scalability, thus meeting the rigid demand for high-end zinc powder from downstream applications such as aqueous zinc-ion batteries, high-end anti-corrosion coatings, and catalyst carriers.

[0033] Further, by mass percentage, the slurry comprises: 60-80% zinc powder raw material, 0.5-2% dispersant, 2-8% binder, 5-15% pore-forming agent, and 5-15% solvent.

[0034] Within the above-mentioned component ratio range, the prepared slurry can achieve suitable viscosity and solid content. During spray granulation, the droplets are uniform and have high sphericity. Furthermore, the ratio of pore-forming agent to binder can be better matched with the segmented sintering and degreasing process, allowing the binder to burn off completely without residue during the degreasing stage. The pore-forming agent decomposes to form interconnected pores, while appropriate sintering necks are formed between zinc powder particles, ensuring that the subsequent precursor particles have sufficient green strength. This results in the stable production of porous zinc powder with high specific surface area, regular morphology, and good batch consistency.

[0035] Further, the segmented sintering and degreasing of the precursor particles includes the following steps: Degreasing stage: under a pressure of 0–0.3 MPa, the temperature is raised to 180–220°C at a heating rate of 6–8°C / min and held for 80–100 min; Medium-temperature sintering stage: under a pressure of 0.2–0.6 MPa, the temperature is raised to 320–340°C at a heating rate of 3.5–4.5°C / min and held for 120–150 min; High-temperature setting stage: under a pressure of 0.5–1.0 MPa, the temperature is raised to 405–408°C at a heating rate of 2.3–2.8°C / min and held for 40–50 min.

[0036] In this embodiment, by introducing a micro-positive pressure of 0–0.3 MPa in the degreasing section, the discharge of organic decomposition products can be accelerated under an inert atmosphere, while suppressing slight oxidation caused by local overheating on the surface of precursor particles. This avoids pore blockage or cracking of the green body in the early stage of degreasing. Furthermore, narrowing the temperature in the degreasing section to 180–220°C and holding it for 80–100 min ensures complete and stable removal of organic components, preventing carbon residue due to excessively low temperatures or premature zinc powder adhesion due to excessively high temperatures. In the medium-temperature sintering section, the pressure is increased to 0.2–0.6 MPa, combined with a sintering temperature (320–340°C) and heating rate (3.5–4.5°C / min), and the holding time is precisely controlled at 120–150 min. This promotes the uniform growth of sintering necks between zinc particles, allowing adjacent particles to achieve higher mechanical strength while maintaining the microporous structure, while preventing excessive pore closure due to excessive pressure. During the aforementioned heat preservation period, the pore-forming agent can fully decompose and form interconnected channels, preventing grain coarsening and reduction of specific surface area due to prolonged heat preservation. In the high-temperature setting stage, the pressure is further increased to 0.5–1.0 MPa, the temperature is strictly controlled at 405–408 °C, and the holding time is locked at 40–50 min. At this time, the micro-positive pressure can significantly inhibit the volatilization loss of zinc at near melting point temperature and enhance particle surface diffusion, allowing the formed porous skeleton to reach a stable sintering state in the shortest time without melting and collapse. In this high-temperature stage, the heating rate is reduced to 2.3–2.8 °C / min, further mitigating thermal shock. Combined with the micro-positive pressure environment, this allows the surface atoms of the particles more time to migrate and complete the orderly growth of the sintering neck, thereby obtaining a higher and more stable specific surface area without adding any external high-pressure equipment, while controlling the porosity fluctuation between product batches within ±1.5%.

[0037] Further, the dispersant is at least one of polyethylene glycol and sodium dodecylbenzenesulfonate; the binder is at least one of polyvinyl alcohol and sodium carboxymethyl cellulose; the pore-forming agent is at least one of starch, PMMA, and ammonium bicarbonate; and the solvent is at least one of deionized water and ethanol.

[0038] Furthermore, the slurry spray granulation process includes the following steps: the slurry is fed into a spray dryer, and an inert gas is simultaneously introduced into the spray dryer to maintain the pressure inside the spray dryer at 0.01 to 0.03 MPa. After atomization and drying, spherical and porous precursor particles are obtained. The spray dryer has an inlet hot air temperature of 120–180°C, an outlet hot air temperature of 60–100°C, and a feed rate of 5–15 kg / h.

[0039] In the spray granulation step, inert gas is introduced into the spray dryer to maintain a slight positive pressure of 0.01–0.03 MPa. The hot air temperature parameters are 100–380℃ at the inlet, 60–100℃ at the outlet, and a feed rate of 5–50 kg / h. This slight positive pressure inert environment effectively inhibits the oxidation of zinc powder during spraying, while also preventing severe droplet turbulence and ensuring uniform atomization. Combined with a suitable hot air temperature and feed rate, the solvent evaporates smoothly without droplet bursting or incomplete drying, resulting in precursor particles with high sphericity, smooth surfaces, and uniform internal pore distribution.

[0040] Furthermore, before preparing the slurry, the zinc powder raw material undergoes the following pretreatment steps: selecting zinc powder raw material with a purity ≥99% and drying it to remove surface moisture, thereby obtaining zinc powder raw material with a particle size of 1~90μm.

[0041] The above pretreatment steps can significantly improve the surface cleanliness and activity of zinc powder raw materials, and avoid pore blockage or local overburning caused by moisture and oxide scale in subsequent sintering. At the same time, controlling the particle size within a narrow range can ensure uniform slurry dispersion and consistent droplet size during spray granulation, thereby obtaining precursor particles with high sphericity and regular internal structure. Ultimately, this is conducive to effectively improving the specific surface area of ​​porous zinc powder and further improving batch stability.

[0042] Furthermore, the vacuum drying temperature is 50–120°C, and the drying time is 2–4 hours. These conditions can effectively remove trace amounts of moisture, residual organic decomposition products, and inert gases adsorbed inside and on the surface of the sintered particles without damaging the porous structure. This avoids oxidation of the zinc powder surface or collapse of the pores caused by high-temperature drying, and the shorter drying time effectively maintains the high specific surface area and particle strength already formed.

[0043] In particular, the present invention also proposes a preparation apparatus for high specific surface area porous zinc powder, using the above-described preparation method for high specific surface area porous zinc powder. The preparation apparatus includes a slurry preparation system 1, a spray granulation system 2, a sintering and degreasing system 3, a cooling system 4, and a collection system 5 connected in sequence. The control system 6 is electrically connected to the slurry preparation system 1, the spray granulation system 2, the sintering and degreasing system 3, the cooling system 4, and the collection system 5, respectively.

[0044] The above-mentioned apparatus can be used to prepare various types of metal powders, and is particularly suitable for the preparation of porous zinc powder. Specifically, for example... Figures 3 to 7As shown, the device achieves fully automated collaboration through the coordination of a slurry preparation system 1, a spray granulation system 2, a sintering and degreasing system 3, a cooling system 4, a collection system 5, and a control system 6. Specifically, the slurry preparation system 1 ensures uniform mixing of zinc powder, dispersant, binder, pore-forming agent, and solvent, providing a homogeneous slurry for subsequent processes; the spray granulation system 2 atomizes and dries the slurry to obtain precursor particles with high sphericity and porous structure; the sintering and degreasing system 3 performs segmented temperature control and micro-positive pressure inert atmosphere sintering, precisely removing organic matter and forming a stable pore structure while preventing zinc powder oxidation or melting; the cooling system 4 enables rapid cooling of the zinc powder, avoiding grain coarsening and pore collapse; the collection system 5 is used for efficient screening and recovery of the finished product; and the control system 6 monitors and adjusts parameters such as temperature, pressure, and feed rate of each unit in real time to ensure batch consistency.

[0045] The entire device has a compact structure and a coherent process, enabling the large-scale and low-cost production of porous zinc powder with high specific surface area and high stability.

[0046] Furthermore, the slurry preparation system 1 includes a preparation tank 11, which is equipped with a stirring mechanism 12 and a temperature control device. The temperature control device is used to control the temperature inside the preparation tank 11 to be 25-50°C. The spray granulation system 2 includes a spray dryer 21, which is connected to a first inert gas supply device and to the preparation tank 11; The sintering and degreasing system 3 includes an atmosphere sintering furnace 31 and a heating device 32. The atmosphere sintering furnace 31 is connected to a second inert gas supply device. The atmosphere sintering furnace 31 is equipped with a temperature sensor and a flow control device. The flow control device is used to control the flow rate of the inert gas introduced into the atmosphere sintering furnace 31 to be 0.5 to 2 L / min. The cooling system 4 is provided with a cooling chamber 41, which is connected to the atmosphere sintering furnace 31 and a third inert gas supply device to introduce inert gas at -5 to 10°C into the cooling chamber 41. The collection system 5 includes a powder collection tank 51, which is equipped with a sieving mechanism 52 and a dust removal device. The sieving mechanism 52 is used to sieve zinc powder to obtain porous zinc powder with a high specific surface area and a particle size of 20-200 μm.

[0047] Specifically, the mixing tank 11 of the slurry preparation system 1 is equipped with a stirring mechanism 12 and a temperature control device. The stirring mechanism 12 (such as a spiral stirrer) can ensure that the zinc powder raw material is fully and evenly mixed with the dispersant, binder, pore-forming agent and solvent, avoiding agglomeration and sedimentation. The stirring speed of the stirring mechanism 12 is 200 to 500 r / min. The temperature control device can maintain the slurry within a suitable temperature window of 25 to 50°C, which can prevent the viscosity from being too high at low temperatures, resulting in uneven mixing, and also prevent the solvent from evaporating too quickly or the binder from reacting prematurely at high temperatures. This results in a homogeneous slurry with stable solid content and good fluidity, providing a consistent raw material base for subsequent spray granulation.

[0048] The spray dryer 21 of the spray granulation system 2 is connected to the first inert gas supply device and also directly connected to the preparation tank 11. The spray dryer can adopt a centrifugal or pressure atomization structure, with an atomization speed of 10,000 to 25,000 r / min (centrifugal) or an atomization pressure of 0.3 to 0.8 MPa (pressure). The spray dryer is equipped with a feed inlet, a hot air inlet, a hot air outlet, and a granulated product outlet. The feed inlet is connected to the discharge outlet of the preparation tank 11. The inert gas introduced by the first inert gas supply device can isolate oxygen during the atomization drying process, significantly inhibiting the oxidation of zinc powder. At the same time, by using the coordinated control of the inlet / outlet hot air temperature and the feed rate, the droplets are dried and shaped smoothly, resulting in precursor particles with high sphericity, smooth surface, and porous interior. The particles do not stick together and have good flowability, greatly improving granulation efficiency and product consistency.

[0049] The atmosphere sintering furnace 31 of the sintering and degreasing system 3 achieves multi-stage sintering through the heating device 32. In addition, the atmosphere sintering furnace 31 is connected to the second inert gas supply device. The furnace is equipped with a temperature sensor and a flow control device. The flow control device (such as a flow control valve) controls the flow rate of the inert gas to 0.5-2L / min to maintain the inert atmosphere in the furnace and prevent zinc powder from oxidizing / vaporizing. The temperature sensor provides real-time feedback on the temperature in the furnace, which, together with the heating device 32, achieves precise segmented heating.

[0050] The cooling chamber 41 of the cooling system 4 is connected to the discharge port of the atmosphere sintering furnace 31. In addition, it is also connected to the third inert gas supply device to introduce low-temperature inert gas at -5 to 10°C, so that the high-temperature porous zinc powder sintered in the cooling chamber 41 can achieve rapid and uniform cooling, preventing grain coarsening or zinc powder surface re-oxidation or agglomeration during slow cooling. At the same time, the low-temperature gas can avoid particle cracking caused by thermal stress, and preserve the high specific surface area and pore morphology formed, thereby improving product yield and quality.

[0051] The powder collection tank 51 of the collection system 5 is equipped with a screening mechanism 52 and a dust removal device. The powder collection tank 51 is connected to the discharge port of the cooling chamber 41. The screening mechanism 52 can classify the porous zinc powder after sintering and cooling according to the particle size to obtain the target product that meets the particle size requirements (20~200μm), remove excessively large agglomerates or excessively fine debris, and ensure that the product has a narrow particle size distribution and high batch stability. The dust removal device effectively collects the flying fine powder, reduces material loss and avoids dust pollution of the environment, and achieves clean production.

[0052] All the above systems are coordinated by the control system 6 to form an automated continuous production line from slurry preparation to finished product screening. Each component plays a precise role in its respective section, and together they realize the large-scale, low-oxidation, and highly consistent preparation of high specific surface area porous zinc powder.

[0053] Furthermore, the powder collection tank 51 is connected to the preparation tank 11 and is used to recover high specific surface area porous zinc powder with a particle size not in the range of 20-200 μm to the preparation tank 11 for reprocessing into a slurry. The fine / coarse powder in the powder collection tank 51 can be returned to the preparation system for reuse in the above manner, thereby improving the overall raw material utilization rate.

[0054] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are only used to explain the present invention and are not intended to limit the present invention.

[0055] Example 1 A method for preparing high specific surface area porous zinc powder includes the following steps: S1. Raw material pretreatment: Select zinc powder raw material with a purity of 99.95% and a particle size of 5μm, put it into a vacuum drying oven and dry it at 80℃ for 3h to remove surface moisture; S2. Slurry preparation: Add 70% zinc powder raw material, 1% polyethylene glycol (dispersant), 5% polyvinyl alcohol (binder), 12% starch (pore-forming agent) and 12% deionized water (solvent) to preparation tank 11, adjust the preparation temperature to 35℃, stir at 300 r / min for 45 min to obtain a uniformly dispersed slurry; S3. Spray granulation: The slurry is granulated using a centrifugal spray dryer. The parameters are adjusted to an inlet hot air temperature of 150℃, an outlet hot air temperature of 80℃, an atomization speed of 18000 r / min, and a feed rate of 10 kg / h. Nitrogen gas is introduced into the spray dryer to maintain an internal pressure of 0.02 MPa. After atomization and drying, spherical porous precursor particles with a particle size of 50–80 μm are obtained. S4. Segmented sintering and debinding: The precursor particles are fed into atmosphere sintering furnace 31, nitrogen is introduced, and the atmosphere flow rate is maintained at 1L / min. The temperature is increased in segments (all under atmospheric pressure). ① Degreasing section: Heat to 200℃ at a rate of 8℃ / min and hold for 90min; ②Medium-temperature sintering section: Heat to 350℃ at a rate of 4℃ / min and hold for 120min; ③ High-temperature setting section: Heat to 405℃ at a rate of 2.5℃ / min and hold for 45min; S5. Cooling and collection: The zinc powder after sintering and degreasing is sent into the cooling chamber 41 and rapidly cooled to room temperature by 5°C nitrogen gas. Zinc powder of 50-80μm is screened out by the sieving mechanism 52 and collected by the powder collection tank 51. S6. Post-processing: The collected zinc powder is placed in a vacuum drying oven and dried at 90°C for 3 hours to obtain a high specific surface area porous zinc powder product.

[0056] Example 2 A method for preparing high specific surface area porous zinc powder includes the following steps: S1. Raw material pretreatment: Select zinc powder raw material with a purity of 99.9% and a particle size of 3μm, put it into a vacuum drying oven and dry it at 100℃ for 2 hours to remove surface moisture; S2. Slurry preparation: Add 75% zinc powder raw material, 0.8% sodium dodecylbenzenesulfonate (dispersant), 3% sodium carboxymethyl cellulose (binder), 10% PMMA (pore-forming agent) and 11.2% ethanol (solvent) to preparation tank 11, adjust the preparation temperature to 40℃, stir at 400 r / min for 50 min to obtain a uniform slurry; S3. Spray granulation: The slurry is granulated using a pressure spray dryer with the following parameters: inlet hot air temperature 160℃, outlet hot air temperature 85℃, atomization pressure 0.5MPa, and feed rate 8kg / h. Argon gas is introduced into the spray dryer to maintain the internal pressure at 0.025MPa, resulting in spherical porous precursor particles with a particle size of 30-60μm. S4. Segmented sintering and debinding: The precursor particles are fed into atmosphere sintering furnace 31, argon gas is introduced, and the atmosphere flow rate is maintained at 1.5 L / min. The temperature is increased in segments (all under atmospheric pressure): ① Degreasing section: Heat to 220℃ at 7℃ / min and hold for 80min; ②Medium-temperature sintering section: Heat to 360℃ at a rate of 3.5℃ / min and hold for 150min; ③ High-temperature setting section: Increase the temperature to 400℃ at a rate of 2℃ / min and hold for 50min; S5. Cooling and collection: The zinc powder after sintering and degreasing is sent into the cooling chamber 41 and cooled to room temperature by 0℃ argon gas. The 30-60μm zinc powder is screened out by the sieving mechanism 52 and collected by the powder collection tank 51. S6. Post-processing: The collected zinc powder is placed in a vacuum drying oven and dried at 85°C for 3.5 hours to obtain a high specific surface area porous zinc powder product.

[0057] Example 3 A method for preparing high specific surface area porous zinc powder includes the following steps: S1. Raw material pretreatment: Select zinc powder raw material with a purity of 99.95% and a particle size of 1μm, put it into a vacuum drying oven and dry it at 100℃ for 2 hours to remove surface moisture; S2. Slurry preparation: Add 76% zinc powder raw material, 2% sodium dodecylbenzenesulfonate (dispersant), 5% sodium carboxymethyl cellulose (binder), 4% PMMA (pore-forming agent) and 13% ethanol (solvent) to preparation tank 11, adjust the preparation temperature to 50℃, stir at 450 r / min for 50 min to obtain a uniform slurry; S3. Spray granulation: The slurry is granulated using a pressure spray dryer with the following parameters: inlet hot air temperature 280℃, outlet hot air temperature 60℃, atomization pressure 0.7MPa, and feed rate 15kg / h. Argon gas is introduced into the spray dryer to maintain the internal pressure at 0.02MPa, resulting in spherical porous precursor particles with a particle size of 20-70μm. S4. Segmented sintering and debinding: The precursor particles are fed into atmosphere sintering furnace 31, argon gas is introduced, and the atmosphere flow rate is maintained at 2L / min. The temperature is increased in segments (all under normal pressure). ① Degreasing section: Heat to 220℃ at 8℃ / min and hold for 100min; ②Medium-temperature sintering section: Heat to 380℃ at a rate of 4℃ / min and hold for 80min; ③ High-temperature setting section: Increase the temperature to 390℃ at a rate of 2℃ / min and hold for 30 minutes; S5. Cooling and collection: The zinc powder after sintering and degreasing is sent into the cooling chamber 41 and cooled to room temperature by 5°C argon gas. The zinc powder of 20-40μm is screened out by the sieving mechanism 52 and collected by the powder collection tank 51. S6. Post-processing: The collected zinc powder is placed in a vacuum drying oven and dried at 120°C for 2 hours to obtain a high specific surface area porous zinc powder product.

[0058] Comparative Example 1 In this comparative example, all preparation steps and parameters are the same as in Example 2, except that: 1. The slurry is not spray-granulated, but is formed into granules by stirring and tumbling in a mixing granulator, and then dried to obtain particles; 2. The sintering parameters are adjusted to: heating from room temperature to 400℃ at a heating rate of 5℃ / min and holding for 280min.

[0059] Comparative Example 2 In this comparative example, all preparation steps and parameters are the same as in Example 2, except that the sintering parameters are adjusted to: heating from room temperature to 400℃ at a heating rate of 5℃ / min and holding for 180min.

[0060] Comparative Example 3 In this comparative example, all preparation steps and parameters are the same as in Example 2, except that the sintering temperature of the ③ high-temperature shaping section is adjusted to 415℃.

[0061] The zinc powders prepared in Examples 1-3 and Comparative Examples 1-3 were subjected to the following performance tests, and the specific test results are shown in the table below.

[0062]

[0063] Note: Batch stability is primarily evaluated through intra-batch repeatability, with the core statistical indicator being the relative standard deviation (RSD). Intra-batch repeatability (multiple tests on the same batch of samples): At least six samples are randomly selected from the same batch of products for specific surface area and porosity testing. The standard deviation and relative standard deviation are calculated (RSD = standard deviation / average value × 100%). A smaller RSD value indicates better uniformity of the batch. Acceptable range reference: RSD ≤ 5%, considered good batch stability; RSD ≤ 3%, considered excellent batch stability.

[0064] As shown in the test results of Comparative Example 1 in the table above, the high specific surface area porous zinc powders prepared in Examples 1-3 have a specific surface area of ​​approximately 880-960 cm² / g and a porosity of 32-38% (excluding Examples 1-3, the test data of all high specific surface area porous zinc powders were summarized, and the measured product specific surface area was 600-2250 cm² / g, and the porosity was 32-40%). This proves that the prepared zinc powder has a high specific surface area and the batch stability of the product is high. Comparative Example 1, because it did not use a segmented sintering and degreasing process or spray granulation technology, produced zinc powder with a specific surface area of ​​only 480 cm² / g, close to the original zinc powder, and a porosity of only 8%, with almost no porous structure. Comparative Example 2 involved spray granulation but did not employ segmented sintering for degreasing. The resulting product had a specific surface area of ​​650 cm² / g and a porosity of 18%, which, while better than Comparative Example 1, was still significantly lower than the example, indicating that segmented sintering played a crucial role in pore formation. In Comparative Example 3, due to the use of a high sintering temperature of 415℃ in the third high-temperature section, the zinc alloy powder and the new alloy powder initially diffused and bonded together during sintering. However, as time progressed and the temperature increased, localized melting and collapse occurred, reducing porosity. The specific surface area decreased to 500 cm² / g, and the porosity dropped to 9%.

[0065] Example 4 In this embodiment, all preparation steps and parameters are the same as in Example 2, except that the sintering parameters are adjusted as follows: ① Degreasing section: Under pressure of 0.15MPa and 7℃ / min, the temperature is raised to 200℃ and held for 90min; ②Medium-temperature sintering section: Under the conditions of pressure increased to 0.4MPa and temperature increased to 330℃ at 4℃ / min, the temperature was held for 100min; ③ High-temperature setting section: The pressure is further increased to 0.8MPa and the temperature is raised to 406℃ at 2.5℃ / min, and held for 15min.

[0066] Comparative Example 4 In this comparative example, all preparation steps and parameters are the same as in Example 4, except that sintering is carried out under normal pressure.

[0067] Comparative Example 5 In this comparative example, all preparation steps and parameters are the same as in Example 4, except that sintering is carried out at a uniform 0.5 MPa.

[0068] The zinc powders prepared in the above examples and comparative examples were subjected to the following performance tests, and the specific test results are shown in the table below:

[0069] As shown in the test data in the table above, Example 4 further limited the pressure conditions during sintering based on Example 2, and also selected better sintering parameters. The zinc powder obtained can reach a specific surface area of ​​1125 cm² / g, porosity of 42%, and RSD (specific surface area 4.0%, porosity 3.8%). The overall performance is better, which can greatly improve process consistency and product reliability.

[0070] Comparative Example 4 was sintered directly under normal pressure, and its specific surface area and porosity were lower than those of Example 4. Comparative Example 5 was sintered under constant pressure (0.5 MPa) throughout the process, and its specific surface area and porosity were between those of Example 4 and Comparative Example 4, but the intra-batch RSD of porosity was higher, indicating that the segmented pressure progression has a unique improvement on the uniformity of the pores.

[0071] Furthermore, when the segmented sintering and degreasing process of this scheme is further adjusted to the following parameters based on Example 4, the finished zinc powder product achieves optimal performance: ① Degreasing section: Under pressure of 0.15MPa and 7.5℃ / min, the temperature is raised to 200℃ and held for 90min. The flow rate of inert gas is 1.2L / min. ②Medium-temperature sintering section: The temperature is increased to 330℃ under the condition of pressure of 0.4MPa and 4℃ / min, and held for 100min; when the pressure increases from 0.15MPa to 0.4MPa, the flow rate increases by 0.2 L / min for every 0.1MPa increase in pressure (when the pressure is 0.35-0.4MPa, the flow rate increases by 0.1 L / min). ③ High-temperature setting stage: The pressure is further increased to 0.8 MPa, and the temperature is raised to 406℃ at a rate of 2.5℃ / min, and held for 15 minutes. Ten minutes before the end of the holding period, the temperature is reduced to 400℃ at a rate of 0.1℃ / min, followed by an inert gas cooling process. This slow transition releases residual thermal stress from the sintering neck formation process and prevents microcracks caused by direct rapid cooling, thus maintaining a high specific surface area and porosity integrity.

[0072] The zinc powder prepared under the above parameters can achieve a specific surface area of ​​up to 1350 cm². 2 / g, porosity 45%, RSD (specific surface area 3.8%, porosity 3.5%).

[0073] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for preparing high specific surface area porous zinc powder, characterized in that, The process includes the following steps: mixing zinc powder raw materials, dispersant, binder, pore-forming agent and solvent and stirring evenly to obtain a slurry; spray granulation of the slurry to obtain precursor particles; and after the precursor particles are sintered, degreased, cooled, sieved and vacuum dried, the high specific surface area porous zinc powder is obtained. After introducing inert gas, the precursor particles undergo the following segmented sintering and degreasing steps: Degreasing stage: heating to 150-250℃ at a heating rate of 5-10℃ / min and holding for 10-120min; Medium-temperature sintering stage: heating to 300-380℃ at a heating rate of 3-5℃ / min and holding for 20-180min; High-temperature setting stage: heating to 385-410℃ at a heating rate of 2-3℃ / min and holding for 10-60min.

2. The method for preparing high specific surface area porous zinc powder according to claim 1, characterized in that, The slurry comprises, by weight percentage: 60-80% zinc powder raw material, 0.5-2% dispersant, 2-8% binder, 5-15% pore-forming agent, and 5-15% solvent.

3. The method for preparing high specific surface area porous zinc powder according to claim 1, characterized in that, The segmented sintering and debinding of the precursor particles includes the following steps: Degreasing section: Under a pressure of 0 to 0.3 MPa, the temperature is raised to 180 to 220°C at a heating rate of 6 to 8°C / min, and held for 80 to 100 minutes; Medium-temperature sintering section: Under a pressure of 0.2 to 0.6 MPa, the temperature is raised to 320 to 340°C at a heating rate of 3.5 to 4.5°C / min, and held for 120 to 150 min; High-temperature setting section: Under a pressure of 0.5 to 1.0 MPa, the temperature is raised to 405 to 408°C at a heating rate of 2.3 to 2.8°C / min, and held for 40 to 50 minutes.

4. The method for preparing high specific surface area porous zinc powder according to claim 1, characterized in that, The dispersant is at least one of polyethylene glycol and sodium dodecylbenzenesulfonate; the binder is at least one of polyvinyl alcohol and sodium carboxymethyl cellulose; the pore-forming agent is at least one of starch, PMMA, and ammonium bicarbonate; and the solvent is at least one of deionized water and ethanol.

5. The method for preparing high specific surface area porous zinc powder according to claim 1, characterized in that, The slurry spray granulation process includes the following steps: the slurry is fed into a spray dryer, and an inert gas is simultaneously introduced into the spray dryer to maintain the pressure inside the spray dryer at 0.01 to 0.03 MPa. After atomization and drying, spherical and porous precursor particles are obtained. The spray dryer has an inlet hot air temperature of 100–380°C, an outlet hot air temperature of 60–100°C, and a feed rate of 5–50 kg / h.

6. The method for preparing high specific surface area porous zinc powder according to claim 1, characterized in that, Before preparing the slurry, the zinc powder raw material undergoes the following pretreatment steps: zinc powder raw material with a purity of ≥99% is selected and dried to remove surface moisture, resulting in zinc powder raw material with a particle size of 1-90μm.

7. The method for preparing high specific surface area porous zinc powder according to claim 1, characterized in that, The vacuum drying temperature is 50–120°C, and the drying time is 2–4 hours.

8. An apparatus for preparing high specific surface area porous zinc powder, characterized in that, The method for preparing high specific surface area porous zinc powder according to any one of claims 1-7 includes a slurry preparation system (1), a spray granulation system (2), a sintering and degreasing system (3), a cooling system (4), and a collection system (5) connected in sequence; and a control system (6) electrically connected to the slurry preparation system (1), the spray granulation system (2), the sintering and degreasing system (3), the cooling system (4), and the collection system (5).

9. The apparatus for preparing high specific surface area porous zinc powder according to claim 8, characterized in that, The slurry preparation system (1) includes a preparation tank (11), which is equipped with a stirring mechanism (12) and a temperature control device. The temperature control device is used to control the temperature inside the preparation tank (11) to be 25-50°C. The spray granulation system (2) includes a spray dryer, which is connected to a first inert gas supply device and to the preparation tank (11); The sintering degreasing system (3) includes an atmosphere sintering furnace (31) and a heating device (32). The atmosphere sintering furnace (31) is connected to a second inert gas supply device. The atmosphere sintering furnace (31) is equipped with a temperature sensor and a flow control device. The flow control device is used to control the flow rate of the inert gas introduced into the atmosphere sintering furnace (31) to be 0.5 to 2 L / min. The cooling system (4) is provided with a cooling chamber (41), which is connected to the atmosphere sintering furnace (31) and a third inert gas supply device to introduce inert gas at -5 to 10°C into the cooling chamber (41). The collection system (5) includes a powder collection tank (51), which is equipped with a sieving mechanism (52) and a dust removal device. The sieving mechanism (52) is used to sieve zinc powder to obtain porous zinc powder with a particle size of 20 to 200 μm and a high specific surface area.

10. The apparatus for preparing high specific surface area porous zinc powder according to claim 9, characterized in that, The powder collection tank (51) is connected to the preparation tank (11) and is used to recover high specific surface area porous zinc powder with a particle size not in the range of 20 to 200 μm to the preparation tank (11) to re-prepare the slurry.

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