Iron extraction method from red mud based on electric arc furnace hydrogen plasma melting reduction technology

Abstract

The present invention relates to the technical field of red mud recycling and utilization, and in particular to a red mud iron extraction method based on electric arc furnace hydrogen plasma melting reduction technology, which utilizes electric arc furnace and hydrogen plasma technology to perform melting reduction to extract industrial pure iron from Bayer process red mud. The red mud iron extraction method comprises the following steps: pressing into billets; roasting; molten hydrogen plasma reduction; crushing; and screening. The present invention provides a red mud iron extraction method based on electric arc furnace hydrogen plasma melting reduction technology, which achieves the goal of efficiently extracting iron from red mud. Through an innovative process flow and optimized parameter settings, the method achieves the goal of efficiently and environmentally friendly extraction of high-grade iron from red mud, while achieving complete utilization of waste, thereby having significant economic and environmental benefits.

Description

Technical Field

[0001] The present invention relates to the technical field of red mud recycling, and in particular to a red mud iron extraction method based on electric arc furnace hydrogen plasma melting reduction technology, which utilizes electric arc furnace and hydrogen plasma technology for melting reduction to extract industrial pure iron from Bayer process red mud. Background Art

[0002] Red mud, a highly alkaline industrial solid waste generated after alumina extraction from bauxite, contains a large number of valuable components, such as SiO2, Al2O3, CaO, and Fe2O3. Bayer red mud contains a particularly significant amount of iron, typically ranging from 30-60 wt.%. However, despite my country's abundant red mud resources, its utilization rate is currently less than 10%. A large amount of red mud is still disposed of by damming and stockpiling, which not only occupies valuable land resources but also poses serious environmental and safety risks.

[0003] In recent years, various technologies have been proposed to improve the utilization rate of red mud and recover its valuable components, particularly iron. For example, one patent proposes a method for melting red mud in an electric furnace. By adding reducing agents and binders, the mixture is granulated, followed by preheating, roasting, and electric furnace reduction to extract molten iron. Another patent uses biomass pyrolysis gas as a reducing agent to perform low-temperature fluidized bed reduction of iron oxide in red mud. Furthermore, methods such as fluidized bed reduction and magnetization, suspension roasting, and direct reduction in rotary hearth furnaces have been proposed to produce iron concentrate or recover iron.

[0004] However, these methods all have certain limitations in practical applications. First, most methods require the red mud to be dried and crushed in advance, and auxiliary materials such as reducing agents and binders need to be added, which not only increases the complexity of the process, but may also introduce new impurities. Secondly, in the traditional reduction roasting process, coal powder or coke powder is often used as a reducing agent, resulting in large carbon dioxide emissions, which does not meet current environmental protection requirements. Furthermore, the iron produced by reduction mostly exists in the form of iron powder, which is difficult to extract and has a high cost. Summary of the Invention

[0005] To address the shortcomings of existing technologies, there is an urgent need to develop a new method for extracting iron from red mud that is efficient, energy-saving, and environmentally friendly. This present invention addresses this need and aims to achieve efficient and clean extraction of iron resources from Bayer red mud through electric arc furnace hydrogen plasma melting reduction technology.

[0006] The technical solution adopted by the present invention is: a red mud iron extraction method based on electric arc furnace hydrogen plasma melting reduction technology, the red mud iron extraction method comprising the following steps:

[0007] Pressing into blanks: First, the red mud raw materials are shaped through a pressing process to form blanks with a certain shape and density, ensuring the initial form and physical properties of the raw materials;

[0008] Calcination: Next, the pressed green body is calcined. The calcination process causes physical and chemical changes inside the green body through high temperature, further stabilizing its structure and preparing for the subsequent reduction process.

[0009] Molten hydrogen plasma reduction: After calcination, the green body is reduced using molten hydrogen plasma technology. This step uses the special properties of molten hydrogen plasma to deeply reduce the green body, making its composition more uniform and removing impurities.

[0010] Crushing: The green body after reduction treatment is sent to the crusher for crushing. Through crushing, the green body is broken into fine powder, which is convenient for subsequent screening and separation;

[0011] Screening: Finally, the crushed powder is screened and the residual powder, iron ingots and iron beads of different particle sizes are separated through a sieve or other screening equipment to ensure the purity and quality of the final product.

[0012] In the pressing process, the red mud raw material is pressed under 5-10 MPa conditions to form red mud blanks.

[0013] In the roasting process, the pressed red mud blank is calcined at 800 to 1200 degrees Celsius for 30 to 120 minutes.

[0014] In the molten hydrogen plasma reduction process, the calcined red mud blank is placed in a vacuum arc melting furnace for hydrogen plasma reduction treatment. The specific treatment method includes a first step of pre-melting and a second step of removing residual gas.

[0015] The first step of pre-melting is to introduce 0.06MPa high-purity Ar gas into an electric arc furnace with a current of 100-200A to melt the red mud billet into a melt.

[0016] The second step of removing residual gas is to remove the residual gas in the first step, introduce 80-90 vol.% Ar gas and 10-20 vol.% H2, with a total pressure of the mixed gas above 0.06 MPa and a current of 80-200 A, and perform hydrogen plasma reduction treatment. Each treatment lasts 1-5 minutes, and this step is repeated more than 3 times to complete the reduction treatment.

[0017] After the reduced red mud ingots are crushed and screened, large pieces of pure iron with a purity higher than 98% can be obtained.

[0018] The vacuum arc melting furnace has a device for introducing a mixed gas of Ar gas and H2, and a device for controlling current and pressure.

[0019] The technical effects of the technical solution of the present invention are as follows: the present invention provides a method for extracting iron from red mud based on electric arc furnace hydrogen plasma melting reduction technology. The method achieves the goal of efficiently extracting iron from red mud. Through an innovative process flow and optimized parameter settings, the goal of efficiently and environmentally friendly extraction of high-grade iron from red mud is achieved, while achieving full utilization of waste. The method has significant economic and environmental benefits, which are specifically reflected as follows:

[0020] First, by using plasma hydrogen as a reducing agent, this method avoids the tedious steps of drying, crushing, and mixing required for conventional solid reducing agents, thereby simplifying the process and improving production efficiency. Furthermore, since the reduced product is water, the emission of greenhouse gases such as carbon dioxide is effectively avoided, resulting in significant environmental benefits.

[0021] Secondly, by optimizing the process flow and parameter settings, this method ensures that the extracted and reduced iron is in the form of iron blocks with a purity of over 98%. This high-grade, high-purity iron product is not only easier to extract and process later, but also has greater market value and application prospects.

[0022] Furthermore, this method fully utilizes red mud. The low-alkalinity residue can be directly used in engineering applications such as road paving and backfilling, solving the problem of red mud waste disposal while also achieving resource recycling and sustainable development. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a process flow diagram of the present invention. DETAILED DESCRIPTION

[0024] The following describes in detail the specific embodiments of the present invention in conjunction with the accompanying drawings:

[0025] like Figure 1 As shown, a red mud iron extraction method based on electric arc furnace hydrogen plasma melting reduction technology, the red mud iron extraction method comprises the following steps:

[0026] Pressing into blanks: First, the red mud raw materials are shaped through a pressing process to form blanks with a certain shape and density, ensuring the initial form and physical properties of the raw materials;

[0027] Calcination: Next, the pressed green body is calcined. The calcination process causes physical and chemical changes inside the green body through high temperature, further stabilizing its structure and preparing for the subsequent reduction process.

[0028] Molten hydrogen plasma reduction: After calcination, the green body is reduced using molten hydrogen plasma technology. This step uses the special properties of molten hydrogen plasma to deeply reduce the green body, making its composition more uniform and removing impurities.

[0029] Crushing: The green body after reduction treatment is sent to the crusher for crushing. Through crushing, the green body is broken into fine powder, which is convenient for subsequent screening and separation;

[0030] Screening: Finally, the crushed powder is screened and the residual powder, iron ingots and iron beads of different particle sizes are separated through a sieve or other screening equipment to ensure the purity and quality of the final product.

[0031] The implementation objectives and principles of this invention are mainly controlled by the following contents:

[0032] 1. Raw material preparation: Red mud, a toxic waste generated during the bauxite refining process, is used as the main raw material. This red mud usually contains a large amount of iron oxide and other metal oxides.

[0033] 2. Reducing Agents and Equipment

[0034] Reducing agent: Plasma hydrogen is used as the reducing agent. Compared with traditional solid reducing agents, plasma hydrogen has higher reactivity and is more environmentally friendly.

[0035] Equipment: A device similar to an electric arc furnace is used in which hydrogen plasma is generated.

[0036] 3. Process steps

[0037] Melting: Red mud is placed in an electric arc furnace and melted by high temperatures to form a viscous melt.

[0038] Reduction: Molten red mud is exposed to hydrogen plasma for rapid liquid reduction. During this process, iron oxide is reduced to iron, with water being the main byproduct, thus avoiding the emission of greenhouse gases such as carbon dioxide.

[0039] Separation: After the reduction reaction, liquid iron and liquid oxide will naturally separate due to differences in density and viscosity.

[0040] Extraction: Liquid iron can be easily extracted and after it cools and solidifies, high-purity iron blocks can be obtained.

[0041] 4. Product Features

[0042] Purity: The extracted iron has high purity, usually reaching above 95%, or even up to 98%, with extremely low content of harmful elements, and can be directly used for steelmaking or other high-end applications.

[0043] Environmental protection: The only by-product produced during the entire process is water, which fully meets environmental protection requirements.

[0044] 5. Optimization direction

[0045] Fume treatment: Fumes may be generated during the reduction and extraction process, and appropriate treatment equipment is required to ensure environmental safety.

[0046] Process optimization: Although the current reduction time is relatively short (e.g., 10-15 minutes), there is still room for further process optimization and improvement of reduction efficiency.

[0047] Large-scale application: At present, this technology may still be in the laboratory or small-scale test stage. To achieve industrial application, a large number of pilot and large-scale tests are needed to verify its economy and feasibility.

[0048] The following will provide additional explanations through specific examples. The Bayer red mud used in the following experiments comes from Zhongzhou Aluminum. The iron content of the red mud measured by IPC-MS is 53%.

[0049] Example 1:

[0050] Pressing into blanks: The pH value of the red mud residual liquid is 10-11, and it is pressed into red mud blanks under 5-10MPa conditions.

[0051] Calcination: The pressed red mud blank was calcined at 800 degrees Celsius for 60 minutes.

[0052] Molten Hydrogen Plasma Reduction: 30g of the calcined red mud ingot was placed in a vacuum arc melting furnace for hydrogen plasma reduction. The first step involved pre-melting. High-purity Ar gas (0.06MPa) was introduced into the arc furnace at a current of 80A to melt the red mud into a molten mass. In the second step, residual gases from the first step were removed. Hydrogen plasma reduction was then carried out by introducing 90vol% Ar gas and 10vol% H2 at a total pressure of 0.06MPa and a current of 80A. Each treatment lasted 2 minutes. This cycle was repeated twice to complete the reduction process.

[0053] Crushing and screening: After crushing and screening the reduced red mud ingots, approximately 8g of iron beads with a diameter of 5-10mm can be obtained. Scanning electron microscope energy spectrum analysis shows an iron content of 99.6wt% and an extraction rate of 50.3%. The pH of the residue is between 7.5-8.

[0054] Example 2:

[0055] Pressing into blanks: The pH value of the red mud residual liquid is 10-11, and it is pressed into red mud blanks under 5-10MPa conditions.

[0056] Calcination: The pressed red mud blank was calcined at 800 degrees Celsius for 60 minutes.

[0057] Molten Hydrogen Plasma Reduction: 30g of the calcined red mud ingot was placed in a vacuum arc melting furnace for hydrogen plasma reduction. The first step involved pre-melting. High-purity Ar gas (0.06MPa) was introduced into the arc furnace at a current of 130A to melt the red mud into a molten mass. In the second step, residual gases from the first step were removed. Hydrogen plasma reduction was then carried out by introducing 90vol% Ar gas and 10vol% H2 at a total pressure of 0.06MPa and a current of 130A. Each treatment lasted 2 minutes. This process was repeated four times to complete the reduction process.

[0058] Crushing and screening: After crushing and screening the reduced red mud ingots, approximately 8.8g of iron beads with a diameter of 5-10mm can be obtained. Scanning electron microscope energy spectrum analysis shows an iron content of 99.8wt% and an extraction rate of 55%. The pH of the residue is between 7.5-8.

[0059] Example 3:

[0060] Pressing into blanks: The pH value of the red mud residual liquid is 10-11, and it is pressed into red mud blanks under 5-10MPa conditions.

[0061] Calcination: The pressed red mud blank was calcined at 1200 degrees Celsius for 60 minutes.

[0062] Molten Hydrogen Plasma Reduction: 60g of the calcined red mud ingot was placed in a vacuum arc melting furnace for hydrogen plasma reduction. The first step involved pre-melting. High-purity Ar gas (0.06MPa) was introduced into the arc furnace at a current of 200A to melt the red mud into a molten mass. In the second step, residual gases from the first step were removed. Hydrogen plasma reduction was then carried out by introducing a mixture of 90vol% Ar and 10vol% H2 at a total pressure of 0.06MPa and a current of 200A. Each treatment lasted 4 minutes, and this process was repeated five times to complete the reduction.

[0063] Crushing and screening: After crushing and screening the reduced red mud ingots, approximately 18.8g of iron nuggets with a diameter of 10-20mm were obtained. Scanning electron microscope (EDS) analysis showed an iron content of 99.6wt% and an extraction rate of 59%. The pH of the residue was between 7.5-8.

[0064] Example 4:

[0065] This embodiment provides an optimized method for extracting iron from red mud. The method is further improved and optimized based on the first embodiment to increase the extraction rate and purity of iron.

[0066] Pressing into green bodies: Pretreated red mud raw materials are selected and formed through an efficient pressing process to form high-density green bodies. Pretreatment includes dehydration and impurity removal to ensure the purity and uniformity of the raw materials. During the pressing process, advanced pressure control technology is used to ensure that the green bodies are evenly compressed at 5-10 MPa, resulting in green bodies with excellent physical properties.

[0067] Calcination: The pressed green body is calcined under a precisely controlled temperature curve at 900-1100 degrees Celsius for 45-90 minutes. By optimizing the calcination temperature and time, the physical and chemical changes within the green body are further promoted, creating more favorable conditions for the subsequent reduction process.

[0068] Molten hydrogen plasma reduction: Advanced electric arc furnace equipment is used, equipped with high-precision gas control and current regulation systems. In the first pre-melting stage, 0.6MPa of high-purity Ar gas is introduced, and the current is precisely controlled within the range of 120-180A to ensure that the red mud billet is completely melted into a melt. In the second step of removing residual gases, the mixing ratio of the introduced Ar gas and H2, as well as the current and pressure parameters are optimized to improve the reduction efficiency. Specifically, 85-95vol.% Ar gas and 5-15vol.% H2 are introduced, the total pressure of the mixed gas is maintained at 0.6-0.8MPa, the current is controlled within the range of 100-180A, each processing time is 2-4 minutes, and this step is repeated more than 4 times to ensure sufficient reduction.

[0069] Crushing and Screening: High-efficiency crushing equipment is used to crush the reduced green body into fine powder. A multi-stage screening system accurately separates the residual powder, iron ingots, and iron beads of different particle sizes to ensure the purity and quality of the final product.

[0070] Embodiment 5:

[0071] This embodiment focuses on improving the environmental protection and resource utilization rate of the red mud iron extraction method.

[0072] Environmental Protection Measures: Throughout the entire iron extraction process, emissions of waste gas, wastewater, and solid waste are strictly controlled. Advanced waste gas treatment systems are used to ensure that emissions meet national environmental standards. Wastewater is deeply treated to ensure recycling or safe discharge. Solid waste generated is classified, with recyclable components reused and non-recyclable components safely disposed of.

[0073] Resource Utilization: The extracted high-purity iron nuggets can be directly used in steel production or other industries requiring high-purity iron. The low-alkalinity residue produced during the reduction process can be further processed and used in construction materials, roadbed materials, and other fields, achieving resource recycling.

[0074] This invention innovatively utilizes plasma hydrogen as a reducing agent and red mud, an industrial waste product, as the sole raw material, achieving efficient and environmentally friendly resource utilization. This technical solution not only significantly simplifies the complex drying, crushing, and mixing processes typically encountered in traditional processes, but also, due to its unique use of plasma hydrogen, avoids the environmental and operational inconveniences associated with conventional solid reducing agents. Water is the only byproduct produced during the reduction process, a significant environmental advantage that completely eliminates the emission of greenhouse gases such as carbon dioxide, significantly contributing to the development of a green, environmentally friendly, and low-carbon economy. The iron reduced by this method is present in the form of iron blocks with a purity exceeding 90%, with purity exceeding 98%. This high-grade, high-purity iron is not only of superior quality but also facilitates subsequent extraction and processing, significantly improving production efficiency and product quality. Furthermore, the process is simple to understand and easy to operate, reducing production costs while also improving efficiency. Furthermore, its environmentally friendly nature meets society's urgent need for sustainable development, achieving both economic benefits and environmental protection. The implementation of this invention undoubtedly opens up a new avenue for the comprehensive utilization of red mud, not only improving resource utilization but also promising significant impact in future industrial production. Its broad application prospects and market potential will undoubtedly lead to technological innovation and industrial upgrading in related industries.

Claims

1. A method for extracting iron from red mud based on electric arc furnace hydrogen plasma melting reduction technology, characterized by: The method for extracting iron from red mud comprises the following steps: Pressing into blanks: First, the red mud raw materials are shaped through a pressing process to form a blank with a certain shape and density. The red mud raw materials are pressed under 5-10MPa conditions to form red mud blanks; Calcination: Calcination treatment is performed on the pressed green body, and the pressed red mud green body is calcined at 800-1200 degrees Celsius for 30-120 minutes; Molten hydrogen plasma reduction: After calcination, the green body is reduced using molten hydrogen plasma technology, including: The first step is pre-melting: 0.06MPa high-purity Ar gas is introduced into the electric arc furnace with a current of 100-200A to melt the red mud into a melt; The second step is to remove residual gas: introduce 80-90 vol.% Ar gas and 10-20 vol.% H2, with a total pressure of the mixed gas of more than 0.06 MPa and a current of 80-200 A, and perform hydrogen plasma reduction treatment for 1-5 minutes each time. This step should be repeated more than 3 times; Crushing: The green body after reduction treatment is sent to the crusher for crushing; Screening: The crushed powder is screened to separate the residue powder, iron ingots and iron beads of different particle sizes; the reduced red mud ingots are crushed and screened to obtain pure iron with a purity higher than 98%, and the pH value of the residue is 7.5-8.

2. The method for extracting iron from red mud based on electric arc furnace hydrogen plasma melting reduction technology according to claim 1, characterized in that: In the molten hydrogen plasma reduction process, the calcined red mud blank is placed in a vacuum arc melting furnace for hydrogen plasma reduction treatment. The vacuum arc melting furnace has a device for introducing a mixed gas of Ar gas and H2, as well as a device for controlling current and pressure.

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