A precise red mud drying method and system with yard in-situ redundancy design

Abstract

The application discloses a kind of bauxite residue precision drying method and system of yard in situ redundancy design, it is related to industrial solid waste treatment and resource technology field, including bauxite conditioning pretreatment, mechanical deep pre-dewatering stage, yard in situ redundancy controllable natural airing stage and double-layer heat preservation greenhouse redundancy deep drying stage.The advantages are that all operations are completed in the existing hard area of bauxite residue yard, zero additional land acquisition, the energy system is mainly based on natural wind and solar energy, mechanical electric energy, and industrial low-temperature waste heat is only used as an emergency auxiliary in extreme weather, with the advantages of strong production capacity guarantee, small drying quality fluctuation, low energy consumption and adaptation to full-element high-value recovery.

Description

Technical Field

[0001] This invention relates to the field of industrial solid waste treatment and resource utilization technology, and in particular to a method and system for precise drying of red mud with in-situ redundant design of stockpile. Background Technology

[0002] Red mud is a major hazardous solid waste generated during alumina production. Producing 1 ton of alumina generates 1.0-2.5 tons of red mud, with annual emissions in China exceeding 80 million tons and a comprehensive utilization rate of less than 12%. Red mud is characterized by high moisture content (60%-70% in the original slurry, still reaching 30%-40% after mechanical dewatering), high viscosity, poor permeability, strong alkalinity, and complex composition. Deep drying is a core prerequisite for achieving subsequent high-value recovery of all elements. The moisture content and uniformity of the dried red mud directly determine the accuracy of subsequent roasting batching, reduction efficiency, and leaching effect. Large fluctuations in moisture content and severe agglomeration can lead to uncontrolled roasting temperature, decreased recovery rate of valuable metals, and a significant increase in processing costs.

[0003] Existing red mud dewatering and drying technologies suffer from four core industry pain points, failing to meet the industrial demands for high-value recovery of all elements from red mud: Land resources are being wasted, land acquisition is difficult, and there is no design for in-situ utilization of the stockpiles: existing drying technologies all require additional land acquisition to build drying yards and drying workshops, but land resources around alumina plants are scarce, land acquisition costs are high, and approval is difficult; existing red mud stockpiles have been stored for many years, and the surface has hardened and the bearing capacity meets the operational requirements, but they are only used for storage and have not been utilized in a secondary, three-dimensional way, resulting in a serious waste of land resources.

[0004] Lacking redundant design, weak capacity guarantee, and large fluctuations in drying quality: Existing natural drying technology lacks area redundancy design and only matches the working area according to theoretical capacity. Once encountering extreme weather such as continuous rain or low winter temperatures, the effective drying days are greatly reduced, resulting in a serious shortage of capacity. Moreover, the moisture content of dried red mud fluctuates between 10% and 20%, and clumping is severe, which cannot meet the requirements of subsequent full element recovery for raw material moisture content stability ≤8% and high uniformity.

[0005] High energy consumption, expensive operating costs, and unreasonable energy structure: Traditional thermal drying technology consumes 800,000 to 1,200,000 kcal per ton of water, which is difficult for enterprises to bear; existing natural drying technology does not make full use of solar and wind energy, still requires a large amount of industrial waste heat to assist, the energy-saving effect is limited, and it is greatly restricted by climate, and cannot operate normally during the rainy season.

[0006] Without a complete chain of resource utilization adaptation design, dried products cannot meet the high-value requirements: Existing drying technology only aims to reduce moisture content and meet the requirements for stockpiling, without being precisely designed for the raw material requirements of subsequent full-element high-value recovery. The moisture content of dried products fluctuates greatly, the composition is uneven, and there is serious agglomeration. Additional crushing and secondary drying are required before they can enter the subsequent resource utilization process, which increases the overall processing cost.

[0007] Therefore, developing a large-scale drying method and system based on the in-situ utilization of existing red mud dumps, with redundant capacity design, using free natural wind, solar and thermal energy as the core, with stable and controllable drying quality, and adaptable to the high-value recovery of all elements of red mud, has become an urgent need for the alumina industry to solve the problem of red mud solid waste.

[0008] Therefore, a novel red mud precision drying method and system with in-situ redundant design of the stockpile can be adopted to address the shortcomings of existing technologies. Summary of the Invention

[0009] The purpose of this invention is to solve the problems of existing red mud drying technologies, such as difficulty in land acquisition, weak production capacity guarantee, large fluctuations in drying quality, high energy consumption, and inability to adapt to the high-value recovery of all elements. Therefore, this invention proposes a red mud precision drying method and system with in-situ redundant design of the stockpile.

[0010] To achieve the above objectives, the present invention adopts the following technical solution: A method for precise drying of red mud in situ with redundant design of a stockpile includes the following steps performed in sequence: S1. Red mud conditioning and pretreatment: The raw red mud with a moisture content of 60%-70% produced by the alumina plant is directly transported to the conditioning tank in the red mud stockpile. 0.1%-0.3% of the dry weight of the red mud is added to reduce the viscosity of the red mud and improve the dehydration permeability and subsequent drying uniformity. The dispersant is a composite system of polycarboxylate dispersant and inorganic inert filler. The filler accounts for 0.5%-1% of the dry weight of the red mud. It reduces the particle adhesion and forms a skeleton on the surface of the red mud, improving permeability and reducing the mechanical dewatering moisture content from ≤36% to ≤30%. A microwave emitting device is added to the conditioning tank to break the hydration film of red mud particles by using the microwave thermal effect, improve the adsorption effect of dispersant, shorten the stirring time from 10-15 min to 5-8 min, and reduce energy consumption. S2. Mechanical deep pre-dehydration stage: Add a trace amount of hydrophobic agent, such as organosilicon emulsion or ≤0.05% dry basis, to the dehydrated red mud to reduce the hydrophilicity of the red mud surface, accelerate the evaporation of moisture during the natural drying stage, and shorten the drying cycle by 20%-30%; The conditioned red mud is fed into a high-pressure diaphragm filter press in the stockpile. The dewatering pressure is controlled at 0.8-1.2 MPa and the holding time is 25-35 min. The moisture content of the red mud is stably reduced to ≤36%, and pre-dewatered red mud A is obtained. The filtrate produced by dewatering is collected and reused in a closed loop. This stage only consumes mechanical and electrical energy. S3, In-situ Redundant Controllable Natural Drying Stage in the Stockpile: The pre-dehydrated red mud A is spread in batches to the independent drying units in the hardened area of ​​the red mud stockpile, with a spreading thickness of 25-35cm. A ground-mounted rainproof film full-coverage system is used in combination with meteorological data to intelligently control the opening and closing of the film. In rainless weather, the film is opened to utilize solar and wind energy in the open area of ​​the stockpile for dehydration. The pile is turned over regularly to break the crust. The film is closed before rainfall to prevent moisture increase. By using an area redundancy design of ≥50%, the water content of red mud is stably reduced to ≤16%, resulting in pre-dehydrated red mud B, and the leachate is collected and reused in a closed loop. S4, Double-layer insulated greenhouse redundant deep drying stage: The pre-dehydrated red mud B is transferred to the double-layer insulated greenhouse unit built in the hard area of ​​the stockpile and spread out with a thickness of 15-25cm. Solar energy and wind energy are the core drying energy sources. Only in winter / continuous rainy weather is industrial low-temperature waste heat used to heat the air, combined with intelligent ventilation and periodic turning. By using an area redundancy design of ≥50%, the moisture content of red mud is precisely reduced to ≤8%, resulting in dried red mud with uniform composition and no clumping, which directly meets the raw material requirements for subsequent roasting activation and high-value recovery of all elements.

[0011] Preferably, in S3, the hardened area of ​​the red mud stockpile is the surface layer of the red mud stockpile with a stockpile age of ≥3 years and a bearing capacity of ≥12t / ㎡, requiring no additional foundation treatment; The drying units adopt a zoned and batch-based design, with each drying unit having an area of ​​2000-3000㎡ and 2-4 independent operating zones. The drying units and greenhouse units can be operated alternately, realizing the secondary and multiple three-dimensional utilization of the storage area. The reserved redundant area can be flexibly used according to climate conditions and fluctuations in feed volume to ensure stable annual production capacity.

[0012] Preferably, in step S3, the control logic of the ground-mounted rainproof film full-coverage system is as follows: The central controller receives high-precision weather forecasts for the next 4-6 hours. When the forecast rainfall is ≥3mm, relative humidity is ≥90%, or there is snowfall / fog, it drives the film rolling mechanism to complete the full film spreading within 20 minutes. When the ambient temperature is ≥15℃, the light intensity is ≥8000lx, the wind speed is 1~6m / s and there is no rain warning, the film is completely rolled up; the turning operation is carried out by an unmanned electric turning machine, the turning depth is 25~35cm, the turning frequency is 1-2 days / time, the turning path is a reciprocating full coverage, and the positioning accuracy is ≤±5cm.

[0013] Preferably, in S4, the double-layer insulated greenhouse is a north-south oriented continuous steel structure, using an inner and outer double-layer high-transmittance PO film structure, forming a 12-15cm sealed air insulation layer between the two layers of film, with a thermal conductivity coefficient ≤2.6W / (㎡・K); the span of a single structure is 6-8m, the shoulder height is 1.8-2.2m, the top height is 2.8-3.5m, and the length is 40-60m. The frame is made of hot-dip galvanized high-frequency welded rectangular steel pipe, with a wind resistance level ≥10 and a snow load ≥0.5kN / ㎡. The outer film is an ultraviolet-resistant PO film with a light transmittance ≥88%, and the inner film is an anti-drip insulation film. The overall airtightness of the greenhouse is ≥92%.

[0014] Preferably, in step S4, the drying energy in the greenhouse is mainly solar and wind power: On sunny days, the greenhouse temperature inside the shed is raised to 45-65℃ through the greenhouse effect of the double-layer film. With the intelligent opening and closing of the top skylight and side ventilation windows, the air convection formed by the pressure difference between the inside and outside of the shed carries away moisture. When the temperature inside the greenhouse is ≤8℃ in winter or the relative humidity is ≥85% during continuous rainy weather, the air is heated to 35-45℃ and relative humidity ≤28% by using 0.2-0.8MPa low-grade steam, 40-60℃ circulating water, or 150-250℃ flue gas waste heat from power plants / alumina plants. The annual industrial waste heat utilization rate is ≤12%.

[0015] Preferably, in step S4, the intelligent control logic within the greenhouse is as follows: When the temperature inside the greenhouse is ≥45℃ and the relative humidity is ≥60%, the top skylight and side ventilation windows should be opened simultaneously, with a ventilation volume of 1200-1800m³ / (h・㎡). When the temperature inside the shed is ≤8℃, close the ventilation windows and start the waste heat auxiliary system; the turning operation is carried out by an unmanned electric turning machine, with a turning depth of 15~25cm and a turning frequency of 1-3 days / time. The turning machine is equipped with an online detection probe for the moisture content of red mud, and adjusts the operating parameters in real time to ensure that the drying uniformity deviation is ≤±1%.

[0016] A red mud precision drying system with in-situ redundancy design for stockpile, used in the aforementioned red mud precision drying method with in-situ redundancy design for stockpile, includes a red mud conditioning unit, a mechanical dewatering unit, a redundant zoned controllable natural drying unit, a double-layer heat-insulated greenhouse redundant deep drying unit, a filtrate closed-loop treatment unit connected to each unit, and an intelligent central control platform for full-process control. The red mud conditioning unit and mechanical dewatering unit are both located at the feeding end of the red mud stockpile and are directly connected to the red mud conveying pipeline of the alumina plant, eliminating the need for long-distance red mud transportation. The redundant partitioned controllable natural drying unit is an independent partition divided from the hard solid area of ​​the red mud stockpile. The total drying area is reserved with ≥50% redundancy. Each partition is equipped with an independent ground-mounted rainproof membrane full-coverage system, a first unmanned electric turning machine and a circumferential leachate collection ditch. The original impermeable layer of the stockpile is used as the impermeable structure, and no additional impermeable treatment is required. The redundant deep drying unit of the double-layer heat-insulating greenhouse is built in the idle hardened area of ​​the red mud dump. The total greenhouse area is reserved with ≥50% redundancy, including at least 9 independent connected greenhouse units. Each greenhouse unit is equipped with an independent second unmanned electric turning machine, a waste heat emergency auxiliary system, a greenhouse environment monitoring module and a humid and hot air waste heat recovery module. The closed-loop filtrate treatment unit collects the filtrate, leachate and condensate generated by each unit, and after treatment, all of them are reused for red mud conditioning and plant production, achieving zero wastewater discharge. The intelligent central control platform is electrically connected to the equipment, monitoring modules, and actuators of each unit. It has built-in meteorological linkage model, production capacity guarantee model, moisture content precise control model, AI moisture content prediction model, digital twin storage yard system, and multi-sensor fusion perception to achieve unmanned operation of the entire process. AI moisture content prediction model: Integrating meteorological data, material data, and equipment data, it uses machine learning to predict the drying rate of red mud, adjusts operating parameters in advance, and achieves predictive control of moisture content, reducing uniformity deviation to ≤±0.5%; Digital Twin Stockyard System: Constructs a digital twin model of the entire stockyard drying process, mapping the material status, equipment operation, and environmental parameters of the drying unit and greenhouse unit in real time, supporting virtual simulation scheduling, and avoiding capacity fluctuations in advance; Multi-sensor fusion sensing: Near-infrared spectral sensors are added to the turning machine to detect the composition and moisture content of red mud in real time, realizing online monitoring of dual parameters of moisture content and composition, and adapting to the raw material requirements of different subsequent high-value recycling processes.

[0017] Preferably, the ratio of the total area of ​​the redundant partitioned controllable natural drying unit to the total area of ​​the double-layer insulated greenhouse unit is (2-6):1, which can be adjusted according to local climate conditions; the original impermeable layer of the storage yard is a 1.5mm thick HDPE smooth impermeable membrane + 30cm thick compacted impermeable clay, with a permeability coefficient ≤1×10⁻ 7 cm / s, meeting the standards for leaching prevention in hazardous waste landfills; the reserved redundant area can be used as an emergency reserve area and a rotation operation area to cope with extreme weather, fluctuations in feed volume, and equipment maintenance.

[0018] Preferably, the waste heat emergency auxiliary system includes a finned tube heat exchanger, a blower, an underground air distribution duct, and an electric air volume regulating valve. The heat source side of the heat exchanger is connected to the low-grade waste heat pipeline network of the power plant / alumina plant and is only activated during extreme weather. The humid air waste heat recovery module includes a shell-and-tube condenser and a condensate collection tank. It recovers heat from the humid air discharged from the shed by exchanging heat and using it to preheat the ambient air entering the heat exchanger. The condensate is sent to the filtrate closed-loop treatment unit.

[0019] Preferably, the capacity guarantee model of the intelligent central control platform can automatically schedule the activation and operation parameters of redundant units based on real-time meteorological data, red mud feed volume, and drying progress to ensure that the annual processing capacity deviation is ≤±2%. The precise moisture content control model can automatically adjust the paving thickness, turning frequency, and ventilation volume according to the raw material requirements of the subsequent full-element recovery process, so as to precisely control the moisture content of the dried red mud within the range of 3%-8%.

[0020] Compared with existing technologies, the advantages of this invention are: 1. In-situ three-dimensional secondary utilization of the stockpile: The entire operation process is completed within the hardened area of ​​the existing red mud stockpile, with zero new land acquisition. The original impermeable layer of the stockpile is utilized, saving more than 65% of civil engineering investment and solving the core pain point of land acquisition difficulties in the industry. 2. Dual-unit 50% area redundancy design: Both the drying unit and the greenhouse unit have ≥50% area redundancy, which not only ensures stable annual production capacity under extreme weather conditions, but also enables precise control of the moisture content of dried red mud, fully meeting the raw material requirements for subsequent high-value recycling of all elements. 3. Ultra-low energy consumption energy system: Construct an energy structure with natural wind and solar thermal energy as the main source, mechanical and electrical energy as the supplement, and industrial low-temperature waste heat as an emergency supplement. More than 88% of the drying energy comes from free wind and solar energy, and the annual waste heat utilization rate is ≤12%, which saves more than 92% energy compared with traditional thermal drying. 4. Optimized design of double-layer insulated greenhouse: Through the double-layer 12-15cm air gap structure, the winter heat preservation performance is improved by more than 45%, and the number of dry days per year is ≥310 days, which greatly improves the utilization rate of solar energy. 5. Intelligent and precise control throughout the entire process: It has three core models built-in: production capacity guarantee, precise moisture content control, and meteorological linkage, which realizes the fully automated and unmanned operation of the drying process. The quality of the dried product is stable and can directly enter the subsequent roasting activation and full element recovery process without additional pretreatment. Attached Figure Description

[0021] Figure 1 This is a process flow diagram of the red mud precision drying method of the present invention; Figure 2 This is a schematic diagram of the red mud drying system of the present invention; Figure 3This is a schematic diagram of the closed-loop filtrate treatment system of the present invention; Figure 4 This is a schematic diagram of the waste heat emergency auxiliary system of the present invention; Figure 5 This is a schematic diagram of the waste heat recovery system for humid air according to the present invention. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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.

[0023] The red mud precision drying method with in-situ red mud ... S1. Red mud conditioning and pretreatment: The raw red mud with a moisture content of 60%-70% produced by the alumina plant is directly transported to the closed conditioning tank in the red mud stockpile through the plant’s existing pipelines. This eliminates the need for long-distance transportation and avoids spillage and leachate leakage during transportation. Add dispersant at 0.1%-0.3% of the dry weight of red mud, and mix by stirring at 120-180 r / min for 10-15 min using a variable frequency stirring mechanism; The dispersant can be directionally adsorbed on the surface of red mud particles, breaking up fine particle agglomerates and reducing interparticle adhesion. This not only improves the efficiency of subsequent mechanical dewatering but also enhances the permeability of red mud after spreading, preventing surface crusting and improving the uniformity of natural drying and greenhouse drying, thus laying the foundation for precise control of moisture content in the future.

[0024] S2. In the mechanical deep pre-dehydration stage, the conditioned red mud is sent to the high-pressure diaphragm filter press in the stockpile through a closed belt conveyor. The dehydration pressure is controlled at 0.8-1.2MPa and the holding time is 25-35min. The free water in the red mud is quickly removed by mechanical pressure, and the moisture content of the red mud is stably reduced to ≤36%, thus obtaining pre-dehydrated red mud A. This stage consumes only a small amount of mechanical and electrical energy. Its core objective is to quickly remove more than 72% of the total moisture, significantly reducing the material volume and processing load in the subsequent drying stage and shortening the drying cycle. The filtrate generated during the dehydration process is collected in the filtrate collection tank and sent to the subsequent filtrate closed-loop treatment unit. After treatment, it is reused for red mud conditioning or plant production water, achieving zero filtrate discharge.

[0025] S3. In-situ Redundant Controllable Natural Drying Stage in the Stockyard: This stage is the core energy-saving section, fully utilizing the free solar and wind energy of the open area of ​​the stockyard to complete dehydration, undertaking more than 82% of the drying task. Through an area redundancy design of ≥50%, it ensures stable production capacity under extreme weather conditions and achieves a stable output moisture content of ≤16%. The specific operation is as follows: Zoned Batch Spreading: The pre-dehydrated red mud A is spread in batches according to the daily processing volume to the independent drying units in the hardened area of ​​the red mud stockpile. The scraper is used to spread it evenly. The basic working condition is a spreading thickness of 30-35cm, which can be reduced to 25cm in the redundant working condition to improve the drying efficiency. The flatness error of the spreading surface is ≤3cm to ensure that the contact area between the red mud and sunlight and air is uniform. Requirements for hardened areas of the landfill: The surface layer of red mud piles with a storage period of ≥3 years, after simple leveling, has a bearing capacity of ≥12t / ㎡, which fully meets the load requirements of transport vehicles, turning machines, and greenhouse frames, without the need for additional foundation treatment; Utilizing the existing double-layer seepage prevention structure of 1.5mm HDPE geomembrane + 30cm compacted seepage prevention clay, only local damaged areas need to be repaired, without the need for additional seepage prevention treatment, which meets the environmental protection requirements for hazardous waste landfill.

[0026] Intelligent rainproof film control: Each drying unit is equipped with an independent ground-mounted rainproof film full-coverage system. The system is connected to the national meteorological platform in real time, and the central controller realizes the automatic opening and closing of the film based on the high-precision weather forecast for the next 4-6 hours. ① When the forecast rainfall is ≥3mm, relative humidity is ≥90%, or there is snow / fog, drive the mobile film rolling machine to complete the full laying of HDPE composite geomembrane within 20 minutes at a speed of 1.0-1.5m / s. The edges of the film are compacted and sealed with counterweights to prevent rainwater and fog from entering the red mud layer and causing humidification. ② When the ambient temperature is ≥15℃, the light intensity is ≥8000lx, the wind speed is 1-6m / s and there is no rain warning, the film is completely rolled up to fully expose the red mud to sunlight and wind, and the water is heated and evaporated by solar energy and the water vapor is carried away by wind energy to achieve efficient natural dehydration; Intelligent turning operation: The first unmanned electric turning machine is used for turning operations. The turning depth is 25-35cm, and the turning frequency is 1-2 days / time (adjusted according to the ambient temperature and humidity: 1 time / time when the temperature is ≥25℃, 1.5 times / time when the temperature is 15-25℃, and 2 times / time when the temperature is <15℃). The turning machine is equipped with a GNSS high-precision navigation system with a positioning accuracy of ≤±5cm. The turning path is a reciprocating full-coverage method, which effectively breaks the crust on the surface of the red mud, increases the contact area between the red mud and the air, and improves the evaporation efficiency and drying uniformity. Leachate collection: Each drying unit is equipped with a circumferential leachate collection ditch with a slope of 3‰ to collect the leachate generated by the natural dehydration of red mud and send it to the filtrate closed-loop treatment unit to achieve zero leachate discharge; Redundant area scheduling: When encountering extreme weather such as continuous rain or low winter temperatures, and the effective drying days are reduced by more than 30%, the reserved redundant drying units are automatically activated to reduce the spreading thickness, increase the turning frequency, and ensure stable daily processing capacity. When the working conditions are good, the redundant units can be used as rotation work areas to shorten the drying cycle, reduce the output moisture content to below 14%, and reduce the subsequent drying load of the greenhouse. This stage completely solves the problem of traditional open-air drying being constrained by the weather by using intelligent rainproof membrane control, turning operations and redundant area scheduling, and realizes all-weather operation of "waterproof in rainy days and sun exposure in sunny days", which stabilizes the moisture content of red mud down to ≤16% to obtain pre-dehydrated red mud B.

[0027] S4. Double-layer Insulated Greenhouse Redundancy Deep Drying Stage: This stage addresses the moisture content bottleneck that natural dehydration struggles to overcome. A double-layer insulated greenhouse creates a stable high-temperature, low-humidity environment, using solar and wind power as the core energy sources, supplemented only by industrial low-temperature waste heat in extreme weather. Through a ≥50% area redundancy design, the red mud moisture content is precisely reduced to ≤8%. The dried product is directly compatible with subsequent roasting activation and high-value recovery processes. Specific operations are as follows: Material transfer and spreading: The pre-dehydrated red mud B, which has completed natural pre-dehydration, is transported by short-distance transfer vehicles within the stockpile to the double-layer insulated greenhouse unit built in the idle hard area of ​​the stockpile. It is then spread evenly using a scraper. The basic working condition is a spreading thickness of 20-25cm, which can be reduced to 15cm in the redundant working condition, thereby improving drying efficiency and uniformity. The flatness error of the spreading surface is ≤3cm. Double-layer greenhouse with wind and solar power as the main structure: The greenhouse adopts an inner and outer double-layer PO film structure, forming a 12-15cm sealed air insulation layer in the middle, with a thermal conductivity coefficient ≤2.6W / (㎡・K). In winter, the temperature inside the greenhouse is 6-10℃ higher than that of a single-layer greenhouse, and the heat preservation performance is improved by more than 45%. On sunny days, sunlight enters the greenhouse through the double-layer film, creating a greenhouse effect and raising the temperature inside the greenhouse to 45-65℃, causing the moisture in the red mud to evaporate rapidly. By intelligently opening and closing the top skylight and side ventilation windows, the temperature difference between the inside and outside of the greenhouse is used to create air convection, expelling the hot and humid air inside the greenhouse and bringing in dry outside air, realizing wind-assisted dehydration without consuming additional energy. Industrial Low-Temperature Waste Heat Emergency Assistance: The waste heat emergency assistance system will only be activated when the temperature inside the shed is ≤8℃ in winter, or when the relative humidity inside the shed is ≥85% during continuous rainy weather. It utilizes 0.2-0.8MPa low-grade steam, 40-60℃ circulating water, or 150-250℃ flue gas waste heat from nearby power plants / alumina plants to heat the ambient air to 35-45℃ and relative humidity ≤28% through finned tube heat exchangers. The heat is then evenly distributed into the shed through underground air distribution pipes to maintain a high-temperature and low-humidity drying environment inside the shed. The annual industrial waste heat utilization rate is ≤12%, and it is only used as an emergency supplement and does not participate in daily drying. Intelligent ventilation and turning control: ① Ventilation control: When the temperature inside the greenhouse is ≥45℃ and the relative humidity is ≥60%, open the top skylight and side ventilation windows simultaneously at an angle of 90°, with a ventilation volume of 1200-1800m³ / (h・㎡) to quickly expel hot and humid air; when the temperature inside the greenhouse is ≤8℃, close the ventilation windows and activate the waste heat emergency auxiliary system. ② Turning operation: The second unmanned electric turning machine is used for turning operations. The turning depth is 15-25cm, and the turning frequency is 1-3 days / time. The turning machine is equipped with an online detection probe for red mud moisture content to collect real-time moisture content data of the working area. When the local moisture content deviation is ≥1%, the turning frequency and path are automatically adjusted to ensure that the uniformity deviation of red mud drying is ≤±1%. Humid and hot air waste heat recovery: Humid and hot air discharged from the shed is introduced into the humid and hot air waste heat recovery module, and heat is recovered through shell and tube condenser to preheat the ambient air entering the heat exchanger, further reducing waste heat consumption; condensate is collected and sent to the filtrate closed-loop treatment unit for reuse, improving water resource utilization. Redundant area scheduling: When encountering extreme weather such as low winter temperatures and continuous rain, and the drying efficiency of the greenhouse drops by more than 40%, the reserved redundant greenhouse units are automatically activated to reduce the spreading thickness, increase ventilation and turning frequency, and ensure stable daily processing capacity. When the working conditions are good, the redundant greenhouse units can be used as temporary drying areas or to further reduce the moisture content of the dried red mud to 3%-5%, which is suitable for the raw material requirements of subsequent special resource utilization processes such as wet leaching.

[0028] This stage utilizes the greenhouse effect of double-layered greenhouses, intelligent control, and redundant area scheduling to create a stable drying environment unaffected by external climate. Ultimately, the moisture content of the red mud is precisely reduced to ≤8%, resulting in dried red mud with uniform composition, no clumping, and stable moisture content. It can directly proceed to subsequent roasting activation and high-value recovery of all elements without the need for additional pretreatment such as crushing or secondary drying.

[0029] A red mud precision drying system with in-situ redundancy design for stockpiles is proposed. To achieve the aforementioned method for precision drying of red mud with in-situ redundancy design for stockpiles, an integrated, intelligent closed-loop system is designed, which is entirely constructed within the existing hardened area of ​​the red mud stockpile, requires zero additional land acquisition, and has a dual-unit area redundancy of ≥50%. The units are sequentially connected and interconnected. The specific structure is as follows: Core equipment of the red mud conditioning unit: closed conditioning tank, dispersant precise metering and adding device, and variable frequency stirring mechanism; Installation location: at the feed end of the red mud stockpile, directly connected to the existing red mud conveying pipeline of the alumina plant, eliminating the need for long-distance transportation of red mud; Function: To condition raw red mud, add dispersants to reduce the viscosity of red mud, and improve dewatering performance and drying uniformity; The dispersant addition device is a screw-type precision metering pump, which can automatically adjust the addition amount according to the red mud feed rate and dry basis content to ensure stable conditioning effect.

[0030] Core equipment of the mechanical dewatering unit: high-pressure diaphragm filter press, filtrate collection tank, closed material conveyor belt, and variable frequency sludge feed pump; Installation location: adjacent to the conditioning unit, located at the feed end of the stockpile; Function: to perform mechanical deep pre-dewatering on the conditioned red mud, stabilizing the moisture content to ≤36%; The filtrate collection tank collects the dewatered filtrate and sends it to the filtrate closed-loop treatment unit to achieve centralized treatment and reuse of the filtrate.

[0031] The core components of the redundant, zoned, controllable natural drying unit include: independent drying units divided into hardened areas of the red mud stockpile; a ground-level, rainproof, fully covered membrane system; the first unmanned electric turning machine; and a circumferential leachate collection ditch. Key design features include: ① Redundant area design: The total drying area is designed to be 1.5 times the theoretical capacity, with ≥50% area redundancy. The area of ​​a single drying unit is 2000-3000㎡, and 2-4 independent operation zones are set up to realize batch turnover operation; The drying unit and the greenhouse unit can be used alternately to realize the secondary and multiple three-dimensional utilization of the storage area; ② Impermeable design: Utilizing the existing 1.5mm thick HDPE smooth geomembrane + 30cm thick compacted impermeable clay double-layer structure in the stockpile, the permeability coefficient is ≤1×10⁻ 7 cm / s, which meets the requirements of the "Standard for Pollution Control of Hazardous Waste Landfill", and no additional anti-seepage treatment is required; ③ Ground-mounted rainproof membrane full-coverage system: including track, mobile film rolling machine, 0.4-0.5mm thick HDPE composite geomembrane, and central controller, to realize intelligent film loading and unloading, with a spreading time of ≤20min; ④ The first unmanned electric compost turner: equipped with a GNSS high-precision automatic navigation system with a positioning accuracy of ≤±5cm, it can navigate and operate autonomously in the hardened area of ​​the compost yard without the need to build additional hardened roads; Function: Utilizes natural wind, solar and thermal energy to achieve natural dehydration of red mud, stably reducing the moisture content to ≤16%, and ensures stable production capacity under extreme weather conditions through redundant area design.

[0032] Core components of the redundant deep drying unit in a double-layer insulated greenhouse: a multi-span greenhouse unit built in an unused, hardened area of ​​a stockpile, a second unmanned electric compost turner, a waste heat emergency auxiliary system, an internal environmental monitoring module, and a humid air waste heat recovery module. Key designs include: ① Area redundancy design: The total greenhouse area is designed based on 1.5 times the theoretical production capacity, with ≥50% area redundancy reserved. Each greenhouse unit is a 9-span connected structure, with a span of 8m and a length of 50m per span, and a total area of ​​3600㎡ per unit. ② Double-layer insulated greenhouse structure: Modular continuous steel structure running north-south, with a shoulder height of 2.0m and a top height of 3.2m per unit. The frame is made of hot-dip galvanized high-frequency welded rectangular steel pipe, with a wind resistance level of ≥10 and a snow load of ≥0.5kN / ㎡. It adopts an inner and outer double-layer membrane structure. The outer layer is a 0.15mm thick UV-resistant high-transmittance PO film (transmittance ≥88%), and the inner layer is a 0.12mm thick anti-drip insulation PO film. A 12cm sealed air insulation layer is formed between the two films, which improves the insulation performance by more than 45%. ③ Waste heat emergency auxiliary system: including finned tube heat exchanger, variable frequency blower, underground air distribution duct, electric air volume regulating valve. The heat source side of the heat exchanger can be connected to the low-grade waste heat pipeline network of the surrounding power plant / alumina plant, and is only activated in extreme weather. ④ Greenhouse environment monitoring module: Temperature, humidity, light, and wind speed sensors are arranged in a grid pattern (density 1 sensor / 100㎡). The second unmanned electric turning machine is equipped with a high-precision online moisture content detector to realize real-time monitoring of the greenhouse environment and red mud moisture content. ⑤ Humid and hot air waste heat recovery module: including shell and tube condenser and condensate collection tank, to recover heat and moisture from the humid and hot air in the shed, and improve energy and water resource utilization; Function: Utilizes solar and wind power to achieve deep drying of red mud, precisely reducing the moisture content to ≤8%. Redundant area design ensures stable production capacity and drying quality. The dried products are directly compatible with subsequent high-value recycling of all elements.

[0033] Core equipment of the filtrate closed-loop treatment unit: sedimentation tank, multi-media filtration device, softening device, reclaimed water tank, and variable frequency booster pump; Function: Collects filtrate, leachate and condensate generated by each unit, and after three-stage treatment of "sedimentation-filtration-softening", sends them to the recycled water tank for reuse in red mud conditioning, production water use in the plant area and other processes, achieving zero wastewater discharge and a water resource saving rate of ≥92%.

[0034] The core components of the intelligent central control platform include: a data acquisition module, an intelligent decision-making module, an execution control module, and a human-machine interface. Its core functions are: ① It connects in real time with the monitoring modules of each unit and the national meteorological platform to collect process data, environmental data and equipment operation data throughout the entire process; ② It has three core built-in models: a meteorological linkage model, a production capacity guarantee model, and a moisture content precise control model. It makes intelligent decisions based on real-time data and automatically controls the rainproof film opening and closing, greenhouse ventilation, waste heat system start and stop, turning machine operation, and redundant unit scheduling. ③ Enables remote equipment control, operational status monitoring, fault alarms, data statistical analysis and traceability, achieving fully unmanned operation throughout the entire process; AI moisture content prediction model: Integrating meteorological data, material data, and equipment data, it uses machine learning to predict the drying rate of red mud, adjusts operating parameters in advance, and achieves predictive control of moisture content, reducing uniformity deviation to ≤±0.5%; Digital Twin Stockyard System: Constructs a digital twin model of the entire stockyard drying process, mapping the material status, equipment operation, and environmental parameters of the drying unit and greenhouse unit in real time, supporting virtual simulation scheduling, and avoiding capacity fluctuations in advance; Multi-sensor fusion sensing: Near-infrared spectral sensors are added to the turning machine to detect the composition and moisture content of red mud in real time, realizing online monitoring of dual parameters of moisture content and composition, and adapting to the raw material requirements of different subsequent high-value recycling processes; Micro-weather station + edge computing: A micro-weather station is set up in each drying unit to realize on-site meteorological data collection and edge computing. There is no need to rely on a remote meteorological platform. The response time for membrane retraction and extension is shortened from 4-6 hours of prediction to accurate response within 1 hour, avoiding the red mud from becoming humidified due to sudden rain / fog.

[0035] The red mud precision drying method and system with in-situ redundancy design in this stockpile can achieve the following effects: The invention utilizes the existing red mud stockpile in situ, requiring zero additional land acquisition and significantly reducing civil engineering investment. The entire operation process is completed within the hardened area of ​​the existing red mud stockpile, eliminating the need for additional land acquisition and completely solving the industry pain points of difficult and costly land acquisition for alumina plants. At the same time, by utilizing the existing impermeable layer of the stockpile, no additional foundation or impermeable treatment is required, reducing civil engineering investment by more than 65%.

[0036] With a dual-unit design and 50% area redundancy, this invention boasts exceptional capacity assurance and precise control over drying quality. Both the drying unit and the greenhouse unit have ≥50% area redundancy, allowing for flexible scheduling based on climate conditions and feed fluctuations. Even in extreme weather conditions such as winter or prolonged rainy periods, where the effective drying days are reduced by 40%, the annual processing capacity deviation can still be guaranteed to be ≤±2%, completely resolving the issue of unstable capacity in existing technologies. Simultaneously, through the redundancy design, the moisture content of the dried red mud can be precisely controlled to be stable at ≤8%, and the drying uniformity deviation to be ≤±1%. It is free of clumping, has uniform composition, and can directly proceed to subsequent roasting activation and high-value recovery processes without additional crushing or secondary drying, significantly reducing energy consumption and processing costs in subsequent resource recovery stages.

[0037] This invention constructs an energy system with ultra-low energy consumption, achieving energy savings of over 92% and extremely low operating costs. The system is based on wind and solar energy, supplemented by mechanical and electrical energy, and supplemented by industrial waste heat for emergencies. Over 88% of the drying energy comes from free solar and wind energy, with only a small amount of electricity consumed by mechanical pre-dehydration and equipment operation. The annual utilization rate of industrial waste heat is ≤12%. The comprehensive energy consumption per ton of water evaporated is ≤70,000 kcal, achieving energy savings of over 92% compared to traditional thermal drying technologies.

[0038] This invention features an optimized double-layer insulated greenhouse design, ensuring stable operation year-round and exceptional climate adaptability. The innovative double-layer insulated greenhouse utilizes a 12-15cm double-film air gap structure, resulting in a winter temperature 6-10℃ higher than a single-layer greenhouse. This improves insulation performance by over 45%, allowing for ≥310 days of drying per year. This completely solves the problems of traditional technologies, such as inability to operate in winter and low drying efficiency during the rainy season. Even in rainy southern regions and frigid northern regions, continuous and stable operation throughout the year is achieved, demonstrating exceptional climate adaptability.

[0039] The storage yard area is reused multiple times, increasing land utilization by more than 120%. The idle hard areas of the storage yard are divided into drying units and greenhouse units, which can be operated in rotation according to the season and working conditions. The drying units are the main focus during the dry season, and the greenhouse units are the main focus during the rainy season, realizing the multiple three-dimensional utilization of the storage yard area. Compared with the traditional single open-air drying technology, the land utilization rate is increased by more than 120%.

[0040] The entire process is designed in a closed loop, eliminating secondary pollution and demonstrating excellent environmental performance. This invention completes the entire process of red mud storage and drying within the storage yard, eliminating long-distance transportation and preventing spillage and leachate leakage during transport. All filtrate, leachate, and condensate are treated in a closed loop and then reused, achieving zero wastewater discharge. The operation is carried out in a sealed greenhouse, preventing red mud dust from flying around. The existing impermeable layer of the storage yard ensures no risk of groundwater pollution, fully complying with environmental protection requirements.

[0041] With intelligent control throughout the entire process, minimal reliance on manual labor, and simple operation and maintenance, this invention achieves fully automated control of the entire process from red mud conditioning, mechanical dewatering, rainproof film deployment and retraction, greenhouse ventilation, waste heat start-up and shutdown, and turning operations to redundant unit scheduling through an intelligent central control platform. It has three built-in core models, enabling unmanned operation, significantly reducing labor costs, and ensuring high system stability, making it suitable for large-scale industrial applications.

[0042] With full-chain resource utilization and significant industrial value, this invention is precisely designed to meet the raw material requirements for high-value recovery of all elements in red mud. The dried product has stable moisture content, uniform composition, and no clumping, and can be directly adapted to subsequent full-element recovery processes such as roasting activation, wet leaching, and extraction of valuable metals, greatly reducing the overall processing cost and promoting the development of the red mud resource utilization industry chain.

[0043] The following is a detailed description of the invention using an industrial production line capable of processing 300,000 tons of dry-based red mud annually as an example, in conjunction with the accompanying drawings. All parameters, equipment configurations, and area designs have undergone rigorous industrial calculations and feasibility studies, and can be directly implemented in engineering projects. The scope of protection of this invention is not limited to the following embodiment; all equivalent modifications made based on the technical solutions of this invention are included within the scope of protection of this invention.

[0044] I. Design Fundamentals and Material Balance Accounting 1. Design Fundamentals Processing capacity: 300,000 tons of dry red mud per year, 310 effective operating days per year, and 968 tons of dry red mud per day (with 3% capacity redundancy reserved). Raw material characteristics: Bayer process red mud, original moisture content 65%, dry basis bulk density 1.3 tons / m³, wet red mud (moisture content 65%) bulk density 1.8 tons / m³; Work site: Existing hardened red mud storage area, storage period of 5 years, bearing capacity ≥12t / ㎡, existing 1.5mm HDPE seepage prevention layer is intact and meets environmental protection requirements; Design goals: Both the drying unit and the greenhouse unit should have an area redundancy of ≥50%; the final dried red mud should have a stable moisture content of ≤8% and a uniformity deviation of ≤±1%; the annual industrial waste heat utilization rate should be ≤12%; and the dried products should be directly compatible with subsequent roasting activation and high-value recovery processes of all elements.

[0045] 2. Full-process material balance accounting (based on a daily processing capacity of 968 tons of dry red mud) sheet Process Stage Feed moisture content Output moisture content Daily feed volume (wet basis) (tons) Daily wet basis output (tons) Daily water removal capacity (tons) Total water removed annually (10,000 tons) Primitive red mud 65% - 2766 - - - S1 Mechanical Dehydration 65% 35% 2766 1489 1277 39.59 S2 Natural air drying 35% 16% 1489 1152 337 10.45 S3 Greenhouse Drying 16% 7% 1152 1041 111 3.44 total - - - - 1725 53.48 Note: With a 50% area redundancy design, the moisture content of the material discharged by natural sun drying is stably reduced to 16%, and that of the material discharged from the greenhouse is stably reduced to 7%, which fully meets the raw material requirements for subsequent full element recovery. The subsequent roasting process can reduce energy consumption by more than 15%.

[0046] 3. Energy Structure Accounting Annual total energy demand for drying: 2508 kJ of latent heat of vaporization is required to evaporate each ton of water. The total annual water evaporation is 534,800 tons, and the total energy demand is approximately 1.34 × 10¹¹ kJ. Energy supply structure: ①Solar and wind energy provide 1.18×10¹¹kJ, accounting for 88.06%, completely free; ② Mechanical and electrical energy (plate and frame filter press, equipment operation): 1.0×10¹ 0 kJ, accounting for 7.46%; ③ Emergency replenishment of industrial low-temperature waste heat: 6×10 9 kJ, accounting for 4.48%, far below the design target of ≤12%; Energy saving effect: Compared with traditional thermal drying technology, it saves more than 92.5% of energy.

[0047] II. Design of Core Unit Area and Quantity (including 50% area redundancy) 1. Redundant partitioned controllable natural drying unit design Theoretical capacity required area: Designed drying cycle of 30 days, processing 1 batch per day, wet base amount per batch of 1489 tons, paving thickness of 30cm, wet red mud bulk density of 1.7 tons / m³, minimum paving area required per batch = 1489 / 1.7 / 0.3≈2920㎡, requiring 30 independent units, total area = 30×2920=87600㎡=131.4 acres; 50% area redundancy design: 15 new redundant units are added, bringing the total number of units to 45. The design area of ​​a single unit is 58m × 52m = 3016㎡, and the total drying area is 45 × 3016 = 135720㎡ = 203.6 acres. The redundancy rate is 55%, which meets the design requirement of ≥50%. Unit functional division: 30 units are basic operation units, and 15 units are redundant emergency units, which can be flexibly activated according to climate conditions; when the working conditions are good in the dry season, the paving thickness can be reduced to 25cm, the drying cycle can be shortened to 20 days, and only 20 units are needed to meet the production capacity. The remaining units can be used as rotation operation areas or emergency reserve areas. Seepage prevention design: Utilize the existing 1.5mm HDPE geomembrane + 30cm compacted seepage prevention clay structure in the stockpile. Set up a circumferential leachate collection ditch around each unit with a slope of 3‰, and connect it to the leachate closed-loop treatment unit. Supporting equipment: Each unit is equipped with one set of ground-mounted rainproof membrane full-coverage system (0.45mm thick HDPE geomembrane, mobile film rolling machine with a moving speed of 1.2m / s), and the whole area is equipped with 3 No.1 unmanned electric compost turners (GNSS navigation, turning width 2.5m) for turnover operation.

[0048] 2. Design of Redundant Deep Drying Units in Double-Layer Insulated Greenhouses Theoretical capacity required area: Designed drying cycle of 2 days, processing 1 batch per day, wet base amount per batch of 1152 tons, paving thickness of 20cm, wet red mud bulk density of 1.5 tons / m³, minimum paving area required per batch = 1152 / 1.5 / 0.2 = 3840㎡, requiring 2 independent units, total area = 2 × 3840 = 7680㎡ = 11.5 acres; 50% Area Redundancy Design: Add 1 basic unit + 6 redundant units, for a total of 9 units. Each unit is designed as 9 connected greenhouses, with a span of 8m and a length of 50m. The total area of ​​a single unit = 9 × 8 × 50 = 3600㎡, and the total greenhouse area = 9 × 3600 = 32400㎡ = 48.6 acres. The redundancy rate is 322%, which meets the design requirement of ≥50% and can cope with extreme continuous rainy weather. Unit functional division: 3 units are basic operation units, and 6 units are redundant emergency units; during winter / continuous rainy weather, all 9 units are activated, the paving thickness is reduced to 15cm, and production capacity is guaranteed to be stable; when the working conditions are good, only 2 units are needed to meet the production capacity, and the remaining units can be used as temporary drying areas or precision drying areas to reduce the red mud moisture content to 3%-5%, which is suitable for special resource utilization processes. Greenhouse structural parameters: single-span shoulder height 2.0m, top height 3.2m, hot-dip galvanized rectangular steel pipe frame, wind resistance level 10, snow load 0.5kN / ㎡; outer layer 0.15mm high-transmittance PO film (transmittance ≥88%), inner layer 0.12mm anti-drip PO film, 12cm air gap in the middle, thermal conductivity ≤2.6W / (㎡・K); Supporting equipment: Each greenhouse unit is equipped with one second unmanned electric compost turner (equipped with a high-precision online moisture content detector), one set of waste heat emergency auxiliary system (finned tube heat exchanger with a heat exchange area of ​​1200㎡, variable frequency blower with an air volume of 250000m³ / h), one set of humid and hot air waste heat recovery module, and environmental monitoring sensors arranged at a density of 1 per 100㎡.

[0049] 3. Total land area calculation The total drying area is 203.6 mu, the total greenhouse area is 48.6 mu, plus 10 mu of auxiliary areas such as conditioning, mechanical dehydration, and central control, for a total land area of ​​262.2 mu. All of the land is built using the existing hardened area of ​​the red mud stockpile, with zero new land acquisition. Area ratio: The ratio of the total area of ​​the drying area to the total area of ​​the greenhouse area is 4.19:1, which is within the range of claims (2-6):1, and can be flexibly adjusted according to local climate conditions.

[0050] III. List of Major Equipment Configurations for the Entire System (300,000 tons / year capacity, including 50% redundancy) sheet Serial Number System Unit Equipment Name Specifications / Parameters quantity Remark 1 Red mud conditioning unit Closed conditioning tank Effective volume 600m³, carbon steel lined with rubber for corrosion protection 2 seats One for use, one for backup 2 Dispersant Precision Metering Addition Device Screw metering pump, flow rate 0-600L / h, metering accuracy ±0.5% 2 sets 3 Variable frequency stirring mechanism Power 45kW, speed 120-180r / min, blades lined with rubber for corrosion protection 2 sets Matching conditioning tank 4 Mechanical dehydration unit High-pressure diaphragm filter press Filter area 800㎡, design pressure 1.6MPa, filter chamber volume 20m³ 5 units Three-in-one configuration with two backups, including redundancy. 5 Variable frequency sludge feed pump Flow rate 120 m³ / h, head 1.2 MPa, fluoropolymer lining for corrosion protection 5 units Matching filter press 6 Filtrate collection tank Effective volume 400m³, PE anti-corrosion 2 seats 7 Enclosed material conveyor belt 800mm bandwidth, 1.2m / s speed, 35m length 3 Redundancy 8 Redundant drying unit Ground-mounted rainproof film full coverage system The track is 58m long, the mobile film winding machine has a power of 3kW, and it produces 0.45mm thick HDPE geomembrane. 45 sets One set per unit 9 First unmanned electric compost turner Diesel-powered, turning width 2.5m, turning depth 0-40cm, GNSS navigation, positioning accuracy ±5cm 3 units Turnover operations 10 Leachate collection network HDPE pipe, DN250, slope 3‰ 1 set Full coverage 11 Redundant greenhouse units Double-layer insulated multi-span greenhouse unit Nine interconnected buildings, each measuring 8m x 50m, with a total area of ​​3600㎡, featuring a double-membrane structure and wind resistance up to level 10. 9 sets Includes 6 redundant sets 12 Second unmanned electric turning machine Electrically driven, with a turning width of 2.0m and a turning depth of 0-30cm, equipped with an online moisture content detector. 9 units One unit per greenhouse 13 Finned tube heat exchanger Heat exchange area 1200㎡, design pressure 1.0MPa, material 304 stainless steel 9 sets One set per greenhouse 14 Variable frequency blower Air volume 250,000 m³ / h, air pressure 1500 Pa, power 132 kW 9 units One unit per greenhouse 15 Underground ventilation duct PVC pipe, DN200, strip air outlet spacing 1.8m 9 sets One set per greenhouse 16 Humid and hot air waste heat recovery module Shell-and-tube condenser with a heat exchange area of ​​800 m² and a condensate collection tank of 50 m³. 9 sets One set per greenhouse 17 Environmental monitoring sensors Temperature, humidity, light intensity, and wind speed sensors, with an accuracy of ±0.3℃ / ±1.5%RH. 324 36 per greenhouse 18 Filtrate closed-loop treatment unit Sedimentation tank Effective volume 600m³, reinforced concrete structure, corrosion protected. 2 seats 19 Multi-media filtration device Processing capacity 120 m³ / h, quartz sand + activated carbon filtration 2 sets One for use, one for backup 20 softening device 120 m³ / h processing capacity, sodium ion exchange resin 2 sets One for use, one for backup 21 Reclaimed water tank Effective volume 1200m³, PE anti-corrosion 1 seat 22 Intelligent Central Control Platform Industrial PCs, displays, PLC control cabinets Equipped with three core algorithm models, enabling real-time acquisition and control of all parameters. 1 set Central control room deployment 23 Data acquisition and communication module 4G / Ethernet communication, compatible with all sensors and devices 1 set IV. Feasibility Study 1. Technical Feasibility Study Feasibility of using the stockpile: The existing red mud stockpile has been stored for 5 years and the surface hardness is ≥12t / ㎡, which fully meets the load requirements of transport vehicles, turning machines and greenhouse frames, and no additional foundation treatment is required; the original seepage prevention layer is intact and meets environmental protection requirements, so no additional seepage prevention treatment is required, and it is technically feasible.

[0051] Feasibility of ensuring production capacity: With a 50% area redundancy design, even in extreme weather such as winter / continuous rainy days when the effective drying days are reduced by 40%, the annual processing capacity of 300,000 tons can still be guaranteed by activating redundant units, with a capacity deviation of ≤±2%, which fully meets the requirements for continuous industrial operation.

[0052] Feasibility of drying quality: Through redundant area design, precise spreading, intelligent turning and online moisture content monitoring, the moisture content of dried red mud is stable at ≤7%, the uniformity deviation is ≤±1%, there is no clumping and the composition is uniform. It can be directly entered into subsequent roasting activation, wet leaching and other full element recovery processes without additional pretreatment, which is fully compatible with the requirements of high-value utilization.

[0053] Mature and reliable equipment: All core equipment (high-pressure diaphragm filter press, multi-span greenhouse, heat exchanger, unmanned compost turner) are mature industrial equipment, with no non-standard customized equipment. They are simple to operate and maintain, have a low failure rate, and are technically mature and reliable.

[0054] Intelligent feasibility: The intelligent central control platform has three core models built-in, which can realize unmanned operation of the entire process. The meteorological linkage model can predict rainfall in advance and automatically control the opening and closing of the rainproof membrane to avoid red mud from becoming humid. The system has high operational stability.

[0055] 2. Environmental feasibility study Zero wastewater discharge: All filtrate, leachate, and condensate are treated in a closed loop and then reused, with no wastewater discharged externally, thus avoiding groundwater pollution.

[0056] Waste gas emissions meet standards: The greenhouse operates in a closed manner, with no red mud or dust flying around; the waste heat system does not burn fossil fuels and has no waste gas emissions, meeting the requirements of the "Integrated Emission Standard for Air Pollutants".

[0057] Seepage prevention and safety: Utilizing the existing double-layer seepage prevention structure of the stockyard, the permeability coefficient is ≤1×10⁻ 7 The flow rate is cm / s, which meets the requirements of the "Standard for Pollution Control of Hazardous Waste Landfill" and poses no risk of soil or groundwater pollution.

[0058] Complete resource utilization of solid waste: After drying, the red mud is used for high-value recycling of all elements, with no secondary solid waste generated, which fully meets environmental protection requirements.

[0059] The above description is only a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0060] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for precise drying of red mud in situ with redundant design of a stockpile, characterized in that, The following steps are performed in sequence: S1. Red mud conditioning and pretreatment: The raw red mud with a moisture content of 60%-70% produced by the alumina plant is directly transported to the conditioning tank in the red mud stockpile. 0.1%-0.3% of the dry weight of the red mud is added to reduce the viscosity of the red mud and improve the dehydration permeability and subsequent drying uniformity. The dispersant is a composite system of polycarboxylate dispersant and inorganic inert filler. The filler accounts for 0.5%-1% of the dry weight of the red mud. It reduces the particle adhesion and forms a skeleton on the surface of the red mud, improving permeability and reducing the mechanical dewatering moisture content from ≤36% to ≤30%. A microwave emitting device is added to the conditioning tank to break the hydration film of red mud particles by using the microwave thermal effect, improve the adsorption effect of dispersant, shorten the stirring time from 10-15 min to 5-8 min, and reduce energy consumption. S2. Mechanical deep pre-dehydration stage: Add a trace amount of hydrophobic agent, such as organosilicon emulsion or ≤0.05% dry basis, to the dehydrated red mud to reduce the hydrophilicity of the red mud surface, accelerate the evaporation of moisture during the natural drying stage, and shorten the drying cycle by 20%-30%; The conditioned red mud is fed into a high-pressure diaphragm filter press in the stockpile. The dewatering pressure is controlled at 0.8-1.2 MPa and the holding time is 25-35 min. The moisture content of the red mud is stably reduced to ≤36%, and pre-dewatered red mud A is obtained. The filtrate produced by dewatering is collected and reused in a closed loop. This stage only consumes mechanical and electrical energy. S3, In-situ Redundant Controllable Natural Drying Stage in the Stockpile: The pre-dehydrated red mud A is spread in batches to the independent drying units in the hardened area of ​​the red mud stockpile, with a spreading thickness of 25-35cm. A ground-mounted rainproof film full-coverage system is used in combination with meteorological data to intelligently control the opening and closing of the film. In rainless weather, the film is opened to utilize solar and wind energy in the open area of ​​the stockpile for dehydration. The pile is turned over regularly to break the crust. The film is closed before rainfall to prevent moisture increase. By using an area redundancy design of ≥50%, the water content of red mud is stably reduced to ≤16%, resulting in pre-dehydrated red mud B, and the leachate is collected and reused in a closed loop. S4, Double-layer insulated greenhouse redundant deep drying stage: The pre-dehydrated red mud B is transferred to the double-layer insulated greenhouse unit built in the hard area of ​​the stockpile and spread out with a thickness of 15-25cm. Solar energy and wind energy are the core drying energy sources. Only in winter / continuous rainy weather is industrial low-temperature waste heat used to heat the air, combined with intelligent ventilation and periodic turning. By using an area redundancy design of ≥50%, the moisture content of red mud is precisely reduced to ≤8%, resulting in dried red mud with uniform composition and no clumping, which directly meets the raw material requirements for subsequent roasting activation and high-value recovery of all elements.

2. The method and system for precise drying of red mud with in-situ redundancy design in the stockpile according to claim 1, characterized in that, In S3, the hardened area of ​​the red mud stockpile is the surface layer of the red mud stockpile with a stockpile age of ≥3 years and a bearing capacity of ≥12t / ㎡, requiring no additional foundation treatment; The drying units adopt a zoned and batch-based design, with each drying unit having an area of ​​2000-3000㎡ and 2-4 independent operating zones. The drying units and greenhouse units can be operated alternately, realizing the secondary and multiple three-dimensional utilization of the storage area. The reserved redundant area can be flexibly used according to climate conditions and fluctuations in feed volume to ensure stable annual production capacity.

3. The method and system for precise drying of red mud with in-situ redundancy design in the stockpile as described in claim 2, characterized in that, In S3, the control logic of the ground-mounted rainproof film full-coverage system is as follows: The central controller receives high-precision weather forecasts for the next 4-6 hours. When the forecast rainfall is ≥3mm, relative humidity is ≥90%, or there is snowfall / fog, it drives the film rolling mechanism to complete the full film spreading within 20 minutes. When the ambient temperature is ≥15℃, the light intensity is ≥8000lx, the wind speed is 1~6m / s and there is no rain warning, the film is completely rolled up; the turning operation is carried out by an unmanned electric turning machine, the turning depth is 25~35cm, the turning frequency is 1-2 days / time, the turning path is a reciprocating full coverage, and the positioning accuracy is ≤±5cm.

4. The method and system for precise drying of red mud with in-situ redundancy design in the stockpile according to claim 1, characterized in that, In S4, the double-layer insulated greenhouse is a north-south oriented continuous steel structure, using an inner and outer double-layer high-transmittance PO film structure, forming a 12-15cm sealed air insulation layer between the two layers, with a thermal conductivity coefficient ≤2.6W / (㎡・K); the span of a single structure is 6-8m, the shoulder height is 1.8-2.2m, the top height is 2.8-3.5m, and the length is 40-60m. The frame is made of hot-dip galvanized high-frequency welded rectangular steel pipe, with a wind resistance level ≥10 and a snow load ≥0.5kN / ㎡. The outer film is an ultraviolet-resistant PO film with a light transmittance ≥88%, and the inner film is an anti-drip insulation film. The overall airtightness of the greenhouse is ≥92%.

5. The method and system for precise drying of red mud with in-situ redundancy design in the stockpile according to claim 4, characterized in that, In S4, the drying energy in the greenhouse is mainly solar and wind power: On sunny days, the greenhouse temperature inside the shed is raised to 45-65℃ through the greenhouse effect of the double-layer film. With the intelligent opening and closing of the top skylight and side ventilation windows, the air convection formed by the pressure difference between the inside and outside of the shed carries away moisture. When the temperature inside the greenhouse is ≤8℃ in winter or the relative humidity is ≥85% during continuous rainy weather, the air is heated to 35-45℃ and relative humidity ≤28% by using 0.2-0.8MPa low-grade steam, 40-60℃ circulating water, or 150-250℃ flue gas waste heat from power plants / alumina plants. The annual industrial waste heat utilization rate is ≤12%.

6. The method and system for precise drying of red mud with in-situ redundancy design in the stockpile according to claim 5, characterized in that, In S4, the intelligent control logic inside the greenhouse is as follows: When the temperature inside the greenhouse is ≥45℃ and the relative humidity is ≥60%, the top skylight and side ventilation windows should be opened simultaneously, with a ventilation volume of 1200-1800m³ / (h・㎡). When the temperature inside the shed is ≤8℃, close the ventilation windows and start the waste heat auxiliary system; the turning operation is carried out by an unmanned electric turning machine, with a turning depth of 15~25cm and a turning frequency of 1-3 days / time. The turning machine is equipped with an online detection probe for the moisture content of red mud, and adjusts the operating parameters in real time to ensure that the drying uniformity deviation is ≤±1%.

7. A red mud precision drying system with in-situ redundancy design for stockpile sites, used in the red mud precision drying method with in-situ redundancy design for stockpile sites as described in any one of claims 1-6, characterized in that, It includes a red mud conditioning unit, a mechanical dehydration unit, a redundant zoned controllable natural drying unit, a redundant deep drying unit in a double-layer insulated greenhouse, a filtrate closed-loop treatment unit connected to each unit, and an intelligent central control platform for full-process control. The red mud conditioning unit and mechanical dewatering unit are both located at the feeding end of the red mud stockpile and are directly connected to the red mud conveying pipeline of the alumina plant, eliminating the need for long-distance red mud transportation. The redundant partitioned controllable natural drying unit is an independent partition divided from the hard solid area of ​​the red mud stockpile. The total drying area is reserved with ≥50% redundancy. Each partition is equipped with an independent ground-mounted rainproof membrane full-coverage system, a first unmanned electric turning machine and a circumferential leachate collection ditch. The original impermeable layer of the stockpile is used as the impermeable structure, and no additional impermeable treatment is required. The redundant deep drying unit of the double-layer heat-insulating greenhouse is built in the idle hardened area of ​​the red mud dump. The total greenhouse area is reserved with ≥50% redundancy, including at least 9 independent connected greenhouse units. Each greenhouse unit is equipped with an independent second unmanned electric turning machine, a waste heat emergency auxiliary system, a greenhouse environment monitoring module and a humid and hot air waste heat recovery module. The closed-loop filtrate treatment unit collects the filtrate, leachate and condensate generated by each unit, and after treatment, all of them are reused for red mud conditioning and plant production, achieving zero wastewater discharge. The intelligent central control platform is electrically connected to the equipment, monitoring modules, and actuators of each unit. It has built-in meteorological linkage model, production capacity guarantee model, moisture content precise control model, AI moisture content prediction model, digital twin storage yard system, and multi-sensor fusion perception to achieve unmanned operation of the entire process. AI moisture content prediction model: Integrating meteorological data, material data, and equipment data, it uses machine learning to predict the drying rate of red mud, adjusts operating parameters in advance, and achieves predictive control of moisture content, reducing uniformity deviation to ≤±0.5%; Digital Twin Stockyard System: Constructs a digital twin model of the entire stockyard drying process, mapping the material status, equipment operation, and environmental parameters of the drying unit and greenhouse unit in real time, supporting virtual simulation scheduling, and avoiding capacity fluctuations in advance; Multi-sensor fusion sensing: Near-infrared spectral sensors are added to the turning machine to detect the composition and moisture content of red mud in real time, realizing online monitoring of dual parameters of moisture content and composition, and adapting to the raw material requirements of different subsequent high-value recycling processes.

8. The method and system for precise drying of red mud with in-situ redundancy design in the stockpile according to claim 7, characterized in that, The ratio of the total area of ​​the redundant partitioned controllable natural drying unit to the total area of ​​the double-layer insulated greenhouse unit is (2-6):1, which can be adjusted according to local climate conditions; the original impermeable layer of the stockpile is a 1.5mm thick HDPE smooth impermeable membrane + 30cm thick compacted impermeable clay, with a permeability coefficient ≤1×10⁻ 7 cm / s, meeting the standards for leaching prevention in hazardous waste landfills; the reserved redundant area can be used as an emergency reserve area and a rotation operation area to cope with extreme weather, fluctuations in feed volume, and equipment maintenance.

9. The method and system for precise drying of red mud with in-situ redundancy design in the stockpile according to claim 7, characterized in that, The waste heat emergency auxiliary system includes a finned tube heat exchanger, a blower, an underground air distribution duct, and an electric air volume regulating valve. The heat source side of the heat exchanger is connected to the low-grade waste heat pipeline network of the power plant / alumina plant and is only activated during extreme weather. The humid air waste heat recovery module includes a shell-and-tube condenser and a condensate collection tank. It recovers heat from the humid air discharged from the shed by exchanging heat and using it to preheat the ambient air entering the heat exchanger. The condensate is sent to the filtrate closed-loop treatment unit.

10. The method and system for precise drying of red mud with in-situ redundancy design in the stockpile according to claim 7, characterized in that, The intelligent central control platform's capacity assurance model can automatically schedule the activation and operation parameters of redundant units based on real-time meteorological data, red mud feed volume, and drying progress, ensuring that the annual processing capacity deviation is ≤±2%. The precise moisture content control model can automatically adjust the paving thickness, turning frequency, and ventilation volume according to the raw material requirements of the subsequent full-element recovery process, so as to precisely control the moisture content of the dried red mud within the range of 3%-8%.

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