Production process and production device for preparing solid waste-based reclaimed sand from fly ash at normal temperature

Abstract

The invention belongs to the technical field of solid waste resource utilization, and particularly relates to a production process for preparing solid waste-based reclaimed sand from fly ash at normal temperature, which comprises the process steps of preparing mixed powder, preparing granular fly ash, preparing semi-finished solid waste-based reclaimed sand, soaking the semi-finished solid waste-based reclaimed sand, and maintaining the semi-finished solid waste-based reclaimed sand. The process is carried out under a normal temperature condition; a solid waste-based material is used as a curing stabilizer, and meanwhile, a composite curing stabilizer is used; and a harmless treatment method with multiple measures of synergistic solidification and stabilization and solidification and stabilization in different stages is used. According to the process, the safety, the environmental protection property, the economical efficiency and the low-carbon property of fly ash recycling are considered, and a new effective technical approach is opened up for consumption of hazardous waste fly ash. The solid-waste-based reclaimed sand prepared by recycling the fly ash is wide in application field and can be used in a large amount, the fly ash can be consumed in a large amount, the process of low-carbon circular economy, sustainable development and green industry is promoted, carbon can be assisted to achieve peak carbon neutralization, and green transformation of economic and social development is promoted.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid waste resource utilization, and particularly relates to a production process and a production device for preparing solid waste-based recycled sand from fly ash at normal temperature. Background Art

[0002] Fly ash is a product of municipal solid waste reduction, which is solid waste generated during the incineration of municipal solid waste in a waste power plant. It contains various heavy metals and harmful substances such as Pb, Cd, Cr, and Zn, and its content exceeds the standard of "Identification Standard for Toxicity Characteristic Leaching Procedure of Hazardous Wastes" (GB5085.3), so it is listed as solid hazardous waste. Fly ash is large in quantity and complex in composition, with a high environmental pollution risk, and it belongs to solid hazardous waste with relatively high treatment difficulty. Currently, the basic method is to carry out harmless treatment on fly ash and then landfill it in a landfill after meeting the standard of "Pollution Control Standard for Domestic Waste Landfill Sites" (GB16889). The harmless treatment of fly ash requires relatively high costs, and landfills need to occupy a large amount of land. With the rapid economic development and the acceleration of the urbanization process, due to reasons such as the shortage of urban land, it has become increasingly difficult to select landfill sites. At the same time, in order to reduce the risk of secondary pollution caused by fly ash landfill, the construction standards of landfills are relatively high, resulting in large investments.

[0003] The resource utilization of hazardous waste fly ash and the reuse of products are difficult problems that are widely recognized and concerned at home and abroad. In the existing technology, the preparation of building materials from fly ash mostly relies on high-temperature sintering or high-proportion cement solidification, etc., and it is impossible to balance safety, environmental protection, economy, and low carbon. Currently, although there are more and more fly ash resource utilization product technologies, there are fewer product technologies that can resourceize fly ash under normal temperature conditions with relatively simple processes, relatively short production devices, relatively low costs, and relatively small energy consumption, especially those that can be converted into bulk recycled materials with wide application fields, large usage amounts, and low preparation costs. Even fewer can consume a large amount of fly ash to prepare recycled materials for a large number of practical applications.

[0004] In recent years, there have been relatively many technical reports on the preparation of recycled materials from fly ash resource utilization. The published invention patents include: 1. A low-temperature fly ash resource utilization system and its treatment method (CN117380711B). This method provides a low-temperature fly ash resource utilization system and its treatment method. Through the setting of this system, the treated fly ash is used to make bricks, and the washing liquid generated during the fly ash treatment process is used to make salt.

[0005] This method has the following defects: washing fly ash consumes a large amount of water resources, the energy consumption for evaporation and salt production is relatively high, there is a risk that the heavy metals in the prepared salt exceed the national standard limits, the process flow is long and the system is complex, and the fly ash resource utilization cost is relatively high.

[0006] 2. A solid waste high flexural strength concrete and its preparation method (authorization announcement number: CN110078436B). This method provides a concrete preparation method that can not only solidify heavy metals in waste incineration fly ash but also has high flexural strength.

[0007] This method has the following defects: The weight fraction of fly ash used in the prepared concrete is relatively low (less than 5%), the efficiency of fly ash consumption is low, and the contents of CaO, SiO2, Al2O3, heavy metal oxides, and chloride ions in the fly ash components need to be within a specified range, with harsh conditions. Moreover, the contents of the above components in fly ash are volatile and cannot be guaranteed to be within their condition range at all times, resulting in limited use of this method.

[0008] 3. A fly ash resource utilization method (authorization announcement number: CN108715520B). This method provides a fly ash resource utilization method, which solidifies fly ash into fly ash blocks with the PCSB geotechnical solidifying agent disclosed in the patent number "ZL201110291183.3", and then crushes them into powder particles and incorporates them into concrete to replace a certain proportion of aggregates in the concrete.

[0009] This method has the following defects: Using the PCSB geotechnical solidifying agent disclosed in the patent number "ZL201110291183.3" to solidify fly ash limits the solidifying stabilizer for fly ash resource utilization. The powder particles obtained by crushing the solidified fly ash blocks, as a raw material for concrete, have the risk of heavy metals exceeding the national standard limits during use. The weight fraction of fly ash used in the prepared concrete is relatively low (less than 5%), and there is a risk of secondary pollution in the resource utilization products.

[0010] 4. A fly ash resource treatment method and the application of the obtained high-strength sand (authorization announcement number: CN114292637B). This method provides a fly ash resource treatment method and the application of the obtained high-strength sand, which grinds the fly ash after treatment, granulates it multiple times, and then sinters it to obtain high-strength sand.

[0011] This method has the following defects: The process system requires complex technological steps such as drying, grinding, sieving, and granulating multiple times, and the process flow is long. The energy consumption of the drying and high-temperature sintering processes is high, the investment in equipment and facilities is large during the implementation process, and the fly ash resource utilization cost is relatively high.

[0012] 5. A method for preparing facing bricks with fly ash (authorization announcement number: CN100491096C). This method provides a method for preparing facing bricks with fly ash. After drying fly ash, yellow rice mud, etc., they are mixed and ground, then water is added for stirring, aging, and sieving, and finally bricks are made, dried, and calcined to obtain facing bricks.

[0013] The method has the following defects: The process system requires complex process steps such as drying, grinding, aging, sieving, pressure forming, drying, and calcination, and the process flow is long. The energy consumption of the drying and calcination processes is high. The prepared facing bricks belong to a product with a relatively narrow application field and small consumption, the efficiency of fly ash consumption is low, the investment in equipment and facilities is large, and the cost of fly ash resource utilization is relatively high.

[0014] 6. Process methods for fly ash resource utilization such as a preparation method for producing mineral powder cementitious materials by activating fly ash solidified with industrial waste residues (authorization announcement number CN109761515B), a process and system for resource treatment of municipal solid waste incineration fly ash (authorization announcement number CN113172081B), a special granulation method for fly ash resource utilization (application announcement number CN117964269A), a granulation and solidification desalination method for municipal solid waste incineration fly ash (application announcement number CN113501690A), etc. can all convert fly ash into recycled materials through resource utilization.

[0015] Some of the above methods have defects such as relatively complex production equipment, long process flow, high energy consumption, small amount of fly ash consumption, limitation of components in fly ash, high cost of fly ash resource utilization, or risk of secondary pollution in fly ash resource utilization. As a result, fly ash resource utilization cannot balance safety, environmental protection, economy, and low carbon. These methods are feasible from a technical level but difficult to implement from the aspects of large-scale production and commercial operation.

[0016] Sand, as fine aggregate (fine aggregate), refers to gravel or crushed stone materials with a particle size less than 5 mm, which is divided into natural sand and manufactured sand and is widely used in projects such as construction and road subgrades. Solid waste-based recycled sand is a recycled material made by processing solid waste through a certain process and having a particle size less than 5 mm to replace part of the sand.

[0017] Preparing solid waste-based recycled sand after harmless treatment of fly ash has the characteristics of a wide application field and large consumption. It can replace part of natural sand or manufactured sand and be applied to projects with lower technical requirements such as construction and road subgrades. It can not only convert hazardous waste fly ash into engineering materials with wide applications and consume a large amount of fly ash, but also replace the method of landfilling fly ash in landfills to reduce land occupation. It can not only eliminate the risk of secondary pollution but also reduce the exploitation of natural mineral resources, thus saving non-renewable resources and turning fly ash into a valuable resource. Summary of the Invention

[0018] To solve the above technical problems, on the one hand, the object of the present invention is to provide a production process for preparing solid waste-based recycled sand from fly ash at normal temperature. By using various methods under normal temperature conditions, heavy metals in fly ash are synergistically solidified in stages, while solid waste-based recycled sand is prepared from fly ash, realizing the harmlessness and resource utilization of hazardous waste fly ash. On the other hand, the object of the present invention is to provide a production device for preparing solid waste-based recycled sand from fly ash at normal temperature.

[0019] To solve the above technical problems, the technical solution adopted by the present invention is as follows: A production process for preparing solid waste-based recycled sand from fly ash at normal temperature, comprising the following steps: S1. Prepare mixed powder: Stir and mix fly ash, powdered solid waste-based cementitious material and water evenly to obtain mixed powder; S2. Prepare granular fly ash: Mechanically extrude and granulate the mixed powder obtained in step S1, and after granulation, it coagulates and hardens to obtain granular fly ash; S3. Prepare semi-finished solid waste-based recycled sand: Crush the granular fly ash obtained in step S2 into sand-like particles to obtain semi-finished solid waste-based recycled sand; S4. Immerse the semi-finished solid waste-based recycled sand: Immerse the semi-finished solid waste-based recycled sand obtained in step S3 with a composite curing liquid; S5. Cure the semi-finished solid waste-based recycled sand: Keep the semi-finished solid waste-based recycled sand immersed in step S4 under moisturizing conditions to obtain solid waste-based recycled sand.

[0020] In step S1, the powdered solid waste-based cementitious material is a cementitious material made using industrial solid waste as the main raw material (such as slag, fly ash, steel slag, coal gangue, red mud, etc.) through a certain treatment process. It is a solid waste resource utilization product that can replace traditional cement under certain conditions and has standards to follow.

[0021] Specifically, 70-90 parts of hazardous waste fly ash from a domestic waste power plant and 10-30 parts of powdered solid waste-based cementitious material are added to a forced mixing and stirring device and mixed and stirred for 20-40 seconds, then 2-20 parts of water are added, and mixing and stirring continue for 30-60 seconds.

[0022] In step S2, the density of the particles reaches more than 2200 Kg / m³ after mechanical extrusion granulation; the particle size of the granular fly ash is 2-10 mm; the mechanical extrusion granulation uses a pair-roll extrusion granulation device or a screw extrusion granulation device; After mechanical extrusion granulation, the powdered solid waste-based cementitious material in the granular fly ash undergoes a hydration reaction for 10-20 hours to form hydration products (C-A-S-H gel, ettringite, calcium aluminate hydrate), and the granular fly ash coagulates and hardens. The coagulation and hardening of the granular fly ash are carried out in a particle hardening bin.

[0023] In step S3, the coagulated and hardened granular fly ash is added to a crushing and sand-making device for crushing. The aperture of the discharge sieve plate of the crushing and sand-making device is less than 5 mm, and all the granular fly ash is broken into sand-like particles with a particle size of less than 5 mm by the impact of the crushing hammers.

[0024] In step S4, the composite curing liquid used for soaking the semi-finished solid waste-based recycled sand is a composite curing liquid prepared by adding silica fume, liquid heavy metal chelating agent and styrene-acrylic emulsion into hot water and stirring evenly.

[0025] Specifically, 3-5 parts of silica fume, 1-3 parts of liquid heavy metal chelating agent, 0-5 parts of styrene-acrylic emulsion and 90-100 parts of hot water with a temperature of 50-80 °C are stirred evenly in a batching device to prepare the composite curing liquid. Soaking the semi-finished solid waste-based recycled sand is carried out in a particle soaking tank.

[0026] In step S5, the soaked semi-finished solid waste-based recycled sand is added to a particle curing device for normal temperature moisture conservation curing for 300-600 degree-days, and the humidity in the particle curing device is 85-95%. Under the condition of a temperature of 18-22 °C, the curing time of the semi-finished solid waste-based recycled sand particles is 15-30 days.

[0027] A production device for preparing solid waste-based recycled sand at normal temperature with fly ash includes a mixer, a granulator, a particle hardening bin, a crushing and sand-making machine, a particle soaking tank and a closed curing bin; the fly ash, gelling material and water are stirred and mixed into a mixed powder by the mixer, and the mixed powder is successively granulated by the granulator, coagulated and hardened in the particle hardening bin, sanded by the crushing and sand-making machine, soaked in the particle soaking tank and cured in the closed curing bin.

[0028] It further includes a composite curing liquid batching tank, and a heating device is provided on the composite curing liquid batching tank to heat the inside of the composite curing liquid batching tank; the composite curing liquid batching tank is communicated with the particle soaking tank through a composite curing liquid feeding pump.

[0029] It further includes a composite curing liquid recovery pump, and the liquid recovery pool in the closed curing bin is communicated with the particle soaking tank through the composite curing liquid recovery pump.

[0030] Compared with the prior art, the beneficial effects of the present invention are: 1. The production process and device are carried out at normal temperature, without high-temperature processes, and only a small amount of water is used as process water, without using water as a medium to consume a large amount of water, realizing energy conservation and low carbon.

[0031] 2. Use the powder solid waste-based cementitious material as a solidifying and stabilizing agent to solidify and stabilize heavy metals in powdered fly ash, and rely on mechanical extrusion for collaborative solidification and stabilization. Use the composite solidifying liquid prepared with heavy metal chelating agent, silica fume, and architectural styrene-acrylic emulsion as a composite solidifying and stabilizing agent to solidify and stabilize heavy metals in granular fly ash, and rely on moisture conservation for collaborative solidification and stabilization. That is, a process method of using solidification and stabilization twice and collaborative solidification and stabilization twice, and solidifying and stabilizing heavy metals in fly ash at different stages, improves the solidification and stabilization effect, ensures that heavy metals in the solid waste-based recycled sand products are effectively fixed, and ensures that the heavy metal leaching in the subsequent use of the solid waste-based recycled sand products is within the standard limits.

[0032] 3. The dosage of the solidifying and stabilizing agent is less, which increases the weight ratio of fly ash in the fly ash resource utilization products, reduces the fly ash resource utilization cost, and decreases the volume expansion of fly ash during the resource utilization process.

[0033] 4. The fly ash resource utilization process and system operate in a closed manner, without by-products production and the risk of secondary pollution, avoiding the diffusion of dust and volatile pollutants, without the generation of three wastes, and achieving green environmental protection.

[0034] 5. The powder solid waste-based cementitious material belongs to the solid waste resource utilization products. Using the powder solid waste-based cementitious material as the solidifying and stabilizing agent for fly ash realizes waste utilization, increases the content of solid waste in the fly ash resource utilization products; the quality of various solidifying and stabilizing agents used meets the relevant standards, replacing traditional materials such as cement and non-standard specific materials such as non-standard solidifying agents, and stabilizing the quality of the fly ash resource utilization products.

[0035] 6. The production process and device of the process are short, the device is simple, the investment is small, and the energy consumption is low. It does not require processes with high energy consumption and water consumption such as drying and calcination, water washing, etc., and long and complex devices. It reduces the cost of fly ash resource utilization products and lays a foundation for the large-scale production and commercial operation of fly ash resource utilization products.

[0036] 7. During the preparation of the solid waste-based recycled sand, there is only one product, the solid waste-based recycled sand, without by-products. The prepared solid waste-based recycled sand products are safe and environmentally friendly, and the main quality indicators of the products meet the relevant standard requirements. It can replace part of natural sand and machine-made sand and be widely used in construction, road subgrade engineering materials, etc. with relatively low technical requirements and without the use of steel bars.

[0037] 8. The safety, environmental protection, economy, and low-carbon characteristics of hazardous waste fly ash resource utilization are taken into account, opening up a new effective technical way for a large amount of hazardous waste fly ash to be disposed of, and promoting the process of low-carbon circular economy, sustainable development, and green industries. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 is the flow chart of the production process of the present invention; Figure 2This is the schematic diagram of the production device of the present invention; Among them: 1 is a mixer, 2 is a granulator, 3 is a particle hardening bin, 4 is a crushing and sand-making machine, 5 is a particle soaking tank, 6 is an airtight curing bin, 7 is a compound curing liquid batching tank, 8 is a compound curing liquid recovery pump, 9 is a raw material bin (storage tank), 10 is a weighing device, 11 is a feeder, 12 is a compound curing liquid feeding pump, 13 is a mixed powder bin, 14 is a forced feeder, and 15 is a liquid recovery pond. Specific implementation manners

[0039] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments.

[0040] As Figure 1 shown, a production process for preparing solid waste-based recycled sand from fly ash at normal temperature is carried out according to the following steps: S1. Prepare mixed powder At normal temperature, a certain proportion of powdered solid waste-based cementitious material and water are incorporated into fly ash and stirred and mixed evenly to prepare mixed powder. In this stage, the method of adding powdered solid waste-based cementitious material to powdered fly ash as a curing stabilizer is used to cure and stabilize heavy metals in powdered fly ash for the first time.

[0041] S2. Prepare granular fly ash At normal temperature, the mixed powder is mechanically extruded and granulated, and the powdered fly ash is transformed into granular fly ash and then coagulated and hardened to prepare granular fly ash. In this stage, while transforming powdered fly ash into hardened granular fly ash, the first synergistic curing and stabilization of heavy metals in fly ash is achieved by mechanical extrusion, and the density and compressive properties of granular fly ash are improved.

[0042] S3. Prepare semi-finished solid waste-based recycled sand At normal temperature, the coagulated and hardened granular fly ash is crushed to prepare semi-finished solid waste-based recycled sand. In this stage, the granular fly ash is transformed into sand-like granular fly ash with reasonable particle size distribution and low powder content.

[0043] S4. Soak the semi-finished solid waste-based recycled sand At normal temperature, the semi-finished solid waste-based recycled sand is soaked with a compound curing liquid. In this stage, the method of adding a compound curing liquid to granular fly ash as a composite curing stabilizer is used to cure and stabilize heavy metals in fly ash for the second time and reduce the water absorption rate of granular fly ash.

[0044] The preparation method of the compound curing liquid is: at normal temperature, silica fume, liquid heavy metal chelating agent, and styrene-acrylic emulsion are added to hot water according to a certain proportion and stirred evenly to obtain the compound curing liquid.

[0045] S5. Cure the semi-finished solid waste-based recycled sand Under normal temperature conditions, the soaked semi-finished solid waste-based recycled sand is subjected to moisture conservation for a certain period of time to prepare the solid waste-based recycled sand. In this stage, relying on moisture conservation, the heavy metals in the semi-finished solid waste-based recycled sand are synergistically solidified and stabilized for the second time, and the compressive strength of the solid waste-based recycled sand is further improved.

[0046] Preferably, in the above step S1: 80 parts of hazardous waste fly ash from a domestic waste power plant and 20 parts of powdered solid waste-based cementitious material are added to a forced mixing and stirring device and mixed and stirred for 20 - 40 seconds, then 2 - 20 parts of water are added, and the mixture is continuously mixed and stirred for 30 - 60 seconds. Through forced stirring, various materials are fully mixed evenly to obtain a mixed powder suitable for extrusion granulation.

[0047] The amount of water added above can be adjusted to achieve the purpose of smoothly extruding and granulating the mixed powder; the amount of solid waste-based cementitious material incorporated above can be adjusted to achieve the purpose of initially solidifying and stabilizing the heavy metals in the fly ash.

[0048] In this process method and steps, the powdered fly ash, powdered solid waste-based cementitious material, and water in the mixed powder undergo a hydration reaction, and the heavy metals in the powdered fly ash are solidified and stabilized for the first time. The solidification stabilizer used is the powdered solid waste-based cementitious material. The quality meets the requirements of the "Technical Specification for the Application of Solid Waste-based Cementitious Material" (T / CECS689) standard. Instead of using traditional materials such as cement and non-standard specific materials such as non-standard solidifying agents.

[0049] Preferably, in the above step S2: the above mixed powder is uniformly and quantitatively added to the extrusion granulation device through a forced feeding device. The feeding speed is adjusted by adjusting the rotation speed of the feeding device to ensure continuous feeding and stable operation of the extrusion granulation device.

[0050] Furthermore, the above mixed powder is forcibly added into the feeding port of the extrusion granulation device. The extrusion granulation device is a pair-roll extrusion granulation device or a screw extrusion granulation device. Under mechanical extrusion, the density of the extruded mixed powder is increased to more than 2200 Kg / m³, and the mixed powder is transformed into particulate fly ash with a particle size of 2 - 10 mm and compressive strength through a granulation die, and comes out from the discharge port of the extrusion granulation device.

[0051] Furthermore, the above particulate fly ash enters the particle hardening device. The solid waste-based cementitious material in the particulate fly ash undergoes a hydration reaction for 10 - 20 hours to form hydration products (such as C-A-S-H gel, ettringite, calcium aluminate hydrate, etc.), and the particulate fly ash coagulates and hardens, and its compressive strength is improved to obtain particulate fly ash.

[0052] The parameters such as the level of extrusion pressure of the above extrusion granulation device and the size of the ball sockets on the pair of rolls can be adjusted to achieve the purpose of increasing the density of the particulate fly ash and being suitable for powder granulation.

[0053] In this process method and steps, while the mixed powder containing moisture is extruded and granulated, due to mechanical extrusion, the hydration reaction is accelerated, and the solid waste-based cementitious material binds the powdered fly ash together to form a dense structure, synergistically solidifying and stabilizing heavy metals for the first time and improving the density and compressive performance of granular fly ash.

[0054] Preferably, in the above step S3: The hardened granular fly ash is added to a crushing and sand-making device for crushing. The aperture of the discharge sieve plate of the crushing and sand-making device is less than 5 mm. The granular fly ash is completely crushed into sand-like particles with a particle size of less than 5 mm by the impact of the crushing hammer, and a semi-finished solid waste-based recycled sand with reasonable particle gradation and low powder content is obtained.

[0055] The rotation speed of the crushing hammer and the aperture of the discharge sieve plate of the above crushing and sand-making device can be adjusted to achieve the purpose of reasonable particle gradation of the semi-finished solid waste-based recycled sand and low powder content in the particles.

[0056] Preferably, in the above step S4: 3 - 5 parts of silica fume, 1 - 3 parts of liquid heavy metal chelating agent, 0 - 5 parts of styrene-acrylic emulsion, and 90 - 100 parts of hot water at a temperature of 50 - 80 °C are stirred evenly in a batching device to prepare a composite curing liquid.

[0057] The quantity and proportion of various materials for preparing the above composite curing liquid can be adjusted according to the quality of fly ash to achieve the purpose of solidifying and stabilizing heavy metals in granular fly ash and reducing the water absorption rate of granular fly ash. The quality of the silica fume used for preparing the composite curing liquid meets the requirements of the "Silica Fume for Mortar and Concrete" (GB / T 27690) standard, the quality of the heavy metal chelating agent meets the requirements of the "Metal Chelating Agent" (QSL005) standard, and the quality of the styrene-acrylic emulsion meets the requirements of the "Styrene-Acrylic Emulsion" (Q / 320400JZ006) standard.

[0058] Furthermore, the semi-finished solid waste-based recycled sand is added to a particle soaking device, and the semi-finished solid waste-based recycled sand is soaked with the composite curing liquid in the particle soaking device containing the composite curing liquid to obtain the soaked semi-finished solid waste-based recycled sand. The composite curing liquid vacated from the semi-finished solid waste-based recycled sand remains in the particle soaking device for continued use.

[0059] In this process method and steps, the composite curing liquid penetrates into the particles through the capillary pores of the semi-finished solid waste-based recycled sand. The heavy metal chelating agent chelates with the heavy metals in the granular fly ash, and the silica fume fine powder chemically reacts with the active components in the granular fly ash, solidifying and stabilizing the heavy metals in the granular fly ash for the second time. The curing stabilizer used is the prepared composite curing liquid. The styrene-acrylic emulsion and the silica fume fine powder synergistically block the capillary pores of the particles and reduce the water absorption rate of the semi-finished solid waste-based recycled sand.

[0060] Preferably, the soaked semi-finished solid waste-based recycled sand is added to a particle curing device for normal-temperature moisturizing curing for 300 - 600 degree-days to obtain the solid waste-based recycled sand. The composite curing liquid emptied from the semi-finished solid waste-based recycled sand flows into a liquid recovery pool and is returned to the particle soaking device for reuse.

[0061] In this process method and steps, various components such as active SiO2, Al2O3, CaSO4, etc. in the semi-finished solid waste-based recycled sand and the composite curing liquid infiltrated into the granular fly ash further undergo various chemical reactions such as chelation, hydration, and polycondensation with each other sufficiently in a relatively high humidity environment. The formed C-A-S-H gel, etc. continuously grows and densifies, with crystal interweaving, forming a dense and stable product. Relying on the second-time moisturizing curing to synergistically solidify and stabilize heavy metals in the semi-finished solid waste-based recycled sand and further improve the compressive performance of the solid waste-based recycled sand.

[0062] Preferably, in the above step S5: The above particle curing device takes closed moisturizing measures to keep the humidity in the particle curing device at 85 - 95%. When the temperature in the particle curing device is high, the chemical reaction speeds up and the curing time shortens; when the temperature is low, the chemical reaction slows down and the curing time lengthens. Under the conditions of a humidity of about 90% and a temperature of 18 - 22 °C, the curing time of the semi-finished solid waste-based recycled sand particles is 15 - 30 days.

[0063] The solid waste-based recycled sand product prepared by the above process method and steps using hazardous waste fly ash complies with the requirements of the "Limit of Radionuclides in Building Materials" (GB6566) standard for radionuclides, and the leaching toxicity complies with the requirements of the "Identification Standard for Leaching Toxicity of Hazardous Wastes - Identification of Leaching Toxicity" (GB5085.3) and "Pollution Control Standard for Domestic Waste Landfill" (GB16889) standards. The crushing value, particle gradation, and powder content comply with the requirements of the "Recycled Fine Aggregates for Concrete and Mortar" (GB / T25176) and "Recycled Sand Powder from Construction Solid Wastes" (JC / T2548) standards.

[0064] Example 1 A production process for preparing solid waste-based recycled sand at normal temperature using fly ash is verified in the laboratory.

[0065] Weigh 24 kg of fly ash from a domestic waste power plant and 6 kg of powdered solid waste-based cementitious material and add them to a HJW-60 type experimental concrete mixer for mixing and stirring for 30 seconds. Then weigh 1.5 kg of water and add it, and continue to mix and stir for 60 seconds. Through forced stirring, all materials are fully mixed evenly. The evenly mixed powder is put into a 50-liter plastic bucket to obtain about 31 kg of mixed powder suitable for extrusion granulation.

[0066] The above-mentioned amount of added water is determined through experiments based on the existing test extrusion granulator used, and can be adjusted according to the extrusion form of the extrusion granulator, etc., to achieve the purpose of smoothly carrying out extrusion granulation with the mixed powder; the above-mentioned amount of added solid waste-based cementitious material is determined through experiments based on the quality of the existing fly ash used, and can be adjusted according to the quality of the fly ash, to achieve the purpose of initially solidifying and stabilizing heavy metals in the fly ash.

[0067] In this process method and steps, the method of adding powdered solid waste-based cementitious material to powdered fly ash as a solidification stabilizer is used to solidify and stabilize heavy metals in the powdered fly ash for the first time.

[0068] The fly ash used is untreated hazardous waste fly ash discharged from a domestic waste incineration power plant. After testing, the heavy metal leaching data are as shown in the following table (Table 1): Table 1 The solidification stabilizer used is a purchased powdered solid waste-based cementitious material product, whose quality meets the requirements of the "Technical Specification for the Application of Solid Waste-based Cementitious Materials" (T / CECS 689) standard, and the 28-day general mortar strength is 25.5 MPa.

[0069] Furthermore, the above-mentioned mixed powder is forcibly added to the feed inlet at the upper end of the test DJZ-1T type double-roll extrusion granulator with a pestle. Control the feeding speed to ensure the continuous and stable operation of the extrusion granulator.

[0070] Furthermore, the mixed powder enters the test DJZ-1T type double-roll extrusion granulator. Under the extrusion of the double rolls of the extrusion granulator, the apparent density is increased to more than 2200 Kg / m³. The powdered fly ash is extruded and granulated through the ball sockets on the double rolls, and is transformed into granular fly ash with a particle size of 3 - 10 mm and compressive properties, and comes out from the discharge port at the lower end of the DJZ-1T type double-roll extrusion granulator.

[0071] Furthermore, the above-mentioned granular fly ash is put into a 50-liter plastic bucket, covered with a plastic film for moisture preservation, and left for 12 hours. The granular fly ash coagulates and hardens, and its compressive property is improved, thus obtaining granular fly ash. After testing, the apparent density of the granular fly ash is 2260 Kg / m³.

[0072] The diameter of the ball sockets on the double rolls of the above-mentioned test extrusion granulator is φ8 mm. Parameters such as the level of extrusion pressure and the size of the ball sockets on the double rolls can be adjusted to achieve the purpose of increasing the density of the granular fly ash and being suitable for powder granulation.

[0073] In this process method and steps, while carrying out extrusion granulation, the heavy metals are co-solidified and stabilized for the first time by mechanical extrusion while increasing the density and compressive property of the granular fly ash, and the compressive property of the granular fly ash is further improved by coagulation and hardening.

[0074] Furthermore, add the above coagulated and hardened granular fly ash to the feed inlet at the upper end of the 150×300 type hammer crushing sand making machine for the test. Control the feeding speed to ensure the continuous and stable operation of the crushing sand making machine.

[0075] In the hammer crushing sand making machine, the granular fly ash is all crushed into sand-like particles with a particle size of less than 5 mm by the impact of the crushing hammers and continuously comes out from the discharge port at the lower end of the crusher. A semi-finished solid waste-based recycled sand with reasonable particle gradation and low powder content is obtained.

[0076] The rotation speed of the above hammer crushing sand making machine is 800 revolutions per minute, and the aperture of the discharge screen plate is 4.0 mm. The rotation speed and the aperture of the screen plate can be adjusted to achieve the purpose of reasonable particle gradation of the crushed granular fly ash and reducing the powder content in the particles.

[0077] Weigh 500 grams of the above semi-finished solid waste-based recycled sand and put it into a standard square-hole sand and gravel sleeve sieve for a screening test with a screening testing machine to detect the particle gradation of the semi-finished solid waste-based recycled sand. After testing, the particle gradation data are as follows: 0% with a particle size (mm) greater than 4.75; 9% with a particle size of 4.75 - 2.36; 53% with a particle size of 2.36 - 1.18; 21% with a particle size of 1.18 - 0.6; 14% with a particle size of 0.6 - 0.3; 2% with a particle size of 0.3 - 0.15; and 1% with a particle size less than 0.15. After calculation, the fineness modulus of the semi-finished solid waste-based recycled sand is 3.5, the particle gradation zone is Zone 1, and the powder content is 1%.

[0078] Furthermore, prepare a composite curing liquid. Weigh 0.4 kg of silica fume, 0.2 kg of liquid fly ash heavy metal chelating agent, and 0.2 kg of styrene-acrylic emulsion, and add them together to the HJW-60 type concrete mixer for the test containing 9.2 kg of hot water at 60 - 80 °C, and mix and stir for 60 seconds. The composite curing liquid is obtained.

[0079] The above various materials for preparing the composite curing liquid are purchased. The quality of the silica fume meets the requirements of the standard "Silica Fume for Mortar and Concrete" (GB / T27690), with a specific surface area greater than 15000 m² / kg; the quality of the fly ash heavy metal chelating agent meets the requirements of the standard "Metal Chelating Agent" (QSL005), and the quality of the styrene-acrylic emulsion meets the requirements of the standard "Styrene-Acrylic Emulsion" (Q / 320400JZ006). The dosage and proportion of various materials are determined through tests according to the quality of the existing fly ash used and can be adjusted according to the quality of the fly ash to achieve the purpose of solidifying heavy metals in the granular fly ash and reducing the water absorption rate of the granular fly ash.

[0080] Further, add the above-mentioned semi-finished solid waste-based recycled sand of about 31 kg into a test HJW-60 type concrete mixer containing the above-mentioned composite curing liquid, stir for 10 seconds, soak the semi-finished solid waste-based recycled sand with the composite curing liquid, pour out the soaked semi-finished solid waste-based recycled sand, and empty the composite curing liquid in the semi-finished solid waste-based recycled sand.

[0081] In this process method and steps, the method of adding a composite curing liquid to granular fly ash as a composite curing stabilizer is used to secondarily solidify and stabilize heavy metals in the granular fly ash, and at the same time block the capillary pores of the particles and reduce the water absorption rate of the semi-finished solid waste-based recycled sand.

[0082] Further, put the above-mentioned semi-finished solid waste-based recycled sand that has been soaked and emptied of the composite curing liquid into a 50-liter plastic bucket, cover it with a plastic film for moisture conservation and curing, and place it indoors at a temperature of 18 - 22 °C for 28 days to obtain a solid waste-based recycled sand product.

[0083] In this process method and steps, rely on moisture conservation and curing to secondarily synergistically solidify and stabilize heavy metals in the semi-finished solid waste-based recycled sand and further improve the compressive strength of the solid waste-based recycled sand.

[0084] Further, dry the above-mentioned solid waste-based recycled sand product and take samples for testing.

[0085] Specifically, entrust an inspection and testing agency to detect the radionuclides in the product according to the standard of "Limits of Radionuclides in Building Materials" (GB6566). The specific activity of natural radionuclides radium-226, thorium-232, and potassium-40, CRa, CTh, and Ck are 15.3, 4.6, and 21.4 respectively, and the internal exposure index IRa and external exposure index Ir are 0.1 and 0.1 respectively. It meets the requirements of the standard of "Limits of Radionuclides in Building Materials" (GB6566).

[0086] Similarly, entrust an inspection and testing agency to detect the heavy metal leaching situation in the product according to the standards of "Identification Standard for Toxicity Characteristics of Hazardous Wastes - Leaching Toxicity" (GB5085.3) and "Pollution Control Standard for Landfills of Municipal Solid Waste" (GB16889), and use the "Leaching Method for Solid Wastes - Tumbling Method" (GB5086.1) for leaching. At the same time, detect the heavy metal leaching situation of the sample solid waste-based recycled sand after detecting the crushing value, that is, the damaged solid waste-based recycled sand, observe the change of heavy metal leaching after the solid waste-based recycled sand is damaged, evaluate the change of heavy metal leaching in the damaged situation during the subsequent use of the solid waste-based recycled sand product, and compare it with the heavy metal leaching data of untreated hazardous waste fly ash. The specific comparison data are as follows in Table 2: Note: ND means not detected Table 2 The above comparative detection data of heavy metal leaching shows that: compared with the untreated hazardous waste fly ash, the heavy metal leaching value of the solid waste-based recycled sand product prepared by this process method and system is significantly reduced, meeting the requirements of the "Identification Standard for Toxicity Leaching of Hazardous Wastes" (GB5085.3) and the "Pollution Control Standard for Municipal Solid Waste Landfills" (GB16889).

[0087] When the solid waste-based recycled sand is damaged, the heavy metal leaching value does not increase significantly. It still meets the requirements of the "Identification Standard for Toxicity Leaching of Hazardous Wastes" (GB5085.3) and the "Pollution Control Standard for Municipal Solid Waste Landfills" (GB16889).

[0088] Similarly, a testing and inspection agency was entrusted to detect the main properties of the solid waste-based recycled sand product with reference to the standards of "Recycled Fine Aggregates for Concrete and Mortar" (GB / T25176) and "Recycled Sand Powder from Construction Solid Wastes" (JC / T2548).

[0089] The specific data are as follows: apparent density 2260 Kg / m³, fineness modulus 3.4, particle size distribution zone 1, powder content 2.3%, crushing value 26.8%. It meets the requirements of the standards of "Recycled Fine Aggregates for Concrete and Mortar" (GB / T25176) and "Recycled Sand Powder from Construction Solid Wastes" (JC / T2548).

[0090] The above detection data shows that the radionuclides of the solid waste-based recycled sand product prepared by this process method and system are qualified. Heavy metals are effectively fixed, and even when damaged during use, the heavy metal leaching still meets the standard requirements. The solid waste-based recycled sand has a relatively good particle size distribution, a relatively low crushing value, and a relatively low powder content, and can replace part of the sand in materials such as non-reinforced buildings and road subgrade projects with relatively low technical requirements. When used in engineering materials without using steel bars (due to the unstable chloride ion content in the product, it is not suitable for use in reinforced cement structures), the quality meets the relevant standard requirements.

[0091] Example 2 Devices with various structures can be used to achieve the purpose of Example 1. As long as the used mixing and stirring device can stir the powder and water evenly and can extrude and granulate, the used extrusion granulation device can extrude and granulate the mixed powder and increase the density of the granular fly ash to more than 2200 Kg / m³, the used crushing and sand-making device can crush the granular fly ash into sand-like particles with a particle size less than 5 mm, the used batching device can heat and stir evenly the silica fume, liquid heavy metal chelating agent, styrene-acrylic emulsion, and water, the used particle soaking device can soak the granular fly ash, and the used particle curing device can moisturize and cure the granular fly ash.

[0092] Therefore, for the large-scale industrial implementation of this process method and production device, the following specific solutions are designed.

[0093] As shown Figure 2 in the figure, a production device for preparing solid waste-based recycled sand from fly ash at normal temperature includes a mixer 1, a granulator 2, a particle hardening bin 3, a crushing and sand-making machine 4, a particle soaking tank 5, and an airtight curing bin 6. The fly ash, cementitious material, and water are stirred and mixed by the mixer 1 to form a mixed powder. The mixed powder is successively granulated by the granulator 2, coagulated and hardened in the particle hardening bin 3, sanded by the crushing and sand-making machine 4, soaked in the particle soaking tank 5, and cured in the airtight curing bin 6.

[0094] Specifically, the discharge port of the mixer 1 is successively connected to a mixed powder bin 13 and a forced feeder 14. The evenly stirred mixed powder is sent into the mixed powder bin 13, and the mixed powder in the mixed powder bin 13 is sent into the granulator 2 through the forced feeder 14. The mixed powder is extruded into particles by the granulator 2. The discharge port of the granulator 2 is connected to the particle hardening bin 3 through a conveying device. The granular fly ash is stored in the particle hardening bin 3 for about 10 hours, and the granular fly ash coagulates and hardens to form granular fly ash. The particle hardening bin 3 is connected to the crushing and sand-making machine 4 through a feeder 11, and the coagulated and hardened granular fly ash is sent into the crushing and sand-making machine 4. The granular fly ash is crushed by the crushing and sand-making machine 4 to form sand-like granular fly ash. The crushing and sand-making machine 4 is connected to the particle soaking tank 5, and the sand-like granular fly ash enters the particle soaking tank 5 for soaking. After soaking, it is sent into the airtight curing bin 6 through a conveying device for curing, and is kept moist at 600 degree-days to form a solid waste-based recycled sand product.

[0095] It also includes a raw material bin (storage tank) 9 and a weighing device 10. Each raw material (silica fume, solid waste-based cementitious material, hazardous waste fly ash, heavy metal chelating agent solution, styrene-acrylic emulsion, tap water) corresponds to a raw material bin (storage tank) 9. After weighing the required amount of raw materials by the weighing device 10 (specifically, an electronic weighing scale can be used), they are sent into the corresponding device. At the same time, an automatic control device can also be set for automatic control.

[0096] It also includes a composite curing liquid batching tank 7. The composite curing liquid batching tank 7 is equipped with a heating device to heat the inside of the composite curing liquid batching tank 7. The composite curing liquid batching tank 7 is connected to the particle soaking tank 5 through a composite curing liquid feeding pump 12, and the composite curing liquid is sent into the particle soaking tank 5 through the composite curing liquid feeding pump 12.

[0097] It also includes a liquid recovery tank 15 and a composite curing liquid recovery pump 8 in the airtight curing bin 6. The liquid recovery tank 15 is connected to the particle soaking tank 5 through the composite curing liquid recovery pump 8. The composite curing liquid vacated from the semi-finished solid waste-based recycled sand stored in the airtight curing bin 6 flows into the liquid recovery tank 15 and enters the particle soaking bin 5 through the composite curing liquid recovery pump 8 to realize the recycling of the composite curing liquid.

[0098] Specifically, complete sets of equipment and facilities in the fly ash solidification industry and concrete mixing equipment and facilities in the ready-mixed concrete industry can be used to prepare mixed powder materials, roller or screw extrusion granulation equipment and facilities in the compound fertilizer granulation industry can be used to prepare granular fly ash, hammer or impact crushing equipment and facilities in the sand and gravel processing industry can be used to prepare crushed granular fly ash, batching equipment and facilities in the admixture compounding industry can be used to prepare compound solidification liquid, spiral or wheel sand washing equipment and facilities in the sand and gravel processing industry can be used to soak granular fly ash, and a sealed storage warehouse (room) can be used for the moisture conservation and maintenance of granular fly ash.

[0099] Select models for the above equipment and facilities and match the production capacity between the equipment and facilities. Use conveying equipment to transport the materials from the previous process to the next process, and scientifically combine them into a device system according to the process method and steps of this process, then the industrial large-scale implementation of this process method and device for preparing solid waste-based recycled sand can be realized.

[0100] Example 3 Use the solid waste-based recycled sand product prepared in Example 1 to replace part of the sand for non-structural and non-reinforced ready-mixed concrete for comparative tests to verify the feasibility and reliability of using the solid waste-based recycled sand product as a raw material in ready-mixed concrete. The following comparative tests are verified in the laboratory.

[0101] The main relevant standards and specifications are: "Ready-mixed Concrete" (GB / T14902), "Code for Design of Mix Proportions of Ordinary Concrete" (JGJ55), "Technical Specification for Application of Recycled Aggregates" (JGJ / T240).

[0102] Specifically, use existing raw materials such as cement, mineral powder, fly ash, manufactured sand, stones, pumping agent, etc. to design the mix proportion of C20 ready-mixed pumped concrete as the reference concrete mix proportion (No. 1). Use the solid waste-based recycled sand prepared in Embodiment 1 to replace part of the manufactured sand as the comparative concrete mix proportion (No. 2). The volume replacement rate of the solid waste-based recycled sand replacing the manufactured sand is 50%. The specific mix proportion of each cubic meter of concrete is shown in the following table (Table 3), and the weight unit is Kg.

[0103] Table 3 Since the apparent density of the above solid waste-based recycled sand is 2260 Kg / m³ and the apparent density of the used manufactured sand is 2680 Kg / m³, the volume of 337 Kg of solid waste-based recycled sand is the same as that of 400 Kg of manufactured sand, and the weight replacement rate of the solid waste-based recycled sand replacing the manufactured sand is 45.7%.

[0104] Since the solid waste-based recycled sand has a fast water absorption rate, a high water absorption rate, and adsorbing the pumping agent will result in a reduction in the workability of the ready-mixed concrete, when conducting the comparative concrete (No. 2) test, measures are taken to pre-wet the solid waste-based recycled sand with water in advance to make the moisture content of the solid waste-based recycled sand reach 5%, and a special pumping agent for recycled aggregates is used.

[0105] After calculation, the weight proportion of fly ash in the prepared solid waste-based recycled sand reaches more than 70%. Therefore, the above 337 Kg of solid waste-based recycled sand contains more than 236 Kg of fly ash. The theoretical bulk density of the comparative concrete (No. 2) is 2285 Kg / m³, and the amount of fly ash consumed per cubic meter of the comparative concrete (No. 2) is 236 Kg. The weight proportion of fly ash in each ton of concrete is 10.3%.

[0106] Furthermore, weigh out the above various raw materials corresponding to 25 liters of concrete and add them to the HJW-60 type experimental concrete mixer for comparative tests.

[0107] The various raw materials required for the 25-liter concrete comparative test are as follows in the following table (Table 4), and the weight unit is Kg.

[0108] Table 4 Furthermore, use the HJW-60 type experimental concrete mixer to prepare the reference concrete (No. 1) mixture and the comparative concrete (No. 2) mixture, conduct comparative inspection and testing in accordance with the "Test Methods for Performance of Ordinary Concrete Mixtures" (GB / T 50080), make test blocks respectively in accordance with the "Test Methods for Mechanical Properties of Ordinary Concrete" (GB / T 50081) and conduct comparative inspection and testing after standard curing. The specific data is as follows in the following table (Table 5).

[0109] Table 5 The above comparative inspection and testing data show that using the solid waste-based recycled sand product prepared by this process method and system to replace more than 45% by weight of the manufactured sand in the non-structural and non-reinforced ready-mixed concrete of C20 strength grade, the concrete quality meets the requirements of the "Ready-Mixed Concrete" (GB / T 14902) standard.

[0110] The above comparative verification shows that the weight proportion of fly ash in each ton of concrete can reach more than 10%, and each cubic meter of concrete can consume more than 230 Kg of fly ash.

[0111] Example 4 The solid waste-based recycled sand product prepared in Example 1 was used to replace part of the stone chips (fine aggregate) for the cement stabilized material (cement stabilized subbase) of the roadbed of roads at or below the second level for a comparative test to verify the feasibility and reliability of using the solid waste-based recycled sand product as a raw material in the cement stabilized material (cement stabilized base course) of the roadbed of roads at or below the second level.

[0112] The following comparative test was verified in the laboratory. The main relevant standards and specifications relied on were: "Recycled Aggregate Inorganic Mixture for Road Use" (JC / T 2281), "Technical Rules for Construction of Highway Pavement Base Course" (JTG / T F20).

[0113] Specifically, using existing coarse aggregate (5 - 31.5 mm crushed stone), fine aggregate (stone chips), and cement (PO.42.5), after conducting a compaction test in accordance with "Test Procedures for Inorganic Binding Material Stabilized Materials in Highway Engineering" (JTGE 51), the mix proportion of the cement stabilized material for the road subbase was designed as the reference mix proportion (No. 1), and the prepared solid waste-based recycled sand was used to replace part of the stone chips as the comparative mix proportion (No. 2). The weight replacement rate of the solid waste-based recycled sand replacing part of the fine aggregate (stone chips) was 50%.

[0114] The mix proportion of each ton of the cement stabilized material for the road subbase is as follows in Table 6 below, with the weight unit being Kg.

[0115] Table 6 Since the solid waste-based recycled sand has a fast water absorption rate and a high water absorption rate, which will lead to poor construction performance of the cement stabilized material for the road subbase, therefore, when conducting the comparative test (No. 2), measures were taken to wet the solid waste-based recycled sand with water in advance to make the moisture content of the solid waste-based recycled sand reach 5%.

[0116] After calculation, the weight proportion of fly ash in the prepared solid waste-based recycled sand reached more than 70%. Therefore, the above 275 Kg of solid waste-based recycled sand contains more than 193 Kg of fly ash. The amount of fly ash consumed per ton of the comparative road subbase cement stabilized material (No. 2) is 172 Kg, and the weight proportion of fly ash is 17.2%.

[0117] Furthermore, the above various raw materials corresponding to 40 Kg of the cement stabilized material for the road subbase were weighed and added to an HJW-60 type experimental concrete mixer for a comparative test verification.

[0118] The various raw materials required for the 40 Kg of the cement stabilized material for the road subbase comparative test are as follows in Table 7 below, with the weight unit being Kg.

[0119] Table 7 Further, the reference road subbase cement stabilized material (Serial No. 1) and the comparative road subbase cement stabilized material (Serial No. 2) were prepared using a HJW-60 type test concrete mixer. Specimens were made respectively in accordance with the "Test Regulations for Inorganic Binding Material Stabilized Materials in Highway Engineering" (JTGE51) and subjected to standard curing, and then the unconfined compressive strength at 7 days was compared and tested.

[0120] Through comparative inspection and testing, the unconfined compressive strength at 7 days of the reference road subbase cement stabilized material (Serial No. 1) was 2.4 MPa, and the unconfined compressive strength at 7 days of the comparative road subbase cement stabilized material (Serial No. 2) was 2.1 MPa.

[0121] The above comparative inspection and testing data show that the solid waste-based recycled sand product prepared by the present process method and system replaces 50% by weight of the fine aggregate (stone chips) for the cement stabilized material (cement stabilized subbase) of the roadbed below the second level, and the quality meets the requirements of the "Recycled Aggregate Inorganic Mixture for Road Use" (JC / T2281) standard and complies with the provisions of the "Technical Rules for Construction of Highway Pavement Base" (JTG / TF20) standard.

[0122] The above comparative verification shows that the weight proportion of fly ash in each ton of cement stabilized material (cement stabilized subbase) can reach more than 17%, and each ton of cement stabilized material (cement stabilized subbase) can consume more than 170 Kg of fly ash.

[0123] Through the above embodiments, the beneficial effects of the present invention are verified.

[0124] Only the preferred embodiments of the present invention are described in detail above, but the present invention is not limited to the above embodiments.

Claims

1. A production process for preparing solid waste-based recycled sand from fly ash at normal temperature, characterized in that, It includes the following steps: S1. Prepare the mixed powder: Stir and mix fly ash, powdered solid waste-based cementitious material and water evenly to obtain the mixed powder; S2. Prepare granular fly ash: Mechanically extrude and granulate the mixed powder obtained in step S1, and after granulation, it coagulates and hardens to obtain granular fly ash; S3. Prepare semi-finished solid waste-based recycled sand: Crush the granular fly ash obtained in step S2 into sand-like particles to obtain semi-finished solid waste-based recycled sand; S4. Immerse the semi-finished solid waste-based recycled sand: Immerse the semi-finished solid waste-based recycled sand obtained in step S3 with a composite curing liquid; S5. Cure the semi-finished solid waste-based recycled sand: Keep the semi-finished solid waste-based recycled sand soaked in step S4 under moisturizing conditions to obtain solid waste-based recycled sand.

2. The production process of preparing solid waste-based recycled sand from fly ash at normal temperature according to claim 1, characterized in that: In step S1, first add 70 - 90 parts of hazardous waste fly ash from a domestic waste power plant and 10 - 30 parts of powdered solid waste-based cementitious material into a forced mixing and stirring device, mix and stir for 20 - 40 seconds, then add 2 - 20 parts of water, and continue to mix and stir for 30 - 60 seconds.

3. The production process of preparing solid waste-based recycled sand from fly ash at normal temperature according to claim 1, characterized in that: In step S2, the density of the granular fly ash reaches more than 2200 Kg / m³ through mechanical extrusion granulation, and the particle size of the granular fly ash is 2 - 10 mm; the mechanical extrusion granulation uses a pair-roll extrusion granulation device or a screw extrusion granulation device.

4. The production process of preparing solid waste-based recycled sand from fly ash at room temperature according to claim 1, characterized in that: In step S3, add the coagulated and hardened granular fly ash into a crushing and sand-making device for crushing into sand-like particles with a particle size of less than 5 mm.

5. The production process of preparing solid waste-based recycled sand from fly ash at normal temperature according to claim 1, characterized in that, In step S4, the composite curing liquid used for immersing the semi-finished solid waste-based recycled sand is a composite curing liquid prepared by adding silica fume, liquid heavy metal chelating agent and styrene-acrylic emulsion into hot water and stirring evenly.

6. The production process for preparing solid waste-based recycled sand from fly ash at normal temperature according to claim 5, characterized in that: Mix 3 - 5 parts of silica fume, 1 - 3 parts of liquid heavy metal chelating agent, 0 - 5 parts of styrene-acrylic emulsion and 90 - 100 parts of hot water at a temperature of 50 - 80 °C evenly in a batching device to obtain the composite curing liquid.

7. The production process of preparing solid waste-based recycled sand from fly ash at normal temperature according to claim 1, characterized in that: In step S5, add the soaked semi-finished solid waste-based recycled sand into a particle curing device for normal temperature moisturizing curing for 300 - 600 degree-days; the humidity in the particle curing device is 85 - 95%.

8. A production device for preparing solid waste-based recycled sand from fly ash at normal temperature, characterized in that: It includes a mixer (1), a granulator (2), a particle hardening bin (3), a crushing and sand-making machine (4), a particle soaking tank (5) and an airtight curing bin (6); through the mixer (1), fly ash, powdered solid waste-based cementitious material and water are stirred and mixed into a mixed powder, and the mixed powder sequentially passes through granulation by the granulator (2), coagulation and hardening in the particle hardening bin (3), sand-making by the crushing and sand-making machine (4), soaking in the particle soaking tank (5) and curing in the airtight curing bin (6).

9. The production device for preparing solid waste-based recycled sand from fly ash at normal temperature according to claim 8, characterized in that: It further includes a composite curing liquid batching tank (7), and a heating device is provided on the composite curing liquid batching tank (7) to heat the inside of the composite curing liquid batching tank (7); the composite curing liquid batching tank (7) is connected to the particle soaking tank (5) through a composite curing liquid feeding pump (12).

10. A production device for preparing solid waste-based recycled sand from fly ash at normal temperature according to claim 8, characterized in that: It further includes a composite curing liquid recovery pump (8), and a liquid recovery tank (15) in the airtight curing bin (6) is connected to the particle soaking tank (5) through the composite curing liquid recovery pump (8).

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