A method and system for full component cascade recovery of fly ash

Abstract

The present application belongs to the technical field of comprehensive utilization of industrial solid waste resources, and relates to a full-component gradient recovery method and system of fly ash, comprising the following steps: pretreatment of powder; impurity removal of powder; magnetic bead product and demagnetization of powder; carbon-rich product and decarburization of powder; floating beads, sinking beads and ultra-fine fly ash. The present application can effectively reduce the water content of fly ash and eliminate the agglomeration and adhesion between particles by sequentially performing drying, depolymerization and homogenization pretreatment, so that the original small physical property differences between components can be highlighted and enlarged, creating good material conditions for subsequent separation. On this basis, by sequentially performing sorting, magnetic separation, electric separation and multi-stage air classification, each component can be accurately separated and gradually enriched by using the differences in particle size, magnetism, electrical property and density, thereby forming a systematic and gradient full-component sorting and recovery process, effectively improving the sorting efficiency and recovery rate of each component, and improving the product purity and quality stability.

Description

Technical Field

[0001] This invention belongs to the field of comprehensive utilization technology of industrial solid waste resources, and relates to a method and system for the full-component cascade recovery of fly ash. Background Technology

[0002] Fly ash is a fine particulate solid waste produced during the combustion process of coal-fired power plants. Its storage not only requires a large amount of land resources but also poses a potential threat to soil, water, and atmospheric environments. However, fly ash is not entirely waste. Its chemical composition mainly includes 40%–60% SiO2, 20%–35% Al2O3, 4%–10% Fe2O3, 2%–10% CaO, and 3%–20% unburned carbon. It is also rich in high-value-added components such as hollow microspheres (including cenospheres and sedimentary beads), magnetic beads, and highly active fine ash, forming "artificial minerals." These components have broad application prospects in building materials, chemicals, environmental protection, metallurgy, ceramics, and other fields. Therefore, fly ash is considered a "resource in the wrong place."

[0003] Currently, for the separation and extraction of high-value-added components in fly ash, a single physical sorting method, such as gravity settling or sieving, can be used to achieve the preliminary recovery of one or more target components, such as cenospheres, magnetic beads, unburned carbon, and fine ash.

[0004] However, due to the small differences in physical properties among the components of fly ash, single physical sorting can easily lead to insufficient dissociation and precise separation of the target components during the sorting process, resulting in significantly low recovery rates of useful components and product purity. At the same time, it causes large fluctuations in product quality and poor batch stability, making it difficult to meet the requirements for subsequent utilization. Summary of the Invention

[0005] The purpose of this invention is to provide a method and system for the full-component cascade recovery of fly ash, which can achieve efficient separation and high-value recovery of multiple components such as cenospheres, magnetic beads, unburned carbon and highly active fine ash, effectively improve the recovery rate and product purity of each component, and ensure the stability of product quality.

[0006] To achieve the above objectives, the technical solution provided by the present invention is as follows: A method for the full-component cascade recovery of fly ash, comprising the following steps: The raw fly ash is dried, deagglomerated and homogenized to obtain pretreated powder with a preset moisture content and preset particle size. The pretreated powder is sorted to remove coarse foreign matter, resulting in purified powder. The impurity-removing powder is subjected to magnetic separation to separate the magnetic components, resulting in magnetic bead products and demagnetized powder. The demagnetized powder is subjected to electrostatic separation to separate unburned carbon particles with good conductivity, resulting in carbon-rich products and decarbonized powder. The decarbonized powder is subjected to multi-stage air classification to separate cenospheres, sediments, and ultrafine fly ash in sequence.

[0007] The invention is further characterized by: The preset moisture content is 0.5%~0.8%, and the preset particle size is 0.5μm~300μm.

[0008] The coarse-grained heterogeneous impurities include unburned coarse carbon particles, bottom slag particles, and metal oxide debris.

[0009] The specific surface area of ​​the ultrafine fly ash is 600 m². 2 / kg~800m 2 / kg.

[0010] Before the raw fly ash undergoes drying, deagglomeration, and homogenization treatments, it is first ground to a specific surface area of ​​400 m². 2 / kg~550m 2 / kg.

[0011] A complete component cascade recovery system for fly ash, comprising: The pretreatment unit is used to dry, deagglomerate and homogenize the raw fly ash to obtain pretreated powder with a preset moisture content and preset particle size. The sorting unit is used to sort the pretreated powder, remove coarse foreign matter from the pretreated powder, and obtain impurity-free powder. The magnetic separation unit is used to perform magnetic separation on the impurity-removing powder, separating the magnetic components to obtain magnetic bead products and demagnetized powder; The electro-separation unit is used to electro-separate the demagnetized powder, separating unburned carbon particles with good conductivity to obtain carbon-rich products and decarbonized powder. The wind-powered classification unit is used to classify decarbonized powder into multiple stages by wind power, separating cenospheres, sediments, and ultrafine fly ash in sequence.

[0012] The sorting unit includes an air classifier, the magnetic separation unit includes a high-gradient magnetic separator, and the electro-separation unit is a high-voltage electro-separator.

[0013] The air classifier is either a vertical vortex air classifier or a horizontal turbine air classifier, and the cutting particle size of the air classifier is 45μm~75μm.

[0014] The wind-based classification unit includes a three-stage eddy current classifier. The first-stage eddy current classifier separates the floating beads, the second-stage eddy current classifier separates the sinking beads, and the third-stage eddy current classifier separates the fine fly ash.

[0015] The classifying wheel speed of the first-stage eddy classifier is 300 r / min to 600 r / min, the classifying wheel speed of the second-stage eddy classifier is 600 r / min to 1000 r / min, and the classifying wheel speed of the third-stage eddy classifier is 1200 r / min to 2500 r / min.

[0016] The method and system for the full-component cascade recovery of fly ash of the present invention have the following advantages: This invention, through sequential drying, deagglomeration, and homogenization pretreatment, effectively reduces the moisture content of fly ash and eliminates particle agglomeration and adhesion. This highlights and amplifies the originally subtle differences in physical properties between components, creating favorable material conditions for subsequent separation. Based on this, sequential sorting, magnetic separation, electrostatic separation, and multi-stage air classification are performed. These processes utilize differences in particle size, magnetism, electrical properties, and density to precisely separate and progressively enrich each component, forming a systematic and tiered full-component sorting and recovery process. This effectively improves the sorting efficiency and recovery rate of each component, enhances product purity and quality stability, and simultaneously achieves efficient, high-purity, and separate recovery of various high-value-added components such as cenospheres, sedimentary beads, magnetic beads, carbon-rich products, and highly active ultrafine fly ash, significantly improving resource utilization and product added value. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the overall process of the present invention.

[0018] Figure 2 This is a schematic diagram of the overall structure of the present invention. Detailed Implementation

[0019] The technical solutions of the present invention will now be described clearly and in detail with reference to the accompanying drawings. In the description of the embodiments of the present invention, unless otherwise stated, " / " indicates "or," for example, A / B can mean A or B. "And / or" in the text is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, and B alone. Furthermore, in the description of the embodiments of the present invention, "multiple" refers to two or more. The terms "first" and "second" are used for descriptive purposes only and should not be construed as implying or suggesting relative importance or implicitly indicating the number of indicated technical features. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature.

[0020] like Figure 1 As shown, the present invention provides a method for the full-component cascade recovery of fly ash, comprising the following steps: Raw fly ash is dried, deagglomerated, and homogenized to obtain pretreated powder with a preset moisture content and particle size.

[0021] The pretreated powder is sorted to remove coarse foreign matter, resulting in purified powder.

[0022] The impurity-removing powder is subjected to magnetic separation to separate the magnetic components, resulting in magnetic bead products and demagnetized powder.

[0023] The demagnetized powder is subjected to electrostatic separation to separate unburned carbon particles with good conductivity, resulting in carbon-rich products and decarbonized powder.

[0024] The decarbonized powder is subjected to multi-stage air classification to separate cenospheres, sediments, and ultrafine fly ash in sequence.

[0025] In summary, this invention first dries, deagglomerates, and homogenizes the raw fly ash to obtain pretreated powder with a preset moisture content and particle size. Then, the pretreated powder is sorted to remove coarse impurities, resulting in impurity-removed powder. Next, the demagnetized powder is electrostatically separated to separate unburned carbon particles with good conductivity, resulting in carbon-rich products and decarbonized powder. Finally, the decarbonized powder is subjected to multi-stage wind classification to sequentially separate cenospheres, sediments, and ultrafine fly ash. This invention, through sequential drying, deagglomeration, and homogenization pretreatment, effectively reduces the moisture content of fly ash and eliminates particle agglomeration and adhesion. This highlights and amplifies the originally subtle differences in physical properties between components, creating favorable material conditions for subsequent separation. Based on this, sequential sorting, magnetic separation, electrostatic separation, and multi-stage air classification are performed. These processes utilize differences in particle size, magnetism, electrical properties, and density to precisely separate and progressively enrich each component, forming a systematic and tiered full-component sorting and recovery process. This effectively improves the sorting efficiency and recovery rate of each component, enhances product purity and quality stability, and simultaneously achieves efficient, high-purity, and separate recovery of various high-value-added components such as cenospheres, sedimentary beads, magnetic beads, carbon-rich products, and highly active ultrafine fly ash, significantly improving resource utilization and product added value.

[0026] The preset moisture content of 0.5% to 0.8% effectively reduces the agglomeration and adhesion between fly ash particles, improves material dispersibility, and provides a stable and homogeneous material state for subsequent dry separation (separation, magnetic separation, electrostatic separation, and air classification), avoiding decreased separation efficiency or equipment blockage due to excessive moisture. The preset particle size of 0.5μm to 300μm controls the fly ash particle size within a suitable range for dry separation, avoiding excessive dust generation and recovery difficulties caused by overly fine particles during separation, while ensuring effective separation and enrichment of target components by subsequent magnetic separation, electrostatic separation, and air classification.

[0027] Among them, more than 95% of the pretreated powder has a particle size of 0.5μm to 300μm, and less than 5% has a particle size greater than 300μm.

[0028] Among them, coarse foreign matter includes unburned coarse carbon particles, bottom slag particles and metal oxide debris. The particle size of coarse foreign matter is 150μm~1000μm, and the removal efficiency is ≥85%. The formula for calculating the removal efficiency is: Removal efficiency = (mass of removed foreign matter / total mass of foreign matter in raw material) ×100%. Through the above settings, coarse foreign matter in pretreated powder is effectively removed, achieving efficient and non-destructive physical removal, protecting subsequent magnetic separation, electric separation and air classification equipment, extending equipment life and improving overall sorting stability.

[0029] Among them, the specific surface area of ​​ultrafine fly ash is 600 m². 2 / kg~800m 2 / kg can significantly improve the pozzolanic activity and surface reactivity of fly ash, enabling it to have excellent filling effect, water reduction effect and strength contribution when used as a high-performance concrete admixture or functional filler.

[0030] Before the raw fly ash undergoes drying, deagglomeration, and homogenization treatments, it is first ground to a specific surface area of ​​400 m². 2 / kg~550m 2 / kg, which can effectively open up the fine particles encapsulated in fly ash, promote particle dissociation and homogenization, and provide a raw material base with uniform particle size distribution and suitable specific surface area for subsequent drying, deagglomeration and sorting processes, significantly improving the sorting efficiency and recovery rate of target components in each sorting process.

[0031] like Figure 2 As shown, the present invention also provides a full-component cascade recovery system for fly ash, comprising: The pretreatment unit is used to dry, deagglomerate and homogenize the raw fly ash to obtain pretreated powder with a preset moisture content and preset particle size.

[0032] The sorting unit is used to sort the pretreated powder, remove coarse foreign matter from the pretreated powder, and obtain impurity-free powder.

[0033] The magnetic separation unit is used to perform magnetic separation on the impurity-removing powder, separating the magnetic components to obtain magnetic bead products and demagnetized powder.

[0034] The electrostatic separation unit is used to electrostatically separate the demagnetized powder, separating unburned carbon particles with good conductivity, and obtaining carbon-rich products and decarbonized powder.

[0035] The wind-powered classification unit is used to classify decarbonized powder into multiple stages by wind power, separating cenospheres, sediments, and ultrafine fly ash in sequence.

[0036] like Figure 2As shown, the sorting unit includes an air classifier, which can be a vertical vortex air classifier or a horizontal turbine air classifier. The air classifier cuts particles with a diameter of 45μm to 75μm. The airflow of the induced draft fan is adjusted to 15000m³ / h. 3 / h~60000m 3 The speed is adjusted to 200r / min-500r / min, allowing fine particles smaller than the cutting diameter to rise with the airflow and enter the subsequent process, while coarse foreign matter larger than the cutting diameter is discharged from the discharge port at the bottom of the classifier. The higher the speed, the finer the cutting diameter; the larger the air volume, the stronger the processing capacity, but excessive air volume will coarsen the grading particle size.

[0037] like Figure 2 As shown, the magnetic separation unit includes a high-gradient magnetic separator, which can effectively capture weakly magnetic fine magnetic beads in fly ash and achieve high selectivity and high recovery rate separation of magnetic components under an electric field strength of 0.5T~0.8T.

[0038] like Figure 2 As shown, the electrostatic separation unit includes a high-voltage electrostatic separator. The high-voltage electrostatic separator can utilize the significant difference in conductivity between unburned carbon and decarbonized ash to achieve efficient and high-purity separation of carbon components in a high-voltage electric field of 25kV~45kV.

[0039] like Figure 2 As shown, the wind-powered classification unit includes a three-stage vortex classifier in series. The first-stage vortex classifier separates the cenospheres, the second-stage vortex classifier separates the sediments, and the third-stage vortex classifier separates the fine fly ash. Through the three-stage series classification, the cenospheres, sediments, and fine fly ash can be accurately separated step by step according to their density and particle size differences, achieving the recovery of graded products with narrow particle size distribution and high purity.

[0040] The first-stage vortex classifier operates at a classifying wheel speed of 300 r / min to 600 r / min. By using low speed and low airflow, it prioritizes the separation of hollow cenospheres with the lowest density, ensuring high purity and low breakage rate of the cenosphere product. The second-stage vortex classifier operates at a classifying wheel speed of 600 r / min to 1000 r / min. By using medium speed and high airflow, it efficiently separates solid cenospheres with higher density, achieving high-value recovery of spherical microspheres. The third-stage vortex classifier operates at a classifying wheel speed of 1200 r / min to 2500 r / min. By using high speed and precise airflow control, it enriches highly active ultrafine fly ash to a specific surface area ≥ 600 m². 2 / kg, meeting the application requirements of high-end building materials and functional fillers.

[0041] like Figure 2 As shown, the pretreatment unit also includes a raw ash silo, a drying device, a grinding device, and a homogenization silo connected in sequence.

[0042] like Figure 2 As shown, the sorting unit is connected to the outlet of the homogenization bin and also includes a material dispersion device, a classifying wheel, an induced draft fan and a discharge port, used to remove coarse foreign matter from the pretreated powder to obtain impurity-free powder.

[0043] like Figure 2 As shown, the magnetic separation unit is connected to the impurity removal powder outlet of the sorting unit, and also includes a feeder, a high-gradient magnetic separator, a magnetic product collector, and a non-magnetic product conveyor for extracting magnetic products.

[0044] like Figure 2 As shown, the electrostatic separation unit is connected to the demagnetized powder outlet of the magnetic separation unit, and also includes a high-voltage power supply, a grounded roller, a corona electrode, an electrostatic electrode, and a zoned collection device for extracting carbon products.

[0045] like Figure 2 As shown, the wind-powered classification unit is connected to the decarbonized powder outlet of the electrostatic separation unit, and also includes a cyclone collector and a bag filter to achieve continuous, narrow-size classification of cenospheres, sediments, and ultrafine ash.

[0046] like Figure 2 As shown, the present invention provides a full-component cascade recovery system for fly ash, which also includes a control and conveying system, comprising a closed pneumatic conveyor, a mechanical conveyor, and a central control unit connecting each unit. The central control unit receives online monitoring data from key nodes of each unit and dynamically adjusts the sorting and identification threshold, magnetic field strength, electrostatic voltage, and wind classifier speed parameters.

[0047] like Figure 2 As shown, the control and conveying system also includes online detection devices, including a moisture meter, a particle size analyzer, a carbon content detector, and an iron content detector. These devices monitor key process parameters in real time. The moisture meter is used to detect the moisture content in real time to adjust the threshold of the sorting unit. The particle size analyzer is used to detect the particle size in real time to adjust the field strength of the magnetic separation unit. The carbon content detector is used to detect the carbon content in real time to adjust the voltage of the electrostatic separation unit. The iron content detector is used to detect the iron content in real time to adjust the rotational speed of each stage of the wind-powered grading unit.

[0048] Example 1 Dry fly ash from a coal-fired power plant was processed. The original fly ash had a moisture content of 2.5%, a loss on ignition of 10.2%, an Fe2O3 content of 7.5%, and a residue of 18% on a 45μm sieve.

[0049] Pretreatment process: Raw fly ash is dried to a moisture content of 0.5% by a cyclone dryer, and then lightly ground and homogenized by a vertical mill. The residue on the 80μm sieve of the material exiting the mill is reduced to 10%.

[0050] Sorting process: Connected to the outlet of the homogenization bin, an air classifier (vertical vortex or horizontal turbine classifier) ​​is used to classify and cut particles with a diameter of 45μm~75μm. By adjusting the air volume and speed, coarse foreign matter with a diameter of 150μm~1000μm is removed, with a removal efficiency of ≥85%.

[0051] Magnetic separation process: The material enters a high gradient magnetic separator with an electric field strength of 0.8T, and magnetic beads, which account for about 2.8% of the total weight of the raw material, are separated. The iron content of the beads is 60%.

[0052] Electrostatic separation process: Non-magnetic materials enter a high-voltage electrostatic separator, which separates refined carbon products with a loss on ignition of 72% under a working voltage of 40kV, with a yield of 7.5% and a carbon recovery rate of 85%.

[0053] Air classification process: Decarbonized ash enters a three-stage vortex air classifier unit. The first stage (low speed) separates ash with a bulk density of 0.5 g / cm³. 3 First, the float beads (yield 1.2%) are sorted; second-stage grading (medium speed) sorts out sinking beads with good sphericity of 325 mesh or higher (yield 31%); third-stage grading (high speed) sorts out beads with a specific surface area >600m². 2 / kg of ultrafine activated ash (yield 55%).

[0054] Results: The overall recovery rate of the entire process exceeds 97%, the purity of each main product meets the requirements of high-end applications, and the comprehensive power consumption per unit product of the system is 22kWh / t.

[0055] Example 2 Based on the system in Example 1, the central control unit automatically adjusts according to the data from the particle size analyzer and carbon content detector: When the particle size of the material before electro-separation is detected to be too coarse, the rotation speed of the electro-separator rollers is increased to improve the separation effect.

[0056] When the carbon content of the material entering the classifier is detected to be above the standard (>1%), a feedback signal is sent to the electrostatic separator to appropriately increase the voltage and at the same time fine-tune the air volume of the classifier to ensure that the loss on ignition of the cenosphere product meets the standard.

[0057] The method and system for the full-component cascade recovery of fly ash of the present invention have the following other advantages: First, this invention redefines "sorting" as a pre-treatment protective impurity removal step and establishes the main sorting logic of "magnetic separation-electric separation-wind grading," which solves the problem of low efficiency caused by the misalignment of the order in the traditional approach. The four processes each perform their respective functions (impurity removal, iron removal, decarbonization, and bead separation), forming a highly efficient and coordinated production line.

[0058] Secondly, this invention sequentially recovers impurities, high-grade magnetic beads, refined carbon, high-purity cenospheres / sinking beads, and highly active ultrafine ash, achieving full-component cascade recovery. Since iron and carbon are removed first through magnetic separation and electrostatic separation, pure aluminosilicate raw materials are provided for subsequent wind grading, significantly improving the purity of the microbead product.

[0059] Third, the central control unit of this invention dynamically adjusts the parameters of subsequent units based on online data. For example, it fine-tunes the parameters of the classifier based on the carbon content of the ash after electro-separation, ensuring the stability of the final product and the system's adaptability to fluctuations in incoming materials.

[0060] Fourth, this invention is based on a combination of mature industrial equipment, with a clear process that is easy to scale up. The sorting process, as a pre-protection step, extends the life of subsequent precision equipment and reduces maintenance costs.

[0061] Fifth, the entire process of this invention is mainly dry, requiring no water or chemical reagents, thus avoiding wastewater generation and secondary dust pollution, achieving clean production. At the same time, the modular design allows the system to flexibly adapt to fly ash raw materials from different power plants and of different qualities.

[0062] It is understood that this invention has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of this invention. Furthermore, under the teachings of this invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of this invention. Therefore, this invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this invention are within the protection scope of this invention.

Claims

1. A method for the full-component cascade recovery of fly ash, characterized in that, Includes the following steps: The raw fly ash is dried, deagglomerated and homogenized to obtain pretreated powder with a preset moisture content and preset particle size. The pretreated powder is sorted to remove coarse foreign matter, resulting in purified powder. The impurity-removing powder is subjected to magnetic separation to separate the magnetic components, resulting in magnetic bead products and demagnetized powder. The demagnetized powder is subjected to electrostatic separation to separate unburned carbon particles with good conductivity, resulting in carbon-rich products and decarbonized powder. The decarbonized powder is subjected to multi-stage air classification to separate cenospheres, sediments, and ultrafine fly ash in sequence.

2. The method for full-component cascade recovery of fly ash according to claim 1, characterized in that, The preset moisture content is 0.5%~0.8%, and the preset particle size is 0.5μm~300μm.

3. The method for full-component cascade recovery of fly ash according to claim 1, characterized in that, The coarse-grained heterogeneous impurities include unburned coarse carbon particles, bottom slag particles, and metal oxide debris.

4. The method for full-component cascade recovery of fly ash according to claim 1, characterized in that, The specific surface area of ​​the ultrafine fly ash is 600 m². 2 / kg~800m 2 / kg.

5. The method for full-component cascade recovery of fly ash according to claim 1, characterized in that, When drying, deagglomerating, and homogenizing raw fly ash, the raw fly ash is first ground to a specific surface area of ​​400 m². 2 / kg~550m 2 / kg.

6. A full-component cascade recovery system for fly ash, characterized in that, The method described in claims 1-5 includes the following sequentially connected components: The pretreatment unit is used to dry, deagglomerate and homogenize the raw fly ash to obtain pretreated powder with a preset moisture content and preset particle size. The sorting unit is used to sort the pretreated powder, remove coarse foreign matter from the pretreated powder, and obtain impurity-free powder. The magnetic separation unit is used to perform magnetic separation on the impurity-removing powder, separating the magnetic components to obtain magnetic bead products and demagnetized powder; The electro-separation unit is used to electro-separate the demagnetized powder, separating unburned carbon particles with good conductivity to obtain carbon-rich products and decarbonized powder. The wind-powered classification unit is used to classify decarbonized powder into multiple stages by wind power, separating cenospheres, sediments, and ultrafine fly ash in sequence.

7. A full-component cascade recovery system for fly ash according to claim 6, characterized in that, The sorting unit includes an air classifier, the magnetic separation unit includes a high-gradient magnetic separator, and the electrostatic separation unit includes a high-voltage electrostatic separator.

8. A full-component cascade recovery system for fly ash according to claim 7, characterized in that, The air classifier is a vertical vortex air classifier or a horizontal turbine air classifier, and the cutting particle size of the air classifier is 45μm~75μm.

9. A full-component cascade recovery system for fly ash according to claim 6, characterized in that, The wind-based classification unit includes a three-stage vortex classifier in series. The first-stage vortex classifier separates floating beads, the second-stage vortex classifier separates sinking beads, and the third-stage vortex classifier separates fine fly ash.

10. A full-component cascade recovery system for fly ash according to claim 9, characterized in that, The classifying wheel speed of the first-stage eddy classifier is 300 r / min to 600 r / min, the classifying wheel speed of the second-stage eddy classifier is 600 r / min to 1000 r / min, and the classifying wheel speed of the third-stage eddy classifier is 1200 r / min to 2500 r / min.

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