Treatment system and method for producing slurry admixture for concrete by using tail ash after low-temperature thermal decomposition

Abstract

The invention belongs to the technical field of household garbage incineration fly ash treatment and resource comprehensive utilization treatment. After fly ash is subjected to low-temperature thermal decomposition to remove dioxins, discharged tail ash is subjected to pulping, defoaming, heavy metal chelating, washing dechlorination and dehydration, and the tail ash and washing water for impurity removal and calcium removal sludge are dehydrated together and can be directly used as a slurry admixture for low-activity concrete; other one or more oxides of silicon, aluminum, calcium and the like are further added, and the slurry admixture for concrete with higher activity can be prepared through wet grinding. Dioxins in the fly ash, heavy metals in the washing water and chlorine salts are treated, and tail ash solid content treatment products are used as common solid wastes for resource utilization; the prepared slurry admixture for concrete is low in ignition loss and chloride ion content, and can be used as a commodity. The technology provides a comprehensive utilization approach of fly ash solid content treatment products, broadens utilization channels of fly ash low-temperature thermal decomposition treatment products, is short in technological process, compact in equipment arrangement, high in water requirement for washing and high in treatment adaptability of fly ash with different chlorine contents, optimizes reduction of heavy metals, and is stable in production process and product quality, environment-friendly and suitable for industrial production. Therefore, the method has the characteristics of saving investment and production cost.

Description

Technical Field

[0001] This technology belongs to the field of municipal solid waste incineration fly ash treatment and resource utilization technology, realizing the harmless treatment and resource utilization of municipal solid waste incineration fly ash, specifically involving a treatment system and method for producing concrete slurry admixtures using low-temperature pyrolysis tail ash. Background Technology

[0002] Incineration of municipal solid waste produces a large amount of fly ash. Fly ash contains high levels of dioxins, chlorobenzene compounds, leaching heavy metals, and soluble chlorides. Fly ash treatment is a process that removes one or more of the heavy metals, dioxins, and chlorides in fly ash to a certain extent or inhibits their leaching by physical or chemical reactions, so that the treated fly ash meets the requirements for subsequent utilization or disposal.

[0003] Fly ash treatment processes include water washing, solidification / stabilization, molding, low-temperature pyrolysis, high-temperature sintering, and high-temperature melting. Among existing technologies, low-temperature pyrolysis is the process route that can form industrialized and large-scale treatment. Low-temperature pyrolysis technology removes dioxins at 400-500℃. The treated fly ash is generally washed with water for dechlorination and weight removal. The wash water is then evaporated, crystallized, and desalinated. The treatment and discharge processes must meet the environmental protection requirements of HJ 1134—2020 Technical Specification for Pollution Control of Fly Ash from Municipal Solid Waste Incineration.

[0004] Admixtures are used in the processing of cement concrete. Their use in concrete not only replaces cement, saves energy and reduces environmental pollution, but also improves the workability of concrete and has a significant improvement on concrete durability. They are known as the indispensable "sixth component" of concrete.

[0005] The standard for concrete paste admixtures, initiated and edited by Professor He Xingyang of Hubei University of Technology, was reviewed in 2024. The standard requires the finished product to have a solid content between 20% and 70%. Using low-temperature thermal decomposition fly ash to produce concrete paste admixtures is a beneficial approach for the comprehensive utilization of resources.

[0006] Currently, a green circular development model has been fully launched, which aims to minimize environmental impact by continuously promoting waste reduction and resource utilization at the source and reducing landfill volume to the minimum. In order to achieve the construction of "zero-waste cities", the resource utilization of fly ash after harmless treatment of municipal solid waste incineration is an important way to solve its disposal problem. The subsequent resource utilization of fly ash has become a problem. Water washing of fly ash consumes a lot of water, and the cost of wastewater treatment increases accordingly. How to save energy has also become a problem.

[0007] Although there are already many methods for the comprehensive utilization of fly ash from municipal solid waste incineration, their actual implementation still faces various problems, such as:

[0008] Application publication number CN 118878228 A, "A Low-Carbon Cementitious Material Based on Waste Incineration Fly Ash," discloses a waste incineration fly ash-based composite admixture, a low-carbon cementitious material, and its preparation method. The main product is a dry powder, and the treated fly ash needs to be dried, resulting in high energy consumption. Application publication number CN117380711A, "A Low-Temperature Fly Ash Resource Utilization Treatment System and its Treatment Method," provides a low-temperature fly ash resource utilization treatment system and its method. This system is used to process the treated fly ash into bricks and to produce salt from the washing liquid generated during the fly ash treatment process. The invention, with publication number CN119461961A [A Method for Preparing Concrete Blocks from Fly Ash], specifically relates to a method for preparing concrete blocks from fly ash. This method includes washing the fly ash with water to obtain dechlorinated fly ash, mixing the dechlorinated fly ash with additives, ball milling to obtain detoxified fly ash, and mixing the detoxified fly ash, cement, bluestone, and fine sand, followed by constant temperature and humidity curing to obtain concrete blocks. Both of these methods suffer from low chloride ion content standards in the treated fly ash and limited applicability. Summary of the Invention

[0009] This invention, incorporating the latest national and industry standards and specifications for building materials and environmental protection, provides a processing system and method for producing admixtures for slurry concrete using low-temperature pyrolysis fly ash, aiming to overcome the aforementioned problems existing in the prior art.

[0010] This invention provides a method for removing dioxins from fly ash using a low-temperature pyrolysis device. The resulting ash, after defoaming, degravimetric analysis, and water washing and dewatering, continuously produces a paste-like concrete admixture that meets relevant industry standards. The process complies with environmental protection requirements. The treatment fully utilizes the rapid cooling heat of the fly ash, intensifying the precipitation of dissolved salts. The amount of wastewater generated during the treatment is small, reducing the amount of water evaporated for crystallization. This results in lower energy consumption per unit of fly ash treated, lowering treatment costs, and broadening the channels for comprehensive utilization of the treated material. The process produces fly ash solids and chloride crystals, achieving the goal of comprehensive resource utilization of fly ash.

[0011] To achieve the above-mentioned technical objectives, the present invention is implemented through the following technical solution:

[0012] After the tailings ash is treated for dioxins by the low-temperature pyrolysis unit 1, it is rapidly cooled to about 100°C by the ash discharge auger 2 and discharged into the pulping tank 3. The discharge temperature and quantity are monitored when the temperature in the pulping tank 3 is about 80°C. The dioxin-containing gas generated by the low-temperature pyrolysis unit 1 is treated by adsorption, and the adsorbent is disposed of separately as a reduced-volume hazardous waste.

[0013] In the pulping tank 3, the tailings are stirred and pulped at a ratio of 1:1 to 1.5 ash to water. The soluble salts and highly leaching heavy metals in the tailings dissolve into the water in the pulping tank.

[0014] According to the different heavy metal contents of fly ash, heavy metal chelating agents are added to the makeup water in the pulping tank 3 in the appropriate proportion, and the captured heavy metals are combined in the solid contents of the washed tailings.

[0015] A demister 3.1 is installed in the pulping tank. Unburned carbon remaining due to incomplete combustion floats on the surface of the pulping tank during the pulping process and is removed by the demister 3.1, which reduces the loss on ignition index of the processed product.

[0016] The unburned material produced by the demister 3.1 can be recycled back into the waste incinerator for combustion and heat recovery.

[0017] The slurry discharged from the pulping tank 3 enters the vacuum belt conveyor 4, where it is dewatered, washed, dewatered again, and washed again about 2-3 times. The number of washes and the amount of water are determined according to the chlorine content of the raw ash.

[0018] The washing water is recycled from the tail end to the head end of the vacuum belt conveyor. The last stage of washing water at the tail end uses condensate produced by evaporation and salt production, plus tap water.

[0019] The product after final stage water washing and dehydration at the tail end of vacuum belt conveyor 4 has a moisture content of about 30% and a chloride ion content of less than 0.06%, producing slurry-like concrete admixture 1, which can be directly used as a commercial product if the activity index meets the requirements. Further, slurry-like concrete admixture 1, made from industrial water and composed of one or more oxides such as silicon, aluminum, and calcium, is ground in a wet ball mill 9 according to different proportions, and the moisture content of the slurry is controlled at 60-70%, producing pumpable slurry-like concrete admixture 2 with a high activity index.

[0020] The first dehydration stage of the vacuum belt conveyor 4, as the raw liquid, passes through the filtration device 5 for impurity removal, the calcium removal device 6 for calcium removal, and the weight removal device 7 for weight removal. It then enters the evaporation crystallization salt production device 8, producing crystallized salt and discharging condensate. The waste liquid generated by evaporation crystallization flows into the filtration device 5, achieving zero wastewater discharge.

[0021] The filtered sludge and calcium-removed sludge are added to the last dewatering zone at the tail end of the vacuum belt conveyor 4. After being dewatered together with the tailings ash that has been washed, they are used as admixture 1 for slurry concrete.

[0022] If the heavy sludge has a high heavy metal content, it can be disposed of separately as hazardous waste of reduced volume.

[0023] The implementation mechanism of this invention is as follows:

[0024] The implementation mechanism of this invention is based on the following three aspects: 1. the physical and chemical properties of fly ash; 2. experimental research on the use of water-washed municipal solid waste incineration fly ash as a concrete admixture; 3. the building materials industry standard "slurry admixtures for concrete".

[0025] The chemical composition of fly ash from municipal solid waste incineration varies significantly depending on the type of incinerator and the composition of waste in different regions. There are also significant differences in the amount and chloride content of fly ash produced by mechanical grate incinerators and fluidized bed incinerators. Fluidized bed incinerators produce a large amount of fly ash with a low chloride ion content. A high percentage of fly ash particles are smaller than 30μm, and most can achieve a D50 of no more than 20μm, with some manufacturers even achieving a D50 of no more than 10μm.

[0026] According to the test results, particles smaller than 20μm have better dispersion performance and are less prone to settling due to their lighter specific mass and larger specific surface area. This is the most basic performance requirement when used as a slurry admixture for concrete. When the particles are further refined to less than 10μm, the activity of potentially active particles is improved, and the filling effect of micro-aggregates is also further enhanced. The physical and chemical properties of fly ash from municipal solid waste incineration determine the process of processing it into a slurry admixture for concrete.

[0027] The inorganic components of fly ash from municipal solid waste incineration mainly include the following categories: Silicates: SiO2 (silicon dioxide) accounts for about 20%-40%; Al2O3 (alumina) accounts for about 10%-20%; CaO (calcium oxide) accounts for 5%-15%; there are also CaSO4 (calcium sulfate), CaCO3 (calcium carbonate), and iron oxides (Fe2O3), belonging to the CaO-SiO2-Al2O3 (Fe2O3) system; Although the particle size of fly ash produced by different municipal solid waste incinerators varies, it is generally fine, with a D50 of about 30μm. It has the morphological effect of mineral materials, the activity effect of volcanic ash, and the micro-aggregate effect, and has a certain degree of cementing activity;

[0028] Fly ash is a carrier for the enrichment of heavy metals. The content of heavy metals in fly ash is widely distributed, such as lead (Pb) 500-2000 mg / kg, cadmium (Cd) 10-100 mg / kg, zinc (Zn) 1000-5000 mg / kg, copper (Cu) 100-500 mg / kg, chromium (Cr) 50-300 mg / kg, and mercury (Hg) 0.1-10 mg / kg. In waste incinerators, due to the high temperature, some heavy metals in combustibles and non-combustibles undergo chemical reactions within the furnace, in addition to being carried out by gasification flue gas, entrained by flue gas, or entering the slag. These reactions form common metal oxides and metal chlorides. When these newly generated substances continue to be heated in the incinerator, they undergo further chemical reactions under high temperature to form new chemical substances. These substances may exist as elemental heavy metals, heavy metal oxides, and salts. Furthermore, the volatilized heavy metals enter the flue gas in gaseous form and eventually cool and solidify in the fly ash. The boiling point of the metal (including heavy metals) determines the different distribution characteristics of these metals. Because the boiling points of various metals are different, their final destination is determined by whether they exist inside the incineration fly ash particle matrix or adhere to the particle surface.

[0029] Heavy metals in fly ash have high leaching toxicity and need to be stabilized to reduce environmental risks. Generally, cement or other materials are used for solidification, and the leaching rate is controlled by detection.

[0030] In this technology, the slurry-like admixture replaces about 15-20% of cement in cement concrete. During the treatment process, heavy metals are chelated and removed. In comprehensive utilization, it can be further solidified in concrete, and its leaching rate can meet relevant standards. This provides a process basis for optimizing the treatment of heavy metals in this technology.

[0031] The proportion of soluble chloride salts (Cl-) in fly ash is 10%-30%. In the cement kiln co-processing specifications, it is best to have 1% after water washing. When used as a concrete admixture, it should be controlled at 0.06%. Through multi-stage countercurrent water washing, the product can meet the standards.

[0032] Other inorganic components in fly ash are mainly unburned carbon, accounting for 1%-5%. Due to incomplete combustion, most of them are removed by rinsing during the pulping process in this technology, so as to meet the requirements of loss on ignition index in the blend.

[0033] [Experimental Study on the Use of Washed Municipal Solid Waste Incineration Fly Ash as a Concrete Admixture] – A National Environmental Protection Public Welfare Industry Scientific Research Project undertaken by the Key Laboratory of Advanced Civil Engineering Materials of the Ministry of Education and the Institute of Environmental Materials, Tongji University. This project did not mention the treatment of dioxins and heavy metals in the washed fly ash. The conclusions are as follows: Washed municipal solid waste incineration fly ash possesses certain cementitious activity and is feasible as a concrete admixture; increasing the admixture dosage does not affect concrete forming; the admixture dosage affects concrete strength in all cases, meeting concrete strength requirements; and its use as a concrete admixture meets the durability requirements of ordinary concrete.

[0034] [Slurry Admixtures for Concrete] – A building materials industry standard initiated and edited by Professor He Xingyang of Hubei University of Technology, and reviewed in 2024; Slurry admixtures for concrete refer to materials composed of one or more raw materials listed in this standard (including waste slurry from commercial concrete, stone powder, iron tailings powder, copper tailings powder, phosphorus tailings powder, fly ash, lithium slag, steel slag powder, granulated blast furnace slag powder, granulated electric furnace phosphorus slag powder, limestone powder, and recycled micro powder, etc., industrial or construction solid waste), with the main components being one or more oxides such as silicon, aluminum, and calcium. After wet grinding, these materials contain a certain amount of water and a specified fineness, and can be added to concrete to improve its performance. Except for the requirements for waste slurry from commercial concrete, all other raw materials should comply with national or industry standards, requiring that the D50 of Grade I products not exceed 10μm and the D50 of Grade II products not exceed 20μm.

[0035] The performance requirements for slurry admixtures for concrete are shown in Table 1;

[0036]

[0037] Table 1

[0038] [Fly Ash from Municipal Solid Waste Incineration for Concrete] - The standard plan number is 2020-0458T-JC. It was drafted by relevant units organized by Beijing Building Materials Science Research Institute Co., Ltd., and has now been publicized.

[0039] The fly ash treatment process of this invention complies with HJ 1134—2020 Technical Specification for Pollution Control of Fly Ash from Municipal Solid Waste Incineration; it meets the pollution control requirements: the total amount of dioxin residues should not exceed 50 ng-TEQ / kg (based on the dry weight of fly ash), the leaching concentration of heavy metals should not exceed the maximum allowable emission concentration limit specified in GB8978 (the maximum allowable emission concentration for Class II pollutants shall be implemented according to the Class I standard), and the soluble chlorine content should not exceed 2%, preferably not exceeding 1%. Pollution prevention and control during the utilization of fly ash and its treatment products should comply with the requirements of HJ1091; according to GB34330, the tailings ash after water washing and detoxification of fly ash treated by this technology is classified as solid waste and can be managed as general industrial solid waste.

[0040] The beneficial effects of this invention are:

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] 1. This paper provides a comprehensive utilization method for the solid content of fly ash after low-temperature pyrolysis treatment, which broadens the utilization channels of fly ash low-temperature pyrolysis treatment products.

[0043] 2. This technology features a short process flow, compact equipment, low water and energy consumption for washing, strong adaptability to fly ash treatment with varying chlorine content, and stable, environmentally friendly, and controllable production process and product quality, thus saving investment and production costs; 3. This technology optimizes the reduction process of heavy metal components in fly ash treatment, and based on the use of the solid products treated by this technology...

[0044] In this process, some heavy metals are chelated and aggregated in the solid treatment product during the treatment process. They are further solidified in cement stone during concrete production, which further reduces the heavy metal leaching rate within the limit range. Consequently, it reduces the amount of heavy metal-containing sludge generated after heavy metal leaching and subsequent heavy metal removal during the treatment process, and reduces the amount of sludge to be disposed of. Attached Figure Description

[0045] Figure 1 This is a flowchart of the present invention.

[0046] In the diagram: 1. Low-temperature pyrolysis device, 2. Ash discharge quenching auger, 3. Pulping tank, 3.1 Demister, 4. Vacuum belt conveyor, 5. Filtration device, 6. Calcium removal device, 7. Gravity removal device, 8. Evaporation salt production device, 9. Wet ball mill device.

[0047] The following examples illustrate preferred embodiments of the present 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 present invention, and therefore can be considered preferred embodiments of 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; unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art, and all references herein and their cited materials are incorporated herein by reference; many equivalent techniques of the specific embodiments of the invention described herein will be recognized or understood by those skilled in the art through conventional experimentation; these equivalents will be included in the claims.

[0048] The technical solution of this application will be further described in detail below with reference to specific embodiments.

[0049] Example 1: Fluidized bed incineration fly ash of municipal solid waste, with a chloride ion content of 5-6% and a fly ash fineness of 30% residue on a 45μm sieve (cement negative pressure sieve). The raw ash was tested according to GB / T5762-2000 and the quality composition content is shown in Table 2.

[0050] ％ Moisture content 0.24 LOSS 9.77 SO3 6.22 CaO 32.92 MgO 3.38 Fe2O3 2.15 Al2O3 8.01 SIO2 12.85

[0051] Table 2

[0052] Tailings and water were washed twice in a countercurrent manner at a ratio of 1:1.0. The chloride ion content of the treated product reached 600 ppm. The compressive strength, radioactivity and heavy metal leaching content of the reference mortar and the test mortar at the corresponding age were determined according to GB / T17671, which met the requirements of building materials in GB6566 and the limits in GB / T30760-2014.

[0053] Example 2: Fluidized bed incineration fly ash of municipal solid waste, with a chloride ion content of 5-6% and a fly ash fineness of 15% residue on a 45μm sieve (cement negative pressure sieve). The raw ash quality composition is the same as in Table 2. It was treated and tested using the method of Example 1.

[0054] Example 3: The fly ash from the incineration of municipal solid waste in a grate furnace has a chloride ion content of about 18-20% and a fly ash fineness of 30% on a 45μm sieve (cement negative pressure sieve). The raw ash mass composition is shown in Table 3.

[0055] ％ Moisture content 5.16 LOSS 18.21 SO3 13.02 CaO 32.92 MgO 4.53 Fe2O3 2.19 Al2O3 10.33 SIO2 6.51

[0056] Table 3

[0057] The tailings were washed three times in a countercurrent manner with water at a ratio of 1:1.5. The chloride ion content of the treated product reached 600 ppm. The compressive strength, radioactivity, and heavy metal leaching content of the reference mortar and the test mortar at the corresponding age were determined according to GB / T17671, which met the requirements of building materials in GB6566 and the limits in GB / T30760-2014.

[0058] Example 4: The fly ash from the incineration of municipal solid waste grate furnace has a chloride ion content of about 15% and a fly ash fineness of 15% on a 45μm sieve (cement negative pressure sieve). The raw ash quality composition is the same as in Table 3. It is processed and tested using the method of Example 3.

[0059] Examples 1 to 4 describe the treatment of municipal solid waste incineration fly ash with different particle sizes and chlorine contents according to this technology, in order to test the implementation effect of this technology and the performance of the treated product as admixture 1 for slurry concrete. Detailed data are shown in Table 4.

[0060] Example 5: The solid body containing about 30% moisture (admixture 1 for slurry concrete) that has been dehydrated by the last stage of vacuum belt conveyor 4 is ground by a wet ball mill with 50% by weight, 15% by weight of blast furnace slag and 35% by weight of industrial water. The resulting slurry concrete admixture 2 has a particle size of 45μm and a sieve residue of 10%. The compressive strength, radioactivity and heavy metal leaching content of the reference mortar and the test mortar at the corresponding age are determined according to GB / T 17671, which meets the requirements of building materials in GB6566 and the limits in GB / T30760-2014.

[0061] Example 6: Admixture 1 for slurry concrete with a moisture content of about 30% was prepared by using the same method as in Example 5, comprising 50% by weight of blast furnace slag, 10% by weight of industrial water, and tested.

[0062] Example 7: Admixture 1 for slurry concrete with a moisture content of about 35% was prepared by using 50% by weight of bottom slag, 15% by weight of industrial water, and the same method as in Example 5, and tested.

[0063] Example 8: Admixture 1 for slurry concrete with a moisture content of about 35% was prepared by mixing 50% by weight of bottom slag, 10% by weight of industrial water, and 40% by weight of admixture 1, using the same method as in Example 5, and tested.

[0064] Example 9: Admixture 1 for slurry concrete with a moisture content of about 30% is prepared by mixing 50% by weight of quartz tailings sand (0 to 5 mm) and 35% of industrial water, using the same method as in Example 5, and tested.

[0065] Example 10: Admixture 1 for slurry concrete with a moisture content of about 30% is prepared by mixing 50% by weight of quartz tailings sand (0 to 5 mm) and 40% industrial water, using the same method as in Example 5, and tested.

[0066] Example 11: Admixture 1 for slurry concrete with a moisture content of about 35% is prepared by mixing 50% by weight of limestone tailings (0 to 5 mm) and 35% industrial water, using the treatment method of Example 5, to produce slurry concrete admixture 2, which is then tested.

[0067] Example 12: Admixture 1 for slurry concrete with a moisture content of about 35% is prepared by mixing 50% by weight of limestone tailings (0 to 5 mm) and 40% industrial water, using the same method as in Example 5, to produce slurry concrete admixture 2, which is then tested.

[0068] Examples 5 to 12 describe the preparation of high-performance slurry concrete admixture 2 by adding slurry concrete admixture 1 to raw materials whose main components are one or more oxides such as silicon, aluminum, and calcium, in order to test the implementation effect of this technology and the performance of composite slurry concrete admixture 2. Detailed data are shown in Table 4.

[0069]

[0070] Note: Radioactivity meets the requirements for main building materials in GB6566, and the heavy metal leaching content meets the limits in GB / T30760-2014.

[0071] Table 4

[0072] The admixtures for slurry concrete based on incineration fly ash prepared according to the schemes of Examples 1 to 12 were subjected to performance testing in accordance with the standards of [Slurry Admixtures for Concrete] and [Composite Admixtures for Concrete (JGT486-2015)].

[0073] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0074] The foregoing has shown and described the basic principles, main features, and advantages of this technology. Those skilled in the art should understand that this technology is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the method. Various changes and modifications can be made to this method without departing from its spirit and scope, and all such changes and modifications fall within the scope of the invention as claimed.

Claims

1. A system and method for producing concrete paste-like admixtures from tailings ash after low-temperature pyrolysis, characterized in that, The processing system consists of a low-temperature pyrolysis unit, an ash discharge quenching auger, a pulping tank, a demister, a vacuum belt conveyor, a filtration unit, a calcium removal unit, a weight removal unit, an evaporation salt production unit, and a wet ball milling unit. The method is as follows: After dioxins are removed from fly ash through low-temperature thermal decomposition, the discharged tailings are pulped, defoamed, chelated for heavy metals, dechlorinated by washing, and dehydrated. After further dehydration with the washing water and decalcified sludge, the solids-treated product passes type testing and can be directly used as a slurry admixture for low-activity concrete. Further addition of one or more oxides such as silicon, aluminum, and calcium, followed by wet grinding, produces a slurry admixture for higher-activity concrete. Dioxins in the fly ash and heavy metals and chlorides in the washing water are treated. The resulting slurry admixture for concrete has low loss on ignition and low chloride ion content, making it commercially viable.

2. The processing system and method for producing concrete paste admixtures using tailings from low-temperature pyrolysis as described in claim 1, characterized in that: After dioxin treatment in the low-temperature pyrolysis unit, the tailings are rapidly cooled to about 1000°C by a quenching auger and discharged into a pulping tank. The discharge temperature and quantity are monitored at a temperature of about 800°C in the pulping tank. The dioxin-containing gases generated by the low-temperature pyrolysis unit are adsorbed, and the adsorbent is disposed of separately as hazardous waste with reduced volume.

3. The processing system and method for producing concrete paste admixtures using tailings from low-temperature pyrolysis as described in claim 1, characterized in that: The pulping tank is used to mix and pulp the tailings at a ratio of 1:1 to 1.5 of ash to water. The soluble salts and highly leaching heavy metals in the tailings dissolve into the water in the pulping tank.

4. The processing system and method for producing concrete paste admixtures using tailings from low-temperature pyrolysis as described in claim 1, characterized in that: Depending on the heavy metal content of different fly ash, a heavy metal chelating agent is added to the makeup water in the pulping tank in an appropriate proportion, and the captured heavy metals are aggregated in the solids of the washed tailings.

5. The processing system and method for producing concrete paste admixtures using tailings from low-temperature pyrolysis as described in claim 1, characterized in that: A demister is installed in the pulping tank. Unburned carbon remaining due to incomplete combustion floats on the surface of the pulping tank during the pulping process and is removed by the demister, thus reducing the loss on ignition index of the processed product.

6. The processing system and method for producing concrete paste admixtures using tailings from low-temperature pyrolysis as described in claim 1, characterized in that: Unburned material produced by the demister can be returned to the waste incinerator for combustion to recover heat energy.

7. The processing system and method for producing concrete paste admixtures using tailings from low-temperature pyrolysis as described in claim 1, characterized in that: The slurry discharged from the pulping tank enters the vacuum belt conveyor, where it is dewatered, washed, dewatered again, and washed again about 2-3 times. The number of washes and the amount of water are determined according to the chlorine content of the raw ash.

8. The processing system and method for producing concrete paste admixtures using tailings from low-temperature pyrolysis as described in claim 1, characterized in that: The washing water is recycled from the tail end to the head end of the vacuum conveyor belt. The last stage of washing water at the tail end uses condensate produced by evaporation and salt production, plus tap water.

9. The processing system and method for producing concrete paste-like admixtures using tailings from low-temperature pyrolysis as described in claim 1, characterized in that: The product after the final stage of water washing and dehydration at the tail end of the vacuum belt conveyor has a moisture content of about 30% and a chloride ion content of less than 0.06%, producing a raw slurry-like concrete admixture 1, which can be directly used as a commodity if the activity index meets the requirements.

10. The processing system and method for producing concrete paste admixtures using tailings from low-temperature pyrolysis as described in claim 1, characterized in that: Furthermore, the admixture 1 for slurry concrete, made of industrial water, and composed of one or more oxides such as silicon, aluminum, and calcium, is ground in a wet ball mill according to different mixing ratios, and the water content of the slurry is controlled at 60-70%, producing a pumpable admixture 2 for slurry concrete with high activity index.

11. The processing system and method for producing concrete paste admixtures using tailings from low-temperature pyrolysis as described in claim 1, characterized in that: The first stage of dehydration in the vacuum belt conveyor is used as raw liquid. After passing through a filtration device to remove impurities, a calcium removal device to remove calcium, and a weight removal device to remove weight, it enters the evaporation crystallization salt production device, producing crystallized salt and discharging condensate. The waste liquid generated by evaporation crystallization flows into the filtration device, achieving zero wastewater discharge.

12. The processing system and method for producing concrete paste admixtures using tailings from low-temperature pyrolysis as described in claim 1, characterized in that: The filtered sludge and calcium-removed sludge are added to the last stage of dewatering at the tail end of the vacuum conveyor belt. After being dewatered together with the tailings ash that has been washed, they are used as admixture 1 for slurry concrete.

13. The processing system and method for producing concrete paste admixtures using tailings from low-temperature pyrolysis as described in claim 1, characterized in that: If the heavy sludge has a high heavy metal content, it can be disposed of separately as hazardous waste of reduced volume.

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