A method for preparing SiO2 thermal insulation composite aerogel materials using gasification ash slag as a silicon source

Abstract

The application discloses a method for preparing SiO2 thermal insulation composite aerogel materials by taking gasification ash as a silicon source, and the method comprises the following steps: 1, crushing and grinding the gasification ash to obtain fine ash; 2, performing floatation treatment on undersize material of the fine ash after vibration screening, and collecting the bottom precipitate; 3, cleaning the bottom precipitate after acid washing to obtain a water washing product; 4, preparing a silicon source precursor by heating and refluxing the water washing product and a NaOH solution; 5, adding a crosslinking agent into the silicon source precursor to perform a gelation reaction, thereby obtaining a composite gel; the composite gel is immersed into a modifier / tert-butyl alcohol solution to modify the composite gel, thereby obtaining a modified composite gel; and 6, performing vacuum freeze drying on the composite gel or the modified composite gel. The method takes the cheap and non-toxic gasification ash as the silicon source, adopts a sol-gel and vacuum freeze drying process, realizes efficient and high-value utilization of the gasification ash resources, and is suitable for the fields of building energy-saving materials, dielectric materials, thermal insulation materials and the like.

Description

Technical Field

[0001] This invention belongs to the field of value-added utilization technology of gasification ash residue, specifically relating to a method for preparing SiO2 thermal insulation composite aerogel material using gasification ash residue as a silicon source. Background Technology

[0002] Coal gasification technology is the leading technology in modern coal chemical industry and a core technology for achieving clean and efficient utilization of coal. Currently, a large number of industrial-scale plants are operating stably. However, coal gasification ash is inevitably generated during the gasification process, and the output is enormous, exceeding 33 million tons annually. Currently, the main methods for disposing of gasification ash are stockpiling and landfilling, which incur additional processing costs. To expand the coal chemical industry chain and promote the low-carbon and zero-emission development of coal chemical industry, the large-scale resource utilization and harmless disposal of coal gasification ash are pressing issues that need to be addressed in the modern coal chemical industry. Although the composition of gasification ash varies depending on the raw coal, gasification technology, and operating conditions, it generally consists mainly of ash and residual carbon. The ash consists of SiO2, Al2O3, CaO, Fe2O3, etc. In some fluidized bed gasification ash, the SiO2 content can reach over 50%, and the SiO2 content is even higher in the solid ash after screening and decarbonization, as shown in Table 1. These substances are rich in silicon, making them suitable raw materials for preparing high-value-added silicon-based products. Extracting and utilizing silicon from them can not only improve and extend the comprehensive utilization industrial chain of gasification ash, but also solve a series of negative problems caused by gasification ash, promote the greening of the industrial chain structure, and realize the high-value-added utilization of gasification ash.

[0003] Table 1 Chemical composition of gasification ash

[0004]

[0005]

[0006] Aerogel materials possess structural characteristics such as low density, high specific surface area, and high porosity, giving them unique optical, thermal, and acoustic properties, including high temperature resistance, low thermal conductivity, and sound absorption and insulation. This makes them promising for applications in various fields such as thermal insulation, high-energy particle trapping, and sound absorption and insulation. There are many types of aerogel materials, among which SiO2 aerogel has the most mature commercial application, and its high-performance thermal insulation materials have broad application prospects. SiO2 aerogel possesses the characteristics of aerogel materials; its nanoporous network structure inhibits heat conduction by gas molecules, effectively limiting the propagation of localized thermal excitation. Its solid-state thermal conductivity is 2-3 orders of magnitude lower than that of corresponding glassy materials, with a room temperature thermal conductivity as low as 0.012 W / m·K. Furthermore, its high porosity (80%–99.8%) and low density (~0.003 g / cm³) also contribute to its advantages. 3 High specific surface area (>500m²)2 Properties such as ( / g) have attracted widespread attention and are now widely used in many fields such as thermal insulation.

[0007] Currently, improving energy efficiency and reducing energy consumption in SiO2 aerogels, as well as developing novel silicon sources, have become research hotspots. Furthermore, the preparation process parameters for SiO2 aerogels require continuous optimization. For example, patent 202010446290.8 uses tetraethyl orthosilicate as a silicon source to prepare SiO2 aerogels; patent 202010248939.5 utilizes tungsten oxide to improve the thermal insulation performance of SiO2 gels; and patent 202111583313.0 uses coal gasification slag as a silicon source and employs high-temperature calcination to prepare silicon source precursors. However, existing technologies suffer from drawbacks such as the use of toxic organosilicon sources and the high cost of inorganic silicon sources. Summary of the Invention

[0008] The technical problem to be solved by this invention is to address the shortcomings of the prior art by providing a method for preparing SiO2 thermal insulation composite aerogel materials using gasification ash as a silicon source. This method uses inexpensive and non-toxic gasification ash as a silicon source, leveraging its high silicon content, and employs sol-gel and vacuum freeze-drying processes to prepare SiO2 thermal insulation composite aerogel materials. This achieves efficient and high-value utilization of gasification ash resources, saves on gasification ash treatment costs, reduces pollution, and solves the problems of high raw material costs for both coal chemical gasification ash utilization and SiO2 aerogel.

[0009] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: a method for preparing SiO2 thermal insulation composite aerogel material using gasified ash slag as a silicon source, characterized in that the method includes the following steps:

[0010] Step 1: Crushing and Grinding

[0011] The collected gasification ash residue is crushed using a crusher and then ground using a wet ball mill to obtain fine slag.

[0012] Step 2: Screening and Floating / Sinking

[0013] Step 201: The fine slag obtained in Step 1 is vibrated and screened through a vibrating screen equipped with an iron remover to remove magnetic materials and some moisture. The material on the screen is then returned to Step 1 for grinding, and the material under the screen is collected. At the same time, the magnetic materials adsorbed on the iron remover are collected and processed centrally.

[0014] Step 202: Use ZnCl2 heavy liquid to perform flotation and sedimentation treatment on the sieve material collected in step 201, and collect the bottom precipitate;

[0015] Step 3: Removal of soluble ions

[0016] The bottom precipitate collected in step 202 was washed with acid solution in a tank equipped with a rotating stirrer, and then washed with deionized water to obtain the water-washed product.

[0017] Step 4: Preparation of silicon source precursor

[0018] The water-washed product obtained in step 3 was mixed with NaOH solution, stirred and heated under reflux, cooled to room temperature and then filtered to remove solid residues, thus obtaining the silicon source precursor.

[0019] Step 5: Gelization / Gel Modification

[0020] Add a crosslinking agent to the silicon source precursor obtained in step five and stir thoroughly. Then slowly add oxalic acid solution to adjust the pH and carry out the gelation reaction. After the gel is aged at room temperature, it is soaked in deionized water to remove excess water-soluble components and obtain a composite gel.

[0021] The composite gel was immersed in a modifier / tert-butanol solution to modify the functional groups on the surface of the composite gel. Then, the surface was washed with anhydrous ethanol to remove excess solution and obtain the modified composite gel.

[0022] Step 6: Vacuum freeze drying

[0023] The composite gel or modified composite gel obtained in step five is pre-frozen and then vacuum freeze-dried to obtain a SiO2 thermal insulation composite aerogel material.

[0024] This invention uses gasification ash as raw material. First, the gasification ash is thoroughly crushed and ground to fully expose its components. It is then subjected to vibrating sieving to remove magnetic substances and some moisture. After flotation and sedimentation, a precipitate is obtained, followed by acid washing and water washing to remove soluble ions. The precipitate is then heated and refluxed with an alkaline solution to transform it into a silicon source precursor solution. This solution is then gelled / modified to obtain a composite gel or modified composite gel. Finally, it is freeze-dried under vacuum to obtain a SiO2 thermal insulation composite aerogel material, which can be applied to thermal insulation materials. This invention uses readily available and inexpensive coal gasification byproducts—gasification ash—as a silicon source. This raw material is safe, non-toxic, abundant, and inexpensive, possessing a well-developed porous structure, a large specific surface area, and a high silicon content. This ensures that the SiO2 thermal insulation composite aerogel material retains the aforementioned high performance. This not only achieves high-value utilization of gasification ash resources but also solves the problem of high raw material costs in the preparation of SiO2 aerogels, providing a new approach for the high-value-added functional utilization of gasification ash.

[0025] The above-described method for preparing SiO2 thermal insulation composite aerogel material using gasification ash as a silicon source is characterized in that the gasification ash in step one can be replaced with silicon-containing ash from coal chemical byproducts, including coal direct liquefaction residue ash, coal pyrolysis residue ash, coal gangue, fly ash, and screened decarbonization solid phase ash, and the silicon content is 20% or more. More preferably, the silicon content is 40% or more.

[0026] The above-described method for preparing SiO2 thermal insulation composite aerogel material using gasification ash as a silicon source is characterized in that, in step one, the wet ball milling uses deionized water as the grinding solvent, and the mass ratio of solvent, grinding balls, and crushed gasification ash is 1:2:2 to 1:4:2, with a particle size of 0.125 mm or higher passing rate in the finely ground ash. This invention, by controlling the particle size of 0.125 mm to be above 70%, ensures the structural composition of the raw material gasification ash is broken down, facilitating the exposure of each component, simplifying subsequent separation steps, and promoting full reaction of the raw material. This avoids excessively fine particle size and high fly ash content, which can lead to operational difficulties, increased production energy consumption, and reduced economic efficiency of the preparation method. Simultaneously, it avoids excessively coarse particle size, which can cause the gasification ash to adhere, resulting in insufficient reaction and reduced performance of the composite aerogel product.

[0027] The method described above for preparing SiO2 thermal insulation composite aerogel material using gasified ash as a silicon source is characterized in that the density of the ZnCl2 heavy liquid in step 202 is 1.6 kg / L to 1.9 kg / L. More preferably, the density of the ZnCl2 heavy liquid is 1.7 kg / L to 1.9 kg / L. The precipitate obtained from treatment within this ZnCl2 heavy liquid density range has the highest content of gasified ash, reaching over 70%.

[0028] The above-described method for preparing SiO2 thermal insulation composite aerogel material using gasified ash as a silicon source is characterized in that, in step three, the stirring speed during the stirring and cleaning process is 700 r / min to 1000 r / min, the stirring time is 10 min to 50 min, and the mass concentration of the acid solution is 30% to 60%. More preferably, the acid solution is an H2SO4 solution or an HNO3 solution.

[0029] The above-described method for preparing SiO2 thermal insulation composite aerogel material using gasified ash slag as a silicon source is characterized in that, in step four, the concentration of the NaOH solution is 0.5 mol / L to 3.5 mol / L, the mass ratio of the water-washed product to the volume of the NaOH solution is 1:10, with mass measured in g and volume in mL; the reflux heating temperature is 100℃, and the time is 4 h. Reflux heating reduces NaOH solution volatilization, improves reaction efficiency, and thus increases the utilization rate of the reactant material.

[0030] The method described above for preparing SiO2 thermal insulation composite aerogel material using gasified ash as silicon source is characterized in that the crosslinking agent in step five is one of Na2CO3, sodium alginate, hydroxypropyl methylcellulose, polyimide, and β-cyclodextrin.

[0031] The method described above for preparing SiO2 thermal insulation composite aerogel material using gasification ash as a silicon source is characterized in that the concentration of the oxalic acid solution in step five is 0.5 mol / L to 3.5 mol / L, and the pH is adjusted to 7 by adding the oxalic acid solution to carry out the gelation reaction. More preferably, the concentration of the oxalic acid solution is 1.0 mol / L to 3.0 mol / L. This invention uses a strongly acidic oxalic acid solution, reducing the amount of pH adjusted during neutralization with NaOH. Simultaneously, considering the characteristics of the raw material, gasification ash contains a large number of metal ions, and oxalic acid can form water-soluble complexes with many metals, which can remove some of the metal ions not removed during the acid washing process to a certain extent, thus improving the performance of the composite aerogel material.

[0032] The method described above for preparing SiO2 thermal insulation composite aerogel material using gasified ash as a silicon source is characterized in that the modifier in the modifier / tert-butanol solution in step five is at least one selected from trimethylchlorosilane, hexamethyldisilazane, dodecyltrimethoxysilane, vinyltrimethylsilane, 3-(aminopropyl)triethoxysilane, tetrabutyl titanate, and hexadecyltrimethylammonium bromide, and the volume ratio of the modifier to tert-butanol is 1:5. Under the action of the above modifier, the SiO2 thermal insulation composite aerogel material prepared by this invention has a more uniform microstructure, lower density and thermal conductivity, and better hydrophobic and mechanical properties.

[0033] The above-mentioned method for preparing SiO2 thermal insulation composite aerogel material using gasified ash as silicon source is characterized in that the pre-freezing temperature in step six is ​​-196℃ to -5℃, and the time is 0.1h to 6h; the vacuum freeze-drying temperature of the modified composite gel or composite gel is -60℃ to -50℃, and the vacuum degree is 1.5Pa to 10Pa.

[0034] Compared with the prior art, the present invention has the following advantages:

[0035] 1. This invention uses inexpensive, readily available, safe, and non-toxic gasification ash as raw material. Taking advantage of the high silicon content of the gasification ash, a SiO2 thermal insulation composite aerogel material is prepared using sol-gel and vacuum freeze-drying processes. This composite aerogel material has a three-dimensional spatial network structure with richer pores, low thermal conductivity, and high elasticity. Its performance is comparable to that of thermal insulation aerogel materials prepared with conventional silicon sources. This invention realizes the high-value, resource-based, and harmless utilization of gasification ash resources and effectively reduces the preparation cost of aerogel materials.

[0036] 2. Unlike silicon sources derived from pure precursors, the silicon source gasification ash of this invention is derived from coal and contains components not found in pure silicon sources, such as carbides and inorganic components like Al2O3 and TiO2. No additional supplementation is required. The content of these inorganic components is moderate, and they are embedded in the gel network during the gelation process, effectively improving the radiative heat conduction performance of SiO2 gel and also having reinforcing and toughening functions, thereby improving the mechanical properties, elasticity, and thermal insulation performance of SiO2 thermal insulation composite aerogel materials.

[0037] 3. The present invention modifies the surface of the composite gel, which is beneficial to improve its microstructure uniformity, enhance the hydrophobicity and mechanical properties of the composite aerogel material, and reduce the thermal conductivity. Typically, the contact angle, which characterizes the hydrophobicity of the composite aerogel material, can be increased by 30%, the thermal conductivity can be reduced by 9%, and the mechanical properties can be improved by about 3%. Moreover, the high hydrophobicity of the modified composite aerogel material allows it to maintain a stable structure and thermal insulation effect during long-term use, showing great application potential.

[0038] 4. The raw materials of this invention are widely available. In addition to gasification fine slag, they can also be derived from coal direct liquefaction residue ash, coal pyrolysis residue ash, coal gangue, fly ash, and solid phase ash from screening and decarbonization, as well as silica-containing ash slag, which are byproducts of coal chemical industry. This invention effectively utilizes the SiO2 and some components that are difficult to remove, achieving secondary clean utilization of coal chemical byproducts. Since most of the raw materials require additional processing costs, the raw material utilization of this invention improves economic efficiency, reduces the amount of ash slag landfill, and mitigates the impact of ash slag from coal chemical plants on the surrounding environment, achieving an economical, green, and low-carbon effect.

[0039] 5. The entire process route of this invention uses industrial by-product gasification ash as raw material, and can achieve high added value utilization through a series of treatments. The required equipment and process conditions are simple, the threshold is low, and it is suitable for large-scale industrial production. The prepared SiO2 thermal insulation composite aerogel material is applicable to building energy-saving materials, dielectric materials, thermal insulation materials and other fields, and has a wide range of application prospects.

[0040] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0041] Figure 1 This is a process flow diagram of the present invention for preparing SiO2 thermal insulation composite aerogel material using gasified ash slag as silicon source. Detailed Implementation

[0042] Example 1

[0043] like Figure 1 As shown, this embodiment includes the following steps:

[0044] Step 1: Crushing and Grinding

[0045] The collected coarse slag from the multi-component slurry gasifier was crushed using a crusher and then ground using a wet ball mill. Deionized water was used as the grinding solvent in the wet ball mill, and the mass ratio of solvent, grinding balls, and crushed coarse slag from the multi-component slurry gasifier was 1:3:2. This yielded fine slag with a particle size of 0.125 mm and a throughput of over 70%. The silicon content of the coarse slag from the multi-component slurry gasifier was greater than 40%.

[0046] Step 2: Screening and Floating / Sinking

[0047] Step 201: The fine slag obtained in Step 1 is vibrated and screened through a vibrating screen equipped with an iron remover to remove magnetic materials and some moisture. The material on the screen is then returned to Step 1 for grinding, and the material under the screen is collected. At the same time, the magnetic materials adsorbed on the iron remover are collected and processed centrally.

[0048] Step 202: Use ZnCl2 heavy liquid with a density of 1.7 kg / L to perform flotation and sedimentation treatment on the sieve material collected in step 201, collect the bottom sediment, and collect the floating matter for centralized processing.

[0049] Step 3: Removal of soluble ions

[0050] The bottom precipitate collected in step 202 was washed with a 40% H2SO4 solution in a tank equipped with a rotary stirrer. The stirring speed was 800 r / min and the stirring time was 30 min. Then, the residue after stirring and washing was washed with deionized water for 15 min. The solution was recycled for stirring and washing to obtain the water-washed product.

[0051] Step 4: Preparation of silicon source precursor

[0052] The water-washed product obtained in step 3 was mixed with a 1.5 mol / L NaOH solution at a mass-to-volume ratio of 1:10 (mass in g, volume in mL). The mixture was then stirred and refluxed at 100°C for 4 hours. After cooling to room temperature, the mixture was filtered to remove solid residues and obtain the silicon source precursor.

[0053] Step 5: Gelization / Gel Modification

[0054] Add crosslinking agent Na2CO3 to the silicon source precursor obtained in step 5 and stir thoroughly. The ratio of the mass of crosslinking agent Na2CO3 added to the mass of coarse slag added in the multi-component slurry gasifier is 0.5:1. Then, slowly add oxalic acid solution with a concentration of 1.5 mol / L to adjust the pH to 7 to carry out the gelation reaction. After the gel is aged at room temperature for 24 hours, it is soaked in deionized water for 2 hours to remove excess water-soluble components and obtain composite gel.

[0055] The composite gel was immersed in a trimethylchlorosilane / tert-butanol solution with a volume ratio of 1:5 for 12 hours to modify the functional groups on the surface of the composite gel and realize the construction of gel functional groups. Then, the surface excess solution was washed with anhydrous ethanol to obtain the modified composite gel.

[0056] Step 6: Vacuum freeze drying

[0057] The modified composite gel obtained in step 5 was pre-frozen at -196℃ to -190℃ for 0.1h, and then vacuum freeze-dried at -60℃ to -58℃ and a vacuum degree of 1.5Pa to 3Pa to obtain SiO2 thermal insulation composite aerogel material.

[0058] The crosslinking agent in this embodiment can also be replaced with polyimide or β-cyclodextrin.

[0059] The modifier in this example can also be replaced with at least one of the following: trimethylchlorosilane, hexamethyldisilazane, dodecyltrimethoxysilane, vinyltrimethylsilane, 3-(aminopropyl)triethoxysilane, tetrabutyl titanate, and hexadecyltrimethylammonium bromide, in addition to trimethylchlorosilane.

[0060] Example 2

[0061] like Figure 1 As shown, this embodiment includes the following steps:

[0062] Step 1: Crushing and Grinding

[0063] The collected coarse slag from the multi-component slurry gasifier was crushed using a crusher and then ground using a wet ball mill. Deionized water was used as the grinding solvent in the wet ball mill, and the mass ratio of solvent, grinding balls, and crushed coarse slag from the multi-component slurry gasifier was 1:3:2. This yielded fine slag with a particle size of 0.125 mm and a throughput of over 70%. The silicon content of the coarse slag from the multi-component slurry gasifier was greater than 40%.

[0064] Step 2: Screening and Floating / Sinking

[0065] Step 201: The fine slag obtained in Step 1 is vibrated and screened through a vibrating screen equipped with an iron remover to remove magnetic materials and some moisture. The material on the screen is then returned to Step 1 for grinding, and the material under the screen is collected. At the same time, the magnetic materials adsorbed on the iron remover are collected and processed centrally.

[0066] Step 202: Use ZnCl2 heavy liquid with a density of 1.7 kg / L to perform flotation and sedimentation treatment on the sieve material collected in step 201, collect the bottom sediment, and collect the floating matter for centralized processing.

[0067] Step 3: Removal of soluble ions

[0068] The bottom precipitate collected in step 202 was washed with a 40% HNO3 solution in a tank equipped with a rotary stirrer. The stirring speed was 800 r / min and the stirring time was 30 min. Then, the residue after stirring and washing was washed with deionized water for 15 min. The solution was recycled for stirring and washing to obtain the water-washed product.

[0069] Step 4: Preparation of silicon source precursor

[0070] The water-washed product obtained in step 3 was mixed with a 1.5 mol / L NaOH solution at a mass-to-volume ratio of 1:10 (mass in g, volume in mL). The mixture was then stirred and refluxed at 100°C for 4 hours. After cooling to room temperature, the mixture was filtered to remove solid residues and obtain the silicon source precursor.

[0071] Step 5: Gelation

[0072] Add crosslinking agent Na2CO3 to the silicon source precursor obtained in step 5 and stir thoroughly. The ratio of the mass of crosslinking agent Na2CO3 added to the mass of coarse slag added in the multi-component slurry gasifier is 0.5:1. Then, slowly add oxalic acid solution with a concentration of 1.5 mol / L to adjust the pH to 7 to carry out the gelation reaction. After the gel is aged at room temperature for 24 hours, it is soaked in deionized water for 2 hours to remove excess water-soluble components and obtain composite gel.

[0073] Step 6: Vacuum freeze drying

[0074] The composite gel obtained in step 5 was pre-frozen at -25℃ to -20℃ for 4 hours, and then vacuum freeze-dried at -57℃ to -55℃ and a vacuum degree of 6Pa to 7Pa to obtain SiO2 thermal insulation composite aerogel material.

[0075] The crosslinking agent in this embodiment can also be replaced with polyimide or β-cyclodextrin.

[0076] Example 3

[0077] like Figure 1 As shown, this embodiment includes the following steps:

[0078] Step 1: Crushing and Grinding

[0079] The collected gasification slag from the multi-component slurry gasifier was crushed using a crusher and then ground using a wet ball mill. Deionized water was used as the grinding solvent in the wet ball mill, and the mass ratio of solvent, grinding balls, and crushed multi-component slurry gasification slag was 1:2:2. This resulted in finely ground slag with a particle size of 0.125 mm and a throughput of over 70%. The silicon content of the multi-component slurry gasification slag was greater than 30%.

[0080] Step 2: Screening and Floating / Sinking

[0081] Step 201: The fine slag obtained in Step 1 is vibrated and screened through a vibrating screen equipped with an iron remover to remove magnetic materials and some moisture. The material on the screen is then returned to Step 1 for grinding, and the material under the screen is collected. At the same time, the magnetic materials adsorbed on the iron remover are collected and processed centrally.

[0082] Step 202: Use ZnCl2 heavy liquid with a density of 1.8 kg / L to perform flotation and sedimentation treatment on the sieve material collected in step 201, collect the bottom sediment, and collect the floating matter for centralized processing.

[0083] Step 3: Removal of soluble ions

[0084] The bottom precipitate collected in step 202 was washed with a 45% H2SO4 solution in a tank equipped with a rotary stirrer. The stirring speed was 800 r / min and the stirring time was 30 min. Then, the residue after stirring and washing was washed with deionized water for 15 min. The solution was recycled for stirring and washing to obtain the water-washed product.

[0085] Step 4: Preparation of silicon source precursor

[0086] The water-washed product obtained in step 3 was mixed with a 1.0 mol / L NaOH solution at a mass-to-volume ratio of 1:10 (mass in g, volume in mL). The mixture was then stirred and heated under reflux at 100°C for 4 hours. After cooling to room temperature, the mixture was filtered to remove solid residues and obtain the silicon source precursor.

[0087] Step 5: Gelization / Gel Modification

[0088] Add sodium alginate, a crosslinking agent, to the silicon source precursor obtained in step five and stir thoroughly. The ratio of the mass of sodium alginate added to the mass of fine slag added in the multi-component slurry gasifier is 0.2:1. Then, slowly add oxalic acid solution with a concentration of 1.0 mol / L to adjust the pH to 7 to carry out the gelation reaction. After the gel is aged at room temperature for 24 hours, it is soaked in deionized water for 2 hours to remove excess water-soluble components and obtain a composite gel.

[0089] The composite gel was immersed in a dodecyltrimethoxysilane / tert-butanol solution with a volume ratio of 1:5 for 12 hours to modify the functional groups on the surface of the composite gel and realize the construction of gel functional groups. Then, the surface excess solution was washed with anhydrous ethanol to obtain the modified composite gel.

[0090] Step 6: Vacuum freeze drying

[0091] The modified composite gel obtained in step 5 was pre-frozen at -25℃ to -20℃ for 4 hours, and then vacuum freeze-dried at -52℃ to -50℃ and a vacuum degree of 8Pa to 10Pa to obtain SiO2 thermal insulation composite aerogel material.

[0092] The crosslinking agent in this embodiment can also be replaced with polyimide or β-cyclodextrin.

[0093] The modifier in this example can also be replaced with at least one of the following: trimethylchlorosilane, hexamethyldisilazane, dodecyltrimethoxysilane, vinyltrimethylsilane, 3-(aminopropyl)triethoxysilane, tetrabutyl titanate, and hexadecyltrimethylammonium bromide, in addition to dodecyltrimethoxysilane.

[0094] Example 4

[0095] like Figure 1 As shown, this embodiment includes the following steps:

[0096] Step 1: Crushing and Grinding

[0097] The collected fly ash was crushed using a crusher and then ground using a wet ball mill. Deionized water was used as the grinding solvent in the wet ball mill, and the mass ratio of solvent, grinding balls and crushed fly ash was 1:2:2, resulting in fine slag with a particle size of 0.125 mm and a throughput of over 70%. The fly ash had a silicon content of over 40%.

[0098] Step 2: Screening and Floating / Sinking

[0099] Step 201: The fine slag obtained in Step 1 is vibrated and screened through a vibrating screen equipped with an iron remover to remove magnetic materials and some moisture. The material on the screen is then returned to Step 1 for grinding, and the material under the screen is collected. At the same time, the magnetic materials adsorbed on the iron remover are collected and processed centrally.

[0100] Step 202: Use ZnCl2 heavy liquid with a density of 1.8 kg / L to perform flotation and sedimentation treatment on the sieve material collected in step 201, collect the bottom sediment, and collect the floating matter for centralized processing.

[0101] Step 3: Removal of soluble ions

[0102] The bottom precipitate collected in step 202 was washed with a 50% H2SO4 solution in a tank equipped with a rotary stirrer. The stirring speed was 800 r / min and the stirring time was 30 min. Then, the residue after stirring and washing was washed with deionized water for 15 min. The solution was recycled for stirring and washing to obtain the water-washed product.

[0103] Step 4: Preparation of silicon source precursor

[0104] The water-washed product obtained in step 3 was mixed with a 2.5 mol / L NaOH solution at a mass-to-volume ratio of 1:10 (mass in g, volume in mL). The mixture was then stirred and heated under reflux at 100°C for 4 hours. After cooling to room temperature, the mixture was filtered to remove solid residues and obtain the silicon source precursor.

[0105] Step 5: Gelization / Gel Modification

[0106] Hydroxypropyl methylcellulose was added to the silicon source precursor obtained in step five and stirred thoroughly. The mass ratio of the added crosslinking agent hydroxypropyl methylcellulose to the added fly ash was 0.1:1. Then, oxalic acid solution with a concentration of 2.5 mol / L was slowly added to adjust the pH to 7 to carry out the gelation reaction. The resulting gel was allowed to stand at room temperature for 24 hours and then soaked in deionized water for 2 hours to remove excess water-soluble components, thus obtaining a composite gel.

[0107] The composite gel was immersed in a vinyltrimethylsilane / tert-butanol solution with a volume ratio of 1:5 for 12 hours to modify the functional groups on the surface of the composite gel and construct the gel functional groups. Then, the surface excess solution was washed with anhydrous ethanol to obtain the modified composite gel.

[0108] Step 6: Vacuum freeze drying

[0109] The modified composite gel obtained in step 5 was pre-frozen at -196℃ to -190℃ for 0.1h, and then vacuum freeze-dried at -57℃ to -55℃ and a vacuum degree of 6Pa to 7Pa to obtain SiO2 thermal insulation composite aerogel material.

[0110] The crosslinking agent in this embodiment can also be replaced with polyimide or β-cyclodextrin.

[0111] The modifier in this example can also be replaced with at least one of the following: trimethylchlorosilane, hexamethyldisilazane, dodecyltrimethoxysilane, vinyltrimethylsilane, 3-(aminopropyl)triethoxysilane, tetrabutyl titanate, and hexadecyltrimethylammonium bromide, in addition to vinyltrimethylsilane.

[0112] Example 5

[0113] like Figure 1 As shown, this embodiment includes the following steps:

[0114] Step 1: Crushing and Grinding

[0115] The collected decarburized solid ash was crushed using a crusher and then ground using a wet ball mill. Deionized water was used as the grinding solvent in the wet ball mill, and the mass ratio of solvent, grinding balls, and crushed decarburized solid ash was 1:3:2, resulting in fine slag with a particle size of 0.125 mm and a passing rate of over 70%. The silicon content of the decarburized solid ash was greater than 60%.

[0116] Step 2: Screening and Floating / Sinking

[0117] Step 201: The fine slag obtained in Step 1 is vibrated and screened through a vibrating screen equipped with an iron remover to remove magnetic materials and some moisture. The material on the screen is then returned to Step 1 for grinding, and the material under the screen is collected. At the same time, the magnetic materials adsorbed on the iron remover are collected and processed centrally.

[0118] Step 202: Use ZnCl2 heavy liquid with a density of 1.8 kg / L to perform flotation and sedimentation treatment on the sieve material collected in step 201, collect the bottom sediment, and collect the floating matter for centralized processing.

[0119] Step 3: Removal of soluble ions

[0120] The bottom precipitate collected in step 202 was washed with a 50% H2SO4 solution in a tank equipped with a rotary stirrer. The stirring speed was 700 r / min and the stirring time was 30 min. Then, the residue after stirring and washing was washed with deionized water for 15 min. The solution was recycled for stirring and washing to obtain the water-washed product.

[0121] Step 4: Preparation of silicon source precursor

[0122] The water-washed product obtained in step 3 was mixed with a 3.0 mol / L NaOH solution at a mass-to-volume ratio of 1:10 (mass in g, volume in mL). The mixture was then stirred and heated under reflux at 100°C for 4 hours. After cooling to room temperature, the mixture was filtered to remove solid residues and obtain the silicon source precursor.

[0123] Step 5: Gelization / Gel Modification

[0124] Add sodium alginate, a crosslinking agent, to the silicon source precursor obtained in step five and stir thoroughly. The ratio of the mass of sodium alginate added to the mass of the decarbonized solid ash slag after sieving is 0.3:1. Then, slowly add oxalic acid solution with a concentration of 3.0 mol / L to adjust the pH to 7 to carry out the gelation reaction. After the gel is aged at room temperature for 24 hours, it is soaked in deionized water for 2 hours to remove excess water-soluble components and obtain a composite gel.

[0125] The composite gel was immersed in a 3-(aminopropyl)triethoxysilane / tert-butanol solution with a volume ratio of 1:5 (3:5) for 12 hours to modify the functional groups on the surface of the composite gel and construct the gel functional groups. Then, the surface excess solution was washed with anhydrous ethanol to obtain the modified composite gel.

[0126] Step 6: Vacuum freeze drying

[0127] The modified composite gel obtained in step 5 was pre-frozen at -196℃ to -190℃ for 0.1h, and then vacuum freeze-dried at -52℃ to -50℃ and a vacuum degree of 8Pa to 10Pa to obtain SiO2 thermal insulation composite aerogel material.

[0128] The crosslinking agent in this embodiment can also be replaced with polyimide or β-cyclodextrin.

[0129] The modifier in this example can also be replaced with at least one of the following: trimethylchlorosilane, hexamethyldisilazane, dodecyltrimethoxysilane, vinyltrimethylsilane, 3-(aminopropyl)triethoxysilane, tetrabutyl titanate, and hexadecyltrimethylammonium bromide, in addition to 3-(aminopropyl)triethoxysilane.

[0130] Example 6

[0131] like Figure 1 As shown, this embodiment includes the following steps:

[0132] Step 1: Crushing and Grinding

[0133] The collected coal gangue was crushed using a crusher and then ground using a wet ball mill. Deionized water was used as the grinding solvent in the wet ball mill, and the mass ratio of solvent, grinding balls and crushed coal gangue was 1:4:2, resulting in fine grinding residue with a particle size of 0.125mm and a throughput of over 70%. The silicon content of the coal gangue was greater than 30%.

[0134] Step 2: Screening and Floating / Sinking

[0135] Step 201: The fine slag obtained in Step 1 is vibrated and screened through a vibrating screen equipped with an iron remover to remove magnetic materials and some moisture. The material on the screen is then returned to Step 1 for grinding, and the material under the screen is collected. At the same time, the magnetic materials adsorbed on the iron remover are collected and processed centrally.

[0136] Step 202: Use ZnCl2 heavy liquid with a density of 1.9 kg / L to perform flotation and sedimentation treatment on the sieve material collected in step 201, collect the bottom sediment, and collect the floating matter for centralized processing.

[0137] Step 3: Removal of soluble ions

[0138] The bottom precipitate collected in step 202 was washed with a 45% H2SO4 solution in a tank equipped with a rotary stirrer. The stirring speed was 900 r / min and the stirring time was 30 min. Then, the residue after stirring and washing was washed with deionized water for 20 min. The solution was recycled for stirring and washing to obtain the water-washed product.

[0139] Step 4: Preparation of silicon source precursor

[0140] The water-washed product obtained in step 3 was mixed with a 2.0 mol / L NaOH solution at a mass-to-volume ratio of 1:10 (mass in g, volume in mL). The mixture was then stirred and refluxed at 100°C for 4 hours. After cooling to room temperature, the mixture was filtered to remove solid residues and obtain the silicon source precursor.

[0141] Step 5: Gelization / Gel Modification

[0142] Add sodium alginate, a crosslinking agent, to the silicon source precursor obtained in step five and stir thoroughly. The mass ratio of sodium alginate to coal gangue is 0.2:1. Then, slowly add 2 mol / L oxalic acid solution to adjust the pH to 7 to carry out the gelation reaction. After the gel is aged at room temperature for 24 hours, it is soaked in deionized water for 2 hours to remove excess water-soluble components and obtain a composite gel.

[0143] The composite gel was immersed in a trimethylchlorosilane and 3-(aminopropyl)triethoxysilane / tert-butanol solution with a total volume ratio of trimethylchlorosilane and 3-(aminopropyl)triethoxysilane to tert-butanol of 1:5 for 12 hours to modify the functional groups on the surface of the composite gel and realize the construction of gel functional groups. Then, the excess solution on the surface was washed with anhydrous ethanol to obtain the modified composite gel.

[0144] Step 6: Vacuum freeze drying

[0145] The modified composite gel obtained in step 5 was pre-frozen at -10℃ to -5℃ for 6 hours, and then vacuum freeze-dried at -60℃ to -58℃ and a vacuum degree of 1.5Pa to 3Pa to obtain SiO2 thermal insulation composite aerogel material.

[0146] The crosslinking agent in this embodiment can also be replaced with polyimide or β-cyclodextrin.

[0147] The modifier in this example can also be replaced with at least one of the following: trimethylchlorosilane, hexamethyldisilazane, dodecyltrimethoxysilane, vinyltrimethylsilane, 3-(aminopropyl)triethoxysilane, tetrabutyl titanate, and hexadecyltrimethylammonium bromide, in addition to the combination of trimethylchlorosilane and 3-(aminopropyl)triethoxysilane.

[0148] Example 7

[0149] like Figure 1 As shown, this embodiment includes the following steps:

[0150] Step 1: Crushing and Grinding

[0151] The collected GSP gasifier ash was crushed using a crusher and then ground using a wet ball mill. Deionized water was used as the grinding solvent in the wet ball mill, and the mass ratio of solvent, grinding balls, and crushed GSP gasifier ash was 1:3:2. This yielded fine slag with a particle size of 0.125 mm and a throughput of over 70%. The silicon content of the GSP gasifier ash was greater than 50%.

[0152] Step 2: Screening and Floating / Sinking

[0153] Step 201: The fine slag obtained in Step 1 is vibrated and screened through a vibrating screen equipped with an iron remover to remove magnetic materials and some moisture. The material on the screen is then returned to Step 1 for grinding, and the material under the screen is collected. At the same time, the magnetic materials adsorbed on the iron remover are collected and processed centrally.

[0154] Step 202: Use ZnCl2 heavy liquid with a density of 1.7 kg / L to perform flotation and sedimentation treatment on the sieve material collected in step 201, collect the bottom sediment, and collect the floating matter for centralized processing.

[0155] Step 3: Removal of soluble ions

[0156] The bottom precipitate collected in step 202 was washed with a 45% H2SO4 solution in a tank equipped with a rotary stirrer. The stirring speed was 800 r / min and the stirring time was 30 min. Then, the residue after stirring and washing was washed with deionized water for 15 min. The solution was recycled for stirring and washing to obtain the water-washed product.

[0157] Step 4: Preparation of silicon source precursor

[0158] The water-washed product obtained in step 3 was mixed with a 2.5 mol / L NaOH solution at a mass-to-volume ratio of 1:10 (mass in g, volume in mL). The mixture was then stirred and heated under reflux at 100°C for 4 hours. After cooling to room temperature, the mixture was filtered to remove solid residues and obtain the silicon source precursor.

[0159] Step 5: Gelization / Gel Modification

[0160] Add the crosslinking agent hydroxypropyl methylcellulose to the silicon source precursor obtained in step five and stir thoroughly. The mass ratio of the added crosslinking agent hydroxypropyl methylcellulose to the added GSP gasifier ash is 0.1:1. Then, slowly add 2.5 mol / L oxalic acid solution to adjust the pH to 7 to carry out the gelation reaction. After the obtained gel is aged at room temperature for 24 hours, it is soaked in deionized water for 2 hours to remove excess water-soluble components and obtain a composite gel.

[0161] The composite gel was immersed in a tetrabutyl titanate / tert-butanol solution with a volume ratio of 1:5 for 12 hours to modify the functional groups on the surface of the composite gel and realize the construction of gel functional groups. Then, the surface excess solution was washed with anhydrous ethanol to obtain the modified composite gel.

[0162] Step 6: Vacuum freeze drying

[0163] The modified composite gel obtained in step 5 was pre-frozen at -25℃ to -20℃ for 4 hours, and then vacuum freeze-dried at -57℃ to -55℃ and a vacuum degree of 6Pa to 8Pa to obtain SiO2 thermal insulation composite aerogel material.

[0164] The crosslinking agent in this embodiment can also be replaced with polyimide or β-cyclodextrin.

[0165] The modifier in this example can also be replaced with at least one of the following: trimethylchlorosilane, hexamethyldisilazane, dodecyltrimethoxysilane, vinyltrimethylsilane, 3-(aminopropyl)triethoxysilane, tetrabutyl titanate, and hexadecyltrimethylammonium bromide, in addition to tetrabutyl titanate.

[0166] Example 8

[0167] like Figure 1 As shown, this embodiment includes the following steps:

[0168] Step 1: Crushing and Grinding

[0169] The collected coarse slag from the multi-component slurry gasifier was crushed using a crusher and then ground using a wet ball mill. Deionized water was used as the grinding solvent in the wet ball mill, and the mass ratio of solvent, grinding balls, and crushed coarse slag from the multi-component slurry gasifier was 1:2:2. This yielded fine slag with a particle size of 0.125 mm and a throughput of over 70%. The silicon content of the coarse slag from the multi-component slurry gasifier was greater than 40%.

[0170] Step 2: Screening and Floating / Sinking

[0171] Step 201: The fine slag obtained in Step 1 is vibrated and screened through a vibrating screen equipped with an iron remover to remove magnetic materials and some moisture. The material on the screen is then returned to Step 1 for grinding, and the material under the screen is collected. At the same time, the magnetic materials adsorbed on the iron remover are collected and processed centrally.

[0172] Step 202: Use ZnCl2 heavy liquid with a density of 1.6 kg / L to perform flotation and sedimentation treatment on the sieve material collected in step 201, collect the bottom sediment, and collect the floating matter for centralized processing.

[0173] Step 3: Removal of soluble ions

[0174] The bottom precipitate collected in step 202 was washed with a 30% H2SO4 solution in a tank equipped with a rotary stirrer. The stirring speed was 700 r / min and the stirring time was 10 min. Then, the residue after stirring and washing was washed with deionized water for 15 min. The solution was recycled for stirring and washing to obtain the water-washed product.

[0175] Step 4: Preparation of silicon source precursor

[0176] The water-washed product obtained in step 3 was mixed with a 0.5 mol / L NaOH solution at a mass-to-volume ratio of 1:10 (mass in g, volume in mL). The mixture was then stirred and refluxed at 100°C for 4 hours. After cooling to room temperature, the mixture was filtered to remove solid residues and obtain the silicon source precursor.

[0177] Step 5: Gelization / Gel Modification

[0178] Add sodium alginate, a crosslinking agent, to the silicon source precursor obtained in step five and stir thoroughly. The ratio of the mass of sodium alginate added to the mass of coarse slag added in the multi-component slurry gasifier is 0.2:1. Then, slowly add 0.5 mol / L oxalic acid solution to adjust the pH to 7 to carry out the gelation reaction. After the gel is aged at room temperature for 24 hours, it is soaked in deionized water for 2 hours to remove excess water-soluble components and obtain a composite gel.

[0179] The composite gel was immersed in a trimethylchlorosilane / tert-butanol solution with a volume ratio of 1:5 for 12 hours to modify the functional groups on the surface of the composite gel and realize the construction of gel functional groups. Then, the surface excess solution was washed with anhydrous ethanol to obtain the modified composite gel.

[0180] Step 6: Vacuum freeze drying

[0181] The modified composite gel obtained in step 5 was pre-frozen at -196℃ to -190℃ for 0.1h, and then vacuum freeze-dried at -52℃ to -50℃ and a vacuum degree of 8Pa to 10Pa to obtain SiO2 thermal insulation composite aerogel material.

[0182] The crosslinking agent in this embodiment can also be replaced with polyimide or β-cyclodextrin.

[0183] The modifier in this example can also be replaced with at least one of the following: trimethylchlorosilane, hexamethyldisilazane, dodecyltrimethoxysilane, vinyltrimethylsilane, 3-(aminopropyl)triethoxysilane, tetrabutyl titanate, and hexadecyltrimethylammonium bromide, in addition to trimethylchlorosilane.

[0184] Example 9

[0185] like Figure 1 As shown, this embodiment includes the following steps:

[0186] Step 1: Crushing and Grinding

[0187] The collected coarse slag from the multi-component slurry gasifier was crushed using a crusher and then ground using a wet ball mill. Deionized water was used as the grinding solvent in the wet ball mill, and the mass ratio of solvent, grinding balls, and crushed coarse slag from the multi-component slurry gasifier was 1:4:2. This yielded fine slag with a particle size of 0.125 mm and a throughput of over 70%. The silicon content of the coarse slag from the multi-component slurry gasifier was greater than 40%.

[0188] Step 2: Screening and Floating / Sinking

[0189] Step 201: The fine slag obtained in Step 1 is vibrated and screened through a vibrating screen equipped with an iron remover to remove magnetic materials and some moisture. The material on the screen is then returned to Step 1 for grinding, and the material under the screen is collected. At the same time, the magnetic materials adsorbed on the iron remover are collected and processed centrally.

[0190] Step 202: Use ZnCl2 heavy liquid with a density of 1.9 kg / L to perform flotation and sedimentation treatment on the sieve material collected in step 201, collect the bottom sediment, and collect the floating matter for centralized processing.

[0191] Step 3: Removal of soluble ions

[0192] The bottom precipitate collected in step 202 was washed with a 60% H2SO4 solution in a tank equipped with a rotary stirrer. The stirring speed was 1000 r / min and the stirring time was 50 min. Then, the residue after stirring and washing was washed with deionized water for 20 min. The solution was recycled for stirring and washing to obtain the water-washed product.

[0193] Step 4: Preparation of silicon source precursor

[0194] The water-washed product obtained in step 3 was mixed with a 3.5 mol / L NaOH solution at a mass-to-volume ratio of 1:10 (mass in g, volume in mL). The mixture was then stirred and refluxed at 100°C for 4 hours. After cooling to room temperature, the mixture was filtered to remove solid residues and obtain the silicon source precursor.

[0195] Step 5: Gelization / Gel Modification

[0196] Add the crosslinking agent hydroxypropyl methylcellulose to the silicon source precursor obtained in step five and stir thoroughly. The ratio of the mass of the crosslinking agent hydroxypropyl methylcellulose added to the mass of the gasification coarse slag added in the multi-component slurry gasifier is 0.1:1. Then, slowly add oxalic acid solution with a concentration of 3.5 mol / L to adjust the pH to 7 to carry out the gelation reaction. After the gel is aged at room temperature for 24 hours, it is soaked in deionized water for 2 hours to remove excess water-soluble components and obtain a composite gel.

[0197] The composite gel was immersed in a trimethylchlorosilane / tert-butanol solution with a volume ratio of 1:5 for 12 hours to modify the functional groups on the surface of the composite gel and realize the construction of gel functional groups. Then, the surface excess solution was washed with anhydrous ethanol to obtain the modified composite gel.

[0198] Step 6: Vacuum freeze drying

[0199] The modified composite gel obtained in step 5 was pre-frozen at -10℃ to -5℃ for 6 hours, and then vacuum freeze-dried at -60℃ to -58℃ and a vacuum degree of 8Pa to 10Pa to obtain SiO2 thermal insulation composite aerogel material.

[0200] The crosslinking agent in this embodiment can also be replaced with polyimide or β-cyclodextrin.

[0201] The modifier in this example can also be replaced with at least one of the following: trimethylchlorosilane, hexamethyldisilazane, dodecyltrimethoxysilane, vinyltrimethylsilane, 3-(aminopropyl)triethoxysilane, tetrabutyl titanate, and hexadecyltrimethylammonium bromide, in addition to trimethylchlorosilane.

[0202] The performance of SiO2 thermal insulation composite aerogel materials prepared from gasified ash slag using different silicon sources in Examples 1-9 of this invention and aerogels in the prior art were tested, and the results are shown in Table 2 below.

[0203] Table 2. Performance of composite aerogel materials prepared in Examples 1-9 compared with aerogels in the prior art.

[0204]

[0205] In Table 2, "-" indicates that there are no test results for this performance; "*" in the cost savings column indicates additional revenue received without the need to purchase raw materials.

[0206] [1] Zheng Jilin, Jin Chengli, Liu Xiaoming. Green and low-cost preparation process of silica aerogel and its application in steam pipeline insulation [J]. China Building Materials Science and Technology, 2023, 32(04):77-81.

[0207] [2] Zhou Youdong. Preparation and performance study of flame-retardant high-elastic polyimide nanofiber / silica composite aerogel [D]. Beijing University of Chemical Technology, 2023. DOI:10.26939 / d.cnki.gbhgu.2023.000510.

[0208] As shown in Table 2, the thermal conductivity, density, specific surface area, and porosity of the SiO2 thermal insulation composite aerogel materials prepared using gasification ash from different silicon sources in Examples 1-9 of this invention are comparable to or close to those of aerogels in the prior art. This indicates that this invention utilizes chemical solid waste such as gasification ash, sieved decarburized ash, and coal gangue, as well as inexpensive raw materials, to prepare SiO2 thermal insulation composite aerogel materials, enabling high-value utilization of waste and producing high-performance alternative materials as novel insulation materials at low cost. Simultaneously, it reduces solid waste treatment costs and can generate additional revenue. Comparing Example 2 with Examples 1, 8, and 9, it is evident that the thermal conductivity and specific surface area of ​​the modified SiO2 thermal insulation composite aerogel materials are significantly improved, while the porosity is slightly increased, indicating that the modifier used in this invention significantly improves product performance.

[0209] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Any simple modifications, alterations, and equivalent changes made to the above embodiments based on the inventive essence shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing SiO2 thermal insulation composite aerogel material using gasification ash slag as a silicon source, characterized in that, The method includes the following steps: Step 1: Crushing and Grinding The collected gasification ash is crushed using a crusher and then ground using a wet ball mill to obtain fine slag. The wet ball mill uses deionized water as the grinding solvent, and the mass ratio of solvent, grinding balls and crushed gasification ash is 1:2:2 to 1:4:

2. The passing rate of 0.125mm particles in the fine slag is over 70%. Step 2: Screening and Floating / Sinking Step 201: The fine slag obtained in Step 1 is vibrated and screened through a vibrating screen equipped with an iron remover to remove magnetic materials and some moisture. The material on the screen is then returned to Step 1 for grinding, and the material under the screen is collected. At the same time, the magnetic materials adsorbed on the iron remover are collected and processed centrally. Step 202: The undersize material collected in step 201 is subjected to flotation and sedimentation treatment using ZnCl2 heavy liquid, and the bottom precipitate is collected; the density of the ZnCl2 heavy liquid is 1.6 kg / L~1.9 kg / L; Step 3: Removal of soluble ions The bottom precipitate collected in step 202 was washed with acid solution in a tank equipped with a rotating stirrer, and then washed with deionized water to obtain the water-washed product. Step 4: Preparation of silicon source precursor The water-washed product obtained in step 3 was mixed with NaOH solution, stirred and heated under reflux, cooled to room temperature and then filtered to remove solid residues, thus obtaining the silicon source precursor. Step 5: Gelization / Gel Modification Add a crosslinking agent to the silicon source precursor obtained in step four and stir thoroughly. Then, slowly add oxalic acid solution to adjust the pH to 7 to carry out the gelation reaction. After the gel is aged at room temperature, it is soaked in deionized water to remove excess water-soluble components and obtain a composite gel. The crosslinking agent is one of Na2CO3, sodium alginate, hydroxypropyl methylcellulose, polyimide and β-cyclodextrin. The composite gel was immersed in a modifier / tert-butanol solution to modify the functional groups on the surface of the composite gel. Then, the surface was washed with anhydrous ethanol to remove excess solution and obtain the modified composite gel. Step 6: Vacuum freeze drying The modified composite gel obtained in step five was pre-frozen and then vacuum freeze-dried to obtain a SiO2 thermal insulation composite aerogel material. In step five, the modifier in the modifier / tert-butanol solution is at least one of trimethylchlorosilane, hexamethyldisilazane, dodecyltrimethoxysilane, vinyltrimethylsilane, 3-(aminopropyl)triethoxysilane, tetrabutyl titanate, and hexadecyltrimethylammonium bromide, and the volume ratio of the modifier to tert-butanol is 1:

5.

2. The method for preparing SiO2 thermal insulation composite aerogel material using gasified ash slag as a silicon source according to claim 1, characterized in that, The stirring speed for the stirring and cleaning process in step three is 700 r / min to 1000 r / min, the stirring time is 10 min to 50 min, and the mass concentration of the acid solution is 30% to 60%.

3. The method for preparing SiO2 thermal insulation composite aerogel material using gasified ash slag as a silicon source according to claim 1, characterized in that, In step four, the concentration of the NaOH solution is 0.5 mol / L to 3.5 mol / L, the mass ratio of the water washing product to the volume of the NaOH solution is 1:10, the mass unit is g, and the volume unit is mL; the heating reflux temperature is 100℃, and the time is 4 h.

4. The method for preparing SiO2 thermal insulation composite aerogel material using gasified ash slag as a silicon source according to claim 1, characterized in that, The concentration of the oxalic acid solution mentioned in step five is 0.5 mol / L to 3.5 mol / L.

5. The method for preparing SiO2 thermal insulation composite aerogel material using gasified ash slag as a silicon source according to claim 1, characterized in that, The pre-freezing temperature in step six is ​​-196℃ to -5℃, and the time is 0.1h to 6h; the vacuum freeze-drying temperature of the modified composite gel is -60℃ to -50℃, and the vacuum degree is 1.5Pa to 10Pa.

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