A household garbage incineration fly ash washing grading-low temperature plasma detoxification-grinding-floating combined treatment system and method

Abstract

The application discloses a kind of life garbage incineration fly ash washing grading-low temperature plasma detoxification-grinding and floating combined processing system and method, and it relates to solid waste treatment technical field.The method includes ultrasonic water washing grading desalination, low temperature plasma solid phase pre-detoxification, mechanical chemical acid leaching grinding, once flotation decarburization, secondary flotation heavy metal removal.This scheme utilizes low temperature plasma to degrade the surface of fly ash dioxin, and realizes lattice package type heavy metal efficient dissociation in situ with acid leaching mechanical force grinding.The bottleneck of carbon material hydrophilization caused by low temperature plasma oxidation is solved by using polar collector to specifically bind carbon surface oxidation sites through hydrogen bond association, and the hydrophobicity of unburned carbon surface is reconstructed and modified.Finally, through two-stage step flotation, carbon concentrate, heavy metal concentrate and inorganic residual ash tailings are separated.The existing process chlorine salt interference, carbon flotation failure, low heavy metal dissociation rate, harmless and resource utilization are difficult to consider.

Description

Technical Field

[0001] This invention relates to the field of solid waste treatment technology, and more particularly to the field of municipal solid waste incineration fly ash treatment technology, specifically to a combined treatment system and method for municipal solid waste incineration fly ash by water washing and grading, low-temperature plasma detoxification, and grinding and flotation. Background Technology

[0002] With the acceleration of urbanization and the promotion of waste sorting, municipal solid waste incineration technology has become the mainstream technology for urban solid waste treatment worldwide due to its advantages such as significant volume reduction, high degree of harmlessness, and resource recovery through waste heat power generation. However, the large amount of fly ash generated during the incineration process (accounting for approximately 10% to 20% of the total waste incineration residue) is also increasing year by year. Fly ash is enriched with high concentrations of heavy metals such as lead, zinc, copper, cadmium, chromium, and mercury, and adsorbs highly toxic persistent organic pollutants such as polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD / Fs, collectively known as dioxins). Therefore, it is clearly classified as hazardous waste in various countries.

[0003] Traditional landfill and cement co-processing are gradually being limited by policies, costs, and chloride ion restrictions. The industry is developing an integrated approach of water washing, detoxification, and resource recovery, but existing processes have multiple shortcomings.

[0004] 1. Single water washing process (such as CN118023256A, CN118060313A): only removes free chlorine and water-soluble heavy metals, leaving dioxins completely, and the washing ash is still hazardous waste; there is no carbon or metal separation, and the residue is only used for low-end building materials, with extremely low resource value.

[0005] 2. High-temperature plasma melting (e.g., CN119281802B): The high temperature above 1000℃ completely detoxifies the metals, but it burns unburned carbon and causes heavy metals such as lead and zinc to be lost through gasification. It has high energy consumption, serious equipment corrosion, and only produces a single glassy substance with no valuable concentrate recovery value.

[0006] 3. Low-temperature pyrolysis process (such as CN121373031A, CN113814207B): 350-500℃ degrades some dioxins, but cannot dissociate lattice heavy metals, and the product toxicity does not meet the standards; there is no sorting process, and the flue gas is prone to secondary generation of dioxins.

[0007] 4. Standalone low-temperature plasma solid-phase treatment (e.g., CN121535008A, CN115121593A): can decompose dioxins at low temperatures and retain solid materials, but is mostly used as an end-stage stabilization process; there is no pre-washing desalting, chloride salts corrode the electrodes and reduce the processing efficiency; after treatment, hydroxyl and carboxyl hydrophilic groups are generated on the carbon surface, and conventional flotation cannot recover carbon. Existing technologies have not found and solved this problem.

[0008] 5. Flotation-plasma combined process (e.g., CN113617531A): This process suffers from inherent industry biases. It adopts a route of first flotation and then carbon slag detoxification, resulting in all dioxins being enriched in the carbon slag, posing a risk of leakage during transport. There is no desalination before flotation, and chloride salts are used to inhibit collectors, resulting in a carbon recovery rate of less than 30%. It only involves one stage of flotation, without heavy metal leaching and separation processes, leading to the loss of all valuable metals. Furthermore, there are no carbon-modified flotation reagents suitable for carbon.

[0009] 6. Simple mechanical grinding (e.g., CN118023256A): Relying solely on physical lattice breaking, lacking the synergistic dissolution of dilute acid, the heavy metal dissociation rate is less than 60%, and it is not equipped with detoxification and sorting units. Summary of the Invention

[0010] The technical problem to be solved by this invention is: in order to address the issues of low-energy consumption and high-efficiency synergistic treatment processes for heavy metals and dioxins in existing technologies, and the difficulty in simultaneously achieving high-quality, stepwise resource recovery of multiple components, this invention provides a combined treatment system and method for municipal solid waste incineration fly ash, including water washing and grading, low-temperature plasma detoxification, and grinding and flotation. This system can achieve efficient "detoxification" of dioxins and heavy metals in the solid phase of fly ash, while also ensuring efficient recovery of high-purity, multi-component chloride salts from the leachate. Furthermore, the fly ash treatment process is economical and environmentally friendly.

[0011] The technical solution adopted by this invention to solve its technical problem is: a method for combined treatment of fly ash from municipal solid waste incineration by water washing and grading, low-temperature plasma detoxification, and grinding and flotation, comprising the following steps: S1. Add water to the fly ash from the original municipal solid waste incineration and wash it with ultrasonic stirring. After washing, separate the solid and liquid to obtain primary water washing residue and primary water washing filtrate. S2. The primary water washing residue is dried and then sent to a low-temperature non-thermal plasma treatment device for surface oxidation and detoxification treatment to deeply destroy dioxin-like organic pollutants and obtain detoxified fly ash. S3. The detoxified fly ash is added to an aqueous solution of acid leaching extractant to form a slurry, and then subjected to mechanical grinding. Under the synergistic effect of mechanical and chemical shearing force and acid, the crystal lattice is dissociated, allowing the encapsulated heavy metal ions to be released and dissolved in situ quickly, thus obtaining activated fly ash slurry. S4. Add water to the activated fly ash slurry to mix and adjust the slurry, add pH adjuster to adjust the slurry environment, and then add polar collector and frother in sequence to carry out one flotation to obtain carbon-rich concentrate and one flotation decarbonization tailings. S5. The decarbonized tailings from the primary flotation are thoroughly mixed with the heavy metal collector; xanthate collectors and frothers are added to the mixture for secondary flotation to obtain heavy metal concentrate and inorganic residual ash tailings.

[0012] This method constructs a cascade process for deep harmlessness and multi-component stepwise high-value resource recovery, consisting of "water washing and grading - low-temperature plasma detoxification - grinding and flotation combined". At the front end, room-temperature wet desalination is employed, and low-temperature plasma is used to directionally degrade dioxins on the solid surface in step S2, completely eliminating the risk of toxic release and secondary pollution of dioxins during transport and wet treatment. In the middle stage, mechanical grinding and acid leaching work synergistically in situ to enhance the leaching activity and release rate of lattice-encapsulated heavy metals. At the back end, a specific polar collector is used to target and reconstruct the hydrophobicity of hydrophilic unburned carbon through hydrogen bonding association. Combined with two-stage stepwise flotation, the selective and precise separation and efficient high-purity recovery of modified unburned carbon, heavy metal sulfide concentrate, and non-toxic residual ash are achieved sequentially, truly realizing the full "zero-waste" high-value recycling of fly ash.

[0013] In some embodiments, in step S1, the liquid-solid mass ratio of the municipal solid waste incineration fly ash to water is 3:1 to 10:1.

[0014] The primary water washing filtrate is mainly a soluble chloride salt solution.

[0015] By removing chloride ions in advance, the problem of high chloride ion content promoting the volatilization of heavy metals and forming highly toxic secondary fly ash in subsequent melting or thermal processes is avoided; the interference of high electrolyte chloride salts on the selective adsorption of subsequent flotation reagents is eliminated, ensuring the selectivity and purity of flotation; the high-purity industrial salt recovered from the primary water washing filtrate through evaporation and crystallization can be directly sold as a by-product, which has good economic benefits.

[0016] In some embodiments, in step S2, the moisture content of the primary water washing residue after drying is less than 5 wt%.

[0017] By controlling the moisture content of the primary water washing residue (powder) to be below 5 wt%, the risk of high-voltage dielectric breakdown, arcing, or electrode short circuit caused by the moisture and high conductivity of the powder in the high-frequency, high-voltage, low-temperature plasma discharge area is eliminated, ensuring the electromagnetic safety and continuous stability of the equipment operation.

[0018] In some embodiments, in step S3, the amount of acid leaching extractant added is such that the pH of the detoxified fly ash slurry is maintained between 1.5 and 3.5.

[0019] It should be noted that in the above scheme, the acid leaching extractant is not only used to adjust the pH of the slurry, but also integrates mechanical grinding and in-situ acid leaching in the same step. The high-energy collision and mechanical shear friction of the grinding media can directly and powerfully erode the inorganic matrix and porous aluminosilicate lattice of the detoxified fly ash. While exposing the encapsulated heavy metal ions such as lead, zinc, and copper, the mechanochemical activation effect of the shear interface allows them to react rapidly and dissolve directly in situ with the acid leaching extractant, significantly improving the acid leaching rate of heavy metals such as Pb and Zn, and significantly shortening the acid leaching reaction time.

[0020] In some embodiments, in step S4, the amount of pH adjuster added is such that the pH value of the slurry environment is maintained between 1.5 and 3.5.

[0021] The pH adjustment of the pulp environment provides an optimal weakly alkaline pulp potential environment for the first-stage flotation, which is conducive to the specific adsorption of polar collectors on the surface of unburned carbon.

[0022] In some embodiments, in step S4, the polar collector is a nonionic heteropolar surfactant containing ether bonds, carboxyl groups, hydroxyl groups, or ester groups, or a compound collector formed by mixing with nonpolar hydrocarbon oils.

[0023] Addressing the common industry pain point that after fly ash undergoes pre-treatment with strong oxidizing plasma detoxification, the residual unburned carbon and activated carbon surfaces are grafted with a large number of polar oxygen-containing functional groups such as carboxyl and hydroxyl groups, resulting in complete hydrophilization and the complete ineffectiveness of traditional diesel collectors, this solution introduces nonionic heteropolar surfactants containing ether bonds, carboxyl groups, hydroxyl groups, or ester groups as polar collectors. These surfactants can undergo directional and specific hydrogen bond association and adsorption with the polar functional groups on the surface of oxidized modified carbon, exposing its hydrophobic nonpolar hydrocarbon chains to the outside. This forcibly reconstructs the hydrophobicity of the modified unburned carbon in an aqueous medium, successfully achieving high-purity and precise foam separation of carbon-rich concentrates.

[0024] In some embodiments, in step S5, the molar amount of the heavy metal trapping agent is 1.0 to 2.0 times the total molar amount of soluble heavy metal ions in the tailings of the primary flotation decarbonization.

[0025] Adding a heavy metal collector to the decarbonization tailings after primary flotation can specifically and rapidly capture the dissolved heavy metal ions in the primary flotation tailings and convert them into fine heavy metal sulfide or chelate precipitates with good floatability. With the synergistic effect of xanthate collectors, high-selectivity flotation enrichment and metallurgical-grade purification and reuse of heavy metal precipitates such as Pb and Zn can be achieved through secondary froth flotation.

[0026] This solution also discloses a combined treatment system for municipal solid waste incineration fly ash, including: water washing and grading, low-temperature plasma detoxification, and grinding and flotation. An ultrasonic mixer and disperser is used to perform ultrasonic mixing in step S1. The filtration equipment is used for solid-liquid separation to obtain the primary water washing residue and the primary water washing filtrate; A drying device, wherein the drying device is used to dry the primary water washing residue; The uniform material spreading machine and the low-temperature non-thermal plasma treatment device are used to continuously feed the dried primary water washing residue into the low-temperature non-thermal plasma treatment device for surface oxidation and detoxification treatment. A mechanical grinding mill, wherein the mechanical grinding mill is used to mechanically grind the detoxified fly ash into a slurry formed by adding an acid leaching extractant; A flotation device for primary and secondary flotation operations; The mixing equipment includes a first slurry conditioning tank and a reagent reaction tank, which are used for mixing and diluting the activated fly ash slurry with water, and for mixing the primary flotation decarbonization tailings slurry with the heavy metal collector.

[0027] The beneficial effects of this invention are: 1. Achieving Dual Deep Detoxification of Heavy Metals and Dioxins: This invention innovatively employs a low-temperature non-thermal plasma treatment device at the front end. Utilizing its high ionization activity, it directly achieves highly efficient, directional, and deep degradation of dioxins on the solid-phase surface, resulting in a high and thorough removal rate. This eliminates the risk of secondary toxicity diffusion during transportation and subsequent wet processing. Simultaneously, it introduces a powerful in-situ synergistic effect of mechanical grinding and acid leaching. The mechanical and chemical shearing forces directly and forcefully erode the inorganic mineral lattice, breaking the physical encapsulation of heavy metals within the mineral lattice. This promotes rapid release, dissolution, and in-situ reconstruction of heavy metals, completely solving the bottleneck problem of low removal efficiency caused by the lack of heavy metal dissociation in traditional wet processes.

[0028] 2. Achieved high-purity and precise recovery of multi-component resources: Unlike traditional high-temperature plasma melting and vitrification processes, which completely incinerate unburned carbon at ultra-high temperatures (1200℃~1700℃), resulting in the complete loss of the material basis for solid carbon concentrate recovery, this invention, while employing low-temperature plasma detoxification to preserve the carbon solid phase, addresses the technical challenge of carbon hydrophilization caused by plasma surface oxidation. It utilizes a heteropolar collecting system with specific hydrogen bond association to successfully reconstruct the surface hydrophobicity of unburned carbon. Combined with a two-stage stepwise froth flotation process, it sequentially achieves selective and precise separation and efficient, high-purity recovery of modified unburned carbon, heavy metal sulfide concentrate, and inorganic residual ash tailings, truly realizing the full-scale, high-value resource utilization of fly ash.

[0029] 3. Significantly reduces overall system energy consumption and effectively avoids the risk of secondary pollution from volatile heavy metals: Traditional high-temperature melting or sintering methods not only have extremely high energy consumption (such as electricity consumption), but also easily lead to the secondary escape of low-boiling-point volatile heavy metals such as lead and zinc with the exhaust gas, and secondary synthesis of dioxins during the cooling stage, resulting in a large exhaust gas purification system with extremely high operating costs. This invention operates entirely in a low-temperature / normal-pressure and wet-process ambient-temperature environment, significantly reducing energy consumption during the recovery process. Furthermore, low-boiling-point heavy metals are directly activated and purified in situ in the solid phase as stable salts or insoluble sulfide precipitates, avoiding the generation of highly toxic secondary fly ash and reducing severe corrosion to production equipment, resulting in optimal industrial economic benefits and environmental safety. Attached Figure Description

[0030] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0031] Figure 1 This is a flowchart of the steps of the method of the present invention.

[0032] Figure 2 This is a flowchart of the processing flow of the system of the present invention. Detailed Implementation

[0033] The present invention will now be described in further detail with reference to the accompanying drawings. These drawings are simplified schematic diagrams, illustrating only the basic structure of the invention, and therefore only show the components relevant to the invention.

[0034] like Figure 1 As shown, a combined treatment method for fly ash from municipal solid waste incineration, including water washing and grading, low-temperature plasma detoxification, and grinding and flotation, comprises the following steps: S1. Add water to the fly ash from the original municipal solid waste incineration, with a liquid-to-solid mass ratio of 3:1 to 10:1. Then, use an ultrasonic agitator (such as an ultrasonic agitator washing tank) to perform ultrasonic agitation and washing to accelerate the dissolution of soluble chloride salts. After washing, use a filtration device (such as a vacuum filter) to separate the solid and liquid, and obtain a primary water washing residue containing heavy metals and dioxins, as well as a primary water washing filtrate mainly consisting of soluble chloride salt solution.

[0035] The primary washing filtrate can be sent to an evaporation crystallization system to prepare industrial salt. The primary washing residue enters step S2 for detoxification treatment.

[0036] S2. The primary washing residue is dried using a drying device. After drying, the moisture content of the primary washing residue is controlled to be below 5 wt%. The dried solid phase is then dispersed by a uniform material distributor and fed into a low-temperature non-thermal plasma treatment device in a thin layer. The high ionization activity of the low-temperature plasma is used to directionally and deeply degrade dioxin-like organic pollutants on the surface of the solid phase, completely eliminating the risk of toxicity diffusion at the source and obtaining detoxified fly ash. The condensate discharged from the drying device can be recycled as water for the original municipal solid waste incineration fly ash.

[0037] Steps S1 and S2 together form the front-end process to achieve desalination and detoxification: First, soluble chloride salts are thoroughly removed by ambient temperature ultrasonic wet classification, avoiding chloride salt corrosion of low-temperature non-thermal plasma treatment equipment and interference with downstream flotation reagents; then, dioxins are degraded. Unlike the existing process route of first flotation and then separately treating carbon slag, this avoids dioxins accumulating in carbon slag, eliminating the secondary pollution risks of organic toxicity leakage and low-temperature resynthesis of dioxins from the source of carbon slag transportation, slurry preparation and flotation process. At the same time, valuable carbon and heavy metal resources are preserved to provide qualified solid raw materials for subsequent mechanochemical dissociation and flotation recovery.

[0038] S3. Add the detoxified fly ash to the acid leaching extractant to form a slurry. The pH value of the slurry is maintained between 1.5 and 3.5. The slurry is then ground in a mechanical grinding mill under the synergistic effect of mechanical and chemical shearing force and acid. The grinding time is controlled between 10 min and 60 min (controlling the grinding time and particle size ensures the full dissociation of the encapsulated heavy metals and effectively prevents the "mudification" of the powder caused by excessive grinding, as the "mudification" phenomenon seriously deteriorates the separation index of subsequent flotation). This achieves the dissociation of the crystal lattice, allowing the encapsulated heavy metal ions to be released and dissolved rapidly in situ, thus transforming them into an enriched form that is easy to float, and obtaining an activated fly ash slurry.

[0039] The acid leaching extractant is at least one of hydrochloric acid, dilute sulfuric acid, or nitric acid.

[0040] It should be noted that the use of acid leaching extractant is not only for adjusting the pH value of the pulp, but also has the following main functions: 1. As the main reaction component in chemical leaching (chemical extraction of Pb, Zn, and Cu from detoxified fly ash): Under the compression and shearing impact of a mechanical grinding mill (such as a planetary ball mill), the crystal lattice of detoxified fly ash particles is destroyed, physically exposing heavy metals such as lead, zinc, and copper that were originally deeply encapsulated within aluminosilicates and porous glass bodies. At this point, the added acid leaching extractant directly reacts with the exposed heavy metal oxides, carbonates, or basic salts, breaking the chemical bonds between their ions and transforming them into highly soluble metal cations that are released into the liquid phase of the slurry, thus achieving direct chemical extraction.

[0041] 2. Achieving In-situ Synergistic Abrasion and Activation through Mechanochemical Processes: If ball milling is performed before adding acid (acid leaching extractant), the detached fine particles are highly susceptible to heterogeneous agglomeration in the air, thus passivating their surface reactivity. This invention combines acid leaching with mechanical grinding. The ball milling collisions continuously peel away the reaction product layer from the surface of the detoxified fly ash particles, while the acid immediately wets and attacks the newly exposed, highly free-energy, and chemically active microscopic fracture surfaces. This immediate in-situ synergistic effect of ball milling shear friction and strong protic acid significantly accelerates the interfacial diffusion mass transfer kinetics, dramatically increasing the originally slow room-temperature acid leaching rate and heavy metal release rate.

[0042] 3. Decalcification, descaling, and cleaning of the micropores of unburned carbon particles to expose their active sites: The micropores and surfaces of unburned carbon and activated carbon in detoxified fly ash are usually severely encapsulated and blocked by alkaline calcium compounds and sulfate scale, which hinders the subsequent contact between the polar collector and the oxygen-containing polar functional groups on the surface of unburned carbon. The addition of an acid leaching extractant can dissolve the calcium salt scale in the micropores of unburned carbon, thereby unblocking the micropores and cleaning the surface. This allows the active oxygen-containing sites generated by plasma surface modification to be fully exposed, thus providing the necessary prerequisite for the adsorption of the polar collector through strong hydrogen bonding in step S4 below.

[0043] S4. Add water to the activated fly ash slurry and mix and adjust the slurry using a mixing device. Add a pH adjuster to adjust the pH value of the slurry environment to between 6.0 and 8.5 (weakly alkaline, which is conducive to the specific adsorption of the polar collector on the surface of unburned carbon). Then add the polar collector and frother in sequence, and perform a first flotation using a flotation device to obtain a carbon-rich concentrate and a first flotation decarbonization tailings.

[0044] The pH adjuster is at least one of industrial sodium carbonate, potassium carbonate, lime, sodium hydroxide, or potassium hydroxide; the polar collector is a nonionic heteropolar surfactant containing ether bonds, carboxyl groups, hydroxyl groups, or ester groups, or a compound collector formed by mixing with nonpolar hydrocarbon oils.

[0045] Addressing the common industry pain point that after front-end detoxification, the surface of residual unburned carbon and activated carbon from municipal solid waste incineration is grafted with a large number of polar oxygen-containing functional groups such as carboxyl and hydroxyl groups, resulting in complete hydrophilization and the complete ineffectiveness of traditional diesel collectors, a novel nonionic heteropolar surfactant containing ether bonds, carboxyl groups, hydroxyl groups, or ester groups is introduced as a polar collector. The long-chain polar end of this polar collector can undergo directional and specific hydrogen bond association and adsorption with the polar functional groups on the surface of oxidized modified carbon, exposing its hydrophobic nonpolar hydrocarbon chains to the outside, forcibly reconstructing the hydrophobicity of modified unburned carbon in an aqueous medium; successfully achieving high-purity and precise foam separation of carbon-rich concentrate.

[0046] S5. The tailings slurry from the primary flotation decarbonization is transported to a mixing device, where a heavy metal chelating agent is added and thoroughly stirred. The heavy metal chelating agent is either an inorganic sulfiding agent or an organic heavy metal chelating precipitant. The molar amount of the agent added is 1.0 to 2.0 times the total molar amount of soluble heavy metal ions in the liquid phase of the primary flotation decarbonization tailings slurry. Adding the inorganic sulfiding agent or organic heavy metal chelating precipitant allows for the specific and rapid in-situ capture of heavy metal ions, converting them into finely floatable heavy metal sulfide or chelate precipitate particles.

[0047] Xanthate collectors and frothers are then added to the mixture, followed by secondary flotation in a flotation device to obtain heavy metal concentrate and inorganic tailings ash. Under the synergistic effect of the xanthate collectors, secondary flotation achieves highly selective flotation enrichment and metallurgical-grade purification and reuse of heavy metal precipitates such as Pb and Zn. The leaching toxicity of heavy metals from the inorganic tailings ash at the bottom of the final flotation tank is extremely low.

[0048] The precise separation and efficient recovery of modified unburned carbon and heavy metal concentrate are achieved through the coordinated use of two-stage gradient flotation processes in steps S4 and S5.

[0049] like Figure 2 As shown, a combined treatment system for municipal solid waste incineration fly ash, including water washing and grading, low-temperature plasma detoxification, and grinding and flotation, comprises the ultrasonic stirring and dispersing machine, filtration equipment, drying equipment, uniform feeding machine, low-temperature non-thermal plasma treatment device, mechanical grinding mill, flotation equipment, and mixing equipment mentioned in the above combined treatment method.

[0050] The low-temperature non-thermal plasma treatment device is selected from at least one of dielectric barrier discharge (DBD) plasma reactor, atmospheric pressure corona discharge plasma reactor, microwave discharge low-temperature plasma reactor, high-voltage pulse discharge plasma reactor, plasma-assisted ball mill, or high-energy electron beam irradiation reaction device; the working gas of the low-temperature non-thermal plasma treatment device is at least one of air, oxygen, ozone, water vapor, or inert gas.

[0051] Employing dielectric barrier discharge (DBD) or atmospheric pressure corona discharge, it can operate stably under isothermal conditions at room temperature and pressure, with energy consumption significantly lower than that of high-temperature melting processes. It efficiently dechlorinates and breaks down dioxin molecules on the solid surface through high-energy electrons, excited-state oxygen, and ·OH free radicals, thus completely eliminating the hazards of dioxins.

[0052] Mechanical grinding mills can be planetary ball mills, vibratory mills, or drum ball mills.

[0053] The technical solution of the present invention will be further described in detail below with reference to specific embodiments, comparative examples, and experimental data. The experimental raw material used in the present invention, municipal solid waste incineration fly ash, was taken from a municipal solid waste incineration power plant.

[0054] Example 1: The specific steps of the combined treatment method for fly ash from municipal solid waste incineration—water washing and grading, low-temperature plasma detoxification, and grinding and flotation—are as follows: S1. Water washing, screening, and desalination: 1 kg of raw municipal solid waste incineration fly ash is added to water, controlling the liquid-to-solid mass ratio at 5:1. The mixture is fed into an ultrasonic stirring and washing tank, and stirred and washed for 30 min under ultrasonic enhancement. After washing, solid-liquid separation is performed using a vacuum filter to obtain primary water washing residue and primary water washing filtrate. The primary water washing filtrate is mainly a soluble chloride salt solution, which is sent to an evaporation crystallization system (such as a rotary evaporator) for thermal evaporation crystallization to prepare a high-purity industrial salt product.

[0055] S2. Low-temperature plasma detoxification: The primary water washing residue is sent to an oven for drying, and its moisture content is controlled to be 3 wt%.

[0056] The dried primary washing residue (solid phase) is continuously and uniformly fed into a dielectric barrier discharge (DBD) plasma reactor (hereinafter referred to as a low-temperature plasma reactor) using a uniform feeder. The low-temperature plasma reactor employs dielectric barrier discharge (DBD), with air as the working gas, controlling the plasma discharge power at 2 kW and the processing time at 40 min. The solid phase undergoes surface oxidation and detoxification treatment within the low-temperature plasma reactor, utilizing its high ionization activity to deeply destroy and degrade dioxin-like organic pollutants, yielding detoxified fly ash upon discharge.

[0057] S3. Acid Leaching and In-situ Grinding: The detoxified fly ash is continuously fed into a planetary ball mill, and hydrochloric acid is added as an acid leaching extractant to form a slurry with the detoxified fly ash. By adjusting the amount of hydrochloric acid added, the pH value of the slurry is stably maintained at around 2. Under the synergistic effect of the mechanochemical shear force of the planetary ball mill and the strong in-situ action of the acid, mechanical grinding is carried out for 30 minutes, which erodes the inorganic mineral lattice, breaks the lattice binding, and promotes the rapid release, dissolution, and in-situ reconstruction of the encapsulated heavy metal ions, ultimately obtaining an activated fly ash slurry.

[0058] S4. Primary Flotation Decarbonization: The activated fly ash slurry is mixed with water and prepared, then fed into the flotation cell of the primary flotation equipment. First, industrial sodium carbonate is added to the activated fly ash slurry as a pH adjuster to adjust the pH of the slurry environment to approximately 7.5. Then, 2000 g / t of tetrahydrofurfuryl butyrate polar collector and 500 g / t of methyl isobutyl methanol frother are added sequentially to rebuild the surface hydrophobicity of unburned carbon through hydrogen bonding. After primary froth flotation, the froth is scraped and collected to obtain a carbon-rich concentrate. The residue remaining in the flotation cell serves as the primary flotation decarbonization tailings.

[0059] S5. Secondary Flotation for Heavy Metal Removal: The decarbonized tailings from the primary flotation are introduced into the secondary flotation cell of the flotation equipment. A dithiocarbamate heavy metal collector is added, with the molar amount controlled to be 1.5 times the total molar amount of soluble heavy metal ions in the primary flotation tailings. The mixture is thoroughly stirred to form a mixed solution, converting the released heavy metal ions into insoluble sulfide precipitates. Subsequently, 500 g / t butylammonium black reagent collector and 300 g / t methyl isobutyl methanol frother are added to the mixed solution for secondary flotation. The heavy metal concentrate is obtained by skimming and separating the bubbles. The residue at the bottom of the secondary flotation cell is discharged and filtered and dewatered to obtain inorganic residual ash tailings.

[0060] Example 2: Based on Example 1, the "liquid-solid mass ratio 5:1" in step S1 of Example 1 is replaced with "liquid-solid mass ratio 3:1", and the other process steps and control parameters are exactly the same as in Example 1.

[0061] Example 3: Based on Example 1, the "discharge working gas is air" in step S2 of Example 1 is replaced with "discharge working gas is pure oxygen", the "discharge power 2 kW" is increased to "discharge power 10 kW", and the processing time is controlled to 20 min. Other process steps and control parameters are exactly the same as in Example 1.

[0062] Example 4: Based on Example 1, the "grinding time 30 min" in step S3 of Example 1 is replaced with "grinding time 15 min", and the other process steps and control parameters are exactly the same as in Example 1.

[0063] Example 5: Based on Example 1, the phrase "the pH value of the slurry is stably maintained at around 2" in step S3 of Example 1 is replaced with "the pH value of the slurry is stably maintained at around 5". The other process steps and control parameters are exactly the same as in Example 1.

[0064] Example 6: Based on Example 1, the polar collector "tetrahydrofurfuryl butyrate" in step S4 of Example 1 was replaced with an equal dose of a compound collector "tetrahydrofurfuryl butyrate and diesel oil in a mass ratio of 1:1". Other process steps and control parameters were exactly the same as in Example 1.

[0065] Example 7: Based on Example 1, the “dithiocarbamate heavy metal scavenger” in step S5 of Example 1 is replaced with an equimolar ratio of “inorganic sodium sulfide”, while the other process steps and control parameters are exactly the same as in Example 1.

[0066] Example 8: Based on Example 1, the "dosage of heavy metal trapping agent 1.5 times" in step S5 of Example 1 is replaced with "dosage of heavy metal trapping agent 1.1 times", and the other process steps and control parameters are exactly the same as in Example 1.

[0067] Comparative Example 1: Compared to Example 1, this comparative example omits the in-situ grinding and acid leaching process in step S3. The "detoxified fly ash" obtained in step S2 is directly mixed with deionized water to adjust the slurry to the same solid content without mechanical grinding or acid leaching. Then, the slurry is directly prepared, pH is adjusted, reagents are added, and two-stage gradient flotation separation is performed according to the methods in steps S4 and S5. The remaining process steps and conditions are exactly the same as in Example 1.

[0068] Comparative Example 2: Compared to Example 1, this comparative example omits the low-temperature plasma detoxification pretreatment step S2. The "primary water-washed residue" obtained after solid-liquid separation and drying in step S1 is directly fed into step S3 without undergoing surface oxidation detoxification in a low-temperature plasma reactor, where it is added with an acid leaching extractant for mechanical grinding and subsequent gradient flotation. The remaining process steps and conditions are exactly the same as in Example 1.

[0069] Comparative Example 3: Compared to Example 1, this comparative example changed the flotation reagent system in step S4. The polar collector with specific hydrogen bonding was removed and replaced with an equal dose of a conventional non-polar hydrocarbon diesel oil collector. The remaining process steps and slurry conditioning parameters were exactly the same as in Example 1.

[0070] Comparative Example 4: Compared to Example 1, this comparative example omits the pre-washing, screening, and desalination step in step S1. The raw municipal solid waste incineration fly ash is fed directly into a low-temperature plasma reactor for surface detoxification, following the method in step S2, without water washing, while maintaining the same moisture content. Subsequent acid leaching, grinding, and two-stage flotation are then carried out sequentially. All other process steps and parameters are identical to those in Example 1.

[0071] The final inorganic residual ash tailings, recovered products, and system operating status prepared in each embodiment and comparative example were tested: the overall removal rate of heavy metals (taking lead and cadmium as examples) in the final inorganic residual ash tailings was determined according to "Determination of 22 Metallic Elements in Solid Waste by Inductively Coupled Plasma Atomic Emission Spectrometry" (HJ 781-2016); the residual amount (toxicity equivalent) of dioxins in the final inorganic residual ash tailings was determined according to "Determination of Dioxins in Water by Isotope Dilution / High-Resolution Gas Chromatography-High-Resolution Mass Spectrometry" (HJ 77.1-2025), and the total degradation rate of dioxins by the entire system was calculated. The relative energy consumption was evaluated using the comprehensive power consumption of the entire process in Example 1 as a baseline (100%), and the comparison is shown in Table 1.

[0072] Table 1 Comparison of experimental results between each embodiment and the comparative example

[0073] The comparative analysis results of the examples and the comparative examples are as follows: First, the comparison of experimental data from each embodiment and the comparative example shows that the cascade process proposed in this scheme, which involves "first water washing and desalination, then low-temperature plasma detoxification and in-situ synergy of acid leaching and grinding, followed by two-stage gradient flotation," has successfully overcome the resource utilization bottleneck caused by the complex composition and mutual interference of harmful components in waste incineration fly ash.

[0074] Specifically, this manifests in: 1. Regarding heavy metal dissociation and efficient recovery: A comparison between Example 1 and Comparative Example 1 shows that without the acid leaching and grinding process (Comparative Example 1), the recovery rates of lead and zinc in the heavy metal concentrate are only 51.3% and 55.6%, respectively. However, after introducing in-situ acid leaching and grinding in Example 1, the recovery rates of lead and zinc soared to 89.2% and 92.5%, respectively. This strongly demonstrates that the mechanochemical shearing force of the planetary ball mill and the powerful in-situ synergy of the acid can strongly erode the inorganic mineral lattice, break the physical encapsulation of heavy metals by the lattice, and completely dissociate and release the encapsulated heavy metals, which are then enriched in the heavy metal concentrate. Comparing Examples 1 with Examples 4 and 5, it can be seen that shortening the grinding time (Example 4) or increasing the pulp pH to around 5 (Example 5) will result in incomplete inorganic lattice erosion, leading to a significant decline in lead and zinc recovery rates. Furthermore, because some undissociated heavy metal minerals are trapped in the micropores of unburned carbon, the purity of the carbon-rich concentrate decreases during the first flotation (the loss on ignition drops to 80.3% and 78.4%, respectively), and the purification effect of inorganic matter in the residual ash tailings deteriorates (the loss on ignition of residual ash increases to 1.12% and 1.25%, respectively).

[0075] 2. Regarding the targeted and deep degradation of dioxins: In Example 1, after introducing low-temperature plasma detoxification at the front end, the residual dioxin levels in the carbon-rich concentrate and residual ash tailings were as low as 15.2 ng-TEQ / kg and 10.2 ng-TEQ / kg, respectively. In contrast, in Comparative Example 2, which eliminated the low-temperature plasma pretreatment, the dioxin content in the carbon-rich concentrate and residual ash tailings was as high as 485.4 ng-TEQ / kg and 254.1 ng-TEQ / kg, respectively. This fully demonstrates that the pre-treatment low-temperature plasma technology, with its extremely high ionization activity, can rapidly and targetedly destroy dioxin-like pollutants in solid fly ash at the source, completely avoiding the technical defects of traditional wet processes where the lack of pre-treatment leads to the accumulation of toxicity in the end product (such as carbon-rich concentrate). Example 3, by introducing pure oxygen and increasing the discharge power, generated a higher density of highly oxidizing active free radicals, which further reduced the residual amount of biphasic dioxins (5.4 ng-TEQ / kg for carbon-rich concentrate and 3.2 ng-TEQ / kg for residual ash tailings).

[0076] 3. Regarding the hydrophobic reconstruction of carbon surfaces and two-stage selective separation: Comparative Example 3, due to the elimination of the polar collector with hydrogen bonding and its replacement with conventional non-polar diesel, experienced a precipitous drop in the loss on ignition (LOI) and recovery rate of the carbon-rich concentrate (only 45.2% and 28.7%, respectively), while the LOI of the residual ash tailings reached as high as 4.35%. This is because plasma surface oxidation treatment leads to hydrophilic modification of the unburned carbon surface; conventional diesel cannot effectively bind to the hydrophilic carbon surface, resulting in a large amount of carbon not being collected during the flotation stage. In contrast, Example 1 used tetrahydrofurfuryl butyrate, which specifically binds to the oxidation sites on the carbon surface through hydrogen bonding, reconstructing its surface hydrophobicity and achieving precise separation of the carbon-rich concentrate with high purity (LOI 88.5%) and high recovery (92.4%). In Example 6, when the mixture was combined with diesel, the synergistic effect of polar and non-polar compounding was achieved, which further increased the recovery rate of carbon-rich concentrate to 95.8% and reduced the heat loss rate of residual ash concentrate to an extremely low 0.28%, thus achieving a better resource-based purification effect.

[0077] This invention utilizes a deep co-processing technology for the resource recovery of municipal solid waste incineration fly ash, combining water washing and grading with low-temperature plasma detoxification and grinding-flotation. At the front end, a high-efficiency water washing and screening process removes and recovers readily soluble chlorides from the original municipal solid waste incineration fly ash with low energy consumption. Subsequently, the high ionization activity of low-temperature plasma is used to directionally and deeply degrade dioxin-like organic pollutants on the solid surface of the fly ash, completely eliminating the risk of toxicity diffusion at the source. An acid leaching-mechanical grinding system is introduced to exert a mechanochemical effect, using strong shear force to erode the inorganic mineral lattice at room temperature and low energy consumption, breaking the lattice binding and rapidly releasing encapsulated heavy metals, transforming them in situ into an enriched form easily floatable. Finally, addressing the hydrophilic properties of carbon materials caused by plasma surface oxidation, a polar collector is introduced to modify the surface hydrophobicity of unburned carbon. Ultimately, a two-stage gradient flotation process is used to achieve precise separation and efficient recovery of modified unburned carbon and heavy metal concentrate.

[0078] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A method for combined treatment of municipal solid waste incineration fly ash by water washing, low-temperature plasma detoxification and grinding-flotation, characterized in that, Includes the following steps: S1. Water washing and screening desalination: Add water to the fly ash from the original municipal solid waste incineration and wash it with ultrasonic stirring. After washing, the solid and liquid are separated to obtain primary water washing residue and primary water washing filtrate containing soluble chloride salts. S2, Low-temperature plasma detoxification: The primary water washing residue is dried to obtain a solid phase. The high ionization activity of low-temperature plasma is used to directionally and deeply degrade dioxin-like organic pollutants on the surface of the solid phase, thereby achieving surface oxidation detoxification treatment and deeply destroying the dioxin-like organic pollutants therein to obtain detoxified fly ash. S3. Acid leaching and in-situ grinding: The detoxified fly ash is added to an aqueous solution of acid leaching extractant to form a slurry, and then mechanical grinding is performed. Under the synergistic effect of mechanical and chemical shearing force and acid, the crystal lattice is dissociated, so that the encapsulated heavy metal ions are released and dissolved in situ to obtain activated fly ash slurry. S4. Primary flotation decarbonization: The activated fly ash slurry is mixed with water and adjusted, and a pH adjuster is added to regulate the slurry environment. Then, a polar collector and a frother are added in sequence to carry out primary flotation to obtain a carbon-rich concentrate and primary flotation decarbonization tailings. S5. Secondary flotation for heavy metal removal: The tailings from the primary flotation decarbonization are thoroughly mixed with the heavy metal collector; a collector and a frother are added to the mixture for secondary flotation to obtain heavy metal concentrate and inorganic residual ash tailings.

2. The method for combined treatment of municipal solid waste incineration fly ash by water washing and grading, low-temperature plasma detoxification, and grinding and flotation according to claim 1, is characterized in that, In step S1, the mass ratio of water to fly ash from municipal solid waste incineration is 3:1 to 10:

1.

3. The method for combined treatment of municipal solid waste incineration fly ash by water washing and grading, low-temperature plasma detoxification, and grinding and flotation according to claim 1, is characterized in that, In step S2, the moisture content of the primary water washing residue is controlled to be less than 5 wt% after drying.

4. The method for combined treatment of municipal solid waste incineration fly ash by water washing and grading, low-temperature plasma detoxification, and grinding and flotation according to claim 1, is characterized in that, The acid leaching extractant is at least one of hydrochloric acid, dilute sulfuric acid, or nitric acid; The amount of acid leaching extractant added is such that the pH of the slurry is between 1.5 and 3.

5.

5. The method for combined treatment of municipal solid waste incineration fly ash by water washing and grading, low-temperature plasma detoxification, and grinding and flotation according to claim 1, characterized in that, In step S4, the pH adjuster is at least one of industrial sodium carbonate, potassium carbonate, lime, sodium hydroxide, or potassium hydroxide, used to adjust the pH value of the slurry environment to 6.0 to 8.5; The polar collector is a nonionic heteropolar surfactant containing ether bonds, carboxyl groups, hydroxyl groups, or ester groups, or a compound collector formed by mixing with nonpolar hydrocarbon oils.

6. The method for combined treatment of municipal solid waste incineration fly ash by water washing and grading, low-temperature plasma detoxification, and grinding and flotation according to claim 1, is characterized in that, In step S5, the heavy metal chelating agent is an inorganic sulfiding agent or an organic heavy metal chelating precipitant. The molar amount of the heavy metal catcher is 1.0 to 2.0 times the total molar amount of soluble heavy metal ions in the tailings of the primary flotation decarbonization.

7. The method for combined treatment of municipal solid waste incineration fly ash by water washing and grading, low-temperature plasma detoxification, and grinding and flotation according to claim 1, is characterized in that, The mechanical grinding time is controlled between 10 min and 60 min.

8. A combined treatment system for municipal solid waste incineration fly ash water washing and grading-low-temperature plasma detoxification-grinding and flotation according to any one of claims 1-7, characterized in that, include An ultrasonic mixer and disperser is used to perform ultrasonic mixing in step S1. A filtration device that performs solid-liquid separation in step S1; A drying device, wherein the drying device is used to dry the primary water washing residue in step S2; The uniform material spreading machine and the low-temperature non-thermal plasma treatment device are used to continuously feed the dried primary water washing residue into the low-temperature non-thermal plasma treatment device for surface oxidation and detoxification treatment. A mechanical grinding mill, used for mechanically grinding the slurry in step S3; A flotation device, wherein the flotation device is used to complete the primary flotation in step S4 and the secondary flotation in step S5; The mixing equipment includes a first slurry preparation tank for diluting activated fly ash slurry with water in step S4, and a reagent reaction tank for uniformly mixing primary flotation decarbonization tailings with heavy metal collectors in step S5.

9. The combined treatment system for municipal solid waste incineration fly ash water washing and grading-low-temperature plasma detoxification-grinding and flotation as described in claim 8, is characterized in that, The low-temperature non-thermal plasma treatment device is selected from at least one of the following: dielectric barrier discharge plasma reactor, atmospheric pressure corona discharge plasma reactor, microwave discharge low-temperature plasma reactor, high-voltage pulse discharge plasma reactor, plasma-assisted ball mill, or high-energy electron beam irradiation reaction device. The working gas of the low-temperature non-thermal plasma processing device is at least one of air, oxygen, ozone, water vapor, or inert gas.

10. The combined treatment system for municipal solid waste incineration fly ash water washing and grading-low-temperature plasma detoxification-grinding and flotation as described in claim 8, characterized in that, The mechanical grinding mill is a planetary ball mill, a vibratory mill, or a drum ball mill.

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