Process and device for preparing four types of high-purity iron-based powder by single-system water atomization coupled fractional oxidation

Abstract

The application discloses a process and device for preparing four types of high-purity iron-based powder by single-system water atomization coupled grading oxidation, relates to the technical field of metallurgical powder and new energy lithium battery raw material preparation, and comprises high-temperature and high-pressure water atomization powdering under the protection of nitrogen inert micro-positive pressure, online magnetic separation solid-liquid precise separation, high-temperature water circulation reuse, fluidized pre-oxidation closed-loop treatment, multi-path powder fine processing procedure, and a supporting integrated preparation system. The adjustable atomization pressure is adopted to control the primary powder particle size, so that the uniformity and stability of the powder particle size are ensured, and four types of differentiated products, namely, coarse high-purity iron powder, superfine high-purity iron powder, low-oxidation-degree pre-oxidized iron powder and high-purity ferric oxide powder, can be synchronously produced. Through the single-set integrated process of high-pressure water atomization, online magnetic separation and grading oxidation, the synchronous flexible production of the four types of differentiated high-purity iron-based powder is realized.

Description

Technical Field

[0001] This invention relates to the field of metallurgical powder and new energy lithium battery raw material preparation technology, specifically to a process and apparatus for preparing four types of high-purity iron-based powders by single-system water atomization coupled with graded oxidation. Background Technology

[0002] High-purity iron-based powders are core raw materials for cathode materials in new energy lithium iron phosphate batteries, reducing agents in fine chemicals, high-end soft / hard magnetic materials, and binder phases in superhard tools. Market demand covers differentiated products with multiple particle size grades and oxidation degree ranges. According to industry statistics, the current annual demand for high-purity iron-based powders in China exceeds 800,000 tons, and is growing at an average annual rate of 18% with the expansion of the lithium battery industry. Currently, the four core types of iron-based powders in the industry—coarse-grained high-purity iron powder, submicron-sized ultrafine high-purity iron powder, low-hydrogen-evolution pre-oxidized iron powder, and high-purity ferric oxide powder—are all prepared separately on independent production lines. The investment in equipment for a single production line is high, and the layout of multiple production lines leads to high equipment redundancy, large plant space occupation, and easy introduction of impurities during material transfer. The overall production cost is more than 40% higher than that of integrated processes.

[0003] Current high-pressure water atomization powder production technology still has several technical shortcomings: First, insufficient particle size control precision and lack of ultrafine powder preparation capability. Conventional processes use room-temperature water atomization, where molten iron droplets are rapidly cooled upon contact with cold water, resulting in a wide particle size distribution, with the difference between D10 and D90 reaching over 15μm. The minimum D50 of native iron powder can only reach 5μm, making it impossible to directly prepare ultrafine powders of 1μm and below. The industry generally uses offline grinding processes, which are prone to oxidation and introduce impurities when exposed to air, and lack integrated inert grinding solutions linked to the atomization production line. Second, low solid-liquid separation efficiency affects the quality of subsequent oxidation. Traditional processes lack online solid-liquid separation structures, resulting in iron powder carrying more than 20% moisture into subsequent processes after atomization. This directly leads to powder agglomeration and uneven oxidation during the oxidation process, with localized over-burning or under-oxidation. It is also impossible to accurately control the oxygen content fluctuation of low-oxidation pre-oxidized products, and the oxidation degree error of existing products generally exceeds ±5%. Third, the risk of hydrogen evolution during iron phosphate synthesis is prominent. When pure iron powder reacts with phosphoric acid, a large amount of hydrogen gas is released, with each kilogram of iron powder producing over 400 liters of hydrogen. Existing iron phosphate production lines generally pose a risk of hydrogen accumulation and explosion. The oxidation degree of commercially available pre-oxidized iron powder is uncontrollable; too high an oxidation level results in insufficient reactivity, while too low an oxidation level still leads to significant hydrogen release, making it unsuitable for the specific production requirements of lithium-ion battery iron phosphate. Fourth, the atomization process suffers from insufficient safety protection. The contact between high-temperature molten iron and atomized water results in a water-gas reaction, releasing hydrogen gas. The hydrogen concentration within the sealed atomization tower can easily reach the explosion limit. Conventional equipment relies solely on ventilation for dilution, lacking full-process inert atmosphere protection and hydrogen concentration interlocking control, posing significant safety hazards during long-term continuous production. Fifth, resource utilization is low, and energy and water consumption are high. Traditional atomization processes have a water resource utilization rate of less than 30%, with large amounts of high-temperature wastewater being directly discharged, wasting thermal energy and increasing water treatment costs. Simultaneously, the fine powder settled during atomization lacks a closed-loop recovery path, resulting in a material loss rate exceeding 2%, leading to persistently high production costs. Finally, existing technologies cannot achieve flexible production of multiple products in a single system, and cannot simultaneously meet the diversified market demands for materials used in extensive industrial applications, ultra-fine precision applications, low-hydrogen lithium battery applications, and high-purity oxidation applications.

[0004] To address the above industry pain points, there is an urgent need to develop an integrated, highly safe, multi-category, and low-energy-consumption iron-based powder preparation process that can simultaneously mass-produce four types of differentiated high-purity iron-based powders in a single system, while taking into account the core requirements of controllable particle size, adjustable oxidation degree, low hydrogen production, high purity, and low cost. Summary of the Invention

[0005] The purpose of this invention is to provide a process and apparatus for preparing four types of high-purity iron-based powders by single-system water atomization coupled with staged oxidation, in order to solve the problems of insufficient flexibility of single line and single product in existing processes, low precision in particle size and oxidation degree control, and hydrogen evolution in phosphoric acid reaction.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] According to the first aspect of this disclosure, a process for preparing four types of high-purity iron-based powders by single-system water atomization coupled with staged oxidation is proposed, comprising the following steps:

[0008] S1. High-purity iron is melted to 1720–1780℃ to obtain high-temperature molten iron, which is then fed into a closed atomization tower. High-pressure water atomization is performed using 85–95℃ high-temperature pure water with an adjustable pressure of 20–140MPa. The atomization water pressure is matched according to the target powder particle size. Throughout the atomization process, nitrogen gas is introduced into the closed atomization tower to maintain an inert micro-positive pressure atmosphere, and the oxygen content in the tower is controlled to be <1% to inhibit the reaction of molten iron with water and hydrogen evolution. High-purity iron powder with a native D50 of 5μm is obtained by high-pressure water atomization.

[0009] S2. After the atomized mixture is stabilized, online magnetic separation is performed. High-temperature ultrafine iron powder is adsorbed by an adjustable magnetic field of 0.2–1.2T to achieve the separation of iron powder and unvaporized liquid atomized water. The separated liquid atomized water and settled iron powder are collected into a water storage tank.

[0010] S3. The high-temperature atomized water in the storage tank is filtered to remove impurities, and after being kept at a constant temperature of 85–95℃, it is returned to the atomized water tank for recycling. The iron powder deposited in the storage tank is dried and then transported in a sealed manner to the oxidation process to participate in the oxidation reaction.

[0011] S4. The high-temperature dehydrated high-purity iron powder obtained by separation enters the oxidation tower for fluidized pre-oxidation, and the pre-oxidation temperature in the tower is controlled at 550–820℃. The dust-containing tail gas discharged from the oxidation tower is treated by cyclone dust removal, and the separated fine powder is returned to the oxidation tower in a closed loop for further oxidation to prepare low-oxidation-degree high-purity pre-oxidized iron powder.

[0012] S5. Through a single-system, four-product differentiated preparation, four types of iron-based powders are produced simultaneously, including:

[0013] Path 1: Some of the original high-purity iron powder collected under nitrogen protection is directly discharged as a coarse-grained high-purity iron powder product;

[0014] Pathway 2: Select a portion of native 5μm high-purity iron powder and grind it under a nitrogen-sealed protective environment to prepare an ultrafine high-purity iron powder product with a D50 of 1μm.

[0015] Path 3: Some of the low-oxidation-degree high-purity pre-oxidized iron powder is directly discharged as a low-hydrogen-evolution raw material for iron phosphate synthesis;

[0016] Path 4: The remaining low-oxidation-degree high-purity pre-oxidized iron powder is subjected to ultrafine grinding and then transported to an electromagnetic induction rotary kiln for deep oxidation at 600–900℃ to generate high-purity ferric oxide powder product.

[0017] Furthermore, in step S1, the feed mass ratio of atomized water to high-temperature molten iron is controlled to be (5–12):1.

[0018] Furthermore, in step S2, the magnetic field strength of the magnetic separation is adjusted in real time according to the online detection results of the iron powder particle size, and the iron powder separation and recovery rate is ≥99%.

[0019] Furthermore, in step S4, the flow rate of oxygen or oxygen-enriched air used for oxidation is adjusted in a closed loop according to the oxygen content and powder concentration in the oxidation tower, and the gas-solid mass ratio in the tower is controlled at (0.3–0.8):1; the oxidation degree of the pre-oxidized iron powder prepared is 15%–35%, and the oxidation degree control accuracy is ±1.5%.

[0020] Furthermore, in step S5, the deep oxidation process is divided into three stages: preheating, deep reaction, and cooling, with temperature controlled. The total residence time of the material in the electromagnetic induction rotary kiln is 40–90 min, and the rotary kiln operating speed is 1–5 r / min. The final ferric oxide powder produced has a purity of ≥99.9% and a total iron content of ≥69.8%.

[0021] According to the second aspect of this disclosure, a device for preparing four types of high-purity iron-based powders by single-system water atomization coupled with graded oxidation is proposed to realize the process of the first aspect, including atomization powder preparation explosion-proof system, online magnetic separation system, high-temperature water circulation system, spray pre-oxidation system, fine powder closed-loop recovery system, and powder fine processing system connected in sequence.

[0022] The explosion-proof atomization powder production system includes a sealed atomization tower, a high-pressure adjustable atomizing unit, a pure water constant-temperature heating tank, and a nitrogen micro-positive pressure gas supply unit. The pressure adjustment range of the high-pressure adjustable atomizing unit is 20–140 MPa, the temperature control range of the pure water constant-temperature heating tank is 85–95℃, and the nitrogen micro-positive pressure gas supply unit is connected to the sealed atomization tower to maintain an inert explosion-proof environment inside the tower.

[0023] The online magnetic separation system includes an adjustable electromagnet, a vertical buffer flow stabilizing section, and a diversion discharge mechanism; the vertical buffer flow stabilizing section is connected to the bottom main discharge port of the sealed atomizing tower, and its end is provided with a downward inclined discharge port and a direct downward water discharge port; the adjustable electromagnet is installed above the downward inclined discharge port for magnetically separating high-temperature iron powder.

[0024] The high-temperature water circulation system includes a dual-compartment water storage tank, a filtration and slag removal unit, and a circulating water pump. The dual-compartment water storage tank is divided into a water storage tank and an iron powder sedimentation tank. The water storage tank is connected to the pure water constant temperature heating tank through the filtration and slag removal unit to form a high-temperature water closed-loop atomization circuit.

[0025] The spray-type pre-oxidation system includes a spray granulation oxidation tower and three directional oxygen nozzles; the three oxygen nozzles are evenly distributed circumferentially at 120° and installed at a vertical upward inclination of 30° in the lower middle part of the spray granulation oxidation tower.

[0026] The fine powder closed-loop recovery system includes a cyclone dust collector. The air inlet of the cyclone dust collector is connected to the top of the spray granulation oxidation tower, and the bottom return port of the cyclone dust collector is connected to the lower part of the spray granulation oxidation tower for fine powder recycling oxidation.

[0027] The powder refining system includes a nitrogen-protected grinding mill, a through-type vibratory mill, and an electromagnetic induction rotary kiln; and is equipped with four independent discharge branches, which respectively output four types of products: raw high-purity iron powder, ultrafine high-purity iron powder, low-oxidation pre-oxidized iron powder, and high-purity ferric oxide powder.

[0028] Furthermore, the adjustable electromagnet is a water-cooled electromagnet, equipped with an online particle size analyzer and a magnetic field control module, used to adjust the magnetic field strength in real time according to the particle size of the discharged iron powder.

[0029] Furthermore, the nitrogen-protected grinding mill is a fully enclosed inert atmosphere airflow mill used to grind virgin iron powder into 1μm-level ultrafine powder in an inert environment.

[0030] Furthermore, the electromagnetic induction rotary kiln is a horizontal, multi-temperature zone, sealed structure that uses electromagnetic induction heating. The kiln body temperature uniformity is ±5℃, and it is equipped with an atmosphere control unit to achieve complete and deep oxidation of the pre-oxidized powder.

[0031] Furthermore, the fine powder closed-loop recovery system also includes a bag filter, the air inlet of which is connected to the air outlet of the cyclone dust collector, and the material collection port of which is connected to the lower part of the spray granulation oxidation tower, for secondary dust collection and material recovery.

[0032] Compared with existing technologies, the process and apparatus for preparing four types of high-purity iron-based powders by single-system water atomization coupled with staged oxidation provided by the present invention have the following beneficial effects:

[0033] 1. A single system can simultaneously produce four types of high-purity iron-based powders with different particle sizes and oxidation degrees. The production capacity ratio of each product can be flexibly adjusted according to demand, adapting to downstream applications in multiple fields and exhibiting strong production adaptability. Furthermore, the primary iron powder prepared by atomization has uniform and stable particle size, and can be further refined through subsequent inert protection grinding processes to obtain ultrafine iron powder, meeting the application requirements of different precision levels.

[0034] 2. Through the pre-oxidation process, the powder is fully in contact with the oxidizing atmosphere, and with the fine powder closed-loop reflux treatment, the oxidation is uniform and sufficient, and the degree of powder oxidation can be stably controlled. When the obtained pre-oxidized iron powder is used for iron phosphate synthesis, it can effectively inhibit hydrogen evolution in the reaction. Furthermore, the iron powder and atomized water are separated online by magnetic separation. The iron powder after separation has a low moisture content, which avoids moisture being carried into the subsequent oxidation process, ensuring the stability of the oxidation process and the quality of the product.

[0035] 3. The entire atomization process is protected by a nitrogen inert atmosphere, which inhibits the reaction between molten iron and water to produce hydrogen, avoids the safety hazards of hydrogen accumulation, and can support long-term continuous production. The atomized water can be recycled and reused after filtration and temperature adjustment, and the settled iron powder can be recovered and reused in subsequent processes. The loss of materials and water resources is low, and the operating cost is low. At the same time, the high-temperature atomized water can be recycled to recover waste heat, and the high-temperature iron powder can use its own waste heat to enter the oxidation process, reducing the energy consumption of secondary heating, resulting in low overall production energy consumption. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0037] Figure 1 The process flow diagram for preparing four types of high-purity iron-based powders by single-system water atomization coupled with staged oxidation provided by the present invention;

[0038] Figure 2 The system module diagram of the apparatus for preparing four types of high-purity iron-based powders by single-system water atomization coupled with staged oxidation provided by the present invention is shown. Detailed Implementation

[0039] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0040] The preparation process described in this embodiment can be achieved using conventional equipment in the metallurgical powder industry. These mainly include a closed high-pressure water atomizing tower, a high-pressure adjustable atomizing water pump, a pure water constant temperature heating tank, a nitrogen supply system, a wet magnetic separator, a circulating water storage tank, a multi-stage filtration device, a fluidized oxidation tower, a cyclone dust collector, a nitrogen-protected airflow mill, a through-type vibrating mill, and an electromagnetic induction rotary kiln. All equipment are mature and conventional products in the industry and do not require the customization of special mechanical structures.

[0041] Example 1:

[0042] This embodiment provides a process for preparing four types of high-purity iron-based powders using a single-system water atomization coupled with staged oxidation, including the following steps:

[0043] S1. High-purity molten iron atomization explosion-proof powder production: High-purity iron raw materials with a purity ≥99.95% are selected and heated in a medium-frequency induction melting furnace. Once the molten iron reaches a temperature of 1750℃ and its composition is uniform, it is fed into a closed high-pressure water atomization tower via a guiding device. A high-pressure water pump provides an atomization pressure of 80MPa, using 90℃ high-temperature pure water as the atomization medium to impact and break up the falling molten iron jet. The feed mass ratio of atomizing water to molten iron is controlled at 8:1. During atomization, high-purity nitrogen is continuously introduced into the atomization tower to maintain a slightly positive pressure state and control the oxygen content inside the tower to be below 1%, inhibiting hydrogen evolution from the reaction between molten iron and water at the source, while also preventing premature oxidation of the powder. After high-pressure water atomization, high-purity iron powder with a stable D50 of 5μm is obtained. By using 85–95℃ high-temperature water instead of room-temperature water as the atomizing medium, the temperature difference between the molten iron droplets and the high-temperature water decreases from over 1700℃ to around 1600℃. This slows down the cooling rate of the droplet surface, preventing rapid solidification of the droplet surface and the formation of a hard shell that would lead to uneven internal breakage. As a result, the powder particle size becomes more uniform, reducing the extreme distribution of coarse particles and ultrafine powder, and obtaining primary iron powder with a narrow particle size distribution.

[0044] S2. Online Magnetic Separation: The mixture of iron powder and water formed after atomization is stabilized at the bottom outlet of the atomization tower and then sent to a wet magnetic separator for online magnetic separation. Based on the original iron powder particle size, the magnetic field strength of the magnetic separator is adjusted to 0.38T. High-temperature ultrafine iron powder is separated by magnetic adsorption, achieving efficient separation of iron powder and liquid atomized water, with an iron powder recovery rate ≥99%. The separated liquid atomized water and a small amount of settled iron powder are sent to a circulating water tank. Utilizing the strong ferromagnetism of the iron powder, after the material flow is stabilized, a directional magnetic field is applied to change the trajectory of the iron powder particles, causing them to deflect towards the downward-sloping outlet; while the liquid water and non-magnetic impurities are not affected by the magnetic force and flow out from the direct downward outlet along the direction of gravity.

[0045] S3. High-Temperature Water Circulation and Iron Powder Recovery: Materials in the circulating water tank undergo natural sedimentation and separation. The upper layer of high-temperature clear liquid is filtered through a multi-stage filtration system to remove impurities. The water temperature is then maintained between 85–95℃ through constant temperature control before being transferred to a pure water constant-temperature heating tank and returned to the atomization system for reuse. A small amount of iron powder deposited at the bottom of the water tank is collected, dried at low temperature, and then transported in a sealed environment to the oxidation process for pre-oxidation reaction, achieving full material recovery.

[0046] S4. Fluidized Pre-oxidation Treatment: The high-temperature dehydrated high-purity iron powder obtained from the separation is fed into a fluidized oxidation tower for pre-oxidation treatment using its own waste heat. The pre-oxidation temperature in the oxidation tower is controlled at 680℃, and oxygen-enriched air is continuously introduced into the tower. The air supply flow rate is adjusted in a closed loop according to the oxygen content and powder concentration in the tower, and the gas-solid mass ratio in the tower is controlled at 0.5:1, so that the powder can fully contact and react with oxygen in a fluidized state. The dust-containing tail gas discharged from the oxidation tower is separated into gas and solid by a cyclone dust collector. The separated incompletely reacted fine powder is returned to the oxidation tower in a closed loop for further oxidation, and finally, a low-oxidation-degree high-purity pre-oxidized iron powder is obtained. The product oxidation degree is about 25%, and the oxidation degree control accuracy is ±1.5%. In the pre-oxidation stage, by controlling the oxidation temperature and oxygen supply, a thin iron oxide passivation layer is formed on the surface of the iron powder, which retains the reactivity of the internal iron and avoids the internal iron from directly contacting hydrogen ions and generating a large amount of hydrogen during the phosphoric acid reaction. In the deep oxidation stage, the powder is completely converted into ferric oxide through high-temperature and long-term oxidation. Uniformly arranged nozzles at a 30° elevation angle (120° each) create a swirling fluidization field, suspending and fully tumbling the powder. Combined with a closed-loop cyclone return system, this ensures that each particle has sufficient contact with oxygen, achieving uniform oxidation. Furthermore, the slightly positive nitrogen pressure environment reduces the oxygen content within the tower, inhibiting the oxidation reaction of iron and ensuring product purity. On the other hand, the hydrogen evolution reaction between molten iron and water is significantly reduced in this low-oxygen, high-nitrogen environment. Simultaneously, the continuously introduced nitrogen dilutes the trace amounts of hydrogen generated, keeping the hydrogen concentration below the explosion limit. Combined with concentration monitoring and interlocking, intrinsic safety is achieved.

[0047] S5. Differentiated Production of Four Types of Products: By adjusting the material distribution ratio of each branch within the system, four types of high-purity iron-based powder products can be produced simultaneously.

[0048] Path 1: A portion of the raw high-purity iron powder collected under nitrogen protection is cooled, sieved, and then directly packaged and discharged to obtain a coarse-grained high-purity iron powder product, which can be used in conventional iron phosphate production, chemical reduction, and other scenarios.

[0049] Pathway 2: Select a portion of virgin 5μm high-purity iron powder and feed it into a nitrogen-protected flow mill for ultra-fine grinding under a completely sealed inert atmosphere. The particle size is precisely controlled by a classifying wheel to finally obtain an ultra-fine high-purity iron powder product with a D50 of 1μm.

[0050] Pathway 3: After cooling and sieving, some of the pre-oxidized iron powder is directly packaged and discharged to obtain a low-oxidation pre-oxidized iron powder product, which can replace pure metallic iron powder for iron phosphate synthesis and can suppress hydrogen evolution phenomenon from the source.

[0051] Path 4: The remaining pre-oxidized iron powder is first fed into a through-type vibratory mill for ultrafine grinding, and then conveyed to an electromagnetic induction rotary kiln for deep oxidation. The deep oxidation process is divided into three stages: preheating, deep reaction, and cooling. The temperature in the reaction section of the kiln is controlled at 760℃, the total residence time of the material is 60min, and the rotation speed of the rotary kiln is 2r / min, so that the powder is completely oxidized, and finally high-purity ferric oxide powder is obtained with a purity ≥99.9% and a total iron content ≥69.8%.

[0052] Example 2:

[0053] The preparation process steps in this embodiment are basically the same as those in Example 1, except for the process parameters:

[0054] In S1, the atomizing water pressure is adjusted to 40MPa, the atomizing water temperature is controlled at 87℃, the mass ratio of atomizing water to molten iron is 7:1, and the molten iron melting temperature is 1730℃.

[0055] In S2, the magnetic field strength of the magnetic separation is adjusted to 0.32T;

[0056] In S4, the pre-oxidation temperature of the oxidation tower is controlled at 620℃, the gas-solid mass ratio in the tower is 0.4:1, and the pre-oxidized iron powder obtained has an oxidation degree of about 18%.

[0057] In S5, the deep oxidation temperature of the electromagnetic induction rotary kiln is 720℃, the material residence time is 50min, and the rotary kiln speed is 3r / min.

[0058] This embodiment can also stably produce four types of qualified high-purity iron-based powders: the primary iron powder has uniform particle size, the ultrafine iron powder meets the purity standard, the pre-oxidized iron powder has stable oxidation degree, and the ferric oxide powder has pure phase. All performance indicators meet the requirements of high-end applications.

[0059] Example 3:

[0060] The preparation process steps in this embodiment are basically the same as those in Embodiment 1, except for the process parameters:

[0061] In S1, the atomizing water pressure is adjusted to 120MPa, the atomizing water temperature is controlled at 92℃, the mass ratio of atomizing water to molten iron is 10:1, and the molten iron melting temperature is 1770℃.

[0062] In S2, the magnetic field strength of the magnetic separation is adjusted to 0.6T;

[0063] In S4, the pre-oxidation temperature of the oxidation tower is controlled at 780℃, the gas-solid mass ratio in the tower is 0.7:1, and the pre-oxidized iron powder obtained has an oxidation degree of about 32%.

[0064] In S5, the deep oxidation temperature of the electromagnetic induction rotary kiln is 850℃, the material residence time is 80min, and the rotary kiln speed is 1.5r / min.

[0065] The native iron powder produced in this embodiment has a finer particle size, and the ultrafine iron powder can achieve higher precision. The pre-oxidized iron powder has a reactivity adapted to the special iron phosphate process, and the ferric oxide powder has a higher crystallinity, making it suitable for high-end application scenarios such as high-performance magnetic materials.

[0066] The foregoing has only described certain exemplary embodiments of the present invention by way of illustration. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the foregoing drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A process for preparing four types of high-purity iron-based powders using a single-system water atomization coupled with staged oxidation, characterized in that, Includes the following steps: S1. High-purity iron is melted to 1720–1780℃ to obtain high-temperature molten iron, which is then fed into a closed atomization tower. High-pressure water atomization is performed using 85–95℃ high-temperature pure water with an adjustable pressure of 20–140MPa. The atomization water pressure is matched according to the target powder particle size. Throughout the atomization process, nitrogen gas is introduced into the closed atomization tower to maintain an inert micro-positive pressure atmosphere, and the oxygen content in the tower is controlled to be <1% to inhibit the reaction of molten iron with water and hydrogen evolution. High-purity iron powder with a native D50 of 5μm is obtained by high-pressure water atomization. S2. After the atomized mixture is stabilized, online magnetic separation is performed. High-temperature ultrafine iron powder is adsorbed by an adjustable magnetic field of 0.2–1.2T to achieve the separation of iron powder and unvaporized liquid atomized water. The separated liquid atomized water and settled iron powder are collected into a water storage tank. S3. The high-temperature atomized water in the storage tank is filtered to remove impurities, and after being kept at a constant temperature of 85–95℃, it is returned to the atomized water tank for recycling. The iron powder deposited in the storage tank is dried and then transported in a sealed manner to the oxidation process to participate in the oxidation reaction. S4. The high-temperature dehydrated high-purity iron powder obtained by separation enters the oxidation tower for fluidized pre-oxidation, and the pre-oxidation temperature in the tower is controlled at 550–820℃. The dust-containing tail gas discharged from the oxidation tower is treated by cyclone dust removal, and the separated fine powder is returned to the oxidation tower in a closed loop for further oxidation to prepare low-oxidation-degree high-purity pre-oxidized iron powder. S5. Through a single-system, four-product differentiated preparation, four types of iron-based powders are produced simultaneously, including: Path 1: Some of the original high-purity iron powder collected under nitrogen protection is directly discharged as a coarse-grained high-purity iron powder product; Pathway 2: Select a portion of native 5μm high-purity iron powder and grind it under a nitrogen-sealed protective environment to prepare an ultrafine high-purity iron powder product with a D50 of 1μm. Path 3: Some of the low-oxidation-degree high-purity pre-oxidized iron powder is directly discharged as a low-hydrogen-evolution raw material for iron phosphate synthesis; Path 4: The remaining low-oxidation-degree high-purity pre-oxidized iron powder is subjected to ultrafine grinding and then transported to an electromagnetic induction rotary kiln for deep oxidation at 600–900℃ to generate high-purity ferric oxide powder product.

2. The process for preparing four types of high-purity iron-based powders using a single-system water atomization coupled with staged oxidation according to claim 1, characterized in that, In step S1, the feed mass ratio of atomized water to high-temperature molten iron is controlled to be (5–12):

1.

3. The process for preparing four types of high-purity iron-based powders using a single-system water atomization coupled with staged oxidation according to claim 1, characterized in that, In step S2, the magnetic field strength of the magnetic separation is adjusted in real time according to the online detection results of the iron powder particle size, and the iron powder separation and recovery rate is ≥99%.

4. The process for preparing four types of high-purity iron-based powders by single-system water atomization coupled with staged oxidation according to claim 1, characterized in that, In step S4, the flow rate of oxygen or oxygen-enriched air used for oxidation is adjusted in a closed loop according to the oxygen content and powder concentration in the oxidation tower, and the gas-solid mass ratio in the tower is controlled at (0.3–0.8):1; the oxidation degree of the pre-oxidized iron powder is 15%–35%, and the oxidation degree control accuracy is ±1.5%.

5. The process for preparing four types of high-purity iron-based powders by single-system water atomization coupled with staged oxidation according to claim 1, characterized in that, In step S5, the deep oxidation process is divided into three stages: preheating, deep reaction, and cooling. The temperature is controlled. The total residence time of the material in the electromagnetic induction rotary kiln is 40–90 min, and the rotary kiln operating speed is 1–5 r / min. The final ferric oxide powder produced has a purity of ≥99.9% and a total iron content of ≥69.8%.

6. An apparatus for preparing four types of high-purity iron-based powders using a single-system water atomization coupled with staged oxidation, for implementing the process described in any one of claims 1-5, characterized in that, It includes a sequentially connected atomized powder production explosion-proof system, online magnetic separation system, high-temperature water circulation system, spray pre-oxidation system, fine powder closed-loop recovery system, and powder fine processing system; The explosion-proof atomization powder production system includes a sealed atomization tower, a high-pressure adjustable atomizing unit, a pure water constant-temperature heating tank, and a nitrogen micro-positive pressure gas supply unit. The pressure adjustment range of the high-pressure adjustable atomizing unit is 20–140 MPa, the temperature control range of the pure water constant-temperature heating tank is 85–95℃, and the nitrogen micro-positive pressure gas supply unit is connected to the sealed atomization tower to maintain an inert explosion-proof environment inside the tower. The online magnetic separation system includes an adjustable electromagnet, a vertical buffer flow stabilizing section, and a diversion discharge mechanism; the vertical buffer flow stabilizing section is connected to the bottom main discharge port of the sealed atomizing tower, and its end is provided with a downward inclined discharge port and a direct downward water discharge port; the adjustable electromagnet is installed above the downward inclined discharge port for magnetically separating high-temperature iron powder. The high-temperature water circulation system includes a dual-compartment water storage tank, a filtration and slag removal unit, and a circulating water pump. The dual-compartment water storage tank is divided into a water storage tank and an iron powder sedimentation tank. The water storage tank is connected to the pure water constant temperature heating tank through the filtration and slag removal unit to form a high-temperature water closed-loop atomization circuit. The spray-type pre-oxidation system includes a spray granulation oxidation tower and three directional oxygen nozzles; the three oxygen nozzles are evenly distributed circumferentially at 120° and installed at a vertical upward inclination of 30° in the lower middle part of the spray granulation oxidation tower. The fine powder closed-loop recovery system includes a cyclone dust collector. The air inlet of the cyclone dust collector is connected to the top of the spray granulation oxidation tower, and the bottom return port of the cyclone dust collector is connected to the lower part of the spray granulation oxidation tower for fine powder recycling oxidation. The powder refining system includes a nitrogen-protected grinding mill, a through-type vibratory mill, and an electromagnetic induction rotary kiln; and is equipped with four independent discharge branches, which respectively output four types of products: raw high-purity iron powder, ultrafine high-purity iron powder, low-oxidation pre-oxidized iron powder, and high-purity ferric oxide powder.

7. The apparatus for preparing four types of high-purity iron-based powders by single-system water atomization coupled with staged oxidation according to claim 6, characterized in that, The adjustable electromagnet is a water-cooled electromagnet, equipped with an online particle size analyzer and a magnetic field control module, which are used to adjust the magnetic field strength in real time according to the particle size of the discharged iron powder.

8. The apparatus for preparing four types of high-purity iron-based powders by single-system water atomization coupled with staged oxidation according to claim 6, characterized in that, The nitrogen-protected grinding mill is a fully enclosed inert atmosphere airflow mill used to grind virgin iron powder into 1μm ultrafine powder in an inert environment.

9. The apparatus for preparing four types of high-purity iron-based powders by single-system water atomization coupled with staged oxidation according to claim 6, characterized in that, The electromagnetic induction rotary kiln is a horizontal, multi-temperature zone, closed structure that uses electromagnetic induction heating. The kiln body temperature uniformity is ±5℃, and it is equipped with an atmosphere control unit to achieve complete and deep oxidation of pre-oxidized powders.

10. The apparatus for preparing four types of high-purity iron-based powders by single-system water atomization coupled with staged oxidation according to claim 6, characterized in that, The fine powder closed-loop recovery system also includes a bag filter, the air inlet of which is connected to the air outlet of the cyclone dust collector, and the material collection port of the bag filter is connected to the lower part of the spray granulation oxidation tower for secondary dust collection and material recovery.

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