Red mud resourceful treatment system and method based on mineral carbonization and passivation

Abstract

The invention discloses a red mud resourceful treatment system and method based on mineral carbonization and passivation, and the system comprises a red mud pretreatment unit, a mineral carbonization and passivation unit, a solid-liquid separation and desalination unit, a metal recovery pretreatment unit, a metal recovery unit and a residue material utilization unit which are communicated in sequence, the three-waste treatment and cyclic utilization unit and the process detection and automatic control unit are respectively communicated with all the units; the method comprises the following steps: (1) pretreating red mud; (2) mineral carbonization and passivation; (3) solid-liquid separation and desalination; (4) metal recovery pretreatment; (5) metal recovery; (6) performing material utilization on the residues; and (7) treating and recycling three wastes. According to the method, the alkalinity and the soluble salt content of the red mud can be remarkably reduced, the adaptability of the subsequent process is improved, the metal recovery efficiency and economical efficiency are improved, coupling of fixation of acid gas minerals such as CO2 / SO2 and reduction of the red mud is achieved, material utilization of residues is achieved, and the solid waste stockpiling pressure is remarkably relieved.

Description

Technical Field

[0001] This invention relates to the field of solid waste resource utilization and synergistic pollutant emission reduction technology, and more specifically to a red mud resource utilization system and method based on mineral carbonization and passivation. Background Technology

[0002] The Bayer process for producing alumina from bauxite generates a large amount of highly alkaline solid waste, red mud. Red mud generally exhibits the following typical characteristics: 1. Strong alkalinity and high salinity Red mud contains high levels of alkaline components such as Na2O and CaO, and its pH is often greater than 12. It is prone to producing highly alkaline leachate, which poses a long-term environmental risk to the surrounding soil and water bodies.

[0003] 2. Enriched with various valuable metals Typical red mud contains 20-45% Fe2O3, 10-25% Al2O3, 3-8% TiO2, and a certain amount of rare and dispersed elements such as Sc and V. From the perspective of resource attributes, red mud has the characteristics of "low-grade polymetallic ore".

[0004] 3. Large stockpile and heavy historical burden With the continuous growth of alumina production capacity, the amount of red mud stockpiles is increasing year by year. This results in long-term land occupation, high construction and maintenance costs for stockpiles, and environmental and safety hazards such as dam safety, rainstorm erosion, and dust diffusion.

[0005] 4. Existing utilization methods are limited and scattered. Currently, the main uses of red mud include: as an admixture in cement and building materials; and for recovering metals such as iron and aluminum through partial roasting or acid leaching.

[0006] Some literature proposes using red mud for carbon dioxide mineral carbonization and passivation, but existing technologies have the following shortcomings: 1. Single-point utilization, lack of systemic collaboration Existing technologies are mostly aimed at a single objective, either emphasizing metal recovery, building material utilization, or CO2 fixation. They have not yet formed a systematic process chain that takes red mud as the core object and takes into account "alkalinity passivation - metal recovery - residue materialization - carbon sequestration".

[0007] 2. The problems of alkalinity and soluble salts have not been fundamentally resolved. Direct acid leaching or building material processing without sufficient dealkali and desalination often leads to high acid consumption, unstable metal leaching behavior, product performance fluctuations, and leachate risks.

[0008] 3. The advantages of red mud in mineral carbonization were not fully utilized. Red mud is rich in alkaline minerals such as CaO and NaOH, which have the potential to react with SO2 and CO2 to form carbonates. However, existing research on mineral carbonization is mostly limited to laboratory or unit process levels, and has not been clearly integrated into the entire process of red mud resource utilization. There is a lack of an overall approach that considers "carbonization and passivation" as a pretreatment step for subsequent metal recovery and materialization.

[0009] Currently, although some studies have proposed that red mud can be used for mineralization and CO2 fixation, these studies are generally limited to unit processes or laboratory levels and have not yet formed a systematic solution for red mud multi-metal recovery, residue building materials, and synergistic treatment of industrial waste gas.

[0010] Therefore, it is necessary to propose a systematic resource-based treatment system and method for red mud, a typical solid waste object, which takes mineral carbonization and passivation as the core entry point and connects metal recovery and residue material utilization in series, in order to solve the above problems. Summary of the Invention

[0011] In view of this, the purpose of the present invention is to provide a resource-based treatment system and method that utilizes acidic gas to perform mineral carbonization and passivation on red mud, and links it with the deep recovery of metals such as iron, aluminum, and titanium and the material utilization of residues, so as to recover iron resources in red mud and realize the material utilization of residues, thereby overcoming the shortcomings of the prior art.

[0012] To achieve the above objectives, the present invention adopts the following technical solution: A red mud resource utilization system based on mineral carbonization and passivation includes a red mud pretreatment unit, a mineral carbonization and passivation unit, a solid-liquid separation and desalination unit, a metal recovery pretreatment unit, a metal recovery unit, and a residue material utilization unit connected in sequence, as well as a waste treatment and recycling unit and a process detection and automatic control unit connected to each of the above units respectively. The red mud pretreatment unit is used to pre-dehydrate, control particle size and / or adjust moisture content of red mud to obtain pretreated red mud material; The mineral carbonization and passivation unit is used to perform mineral carbonization and passivation reactions on pretreated red mud materials in the presence of acidic gases or media. By controlling the gas partial pressure, inlet rate, and alkalinity of the reaction slurry during the reaction process, the mineral carbonization reaction is kept in a dynamic equilibrium range of "carbonization-dissolution-redeposition". The alkaline components in the pretreated red mud materials are converted into carbonate and / or sulfate minerals, and the pH value of the system is reduced from greater than 12 before the reaction to 8-11. In some embodiments, the pH at the end of the reaction can be controlled at 8-10.5. In specific embodiments, the pH is controlled at about 8-10 to achieve alkalinity reduction and carbonate formation. The dynamic equilibrium range is determined and regulated by online or offline monitoring of the slurry pH change rate, conductivity change trend, CO2 consumption rate, or tail gas CO2 concentration. The dynamic equilibrium range is not a thermodynamic equilibrium state, but refers to the operating range in which the mineral carbonization reaction is kept stable during continuous operation under engineering operating conditions through the coordinated monitoring and regulation of the above parameters. The solid-liquid separation and desalination unit is used to separate the solid and liquid components of the material after mineral carbonization and passivation. By controlling the solid-liquid ratio, the amount of washing liquid and the conductivity threshold, soluble salts are selectively migrated from the red mud matrix to the liquid phase, and the liquid phase containing soluble salts is separated to obtain the dealkalized red mud solid product. The metal recovery pretreatment unit is used to pretreat the dealkalized red mud solids to obtain metal recovery pretreated materials; The metal recycling unit is used to perform metal recycling operations on pre-treated metal materials to recover iron, aluminum and / or titanium, and obtain metal products and metal recycling residues. The residue material utilization unit is used to stabilize and / or solidify metal recycling residues to realize the resource utilization of the residues; The waste treatment and recycling unit is used to treat waste gas, wastewater and dust generated during system operation, so as to achieve partial recycling of water and solids and exhaust gas emissions that meet standards. The process monitoring and automatic control unit is used to monitor the pH, temperature, pressure, and flow rate in the mineral carbonization and passivation unit and the metal recovery unit. Based on the monitoring results, it adjusts the amount of acidic gas or waste gas introduced, the amount of red mud feedstock added, and the reaction time, and displays the conductivity / Na + As a desalination control indicator, it is used to adjust the washing liquid volume, washing frequency, or endpoint conditions of the solid-liquid separation and desalination unit; the acidic gas or medium is a gas or fluid medium that can provide acidic components to the reaction system and react with the alkaline components in the red mud through neutralization, carbonation, and / or other mineralization reactions, wherein the acidic components include at least CO2, and optionally further include SO2, HCl, or other acidic components.

[0013] The technical problems solved by this invention include: 1. Utilize acidic industrial waste gas to perform mineral carbonization and passivation on red mud, thereby significantly reducing alkalinity and achieving mineral immobilization of acidic gases; 2. Effectively link the mineral carbonization and passivation steps with subsequent iron, aluminum, titanium and other metal recovery processes to reduce acid consumption or reduction energy consumption, and improve metal recovery efficiency and product quality; 3. After metal recovery, the residual inert mineral skeleton is utilized as a material to reduce the generation of secondary solid waste and achieve near-zero waste of red mud; 4. A continuous or semi-continuous engineered system was constructed to enable the above processes to operate controllably and stably at the industrial scale, and to facilitate integration with existing aluminum industry, metallurgy or building materials systems, and to enable the system structure to operate in synergy with emission sources.

[0014] Furthermore, the aforementioned mineral carbide passivation unit includes at least one of a stirred tank reactor, a bubble column reactor, a fluidized bed reactor, and a slurry bubble column. Specifically, the inlet of the mineral carbide passivation unit is connected to the flue gas duct of the industrial emission source via a pretreatment device. The pretreatment device is used to remove dust and cool the industrial flue gas, and to feed the pretreated flue gas as an acidic gas into the mineral carbide passivation unit.

[0015] The further beneficial effect of adopting the above-mentioned method lies in the synergistic effect: after the minerals are carbonized and passivated, the reduced alkalinity and altered mineral structure make iron, aluminum, and titanium more readily leached. Simultaneously, the carbonized and passivated red mud can be used as building materials, fillers, road base materials, or carbon sink materials.

[0016] Furthermore, the aforementioned metal recycling pretreatment unit includes at least one of a rotary kiln, a vertical roasting furnace, a belt roasting furnace, a crusher, and a ball mill.

[0017] Furthermore, the aforementioned metal recovery unit includes at least one of a reduction roasting device, a magnetic separation device, a wet leaching device, an extraction device, and a precipitation / crystallization device.

[0018] The further beneficial effects of the above-mentioned method are that the reduction roasting device is used to reduce and magnetize the dealkalized red mud solids, the magnetic separation device is used to magnetically separate the roasted products to obtain iron concentrate, and the wet leaching device, extraction device and precipitation / crystallization device are used to recover aluminum and / or titanium products.

[0019] A method for resource recovery of red mud based on mineral carbonization and passivation, employing the aforementioned system, specifically includes the following steps: (1) Red mud pretreatment Red mud raw material containing alkaline components is fed into the red mud pretreatment unit for pre-dehydration, particle size control and / or moisture content adjustment to obtain red mud pretreated material; (2) Mineral carbonization and passivation The pretreated red mud material is fed into a mineral carbonization and passivation unit, where acidic gas or medium is introduced to carry out the mineral carbonization and passivation reaction. By controlling the gas partial pressure, the rate of gas introduction, and the alkalinity of the reaction slurry during the reaction process, the mineral carbonization reaction is kept in a dynamic equilibrium range of "carbonization-dissolution-redeposition". The alkaline components in the pretreated red mud material react with the acidic gas to generate carbonate and / or sulfate minerals, and the pH value of the system is reduced from greater than 12 before the reaction to 8-11. In some embodiments, the final pH of the reaction can be controlled at 8-10.5; in specific embodiments, the pH is controlled at approximately 8-10. (3) Solid-liquid separation and desalination The material after mineral carbonization and passivation is sent to the solid-liquid separation and desalination unit for solid-liquid separation. By controlling the solid-liquid ratio, washing liquid volume and conductivity threshold, soluble salts are selectively migrated from the red mud matrix to the liquid phase. The liquid phase containing soluble salts is separated and returned to the process system or discharged after neutralization, sedimentation and / or membrane treatment. The solid phase is used as the dealkali red mud solid product. (4) Metal recycling pretreatment The solid products of dealkalized red mud are sent to a metal recovery pretreatment unit for pretreatment to obtain metal recovery pretreated material. (5) Metal recycling The pre-treated metal recycling material is fed into the metal recycling unit for metal recycling operations to recover iron, aluminum and / or titanium, and obtain metal products and metal recycling residue. (6) Utilization of residue materials Metal recycling residues are sent to a residue material utilization unit for stabilization and / or solidification treatment, and then used as raw materials for building material admixtures, mineral admixtures in concrete or mortar, road subgrade materials or other material products, thereby realizing the resource utilization of residues. (7) Treatment and recycling of waste The waste gas, wastewater and dust generated during the above process are collected and treated to form an internal water circulation and exhaust gas emission standard compliance system; residual dust in the waste gas is captured and recovered by a dust removal device, and wastewater is reused or discharged after sedimentation, neutralization and necessary deep treatment, forming a closed-loop system of "waste gas dust removal / emission reduction, wastewater sedimentation, reuse and dust recovery".

[0020] Furthermore, in step (1) above, the red mud raw material is red mud produced by the Bayer process of alumina production, and / or red mud produced by the sintering process of alumina production; the alkaline components include NaOH and CaO; pre-dehydration includes mechanical dehydration, natural air drying and / or low-temperature drying; particle size control includes crushing, sieving and mixing homogenization.

[0021] Furthermore, in step (2) above, the acidic gas originates from industrial waste gas from cement kilns, steel mills, coal-fired power plants, waste incineration plants, or chemical plants; the acidic gas or medium is a gas or fluid medium capable of providing acidic components to the reaction system and undergoing neutralization, carbonation, and / or other mineralization reactions with the alkaline components in the red mud; the acidic components include at least CO2, and optionally further include SO2, HCl, or other acidic components; the reaction temperature of the mineral carbonization and passivation reaction is 20–120°C, the reaction pressure is atmospheric pressure to 2.0 MPa, the reaction time is 10–240 min, and the reaction endpoint is controlled by online pH monitoring to stabilize the pH value of the system at 8–11, preferably 8–10.5, and more preferably 8–10.

[0022] The further beneficial effect of the above-mentioned method is that carbon fixation is mainly achieved by the formation of stable carbonates from Ca groups, while Na salts and carbonates are carried away and recovered / treated through the desalination liquid phase.

[0023] Furthermore, in step (3) above, solid-liquid separation includes at least one of pressure filtration, vacuum filtration, centrifugal separation and sedimentation clarification.

[0024] The further beneficial effect of the above-mentioned method is that this step can further reduce soluble sodium salts and other components in the red mud. The slurry undergoes solid-liquid separation; the liquid phase carries away some soluble salts, while the solid phase, as dealkalized red mud, enters subsequent processes.

[0025] Furthermore, in step (4) above, the pretreatment includes at least one of calcination, reduction magnetization and / or grinding.

[0026] The further beneficial effect of adopting the above-mentioned method is that by adjusting the mineral phase composition, particle size distribution and pore structure of red mud, a precursor material that is conducive to the recovery of metals such as iron, aluminum and titanium is formed, and a metal recovery pretreatment material is obtained.

[0027] Furthermore, in step (5) above, the metal recovery operation includes at least one of reduction magnetic separation, leaching, extraction, precipitation or crystallization, as well as selective leaching, solvent extraction and / or chlorination volatilization.

[0028] The further beneficial effects of the above-mentioned methods are that iron in red mud can be recovered by reducing magnetization roasting combined with magnetic separation to obtain iron concentrate; aluminum in red mud can be recovered by leaching (acid leaching), extraction and precipitation or crystallization to obtain aluminum hydroxide or aluminum oxide; and titanium and other valuable metals in red mud can be recovered by selective leaching, solvent extraction and / or chlorination volatilization.

[0029] As can be seen from the above technical solution, compared with the prior art, the beneficial effects of the present invention are as follows: 1. A systematic process chain with mineral carbonization and passivation as the core was constructed. The system achieves a synergistic integration of industrial waste gas treatment, red mud passivation, multi-metal recovery, and building material utilization, forming a comprehensive and integrated resource-based pollution control system. This invention does not merely use red mud for single metal recovery or building material utilization, but proposes a continuous process route of "red mud - mineral carbonization and passivation - metal recovery - residue material utilization," organically combining CO2 fixation, red mud passivation, and deep metal recovery, demonstrating integrity and synergy.

[0030] 2. Significantly reduces the alkalinity and soluble salt content of red mud, improving compatibility with subsequent processes. Through mineral carbonization and solid-liquid separation steps, the pH of the red mud system can be reduced from greater than 12 to the range of 8-11. Soluble sodium salts are removed through the liquid phase, which reduces acid consumption in the subsequent acid leaching process and weakens the potential environmental impact of the leachate.

[0031] 3. Improve the efficiency and economics of metal recycling. After carbonization and passivation, the mineral phases of red mud are more suitable for reduction magnetization or leaching. Metal components such as iron, aluminum, and titanium are more easily selectively enriched and separated, thereby improving the metal recovery rate. At the same time, due to the reduction in the ionic strength and alkalinity of the system, the consumption of acid, reducing agent, and post-treatment load are reduced, thus improving the overall economic efficiency of the process.

[0032] 4. Achieving coupling between the fixation of acidic gases such as CO2 / SO2 and the reduction of red mud volume. This invention utilizes alkaline minerals in red mud as mineral carbonization carriers for CO2, realizing the conversion of carbon dioxide from gaseous to solid carbonates, increasing the carbon sequestration function of the system, and providing a new engineering path for carbon emission reduction.

[0033] 5. The residue is utilized as a material, significantly alleviating the pressure of solid waste stockpiling. After metal recycling, the residual inert skeleton material can be used as a building material admixture or road material, achieving near-zero waste of red mud from source to end-use, reducing the land occupation of red mud dumps and the need for long-term management.

[0034] 6. This invention focuses on iron resource recovery while also considering the synergistic separation and enrichment of valuable metals such as aluminum and titanium, thereby transforming red mud from hazardous waste into resource-based mineral materials. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of a red mud resource recovery system based on mineral carbonization and passivation. Figure 2 This is a process flow diagram of a red mud resource utilization method based on mineral carbonization and passivation. Detailed Implementation

[0036] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] Example 1 Red mud resource utilization system based on mineral carbonization and passivation, such as Figure 1 As shown, it includes a red mud pretreatment unit, a mineral carbonization and passivation unit, a solid-liquid separation and desalination unit, a metal recovery pretreatment unit, a metal recovery unit, and a residue material utilization unit connected in sequence, as well as a waste treatment and recycling unit and a process detection and automatic control unit connected to each of the above units respectively. The red mud pretreatment unit is used to pre-dehydrate, control particle size and / or adjust moisture content of red mud to obtain pretreated red mud material; The mineral carbonization and passivation unit is used to carry out mineral carbonization and passivation reactions on red mud pretreated materials in the presence of acidic gases or media. By controlling the gas partial pressure, inlet rate, and alkalinity of the reaction slurry during the reaction process, the mineral carbonization reaction is kept in a dynamic equilibrium range of "carbonization-dissolution-redeposition". The alkaline components in the red mud pretreated materials are converted into carbonate and / or sulfate minerals, and the pH value of the system is reduced from greater than 12 before the reaction to 8, achieving alkalinity reduction and carbonate formation. The dynamic equilibrium range is determined and controlled by online or offline monitoring of the slurry pH change rate, conductivity change trend, CO2 consumption rate, or tail gas CO2 concentration. The dynamic equilibrium range is not a thermodynamic equilibrium state, but refers to the operating range in which the mineral carbonization reaction is kept stable during continuous operation under engineering operating conditions through the coordinated monitoring and control of the above parameters. The solid-liquid separation and desalination unit is used to separate the solid and liquid components of the material after mineral carbonization and passivation. By controlling the solid-liquid ratio, the amount of washing liquid and the conductivity threshold, soluble salts are selectively migrated from the red mud matrix to the liquid phase, and the liquid phase containing soluble salts is separated to obtain the dealkalized red mud solid product. The metal recovery pretreatment unit is used to pretreat the dealkalized red mud solids to obtain metal recovery pretreated materials; The metal recycling unit is used to perform metal recycling operations on pre-treated metal materials to recover iron, aluminum and / or titanium, and obtain metal products and metal recycling residues. The residue material utilization unit is used to stabilize and / or solidify metal recycling residues to realize the resource utilization of the residues; The waste treatment and recycling unit is used to treat waste gas, wastewater and dust generated during system operation, so as to achieve partial recycling of water and solids and exhaust gas emissions that meet standards. The process monitoring and automatic control unit is used to monitor the pH, temperature, pressure, and flow rate in the mineral carbonization and passivation unit and the metal recovery unit. Based on the monitoring results, it adjusts the amount of acidic gas or waste gas introduced, the amount of red mud feedstock added, and the reaction time, and displays the conductivity / Na + As a desalination control indicator, it is used to adjust the washing liquid volume, washing frequency, or endpoint conditions of the solid-liquid separation and desalination unit; the acidic gas or medium is a gas or fluid medium that can provide acidic components to the reaction system and react with the alkaline components in the red mud through neutralization, carbonation, and / or other mineralization reactions, wherein the acidic components include at least CO2, and optionally further include SO2, HCl, or other acidic components.

[0038] Example 2 Red mud resource recovery methods based on mineral carbonization and passivation (red mud resource recovery process based on mineral carbonization and passivation-iron recovery-residue building material conversion), such as Figure 2 As shown, the system of Example 1 is used, specifically including the following steps: (1) Red mud pretreatment The wet red mud generated during the Bayer process of alumina production is fed into the red mud pretreatment unit as raw material. The red mud is mechanically dehydrated to a moisture content of 40%, and then crushed and homogenized by a pulverizer so that the portion of the material with a particle size ≤5 mm accounts for 80% of the total mass of the raw material, thus obtaining the red mud pretreated material. (2) Mineral carbonization and passivation The pretreated red mud material was fed into a stirred mineral carbonization reactor. A gas containing 50% (volume fraction) CO2 and 50% (volume fraction) SO2 was introduced into the bottom of the reactor (this gas can also be a simulated enriched acidic gas used to verify the mineral passivation capability under extreme conditions; the gas ratio is only used to verify the adaptability of mineral carbonization passivation under high acid load conditions and does not constitute a limitation on the actual industrial gas composition). The reactor was then subjected to a gas-solid or slurry contact reaction at 70°C. The gas partial pressure, introduction rate, and alkalinity of the reaction slurry were compared with the solid-liquid ratio of the red mud slurry at a ratio of 1:1 (mass ratio). The reaction time was 120 min, the reactor pressure was atmospheric pressure, and continuous stirring was maintained within the reactor to keep the mineral carbonization reaction in a dynamic equilibrium range of "carbonization-dissolution-redeposition." The mineral carbonization passivation reaction caused alkaline components such as NaOH and CaO in the red mud to react with CO2 and SO2 to generate carbonates and sulfates. The reaction endpoint was controlled based on online pH monitoring results, reducing the system pH from greater than 12 before the reaction to 10. (3) Solid-liquid separation and desalination After carbonization, the slurry is sent to a solid-liquid separation device (plate and frame filter press) for solid-liquid separation, separating the filtrate and filter residue; the soluble sodium salt contained in the filtrate is partially reused for system makeup water after pH adjustment and sedimentation treatment; the filter residue is used as a solid product of dealkalized red mud for subsequent metal recovery. (4) Metal (iron) recycling pretreatment The solid product of dealkali-treated red mud was subjected to reduction and magnetization roasting in a rotary kiln. The roasting conditions were controlled as follows: temperature 1000℃, atmosphere was a mixed atmosphere containing reducing gases (CO, H2, natural gas), roasting time 90 min. After roasting, the iron oxide was converted into a magnetic phase, and metal recovery pretreated material was obtained. (5) Metal recycling (magnetic separation for iron recovery) After cooling and crushing the pre-treated metal recycling material, magnetic separation is performed to obtain magnetic iron concentrate and non-magnetic tailings. The magnetic iron concentrate is sold as an iron resource product or further smelted and utilized. (6) Utilization of residue materials Non-magnetic tailings are ground and used as mineral admixtures for cement, concrete, mortar or road base materials, and mixed with cementitious materials to formulate building material products. (7) Treatment and recycling of waste The waste gas, wastewater and dust generated during the above process are collected and treated to form an internal water circulation and exhaust gas emission standard compliance system; residual dust in the waste gas is captured and recovered by a dust removal device, and wastewater is reused or discharged after sedimentation, neutralization and necessary deep treatment, forming a closed-loop system of "waste gas dust removal / emission reduction, wastewater sedimentation, reuse and dust recovery".

[0039] This embodiment significantly reduces the alkalinity of red mud and forms a stable carbonate structure through a mineral carbonization step, making the subsequent reduction magnetization roasting and magnetic separation processes more stable. At the same time, it reduces the soluble salt content in the system, which is beneficial for the subsequent utilization of residue materials.

[0040] Example 3 Red mud resource recovery methods based on mineral carbonization and passivation (mineral carbonization and passivation - desalination treatment - wet aluminum recovery process), such as Figure 2 As shown, the system of Example 1 is used, specifically including the following steps: (1) Red mud pretreatment After the dry-discharged red mud is crushed, it is ball-milled to make the D90 particle size ≤75 μm, and then mixed with water to make a slurry with the solid-liquid ratio controlled at 1:4 to obtain the red mud pretreated material. (2) Mineral carbonization and passivation The above slurry was fed into a carbonization reactor, and a gas containing 50% CO2 was introduced. The reaction was carried out at 50°C for 90 min, while maintaining uniform stirring. The pH of the slurry at the reaction endpoint was controlled to be 9, and the oxidation-reduction conditions were close to a neutral system. (3) Solid-liquid separation and desalination Separation is achieved by pressure filtration. The filtrate carries away soluble sodium salts from the system, and the filter residue serves as dealkalized red mud for subsequent leaching. In this step, the conductivity and sodium content of the filtrate are monitored.+ Concentration changes are used as the basis for determining the desalination endpoint to ensure that the red mud solids entering the subsequent metal recovery steps have stable low-salt characteristics. (4) Metal (aluminum) recycling pretreatment The dealkalized red mud was leached with hydrochloric acid solution to allow aluminum to dissolve into the solution phase. The temperature was controlled at 70℃ and the leaching time was 120 min to obtain an aluminum-enriched leachate. (5) Metal recycling (hydrometallurgical aluminum recycling) Alumina products are obtained through neutralization precipitation and seed crystal precipitation; (6) Utilization of residue materials After leaching, the solid residue is washed, dehydrated and ground, and then used as an admixture for cementitious materials. (7) Treatment and recycling of waste The waste gas, wastewater and dust generated during the above process are collected and treated to form an internal water circulation and exhaust gas emission standard compliance system; residual dust in the waste gas is captured and recovered by a dust removal device, and wastewater is reused or discharged after sedimentation, neutralization and necessary deep treatment, forming a closed-loop system of "waste gas dust removal / emission reduction, wastewater sedimentation, reuse and dust recovery".

[0041] This embodiment employs carbonization and passivation pretreatment combined with desalination, which significantly reduces acid consumption, improves leaching selectivity, reduces interference from impurity ions on aluminum, and makes the residue more stable and conducive to materialization.

[0042] Example 4 Red mud resource utilization methods based on mineral carbonization and passivation (based on mineral carbonization and passivation-iron-aluminum co-recovery-closed-loop system for three wastes), such as Figure 2 As shown, the system of Example 1 is used, specifically including the following steps: (1) Red mud pretreatment The wet red mud generated during the Bayer process of alumina production is fed into the red mud pretreatment unit as raw material. The red mud is mechanically dehydrated to a moisture content of 40%, and then crushed and homogenized by a pulverizer so that the portion of the material with a particle size ≤5 mm accounts for 80% of the total mass of the raw material, thus obtaining the red mud pretreated material. (2) Mineral carbonization and passivation The pretreated red mud material was fed into a stirred mineral carbonization reactor. A gas containing 50% (volume fraction) CO2 was introduced into the bottom of the reactor, allowing for a gas-solid or slurry contact reaction at 70°C. The reaction process was controlled by adjusting the gas partial pressure, the introduction rate, and the alkalinity of the reaction slurry. The solid-liquid ratio of the red mud slurry was maintained at 1:1 (mass ratio). The reaction time was 120 min, the reactor pressure was atmospheric pressure, and continuous stirring was maintained within the reactor to ensure the mineral carbonization reaction remained in a dynamic equilibrium range of "carbonization-dissolution-redeposition." The mineral carbonization passivation reaction caused alkaline components such as NaOH and CaO in the red mud to react with CO2 to form carbonates. In the presence of SO2, further sulfates or other acidic components were reacted and passivated, achieving multi-ion mineralization and fixation. The reaction endpoint was controlled based on online pH monitoring results, reducing the system pH from greater than 12 before the reaction to 8. (3) Solid-liquid separation and desalination After the carbonization reaction is completed, the slurry is filtered or centrifuged to separate the solid and liquid, and the filtrate and filter residue are obtained. The filtrate is returned to the system as process water after adjustment, neutralization and sedimentation. The filter residue is used as the solid product of dealkali red mud and enters step (4) for iron-aluminum co-recycling and residue material utilization. (4) Metal recycling and residue material utilization After carbonization and dealkalization, the red mud is first subjected to reduction, magnetization, roasting and magnetic separation to obtain iron concentrate and non-magnetic tailings. The non-magnetic tailings are then fed into the wet aluminum leaching section. The leaching solution is used to prepare aluminum products, and the leaching residue is used as building material aggregate. (5) Treatment and recycling of waste The waste gas, wastewater and dust generated during the above process are collected and treated to form an internal water circulation and exhaust gas emission standard compliance system; residual dust in the waste gas is captured and recovered by a dust removal device, and wastewater is reused or discharged after sedimentation, neutralization and necessary deep treatment, forming a closed-loop system of "waste gas dust removal / emission reduction, wastewater sedimentation, reuse and dust recovery".

[0043] This embodiment forms a complete integrated circular chain that includes CO2 carbon fixation, desulfurization, alkali reduction and desalination, iron and aluminum recycling, residue material utilization, and closed-loop management of waste.

[0044] Example 5 Red mud resource recovery methods based on mineral carbonization and passivation (red mud resource recovery process based on mineral carbonization-titanium enrichment-titanium recovery-comprehensive utilization of residues), such as Figure 2 As shown, the system of Example 1 is used, specifically including the following steps: (1) Red mud pretreatment The wet red mud generated during the Bayer process of alumina production is fed into the red mud pretreatment unit as raw material. The red mud is mechanically dehydrated to reduce its moisture content to 35%. Then, the dehydrated red mud is crushed and homogenized using a pulverizer to ensure that the portion with a particle size ≤4mm accounts for 75% of the total mass of the raw material, and finally the red mud pretreated material is obtained. (2) Mineral carbonization The pretreated red mud material was transported to a stirred mineral carbonization reactor. A gas containing 60% (volume fraction) CO2 and 40% (volume fraction) SO2 was introduced into the bottom of the reactor (this gas could also be a simulated enriched acidic gas used to verify the mineral passivation ability under extreme conditions). The gas and material underwent a gas-solid or slurry contact reaction at 65°C. By controlling the gas partial pressure, the introduction rate, and the alkalinity of the reaction slurry, the solid-liquid ratio of the red mud slurry was set to 1:1.2 (mass ratio). The reaction time lasted 150 minutes, the pressure inside the reactor was maintained at atmospheric pressure, and continuous stirring was maintained inside the reactor to keep the mineral carbonization reaction in a dynamic equilibrium range of "carbonization-dissolution-redeposition." Through the mineral carbonization reaction, alkaline components such as NaOH and CaO in the red mud reacted with CO2 and SO2 to generate carbonates, sulfates, and other substances. The reaction endpoint was precisely controlled based on online pH monitoring results, reducing the system pH from greater than 12 before the reaction to 8. (3) Solid-liquid separation and preliminary purification After the carbonization reaction is completed, the slurry is sent to a solid-liquid separation device (plate and frame filter press) for solid-liquid separation, thereby separating the filtrate and the filter residue. The soluble sodium salt contained in the filtrate is first treated by adjusting the pH value and sedimentation, and then part of it is recycled for the system water replenishment process. The filter residue is used as the solid product of the carbonized red mud for subsequent titanium enrichment treatment. (4) Metal recycling pretreatment (titanium enrichment pretreatment) The carbonized red mud solid product was placed in a rotary kiln for roasting pretreatment. The roasting conditions were controlled as follows: the temperature was set at 850℃, the atmosphere was a mixed atmosphere containing reducing gases (CO, H2, natural gas), and the roasting time was 120 min. During this process, the titanium element in the red mud reacted with other substances and was transformed into a phase that was easier to extract in the subsequent process, thus obtaining titanium-enriched pretreated material. (5) Metal recovery (wet leaching-extraction separation of titanium) Wet leaching: After cooling the titanium-enriched pretreated material, add hydrochloric acid solution to carry out the leaching reaction. Control the reaction temperature at 70℃ and the reaction time at 180min to allow titanium elements to enter the solution in ionic form, thus obtaining titanium-containing leachate. Extraction and separation: The titanium-containing leachate is extracted using an extractant. Through multi-stage extraction and back-extraction processes, titanium elements are separated from the solution to obtain a titanium-rich solution. The titanium-rich solution is then subjected to precipitation, calcination, etc., to finally obtain a high-purity titanium dioxide product, which can be sold as a titanium resource product or used in related industrial production. (6) Comprehensive utilization of residues After titanium recycling, the remaining non-titanium residue can be ground and then used as a raw material for various building materials based on its chemical composition and physical properties. For example, it can be used as a cement admixture, mixed with cement clinker in a certain proportion to prepare cement products; it can also be used as a concrete admixture to improve the performance of concrete; and it can also be used to prepare mortar or as a road base material, thus realizing the resource utilization of the residue. (7) Treatment and recycling of waste The waste gas, wastewater and dust generated during the above process are collected and treated to form an internal water circulation and exhaust gas emission standard compliance system; residual dust in the waste gas is captured and recovered by a dust removal device, and wastewater is reused or discharged after sedimentation, neutralization and necessary deep treatment, forming a closed-loop system of "waste gas dust removal / emission reduction, wastewater sedimentation, reuse and dust recovery".

[0045] This embodiment effectively reduces the alkalinity of red mud through a mineral carbonization step, forming a stable compound structure and creating stable conditions for subsequent titanium enrichment and recovery processes. Simultaneously, it reduces the soluble salt content in the system, facilitating the comprehensive utilization of subsequent residues and achieving the resource-based and harmless treatment of red mud.

[0046] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. 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 the invention. Therefore, the invention 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 disclosed herein.

Claims

1. A red mud resource utilization system based on mineral carbonization and passivation, characterized in that, It includes a red mud pretreatment unit, a mineral carbonization and passivation unit, a solid-liquid separation and desalination unit, a metal recovery pretreatment unit, a metal recovery unit, and a residue material utilization unit connected in sequence, as well as a waste treatment and recycling unit and a process detection and automatic control unit connected to each of the above units respectively. The red mud pretreatment unit is used to pre-dehydrate, control particle size and / or adjust moisture content of red mud to obtain pretreated red mud material; The mineral carbonization and passivation unit is used to perform mineral carbonization and passivation reactions on pretreated red mud materials in the presence of acidic gases or media. By controlling the gas partial pressure, inlet rate, and alkalinity of the reaction slurry during the reaction process, the mineral carbonization reaction is kept in a dynamic equilibrium range of "carbonization-dissolution-redeposition". The alkaline components in the pretreated red mud materials are converted into carbonate and / or sulfate minerals, and the pH value of the system is reduced from greater than 12 before the reaction to 8-11, achieving alkalinity reduction and carbonate formation. The acidic gas or media is a gas or fluid medium that can provide acidic components to the reaction system and react with the alkaline components in the red mud through neutralization, carbonation, and / or other mineralization reactions. The acidic components include at least CO2. The dynamic equilibrium range is determined and controlled by online or offline monitoring of the slurry pH change rate, conductivity change trend, CO2 consumption rate, or tail gas CO2 concentration. The dynamic equilibrium range is not a thermodynamic equilibrium state, but refers to the operating range in which the mineral carbonization reaction is kept stable during continuous operation under engineering operating conditions through the coordinated monitoring and control of the above parameters. The solid-liquid separation and desalination unit is used to perform solid-liquid separation on the material after mineral carbonization and passivation. By controlling the solid-liquid ratio, the amount of washing liquid and the conductivity threshold, soluble salts are selectively migrated from the red mud matrix to the liquid phase, and the liquid phase containing soluble salts is separated to obtain the dealkalized red mud solid product. The metal recovery pretreatment unit is used to pretreat the dealkalized red mud solids to obtain metal recovery pretreated materials. The metal recycling unit is used to perform metal recycling operations on the pre-treated metal materials to recover iron, aluminum and / or titanium, and obtain metal products and metal recycling residues. The residue material utilization unit is used to stabilize and / or solidify the metal recycling residue to realize the resource utilization of the residue. The waste treatment and recycling unit is used to treat waste gas, wastewater and dust generated during system operation, so as to achieve partial recycling of water and solids and exhaust gas emission in compliance with standards. The process monitoring and automatic control unit is used to monitor the pH value, temperature, pressure, and flow rate in the mineral carbonization and passivation unit and the metal recovery unit, and adjusts the acid gas / waste gas introduction rate, red mud raw material dosage, and reaction time based on the monitoring results, and also adjusts the conductivity / Na + As a desalination control indicator, it is used to adjust the washing liquid volume, washing frequency, or endpoint conditions of the solid-liquid separation and desalination unit.

2. The red mud resource utilization system based on mineral carbonization and passivation according to claim 1, characterized in that, The mineral carbonization and passivation unit includes at least one of a stirred tank reactor, a bubble column reactor, a fluidized bed reactor, and a slurry bubble column.

3. The red mud resource utilization system based on mineral carbonization and passivation according to claim 1, characterized in that, The metal recycling pretreatment unit includes at least one of a rotary kiln, a vertical roasting furnace, a belt roasting furnace, a crusher, and a ball mill.

4. The red mud resource utilization system based on mineral carbonization and passivation according to claim 1, characterized in that, The metal recovery unit includes at least one of a reduction roasting device, a magnetic separation device, a wet leaching device, an extraction device, and a precipitation / crystallization device.

5. A method for the resource utilization of red mud based on mineral carbonization and passivation, characterized in that, The system described in claim 1 specifically includes the following steps: (1) Red mud pretreatment Red mud raw material containing alkaline components is fed into the red mud pretreatment unit for pre-dehydration, particle size control and / or moisture content adjustment to obtain red mud pretreated material; (2) Mineral carbonization and passivation The pretreated red mud material is fed into the mineral carbonization and passivation unit, where acidic gas or medium is introduced to carry out the mineral carbonization and passivation reaction. By controlling the partial pressure of gas, the rate of gas introduction and the alkalinity of the reaction slurry during the reaction process, the mineral carbonization reaction is kept in a dynamic equilibrium range of "carbonization-dissolution-redeposition". The alkaline components in the pretreated red mud material react with the acidic gas to generate carbonate and / or sulfate minerals, and the pH value of the system is reduced from greater than 12 before the reaction to 8-11. (3) Solid-liquid separation and desalination The material after mineral carbonization and passivation is sent to the solid-liquid separation and desalination unit for solid-liquid separation. By controlling the solid-liquid ratio, washing liquid volume and conductivity threshold, soluble salts are selectively migrated from the red mud matrix to the liquid phase. The liquid phase containing soluble salts is separated and returned to the process system or discharged after neutralization, sedimentation and / or membrane treatment. The solid phase is used as the dealkali red mud solid product. (4) Metal recycling pretreatment The solid products of dealkalized red mud are sent to a metal recovery pretreatment unit for pretreatment to obtain metal recovery pretreated material. (5) Metal recycling The pre-treated metal recycling material is fed into the metal recycling unit for metal recycling operations to recover iron, aluminum and / or titanium, and obtain metal products and metal recycling residue. (6) Utilization of residue materials Metal recycling residues are sent to a residue material utilization unit for stabilization and / or solidification treatment, and then used as raw materials for building material admixtures, mineral admixtures in concrete or mortar, road subgrade materials or other material products, thereby realizing the resource utilization of residues. (7) Treatment and recycling of waste The waste gas, wastewater and dust generated during the above process are collected and treated to form an internal water circulation and exhaust gas emission standard compliance system; residual dust in the waste gas is captured and recovered by a dust removal device, and wastewater is reused or discharged after sedimentation, neutralization and necessary deep treatment, forming a closed-loop system of "waste gas dust removal / emission reduction, wastewater sedimentation, reuse and dust recovery".

6. The method for resource recovery of red mud based on mineral carbonization and passivation according to claim 5, characterized in that, In step (1), the red mud raw material is red mud produced by the Bayer process of alumina production and / or red mud produced by the sintering process of alumina production; the alkaline components include NaOH and CaO; the pre-dehydration includes mechanical dehydration, natural air drying and / or low-temperature drying; the particle size control includes crushing, sieving and mixing homogenization.

7. The method for resource recovery of red mud based on mineral carbonization and passivation according to claim 5, characterized in that, In step (2), the acidic gas originates from industrial waste gas from cement kilns, steel plants, coal-fired power plants, waste incineration plants, or chemical plants; the acidic gas or medium is a gas or fluid medium capable of providing acidic components to the reaction system and reacting with alkaline components in red mud through neutralization, carbonation, and / or other mineralization reactions; the acidic components include at least CO2; the reaction temperature of the mineral carbonization and passivation reaction is 20–120°C, the reaction pressure is atmospheric pressure to 2.0 MPa, the reaction time is 10–240 min, and the reaction endpoint is controlled by online pH monitoring to stabilize the pH value of the system at 8–11.

8. The method for resource recovery of red mud based on mineral carbonization and passivation according to claim 5, characterized in that, In step (3), the solid-liquid separation includes at least one of pressure filtration, vacuum filtration, centrifugal separation and sedimentation clarification.

9. A method for resource recovery of red mud based on mineral carbonization and passivation according to claim 5, characterized in that, In step (4), the pretreatment includes at least one of calcination, reduction magnetization and / or grinding.

10. A method for resource recovery of red mud based on mineral carbonization and passivation according to claim 5, characterized in that, In step (5), the metal recovery operation includes at least one of reduction magnetic separation, leaching, extraction, precipitation or crystallization, as well as selective leaching, solvent extraction and / or chlorination volatilization.

Images