A method for calcining solid waste tailings by using a vertical mill grinding in cooperation with a rotary kiln

Abstract

This invention discloses a method and system for treating solid waste tailings using vertical mill grinding combined with rotary kiln calcination. The method includes: crushing and homogenizing the solid waste tailings and identifying their components; injecting a reactive coating precursor liquid during the vertical mill grinding process, and forming reactive coated particles with a pore-inducing layer, a phase-inversion activation layer, and a slow-release protective layer through layered granulation; feeding the reactive coated particles into a rotary kiln for segmented atmospheric catalytic calcination, transforming the mineral phase containing the target element from a difficult-to-leach phase to an easily leached phase; subjecting the calcined particles to hot-quenching negative pressure pulse wetting before cooling to room temperature to obtain an activated slurry; and then sequentially performing primary acid leaching, primary solid-liquid separation, secondary deep leaching, and in-situ magnetic capture, magnetic separation, and desorption to obtain a target element-enriched solution. This invention can improve the release, leaching, and enrichment efficiency of target elements in solid waste tailings, and reduce acid and alkali consumption and tail gas treatment pressure.

Description

Technical Field

[0001] This invention relates to the field of industrial solid waste resource utilization technology, specifically a method for treating solid waste tailings by using vertical mill grinding in conjunction with rotary kiln calcination. Background Technology

[0002] Industrial solid waste refers to the large quantities of byproducts generated during mining, mineral processing, metallurgical smelting, chemical production, and energy utilization. Common solid waste tailings include bauxite tailings, coal gangue, smelting tailings, and chemical tailings. These solid waste tailings are typically characterized by large discharge volumes, complex compositions, stable mineral phases, and uneven particle size distribution. In addition to conventional components such as silicon, aluminum, iron, calcium, and magnesium, they may also contain target elements with recycling value, such as scandium, gallium, rhenium, vanadium, cerium, and neodymium. If solid waste tailings are stored for a long period, they not only occupy land resources but may also generate environmental risks such as dust and leaching pollution. Therefore, the reduction, harmlessness, and resource recovery of solid waste tailings are of great significance.

[0003] Existing solid waste tailings resource utilization processes typically include steps such as crushing, screening, grinding, homogenization, roasting, acid leaching, alkali leaching, magnetic separation, extraction, and adsorption. For example, patent document CN103898330B discloses a method for comprehensively recovering valuable metals such as iron, aluminum, scandium, titanium, and vanadium from red mud. This method mainly involves steps such as red mud reduction roasting, magnetic separation, ammonia leaching of alumina, absorption of SO2 from coal-fired flue gas by washing slag, high-concentration acid hydrolysis, and subsequent extraction to achieve valuable metal recovery. Patent document CN111842411B discloses a method for the full resource utilization of red mud, which involves steps such as red mud washing, concentrated acid rotary kiln stirring leaching, precipitation separation, ion exchange enrichment of scandium, vanadium, titanium, and gallium, and evaporation crystallization recovery of ammonium sulfate to achieve comprehensive utilization of red mud. Patent document CN107058744A discloses a method for the comprehensive recovery of useful metals from red mud, which involves mixing and roasting red mud with an alkali-enhancing agent and a reducing agent, followed by sequential treatments such as water leaching to recover aluminum, magnetic separation to recover iron, acid leaching to recover scandium, and precipitating scandium. The aforementioned existing technologies can recover some valuable metals from red mud or similar solid waste to a certain extent, but their process focus is mainly on post-processing steps such as conventional roasting, leaching, magnetic separation, precipitation, ion exchange or extraction. They fail to fully solve the problems of insufficient release of low-content target elements, limited mass transfer, and low degree of multi-media recycling in complex tailings.

[0004] Specifically, the grinding step in existing technologies is typically used primarily to reduce material particle size and increase specific surface area. Vertical mills or ball mills are mostly limited to pulverization and drying, rarely working synergistically with the introduction of reactive components, particle surface structure regulation, or subsequent mineral phase transformation processes. The aforementioned schemes CN103898330B, CN111842411B, and CN107058744A also fail to disclose the simultaneous injection of reactive coating precursor liquid during vertical mill grinding, and further fail to form gradient multilayer reactive coated particles with a pore-inducing layer, a phase-inversion activation layer, and a slow-release protective layer. Therefore, existing technologies struggle to achieve uniform pre-loading of reactive components during the grinding stage, and also find it difficult to control pore formation, reactive component release, and target element mineral phase transformation during subsequent calcination through particle surface coating structures.

[0005] In the calcination and leaching stages, existing rotary kilns or roasting furnaces mostly employ methods such as ordinary roasting, reduction roasting, or concentrated acid stirring leaching, primarily focusing on the overall heat treatment or overall acid leaching effect of the material. They lack a synergistic design targeting the stepwise pyrolysis of the coating layer, the formation of internal pores within the particles, and the directional phase transformation of target elements. Furthermore, current processes typically involve naturally or conventionally cooling the high-temperature calcined material before feeding it into the leaching system, failing to fully utilize the thermal shock generated during rapid cooling of high-temperature particles, and neglecting to promote the entry of the liquid medium into the microcracks and interconnected channels within the calcined particles using negative pressure pulses. In addition, current target element enrichment methods often involve ion exchange, extraction, or precipitation after leaching, failing to combine secondary deep leaching with in-situ capture using magnetically selective adsorption materials. Therefore, there are still shortcomings in reducing interference from impurities in complex leachates and improving the immediate capture efficiency of low-content target elements.

[0006] On the other hand, the kiln tail gas generated during rotary kiln calcination typically contains dust, sulfur-containing components, and nitrogen-containing components. Existing processes mostly treat this as an end-of-pipe pollutant or only use a portion of its components for single absorption treatment, failing to fully convert the sulfur- and nitrogen-containing components in the tail gas into process media that can be reused in primary acid leaching, secondary deep leaching, and precursor liquor conditioning. Furthermore, alkaline components such as CaO and MgO in solid waste tailings or leaching residues, as well as acid leaching mother liquor, are not fully recycled.

[0007] Patent document CN113582224B discloses a method for the resource utilization of molten salt chlorination slag extracted from titanium dioxide waste acid, which involves water quenching of molten salt chlorination slag and then leaching it with titanium dioxide waste acid; CN109395692B discloses a modified magnetic perlite adsorbent and its method for enriching rare earths from yttrium rare earth wastewater, which utilizes a magnetic adsorbent to adsorb and enrich rare earth ions in rare earth wastewater. The above technologies involve leaching after high-temperature slag quenching and enriching rare earths with magnetic adsorbents, respectively. However, they do not integrate the following technical solutions: vertical mill spray grinding, gradient multi-layer reactive particle coating, rotary kiln segmented phase inversion, hot-quenched negative pressure pulse wetting, two-stage deep leaching in-situ magnetic capture, and resource utilization of kiln tail gas for pretreatment of the precursor liquid. Therefore, existing technologies still struggle to simultaneously address the problems of insufficient release of target elements in complex solid waste tailings, limited liquid-phase mass transfer, low efficiency of immediate capture of low-content target elements, and insufficient recycling of process media.

[0008] Therefore, based on the above problems, there is an urgent need to provide a solid waste tailings treatment method and system that can synergistically design grinding and coating, particle structure control, segmented calcination and phase inversion, hot quenching and negative pressure wetting, graded leaching, in-situ collection, and resource recovery and reuse of kiln tail gas, so as to improve the release, leaching and enrichment efficiency of conventional metals and target elements in solid waste tailings, and reduce acid and alkali consumption and tail gas and waste liquid treatment pressure. Summary of the Invention

[0009] The technical problem this invention aims to solve is to overcome the shortcomings of existing solid waste tailings treatment processes, such as low release efficiency of target elements, insufficient connection between calcination activation and leaching processes, difficulty in separating and enriching conventional metals and low-content target elements, and low recycling rate of kiln tail gas and acid-base media. This invention provides a method for treating solid waste tailings using a vertical mill grinding process combined with rotary kiln calcination. Through the synergistic treatment of vertical mill spray grinding, gradient multi-layer reactive coating particle preparation, rotary kiln segmented atmosphere catalytic calcination, hot-state quenching negative pressure pulse wetting, staged leaching, in-situ magnetic capture, and resource recovery of kiln tail gas, this method improves the release, leaching, and enrichment efficiency of conventional metals and target elements in solid waste tailings, while reducing acid-base consumption and the pressure of tail gas and waste liquid treatment. This effectively solves the problems in the background technology.

[0010] To achieve the above objectives, the present invention provides the following technical solution: a method for treating solid waste tailings by using a vertical mill for grinding and a rotary kiln for calcination, comprising the following steps: Step 1: Feed the solid waste tailings raw material into the crushing and homogenization unit for crushing and homogenization treatment, so that the particle size of the solid waste tailings raw material is 10-30mm. Step 2: The solid waste tailings raw material processed in Step 1 is sent to the component identification unit for component identification, and the reactive coating precursor liquid is prepared according to the identification results. Step 3: The solid waste tailings raw material, after component identification, is fed into the vertical mill spray grinding unit for grinding. During the grinding process, a reactive coating precursor liquid is sprayed in to make the fineness of the ground powder reach 200 mesh, and the sieve residue is no more than 10%. Step 4: The powder obtained in Step 3 is fed into the layered granulation unit for granulation, and during the granulation process, pore-inducing components, phase-inversion activating components and slow-release film-forming components are introduced in sequence to form reactive coated particles. The reactive coated particles include a solid waste tailings powder core and a gradient multilayer reactive coating layer covering the outside of the solid waste tailings powder core. The gradient multilayer reactive coating layer includes a pore induction layer, a phase inversion activation layer and a slow-release protection layer arranged sequentially from the inside to the outside. Step 5: The reactive coated particles are fed into a rotary kiln for staged atmosphere catalytic calcination. Staged atmosphere catalytic calcination includes preheating and desorption, progressive cracking of the coating layer, and directional phase inversion, which are carried out sequentially along the material movement direction. During the progressive cracking of the coating layer, the pore-inducing layer decomposes to form a pore structure, and the phase inversion activation layer releases reactive gases and / or forms a molten salt activation layer. During the directional phase inversion process, the mineral phase containing the target element in the solid waste tailings is transformed from a difficult-to-leach phase to an easily leached phase, resulting in calcined particles and kiln tail gas. Step 6: The calcined particles obtained in Step 5 are introduced into the hot quenching negative pressure leaching unit before being cooled to room temperature, so that the calcined particles come into contact with the weakly acidic circulating liquid or circulating mother liquor. A negative pressure pulse is applied to the closed leaching chamber through a negative pressure pulse generator, so that the weakly acidic circulating liquid or circulating mother liquor enters the micro-cracks and connecting channels inside the calcined particles to obtain an activated slurry. The temperature of the calcined particles entering the hot-quenched negative pressure leaching unit is 450–850℃; the temperature of the weakly acidic circulating liquid or circulating mother liquor is 20–80℃; the contact time between the calcined particles and the weakly acidic circulating liquid or circulating mother liquor is 10s–10min; the absolute value of the negative pressure of the negative pressure pulse is 5–80kPa, the duration of a single negative pressure pulse is 2–120s, and the number of negative pressure pulse cycles is 1–20. Step 7: The activated slurry obtained in Step 6 is sent to the primary acid leaching unit for primary acid leaching, so that one or more of iron, aluminum, and copper preferentially enter the liquid phase. Then it is sent to the primary solid-liquid separation unit for primary solid-liquid separation to obtain primary leachate and primary leachate residue. The first-stage acid leaching uses a dilute sulfuric acid system with a mass concentration of 5-25 wt%, a liquid-to-solid ratio of 3:1-8:1 mL / g, a leaching temperature of 60-110℃, and a leaching time of 1-4 h. Step 8: The primary leaching residue obtained in Step 7 is sent to the secondary deep leaching and magnetic trapping unit for secondary deep leaching. During the secondary deep leaching process, magnetic selective adsorption material is added to allow one or more target elements among scandium, gallium, rhenium, vanadium, cerium, and neodymium to be trapped in situ during the leaching process. The secondary deep leaching uses a nitric acid system or a nitric acid-containing composite acid system, wherein the mass concentration of nitric acid in the nitric acid or composite acid system is 20-45 wt%, the liquid-solid ratio is 3:1-10:1 mL / g, the leaching temperature is 80-130℃, and the leaching time is 1-6h. Step 9: The magnetic selective adsorption material loaded with the target element is sent into the magnetic separation and desorption unit. The magnetic selective adsorption material is separated by an external magnetic field and then desorbed to obtain the target element enrichment solution. Step 10: The kiln tail gas obtained in Step 5 is sent to the tail gas separation and purification and resource utilization unit for dust removal, separation and purification and resource utilization conversion. At least part of the sulfur-containing tail gas is converted into sulfate-containing absorbent through the sulfur-containing tail gas oxidation absorption branch, and at least part of the nitrogen-containing tail gas is converted into nitrate-containing absorbent through the nitrogen-containing tail gas oxidation absorption branch. The sulfate-containing absorbent is recycled to the primary acid leaching unit and / or the precursor liquid conditioning unit, and the nitrate-containing absorbent is recycled to the secondary deep leaching and magnetic capture unit and / or the precursor liquid conditioning unit. The precursor liquid after conditioning by the precursor liquid conditioning unit is recycled to the vertical mill spray grinding unit.

[0011] Among them, steps two to six also include a mineral phase-tail gas-negative pressure wetting linkage control step: determining the mineral phase activation difficulty level based on the main oxide content, target element content, moisture content, loss on ignition, and mineral phase composition in the solid waste tailings raw material, and adjusting the ratio of reactive coating precursor liquid, pore-inducing component, phase inversion activation component, and slow-release film-forming component according to the mineral phase activation difficulty level; the phase inversion activation layer includes dual-temperature zone controllable pyrolysis microcapsules, and the dual-temperature zone controllable pyrolysis microcapsules include a first microcapsule that releases reactive components during the stepwise pyrolysis process of the coating layer. Furthermore, during the directional phase inversion process, second microcapsules release phase inversion promoting components; during the rotary kiln segmented atmosphere catalytic calcination process, the temperature, heating rate, and / or residence time of the coating layer are adjusted according to the peak release time of sulfur-containing components, nitrogen-containing components, and / or water vapor in the kiln tail gas; during the hot-quenching negative pressure pulse immersion process, the endpoint of the negative pressure pulse immersion is determined according to the exhaust volume, pressure recovery time, and / or the change rate of conductivity of the activated slurry in the sealed leaching chamber; and during the secondary deep leaching process, magnetically selective adsorption materials are added in a segmented manner.

[0012] Furthermore, the mineral phase-tail gas-negative pressure wetting linkage control steps include a mineral phase activation type determination step, a coating formula adjustment step, a rotary kiln atmosphere adjustment step, and a negative pressure wetting endpoint determination step.

[0013] In the mineral phase activation type determination step, the component identification unit detects the contents of SiO2, Al2O3, Fe2O3, CaO, MgO, TiO2, target element content, moisture content, loss on ignition, and mineral phase composition in the solid waste tailings raw material. When the total mass content of SiO2 and Al2O3 is not less than 60 wt%, and / or the proportion of aluminosilicate phase obtained by X-ray diffraction is not less than 40 wt%, the solid waste tailings raw material is determined to be of the aluminosilicate high activation difficulty type. When the total mass content of Fe2O3 and Al2O3 is not less than 50 wt%, and / or the target element is mainly present in the iron-aluminum composite phase or the iron-aluminum-silicon composite phase, it is determined to be of the iron-aluminum composite phase activation type. When the total mass content of CaO and MgO is not less than 15 wt%, it is determined to be of the high alkalinity component type. When the sum of moisture content and loss on ignition is not less than 8 wt%, it is determined to be of the high volatile component type.

[0014] In the coating formulation adjustment step, when the solid waste tailings raw material is a type of aluminosilicate with high activation difficulty, the proportion of sulfate precursors, carbonate precursors, or molten salt precursors in the phase inversion activation component is increased, and the proportion of the second microcapsule in the dual-temperature zone controllable pyrolysis microcapsule is increased; when the solid waste tailings raw material is an iron-aluminum composite phase activation type, the proportion of phase inversion promoters and sulfate precursors added is increased to enhance the destruction of the iron-aluminum composite phase and the migration and release of target elements; when the solid waste tailings raw material is a high-alkaline component type, the amount of acidic precursors added is reduced, and tailings or leaching residues rich in CaO and / or MgO are used in the alkaline absorbent preparation unit; when the solid waste tailings raw material is a high-volatile component type, the heating rate of the rotary kiln preheating desorption section is reduced, and the preheating desorption residence time is extended to reduce particle bursting and pulverization.

[0015] In the rotary kiln atmosphere conditioning step, based on the online detection results of sulfur-containing components, nitrogen-containing components, water vapor, and oxygen content in the kiln tail gas, the oxygen content, heating rate, tail gas recirculation ratio, and residence time of the coating layer's stepwise pyrolysis section and directional phase inversion section are adjusted; when the release peak of sulfur-containing components, nitrogen-containing components, or water vapor is earlier than the preset time window, the heating rate of the coating layer's stepwise pyrolysis section is reduced or the proportion of slow-release film-forming components is increased; when the release peak is later than the preset time window, the temperature of the coating layer's stepwise pyrolysis section is increased or the residence time of this section is extended.

[0016] In the negative pressure immersion endpoint determination step, the exhaust volume, pressure recovery time, and change rate of activated slurry conductivity after each negative pressure pulse in the sealed immersion chamber are detected. When the difference in exhaust volume between two consecutive negative pressure pulse cycles is less than 5-15% of the previous exhaust volume, and / or the change rate of activated slurry conductivity within 30-180s is less than 1-5%, it is determined that the gas discharge inside the calcined particles has stabilized, the weakly acidic circulating liquid or circulating mother liquor has entered the microcracks and connecting channels inside the calcined particles, and the negative pressure pulse immersion step is terminated.

[0017] Furthermore, the solid waste tailings raw materials are selected from one or more of bauxite tailings, coal gangue, smelting tailings, and chemical tailings; the target elements are selected from one or more of scandium, gallium, rhenium, vanadium, cerium, and neodymium.

[0018] Furthermore, the component identification unit is used to detect one or more of the following in solid waste tailings raw materials: Fe2O3, Al2O3, SiO2, CaO, MgO, TiO2 content, target element content, moisture content, and loss on ignition. Based on the detection results, the ratio of reactive coating precursor liquid, pore-inducing component, phase-inversion activating component, and slow-release film-forming component is adjusted.

[0019] Furthermore, the reactive coating precursor liquid includes a sulfate precursor, a pore-forming agent, and a binder; the sulfate precursor is selected from one or more of ammonium sulfate, ammonium bisulfate, and sodium sulfate; the pore-forming agent is selected from one or more of ammonium bicarbonate, starch, lignin, and sawdust; and the binder is selected from one or more of water glass, bentonite, polyvinyl alcohol, and silica sol.

[0020] Furthermore, the pore-inducing layer includes a pore-forming agent and a first binder; the phase-inversion activation layer includes one or more of sulfate precursors, nitrate precursors, carbonate precursors, and fluoride precursors; and the slow-release protective layer includes one or more slow-release film-forming components selected from water glass, bentonite, polyvinyl alcohol, and silica sol.

[0021] Furthermore, the total mass of the gradient multilayer reactive coating layer accounts for 1–15 wt% of the total mass of the reactive coated particles; among which, the pore-inducing layer accounts for 0.2–5 wt% of the total mass of the reactive coated particles, the phase-inversion activation layer accounts for 0.5–8 wt% of the total mass of the reactive coated particles, and the sustained-release protective layer accounts for 0.1–3 wt% of the total mass of the reactive coated particles; the particle size of the reactive coated particles is 0.5–5 mm.

[0022] Furthermore, in the vertical mill spray grinding unit, the working pressure of the vertical mill is 6-14 MPa, the separator speed is 400-900 rpm, and the residence time of the material in the vertical mill is 3-12 min.

[0023] Furthermore, in the rotary kiln, the preheating and desorption temperature is 200–450°C; the temperature for the stepwise pyrolysis of the coating layer is 350–650°C; the temperature for directional phase inversion is 550–900°C; and the total residence time of the reactive coated particles in the rotary kiln is 20–120 min.

[0024] Furthermore, the hot-quenching negative pressure leaching unit includes a calcined particle inlet, a sealed leaching chamber, a weakly acidic circulating liquid inlet, a circulating mother liquor inlet, a negative pressure pulse generator, a steam / tail gas outlet, an activated slurry outlet, and an internal immersion zone or wetting zone. The calcined particles enter the sealed leaching chamber through the calcined particle inlet, the weakly acidic circulating liquid enters the sealed leaching chamber through the weakly acidic circulating liquid inlet, and the circulating mother liquor enters the sealed leaching chamber through the circulating mother liquor inlet. Under the action of the negative pressure pulse generator, hot-quenching negative pressure pulse wetting is completed.

[0025] Furthermore, the present invention also provides a system for implementing the above-mentioned method of treating solid waste tailings by using vertical mill grinding in conjunction with rotary kiln calcination, comprising: a crushing and homogenization unit, a component identification unit, a vertical mill spray grinding unit, a layered granulation unit, a rotary kiln, a hot quenching negative pressure leaching unit, a primary acid leaching unit, a primary solid-liquid separation unit, a secondary deep leaching and magnetic trapping unit, a magnetic separation and desorption unit, a tail gas separation and purification and resource utilization unit, a tail gas reflux branch, and a mother liquor regeneration unit; The crushing and homogenization unit, component identification unit, vertical mill spray grinding unit, layered granulation unit, rotary kiln, hot quenching negative pressure leaching unit, primary acid leaching unit, primary solid-liquid separation unit, secondary deep leaching and magnetic collection unit, and magnetic separation and desorption unit are connected in sequence. The tail gas separation, purification and resource utilization unit is connected to the tail gas outlet of the rotary kiln. The tail gas separation, purification and resource utilization unit includes a dust removal device, a sulfur-containing tail gas oxidation absorption branch, a nitrogen-containing tail gas oxidation absorption branch, a purified tail gas reflux branch, a precursor liquid conditioning unit and an alkaline absorption liquid preparation unit. The sulfur-containing tail gas oxidation and absorption branch is used to form a sulfate-containing absorbent, and the nitrogen-containing tail gas oxidation and absorption branch is used to form a nitrate-containing absorbent. The alkaline absorbent preparation unit is connected to the alkaline oxide source in the solid waste tailings or leaching residue, and is used to prepare alkaline absorbent for supplying the sulfur-containing tail gas oxidation absorption branch and / or the nitrogen-containing tail gas oxidation absorption branch. The exhaust gas return branch is used to return a portion of the purified exhaust gas to the rotary kiln. The mother liquor regeneration unit is connected to the primary acid leaching unit, the secondary deep leaching and magnetic capture unit, and the tail gas separation, purification and resource recovery unit, respectively. It is used to regenerate the primary acid leaching mother liquor and / or the secondary deep leaching mother liquor, and to reuse the regenerated acid liquor in the primary acid leaching unit and / or the secondary deep leaching and magnetic capture unit, and to reuse the regenerated alkali liquor in the tail gas separation, purification and resource recovery unit.

[0026] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention combines vertical mill grinding with the injection of reactive coating precursor liquid, enabling the solid waste tailings to undergo mechanical activation and pre-loading of reactive components while reducing particle size. This method no longer treats the grinding process as a simple crushing and grinding step, but rather forms an activation foundation on the surface of the solid waste tailings powder that is conducive to subsequent calcination and phase transformation, thereby increasing the possibility of stable mineral phase dissociation, activation, and release of target elements, which is beneficial to improving the subsequent leaching efficiency of target elements such as scandium, gallium, rhenium, vanadium, cerium, and neodymium.

[0027] 2. This invention forms reactive coated particles with gradient multi-layer reactive coatings through layered granulation, allowing different layer structures to undertake the functions of pore induction, phase transformation activation, and slow-release protection. During the staged atmosphere catalytic calcination process in a rotary kiln, the pore induction layer can decompose to form a pore structure, the phase transformation activation layer can release reactive gases and / or form a molten salt activation layer, and the slow-release protection layer can improve the particle forming strength and delay the premature release of active components. As a result, the formation of pores inside the particles, surface reactions, and the transformation of the target element mineral phase can occur gradually according to the calcination temperature zone, improving the directionality and stability of the transformation of the target element from a difficult-to-leach phase to a easily leached phase.

[0028] 3. In this invention, calcined particles are directly subjected to hot quenching before being cooled to room temperature, and a negative pressure pulse is applied during the quenching process. On the one hand, after the high-temperature particles come into rapid contact with the weakly acidic circulating liquid or circulating mother liquor, microcracks and interconnected channels can be formed inside the particles by thermal shock. On the other hand, the negative pressure pulse can promote the discharge of gas from the pores and cracks of the particles and allow the liquid medium to enter the particles more fully. This synergistic effect improves the liquid-solid contact conditions and mass transfer efficiency in the subsequent acid leaching process, and reduces the problem of insufficient leaching caused by limited diffusion inside the particles.

[0029] 4. This invention employs a staged leaching method combining primary acid leaching and secondary deep leaching. This allows conventional metals such as iron, aluminum, and copper to preferentially enter the primary leaching solution, followed by secondary deep leaching and enrichment of target elements on the primary leaching residue. This method can reduce the impurity ion load in the secondary deep leaching system and minimize the interference of coexisting components such as iron, aluminum, calcium, and magnesium on the enrichment process of low-content target elements. Simultaneously, the addition of magnetic selective adsorption materials during the secondary deep leaching process allows the target elements to be captured in situ as they are released into the liquid phase. This reduces the risk of redeposition, re-adsorption, or competitive complexation by impurity ions, thereby improving the capture efficiency of target elements and the convenience of subsequent desorption and enrichment.

[0030] 5. This invention also couples the separation and purification of kiln tail gas, reuse of acidic absorbent, conditioning of precursor liquid, tail gas reflux, and mother liquor regeneration, so that sulfur-containing tail gas and nitrogen-containing tail gas are respectively converted into process media that can be used for primary acid leaching, secondary deep leaching, or conditioning of reactive coating precursor liquid; at the same time, alkaline oxides in solid waste tailings or leaching residues can be used to prepare absorbent, and acid leaching mother liquor and deep leaching mother liquor can be reused in the system after regeneration; thus, this invention can reduce the consumption of fresh acid and alkali, reduce the pressure of tail gas and waste liquid treatment, improve the recycling rate of solid waste tailings, tail gas components and process media, and form a solid waste resource utilization system that integrates grinding, calcination, leaching, enrichment and tail gas resource utilization. Attached Figure Description

[0031] Figure 1 This is a flowchart illustrating the overall process flow of the method of the present invention. Figure 2 This is a schematic diagram of the system structure connection of the present invention; Figure 3 This is a schematic diagram of the gradient multilayer structure of the reactive coated particles of the present invention; Figure 4 This is a schematic diagram of the hot-quenching negative pressure pulse leaching unit structure of the present invention; Figure 5 This is a schematic diagram of the kiln tail gas resource utilization and precursor liquid conditioning and circulation of the present invention. Figure 6 This is a schematic diagram of the rotary kiln segmented atmosphere catalytic calcination structure of the present invention.

[0032] In the diagram: 10 Crushing and homogenization unit, 20 Component identification unit, 30 Vertical mill spray grinding unit, 40 Layered granulation unit, 50 Rotary kiln, 60 Hot quenching negative pressure leaching unit, 61 Calcined particle inlet, 62 Sealed leaching chamber, 63 Weakly acidic circulating liquid inlet, 64 Circulating mother liquor inlet, 65 Negative pressure pulse generator, 66 Steam / tail gas outlet, 67 Activated slurry outlet, 68 Internal immersion zone or wetting zone, 70 Primary acid leaching unit, 80 Primary solid-liquid separation unit, 90 Secondary deep leaching and magnetic capture unit, 100 Magnetic separation and desorption unit, 110 Tail gas separation, purification and resource utilization unit, 111 Dust removal device, 112 Sulfur-containing tail gas oxidation absorption branch, 113 Nitrogen-containing tail gas oxidation absorption... 114 Purified tail gas recirculation branch, 115 Precursor liquid conditioning unit, 116 Alkaline absorbent preparation unit, 117 Sulfate-containing absorbent, 118 Nitrate-containing absorbent, 119 Source of alkaline oxides in solid waste tailings or leaching residue, 120 Tail gas recirculation branch, 130 Mother liquor regeneration unit, 140 Reactive coated particles, 141 Solid waste tailings powder core, 142 Pore induction layer, 143 Phase transformation activation layer, 144 Slow-release protective layer, 145 Rotary kiln body, 146 Preheating desorption section, 147 Coating layer stepwise pyrolysis section, 148 Directional phase transformation section, 149 Feed end, 150 Phase transformation promoter injection inlet, 151 Tail gas recirculation interface, 152 Kiln tail gas outlet, 153 Discharge end. Detailed Implementation

[0033] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the following embodiments are only for illustrating the present invention and are not intended to limit the scope of protection of the present invention. Without departing from the technical concept of the present invention, those skilled in the art can make appropriate adjustments to the raw material ratio, precursor liquid composition, calcination temperature, residence time, leaching conditions, adsorbent material type, tail gas reflux ratio, and mother liquor regeneration method according to the source of solid waste tailings, mineral phase composition, target element types, treatment scale, and on-site equipment conditions.

[0034] This invention provides a method and system for treating solid waste tailings using vertical mill grinding in conjunction with rotary kiln calcination; see also Figure 1 and Figure 2 The system includes a crushing and homogenization unit 10, a component identification unit 20, a vertical mill spray grinding unit 30, a layered granulation unit 40, a rotary kiln 50, a hot quenching negative pressure leaching unit 60, a primary acid leaching unit 70, a primary solid-liquid separation unit 80, a secondary deep leaching and magnetic capture unit 90, a magnetic separation and desorption unit 100, a tail gas separation, purification and resource utilization unit 110, a tail gas reflux branch 120, and a mother liquor regeneration unit 130.

[0035] Solid waste tailings can be one or more of bauxite tailings, coal gangue, smelting tailings, and chemical tailings, or other industrial solid wastes containing target elements such as iron, aluminum, copper, calcium, magnesium, silicon, scandium, gallium, rhenium, vanadium, cerium, and neodymium; the target elements can be one or more of scandium, gallium, rhenium, vanadium, cerium, and neodymium.

[0036] The transformation of the mineral phase containing the target element in this invention from a difficult-to-leach phase to an easily leached phase means that the target element originally existed in a mineral structure that was embedded in aluminosilicate phase, iron-aluminum composite phase, stable oxide phase, or other mineral structures that were difficult to release by acid leaching. After treatment such as mechanical activation by vertical mill, reactive coating, segmented calcination, hot quenching and negative pressure wetting, it was transformed into an oxide, sulfate, nitrate, composite salt, activated aluminosilicate phase, or other easily leached state that was more easily leached by acidic systems.

[0037] See Figure 3 The reactive coated particles 140 of this invention include a solid waste tailings powder core 141 and a gradient multilayer reactive coating layer covering the outside of the solid waste tailings powder core 141. The gradient multilayer reactive coating layer includes a pore-inducing layer 142, a phase-inversion activation layer 143, and a slow-release protective layer 144 arranged sequentially from the inside to the outside. The pore-inducing layer 142 is used to decompose, volatilize, or burn out during calcination, thereby forming a pore structure on the particle surface and near the surface. The phase-inversion activation layer 143 is used to release reactive gases and / or form a molten salt activation layer during calcination to promote the transformation of the mineral phase containing the target element. The slow-release protective layer 144 is used to improve the particle forming strength, reduce pulverization during the kiln entry process, and delay the premature release of the phase-inversion activation component in the early stage of heating.

[0038] See Figure 6 The rotary kiln 50 includes a rotary kiln body 145, which is divided into a preheating desorption section 146, a coating layer step-by-step pyrolysis section 147, and a directional phase transformation section 148 along the material movement direction. One end of the rotary kiln body 145 is provided with a feed end 149 for receiving reactive coated particles 140 from the layered granulation unit 40. The other end of the rotary kiln body 145 is provided with a discharge end 153 for outputting calcined particles after segmented atmosphere catalytic calcination. The preheating desorption section 146 is used to remove free water, adsorbed water, and some volatile components from the reactive coated particles 140. The coating layer step-by-step pyrolysis section 147 is used to decompose the pore-inducing layer 142 to form a pore structure and to release reactive gases and / or form a molten salt activation layer from the phase transformation activation layer 143. The directional phase transformation section 148 is used to promote the transformation of the mineral phase containing the target element in the solid waste tailings from a difficult-to-leach phase to a easily leached phase.

[0039] In a preferred embodiment, the segmented atmosphere catalytic calcination of the rotary kiln 50 is achieved through segmented temperature control, segmented oxygen control, tail gas reflux, and the injection of a phase inversion promoter. Air, hot air, or a portion of purified tail gas is introduced into the preheating desorption section 146, with the oxygen content controlled at 5–21 vol% and the temperature controlled at 200–450°C, to remove free water, adsorbed water, and some volatile components from the reactive coated particles 140. Air, low-oxygen hot air, and purified tail gas are introduced into the staged cracking section 147 of the coating layer. Or a mixture thereof, with an oxygen content controlled at 3-15 vol%, and a temperature controlled at 350-650℃, is used to decompose the pore-inducing layer 142 to form a pore structure and to release reactive components from the first microcapsule; air, oxygen-enriched hot air, purified tail gas or a mixture thereof are introduced into the directional phase-inversion section 148, with an oxygen content controlled at 5-21 vol%, and a temperature controlled at 550-900℃, to release phase-inversion promoting components from the second microcapsule and to promote the transformation of the mineral phase containing the target element from a difficult-to-leach phase to a easily-leachable phase.

[0040] Furthermore, the pressure inside the rotary kiln 50 is maintained at -50 to -300 Pa, and the heating rate is controlled at 2 to 15 °C / min. The purified tail gas after being treated by the tail gas separation and resource utilization unit 110 is 5 to 30% of the total tail gas volume and is returned to the coating layer step-by-step cracking section 147 and / or directional phase transformation section 148 via the tail gas return branch 120 to adjust the oxygen content, water vapor content and acid gas trace component content inside the kiln. The acid gas trace components include sulfur-containing components and / or nitrogen-containing components released by the cracking of the reactive coating layer or brought in by the tail gas return. They can synergistically act with sulfate precursors, nitrate precursors, carbonate precursors or fluoride precursors in the phase transformation activation layer 143 to form a local molten salt activation environment or reactive atmosphere, thereby enhancing the transformation of the mineral phase in which the target element is located.

[0041] When the peak release of sulfur-containing or nitrogen-containing components in the kiln tail gas is earlier than the preset time window, reduce the heating rate of the coating layer stepwise pyrolysis section 147 or reduce the tail gas recirculation ratio; when the peak release of sulfur-containing or nitrogen-containing components in the kiln tail gas is later than the preset time window, increase the temperature of the coating layer stepwise pyrolysis section 147, extend the residence time, or increase the tail gas recirculation ratio; when the mineral phase transformation degree of the material at the outlet of the directional phase transformation section 148 is lower than the preset requirement, increase the amount of phase transformation promoter injected into the phase transformation promoter inlet 150, or extend the residence time of the reactive coating particles 140 in the directional phase transformation section 148.

[0042] A phase transformation promoter injection inlet 150 is provided on the progressive pyrolysis section 147 and / or the directional phase transformation section 148 of the coating layer. The phase transformation promoter injection inlet 150 is used to inject a phase transformation promoter into the rotary kiln shell 145 to enhance the transformation effect of the mineral phase containing the target element. The rotary kiln shell 145 is also provided with a tail gas return port 151. The tail gas return port 151 is used to receive part of the purified tail gas after being treated by the tail gas separation and purification and resource utilization unit 110, so that this part of the purified tail gas is returned to the progressive pyrolysis section 147 and / or the directional phase transformation section 148 of the coating layer. Within 48, the atmosphere inside the kiln is regulated and the coating layer is involved in the cracking and mineral phase transformation process. The rotary kiln body 145 is also provided with a kiln tail gas outlet 152, which is connected to the tail gas separation, purification and resource utilization unit 110 to export the kiln tail gas generated by the rotary kiln 50 for subsequent separation, purification and resource utilization treatment. Through the above segmented structure, the reactive coated particles 140 can sequentially complete preheating desorption, coating layer step-by-step cracking and directional phase transformation in the rotary kiln 50, thereby improving the release of target elements in solid waste tailings and subsequent leaching efficiency.

[0043] In a preferred embodiment, the present invention further includes a mineral phase-tail gas-negative pressure wetting linkage control step; this linkage control step is set in the coordinated operation of the component identification unit 20, the vertical mill spray grinding unit 30, the layered granulation unit 40, the rotary kiln 50, and the hot quenching negative pressure leaching unit 60, so as to match the mineral phase composition of solid waste tailings, the layer structure of reactive coated particles 140, the cracking and release process of the coating layer in the rotary kiln 50, and the liquid phase wetting process of calcined particles, thereby improving the stability of the treatment process of solid waste tailings from different sources and the release efficiency of target elements.

[0044] Specifically, in step two, the component identification unit 20 tests the solid waste tailings raw material. The test items include one or more of the following: Fe2O3, Al2O3, SiO2, CaO, MgO, TiO2 content, target element content, moisture content, and loss on ignition. Furthermore, the proportion of aluminosilicate phase, iron-aluminum composite phase, stable oxide phase, or composite mineral phase containing target elements in the solid waste tailings can be obtained through X-ray diffraction, mineral phase analysis, thermogravimetric analysis, or other mineral phase identification methods. Based on the above test results, the mineral phase activation difficulty level of the solid waste tailings is determined, and the ratio of reactive coating precursor liquid, pore induction component, phase transformation activation component, and slow-release film-forming component is adjusted according to the mineral phase activation difficulty level so that the reactive coating particles 140 formed in the subsequent layered granulation unit 40 match the mineral phase composition of the solid waste tailings.

[0045] When the total content of SiO2 and Al2O3 in the solid waste tailings is high, and the proportion of aluminosilicate phase is high, it is difficult to determine the activation of its mineral phase. In this case, the proportion of sulfate precursor, carbonate precursor or molten salt precursor in the phase transformation activation component is increased, and the proportion of slow-release film-forming component can be appropriately increased, so that the active component in the phase transformation activation layer 143 is gradually released in the high temperature zone of the rotary kiln 50. When the content of Fe2O3 and Al2O3 in the solid waste tailings is high, and the target element is embedded in the iron-aluminum composite phase, the addition ratio of phase transformation activation component and phase transformation promoter is increased to enhance the destruction of the iron-aluminum composite phase and the migration and release of the target element. When the content of CaO and / or MgO in the solid waste tailings is high, the proportion of pore-inducing component in the pore-inducing layer 142 is appropriately increased, and the amount of acidic precursor added is reduced to reduce the acid consumption in the subsequent primary acid leaching unit 70 and the secondary deep leaching and magnetic trapping unit 90. At the same time, its alkaline component is used to participate in the preparation of the absorbent in the alkaline absorbent preparation unit 116.

[0046] In a preferred embodiment, the phase inversion activation layer 143 includes dual-temperature zone controllable pyrolysis microcapsules; the dual-temperature zone controllable pyrolysis microcapsules include a first microcapsule and a second microcapsule, wherein the first microcapsule is used to release reactive components in the stepwise pyrolysis section 147 of the coating layer, and the second microcapsule is used to release phase inversion promoting components in the directional phase inversion section 148; by setting microcapsules with different pyrolysis or rupture temperature zones, pore formation, release of reactive components and transformation of target element mineral phases can occur in corresponding temperature zones, avoiding premature release of active components in the initial stage of heating, thereby improving the directional phase inversion efficiency of reactive coated particles 140.

[0047] The first microcapsule comprises a first core material and a first shell layer covering the outside of the first core material; the first core material comprises one or more of ammonium sulfate, ammonium bisulfate, and ammonium bicarbonate, and the first shell layer comprises one or more of polyvinyl alcohol, water glass, bentonite, and silica sol; the first microcapsule has a pyrolysis or rupture temperature of 350–650°C, and is used to release sulfur-containing, nitrogen-containing, or pore-inducing components in the stepwise pyrolysis section 147 of the coating layer, and to cooperate with the pore-inducing layer 142 to decompose and form a pore structure; the second microcapsule comprises a second core material and a second shell layer covering the outside of the second core material; the second core material comprises one or more of sodium sulfate, sodium carbonate, calcium fluoride, and iron oxide, and the second shell layer comprises one or more of water glass, silica sol, and bentonite; the second microcapsule has a pyrolysis or rupture temperature of 550–900°C, and is used to form a molten salt activation environment or release phase-transformation promoting components in the directional phase-transformation section 148, so that the mineral phase containing the target element is transformed from a difficult-to-leach phase to an easily leached phase.

[0048] In one specific preparation method, the first microcapsule and the second microcapsule can be prepared by spray drying, fluidized bed coating or in-situ gel coating.

[0049] When preparing the first microcapsules using spray drying, one or more of ammonium sulfate, ammonium bisulfate, and ammonium bicarbonate are used as the first core material, and one or more of polyvinyl alcohol, water glass, bentonite, and silica sol are used as the first shell material. The first core material is pulverized to a particle size of 1–50 μm and then dispersed in a solution of the first shell material. The mass ratio of the first core material to the first shell material is controlled at 1:0.1–1:0.8, and the mixture is stirred to form a suspension slurry. Spray drying is then performed at an inlet temperature of 120–180 °C and an outlet temperature of 60–95 °C to obtain the first microcapsules with a particle size of 10–200 μm. The obtained first microcapsules undergo shell softening, pyrolysis, or rupture within the temperature range of 350–650 °C, releasing the reactive components in the first core material.

[0050] When preparing the second microcapsules using spray drying, one or more of sodium sulfate, sodium carbonate, calcium fluoride, and iron oxide are used as the second core material, and one or more of water glass, silica sol, bentonite, and alumina sol are used as the second shell material. The second core material is pulverized to a particle size of 1–50 μm and then dispersed in a solution of the second shell material. The mass ratio of the second core material to the second shell material is controlled at 1:0.2–1:1, and the mixture is stirred to form a suspension slurry. Subsequently, spray drying is performed at an inlet temperature of 130–200 °C and an outlet temperature of 70–110 °C to obtain second microcapsules with a particle size of 10–250 μm. The obtained second microcapsules undergo shell softening, sintering cracking, or rupture within the range of 550–900 °C, releasing the phase inversion promoting components in the second core material.

[0051] After the first and second microcapsules are prepared, they are mixed with one or more of sulfate precursors, nitrate precursors, carbonate precursors, and fluoride precursors to form a phase-inversion activating component. This component is then coated on the outside of the pore-inducing layer 142 in the layered granulation unit 40 to form a phase-inversion activating layer 143. Through the above preparation method, the first and second microcapsules can release reactive components in the stepwise pyrolysis section and the directional phase-inversion section of the coating layer in the rotary kiln 50, respectively, so that pore formation, release of reactive components, and transformation of target element mineral phases occur in stages in different temperature zones.

[0052] Preferably, the mass ratio of the first microcapsule to the second microcapsule is 1:0.5 to 1:3, and the dual-temperature zone controllable pyrolysis microcapsule accounts for 20 to 80 wt% of the total mass of the phase inversion activation layer 143. When the target element in the solid waste tailings is mainly embedded in the aluminosilicate phase, the proportion of the second microcapsule is increased. When the water content or loss on ignition in the solid waste tailings is high, the proportion of the first microcapsule is increased to enhance the pore formation ability and volatile component release ability in the stepwise pyrolysis section 147 of the coating layer.

[0053] During the 50-segment atmospheric catalytic calcination process in the rotary kiln, the release peak time of sulfur-containing components, nitrogen-containing components, and / or water vapor in the kiln tail gas at kiln tail gas outlet 152 is detected, and the temperature, heating rate, and / or residence time of the coating layer stepwise pyrolysis section 147 are adjusted according to the release peak time. The release peak time can be obtained by a gas detection device, infrared gas analysis device, humidity detection device, or online flue gas detection device installed at kiln tail gas outlet 152. When the release peak of sulfur-containing components, nitrogen-containing components, or water vapor is earlier than the preset time window, it indicates that the reactive components in the coating layer are released too early. At this time, the heating rate of the coating layer stepwise pyrolysis section 147 is reduced, the temperature of this section is reduced, or the proportion of slow-release film-forming components in the slow-release protective layer 144 is increased. When the release peak is later than the preset time window, it indicates that the pyrolysis release of the phase inversion activation layer 143 is insufficient or delayed. At this time, the temperature of the coating layer stepwise pyrolysis section 147 is increased, the residence time of this section is extended, or the proportion of the first microcapsule is increased.

[0054] Through the above control, the release process of reactive components in the phase transformation activation layer 143 is matched with the phase transformation process of target elements in the rotary kiln 50. Specifically, the first microcapsule releases reactive components in the stepwise pyrolysis section 147 of the coating layer and forms a porous structure, while the second microcapsule releases phase transformation promoting components in the directional phase transformation section 148 and forms a local molten salt activation environment. Thus, the reactive coated particles 140 sequentially complete preheating desorption, pore induction, release of reactive components, and directional phase transformation of target elements in the rotary kiln shell 145.

[0055] During the hot-quenching negative pressure pulse immersion process, the endpoint of the negative pressure pulse immersion is determined based on the exhaust volume, pressure recovery time, and / or the change rate of conductivity of the activated slurry within the sealed immersion chamber 62. Specifically, after the calcined particles enter the sealed immersion chamber 62 through the calcined particle inlet 61 and come into contact with the weakly acidic circulating liquid or circulating mother liquor, the negative pressure pulse generator 65 applies periodic negative pressure to the sealed immersion chamber 62, causing the gas and vapor in the pores and microcracks inside the particles to be discharged through the steam / tail gas outlet 66, and prompting the weakly acidic circulating liquid to enter through the weakly acidic circulating liquid inlet 63. The weakly acidic circulating liquid and the circulating mother liquid entering through the circulating mother liquid inlet 64 enter the internal connecting channels of the particles; the exhaust volume, pressure recovery time, and change rate of conductivity of the activated slurry are detected after each negative pressure pulse. When the difference in exhaust volume between two consecutive negative pressure pulse cycles is lower than a preset threshold, and / or the pressure recovery time tends to stabilize, and / or the change rate of conductivity of the activated slurry is lower than a preset threshold, it is determined that the liquid phase medium has sufficiently entered the microcracks and connecting channels inside the calcined particles, the negative pressure pulse wetting step is ended, and the activated slurry is discharged through the activated slurry outlet 67.

[0056] Preferably, when the difference in exhaust volume between two consecutive negative pressure pulse cycles is less than 5-15% of the previous exhaust volume, it is determined that the gas discharge inside the particles tends to be stable; when the rate of change of the conductivity of the activated slurry within 30-180s is less than 1-5%, it is determined that the contact between the weakly acidic circulating liquid or circulating mother liquor and the impregnable components inside the particles tends to be stable; by judging the above endpoints, it is possible to avoid insufficient impregnation due to excessively short negative pressure pulse time, and also to avoid increased energy consumption, excessive particle breakage, or increased fine powder due to excessively long negative pressure pulse time.

[0057] In a preferred embodiment, the magnetically selective adsorbent material is added in stages during the secondary deep leaching process. Specifically, the secondary deep leaching process in the secondary deep leaching and magnetic trapping unit 90 is divided into a pre-leaching period, a mid-release period, and a post-stabilization period. A first part of the magnetically selective adsorbent material is added during the pre-leaching period, a second part of the magnetically selective adsorbent material is added during the mid-release period, and the magnetically selective adsorbent material loaded with the target element is separated by an external magnetic field during the post-stabilization period.

[0058] The initial leaching period is 0-30% of the total leaching time after the start of secondary deep leaching, the intermediate release period is 30-80% of the total leaching time, and the final stabilization period is 80-100% of the total leaching time. Preferably, the amount of the first part of the magnetic selective adsorbent material added accounts for 20-50 wt% of the total amount of magnetic selective adsorbent material added, and the amount of the second part of the magnetic selective adsorbent material added accounts for 50-80 wt% of the total amount of magnetic selective adsorbent material added. In the initial leaching period, the first part of the magnetic selective adsorbent material is used to capture the target elements released in the early stage. In the intermediate release period, as the release rate of the target elements increases, the second part of the magnetic selective adsorbent material is used to provide new effective adsorption sites to reduce the situation where the adsorption sites are occupied by impurity ions such as iron, aluminum, calcium, and magnesium in the early stage of leaching.

[0059] By using the above-mentioned segmented addition method, the addition time of the magnetic selective adsorption material can be matched with the release time of the target element from the primary leaching residue, so that the target element is adsorbed and enriched in time after entering the liquid phase, reducing the possibility of the target element undergoing reprecipitation, re-adsorption or competitive complexation in the complex leaching system; after leaching, the magnetic selective adsorption material loaded with the target element is recovered by the magnetic separation and desorption unit 100 and desorbed to obtain the target element enriched solution.

[0060] By employing the aforementioned linkage control of mineral phase, tail gas, and negative pressure wetting, dual-temperature zone controllable pyrolysis microcapsules, and segmented addition of magnetic selective adsorption materials, this invention can form a continuous and coordinated control chain from raw material identification, coated particle design, rotary kiln segmented release, hot quenching wetting endpoint determination to in-situ capture of target elements. This control chain ensures that the layered pyrolysis process of reactive coated particles 140, the mineral phase transformation process of target elements in rotary kiln 50, the liquid phase wetting process of calcined particles in hot quenching negative pressure leaching unit 60, and the in-situ capture process in secondary deep leaching and magnetic capture unit 90 are mutually matched, thereby further improving the release, leaching, and enrichment efficiency of low-content target elements in solid waste tailings and reducing the fluctuation of treatment effect caused by raw material fluctuations, mismatched release timing, or competition for adsorption sites. Example 1

[0061] This embodiment describes a treatment method using bauxite tailings as raw material. The bauxite tailings primarily contain iron oxide, aluminum oxide, silicon dioxide, calcium oxide, and small amounts of target elements such as scandium, gallium, cerium, and neodymium.

[0062] First, the bauxite tailings are fed into the crushing and homogenization unit 10 for crushing and homogenization. The particle size of the crushed bauxite tailings is controlled to be 10-20 mm. Then, they are mixed and homogenized in the homogenization chamber for 4 hours to reduce the fluctuations in the content of iron, aluminum, silicon, calcium and target elements in different batches of bauxite tailings.

[0063] Then, the homogenized bauxite tailings are fed into the component identification unit 20. The component identification unit 20 is used to detect the contents of Fe2O3, Al2O3, SiO2, CaO, MgO, TiO2, target element content, moisture content, and loss on ignition in the bauxite tailings. Based on the detection results, the ratio of reactive coating precursor liquid, pore-inducing component, phase-inversion activating component, and slow-release film-forming component is determined. In this embodiment, the bauxite tailings contain high contents of Fe2O3 and Al2O3, and contain small amounts of scandium, gallium, and rare earth elements. Therefore, the addition ratio of sulfate precursor and phase-inversion promoter is increased to enhance the activation effect of iron-aluminum composite mineral phase and the transformation effect of target element mineral phase in the subsequent calcination process.

[0064] Next, the bauxite tailings, after component identification, are fed into the vertical mill spray grinding unit 30 for grinding. The working pressure of the vertical mill is controlled at 10 MPa, the separator speed is controlled at 650 rpm, the system air temperature is controlled at 120℃, and the average residence time of the material in the vertical mill is 8 min. During the grinding process, a reactive coating precursor liquid is sprayed simultaneously. The reactive coating precursor liquid, by mass, includes: 8 parts ammonium sulfate, 3 parts sodium sulfate, 2 parts starch, 1 part water glass, and the remainder is water. On a dry basis, the amount added is 6 wt% of the dry mass of the bauxite tailings. During the grinding process in the vertical mill, the bauxite tailings are subjected to crushing, shearing, and impact, resulting in microcracks, lattice defects, and activation sites on the particle surface. At the same time, the reactive coating precursor liquid adheres to the surface of the tailings powder, so that grinding, mechanical activation, and preloading of reactive components are completed simultaneously. The powder obtained after grinding reaches 200 mesh, and the sieve residue is no higher than 8%.

[0065] Subsequently, the ground bauxite tailings powder is fed into the layered granulation unit 40 for granulation. The layered granulation unit 40 sequentially introduces a pore-inducing component, a phase-inversion activating component, and a slow-release film-forming component to form reactive coated particles 140. Specifically, a pore-inducing component is first sprayed onto the surface of the powder to form a pore-inducing layer 142 on the outside of the solid waste tailings powder core 141. The pore-inducing component includes starch, ammonium bicarbonate, and a small amount of polyvinyl alcohol. The starch and ammonium bicarbonate are used to decompose, volatilize, or burn out during subsequent calcination to form pores, while the polyvinyl alcohol is used to improve the bonding force between the pore-inducing layer 142 and the solid waste tailings powder core 141.

[0066] Subsequently, a phase-inversion activating component is sprayed in, forming a phase-inversion activating layer 143 on the outside of the pore-inducing layer 142. The phase-inversion activating component includes ammonium sulfate, sodium sulfate, and a small amount of Fe2O3. The phase-inversion activating layer 143 is used to release reactive components during the stepwise cracking stage and directional phase-inversion stage of the coating layer in the rotary kiln 50, and to form a local activation environment on the particle surface. Finally, a slow-release film-forming component is sprayed in, forming a slow-release protective layer 144 on the outside of the phase-inversion activating layer 143. The slow-release film-forming component includes water glass and bentonite. The slow-release protective layer 144 is used to improve the particle's resistance to pulverization and delay the premature release of the phase-inversion activating component in the early stage of heating. The resulting reactive coated particles 140 have a particle size of 1-3 mm, and the total mass of the gradient multilayer reactive coating layer accounts for about 6 wt% of the total mass of the reactive coated particles 140, of which the pore-inducing layer 142 accounts for about 2 wt%, the phase-inversion activating layer 143 accounts for about 3 wt%, and the slow-release protective layer 144 accounts for about 1 wt%.

[0067] The reactive coated particles 140 are fed into a rotary kiln 50 for staged atmospheric catalytic calcination. The rotary kiln 50 sequentially performs preheating desorption, progressive pyrolysis of the coating layer, and directional phase inversion along the material movement direction. The rotary kiln speed is controlled at 0.6 rpm, and the negative pressure inside the kiln is maintained at around -120 Pa. The temperature of the preheating desorption stage is controlled at 350℃, and the material residence time is 20 min. In this stage, free water, adsorbed water, and some volatile components in the particles are removed, and the slow-release protective layer 144 maintains the integrity of the particles and reduces particle breakage due to rapid heating.

[0068] The temperature of the progressive pyrolysis stage of the coating layer is controlled at 520℃, and the material residence time is 15 min. During this stage, the starch, ammonium bicarbonate and other components in the pore-inducing layer 142 decompose, volatilize or burn out, forming a porous structure on the particle surface and near the surface. At the same time, some sulfate precursors in the phase-inversion activation layer 143 begin to decompose or react, releasing reactive gases and / or forming a molten salt activation layer on the particle surface. The temperature of the directional phase-inversion stage is controlled at 820℃, and the material residence time is 60 min. During this stage, the molten salt activation layer and reactive components on the particle surface interact with the iron-aluminum composite phase, aluminosilicate phase and mineral phases containing target elements such as scandium, gallium, cerium and neodymium in the bauxite tailings, causing the mineral phase containing the target elements to transform from a difficult-to-leach phase to a easily leached phase.

[0069] Between the stage of progressive pyrolysis of the coating layer and the stage of directional phase inversion, a phase inversion promoter is injected into the rotary kiln 50. The phase inversion promoter is composed of Na2SO4 and Fe2O3, and the amount added is 2wt% of the dry basis of bauxite tailings. After staged atmospheric catalytic calcination, calcined particles and kiln tail gas are obtained.

[0070] See Figure 4The calcined particles, with an outlet temperature of approximately 700℃, are introduced directly into the sealed leaching chamber 62 of the hot-quenching negative pressure leaching unit 60 without being cooled at room temperature. A weakly acidic circulating liquid enters the sealed leaching chamber 62 through the weakly acidic circulating liquid inlet 63, and the circulating mother liquor enters the sealed leaching chamber 62 through the circulating mother liquor inlet 64. The quenching liquid is a mixture of 5wt% dilute sulfuric acid and a portion of the circulating mother liquor, with the liquid temperature controlled at 60℃. The contact time between the calcined particles and the liquid is 3 minutes. During the contact process, a negative pressure is applied to the sealed leaching chamber 62 via a negative pressure pulse generator 65. The pulse negative pressure value is controlled at -30 kPa, the single negative pressure holding time is 20 s, and the number of negative pressure pulse cycles is 5. After the high-temperature calcined particles come into rapid contact with the lower-temperature liquid medium, microcracks and interconnected channels are formed under the action of thermal shock. The negative pressure pulse causes the gas and steam in the pores and cracks inside the particles to be discharged, and promotes the weak acid circulating liquid or circulating mother liquor to enter the particle interior, thereby forming an activated slurry with a high degree of wetting in the internal immersion zone or wetting zone 68. The generated steam or tail gas can be discharged through the steam / tail gas outlet 66, and the activated slurry is discharged through the activated slurry outlet 67 and enters the subsequent first-stage acid leaching.

[0071] The activated slurry was fed into the primary acid leaching unit 70, and 12wt% dilute sulfuric acid was added. The liquid-to-solid ratio was controlled at 5:1 mL / g, the leaching temperature was controlled at 85℃, the stirring speed was controlled at 350 rpm, and the leaching time was 2 hours. During the primary acid leaching process, one or more conventional metals, such as iron and aluminum, preferentially entered the liquid phase. Since the aforementioned hot-quenched negative pressure pulse wetting had formed microcracks and liquid phase channels inside the calcined particles, the dilute sulfuric acid could more easily enter the particles and contact the easily leached mineral phase, thereby improving the leaching efficiency of conventional metals.

[0072] After the first-stage acid leaching is completed, the slurry is sent to the first-stage solid-liquid separation unit 80 for solid-liquid separation. The first-stage solid-liquid separation can be carried out by pressure filtration, centrifugation or sedimentation filtration. In this embodiment, a filter press is used for separation, and the pressure is controlled at 0.8 MPa to obtain the first-stage leachate and the first-stage leach residue. The first-stage leachate can be further used to recover conventional metals such as iron and aluminum, and the first-stage leach residue enters the second-stage deep leaching and magnetic collection unit 90.

[0073] The primary leaching residue is fed into the secondary deep leaching and magnetic trapping unit 90, and a nitric acid system with a mass concentration of 30 wt% is added. The liquid-to-solid ratio is controlled at 5:1 mL / g, the leaching temperature is controlled at 105℃, and the leaching time is 3 h. During the secondary deep leaching process, hydrogen peroxide with a mass of 2 wt% of the nitric acid system is added as an auxiliary oxidant, and magnetic phosphonic acid-based adsorbent material is added as a magnetic selective adsorbent material. The magnetic phosphonic acid-based adsorbent material has magnetic Fe3O4 particles or magnetic porous carriers as the core, and phosphonic acid functional groups are grafted onto its surface. The phosphonic acid functional groups can undergo complexation, coordination, ion exchange, or surface adsorption with one or more target elements among scandium, gallium, cerium, and neodymium.

[0074] During the secondary deep leaching process, after the target element is released from the primary leaching residue into the liquid phase, it is immediately captured in situ by the magnetic selective adsorption material. After the secondary deep leaching is completed, the magnetic selective adsorption material loaded with the target element is sent to the magnetic separation and desorption unit 100, where it is separated from the leaching system by an external magnetic field. Subsequently, 2 mol / L hydrochloric acid is used as the desorption solution to desorb the magnetic selective adsorption material loaded with the target element, resulting in a target element enrichment solution. The obtained target element enrichment solution can be further refined by extraction, back-extraction, precipitation, crystallization, or other hydrometallurgical methods to obtain enriched products of target elements such as scandium, gallium, cerium, and neodymium. After washing and regeneration, the desorbed magnetic selective adsorption material can be returned to the secondary deep leaching and magnetic capture unit 90 for reuse.

[0075] In a preferred embodiment, the magnetic selective adsorption material is selected according to the type of target element. For rare earth target elements such as scandium, cerium, and neodymium, magnetic adsorption materials modified with phosphonic acid, carboxylic acid, or hydroxamic acid groups are preferred. For gallium, magnetic adsorption materials modified with hydroxamic acid, mercapto, or nitrogen-containing coordination groups are preferred. For vanadium, amine, quaternary ammonium salt, or porous oxide-supported magnetic adsorption materials are preferred. For rhenium, quaternary ammonium salt, amine, or anion-exchange magnetic adsorption materials are preferred. Through the complexation, coordination, ion exchange, or electrostatic adsorption between the above functional groups and the target element, the target element is captured in situ during the secondary deep leaching process.

[0076] Magnetic selective adsorption materials can use magnetic Fe3O4, magnetic porous silica, magnetic alumina, magnetic titanium dioxide, or magnetic porous composite oxides as magnetic cores. The surface of the magnetic core can be introduced with one or more functional groups from phosphonic acid, carboxylic acid, hydroxamic acid, amine, quaternary ammonium salt, and thiol groups through silane coupling, polymerization coating, grafting reaction, or impregnation loading. The particle size of the magnetic selective adsorption material is 50 nm to 500 μm, the specific surface area is 20 to 500 m² / g, and the saturation magnetization is 5 to 80 emu / g.

[0077] In the secondary deep leaching process, the amount of magnetic selective adsorbent added is 0.5–10 wt% of the dry basis mass of the primary leaching residue, preferably 1–5 wt%. When the magnetic selective adsorbent is added in stages, 20–50 wt% of the total amount is added in the first stage of leaching, and 50–80 wt% of the total amount is added in the middle stage of release. The first stage of leaching is used to capture the target elements released in the early stage, and the middle stage of release is used to provide new effective adsorption sites to reduce the competition for adsorption sites by impurity ions such as iron, aluminum, calcium, and magnesium. After leaching, the magnetic selective adsorbent loaded with the target elements is separated from the leaching system by an external magnetic field, and desorbed by acidic desorption solution, salt solution, or complex desorption solution to obtain a target element enriched solution.

[0078] See Figure 5 The kiln tail gas generated by rotary kiln 50 is purified by dust removal device 111 and then enters tail gas separation and purification and resource utilization unit 110. Tail gas separation and purification and resource utilization unit 110 includes sulfur-containing tail gas oxidation absorption branch 112, nitrogen-containing tail gas oxidation absorption branch 113, purified tail gas reflux branch 114, precursor liquid conditioning unit 115, and alkaline absorbent preparation unit 116. The sulfur-containing tail gas is converted into sulfate-containing absorbent 117 by sulfur-containing tail gas oxidation absorption branch 112. Part of sulfate-containing absorbent 117 is recycled to primary acid leaching unit 70, and the other part enters... Precursor liquid conditioning unit 115: Nitrogen-containing tail gas is converted into nitrate-containing absorbent liquid 118 through nitrogen-containing tail gas oxidation absorption branch 113. Part of the nitrate-containing absorbent liquid 118 is recycled to the secondary deep leaching and magnetic collection unit 90, and the other part enters the precursor liquid conditioning unit 115. The precursor liquid conditioning unit 115 mixes sulfate-containing absorbent liquid 117 and / or nitrate-containing absorbent liquid 118 with sulfate precursor, pore forming agent, binder or phase inversion activating component to obtain a conditioned reactive coating precursor liquid, which is then recycled to the vertical mill spray grinding unit 30.

[0079] Meanwhile, alkaline oxides from solid waste tailings or leaching residues (source 119) enter alkaline absorbent preparation unit 116. The alkaline oxides mainly include CaO and / or MgO. Alkaline absorbent preparation unit 116 contacts solid waste tailings or leaching residues rich in CaO and / or MgO with water to prepare an alkaline absorbent with a pH of 7.0–10.5 and a solid content of 5–20 wt%. This alkaline absorbent is then supplied to sulfur-containing tail gas oxidation absorption branch 112 and / or nitrogen-containing tail gas oxidation absorption branch 113. Part of the purified tail gas enters tail gas reflux branch 120 via purified tail gas reflux branch 114 and is refluxed to the coating layer stepwise pyrolysis zone and / or directional phase transformation zone of rotary kiln 50. The reflux flow rate is 15% of the total kiln tail gas, used to regulate the kiln atmosphere and participate in the coating layer pyrolysis and mineral phase transformation process.

[0080] In a preferred embodiment, the sulfate-containing absorbent 117 has a sulfate concentration of 0.05–2.0 mol / L, and the nitrate-containing absorbent 118 has a nitrate concentration of 0.05–2.0 mol / L. When the sulfate-containing absorbent 117 is reused in the primary acid leaching unit 70, sulfuric acid or dilution water is added according to the acid concentration required for primary acid leaching to maintain the sulfuric acid mass concentration in the primary acid leaching system at 5–25 wt%. When the nitrate-containing absorbent 118 is reused in the secondary deep leaching and magnetic collection unit 90, nitric acid or dilution water is added according to the acid concentration required for secondary deep leaching to maintain the nitric acid mass concentration in the secondary deep leaching system at 20–45 wt%.

[0081] When sulfate-containing absorbent 117 and / or nitrate-containing absorbent 118 enter the precursor liquid conditioning unit 115, they are first subjected to sedimentation, filtration, or membrane filtration to remove suspended solids, so that the suspended solids content is not higher than 1 wt%. Then, they are mixed with one or more of ammonium sulfate, ammonium bisulfate, sodium sulfate, nitrate precursor, ammonium bicarbonate, starch, lignin, bentonite, water glass, polyvinyl alcohol, and silica sol to obtain a reactive coating precursor liquid. The obtained reactive coating precursor liquid has a solid content of 5-40 wt%, a pH of 3-9, and a viscosity of 10-500 mPa·s. After being adjusted by the precursor liquid conditioning unit 115, it is sent to the vertical mill spray grinding unit 30.

[0082] When the component identification unit 20 detects that the solid waste tailings raw material is a high-activation-difficulty type of aluminosilicate, the precursor liquid conditioning unit 115 increases the addition ratio of sulfate-containing absorbent 117 and sulfate precursor; when the solid waste tailings raw material is an iron-aluminum composite phase activation type, the addition ratio of sulfate precursor, nitrate precursor or phase inversion promoting component is increased; when the solid waste tailings raw material is a high-alkaline component type, the addition ratio of sulfate-containing absorbent 117 and nitrate-containing absorbent 118 is reduced, and the ratio of pore forming agent and binder is increased to reduce subsequent acid consumption and ensure the molding strength of reactive coated particles 140.

[0083] In this embodiment, a portion of the mother liquor generated from the primary acid leaching and secondary deep leaching is sent to the mother liquor regeneration unit 130. The mother liquor regeneration unit 130 may employ a bipolar membrane electrodialysis device to regenerate the acidic mother liquor, yielding regenerated acid and regenerated alkali. The regenerated acid is recycled to the primary acid leaching unit 70 and / or the secondary deep leaching and magnetic collection unit 90, depending on the acid type and concentration. The regenerated alkali is recycled to the tail gas separation, purification, and resource utilization unit 110 for tail gas absorption or alkaline absorption liquid preparation. Example 2

[0084] This embodiment uses coal gangue as the treatment object. Coal gangue is mainly composed of aluminosilicate mineral phases and contains small amounts of gallium, scandium and rare earth elements.

[0085] Coal gangue is fed into crushing and homogenization unit 10, crushed to 12-25mm, and then sent to homogenization bin for homogenization. The homogenized coal gangue is then sent to component identification unit 20 to detect the contents of Fe2O3, Al2O3, SiO2, CaO, MgO, TiO2, target element content, moisture content, and loss on ignition. The test results show that the total content of SiO2 and Al2O3 in the coal gangue is relatively high, indicating that the proportion of aluminosilicate mineral phase is relatively high. Therefore, the proportion of sulfate precursor and molten salt activation component in the reactive coating precursor liquid and phase transformation activation component is increased to enhance the activation effect of aluminosilicate mineral phase in the subsequent calcination process.

[0086] The homogenized coal gangue is fed into the vertical mill spray grinding unit 30 for grinding; the working pressure of the vertical mill is controlled at 8MPa, the separator speed is controlled at 600rpm, and the residence time of the material in the vertical mill is 6min; during the grinding process, a reactive coating precursor liquid is sprayed simultaneously; the reactive coating precursor liquid, by mass, includes: 6 parts ammonium bisulfate, 2 parts sodium sulfate, 2 parts ammonium bicarbonate, 0.8 parts polyvinyl alcohol, 0.5 parts water glass, and the remainder is water; based on the dry basis of the precursor liquid, its addition amount is 4wt% of the dry basis mass of the coal gangue; the powder obtained after grinding reaches 200 mesh, and the sieve residue is not higher than 10%.

[0087] The ground coal gangue powder is fed into the layered granulation unit 40. First, a pore-inducing component containing ammonium bicarbonate and a small amount of polyvinyl alcohol is sprayed in to form a pore-inducing layer 142 on the outside of the solid waste tailings powder core 141. Then, a phase-inversion activating component containing ammonium bisulfate, sodium sulfate and a small amount of carbonate precursor is sprayed in to form a phase-inversion activating layer 143 on the outside of the pore-inducing layer 142. Finally, a slow-release film-forming component containing water glass and bentonite is sprayed in to form a slow-release protective layer 144 on the outside of the phase-inversion activating layer 143. After granulation, reactive coated particles 140 with a particle size of 1 to 2.5 mm are obtained.

[0088] The reactive coated particles 140 are fed into a rotary kiln 50 for staged atmospheric catalytic calcination. The preheating desorption temperature is controlled at 320℃ to remove free water and adsorbed water from the particles. The stepwise pyrolysis temperature of the coating layer is controlled at 480℃ to decompose the pore-inducing layer 142 to form a pore structure and to release reactive gases from part of the phase-inversion activation layer 143. The directional phase-inversion temperature is controlled at 620℃ to promote the activation of the aluminosilicate mineral phase in the coal gangue and to transform gallium, scandium, and rare earth elements from a relatively stable occurrence state to a more easily leached state. The total residence time of the reactive coated particles 140 in the rotary kiln 50 is 70 min, and the rotary kiln speed is 0.5 rpm.

[0089] Calcined particles with a kiln exit temperature of approximately 550℃ are directly introduced into the hot quenching negative pressure leaching unit 60. The quenching liquid is a 3wt% sulfuric acid mother liquor with a liquid temperature controlled at 40℃. The contact time between the calcined particles and the quenching liquid is 2 minutes. During the quenching process, a negative pressure pulse is applied with a negative pressure value of -20kPa. The duration of a single negative pressure pulse is 15 seconds, and the number of cycles is 4. Through the combined action of thermal shock and negative pressure pulse, microcracks are formed inside the particles, allowing the quenching liquid to enter the internal channels of the particles, thus obtaining an activated slurry.

[0090] The activated slurry is fed into the primary acid leaching unit 70, where 8wt% dilute sulfuric acid is added. The liquid-to-solid ratio is controlled at 6:1 mL / g, the leaching temperature is 75℃, and the leaching time is 2.5h. After the primary acid leaching is completed, the primary leaching solution and primary leaching residue are separated by the primary solid-liquid separation unit 80. The primary leaching solution can be used to recover conventional components such as aluminum and iron, while the primary leaching residue enters the secondary deep leaching and magnetic collection unit 90.

[0091] The primary leaching residue was subjected to secondary deep leaching using a 25wt% nitric acid system with a liquid-to-solid ratio of 4:1 mL / g, a leaching temperature of 95℃, and a leaching time of 2 h. During the secondary deep leaching process, a magnetic hydroxamic acid adsorbent was added to allow gallium and rare earth-related elements to be adsorbed in situ during the leaching release. After leaching, the magnetic adsorbent loaded with the target elements was separated by an external magnetic field, and then desorbed using an acidic desorption solution to obtain a target element enrichment solution.

[0092] In this embodiment, the kiln tail gas enters the tail gas separation and purification and resource utilization unit 110 after being dusted by the dust removal device 111. The sulfur-containing components are oxidized and absorbed to form a sulfate-containing absorbent liquid 117. Part of the absorbent liquid is recycled to the primary acid leaching unit 70, and the other part is mixed with sulfate precursor, pore forming agent and binder and used as a component of the reactive coating precursor liquid, which is recycled to the vertical mill spray grinding unit 30. Part of the purified tail gas is recycled to the rotary kiln 50 through the tail gas return branch 120 at a ratio of 10% of the total kiln tail gas, which is used to adjust the kiln atmosphere in the graded cracking zone of the coating layer. Example 3

[0093] This embodiment describes a treatment method using a mixture of bauxite tailings, coal gangue, and smelting tailings as raw materials. This embodiment focuses on multi-source mixed solid waste tailings; bauxite tailings, coal gangue, and smelting tailings are mixed in a mass ratio of 5:3:2 to obtain a mixed solid waste tailings raw material.

[0094] The mixed raw materials are fed into the crushing and homogenization unit 10 for crushing, so that the particle size is controlled between 10 and 25 mm, and then homogenized in the homogenization chamber for 6 hours. The homogenized mixed raw materials are then fed into the component identification unit 20 to detect the contents of Fe2O3, Al2O3, SiO2, CaO, MgO, TiO2, target element content, moisture content, and loss on ignition. Since the mixed raw materials contain bauxite tailings, coal gangue, and smelting tailings, the mineral phase composition is relatively complex. Therefore, sulfate precursors, pore forming agents, molten salt activating components, and slow-release film-forming components are introduced into the precursor solution to take into account the needs of particle forming, mineral phase transformation, and leaching activation of multi-source tailings.

[0095] The homogenized mixed raw materials are fed into the vertical mill spray grinding unit 30 for grinding; the working pressure of the vertical mill is controlled at 11MPa, the separator speed is 700rpm, and the residence time of the material in the vertical mill is 9min; during the grinding process, a reactive coating precursor liquid is sprayed simultaneously; the reactive coating precursor liquid, by mass, includes: 6 parts ammonium sulfate, 2 parts sodium sulfate, 1.5 parts starch, 1 part bentonite, 0.8 parts water glass, and the remainder is water; the amount added is 7wt% of the dry basis of the precursor liquid; after grinding, the fineness of the material reaches 200 mesh, and the sieve residue is not higher than 6%.

[0096] The ground mixed tailings powder is fed into the layered granulation unit 40; first, a pore-inducing component containing starch and lignin is sprayed in to form a pore-inducing layer 142; then, a phase-inversion activating component containing ammonium sulfate, sodium sulfate, CaF2 and Fe2O3 is sprayed in to form a phase-inversion activating layer 143; finally, a slow-release film-forming component containing bentonite and water glass is sprayed in to form a slow-release protective layer 144; after granulation, reactive coated particles 140 with a particle size of 1-4 mm are obtained.

[0097] Reactive coated particles 140 are fed into a rotary kiln 50 for staged atmospheric catalytic calcination. The preheating desorption temperature is controlled at 330℃, the coating layer pyrolysis temperature is controlled at 560℃, the directional phase transformation temperature is controlled at 760℃, and the total residence time is controlled at 95 min. During the directional phase transformation process, a phase transformation promoter composed of CaF2 and Fe2O3 is injected at an amount of 1.5 wt% of the dry basis of the mixed raw materials. In this process, the pore-inducing layer 142 decomposes to form a pore structure, and the phase transformation activation layer 143 releases reactive components and forms a local molten salt activation environment, promoting the transformation of conventional metal mineral phases such as iron, aluminum, and copper, as well as mineral phases containing vanadium, rhenium, and rare earth elements in multi-source solid waste.

[0098] The calcined particles with an outlet temperature of approximately 650℃ are directly fed into the hot quenching negative pressure leaching unit 60. The quenching liquid is a mixture of sulfuric acid with a mass concentration of 5 wt% and a portion of circulating mother liquor. The liquid temperature is controlled at 50℃ and the contact time is 4 min. During the quenching process, a negative pressure pulse is applied with a negative pressure value of -40 kPa. The single negative pressure is maintained for 30 s and the cycle is repeated 6 times to obtain an activated slurry.

[0099] The activated slurry is fed into the primary acid leaching unit 70, where it is leached with 10wt% dilute sulfuric acid at a liquid-to-solid ratio of 4.5:1mL / g, a leaching temperature of 90℃, and a leaching time of 2.5h. After the primary acid leaching, the slurry is filtered by the primary solid-liquid separation unit 80 to obtain the primary leachate and the primary leachate residue. The primary leachate is used to recover conventional metals such as iron, aluminum, and copper.

[0100] The primary leaching residue was fed into the secondary deep leaching and magnetic trapping unit 90. Secondary deep leaching was carried out using a nitric acid system with a mass concentration of 28wt%, a liquid-to-solid ratio of 5:1 mL / g, a leaching temperature of 100℃, and a leaching time of 3h. During the secondary deep leaching process, magnetic porous oxide-loaded adsorbent material was added to capture vanadium, rhenium, and some rare earth-related elements in situ. After leaching, the magnetic adsorbent material loaded with the target elements was separated from the leaching system by an external magnetic field and desorbed using a desorption solution to obtain a target element enriched solution.

[0101] In this embodiment, a portion of the mother liquor generated from the primary acid leaching and secondary deep leaching is sent to the mother liquor regeneration unit 130 for regeneration to obtain acid and alkali solutions. The regenerated acid solution is returned to the primary acid leaching unit 70 or the secondary deep leaching and magnetic trapping unit 90, and the regenerated alkali solution is used for tail gas absorption in the tail gas separation and purification and resource utilization unit 110. After dust removal and separation purification, the sulfur-containing components of the tail gas from the rotary kiln 50 are converted into sulfate-containing absorbent 117, and the nitrogen-containing components are converted into nitrate-containing absorbent 118. A portion of the sulfate-containing absorbent 117 and the nitrate-containing absorbent 118 are reused in the leaching process, and another portion is used for conditioning the precursor liquid and returned to the vertical mill spray grinding unit 30. A portion of the purified tail gas is returned to the rotary kiln 50 via the tail gas return branch 120 at a ratio of 20% of the total kiln tail gas to adjust the atmosphere in the progressive cracking region and the directional phase inversion region of the coating layer. Example 4

[0102] This embodiment is used to illustrate the adaptive formulation method of the reactive coating precursor liquid in this invention; After the solid waste tailings raw material is crushed and homogenized, it is sent to the component identification unit 20 to detect its Fe2O3, Al2O3, SiO2, CaO, MgO, TiO2 content, target element content, moisture content and loss on ignition; based on the detection results, the proportions of reactive coating precursor liquid, pore induction component, phase inversion activation component and slow-release film-forming component are adjusted.

[0103] When the test results show that the total content of SiO2 and Al2O3 is high, it indicates that there are more aluminosilicate mineral phases in the solid waste tailings, making subsequent calcination and activation more difficult. In this case, the proportion of sulfate precursors, carbonate precursors or molten salt precursors in the phase transformation activation component should be increased to enhance the destruction and activation of aluminosilicate mineral phases during calcination.

[0104] When the test results show that the content of CaO and / or MgO is high, it indicates that there are more alkaline oxides in the tailings, and subsequent acid leaching may result in high acid consumption. At this time, the proportion of pore-inducing components should be increased and the amount of acidic precursor added should be appropriately reduced. At the same time, the tailings or leaching residue rich in CaO and / or MgO should be used to prepare alkaline absorbent to improve the utilization rate of alkaline components in the system.

[0105] When the test results show that the content of the target element is lower than the preset value, or the target element is in a dispersed state, the proportion of phase-integrated activation components is increased, or the residence time of directional phase in the rotary kiln 50 is extended to enhance the transformation degree of the mineral phase in which the target element is located.

[0106] In one specific formulation, for coal gangue with a high silicate mineral phase, the reactive coating precursor liquid includes, by mass, 6-10 parts ammonium bisulfate, 2-5 parts sodium sulfate, 1-4 parts ammonium bicarbonate, 0.5-1.5 parts polyvinyl alcohol, 0.5-2 parts water glass, and the remainder is water.

[0107] In another specific formulation, for smelting tailings with high CaO and MgO content, the reactive coating precursor liquid includes, by mass, 4-8 parts ammonium sulfate, 1-3 parts starch, 1-3 parts lignin, 0.5-2 parts bentonite, 0.5-2 parts silica sol, and the remainder is water.

[0108] By employing the above method, the reactive coating precursor liquid is matched with the mineral phase composition of solid waste tailings, thereby improving the adaptability of this invention to solid waste tailings from different sources. Example 5

[0109] For a system used to implement the method of the present invention, see [link to documentation]. Figure 2This embodiment provides a solid waste tailings treatment system for implementing the above method; the system includes a crushing and homogenization unit 10, a component identification unit 20, a vertical mill spray grinding unit 30, a layered granulation unit 40, a rotary kiln 50, a hot quenching negative pressure leaching unit 60, a primary acid leaching unit 70, a primary solid-liquid separation unit 80, a secondary deep leaching and magnetic capture unit 90, a magnetic separation and desorption unit 100, a tail gas separation, purification and resource utilization unit 110, a tail gas reflux branch 120, and a mother liquor regeneration unit 130.

[0110] The crushing and homogenization unit 10 is used to crush and homogenize the solid waste tailings raw material; the discharge end of the crushing and homogenization unit 10 is connected to the component identification unit 20; the component identification unit 20 is used to detect the content of the main oxides, the content of the target elements, the moisture content and the loss on ignition in the solid waste tailings raw material, and to use the detection results to adjust the ratio of the reactive coating precursor liquid and the coating components of each layer.

[0111] The vertical mill spray grinding unit 30 is connected to the component identification unit 20 and is used to grind the solid waste tailings raw material after crushing, homogenization and component identification, and to spray reactive coating precursor liquid during the grinding process; the vertical mill spray grinding unit 30 is provided with a solid waste tailings feed inlet, a hot air inlet, a reactive coating precursor liquid spray inlet, a powder outlet and a dust removal interface.

[0112] The layered granulation unit 40 is connected to the vertical mill spray grinding unit 30 and is used to form reactive coated particles 140 with gradient multilayer reactive coating layers from the powder after vertical mill grinding. The layered granulation unit 40 includes at least three spray interfaces, which are used to introduce pore-inducing components, phase-inversion activating components and slow-release film-forming components, respectively.

[0113] The rotary kiln 50 is connected to the layered granulation unit 40 and is used to perform segmented atmosphere catalytic calcination of reactive coated particles 140. The rotary kiln 50 forms a preheating desorption zone, a coating layer step-by-step pyrolysis zone, and a directional phase inversion zone in sequence along the material movement direction. The coating layer step-by-step pyrolysis zone and / or the directional phase inversion zone are provided with a phase inversion promoter injection inlet and a tail gas recirculation interface.

[0114] The hot-quenching negative pressure leaching unit 60 is connected to the solid discharge end of the rotary kiln 50, and is used to allow the calcined particles to come into contact with the weakly acidic circulating liquid or circulating mother liquor before they are cooled to room temperature, and to obtain an activated slurry under the action of negative pressure pulses. The hot-quenching negative pressure leaching unit 60 includes a calcined particle inlet 61, a closed leaching chamber 62, a weakly acidic circulating liquid inlet 63, a circulating mother liquor inlet 64, a negative pressure pulse generator 65, a steam / tail gas outlet 66, an activated slurry outlet 67, and an internal immersion zone or wetting zone 68.

[0115] The primary acid leaching unit 70 is connected to the hot quenching negative pressure leaching unit 60 and is used to perform primary acid leaching on the activated slurry; the primary solid-liquid separation unit 80 is connected to the primary acid leaching unit 70 and is used to perform solid-liquid separation on the slurry after primary acid leaching to obtain primary leachate and primary leach residue.

[0116] The secondary deep leaching and magnetic trapping unit 90 is connected to the primary solid-liquid separation unit 80 and is used to perform secondary deep leaching on the primary leaching residue. During the secondary deep leaching process, the target element is captured in situ by magnetic selective adsorption material. The magnetic separation and desorption unit 100 is connected to the secondary deep leaching and magnetic trapping unit 90 and is used to separate the magnetic selective adsorption material loaded with the target element by applying an external magnetic field and desorb it to obtain a target element enriched solution.

[0117] See Figure 5 The tail gas separation, purification, and resource utilization unit 110 is connected to the tail gas outlet of the rotary kiln 50 and is used for dust removal, separation, purification, and resource utilization of the kiln tail gas. The tail gas separation, purification, and resource utilization unit 110 includes a dust removal device 111, a sulfur-containing tail gas oxidation absorption branch 112, a nitrogen-containing tail gas oxidation absorption branch 113, a purified tail gas return branch 114, a precursor liquid conditioning unit 115, and an alkaline absorbent preparation unit 116. The sulfur-containing tail gas oxidation absorption branch 112 is used to form a sulfate-containing absorbent 117, and the nitrogen-containing tail gas oxidation absorption branch 113 is used to form a nitrate-containing absorbent 118. A portion of the sulfate-containing absorbent 117 and the nitrate-containing absorbent 118 is recycled to the primary acid leaching unit 70 and the secondary deep leaching and magnetic collection unit 90, and another portion is recycled to the vertical mill spray grinding unit 30 via the precursor liquid conditioning unit 115.

[0118] The alkaline absorbent preparation unit 116 is connected to the alkaline oxide source 119 in the solid waste tailings or leaching residue, and is used to prepare alkaline absorbent for the sulfur-containing tail gas oxidation absorption branch 112 and / or the nitrogen-containing tail gas oxidation absorption branch 113; one end of the tail gas return branch 120 is connected to the tail gas separation, purification and resource utilization unit 110, and the other end is connected to the coating layer stepwise cracking region and / or directional phase transformation region of the rotary kiln 50, and is used to return part of the purified kiln tail gas to the rotary kiln 50 as an auxiliary reaction gas to participate in the coating layer cracking and mineral phase transformation process.

[0119] The mother liquor regeneration unit 130 is connected to the primary acid leaching unit 70, the secondary deep leaching and magnetic collection unit 90, and the tail gas separation, purification and resource recovery unit 110. It is used to regenerate the primary acid leaching mother liquor or the secondary deep leaching mother liquor to obtain acid and alkali solutions. The obtained acid solution is reused in the primary acid leaching unit 70 and / or the secondary deep leaching and magnetic collection unit 90, and the obtained alkali solution is reused in the tail gas separation, purification and resource recovery unit 110. Example 6

[0120] This embodiment is used to illustrate the mother liquor regeneration and acid-base recycling method in this invention.

[0121] A certain amount of acidic mother liquor is generated during the primary acid leaching and secondary deep leaching processes. Part of the acidic mother liquor is sent to the mother liquor regeneration unit 130 for regeneration treatment. The mother liquor regeneration unit 130 can be a bipolar membrane electrodialysis device or other membrane separation or electrochemical devices that can realize acid and alkali regeneration. After regeneration treatment, regenerated acid and regenerated alkali are obtained.

[0122] The regenerated acid solution can be reused in the primary acid leaching unit 70 or the secondary deep leaching and magnetic trapping unit 90, depending on the type and concentration of acid. When the regenerated acid solution mainly contains sulfate, it is preferentially reused in the primary acid leaching unit 70. When the regenerated acid solution mainly contains nitrate, it is preferentially reused in the secondary deep leaching and magnetic trapping unit 90.

[0123] The regenerated alkaline solution can be sent to the tail gas separation, purification and resource utilization unit 110 to absorb acidic components in the kiln tail gas, or to prepare alkaline absorbent solution together with the solid waste tailings raw materials and the CaO and / or MgO-rich parts of the leaching residue.

[0124] By regenerating the mother liquor, the consumption of fresh acid and alkali solutions can be reduced, the amount of waste liquid discharged can be decreased, and the media recycling rate of the treatment system of this invention can be improved. Example 7

[0125] This embodiment is used to illustrate the subsequent processing method of the target element enrichment solution; The target element enrichment solution obtained after desorption by magnetic selective adsorption materials can be further purified by extraction, back-extraction, precipitation, crystallization, electrowinning or ion exchange, depending on the type of target element.

[0126] When the target element is scandium, it can be enriched by adjusting the acidity of the enrichment solution and using an organic extractant, followed by back-extraction and precipitation. When the target element is gallium, gallium can be separated from the main impurity elements by adjusting the solution pH and complexation state, followed by precipitation or crystallization to obtain gallium-enriched products. When the target element is vanadium or rhenium, appropriate redox control, extraction, or precipitation methods can be selected based on its valence state and complexation form. When the target element is rare earth elements such as cerium and neodymium, further separation can be achieved by extraction grouping, precipitation, or ion exchange.

[0127] The aforementioned subsequent refining methods can be selected according to the type of target element and the composition of the enrichment solution, and do not affect the core technical solution of this invention regarding the activation, leaching and in-situ collection of solid waste tailings. Example 8

[0128] This embodiment illustrates the specific implementation methods of the linkage control of mineral phase-tail gas-negative pressure wetting, dual-temperature zone controllable pyrolysis microcapsules, and segmented addition of magnetic selective adsorption materials.

[0129] Using bauxite tailings containing scandium, gallium, and rare earth elements as the treatment target, the bauxite tailings were crushed to 10-20 mm and then homogenized. The results of the component identification unit 20 showed that the total mass content of SiO2 and Al2O3 in the bauxite tailings was 64 wt%, and the total mass content of Fe2O3 and Al2O3 was 56 wt%. The X-ray diffraction results showed that the content of aluminosilicate phase and iron-aluminum composite phase was high. Therefore, it was determined that the bauxite tailings had the characteristics of both the aluminosilicate type with high activation difficulty and the iron-aluminum composite phase activation type.

[0130] Based on the above judgment results, the reactive coating precursor liquid and the stratified granulation components were prepared. The reactive coating precursor liquid, by mass, included 8 parts ammonium sulfate, 4 parts sodium sulfate, 2 parts ammonium bicarbonate, 2 parts starch, 1 part water glass, 0.5 parts polyvinyl alcohol, and the remainder was water. The amount added was 6 wt% of the dry weight of the bauxite tailings. The bauxite tailings after component identification were sent to the vertical mill spray grinding unit 30. The vertical mill working pressure was 10 MPa, the separator speed was 650 rpm, the material residence time was 8 min, and the reactive coating precursor liquid was sprayed simultaneously during the grinding process so that the obtained powder reached 200 mesh with a sieve residue of no more than 8%.

[0131] The obtained powder is fed into a layered granulation unit 40 for granulation. First, a pore-inducing component containing starch and ammonium bicarbonate is introduced to form a pore-inducing layer 142. Then, a phase-inversion activating component containing a first microcapsule, a second microcapsule, sodium sulfate, and a small amount of calcium fluoride is introduced to form a phase-inversion activating layer 143. Finally, a slow-release film-forming component containing water glass and bentonite is introduced to form a slow-release protective layer 144. The first microcapsule uses ammonium sulfate and ammonium bicarbonate as the core material and polyvinyl alcohol and silica sol as the shell material, with a pyrolysis or rupture temperature of 350-650℃. The second microcapsule uses sodium sulfate, sodium carbonate, and calcium fluoride as the core material and water glass and bentonite as the shell material, with a pyrolysis or rupture temperature of 550-900℃. The mass ratio of the first microcapsule to the second microcapsule is 1:1.5. The resulting reactive coated particles 140 have a particle size of 1-3 mm, and the total mass of the gradient multilayer reactive coating layer accounts for 7 wt% of the total mass of the reactive coated particles 140.

[0132] Reactive coated particles 140 are fed into rotary kiln 50 for segmented atmosphere catalytic calcination. The temperature of the preheating desorption section is controlled at 330℃, the oxygen content is controlled at 12 vol%, and the residence time is 20 min. The temperature of the coating layer stepwise pyrolysis section is controlled at 540℃, the oxygen content is controlled at 8 vol%, and the residence time is 18 min. The temperature of the directional phase inversion section is controlled at 820℃, the oxygen content is controlled at 15 vol%, and the residence time is 55 min. Part of the purified tail gas after treatment by the tail gas separation purification and resource utilization unit 110 is returned to the coating layer stepwise pyrolysis section and the directional phase inversion section via the tail gas return branch 120 at 15% of the total kiln tail gas to regulate the atmosphere inside the kiln. During calcination, when the peak release of sulfur-containing components is detected to be earlier than the preset time window, the heating rate of the coating layer stepwise pyrolysis section is reduced. When the peak release of sulfur-containing components is later than the preset time window, the residence time of the coating layer stepwise pyrolysis section is extended.

[0133] Calcined particles with a kiln exit temperature of approximately 700℃ are directly introduced into the hot-quenching negative pressure leaching unit 60. The quenching liquid is a mixture of 5wt% dilute sulfuric acid and circulating mother liquor, with a liquid temperature of 60℃. The contact time between the calcined particles and the quenching liquid is 3 minutes. The negative pressure pulse generating device 65 applies a negative pressure pulse to the sealed leaching chamber 62, with a negative pressure value of -30 kPa and a single negative pressure holding time of 20 seconds. The exhaust volume and the rate of change of the conductivity of the activated slurry are detected after each negative pressure pulse. When the difference in exhaust volume between two consecutive negative pressure pulse cycles is less than 10% of the previous exhaust volume, and the rate of change of the conductivity of the activated slurry within 120 seconds is less than 3%, the negative pressure pulse leaching is terminated, and the activated slurry is obtained.

[0134] The activated slurry is fed into the primary acid leaching unit 70, where 12wt% dilute sulfuric acid is used for primary acid leaching. The liquid-to-solid ratio is 5:1 mL / g, the leaching temperature is 85℃, and the leaching time is 2h, so that one or more of iron and aluminum preferentially enter the liquid phase. After the primary acid leaching is completed, the primary leaching solution and primary leaching residue are obtained through the primary solid-liquid separation unit 80.

[0135] The primary leaching residue was fed into the secondary deep leaching and magnetic trapping unit 90. Secondary deep leaching was carried out using a 30wt% nitric acid system with a liquid-to-solid ratio of 5:1 mL / g, a leaching temperature of 105℃, and a leaching time of 3h. The magnetic selective adsorbent was a composite functionalized adsorbent material with magnetic Fe3O4 as the core and phosphonic acid and hydroxamic acid groups grafted onto the surface. The amount added was 3wt% of the dry weight of the primary leaching residue. Specifically, 40wt% of the total amount of magnetic selective adsorbent was added within 30min after the start of secondary deep leaching, and the remaining 60wt% was added after 90min of leaching, so that scandium, gallium, and rare earth elements were captured in situ in stages during the leaching release process. After leaching, the magnetic selective adsorbent loaded with the target elements was separated by an external magnetic field and desorbed using 2mol / L hydrochloric acid to obtain a target element enrichment solution.

[0136] This embodiment improves the leaching and enrichment efficiency of scandium, gallium, and rare earth elements in solid waste tailings by matching the release of reactive components, the transformation of target element mineral phases, liquid phase wetting, and target element capture processes through mineral phase activation type determination, dual-temperature zone controllable pyrolysis microcapsule segmented release, rotary kiln segmented oxygen control and tail gas reflux, hot quenching negative pressure wetting endpoint determination, and segmented addition of magnetic selective adsorption materials.

[0137] The above embodiments detail the preferred embodiments of the present invention. It should be noted that, without departing from the technical concept of the present invention, those skilled in the art can make appropriate adjustments or substitutions to the composition of the reactive coating precursor liquid, the gradient multilayer reactive coating layer structure, the rotary kiln temperature zone setting, the hot quenching negative pressure pulse parameters, the primary acid leaching system, the secondary deep leaching system, the type of magnetic selective adsorption material, the kiln tail gas reflux ratio, and the mother liquor regeneration method. As long as the above adjustments or substitutions still adopt the technical route of the present invention, which includes vertical mill spray grinding, layered granulation to form reactive coated particles, rotary kiln segmented atmosphere catalytic calcination, hot quenching negative pressure pulse wetting, staged leaching, secondary deep leaching in-situ magnetic capture, and kiln tail gas resource recycling, all should fall within the protection scope of the present invention.

Claims

1. A method for treating solid waste tailings using vertical mill grinding combined with rotary kiln calcination, comprising the following steps: Step 1: The solid waste tailings raw material is fed into the crushing and homogenization unit (10) for crushing and homogenization treatment, so that the particle size of the solid waste tailings raw material is 10-30mm. Step 2: The solid waste tailings raw material processed in Step 1 is sent to the component identification unit (20) for component identification, and the reactive coating precursor liquid is prepared according to the identification results. Step 3: The solid waste tailings raw material after component identification is sent to the vertical mill spray grinding unit (30) for grinding, and a reactive coating precursor liquid is sprayed in during the grinding process so that the fineness of the powder obtained by grinding reaches 200 mesh and the sieve residue is not higher than 10%; Step 4: The powder obtained in Step 3 is fed into the layered granulation unit (40) for granulation, and during the granulation process, pore-inducing components, phase-inversion activating components and slow-release film-forming components are introduced in sequence to form reactive coated particles (140). in, The reactive coated particles (140) include a solid waste tailings powder core (141) and a gradient multilayer reactive coating layer covering the outside of the solid waste tailings powder core (141). The gradient multilayer reactive coating layer includes a pore-inducing layer (142), a phase-inversion activation layer (143), and a slow-release protection layer (144) arranged sequentially from the inside to the outside. Step 5: The reactive coated particles (140) are fed into a rotary kiln (50) for staged atmosphere catalytic calcination. The staged atmosphere catalytic calcination includes preheating desorption, progressive cracking of the coating layer and directional phase inversion, which are carried out sequentially along the material movement direction. During the stepwise pyrolysis of the coating layer, the pore-inducing layer (142) decomposes to form a pore structure, and the phase-inversion activation layer (143) releases reactive gases and / or forms a molten salt activation layer; during the directional phase inversion process, the mineral phase containing the target element in the solid waste tailings is transformed from a difficult-to-leach phase to an easily-leachable phase, resulting in calcined particles and kiln tail gas. Step 6: The calcined particles obtained in Step 5 are introduced into the hot quenching negative pressure leaching unit (60) before being cooled to room temperature, so that the calcined particles come into contact with the weakly acidic circulating liquid or circulating mother liquor. The negative pressure pulse is applied to the closed leaching chamber (62) by the negative pressure pulse generator (65), so that the weakly acidic circulating liquid or circulating mother liquor enters the microcracks and connecting channels inside the calcined particles to obtain activated slurry. The temperature of the calcined particles entering the hot quenching negative pressure leaching unit (60) is 450-850℃; the temperature of the weakly acidic circulating liquid or circulating mother liquor is 20-80℃; the contact time between the calcined particles and the weakly acidic circulating liquid or circulating mother liquor is 10s-10min; the absolute value of the negative pressure of the negative pressure pulse is 5-80kPa, the single negative pressure holding time is 2-120s, and the number of negative pressure pulse cycles is 1-20. Step 7: The activated slurry obtained in Step 6 is sent to the primary acid leaching unit (70) for primary acid leaching, so that one or more of iron, aluminum and copper preferentially enter the liquid phase, and then sent to the primary solid-liquid separation unit (80) for primary solid-liquid separation to obtain primary leachate and primary leachate residue. The first-stage acid leaching uses a dilute sulfuric acid system with a mass concentration of 5-25 wt%, a liquid-to-solid ratio of 3:1-8:1 mL / g, a leaching temperature of 60-110℃, and a leaching time of 1-4 h. Step 8: The primary leaching residue obtained in Step 7 is sent to the secondary deep leaching and magnetic trapping unit (90) for secondary deep leaching. During the secondary deep leaching process, magnetic selective adsorption material is added so that one or more target elements among scandium, gallium, rhenium, vanadium, cerium and neodymium are trapped in situ during the leaching process. The secondary deep leaching uses a nitric acid system or a nitric acid-containing composite acid system, wherein the mass concentration of nitric acid in the nitric acid or composite acid system is 20-45 wt%, the liquid-solid ratio is 3:1-10:1 mL / g, the leaching temperature is 80-130℃, and the leaching time is 1-6h. Step 9: The magnetic selective adsorption material loaded with the target element is sent into the magnetic separation and desorption unit (100). The magnetic selective adsorption material is separated by an external magnetic field and then desorbed to obtain the target element enrichment solution. Step 10: The kiln tail gas obtained in Step 5 is sent to the tail gas separation and purification and resource utilization unit (110) for dust removal, separation and purification and resource utilization conversion. At least part of the sulfur-containing tail gas is converted into sulfate-containing absorbent liquid (117) through the sulfur-containing tail gas oxidation absorption branch (112), and at least part of the nitrogen-containing tail gas is converted into nitrate-containing absorbent liquid (118) through the nitrogen-containing tail gas oxidation absorption branch (113). The sulfate-containing absorbent liquid (117) is recycled to the primary acid leaching unit (70) and / or the precursor liquid conditioning unit (115), and the nitrate-containing absorbent liquid (118) is recycled to the secondary deep leaching and magnetic capture unit (90) and / or the precursor liquid conditioning unit (115). The precursor liquid after conditioning by the precursor liquid conditioning unit (115) is recycled to the vertical mill spray grinding unit (30).

2. The method for treating solid waste tailings using vertical mill grinding and rotary kiln calcination according to claim 1, characterized in that: The solid waste tailings raw materials are selected from one or more of bauxite tailings, coal gangue, smelting tailings, and chemical tailings; the target elements are selected from one or more of scandium, gallium, rhenium, vanadium, cerium, and neodymium.

3. The method for treating solid waste tailings using vertical mill grinding and rotary kiln calcination according to claim 1, characterized in that: The component identification unit (20) is used to detect one or more of the following in solid waste tailings raw materials: Fe2O3, Al2O3, SiO2, CaO, MgO, TiO2 content, target element content, moisture content and loss on ignition. Based on the detection results, the ratio of reactive coating precursor liquid, pore induction component, phase inversion activation component and slow-release film-forming component is adjusted.

4. The method for treating solid waste tailings using vertical mill grinding and rotary kiln calcination according to claim 1, characterized in that: The reactive coating precursor includes a sulfate precursor, a pore-forming agent, and a binder; the sulfate precursor is selected from one or more of ammonium sulfate, ammonium bisulfate, and sodium sulfate; the pore-forming agent is selected from one or more of ammonium bicarbonate, starch, lignin, and sawdust; and the binder is selected from one or more of water glass, bentonite, polyvinyl alcohol, and silica sol.

5. The method for treating solid waste tailings using vertical mill grinding and rotary kiln calcination according to claim 1, characterized in that: The pore-inducing layer (142) includes a pore-forming agent and a first binder; the phase-inversion activation layer (143) includes one or more of sulfate precursors, nitrate precursors, carbonate precursors, and fluoride precursors; and the slow-release protective layer (144) includes one or more slow-release film-forming components of water glass, bentonite, polyvinyl alcohol, and silica sol.

6. The method for treating solid waste tailings by using vertical mill grinding in conjunction with rotary kiln calcination according to claim 1, characterized in that: The total mass of the gradient multilayer reactive coating layer accounts for 1 to 15 wt% of the total mass of the reactive coated particles (140); among which, the pore-inducing layer (142) accounts for 0.2 to 5 wt% of the total mass of the reactive coated particles (140), the phase-inversion activation layer (143) accounts for 0.5 to 8 wt% of the total mass of the reactive coated particles (140), and the sustained-release protective layer (144) accounts for 0.1 to 3 wt% of the total mass of the reactive coated particles (140); the particle size of the reactive coated particles (140) is 0.5 to 5 mm.

7. The method for treating solid waste tailings using vertical mill grinding and rotary kiln calcination according to claim 1, characterized in that: In the vertical mill spray grinding unit (30), the working pressure of the vertical mill is 6-14 MPa, the speed of the separator is 400-900 rpm, and the residence time of the material in the vertical mill is 3-12 min.

8. The method for treating solid waste tailings by using vertical mill grinding in conjunction with rotary kiln calcination according to claim 1, characterized in that: In the rotary kiln (50), the preheating and desorption temperature is 200-450℃; the temperature for the stepwise pyrolysis of the coating layer is 350-650℃; the temperature for directional phase inversion is 550-900℃; and the total residence time of the reactive coated particles (140) in the rotary kiln (50) is 20-120 min.

9. A method for treating solid waste tailings using vertical mill grinding in conjunction with rotary kiln calcination according to claim 1, characterized in that: The hot-quenching negative pressure leaching unit (60) includes a calcined particle inlet (61), a closed leaching chamber (62), a weakly acidic circulating liquid inlet (63), a circulating mother liquor inlet (64), a negative pressure pulse generator (65), a steam / tail gas outlet (66), an activated slurry outlet (67), and an internal immersion zone or wetting zone (68). The calcined particles enter the closed leaching chamber (62) through the calcined particle inlet (61), the weakly acidic circulating liquid enters the closed leaching chamber (62) through the weakly acidic circulating liquid inlet (63), and the circulating mother liquor enters the closed leaching chamber (62) through the circulating mother liquor inlet (64). Under the action of the negative pressure pulse generator (65), the hot-quenching negative pressure pulse wetting is completed.

10. A system for implementing the method according to any one of claims 1 to 9, characterized in that, include: The unit includes a crushing and homogenization unit (10), a component identification unit (20), a vertical mill spray grinding unit (30), a layered granulation unit (40), a rotary kiln (50), a hot quenching negative pressure leaching unit (60), a primary acid leaching unit (70), a primary solid-liquid separation unit (80), a secondary deep leaching and magnetic capture unit (90), a magnetic separation and desorption unit (100), a tail gas separation, purification and resource utilization unit (110), a tail gas reflux branch (120), and a mother liquor regeneration unit (130). The crushing and homogenization unit (10), the component identification unit (20), the vertical mill spray grinding unit (30), the layered granulation unit (40), the rotary kiln (50), the hot quenching negative pressure leaching unit (60), the primary acid leaching unit (70), the primary solid-liquid separation unit (80), the secondary deep leaching and magnetic trapping unit (90), and the magnetic separation and desorption unit (100) are connected in sequence. The tail gas separation and purification and resource utilization unit (110) is connected to the tail gas outlet of the rotary kiln (50). The tail gas separation and purification and resource utilization unit (110) includes a dust removal device (111), a sulfur-containing tail gas oxidation absorption branch (112), a nitrogen-containing tail gas oxidation absorption branch (113), a purified tail gas return branch (114), a precursor liquid conditioning unit (115), and an alkaline absorption liquid preparation unit (116). The sulfur-containing tail gas oxidation absorption branch (112) is used to form sulfate-containing absorbent (117), and the nitrogen-containing tail gas oxidation absorption branch (113) is used to form nitrate-containing absorbent (118). The alkaline absorbent preparation unit (116) is connected to the alkaline oxide source (119) in the solid waste tailings or leaching residue, and is used to prepare alkaline absorbent for supplying the sulfur-containing tail gas oxidation absorption branch (112) and / or the nitrogen-containing tail gas oxidation absorption branch (113). The exhaust gas return branch (120) is used to return part of the purified exhaust gas to the rotary kiln (50). The mother liquor regeneration unit (130) is connected to the primary acid leaching unit (70), the secondary deep leaching and magnetic collection unit (90), and the tail gas separation, purification and resource utilization unit (110), respectively, for regenerating the primary acid leaching mother liquor and / or the secondary deep leaching mother liquor, and recycling the regenerated acid liquor back to the primary acid leaching unit (70) and / or the secondary deep leaching and magnetic collection unit (90), and recycling the regenerated alkali liquor back to the tail gas separation, purification and resource utilization unit (110).

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