Method for extracting valuable metals in red mud

Abstract

The invention provides a method for extracting valuable metals in red mud, which comprises the following steps: adding pretreated red mud into a first chlorine atmosphere to carry out medium and low temperature chlorination reaction to generate a low-boiling-point and high-volatility metal chloride; adding the red mud subjected to the medium-low temperature chlorination reaction into a second chlorine atmosphere for high-temperature chlorination reaction to generate a high-boiling-point low-volatility metal chloride; recovering the low-boiling-point high-volatility metal chloride and the high-boiling-point low-volatility metal chloride so as to complete the extraction of the valuable metals in the red mud; wherein the temperature range of the medium and low temperature chlorination reaction is 300-600 DEG C, and the temperature range of the high temperature chlorination reaction is 500-1000 DEG C. Through the staged chlorination reaction, the extraction efficiency of the metal is improved, the energy consumption is reduced, meanwhile, high-temperature side reaction is avoided, and the purity of the metal chloride is improved.

Description

Technical Field

[0001] This application relates to the field of resource utilization technology of alumina red mud, and in particular to a method for extracting valuable metals from red mud. Background Technology

[0002] With the rapid development of the aluminum industry, the stockpiles of red mud, a large amount of solid waste generated during the alumina refining process from bauxite, have increased dramatically, becoming a global environmental problem. Red mud contains various valuable metal elements such as iron, aluminum, titanium, and sodium, but due to its complex composition and strong alkalinity, traditional extraction processes suffer from high costs, low efficiency, high energy consumption, and environmental pollution, resulting in extremely low resource utilization rates.

[0003] In existing technologies, hydrometallurgy and pyrometallurgy are common methods for metal extraction. Hydrometallurgy extracts metals through acid or alkali leaching, but suffers from high reagent consumption, generates large amounts of acidic wastewater, and is difficult to treat. Pyrometallurgy extracts metals through high-temperature reduction, which is extremely energy-intensive and generates large amounts of waste gas, placing a significant burden on the environment. Furthermore, these traditional methods have low metal recovery rates when extracting valuable metals from red mud, especially for low-volatile metals (such as iron, aluminum, and titanium), with recovery rates of only 10%–50%, which is insufficient to meet the needs of large-scale industrial processing. Therefore, how to efficiently extract valuable metals from red mud while reducing energy consumption and environmental pollution has become an urgent technical challenge. Summary of the Invention

[0004] This application provides a method for extracting valuable metals from red mud to solve the following technical problem: how to improve the extraction efficiency of valuable metals from red mud.

[0005] This application provides a method for extracting valuable metals from red mud, including:

[0006] The pretreated red mud is added to a first chlorine atmosphere to carry out a medium-low temperature chlorination reaction to generate low-boiling-point, high-volatility metal chlorides.

[0007] The red mud after the low-temperature chlorination reaction is added to a second chlorine atmosphere to carry out a high-temperature chlorination reaction, generating high-boiling-point, low-volatility metal chlorides.

[0008] The low-boiling-point, high-volatility metal chloride and the high-boiling-point, low-volatility metal chloride are recovered to complete the extraction of valuable metals from red mud.

[0009] The temperature range of the medium-low temperature chlorination reaction is 300℃~600℃, and the temperature range of the high temperature chlorination reaction is 500℃~1000℃.

[0010] Optionally, the temperature range of the medium-low temperature chlorination reaction is 350℃~500℃, and the temperature range of the high temperature chlorination reaction is 600℃~950℃.

[0011] Optionally, the low-temperature chlorination reaction time is 1.5 to 2.5 hours, and the high-temperature chlorination reaction time is 1.5 to 2.5 hours.

[0012] Optionally, both the first chlorine atmosphere and the second chlorine atmosphere satisfy the following conditions: flow rate of 10 ml / min to 100 ml / min and pressure of 0.1 MPa to 0.6 MPa.

[0013] Optionally, both the first chlorine atmosphere and the second chlorine atmosphere satisfy the following conditions: flow rate of 20 ml / min to 80 ml / min and pressure of 0.15 MPa to 0.55 MPa.

[0014] Optionally, the red mud is added at a rate of 10 g / min to 50 g / min.

[0015] Optionally, the red mud is added at a rate of 15 g / min to 30 g / min.

[0016] Optionally, the low-boiling-point high-volatility metal chloride and the high-boiling-point low-volatility metal chloride are recovered by staged condensation. The staged condensation includes: first recovering the high-boiling-point low-volatility metal chloride by water-cooled condensation, and then recovering the low-boiling-point high-volatility metal chloride by low-temperature brine condensation.

[0017] Optionally, the pretreatment includes drying, grinding, sieving, and impurity removal.

[0018] Optionally, the drying parameters include: a temperature of 80℃ to 150℃ and a time of 1 to 4 hours; and / or,

[0019] The target particle size for grinding is less than 100 mesh; and / or,

[0020] The sieve aperture size of the sieve is 0.075 mm to 0.25 mm; and / or,

[0021] The impurity removal includes magnetic separation, flotation, or sedimentation washing.

[0022] The technical solutions provided in this application have the following advantages compared with the prior art:

[0023] This application provides a method for extracting valuable metals from red mud. First, a chlorination reaction utilizes the strong oxidizing properties of chlorine to convert metal oxides in the red mud into metal chlorides. These chlorides have low melting and boiling points, making them easy to separate and collect. By conducting a staged low-temperature chlorination reaction (300℃~600℃) and a high-temperature chlorination reaction (500℃~1000℃), low-boiling-point, high-volatility and high-boiling-point, low-volatility metal chlorides can be generated, respectively. In the low-temperature chlorination stage, chlorine reacts with the metal oxides in the red mud to generate low-boiling-point metal chlorides (such as AlCl3, TiCl4, etc.). These chlorides volatilize at relatively low temperatures and can be efficiently recovered using a condensation device. The advantage of this stage is lower energy consumption and higher purity of the metal chlorides. In the high-temperature chlorination stage, chlorine reacts with the remaining metal oxides in the red mud to generate high-boiling-point metal chlorides (such as FeCl3, etc.). These chlorides are stable at high temperatures and can be recovered from the residue using physical separation methods. This stage ensures the complete extraction of all valuable metals from the red mud. This staged chlorination reaction not only improves the metal extraction efficiency but also reduces energy consumption, while avoiding high-temperature side reactions and increasing the purity of metal chlorides. Attached Figure Description

[0024] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0025] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the accompanying drawings necessary for the description of the embodiments or the prior art will be outlined below. Obviously, those skilled in the art can derive other related drawings based on these drawings without creative effort.

[0026] Figure 1 This is a flowchart illustrating a method for extracting valuable metals from red mud, as provided in an embodiment of this application. Detailed Implementation

[0027] To more clearly illustrate the purpose, technical solutions, and advantages of the embodiments of this application, the technical solutions of this embodiment will be described in detail below with reference to the accompanying drawings. Please note that the embodiments described herein are merely exemplary and do not represent all possible implementation paths. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0028] The ranges described in this article, whether numerical or proportional, encompass all subranges and individual numerical values. For example, mentioning '1 to 6' or...

[0029] When '1~6' is used, it means including any sub-interval from 1 to 6 (e.g., 1 to 3, 2 to 5) and all individual numbers (1, 2, 3, 4, 5, 6). Unless otherwise specified, the terms "including" and "contains" as used in this document mean "including but not limited to"; relational terms such as "first" and "second" are used only to distinguish different entities or operations and do not imply an actual order or relationship; "and / or" indicates that multiple situations can exist individually or simultaneously; expressions such as "at least one," "multiple," and "at least one" refer to any combination of the corresponding objects, including combinations of single or multiple objects. Proportional relationships mentioned in this document, such as mass ratio and molar ratio, should be understood as the correspondence between the antecedent and consequent of a proportional expression, according to the order of description. All raw materials, reagents, instruments, and equipment used in this document can be obtained through commercial purchase or prepared using existing methods.

[0030] Figure 1 This is a flowchart illustrating a method for extracting valuable metals from red mud, as provided in an embodiment of this application.

[0031] Please see Figure 1 This application provides a method for extracting valuable metals from red mud, comprising:

[0032] S1. The pretreated red mud is added to the first chlorine atmosphere to carry out a medium-low temperature chlorination reaction to generate low-boiling-point, high-volatility metal chlorides.

[0033] S2. The red mud after the medium-low temperature chlorination reaction is added to a second chlorine atmosphere to carry out a high-temperature chlorination reaction to generate high-boiling-point, low-volatility metal chlorides.

[0034] S3. Recover the low-boiling-point, high-volatile metal chloride and the high-boiling-point, low-volatile metal chloride to complete the extraction of valuable metals from red mud;

[0035] The temperature range of the medium-low temperature chlorination reaction is 300℃~600℃, and the temperature range of the high temperature chlorination reaction is 500℃~1000℃.

[0036] Low-temperature chlorination: This refers to chlorination reactions conducted at relatively low temperatures (300℃~600℃). The main purpose is to react certain metallic elements (such as iron and silicon) in red mud with chlorine gas to form low-boiling-point, highly volatile metal chlorides. These chlorides are easily volatilized and collected during the reaction. High-temperature chlorination: This refers to chlorination reactions conducted at higher temperatures (500℃~1000℃). It is used to extract some metallic elements (such as aluminum and titanium) from red mud that are difficult to chlorinate at low temperatures (such as aluminum and titanium), generating high-boiling-point, low-volatility metal chlorides. Valuable metals: These refer to economically valuable metallic elements found in red mud, such as iron, aluminum, titanium, and sodium. These metals can be extracted and recycled through chlorination reactions.

[0037] This method employs a segmented chlorination process. First, in a low-to-medium temperature chlorination stage, some metal elements (such as iron and silicon) in the red mud react with chlorine gas at a relatively low temperature to generate low-boiling-point, highly volatile metal chlorides, such as silicon tetrachloride (SiCl4) and ferric chloride (FeCl3). Due to their low boiling points and high volatility, these chlorides rapidly volatilize during the reaction and are carried by the gas flow into the subsequent collection system. Next, in a high-temperature chlorination stage, the red mud, after the low-to-medium temperature chlorination, is further heated to an even higher temperature, causing the remaining metal elements (such as aluminum and titanium) to react with chlorine gas to generate high-boiling-point, low-volatility metal chlorides, such as aluminum trichloride (AlCl3) and titanium tetrachloride (TiCl4). These chlorides, generated at high temperatures, are recovered through condensation and other methods. This segmented chlorination method effectively separates and extracts different metal elements from red mud, achieving efficient extraction and resource utilization of valuable metals from the red mud.

[0038] The temperature range for medium- and low-temperature chlorination reactions is 300℃ to 600℃, with individual values ​​including 300℃, 350℃, 400℃, 450℃, 500℃, 550℃, and 600℃. The temperature range for high-temperature chlorination reactions is 500℃ to 1000℃, with individual values ​​including 500℃, 600℃, 700℃, 800℃, 900℃, and 1000℃.

[0039] In some embodiments, the temperature range of the low-temperature chlorination reaction is 350°C to 500°C, and the temperature range of the high-temperature chlorination reaction is 600°C to 950°C.

[0040] The specific temperature ranges for medium-low temperature chlorination and high-temperature chlorination reactions were further defined. The temperature range for medium-low temperature chlorination was refined to 350℃–500℃, and the temperature range for high-temperature chlorination was refined to 600℃–950℃. This is to more precisely control the conditions of the chlorination reactions, thereby improving their selectivity and efficiency. Within the temperature range of 350℃–500℃, the chlorination reaction of specific metal elements (such as iron and silicon) in red mud can be more effectively promoted, while avoiding increased energy consumption and side reactions caused by excessively high temperatures. Conducting high-temperature chlorination reactions within the temperature range of 600℃–950℃ allows for better extraction of other metal elements (such as aluminum and titanium) from the red mud, while ensuring the complete completion of the reaction.

[0041] The temperatures for medium- and low-temperature chlorination reactions can be: 350℃, 360℃, 370℃, 380℃, 390℃, 400℃, 410℃, 420℃, 430℃, 440℃, 450℃, 460℃, 470℃, 480℃, 490℃, 500℃, etc. The temperatures for high-temperature chlorination reactions can be: 600℃, 610℃, 620℃, 630℃, 640℃, 650℃, 660℃, 670℃, 680℃, 690℃, 700℃, 710℃, 720℃, 730℃, 740℃, 750℃, 760℃, 770℃, 780℃, 790℃, 800℃, 810℃, 820℃, 830℃, 840℃, 850℃, 860℃, 870℃, 880℃, 890℃, 900℃, 910℃, 920℃, 930℃, 940℃, 950℃, etc.

[0042] In some embodiments, the low-temperature chlorination reaction takes 1.5 to 2.5 hours, and the high-temperature chlorination reaction takes 1.5 to 2.5 hours.

[0043] Reaction time: refers to the duration of the chlorination reaction between red mud and chlorine gas under specific reaction conditions. The length of the reaction time affects the extent of the chlorination reaction and the amount of products generated.

[0044] The time range for both the low-temperature and high-temperature chlorination reactions is specified as 1.5–2.5 hours. This is to ensure that the chlorination reaction proceeds fully at each stage, while avoiding increased energy consumption and reduced equipment utilization due to excessively long reaction times. In the low-temperature chlorination stage, a reaction time of 1.5–2.5 hours ensures that low-boiling-point metal elements (such as iron and silicon) in the red mud react fully with chlorine gas to generate sufficient low-boiling-point, high-volatility metal chlorides. Similarly, in the high-temperature chlorination stage, a reaction time of 1.5–2.5 hours ensures that high-boiling-point metal elements (such as aluminum and titanium) react fully with chlorine gas to generate high-boiling-point, low-volatility metal chlorides.

[0045] The possible timeframes for medium- and low-temperature chlorination reactions are: 1.5 hours, 1.6 hours, 1.7 hours, 1.8 hours, 1.9 hours, 2.0 hours, 2.1 hours, 2.2 hours, 2.3 hours, 2.4 hours, and 2.5 hours. The possible timeframes for high-temperature chlorination reactions are: 1.5 hours, 1.6 hours, 1.7 hours, 1.8 hours, 1.9 hours, 2.0 hours, 2.1 hours, 2.2 hours, 2.3 hours, 2.4 hours, and 2.5 hours.

[0046] In some embodiments, both the first chlorine atmosphere and the second chlorine atmosphere satisfy the following conditions: flow rate of 10 ml / min to 100 ml / min and pressure of 0.1 MPa to 0.6 MPa.

[0047] Chlorine atmosphere: refers to the environmental conditions under which chlorine comes into contact with red mud during the chlorination reaction, including parameters such as chlorine flow rate and pressure. Controlling the chlorine atmosphere has a significant impact on the chlorination reaction and the formation of products.

[0048] The flow rate and pressure ranges for the first and second chlorine atmospheres are specified as follows: flow rate 10 ml / min to 100 ml / min, pressure 0.1 MPa to 0.6 MPa, respectively. This is to ensure that chlorine gas can fully contact the red mud at appropriate flow rates and pressures during the chlorination reaction, thereby improving the efficiency of the chlorination reaction and the amount of products generated. Controlling the chlorine flow rate ensures sufficient contact time and reaction rate between chlorine and red mud. Too low a flow rate may lead to insufficient chlorine supply, affecting the reaction; too high a flow rate may result in chlorine waste and uneven reaction. Controlling the chlorine pressure affects the diffusion and penetration capacity of chlorine; too high a pressure may put a pressure burden on the equipment, while too low a pressure may prevent effective chlorine penetration and reaction.

[0049] The chlorine flow rate can be: 10ml / min, 20ml / min, 30ml / min, 40ml / min, 50ml / min, 60ml / min, 70ml / min, 80ml / min, 90ml / min, 100ml / min, etc. The chlorine pressure can be: 0.1MPa, 0.2MPa, 0.3MPa, 0.4MPa, 0.5MPa, 0.6MPa, etc.

[0050] In some embodiments, both the first chlorine atmosphere and the second chlorine atmosphere satisfy the following conditions: flow rate of 20 ml / min to 80 ml / min and pressure of 0.15 MPa to 0.55 MPa.

[0051] The flow rate and pressure ranges of the first and second chlorine atmospheres were further defined, with the flow rate refined to 20 ml / min–80 ml / min and the pressure refined to 0.15 MPa–0.55 MPa. This is to more precisely control the chlorine atmosphere conditions, thereby further improving the efficiency of the chlorination reaction and the purity of the product. By controlling the chlorine flow rate at 20 ml / min–80 ml / min, the chlorine supply and reaction rate can be better balanced, avoiding chlorine waste and uneven reaction. Simultaneously, controlling the chlorine pressure at 0.15 MPa–0.55 MPa can reduce the pressure burden on the equipment and safety hazards while ensuring effective diffusion and penetration of chlorine.

[0052] The chlorine flow rate can be: 20ml / min, 25ml / min, 30ml / min, 35ml / min, 40ml / min, 45ml / min, 50ml / min, 55ml / min, 60ml / min, 65ml / min, 70ml / min, 75ml / min, 80ml / min, etc. The chlorine pressure can be: 0.15MPa, 0.20MPa, 0.25MPa, 0.30MPa, 0.35MPa, 0.40MPa, 0.45MPa, 0.50MPa, 0.55MPa, etc.

[0053] In some embodiments, the red mud is added at a rate of 10 g / min to 50 g / min.

[0054] Red mud addition rate: This refers to the rate at which red mud is added to the reaction vessel during the chlorination reaction. This parameter affects the efficiency of the reaction and the quality of the products.

[0055] The specified addition rate of red mud is 10 g / min to 50 g / min. Controlling the addition rate ensures a stable chlorination reaction. Too rapid an addition rate may lead to excessively vigorous localized reactions within the reactor, affecting reaction uniformity; conversely, too slow an addition rate will reduce reaction efficiency and increase production costs. By controlling the addition rate within the range of 10 g / min to 50 g / min, both the reaction rate and the uniformity and stability of the reaction can be guaranteed.

[0056] The addition rate of red mud can be: 10g / min, 15g / min, 20g / min, 25g / min, 30g / min, 35g / min, 40g / min, 45g / min, 50g / min, etc.

[0057] In some embodiments, the red mud is added at a rate of 15 g / min to 30 g / min.

[0058] The addition rate of red mud was further limited to 15 g / min to 30 g / min. This was to more precisely control the addition rate of red mud, thereby improving the uniformity and stability of the reaction. Within the range of 15 g / min to 30 g / min, a better balance between reaction efficiency and reaction quality can be achieved. This addition rate range ensures the uniformity of the reaction within the reactor while avoiding excessively vigorous local reactions caused by excessively rapid addition, thus improving the purity and recovery rate of the product.

[0059] The addition rate of red mud can be: 15 g / min, 16 g / min, 17 g / min, 18 g / min, 19 g / min, 20 g / min, 21 g / min, 22 g / min, 23 g / min, 24 g / min, 25 g / min, 26 g / min, 27 g / min, 28 g / min, 29 g / min, 30 g / min, etc.

[0060] In some embodiments, the low-boiling-point high-volatility metal chloride and the high-boiling-point low-volatility metal chloride are recovered by staged condensation. The staged condensation includes: first recovering the high-boiling-point low-volatility metal chloride by water-cooled condensation, and then recovering the low-boiling-point high-volatility metal chloride by low-temperature brine condensation.

[0061] Segmented condensation: This refers to the process of cooling the gaseous products generated in a reaction through condensation devices at different temperatures in stages, thereby separating and recovering products with different boiling points. This method can improve the recovery efficiency and purity of the products.

[0062] This paper specifies a method for recovering low-boiling-point, high-volatility metal chlorides and high-boiling-point, low-volatility metal chlorides through staged condensation. First, high-boiling-point, low-volatility metal chlorides are recovered via water-cooled condensation, followed by low-boiling-point, high-volatility metal chlorides recovered via low-temperature brine condensation. This staged condensation method utilizes the boiling point differences between the different metal chlorides. High-boiling-point, low-volatility metal chlorides can condense into liquid or solid states at relatively high temperatures (under water-cooling conditions), while low-boiling-point, high-volatility metal chlorides require even lower temperatures (under low-temperature brine condensation conditions) to condense. This method effectively separates and recovers metal chlorides with different boiling points, improving product purity and recovery rate.

[0063] In some embodiments, the pretreatment includes drying, grinding, sieving, and impurity removal.

[0064] Pretreatment: This refers to a series of treatment steps performed on red mud before the chlorination reaction. The purpose is to improve the physical and chemical properties of the red mud and enhance the efficiency and effectiveness of subsequent reactions. Drying: Removing moisture from the red mud through heating to achieve suitable humidity conditions for the reaction. Grinding: Breaking the red mud into finer particles to increase its specific surface area, thereby increasing the reaction rate. Sieving: Separating red mud particles by size using a sieve to remove particles that do not meet the requirements. Impurity Removal: Removing impurities from the red mud that may affect the reaction, such as iron filings and stones.

[0065] The pretreatment steps for red mud are specified, including drying, grinding, sieving, and impurity removal. These steps aim to improve the physical and chemical properties of the red mud, making it more suitable for subsequent chlorination reactions. Drying removes moisture from the red mud, preventing it from affecting the reaction process. Grinding increases the specific surface area of ​​the red mud, improving the reaction rate. Sieving removes unsuitable particles, ensuring the homogeneity of the reaction. Impurity removal removes impurities that may affect the reaction, improving the purity of the product.

[0066] In some embodiments, the drying parameters include: a temperature of 80°C to 150°C and a time of 1 to 4 hours; and / or,

[0067] The target particle size for grinding is less than 100 mesh; and / or,

[0068] The sieve aperture size of the sieve is 0.075 mm to 0.25 mm; and / or,

[0069] The impurity removal includes magnetic separation, flotation, or sedimentation washing.

[0070] Target particle size: refers to the desired size of the red mud particles after grinding, usually expressed in mesh count. The larger the mesh count, the finer the particles. Sieve aperture size: refers to the size of the sieve openings used during sieving, determining the maximum size of particles that can pass through the sieve. Magnetic separation: uses a magnetic field to separate magnetic impurities in red mud, such as iron filings. Flotation: utilizes the differences in the physicochemical properties of mineral surfaces, using air bubbles to float useful mineral particles, thus achieving separation. Sedimentation and washing: uses gravity or centrifugal force to cause solid particles suspended in a liquid to settle, thus achieving solid-liquid separation, and then washing the settled solid particles.

[0071] The specific parameters and methods for pretreatment were further defined. The drying temperature range was 80℃–150℃, and the time was 1–4 hours; the target particle size for grinding was less than 100 mesh; the sieve aperture size was 0.075 mm–0.25 mm; impurity removal methods included magnetic separation or flotation. Controlling the drying temperature and time ensures sufficient removal of moisture from the red mud while avoiding increased energy consumption due to over-drying. Grinding to a target particle size of less than 100 mesh significantly increases the specific surface area of ​​the red mud, improving the reaction rate. Controlling the sieve aperture size to 0.075 mm–0.25 mm removes larger particles that do not meet the requirements, ensuring the uniformity of the reaction. Magnetic separation and flotation are two commonly used impurity removal methods that can effectively remove magnetic and non-magnetic impurities from the red mud, improving its purity.

[0072] The drying temperature range is 80℃~150℃, with individual values ​​including: 80℃, 90℃, 100℃, 110℃, 120℃, 130℃, 140℃, and 150℃. The drying time range is 1~4 hours, with individual values ​​including: 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, and 4 hours. The sieve aperture size range is 0.075mm~0.25mm, with individual values ​​including: 0.075mm, 0.08mm, 0.09mm, 0.10mm, 0.11mm, 0.12mm, 0.13mm, 0.14mm, 0.15mm, 0.16mm, 0.17mm, 0.18mm, 0.19mm, 0.20mm, 0.21mm, 0.22mm, 0.23mm, 0.24mm, and 0.25mm.

[0073] The present application is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the application. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to industry standards. If there is no corresponding industry standard, then generally accepted international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0074] Example 1

[0075] Materials: Low-grade red mud was selected, with main components including approximately 30% iron oxide, approximately 10% aluminum oxide, and approximately 25% silicon oxide. Chlorine gas had a purity of 99% and was supplied by a local chlor-alkali plant.

[0076] Apparatus: A tubular furnace reactor with an inner diameter of 50 mm and a length of 1000 mm was used, with a red mud feed length of 600 mm. The reaction temperature was set at 400℃, heated by an electric heating mantle, with temperature fluctuations controlled within ±5℃. The chlorine gas flow rate was 30 ml / min, and the pressure was 0.3 MPa. Red mud was added via a screw feeder at a rate of 20 g / min.

[0077] Operating steps:

[0078] The pretreated red mud is added to a first chlorine atmosphere to carry out a medium-low temperature chlorination reaction, generating low-boiling-point, high-volatility metal chlorides (such as SiCl4 and FeCl3).

[0079] Red mud after low-temperature chlorination is added to a second chlorine atmosphere for high-temperature chlorination to generate high-boiling-point, low-volatility metal chlorides (such as AlCl3).

[0080] High-boiling-point, low-volatility metal chlorides are recovered by water-cooled condensation, and low-boiling-point, high-volatility metal chlorides are recovered by low-temperature brine condensation.

[0081] The exhaust gas is purified before being discharged.

[0082] Example 2

[0083] Materials: Medium-grade red mud was selected, with main components including approximately 20% alumina, approximately 35% iron oxide, and approximately 5% sodium oxide. Chlorine gas purity was 99.5%.

[0084] Apparatus: A fluidized bed reactor, 80 mm in diameter and 1200 mm in height, with a porous ceramic gas distribution plate. The reaction temperature was set at 500℃ with a temperature control accuracy of ±3℃, and gas heating was used. The chlorine gas flow rate was 40 ml / min, and the pressure was 0.4 MPa. Red mud was added via pneumatic conveying at a feeding rate of 25 g / min.

[0085] Operating steps:

[0086] The pretreated red mud is added to a first chlorine atmosphere to carry out a medium-low temperature chlorination reaction, generating low-boiling-point, high-volatility metal chlorides.

[0087] Red mud after low-temperature chlorination is added to a second chlorine atmosphere for high-temperature chlorination to generate high-boiling-point, low-volatility metal chlorides.

[0088] Metal chlorides are recovered through staged condensation.

[0089] The exhaust gas is purified before being discharged.

[0090] Example 3

[0091] Materials: High-grade red mud is selected, with main components including approximately 25% alumina, approximately 30% iron oxide, and approximately 10% titanium oxide. Chlorine gas purity is 99.8%.

[0092] Apparatus: A tubular furnace reactor with an inner diameter of 60 mm and a length of 1200 mm was used. The reaction temperature was set at 550℃ and heated by an electric heating mantle, with temperature fluctuations controlled within ±4℃. The chlorine gas flow rate was 50 ml / min, and the pressure was 0.35 MPa. Red mud was added via a screw feeder at a rate of 30 g / min.

[0093] Operating steps:

[0094] The pretreated red mud is added to a first chlorine atmosphere to carry out a medium-low temperature chlorination reaction, generating low-boiling-point, high-volatility metal chlorides.

[0095] Red mud after low-temperature chlorination is added to a second chlorine atmosphere for high-temperature chlorination to generate high-boiling-point, low-volatility metal chlorides.

[0096] Metal chlorides are recovered through staged condensation.

[0097] The exhaust gas is purified before being discharged.

[0098] Example 4

[0099] Materials: Red mud containing various metal oxides was selected, with main components including approximately 35% iron oxide, approximately 15% aluminum oxide, approximately 10% sodium oxide, and approximately 8% titanium oxide. Chlorine gas purity was 99.5%.

[0100] The apparatus consists of a fluidized bed reactor and a tubular furnace reactor connected in series. The fluidized bed reactor has a diameter of 80 mm and a height of 1200 mm; the tubular furnace has an inner diameter of 60 mm and a length of 1200 mm. The medium-low temperature chlorination reaction is set at 450℃, and the high-temperature chlorination reaction is set at 800℃, with a temperature control accuracy of ±5℃. A zoned heating method is used. The chlorine gas flow rate is 60 ml / min, and the pressure is 0.45 MPa. Red mud is added through a precision-metered screw feeder at a rate of 28 g / min.

[0101] Operating steps:

[0102] The pretreated red mud is added to a first chlorine atmosphere to carry out a medium-low temperature chlorination reaction, generating low-boiling-point, high-volatility metal chlorides.

[0103] Red mud after low-temperature chlorination is added to a second chlorine atmosphere for high-temperature chlorination to generate high-boiling-point, low-volatility metal chlorides.

[0104] Metal chlorides are recovered through staged condensation.

[0105] The exhaust gas is purified before being discharged.

[0106] Example 5

[0107] Materials: Ordinary red mud was selected, with main components including approximately 30% iron oxide, approximately 20% aluminum oxide, and approximately 20% silicon oxide. Chlorine gas purity was 99%.

[0108] Apparatus: A specially designed tubular reactor with a pressure resistance of 5 MPa and a volume of 3 L is used. The reaction temperature is set at 600℃ and controlled within ±3℃, using an external heating rod. The chlorine gas flow rate is 70 ml / min, and the pressure is 0.5 MPa. Red mud is added via a high-pressure screw feeder at a rate of 35 g / min.

[0109] Operating steps:

[0110] The pretreated red mud is added to a first chlorine atmosphere to carry out a medium-low temperature chlorination reaction, generating low-boiling-point, high-volatility metal chlorides.

[0111] Red mud after low-temperature chlorination is added to a second chlorine atmosphere for high-temperature chlorination to generate high-boiling-point, low-volatility metal chlorides.

[0112] Metal chlorides are recovered through staged condensation.

[0113] The exhaust gas is purified before being discharged.

[0114] Comparative Example 1

[0115] Materials: The same low-grade red mud as in Example 1 was selected.

[0116] Apparatus: A single tubular furnace reactor with an inner diameter of 50 mm and a length of 1000 mm was used. The reaction temperature was set at 400℃, heated by an electric heating mantle, with temperature fluctuations controlled within ±5℃. The chlorine gas flow rate was 30 ml / min, and the pressure was 0.3 MPa. Red mud was added via a screw feeder at a rate of 20 g / min.

[0117] Operating steps:

[0118] The pretreated red mud was added to a single chlorine atmosphere to carry out a chlorination reaction.

[0119] The reaction was carried out at 400°C without staged chlorination.

[0120] After the reaction, the metal chloride is recovered by condensation.

[0121] Comparative Example 2

[0122] Materials: The same medium-grade red mud as in Example 2 was selected.

[0123] Apparatus: A fluidized bed reactor, 80 mm in diameter and 1200 mm in height, with a porous ceramic gas distribution plate. The reaction temperature was set at 500℃ with a temperature control accuracy of ±3℃, and gas heating was used. The chlorine gas flow rate was 40 ml / min, and the pressure was 0.4 MPa. Red mud was added via pneumatic conveying at a feeding rate of 25 g / min.

[0124] Operating steps:

[0125] The pretreated red mud was added to a single chlorine atmosphere to carry out a chlorination reaction.

[0126] The reaction was carried out at 500°C without staged chlorination.

[0127] After the reaction, the metal chloride is recovered by condensation;

[0128] The exhaust gas is purified before being discharged.

[0129] Effect data: The effect data of Examples 1-4 and Comparative Examples 1-2 are shown in Table 1.

[0130] Experimental methods for obtaining effect data:

[0131] 1. Chlorination rate of iron oxide: The chlorination rate of iron oxide is obtained by analyzing the red mud samples before and after the reaction using X-ray fluorescence spectrometry (XRF) and calculating the ratio of the reduction in iron oxide (Fe2O3) to the initial content.

[0132] 2. Chlorination rate of alumina: The chlorination rate of alumina was obtained by analyzing the red mud samples before and after the reaction using X-ray fluorescence spectrometry (XRF) and calculating the ratio of the reduction in alumina (Al2O3) to the initial content.

[0133] 3. Chlorination rate of titanium oxide: The chlorination rate of titanium oxide was obtained by analyzing the red mud samples before and after the reaction using X-ray fluorescence spectrometry (XRF) and calculating the ratio of the reduction in titanium oxide (TiO2) to the initial content.

[0134] 4. Chlorination rate of sodium oxide: The red mud samples before and after the reaction were analyzed by X-ray fluorescence spectrometry (XRF), and the ratio of the reduction of sodium oxide (Na2O) to the initial content was calculated to obtain the chlorination rate of sodium oxide.

[0135] 5. Overall Chloride Collection Efficiency: The metal chlorides generated in the reaction are collected through a condensation system. The masses of the low-boiling-point, high-volatility metal chlorides and the high-boiling-point, low-volatility metal chlorides collected are weighed separately, and the overall collection efficiency is calculated.

[0136] 6. Chlorine emission concentration in exhaust gas: Use a gas analyzer to detect the concentration of chlorine (Cl2) in the exhaust gas to ensure that the exhaust gas emissions meet environmental protection standards.

[0137] Table 1

[0138]

[0139]

[0140] The above data table provides a clear comparison of the differences between various embodiments and comparative examples. The following conclusion can be drawn: the staged chlorination process significantly improves the extraction efficiency of valuable metals from red mud and enhances environmental benefits.

[0141] Regarding chlorination rates, the segmented chlorination process (medium-low temperature chlorination + high temperature chlorination) used in the examples significantly improved the chlorination rates of iron oxide and alumina. For example, in Example 5, the chlorination rate of iron oxide reached 88%, and the chlorination rate of alumina reached 80%, while in Comparative Example 1, the chlorination rates of iron oxide and alumina were only 60% and 40%, respectively. This indicates that the segmented chlorination process can more effectively promote the conversion of metals in red mud. Regarding chloride collection efficiency, the examples achieved extremely high collection efficiency through a segmented condensation recovery process (first water cooling to recover high-boiling-point chlorides, then brine cooling to recover low-boiling-point chlorides). The total chloride collection efficiency of Example 5 reached 95%, far exceeding the 70% of Comparative Example 1 and 75% of Comparative Example 2. This demonstrates that the segmented condensation recovery process can significantly reduce chloride loss and improve resource utilization. Regarding environmental benefits, the examples optimized the tail gas treatment process to ensure that the chlorine emission concentration in the tail gas was far below the environmental standard limit (<5 mg / m³). 3 The exhaust chlorine concentrations of Comparative Example 1 and Comparative Example 2 were higher than 10 mg / m³. 3 and 8mg / m 3 The standard was not met. This indicates that the staged chlorination process not only improves resource recovery efficiency but also significantly reduces environmental impact.

[0142] In summary, the segmented chlorination process has significant advantages in improving the extraction efficiency of valuable metals from red mud and enhancing environmental benefits, providing an effective technical means for the resource utilization and environmentally friendly treatment of red mud.

[0143] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for extracting valuable metals from red mud, comprising: The pretreated red mud is added to a first chlorine atmosphere to carry out a medium-low temperature chlorination reaction to generate low-boiling-point, high-volatility metal chlorides. The red mud after the low-temperature chlorination reaction is added to a second chlorine atmosphere to carry out a high-temperature chlorination reaction, generating high-boiling-point, low-volatility metal chlorides. The low-boiling-point, high-volatility metal chloride and the high-boiling-point, low-volatility metal chloride are recovered to complete the extraction of valuable metals from red mud. The temperature range of the medium-low temperature chlorination reaction is 300℃~600℃, and the temperature range of the high temperature chlorination reaction is 500℃~1000℃.

2. The method according to claim 1, characterized in that, The temperature range for the medium-low temperature chlorination reaction is 350℃~500℃, and the temperature range for the high temperature chlorination reaction is 600℃~950℃.

3. The method according to claim 1 or 2, characterized in that, The low-temperature chlorination reaction takes 1.5 to 2.5 hours, and the high-temperature chlorination reaction takes 1.5 to 2.5 hours.

4. The method according to claim 1, characterized in that, Both the first chlorine atmosphere and the second chlorine atmosphere meet the following requirements: flow rate of 10 ml / min to 100 ml / min and pressure of 0.1 MPa to 0.6 MPa.

5. The method according to claim 4, characterized in that, Both the first chlorine atmosphere and the second chlorine atmosphere meet the following requirements: flow rate of 20 ml / min to 80 ml / min and pressure of 0.15 MPa to 0.55 MPa.

6. The method according to claim 1, 4, or 5, characterized in that, The red mud is added at a rate of 10 g / min to 50 g / min.

7. The method according to claim 6, characterized in that, The red mud is added at a rate of 15 g / min to 30 g / min.

8. The method according to claim 1, characterized in that, The low-boiling-point, high-volatility metal chloride and the high-boiling-point, low-volatility metal chloride are recovered through staged condensation. The staged condensation includes: first recovering the high-boiling-point, low-volatility metal chloride through water-cooled condensation, and then recovering the low-boiling-point, high-volatility metal chloride through low-temperature brine condensation.

9. The method according to claim 1, characterized in that, The pretreatment includes drying, grinding, sieving, and impurity removal.

10. The method according to claim 9, characterized in that, The drying parameters include: a temperature of 80℃ to 150℃, and a time of 1 to 4 hours; and / or, The target particle size for grinding is less than 100 mesh; and / or, The sieve aperture size of the sieve is 0.075 mm to 0.25 mm; and / or, The impurity removal includes magnetic separation, flotation, or sedimentation washing.

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