Method for improving activity of detoxified fly ash and application thereof

Abstract

The application discloses a method for improving activity of detoxified fly ash, and the method comprises the following steps: pretreating waste incineration fly ash through low-temperature thermal decomposition, washing the fly ash three times, separating the fly ash through plate-frame pressure filtration, crushing and sieving to obtain detoxified fly ash; uniformly mixing the detoxified fly ash with a composite activator in a certain proportion, pre-grinding the mixture to a specific surface area of 400-500 m 2 / kg, wet heat curing the ground product, adding a microwave synergist into the detoxified fly ash-based active powder after the curing, synergistically activating the product under microwave-assisted heating, adding an organic silicon water repellent to the powder for surface modification, adding triethanolamine to the powder for auxiliary grinding, and superfine grinding the activated product to a specific surface area of 600-800 m 2 / kg, so that the detoxified fly ash with improved activity is obtained. The method for improving activity of detoxified fly ash adopts a step-by-step activation method of grading grinding-chemical activation-wet heat curing-microwave activation, breaks through a single technical bottleneck, and realizes the dual goals of activity improvement and heavy metal stability.

Description

Technical Field

[0001] This invention belongs to the field of solid waste resource utilization technology, specifically relating to a method for enhancing the activity of detoxified fly ash and its application. Background Technology

[0002] Fly ash from waste incineration is classified as hazardous waste due to the presence of dioxins and heavy metals. After being detoxified by washing and heat treatment, it can be used as a raw material for building materials, but problems such as low activity and insufficient utilization still exist.

[0003] Existing technologies mostly employ single chemical activation (such as alkali activation) or physical grinding, which still have the following drawbacks:

[0004] (1) Low activation efficiency; a single activator is insufficient to destroy the stable glassy structure in fly ash.

[0005] (2) Limited activity enhancement, lack of matching with optimized minerals, resulting in insufficient hydration product generation;

[0006] (3) High cost. Some processes require high-temperature calcination to change the crystal phase composition, resulting in high energy consumption and cost.

[0007] In existing technologies, a single alkali activator (sodium hydroxide) is used to improve activity, but this suffers from low activation efficiency and a tendency for alkali to return. Mechanical grinding combined with mineral modification is used, but the risk of secondary release of heavy metals remains unresolved. Calcination activation is used to improve activity, but this method is energy-intensive and results in severe particle agglomeration. All of these methods generally suffer from limited activity improvement, complex processes, or uncontrolled environmental risks. Summary of the Invention

[0008] To address at least one of the above problems, the present invention provides a method for enhancing the activity of detoxified fly ash and its application.

[0009] To achieve the above objectives, the present invention employs the following technical means:

[0010] The first aspect of the present invention provides a method for enhancing the activity of detoxifying fly ash, comprising the following steps:

[0011] S1. The waste incineration fly ash is pretreated by low temperature pyrolysis, washed in three stages, and separated by plate and frame filter press to obtain detoxified fly ash products. The detoxified fly ash products are crushed and screened to obtain detoxified fly ash.

[0012] S2. Detoxifying fly ash and composite activator are thoroughly mixed at a mass ratio of (70%~85%):(15%~30%) and then pre-ground to a specific surface area of ​​400~500 m² / kg; the composite activator is composed of mineral powder, fly ash and gypsum.

[0013] S3. The product after grinding S2 is cured in a humid heat at 50-70℃ and humidity ≥90% for 6 hours.

[0014] S4. After curing, add a microwave synergist to the detoxified fly ash-based active powder and enhance its activation under microwave-assisted heating; the microwave synergist includes silica slag powder and ferrous oxide;

[0015] S5. Cool the output powder after completing step S4, add 0.5%~1.5% organosilicon hydrophobic agent for surface modification, add 0.1%~0.5% triethanolamine to assist grinding, and then perform ultrafine grinding on the activated material to a specific surface area of ​​600~800 m² / kg to obtain detoxified fly ash with enhanced activity.

[0016] The ultrafine grinding process uses airflow grinding technology, where high-speed airflow (300-500m / s) drives the particles to collide and crush. The built-in classifying wheel realizes dynamic particle size control, controlling the particle size D50≤5μm.

[0017] In some embodiments of the present invention, in step S2, the mass ratio of mineral powder: fly ash: gypsum in the composite activator is (40%~60%):(30%~50%):(10%~20%). The mineral powder in the composite activator must meet the national standard GB / T 18046-2017 for S95 grade commercially available slag, with the following main technical indicators: specific surface area (m2 / kg) ≥400, 7-day activity index ≥70%, 28-day activity index ≥95%, fluidity ratio ≥95%, initial setting time ratio ≤200%, sulfur trioxide (mass fraction) ≤4%, and chloride ion (mass fraction) ≤0.06%; the fly ash must be Grade II low-calcium ash, meeting GB / T 1596-2017, with the following main technical indicators: water requirement ratio ≤105%, SiO2+Al2O3 ≥70%, sulfur trioxide (mass fraction) ≤3%, and 28-day activity index ≥75%; the gypsum must be industrial by-product gypsum, meeting GB / T 21371-2019, with the following main technical indicators: gypsum grade ≥75%, chloride ion (mass fraction) ≤0.5%, and moisture content ≤10%.

[0018] In some embodiments of the present invention, in step S4, the mass ratio of silicon slag powder to ferrous oxide in the microwave enhancer is (90-95%):(5-10%).

[0019] In some embodiments of the present invention, in step S4, the amount of microwave synergist is 5-7% of the mass of the detoxifying fly ash-based active powder.

[0020] In some embodiments of the present invention, in step S4, the microwave-assisted heating conditions are: microwave frequency 2.45 GHz, power density 3~5 W / g.

[0021] In some embodiments of the present invention, in step S1, the low-temperature thermal decomposition pretreatment method is as follows: under oxygen-free conditions and a temperature of 350-400℃, the dioxins in the fly ash are dechlorinated and detoxified.

[0022] In some embodiments of the present invention, in step S1, the detoxified fly ash product obtained by plate and frame filter press separation has a moisture content of 15-20%. The filter press equipment in this step is a novel air-source plate and frame filter press with a feed pressure of 6-10 kg / cm³. 2 Water pressing pressure 12-16 kg / cm 2 Air pressing pressure 4.5-10 kg / cm 2 Pressing time: 10-15 minutes.

[0023] In some embodiments of the present invention, in step S1, the condition for crushing and sieving the detoxified fly ash product is that it passes through a 75μm sieve with a residue not exceeding 15%. In this step, a vertical crusher is used, employing multiple layers of blades and a chain crusher, which effectively achieves multiple effects of crushing, grinding, and granulation, and allows for a material moisture content of 25-50%.

[0024] The dioxin, heavy metal, and soluble chloride content of the detoxified fly ash treated in step S1 must meet the requirements of the "Technical Specification for Pollution Control of Fly Ash from Municipal Solid Waste Incineration" (HJ 1134-2020): the dioxin content of the detoxified fly ash products shall not exceed 50 ng-TEQ / kg, the concentration of heavy metals in the leachate prepared according to HJ 557 shall not exceed the first-level standard of the maximum allowable emission concentration of Class II pollutants in GB 8978, and the soluble chloride content shall not exceed 1%. It shall also be identified as solid waste according to GB 34330 and managed as general industrial solid waste.

[0025] A second aspect of the present invention provides an activity-enhanced detoxifying fly ash prepared according to the method described in the first aspect.

[0026] The third aspect of the present invention provides the application of the activity-enhanced detoxified fly ash described in the second aspect, wherein the activity-enhanced detoxified fly ash is used as a composite admixture in the production of concrete, as an active admixture in the production of cement, as a low-carbon cementitious material to replace 30-50% of cement in the production of cement products, and as an inorganic binder in roadbed materials for stabilizing crushed stone or solidifying soil.

[0027] Beneficial effects of the present invention

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The detoxified fly ash product has a low moisture content, which ensures the particle size distribution during pre-crushing and provides a small amount of reaction water for the subsequent composite chemical activation. After the activator is formulated and initially mixed, pre-grinding increases the surface defects of the powder particles, which is beneficial for Ca... 2+ Ion penetration and dissolution of silicon and aluminum in mineral powder and fly ash; detoxification of large amounts of calcium in fly ash and gypsum. 2+ It can actively interact with active anions such as silicate and aluminate in an alkaline environment, generating hydration products such as CSH, CAH gels, and ettringite (AFt). The CaO-Al2O3-SiO2 glass in the mineral powder, in the alkaline environment provided by the detoxification fly ash and the SO4 provided by the gypsum, 2- Depolymerization occurs, generating CSH gel and ettringite (AFt). Active SiO2 in fly ash reacts with free CaO in detoxified fly ash to generate secondary hydration products, forming a dense network structure and enhancing the activity of the detoxified fly ash products. Aging and curing accelerate ion diffusion and promote the formation of a gel cross-linking network. Microwave selective heating of polar substances such as Ca(OH)2 in fly ash alters the surface chemical state of the material, promoting the desorption or rearrangement of surface hydroxyl groups (-OH), exposing more CaO. 2+ Active sites; inhibiting surface carbonization and reducing the probability of surface carbonation: CaO, Ca(OH)2 → CaCO3. Furthermore, the Fe element in the microwave synergist has a good microwave absorption effect, high electromagnetic energy conversion efficiency, and good projection properties. It can effectively bombard and destroy the silicon-oxygen tetrahedral structure inside and on the surface of powder particles, significantly breaking chemical bonds and maintaining a highly active surface. After ultrafine grinding, the surface energy of the particles increases, promoting ion migration and crystal nucleation. The small amount of heavy metals in the detoxified fly ash forms isomorphous substitution structures with silicate minerals. Simultaneously, the formed cementitious mineral phase has a strong stabilizing and binding effect on heavy metals through adsorption and encapsulation. The organosilicon-modified layer blocks water molecule penetration, providing double protection for leaching safety. The above method, by combining mechanical, chemical, and microwave treatments, achieves multi-dimensional coupled activation of the detoxified fly ash, greatly enhancing its activity.

[0030] This invention employs a step-by-step activation method—graded grinding, chemical activation, moist heat curing, and microwave activation—to enhance the activity of detoxified fly ash, overcoming the bottleneck of single-technology approaches and achieving the dual goals of activity enhancement and heavy metal stabilization. During the detoxification treatment stage of waste incineration fly ash, some inactive substances are separated and removed, reducing calorific value; a large amount of hydrated product gel is formed during product pre-crushing, enhancing activity; by using a suitable activator formulation, particle size decreases, specific surface area increases, and activity is further enhanced; pre-grinding, aging, and microwave activation strengthen and modify the product surface, promoting chemical reactions and mineral crystal transformation; secondary ultrafine grinding of the activated product reduces surface static electricity, prevents powder aggregation, and forms high specific surface area powder, resulting in a significant increase in activity.

[0031] The integrated activation scheme of this invention employs a combined physical-chemical approach, maximizing the activity of detoxified fly ash through synergistic regulation of specific surface area, microscopic mineral crystal phase, and surface energy. This invention utilizes a ternary composite activation system of mineral powder, fly ash, and gypsum, which improves activity by more than 15% compared to a single activator. The cost of the composite activator is 40-60% lower than that of soda ash activation. The entire process produces no strong acid / alkali wastewater discharge, meeting green building material standards. Furthermore, the energy consumption of the graded grinding process is reduced by less than 40% compared to traditional processes. Detailed Implementation

[0032] The following examples are used to illustrate preferred embodiments of the invention. Those skilled in the art will understand that the techniques disclosed in the examples represent techniques discovered by the inventors that can be used to implement the invention, and therefore can be considered preferred embodiments for implementing the invention. However, those skilled in the art should understand from this specification that many modifications can be made to the specific embodiments disclosed herein, still yielding the same or similar results, without departing from the spirit or scope of the invention.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains, and all materials disclosed herein and cited therein are incorporated herein by reference. Many equivalent techniques of specific embodiments of the invention described herein will be recognized or can be understood by ordinary experimentation by those skilled in the art. These equivalents will be included in the claims.

[0034] A method for enhancing the activity of detoxifying fly ash includes the following steps:

[0035] S1. The fly ash from waste incineration is subjected to low-temperature thermal decomposition pretreatment under anoxic conditions and a temperature of 350-400℃ for 60-90 minutes, followed by three-stage water washing and plate and frame filter press separation to obtain detoxified fly ash product with a moisture content of 15-20%. The detoxified fly ash product is then crushed and passed through a 75μm sieve, with the sieve residue not exceeding 15%, to obtain detoxified fly ash.

[0036] S2. Detoxifying fly ash and composite activator are thoroughly mixed at a mass ratio of (70%~85%):(15%~30%), and then pre-ground to a specific surface area of ​​400~500 m². 2 / kg; the composite activator is composed of mineral powder, fly ash, and gypsum; the mass ratio of mineral powder: fly ash: gypsum in the composite activator is (40%~60%):(30%~50%):(10%~20%).

[0037] S3. The product after grinding S2 is cured in a humid heat at 50-70℃ and humidity ≥90% for 6 hours.

[0038] S4. After curing, add a microwave synergist to the detoxified fly ash-based active powder and activate it under microwave-assisted heating; the microwave synergist includes silicon slag powder and ferrous oxide; the mass ratio of silicon slag powder to ferrous oxide in the microwave synergist is (90-95%):(5-10%); the amount of microwave synergist accounts for 5-7% of the mass of the detoxified fly ash-based active powder; the microwave-assisted heating conditions are: microwave frequency 2.45 GHz, power density 3~5 W / g;

[0039] S5. Cool the output powder after completing step S4, add 0.5%~1.5% organosilicon hydrophobic agent for surface modification, add 0.1%~0.5% triethanolamine to assist grinding, and then perform ultrafine grinding on the activated material to a specific surface area of ​​600~800 m² / kg to obtain detoxified fly ash with enhanced activity.

[0040] The technical solution of this application will be further described in detail below with reference to specific embodiments.

[0041] Example 1

[0042] A method for enhancing the activity of detoxifying fly ash includes the following steps:

[0043] S1. Low-temperature pyrolysis pretreatment of waste incineration fly ash: Under oxygen-free conditions and a temperature of 400℃, the fly ash is kept at a temperature of 400℃ for 80 minutes to dechlorinate and detoxify dioxins.

[0044] S2. Three-stage water washing pretreatment of waste incineration fly ash: The waste incineration fly ash that has completed step S1 is subjected to three-stage countercurrent water washing to remove heavy metals, soluble chlorine and salts from the fly ash.

[0045] S3. Formation of detoxified fly ash products: The water-ash mixture from step S2 is filtered by plate and frame filter press to obtain a detoxified fly ash filter cake with a moisture content of 15%.

[0046] S4. Product pre-crushing: The filter cake with low moisture content is pre-crushed to a residue of no more than 15% on a 75µm sieve using a vertical crusher.

[0047] S5. Composite activator formulation: The 75μm sieve material of detoxified fly ash from step S4 is mixed with the composite activator at a mass ratio of 80%:20%. The composite activator is composed of mineral powder, fly ash and gypsum at a mass ratio of 50%:30%:20%.

[0048] S6. Mixing and pre-grinding: Thoroughly mix the detoxifying fly ash with each component of the activator, and pre-grind to a specific surface area of ​​450 m² / kg;

[0049] S7. Aging and curing: Curing in a humid heat at 60℃ and 90% humidity for 6 hours;

[0050] S8. Microwave activation: 6% (w / w) microwave synergist was added to the detoxified fly ash-based active powder after curing for further microwave activation. The mass ratio of silicon slag powder to ferrous oxide in the microwave synergist was 10:1. The microwave activation conditions were: power density 5 W / g and time 15 min.

[0051] S9. Secondary ultrafine grinding: After cooling the output powder of S8, add 1% organosilicon hydrophobic agent for surface modification and 0.5% triethanolamine for grinding assistance. Further ultrafine grinding of the activated material to a specific surface area of ​​700 m² / kg.

[0052] Example 2

[0053] The other steps are the same as in Example 1, except that: S5, composite activator compatibility: the 75μm sieve material of detoxified fly ash in step S4 is mixed with the composite activator at a mass ratio of 85%:15%.

[0054] Example 3

[0055] The other steps are the same as in Example 1, except that: S5, composite activator compatibility: the 75μm sieve material of detoxified fly ash in step S4 is mixed with the composite activator at a mass ratio of 75%:25%.

[0056] Example 4

[0057] The other steps are the same as in Example 1, except that: S5, composite activator compatibility: the 75μm sieve material of detoxified fly ash in step S4 is mixed with the composite activator at a mass ratio of 70%:30%.

[0058] Example 5

[0059] The other steps are the same as in Example 1, except that: S5, composite activator compatibility: the 75μm sieve material of detoxified fly ash in step S4 is mixed with the composite activator at a mass ratio of 65%:35%.

[0060] Example 6

[0061] The other steps are the same as in Example 1, except that: S5, composite activator compatibility: the 75μm sieve material of detoxified fly ash in step S4 is mixed with the composite activator at a mass ratio of 90%:10%.

[0062] Example 7

[0063] The other steps are the same as in Example 1, except that: S7, aging and curing: 6 hours of moist heat curing at 50°C and 90% humidity.

[0064] Example 8

[0065] The other steps are the same as in Example 1, except that: S7, aging and curing: humid heat curing for 6 hours at 70°C and 90% humidity.

[0066] Example 9

[0067] The other steps are the same as in Example 1, except that: S7, aging and curing: 6 hours of moist heat curing at 80°C and 90% humidity.

[0068] Example 10

[0069] The other steps are the same as in Example 1, except that: S7, aging and curing: 6 hours of moist heat curing at 60°C and 80% humidity.

[0070] Example 11

[0071] The other steps are the same as in Example 1, except that: S7, aging and curing: 6 hours of moist heat curing at 60°C and 85% humidity.

[0072] Example 12

[0073] The other steps are the same as in Example 1, except that: S7, aging and curing: 6 hours of moist heat curing at 60°C and 95% humidity.

[0074] Example 13

[0075] The other steps are the same as in Example 1, except that: S8, microwave activation: 6% (w / w) microwave synergist is added to the detoxified fly ash-based active powder after curing for further microwave synergistic activation. The mass ratio of silicon slag powder to ferrous oxide in the microwave synergist is 15:1. The microwave activation conditions are: power density 5 W / g and time 15min.

[0076] Example 14

[0077] The other steps are the same as in Example 1, except that: S8, microwave activation: 6% (w / w) microwave synergist is added to the detoxified fly ash-based active powder after curing for further microwave synergistic activation. The mass ratio of silicon slag powder to ferrous oxide in the microwave synergist is 20:1. The microwave activation conditions are: power density 5 W / g and time 15min.

[0078] Example 15

[0079] The other steps are the same as in Example 1, except that: S8, microwave activation: 6% (w / w) microwave synergist is added to the detoxified fly ash-based active powder after curing for further microwave synergistic activation. The mass ratio of silicon slag powder to ferrous oxide in the microwave synergist is 19:1. The microwave activation conditions are: power density 5 W / g and time 15min.

[0080] Example 16

[0081] The other steps are the same as in Example 1, except that: S8, microwave activation: 6% (w / w) microwave synergist is added to the detoxified fly ash-based active powder after curing for further microwave synergistic activation. The mass ratio of silicon slag powder to ferrous oxide in the microwave synergist is 9:1. The microwave activation conditions are: power density 5 W / g and time 15min.

[0082] Example 17

[0083] The other steps are the same as in Example 1, except that: S8, microwave activation: 5% (w / w) microwave synergist is added to the detoxified fly ash-based active powder after curing for further microwave synergistic activation. The mass ratio of silicon slag powder to ferrous oxide in the microwave synergist is 10:1. The microwave activation conditions are: power density 5 W / g and time 15 min.

[0084] Example 18

[0085] The other steps are the same as in Example 1, except that: S8, microwave activation: 4% (w / w) microwave synergist is added to the cured detoxified fly ash-based active powder for further microwave synergistic activation. The mass ratio of silicon slag powder to ferrous oxide in the microwave synergist is 10:1. The microwave activation conditions are: power density 5 W / g and time 15min.

[0086] Example 19

[0087] The other steps are the same as in Example 1, except that: S8, microwave activation: 8% (w / w) microwave synergist is added to the detoxified fly ash-based active powder after curing for further microwave synergistic activation. The mass ratio of silicon slag powder to ferrous oxide in the microwave synergist is 10:1. The microwave activation conditions are: power density 5 W / g and time 15min.

[0088] Example 20

[0089] The other steps are the same as in Example 1, except that: S8, microwave activation: 7% (w / w) microwave synergist is added to the detoxified fly ash-based active powder after curing for further microwave synergistic activation. The mass ratio of silicon slag powder to ferrous oxide in the microwave synergist is 10:1. The microwave activation conditions are: power density 5 W / g and time 15min.

[0090] Example 21

[0091] The other steps are the same as in Example 1, except that: S8, microwave activation: 6% (w / w) microwave synergist is added to the cured detoxified fly ash-based active powder for further microwave synergistic activation. The mass ratio of silicon slag powder to ferrous oxide in the microwave synergist is 10:1. The microwave activation conditions are: power density 4 W / g and time 15 min.

[0092] Example 22

[0093] The other steps are the same as in Example 1, except that: S8, microwave activation: 6% (w / w) microwave synergist is added to the cured detoxified fly ash-based active powder for further microwave synergistic activation. The mass ratio of silicon slag powder to ferrous oxide in the microwave synergist is 10:1. The microwave activation conditions are: power density 3 W / g and time 15min.

[0094] Example 23

[0095] The other steps are the same as in Example 1, except that: S8, microwave activation: 6% (w / w) microwave synergist is added to the detoxified fly ash-based active powder after curing for further microwave synergistic activation. The mass ratio of silicon slag powder to ferrous oxide in the microwave synergist is 10:1. The microwave activation conditions are: power density 2 W / g and time 15min.

[0096] Example 24

[0097] The other steps are the same as in Example 1, except that: S8, microwave activation: 6% (w / w) microwave synergist is added to the cured detoxified fly ash-based active powder for further microwave synergistic activation. The mass ratio of silicon slag powder to ferrous oxide in the microwave synergist is 10:1. The microwave activation conditions are: power density 6 W / g and time 15min.

[0098] Example 25

[0099] The other steps are the same as in Example 1, except that: S8, microwave activation: 6% (w / w) microwave synergist is added to the detoxified fly ash-based active powder after curing for further microwave synergistic activation. The mass ratio of silicon slag powder to ferrous oxide in the microwave synergist is 10:1. The microwave activation conditions are: power density 5 W / g and time 5 min.

[0100] Example 26

[0101] The other steps are the same as in Example 1, except that: S8, microwave activation: 6% (w / w) microwave synergist is added to the detoxified fly ash-based active powder after curing for further microwave synergistic activation. The mass ratio of silicon slag powder to ferrous oxide in the microwave synergist is 10:1. The microwave activation conditions are: power density 5 W / g and time 10 min.

[0102] Example 27

[0103] The other steps are the same as in Example 1, except that: S8, microwave activation: 6% (w / w) microwave synergist is added to the cured detoxified fly ash-based active powder for further microwave synergistic activation. The mass ratio of silicon slag powder to ferrous oxide in the microwave synergist is 10:1. The microwave activation conditions are: power density 5 W / g and time 25 min.

[0104] Example 28

[0105] The other steps are the same as in Example 1, except that: S8, microwave activation: 6% (w / w) microwave synergist is added to the detoxified fly ash-based active powder after curing for further microwave synergistic activation. The mass ratio of silicon slag powder to ferrous oxide in the microwave synergist is 10:1. The microwave activation conditions are: power density 5 W / g and time 35 min.

[0106] Example 29

[0107] The other steps are the same as in Example 1, except that: S8, microwave activation: 6% (w / w) microwave synergist is added to the detoxified fly ash-based active powder after curing for further microwave synergistic activation. The mass ratio of silicon slag powder to ferrous oxide in the microwave synergist is 10:1. The microwave activation conditions are: power density 5 W / g and time 30 min.

[0108] Comparative Example 1

[0109] A method for enhancing the activity of detoxifying fly ash includes the following steps:

[0110] S1. Low-temperature pyrolysis pretreatment of waste incineration fly ash: Under oxygen-free conditions and a temperature of 400℃, the fly ash is kept at a temperature of 400℃ for 80 minutes to dechlorinate and detoxify dioxins.

[0111] S2. Three-stage water washing pretreatment of waste incineration fly ash: The waste incineration fly ash that has completed step S1 is subjected to three-stage countercurrent water washing to remove heavy metals, soluble chlorine and salts from the fly ash.

[0112] S3. Formation of detoxifying fly ash products: The water-ash mixture from step S2 is filtered by plate and frame filter press to obtain detoxifying fly ash with a moisture content of 15%.

[0113] Comparative Example 2

[0114] A method for enhancing the activity of detoxifying fly ash includes the following steps:

[0115] S1. Low-temperature pyrolysis pretreatment of waste incineration fly ash: Dioxins in fly ash are dechlorinated and detoxified under anaerobic conditions and a temperature of 400℃ for 80 minutes.

[0116] S2. Three-stage water washing pretreatment of waste incineration fly ash: The waste incineration fly ash that has completed step S1 is subjected to three-stage countercurrent water washing to remove heavy metals, soluble chlorine and salts from the fly ash.

[0117] S3. Formation of detoxified fly ash products: The water-ash mixture from step S2 is filtered by plate and frame filter press to obtain a detoxified fly ash filter cake with a moisture content of 15%.

[0118] S4. Output the detoxified fly ash filter cake, add 1% organosilicon hydrophobic agent for surface modification, and 0.5% triethanolamine to assist grinding, and then physically grind to a specific surface area of ​​450m². 2 / kg.

[0119] Comparative Example 3

[0120] A method for enhancing the activity of detoxifying fly ash includes the following steps:

[0121] S1. Low-temperature pyrolysis pretreatment of waste incineration fly ash: Under oxygen-free conditions and a temperature of 400℃, the fly ash is kept at a temperature of 400℃ for 80 minutes to dechlorinate and detoxify dioxins.

[0122] S2. Three-stage water washing pretreatment of waste incineration fly ash: The waste incineration fly ash that has completed step S1 is subjected to three-stage countercurrent water washing to remove heavy metals, soluble chlorine and salts from the fly ash.

[0123] S3. Formation of detoxified fly ash products: The water-ash mixture from step S2 is filtered by plate and frame filter press to obtain a detoxified fly ash filter cake with a moisture content of 15%.

[0124] S4. Product pre-crushing: The filter cake with low moisture content is pre-crushed to a residue of no more than 15% on a 75µm sieve using a vertical crusher.

[0125] S5. Composite activator formulation: The 75μm sieve material of detoxified fly ash from step S4 is mixed with the composite activator at a mass ratio of 80%:20%. The composite activator is composed of mineral powder, fly ash and gypsum at a ratio of 50%:30%:20%.

[0126] S6. Mixing and pre-grinding: Thoroughly mix the detoxifying fly ash with each component of the composite activator and grind it to a specific surface area of ​​450 m² / kg.

[0127] Comparative Example 4

[0128] A method for enhancing the activity of detoxifying fly ash includes the following steps:

[0129] S1. Low-temperature pyrolysis pretreatment of waste incineration fly ash: Under oxygen-free conditions and a temperature of 400℃, the fly ash is kept at a temperature of 400℃ for 80 minutes to dechlorinate and detoxify dioxins.

[0130] S2. Three-stage water washing pretreatment of waste incineration fly ash: The waste incineration fly ash that has completed step S1 is subjected to three-stage countercurrent water washing to remove heavy metals, soluble chlorine and salts from the fly ash.

[0131] S3. Formation of detoxified fly ash products: The water-ash mixture from step S2 is filtered by plate and frame filter press to obtain a detoxified fly ash filter cake with a moisture content of 15%.

[0132] S4. Product pre-crushing: The filter cake with low moisture content is pre-crushed to a residue of no more than 15% on a 75µm sieve using a vertical crusher.

[0133] S5. Composite activator formulation: Mix the 75μm sieve material of detoxified fly ash from step S4 with fly ash of single activator at a mass ratio of 80%:20% and grind it evenly to a specific surface area of ​​450 m² / kg.

[0134] Comparative Example 5

[0135] A method for enhancing the activity of detoxifying fly ash includes the following steps:

[0136] S1. Low-temperature pyrolysis pretreatment of waste incineration fly ash: Under oxygen-free conditions and a temperature of 400℃, the fly ash is kept at a temperature of 400℃ for 80 minutes to dechlorinate and detoxify dioxins.

[0137] S2. Three-stage water washing pretreatment of waste incineration fly ash: The waste incineration fly ash that has completed step S1 is subjected to three-stage countercurrent water washing to remove heavy metals, soluble chlorine and salts from the fly ash.

[0138] S3. Formation of detoxified fly ash products: The water-ash mixture from step S2 is filtered by plate and frame filter press to obtain a detoxified fly ash filter cake with a moisture content of 15%.

[0139] S4. Product pre-crushing: The filter cake with low moisture content is pre-crushed to a residue of no more than 15% on a 75µm sieve using a vertical crusher.

[0140] S5. Composite activator formulation: Mix the 75μm sieve undersize of detoxified fly ash from step S4 with the single activator mineral powder at a mass ratio of 80%:20% and grind it to a specific surface area of ​​450 m² / kg.

[0141] Comparative Example 6

[0142] A method for enhancing the activity of detoxifying fly ash includes the following steps:

[0143] S1. Low-temperature pyrolysis pretreatment of waste incineration fly ash: Under oxygen-free conditions and a temperature of 400℃, the fly ash is kept at a temperature of 400℃ for 80 minutes to dechlorinate and detoxify dioxins.

[0144] S2. Three-stage water washing pretreatment of waste incineration fly ash: The waste incineration fly ash that has completed step S1 is subjected to three-stage countercurrent water washing to remove heavy metals, soluble chlorine and salts from the fly ash.

[0145] S3. Formation of detoxified fly ash products: The water-ash mixture from step S2 is filtered by plate and frame filter press to obtain a detoxified fly ash filter cake with a moisture content of 15%.

[0146] S4. Product pre-crushing: The filter cake with low moisture content is pre-crushed to a residue of no more than 15% on a 75µm sieve using a vertical crusher.

[0147] S5. Microwave activation: 6% (w / w) microwave synergist was added to the detoxified fly ash-based active powder for further microwave activation. The mass ratio of silicon slag powder to ferrous oxide in the microwave synergist was 10:1. The microwave activation conditions were: power density 5 W / g and time 15 min.

[0148] Comparative Example 7

[0149] A method for enhancing the activity of detoxifying fly ash includes the following steps:

[0150] S1. Low-temperature pyrolysis pretreatment of waste incineration fly ash: Under oxygen-free conditions and a temperature of 400℃, the fly ash is kept at a temperature of 400℃ for 80 minutes to dechlorinate and detoxify dioxins.

[0151] S2. Three-stage water washing pretreatment of waste incineration fly ash: The waste incineration fly ash that has completed step S1 is subjected to three-stage countercurrent water washing to remove heavy metals, soluble chlorine and salts from the fly ash.

[0152] S3. Formation of detoxified fly ash products: The water-ash mixture from step S2 is filtered by plate and frame filter press to obtain a detoxified fly ash filter cake with a moisture content of 15%.

[0153] S4. Product pre-crushing: The filter cake with low moisture content is pre-crushed to a residue of no more than 15% on a 75µm sieve using a vertical crusher.

[0154] S5. Composite activator formulation: The 75μm sieve material of detoxified fly ash from step S4 is mixed with the composite activator at a mass ratio of 80%:20%. The composite activator is composed of mineral powder, fly ash and gypsum at a ratio of 50%:30%:20%.

[0155] S6. Mixing and pre-grinding: Thoroughly mix the detoxifying fly ash with each component of the activator, and pre-grind to a specific surface area of ​​450 m² / kg;

[0156] S7. Aging and curing: Curing in a humid heat at 60℃ and 90% humidity for 6 hours;

[0157] S8, Secondary Ultrafine Grinding: After the powder output from S8 is cooled, 1% of organosilicon hydrophobic agent is added for surface modification, and 0.5% triethanolamine is added to assist grinding. The activated material is then further ultrafine ground to a specific surface area of ​​700 m² / kg.

[0158] Comparative Example 8

[0159] S1. Low-temperature pyrolysis pretreatment of waste incineration fly ash: Under oxygen-free conditions and a temperature of 400℃, the fly ash is kept at a temperature of 400℃ for 80 minutes to dechlorinate and detoxify dioxins.

[0160] S2. Three-stage water washing pretreatment of waste incineration fly ash: The waste incineration fly ash that has completed step S1 is subjected to three-stage countercurrent water washing to remove heavy metals, soluble chlorine and salts from the fly ash.

[0161] S3. Formation of detoxified fly ash products: The water-ash mixture from step S2 is filtered by plate and frame filter press to obtain a detoxified fly ash filter cake with a moisture content of 15%.

[0162] S4. Product pre-crushing: The filter cake with low moisture content is pre-crushed to a residue of no more than 15% on a 75µm sieve using a vertical crusher.

[0163] S5. High-temperature sintering: The 75μm sieve material of the detoxified fly ash from step S4 is subjected to high-temperature sintering at 500-800℃ for 1 hour.

[0164] The products prepared in the above examples and comparative examples were subjected to performance testing. The standard for the revitalized fly ash after detoxification was used as a reference for active binders: the strength-activity index was referenced to the S95 grade mineral powder index in GB / T 18046. The product's application directions include admixtures, blends, and cementitious materials. Therefore, the standards "Granulated Blast Furnace Slag Powder for Cement, Mortar and Concrete" (GB / T18046-2024), "Composite Admixtures for Concrete" (JGT486-2015), and "General Portland Cement" (GB175-2023) were comprehensively considered and analyzed.

[0165] The chemical composition of the detoxified fly ash in Example 1 was tested, and the results are shown in Table 1.

[0166] Table 1 Chemical composition of detoxifying fly ash

[0167]

[0168] The results of the performance enhancement of detoxifying fly ash prepared according to the schemes of Examples 1-29 and Comparative Examples 1-8 are shown in Table 2:

[0169] Table 2. Results of performance enhancement of detoxifying fly ash activity in Examples 1-29 and Comparative Examples 1-8.

[0170]

[0171] We used materials whose activity indicators at 7 days and 28 days after the detoxification fly ash activity was improved as active adhesives, and further tested their performance as shown in Table 3. The results of the environmental protection indicators are shown in Table 4.

[0172] Table 3. Performance test results of qualified detoxifying fly ash as an active adhesive material

[0173]

[0174] Table 4. Environmental index determination results of qualified detoxified fly ash as an active adhesive.

[0175]

[0176] Among the above indicators, the water demand ratio is an important indicator reflecting the water consumption of materials. It is a technical indicator for assessing whether the material has a water reduction function. The better the water reduction function, the more significantly the mixing water consumption of the material can be reduced, and the higher the engineering utilization value.

[0177] The content of sulfur trioxide can affect the stability of cement and other products, causing adverse consequences such as expansion and cracking; it can also affect the strength of concrete.

[0178] The flowability ratio measures the flow performance of materials during transportation and stacking.

[0179] The results showed that the percentage of fly ash treatment product to composite activator had a comprehensive impact on the activity index and other performance indicators. The optimal addition ratio of fly ash treatment product to composite activator was (70-85%):(15-30%). The aging and curing conditions after chemical activation and the microwave activation conditions had a certain impact on the activity index. Considering the decomposition temperature of ettringite not exceeding 70℃, the optimal aging and curing conditions were 50-70℃, humidity ≥90%, and time 4-8h. The proportion and dosage of microwave synergist had a relatively small impact.

[0180] Detoxifying fly ash is mainly composed of alkaline calcium-based materials. Under the stimulation of silica-alumina and sulfate, it will form gels such as CSH, CAH, and CASH with early (7d) activity strength, as well as late (28d) activity gels mainly composed of AFt (ettringite). Within a certain range, increasing the amount of detoxifying fly ash will promote early activity strength, but it is not conducive to the formation of late strength.

[0181] The system's control over chloride ions mainly involves the formation of hydrated calcium chloroaluminate, which consumes most of the chloride ions in the material. Secondly, the dense matrix gel composed of various products such as AFt (ettringite) further physically seals off chloride ions.

[0182] The ratio of detoxifying fly ash to composite activator affects the water demand ratio, fluidity ratio, and initial setting time ratio of active adhesives, mainly due to the changes in the Si / Ca / Al ratio and the amount of gel products generated in the system, which alter the physical properties.

[0183] Heavy metals can be adsorbed by chemical binding sites in CSH gel products. In addition, the AFt phase product generated in the system is a layered crystal with chemical binding sites between its layers, which has the ability to adsorb oxygen anion-type heavy metals. Its hydration products undergo a series of physicochemical reactions with heavy metals, such as physical encapsulation, chemical adsorption, ion exchange, and precipitation, so that the heavy metals are physically and chemically bound in the gel matrix. At the same time, the formation of the gel phase will promote the migration of heavy metals (Pb, Cr, Zn, etc.) in fly ash from an unstable state to a stable state.

[0184] Aging and curing accelerate hydration and gel phase formation. Temperatures above 70℃ cause the generated AFt to decompose, releasing more free chlorine, which limits the application scenarios of reactive adhesives. Microwave synergists have little effect on the activity and other properties of reactive adhesives; they mainly assist microwave activation and improve its efficiency. Power density and time in microwave activation have a direct and significant impact on the activation effect. Based on experimental data, a power density of 3-5 W / g and a time of 10-30 min yielded better activity enhancement.

[0185] All documents mentioned in this invention are incorporated herein by reference as if each document were individually incorporated by reference. Furthermore, it should be understood that after reading the foregoing teachings of this invention, those skilled in the art can make various alterations or modifications to this invention, and these equivalent forms also fall within the scope defined by this application.

Claims

1. A method for enhancing the activity of detoxifying fly ash, characterized in that, Includes the following steps: S1. The waste incineration fly ash is pretreated by low temperature pyrolysis, washed in three stages, and separated by plate and frame filter press to obtain detoxified fly ash product with a moisture content of 15~20%. The detoxified fly ash product is crushed and passed through a 75μm sieve, and the sieve residue is not higher than 15%, thus obtaining detoxified fly ash. S2. Detoxifying fly ash and composite activator are thoroughly mixed at a mass ratio of (70%~85%):(15%~30%) and then pre-ground to a specific surface area of ​​400~500 m² / kg; the composite activator is composed of mineral powder, fly ash and gypsum; the mass ratio of mineral powder:fly ash:gypsum in the composite activator is (40%~60%):(30%~50%):(10%~20%). S3. The product after grinding S2 is cured in a humid heat at 50~70℃ and humidity ≥90% for 6 hours. S4. After curing, a microwave synergist is added to the detoxified fly ash-based active powder, and the powder is activated and enhanced under microwave-assisted heating. The microwave synergist includes silica slag powder and ferrous oxide. The mass ratio of silica slag powder to ferrous oxide in the microwave synergist is (90~95%):(5~10%). The amount of microwave synergist used accounts for 5~7% of the mass of the detoxified fly ash-based active powder. The microwave-assisted heating conditions are: microwave frequency 2.45 GHz, power density 3~5 W / g. S5. Cool the output powder after completing step S4, add 0.5%~1.5% organosilicon hydrophobic agent for surface modification, add 0.1%~0.5% triethanolamine to assist grinding, and then perform ultrafine grinding on the activated material to a specific surface area of ​​600~800 m² / kg to obtain detoxified fly ash with enhanced activity.

2. The method for enhancing the activity of detoxifying fly ash according to claim 1, characterized in that, In step S1, the low-temperature thermal decomposition pretreatment method is as follows: under oxygen-free conditions and a temperature of 350~400℃, the dioxins in the fly ash are dechlorinated and detoxified for 60~90 min.

3. The detoxifying fly ash with enhanced activity prepared by the method according to any one of claims 1 to 2.

4. The application of the activity-enhanced detoxifying fly ash according to claim 3, characterized in that: The detoxified fly ash with enhanced activity can be used as a composite admixture in concrete production, as an active admixture in cement production, as a low-carbon cementitious material to replace 30-50% of cement in cement product production, and as an inorganic binder in roadbed materials for stabilizing crushed stone or solidifying soil.

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