In-situ real-time circulating harmless treatment technology for waste incineration fly ash

Abstract

The invention discloses an in-situ real-time circulating harmless treatment technology for waste incineration fly ash, and belongs to the technical field of environmental protection. Fly ash is guided out of a dust removal system, and is subjected to in-situ harmless treatment under the conditions of full sealing and 130-150 DEG C heat preservation; instantly spraying a composite mineralizer containing an alcohol solvent, a surfactant, a high-molecular polymer binder, a fluxing catalyst and a nanoscale inorganic oxide, and mixing and granulating; formed prefabricated particles of 5-25 mm are directly fed into a waste incineration hearth, and are cooperatively sintered along with the household garbage in the temperature range of 450-1050 DEG C of the waste incineration hearth. According to the method, the liquid phase generation temperature is reduced and lattice replacement is induced by utilizing the synergistic effect of the fluxing catalyst and the nano material, and the problem of flying after remelting is solved by utilizing the high-molecular binder. The product is ceramic particles containing silicate mineral phases, the leaching rate of heavy metals is low, and low-cost in-situ harmlessness of the fly ash is achieved.

Description

Technical Field

[0001] This invention belongs to the field of environmental protection technology, specifically relating to a technology for the in-situ real-time recycling and harmless treatment of fly ash from waste incineration. Background Technology

[0002] With the acceleration of urbanization, municipal solid waste incineration for power generation has become the mainstream waste disposal method. However, the fly ash produced during incineration is rich in heavy metals such as lead (Pb), cadmium (Cd), and chromium (Cr), as well as persistent organic pollutants such as dioxins (PCDD / Fs), and is listed as hazardous waste in the National Hazardous Waste List (HW18). Currently, the main technologies for fly ash treatment focus on solidification and landfill, high-temperature melting, and co-processing in cement kilns, but all of these face significant technical bottlenecks in practical applications.

[0003] The first category is traditional chemical stabilization and cement solidification technologies. For example, Chinese patent application CN101972766A discloses a "method for solidification / stabilization treatment of fly ash from waste incineration," which mainly involves adding heavy metal stabilizers and cement to encapsulate the fly ash. However, this type of technology has a significant "volume increase" problem: to meet the landfill strength and leaching indicators, large amounts of cement and agents are often required (typically increasing the weight by 20% to 40%), leading to a significant increase in the final disposal volume and exacerbating the landfill capacity shortage. Furthermore, cement solidification is only a physical encapsulation of pollutants, which is prone to failure in acidic environments or under long-term weathering conditions, and the room-temperature solidification process cannot destroy the highly toxic dioxin structure in the fly ash, leaving long-term environmental hazards.

[0004] The second category is independent high-temperature melting and vitrification technology. For example, Chinese patent application CN1759941B discloses a "method and equipment for heating and melting fly ash from waste incineration," which uses a fuel-fired surface melting furnace to melt fly ash into a glassy state at a high temperature of 1230℃-1300℃. Although this method completely eliminates harmful substances, its industrial application is hindered by extremely high energy consumption and equipment costs: the main component of fly ash is aluminosilicate, and its natural softening and melting temperature is usually above 1250℃. Maintaining such a high temperature requires a large amount of fuel or electricity (such as plasma technology). In addition, the high-temperature melt corrodes refractory materials extremely quickly, and this technology usually requires the construction of an independent melting plant, involving complex approval processes for off-site fly ash transfer and the risk of secondary pollution.

[0005] The third category is off-site sintering technology for ceramsite. For example, Chinese patent application CN1830885A discloses a "ceramsite using waste incineration fly ash as raw material and its preparation method," which requires a sintering temperature of 1000℃-1400℃. Although some improved technologies, such as CN113387715A, attempt to reduce the sintering temperature to 900℃-1000℃, their processes are extremely complex, requiring lengthy steps such as "water washing and dechlorination—hydrothermal reaction—granulation—rotary kiln sintering." This not only generates difficult-to-treat high-salt wastewater (washing liquid) but also requires the construction of independent rotary kiln equipment, making it impossible to directly utilize existing waste incineration furnaces for treatment.

[0006] The fourth category involves technologies that attempt to utilize existing waste incinerators for "in-situ recycling." Some existing technologies (such as CN117732853A) attempt to granulate fly ash and return it to the furnace. However, this type of technology faces severe contradictions between aerodynamics and thermodynamics in practical engineering. Aerodynamic instability: Conventional organic binders decompose rapidly at high temperatures, causing particles to disintegrate and revert to fine dust (10-50 micrometers) the moment they enter the furnace. Under the strong airflow disturbance in the furnace, this dust is quickly blown out and re-enters the dust removal system, forming an ineffective "dead loop," and may even lead to ash accumulation on the boiler heating surface.

[0007] Thermodynamic window mismatch: The furnace temperature of conventional municipal solid waste incinerators is strictly controlled between 450℃ and 1050℃. Without the introduction of an efficient fluxing system, existing technologies can only cause weak solid-phase reactions in fly ash at this temperature, failing to form a liquid phase to encapsulate and lock in heavy metals.

[0008] In summary, the existing technology lacks an in-situ real-time processing technology that can adapt to the existing waste incinerator's operating window of 450℃-1050℃, does not require complex water washing and independent kilns, can solve the aerodynamic stability of particles after entering the furnace, and can achieve deep lattice locking of heavy metals through chemical means. Summary of the Invention

[0009] This invention mainly solves the technical problems of existing municipal solid waste incineration fly ash, which is difficult to undergo liquid phase sintering at conventional incineration furnace temperatures, which easily causes secondary flying and circulation when directly returned to the furnace, and which results in incomplete solidification of heavy metals.

[0010] To achieve the aforementioned objectives, the present invention employs the following technical solution: a real-time, in-situ circulating harmless treatment technology for fly ash from waste incineration, comprising the steps of extracting fly ash generated during waste incineration from a dust removal system and transporting it to an incinerator for high-temperature treatment. The treatment technology also includes the step of spraying a composite mineralizer into the fly ash during the fly ash conveying process for mixing and granulation. The pre-formed granules formed by the mixed granulation are directly fed into the waste incineration furnace and incinerated and sintered together with the municipal solid waste at 450℃-1050℃. The composite mineralizer comprises the following components by total weight: Alcohol solvents, surfactants, polymer binders, fluxing catalysts, nanoscale inorganic oxides, and water.

[0011] Furthermore, the weight percentages of each component in the composite mineralizer are as follows: alcohol solvent 8% - 12%, surfactant 3% - 7%, polymer binder 12% - 18%, fluxing catalyst 3% - 5%, nano-sized inorganic oxide 1.5% - 2.5%, and the balance being water; the sum of the weight percentages of each component is 100%.

[0012] Furthermore, the alcohol solvent is selected from at least one of ethanol, ethylene glycol, glycerol, or polyethylene glycol; the surfactant is selected from at least one of sodium dodecylbenzenesulfonate, fatty alcohol polyoxyethylene ether, or alkylphenol polyoxyethylene ether.

[0013] Furthermore, the polymer binder is selected from at least one of polyacrylamide, polyvinyl alcohol, sodium carboxymethyl cellulose, or modified starch; the molecular weight of the polymer binder is 10 million to 18 million.

[0014] Furthermore, the fluxing catalyst is selected from at least one of sodium carbonate, potassium carbonate, sodium tetraborate, or rare earth tailings extract; the fluxing catalyst is in powder form with a particle size of less than 200 mesh.

[0015] Furthermore, the nanoscale inorganic oxide is characterized in that it is selected from at least one of fumed silica, nano-alumina, nano-titanium oxide, or nano-zinc oxide; the average primary particle size of the nanoscale inorganic oxide is 10 nm-30 nm, and the specific surface area is 180 m². 2 / g-220m 2 / g.

[0016] Furthermore, in the mixing and granulation step, the amount of the composite mineralizer added is 2.5% to 3.5% of the fly ash mass; the mixing and granulation time is 4 min to 6 min.

[0017] Furthermore, the particle size of the pre-formed particles is controlled between 5mm and 25mm; the residence time of the pre-formed particles in the waste incineration furnace is 1h to 1.5h.

[0018] Furthermore, the process of the fly ash being discharged from the dust removal system and entering the incinerator is carried out in a fully enclosed pipeline and a closed mixer, and the temperature of the fly ash when entering the mixer is maintained at 130℃-150℃.

[0019] Furthermore, the product after incineration and sintering is discharged with the slag. The product is ceramic-like particles containing silicate mineral phases formed after liquid phase rearrangement and lattice substitution.

[0020] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention solves the problem of fly ash's difficulty in melting at conventional furnace temperatures (450℃-1050℃), achieving deep mineralization. The invention introduces fluxing catalysts (such as sodium tetraborate and sodium carbonate) into the composite mineralizer, utilizing the principle of low-temperature eutectic to significantly reduce the liquid phase formation temperature of the fly ash system to approximately 800℃, perfectly matching the operating window of existing waste incinerators. In this liquid phase environment, nano-scale inorganic oxides (such as fumed silica) serve as heterogeneous nucleation sites, inducing isomorphic substitution of heavy metal ions, forcibly locking them within the generated feldspar or spinel mineral lattices. Experiments show that the heavy metal leaching concentration of the treated product is "undetectable," and the compressive strength is over 130N, superior to traditional sintering techniques.

[0021] 2. This invention overcomes the aerodynamic bottleneck of in-situ fly ash recycling, preventing secondary scattering. It utilizes a high-molecular-weight polymer binder (such as polyacrylamide) with a molecular weight of 10-18 million, combined with the wetting effect of surfactants, to agglomerate the fly ash into dense pre-formed particles of 5-25mm during transport. This particle size design resists the scouring of strong airflow within the furnace, preventing particle disintegration and scattering, while ensuring heat transfer to the particle core within 1-1.5 hours, achieving "settling upon entering the furnace, with no scattering throughout the process."

[0022] 3. The process is extremely simplified, achieving significant volume reduction and complete dioxin decomposition. Unlike the complex "washing-drying-independent kiln" process in existing technologies, this invention uses a fully enclosed pipeline and a closed mixer, utilizing the sensible heat of fly ash itself (130℃-150℃) to assist granulation, eliminating the need for external heat sources and independent plant construction. The fly ash undergoes high temperatures above 850℃ in the furnace, completely decomposing dioxins. Simultaneously, through high-temperature sintering and densification, a volume reduction of over 70% is achieved, fundamentally solving the "volume increase" problem caused by cement solidification. Attached Figure Description

[0023] Figure 1 This is a process flow diagram of the in-situ real-time recycling and harmless treatment technology for fly ash from waste incineration according to the present invention. Figure 2 This is a trend graph showing the effect of the amount of composite mineralizer added in this invention on the liquidus temperature (melting point) of the fly ash system. Figure 3 This is a bar chart comparing the leaching toxicity of lead (Pb) in the embodiments and comparative examples of the present invention. Figure 4 This is a block diagram showing the overall process equipment connection of the present invention. Detailed Implementation

[0024] The following embodiments further explain and illustrate the technical solutions of the present invention. It should be specifically noted that each specific embodiment is a concretization and explanation of the technical solution and should not be considered as a limitation on the scope of protection of the present invention. Those skilled in the art still have the right to modify the technical solutions of these embodiments and make equivalent substitutions for some or all of the technical features, and these modifications or substitutions do not change the essence of the corresponding technical solutions, nor do they cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions described in the present invention.

[0025] This invention proposes a technology for the in-situ real-time recycling and harmless treatment of fly ash from waste incineration. To verify the feasibility of the technical solution described in this invention and to ensure the authenticity and reliability of the experimental data, this specification first clearly describes the specifications of the experimental raw materials used in the embodiments and comparative examples.

[0026] Fly ash raw material: The fly ash raw material used in the experiment was taken from the ash hopper of a bag filter dust collector in a municipal solid waste incineration power plant. The fly ash was in the form of gray powder with an initial moisture content of 1.5%. The sampling temperature was maintained between 130℃ and 150℃. XRF fluorescence spectroscopy analysis and background value detection showed that its main heavy metal content was 2400 mg / kg for lead and 150 mg / kg for cadmium, classifying it as typical hazardous waste.

[0027] Alcohol solvents: Analytical grade ethylene glycol with a purity greater than 99.5% and analytical grade glycerol with a purity greater than 99.0% were selected.

[0028] Surfactants: Sodium dodecylbenzenesulfonate with an active content greater than 90% is selected and is in powder form; and fatty alcohol polyoxyethylene ether AEO-9 with an active content greater than 99%.

[0029] Polymer binders: Anionic polyacrylamide with a molecular weight of 18 million and a degree of hydrolysis of 25% is selected; and polyvinyl alcohol 1788 with a degree of alcoholysis of 87.0% to 89.0% and an average degree of polymerization of 1700 is selected.

[0030] Fluxing catalyst: Analytical grade sodium tetraborate decahydrate and analytical grade anhydrous sodium carbonate are selected. Both are mechanically pulverized and passed through a 200-mesh standard sieve before use to ensure the particle size meets the requirements for rapid reaction.

[0031] Nanoscale inorganic oxides: Hydrophilic fumed silica Aerosil 200 was selected, with an average native particle size of 12 nm and a specific surface area of ​​200 ± 25 m². 2 / g; and gamma-phase nano-alumina with an average particle size of 20nm and a specific surface area of ​​180m². 2 / g.

[0032] Other: The water was laboratory-made deionized water with a conductivity of less than 5 μS / cm.

[0033] Key equipment: The mixing and granulation equipment is the SHR series high-speed mixing and granulation machine equipped with a heating jacket and a precision spray device; the high-temperature sintering equipment is a muffle furnace with precise temperature control; the heavy metal detection instrument is an Agilent 5110 inductively coupled plasma atomic emission spectrometer; and the dioxin detection instrument is a high-resolution gas chromatography-mass spectrometry system.

[0034] This invention measures various performance indicators of the treated product in accordance with relevant national standards to quantitatively evaluate the technical effect.

[0035] Granulation and pelletizing rate: Take 1000g of the mixed granulated material, sieve it through a standard sieve with a pore size of 3mm, weigh the mass of the material on the sieve and calculate its percentage of the total mass.

[0036] Particle compressive strength: 20 sintered finished particles were randomly selected, and the crushing force of a single particle was measured using a microcomputer-controlled electronic universal testing machine in accordance with the national standard GB / T14201. The average value was taken, and the unit was Newton.

[0037] Volume reduction rate: The percentage of volume reduction relative to the original volume is calculated by measuring the natural accumulation volume of the original fly ash before treatment and the natural accumulation volume of the discharged slag after treatment.

[0038] Heavy metal leaching toxicity: The leachate was prepared strictly in accordance with the environmental protection standard HJ / T300 Solid Waste Leaching Toxicity Leaching Method Acetic Acid Buffer Solution Method, and the heavy metal concentration was determined to meet the standard by referring to GB5085.3 Hazardous Waste Identification Standard Leaching Toxicity Identification.

[0039] Dioxin content: determined according to environmental standard HJ77.2 isotope dilution high-resolution gas chromatography-high-resolution mass spectrometry, with the unit being nanograms of toxicity equivalent per kilogram.

[0040] To enable those skilled in the art to better understand and implement the present invention, unless otherwise specified, the following embodiments and comparative examples are all operated using the following general process flow.

[0041] like Figure 1 As shown, the process mainly includes four core steps: preparation of composite mineralizer, closed conveying and injection of fly ash, micro-modification granulation, and in-situ high-temperature sintering.

[0042] The high-shear preparation of the composite mineralizer begins with the preparation of the solution. In a mixing tank equipped with a heating jacket and a high-shear emulsifier (speed set from 1000 rpm to 3000 rpm), water, alcohol solvent, and surfactant are added in proportion and stirred until completely dissolved. Then, a polymer binder is slowly added to increase the shear rate and prevent agglomeration until a homogeneous viscous liquid is formed. Finally, a pre-crushed fluxing catalyst and nano-sized inorganic oxides are added to the system, and high-shear dispersion is continuously performed for 30 minutes to ensure that the nanomaterials are monodisperse in the liquid phase, thus obtaining a stable emulsion-like composite mineralizer.

[0043] In the fully enclosed conveying and immediate injection stage of fly ash, the fly ash unloaded from the bag filter of the waste incineration dust removal system is directly discharged via a fully enclosed screw conveyor. During the conveying process, heating or insulation measures are used to ensure that the temperature of the fly ash is maintained between 130℃ and 150℃ when it enters the next process, utilizing the sensible heat of the fly ash itself to promote the rapid evaporation of solvents in the subsequent granulation process. At the end of the conveying pipeline or the inlet of the mixer, a precision metering pump and atomizing nozzle are installed to spray the composite mineralizer prepared in step 1 into the flowing hot fly ash in an immediate atomized form.

[0044] like Figure 2 , 4 As shown, The micro-modified fly ash, having adsorbed the mineralizer, is then fed into a continuous high-speed mixing granulator. Under the synergistic effect of mechanical stirring and chemical bonding, the fly ash particles complete the wetting, coating, and agglomeration process within 4 to 6 minutes. Polymer molecules form liquid bridges between the fly ash particles, drawing them together to form dense pre-formed particles with a diameter of 5 mm-5 mm. This process is carried out in a completely enclosed environment, effectively preventing secondary pollution caused by dust escape.

[0045] The pre-formed granules, after in-situ high-temperature sintering and slag removal molding, are conveyed into the furnace of the waste incinerator for co-incineration with municipal solid waste. During the movement of the grate, the pre-formed granules undergo drying, pyrolysis, and sintering stages, remaining in the high-temperature environment of the furnace (450℃-1050℃) for 1 to 1.5 hours. After sintering, the product is transformed into hard, ceramic-like granules, which are discharged from the system along with the slag. After water cooling, they are recycled as general solid waste.

[0046] The reason why this invention can achieve complete harmlessness and high-strength ceramicization of fly ash within the temperature window of 450℃-1050℃ in conventional waste incinerators is fundamentally due to the low-temperature eutectic and lattice-locking mechanism constructed by the composite mineralizer.

[0047] like Figure 2 As shown, In existing technologies, the main mineral component of fly ash is aluminosilicate, whose natural softening and melting temperature is usually above 1200℃, which cannot be melted by ordinary furnace temperatures. In this invention, the fluxing catalyst (such as borate) can chemically react with the silica and calcium oxide on the fly ash surface at around 800℃ to generate a low eutectic, which significantly reduces the starting temperature of liquid phase formation and creates a highly active liquid phase reaction environment on the particle surface.

[0048] In this liquid-phase environment, nanoscale inorganic oxides (such as nano-silica), with their enormous specific surface energy, act as heterogeneous nucleation sites, significantly reducing the nucleation barrier for new phase formation and inducing rapid crystallization of the melt to form stable mineral phases such as feldspar or spinel. During crystal growth, heavy metal ions (such as lead and cadmium ions), due to their similar ionic radii to elements like calcium and sodium, undergo isomorphic substitution under concentration-driven conditions, being forced into the mineral lattice or dissolved in the glassy phase. This chemical-level lattice locking makes it difficult for heavy metals to leach even in acidic environments, thus achieving true long-term stabilization. Simultaneously, the physical framework provided by the polymer binder in the low-temperature range (below 400℃) effectively prevents fly ash from being blown away by the strong gas flow in the furnace before sintering, solving the aerodynamic problem of in-situ return to the furnace.

[0049] Example 1 This embodiment provides an optimal technical solution, aiming to verify the comprehensive processing performance of the technology described in this invention under standard operating conditions. The formula parameters and process conditions selected in this embodiment are all within the center values ​​of the preferred range defined in the claims, representing the best implementation effect of this technology.

[0050] The composite mineralizer was prepared in a stainless steel mixing tank equipped with a heating jacket and a high-shear disperser (speed set to 2800 rpm), with a total volume of 100 kg. The specific formulation composition (by weight percentage) is as follows: Alcohol solvent: 10% (i.e., 10 kg), using analytical grade ethylene glycol; Surfactant: 5% (i.e., 5 kg), sodium dodecylbenzenesulfonate powder is selected; High molecular weight polymer binder: 15% (i.e., 15 kg), using anionic polyacrylamide with a molecular weight of 18 million; Fluxing catalyst: 4% (i.e., 4 kg), sodium tetraborate decahydrate that has passed through a 200-mesh sieve is selected; Nanoscale inorganic oxides: 2% (i.e. 2 kg), using fumed silica (Aerosil200) with an average particle size of 12 nanometers and a specific surface area of ​​200 square meters per gram. Water: 64% (i.e., 64 kg), deionized water is used.

[0051] Synergistic mechanism between components: The surfactant first breaks down the hydrophobic barrier on the fly ash surface, and then the polymer binder unfolds its long chain in the water / alcohol medium, realizing the transformation from "point contact" to "surface bonding". This is the basis for the balling rate of over 95%. The nano-scale inorganic oxides and the fluxing catalyst produce synergy: The fluxing agent creates a "liquid phase environment", and the nano-oxides diffuse rapidly in the liquid phase to strengthen the silicon-oxygen skeleton. The micro-carbon particles formed by the carbonization of the polymer in the initial stage can instantly adsorb volatile metals, and are then completely encapsulated by the silicate mineral phase generated by the nano-oxides and fluxing agent in the high-temperature zone.

[0052] Preparation steps: First, water is added to a mixing tank and heated to 450℃. Ethylene glycol and sodium dodecylbenzenesulfonate are added sequentially, and the mixture is stirred for 5 minutes until completely dissolved. Then, polyacrylamide is slowly added while stirring. Once it has fully swelled and the solution exhibits a uniform, transparent, and high-viscosity state, sodium tetraborate and fumed silica are added. A high-shear disperser is then used for 30 minutes to ensure that the nanoparticles do not agglomerate in the solution, ultimately yielding a milky white, uniform, and stable suspension of the composite mineralizer.

[0053] For the micro-modification and granulation of fly ash, 1000 kg of fresh fly ash at 135℃ (taken from the dust collector hopper) is fed into a continuous high-speed mixing granulator via a closed screw conveyor. The mixer is started (500 rpm), and the prepared composite mineralizer from the mixing tank is delivered to the atomizing nozzle via a precision metering pump. The atomizing nozzle sprays the composite mineralizer into the mixer in an atomized form, thus completing the atomization of the composite mineral into the fly ash. The addition amount is set to 3% of the fly ash mass (i.e., 30 kg). After staying in the mixer for 5 minutes, the fly ash and mineralizer complete wetting and agglomeration. Observing the discharge port, the fly ash has been transformed into spherical pre-formed particles with a particle size distribution between 5 mm and 25 mm. The particle surface is moist and dense, does not crumble when squeezed by hand, and has good drop resistance.

[0054] The pre-formed pellets are fed into an operating waste incinerator via in-situ high-temperature sintering. The temperature in the combustion zone of the furnace is stabilized at 900℃ (±10℃). The pre-formed pellets move along the grate with the municipal solid waste, sequentially undergoing the processes of moisture evaporation, pyrolysis of the organic framework, and liquid-phase sintering of the inorganic components. The grate speed is controlled to ensure that the residence time of the pellets in the high-temperature zone of the furnace is approximately 1.5 hours.

[0055] Product Characterization and Effects: After sintering, the product was discharged with the slag and collected after water cooling. Visually, the product consisted of dark gray, hard, ceramic-like particles with a vitreous luster and no powdering. Electron microscopy (SEM) revealed a dense internal structure, well-developed crystals, and extremely low porosity. This indicates that, under the synergistic effect of the fluxing catalyst and nano-fumed silica, the fly ash underwent sufficient liquid-phase rearrangement and lattice densification at 900℃.

[0056] Example 2 This embodiment aims to verify the feasibility of the technical solution of the present invention under the lower limit of the numerical range and the lower sintering temperature conditions described in the claims, and at the same time verify the applicability of different component types.

[0057] The total amount of the composite mineralizer prepared is 100 kg. The components and proportions (by weight percentage) selected in this embodiment are all set to the lower limit or close to the lower limit of the scope of protection of the claims: Alcohol solvent: 8% (i.e., 8 kg), using analytical grade glycerol; Surfactant: 3% (i.e., 3 kg), using fatty alcohol polyoxyethylene ether (AEO-9). High molecular weight polymer binder: 12% (i.e., 12 kg), using high viscosity polyvinyl alcohol (PVA) with a degree of polymerization of 2400 and a degree of hydrolysis of 99%. Fluxing catalyst: 3% (i.e., 3 kg), a mixture of anhydrous sodium carbonate and potassium carbonate (mass ratio 1:1). Nanoscale inorganic oxides: 1.5% (i.e. 1.5 kg), using gamma-phase nano-alumina with an average particle size of 20 nanometers and a specific surface area of ​​180 square meters per gram; Water: 72.5% (i.e., 72.5 kg), balance.

[0058] Preparation steps: Polyvinyl alcohol was soaked in cold water to swell, then heated to 90℃ and stirred to dissolve. After cooling, glycerol, fatty alcohol polyoxyethylene ether, carbonate mixture, and nano-alumina were added sequentially. The mixture was dispersed for 40 minutes under the action of a high-speed shear press (2500 rpm) to obtain a uniform composite mineralizer emulsion.

[0059] Microscopic modification and granulation of fly ash: 1000 kg of fly ash maintained at 130°C (lower limit of the lower limit of the claim) was used. In a closed mixer, the aforementioned composite mineralizer was injected at 2.5% of the fly ash mass (i.e., 25 kg, lower limit of the addition amount of the claim). The mixing and granulation time was set to 4 minutes (lower limit of the time of the claim). Due to the excellent film-forming properties of the binder PVA, the fly ash could still rapidly agglomerate despite the low addition amount. The pre-formed particles obtained at the discharge port had a particle size mainly distributed at around 5 mm.

[0060] In-situ high-temperature sintering feeds the pre-formed pellets into the waste incinerator. This embodiment simulates fluctuating furnace conditions or low-temperature operation, controlling the combustion zone temperature at 850°C (the lower limit of the temperature described in the claims). To compensate for insufficient reaction kinetics due to the lower temperature, the grate speed is controlled to maintain the residence time of the pellets in the furnace at 1.5 hours.

[0061] Product Characterization and Effects: The product was discharged with the slag. Observations revealed that although the sintering temperature was low, a dense sintered hard shell still formed on the product surface due to the highly active heterogeneous nucleation sites provided by nano-alumina and the effective reduction of the local melting point by the carbonate flux, without any loose powdering. Testing showed that the volume loss rate of the product was approximately 65%, and the leaching concentration of lead was 0.08 mg / L (slightly higher than in Example 1, but still far below the national standard limit), demonstrating that the present invention still possesses reliable harmless treatment capabilities under low formulation content and low-temperature conditions.

[0062] Example 3 This embodiment aims to verify the strengthening effect of the technical solution of the present invention under the upper limit of the numerical range and higher sintering temperature conditions described in the claims, especially the deep mineralization ability of fly ash with extremely high background values ​​of heavy metals or refractory materials.

[0063] The total amount of the composite mineralizer prepared is 100 kg. The formulation used in this embodiment has a high concentration, and all components (by weight percentage) are set to the upper limit of the scope of protection of the claims. Alcohol solvent: 12% (i.e., 12 kg), using analytical grade ethylene glycol; Surfactant: 7% (i.e., 7 kg), sodium dodecylbenzenesulfonate is selected; High molecular weight polymer binder: 18% (i.e., 18 kg), using anionic polyacrylamide (PAM) with a molecular weight of 16 million. Fluxing catalyst: 5% (i.e., 5 kg), sodium tetraborate (borax) is selected; Nanoscale inorganic oxides: 2.5% (i.e., 2.5 kg), using fumed silica (Aerosil200); Water: 55.5% (i.e., 55.5 kg), balance.

[0064] Preparation steps: Due to the high solid content, the order of material addition must be strictly controlled during preparation. First, heat water to 50°C to dissolve ethylene glycol and surfactant. Then, slowly add polyacrylamide under vigorous stirring, extending the stirring time to 60 minutes to ensure complete swelling of the high-concentration colloid and avoid the formation of "fish eyes". Finally, add fluxing catalyst and fumed silica, and perform three cycles of dispersion using a high-shear emulsifier to obtain a high-viscosity but well-flowing milky-white slurry.

[0065] Microscopic modification and granulation of fly ash involved using 1000 kg of fly ash at 150℃ (upper temperature limit). In a high-speed mixer, 3.5% (35 kg, the upper limit of the addition amount as claimed) of the aforementioned high-concentration mineralizer was injected. The mixing and granulation time was set to 6 minutes. Due to the extremely high content of binder and surfactant in the mineralizer, the liquid bridging force between fly ash particles was extremely strong, rapidly agglomerating into dense spheres. Discharge port testing showed that the pre-formed granules were mainly distributed at a particle size of approximately 8 mm, with smooth surfaces and extremely high drop strength, making them difficult to break even under strong external pressure.

[0066] In-situ high-temperature sintering is used to feed the pre-formed pellets into the waste incinerator. In this embodiment, high-temperature conditions are simulated, and the temperature of the combustion zone is controlled at 1050°C. Due to the high temperature, the reaction kinetic rate is accelerated, so the residence time of the pellets in the furnace is shortened to 1 hour to verify the efficiency of "high-temperature rapid combustion".

[0067] Product Characterization and Effects: The product was discharged with the slag. Observation revealed that after high-temperature treatment at 1050℃, the particle surface exhibited obvious glassy melting characteristics, with a smooth and dense glaze. Although the flux content in the mineralizer reached the upper limit (5%), no severe adhesion or coking occurred between the particles, indicating a good match between the formulation and process. Testing showed that the product had a volume reduction rate of over 75%, and the leaching concentrations of heavy metals such as lead and cadmium were all "not detected" (ND), with dioxin content as low as 0.8 nanograms of toxicity equivalent per kilogram. This indicates that under high formulation content and high-temperature conditions, the lattice reconstruction reaction of the fly ash proceeded extremely thoroughly, achieving optimal curing effects.

[0068] Example 4 This embodiment aims to verify the substitutability of different types of components in this invention and to prove that the composite mineralizer formulation described in this invention has a wide range of raw material applicability.

[0069] The total amount of the composite mineralizer prepared is 100 kg. In this embodiment, the addition ratio (weight percentage) of each component is kept within the median of the preferred range, but specific chemical components have been substituted: Alcohol solvents: 10% (i.e., 10 kg), replaced by analytical grade glycerol (glycerol) instead of ethylene glycol; Surfactant: 5% (i.e., 5 kg), replaced by sodium dodecylbenzenesulfonate with fatty alcohol polyoxyethylene ether (AEO-9); High molecular weight polymer binder: 15% (i.e., 15 kg), using anionic polyacrylamide (PAM) with a molecular weight of 15 million. Fluxing catalyst: 4% (i.e., 4 kg), replaced by analytical grade anhydrous sodium carbonate with sodium tetraborate; Nanoscale inorganic oxides: 2% (i.e. 2 kg), replaced by gamma-phase nano-alumina (average particle size 20 nm) from fumed silica. Water: 64% (i.e., 64 kg), balance.

[0070] Preparation steps: Since glycerol has a higher viscosity than ethylene glycol, it was first mixed with water and heated to 60°C to reduce the viscosity of the system. Then, the nonionic surfactant AEO-9 was added and stirred until homogeneous. After adding polyacrylamide, the stirring speed was increased to 3000 rpm to prevent agglomeration. Finally, sodium carbonate powder and nano-alumina were added, and the mixture was treated with a high-shear disperser for 30 minutes. The resulting mineralizer emulsion was slightly thicker than that of Example 1, but still exhibited good pumpability and atomization performance.

[0071] Microscopic modification and granulation of fly ash involved using 1000 kg of fresh fly ash at 135°C. In a closed mixer, 3% (30 kg) of the fly ash mass was injected with the aforementioned composite mineralizer containing glycerol and nano-alumina. The mixing and granulation time was set to 5 minutes. Observations revealed that due to the strong hygroscopic and moisturizing properties of glycerol and its high boiling point (290°C), it had a longer residence time within the fly ash particles, helping to maintain a moist environment during granulation. This resulted in pre-formed particles with a smoother, rounder surface and excellent particle size uniformity (mainly distributed around 6 mm).

[0072] In-situ high-temperature sintering involves feeding pre-formed particles into a waste incinerator, where the combustion zone temperature is controlled at 900℃ and the residence time is 1.5 hours. During this process, nano-alumina plays a crucial role. Unlike silica, alumina directly participates in the construction of the aluminosilicate framework. In the liquid phase environment formed by sodium carbonate flux, nano-alumina, as a highly active aluminum source, rapidly reacts with calcium oxide and silica in fly ash, inducing the formation of a large amount of anorthite (…). It contains a small amount of spinel phase.

[0073] Product Characterization and Effects: The product was discharged with the slag and, after cooling, appeared as light gray, hard particles. Testing showed that the particle compressive strength of this product reached 130 Newtons (slightly higher than Example 1, presumably due to the enhancement of the mechanical properties of the ceramic phase by nano-alumina). The volume loss rate was 71%, and the leaching concentrations of lead and cadmium were both "not detected." The dioxin content was 1.0 nanograms of toxicity equivalent per kilogram. Experimental results confirm that using glycerol as a solvent and nano-alumina as a nucleation inducing agent can also achieve efficient mineralization and detoxification of fly ash.

[0074] Example 5 (Small Particle Size Boundary Verification) This embodiment focuses on examining the processing effect of the technical solution of the present invention under the condition of smaller pre-formed particle size, aiming to verify the performance boundaries of the technical solution in terms of "rapid burning" and "resistance to airflow dispersion".

[0075] In order to control variables and accurately evaluate the influence of particle size on sintering effect, the formulation and preparation process of the composite mineralizer used in this embodiment are completely consistent with those in Example 1 (i.e., 10% ethylene glycol, 5% sodium dodecylbenzenesulfonate, 15% polyacrylamide, 4% sodium tetraborate, 2% fumed silica, and 64% water).

[0076] For the micro-modification and granulation of fly ash, 1000 kg of fresh fly ash at 135°C was placed into a mixer. The amount of composite mineralizer added was maintained at 3% (30 kg). Process adjustment: In order to obtain smaller particle size, the stirring speed of the mixer was increased to 800 rpm, and the granulation time was shortened to 3 minutes (less than 4-6 minutes). Due to the increased stirring shear force and shortened time, the fly ash failed to form large agglomerates, and the pre-formed particles obtained at the discharge port were mainly distributed at a particle size of about 3 mm (less than 5-25 mm). Although the particles were small, thanks to the strong binding force of 15% high-content polyacrylamide, the small particles still maintained good integrity, and no obvious dust was observed.

[0077] In-situ high-temperature sintering involves feeding the aforementioned 3mm particles into a 900℃ waste incineration furnace. Upon entering the furnace, due to their light weight, the particles are slightly lifted by the primary airflow, but are not blown back into the dust collection system. Thanks to the large specific surface area of ​​the small particles, heat conduction is extremely rapid, and the particles complete integral liquid-phase sintering from the outside to the inside in a very short time.

[0078] Product Characterization and Effects: The product was discharged with the slag. Observation revealed that the sintered small particles exhibited extremely high density, similar to glass sand. Testing showed that the lead leaching concentration of this batch of product was "not detected," and the compressive strength reached 140 Newtons (due to its smaller size and denser structure). Experimental Conclusion: Even with a particle size as small as 3mm, the formulation of this invention still provides sufficient binding force to prevent secondary fly ash re-entrainment, and the mineralization effect is excellent. However, considering the interference of airflow within the furnace, it is recommended that particles larger than 5mm as described in the claims be preferred in practical engineering.

[0079] Example 6 (Verification of Large Particle Size Boundaries) This embodiment focuses on examining the processing effect of the technical solution of the present invention under the condition of larger pre-formed particle size, aiming to verify the ability of composite mineralizer to assist in "deep heat conduction" and "internal lattice reconstruction" and challenge the limits of mass and heat transfer.

[0080] Preparation of composite mineralizer: The formulation and preparation process of the composite mineralizer used in this embodiment are completely consistent with those in Example 1.

[0081] For the micro-modification and granulation of fly ash, 1000 kg of fresh fly ash at 135°C was placed into a mixer. The amount of composite mineralizer added was maintained at 3% (30 kg). Process adjustment: In order to obtain larger particle size, the stirring speed of the mixer was reduced to 300 rpm, and the granulation time was extended to 10 minutes (higher than 4-6 minutes). Under long-term low-speed rolling, the fly ash particles grew continuously through the "snowball effect," and the pre-formed particles obtained at the discharge port were mainly distributed in particle size between 10 mm and 12 mm (higher than 5-25 mm). The particles had a coarse spherical appearance, and the surface wettability was slightly lower than that in Example 1.

[0082] In-situ high-temperature sintering involves feeding the aforementioned 10mm large particles into a 900℃ waste incineration furnace. Due to the large particle size, heat transfer from the surface to the core takes longer. To ensure thorough sintering, this embodiment strictly controls grate movement, ensuring the particles remain in the high-temperature zone for 1.5 hours. During this process, the nano-fumed silica and fluxing catalyst in the composite mineralizer play a crucial role. They construct thermally conductive liquid-phase channels within the particles, promoting heat transfer to the core and preventing the "burnt outside, raw inside" sandwich phenomenon.

[0083] Product Characterization and Effects: The product was discharged with the slag. The cooled large particles were broken open, and their cross-sections were observed. The results showed that the particles exhibited a uniform dark gray ceramic phase from the surface to the core, with no black core (unburnt fly ash). The volume loss rate of the product was approximately 68% (slightly lower than Example 1 due to the larger voids in the large particle packing), the heavy metal leaching concentration was "not detected," and the compressive strength was 120 Newtons. Experimental Conclusion: Even with particle sizes exceeding 10 mm, the unique chemical fluxing and nano-induction mechanism of this invention still achieves comprehensive and thorough mineralization, demonstrating the robustness of the technical solution in combating "heat transfer resistance."

[0084] Comparative Example 1 like Figure 4 As shown, this comparative example aims to demonstrate that if physical granulation is carried out solely by polymer binders without the presence of chemical fluxing and mineralizing components, it is impossible to achieve deep harmlessness of fly ash.

[0085] The only difference between the preparation of the composite mineralizer and Example 1 is that the fluxing catalyst (sodium tetraborate) and the nano-sized inorganic oxide (fumed silica) are omitted. The specific formula is adjusted as follows (by weight percentage): 10% ethylene glycol, 5% sodium dodecylbenzenesulfonate, 15% polyacrylamide, and 70% water (the original proportions of catalyst and nanomaterials are made up by water).

[0086] The granulation and sintering processes were performed exactly as described in Example 1 (i.e., 3% addition, sintering at 900℃). Process observations: During the granulation stage, thanks to the 15% polyacrylamide, the pellet formation was excellent. However, during the sintering stage, due to the lack of a flux to lower the melting point, the particles only underwent physical drying and organic carbonization at 900℃, without any signs of liquid-phase melting. After cooling, the particle surface was dull and rough, and crumbled easily when squeezed with a finger.

[0087] Comparative Example 2 This comparative example aims to demonstrate that although the use of flux alone can partially lower the melting point, it lacks the heterogeneous nucleation effect of nanomaterials and cannot achieve deep lattice locking.

[0088] The only difference between the preparation of the composite mineralizer and Example 1 is that the nano-sized inorganic oxide (fumed silica) is omitted, while the fluxing catalyst is retained. The specific formula is adjusted as follows (by weight percentage): 10% ethylene glycol, 5% sodium dodecylbenzenesulfonate, 15% polyacrylamide, 4% sodium tetraborate, and 66% water (the original proportion of nanomaterials is made up by water).

[0089] The process parameters were completely consistent with those of Example 1. Process observations: The sintered particles exhibited a certain strength, and some glassy phase appeared on the surface, but the gloss was not as good as in Example 1. This indicates that although melting occurred in the system, the crystallization process was slow and uneven due to the lack of nanocrystal nuclei, failing to form a dense microcrystalline ceramic structure.

[0090] Comparative Example 3 This comparative example uses the most common cement solidification landfill technology in the industry as a reference, aiming to intuitively demonstrate the significant advantages of this invention in "volume reduction" and "dioxin removal".

[0091] The treatment method does not use the composite mineralizer and in-situ heat treatment process of this invention. Take 1000 kg of fly ash, add 200 kg of No. 425 ordinary Portland cement (addition ratio 20%) and an appropriate amount of water, stir and mix evenly to form blocks. Test after curing under standard curing conditions for 24 hours.

[0092] The process involves no high-temperature steps and is simple to operate. However, due to the addition of a large amount of cement and water, the volume of the treated waste expands significantly (increases in volume), and organic pollutants such as dioxins in the fly ash are not destroyed in any way, but are merely physically encapsulated in cement blocks.

[0093] Comparative Example 4 This comparative example aims to demonstrate that the "450℃-1050℃" specified in this invention is a necessary thermodynamic condition for initiating the liquid phase sintering mechanism, and the technology will fail below this range.

[0094] The preparation formula of the composite mineralizer is completely consistent with that of Example 1.

[0095] The granulation process is the same as in Example 1. The key difference is that during the sintering stage, the combustion zone temperature of the waste incinerator is set to 600℃ (below the lower limit of 850℃), and the particle residence time is maintained at 1.5 hours. The resulting particles are light gray in color and have not undergone vitrification. This is because 600℃ is not yet the initial temperature for the formation of a eutectic between sodium tetraborate and silicate; the liquid-phase reaction cannot be initiated, and the fly ash only undergoes one "hot drying" process.

[0096] Experimental Results and Analysis To quantitatively evaluate the practical application effect of the in-situ real-time recycling and harmless treatment technology for waste incineration fly ash described in this invention, the final products obtained from Examples 1 to 6 and Comparative Examples 1 to 4 were uniformly tested according to the aforementioned "Performance Testing Method". The test results of various key performance indicators are summarized in Table 1.

[0097] Table 1: Summary of Performance Test Results for Each Example and Comparative Example

[0098] The universality verification of the technical solution, as shown in Table 1, reveals that the products obtained in Examples 1 to 6 all outperform the national standards and exhibit high stability. Regardless of whether the formulation fluctuates within the scope defined in the claims (Examples 2 and 3), key components are substituted (Example 4), or process parameters (such as particle size) change (Examples 5 and 6), the compressive strength of the products exceeds 110 Newtons, the leaching concentration of heavy metals is extremely low or even undetectable, and the volume loss rate remains stable above 65%. This fully demonstrates that the technical solution provided by this invention has a broad process adaptability window and extremely high industrial practical value.

[0099] A comparative analysis of the necessity of chemical mineralization components reveals that, in the absence of a fluxing catalyst and nano-oxides, although Comparative Example 1 achieved a high granulation rate (95.2%) using a polymer binder, its particle compressive strength was only 18.5 Newtons, and the lead leaching concentration was as high as 4.25 mg / L, approaching the national standard limit. The reason is that Comparative Example 1 only involved physical bonding and simple drying, lacking a chemical fluxing mechanism. The fly ash particles failed to form a liquid phase at 900°C, thus failing to encapsulate and lock in heavy metals. This demonstrates that the "fluxing catalyst" in this invention is crucial for achieving the transition from "physical granulation" to "chemical mineralization."

[0100] Analysis of the synergistic effect of nanomaterials: Comparative Example 1 and Comparative Example 2 shows that although Comparative Example 2 added a fluxing catalyst, achieving a certain strength (85.2 Newtons) and reduction rate, its lead leaching concentration was still 0.85 mg / L, failing to reach the "undetectable" level of Example 1. Reason analysis: This indicates that simply relying on fluxing agents to lower the melting point is insufficient. The nanoscale inorganic oxides introduced in Example 1, with their enormous specific surface energy, acted as key "heterogeneous nucleation sites" in the liquid phase, significantly reducing the nucleation barrier of mineral crystals and inducing heavy metal ions to enter the deep lattice through isomorphic substitution. This synergistic effect of "1+1>2" is the core inventiveness of this invention in achieving deep harmlessness.

[0101] Compared with the advanced technology of the prior art, Example 1 and Comparative Example 3 (traditional cement solidification) show that although the prior art is simple to operate, it leads to an 18% increase in waste volume (a negative reduction rate) and has no ability to remove highly toxic dioxins (up to 320 ng TEQ / kg). Advantage analysis: The present invention, through in-situ heat treatment, not only completely decomposes dioxins at high temperature (reducing them to 0.8 ng TEQ / kg), but also achieves a volume reduction of more than 70%, significantly reducing subsequent landfill costs and demonstrating huge environmental and economic benefits.

[0102] Critical analysis of process parameters comparing Example 1 and Comparative Example 4 reveals that when the sintering temperature is set to 600℃, even with a correct formulation, the product strength and leaching parameters deteriorate significantly. Reason analysis: This verifies that the "850℃ to 1050℃" range specified in this invention is the necessary thermodynamic condition for initiating liquid-phase sintering with the specific mineralizer of this invention. Below this temperature, the chemical reaction kinetics are insufficient, and a ceramic phase cannot be formed.

[0103] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A technology for the in-situ real-time circulation and harmless treatment of fly ash from waste incineration, comprising the steps of extracting fly ash generated from waste incineration from a dust removal system and transporting it to an incinerator for high-temperature treatment. Its features are: The treatment technology also includes the step of injecting a composite mineralizer into the fly ash during the fly ash conveying process for mixing and granulation. The pre-formed granules formed by the mixed granulation are directly fed into the waste incineration furnace and incinerated and sintered together with the municipal solid waste at a temperature of 450℃-1050℃. The composite mineralizer comprises the following components by total weight: Alcohol solvents, surfactants, polymer binders, fluxing catalysts, nanoscale inorganic oxides, and water.

2. The in-situ real-time recycling and harmless treatment technology for fly ash from waste incineration according to claim 1, characterized in that, The weight percentages of each component in the composite mineralizer are as follows: alcohol solvent 8% - 12%, surfactant 3% - 7%, polymer binder 12% - 18%, fluxing catalyst 3% - 5%, nano-sized inorganic oxide 1.5% - 2.5%, and the balance is water; the sum of the weight percentages of each component is 100%.

3. The in-situ real-time recycling and harmless treatment technology for fly ash from waste incineration according to claim 2, characterized in that, The alcohol solvent is selected from at least one of ethanol, ethylene glycol, glycerol, or polyethylene glycol; the surfactant is selected from at least one of sodium dodecylbenzenesulfonate, fatty alcohol polyoxyethylene ether, or alkylphenol polyoxyethylene ether.

4. The in-situ real-time recycling and harmless treatment technology for fly ash from waste incineration according to claim 2, characterized in that, The polymer binder is selected from at least one of polyacrylamide, polyvinyl alcohol, sodium carboxymethyl cellulose, or modified starch; the molecular weight of the polymer binder is between 10 million and 18 million.

5. The in-situ real-time recycling and harmless treatment technology for fly ash from waste incineration according to claim 2, characterized in that, The fluxing catalyst is selected from at least one of sodium carbonate, potassium carbonate, sodium tetraborate, or rare earth tailings extract; the fluxing catalyst is in powder form with a particle size of less than 200 mesh.

6. The in-situ real-time recycling and harmless treatment technology for fly ash from waste incineration according to claim 2, characterized in that, The nanoscale inorganic oxide is selected from at least one of fumed silica, nano-alumina, nano-titanium oxide, or nano-zinc oxide; the average primary particle size of the nanoscale inorganic oxide is 10 nm to 30 nm, and the specific surface area is 180 m². 2 / g to 220m 2 / g.

7. The in-situ real-time recycling and harmless treatment technology for fly ash from waste incineration according to claim 1, characterized in that, In the mixing and granulation step, the amount of the composite mineralizer added is 2.5% to 3.5% of the fly ash mass; the mixing and granulation time is 4 min to 6 min.

8. The in-situ real-time recycling and harmless treatment technology for fly ash from waste incineration according to claim 1, characterized in that, The particle size of the pre-formed particles is controlled between 5 mm and 25 mm; the residence time of the pre-formed particles in the waste incineration furnace is 1 hour to 1.5 hours.

9. The in-situ real-time recycling and harmless treatment technology for fly ash from waste incineration according to claim 1, characterized in that, The process of the fly ash being discharged from the dust removal system and entering the incinerator is carried out in a fully enclosed pipeline and a closed mixer, and the temperature of the fly ash when entering the mixer is maintained at 130℃-150℃.

10. The in-situ real-time recycling and harmless treatment technology for fly ash from waste incineration according to claim 1, characterized in that, The product after incineration and sintering is discharged with the slag. The product is ceramic-like particles containing silicate mineral phases formed after liquid phase rearrangement and lattice substitution.

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