Method for treating red mud

Abstract

The invention provides a novel red mud treatment method. The method comprises the steps that red mud is subjected to alkaline leaching to dissolve out component aluminum, then a slag phase is subjected to the procedures of drying, grinding, pelletizing and the like to obtain a pellet material, the pellet material is subjected to roasting treatment, then roasted slag is subjected to wet cooling, aluminum in the red mud enters a liquid phase, and iron and titanium are reserved in water-cooled slag; then the water-cooled slag is subjected to magnetic separation, and an iron-rich phase and a titanium-rich phase are obtained; the iron-rich phase is directly subjected to resource utilization; and the titanium-rich phase is further acidized, iron is dissolved into supernate, titanium is reserved in a solid phase, and a titanium-containing material is obtained. By means of the method, separation of aluminum, iron and titanium in the red mud can be well achieved, energy consumption and reagent consumption are effectively reduced, the resource recovery rate is increased, the requirement for environmental protection is met, and a new way is provided for efficient utilization of the red mud.

Description

Technical Field

[0001] The present invention relates to a method for treating solid waste, specifically to a method for disposing of red mud, and belongs to the technical field of solid waste treatment and resource utilization. Background Art

[0002] Red mud is a by-product generated during the process of extracting alumina from bauxite. It is a solid waste with strong alkalinity. Currently, we have not found an economical and efficient method for the treatment and utilization of red mud. However, red mud contains abundant iron elements, which provides a potential way for its reuse. If red mud can be used as a raw material for steel smelting, it will be a very promising solution and can consume a large amount of these waste materials. However, red mud also contains a relatively high proportion of aluminum elements, which becomes an obstacle to its direct use as a raw material for steel smelting. Currently, the addition ratio of red mud in steel smelting is usually limited to less than 2%. In order to more efficiently utilize the iron resources in red mud and achieve its high-value recovery, we must overcome the technical problem of separating iron and aluminum in red mud. At the same time, ordinary processes separate iron and aluminum, but the iron-containing phase also contains titanium, which also has a destructive and influential effect on the iron-making process. Therefore, while treating the separation of iron and aluminum in red mud, the problem of separating iron and titanium also needs to be solved.

[0003] Chinese Patent CN115261540A discloses a method for recovering iron and tailings from red mud. This method presses red mud, a solvent, and a reducing agent into pellets, and after drying, directly conducts high-temperature reduction in a rotary kiln to reduce the iron in the red mud into elemental iron, thereby achieving the separation of iron and aluminum in the red mud. However, this method has the disadvantages of high energy consumption and large consumption of reducing agents.

[0004] Chinese Patent CN112410559A discloses a method for separating and recovering aluminum and iron from high-iron red mud. This technology mixes high-iron red mud with sodium salts and calcium salts, and the mixture is calcined at 800 - 1200 °C for 0.5 - 3 h. After the obtained clinker is leached with water, about 70% of the aluminum in the red mud can be separated, achieving the separation of iron and aluminum. Although the reaction conditions of this method are relatively simple, there are still problems such as rotary kiln ring formation, large water volume, and large alkali consumption that have not been solved during the process of engineering scale-up.

[0005] Therefore, for the treatment of red mud, it is necessary to simultaneously solve the technical problems of separating iron and aluminum and separating iron and titanium, and explore a new method with low energy consumption, high efficiency, and environmental friendliness to achieve the efficient utilization of red mud resources. Summary of the Invention

[0006] In view of the problems of iron-aluminum separation and iron-titanium separation in the existing red mud disposal methods, the present invention proposes a new red mud disposal method. The red mud is subjected to processes such as alkali leaching, drying, grinding, and pelletizing to obtain pellet materials. The pellet materials are subjected to roasting treatment, and then the roasted slag is further cooled by wet method. Aluminum in the red mud enters the liquid phase, while iron and titanium remain in the water-cooled slag. Then, the water-cooled slag is subjected to magnetic separation to obtain an iron-rich phase and a titanium-rich phase. The iron-rich phase is directly used for resource utilization. The titanium-rich phase is further acidified, and iron is dissolved into the supernatant, while titanium remains in the solid phase to obtain titanium-containing materials. Through this method, not only the problems of iron-aluminum and iron-titanium separation in red mud are effectively solved, but also the energy consumption and chemical reagent consumption are significantly reduced, realizing the efficient and environmental protection utilization of red mud resources, and providing a new raw material source for the iron and steel smelting industry. By optimizing the process flow, this method significantly improves the recovery rate of red mud resources, reduces environmental pollution, and conforms to the concept of green development. Its innovation lies in the application of multi-stage separation technology, ensuring the high-purity extraction of each element and opening up a new way for the comprehensive utilization of red mud.

[0007] According to the first embodiment provided by the present invention, a method for disposing of red mud is provided.

[0008] A method for disposing of red mud, the method comprising the following steps: S1. Subject the red mud to alkali leaching, solid-liquid separation to obtain a leaching solution and a leaching residue; S2. Subject the leaching residue to drying, grinding, and pelletizing processes to obtain pellet materials; S3. Subject the pellet materials to roasting treatment to obtain flue gas and roasted slag; S4. Cool the roasted slag by water cooling, solid-liquid separation to obtain a water-cooling solution and a water-cooled slag; S5. Subject the water-cooled slag to magnetic separation to obtain a titanium-rich phase and an iron-rich phase; subject the titanium-rich phase to acidification treatment to obtain titanium-containing materials and a supernatant; S6. Subject the leaching solution and the water-cooling solution to precipitation treatment to obtain aluminum-containing materials and a clarified solution.

[0009] Preferably, in step S1, the alkali solution used in the alkali leaching process of the red mud is sodium carbonate and / or sodium hydroxide; preferably, a mixed solution of sodium carbonate and sodium hydroxide is used.

[0010] Preferably, in the mixed solution of sodium carbonate and sodium hydroxide, the mass fraction of sodium carbonate is 10-30%, and the mass fraction of sodium hydroxide is 5-15%.

[0011] Preferably, the solid-liquid separation is filtration or pressure filtration.

[0012] Preferably, in step S2, calcium carbonate is added in the grinding process.

[0013] Preferably, the addition amount of calcium carbonate is 1-10% of the mass of the leaching residue.

[0014] Preferably, step S2 is: drying the leaching residue, grinding it into powder, adding calcium carbonate and mixing, and performing a pelletizing process to obtain pelletized materials.

[0015] Preferably, the addition amount of calcium carbonate is 1-10% of the mass of the leaching residue.

[0016] Preferably, in step S2, water containing iron ions and calcium ions is added during the pelletizing process.

[0017] Preferably, the addition amount of water containing iron and calcium is 5-10% of the total mass of the pelletized materials. The iron ion concentration in the water containing iron ions and calcium ions is 100-5000 mg / L, and the calcium ion concentration is 100-5000 mg / L.

[0018] Preferably, the water containing iron ions and calcium ions is the supernatant in step S5.

[0019] Preferably, step S4 is specifically: after the calcined slag is cooled by dry cooling, it is then subjected to a water cooling process, and solid-liquid separation is performed to obtain water-cooled liquid and water-cooled slag.

[0020] Preferably, the dry cooling is to input the calcined slag into a dry cooling device, spray pulverized coal on the calcined slag; obtain hot waste gas and dry-cooled slag, and then input the dry-cooled slag into the water cooling process; the dry-cooled slag rapidly cools down in the water cooling process to obtain water-cooled slag and water-cooled liquid rich in minerals.

[0021] Preferably, the injection amount of pulverized coal is 2-10% of the mass of the calcined slag, preferably 3-5%.

[0022] Preferably, the dry cooling cools the kiln slag to 200-500 °C, preferably 300-400 °C.

[0023] Preferably, in step S5, the water-cooled slag is subjected to grinding treatment and then magnetic separation.

[0024] Preferably, the water-cooled slag is ground to a particle size of 50-200 um.

[0025] Preferably, the acidification treatment in step S5 is specifically to carry out an acidification reaction on the titanium-rich phase and the acid solution, and after acidification, solid-liquid separation is performed. The solid phase obtained is titanium-containing material, and the supernatant obtained is a solution containing iron ions and calcium ions.

[0026] Preferably, the acid solution is hydrochloric acid, nitric acid or sulfuric acid. Preferably, the acid used is sulfuric acid.

[0027] Preferably, in the acidification reaction, the pH of the reaction system is controlled to be 2-4.

[0028] Preferably, the concentration of hydrochloric acid is 10% - 20%. The concentration of nitric acid or sulfuric acid is 5% - 15%.

[0029] Preferably, the acidification treatment temperature is controlled at 50 - 80 °C.

[0030] Preferably, the iron-rich phase is transported to the sintering process.

[0031] Preferably, the leaching solution generated in step S1 is used as a coolant in the water cooling process in step S4, while recovering aluminum resources.

[0032] Preferably, the hot waste gas obtained by dry cooling in step S4 is transported to the drying process in step S2 after catalytic oxidation.

[0033] Optionally, the flue gas obtained in step S3 is transported to the drying process in step S2.

[0034] Preferably, step S6 is specifically: passing the water cooling liquid through a Venturi dust collector to obtain purified gas and suspension; transporting the suspension to a clarifying tank for precipitation to obtain aluminum-containing materials and clarified liquid.

[0035] Preferably, the clarified liquid obtained in step S6 is transported to the alkali leaching process in step S1. All or part of the purified gas is used for pulverized coal injection in the dry cooling process in step S4.

[0036] Preferably, the gas discharged from the drying process in step S2 is transported to a Venturi dust collector.

[0037] Preferably, the gas discharged from the drying process in step S2 is transported to a Venturi dust collector after passing through a waste heat boiler.

[0038] In the present invention, the humidity of the pelletizing process in step S2 is controlled at 6% - 15%, preferably 8% - 12%.

[0039] In the present invention, the particle size of the pelletized material obtained after the pelletizing process is 2 - 10 mm, preferably 3 - 8 mm.

[0040] In the present invention, the temperature of the roasting process in step S3 is controlled at 900 - 1250 °C, preferably 950 - 1200 °C, more preferably 1000 - 1100 °C.

[0041] In the present invention, the atmosphere of the roasting process is controlled as an oxidizing atmosphere, preferably with an oxygen concentration of 5% - 21%.

[0042] Preferably, the roasting process uses a rotary kiln.

[0043] Preferably, an ultrasonic generating device is provided in the rotary kiln, and the ultrasonic generating device inputs ultrasonic waves into the rotary kiln.

[0044] More preferably, the ultrasonic generating device is arranged in the temperature section of 950 - 1050 °C in the rotary kiln.

[0045] In the present invention, the water temperature in the water cooling process in step S4 is controlled at 20 - 40 °C, preferably 25 - 30 °C.

[0046] As a preference, the water flow rate in the water cooling process is controlled at 50 - 100 cubic meters per ton of roasted slag, preferably 60 - 80 cubic meters.

[0047] As a preference, the aluminum-containing material is further used for the production of aluminum products.

[0048] As a preference, the titanium-containing material is used for the production of titanium dioxide.

[0049] In the present invention, first, the red mud undergoes an alkali leaching process. Through the dissolution of aluminum in the red mud by the alkali solution, a part of the aluminum in the red mud is removed. Then, through a solid-liquid separation process, a leaching solution rich in component aluminum and a leaching residue rich in iron and titanium are obtained, realizing the first separation of aluminum in the red mud. The leaching solution rich in component aluminum is used for the subsequent water cooling of the roasted slag. Since the leaching solution of component aluminum is still alkaline, the alkaline leaching solution is used as the water cooling liquid to cool the roasted slag (while playing a washing role), further removing the aluminum in the roasted slag. At the same time, the liquid phases containing component aluminum obtained from the two processes are combined and precipitated to obtain the aluminum-containing material. Through this process, not only the recovery rate of aluminum is improved, but also the recycling of resources is realized.

[0050] In the present invention, the leaching residue rich in iron and titanium obtained after the leaching process undergoes drying, grinding, and pelletizing processes to obtain pellet materials. The pellet materials undergo a roasting treatment process to further separate aluminum, iron, and titanium in an oxidizing atmosphere, enabling the effective separation of aluminum, iron, and titanium from the microscopic phase, facilitating the subsequent material separation. The roasted pellet materials undergo a water cooling process, and the cooled roasted slag is washed with the alkaline leaching solution to further remove the residual aluminum in the roasted slag, ensuring the efficient separation of aluminum, iron, and titanium, and finally obtaining high-quality aluminum. Iron and titanium are microscopically separated after the roasting process, but neither is soluble in the alkaline solution and both exist in the water-cooled slag.

[0051] In the present invention, the water-cooled slag is further subjected to magnetic separation. Preferably, it is first ground and then undergoes a magnetic separation process. Since iron and titanium are microscopically separated, the magnetic separation process can effectively separate iron and titanium to obtain high-grade iron-rich phase and titanium-rich phase. The iron-rich phase after magnetic separation can be directly used for steel production, and the titanium-rich phase is used for the preparation of high-quality titanium dioxide or further improving the grade of titanium through an acid treatment process to obtain a high-grade titanium-containing material.

[0052] In a preferred technical solution of the present invention, through further acidification treatment, iron and calcium in the titanium-rich phase react with the acid solution and enter the solution to form iron salts and calcium salts, while titanium remains in the residue. By solid-liquid separation, a solution containing iron salts and calcium salts and a solid-phase titanium-containing material are obtained, further reducing the iron and calcium in the titanium-containing material and increasing the titanium grade in the titanium-containing material. At the same time, a solution containing iron ions and calcium ions is collected, and the solution containing iron ions and calcium ions is used in the pelletizing process, which can improve the pelletizing performance of the pellet material and is also beneficial to the separation of iron from aluminum and titanium in the roasting process of the pellet material, thereby facilitating the enrichment of iron. Through this acidification treatment, not only the titanium grade in the titanium-containing material is improved, but also the effective recovery of iron and calcium is achieved, further optimizing the resource utilization efficiency.

[0053] In a preferred technical solution of the present invention, the red mud is further soaked with a suitable alkali solution, making the aluminum in the red mud more easily soluble and increasing the aluminum leaching rate. By reducing the aluminum content in the leaching residue, it is more beneficial to the separation of aluminum from iron and titanium in the subsequent rotary kiln roasting process.

[0054] In a preferred technical solution of the present invention, calcium carbonate is added in the grinding process, or the leaching residue is mixed with calcium carbonate before or after the grinding process and then pelletized, so that the pellet material contains calcium carbonate. Calcium carbonate plays a fluxing role during roasting, promoting the separation of aluminum, iron, and titanium. At the same time, the generated carbon dioxide helps to form an oxidizing atmosphere, further enhancing the separation effect. Through this method, not only the roasting performance of the pellet material is optimized, but also the recovery rate and grade of aluminum, iron, and titanium are further improved.

[0055] In a preferred technical solution of the present invention, the roasted slag is dry-cooled with pulverized coal and then enters the water-cooling process. Utilizing the high-temperature adsorption characteristics of pulverized coal, the temperature of the roasted slag is further reduced, ensuring uniform cooling and reducing energy consumption. At the same time, using the reducing property of pulverized coal, the roasted slag is prevented from being oxidized during the cooling process, maintaining its chemical stability, further enhancing the subsequent separation effect, and ensuring efficient resource utilization. In addition, using the high-temperature condition of the roasted slag and the reducing property of pulverized coal, the iron component in the roasted slag is reduced from hematite to magnetite, further realizing the separation of iron from aluminum and titanium. At the same time, it is beneficial to the separation of iron and titanium in the subsequent magnetic separation process, increasing the iron grade in the iron-rich phase. At the same time, the iron content in the titanium-rich phase is reduced. Through this comprehensive treatment process, not only the separation efficiency of each element is improved, but also the maximum utilization of resources is achieved.

[0056] In the preferred technical solution of the present invention, the titanium-rich phase is further treated by acidification, so that iron and calcium in the titanium-rich phase dissolve in the acid solution to form iron salts and calcium salts, while titanium remains in the residue. High-purity titanium-containing materials are obtained through solid-liquid separation, further improving the grade of titanium. At the same time, the solution containing iron ions and calcium ions is collected for the subsequent pelletizing process to enhance the pelletizing performance of the pellet materials and optimize the roasting effect.

[0057] In the preferred technical solution of the present invention, the water-cooling liquid enters the precipitation process after dust removal treatment to obtain aluminum-containing materials and clarified liquid. The aluminum-containing materials can be directly used for aluminum resource utilization. The clarified liquid is alkaline and can be recycled for the alkali leaching process to improve the alkali leaching efficiency, avoid wastewater discharge, and thus realize the recycling of water resources; at the same time, alkali resources are recovered.

[0058] In the preferred technical solution of the present invention, the water-cooling liquid is treated by a Venturi dust collector, and the purified gas obtained is used as the conveying carrier of pulverized coal in the dry cooling of roasting slag. In the dry cooling process, the pulverized coal reacts with the high-temperature roasting slag to obtain hot waste gas containing a large amount of carbon monoxide. The hot waste gas is catalytically oxidized and merged with the flue gas discharged from the rotary kiln to obtain high-temperature gas for drying the leaching residue. The gas after drying the leaching residue is recycled back to the Venturi dust removal device after waste heat utilization, thus realizing the recycling of gas. Through this circulation system, not only the energy utilization efficiency is improved, but also environmental pollution is reduced, zero emission of waste gas is achieved, the overall process flow is further optimized, and the green environmental protection of the production process is ensured.

[0059] The specific technical solution of the present invention is as follows: A method for treating red mud, and the specific process flow is as follows: 1) Add red mud into an immersion pool, and add a certain amount of sodium carbonate and / or sodium hydroxide into the immersion pool to maintain the alkalinity; 2) For the red mud after immersion, perform solid-liquid separation by pressure filtration. The solid is further dried and ground, and then mixed with the supernatant containing iron ions and calcium ions obtained subsequently to form pellets; 3) Add the mixed material after pelletizing into a rotary kiln equipped with an ultrasonic device, and roast in the rotary kiln at 1000-1100°C for 30-60 minutes; 4) The kiln slag obtained after being processed by the rotary kiln is introduced into a pulverized coal cooling device to be cooled together with pulverized coal, and then further cooled by water cooling; wherein, during the pulverized coal cooling process, part of the exhaust gas is emptied for direct cooling, and the cooled gas reacts through a catalytic oxidation layer and is used together with the kiln tail exhaust gas for the drying process in step 2); water cooling uses the solution obtained in step 1) for cooling; 5) The water-cooled slag obtained through step 4) is separated by a grab bucket or filtration, and then the slag is separated by magnetic separation to obtain a rich iron phase which is returned to the sintering process for disposal, and a rich titanium phase is subjected to subsequent acidification treatment; 6) The rich titanium phase obtained in step 5) reacts with the dilute acid water obtained subsequently, and the pH of the solution is controlled to be 2-4. The solid phase obtained is a titanium-containing material, and the solution obtained is returned to step 2) for pelletizing; 7) The solution obtained after water cooling through step 4) overflows into a booster pump and is pumped into a Venturi dust collector to react efficiently with the exhaust gas used for drying and waste heat utilization in step 3); 8) Part of the reacted gas is emptied, and part is returned to step 4) for use; 9) The suspension obtained through the reaction in step 7) enters a clarifying tank, and the solid aluminum-containing material can be separated through the clarifying tank, and the liquid is returned to the immersion pool in step 1).

[0060] The principle adopted by the technical solution of the present invention: 1. Alkaline immersion for pre-separating aluminum: Since aluminum is an amphoteric metal, immersing red mud in an alkaline solution can cause partial dissolution and precipitation of aluminum in the red mud, reducing the aluminum content in the red mud. At the same time, through alkaline immersion, the red mud can be fully mixed with the alkaline solution.

[0061] 2. High-strength pelletizing of red mud: The particle size of red mud is relatively fine, generally 0.002-0.05 mm. The pellet strength obtained by using conventional pelletizing technology is relatively low, and it is easy to pulverize in the rotary kiln, increasing the risk of ring formation. The present invention uses the mixed solution of calcium ions and iron ions obtained after acidolysis of red mud calcined material for mixing and pelletizing. Through the bridging and strengthening flocculation effects of iron ions and calcium ions, the pellet strength can be improved, ensuring that the red mud pellets do not pulverize in the rotary kiln and that iron resources can be fully utilized without waste of iron resource recycling.

[0062] 3. Stable separation of iron and aluminum: Iron and aluminum in red mud mainly exist in the form of aluminous goethite. After soaking red mud with sodium hydroxide and / or sodium carbonate, a material with uniform alkaline coating is obtained. Then, iron can be converted into iron oxide and aluminum into sodium aluminate at high temperature (>1000°C). Since sodium aluminate is soluble in water, the separation of iron and aluminum can be achieved through subsequent water cooling. However, since red mud also contains silicon dioxide, which will react with sodium aluminate during the high-temperature process to form sodium aluminosilicate, calcium carbonate needs to be added to mainly convert the silicon in red mud into calcium silicate to prevent it from reacting with sodium aluminate, thereby further improving the separation rate of iron and aluminum. Aiming at the problem of melting of red mud during the high-temperature reaction process, which causes the formation of rings in the rotary kiln equipment and leads to a high failure rate. The present invention preferably adds ultrasonic waves with a frequency of 500-2000 Hz in the temperature range of 950-1050°C to prevent the molten sodium ferrate formed during the high-temperature process from sticking to the inside of the rotary kiln, thus preventing the formation of rings.

[0063] 4. Low-cost magnetization of iron in red mud: To avoid the incomplete reaction of aluminum, titanium, and alkali during the alkali roasting process of red mud, resulting in still relatively high contents of aluminum and titanium in the obtained hematite, the roasted material after roasting in the rotary kiln is cooled by spraying coal, so that the iron in the roasted clinker is reduced from hematite to magnetite, further realizing the separation of iron from aluminum and titanium components. This process does not require additional heating and uses the heat of the roasted material itself for the reaction, with relatively low costs.

[0064] 5. Thermal cycle and efficient utilization: Since red mud needs to be roasted at a temperature >1000°C, the obtained kiln slag and tail gas are both high-temperature media. Based on the characteristic that the kiln slag itself is in a loose granular state after red mud roasting, combined with the coal spraying cooling device, the temperature of the kiln slag is reduced through direct heat exchange of the waste gas, and at the same time, the waste heat of the kiln slag is fully recovered. The recovered hot waste gas still contains a large amount of carbon monoxide. After being heated by catalytic oxidation, it is mixed with the high-temperature tail gas of the rotary kiln for drying red mud, and the mixed hot gas after drying is then heat-recovered through a waste heat boiler. By concentrating the heat energy in the gas phase, the cyclic utilization and full recovery of heat energy are achieved.

[0065] 6. Iron-titanium separation from red mud: Titanium in red mud mainly exists in the rutile phase and is tightly wrapped with iron, and the Ti content is generally 2-4%. Since the iron-making process does not have the ability to consume titanium, its addition amount is limited. The present invention realizes the effective separation of iron and titanium through a magnetic separation coupled with acidification process. First, magnetic separation is carried out on the roasted and water-cooled slag of red mud to obtain a titanium-rich phase and an iron-rich phase. The Fe content in the iron-rich phase can be greater than 60%, and the Ti content can be less than 0.6%, and then it can be returned to the iron and steel sintering for consumption. For the titanium-rich phase, it contains about 40% iron and about 10% titanium. Directly discarding it causes waste of iron resources. The present invention uses an acidic solution to dissolve iron and calcium in the titanium-rich phase and returns them to the front end for strengthening pelletizing, which not only improves the iron recovery rate but also effectively improves the strength of the pellets; at the same time, the titanium grade in the obtained titanium-containing material is significantly improved.

[0066] 7. Alkali recycling: A large amount of alkali needs to be added during the roasting of red mud. Part of the alkali will react with the red mud to become sodium aluminate, and part of the alkali will decompose to provide an alkaline environment. After the reaction, ultimately, it will enter the water in the form of sodium hydroxide and react with carbon dioxide in the flue gas to form a sodium carbonate solution. The traditional method is to evaporate and crystallize the sodium carbonate solution to obtain a solid and then return it. Based on the liquid-solid separation characteristics, the present invention realizes the recycling of the solution by setting two-stage overflow and filtration, and the alkali liquor can be recycled only by one-time lifting. It avoids a large amount of energy consumption loss caused by alkali liquor crystallization.

[0067] 8. High-efficiency carbon capture from flue gas: After high-temperature reaction, a large amount of CO2 will be decomposed from sodium carbonate and calcium carbonate added during the roasting of red mud. Direct emission of CO2 will not only increase carbon emissions but also waste resources. The present invention uses an alkaline solution (water-cooling liquid) to absorb the gas after the heat recovery of the roasting tail gas through the drying process, and uses sodium hydroxide and sodium aluminate in the solution to react with CO2 to obtain sodium carbonate and aluminum hydroxide. At the same time, as CO2 is absorbed, the pH of the solution gradually changes from alkaline to neutral. During this process, aluminum hydroxide will precipitate out, thus realizing the separation of aluminum and alkali.

[0068] Compared with the prior art, the technical solution provided by the present invention has the following beneficial technical effects: 1. The present invention provides a new method for separating iron, aluminum, and titanium from high-iron red mud without wastewater treatment, and realizes the efficient separation of iron, aluminum, and titanium through processes such as alkali leaching, roasting, and acidification treatment.

[0069] 2. The present invention uses the water containing iron ions and calcium ions after acidification treatment for the pelletizing process, which not only solves the problem of wastewater treatment but also improves the pellet strength and iron recovery rate, realizing the maximum utilization of resources.

[0070] 3. Through the two-stage overflow and filtration technology, the present invention realizes the recycling of lye, significantly reducing energy consumption and costs.

[0071] 4. The present invention first subjects the calcined slag to dry cooling by injecting pulverized coal and then to a water cooling process, effectively reducing the slag temperature, reducing water resource consumption, and improving the cooling efficiency at the same time; by utilizing the high-temperature condition of the calcined slag, the gas containing carbon monoxide obtained is used for the drying process after catalytic oxidation.

[0072] 5. The designed red mud enhanced granulation and rotary kiln ultrasonic device of the present invention can effectively avoid the risk of kiln blocking during the red mud disposal process and ensure stable operation. The application of the ultrasonic device can also improve the reaction activity of red mud, further optimize the roasting effect, and ensure the high efficiency and stability of the entire process flow.

[0073] 6. The waste heat recycling and efficient utilization system developed by the present invention can recover heat energy to the greatest extent and reduce disposal costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0074] Figure 1 is the process flow diagram of a red mud disposal method of the present invention.

[0075] Figure 2 is the SEM characterization diagram of the iron-rich phase obtained in Example 9 of the present invention.

[0076] Figure 3 is the XRD characterization pattern of the titanium-containing material obtained in Example 9 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0077] The technical solutions of the present invention will be illustrated by examples below. The scope of protection claimed by the present invention includes but is not limited to the following examples. Example 1

[0078] A method for disposing red mud, characterized in that: the method comprises the following steps: S1. Subject the red mud to alkali leaching and solid-liquid separation to obtain a leaching solution and a leaching residue; the leaching solution generated in step S1 is used for the water cooling process in step S4, and at the same time, aluminum resources are recovered; S2. Subject the leaching residue to drying, grinding, and pelletizing processes to obtain pelletized materials with a particle size of 4 - 6 mm; S3. Subject the pelletized materials to roasting treatment to obtain flue gas and calcined slag; the obtained flue gas is transported to the drying process in step S2; the roasting process uses a rotary kiln; an ultrasonic generating device is provided in the rotary kiln, and the ultrasonic generating device inputs ultrasonic waves into the rotary kiln; the temperature of the roasting process is controlled at 1000 ± 50 °C; S4. Subject the calcined slag to water cooling and solid-liquid separation to obtain a water cooling solution and a water cooling residue; S5. Subject the water-cooled slag to magnetic separation to obtain a titanium-rich phase and an iron-rich phase; subject the titanium-rich phase to acidification treatment to obtain titanium-containing materials and supernatant; the acidification treatment specifically involves carrying out an acidification reaction between the titanium-rich phase and a sulfuric acid solution, followed by solid-liquid separation after acidification. The solid phase obtained is the titanium-containing material, and the supernatant obtained is a solution containing iron ions and calcium ions; during the acidification reaction, control the pH of the reaction system to be 2; the mass concentration of sulfuric acid is 10%; control the acidification treatment temperature at 70 °C; S6. Pass the water-cooling liquid through a Venturi dust collector to obtain purified gas and suspension; convey the suspension to a clarification tank for a precipitation process to obtain aluminum-containing materials and clarified liquid; convey the obtained clarified liquid to the alkali leaching process in step S1. Example 2

[0079] Repeat Example 1, except that in step S1, the alkali solution used in the alkali leaching process of red mud is a sodium carbonate solution; among them, the mass fraction of sodium carbonate is 20%. The volume ratio of the sodium carbonate solution to the mass of red mud is 3000 L / t. Example 3

[0080] Repeat Example 1, except that in step S1, the alkali solution used in the alkali leaching process of red mud is a sodium hydroxide solution; among them, the mass fraction of sodium hydroxide is 20%. The volume ratio of the sodium hydroxide solution to the mass of red mud is 2000 L / t. Example 4

[0081] Repeat Example 1, except that in step S1, the alkali solution used in the alkali leaching process of red mud is a mixed solution of sodium carbonate and sodium hydroxide. Among them, the mass fraction of sodium carbonate is 20%, and the mass fraction of sodium hydroxide is 20%. The volume ratio of the sodium carbonate solution to the mass of red mud is 2000 L / t, and the volume ratio of the sodium hydroxide solution to the mass of red mud is 1000 L / t. Example 5

[0082] Repeat Example 4, except that the solid-liquid separation is filtration. Example 6

[0083] Repeat Example 5, except that in step S2, calcium carbonate is added during the grinding process; the addition amount of calcium carbonate is 5% of the mass of the leaching residue. Example 7

[0084] Repeat Example 5, except that step S2 is: drying the leaching residue, grinding, adding calcium carbonate for mixing, and pelletizing to obtain pellet materials; the addition amount of calcium carbonate is 5% of the mass of the leaching residue. Example 8

[0085] Repeat Example 6, except that in step S2, water containing iron ions and calcium ions is added during the pelletizing process; the addition amount of the water containing iron and calcium is 8% of the total mass of the pellet materials. The water containing iron ions and calcium ions is the supernatant in step S5. Example 9

[0086] Repeat Example 8, except that step S4 is specifically as follows: After the calcined slag is cooled dry, it is then subjected to a water cooling process, and solid-liquid separation is carried out to obtain water-cooled liquid and water-cooled slag; the dry cooling is to input the calcined slag into a dry cooling device, and pulverized coal is sprayed on the calcined slag; hot waste gas and dry-cooled slag are obtained, and then the dry-cooled slag is input into the water cooling process; the dry-cooled slag rapidly cools down in the water cooling process to obtain water-cooled slag and water-cooled liquid rich in minerals; the spraying amount of the pulverized coal is 4% of the mass of the calcined slag; the dry cooling cools the kiln slag to 350 °C. The hot waste gas obtained by dry cooling is sent to the drying process in step S2 after catalytic oxidation. The particle size of the sprayed pulverized coal is 4 mm, and the spraying amount of the pulverized coal is 4% of the mass of the calcined slag. Example 10

[0087] Repeat Example 9, except that in step S5, the water-cooled slag is subjected to grinding treatment and then magnetic separation; the water-cooled slag is ground to a particle size less than 200 um. Example 11

[0088] Repeat Example 10, except that the clarified liquid obtained in step S6 is sent to the alkali leaching process in step S1; 50% by volume of the purified gas is used for the spraying of pulverized coal in the dry cooling process of step S4. The gas discharged from the drying process in step S2 is sent to a Venturi dust collector after passing through a waste heat boiler. Example 12

[0089] Repeat Example 11, except that the obtained aluminum-containing material is further used for the production of aluminum products. Example 13

[0090] Repeat Example 11, except that the obtained titanium-containing material is used for the production of titanium dioxide. Example 14

[0091] Repeat Example 11, except that the obtained iron-rich phase is sent to the sintering process. Application Example

[0092] Select red mud produced from a domestic aluminum mine for treatment. The composition of the red mud raw material is analyzed by the gravimetric method as follows:

[0093] Use the methods described in the above Examples 1-14 to treat the red mud, and analyze the composition of the obtained aluminum-containing material, iron-rich phase, and titanium-rich phase (or titanium-containing material) by the gravimetric method. The experimental results are as follows:

[0094] In the present invention, the purity of aluminum hydroxide is calculated as the mass of aluminum hydroxide in the product (aluminum-containing material) / the total mass of the aluminum-containing material × 100%.

[0095] The aluminum recovery rate is the total mass of aluminum in the aluminum hydroxide product in the aluminum-containing material / the total mass of aluminum in the consumed red mud × 100%.

[0096] The calculation method of the iron grade in the iron-rich phase is the mass of total iron in the iron-rich phase / the total mass of the iron-rich phase × 100%.

[0097] The titanium content in the iron-rich phase is calculated as the mass of titanium in the iron-rich phase / the total mass of the iron-rich phase × 100%.

[0098] The iron content in the titanium-rich phase is calculated as the mass of total iron in the titanium-rich phase / the total mass of the titanium-rich phase × 100%.

[0099] The titanium content in the titanium-rich phase is calculated as the mass of titanium in the titanium-rich phase / the total mass of the titanium-rich phase × 100%.

[0100] The calcium content in the titanium-rich phase is calculated as the mass of calcium in the titanium-rich phase / the total mass of the titanium-rich phase × 100%.

Claims

1. A method for red mud disposal, characterized in that: The method comprises the following steps: S1. Leaching red mud with alkali and separating solid from liquid to obtain leachate and leach residue; S2, drying, grinding and pelletizing the leached residue to obtain pelletized material; S3, the pelletized material is subjected to roasting treatment to obtain flue gas and roasting slag; S4, the roasted slag is water-cooled and solid-liquid separated to obtain water-cooled liquid and water-cooled slag; S5, subjecting the water-cooled slag to magnetic separation to obtain a titanium-rich phase and an iron-rich phase; subjecting the titanium-rich phase to acid treatment to obtain a titanium-containing material and a supernatant; S6. The leaching solution and the water-cooled liquid are subjected to precipitation treatment to obtain aluminum-containing material and clarified liquid.

2. The method for red mud disposal according to claim 1, characterized in that: In step S1, the alkali solution used in the alkali leaching process of red mud is sodium carbonate and / or sodium hydroxide; preferably, a mixed solution of sodium carbonate and sodium hydroxide is used; Preferably, in the mixed solution of sodium carbonate and sodium hydroxide, the mass fraction of sodium carbonate is 10-30%, and the mass fraction of sodium hydroxide is 5-15%; and / or The solid-liquid separation is filtration or filter pressing.

3. The method for red mud disposal according to claim 1 or 2, characterized in that: In step S2, calcium carbonate is added in the grinding process; preferably, the amount of calcium carbonate added is 1-10% of the mass of the leached residue; or Step S2 is: drying, grinding, adding calcium carbonate and mixing, and pelletizing the leached residue to obtain pelletized material; preferably, the amount of calcium carbonate added is 1-10% of the mass of the leached residue.

4. The method for red mud disposal according to any one of claims 1 to 3, characterized in that: In step S2, water containing iron ions and calcium ions is added to the ball-forming process; Preferably, the amount of water containing iron and calcium added is 5-10% of the total mass of the pellet material; the iron ion concentration in the water containing iron ions and calcium ions is 100-5000 mg / L, and the calcium ion concentration is 100-5000 mg / L; Preferably, the water containing iron ions and calcium ions is the supernatant in step S5.

5. The method for red mud disposal according to any one of claims 1 to 4, characterized in that: Step S4 specifically comprises: after the roasting slag is dry-cooled, it is subjected to a water-cooling process, solid-liquid separation, and water-cooled liquid and water-cooled slag are obtained; the dry cooling is to input the roasting slag into a dry cooling device, and spray coal powder on the roasting slag; hot exhaust gas and dry-cooled slag are obtained, and then the dry-cooled slag is input into a water-cooling process; the dry-cooled slag is rapidly cooled in the water-cooling process, and water-cooled slag and mineral-rich water-cooled liquid are obtained; Preferably, the amount of coal powder injected is 2-10% of the mass of the calcined slag, preferably 3-5%; and / or Dry cooling cools the kiln slag to 200~500℃, preferably 300~400℃.

6. The method for red mud disposal according to any one of claims 1 to 5, characterized in that: In step S5, the water-cooled slag is subjected to grinding treatment and then magnetic separation; preferably, the water-cooled slag is ground to a particle size of 50-200 um; and / or The acidification treatment in step S5 is specifically to carry out an acidification reaction between the titanium-rich phase and the acid solution, and to carry out solid-liquid separation after acidification, so that the obtained solid phase is a titanium-containing material, and the obtained supernatant is a solution containing iron ions and calcium ions; Preferably, the acid solution is hydrochloric acid, nitric acid or sulfuric acid, preferably sulfuric acid; during the acidification reaction, the pH of the reaction system is controlled to be 2-4; Preferably, the concentration of hydrochloric acid is 10%-20%, and the concentration of nitric acid or sulfuric acid is 5%-15%; the acidification treatment temperature is controlled at 50-80°C; and / or The iron-rich phase is transported to the sintering process.

7. The method for red mud disposal according to any one of claims 1 to 6, characterized in that: The leaching liquid produced in step S1 is used as a coolant in the water cooling process in step S4, and aluminum resources are recovered at the same time; and / or The hot exhaust gas obtained by dry cooling in step S4 is transported to the drying process in step S2 after catalytic oxidation; Optionally, the flue gas obtained in step S3 is conveyed to the drying process in step S2.

8. The method for red mud disposal according to any one of claims 1 to 7, characterized in that: Step S6 specifically comprises: passing the water-cooled liquid through a venturi dust collector to obtain purified gas and suspended liquid; transporting the suspended liquid to a clarification tank for a sedimentation process to obtain aluminum-containing material and clarified liquid; Preferably, the clarified liquid obtained in step S6 is transported to the alkali leaching process of step S1; all or part of the purified gas is used for coal powder injection in the dry cooling process of step S4.

9. The method for red mud disposal according to claim 8, characterized in that: The gas discharged from the drying process in step S2 is conveyed to the venturi dust collector; Preferably, the gas discharged from the drying process in step S2 is passed through a waste heat boiler and then transported to a venturi dust collector.

10. The method for red mud disposal according to any one of claims 1 to 9, characterized in that: The humidity of the pelletizing process in step S2 is controlled at 6%-15%, preferably 8%-12%; the particle size of the pelletized material obtained after the pelletizing process is 2-10 mm, preferably 3-8 mm; and / or The temperature of the roasting process in step S3 is controlled at 900-1250°C, preferably 950-1200°C, and more preferably 1000-1100°C; the atmosphere of the roasting process is controlled to be an oxidizing atmosphere, preferably with an oxygen concentration of 5%-21%; preferably, the roasting process adopts a rotary kiln; preferably, an ultrasonic generator is provided in the rotary kiln, and the ultrasonic generator inputs ultrasonic waves into the rotary kiln; more preferably, the ultrasonic generator is arranged in a temperature section of 950-1050°C in the rotary kiln; and / or The water temperature of the water cooling process in step S4 is controlled at 20-40° C., preferably 25-30° C. The water flow rate of the water cooling process is controlled at 50-100 cubic meters per ton of roasted slag, preferably 60-80 cubic meters; and / or The aluminum-containing material is further used in the production of aluminum products; and / or The titanium-containing material is used for the production of titanium dioxide.

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