Lightweight high-strength fly ash-based ceramsite and preparation method thereof

Abstract

The application provides a fly ash-based lightweight high-strength ceramsite and a preparation method thereof, and belongs to the technical field of ceramsite. The fly ash-based lightweight high-strength ceramsite comprises the following raw materials in parts by weight: fly ash 10-20 parts, surface treatment sludge 5-10 parts, coal gangue or contaminated soil or a mixture of the two in any ratio 21-32 parts, construction waste 15-25 parts, waste glass 10-17 parts, oil-containing diatomite pyrolysis residue 7-12 parts, and waste emulsion 3-6 parts. The application reasonably utilizes fly ash and solid waste or hazardous waste for synergistic disposal, improves the ceramic performance of fly ash, and prepares the lightweight high-strength ceramsite.

Description

Technical Field

[0001] This invention belongs to the field of ceramsite technology, specifically relating to a lightweight, high-strength ceramsite based on fly ash and its preparation method. Background Technology

[0002] With the acceleration of urbanization and the improvement of people's living standards, the amount of urban domestic waste generated is increasing year by year. Waste incineration, as an effective waste treatment method, can significantly reduce waste volume and recover heat energy, but it also produces a certain amount of fly ash. Fly ash contains a large amount of heavy metals, dioxins, and other harmful substances, which will cause serious environmental pollution if not properly treated. Traditional fly ash treatment methods, such as landfill, not only occupy a large amount of land resources but also pose a risk of secondary pollution. Therefore, finding a method that can both achieve harmless treatment and resource utilization of fly ash is particularly important.

[0003] Expanded clay aggregate (ECA) is a lightweight aggregate with a porous structure, possessing numerous excellent properties such as light weight, high strength, thermal insulation, good fire resistance, and strong seismic performance. In the construction industry, ECA can be widely used in concrete preparation, lightweight partition boards, roof insulation and leveling, and landscaping. Concrete made with ECA as aggregate has a lower density than ordinary concrete, but maintains a higher compressive strength, effectively reducing the building's self-weight and lowering foundation engineering costs. Simultaneously, ECA's thermal insulation properties improve the building's energy efficiency, and its fire resistance enhances the building's fire safety. Furthermore, ECA has certain sound absorption properties, making it suitable for locations with high acoustic design requirements.

[0004] In recent years, the preparation of ceramsite from fly ash has become a research hotspot in the field of solid waste resource utilization. Researchers have successfully produced ceramsite products with certain properties by mixing fly ash with other raw materials such as clay, sludge, and fly ash, followed by pretreatment, granulation, and sintering processes. These studies have, to some extent, achieved the harmlessness and resource utilization of fly ash, providing new ideas for fly ash treatment. However, the technology for preparing ceramsite from fly ash is still in the research and pilot-scale stage. Although it has good application prospects, it still faces some problems that urgently need to be solved in practical applications. To reduce the content of harmful substances in fly ash and improve its ceramsite-forming performance, pretreatment of fly ash is usually required, such as dechlorination, impurity removal, and stabilization. However, these pretreatment methods are often cumbersome and costly. For example, commonly used chemical treatment methods such as acid washing and alkali washing generate large amounts of wastewater, which is difficult to treat and easily causes secondary pollution; while physical methods such as water washing are relatively simple, but their effectiveness in removing certain insoluble impurities and heavy metals is limited. Therefore, if the cumbersome steps of fly ash pretreatment can be reduced through co-processing, the utilization efficiency of fly ash will be greatly improved.

[0005] Furthermore, although fly ash ceramsite is lightweight, its strength still lags behind traditional ceramsite, particularly limiting its application in high-strength building structural materials. Therefore, the co-processing of fly ash to prepare high-performance ceramsite still holds significant potential for optimization and expansion.

[0006] In view of this, the present invention is hereby proposed. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a lightweight and high-strength ceramsite that improves the ceramic-forming performance of fly ash by synergistically treating fly ash, thus addressing the shortcomings of the prior art.

[0008] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a lightweight high-strength ceramsite based on fly ash, comprising the following raw materials in parts by weight: 10-20 parts fly ash, 5-10 parts surface-treated sludge, 21-32 parts coal gangue or contaminated soil or a mixture of both in any proportion, 15-25 parts construction waste, 10-17 parts waste glass, 7-12 parts oily diatomaceous earth pyrolysis residue, and 3-6 parts waste emulsion.

[0009] Optionally, the construction waste contains the following chemical components by mass percentage: SiO2 30-50%, CaO 5-15%, Al2O3 10-20%.

[0010] Optionally, the waste glass contains the following chemical composition by mass percentage: SiO2 ≥ 70%, Na2O 10-15%, CaO 5-10%.

[0011] Optionally, the mass percentage of SiO2 in the oil-containing diatomaceous earth pyrolysis residue is ≥60%.

[0012] Optionally, the particle size of the fly ash, coal gangue, contaminated soil, or a mixture of both in any proportion, construction waste, and oily diatomaceous earth pyrolysis residue is ≤100 mesh.

[0013] Optionally, the effective components and their mass percentage of the aforementioned lightweight high-strength ceramsite based on fly ash are...

[0014] The composition is as follows: SiO2 50-60%, Al2O3 15-23%, Fe2O3 3-5%, CaO 10-13%, MgO 1-3%, Na2O 3-8%, with the CaO / SiO2 ratio controlled at 0.2-0.3.

[0015] SiO2 is the main skeletal component of ceramsite. Through high-temperature sintering, SiO2 reacts with Al2O3 to form a stable silicate structure, and reacts with CaO (CaO / SiO2=0.2-0.3) to form wollastonite (CaSiO3), which reduces the melt viscosity, promotes uniform distribution of the liquid phase, and synergistically improves the strength and stability of ceramsite.

[0016] Al2O3: Enhances the hardness of ceramsite and forms a glassy phase with SiO2 during sintering, thereby increasing the strength of the ceramsite.

[0017] CaO + MgO: CaO can react with components such as SiO2 and Al2O3 to form stable silicates and aluminates, improving the strength of ceramsite. Simultaneously, CaO may react with Cl in fly ash, reducing Cl leaching. MgO, on the other hand, inhibits glass phase crystallization at high temperatures, improving creep resistance and reducing high-temperature deformation rate.

[0018] Fe2O3 undergoes an oxidation-reduction reaction during high-temperature sintering, releasing gases that assist in pore formation, creating a porous structure and reducing the density of the ceramsite.

[0019] Na2O: Lowers the sintering temperature, promotes melting and bonding between particles, improves the strength of ceramsite, and reduces energy consumption.

[0020] This invention also provides a method for preparing lightweight, high-strength ceramsite based on fly ash, comprising the following steps:

[0021] S1: Fly ash, surface treatment sludge, coal gangue or contaminated soil or a mixture of both in any proportion, construction waste, oily diatomaceous earth pyrolysis residue and waste emulsion are thoroughly mixed in a mixing device to obtain a mixture.

[0022] S2: The mixture is fed to a homogenizer for pressure homogenization to obtain a homogenized material;

[0023] S3: The homogeneous material is fed to a spray dryer for spray drying to obtain dry granules;

[0024] S4: The dry granules are conveyed to a high-temperature sintering furnace, which is preheated to 400-500°C and held for 30-50 minutes. Then the temperature is raised to 1050-1150°C and held for 20-40 minutes. After cooling, the product is obtained.

[0025] Optionally, the process parameters for pressurized homogenization include: homogenization pressure of 30-35 MPa, homogenization temperature of 40-50℃, and homogenization time of 15-20 min.

[0026] Optionally, the process parameters for spray drying include: inlet air temperature of 200-230℃, outlet air temperature of 70-80℃, and spray pressure of 0.8-1.0MPa.

[0027] The composition and function of each raw material in this invention are as follows:

[0028] Fly ash: Its main components are oxides such as SiO2, Al2O3, CaO, and Fe2O3, with SiO2 being the most abundant, followed by Al2O3. Fly ash contains heavy metals such as Pb and Cd, the content of which is affected by the composition of the waste and the incineration process. Fly ash provides an aluminosilicate framework, which forms a glassy phase at high temperatures, and heavy metals can be synergistically solidified at high temperatures.

[0029] Surface treatment sludge: belongs to HW17 surface treatment waste, specifically originating from: waste corrosion liquid, waste washing liquid, waste tank liquid, tank residue, and wastewater treatment sludge generated from acid (alkali) washing, degreasing, rust removal (excluding sandblasting), washing, phosphating, brightening, and chemical polishing processes on metal or plastic surfaces (excluding: wastewater treatment sludge from acid (alkali) washing, roughening, sulfuric acid anodizing, and phosphoric acid chemical polishing of aluminum and sheet surfaces; wastewater treatment sludge from chemical corrosion and non-boric acid liquefaction of aluminum electrode foil for aluminum electrolytic capacitors; wastewater treatment sludge from alkaline washing (molding) of aluminum extrusion molds; and wastewater treatment sludge from acid pickling and rust removal of carbon steel, including: phosphating sludge, pickling sludge, fluorine-containing sludge, etc., which contain a certain amount of heavy metal elements and organic matter. Some organic matter can be decomposed at high temperature to foam and create pores, reducing density. Reasonable addition optimizes porosity. At the same time, heavy metals can be fixed in the high-temperature glass phase or mineral phase, reducing the leaching risk.

[0030] Coal gangue: mainly contains SiO2, Al2O3, Fe2O3, and a small amount of C. Specifically, SiO2 accounts for 20-50%, Al2O3 15-30%, Fe2O3 1-7%, and CaO 0.5-5%. It primarily provides the silicon-aluminum source, forming a skeletal structure at high temperatures to improve the strength of the ceramsite. A small amount of carbon can regulate foaming and reduce density. Coal gangue and construction waste provide skeletal support, preventing the ceramsite from collapsing due to excessive micropores, maintaining low density while ensuring strength.

[0031] Contaminated soil: Industrial contaminated soil is selected, which contains not only mineral components such as silicon, aluminum, and iron, but also a certain amount of heavy metals and organic matter. As a raw material for preparing ceramsite, contaminated soil can provide silicon and aluminum sources. When used in combination with coal gangue, the ratio of the two can be adjusted as needed. Preferably, the mass ratio of coal gangue to contaminated soil is (1-9):1 to meet the skeletal structure requirements of ceramsite. At the same time, the heavy metals in the contaminated soil can be solidified at high temperatures to reduce leaching, and the organic matter can be further processed after decomposition. In addition, some gas participates in the pore formation of ceramsite, reducing the density of ceramsite.

[0032] Construction waste mainly contains CaO, SiO2, and Al2O3, with SiO2 accounting for 30-50% by mass, CaO 5-15%, and Al2O3 10-20%. It provides calcium and silicon-aluminum sources for the production of ceramsite, enhances the skeleton structure of coal gangue and / or contaminated soil, promotes the generation of high-temperature liquid phase, and enhances sintering density.

[0033] Waste glass mainly contains SiO2, Na2O, and K2O, with SiO2 ≥ 70%, Na2O 10-15%, and CaO 5-10%. It serves as a low-temperature melting agent, reducing the sintering temperature (1000-1150℃) and energy consumption. At the same time, it promotes the formation of the glass phase, encapsulates heavy metals, and enhances strength.

[0034] Oily diatomaceous earth pyrolysis residue: This is a pyrolysis product of oily diatomaceous earth, which is generated during the production of lubricating oil additives. It is classified as hazardous waste and poses a significant environmental risk. Currently, the treatment of oily diatomaceous earth uses an anaerobic high-temperature pyrolysis distillation process, producing a solid phase consisting of diatomaceous earth, inorganic matter, and residual carbon. Traditional treatment involves separating the deoiled diatomaceous earth, inorganic matter, and residual carbon. This invention directly utilizes this solid phase, which mainly contains SiO2 ≥ 60%, as well as carbon oxides and a small amount of residual carbon. It has a porous structure, and the porous structure of the residual organic matter provides a template for pore formation. Furthermore, the residual organic matter undergoes secondary high-temperature foaming, further reducing the density of the ceramsite.

[0035] Waste emulsions: Classified as HW09 oil / water, hydrocarbon / water mixtures, or emulsions in the National Hazardous Waste List (2025 Edition), containing three sub-codes: 900-005-09, 900-006-09, and 900-007-09. Industries generating waste emulsions primarily include machining, electronics, and surface treatment, with high organic content being a major pollution characteristic. Waste emulsions mainly contain water, oils, and surfactants, which can improve the formability of raw materials. Oils decompose at high temperatures to produce gas, creating foam and pores, optimizing pore distribution, and reducing density.

[0036] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0037] Based on the above technical solution, this invention provides a lightweight and high-strength ceramsite. By synergistically treating fly ash, the ceramsite forming performance of fly ash is improved. The fly ash is combined with a specific amount of surface-treated sludge, coal gangue or contaminated soil or a mixture of both in any proportion, construction waste, oily diatomaceous earth pyrolysis residue and waste emulsion. Through the synergy of components and processes, the strength of the ceramsite is further improved.

[0038] In this invention, oxides in fly ash and surface-treated sludge react with silicon and aluminum components in coal gangue, contaminated soil, or a mixture of both in any proportion, and construction waste to form a robust glassy substance, increasing the strength of the ceramsite. Simultaneously, CaO in the fly ash and heavy metal compounds in the surface-treated sludge undergo a chemical reaction during sintering to form a stable glassy substance, reducing the risk of heavy metal leaching. Coal gangue, contaminated soil, or a mixture of both in any proportion, and construction waste, both rich in SiO2 and Al2O3, synergistically strengthen the ceramsite skeleton, preventing collapse due to excessive micropores, maintaining low density while ensuring strength, improving durability, and reducing the leaching of harmful substances. The fluxing effect of waste glass combined with the micropore-forming effect of the oil-containing diatomaceous earth pyrolysis residue lowers the sintering temperature, reduces energy consumption, and simultaneously forms numerous micropores within the ceramsite, reducing density and improving thermal insulation performance. Both waste emulsion and oil-containing diatomaceous earth pyrolysis residue contain hydrocarbons, which burn and decompose during sintering, forming numerous micropores and further reducing the density of the ceramsite.

[0039] This invention optimizes the conventional ceramsite preparation process based on raw material characteristics. It adopts a process combining premixing, homogenization, spray drying, and high-temperature sintering. This allows the raw materials to be granulated after thorough mixing and homogenization, reducing component segregation and ensuring that all components in the granules react fully during high-temperature sintering. The granulation process uses spray drying with strictly controlled process parameters to controllably transform homogeneous materials into granules. During the drying process, water evaporation forms initial pores, laying the foundation for subsequent pore formation during sintering. The spray-dried granules are then sintered in a high-temperature sintering furnace. The furnace employs two-stage temperature control: first, 400-500℃ is maintained for 30-50 minutes to decompose the organic matter in the granules, preventing excessively rapid decomposition and release that could lead to structural collapse; then, the temperature is increased to 1050-1150℃ and maintained for 20-40 minutes, allowing the components to react and form a dense surface layer and an internal porous structure.

[0040] This invention achieves a bulk density of ≤800 kg / m³ for the obtained ceramsite through synergistic processing of raw materials and technology. 3 In particular, it includes density grades of 800, 700, 600, 500 and 400, with a water absorption rate of 6%-10% in 1 hour, a cylinder compressive strength ≥6.0MPa, a boiling mass loss ≤3.0%, a loss on ignition ≤4.2%, and sulfide and sulfate content (calculated as SO3), organic matter content, chloride content (calculated as chloride ion content), and radioactivity all meet the requirements of GB / T17431.1. Detailed Implementation

[0041] To better understand the present invention, the following embodiments further illustrate the content of the invention, but the scope of protection of the present invention is not limited to the following embodiments. Numerous specific details are set forth in the following description to provide a more thorough understanding of the invention. However, it will be apparent to those skilled in the art that the present invention can be practiced without one or more of these details.

[0042] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0043] Unless otherwise specified, all raw materials are derived from commercially available products and do not contain any unspecified components other than unavoidable impurities.

[0044] In the following cases, the chemical composition of the raw materials is as follows:

[0045] Construction waste contains the following chemical components by mass percentage: SiO2 30-50%, CaO 5-15%, Al2O3 10-20%.

[0046] Waste glass contains the following chemical composition by mass percentage: SiO2 ≥ 70%, Na2O 10-15%, CaO 5-10%.

[0047] The mass percentage of SiO2 in the pyrolysis residue of oil-containing diatomite is ≥60%.

[0048] The particle size of fly ash, coal gangue, contaminated soil, or a mixture of both in any proportion, construction waste, oily diatomaceous earth pyrolysis residue, and waste emulsion is 100 mesh.

[0049] In the following embodiments, a lightweight, high-strength ceramsite based on fly ash is made from the following raw materials in parts by weight: 10-20 parts fly ash, 5-10 parts surface-treated sludge, 21-32 parts coal gangue or contaminated soil or a mixture of both in any proportion, 15-25 parts construction waste, 10-17 parts waste glass, 7-12 parts pyrolysis residue of oily diatomaceous earth, and 3-6 parts waste emulsion.

[0050] Example 1: A lightweight, high-strength ceramsite based on fly ash, made from the following raw materials in parts by weight: 10 parts fly ash, 10 parts surface-treated sludge, 30 parts coal gangue, 20 parts construction waste, 15 parts waste glass, 10 parts oily diatomaceous earth pyrolysis residue, and 5 parts waste emulsion.

[0051] A lightweight, high-strength ceramsite based on fly ash has the following effective components and their mass percentage composition: SiO2 50.0%, Al2O3 21.3%, Fe2O3 3.5%, CaO 10.0%, MgO 2.3%, Na2O 8.0%, with the CaO / SiO2 ratio controlled at 0.20.

[0052] A method for preparing lightweight, high-strength ceramsite based on fly ash includes the following steps:

[0053] S1: Fly ash, surface treatment sludge, coal gangue, construction waste, oily diatomaceous earth pyrolysis residue and waste emulsion are thoroughly mixed in a mixing device to obtain a mixture;

[0054] S2: The mixture is fed to a homogenizer for pressure homogenization to obtain a homogenized material;

[0055] S3: The homogeneous material is fed to a spray dryer for spray drying to obtain dry granules;

[0056] S4: The dry granules are conveyed to the high-temperature sintering furnace, which is preheated to 450°C and held for 42 minutes. Then the temperature is increased to 1100°C and held for 30 minutes. After cooling, the product is obtained.

[0057] The process parameters for pressurized homogenization include: homogenization pressure of 32 MPa, homogenization temperature of 43℃, and homogenization time of 17 min.

[0058] The process parameters for spray drying include: inlet air temperature 210℃, outlet air temperature 75℃, and spray pressure 0.9MPa.

[0059] Example 2: A lightweight, high-strength ceramsite based on fly ash, made from the following raw materials in parts by weight: 18 parts fly ash, 9 parts surface-treated sludge, 28 parts coal gangue, 19 parts construction waste, 13 parts waste glass, 9 parts oily diatomaceous earth pyrolysis residue, and 4 parts waste emulsion.

[0060] A lightweight, high-strength ceramsite based on fly ash has the following effective components and their mass percentage composition: SiO2 60.0%, Al2O3 15.0%, Fe2O3 3.2%, CaO 12.3%, MgO 1.1%, Na2O 3.1%, with the CaO / SiO2 ratio controlled at 0.21.

[0061] A method for preparing lightweight, high-strength ceramsite based on fly ash includes the following steps:

[0062] S1: Fly ash, surface treatment sludge, coal gangue, construction waste, oily diatomaceous earth pyrolysis residue and waste emulsion are thoroughly mixed in a mixing device to obtain a mixture;

[0063] S2: The mixture is fed to a homogenizer for pressure homogenization to obtain a homogenized material;

[0064] S3: The homogeneous material is fed to a spray dryer for spray drying to obtain dry granules;

[0065] S4: The dry granules are conveyed to the high-temperature sintering furnace, which is preheated to 420°C and held for 45 minutes. Then the temperature is increased to 1120°C and held for 27 minutes. After cooling, the product is obtained.

[0066] The process parameters for pressurized homogenization include: homogenization pressure of 35 MPa, homogenization temperature of 40℃, and homogenization time of 15 min.

[0067] The process parameters for spray drying include: inlet air temperature 220℃, outlet air temperature 78℃, and spray pressure 0.8MPa.

[0068] Example 3: A lightweight, high-strength ceramsite based on fly ash, made from the following raw materials in parts by weight: 20 parts fly ash, 8 parts surface-treated sludge, 22 parts coal gangue, 23 parts construction waste, 14 parts waste glass, 82 parts oily diatomaceous earth pyrolysis residue, and 5 parts waste emulsion.

[0069] A lightweight, high-strength ceramsite based on fly ash has the following effective components and their mass percentage composition: SiO2 52.4%, Al2O3 20.8%, Fe2O3 3.0%, CaO 10.5%, MgO 2.5%, Na2O 4.5%, with the CaO / SiO2 ratio controlled at 0.20.

[0070] A method for preparing lightweight, high-strength ceramsite based on fly ash is described in Example 1.

[0071] Example 4: A lightweight, high-strength ceramsite based on fly ash, made from the following raw materials in parts by weight: 17 parts fly ash, 8 parts surface-treated sludge, 27 parts contaminated soil, 15 parts construction waste, 16 parts waste glass, 11 parts oily diatomaceous earth pyrolysis residue, and 6 parts waste emulsion.

[0072] A lightweight, high-strength ceramsite based on fly ash has the following effective components and their mass percentage composition: SiO2 53.0%, Al2O3 22.7%, Fe2O3 3.0%, CaO 11.2%, MgO 2.0%, Na2O 3.0%, with the CaO / SiO2 ratio controlled at 0.21.

[0073] A method for preparing lightweight, high-strength ceramsite based on fly ash includes the following steps:

[0074] S1: Fly ash, surface treatment sludge, contaminated soil, construction waste, oily diatomaceous earth pyrolysis residue and waste emulsion are thoroughly mixed in a mixing device to obtain a mixture;

[0075] S2: The mixture is fed to a homogenizer for pressure homogenization to obtain a homogenized material;

[0076] S3: The homogeneous material is fed to a spray dryer for spray drying to obtain dry granules;

[0077] S4: The dry granules are conveyed to the high-temperature sintering furnace, which is preheated to 500°C and held for 30 minutes. Then the temperature is increased to 1150°C and held for 20 minutes. After cooling, the product is obtained.

[0078] The process parameters for pressurized homogenization include: homogenization pressure of 35 MPa, homogenization temperature of 40℃, and homogenization time of 15 min.

[0079] The process parameters for spray drying include: inlet air temperature 200℃, outlet air temperature 70℃, and spray pressure 0.8MPa.

[0080] Example 5: A lightweight, high-strength ceramsite based on fly ash, made from the following raw materials in parts by weight: 19 parts fly ash, 10 parts surface-treated sludge, 21 parts contaminated soil, 25 parts construction waste, 10 parts waste glass, 12 parts oily diatomaceous earth pyrolysis residue, and 3 parts waste emulsion.

[0081] A lightweight, high-strength ceramsite based on fly ash has the following effective components and their mass percentage composition: SiO2 54.3%, Al2O3 15.5%, Fe2O3 4.8%, CaO 12.5%, MgO 2.3%, Na2O 4.0%, with the CaO / SiO2 ratio controlled at 0.23.

[0082] A method for preparing lightweight, high-strength ceramsite based on fly ash was carried out according to Example 4.

[0083] Example 6: A lightweight, high-strength ceramsite based on fly ash, made from the following raw materials in parts by weight: 17 parts fly ash, 9 parts surface-treated sludge, 24 parts coal gangue and contaminated soil mixture, 21 parts construction waste, 17 parts waste glass, 7 parts oily diatomaceous earth pyrolysis residue, and 5 parts waste emulsion, wherein the mass ratio of coal gangue to contaminated soil mixture is 5:1.

[0084] A lightweight, high-strength ceramsite based on fly ash has the following effective components and their mass percentage composition: SiO2 58.7%, Al2O3 15.0%, Fe2O3 3.2%, CaO 12.9%, MgO 1.0%, Na2O 3.6%, with the CaO / SiO2 ratio controlled at 0.22.

[0085] A method for preparing lightweight, high-strength ceramsite based on fly ash includes the following steps:

[0086] S1: Fly ash, surface treatment sludge, coal gangue and contaminated soil mixture, construction waste, oily diatomaceous earth pyrolysis residue and waste emulsion are thoroughly mixed in a mixing device to obtain a mixture.

[0087] S2: The mixture is fed to a homogenizer for pressure homogenization to obtain a homogenized material;

[0088] S3: The homogeneous material is fed to a spray dryer for spray drying to obtain dry granules;

[0089] S4: The dry granules are conveyed to the high-temperature sintering furnace, which is preheated to 400°C and held for 50 minutes. Then the temperature is increased to 1050°C and held for 40 minutes. After cooling, the product is obtained.

[0090] The process parameters for pressurized homogenization include: homogenization pressure of 30 MPa, homogenization temperature of 50℃, and homogenization time of 20 min.

[0091] The process parameters for spray drying include: inlet air temperature 230℃, outlet air temperature 80℃, and spray pressure 1.0MPa.

[0092] Example 7: A lightweight, high-strength ceramsite based on fly ash, made from the following raw materials in parts by weight: 15 parts fly ash, 7 parts surface-treated sludge, 32 parts coal gangue and contaminated soil mixture, 17 parts construction waste, 12 parts waste glass, 12 parts oily diatomaceous earth pyrolysis residue, and 5 parts waste emulsion, wherein the mass ratio of coal gangue to contaminated soil mixture is 1:1.

[0093] A lightweight, high-strength ceramsite based on fly ash has the following effective components and their mass percentage composition: SiO2 54.1%, Al2O3 16.5%, Fe2O3 3.5%, CaO 13.0%, MgO 1.5%, Na2O 4.5%, with the CaO / SiO2 ratio controlled at 0.24.

[0094] A method for preparing lightweight, high-strength ceramsite based on fly ash was carried out according to Example 6.

[0095] Example 8: A lightweight, high-strength ceramsite based on fly ash, made from the following raw materials in parts by weight: 20 parts fly ash, 5 parts surface-treated sludge, 29 parts coal gangue and contaminated soil mixture, 18 parts construction waste, 12 parts waste glass, 11 parts oily diatomaceous earth pyrolysis residue, and 5 parts waste emulsion, wherein the mass ratio of coal gangue to contaminated soil mixture is 9:1.

[0096] A lightweight, high-strength ceramsite based on fly ash has the following effective components and their mass percentage composition: SiO2 50.8%, Al2O3 17.6%, Fe2O3 4.2%, CaO 12.3%, MgO 1.2%, Na2O 6.7%, with the CaO / SiO2 ratio controlled at 0.24.

[0097] A method for preparing lightweight, high-strength ceramsite based on fly ash was carried out according to Example 6.

[0098] Comparative Example 1: A lightweight, high-strength ceramsite based on fly ash, differing from Example 1 in that fly ash is used instead of coal gangue. The preparation method for this comparative example is the same as that in Example 1.

[0099] Comparative Example 2: A type of ceramsite prepared from fly ash, differing from Example 1 in that the fly ash content was adjusted to 25 parts by weight, while the remaining raw materials and their weights remained unchanged. The preparation method for this comparative example is the same as in Example 1.

[0100] Comparative Example 3: A type of ceramsite prepared from fly ash, differing from Example 1 in that: the waste glass was adjusted to 20 parts by weight, the oily diatomaceous earth pyrolysis residue to 5 parts by weight, and the remaining raw materials and their weights remained unchanged. The preparation method for this comparative example is the same as in Example 1.

[0101] Comparative Example 4: A type of ceramsite prepared from fly ash, differing from Example 1 in that: the waste glass was adjusted to 5 parts by weight, the oily diatomaceous earth pyrolysis residue to 20 parts by weight, and the remaining raw materials and their weights remained unchanged. The preparation method for this comparative example is the same as that in Example 1.

[0102] Comparative Example 5: A type of ceramsite prepared from fly ash, differing from Example 1 in that the waste emulsion is omitted. The preparation method for this comparative example is the same as that in Example 1.

[0103] Comparative Example 6: A lightweight, high-strength ceramsite based on fly ash, differing from Example 1 in that the waste emulsion was adjusted to 10 parts by weight, while other raw materials and their weights remained unchanged. The preparation method for this comparative example is the same as in Example 1.

[0104] Comparative Example 7: A lightweight, high-strength ceramsite based on fly ash, which differs from Example 1 in that diatomaceous earth is used instead of the pyrolysis residue of oil-containing diatomaceous earth, while the other parameters remain unchanged.

[0105] Comparative Example 8: A lightweight, high-strength ceramsite based on fly ash, which differs from Example 1 in that the homogenization step is omitted in the preparation method, and the mixing time in the stirring equipment is increased by 20 min.

[0106] Next, the content of the evaluation test will be explained. The testing items, indicator requirements, and reference standards are shown in the table below:

[0107]

[0108] The ceramsite prepared in Examples 1-6 and Comparative Examples 1-8 were tested according to regulations, and the average value of the results was taken. The test results are recorded in Table 1 and Table 2, respectively.

[0109] Table 1 Performance test results of expanded clay in Examples 1-6

[0110]

[0111] Table 1 shows that the present invention can produce a density grade of 500 kg / m³. 3 600kg / m 3 700kg / m 3 and 800kg / m 3 The ceramsite has a compressive strength that is more than 30% higher than the standard requirement for the corresponding density grade, achieving a significant improvement in strength at the same density grade, while ensuring product safety.

[0112] The bulk density of the expanded clay aggregate of this invention is ≤800kg / m³. 3 The water absorption rate is between 6% and 10% in 1 hour, the cylinder compressive strength is ≥6.0MPa, the boiling mass loss is ≤3.0%, the loss on ignition is ≤4.2%, and the sulfide and sulfate content (calculated as SO3), organic matter content, chloride content (calculated as chloride ion content) and radioactivity all meet the requirements of GB / T17431.1.

[0113] Table 2. Performance test results of ceramsite in Comparative Examples 1-8

[0114]

[0115] Table 2 shows that, compared to Example 1, Comparative Example 1 showed an increase in the density of the expanded clay aggregate, but no significant increase in compressive strength. Comparative Example 2 showed a decrease in the density of the expanded clay aggregate compared to Example 1, but the decrease in compressive strength was more pronounced, failing to achieve the expected effect. Comparative Example 3 showed an increase in the density of the expanded clay aggregate compared to Example 1, but the produced expanded clay aggregate was brittle, and the compressive strength decreased instead of increasing. Comparative Example 4 showed a decrease in the density of the expanded clay aggregate compared to Example 1, and the decrease in compressive strength was more significant. Comparative Example 5 showed an increase in the density of the expanded clay aggregate compared to Example 1, but no significant increase in compressive strength, which is inferior to the present invention. Comparative Example 6 showed a significant decrease in the density of the expanded clay aggregate compared to Example 1, and the compressive strength also showed a significant decrease at the same density level. Comparative Example 7 showed an increase in the density of the expanded clay aggregate compared to Example 1, but no significant increase in strength, which is inferior to the present invention. Comparative Example 8 showed a significant decrease in both the density and compressive strength of the expanded clay aggregate compared to Example 1, indicating that homogenization is more beneficial for improving the performance of the expanded clay aggregate.

[0116] Therefore, it can be seen that the synergistic treatment effect of the ceramsite prepared by the present invention through fly ash and surface-treated sludge, coal gangue or contaminated soil or a mixture of the two in any proportion, construction waste, pyrolysis residue of oily diatomaceous earth and waste emulsion is more significant, the comprehensive performance of the ceramsite is more significant, the preparation process and composition are scientifically and rationally matched, and ceramsite products with higher compressive strength can be obtained under the same density level.

[0117] The expanded clay aggregate produced by this invention can be used as a high-strength lightweight aggregate in building materials or other fields.

[0118] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Any other modifications or equivalent substitutions made by those skilled in the art to the technical solutions of the present invention, as long as they do not depart from the spirit and scope of the technical solutions of the present invention, should be covered within the scope of the claims of the present invention.

Claims

1. A lightweight, high-strength ceramsite based on fly ash, characterized in that: The raw materials include the following parts by weight: fly ash 10-20 parts, surface treatment sludge 5-10 parts, coal gangue or contaminated soil or a mixture of both in any proportion 21-32 parts, construction waste 15-25 parts, waste glass 10-17 parts, oily diatomaceous earth pyrolysis residue 7-12 parts, and waste emulsion 3-6 parts. The effective components and their mass percentage composition are: SiO2 50.8-54.3%, Al2O3 15-17.6%, Fe2O3 3.2-3.5%, CaO 12.3-13%, MgO 2.3-3%, Na2O3 6.7%, and the CaO / SiO2 ratio is controlled at 0.2-0.

3. The lightweight, high-strength ceramsite is prepared through the following steps: S1: Fly ash, surface treatment sludge, coal gangue or contaminated soil or a mixture of both in any proportion, construction waste, oily diatomaceous earth pyrolysis residue and waste emulsion are thoroughly mixed in a mixing device to obtain a mixture. S2: The mixture is fed to a homogenizer for pressure homogenization. The process parameters for pressure homogenization include: homogenization pressure of 30-35 MPa, homogenization temperature of 40-50℃, and homogenization time of 15-20 min, to obtain homogenized material. S3: The homogeneous material is fed to a spray dryer for spray drying to obtain dry granules; S4: The dry granules are conveyed to a high-temperature sintering furnace, which is preheated to 400-500°C and held for 30-50 minutes. Then the temperature is raised to 1050-1150°C and held for 20-40 minutes. After cooling, the product is obtained.

2. The lightweight, high-strength ceramsite based on fly ash as described in claim 1, characterized in that: The construction waste contains the following chemical components by mass percentage: SiO2 30-50%, CaO 5-15%, Al2O3 10-20%.

3. The lightweight, high-strength ceramsite based on fly ash as described in claim 1, characterized in that: The mass percentage of SiO2 in the pyrolysis residue of the oil-containing diatomite is ≥60%.

4. The lightweight, high-strength ceramsite based on fly ash as described in claim 1, characterized in that: The particle size of the fly ash, surface-treated sludge, coal gangue or contaminated soil or a mixture of both in any proportion, construction waste and oily diatomaceous earth pyrolysis residue is ≤100 mesh.

5. The lightweight, high-strength ceramsite based on fly ash as described in claim 1, characterized in that: The process parameters for spray drying include: inlet air temperature 200-230℃, outlet air temperature 70-80℃, and spray pressure 0.8-1.0MPa.

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