A core-shell briquette for degrading dioxin in household garbage incineration fly ash and a treatment method

Abstract

The application discloses a kind of for degrading domestic waste incineration fly ash dioxin core-shell briquetting and processing method, the core-shell briquetting includes core layer and shell layer: core layer is by washing dechlorination after fly ash (Cl ‑ <3%) With composite additive (Fe powder, Al2O3 And SiO) is mixed into (1-2):1, by Fe / Al2O3 reduce dioxin cracking activation energy;Shell layer is by nano iron powder (50-100 nm), lime milk and steel slag / fly ash to wrap core layer, thickness 1-2mm, realize Cl ‑ Stabilization and pressure resistance ≥5MPa.The processing method includes: core-shell briquetting is preheated to moisture content <1% by blast furnace flue gas waste heat (150-180℃), put into blast furnace and handle cooperatively, utilize its temperature gradient (300-600℃ dechlorination in upper part, 1200-1400℃ cracking in middle part) and low oxygen environment (O2<1%), so that dioxin residual concentration ≤0.03 ng TEQ / g, heavy metal is reduced and solid-solution in molten slag.The dioxin degradation rate of the processing method of the application is high, and the comprehensive energy consumption is low, which is suitable for large-scale fly ash harmless and resource treatment.

Description

Technical Field

[0001] This invention relates to the field of biological dioxin decomposition and treatment technology. Background Technology

[0002] Polychlorinated dibenzodioxins / polychlorinated dibenzofurans (PCDD / Fs, hereinafter referred to as dioxins) remaining in fly ash from municipal solid waste incineration are internationally recognized potent carcinogens, with toxic equivalent concentrations (TEQs) typically ranging from 1 to 100 ng TEQ / g. Due to their high thermal stability (decomposition temperature > 800℃) and chemical inertness, efficient degradation of dioxins requires simultaneously meeting the following technical conditions: High-efficiency dechlorination requires the removal of at least 5 chlorine atoms to disrupt the benzene ring structure; Complete pyrolysis: Avoid generating intermediate products in the low temperature range of 200-450℃, which could lead to "resynthesis"; Heavy metal stabilization: Inhibits the volatilization and subsequent leaching risks of heavy metals such as Pb, Cd, and Zn at high temperatures.

[0003] Current mainstream processing technologies have the following limitations: High-temperature melting method (>1200℃): This technology melts fly ash into a glassy state using an electric arc furnace or plasma, and decomposes dioxins at high temperatures. However, it has significant drawbacks: extremely high energy consumption: the energy consumption per unit of treatment reaches 1.5-2.5 kW·h / kg, accounting for more than 30% of the total operating cost of the incineration plant; secondary pollution of heavy metals: under high-temperature conditions, the volatilization rate of heavy metals such as Pb and Cd exceeds 50%, requiring the configuration of a multi-stage exhaust gas purification system (such as bag filter + wet scrubbing), increasing equipment investment costs by more than 40%; residual risk: the residual concentration of dioxins in the molten slag may still reach 0.1-0.5 ng TEQ / g (GC-MS detection, JIS K0312 standard), which cannot meet the limit requirement of 0.05 ng TEQ / g in the "Technical Specification for Pollution Control of Fly Ash from Municipal Solid Waste Incineration (HJ 1134-2020)".

[0004] Low-temperature pyrolysis (300-450℃): This technology uses catalysts such as TiO2 and V2O5 to thermally dechlorinate in an oxygen-deficient environment. However, its application has the following bottlenecks: Dioxin regeneration: During the cooling stage (<300℃), the concentration of dioxins regenerated reaches 10-20% of the initial value due to the "de novo synthesis" reaction; Catalyst deactivation: Components such as Cl⁻ and SO4²⁻ in fly ash combine with the active sites on the catalyst surface, resulting in a shortened catalyst life of 50-100 hours, requiring frequent replacement; Byproduct treatment pressure: The HCl concentration in the tail gas is >200 mg / Nm³ (far exceeding the emission limit of GB 16297-1996), requiring an additional alkaline spray tower, increasing the treatment cost by about 80-120 yuan / ton.

[0005] Chemical stabilization method: Physical sequestration is achieved by adding chelating agents (such as EDTA, sulfides) or cement to solidify fly ash. However, its limitations include: poor long-term stability: dioxins are not decomposed, and the leaching concentration may exceed the limit of GB 16889-2008 standard within 10 years; volume expansion problem: the expansion rate of the solidified body is as high as 15-20%, which cannot be used directly as building material aggregate; insufficient economic efficiency: the cost of chelating agents is 200-500 yuan / ton, and the treated fly ash still needs to be sent to a hazardous waste landfill, with a comprehensive disposal cost of more than 800 yuan / ton.

[0006] The above-mentioned technical solutions generally face the following contradictions in engineering applications: conflict between energy consumption and degradation efficiency: although the high-temperature melting method can partially decompose dioxins, the problems of energy consumption and secondary pollution are prominent; the low-temperature pyrolysis method cannot completely degrade pollutants due to regeneration phenomena; limited resource utilization: existing technology products (such as molten slag and solidified body) are difficult to meet the dual standards of strength (≥5MPa) and leaching safety in the building materials field; insufficient system synergy: exhaust gas treatment, heavy metal stabilization and other links are mostly independent modules, lacking synergistic optimization with industrial processes (such as metallurgical blast furnaces), resulting in low overall energy efficiency.

[0007] In summary, existing fly ash treatment technologies still have significant shortcomings in terms of complete dioxin degradation, energy consumption control, and secondary pollution prevention and control. There is an urgent need for a highly efficient treatment method that takes into account degradation efficiency, energy economy, and environmental safety. Summary of the Invention

[0008] One of the technical problems to be solved by the present invention is to provide a core-shell briquette for degrading dioxins in fly ash from municipal solid waste incineration, in order to solve the problems of excessive energy consumption and serious secondary pollution of heavy metals in the high-temperature melting method, high dioxin regeneration rate and easy catalyst deactivation in the low-temperature pyrolysis method, and the inability of chemical stabilization method to completely decompose dioxins and the instability of solidified body.

[0009] To overcome the shortcomings of the prior art, the present invention provides a core-shell briquette for degrading dioxins in fly ash from municipal solid waste incineration. The core-shell briquette includes a core layer and a shell layer surrounding the core layer. The raw materials of the core layer include water-washed fly ash and composite additives, wherein the composite additives are a mixture of Fe powder, Al2O3 and SiO2. The raw materials of the shell layer include nano-iron powder, lime slurry and industrial waste residue.

[0010] This application presents a core-shell briquette for degrading dioxins in municipal solid waste incineration fly ash, which, compared with existing technologies, has the following advantages: It addresses the shortcomings of existing technologies such as incomplete dioxin degradation, high energy consumption, and the presence of heavy metals and Cl... -To address issues such as severe secondary pollution, this invention provides a core-shell briquette for degrading dioxins in fly ash from municipal solid waste incineration. Through the synergistic effect of the core and shell layers, it achieves gradient decomposition of dioxins and simultaneous stabilization of pollutants. Specifically, it includes: Graded degradation and synergistic stabilization of pollutants: Core-layer catalytic cracking: Fe powder and Al2O3 form redox active sites, reducing the activation energy for dioxin CO bond breaking from 150 kJ / mol to 80-100 kJ / mol, thus promoting the destruction of the benzene ring structure (requiring the removal of ≥5 Cl atoms); SiO2 melts with fly ash at high temperature to form a glassy phase, which encapsulates heavy metals such as Pb, Cd, and Zn, reducing the leaching concentration to 10-25% of the standard limit.

[0011] Shell adsorption and solidification of chlorine: Nano-iron powder (50-100 nm) catalyzes Cl - It is converted to FeCl3 (boiling point 315℃), reducing HCl formation; lime milk (Ca(OH)2) reacts with Cl... - The reaction produces high-melting-point CaCl2 (melting point 772℃), which blocks equipment corrosion.

[0012] Material synergy and cost optimization: Chlorine control at the source: Cl in fly ash after water washing - With a content of <3%, the dechlorination load on the shell is reduced; industrial waste residue (steel slag / fly ash) adjusts the porosity and mechanical strength of the shell, and the compressive strength of the briquettes is ≥5 MPa, while reducing the cost of additives by 30-40%.

[0013] Catalyst protection: Shell-layer nano-iron powder preferentially adsorbs Cl - This avoids poisoning of the Fe / Al2O3 active sites in the core layer, extending the catalyst lifetime by more than 3 times.

[0014] Dual-layer barrier against secondary pollution: Heavy metal stabilization: The synergistic effect of SiO2 glass phase solidification in the core layer and physical barrier in the shell layer reduces the leaching rate of heavy metals by 90%.

[0015] Dioxin regeneration inhibition: The synergistic effect of high-temperature core layer cleavage and low-temperature solid chlorination gradient in the shell blocks the "de novo synthesis" pathway, resulting in low residual concentration.

[0016] In summary, the core-shell compact of this invention, through a gradient design of "core-layer catalytic pyrolysis - shell-layer adsorption and chlorine fixation," combined with the synergistic effect of Fe / Al2O3 / SiO2 and nano-iron / lime slurry components, achieves efficient dioxin degradation, heavy metal stabilization, and Cl- removal in a single structure. - The pollution control system systematically solves industry problems such as incomplete degradation, high energy consumption, and secondary pollution in existing technologies.

[0017] In one possible implementation, the chloride ion content in the fly ash is less than 3% by mass.

[0018] The above technical solution can control the chloride ion mass fraction in fly ash to below 3% by water washing or other pretreatment methods before briquetting. By controlling the chloride ion content to a low level, the chlorine source of dioxins can be directly reduced, the probability of their resynthesis can be reduced, and the release of HCl can be reduced, thus alleviating the burden of tail gas treatment.

[0019] In one possible implementation, the mass ratio of fly ash to composite additive is (1-2):1, and the mass ratio of Fe powder, Al2O3 and SiO2 in the composite additive is 1:(1-2):1.

[0020] Compared with existing technologies, the above technical solution can achieve the synergistic effect of multifunctional reaction components in the core layer while ensuring reaction efficiency and structural strength. Among them, Fe powder acts as a reducing agent and catalyst to promote the breaking of CO and C-Cl bonds in dioxin molecules; Al2O3 provides redox surface sites and improves the thermal stability of the compaction; SiO2 constructs the framework structure and forms a glass phase at high temperature to encapsulate heavy metals. By optimizing the mass ratio of the three components, the three components are evenly distributed in the microstructure, achieving a dynamic balance of dechlorination-pyrolysis-solidification functions.

[0021] In one possible implementation, the shell layer is wrapped around the surface of the core layer by a disc granulator, and the particle size of the nano-iron powder is 50-100 nm. The industrial waste residue is at least one of steel slag or fly ash. The mass ratio of the nano-iron powder, lime slurry and industrial waste residue is (1-5):(10-20):(50-80).

[0022] Compared with existing technologies, the above-mentioned technical solution can achieve uniform coverage of the core layer by the shell material through mechanical granulation, enhancing structural density and preventing core layer particle breakage or contamination release during preheating or low-temperature stages. This is because nano-iron powder, due to its small particle size and large specific surface area, can provide rapid adsorption and catalytic sites, promoting Cl... - Conversion to lower boiling point FeCl3 and reduction of HCl release; lime milk and residual Cl - The reaction produces CaCl2, which further fixes the chlorine element; while industrial waste (steel slag, fly ash) regulates the melting point and gives the briquettes the possibility of resource utilization in the later stage. In addition, the addition of industrial waste can also adjust the melting point of the core and shell briquettes, reducing the cost of additives by 30-40%.

[0023] In one possible implementation, the shell layer has a thickness of 1-2 mm, and the core-shell compact has a compressive strength ≥ 5 MPa.

[0024] Compared with existing technologies, the above-mentioned technical solution can ensure the integrity of the briquette structure while achieving stable transportation and reaction condition control in the multi-stage heat treatment process. The shell thickness of 1-2 mm can provide sufficient protection for the core layer to prevent the escape of cracked gases during the preheating stage or the initial stage of heating, and can also enable the permeation of reaction gases and the emission of products during the high-temperature stage, thereby ensuring the smooth progress of the synergistic reaction. The overall compressive strength of the core-shell briquette is not less than 5 MPa, which can significantly improve its mechanical stability in stacking, transportation, and furnace compaction, and prevent reaction runaway or pollution spread caused by briquette breakage.

[0025] Another technical problem to be solved by the present invention is to provide a treatment method for degrading dioxins in fly ash from municipal solid waste incineration, so as to solve the problems of incomplete degradation, high energy consumption, and heavy metal volatilization and re-pollution in the prior art.

[0026] To overcome the shortcomings of the prior art, the present invention provides a method for treating dioxins in fly ash from municipal solid waste incineration, comprising the following steps: S1. The fly ash is washed with water to remove chlorine until Cl is reached. - The mass content is <3%, and after being mixed with composite additives, it is granulated to form a core layer; the shell material is prepared by mixing nano iron powder, lime milk and industrial waste residue, and then wrapped around the core layer to obtain a core-shell briquette; S2: Preheat the core-shell briquettes obtained in step S1 using the waste heat of blast furnace flue gas to reduce their moisture content to <1%; S3: The preheated core-shell briquettes from step S2 are fed into a blast furnace for co-processing. The temperature gradient and reducing atmosphere within the blast furnace are used to achieve co-degradation of dioxins through dechlorination and cracking, yielding dioxin degradation products and heavy metal-stabilized molten slag. The upper part of the blast furnace is a low-temperature zone, set at 300-600℃, to complete the initial dechlorination of dioxins. The central part of the blast furnace is a high-temperature zone, set at 1200-1400℃, to ensure complete dioxin cracking. The lower part of the blast furnace is a reduction zone, where enriched CO is introduced to reduce heavy metals to elemental metals and encapsulate them in the slag.

[0027] In the low-temperature zone of the upper part of the blast furnace (300–600℃), the nano-iron powder in the shell reacts synergistically with Ca(OH)2 to catalyze dechlorination and fixes the generated Cl. -This effectively weakens the toxicity of dioxins and inhibits their resynthesis. In the high-temperature zone of 1200–1400℃ in the middle, the Fe / Al2O3 / SiO2 composite system in the core layer accelerates the breaking of C–O bonds, reduces the activation energy of the cracking reaction, and promotes the complete cracking of dioxins into CO2 and H2O under anaerobic conditions. In the reducing lower region, the CO atmosphere can reduce highly volatile heavy metals such as Pb and Cd to metallic elements and enter the molten iron. The rest are encapsulated in the slag by the glass phase formed with SiO2, effectively inhibiting the volatilization and subsequent leaching of heavy metals.

[0028] Compared with existing technologies, the treatment method for degrading dioxins in fly ash from municipal solid waste incineration proposed in this application has the following advantages: The treatment method of this invention, through the synergistic mechanism of "core-shell structure design – blast furnace temperature zone matching – reducing atmosphere control", dynamically couples physical structure regulation with thermo-chemical reaction, realizing synergistic effects of multiple key links: that is, in the three stages of dechlorination-pyrolysis-stabilization, a good coordination is formed between structural design, reaction conditions and equipment environment, ultimately achieving efficient and thorough degradation of dioxins (decomposition rate ≥99.9%), significant reduction in energy consumption (energy saving 30-50%), and significant slow release of heavy metal pollution (leaching rate reduced by more than 90%), effectively solving the core pain points of the background technology, and has comprehensive advantages such as high efficiency, safety, economy and resource utilization.

[0029] In one possible implementation, in step S2, the preheating condition is: the core-shell briquettes are preheated to 150-180°C using a porous ceramic heat exchanger.

[0030] Compared with existing technologies, the above-mentioned technical solution can effectively control the briquette structure from being damaged while maintaining good heat transfer efficiency by utilizing the high porosity ceramic heat exchange structure. The waste heat of blast furnace flue gas is efficiently recovered and conducted to the core-shell briquette through thermal convection and radiation, preheating it to 150-180℃ and rapidly reducing its moisture content to <1%. This significantly reduces the energy consumption demand in the subsequent high-temperature section, reduces the heat input load, and ultimately achieves simultaneous optimization of overall energy consumption reduction, briquette structure stability improvement, and system operating costs.

[0031] In one possible implementation, in step S3, the mass content of oxygen in the blast furnace is less than 1% of the gas in the furnace, and the blast furnace is under positive pressure.

[0032] Compared with existing technologies, the above-mentioned technical solution can significantly suppress the resynthesis reaction of dioxins. Under low-oxygen atmosphere, the de novo synthesis pathway of dioxins in the cooling section is significantly weakened. At the same time, the positive pressure environment of the blast furnace combined with the high-speed gas discharge system can shorten the residence time of dioxins and their precursors in the high-temperature zone, thereby greatly reducing the probability of secondary pollution generation, achieving a higher net dioxin removal rate, and effectively protecting the equipment from corrosion by acidic gases (including HCl).

[0033] In one possible implementation, in step S3, the dioxin residual concentration in the molten slag is ≤0.03 ng TEQ / g.

[0034] Compared with existing technologies, the above-mentioned technical solution can ensure that the dioxin residue in the final treated product is far below the limit of the national standard "HJ 1134-2020" (0.05 ng TEQ / g). The synergistic effect of the Fe / Al2O3 catalytic cracking function in the core layer of the compaction block and the high-temperature melting process ensures that the dioxin is completely cracked into non-toxic small molecules. At the same time, the SiO2 framework forms a dense glass phase at high temperature, which effectively encapsulates and solidifies residual pollutants, preventing them from escaping again. This significantly improves the environmental safety of the treated product and gives it potential resource utilization value. Detailed Implementation

[0035] First, those skilled in the art should understand that these embodiments are merely used to explain the technical principles of the embodiments of this application and are not intended to limit the scope of protection of the embodiments of this application. Those skilled in the art can make adjustments as needed to adapt to specific application scenarios.

[0036] This invention provides a core-shell briquette for degrading dioxins in fly ash from municipal solid waste incineration. The core-shell briquette includes a core layer and a shell layer surrounding the core layer. The raw materials of the core layer include water-washed fly ash and composite additives, wherein the composite additives are a mixture of Fe powder, Al2O3 and SiO2. The raw materials of the shell layer include nano-iron powder, lime slurry and industrial waste residue.

[0037] As a preferred embodiment, the chloride ion content in the fly ash is less than 3% by mass.

[0038] As a preferred embodiment, the mass ratio of fly ash to composite additive is (1-2):1, and the mass ratio of Fe powder, Al2O3 and SiO2 in the composite additive is 1:(1-2):1.

[0039] As a preferred embodiment, the shell layer is wrapped around the surface of the core layer by a disc granulator, and the particle size of the nano-iron powder is 50-100 nm. The industrial waste residue is at least one of steel slag or fly ash. The mass ratio of the nano-iron powder, lime slurry and industrial waste residue is (1-5):(10-20):(50-80).

[0040] As a preferred embodiment, the shell layer has a thickness of 1-2 mm, and the core-shell compact has a compressive strength ≥ 5 MPa.

[0041] This invention also provides a method for treating dioxins in fly ash from municipal solid waste incineration, comprising the following steps: S1. The fly ash is washed with water to remove chlorine until Cl is reached. - The mass content is <3%, and after being mixed with composite additives, it is granulated to form a core layer; the shell material is prepared by mixing nano iron powder, lime milk and industrial waste residue, and then wrapped around the core layer to obtain a core-shell briquette; S2: Preheat the core-shell briquettes obtained in step S1 using the waste heat of blast furnace flue gas to reduce their moisture content to <1%; S3: The preheated core-shell briquettes from step S2 are fed into a blast furnace for co-processing. The temperature gradient and reducing atmosphere within the blast furnace are used to achieve co-degradation of dioxins through dechlorination and cracking, yielding dioxin degradation products and heavy metal-stabilized molten slag. The upper part of the blast furnace is a low-temperature zone, set at 300-600℃, to complete the initial dechlorination of dioxins. The central part of the blast furnace is a high-temperature zone, set at 1200-1400℃, to ensure complete dioxin cracking. The lower part of the blast furnace is a reduction zone, where enriched CO is introduced to reduce heavy metals to elemental metals and encapsulate them in the slag.

[0042] As a preferred embodiment, in step S2, the preheating condition is: the core-shell press block is preheated to 150-180°C using a porous ceramic heat exchanger.

[0043] As a preferred embodiment, in step S3, the mass content of oxygen in the blast furnace is less than 1% of the gas in the furnace, and the blast furnace is under positive pressure.

[0044] As a preferred embodiment, in step S3, the dioxin residual concentration in the molten slag is ≤0.03 ngTEQ / g.

[0045] To address the problems of high energy consumption and severe secondary pollution from heavy metals in existing technologies, such as high dioxin regeneration rate and easy catalyst deactivation in low-temperature pyrolysis methods, and the inability of chemical stabilization methods to completely decompose dioxins and the poor stability of the solidified body, this invention provides a core-shell briquette for degrading dioxins in municipal solid waste incineration fly ash. Through gradient reaction design and multi-component synergistic effects, it achieves efficient dioxin degradation under low energy consumption conditions, while simultaneously inhibiting heavy metals and Cl. - The principle behind its secondary pollution is as follows: The technical principle of core-shell briquettes involves the following: Core layer design: Raw material composition: Water-washed fly ash (Cl - <3%) and composite additives (Fe powder, Al2O3, SiO2 mixed in a mass ratio of 1:(1-2):1) are mixed in a ratio of 1-2:1.

[0046] Mechanism of action: Fe / Al2O3 catalytic system: In the briquettes of this invention, Fe powder and Al2O3 form redox active sites, reducing the activation energy of dioxin CO bond breaking (from 150 kJ / mol to 80-100 kJ / mol), and promoting the destruction of the benzene ring structure (requiring the removal of ≥5 Cl atoms); SiO2 framework support: At high temperature, SiO2 and fly ash melt to form a glassy phase, which encapsulates heavy metals (Pb, Cd, Zn) in the silicon-oxygen network, reducing the leaching concentration to 10-25% of the limit in GB 16889-2008.

[0047] Shell design: Raw material composition: nano iron powder (50-100 nm), lime milk (Ca(OH)2) and industrial waste (steel slag / fly ash).

[0048] Mechanism of action: Nano-iron powder catalyzes chlorine fixation: The nano-iron powder possesses a high specific surface area and surface catalytic activity, and chlorine is fixed by surface adsorption. - It is converted to FeCl3 (boiling point 315℃), reducing HCl gas generation (emissions reduced by 30%), while simultaneously inhibiting dioxin "de novo synthesis" in the low-temperature range (200-450℃); lime slurry stabilization: Ca(OH)2 and residual Cl... - The reaction produces high-melting-point CaCl2 (melting point 772℃), preventing corrosion of high-temperature equipment; and further, the melting point and porosity of the briquettes are adjusted by steel slag / fly ash, reducing additive costs by 30-40%.

[0049] After heat treatment experiments at 600℃, the prepared core-shell briquettes reduced the dioxin content in flue gas by 15-40 times. After co-treatment in a simulated blast furnace, the residual dioxin concentration in the briquettes was controlled at ≤0.03 ng TEQ / g, which meets and exceeds the national hazardous waste treatment limit of HJ 1134-2020.

[0050] Compared with the prior art, the present invention solves the following problems: Solving the problem of incomplete dioxin degradation: Gradient dechlorination-pyrolysis: The shell preferentially adsorbs Cl in the low-temperature region (300-600℃). - It also blocks the resynthesis pathway, and the core layer completely decomposes dioxins in the high-temperature zone (1200-1400℃), with a residual concentration ≤0.03ng TEQ / g (HJ 1134-2020 limit 0.05 ng TEQ / g). Compared with the high-temperature melting method (residual 0.1-0.5 ng TEQ / g) and the low-temperature pyrolysis method (regeneration concentration reaches 10-20%), the degradation rate of the treatment method of this invention is increased to ≥99.9%.

[0051] Secondly, the processing method of this invention breaks through the bottlenecks of energy consumption and secondary pollution: the method of this invention uses the waste heat of blast furnace flue gas (150-180℃) to preheat the briquettes, which reduces the overall energy consumption by 40% compared with the traditional melting method. In addition, the SiO2 glass phase solidifies heavy metals, and the shell layer solidifies chlorine to reduce the tail gas treatment load, the heavy metal leaching rate decreases by 90%, and the HCl emission decreases by 30%. In this invention, steel slag / fly ash is used as the shell layer raw material to achieve "waste treatment with waste". The compressive strength of the briquettes is ≥5 MPa, which can be directly used as building material aggregate or metal recycling raw material. Furthermore, the existing blast furnace facilities are used to process fly ash on a large scale (thousands of tons per day), avoiding the investment cost of building a new independent processing unit.

[0052] In summary, the core-shell briquette of this invention systematically solves the industry problems of incomplete dioxin degradation, high energy consumption, and significant secondary pollution risk through a synergistic mechanism of "core-layer catalytic cracking - shell-layer adsorption and solidification of chlorine." Its core innovations lie in the material ratio (Fe / Al2O3 / SiO2), structural design (core-shell gradient reaction), and process coupling (blast furnace synergy), forming multiple technological barriers and demonstrating significant economic and environmental benefits.

[0053] The blast furnace main reactor area zone treatment strategy in this invention is as follows: The blast furnace has a natural temperature gradient (200-1600℃) from top to bottom, which matches the staged reaction requirements of the core-shell briquetting: Upper part (300-600℃): Suitable for completing the initial destruction of dioxins in the shell and Cl. - Stabilization; Central section (1200-1400℃): Provides a high-temperature pyrolysis and melting environment for the core layer fly ash, achieving complete dioxin pyrolysis; Lower section (reduction zone): The CO-enriched atmosphere reduces heavy metal ions (such as Ni and Cr) to their metallic state, which then enters the metallurgical system with the molten iron. The remaining portion is encapsulated in the slag by a SiO2-based glassy body, reducing the risk of heavy metal leaching by up to 90%. The oxygen content in the blast furnace atmosphere is controlled to be below 1% throughout the process, significantly inhibiting the de novo synthesis of dioxins in the cooling section. The positive pressure environment of the blast furnace, combined with the high-speed exhaust system of the top gas, can control the residence time of acidic gases such as HCl to within 2-3 seconds, further reducing the risk of equipment corrosion and enhancing the efficiency of gaseous pollutant collection. Under the same temperature conditions, the dioxin decomposition rate in the low-oxygen atmosphere is 10-25% higher than that in a conventional air environment. The calorific value of the blast furnace gas can also enable energy recovery and reuse by the incineration system.

[0054] The following embodiments, incorporating specific data, further elaborate on the scope of the technical solutions of the present invention: Example

[0055] Example 1 provides a core-shell briquette for degrading dioxins in municipal solid waste incineration fly ash and a treatment method thereof. The preparation method of the core-shell briquette and the treatment method include: S1: Core-shell briquetting preparation: Core material processing: Take 100 kg of fly ash from municipal solid waste incineration, and wash it with water to remove chlorine until Cl is obtained. - The mass content is 2.5% (detection method: ion chromatography, GB / T 15453-2008); the dechlorinated fly ash composite additive is mixed at a mass ratio of 1.5:1, wherein the composite additive is composed of Fe powder, Al2O3 and SiO2 at a mass ratio of 1:1.5:1.

[0056] The mixture is uniformly stirred for 20 minutes by a twin-shaft mixer (80 rpm), and then granulated by a disc granulator (2 m in diameter, 45° inclination) to form core layer particles (5-13 mm in diameter).

[0057] Shell coating process: Shell material ratio: Nano iron powder (particle size 75 nm), lime milk (Ca(OH)2 slurry dry basis content 88%), and steel slag are mixed at a dry basis mass ratio of 3:15:65; the shell material and core particles are fed into a disc granulator (speed 30 rpm, water spray rate 7 L / min), the shell thickness is 1.5 mm, and after the briquettes are naturally dried for 24 hours, the compressive strength is tested to be 8 MPa, thus obtaining core-shell briquettes.

[0058] Preheating treatment: Using a porous ceramic heat exchanger with a porosity of 75%, the briquettes were preheated with waste heat from blast furnace flue gas (165℃), reducing the moisture content of the briquettes to 0.8% (testing method: oven drying method, constant weight at 105℃).

[0059] Blast furnace co-processing: Low-temperature dechlorination zone (450℃): The briquettes remain in the upper part of the blast furnace for 20 minutes. The nano-iron powder in the shell catalyzes the dioxin dechlorination reaction, releasing Cl... - It reacts with lime milk (Ca(OH)2) to form stable CaCl2; the HCl content in the flue gas was detected to be 50 mg / Nm³. 3 (The HCl content of the untreated fly ash is 200 mg / Nm³) 3 Compared with untreated fly ash, the concentration of dioxins was reduced by 75%, and the dioxin dechlorination rate was 97% (HPLC detection, JIS K0312 standard).

[0060] High-temperature pyrolysis zone (1300℃): The dechlorinated briquettes enter the middle of the blast furnace and remain for 10 minutes. The Fe / Al2O3 composite system in the core layer reduces the activation energy of dioxin CO bond breaking to 85 kJ / mol, promoting the complete pyrolysis of dioxins into CO2 and H2O (GC-MS detection, pyrolysis rate 99.95%). SiO2 melts with fly ash to form a glassy phase, and the slag viscosity is 180 Pa·s (rotational viscometer detection, ASTM D2196).

[0061] Reduction stabilization zone (CO concentration 25%): The molten material enters the lower part of the blast furnace and, under a CO-rich reducing atmosphere, heavy metals Pb and Cd are reduced to elemental metals with recovery rates of 88% for Pb and 92% for Cd, and are incorporated into the molten iron; unreduced ZnO is encapsulated by a glassy phase, with a leaching concentration of Zn 1.8 mg / L (national standard limit 5.0 mg / L).

[0062] Processing effect: The residual concentration of dioxins in the slag was 0.025 ng TEQ / g (GC-MS detection).

[0063] Heavy metal leaching concentrations: Pb 0.12 mg / L (national standard limit 0.5 mg / L), Cd 0.03 mg / L (national standard limit 0.15 mg / L).

[0064] The overall energy consumption is 1.0 kW·h / kg, which is 45% lower than that of the traditional melting method. Example

[0065] Example 2 provides a core-shell briquette for degrading dioxins in municipal solid waste incineration fly ash and a treatment method thereof. The preparation method of the core-shell briquette and the treatment method include: S1: Core-shell briquetting preparation: Core material processing: Take 100 kg of fly ash from municipal solid waste incineration, and treat it by washing and dechlorination to obtain Cl. - Content 2.0% (Detection method: ion chromatography, GB / T 15453-2008); the dechlorinated fly ash and the composite additive are mixed at a mass ratio of 1:1, wherein the composite additive is composed of Fe powder, Al2O3 and SiO2 at a mass ratio of 1:1:1.

[0066] The mixture is uniformly stirred for 30 minutes by a twin-shaft mixer (60 rpm), and then granulated by a disc granulator (2 m in diameter, 45° inclination) to form core layer particles (8-12 mm in diameter).

[0067] Shell coating process: Shell material ratio: Nano iron powder (particle size 50 nm), lime milk (Ca(OH)2 dry basis content 85%), and fly ash (particle size ≤100 μm) are mixed at a dry basis mass ratio of 5:10:50; the shell material and core particles are fed into a disc granulator (speed 25 rpm, water spray rate 8 L / min) to form a uniform shell layer with a thickness of 1 mm on the core surface; after the briquettes are naturally dried for 24 hours, the compressive strength is tested to be 5.2 MPa (GB / T 17671-1999), and the core-shell briquettes are obtained.

[0068] S2: Preheating treatment: The core-shell briquettes were preheated to 150°C using a porous ceramic heat exchanger (70% porosity) for 45 minutes until the moisture content of the briquettes dropped to 0.5% (testing method: oven drying method, constant weight at 105°C).

[0069] The flue gas flow rate during the preheating process is 800 m³ / h, and the heat recovery efficiency is 82%.

[0070] S3: Blast Furnace Co-processing: Low-temperature dechlorination zone (300℃): The briquettes remain in the upper part of the blast furnace for 30 minutes. The shell-layer nano-iron powder catalyzes the dioxin dechlorination reaction, and Cl⁻ reacts with Ca(OH)₂ to generate CaCl₂ (detected concentration: HCl content in flue gas 35 mg / Nm³). 3 (70% reduction compared to untreated fly ash), and a dioxin dechlorination rate of 95% (HPLC detection).

[0071] High-temperature pyrolysis zone (1200℃): The briquettes enter the middle of the blast furnace and stay for 15 minutes. The Fe / Al2O3 in the core layer catalyzes the breakage of CO bonds, and dioxins are pyrolyzed into CO2 and H2O (GC-MS detection, pyrolysis rate 99.8%). SiO2 melts with fly ash to form a glassy phase, and the slag viscosity is 150 Pa·s (measured by rotational viscometer, ASTM D2196).

[0072] Reduction Stable Zone (CO Concentration 20%): The molten material enters the lower part of the blast furnace. Under the CO reducing atmosphere, heavy metals Pb and Cd are reduced to elemental metals (recovery rate: Pb 88%, Cd 92%), and unreduced ZnO is encapsulated by the glassy phase (leaching concentration: Zn 1.8 mg / L, national standard limit 5.0 mg / L).

[0073] Processing effect: The residual concentration of dioxins in the slag was 0.015 ng TEQ / g (GC-MS detection).

[0074] Heavy metal leaching concentrations: Pb 0.10 mg / L (national standard limit 0.5 mg / L), Cd 0.02 mg / L (national standard limit 0.15 mg / L).

[0075] The overall energy consumption is 0.9 kW·h / kg, which is 50% lower than that of the traditional melting method. Example

[0076] Example 3 provides a core-shell briquette for degrading dioxins in municipal solid waste incineration fly ash and a treatment method thereof. The preparation method of the core-shell briquette and the treatment method include: S1: Core-shell briquette preparation: Core layer raw material processing: Take 200 kg of fly ash from municipal solid waste incineration, wash with water to remove chlorine until Cl is reached. - Mass content 2.9% (Detection method: ion chromatography, GB / T 15453-2008); the dechlorinated fly ash and composite additive are mixed at a mass ratio of 2:1, and the mass ratio of Fe powder, Al2O3 and SiO2 in the composite additive is 1:2:1; The mixture is processed by a high-speed shear mixer (1200 rpm) for 20 minutes, and then granulated by a disc granulator (2 m in diameter, 45° inclination) to form core layer particles (10-15 mm in diameter).

[0077] Shell coating process: Shell material ratio: Nano iron powder (particle size 100 nm), lime milk (Ca(OH)2 dry basis content 90%), and steel slag (particle size ≤150 μm) are mixed at a dry basis mass ratio of 1:20:80 (i.e., 25 kg of nano iron powder, 75 kg of lime milk, and 25 kg of steel slag); the shell material is coated onto the core layer using a fluidized bed coating machine (inlet air temperature 80℃), with a shell thickness of 2 mm and a briquette compressive strength of 12.5 MPa (GB / T 17671-1999).

[0078] S2: Preheating treatment: The porous ceramic heat exchanger (porosity 80%, silicon carbide material) preheats the core-shell briquettes to 180°C for 30 minutes, with a briquette moisture content of 0.9% (testing method: oven drying method, constant weight at 105°C); the waste heat utilization rate of flue gas is 88%, and the pressure drop of the heat exchanger is 120 Pa.

[0079] S3: Blast Furnace Co-processing: Low-temperature dechlorination zone (600℃): The briquettes remain in the upper part of the blast furnace for 10 minutes, where nano-iron powder catalyzes the dechlorination reaction, resulting in an HCl concentration of 42 mg / Nm³ in the flue gas. 3 (79% reduction compared to traditional pyrolysis method), dioxin dechlorination rate 98.5% (HPLC detection).

[0080] High-temperature pyrolysis zone (1400℃): The core layer stays in the high-temperature zone for 5 minutes, and the dioxin is completely pyrolyzed into CO2 and H2O (pyrolysis rate 99.99%). The slag glass phase forms at a temperature of 1250℃.

[0081] Reduction stability zone (CO concentration 30%): Heavy metals Cr and Ni are reduced to elemental metals by CO (Cr recovery rate 85%, Ni 90%), and unreduced CuO is encapsulated in the glass phase (leaching concentration: Cu: 0.3 mg / L, national standard limit 1.0 mg / L).

[0082] Processing effect: The residual concentration of dioxins in the slag was 0.015 ng TEQ / g (GC-MS detection).

[0083] Heavy metal leaching concentrations: Cr 0.08 mg / L (national standard limit 0.3 mg / L), Ni 0.12 mg / L (national standard limit 0.50 mg / L).

[0084] The overall energy consumption is 1.1 kW·h / kg, which is 40% lower than that of the traditional melting method.

[0085] The above Examples 1-3 further demonstrate that the core-shell briquetting and treatment method of the present invention can achieve efficient degradation of dioxins in municipal solid waste incineration fly ash (residual concentration ≤0.03 ng TEQ / g, far below the HJ 1134-2020 standard), while significantly reducing energy consumption (40-50% energy saving compared to traditional melting methods) and the risk of heavy metal pollution (leaching concentration more than 50% lower than the national standard limit). The core principles of the present invention include: Core-shell gradient reaction design: The core layer (Fe / Al2O3 / SiO2) catalyzes the decomposition of dioxins into CO2 / H2O in the high-temperature region (1200-1400℃), while SiO2 melts to form a glassy phase encapsulating heavy metals; the shell layer (nano-iron powder / lime slurry) adsorbs Cl in the low-temperature region (300-600℃). -It is then converted into stable CaCl2, blocking the formation of HCl and the resynthesis of dioxins; Blast furnace co-processing: Utilizing the temperature gradient and reducing atmosphere of the blast furnace (O2<1%, CO concentration 20-30%), dechlorination, cracking and heavy metal reduction are completed in stages. The slag compressive strength is ≥5 MPa and can be directly used as building material aggregate. Energy cycle optimization: Waste heat from blast furnace flue gas (150-180℃) is used to preheat and press the briquettes, which, combined with gas recycling, reduces overall energy consumption and achieves "waste treatment with waste".

[0086] This invention overcomes three major challenges in existing technologies: incomplete dioxin degradation (high residue in high-temperature methods and high regeneration rate in low-temperature methods), contradiction between energy consumption and pollution (heavy metal volatilization in melting methods and inability to recover resources in chemical methods), and fragmented processes (high cost of independent processing modules). It provides an efficient, low-consumption, and environmentally friendly solution for the harmless and resource-based treatment of fly ash.

[0087] In the description of this application, the references to terms such as "an embodiment," "some embodiments," "in this embodiment," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0088] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for treating dioxins in fly ash from municipal solid waste incineration, characterized in that, Includes the following steps: S1. The fly ash is washed with water to remove chlorine until Cl... - The mass content is <3%, and after being mixed with composite additives, it is granulated to form a core layer; the shell material is prepared by mixing nano iron powder, lime milk and industrial waste residue, and then wrapped around the core layer to obtain a core-shell briquette; The core-shell briquette includes a core layer and a shell layer that surrounds the core layer; the raw materials of the core layer include water-washed fly ash and composite additives, and the composite additives are a mixture of Fe powder, Al2O3 and SiO2; the raw materials of the shell layer include nano iron powder, lime milk and industrial waste residue. S2: Preheat the core-shell briquettes obtained in step S1 using the waste heat of blast furnace flue gas to reduce their moisture content to <1%; S3: The preheated core-shell briquettes from step S2 are fed into a blast furnace for co-processing. The temperature gradient and reducing atmosphere within the blast furnace are used to achieve co-degradation of dioxins through dechlorination and cracking, yielding dioxin degradation products and heavy metal-stabilized molten slag. The upper part of the blast furnace is a low-temperature zone, set at 300-600℃, to complete the initial dechlorination of dioxins. The central part of the blast furnace is a high-temperature zone, set at 1200-1400℃, to ensure complete dioxin cracking. The lower part of the blast furnace is a reduction zone, where enriched CO is set up to reduce heavy metals to elemental metals and encapsulate them in the slag.

2. The treatment method for degrading dioxins in fly ash from municipal solid waste incineration according to claim 1, characterized in that, The mass ratio of fly ash to composite additive is (1-2):1, and the mass ratio of Fe powder, Al2O3 and SiO2 in the composite additive is 1:(1-2):

1.

3. The treatment method for degrading dioxins in fly ash from municipal solid waste incineration according to claim 1, characterized in that, The shell layer is wrapped around the surface of the core layer using a disc granulator, and the particle size of the nano-iron powder is 50-100 nm. The industrial waste residue is at least one of steel slag or fly ash. The dry basis content of Ca(OH)2 in the lime slurry to the dry basis mass ratio of the nano-iron powder, lime slurry, and industrial waste residue is any one of the following: The dry basis content of Ca(OH)2 in the lime milk is 88%, and the dry basis mass ratio of the nano iron powder, lime milk and industrial waste residue is 3:15:

65. The dry basis content of Ca(OH)2 in the lime slurry is 85%, and the dry basis mass ratio of the nano-iron powder, lime slurry, and industrial waste residue is 5:10:50; or The dry basis content of Ca(OH)2 in the lime slurry is 90%, and the dry basis mass ratio of the nano iron powder, lime slurry and industrial waste residue is 1:20:

80.

4. The treatment method for degrading dioxins in fly ash from municipal solid waste incineration according to claim 1, characterized in that, The shell layer has a thickness of 1-2 mm, and the core-shell block has a compressive strength ≥ 5 MPa.

5. The treatment method for degrading dioxins in fly ash from municipal solid waste incineration according to claim 1, characterized in that, In step S2, the preheating condition is: the core-shell press block is preheated to 150-180°C using a porous ceramic heat exchanger.

6. The treatment method for degrading dioxins in fly ash from municipal solid waste incineration according to claim 1, characterized in that, In step S3, the mass content of oxygen in the blast furnace is less than 1% of the gas in the furnace, and the blast furnace is under positive pressure.

7. The treatment method for degrading dioxins in fly ash from municipal solid waste incineration according to claim 1, characterized in that, In step S3, the residual concentration of dioxins in the molten slag is ≤0.03 ng TEQ / g.