Production method for preparing 7N high-purity iron through self-contained hydrogen reduction method
By employing a self-sufficient hydrogen reduction method, using a closed-loop cycle of hydrogen and hydrogen chloride, and carrying out a medium-temperature reduction reaction with conventional equipment, the complexity of the process and the problem of impurity control in the preparation of 7N high-purity iron in the existing technology have been solved, and high-purity, high-efficiency, large-scale production has been achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CARBON SILVER (HEBEI XIONGAN) NEW ENERGY TECHNOLOGY CO LTD
- Filing Date
- 2026-03-02
- Publication Date
- 2026-04-14
AI Technical Summary
Existing technologies are difficult to efficiently prepare 7N high-purity iron due to lengthy and complex processes, insufficient impurity separation capabilities, reliance on high-end and costly equipment, and difficulty in achieving large-scale production.
A self-sufficient hydrogen reduction method is adopted, in which hydrogen is generated through acid hydrolysis to reduce ferrous chloride. The hydrogen and hydrogen chloride are used in a closed-loop cycle, and the medium-temperature reduction reaction is carried out using conventional equipment to achieve impurity control and purity improvement.
Stable production of 7N high-purity iron has been achieved, with a purity of 99.99999% and key impurities controlled below 0.1ppm. This has reduced raw material and energy consumption, facilitated the localization of equipment, simplified the process flow, and improved the robustness and continuity of production.
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Figure CN121847802A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of ultrapure metal processing technology, specifically relating to a production method for preparing 7N high-purity iron by a self-sufficient hydrogen reduction method. Background Technology
[0002] 7N (purity ≥ 99.99999%) high-purity iron is an indispensable key material in strategic emerging fields such as semiconductor chips, high-end soft magnetic materials (e.g., 6G communication devices), aerospace high-temperature alloys, and the nuclear industry. Its purity directly determines the performance limits of end products. For example, if Cr and Ni impurities in iron used for semiconductor lead frames exceed 0.1 ppm, it will lead to a significant decrease in chip carrier mobility; the presence of O and C impurities in high-end soft magnetic materials will seriously deteriorate their magnetic properties and temperature stability.
[0003] With the rapid development of downstream industries, which mainly rely on composite processes centered on "multi-stage electrolysis-vacuum refining," the following prominent bottlenecks exist:
[0004] The process is lengthy and complex, making continuous industrial production difficult: existing typical processes require more than six core steps, including crude iron pretreatment, multiple rounds of electrolytic purification, vacuum annealing, electron beam melting, and zone melting. The electrolysis stage alone requires precise control of more than ten parameters, such as current density, electrolyte pH, and temperature; any fluctuation can lead to substandard product purity. Some processes also require the introduction of organic complexing agents for deep impurity removal, followed by a high-temperature incineration process to remove the complexing agents, further extending the process and making it difficult for the production line to achieve long-term stable operation (typically with a continuous operating cycle of less than 15 days), severely restricting large-scale production.
[0005] Existing technologies are insufficient for separating impurities with properties similar to iron ions (such as Cr²⁺ and Ni²⁺), which are prone to co-deposition during electrolysis, resulting in a typical impurity content of 0.5-1 ppm in the product, failing to meet the 7N grade requirements. To meet the standard, subsequent treatments such as "vacuum distillation-laser purification" are often required, but these processes have low throughput and low efficiency. Furthermore, existing pretreatment processes struggle to consistently reduce the content of non-metallic impurities such as O, C, and S, which exist in compound form, to below 1 ppm.
[0006] At the same time, existing technologies are highly dependent on high-end specialized equipment such as electron beam melting furnaces and zone melting equipment, resulting in extremely high maintenance costs.
[0007] Therefore, there is an urgent need to develop a new method for preparing 7N high-purity iron that is simple in process, has controllable purity, is cost-effective, and is suitable for large-scale production, so as to ensure the supply chain security and self-control of high-end manufacturing industries. Summary of the Invention
[0008] The purpose of this invention is to provide a self-sufficient hydrogen reduction method for preparing 7N high-purity iron, so as to solve the problems mentioned in the background art.
[0009] To achieve the above objectives, the present invention provides the following technical solution:
[0010] A method for producing 7N high-purity iron using a self-sufficient hydrogen reduction process includes the following steps:
[0011] Including the following steps:
[0012] S1. Raw material preparation: Prepare 3N grade metallic iron with a purity of 99.95%, 6N grade pure water with a purity of 99.9999% or higher, ultra-high purity hydrochloric acid solution with a concentration of 8%-12%, and hydrogen gas with a purity of 99.99% or higher.
[0013] S2 and 3N grade metal iron removal:
[0014] The 3N grade metallic iron and the ultra-high purity hydrochloric acid solution were added to a reaction vessel for acid hydrolysis. The reaction was stopped after about 30% of the metallic iron had reacted. The hydrogen gas produced by the reaction was washed with water, dried and collected for later use.
[0015] The ferrous chloride solution obtained after acid hydrolysis was transferred to a purification device, where a high-purity iron-based flocculant was added for purification, followed by filtration using a fiber bundle filter.
[0016] The filtered refined ferrous chloride solution was concentrated and crystallized to obtain anhydrous high-purity ferrous chloride powder.
[0017] Reaction formula:
[0018] HCl + Fe → FeCl₂ + H₂↑;
[0019] S3. Preparation of 7N iron powder by self-sufficient hydrogen reduction method:
[0020] The anhydrous high-purity ferrous chloride powder is added to a closed electrically heated three-bladed rotary kiln at a temperature of 600℃-800℃, and hydrogen collected in step S2 is introduced to carry out a reduction reaction for 120 minutes.
[0021] The reduction reaction products are 7N grade high-purity iron powder and high-purity hydrogen chloride gas, and the high-purity hydrogen chloride gas is recycled for the acidolysis process in step S2.
[0022] Reaction formula:
[0023] FeCl2 + H2 → HCl↑ + Fe.
[0024] Preferably, in step S2, the high-purity iron-based flocculant is one of the following: high-purity polyferric chloride, high-purity ferric chloride, high-purity ferric silicate, and high-purity polyferric chloride.
[0025] Preferably, the high-purity hydrogen chloride gas recycled in the acidolysis process in step S3 needs to be absorbed by 6N-grade pure water and prepared into a hydrochloric acid solution with a concentration of 8%-12%.
[0026] Compared with the prior art, the beneficial effects of the present invention are:
[0027] The 7N high-purity iron powder prepared by this invention has a purity that consistently reaches and exceeds the 99.99999% (7N) standard, and the content of key impurity elements (such as Cr, Ni, O, C, etc.) can be effectively controlled at an extremely low level of ≤0.1ppm. This product fully meets the extreme purity requirements of basic materials in strategic emerging fields such as semiconductor chip lead frames, high-end soft magnetic materials, aerospace high-temperature alloys, and special materials for the nuclear industry, providing reliable core raw materials for downstream high-value-added industries.
[0028] This innovative system achieves closed-loop recycling of the reaction media (H2 and HCl), significantly reducing the external consumption of high-purity hydrogen and hydrochloric acid, thus saving raw material costs at the source. The core production process does not rely on expensive imported equipment such as electron beam melting furnaces and zone melting equipment; it mainly uses conventional equipment such as reaction kettles and rotary kilns, resulting in a high degree of domestic production and a substantial reduction in equipment investment and subsequent maintenance costs. Furthermore, the hydrogen reduction reaction is carried out in the medium-temperature range of 600℃-800℃, far lower than the high temperatures of 1300℃-1500℃ required by traditional vacuum distillation and the high power consumption of electrolysis, resulting in a significant reduction in overall energy consumption.
[0029] It avoids the complex parameter control (such as current density, pH value, etc.) and post-processing problems of organic complexing agents in traditional electrolysis processes. The production process is more robust and easier to achieve continuous and stable production on an industrial scale. The expected continuous operation cycle is far longer than that of existing technologies.
[0030] The targeted purification method solves the global problem of easy co-deposition of Fe²⁺ with similar substances such as Cr²⁺ and Ni²⁺ in traditional electrolysis, which in principle ensures the stability of the purity of the final product and is expected to improve the batch production qualification rate of 7N grade high-purity iron to the international advanced level.
[0031] Furthermore, the entire process system achieves internal circulation of H2 and HCl gases, with almost no harmful waste gas emissions. The hydrogen gas produced by acid hydrolysis is purified and used as a reducing agent, while the hydrogen chloride gas produced by reduction is absorbed and reused in acid hydrolysis, forming a highly efficient internal material circulation, reducing the pressure of waste treatment, and embodying the advanced concepts of clean production and circular economy.
[0032] In summary, this method, with its advantages of controllable cost and technical feasibility, provides a domestic solution for the large-scale production of high-quality 7N high-purity iron. Attached Figure Description
[0033] Figure 1 This is a schematic diagram of the process system of the present invention. Detailed Implementation
[0034] 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 some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0035] Example 1
[0036] The present invention discloses a self-sufficient hydrogen reduction method for preparing 7N high-purity iron, which includes the following steps:
[0037] 1. Raw material situation
[0038] (1) 3N industrial metallic iron: purity 99.95%, 50.00 kg;
[0039] (2) The concentration of ultra-high purity HCl (99.95%) solution is 9%, and the dosage is 122.40 kg;
[0040] (3) High purity (above 99.99%) H2: purity 99.99%, dosage 0.56kg, self-sufficient by acid hydrolysis reaction.
[0041] (4) 6N grade pure water: purity 99.9999%, dosage 147kg.
[0042] 2. Process steps:
[0043] S1. Raw material preparation is the same as above.
[0044] S2 and 3N grade metal iron removal.
[0045] (1) Add 3N grade metallic iron and ultra-high purity HCl solution to the reaction vessel for acid hydrolysis. After about 30% of the metallic iron has undergone acidification, stop the reaction. The H2 generated in the reaction is washed with water to remove acid, dried to remove water, and collected in a sealed negative pressure storage tank for later use.
[0046] (2) The solution after acid hydrolysis reaction enters the impurity removal and purification device, and high-purity iron flocculant is added for impurity removal and purification.
[0047] (3) The purified FeCl2 solution is concentrated and crystallized to produce anhydrous FeCl2 powder.
[0048] Reaction formula:
[0049] HCl + Fe → FeCl2 + H2↑
[0050] S3, 7N iron powder is produced by hydrogen reduction.
[0051] (1) Add anhydrous FeCl2 powder into a closed electric heating three-bladed rotary kiln at 600℃~800℃, and pass hydrogen obtained from acid hydrolysis for high-temperature reduction. The reaction time is 120min.
[0052] (2) The reduction products are 7N iron powder and ultra-high purity HCl gas. The ultra-high purity HCl gas is recycled for the acidolysis process of this invention.
[0053] Reaction formula:
[0054] FeCl2 + H2 → HCl↑ + Fe.
[0055] 3. Technical parameters of the processed product:
[0056] 7N high-purity iron powder, 14.98 kg, raw material utilization rate approximately 29.96%, product purity ≥99.99999%, with impurities such as Cr, Ni, O, and C all ≤0.1 ppm. Technical parameters of the processed product:
[0057] Example 2
[0058] The present invention discloses a self-sufficient hydrogen reduction method for preparing 7N high-purity iron, which includes the following steps:
[0059] 1. Raw material situation
[0060] (1) 3N industrial metallic iron: purity 99.953%, 50.00 kg;
[0061] (2) High-purity (above 99.95%) HCl solution: purity 99.950%, concentration 12%, dosage 95.00 kg;
[0062] (3) High purity (above 99.995%) H2: purity 99.995%, dosage 0.56kg;
[0063] (4) 6N grade pure water: purity 99.9999%, dosage 105.68kg.
[0064] 2. Process steps:
[0065] S1. Raw material preparation is the same as above.
[0066] S2 and 3N grade metal iron removal.
[0067] (1) Add 3N grade metallic iron and ultra-high purity HCl solution to the reaction vessel for acid hydrolysis. After about 30% of the metallic iron has undergone acidification, stop the reaction. The H2 generated in the reaction is washed with water to remove acid, dried to remove water, and collected in a sealed negative pressure storage tank for later use.
[0068] (2) The solution after acid hydrolysis reaction enters the impurity removal and purification device, and high-purity iron flocculant is added for impurity removal and purification.
[0069] (3) The purified FeCl2 solution is concentrated and crystallized to produce anhydrous FeCl2 powder.
[0070] Reaction formula:
[0071] HCl + Fe → FeCl2 + H2↑
[0072] S3, 7N iron powder is produced by hydrogen reduction.
[0073] (1) Add anhydrous FeCl2 powder into a closed electric heating three-bladed rotary kiln at 600℃~800℃, and pass hydrogen obtained from acid hydrolysis for high-temperature reduction. The reaction time is 120min.
[0074] (2) The reduction products are 7N iron powder and ultra-high purity HCl gas. The ultra-high purity HCl gas is recycled for the acidolysis process of this invention.
[0075] Reaction formula:
[0076] FeCl2 + H2 → HCl↑ + Fe.
[0077] 3. Technical parameters of the processed product:
[0078] 7N high-purity iron powder, 14.98kg, raw material utilization rate of about 29.96%, purity ≥99.99999%, among which the content of impurities such as Cr, Ni, O, and C is ≤0.1ppm.
[0079] Example 3
[0080] The present invention discloses a self-sufficient hydrogen reduction method for preparing 7N high-purity iron, which includes the following steps:
[0081] 1. Raw material situation
[0082] (1) 3N industrial metallic iron: purity 99.951%, 80.00 kg;
[0083] (2) High-purity (above 99.95%) HCl solution: purity 99.9951%, concentration 8%, dosage 228.00 kg;
[0084] (3) High purity (above 99.995%) H2: purity 99.996%, dosage 0.89kg;
[0085] (4) 6N grade pure water: purity 99.9999%, dosage 263kg.
[0086] 2. Process steps:
[0087] S1. Raw material preparation is the same as above.
[0088] S2 and 3N grade metal iron removal.
[0089] (1) Add 3N grade metallic iron and ultra-high purity HCl solution to the reaction vessel for acid hydrolysis. After about 30% of the metallic iron has undergone acidification, stop the reaction. The H2 generated in the reaction is washed with water to remove acid, dried to remove water, and collected in a sealed negative pressure storage tank for later use.
[0090] (2) The solution after acid hydrolysis reaction enters the impurity removal and purification device, and high-purity iron flocculant is added for impurity removal and purification.
[0091] (3) The purified FeCl2 solution is concentrated and crystallized to produce anhydrous FeCl2 powder.
[0092] Reaction formula:
[0093] HCl + Fe → FeCl2 + H2↑
[0094] S3, 7N iron powder is produced by hydrogen reduction.
[0095] (1) Add anhydrous FeCl2 powder into a closed electric heating three-bladed rotary kiln at 600℃~800℃, and pass hydrogen obtained from acid hydrolysis for high-temperature reduction. The reaction time is 120min.
[0096] (2) The reduction products are 7N iron powder and ultra-high purity HCl gas. The ultra-high purity HCl gas is recycled for the acidolysis process of this invention.
[0097] Reaction formula:
[0098] FeCl2 + H2 → HCl↑ + Fe.
[0099] 3. Technical parameters of the processed product:
[0100] 7N high-purity iron powder, 23.97kg, with a raw material utilization rate of approximately 29.96% from 3N to 7N, and a purity ≥99.99999%, with impurities such as Cr, Ni, O, and C all ≤0.1ppm.
[0101] It should be understood that numerous specific implementation decisions can be made during the development of any practical implementation, such as in any engineering or design project. Such development efforts may be complex and time-consuming, but for those skilled in the art who benefit from this disclosure, the development effort will be a routine work of design, manufacturing, and production without requiring much experimentation.
[0102] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.
Claims
1. A method for preparing 7N high-purity iron using a self-sufficient hydrogen reduction process, characterized in that, Including the following steps: S1. Raw material preparation: Prepare 3N grade metallic iron with a purity of 99.95%, 6N grade pure water with a purity of 99.9999% or higher, ultra-high purity hydrochloric acid solution with a concentration of 8%-12%, and hydrogen gas with a purity of 99.99% or higher. S2 and 3N grade metal iron removal: The 3N grade metallic iron and the ultra-high purity hydrochloric acid solution were added to a reaction vessel for acidolysis. The reaction was stopped after about 30% of the metallic iron had reacted. The hydrogen gas produced by the reaction was washed with water, dried and collected for later use. The ferrous chloride solution obtained after acid hydrolysis was transferred to a purification device, where a high-purity iron-based flocculant was added for purification, followed by filtration using a fiber bundle filter. The filtered refined ferrous chloride solution was concentrated and crystallized to obtain anhydrous high-purity ferrous chloride powder. Reaction formula: HCl + Fe → FeCl₂ + H₂↑; S3. Preparation of 7N iron powder by self-sufficient hydrogen reduction method: The anhydrous high-purity ferrous chloride powder is added to a closed electrically heated three-bladed rotary kiln at a temperature of 600℃-800℃, and hydrogen collected in step S2 is introduced to carry out a reduction reaction for 120 minutes. The reduction reaction products are 7N grade high-purity iron powder and high-purity hydrogen chloride gas, and the high-purity hydrogen chloride gas is recycled for the acidolysis process in step S2. Reaction formula: FeCl2 + H2 → HCl↑ + Fe.
2. The method for preparing 7N high-purity iron by self-sufficient hydrogen reduction according to claim 1, characterized in that, In step S2, the high-purity iron-based flocculant is one of the following: high-purity polyferric chloride, high-purity ferric chloride, high-purity ferric silicate, and high-purity polyferric chloride.
3. The production method for preparing 7N high-purity iron by self-sufficient hydrogen reduction according to claim 1, characterized in that, The high-purity hydrogen chloride gas recycled in step S3 for the acidolysis process needs to be absorbed by 6N-grade pure water and prepared into a hydrochloric acid solution with a concentration of 8%-12%.