Process for extracting iron from red mud by using hydrogen reduction and electrolysis technology

Abstract

The invention relates to a process for extracting iron from red mud by using hydrogen reduction and electrolysis technologies, the red mud is a by-product generated in the industrial production process of aluminum, the environmental burden caused by the by-product can be solved, the carbon emission can be reduced, and the development of a green metallurgical technology can be promoted. Comprising the following steps: conveying red mud serving as a raw material into a rotary furnace, conveying hydrogen serving as a reducing medium into the rotary furnace, enabling iron oxide in the red mud to form hydrogen reduced iron in a furnace heating state and a hydrogen reducing atmosphere, conveying the red mud containing the hydrogen reduced iron into a sulfuric acid solution, the hydrogen reduced iron is dissolved in the sulfuric acid solution to form a sulfuric acid solution containing iron ions, the sulfuric acid solution containing the iron ions serves as an electrolyte in an electrolysis device, and electrolytic pure iron formed by electrolytic deposition of the iron ions is obtained through the electrolysis device.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hydrometallurgy and environmental engineering, and particularly relates to a process for extracting iron from red mud by hydrogen reduction and electrolysis technology, wherein the red mud is a by-product generated in the production process of the aluminum industry, which is beneficial to solve the environmental burden caused by the by-product, reduce carbon emissions and promote the development of green metallurgical technology. BACKGROUND

[0002] Red mud is a waste residue generated in the process of refining alumina from bauxite, which has high annual output, large stockpile and low utilization rate, and poses a great threat to resources and the environment. Therefore, extracting valuable metal elements, especially iron, from red mud is of great significance for realizing the utilization of red mud resources. Iron oxide in red mud is one of the components with high content, which provides a material basis for iron recovery. Existing iron extraction methods, such as magnetic separation, pyrometallurgy, hydrometallurgy and bio-metallurgy, all face technical challenges. For example, the magnetic separation method has low recovery efficiency, and pyrometallurgy and hydrometallurgy have high energy consumption and cost, and may produce waste gas. Hydrogen reduction technology is explored as a sustainable way to reduce CO2 emissions, in which the reduction kinetics of hematite is a key step. Hydrogen plasma reduction provides an attractive alternative that can achieve complete reduction of hematite in a relatively short time. Electrolysis technology is used in hydrometallurgy to extract iron from iron-containing electrolyte.

[0003] Hydrogen energy can be used as a new form of energy storage through the conversion of electricity-hydrogen-electricity, which can help improve the consumption of renewable energy and provide long-term energy storage. Electricity will be one of the most widely used final energy sources in the current and future. The process and method of extracting resources from red mud by using hydrogen energy and electricity energy are in line with several key trends in future energy development, not only in line with the global energy transformation trend, but also in line with energy strategy and environmental protection policy, and have broad development prospects. SUMMARY

[0004] The present application provides a process for extracting iron from red mud by hydrogen reduction and electrolysis technology, wherein the red mud is a by-product generated in the production process of the aluminum industry, which is beneficial to solve the environmental burden caused by the by-product, reduce carbon emissions and promote the development of green metallurgical technology.

[0005] The technical solution of the present application is as follows:

[0006] A process for extracting iron from red mud by hydrogen reduction and electrolysis technology, characterized in that it comprises the following steps: feeding red mud as raw material into a rotary furnace, feeding hydrogen gas as reducing medium into the rotary furnace, forming hydrogen-reduced iron from iron oxides in the red mud in a heated state in the furnace and in a hydrogen reduction atmosphere, feeding the red mud containing the hydrogen-reduced iron into a sulfuric acid solution, dissolving the hydrogen-reduced iron into the sulfuric acid solution to form a sulfuric acid solution containing iron ions, using the sulfuric acid solution containing iron ions as electrolyte in an electrolysis device, and obtaining electrolytic iron formed by electrolytic deposition of the iron ions through the electrolysis device.

[0007] The process comprises the following steps:

[0008] Step 1, grinding of coarse red mud: grinding the granular and / or blocky red mud to obtain fine red mud capable of passing through a sieve with a mesh size of not less than 120;

[0009] Step 2, removal of alkali from fine red mud: mixing the fine red mud with hydrochloric acid to neutralize the alkali in the red mud with the hydrochloric acid, and forming an alkali-removed red mud solution;

[0010] Step 3, filtration: removing the dissolved alkali and impurity ions in the alkali-removed red mud solution by using a vacuum filter, and obtaining a red mud residue;

[0011] Step 4, drying: heating and drying the red mud residue to obtain dried red mud;

[0012] Step 5, grinding of dried red mud: grinding the dried red mud to obtain fine dried red mud capable of passing through a sieve with a mesh size of not less than 120;

[0013] Step 6, hydrogen reduction treatment: feeding the fine dried red mud into a rotary furnace, excluding air in the rotary furnace by introducing nitrogen gas, introducing hydrogen gas to form a hydrogen reduction atmosphere in the furnace after the air is excluded, setting the reduction temperature to 900-1200°C, introducing nitrogen gas to exclude the hydrogen gas after the reduction reaction is completed, and obtaining hydrogen-reduced iron red mud;

[0014] Step 7, dissolution treatment: mixing the hydrogen-reduced iron red mud with sulfuric acid, the concentration of the sulfuric acid being 0.5 mol / L, and performing a dissolution reaction under a heated state, and obtaining a sulfuric acid solution containing iron ions after the reaction is completed;

[0015] Step 8, electrolysis: using the sulfuric acid solution containing iron ions as electrolyte, and performing electrolysis with an inert electrode, and forming electrolytic iron by electrolytic deposition of the iron ions.

[0016] In Step 2, the reaction temperature is controlled to be 25-80°C, and the volume ratio of hydrochloric acid to red mud is controlled to be between 3 and 6.

[0017] In Step 3, the filtration is performed using filter paper with a pore size of not greater than 45 μm.

[0018] The drying temperature in step 4 is 100-300℃.

[0019] The inert electrode in step 8 is a graphite electrode.

[0020] The electrolysis temperature in step 8 is 25-95℃, and the current density is 50-5000A / m 2 All of them can.

[0021] The technical effects of the present application are as follows: the process for extracting iron from red mud by hydrogen reduction and electrolysis not only improves the efficiency of extracting iron from red mud, but also improves the purity of the extracted iron from red mud, significantly reduces environmental pollution, and reduces the overall production cost. In the current global demand for reducing carbon emissions and achieving sustainable development, the present application provides a solution that meets the future development trend. Red mud, as a byproduct of the aluminum industry production process, has a total iron content of up to 40%, but due to the high content of alkali and aluminum elements, it is difficult to handle. In the present application, the red mud is first pretreated by drying and dealkalization to optimize its physical and chemical properties for the subsequent reduction reaction. This step includes crushing, classification and chemical treatment of the red mud to improve its reactivity and extractability of iron.

[0022] Next, the pretreated red mud is subjected to a reduction reaction with hydrogen gas. This process is carried out under specific temperature and pressure conditions to ensure that the iron oxides in the red mud are effectively reduced to metallic iron. Hydrogen gas, as a clean energy source, not only provides the necessary reduction capacity, but also does not produce harmful byproducts during the reaction, further reducing the environmental burden.

[0023] Subsequently, the reduced red mud enters the electrolysis stage. In this process, the iron in the red mud is extracted by electrolysis, and the byproduct produced is hydrogen gas, which can be recycled, further reducing the environmental impact. Parameters such as current density, electrolyte composition and electrolysis time are precisely controlled and optimized to ensure high-purity extraction of iron and minimize energy consumption.

[0024] Through the above steps, the present application not only enables the preparation of high-purity iron, but also significantly reduces the generation of harmful byproducts. This method not only improves the efficiency of resource utilization and reduces production costs, but also has important significance for reducing carbon emissions and promoting the development of green metallurgical technology. With the growing global demand for sustainable and environmentally friendly technology, the present application is expected to become an important development direction for the future metallurgical industry. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 The macroscopic morphology of the red mud before treatment in Example One of the present application.

[0026] Figure 2 Figure 2 is a macroscopic morphology diagram of the red mud after H2 reduction in the embodiment one of the present application.

[0027] Figure 3 Figure 3 is a diagram of the dissolving and electrolyzing device in the embodiment one of the present application.

[0028] Figure 4 Figure 4 is a macroscopic morphology diagram of the iron obtained by electrolysis in the embodiment one of the present application. DETAILED DESCRIPTION

[0029] The present application will be described below in conjunction with the accompanying drawings Figures 1-4 and examples.

[0030] Figure 1 Figure 1 is a macroscopic morphology diagram of the red mud before treatment in the embodiment one of the present application. Figure 2 Figure 2 is a macroscopic morphology diagram of the red mud after H2 reduction in the embodiment one of the present application. Figure 3 Figure 3 is a diagram of the dissolving and electrolyzing device in the embodiment one of the present application. Figure 4 Figure 4 is a macroscopic morphology diagram of the iron obtained by electrolysis in the embodiment one of the present application. Figures 1 to 4 As shown in Figure 4, a process for extracting iron from red mud by hydrogen reduction and electrolysis technology, comprising: feeding the red mud as raw material into a rotary furnace, feeding hydrogen gas as reducing medium into the rotary furnace, forming hydrogen-reduced iron from the iron oxides in the red mud in the state of heating in the furnace and the hydrogen reduction atmosphere, feeding the red mud containing the hydrogen-reduced iron into a sulfuric acid solution, dissolving the hydrogen-reduced iron into the sulfuric acid solution to form a sulfuric acid solution containing iron ions, using the sulfuric acid solution containing iron ions as electrolyte in an electrolyzing device, and obtaining electrolytic iron formed by electrolytic deposition of the iron ions through the electrolyzing device.

[0031] The method comprises the following steps: Step 1, coarse red mud grinding: the granular and / or blocky red mud is ground to obtain fine red mud which can pass through a screen mesh of not less than 120 meshes; Step 2, fine red mud alkali removal: the fine red mud is mixed with hydrochloric acid to neutralize the alkali in the red mud, and an alkali-removed red mud solution is formed; Step 3, suction filtration: the alkali-removed red mud solution is subjected to suction filtration by using a vacuum suction filter to remove the dissolved alkali and impurity ions in the solution, and a red mud residue is obtained; Step 4, drying: the red mud residue is heated and dried to obtain dried red mud; Step 5, dried red mud grinding: the dried red mud is ground to obtain fine dried red mud which can pass through a screen mesh of not less than 120 meshes; Step 6, hydrogen reduction treatment: the fine dried red mud is fed into a rotary furnace, air in the rotary furnace is removed by introducing nitrogen, hydrogen is introduced to form a hydrogen reduction atmosphere in the furnace after the air is removed, the reduction temperature is 900-1200 DEG C, and after the reduction reaction is completed, the hydrogen is removed by introducing nitrogen, and hydrogen-reduced iron red mud is obtained; Step 7, dissolution treatment: the hydrogen-reduced iron red mud is mixed with sulfuric acid, the concentration of the sulfuric acid is 0.5 mol / L, and the dissolution reaction is carried out under heating, and after the reaction is completed, a sulfuric acid solution containing iron ions is obtained; Step 8, electrolysis: the sulfuric acid solution containing iron ions is used as an electrolyte, and electrolysis is carried out by using an inert electrode, and the iron ions are electrolytically deposited to form electrolytic iron.

[0032] The inert electrode in Step 8 is a graphite electrode. Step 2 comprises a reaction temperature of 25-80 DEG C. Step 3 comprises suction filtration by using filter paper with a pore size of not greater than 45 mu m. Step 4 comprises a drying temperature of 100-300 DEG C. Step 8 comprises an electrolysis temperature of 25-95 DEG C.

[0033] The technical scheme provided by the present application has the following remarkable effects:

[0034] The method for preparing iron by hydrogen reduction and electrolysis of red mud provided by the present application has a complete set of technology and scheme. Firstly, the red mud is ground to increase the specific surface area of the red mud, which is beneficial to the implementation of the subsequent alkali removal process; the not greater than 1 mol / L hydrochloric acid involved in the present application ensures the removal of alkali and the retention of Fe2O3; the third step of suction filtration ensures the separation of alkali and impurity ions, and prepares for the subsequent hydrogen reduction; the fourth step of drying and the fifth step of grinding ensure that the red mud after suction filtration has a large specific surface area, and prepares for the reduction. The sixth step of the present application selects a rotary furnace for reduction treatment, so that the alkali-removed red mud is fully contacted with the reducing medium in the furnace to realize complete reduction; the seventh step uses low-concentration sulfuric acid to dissolve the reduced iron, so that the iron is transferred from the red mud to the solution, which is convenient for the subsequent electrolytic extraction; and the eighth step of electrolysis can obtain pure iron.

[0035] 1. The technical problem to be solved by the present application

[0036] Red mud, a by-product of alumina production, has caused serious environmental and health hazards due to its large-scale production and inefficient utilization. Traditional physical methods such as magnetic separation and flotation, as well as chemical and hydrometallurgical methods such as acid leaching, often encounter problems of low iron recovery and the generation of acidic wastewater. Hydrogen reduction and electrolytic iron extraction technologies improve the recovery of iron through chemical and electrochemical processes and reduce the generation of acidic wastewater. Pyrometallurgical methods, although effective, are hindered by high energy consumption and environmental problems, and traditional red mud treatment methods are often unsustainable.

[0037] In summary, red mud treatment needs to address multiple technical problems in red mud treatment, including environmental impact, iron recovery efficiency, energy consumption, and sustainability, and urgently needs to provide new methods and technical routes for the resource utilization of red mud.

[0038] 2. Technical solutions

[0039] In order to achieve the above-mentioned purposes, the technical solutions provided by the present application are:

[0040] First, the red mud is pretreated, including grinding the granular red mud into powder, sieving with a sieve not less than 120 mesh, and then heating and stirring with low-concentration hydrochloric acid less than 1 mol / L until the reaction is complete. After the reaction, filter paper with a pore size not greater than 45 μm is used for suction filtration, and the red mud after suction filtration is dried. The dried red mud is subjected to high-temperature full reduction using a rotary atmosphere reduction furnace, and the reduction temperature is 900-1200℃. During the reduction process, nitrogen is first introduced for 30 minutes to remove the air in the furnace tube, and then hydrogen is slowly introduced for reduction, with a gas flow rate controlled at not less than 0.8 NL / min (normal liters per minute). After the flow rate is stable, the nitrogen valve is closed. After the heat preservation is completed, the temperature is lowered, and when the temperature drops to about 100℃, nitrogen is introduced and the hydrogen is closed to fully remove the hydrogen in the furnace. During the entire process, the rotary frequency of the rotary atmosphere reduction furnace is 1-8 revolutions per minute, which helps to increase the contact area and time of the red mud with the reducing medium, thereby improving the reduction efficiency. The reduced red mud is dissolved with dilute sulfuric acid, heated at 60-95℃ for 2 hours, and then the solution obtained by the reaction is adjusted to pH 2-3. The electrolyte is electrolyzed using inert electrodes as anode and cathode, and the electrolysis temperature is 25-95℃. Through these steps, iron can be effectively extracted from red mud.

[0041] Preferably, the specific steps include:

[0042] Step 1, red mud grinding

[0043] The granular and blocky red mud is subjected to sufficient grinding treatment to prepare for subsequent alkali removal, and after grinding, sieving is performed with a sieve not less than 120 mesh.

[0044] Step 2, red mud alkali removal

[0045] The ground red mud is reacted with hydrochloric acid with a concentration of not more than 1 mol / L, the volume of the hydrochloric acid is controlled to be between 3 and 6 times the mass of the red mud, the reaction time is not less than 2 hours, and the temperature is 25-80°C.

[0046] Step three, suction filtration

[0047] The solution after the removal of alkali is suction filtered to remove the dissolved alkali and impurity ions, and the pore size of the filter membrane is not greater than 45 μm.

[0048] Step four, drying

[0049] The red mud after the removal of alkali is fully dried at a temperature of 100-300°C.

[0050] Step five, red mud grinding

[0051] The dried red mud is fully ground to prepare for the subsequent reduction, and the ground red mud is sieved through a sieve with a mesh size of not less than 120;

[0052] Step six, reduction treatment

[0053] The dried red mud is fully reduced at a temperature of 900-1200°C, and a reducing medium is selected as the reducing agent.

[0054] Step seven, dissolution treatment

[0055] The reduced red mud is dissolved with low-concentration sulfuric acid, and the pH is adjusted to 2-3.

[0056] Step eight, electrolysis

[0057] The electrolyte containing iron ions after dissolution is electrolyzed with a random electrode, the electrolysis temperature is controlled to be 25-95°C, and the current density is 50-5000 A / m 2 .

[0058] Example 1

[0059] In this example, a process for extracting iron by hydrogen reduction + electrolysis is mainly introduced, and the specific process parameters are set as follows:

[0060] (1) The particle, blocky red mud is ground for more than 1 hour, and then sieved with a 120-mesh sieve. The ground red mud is reacted with 1 mol / L hydrochloric acid at a liquid-solid ratio of 4:1 ml / g, the reaction time is 2 hours, the temperature is controlled at 60°C, and the stirring speed is 300 r / min. The solution after removing the alkali is filtered, and the dissolved alkali and impurity ions are removed. The filter membrane has a pore size of 0.45 μm and a vacuum degree of 0.098 MPa. The separated red mud is dried at a temperature of 200°C for 6 hours. The dried red mud is ground to break the hardening caused by drying, and then sieved with a 120-mesh sieve. The red mud after alkali removal and grinding is placed in a rotary atmosphere reduction furnace for reduction, the reduction medium is H2, the reduction temperature is 1100°C, and the reduction time is set to 2h. During the reduction process, nitrogen is first introduced for 30 minutes to remove the air in the furnace tube, and then hydrogen is slowly introduced, and the gas flow is controlled at 0.8 NI / min. After the flow stabilizes, the nitrogen valve is closed. After the heat preservation is completed, the temperature is reduced to about 100°C, nitrogen is introduced, and hydrogen is closed to fully remove the hydrogen in the furnace. During the whole process, the rotation frequency of the rotary atmosphere reduction furnace is 1-8 turns per minute, which helps to increase the contact area and time of the red mud and the reducing medium, thereby improving the reduction efficiency. The reduced red mud is dissolved in a 0.5 mol / L sulfuric acid solution and heated at 80°C to promote the reaction process. The reaction completed solution is added to NaOH to adjust the pH to 3. Electrolysis of the solution with graphite as the cathode and anode can obtain iron.

[0061] A method for preparing iron by red mud hydrogen reduction and electrolysis, comprising the following steps:

[0062] First, the red mud is pretreated, the granular red mud is crushed into powder by grinding, and the low-concentration hydrochloric acid is reacted under heating and stirring. After filtration, the filter residue is dried in a 250°C drying oven. The dried red mud is first ground, and then high-temperature reduction is carried out by using a rotary atmosphere reduction furnace. The reduced red mud is dissolved in sulfuric acid, and then electrolysis is carried out to extract iron. Through the above steps, iron can be extracted from the red mud.

[0063] The red mud pretreatment includes grinding the red mud through a 120-mesh sieve, and then acid leaching with less than 1 mol / L hydrochloric acid, the reaction temperature is 60°C, the stirring speed is 300 r / min, and the time is 2h. Then, the filter paper with a pore size of 0.45 μm is used for filtration, and the vacuum degree is 0.098 MPa. The filtered red mud is dried at 200°C.

[0064] The pre-processed red mud is put into a rotary furnace, a detachable flange cover is installed on the feeding port, a furnace tube rotation button is started, the reduction temperature is 900-1200 DEG C, the reduction time is 2h, the temperature is raised, the nitrogen valve is opened to introduce nitrogen for 30 minutes, the air in the furnace tube is fully discharged, then hydrogen is slowly introduced, the gas flow is controlled at 0.8 NI / min, when the flow is stable, the nitrogen valve is closed. When the test is finished, the temperature is reduced, when the temperature is about 100 DEG C, nitrogen is introduced, hydrogen is closed, and the hydrogen in the furnace is fully discharged.

[0065] The electrolytic iron production step includes putting the red mud reduced by hydrogen into dilute sulfuric acid to dissolve, and reacting at 80 DEG C for 2h. The solution obtained by the reaction is adjusted to PH 2-3 by NaOH, and the electrolyte is electrolyzed using an inert electrode as the anode and the cathode, and the electrolysis temperature is controlled at 25 DEG C.

[0066] The reduction equipment is a rotary atmosphere furnace, and the rotary frequency of the rotary atmosphere reduction furnace during use is 1-8 turns / min, and the rotary reduction furnace can increase the contact area and time of the red mud and the reducing medium.

[0067] The contents not described in detail in the specification of the present application belong to the prior art known by the skilled in the art. It is indicated herein that the above description is helpful for the skilled in the art to understand the present application, but is not used to limit the protection scope of the present application. Any implementation of the above description, equivalent replacement, modification, improvement and / or deletion of the above description without departing from the essential content of the present application falls into the protection scope of the present application.

Claims

1. A process for extracting iron from red mud using hydrogen reduction and electrolysis technology, characterized by, The method comprises the following steps: feeding red mud into a rotary furnace, feeding hydrogen into the rotary furnace as a reducing medium, forming hydrogen-reduced iron from iron oxides in the red mud in a heated state in the furnace and a hydrogen reduction atmosphere, feeding the red mud containing the hydrogen-reduced iron into a sulfuric acid solution, dissolving the hydrogen-reduced iron into the sulfuric acid solution to form a sulfuric acid solution containing iron ions, and using the sulfuric acid solution containing the iron ions as an electrolyte in an electrolysis device to obtain pure iron by electrolytic deposition of the iron ions.

2. The process for extraction of iron from red mud using hydrogen reduction and electrolysis technology as claimed in claim 1 wherein, The method comprises the following steps: Step 1, grinding of coarse red mud: grinding the red mud in the form of particles and / or blocks to obtain fine red mud capable of passing through a sieve with a mesh size of not less than 120; Step 2, removal of alkali from the fine red mud: mixing the fine red mud with hydrochloric acid with a concentration of not higher than 1 mol / L, controlling the volume ratio of the hydrochloric acid to the mass of the red mud to be between 3 and 6, and forming an alkali-removed red mud solution; Step 3, filtration: removing the dissolved alkali and impurity ions in the alkali-removed red mud solution by using a vacuum filter to obtain a red mud residue; Step 4, drying: heating and drying the red mud residue to obtain dried red mud; Step 5, grinding of the dried red mud: grinding the dried red mud to obtain fine dried red mud capable of passing through a sieve with a mesh size of not less than 120; Step 6, hydrogen reduction treatment: feeding the fine dried red mud into a rotary furnace, removing air in the furnace by introducing nitrogen, introducing hydrogen to form a hydrogen reduction atmosphere in the furnace after the air is removed, and setting the reduction temperature to be between 900 and 1200 degrees Celsius; after the reduction reaction is completed, nitrogen is introduced to remove the hydrogen, and hydrogen-reduced iron-containing red mud is obtained; Step 7, dissolution treatment: mixing the hydrogen-reduced iron-containing red mud with sulfuric acid with a concentration of 0.5 mol / L, and performing a dissolution reaction under heating to obtain a sulfuric acid solution containing iron ions; Step 8, electrolysis: using the sulfuric acid solution containing the iron ions as an electrolyte, and performing electrolysis using an inert electrode to form electrolytic pure iron by electrolytic deposition of the iron ions.

3. The process for extraction of iron from red mud using hydrogen reduction and electrolysis technology as claimed in claim 2 wherein, The inert electrode in Step 8 is a graphite electrode.

4. The process for extraction of iron from red mud using hydrogen reduction and electrolysis technology as claimed in claim 2 wherein, In Step 3, the filtration is performed using filter paper with a pore size of not greater than 45 μm.

5. The process for extraction of iron from red mud using hydrogen reduction and electrolysis technology as claimed in claim 2 wherein, In Step 4, the drying temperature is between 100 and 300 degrees Celsius.

6. The process for extraction of iron from red mud using hydrogen reduction and electrolysis technology as claimed in claim 2 wherein, In Step 2, the reaction temperature is between 25 and 80 degrees Celsius.

7. The process for extraction of iron from red mud using hydrogen reduction and electrolysis technology as claimed in claim 2 wherein, In Step 8, the electrolysis temperature is between 25 and 95 degrees Celsius.

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