Regulation and directional conversion treatment method for components of waste incineration fly ash

Abstract

The invention provides a waste incineration fly ash component regulation and directional conversion treatment method, and belongs to the technical field of solid waste treatment. The method comprises the steps that S1, the waste incineration fly ash is subjected to primary washing to remove most of soluble chlorine salt and heavy metal, solid obtained after solid-liquid separation is subjected to forced leaching with recycled water or clear water, and fly ash obtained after washing and washing waste liquid are obtained; s2, preparing a core-shell structure Fe2O3 / Fe / C composite catalyst, mixing the core-shell structure Fe2O3 / Fe / C composite catalyst with the washed fly ash, granulating, performing catalytic pyrolysis in an inert or micro-aerobic environment, and cracking dioxin organic matters; s3, the washing waste liquid is pretreated and then subjected to segmented evaporation-selective crystallization, and inorganic salt components are recycled according to quality; and flue gas is introduced into the incinerator for synergistic heat treatment. According to the method, inorganic salt and soluble heavy metal in the fly ash can be removed, directional catalytic cracking of dioxin is promoted, the inorganic salt is recycled, and reduction, harmlessness and recycling of the fly ash are achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of solid waste treatment, and in particular to a garbage incineration fly ash component regulation and directional conversion treatment method. BACKGROUND

[0002] With the acceleration of urbanization, the amount of municipal solid waste increases. Garbage incineration for power generation has become the main garbage disposal method in China due to its large processing capacity, significant volume and mass reduction effect, and possible source recycling. However, hazardous waste fly ash is produced during the garbage incineration process, mainly from the capture of the flue gas purification system and the fine ash settled at the bottom of the flue and chimney, containing inorganic salts and heavy metals such as Pb, Cd, Zn, Cu, and excess reagents such as lime added during flue gas purification. According to the current fly ash production rate of 4% of the grate furnace incineration, the annual fly ash production in China is about 10 million tons, which has become an important factor restricting the development of the incineration industry.

[0003] Fly ash is listed as HW18 hazardous waste in the National Hazardous Waste List (2025 edition) because it contains dioxin persistent organic pollutants, heavy metals such as Zn, Pb, Hg, and high content of chlorides, and must be managed and disposed of as hazardous waste. The concentration of some heavy metals in fly ash is tens to hundreds of times higher than that in soil, with lead content of 2000-8000 mg / kg, cadmium content of 50-500 mg / kg, and mercury content of 1-50 mg / kg. The concentration of dioxin in fly ash is generally 1-1000 ng TEQ / kg, and some samples even exceed 10000 ng TEQ / kg. If these harmful substances are not properly disposed of, they will cause serious harm to the environment and human health. The chlorine content in fly ash is usually 8% to 25%, and individual samples can reach more than 30%, which will affect the leaching of heavy metals and the removal of dioxin, hindering the subsequent resource utilization of the product.

[0004] Current fly ash treatment technologies at home and abroad mainly include cement solidification or chemical stabilization followed by landfill, high-temperature melting, and wet extraction. The cement solidification technology mixes fly ash with cement and water in a certain proportion, and uses the cementation characteristics of cement to seal harmful substances such as heavy metals in the cement structure. This technology is simple to operate and has low cost, but has problems such as increased volume of solidified body, chlorine salts in fly ash affecting the cement solidification effect, and long-term stability to be verified. At the same time, this technology is essentially still a pretreatment before landfill, and does not achieve the reduction and resource utilization of fly ash. The chemical stabilization technology is to add chemical reagents (such as chelating agents, sodium sulfide, phosphates, etc.) to fly ash to form higher stability compounds and reduce the leaching toxicity of heavy metals. This technology has good stabilization effect on heavy metals, but the cost of reagents is high, and the treated solid still needs to be landfilled, which does not solve the fundamental problem.

[0005] Landfill disposal is the most mainstream fly ash disposal technology at home and abroad at present. Fly ash usually needs to be pretreated (such as cement solidification, chemical stabilization, etc.) to meet the landfill site entry requirements, and then sent to a special landfill site for safe landfill or zoned landfill in a sanitary landfill site. This technology has the advantages of mature equipment, large processing capacity, relatively low investment, etc., but has the problems of occupying a large amount of land resources, long-term environmental risk, and rising processing cost year by year.

[0006] High-temperature melting technology is to heat fly ash to 1400-1500℃ to make it melt, and to destroy organic pollutants such as dioxins at high temperature, while sealing heavy metals in glassy slag. This technology has complete treatment effect, but has extremely high energy consumption, huge equipment investment, and high operating cost.

[0007] Wet extraction technology is to use acidic or alkaline solution to selectively leach heavy metals in fly ash to realize the separation and recovery of heavy metals. This technology can realize the resource utilization of heavy metals, but the process is complex, a large amount of wastewater containing heavy metals is generated, and the risk of secondary pollution is high.

[0008] In recent years, with the improvement of environmental protection requirements and the popularization of circular economy concept, fly ash treatment technology is developing towards resource utilization. Water washing desalination technology takes advantage of the fact that chloride salts in fly ash are easily dissolved in water, and separates chloride salts from fly ash by water washing method, which not only reduces the danger of fly ash, but also recovers and produces industrial salt, and has good application prospect. Studies have shown that by optimizing the water washing process parameters, the dechlorination effect can be effectively improved, creating good conditions for subsequent treatment.

[0009] Catalytic pyrolysis technology promotes the decomposition of organic pollutants and the stabilization of heavy metals by using catalysts at relatively low temperatures, and has the advantages of low energy consumption and good treatment effect. Studies have shown that under the action of appropriate catalysts, the efficient decomposition of dioxins and the stabilization of heavy metals in fly ash can be realized at a temperature of 300 to 450℃. However, catalytic pyrolysis technology usually needs to be carried out in an inert atmosphere such as nitrogen or argon, and the control of oxygen content is extremely high, usually below 0.1-0.3%. Although it is easy to control the oxygen-free environment in the laboratory, it is very difficult in actual engineering, and has high cost and complicated operation, which is not conducive to engineering application. Therefore, it is urgent to develop a comprehensive treatment method integrating water washing desalination, catalytic pyrolysis and inorganic salt recovery technology to realize the efficient and harmless treatment and resource utilization of fly ash from waste incineration. SUMMARY

[0010] In view of the above problems existing in the prior art, the present application provides a waste incineration fly ash component regulation and directional conversion treatment method.The present application strengthens forced washing through first-stage water washing, prepares oxygen-resistant Fe2O3 / Fe / C catalyst, integrates water washing desalination, micro-oxygen environment catalytic pyrolysis and three major technical units of segmented crystallization-quality inorganic salt recovery, removes inorganic salts and easily soluble heavy metals in fly ash, promotes directional catalytic cracking of dioxins, and realizes resource utilization of inorganic salts, achieving fly ash reduction, harmlessness and resource utilization.

[0011] The technical scheme of the present application is as follows: A waste incineration fly ash component regulation and directional conversion treatment method, the method comprising the following steps: S1, the waste incineration fly ash is first subjected to first-stage water washing to remove soluble chlorides and heavy metals, and the obtained solid after solid-liquid separation is subjected to forced washing using regenerated water or clean water, to obtain water-washed fly ash and water washing waste liquid, and the residual soluble chlorides and heavy metals are deeply separated, and the chlorine source for re-synthesis of dioxins is removed; S2, a core-shell structure Fe2O3 / Fe / C composite catalyst is prepared, mixed with the water-washed fly ash to form a granule, and then subjected to catalytic pyrolysis in an inert or micro-oxygen environment, to crack dioxin organic matter; S3, the water washing waste liquid is subjected to pretreatment and then subjected to segmented evaporation-selective crystallization, to recover inorganic salt components in a quality-specific manner; and flue gas is introduced into a incinerator for cooperative heat treatment.

[0012] Preferably, the specific steps of the fly ash subjected to first-stage water washing and forced washing in step S1 include: A1, the waste incineration fly ash is mixed with condensate water obtained from quality-specific recovery of inorganic salts in step S3 and supplemented clean water according to a liquid-solid ratio of 2-5 L / kg, then stirred at 200-500 r / min at room temperature for 15-60 min, and then subjected to solid-liquid separation, to obtain a solid and a first batch of water washing waste liquid; A2, the obtained solid is subjected to uniform washing using clean water with a liquid-solid ratio of 0.5-1 L / kg, and then subjected to solid-liquid separation again, to obtain water-washed fly ash and a second batch of water washing waste liquid; the soluble chloride content in the water-washed fly ash is less than 1%, and the chlorine source for re-synthesis of dioxins is reduced.

[0013] Further, the amount of clean water used in step A1 is determined according to the liquid-solid ratio of 2-5 L / kg that is not reached after the use of condensate water.

[0014] Preferably, the preparation method of the Fe2O3 / Fe / C composite catalyst in step S2 includes the following steps: N1, using biochar as a carrier, a suspension is prepared by ultrasonic dispersion in deionized water; then iron salt solution is added dropwise under stirring; N2, then slowly drop sodium hydroxide or ammonia solution, control the drop speed is 1~3 ml / min, maintain the pH of the reaction system is 8~10, reaction time 2~4 hours; N3, after the reaction, stand for 6~12 hours, then centrifugal separation, wash with deionized water until the pH of the washing liquid is close to neutral; N4, the resulting product is dried at 80~120℃ for 12~24 hours, Fe2O3 is loaded on the biochar carrier by the co-precipitation method in the above steps, and the Fe loading is 10~20 wt%; N5, the dried product is selectively reduced under H2 / N2 mixed atmosphere, heated to 280~320℃ for 2~3 hours, forming a core-shell structure of Fe2O3 / Fe / C composite catalyst; the particle size of the obtained Fe2O3 / Fe / C composite catalyst is 200~500μm, and the specific surface area is not less than 100 m 2 / g.

[0015] More preferably, the biochar in step N1 is ground to a particle size of less than 150 μm; the iron salt includes ferric chloride, ferric nitrate or ferric sulfate; the stirring speed is 300~500 rpm, and the stirring temperature is 60~80℃.

[0016] More preferably, in step N2, the mass ratio of C, Fe, OH in biochar, iron salt, sodium hydroxide or ammonia water is 1:0.8~1.5:1.2~2.0; in step N3, the centrifugal separation speed is 3000~5000 rpm, and the time is 5~10 min.

[0017] Preferably, after the water washing in step S2, the specific steps of the catalytic pyrolysis after the fly ash and the catalyst are mixed and granulated include: B1, after the water washing, the fly ash and the catalyst are mixed uniformly according to the mass ratio of 5:1~15:1, and are shaped into spherical or cylindrical particles with a diameter of 1~3 centimeters; B2, catalytic pyrolysis under a micro-oxygen atmosphere at a temperature of 250~350℃ for 30~120 minutes, and the flue gas generated by pyrolysis is introduced into an incinerator for heat treatment.

[0018] More preferably, in step B2, the micro-oxygen atmosphere is an atmosphere mainly composed of nitrogen or argon, and the oxygen concentration is ≤1%.

[0019] More preferably, in step B2, Fe2O3 and Fe have a synergistic catalytic effect in the micro-oxygen atmosphere; Fe2O3 provides active oxygen atoms, promoting the oxidative cleavage of dioxin molecules; Fe provides electrons and activates the C-Cl bond, promoting the dechlorination reaction of dioxin; the carrier C provides π electrons, enhancing the adsorption and activation of dioxin molecules.

[0020] Preferably, the specific steps for recovering inorganic salt components from the pretreated water washing waste liquid in step S3 include: C1. Add sodium sulfide or sodium carbonate to the washing waste liquid to a concentration of 0.3–1.2 g / L to precipitate heavy metals and calcium ions; then add Fenton's reagent and adjust the pH to 2–4. H₂O₂ reacts with Fe. 2+ The molar ratio is 2:1 to 4:1 to oxidize organic matter; then adjust the pH to 7.0 to 9.0; then add or not add 20 to 60 mg / L polyaluminum chloride and 1 to 8 mg / L polyacrylamide according to the type of impurities in the washing wastewater to flocculate and precipitate, and remove calcium ions and heavy metals. C2. The wastewater after impurity removal is treated by ultrafiltration and / or nanofiltration membranes to remove suspended solids and organic matter, and to separate monovalent and polyvalent ions according to the inorganic salt component recovery requirements. C3. The treated wastewater is recycled in stages at different temperatures through mechanical steam recompression or multi-effect evaporation crystallizer to recover sodium sulfate, potassium chloride and sodium chloride. The condensate is recycled for the primary washing and rinsing steps of fly ash.

[0021] Furthermore, the soluble chlorine content of the fly ash after final treatment is <1%, and the Pb content in the leachate obtained according to HJ 557-2010 "Solid Waste Leaching Toxicity Level Oscillation Method" is <1.0 mg / L, and the dioxin toxicity equivalent is <20 ng TEQ / kg.

[0022] The beneficial technical effects of this invention are as follows: 1. This invention utilizes primary water washing of fly ash and enhanced rinsing to effectively remove chloride salts and easily soluble heavy metals from fly ash. By removing a large amount of inorganic chlorine from fly ash, the resynthesis of dioxin catalytic cracking process is inhibited, promoting the directional decomposition and transformation of dioxins and reducing the technical difficulty of reaction control.

[0023] 2. This invention prepares a novel oxygen-resistant catalyst that can tolerate oxygen concentrations of <1%, improving the system's oxygen tolerance, reducing equipment investment and operating costs, and promoting the directional conversion of dioxins. The catalytic cracking of fly ash and catalyst after mixing and granulation facilitates full contact between the two and reduces dust or agglomeration, making the system easier to control.

[0024] 3. This invention recovers inorganic salts such as sodium sulfate, potassium chloride, and sodium chloride in stages, which can obtain inorganic salts with high purity, making them easy to sell and profit from. It has the advantages of high processing efficiency, less secondary pollution, and simple operation, providing a new technical approach for the safe disposal of fly ash from municipal solid waste incineration. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the method for regulating and directionally converting fly ash components from waste incineration according to the present invention. Detailed Implementation

[0026] The application will be described in detail below with reference to the drawings and embodiments. Obviously, the described embodiments are only a part of the embodiments of the application, but not all the embodiments. Based on the embodiments in the application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the application.

[0027] Embodiment 1 The embodiment provides a preparation method of a Fe2O3 / Fe / C composite catalyst, and the specific steps are as follows: 10 g of biochar is ground to a particle size of less than 150 μm, ultrasonically dispersed in 100 ml of deionized water for 30 minutes to prepare a suspension. Under the conditions of 400 rpm stirring and 65℃, 180 ml of a 1 mol / L iron chloride solution is added dropwise; then 95 ml of a 4 mol / L sodium hydroxide solution is slowly added dropwise, the dropwise adding speed is controlled to be 2 ml / min, the pH of the reaction system is maintained to be 9, and the reaction time is 3 hours. After the reaction is completed, the reaction system is aged at room temperature for 9 hours, then centrifugal separation is performed at a speed of 3000 rpm for 10 minutes. Washing is performed with deionized water until the pH of the washing liquid is close to neutral, and then drying is performed in a 105℃ oven for 18 hours. Under a mixed gas atmosphere of H2:N2=1:1, selective reduction is performed at 300℃ for 2.5 hours to form a Fe2O3 / Fe / C composite catalyst with a core-shell structure.

[0028] It is found that the particle size of the obtained catalyst is mainly distributed in 200-400 μm, and the specific surface area is 148.6 m 2 / g. TEM detection proves that the catalyst is a core-shell structure.

[0029] Embodiment 2 A waste incineration power plant daily handles 2000 tons of waste, adopts a grate furnace incineration process, and the fly ash production is about 80 tons per day, and the annual output is about 25,000 tons. The main components of the fly ash are as follows: chlorine content 12.5%, calcium content 28.3%, potassium content 3.1%, sodium content 5.8%, silicon content 15.8%, aluminum content 2.2%, and iron content 2.1%; heavy metal content: Pb 4500 mg / kg, Cd 150 mg / kg, and Zn 8500 mg / kg. The dioxin toxicity equivalent is 80 ng TEQ / kg.

[0030] The embodiment provides a waste incineration fly ash component regulation and directional conversion treatment method, and a process flow thereof is shown in Figure 1 The embodiment provides a waste incineration fly ash component regulation and directional conversion treatment method, and a process flow thereof is shown in S1, primary water washing and forced spray washing, the steps are as follows: A1, 1 kg of fly ash was mixed with 3 L of condensed water (liquid-solid ratio 3 L / kg, and if the condensed water was insufficient, water was added), stirred at room temperature at a speed of 350 r / min for 30 min, and then solid-liquid separation was performed by centrifugation to obtain solid residues and a first batch of water washing waste liquid; A2, the solid residues were washed with 0.5 L of water (liquid-solid ratio 0.5 L / kg); after solid-liquid separation, water-washed fly ash and a second batch of water washing waste liquid were obtained; the water-washed fly ash was about 750 g of dry solid; S2, after mixing with the catalyst and granulation, catalytic pyrolysis was performed, and the steps were as follows: B1, the water-washed fly ash dry solid was uniformly mixed with 75 g of Fe2O3 / Fe / C composite catalyst prepared in Example 1, and was pressed into a spherical shape with a diameter of 1.5 cm; B2, under a nitrogen atmosphere (oxygen content about 0.8%), the temperature was raised to 300℃, and pyrolysis was performed at constant temperature for 60 min to obtain solid residues, and the generated flue gas was introduced into a incinerator for co-treatment.

[0031] The dioxin toxicity equivalent in the obtained solid residues was less than 10 ng TEQ / kg. The microspherical Fe2O3 catalyst with a particle size of 250-400 μm and a specific surface area of 60.5 m 2 / g was used for catalytic pyrolysis under the same conditions, and the dioxin toxicity of the solid residues was 25-40 ng TEQ / kg.

[0032] S3, after pretreatment, the two batches of water washing waste liquid were subjected to evaporation and fractionated crystallization to recover inorganic salt components, and the steps were as follows: C1, about 3 L of water washing waste liquid generated by water washing and enhanced leaching was added with 2.5 g of sodium carbonate to precipitate heavy metals and calcium salts, adjusted to pH=4, and then 30% hydrogen peroxide and 0.6 g of ferrous sulfate were added to form Fenton reagent with a molar ratio of 3:1 to oxidize organic matter; after treatment, there was little suspended matter in the waste liquid, so polyaluminum chloride and polyacrylamide were not added for flocculation and precipitation.

[0033] C2, the pH of the water washing waste liquid after impurity removal was adjusted to 7.0 by sodium hydroxide solution, and ultrafiltration membrane with a molecular weight cut-off of 400 Da and nanofiltration membrane with a molecular weight cut-off of 100 Da were used to remove residual trace organic matter and divalent ions; C3, by evaporation and crystallization at different temperature sections at 60℃ and 25℃, respectively, 50 g of NaCl and 20 g of KCl could be recovered, and no sodium sulfate was produced in the fly ash sample used in this example. The condensed water obtained after treatment can be reused in step S1.

[0034] The solid residue dioxin toxicity equivalent <10 ng TEQ / kg; soluble chlorine content <1%; the leaching solution obtained according to the Solid Waste Leaching Toxicity Level Oscillation Method (HJ 557-2010) has Pb <1.0 mg / L, Zn <2.0 mg / L, and Cd <0.1 mg / L.

[0035] Example 3: A waste incineration power plant daily handles 600 tons of waste, adopts fluidized bed incineration process, and the fly ash production is about 90 tons per day, and the annual output is about 30,000 tons. The main components of the fly ash are chlorine content 15.2%, calcium content 22.1%, silicon content 18.5%, aluminum content 8.3%, iron content 5.2%, potassium content 2.1%, sodium content 3.6%, and sulfur content 2%; the heavy metal content is Pb 2800 mg / kg, Zn 4200 mg / kg; and the dioxin toxicity equivalent is 110 ng TEQ / kg.

[0036] The example provides the above-mentioned waste incineration fly ash component regulation and directional conversion treatment method, and the process flow is as shown in Figure 1 The example provides the above-mentioned waste incineration fly ash component regulation and directional conversion treatment method, and the process flow is as shown in S1, primary water washing and forced leaching, the steps are as follows: A1, 90 tons of fly ash in original state are put into a reactor, 360 m 3 of clean water are added according to the liquid-solid ratio 4 L / kg, stirring at 300 r / min at 25℃ for 30 minutes, and after solid-liquid separation, about 335 m 3 of the first batch of water washing waste liquid is obtained, and about 110 tons of solid residue is obtained.

[0037] A2, then the solid residue is leached according to the liquid-solid ratio 0.7 L / kg, 63 m 3 of clean water is added, and leaching treatment is performed for 5 minutes, and about 105 tons of final desalination fly ash residue is obtained, and the water content is about 45%. The chlorine content of the treated fly ash is reduced to 0.42%.

[0038] S2, after mixing with the catalyst and granulation, catalytic pyrolysis is performed, and the steps are as follows: B1, the catalyst prepared in example 1 is used in an amount of 3.8 tons, and the water washing fly ash dry basis mass ratio is about 1:15 (the fly ash dry basis mass is only used for calculation, and drying is not required during granulation). After the water washing fly ash and the catalyst are uniformly mixed, the mixture is pressed into cylindrical particles with a diameter of about 1.2 cm and a length of 2 cm, and the water content is adjusted to 8%.

[0039] B2, catalytic pyrolysis is performed in a fixed bed reactor, nitrogen is introduced for protection, the oxygen content is maintained to be less than 1%, preferably between 0.5-1%, pyrolysis is performed at 250℃ for 100 minutes, and the generated flue gas is introduced into a incinerator for cooperative heat treatment.

[0040] The dioxin toxicity equivalent of the treated fly ash is less than 10 ng TEQ / kg. According to the HJ 557-2010 standard leaching test, the lead leaching concentration is 0.9 mg / L, and other heavy metals are not detected. At the same time, a commercial catalyst (microspherical Fe2O3, particle size is 200-400 μm, specific surface area is 62 m 2 / g) is used, the oxygen concentration is controlled to be less than 0.1% and the mixing ratio is 10:1 according to the requirements of the manufacturer, and the dioxin toxicity equivalent of the treated fly ash is 20 ng TEQ / kg.

[0041] S3, two batches of water washing waste liquid are pretreated and then subjected to stepwise evaporation and quality-specific crystallization to recover inorganic salt components, and the steps are as follows: C1, the total amount of water washing waste liquid is about 400 m 3 L, sodium carbonate is added to 0.6 g / L to precipitate calcium ions and heavy metals; the pH is adjusted to 4.0, Fenton reagent is used, the molar ratio of H2O2 to Fe 2+ is 2.5:1, and organic matter is oxidized; the pH is adjusted to 8.0, 45 mg / L of polyaluminum chloride and 3 mg / L of polyacrylamide are added, and flocculation and sedimentation are performed; C2, the ultrafiltration membrane with a molecular weight cut-off of 500 Da is used to remove suspended solids and organic matter; C3, MVR is used for quality-specific crystallization, in which potassium chloride crystallization is performed at 58℃, about 1 ton of potassium chloride is obtained per day, and the purity is 90.8%; sodium chloride crystallization is performed at 25℃, about 2.5 tons of sodium chloride crystals are precipitated per day, and the purity is 97.6%; the remaining mother liquor continues to precipitate sodium sulfate, about 1.0 tons of sodium sulfate crystals are obtained per day, and the purity is 85.2%.

[0042] Although the embodiments of the present application have been disclosed as above, they are not limited to the applications listed in the specification and embodiments, and can be fully applied to various fields suitable for the present application. For those skilled in the art and ordinary skilled in the art, various changes, modifications, replacements and modifications can be made to these embodiments without departing from the principles and spirits of the present application, and therefore the present application is not limited to specific details without departing from the general concept defined by the claims and equivalent ranges.

Claims

1. A method for the controlled and directed conversion of municipal solid waste incineration fly ash components, comprising: The method comprises the following steps: ​ S1, the waste incineration fly ash is first washed with water to remove soluble chlorides and heavy metals, and the obtained solid is subjected to forced leaching using recycled water or clean water after solid-liquid separation, to obtain washed fly ash and washing waste liquid, and deeply separate the residual soluble chlorides and heavy metals, and remove the chlorine source for the re-synthesis of dioxins; S2, a core-shell structure Fe2O3 / Fe / C composite catalyst is prepared, mixed with the washed fly ash to form granules, and then subjected to catalytic pyrolysis in an inert or micro-oxygen environment to crack dioxin organic matter; S3, the washing waste liquid is subjected to pretreatment and then subjected to step-by-step evaporation-selective crystallization to recover inorganic salt components by quality; and the flue gas is introduced into an incinerator for cooperative heat treatment.

2. The method of claim 1, wherein, The specific steps of the fly ash in step S1 subjected to first-stage water washing and forced leaching include: A1, the waste incineration fly ash is mixed with the condensate water obtained from the quality-recovered inorganic salt in step S3 and supplemented clean water at a liquid-solid ratio of 2-5 L / kg, stirred at 200-500 r / min at room temperature for 15-60 min, and then subjected to solid-liquid separation to obtain a solid and a first batch of washing waste liquid; A2, the obtained solid is uniformly leached with clean water at a liquid-solid ratio of 0.5-1 L / kg, and then subjected to solid-liquid separation again to obtain washed fly ash and a second batch of washing waste liquid; the soluble chlorine content in the washed fly ash is less than 1%, reducing the chlorine source for the re-synthesis of dioxins.

3. The method of claim 1, wherein, The preparation method of the Fe2O3 / Fe / C composite catalyst in step S2 comprises the following steps: N1, biochar is used as a carrier, and a suspension is prepared by ultrasonic dispersion in deionized water; then, an iron salt solution is added dropwise under stirring; N2, then, a sodium hydroxide or ammonia water solution is slowly added dropwise, the dropwise adding speed is controlled to be 1-3 ml / min, the pH of the reaction system is maintained at 8-10, and the reaction time is 2-4 hours; N3, after the reaction is completed, the mixture is left to stand for 6-12 hours, and then subjected to centrifugal separation, and washed with deionized water until the pH of the washing liquid is neutral; N4, the obtained product is dried at 80-120℃ for 12-24 hours, Fe2O3 is loaded on the biochar carrier by the co-precipitation method in the above steps, and the Fe loading amount is 10-20 wt%; N5. The dried product is selectively reduced at 280-320℃ for 2-3 hours under a H2 / N2 mixed atmosphere to form a core-shell Fe2O3 / Fe / C composite catalyst; the obtained Fe2O3 / Fe / C composite catalyst has a particle size of 200-500 μm and a specific surface area of ​​not less than 100 m². 2 / g.

4. The method of claim 3, wherein, In step N1, the biochar is ground to a particle size of less than 150 μm; the iron salt includes ferric chloride, ferric nitrate or ferric sulfate; the stirring speed is 300-500 rpm, and the stirring temperature is 60-80℃.

5. The method of claim 3, wherein, In step N2, the mass ratio of C, Fe and OH in the biochar, iron salt, sodium hydroxide or ammonia water is 1:0.8-1.5:1.2-2.0; in step N3, the centrifugal separation speed is 3000-5000 rpm, and the time is 5-10 min.

6. The method of claim 1, wherein, The specific steps of the catalytic pyrolysis of the washed fly ash and the catalyst mixed granules in step S2 include: B1, the washed fly ash and the catalyst are uniformly mixed at a mass ratio of 5:1-15:1, and then shaped into spherical or cylindrical particles with a diameter of 1-3 centimeters; B2, the catalytic pyrolysis is carried out at a temperature of 250-350℃ for 30-120 minutes in a micro-oxygen atmosphere, and the flue gas generated by pyrolysis is introduced into an incinerator for cooperative heat treatment.

7. The method of claim 6, wherein, The micro-oxygen atmosphere in step B2 is an atmosphere with nitrogen or argon as the main component, and the oxygen concentration is ≤1% of the nitrogen or argon.

8. The method of claim 6, wherein, In step B2, Fe2O3 and Fe have a synergistic catalytic effect in the micro-oxygen atmosphere; Fe2O3 provides active oxygen atoms to promote the oxidative cleavage of dioxin molecules; Fe provides electrons and activates the C-Cl bond to promote the dechlorination of dioxins; and the carrier C provides π electrons to enhance the adsorption and activation of dioxin molecules.

9. The method of claim 1, wherein, The specific steps for recovering the inorganic salt components by pre-treatment and fractional evaporation-crystallization of the water washing waste liquid in step S3 include: C1, add sodium sulfide or sodium carbonate to 0.3~1.2 g / L in the water washing waste liquid, precipitate heavy metals and calcium ions; then add Fenton reagent and adjust pH to 2~4, H2O2 and Fe 2+ molar ratio of 2:1~4:1, oxidize organic matter; then adjust pH to 7.0~9.0; then add or do not add 20~60 mg / L polyaluminum chloride and 1~8 mg / L polyacrylamide according to the impurity type of the water washing waste liquid, flocculate and precipitate, remove calcium ions and heavy metals; C2, after impurity removal, the water washing waste liquid is treated by ultrafiltration membrane and / or nanofiltration membrane to remove suspended solids and organic matter, and monovalent and multivalent ions are separated according to the inorganic salt component recovery requirements; C3, the treated water washing waste liquid is recovered by mechanical vapor recompression or multi-effect evaporation crystallizer at different temperatures to recover sodium sulfate, potassium chloride and sodium chloride, and the condensed water is recovered for use in the first-stage water washing and leaching of fly ash.

10. The method of claim 1, wherein, After the final treatment, the soluble chlorine content of the fly ash is less than 1%, the Pb content in the leaching solution obtained according to HJ557-2010 "Solid Waste Leaching Toxicity Level Oscillation Method" is less than 1.0 mg / L, and the dioxin toxicity equivalent is less than 20 ng TEQ / kg.

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