A method for dechlorination and degradation of dioxin and inhibition of its resynthesis by using steelmaking furnace dust and waste incineration fly ash in cooperation with roasting

Abstract

The present application relates to waste treatment technical field, specifically to a kind of method for dechlorination degradation dioxin and inhibiting its resynthesis by using steelmaking furnace dust and garbage incineration fly ash synergic roasting, comprising the following steps: S100: in the high temperature reaction zone of closed heating equipment, garbage incineration fly ash and electric furnace ash are added according to mass ratio, and synergic roasting is carried out under air atmosphere;S200: after roasting, using toluene solution, tail gas and solid product are purified by gas washing bottle, dioxin volatile is captured and collected;S300: using gas chromatography-mass spectrometry (GC-MS) to the dioxin content detection of solid residue after roasting;The present application is based on the in-depth study of steelmaking furnace dust and garbage incineration fly ash mineral phase composition, aiming at the problem that dioxin in garbage incineration fly ash is difficult to degrade and easy to resynthesize, the dechlorination effect of alkaline oxide in steelmaking furnace dust is innovatively used, two kinds of hazardous wastes are mixed and synergic roasting is carried out, organic chlorine is converted into inorganic chloride salt, not only dioxin is efficiently degraded, but also its resynthesis is avoided.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of waste treatment, in particular to a method for dechlorination and degradation of dioxins and inhibition of their resynthesis by synergistic roasting of steelmaking furnace dust and waste incineration fly ash. BACKGROUND

[0002] Currently, common treatment methods for zinc-containing steelmaking furnace dust include carbon thermal reduction and strong acid leaching. Carbon thermal reduction involves adding a reducing agent to make zinc volatilize at high temperatures, which is simple and efficient to operate, but produces greenhouse gas CO2, affecting environmental sustainability. Strong acid leaching uses an acidic solution to extract target elements, which reduces carbon emissions, but the process is complex and requires a large amount of acid and base reagents, and improper handling can cause serious harm to the environment.

[0003] To solve the above environmental problems, this paper proposes an innovative method - dechlorination treatment of waste incineration fly ash and zinc-containing steelmaking furnace dust. This method takes advantage of the complementarity of the two hazardous wastes, combining zinc oxide in zinc-containing steelmaking furnace dust with chlorine-containing organic matter in waste incineration fly ash, and through dechlorination reaction, not only effectively removes dioxins from waste incineration fly ash, but also prevents dioxin resynthesis, achieving self-carrying and harmless treatment. At the same time, the treated waste can be recycled, contributing to environmental protection and resource conservation.

[0004] This innovative method has significant advantages in treating waste incineration fly ash and zinc-containing steelmaking furnace dust compared to existing technologies:

[0005] Compared with the existing technology CN109437573B "Waste Incineration Fly Ash Dioxin Harmless Treatment Method", the present application removes dioxins through dechlorination and degradation, and significantly reduces the leaching toxicity of heavy metals (such as Hg, Pb, Zn, etc.), ensuring waste harmless treatment. Specifically, the present application utilizes the synergistic roasting reaction of steelmaking furnace dust and waste incineration fly ash, which effectively promotes the mineralization of organic chlorine at high temperatures through the reaction of zinc oxide (ZnO) and chlorides, avoids the resynthesis of dioxins, and improves the degradation rate of dioxins. At the same time, through the chlorination and volatilization of heavy metals, the environmental hazards of heavy metals are reduced, ensuring the resource utilization of fly ash. The existing technology enhances the solidification capacity of fly ash through high-temperature reaction of magnesium and calcium salts, reducing heavy metal leaching, but does not specifically address the degradation and prevention of dioxin resynthesis. SUMMARY

[0006] In order to solve the above problems, the present application provides a method for dechlorination and degradation of dioxin and inhibition of its resynthesis by using steelmaking furnace dust and waste incineration fly ash.

[0007] A method for dechlorination and degradation of dioxin and inhibition of its resynthesis by using steelmaking furnace dust and waste incineration fly ash, the method comprising the following steps:

[0008] S100: In the high-temperature reaction zone of the closed heating equipment, waste incineration fly ash and electric furnace dust are added in a mass ratio of 2-6:1, and are co-calcined under air atmosphere for 1-6 hours, and the reaction temperature is 1000-1250℃; by the reaction of ZnO and PbO in the electric furnace dust with HCl generated by the conversion of chlorine-containing organic matter in the waste incineration fly ash, the synthesis of dioxin precursors is reduced;

[0009] S200: After calcination, toluene solution is used to purify the reaction tail gas and solid products through a gas washing bottle to capture dioxin volatiles and collect them;

[0010] S300: The dioxin content of the calcined solid residue is detected by gas chromatography-mass spectrometry (GC-MS) to ensure that the degradation rate and toxicity equivalent meet the requirements of the Technical Code for Pollution Control of Waste Incineration Fly Ash HJ1134-2020.

[0011] As a further technical solution, the closed heating equipment is a horizontal or vertical closed heating furnace, and the temperature uniformity of the reaction zone is controlled within ±20℃.

[0012] As a further technical solution, the mass ratio of waste incineration fly ash to electric furnace dust in step S100 is 6:1, the calcination temperature is 1100℃, and the calcination time is 5 hours.

[0013] As a further technical solution, the ZnO content of the electric furnace dust in step S100 is ≥6wt%, and the particle size is ≤150μm.

[0014] As a further technical solution, the concentration of toluene solution in step S200 is 0.05-0.1mol / L, and the solution volume is 500-1000mL.

[0015] As a further technical solution, the method further comprises pretreatment of the waste incineration fly ash and the electric furnace dust before step S100:

[0016] (1) The electric furnace dust is crushed to a particle size of ≤150μm;

[0017] (2) mixing the pretreated electric furnace dust with the waste incineration fly ash.

[0018] As a further technical solution, the oxygen content of the air atmosphere in step S100 is 18-21 vol%, and the reaction zone heating rate is controlled to be 5-10℃ / min by adjusting the air flow.

[0019] As a further technical solution, the purified tail gas in step S200 is subjected to secondary adsorption purification by an adsorption column filled with activated carbon fiber and molecular sieve composite adsorbent, to ensure that the dioxin emission concentration is ≤0.1 ng-TEQ / Nm3.

[0020] The activated carbon fiber and molecular sieve composite adsorbent are prepared by the following method:

[0021] (1) precursor pretreatment: carbonize the phenolic-based activated carbon fiber in a nitrogen atmosphere in a muffle furnace at a temperature of 400-500℃ for 2-3 hours, with a heating rate controlled to be 5℃ / min; then immerse the carbonized activated carbon fiber in a 3-5wt% nitric acid solution, soak for 12-15 hours, and then rinse with deionized water multiple times until the pH value of the rinse liquid is 7, and finally dry in a forced air drying oven at a temperature of 105℃ to constant weight, ready for use;

[0022] (2) molecular sieve loading: immerse the pretreated activated carbon fiber into an ethanol solution containing ZSM-5 molecular sieve seeds, the mass concentration of ZSM-5 molecular sieve seeds in the ethanol solution is 10-20g / L, the ethanol solution is prepared by mixing anhydrous ethanol and deionized water at a volume ratio of 9:1; under the condition of ultrasonic oscillation at a frequency of 40kHz and a power of 200W, oscillate for 30-40 minutes to make the seeds uniformly adhere to the surface of the fiber, and then dry in a vacuum drying oven at a temperature of 135-150℃ for 4-6 hours;

[0023] (3) in-situ growth: place the activated carbon fiber loaded with seeds in a hydrothermal reaction kettle, add a synthesis solution containing a silicon source (tetraethyl orthosilicate), an aluminum source (isopropyl alcohol aluminum), and a template agent (tetrapropylammonium hydroxide), the molar ratio of the silicon source, the aluminum source, and the template agent in the synthesis solution is 1:0.05:0.3, and the solvent is deionized water; under the condition of a temperature of 160-180℃ and a pressure of autogenous pressure, crystallize for 18-24 hours to make the molecular sieve grow in-situ on the surface of the activated carbon fiber;

[0024] (4) Metal modification: the composite adsorbent of in-situ grown molecular sieve is immersed in a solution containing 1.2-2wt% manganese nitrate, taken out after 12-14 hours of immersion, dried in an electric heating constant temperature drying oven at a temperature of 75-80℃ for 10-12 hours, and then calcined in a muffle furnace in an air atmosphere at a temperature of 400-500℃ at a temperature rising rate of 5℃ / min for 3-5 hours;

[0025] (5) Hydrophobic treatment: the composite adsorbent after metal modification is placed in a toluene solution containing 1.8-3wt% methyltrimethoxysilane, refluxed in an oil bath at a temperature of 80-100℃ for 6-12 hours, then filtered through a suction filtration device, washed with toluene for multiple times, and finally dried in a forced air drying oven at a temperature of 105℃ to obtain an activated carbon fiber and molecular sieve composite adsorbent with hydrophobic groups on the surface. The adsorption of dioxins by the activated carbon fiber and molecular sieve composite adsorbent is based on a synergistic mechanism of physical and chemical mechanisms. The activated carbon fiber has a high specific surface area and a rich microporous structure, and can physically adsorb dioxins through van der Waals force; the oxygen-containing functional groups (such as carboxyl and hydroxyl) on the surface of the activated carbon fiber can form hydrogen bonds with dioxin molecules, enhancing the adsorption stability. The molecular sieve has a regular pore structure with a pore size matching the size of dioxin molecules, which can produce a molecular sieve effect to accurately intercept dioxins; at the same time, the active sites (such as acid sites) on the surface of the molecular sieve can chemically react with dioxin molecules to achieve chemical adsorption. After metal modification, the transition metal oxides can catalyze the oxidation of dioxins to decompose them into CO2 and HCl; the hydrophobic treatment makes the adsorbent avoid water competition adsorption in a high humidity environment and preferentially adsorb dioxins. The synergistic effect of multiple mechanisms greatly improves the adsorption and degradation efficiency of the composite adsorbent for dioxins.

[0026] As a further technical solution, the dioxin degradation rate in step S300 is ≥99%, and the toxicity equivalent is ≤0.1μg-TEQ / kg.

[0027] As a further technical solution, the method realizes high-temperature dechlorination degradation of dioxins by dechlorination of ZnO in the electric furnace ash to make the Cl content in the solid residue ≤1wt%.

[0028] Beneficial effects:

[0029] (1) The present application is based on the in-depth study of the mineral phase composition of steel furnace dust and waste incineration fly ash, and aims at the re-synthesis of dioxins in waste incineration fly ash and steel furnace dust. The two kinds of hazardous waste are mixed and treated by synergistic composite harmless treatment. Chlorinated organic compounds in waste incineration fly ash will produce HCl in the process of mutual transformation. The electric furnace dust contains ZnO, PbO and other components. The reaction of the two generates stable chlorides, promotes the mineralization of organic chlorine, and promotes the forward progress of dioxin dechlorination decomposition reaction. In addition, the mineralization of organic chlorine reduces the chlorine source required for dioxin synthesis, effectively avoids its low-temperature regeneration, and realizes the effective control of dioxin.

[0030] (2) The present application not only makes waste incineration fly ash and steel furnace dust harmless, but also carries out dechlorination treatment on chlorinated organic compounds. In the high-temperature reaction zone, waste incineration fly ash and electric furnace dust are synergistically roasted in high-temperature air atmosphere at a specific ratio. In this process, the zinc oxide and other components in the electric furnace dust react with the chlorides in the waste incineration fly ash, which not only effectively removes dioxins in waste incineration fly ash, but also avoids the re-synthesis of dioxins, achieving the purpose of self-synergistic harmless treatment. Through this treatment, the synthesis of dioxins can be inhibited, and the precursors can be dechlorinated by zinc-containing substances, with outstanding environmental benefits. Moreover, the treated waste can be recycled, which has certain economic benefits.

[0031] (3) In the treatment process, the reaction tail gas is purified by toluene solution in the gas washing bottle, which can effectively capture and collect dioxin volatiles for subsequent analysis, ensuring that the concentration of dioxin in the reaction tail gas is minimized, further improving the environmental protection effect.

[0032] (4) In the pretreatment link, the electric furnace dust is crushed to a certain particle size, ensuring better surface activity and being suitable for synergistic reaction with waste incineration fly ash. Through reasonable mixing and proportioning, the components of the two are uniform, achieving the best reaction effect, laying a foundation for the effectiveness and stability of the whole treatment process.

[0033] (5) The present application detects the dioxin content of the roasted solid residue by gas chromatography-mass spectrometry (GC-MS), ensuring that the degradation effect meets the national standard (such as "Waste Incineration Fly Ash Pollution Control Technology Specification HJ1134-2020"), and ensuring the reliability and safety of the treatment results.

[0034] (6) Compared with the prior art, the present application has obvious advantages in heavy metal control and dioxin degradation control. In the control of heavy metals, the removal of dioxins by dechlorination degradation significantly reduces the leaching toxicity of heavy metals (such as Hg, Pb, Zn, etc.), ensuring the harmless treatment of waste.

[0035] Drawings

[0036] Figure 1 is a dioxin synthesis inhibition diagram. DETAILED DESCRIPTION

[0037] The technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0038] The present application provides a method for dechlorination and degradation of dioxin and inhibition of its resynthesis by synergistic roasting of steelmaking furnace dust and waste incineration fly ash, comprising the following core steps:

[0039] S100: mix the waste incineration fly ash and the electric furnace dust at a mass ratio of 5.5-6:1, and synergistically roast at 1050-1150℃ under air atmosphere for 1-6 hours to inhibit the synthesis of dioxin precursors by the reaction of ZnO, PbO in the electric furnace dust with HCl.

[0040] S200: use toluene solution (0.05-0.1 mol / L, 500-1000 mL) to purify the reaction product and capture dioxin volatiles.

[0041] S300: detect the solid residue by gas chromatography-mass spectrometry (GC-MS) to ensure that the degradation rate of dioxin is ≥99% and the toxicity equivalent is ≤0.1 μg-TEQ / kg, meeting the requirements of "Technical Code for Pollution Control of Waste Incineration Fly Ash HJ1134-2020".

[0042] Process parameters and raw materials

[0043] 1. Pretreatment

[0044] Electric furnace dust: ZnO content ≥6wt%, crushed to a particle size ≤150μm (such as using a ball mill for crushing).

[0045] Mixing ratio: mix the electric furnace dust and the waste incineration fly ash at a mass ratio of 2-6:1, and stir uniformly with a double-shaft stirrer; rotation speed 50-80r / min, time 10-20min.

[0046] 2. Roasting process

[0047] Equipment: horizontal or vertical closed heating furnace, reaction zone temperature uniformity within ±20℃.

[0048] Atmosphere control: air oxygen content 18-21vol%, adjust air flow by flow meter, control heating rate 5-10℃ / min.

[0049] Baking parameters: temperature 1000-1250℃, time 4-6 hours, ensure that HCl is fully reacted.

[0050] 3. Purification and detection

[0051] Toluene purification: toluene solution concentration in the gas washing bottle is 0.05-0.1 mol / L, volume is 500-1000 mL, ensure that dioxin is fully dissolved.

[0052] Tail gas treatment: the tail gas purified in step S200 is subjected to secondary adsorption purification by an adsorption column filled with activated carbon fiber and molecular sieve composite adsorbent, to ensure that the dioxin emission concentration is ≤0.1 ng-TEQ / Nm 3 ;

[0053] The activated carbon fiber and molecular sieve composite adsorbent are prepared by the following method:

[0054] (1) Precursor pretreatment: phenolic-based activated carbon fiber is carbonized and pretreated in a muffle furnace in a nitrogen atmosphere at a temperature of 400-500℃ for 2-3 hours, with a heating rate controlled at 5℃ / min; then the carbonized activated carbon fiber is soaked in a nitric acid solution with a concentration of 3-5wt%, soaked for 12-15 hours, then washed with deionized water multiple times until the pH value of the washing liquid is 7, and finally dried to constant weight in a forced air drying oven at a temperature of 105℃, ready for use;

[0055] (2) Molecular sieve loading: the pretreated activated carbon fiber is immersed in an ethanol solution containing ZSM-5 molecular sieve seeds, the mass concentration of ZSM-5 molecular sieve seeds in the ethanol solution is 10-20g / L, the ethanol solution is prepared by mixing anhydrous ethanol and deionized water at a volume ratio of 9:1; under the condition of ultrasonic oscillation at a frequency of 40kHz and a power of 200W, oscillate for 30-40 minutes to make the seeds uniformly adhere to the surface of the fiber, and then dry in a vacuum drying oven at a temperature of 135-150℃ for 4-6 hours;

[0056] (3) In-situ growth: the activated carbon fiber loaded with seeds is placed in a hydrothermal reaction kettle, and a synthesis solution containing a silicon source (tetraethyl orthosilicate), an aluminum source (isopropyl alcohol aluminum), and a template agent (tetrapropylammonium hydroxide) is added, the molar ratio of the silicon source, the aluminum source, and the template agent in the synthesis solution is 1:0.05:0.3, and the solvent is deionized water; under the condition of a temperature of 160-180℃ and a pressure of autogenous pressure, crystallize for 18-24 hours to make the molecular sieve grow in-situ on the surface of the activated carbon fiber;

[0057] (4) Metal modification: The composite adsorbent of in-situ grown molecular sieve was immersed in a solution containing 1.2-2wt% manganese nitrate, taken out after 12-14 hours of immersion, dried in an electric thermostatic drying oven at a temperature of 75-80°C for 10-12 hours, and then calcined in a muffle furnace in an air atmosphere at a temperature of 400-500°C at a temperature rising rate of 5°C / min for 3-5 hours;

[0058] (5) Hydrophobic treatment: The composite adsorbent after metal modification was placed in a toluene solution containing 1.8-3wt% methyltrimethoxysilane, refluxed in an oil bath at a temperature of 80-100°C for 6-12 hours, then filtered through a suction filtration device, washed with toluene for several times, and finally dried in a forced air drying oven at a temperature of 105°C to obtain an activated carbon fiber and molecular sieve composite adsorbent with hydrophobic groups on the surface.

[0059] Detection standard: dioxin degradation rate in solid residue ≥99%, toxicity equivalent ≤0.1μg-TEQ / kg, and Cl content ≤1wt%.

[0060] The following are specific examples

[0061] Example 1

[0062] Step S100

[0063] Raw material: waste incineration fly ash (Cl content 12wt%) and electric furnace ash (ZnO content 18wt%) were mixed in a mass ratio of 6:1, and the particle size of the electric furnace ash was 100μm.

[0064] Calcination: vertical closed heating furnace, air oxygen content 20vol%, temperature rising rate 8°C / min, calcination at 1100°C for 5 hours.

[0065] Step S200

[0066] Purification: 0.1mol / L toluene solution 800mL, residence time in gas washing bottle 15min, capturing dioxin volatiles; the tail gas after purification was subjected to secondary adsorption purification by an adsorption column filled with activated carbon fiber and molecular sieve composite adsorbent, to ensure that the dioxin emission concentration was ≤0.1ng-TEQ / Nm 3 ;

[0067] The activated carbon fiber and molecular sieve composite adsorbent was prepared by the following method:

[0068] (1) Precursor pretreatment: the phenolic-based activated carbon fiber was carbonized in a muffle furnace under nitrogen atmosphere at a temperature of 400℃ for 2 hours, and the heating rate was controlled at 5℃ / min; then the carbonized activated carbon fiber was soaked in a 3wt% nitric acid solution for 12 hours, and then washed with deionized water for several times until the pH value of the washing liquid was 7, and finally dried in a blast drying oven at a temperature of 105℃ to constant weight, ready for use;

[0069] (2) Molecular sieve loading: the pretreated activated carbon fiber was immersed in an ethanol solution containing ZSM-5 molecular sieve seeds, the mass concentration of ZSM-5 molecular sieve seeds in the ethanol solution was 10g / L, and the ethanol solution was prepared by mixing anhydrous ethanol and deionized water at a volume ratio of 9:1; under the condition of ultrasonic oscillation at a frequency of 40kHz and a power of 200W, the solution was oscillated for 30 minutes to make the seeds uniformly adhere to the surface of the fiber, and then dried in a vacuum drying oven at a temperature of 135℃ for 4 hours;

[0070] (3) In-situ growth: the activated carbon fiber loaded with seeds was placed in a hydrothermal reaction kettle, and a synthesis solution containing a silicon source (tetraethyl orthosilicate), an aluminum source (aluminum isopropylate), and a template agent (tetrapropylammonium hydroxide) was added, the molar ratio of the silicon source, the aluminum source, and the template agent in the synthesis solution was 1:0.05:0.3, and the solvent was deionized water; under the condition of a temperature of 160℃ and a pressure of autogenous pressure, the crystal was grown for 18-24 hours to make the molecular sieve grow in-situ on the surface of the activated carbon fiber;

[0071] (4) Metal modification: the composite adsorbent with in-situ grown molecular sieve was immersed in a 1.2wt% manganese nitrate solution, taken out after 12 hours of immersion, dried in an electric heating constant temperature drying oven at a temperature of 75℃ for 10 hours, and then calcined in a muffle furnace under air atmosphere at a temperature of 400℃ for 3 hours at a heating rate of 5℃ / min;

[0072] (5) Hydrophobic treatment: the composite adsorbent after metal modification was placed in a toluene solution containing 1.8wt% methyltrimethoxysilane, refluxed in an oil bath at a temperature of 80℃ for 6 hours, then filtered through a suction filtration device, washed with toluene for several times, and finally dried in a blast drying oven at a temperature of 105℃ to obtain an activated carbon fiber and molecular sieve composite adsorbent with hydrophobic groups on the surface.

[0073] Step S300

[0074] Test results: dioxin degradation rate 99.2%, toxicity equivalent 0.08μg-TEQ / kg, Cl content 0.8wt%, meeting the national standard.

[0075] Example 2

[0076] Step S100

[0077] Raw material: waste incineration fly ash (Cl content 10wt%) and electric furnace ash (ZnO content 15wt%) mixed in a mass ratio of 4:1, electric furnace ash particle size 150μm.

[0078] Roasting: horizontal closed heating furnace, air oxygen content 18vol%, heating rate 5℃ / min, 1100℃ roasting for 6 hours.

[0079] Step S200

[0080] Purification: 0.05mol / L toluene solution 1000mL, residence time in the gas washing bottle 20min; the tail gas after purification is subjected to secondary adsorption purification by an adsorption column filled with activated carbon fiber and molecular sieve composite adsorbent, to ensure that the dioxin emission concentration is ≤0.1ng-TEQ / Nm3;

[0081] The activated carbon fiber and molecular sieve composite adsorbent are prepared by the following method:

[0082] (1) Precursor pretreatment: phenolic-based activated carbon fiber is carbonized in a muffle furnace under a nitrogen atmosphere at a temperature of 460℃ for 2.5 hours, with a heating rate controlled at 5℃ / min; then the carbonized activated carbon fiber is soaked in a 3.5wt% nitric acid solution, soaked for 14 hours, then washed with deionized water multiple times until the pH value of the washing liquid is 7, and finally dried in a forced air drying oven at a temperature of 105℃ to constant weight, ready for use;

[0083] (2) Molecular sieve loading: the pretreated activated carbon fiber is immersed in an ethanol solution containing ZSM-5 molecular sieve seeds, the mass concentration of ZSM-5 molecular sieve seeds in the ethanol solution is 18g / L, and the ethanol solution is prepared by mixing anhydrous ethanol and deionized water in a volume ratio of 9:1; under the condition of ultrasonic oscillation at a frequency of 40kHz and a power of 200W, oscillate for 35 minutes to make the seeds uniformly adhere to the surface of the fiber, and then dry in a vacuum drying oven at a temperature of 140℃ for 5 hours;

[0084] (3) In-situ growth: the activated carbon fiber loaded with seeds is placed in a hydrothermal reaction kettle, and a synthesis solution containing a silicon source (tetraethyl orthosilicate), an aluminum source (isopropyl alcohol aluminum), and a template agent (tetrapropylammonium hydroxide) is added, the molar ratio of the silicon source, the aluminum source, and the template agent in the synthesis solution is 1:0.05:0.3, and the solvent is deionized water; under the condition of a temperature of 170℃ and a pressure of autogenous pressure, crystallize for 20 hours to make the molecular sieve grow in-situ on the surface of the activated carbon fiber;

[0085] (4) Metal modification: the composite adsorbent of in-situ grown molecular sieve was immersed in a solution containing 1.6wt% manganese nitrate, taken out after 13 hours of immersion, dried in an electric heating constant temperature drying oven at a temperature of 78°C for 11 hours, and then calcined in a muffle furnace in an air atmosphere at a temperature of 440°C for 4 hours at a temperature rising rate of 5°C / min;

[0086] (5) Hydrophobic treatment: the composite adsorbent after metal modification was placed in a toluene solution containing 2.2wt% methyltrimethoxysilane, refluxed in an oil bath at a temperature of 90°C for 8 hours, then filtered through a suction filtration device, washed with toluene for several times, and finally dried in a forced air drying oven at a temperature of 105°C to obtain an activated carbon fiber and molecular sieve composite adsorbent with hydrophobic groups on the surface.

[0087] Step S300

[0088] Test results: dioxin degradation rate 99.0%, toxicity equivalent 0.10μg-TEQ / kg, Cl content 1.0wt%, up to standard.

[0089] Example 3

[0090] Step S100

[0091] Raw material: waste incineration fly ash (Cl content 15wt%) and electric furnace ash (ZnO content 20wt%) mixed at a mass ratio of 2:1, electric furnace ash particle size 80μm.

[0092] Calcination: vertical closed heating furnace, air oxygen content 21vol%, temperature rising rate 10°C / min, calcination at 1250°C for 4 hours.

[0093] Step S200

[0094] Purification: 500mL of 0.08mol / L toluene solution, residence time in the gas washing bottle 10min; the tail gas after purification was subjected to secondary adsorption purification by an adsorption column filled with activated carbon fiber and molecular sieve composite adsorbent, to ensure that the dioxin emission concentration was ≤0.1ng-TEQ / Nm3;

[0095] The activated carbon fiber and molecular sieve composite adsorbent was prepared by the following method:

[0096] (1) Precursor pretreatment: phenolic-based activated carbon fiber was subjected to carbonization pretreatment in a muffle furnace in a nitrogen atmosphere at a temperature of 500°C for 3 hours, with the temperature rising rate controlled at 5°C / min; then the carbonized activated carbon fiber was soaked in a 5wt% nitric acid solution, washed with deionized water for several times after 15 hours of soaking until the pH value of the washing liquid was 7, and finally dried in a forced air drying oven at a temperature of 105°C to constant weight for standby use;

[0097] (2) Molecular sieve loading: the pretreated activated carbon fiber was immersed in an ethanol solution containing ZSM-5 molecular sieve seeds, the mass concentration of the ZSM-5 molecular sieve seeds in the ethanol solution was 20 g / L, the ethanol solution was prepared by mixing anhydrous ethanol and deionized water at a volume ratio of 9:1; under the condition of ultrasonic oscillation at a frequency of 40 kHz and a power of 200 W, the seeds were oscillated for 40 minutes to uniformly adhere to the surface of the fiber, and then the fiber was dried in a vacuum drying oven at a temperature of 150 ℃ for 6 hours;

[0098] (3) In-situ growth: the activated carbon fiber loaded with seeds was placed in a hydrothermal reaction kettle, a synthesis solution containing a silicon source (tetraethyl orthosilicate), an aluminum source (aluminum isopropoxide), and a template agent (tetrapropylammonium hydroxide) was added, the molar ratio of the silicon source, the aluminum source, and the template agent in the synthesis solution was 1:0.05:0.3, and the solvent was deionized water; under the condition of a temperature of 180 ℃ and a pressure of autogenous pressure, the seeds were crystallized for 24 hours to grow the molecular sieve in-situ on the surface of the activated carbon fiber;

[0099] (4) Metal modification: the composite adsorbent with in-situ grown molecular sieve was immersed in a 2wt% manganese nitrate solution, taken out after 14 hours of immersion, dried in an electric heating constant temperature drying oven at a temperature of 80 ℃ for 12 hours, and then calcined in a muffle furnace at a temperature of 500 ℃ for 5 hours at a temperature rising rate of 5 ℃ / min in an air atmosphere;

[0100] (5) Hydrophobic treatment: the composite adsorbent after metal modification was placed in a toluene solution containing 3wt% methyltrimethoxysilane, refluxed in an oil bath at a temperature of 100 ℃ for 12 hours, then filtered through a suction filtration device, washed with toluene for multiple times, and finally dried in a forced air drying oven at a temperature of 105 ℃ to obtain the activated carbon fiber and molecular sieve composite adsorbent with hydrophobic groups on the surface.

[0101] Step S300

[0102] Detection results: dioxin degradation rate 99.5%, toxicity equivalent 0.06 μg-TEQ / kg, Cl content 0.6wt%, performance better than standard.

[0103] Comparative Example 1

[0104] The difference from Example 1 is:

[0105] Step S100: the mass ratio of waste incineration fly ash to electric furnace ash was 3:1, the ZnO content was 10wt%, and the calcination was performed at 1050 ℃ for 5 hours.

[0106] Detection results

[0107] Dioxin degradation rate 85.2%, toxicity equivalent 0.81 μg-TEQ / kg, Cl content 3.5wt%, not up to standard.

[0108] Comparative Example 2

[0109] The difference from Example 1 is that no secondary adsorption purification treatment is performed.

[0110] Test results

[0111] The dioxin degradation rate is 60.7%, the toxicity equivalent is 2.52 μg-TEQ / kg, and the Cl content is 8.0 wt%, which is seriously over-standard.

[0112] Test

[0113] Test method

[0114] 1. Dioxin content detection (step S300)

[0115] Instrument: gas chromatography-mass spectrometry (GC-MS, such as Agilent 7890B / 5977A).

[0116] Sample pretreatment:

[0117] Weigh 5 g of solid residue, add 10 mL of toluene, ultrasonic extraction for 30 min, repeat 2 times, and combine the extraction liquid.

[0118] Purify by silica gel column chromatography (silica gel column is pre-activated with n-hexane), collect the eluent and concentrate to 1 mL.

[0119] Analysis conditions:

[0120] Chromatographic column: DB-5MS capillary column (30 m x 0.25 mm x 0.25 μm).

[0121] Temperature program: initial temperature 100℃, increase to 280℃ at 20℃ / min, hold for 15 min.

[0122] Mass spectrometry mode: selected ion monitoring (SIM), monitoring characteristic ions with mass-to-charge ratio (m / z) 320, 322, etc.

[0123] Quantitative method: internal standard method, using 13C-labeled dioxin standard as internal standard, calculating the concentration of dioxin in the sample, toxicity equivalent (TEQ).

[0124] Judgment standard: in accordance with “Technical Code for Pollution Control of Domestic Waste Incineration Fly Ash HJ1134-2020”, i.e. toxicity equivalent ≤0.1 μg-TEQ / kg.

[0125] 2. Determination of Cl content in solid residue

[0126] Method: combustion-ion chromatography method (GB / T 15453-2018).

[0127] Steps:

[0128] Weigh 0.5g sample in a ceramic boat, put it in a high temperature combustion furnace (900℃), and burn it by passing oxygen, and the generated HCl is absorbed by deionized water.

[0129] After the absorption liquid is filtered through a 0.45μm filter membrane, it is injected into an ion chromatograph (such as Dionex ICS-5000+) to determine Cl - Concentration.

[0130] Calculation: Cl content (wt%) = (Cl - mass / sample mass) x 100%.

[0131] 3. Process parameter monitoring

[0132] Temperature uniformity: 3 thermocouples (such as K-type thermocouples) are arranged in the reaction zone of the closed heating furnace to record the temperature in real time, and whether the maximum temperature difference is within ±20℃ is calculated.

[0133] Air oxygen content: an online gas analyzer (such as ABBAO2020) is used to monitor the oxygen concentration of the inlet air to ensure that it is within the range of 18-21vol%.

[0134] Toluene solution concentration: the acid-base titration method (with phenolphthalein as the indicator, and NaOH standard solution is used for titration) is used to determine the content of hydrochloric acid in toluene, which is indirectly calculated to calculate the adsorption amount of dioxin and the degradation rate of dioxin;

[0135] The specific results are as follows:

[0136] Table 1

[0137]

[0138] As can be seen from Table 1, the method of the present application has a high degradation rate of dioxin, and can effectively inhibit the regeneration of dioxin.

[0139] The preferred embodiments of the present application disclosed above are only used to help illustrate the present application. The preferred embodiments do not describe all the details, and the present application is not limited to the specific embodiments described. Obviously, many modifications and changes can be made according to the content of the present application.

Claims

1. A method for dechlorination and degradation of dioxins and inhibition of their resynthesis by synergistic roasting of steelmaking furnace dust and waste incineration fly ash, characterized in that, The method comprises the following steps: S100: in a high-temperature reaction zone of a closed heating device, waste incineration fly ash and electric furnace ash are added in a mass ratio of 2-6:1, and are roasted together under an air atmosphere for 1-6 hours, and the reaction temperature is 1000-1250 DEG C; through the reaction of ZnO and PbO in the electric furnace ash with HCl generated by the conversion of chlorine-containing organic matter in the waste incineration fly ash, the mineralization of organic chlorine is promoted, and the forward progress of the dechlorination and decomposition reaction of dioxins is promoted; S200: after roasting, a toluene solution is used to purify the reaction tail gas and solid products through a gas washing bottle, and dioxin volatiles are captured and collected; S300: gas chromatography-mass spectrometry technology is used to detect the dioxin content of the solid residue after roasting, so that the degradation rate and the toxicity equivalent meet the requirements; The tail gas purified in the step S200 is subjected to secondary adsorption purification by an adsorption column provided with a composite adsorbent of activated carbon fiber and molecular sieve, so as to ensure that the dioxin emission concentration is ≤0.1 ng-TEQ / Nm 3 ; The active carbon fiber and molecular sieve composite adsorbent are prepared by the following method: (1) precursor pretreatment: the phenolic-based active carbon fiber is carbonized and pretreated in a muffle furnace under a nitrogen atmosphere at a temperature of 400-500 DEG C for 2-3 hours, and the heating rate is controlled to be 5 DEG C / min; then the carbonized active carbon fiber is soaked in a concentrated nitric acid solution with a concentration of 3-5 wt%, and after soaking for 12-15 hours, it is washed with deionized water for multiple times until the pH value of the washing liquid is 7, and finally it is dried in a blowing drying oven at a temperature of 105 DEG C until the weight is constant, and is ready for use; (2) molecular sieve loading: the pretreated active carbon fiber is immersed in an ethanol solution containing ZSM-5 molecular sieve seeds, the mass concentration of the ZSM-5 molecular sieve seeds in the ethanol solution is 10-20 g / L, and the ethanol solution is prepared by mixing anhydrous ethanol and deionized water at a volume ratio of 9:1; under the condition of ultrasonic oscillation at a frequency of 40 kHz and a power of 200 W, the solution is oscillated for 30-40 minutes to make the seeds uniformly adhere to the surface of the fiber, and then the solution is dried in a vacuum drying oven at a temperature of 135-150 DEG C for 4-6 hours; (3) in-situ growth: the active carbon fiber loaded with the seeds is placed in a hydrothermal reaction kettle, and a synthesis solution containing tetraethyl orthosilicate, aluminum isopropoxide and tetrapropylammonium hydroxide is added, the molar ratio of tetraethyl orthosilicate, aluminum isopropoxide and tetrapropylammonium hydroxide in the synthesis solution is 1:0.05:0.3, and the solvent is deionized water; under the condition of a temperature of 160-180 DEG C and a pressure of autogenous pressure, the solution is crystallized for 18-24 hours to make the molecular sieve grow in-situ on the surface of the active carbon fiber; (4) metal modification: the composite adsorbent with in-situ grown molecular sieve is immersed in a manganese nitrate solution containing 1.2-2 wt%, and after immersion for 12-14 hours, it is taken out and dried in an electric heating constant temperature drying oven at a temperature of 75-80 DEG C for 10-12 hours, and then it is roasted in a muffle furnace under an air atmosphere at a temperature of 400-500 DEG C at a heating rate of 5 DEG C / min for 3-5 hours. (5) hydrophobic treatment: the modified composite adsorbent is placed in a toluene solution containing 1.8-3wt% methyltrimethoxysilane, and refluxed in an oil bath at 80-100℃ for 6-12 hours, then filtered through a suction filter, washed with toluene several times, and finally dried in a forced air drying oven at 105℃ to obtain activated carbon fiber and molecular sieve composite adsorbent with hydrophobic groups on the surface.

2. The method of claim 1, wherein, The closed heating equipment is a horizontal or vertical closed heating furnace, and the temperature uniformity of the reaction zone is controlled within ±20℃.

3. The method of claim 1, wherein, The mass ratio of the waste incineration fly ash to the electric furnace dust in the step S100 is 6:1, the calcination temperature is 1100℃, and the calcination time is 5 hours.

4. The method of claim 1, wherein, The ZnO content of the electric furnace dust in the step S100 is ≥6wt%, and the particle size is ≤150μm.

5. The method of claim 1, wherein, The concentration of the toluene solution in the step S200 is 0.05-0.1mol / L, and the solution volume is 500-1000mL.

6. The method of claim 1, wherein, The step S100 further includes pretreatment of the waste incineration fly ash and the electric furnace dust: (1) the electric furnace dust is crushed to a particle size of ≤150μm; (2) the pretreated electric furnace dust is mixed with the waste incineration fly ash.

7. The method of claim 1, wherein, The oxygen content of the air atmosphere in the step S100 is 18-21vol%, and the air flow rate is adjusted to control the temperature rise rate of the reaction zone to be 5-10℃ / min.

8. The method of claim 1, wherein, The dioxin degradation rate in the step S300 is ≥99%, and the toxicity equivalent is ≤0.1μg-TEQ / kg.

9. The method according to any one of claims 1 to 8, characterized in that, The method realizes high-temperature dechlorination degradation of dioxin by the dechlorination effect of ZnO in the electric furnace dust, so that the Cl content in the solid residue is ≤1wt%.

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