Household garbage incineration fly ash granulation collaborative remelting recycling method

Abstract

The invention discloses a method for recycling household garbage incineration fly ash through granulation and remelting cooperation, and belongs to the technical field of hazardous waste treatment and recycling. The method comprises the following steps: detecting the contents of heavy metal, dioxin and soluble chlorine salt in the raw fly ash; dynamically judging and executing washing pretreatment based on a detection result; then adding a composite additive composed of a molding agent, a heavy metal curing agent, a pore forming agent and a dioxin resynthesis inhibitor into the treated fly ash; granulating, wherein the porosity and the diameter of granulated granules are regulated and controlled according to the formulation of the dioxin and the heavy metal content; and finally, the particles are put into an incinerator for collaborative sintering, and products are subjected to resource utilization after separation verification. According to the method, the process parameters of each link are directly calculated by using the pollutant concentration which can be measured in a laboratory, so that the fly ash sintered body and the slag can be separated, monitored and traced, the total amount of heavy metals, dioxin and soluble chlorine salt and the leaching toxicity simultaneously meet related standard limit values, and the method has the advantages of high adaptability, stable effect and good economical efficiency.

Description

Technical Field

[0001] This invention relates to the field of hazardous waste treatment and resource utilization technology, specifically to a method for the granulation and co-recycling of fly ash from municipal solid waste incineration. Background Technology

[0002] Waste incineration fly ash is a solid, powdery material collected by bag filters during the waste incineration process. It includes grate furnace fly ash and fluidized bed fly ash. Fly ash contains large amounts of soluble salts, easily leached heavy metals, and highly toxic organic pollutants (dioxins, furans, etc.). Municipal solid waste incineration fly ash is classified as hazardous waste (HW18) due to its enrichment in heavy metals (such as Pb, Cd, Cr), dioxins, and soluble chlorides (Cl⁻ content reaching 15-30%). The amount of municipal solid waste incinerated has been increasing year by year, and the amount of fly ash generated has also shown a rapid growth trend. Fly ash poses an extremely high environmental risk, characterized by "three highs": high chloride content, high heavy metal concentration, and high persistent organic pollution. The fly ash problem has become a major bottleneck for the waste incineration industry.

[0003] Currently, the treatment and disposal technologies for fly ash from waste incineration are showing a diversified development trend both domestically and internationally. Traditional treatment methods (landfill, stabilization) have problems such as large land occupation and high risk of secondary pollution. While high-temperature melting and sintering technologies and cement kiln co-processing can achieve harmlessness, they rely on external facilities and have high energy consumption. Returning fly ash to the incinerator for co-thermal treatment (co-recycled incinerator) is a promising technology. Its advantage lies in utilizing existing incineration facilities to achieve fly ash reduction, harmlessness, and resource recovery.

[0004] However, existing fly ash co-recycling technologies generally have shortcomings. First, the composition (heavy metals, chlorides, and dioxins, etc.) of fly ash varies greatly depending on its source and time. Some existing processes use relatively fixed pretreatment formulas and operating parameters, lacking the ability to dynamically adjust fly ash characteristics, which may lead to incomplete pollutant removal or unstable resource utilization efficiency. Second, some processes directly return untreated or simply treated fly ash to the furnace, causing chlorides to circulate and accumulate within the incineration system (condensing in the fly ash after volatilization) or enter the slag, leading to increased slag chloride content, resulting in dilution emissions or equipment corrosion problems. Finally, regarding dioxin inhibition and heavy metal stabilization, there is a lack of additive control methods that precisely correlate with the pollutant content of the fly ash itself.

[0005] For example, Chinese patent application CN 117655071 A discloses a method for treating fly ash from municipal solid waste incineration. This method involves washing the fly ash with water to remove chlorine, adding a plasticizer to the washed fly ash, granulating it, and then placing it into a waste incinerator for heat treatment. This achieves a significant reduction in pollutants in the fly ash, and the treated fly ash products are fully utilized or disposed of. However, the composition and pollutant characteristics of fly ash vary considerably across different regions, projects, and time periods. This method does not propose a dynamically adjustable formulation method based on the real-time composition characteristics of the fly ash.

[0006] Chinese patent application CN 117324348 A discloses a co-processing system and method for the thermal treatment of fly ash and municipal solid waste. The method involves adding water and a binder to the fly ash produced by a waste incineration system, mixing and granulating it, and then sending the granulated particles along with the waste to the incinerator for thermal treatment. However, this method returns the granulated fly ash to the incinerator for thermal treatment. In the high-temperature zone of the incinerator, some chloride salts such as sodium chloride and potassium chloride in the fly ash will volatilize and enter the flue gas system, resulting in a cycle of accumulation. Furthermore, the unvolatilized chloride salts will be incorporated into the slag along with the fly ash treatment products. Since sodium chloride and potassium chloride are both soluble salts, this ultimately leads to an increase in the soluble chloride in the slag, posing a dilution and emission problem.

[0007] Chinese patent application CN 117732853 A discloses a solidification and recycling system, method, and application for waste incineration fly ash. This method involves dry granulation of fly ash and a binder to form pellets, followed by layering and pressing of the pellets and combustion aids to create precast blocks. These precast blocks are then fed into the incinerator along with the waste for incineration. This application uses raw ash granulation before incineration. Because the precast blocks are mixed with fuel, they reach a relatively high heat treatment temperature. Data from the heat treatment products shows a low chloride ion content, indicating that most of the chloride salts in the fly ash volatilize into the flue gas and eventually condense and accumulate in the fly ash of the waste incineration system, leading to a cumulative effect over time.

[0008] Chinese patent application CN 115681981 A discloses a technology and method for the immediate recycling of fly ash from waste incineration. This method mixes fly ash with SH additives, polymerizes them into large particles, and feeds them into a waste incinerator, where the high temperature decomposes dioxins and solidifies heavy metals. Both this method and the aforementioned technologies face the problem of ash return to the incinerator. In the high-temperature zone of the incinerator, some chloride salts such as sodium chloride and potassium chloride in the fly ash will volatilize and enter the flue gas system, resulting in cyclic enrichment. Secondly, unvolatilized chloride salts will be incorporated into the slag along with the fly ash treatment products. Sodium chloride and potassium chloride are both soluble salts, ultimately leading to an increase in the soluble chloride in the slag, posing a dilution emission problem.

[0009] Therefore, it is of great significance to develop a fly ash co-processing technology that can precisely control the entire treatment process based on the fly ash composition, and achieve efficient and thorough removal of pollutants, effective separation of chloride salts, and stable resource utilization of products. Summary of the Invention

[0010] Technical Problem Solved: Addressing the problems existing in the prior art, this invention proposes a method for the granulation and co-recycling of municipal solid waste incineration fly ash. This method establishes a closed-loop control system encompassing "detection → pretreatment → compatibility → molding → sintering → verification." Based on real-time monitoring results (heavy metal, chloride, and dioxin content) for each batch of fly ash, the washing, mixing formula (plasticizer, curing agent, pore-forming agent, and inhibitor, etc.), granulation, and furnace feeding parameters are dynamically adjusted to prepare pretreated fly ash into particles meeting specific particle size, porosity, and mechanical strength. The granulated fly ash particles are then fed into the drying or combustion section grate of the incinerator via a conveying and metering device for heat treatment at the high temperature of the incinerator. Ultimately, this achieves effective removal of fly ash pollutants, and the heat-treated fly ash products are recycled along with the bottom ash.

[0011] Technical solution: A method for the granulation and co-recycling of fly ash from municipal solid waste incineration, comprising the following steps:

[0012] Step 1: Fly ash testing: The fly ash produced by the waste incineration system is tested and analyzed. The test items include total heavy metal content, dioxin content, and soluble chloride content.

[0013] Step 2, Pretreatment: Based on the test results from Step 1, determine whether the fly ash needs to be washed with water. If the content of soluble chloride salts in the fly ash exceeds the set threshold X1, or the total heavy metal content exceeds the set threshold X2, then water washing is required. If the determination is yes, then the water washing process parameters are dynamically determined based on the test results, and water washing desalination and heavy metal removal treatment are performed to obtain washed ash. If the determination is no, then the original fly ash is used for subsequent steps.

[0014] Step 3, compatibility: Additives are added to the fly ash obtained in Step 2 for mixing. The additives include plasticizers, heavy metal curing agents, pore-forming agents and dioxin resynthesis inhibitors.

[0015] Step 4: Granulation: The mixture obtained in Step 3 is granulated. The porosity P of the granulated particles is... k Based on the total heavy metal content C of fly ash MH and dioxin-like substance content C DN The calculation is as follows:

[0016] ,

[0017] In the formula, P kP0 represents the porosity of the granulated particles; P0 is the basic porosity, ranging from 0.3 to 0.5; C0 represents the porosity of the granulated particles. MH Total heavy metal content, mg / kg; C DN The content of dioxin-like substances is expressed in ng-TEQ / kg; g and h are empirical coefficients, with g ranging from 0.0012 to 0.0018 (unit: kg / mg) and h ranging from 0.003 to 0.004 (unit: kg / (ng-TEQ)).

[0018] The particle size of granulated particles is determined based on the total heavy metal content (C) of fly ash. MH and dioxin-like substance content C DN The calculation is as follows:

[0019] ,

[0020] Among them, D f D0 represents the diameter of the granulated fly ash, in mm; D0 is the base diameter, ranging from 10 to 15 mm; C MH Total heavy metal content, mg / kg; C DN The value represents the content of dioxin-like substances, ng-TEQ / kg; i and j are empirical coefficients, with i ranging from 0.0008 to 0.0009 (unit: mm·kg / (ng-TEQ)) and j ranging from 0.001 to 0.003 (unit: mm·kg / mg).

[0021] Step 5, Furnace Feeding: The granulated particles obtained in Step 4 are fed into the municipal solid waste incinerator for co-sintering treatment.

[0022] Step 6, Product Separation and Verification: The sintering products are separated from the slag, and the environmental indicators and physical properties of the separated fly ash sintered body are tested and verified.

[0023] Preferably, the heavy metals in step one include at least one of lead, mercury, cadmium, chromium, nickel and copper, and the total heavy metal content is the sum of the detection results of individual heavy metals. The soluble chloride salts include at least one of sodium chloride, potassium chloride and calcium chloride, and the dioxin-like substances are 2,3,7,8-PCDD / Fs.

[0024] Preferably, in step two, the set threshold X1 for the content of soluble chloride salts is 1.5 wt%, and the set threshold X2 for the content of heavy metals is 80 mg / kg.

[0025] Preferably, the water washing process parameters in step two include the water washing pH value, water-ash ratio, and water washing time, wherein the water washing pH value is based on the total heavy metal content C of the fly ash. MH Confirmed, the calculation formula is as follows:

[0026] ,

[0027] In the formula, C MH The total heavy metal content is expressed in mg / kg; a and b are empirical coefficients, with a ranging from 24,000 to 26,000 and b ranging from 0.9 to 0.96.

[0028] The water-ash ratio is based on the soluble chloride content (C) in fly ash. Cl The determination and calculation formula are as follows:

[0029] ,

[0030] In the formula, R WF The water-ash ratio, i.e., the mass ratio of water to fly ash; C Cl denoted as the mass percentage of soluble chloride salts in fly ash; c and d are empirical coefficients, with c ranging from 0.48 to 0.5 and d ranging from 0.095 to 0.098.

[0031] Washing time depends on the soluble chloride content (C) of the fly ash. Cl Confirmed, the calculation formula is as follows:

[0032] ,

[0033] In the formula, T w T0 is the basic washing time, in minutes; C is the washing time. Cl The value represents the mass percentage of soluble chloride salts in fly ash; e and f are empirical coefficients, with e ranging from 0.16 to 0.18 (in min / %) and f ranging from 0.04 to 0.045 (in min / %). 2 ).

[0034] Preferably, the process parameters of the water washing process in step two also include the number of water washing cycles, which is 2-4 stages.

[0035] Preferably, in step three, the amount of pore-forming agent added is 2-10% of the dry weight of fly ash, and the amount of shaping agent added is 5-15% of the dry weight of fly ash.

[0036] Preferably, in step three, the amount of heavy metal curing agent added is 2-15% of the dry weight of fly ash; and the amount of dioxin resynthesis inhibitor added is 1-10% of the dry weight of fly ash.

[0037] Preferably, in step four, the porosity limit of the granulated particles is controlled within the range of 0.25-0.45; the diameter D of the granulated fly ash is... fThe limit control range is 7-15 mm. If the result calculated by the formula exceeds the process range, is lower than the lower limit of the control range, the lower limit shall prevail; if it is higher than the upper limit of the control range, the upper limit shall prevail.

[0038] Preferably, the furnace feeding parameters for the co-sintering treatment in step five are as follows: the temperature of the feeding zone is controlled at 400-800℃, and the calcination reaction time is controlled at 0.5-2 h.

[0039] Preferably, the environmental protection indicators and physical performance testing and verification in step six include: heavy metal leaching concentration testing, dioxin content testing, soluble chloride content testing, and mechanical strength testing. If the test results do not meet the standards, return to step three to adjust the additive ratio or return to step five to adjust the furnace parameters and reprocess.

[0040] Beneficial effects:

[0041] (1) The method provided in this application can be dynamically controlled. By using the detection data of different fly ash, the key process parameters of each link such as water washing, compatibility and granulation can be quantitatively calculated to form a closed-loop control. This overcomes the shortcomings of fixed process parameters and poor adaptability of traditional processes, and ensures that the treatment effect of fly ash with different components is stable and meets the standards. This makes the fly ash sintered body and slag separable, monitorable and traceable, and the total amount of heavy metals, dioxins, soluble chloride salts and leaching toxicity meet the relevant standard limits at the same time.

[0042] (2) The method provided in this application can efficiently remove soluble chloride salts and some heavy metals, and can avoid the problems of chloride salt cycling and excessive chlorine in slag. By rationally adding curing agent and dioxin resynthesis inhibitor during formulation, the efficient stabilization of heavy metals and effective inhibition of dioxin resynthesis are achieved.

[0043] (3) The method provided in this application optimizes the microstructure and macroscopic properties of the sintered body by controlling the granulation porosity and particle size, so that it has sufficient mechanical strength and stability and can realize the efficient resource utilization of fly ash;

[0044] (4) Meanwhile, the water-ash ratio, pH value and additive ratio in the pretreatment stage of this method are all dynamic variables based on the test results. It can flexibly handle various types of fly ash, from high chlorine and high heavy metal to low chlorine and high dioxin. It makes full use of existing incinerator facilities and does not require additional high-temperature melting equipment. It has good economy and adaptability. Attached Figure Description

[0045] Figure 1 This is a process flow diagram of a method for the granulation and co-recycling of fly ash from municipal solid waste incineration according to the present invention. Detailed Implementation

[0046] The present invention will now be further described with reference to the accompanying drawings.

[0047] Definitions:

[0048] Waste incineration fly ash: This is a solid powdery material collected by a bag filter during the waste incineration process. It includes grate furnace fly ash and fluidized bed fly ash. Because fly ash contains a large amount of soluble salts, easily leached heavy metals and highly toxic organic pollutants (dioxins, furans, etc.), it is classified as HW18 hazardous waste.

[0049] Fly ash co-sintering: Fly ash co-sintering technology for municipal solid waste incineration is a treatment method for fly ash (a hazardous waste rich in heavy metals, dioxins, and soluble chlorides) generated during municipal solid waste incineration. This technology involves component analysis and pretreatment of the fly ash (including washing, mixing formulation, and granulation), and adjustment of furnace parameters (such as temperature, atmosphere, and time) based on the analysis results. This allows the fly ash to co-sinter with the slag in the incinerator, ultimately stabilizing and neutralizing the harmful substances in the fly ash, meeting environmental emission standards, and simultaneously improving the resource utilization rate of the fly ash.

[0050] Washed fly ash: Fly ash is washed and desalinated using a tiered washing process. The solid material produced by solid-liquid separation through centrifugation or plate and frame filter press has a moisture content between 28% and 40%.

[0051] Example 1

[0052] A method for the co-processing and recycling of fly ash from municipal solid waste incineration, with a process diagram shown below. Figure 1 The specific steps are as follows:

[0053] Step S1: Fly ash sampling and composition analysis:

[0054] For raw fly ash, the fly ash generated by the waste incineration system is tested and analyzed. Details are as follows:

[0055] (1) Detection of heavy metal content:

[0056] The heavy metal content in fly ash includes at least one of lead (Pb), mercury (Hg), cadmium (Cd), chromium (Cr), nickel (Ni), and copper (Cu). These heavy metals may exist in fly ash in different chemical forms, such as oxides, chlorides, and sulfates. Detection methods: The leaching toxicity of heavy metals was determined using HJ 781-2016 "Leaching Toxicity Method for Heavy Metals in Solid Waste - Acetic Acid Buffer Solution Method," combined with HJ 702-2014 "Determination of Mercury in Solid Waste - Cold Atomic Absorption Spectrophotometry" for specific mercury detection. Result units: The unit for heavy metal content is mg / kg (milligrams per kilogram). The total heavy metal content is the sum of the results of each individual heavy metal test.

[0057] (2) Detection of dioxin-like substances:

[0058] The dioxin-like substances in fly ash mainly include 2,3,7,8-PCDD / Fs. Dioxins are persistent organic pollutants with extremely high toxicity. Detection method: The method employed was HJ 77.3-2008, "Determination of Dioxins in Solid Waste: Isotope Dilution High-Resolution Gas Chromatography-High-Resolution Mass Spectrometry." Quantitative analysis was performed using high-resolution gas chromatography-high-resolution mass spectrometry (HRGC-HRMS). Result unit: The unit for dioxin-like substance content is ng-TEQ / kg (nanogram toxic equivalent per kilogram).

[0059] (3) Detection of soluble chloride content:

[0060] The soluble chloride content in fly ash mainly includes sodium chloride (NaCl), potassium chloride (KCl), and calcium chloride (CaCl2). These chlorides exist in soluble form in fly ash and have a significant impact on subsequent treatment processes. Detection method: HJ 557-2010 "Determination of Chloride in Solid Waste - Ion Chromatography" was used for detection (HJ / T 299-2007 or HJ / T 299-2007 can be used depending on specific process requirements). Soluble chlorides were extracted using a horizontal oscillation method and quantitatively analyzed using ion chromatography (IC). Result unit: The unit for soluble chloride content is mass percentage (wt%).

[0061] Precise detection of heavy metals, dioxins, and soluble chlorides in fly ash provides a scientific basis for subsequent water washing, mixing formulation, granulation, and furnace feed parameter adjustment. These test results not only directly affect the selection of pretreatment processes and parameter settings but also play a crucial role in the environmental performance and mechanical strength of the final sintered body. Therefore, accurate component detection is fundamental to achieving compliant emissions and resource utilization through co-processing and recycling of fly ash. The aforementioned test data is added to the process parameter database, providing a basis for the dynamic adjustment of subsequent process parameters.

[0062] Step S2, Preprocessing:

[0063] Water washing is an important pretreatment step in the co-processing of fly ash for remelting. Its purpose is to remove soluble chlorides and some heavy metals from fly ash through water washing, thereby reducing the negative impact of these harmful substances on the subsequent sintering process.

[0064] The following are the specific operating procedures and parameter determination methods for the water washing process:

[0065] (1) Water washing strategy: First, determine whether the fly ash needs to be washed with water, based on the content of soluble chloride salts in the fly ash (C Cl ) and total heavy metal content (C MHThe decision to perform water washing is determined by the following parameters: If the content of soluble chlorides in the fly ash exceeds a set threshold X1 (1.5 wt% in this example), or the total heavy metal content exceeds a set threshold X2 (80 mg / kg in this example), then water washing is required. The water washing process parameters include the pH value, water-to-ash ratio, number of washing cycles, and washing time.

[0066] (2) Water washing process parameters:

[0067] I) Water washing pH value: The pH value of the water washing has a significant impact on the removal effect. Based on the total heavy metal content (C) in fly ash... MH ), determine the pH value of the water wash.

[0068] The specific pH formula is as follows:

[0069] ,

[0070] Equivalent to:

[0071] ,

[0072] Among them, C MH The total heavy metal content is expressed in mg / kg. a and b are empirical coefficients, where a ranges from 24000 to 26000, with an optimal value of 24688 in this embodiment. b ranges from 0.9 to 0.96, with an optimal value of 0.943 in this embodiment.

[0073] The pH range is 2.2-7.8. If the value calculated by the pH formula exceeds the upper / lower limit of the range, the upper / lower limit of the range shall prevail.

[0074] Experiments revealed that different heavy metal contents and types have different requirements for the optimal pH value for water washing. For example, higher heavy metal contents require lower pH values ​​to promote the dissolution of heavy metals, thereby improving removal efficiency.

[0075] II) Water-to-ash ratio: This refers to the mass ratio of water to fly ash, and this parameter is also crucial to the washing effect. It is determined based on the soluble chloride content (C) in the fly ash. Cl ), determine the water-cement ratio.

[0076] Fly ash washing mainly involves adjusting the mass ratio of water to fly ash (referred to as water-ash ratio) during the washing process to transfer soluble chloride salts and some heavy metals in the fly ash to the washing liquid phase, so that the soluble chloride content in the washed ash is <1wt% (dry basis).

[0077] The formula for calculating the water-cement ratio is as follows:

[0078] ,

[0079] In the formula: RWF Water-to-ash ratio (mass ratio of water to fly ash); C Cl The soluble chloride content in fly ash is wt%; c and d are empirical coefficients, where c ranges from 0.48 to 0.5, preferably 0.4976; and d ranges from 0.095 to 0.098, preferably 0.0967.

[0080] The upper and lower limits of the water-cement ratio are 1.2-4. When the value calculated by the water-cement ratio formula exceeds the upper / lower limit of the range, the upper / lower limit of the range shall prevail.

[0081] The water-ash ratio here refers to the first stage of fly ash washing (the stage with the most concentrated washing liquid). It should be noted that only the first stage output liquid enters the evaporation process during the washing process. The water from the other two stages goes to the previous stage. In other words, the first stage is the one that truly affects the evaporation energy consumption and has the most significant impact on the washing effect. The water-ash ratio of other stages can be a fixed value such as (1:3) or the same as the first stage. In this embodiment, the water-ash ratio of other stages is kept consistent with the water-ash ratio of the first stage.

[0082] III) Washing Cycles and Duration: The number and duration of washing cycles also significantly affect the removal efficiency. This is based on the soluble chloride content (C...) in the fly ash. Cl This allows us to determine the number of wash cycles and the duration of the wash.

[0083] The number of washing cycles is 2-4, with 3 being preferred. The specific number of cycles depends on the composition of the fly ash and the specific operating process. If all chloride salts are soluble and the fly ash particle size is uniform and stable (center particle size less than or equal to 200 mesh), choose 2-3. If the fly ash particle size is large (center particle size greater than 200 mesh), choose 4.

[0084] The formula for water washing time is as follows:

[0085] ,

[0086] Where T w T0 is the washing time, in minutes; T0 is the basic washing time, ranging from 15-18 minutes, preferably 16.5 minutes; C Cl The value represents the mass percentage of soluble chloride salts in fly ash; e and f are empirical coefficients, with e ranging from 0.16 to 0.18, preferably 0.1714, in units of min / %; and f ranging from 0.04 to 0.045, preferably 0.0428, in units of min / %. 2 .

[0087] Step S3, Compatibility (Mixing Formulation):

[0088] In the co-processing of fly ash from municipal solid waste incineration, the rational selection and proportioning of additives are crucial for improving the treatment efficiency and environmental performance of fly ash.

[0089] The additives used in this embodiment consist of a plasticizer, a heavy metal curing agent, a pore-forming agent, and a dioxin resynthesis inhibitor. The amount of plasticizer added is 5-15% of the dry weight of fly ash, the amount of heavy metal curing agent is 2-15% of the dry weight of fly ash, the amount of pore-forming agent is 2-10% of the dry weight of fly ash, and the amount of dioxin resynthesis inhibitor is 1-10% of the dry weight of fly ash. The functions of each additive are as follows:

[0090] (1) Plasticizer: To improve the mechanical strength of the granulated particles and ensure that the particles do not pulverize during transportation and subsequent furnace heat treatment. It is composed of clay-based materials (45-60 wt%), sodium silicate (25-35 wt%), and bentonite (10-20 wt%). Through reasonable proportioning, the mechanical strength of fly ash particles can be significantly enhanced, and their stability in subsequent processing can be improved.

[0091] (2) Heavy metal solidifying agent, used to transform the chemical form of heavy metals and reduce their leaching concentration. It is composed of one or more of the following: active SiO2 (2% by dry weight of fly ash), silica sol containing Al2O3 (1% by dry weight of fly ash), fly ash (6% by dry weight of fly ash), and granulated blast furnace slag (3% by dry weight of fly ash). By adding it appropriately, the heavy metals can be stabilized in subsequent treatment processes, reducing their leaching risk.

[0092] (3) Pore-forming agent, which decomposes or volatilizes during heat treatment (100-500℃ range), creating pores and providing diffusion channels for the thermal desorption of dioxins during heat treatment. It consists of at least one of carbonates and starch. By adding it appropriately, the porosity of fly ash particles can be effectively increased, promoting the thermal desorption of dioxins and reducing their generation in subsequent treatment processes.

[0093] (4) Dioxin resynthesis inhibitors can react with metal catalysts in fly ash, passivating the metal catalysts and consuming the chlorine source required for dioxin formation. The composite inhibitors, composed of calcium-based and phosphorus-based substances, have an adjustable calcium-to-phosphorus molar ratio within a certain range (e.g., a Ca:P molar ratio of 2:1). By adding them appropriately, it can be ensured that the inhibitors can effectively passivate the metal catalysts and consume the chlorine source, thereby reducing dioxin formation.

[0094] Step S4, Granulation:

[0095] Granulation is an important step in the co-processing of fly ash in the incinerator. Its purpose is to improve the mechanical strength and sintering performance of fly ash by controlling the porosity and particle size of the fly ash particles, thereby ensuring that the fly ash can be stably sintered in the incinerator.

[0096] The following are the specific operating procedures and parameter determination methods for the granulation process:

[0097] (1) Porosity, the porosity of granulated particles (P) k Porosity has a significant impact on the mechanical strength and sintering properties of fly ash particles. Porosity refers to the ratio of the volume of pores within a particle to its total volume. Higher porosity can improve the air permeability of the particles, but may reduce mechanical strength. Therefore, it is necessary to precisely control the porosity based on the composition of the fly ash and its state after pretreatment. The specific porosity formula is:

[0098]

[0099] Among them, P k P0 represents the porosity of the granulated particles, dimensionless; P0 is the basic porosity, ranging from 0.3 to 0.5, preferably 0.32 in this embodiment; C0 DN This refers to the content of dioxin-like substances, expressed in ng-TEQ / kg; C MH The total heavy metal content is expressed in mg / kg; g and h are empirical coefficients, where g ranges from 0.0012 to 0.0018, and is preferably 0.0015 in this embodiment, in kg / mg; h ranges from 0.003 to 0.004, and is preferably 0.0033 in this embodiment, in kg / (ng-TEQ).

[0100] The porosity limit control range is 0.25-0.45. If the value calculated by the porosity formula exceeds the upper / lower limit of the range, the upper / lower limit of the range shall prevail.

[0101] Experiments revealed that the total heavy metal content (C) MH ) and dioxin-like substances content (C DN This has a significant impact on porosity. For example, a higher content of soluble chlorides may require a higher porosity to improve permeability, thereby promoting sintering.

[0102] (2) Particle size refers to the average diameter of the particles. A suitable particle size can ensure that the fly ash is evenly distributed in the incinerator and improve the sintering efficiency. Therefore, it is necessary to accurately control the particle size according to the composition of the fly ash and its state after pretreatment.

[0103] The specific granularity formula is as follows:

[0104]

[0105] Among them, D f The diameter of the granulated fly ash (spherical or cylindrical; if cylindrical, the aspect ratio is controlled to be 1.5-4), in mm; D0 is the base diameter, ranging from 10-15, preferably 12 in this embodiment, in mm; C DN This refers to the content of dioxin-like substances, expressed in ng-TEQ / kg; C MHThe total heavy metal content is expressed in mg / kg; i and j are empirical coefficients, where i ranges from 0.0008 to 0.0009 (unit: mm·kg / (ng-TEQ). Note that this term has a very weak effect under normal circumstances because dioxins usually do not reach high concentrations that affect particle size, and only play a role under special circumstances). In this embodiment, i is preferably 0.00085; j ranges from 0.001 to 0.003 (unit: mm·kg / mg. The dimension of the parameter cancels out the dimension of this term, leaving only mm after cancellation). In this embodiment, j is preferably 0.0015. The diameter limit is controlled within the range of 7-15 mm. If the calculated result exceeds this range, the corresponding extreme value is taken.

[0106] Step S5: Incineration in the furnace:

[0107] Fly ash co-recycling, with the incinerator as the primary carrier, requires highly adaptable and broad-spectrum pre-processes to reduce dependence on furnace parameters and impact on the incineration process. Therefore, adjusting furnace parameters is not a necessary step. However, precise adjustment of feed parameters has a positive impact on ensuring sufficient sintering of fly ash within the incinerator and meeting environmental requirements, thus making it an alternative process step and method.

[0108] The following are the specific steps for adjusting furnace feed parameters and the methods for determining those parameters:

[0109] 1. Temperature: Adjusting the temperature after the fly ash enters the furnace is a key factor affecting the sintering effect and pollutant removal efficiency. Excessive temperature may lead to energy waste and equipment damage, while insufficient temperature may prevent the effective sintering of harmful substances in the fly ash. Therefore, the furnace entry temperature needs to be precisely determined based on the composition of the fly ash and its pre-treatment state.

[0110] The temperature range of the furnace feeding zone is controlled between 400-800℃, and in this embodiment, the preferred temperature is 550℃.

[0111] 2. Time: Adjusting the time after the fly ash is fed into the furnace is another key factor affecting the sintering effect and pollutant removal efficiency. Too short a time may result in insufficient sintering of harmful substances in the fly ash, while too long a time may lead to energy waste and equipment damage. Therefore, the feeding time needs to be precisely determined based on the composition of the fly ash and its pre-treatment state. For example, a higher heavy metal content may require a longer time to ensure the stabilization of heavy metals, while a higher dioxin content may require an appropriate amount of time to inhibit the resynthesis of dioxins.

[0112] The calcination reaction time is controlled within the range of 0.5-2 h, and in this embodiment, it is preferably 1 h.

[0113] Step S6, Product Separation and Performance Verification:

[0114] In the co-processing of fly ash from municipal solid waste incineration, the fly ash particles entering the furnace must be separated from the slag, and the treatment effect must be verified. The separation process includes cooling and screening, magnetic separation and air separation, supplemented by water washing and flotation when necessary, to ensure effective separation of fly ash and slag. Result verification covers heavy metal leaching concentration, dioxin content, soluble chloride content, and mechanical strength testing, and must comply with relevant environmental standards. If standards are not met, corresponding measures are taken: if heavy metals exceed the standard, return to step S3 to adjust the additive ratio or return to step S5 to adjust the furnace feed parameters and reprocess; if dioxins exceed the standard, return to step S3 to adjust the additive ratio (increase the amount of dioxin resynthesis inhibitor) or return to step S5 to adjust the furnace feed parameters and reprocess; if soluble chlorides exceed the standard, return to step S2 for pretreatment or return to step S5 to adjust the furnace feed parameters and reprocess; if mechanical strength is insufficient, return to step S3 to adjust the additive ratio (increase the amount of plasticizer) or return to step S4 to optimize the granulation process. Fly ash particles that still fail to meet standards after these adjustments will be safely packaged and sent to a professional hazardous waste disposal center for harmless treatment, ensuring the environmental friendliness and safety of the entire treatment process and preventing secondary pollution to the environment.

[0115] Example 2: Co-processing of high-chlorine and high-heavy-metal fly ash for remelting

[0116] Same as Example 1, except that this example is for fly ash with high chlorine and high heavy metal content from southern Jiangsu.

[0117] Step S1, Fly Ash Detection: The fly ash was detected using the method described above, and the results are as follows:

[0118] Heavy metal content: Pb: 120 mg / kg, Cd: 15 mg / kg, Cr: 80 mg / kg; total heavy metal content is 215 mg / kg, which exceeds the threshold X2 = 80 mg / kg;

[0119] Soluble chloride content: 28 wt% (far exceeding the threshold X1=1.5 wt%);

[0120] Dioxin content: 50 ng-TEQ / kg.

[0121] Step S2, Preprocessing:

[0122] Based on the detection results of step S1, determine whether the fly ash needs to be washed with water.

[0123] The soluble chloride content in fly ash was 28 wt%, far exceeding the set threshold X1 = 1.5 wt%.

[0124] The total heavy metal content exceeds the set threshold X2=80 mg / kg.

[0125] It was determined that a water wash was required.

[0126] The water washing process parameters are as follows:

[0127] pH value calculation for water washing:

[0128] ,

[0129] Where b is 0.96 and a is 24000, the calculated pH is approximately 4.9;

[0130] Water-cement ratio calculation:

[0131] ,

[0132] Where c is 0.5 and d is 0.096, the calculation yields:

[0133] Water-cement ratio = 0.5 + 0.096 * 28 = 3.188;

[0134] Washing time:

[0135] ,

[0136] Where T0 is 15, e is 0.18, and f is 0.04, the calculation yields:

[0137] Washing time = 15 - 0.18 * 28 + 0.04 * 28 * 28 = 41.32 minutes

[0138] Washing cycles: 3 stages;

[0139] The chlorine content in the fly ash was tested after washing. The chlorine content after washing was 0.8 wt% (dry basis).

[0140] Step S3, Compatibility (Amount added based on dry fly ash mass):

[0141] In this embodiment, the amount of plasticizer added is 5%; the amount of heavy metal curing agent added is 7.5%; the amount of pore-forming agent (ammonium bicarbonate) added is 4%; and the amount of dioxin resynthesis inhibitor added is 5%.

[0142] Step S4, Granulation:

[0143] Calculation of porosity of granulated particles:

[0144] ,

[0145] Where P0 is 0.32, g is 0.0015, and h is 0.0033, the calculation yields:

[0146] Porosity = 0.32 + 0.0015 * 215 + 0.0033 * 50 = 0.8075. The calculated porosity exceeds the limit value, so we take the limit value range of 0.25-0.45 and choose 0.45.

[0147] Particle size of pore-forming particles:

[0148] ,

[0149] Where D0 is 10 mm, i is 0.0008, and j is 0.001, the calculation yields:

[0150] The diameter of the granulated fly ash is approximately 9.8 mm (10 - 0.0008 * 215 - 0.001 * 50).

[0151] Step S5, Place in the furnace:

[0152] Furnace feeding zone temperature: 550℃ (feeding in the drying section);

[0153] Calcination reaction time: 1 hour.

[0154] Step S6, Product Separation and Verification:

[0155] The fly ash particles are separated from the slag after entering the furnace. The separation process includes cooling screening and magnetic separation and air separation. The composition of the separated fly ash is then tested.

[0156] Pollutant removal rate:

[0157] Chloride removal rate: 97.2% (soluble chlorine in slag <0.5%);

[0158] Heavy metal leaching concentrations: Pb: 0.1 mg / L, Cd: 0.02 mg / L, Cr: 0.3 mg / L (all below the limits specified in GB 5085.3-2007);

[0159] Dioxin content: <0.1 ng-TEQ / kg (degradation rate 99.8%).

[0160] Resource utilization results:

[0161] The granulated particles have a compressive strength of 3.2 MPa and a drop strength of 5 times from 2.5m.

[0162] The slag is used to make permeable bricks, and the fly ash is 100% recycled.

[0163] The total amount of heavy metals, dioxins, soluble chlorides, and leaching toxicity all meet the relevant standard limits.

[0164] Example 3: Co-processing of low-chlorine, high-dioxin fly ash exceeding standard for remelting

[0165] Same as Example 1, except that this example targets low-chlorine, high-dioxin fly ash from Zhejiang province.

[0166] Step S1, Fly Ash Detection: The fly ash was detected using the method described above, and the results are as follows:

[0167] Heavy metal content: Pb: 45 mg / kg, Cd: 5 mg / kg, Cr: 30 mg / kg, total heavy metal content is 80 mg / kg, the total heavy metal content does not exceed the threshold X2=80 mg / kg;

[0168] Soluble chloride content: 1.2 wt% (below threshold X1=1.5 wt%);

[0169] Dioxin content: 120 ng-TEQ / kg (exceeding the standard).

[0170] Step S2, Preprocessing:

[0171] Based on the detection results of step S1, determine whether the fly ash needs to be washed with water.

[0172] The soluble chloride content in fly ash was 1.2 wt%, which is lower than the set threshold X1 = 1.5 wt%.

[0173] The total heavy metal content did not exceed the set threshold X2 = 80 mg / kg.

[0174] It was determined that no water washing was required.

[0175] Step S3, Compatibility (Amount added based on dry fly ash mass):

[0176] In this embodiment, the amount of shaping agent added is 6%; the amount of heavy metal curing agent added is 2%; the amount of pore-forming agent (ammonium bicarbonate) added is 4%; and the amount of dioxin resynthesis inhibitor added is 10%.

[0177] Step S4, Granulation:

[0178] Calculation of porosity of granulated particles:

[0179] ,

[0180] Where P0 is 0.32, g is 0.0015, and h is 0.0033, the calculation yields:

[0181] Porosity = 0.32 + 0.0015 * 80 + 0.0033 * 120 = 0.836. The calculated porosity exceeds the limit value, so we take the limit value range of 0.25-0.45 and choose 0.45.

[0182] Particle size of pore-forming particles:

[0183] ,

[0184] Where D0 is 12 mm, i is 0.00085, and j is 0.0015, the calculation yields:

[0185] The diameter of the granulated fly ash is approximately 11.8 mm (12 - 0.00085 * 80 - 0.0015 * 120).

[0186] Step S5, Place in the furnace:

[0187] Furnace feeding zone temperature: 800℃ (feeding in the drying section);

[0188] Calcination reaction time: 0.5 hours.

[0189] Step S6, Product Separation and Verification:

[0190] The fly ash particles are separated from the slag after entering the furnace. The separation process includes cooling screening and magnetic separation and air separation. The composition of the separated fly ash is then tested.

[0191] Pollutant removal rate:

[0192] Chloride removal rate: over 90%;

[0193] Dioxin content: <0.05 ng-TEQ / kg (degradation rate 99.96%);

[0194] Heavy metal leaching concentrations: Pb: 0.05 mg / L, Cd: 0.01 mg / L, Cr: 0.15 mg / L (all met the standards).

[0195] Resource utilization results:

[0196] The granulated particles have a compressive strength of 2.8 MPa and a drop strength of 4 times at a height of 2.5 m.

[0197] Fly ash, as a substitute for bottom ash in incinerators, saves 12,000 tons of natural sand and gravel annually.

[0198] The total amount of heavy metals, dioxins, soluble chlorides, and leaching toxicity all meet the relevant standard limits.

[0199] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for the granulation and co-recycling of fly ash from municipal solid waste incineration, characterized in that, The steps are as follows: Step 1: Fly ash testing: The fly ash produced by the waste incineration system is tested and analyzed. The test items include total heavy metal content, dioxin content, and soluble chloride content. Step 2, Pretreatment: Based on the test results of Step 1, determine whether the fly ash needs to be washed with water. If the content of soluble chloride salts in the fly ash exceeds the set threshold X1, or the total heavy metal content exceeds the set threshold X2, then water washing is required. If the determination is yes, then the water washing process parameters are dynamically determined based on the test results, and water washing desalination and heavy metal removal treatment are carried out to obtain water-washed ash. If the determination is no, then use the original fly ash for subsequent steps; Step 3, compatibility: Additives are added to the fly ash obtained in Step 2 for mixing. The additives include plasticizers, heavy metal curing agents, pore-forming agents and dioxin resynthesis inhibitors. Step 4: Granulation: The mixture obtained in Step 3 is granulated. The porosity P of the granulated particles is... k Based on the total heavy metal content C of fly ash MH and dioxin-like substance content C DN The calculation is as follows: ， In the formula, P k P0 represents the porosity of the granulated particles; P0 is the basic porosity, ranging from 0.3 to 0.5; C0 represents the porosity of the granulated particles. MH Total heavy metal content, mg / kg; C DN The content of dioxin-like substances is expressed in ng-TEQ / kg; g and h are empirical coefficients, with g ranging from 0.0012 to 0.0018 and h ranging from 0.003 to 0.

004. The particle size of granulated particles is determined based on the total heavy metal content (C) of fly ash. MH and dioxin-like substance content C DN The calculation is as follows: ， Among them, D f D0 is the diameter of the granulated fly ash, in mm; D0 is the base diameter, ranging from 10 to 15 mm; C MH Total heavy metal content, mg / kg; C DN The content of dioxin-like substances is expressed in ng-TEQ / kg; i and j are empirical coefficients, with i ranging from 0.0008 to 0.0009 and j ranging from 0.001 to 0.

003. Step 5, Furnace Feeding: The granulated particles obtained in Step 4 are fed into the municipal solid waste incinerator for co-sintering treatment. Step 6, Product Separation and Verification: The sintering products are separated from the slag, and the environmental indicators and physical properties of the separated fly ash sintered body are tested and verified.

2. The method for co-processing and recycling fly ash from municipal solid waste incineration as described in claim 1, characterized in that, In step one, the heavy metals include at least one of lead, mercury, cadmium, chromium, nickel, and copper. The total heavy metal content is the sum of the detection results of individual heavy metals. Soluble chlorides include at least one of sodium chloride, potassium chloride, and calcium chloride. Dioxins are 2,3,7,8-PCDD / Fs.

3. The method for co-processing and recycling fly ash from municipal solid waste incineration as described in claim 1, characterized in that, In step two, the set threshold X1 for the content of soluble chloride salts is 1.5 wt%, and the set threshold X2 for the content of heavy metals is 80 mg / kg.

4. The method for co-processing and recycling fly ash from municipal solid waste incineration as described in claim 1, characterized in that, The water washing process parameters in step two include the water washing pH value, water-ash ratio, and water washing time. The water washing pH value is determined based on the total heavy metal content (C) of the fly ash. MH Confirmed, the calculation formula is as follows: ， In the formula, C MH The total heavy metal content is expressed in mg / kg; a and b are empirical coefficients, with a ranging from 24,000 to 26,000 and b ranging from 0.9 to 0.

96. The water-ash ratio is based on the soluble chloride content (C) in fly ash. Cl The determination and calculation formula are as follows: ， In the formula, R WF The water-ash ratio, i.e., the mass ratio of water to fly ash; C Cl denoted as the mass percentage of soluble chloride salts in fly ash; c and d are empirical coefficients, with c ranging from 0.48 to 0.5 and d ranging from 0.095 to 0.

098. Washing time depends on the soluble chloride content (C) of the fly ash. Cl Confirmed, the calculation formula is as follows: ， In the formula, T w T0 is the basic washing time, in minutes; C is the washing time. Cl denoted as the mass percentage of soluble chloride salts in fly ash; e and f are empirical coefficients, with e ranging from 0.16 to 0.18 and f ranging from 0.04 to 0.

045.

5. The method for co-processing and recycling fly ash from municipal solid waste incineration as described in claim 4, characterized in that, The process parameters for the water washing process in step two also include the number of water washing cycles, which is 2-4 stages.

6. The method for co-processing and recycling fly ash from municipal solid waste incineration as described in claim 1, characterized in that, In step three, the amount of pore-forming agent added is 2-10% of the dry weight of fly ash, and the amount of shaping agent added is 5-15% of the dry weight of fly ash.

7. The method for co-processing and recycling fly ash from municipal solid waste incineration as described in claim 1, characterized in that, In step three, the amount of heavy metal curing agent added is 2-15% of the dry weight of fly ash, and the amount of dioxin resynthesis inhibitor added is 1-10% of the dry weight of fly ash.

8. The method for co-processing and recycling fly ash from municipal solid waste incineration as described in claim 1, characterized in that, In step four, the porosity limit of the granulated particles is controlled within the range of 0.25-0.45; the diameter D of the granulated fly ash... f The limit control range is 7-15 mm. If the result calculated by the formula exceeds the process range, is lower than the lower limit of the control range, the lower limit shall prevail; if it is higher than the upper limit of the control range, the upper limit shall prevail.

9. The method for co-processing and recycling fly ash from municipal solid waste incineration as described in claim 1, characterized in that, The furnace feeding parameters for the co-sintering treatment in step five are as follows: the temperature of the feeding zone is controlled at 400-800℃, and the calcination reaction time is controlled at 0.5-2 h.

10. The method for co-processing and recycling fly ash from municipal solid waste incineration as described in claim 1, characterized in that, The environmental protection indicators and physical performance testing and verification in step six include: heavy metal leaching concentration testing, dioxin content testing, soluble chloride content testing, and mechanical strength testing. If the test results do not meet the standards, return to step three to adjust the additive ratio or return to step five to adjust the furnace parameters and reprocess.

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