Dust suppression crust agent and its preparation and construction method

Abstract

This invention provides a dust-suppressing crusting agent and its preparation and application method, belonging to the field of mine dust control and environmental protection technology. It includes a dust-suppressing base liquid and a composite reinforcing agent dry powder. The dust-suppressing base liquid comprises the following components by mass percentage: polyvinyl alcohol 2.5-3.5%, acrylate copolymer emulsion 5.0-10.0%, penetration promoter 0.3-0.8%, hydrophobic modifier 1.0-2.5%, pH adjuster 1.0-2.0%, with the balance being water. The composite reinforcing agent dry powder comprises the following components by mass percentage: metakaolin 20-30%, silica fume 8-15%, polypropylene fiber 2-5%, sodium gluconate 0.4-0.8%, with the balance being sulfoaluminate cement. The penetration promoter significantly reduces the surface tension of the liquid, and the hydrophobic components are uniformly fixed in the composite network through an organic film-forming process, making the crust hydrophobic from the surface to the interior. The multi-level inorganic hydration materials in the composite reinforcing agent dry powder form a crust with the organic polymer, effectively improving crack resistance and peel resistance.

Description

Technical Field

[0001] This invention belongs to the field of mine dust control and environmental protection technology, and particularly relates to a dust suppressant and crusting agent and its preparation and application method. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Coal dust generated during open-pit coal mining, storage, and transportation is one of the main sources of pollution. For coal seams with strong hydrophobic surfaces (such as anthracite and some air-separated clean coal), conventional water mist or ordinary dust suppressants cannot effectively wet the coal dust surface, resulting in extremely low dust suppression efficiency. Existing technologies have limitations in their solutions: the crust formed by a single polymeric film-forming agent (such as polyvinyl alcohol or acrylic acid) is brittle and prone to drying shrinkage and cracking; a single inorganic salt hygroscopic agent (such as calcium chloride or magnesium sulfate) has almost no mechanical strength and is easily washed away by rain; while directly adding cementitious materials such as cement can improve hardness, it often results in poor compatibility with organic components and improper control of setting time, leading to poor overall crust integrity, insufficient toughness, and susceptibility to shrinkage cracks.

[0004] Therefore, designing a dust suppressant and crusting agent with rapid wetting, high-strength crusting, and long-lasting resistance to rainwater erosion is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a dust-suppressing crusting agent and its preparation and application method. It employs an on-site mixing system of "base liquid + dry powder" to enable multifunctional units such as organic bonding, inorganic reinforcement, penetration promotion, and hydrophobic modification to produce synergistic effects in time and space, ultimately forming a composite crusting layer with excellent early strength, high toughness, outstanding impermeability, and durability.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows: In a first aspect, the present invention provides a dust suppressant and crusting agent, comprising a dust suppressant base liquid and a composite reinforcing agent dry powder; The dust-suppressing base liquid comprises the following components by mass percentage: 2.5-3.5% polyvinyl alcohol, 5.0-10.0% acrylate copolymer emulsion, 0.3-0.8% penetration enhancer, 1.0-2.5% hydrophobic modifier, 1.0-2.0% pH adjuster, and the balance being water; The composite reinforcing agent dry powder comprises the following components by mass percentage: metakaolin 20-30%, silica fume 8-15%, polypropylene fiber 2-5%, sodium gluconate 0.4-0.8%, with the balance being sulfoaluminate cement.

[0007] Secondly, the preparation method of the aforementioned dust suppressant and crusting agent includes: Polyvinyl alcohol is dissolved in water, and acrylate copolymer emulsion, penetration enhancer, hydrophobic modifier and pH adjuster are added and mixed to obtain dust-suppressing base liquid; A composite reinforcing agent dry powder is obtained by mixing sulfoaluminate cement, metakaolin, silica fume, polypropylene fiber and sodium gluconate.

[0008] Thirdly, the construction method of the aforementioned dust-suppressing and crust-forming agent includes: Add 7-11% of the dry powder of composite reinforcing agent by mass to the dust-suppressing base liquid to obtain a mixed suspension; first spray the dust-suppressing base liquid as a penetrating layer, and then spray the mixed suspension to cover the penetrating layer as a reinforcing layer.

[0009] The beneficial effects of this invention are as follows: 1. The penetration promoter in the dust suppression liquid of this invention can greatly reduce the surface tension of the liquid, allowing it to spread instantly on the surface of hydrophobic coal, breaking through the wetting barrier and laying the foundation for subsequent bonding and reinforcement; the organic polymer forms a composite network, playing a flexible bonding role, toughening and preventing cracking; the hydrophobic component is uniformly fixed in the composite network through the organic film-forming process, making the crust hydrophobic from the surface to the inside; rainwater has difficulty penetrating into the softened internal structure, and can only form water droplets on the surface and roll off, greatly extending the time of rainwater erosion resistance; the multi-level inorganic hydration materials in the composite reinforcement agent dry powder form a rigid skeleton, which, together with the tough composite network formed by the organic polymer, forms a crust, which not only has high early strength (24h compressive strength > 3.0 MPa), but also continues to increase in later strength, and the flexural strength is significantly improved, effectively improving the crack resistance and peel resistance.

[0010] 2. The preparation method of this invention adopts a mode of separate storage of base liquid and dry powder, and on-site mixing during construction, which solves the problems of short storage period and easy sedimentation and stratification of traditional composite dust suppressants. The dual spraying process ensures the realization of functional gradient. The penetrating layer is used to spread and wet the coal surface and activate the active sites on the coal dust surface, providing a chemical anchoring base for the reinforcing layer; the reinforcing layer is used to form a composite crust with both rigidity and flexibility, improving crack resistance and peeling resistance, thereby significantly extending the dust suppression cycle; the reinforcing layer and the penetrating layer both use the dust suppressing base liquid as the parent material, ensuring molecular-level fusion and tight bonding at the interface between the two; at the same time, since the base liquid and dry powder are stored separately, the premature hydration of cement and other cementitious materials in the aqueous system is avoided. After on-site mixing, the retarder (sodium gluconate) precisely controls the hydration process, so that the mixed suspension maintains stable flow within 60~90 minutes, with a wide operating window and good compatibility with existing spraying equipment (such as water trucks and spray pump trucks), and can be directly applied without special modification. Detailed Implementation

[0011] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0012] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0013] One or more embodiments of the present invention provide a dust suppressant and crusting agent, comprising a dust suppressant base liquid and a composite reinforcing agent dry powder; The dust-suppressing base liquid comprises the following components by mass percentage: 2.5-3.5% polyvinyl alcohol, 5.0-10.0% acrylate copolymer emulsion, 0.3-0.8% penetration enhancer, 1.0-2.5% hydrophobic modifier, 1.0-2.0% pH adjuster, and the balance being water; The composite reinforcing agent dry powder comprises the following components by mass percentage: metakaolin 20-30%, silica fume 8-15%, polypropylene fiber 2-5%, sodium gluconate 0.4-0.8%, with the balance being sulfoaluminate cement.

[0014] In the above components, polyvinyl alcohol and acrylate copolymer emulsion serve as organic film-forming components. Their combination forms a highly tough organic polymer network, providing flexibility and a bonding foundation for the crust layer. The penetration enhancer significantly reduces the surface tension of the liquid, allowing the base liquid to spread rapidly, wet, and uniformly form a film on the hydrophobic coal seam, ensuring a strong bond between the subsequent reinforcement layer and the base layer. The hydrophobic components of the hydrophobic modifier (such as silicone emulsion) are uniformly dispersed and fixed throughout the organic-inorganic composite network during film formation, giving the cured crust layer excellent hydrophobicity from the surface to the interior, effectively blocking rainwater penetration. Metakaolin, silica fume, and sulfoaluminate cement constitute an inorganic cementing system, generating a dense, rigid skeleton through hydration reactions, ensuring the crust layer has high early strength and continuously increasing later strength. Polypropylene fibers are dispersed within as a three-dimensional reinforcing material, significantly improving the crust layer's flexural strength, crack resistance, and peel resistance. The synergistic effect of these functional units ultimately forms a composite crust layer with both excellent mechanical properties and long-term protective performance.

[0015] Optionally, the polyvinyl alcohol has a 99% degree of hydrolysis. Choosing a 99% degree of hydrolysis polyvinyl alcohol is primarily to achieve optimal film strength, water resistance, and compatibility with cement-based inorganic materials while ensuring good water solubility. This ensures: ① Stable water solubility. The degree of hydrolysis represents the proportion of side groups in the polyvinyl alcohol molecule that are converted from "acetate" to "hydroxyl". 99% represents complete hydrolysis, meaning that very few hydrophobic acetate groups remain on the molecular chain. Although a slightly higher temperature (90-95℃) is required for dissolution, it forms a stable true solution in water, avoiding turbidity or viscosity fluctuations due to excessive residual acetate groups. This is fundamental to ensuring stable construction quality. ② Optimal film strength. Hydroxyl groups (-OH) can form extremely strong hydrogen bonds. The 99% degree of hydrolysis polyvinyl alcohol molecular chain is densely packed with hydroxyl groups, resulting in much stronger intermolecular forces than products with low degrees of hydrolysis. Therefore, the formed organic film has higher strength and better toughness, providing a solid bonding framework for the crust layer. ③ Improved water resistance after curing: Although polyvinyl alcohol itself is hydrophilic, the fully hydrolyzed product has a more regular molecular arrangement and higher crystallinity after film formation. This highly crystalline structure effectively hinders the penetration of water molecules, giving the dried film a certain degree of water resistance and making it less prone to softening due to moisture. Combined with the hydrophobic modifier in the formula, it can better achieve the goal of "water repellency inside and out". ④ Better compatibility with inorganic materials: For alkaline inorganic materials such as sulfoaluminate cement and metakaolin in the composite reinforcing agent dry powder, 99% hydrolyzed polyvinyl alcohol is more chemically stable in an alkaline environment and less prone to reaction. At the same time, the large number of hydroxyl groups on its molecular chain can form hydrogen bonds with the surface of inorganic particles, enhancing the interfacial bonding force between the organic film and the inorganic skeleton and preventing delamination. In summary, the selection of 99% hydrolyzed polyvinyl alcohol is the result of comprehensive consideration of four dimensions: solution stability, film strength, water resistance, and inorganic compatibility, ensuring that it can form an ideal composite network with acrylate emulsions, cement, etc. in the formula.

[0016] Optionally, the glass transition temperature of the acrylate copolymer emulsion is not higher than 0°C. The core purpose of selecting an acrylate copolymer emulsion with a glass transition temperature (Tg) not higher than 0°C is to ensure that the shelling agent can maintain its flexibility, bonding strength and structural integrity under low temperature environment and diurnal temperature difference, and prevent brittle failure.

[0017] Optionally, the penetration enhancer is one or more of alkyl glycoside surfactants and organosilicon surfactants; used to promote the penetration of the base liquid into the hydrophobic coal seam during construction, so as to improve the bonding strength with the coal seam and form a uniform film on the surface.

[0018] Optionally, the hydrophobic modifier is an organosilicon waterproofing emulsion; the hydrophobic component is uniformly fixed throughout the entire crust through an organic film-forming process, serving to exert a hydrophobic effect after the crust is formed, thus achieving a leap from surface waterproofing to bulk impermeability; the bulk impermeability is a volumetric phenomenon, referring to the ability of the entire three-dimensional structure of the material, from the outside to the inside, to resist water penetration through chemical or physical means. In this technical solution, the hydrophobic component of the organosilicon is not merely floating on the surface, but is uniformly distributed in a composite network composed of organic polymers and inorganic hydration products, ensuring that each internal part also has a waterproof effect. Its advantages are reflected in the following three aspects. ① Durability and abrasion resistance; The limitation of surface waterproofing is that in the mining site, coal flow, vehicles, and sandstorms will continuously rub and impact the crust layer. Once this extremely thin "raincoat" is scratched, rainwater will seep in through the gap and spread laterally along the interface between the crust layer and the coal body, causing the crust layer to peel off from the base layer and flake off; In contrast, in bulk impermeability, since the entire crust layer is hydrophobic from the inside out, even if a layer is worn away from the surface, the newly exposed cross-section is still waterproof. Rainwater cannot find a hydrophilic "channel" to enter the interior, and the crust layer can maintain a firm bond with the base layer. ② Crack resistance; The limitation of surface waterproofing is that if the crust layer develops micro-cracks due to base settlement or shrinkage, the surface waterproofing layer will break at this point, allowing rainwater to directly enter along the crack and causing it to expand rapidly. In contrast, when bulk waterproofing materials develop cracks, the two new cross-sections of the crack are hydrophobic. Water has difficulty penetrating along the hydrophobic walls due to capillary action, which greatly slows down the erosion of the crack tip, achieving "crack self-limitation" and preventing the crack from expanding rapidly due to water wedge action. ③ Long-term stability; The limitation of surface waterproofing is that ultraviolet rays and acid / alkali rain in outdoor environments accelerate the aging and degradation of the surface organic waterproofing coating. Once the molecular chains on the surface break, the waterproofing performance will drop sharply. In bulk waterproofing, the hydrophobic groups of organosilicon (such as -Si-CH3) are fixed on the pore walls of the entire three-dimensional skeleton (cement hydration products and polymer network). Even if the outermost molecules age, the hydrophobic groups inside the skeleton still function, providing a longer protective lifespan for the crust layer. By uniformly fixing the hydrophobic component of organosilicon to the entire composite network, the crusting agent achieves the same waterproof capability inside even if the surface is weathered or worn, thus significantly extending the dust suppression cycle.

[0019] Optionally, the pH adjuster is one or more of calcium oxide and calcium hydroxide; the core purpose of adding the pH adjuster is to activate and match the chemical reaction of the "composite reinforcing agent dry powder"; the dust suppression base liquid is not simply mixed with coal, but its more important role is to serve as a hydration medium for inorganic materials such as sulfoaluminate cement in the composite reinforcing agent. Its functions are as follows: ① Triggering the hydration reaction: The inorganic cementitious system composed of sulfoaluminate cement, metakaolin, and silica fume must undergo a hydration reaction in an alkaline environment to generate ettringite and CSH gel, which provide strength. If the base liquid is acidic, the cement hydration process will be severely inhibited or even stopped. ② Activating the pozzolanic effect: The activity of metakaolin and silica fume requires an alkaline activator (OH-). - This process "activates" the coal dust, prompting it to undergo a secondary reaction with calcium hydroxide produced during cement hydration, generating more cementitious substances and increasing the density and later strength of the crust. ③ It maintains system stability; acrylic copolymer emulsions are typically most stable in weakly alkaline to neutral environments, while strong acids can cause demulsification. Adjusting the pH to alkaline also ensures the stable formation of the organic polymer network. ④ The bonding between simple organic polymers (such as PVA) and coal seams mainly relies on physical interactions (such as van der Waals forces and mechanical interlocking). However, by introducing an alkaline pH adjuster, chemical activation transforms the inert groups on the coal dust surface into reactive active sites, achieving a leap from "physical bonding" to "physical-chemical synergistic bonding," thereby significantly improving the bonding force between the crust layer and the coal seam.

[0020] The advantages are mainly reflected in the following aspects: ① Chemical activation of coal dust surface: Coal dust, especially the surface of low-rank coal or weathered coal, contains a large number of oxygen-containing functional groups (such as carboxyl groups -COOH, phenolic hydroxyl groups -OH). Under alkaline conditions, these functional groups will be ionized (for example, -COOH becomes -COO). - These negatively charged ionization sites can react with Ca²⁺ produced during cement hydration. + Plasma forms ionic bonds or stronger chemisorption, thus "anchoring" the inorganic gel network to the surface of coal dust particles. This chemical bonding force is far stronger than simple physical adsorption. ② Improved interfacial transition zone: Between coal dust (usually acidic or weakly acidic) and alkaline cement paste, pH adjusters create a gentle alkaline gradient, preventing excessive concentration of hydration products at the interface or the formation of a loosely structured layer due to sudden pH changes. This allows the organic-inorganic composite network to bond more tightly to the coal dust substrate. ③ Promoted spreading of organic components: The alkaline environment helps improve the spreading efficiency of penetration enhancers (such as alkyl glycosides), allowing the base liquid to more fully wet the coal dust surface, creating a perfect foundation for the penetration and anchoring of subsequent reinforcing agents.

[0021] Optionally, the metakaolin has a particle size of 800-1250 mesh. As a highly active mineral admixture, its disordered amorphous silica and alumina can undergo a secondary hydration reaction with the calcium hydroxide produced by cement hydration (i.e., the "volcanic ash effect") to generate hydrated calcium silicate and hydrated calcium aluminate with cementitious properties, which fill the pores of cement stone and significantly improve the density, later strength and impermeability of the crust layer.

[0022] Optionally, the silica fume has a particle size of 0.1~0.3 micrometers. As an ultrafine aggregate and volcanic ash material, its tiny spherical particles can fill the nanoscale voids between cement and metakaolin particles, producing a "micro-aggregate filling effect" and significantly reducing the porosity of the crust layer. At the same time, its highly active amorphous silica can react rapidly with calcium hydroxide, improving the interface structure between cement paste and aggregate, thereby significantly improving the strength, erosion resistance and durability of the crust layer.

[0023] Optionally, the sulfoaluminate cement is selected because of its four key characteristics: rapid hardening and early strength, high impermeability, low alkalinity, and micro-expansion. These characteristics perfectly align with the "instant molding, long-term dense formation, and synergistic effect" goals pursued in this invention. Compared to ordinary silicate cement, its advantages are: ① High early strength and construction efficiency, achieving "instant dust suppression." ② High impermeability and durability, achieving "long-term rain resistance." The cement stone structure formed after sulfoaluminate cement hydration is extremely dense, with low total porosity and small average pore size. Its concrete impermeability is 2-3 times that of ordinary silicate cement of the same grade; simultaneously, it has excellent corrosion resistance to seawater, chlorides, sulfates, etc.; the dense structure effectively prevents rainwater penetration and protects the internal coal dust from wetting, which is the physical basis for achieving "bulk phase impermeability." Excellent corrosion resistance ensures the long-term stability of the crust layer under complex outdoor environments (such as acid rain and salts). ③ Low alkalinity achieves "organic-inorganic synergy". In the composite system of organic polymers (PVA, acrylate) and inorganic materials (cement), the compatibility between components is crucial. The liquid phase alkalinity of sulfoaluminate cement after hydration is relatively low (pH value is usually between 10.5 and 11.5), while the alkalinity of ordinary silicate cement is very high (pH>12.5). The high alkalinity environment will exacerbate the risk of hydrolysis or demulsification of organic polymers (such as acrylate emulsions), destroying their film-forming properties and flexibility. The low alkalinity of sulfoaluminate cement greatly protects the structure and performance of organic components, allowing the organic tough network and the inorganic rigid skeleton to be perfectly integrated, rather than weakening each other. ④ Volume stability and low temperature adaptability: Achieving "crack resistance and freeze resistance", cracking of the crust layer is one of the main forms of failure, and sulfoaluminate cement also performs excellently in this regard; during the hydration process, sulfoaluminate cement can generate ettringite, producing a micro-expansion effect, which can compensate for shrinkage and reduce the generation of drying shrinkage cracks; giving it excellent freeze-thaw resistance, and in low temperature environments from 0℃ to -20℃, its early strength development is still far superior to that of ordinary cement, making it suitable for winter construction.

[0024] Optionally, the sodium gluconate is used to extend the setting time of sulfoaluminate cement without sacrificing the final strength, thereby reserving a sufficient operating window for construction and improving the fluidity and uniformity of the slurry.

[0025] Optionally, the length of the polypropylene fiber is 3~6 mm.

[0026] Optionally, the dust-suppressing base liquid is used to form a penetrating layer; the dust-suppressing base liquid and the composite reinforcing agent dry powder are mixed in a ratio of 100:(7~11) to form a mixed suspension, which is used to form a reinforcing layer.

[0027] One or more embodiments of the present invention provide a method for preparing the above-mentioned dust suppressant and crusting agent, comprising: Polyvinyl alcohol is dissolved in water, and acrylate copolymer emulsion, penetration enhancer, hydrophobic modifier and pH adjuster are added in sequence to obtain dust-suppressing base liquid. A composite reinforcing agent dry powder is obtained by mixing sulfoaluminate cement, metakaolin, silica fume, polypropylene fiber and sodium gluconate.

[0028] One or more embodiments of the present invention provide a method for applying the above-mentioned dust suppressant and crusting agent, comprising: A mixed suspension is obtained by adding 7-11% (by weight) of composite reinforcing agent dry powder to the dust-suppressing base liquid; First, a dust-suppressing base liquid is sprayed as a penetrating layer, and then a mixed suspension is sprayed to cover the penetrating layer as a reinforcing layer.

[0029] This dual-spraying process, which involves first spraying the pure base liquid and then the mixed liquid, is a functional gradient construction method designed for hydrophobic coal dust and "organic-inorganic composite" systems. Its advantage lies in solving the three core pain points of traditional single-layer construction—difficult wetting, weak bonding, and easy cracking—through layered functionalization. It is a synergistic process of applying a base coat followed by a top coat. Specific advantages are as follows: ① Overcoming the wetting barrier to achieve "root anchoring" is the core advantage of this method, specifically targeting the "hydrophobic coal seams" mentioned in the background technology. If only a mixed suspension is sprayed once, due to the hydrophobic surface of coal dust (contact angle >105°), the slurry containing a large number of solid particles such as cement is difficult to spread and penetrate, often just floating on the surface and failing to form effective adhesion. The first layer of base liquid is rich in penetration promoters (such as alkyl glycosides) with extremely low surface tension. It spreads and wets instantly on the hydrophobic coal surface and penetrates into the micropores, forming a hydrophilic transition layer rich in hydroxyl groups (-OH) and active functional groups. This layer is firmly adsorbed onto the coal dust surface; when the second layer of mixed liquid containing cement and other reinforcing agents is sprayed on, it comes into contact with the moist, hydrophilic base liquid film. Both are of the same origin, thus achieving chemical anchoring between the reinforcing layer and the coal base layer, rather than simple physical adhesion.

[0030] ② Constructing a "gradient structure" eliminates weak bonding surfaces. If cement and other solids are directly mixed into the base liquid and sprayed in one go, due to uneven particle settling or wetting, a "fragile layer" rich in cement particles but lacking polymers can easily form at the interface between the crust layer and the coal body. This interface is highly susceptible to becoming the starting point for stress concentration and cracking in the future. However, if the pure base liquid (without solid particles) is sprayed first, it penetrates into the surface of the coal body, forming a flexible, polymer-rich bottom layer (transition layer). The mixed suspension sprayed later forms a reinforcing layer rich in inorganic skeleton on top. Since both layers use the same base liquid as the parent material, at the interface, the polymer network of the bottom layer and the inorganic skeleton of the upper layer will penetrate and intertwine with each other, forming a composite transition zone with gradually changing properties, rather than a distinctly weak interface. This structure greatly enhances the interlayer bonding force.

[0031] ③ Controlling shrinkage stress and inhibiting crack formation: During the hardening process, slurry containing a large amount of inorganic materials such as cement will inevitably produce chemical shrinkage and drying shrinkage. If this shrinkage stress is not effectively released, the crust layer will produce network cracks, becoming channels for dust to escape and rainwater to penetrate. The lower pure base liquid layer has high toughness. When the upper reinforcement layer generates stress due to shrinkage, the lower flexible polymer layer can undergo slight deformation to absorb and buffer this stress, preventing stress concentration from leading to through cracks. At the same time, the moist environment of the lower layer can provide additional moisture for the hydration of the upper cement, playing a certain role in internal curing and reducing the drying shrinkage cracks caused by excessive water loss in the upper layer.

[0032] Optionally, after spraying the dust-suppressing base liquid, wait 15-30 minutes before spraying the mixed suspension; the 15-30 minute interval is quantitatively designed based on the surface moisture evaporation rate: ① At this time, the surface moisture of the permeable layer has evaporated to 60-70% of the initial amount, which is the optimal time for spraying; the surface free water has basically dissipated, but the lower 0.5-1 mm depth still maintains a moisture content of about 40-50%, forming a gradient structure of "dry on the surface and moist on the inside"; if the evaporation rate is <50% (the surface is still liquid), the mixed liquid will cause cement particles to settle and penetrate after spraying; if the evaporation rate is >80% (the surface is too dry), it will be difficult for the two layers to achieve molecular-level fusion; ② The apparent viscosity of the permeable layer increases from the initial 10-50 mPa•s to 2000-5000. At a viscosity of mPa•s, the optimal spraying state is reached. This viscosity range corresponds to the polymer molecular chains transitioning from a freely extended state to a semi-entangled gel state, which can firmly adhere to the subsequently sprayed mixture particles without causing uneven distribution due to excessive fluidity; ③ Visually, the surface of the penetration layer loses its obvious watery sheen and presents a uniformly moist matte state; when lightly touching the surface with a fingertip, there is a noticeable stickiness but it is not sticky, and when the finger is removed, fine filaments can be pulled up, indicating the optimal time. If there is still water accumulation and reflection on the surface, it indicates that the waiting time is insufficient; if the surface is completely dry and white, the optimal window has been missed; ④ Environmental adaptation adjustment: in a high-temperature dry environment (>30℃, humidity <40%), the waiting time is shortened to 10~15min; in a low-temperature high-humidity environment (<15℃, humidity >80%), the waiting time is extended to 25~35min. Specifically, it can be determined through a field test: after spraying 0.8 L / m² base liquid on the area to be constructed, observe the surface condition every 5 minutes and record the time required to reach the above standards. If sprayed too early (<15 minutes), the base liquid layer will have excessive moisture and be completely liquid. Spraying the mixed suspension at this time will cause two problems: First, cement particles may settle and penetrate the base liquid layer, directly contacting the coal dust surface and forming a fragile cement-rich interface layer; second, excessive mixing of the two slurry layers will destroy the design intent of the "gradient structure," weakening the flexible buffering effect of the lower layer. If sprayed too late (>30 minutes), the base liquid layer will have completely dried and formed a film, with a continuous and dense polymer film on the surface. Spraying the mixed liquid at this time will result in a "solid-solid interface" between the two layers, making it impossible to achieve molecular-level entanglement. Ultimately, the crust layer will adhere to the base film like a skin, with a significant decrease in adhesion, making it easy to peel off under external force. At 15-30 minutes: The base liquid layer is in a gel state of "dry on the surface and moist on the inside". When the mixed suspension is sprayed at this time, the water in the upper slurry will not dilute the base liquid layer excessively, but the polymer molecular chains still have enough mobility to diffuse and entangle with the polymers in the upper slurry, forming a strong interface of chemical bonding and physical interpenetration. At the same time, the base liquid layer in the gel state can effectively prevent cement particles from settling, maintain the polymer-rich transition zone of the interface, and play a role in buffering stress.

[0033] Optionally, the dosage of the dust-suppressing base liquid for the penetrating layer is 0.7-0.9 L / m², with a thickness of approximately 0.5-1.0 mm; the dosage of the mixed suspension for the reinforcing layer is 1.4-1.6 L / m², with a thickness of approximately 1.5-2.5 mm. This method is suitable for locations such as open-pit coal mines, coal wharves, and railway coal stations where hydrophobic coal dust exists and where there are high requirements for dust suppression cycles and erosion resistance. The dosage should be dynamically adjusted according to the coal dust particle size distribution, surface hydrophobicity, ambient temperature and humidity, and the target dust suppression cycle. The specific determination method is as follows: First, select the dosage range based on the coal dust fineness (the proportion of fine powder below 200 mesh), taking the upper limit when there is more fine powder and the lower limit when there is less fine powder; second, conduct small-area field tests to determine the optimal dosage when the surface of the penetrating layer is uniformly gelled and free of liquid accumulation 15-30 minutes after spraying; finally, combined with the target dust suppression cycle (1-3 months), the dosage of the reinforcing layer should be linearly adjusted at 1.4-1.6 L / m², with a larger dosage for longer cycles.

[0034] The present invention will be further described below with reference to specific embodiments.

[0035] Example 1 A dust suppressant and crusting agent includes a dust suppressant base liquid and a composite reinforcing agent dry powder.

[0036] The dust suppression base liquid comprises the following components in parts by weight: 30 parts polyvinyl alcohol, 80 parts acrylate copolymer emulsion, 5 parts penetration enhancer, 20 parts hydrophobic modifier, 15 parts pH adjuster, and 850 parts deionized water.

[0037] Polyvinyl alcohol is used as the main binder, with the model selected as PVA-1799 and a degree of alcoholysis of over 99%.

[0038] Acrylic ester copolymer emulsion is used as an auxiliary film-forming agent with a solid content of 50% and a glass transition temperature (Tg) of -10℃.

[0039] The penetration enhancer was selected as an alkyl glycoside, model APG-0810.

[0040] The hydrophobic modifier was selected as an organosilicon waterproofing emulsion with a solid content of 30%.

[0041] The pH adjuster was selected as industrial-grade calcium oxide fine powder, 200 mesh.

[0042] The preparation methods of dust-suppressing base liquid include: Deionized water is placed in a reaction vessel and heated to 90-95°C. Polyvinyl alcohol is added while stirring, and the temperature is maintained and stirring is continued for 40-60 minutes until it is completely dissolved. At this point, the solution becomes clear and transparent. Heating is stopped, and the reaction vessel is cooled with water to below 50°C to obtain the first solution. The acrylic emulsion and the silicone waterproofing agent emulsion are placed in a mixing tank and mixed evenly by low-speed stirring to obtain a first premix. The first premix is ​​added to the first solution and stirred evenly to obtain a second premix. Add the penetration enhancer and pH adjuster to the second premix in sequence, and stir continuously for more than 30 minutes until all components are fully dispersed and a stable milky white viscous liquid is formed, thus obtaining about 1000 parts of dust suppression base liquid, which is then sealed and stored for later use.

[0043] The composite reinforcing agent dry powder comprises the following components in parts by weight: 180 parts metakaolin, 70 parts silica fume, 20 parts polypropylene monofilament fiber, 4 parts sodium gluconate, and 376 parts sulfoaluminate cement.

[0044] Metakaolin is used as a fast-hardening skeleton material, with a specification of 800 mesh.

[0045] Silica fume is used as a micro-aggregate filler material with a SiO2 content of ≥92%.

[0046] Polypropylene monofilament fiber, 6mm in length, is used as a three-dimensional toughening material.

[0047] Sodium gluconate is used as a coagulation regulator.

[0048] Sulfoaluminate cement, as a rapid-hardening skeleton material, is specified as SAC, grade 42.5R.

[0049] The preparation methods of composite reinforcing agent dry powder include: Place the raw materials in a mixing device and mix for 18±2 minutes until the powder color is uniform and the fibers are well dispersed, to obtain approximately 650 parts of composite reinforcing agent dry powder, which is then packaged in a moisture-proof container for later use.

[0050] Construction methods include: Select hydrophobic anthracite coal (surface contact angle >105°) from a certain mine, add the dust suppression base liquid to the storage tank of a spray truck equipped with a high-speed shear mixing head, start low-speed mixing, and slowly and evenly add 6.45wt% of composite reinforcing agent dry powder to the dust suppression base liquid. After the material is added, switch to high-speed shear mixing mode and continue mixing for 8 minutes until the material in the tank forms a uniform gray-white suspension with no obvious particles and good fluidity. This is the dust suppression crusting agent working liquid. The working liquid should be used within 60 minutes after the mixing is completed. First, a dust-suppressing base liquid is sprayed evenly and comprehensively onto the surface of the target coal seam using a spraying system, at a dosage of 0.8 L / m². 2 The base liquid is used to wet the coal body using its strong penetrability; after about 30 minutes, when the surface of the permeable layer is visually dry but still feels damp to the touch, 1.5 L / m³ is applied. 2 The amount of working fluid used is sprayed to form the final composite crust; After construction, the coal was cured under natural conditions for 36 hours to obtain a solid, dense, and hydrophobic gray-black composite crust on the surface of the hydrophobic anthracite.

[0051] Comparative Example 1 A 20wt% calcium chloride solution is sprayed once, with a dosage of 2.3 L / m².

[0052] Comparative Example 2 A 3wt% PVA solution is sprayed once, with a dosage of 2.3 L / m².

[0053] Comparative Example 3 The first mixture obtained by adding 5 parts of ordinary silicate cement to 100 parts of the dust-suppressing base liquid of Example 1 was sprayed once, with a construction dosage of 2.3 L / m².

[0054] Comparative Example 4 100 parts of the dust-suppressing base liquid from Example 1 were mixed with 5 parts of ordinary silicate cement to obtain a mixture. During construction, the dust-suppressing base liquid was sprayed at 0.8 L / m², and after waiting for 30 minutes, the mixture was sprayed at 1.5 L / m². The mixture was then cured for 36 hours.

[0055] Comparative Example 5 The dust-suppressing base liquid was prepared according to the method of Example 1, but during the preparation process, the amount of acrylate copolymer emulsion was adjusted from 80 parts to 20 parts, and 60 parts of deionized water were added in equal amounts to make up the total mass of the formula, thus obtaining the second dust-suppressing base liquid; then the working liquid was prepared by the second dust-suppressing base liquid and the composite reinforcing agent dry powder.

[0056] During construction, the original dust-suppressing base liquid (containing 80 parts of acrylic emulsion) was first sprayed at a rate of 0.8 L / m² to wet the coal matrix; after waiting for 30 minutes, the working liquid was sprayed at a rate of 1.5 L / m². Subsequent curing and testing conditions were consistent with those in Example 1.

[0057] Comparative Example 6 The dust-suppressing base liquid was prepared according to the method in Example 1 and set aside for later use.

[0058] When preparing the composite reinforcing agent dry powder, its internal ratio was adjusted: the amount of silica fume in Example 1 was reduced from 70 parts to 20 parts (a reduction of 50 parts), and the amount of sulfoaluminate cement was increased by 50 parts (from 376 parts to 426 parts). The amounts of the remaining components, metakaolin (180 parts), polypropylene monofilament fiber (20 parts), and sodium gluconate (4 parts), remained unchanged. After mixing evenly, the second composite reinforcing agent dry powder was obtained. The second composite reinforcing agent dry powder was mixed with dust suppression base liquid to prepare the working solution.

[0059] During construction, the same dual process as in Example 1 was used: first, the dust-suppressing base liquid was sprayed at a rate of 0.8 L / m²; after waiting for 30 minutes, the working liquid was sprayed at a rate of 1.5 L / m². Subsequent curing and testing conditions were consistent with those in Example 1.

[0060] Test case According to the test methods for inorganic binder strength in the "Test Procedures for Inorganic Binder Stabilized Materials in Highway Engineering" (JTG E51-2009) and the relevant requirements for dust suppressant performance evaluation in the "Technical Specifications for Comprehensive Treatment and Restoration of Open-pit Coal Mines" (GB / T 39775-2021), a systematic test was conducted on the surface crust layer of hydrophobic anthracite after construction in Example 1 and Comparative Examples 1 to 6. The specific test methods are as follows, and the results are shown in Table 1.

[0061] Compressive / flexural strength: Prepare test blocks with dimensions of 50mm×50mm×50mm according to method T0805-94 in JTG E51-2009, and test after curing to the specified age.

[0062] Surface water absorption rate: According to the method in Appendix B of GB / T 39775-2021, water was continuously sprayed onto the surface of the crust for 1 hour, and the water absorption per unit area was measured.

[0063] Spray erosion resistance time: Simulate heavy rain conditions (spray intensity 20mm / h) and record the time when the crust layer begins to break down.

[0064] Outdoor validity period: The time range during which the crust layer remains intact and effectively suppresses dust under typical mining environments (open-pit mining in all seasons).

[0065] Table 1

[0066] The above data demonstrates that this invention, through multi-component synergistic design, achieves a simultaneous leap in mechanical properties and impermeability, exhibiting significant comprehensive advantages. Details are as follows: Synergistic reinforcement of organic-inorganic interpenetrating network: The 24h compressive strength (3.2 MPa) and 7d flexural strength (1.5 MPa) of Example 1 were significantly higher than those of Comparative Example 2 (pure PVA film, compressive strength 0.8 MPa, flexural strength very low) and Comparative Example 5 (low acrylate emulsion, flexural strength 1.0 MPa), proving that the tough organic network formed by polyvinyl alcohol and low Tg acrylate copolymer emulsion is interpenetrating with the rigid inorganic skeleton constructed by sulfoaluminate cement, metakaolin, and silica fume, which not only ensures early rapid molding but also endows the crust layer with excellent crack resistance.

[0067] Micro-nano hierarchical dense synergistic impermeability: The surface water absorption rate of Example 1 (<20 g / m²·h) is much lower than that of Comparative Example 6 (low silica fume, 36 g / m²·h) and Comparative Example 3 / 4 (ordinary cement, 56~70 g / m²·h), indicating that the ultrafine filling effect of silica fume and the volcanic ash activity of metakaolinite work synergistically to significantly reduce porosity; at the same time, the organosilicon hydrophobic agent is evenly distributed throughout the network to achieve bulk impermeability, not just surface waterproofing, thereby extending the spray erosion resistance time to more than 40 min.

[0068] Synergistic toughening through three-dimensional reinforcement and interfacial anchoring: Polypropylene fibers form a three-dimensional reinforcing skeleton in an organic-inorganic composite system. Combined with the gradient interfacial bonding brought about by the penetration promoter and the dual construction process, the 7-day flexural strength of Example 1 reaches 1.5 MPa, which is significantly higher than that of Comparative Example 5 (1.0 MPa), effectively suppressing the generation of shrinkage cracks.

[0069] Synergistic time control of retarding components and fast-hardening system: Sodium gluconate precisely regulates the setting speed of sulfoaluminate cement, which not only ensures the construction fluidity of the mixed suspension within 60 minutes, but also avoids interface defects caused by excessively rapid hydration, providing a time window for the full integration of the penetration layer and the reinforcement layer.

[0070] In summary, the components of this invention are not simply superimposed, but rather achieve a synergistic effect of "1+1>2" by employing multiple synergistic mechanisms such as organic-inorganic interpenetration, micro-nano filling density, bulk hydrophobic modification, fiber three-dimensional reinforcement, and gradient interface anchoring.

[0071] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A dust suppressant and crusting agent, characterized in that, Includes dust-suppressing liquid and composite reinforcing agent dry powder; The dust-suppressing base liquid comprises the following components by mass percentage: 2.5-3.5% polyvinyl alcohol, 5.0-10.0% acrylate copolymer emulsion, 0.3-0.8% penetration enhancer, 1.0-2.5% hydrophobic modifier, 1.0-2.0% pH adjuster, and the balance being water; The composite reinforcing agent dry powder comprises the following components by mass percentage: metakaolin 20-30%, silica fume 8-15%, polypropylene fiber 2-5%, sodium gluconate 0.4-0.8%, with the balance being sulfoaluminate cement.

2. The dust suppressant and crusting agent according to claim 1, characterized in that, The polyvinyl alcohol has a degree of alcoholysis of 99%; the glass transition temperature of the acrylate copolymer emulsion is not higher than 0°C.

3. The dust suppressant and crusting agent according to claim 1, characterized in that, The penetration enhancer is one or more of alkyl glycoside surfactants and organosilicon surfactants; the hydrophobic modifier is an organosilicon waterproofing emulsion.

4. The dust suppressant and crusting agent according to claim 1, characterized in that, The pH adjuster is one or more of calcium oxide and calcium hydroxide; the metakaolin is 800~1250 mesh.

5. The dust suppressant and crusting agent according to claim 1, characterized in that, The length of the polypropylene fiber is 3~6mm.

6. The dust suppressant and crusting agent according to claim 1, characterized in that, The dust-suppressing base liquid is used to form a penetrating layer; the dust-suppressing base liquid and the composite reinforcing agent dry powder are mixed in a ratio of 100:(7~11) to form a mixed suspension, which is used to form a reinforcing layer.

7. A method for preparing a dust suppressant and crusting agent as described in any one of claims 1-6, characterized in that, Polyvinyl alcohol is dissolved in water, and acrylate copolymer emulsion, penetration enhancer, hydrophobic modifier and pH adjuster are added in sequence to obtain dust-suppressing base liquid. A composite reinforcing agent dry powder is obtained by mixing sulfoaluminate cement, metakaolin, silica fume, polypropylene fiber and sodium gluconate.

8. A method for applying a dust-suppressing and crust-forming agent as described in any one of claims 1-6, characterized in that, include: A mixed suspension is obtained by adding 7-11% (by weight) of composite reinforcing agent dry powder to the dust-suppressing base liquid; First, a dust-suppressing base liquid is sprayed as a penetrating layer, and then a mixed suspension is sprayed to cover the penetrating layer as a reinforcing layer.

9. The construction method of the dust suppressant and crusting agent as described in claim 8, characterized in that... After spraying the dust-suppressing base liquid, wait 15-30 minutes before spraying the mixed suspension.

10. The construction method of the dust suppressant and crusting agent as described in claim 8, characterized in that, The amount of dust-suppressing base liquid used in the permeable layer is 0.7-0.9 L / m², and the amount of mixed suspension used in the reinforcing layer is 1.4-1.6 L / m².

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