Coal gasification fly ash microcapsule modification method based on combined modified agent compounding synergy

Abstract

The application discloses a coal gasification fly ash microcapsule modification method based on combined modification reagent compounding and cooperation, relates to the technical field of coal gasification fly ash treatment, and comprises the following steps: continuously feeding dried coal gasification fly ash and a combined modification reagent solution into a mechanical force chemical treatment equipment, allowing the coal gasification fly ash particles to depolymerize under the mechanical force of the mechanical force chemical treatment equipment, and allowing the combined modification reagent to form a coating layer on the particle surface and to be chemically activated; collecting the modified material, transferring the modified material into a sealed container for maintenance, and allowing the modification reaction to fully proceed; drying the maintained material to constant weight, grinding and sieving the maintained material, and obtaining modified fly ash with an inorganic gel coating layer and an organic hydrophobic coating layer. By adjusting the mass ratio of the combined modification reagent, the surface properties can be directionally adjusted between hydrophobicity and hydrophilicity, high dispersity and high activity, thereby providing a reliable and controllable technical path for high-value-added consumption of coal gasification fly ash in the field of building materials.

Description

Technical Field

[0001] This invention relates to the field of coal gasification fly ash treatment technology, specifically to a method for modifying coal gasification fly ash microcapsules based on the synergistic effect of combined modifying agents. Background Technology

[0002] Surface modification of coal gasification fly ash, a key technology for the resource utilization of industrial solid waste, aims to control the physicochemical properties of particle surfaces through physical or chemical means, transforming gasification residues into usable auxiliary cementitious materials. With the expansion of the coal chemical industry and increasingly stringent environmental policies, the utilization of coal gasification fly ash in the building materials sector has become a research hotspot.

[0003] Traditional fly ash modification often relies on single-agent pathways such as sodium silicate alkali activation or silane coupling agent hydrophobication, improving gelling properties or surface energy by adjusting agent concentration. However, these methods have significant limitations. First, while sodium silicate modification alone can increase the system's pH and promote the dissolution of the silica-alumina phase and NASH gel formation, high alkalinity compresses the electric double layer on the particle surface and weakens electrostatic repulsion, causing the slurry fluidity to decrease sharply with increasing admixture dosage, resulting in deteriorated casting density. Second, while sodium methylsilicate modification alone can graft hydrophobic methyl groups onto the particle surface, the degree of hydrolysis is limited, contributing little to the system's gelling activity and making it difficult to simultaneously achieve the construction of gelling material properties and hydrophobic properties. Third, when two agents are simply mixed, there is a lack of understanding of the correlation between the mixing ratio and the surface properties of the product.

[0004] In summary, although existing technologies have made breakthroughs in single indicators, they still have shortcomings in practical engineering applications, such as the inability to simultaneously construct inorganic gelling and hydrophobic functions, the unclear directional control mechanism between compounding ratio and product surface properties, and the difficulty in coordinating depolymerization and uniform coating in dry coating processes. Therefore, a method for modifying coal gasification fly ash microcapsules based on the synergistic compounding of combined modifying agents is proposed. Summary of the Invention

[0005] The main objective of this invention is to provide a method for modifying coal gasification fly ash microcapsules based on the synergistic combination of different modifying agents. By constructing a thin and dense coating layer on the surface of coal gasification fly ash particles, the physicochemical properties of the particle surface can be precisely controlled. This aims to solve the problems of the inability to simultaneously construct inorganic cementing and hydrophobic functions in coal gasification fly ash modified by a single agent, the unclear directional control mechanism between the compounding ratio and the surface properties of the product, and the difficulty in coordinating deagglomeration and uniform coating in dry coating processes.

[0006] Based on the first main aspect of the present invention, a method for modifying coal gasification fly ash microcapsules based on the synergistic effect of combined modifying agents is provided, comprising the following steps:

[0007] The dried coal gasification fly ash and the combined modifying agent solution are continuously fed into a mechanochemical treatment device. Under the mechanical force of the mechanochemical treatment device, the coal gasification fly ash particles are deagglomerated, and at the same time, the combined modifying agent forms a coating layer on the particle surface and is chemically activated. The combined modifying agent is prepared by mixing sodium silicate solution and sodium methylsilicate solution in a predetermined mass ratio.

[0008] Collect the modified material and transfer it to a sealed container for curing to allow the modification reaction to proceed fully;

[0009] The cured material was dried to constant weight, ground and sieved to obtain modified fly ash with an inorganic gel coating layer and an organic hydrophobic coating layer.

[0010] As a further preferred embodiment, in the aforementioned method, the sodium silicate solution is prepared by adding sodium hydroxide and free silica to the original sodium silicate to reduce its modulus.

[0011] As a further preferred embodiment, in the aforementioned method, the predetermined mass ratio is 1:1, 2:1, or 3:1.

[0012] As a further preferred embodiment, in the aforementioned method, the modulus of the sodium silicate solution is 2.4 to 2.7, and the mass fraction of the sodium methylsilicate solution is 20% to 30%.

[0013] As a further preferred embodiment, in the aforementioned method, when preparing the sodium silicate solution, the amount of sodium hydroxide to be added is calculated according to the following formula:

[0014] ;

[0015] in, This indicates the required mass of sodium hydroxide to be added. Indicates the original sodium silicate modulus. Indicates the target modulus.

[0016] As a further preferred embodiment, in the aforementioned method, the mechanochemical treatment equipment is a honeycomb mill, and its operating parameters are: main unit frequency of 30Hz, feeding frequency of 10Hz, and temperature set to 90-120℃.

[0017] When continuously feeding coal gasification fly ash and combined modified agent solution into the mechanochemical treatment equipment, a peristaltic pump is used for conveying at a frequency of 0.1.

[0018] As a further preferred embodiment, in the aforementioned method, the curing temperature is 60°C, the curing time is 24 hours, and the drying temperature for drying the cured material to constant weight is 105°C.

[0019] Based on the second main aspect of the present invention, a microencapsulated modified coal gasification fly ash is provided, which is obtained by the aforementioned method for modifying coal gasification fly ash by microencapsulation based on the synergistic compounding of combined modifying agents.

[0020] As a further preferred embodiment, the surface of the microcapsule-modified coal gasification fly ash has an inorganic gel layer formed by silicate reaction products and a hydrophobic layer formed by organosilane condensation products.

[0021] Based on a third key aspect of the present invention, a microcapsule-modified coal gasification fly ash cementitious material is provided, comprising the microcapsule-modified coal gasification fly ash as described above and a cementitious component, wherein the microcapsule-modified coal gasification fly ash accounts for 15% to 40% of the total mass of the cementitious material.

[0022] Compared with existing technologies, this invention first uses coal gasification fly ash as the modification target, employing a combined modifying agent formed by the compounding of sodium silicate and sodium methylsilicate. Dry microencapsulation modification is carried out under the mechanical force provided by a mechanochemical treatment device. Both sodium silicate and sodium methylsilicate are bulk chemical raw materials, widely available and cost-controllable. The mechanochemical treatment device is mature equipment used in large-scale industrial production. The entire process requires no reaction medium, generates no process wastewater, and the drying energy consumption is concentrated on the material itself rather than a large amount of liquid phase evaporation, reducing the overall energy consumption and environmental impact of the modification process.

[0023] Secondly, this invention combines sodium silicate and sodium methylsilicate in a predetermined mass ratio to simultaneously construct an inorganic gel network layer formed by the hydrolysis and condensation of sodium silicate and an organosilane hydrophobic layer formed by the hydrolysis and condensation of sodium methylsilicate on the surface of fly ash particles. The organic hydrophobic layer provides controllable surface wettability, realizing the synergistic expression of inorganic gelation and organic hydrophobic functions on a single particle surface, and solving the problem that inorganic gelation function and organic hydrophobic function cannot be constructed simultaneously in the prior art.

[0024] Furthermore, this invention addresses the technical problem of the lack of correlation between compounding ratio and product surface properties in existing technologies. It establishes a quantitative control relationship between the ratio of combined agents and the surface properties of fly ash. By adjusting the compounding ratio, the surface properties can be controlled in a directional gradient between hydrophobicity and hydrophilicity, and between high dispersion and high activity, providing an integrated material solution for different engineering scenarios.

[0025] Finally, this invention utilizes a mechanochemical treatment device to apply shearing, impact, and friction to the fly ash particles, simultaneously depolymerizing the particles and achieving in-situ coating and chemical activation of the combined modifying agent on the newly formed surface. Depolymerization and coating are completed synchronously in the same step. After curing and drying, dual-functional fly ash with both an inorganic gel coating layer and an organic hydrophobic coating layer is obtained. By introducing the modified fly ash into the cementitious material system, the workability of the slurry and the mechanical properties of the hardened body can be optimized simultaneously through proportioning control. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, obtaining other drawings based on these drawings without creative effort still falls within the scope of the present invention.

[0027] Figure 1 A schematic diagram of the synergistic modification mechanism of sodium silicate and sodium methylsilicate in one embodiment of the present invention is shown;

[0028] Figure 2 The XRD patterns of the combined modified agent gelling materials with different proportions in one embodiment of the present invention are shown.

[0029] Figure 3 A schematic diagram showing the contact angle variation of the combined modified agent cementitious material with different ratios in one embodiment of the present invention is shown.

[0030] Figure 4 A schematic diagram of the Zeta potential values ​​of combined modified agent gelling materials with different ratios in one embodiment of the present invention is shown.

[0031] Figure 5 Infrared images of combined modified pharmaceutical gelling materials with different proportions in one embodiment of the present invention are shown;

[0032] Figure 6 SEM images of combined modified agent gelling materials with different proportions in one embodiment of the present invention are shown.

[0033] Figure 7 A schematic diagram showing the changes in slurry flowability of combined modified agent cementitious materials with different ratios in one embodiment of the present invention is shown.

[0034] Figure 8 This diagram illustrates the variation in compressive strength of cementitious materials with different proportions of the combined modified agent in one embodiment of the present invention.

[0035] Figure 9The diagram shows the functional group diagram of sodium silicate-modified cementitious materials with different moduli in one embodiment of the present invention;

[0036] Figure 10 This diagram illustrates the Zeta potential values ​​of individually modified cementitious materials with different moduli of sodium silicate in one embodiment of the present invention.

[0037] Figure 11 This diagram illustrates the pH variation of sodium silicate-modified cementitious materials with different moduli in one embodiment of the present invention.

[0038] Figure 12 This diagram illustrates the changes in slurry flowability of sodium silicate-modified cementitious materials with different moduli in one embodiment of the present invention.

[0039] Figure 13 This diagram illustrates the variation in compressive strength of sodium silicate-modified cementitious materials with different moduli in one embodiment of the present invention.

[0040] Figure 14 The XRD patterns of cementitious materials modified with sodium methylsilicate alone at different concentrations are shown in one embodiment of the present invention.

[0041] Figure 15 The particle size distribution of the cementitious material modified by sodium methylsilicate alone in one embodiment of the present invention is shown.

[0042] Figure 16 A schematic diagram of the Zeta potential values ​​of cementitious materials modified by sodium methylsilicate alone at different concentrations is shown in one embodiment of the present invention;

[0043] Figure 17 A schematic diagram illustrating the variation of the surface contact angle of a cementitious material modified solely with sodium methylsilicate of different concentrations is shown in one embodiment of the present invention. Detailed Implementation

[0044] The preferred embodiments of the present invention will be described in detail below to provide a clearer understanding of the purpose, features, and advantages of the invention. It should be understood that the following embodiments are not intended to limit the scope of the invention, but are merely illustrative of the essential spirit of the technical solution of the invention.

[0045] In the following description, certain specific details are set forth for the purpose of illustrating various disclosed embodiments in order to provide a thorough understanding of the various disclosed embodiments. However, those skilled in the art will recognize that embodiments may be practiced without one or more of these specific details. In other instances, well-known techniques associated with the invention may not have been shown or described in detail to avoid unnecessarily obscuring the description of the embodiments.

[0046] Throughout this specification, references to "an embodiment" or "an embodiment" indicate that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Therefore, the appearance of "in an embodiment" or "an embodiment" in various places throughout the specification does not necessarily refer to the same embodiment. Furthermore, a particular feature, structure, or characteristic may be combined in any manner in one or more embodiments.

[0047] This invention provides a method for modifying coal gasification fly ash microcapsules based on the synergistic effect of combined modifying agents, comprising the following steps:

[0048] The dried coal gasification fly ash and the combined modifying agent solution are continuously fed into a mechanochemical treatment device. Under the mechanical force of the mechanochemical treatment device, the coal gasification fly ash particles are deagglomerated, and at the same time, the combined modifying agent forms a coating layer on the particle surface and is chemically activated. The combined modifying agent is prepared by mixing sodium silicate solution and sodium methylsilicate solution in a predetermined mass ratio.

[0049] Collect the modified material and transfer it to a sealed container for curing to allow the modification reaction to proceed fully;

[0050] The cured material was dried to constant weight, ground and sieved to obtain modified fly ash with an inorganic gel coating layer and an organic hydrophobic coating layer.

[0051] Example 1:

[0052] (1) Pretreatment of fly ash from coal gasification.

[0053] Take coal gasification fly ash (CGFA) and place it in an oven to dry it for 1 hour to remove free water from the fly ash.

[0054] (2) Preparation of sodium silicate solution.

[0055] Take a sodium silicate solution (NA) with an original modulus of 3.2, add 20% sodium hydroxide solution and free SiO2 to it, and reduce the sodium silicate modulus from 3.2 to 2.6.

[0056] The amount of sodium hydroxide to be added is calculated using the following formula:

[0057] ;

[0058] in, This indicates the required mass of sodium hydroxide to be added. Indicates the original sodium silicate modulus. Indicates the target modulus.

[0059] (3) Preparation of sodium methylsilicate solution.

[0060] Sodium methylsilicate was diluted with water to prepare a 30% sodium methylsilicate solution (SMS).

[0061] (4) Combined modified drugs.

[0062] A sodium silicate solution with a modulus of 2.6 and a sodium methyl silicate solution with a mass fraction of 30% were mixed at a mass ratio of 3:1 and stirred until homogeneous to obtain a combined modified agent solution.

[0063] (5) Honeycomb grinding and drying method for microcapsule modification.

[0064] The dried coal gasification fly ash and the combined modified agent solution are continuously fed into the honeycomb mill feed port at a frequency of 0.1 Hz by a peristaltic pump. The main motor frequency is 30 Hz, the feed frequency is 10 Hz, and the temperature is set to 90-120℃. The fly ash and the combined agent are subjected to shearing force, impact force and friction force generated by high-speed rotation in the mill cavity. The particles achieve deep deagglomeration and expose new surfaces. The agent simultaneously completes coating and chemical activation on the new surfaces.

[0065] (6) Maintenance.

[0066] Collect the modified material and immediately transfer it to a sealed container. Cure it at 60°C for 24 hours to allow the modification reaction to proceed fully.

[0067] (7) Post-processing.

[0068] After curing, the material is dried at 105℃ to constant weight, ground, sieved, and then sealed for storage.

[0069] The microcapsule-modified coal gasification fly ash obtained in this embodiment is mixed with silicate cement to prepare a cementitious material. The microcapsule-modified coal gasification fly ash accounts for 25% of the total mass of the cementitious material and can be mixed with aggregates, water, etc. to form a slurry. After molding and curing, blocks are obtained.

[0070] Example 2:

[0071] The difference between this embodiment and Embodiment 1 is that the mass ratio of sodium silicate solution to sodium methylsilicate solution is 1:1 in step 4.

[0072] (1) Pretreatment of fly ash from coal gasification.

[0073] Take coal gasification fly ash and place it in an oven to dry it for 1 hour to remove free water from the fly ash.

[0074] (2) Preparation of sodium silicate solution.

[0075] Take a sodium silicate solution (NA) with an original modulus of 3.2, add 20% sodium hydroxide solution and free SiO2 to it, and reduce the sodium silicate modulus from 3.2 to 2.6.

[0076] The amount of sodium hydroxide to be added is calculated using the following formula:

[0077] ;

[0078] in, This indicates the required mass of sodium hydroxide to be added. Indicates the original sodium silicate modulus. Indicates the target modulus.

[0079] (3) Preparation of sodium methylsilicate solution.

[0080] Sodium methylsilicate was diluted with water to prepare a 30% sodium methylsilicate solution (SMS).

[0081] (4) Combined modified drugs.

[0082] A sodium silicate solution with a modulus of 2.6 and a sodium methyl silicate solution with a mass fraction of 30% were mixed at a mass ratio of 1:1 and stirred until homogeneous to obtain a combined modified agent solution.

[0083] (5) Honeycomb grinding and drying method for microcapsule modification.

[0084] The dried coal gasification fly ash and the combined modified agent solution are continuously fed into the honeycomb mill feed port at a frequency of 0.1 Hz by a peristaltic pump. The main motor frequency is 30 Hz, the feed frequency is 10 Hz, and the temperature is set to 90-120℃. The fly ash and the combined agent are subjected to shearing force, impact force and friction force generated by high-speed rotation in the mill cavity. The particles achieve deep deagglomeration and expose new surfaces. The agent simultaneously completes coating and chemical activation on the new surfaces.

[0085] (6) Maintenance.

[0086] Collect the modified material and immediately transfer it to a sealed container. Cure it at 60 °C for 24 hours to allow the modification reaction to proceed fully.

[0087] (7) Post-processing.

[0088] After curing, the material is dried at 105℃ to constant weight, ground, sieved, and then sealed for storage.

[0089] The microcapsule-modified coal gasification fly ash obtained in this embodiment is mixed with silicate cement to prepare a cementitious material. The microcapsule-modified coal gasification fly ash accounts for 25% of the total mass of the cementitious material and can be mixed with aggregates, water, etc. to form a slurry. After molding and curing, blocks are obtained.

[0090] Example 3:

[0091] The difference between this embodiment and Embodiment 1 is that the mass ratio of sodium silicate solution to sodium methylsilicate solution in step 4 is 2:1.

[0092] (1) Pretreatment of fly ash from coal gasification.

[0093] Take coal gasification fly ash and place it in an oven to dry it for 1 hour to remove free water from the fly ash.

[0094] (2) Preparation of sodium silicate solution.

[0095] Take a sodium silicate solution (NA) with an original modulus of 3.2, add 20% sodium hydroxide solution and free SiO2 to it, and reduce the sodium silicate modulus from 3.2 to 2.6.

[0096] The amount of sodium hydroxide to be added is calculated using the following formula:

[0097] ;

[0098] in, This indicates the required mass of sodium hydroxide to be added. Indicates the original sodium silicate modulus. Indicates the target modulus.

[0099] (3) Preparation of sodium methylsilicate solution.

[0100] Sodium methylsilicate was diluted with water to prepare a 30% sodium methylsilicate solution (SMS).

[0101] (4) Combined modified drugs.

[0102] A sodium silicate solution with a modulus of 2.6 and a sodium methyl silicate solution with a mass fraction of 30% were mixed at a mass ratio of 2:1 and stirred until homogeneous to obtain a combined modified agent solution.

[0103] (5) Honeycomb grinding and drying method for microcapsule modification.

[0104] The dried coal gasification fly ash and the combined modified agent solution are continuously fed into the honeycomb mill feed port at a frequency of 0.1 Hz by a peristaltic pump. The main motor frequency is 30 Hz, the feed frequency is 10 Hz, and the temperature is set to 90-120℃. The fly ash and the combined agent are subjected to shearing force, impact force and friction force generated by high-speed rotation in the mill cavity. The particles achieve deep deagglomeration and expose new surfaces. The agent simultaneously completes coating and chemical activation on the new surfaces.

[0105] (6) Maintenance.

[0106] Collect the modified material and immediately transfer it to a sealed container. Cure it at 60°C for 24 hours to allow the modification reaction to proceed fully.

[0107] (7) Post-processing.

[0108] After curing, the material is dried at 105℃ to constant weight, ground, sieved, and then sealed for storage.

[0109] The microcapsule-modified coal gasification fly ash obtained in this embodiment is mixed with silicate cement to prepare a cementitious material. The microcapsule-modified coal gasification fly ash accounts for 25% of the total mass of the cementitious material and can be mixed with aggregates, water, etc. to form a slurry. After molding and curing, blocks are obtained.

[0110] Combination Figure 1 In terms of its mechanism of action, sodium silicate acts as an inorganic gelling agent, providing Na... + It promotes the dissolution and repolymerization of aluminosilicates in coal gasification fly ash, forming a continuous NASH gel network between particles, providing the material with a structural framework and basic mechanical strength.

[0111] Sodium methylsilicate, as an organic coupling agent, undergoes a condensation reaction between its hydrolysis products and the hydroxyl groups on the surface of coal gasification fly ash, grafting a hydrophobic methyl (-CH3) monolayer onto the particle surface in the form of Si-O-Si covalent bonds, thereby significantly altering the surface wettability of the material.

[0112] The performance exhibits a regular evolution with varying formulation ratios. When sodium silicate dominates, the system forms a dense gel structure, exhibiting hydrophilicity and low surface electronegativity.

[0113] When the proportion of sodium methylsilicate increases, the organic graft layer becomes dominant, the hydrophobicity of the material is enhanced, the absolute value of the surface charge increases, but the development of the gel network is inhibited.

[0114] A balanced performance was achieved when sodium silicate and sodium methylsilicate were mixed in a synergistic ratio of 2:1. Under these conditions, the inorganic gel network and the organic hydrophobic layer synergistically constructed a dense composite structure of particles-gel-organic layer. The material maintained good structural strength while also exhibiting optimized hydrophobic properties.

[0115] In summary, by synergistically modifying sodium silicate and sodium methylsilicate, the structural strength of inorganic gels and the surface hydrophobicity of organic grafts can be effectively combined to obtain a structurally stable, interface-enhanced, and performance-controllable coal gasification fly ash-based composite, providing a feasible technical route for its resource utilization in fields such as hydrophobic functional materials and geopolymers.

[0116] In the following examples, the microcapsule-modified coal gasification fly ash, cementing materials, and blocks obtained in Examples 1, 2, and 3 are analyzed:

[0117] 1. Phase composition and crystal structure analysis

[0118] As shown in Table 1, the chemical compositions of the three different ratios of combined modified coal gasification fly ash are highly similar, with SiO2 and Al2O3 as the main components, indicating that the pozzolanic properties of the coal gasification fly ash are maintained after modification. The secondary modification did not significantly change the main elemental composition of the coal gasification fly ash, suggesting that the modifier mainly acts on surface chemistry and structure, rather than bulk stoichiometry.

[0119] Table 1 Chemical composition analysis of cementitious material samples

[0120]

[0121] Combination Figure 2 As shown in the examples, the effects of different NA:SMS ratios on the mineral phase composition of the alkali-activated coal gasification fly ash cementing system were clearly demonstrated. Analysis indicates that the combined modification ratio is a key factor determining the system's reaction pathway and product stability.

[0122] In all formulation systems, the quartz (SiO2) phase (characteristic peak located at 2θ≈20°) inherent in the coal gasification fly ash feedstock was stably present, indicating that it was not significantly consumed as an inert crystalline phase.

[0123] In the XRD pattern at NA:SMS = 1:1, strong diffraction peaks of quartz were detected, indicating that the iron phase did not undergo significant crystallization or transformation under these conditions. When the ratio was increased to NA:SMS = 2:1, hematite diffraction peaks began to appear weakly, suggesting that under moderate NA:SMS conditions, the iron phase began to participate in the reaction or undergo local crystallization. Under NA:SMS = 3:1 conditions, the intensity of quartz diffraction peaks was relatively weakened, while the intensity of hematite diffraction peaks was significantly enhanced, clearly indicating that the high NA:SMS environment promoted the crystallization and enrichment of the iron phase in the system. This phenomenon may be related to the higher concentration of polymeric silicate ions in the activator under high NA:SMS (3:1) conditions, which promoted a more complete aluminosilicate dissolution-polymerization reaction, thereby changing the local chemical environment of the system and creating thermodynamic conditions for the crystallization and precipitation of hematite.

[0124] The crystallization and enrichment of the iron phase (hematite) may serve as micro-aggregates filling the gel network, forming a more stable composite structure with NASH gel, thereby making a positive contribution to the structural stability and mechanical strength of the gel products.

[0125] 2. Analysis of hydrophobicity changes

[0126] like Figure 3 As shown, as the ratio changes from 1:1 to 3:1, the contact angle continues to decrease, from 105.5° (strong hydrophobic) to 99.9° (hydrophobic), and finally transforms into 85.1° (hydrophilic).

[0127] This pattern indicates that increasing the proportion of sodium silicate solution systematically weakens the hydrophobicity of the material surface, eventually causing it to transform into a hydrophilic surface. Mechanistically, a 1:1 ratio suggests that a stable surface structure rich in hydrophobic groups may be formed under these conditions. The contact angle being below 90° at a 3:1 ratio is attributed to the introduction of more polar groups or the densification of the surface structure by the higher proportion of sodium silicate solution, thereby increasing the surface energy.

[0128] 3. Analysis of changes in surface electrical properties

[0129] Combination Figure 4 As shown, the zeta potential is a key parameter characterizing the stability of colloidal systems; the larger its absolute value, the stronger the electrostatic repulsion between particles, and the more stable the dispersion system. The results show that, compared with the unmodified coal gasification fly ash, all modified samples exhibited significantly enhanced negative charge.

[0130] As the proportion of sodium methylsilicate in the modifier increases relatively, the Zeta potential increases systematically, i.e., the absolute value of the negative value decreases sequentially.

[0131] The combined modifier effectively enhances the surface negative charge of coal gasification fly ash particles. This change originates from the adsorption of modifier molecules on the particle surface, introducing negatively charged groups or altering the dissociation state of existing surface groups. The modifier ratio directly affects the final electrochemical properties; increasing the proportion of sodium methylsilicate solution changes the charge density or structure of the adsorption layer, leading to a decreasing trend in electrostatic repulsion.

[0132] By adjusting the ratio of combined modifiers, the surface electrical properties and colloidal stability of coal gasification fly ash can be effectively and directionally controlled, thereby providing key electrochemical parameter basis for different industrial application scenarios.

[0133] 4. Analysis of pH Changes

[0134] The original coal gasification fly ash exhibits typical medium-to-strong alkalinity characteristics, as shown in Table 5. After introducing the combined modifier, the alkalinity of the system is significantly enhanced, and the pH value increases stepwise with the increase of the proportion of sodium silicate solution: when the ratio is 1:1, the pH rises to 11.25; when adjusted to 2:1, it further increases to 11.49; and at the highly alkaline 3:1 ratio, the pH reaches a peak of 11.76. In terms of the increase, the pH increases by about 0.24 when increasing from 1:1 to 2:1, and by about 0.27 when increasing from 2:1 to 3:1, indicating that as the proportion of sodium silicate solution increases, its effect on the increase of the system pH shows a slight marginal expansion trend.

[0135] This regularity is mainly attributed to the dominant role of the strongly alkaline sodium silicate solution in the composite system; its increase directly determines the OH content of the system. - The upper limit of concentration.

[0136] In contrast, sodium methylsilicate solution contributes less to alkalinity due to its limited degree of hydrolysis.

[0137] Table 2. Changes in pH values ​​due to combined drug modification

[0138]

[0139] 5. Analysis of changes in molecular structure

[0140] like Figure 5 As shown, 3400-3500cm -1 The broad peaks indicate the presence of hydroxyl vibrations in the sample. The peak intensity is most significant in the sample with a NA:SMS ratio of 1:1, suggesting high surface hydrophilicity or a high content of residual hydroxyl groups. (2900 cm⁻¹) -1 The weak CH stretching vibration peaks in the vicinity confirm the variation in the bending vibration peak intensity of the organic components in the modifier within the coal gasification fly ash, reflecting the exposure degree and structural state of the inorganic framework under different ratios. The 1:1 ratio sample showed the strongest signal in this region. Combined with Zeta potential data analysis, the 1:1 ratio sample, while maintaining strong inorganic framework characteristics, possesses abundant surface hydroxyl groups and moderate organic coverage. This corresponds to its optimal negative potential and high dispersion stability, indicating that this ratio achieves an optimal balance between surface charge regulation and colloidal stability.

[0141] 6. Microscopic morphology analysis

[0142] With the increase of sodium silicate ratio, combined with Figure 6 As shown, (a) indicates that the ratio of the combined modifying agent is 1:1; (b) indicates that the ratio of the combined modifying agent is 2:1; and (c) indicates that the ratio of the combined modifying agent is 3:1.

[0143] The microstructure of coal gasification fly ash exhibits a significant and regular evolution trend. Specifically, when the ratio of the combined modifier is 1:1, the sample displays a typical porous and loose structure with well-developed interparticle pores and high surface roughness. This open flocculent structure is conducive to liquid phase penetration and dispersion. When the ratio is adjusted to 2:1, the particle packing tends to be more compact, the porosity decreases, and plate-like stacking occurs, enhancing structural continuity. When the sodium silicate ratio increases to 3:1, the microstructure becomes further densified, exhibiting a compact blocky structure with minimal pores and a smooth surface, displaying the lowest porosity.

[0144] 7. Slurry flowability test

[0145] Combination Figure 7 As shown, the fluidity of cementitious materials shows a systematic decreasing trend with increasing admixture dosage. Under any fixed ratio of combined modifier, the fluidity of the slurry shows a monotonically decreasing trend with increasing admixture dosage of cementitious materials (including modified coal gasification fly ash and cement and other active components).

[0146] When the admixture dosage increased from 15% to 35%, the fluidity decreased significantly. This trend is mainly attributed to the increased physical filling and cohesion. As the admixture dosage increases, the total concentration of solid particles in the system rises sharply, the interparticle spacing decreases, leading to enhanced physical effects such as van der Waals forces and capillary forces, increased internal frictional resistance of the slurry, and increased yield stress, which macroscopically manifests as a decrease in fluidity.

[0147] Under the same cementitious material dosage, the proportion of combined modifier has a significant regulatory effect on fluidity, showing a clear rule: the higher the proportion of combined modifier, the worse the fluidity.

[0148] Specifically, at the same dosage, the fluidity follows the order NA:SMS=1:1>2:1>3:1.

[0149] The ratio of combined modifiers essentially reflects the amount of Na providing alkalinity in the activator. + With SiO2 that provides the degree of polymerization of silicate 2- The relative content of Na. When the proportion of the combined modifier increases, it means that the Na content in the system... + The relative excess results in an excessively high alkalinity in the solution.

[0150] This leads to a decrease in the absolute value of the Zeta potential on the surface of fly ash particles, compressing the electrical double layer and weakening the electrostatic repulsion between particles, thereby intensifying flocculation and thickening the slurry. Simultaneously, excessively high alkalinity may also accelerate early hydration / polymerization reactions, generating more gel products and further increasing slurry viscosity. Conversely, a lower Na:SMS ratio provides a more balanced Na... + With SiO2 2- This ensures the necessary activation alkalinity, while the abundant silicate groups may also play a certain role in plasticizing or dispersing, thus maintaining good fluidity.

[0151] If high fluidity is required for engineering applications, a scheme with low cementitious material content (≤20%) and low combined modifier ratio (1:1) should be preferred. If a high content (≥30%) must be used due to strength or durability requirements, the workability can be significantly improved by adjusting the combined modifier ratio from 3:1 to 1:1.

[0152] 8. Mechanical property testing

[0153] Combination Figure 8 As shown, the systematic law of the change of compressive strength of modified cementitious materials with age and dosage under the NA:SMS=3:1 ratio is presented.

[0154] The compressive strength increased continuously with age at all admixture levels, which is consistent with the strength development kinetics of cement-based materials, which involves early hydration initiation and subsequent continuous hardening. Meanwhile, the compressive strength showed a significant trend of first increasing and then decreasing with increasing admixture dosage.

[0155] The optimal admixture ratio is 20% to 25%, with peak strength achieved at 28 and 60 days. At this ratio, the micro-aggregate filling effect and potential pozzolanic activity effect of the coal gasification fly ash achieve optimal synergy, resulting in the best structural density. When the admixture ratio is too low, the activity and filling effects are not fully utilized, leading to lower strength; when the admixture ratio is too high, the dilution effect and particle agglomeration cause an increase in porosity, significantly suppressing strength.

[0156] Considering the high proportion of sodium silicate solution, high hydrophilicity, and dense surface of this formulation, although its early strength is lower than that of the loose and hydrophobic 1:1 formulation, its long-term strength can still steadily increase at the optimal dosage. This result provides clear guidance for engineering applications: if high early strength is desired, a dosage of 15%–20% can be selected; if long-term (28d / 60d) strength and durability are key indicators, a dosage of 20%–25% should be prioritized to achieve the best match between material properties and engineering requirements.

[0157] Example 4: Modification using sodium silicate solution alone.

[0158] Unlike Example 1, sodium silicate with an original modulus of 3.2 was adjusted to four solutions with moduli of 2.4, 2.5, 2.6 and 2.7, respectively, to obtain sodium silicate solutions with different moduli as single modifying agents. The remaining steps followed the same honeycomb mill process parameters, curing conditions and post-processing procedures as in Example 1, to obtain coal gasification fly ash modified with sodium silicate alone under different moduli.

[0159] The coal gasification fly ash and cementing materials modified with sodium silicate solutions of different moduli obtained in Example 4 were analyzed:

[0160] 1. Phase composition analysis

[0161] As the modulus of the modifier increases, as shown in Table 3, the SiO2 content fluctuates, while Al2O3 and Fe2O3 are significantly enriched, reflecting that the modification process may promote the dissolution or surface enrichment of the aluminum and iron phases. Na2O increases with the degree of modification, proving the effective introduction of sodium silicate solution; the changes in other elements are gradual. Sodium silicate solution modification, through elemental enrichment and compositional regulation, provides a material basis for activating the gelling activity of coal gasification fly ash. Further phase analysis is needed to verify the reaction mechanism.

[0162] Table 3 Chemical composition analysis of cementitious material samples

[0163]

[0164] 2. Analysis of changes in molecular structure

[0165] At 3400cm -1 The broad peaks nearby correspond to OH stretching vibrations, reflecting the presence of hydroxyl groups and their binding. Figure 9 As shown, the peak intensity did not change significantly after modification, indicating that the hydroxyl content was relatively stable; 2900 cm⁻¹ -1 The weak CH stretching vibration peaks in the vicinity indicate low organic impurity content; 1000-1200 cm⁻¹ -1 The strong peak in the region is due to the Si-O-Si stretching vibration, a key characteristic of cementitious activity. After modification, the intensity of this peak increased and broadened, indicating that sodium silicate modification promoted the formation or polymerization of silicon-oxygen bonds, enhancing the cementitious potential of coal gasification fly ash; 500-800 cm⁻¹ -1 The peaks in the region correspond to the vibrations of metal oxides, and the changes in peak shape in this region after modification reflect the degree of reaction of the aluminum-iron phase. Sodium silicate solution modification enhances the cementitious active material basis of coal gasification fly ash by strengthening Si-O bonds and regulating the vibrational characteristics of hydroxyl and metal-oxygen bonds.

[0166] 3. Analysis of changes in surface electrical properties

[0167] Combination Figure 10 As shown, the Zeta potential of the original coal gasification fly ash is negative, indicating that under the test conditions, the surface of the coal gasification fly ash particles carries a negative charge.

[0168] In this embodiment, the absolute value of the Zeta potential of all samples was less than 10mV (between -5mV and +2mV), which indicates that the coal gasification fly ash particles in the aqueous solution mainly rely on secondary forces such as van der Waals forces to attract each other, making them very easy to agglomerate and settle, which is not conducive to the formation of a stable suspension.

[0169] With increasing concentration of sodium silicate solution, the Zeta potential of the cementitious material showed a significant upward trend. The original Zeta potential was approximately -5 mV, but it gradually increased with increasing modifier concentration, even turning positive under 2.6% and 2.7% sodium silicate solution conditions. This trend indicates that the introduction of sodium silicate solution altered the double-layer structure on the surface of coal gasification fly ash particles. On one hand, the OH groups generated by the hydrolysis of sodium silicate solution... - Ions may neutralize some of the negative charge on the surface; on the other hand, Na + The adsorption of ions or the formation of a surface silicate gel layer may alter the surface potential distribution, causing the Zeta potential to shift in the positive direction.

[0170] 4. Analysis of pH Changes

[0171] Combination Figure 11As shown, the original coal gasification fly ash has a pH of approximately 10.5, exhibiting moderately strong alkalinity. After modification with sodium silicate solution, the alkalinity of the material is significantly enhanced, showing a stepwise upward trend with increasing modulus. During the process of increasing the modulus from 2.4 to 2.7, the pH steadily climbed from 11.25 to 11.95, with the sample at modulus 2.4 showing a significant jump compared to the original sample. This indicates that low-modulus sodium silicate rapidly enhances the ionic strength and alkalinity of the system by introducing soluble alkali metal ions.

[0172] As the modulus further increases, the SiO2 content increases, which promotes the synergistic reaction between silicate and active metal oxides in coal gasification fly ash, continuously releasing alkaline substances. However, the increase tends to slow down, showing a diminishing marginal effect.

[0173] Overall, the modulus of sodium silicate solution is a key parameter that determines the pH value of modified fly ash; the higher the modulus, the stronger the alkalinity of the material.

[0174] 5. Slurry flowability test

[0175] The results of slurry fluidity are as follows Figure 12 As shown, the compressive strength of cementitious materials is significantly affected by the cementitious material dosage and the activator modulus. At any given activator modulus, the water-cement ratio decreases with increasing cementitious material dosage. At the same cementitious material dosage, the overall compressive strength increases with decreasing activator modulus. This is because a lower modulus (M=2.6) corresponds to higher alkalinity, which more effectively disrupts the Si-O network on the surface of the glassy body of coal gasification fly ash, promoting the formation of more low-calcium-to-silicon ratio CSH gel, thereby increasing strength; while a higher modulus has weaker alkalinity, limiting activating efficiency. To obtain optimal mechanical properties, the cementitious material dosage and activator modulus should be optimized synergistically. Using a sodium silicate solution with a modulus of 2.6 can achieve the highest compressive strength.

[0176] 6. Mechanical property testing

[0177] Combination Figure 13 As shown, the compressive strength of cementitious blocks exhibits the best performance when the sodium silicate solution modulus is in the range of 2.5-2.7, with the most significant strength development observed when the sodium silicate solution modulus is 2.6. With increasing sodium silicate solution modulus, the strength at all ages and the rate of increase in later-stage strength both significantly improve. This is attributed to the fact that a higher sodium silicate solution modulus provides more abundant polymeric silicate groups, which is beneficial for forming a denser and more stable NASH gel structure.

[0178] Meanwhile, the strength continued to increase with the increase of cementitious material content, verifying the necessity of chemical activation for releasing the activity of fly ash.

[0179] Example 5: Modification using sodium methylsilicate alone.

[0180] Unlike Example 1, a 30% sodium methylsilicate solution was prepared and used as the sole modifying agent. The sodium methylsilicate solution was used to modify the coal gasification fly ash at a mass ratio of 0.1 and 0.2, respectively. The remaining steps followed the same honeycomb mill process parameters, curing conditions and post-processing procedures as in Example 1, to obtain coal gasification fly ash modified with sodium methylsilicate alone at different concentrations.

[0181] The coal gasification fly ash and cementitious materials modified with different concentrations obtained in Example 5 were analyzed:

[0182] 1. Phase composition and crystal structure analysis

[0183] The main components of the two concentrations of sodium methylsilicate modified coal gasification fly ash are SiO2 and Al2O3, and they also contain a high content of Fe2O3 and trace components.

[0184] Comparative analysis reveals that the phase composition characteristics of cementitious materials are as follows: Figure 14 As shown, the strongest diffraction peak was observed in all samples, located near 2θ≈26°, indicating that quartz is the main crystalline mineral component in coal gasification fly ash and maintains chemical stability during modification. A significant diffraction peak appeared at 2θ≈33.5°, representing another major crystalline phase in coal gasification fly ash, reflecting the presence of iron oxides. Broadened diffuse peaks were visible in the low-angle region, a typical characteristic of amorphous glassy phases in coal gasification fly ash and a major source of its pozzolanic activity. Compared to unmodified coal gasification fly ash, the diffraction peak intensity of the 0.1 sodium methylsilicate modified sample was slightly reduced, especially the peak heights of quartz and hematite, which were slightly weakened. Under 0.1 SMS modification, some crystalline phases underwent slight dissolution or structural disorder, promoting the formation of amorphous phases.

[0185] The diffraction peak intensity of the 0.2-methylsilicate modified sample was significantly reduced, the quartz peak was almost covered by background noise, and the low-angle amorphous peak was more broadened.

[0186] This indicates that under higher concentrations of modifier, the solubility of the crystalline phase intensifies, the content of the amorphous phase increases significantly, and a more disordered silicon-aluminum-oxygen network structure is formed. Sodium methylsilicate hydrolyzes in aqueous solution to produce silicate and methyl groups. Its strong alkalinity and coordination ability promote the dissolution of sparingly soluble minerals such as quartz in coal gasification fly ash. Simultaneously, the silicate groups combine with aluminum and calcium ions dissolved from the coal gasification fly ash to form new amorphous silicate / aluminate gels. This process leads to a decrease in the crystalline phase and an increase in the amorphous phase, thereby enhancing the reactivity of the coal gasification fly ash.

[0187] Analysis results show that sodium methylsilicate modification significantly alters the phase composition of coal gasification fly ash. With increasing modifier concentration, crystalline phases such as quartz and hematite gradually dissolve and transform into an amorphous structure. This change enhances the pozzolanic activity and reactivity of coal gasification fly ash, providing a structural basis for its application in cementitious materials.

[0188] 2. Particle size characteristic analysis

[0189] Combination Figure 15 As shown, compared with the 0.1 methylsilicate modified sample, the main peak of the 0.2 methylsilicate modified sample shifts slightly towards larger particle sizes, and the peak value is higher and the peak shape is broader. This indicates that as the modifier concentration increases, the average particle size of the sample increases slightly, while the uniformity of particle size distribution decreases and the dispersibility increases. Furthermore, in the small particle size range of 200-400 μm, the proportion of the 0.2 methylsilicate modified sample increases, suggesting that high concentrations of modifier may induce the formation of some fine particles or agglomeration behavior within a specific particle size range.

[0190] The silicate ions and negatively charged groups generated by the hydrolysis of the modifier alter the zeta potential and electric double-layer structure of the particle surface, thereby affecting the electrostatic interactions and steric hindrance between particles. At low concentrations, a moderate increase in surface charge helps particle dispersion and maintains a relatively uniform particle size distribution; however, at high concentrations, excessive modifier may lead to bridging agglomeration effects or promote the formation of new particles of varying sizes by promoting the surface dissolution-recrystallization process, resulting in a broadened particle size distribution.

[0191] Differences in particle size distribution directly affect the subsequent performance of modified coal gasification fly ash as a cementitious material component. 0.1-methylsilicate modified samples with more uniform particle size are beneficial for optimizing particle packing density and slurry flowability; while 0.2-methylsilicate modified cementitious material samples with slightly larger particle size dispersion and a slightly higher proportion of fine particles may exhibit higher early-stage reactivity due to their larger specific surface area.

[0192] 3. Analysis of changes in surface electrical properties

[0193] The zeta potential test results of the microcapsule-encapsulated modified gel material are as follows: Figure 16 As shown, the Zeta potentials of the three samples were all negative, but the potential values ​​gradually increased with increasing modifier concentration. The original coal gasification fly ash sample had the lowest Zeta potential, followed by the sample modified with 0.1% sodium methylsilicate, and the sample modified with 0.2% sodium methylsilicate had the highest. Error bars indicate some fluctuations at each test point, but the overall trend is clear. These results suggest that sodium methylsilicate modification can increase the negative charge on the surface of coal gasification fly ash particles, and the higher the concentration, the more significant this effect. This may be related to the adsorption and charge regulation mechanism of the modifier on the particle surface.

[0194] 4. Analysis of hydrophobicity changes

[0195] Contact angle test results of cementitious materials are as follows Figure 17 As shown in the figure. The results show that the contact angles of the three cementitious material samples are all less than 90°, indicating hydrophilicity. Furthermore, the contact angles continuously increase with increasing sodium methylsilicate modifier concentration. The unmodified coal gasification fly ash had the smallest contact angle, while the contact angle of the cementitious material sample modified with 0.1% sodium methylsilicate increased to 29.6°, and the contact angle of the sample modified with 0.2% sodium methylsilicate further increased to 32.8°. These results indicate that sodium methylsilicate modification can effectively improve the hydrophobicity of coal gasification fly ash particle surfaces, and the higher the modifier concentration, the more significant the hydrophobic enhancement effect. This is consistent with the trend of Zeta potential changes, jointly reflecting the adsorption and surface energy regulation mechanism of the modifier on the particle surface.

[0196] 5. Analysis of pH Changes

[0197] The pH changes of the coal gasification fly ash system after modification with sodium methylsilicate are shown in Table 4. The original coal gasification fly ash is moderately alkaline. After modification with sodium methylsilicate at a concentration of 0.1%, the pH value increased to 10.72. When the concentration was increased to 0.2%, the pH value further increased to 10.89.

[0198] Overall, a clear positive correlation is observed, meaning that as the concentration of the modifier increases, the alkalinity of the cementitious material increases accordingly.

[0199] The relatively small change in pH value is mainly due to the limited hydrolysis process of sodium methylsilicate in the aqueous phase. Its silanol groups ionize to produce a small amount of hydroxide ions, and the higher the concentration, the more alkaline sites are contributed. However, since the organosilicon modifier is not a strong base and its degree of hydrolysis is limited, the increase in pH value of the system is much smaller than that of inorganic sodium silicate, exhibiting a mild and gradual alkaline regulation characteristic.

[0200] Table 4 pH Change Values

[0201]

[0202] In summary, this invention utilizes a honeycomb mill to perform mechanochemical activation of coal gasification fly ash and employs an activator to coat and modify the fly ash, effectively reducing its particle size, increasing its specific surface area, and activating its surface activity, thus laying a physical foundation for chemical modification. Single modification results show that the modulus of sodium silicate is a key parameter. When the modulus is 2.6, the modified coal gasification fly ash exhibits the best mechanical properties at the optimal dosage, attributed to the effective activation of its pozzolanic activity by suitable alkalinity.

[0203] Sodium methylsilicate modification mainly affects the crystal structure and surface properties of the material. With the increase of sodium methylsilicate concentration, the degree of amorphization of the material is enhanced, the reactivity is improved, the surface contact angle increases, and the Zeta potential rises, achieving an effective transformation from a hydrophilic to a hydrophobic surface.

[0204] In the composite modification study, the synergistic regulatory mechanism of sodium silicate and sodium methylsilicate on material properties was revealed by adjusting the mass ratio of sodium silicate to sodium methylsilicate. As the proportion of sodium silicate increases, the absolute value of the negative Zeta potential on the material surface decreases, and the contact angle decreases from hydrophobic to hydrophilic.

[0205] This change corresponds to the evolution of the microstructure from loose and porous to dense and massive, directly affecting its dispersion stability. Further performance testing of the cementitious material confirmed that the mass ratio of sodium silicate to sodium methylsilicate is the core factor balancing workability and mechanical strength; the higher the ratio, the worse the slurry fluidity. At a specific mass ratio of 3:1 for sodium silicate to sodium methylsilicate, the cementitious material achieves the highest long-term compressive strength within the 20%–25% content range.

[0206] The technical terms, principles, or means related to the technical solutions of the present invention mentioned in the above embodiments, which are not described in detail above, are all well-known technologies or common practices that are known to those skilled in the art.

[0207] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A coal gasification fly ash microcapsule modification method based on the combination of modified agents, characterized in that, Includes the following steps: The dried coal gasification fly ash and the combined modifying agent solution are continuously fed into a mechanochemical treatment device. Under the mechanical force of the mechanochemical treatment device, the coal gasification fly ash particles are deagglomerated, and at the same time, the combined modifying agent forms a coating layer on the particle surface and is chemically activated. The combined modifying agent is prepared by mixing sodium silicate solution and sodium methylsilicate solution in a predetermined mass ratio. Collect the modified material and transfer it to a sealed container for curing to allow the modification reaction to proceed fully; The cured material was dried to constant weight, ground and sieved to obtain modified fly ash with an inorganic gel coating layer and an organic hydrophobic coating layer.

2. The method for modifying coal gasification fly ash microcapsules based on the synergistic effect of combined modifying agents according to claim 1, characterized in that, The sodium silicate solution is prepared by adding sodium hydroxide and free silicon dioxide to the original sodium silicate to reduce its modulus.

3. The method for modifying coal gasification fly ash microcapsules based on the synergistic effect of combined modifying agents according to claim 2, characterized in that, The predetermined mass ratio is 1:1, 2:1 or 3:

1.

4. The method for modifying coal gasification fly ash microcapsules based on the synergistic effect of combined modifying agents according to claim 2, characterized in that, The sodium silicate solution has a modulus of 2.4 to 2.7, and the methylsodium silicate solution has a mass fraction of 20% to 30%.

5. The method for modifying coal gasification fly ash microcapsules based on the synergistic effect of combined modifying agents according to claim 2, characterized in that, When preparing a sodium silicate solution, calculate the amount of sodium hydroxide to be added using the following formula: ； in, This indicates the required mass of sodium hydroxide to be added. Indicates the original sodium silicate modulus. Indicates the target modulus.

6. The method for modifying coal gasification fly ash microcapsules based on the synergistic effect of combined modifying agents according to claim 1, characterized in that, The mechanochemical treatment equipment is a honeycomb mill, and its operating parameters are: main unit frequency of 30Hz, feeding frequency of 10Hz, and temperature set to 90-120℃. When continuously feeding coal gasification fly ash and combined modified agent solution into the mechanochemical treatment equipment, a peristaltic pump is used for conveying at a frequency of 0.

1.

7. The method for modifying coal gasification fly ash microcapsules based on the synergistic effect of combined modifying agents according to claim 1, characterized in that, The curing temperature is 60℃, the curing time is 24 hours, and the drying temperature for drying the cured material to constant weight is 105℃.

8. A microencapsulated modified coal gasification fly ash, characterized in that, It is obtained by the coal gasification fly ash microcapsule modification method based on the synergistic combination of combined modified agents as described in any one of claims 1 to 7.

9. The modified coal gasification fly ash according to claim 8, characterized in that, The surface of the microcapsule-modified coal gasification fly ash has an inorganic gel layer formed by silicate reaction products and a hydrophobic layer formed by organosilane condensation products.

10. A microencapsulated modified coal gasification fly ash cementitious material, characterized in that, It comprises microencapsulated modified coal gasification fly ash as described in claim 8 and a cementing component, wherein the microencapsulated modified coal gasification fly ash accounts for 15% to 40% of the total mass of the cementing material.

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