A method for preparing building blocks using fly ash from waste incineration and waste clay.

Abstract

This invention discloses a method for preparing building blocks using waste incineration fly ash and waste clay. The method includes first calcining the waste incineration fly ash and drying the waste clay, then grinding and sieving them to control the particle size of the raw materials; next, uniformly mixing the waste incineration fly ash, waste clay, and a calcium / alkalinity regulator, and adding water to adjust the moisture content to a specific level; pressing the uniformly mixed material into molds, aging it for a period of time, and then hydrothermally curing it; finally, low-temperature drying the cured body, followed by surface treatment, to obtain finished building blocks with a certain strength. The raw materials of this invention undergo a phase change under hydrothermal conditions to form a cured body with a certain strength, which not only effectively solidifies heavy metals and chlorine pollutants in the fly ash, but also achieves the synergistic utilization of waste incineration fly ash and waste clay.

Description

Technical Field

[0001] This invention belongs to the field of building block preparation method in the technical field of harmless disposal and resource utilization of inorganic waste, and in particular relates to a method for preparing building blocks using fly ash from waste incineration and waste clay. Background Technology

[0002] Fly ash is a byproduct collected in incineration flue gas purification systems and is classified as hazardous waste. It must be disposed of in hazardous waste landfills or, after harmless treatment, in sanitary landfills. With the increasing scarcity of land resources in cities and surrounding areas, landfill disposal of incineration fly ash is no longer sustainable, and resource utilization is imperative.

[0003] The current research on the resource utilization of waste incineration fly ash mainly includes: (1) producing cement auxiliary materials or concrete products, such as "Method for recycling waste incineration fly ash as cement material", "Method for using incineration fly ash as admixture to prepare ecological concrete", "A lightweight ceramsite concrete and its preparation method"; (2) preparing ceramsite, ceramics and brick building products by high-temperature sintering, such as "A waste incineration fly ash waste utilization sintered ceramsite and its preparation method", "A phase change ceramsite based on waste incineration fly ash and its preparation method and application", "A method for reusing waste incineration fly ash to produce thin ceramic bricks", "A method for preparing building ceramics using waste incineration fly ash and its preparation method", "A brick making process of municipal solid waste incineration fly ash"; (3) applying geopolymer solidifying agent to co-treat pollutants to obtain geopolymer impermeable clay, such as "A point-to-point targeted disposal and utilization method of waste incineration fly ash". However, due to the high chloride ion content in fly ash, its use in concrete engineering easily leads to steel reinforcement rusting. When used as a cement additive, it requires pre-treatment through washing, generating large amounts of hazardous wastewater and posing environmental pollution risks, making large-scale application difficult. High-temperature sintering methods also suffer from high energy consumption and cannot effectively solve the growing problem of incineration fly ash emissions. The method of using geopolymer solidifiers to treat fly ash to obtain geopolymer impermeable clay remains a low-value utilization of materials, and its application is limited to the protective layer of landfill impermeable systems. The amount of fly ash that can be disposed of is very limited.

[0004] In fact, waste clay in the southeastern coastal areas of my country usually contains a large amount of clay minerals, such as kaolinite, illite, and montmorillonite. Under alkaline and hydrothermal conditions, clay minerals easily react with Ca(OH)2 to form tobermorite, thus solidifying the weak soil into a high-strength solidified body. The patent "A Method for Solidifying Waste Incineration Fly Ash into a High-Strength Material" is based on hydrothermal solidification technology. It achieves the harmless treatment and resource utilization of fly ash through pretreatment by washing the fly ash with water and adding quartz and lime. This patent uses quartz as the main siliceous raw material, so the raw material does not have water sensitivity issues. Furthermore, this patent does not address the water stability and durability of the hydrothermally solidified product. The finished product has a rich capillary structure on its surface, which limits its large-scale application. Summary of the Invention

[0005] In order to solve the problems existing in the background art, the purpose of this invention is to provide a method for preparing building blocks using waste incineration fly ash and waste clay, aiming to solve the problems of harmless disposal of waste incineration fly ash and synergistic utilization of waste incineration fly ash and waste clay.

[0006] The technical solution adopted in this invention includes the following steps:

[0007] Step S1: Collect waste incineration fly ash and waste clay. Calcinate the collected waste incineration fly ash at 900~1000℃ for 10~15 minutes, while simultaneously drying the waste clay. Then, grind and sieve the calcined waste incineration fly ash and dried waste clay respectively to obtain waste incineration fly ash raw materials and waste clay raw materials with a particle size of less than 0.3mm.

[0008] Step S2: Mix the waste incineration fly ash raw material, waste clay raw material and calcium / alkalinity regulator evenly according to a certain mass fraction to obtain a mixture;

[0009] Step S3: Add tap water to the mixture obtained in step S2 to adjust the moisture content of the mixture to a specific moisture content, and then prepare the mixture into a shaped block sample by pressing, and control the dry density of the block sample to be between 90 and 95% of the maximum dry density of the mixture.

[0010] In step S3, the mixture and tap water should be thoroughly mixed within half an hour, and the block sample molding should be completed within one hour after obtaining the homogeneous mixture. This is to avoid excessive time, which could cause changes in the liquid and plastic limits of the raw materials and affect the molding quality of the specimens. The maximum dry density and optimum moisture content of the mixture are determined by standard compaction tests.

[0011] Step S4: The formed block sample is aged at 20~30℃ for 4~7 days, and then hydrothermally cured at 100~150℃ under saturated vapor pressure. After hydrothermal curing for 0~24 hours, the hydrothermal cured body is obtained.

[0012] In step S4, the formed block sample is sealed and aged to reduce the contact between the raw materials and carbon dioxide in the air.

[0013] Step S5: After low-temperature drying and surface treatment of the hydrothermal curing body obtained in step S4, the finished building blocks are finally prepared.

[0014] In step S1, the mass content of CaO in the waste incineration fly ash raw material is 20-40%, and the mass content of SiO2 in the waste clay raw material is 60-75%.

[0015] In step S2, the mass fraction of the waste incineration fly ash raw material is 48-70%, the mass fraction of the waste clay raw material is 30-52%, and the mass fraction of the calcium / alkalinity regulator is 0-10%.

[0016] In step S2, the calcium / alkalinity regulator is one or more of lime, calcium hydroxide, and sodium hydroxide.

[0017] In step S3, the specific moisture content is W. opt ~ W opt +5%, of which, W opt This represents the optimum moisture content of the mixture.

[0018] In step S5, the temperature for low-temperature drying is 60~80℃, and the drying time is 24~48h.

[0019] In step S5, the surface treatment method is one or a combination of two of the following: carbonization treatment and spraying liquid treatment agent.

[0020] In step S5, the compressive strength of the finished building blocks prepared is not less than 15 MPa.

[0021] The specific steps of the carbonization process are as follows:

[0022] First, a layer of magnesium oxide slurry is uniformly coated on the surface of the hydrothermal curing body, and then carbonization is carried out using CO2 to form a composite structure.

[0023] The liquid treatment agent includes one or more compositions of silane and organosilicon.

[0024] The method of this invention does not involve washing the fly ash with water, but utilizes the chloride ions present in the fly ash to lower the reaction temperature required for hydrothermal curing.

[0025] Waste incineration fly ash typically contains high levels of calcium oxide, and the leachate is highly alkaline, with the pH value of the fly ash in some areas even exceeding 12. Waste clay usually contains high levels of silicon but lacks calcium. When the two are mixed in a certain proportion, under hydrothermal and strongly alkaline conditions, high-strength tobermorite can be formed.

[0026] When the moisture content of the mixture is at (W) opt ~ W opt It is easier to ensure the quality of sample molding when the concentration is between +5% and 5%, where W opt The optimal moisture content is achieved by appropriately increasing the dry density of the molded block sample, which can improve the strength of the hydrothermal cured body. However, when the sample density exceeds 95%, hydrothermal curing treatment can easily lead to cracks in the cured body, thus affecting product quality.

[0027] Compared to existing technologies, this invention performs surface treatment on the solidified body after the hydrothermal reaction to form a composite structure. This not only enhances the durability of the finished specimen but also more firmly solidifies harmful substances in the fly ash within the specimen, greatly reducing their leakage and leaching. The purpose of calcining the fly ash in this invention is to decompose dioxins in the fly ash into harmless gases.

[0028] By modifying the surface of the solidified body, its water absorption rate can be significantly reduced and its durability increased.

[0029] The method of this invention mainly utilizes the characteristics of fly ash being highly alkaline and rich in calcium, and waste clay being rich in silicon, to cause the raw materials to undergo a phase change under hydrothermal conditions to form a solidified body with a certain strength. This not only achieves effective solidification of heavy metals and chlorine pollutants in fly ash, but also realizes the synergistic utilization of waste incineration fly ash and waste clay.

[0030] The beneficial effects of this invention are as follows:

[0031] 1. This invention mainly uses waste incineration fly ash and waste clay as raw materials, combined with appropriate amounts of calcium or alkalinity regulators, to prepare a solidified body, and further utilizes surface treatment technology to obtain high-performance block products. The method of this invention fully utilizes the calcium element in fly ash and the silicon element in clay; only a small amount of calcium agent and alkaline substances are needed for adjustment, which can produce building materials with low density, high strength, and good durability, resulting in good economic efficiency.

[0032] 2. The method of the present invention can effectively solidify heavy metals and chlorine and other pollutants in waste incineration fly ash, and at the same time realize the high-value utilization of waste incineration fly ash and waste clay.

[0033] 3. This invention does not perform water washing pretreatment on the fly ash from waste incineration. Instead, it utilizes elements such as chloride ions present in the fly ash to reduce the reaction temperature required for hydrothermal solidification by 50-100°C compared to the conventional CaO-SiO2-H2O reaction system, which further reduces energy consumption.

[0034] 4. This invention represents a breakthrough in the disposal and utilization of waste materials such as incineration fly ash and waste clay, and is of great significance in the fields of new building materials and environmental engineering. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the process flow of the method of the present invention.

[0036] Figure 2 This is a product display image of the building blocks prepared by the method of the present invention. Detailed Implementation

[0037] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0038] The implementation process of the embodiments of the present invention is as follows: Example 1

[0039] Step S1: Collect waste incineration fly ash and waste clay. Calcinate the waste incineration fly ash at 900℃ for 10 minutes, while drying the waste clay. Then, grind and sieve the calcined waste incineration fly ash and dried waste clay respectively to obtain waste incineration fly ash raw material and waste clay raw material with a particle size of less than 0.3mm.

[0040] Step S2: Mix the waste incineration fly ash, waste clay, and calcium hydroxide evenly to obtain a mixture; wherein the mass fraction of the waste incineration fly ash is 50%, the mass fraction of the waste clay is 45%, and the mass fraction of calcium hydroxide is 5%.

[0041] Step S3: Add tap water to the mixture obtained in step S2 to adjust the moisture content of the mixture to 29%. Use a mold and press to prepare the mixture into a shaped block sample, and control the dry density of the block sample to be 90% of the maximum dry density of the mixture.

[0042] Step S4: The formed block sample is aged at 20℃ for 5 days, and then hydrothermally cured at 140℃ and corresponding saturated steam pressure for 12 hours to obtain the hydrothermally cured body.

[0043] Step S5: Dry the hydrothermal curing body obtained in step S4 in an oven at 60°C for 24 hours. Then, coat the hydrothermal curing body with a layer of magnesium oxide slurry and perform carbonization treatment to finally obtain the finished building blocks. Example 2

[0044] Step S1: Collect waste incineration fly ash and waste clay. Calcinate the waste incineration fly ash at 950℃ for 15 minutes, while drying the waste clay. Then, grind and sieve the calcined waste incineration fly ash and dried waste clay respectively to obtain waste incineration fly ash raw material and waste clay raw material with a particle size of less than 0.3mm.

[0045] Step S2: Mix the waste incineration fly ash, waste clay, and calcium hydroxide evenly to obtain a mixture; wherein the mass fraction of the waste incineration fly ash is 45%, the mass fraction of the waste clay is 45%, and the mass fraction of calcium hydroxide is 10%.

[0046] Step S3: Add tap water to the mixture obtained in step S2 to adjust the moisture content of the mixture to 30%. Use a mold and press to prepare the mixture into a shaped block sample, and control the dry density of the block sample to be 90% of the maximum dry density of the mixture.

[0047] Step S4: The formed block sample is aged at 20℃ for 5 days, and then hydrothermally cured at 140℃ and corresponding saturated steam pressure for 12 hours to obtain the hydrothermally cured body.

[0048] Step S5: Dry the hydrothermal curing body obtained in step S4 in an oven at 60°C for 24 hours. Then, coat the hydrothermal curing body with a layer of magnesium oxide slurry and perform carbonization treatment. Finally, spray silane evenly on the surface of the hydrothermal curing body to obtain the finished building block. Example 3

[0049] Step S1: Collect waste incineration fly ash and waste clay. Calcinate the waste incineration fly ash at 950℃ for 10 minutes, while drying the waste clay. Then, grind and sieve the calcined waste incineration fly ash and dried waste clay respectively to obtain waste incineration fly ash raw materials and waste clay raw materials with a particle size of less than 0.3mm.

[0050] Step S2: Mix the waste incineration fly ash, waste clay, and calcium hydroxide evenly to obtain a mixture; wherein the mass fraction of the waste incineration fly ash is 45%, the mass fraction of the waste clay is 45%, and the mass fraction of calcium hydroxide is 10%.

[0051] Step S3: Add tap water to the mixture obtained in step S2 to adjust the moisture content of the mixture to 30%. Use a mold and press to prepare the mixture into a shaped block sample, and control the dry density of the block sample to be 95% of the maximum dry density of the mixture.

[0052] Step S4: The formed block sample is aged at 20℃ for 5 days, and then hydrothermally cured at 130℃ and corresponding saturated steam pressure for 18 hours to obtain the hydrothermally cured body.

[0053] Step S5: Dry the hydrothermal curing body obtained in step S4 in an oven at 70°C for 24 hours. Then, coat the hydrothermal curing body with a layer of magnesium oxide slurry and perform carbonization treatment. Finally, spray silane evenly on the surface of the hydrothermal curing body to obtain the finished building block.

[0054] The parameters and indicators of the example are shown in Table 1 below:

[0055] Table 1

[0056] index Example 1 Example 2 Example 3 Compressive strength / MPa 17.2 19.6 22.7 Water absorption rate / % / 4.2 3.6

[0057] As can be seen from the data in the table above, the blocks prepared by the method of this invention have excellent mechanical properties and can meet the relevant performance requirements of "Autoclaved Lime Sand Solid Bricks and Solid Blocks" (GB / T 11945-2019). Figure 2 The prepared building block product is shown. Combined with test data, it can be seen that through the process of this invention, specifically as follows... Figure 1 As shown, this invention enables the synergistic utilization of fly ash from waste incineration and waste clay. This invention significantly reduces the production cost of building blocks.

[0058] The examples described above are merely results of this invention in this instance, but the specific implementation of this invention is not limited to this example. Any alternative solutions with similar effects proposed in accordance with the principles and ideas of this invention should be considered within the scope of protection of this invention.

Claims

1. A method for preparing building blocks using fly ash from waste incineration and waste clay, characterized in that, Includes the following steps: Step S1: Collect waste incineration fly ash and waste clay. Calcinate the waste incineration fly ash at 900~1000℃ for 10~15 minutes, while drying the waste clay. Then, grind and sieve the calcined waste incineration fly ash and dried waste clay respectively to obtain waste incineration fly ash raw material and waste clay raw material with a particle size of less than 0.3mm. In step S1, the mass content of CaO in the waste incineration fly ash raw material is 20-40%, and the mass content of SiO2 in the waste clay raw material is 60-75%. Step S2: Mix the waste incineration fly ash raw material, waste clay raw material and calcium / alkalinity regulator evenly according to a certain mass fraction to obtain a mixture; In step S2, the mass fraction of the waste incineration fly ash raw material is 48-70%, the mass fraction of the waste clay raw material is 30-52%, and the mass fraction of the calcium / alkalinity regulator is 0-10%. Step S3: Add tap water to the mixture obtained in step S2 to adjust the moisture content of the mixture to a specific moisture content, and then prepare the mixture into a block sample by pressing, and control the dry density of the block sample to be between 90% and 95% of the maximum dry density of the mixture. In step S3, the specific moisture content is W opt ~ W opt +5%, of which W opt The optimum moisture content of the mixture; Step S4: The formed block sample is aged at 20~30℃ for 4~7 days, and then hydrothermally cured at 100~150℃ under saturated vapor pressure. After hydrothermal curing for 0~24 hours, the hydrothermal cured body is obtained. Step S5: After low-temperature drying and surface treatment of the hydrothermal curing body obtained in step S4, the finished building blocks are finally prepared; in step S5, the surface treatment method is carbonization treatment, spraying liquid treatment agent, carbonization treatment only, or a combination of both; in step S5, the compressive strength of the finished building blocks is not less than 15MPa. The specific steps of the carbonization process are as follows: First, a layer of magnesium oxide slurry is evenly coated on the surface of the hydrothermal curing body, and then carbonization is carried out using CO2.

2. The method for preparing building blocks using fly ash from waste incineration and waste clay according to claim 1, characterized in that: In step S2, the calcium / alkalinity regulator is one or more of lime, calcium hydroxide, and sodium hydroxide.

3. The method for preparing building blocks using fly ash from waste incineration and waste clay according to claim 1, characterized in that: In step S5, the temperature for low-temperature drying is 60~80℃, and the drying time is 24~48h.

4. The method for preparing building blocks using fly ash from waste incineration and waste clay according to claim 1, characterized in that: The liquid treatment agent includes one or more of silanes and organosilicones.

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